FN Thomson Reuters Web of Science™ VR 1.0 PT J AU Bondyopadhyay, PK AF Bondyopadhyay, PK TI Introduction to "radio communication" SO PROCEEDINGS OF THE IEEE LA English DT Editorial Material C1 NASA, Johnson Space Ctr, Avion Hardware Branch, Houston, TX 77058 USA. RP Bondyopadhyay, PK (reprint author), NASA, Johnson Space Ctr, Avion Hardware Branch, Houston, TX 77058 USA. NR 5 TC 0 Z9 0 U1 0 U2 0 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 0018-9219 J9 P IEEE JI Proc. IEEE PD OCT PY 1998 VL 86 IS 10 BP 2090 EP 2093 PG 4 WC Engineering, Electrical & Electronic SC Engineering GA 122BG UT WOS:000076050100011 ER PT J AU Woodgate, BE Kimble, RA Bowers, CW Kraemer, S Kaiser, ME Danks, AC Grady, JF Loiacono, JJ Brumfield, M Feinberg, L Gull, TR Heap, SR Maran, SP Lindler, D Hood, D Meyer, W VanHouten, C Argabright, V Franka, S Bybee, R Dorn, D Bottema, M Woodruff, R Michika, D Sullivan, J Hetlinger, J Ludtke, C Stocker, R Delamere, A Rose, D Becker, I Garner, K Timothy, JG Blouke, M Joseph, CL Hartig, G Green, RF Jenkins, EB Linsky, JL Hutchings, JB Moos, HW Boggess, A Roesler, F Weistrop, D AF Woodgate, BE Kimble, RA Bowers, CW Kraemer, S Kaiser, ME Danks, AC Grady, JF Loiacono, JJ Brumfield, M Feinberg, L Gull, TR Heap, SR Maran, SP Lindler, D Hood, D Meyer, W VanHouten, C Argabright, V Franka, S Bybee, R Dorn, D Bottema, M Woodruff, R Michika, D Sullivan, J Hetlinger, J Ludtke, C Stocker, R Delamere, A Rose, D Becker, I Garner, K Timothy, JG Blouke, M Joseph, CL Hartig, G Green, RF Jenkins, EB Linsky, JL Hutchings, JB Moos, HW Boggess, A Roesler, F Weistrop, D TI The Space Telescope Imaging Spectrograph design SO PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF THE PACIFIC LA English DT Article ID DETECTORS AB The Space Telescope Imaging Spectrograph (STIS) instrument was installed on the Hubble Space Telescope (HST) during the second servicing mission, in 1997 February. Four bands cover the wavelength range of 115-1000 nm, with spectral resolving powers between 26 and 200,000. Camera modes are used for target acquisition and deep imaging. Correction for HST's spherical aberration and astigmatism is included. The 115-170 nm range is covered by a CsI MAMA (Multianode Microchannel Array) detector and the 165-310 nm range by a Cs,Te MAMA, each with a format of 2048 x 2048 pixels, while the 305-555 and 550-1000 nm ranges are covered by a single CCD with a format of 1024 x 1024 pixels. The multiplexing advantage of using these two-dimensional detectors compared with the 1 x 512 pixel detectors of the first-generation spectrographs is 1 or 2 orders of magnitude, depending on the mode used. The relationship between the scientific goals and the instrument specifications and design is discussed. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Ball Aerosp Technol Corp, Boulder, CO 80301 USA. York Univ, Ctr Res Earth & Space Sci, N York, ON M2N 5X2, Canada. SITe Corp, Beaverton, OR 97006 USA. Rutgers State Univ, Dept Phys, New Brunswick, NJ 08903 USA. Space Telescope Sci Inst, Baltimore, MD 21218 USA. Natl Opt Astron Observ, Tucson, AZ 85726 USA. Princeton Univ Observ, Princeton, NJ 08544 USA. Univ Colorado, Joint Inst Lab Astrophys, Boulder, CO 80309 USA. Natl Inst Stand & Technol, Boulder, CO 80309 USA. Dominion Astrophys Observ, Victoria, BC V8X 4M6, Canada. Johns Hopkins Univ, Baltimore, MD 21218 USA. Catholic Univ Amer, Washington, DC 20064 USA. Univ Wisconsin, Madison, WI 53706 USA. Univ Nevada, Las Vegas, NV 89154 USA. RP Woodgate, BE (reprint author), NASA, Goddard Space Flight Ctr, Code 6681, Greenbelt, MD 20771 USA. EM woodgate@s2.gsfc.nasa.gov RI Gull, Theodore/D-2753-2012; Woodgate, Bruce/D-2970-2012; Kimble, Randy/D-5317-2012; heap, sara/E-2237-2012; Jenkins, Edward/P-5684-2014 OI Gull, Theodore/0000-0002-6851-5380; Jenkins, Edward/0000-0003-1892-4423 NR 20 TC 229 Z9 229 U1 0 U2 4 PU ASTRONOMICAL SOC PACIFIC PI SAN FRANCISCO PA 390 ASHTON AVE, SAN FRANCISCO, CA 94112 USA SN 0004-6280 J9 PUBL ASTRON SOC PAC JI Publ. Astron. Soc. Pac. PD OCT PY 1998 VL 110 IS 752 BP 1183 EP 1204 DI 10.1086/316243 PG 22 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 134LU UT WOS:000076745200007 ER PT J AU Lin, SJ AF Lin, SJ TI Reply to comments by T. Janjic on 'A finite-volume integration method for computing pressure gradient force in general vertical coordinates' (July B, 1997, 123, 1749-1762) SO QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY LA English DT Editorial Material DE numerical methods; terrain-following coordinates C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Maryland Baltimore Cty, Baltimore, MD 21228 USA. RP Lin, SJ (reprint author), NASA, Goddard Space Flight Ctr, Code 910-3, Greenbelt, MD 20771 USA. NR 4 TC 8 Z9 8 U1 0 U2 1 PU ROYAL METEOROLOGICAL SOC PI READING PA 104 OXFORD ROAD, READING, BERKS, ENGLAND RG1 7LJ SN 0035-9009 J9 Q J ROY METEOR SOC JI Q. J. R. Meteorol. Soc. PD OCT PY 1998 VL 124 IS 551 BP 2531 EP 2533 DI 10.1002/qj.49712455119 PN A PG 3 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 137XU UT WOS:000076943000018 ER PT J AU Das, S Sud, YC Suarez, MJ AF Das, S Sud, YC Suarez, MJ TI Inclusion of a prognostic cloud scheme with the relaxed Arakawa-Schubert cumulus parametrization: Single-column model studies SO QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY LA English DT Article DE GATE; tropical convection ID TOP ENTRAINMENT INSTABILITY; GENERAL-CIRCULATION MODELS; SOLAR-RADIATION; WATER-CONTENT; PARAMETERIZATION; STRATOCUMULUS; PREDICTION; CLIMATE; LAYER; GATE AB A prognostic cloud-prediction scheme has been tested with the relaxed Arakawa-Schubert cumulus-parametrization scheme using the GATE phase III data set. Observed profiles of temperature, moisture and wind fields have been used as initial conditions for a semi-prognostic as well as a fully prognostic study. The subsequent profiles of cloud liquid-water/ice, cloud fraction and precipitation rates besides several other fields have been generated by using these schemes. The cloud water substance and the cloud mass fraction are allowed to evolve prognostically along with the temperature and moisture fields. Results indicate that errors in the temperature and moisture profiles are lowest when the cloud scheme is allowed to interact with radiation and downdraughts are included in the model. Sensitivity studies have been carried out to understand the role of cloud-top entrainment instability. Results indicate that the cloud-top entrainment instability leads to a reduction of the cloud mass fraction and liquid-water content by 5-10% due to mixing with the environment. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Das, S (reprint author), Natl Ctr Medium Range Weather Forecasting, POB 3090,Mausam Bhawan,Lodi Rd, New Delhi 110003, India. NR 38 TC 5 Z9 5 U1 0 U2 0 PU ROYAL METEOROLOGICAL SOC PI READING PA 104 OXFORD ROAD, READING, BERKS, ENGLAND RG1 7LJ SN 0035-9009 J9 Q J ROY METEOR SOC JI Q. J. R. Meteorol. Soc. PD OCT PY 1998 VL 124 IS 552 BP 2671 EP 2692 DI 10.1256/smsqj.55206 PN B PG 22 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 157HW UT WOS:000078052700006 ER PT J AU Holben, BN Eck, TF Slutsker, I Tanre, D Buis, JP Setzer, A Vermote, E Reagan, JA Kaufman, YJ Nakajima, T Lavenu, F Jankowiak, I Smirnov, A AF Holben, BN Eck, TF Slutsker, I Tanre, D Buis, JP Setzer, A Vermote, E Reagan, JA Kaufman, YJ Nakajima, T Lavenu, F Jankowiak, I Smirnov, A TI AERONET - A federated instrument network and data archive for aerosol characterization SO REMOTE SENSING OF ENVIRONMENT LA English DT Article ID SKY BRIGHTNESS MEASUREMENTS; VAPOR COLUMN ABUNDANCE; WATER-VAPOR; OPTICAL-PROPERTIES; SUN PHOTOMETRY; AVHRR DATA; SOLAR; EXTINCTION; RADIATION; RETRIEVAL AB The concept and description of a remote sensing aerosol monitoring network initiated by NASA, de;eloped to support NASA, CNES, and NASDA's Earth satellite systems under the name AERONET and expanded by national and international collaboration, is described. Recent development of weather-resistant automatic sun and sky scanning spectral radiometers enable frequent measurements of atmospheric aerosol optical properties and precipitable water at remote sites. Transmission of automatic measurements via the geostationary satellites GOES and METEOSATS' Data Collection Systems allows reception and processing in near real-time from approximately 75% of the Earth's surface and with the expected addition of GMS, the coverage will increase to 90% in 1998. NASA developed a UNIX-based near real-time processing, display emerging global database. Information on the system is available on the project homepage, http://spamer.gsfc.nasa.gov. The philosophy of an open access database, centralized processing and a user-friendly graphical interface has contributed to the growth of international cooperation for ground-based aerosol monitoring and imposes a standardization for these measurements. The system's automatic data acquisition, transmission, and processing facilitates aerosol characterization on local, regional, and global scales with applications to transport and radiation budget studies, radiative transfer-modeling and validation of satellite aerosol retrievals. This article discusses the operation and philosophy of the monitoring system, the precision and accuracy of the measuring radiometers, a brief description of the processing system, and access to the database. (C) Elsevier Science Inc., 1998. C1 NASA, Goddard Space Flight Ctr, Hughes STX Corp, Greenbelt, MD 20771 USA. NASA, Goddard Space Flight Ctr, Sci Syst & Applicat Inc, Greenbelt, MD 20771 USA. UST Lille, Opt Atmospher Lab, Villeneuve Dascq, France. CIMEL Elect, Paris, France. Inst Pesquisas Espaciais, BR-12201 Sao Jose Dos Campos, Brazil. Univ Maryland, NASA, Goddard Space Flight Ctr, College Pk, MD 20742 USA. Univ Arizona, Tucson, AZ USA. Univ Tokyo, Meguro Ku, Tokyo, Japan. Ecole Normale Super, Ecol Lab, F-75231 Paris, France. RP Holben, BN (reprint author), NASA, Goddard Space Flight Ctr, Hughes STX Corp, Code 923, Greenbelt, MD 20771 USA. EM brent@kratmos.gsfc.nasa.gov RI Smirnov, Alexander/C-2121-2009; ECK, THOMAS/D-7407-2012; Vermote, Eric/K-3733-2012; Nakajima, Teruyuki/H-2370-2013 OI Smirnov, Alexander/0000-0002-8208-1304; Nakajima, Teruyuki/0000-0002-9042-504X NR 46 TC 3161 Z9 3329 U1 57 U2 420 PU ELSEVIER SCIENCE INC PI NEW YORK PA 655 AVENUE OF THE AMERICAS, NEW YORK, NY 10010 USA SN 0034-4257 J9 REMOTE SENS ENVIRON JI Remote Sens. Environ. PD OCT PY 1998 VL 66 IS 1 BP 1 EP 16 DI 10.1016/S0034-4257(98)00031-5 PG 16 WC Environmental Sciences; Remote Sensing; Imaging Science & Photographic Technology SC Environmental Sciences & Ecology; Remote Sensing; Imaging Science & Photographic Technology GA 122VV UT WOS:000076092900001 ER PT J AU Rhim, WK Ishikawa, T AF Rhim, WK Ishikawa, T TI Noncontact electrical resistivity measurement technique for molten metals SO REVIEW OF SCIENTIFIC INSTRUMENTS LA English DT Article ID ROTATING LIQUID-DROPS AB A noncontact technique of measuring the changes in electrical conductivity (or resistivity) of conducting liquids is reported. The technique is based on a conducting drop that is levitated by the high-temperature electrostatic levitator in a high vacuum. This technique, which utilizes the principle of the asynchronous induction motor, measures the relative changes in torque as a function of temperature by applying a rotating magnetic field to the sample. Changes in electrical resistivity are related to the changes in measured torque using the formula developed for the induction motor. Validity of this technique was demonstrated using a pure aluminum sample around its melting temperature. When the measurement results were calibrated by a literature value of resistivity at the melting point, our resistivity data around the melting point could be expressed by r(liq)=24.19 + 1.306X10(-2)(T-T-m) mu Omega cm over T(m)similar to 1160 K, r(solid)=10.77 + 1.421X10(-2)(T-T-m) mu Omega cm over 700 K similar to T-m, and the thermal conductivity as determined by the Wiedemann-Franz-Lorenz law from the resistivity data was given by kappa(liq)(T)=94.61 + 4.41X10(-2)(T-T-m) W m(-1) K-1, kappa(solid)(T)=211.13-7.57X10(-2)(T-T-m) W m(-1) K-1. Both electrical resistivity and thermal conductivity are in close agreement with the literature, confirming the validity of the present technique. (C) 1998 American Institute of Physics. [S0034-6748(98)03510-2]. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Rhim, WK (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 16 TC 62 Z9 64 U1 2 U2 16 PU AMER INST PHYSICS PI WOODBURY PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 USA SN 0034-6748 J9 REV SCI INSTRUM JI Rev. Sci. Instrum. PD OCT PY 1998 VL 69 IS 10 BP 3628 EP 3633 DI 10.1063/1.1149150 PG 6 WC Instruments & Instrumentation; Physics, Applied SC Instruments & Instrumentation; Physics GA 128VX UT WOS:000076430000028 ER PT J AU Meier, SR Tveekrem, JL Keski-Kuha, RAM AF Meier, SR Tveekrem, JL Keski-Kuha, RAM TI A far-ultraviolet contamination-irradiation facility for in situ reflectance measurements SO REVIEW OF SCIENTIFIC INSTRUMENTS LA English DT Article AB In this article, a contamination-irradiation facility designed to measure contamination effects on far-ultraviolet optical surfaces is described. An innovative feature of the facility is the capability of depositing a contaminant, photopolymerizing the contaminant with far-ultraviolet light, and measuring the reflectance of the contaminated sample, all in situ. In addition to describing the facility, we present far-ultraviolet reflectance measurements for a contaminated mirror. (C) 1998 American Institute of Physics. [S0034-6748(98)04210-5]. C1 Hughes STX, Greenbelt, MD 20771 USA. NASA, Opt Branch, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Meier, SR (reprint author), USN, Res Lab, Div Opt Sci, Code 5622, Washington, DC 20375 USA. NR 9 TC 2 Z9 2 U1 0 U2 0 PU AMER INST PHYSICS PI WOODBURY PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 USA SN 0034-6748 J9 REV SCI INSTRUM JI Rev. Sci. Instrum. PD OCT PY 1998 VL 69 IS 10 BP 3642 EP 3644 DI 10.1063/1.1149152 PG 3 WC Instruments & Instrumentation; Physics, Applied SC Instruments & Instrumentation; Physics GA 128VX UT WOS:000076430000031 ER PT J AU Sovers, OJ Fanselow, JL Jacobs, CS AF Sovers, OJ Fanselow, JL Jacobs, CS TI Astrometry and geodesy with radio interferometry: experiments, models, results SO REVIEWS OF MODERN PHYSICS LA English DT Review ID BASE-LINE INTERFEROMETRY; SOLAR GRAVITATIONAL DEFLECTION; ATMOSPHERIC ANGULAR-MOMENTUM; GLOBAL POSITIONING SYSTEM; CRUSTAL DYNAMICS PROJECT; CURRENT PLATE MOTIONS; RIGID-EARTH NUTATION; FORCED NUTATIONS; REFERENCE FRAME; OCEAN TIDES AB Interferometry at radio frequencies between Earth-based receivers separated by intercontinental distances has made significant contributions to astrometry and geophysics during the past three decades. Analyses of such very long baseline interferometric (VLBI) experiments now permit measurements of relative positions of points on the Earth's surface and of angles between celestial objects at levels of better than one cm and one nanoradian, respectively. The relative angular positions of extragalactic radio sources inferred from this technique presently form the best realization of an inertial reference frame. This review summarizes the current status of radio interferometric measurements for astrometric and geodetic applications. It emphasizes the theoretical models that are required to extract results from the VLBI observables at present accuracy levels. An unusually broad cross section of physics contributes to the required modeling. Both special and general relativity need to be considered in properly formulating the geometric part of the propagation delay. While high-altitude atmospheric charged-particle (ionospheric) effects are easily calibrated for measurements employing two well-separated frequencies, the contribution of the neutral atmosphere at lower altitudes is more difficult to remove. In fact, mismodeling of the troposphere remains the dominant error source. Plate tectonic motions of the observing stations need to be taken into account, as well as the nonpointlike intensity distributions of many sources. Numerous small periodic and quasiperiodic tidal effects also make important contributions to space geodetic observables at the centimeter level, and some of these are just beginning to be characterized. Another area of current rapid advances is the specification of the orientation of the Earth's spin axis in inertial space: nutation and precession. Highlights of the achievements of very long baseline interferometry are presented in four areas: reference frames, Earth orientation, atmospheric effects on microwave propagation, and relativity. The order-of-magnitude improvement of accuracy that was achieved during the last decade has provided essential input to geophysical models of the Earth's internal structure. Most aspects of VLBI modeling are also directly applicable to interpretation of other space geodetic measurements, such as active and passive ranging to Earth-orbiting satellites, interplanetary spacecraft, and the Moon. [S0034-6861(98)00104-4]. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Remote Sensing Anal Syst Inc, Altadena, CA 91001 USA. RP CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 318 TC 119 Z9 130 U1 3 U2 12 PU AMER PHYSICAL SOC PI COLLEGE PK PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA SN 0034-6861 EI 1539-0756 J9 REV MOD PHYS JI Rev. Mod. Phys. PD OCT PY 1998 VL 70 IS 4 BP 1393 EP 1454 DI 10.1103/RevModPhys.70.1393 PN 2 PG 62 WC Physics, Multidisciplinary SC Physics GA 139AG UT WOS:000077004800004 ER PT J AU Samtaney, R Pullin, DI AF Samtaney, R Pullin, DI TI Self-similar hypervelocity shock interactions with oblique contact discontinuities SO SHOCK WAVES LA English DT Article DE self-similar flow; shock-wave refraction; ideal dissociating gas ID DENSITY-STRATIFIED INTERFACES; COMPRESSIBLE EULER EQUATIONS; FAST GAS INTERFACE; WAVES; DEPOSITION AB The two-dimensional inviscid refraction of a shock wave at an oblique contact discontinuity is self-similar; i.e. it depends only upon the variables xi = x/t, eta = y/t. We transform the compressible Euler equations into the self-similar (xi,eta) coordinates and solve the resulting boundary-value problem by an implicit equilibrium flux method. We present results for strong shock (M greater than or equal to 10 where M is the incident shock Mach number) interactions with an oblique contact discontinuity separating an inert gas from a gas which exhibits high-temperature gas chemistry effects. To model high-temperature effects we employ Lighthill's ideal dissociating gas (IDG) model. Comparison between the frozen and equilibrium limits, both of which are self-similar, indicate large changes in peak density and temperatures. Significant differences in the overall flow pattern between the frozen and equilibrium limits are observed for interfaces with low negative Atwood ratio and high positive Atwood ratio. Results from a local analysis are presented when the shock refraction is regular. The critical angle at which the transition from regular to irregular refraction occurs is slightly larger for the equilibrium chemistry case. C1 NASA, Ames Res Ctr, MRJ Technol Solut, Moffett Field, CA 94035 USA. CALTECH, Grad Aeronaut Labs, Pasadena, CA 91125 USA. RP Samtaney, R (reprint author), NASA, Ames Res Ctr, MRJ Technol Solut, Moffett Field, CA 94035 USA. NR 17 TC 1 Z9 1 U1 1 U2 4 PU SPRINGER VERLAG PI NEW YORK PA 175 FIFTH AVE, NEW YORK, NY 10010 USA SN 0938-1287 J9 SHOCK WAVES JI Shock Waves PD OCT PY 1998 VL 8 IS 5 BP 299 EP 310 DI 10.1007/s001930050122 PG 12 WC Mechanics SC Mechanics GA 137PU UT WOS:000076925000005 ER PT J AU Deming, D Jennings, DE McCabe, G Moran, T Loewenstein, R AF Deming, D Jennings, DE McCabe, G Moran, T Loewenstein, R TI Limb observations of the 12.32-micron Mg I emission line during the 1994 annular eclipse SO SOLAR PHYSICS LA English DT Article ID SOLAR MAGNETIC-FIELD; SUBMILLIMETER WAVELENGTHS; 12 MICRONS; QUIET SUN; PROFILES; 12-MU-M AB We determined the limb profile of the extremely Zeeman-sensitive emission line of Mg I at 12.32 mu m (811.58 cm(-1)) during the May 1994 annular eclipse, using the 3.5-m ARC telescope at the Apache Point site on Sacramento Peak, New Mexico. Spectra were recorded at 0.1 cm(-1) spectral resolution and 1 s time resolution using a cryogenic grating spectrometer. The time derivatives of the observed line energy and continuum intensity were used to infer high-resolution profiles of the solar limb. Data were obtained at second contact only, since clouds prevented observations at third contact. We find that the emission line energy peaks very close to the 12 mu m continuum limb. This agrees with our result from the 1991 total eclipse over Mauna Kea, and also with non-LTE radiative transfer theory for this line, which predicts an upper-photospheric origin. However, in 1991, line emission remained observable as high as 2000 km above the continuum limb, whereas the 1994 data show observable emission to only 500 km. This difference greatly exceeds any applicable errors, or sensitivity differences in either data set, and must be attributed to spatial and/or temporal inhomogeneities in the solar limb emission of this line. We discuss possible causes of these inhomogeneities, and implications for observations at far-IR and submillimeter wavelengths. C1 NASA, Goddard Space Flight Ctr, Planetary Syst Branch, Greenbelt, MD 20771 USA. Raytheon STX Corp, Lanham, MD 20706 USA. Goddard Space Flight Ctr, Planetary Syst Branch, Lanham, MD 20706 USA. Goddard Space Flight Ctr, Planetary Syst Branch, Vienna, VA 22180 USA. Space Applicat Corp, Vienna, VA 22180 USA. Univ Chicago, Yerkes Observ, Williams Bay, WI 53191 USA. RP NASA, Goddard Space Flight Ctr, Planetary Syst Branch, Code 693, Greenbelt, MD 20771 USA. RI Jennings, Donald/D-7978-2012 NR 19 TC 6 Z9 6 U1 0 U2 0 PU SPRINGER PI DORDRECHT PA VAN GODEWIJCKSTRAAT 30, 3311 GZ DORDRECHT, NETHERLANDS SN 0038-0938 EI 1573-093X J9 SOL PHYS JI Sol. Phys. PD OCT PY 1998 VL 182 IS 2 BP 283 EP 291 DI 10.1023/A:1005083105249 PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 144PE UT WOS:000077322300002 ER PT J AU Padula, SL Stone, SC AF Padula, SL Stone, SC TI Parallel implementation of large-scale structural optimization SO STRUCTURAL OPTIMIZATION LA English DT Article ID AIRCRAFT AB Advances in computer technology and performance allow researchers to pose useful optimization problems that were previously too large for consideration. For example, NASA Langley Research Center is investigating the large structural optimization problems that arise in aircraft design. The total number of design variables and constraints for these nonlinear optimization problems is now an order of magnitude larger than anything previously reported. To find solutions in a reasonable amount of time, a coarse-grained parallel-processing algorithm is recommended. This paper studies the effects of problem size on sequential and parallel versions of this algorithm. For initial testing of this algorithm, a hub frame optimization problem is devised such that the size of the problem can be adjusted by adding members and load cases. Numerous convergence histories demonstrate that the algorithm performs correctly and in a robust manner. Timing profiles for a. wide range of randomly generated problems highlight the changes in the subroutine timings that are caused by the increase in problem size. The potential benefits and drawbacks associated with the parallel approach are summarized. C1 NASA, Langley Res Ctr, Hampton, VA 23681 USA. RP Padula, SL (reprint author), NASA, Langley Res Ctr, Hampton, VA 23681 USA. NR 12 TC 7 Z9 8 U1 0 U2 1 PU SPRINGER VERLAG PI NEW YORK PA 175 FIFTH AVE, NEW YORK, NY 10010 USA SN 0934-4373 J9 STRUCT OPTIMIZATION JI Struct. Optim. PD OCT PY 1998 VL 16 IS 2-3 BP 176 EP 185 DI 10.1007/BF01202828 PG 10 WC Computer Science, Interdisciplinary Applications; Engineering, Multidisciplinary; Mechanics SC Computer Science; Engineering; Mechanics GA 137PW UT WOS:000076925200010 ER PT J AU Dyall, KG AF Dyall, KG TI Relativistic and nonrelativistic finite nucleus optimized double zeta basis sets for the 4p, 5p and 6p elements SO THEORETICAL CHEMISTRY ACCOUNTS LA English DT Article DE Gaussian basis sets; relativistic basis sets; p block; double zeta; correlation consistent; finite nucleus ID GAUSSIAN-BASIS SETS; ATOMS AB Relativistic and nonrelativistic valence double zeta basis sets have been optimized at the self-consistent held (SCF) level with a Gaussian nuclear charge distribution for the 4p, 5p and 6p elements. The basis sets were optimized on the weighted average energy of the nonrelativistic p(n) configuration. Each basis set has been supplemented with a correlating d function optimized in multireference singles and doubles CI calculations out of the SCF reference configuration set, a diffuse s and p function optimized at the SCF level for the negative ion for all except the rare gases, and a diffuse correlating d function optimized in multireference singles and doubles CI calculations out of the negative ion SCF reference configuration set. These basis sets are therefore the equivalent of the correlation-consistent double zeta basis sets of Dunning and coworkers. In addition to the valence correlation and diffuse functions, each basis set has also been supplemented with two f functions, one for correlation and one for polarization of the sub-valence d shell, and prescriptions given for obtaining s and p functions for sub-valence shell correlation. C1 NASA, Ames Res Ctr, Thermosci Inst, Moffett Field, CA 94035 USA. RP Dyall, KG (reprint author), NASA, Ames Res Ctr, Thermosci Inst, Mail Stop 230-3, Moffett Field, CA 94035 USA. NR 11 TC 96 Z9 96 U1 0 U2 12 PU SPRINGER PI NEW YORK PA 233 SPRING ST, NEW YORK, NY 10013 USA SN 1432-881X J9 THEOR CHEM ACC JI Theor. Chem. Acc. PD OCT PY 1998 VL 99 IS 6 BP 366 EP 371 PG 6 WC Chemistry, Physical SC Chemistry GA 139LF UT WOS:000077029500003 ER PT J AU Pinel, SI Signer, HR Zaretsky, EV AF Pinel, SI Signer, HR Zaretsky, EV TI Design and operating characteristics of high-speed, small-bore ball bearings SO TRIBOLOGY TRANSACTIONS LA English DT Article; Proceedings Paper CT 53rd Annual Meeting of the Society-of-Tribologists-and-Lubrication-Engineers CY MAY 17-21, 1998 CL DETROIT, MICHIGAN SP Soc Tribologists & Lubricat Engineers DE rolling-element bearings; ball bearings; engineering analysis and computing; life prediction methods AB The computer program SHABERTH was used to analyze 35-mm-bore, angular-contact ball bearings designed and manufactured for high-speed turbomachinery applications. Parametric tests of the bearings were conducted on a high-speed, high-temperature bearing tester and were compared with the computet predictions. Four bearing and cage designs were studied. The bearings were lubricated either by jet lubrication or through the split inner ring with and without outer-ring cooling. The predicted bearing life decreased with increasing speed because of increased operating contact stresses caused by changes in contact angle and centrifugal load. For thrust loads only, the differences in calculated life for the 24 degrees and 30 degrees contact-angle bearings was insignificant. However, for combined loading, the 24 degrees contact-angle bearing gave longer life. Fm split-inner-ring bearings, optimal operating conditions were obtained with a 24 degrees contact angle and an inner-ring, land-guided cage, using outer-ring cooling in conjunction with low lubricant flow rates. Lower temperature and power losses were obtained with a single-outer-ring land-guided cage for the 24 degrees contact-angle bearing having a relieved inner ring and partially relieved outer ring. Inner-ring temperatures were independent of lubrication mode and cage design. in comparison with measured values, reasonably good engineering correlation was obtained using the computer program SHABERTH for predicted bearing power loss and for inner- and outer-ring temperatures. The Parker formula for XCAV (used in SHABERTH, a measure of oil volume in the bearing cavity) may need to be refined to reflect bearing lubrication mode, cage design, and location of cage-controlling land. C1 Pinel Engn, Placentia, CA USA. Signer Tech Serv, Fullerton, CA USA. NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. RP Pinel, SI (reprint author), Pinel Engn, Placentia, CA USA. NR 18 TC 4 Z9 6 U1 1 U2 1 PU SOC TRIBOLOGISTS & LUBRICATION ENGINEERS PI PARK RIDGE PA 840 BUSSE HIGHWAY, PARK RIDGE, IL 60068 USA SN 1040-2004 J9 TRIBOL T JI Tribol. Trans. PD OCT PY 1998 VL 41 IS 4 BP 423 EP 434 DI 10.1080/10402009808983767 PG 12 WC Engineering, Mechanical SC Engineering GA 142XF UT WOS:000077225200003 ER PT J AU Galloway, DL Hudnut, KW Ingebritsen, SE Phillips, SP Peltzer, G Rogez, F Rosen, PA AF Galloway, DL Hudnut, KW Ingebritsen, SE Phillips, SP Peltzer, G Rogez, F Rosen, PA TI Detection of aquifer system compaction and land subsidence using interferometric synthetic aperture radar, Antelope Valley, Mojave Desert, California SO WATER RESOURCES RESEARCH LA English DT Article ID SURFACE DEFORMATION; SAR INTERFEROMETRY; CONFINED SYSTEM; EARTHQUAKE; MOVEMENT; FIELD; FLOW AB Interferometric synthetic aperture radar (InSAR) has great potential to detect and quantify land subsidence caused by aquifer system compaction. InSAR maps with high spatial detail and resolution of range displacement (+/-10 mm in change of land surface elevation) were developed for a groundwater basin (similar to 10(3) km(2)) in Antelope Valley, California, using radar data collected from the ERS-1. satellite. These data allow comprehensive comparison between recent (1993-1995) subsidence patterns and those detected historically (1926-1992) by more traditional methods. The changed subsidence patterns are generally compatible with recent shifts in land and water use. The InSAR-detected patterns are generally consistent with predictions based on a coupled model of groundwater flow and aquifer system compaction. The minor inconsistencies may reflect our imperfect knowledge of the distribution and properties of compressible sediments. When used in conjunction with coincident measurements of groundwater levels and other geologic information, InSAR data may be useful for constraining parameter estimates in simulations of aquifer system compaction. C1 Calif State Univ Sacramento, US Geol Survey, Sacramento, CA 95819 USA. US Geol Survey, Pasadena, CA 91106 USA. US Geol Survey, Menlo Park, CA 94025 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Galloway, DL (reprint author), Calif State Univ Sacramento, US Geol Survey, Placer Hall,6000 J St, Sacramento, CA 95819 USA. EM dlgallow@usgs.gov RI Hudnut, Kenneth/B-1945-2009; Hudnut, Kenneth/G-5713-2010; OI Hudnut, Kenneth/0000-0002-3168-4797; Galloway, Devin/0000-0003-0904-5355 NR 58 TC 187 Z9 195 U1 4 U2 43 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0043-1397 J9 WATER RESOUR RES JI Water Resour. Res. PD OCT PY 1998 VL 34 IS 10 BP 2573 EP 2585 DI 10.1029/98WR01285 PG 13 WC Environmental Sciences; Limnology; Water Resources SC Environmental Sciences & Ecology; Marine & Freshwater Biology; Water Resources GA 124UN UT WOS:000076200900011 ER PT J AU Ramesham, R Ellis, CD Olivas, JD Bolin, S AF Ramesham, R Ellis, CD Olivas, JD Bolin, S TI Fabrication of diamond membranes for MEMS using reactive ion etching of silicon SO THIN SOLID FILMS LA English DT Letter DE diamond; membrane; reactive ion etching; etching of silicon ID DEPOSITION; FILMS AB Polycrystalline diamond thin film has been grown on a silicon substrate using high pressure microwave plasma-assisted chemical vapor deposition from a gas mixture of methane and hydrogen at a substrate temperature of 950 degrees C. A simple process flow has been developed to fabricate optically transparent polycrystalline synthetic diamond membranes/windows employing reactive ion etching (RIE) of a single crystal silicon substrate using an electron beam evaporated aluminum thin film mask pattern formed by photolithography. Scanning electron microscopy has been used to study the morphology of as-grown diamond thin films. (C) 1998 Elsevier Science S.A. All rights reserved. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Auburn Univ, Dept Elect Engn, Alabama Microelect Sci & Technol Ctr, Auburn, AL 36849 USA. RP Ramesham, R (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. EM rajeshuni.ramesham@jpl.nasa.gov NR 16 TC 9 Z9 9 U1 2 U2 5 PU ELSEVIER SCIENCE SA PI LAUSANNE PA PO BOX 564, 1001 LAUSANNE, SWITZERLAND SN 0040-6090 J9 THIN SOLID FILMS JI Thin Solid Films PD SEP 30 PY 1998 VL 330 IS 2 BP 62 EP 66 DI 10.1016/S0040-6090(98)00825-6 PG 5 WC Materials Science, Multidisciplinary; Materials Science, Coatings & Films; Physics, Applied; Physics, Condensed Matter SC Materials Science; Physics GA 129YB UT WOS:000076490700002 ER PT J AU Mace, GG Ackerman, TP Minnis, P Young, DF AF Mace, GG Ackerman, TP Minnis, P Young, DF TI Cirrus layer microphysical properties derived from surface-based millimeter radar and infrared interferometer data SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID CLOUD PROPERTIES; RADIATIVE PROPERTIES; MULTIPLE-SCATTERING; OPTICAL-PROPERTIES; HEATING RATES; DOPPLER RADAR; ICE CRYSTALS; 94-GHZ RADAR; CLIMATE; PARAMETERIZATION AB Observational data regarding the properties of cirrus clouds are needed to aid in the development of accurate, physically based parameterizations in climate models. The Atmospheric Radiation Measurement (ARM) program, sponsored by the U.S. Department of Energy, is providing continuous observations of cirrus clouds with a suite of instrumentation at several locales. In this paper, we describe an algorithm to derive the microphysical properties of optically thin cirrus clouds. This algorithm uses radar reflectivity and infrared emission spectra from an interferometer and is tailored for the specific instruments at the ARM sites. We present in situ validation of the technique and examine a cirrus case study to illustrate the sensitivity of the algorithm. In the case study, solar fluxes calculated from the retrieved microphysical parameters are compared to observed fluxes to build confidence in the algorithm results. Comparison of the retrieved quantities to microphysical parameters retrieved from satellite data is also presented. C1 Univ Utah, Dept Meteorol, Salt Lake City, UT 84112 USA. Penn State Univ, Dept Meteorol, University Pk, PA 16802 USA. NASA, Langley Res Ctr, Div Atmospher Sci, Hampton, VA 23665 USA. RP Mace, GG (reprint author), Univ Utah, Dept Meteorol, 819 Browning Bldg, Salt Lake City, UT 84112 USA. EM mace@atmos.met.utah.edu RI Minnis, Patrick/G-1902-2010 OI Minnis, Patrick/0000-0002-4733-6148 NR 36 TC 83 Z9 83 U1 0 U2 2 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD SEP 27 PY 1998 VL 103 IS D18 BP 23207 EP 23216 DI 10.1029/98JD02117 PG 10 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 126PT UT WOS:000076302900013 ER PT J AU Redemann, J Turco, RP Pueschel, RF Fenn, MA Browell, EV Grant, WB AF Redemann, J Turco, RP Pueschel, RF Fenn, MA Browell, EV Grant, WB TI A multi-instrument approach for characterizing the vertical structure of aerosol properties: case studies in the Pacific Basin troposphere SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID SCATTERING SPECTROMETER PROBE; DOPPLER LIDAR; OZONE; BACKSCATTER; INVERSION AB During February/March 1994, a series of aircraft-based aerosol measurements were carried out in the Pacific Basin troposphere using a differential absorption lidar system deployed by NASA Langley, and optical spectrometer probes and a wire-impactor system operated by NASA Ames. A modified Klett inversion algorithm was applied to extract altitude profiles of aerosol backscattering from the IR lidar signal. The algorithm that we have designed for this purpose utilizes the in situ aerosol measurements to normalize the lidar profile at the aircraft altitude and to supply the lidar ratio as a function of height. The lidar-derived aerosol backscattering coefficients were then compared to the backscattering coefficients calculated from the in situ measurements. During several local aircraft descents, we found good agreement between the remote lidar and in situ results for the absolute value of the aerosol backscattering coefficient and its altitude variation only when we allowed fdr several layers with different aerosol refractive indices. The agreement validates our lidar calibration method and provides an indication of the variation in aerosol refractive index as a function of altitude. Two of the three case studies performed in this paper reveal layers of anthropogenic aerosols transported long distances into the Pacific Basin troposphere. A third case implies the existence of a layer of dustlike aerosol particles in the lower troposphere, most likely of Asian origin. C1 Univ Calif Los Angeles, Dept Atmospher Sci, Los Angeles, CA 90095 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Sci Applicat Int Corp, Hampton, VA 23681 USA. NASA, Langley Res Ctr, Hampton, VA 23681 USA. RP Redemann, J (reprint author), Univ Calif Los Angeles, Dept Atmospher Sci, 7221 Math Sci,405 Hilgard Ave, Los Angeles, CA 90095 USA. EM redemann@atmos.ucla.edu RI Grant, William/B-8311-2009 OI Grant, William/0000-0002-1439-3285 NR 29 TC 12 Z9 12 U1 0 U2 2 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD SEP 27 PY 1998 VL 103 IS D18 BP 23287 EP 23298 DI 10.1029/98JD02005 PG 12 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 126PT UT WOS:000076302900019 ER PT J AU Ricca, A AF Ricca, A TI Heats of formation for NF(n) (n=1-3) and NF(n)(+) (n=1-3) SO CHEMICAL PHYSICS LETTERS LA English DT Article ID COUPLED-CLUSTER THEORY; GAUSSIAN-BASIS SETS; ELECTRON CORRELATION; WAVE-FUNCTIONS; MOLECULES; ENERGIES; THERMOCHEMISTRY AB Accurate heats of formation are computed for NF(n) and NF(n)(+), for n = 1-3. The geometries and vibrational frequencies are determined at the B3LYP level of theory. The energetics are determined at the CCSD(T) level of theory. Basis set limit values are obtained by extrapolation. In those cases where the CCSD(T) calculations became prohibitively large, the basis set extrapolation is performed at the MP2 level. The temperature dependence of the heat of formation, heat capacity, and entropy are computed for the temperature range of 300-4000 K and fit to a polynomial. (C) 1998 Published by Elsevier Science B.V. All rights reserved. C1 NASA, Ames Res Ctr, Thermosci Inst, Moffett Field, CA 94035 USA. RP Ricca, A (reprint author), NASA, Ames Res Ctr, Thermosci Inst, Mail Stop 230-3, Moffett Field, CA 94035 USA. EM ricca@pegasus.arc.nasa.gov NR 27 TC 17 Z9 17 U1 0 U2 2 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0009-2614 J9 CHEM PHYS LETT JI Chem. Phys. Lett. PD SEP 25 PY 1998 VL 294 IS 6 BP 454 EP 458 DI 10.1016/S0009-2614(98)00910-5 PG 5 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA 124RP UT WOS:000076195900002 ER PT J AU Arvidson, RE Acton, C Blaney, D Bowman, J Kim, S Klingelhofer, G Marshall, J Niebur, C Plescia, J Saunders, RS Ulmer, CT AF Arvidson, RE Acton, C Blaney, D Bowman, J Kim, S Klingelhofer, G Marshall, J Niebur, C Plescia, J Saunders, RS Ulmer, CT TI Rocky 7 prototype Mars rover field geology experiments - 1. Lavic Lake and Sunshine Volcanic Field, California SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS LA English DT Article ID MOSSBAUER; EVOLUTION; DESERT; SOIL AB Experiments with the Rocky 7 rover were performed in the Mojave Desert to better understand how to conduct rover-based, long-distance (kilometers) geological traverses on Mars, The rover was equipped with stereo imaging systems for remote sensing science and hazard avoidance and Fe-57 Mossbauer and nuclear magnetic resonance spectrometers for in situ determination of mineralogy of unprepared rock and soil surfaces. Laboratory data were also obtained using the spectrometers and an X ray diffraction (XRD)/XRF instrument for unprepared samples collected from the rover sites. Simulated orbital and descent image data assembled for the test sites were found to be critical for assessing the geologic setting, formulating hypotheses to be tested with rover observations, planning traverses, locating the rover, and providing a regional context for interpretation of rover-based observations. Analyses of remote sensing and in situ observations acquired by the rover confirmed inferences made from orbital and simulated descent images that the Sunshine Volcanic Field is composed of basalt flows. Rover data confirmed the idea that Lavic Lake is a recharge playa and that an alluvial fan composed of sediments with felsic compositions has prograded onto the playa. Rover-based discoveries include the inference that the basalt flows are mantled with aeolian sediment and covered with a dense pavement of varnished basalt cobbles. Results demonstrate that the combination of rover remote sensing and in situ analytical observations will significantly increase our understanding of Mars and provide key connecting links between orbital and descent data and analyses of returned samples. C1 Washington Univ, Dept Earth & Planetary Sci, St Louis, MO 63130 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Tech Univ Darmstadt, Inst Nucl Phys, D-64289 Darmstadt, Germany. US Geol Survey, Flagstaff, AZ 86001 USA. Ulmer Syst Inc, Pasadena, CA 91106 USA. Search Extraterr Intelligence Inst, Mt View, CA USA. RP Arvidson, RE (reprint author), Washington Univ, Dept Earth & Planetary Sci, Box 1169,1 Brookings Dr, St Louis, MO 63130 USA. EM arvidson@wunder.wustl.edu RI Plescia, Jeffrey/B-7738-2016 NR 32 TC 19 Z9 19 U1 0 U2 4 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0148-0227 J9 J GEOPHYS RES-PLANET JI J. Geophys. Res.-Planets PD SEP 25 PY 1998 VL 103 IS E10 BP 22671 EP 22688 DI 10.1029/98JE01768 PG 18 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 168VC UT WOS:000078713000001 ER PT J AU Young, RE AF Young, RE TI The Galileo probe mission to Jupiter: Science overview SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS LA English DT Review ID NORTH EQUATORIAL BELT; TROPOSPHERIC GAS-COMPOSITION; JOVIAN UPPER-ATMOSPHERE; VOYAGER IRIS SPECTRA; CLOUD STRUCTURE; OUTER PLANETS; GIANT PLANETS; LIGHTNING GENERATION; GRAVITATIONAL TIDES; HELIUM ABUNDANCE AB This paper is an introduction to and overview of the accompanying papers in this issue which give detailed results from the Galileo probe mission to Jupiter, including results from the Galileo orbiter and Earth-based observations that are relevant for understanding the probe data and placing them in context. A summary of prior knowledge of Jupiter's atmosphere is also presented. All probe scientific investigations were successful. As anticipated, the Galileo probe results confirm some expectations about Jupiter, refute others, and raise important new questions. The Galileo probe defined the atmospheric thermal structure at the probe entry site from similar to 1000 km above the 1 bar pressure level to a depth near 22 bars. During direct atmospheric sampling beginning near 0.4 bar, instruments on the probe measured composition, cloud properties, thermal structure, winds, radiative energy balance, and electrical properties of the Jovian atmosphere. Prior to reaching the Jovian atmosphere, probe instruments measured properties of the inner magnetosphere, observing regions not previously sampled by any spacecraft. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Young, RE (reprint author), NASA, Ames Res Ctr, MS 245-3, Moffett Field, CA 94035 USA. NR 127 TC 26 Z9 26 U1 1 U2 3 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0148-0227 J9 J GEOPHYS RES-PLANET JI J. Geophys. Res.-Planets PD SEP 25 PY 1998 VL 103 IS E10 BP 22775 EP 22790 DI 10.1029/98JE01051 PG 16 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 168VC UT WOS:000078713000007 ER PT J AU Orton, GS Fisher, BM Baines, KH Stewart, ST Friedson, AJ Ortiz, JL Marinova, M Ressler, M Dayal, A Hoffmann, W Hora, J Hinkley, S Krishnan, V Masanovic, M Tesic, J Tziolas, A Parija, KC AF Orton, GS Fisher, BM Baines, KH Stewart, ST Friedson, AJ Ortiz, JL Marinova, M Ressler, M Dayal, A Hoffmann, W Hora, J Hinkley, S Krishnan, V Masanovic, M Tesic, J Tziolas, A Parija, KC TI Characteristics of the Galileo probe entry site from Earth-based remote sensing observations SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS LA English DT Article ID INFRARED TELESCOPE FACILITY; LARGE PHASE ANGLES; JUPITER ATMOSPHERE; CLOUD STRUCTURE; UPPER TROPOSPHERE; EQUATORIAL BELT; JOVIAN PLANETS; ARRAY CAMERA; STRATOSPHERE; POLARIMETRY AB A reassessment of ground-based observations confirms to better than a 98% confidence level that the Galileo probe entered a 5-mu m hot spot, a region of unusual clarity and dryness, some 900 +/- 300 km north of its southern boundary. Cloud conditions at that point were similar to those in the center of this region, some 600 km further north. At the time of the probe entry, the region was evolving to a slightly larger size and even thinner cloud conditions, as evidenced by its rapidly brightening appearance at 4.78 mu m. The low reflectivity of the region in red light is highly anticorrelated with 4.78-mu m thermal emission, but this correlation breaks down in the blue. In general, the reflectivity of most hot spots is remarkably uniform, although the 4.78-mu m thermal emission is highly variable. A cloud structure most consistent with both the observed reflected sunlight and thermal emission properties consists of two layers: (1) a cloud layer above the 450-mbar level extending up to the 150-mbar level that probably consists of submicron sized particles and (2) a tropospheric cloud that is probably below the 1-bar level, possibly ammonia hydrosulfide, with low optical thickness in the infrared. A population of particles larger than similar to 3 mu m, clearly present at the NH3 ice cloud level outside hot spots, is absent inside them. The NH3 gas abundance near 300-400 mbar pressure does not appear to be unusually depleted in hot spots. Zonal structures in the tropospheric temperature field near the probe entry site were not correlated with the location of 5-mu m hot spots but moved at speeds closer to the internal rotation rate of the planet. The propel ties of the tropospheric thermal waves at the probe entry latitude show little correlation to the properties of the 5-mu m hot spot waves. Temperatures at the probe entry site derived from remote sensing are warmer than the Atmospheric Structure Instrument (ASI) experiment results near the tropopause, probably because the low-temperature ASI features are confined to regions smaller than the similar to 6000-km resolution characteristic of the remote sensing. C1 CALTECH, Jet Prop Lab, Div Earth & Space Sci, Pasadena, CA 91125 USA. Reed Coll, Dept Phys, Portland, OR 97202 USA. Univ Arizona, Stewart Observ, Tucson, AZ 85721 USA. Univ Cambridge, Trinity Coll, Cambridge CB3 9EW, England. CALTECH, Dept Comp Sci, Pasadena, CA 91125 USA. Smithsonian Astrophys Observ, Cambridge, MA 02138 USA. Univ Belgrade, Sch Elect Engn, YU-11000 Belgrade, Yugoslavia. CSIC, Inst Astrofis Andalucia, E-18080 Granada, Spain. Exel Internet Serv, Madras 600014, Tamil Nadu, India. Univ Leicester, Dept Phys & Astron, Leicester LE1 7RH, Leics, England. RP Orton, GS (reprint author), CALTECH, Jet Prop Lab, Div Earth & Space Sci, Pasadena, CA 91125 USA. OI Hora, Joseph/0000-0002-5599-4650 NR 47 TC 53 Z9 53 U1 0 U2 4 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0148-0227 J9 J GEOPHYS RES-PLANET JI J. Geophys. Res.-Planets PD SEP 25 PY 1998 VL 103 IS E10 BP 22791 EP 22814 DI 10.1029/98JE02380 PG 24 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 168VC UT WOS:000078713000008 ER PT J AU Niemann, HB Atreya, SK Carignan, GR Donahue, TM Haberman, JA Harpold, DN Hartle, RE Hunten, DM Kasprzak, WT Mahaffy, PR Owen, TC Way, SH AF Niemann, HB Atreya, SK Carignan, GR Donahue, TM Haberman, JA Harpold, DN Hartle, RE Hunten, DM Kasprzak, WT Mahaffy, PR Owen, TC Way, SH TI The composition of the Jovian atmosphere as determined by the Galileo probe mass spectrometer SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS LA English DT Article ID TROPOSPHERIC GAS-COMPOSITION; NORTH EQUATORIAL BELT; JUPITER ATMOSPHERE; GIANT PLANETS; WATER ICE; MU-M; SOLAR; ABUNDANCES; HELIUM; MODELS AB The Galileo probe mass spectrometer determined the composition of the Jovian atmosphere for species with masses between 2 and 150 amu from 0.5 to 21.1 bars. This paper presents the results of analysis of some of the constituents detected: H-2, He, Ne, Ar, Kr, Xe, CH4, NH3, H2O, H2S, C-2 and C-3 nonmethane hydrocarbons, and possibly PH3 and Cl. He-4/H-2 in the Jovian atmosphere was measured to be 0.157 +/- 0.030. C-13/C-12 was found to be 0.0108 +/- 0.0005, and D/H and He-3/He-4 were measured. Ne was depleted, less than or equal to 0.13 times solar, Ar less than or equal to 1.7 solar, Kr less than or equal to 5 solar, and Xe less than or equal to 5 solar. CH4 has a constant mixing ratio of (2.1 +/- 0.4) x 10(-3) (C-12, 2.9 solar), where the mixing ratio is relative to H-2. Upper limits to the H2O mixing ratio rose from 8 x 10(-7) at pressures <3.8 bars to (5.6 +/- 2.5) x 10(-5) (O-16, 0.033 +/- 0.015 solar) at 11.7 bars and, provisionally, about an order of magnitude larger at 18.7 bars. The mixing ratio of H2S was <10(-6) at pressures less than 3.8 bars but rose from about 0.7 x 10(-5) at 8.7 bars to about 7.7 x 10(-5) (S-32, 2.5 solar) above 15 bars. Only very large upper limits to the NH3 mixing ratio have been set at present. If PH, and Cl were present, their mixing ratios also increased with pressure. Species were detected at mass peaks appropriate for C-2 and C-3 hydrocarbons. It is not yet clear which of these were atmospheric constituents and which were instrumentally generated. These measurements imply (1) fractionation of He-4, (2) a local, altitude-dependent depletion of condensables, probably because the probe entered the descending arm of a circulation cell, (3) that icy planetesimals made significant contributions to the volatile inventory, and (4) a moderate decrease in D/H but no detectable change in (D + He-3)/H in this part of the galaxy during the past 4.6 Gyr. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Michigan, Dept Atmospher Ocean & Space Sci, Ann Arbor, MI 48109 USA. Univ Arizona, Lunar & Planetary Lab, Tucson, AZ 85721 USA. Univ Hawaii, Inst Astron, Honolulu, HI 96822 USA. RP Niemann, HB (reprint author), NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. EM tmdonahue@umich.edu RI Mahaffy, Paul/E-4609-2012; Harpold, Dan/I-3345-2013 NR 49 TC 183 Z9 183 U1 3 U2 9 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0148-0227 J9 J GEOPHYS RES-PLANET JI J. Geophys. Res.-Planets PD SEP 25 PY 1998 VL 103 IS E10 BP 22831 EP 22845 DI 10.1029/98JE01050 PG 15 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 168VC UT WOS:000078713000010 PM 11543372 ER PT J AU Folkner, WM Woo, R Nandi, S AF Folkner, WM Woo, R Nandi, S TI Ammonia abundance in Jupiter's atmosphere derived from the attenuation of the Galileo probe's radio signal SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS LA English DT Article ID LABORATORY MEASUREMENTS; MILLIMETER; SOLAR; OPACITY; WINDS; NH3 AB The radio signal from the Galileo probe to the orbiter experienced attenuation due to ammonia in Jupiter's atmosphere during the probe descent. A profile of the ammonia content as a function of depth in the atmosphere has been derived from the measurements of the attenuation. The derived ammonia abundance rises to a molar fraction of 700 +/- 100 parts per million for pressures greater than 7 bars, about 4 times that expected based on the solar abundance of nitrogen. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Folkner, WM (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 27 TC 65 Z9 65 U1 2 U2 3 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0148-0227 J9 J GEOPHYS RES-PLANET JI J. Geophys. Res.-Planets PD SEP 25 PY 1998 VL 103 IS E10 BP 22847 EP 22855 DI 10.1029/98JE01635 PG 9 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 168VC UT WOS:000078713000011 ER PT J AU Seiff, A Kirk, DB Knight, TCD Young, RE Mihalov, JD Young, LA Milos, FS Schubert, G Blanchard, RC Atkinson, D AF Seiff, A Kirk, DB Knight, TCD Young, RE Mihalov, JD Young, LA Milos, FS Schubert, G Blanchard, RC Atkinson, D TI Thermal structure of Jupiter's atmosphere near the edge of a 5-mu m hot spot in the north equatorial belt SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS LA English DT Article ID GALILEO PROBE; JOVIAN ATMOSPHERE; GRAVITATIONAL TIDES; GIANT PLANETS; OUTER PLANETS; CONVECTION; PROFILES; WAVES; WINDS; ENTRY AB Thermal structure of the atmosphere of Jupiter was measured from 1029 km above to 133 km below the 1-bar level during entry and descent of the Galileo probe. The data confirm the hot exosphere observed by Voyager (similar to 900 K at 1 nanobar). The deep atmosphere, which reached 429 K at 22 bars, was close to dry adiabatic from 6 to 16 bars within an uncertainty similar to 0.1 K/km. The upper atmosphere was dominated by gravity waves from the tropopause to the exosphere. Shorter waves were fully absorbed below 300 km, while longer wave amplitudes first grew, then were damped at the higher altitudes. A remarkably deep isothermal layer was found in the stratosphere from 90 to 290 km with T similar to 160 K. Just above the tropopause at 260 mbar, there was a second isothermal region similar to 25 km deep with T similar to 112 K. Between 10 and 1000 mbar, the data substantially agree with Voyager radio occultations. The Voyager 1 equatorial occultation was similar in detail to the present sounding through the tropopause region. The Voyager IRIS average thermal structure in the north equatorial belt (NEB) approximates a smoothed fit to the present data between 0.03 and 400 mbar. Differences are partly a result of large differences in vertical resolution but may also reflect differences between a hot spot and the average NEB. At 15 < p < 22 bars, where it was necessary to extrapolate the pressure calibration to sensor temperatures up to 118 degrees C, the data indicate a stable layer in which stability increases with depth. Consistent with the indication of stability, regular fluctuations in probe vertical velocity imply gravity waves in this layer. At p > 4 bars, probe descent velocities derived from the data are consistently unsteady, suggesting the presence of large-scale turbulence or gravity waves. However, there was no evidence of turbulent temperature fluctuations >0.12 K. A conspicuous pause in the rate of decrease of descent velocity between 1.1 and 1.35 bars, where a disturbance was also detected by the two radio Doppler experiments, implies strong vertical flow in the cloud seen by the probe nephelometer. At p < 0.6 bar, measured temperatures were similar to 3 K warmer than the dry adiabat, possible evidence of radiative warming. This could be associated with a tenuous cloud detected by the probe nephelometer above the 0.51 bar level. For an ammonia cloud to form at this level, the required abundance is similar to 0.20 x solar. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. NASA, Langley Res Ctr, Hampton, VA 23681 USA. Univ Oregon, Dept Phys, Eugene, OR 97403 USA. Univ Calif Los Angeles, Dept Earth & Space Sci, Los Angeles, CA 90024 USA. Boston Univ, Ctr Space Phys, Boston, MA 02215 USA. San Jose State Univ Fdn, Dept Meteorol, San Jose, CA 95192 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Martin Marietta Aerosp Co, Denver, CO USA. RP Seiff, A (reprint author), NASA, Ames Res Ctr, MS 245-1, Moffett Field, CA 94035 USA. NR 76 TC 154 Z9 154 U1 0 U2 9 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0148-0227 J9 J GEOPHYS RES-PLANET JI J. Geophys. Res.-Planets PD SEP 25 PY 1998 VL 103 IS E10 BP 22857 EP 22889 DI 10.1029/98JE01766 PG 33 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 168VC UT WOS:000078713000012 ER PT J AU Ragent, B Colburn, DS Rages, KA Knight, TCD Avrin, P Orton, GS Yanamandra-Fisher, PA Grams, GW AF Ragent, B Colburn, DS Rages, KA Knight, TCD Avrin, P Orton, GS Yanamandra-Fisher, PA Grams, GW TI The clouds of Jupiter: Results of the Galileo Jupiter Mission Probe Nephelometer Experiment SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS LA English DT Article ID DISCRETE-DIPOLE APPROXIMATION; LABORATORY MEASUREMENTS; VERTICAL STRUCTURE; OPTICAL-PROPERTIES; IRIS OBSERVATIONS; LIGHT-SCATTERING; EQUATORIAL BELT; WATER-VAPOR; ATMOSPHERE; ABSORPTION AB The results of the nephelometer experiment conducted aboard the probe of the Galileo mission to Jupiter are presented. The tenuous clouds and sparse particulate matter in the relatively particle-free 5-mu m "hot spot" region of the probe's descent were documented from about 0.46 bar to about 12 bars. Three regions of apparent coherent structure were noted, in addition to many indications of extremely small particle concentrations along the descent path. From the first valid measurement at about 0.46 bar down to about 0.55 bar, a feeble decaying lower portion of a cloud, corresponding with the predicted ammonia particle cloud, was encountered. A denser, but still very modest, particle structure was present in the pressure regime extending from about 0.76 bar to a distinctive base at 1.34 bars and is compatible with the expected ammonium hydrosulfide cloud. No massive water cloud was encountered, although below the second structure, a small, vertically thin layer at about 1.65 bars may be detached from the cloud above, but may also be water condensation, compatible with reported measurements of water abundance from other Galileo Mission experiments. A third small signal region, extending from about 1.9 to 4.5 bars, exhibited quite weak but still distinctive structure and, although the identification of the light scatterers in this region is uncertain, may also be a water cloud, perhaps associated with lateral atmospheric motion and/or reduced to a small mass density by atmospheric subsidence or other causes. Rough descriptions of the particle size distributions and cloud properties in these regions have been derived, although they may be imprecise because of the small signals and experimental difficulties. These descriptions document the small number densities of particles, the moderate particle sizes, generally in the slightly submicron to few micron range, and the resulting small optical depths, mass densities due to particles, column particle number loading, and column mass loading in the atmosphere encountered by the Galileo probe during its descent. C1 San Jose State Univ Fdn, San Jose, CA 95192 USA. Space Phys Res Inst, Sunnyvale, CA 94087 USA. Aerosp Corp, Colorado Springs, CO 80912 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Clark Atlanta Univ, Res Ctr Sci & Technol, Atlanta, GA 30314 USA. RP San Jose State Univ Fdn, 1 Washington Sq, San Jose, CA 95192 USA. EM ragent@ssa1.arc.nasa.gov NR 62 TC 50 Z9 50 U1 2 U2 5 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-9097 EI 2169-9100 J9 J GEOPHYS RES-PLANET JI J. Geophys. Res.-Planets PD SEP 25 PY 1998 VL 103 IS E10 BP 22891 EP 22909 DI 10.1029/98JE00353 PG 19 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 168VC UT WOS:000078713000013 ER PT J AU Atkinson, DH Pollack, JB Seiff, A AF Atkinson, DH Pollack, JB Seiff, A TI The Galileo Probe Doppler Wind Experiment: Measurement of the deep zonal winds on Jupiter SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS LA English DT Article ID JOVIAN MAGNETOSPHERE; STABILITY-CRITERION; THERMAL STRUCTURE; RADIO TRACKING; OUTER PLANETS; INTERNAL HEAT; PARA-HYDROGEN; ATMOSPHERE; DYNAMICS; SATURN AB During its descent into the upper atmosphere of Jupiter, the Galileo probe transmitted data to the orbiter for 57.5 min. Accurate measurements of the probe radio frequency? driven by an ultrastable oscillator, allowed an accurate time history of the probe motions to be reconstructed. Removal from the probe radio frequency profile of known Doppler contributions, including the orbiter trajectory, the probe descent velocity, and the rotation of Jupiter, left a measurable frequency residual due to Jupiter's zonal winds, and microdynamical motion of the probe from spin, swing under the parachute, atmospheric turbulence, and aerodynamic buffeting. From the assumption of the dominance of the zonal horizontal winds, the frequency residuals were inverted and resulted in the first in situ measurements of the vertical profile of Jupiter's deep zonal winds. A number of error sources with the capability of corrupting the frequency measurements or the interpretation of the frequency residuals were considered using reasonable assumptions and calibrations from prelaunch and in-flight testing. It is found that beneath the cloud tops (about 700 mbar) the winds are prograde and rise rapidly to 170 m/s at 4 bars. Beyond 4 bars to the depth at which the link with the probe was lost, nearly 21 bars, the winds remain constant and strong. Corrections for the high temperatures encountered by the probe have recently been completed and provide no evidence of diminishing or strengthening of the zonal wind profile in the deeper regions explored by the Galileo probe. C1 Univ Idaho, Dept Elect Engn, Moscow, ID 83844 USA. San Jose State Univ, Dept Meteorol, San Jose, CA 95192 USA. NASA, Ames Res Ctr, Div Space Sci, Moffett Field, CA 94035 USA. RP Atkinson, DH (reprint author), Univ Idaho, Dept Elect Engn, Moscow, ID 83844 USA. NR 59 TC 75 Z9 75 U1 0 U2 4 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0148-0227 J9 J GEOPHYS RES-PLANET JI J. Geophys. Res.-Planets PD SEP 25 PY 1998 VL 103 IS E10 BP 22911 EP 22928 DI 10.1029/98JE00060 PG 18 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 168VC UT WOS:000078713000014 ER PT J AU Sromovsky, LA Collard, AD Fry, PM Orton, GS Lemmon, MT Tomasko, MG Freedman, RS AF Sromovsky, LA Collard, AD Fry, PM Orton, GS Lemmon, MT Tomasko, MG Freedman, RS TI Galileo probe measurements of thermal and solar radiation fluxes in the Jovian atmosphere SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS LA English DT Article ID LINE-SHAPE THEORY; TROPOSPHERIC GAS-COMPOSITION; WATER CONTINUUM ABSORPTION; COLLISION-BROADENED LINES; NORTH EQUATORIAL BELT; JUPITER ATMOSPHERE; MULTIPLE-SCATTERING; VERTICAL STRUCTURE; OPTICAL-PROPERTIES; NU(4) BAND AB The Galileo probe net flux radiometer (NFR) measured radiation fluxes in Jupiter's atmosphere from about 0.44 to 14 bars, using five spectral channels to separate solar and thermal components. Onboard calibration results confirm that the NFR responded to radiation approximately as expected. NFR channels also responded to a superimposed thermal perturbation, which can be approximately removed using blind channel measurements and physical constraints. Evidence for the expected NH3 cloud was seen in the spectral character of spin-induced modulations of the direct solar beam signals. These results are consistent with an overlying cloud of small NH3 ice particles (0.5-0.75 mu m in radius) of optical depth 1.5-2 at 0.5 mu m. Such a cloud would have so little effect on thermal fluxes that NFR thermal channels provide no additional constraints on its properties. However, evidence for heating near 0.45 bar in the NFR thermal channels would seem to require either an additional opacity source beyond this small-particle cloud, implying a heterogeneous cloud structure to avoid conflicts with solar modulation results, or a change in temperature lapse rate just above the probe measurements. The large thermal flux levels imply water vapor mixing ratios that are only 6% of solar at 10 bars, but possibly increasing with depth, and significantly subsaturated ammonia at pressures less than 3 bars. If deep NH3 mixing ratios at the probe entry site are 3-4 times ground-based inferences, as suggested by probe radio signal attenuation, then only half as much water is needed to match NFR observations. No evidence of a water cloud was seen near the 5-bar level. The 5-mu m thermal channel detected the presumed NH4SH cloud base near 1.35 bars. Effects of this cloud were also seen in the solar channel upflux measurements but not in the solar net fluxes, implying that the cloud is a conservative scatterer of sunlight. The minor thermal signature of this cloud is compatible with particle radii near 3 mu m, but it cannot rule out smaller particles. Deeper than about 3 bars, solar channels indicate unexpectedly large absorption of sunlight at wavelengths longer than 0.6 mu m, which might be due to unaccounted-for absorption by NH3 between 0.65 and 1.5 mu m. C1 Univ Wisconsin, Ctr Space Sci & Engn, Madison, WI 53706 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91103 USA. Univ Arizona, Lunar & Planetary Lab, Tucson, AZ 85721 USA. Space Phys Res Inst, Moffett Field, CA 94035 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Sromovsky, LA (reprint author), Univ Wisconsin, Ctr Space Sci & Engn, 1225 W Dayton St, Madison, WI 53706 USA. EM lsromovsky@ssec.wisc.edu RI Lemmon, Mark/E-9983-2010 OI Lemmon, Mark/0000-0002-4504-5136 NR 92 TC 47 Z9 47 U1 0 U2 4 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0148-0227 J9 J GEOPHYS RES-PLANET JI J. Geophys. Res.-Planets PD SEP 25 PY 1998 VL 103 IS E10 BP 22929 EP 22977 DI 10.1029/98JE01048 PG 49 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 168VC UT WOS:000078713000015 ER PT J AU Irwin, PGJ Weir, AL Smith, SE Taylor, FW Lambert, AL Calcutt, SB Cameron-Smith, PJ Carlson, RW Baines, K Orton, GS Drossart, P Encrenaz, T Roos-Serote, M AF Irwin, PGJ Weir, AL Smith, SE Taylor, FW Lambert, AL Calcutt, SB Cameron-Smith, PJ Carlson, RW Baines, K Orton, GS Drossart, P Encrenaz, T Roos-Serote, M TI Cloud structure and atmospheric composition of Jupiter retrieved from Galileo near-infrared mapping spectrometer real-time spectra SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS LA English DT Article ID TROPOSPHERIC GAS-COMPOSITION; NORTH EQUATORIAL BELT; ABSORPTION-SPECTRA; PLANETARY ATMOSPHERES; MULTIPLE-SCATTERING; RADIATIVE-TRANSFER; OPTICAL-CONSTANTS; BROADENED METHANE; PAIRS; TEMPERATURES AB The first four complete spectra recorded by the near infrared mapping spectrometer (NIMS) instrument on the Galileo spacecraft in 1996 have been analyzed. These spectra remain the only ones which have been obtained at maximum resolution over the entire NIMS wavelength range of 0.7 - 5.2 mu m. The spectra cover the edge of a "warm" spot at location 5 degrees N, 85 degrees W. We have analyzed the spectra first with reflecting layer models and then with full multiple scattering models using the method of correlated-k. We find that there is strong evidence for three different cloud layers composed of a haze consistent with 0.5-mu m radius tholins at 0.2 bar, a cloud of 0.75-mu m NH3 particles at about 0.7 bar, and a two-component NH4SH cloud at about 1.4 bars with both 50.0- and 0.45-mu m particles, the former being responsible for the main 5-mu m cloud opacity. The NH3 relative humidity above the cloud tops is found to decrease slightly as the 5-mu m brightness increases, with a mean value of approximately 14%. We also find that the mean volume mixing ratio of ammonia above the middle (NH4SH) cloud deck is (1.7+/-0.1) x 10(-4) and shows a similar, though less discernible decrease with increasing 5-mu m brightness. The deep volume mixing ratios of deuterated methane and phosphine are found to be constant and we estimate their mean values to be (4.9+/-0.2) x 10(-7) and (7.7+/-0.2) x 10(-7), resprstively. The fractional scale height of phosphine above the 1 bar level is found to be 27.1+/-1.4% and shows a slight decrease with increasing 5-mu m brightness. The relative humidity of water vapor is found to be approximately 7%, but while this and all the previous observations are consistent with the assumption that "hot spots" an regions of downwelling, desiccated air, we find that the water vapor relative humidity increases as the 5-mu m brightness increases. C1 Univ Oxford, Clarendon Lab, Oxford OX1 3PU, England. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Observ Paris, CNRS, URA 264, Dept Spatial, F-92195 Meudon, France. RP Univ Oxford, Clarendon Lab, Parks Rd, Oxford OX1 3PU, England. EM irwin@atm.ox.ac.uk RI Cameron-Smith, Philip/E-2468-2011; OI Cameron-Smith, Philip/0000-0002-8802-8627; Calcutt, Simon/0000-0002-0102-3170; Irwin, Patrick/0000-0002-6772-384X NR 49 TC 47 Z9 47 U1 0 U2 3 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-9097 EI 2169-9100 J9 J GEOPHYS RES-PLANET JI J. Geophys. Res.-Planets PD SEP 25 PY 1998 VL 103 IS E10 BP 23001 EP 23021 DI 10.1029/98JE00948 PG 21 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 168VC UT WOS:000078713000018 ER PT J AU Roos-Serote, M Drossart, P Encrenaz, T Lellouch, E Carlson, RW Baines, KH Kamp, L Mehlman, R Orton, GS Calcutt, S Irwin, P Taylor, F Weir, A AF Roos-Serote, M Drossart, P Encrenaz, T Lellouch, E Carlson, RW Baines, KH Kamp, L Mehlman, R Orton, GS Calcutt, S Irwin, P Taylor, F Weir, A TI Analysis of Jupiter North Equatorial Belt hot spots in the 4-5 mu m range from Galileo near-infrared mapping spectrometer observations: Measurements of cloud opacity, water, and ammonia SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS LA English DT Article ID TROPOSPHERIC GAS-COMPOSITION; VOYAGER IRIS DATA; ABSORPTION-SPECTRA; CARBON-MONOXIDE; JOVIAN SYSTEM; ATMOSPHERE; PROBE; ABUNDANCE; 5-MU-M; PLANETS AB This paper presents the analysis of hot spot observations in the Jovian North Equatorial Belt obtained with the near-infrared mapping spectrometer (NIMS) instrument on the Galileo spacecraft. The data were acquired during the closest approach sequences between June 1996 and April 1997. We focus on the spectral window between 4.5 and 5.2 mu m determining the cloud opacity above 2 bar, the water vapor relative humidity, and the ammonia abundance between 4 and 8 bar. We find a linear relationship between the cloud opacity and the continuum level of the spectrum. For a given radiance level of an individual spectrum, significant variations in the water vapor relative humidity are seen. However, no clear evidence for a relationship between the cloud opacity and the water relative humidity is seen. A cloud structure similar to that measured by the Galileo entry probe, with no significant cloud opacity below 2 bar, is adequate. The air in the hot spots is found to be overall dry, consistent with the probe measurements. None of the considered spectra show water vapor relative humidities exceeding 10%. Significant spatial variations of the water vapor relative humidity are found, and the distribution over the observed hot spot regions is complex. Because of a low sensitivity of the NIMS spectra to ammonia, uncertainties in the derived ammonia abundance are much higher than for water. There is, however, a possible trend in all the observed hot spots toward more ammonia inside than outside the hot spots at the sounded pressure levels. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ Oxford, Dept Atmospher Ocean & Planetary Phys, Oxford OX1 2JD, England. Observ Paris, CNRS, URA 264, Dept Rech Spatiale, F-92195 Meudon, France. RP Roos-Serote, M (reprint author), Astron Observ, Tapada Ajuda, P-1300 Lisbon, Portugal. OI Calcutt, Simon/0000-0002-0102-3170 NR 41 TC 39 Z9 39 U1 1 U2 2 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0148-0227 J9 J GEOPHYS RES-PLANET JI J. Geophys. Res.-Planets PD SEP 25 PY 1998 VL 103 IS E10 BP 23023 EP 23041 DI 10.1029/98JE01049 PG 19 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 168VC UT WOS:000078713000019 ER PT J AU Drossart, P Roos-Serote, M Encrenaz, T Lellouch, E Baines, KH Carlson, RW Kamp, LW Orton, GS Calcutt, S Irwin, P Taylor, FW Weir, A AF Drossart, P Roos-Serote, M Encrenaz, T Lellouch, E Baines, KH Carlson, RW Kamp, LW Orton, GS Calcutt, S Irwin, P Taylor, FW Weir, A TI The solar reflected component in Jupiter's 5-mu m spectra from NIMS/Galileo observations SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS LA English DT Article ID TROPOSPHERIC GAS-COMPOSITION; NORTH EQUATORIAL BELT; INFRARED OBSERVATIONS; CLOUD STRUCTURE; ATMOSPHERE; ABUNDANCES; CH3D; GEH4; PH3 AB A comparison between low-flux: dayside and nightside spectra of Jupiter recorded by the Galileo near-infrared mapping spectrometer (NIMS) experiment gives the first accurate estimate of the solar reflected component at 5 mu m, in the equatorial zone of Jupiter. A minimum flux level of about 0.6 mu W cm(-2) sr(-1)/mu m is found on the dayside, compared with 0.1 mu W cm(-2) sr(-1)/mu m On the nightside. These fluxes are 100-800 times lower respectively than the bright 5-mu m thermal emission in the north equatorial belt (NEB) hot spots. The day/night difference can be interpreted as a solar reflected component from a cloud, presumably the ammonia cloud, with an albedo of the order of 15%, located at a pressure level of 0.79 bar or at higher altitudes (corresponding to cloud temperature of 160 K or lower). Compared to the measurements in hot spots made at other wavelengths from ground-based observations and from NIMS real time spectra, they imply a high cloud opacity in cold regions at atmospheric levels where the cloud optical depth in the hot spots is very low. The residual flux on the nightside arises from (1) a very small cloud transparency giving some access to deeper thermal emission or (2) as high-resolution solid-state imaging (SSI) images of Galileo suggest, to cloud inhomogeneities, with clearer regions of medium brightness temperatures, mixed with dark regions of much lower thermal emission. If the former have the same brightness as a typical hot spot, a filling factor of a few percent is sufficient to explain the observed flux level on the nightside cold regions. C1 Observ Meudon, F-92195 Meudon, France. Jet Propuls Lab, Pasadena, CA 91103 USA. Univ Oxford, Dept Atmospher Ocean & Atmosph Phys, Oxford OX1 3PV, England. RP Drossart, P (reprint author), Observ Meudon, 5 Pl Janssen, F-92195 Meudon, France. OI Calcutt, Simon/0000-0002-0102-3170 NR 23 TC 8 Z9 8 U1 0 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0148-0227 J9 J GEOPHYS RES-PLANET JI J. Geophys. Res.-Planets PD SEP 25 PY 1998 VL 103 IS E10 BP 23043 EP 23049 DI 10.1029/98JE01899 PG 7 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 168VC UT WOS:000078713000020 ER PT J AU Ortiz, JL Orton, GS Friedson, AJ Stewart, ST Fisher, BM Spencer, JR AF Ortiz, JL Orton, GS Friedson, AJ Stewart, ST Fisher, BM Spencer, JR TI Evolution and persistence of 5-mu m hot spots at the Galileo probe entry latitude SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS LA English DT Article ID TROPOSPHERIC THERMAL EMISSION; COMET SHOEMAKER-LEVY-9; SPATIAL-ORGANIZATION; EQUATORIAL WAVES; PLANETARY-WAVES; TIME-DEPENDENCE; JUPITER; ATMOSPHERE; SHEAR; TEMPERATURES AB We present a study on the longitudinal locations, morphology, and evolution of the 5-mu m hot spots at 6.5 degrees N latitude (planetocentric) from an extensive Infrared Telescope Facility-National Science Foundation Camera (IRTF-NSFCAM) data set spanning more than 3 years, which includes the date of the Galileo probe entry. A probabilistic analysis of the data shows that within periods of several months to even more than a year, there are eight or nine longitudinal areas with high likelihood of containing a 5-mu m hot spot. These areas drift together with respect to System III at a rate which changes only slowly in time, and they are quasi evenly spaced, suggesting a wave feature. A spectral analysis of the radiance data reveals that planetary wavenumbers 8, 9, and 10 are predominant in the data, 10 having more spectral power in several time periods when the speed was 103.5-102.5 mis, while planetary wavenumber 8 has much more power when the speed is (99.5 +/- 0.5) m/s. By using the Galileo probe zonal wind speed [Atkinson et al., 1997] at the level of the main cloud that is opaque to the radiation at 5 mu m (similar to 2 bar), our drift corrections imply a westward phase speed for the proposed wave. The wavenumbers and phase speeds are found to be consistent with an equatorial Rossby wave, and the dispersive properties of this wave can account for the observed simultaneous changes in the dominant wavenumber and drift speed. We take advantage of this interpretation to infer properties of the vertical structure at 6.5 degrees N. C1 CSIC, Inst Astrofis Andaluca, E-18080 Granada, Spain. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Lowell Observ, Flagstaff, AZ 86001 USA. CALTECH, Div Geol & Planetary Sci, Pasadena, CA 91125 USA. RP Ortiz, JL (reprint author), CSIC, Inst Astrofis Andaluca, Apdo 3004, E-18080 Granada, Spain. NR 38 TC 48 Z9 48 U1 0 U2 2 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0148-0227 J9 J GEOPHYS RES-PLANET JI J. Geophys. Res.-Planets PD SEP 25 PY 1998 VL 103 IS E10 BP 23051 EP 23069 DI 10.1029/98JE00696 PG 19 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 168VC UT WOS:000078713000021 ER PT J AU Anderson, JD Schubert, G Jacobson, RA Lau, EL Moore, WB Sjogren, WL AF Anderson, JD Schubert, G Jacobson, RA Lau, EL Moore, WB Sjogren, WL TI Europa's differentiated internal structure: Inferences from four Galileo encounters SO SCIENCE LA English DT Article ID SATELLITES; MOMENTS; MODELS AB Radio Doppler data from four encounters of the Galileo spacecraft with the jovian moon Europa have been used to refine models of Europa's interior. Europa is most Likely differentiated into a metallic core surrounded by a rock mantle and a water ice-liquid outer shell, but the data cannot eliminate the possibility of a uniform mixture of dense silicate and metal beneath the water ice-liquid shell. The size of a metallic core is uncertain because of its unknown composition, but it could be as targe as about 50 percent of Europa's radius. The thickness of Europa's outer shell of water ice-liquid must lie in the range of about 80 to 170 kilometers. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ Calif Los Angeles, Inst Geophys & Planetary Phys, Los Angeles, CA 90095 USA. RP Anderson, JD (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 27 TC 209 Z9 214 U1 1 U2 40 PU AMER ASSOC ADVANCEMENT SCIENCE PI WASHINGTON PA 1200 NEW YORK AVE, NW, WASHINGTON, DC 20005 USA SN 0036-8075 J9 SCIENCE JI Science PD SEP 25 PY 1998 VL 281 IS 5385 BP 2019 EP 2022 DI 10.1126/science.281.5385.2019 PG 4 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA 124BV UT WOS:000076161800053 PM 9748159 ER PT J AU Choi, W Leu, MT AF Choi, W Leu, MT TI Nitric acid uptake and decomposition on black carbon (soot) surfaces: Its implications for the upper troposphere and lower stratosphere SO JOURNAL OF PHYSICAL CHEMISTRY A LA English DT Article ID HEXANE SOOT; HETEROGENEOUS REACTIONS; AMORPHOUS-CARBON; HNO3/NOX RATIO; ICE FILMS; PARTICLES; KINETICS; OZONE; NO2/N2O4; AEROSOLS AB The uptake and decomposition of HNO3 on black carbon (soot) surfaces were investigated in order to evaluate the proposal that HNO3 decomposition on aircraft-generated soot aerosols may alter the NOx/NOy partitioning in the upper troposphere and lower stratosphere. The experimental measurements were performed by using a fast flow-tube reactor coupled to a quadrupole mass spectrometer. Black carbon samples used as surrogate material for aircraft soot in this study included Degussa FW2 tan amorphous carbon black comprising medium oxides), graphite, hexane soot, and kerosene soot. The measurements of uptake were performed by varying P(HNO3) in the range of 5 x 10(-7) to 5 x 10(-4) Ton. at 220 and 295 K. The results are summarized as follows. Significant HNO3 decomposition was observed on FW2 at 295 K with P(HNO3) greater than or equal to 1 x 10(-4) Ton, while it did not occur at 220 K. Similar HNO3 decomposition behavior on graphite was also observed under the condition of P(HNO3) greater than or equal to 10(-4) Ton and T = 295 K, although the extent of the decomposition was much smaller than that on FW2. The decomposition of HNO3 on soot produced NO, NO2, H2O, oxidized soot surface, and some unidentified volatile products. To explain the observed decomposition behavior at higher partial pressures of HNO3, a bimolecular HNO3 decomposition mechanism on soot surfaces was proposed. However, HNO3 immediately decomposed on an FW2 surface at 503 K even at lower partial pressure (similar to 10(-6) Ton). On flame-deposited hexane and kerosene soot film, no HNO3 decomposition was observed up to P(HNO3) = 5 x 10-4 Ton. Moreover, the uptake and desorption of HNO3 were reversible at 295 K and irreversible at 230 K. Adsorbed HNO3 molecules on hexane soot film were saturated to a monolayer coverage at P(HNO3) similar to 2 x 10(-4) Torr according to Langmuir adsorption isotherm; further increase in P(HNO3) resulted in multilayer adsorption. Under the experimental conditions (P(HNO3) = 5 x 10(-7) Ton and T = 220 K), the uptake of HNO3 was found to involve purely physical adsorption without showing any sign of irreversible decomposition over all black carbon samples. Subsequent heating of the sample following the uptake at 220 K desorbed most of the adsorbed HNO3 molecules. Physical adsorption of HNO3 was found to take place on the surface of concentrated H2SO4-coated soot at 230 K, but decomposition of HNO3 took place at 296 K. Finally, the present results suggest that the HNO3 decomposition on soot aerosols through a direct gas-solid interaction, which was proposed as a possible NOy-reactivation mechanism in the atmospheric modeling of upper troposphere and lower stratosphere, should be dismissed. C1 CALTECH, Jet Prop Lab, Div Earth & Space Sci, Pasadena, CA 91109 USA. RP Leu, MT (reprint author), CALTECH, Jet Prop Lab, Div Earth & Space Sci, Pasadena, CA 91109 USA. RI Choi, Wonyong/F-8206-2010 OI Choi, Wonyong/0000-0003-1801-9386 NR 36 TC 51 Z9 52 U1 3 U2 19 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA SN 1089-5639 J9 J PHYS CHEM A JI J. Phys. Chem. A PD SEP 24 PY 1998 VL 102 IS 39 BP 7618 EP 7630 DI 10.1021/jp981647x PG 13 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA 127WR UT WOS:000076374000012 ER PT J AU Alpert, P Kaufman, YJ Shay-El, Y Tanre, D da Silva, A Schubert, S Joseph, JH AF Alpert, P Kaufman, YJ Shay-El, Y Tanre, D da Silva, A Schubert, S Joseph, JH TI Quantification of dust-forced heating of the lower troposphere SO NATURE LA English DT Article ID NORTH-ATLANTIC; SAHARAN DUST; AEROSOLS; CLIMATE; IMPACT; OCEANS AB Aerosols may affect climate through the absorption and scattering of solar radiation and, in the case of Large dust particles, by interacting with thermal radiation(1-3). But whether atmospheric temperature responds significantly to such forcing has not been determined; feedback mechanisms could increase or decrease the effects of the aerosol forcing. Here we present an indirect measure of the tropospheric temperature response by explaining the 'errors' in the NASA/Goddard model/data-assimilation system. These errors, which provide information about physical processes missing from the predictive model, have monthly mean patterns that bear a striking similarity to observed patterns of dust over the eastern tropical North Atlantic Ocean. This similarity, together with the high correlations between latitudinal location of inferred maximum atmospheric heating rates and that of the number of dusty days, suggests that dust aerosols are an important source of inaccuracies in numerical weather-prediction models in this region. For the average dust event, dust is estimated to heat the lower atmosphere (1.5-3.5 km altitude) by similar to 0.2 K per day. At about 30 dusty days per year, the presence of the dust leads to a regional heating rate of similar to 6 K per year. C1 Tel Aviv Univ, Dept Geophys & Planetary Sci, IL-69978 Tel Aviv, Israel. NASA, Climate & Radiat Branch, GSFC, Greenbelt, MD 20771 USA. Univ Sci & Tech Lille Flandres Artois, Opt Atmospher Lab, F-59655 Villeneuve Dascq, France. NASA, Data Assimilat Off, GSFC, Greenbelt, MD 20771 USA. RP Alpert, P (reprint author), Tel Aviv Univ, Dept Geophys & Planetary Sci, IL-69978 Tel Aviv, Israel. RI da Silva, Arlindo/D-6301-2012 OI da Silva, Arlindo/0000-0002-3381-4030 NR 24 TC 132 Z9 139 U1 2 U2 10 PU MACMILLAN MAGAZINES LTD PI LONDON PA PORTERS SOUTH, 4 CRINAN ST, LONDON, ENGLAND N1 9XW SN 0028-0836 J9 NATURE JI Nature PD SEP 24 PY 1998 VL 395 IS 6700 BP 367 EP 370 DI 10.1038/26456 PG 4 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA 122QW UT WOS:000076083800049 ER PT J AU Anderson, JD McDonald, EM Lee, PA Anderson, ML Ritchie, EL Hall, HK Hopkins, T Mash, EA Wang, J Padias, A Thayumanavan, S Barlow, S Marder, SR Jabbour, GE Shaheen, S Kippelen, B Peyghambarian, N Wightman, RM Armstrong, NR AF Anderson, JD McDonald, EM Lee, PA Anderson, ML Ritchie, EL Hall, HK Hopkins, T Mash, EA Wang, J Padias, A Thayumanavan, S Barlow, S Marder, SR Jabbour, GE Shaheen, S Kippelen, B Peyghambarian, N Wightman, RM Armstrong, NR TI Electrochemistry and electrogenerated chemiluminescence processes of the components of aluminum quinolate/triarylamine, and related organic light-emitting diodes SO JOURNAL OF THE AMERICAN CHEMICAL SOCIETY LA English DT Article ID HIGH-FREQUENCY GENERATION; P-N-JUNCTION; ELECTROLUMINESCENT DEVICES; IMPROVED STABILITY; IONIC-STRENGTH; POLYMER; ELECTROCHEMILUMINESCENCE; ELECTRON; CELLS; FILMS AB Solution electrochemical studies have been conducted of the principle lumophores, dopants, and hole-transport agents of aluminum-quinolate(Alq(3))-based organic light-emitting diodes (OLEDs) along with the characterization of their electrogenerated chemiluminescence (ECL). In acetonitrile/bcnzene solvent mixtures, Alq(3) shows single one-electron reduction and oxidation processes, with a separation between the first oxidation and first reduction potentials, Delta E-electrochemical = 3.03 V, close to the estimates of energy difference between HOMO and LUMO levels obtained from absorbance spectra of thin films of Alq(3), Delta E-optical = 3.17 eV. A new sulfonamide derivative of Alq(3), (Al(qs)(3)), showed a positive shift (ca. 0.32 V) in the first reduction potential versus the parent molecule, and resolution of the overall reduction process into three successive, chemically reversible, one-electron reductions. Two successive one-electron oxidations are seen for 4,4'-bis-(m-tolyphenylamino)biphenyl (TPD), a hole-transporting material in many bilayer OLEDs, and for TPDF2, a fluorinated version of TPD, with TPDF2 oxidation occurring 0.1 V positive of that for TPD. Electrogenerated chemiluminescence reactions (Alq(3)(-.)/TPD+. (or TPDF2+.) and Al(qs)(3)(-.)/TPD+. (or TPDF2+.)) were found to produce emission spectra from Alq(3)*(s) or Al(qs)(3)*(s) states which were nearly identical to those seen from OLEDs based upon these molecules. Emission intensities increased with the increasing potential difference between the relevant redox couples. The diisoamyl derivative of quinacridone (DIQA), a quinacridone dopant for certain Alq(3)-based OLEDs, undergoes two successive one-electron reductions and two successive one-electron oxidations. The ECL reactions DIQA(-.)/DIQA(+.), DIQA(+.)/Alq(3)(-.), DIQA(+.)/Al(qs)(3)(-.), DIQA(-.)/TPD+. and DIQA(-.)/TPDF2+. all produce the same singlet emissive state, DIQA*(s), and the same emission spectral response seen in quinacridone and DIQA-doped OLEDs. C1 Univ N Carolina, Dept Chem, Chapel Hill, NC 27514 USA. Univ Arizona, Dept Chem, Tucson, AZ 85721 USA. CALTECH, Beckman Inst, Jet Prop Lab, Pasadena, CA 91125 USA. Univ Arizona, Ctr Opt Sci, Tucson, AZ 85721 USA. RP Armstrong, NR (reprint author), Univ N Carolina, Dept Chem, CB 3290, Chapel Hill, NC 27514 USA. EM nra@u.arizona.edu RI Kippelen, Bernard/I-4058-2013; Shaheen, Sean/M-7893-2013; Barlow, Stephen/E-9754-2010 OI Kippelen, Bernard/0000-0002-8417-7051; NR 54 TC 179 Z9 181 U1 6 U2 39 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA SN 0002-7863 J9 J AM CHEM SOC JI J. Am. Chem. Soc. PD SEP 23 PY 1998 VL 120 IS 37 BP 9646 EP 9655 DI 10.1021/ja980707+ PG 10 WC Chemistry, Multidisciplinary SC Chemistry GA 123GJ UT WOS:000076117200030 ER PT J AU Bauschlicher, CW Partridge, H AF Bauschlicher, CW Partridge, H TI Do bond functions help for the calculation of accurate bond energies? SO JOURNAL OF CHEMICAL PHYSICS LA English DT Article ID GAUSSIAN-BASIS SETS; CORRELATED MOLECULAR CALCULATIONS; TOTAL ATOMIZATION ENERGIES; COUPLED-CLUSTER THEORY; DISSOCIATION-ENERGIES; ELECTRON CORRELATION; 1S CORRELATION; WAVE-FUNCTIONS; OMEGA(E); 1ST-ROW AB The bond energies of eight chemically bound diatomics are computed using several basis sets with and without bond functions (BF). The bond energies obtained using the aug-cc-pVnZ+BF basis sets (with a correction for basis set superposition error, BSSE) tend to be slightly smaller that the results obtained using the aug-cc-pV(n+1)Z basis sets, but slightly larger than the BSSE corrected aug-cc-pV(n+1)Z results. The aug-cc-pVDZ+BF and aug-cc-pVTZ+BF basis sets yield reasonable estimates of bond energies, but, in most cases, these results cannot be considered highly accurate. Extrapolation of the results obtained with basis sets including bond functions appears to be inferior to the results obtained by extrapolation using atom-centered basis sets. Therefore bond functions do not appear to offer a path for obtaining highly accurate results for chemically bound systems at a lower computational cost than atom centered basis sets. (C) 1998 American Institute of Physics. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Bauschlicher, CW (reprint author), NASA, Ames Res Ctr, STC-230-3, Moffett Field, CA 94035 USA. NR 30 TC 13 Z9 13 U1 0 U2 1 PU AMER INST PHYSICS PI WOODBURY PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 USA SN 0021-9606 J9 J CHEM PHYS JI J. Chem. Phys. PD SEP 22 PY 1998 VL 109 IS 12 BP 4707 EP 4712 DI 10.1063/1.477016 PG 6 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA 122CY UT WOS:000076054500002 ER PT J AU Dimandja, JMD Kaljurand, M Phillips, JB Valentin, J AF Dimandja, JMD Kaljurand, M Phillips, JB Valentin, J TI Maximum entropy chromatogram reconstruction SO ANALYTICA CHIMICA ACTA LA English DT Article DE maximum entropy deconvolution; data processing; signal to noise ratio AB Maximum entropy has been successfully applied to problems of optical images and NMR spectroscopy. In this paper, we present the results of maximum entropy deconvolution applied to simulated and real chromatographic data. A brief theoretical discussion is given. The technique is tested both qualitatively and quantitatively using simulated data. Peak resolution can be dramatically improved but quantitative accuracy is limited. The technique is applied to a re-analysis of Pioneer Venus chromatographic data and to storage column data. (C) 1998 Elsevier Science B.V. All rights reserved. C1 NASA, Ames Res Ctr, Exobiol Branch, Moffett Field, CA 94035 USA. RP Kaljurand, M (reprint author), Ctr Dis Control & Prevent, MS F17,4770 Buford Hwy, Atlanta, GA 30341 USA. NR 16 TC 4 Z9 4 U1 0 U2 0 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0003-2670 J9 ANAL CHIM ACTA JI Anal. Chim. Acta PD SEP 21 PY 1998 VL 371 IS 1 BP 1 EP 8 DI 10.1016/S0003-2670(98)00271-2 PG 8 WC Chemistry, Analytical SC Chemistry GA 118FH UT WOS:000075827400001 ER PT J AU Fischer, PF AF Fischer, PF TI Projection techniques for iterative solution of Ax=b with successive right-hand sides SO COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING LA English DT Article ID SOLVERS AB Projection techniques are developed for computing approximate solutions to linear systems of the form A (x) under bar(n) = (b) under bar(n), for a sequence n = 1,2,..., e.g. arising from time discretization of a partial differential equation. The approximate solutions are based upon previous solutions, and can be used as initial guesses for iterative solution of the system, resulting insignificantly reduced computational expense. Examples of two- and three-dimensional incompressible Navier-Stokes calculations are presented in which (x) under bar(n) represents the pressure at time level t(n), and A is a consistent discrete Poisson operator. In flows containing significant dynamic activity, these projection techniques lead to as much as a two-fold reduction in solution time. (C) 1998 Elsevier Science S.A. All rights reserved. C1 Brown Univ, Div Appl Math, Providence, RI 02912 USA. NASA, Langley Res Ctr, Inst Comp Applicat Sci & Engn, Hampton, VA 23665 USA. RP Fischer, PF (reprint author), Brown Univ, Div Appl Math, Providence, RI 02912 USA. NR 23 TC 29 Z9 29 U1 0 U2 0 PU ELSEVIER SCIENCE SA PI LAUSANNE PA PO BOX 564, 1001 LAUSANNE, SWITZERLAND SN 0045-7825 J9 COMPUT METHOD APPL M JI Comput. Meth. Appl. Mech. Eng. PD SEP 21 PY 1998 VL 163 IS 1-4 BP 193 EP 204 DI 10.1016/S0045-7825(98)00012-7 PG 12 WC Engineering, Multidisciplinary; Mathematics, Interdisciplinary Applications; Mechanics SC Engineering; Mathematics; Mechanics GA 134JR UT WOS:000076740200013 ER PT J AU Day, PK Moeur, WA McCready, SS Sergatskov, DA Liu, FC Duncan, RV AF Day, PK Moeur, WA McCready, SS Sergatskov, DA Liu, FC Duncan, RV TI Breakdown of Fourier's Law near the superfluid transition in He-4 SO PHYSICAL REVIEW LETTERS LA English DT Article ID THERMAL-CONDUCTIVITY; VAPOR-PRESSURE; HEAT CURRENT; FLOW; DEPRESSION; TRANSPORT; GRAVITY; HELIUM; BARS AB The behavior of the superfluid-normal fluid interface in He-4 has been studied in the presence of a heat flux, (Q) over right arrow, in the range 0.1 < Q < 6 erg s(-1) cm(-2). Fourier's Law, (Q) over right arrow = -kappa del T, has been observed, for the first time, to break down very close to the interface. In the nonlinear region, kappa depends on Q. Theoretical predictions, which do not take gravity into account, are compared with these experimental results. The predicted extent of the nonlinear region agrees well with the data; however, at lower Q, a systematic discrepancy is found that may be ascribed to the effect of gravity on the interface. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ New Mexico, Albuquerque, NM 87131 USA. RP Day, PK (reprint author), CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. NR 24 TC 24 Z9 24 U1 2 U2 5 PU AMERICAN PHYSICAL SOC PI COLLEGE PK PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA SN 0031-9007 J9 PHYS REV LETT JI Phys. Rev. Lett. PD SEP 21 PY 1998 VL 81 IS 12 BP 2474 EP 2477 DI 10.1103/PhysRevLett.81.2474 PG 4 WC Physics, Multidisciplinary SC Physics GA 122LM UT WOS:000076073100019 ER PT J AU Leon, R Lobo, C Zou, J Romeo, T Cockayne, DJH AF Leon, R Lobo, C Zou, J Romeo, T Cockayne, DJH TI Stable and metastable InGaAs/GaAs island shapes and surfactantlike suppression of the wetting transformation SO PHYSICAL REVIEW LETTERS LA English DT Article ID SELF-ORGANIZED GROWTH; CRITICAL THICKNESS; EPITAXIAL-GROWTH; GE; HETEROEPITAXY; MORPHOLOGY; INXGA1-XAS; GAAS(100); SI(100); SURFACE AB Contrasting behaviors are observed in InGaAs/GaAs island formation during vapor phase epitaxy: variation of group V partial pressures gives different critical thicknesses for the onset of the Stranski-Krastanow transformation, surface coverages, ratios between coherent and incoherent islands, and dissimilar morphologies upon annealing. The latter experiments show that small lens-shaped islands can be found in equilibrium if InGaAs surface energies are minimized, leading to the conclusion that AsH3 can raise surface energies and act as an impurity-free "morphactant." C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Australian Natl Univ, Res Sch Phys Sci & Engn, Canberra, ACT 0200, Australia. Univ Sydney, Australian Key Ctr Microscopy & Microanal, Sydney, NSW 2006, Australia. RP Leon, R (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. RI Zou, Jin/B-3183-2009; Lobo, Charlene/B-3977-2013; Lobo, Charlene/G-5003-2011 OI Zou, Jin/0000-0001-9435-8043; Lobo, Charlene/0000-0002-2746-1363; Lobo, Charlene/0000-0002-2746-1363 NR 21 TC 52 Z9 52 U1 0 U2 3 PU AMERICAN PHYSICAL SOC PI COLLEGE PK PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA SN 0031-9007 J9 PHYS REV LETT JI Phys. Rev. Lett. PD SEP 21 PY 1998 VL 81 IS 12 BP 2486 EP 2489 DI 10.1103/PhysRevLett.81.2486 PG 4 WC Physics, Multidisciplinary SC Physics GA 122LM UT WOS:000076073100022 ER PT J AU Orr, A Yaqoob, T Parmar, AN Piro, L White, NE Grandi, P AF Orr, A Yaqoob, T Parmar, AN Piro, L White, NE Grandi, P TI Quasi-simultaneous observations of 3C273 by BeppoSAX and ASCA SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE instrumentation : miscellaneous; quasars : individual : 3C273; quasars : absorption lines; X-rays : galaxies ID X-RAY-EMISSION; SPECTRUM; GALAXIES; 3C-273 AB We report the results of quasi-simultaneous observations of the bright quasar 3C 273 using the BeppoSAX Low-Energy Concentrator Spectrometer (LECS) and the ASCA Solid-State Imaging Spectrometer (SIS). These observations are part of an intercalibration programme and demonstrate good agreement between both instruments in the common energy range 0.5-10 keV. In particular, the absorption feature discovered by BeppoSAX/LECS at similar to 0.5 keV is consistently seen by ASCA/SIS. We present the most accurate measurement yet of the spectral shape of this absorption feature and provide constraints on its physical interpretation. A self-consistent warm absorber model in photoionization equilibrium only gives an adequate spectral fit if a very high velocity inflow is allowed for the warm absorber (v similar to 0.36 c). The ionization parameter and the column density of the warm absorber are then similar to 1 and similar to 1.3 x 10(21) cm(-2), respectively. If the differences in best-fit neutral absorption column density between the LEGS and each SIS are taken as estimates of the systematic spectral uncertainties, then these are <0.8 x 10(20) and <2.0 x 10(20) cm(-2) (at 90% confidence) for SIS0 and SIS1, respectively. C1 European Space Technol Ctr, European Space Agcy, Dept Space Sci, Div Astrophys, NL-2200 AG Noordwijk, Netherlands. NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. CNR, Ist Astrofis Spaziale, I-00133 Rome, Italy. CNR, Ist Astrofis Spaziale, I-00044 Frascati, Italy. RP Orr, A (reprint author), European Space Technol Ctr, European Space Agcy, Dept Space Sci, Div Astrophys, POB 299, NL-2200 AG Noordwijk, Netherlands. EM aorr@astro.estec.esa.nl RI White, Nicholas/B-6428-2012; PIRO, LUIGI/E-4954-2013 OI White, Nicholas/0000-0003-3853-3462; PIRO, LUIGI/0000-0003-4159-3984 NR 31 TC 19 Z9 19 U1 0 U2 0 PU EDP SCIENCES S A PI LES ULIS CEDEX A PA 17, AVE DU HOGGAR, PA COURTABOEUF, BP 112, F-91944 LES ULIS CEDEX A, FRANCE SN 0004-6361 J9 ASTRON ASTROPHYS JI Astron. Astrophys. PD SEP 20 PY 1998 VL 337 IS 3 BP 685 EP 690 PG 6 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 123KJ UT WOS:000076124100006 ER PT J AU Vangioni-Flam, E Ramaty, R Olive, KA Casse, M AF Vangioni-Flam, E Ramaty, R Olive, KA Casse, M TI Testing the primary origin of Be and B in the early galaxy SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE cosmic rays; Galaxy : abundances; Galaxy : evolution; nuclear reactions, nucleosynthesis, abundances ID GALACTIC COSMIC-RAYS; LIGHT-ELEMENTS; HALO STARS; PRIMORDIAL NUCLEOSYNTHESIS; SUPERNOVA-REMNANTS; NEUTRAL-BORON; BERYLLIUM; ABUNDANCES; EVOLUTION; LINES AB Beryllium and boron measurements in metal poor stars have had a major impact on our understanding of the origin of the light elements in the universe. Two types of models have been proposed to explain the linear rise of the Be and B abundances as a function of iron observed in metal poor halo stars. In both cases, this Linearity indicates that fleshly synthesized C and O are accelerated by Type II supernovae and subsequently fragmented into Be and B. One mechanism advocates shock acceleration in the gaseous phase of superbubbles excavated by collective SNII explosions. Because of their short lifetimes, only the most massive stars (with an initial mass greater than 60 M-.) do not drift out of superbubbles, and participate in BeB production. The second mechanism is based on the acceleration of the debris of grains formed in the ejecta of all SNIIs (originating from stars with initial mass greater than 8 M-.) Here again, fresh C and O are sped up to cosmic ray energies by shocks. We propose a possible test to discriminate between the two scenarios. If supernovae of all masses are involved in BeB production, the Be/Fe ratio is constant, since both elements are produced in the same events. Alternatively, when only the most massive stars are involved in Be production, Be/Fe is enhanced at very early times because of the shorter lifetimes of these stars. This predicted difference in the behavior of Be/Fe could be tested by high quality observations at [Fe/H] less than or similar to - 3. We also note that the solution invoking only the most massive supernovae mimics a flat evolution of both Be/H and B/H as a function of Fe/H at low metallicity, and could thus resemble a "plateau" for these elements despite a lack of a primordial Big Bang nucleosynthesis origin. Consequently, there may be no need to invoke inhomogeneous Big Bang models to explain the initial production of BeB should a plateau be discovered. C1 Inst Astrophys Paris, F-75014 Paris, France. NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. Univ Minnesota, Sch Phys & Astron, Minneapolis, MN 55455 USA. CEA, DAPNIA, DSM, Serv Astrophys, Paris, France. RP Vangioni-Flam, E (reprint author), Inst Astrophys Paris, 98 Bis Blvd Arago, F-75014 Paris, France. NR 56 TC 57 Z9 57 U1 0 U2 1 PU EDP SCIENCES S A PI LES ULIS CEDEX A PA 17, AVE DU HOGGAR, PA COURTABOEUF, BP 112, F-91944 LES ULIS CEDEX A, FRANCE SN 0004-6361 J9 ASTRON ASTROPHYS JI Astron. Astrophys. PD SEP 20 PY 1998 VL 337 IS 3 BP 714 EP 720 PG 7 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 123KJ UT WOS:000076124100010 ER PT J AU Jackson, PD Winkler, C Stacy, JG Bontekoe, TR AF Jackson, PD Winkler, C Stacy, JG Bontekoe, TR TI Simultaneous observations of Compton Gamma Ray Observatory-BATSE gamma-ray bursts with the COBE DMR SO ASTROPHYSICAL JOURNAL LA English DT Article DE cosmic microwave background; gamma rays : bursts; radiation mechanisms : nonthermal; radio continuum : general ID DIFFERENTIAL MICROWAVE RADIOMETERS; 28 FEBRUARY 1997; OPTICAL COUNTERPART; AFTERGLOW; DISTRIBUTIONS; CONSTRAINTS; EMISSION; SEARCH AB Data acquired with the COBE Differential Microwave Radiometer (DMR) provide a unique opportunity to observe simultaneous emission from cosmic gamma-ray bursts in the previously unexplored microwave region of the spectrum. We have searched the COBE DMR time-ordered data sets for instances when one of the DMR horns (FWHM similar to 7 degrees) was pointing in the direction of a gamma-ray burst at the time of burst occurrence. During the overlap period 1991 April-December corresponding to the first public release of COBE data, 210 Compton Gamma Ray Observatory (CGRO)/BATSE gamma-ray bursts listed in the Third BATSE (3B) Catalog were viewable by the COBE DMR. For five of these events the DMR was pointing within 7 degrees of the burst positions at the exact moment of burst occurrence. For another four events the DMR was pointed within 2 degrees of the BATSE positions within 10 s of the burst trigger time. No obvious microwave emission (at 31.5, 53, or 90 GHz), with upper limits in the 10-100 kJy range, can be associated with any of these events. The COBE DMR has a relatively low sensitivity for the detection of point sources within its field of view. A positive detection of a gamma-ray burst by the COBE DMR would imply that the integrated microwave flux must be of the same order as the energy observed in gamma rays. By extending an acceptance window in time of up to 20 minutes before and after a gamma-ray burst another 60 bursts are sampled by the DMR, whose signals are analyzed statistically. We conclude that the "average" gamma-ray burst produces less than about 7-42 kJy in simultaneous microwave radiation. C1 NASA, Goddard Space Flight Ctr, Raytheon STX Corp, Greenbelt, MD 20771 USA. European Space Agcy, Estec, Div Astrophys, NL-2200 AG Noordwijk, Netherlands. Louisiana State Univ, Dept Phys & Astron, Baton Rouge, LA 70803 USA. Bontekoe Data Consultancy, NL-2312 LC Leiden, Netherlands. Southern Univ, Dept Phys, Baton Rouge, LA 70813 USA. Univ Amsterdam, Astron Inst Anton Pannekoek, Amsterdam, Netherlands. RP Jackson, PD (reprint author), NASA, Goddard Space Flight Ctr, Raytheon STX Corp, Greenbelt, MD 20771 USA. NR 39 TC 2 Z9 2 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD SEP 20 PY 1998 VL 505 IS 1 BP 1 EP 7 DI 10.1086/306132 PN 1 PG 7 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 152LA UT WOS:000077777900001 ER PT J AU Ratra, B Ganga, K Sugiyama, N Tucker, GS Griffin, GS Nguyen, HT Peterson, JB AF Ratra, B Ganga, K Sugiyama, N Tucker, GS Griffin, GS Nguyen, HT Peterson, JB TI Using White Dish CMB anisotropy data to probe open and flat-Lambda CDM cosmogonies SO ASTROPHYSICAL JOURNAL LA English DT Article DE cosmic microwave background; cosmology : observations; large-scale structure of universe ID COLD-DARK-MATTER; MICROWAVE-BACKGROUND ANISOTROPY; LARGE-SCALE STRUCTURE; OPEN UNIVERSE; RADIATION; CONSTRAINTS; INFLATION AB We use data from the White Dish experiment to set limits on cosmic microwave background radiation anisotropies in open and spatially flat-Lambda cold dark matter cosmogonies. We account for the White Dish calibration uncertainty and marginalize over the offset and gradient removed from the data. Our 2 sigma upper limits on the amplitude of the cosmic microwave background radiation anisotropy are larger than those derived previously. These upper limits are consistent with those derived from the COBE Differential Microwave Radiometer data for all models tested. C1 Kansas State Univ, Dept Phys, Manhattan, KS 66506 USA. CALTECH, IPAC, Pasadena, CA 91125 USA. Kyoto Univ, Dept Phys, Sakyo Ku, Kyoto 6068502, Japan. Brown Univ, Dept Phys, Providence, RI 02912 USA. Carnegie Mellon Univ, Dept Phys, Pittsburgh, PA 15213 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Ratra, B (reprint author), Kansas State Univ, Dept Phys, Cardwell Hall, Manhattan, KS 66506 USA. RI Ratra, Bharat/I-4979-2012; Peterson, Jeffrey/O-4794-2014 OI Peterson, Jeffrey/0000-0003-1340-818X NR 36 TC 12 Z9 12 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD SEP 20 PY 1998 VL 505 IS 1 BP 8 EP 11 DI 10.1086/306139 PN 1 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 152LA UT WOS:000077777900002 ER PT J AU Valinia, A Marshall, FE AF Valinia, A Marshall, FE TI RXTE measurement of the diffuse X-ray emission from the galactic ridge: Implications for the energetics of the interstellar medium SO ASTROPHYSICAL JOURNAL LA English DT Article DE diffuse radiation; Galaxy : structure; supernova remnants; X-rays : ISM ID SUPERNOVA REMNANT; CASSIOPEIA-A; ENERGY; ACCELERATION; ELECTRONS; CATALOG; PLANE AB The diffuse X-ray emission from the thin disk surrounding the Galactic midplane (the so-called Galactic ridge) was measured with the Rossi X-Ray Timing Explorer proportional counter array in order to determine the spatial extent, spectral nature, and origin of the emission. Spatial examination of the diffuse emission in the central 30 degrees of the plane in Galactic longitude reveals the presence of two components: a thin disk of full width less than or similar to 0.degrees 5 centered roughly on the Galactic midplane and a broad component that can be approximated as a Gaussian distribution with FWHM of about 4 degrees. Assuming an average distance of 16 kpc to the edge of the Galaxy, a scale height of about 70 pc and 500 pc is derived for the thin and broad disk components, respectively. Spectral examination of the emission clearly reveals the presence of a hard power-law tail above 10 keV and an emission line from He-like iron, indicating both thermal and possibly nonthermal origins for the diffuse emission. The averaged spectrum from the ridge in the 3-35 keV band can be modeled with a Raymond-Smith plasma component of temperature similar to 2-3 keV and a power-law component of photon index similar to 1.8. Based on this finding, we argue that the temperature of the hot phase of the interstellar medium (ISM) is less than the previously reported values of 5-15 keV. Motivated by the similarities between the characteristics of the thermal component of the Galactic ridge emission in our model and the thermal emission from supernova remnants (SNRs), we discuss the origin of the thermal emission in terms of a population of SNRs residing in the Galactic disk. We find that a supernova explosion rate of less than 5 century(-1) is adequate to power the thermal emission from the ridge. The origin of the emission in the hard X-ray band modeled by a power law remains uncertain. Possible contributions from nonthermal bremsstrahlung of cosmic-ray electrons and protons; inverse Compton scattering of energetic electrons from ambient microwave, infrared and optical photons; nonthermal emission from SNRs; and emission from discrete X-ray sources are discussed. We speculate that bremsstrahlung of accelerated electrons and protons in SNR sites can play a significant role in producing the hard tail of the spectrum. Moreover, their collisional losses can play a major role in the ionization of the ISM. C1 NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. RP Valinia, A (reprint author), NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Code 662, Greenbelt, MD 20771 USA. NR 46 TC 158 Z9 158 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD SEP 20 PY 1998 VL 505 IS 1 BP 134 EP 147 DI 10.1086/306155 PN 1 PG 14 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 152LA UT WOS:000077777900012 ER PT J AU Turner, A Ferrarese, L Saha, A Bresolin, F Kennicutt, RC Stetson, PB Mould, JR Freedman, WL Gibson, BK Graham, JA Ford, H Han, MS Harding, P Hoessel, JG Huchra, JP Hughes, SMG Illingworth, GD Kelson, DD Macri, L Madore, BF Phelps, R Rawson, D Sakai, S Silbermann, NA AF Turner, A Ferrarese, L Saha, A Bresolin, F Kennicutt, RC Stetson, PB Mould, JR Freedman, WL Gibson, BK Graham, JA Ford, H Han, MS Harding, P Hoessel, JG Huchra, JP Hughes, SMG Illingworth, GD Kelson, DD Macri, L Madore, BF Phelps, R Rawson, D Sakai, S Silbermann, NA TI The Hubble Space Telescope Key Project on the Extragalactic Distance Scale. XI. The Cepheids in NGC 4414 SO ASTROPHYSICAL JOURNAL LA English DT Article DE Cepheids; galaxies : distances and redshifts; galaxies : individual (NGC 4414) ID IA SUPERNOVAE; PEAK BRIGHTNESS; STELLAR PHOTOMETRY; NEARBY GALAXIES; SPIRAL GALAXIES; VELOCITY-FIELD; LIGHT CURVES; CALIBRATION; DISCOVERY; CONSTANT AB We report the discovery of Cepheid variable stars in the galaxy NGC 4414, as part of the Hubble Space Telescope (HST) Key Project on the Extragalactic Distance Scale. Observations were obtained with the HST Wide-Field and Planetary Camera 2 (WFPC2) for 13 epochs at V (F555W) and 4 at I (F814W). Photometry was performed using two independent programs, DoPHOT and DAOPHOT/ALLFRAME. We find 11 Cepheids with high-quality light curves and well-determined periods of 19-70 days. Nine of these Cepheids are used in fitting the period-luminosity relation. Assuming an LMC distance modulus of 18.50 mag and E(B-V) = 0.10 mag, we derive a reddening-corrected distance modulus for NGC 4414 of 31.41 +/- 0.17 (random) +/- 0.16 (systematic) mag, corresponding to a distance of 19.1 +/- 1.5 (random) +/- 1.4 (systematic) Mpc. We derive a mean color excess for NGC 4414 of E(V-I) = 0.02 +/- 0.05 mag. NGC 4414 is a calibrator of the Tully-Fisher and Type Ia supernova secondary distance indicators, and we briefly discuss the implications of the new distance for these methods. C1 Univ Arizona, Steward Observ, Tucson, AZ 85721 USA. CALTECH, Pasadena, CA 91125 USA. Space Telescope Sci Inst, Baltimore, MD 21218 USA. Dominion Astrophys Observ, Victoria, BC V8X 4M6, Canada. Australian Natl Univ, Mt Stromlo & Siding Spring Observ, Inst Adv Studies, Weston, ACT 2611, Australia. Observ Carnegie Inst Washington, Pasadena, CA 91101 USA. Carnegie Inst Washington, Dept Terr Magnetism, Washington, DC 20015 USA. Johns Hopkins Univ, Baltimore, MD 21218 USA. Univ Wisconsin, Madison, WI 53706 USA. Harvard Smithsonian Ctr Astrophys, Cambridge, MA 02138 USA. Royal Greenwich Observ, Cambridge CB3 0EZ, England. Univ Calif Santa Cruz, Lick Observ, Santa Cruz, CA 95064 USA. CALTECH, Jet Prop Lab, Ctr Infrared Proc & Anal, Pasadena, CA 91125 USA. RP Turner, A (reprint author), Univ Arizona, Steward Observ, Tucson, AZ 85721 USA. RI Gibson, Brad/M-3592-2015 OI Gibson, Brad/0000-0003-4446-3130 NR 57 TC 47 Z9 47 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD SEP 20 PY 1998 VL 505 IS 1 BP 207 EP 229 DI 10.1086/306150 PN 1 PG 23 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 152LA UT WOS:000077777900017 ER PT J AU Cole, AA Gallagher, JS Mould, JR Clarke, JT Trauger, JT Watson, AM Ballester, GE Burrows, CJ Casertano, S Crisp, D Griffiths, RE Grillmair, CJ Hester, JJ Hoessel, JG Holtzman, JA Scowen, PA Stapelfeldt, KR Westphal, JR AF Cole, AA Gallagher, JS Mould, JR Clarke, JT Trauger, JT Watson, AM Ballester, GE Burrows, CJ Casertano, S Crisp, D Griffiths, RE Grillmair, CJ Hester, JJ Hoessel, JG Holtzman, JA Scowen, PA Stapelfeldt, KR Westphal, JR TI Far-ultraviolet and visible imaging of the nucleus of M32 SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies : individual (M32); galaxies : nuclei; galaxies : stellar content; ultraviolet : galaxies ID COLOR-MAGNITUDE DIAGRAM; HUBBLE-SPACE-TELESCOPE; EARLY-TYPE GALAXIES; STELLAR POPULATIONS; ELLIPTIC GALAXIES; WFPC2; PERFORMANCE; PHOTOMETRY; CALIBRATION; CLUSTERS AB We have imaged the nucleus of M32 at 1600 Angstrom (FUV) and 5500 Angstrom (V) using the Wide-Field/Planetary Camera 2 (WFPC2) aboard the Hubble Space Telescope. We detected the nucleus at 1600 Angstrom using the redleak-free Woods filter on WFPC2 The far-ultraviolet (FUV) light profile can be fitted with a Gaussian of FWHM 0." 46 (4.6 pixels) but cannot be resolved into individual stars; no UV-bright nuclear structure was detected. The (FUV - V) color of the nucleus is 4.9 +/- 0.3, which is consistent with earlier observations. We are unable to confirm any radial variation in (FUV - V) within 0." 8 of the nucleus; beyond that radius the FUV surface brightness drops below our detection threshold. We also performed surface photometry in V and found our results to be in excellent agreement with deconvolved WFPC1 results. M32's light profile continues to rise in a nuclear cusp even within 0." 1 of its center. No intermediate-age stellar population is required by evolutionary population synthesis models to reproduce the (FUV - V) color of the nucleus, although these data and current models are insufficient to resolve this issue. C1 Univ Wisconsin, Dept Astron, Madison, WI 53706 USA. Australian Natl Univ, Mt Stromlo & Siding Spring Observ, Inst Adv Studies, Weston, ACT 2611, Australia. Univ Michigan, Dept Atmospher & Ocean Sci, Ann Arbor, MI 48109 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. New Mexico State Univ, Dept Astron, Las Cruces, NM 88003 USA. Space Telescope Sci Inst, Baltimore, MD 21218 USA. Johns Hopkins Univ, Dept Astron, Baltimore, MD 21218 USA. Arizona State Univ, Dept Phys & Astron, Tempe, AZ 85287 USA. CALTECH, Div Geol & Planetary Sci, Pasadena, CA 91125 USA. RP Univ Wisconsin, Dept Astron, 475 N Charter St, Madison, WI 53706 USA. EM cole@ninkasi.astro.wisc.edu; jsg@tiger.astro.wisc.edu; jrm@mso.anu.edu.au RI Stapelfeldt, Karl/D-2721-2012; Clarke, John/C-8644-2013; OI Cole, Andrew/0000-0003-0303-3855 NR 36 TC 12 Z9 12 U1 0 U2 3 PU IOP PUBLISHING LTD PI BRISTOL PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND SN 0004-637X EI 1538-4357 J9 ASTROPHYS J JI Astrophys. J. PD SEP 20 PY 1998 VL 505 IS 1 BP 230 EP 235 DI 10.1086/306169 PN 1 PG 6 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 152LA UT WOS:000077777900018 ER PT J AU Stephens, SA Streitmatter, RE AF Stephens, SA Streitmatter, RE TI Cosmic-ray propagation in the Galaxy: Techniques and the mean matter traversal SO ASTROPHYSICAL JOURNAL LA English DT Article DE cosmic rays; diffusion; methods : numerical ID PATH-LENGTH DISTRIBUTION; ENERGY-SPECTRA; ISOTOPIC COMPOSITION; SOLAR MODULATION; CROSS-SECTIONS; NUCLEI; ANTIPROTONS; CHARGE; AGE AB After examining the techniques used for solving the equations describing the propagation of cosmic-ray nuclei in the Galaxy, we have introduced a technique that yields exact numerical solutions for the steady state equations. We have implemented this in a new code, which uses the Runge-Kutta numerical method and incorporates current knowledge of relevant physical parameters to carry out simultaneous integration of the steady state equations. Comparing results from the steady state solution with those obtained using the weighted-slab approximation, we find that the weighted slab underestimates the equilibrium flux at low energies for all nuclei and does so most severely for secondary nuclei. At high energies, the fluxes of secondary nuclei also differ from the steady state results, depending upon the value of the parameter U, the ratio of the of the daughter and parent nuclei (A/Z). R-asy, the high-energy asymptotic ratio of the secondary fluxes obtained from the weighted-slab and steady state solutions, is well parameterized by the useful relationship R-asy = U-0.53. Our results are in qualitative, but not quantitative, agreement with the seminal work of Ptuskin, Jones & Ormes. We have determined the path length traversed by cosmic rays by making use of the steady state technique and the observed B/C ratio for various compositions of interstellar gas. Our results agree well with those derived by Webber, but vary from those of Heinbach & Simon. C1 Tata Inst Fundamental Res, Bombay 400005, Maharashtra, India. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Stephens, SA (reprint author), Tata Inst Fundamental Res, Homi Bhabha Rd, Bombay 400005, Maharashtra, India. NR 42 TC 44 Z9 44 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD SEP 20 PY 1998 VL 505 IS 1 BP 266 EP 277 DI 10.1086/306142 PN 1 PG 12 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 152LA UT WOS:000077777900023 ER PT J AU Cannizzo, JK Mattei, JA AF Cannizzo, JK Mattei, JA TI A study of the outbursts in SS Cygni SO ASTROPHYSICAL JOURNAL LA English DT Article DE accretion, accretion disks; novae, cataclysmic variables; stars : individual (SS Cygni) ID LONG-TERM BEHAVIOR; X-RAY NOVAE; ACCRETION DISKS; DWARF NOVAE; COOLING FRONTS; LIGHT CURVES; INSTABILITY; DECAY AB We present a study of the characteristics of the rise and decay times in SS Cygni utilizing the daily means obtained by the American Association of Variable Star Observers. We concentrate on the most recent similar to 34 yr of data for which the most optimal daily means contain greater than or similar to 10 individual observations per daily mean. Our primary findings are the following: (1) the distribution of rise times shows a peak at [t(rise)] similar or equal to 0.5 days mag(-1) containing similar or equal to 82% of all outbursts. The points within this peak form a distribution with delta t(rise)/[t(rise)] similar or equal to 0.25. The rise-time value of similar to 0.5 days mag(-1) may be strongly influenced by the similar to 1 day spacing in the daily means, and therefore represents an upper limit; (2) slow rise outbursts (historically referred to as "anomalous") form a broad distribution with no dominant peak; (3) the decay times show a peak at [t(decay)] similar or equal to 2.5 days mag(-1) containing similar to 86% of all outbursts. The points within this peak form a distribution with delta t(decay)/[t(decay)] similar or equal to 0.11; and (4) binned, composite light curves of the decay show that the functional form of the decay is close to exponential during the first half of the decay. During the second half, however, one sees a similar to 1-2 day interval, during which the locally defined decay time increases, sometimes substantially. Following this increase, the decay time returns to its previous level for similar to 1 day before entering quiescence. The two main implications for accretion disk instability theory are that (a) most outbursts must be triggered far from the inner disk to account for the preponderance of fast rises, and (b) the cooling wave that traverses the disk during the decay must travel slower for similar to 1 day near the end of the outburst to account for the temporary increase in the decay time. We also attempt to place our findings for SS Cygni in a broader context by considering the Bailey relation t(decay) proportional to P-orbital observed for dwarf novae, and its possible relevance for other types of interacting binaries. C1 NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. Amer Assoc Variable Star Observers, Cambridge, MA 02138 USA. RP NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Code 662, Greenbelt, MD 20771 USA. EM cannizzo@lheavx.gsfc.nasa.gov; jmattei@aavso.org NR 39 TC 17 Z9 17 U1 0 U2 0 PU IOP PUBLISHING LTD PI BRISTOL PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND SN 0004-637X EI 1538-4357 J9 ASTROPHYS J JI Astrophys. J. PD SEP 20 PY 1998 VL 505 IS 1 BP 344 EP 351 DI 10.1086/306165 PN 1 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 152LA UT WOS:000077777900029 ER PT J AU Fletcher, L Martens, PCH AF Fletcher, L Martens, PCH TI A model for hard X-ray emission from the top of flaring loops SO ASTROPHYSICAL JOURNAL LA English DT Article DE Sun : corona; Sun : flares; Sun : X-rays, gamma rays ID SOLAR LIMB FLARE; 2-RIBBON FLARES; MAGNETIC RECONNECTION; HEIGHT DISTRIBUTION; IMPULSIVE PHASE; YOHKOH HARD; TARGET; BREMSSTRAHLUNG; TELESCOPE; PARTICLES AB The frequent occurrence of hard X-ray emission from the top of flaring loops was one of the discoveries by the Hard X-Ray Telescope on board the Japanese Yohkoh satellite. In this paper we take a hare current-sheet geometry and show how the combined effect of magnetic field convergence and pitch-angle scattering of nonthermal electrons injected at the top of the loop results in the generation of a looptop source with properties akin to those observed by Yohkoh. We demonstrate that a looptop source can be produced in both impulsive and gradual phase loops. We further present a possible mechanism for the generation of high-temperature "ridges" in the loop legs. C1 European Space Agcy, ESTEC, Dept Space Sci, Solar Syst Div, NL-2200 AG Noordwijk, Netherlands. NASA, Goddard Space Flight Ctr, ESA,Space Sci Dept, Solar Syst Div, Greenbelt, MD 20771 USA. RP Lockheed Martin Solar & Astrophys Lab, Org H1 12, Bldg 252,3251 Hanover St, Palo Alto, CA 94304 USA. NR 37 TC 57 Z9 58 U1 0 U2 2 PU IOP PUBLISHING LTD PI BRISTOL PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND SN 0004-637X EI 1538-4357 J9 ASTROPHYS J JI Astrophys. J. PD SEP 20 PY 1998 VL 505 IS 1 BP 418 EP 431 DI 10.1086/306137 PN 1 PG 14 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 152LA UT WOS:000077777900036 ER PT J AU Canuto, VM AF Canuto, VM TI Missing mixing? SO ASTROPHYSICAL JOURNAL LA English DT Article DE convection; hydrodynamics; stars : evolution; stars : interiors; stars : rotation ID LARGE-EDDY SIMULATION; ROTATION; MODELS; STARS; TURBULENCE; EVOLUTION; SHEAR; LAYER; SUN AB Shear-generated turbulent mixing in stellar radiative regions (stably stratified) has recently been found to be too weak. This has stimulated the search for the missing mixing. We suggest that there may not be a missing mixing problem. Phenomenological models have underestimated its real strength, thus leading to a negative assessment of its real potential. C1 NASA, Goddard Inst Space Studies, New York, NY 10025 USA. Columbia Univ, Dept Appl Phys, New York, NY 10027 USA. RP Canuto, VM (reprint author), NASA, Goddard Inst Space Studies, 2880 Broadway, New York, NY 10025 USA. NR 19 TC 6 Z9 6 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD SEP 20 PY 1998 VL 505 IS 1 BP L47 EP L50 DI 10.1086/311596 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 152LC UT WOS:000077778200012 ER PT J AU Chan, KW Roellig, TL Onaka, T Yamamura, I Tanabe, T AF Chan, KW Roellig, TL Onaka, T Yamamura, I Tanabe, T TI The nature of the mid-infrared background radiation in the galactic bulge from the infrared telescope in space observations SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxy : stellar content; infrared : stars; stars : AGB and post-AGB ID STELLAR CONTENT; NUCLEAR BULGE; AGB STARS; IRTS; MICRONS; WINDOW AB Using the Mid-Infrared Spectrometer on board the Infrared Telescope in Space, we obtained the 4.5-11.7 mu m spectra of the stellar populations and diffuse interstellar medium in the Galactic bulge (l = 8.degrees 7, b approximate to 2.degrees 9, 4.degrees 0, 4.degrees 7, and 5.degrees 7). Below Galactic latitudes of 4.degrees 0, the mid-infrared background spectra in the bulge are similar to the spectra of M and K giants. The unidentified infrared emission bands (6.2, 7.7, 8.6, and 11.3 mu m) are also detected in these regions and likely arise from the diffuse interstellar medium in the disk. Above Galactic latitudes of 4.degrees 0, the mid-infrared background spectra are similar to the spectra of those oxygen-rich evolved stars with high mass-loss rates detected by IRAS. One likely interpretation is that this background emission arises predominantly from those stars with very low luminosities that have not been detected by IRAS. The age for such low-luminosity evolved stars could be 15 Gyr, and the existence of a large number of evolved stars with high mass loss rates in the bulge has a significant impact on our understanding of the stellar content in the Galactic bulge. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Univ Tokyo, Dept Astron, Tokyo 1130033, Japan. Univ Tokyo, Inst Astron, Tokyo 1818588, Japan. RP Chan, KW (reprint author), NASA, Ames Res Ctr, MS 245-6, Moffett Field, CA 94035 USA. NR 27 TC 6 Z9 6 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD SEP 20 PY 1998 VL 505 IS 1 BP L31 EP L34 DI 10.1086/311592 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 152LC UT WOS:000077778200008 ER PT J AU Duvall, TL Kosovichev, AG Murawski, K AF Duvall, TL Kosovichev, AG Murawski, K TI Random damping and frequency reduction of the solar f-mode SO ASTROPHYSICAL JOURNAL LA English DT Article DE convection; Sun : interior; Sun : oscillations ID VELOCITY-FIELD CORRECTIONS; OSCILLATIONS; FLOW AB We present observations showing that the frequency of the high-degree f-mode is significantly lower than the frequency given by the simple dispersion relation, omega(2) = gk, and that the line width grows with the wavenumber k. We attempt to explain that this behavior is the result of the interaction with granulation, which we model as a random flow. Because the f-mode spends more time propagating against the how than with the flow, its effective speed and, consequently, frequency are reduced. Additionally, an eddy viscosity introduces the negative imaginary part of frequency. This negative imaginary part represents the damping of the coherent field due to scattering. The line width is proportional to the magnitude of the imaginary part of the frequency. We apply an analytical perturbation technique and numerical methods to estimate the line width and the frequency shift, and we show that the results are consistent with the properties of the f-mode obtained from the high-resolution Michelson Doppler Imager data from the Solar and Heliospheric Observatory. C1 NASA, Astron & Solar Phys Lab, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Stanford Univ, WW Hansen Expt Phys Lab, Stanford, CA 94305 USA. Tech Univ Lublin, PL-20618 Lublin, Poland. RP Duvall, TL (reprint author), NASA, Astron & Solar Phys Lab, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RI Duvall, Thomas/C-9998-2012 NR 13 TC 30 Z9 30 U1 0 U2 3 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD SEP 20 PY 1998 VL 505 IS 1 BP L55 EP L58 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 152LC UT WOS:000077778200014 ER PT J AU Koralesky, B Rudnick, L Gotthelf, EV Keohane, JW AF Koralesky, B Rudnick, L Gotthelf, EV Keohane, JW TI The x-ray expansion of the supernova remnant Cassiopeia A SO ASTROPHYSICAL JOURNAL LA English DT Article DE ISM : individual (Cassiopeia A); ISM : kinematics and dynamics; supernova remnants ID SYNCHROTRON EMISSION; NOVA REMNANT; VELOCITY; EJECTA; SHELL; MASS AB We present the first X-ray expansion measurements of the young, bright supernova remnant Cas A. We have acquired a deep (232 ks) ROSAT high-resolution image of Cas A that is compared with archival images of similar quality taken 17 yr earlier with the Einstein Observatory. The average expansion rate between the two epochs is found to be 0.20% +/- 0.01% yr(-1), twice as fast as the expansion of the bright radio ring and two-thirds as fast as the ensemble of optical fast-moving knots. This argues that we are observing a fundamentally different hydrodynamical structure in each band, although all of these components are located on the same patchy ring. In addition, we detect significant variations in the expansion rate as a function of azimuth around the bright X-ray ring. These results are discussed in the context of two classes of models, one involving a preexisting circumstellar shell and the other having a uniform or gradiated density profile that decreases monotonically away from the center. C1 Univ Minnesota, Dept Astron, Minneapolis, MN 55455 USA. NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. RP Koralesky, B (reprint author), Univ Minnesota, Dept Astron, 116 Church St SE, Minneapolis, MN 55455 USA. NR 29 TC 34 Z9 34 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD SEP 20 PY 1998 VL 505 IS 1 BP L27 EP L30 DI 10.1086/311604 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 152LC UT WOS:000077778200007 ER PT J AU Ohl, RG O'Connell, RW Bohlin, RC Collins, NR Dorman, B Fanelli, MN Neff, SG Roberts, MS Smith, AM Stecher, TP AF Ohl, RG O'Connell, RW Bohlin, RC Collins, NR Dorman, B Fanelli, MN Neff, SG Roberts, MS Smith, AM Stecher, TP TI Far-ultraviolet color gradients in early-type galaxies SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies : individual (M32, M49, M60, M87, M89, NGC 1399, NGC 3115, NGC 3379); galaxies : photometry; galaxies : stellar content; ultraviolet : galaxies ID ELLIPTIC GALAXIES; STELLAR POPULATIONS; IMAGING TELESCOPE; CENTRAL BULGE; M32; PHOTOMETRY; RESOLUTION; SPECTRUM; IMAGES; ORIGIN AB We discuss far-UV (FUV) (1500 Angstrom) surface photometry and FUV-B color profiles for eight E/S0 galaxies from images taken with the Ultraviolet Imaging Telescope, primarily during the Astro-2 mission. In three cases, the FUV radial profiles are more consistent with an exponential than a de Vaucouleurs function, but there is no other evidence for the presence of a disk or of young, massive stars. In all cases except M32, the FUV-B color becomes redder at larger radii. There is a wide range of internal radial FUV-B color gradients. However, we find no correlation between the FUV-B color gradients and internal metallicity gradients based-on Mg absorption features. We conclude that metallicity is not the sole parameter controlling the "UV upturn component" in old populations. C1 Univ Virginia, Dept Astron, Charlottesville, VA 22903 USA. Space Telescope Sci Inst, Baltimore, MD 21218 USA. NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, Greenbelt, MD 20771 USA. Natl Radio Astron Observ, Charlottesville, VA 22903 USA. Johns Hopkins Univ, Dept Phys & Astron, Baltimore, MD 21218 USA. RP Ohl, RG (reprint author), Univ Virginia, Dept Astron, POB 3818, Charlottesville, VA 22903 USA. NR 47 TC 35 Z9 35 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD SEP 20 PY 1998 VL 505 IS 1 BP L11 EP L14 DI 10.1086/311605 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 152LC UT WOS:000077778200003 ER PT J AU Judge, RA Forsythe, EL Pusey, ML AF Judge, RA Forsythe, EL Pusey, ML TI The effect of protein impurities on lysozyme crystal growth SO BIOTECHNOLOGY AND BIOENGINEERING LA English DT Article DE protein crystallization; impurities; lysozyme; purification; solubility ID EGG-WHITE LYSOZYME; CRYSTALLIZATION; PURIFICATION; RATES; SOLUBILITY; MODEL; NACL AB While bulk crystallization from impure solutions is used industrially as a purification step for a wide variety of materials, it is a technique that has rarely been used for proteins. Proteins have a reputation for being difficult to crystallize and high purity of the initial crystallization solution is considered paramount for success in the crystallization. Although little is written on the purifying capability of protein crystallization or of the effect of impurities on the various aspects of the crystallization process, recent published reports show that crystallization shows promise and feasibility as a purification technique for proteins. To further examine the issue of purity in macromolecule crystallization, this study investigates the effect of the protein impurities, avidin, ovalbumin, and conalbumin at concentrations up to 50%, on the solubility, crystal face growth rates, and crystal purity of the protein lysozyme. Solubility was measured in batch experiments while a computer controlled video microscope system was used to measure the {110} and {101} lysozyme crystal face growth rates. While little effect was observed on solubility and high crystal purity was obtained (>99.99%), the effect of the impurities on the face growth rates varied from no effect to a significant face specific effect leading to growth cessation, a phenomenon that is frequently observed in protein crystal growth. The results shed interesting light on the effect of protein impurities on protein crystal growth and strengthen the feasibility of using crystallization as a unit operation for protein purification. (C) 1998 John Wiley & Sons, Inc. C1 NASA, George C Marshall Space Flight Ctr, Biophys Branch ES76, Huntsville, AL 35812 USA. NASA, George C Marshall Space Flight Ctr, Alliance Micrograv Mat Sci & Applicat, Huntsville, AL 35812 USA. NASA, George C Marshall Space Flight Ctr, Univ Space Res Assoc, Huntsville, AL 35812 USA. RP NASA, George C Marshall Space Flight Ctr, Biophys Branch ES76, Huntsville, AL 35812 USA. EM marc.pusey@msfc.nasa.gov NR 31 TC 52 Z9 53 U1 1 U2 13 PU WILEY-BLACKWELL PI HOBOKEN PA 111 RIVER ST, HOBOKEN 07030-5774, NJ USA SN 0006-3592 EI 1097-0290 J9 BIOTECHNOL BIOENG JI Biotechnol. Bioeng. PD SEP 20 PY 1998 VL 59 IS 6 BP 776 EP 785 DI 10.1002/(SICI)1097-0290(19980920)59:6<776::AID-BIT14>3.0.CO;2-3 PG 10 WC Biotechnology & Applied Microbiology SC Biotechnology & Applied Microbiology GA 110TL UT WOS:000075396400014 PM 10099398 ER PT J AU Kimes, DS Nelson, RF AF Kimes, DS Nelson, RF TI Attributes of neural networks for extracting continuous vegetation variables from optical and radar measurements SO INTERNATIONAL JOURNAL OF REMOTE SENSING LA English DT Review ID CANOPY REFLECTANCE MODEL; BIDIRECTIONAL REFLECTANCE; BACKSCATTER MODEL; FOREST BIOMASS; INFORMATION CRITERION; SCATTERING MODEL; THEMATIC MAPPER; SAR DATA; INVERSION; INDEX AB Efficient algorithms that incorporate different types of spectral data and ancillary data are being developed to extract continuous vegetation variables. Inferring continuous variables implies that functional relationships must be found among the predicted variable(s), the remotely sensed data and the ancillary data. Neural networks have attributes which facilitate the extraction of vegetation variables. The advantages and power of neural networks for extracting continuous vegetation variables using optical and/or radar data and ancillary data are discussed and compared to traditional techniques. Studies that have made advances in this research area are reviewed and discussed. Neural networks can provide accurate initial models for extracting vegetation variables when an adequate amount of data is available. Networks provide a performance standard for evaluating existing physically based models. Many practical problems occur when inverting physically based models using traditional techniques and neural network techniques can provide a solution to these problems. Networks can be used as a tool to find a set of variables relevant to the desired variables to be inferred for measurement and modelling studies. Neural networks adapt to incorporate new data sources that would be difficult or impossible to use with conventional techniques. Neural networks employ a more powerful and adaptive nonlinear equation form as compared to traditional linear and simple nonlinear analyses. This power and flexibility is gained by repeating nonlinear activation functions in a network structure. This unique structure allows the neural network to learn complex functional relationships between the input and output data that cannot be envisioned by a researcher. C1 NASA, Goddard Space Flight Ctr, Extraterr Phys Lab, Biospher Sci Branch, Greenbelt, MD 20771 USA. Univ Texas, Dept Elect Engn, Arlington, TX 76019 USA. RP Kimes, DS (reprint author), NASA, Goddard Space Flight Ctr, Extraterr Phys Lab, Biospher Sci Branch, Code 923, Greenbelt, MD 20771 USA. RI Nelson, Ross/H-8266-2014 NR 115 TC 92 Z9 96 U1 0 U2 8 PU TAYLOR & FRANCIS LTD PI LONDON PA ONE GUNPOWDER SQUARE, LONDON EC4A 3DE, ENGLAND SN 0143-1161 J9 INT J REMOTE SENS JI Int. J. Remote Sens. PD SEP 20 PY 1998 VL 19 IS 14 BP 2639 EP 2663 DI 10.1080/014311698214433 PG 25 WC Remote Sensing; Imaging Science & Photographic Technology SC Remote Sensing; Imaging Science & Photographic Technology GA 121FZ UT WOS:000076003800003 ER PT J AU Shariff, K Moser, RD AF Shariff, K Moser, RD TI Two-dimensional mesh embedding for B-spline methods SO JOURNAL OF COMPUTATIONAL PHYSICS LA English DT Article ID FLOWS AB Many factors motivate consideration of B-splines as basis functions for solving partial differential equations. These are arbitrary orders of accuracy and high resolving powers similar to those of compact schemes. Furthermore, if one uses a Galerkin scheme one gets, in addition to conservation of the discretized quantities, conservation of quadratic invariants such as energy. This work develops another property, namely, the ability to treat semi-structured embedded or zonal meshes for two-dimensional geometries. This can drastically reduce the number of grid points in many applications. An algorithm is presented for constructing a global spline basis that automatically has d - 1 continuous derivatives at mesh-block boundaries as everywhere else (here d is the polynomial degree). The basis functions are simply suitable products of one-dimensional B-splines. Both integer and noninteger refinement ratios are allowed across mesh blocks. Finally, test cases for linear scalar equations such as the Poisson and advection equation are presented. (C) 1998 Academic Press. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Univ Illinois, Dept Theoret & Appl Mech, Urbana, IL 61801 USA. RP Shariff, K (reprint author), NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. OI Shariff, Karim/0000-0002-7256-2497 NR 12 TC 23 Z9 23 U1 0 U2 1 PU ACADEMIC PRESS INC PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA SN 0021-9991 J9 J COMPUT PHYS JI J. Comput. Phys. PD SEP 20 PY 1998 VL 145 IS 2 BP 471 EP 488 DI 10.1006/jcph.1998.6053 PG 18 WC Computer Science, Interdisciplinary Applications; Physics, Mathematical SC Computer Science; Physics GA 120KA UT WOS:000075954500001 ER PT J AU Shipham, MC Crill, PM Bartlett, KB Goldstein, AH Czepiel, PM Harriss, RC Blaha, D AF Shipham, MC Crill, PM Bartlett, KB Goldstein, AH Czepiel, PM Harriss, RC Blaha, D TI Methane measurements in central New England: An assessment of regional transport from surrounding sources SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID NONMETHANE HYDROCARBON; ATMOSPHERIC METHANE; FOREST; DEPOSITION; EMISSIONS; EXCHANGE; SULFATE; OZONE AB The Harvard Forest research site located in central New England is influenced by numerous anthropogenic methane sources on a year-round basis. Methane is strongly correlated to other chemical species that have an anthropogenic component, including acetylene, propane, ethane, hexane, and additional short-lived nonmethane hydrocarbons. The correlation between methane and acetylene is due to the colocation of landfills and cities. The correlation between methane and other short-lived species implies that emissions from local and regional rather than distant sources are the primary cause of elevated events. Wind roses of chemical species are examined for annual and seasonal time periods with enhancements in anthropogenic species corresponding to the location of large cities and landfills. The southwest quadrant is subjected to the most severe pollution events and is impacted by outflow from nearby cities in that sector, including Northampton and Springfield, Massachusetts. Emissions from cities in other quadrants, including Boston and Worcester, Massachusetts, Providence, Rhode Island, and the close-by town of Petersham, Massachusetts, also affect the site, but to a lesser degree. Case studies are used to identify atmospheric conditions that lead to high concentrations of methane and other species. The co-occurrence of a persistent wind direction, light wind speed, and stable atmospheric conditions is the ideal scenario in which emissions from nearby cities and landfills are advected to the site. Emissions from local and regional, rather than distant sources, are the primary cause of elevated events. C1 Univ New Hampshire, Inst Study Earth Oceans & Space, Complex Syst Res Ctr, Durham, NH 03824 USA. Harvard Univ, Dept Planetary Sci, Cambridge, MA 02138 USA. Univ Calif Berkeley, Environm Sci Policy & Management Dept, Berkeley, CA 94720 USA. NASA, Mission Planet Earth, Washington, DC USA. NASA, Langley Res Ctr, Div Atmospher Sci, Hampton, VA 23681 USA. RP Shipham, MC (reprint author), Fullmoon Consulting, LLC, POB 4278, Portsmouth, NH USA. EM m.c.shipham@larc.nasa.gov RI Goldstein, Allen/A-6857-2011; OI Goldstein, Allen/0000-0003-4014-4896; Crill, Patrick/0000-0003-1110-3059 NR 19 TC 12 Z9 12 U1 1 U2 4 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD SEP 20 PY 1998 VL 103 IS D17 BP 21985 EP 22000 DI 10.1029/98JD00967 PG 16 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 120WM UT WOS:000075980400006 ER PT J AU Weinheimer, AJ Montzka, DD Campos, TL Walega, JG Ridley, BA Donnelly, SG Keim, ER Del Negro, LA Proffitt, MH Margitan, JJ Boering, KA Andrews, AE Daube, BC Wofsy, SC Anderson, BE Collins, JE Sachse, GW Vay, SA Elkins, JW Wamsley, PR Atlas, EL Flocke, F Schauffler, S Webster, CR May, RD Loewenstein, M Podolske, JR Bui, TP Chan, KR Bowen, SW Schoeberl, MR Lait, LR Newman, PA AF Weinheimer, AJ Montzka, DD Campos, TL Walega, JG Ridley, BA Donnelly, SG Keim, ER Del Negro, LA Proffitt, MH Margitan, JJ Boering, KA Andrews, AE Daube, BC Wofsy, SC Anderson, BE Collins, JE Sachse, GW Vay, SA Elkins, JW Wamsley, PR Atlas, EL Flocke, F Schauffler, S Webster, CR May, RD Loewenstein, M Podolske, JR Bui, TP Chan, KR Bowen, SW Schoeberl, MR Lait, LR Newman, PA TI Comparison between DC-8 and ER-2 species measurements in the tropical middle troposphere: NO, NOy, O-3, CO2, CH4, and N2O SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID LOWER STRATOSPHERE; NITRIC-OXIDE; NITROGEN; AIRCRAFT; OZONE; DIOXIDE AB We compare measurements of six species taken aboard NASA DC-8 and ER-2 aircraft during two flight legs in the tropical middle troposphere near Hawaii. NO, NOy. O-3, CH4, and N2O measurements agree to within the limits set by the known systematic errors. For CO2, which can be measured with better relative precision than the other five species, differences in measured values from the two platforms are slightly larger than expected if the air masses sampled by the two aircraft were indeed similar in CO2 composition to better than 0.08%. C1 Natl Ctr Atmospher Res, Boulder, CO 80307 USA. Harvard Univ, Div Appl Sci, Cambridge, MA 02138 USA. Harvard Univ, Dept Earth & Planetary Sci, Cambridge, MA 02138 USA. NASA, Langley Res Ctr, Hampton, VA 23665 USA. NASA, Ames Res Ctr, Earth Syst Sci Div, Moffett Field, CA 94035 USA. Sci & Technol Corp, Hampton, VA 23665 USA. Natl Ocean & Atmospher Adm, Aeron Lab, Boulder, CO 80302 USA. NOAA, Climate Monitoring & Diagnost Lab, Boulder, CO 80302 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. NASA, Jet Prop Lab, Pasadena, CA 91109 USA. Univ Colorado, Cooperat Inst Res Environm Sci, Boulder, CO 80309 USA. Univ Colorado, Dept Biol & Chem, Boulder, CO 80309 USA. RP Weinheimer, AJ (reprint author), Natl Ctr Atmospher Res, Pob 3000, Boulder, CO 80307 USA. EM wein@ucar.edu RI Newman, Paul/D-6208-2012; Andrews, Arlyn/K-3427-2012; Atlas, Elliot/J-8171-2015 OI Newman, Paul/0000-0003-1139-2508; NR 16 TC 15 Z9 15 U1 1 U2 6 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD SEP 20 PY 1998 VL 103 IS D17 BP 22087 EP 22096 DI 10.1029/98JD01421 PG 10 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 120WM UT WOS:000075980400013 ER PT J AU Ziemke, JR Chandra, S Bhartia, PK AF Ziemke, JR Chandra, S Bhartia, PK TI Two new methods for deriving tropospheric column ozone from TOMS measurements: Assimilated UARS MLS/HALOE and convective-cloud differential techniques SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID MAPPING SPECTROMETER; STRATOSPHERIC OZONE; TRACE-A; TROPICS; SATELLITE; RADIANCES AB This study introduces two new approaches for determining tropospheric column ozone from satellite data. In the first method, stratospheric column ozone is derived by combining Upper Atmosphere Research Satellite (UARS) halogen occultation experiment (HALOE) and microwave Limb sounder (MLS) ozone measurements. Tropospheric column ozone is then obtained by subtracting these stratospheric amounts from the total column, Total column ozone in this study include retrievals from Nimbus 7 (November 1978 to May 1993) and Earth probe (July 1996 to present) total ozone mapping spectrometer (TOMS). Data from HALOE are used in this first method to extend the vertical span of MLS (highest pressure level 46 hPa) using simple regression, This assimilation enables high-resolution daily maps of tropospheric and stratospheric ozone which is not possible from solar occultation measurements alone, such as from HALOE or Stratospheric Aerosols and Gas Experiment (SAGE), We also examine another new and promising technique that yields tropospheric column ozone directly from TOMS high-density footprint measurements in regions of high convective clouds. We define this method as the convective cloud differential (CCD) technique. The CCD method is shown to provide long time series (essentially late 1978 to the present) of tropospheric ozone in regions dominated by persistent high tropopause-level clouds; such as the maritime tropical Pacific and within or near midlatitude continental landmasses, In this our first study of the CCD and MLS/HALOE methods we limit analyses to tropical latitudes, Separation of stratospheric from tropospheric column ozone in the eastern Pacific tropics for January 1979 to December 1997 shows that the dominant interannual variability of stratospheric ozone is the quasi-biennial oscillation (QBO), whereas for tropospheric ozone it is driven by El Nino events. For validation purposes, both the CCD and assimilated UARS MLS/HALOE results are compared with ozonesonde data from several southern tropical stations. Despite all three measurements being distinctly different in sampling and technique, all three show good qualitative agreement. C1 Software Corp Amer, Lanham, MD 20706 USA. NASA, Goddard Space Flight Ctr, Chem & Dynam Branch, Greenbelt, MD 20771 USA. RP Ziemke, JR (reprint author), Software Corp Amer, Lanham, MD 20706 USA. EM ziemke@jwocky.gsfc.nasa.gov; chandra@chapman.gsfc.nasa.gov; bhartia@carioca.gsfc.nasa.gov RI Bhartia, Pawan/A-4209-2016 OI Bhartia, Pawan/0000-0001-8307-9137 NR 25 TC 117 Z9 119 U1 2 U2 2 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD SEP 20 PY 1998 VL 103 IS D17 BP 22115 EP 22127 DI 10.1029/98JD01567 PG 13 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 120WM UT WOS:000075980400015 ER PT J AU Hudson, RD Thompson, AM AF Hudson, RD Thompson, AM TI Tropical tropospheric ozone from total ozone mapping spectrometer by a modified residual method SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID GAS EXPERIMENT DATA; TRACE-A; STRATOSPHERIC AEROSOL; BOUNDARY-LAYER; COLUMN OZONE; SATELLITE; PACIFIC; CHEMISTRY; REGION; SMOKE AB A modified residual method for deriving time-averaged tropical tropospheric ozone (TTO) from total ozone mapping spectrometer (TOMS) has been refined [cf Kim et al., 1996] and applied to a 2-year period, 1991-1992. This period was selected because of the availability of a unique sonde record at tropical Atlantic and near-Atlantic sites: Natal, Brazil; Ascension Island; and Brazzaville. The essentials of the modified-residual method are (1) Fourier analysis to identify the latitude range for use of the method; (2) use of the wave-like pattern to estimate stratospheric ozone column and a background tropospheric ozone column, which is defined as the amount of ozone expected in the absence of chemical pollution (3) assumption that the wave-one feature is tropospheric; and (4) the stratospheric and background tropospheric ozone amounts consistent with the constraint of the three station ozonesonde measurements for total tropospheric ozone. An excess ozone (pollution) signal is also derived from TOMS total ozone. Parameters derived from the modified residual method are evaluated with independent data to verify the quality of the TTO. Derived tropical stratospheric column ozone for 1991-1992 agrees very well with the corresponding UARS Microwave Limb Sounder and Stratospheric Aerosol and Gas Experiment records (to within 5 Dobson units (DU) for the tatter). Background tropospheric ozone, which exhibits a seasonality in 1991-1992, has a 24 +/- 4.8 DU mean value at wave maximum (similar to 0 degrees longitude) and a 15.2 +/- 6.0 DU mean value at 180 degrees longitude. The Atlantic value is remarkably similar to the climatological 26 DU previously inferred from subtropical sondes [Kim et al., 1996; Komhyr et al., 1989]. The similar to 5 DU standard deviation is the accuracy of the modified-residual method and is the best that can be achieved given the 15-day averaging of the sondes (1 sigma = 5.3 DU). The wave-like pattern in 1991-1992 has a semiannual periodicity with zero wave amplitude in June and December. C1 Univ Maryland, Dept Meteorol, College Pk, MD 20742 USA. NASA, Goddard Space Flight Ctr, Atmospheres Lab, Greenbelt, MD 20771 USA. RP Hudson, RD (reprint author), Univ Maryland, Dept Meteorol, College Pk, MD 20742 USA. EM hudson@atmos.umd.edu RI Hudson, Robert/F-4506-2010; Thompson, Anne /C-3649-2014 OI Thompson, Anne /0000-0002-7829-0920 NR 32 TC 74 Z9 74 U1 0 U2 3 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD SEP 20 PY 1998 VL 103 IS D17 BP 22129 EP 22145 DI 10.1029/98JD00729 PG 17 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 120WM UT WOS:000075980400016 ER PT J AU Parrish, A Connor, BJ Tsou, JJ Beyerle, G McDermid, IS Hollandsworth, SM AF Parrish, A Connor, BJ Tsou, JJ Beyerle, G McDermid, IS Hollandsworth, SM TI Microwave ozone and lidar aerosol profile observations at Table Mountain, California, following the Pinatubo eruption SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID STRATOSPHERIC OZONE; HETEROGENEOUS CHEMISTRY; SATELLITE; EUROPE; JAPAN AB Ozone profiles measured with a ground-based microwave instrument in years from 1989 through 1992 at latitude 34 degrees N. were searched for effects arising from the eruption of Mount Pinatubo in 1991. Between 20 and 24 km, ozone values after November 1991 were systematically less than in earlier years, and the deviation generally grew with time through May 1992, The minimum was 11 to 15% below values in earlier years, and occurred later than minima observed with ozonesondes at higher latitudes or predicted by some models. Although there was a steady increase in ozone levels in the 18-10 hPa range between February and May 1992, the highest values were not significantly above normal. Effects of the quasi-biennial oscillation on ozone values are much smaller than the observed changes. Colocated lidar observations show that stratospheric aerosol levels were steadily elevated from November 1991 through at least March 1992, with some intermittent activity in late August through October 1991. The main aerosol cloud thus arrived at the same time as depletion first appeared. C1 Univ Massachusetts, Amherst, MA 01003 USA. JPL Table Mt Facil, Wrightwood, CA 92397 USA. Natl Inst Water & Atmospher Res, Cent Omakau, New Zealand. NASA, Goddard Space Flight Ctr, SAC, Greenbelt, MD 20771 USA. GATS Inc, Hampton, VA 23666 USA. RP Parrish, A (reprint author), Univ Massachusetts, 6191 LGRT Tower B, Amherst, MA 01003 USA. EM parrish@fcrao1.phast.umass.edu NR 21 TC 3 Z9 3 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD SEP 20 PY 1998 VL 103 IS D17 BP 22201 EP 22208 DI 10.1029/98JD01806 PG 8 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 120WM UT WOS:000075980400020 ER PT J AU Hubler, G Alvarez, R Daum, P Dennis, R Gillani, N Kleinman, L Luke, W Meagher, J Rider, D Trainer, M Valente, R AF Hubler, G Alvarez, R Daum, P Dennis, R Gillani, N Kleinman, L Luke, W Meagher, J Rider, D Trainer, M Valente, R TI An overview of the airborne activities during the Southern Oxidants Study (SOS) 1995 Nashville Middle Tennessee Ozone Study SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article AB The cause and extent of elevated ozone levels which are often found during summer in the southeastern United States were the focus of the intensive Southern Oxidants Study (SOS) 1995 Nashville/Middle Tennessee Ozone Study. Six aircraft were extensively instrumented and were deployed in concert during the summer of 1995 from the Nashville Metropolitan Airport. This overview describes the capabilities of the deployed assets, and how their use was managed. Results from the measurements on individual aircraft and their interpretation are contained in the individual papers that follow. C1 NOAA, Aeron Lab, REAL7, Boulder, CO 80303 USA. NOAA, Environm Technol Lab, Boulder, CO 80303 USA. Brookhaven Natl Lab, Upton, NY 11973 USA. US EPA, NERL, Res Triangle Pk, NC 27711 USA. Tennessee Valley Author, Environm Res Ctr, Muscle Shoals, AL 35660 USA. NOAA, Air Resources Lab, Silver Spring, MD 20910 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Hubler, G (reprint author), NOAA, Aeron Lab, REAL7, 325 Broadway, Boulder, CO 80303 USA. EM ghubler@al.noaa.gov RI Hubler, Gerhard/E-9780-2010; Trainer, Michael/H-5168-2013; Alvarez, Raul/I-4879-2013; Luke, Winston/D-1594-2016 OI Luke, Winston/0000-0002-1993-2241 NR 2 TC 24 Z9 24 U1 0 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD SEP 20 PY 1998 VL 103 IS D17 BP 22245 EP 22259 DI 10.1029/98JD01638 PG 15 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 120WM UT WOS:000075980400024 ER PT J AU Fay, CC Clair, AKS AF Fay, CC Clair, AKS TI Dimensionally stable polyimide copolymers for microelectronics applications SO JOURNAL OF APPLIED POLYMER SCIENCE LA English DT Article DE polyimide copolymers; dimensionally stable; microelectronics applications ID LIFETIME; FILMS AB Polyimides are finding increased applications in microelectronics due to their high thermal stability, good chemical resistance, good adhesion, low moisture absorption, good mechanical properties, and low coefficient of thermal expansion (CTE). Four series of random copolyimides were synthesized and characterized for potential application as encapsulants, stress-relief layers, and interlevel dielectrics. Several candidates exhibited good combinations of physical and mechanical properties with inherent viscosities from 1.21 to 1.42 dL/g, T-g's ranging from 251 to 277 degrees C, 10% weight loss temperatures between 503 and 527 degrees C, and CTEs ranging from 33 to 39 ppm/degrees C. Mechanical properties at room temperature for the best candidates included tensile strengths of 17.8-21.3 ksi, moduli between 388 and 506 ksi, and elongations of 11-43%. Moisture absorption for these copolyimides ranged between 0.85 and 1.38 wt %. (C) 1998 John Wiley & Sons, Inc. C1 NASA, Langley Res Ctr, Div Mat, Hampton, VA 23681 USA. RP Fay, CC (reprint author), NASA, Langley Res Ctr, Div Mat, Hampton, VA 23681 USA. NR 21 TC 12 Z9 13 U1 0 U2 1 PU JOHN WILEY & SONS INC PI NEW YORK PA 605 THIRD AVE, NEW YORK, NY 10158-0012 USA SN 0021-8995 J9 J APPL POLYM SCI JI J. Appl. Polym. Sci. PD SEP 19 PY 1998 VL 69 IS 12 BP 2383 EP 2393 DI 10.1002/(SICI)1097-4628(19980919)69:12<2383::AID-APP10>3.0.CO;2-Z PG 11 WC Polymer Science SC Polymer Science GA 111CH UT WOS:000075419400010 ER PT J AU Collatz, CJ Kaufman, Y AF Collatz, CJ Kaufman, Y TI NRC on global change SO SCIENCE LA English DT Letter C1 NASA, Goddard Space Flight Ctr, Biospher Sci Branch, Greenbelt, MD 20771 USA. NASA, Goddard Space Flight Ctr, Climate & Radiat Branch, Greenbelt, MD 20771 USA. RP Collatz, CJ (reprint author), NASA, Goddard Space Flight Ctr, Biospher Sci Branch, Code 923, Greenbelt, MD 20771 USA. NR 2 TC 0 Z9 0 U1 0 U2 0 PU AMER ASSOC ADVANCEMENT SCIENCE PI WASHINGTON PA 1200 NEW YORK AVE, NW, WASHINGTON, DC 20005 USA SN 0036-8075 J9 SCIENCE JI Science PD SEP 18 PY 1998 VL 281 IS 5384 BP 1807 EP 1808 PG 2 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA 121HK UT WOS:000076007100028 ER PT J AU Hirabayashi, H Hirosawa, H Kobayashi, H Murata, Y Edwards, PG Fomalont, EB Fujisawa, K Ichikawa, T Kii, T Lovell, JEJ Moellenbrock, GA Okayasu, R Inoue, M Kawaguchi, N Kameno, S Shibata, KM Asaki, Y Bushimata, T Enome, S Horiuchi, S Miyaji, T Umemoto, T Migenes, V Wajima, K Nakajima, J Morimoto, M Ellis, J Meier, DL Murphy, DW Preston, RA Smith, JG Tingay, SJ Traub, DL Wietfeldt, RD Benson, JM Claussen, MJ Flatters, C Romney, JD Ulvestad, JS D'Addario, LR Langston, GI Minter, AH Carlson, BR Dewdney, PE Jauncey, DL Reynolds, JE Taylor, AR McCulloch, PM Cannon, WH Gurvits, LI Mioduszewski, AJ Schilizzi, RT Booth, RS AF Hirabayashi, H Hirosawa, H Kobayashi, H Murata, Y Edwards, PG Fomalont, EB Fujisawa, K Ichikawa, T Kii, T Lovell, JEJ Moellenbrock, GA Okayasu, R Inoue, M Kawaguchi, N Kameno, S Shibata, KM Asaki, Y Bushimata, T Enome, S Horiuchi, S Miyaji, T Umemoto, T Migenes, V Wajima, K Nakajima, J Morimoto, M Ellis, J Meier, DL Murphy, DW Preston, RA Smith, JG Tingay, SJ Traub, DL Wietfeldt, RD Benson, JM Claussen, MJ Flatters, C Romney, JD Ulvestad, JS D'Addario, LR Langston, GI Minter, AH Carlson, BR Dewdney, PE Jauncey, DL Reynolds, JE Taylor, AR McCulloch, PM Cannon, WH Gurvits, LI Mioduszewski, AJ Schilizzi, RT Booth, RS TI Overview and initial results of the very long baseline interferometry space observatory programme SO SCIENCE LA English DT Article ID EXTRAGALACTIC RADIO-SOURCES; VLBI SURVEY; GHZ; SATELLITE; EVOLUTION; REDSHIFTS; EMISSION; MOTION; SCALE; JETS AB High angular resolution images of extragalactic radio sources are being made with the Highly Advanced Laboratory for Communications and Astronomy (HALCA) satellite and ground-based radio telescopes as part of the Very Long Baseline Interferometry (VLBI) Space Observatory Programme (VSOP). VSOP observations at 1.6 and 5 gigahertz of the milli-arc-second-scale structure of radio quasars enable the quasar core size and the corresponding brightness temperature to be determined, and they enable the motions of jet components that are close to the core to be studied. Here, VSOP images of the gamma-ray source 1156 + 295, the quasar 1548 + 056, the ultraluminous quasar 0014 + 813, and the superluminal quasar 0212 + 735 are presented and discussed. C1 Inst Space & Astronaut Sci, Kanagawa 2298510, Japan. Natl Astron Observ, Tokyo 1818588, Japan. Univ Guanajuato, Guanajuato, Mexico. Commun Res Labs, Mito, Ibaraki 3108512, Japan. Kagoshima Univ, Kagoshima 8900064, Japan. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Natl Radio Astron Observ, Socorro, NM 87801 USA. Natl Radio Astron Observ, Green Bank, WV 24944 USA. Natl Res Council Canada, Herzberg Inst Astrophys, Dominion Radio Astrophys Observ, Penticton, BC V2A 6K3, Canada. Australia Telescope Natl Facil, Epping, NSW 2122, Australia. Univ Calgary, Calgary, AB T2N 1N4, Canada. Univ Tasmania, Hobart, Tas 7000, Australia. York Univ, Ctr Res Earth & Space Technol, Downsview, ON M3J 3K1, Canada. Joint Inst VLBI Europe, NL-7991 PD Dwingeloo, Netherlands. PN Lebedev Phys Inst, Ctr Astro Space, Moscow 117810, Russia. Chalmers, Onsala Space Observ, S-43662 Onsala, Sweden. RP Hirabayashi, H (reprint author), Inst Space & Astronaut Sci, Kanagawa 2298510, Japan. EM hirax@vsop.isas.ac.jp RI Tingay, Steven/B-5271-2013 NR 31 TC 149 Z9 154 U1 0 U2 11 PU AMER ASSOC ADVANCEMENT SCIENCE PI WASHINGTON PA 1200 NEW YORK AVE, NW, WASHINGTON, DC 20005 USA SN 0036-8075 J9 SCIENCE JI Science PD SEP 18 PY 1998 VL 281 IS 5384 BP 1825 EP 1829 DI 10.1126/science.281.5384.1825 PG 5 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA 121HK UT WOS:000076007100044 ER PT J AU Davis, L Young, MG Dougherty, D Keo, S Muller, R Maker, P AF Davis, L Young, MG Dougherty, D Keo, S Muller, R Maker, P TI Multiwavelength modelocked laser arrays for WDM applications SO ELECTRONICS LETTERS LA English DT Article ID PULSE AB Multiwavelength arrays of colliding pulse modelocked lasers have been demonstrated for wavelength division multiplexing applications. Arrays with up to nine wavelengths have been fabricated, operating at repetition rates of similar to 18GHz with pulsewidths < 10ps. C1 CALTECH, Jet Prop Lab, Ctr Space Microelect, Pasadena, CA 91109 USA. RP Davis, L (reprint author), CALTECH, Jet Prop Lab, Ctr Space Microelect, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 5 TC 3 Z9 3 U1 0 U2 3 PU IEE-INST ELEC ENG PI HERTFORD PA MICHAEL FARADAY HOUSE SIX HILLS WAY STEVENAGE, HERTFORD SG1 2AY, ENGLAND SN 0013-5194 J9 ELECTRON LETT JI Electron. Lett. PD SEP 17 PY 1998 VL 34 IS 19 BP 1858 EP 1860 DI 10.1049/el:19981292 PG 3 WC Engineering, Electrical & Electronic SC Engineering GA 126HH UT WOS:000076287500042 ER PT J AU Thomsen, MF Borovsky, JE McComas, DJ Collier, MR AF Thomsen, MF Borovsky, JE McComas, DJ Collier, MR TI Variability of the ring current source population SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID MAGNETIC-FIELD; PLASMA SHEET; STORM AB The relationship between the strength of the storm-time ring current and the available density in the presumed source region, the plasma sheet, is examined for 23 storms with Dst* (minimum Dst corrected for magnetopause currents) ranging from -50 to -164 nT. A good correlation is found between the plasma-sheet density at geosynchronous orbit and the minimum Dst*. The minimum Dst* is also well correlated with the eastward interplanetary electric field measured upstream by the Wind spacecraft, in agreement with previous studies, but the dependence of Dst* on plasma-sheet density is unrelated to its dependence on the electric field. The best correlation is between the minimum Dst* and the product of the plasma-sheet density and the eastward interplanetary electric field. These results are consistent with a scenario in which the intensity of the storm-time ring current is determined by a combination of source strength (plasma-sheet density) and injection strength (interplanetary electric field). C1 Univ Calif Los Alamos Natl Lab, Los Alamos, NM 87545 USA. NASA, Goddard Space Flight Ctr, Extraterr Phys Lab, Greenbelt, MD 20771 USA. RP Thomsen, MF (reprint author), Univ Calif Los Alamos Natl Lab, MS D466, Los Alamos, NM 87545 USA. RI Collier, Michael/I-4864-2013 OI Collier, Michael/0000-0001-9658-6605 NR 24 TC 54 Z9 55 U1 0 U2 3 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD SEP 15 PY 1998 VL 25 IS 18 BP 3481 EP 3484 DI 10.1029/98GL02633 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 119MK UT WOS:000075900100025 ER PT J AU Yu, LA Rienecker, MM AF Yu, LA Rienecker, MM TI Evidence of an extratropical atmospheric influence during the onset of the 1997-98 El Nino SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID SOUTHERN OSCILLATION; TROPICAL PACIFIC; MODEL; PERIOD; WINDS AB The major 1997-98 El Nino episode was initiated by a series of very energetic westerly wind bursts in late 1996 and early 1997. Downwelling oceanic Kelvin waves were subsequently generated and propagated rapidly eastward across the equatorial Pacific Ocean and induced significant warming in the eastern basin. By analyzing newly available wind products derived from SSM/I satellite observations, we found indications that these westerly wind bursts were embedded within the active phase of the tropical intraseasonal oscillation (the Madden-Julian Oscillation) but their amplitudes were greatly enhanced in the western Pacific sector. The local enhancement involved the development of equatorial twin cyclones which themselves were induced by northerly cold surges from East Asia/Western North Pacific into the tropical Pacific, demonstrating an extratropical atmospheric influence on tropical processes. C1 Univ Maryland, NASA, Joint Ctr Earth Syst Sci, Dept Meteorol, College Pk, MD 20742 USA. NASA, Goddard Space Flight Ctr, Lab Hydrospher Proc, Greenbelt, MD 20771 USA. RP Yu, LA (reprint author), Univ Maryland, NASA, Joint Ctr Earth Syst Sci, Dept Meteorol, College Pk, MD 20742 USA. NR 16 TC 61 Z9 67 U1 2 U2 6 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD SEP 15 PY 1998 VL 25 IS 18 BP 3537 EP 3540 DI 10.1029/98GL02628 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 119MK UT WOS:000075900100040 ER PT J AU Dyall, KG AF Dyall, KG TI Interfacing relativistic and nonrelativistic methods. II. Investigation of a low-order approximation SO JOURNAL OF CHEMICAL PHYSICS LA English DT Article ID GAUSSIAN-BASIS SETS; HARTREE-FOCK CALCULATIONS; PERTURBATION-THEORY; DIRAC-EQUATION AB The formalism presented in a previous paper for the introduction of relativistic effects into nonrelativistic calculations is used to develop an approximation which is correct to order alpha(2) and is similar to the Breit-Pauli approximation. Although it corresponds to a projection of the Dirac Hamiltonian onto the nonrelativistic (Levy-Leblond) states which in principle should guarantee a lower bound, the bound depends on the form of the potential. The physical eigenstates correspond to a local minimum in the exponential parameter space which vanishes at large Z. In an extended basis set an approximation to the hydrogenic ground state can always be identified, but the relativistic correction to the energy is grossly overestimated. In molecular calculations, the restriction of the variational space involving the high-exponent functions by general contraction did not yield improved numerical stability in a variational scheme. The use of a low-order approximation in a quasivariational method is therefore not expected to yield reliable results. (C) 1998 American Institute of Physics. C1 NASA, Ames Res Ctr, Thermosci Inst, Moffett Field, CA 94035 USA. RP Dyall, KG (reprint author), NASA, Ames Res Ctr, Thermosci Inst, Mail Stop 230-3, Moffett Field, CA 94035 USA. EM dyall@pegasus.arc.nasa.gov NR 23 TC 49 Z9 49 U1 0 U2 1 PU AMER INST PHYSICS PI MELVILLE PA CIRCULATION & FULFILLMENT DIV, 2 HUNTINGTON QUADRANGLE, STE 1 N O 1, MELVILLE, NY 11747-4501 USA SN 0021-9606 J9 J CHEM PHYS JI J. Chem. Phys. PD SEP 15 PY 1998 VL 109 IS 11 BP 4201 EP 4208 DI 10.1063/1.477026 PG 8 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA 118LF UT WOS:000075839100009 ER PT J AU Murtugudde, R Busalacchi, AJ Beauchamp, J AF Murtugudde, R Busalacchi, AJ Beauchamp, J TI Seasonal-to-interannual effects of the Indonesian throughflow on the tropical Indo-Pacific Basin SO JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS LA English DT Article ID NINO SOUTHERN OSCILLATION; SEA-SURFACE TEMPERATURE; INDIAN OCEANS THROUGHFLOW; GENERAL-CIRCULATION MODEL; MIXED-LAYER MODEL; WIND STRESS; THERMOHALINE CIRCULATION; SIMULATION; PRECIPITATION; THERMOCLINE AB The effects of the Indonesian throughflow (ITF) are studied in a reduced gravity, primitive equation, sigma coordinate model. The model domain includes the flow south of Australia. Unlike previous studies, this model includes a completely interactive upper ocean hydrology and the surface heat fluxes are provided by coupling the ocean general circulation model (GCM) to an advective atmospheric mixed layer model. It is shown that model simulation of the ITF on seasonal and interannual (1980-1995) timescales is in very good agreement with available estimates and other model studies. Effects of increased mixing in the Indonesian seas are also presented. There is an El Nino-Southern Oscillation (ENSO) related signal in the ITF, but the correlation with the Southern Oscillation Index (SOI) is only -0.31. When the winds over the Indian Ocean are held to climatology, this correlation jumps to -0.65 indicating that the non-ENSO signal in the ITF is caused by the downstream winds. On interannual timescales the ITF can be explained in terms of sea level differences between the western Pacific and eastern Indian Oceans when appropriate representative locations are chosen as demonstrated in both model and TOPEX data. It is shown that the main climatological effect of the ITF is to warm the Indian Ocean and to cool the Pacific. Spreading of the thermocline due to ITF in the Indian Ocean leads to reduced cooling of SST due to upwelling along the coasts of Java, western Australia, and Somalia. The seasonal cycle of sea surface temperature (SST) are shifted in the eastern equatorial Pacific and in the Leeuwin Current region and large-scale dynamic effects of the ITF are also seen. Over the period 1980-1995, the effect of the ITF has interannual variability. While the main ENSO indices, NINO3 and NINO4, are almost identical with and without the ITF, the total SSTs show significant ENSO dependence. SSTs in the central Indian Ocean linked previously to rainfall deficit in the western Australian winter may be dependent on the ENSO related variability of the ITF. C1 NASA, Goddard Space Flight Ctr, Lab Hydrospher Proc, Greenbelt, MD 20771 USA. Univ Maryland, Earth Syst Interdisciplinary Ctr, College Pk, MD 20742 USA. NASA, Goddard Space Flight Ctr, Hughes STX Lab Hydrospher Proc, Greenbelt, MD 20771 USA. RP Murtugudde, R (reprint author), NASA, Goddard Space Flight Ctr, Lab Hydrospher Proc, Code 970,Bldg 22, Greenbelt, MD 20771 USA. EM ragu@seetha.gsfc.nasa.gov NR 55 TC 84 Z9 90 U1 1 U2 6 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA J9 J GEOPHYS RES-OCEANS JI J. Geophys. Res.-Oceans PD SEP 15 PY 1998 VL 103 IS C10 BP 21425 EP 21441 DI 10.1029/98JC02063 PG 17 WC Oceanography SC Oceanography GA 118WG UT WOS:000075863500007 ER PT J AU Arrigo, KR Robinson, DH Worthen, DL Schieber, B Lizotte, MP AF Arrigo, KR Robinson, DH Worthen, DL Schieber, B Lizotte, MP TI Bio-optical properties of the southwestern Ross Sea SO JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS LA English DT Article ID PHYTOPLANKTON PRODUCTION; ABSORPTION-SPECTRA; SOUTHERN-OCEAN; PACIFIC-OCEAN; WATERS; MATTER; DISTRIBUTIONS; FLUORESCENCE; CHLOROPHYLL; ANTARCTICA AB The bio-optical properties of the southwestern Ross Sea were measured as part of the Antarctic research program Research on Atmospheric Variability and Atmospheric Response in the Ross Sea (ROAVERRS), The study area contained three distinct phytoplankton blooms, distinguishable by species composition, The largest in area was located to the north of the Ross Ice Shelf and was dominated by the prymnesiophyte Phaeocystis antarctica; chlorophyll a (Chl a) ranged from 0.45 to 8.2 mg m(-3). Beam attenuation and particle absorption at 435 nm were as high as 3.4 m(-1) and 0.35 m(-1), respectively. A bloom of diatoms was more spatially restricted, located to the north and west of the P. antarctica bloom, with Chl a generally below 4 mg m(-3). Neither diatoms nor P. antarctica exhibited evidence of the level of pigment packaging measured in waters near the Antarctic Peninsula during the Research on Antarctic Coastal Ecosystem Rates (RACER) program, possibly because of their smaller sizes. A much smaller cryptophyte bloom, located south of the Drygalski Ice Tongue, displayed a lower pigment-specific absorption spectra than did P. antarctica or diatoms, a sign of greater pigment packaging. Pigment-specific diffuse attenuation coefficients were consistent with the pigment-specific particle absorption coefficients (a (ph)*), both being similar to 3 times greater than similar measurements made during RACER. Spectral absorption by solutes determined through regression analysis of K(d) against Chl a for the ROAVERRS data set was nearly identical to that measured during RACER, Total diffuse attenuation spectra at a given station could be reconstructed by summing the inherent optical properties of the major optical components (pure water, soluble material, detritus, phytoplankton) measured there. Differences in the absorption ratio of a(ph)*(lambda) at 490 nm to a(ph)*(lambda) at 555 nm among the three dominant phytoplankton taxa in the southwestern Ross Sea were responsible for most of the variability in the ratio of remote sensing reflectance (R(rs)) at these same wavelengths. At a given concentration of Chl a, the ratio log [R(rs)(490):R(rs)(555)] was greatest in cryptophyte-dominated waters, which also possessed the lowest a(ph)*(490): a(ph)*(555) ratio, and lowest in P. antarctica-dominated waters. These bio-optical differences suggest that no simple empirical relationship between Chl a and log [R(rs)(490): R(rs)(555)] will apply to all three taxonomically distinct phytoplankton blooms in the southwestern Ross Sea. C1 NASA, Oceans & Ice Branch, Goddard Space Flight Ctr, Univ Space Res Assoc, Greenbelt, MD 20771 USA. Sci Syst & Applicat Inc, Lanham, MD 20706 USA. Gen Sci Corp, Laurel, MD 20707 USA. Univ Wisconsin, Dept Biol & Microbiol, Oshkosh, WI 54901 USA. RP Arrigo, KR (reprint author), NASA, Oceans & Ice Branch, Goddard Space Flight Ctr, Univ Space Res Assoc, Code 971-0, Greenbelt, MD 20771 USA. EM kevin@shark.gsfc.nasa.gov NR 30 TC 63 Z9 64 U1 0 U2 6 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0148-0227 J9 J GEOPHYS RES-OCEANS JI J. Geophys. Res.-Oceans PD SEP 15 PY 1998 VL 103 IS C10 BP 21683 EP 21695 DI 10.1029/98JC02157 PG 13 WC Oceanography SC Oceanography GA 118WG UT WOS:000075863500022 ER PT J AU Geiger, CA Hibler, WD Ackley, SF AF Geiger, CA Hibler, WD Ackley, SF TI Large-scale sea ice drift and deformation: Comparison between models and observations in the western Weddell Sea during 1992 SO JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS LA English DT Article ID PACK ICE AB Statistical comparisons between numerical sea ice models and an observed large-scale strain array in the western Weddell Sea during 1992 are used to evaluate the performance of three of the more generally utilized sea ice rheology formulations. Results show that sea ice velocity is reproduced with relatively high accuracy (90% coherence, >80% normalized cross correlation) in models having high-quality atmospheric forcing fields (e.g., the European Centre for Medium-Range Weather Forecasts). On the other hand, temporal and spatial variability of the velocity field, as exemplified by progressive vector plots and ice deformation, respectively, are reproduced less accurately (coherence and normalized cross correlation <50%). In terms of model sensitivity, this means that deformation and temporal variability are more discriminating in terms of elucidating specifics about the constitutive relation and mechanical properties of sea ice on a large scale. For example, inclusion of both compressive and shear stresses is important in attaining a proper probability distribution of deformation relative to observations. Additional analysis shows that adjustments to specific model parameters improve the model results for either drift or select deformation components, but no best solution could be found, given the models examined here. Results suggest that inclusion of more physically based processes, such as subdaily tidal and inertial oscillations; reconsideration of the boundary layer formulation, and consideration of anisotropy, may be necessary to include in next-generation sea ice models, especially those that are intended for coupling with high-resolution (eddy resolving) ocean models. C1 NASA, Univ Space Res Assoc, Oceans & Ice Branch, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Texas, Inst Geophys, Austin, TX USA. USA, Cold Reg Res & Engn Lab, Snow & Ice Branch, Hanover, NH 03755 USA. RP Geiger, CA (reprint author), NASA, Univ Space Res Assoc, Oceans & Ice Branch, Goddard Space Flight Ctr, Code 971, Greenbelt, MD 20771 USA. EM Cath-leen.A.Geiger.1@gsfc.nasa.gov; sackley@crrel.usace.army.mil NR 22 TC 35 Z9 36 U1 0 U2 5 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA J9 J GEOPHYS RES-OCEANS JI J. Geophys. Res.-Oceans PD SEP 15 PY 1998 VL 103 IS C10 BP 21893 EP 21913 DI 10.1029/98JC01258 PG 21 WC Oceanography SC Oceanography GA 118WG UT WOS:000075863500040 ER PT J AU Loeb, NG Varnai, T Winker, DM AF Loeb, NG Varnai, T Winker, DM TI Influence of subpixel-scale cloud-top structure on reflectances from overcast stratiform cloud layers SO JOURNAL OF THE ATMOSPHERIC SCIENCES LA English DT Article ID SOLAR RADIATIVE-TRANSFER; INDEPENDENT PIXEL; OPTICAL DEPTH; STRATOCUMULUS; SATELLITE; FLUXES; DEPENDENCE; FIELDS AB Recent observational studies have shown that satellite retrieval of cloud optical depth based on plane-parallel model theory suffer from systematic biases that depend on viewing geometry, even when observations are restricted to overcast marine stratus layers, arguably the closest to plane parallel in nature. At moderate to low sun elevations, the plane-parallel model significantly overestimates the reflectance dependence on view angle in the forward-scattering direction but shows a similar dependence in the backscattering direction. Theoretical simulations are performed that show that the likely cause for this discrepancy is because the plane-parallel model assumption does not account for subpixel-scale variations in cloud-top height (i.e., "cloud bumps"). Monte Carlo simulations comparing 1D model radiances to radiances from overcast cloud fields with 1) cloud-top height variations but constant cloud volume extinction, 2) flat tops but horizontal variations in cloud volume extinction, and 3) variations in both cloud-top height and cloud extinction are performed over a approximate to 4 km x 4 km domain (roughly the size of an individual GAC AVHRR pixel). The comparisons show that when cloud-top height variations are included, departures from 1D theory are remarkably similar (qualitatively) to those obtained observationally. In contrast, when clouds are assumed Ant and only cloud extinction is variable, reflectance differences are much smaller and do not show any view-angle dependence. When both cloud-top height and cloud extinction variations are included, however large increases in cloud extinction variability can enhance reflectance differences. The reason 3D-1D reflectance differences are more sensitive to cloud-top height variations in the forward-scattering direction (at moderate to low sun elevations) is because photons leaving the cloud field in that direction experience fewer scattering events ((low-order scattering) and are restricted to the topmost portions of the cloud. While reflectance deviations from 1D theory are much larger for bumpy clouds than for flat clouds with variable cloud extinction, differences in cloud albedo are comparable for these two cases. C1 NASA, Langley Res Ctr, Div Atmospher Sci, Hampton, VA 23681 USA. Oregon State Univ, Coll Ocean & Atmospher Sci, Corvallis, OR 97331 USA. Univ Arizona, Inst Atmospher Phys, Tucson, AZ 85721 USA. RP Loeb, NG (reprint author), NASA, Langley Res Ctr, Div Atmospher Sci, Mail Stop 420, Hampton, VA 23681 USA. NR 24 TC 47 Z9 48 U1 2 U2 7 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 USA SN 0022-4928 J9 J ATMOS SCI JI J. Atmos. Sci. PD SEP 15 PY 1998 VL 55 IS 18 BP 2960 EP 2973 DI 10.1175/1520-0469(1998)055<2960:IOSSCT>2.0.CO;2 PG 14 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 117TV UT WOS:000075799000006 ER PT J AU Klimeck, G Lake, R Blanks, DK AF Klimeck, G Lake, R Blanks, DK TI Role of interface roughness scattering in self-consistent resonant-tunneling-diode simulations SO PHYSICAL REVIEW B LA English DT Article ID INTRINSIC BISTABILITY; VALLEY CURRENT; DEVICES AB The effects of interface roughness scattering in a resonant-tunneling diode are examined with the self-consistent Born and the multiple sequential scattering algorithm for various interface roughness correlation lengths. The effect of a self-consistent treatment of the scattering self-energies with the quantum charge and the electrostatic and exchange-correlation potentials is demonstrated. The effects of the scattering assisted charge and the exchange and correlation potential on the spurious bistability obtained in simulations of a symmetric resonant-tunneling diode is shown. C1 Raytheon Syst, Dallas, TX 75243 USA. RP CALTECH, Jet Prop Lab, 4800 Oak Grove Dr,MS 168-522, Pasadena, CA 91109 USA. EM gekco@jpl.nasa.gov RI Klimeck, Gerhard/A-1414-2012 OI Klimeck, Gerhard/0000-0001-7128-773X NR 26 TC 26 Z9 26 U1 0 U2 0 PU AMER PHYSICAL SOC PI COLLEGE PK PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA SN 2469-9950 EI 2469-9969 J9 PHYS REV B JI Phys. Rev. B PD SEP 15 PY 1998 VL 58 IS 11 BP 7279 EP 7285 DI 10.1103/PhysRevB.58.7279 PG 7 WC Physics, Condensed Matter SC Physics GA 122EK UT WOS:000076058800083 ER PT J AU Plag, HP Ambrosius, B Baker, TF Beutler, G Bianco, G Blewitt, G Boucher, C Davis, JL Degnan, JJ Johansson, JM Kahle, HG Kumkova, I Marson, I Mueller, S Pavlis, EC Pearlman, MR Richter, B Spakman, W Tatevian, SK Tomasi, P Wilson, P Zerbini, S AF Plag, HP Ambrosius, B Baker, TF Beutler, G Bianco, G Blewitt, G Boucher, C Davis, JL Degnan, JJ Johansson, JM Kahle, HG Kumkova, I Marson, I Mueller, S Pavlis, EC Pearlman, MR Richter, B Spakman, W Tatevian, SK Tomasi, P Wilson, P Zerbini, S TI Scientific objectives of current and future WEGENER activities SO TECTONOPHYSICS LA English DT Review DE Space Geodesy; gravity; sea level; post-glacial rebound; African-Eurasian plate boundary; 3-D deformation of the Earth ID MEAN-SEA-LEVEL; GLACIAL ISOSTATIC-ADJUSTMENT; COMPUTING 3-DIMENSIONAL DEFORMATIONS; LINE INTERFEROMETRY MEASUREMENTS; VISCOELASTIC RELAXATION SPECTRA; SCALE CLIMATE VARIABILITY; GLOBAL POSITIONING SYSTEM; HORIZONTAL CRUSTAL MOTION; CURRENT PLATE MOTIONS; ATMOSPHERIC-PRESSURE AB The WEGENER group has promoted the development of scientific space-geodetic activities in the Mediterranean and in the European area for the last fifteen years and has contributed to the establishment of geodetic networks designed particularly for earth science research. WEGENER currently has three scientific objectives which are related to plate-boundary processes, sea-level and height changes, and postglacial rebound. Tn a full exploitation of the space-geodetic techniques, namely SLR, VLBI and GPS, the individual scientific projects do not only pursue these objectives but also contribute to improving and developing the observation techniques as well as the modelling theories. Tn the past, particularly SLR observations within WEGENER-MEDLAS have provided a fundamental contribution to determine the regional kinematics of the tectonic plates in the Mediterranean with high precision. With GPS, spatially denser site distributions are feasible, and in several WEGENER projects detailed studies of tectonically active areas were possible on the basis of repeated episodic GPS observations. Current projects associated with WEGENER are successful in separating crustal movements and absolute sea-level variations as well as in monitoring postglacial rebound. These tasks require high-precision height determinations, a problem central to all of the present WEGENER activities. In these projects, continuously occupied GPS sites are of increasing importance. Time series of heights observed with continuous GPS can be determined with a few centimeters RMS error thus enabling the reliable estimates of vertical rates over relatively shea time intervals. Regional networks of continuous GPS sites are already providing results relevant, for example, for the study of postglacial rebound. The Mediterranean area is an extraordinary natural laboratory for the study of seismotectonic processes, and the wealth of observations acquired in previous WEGENER projects together with new space-geodetic observations will allow the test of geophysical hypotheses linking three-dimensional deformations of the Earth's surface to the dynamics of the Earth's interior. In particular, it is anticipated that WEGENER projects will aim at a test of the slab-detachment hypothesis. The complex investigations on sea-level fluctuations presently carried out at basin scale from the Strait of Gibraltar to the Black Sea make it possible to study the present and recent past interactions of ocean, atmosphere and solid Earth, as well as to develop appropriate models to assess future aspects. (C) 1998 Elsevier Science B.V. All rights reserved. C1 Norwegian Mapping Author, Honefoss, Norway. Delft Univ Technol, Fac Aerosp Engn, Delft, Netherlands. Proudman Oceanog Lab, Bidston, Merseyside, England. Astron Inst Berne, Bern, Switzerland. Agenzia Spaziale Italiana, Matera, Italy. Univ Newcastle Upon Tyne, Dept Surveying, Newcastle Upon Tyne, Tyne & Wear, England. Inst Geog Natl, St Mande, France. Harvard Smithsonian Ctr Astrophys, Cambridge, MA 02138 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD USA. Chalmers Univ Technol, Onsala Space Observ, S-43900 Onsala, Sweden. ETH Honggerberg, Inst Geodasie & Photogrammetrie, Zurich, Switzerland. Russian Acad Sci, Inst Appl Astron, St Petersburg, Russia. Univ Trieste, DINMA, Trieste, Italy. Smithsonian Astrophys Observ, Cambridge, MA USA. Inst Angew Geodasie, Frankfurt, Germany. Univ Utrecht, Fac Earth Sci, Geodynam Res Inst, Utrecht, Netherlands. Russian Acad Sci, Astron Council, Space Geodesy Dept, Moscow, Russia. CNR, Ist Radioastron, Area Ric, Bologna, Italy. Geoforschungszentrum Potsdam, D-14473 Potsdam, Germany. Univ Bologna, Dept Phys, I-40126 Bologna, Italy. RP Plag, HP (reprint author), Norwegian Mapping Author, Honefoss, Norway. RI Boucher, Claude/A-2843-2011; Davis, James/D-8766-2013; OI Davis, James/0000-0003-3057-477X; Bianco, Giuseppe/0000-0002-4538-6467 NR 166 TC 6 Z9 6 U1 0 U2 1 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0040-1951 J9 TECTONOPHYSICS JI Tectonophysics PD SEP 15 PY 1998 VL 294 IS 3-4 BP 177 EP 223 DI 10.1016/S0040-1951(98)00100-0 PG 47 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 138GV UT WOS:000076964400003 ER PT J AU Kahle, HG Straub, C Reilinger, R McClusky, S King, R Hurst, K Veis, G Kastens, K Cross, P AF Kahle, HG Straub, C Reilinger, R McClusky, S King, R Hurst, K Veis, G Kastens, K Cross, P TI The strain rate field in the eastern Mediterranean region, estimated by repeated GPS measurements SO TECTONOPHYSICS LA English DT Article DE GPS; strain; crustal deformation; eastern Mediterranean ID ACTIVE CRUSTAL DEFORMATION; MARMARA SEA REGION; GLOBAL POSITIONING SYSTEM; CENTRAL GREECE; HELLENIC ARC; AEGEAN SEA; SURROUNDING AREA; PLATE COLLISION; MOMENT TENSORS; IONIAN-ISLANDS AB We use the combined GPS velocity field of the eastern Mediterranean for the period 1988 to 1996 to determine crustal deformation strain rates in a region comprising the Hellenic are, the Aegean Sea, and western Anatolia. We interpret the velocity field and determine the strain rate tensor by the spatial derivatives of the collocated motion vectors. The region following the line Marmara Sea, North Aegean Trough, northern central Greece, and the central Ionian islands is associated with strong right-lateral shear motion, with maximum shear strain rates of 180 nano-strain/a (180 x 10(-9)/a). In the central Aegean Sea, N-S-oriented extensional processes prevail, reaching 100 nano-strain/a. The southern Aegean is characterized by relatively small strain rates. Maximum extensional components of the strain rate tensor, reaching 150 nano-strain/a in a N-S direction, are found in central Greece. The Hellenic are is associated with moderate are-parallel extension and strong compression perpendicular to it. Projections of the strain rates parallel to the major fault zones reveal that the northern Aegean is governed by the westward continuation of the North Anatolian Fault Zone which is associated with strong dextral shearing (maximum 220 nano-strain/a), accompanied by numerous large earthquakes in this century. (C) 1998 Elsevier Science B.V. All rights reserved. C1 Swiss Fed Inst Technol, Inst Geodesy & Photogrammetry, Geodesy & Geodynam Lab, CH-8093 Zurich, Switzerland. MIT, Dept Earth Atmospher & Planetary Sci, Boston, MA USA. CALTECH, Jet Prop Lab, Pasadena, CA USA. NTU, Higher Geodesy Lab, Athens, Greece. Columbia Univ, Lamont Doherty Earth Observ, New York, NY USA. UCL, Dept Geomat Engn, London WC1E 6BT, England. RP Kahle, HG (reprint author), Swiss Fed Inst Technol, Inst Geodesy & Photogrammetry, Geodesy & Geodynam Lab, CH-8093 Zurich, Switzerland. EM kahle@geod.ethz.ch OI McClusky, Simon/0000-0003-4040-925X NR 79 TC 101 Z9 101 U1 1 U2 2 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0040-1951 J9 TECTONOPHYSICS JI Tectonophysics PD SEP 15 PY 1998 VL 294 IS 3-4 BP 237 EP 252 DI 10.1016/S0040-1951(98)00102-4 PG 16 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 138GV UT WOS:000076964400005 ER PT J AU Dai, HJ Franklin, N Han, J AF Dai, HJ Franklin, N Han, J TI Exploiting the properties of carbon nanotubes for nanolithography SO APPLIED PHYSICS LETTERS LA English DT Article ID ATOMIC-FORCE MICROSCOPE; SCANNING-TUNNELING-MICROSCOPY; FABRICATION; SILICON; OXIDATION; SURFACES; FIELD AB Carbon nanotube tips are explored in fabricating oxide nanostructures on silicon surfaces with an atomic force microscope, Nanotubes can write nanostructures at speeds up to 0.5 mm/s over large surface areas, and present a solution to the long-standing tip-wear problem. Experimental and theoretical work find that nanotube tips are impervious to high compressive and lateral forces and breakdown in high electric fields, A "cleaving" method is developed to reproducibly obtain dome-closed multi-walled nanotube tips with suitable length. Nanotube materials could become key elements for future miniaturization applications, (C) 1998 American Institute of Physics. C1 Stanford Univ, Dept Chem, Stanford, CA 94305 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Dai, HJ (reprint author), Stanford Univ, Dept Chem, Stanford, CA 94305 USA. EM hdai@chem.stanford.edu NR 20 TC 194 Z9 198 U1 3 U2 44 PU AMER INST PHYSICS PI WOODBURY PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 USA SN 0003-6951 J9 APPL PHYS LETT JI Appl. Phys. Lett. PD SEP 14 PY 1998 VL 73 IS 11 BP 1508 EP 1510 DI 10.1063/1.122188 PG 3 WC Physics, Applied SC Physics GA 118VK UT WOS:000075861100018 ER PT J AU Garg, A Han, J Sinnott, SB AF Garg, A Han, J Sinnott, SB TI Interactions of carbon-nanotubule proximal probe tips with diamond and graphene SO PHYSICAL REVIEW LETTERS LA English DT Article ID ELASTIC PROPERTIES; MICROSCOPE; TUBULES; FILMS AB Interactions between proximal probe tips composed of carbon nanotubules (CNTs) and diamond and graphene surfaces are investigated using molecular dynamics simulations. The simulations reveal the mechanisms of buckling, bending, slipping, and elastic recovery of the CNT tips on these surfaces and suggest that they will not wear out when crashed as conventional tips often do unless the surface is highly reactive. The simulations also show how the deformation mechanism changes as a function of tubule length and the effect of these changes on the buckling force is discussed quantitatively. C1 Univ Kentucky, Dept Chem & Mat Engn, Lexington, KY 40506 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Garg, A (reprint author), Univ Kentucky, Dept Chem & Mat Engn, Lexington, KY 40506 USA. RI Sinnott, Susan/P-8523-2014 OI Sinnott, Susan/0000-0002-3598-0403 NR 19 TC 109 Z9 110 U1 5 U2 26 PU AMERICAN PHYSICAL SOC PI COLLEGE PK PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA SN 0031-9007 J9 PHYS REV LETT JI Phys. Rev. Lett. PD SEP 14 PY 1998 VL 81 IS 11 BP 2260 EP 2263 DI 10.1103/PhysRevLett.81.2260 PG 4 WC Physics, Multidisciplinary SC Physics GA 119LH UT WOS:000075897300020 ER PT J AU Barstow, MA Hubeny, I AF Barstow, MA Hubeny, I TI An alternative explanation of the EUV spectrum of the white dwarf G191-B2B invoking a stratified H+He envelope including heavier elements SO MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY LA English DT Article DE stars : abundances; stars : atmospheres; stars : individual : G191-B2B; stars : white dwarfs; ultraviolet : stars; X-rays : stars ID MODEL STELLAR ATMOSPHERES; RADIATIVE LEVITATION; EXTREME-ULTRAVIOLET; INTERSTELLAR-MEDIUM; LUMINOSITY FUNCTION; HOT; HELIUM; HYDROGEN; OPACITY; SPECTROSCOPY AB Only recently has it been possible to find an effective temperature and composition for the hot DA white dwarf G191-B2B which can consistently match the optical, far-UV and EUV data simultaneously, by using new non-LTE model calculations that include the effects of line blanketing from more than 9 million (mainly Fe and Ni) transitions. However, to maintain agreement below the He Pi 228-Angstrom Lyman limit requires the inclusion of additional He Pi opacity in the form of photospheric, circumstellar or interstellar material. If photospheric, the homogeneous H+He structure adopted predicted a He Pi 1640-Angstrom line strength well above the IUE detection limit, while an unusually high He ionization fraction was required in this particular line of sight if the material was in the local ISM. We show that, by considering the effects of a stratified H upon He photospheric structure within the heavy-element blanketed models, a lower interstellar He Pi column density is obtained, leading to a more reasonable He ionization fraction for the G191-B2B line of sight. In addition, the absence of a He Pi 1640-Angstrom feature in the far-UV data is consistent with the equivalent width predicted by the stratified model. However, while this alternative interpretation offers a better description of certain aspects of the G191-B2B optical-to-EUV spectra, a new problem is introduced, namely that the He Pi Lyman lines are predicted to be stronger than can be comfortably accommodated by the observational data. C1 Univ Leicester, Dept Phys & Astron, Leicester LE1 7RH, Leics, England. NASA, Astron & Solar Phys Lab, GSFC, Greenbelt, MD 20711 USA. RP Barstow, MA (reprint author), Univ Leicester, Dept Phys & Astron, Univ Rd, Leicester LE1 7RH, Leics, England. NR 46 TC 15 Z9 15 U1 0 U2 0 PU WILEY-BLACKWELL PI MALDEN PA COMMERCE PLACE, 350 MAIN ST, MALDEN 02148, MA USA SN 0035-8711 J9 MON NOT R ASTRON SOC JI Mon. Not. Roy. Astron. Soc. PD SEP 11 PY 1998 VL 299 IS 2 BP 379 EP 388 DI 10.1046/j.1365-8711.1998.01711.x PG 10 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 121NW UT WOS:000076021100011 ER PT J AU Wozniak, PR Zdziarski, AA Smith, D Madejski, GM Johnson, WN AF Wozniak, PR Zdziarski, AA Smith, D Madejski, GM Johnson, WN TI X-ray and soft gamma-ray spectra of broad-line radio galaxies SO MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY LA English DT Article DE line : profiles; galaxies : active; galaxies : Seyfert; gamma-rays : observations; radio continuum : galaxies; X-rays : galaxies ID ACTIVE GALACTIC NUCLEI; K-ALPHA-LINES; CENTAURUS-A; COLD MATTER; SUPERLUMINAL MOTION; SEYFERT-1 GALAXIES; OSSE OBSERVATIONS; EMISSION; 3C-120; REFLECTION AB We study X-ray and soft gamma-ray spectral properties of nearby broad-line radio galaxies (BLRGs) using data from Ginga, ASCA, OSSE and EXOSAT. The X-ray spectra are well fitted by an intrinsic power-law continuum with an energy index of alpha similar to 0.7, moderately absorbed by a cold medium. In addition, the Ginga spectra show fluorescent Fe K alpha lines with an average equivalent width of similar to 100 eV, and, in some cases, Compton reflection humps. However, the latter are significantly weaker than both those seen in radio-quiet Seyfert Is and those expected if the Fe K alpha lines were due to reflection. We find that this weakness of reflection cannot be explained by dilution by another continuum component, e.g. from a jet, Some ASCA and EXOSAT spectra show soft X-ray excesses below similar to 3 keV. When that component is taken into account, the Fe Ka lines in the ASCA data are found to be unresolved in most cases, and to have equivalent widths less than or similar to 200 eV, consistent with the Ginga data. Multiple observations of 3C 382 and 390.3 show the Fe K alpha line approximately constant in flux but accompanied by strong continuum variations. This indicates the bulk of the line is formed by matter at a distance much larger than an accretion-disc scale, consistent with the ASCA line width measurements. The column density of the matter required to account for the observed line fluxes is N-H greater than or similar to 10(23) cm(-2). Such a medium is in the line of sight of 3C 445, but it has to be out of it in other objects in which the observed NH are substantially lower. Thus a cold medium with that N-H and covering a large solid angle is common in BLRGs, but in most objects it is out of the line of sight, consistent with the unified AGN model. The spectra of BLRGs break and become softer above similar to 100 keV, as shown by a simultaneous ASCA/OSSE observation of 3C 120 and by the OSSE spectra being on average much softer than the X-ray spectra. Finally, we find the X-ray and gamma-ray spectral properties of Cen A, a bright narrow-line radio galaxy - alpha similar or equal to 0.8, no or weak Compton reflection, N-H greater than or similar to 10(23) cm(-2) (which is consistent with its Fe K alpha line flux), and a high-energy break at similar to 100 keV - consistent with Cen A being intrinsically very similar to BLRGs studied here, again in agreement with the unified model. C1 Princeton Univ, Dept Astrophys Sci, Princeton, NJ 08544 USA. N Copernicus Astron Ctr, PL-00716 Warsaw, Poland. Univ Leicester, Dept Phys, Leicester LE1 7RH, Leics, England. NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. Univ Maryland, Dept Astron, College Pk, MD 20742 USA. USN, Res Lab, EO Hulburt Ctr Space Res, Washington, DC 20375 USA. RP Wozniak, PR (reprint author), Princeton Univ, Dept Astrophys Sci, Peyton Hall, Princeton, NJ 08544 USA. RI Johnson, Neil/G-3309-2014 NR 78 TC 78 Z9 78 U1 0 U2 0 PU BLACKWELL SCIENCE LTD PI OXFORD PA P O BOX 88, OSNEY MEAD, OXFORD OX2 0NE, OXON, ENGLAND SN 0035-8711 J9 MON NOT R ASTRON SOC JI Mon. Not. Roy. Astron. Soc. PD SEP 11 PY 1998 VL 299 IS 2 BP 449 EP 466 DI 10.1046/j.1365-8711.1998.01831.x PG 18 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 121NW UT WOS:000076021100019 ER PT J AU Barstow, MA Hubeny, I Holberg, JB AF Barstow, MA Hubeny, I Holberg, JB TI The effect of photospheric heavy elements on the hot DA white dwarf temperature scale SO MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY LA English DT Article DE stars : abundances; stars : atmospheres; white dwarfs; ultraviolet : stars; X-rays : stars ID MODEL STELLAR ATMOSPHERES; MASS-DISTRIBUTION; LUMINOSITY FUNCTION; PLANETARY NUCLEUS; HYDROGEN-RICH; G191-B2B; ROSAT; IRON; EUV; INTERSTELLAR AB Using the latest non-local thermodynamic equilibrium (non-LTE) synthetic spectra and stellar model calculations, we have evaluated the potential effect of the presence of heavy elements in the photospheres of hot H-rich DA white dwarfs. In particular, we have examined their influence on the effective temperature and surface gravity perceived from analysis of the Balmer line profiles. It is apparent that both the inclusion of non-LTE effects in the models and significant quantities of heavy elements act independently to lower the value of T(eff) determined from a particular spectrum. Hence, the true effective temperatures of the heavy element-rich DA white dwarfs, currently estimated to be above 55000 K, are apparently lower than previously reported from pure-H LTE analyses, by some 4000-7000 K. We do not see any similar influence on measurements of log g. This work concentrates on a group of relatively bright well-studied objects, for which heavy element abundances are known. As a consequence of this, establishment of correct temperatures for all other hot white dwarfs will require a programme of far-UV spectroscopy in order to obtain the essential compositional information. Since only stars with effective temperatures lying notionally in the range from approximate to 55000 to 70000 K (52000-62000 K when the non-LTE effects and heavy elements are taken into account) have been considered here, important questions remain regarding the magnitude of any similar effects in even hotter white dwarfs and pre-white dwarfs. The resulting implications for the plausibility of the evolutionary link between the main hot DA population and their proposed precursors, the II-rich central stars of planetary nebulae, need to be investigated. C1 Univ Leicester, Dept Phys & Astron, Leicester LE1 7RH, Leics, England. NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, Greenbelt, MD 20771 USA. Univ Arizona, Lunar & Planetary Lab, Tucson, AZ 85721 USA. RP Barstow, MA (reprint author), Univ Leicester, Dept Phys & Astron, Univ Rd, Leicester LE1 7RH, Leics, England. NR 65 TC 53 Z9 53 U1 0 U2 0 PU WILEY-BLACKWELL PI MALDEN PA COMMERCE PLACE, 350 MAIN ST, MALDEN 02148, MA USA SN 0035-8711 J9 MON NOT R ASTRON SOC JI Mon. Not. Roy. Astron. Soc. PD SEP 11 PY 1998 VL 299 IS 2 BP 520 EP 534 DI 10.1046/j.1365-8711.1998.01794.x PG 15 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 121NW UT WOS:000076021100025 ER PT J AU Wilson, CR AF Wilson, CR TI Geophysics - Oceanic effects on Earth's rotation rate SO SCIENCE LA English DT Editorial Material C1 NASA, Off Earth Sci, Washington, DC 20546 USA. Univ Texas, Dept Geol Sci, Austin, TX 78712 USA. RP Wilson, CR (reprint author), NASA, Off Earth Sci, Washington, DC 20546 USA. NR 3 TC 5 Z9 5 U1 0 U2 1 PU AMER ASSOC ADVANCEMENT SCIENCE PI WASHINGTON PA 1200 NEW YORK AVE, NW, WASHINGTON, DC 20005 USA SN 0036-8075 J9 SCIENCE JI Science PD SEP 11 PY 1998 VL 281 IS 5383 BP 1623 EP 1624 DI 10.1126/science.281.5383.1623 PG 2 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA 118TR UT WOS:000075856500032 ER PT J AU Albota, M Beljonne, D Bredas, JL Ehrlich, JE Fu, JY Heikal, AA Hess, SE Kogej, T Levin, MD Marder, SR McCord-Maughon, D Perry, JW Rockel, H Rumi, M Subramaniam, C Webb, WW Wu, XL Xu, C AF Albota, M Beljonne, D Bredas, JL Ehrlich, JE Fu, JY Heikal, AA Hess, SE Kogej, T Levin, MD Marder, SR McCord-Maughon, D Perry, JW Rockel, H Rumi, M Subramaniam, C Webb, WW Wu, XL Xu, C TI Design of organic molecules with large two-photon absorption cross sections SO SCIENCE LA English DT Article ID 2-PHOTON; MICROSCOPY; EXCITATION; SPECTROSCOPY; NM AB A strategy for the design of molecules with Large two-photon absorption cross sections, delta, was developed, on the basis of the concept that symmetric charge transfer, from the ends of a conjugated system to the middle, or vice versa, upon excitation is correlated to enhanced values of delta. Synthesized bis(styryl)benzene derivatives with donor-pi-donor, donor-acceptor-donor, and acceptor-donor-acceptor structural motifs exhibit exceptionally Large values of delta, up to about 400 times that of trans-stilbene. Quantum chemical calculations performed on these molecules indicate that substantial symmetric charge redistribution occurs upon excitation and provide delta values in good agreement with experimental values. The combination of Large delta and high fluorescence quantum yield or triplet yield exhibited by molecules developed here offers potential for unprecedented brightness in two-photon fluorescent imaging or enhanced photosensitivity in two-photon sensitization, respectively. C1 Univ Mons, Ctr Res Mol Elect & Photon, B-7000 Mons, Belgium. Cornell Univ, Sch Appl & Engn Phys, Ithaca, NY 14853 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. CALTECH, Beckman Inst, Mol Mat Resource Ctr, Pasadena, CA 91125 USA. Univ Arizona, Dept Chem, Tucson, AZ 85721 USA. Penn State Univ, Dept Chem, Hazleton, PA 18201 USA. RP Bredas, JL (reprint author), Univ Mons, Ctr Res Mol Elect & Photon, Pl Parc 20, B-7000 Mons, Belgium. RI Webb, Watt/B-5905-2011; Bredas, Jean-Luc/A-3431-2008; Rumi, Mariacristina/C-9474-2009; Perry, Joseph/B-7191-2011 OI Bredas, Jean-Luc/0000-0001-7278-4471; Rumi, Mariacristina/0000-0002-4597-9617; Perry, Joseph/0000-0003-1101-7337 NR 20 TC 1673 Z9 1718 U1 46 U2 425 PU AMER ASSOC ADVANCEMENT SCIENCE PI WASHINGTON PA 1200 NEW YORK AVE, NW, WASHINGTON, DC 20005 USA SN 0036-8075 J9 SCIENCE JI Science PD SEP 11 PY 1998 VL 281 IS 5383 BP 1653 EP 1656 DI 10.1126/science.281.5383.1653 PG 4 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA 118TR UT WOS:000075856500040 PM 9733507 ER PT J AU Marcus, SL Chao, Y Dickey, JO Gegout, P AF Marcus, SL Chao, Y Dickey, JO Gegout, P TI Detection and modeling of nontidal oceanic effects on Earth's rotation rate SO SCIENCE LA English DT Article ID GENERAL-CIRCULATION MODEL; ATMOSPHERIC ANGULAR-MOMENTUM; ISOPYCNIC COORDINATE MODEL; SEA-LEVEL; BUDGET AB Subdecadal changes in Earth's rotation rate, and hence in the Length of day (LOD), are largely controlled by variations in atmospheric angular momentum. Results from two oceanic general circulation models (OGCMs), forced by observed wind stress and heat flux for the years 1992 through 1994 show that ocean current and mass distribution changes also induce detectable LOD variations. The close similarity of axial oceanic angular momentum (OAM) results from two independent OGCMs, and their coherence with LOD, demonstrate that global ocean models can successfully capture the large-scale circulation changes that drive OAM variability on seasonal and shorter time scales. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Marcus, SL (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. OI Marcus, Steven/0000-0002-5763-6961 NR 28 TC 69 Z9 72 U1 1 U2 7 PU AMER ASSOC ADVANCEMENT SCIENCE PI WASHINGTON PA 1200 NEW YORK AVE, NW, WASHINGTON, DC 20005 USA SN 0036-8075 J9 SCIENCE JI Science PD SEP 11 PY 1998 VL 281 IS 5383 BP 1656 EP 1659 DI 10.1126/science.281.5383.1656 PG 4 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA 118TR UT WOS:000075856500041 ER PT J AU Budd, CJ Koomullil, GP Stuart, AM AF Budd, CJ Koomullil, GP Stuart, AM TI On the solution of convection-diffusion boundary value problems using equidistributed grids SO SIAM JOURNAL ON SCIENTIFIC COMPUTING LA English DT Article DE convection-diffusion equations; mesh adaptation; equidistribution; continuation ID DIFFERENTIAL EQUATIONS; MESH SELECTION; DYNAMICS; MOTION AB The effect of using grid adaptation on the numerical solution of model convection-diffusion equations with a conservation form is studied. The grid adaptation technique studied is based on moving a fixed number of mesh points to equidistribute a generalization of the arc-length of the solution. In particular, a parameter-dependent monitor function is introduced which incorporates fixed meshes, approximate arc-length equidistribution, and equidistribution of the absolute value of the solution, in a single framework. Thus the resulting numerical method is a coupled nonlinear system of equations for the mesh spacings and the nodal values. A class of singularly perturbed problems, including Burgers's equation in the limit of small viscosity, is studied. Singular perturbation and bifurcation techniques are used to analyze the solution of the discretized equations, and numerical results are compared with the results from the analysis. Computation of the bifurcation diagram of the system is performed numerically using a continuation method and the results are used to illustrate the theory. It is shown that equidistribution does not remove spurious solutions present on a fixed mesh and that, furthermore, the spurious solutions can be stable for an appropriate moving mesh method. C1 Univ Bath, Dept Math, Bath BA2 7AY, Avon, England. NASA, Fluid Dynam Div, Ames Res Ctr, Moffett Field, CA 94035 USA. Stanford Univ, Div Appl Mech, Stanford, CA 94305 USA. RP Budd, CJ (reprint author), Univ Bath, Dept Math, Claverton Down, Bath BA2 7AY, Avon, England. NR 20 TC 7 Z9 7 U1 0 U2 1 PU SIAM PUBLICATIONS PI PHILADELPHIA PA 3600 UNIV CITY SCIENCE CENTER, PHILADELPHIA, PA 19104-2688 USA SN 1064-8275 J9 SIAM J SCI COMPUT JI SIAM J. Sci. Comput. PD SEP 11 PY 1998 VL 20 IS 2 BP 591 EP 618 DI 10.1137/S1064827595280454 PG 28 WC Mathematics, Applied SC Mathematics GA 118QW UT WOS:000075852300004 ER PT J AU Randich, S Singh, KP Simon, T Drake, SA Schmitt, JHMM AF Randich, S Singh, KP Simon, T Drake, SA Schmitt, JHMM TI ROSAT HRI observations of the intermediate-age open cluster IC 4756 SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE stars : activity; X-rays : stars; open clusters and associations : individual : IC 4756 ID X-RAY SURVEY; HYADES CLUSTER; STARS; PLEIADES; IC-4756; CORONAE; GIANTS AB We have obtained an 88 kilosecond ROSAT HRI exposure of the intermediate-age open cluster IC 4756 with the purpose of detecting stars in the high luminosity tail (log L-X greater than or equal to 10(29) erg s(-1)) of its X-ray luminosity distribution. However, only 1 cluster member (HSS 201) out of the 60 members inside the central high-sensitivity region of the HRI field of view (FOV) was detected. This star has spectral type A8, suggesting a close binary system with a low mass X-ray emitting companion. We compare the distribution of upper limits for F and G-type dwarfs in IC 4756 with the X-ray distribution functions of the similarly aged Hyades and Praesepe clusters. The results of this statistical analysis are inconclusive for G-type stars, but suggest that at least F-type stars in IC 4756 are not as X-ray luminous as their Hyades counterparts, thus indicating intrinsic differences between the two clusters. Finally, our data indicate a deficit of very active binaries with respect to both Hyades and Praesepe, and older open clusters. C1 Osservatorio Astrofis Arcetri, I-50125 Florence, Italy. Tata Inst Fundamental Res, Bombay 400005, Maharashtra, India. Univ Hawaii, Astron Inst, Honolulu, HI 96822 USA. NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. Univ Hamburg, Hamburger Sternwarte, D-21029 Hamburg, Germany. RP Randich, S (reprint author), Osservatorio Astrofis Arcetri, Largo E Fermi 5, I-50125 Florence, Italy. EM randich@arcetri.astro.it OI Randich, Sofia/0000-0003-2438-0899 NR 38 TC 17 Z9 17 U1 0 U2 0 PU EDP SCIENCES S A PI LES ULIS CEDEX A PA 17, AVE DU HOGGAR, PA COURTABOEUF, BP 112, F-91944 LES ULIS CEDEX A, FRANCE SN 0004-6361 J9 ASTRON ASTROPHYS JI Astron. Astrophys. PD SEP 10 PY 1998 VL 337 IS 2 BP 372 EP 378 PG 7 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 123KH UT WOS:000076124000009 ER PT J AU Schmitz, F Fleck, B AF Schmitz, F Fleck, B TI On wave equations and cut-off frequencies of plane atmospheres SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE Sun : atmosphere; Sun : oscillations; stars : atmospheres ID ACOUSTIC-WAVES; OSCILLATIONS; REFLECTION AB This paper deals with the one-dimensional vertical propagation of linear adiabatic waves in plane atmospheres. In the literature there are various representations of the standard form of the wave equation from which different forms of the so called cut-off frequency are inferred. It is not uncommon that statements concerning the propagation behavior of waves are made which are based on the height dependence of a cutoff frequency. In this paper, first we critically discuss concepts resting on the use of cut-off frequencies. We add a further wave equation to three wave equations previously presented in the literature, yielding an additional cut-off frequency. Comparison among the various cut-off frequencies of the VAL-atmosphere reveals significant differences, which illustrate the difficulties of interpreting a height dependent cut-off frequency. We also discuss the cut-off frequency of the parabolic temperature profile and the behavior of the polytropic atmosphere. The invariants of the four wave equations presented contain first and second derivatives of the adiabatic sound speed. These derivatives cause oscillations and peaks in the space dependent part of the invariants, which unnecessarily complicate the discussion. We therefore present a new form of the wave equation, the invariant of which is extremely simple and does not contain derivatives of the thermodynamic variables. It is valid for any LTE equation of state. It allows us to make effective use of strict oscillation theorems. We calculate the height-dependent part of the invariant of this equation for the VAL-atmosphere including ionization and dissociation. For this real atmosphere, there is no obvious correspondence between the behavior of the invariant and the temperature structure or the sound speed profile. The invariant of the wave equation is nearly constant around the temperature minimum. In the chromosphere, the invariant is almost linear. The case of the wave equation with a linear invariant is studied analytically. C1 Univ Wurzburg, Astron Inst, D-97074 Wurzburg, Germany. NASA, ESA, Dept Space Sci, GSFC, Greenbelt, MD 20771 USA. RP Schmitz, F (reprint author), Univ Wurzburg, Astron Inst, Hubland, D-97074 Wurzburg, Germany. RI Fleck, Bernhard/C-9520-2012 NR 18 TC 23 Z9 25 U1 0 U2 0 PU EDP SCIENCES S A PI LES ULIS CEDEX A PA 17, AVE DU HOGGAR, PA COURTABOEUF, BP 112, F-91944 LES ULIS CEDEX A, FRANCE SN 0004-6361 J9 ASTRON ASTROPHYS JI Astron. Astrophys. PD SEP 10 PY 1998 VL 337 IS 2 BP 487 EP 494 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 123KH UT WOS:000076124000022 ER PT J AU Natta, A Hollenbach, D AF Natta, A Hollenbach, D TI The evolution of the neutral gas in planetary nebulae: theoretical models SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE shock waves; ISM : lines and bands; ISM : molecules; ISM : planetary nebulae; infrared : ISM : lines and bands ID MOLECULAR-HYDROGEN EMISSION; CARBON-MONOXIDE EMISSION; NEAR-INFRARED STRUCTURE; PHOTODISSOCIATION REGIONS; CENTRAL STARS; HELIX NEBULA; STELLAR EVOLUTION; CO ENVELOPES; MASS-LOSS; NGC-7027 AB This paper theoretically models the emission expected from shells (generalized to include tori or clumps) expanding away from the hot central stars of PNe. We examine the effects of shocks, FUV (6 eV < h nu < 13.6 eV), and soft X rays (50 eV less than or similar to h nu less than or similar to 1 KeV) on the predominantly neutral gas and follow the time dependent chemistry for H-2, solving for the chemical and temperature structure and the emergent spectrum of the evolving shell. We consider a large interval of values for the mass of the central star (from 0.6 to 0.836 M.) and for the shell properties, using its density and filling factor as free parameters. The calculations give the time dependent physical and chemical properties of the shell (temperature, fractional abundances of HII, HI, H-2 and electrons), as well as the intensities of a number of lines of molecular hydrogen (H-2 v=1-0S(1); v=2-1S(1); and v=0-0S(0), Si(1), S(2), S(3), and S(4)) Br gamma and the metal lines CLI 158 mu m, OI 63 mu m, SiII 35 mu m, OI 6300 Angstrom, FeII 1.26 mu m, which can be compared to the observations and used to determine the physical parameters of the ejection process. We focus on the shell evolution after the star has achieved T-* greater than or similar to 30,000 K. If the column density in the shell is sufficiently high, a three-layered shell is produced with an inner HII region, a central HI region, and an outer H-2 region. In this case, we can identify three phases in the evolution of the neutral shell. i) The early evolution (T-* similar to 30,000 K) is dominated by FUV photons, as the FUV photon luminosity Phi(FUV) of the central star peaks. The shell has a large column of warm H-2 and is very bright in all lines. The vibrationally excited H-2 lines at 2 mu m are dominated by thermal emission from collisionally excited levels; the heating is predominantly by grain photoelectric heating and FUV pumping of H-2. ii) At somewhat later times, as Phi(FUV) and gas density decline, the molecular gas becomes cooler and the line intensity decreases rapidly. This is the only phase in which the emission of the v=1-0 H-2 lines can be dominated by fluorescence, and this fluorescent phase is present only in PNe with low-mass central stars. iii) At even later times, the star heats to T-* > 100,000 K and soft X-rays heat and partially ionize the neutral gas well above the values determined by the FUV stellar radiation. The duration land presence) of these phases depends on the evolution with time of the stellar radiation field (i.e., on the mass of the central star), which is the main parameter that controls the PN evolution. For example, we find that a standard M-* = 0.6 M. central star produces phase (i) from roughly 1000 to 5000 yrs, phase iii) from 5000 to 7000 yrs, and phase (iii) from 7000 yrs onward. PNe with high mass central stars reach high effective temperatures very quickly, and spend most of their life in the X-ray dominated phase. A M-* = 0.836 M. case reaches phase (iii) in roughly 1000 yrs. The decrease with time of the Hz line intensity (both in the near and mid-infrared) is less rapid than in PNe with low-mass central stars. Time-dependent Hz chemistry enhances even further the intensity of these lines. As a result, we find that models with high-mass central stars are the only cases which radiatively produce strong hydrogen molecular line intensities in old (large) PNe. For standard values of the parameters the emission in the vibrationally excited Ha lines produced in the shock between the expanding shell and the precursor red giant wind is generally small compared to the PDR emission. However, for large red giant wind mass loss rates, (M)over dot(RG) greater than or similar to 10(-5) M. yr(-1), the shock emission can be significant. Therefore, strong H-2 2 mu m emission may also arise from shocks in old PNe. C1 Osserv Astrofis Arcetri, I-50125 Florence, Italy. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Natta, A (reprint author), Osserv Astrofis Arcetri, Largo E Fermi 5, I-50125 Florence, Italy. NR 92 TC 50 Z9 50 U1 0 U2 0 PU EDP SCIENCES S A PI LES ULIS CEDEX A PA 17, AVE DU HOGGAR, PA COURTABOEUF, BP 112, F-91944 LES ULIS CEDEX A, FRANCE SN 0004-6361 J9 ASTRON ASTROPHYS JI Astron. Astrophys. PD SEP 10 PY 1998 VL 337 IS 2 BP 517 EP 538 PG 22 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 123KH UT WOS:000076124000026 ER PT J AU Netzer, H Turner, TJ George, IM AF Netzer, H Turner, TJ George, IM TI The soft X-ray spectrum of scattering-dominated active galactic nuclei SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies : abundances; galaxies : active; galexies : nuclei; galaxies : Seyfert; line : formation; X-rays : galaxies ID TYPE-2 SEYFERT-GALAXIES; ASCA OBSERVATIONS; COLD MATTER; REFLECTION; NGC-1068; FEATURES; COMPLEX; REGION; LINES AB This paper discusses the properties of scattering-dominated active galactic nuclei (AGNs). We define these to be AGNs for which the direct line of sight to the continuum source is obscured by Compton-thick material. The aim is to construct, for the first time, a model consistent with X-ray line luminosities, line ratios, and various luminosity indicators. The ASCA spectra of six such sources show several X-ray lines that can be reliably measured, mostly due to highly ionized magnesium, silicon, sulfur, and iron. These enable us to investigate the physical conditions of the scattering material. The sources show evidence of He-like and H-like iron lines that are likely to be produced in hot (T similar to 10(6) K) photoionized gas. By measuring the equivalent widths of the lines, and by constructing a diagnostic line-ratio diagram, we demonstrate that the silicon and magnesium lines are produced by the same gas that emits the highly ionized iron lines. The properties of this gas are rather different from the properties of warm absorbers in type I AGNs. Neutral 6.4 keV iron lines are also detected, originating in a different component which can be either Compton-thin or Compton-thick. The best-measured iron lines suggest an enhancement of n(Fe)/n(H) by a factor of similar to 2 compared to solar, in both the hot and cool Compton-thin components. We further show that in four of the sources, the Fe K alpha 6.4 keV/H beta (4861 Angstrom) line ratio is consistent with that predicted for typical narrow-line region clouds, provided the column density is larger than similar to 10(22.5) cm(-2), alpha(ox) is smaller than 1.3, and the reddening-corrected H beta is known. For some sources, this is a viable alternative to the commonly assumed Compton-thick medium as the origin of the 6.4 keV iron line. C1 Tel Aviv Univ, Raymond & Beverly Sackler Fac Exact Sci, Sch Phys & Astron, IL-69978 Tel Aviv, Israel. Tel Aviv Univ, Raymond & Beverly Sackler Fac Exact Sci, Wise Observ, IL-69978 Tel Aviv, Israel. NASA, High Energy Astrophys Lab, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Space Res Assoc, Washington, DC USA. RP Netzer, H (reprint author), Tel Aviv Univ, Raymond & Beverly Sackler Fac Exact Sci, Sch Phys & Astron, IL-69978 Tel Aviv, Israel. NR 31 TC 42 Z9 42 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD SEP 10 PY 1998 VL 504 IS 2 BP 680 EP 692 DI 10.1086/306109 PN 1 PG 13 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 152KW UT WOS:000077777500009 ER PT J AU Kubo, H Takahashi, T Madejski, G Tashiro, M Makino, F Inoue, S Takahara, F AF Kubo, H Takahashi, T Madejski, G Tashiro, M Makino, F Inoue, S Takahara, F TI ASCA observations of blazars and multiband analysis SO ASTROPHYSICAL JOURNAL LA English DT Review DE BL Lacertae objects : general; quasars : general; radiation mechanisms : nonthermal; X-rays : galaxies ID BL-LACERTAE OBJECT; GAMMA-RAY EMISSION; ACTIVE GALACTIC NUCLEI; SPECTRUM RADIO QUASARS; GAS IMAGING SPECTROMETER; SELF-COMPTON MODEL; X-RAY; LAC OBJECTS; EGRET OBSERVATIONS; RELATIVISTIC JETS AB We present data for 18 blazars observed with the X-ray satellite ASCA, half of which were also observed contemporaneously with the EGRET instrument onboard Compton Gamma Ray Observatory as parts of multiwavelength campaigns. The observations show a clear difference in the spectra between three subclasses of blazars, namely, high-energy peaked BL Lacertae objects (HBLs), low-energy peaked BL Lac objects (LBLs), and quasar-hosted blazars (QHBs). The ASCA X-ray spectra of HBLs are the softest, with the power-law energy index alpha similar to 1-2, and they form the highest observable energy tail of the low-energy (LE, synchrotron) component. The X-ray spectra of the QHBs are the hardest (alpha similar to 0.6) and are consistent with the lowest observable energy end of the high-energy (HE, Compton) component. For LBLs, the X-ray spectra are intermediate. We find that the radiation process responsible for the HE peak for HBLs can be explained solely by Doppler-boosted synchrotron self-Compton (SSC) emission, with the Doppler factor delta consistent with the VLBI and/or gamma-ray variability data. For many QHBs, on the other hand, the gamma-rays cannot be solely a result of the SSC mechanism unless delta is significantly in excess of that inferred from VLBI data. We consider an alternative scenario consistent with the measured values of delta, where the SSC component is still present in QHBs and dominates in the X-ray band but is below the observed gamma-ray spectrum. With an assumption that the peak of the SSC emission is on the extrapolation of the X-ray spectrum, and adopting a value of 10 for delta, we infer the magnetic field B to be 0.1-1 G and Lorentz factors gamma(b) of electrons radiating at the peak of the nu F(nu) spectrum of similar to 10(3) for QHBs; this is much lower than gamma(b) similar to 10(5) for HBLs, even though the Values of B are comparable in the two subclasses. This difference of gamma(b) is most likely due to the large photon density expected in QHBs (e.g., from thermal components visible in these objects) as compared with that of HBLs; Compton upscattering of these photons may well provide the observed GeV flux. C1 Inst Phys & Chem Res, Wako, Saitama 3510198, Japan. Inst Space & Astronaut Sci, Kanagawa 2298510, Japan. NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. Univ Maryland, College Pk, MD 20742 USA. Univ Tokyo, Dept Phys, Bunkyo Ku, Tokyo 1130033, Japan. Tokyo Metropolitan Univ, Hachioji, Tokyo 1920397, Japan. Osaka Univ, Grad Sch Sci, Dept Earth & Space Sci, Osaka 5600043, Japan. RP Kubo, H (reprint author), Inst Phys & Chem Res, 2-1 Hirosawa, Wako, Saitama 3510198, Japan. RI Tashiro, Makoto/J-4562-2012 NR 104 TC 158 Z9 160 U1 0 U2 1 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD SEP 10 PY 1998 VL 504 IS 2 BP 693 EP 701 DI 10.1086/306125 PN 1 PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 152KW UT WOS:000077777500010 ER PT J AU Lister, ML Marscher, AP Gear, WK AF Lister, ML Marscher, AP Gear, WK TI Submilliarcsecond polarimetric imaging of blazar jets at 43 GHz SO ASTROPHYSICAL JOURNAL LA English DT Article DE BL Lacertae objects : general; galaxies : active; galaxies : jets; polarization; quasars : general; shock waves ID EXTRAGALACTIC RADIO-SOURCES; BL-LACERTAE OBJECTS; FREQUENCY VARIABLE SOURCES; SCALE POLARIZATION STRUCTURE; EPOCH VLBI OBSERVATIONS; ACTIVE GALACTIC NUCLEI; LINEAR-POLARIZATION; SUPERLUMINAL MOTION; VLA OBSERVATIONS; COMPLETE SAMPLE AB We present 43 GHz polarization images obtained with the Very Long Baseline Array of four blazars (0829 + 046, 1055 + 018, 1334-127, and AP Librae), as well as four active galactic nuclei, which served as polarization calibrators (DA 193, OJ 287, 3C 279, and 1611 + 343). Six of these objects are members of the Nartallo et al. millimeter-wave polarization blazar monitoring sample. We find no differences in the overall millimeter-wave polarization properties of the BL Lacertae objects and quasars in our sample. This is in contrast to previous findings at centimeter wavelengths, in which the inferred magnetic fields of quasars are found to be predominantly aligned with the jet, while perpendicular configurations are found in BL Lac objects. With the exception of 1611 + 343, a low optical polarization quasar, all of the unresolved blazar cores in our sample have inferred magnetic field orientations perpendicular to the inner jet direction. Past nonimaging millimeter-wave polarization monitoring data have shown that these core orientations are stable in three of our sample objects; this may be due to strong, unresolved standing shocks located very close to the base of the jet. We also detect in the jets of blazars a moderate-sized population of polarized components having electric vectors that lie at an oblique angle to the local jet direction. We find that the observed distribution of electric vector misalignment angles cannot be fitted by a single population of oblique shocks having arbitrary inclinations with respect to the jet axis. Such a population predicts an overabundance of shocks with electric polarization vectors aligned with the jet axis, produced by relativistic effects associated with the jet how. We find the data to be more consistent with a scenario in which the polarized jet components are merely enhanced regions whose magnetic field orientations are controlled by some mechanism other than shocks. C1 Boston Univ, Dept Astron, Boston, MA 02215 USA. UCL, Mullard Space Sci Lab, Dorking RH5 6NT, Surrey, England. RP CALTECH, Jet Prop Lab, MS 238-332,4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 85 TC 43 Z9 44 U1 0 U2 0 PU IOP PUBLISHING LTD PI BRISTOL PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND SN 0004-637X EI 1538-4357 J9 ASTROPHYS J JI Astrophys. J. PD SEP 10 PY 1998 VL 504 IS 2 BP 702 EP 719 DI 10.1086/306112 PN 1 PG 18 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 152KW UT WOS:000077777500011 ER PT J AU Shelton, RL AF Shelton, RL TI Simulations of supernova remnants in diffuse media and their application to the lower halo of the Milky Way. I. The high-stage ions SO ASTROPHYSICAL JOURNAL LA English DT Article DE Galaxy : halo; hydrodynamics; ISM : general; methods : numerical; supernova remnants ID IONIZED INTERSTELLAR GAS; X-RAY-SPECTRUM; GALACTIC HALO; CORONAL GAS; HOT GAS; O VI; ORFEUS OBSERVATIONS; ROSAT DETECTION; GALAXY NGC-891; MAGNETIC-FIELD AB This paper reports on detailed, nonequilibrium hydrodynamic simulations of supernova remnants (SNRs) evolving in a warm, low-density, nonthermal pressure-dominated ambient medium (T = 10(4) K, n = 0.01 cm(-3), P-nt = 1.8 x 10(3) K cm(-3)), with the goals of characterizing their structure and C+3, N+4 and O+5 content, emission, and line profiles and investigating the effects of supernova remnants in the lower Galactic halo. If undisturbed by external objects, these remnants have great longevity, surviving for similar to 1.7 x 10(7) yr. During the adiabatic phase, they contain large quantities of C+3, N+4, and O+5 in the hot gas behind their shock fronts. They emit brightly in the ultraviolet resonance lines and would appear edge brightened to observations of column density and emission. At the end of the adiabatic phase, each SNR develops a zone of cooling and recombining C+3, N+4, and O+5 in th, transition region between the hot bubble and the cool shell. The resonance line luminosities plummet, and the edge brightening diminishes. As the remnants evolve, the interiors cool faster than the ions can recombine to their equilibrium levels. Thus, during most of the remnants' lifetimes the C+3 line widths are smaller than expected from collisional equilibrium, and after the remnants have completely cooled, some C+3 remains. The O+5, N+4, and C+3 distributions overlap incompletely. The O+5 ions are more plentiful in the warmer gas at smaller radii than are the N+4 or C+3 ions. As a result, after the shell forms the thermal pressure in the O+5-rich gas is at least twice as large as that in the C+3-rich gas. During most of its lifetime, the remnant's interior is less than 10(6) K. Therefore, the fraction of area covered or volume filled by very hot SNR gas is much smaller than that filled by warm SNR gas. These simulations have been combined with the statistical distribution of isolated supernova progenitors in order to derive rough estimates of the appearance of the ensemble of isolated supernova remnants in the lower halo. The agreement between the simulation results and observational results in terms of average column density and spatial patchiness shows that much, if not all, of the high-latitude O+5, N+4, and C+3 between the local bubble and roughly a kiloparsec can be attributed to isolated SNRs in the lower halo. The simulations may also be of interest to studies of the external galaxies and the hypothesis that the Local Bubble is a single supernova remnant evolving in a low-density ambient medium. C1 NASA, GSFC, Greenbelt, MD 20706 USA. RP NASA, GSFC, Code 662, Greenbelt, MD 20706 USA. EM shelton@spots.gsfc.nasa.gov NR 75 TC 59 Z9 59 U1 0 U2 0 PU IOP PUBLISHING LTD PI BRISTOL PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND SN 0004-637X EI 1538-4357 J9 ASTROPHYS J JI Astrophys. J. PD SEP 10 PY 1998 VL 504 IS 2 BP 785 EP 804 DI 10.1086/306107 PN 1 PG 20 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 152KW UT WOS:000077777500018 ER PT J AU Stauffer, JR Schild, R Navascues, DBY Backman, DE Angelova, AM Kirkpatrick, JD Hambly, N Vanzi, L AF Stauffer, JR Schild, R Navascues, DBY Backman, DE Angelova, AM Kirkpatrick, JD Hambly, N Vanzi, L TI Results of a deep imaging survey of one square degree of the Pleiades for low-luminosity cluster members SO ASTROPHYSICAL JOURNAL LA English DT Article DE infrared : stars; open clusters and associations : individual (Pleiades); stars : evolution; stars : low-mass, brown dwarfs ID LOW-MASS STARS; BROWN DWARF CANDIDATES; MODEL ATMOSPHERES; SPECTRAL SEQUENCE; MAIN-SEQUENCE; SPECTROSCOPY; PHOTOMETRY; LITHIUM; AGE; SEARCH AB We have obtained relatively deep imaging in two colors, with limiting magnitudes of V similar to 22.5 and I-c similar to 21, of about one square degree of the Pleiades open cluster. Our primary goal was to identify new candidate brown dwarf members of this similar to 100 Myr-old open cluster. In the process, we have also obtained V and I-c photometry for a large number of brighter proper-motion members of the cluster for which only photographic photometry had been available up until now. We identify six candidate objects whose locations in a V versus (V-I)(c) color-magnitude diagram are consistent with their being Pleiades members near or below the hydrogen-burning mass limit. We have obtained near-infrared photometry for several of these brown dwarf candidates, as well. as for a selection of previously identified very low mass Pleiades members, and we use this new photometry to help determine whether the objects identified in the visual are indeed Pleiades members or not. Finally, we have obtained a moderate-resolution spectrum of one of the new brown dwarf candidates with the Keck LRIS spectrograph The spectrum shows that the star has a spectral type of M7 which is compatible with its photometric colors, and that it has an H alpha equivalent width of about 14 Angstrom and a marginally detected lithium 6708 Angstrom absorption equivalent width of about 0.4 Angstrom. These spectroscopic characteristics suggest that this object (MHObd1) is indeed a Pleiades member with a mass at or slightly above the hydrogen-burning mass limit. C1 Smithsonian Astrophys Observ, Cambridge, MA 02138 USA. Franklin & Marshall Coll, Dept Phys & Astron, Lancaster, PA 17604 USA. CALTECH, Jet Prop Lab, IPAC, Pasadena, CA 91125 USA. Royal Observ, Edinburgh EH9 3HJ, Midlothian, Scotland. Osserv Astrofis Arcetri, I-50125 Florence, Italy. RP Smithsonian Astrophys Observ, 60 Garden St, Cambridge, MA 02138 USA. RI Vanzi, Leonardo/D-1381-2014; Barrado Navascues, David/C-1439-2017 OI Barrado Navascues, David/0000-0002-5971-9242 NR 55 TC 40 Z9 40 U1 0 U2 0 PU IOP PUBLISHING LTD PI BRISTOL PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND SN 0004-637X EI 1538-4357 J9 ASTROPHYS J JI Astrophys. J. PD SEP 10 PY 1998 VL 504 IS 2 BP 805 EP 820 DI 10.1086/306095 PN 1 PG 16 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 152KW UT WOS:000077777500019 ER PT J AU Tatischeff, V Ramaty, R Kozlovsky, B AF Tatischeff, V Ramaty, R Kozlovsky, B TI X-rays from accelerated ion interactions SO ASTROPHYSICAL JOURNAL LA English DT Article DE acceleration of particles; atomic processes; gamma rays : theory; ISM : individual (Orion); line : formation; X-rays : general ID ORION COMPLEX; COMPTEL OBSERVATIONS; ELECTRON-CAPTURE; ATOM COLLISIONS; CROSS-SECTIONS; ENERGY; LINES; ELEMENTS; HYDROGEN; EMISSION AB We have developed in detail the theory of X-ray line and continuum production due to atomic interactions of accelerated ions, incorporating in our calculations information from a broad range of laboratory measurements. We applied our calculations to the Orion region from which nuclear gamma-ray line observations with the COMPTEL instrument on the Compton Gamma Ray Observatory (CGRO) were reported. The accelerated particles which produce this gamma-ray emission via nuclear reactions also produce X-ray lines via atomic interactions. We predict strong, relatively broad line emission in the range from 0.5 to 1 keV, mainly due to de-excitations in fast O ions. Current ROSAT observations of Orion do not provide unambiguous signatures for X-ray production by accelerated ions. However, if future X-ray observations with high spectral resolution would confirm the predicted X-rays, the combined analysis of the X-ray and gamma-ray data will set important constraints on the origin of the accelerated particles and their interaction model. C1 NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. Tel Aviv Univ, Sackler Fac Exact Sci, IL-69978 Tel Aviv, Israel. RP Tatischeff, V (reprint author), NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. NR 74 TC 35 Z9 35 U1 0 U2 1 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD SEP 10 PY 1998 VL 504 IS 2 BP 874 EP 888 DI 10.1086/306118 PN 1 PG 15 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 152KW UT WOS:000077777500024 ER PT J AU Mitrofanov, IG Pozanenko, AS Briggs, MS Paciesas, WS Preece, RD Pendleton, GN Meegan, CA AF Mitrofanov, IG Pozanenko, AS Briggs, MS Paciesas, WS Preece, RD Pendleton, GN Meegan, CA TI Generic signatures of the time profiles of BATSE cosmic gamma-ray bursts SO ASTROPHYSICAL JOURNAL LA English DT Article DE gamma rays : bursts; methods : statistical ID DURATION AB A new method is proposed, which allows the study of generic signatures of cosmic gamma-ray burst time histories. We average the 64 ms resolution time profiles of 275 bright bursts detected by BATSE. The profile of each burst is normalized by the maximum number of counts at the peak of the primary pulse, and individual pulses and interpulse valleys are selected from the normalized pro files by identical selection criteria. New generic temporal parameters are introduced, which characterize the duration and equivalent width of each pulse and the duration of each valley. The histograms of the total equivalent pulse width and summed pulse duration are bimodal. Bimodality is also seen in the histogram of the mean duration of individual pulses. Bursts from the short and long peaks of these distributions correspond to the two modes of the Third BATSE Burst Catalog T-50 and T-90 distributions. Therefore, these new burst parameters demonstrate that the observed bimodal temporal behavior results from properties of the pulsed emission of gamma-ray bursts. The long mode of the T-90 histogram includes bursts with from one to similar to 20 pulses; the logarithmic mean pulse duration is 1.17 +/- 0.09 s; for the long events with more than one pulse, the logarithmic mean valley duration is 1.28 +/- 0.15 s. Bursts of the short mode of T-90 are mainly single-pulse events, and the logarithmic mean pulse duration is much smaller, 0.20 +/- 0.01 s. For multipulse bursts of the T-90 long mode, marginal correlations were found between the parameters of the pulses and valleys and the number of pulses. The basic signatures of the evolution of pulses and valleys along the time course of bursts are examined. Conclusions are drawn concerning the physics of gamma-ray emission by taking into account these signatures. C1 Moscow Space Res Inst, Moscow 117810, Russia. Univ Alabama, Dept Phys, Huntsville, AL 35899 USA. NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. RP Mitrofanov, IG (reprint author), Moscow Space Res Inst, Profsojuznaya 84-32, Moscow 117810, Russia. NR 13 TC 13 Z9 15 U1 0 U2 1 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD SEP 10 PY 1998 VL 504 IS 2 BP 925 EP 934 DI 10.1086/306093 PN 1 PG 10 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 152KW UT WOS:000077777500029 ER PT J AU Reames, DV Ng, CK AF Reames, DV Ng, CK TI Streaming-limited intensities of solar energetic particles SO ASTROPHYSICAL JOURNAL LA English DT Article DE acceleration of particles; shock waves; Sun : corona; Sun : particle emission ID HYDROMAGNETIC WAVE EXCITATION; EJECTION-DRIVEN SHOCKS; INTERPLANETARY MEDIUM; ION-ACCELERATION; CHARGE-STATE; FLARES AB Energetic particles streaming outward from an intense source near the Sun reach a maximum-intensity plateau when scattering by self-generated waves restricts the streaming. We compare calculated theoretical values of the streaming-limited intensities with observations from the Hellos 1 and 2 and the NOAA Geostationary Operational Environmental Satellites (GOES) spacecraft and examine the energy dependence and radial gradient of the intensities. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Royal Melbourne Inst Technol, Dept Math, Melbourne, Vic 3001, Australia. RP Reames, DV (reprint author), NASA, Goddard Space Flight Ctr, Code 661, Greenbelt, MD 20771 USA. NR 19 TC 84 Z9 84 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD SEP 10 PY 1998 VL 504 IS 2 BP 1002 EP 1005 DI 10.1086/306124 PN 1 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 152KW UT WOS:000077777500036 ER PT J AU Willson, RF Redfield, SL Lang, KR Thompson, BJ St Cyr, OC AF Willson, RF Redfield, SL Lang, KR Thompson, BJ St Cyr, OC TI First VLA observations of nonthermal metric bursts associated with coronal mass ejections detected by the Solar and Heliospheric Observatory SO ASTROPHYSICAL JOURNAL LA English DT Article DE Sun : corona; Sun : radio radiation ID NOISE STORMS; RADIO; EMISSION; WAVELENGTHS AB We present the first observations of nonthermal decimetric burst emission of the Sun using the new 400 cm (74 MHz) system at the VLA. Our VLA observations were carried out in collaboration with the Large Angle Spectroscopic Coronagraph (LASCO) and the Extreme-Ultraviolet Imaging Telescope (EIT) on board the Solar and Heliospheric Observatory spacecraft. Full-disk observations at 400 and 91 cm were used to study the spatial and temporal variations of nonthermal radio bursts during coronal mass ejections (CMEs) detected by LASCO as well as transient extreme-ultraviolet brightenings detected by the EIT. VLA snapshot maps at 400 cm revealed impulsive burst emission in the low corona that began near the estimated start time of the CME activity; that beginning also coincided with a C1.1 GOES X-ray burst and an EIT flarelike brightening. The nonthermal metric bursts then continued sporadically during the next several hours, which included the ejection of spatially separated CME components. The 400 cm bursts are contained within curved, or archlike, sources at a fixed radial distance but with a varying position between two active regions detected by the EIT near the limb, suggesting that they were emitted within large-scale magnetic loops. Our 91 cm observations also show the onset of a long-lasting type I noise storm following the initiation of CME activity, again suggesting an intimate relationship between the production of nonthermal particles and large-scale evolving plasma-magnetic field structures in the corona. C1 Tufts Univ, Dept Phys & Astron, Medford, MA 02155 USA. NASA, Goddard Space Flight Ctr, SOHO Expt Operat & Anal Facil, Greenbelt, MD 20771 USA. NASA, Goddard Space Flight Ctr, CPI, USN,Res Lab, Greenbelt, MD 20771 USA. RP Willson, RF (reprint author), Tufts Univ, Dept Phys & Astron, Medford, MA 02155 USA. RI Thompson, Barbara/C-9429-2012; OI Redfield, Seth/0000-0003-3786-3486 NR 21 TC 15 Z9 15 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD SEP 10 PY 1998 VL 504 IS 2 BP L117 EP L121 DI 10.1086/311585 PN 2 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 152KY UT WOS:000077777700015 ER PT J AU Donnellan, A Lyzenga, GA AF Donnellan, A Lyzenga, GA TI GPS observations of fault afterslip and upper crustal deformation following the Northridge earthquake SO JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH LA English DT Article ID LOS-ANGELES BASIN; 1989 LOMA-PRIETA; SOUTHERN-CALIFORNIA; 1994 NORTHRIDGE; VENTURA-BASIN; KINEMATICS; REGION; MOTION; RATES; SCALE AB Global Positioning System (GPS) observations indicate that significant aseismic deformation occurred in the year following the January 17, 1994, Northridge earthquake. The postseismic observations show the same sense of motion as the coseismic. Compared with the coseismic displacements, the far-field postseismic motions (1-2 fault dimensions away) are proportionally larger than those seen in the near field. The postseismic data are best modeled with two faults: one on the rupture plane and one located in the shallow crust. The upper crustal fault may represent an actual fault or may be indicative of viscous relaxation occurring in the upper crust. The inferred afterslip and/or relaxation moment is approximately 2.9 x 10(18) N m or 22% of the mainshock moment release. We expect that the moment release due to the afterslip and relaxation effectively reduce the earthquake hazard locally. It is not clear from this study how the postseismic deformation loads the surrounding faults or alters the state of stress oil those faults. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Harvey Mudd Coll, Claremont, CA 91711 USA. RP CALTECH, Jet Prop Lab, Mail Stop 238-600,4800 Oak Grove Dr, Pasadena, CA 91109 USA. EM andrea@cobra.jpl.nasa.gov; gal@cobra.jpl.nasa.gov NR 33 TC 45 Z9 45 U1 0 U2 3 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-9313 EI 2169-9356 J9 J GEOPHYS RES-SOL EA JI J. Geophys. Res.-Solid Earth PD SEP 10 PY 1998 VL 103 IS B9 BP 21285 EP 21297 DI 10.1029/98JB01487 PG 13 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 119WE UT WOS:000075920500032 ER PT J AU Antipin, MY Timofeeva, TV Clark, RD Nesterov, VN Sanghadasa, M Barr, TA Penn, B Romero, L Romero, M AF Antipin, MY Timofeeva, TV Clark, RD Nesterov, VN Sanghadasa, M Barr, TA Penn, B Romero, L Romero, M TI Molecular crystal structures and nonlinear optical properties in the series of dicyanovinylbenzene and its derivatives SO JOURNAL OF PHYSICAL CHEMISTRY A LA English DT Article ID MM3 FORCE-FIELD; ORGANIC-MOLECULES; ELECTRIC-FIELD; X-RAY; POLARIZABILITIES; HYPERPOLARIZABILITIES; MECHANICS; SUSCEPTIBILITY; HYDROCARBONS; COMPOUND AB X-ray single-crystal structures, molecular mechanics (MM) calculations of the optimal molecular dimers, and calculations of the static second-order polarizabilities (beta) were performed for a large series of methoxy-and dimethylamino-substituted derivatives of dicyanovinylbenzene and some of its analogues having large values of the molecular nonlinear optical susceptibilities. X-ray structural analysis has been performed for 3,4-dimethoxy- and 3,4,5-trimethoxy-dicyanovinylbenzenes (I, II), p-(dimethylamino)-dicyanovinylbenzene (III), 1,1-dicyano-2-phenyl-2-(2-methoxyphenyl) (2-MeO-C6H4-C(C6H5)=C(CN)(2)) (IV), and 4-(4-methoxyphenyl)-1,1-dicyano-1,3-butadiene (4-MeO-C6P4-CH=CH-CH=C(CN)(2)) (V). Crystal packing analysis and energetic MM calculations revealed the factors responsible for the formation of the centrosymmetric crystals. Compounds III and V were found to form acentric crystal structures (space groups P2(1) and Pc, respectively) and therefore are capable to the second-harmonic generation (SHG) in solid state. Qualitative data have demonstrated that compound V is rather active in SHG in the powder state (using Nd:YAG laser with lambda = 1064 nm) that may be important for its application. On the contrary, the powder of III is not active in SHG despite the "optimal" crystal packing that might be related to the strong absorption of the second harmonic light at lambda = 532 nm, but this compound gives strong SHG signal using the laser light with lambda = 1907 nm. Analysis of the influence of the different substituents in the aromatic ring on the calculated beta values in the series of the compounds studied was made. C1 New Mexico Highlands Univ, Dept Phys Sci, Las Vegas, NM 87701 USA. Russian Acad Sci, Inst Organoelement Cpds, Moscow, Russia. Univ Alabama, Huntsville, AL 35899 USA. NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. RP Antipin, MY (reprint author), New Mexico Highlands Univ, Dept Phys Sci, Las Vegas, NM 87701 USA. NR 47 TC 24 Z9 24 U1 0 U2 4 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA SN 1089-5639 J9 J PHYS CHEM A JI J. Phys. Chem. A PD SEP 10 PY 1998 VL 102 IS 37 BP 7222 EP 7232 DI 10.1021/jp9806765 PG 11 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA 125CG UT WOS:000076219400004 ER PT J AU Morano, E Mavriplis, DJ Venkatakrishnan, V AF Morano, E Mavriplis, DJ Venkatakrishnan, V TI Coarsening strategies for unstructured multigrid techniques with application to anisotropic problems SO SIAM JOURNAL ON SCIENTIFIC COMPUTING LA English DT Article DE multigrid method; unstructured meshes; semicoarsening; anisotropic problems ID EULER EQUATIONS; VOLUME-AGGLOMERATION; MESHES; GRIDS AB Over the years, multigrid has been demonstrated as an efficient technique for solving inviscid flow problems. However, for viscous flows, convergence rates often degrade. This is generally due to the required use of stretched meshes (i.e., the aspect ratio AR = Delta y/Delta x <<1) in order to capture the boundary layer near the body. Usual techniques for generating a sequence of grids that produce proper convergence rates on isotropic meshes are not adequate for stretched meshes. This work focuses on the solution of Laplace's equation, discretized through a Galerkin fnite-element formulation on unstructured stretched triangular meshes. A coarsening strategy is proposed and results are discussed. C1 CALTECH, Grad Aeronaut Labs, Pasadena, CA 91125 USA. NASA, Inst Comp Applicat Sci & Engn, Langley Res Ctr, Hampton, VA 23681 USA. RP Morano, E (reprint author), CALTECH, Grad Aeronaut Labs, MS 205-45, Pasadena, CA 91125 USA. EM eric@galcit.caltech.edu; dimitri@icase.edu; venkat@icase.edu NR 23 TC 7 Z9 7 U1 2 U2 3 PU SIAM PUBLICATIONS PI PHILADELPHIA PA 3600 UNIV CITY SCIENCE CENTER, PHILADELPHIA, PA 19104-2688 USA SN 1064-8275 J9 SIAM J SCI COMPUT JI SIAM J. Sci. Comput. PD SEP 10 PY 1998 VL 20 IS 2 BP 393 EP 415 DI 10.1137/S1064827595287638 PG 23 WC Mathematics, Applied SC Mathematics GA 118MK UT WOS:000075842100001 ER PT J AU Knox, L Scoccimarro, R Dodelson, S AF Knox, L Scoccimarro, R Dodelson, S TI Impact of inhomogeneous reionization on cosmic microwave background anisotropy SO PHYSICAL REVIEW LETTERS LA English DT Article ID COLD DARK-MATTER; UNIVERSE; RADIATION AB Ir is likely that the reionization of the Universe did not occur homogeneously. Using a model that associates ionized patches with overdense regions, we find that the resulting cosmic microwave background (CMB) anisotropy power spectrum peaks at angular scales corresponding to the extent of the ionized regions, and has a width that reflects the correlations between them. There is considerable uncertainty in the amplitude. Neglecting inhomogeneous reionization in the determination of cosmological parameters from high resolution CMB maps may cause significant systematic error. C1 Canadian Inst Theoret Astrophys, Toronto, ON M5S 3H8, Canada. NASA, Fermi Natl Accelerator Lab, Ctr Astrophys, Batavia, IL 60510 USA. RP Knox, L (reprint author), Canadian Inst Theoret Astrophys, 60 St George St, Toronto, ON M5S 3H8, Canada. NR 27 TC 121 Z9 121 U1 0 U2 1 PU AMERICAN PHYSICAL SOC PI COLLEGE PK PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA SN 0031-9007 J9 PHYS REV LETT JI Phys. Rev. Lett. PD SEP 7 PY 1998 VL 81 IS 10 BP 2004 EP 2007 DI 10.1103/PhysRevLett.81.2004 PG 4 WC Physics, Multidisciplinary SC Physics GA 115TW UT WOS:000075682400005 ER PT J AU Konopliv, AS Binder, AB Hood, LL Kucinskas, AB Sjogren, WL Williams, JG AF Konopliv, AS Binder, AB Hood, LL Kucinskas, AB Sjogren, WL Williams, JG TI Improved gravity field of the moon from lunar prospector SO SCIENCE LA English DT Article ID ISOSTATIC COMPENSATION; BASIN FORMATION; CLEMENTINE; TECTONICS; EVOLUTION; MOMENTS; VENUS AB An improved gravity model from Doppler tracking of the Lunar Prospector (LP) spacecraft reveals three new Large mass concentrations (mascons) on the nearside of the moon beneath the impact basins Mare Humboltianum, Mendel-Ryberg, and Schiller-Zucchius, where the Latter basin has no visible mare fill. Although there is no direct measurement of the Lunar farside gravity, LP partially resolves four mascons in the Large farside basins of Hertzsprung, Coulomb-Sarton, Freundlich-Sharonov, and Mare Moscoviense. The center of each of these basins contains a gravity maximum relative to the surrounding basin. The improved normalized polar moment of inertia (0.3932 +/- 0.0002) is consistent with an iron core with a radius of 220 to 450 kilometers. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Lunar Res Inst, Gilroy, CA 95020 USA. Univ Arizona, Lunar & Planetary Lab, Tucson, AZ 85721 USA. RP Konopliv, AS (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 41 TC 188 Z9 231 U1 3 U2 12 PU AMER ASSOC ADVANCEMENT SCIENCE PI WASHINGTON PA 1200 NEW YORK AVE, NW, WASHINGTON, DC 20005 USA SN 0036-8075 J9 SCIENCE JI Science PD SEP 4 PY 1998 VL 281 IS 5382 BP 1476 EP 1480 DI 10.1126/science.281.5382.1476 PG 5 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA 116RJ UT WOS:000075738100032 ER PT J AU Lin, RP Mitchell, DL Curtis, DW Anderson, KA Carlson, CW McFadden, J Acuna, MH Hood, LL Binder, A AF Lin, RP Mitchell, DL Curtis, DW Anderson, KA Carlson, CW McFadden, J Acuna, MH Hood, LL Binder, A TI Lunar surface magnetic fields and their interaction with the solar wind: Results from lunar prospector SO SCIENCE LA English DT Article ID IMPACT BASINS AB The magnetometer and electron reflectometer experiment on the Lunar Prospector spacecraft has obtained maps of Lunar crustal magnetic fields and observed the interaction between the solar wind and regions of strong crustal magnetic fields at high selenographic Latitude (30 degrees S to 80 degrees S) and Low (similar to 100 kilometers) altitude. Electron reflection maps of the regions antipodal to the Imbrium and Serenitatis impact basins, extending to 80 degrees S Latitude, show that crustal magnetic fields fill most of the antipodal zones of those basins. This finding provides further evidence for the hypothesis that basin-forming impacts result in magnetization of the lunar crust at their antipodes. The crustal magnetic fields of the Imbrium antipode region are strong enough to deflect the solar wind and form a miniature (100 to several hundred kilometers across) magnetosphere, magnetosheath, and bow shock system. C1 Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA. Univ Calif Berkeley, Dept Phys, Berkeley, CA 94720 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Lunar Res Inst, Gilroy, CA 95020 USA. Univ Arizona, Lunar & Planetary Lab, Tucson, AZ 85721 USA. RP Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA. EM mitchell@ssl.berkeley.edu NR 36 TC 141 Z9 149 U1 0 U2 14 PU AMER ASSOC ADVANCEMENT SCIENCE PI WASHINGTON PA 1200 NEW YORK AVE, NW, WASHINGTON, DC 20005 USA SN 0036-8075 EI 1095-9203 J9 SCIENCE JI Science PD SEP 4 PY 1998 VL 281 IS 5382 BP 1480 EP 1484 DI 10.1126/science.281.5382.1480 PG 5 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA 116RJ UT WOS:000075738100033 ER PT J AU Madore, BF Freedman, WL Silbermann, N Harding, P Huchrall, J Mould, JR Graham, JA Ferrarese, L Gibson, BK Han, MS Hoessel, JG Hughes, SM Illingworth, GD Phelps, R Sakai, S Stetson, P AF Madore, BF Freedman, WL Silbermann, N Harding, P Huchrall, J Mould, JR Graham, JA Ferrarese, L Gibson, BK Han, MS Hoessel, JG Hughes, SM Illingworth, GD Phelps, R Sakai, S Stetson, P TI A Cepheid distance to the Fornax cluster and local expansion rate of the Universe SO NATURE LA English DT Article ID HUBBLE-SPACE-TELESCOPE; TULLY-FISHER RELATION; VELOCITY-FIELD; NEARBY GALAXIES; SUPERCLUSTER; POPULATION; CONSTANT; CATALOG; MODEL AB Both galaxy distances and velocities are required for the determination of the expansion rate of the Universe, as described by the Hubble constant H-0. The radial velocities of galaxies arise not just from this expansion but also from random components and large-scale flows. To reach out to distances dominated by the overall cosmic expansion, it is necessary to probe large physical scales where galaxy-galaxy and galaxy-cluster interactions become less important. But accurate distances of nearby galaxies and clusters (commonly measured(1) using Cepheid variable stars) are nevertheless required to calibrate the indirect distance indicators generally used to measure these large scales. Here we report a Cepheid distance of 18.6 +/- 1.9 (statistical error) +/- 1.9 Mpe (systematic error) for the galaxy NGC1365 in Fornax, a cluster of galaxies in the Southern Hemisphere. We find a value of H-0 = 70 km s(-1) Mpc(-1) from Fornax alone, and 73 km s(-1) Mpc.(-1) from the intervening galaxy flow, each corrected for infall into the Virgo cluster. These values are consistent with the Hubble constant measured in the far field using secondary methods(2). Our data support previous suggestions(3-5) that the local small-scale velocity field has very small scatter (similar to+/-70km s(-1)). C1 CALTECH, Jet Prop Lab, Ctr Infrared Proc & Anal, NASA IPAC Extragalact Database, Pasadena, CA 91125 USA. Carnegie Inst Washington Observ, Pasadena, CA 91101 USA. Univ Arizona, Steward Observ, Tucson, AZ 85721 USA. Harvard Smithsonian Inst, Ctr Astrophys, Cambridge, MA 02138 USA. Australian Natl Univ, Mt Stromlo & Siding Spring Observ, Inst Adv Studies, Weston, ACT 2611, Australia. Carnegie Inst Washington, Dept Terr Magnetism, Washington, DC 20015 USA. CALTECH, MS Robinson Lab 105 24, Pasadena, CA 91125 USA. Univ Wisconsin, Dept Astron, Madison, WI 53706 USA. Royal Greenwich Observ, Cambridge CB3 0HA, England. Univ Calif Santa Cruz, Lick Observ, Santa Cruz, CA 95064 USA. Dominion Astrophys Observ, Victoria, BC V8X 4M6, Canada. RP Madore, BF (reprint author), CALTECH, Jet Prop Lab, Ctr Infrared Proc & Anal, NASA IPAC Extragalact Database, MS 100-22, Pasadena, CA 91125 USA. EM barry@ipac.caltech.edu RI Gibson, Brad/M-3592-2015 OI Gibson, Brad/0000-0003-4446-3130 NR 26 TC 46 Z9 46 U1 0 U2 3 PU MACMILLAN MAGAZINES LTD PI LONDON PA PORTERS SOUTH, 4 CRINAN ST, LONDON, ENGLAND N1 9XW SN 0028-0836 J9 NATURE JI Nature PD SEP 3 PY 1998 VL 395 IS 6697 BP 47 EP 50 DI 10.1038/25678 PG 4 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA 116JY UT WOS:000075722200040 ER PT J AU Lim, K Nadarajah, A Forsythe, EL Pusey, ML AF Lim, K Nadarajah, A Forsythe, EL Pusey, ML TI Locations of bromide ions in tetragonal lysozyme crystals SO ACTA CRYSTALLOGRAPHICA SECTION D-BIOLOGICAL CRYSTALLOGRAPHY LA English DT Article ID EGG-WHITE LYSOZYME; GROWTH-MECHANISM; CRYSTALLIZATION; REFINEMENT; RESOLUTION; APPARATUS; PROTEINS AB Anions have been shown to play a dominant role in the crystallization of chicken egg-white lysozyme from salt solutions. Previous studies employing X-ray crystallography have found one chloride ion binding site in the tetragonal crystal form of the protein and four nitrate ion binding sites in the monoclinic form. In this study the anion positions in the tetragonal form were determined from the difference Fourier map obtained from lysozyme crystals grown in bromide and chloride solutions. Five possible anion-binding sites were found in this manner. Some of these sites were in pockets containing basic residues while others were near neutral, but polar, residues. The sole chloride ion binding site found in previous studies was confirmed, while four further sites were found which corresponded to the four binding sites found for nitrate ions in monoclinic crystals. The study suggests that most of the anion-binding sites in lysozyme remain unchanged even when different anions and different crystal forms of lysozyme are employed. C1 Texas A&M Univ, Dept Biochem & Biophys, College Stn, TX 77843 USA. Univ Toledo, Dept Environm Chem & Engn, Toledo, OH 43606 USA. Univ Space Res Assoc, Huntsville, AL 35806 USA. NASA, Biophys Branch ES76, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. RP Lim, K (reprint author), Texas A&M Univ, Dept Biochem & Biophys, College Stn, TX 77843 USA. NR 24 TC 37 Z9 37 U1 0 U2 5 PU MUNKSGAARD INT PUBL LTD PI COPENHAGEN PA 35 NORRE SOGADE, PO BOX 2148, DK-1016 COPENHAGEN, DENMARK SN 0907-4449 J9 ACTA CRYSTALLOGR D JI Acta Crystallogr. Sect. D-Biol. Crystallogr. PD SEP 1 PY 1998 VL 54 BP 899 EP 904 DI 10.1107/S0907444998002844 PN 5 PG 6 WC Biochemical Research Methods; Biochemistry & Molecular Biology; Biophysics; Crystallography SC Biochemistry & Molecular Biology; Biophysics; Crystallography GA 120JA UT WOS:000075952200022 PM 9757106 ER PT J AU So, RMC Gatski, TB Sommer, TP AF So, RMC Gatski, TB Sommer, TP TI Morkovin hypothesis and the modeling of wall-bounded compressible turbulent flows SO AIAA JOURNAL LA English DT Article ID REYNOLDS-STRESS CLOSURE; NUMBER TURBULENCE; 2-EQUATION MODEL; CHANNEL FLOW; SHEAR-FLOW; SIMULATION; SUBLAYER; LAYERS AB Modeling of compressible wall-bounded turbulent flows relies on the hypothesis of Morkovin, who suggested that compressibility effects on turbulence could be accounted for by the mean density variations alone. This hypothesis has been shown to yield good results for the mean velocity and mean temperature fields when the incompressible turbulence models are extended directly to calculate compressible turbulent boundary layers. However, its applicability for the turbulence field has been less closely scrutinized. The reason is the lack of sufficiently detailed compressible turbulence data for comparison. Such data are now becoming available. Therefore, the purpose here is to assess the applicability of the Morkovin hypothesis to the turbulence field using direct numerical simulation data of a supersonic, flat plate boundary layer A near-wall Reynolds-stress closure based on a quasi-linear pressure-strain model is used to calculate this supersonic, boundary-layer flow. Comparisons between calculations and direct numerical simulation data show that the Morkovin hypothesis is just as applicable for the turbulence field and there is a dynamic similarity between the near-wall turbulence field of an incompressible and a compressible wall-bounded turbulent flow, In addition, the validation of this model is reported for compressible flow calculations covering a wide range of Mach numbers with adiabatic and constant-temperature wall boundary conditions, These results show that the model yields good predictions of Bat-plate turbulent boundary layers up to a Mach number of 10.31. C1 Hong Kong Polytech Univ, Dept Mech Engn, Kowloon, Hong Kong. NASA, Langley Res Ctr, Flow Phys Branch, Hampton, VA 23681 USA. ABB Power Generat Ltd, Gas Turbine Grp, CH-5401 Baden, Switzerland. RP So, RMC (reprint author), Hong Kong Polytech Univ, Dept Mech Engn, Kowloon, Hong Kong. NR 42 TC 10 Z9 10 U1 0 U2 2 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0001-1452 J9 AIAA J JI AIAA J. PD SEP PY 1998 VL 36 IS 9 BP 1583 EP 1592 DI 10.2514/2.584 PG 10 WC Engineering, Aerospace SC Engineering GA 114QM UT WOS:000075620400005 ER PT J AU Wright, MJ Candler, GV Bose, D AF Wright, MJ Candler, GV Bose, D TI Data-parallel line relaxation method for the Navier-Stokes equations SO AIAA JOURNAL LA English DT Article AB The Gauss-Seidel line relaxation method is modified for the simulation of viscous flows on massively parallel computers. The resulting data-parallel line relaxation method is shown to have good convergence properties for a series of test cases. The new method requires significantly more memory than the previously developed data-parallel relaxation methods, but it reaches a steady-state solution in much less time for all cases tested to date. In addition, the data-parallel line relaxation method shows good convergence properties even on the high-cell-aspect-ratio grids required to simulate high-Reynolds-number hows, The new method is implemented using message passing on the Gray T3E, and the parallel performance of the method on this machine is discussed. The data-parallel line relaxation method combines the fast convergence of the Gauss-Seidel line relaxation method with a high parallel efficiency and thus shows promise for large-scale simulation of viscous flows. C1 Univ Minnesota, Dept Aerosp Engn & Mech, Minneapolis, MN 55455 USA. Univ Minnesota, Army High Performance Comp Res Ctr, Minneapolis, MN 55455 USA. RP Wright, MJ (reprint author), NASA, Ames Res Ctr, Thermosci Inst, Mail Stop 230-3, Moffett Field, CA 94035 USA. NR 14 TC 131 Z9 134 U1 2 U2 5 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0001-1452 J9 AIAA J JI AIAA J. PD SEP PY 1998 VL 36 IS 9 BP 1603 EP 1609 DI 10.2514/2.586 PG 7 WC Engineering, Aerospace SC Engineering GA 114QM UT WOS:000075620400007 ER PT J AU Edwards, JR Liou, MS AF Edwards, JR Liou, MS TI Low-diffusion flux-splitting methods for flows at all speeds SO AIAA JOURNAL LA English DT Article; Proceedings Paper CT AIAA 13th Computational Fluid Dynamics Conference CY JUN 29-JUL 02, 1997 CL SNOWMASS VILLAGE, COLORADO SP Amer Inst Aeronaut & Astronaut ID BACKWARD-FACING STEP; VISCOUS FLOWS; SCHEME AB Methods for extending the advective upwind splitting method (AUSM) family of low-diffusion flux-splitting schemes to operate effectively at all how speeds are developed. The extensions developed are designed for use with time-derivative preconditioning and are based on the idea that the speed of sound should cease to be an important scaling parameter for the diffusive contributions to the interface flux as the Mach number becomes small. Using this criterion, alternative definitions for the interface Mach numbers are developed, and methods for ensuring pressure-velocity coupling at low speeds are formulated. Results are presented for inviscid flows through a channel at various Mach numbers, developing viscous flow in a two-dimensional duct, driven-cavity Bows at various Mach and Reynolds numbers, flow over a backward-facing step, and hydrogen-nitrogen mixing lagers. C1 N Carolina State Univ, Dept Mech & Aerosp Engn, Raleigh, NC 27695 USA. NASA, Lewis Res Ctr, Turbomachinery & Prop Syst Div, Cleveland, OH 44135 USA. RP Edwards, JR (reprint author), N Carolina State Univ, Dept Mech & Aerosp Engn, Campus Box 7910, Raleigh, NC 27695 USA. NR 23 TC 109 Z9 125 U1 0 U2 7 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0001-1452 J9 AIAA J JI AIAA J. PD SEP PY 1998 VL 36 IS 9 BP 1610 EP 1617 DI 10.2514/2.587 PG 8 WC Engineering, Aerospace SC Engineering GA 114QM UT WOS:000075620400008 ER PT J AU Sonnenfroh, DM Kessler, WJ Magill, JC Upschulte, BL Allen, MG Barrick, JDW AF Sonnenfroh, DM Kessler, WJ Magill, JC Upschulte, BL Allen, MG Barrick, JDW TI In-situ sensing of tropospheric water vapor using an airborne near-IR diode laser hygrometer SO APPLIED PHYSICS B-LASERS AND OPTICS LA English DT Article ID SPECTROMETER; ABSORPTION AB We describe a near-IR diode laser hygrometer developed for in-situ measurement of water vapor from airborne platforms throughout the troposphere. The sensor is based on the absorption of a 1.39-mu m diode laser beam and employs an open, folded 50-cm absorption path placed in the freestream air using an external probe. Water vapor number density is continuously recorded at 10 Hz. Extensive laboratory testing showed a sensitivity of 10(12) molecules cm(-3) Hz(-1/2) (signal-to-noise ratio 3). This is equivalent to a mixing ratio of 0.3 ppmv at average midlatitude tropopause conditions or a mixing ratio of 0.6 ppmv under boundary-layer conditions. The corresponding minimum measurable absorbance is 10-5 Hz(-1/2). Th, laser hygrometer was field-demonstrated aboard the NASA P3B research aircraft, during a series of flights spanning several weeks in the summer of 1997. During this demonstration, the laser hygrometer was intercompared with two optical chilled minor hygrometers. In general, the laser hygrometer performed well; however, under some conditions, it reported water vapor number densities 20% greater than the cryogenic frost-point hygrometer. This difference is currently under study. C1 Phys Sci Inc, Andover, MA 01810 USA. NASA, Langley Res Ctr, Hampton, VA 23681 USA. RP Sonnenfroh, DM (reprint author), Phys Sci Inc, 20 New England Business Ctr, Andover, MA 01810 USA. EM sonnenfroh@psicorp.com; kessler@psicorp.com; magill@psicorp.com; upschulte@psicorp.com; allen@psicorp.com; j.d.barrick@larc.nasa.gov NR 16 TC 33 Z9 34 U1 0 U2 2 PU SPRINGER VERLAG PI NEW YORK PA 175 FIFTH AVE, NEW YORK, NY 10010 USA SN 0946-2171 J9 APPL PHYS B-LASERS O JI Appl. Phys. B-Lasers Opt. PD SEP PY 1998 VL 67 IS 3 BP 275 EP 282 DI 10.1007/s003400050506 PG 8 WC Optics; Physics, Applied SC Optics; Physics GA 118UW UT WOS:000075859600003 ER PT J AU De Propris, R Pritchet, CJ AF De Propris, R Pritchet, CJ TI The faint end of the galaxy luminosity function in Abell 426 and 539 SO ASTRONOMICAL JOURNAL LA English DT Article DE galaxies : clusters : individual (Abell 426, Abell 539); galaxies : luminosity function, mass function ID DWARF GALAXIES; COMA CLUSTER; REDSHIFT SURVEY; RICH CLUSTERS; PHOTOMETRY; SAMPLE; COUNTS; ORIGIN; CFHT AB We derive I-band luminosity functions for galaxies in Abell 426 (Perseus and Abell 539, two rich, low Galactic latitude clusters at moderate redshift. Cluster members are selected via the color-magnitude relation for bright galaxies. We find alpha = - 1.56 +/- 0.07 for Perseus over the range - 19.4 < M(I) < - 13.4 (15 < I < 21) and alpha = -1.42 +/- 0.14 for - 18.5 < M(I) < - 14 (17 < I < 21.5) for A539. These luminosity functions are similar to those derived in Virgo and Fornax, weakly supporting claims for the existence of a universal luminosity function for galaxies in clusters. C1 Univ Victoria, Dept Phys & Astron, Victoria, BC V8W 3P6, Canada. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP De Propris, R (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. EM propris@coma.jpl.nasa.gov; pritchet@clam.phys.uvic.ca NR 51 TC 19 Z9 19 U1 0 U2 1 PU IOP PUBLISHING LTD PI BRISTOL PA DIRAC HOUSE, TEMPLE BACK, BRISTOL BS1 6BE, ENGLAND SN 0004-6256 J9 ASTRON J JI Astron. J. PD SEP PY 1998 VL 116 IS 3 BP 1118 EP 1124 DI 10.1086/300479 PG 7 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 121XG UT WOS:000076040700008 ER PT J AU Sahu, MS AF Sahu, MS TI Interstellar absorption lines in the spectrum of the starburst galaxy NGC 1705 SO ASTRONOMICAL JOURNAL LA English DT Article DE galaxies : individual (NGC 1705); galaxies : ISM; ultraviolet emission ID NGC-1705; POPULATIONS; REDSHIFTS; CLOUDS; STARS; DISK; HALO AB A Goddard High Resolution Spectrograph archival study of the interstellar absorption lines in the line of sight to the H I-rich, starburst dwarf galaxy NGC 1705 in the 1170 to 1740 Angstrom range at similar to 120 km s(-1) resolution is presented. The absorption features arising because of photospheric lines are distinctly different from the interstellar lines: the photospheric lines are weak, broad (equivalent widths >1 Angstrom), asymmetric, and centered around the systemic LSR velocity of NGC 1705 (similar to 610 km s(-1)). The interstellar lines consist of three relatively narrow components at LSR velocities of -20, 260, and 540 km s(-1), and include absorption by neutral atoms (N I lambda 1200 triplet and O I lambda 1302), singly ionized atoms (Si II lambda lambda 1190, 1193, 1260, 1304, and 1526, S II lambda 1253, C II lambda 1334, C II* lambda 1336, Fe II lambda 1608, and Al II lambda 1670), and atoms in higher ionization states (Si III lambda 1206, Si Iv lambda lambda 1393, 1402, and C Iv lambda lambda 1548, 1550). The Si Iv and C Iv absorption features have both interstellar and photospheric contributions. In an earlier study, Sahu & Blades identified the absorption system at -20 km s(-1) with Milky Way disk/halo gas, and the 260 km s(-1) system with a small, isolated high-velocity cloud HVC 487, which is probably associated with Magellanic Stream gas. The 540 km s(-1) absorption system is associated with a kiloparsec-scale expanding, ionized supershell centered on the super-star cluster NGC 1705-1. The analysis presented in this paper consists of (1) a list of all interstellar absorption features with greater than 3 sigma significance and their measured equivalent widths, (2) plots of the lines in the various atomic species together with the results of nonlinear least-squares fit profiles to the observed data, and (3) unpublished 21 cm maps from the Wakker & van Woerden survey showing the large-scale H I distribution in the region near the NGC 1705 sight line and HVC 487. Furthermore, weak N I lambda 1200 triplet absorption for the supershell component is reported, which in the absence of dust depletion and ionization corrections implies a low N abundance. A low N abundance for the supershell is consistent with an interpretation of nucleosynthetic enrichment by time-delayed primary nitrogen production, the age estimate of (10-20) x 10(6) yr for the central super-star cluster NGC 1705-1 of Heckman & Leitherer, and the underabundance of Fe reported by Sahu & Blades. However, using the N I lambda 1200 triplet alone to estimate the total N abundance could result in a severe underestimation of this quantity: although N does not deplete onto interstellar dust grains, photoionization and collisional ionization effects could increase the fraction of N found in higher ionization stages. Uncertainties in the total N abundance caused by photoionization and collisional ionization effects can only be addressed by future observations of the higher ionization lines, namely, N II lambda 1084 and N III lambda 989. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Natl Opt Astron Observ, Tucson, AZ USA. RP Sahu, MS (reprint author), NASA, Goddard Space Flight Ctr, Code 681, Greenbelt, MD 20771 USA. NR 27 TC 11 Z9 11 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5801 S ELLIS AVENUE, CHICAGO, IL 60637 USA SN 0004-6256 J9 ASTRON J JI Astron. J. PD SEP PY 1998 VL 116 IS 3 BP 1205 EP 1211 DI 10.1086/300524 PG 7 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 121XG UT WOS:000076040700014 ER PT J AU Sahai, R Trauger, JT AF Sahai, R Trauger, JT TI Multipolar bubbles and jets in low-excitation planetary nebulae: Toward a new understanding of the formation and shaping of planetary nebulae SO ASTRONOMICAL JOURNAL LA English DT Article DE circumstellar matter; planetary nebulae : general; planets and satellites : general; stars : AGB and post-AGB; stars : mass loss ID STATISTICAL DISTANCE SCALE; MASS-LOSS; CIRCUMSTELLAR ENVELOPES; BROWN DWARFS; RED GIANTS; STARS; EVOLUTION; EMISSION; BIPOLAR; CATALOG AB First results from a Hubble Space Telescope Wide Field Planetary Camera 2 H alpha imaging survey of young planetary nebulae (PNs) are reported. The PNs have been selected on the basis of their low excitation characteristics. All objects imaged so far show highly aspherical morphology, with a majority characterized by multipolar bubbles distributed roughly point-symmetrically around the central star. In some objects, bipolar ansae or collimated radial structures are seen, indicating the presence of jets, whereas in others bright structures near the minor axes indicate the presence of disks or torii. The complexity, organization, and symmetry of the above structures lead us to propose that the primary agent for shaping PNs is high-speed collimated outflows or jets that operate during the late asymptotic galactic branch (AGB) and/or early post-AGB evolutionary phase, and not a preexisting equatorial density enhancement as envisioned in the currently popular model. These outflows carve out a complex imprint within an intrinsically spherical AGB circumstellar envelope (CSE). Subsequent expansion of a hot, tenuous stellar wind from the post-AGB star inside the imprinted AGB CSE then produces the observed PN, whose shape and structure depend in detail on how the characteristics of the jets change with time. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Sahai, R (reprint author), CALTECH, Jet Prop Lab, Mail Stop 183-900,4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 59 TC 319 Z9 319 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5801 S ELLIS AVENUE, CHICAGO, IL 60637 USA SN 0004-6256 J9 ASTRON J JI Astron. J. PD SEP PY 1998 VL 116 IS 3 BP 1357 EP 1366 DI 10.1086/300504 PG 10 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 121XG UT WOS:000076040700029 ER PT J AU Noriega-Crespo, A Garnavich, PM Molinari, S AF Noriega-Crespo, A Garnavich, PM Molinari, S TI Isocam molecular hydrogen images of the Cepheus E outflow SO ASTRONOMICAL JOURNAL LA English DT Article DE infrared radiation; ISM : jets and outflows; stars : formation; stars : pre-main-sequence ID CEP-E; DUST; EMISSION; OBJECTS; CLOUD AB The physical characteristics of the Cepheus E "embedded" outflow are analyzed using ISOCAM images in the upsilon = 0-0 S(5) 6.91 mu m and S(3) 9.66 mu m molecular hydrogen lines. We find that the morphology of the Cep E outflow in the ground vibrational H-2 lines is similar to that in the near-infrared upsilon = 1-0 2.12 mu m line. At these mid-infrared wavelengths, we detect neither the second H-2 outflow that is almost perpendicular to the Cep E 2.12 mu m flow nor traces of H-2 emission along the second (CO)-C-12 J = 2-1 outflow, at an angle of similar to 52 degrees, down to a surface brightness of 12-46 mu Jy arcsec(-2). We do detect at 6.91 mu m the likely source of the main H-2 and CO outflows, IRAS 23011 + 6126, and show that the source is easily seen in all IRAS bands using HIRES images. The source is not detected at 9.66 mu m, but we think this agrees with the interstellar extinction curve, which has a minimum at similar to 7 mu m but rises at similar to 9.7 mu m as a result of the strong absorption silicate feature, enhanced in this case by a cocoon surrounding the Class 0 object. This idea is supported by our models of the spectral energy distribution (SED) of the central object. The models assume that the main source of opacity is due to bare silicates, and our best fit for the SED yields a total envelope mass of 17 M. and a dust temperature of 18 K. C1 CALTECH, Ctr Infrared Proc & Anal, Pasadena, CA 91125 USA. Harvard Smithsonian Ctr Astrophys, Cambridge, MA 02138 USA. CALTECH, Jet Prop Lab, Ctr Infrared Proc & Anal, Pasadena, CA 91125 USA. RP Noriega-Crespo, A (reprint author), CALTECH, Ctr Infrared Proc & Anal, Mail Stop 100-22, Pasadena, CA 91125 USA. RI Molinari, Sergio/O-4095-2016 OI Molinari, Sergio/0000-0002-9826-7525 NR 21 TC 16 Z9 16 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5801 S ELLIS AVENUE, CHICAGO, IL 60637 USA SN 0004-6256 J9 ASTRON J JI Astron. J. PD SEP PY 1998 VL 116 IS 3 BP 1388 EP 1395 DI 10.1086/300521 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 121XG UT WOS:000076040700032 ER PT J AU Reipurth, B Devine, D Bally, J AF Reipurth, B Devine, D Bally, J TI Herbig-Haro flows from the L1641-N embedded infrared cluster SO ASTRONOMICAL JOURNAL LA English DT Article DE ISM : clouds; ISM : jets and outflows; stars : formation; stars : pre-main-sequence ID COLD IRAS SOURCES; STELLAR POPULATION; STAR-FORMATION; MOLECULAR GAS; YOUNG STARS; DARK CLOUD; OUTFLOWS; OBJECTS; ORION; REGION AB We have discovered a large number of Herbig-Haro (HH) flows associated with the embedded infrared cluster surrounding the IRAS source 05338-0624, the driving source of the L1641-N molecular outflow. The best collimated HH flow in the region, HH 303, stretches in two groups of knots along a well-defined axis from the VLA source that coincides with the IRAS source. This HH flow is coaxial with the blue northern lobe of the molecular flow. To the north-northwest of the cluster we find a long series of very large and finely shaped bow shocks, which stretch on a well-defined axis away from the cluster. The most distant HH object, HH 310, is 6.3 pc in projection from the center of the cluster, making it the largest HH lobe known from a low-mass star. We identify the counterlobe with an already known chain of infrared H-2 emission knots. Additionally, we find two very large fragmented bow shocks, HH 403 and 404, to the northeast of and facing away from the cluster. They lie on an axis that passes through the cluster at projected distances of 4.2 and 5.4 pc. In the opposite direction, to the southwest we identify the previously known object HH 127 at a projected distance of 5.2 pc from the cluster and within an angle of 10 degrees of the HH 403/404 axis. HH 127 consists of three faint knots also on a line through the cluster. Precisely south of the VLA source and on the axis of the HH 303 jet, we find a large bow shock, HH 61, which is 5.9 pc in projection from the cluster, and which we believe is part of the counterflow to the HH 303 jet. Our CCD images and (CO)-C-13 maps clearly show that HH 61 and HH 127 are located just beyond the well-defined edge of the L1641 cloud, which explains why they are optically visible. Our extensive (CO)-O-18 map of the region shows that the cluster is associated with a prominent cloud core. Our (CO)-C-12 map reveals, in addition to the known L1641-N outflow, a large pair of compact low-velocity outflow lobes, a southeastern blueshifted lobe, and a northwestern redshifted lobe, separated by 2.7 pc and centered on the infrared cluster. The numerous outflows in the region provide evidence that a large number of the young stars in the loose cluster are presently in active mass-losing phases. The L1641-N cluster is clearly the presently most active site of low-mass star formation in the L1641 molecular cloud. C1 Univ Colorado, Ctr Astrophys & Space Astron, Boulder, CO 80309 USA. NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, Greenbelt, MD 20771 USA. Univ Colorado, Dept Astrophys & Planetary Sci, Boulder, CO 80309 USA. Univ Colorado, Ctr Astrophys & Space Astron, Boulder, CO 80309 USA. RP Reipurth, B (reprint author), Univ Colorado, Ctr Astrophys & Space Astron, Campus Box 389, Boulder, CO 80309 USA. OI BALLY, JOHN/0000-0001-8135-6612 NR 34 TC 34 Z9 34 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5801 S ELLIS AVENUE, CHICAGO, IL 60637 USA SN 0004-6256 J9 ASTRON J JI Astron. J. PD SEP PY 1998 VL 116 IS 3 BP 1396 EP 1411 DI 10.1086/300513 PG 16 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 121XG UT WOS:000076040700033 ER PT J AU Ozernoy, LM Fridman, AM Biermann, PL AF Ozernoy, LM Fridman, AM Biermann, PL TI Angular momentum transport in the central region of the Galaxy SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE Galaxy : center; accretion, accretion disks; turbulence; ISM : clouds; ISM : kinematics and dynamics ID GALACTIC-CENTER; MOLECULAR CLOUDS; DYNAMICS AB We discuss mechanisms for angular momentum transport in the clumpy medium of the circumnuclear disk at the Galactic center. The viscosity due to clump-clump collisions is found to be less than some critical viscosity; this meets the conditions at which a collective mode of nonaxisymmetric shear perturbations in the disk is able to grow until going into the saturation regime where fully developed turbulence is established. We find that the angular momentum transfer-due to this turbulent viscosity turns out to comparable to the transport due to magnetic torques. Taken together, the turbulent and magnetic transfer of angular momentum are able to provide the inflow of mass into the central parsec with a rate of about 10(-2) M-., yr(-1) consistent with the available data. C1 George Mason Univ, Computat Sci Inst, Fairfax, VA 22030 USA. George Mason Univ, Dept Phys & Astron, Fairfax, VA 22030 USA. NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, Greenbelt, MD 20771 USA. Russian Acad Sci, Inst Astron, Moscow 109017, Russia. Moscow State Univ, Moscow 119899, Russia. Max Planck Inst Radioastron, D-53010 Bonn, Germany. RP Ozernoy, LM (reprint author), George Mason Univ, Computat Sci Inst, Fairfax, VA 22030 USA. EM ozernoy@science.gmu.edu; afridman@inasan.rssi.ru; p165bie@mpifr-bonn.mpg.de NR 26 TC 6 Z9 6 U1 0 U2 0 PU EDP SCIENCES S A PI LES ULIS CEDEX A PA 17, AVE DU HOGGAR, PA COURTABOEUF, BP 112, F-91944 LES ULIS CEDEX A, FRANCE SN 0004-6361 J9 ASTRON ASTROPHYS JI Astron. Astrophys. PD SEP PY 1998 VL 337 IS 1 BP 105 EP 112 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 119ZQ UT WOS:000075929500019 ER PT J AU Schutte, WA van der Hucht, KA Whittet, DCB Boogert, ACA Tielens, AGGM Morris, PW Greenberg, JM Williams, PM van Dishoeck, EF Chiar, JE de Graauw, T AF Schutte, WA van der Hucht, KA Whittet, DCB Boogert, ACA Tielens, AGGM Morris, PW Greenberg, JM Williams, PM van Dishoeck, EF Chiar, JE de Graauw, T TI ISO-SWS observations of infrared absorption bands of the diffuse interstellar medium: The 6.2 mu m feature of aromatic compounds SO ASTRONOMY & ASTROPHYSICS LA English DT Review DE infrared : ISM : lines and bands; Galaxy : abundances; ISM : dust, extinction; methods : observational ID HYDROGENATED AMORPHOUS-CARBON; WOLF-RAYET STARS; GALACTIC-CENTER; MOLECULAR CLOUDS; SIZE DISTRIBUTION; EMISSION BANDS; SOLID-STATE; MILKY-WAY; DUST; SPECTROSCOPY AB We present ISO-SWS spectroscopy of eight strong infrared sources with large extinction through the diffuse interstellar medium. These are five late-type Wolf-Rayet stars, the blue hypergiant Cyg OB2 #12 and the Galactic Center Sources 3 and 4. The spectra show a number of absorption features that can be ascribed to interstellar dust and gas. Features at 3.0, 3.4, 4.66 and 5.95 mu m were already known from ground and airborne observations, while features at 4.27 and 6.21 mu m are for the first time observed by ISO. We ascribe the 3.0, 4.27 and 4.66 mu m features to H(2)O ice, CO(2) ice and gaseous CO, respectively, located in dense clouds along four lines-of-sight in our study. Based on an excellent correspondence with the well-known emission feature observed in many other objects, the 6.2 mu m absorption band is identified with aromatic materials. The profile of the feature indicates that its carriers are PAHs or PAH clusters containing up to a few thousand carbon atoms. The lack of strong infrared features of hydroxy (OH), carbonyl (C=O) and aromatic CH groups towards the objects of the present study shows that the carbonaceous dust material in the diffuse ISM is poor in oxygen as well as hydrogen. C1 Leiden Observ, NL-2300 RA Leiden, Netherlands. SRON, NL-3584 CA Utrecht, Netherlands. Rensselaer Polytech Inst, Dept Phys Appl Phys & Astron, Troy, NY 12180 USA. Kapteyn Astron Inst, NL-9700 AV Groningen, Netherlands. VILSPA, ESA Astrophys Div, ISO Sci Operat Ctr, E-28080 Madrid, Spain. Royal Observ, Edinburgh EH9 3HJ, Midlothian, Scotland. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Space Res Org Netherlands, NL-9700 AV Groningen, Netherlands. RP Schutte, WA (reprint author), Leiden Observ, POB 9513, NL-2300 RA Leiden, Netherlands. NR 101 TC 76 Z9 77 U1 0 U2 2 PU EDP SCIENCES S A PI LES ULIS CEDEX A PA 17, AVE DU HOGGAR, PA COURTABOEUF, BP 112, F-91944 LES ULIS CEDEX A, FRANCE SN 0004-6361 J9 ASTRON ASTROPHYS JI Astron. Astrophys. PD SEP PY 1998 VL 337 IS 1 BP 261 EP 274 PG 14 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 119ZQ UT WOS:000075929500034 ER PT J AU Ruzmaikin, A Berger, MA AF Ruzmaikin, A Berger, MA TI On a source of Alfven waves heating the solar corona SO ASTRONOMY & ASTROPHYSICS LA English DT Letter DE solar corona heating : magnetic fields ID CROSSING NUMBER; MAGNETIC-FIELDS; ENERGY-SPECTRUM; WIND; ACCELERATION; FLUX AB Studies of the origin of coronal heating and acceleration of the solar wind invoke high-frequency Alfven waves. Here we suggest a source for such waves associated with twisted magnetic loops emerging on the solar surface and reconnecting with the open field. We identify the loops with the ephemeral regions (small-scale bipoles) observed by ground-based instruments and by SOHO. To characterize the loops we employ the concept of a minimum energy state for topologically complex fields. Emerging loops release energy relaxing to the minimum state. Relaxation along the minimum state-due to a competition between footpoint twisting by photospheric motions and reconnections inside the loops- releases blinks of energy into the solar atmosphere. We estimate the power released and the range of wave frequencies. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. UCL, Dept Math, London WC1E 6BT, England. RP Ruzmaikin, A (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. EM aruzmaikin@jplsp.jpl.nasa.gov; mberger@math.ucl.ac.uk NR 20 TC 38 Z9 38 U1 2 U2 2 PU EDP SCIENCES S A PI LES ULIS CEDEX A PA 17, AVE DU HOGGAR, PA COURTABOEUF, BP 112, F-91944 LES ULIS CEDEX A, FRANCE SN 0004-6361 J9 ASTRON ASTROPHYS JI Astron. Astrophys. PD SEP PY 1998 VL 337 IS 1 BP L9 EP L12 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 119ZQ UT WOS:000075929500003 ER PT J AU Wietfeldt, R Van Straten, W Del Rizzo, D Bartel, N Cannon, W Novikov, A AF Wietfeldt, R Van Straten, W Del Rizzo, D Bartel, N Cannon, W Novikov, A TI The S2 baseband processing system for phase-coherent pulsar applications SO ASTRONOMY & ASTROPHYSICS SUPPLEMENT SERIES LA English DT Article DE pulsars; radio astronomy; baseband recording; coherent de-dispersion AB The S2 baseband processing system (S2-BPS) is designed for a variety of pulsar measurements such as ultrafast signal fluctuations and pulse timing. Its key features are: the S2 recorder; the S2 Tape-to-Computer Interface (S2-TCI) which provides an efficient high data rate transfer from S2 tapes to computer; and the tightly coupled control interface to the computer which enables automated data transfer and processing. Developed originally for VLBI applications, the S2 recorder is based on the use of commercial VHS tape transports (VCR's), modified for use in digital high density, high data rate applications, A single S2 recorder "tape-set" of eight SVHS tapes provides up to 500 GBytes of data storage, and an unattended operating time of up to 8.5 hours at the maximum data rate of 128 Mbits/s or 16 MBytes/s, corresponding typically to 16 MHz bandwidth in two circular polarizations at 2-bit quantization, which generates a data rate of up to 1 GByte/minute. With 16 MHz individual record channels, a single S2 yields a sample time resolution of 31 ns, For more challenging applications, multiple S2's may be used for increased bandwidth and higher time resolutions. In this paper, we present an overview of the S2 baseband processing system and plans for future implementations of the system, and demonstrate first results of Vela pulsar recordings at Parkes in September 1995. We pay specific attention to the S2-TCI, a system designed to transfer S2 recorded data from tape to computer memory (RAM) via direct memory access (DMA). Computer data may be processed locally or sent to a more powerful "remote'' (super) computer for processing. C1 Inst Space & Terr Sci, Toronto, ON M3J 3K1, Canada. York Univ, N York, ON M3J 1P3, Canada. RP CALTECH, Jet Prop Lab, 4800 Oak Grove Dr,MS 264-832, Pasadena, CA 91109 USA. NR 13 TC 11 Z9 11 U1 0 U2 0 PU EDP SCIENCES S A PI LES ULIS CEDEX A PA 17, AVE DU HOGGAR, PA COURTABOEUF, BP 112, F-91944 LES ULIS CEDEX A, FRANCE SN 0365-0138 J9 ASTRON ASTROPHYS SUP JI Astron. Astrophys. Suppl. Ser. PD SEP PY 1998 VL 131 IS 3 BP 549 EP 554 PG 6 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 111PT UT WOS:000075447400014 ER PT J AU Furuzawa, A Tawara, Y Kunieda, H Yamashita, K Sonobe, T Tanaka, Y Mushotzky, R AF Furuzawa, A Tawara, Y Kunieda, H Yamashita, K Sonobe, T Tanaka, Y Mushotzky, R TI ASCA observation of the distant cluster of galaxies Cl 0016+16 and implication for H-0 SO ASTROPHYSICAL JOURNAL LA English DT Article DE cosmology : observations; galaxies : clusters : individual (Cl 0016+16); X-rays : galaxies ID X-RAY-PROPERTIES; GAS IMAGING SPECTROMETER; HUBBLE CONSTANT; 3 CLUSTERS; ABELL-665; EVOLUTION AB We report the 0.5-10 keV X-ray image and spectrum of Cl 0016 + 16, which, at a redshift of 0.541, is one of the most distant clusters of galaxies observed with ASCA. The ASCA X-ray image is well represented by an isothermal beta model. The best-fit parameters for the core radius (theta(c)) and beta are 0.'6 and 0.7, respectively. However, because of ASCA's moderate spatial resolution, these two parameters are strongly correlated. The observed spectrum within a 6' radius is well fitted by a thin thermal emission model with a plasma temperature of 8.0 +/- 1.0 keV. The Sunyaev-Zeldovich (SZ) effect in Cl 0016+16 has been observed by Carlstrom et al. using an interferometer and by Birkinshaw et al. using a single-dish radio telescope. Combining the SZ microwave decrement with the plasma density and temperature profiles derived from our X-ray observation, we obtained a value of the Hubble constant of 47 +/- 14 km s(-1) Mpc(-1) with the profile parameters obtained by interferometric data, and 52 +/- 20 km s(-1) Mpc(-1) with our best-fit shape parameters and single-dish telescope data. C1 Nagoya Univ, Dept Phys, Chikusa Ku, Nagoya, Aichi 4648602, Japan. Inst Space & Astronaut Sci, Sagamihara, Kanagawa 2298510, Japan. NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. RP Furuzawa, A (reprint author), Nagoya Univ, Dept Phys, Chikusa Ku, Furo Cho, Nagoya, Aichi 4648602, Japan. EM furuzawa@u.phys.nagoya-u.ac.jp; tawara@u.phys.nagoya-u.ac.jp; kunieda@u.phys.nagoya-u.ac.jp; yamasita@u.phys.nagoya-u.ac.jp; sonobe@astro.isas.ac.jp; Y.Tanaka@sron.ruu.nl; richard@xray-5.gsfc.nasa.gov NR 39 TC 11 Z9 11 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD SEP 1 PY 1998 VL 504 IS 1 BP 35 EP 41 DI 10.1086/306040 PN 1 PG 7 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 152KT UT WOS:000077777200005 ER PT J AU Levine, DA Lonsdale, CJ Hurt, RL Smith, HE Helou, G Beichman, C Cesarsky, C Elbaz, D Klaas, U Laureijs, R Lemke, D Lord, S McMahon, R Moshir, M Neugebauer, G Soifer, BT Van Buren, D Wehrle, A Wolstencroft, R AF Levine, DA Lonsdale, CJ Hurt, RL Smith, HE Helou, G Beichman, C Cesarsky, C Elbaz, D Klaas, U Laureijs, R Lemke, D Lord, S McMahon, R Moshir, M Neugebauer, G Soifer, BT Van Buren, D Wehrle, A Wolstencroft, R TI First results from the ISO-IRAS Faint Galaxy Survey SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies : active; galaxies : photometry; infrared : galaxies; surveys ID EMISSION-LINE SPECTRA; INFRARED GALAXIES; QUASAR AB We present the first results from the ISO-IRAS Faint Galaxy Survey (IIFGS), a program designed to obtain ISO observations of the most distant and luminous galaxies in the IRAS Faint Source Survey by filling short gaps in the ISO observing schedule with pairs of 12 mu m ISOCAM and 90 mu m ISOPHOT observations. As of 1997 October, over 500 sources have been observed, with an ISOCAM detection rate over 80%, covering over 1.25 deg(2) of sky to an 11.5 mu m point-source completeness limit of approximately 1.0 mJy (corresponding to a similar to 10 sigma detection sensitivity). Observations are presented for nine sources detected by ISOPHOT and ISOCAM early in the survey for which we have ground-based G- and I-band images and optical spectroscopy. The ground-based data confirm that the IIFGS strategy efficiently detects moderate-redshift (z = 0.11-0.38 for this small sample) strong emission line galaxies with L-60 mu m greater than or similar to 10(11) L.; one of our sample has L-60 mu m > 10(12) L. (H-0 = 75 km s(-1) Mpc(-1), Omega = 1). The infrared-optical spectral energy distributions are comparable to those of nearby luminous infrared galaxies, which span the range from pure starburst (e.g., Arp 220) to infrared QSO (Mrk 231). Two of the systems show signs of strong interaction, and four show active galactic nucleus (AGN)-like excitation; one of the AGNs, F15390+6038, which shows a high excitation Seyfert 2 spectrum, has an unusually warm far- to mid-infrared color and may be an obscured QSO. The IIFGS sample is one of the largest and deepest samples of infrared-luminous galaxies available, promising to be a rich sample for studying infrared-luminous galaxies up to,z similar to 1 and for understanding the evolution of infrared galaxies and the star formation rate in the universe. C1 CALTECH, Jet Prop Lab, Infrared Proc & Anal Ctr, Pasadena, CA 91125 USA. ISO Sci Operat Ctr, E-28080 Madrid, Spain. Univ Calif San Diego, Ctr Astrophys & Space Sci, La Jolla, CA 92093 USA. CEA Saclay, DSM, Serv Astrophys, F-91191 Gif Sur Yvette, France. Max Planck Inst Astron, D-69117 Heidelberg, Germany. Univ Cambridge, Inst Astron, Cambridge CB3 0HA, England. Royal Observ, Edinburgh EH9 3HJ, Midlothian, Scotland. RP CALTECH, Jet Prop Lab, Infrared Proc & Anal Ctr, 4800 Oak Grove Dr, Pasadena, CA 91125 USA. NR 27 TC 4 Z9 4 U1 0 U2 0 PU IOP PUBLISHING LTD PI BRISTOL PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND SN 0004-637X EI 1538-4357 J9 ASTROPHYS J JI Astrophys. J. PD SEP 1 PY 1998 VL 504 IS 1 BP 64 EP 76 DI 10.1086/306065 PN 1 PG 13 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 152KT UT WOS:000077777200009 ER PT J AU Brown, TM Ferguson, HC Stanford, SA Deharveng, JM AF Brown, TM Ferguson, HC Stanford, SA Deharveng, JM TI Color-luminosity relations for the resolved hot stellar populations in the centers of M31 and M32 SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies : evolution; galaxies : individual(M31, M32); galaxies : stellar content; Hertzsprung-Russell diagram; ultraviolet : galaxies ID FAR-ULTRAVIOLET ANALYSIS; HUBBLE-SPACE-TELESCOPE; ELLIPTIC GALAXIES; PLANETARY-NEBULAE; GIANT BRANCH; ORIGIN; EVOLUTION; BULGE; EXTINCTION; RADIATION AB We present Faint Object Camera (FOC) ultraviolet images of the central 14 " x 14 " of Messier 31 and Messier 32. The hot stellar populations detected in the composite UV spectra of these nearby galaxies are partially resolved into individual stars, and their individual colors and apparent magnitudes are measured. We detect 433 stars in M31 and 138 stars in M32, down to detection limits m(F275W) = 25.5 mag and m(F175W) = 24.5 mag. We investigate the luminosity functions of the sources, their spatial distribution, their color-magnitude diagrams, and their total integrated far-UV flux. Comparison to IUE and Hopkins Ultraviolet Telescope (HUT) spectrophotometry and WFPC2 stellar photometry indicates consistency at the 0.3 mag level, with possible systematic offsets in the FOC photometry at a level less than this. Further calibrations or observations with the Space Telescope Imaging Spectrograph (STIS) will be necessary to resolve the discrepancies. Our interpretation rests on the assumption that the published FOC on-orbit calibration is correct. Although M32 has a weaker UV upturn than M31, the luminosity functions and color-magnitude diagrams (CMDs) of M31 and M32 are surprisingly similar and are inconsistent with a majority contribution from any of the following: post-asymptotic giant branch (PAGB) stars more massive than 0.56 M. (with or without associated planetary nebulae), main sequence stars, and blue stragglers. Both the luminosity functions and color-magnitude diagrams are consistent with a dominant population of stars that have evolved from the extreme horizontal branch (EHB) along tracks with masses between 0.47 and 0.53 M.. These stars are well below the detection limits of our images while on the zero-age EHB but become detectable while in the more luminous (but shorter) AGB-manque and post-early asymptotic giant branch (PEAGB) phases. The FOC observations require that only very small fractions of the main-sequence populations (2% in M31 and 0.5% in M32) in these two galaxies evolve though the EHB and post-EHB phases, with the remainder evolving through bright PAGE evolution that is so rapid that few if any stars are expected in the small held of view covered by the FOG. A model with a flat EHB star mass distribution reproduces the HUT and IUE spectra of these two galaxies reasonably well, although there is some indication that an additional population of very hot (T-eff > 25,000 K) EHB stars may be needed to reproduce the HUT spectrum of M31 near the Lyman limit and to bring integrated far-UV fluxes of M31 and M32 into agreement with IUE. In addition to the post-EHB population detected in the FOG, we find a minority population (similar to 10%) of brighter stars that populate a region of the CMD that cannot be explained by canonical post-MB evolutionary tracks. The nature of these stars remains open to interpretation. The spatial distributions of the resolved UV-bright stars in both galaxies are more centrally concentrated than the underlying diffuse emission, implying that stellar populations of different ages and/or metallicities might be responsible for each component. C1 NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, Greenbelt, MD 20771 USA. NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, Greenbelt, MD 20771 USA. Space Telescope Sci Inst, Baltimore, MD 21218 USA. Univ Calif Lawrence Livermore Natl Lab, Inst Geophys & Planetary Phys, Livermore, CA 94550 USA. CNRS, Astron Spatiale Lab, F-13376 Marseille, France. RP Brown, TM (reprint author), NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, Code 681, Greenbelt, MD 20771 USA. NR 42 TC 52 Z9 52 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD SEP 1 PY 1998 VL 504 IS 1 BP 113 EP 138 DI 10.1086/306079 PN 1 PG 26 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 152KT UT WOS:000077777200013 ER PT J AU Sankrit, R Hester, JJ Scowen, PA Ballester, GE Burrows, CJ Clarke, JT Crisp, D Evans, RW Gallagher, JS Griffiths, RE Hoessel, JG Holtzman, JA Krist, J Mould, JR Stapelfeldt, KR Trauger, JT Watson, A Westphal, JA AF Sankrit, R Hester, JJ Scowen, PA Ballester, GE Burrows, CJ Clarke, JT Crisp, D Evans, RW Gallagher, JS Griffiths, RE Hoessel, JG Holtzman, JA Krist, J Mould, JR Stapelfeldt, KR Trauger, JT Watson, A Westphal, JA TI WFPC2 studies of the Crab Nebula. II. Ionization structure of the Crab filaments SO ASTROPHYSICAL JOURNAL LA English DT Article DE ISM : individual (Crab Nebula); ISM : structure; supernova remnants ID SPECTROPHOTOMETRY; TELESCOPE; SPECTRA AB Narrowband images of the Crab Nebula taken with the Hubble Space Telescope (HST) WFPC2 show the morphology and ionization structure of the filaments in great detail. At HST resolution, low- and high-ionization emission from filaments in the Crab differ in two complementary respects. First, low-ionization emission is found to be concentrated in very sharp structures, while high-ionization emission is predominantly found in a much more diffuse component. For example, approximately 80% of emission from [O I] lambda 6300 arises in features with scales of less than 0." 5, while only 10% of CO mi lambda 5007 emission arises in such compact structures. Second, individual filaments are found to lie along a sequence of ionization structures, ranging from features in which all lines are concentrated in the same compact volume through features with low-ionization cores surrounded by high-ionization envelopes. Hester and coworkers proposed in 1996 that this sequence can be understood as the result of the nonlinear development of magnetic Rayleigh-Taylor (R-T) instabilities along the interface between the Crab synchrotron nebula and swept-up ejecta. We present photoionization models of cylindrically symmetrical filaments consisting of a quadratic core surrounded by an extended envelope. A good deal of the observed variation in filament structure in the Crab can be matched by varying the assumed density profiles in these models. This implies that variations in the development of R-T instabilities in the Crab account for much of the spectral variation within the remnant. We also present a photoionization model of a uniform, low-density medium, which reasonably matches the extended diffuse component that dominates the high-ionization emission. This envelope model produces strong CO mi but virtually no CO II. While the He I/H beta ratio remains fairly constant throughout a range of filament models, this ratio is a factor of 5 lower in the envelope model. We find that the apertures used in ground-based spectroscopy of the Crab generally include emission from several discrete filaments as well as a component of diffuse emission. This places a fundamental limit on what can be inferred reliably from comparison of spectra with one-dimensional photoionization models. Many filament cores coincide with dust extinction features seen in a continuum image of the Crab. We consider one such feature in detail and find that the extinction of about 1.2 mag suggests that the dust-to-gas mass ratio may be an order of magnitude higher than is typical in the interstellar medium. C1 Arizona State Univ, Dept Phys & Astron, Tempe, AZ 85287 USA. Univ Michigan, Ann Arbor, MI 48109 USA. Space Telescope Sci Inst, Baltimore, MD 21218 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ Wisconsin, Madison, WI 53706 USA. Carnegie Mellon Univ, Pittsburgh, PA 15213 USA. New Mexico State Univ, Las Cruces, NM 88003 USA. Australian Natl Univ, Mt Stromlo & Siding Spring Observ, Weston, ACT 2611, Australia. Univ Nacl Autonoma Mexico, Inst Astron, Morelia, Michoacan, Mexico. CALTECH, Pasadena, CA 91125 USA. RP Arizona State Univ, Dept Phys & Astron, Box 871504, Tempe, AZ 85287 USA. RI Stapelfeldt, Karl/D-2721-2012; Clarke, John/C-8644-2013 NR 27 TC 39 Z9 39 U1 0 U2 4 PU IOP PUBLISHING LTD PI BRISTOL PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND SN 0004-637X EI 1538-4357 J9 ASTROPHYS J JI Astrophys. J. PD SEP 1 PY 1998 VL 504 IS 1 BP 344 EP 358 DI 10.1086/306078 PN 1 PG 15 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 152KT UT WOS:000077777200029 ER PT J AU Goetz, JA Pipher, JL Forrest, WJ Watson, DM Raines, SN Woodward, CE Greenhouse, MA Smith, HA Hughes, VA Fischer, J AF Goetz, JA Pipher, JL Forrest, WJ Watson, DM Raines, SN Woodward, CE Greenhouse, MA Smith, HA Hughes, VA Fischer, J TI Cepheus A East: Unraveling the mysteries SO ASTROPHYSICAL JOURNAL LA English DT Article DE H II regions; infrared : stars; ISM : individual (Cepheus A East); ISM : molecules; stars : formation; stars : pre-main-sequence ID STAR-FORMING REGION; HERBIG-HARO OBJECTS; THERMAL RADIO JET; NEAR-INFRARED EMISSION; MOLECULAR OUTFLOWS; REFLECTION NEBULAE; VELOCITY; CLOUDS; POLARIMETRY; ARRAYS AB New infrared images of Cep A East are presented that show two regions of shock-excited line emission from separate bipolar hows. We identify the dominant sources powering the outflows and argue that the results support a multiple outflow model (Narayanan gr Walker) as opposed to a quadrupolar outflow scenario. The images include near-infrared broadband (jr [2.158 mu m], L " [3.81 mu m], and M' [4.67 mu m]) and spectral line ([Fe II] emission line at 1.644 mu m and H-2 1-0 S[1] line at 2.122 mu m) observations, as well as continuum emission, at 1.644 mu m and 2.122 mu m. Considering our data and other results, we present a unified, self-consistent picture of the disk and shock structure. The northern emission region appears to be the result of the ablation of a dense molecular clump (coincident with HW 6) in the path of a diverting jet from YSO HW 2 and subsequent multiple bow shocks with prompt entrainment arising from the interaction of the jet with the molecular cloud Cep A-2. The southern line emission region near HW 7 resembles the "artillery shell" bow shocks found in Orion and is most likely a J-type shock caused by a jet from another YSO, possibly HW 3(d)ii. C1 Univ Rochester, Dept Phys & Astron, Rochester, NY 14627 USA. Univ Rochester, CEK Mees Observ, Rochester, NY 14627 USA. Univ Wyoming, Wyoming Infrared Observ, Dept Phys & Astron, Laramie, WY 82071 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Smithsonian Astrophys Observ, Cambridge, MA 02138 USA. Queens Univ, Dept Phys, Astron Grp, Kingston, ON K7L 3N6, Canada. USN, Res Lab, Remote Sensing Div, Washington, DC 20375 USA. RP Goetz, JA (reprint author), Univ Rochester, Dept Phys & Astron, Rochester, NY 14627 USA. NR 69 TC 28 Z9 28 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD SEP 1 PY 1998 VL 504 IS 1 BP 359 EP 374 DI 10.1086/306058 PN 1 PG 16 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 152KT UT WOS:000077777200030 ER PT J AU Scargle, JD AF Scargle, JD TI Studies in astronomical time series analysis. V. Bayesian blocks, a new method to analyze structure in photon counting data SO ASTROPHYSICAL JOURNAL LA English DT Article DE gamma rays : bursts; methods : numerical; methods : data analysis; methods : statistical ID CHANGE-POINT; DRIPPING HANDRAIL; RANDOM-VARIABLES; TRANSIENT CHAOS; SEQUENCE AB I describe a new time-domain algorithm for detecting localized structures (bursts), revealing pulse shapes, and generally characterizing intensity variations. The input is raw counting data, in any of three forms: time-tagged photon events (TTE), binned counts, or time-to-spill (TTS) data. The output is the most probable segmentation of the observation into time intervals during which the photon arrival rate is perceptibly constant, i.e., has no statistically significant variations. The idea is not that the source is deemed to have this discontinuous, piecewise constant form, rather that such an approximate and generic model is often useful. Since the analysis is based on Bayesian statistics, I call the resulting structures Bayesian blocks. Unlike most, this method does not stipulate time bins-instead the data determine a piecewise constant representation. Therefore the analysis procedure itself does not impose a lower limit to the timescale on which variability can be detected. Locations, amplitudes, and rise and decay times of pulses within a time series can be estimated independent of any pulse-shape model-but only if they do not overlap too much, as deconvolution is not incorporated. The Bayesian blocks method is demonstrated by analyzing pulse structure in BATSE gamma-ray data.(2). C1 NASA, Ames Res Ctr, Div Space Sci, Moffett Field, CA 94035 USA. RP Scargle, JD (reprint author), NASA, Ames Res Ctr, Div Space Sci, Moffett Field, CA 94035 USA. NR 38 TC 220 Z9 221 U1 0 U2 9 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD SEP 1 PY 1998 VL 504 IS 1 BP 405 EP 418 DI 10.1086/306064 PN 1 PG 14 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 152KT UT WOS:000077777200034 ER PT J AU Pickett, BK Cassen, P Durisen, RH Link, R AF Pickett, BK Cassen, P Durisen, RH Link, R TI The effects of thermal energetics on three-dimensional hydrodynamic instabilities in massive protostellar disks SO ASTROPHYSICAL JOURNAL LA English DT Article DE hydrodynamics; instabilities; solar system : formation; stars : formation ID SELF-GRAVITATING DISKS; STAR-FORMATION; NONAXISYMMETRIC INSTABILITY; ROTATING PROTOSTARS; PARTICLE HYDRODYNAMICS; ACCRETION DISK; EVOLUTION; MODELS; BINARY; SYSTEMS AB We use numerical three-dimensional hydrodynamics to investigate how assumptions about local thermal conditions affect the strength and outcome of nonaxisymmetric instabilities in massive protostellar disks. Building on work presented in earlier papers, we generate two protostellar core models that represent equilibrium states that could form from the axisymmetric collapse of uniformly rotating, singular isothermal spheres. Both models are continuous star/disk systems, in which the star, the disk, the star/disk boundary, and the free disk outer boundary are resolved in three dimensions. The models are distinguished primarily by the temperature distribution in the disk, and both can be considered to represent the same early evolutionary stage of disk development, when the disk is massive but small in radial extent. In the "hot" model, the disk is assumed to have the same entropy per gram as the central isentropic star, giving a Toomre Q-parameter similar to 2.5 over the disk region. In the "cool" model, the entropy per gram decreases radially outward in the disk, resulting in more realistic, cooler disk temperatures and Q approximate to 1.5. Each of these protostellar star/disk systems is evolved in our three-dimensional hydrodynamics code under two different assumptions about thermal equilibrium in the disk, namely that either the entropy per gram or the temperature remains constant with position in the disk. We refer to these two cases as locally isentropic evolution and locally isothermal evolution, respectively. All four calculations have been run for at least two outer rotation periods of the disk. With either assumption about the thermal equilibrium, one- and two-armed spiral disturbances, which grow in the hot models, saturate at low amplitude (similar to 1%) and do not alter the protostellar core significantly. On the other hand, the cool model is highly unstable to multiple low-order spirals, which induce significant mass and angular momentum transport in a few dynamical times. Under locally isentropic evolution, the star and star/disk boundary in the cool model are unstable to three- and four-armed disturbances and the disk is unstable to a two-armed spiral, but all these modes saturate at moderate nonlinear (a few tens percent) amplitudes after about 1.5 outer rotation periods. The same instabilities occur under locally isothermal evolution; however, the two-armed spiral in the disk grows more vigorously and does not saturate, ultimately disrupting the disk and concentrating material into thin, dense arcs and arclets that approach stellar densities. In both cool model calculations, there is substantial inward transport of mass and outward transport of angular momentum during the growth phase of the two-armed spiral, but the transport rate drops by over an order of magnitude for locally isentropic evolution when the two-armed spiral saturates. It is clear from these calculations that thermal energetics play a critical role in the development of self-gravitating instabilities and that, under conditions of strong cooling, such instabilities can disrupt a disk very early in its development. We compare these calculations with previous work on gravitational instabilities in disks and discuss implications for star and planet formation. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Indiana Univ, Dept Astron, Bloomington, IN 47405 USA. CALTECH, Div Geol & Planetary Sci, Pasadena, CA 91125 USA. Max Planck Inst Extraterr Phys, D-85740 Garching, Germany. RP Pickett, BK (reprint author), NASA, Ames Res Ctr, MS 245-3, Moffett Field, CA 94035 USA. NR 63 TC 64 Z9 64 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD SEP 1 PY 1998 VL 504 IS 1 BP 468 EP 491 DI 10.1086/306059 PN 1 PG 24 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 152KT UT WOS:000077777200040 ER PT J AU Sahu, MS Blades, JC He, L Hartmann, D Barlow, MJ Crawford, IA AF Sahu, MS Blades, JC He, L Hartmann, D Barlow, MJ Crawford, IA TI Atomic and molecular interstellar absorption lines toward the high galactic latitude stars HD 141569 and HD 157841 at ultra-high resolution SO ASTROPHYSICAL JOURNAL LA English DT Article DE atomic data; ISM : abundances; ISM : kinematics and dynamics; stars : individual (HD 141569 and HD 157841) ID HEAVY ELEMENT DEPLETION; CA-II; NA-I; SPECTROSCOPIC ANALYSIS; CLOUDS; LYNDS-134; HYDROGEN; REGIONS; DUST; CH+ AB We present ultra-high-resolution (0.32 bm s(-1)) spectra obtained with the 3.9 m Anglo-Australian Telescope (AAT) and Ultra-High-Resolution Facility (UHRF) of interstellar Na I D1, Na I D2, Ca II K, K I and CH absorption toward two high Galactic latitude stars HD 141569 and HD 157841. We have compared our data with 21 cm observations obtained from the Leiden/Dwingeloo H I survey. We derive the velocity structure and column densities of the clouds represented by the various components and identify the clouds with ISM structures seen in the region at other wavelengths. We further derive abundances, linear depletions, and H-2 fractional abundances for these clouds wherever possible. Both stars are located in regions of IRAS 100 mu m emission associated with high Galactic latitude molecular clouds (HLCs): HD 141569 lies, in projection, close to MBM 37 and the Lynds dark cloud L134N, whereas HD 157841 is in the vicinity of the MBM 151. Toward HD 141569 we detect two components in our UHRF spectra: a weak, broad b = 4.5 km s(-1) component at -15 km s(-1), seen only in Ca rr K absorption, and another component at 0 km s(-1), seen in Na I DI, Na I D2, Ca II K, K I, and CH absorption. The cloud represented by the -15 km s(-1) component is warm and may be located in a region close to the star. The cloud represented by the 0 km s(-1) component has a Ca linear depletion delta(Ca) = 1.4 x 10(-4) and shows evidence for the presence of dust, consistent with strong 100 mu m emission seen in this region. The H-2 fractional abundance f(H-2) derived for this cloud is 0.4, which is typically what is observed toward HLCs. We conclude that this 0 km s(-1) cloud is associated with MBM 37 and L134N based on the presence of dust and molecular gas (CH) and good velocity agreement with CO emission from these two clouds. This places HD 141569 beyond MBM 37 and L134N, which are estimated to be at approximate to 110 pc. In the case of the HD 157841 sight line, a total of six components are seen on our UHRF spectra in Na I D1, Na I D2, Ca II K, K I, and CH absorption. Two of these six components are seen only in a single species. The cloud represented by the components at 1.85 km s(-1) has a Ca linear depletion delta(Ca)= 2.8 x 10(-4), indicating the presence of dust. The f(H-2) derived for this cloud is 0.45, and there is good velocity agreement with CO emission from MBM 151. To the best of our knowledge, this 1.85 km s(-1) component toward HD 157841 is the first one found to have relative line widths that are consistent with pure thermal broadening only. We associate the 1.85 km s(-1) cloud seen in our UHRF spectra with MBM 151 and conclude that HD 157841 must lie beyond similar to 200 pc, the estimated distance to MBM 151. C1 Space Telescope Sci Inst, Baltimore, MD 21218 USA. Ctr Astrophys, Cambridge, MA 02138 USA. Univ London Univ Coll, Dept Phys & Astron, London WC1E 6BT, England. RP Sahu, MS (reprint author), NASA, Goddard Space Flight Ctr, Code 681, Greenbelt, MD 20771 USA. RI Barlow, Michael/A-5638-2009; Crawford, Ian/H-7510-2012 OI Barlow, Michael/0000-0002-3875-1171; Crawford, Ian/0000-0001-5661-7403 NR 39 TC 17 Z9 17 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD SEP 1 PY 1998 VL 504 IS 1 BP 522 EP 532 DI 10.1086/306042 PN 1 PG 11 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 152KT UT WOS:000077777200044 ER PT J AU Bock, JJ Marsh, KA Ressler, ME Werner, MW AF Bock, JJ Marsh, KA Ressler, ME Werner, MW TI High-resolution mid-infrared imaging of the nucleus of NGC 1068 SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxie : active; galaxies : Seyfert; infrared : galaxies ID ACTIVE GALACTIC NUCLEI; NARROW-LINE REGION; SEYFERT-GALAXY NGC-1068; RADIO STRUCTURE; EMISSION; DUST; SCHEMES; SPECTRA; MODELS; TORUS AB We have obtained mid-infrared images of the nucleus of NGC 1068 from the Hale 5 m telescope at Mount Palomar with diffraction-limited resolution and high sensitivity at lambda = 8.8, 10.3, and 12.5 mu m. Deconvolved images show that the infrared emission extends north to south in the inner 2 ", consisting of a central peak, a component extending 1 " north of the central source, a component extending 1 " south of the central source, and several smaller structures located 1 " to the northeast. The central peak is extended 0." 4 N-S and unresolved (less than or equal to 0." 2) E-W. We find that 50% +/- 5% of the flux emerges from the central 0." 4 and that a single unresolved point source can account for only 27% +/- 5% of the total flux. However, if the central peak arises from optically thick emission, we estimate that the emitting region has a projected area greater than or equal to 2 pc(2) and thus may contain a compact source such as a parsec-scale torus. We observe a correspondence between the northern extension and northeastern sources appearing on the mid-infrared images and the [O III] clouds A-C and E. We interpret the faint optical counterpart to the mid-infrared southern extension as being due to a partial obscuration by the intervening disk of the host galaxy. The N-S extension of the mid-infrared emission coincides with one wall of the conical narrow-line region and aligns with the N-S orientation of the radio jet close to the nucleus. We interpret the infrared emission as arising from the optically thick dust that lines the walls of the low-density cavity formed by the radio jet and heated by radiation from the central source. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Bock, JJ (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 31 TC 20 Z9 20 U1 0 U2 1 PU IOP PUBLISHING LTD PI BRISTOL PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD SEP 1 PY 1998 VL 504 IS 1 BP L5 EP L10 DI 10.1086/311559 PN 2 PG 6 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 152KV UT WOS:000077777400002 ER PT J AU Boden, AF van Belle, GT Colavita, MM Dumont, PJ Gubler, J Koresko, CD Kulkarni, SR Lane, BF Mobley, DW Shao, M Wallace, JK AF Boden, AF van Belle, GT Colavita, MM Dumont, PJ Gubler, J Koresko, CD Kulkarni, SR Lane, BF Mobley, DW Shao, M Wallace, JK TI An interferometric search for bright companions to 51 Pegasi SO ASTROPHYSICAL JOURNAL LA English DT Article DE binaries : spectroscopic; planetary systems; stars : individual (51 Pegasi); techniques : interferometric ID 51-PEGASI; PLANET; STARS AB We report on a near-infrared, long-baseline interferometric search for luminous companions to the star 51 Pegasi conducted with the Palomar Testbed Interferometer. Our data is completely consistent with a single-star hypothesis. We find no evidence to suggest a luminous companion to 51 Pegasi, and we can exclude a companion brighter than a Delta K of 4.27 at the 99% confidence level for the 4.2 day orbital period indicated by spectroscopic measurements. This Delta K corresponds to an upper limit in the companion M-K of 7.30, which in turn implies a main-sequence companion mass of less than 0.22 M-.. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91125 USA. Univ Calif San Diego, La Jolla, CA 92093 USA. CALTECH, Palomar Observ, Pasadena, CA 91125 USA. RP Boden, AF (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91125 USA. NR 13 TC 30 Z9 30 U1 0 U2 1 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD SEP 1 PY 1998 VL 504 IS 1 BP L39 EP L42 DI 10.1086/311560 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 152KV UT WOS:000077777400009 ER PT J AU Cui, W Morgan, EH Titarchuk, LG AF Cui, W Morgan, EH Titarchuk, LG TI Soft phase lags of pulsed emission from the millisecond X-ray pulsar SAX J1808.4-3658 SO ASTROPHYSICAL JOURNAL LA English DT Article DE accretion, accretion disks; pulsars : individual (SAX J1808.4-3658); stars : neutron; X-rays : stars ID NEUTRON-STARS; PULSATIONS; SEARCHES; BINARIES; COMPTONIZATION; OSCILLATIONS; ACCRETION; SPECTRA AB We report the discovery of phase shifts between X-ray pulses at different energies in the newly discovered millisecond X-ray pulsar SAX J1808.4-3658. The results show that low-energy pulses lag high-energy pulses by as much as similar to 0.2 ms (or similar to 8% of the pulse period). The measurements were made in two different ways: (1) computing cross-power spectra between different energy bands, and (2) cross-correlating the folded pulse profiles in different energy bands; consistent results were obtained. We speculate that the observed soft lags might be related to the lateral expansion and subsequent cooling of a "hot spot" on the neutron star surface in which the pulsed X-ray emission originates. Also presented is the possibility of producing soft lags via Compton downscattering of hard X-ray photons from the hot spot in the cool surrounding atmosphere. We will discuss possible X-ray production mechanisms for SAX J1808.4-3658 and constraints on the emission environment, based on the observed soft lags, pulse profiles, and energy spectrum. C1 MIT, Ctr Space Res, Cambridge, MA 02139 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. George Mason Univ, Inst Computat Sci & Informat, Fairfax, VA 22030 USA. RP MIT, Ctr Space Res, Cambridge, MA 02139 USA. EM cui@space.mit.edu; ehm@space.mit.edu; titarchuk@lheavx.gsfc.nasa.gov NR 33 TC 64 Z9 65 U1 0 U2 0 PU IOP PUBLISHING LTD PI BRISTOL PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND SN 0004-637X EI 1538-4357 J9 ASTROPHYS J JI Astrophys. J. PD SEP 1 PY 1998 VL 504 IS 1 BP L27 EP L30 DI 10.1086/311569 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 152KV UT WOS:000077777400006 ER PT J AU Juszkiewicz, R Fisher, KB Szapudi, I AF Juszkiewicz, R Fisher, KB Szapudi, I TI Skewed exponential pairwise velocities from Gaussian initial conditions SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies : interactions; large-scale structure of universe ID LARGE-SCALE STRUCTURE; PECULIAR VELOCITIES; REDSHIFT-SPACE; FLUCTUATIONS; GALAXIES; DENSITY; DISTRIBUTIONS; PERTURBATIONS; SKEWNESS; CLUSTERS AB Using an Eulerian perturbative calculation, we show that the distribution of relative pairwise velocities that arises from the gravitational instability of Gaussian density fluctuations has asymmetric (skewed) exponential tails. The negative skewness is induced by the negative mean streaming velocity of pairs (the infall prevails over expansion), while the exponential tails arise because the relative pairwise velocity is a number-weighted, not a volume-weighted, statistic. The derived probability distribution is compared with N-body simulations and is shown to provide a reasonable fit. C1 Copernicus Astron Ctr, PL-00716 Warsaw, Poland. Univ Penn, Dept Phys, Philadelphia, PA 19104 USA. Inst Adv Study, Sch Nat Sci, Princeton, NJ 08540 USA. NASA, Fermi Natl Accelerator Lab, Ctr Astrophys, Batavia, IL USA. RP Juszkiewicz, R (reprint author), Copernicus Astron Ctr, Bartycka 18, PL-00716 Warsaw, Poland. NR 30 TC 21 Z9 21 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD SEP 1 PY 1998 VL 504 IS 1 BP L1 EP L4 DI 10.1086/311558 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 152KV UT WOS:000077777400001 ER PT J AU Luhman, ML Satyapal, S Fischer, J Wolfire, MG Cox, P Lord, SD Smith, HA Stacey, GJ Unger, SJ AF Luhman, ML Satyapal, S Fischer, J Wolfire, MG Cox, P Lord, SD Smith, HA Stacey, GJ Unger, SJ TI Infrared Space Observatory measurements of a [C II] 158 micron line deficit in ultraluminous infrared galaxies SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies : active; galaxies : ISM; galaxies : starburst; infrared : galaxies; infrared : ISM : lines and bands; ISM : atoms ID LONG-WAVELENGTH SPECTROMETER; PHOTODISSOCIATION REGIONS; INTERSTELLAR-MEDIUM; GALACTIC NUCLEI; MOLECULAR GAS; EMISSION; SPECTROSCOPY; TRANSITION; ORIGIN; FIELD AB We report measurements of the [C II] 157.74 mu m fine-structure line in a sample of seven ultraluminous infrared galaxies (ULIGs) (L-1R > 10(12) L-.) with the Long Wavelength Spectrometer on the Infrared Space Observatory. The [C II] line is an important coolant in galaxies and arises in interstellar gas exposed to far-ultraviolet photons (hv greater than or equal to 11.26 eV); in ULIGs, this radiation stems from the bursts of star formation and/or from the active galactic nuclei that power the tremendous infrared luminosity. The [C II] 158 mu m line is detected in four of the seven ULIGs; the absolute line flux (about a few times 10(-20) W cm(-2)) represents some of the faintest extragalactic [C II] emission yet observed. Relative to the far-infrared continuum, the [C II] flux from the observed ULIGs is similar to 10% of that seen from nearby normal and starburst galaxies. We discuss possible causes for the [C II] deficit, namely (1) self-absorbed or optically thick [C II] emission, (2) saturation of the [C II] emission in photodissociated gas with high gas density n (much greater than 3 x 10(3) cm(-3)) or with a high ratio of incident W flux G(o) to n (G(o)/n greater than or similar to 10 cm(3)), or (3) the presence of a soft ultraviolet radiation field caused, for example, by a stellar population deficient in massive main-sequence stars. As nearby examples of colliding galaxies, ULIGs may resemble high-redshift protogalaxies in both morphology and spectral behavior. If true, the suggested [C II] deficit in ULIGs poses limitations on the detection rate of high-z sources and on the usefulness of [C II] as an eventual tracer of protogalaxies. C1 USN, Res Lab, Remote Sensing Div, Washington, DC 20375 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Maryland, Dept Astron, College Pk, MD 20742 USA. Towson State Univ, Dept Phys, Towson, MD 21252 USA. Univ Paris 11, Inst Astrophys Spatiale, Orsay, France. CALTECH, IPAC, Pasadena, CA 91125 USA. Harvard Smithsonian Ctr Astrophys, Cambridge, MA 02138 USA. Cornell Univ, Dept Astron, Ithaca, NY 14853 USA. Univ London Queen Mary & Westfield Coll, London, England. RP Luhman, ML (reprint author), USN, Res Lab, Remote Sensing Div, Code 7217, Washington, DC 20375 USA. NR 48 TC 120 Z9 120 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD SEP 1 PY 1998 VL 504 IS 1 BP L11 EP L15 DI 10.1086/311562 PN 2 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 152KV UT WOS:000077777400003 ER PT J AU White, NE Ghosh, P AF White, NE Ghosh, P TI Low-mass X-ray binaries, millisecond radio pulsars, and the cosmic star formation rate SO ASTROPHYSICAL JOURNAL LA English DT Article DE binaries : close; galaxies : evolution; pulsars : general; stars : evolution; stars : formation; X-rays : galaxies; X-rays : stars ID GALAXIES AB We report on the implications of the peak in the cosmic star formation rate (SFR) at redshift z approximate to 1.5 for the resulting population of low-mass X-ray binaries (LMXBs) and for that of their descendants, the millisecond radio pulsars (MRPs). Since the evolutionary timescales of LMXBs, their progenitors, and their descendants are thought be significant fractions of the time interval between the SFR peak and the present epoch, there is a lag in the turn-on of the LMXB population, with the peak activity occurring at z similar to 0.5-1. The peak in the MRP population is delayed further, occurring at z less than or similar to 0.5. We show that the discrepancy between the birthrate of LMXBs and the birthrate of MRPs. found under the assumption of a steady state SFR, can be resolved for the population as a whole when the effects of a time-variable SFR are included. A discrepancy may persist for LMXBs with short orbital periods, although a detailed population synthesis will be required to confirm this. Furthermore, since the integrated X-ray luminosity distribution of normal galaxies is dominated by X-ray binaries, it should show strong luminosity evolution with redshift. In addition to an enhancement near the peak (z approximate to 1.5) of the SFR due to the prompt turn-on of the relatively short-lived massive X-ray binaries and young supernova remnants, we predict a second enhancement by a factor of similar to 10 at a redshift between similar to 0.5 and similar to 1 due to the delayed turn-on of the LMXB population. Deep X-ray observations of galaxies out to z approximate to 1 by the Advanced X-Ray Astrophysics Facility will be able to observe this enhancement and, by determining its shape as a function of redshift, will provide an important new method for constraining evolutionary models of X-ray binaries. C1 NASA, High Energy Astrophys Lab, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP White, NE (reprint author), NASA, High Energy Astrophys Lab, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RI White, Nicholas/B-6428-2012 OI White, Nicholas/0000-0003-3853-3462 NR 16 TC 48 Z9 48 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD SEP 1 PY 1998 VL 504 IS 1 BP L31 EP L34 DI 10.1086/311568 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 152KV UT WOS:000077777400007 ER PT J AU Waldron, WL Corcoran, MF Drake, SA Smale, AP AF Waldron, WL Corcoran, MF Drake, SA Smale, AP TI X-ray and radio observations of the Cygnus OB2 association SO ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES LA English DT Article DE galaxy, open clusters and associations, individual (Cygnus OB2); stars, early-type; stars, mass loss; x-rays, stars ID EARLY-TYPE STARS; O-TYPE STARS; MASS-LOSS RATES; ALL-SKY SURVEY; STELLAR WINDS; SUPER-GIANTS; HOT STARS; LUMINOUS STARS; ZETA-PUPPIS; H-ALPHA AB Several OB stars in the Cygnus OB2 association are among the strongest stellar x-ray and radio sources in the Galaxy. The radio emission is particularly unusual, displaying a high level of variability and nonthermal behavior. We obtained two ROSAT PSPC observations, a ROSAT HRI observation, and three VLA observations of the association during a 2 yr time span. Our study will focus on four stars, Cyg OB2 No. 5, No. 8A, No. 9, and No. 12. Three of the four (Cyg No. 5, No. 9, and No. 12) were relatively constant in their x-ray emission over the 2 yr time frame. The fourth, Cyg OB2 No. 8A, increased in intensity by similar to 34%. No short-term (hourly) variability was detected. The observed x-ray characteristics (e.g., luminosity, temperature) are found to be consistent with the x-ray properties of other OB stars. The exception is Cyg OB2 No. 12, whose x-ray characteristics are found to be inconsistent with its spectral classification. Detailed spectral analyses of the PSPC data are presented for two absorption models: (1) ISM (cold absorber) and (2) Wind + ISM (warm absorber). The spectral fits suggest that the x-ray sources are located within the stellar wind, and estimates of the x-ray locations are presented. Adopting the radio-derived mass-loss rates, these x-ray locations are found to be consistent with the shock scenario proposed for OB stars. As expected, the radio emission has continued to be highly variable. Nonthermal characteristics are observed in Cyg OB2 No. 8A and No. 12. One of the most unusual nonthermal radio sources, Cyg OB2 No. 9, was found to be thermal in one of our observations. An observation of Cyg OB2 No. 5 also displayed a thermal radio spectrum. A comparison of the observed and intrinsic x-ray fluxes with the observed radio fluxes suggests that these quantities are anticorrelated; the strongest x-ray source is the weakest radio source. This is contrary to normal expectations for a wind-generated model of x-ray and radio emission. We investigate the long-term temporal behavior of both the x-ray and radio emission by comparing our newly acquired data with the previous x-ray (IPC) and radio data over the past 15 yr. Except for three events observed in Cyg OB2 No. 5, which displayed significant increases in its x-ray emission, the x-ray emission has remained relatively constant with a variability level less than 20% over this time span, whereas the radio emission has stayed highly variable with various levels of nonthermal behavior. We present a model to investigate the case in which the x-ray and radio emission are controlled by stellar wind properties and find that the predicted variability should be comparable in both emission processes. This is not observed. It is very intriguing that every time we observe the radio emission, it is different, whereas the x-ray emission always appears to be constant. If the stellar wind is as variable as suggested by the radio data, we believe it is highly implausible that we just happened to miss all periods of x-ray variability. We also investigate the implications of the observed nonthermal radio spectrum of Cyg OB2 No. 8A. Using the synchrotron emission model of White, we find that this nonthermal radio spectrum predicts a mass-loss rate almost 2 orders of magnitude less than that expected for a thermal radio spectrum. This lower mass-loss rate is consistent with an x-ray source located at the base of the stellar wind, contrary to the basic shock scenario. Since these stars show evidence of changing from thermal to nonthermal radio characteristics, it is difficult to understand how such a large change in mass loss did not produce a significant change in the observed x-rays. C1 Space Applicat Corp, Appl Res Div, Largo, MD 20774 USA. NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. Univ Space Res Assoc, Greenbelt, MD USA. RP Waldron, WL (reprint author), Space Applicat Corp, Appl Res Div, 9315 Largo Dr,Suite 250, Largo, MD 20774 USA. EM wwaldron@eos.hitc.com; corcoran@barnegat.gsfc.nasa.gov; drake@olegacy.gsfc.nasa.gov; alan@osiris.gsfc.nasa.gov NR 80 TC 56 Z9 56 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5801 S ELLIS AVENUE, CHICAGO, IL 60637 USA SN 0067-0049 J9 ASTROPHYS J SUPPL S JI Astrophys. J. Suppl. Ser. PD SEP PY 1998 VL 118 IS 1 BP 217 EP 238 DI 10.1086/313131 PG 22 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 119UE UT WOS:000075915400005 ER PT J AU Bautista, MA Romano, P Pradhan, AK AF Bautista, MA Romano, P Pradhan, AK TI Resonance-averaged photoionization cross sections for astrophysical models SO ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES LA English DT Article DE atomic data; atomic processes ID ELECTRON-ION RECOMBINATION; ATOMIC DATA; OPACITY CALCULATIONS; ISOELECTRONIC SEQUENCE; IRON PROJECT; OSCILLATOR-STRENGTHS; ABUNDANT ELEMENTS; RATE COEFFICIENTS; CARBON; HE AB We present ground-state photoionization cross sections of atoms and ions averaged over resonance structures for photoionization modeling of astrophysical sources. The detailed cross sections calculated in the close-coupling approximation using the R-matrix method, with resonances delineated at thousands of energies, are taken from the Opacity Project database TOPbase and the Iron Project, including new data for the low ionization stages of iron Fe I-Fe v. The resonance-averaged cross sections are obtained by convolving the detailed cross sections with a Gaussian distribution over the autoionizing resonances. This procedure is expected to minimize errors in the derived ionization rates that could result from small uncertainties in computed positions of resonances while preserving the overall resonant contribution to the cross sections in the important near-threshold regions. The detailed photoionization cross sections at low photon energies are complemented by new relativistic distorted-wave calculations for Z less than or equal to 12 and from central-held calculations for Z > 12 at high energies, including inner shell ionization. The effective cross sections are then represented by a small number of points that can be readily interpolated linearly for practical applications; a FORTRAN subroutine and data are available. The present numerically averaged cross sections are compared with analytic fits that do not accurately represent the effective cross sections in regions dominated by resonances. C1 NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. Ohio State Univ, Dept Astron, Columbus, OH 43210 USA. RP Bautista, MA (reprint author), NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Code 662, Greenbelt, MD 20771 USA. OI Romano, Patrizia/0000-0003-0258-7469 NR 39 TC 54 Z9 54 U1 0 U2 3 PU UNIV CHICAGO PRESS PI CHICAGO PA 5801 S ELLIS AVENUE, CHICAGO, IL 60637 USA SN 0067-0049 J9 ASTROPHYS J SUPPL S JI Astrophys. J. Suppl. Ser. PD SEP PY 1998 VL 118 IS 1 BP 259 EP 265 DI 10.1086/313132 PG 7 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 119UE UT WOS:000075915400007 ER PT J AU Greenleaf, JE Jackson, CGR Geelen, G Keil, LC Hinghofer-Szalkay, H Whittam, JH AF Greenleaf, JE Jackson, CGR Geelen, G Keil, LC Hinghofer-Szalkay, H Whittam, JH TI Plasma volume expansion with oral fluids in hypohydrated men at rest and during exercise SO AVIATION SPACE AND ENVIRONMENTAL MEDICINE LA English DT Article ID ORTHOSTATIC INTOLERANCE; GRADED-EXERCISE; VASOPRESSIN; OSMOLALITY; RESPONSES; HUMANS; RENIN; BLOOD AB Background: The purpose for this study was to evaluate various carbohydrate (CHO)-electrolyte fluid formulations for consumption by astronauts to maintain or restore their plasma volume (PV! and total body water (TBW) during and after extravehicular activity (exercise experiment, EE) and for a few hours before reentry and immediately after landing (rest experiment RE). Hypothesis: That fluid formulation electrolyte content would be more important than osmotic (Osm) content for increasing or maintaining PV during the RE and EE. Methods: In the RE, 5 healthy men (23-44 yr), previously dehydrated for 24 h, drank 6 fluid formulations (Water, 19.6 Na, 157 Na, 19.6 Na + glucose, and the prepared drinks Performance(R) and Power)-one each at weekly intervals, and then sat for 70 min. In the EE, four healthy 24-h dehydrated men (30-46 yr) exercised for 70 min supine on a cycle ergometer (load = 71 +/- 1% peak (V) over dot O-2). Results: Rest: Subjects who consumed formulations With total Osm concentrations nearer the normal range (157 Na - 270 mOsm.kg(-1), Performance(R) with 19.6 mEq.L-1 Na - 380 mOsm, and to some extent Power with 23.5 mEq.L-1 Na - 390 mOsm) had the greater increases in PV; intake of drink 157 Na, with the largest Na content, induced the greatest hypervolemia of 7.6% (p < 0.05). The various additional ions, in addition to 19.6 Na, probably contributed to the 4.6% (p < 0.05) hypervolemia with Performance(R). Water was not effective. Exercise: Stabilization of PV between 15-70 min was not related to drink total CHO, Na or Osm content. Performance(R) and 157 Na were no more effective than 19.6 Na or 19.6 Na + glu for PV stabilization. Water was the least effective. Regulatory mechanisms controlling PV during exercise appear to be independent of oral fluid formulation Osm-electrolyte content. Conclusions: Drink cation (sodium) content is more important that its total osmotic content for increasing plasma volume at rest. Fluid formulations with greater hypervolemic action in resting subjects may not be as effective during exercise; therefore different formulations for use during exercise appear to be necessary. C1 NASA, Ames Res Ctr, Div Life Sci,Gravitat Res Branch 23911, Lab Human Environm Physiol, Moffett Field, CA 94035 USA. Shaklee Technica, San Francisco, CA USA. RP Greenleaf, JE (reprint author), NASA, Ames Res Ctr, Div Life Sci,Gravitat Res Branch 23911, Lab Human Environm Physiol, Moffett Field, CA 94035 USA. NR 19 TC 20 Z9 21 U1 1 U2 2 PU AEROSPACE MEDICAL ASSOC PI ALEXANDRIA PA 320 S HENRY ST, ALEXANDRIA, VA 22314-3579 USA SN 0095-6562 J9 AVIAT SPACE ENVIR MD JI Aviat. Space Environ. Med. PD SEP PY 1998 VL 69 IS 9 BP 837 EP 844 PG 8 WC Public, Environmental & Occupational Health; Medicine, General & Internal; Sport Sciences SC Public, Environmental & Occupational Health; General & Internal Medicine; Sport Sciences GA 115CU UT WOS:000075646600002 PM 9737753 ER PT J AU Gander, PH Graeber, RC Connell, LJ Gregory, KB Miller, DL Rosekind, MR AF Gander, PH Graeber, RC Connell, LJ Gregory, KB Miller, DL Rosekind, MR TI Flight crew fatigue I: Objectives and methods SO AVIATION SPACE AND ENVIRONMENTAL MEDICINE LA English DT Article ID CIRCADIAN-RHYTHMS; SLEEP; TEMPERATURE; PERFORMANCE; WORK AB In 1980, NASA-Ames Research Center, Moffett Field, CA, initiated a program to assess flight crew fatigue, determine its potential operational consequences, and provide practical countermeasure suggestions. To assess the extent of the problem, crewmembers were monitored before, during, and after commercial short-haul (fixed-wing and helicopter aircraft), overnight cargo, and long-haul operations. A total of 197 volunteers were studied on 94 trip patterns with 1299 flight segments and 2046 h of flying time. The present paper outlines the program and describes the common methodology used in these studies, which are then presented in detail in the four subsequent papers. The sixth paper offers a synthesis of this work, reviewing the major causes of flight crew fatigue and making specific suggestions about ways to manage it in different operations. C1 NASA, Ames Res Ctr, Fatigue Countermeasures Program, Moffett Field, CA 94035 USA. San Jose State Univ Fdn, Moffett Field, CA USA. Boeing Commercial Airplane Grp, Seattle, WA 98124 USA. Sterling Software Inc, Palo Alto, CA USA. RP Gander, PH (reprint author), Univ Otago, Wellington Sch Med, Dept Publ Hlth, POB 7343, Wellington, New Zealand. NR 42 TC 9 Z9 9 U1 0 U2 0 PU AEROSPACE MEDICAL ASSOC PI ALEXANDRIA PA 320 S HENRY ST, ALEXANDRIA, VA 22314-3579 USA SN 0095-6562 J9 AVIAT SPACE ENVIR MD JI Aviat. Space Environ. Med. PD SEP PY 1998 VL 69 IS 9 SU S BP B1 EP B7 PG 7 WC Public, Environmental & Occupational Health; Medicine, General & Internal; Sport Sciences SC Public, Environmental & Occupational Health; General & Internal Medicine; Sport Sciences GA 116LY UT WOS:000075727600002 PM 9749935 ER PT J AU Gander, PH Barnes, RM Gregory, KB Graeber, RC Connell, LJ Rosekind, MR AF Gander, PH Barnes, RM Gregory, KB Graeber, RC Connell, LJ Rosekind, MR TI Flight crew fatigue III: North Sea helicopter air transport operations SO AVIATION SPACE AND ENVIRONMENTAL MEDICINE LA English DT Article ID CIRCADIAN-RHYTHM; SLEEP; TEMPERATURE AB We studied 32 helicopter pilots before, during, and after 4-5 d trips from Aberdeen, Scotland, to service North Sea oil rigs. On duty days, subjects awoke 1.5 h earlier than pretrip or posttrip, after having slept nearly an hour less. Subjective fatigue was greater posttrip than pretrip. By the end of trip days, fatigue was greater and mood more negative than by the end of pretrip days. During trips, daily caffeine consumption increased 42%, reports of headache doubled, reports of back pain increased 12-fold, and reports of burning eyes quadrupled. in the cockpits studied, thermal discomfort and high vibration levels were common. Subjective workload during preflight, taxi, climb, and cruise was related to the crewmembers' ratings of the quality of the aircraft systems. During descent and approach, workload was affected by weather at the landing site. During landing, it was influenced by the quality of the landing site and air traffic control. Beginning duty later, and greater attention to aircraft comfort and maintenance, should reduce fatigue in these operations. C1 NASA, Ames Res Ctr, Fatigue Countermeasures Program, Moffett Field, CA 94035 USA. San Jose State Univ Fdn, Moffett Field, CA USA. Sterling Software Inc, Palo Alto, CA USA. Boeing Commercial Airplane Grp, Seattle, WA USA. RP Gander, PH (reprint author), Univ Otago, Wellington Sch Med, Dept Publ Hlth, POB 7343, Wellington, New Zealand. NR 17 TC 9 Z9 9 U1 0 U2 2 PU AEROSPACE MEDICAL ASSOC PI ALEXANDRIA PA 320 S HENRY ST, ALEXANDRIA, VA 22314-3579 USA SN 0095-6562 J9 AVIAT SPACE ENVIR MD JI Aviat. Space Environ. Med. PD SEP PY 1998 VL 69 IS 9 SU S BP B16 EP B25 PG 10 WC Public, Environmental & Occupational Health; Medicine, General & Internal; Sport Sciences SC Public, Environmental & Occupational Health; General & Internal Medicine; Sport Sciences GA 116LY UT WOS:000075727600004 PM 9749937 ER PT J AU Gander, PH Gregory, KB Connell, LJ Graeber, RC Miller, DL Rosekind, MR AF Gander, PH Gregory, KB Connell, LJ Graeber, RC Miller, DL Rosekind, MR TI Flight crew fatigue IV: Overnight cargo operations SO AVIATION SPACE AND ENVIRONMENTAL MEDICINE LA English DT Article ID CIRCADIAN SYSTEM; SLEEP; TEMPERATURE; RHYTHM; WORK AB We monitored 34 B-727 crewmembers before, during, and after 8-d commercial overnight cargo trips crossing no more than one lime zone per 24 h. Daytime sleep episodes were 41% shorter and were rated as poorer than nighttime sleep episodes. When the layover was long enough, crewmembers usually slept again in the evening before going back on night duty. Nevertheless, the total sleep per 24 h on duty days averaged 1.2 h less than pretrip. The circadian temperature rhythm did not adapt completely to night duty, delaying by about 3 h. Self-rated fatigue was highest around the time of the temperature minimum, which occurred near the end of the nighttime duty period. On trip days, crewmembers ate more snacks and there was a marked increase in reports of headaches, congested noses, and burning eyes. Comparisons with daytime short-haul operations confirm that a daytime rest period does not represent the same sleep opportunity as a nighttime rest period of the same duration. We examine regulatory and scheduling options, and personal countermeasure strategies, that could help to reduce sleep loss during overnight cargo operations. C1 NASA, Ames Res Ctr, Fatigue Countermeasures Program, Moffett Field, CA 94035 USA. San Jose State Univ Fdn, Moffett Field, CA USA. Sterling Software Inc, Palo Alto, CA USA. Boeing Commercial Airplane Grp, Seattle, WA USA. RP Gander, PH (reprint author), Univ Otago, Wellington Sch Med, Dept Publ Hlth, POB 7343, Wellington S, New Zealand. NR 38 TC 13 Z9 13 U1 0 U2 0 PU AEROSPACE MEDICAL ASSOC PI ALEXANDRIA PA 320 S HENRY ST, ALEXANDRIA, VA 22314-3579 USA SN 0095-6562 J9 AVIAT SPACE ENVIR MD JI Aviat. Space Environ. Med. PD SEP PY 1998 VL 69 IS 9 SU S BP B26 EP B36 PG 11 WC Public, Environmental & Occupational Health; Medicine, General & Internal; Sport Sciences SC Public, Environmental & Occupational Health; General & Internal Medicine; Sport Sciences GA 116LY UT WOS:000075727600005 PM 9749938 ER PT J AU Gander, PH Gregory, KB Miller, DL Graeber, RC Connell, LJ Rosekind, MR AF Gander, PH Gregory, KB Miller, DL Graeber, RC Connell, LJ Rosekind, MR TI Flight crew fatigue V: Long-haul air transport operations SO AVIATION SPACE AND ENVIRONMENTAL MEDICINE LA English DT Article ID CIRCADIAN-RHYTHMS; SLEEP; TEMPERATURE; AIRCREW AB We monitored 32 flight crewmembers before, during, and after 4-9 d commercial long-haul trips crossing up to 8 time zones per 24 h. The average duty day lasted 9.8 h, and the average layover 24.8 h. Layover sleep episodes averaged 105 min shorter than pretrip sleep episodes. However, in two-thirds of layovers, crewmembers slept twice so that their total sleep per 24 h on trips averaged 49 min less than pretrip. Greater sleep loss was associated with nighttime flights than with daytime fights. The organization of layover sleep depended on prior fight direction, local time, and the circadian cycle. The circadian temperature rhythm did not synchronize to the erratic environmental time cues. Consequently, the circadian low point in alertness and performance sometimes occurred in flight. On trip days, by comparison with pretrip, crewmembers reported higher fatigue and lower activation; drank more caffeine; ate more snacks and fewer meals; and there were marked increases in reports of headaches, congested nose, and back pain. Scheduling strategies and countermeasures to improve layover sleep, cockpit alertness, and performance, are discussed. C1 NASA, Ames Res Ctr, Fatigue Countermeasures Program, Moffett Field, CA 94035 USA. San Jose State Univ Fdn, Moffett Field, CA USA. Sterling Software Inc, Palo Alto, CA USA. Boeing Commercial Airplane Grp, Seattle, WA USA. RP Gander, PH (reprint author), Univ Otago, Wellington Sch Med, Dept Publ Hlth, POB 7343, Wellington, New Zealand. NR 42 TC 21 Z9 22 U1 0 U2 0 PU AEROSPACE MEDICAL ASSOC PI ALEXANDRIA PA 320 S HENRY ST, ALEXANDRIA, VA 22314-3579 USA SN 0095-6562 J9 AVIAT SPACE ENVIR MD JI Aviat. Space Environ. Med. PD SEP PY 1998 VL 69 IS 9 SU S BP B37 EP B48 PG 12 WC Public, Environmental & Occupational Health; Medicine, General & Internal; Sport Sciences SC Public, Environmental & Occupational Health; General & Internal Medicine; Sport Sciences GA 116LY UT WOS:000075727600006 PM 9749939 ER PT J AU Gander, PH Rosekind, MR Gregory, KB AF Gander, PH Rosekind, MR Gregory, KB TI Flight crew fatigue VI: A synthesis SO AVIATION SPACE AND ENVIRONMENTAL MEDICINE LA English DT Article ID SLEEP; WORK; TEMPERATURE; AIRCREW; RHYTHM AB Sleep, circadian rhythms, subjective fatigue, mood, nutrition, and physical symptoms were monitored in flight crews before, during, and after scheduled commercial operations. Duty-related changes in these measures were examined in four different types of air transport: short-haul fixed-wing; short-haul helicopter; domestic overnight cargo; and long-haul. The extent of these changes, and the duty-related and physiological factors contributing to them, are compared among the different operations. During all operations, the level of sleep loss was such that the majority of crewmembers would be expected to have become increasingly sleepy across trip days, with some experiencing performance decrements. In addition, during overnight cargo and long-haul operations, crewmembers were sometimes flying aircraft during the circadian low point in alertness and performance. Specific recommendations for reducing flight crew fatigue are offered for each operating environment. C1 NASA, Ames Res Ctr, Fatigue Countermeasures Program, Moffett Field, CA 94035 USA. San Jose State Univ Fdn, Moffett Field, CA USA. Sterling Software Inc, Palo Alto, CA USA. RP Gander, PH (reprint author), Univ Otago, Wellington Sch Med, Dept Publ Hlth, POB 7343, Wellington S, New Zealand. NR 55 TC 10 Z9 11 U1 0 U2 0 PU AEROSPACE MEDICAL ASSOC PI ALEXANDRIA PA 320 S HENRY ST, ALEXANDRIA, VA 22314-3579 USA SN 0095-6562 J9 AVIAT SPACE ENVIR MD JI Aviat. Space Environ. Med. PD SEP PY 1998 VL 69 IS 9 SU S BP B49 EP B60 PG 12 WC Public, Environmental & Occupational Health; Medicine, General & Internal; Sport Sciences SC Public, Environmental & Occupational Health; General & Internal Medicine; Sport Sciences GA 116LY UT WOS:000075727600007 PM 9749940 ER PT J AU Gander, PH Gregory, KB Graeber, RC Connell, LT Miller, DL Rosekind, MR AF Gander, PH Gregory, KB Graeber, RC Connell, LT Miller, DL Rosekind, MR TI Flight crew fatigue II: Short-haul fixed-wing air transport operations SO AVIATION SPACE AND ENVIRONMENTAL MEDICINE LA English DT Article ID CIRCADIAN-RHYTHM; SLEEP; TEMPERATURE AB We monitored 74 crewmembers before, during, and after 3-4-d commercial short-haul trips crossing no more than one time zone per 24 h. The average duty day lasted 10.6 duty hours, with 4.5 flight hours and 5.5 flights. On trips, crewmembers slept less, woke earlier, and reported having more difficulty falling asleep, with lighter, less restful sleep than pretrip. The consumption of caffeine, alcohol, and snacks increased on trip days, as did reports of headaches, congested nose, and back pain. The study suggests the following ways of reducing fatigue during these operations: base the duration of rest periods on duty hours as well as flight hours; avoid scheduling rest periods progressively earlier across a trip; minimize early duty report times; and inform crewmembers about strategic use of caffeine and alternatives to alcohol for relaxing before sleep. C1 NASA, Ames Res Ctr, Fatigue Countermeasures Program, Moffett Field, CA 94035 USA. San Jose State Univ Fdn, Moffett Field, CA USA. Sterling Software Inc, Palo Alto, CA USA. Boeing Commercial Airplane Grp, Seattle, WA USA. RP Gander, PH (reprint author), Univ Otago, Wellington Sch Med, Dept Publ Hlth, POB 7343, Wellington, New Zealand. NR 26 TC 18 Z9 18 U1 0 U2 0 PU AEROSPACE MEDICAL ASSOC PI ALEXANDRIA PA 320 S HENRY ST, ALEXANDRIA, VA 22314-3579 USA SN 0095-6562 J9 AVIAT SPACE ENVIR MD JI Aviat. Space Environ. Med. PD SEP PY 1998 VL 69 IS 9 SU S BP B8 EP B15 PG 8 WC Public, Environmental & Occupational Health; Medicine, General & Internal; Sport Sciences SC Public, Environmental & Occupational Health; General & Internal Medicine; Sport Sciences GA 116LY UT WOS:000075727600003 PM 9749936 ER PT J AU Wisniewski, R AF Wisniewski, R TI Checkmate SO BIOPHARM-THE APPLIED TECHNOLOGIES OF BIOPHARMACEUTICAL DEVELOPMENT LA English DT Letter C1 NASA, Ames Res Ctr, Mt View, CA USA. NR 2 TC 0 Z9 0 U1 0 U2 0 PU ADVANSTAR COMMUNICATIONS PI DULUTH PA 131 W FIRST ST, DULUTH, MN 55802 USA SN 1040-8304 J9 BIOPHARM-APPL T BIO JI Biopharm-Appl Technol. Biopharm. Dev. PD SEP PY 1998 VL 11 IS 9 BP 10 EP 10 PG 1 WC Biotechnology & Applied Microbiology; Pharmacology & Pharmacy SC Biotechnology & Applied Microbiology; Pharmacology & Pharmacy GA 119RN UT WOS:000075911100005 ER PT J AU Wisniewski, R AF Wisniewski, R TI Large-scale cryopreservation of cells, cell components, and biological solutions SO BIOPHARM-THE APPLIED TECHNOLOGIES OF BIOPHARMACEUTICAL DEVELOPMENT LA English DT Article ID INTRACELLULAR ICE FORMATION; FREEZING-INJURY; LIVING CELLS; MECHANISMS; GLYCEROL; STRESS; WATER C1 NASA, Ames Res Ctr, Mt View, CA USA. Integrated Biosyst, Benicia, CA USA. EM rwisniewski@mail.arc.nasa.gov NR 33 TC 2 Z9 3 U1 1 U2 2 PU ADVANSTAR COMMUNICATIONS PI DULUTH PA 131 W FIRST ST, DULUTH, MN 55802 USA SN 1040-8304 J9 BIOPHARM-APPL T BIO JI Biopharm-Appl Technol. Biopharm. Dev. PD SEP PY 1998 VL 11 IS 9 BP 42 EP + PG 9 WC Biotechnology & Applied Microbiology; Pharmacology & Pharmacy SC Biotechnology & Applied Microbiology; Pharmacology & Pharmacy GA 119RN UT WOS:000075911100011 ER PT J AU Lau, KM Wu, HT Yang, S AF Lau, KM Wu, HT Yang, S TI Hydrologic processes associated with the first transition of the Asian summer monsoon: A pilot satellite study SO BULLETIN OF THE AMERICAN METEOROLOGICAL SOCIETY LA English DT Article ID PRECIPITATION CLIMATOLOGY PROJECT; VERTICAL STRUCTURE INFORMATION; PASSIVE MICROWAVE TECHNIQUE; ESTIMATING RAINFALL; EAST-ASIA; OSCILLATIONS; DYNAMICS; DATASET; PACIFIC; CYCLES AB Results of a pilot study of the evolution of large-scale hydrologic processes associated with the first transition of the Asian summer monsoon in conjunction with the launching of the South China Sea Monsoon Experiment (SCSMEX) in May 1998 are presented. SCSMEX is a major international field experiment to study the water and energy cycles of the Asian monsoon region, with the aim toward better understanding and improved prediction of the onset, maintenance, and variability of the monsoon of southern China, Southeast Asia, and the western pacific region. In this paper, the utility of reliable satellite data in revealing characteristics of the South China Sea (SCS) monsoon is emphasized. Using a combination of satellite-estimated rainfall, moisture, surface wind, and sea surface temperature, the authors present some interesting and hitherto unknown features in large-scale atmospheric and oceanic hydrologic processes associated with the fluctuation of the SCS monsoon. Results show that, climatologically, the SCS monsoon occurs during mid-May when a major convection zone shifts from the eastern Indian Ocean-southern Indochina to the SCS. Simultaneous with the SCS monsoon onset is the development of a moist tongue and frontal rainband emanating from the northern SCS, across southern China and the East China Sea to southern Japan, as well as the enhancement of equatorial convection in the western Pacific ITCZ. Analysis of the satellite-derived moisture and rainfall shows that the onset of the SCS monsoon during 1997 was preceded by the development of eastward-propagating supercloud clusters over the Indian Ocean. The satellite data also reveal a strong onset vortex over the SCS and large-scale cooling and warming patterns over the Indian Ocean and western Pacific. These features signal a major shift of the large-scale hydrologic cycle in the ocean-atmosphere system, which underpins the SCS monsoon onset. The paper concludes with a brief discussion of the observational platform of SCSMEX and a call for the use of satellite data, field observations, and models for comprehensive studies of the Asian monsoon. C1 NASA, Goddard Space Flight Ctr, Climate & Radiat Branch, Atmospheres Lab, Greenbelt, MD 20771 USA. Space Applicat Corp, Vienna, VA USA. Gen Sci Corp, SAIC, Laurel, MD USA. RP Lau, KM (reprint author), NASA, Goddard Space Flight Ctr, Climate & Radiat Branch, Atmospheres Lab, Code 913, Greenbelt, MD 20771 USA. EM lau@climate.gsfc.noaa.gov RI Yang, Song/B-4952-2009; Lau, William /E-1510-2012 OI Lau, William /0000-0002-3587-3691 NR 32 TC 64 Z9 70 U1 0 U2 4 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 USA SN 0003-0007 J9 B AM METEOROL SOC JI Bull. Amer. Meteorol. Soc. PD SEP PY 1998 VL 79 IS 9 BP 1871 EP 1882 DI 10.1175/1520-0477(1998)079<1871:HPAWTF>2.0.CO;2 PG 12 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 122GT UT WOS:000076064100003 ER PT J AU Short, JW Heintz, RA AF Short, JW Heintz, RA TI Source of polynuclear aromatic hydrocarbons in Prince William Sound, Alaska, USA, subtidal sediments SO ENVIRONMENTAL TOXICOLOGY AND CHEMISTRY LA English DT Letter C1 Natl Marine Fisheries Serv, Auke Bay Lab, NOAA, Juneau, AK USA. RP Short, JW (reprint author), Natl Marine Fisheries Serv, Auke Bay Lab, NOAA, Juneau, AK USA. NR 3 TC 0 Z9 0 U1 1 U2 2 PU SETAC PRESS PI PENSACOLA PA 1010 NORTH 12TH AVE, PENSACOLA, FL 32501-3370 USA SN 0730-7268 J9 ENVIRON TOXICOL CHEM JI Environ. Toxicol. Chem. PD SEP PY 1998 VL 17 IS 9 BP 1651 EP 1651 PG 1 WC Environmental Sciences; Toxicology SC Environmental Sciences & Ecology; Toxicology GA 112NX UT WOS:000075501600001 ER PT J AU Fielding, EJ Blom, RG Goldstein, RM AF Fielding, EJ Blom, RG Goldstein, RM TI Rapid subsidence over oil fields measured by SAR interferometry SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID RADAR INTERFEROMETRY; SURFACE DEFORMATION; TOPOGRAPHIC MAPS; LAND SUBSIDENCE AB The Lost Hills and Belridge oilfields are in the San Joaquin Valley, California. The major oil reservoir is high porosity and low permeability diatomite. Extraction of large volumes from shallow depths causes reduction in pore pressure and subsequent compaction, forming a surface subsidence bowl. We measure this subsidence from space using interferometric analysis of SAR (Synthetic Aperture Radar) data collected by the European Space Agency Remote Sensing Satellites (ERS-1 and ERS-2). Maximum subsidence rates are as high as 40 mm in 35 days or > 400 mm/yr, measured from interferograms with time separations ranging from one day to 26 months. The 8- and 26-month interferograms contain areas where the subsidence gradient exceeds the measurement possible with ERS SAR, but shows increased detail in areas of less rapid subsidence. Synoptic mapping of subsidence distribution from satellite data powerfully complements ground-based techniques, permits measurements where access is difficult, and aids identification of underlying causes. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Fielding, EJ (reprint author), CALTECH, Jet Prop Lab, Mailstop 300-233,4800 Oak Grove Dr, Pasadena, CA 91109 USA. RI Fielding, Eric/A-1288-2007 OI Fielding, Eric/0000-0002-6648-8067 NR 24 TC 98 Z9 109 U1 1 U2 10 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD SEP 1 PY 1998 VL 25 IS 17 BP 3215 EP 3218 DI 10.1029/98GL52260 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 116TC UT WOS:000075739800001 ER PT J AU Johnson, RE Killen, RM Waite, JH Lewis, WS AF Johnson, RE Killen, RM Waite, JH Lewis, WS TI Europa's surface composition and sputter-produced ionosphere SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID ION MASS-SPECTROMETRY; ICY SATELLITES; PLANETARY-ATMOSPHERES; COMETARY COMAE; LUNAR-SURFACE; SODIUM; IRRADIATION; BOMBARDMENT; SPECTRA; PLASMA AB The efficient sputtering and decomposition of Europa's regolith by energetic charged particles produces an atmosphere representative of its surface composition. In addition to O(2) and H(2) from the decomposition of ice, we show that molecules representative of organics and salts will be present in ionic form at levels detectable using an ion mass spectrometer on an orbiting spacecraft. Such an instrument can also measure isotope ratios to determine surface age. C1 Univ Virginia, Charlottesville, VA 22903 USA. NASA, Goddard Inst Space Studies, New York, NY 10025 USA. SW Res Inst, San Antonio, TX USA. RP Johnson, RE (reprint author), Univ Virginia, Charlottesville, VA 22903 USA. EM rej@virginia.edu; rkillen@swri.edu; hunter@kronos.space.swri.edu; wlewis@swri.edu NR 44 TC 45 Z9 46 U1 1 U2 7 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD SEP 1 PY 1998 VL 25 IS 17 BP 3257 EP 3260 DI 10.1029/98GL02565 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 116TC UT WOS:000075739800013 ER PT J AU Takeuchi, T Araki, T Lepping, RP Yamamoto, T Kokubun, S Nagai, T Iyemori, T AF Takeuchi, T Araki, T Lepping, RP Yamamoto, T Kokubun, S Nagai, T Iyemori, T TI A magnetic cloud with unusual structure and corresponding bow shock movement observed on May 13, 1995 SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID INTER-PLANETARY; IMP-8 OBSERVATIONS; UNUSUAL LOCATIONS; SOLAR-WIND; MAGNETOPAUSE; SHAPE AB A magnetic cloud embedded in a corotating interaction region was observed by Wind 244 Re upstream of Earth on May 13, 1995. This cloud was unusual as it had at least two internal structures and the profile of the magnetic field strength was far from that predicted by a simple force-free flux rope model, although the field direction fit well. About 90 min later, this cloud was detected by the IMP 8 and Geotail satellites in front of Earth's bow shock. Geotail observed a sunward movement of the bow shock 8 min after the passage of the front boundary. An earthward movement of the bow shock was observed about 3 hours later. From the normal vector of the bow shock front, are deduce that the shape of the expanding bow shock was distorted from an axially symmetric geometry. The shape was consistent with distortion due to the observed inclination of the front boundary of the magnetic cloud. C1 Kyoto Univ, Grad Sch Sci, Dept Geophys, Kyoto 6068502, Japan. NASA, Extraterr Phys Lab, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Inst Space & Astronaut Sci, Kanagawa 2290022, Japan. Nagoya Univ, Solar Terr Environm Lab, Aichi 4420061, Japan. Tokyo Inst Technol, Dept Earth & Planetary Sci, Tokyo 1528551, Japan. Kyoto Univ, Grad Sch Sci, DACGSM, Kyoto 6068502, Japan. RP Takeuchi, T (reprint author), Kyoto Univ, Grad Sch Sci, Dept Geophys, Kyoto 6068502, Japan. NR 13 TC 6 Z9 6 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD SEP 1 PY 1998 VL 25 IS 17 BP 3269 EP 3272 DI 10.1029/98GL02560 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 116TC UT WOS:000075739800016 ER PT J AU Winker, DM Trepte, CR AF Winker, DM Trepte, CR TI Laminar cirrus observed near the tropical tropopause by LITE SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID STRATOSPHERIC AEROSOL; WARM POOL; CLOUDS; PACIFIC AB The Lidar In-space Technology Experiment (LITE) provided near-global observations of optically thin clouds during a 10-day Space Shuttle mission in September 1994. We report here on layers of cirrus occurring in thin sheets, which we refer to as 'laminar' cirrus, observed near the tropical tropopause. The layers were observed to have thicknesses generally between a few hundred meters and one kilometer and to be unusually homogeneous in the horizontal, with extents of up to 2700 km. Layers were observed near and possibly above the mean tropical tropopause, both in clear air and above intense tropical thunderstorms, but only in the tropics (35 degrees N to 20 degrees S). Thin layers near the tropopause were found to be common, but not pervasive, throughout the tropics including regions characterized by large scale subsidence in the middle troposphere. C1 NASA, Langley Res Ctr, Div Atmospher Sci, Dept Atmospher Sci, Hampton, VA 23681 USA. RP Winker, DM (reprint author), NASA, Langley Res Ctr, Div Atmospher Sci, Dept Atmospher Sci, Hampton, VA 23681 USA. NR 17 TC 169 Z9 170 U1 1 U2 3 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD SEP 1 PY 1998 VL 25 IS 17 BP 3351 EP 3354 DI 10.1029/98GL01292 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 116TC UT WOS:000075739800037 ER PT J AU Zhou, YH Zheng, DW Zhao, M Chao, BF AF Zhou, YH Zheng, DW Zhao, M Chao, BF TI Interannual polar motion with relation to the North Atlantic Oscillation SO GLOBAL AND PLANETARY CHANGE LA English DT Article; Proceedings Paper CT Pole-Equator-Pole Symposium on Past Global Change at the 30th International Geological Congress CY AUG, 1996 CL BEIJING, PEOPLES R CHINA DE North Atlantic Oscillation; interannual polar motion; north-south seesaw ID SEA-SURFACE TEMPERATURE; SOUTHERN OSCILLATION; ATMOSPHERIC EXCITATION; GEOPOTENTIAL HEIGHT; EARTHS WOBBLE; EL-NINO; HEMISPHERE; SEASONALITY; LENGTH; FIELDS AB The North Atlantic Oscillation (NAO) is an interannual, north-south seesaw in the atmosphere and ocean. The associated motion and mass redistribution will inevitably cause variations in the Earth's polar motion. The present paper studies the relation of NAO with interannual polar motion. Two monthly series for the period of 1964-1994 are employed: the NAO index (NAOI), which is used as a proxy to measure the intensity of NAG, and the polar motion series. The latter is further processed to obtain the interannual polar motion excitation function psi by deconvolution and subsequent removal of the drift, the seasonal terms and short period variations. The time-domain cross correlation and frequency-domain coherence studies show significant correlations between NAOI and psi especially on the x-component of psi as anticipated from the general pattern of NAG. This suggests possible significant contribution of NAO in exciting interannual polar motion. (C) 1998 Elsevier Science B.V. All rights reserved. C1 Acad Sinica, Shanghai Observ, Shanghai 200030, Peoples R China. NASA, Terr Phys Lab, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Acad Sinica, Shanghai Observ, Shanghai 200030, Peoples R China. RI Chao, Benjamin Fong/N-6156-2013 NR 23 TC 7 Z9 9 U1 1 U2 6 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0921-8181 EI 1872-6364 J9 GLOBAL PLANET CHANGE JI Glob. Planet. Change PD SEP PY 1998 VL 18 IS 3-4 BP 79 EP 84 DI 10.1016/S0921-8181(98)00008-3 PG 6 WC Geography, Physical; Geosciences, Multidisciplinary SC Physical Geography; Geology GA 112TH UT WOS:000075509900002 ER PT J AU Connell, JW Smith, JG Hergenrother, PM AF Connell, JW Smith, JG Hergenrother, PM TI Imide oligomers containing pendent and terminal phenylethynyl groups - II SO HIGH PERFORMANCE POLYMERS LA English DT Article ID POLYIMIDE OLIGOMERS; ANHYDRIDES AB As part of a programme to develop high-performance/high-temperature structural resins for aeronautical applications, imide oligomers containing pendent and terminal phenylethynyl groups were prepared, characterized and the cured resins evaluated as composite matrices. The oligomers were prepared at a calculated number-average molecular weight of 5000 g mol(-1) and contained 15-20 mol% pendent phenylethynyl groups. In previous work. an oligomer containing pendent and terminal phenylethynyl groups exhibited a high glass transition temperature (similar to 313 degrees C), and laminates therefrom exhibited high compressive properties, but processability, fracture toughness, microcrack resistance and damage tolerance were less than desired. In an attempt to improve these deficiencies, modifications in the oligomeric backbone involving the incorporation of 1,3-bis(3-aminophenoxy)benzene were investigated as a means of improving processability and toughness without detracting from the high glass transition temperature and high compressive properties. The amide acid oligomeric solutions were prepared in N-methyl-2-pyrrolidinone and were subsequently processed into imide powder, thin films, adhesive tape and carbon fibre prepreg. Neat resin plaques were fabricated from imide powder by compression moulding. The maximum processing pressure was 1.4 MPa and the cure temperature ranged from 350 to 371 degrees C for 1 h for the mouldings, adhesives, films and composites. The properties of the 1,3-bis(3-aminophenoxy)benzene modified cured imide oligomers containing pendent and terminal phenylethynyl groups are compared with those of previously prepared oligomers containing pendent and terminal phenylethynyl groups of similar composition and molecular weight. C1 NASA, Langley Res Ctr, Div Mat, Hampton, VA 23681 USA. RP Connell, JW (reprint author), NASA, Langley Res Ctr, Div Mat, Hampton, VA 23681 USA. NR 22 TC 23 Z9 25 U1 0 U2 2 PU IOP PUBLISHING LTD PI BRISTOL PA DIRAC HOUSE, TEMPLE BACK, BRISTOL BS1 6BE, ENGLAND SN 0954-0083 J9 HIGH PERFORM POLYM JI High Perform. Polym. PD SEP PY 1998 VL 10 IS 3 BP 273 EP 283 DI 10.1088/0954-0083/10/3/005 PG 11 WC Polymer Science SC Polymer Science GA 131CU UT WOS:000076558800005 ER PT J AU Ellis, SR Menges, BM AF Ellis, SR Menges, BM TI Localization of virtual objects in the near visual field SO HUMAN FACTORS LA English DT Article ID DISTANCE TENDENCY; ACCOMMODATION AB We examined errors in the localization of nearby virtual objects presented via see-through helmet-mounted displays as a function of viewing conditions and scene content in four experiments using a total of 38 participants. Monocular, biocular, and stereoscopic presentation of the virtual objects, accommodation (required focus), participants' age, and the position of physical surfaces were examined. Nearby physical surfaces were found to introduce localization errors that differ depending on the other experimental factors. These errors apparently arise from the occlusion of the physical background by the optically superimposed virtual objects, but they are modified by participants' accommodative competence and specific viewing conditions. The apparent physical size and transparency of the virtual objects and physical surfaces, respectively, are influenced by their relative position when superimposed. The design implications of the findings are discussed in a concluding section. Head-mounted displays of virtual objects are currently being evaluated as aids for mechanical assembly and equipment maintenance. Other applications include telesurgery, surgical planning, telerobotics, and visualization aids for robotic programming. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. San Jose State Univ, San Jose, CA 95192 USA. RP Ellis, SR (reprint author), MS 262-2, Moffett Field, CA 94035 USA. NR 22 TC 34 Z9 34 U1 0 U2 8 PU HUMAN FACTORS SOC PI SANTA MONICA PA BOX 1369, SANTA MONICA, CA 90406 USA SN 0018-7208 J9 HUM FACTORS JI Hum. Factors PD SEP PY 1998 VL 40 IS 3 BP 415 EP 431 DI 10.1518/001872098779591278 PG 17 WC Behavioral Sciences; Engineering, Industrial; Ergonomics; Psychology, Applied; Psychology SC Behavioral Sciences; Engineering; Psychology GA 144CW UT WOS:000077297000006 PM 11536894 ER PT J AU Greeley, R Sullivan, R Klemaszewski, J Homan, K Head, JW Pappalardo, RT Veverka, J Clark, BE Johnson, TV Klaasen, KP Belton, M Moore, J Asphaug, E Carr, MH Neukum, G Denk, T Chapman, CR Pilcher, CB Geissler, PE Greenberg, R Tufts, R AF Greeley, R Sullivan, R Klemaszewski, J Homan, K Head, JW Pappalardo, RT Veverka, J Clark, BE Johnson, TV Klaasen, KP Belton, M Moore, J Asphaug, E Carr, MH Neukum, G Denk, T Chapman, CR Pilcher, CB Geissler, PE Greenberg, R Tufts, R TI Europa: Initial Galileo geological observations SO ICARUS LA English DT Article DE Europa; Europa geology; Galileo; Galilean satellites; jovian satellites ID TIDAL STRESSES; ICY SATELLITES; JUPITER; PATTERNS; WATER; FRACTURE; STATE; SHELL AB Images of Europa from the Galileo spacecraft show a surface with a complex history involving tectonic deformation, impact cratering, and possible emplacement of ice-rich materials and perhaps liquids on the surface, Differences in impact crater distributions suggest that some areas have been resurfaced more recently than others; Europa could experience current cryovolcanic and tectonic activity. Global-scale patterns of tectonic features suggest deformation resulting from non-synchronous rotation of Europa around Jupiter. Some regions of the lithosphere have been fractured, with icy plates separated and rotated into new positions. The dimensions of these plates suggest that the depth to liquid or mobile ice was only a few kilometers at the time of disruption. Some surfaces have also been up-warped, possibly by diapirs, cryomagmatic intrusions, or convective upwelling. In some places, this deformation has led to the development of chaotic terrain in which surface material has collapsed and/or been eroded. (C) 1998 Academic Press. C1 Arizona State Univ, Dept Geol, Tempe, AZ 85287 USA. Brown Univ, Dept Geol Sci, Providence, RI 02912 USA. Cornell Univ, Ithaca, NY 14853 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Natl Opt Astron Observ, Tucson, AZ 85726 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. US Geol Survey, Branch Astrogeol Studies, Menlo Park, CA 94025 USA. DLR, Inst Planetary Explorat, D-12489 Berlin, Germany. SW Res Inst, Boulder, CO 80302 USA. NASA, Washington, DC 20546 USA. Univ Arizona, Lunar & Planetary Lab, Tucson, AZ 85271 USA. RP Greeley, R (reprint author), Arizona State Univ, Dept Geol, Box 871404, Tempe, AZ 85287 USA. EM greeley@asu.edu NR 82 TC 90 Z9 90 U1 0 U2 8 PU ACADEMIC PRESS INC PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA SN 0019-1035 J9 ICARUS JI Icarus PD SEP PY 1998 VL 135 IS 1 BP 4 EP 24 DI 10.1006/icar.1998.5969 PG 21 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 129WZ UT WOS:000076488200002 ER PT J AU Greeley, R Sullivan, R Coon, MD Geissler, PE Tufts, BR Head, JW Pappalardo, RT Moore, JM AF Greeley, R Sullivan, R Coon, MD Geissler, PE Tufts, BR Head, JW Pappalardo, RT Moore, JM TI Terrestrial sea ice morphology: Considerations for Europa SO ICARUS LA English DT Article DE Europa; geological processes (Europa); surfaces (satellites); planetary ices ID GALILEAN SATELLITES; JUPITER; SYSTEM; WATER AB The Galileo mission has returned the first high-resolution (21 m/pixel) images of the surface of Europa, These images reveal structures with morphologies reminiscent of those seen on terrestrial sea ice. Although it is premature to make one-to-one analogies between sea ice and Europa's surface, a review of the types of surface features commonly formed on Earth and of various sea-ice processes can provide insight into the complex geology of Europa. For example, deformation of terrestrial sea ice results from winds, tides, and currents and from thermally induced stresses; the resulting features include fractures ranging in width from millimeters to kilometers, pressure ridges, shear ridges, and rafted ice. Potential agents of deformation on Europa are more likely to be limited to tidal flexing and possibly convection, but could produce similar features and perhaps account for the ridges and fractures seen in many areas. Subtle differences in albedo and color in terrestrial sea ice result from differences in ice thickness and grain size, attributed to factors such as the rate of ice-crystal growth, water turbulence, age of the ice, and deformation. Similar factors could account for differences observed in the bright icy plains of Europa, Moreover, salts in both the solid form and as brine vary in concentration and composition as a function of space and time on Earth, leading to differences in density and the strength of ice sheets. Salts are also suspected in the europan ice and could lead to similar differences, enhancing the creation of topographic relief from density contrasts and the formation of fractures from brittle failure of the ice. Differences in the environments between Europa and terrestrial sea ice in terms of parameters such as temperature, gravity, time, and ice compositions suggest caution in drawing direct analogies. Future work by the planetary and sea-ice communities must include understanding the terrestrial processes sufficiently for extrapolation in Europa. (C) 1998 Academic Press. C1 Arizona State Univ, Dept Geol, Tempe, AZ 85287 USA. NW Res Associates Inc, Bellevue, WA 98007 USA. Univ Arizona, Lunar & Planetary Lab, Tucson, AZ 85271 USA. Brown Univ, Dept Geol Sci, Providence, RI 02912 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Greeley, R (reprint author), Arizona State Univ, Dept Geol, Box 871404, Tempe, AZ 85287 USA. EM greeley@asu.edu NR 48 TC 23 Z9 23 U1 1 U2 4 PU ACADEMIC PRESS INC PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA SN 0019-1035 J9 ICARUS JI Icarus PD SEP PY 1998 VL 135 IS 1 BP 25 EP 40 DI 10.1006/icar.1998.5977 PG 16 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 129WZ UT WOS:000076488200003 ER PT J AU Helfenstein, P Currier, N Clark, BE Veverka, J Bell, M Sullivan, R Klemaszewski, J Greeley, R Pappalardo, RT Head, JW Jones, T Klaasen, K Magee, K Geissler, P Greenberg, R McEwen, A Phillips, C Colvin, T Davies, M Denk, T Neukum, G Belton, MJS AF Helfenstein, P Currier, N Clark, BE Veverka, J Bell, M Sullivan, R Klemaszewski, J Greeley, R Pappalardo, RT Head, JW Jones, T Klaasen, K Magee, K Geissler, P Greenberg, R McEwen, A Phillips, C Colvin, T Davies, M Denk, T Neukum, G Belton, MJS TI Galileo observations of Europa's opposition effect SO ICARUS LA English DT Article DE Europa; photometry; regolith; spectrophotometry; ices; albedo; spectra; geological processes; Galileo; Voyager ID OUTER PLANET SATELLITES; COHERENT BACKSCATTER; WEAK LOCALIZATION; SURFACE; CLEMENTINE; JUPITER; LIGHT; MOON AB During Galileo's G7 orbit, the Solid State Imaging (SSI) camera acquired pictures of the spacecraft shadow point on Europa's surface as well as a comparison set of images showing the same geographic region at phase angle alpha = 5 degrees. Coverage, obtained at three spectral bandpasses (VLT, 0.41 mu m, GRN, 0.56 mu m; and 1MC, 0.99 mu m) at a spatial resolution of 404 m/ pixel, shows a 162 x 220-km region of Europa's surface located at 30 degrees N, 162 degrees W, We have used these images to measure the near-opposition spectrophotometric behavior of four primary europan terrain materials: IR-bright icy material, IR-dark icy material, dark lineament material, and dark spot material. The high spatial resolution of the G7 images reveal low-albedo materials in dark spots that are among the darkest features (17% albedo at 0.56 mu m and 5 degrees phase) yet found on icy Galilean satellites, While material of comparable albedo is found on Ganymede and Callisto, low-albedo europan materials are much redder, All europan surface materials exhibit an opposition effect; however, the strength of the effect, as measured by the total increase in reflectance as phase angle decreases from alpha = 5 degrees to alpha = 0 degrees, varies among terrains, The opposition effects of IR-bright icy and IR-dark icy materials which dominate Europa's surface are about 1.5 times larger than predicted from pre-Galileo studies, Low-albedo materials in dark spots exhibit unusually intense opposition effects (up to four times larger than bright icy europan terrains), consistent with the presence of a strong shadow-hiding opposition surge. The strengths of the opposition surges among average europan terrains systematically vary with terrain albedo and can be explained in terms of the simultaneous contributions of shadow-hiding and coherent-backscatter to the total opposition effect. Coherent backscatter introduces a narrow angular contribution (<0.2 degrees wide) to all europan terrains while the presence of a shadow-hiding contribution is revealed by the fact that the opposition surge is especially strong in low-albedo terrain materials. Stratigraphically young ridges with relatively high topographic relief exhibit anomalously weak opposition surges that could be caused by the presence of relatively coarse-grained regolith, highly compacted particulates, exposures of solid ice, or some combination of these. Very-high resolution images (22 m/pixel) of young-appearing ridges suggest that downslope wasting of particulate cover exposes more lithified ice along ridge crests and wall escarpments. We propose that over time, erosion of ridge topography accompanied by accumulation of detritus and mantling by regolith cover results in more mature ridge surfaces of increasingly lower (mature) porosity. We interpret the dark, reddish color of dark ridges and lineaments as a particulate coating of low-albedo materials vented from (or collected adjacent to) reactivated ridge-margins and within lenticulae. (C) 1998 Academic Press. C1 Cornell Univ, Ctr Radiophys & Space Res, Ithaca, NY 14853 USA. Arizona State Univ, Dept Geol, Tempe, AZ 85287 USA. Brown Univ, Dept Geol Sci, Providence, RI 02912 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Sterling Software Inc, Pasadena, CA 91117 USA. Univ Arizona, Lunar & Planetary Lab, Tucson, AZ 85721 USA. Rand Corp, Santa Monica, CA 90406 USA. DLR, Inst Planetenerkundung, D-12484 Berlin, Germany. Natl Opt Astron Observ, Tucson, AZ 85719 USA. RP Helfenstein, P (reprint author), Cornell Univ, Ctr Radiophys & Space Res, Ithaca, NY 14853 USA. NR 64 TC 55 Z9 55 U1 0 U2 3 PU ACADEMIC PRESS INC PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA SN 0019-1035 J9 ICARUS JI Icarus PD SEP PY 1998 VL 135 IS 1 BP 41 EP 63 DI 10.1006/icar.1998.5975 PG 23 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 129WZ UT WOS:000076488200004 ER PT J AU Hendrix, AR Barth, CA Hord, CW Lane, AL AF Hendrix, AR Barth, CA Hord, CW Lane, AL TI Europa: Disk-resolved ultraviolet measurements using the Galileo ultraviolet spectrometer SO ICARUS LA English DT Article DE Europa; Galileo spacecraft; spectroscopy; ultraviolet observations ID MAGNETOSPHERIC ION-BOMBARDMENT; ABSORPTION-BAND; SATELLITES; SURFACE; SPECTROSCOPY; REFLECTANCE; TERRAINS; JUPITER; ALBEDO AB The Galileo ultraviolet spectrometer has measured the first-ever disk-resolved spectral ultraviolet albedos of regions on Europa's trailing and antijovian hemispheres at spatial resolutions approaching 55 km. We find that the ultraviolet albedo (2400-3200 Angstrom) increases with distance from the trailing hemisphere apex (270 degrees W). Regions close to 270 degrees W display an absorption feature centered near 2800 Angstrom, which generally decreases with distance from the trailing hemisphere apex. These results substantiate the idea that magnetospheric bombardment darkens the surface of the entire trailing hemisphere and creates an absorber in the central portion of the trailing hemisphere. The absorption is related to sulfur, but is much darker than any laboratory spectra, likely due to the large grain size on Europa's trailing hemisphere. The disk-resolved observations, in combination with three disk-integrated observations, are used to derive the ultraviolet particle scattering function for Europa's trailing hemisphere. (C) 1998 Academic Press. C1 Univ Colorado, Atmospher & Space Phys Lab, Boulder, CO 80309 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Hendrix, AR (reprint author), Univ Colorado, Atmospher & Space Phys Lab, 1234 Innovat Dr, Boulder, CO 80309 USA. NR 36 TC 22 Z9 22 U1 0 U2 2 PU ACADEMIC PRESS INC PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA SN 0019-1035 J9 ICARUS JI Icarus PD SEP PY 1998 VL 135 IS 1 BP 79 EP 94 DI 10.1006/icar.1998.5983 PG 16 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 129WZ UT WOS:000076488200006 ER PT J AU Clark, BE Helfenstein, P Veverka, J Ockert-Bell, M Sullivan, RJ Geissler, PE Phillips, CB McEwen, AS Greeley, R Neukum, G Denk, T Klaasen, K AF Clark, BE Helfenstein, P Veverka, J Ockert-Bell, M Sullivan, RJ Geissler, PE Phillips, CB McEwen, AS Greeley, R Neukum, G Denk, T Klaasen, K CA Galileo SSI Team TI Multispectral terrain analysis of Europa from Galileo images SO ICARUS LA English DT Article DE Europa; Galileo; multispectral imaging ID SATELLITES; SURFACE; BOMBARDMENT; PHOTOMETRY; JUPITER AB Galileo's Solid State Imaging camera recorded six images at wavelengths from 0.41 to 0.99 mu m of Europa's trailing hemisphere (similar to 1.6 km/pixel resolution) during the G1 orbit (1st orbit-target Ganymede) of the nominal mission. We have photometrically corrected these data and extracted spectra representing Europa's diverse geologic terrains. The goals of the analysis of these spectra are (1) to determine whether Europa's geologic units differ spectrally from one another, (2) to determine the number of color components necessary to explain Europa's dark material spectral behavior, and (3) to examine how europan dark materials may change in color with time. Our data indicate that europan dark spots, lineaments and triple band side materials represent a single "dark" and reddish endmember component. We see no evidence for more than one dark endmember; however the dark endmember seen in these G1 data is probably not a "pure" exposure of europan dark material. Mottled terrains, brighter lineaments, and aging triple bands can be modeled by a mixture of bright plains materials and the dark component. Exposures of europan dark materials may thus be brightening with time, eventually blending into the surrounding bright plains. (C) 1998 Academic Press. C1 Cornell Univ, Ctr Radiophys & Space Res, Ithaca, NY 14853 USA. Univ Arizona, Lunar & Planetary Lab, Tucson, AZ 85724 USA. Arizona State Univ, Dept Geol, Tempe, AZ 85287 USA. Deutsch Forschungsanstalt Luft & Raumfahrt, Inst Planetenerkundung, D-12484 Berlin, Germany. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Clark, BE (reprint author), Cornell Univ, Ctr Radiophys & Space Res, Ithaca, NY 14853 USA. NR 28 TC 20 Z9 20 U1 1 U2 2 PU ACADEMIC PRESS INC PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA SN 0019-1035 J9 ICARUS JI Icarus PD SEP PY 1998 VL 135 IS 1 BP 95 EP 106 DI 10.1006/icar.1998.5968 PG 12 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 129WZ UT WOS:000076488200007 ER PT J AU Moore, JM Asphaug, E Sullivan, RJ Klemaszewski, JE Bender, KC Greeley, R Geissler, PE McEwen, AS Turtle, EP Phillips, CB Tufts, BR Head, JW Pappalardo, RT Jones, KB Chapman, CR Belton, MJS Kirk, RL Morrison, D AF Moore, JM Asphaug, E Sullivan, RJ Klemaszewski, JE Bender, KC Greeley, R Geissler, PE McEwen, AS Turtle, EP Phillips, CB Tufts, BR Head, JW Pappalardo, RT Jones, KB Chapman, CR Belton, MJS Kirk, RL Morrison, D TI Large impact features on Europa: Results of the Galileo nominal mission SO ICARUS LA English DT Article ID GANYMEDE; ICE; CALLISTO; CORONAE; ORIGIN; VENUS; SATELLITES; RELAXATION; EVOLUTION; RHEOLOGY AB The Galileo Orbiter examined several impact features on Europa at considerably better resolution than was possible from Voyager. The new data allow us to describe the morphology and infer the geology of the largest impact features on Europa, which are probes into the crust, We observe two basic types of large impact features: (1) "classic" impact craters that grossly resemble well-preserved lunar craters of similar size but are more topographically subdued (e.g., Pwyll) and (2) very flat circular features that lack the basic topographic structures of impact craters such as raised rims, a central depression, or central peaks, and which largely owe their identification as impact features to the field of secondary craters radially sprayed about them (e.g., Callanish), Our interpretation is that the classic craters (all <30 km diameter) formed entirely within a solid target at least 5 to 10 km thick that exhibited brittle behavior an time scales of the impact events. Some of the classic craters have a more subdued topography than fresh craters of similar size on other icy bodies such as Ganymede and Callisto, probably due to the enhanced viscous relaxation produced by a steeper thermal gradient on Europa, Pedestal ejecta facies on Europa (and Ganymede) may be produced by the relief-flattening movement of plastically deforming but otherwise solid ice that was warm at the time of emplacement, Callanish and Tyre do not appear to be larger and even more viscously relaxed versions of the classic craters; rather they display totally different morphologies such as distinctive textures and a series of large concentric structural rings cutting impact-feature-related materials. Impact simulations suggest that the distinctive morphologies would not be produced by impact into a solid ice target, but may be explained by impact into an ice layer similar to 10 to 15 km thick overlying a low-viscosity material such as water. The very wide (near antipodal) separation of Callanish and Tyre imply that similar to 10-15 km may have been the global average thickness of the rigid crust of Europa when these impacts occurred. The absence of detectable craters superposed on the interior deposits of Callanish suggests that it is geologically young (<10(8) years). Hence, it seems likely that our preliminary conclusions about the subsurface structure of Europa apply to the current day. (C) 1998 Academic Press. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Arizona State Univ, Dept Geol, Tempe, AZ 85287 USA. Univ Arizona, Lunar & Planetary Lab, Tucson, AZ 85721 USA. Brown Univ, Dept Geol Sci, Providence, RI 02912 USA. SW Res Inst, Boulder, CO 80302 USA. Natl Opt Astron Observ, Tucson, AZ 85717 USA. US Geol Survey, Flagstaff, AZ 86001 USA. RP Moore, JM (reprint author), NASA, Ames Res Ctr, MS 245-3, Moffett Field, CA 94035 USA. RI Turtle, Elizabeth/K-8673-2012; Jones, Kevin/A-7449-2014 OI Turtle, Elizabeth/0000-0003-1423-5751; Jones, Kevin/0000-0002-6386-2623 NR 52 TC 71 Z9 71 U1 0 U2 7 PU ACADEMIC PRESS INC PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA SN 0019-1035 J9 ICARUS JI Icarus PD SEP PY 1998 VL 135 IS 1 BP 127 EP 145 DI 10.1006/icar.1998.5973 PG 19 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 129WZ UT WOS:000076488200009 ER PT J AU Simonelli, DP Veverka, J Senske, DA Fanale, FP Schubert, G Belton, MJS AF Simonelli, DP Veverka, J Senske, DA Fanale, FP Schubert, G Belton, MJS TI Galileo search for SO2-frost condensation on Io's nightside SO ICARUS LA English DT Article DE atmospheres, dynamics; Galileo spacecraft; Io; surfaces, satellite ID SO2 ATMOSPHERE; SATELLITES; PHOTOMETRY; IMAGES; UV AB New, high-quality Galileo images of Io's dayside and Jupiterlit nightside, examined for diurnal changes in violet albedo patterns and diurnal changes in hemispheric color, do not provide any evidence for significant nighttime condensation of the satellite's thin SO2 atmosphere. In particular, the Galileo images do not show the major change in Io's average hemispheric color between day and night that was reported by Buratti et al. (1995, Icarus 118, 418-422) in a study of Voyager data. The lack of detectable nighttime frost deposition in the Galileo images is not surprising, given the tenuous, "patchy" nature of Io's SO2 atmosphere and the associated difficulty in producing optically thick nighttime frost layers. (C) 1998 Academic Press. C1 Cornell Univ, Ctr Radiophys & Space Res, Ithaca, NY 14853 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ Hawaii, Inst Geophys, Honolulu, HI 96822 USA. Univ Calif Los Angeles, Dept Earth & Space Sci, Los Angeles, CA 90095 USA. Natl Opt Astron Observ, Tucson, AZ 85719 USA. RP Simonelli, DP (reprint author), Cornell Univ, Ctr Radiophys & Space Res, Space Sci Bldg, Ithaca, NY 14853 USA. NR 18 TC 10 Z9 10 U1 0 U2 0 PU ACADEMIC PRESS INC PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA SN 0019-1035 J9 ICARUS JI Icarus PD SEP PY 1998 VL 135 IS 1 BP 166 EP 174 DI 10.1006/icar.1998.5974 PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 129WZ UT WOS:000076488200011 ER PT J AU McEwen, AS Keszthelyi, L Geissler, P Simonelli, DP Carr, MH Johnson, TV Klaasen, KP Breneman, HH Jones, TJ Kaufman, JM Magee, KP Senske, DA Belton, MJS Schubert, G AF McEwen, AS Keszthelyi, L Geissler, P Simonelli, DP Carr, MH Johnson, TV Klaasen, KP Breneman, HH Jones, TJ Kaufman, JM Magee, KP Senske, DA Belton, MJS Schubert, G TI Active volcanism on to as seen by Galileo SSI SO ICARUS LA English DT Article DE Io; volcanism; infrared observations; satellites of Jupiter; spacecraft ID INFRARED MAPPING SPECTROMETER; JUPITERS SATELLITE IO; SILICATE VOLCANISM; SULFUR FLOWS; GLOBAL DISTRIBUTION; INTERNAL STRUCTURE; TIDAL DISSIPATION; THERMAL EMISSION; SOLID SULFUR; LAVA FLOWS AB Active volcanism on Io has been monitored during the nominal Galileo satellite tour from mid 1996 through late 1997, The Solid State Imaging (SSI) experiment was able to observe many manifestations of this active volcanism, including (1) changes in the color and albedo of the surface, (2) active airborne plumes, and (3) glowing vents seen in eclipse. About 30 large-scale (tens of kilometers) surface changes are obvious from comparison of the SSI images to those acquired by Voyager in 1979, These include new pyroclastic deposits of several colors, bright and dark flows, and caldera-floor materials. There have also been significant surface changes on Io during the Galileo mission itself, such as a new 400-km-diameter dark pyroclastic deposit around Pillan Patera, While these surface changes are impressive, the number of large-scale changes observed in the four months between the Voyager 1 and Voyager 2 flybys in 1979 suggested that over 17 years the cumulative changes would have been much more impressive. There are two reasons why this was not actually the case, First, it appears that the most widespread plume deposits are ephemeral and seem to disappear within a few years. Second, it appears that a large fraction of the volcanic activity is confined to repeated resurfacing of dark calderas and flow fields that cover only a few percent of Io's surface. The plume monitoring has revealed 10 active plumes, comparable to the 9 plumes observed by Voyager. One of these plumes was visible only in the first orbit and three became active in the later orbits, Only the Prometheus plume has been consistently active and easy to detect. Observations of the Pele plume have been particularly intriguing since it was detected only once by SSI, despite repeated attempts, but has been detected several times by the Hubble Space Telescope at 255 nm, Pele's plume is much taller (460 km) than during Voyager 1 (300 km) and much fainter at visible wavelengths. Prometheus-type plumes (50-150 km high, long-lived, associated with high-temperature hot spots) may result from silicate lava flows or shallow intrusions interacting with near-surface SO2. A major and surprising result is that similar to 30 of Io's volcanic vents glow in the dark at the short wavelengths of SSI, These are probably due to thermal emission from surfaces hotter than 700 K (with most hotter than 1000 K), well above the temperature of pure sulfur volcanism. Active silicate volcanism appears ubiquitous, There are also widespread diffuse glows seen in eclipse, related to the interaction of energetic particles with the atmosphere. These diffuse glows are closely associated with the most active volcanic vents, supporting suggestions that Io's atmosphere is dominated by volcanic outgassing. Globally, volcanic centers are rather evenly distributed. However, 14 of the 15 active plumes seen by Voyager and/or Galileo are within 30 degrees of the equator, and there are concentrations of glows seen in eclipse at both the sub- and antijovian points. These patterns might be related to asthenospheric tidal heating or tidal stresses. Io will continue to be observed during the Galileo Europa Mission, which will climax with two close flybys of Io in late 1999. (C) 1998 Academic Press. C1 Univ Arizona, Lunar & Planetary Lab, Tucson, AZ 85721 USA. Cornell Univ, Ctr Radiophys & Space Res, Ithaca, NY 14853 USA. US Geol Survey, Menlo Park, CA 94025 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Natl Opt Astron Observ, Tucson, AZ 85726 USA. Univ Calif Los Angeles, Dept Earth & Space Sci, Los Angeles, CA 90095 USA. RP McEwen, AS (reprint author), Univ Arizona, Lunar & Planetary Lab, Tucson, AZ 85721 USA. EM mcewen@pirl.lpl.arizona.edu NR 95 TC 131 Z9 131 U1 0 U2 5 PU ACADEMIC PRESS INC PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA SN 0019-1035 J9 ICARUS JI Icarus PD SEP PY 1998 VL 135 IS 1 BP 181 EP 219 DI 10.1006/icar.1998.5972 PG 39 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 129WZ UT WOS:000076488200013 ER PT J AU Banfield, D Gierasch, PJ Bell, M Ustinov, E Ingersoll, AP Vasavada, AR West, RA Belton, MJS AF Banfield, D Gierasch, PJ Bell, M Ustinov, E Ingersoll, AP Vasavada, AR West, RA Belton, MJS TI Jupiter's cloud structure from Galileo imaging data SO ICARUS LA English DT Article DE atmospheres, composition, structure; clouds; Jupiter atmosphere; radiative transfer; spectrophotometry ID SOUTH EQUATORIAL BELT; METHANE BAND PHOTOMETRY; LARGE PHASE ANGLES; IRIS OBSERVATIONS; WATER-VAPOR; ATMOSPHERE; PROBE; ZONE; TROPOSPHERE; CIRCULATION AB The vertical structure of aerosols on Jupiter is inferred from data obtained by the NASA Galileo Solid State Imaging system during the first six orbits of the spacecraft. Images at 889 nm (a strong methane band), 727 nm (a weaker methane band), and 756 nn (continuum) taken at a variety of lighting and viewing angles are used. The images are displayed and described in the companion paper by Vasavada et al. (1998, Icarus 135, 265-275). Conservative scattering cloud particles with laterally uniform single scattering properties are assumed in the analysis and are shown to be consistent with the data at these wavelengths. Particles are bright, and the darkest locations on Jupiter correspond to the smallest optical thickness of aerosols, Optical depths and vertical positions of aerosol layers vary from place to place and are the retrieved quantities in the analysis. Only mid and low latitudes are sampled in this data set. A stratospheric haze with an optical depth of roughly a tenth and an upper tropospheric haze with an optical depth of 2 to 6 exist over all regions. Both are consistent with previous conclusions based on data of lower spatial resolution (e.g., West et al. 1986, Icarus 65, 161-217). The new data show that these layers contain little lateral structure on scales smaller than the planetary jets. On scales of the jets and ovals, the top and bottom of the upper tropospheric haze vary in elevation. The concentration of particles (optical depth per pressure interval) varies less than does the total optical depth. Near the base of the upper tropospheric haze is a third cloud component, usually at pressure p = 750 +/- 200 mb, which is less than a scale height in geometric thickness. Its optical depth varies from zero to about 20 on regional scales and often varies by 50% on scales of a few tens of kilometers. Optical depth variations in this cloud are the principal cause of the features in Jupiter's atmosphere seen at red and longer wavelengths. It is probably composed of ammonia. The expected NH4SH cloud has not been identified in this work, perhaps because it exists only at locations where it is concealed beneath higher clouds. Our retrievals also cannot rule out a pervasive deep haze without small-scale structure. Finally, in one region northwest of the Great Red Spot, a deeper cloud is identified. Parts of it lie at a pressure greater than four bars. It is associated with a rapidly changing storm system with optical depth of several tens (or more) and a range of cloud heights between p > 4 bars to p similar to 400 mb. It is probably composed of water. (C) 1998 Academic Press. C1 Cornell Univ, Dept Astron, Ithaca, NY 14853 USA. CALTECH, Pasadena, CA 91125 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Natl Opt Astron Observ, Tucson, AZ 85719 USA. RP Banfield, D (reprint author), Cornell Univ, Dept Astron, Ithaca, NY 14853 USA. RI Ustinov, Eugene/D-1350-2015; OI Ustinov, Eugene/0000-0003-0227-4286; Banfield, Don/0000-0003-2664-0164 NR 42 TC 118 Z9 118 U1 0 U2 5 PU ACADEMIC PRESS INC PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA SN 0019-1035 J9 ICARUS JI Icarus PD SEP PY 1998 VL 135 IS 1 BP 230 EP 250 DI 10.1006/icar.1998.5985 PG 21 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 129WZ UT WOS:000076488200015 ER PT J AU Ingersoll, AP Vasavada, AR Little, B Anger, CD Bolton, SJ Alexander, C Tobiska, WK AF Ingersoll, AP Vasavada, AR Little, B Anger, CD Bolton, SJ Alexander, C Tobiska, WK CA Galileo SSI Team TI Imaging Jupiter's aurora at visible wavelengths SO ICARUS LA English DT Article DE Aurorae; Jupiter, atmosphere, general; atmospheres, structure, Jupiter; ionospheres, Jupiter; magnetospheres, Io ID ATMOSPHERE; IMAGES; MORPHOLOGY; VOYAGER-1; ENCOUNTER; EMISSIONS; REGIONS; H-3+ AB On November 9, 1996 and again on April 2, 1997, the Galileo spacecraft's Solid State Imaging (SSI) camera targeted the northern auroral region of Jupiter, These observations represent (i) the first spatially resolved images of the jovian auroral oval either at visible wavelengths or on the nightside of the planet, (ii) the first image at visible wavelengths of an auroral footprint of the Io Flux Tube (IFT), (iii) the first unambiguous detection at visible wavelengths of auroral emission on the jovian limb, and (iv) the first images of the aurora with spatial resolution below 100 km per pixel (46 and 35 km, respectively). Relative to many prior expectations, the visible aurora is (i) lower in altitude, (ii) associated with magnetic field lines that cross the equator closer to the planet, and (iii) more variable in time and space. The 1996 images used a clear (broadband) filter, while the 1997 images used both the clear filter and five narrower filters over wavelengths ranging from violet to 968 nm. The filtered images imply that the visible auroral emission contains atomic hydrogen lines, although there is also a continuum component. We were able to position the aurora in three-dimensional space and found the limb emission to be similar to 240 km above the surface of a standard (P approximate to 1 bar) reference ellipsoid. Our most accurate analysis of the equatormost part of the oval placed it at 54.5 degrees planetocentric latitude and 168 degrees west longitude. Combined with the latest magnetic field models, our results imply that the particles that cause the aurora originate in Jupiter's equatorial plane similar to 13 R-J from the center of the planet. The oval was brighter and wider in the 1996 images than in the 1997 images. The broadband radiance of a typical place on the oval as seen directly overhead varied from similar to 80 kR in 1997 to similar to 300 kR in 1996. Our estimates of the full width of the oval varied from under 500 km to over 8000 km, partly depending on the signal-to-noise ratio of the image. The radiated power per unit length along the oval ranged from similar to 60 to similar to 700 W/m, with the associated radiated power from the entire oval varying from similar to 10(9) to similar to 9 x 10(10) W, Appreciable auroral emission also occurred both north and south of the main oval. One image contains the northern footprint of the IFT, which appears as a central ellipse with a tail of emission that lies downstream with respect to the plasma flow past Io. The central ellipse is similar to 1200 km downstream by similar to 500 km cross stream. The IFT is comparable in brightness to the nearby auroral oval (similar to 250 kR) and has a total radiated power of similar to 3 x 10(8) W. (C) 1998 Academic Press. C1 CALTECH, Div Geol & Planetary Sci, Pasadena, CA 91125 USA. ITRES Res, Calgary, AB T1Y 5Z6, Canada. Fed Data Corp, Jet Prop Lab, Pasadena, CA 91109 USA. RP Ingersoll, AP (reprint author), CALTECH, Div Geol & Planetary Sci, Pasadena, CA 91125 USA. NR 31 TC 42 Z9 42 U1 1 U2 5 PU ACADEMIC PRESS INC PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA SN 0019-1035 J9 ICARUS JI Icarus PD SEP PY 1998 VL 135 IS 1 BP 251 EP 264 DI 10.1006/icar.1998.5971 PG 14 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 129WZ UT WOS:000076488200016 ER PT J AU Vasavada, AR Ingersoll, AP Banfield, D Bell, M Gierasch, PJ Belton, MJS Orton, GS Klaasen, KP DeJong, E Breneman, HH Jones, TJ Kaufman, JM Magee, KP Senske, DA AF Vasavada, AR Ingersoll, AP Banfield, D Bell, M Gierasch, PJ Belton, MJS Orton, GS Klaasen, KP DeJong, E Breneman, HH Jones, TJ Kaufman, JM Magee, KP Senske, DA TI Galileo imaging of Jupiter's atmosphere: The Great Red Spot, equatorial region, and White Ovals SO ICARUS LA English DT Article DE Jupiter atmosphere; atmospheric dynamics; image processing; spacecraft ID IMAGES; PROBE; FLOW AB During the first six orbits of the Galileo spacecraft's prime mission, the Solid State Imaging (SSI) system acquired multispectral image mosaics of Jupiter's Great Red Spot, an equatorial belt/zone boundary, a "5-mu m hot spot" similar to the Galileo Probe entry site, and two of the classic White Ovals. We present mosaics of each region, approximating their appearance at visible wavelengths and showing cloud height and opacity variations. The local wind field is derived by tracking cloud motions between multiple observations of each region with time separations of roughly 1 and 10 hr. Vertical cloud structure is derived in a companion paper by Banfield et al, (Icarus 135, 230-250). Galileo's brief, high-resolution observations complement Earth-based and Voyager studies and offer local meteorological context for the Galileo Probe results. Our results show that the dynamics of the zonal jets and large vortices have changed little since Voyager, with a few exceptions. We detect a cyclonic current within the center of the predominantly anticyclonic Great Red Spot, The zonal velocity difference between 0 degrees S and 6 degrees S has increased by 20 m sec(-1). We measure a strong northeast flow approaching the hot spot, This flow indicates either massive horizontal convergence or the presence of a large anticyclonic vortex southeast of the hot spot, The current compact arrangement of two White Ovals and a cyclonic structure greatly perturbs the zonal jets in that region. (C) 1998 Academic Press. C1 CALTECH, Div Geol & Planetary Sci, Pasadena, CA 91125 USA. Cornell Univ, Dept Astron, Ithaca, NY 14853 USA. Natl Opt Astron Observ, Tucson, AZ 85719 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Vasavada, AR (reprint author), CALTECH, Div Geol & Planetary Sci, Mail Stop 150-21, Pasadena, CA 91125 USA. EM ashwin@gps.caltech.edu OI Banfield, Don/0000-0003-2664-0164 NR 21 TC 73 Z9 73 U1 0 U2 1 PU ACADEMIC PRESS INC PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA SN 0019-1035 J9 ICARUS JI Icarus PD SEP PY 1998 VL 135 IS 1 BP 265 EP 275 DI 10.1006/icar.1998.5984 PG 11 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 129WZ UT WOS:000076488200017 ER PT J AU Pappalardo, RT Head, JW Collins, GC Kirk, RL Neukum, G Oberst, J Giese, B Greeley, R Chapman, CR Helfenstein, P Moore, JM McEwen, A Tufts, BR Senske, DA Breneman, HH Klaasen, K AF Pappalardo, RT Head, JW Collins, GC Kirk, RL Neukum, G Oberst, J Giese, B Greeley, R Chapman, CR Helfenstein, P Moore, JM McEwen, A Tufts, BR Senske, DA Breneman, HH Klaasen, K TI Grooved terrain on Ganymede: First results from Galileo high-resolution imaging SO ICARUS LA English DT Article DE Ganymede; satellites of Jupiter; tectonics; surfaces, satellite ID EXTENSIONAL TECTONICS; SATELLITES; JUPITER; FEATURES; SYSTEM; PHOTOCLINOMETRY; TRANSPRESSION; EVOLUTION; IMAGES; FAULTS AB High-resolution Galileo imaging has provided important insight into the origin and evolution of grooved terrain on Ganymede, The Uruk Sulcus target site was the first imaged at high resolution, and considerations of resolution, viewing geometry, low image compression, and complementary stereo imaging make this region extremely informative. Contrast variations in these low-incidence angle images are extreme and give the visual impression of topographic shading. However, photometric analysis shows that the scene must owe its character to albedo variations. A close correlation of albedo variations to topography is demonstrated by limited stereo coverage, allowing extrapolation of the observed brightness and topographic relationships to the rest of the imaged area. Distinct geological units are apparent across the region, and ridges and grooves are ubiquitous within these units. The stratigraphically lowest and most heavily cratered units ("lineated grooved terrain") generally show morphologies indicative of horst-and-graben-style normal faulting. The stratigraphically highest groove lanes ("parallel ridged terrain") exhibit ridges of roughly triangular cross section, suggesting that tilt-block-style normal faulting has shaped them. These extensional-tectonic models are supported by crosscutting relationships at the margins of groove lanes. Thus, a change in tectonic style with time is suggested in the Uruk Sulcus region, varying from horst and graben faulting for the oldest grooved terrain units to tilt block normal faulting for the latest units. The morphologies and geometries of some stratigraphically high units indicate that a strike-slip component of deformation has played an important role in shaping this region of grooved terrain. The most recent tectonic episode is interpreted as right-lateral transtension, with its tectonic pattern of two contemporaneous structural orientations superimposed on older units of grooved terrain. There is little direct evidence for cryovolcanic resurfacing in the Uruk Sulcus region; instead tectonism appears to be the dominant geological process that has shaped the terrain. A broad wavelength of deformation is indicated, corresponding to the Voyager-observed topography, and may be the result of ductile necking of the lithosphere, while a finer scale of deformation probably reflects faulting of the brittle near surface. The results here form a basis against which other Galileo grooved terrain observations can be compared. (C) 1998 Academic Press. C1 Brown Univ, Dept Geol Sci, Providence, RI 02912 USA. US Geol Survey, Flagstaff, AZ 86001 USA. DLR, Inst Planetary Explorat, D-12489 Berlin, Germany. SW Res Inst, Boulder, CO 80302 USA. Cornell Univ, Lab Planetary Sci, Ithaca, NY 14853 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Univ Arizona, Lunar & Planetary Lab, Tucson, AZ 85721 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Pappalardo, RT (reprint author), Brown Univ, Dept Geol Sci, Providence, RI 02912 USA. EM robert_pappalardo@brown.edu NR 66 TC 56 Z9 56 U1 0 U2 4 PU ACADEMIC PRESS INC PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA SN 0019-1035 J9 ICARUS JI Icarus PD SEP PY 1998 VL 135 IS 1 BP 276 EP 302 DI 10.1006/icar.1998.5966 PG 27 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 129WZ UT WOS:000076488200018 ER PT J AU Prockter, LM Head, JW Pappalardo, RT Senske, DA Neukum, G Wagner, R Wolf, U Oberst, J Giese, B Moore, JM Chapman, CR Helfenstein, P Greeley, R Breneman, HH Belton, MJS AF Prockter, LM Head, JW Pappalardo, RT Senske, DA Neukum, G Wagner, R Wolf, U Oberst, J Giese, B Moore, JM Chapman, CR Helfenstein, P Greeley, R Breneman, HH Belton, MJS TI Dark terrain on Ganymede: Geological mapping and interpretation of Galileo Regio at high resolution SO ICARUS LA English DT Article DE Ganymede; geological processes; satellites, general; satellites of Jupiter; surfaces, satellite ID POLAR CAPS; CALLISTO; JUPITER; SATELLITES; EVOLUTION; ICE; SYSTEM; SURFACES; CRATERS; IMAGES AB During its first two encounters with Ganymede, the Galileo spacecraft obtained images of a 16,500 km(2) portion of Galileo Regio, a large expanse of dark terrain, at high resolution (76-86 m/pixel). Through mapping of the G1 and G2 target sites within Galileo Regio, we are able to characterize geological units based on their morphology and relative albedo. We find three generally low albedo units: an intermediate albedo plains unit, a lower albedo plains unit, and the lowest albedo unit which is found on furrow and crater floors. We also find high albedo units which include crater rims, furrow rims, and isolated knobs and massifs. Other features include an intermediate albedo lobate feature interpreted to be a palimpsest and a hummocky unit interpreted to be impact ejecta, Several processes are interpreted to have occurred within Galileo Regio, These include tectonic deformation, mass wasting, sublimation, resurfacing by impact ejecta, and possibly cryovolcanism and isostatic adjustment. We observe that the NW-SE trending furrows (Lakhmu Fossae) in Galileo Regio are degraded and are crosscut by the younger N-S trending furrows (Zu Fossae). We also find several other tectonic features which may be minor faults or fractures related to one or other of these systems. Through mapping and crater size-frequency distributions, are are able to propose a stratigraphy for the Galileo Regio target site. The oldest features in the area are high albedo knobs and massifs, which are interpreted to be remnants of early impact-related features and furrow rims. These may have formed at approximately the same time as the intermediate and low albedo plains units and the furrow systems. The lowest albedo unit of furrow floors probably subsequently evolved through sublimation and mass wasting. Much of the northeast portion of the target area was subsequently obscured by one of the youngest units, ejecta from an impact just to the north. We use our mapping of the high-resolution images of Galileo Regio to evaluate three end-member models for the formation of dark terrain: (1) the crust is dark throughout, (2) material on the surface is the result of a low albedo cryovolcanic layer over a higher albedo crust, and (3) dark material is distributed in small quantities throughout the crust, and geological processes have acted to concentrate low albedo material on the surface. Although it is possible that elements of more than one of these models are present within the dark terrain, we find that the third model, that of a thin veneer of low albedo material, best fits observations of Galileo Regio. (C) 1998 Academic Press. C1 Brown Univ, Dept Geol Sci, Providence, RI 02912 USA. Sterling Software, Jet Prop Lab, Pasadena, CA 91109 USA. DLR, Inst Planetary Explorat, D-12489 Berlin, Germany. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. SW Res Inst, Boulder, CO 80302 USA. Cornell Univ, Dept Astron, Ithaca, NY 14853 USA. Arizona State Univ, Dept Geol, Tempe, AZ 85287 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Natl Opt Astron Observ, Tucson, AZ 85719 USA. RP Prockter, LM (reprint author), Brown Univ, Dept Geol Sci, Box 1846, Providence, RI 02912 USA. EM Louise_Prockter@brown.edu NR 63 TC 46 Z9 46 U1 0 U2 3 PU ACADEMIC PRESS INC PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA SN 0019-1035 J9 ICARUS JI Icarus PD SEP PY 1998 VL 135 IS 1 BP 317 EP 344 DI 10.1006/icar.1998.5981 PG 28 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 129WZ UT WOS:000076488200020 ER PT J AU Thomas, PC Burns, JA Rossier, L Simonelli, D Veverka, J Chapman, CR Klaasen, K Johnson, TV Belton, MJS AF Thomas, PC Burns, JA Rossier, L Simonelli, D Veverka, J Chapman, CR Klaasen, K Johnson, TV Belton, MJS TI The small inner satellites of Jupiter SO ICARUS LA English DT Article DE satellites; Jupiter; cratering; photometry ID CHARGED DUST; AMALTHEA; EJECTION; DYNAMICS; SURFACE; IMPACT; GRAINS; SHAPE; IDA AB The images of the four inner small jovian satellites obtained by the Galileo Solid State Imaging (SSI) experiment have much more detailed shape, color, and photometric information than were provided previously by Voyager images. The satellites are in synchronous rotation and show no binary or bifurcated shapes. Thebe and Amalthea have densities of large craters approximately at "empirical equilibrium" levels, The leading sides of Metis, Amalthea, and Thebe are all 25-35% brighter than their trailing sides; the global-average, clear-filter (lambda = 0.64 mu m) geometric albedos of these three satellites are 0.063, 0.091, and 0.049, respectively. A definite color gradient is observed, with the satellites closer to Jupiter being redder: the mean violet/green ratio (0.42/0.56 mu m) decreases from Thebe to Metis. This ratio also is lower for the trailing sides of Thebe and Amalthea than for their leading sides. Bright spots on Amalthea and Thebe are small (<20 km) patches on ridges or near crater rims and have albedo contrasts with their surroundings of more than 2:1. The colors of the spots are slightly different from the average surrounding surfaces. There are suggestions of absorption features near 1 pm on Thebe and Amalthea, While the colors of the small satellites indicate possible contamination by materials lost from Io, the brighter leading sides of all three well-measured objects, spanning a region from inside to outside the synchronous orbit distance, suggest that macroscopic impacts may have a substantial influence on surface photometric properties, (C) 1998 Academic Press. C1 Cornell Univ, CRSR, Ithaca, NY 14853 USA. SW Res Inst, Boulder, CO 80302 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Kitt Peak Natl Observ, Tucson, AZ 85726 USA. RP Thomas, PC (reprint author), Cornell Univ, CRSR, Space Sci Bldg, Ithaca, NY 14853 USA. NR 42 TC 39 Z9 39 U1 0 U2 3 PU ACADEMIC PRESS INC PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA SN 0019-1035 J9 ICARUS JI Icarus PD SEP PY 1998 VL 135 IS 1 BP 360 EP 371 DI 10.1006/icar.1998.5976 PG 12 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 129WZ UT WOS:000076488200022 ER PT J AU Doyle, RJ AF Doyle, RJ TI Spacecraft autonomy and the missions of exploration SO IEEE INTELLIGENT SYSTEMS & THEIR APPLICATIONS LA English DT Editorial Material C1 CALTECH, Jet Prop Lab, Informat & Comp Technol Res Sect, Pasadena, CA 91109 USA. CALTECH, Jet Prop Lab, Autonoma Technol Program, Pasadena, CA 91109 USA. RP Doyle, RJ (reprint author), CALTECH, Jet Prop Lab, Informat & Comp Technol Res Sect, 4800 Oak Grove Dr,Mail Stop 126-347, Pasadena, CA 91109 USA. NR 13 TC 3 Z9 3 U1 0 U2 0 PU IEEE COMPUTER SOC PI LOS ALAMITOS PA 10662 LOS VAQUEROS CIRCLE, PO BOX 3014, LOS ALAMITOS, CA 90720-1314 USA SN 0885-9000 J9 IEEE INTELL SYST APP JI IEEE Intell. Syst. Appl. PD SEP-OCT PY 1998 VL 13 IS 5 BP 36 EP 44 DI 10.1109/5254.722355 PG 9 WC Computer Science, Artificial Intelligence; Engineering, Electrical & Electronic SC Computer Science; Engineering GA 126FH UT WOS:000076282000009 ER PT J AU Lowry, M Dvorak, D AF Lowry, M Dvorak, D TI Analytic verification of flight software SO IEEE INTELLIGENT SYSTEMS & THEIR APPLICATIONS LA English DT Article C1 NASA, Ames Res Ctr, Computat Sci Div, Moffett Field, CA 94035 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Lowry, M (reprint author), NASA, Ames Res Ctr, Computat Sci Div, M-S 269-2, Moffett Field, CA 94035 USA. NR 9 TC 4 Z9 4 U1 0 U2 0 PU IEEE COMPUTER SOC PI LOS ALAMITOS PA 10662 LOS VAQUEROS CIRCLE, PO BOX 3014, LOS ALAMITOS, CA 90720-1314 USA SN 0885-9000 J9 IEEE INTELL SYST APP JI IEEE Intell. Syst. Appl. PD SEP-OCT PY 1998 VL 13 IS 5 BP 45 EP 49 DI 10.1109/5254.722359 PG 5 WC Computer Science, Artificial Intelligence; Engineering, Electrical & Electronic SC Computer Science; Engineering GA 126FH UT WOS:000076282000010 ER PT J AU Chien, S Smith, B Rabideau, G Muscettola, N Rajan, K AF Chien, S Smith, B Rabideau, G Muscettola, N Rajan, K TI Automated planning and scheduling for goal-based autonomous spacecraft SO IEEE INTELLIGENT SYSTEMS & THEIR APPLICATIONS LA English DT Article C1 CALTECH, Jet Prop Lab, Artificial Intelligence Grp, Informat & Comp Technol Res Sect, Pasadena, CA 91125 USA. NASA, Ames Res Ctr, Computat Sci Div, Moffett Field, CA 94035 USA. RP CALTECH, Jet Prop Lab, Artificial Intelligence Grp, Informat & Comp Technol Res Sect, Pasadena, CA 91125 USA. EM chien@jpl.nasa.gov; benjamin.smith@jpl.nasa.gov; gregg.rabideau@jpl.nasa.gov; mus@ptolemy.arc.nasa.gov; kanna@ptolemy.arc.nasa.gov NR 24 TC 13 Z9 15 U1 1 U2 3 PU IEEE COMPUTER SOC PI LOS ALAMITOS PA 10662 LOS VAQUEROS CIRCLE, PO BOX 3014, LOS ALAMITOS, CA 90720-1314 USA SN 1094-7167 J9 IEEE INTELL SYST APP JI IEEE Intell. Syst. Appl. PD SEP-OCT PY 1998 VL 13 IS 5 BP 50 EP 55 DI 10.1109/5254.722362 PG 6 WC Computer Science, Artificial Intelligence; Engineering, Electrical & Electronic SC Computer Science; Engineering GA 126FH UT WOS:000076282000011 ER PT J AU Gat, E Pell, B AF Gat, E Pell, B TI Smart executives for autonomous spacecraft SO IEEE INTELLIGENT SYSTEMS & THEIR APPLICATIONS LA English DT Article C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. NASA, Ames Res Ctr, Informat Syst Div, Moffett Field, CA 94035 USA. RP Gat, E (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr,MS 301-270, Pasadena, CA 91109 USA. NR 18 TC 1 Z9 1 U1 0 U2 0 PU IEEE COMPUTER SOC PI LOS ALAMITOS PA 10662 LOS VAQUEROS CIRCLE, PO BOX 3014, LOS ALAMITOS, CA 90720-1314 USA SN 0885-9000 J9 IEEE INTELL SYST APP JI IEEE Intell. Syst. Appl. PD SEP-OCT PY 1998 VL 13 IS 5 BP 56 EP 61 DI 10.1109/5254.722365 PG 6 WC Computer Science, Artificial Intelligence; Engineering, Electrical & Electronic SC Computer Science; Engineering GA 126FH UT WOS:000076282000012 ER PT J AU Stolorz, P Cheeseman, P AF Stolorz, P Cheeseman, P TI Onboard science data analysis: Applying data mining to science-directed autonomy SO IEEE INTELLIGENT SYSTEMS & THEIR APPLICATIONS LA English DT Article C1 CALTECH, Jet Prop Lab, Machine Learning Syst Grp, Pasadena, CA 91109 USA. NASA, Ames Res Ctr, Computat Sci Div, Res Inst Adv Comp Sci, Moffett Field, CA 94035 USA. RP CALTECH, Jet Prop Lab, Machine Learning Syst Grp, 4800 Oak Grove Dr,MS 126-347, Pasadena, CA 91109 USA. EM pauls@aig.jpl.nasa.gov; cheesem@ptolemy.arc.nasa.gov NR 7 TC 3 Z9 3 U1 0 U2 1 PU IEEE COMPUTER SOC PI LOS ALAMITOS PA 10662 LOS VAQUEROS CIRCLE, PO BOX 3014, LOS ALAMITOS, CA 90720-1314 USA SN 1094-7167 J9 IEEE INTELL SYST APP JI IEEE Intell. Syst. Appl. PD SEP-OCT PY 1998 VL 13 IS 5 BP 62 EP 68 DI 10.1109/5254.722368 PG 7 WC Computer Science, Artificial Intelligence; Engineering, Electrical & Electronic SC Computer Science; Engineering GA 126FH UT WOS:000076282000013 ER PT J AU Gamble, EB Simmons, R AF Gamble, EB Simmons, R TI The impact of autonomy technology on spacecraft software architecture: A case study SO IEEE INTELLIGENT SYSTEMS & THEIR APPLICATIONS LA English DT Article C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Carnegie Mellon Univ, Sch Comp Sci, Pittsburgh, PA 15213 USA. RP Gamble, EB (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 8 TC 0 Z9 0 U1 0 U2 1 PU IEEE COMPUTER SOC PI LOS ALAMITOS PA 10662 LOS VAQUEROS CIRCLE, PO BOX 3014, LOS ALAMITOS, CA 90720-1314 USA SN 0885-9000 J9 IEEE INTELL SYST APP JI IEEE Intell. Syst. Appl. PD SEP-OCT PY 1998 VL 13 IS 5 BP 69 EP 75 DI 10.1109/5254.722373 PG 7 WC Computer Science, Artificial Intelligence; Engineering, Electrical & Electronic SC Computer Science; Engineering GA 126FH UT WOS:000076282000014 ER PT J AU Callahan, JR Khatsuriya, RR Hefner, R AF Callahan, JR Khatsuriya, RR Hefner, R TI Web-based issue tracking for large software projects SO IEEE INTERNET COMPUTING LA English DT Article C1 W Virginia Univ, Dept Comp Sci & Elect Engn, Morgantown, WV 26506 USA. WVU, NASA, Software Res Lab, Software IV&V Facil, Fairmont, WV USA. Intermetr Inc, Cambridge, MA 02138 USA. RP Callahan, JR (reprint author), W Virginia Univ, Dept Comp Sci & Elect Engn, Morgantown, WV 26506 USA. NR 6 TC 0 Z9 0 U1 0 U2 0 PU IEEE COMPUTER SOC PI LOS ALAMITOS PA 10662 LOS VAQUEROS CIRCLE, PO BOX 3014, LOS ALAMITOS, CA 90720-1314 USA SN 1089-7801 J9 IEEE INTERNET COMPUT JI IEEE Internet Comput. PD SEP-OCT PY 1998 VL 2 IS 5 BP 25 EP 33 DI 10.1109/4236.722227 PG 9 WC Computer Science, Software Engineering SC Computer Science GA 124AF UT WOS:000076157600010 ER PT J AU Hench, JJ He, C Kucera, V Mehrmann, V AF Hench, JJ He, C Kucera, V Mehrmann, V TI Dampening controllers via a Riccati equation approach SO IEEE TRANSACTIONS ON AUTOMATIC CONTROL LA English DT Letter DE damped dynamics; dampening feedback; linear quadratic controller; periodic systems; Riccati equation ID MATRICES AB An algorithm is presented which computes a state feedback for a standard linear system which not only stabilizes, but also dampens the closed-loop system dynamics. In other words, a feedback gain matrix is computed such that the eigenvalues of the closed-loop state matrix are within the region of the left half-plane where the magnitude of the real part of each eigenvalue is greater than that of the imaginary part. This may be accomplished by solving a damped algebraic Riccati equation and a degenerate Riccati equation. The solution to these equations are computed using numerically robust algorithms. Damped Riccati equations are unusual in that they may be formulated as an invariant subspace problem of a related periodic Hamiltonian system. This periodic Hamiltonian system induces two damped Riccati equations: one with a symmetric solution and another with a skew-symmetric solution. These two solutions result in two different state feedbacks, both of which dampen the system dynamics, but produce different closed-loop eigenvalues, thus giving the controller designer greater freedom in choosing a desired feedback. C1 Acad Sci Czech Republ, Inst Informat Theory & Automat, Praha 12808 8, Czech Republic. Univ Kansas, Dept Math, Lawrence, KS 66045 USA. Tech Univ Chemnitz Zwickau, Fak Math, D-09107 Chemnitz, Germany. RP Hench, JJ (reprint author), CALTECH, Jet Prop Lab, Guidance & Control Anal Grp, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. EM John.Hench@jpl.nasa.gov RI Kucera, Vladimir/D-4209-2014 OI Kucera, Vladimir/0000-0001-9397-6931 NR 19 TC 7 Z9 7 U1 0 U2 0 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 0018-9286 J9 IEEE T AUTOMAT CONTR JI IEEE Trans. Autom. Control PD SEP PY 1998 VL 43 IS 9 BP 1280 EP 1284 DI 10.1109/9.718617 PG 5 WC Automation & Control Systems; Engineering, Electrical & Electronic SC Automation & Control Systems; Engineering GA 116HZ UT WOS:000075720000013 ER PT J AU Bayard, DS Spanos, S Rahman, Z AF Bayard, DS Spanos, S Rahman, Z TI A result on exponential tracking error convergence and persistent excitation SO IEEE TRANSACTIONS ON AUTOMATIC CONTROL LA English DT Letter DE adaptive gradient algorithm; exponential stability; tracking performance ID STABILITY AB Conditions are investigated for exponential convergence of the tracking error in feedforward adaptive systems having insufficient excitation. Particular attention is paid to the adaptive gradient algorithm with periodic excitation in the overparameterized case. A main result is that for a bounded periodic regressor, the tracking error converges exponentially without regard to parameter convergence or to the degree of overparameterization. These results weaken the persistent excitation (PE) conditions and parameter convergence renditions generally considered necessary to ensure exponential tracking convergence in this class of systems. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Bayard, DS (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 14 TC 4 Z9 5 U1 1 U2 2 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 0018-9286 J9 IEEE T AUTOMAT CONTR JI IEEE Trans. Autom. Control PD SEP PY 1998 VL 43 IS 9 BP 1334 EP 1338 DI 10.1109/9.718629 PG 5 WC Automation & Control Systems; Engineering, Electrical & Electronic SC Automation & Control Systems; Engineering GA 116HZ UT WOS:000075720000025 ER PT J AU Middlebrook, RD Vorperian, V Lindal, J AF Middlebrook, RD Vorperian, V Lindal, J TI The N Extra Element Theorem SO IEEE TRANSACTIONS ON CIRCUITS AND SYSTEMS I-FUNDAMENTAL THEORY AND APPLICATIONS LA English DT Article ID FEEDBACK AB The N Extra Element Theorem (NEET) is an alternative means of analysis for any transfer function of any linear system model, not restricted to electrical systems, Its principal distinction from conventional loop or node analysis is that a simpler reference system model in the absence of N designated "extra" elements is solved first, and the N extra elements are then restored via a correction factor, Parameters in the correction factor are various single injection and null double injection driving point immittances seen by the extra elements, and are all calculated upon the reference model. Thus, no calculation is performed upon a model containing any of the designated extra elements, and the final result is obtained by assembly of sequentially obtained results in a "divide and conquer" approach that is potentially easier, shorter, and which produces lower entropy forms than does the conventional approach, The NEET correction factor is a simultaneous bilinear representation of the extra elements, which can be immittances or dependent generators in any combination, and thus exposes explicitly the contribution of each extra element. An especially useful implementation of the NEET is to designate all the reactances as extra elements. The frequency response of the transfer function is then contained entirely in the NEET correction factor, which emerges directly as a ratio of polynomials in complex frequency s, The zeros as well as the poles can thus be obtained directly from the driving point resistances seen by the reactances, and it can also be determined whether;any of the zeros or poles are exactly factorable, The approach throughout is to show how the NEET theorem can be useful in practical Design-Oriented Analysis, and emphasis is on the criteria by which the designer-analyst can take maximum advantage of the numerous choices of which elements to designate as "extra," and which of the many versions of the theorem to adopt. C1 CALTECH, Dept Elect Engn, Pasadena, CA 91125 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91125 USA. RP Middlebrook, RD (reprint author), CALTECH, Dept Elect Engn, Pasadena, CA 91125 USA. NR 17 TC 24 Z9 25 U1 0 U2 0 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 1057-7122 J9 IEEE T CIRCUITS-I JI IEEE Trans. Circuits Syst. I-Fundam. Theor. Appl. PD SEP PY 1998 VL 45 IS 9 BP 919 EP 935 DI 10.1109/81.721258 PG 17 WC Engineering, Electrical & Electronic SC Engineering GA 126YB UT WOS:000076321900007 ER PT J AU Jackson, ME Shtessel, YB AF Jackson, ME Shtessel, YB TI Sliding mode thermal control system for space station furnace facility SO IEEE TRANSACTIONS ON CONTROL SYSTEMS TECHNOLOGY LA English DT Article DE decoupled control; nonlinear control; robust control; sliding mode control; thermal control AB This paper addresses the decoupled control of the nonlinear, multiinput-multioutput, and highly coupled space station furnace facility (SSFF) thermal control system. Sliding mode control theory, a subset of variable-structure control theory, is employed to increase the performance, robustness, and reliability of the SSFF's currently designed control system. This paper presents the nonlinear thermal control system description and develops the sliding mode controllers that cause the interconnect-edw subsystems to operate in their local sliding modes, resulting in control system invariance to plant uncertainties and external and interaction disturbances. The desired decoupled flow-rate tracking is achieved by optimization of the local linear sliding mode equations, The controllers are implemented digitally and extensive simulation results are presented to show the flowrate tracking robustness and invariance to plant uncertainties, nonlinearities, external disturbances, and variations of the system pressure supplied to the controlled subsystems. C1 NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35807 USA. Univ Alabama, Dept Elect & Comp Engn, Huntsville, AL 35807 USA. RP Jackson, ME (reprint author), NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35807 USA. NR 14 TC 1 Z9 2 U1 0 U2 1 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 1063-6536 J9 IEEE T CONTR SYST T JI IEEE Trans. Control Syst. Technol. PD SEP PY 1998 VL 6 IS 5 BP 612 EP 622 DI 10.1109/87.709496 PG 11 WC Automation & Control Systems; Engineering, Electrical & Electronic SC Automation & Control Systems; Engineering GA 113RG UT WOS:000075564600003 ER PT J AU Gunapala, SD Bandara, SV Liu, JK Hong, W Sundaram, M Maker, PD Muller, RE Shott, CA Carralejo, R AF Gunapala, SD Bandara, SV Liu, JK Hong, W Sundaram, M Maker, PD Muller, RE Shott, CA Carralejo, R TI Long-wavelength 640 x 486 GaAs/AlGaAs quantum well infrared photodetector snap-shot camera SO IEEE TRANSACTIONS ON ELECTRON DEVICES LA English DT Article ID FOCAL-PLANE ARRAY; PERFORMANCE AB A 9-mu m cutoff 630 x 486 snap-shot quantum well infrared photodetector (QWIP) camera has been demonstrated. The performance of this QWIP camera is reported including indoor and outdoor imaging. The noise equivalent differential temperature (NE Delta T) of 36 mK has been achieved at 300 K background with f/2 optics. This is in good agreement with expected focal plane array sensitivity due to the practical limitations on charge handling capacity of the multiplexer, read noise, bias voltage, and operating temperature. C1 CALTECH, Jet Prop Lab, Ctr Space Microelect Technol, Pasadena, CA 91109 USA. Raytheon Co, Adv Proc Dept, Goleta, CA 93117 USA. RP Gunapala, SD (reprint author), CALTECH, Jet Prop Lab, Ctr Space Microelect Technol, Pasadena, CA 91109 USA. NR 9 TC 80 Z9 80 U1 1 U2 4 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 0018-9383 J9 IEEE T ELECTRON DEV JI IEEE Trans. Electron Devices PD SEP PY 1998 VL 45 IS 9 BP 1890 EP 1895 DI 10.1109/16.711352 PG 6 WC Engineering, Electrical & Electronic; Physics, Applied SC Engineering; Physics GA 112GQ UT WOS:000075486100005 ER PT J AU Foote, MC Jones, EW Caillat, T AF Foote, MC Jones, EW Caillat, T TI Uncooled thermopile infrared detector linear arrays with detectivity greater than 10(9) cmHz(1/2)/W SO IEEE TRANSACTIONS ON ELECTRON DEVICES LA English DT Article DE arrays; detectors; infrared detectors; microelectromechanical devices; noise measurement; thermoelectric materials/devices AB We have fabricated 63-element linear arrays of micromachined thermopile infrared detectors on silicon substrates. Each detector consists of a suspended silicon nitride membrane with II thermocouples of sputtered Bi-Te and Bi-Sb-Te films, At room temperature and under vacuum these detectors exhibit response times of 99 ms, zero frequency D* values of 1.4 x 10(9) cmHz(1/2)/W and responsivity values of 1100 V/W when viewing a 1000 K blackbody source. The only measured source of noise above 20 mHz is Johnson noise from the detector resistance. These results represent the best performance reported to date for an array of thermopile detectors. A test procedure is described that measures many of the relevant electrical, optical, and thermal properties of the detectors without specialized test structures. C1 CALTECH, Jet Prop Lab, Ctr Space Microelect Technol, Pasadena, CA 91109 USA. RP Foote, MC (reprint author), CALTECH, Jet Prop Lab, Ctr Space Microelect Technol, Pasadena, CA 91109 USA. NR 21 TC 36 Z9 38 U1 0 U2 5 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 0018-9383 J9 IEEE T ELECTRON DEV JI IEEE Trans. Electron Devices PD SEP PY 1998 VL 45 IS 9 BP 1896 EP 1902 DI 10.1109/16.711353 PG 7 WC Engineering, Electrical & Electronic; Physics, Applied SC Engineering; Physics GA 112GQ UT WOS:000075486100006 ER PT J AU Kory, CL Dayton, JA AF Kory, CL Dayton, JA TI Computational investigation of experimental interaction impedance obtained by perturbation for helical traveling-wave tube structures SO IEEE TRANSACTIONS ON ELECTRON DEVICES LA English DT Article DE Helix; interaction impedance; perturbation; simulation; traveling-wave tube (TWT) AB Conventional methods used to measure the cold-test interaction impedance of helical slow-wave structures involve perturbing a helical circuit with a cylindrical dielectric rod placed on the central axis of the circuit. It has been shown that the difference in resonant frequency or axial phase shift between the perturbed and unperturbed circuits can be related to the interaction impedance. However, because of the complex configuration of the helical circuit, deriving this relationship involves several approximations. With the advent of accurate three-dimensional (3-D) helical circuit models [1]-[3], these standard approximations can be fully investigated. This paper addresses the most prominent approximations made in the analysis for measured interaction impedance by Lagerstrom [4] and investigates their accuracy using the 3-D simulation code MAFIA. It is shown that a more accurate value of interaction impedance can be obtained by using 3-D computational methods rather than performing costly and time consuming experimental cold-test measurements. C1 NASA, Lewis Res Ctr, ANALEX Corp, Cleveland, OH 44135 USA. RP Kory, CL (reprint author), NASA, Lewis Res Ctr, ANALEX Corp, Cleveland, OH 44135 USA. NR 13 TC 22 Z9 25 U1 0 U2 2 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 0018-9383 J9 IEEE T ELECTRON DEV JI IEEE Trans. Electron Devices PD SEP PY 1998 VL 45 IS 9 BP 2063 EP 2071 DI 10.1109/16.711375 PG 9 WC Engineering, Electrical & Electronic; Physics, Applied SC Engineering; Physics GA 112GQ UT WOS:000075486100028 ER PT J AU Jackson, TJ Schmugge, TJ O'Neill, PE Parlange, MB AF Jackson, TJ Schmugge, TJ O'Neill, PE Parlange, MB TI Soil water infiltration observation with microwave radiometers SO IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING LA English DT Article; Proceedings Paper CT 1997 International Geoscience and Remote Sensing Symposium (IGARSS 97) on Remote Sensing - A Scientific Vision for Sustainable Development CY AUG 03-08, 1997 CL SINGAPORE, SINGAPORE SP IEEE Geosci & Remote Sensing Soc, Natl Univ Singapore, Ctr Remote Imaging Sensing & Proc, NASA, NOAA, USN, Off Naval Res, Int Union Radio Sci DE microwave; radiometry; soil moisture ID SURFACE SOIL; MOISTURE; ROUGHNESS; EMISSION AB Experiments were conducted using truck-based microwave radiometers operating at 1.41- (L-band) and 2.65-GHz (S-band) horizontal polarization to observe small plots during and following sprinkler irrigation. These experiments were conducted on a sandy loam soil in 1994 and a silt loam in 1995. Sandy loam soils typically have higher infiltration capabilities than clays, and in our studies, we were not able to exceed this with the irrigation system. The observed brightness temperature (T-B) quickly reached a nominally constant value during irrigation, When the irrigation was stopped, the T-B began to increase as drainage took place. Contributing depth-related differences were observed for L- and S-band as expected, The irrigation rates in 1995 with the silt loam soil exceeded the saturated conductivity of the soil. During irrigation, the T-B values exhibited a phenomenon that had not been previously observed and identified and is associated with coherent interference. The L- and S-band exhibited similar patterns but were not identical due to contributing depth. These results suggested the existence of a sharp dielectric boundary (wet over dry soil) that was increasing in depth with time. The temporal description of the wetting front boundary was used with a coherent radiative transfer model to predict T-B for L- and S-band. C1 USDA ARS, Hydrol Lab, Beltsville, MD 20705 USA. NASA, Goddard Space Flight Ctr, Hydrol Sci Branch, Greenbelt, MD 20771 USA. Johns Hopkins Univ, Dept Geog & Environm Sci, Baltimore, MD 21218 USA. RP Jackson, TJ (reprint author), USDA ARS, Hydrol Lab, Beltsville, MD 20705 USA. EM tjackson@hydrolab.arsusda.gov RI O'Neill, Peggy/D-2904-2013; Parlange, Marc/A-3403-2015 NR 21 TC 7 Z9 7 U1 1 U2 4 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 0196-2892 J9 IEEE T GEOSCI REMOTE JI IEEE Trans. Geosci. Remote Sensing PD SEP PY 1998 VL 36 IS 5 BP 1376 EP 1383 DI 10.1109/36.718838 PN 1 PG 8 WC Geochemistry & Geophysics; Engineering, Electrical & Electronic; Remote Sensing; Imaging Science & Photographic Technology SC Geochemistry & Geophysics; Engineering; Remote Sensing; Imaging Science & Photographic Technology GA 121UU UT WOS:000076033700003 ER PT J AU Shih, SE Ding, KH Nghiem, SV Hsu, CC Kong, JA Jordan, AK AF Shih, SE Ding, KH Nghiem, SV Hsu, CC Kong, JA Jordan, AK TI Thin saline ice thickness retrieval using time-series C-band polarimetric radar measurements SO IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING LA English DT Article; Proceedings Paper CT 1997 International Geoscience and Remote Sensing Symposium (IGARSS 97) on Remote Sensing - A Scientific Vision for Sustainable Development CY AUG 03-08, 1997 CL SINGAPORE, SINGAPORE SP IEEE Geosci & Remote Sensing Soc, Natl Univ Singapore, Ctr Remote Imaging Sensing & Proc, NASA, NOAA, USN, Off Naval Res, Int Union Radio Sci DE electromagnetic scattering inverse problems; radar polarimetry; sea ice; time series ID SEA-ICE; MICROWAVE-FREQUENCIES; SIGNATURES; BRINE; CONSTANT; GROWTH; MODEL AB The application of time-series radar measurements to accurately invert the thickness of saline ice is presented in this study. We describe briefly some experimental observations from the United States Army Cold Regions Research and Engineering Laboratory, Hanover, NEI, 1993 (CRRELEX'93) campaign of microwave scattering from sea ice. We demonstrate that volume scattering from brine inclusions is an important contribution to the backscatter response of saline ice in this case. From the experimental findings and the thermophysics of ice growth, we develop an inversion algorithm for the ice thickness based on a dynamic electromagnetic scattering model of saline ice. This inversion algorithm uses a parametric estimation approach in which the radiative transfer equation is used as the direct scattering model to calculate the backscattering signatures from ice medium and the Levenberg-Marquardt method is employed to retrieve ice thickness iteratively, Additional information provided by the saline ice thermodynamics is applied to constrain the electromagnetic inverse problem to achieve a reasonably accurate reconstruction. The inversion results using this algorithm and the data from CRRELEX'93 experiment are compared. The accurate thickness retrieval suggests the potential use of this algorithm for retrieving geophysical parameters from satellite remote-sensing data. C1 MIT, Dept Elect Engn & Comp Sci, Cambridge, MA 02139 USA. MIT, Elect Res Lab, Cambridge, MA 02139 USA. CALTECH, Jet Prop Lab, Ctr Space Microelect Technol, Pasadena, CA 91109 USA. USN, Res Lab, Remote Sensing Div, Washington, DC 20375 USA. RP Shih, SE (reprint author), MIT, Dept Elect Engn & Comp Sci, Cambridge, MA 02139 USA. EM shih@ewt.mit.edu NR 33 TC 12 Z9 13 U1 0 U2 1 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 0196-2892 J9 IEEE T GEOSCI REMOTE JI IEEE Trans. Geosci. Remote Sensing PD SEP PY 1998 VL 36 IS 5 BP 1589 EP 1598 DI 10.1109/36.718862 PN 1 PG 10 WC Geochemistry & Geophysics; Engineering, Electrical & Electronic; Remote Sensing; Imaging Science & Photographic Technology SC Geochemistry & Geophysics; Engineering; Remote Sensing; Imaging Science & Photographic Technology GA 121UU UT WOS:000076033700023 ER PT J AU Gregg, WW Esaias, WE Feldman, GC Frouin, R Hooker, SB McClain, CR Woodward, RH AF Gregg, WW Esaias, WE Feldman, GC Frouin, R Hooker, SB McClain, CR Woodward, RH TI Coverage opportunities for global ocean color in a multimission era SO IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING LA English DT Article; Proceedings Paper CT 1997 International Geoscience and Remote Sensing Symposium (IGARSS 97) on Remote Sensing - A Scientific Vision for Sustainable Development CY AUG 03-08, 1997 CL SINGAPORE, SINGAPORE SP IEEE Geosci & Remote Sensing Soc, Natl Univ Singapore, Ctr Remote Imaging Sensing & Proc, NASA, NOAA, USN, Off Naval Res, Int Union Radio Sci ID TEMPERATURE; SENSORS; SEA AB The international community, recognizing the importance of global ocean color observations in the global carbon cycle, has proposed or flown six global ocean color missions over the next decade: the Ocean Color and Temperature Sensor (OCTS), Sea-viewing Wide Field-of-view Sensor (SeaWiFS), Moderate Resolution Imaging Spectrometer-AM (MODIS-AM), Medium Resolution Imaging Spectrometer (MERIS), Global Imager (GLI), and MODIS-PM. Each of these missions contains the spectral band complement considered necessary to derive oceanic pigment concentrations (i.e., phytoplankton abundance). This paper assesses whether assembling and merging data from these missions can improve ocean coverage, since clouds and sun glint prevent any single satellite from observing more than about 15% of the ocean surface in a single day, and whether new information about diel cycles of phytoplankton abundance is possible, Extensive numerical analysis, given the orbit and sensor characteristics of each mission, showed that merging data from three satellites can produce better ocean coverage in less time. Data from three satellites can improve coverage by 58% for a single day, including the obscuring effects of clouds and sun glint. Thus, observation of approximately 25% of the ocean can be provided, instead of only about 15-16% from a single satellite. After four days, approximately 62% of the ocean surface was observed, an increase from 43% observed by a single satellite, The addition of more satellites produced diminishing returns, Since the proposed missions have different orbits, they view the same location of the ocean at different times of day, This leads to the possibility of using data from the set of six missions to help understand diel phytoplankton dynamics. The missions produced colocated observations as much as 16 h apart in the high latitudes. However, given the distributions of land masses and ice cover, only a maximum of 14-h spacing could actually be achieved, and this only at high latitudes at the solstices, However, large differences of 4-10 h are readily available at other latitudes and in frequencies numbering in the tens of thousands at 20 degrees latitude bands. This suggests that combinations of these missions can support new observations of the higher frequency dynamics of phytoplankton populations in the oceans and help determine how well observations taken at a single time represent the daily abundance. C1 NASA, Goddard Space Flight Ctr, Lab Hydrospher Proc, Greenbelt, MD 20771 USA. NASA, Goddard Space Flight Ctr, Global Change Data Ctr, Greenbelt, MD 20771 USA. Univ Calif San Diego, Scripps Inst Oceanog, La Jolla, CA 92093 USA. NASA, Off Mission Planet Earth, Washington, DC 20546 USA. Gen Sci Corp, Laurel, MD 20707 USA. RP Gregg, WW (reprint author), NASA, Goddard Space Flight Ctr, Lab Hydrospher Proc, Greenbelt, MD 20771 USA. RI Hooker, Stanford/E-2162-2012 NR 16 TC 32 Z9 34 U1 0 U2 2 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 0196-2892 J9 IEEE T GEOSCI REMOTE JI IEEE Trans. Geosci. Remote Sensing PD SEP PY 1998 VL 36 IS 5 BP 1620 EP 1627 DI 10.1109/36.718865 PN 1 PG 8 WC Geochemistry & Geophysics; Engineering, Electrical & Electronic; Remote Sensing; Imaging Science & Photographic Technology SC Geochemistry & Geophysics; Engineering; Remote Sensing; Imaging Science & Photographic Technology GA 121UU UT WOS:000076033700026 ER PT J AU Jezek, KC Perovich, DK Golden, KM Luther, C Barber, DG Gogineni, P Grenfell, TC Jordan, AK Mobley, CD Nghiem, SV Onstott, RG AF Jezek, KC Perovich, DK Golden, KM Luther, C Barber, DG Gogineni, P Grenfell, TC Jordan, AK Mobley, CD Nghiem, SV Onstott, RG TI A broad spectral, interdisciplinary investigation of the electromagnetic properties of sea ice SO IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING LA English DT Article DE electromagnetic (EM) scattering; geophysics; optics; sea ice ID RADAR BACKSCATTER AB This paper highlights the interrelationship of research completed by a team of investigators and presented in the several individual papers comprising this Special Section on the Office of Naval Research (ONR), Arlington, VA, Sponsored Sea Ice Electromagnetics Accelerated Research Initiative (ARI). The objectives of the initiative were the following: 1) understand the mechanisms and processes that link the morphological and physical properties of sea ice to its electromagnetic (EM) characteristics; 2) develop and verify predictive models for the interaction of visible, infrared, and microwave radiation with sea ice; 3) develop and verify inverse scattering techniques applicable to problems involving the interaction of EM radiation with sea ice. Guiding principles for the program were that all EM data be taken with concurrent physical property data (salinity, density, roughness, etc.) and that broad spectral data be acquired in as nearly a simultaneous fashion as possible. Over 30 investigators participated in laboratory, field, and modeling studies that spanned the EM spectrum from radio to ultraviolet wavelengths. An interdisciplinary approach that brought together sea ice physicists, remote-sensing experts tin EM measurements), and forward and inverse modelers (primarily mathematicians and EM theorists) was a hallmark of the program. Along with describing results from experiments and modeling efforts, possible paradigms for using broad spectral data in developing algorithms for analyzing remote-sensing data in terms of ice concentration, age, type, and possibly thickness are briefly discussed. C1 Ohio State Univ, Byrd Polar Res Ctr, Columbus, OH 43210 USA. USA, Cold Reg Res & Engn Lab, Hanover, NH 03755 USA. Univ Utah, Dept Math, Salt Lake City, UT 84112 USA. Off Naval Res, Arlington, VA 22217 USA. Univ Manitoba, Dept Geog, Winnipeg, MB R3T 2N2, Canada. Univ Kansas, Radar Syst & Remote Sensing Lab, Lawrence, KS 66045 USA. Univ Washington, Dept Atmospher Sci, Seattle, WA 98195 USA. USN, Res Lab, Remote Sensing Div, Washington, DC 20375 USA. Sequoia Sci Inc, Mercer Isl, WA 98040 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Environm Res Inst Michigan, Ann Arbor, MI 48107 USA. RP Jezek, KC (reprint author), Ohio State Univ, Byrd Polar Res Ctr, Columbus, OH 43210 USA. NR 21 TC 13 Z9 13 U1 0 U2 3 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 0196-2892 J9 IEEE T GEOSCI REMOTE JI IEEE Trans. Geosci. Remote Sensing PD SEP PY 1998 VL 36 IS 5 BP 1633 EP 1641 DI 10.1109/36.718635 PN 2 PG 9 WC Geochemistry & Geophysics; Engineering, Electrical & Electronic; Remote Sensing; Imaging Science & Photographic Technology SC Geochemistry & Geophysics; Engineering; Remote Sensing; Imaging Science & Photographic Technology GA 121ZQ UT WOS:000076046300002 ER PT J AU Grenfell, TC Barber, DG Fung, AK Gow, AJ Jezek, KC Knapp, EJ Nghiem, SV Onstott, RG Perovich, DK Roesler, CS Swift, CT Tanis, F AF Grenfell, TC Barber, DG Fung, AK Gow, AJ Jezek, KC Knapp, EJ Nghiem, SV Onstott, RG Perovich, DK Roesler, CS Swift, CT Tanis, F TI Evolution of electromagnetic signatures of sea ice from initial formation to the establishment of thick first-year ice SO IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING LA English DT Article DE forward modeling; microwave; optical; sea ice; temporal evolution; thermal infrared (TIR) ID POLARIMETRIC SIGNATURES; BRIGHTNESS TEMPERATURE; MODEL; MICROWAVE; SNOW; CONSTANT AB The spatial and temporal distribution of new and young sea ice types are of particular interest because of the influence this can exert on the heat and mass balance of the polar sea ice. The objective of the present work is to characterize the temporal evolution of the electromagnetic (EM) signatures of sea ice from initial formation through the development of first-year (FY) ice on the basis of the temporal variations in the physical properties of the ice. The time series of young sea ice signatures, including microwave emissivity, radar backscatter, and visible and infrared spectral albedo, has been measured at successive stages in the growth and development of sea ice, both under laboratory and field conditions. These observations have been accompanied by studies of the physical properties that influence the interaction between radiation and the ice. This has resulted in a consistent data set of concurrent multispectral observations that covers essentially all phases of the development of the different types of sea ice from initial formation to thick FY ice. Mutually consistent theoretical models covering the entire wavelength range of the observations are applied to selected cases and successfully match the observations. Principal component analysis (PCA) of the data set suggests combinations of the set of frequencies to effectively distinguish among different stages in the temporal evolution of the sea ice. C1 Univ Washington, Dept Atmospher Sci, Seattle, WA 98195 USA. Univ Manitoba, Dept Geog, Winnipeg, MB R3T 2N2, Canada. Univ Texas, Dept Elect Engn, Arlington, TX 76019 USA. USA, Cold Reg Res & Engn Lab, Hanover, NH 03755 USA. Ohio State Univ, Byrd Polar Res Ctr, Columbus, OH 43210 USA. Univ Massachusetts, Microwave Remote Sensing Lab, Amherst, MA 01003 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Environm Res Inst Michigan, Ann Arbor, MI 48107 USA. Univ Connecticut, Dept Marine Sci, Groton, CT 06340 USA. RP Grenfell, TC (reprint author), Univ Washington, Dept Atmospher Sci, Seattle, WA 98195 USA. EM dbarber@ms.umanitoba.ca NR 32 TC 37 Z9 40 U1 1 U2 4 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 0196-2892 J9 IEEE T GEOSCI REMOTE JI IEEE Trans. Geosci. Remote Sensing PD SEP PY 1998 VL 36 IS 5 BP 1642 EP 1654 DI 10.1109/36.718636 PN 2 PG 13 WC Geochemistry & Geophysics; Engineering, Electrical & Electronic; Remote Sensing; Imaging Science & Photographic Technology SC Geochemistry & Geophysics; Engineering; Remote Sensing; Imaging Science & Photographic Technology GA 121ZQ UT WOS:000076046300003 ER PT J AU Golden, KM Cheney, M Ding, KH Fung, AK Grenfell, TC Isaacson, D Kong, JA Nghiem, SV Sylvester, J Winebrenner, DP AF Golden, KM Cheney, M Ding, KH Fung, AK Grenfell, TC Isaacson, D Kong, JA Nghiem, SV Sylvester, J Winebrenner, DP TI Forward electromagnetic scattering models for sea ice SO IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING LA English DT Review DE dielectric materials; electromagnetic scattering by random media; nonhomogeneous media; remote sensing; sea ice; snow ID COMPLEX-DIELECTRIC-CONSTANT; STRONG FLUCTUATION THEORY; PASSIVE MICROWAVE OBSERVATIONS; ANISOTROPIC RANDOM MEDIUM; MULTICOMPONENT COMPOSITES; POLARIMETRIC SIGNATURES; HALF-SPACE; BRIGHTNESS TEMPERATURE; RENORMALIZATION METHOD; 2-COMPONENT COMPOSITE AB Recent advances in forward modeling of the electromagnetic scattering properties of sea ice are presented. En particular, the principal results include the following: 1) approximate calculations of electromagnetic scattering from multilayer random media with rough interfaces, based on the distorted Born approximation and radiative transfer (RT) theory; 2) comprehensive theory of the effective complex permittivity of sea ice based on rigorous bounds in the quasi-static case and strong fluctuation theory in the weakly scattering regime; 3) rigorous analysis of the Helmholtz equation and its solutions for idealized sea ice models, which has led in the one dimensional (1-D) case to nonlinear generalizations of classical theorems in Fourier analysis. The forward models considered here incorporate many detailed features of the sea ice system and compare well with experimental data. The results have advanced the general theory of scattering of electromagnetic waves from complex media as well as homogenization theory, which relates bulk properties of composite media to their microstructural characteristics. Furthermore, the results have direct application to microwave remote sensing and serve as the basis for inverse algorithms for reconstructing the physical properties of sea ice from scattering data. C1 Univ Utah, Dept Math, Salt Lake City, UT 84112 USA. Rensselaer Polytech Inst, Dept Math Sci, Troy, NY 12180 USA. MIT, Dept Elect Engn, Cambridge, MA 02139 USA. Univ Texas, Dept Elect Engn, Arlington, TX 76019 USA. Univ Washington, Dept Atmospher Sci, Seattle, WA 98195 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ Washington, Dept Math, Seattle, WA 98195 USA. Univ Washington, Appl Phys Lab, Seattle, WA 98195 USA. RP Golden, KM (reprint author), Univ Utah, Dept Math, Salt Lake City, UT 84112 USA. EM golden@math.utah.edu NR 102 TC 25 Z9 26 U1 0 U2 4 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 0196-2892 J9 IEEE T GEOSCI REMOTE JI IEEE Trans. Geosci. Remote Sensing PD SEP PY 1998 VL 36 IS 5 BP 1655 EP 1674 DI 10.1109/36.718637 PN 2 PG 20 WC Geochemistry & Geophysics; Engineering, Electrical & Electronic; Remote Sensing; Imaging Science & Photographic Technology SC Geochemistry & Geophysics; Engineering; Remote Sensing; Imaging Science & Photographic Technology GA 121ZQ UT WOS:000076046300004 ER PT J AU Golden, KM Borup, D Cheney, M Cherkaeva, E Dawson, MS Ding, KH Fung, AK Isaacson, D Johnson, SA Jordan, AK Kong, JA Kwok, R Nghiem, SV Onstott, RG Sylvester, J Winebrenner, DP Zabel, IHH AF Golden, KM Borup, D Cheney, M Cherkaeva, E Dawson, MS Ding, KH Fung, AK Isaacson, D Johnson, SA Jordan, AK Kong, JA Kwok, R Nghiem, SV Onstott, RG Sylvester, J Winebrenner, DP Zabel, IHH TI Inverse electromagnetic scattering models for sea ice SO IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING LA English DT Review DE dielectric materials; electromagnetic scattering by random media; electromagnetic scattering inverse problems; nonhomogeneous media; remote sensing; sea ice; snow ID SALINE ICE; POLARIMETRIC SIGNATURES; COMPLEX PERMITTIVITY; MICROWAVE RADIOMETER; DIELECTRIC-CONSTANT; HELMHOLTZ-EQUATION; BOUNDS; CLASSIFICATION; COMPOSITES; THICKNESS AB Inverse scattering algorithms for reconstructing the physical properties of sea Tee from scattered electromagnetic field data are presented. The development of these algorithms has advanced the theory of remote sensing, particularly in the microwave region, and has the potential to form the basis for a new generation of techniques for recovering sea ice properties, such as ice thickness, a parameter of geophysical and climatological importance. Moreover, the analysis underlying the algorithms has led to significant advances in the mathematical theory of inverse problems. In particular, the principal results include the following. 1) Inverse algorithms for reconstructing the complex permittivity in the Helmholtz equation in one and higher dimensions, based on layer stripping and nonlinear optimization, have been obtained and successfully applied to a (lossless) laboratory system. In one dimension, causality has been imposed to obtain stability of the solution and layer thicknesses can be obtained from the recovered dielectric profile, or directly from the reflection data through a nonlinear generalization of the Paley-Wiener theorem in Fourier analysis. 2) When the wavelength is much larger than the microstructural scale, the above algorithms reconstruct a profile of the effective complex permittivity of the sea ice, a composite of pure ice with random brine and air inclusions. A theory of inverse homogenization has been developed, which in this quasistatic regime, further inverts the reconstructed permittivities for microstructural information beyond the resolution of the wave. Rigorous bounds on brine volume and inclusion separation for a given value of the effective complex permittivity have been obtained as,well as an accurate algorithm for reconstructing the brine volume from a set of values. 3) Inverse algorithms designed to recover sea ice thickness have been developed. A coupled radiative transfer-thermodynamic sea ice inverse model has accurately reconstructed the growth of a thin, artificial sea ice sheet from time-series electromagnetic scattering data. Inversions for sea ice thickness have also been obtained through the application of neural networks to an analytic wave theory model,a reflectivity inversion Scheme, and the use of proxy indicators. The role of neural networks in sea ice classification is also considered. It is anticipated that the broad-ranging advances in inverse scattering theory presented here may find application to closely related problems, such as medical imaging, geophysical exploration, and nondestructive testing of materials as well as generating new techniques for remotely reconstructing sea ice parameters. C1 Univ Utah, Dept Math, Salt Lake City, UT 84112 USA. Univ Utah, Dept Bioengn, Salt Lake City, UT 84112 USA. Rensselaer Polytech Inst, Dept Math Sci, Troy, NY 12180 USA. Univ Texas, Dept Elect Engn, Arlington, TX 76019 USA. MIT, Dept Elect Engn, Cambridge, MA 02139 USA. USN, Res Lab, Remote Sensing Div, Washington, DC 20375 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Environm Res Inst Michigan, Ann Arbor, MI 48113 USA. Univ Washington, Dept Math, Seattle, WA 98195 USA. Univ Washington, Appl Phys Lab, Seattle, WA 98195 USA. Ohio State Univ, Byrd Polar Res Ctr, Columbus, OH 43210 USA. RP Golden, KM (reprint author), Univ Utah, Dept Math, Salt Lake City, UT 84112 USA. RI Kwok, Ron/A-9762-2008 OI Kwok, Ron/0000-0003-4051-5896 NR 110 TC 29 Z9 30 U1 2 U2 7 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 0196-2892 J9 IEEE T GEOSCI REMOTE JI IEEE Trans. Geosci. Remote Sensing PD SEP PY 1998 VL 36 IS 5 BP 1675 EP 1704 DI 10.1109/36.718638 PN 2 PG 30 WC Geochemistry & Geophysics; Engineering, Electrical & Electronic; Remote Sensing; Imaging Science & Photographic Technology SC Geochemistry & Geophysics; Engineering; Remote Sensing; Imaging Science & Photographic Technology GA 121ZQ UT WOS:000076046300005 ER PT J AU Kwok, R Nghiem, SV Martin, S Winebrenner, DP Gow, AJ Perovich, DK Swift, CT Barber, DG Golden, KM Knapp, EJ AF Kwok, R Nghiem, SV Martin, S Winebrenner, DP Gow, AJ Perovich, DK Swift, CT Barber, DG Golden, KM Knapp, EJ TI Laboratory measurements of sea ice: Connections to microwave remote sensing SO IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING LA English DT Article ID FROST FLOWER GROWTH; APERTURE RADAR DATA; POLARIMETRIC SIGNATURES; BACKSCATTER; SURFACE; MODEL; SNOW AB The connections between laboratory measurements and remote-sensing observations of sea ice are explored. The focus of this paper is on thin ice, which is more easily simulated in a laboratory environment. We summarize results of C-band scatterometer measurements and discuss how they may help in the interpretation of remote-sensing data. We compare the measurements with observations of thin ice from ERS and airborne radar data sets. We suggest that laboratory backscatter signatures should serve as bounds on the interpretation of remote-sensing data. We examine these bounds from the perspective of thin ice signatures, the effect of temperature, and surface processes, such as frost flowers and slush on these signatures. Controlled experiments also suggest new directions in remote-sensing measurements. The potential of polarimetric radar measurements in the retrieval of thickness of thin ice is discussed. In addition to the radar results, we discuss the importance of low-frequency passive measurements with respect to the thickness of thin ice. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ Washington, Sch Oceanog, Seattle, WA 98195 USA. Univ Washington, Appl Phys Lab, Seattle, WA 98105 USA. USA, Cold Reg Res & Engn Lab, Snow & Ice Branch, Hanover, NH 03755 USA. Univ Massachusetts, Microwave Remote Sensing Lab, Amherst, MA 01003 USA. Univ Manitoba, Dept Geog, Winnipeg, MB R3T 2N2, Canada. Univ Utah, Dept Math, Salt Lake City, UT 84112 USA. RP Kwok, R (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. RI Kwok, Ron/A-9762-2008 OI Kwok, Ron/0000-0003-4051-5896 NR 34 TC 9 Z9 9 U1 0 U2 2 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 0196-2892 J9 IEEE T GEOSCI REMOTE JI IEEE Trans. Geosci. Remote Sensing PD SEP PY 1998 VL 36 IS 5 BP 1716 EP 1730 DI 10.1109/36.718640 PN 2 PG 15 WC Geochemistry & Geophysics; Engineering, Electrical & Electronic; Remote Sensing; Imaging Science & Photographic Technology SC Geochemistry & Geophysics; Engineering; Remote Sensing; Imaging Science & Photographic Technology GA 121ZQ UT WOS:000076046300007 ER PT J AU Shih, SE Ding, KH Kong, JA Nghiem, SV Jordan, AK AF Shih, SE Ding, KH Kong, JA Nghiem, SV Jordan, AK TI Saline ice thickness retrieval under diurnal thermal cycling conditions SO IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING LA English DT Article DE electromagnetic scattering inverse problems; radar polarimetry; sea ice; time series ID SEA-ICE; POLARIMETRIC SIGNATURES; MICROWAVE-FREQUENCIES; CONSTANT; EXCHANGE; GROWTH; BRINE AB An inverse scattering algorithm is presented that reconstructs ice growth under thermal cycling conditions by using time-series active microwave measurements. The algorithm uses a direct scattering model consisting of a physically based electromagnetic model that accounts for thermal and electromagnetic properties of ice and combined volume and surface scattering effects as well as a one-dimensional (1-D) thermodynamic model of saline ice growth that includes thermal interactions with the atmosphere. The combined thermodynamic-electromagnetic scattering model is applied to interpret the United States Army Cold Regions Research and Engineering Laboratory, Hanover, NH, 1994 experimental observations (CRRELEX'94) on both the ice growth and the diurnal cycles in C-band polarinetric backscatter, The crucial part of the inversion algorithm is the use of sequentially measured radar data together with the direct scattering model to retrieve the sea ice parameters. The algorithm was applied to CRRELEX'94 data and successfully reconstructed the evolution of ice growth under a thermal cycling environment. This work shows that the inversion algorithm using time-series data offers a distinct advantage over algorithms using individual microwave data set. C1 MIT, Dept Elect Engn & Comp Sci, Cambridge, MA 02139 USA. MIT, Elect Res Lab, Cambridge, MA 02139 USA. CALTECH, Jet Prop Lab, Ctr Space Microelect Technol, Pasadena, CA 91109 USA. USN, Res Lab, Remote Sensing Div, Washington, DC 20375 USA. RP Shih, SE (reprint author), MIT, Dept Elect Engn & Comp Sci, Cambridge, MA 02139 USA. NR 24 TC 2 Z9 2 U1 0 U2 1 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 0196-2892 J9 IEEE T GEOSCI REMOTE JI IEEE Trans. Geosci. Remote Sensing PD SEP PY 1998 VL 36 IS 5 BP 1731 EP 1742 DI 10.1109/36.718641 PN 2 PG 12 WC Geochemistry & Geophysics; Engineering, Electrical & Electronic; Remote Sensing; Imaging Science & Photographic Technology SC Geochemistry & Geophysics; Engineering; Remote Sensing; Imaging Science & Photographic Technology GA 121ZQ UT WOS:000076046300008 ER PT J AU Barber, DG Fung, AK Grenfell, TC Nghiem, SV Onstott, RG Lytle, VI Perovich, DK Gow, AJ AF Barber, DG Fung, AK Grenfell, TC Nghiem, SV Onstott, RG Lytle, VI Perovich, DK Gow, AJ TI The role of snow on microwave emission and scattering over first-year sea ice SO IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING LA English DT Article ID SIGNATURES; COEFFICIENT; EVOLUTION AB The primary objective of this paper is to investigate the geophysical and thermodynamic effects of snow on sea ice in defining the electromagnetic (EM) interaction within the microwave portion of the spectrum. We combine observational evidence of both the physical and thermodynamic characteristics of snow with direct measurements of scattering and emission at a variety of frequencies. We explain our observational results using various "state-of-the-art" forward scattering and emission models. Results show that geophysical characteristics of snow effect emission above about 37 GHz and above 5 GHz for active microwave scattering. We understand these effects to be driven by grain size and its contribution to volume scattering in both passive and active interactions within the volume. With snow cover, the Brewster angle effect is not significant and there is a gradual rise in emission from 10 to 37 GHz, We find emissivity to be dominated by direct emission from saline ice through the snow layer. Hence, the influence of grain size is small but the trend is clearly a drop in total emission as the grain size increases. We find that the role of the volume fraction of snow on emission and scattering is a complex relationship between the number density of scatterers relative to the coherence of this scattering ensemble. At low volume fractions, we find that independent scattering dominates, resulting in an increase in albedo and the extinction coefficient of the snow with frequency. The thermodynamic effects of snow on microwave scattering and emission are driven by the role that thermal diffusivity and conductivity play in the definition of brine volumes at the ice surface and within the snow volume, Prior to the presence of water in liquid phase within the snow volume, we find that the indirect effects are dominated by an impedance matching process across the snow-ice interface. We find that the complex permittivity at the snow-ice interface is considerably higher than over the bare ice surface. Our results showed that only a small change occurs between the cold and warm cases at lower frequencies, but as expected, the change in emissivity is larger at higher frequencies. Once water in liquid phase appears within the snow cover, we find that both emission and scattering are directly affected by the high complex permittivity of this volume fraction within the snow layer. C1 Univ Manitoba, Dept Geog, Winnipeg, MB R3T 2N2, Canada. Univ Texas, Dept Elect Engn, Arlington, TX 76019 USA. Univ Washington, Dept Atmospher Sci, Seattle, WA 98195 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Environm Res Inst Michigan, Ann Arbor, MI 48107 USA. Antarctic CRC & Australian Antarctic Div, Hobart, Tas 7001, Australia. USA, Cold Reg Res & Engn Lab, Hanover, NH 03755 USA. RP Barber, DG (reprint author), Univ Manitoba, Dept Geog, Winnipeg, MB R3T 2N2, Canada. EM dbarber@ms.umanitoba.ca NR 20 TC 35 Z9 35 U1 0 U2 2 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 0196-2892 J9 IEEE T GEOSCI REMOTE JI IEEE Trans. Geosci. Remote Sensing PD SEP PY 1998 VL 36 IS 5 BP 1750 EP 1763 DI 10.1109/36.718643 PN 2 PG 14 WC Geochemistry & Geophysics; Engineering, Electrical & Electronic; Remote Sensing; Imaging Science & Photographic Technology SC Geochemistry & Geophysics; Engineering; Remote Sensing; Imaging Science & Photographic Technology GA 121ZQ UT WOS:000076046300010 ER PT J AU Hunewinkel, T Markus, T Heygster, GC AF Hunewinkel, T Markus, T Heygster, GC TI Improved determination of the sea ice edge with SSM/I data for small-scale analyses SO IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING LA English DT Article DE Backus-Gilbert restoration and interpolation; ice edge; Polynya Signature Simulation Method (PSSM); sea ice; Special Sensor Microwave/Imager (SSM/I); superresolution; Weddell Sea ID RADIATIVE-TRANSFER; MICROWAVE; RESOLUTION; INSTRUMENT; WEATHER; WINTER; CLOUDS; WATER AB A method to derive the sea ice edges from the 37- and 85-GHz channels of the spaceborne Special Sensor Microwave/Imager (SSM/I) with higher resolution than operational ice concentration analyses is developed. A combined ice-atmosphere model to evaluate atmospheric influences showed that under clear sky conditions the error of the ice edge position is 3.1 km an average. The method performs well up to total liquid water content (TWC) of 125 g/m(2) and overestimates the ice extent when TWC increases up to 250 g/m(2). The algorithm is suitable to classify open water, the interior ice pack, and thin ice (nilas) or low ice concentrations caused by a mixture of open water and pancake ice. Simulations showed that interpolation and resolution-matching techniques may improve the retrieval results with emphasis on interpolation, Validation of the algorithm with high-resolution infrared data shows errors of the ice edge on average less than 5 km, Comparison with the NASA Team ice concentration algorithm in the Weddell Sea, Antarctica, shows best agreement with the contour line of 33% ice concentration. The suitability of the method for mesoscale investigations is demonstrated with a time series of a meander structure in the marginal ice zone (MIZ). C1 Univ Bremen, Inst Environm Phys, D-28334 Bremen, Germany. NASA, Goddard Space Flight Ctr, Lab Hydrospher Proc, Greenbelt, MD 20771 USA. RP Hunewinkel, T (reprint author), Werum GMBH Software & Syst, D-21337 Luneburg, Germany. EM heygster@physik.uni-bremen.de RI Markus, Thorsten/D-5365-2012 NR 33 TC 17 Z9 17 U1 0 U2 0 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 0196-2892 J9 IEEE T GEOSCI REMOTE JI IEEE Trans. Geosci. Remote Sensing PD SEP PY 1998 VL 36 IS 5 BP 1795 EP 1808 DI 10.1109/36.718647 PN 2 PG 14 WC Geochemistry & Geophysics; Engineering, Electrical & Electronic; Remote Sensing; Imaging Science & Photographic Technology SC Geochemistry & Geophysics; Engineering; Remote Sensing; Imaging Science & Photographic Technology GA 121ZQ UT WOS:000076046300014 ER PT J AU Hattori, M McEliece, RJ Solomon, G AF Hattori, M McEliece, RJ Solomon, G TI Subspace subcodes of Reed-Solomon codes SO IEEE TRANSACTIONS ON INFORMATION THEORY LA English DT Article DE error-correcting codes; nonbinary codes; Reed-Solomon codes ID LINEAR BLOCK-CODES; MINIMUM DISTANCE; TRELLIS AB In this paper me introduce a class of nonlinear cyclic error-correcting codes, which me call subspace subcodes of Reed-Solomon (SSRS) codes. An SSRS code is a subset of a parent Reed-Solomon (RS) code consisting of the RS codewords whose components all lie in a fixed v-dimensional vector subspace S of GF (2(m)). SSRS codes are constructed using properties of the Galois field GF (2(m)). They are not linear over the field GF(2(nu)), which does not come into play, but rather are Abelian group codes over S. However, they are linear over GF(2), and the symbol-wise cyclic shift of any codeword is also a codeword. Our main result is an explicit but complicated formula for the dimension of an SSRS code. It implies a simple lower bound, which gives the true value of the dimension for most, though not all, subspaces.We also prove several important duality properties, We present some numerical examples, which show, among other things, that 1) SSRS codes can have a higher dimension than comparable subfield subcodes of RS codes, so that even if GF(2(nu)) is a subfield of GF (2(m)), it may not be the best nu-dimensional subspace for constructing SSRS codes; and 2) many high-rate SSRS codes have larger dimension than any previously known code with the same values of n, d, and q, including algebraic-geometry codes.These examples suggest that high-rate SSRS codes are promising candidates to replate Reed-Solomon codes in high-performance transmission and storage systems. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91125 USA. CALTECH, Dept Elect Engn, Pasadena, CA 91125 USA. RP Hattori, M (reprint author), Sony Corp, Res Ctr, Shinagawa Ku, 6-7-35 Kitashinagawa, Tokyo 141, Japan. NR 30 TC 16 Z9 16 U1 0 U2 1 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 0018-9448 J9 IEEE T INFORM THEORY JI IEEE Trans. Inf. Theory PD SEP PY 1998 VL 44 IS 5 BP 1861 EP 1880 DI 10.1109/18.705564 PG 20 WC Computer Science, Information Systems; Engineering, Electrical & Electronic SC Computer Science; Engineering GA 109HX UT WOS:000075317000011 ER PT J AU Lalli, VR AF Lalli, VR TI Space-system reliability: A historical perspective SO IEEE TRANSACTIONS ON RELIABILITY LA English DT Article DE statistical concepts; maintainability; system safety; quality assurance; logistics support; human factors; software assurance; system effectiveness AB The NASA Strategic Plan is the backbone of its new Strategic Management System, an important aspect of which is risk management. Coincident with a decreasing NASA budget is the new working environment that demands a better, faster, cheaper way to conduct business. In such an environment where risk is considered a knowledge-based resource, mission assurance is important in understanding risk. Through the years, much of mission assurance has been aimed at increasing independent systems engineering and further refining basic design approaches. Now the time has come to direct NASA's attention to managing the risks that come from system interactions during a mission. To understand such risks, all engineering techniques are important. Mission-assurance engineers are entering the era of interaction in which engineering and system engineering must work closely to achieve better performance on time and within cost. A structured risk-management approach is critical to a successful project - this is nothing new. A risk policy must be integral to the program as part of a concurrent engineering process, and risk and risk drivers must be monitored throughout. Risk can also be managed as a resource: the new way of managing better, faster, cheaper programs encompasses up-front, knowledge-based risk assessment. The safety and mission assurance community can provide valuable support as risk management consultants. C1 NASA, Lewis Res Ctr, Off Safety Environm & Mission Assurance, Cleveland, OH 44135 USA. RP Lalli, VR (reprint author), NASA, Lewis Res Ctr, Off Safety Environm & Mission Assurance, 21000 Brookpk Rd, Cleveland, OH 44135 USA. NR 6 TC 2 Z9 3 U1 0 U2 0 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 0018-9529 J9 IEEE T RELIAB JI IEEE Trans. Reliab. PD SEP PY 1998 VL 47 IS 3 SI SI BP 355 EP 360 PN 2 PG 6 WC Computer Science, Hardware & Architecture; Computer Science, Software Engineering; Engineering, Electrical & Electronic SC Computer Science; Engineering GA 158NP UT WOS:000078121900011 ER PT J AU Everett, W Keene, S Nikora, A AF Everett, W Keene, S Nikora, A TI Applying software reliability engineering in the 1990s SO IEEE TRANSACTIONS ON RELIABILITY LA English DT Article DE software reliability; reliability modeling & prediction; software reliability tool kits; software reliability engineering (SRE) AB This paper reviews the progress in software-reliability since 1975, and discusses the best tools & practices that can be applied today. Software is increasingly vital over time, vis-a-vis hardware, in terms of system content. The software content is increasing and, often today, is a key factor in safety-critical applications in medicine, transportation, and nuclear energy. Appreciable software content is in almost every system, appliance, and machine which we use; and software is the backbone of our business enterprise operations. Consequently, producing reliable software is a mandate. Its development is often the 'long pole in the tent' - driving the cycle-time required to produce & field a product. Most often, software is the main source of system reliability problems. The best development practices are recommended herein, for managing the reliability of software. The development of software-reliability models and user-friendly tool kits is described. These tools allow software-reliability to be measured, tracked, and improved to meet the customer-specified reliability. The ability to measure software-reliability promotes development focus, and consequently, its improvement. The 1990s have seen much growth in the software content of products. The problems have grown as the software mushrooms both in size & complexity. Further, software is increasingly important in safety critical applications. To counter these concerns, there has been a great collective effort to improve the reliability & quality of software, through better development-focus exemplified by the Software Engineering Institute's Capability-Maturing-Model levels. Software-reliability-engineering has shown best practices for developing & measuring software-reliability. The 1990s have brought collective focus on managing reliability. Such collaboration has been in packaging software-reliability models in user-friendly packages such as SMERFS & CASRE. This reliability collaboration has also led to the International Software Reliability Engineering Conferences, for which the IEEE Reliability Society is a 1998 joint sponsor. Software-reliability experts have joined to develop the Handbook on Software Reliability. This is a very complete reference and is a fundamental library addition to anyone interested in exploring this field. The boob: contains a CD that has the reliability tools mentioned in this paper. C1 Software Proc & Reliabil Engn, Albuquerque, NM USA. Performance Technol, Boulder, CO USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Everett, W (reprint author), SPRE Inc, 4212 Rancho Ctr NW, Albuquerque, NM 87120 USA. EM w.w.everett@computer.org; s.keene@ieee.org NR 25 TC 5 Z9 6 U1 0 U2 1 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 0018-9529 J9 IEEE T RELIAB JI IEEE Trans. Reliab. PD SEP PY 1998 VL 47 IS 3 SI SI BP 372 EP 378 PN 2 PG 7 WC Computer Science, Hardware & Architecture; Computer Science, Software Engineering; Engineering, Electrical & Electronic SC Computer Science; Engineering GA 158NP UT WOS:000078121900014 ER PT J AU Bondyopadhyay, PK AF Bondyopadhyay, PK TI Sir J C Bose's diode detector received Marconi's first transatlantic wireless signal of December 1901 (The "Italian Navy Coherer" scandal revisited) SO IETE TECHNICAL REVIEW LA English DT Reprint DE detection of first transatlantic wireless signal; Italian Navy Coherer; Marconi's 1901 transatlantic wireless experiment; mercury coherer with a telephone; origin of the Italian Navy coherer; self-restoring coherer; semiconductor diode detector AB The true origin of the "mercury coherer with a telephone" receiver that was used by G Marconi to receive the first transatantic wireless signal on December 12, 1901, has been investigated and determined. Incontrovertible evidence is presented to show that this novel wireless detection device was invented by Sir J C Bose of Presidency College, Calcutta, India. His epochmaking work was communicated by Lord Rayleigh, F.R.S., to the Royal Society, London, U.K., on March 6, 1899, and read at the Royal Society Meeting of Great Britain on April 27, 1899. Soon after, it was published in the Proceedings of the Royal Society. Twenty-one months after that disclosure (in February 1901, as the records indicate), Lieutenant L. Solari of the Royal Italian Navy, a childhood friend of G. Marconi's, experimented with this detector device and presented a trivially modified version to Marconi, who then applied for a British patent on the device. Surrounded by a scandal, this detection device, actually a semiconductor diode, is known to the outside world as the "Italian Navy Coherer." This scandal, first brought to light by Prof. A Banti of Italy, has been critically analyzed and expertly presented in a time sequence of events by British historian V J Phillips but without discovering the true origin of the novel detector, in this paper, the scandal Is revisited and the mystery of the device's true origin is solved, thus correcting the century-old misinformation on an epoch-making chapter in the history of semiconductor devices. C1 NASA, Lyndon B Johnson Space Ctr, Avion Hardware Branch, Houston, TX 77058 USA. RP Bondyopadhyay, PK (reprint author), NASA, Lyndon B Johnson Space Ctr, Avion Hardware Branch, Houston, TX 77058 USA. NR 34 TC 0 Z9 0 U1 0 U2 0 PU INST ELECTRONICS TELECOMMUNICATION ENGINEERS PI NEW DELHI PA 2 INSTITUTIONAL AREA, LODI ROAD, NEW DELHI 110 003, INDIA SN 0256-4602 J9 IETE TECH REV JI IETE Tech. Rev. PD SEP-OCT PY 1998 VL 15 IS 5 BP 377 EP 406 PG 30 WC Engineering, Electrical & Electronic; Telecommunications SC Engineering; Telecommunications GA 221YF UT WOS:000081754800010 ER PT J AU Siegel, R AF Siegel, R TI Transient effects of radiative transfer in semitransparent materials SO INTERNATIONAL JOURNAL OF ENGINEERING SCIENCE LA English DT Article; Proceedings Paper CT Chandrasekhar Memorial Symposium of the Society-of-Engineering-Science CY OCT 21-23, 1996 CL ARIZONA STATE UNIV, TEMPE, AZ HO ARIZONA STATE UNIV ID FINITE-DIFFERENCE SOLUTION; CONDUCTIVE HEAT-TRANSFER; FLUX BOUNDARY-CONDITION; LAYER; SCATTERING; TEMPERATURE; MEDIA; SOLIDIFICATION; COMPOSITE; GLASS AB Temperature distributions within semitransparent materials can be strongly affected by internal emission, absorption and scattering of radiant thermal energy. This is important for translucent materials at elevated temperatures, in high temperature surroundings, or with large incident radiation. Transient behavior must be examined since translucence can result in internal temperature responses that are much more rapid and have different distributions than by heat conduction alone. Radiation effects on transients have been studied less than for steady state because of additional mathematical and computational complexities, but an appreciable literature has gradually developed. Detailed transient solutions are necessary to examine heat transfer and thermal stresses in ceramic components, ceramic thermal protection coatings, forming and tempering of glass windows, porous burners and insulation systems, energy dissipation from liquid drop and liquid sheet space radiators, some high temperature ceramic components in advanced aircraft engines, and other scientific and engineering applications. In this article, some of the governing equations are summarized along with the required radiative and convective boundary conditions. The literature is reviewed to provide an overview of the computational methods, geometries and types of conditions that have been analyzed. Analytical results are given to demonstrate transient effects and comparisons are made with transient experimental measurements. Published by Elsevier Science Ltd. All rights reserved. C1 NASA, Lewis Res Ctr, Res & Technol Directorate, Cleveland, OH 44135 USA. RP Siegel, R (reprint author), NASA, Lewis Res Ctr, Res & Technol Directorate, Cleveland, OH 44135 USA. NR 77 TC 30 Z9 33 U1 0 U2 7 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0020-7225 EI 1879-2197 J9 INT J ENG SCI JI Int. J. Eng. Sci. PD SEP-NOV PY 1998 VL 36 IS 12-14 BP 1701 EP 1739 DI 10.1016/S0020-7225(98)00054-8 PG 39 WC Engineering, Multidisciplinary SC Engineering GA 148ZT UT WOS:000077581800022 ER PT J AU Miller, RS Harstad, K Bellan, J AF Miller, RS Harstad, K Bellan, J TI Evaluation of equilibrium and non-equilibrium evaporation models for many-droplet gas-liquid flow simulations SO INTERNATIONAL JOURNAL OF MULTIPHASE FLOW LA English DT Article DE condensation; droplet; evaporation; non-equilibrium; spray ID CONVECTIVE EVAPORATION; VARIABLE PROPERTIES; TURBULENCE; DYNAMICS; COMBUSTION; RESONANCES; CLUSTERS; SPRAYS AB A variety of liquid droplet evaporation models, including both classical equilibrium and nonequilibrium Langmuir-Knudsen formulations, are evaluated through comparisons with experiments with particular emphasis on computationally efficient procedures for gas-liquid flow simulations. The models considered are those used in droplet laden flow calculations such as direct numerical simulations for which large numbers of individual (isolated) droplet solutions are obtained. Diameter and temperature evolution predictions are made for single-component droplets of benzene, decane, heptane, hexane and water with relatively large initial sizes similar to 1 mm vaporizing in convective air flows. All of the models perform nearly identically for low evaporation rates at gas temperatures significantly lower than the boiling temperature. For gas temperatures at and above the boiling point, large deviations are found between the various model predictions. The simulated results reveal that non-equilibrium effects become significant when the initial droplet diameter is <50 mu m and that these effects are enhanced with increasing slip velocity. It is additionally observed that constant properties can be used throughout each simulation if both the gas and vapor values are calculated at either the wet-bulb or boiling temperature. The models based on the Langmuir-Knudsen law and a corrected (for evaporation effects) analytical heat transfer expression derived from the quasi-steady gas phase assumption are shown to agree most favorably with a wide variety of experimental results. Since the experimental droplet sizes are all much larger than the limit for non-equilibrium effects to be important, for these conditions the most crucial aspect of the current Langmuir-Knudsen models is the corrected analytical form for the heat transfer expression as compared to empirical relations used in the remaining models. (C) 1998 Elsevier Science Ltd. All rights reserved. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Bellan, J (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 51 TC 228 Z9 239 U1 6 U2 63 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0301-9322 J9 INT J MULTIPHAS FLOW JI Int. J. Multiph. Flow PD SEP PY 1998 VL 24 IS 6 BP 1025 EP 1055 DI 10.1016/S0301-9322(98)00028-7 PG 31 WC Mechanics SC Mechanics GA 142EY UT WOS:000077188000008 ER PT J AU Tai, H AF Tai, H TI Dependence of the transverse thermal conductivity of unidirectional composites on fiber shape SO INTERNATIONAL JOURNAL OF THERMOPHYSICS LA English DT Article DE transverse thermal conductivity; unidirectional composites; fiber shape AB The model for the traverse thermal conductivity of unidirectional composite materials published by Springer and Tsai, which yields good results when compared to experimental results, is generalized to include fibers having elliptical cross sections. It is shown that the thermal conductivity of the unidirectional composite normal to the filaments depends strongly on fiber shape. C1 NASA, Langley Res Ctr, Hampton, VA 23665 USA. RP Tai, H (reprint author), NASA, Langley Res Ctr, MS 188b, Hampton, VA 23665 USA. NR 3 TC 6 Z9 6 U1 0 U2 1 PU KLUWER ACADEMIC/PLENUM PUBL PI NEW YORK PA 233 SPRING ST, NEW YORK, NY 10013 USA SN 0195-928X J9 INT J THERMOPHYS JI Int. J. Thermophys. PD SEP PY 1998 VL 19 IS 5 BP 1485 EP 1492 DI 10.1023/A:1021943821245 PG 8 WC Thermodynamics; Chemistry, Physical; Mechanics; Physics, Applied SC Thermodynamics; Chemistry; Mechanics; Physics GA 153PT UT WOS:000077842000013 ER PT J AU Parks, EK Bach, RE Shin, JH AF Parks, EK Bach, RE Shin, JH TI Reconstruction of the 1994 Pittsburgh airplane accident using a computer simulation SO JOURNAL OF AIRCRAFT LA English DT Article; Proceedings Paper CT AIAA 36th Aerospace Sciences Meeting CY JAN 12-15, 1998 CL RENO, NEVADA SP Amer Inst Aeronaut & Astronaut AB On Sept. 8, 1994, a Boeing 737-300 passenger airplane was on a downwind approach to the Pittsburgh International Airport at an altitude of 5000 ft above ground level. While in a shallow left turn onto a downwind-approach heading, the airplane crossed into the vortex trail of a Boeing 727 flying in the same approach pattern about 4 miles ahead. The B-737 airplane rolled and turned sharply to the left, exited the vortex wake, and plunged into the ground. The airplane was equipped with a 11+ channel digital night data recorder (FDR) and a multiple-channel cockpit voice recorder. Both recorders were recovered from the crash site and provided excellent data for the development of an accident scenario. Radar tracking of the two airplanes as well as the indicated airspeed perturbations clearly visible on the B-737 FDR recordings indicate that the upset was apparently initiated by the airplane's crossing into the wake of the B-727. A 6-degree-of-freedom simulation program for the B-737 airplane was constructed. The simulation was initialized at the stabilized night conditions of the airplane about 13 s prior to its entry into the vortex trail of the B-727 airplane. By assuming a certain combination of control inputs, it was possible to produce a simulated motion that closely matched that recorded on the FDR. C1 Univ Arizona, Tucson, AZ 85721 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Parks, EK (reprint author), Univ Arizona, Tucson, AZ 85721 USA. NR 13 TC 1 Z9 1 U1 0 U2 0 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0021-8669 J9 J AIRCRAFT JI J. Aircr. PD SEP-OCT PY 1998 VL 35 IS 5 BP 665 EP 670 DI 10.2514/2.2363 PG 6 WC Engineering, Aerospace SC Engineering GA 129UP UT WOS:000076482300001 ER PT J AU Lockard, DP Morris, PJ AF Lockard, DP Morris, PJ TI Wing-tip vortex calculations using a high-accuracy scheme SO JOURNAL OF AIRCRAFT LA English DT Article AB The objective of the research described in this paper is to investigate the use of computational aeroacoustics methodology and parallel computers to simulate the development of a tip vortex. A three-dimensional Euler code, implemented using the message passing library and Fortran 90 on the IBM SP2, is used to perform calculations of the steady now. Results are presented for low-speed now over a finite span NACA 0012 wing. Comparisons with experimental data show that the tip vortex is predicted to diffuse too rapidly, but the high-accuracy scheme does reduce numerical errors. It is argued that Navier-Stokes calculations on a much finer mesh would improve the solutions, but they would be prohibitively expensive for unsteady calculations. C1 Penn State Univ, University Pk, PA 16802 USA. RP Lockard, DP (reprint author), NASA, Langley Res Ctr, Dept Aerosp Engn, Hampton, VA 23681 USA. EM d.p.lockard@larc.nasa.gov; pjm@psu.edu NR 22 TC 3 Z9 3 U1 0 U2 1 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0021-8669 J9 J AIRCRAFT JI J. Aircr. PD SEP-OCT PY 1998 VL 35 IS 5 BP 728 EP 738 DI 10.2514/2.2383 PG 11 WC Engineering, Aerospace SC Engineering GA 129UP UT WOS:000076482300009 ER PT J AU Lind, R Freudinger, LC Voracek, DF AF Lind, R Freudinger, LC Voracek, DF TI Comparison of aeroelastic excitation mechanisms SO JOURNAL OF AIRCRAFT LA English DT Article C1 NASA, Dryden Flight Res Ctr, Struct Dynam Branch, Edwards, CA 93523 USA. RP Lind, R (reprint author), NASA, Dryden Flight Res Ctr, Struct Dynam Branch, Edwards, CA 93523 USA. NR 5 TC 3 Z9 3 U1 0 U2 0 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0021-8669 J9 J AIRCRAFT JI J. Aircr. PD SEP-OCT PY 1998 VL 35 IS 5 BP 830 EP 832 DI 10.2514/2.7585 PG 3 WC Engineering, Aerospace SC Engineering GA 129UP UT WOS:000076482300025 ER PT J AU Bridge, KY Smith, CK Young, RB AF Bridge, KY Smith, CK Young, RB TI Beta-adrenergic receptor gene expression in bovine skeletal muscle cells in culture SO JOURNAL OF ANIMAL SCIENCE LA English DT Article DE cattle; muscles; cell cultures; beta-adrenergic receptors ID PROTEIN-METABOLISM; AGONISTS AB Beta-adrenergic receptors (beta AR) are abundant in fetal, neonatal, and adult skeletal muscles of cattle; however, only minimal levels of functional beta AR were detected in multinucleated muscle cell cultures prepared from 90- to 150-d fetal bovine skeletal muscle. Two other lines of evidence were consistent with low levels of beta AR expression in bovine muscle cultures. First, treating the cells with 10(-6) M isoproterenol for up to 20 min did not increase intracellular cAMP concentration. Second, neither the quantity of myosin heavy chain (MHC) nor its apparent synthesis rate were changed by treating the cells for 4 d with 10(-7) or 10(-6) M isoproterenol. Despite these results, the mRNA for the beta(2)AR could be detected in muscle cultures by PCR and on slot blots. Thus, the beta(2)AR mRNA was expressed, but significant levels of functional receptors could not be detected. Glucocorticoids are known to activate expression of beta AR genes in several tissues, and the effect of dexamethasone on beta AR gene expression in bovine multinucleated muscle cell cultures was evaluated. The intracellular concentration of cAMP following treatment with isoproterenol was elevated 10-fold by dexamethasone, and the population of functional receptors was elevated by approximately 50%. The effect of dexamethasone on muscle protein synthesis and accumulation was analyzed after pretreating the cells with dexamethasone for 24 h, followed by treatment with dexamethasone and 10(-6) M isoproterenol for an additional 48 h. The quantity of MHC synthesized and the apparent synthesis rate of MHC were stimulated by 10 to 35%. These effects seem to be due to posttranscriptional events, because the quantity of beta(2)AR receptor mRNA on slot blots was not increased by treatment with dexamethasone. Results of this study emphasize the importance of verifying that muscle cells contain functional beta AR when they are used to study the effects of beta AR agonists on muscle protein metabolism. C1 Univ Alabama, Dept Biol Sci, Huntsville, AL 35899 USA. Lilly Res Labs, Greenfield, IN 46140 USA. RP Young, RB (reprint author), NASA, George C Marshall Space Flight Ctr, ES 76,Bldg 4481, Huntsville, AL 35812 USA. EM ronald.young@msfc.nasa.gov NR 22 TC 10 Z9 10 U1 1 U2 2 PU AMER SOC ANIMAL SCIENCE PI SAVOY PA 1111 NORTH DUNLAP AVE, SAVOY, IL 61874 USA SN 0021-8812 J9 J ANIM SCI JI J. Anim. Sci. PD SEP PY 1998 VL 76 IS 9 BP 2382 EP 2391 PG 10 WC Agriculture, Dairy & Animal Science SC Agriculture GA 124EV UT WOS:000076169300019 PM 9781494 ER PT J AU Ravat, D Taylor, PT AF Ravat, D Taylor, PT TI Determination of depths to centroids of three-dimensional sources of potential-field anomalies with examples from environmental and geologic applications SO JOURNAL OF APPLIED GEOPHYSICS LA English DT Article DE centroid; potential-field anomaly; anomaly attenuation rate method ID MAGNETIC BOUNDARY; MAGSAT; MOHO AB A method is developed for determining the depth to the centroid (the geometric center) of 'semi-compact' sources. The method, called the anomaly attenuation rate (AAR) method, involves computing radial averages of AARs with increasing distances from a range of assumed source centers. For well-isolated magnetic anomalies from 'semi-compact' sources, the theoretical AARs range from similar to 2 (close to the sources) to similar to 3 (in the far-field region); the corresponding theoretical range of AARs for gravity anomalies is similar to 1 to similar to 2. When the estimated source centroid is incorrect, the AARs either exceed or fall short of the theoretical values. The levelling-off of the far-field AARs near their theoretical maximum values indicates the upper (deeper) bound of the centroid location. Similarly, near-field AARs lower than the theoretical minimum indicate the lower (shallower) bound of the centroid location. It is not always possible to determine usable upper and lower bounds of the centroids because the method depends on characteristics of sources/anomalies and the noise level of the data. For the environmental magnetic examples considered in this study, the determined deeper bounds were within 4% of the true centroid-to-observation distance. For the case of the gravity anomaly from the Bloomfield Pluton, Missouri, USA, determination of only the shallower bound of the centroid location (similar to 7 km) was possible. This estimate agrees closely with the centroid of a previously determined three-dimensional model of the Bloomfield Pluton. For satellite magnetic anomalies, the method is appropriate only for high-amplitude, near-circular anomalies due to the inherent low signal-to-noise ratio of satellite magnetic anomalies. Model studies indicate that the AAR method is able to place depths within +/- 20-30 km of actual center locations from a 400-km observation altitude. Thus, the method may be able to discriminate between upper crustal, lower crustal, and mantle magnetic sources. The results from the prominent Kentucky anomaly are relatively well-resolved (centroid depth similar to 30 km below the Earth's surface). For the Kiruna Magsat anomaly, the deleterious effects from neighboring anomalies make a determination difficult (possible depth could be between 20 and 30 km). The centroid depths are deeper for the Kursk anomaly (similar to 40-50 km). These depths may indicate that magnetic anomalies from the near-surface Kursk iron formations (a known contributor) and deep crustal magnetic sources could combine to form the Kursk Magsat anomaly. (C) 1998 Elsevier Science B.V. All rights reserved. C1 So Illinois Univ, Dept Geol, Carbondale, IL 62901 USA. NASA, Goddard Space Flight Ctr, Geodynam Branch, Greenbelt, MD 20771 USA. RP Ravat, D (reprint author), So Illinois Univ, Dept Geol, MS 4324, Carbondale, IL 62901 USA. RI Taylor, Patrick/D-4707-2012; OI Taylor, Patrick/0000-0002-1212-9384; Ravat, Dhananjay/0000-0003-1962-4422 NR 24 TC 5 Z9 5 U1 0 U2 2 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0926-9851 J9 J APPL GEOPHYS JI J. Appl. Geophys. PD SEP PY 1998 VL 39 IS 4 BP 191 EP 208 DI 10.1016/S0926-9851(98)00021-4 PG 18 WC Geosciences, Multidisciplinary; Mining & Mineral Processing SC Geology; Mining & Mineral Processing GA 123WQ UT WOS:000076148900001 ER PT J AU Ulbrich, CW Atlas, D AF Ulbrich, CW Atlas, D TI Rainfall microphysics and radar properties: Analysis methods for drop size spectra SO JOURNAL OF APPLIED METEOROLOGY LA English DT Article ID DISTRIBUTION TRUNCATION; CONVECTIVE CLOUDS; RAINDROP SPECTRA AB Analyses are performed of experimental drop size spectra to explore the relationships among integral parameters for rain. The data used in this work were acquired with an airborne optical 2D precipitation probe in TOGA COARE during a 4-month period in 1992-93. It is assumed that the experimental size spectra can be described by a gamma drop size distribution (DSD) of the form N(D) = N0Dmu exp(-Lambda D) involving three parameters (N-0, mu, Lambda), which are determined using a new method of truncated moments. The method allows for truncation of the DSD at the large-diameter end of the spectrum due in part to instrumental effects and also in part to the trajectory of the aircraft through a rain streamer that has been sorted by wind shear. An effect analogous to truncation can occur at the small-diameter end of the size spectrum due to evaporation. However, truncation of the spectrum at the small-diameter end is not considered in this work. It is found that spectra with small space and timescales display considerable fluctuations in all three of the DSD parameters. It is also shown that the method of truncated moments yields distributions of the DSD parameters that have smaller average and modal values than when using untruncated moments. The data are stratified separately into classes according to each of the two DSD parameters D-m (mass-weighted mean diameter) and mu. The latter parameter describes the shape of the distribution. Empirical analyses between the reflectivity factor Z and rainfall rate R are performed for the data in each of these classes, and it is found that the results are consistent with that predicted by theory. A synthesis of the results of these empirical analyses is presented in the form of a new rain parameter diagram, which allows for changes in DSD shape. C1 Clemson Univ, Dept Phys & Astron, Clemson, SC 29634 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Ulbrich, CW (reprint author), Clemson Univ, Dept Phys & Astron, Clemson, SC 29634 USA. NR 22 TC 112 Z9 119 U1 0 U2 5 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 USA SN 0894-8763 J9 J APPL METEOROL JI J. Appl. Meteorol. PD SEP PY 1998 VL 37 IS 9 BP 912 EP 923 DI 10.1175/1520-0450(1998)037<0912:RMARPA>2.0.CO;2 PG 12 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 115ZP UT WOS:000075696700004 ER PT J AU Meneghini, R AF Meneghini, R TI Application of a threshold method to airborne-spaceborne attenuating-wavelength radars for the estimation of space-time rain-rate statistics SO JOURNAL OF APPLIED METEOROLOGY LA English DT Article ID PROBABILITY-DISTRIBUTION FUNCTIONS; CONVECTIVE RAINFALL; SINGLE-FREQUENCY; AREA INTEGRALS; SATELLITE AB A method is proposed for estimating the area-average rain-rate distribution from attenuating-wavelength spaceborne or airborne radar data. Because highly attenuated radar returns yield unreliable estimates of the rain rate, these are eliminated by means of a proxy variable, Q, derived from the apparent radar reflectivity factors and a power law relating the attenuation coefficient and the reflectivity factor. In determining the probability distribution function of areawide rain rates, the elimination of attenuated measurements at high rain rates and the loss of data at light rain rates, because of low Signal-to-noise ratios, leads to truncation of the distribution at the low and high ends. To estimate it over all rain rates, a lognormal distribution is assumed, the parameters of which are obtained from a nonlinear least squares fit to the truncated distribution. Implementation of this type of threshold method depends on the method used in estimating the high-resolution rain-rate estimates either the standard Z-R or the Hitschfeld-Bordan estimate) and on the type of rain-rate estimate (either point or path averaged). To test the method, measured drop size distributions are used to characterize the rain along the radar beam. Comparisons with the standard single-threshold method or with the sample mean, taken over the high-resolution estimates, show that the present method usually provides more accurate determinations of the area-averaged rain rate if the values of the threshold parameter, Q(r), are chosen in the range from 0.2 to 0.4. C1 NASA, Goddard Space Flight Ctr, Microwave Sensors Branch, Greenbelt, MD 20771 USA. RP Meneghini, R (reprint author), NASA, Goddard Space Flight Ctr, Microwave Sensors Branch, Code 975, Greenbelt, MD 20771 USA. NR 30 TC 6 Z9 8 U1 0 U2 0 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 USA SN 0894-8763 J9 J APPL METEOROL JI J. Appl. Meteorol. PD SEP PY 1998 VL 37 IS 9 BP 924 EP 938 DI 10.1175/1520-0450(1998)037<0924:AOATMT>2.0.CO;2 PG 15 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 115ZP UT WOS:000075696700005 ER PT J AU Islam, NE Pugh, RD Brothers, CP Shedd, WM Singaraju, BK Howard, JW Dussault, H Fageeha, O AF Islam, NE Pugh, RD Brothers, CP Shedd, WM Singaraju, BK Howard, JW Dussault, H Fageeha, O TI Basic mechanisms for enhanced prompt charge collection in a n(+)p junction following single charged particle interaction SO JOURNAL OF APPLIED PHYSICS LA English DT Article ID ION TRACKS; SIMULATION; SILICON; DEVICES; UPSET AB This study shows that in the early stages of a single particle transient, the presence of residual holes in the depletion region of a n(+)p junction affect depletion profile and terminal currents. Due to their greater mobility, electrons deposited in the depletion region move out faster than holes, leaving residual holes in the region. The resulting charge imbalance in the depletion region may cause the depletion region to briefly extend into the substrate before the beginning of recovery process. This extended depletion region influences prompt collection of carriers in the vicinity. In particular, carrier response to this field produces a conduction and/or displacement current. The sum of the conduction plus displacement current is immediately seen as an enhanced prompt conduction current at the device terminals. Enhanced prompt charge collection depends on substrate doping, junction bias, and the density of charge deposited. Low-doped p-type substrates, with longer hole residence time in the depletion region, are more susceptible to enhanced prompt collection and substrate field disturbances. Response of p-Si and n-Si substrates to single event effects and the effects of laser beams for enhanced prompt collection are also analyzed. (C) 1998 American Institute of Physics. [S0021-8979(98)04417-X]. C1 USAF, Phillips Lab, Space Miss Technol Div, Kirtland AFB, NM 87117 USA. Comp Sci Corp, George C Marshall Space Flight Ctr, MSFC EL23, Huntsville, AL 35812 USA. RL CA 2, Rome, NY 13441 USA. Rensselaer Polytech Inst, Dept Nucl Engn & Engn Phys, Troy, NY 12180 USA. RP Islam, NE (reprint author), USAF, Phillips Lab, Space Miss Technol Div, 3550 Aberdeen Ave SE, Kirtland AFB, NM 87117 USA. EM naz@eece.unm.edu NR 20 TC 5 Z9 5 U1 0 U2 1 PU AMER INST PHYSICS PI WOODBURY PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 USA SN 0021-8979 J9 J APPL PHYS JI J. Appl. Phys. PD SEP 1 PY 1998 VL 84 IS 5 BP 2690 EP 2696 DI 10.1063/1.368441 PG 7 WC Physics, Applied SC Physics GA 114CC UT WOS:000075590700045 ER PT J AU Topaler, MS Allison, TC Schwenke, DW Truhlar, DG AF Topaler, MS Allison, TC Schwenke, DW Truhlar, DG TI What is the best semiclassical method for photochemical dynamics of systems with conical intersections? SO JOURNAL OF CHEMICAL PHYSICS LA English DT Article ID STATE TRANSITION-PROBABILITIES; VIBRATIONAL ENERGY-TRANSFER; SURFACE-HOPPING APPROACH; CLASSICAL S-MATRIX; MOLECULAR-DYNAMICS; ELECTRONIC-TRANSITIONS; NONADIABATIC PROCESSES; COLLISIONS; SCATTERING; TRAJECTORIES AB We present a systematic test of four general semiclassical procedures for the theoretical treatment of multistate molecular processes such as electronically nonadiabatic photochemical reactions. The methods are tested by comparing their predictions to accurate quantal results for three two-state model reactions involving conical intersections. The four methods tested are Tully's fewest-switches version of trajectory surface hopping (1990), the Blais-Truhlar trajectory surface hopping method (1983), the Ehrenfest scheme (1975-1979), and the Meyer-Miller method (1979). We test the ability of the classical path methods to predict both electronic probabilities and product rovibrational distributions. For each of the four basic approaches we test six options for extracting final-state information from the calculated dynamics. We find that, although in most cases there is qualitative agreement between average quantum mechanical and trajectory results, the overall average error is about 50% for Tully's fewest-switches method, the Ehrenfest method, and the Meyer-Miller method, and even higher, about 60%, for the Blais-Truhlar method. These values do not include additional errors in the below-threshold regions, which are especially large for the Meyer-Miller method because of the electronic zero-point energy in the Meyer-Miller classical analog Hamiltonian. (C) 1998 American Institute of Physics. C1 Univ Minnesota, Dept Chem, Minneapolis, MN 55455 USA. Univ Minnesota, Inst Supercomp, Minneapolis, MN 55455 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Topaler, MS (reprint author), Univ Minnesota, Dept Chem, 207 Pleasant St SE, Minneapolis, MN 55455 USA. RI schwenke, david/I-3564-2013; Truhlar, Donald/G-7076-2015 OI Truhlar, Donald/0000-0002-7742-7294 NR 76 TC 70 Z9 71 U1 0 U2 6 PU AMER INST PHYSICS PI WOODBURY PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 USA SN 0021-9606 J9 J CHEM PHYS JI J. Chem. Phys. PD SEP 1 PY 1998 VL 109 IS 9 BP 3321 EP 3345 DI 10.1063/1.477684 PG 25 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA 114ZP UT WOS:000075639300005 ER PT J AU Mehta, VM AF Mehta, VM TI Variability of the tropical ocean surface temperatures at decadal-multidecadal timescales. Part I: The Atlantic Ocean SO JOURNAL OF CLIMATE LA English DT Article ID EMPIRICAL ORTHOGONAL FUNCTIONS; PRINCIPAL COMPONENT ANALYSIS; INTERANNUAL VARIABILITY; SEASONAL RAINFALL; NORMAL-MODES; TIME-SERIES; PREDICTION; DYNAMICS; SCALES AB Gridded time series from the Global Ocean Surface Temperature Atlas were analyzed with a variety of techniques to identify spatial structures and oscillation periods of the tropical Atlantic sea surface temperature (SST) variations at decadal timescales, and to develop physical interpretations of statistical patterns of decadal SST variations. Each time series was 110 yr (1882-1991) long. The tropical Atlantic SST variations were compared with decadal variations in a 74-yr-long (1912-85) north Nordeste Brazil rainfall time series and a 106-yr-lang (1886-1991) tropical Atlantic cyclone activity index time series. The tropical Atlantic SST variations were also compared with decadal variations in the extratropical Atlantic SST. Multiyear to multidecadal variations in the cross-equatorial dipole pattern identified as a dominant empirical pattern of the tropical Atlantic SST variations in earlier and present studies are shown to be variations in the approximately north-south gradient of SST anomalies. It is also shown that there was no dynamical-thermodynamical, dipole mode of SST variations during the analysis period. There was a distinct decadal timescale (12-13 yr) of SST variations in the tropical South Atlantic, whereas no distinct decadal timescale was found in the tropical North Atlantic SST variations. Approximately 80% of the coherent decadal variance in the cross-equatorial SST gradient was "explained" by coherent decadal oscillations in the tropical South Atlantic SSTs. There were three, possibly physical, modes of decadal variations in the tropical Atlantic SSTs during the analysis period. In the more energetic mode of the North Atlantic decadal SST variations, anomalies traveled into the tropical North Atlantic from the extratropical North Atlantic along the eastern boundary of the basin. The anomalies strengthened and resided in the tropical North Atlantic for several years, then frequently traveled northward into the mid-high-latitude North Atlantic along the western boundary of the basin, and completed a clockwise rotation around the North Atlantic basin. In the less energetic North Atlantic decadal made, SST anomalies originated in the tropical-subtropical North Atlantic near the African coast, and traveled northwestward and southward. In the South Atlantic decadal SST mode, anomalies either developed in situ or traveled into the tropical South Atlantic from the subtropical South Atlantic along the eastern boundary of the basin. The anomalies strengthened and resided in the tropical South Atlantic for several years, then frequently traveled southward into the subtropical South Atlantic along the western boundary of the basin, and completed a counterclockwise rotation around the South Atlantic basin. These decadal modes were not a permanent feature of the tropical Atlantic SST variations. The tropical North and South Atlantic SST anomalies frequently extended across the equator. Uncorrelated alignments of decadal SST anomalies having opposite signs on two sides of the equator occasionally created the apperance of a dipole. Independent analyses of the north Nordeste Brazil rainfall showed physical consistency and high coherence with the cross-equatorial SST gradient oscillations at 12-13-yr period. The tropical Atlantic cyclone index showed physical consistency but moderate coherence with the tropical North Atlantic decadal SST variations. The quasi-regularity of the 12-13-yr oscillations in the cross-equatorial SST gradient may provide an opportunity for long lead-time, skillful predictions of climate anomalies in the tropical Atlantic sector. C1 Univ Maryland, Dept Meteorol, Joint Ctr Earth Syst Sci, NASA, College Pk, MD 20742 USA. RP Mehta, VM (reprint author), Univ Maryland, Dept Meteorol, Joint Ctr Earth Syst Sci, NASA, College Pk, MD 20742 USA. NR 39 TC 77 Z9 78 U1 0 U2 6 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 USA SN 0894-8755 J9 J CLIMATE JI J. Clim. PD SEP PY 1998 VL 11 IS 9 BP 2351 EP 2375 DI 10.1175/1520-0442(1998)011<2351:VOTTOS>2.0.CO;2 PG 25 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 123YG UT WOS:000076152800013 ER PT J AU Hixon, R AF Hixon, R TI Evaluation of a high-accuracy MacCormack-type scheme using benchmark problems SO JOURNAL OF COMPUTATIONAL ACOUSTICS LA English DT Article ID BOUNDARY-CONDITIONS AB Due to their inherent dissipation and stability, the MacCormack scheme and its variants have been widely used in the computation of unsteady flow and acoustic problems. However, these schemes require many points per wavelength in order to propagate waves with a reasonable amount of accuracy. Recently, much progress has been made in improving the wave propagation qualities of MacCormack-type schemes. In this work, the linear wave propagation characteristics of MacCormack-type schemes are compared using several of the CAA Benchmark Problems. C1 NASA, Lewis Res Ctr, Inst Computat Mech Prop, Cleveland, OH 44135 USA. RP Hixon, R (reprint author), NASA, Lewis Res Ctr, Inst Computat Mech Prop, Cleveland, OH 44135 USA. NR 22 TC 10 Z9 11 U1 0 U2 3 PU WORLD SCIENTIFIC PUBL CO PTE LTD PI SINGAPORE PA JOURNAL DEPT PO BOX 128 FARRER ROAD, SINGAPORE 912805, SINGAPORE SN 0218-396X J9 J COMPUT ACOUST JI J. Comput. Acoust. PD SEP PY 1998 VL 6 IS 3 BP 291 EP 305 DI 10.1142/S0218396X9800020X PG 15 WC Acoustics; Mathematics, Interdisciplinary Applications SC Acoustics; Mathematics GA 157WM UT WOS:000078084700001 ER PT J AU Mankbadi, RR Shih, SH Hixon, DR Stuart, JT Povinelli, LA AF Mankbadi, RR Shih, SH Hixon, DR Stuart, JT Povinelli, LA TI A surface-integral formulation for jet noise prediction based on the pressure signal alone SO JOURNAL OF COMPUTATIONAL ACOUSTICS LA English DT Article ID RADIATED SOUND AB While large-scale simulation of jet noise is the most thorough technique currently available for jet noise prediction, three-dimensional direct computation: of both the near and far field requires prohibitive computational capability. In this work we propose to limit large-scale simulation to the near held to provide the pressure distribution over a cylindrical surface surrounding the jet. A surface-integral formulation is presented herein in which the calculated pressure on the cylindrical surface is used to obtain the far-field sound, without the need for the normal derivative of the pressure. The results are compared to that of direct large-scale simulation and to the zonal approach in which linearized Euler equations are used as an extension tool. C1 NASA, Lewis Res Ctr, Inst Computat Mech Prop, Cleveland, OH 44135 USA. Univ London Imperial Coll Sci Technol & Med, Dept Math, London, England. RP Mankbadi, RR (reprint author), NASA, Lewis Res Ctr, Inst Computat Mech Prop, Cleveland, OH 44135 USA. NR 14 TC 3 Z9 3 U1 0 U2 0 PU WORLD SCIENTIFIC PUBL CO PTE LTD PI SINGAPORE PA JOURNAL DEPT PO BOX 128 FARRER ROAD, SINGAPORE 912805, SINGAPORE SN 0218-396X J9 J COMPUT ACOUST JI J. Comput. Acoust. PD SEP PY 1998 VL 6 IS 3 BP 307 EP 320 DI 10.1142/S0218396X98000211 PG 14 WC Acoustics; Mathematics, Interdisciplinary Applications SC Acoustics; Mathematics GA 157WM UT WOS:000078084700002 ER PT J AU Barth, TJ Sethian, JA AF Barth, TJ Sethian, JA TI Numerical schemes for the Hamilton-Jacobi and level set equations on triangulated domains SO JOURNAL OF COMPUTATIONAL PHYSICS LA English DT Article ID CONSERVATION-LAWS; PROPAGATING INTERFACES; UNIFIED MODEL; ALGORITHMS; LITHOGRAPHY; SIMULATIONS; DEPOSITION; FRONTS AB Borrowing from techniques developed for conservation law equations, numerical schemes which discretize the Hamilton-Jacobi (H-J), level set, and Eikonal equations on triangulated domains are presented. The first scheme is a provably monotone discretization for the H-J equations. Unfortunately, the basic scheme lacks Lipschitz continuity of the numerical Hamiltonian. By employing a "virtual" edge flipping technique local Lipschitz continuity of the numerical flux is restored on acute triangulations. Next, schemes are introduced and developed based on the weaker concept of positive coefficient approximations for homogeneous Hamiltonians. These schemes possess a discrete maximum principle on arbitrary triangulations and exhibit local Lipschitz continuity of the numerical Hamiltonian. Finally, a class of Petrov-Galerkin approximations is considered. These schemes are stabilized via a least-squares bilinear form. The Petrov-Galerkin schemes do not possess a discrete maximum principle but generalize to high order accuracy. Discretization of the level set equation also requires the numerical approximation of a mean curvature term. A simple mass-lumped Galerkin approximation is presented in Section 6 and analyzed using maximum principle analysis. The use of unstructured meshes permits several forms of mesh adaptation which have been incorporated into numerical examples. These numerical examples include discretizations of convex and nonconvex forms of the H-J equation, the Eikonal equation, and the level set equation. (C) 1998 Academic Press. C1 NASA, Ames Res Ctr, Informat Sci Directorate, Moffett Field, CA 94035 USA. Univ Calif Berkeley, Dept Math, Berkeley, CA 94720 USA. RP Barth, TJ (reprint author), NASA, Ames Res Ctr, Informat Sci Directorate, Moffett Field, CA 94035 USA. NR 32 TC 148 Z9 156 U1 2 U2 10 PU ACADEMIC PRESS INC PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA SN 0021-9991 J9 J COMPUT PHYS JI J. Comput. Phys. PD SEP 1 PY 1998 VL 145 IS 1 BP 1 EP 40 DI 10.1006/jcph.1998.6007 PG 40 WC Computer Science, Interdisciplinary Applications; Physics, Mathematical SC Computer Science; Physics GA 114PE UT WOS:000075617200001 ER PT J AU Mavriplis, DJ AF Mavriplis, DJ TI Multigrid strategies for viscous flow solvers on anisotropic unstructured meshes SO JOURNAL OF COMPUTATIONAL PHYSICS LA English DT Article ID EULER EQUATIONS; AGGLOMERATION; SCHEMES; GRIDS AB Unstructured multigrid techniques for relieving the stiffness associated with high-Reynolds number viscous flow simulations on extremely stretched grids are investigated. One approach consists of employing a semi-coarsening or directional-coarsening technique, based on the directions of strong coupling within the mesh, in order to construct more optimal coarse grid levels. An alternate approach is developed which employs directional implicit smoothing with regular fully coarsened multigrid levels. The directional implicit smoothing is obtained by constructing implicit lines in the unstructured mesh based on the directions of strong coupling. Both approaches yield large increases in convergence rates over the traditional explicit full-coarsening multigrid algorithm. However, maximum benefits are achieved by combining the two approaches in a coupled manner into a single algorithm. An order of magnitude increase in convergence rate over the traditional explicit full-coarsening algorithm is demonstrated, and convergence rates for high-Reynolds number viscous hows which are independent of the grid aspect ratio are obtained. Further acceleration is provided by incorporating low-Mach-number preconditioning techniques, and a Newton-GMRES strategy which employs the multigrid scheme as a preconditioner. The compounding effects of these various techniques on speed of convergence is documented through several example test cases. (C) 1998 Academic Press. C1 NASA, Langley Res Ctr, Inst Comp Appl Sci & Engn, Hampton, VA 23681 USA. RP Mavriplis, DJ (reprint author), NASA, Langley Res Ctr, Inst Comp Appl Sci & Engn, Hampton, VA 23681 USA. EM dimitri@icase.edu NR 46 TC 63 Z9 65 U1 0 U2 0 PU ACADEMIC PRESS INC PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA SN 0021-9991 J9 J COMPUT PHYS JI J. Comput. Phys. PD SEP 1 PY 1998 VL 145 IS 1 BP 141 EP 165 DI 10.1006/jcph.1998.6036 PG 25 WC Computer Science, Interdisciplinary Applications; Physics, Mathematical SC Computer Science; Physics GA 114PE UT WOS:000075617200006 ER PT J AU Su, CH Palosz, W Feth, S Lehoczky, SL AF Su, CH Palosz, W Feth, S Lehoczky, SL TI Heat treatments of ZnSe starting materials for physical vapor transport SO JOURNAL OF CRYSTAL GROWTH LA English DT Article ID OPTICAL-DENSITY MEASUREMENTS; SILICA GLASS AMPOULES; CDTE SOLID-SOLUTIONS; MOLE PERCENT CDTE; PARTIAL PRESSURES; THERMODYNAMIC PROPERTIES; RESIDUAL-GAS; MASS FLUX; GROWTH; TE AB The effect of different heat treatments on stoichiometry and residual gas pressure in ZnSe physical vapor transport system was investigated. The dependence of the amount and composition of the residual gas on various heat treatment procedures is reported. Heat treatment of ZnSe starting materials by baking under the condition of dynamic vacuum to adjust its stoichiometry was performed and the effectiveness of the treatment was confirmed by the measurements of the partial pressure of Se-2, P-Se2, in equilibrium with the heat treated samples. Optimum heat treatment procedures on the ZnSe starting material for the physical vapor transport process are discussed and verified experimentally. (C) 1998 Elsevier Science B.V. All rights reserved. C1 NASA, George C Marshall Space Flight Ctr, Space Sci Lab, Huntsville, AL 35812 USA. RP Su, CH (reprint author), NASA, George C Marshall Space Flight Ctr, Space Sci Lab, Huntsville, AL 35812 USA. RI Feth, Shari/F-6302-2013 OI Feth, Shari/0000-0003-3545-5649 NR 35 TC 16 Z9 18 U1 0 U2 1 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0022-0248 J9 J CRYST GROWTH JI J. Cryst. Growth PD SEP PY 1998 VL 192 IS 3-4 BP 386 EP 394 DI 10.1016/S0022-0248(98)00365-0 PG 9 WC Crystallography; Materials Science, Multidisciplinary; Physics, Applied SC Crystallography; Materials Science; Physics GA 118LN UT WOS:000075840000005 ER PT J AU Dahl, MD Morris, PJ AF Dahl, MD Morris, PJ TI Supersonic jet noise reductions predicted with increased jet spreading rate SO JOURNAL OF FLUIDS ENGINEERING-TRANSACTIONS OF THE ASME LA English DT Article ID INSTABILITY WAVES; COAXIAL JETS AB In this paper, predictions are made of noise radiation from single, supersonic, axisymmetric jets. We examine the effects of changes in operating conditions and the effects of simulated enhanced mixing that would increase the spreading rate of the jet shear layer on radiated noise levels. The radiated noise in the downstream? direction is dominated by mixing noise and at higher speeds, it is well described by the instability wave noise radiation model. Further analysis with the model shows a relationship between changes in spreading rate due to enhanced mixing and changes in the far field radiated peak noise levels. The calculations predict that enhanced jet spreading results in a reduction of the radiated peak noise level. C1 NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. Penn State Univ, University Pk, PA 16802 USA. RP Dahl, MD (reprint author), NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. NR 15 TC 2 Z9 2 U1 0 U2 0 PU ASME-AMER SOC MECHANICAL ENG PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017 USA SN 0098-2202 J9 J FLUID ENG-T ASME JI J. Fluids Eng.-Trans. ASME PD SEP PY 1998 VL 120 IS 3 BP 471 EP 476 DI 10.1115/1.2820686 PG 6 WC Engineering, Mechanical SC Engineering GA 125RY UT WOS:000076251900011 ER PT J AU Lang, HR Frerichs, WE AF Lang, HR Frerichs, WE TI New planktic foraminiferal data documenting Coniacian Age for Laramide orogeny onset and paleooceanography in southern Mexico SO JOURNAL OF GEOLOGY LA English DT Article ID EAST-CENTRAL MEXICO; FOLD-THRUST BELT; REGION; GULF AB A Late Cretaceous flysch comprising the 2600-m-thick Mexcala Formation records the initial local pulse of the Laramide Orogeny on the southern arm of the Mexican fold-thrust belt in northeastern Guerrero State. We identified 15 planktic foraminiferal species from 35 productive shale samples that demonstrate that the Mexcala is assignable to the Dicarinella concavata biozone. Thus, in agreement with evidence from northern Mexico, the Laramide onset in southern Mexico occurred during Coniacian time. Paleozoogeographic interpretation of our faunas shows an oceanic connection with the Caribbean, and that the southern margin of the North American Plate in northern Guerrero must have been isolated from the Coniacian-early Santonian Pacific Ocean. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ Wyoming, Dept Geol & Geophys, Laramie, WY 82071 USA. RP Lang, HR (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr,MS183-501, Pasadena, CA 91109 USA. NR 19 TC 10 Z9 11 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5801 S ELLIS AVENUE, CHICAGO, IL 60637 USA SN 0022-1376 J9 J GEOL JI J. Geol. PD SEP PY 1998 VL 106 IS 5 BP 635 EP 640 PG 6 WC Geology SC Geology GA 121AF UT WOS:000075989400009 ER PT J AU Klimas, AJ Vassiliadis, D Baker, DN AF Klimas, AJ Vassiliadis, D Baker, DN TI Dst index prediction using data-derived analogues of the magnetospheric dynamics SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID MAGNETIC STORMS; PARAMETERS AB The method of Klimas et al. [1997] for constructing dynamical analogues of physical input-output systems is generalized. Higher-order analogues with sensitivity to more features of the input data are derived. Solar wind VBs parameter data are used for input and Dst index data are used for output to construct analogues of the magnetospheric dynamics responsible for Dst storms. A detailed study of the dynamics involved in a single storm is presented. It is shown that the relationship between VBs input and Dst output for this storm can be described in the context of the model of Burton et al. [1975] but with variable decay time and strength of coupling to the solar wind VBs parameter. During the storm recovery it is found that the decay time varies from approximate to 4 hours at the storm maximum to approximate to 20 hours midway in the recovery and then back to approximate to 10 hours. There appears to be nothing in the simultaneous solar wind data to explain this reversal in the evolution of the decay time. It is shown that the strength of coupling to the solar wind VBs parameter varies considerably. The coupling strength peaks strongly at the time of the storm maximum and decays to low values during the storm recovery. Solar wind VBs input during the storm recovery does not affect the recovery rate. Using this storm data, empirical nonlinear analogues are constructed, These analogues are tested out of sample for their prediction effectiveness. Comparisons with the predictions of the model due to Burton et al. are given. It is shown that these analogues are promising prediction tools, but their lack of sensitivity to solar wind dynamic pressure must be corrected. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Space Res Associates, Lanham, MD 20706 USA. Univ Colorado, Atmospher & Space Phys Lab, Boulder, CO 80309 USA. RP Klimas, AJ (reprint author), NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. NR 10 TC 48 Z9 49 U1 0 U2 2 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA J9 J GEOPHYS RES-SPACE JI J. Geophys. Res-Space Phys. PD SEP 1 PY 1998 VL 103 IS A9 BP 20435 EP 20447 DI 10.1029/98JA01559 PG 13 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 118BG UT WOS:000075817300009 ER PT J AU Launius, RD AF Launius, RD TI Area 51: The dreamland chronicles. SO JOURNAL OF GOVERNMENT INFORMATION LA English DT Book Review C1 NASA, Hist Off, Code ZH, Washington, DC 20546 USA. RP Launius, RD (reprint author), NASA, Hist Off, Code ZH, Washington, DC 20546 USA. NR 1 TC 0 Z9 0 U1 0 U2 0 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 1352-0237 J9 J GOV INFORM JI J. Gov. Inf. PD SEP-OCT PY 1998 VL 25 IS 5 BP 511 EP 512 PG 2 WC Information Science & Library Science SC Information Science & Library Science GA 134UD UT WOS:000076761200008 ER PT J AU Lim, KB Lake, RC Heeg, J AF Lim, KB Lake, RC Heeg, J TI Effective selection of piezoceramic actuators for an experimental flexible wing SO JOURNAL OF GUIDANCE CONTROL AND DYNAMICS LA English DT Article; Proceedings Paper CT AIAA Guidance, Navigation, and Control Conference and Exhibit CY JUL 29-31, 1996 CL SAN DIEGO, CALIFORNIA SP AIAA ID SENSOR PLACEMENT; MODEL-REDUCTION AB The effectiveness of individual or subsets of piezoceramic actuators are investigated in terms of their contributions to the joint controllability and observability for a fixed set of sensors. The method used is based on the decomposition of the Hankel singular values in terms of individual sensor and actuator combinations for flexible structures, The degree of participation of the individual structural modes in the butter control problem is used to weigh the actuator selection metric in the feedback loop. Simulation results based on H-2 and H-infinity control law designs indicate that closed loop performance can be improved significantly and the performance improvement is independent of the particular type of control law. C1 NASA, Langley Res Ctr, Guidance & Control Branch, Flight Dynam & Control Div, Hampton, VA 23681 USA. NASA, Langley Res Ctr, Aeroelast Branch, Struct Div, Hampton, VA 23681 USA. RP Lim, KB (reprint author), NASA, Langley Res Ctr, Guidance & Control Branch, Flight Dynam & Control Div, Hampton, VA 23681 USA. EM k.b.lim@larc.nasa.gov; r.c.lake@larc.nasa.gov; j.heeg@larc.nasa.gov NR 13 TC 6 Z9 6 U1 0 U2 0 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0731-5090 J9 J GUID CONTROL DYNAM JI J. Guid. Control Dyn. PD SEP-OCT PY 1998 VL 21 IS 5 BP 704 EP 709 DI 10.2514/2.4315 PG 6 WC Engineering, Aerospace; Instruments & Instrumentation SC Engineering; Instruments & Instrumentation GA 114PM UT WOS:000075617900005 ER PT J AU Devasia, S Meyer, G AF Devasia, S Meyer, G TI Recovery guidance satisfying input and state constraints: Rate saturating actuator example SO JOURNAL OF GUIDANCE CONTROL AND DYNAMICS LA English DT Article ID LINEAR-SYSTEMS; OUTPUT TRACKING; FLIGHT CONTROL; DESIGN AB When a fixed regulator is used to stabilize a desired state trajectory (guidance law), large initial tracking errors can lead to input saturation, which can result in performance deterioration. A method to modify the guidance law for recovering state-trajectory tracking (without violating input and state constraints) is presented. Although it may be feasible to find such a satisfactory recovery guidance maneuver for a given initial tracking error, online development of recovery guidance maneuvers may not be computationally tractable. A technique Is developed to use precomputed recovery guidance maneuvers (precomputed for a finite set of initial tracking errors) to generate recovery guidance maneuvers for other initial errors. The technique is applied to an illustrative example with a rate-limited servoactuator, and simulation results are presented. C1 NASA, Ames Res Ctr, Human & Syst Technol Branch, Moffett Field, CA 94035 USA. RP Devasia, S (reprint author), Univ Utah, Dept Mech Engn, 50 S,Campus Ctr Dr,Room 2202, Salt Lake City, UT 84106 USA. EM santosh@me.utah.edu; gmeyer@mail.arc.nasa.gov NR 23 TC 2 Z9 2 U1 0 U2 1 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0731-5090 J9 J GUID CONTROL DYNAM JI J. Guid. Control Dyn. PD SEP-OCT PY 1998 VL 21 IS 5 BP 733 EP 741 DI 10.2514/2.4319 PG 9 WC Engineering, Aerospace; Instruments & Instrumentation SC Engineering; Instruments & Instrumentation GA 114PM UT WOS:000075617900009 ER PT J AU Phan, MQ Juang, JN AF Phan, MQ Juang, JN TI Predictive controllers for feedback stabilization SO JOURNAL OF GUIDANCE CONTROL AND DYNAMICS LA English DT Article ID SYSTEM-IDENTIFICATION; OBSERVER AB Predictive control is a strategy where the current control action is based on a prediction of the system response at some number of time steps into the future. This approach allows one to work directly with an input-output model of the system, in contrast to a state-space based approach where the state variable is involved explicitly in the controller design and implementation. A connection is provided between the two design approaches by showing that simple predictive controllers can be thought of as generalizations of the observer-based deadbeat (minimum-time) controllers in discrete time state-space theory. The excessive and, hence, impractical control effort demanded by the standard deadbeat controllers is removed in this predictive extension. By varying the prediction horizon, controllers that range from those exhibiting the extreme deadbeat behavior to those approximating the minimum-energy solution are subsumed in a common framework. Although these predictive controllers can be understood as observer based, no explicit observer is actually involved in the implementation. Instead, these controllers can be derived directly from the coefficients of an identified input-output model, which has been rec entry shown to subsume an implicit observer. It is also shown that the two primary parameters of a predictive controller can be understood in the state-space framework as those governing the speed of an implicit observer and the speed of an implicit state-feedback controller. This understanding allows one to select optimal choices for these parameters in practice. C1 Princeton Univ, Dept Mech & Aerosp Engn, Princeton, NJ 08544 USA. NASA, Langley Res Ctr, Struct Dynam Branch, Hampton, VA 23681 USA. RP Phan, MQ (reprint author), Princeton Univ, Dept Mech & Aerosp Engn, Princeton, NJ 08544 USA. NR 20 TC 13 Z9 13 U1 0 U2 0 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0731-5090 J9 J GUID CONTROL DYNAM JI J. Guid. Control Dyn. PD SEP-OCT PY 1998 VL 21 IS 5 BP 747 EP 753 DI 10.2514/2.4301 PG 7 WC Engineering, Aerospace; Instruments & Instrumentation SC Engineering; Instruments & Instrumentation GA 114PM UT WOS:000075617900011 ER PT J AU Garrison, JL Axelrad, P Kasdin, NJ AF Garrison, JL Axelrad, P Kasdin, NJ TI Ill-conditioned covariance matrices in the first-order two-step estimator SO JOURNAL OF GUIDANCE CONTROL AND DYNAMICS LA English DT Article; Proceedings Paper CT AAS/AIAA Space Flight Mechanics Conference CY FEB 10-12, 1997 CL HUNTSVILLE, ALABAMA SP Amer Astronaut Soc, Amer Inst Aeronaut & Astronaut AB The first-order two-step estimator is found to occasionally produce first-step covariance matrices with very low, sometimes negative, eigenvalues. These low eigenvalues can cause large errors or meaningless estimates. A single matrix is found, which is shown to have a rank equal to the difference between the number of first and second-step states. Furthermore, it is demonstrated that the basis of the column space of this matrix remains fixed once the large initial state error has decreased. A test matrix containing the (constant) basis of this column space and the partial derivative matrix relating first and second step states is derived. This matrix numerically drops rank at the same locations that the first-step covariance does. A simple example problem involving dynamics described by two states and a range measurement illustrates the cause of this anomaly and application of the aforementioned numerical test. Suggested modifications to the filter that can mitigate the numerical problems caused by this anomaly are given. C1 NASA, Langley Res Ctr, Spacecraft & Sensors Branch, Hampton, VA 23681 USA. Univ Colorado, Dept Aerosp Engn Sci, Boulder, CO 80309 USA. Stanford Univ, Grav Probe B Relat Mission, WW Hansen Expt Phys Lab, Stanford, CA 94305 USA. RP Garrison, JL (reprint author), NASA, Langley Res Ctr, Spacecraft & Sensors Branch, MS 328, Hampton, VA 23681 USA. NR 5 TC 3 Z9 3 U1 0 U2 0 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0731-5090 J9 J GUID CONTROL DYNAM JI J. Guid. Control Dyn. PD SEP-OCT PY 1998 VL 21 IS 5 BP 754 EP 760 DI 10.2514/2.4302 PG 7 WC Engineering, Aerospace; Instruments & Instrumentation SC Engineering; Instruments & Instrumentation GA 114PM UT WOS:000075617900012 ER PT J AU Bergman, L Morookian, J Yeh, C AF Bergman, L Morookian, J Yeh, C TI An all-optical long-distance multi-Gbytes/s bit-parallel WDM single-fiber link SO JOURNAL OF LIGHTWAVE TECHNOLOGY LA English DT Article DE optical fiber communication; optical propagation in nonlinear media; optical pulses; optical solitons; optical waveguides; single-mode fiber; wavelength division multiplexing AB An all-optical long-distance (>30 km) bit-parallel wavelength division multiplexed (WDM) single-fiber link with 12 bit-parallel channels having 1 Gbyte/s capacity has been designed. That system functionally resembles an optical fiber ribbon cable, except that all the bits pass on one fiber-optic waveguide. This single-fiber bit parallel wavelength link can be used to extend the (speed x distance) product of emerging cluster computer networks, such as, the MyriNet, SCI, Hippi-6400, ShuffleNet, etc. Here, the detailed design of this link using the commercially available Coming DS (dispersion-shifted) fiber is given, To demonstrate the viability of this link, two WDM channels at wavelengths 1530 and 1545 nm carrying 1 ns pulses on each channel were sent through a single 25.2-km long Coming DS fiber. The walkoff was 200 ps, well within the allowable setup and hold time for the standard ECL logic which is 350 ps for a bit period of 1 ns, This result implies that 30 bit-parallel beams spaced 1 nm apart between 1530-1560 nm, each carrying 1 Gbits/s signal, can be sent through a 25.2-km Coming DS fiber carrying information at a 30 Gb/s rate. C1 CALTECH, Jet Prop Lab, Ctr Space Microelect Technol, Pasadena, CA 91109 USA. RP Bergman, L (reprint author), CALTECH, Jet Prop Lab, Ctr Space Microelect Technol, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 15 TC 17 Z9 17 U1 0 U2 0 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 0733-8724 J9 J LIGHTWAVE TECHNOL JI J. Lightwave Technol. PD SEP PY 1998 VL 16 IS 9 BP 1577 EP 1582 DI 10.1109/50.712239 PG 6 WC Engineering, Electrical & Electronic; Optics; Telecommunications SC Engineering; Optics; Telecommunications GA 117GG UT WOS:000075772700005 ER PT J AU Menon, M Srivastava, D AF Menon, M Srivastava, D TI Carbon nanotube based molecular electronic devices SO JOURNAL OF MATERIALS RESEARCH LA English DT Article ID NEGATIVE CURVATURE; TUBULES; GROWTH; MICROTUBULES; CLUSTERS AB Complex three-point junctions of single-walled carbon nanotubes are proposed as building blocks of nanoscale electronic devices. Both T- and Y-junctions, made up of tubes with differing diameters and chiralities, are studied as prototypes. All the proposed complex junctions have been found to be local minima of the total energy on relaxation with a generalized tight-binding molecular dynamics scheme. C1 Univ Kentucky, Dept Phys & Astron, Lexington, KY 40506 USA. NASA, Ames Res Ctr, IT Modeling & Simulat Grp, MRJ, Moffett Field, CA 94035 USA. RP Menon, M (reprint author), Univ Kentucky, Dept Phys & Astron, Lexington, KY 40506 USA. NR 23 TC 54 Z9 54 U1 0 U2 2 PU MATERIALS RESEARCH SOCIETY PI WARRENDALE PA 506 KEYSTONE DR, WARRENDALE, PA 15086 USA SN 0884-2914 J9 J MATER RES JI J. Mater. Res. PD SEP PY 1998 VL 13 IS 9 BP 2357 EP 2362 DI 10.1557/JMR.1998.0328 PG 6 WC Materials Science, Multidisciplinary SC Materials Science GA 114RA UT WOS:000075621600002 ER PT J AU Bansal, NP AF Bansal, NP TI Effects of HF treatments on tensile strength of Hi-Nicalon fibres SO JOURNAL OF MATERIALS SCIENCE LA English DT Article ID WEIBULL MODULUS AB Tensile strengths of as-received Hi-Nicalon fibres and those having a dual BN-SiC surface coating, deposited by chemical vapour deposition, have been measured at room temperature. These fibres were also treated with HF for 24 h followed by tensile strength measurements. Strengths of uncoated and BN-SiC coated Hi-Nicalon fibres extracted from celsian matrix composites, by dissolving away the matrix in HF for 24 h, were also determined. The average tensile strength of uncoated Hi-Nicalon was 3.19+/-0.73 GPa with a Weibull modulus of 5.41. The Hi-Nicalon-BN-SiC fibres showed an average strength of 3.04+/-0.53 GPa and Weibull modulus of 6.66. After HF treatment, the average strengths of the uncoated and BN-SiC coated Hi-Nicalon fibres were 2.69+/-0.67 and 2.80+/-0.53 GPa and the Weibull moduli were 4.93 and 5.96, respectively. The BN-SiC coated fibres extracted from the celsian matrix composite exhibited a strength of 2.38+/-0.40 GPa and a Weibull modulus of 7.15. The strength of the uncoated Hi-Nicalon fibres in the composite was so severely degraded that they disintegrated into small fragments during extraction with HF. The uncoated fibres probably undergo mechanical surface damage during hot pressing of the composites. Also, the BN layer on the coated fibres acts as a compliant layer, which protects the fibres from mechanical damage during composite processing. The elemental composition and thickness of the fibre coatings were determined using scanning Auger analysis. Microstructural analyses of the fibres and the coatings were done by scanning electron microscopy and transmission electron microscopy. Stengths of fibres calculated using ave rage a nd measured fibre diameters we re in good agreement. Th us, the strengths of fibres can be evaluated using an average fibre diameter instead of the measured diameter of each filament. (C) 1998 Kluwer Academic Publishers. C1 NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. RP Bansal, NP (reprint author), NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. NR 7 TC 3 Z9 3 U1 0 U2 3 PU KLUWER ACADEMIC PUBL PI DORDRECHT PA SPUIBOULEVARD 50, PO BOX 17, 3300 AA DORDRECHT, NETHERLANDS SN 0022-2461 J9 J MATER SCI JI J. Mater. Sci. PD SEP 1 PY 1998 VL 33 IS 17 BP 4287 EP 4295 DI 10.1023/A:1004431420412 PG 9 WC Materials Science, Multidisciplinary SC Materials Science GA 183GQ UT WOS:000079546200002 ER PT J AU Chackerian, C Brown, LR Lacome, N Tarrago, G AF Chackerian, C Brown, LR Lacome, N Tarrago, G TI Methyl chloride nu(5) region lineshape parameters and rotational constants for the nu(2), nu(5), and 2 nu(3) vibrational bands SO JOURNAL OF MOLECULAR SPECTROSCOPY LA English DT Article ID SELF-BROADENING COEFFICIENTS; DIODE-LASER MEASUREMENTS; LINE STRENGTHS; INFRARED INTENSITIES; ATMOSPHERIC INTEREST; FUNDAMENTAL-BAND; DOUBLE-RESONANCE; NU(3) BAND; (CH3CL)-CL-35; TEMPERATURE AB Fourier spectra of methyl chloride have been obtained at ambient laboratory temperature under self-broadening conditions. Five thousand two hundred and sixty rovibrational transitions of the (nu(2), nu(5), 2 nu(3))-vibrational-band tried have been assigned, and new ground and excited state rotational constants for (CH3Cl)-Cl-35 and (CH3Cl)-Cl-27 have been determined. The nu(5) and nu(2) vibrational-band intensities are determined to be, respectively, 42(1.2) and 31.7(0.9) cm(-2) atm(-1). Self-broadening coefficients of individual rovibrational lines are determined for the nu(5) band of (CH3Cl)-Cl-35 and (CH3Cl)-Cl-37 at 296 K. The self-broadening coefficients peak broadly close to the maximum in the Boltzmann rotational population; no specific trends of the broadening coefficients are observed with the rotational quantum number K. With the exception of the (R)Q(J, 0) branch, the 1260-1650 cm(-1) spectral region can be well modeled by the superposition of overlapping Voigt line profiles. To adequately model the densely packed (R)Q(J, 0) branch, however, we included collisional line mixing with A(+) to A(-) in addition to A(-) to A(-) and A(+) to A(+) \Delta J\ greater than or equal to 1, Delta K = 0 collisional transitions allowed. (C) 1998 Academic Press. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ Paris 06, URA CNRS 508, Lab Spectrochim Mol, F-75252 Paris, France. CNRS, LADIR, CNRS UPR A1580, F-94320 Thiais, France. Univ Paris 11, LPMA, F-91405 Orsay, France. RP Chackerian, C (reprint author), NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RI Lacome, Nelly/A-7043-2008 NR 34 TC 33 Z9 33 U1 0 U2 2 PU ACADEMIC PRESS INC PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA SN 0022-2852 J9 J MOL SPECTROSC JI J. Mol. Spectrosc. PD SEP PY 1998 VL 191 IS 1 BP 148 EP 157 DI 10.1006/jmsp.1998.7591 PG 10 WC Physics, Atomic, Molecular & Chemical; Spectroscopy SC Physics; Spectroscopy GA 116WR UT WOS:000075748500018 ER PT J AU Wolfenstine, J Sakamoto, J Huang, CK AF Wolfenstine, J Sakamoto, J Huang, CK TI Tin oxide tin composite anodes for use in Li-ion batteries SO JOURNAL OF POWER SOURCES LA English DT Letter DE tin oxides; composite; irreversible loss; Li-ion batteries; phase diagram ID LITHIUM; ELECTRODES; ALLOYS C1 USA, Res Lab, Geo Ctr, AMSRL SE C Shady Grove, Adelphi, MD 20783 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Wolfenstine, J (reprint author), USA, Res Lab, Geo Ctr, AMSRL SE C Shady Grove, 2800 Powder Mill Rd, Adelphi, MD 20783 USA. NR 12 TC 11 Z9 11 U1 3 U2 8 PU ELSEVIER SCIENCE SA PI LAUSANNE PA PO BOX 564, 1001 LAUSANNE, SWITZERLAND SN 0378-7753 J9 J POWER SOURCES JI J. Power Sources PD SEP 1 PY 1998 VL 75 IS 1 BP 181 EP 182 PG 2 WC Chemistry, Physical; Electrochemistry; Energy & Fuels; Materials Science, Multidisciplinary SC Chemistry; Electrochemistry; Energy & Fuels; Materials Science GA 121MX UT WOS:000076018600025 ER PT J AU Palaszewski, B Ianovski, LS Carrick, P AF Palaszewski, B Ianovski, LS Carrick, P TI Propellant technologies: Far-reaching benefits for aeronautical and space-vehicle propulsion SO JOURNAL OF PROPULSION AND POWER LA English DT Article; Proceedings Paper CT 3rd International Symposium on Space Propulsion CY AUG 11-13, 1997 CL BEIJING, PEOPLES R CHINA ID LAUNCH VEHICLE; SINGLE-STAGE; METALLIZED PROPELLANTS; SECONDARY ATOMIZATION; PERFORMANCE; SYSTEM; HYDROGEN; DESIGN; FUEL; COMBUSTION AB Rocket propellant and propulsion technology improvements can be used to reduce the development time and operational costs of new space-vehicle programs. Advanced propellant technologies can make the space vehicles safer, more operable, and better performing. Five technology areas are described: monopropellants, alternative hydrocarbons, gelled hydrogen, metalized gelled propellants, and high-energy density materials. The benefits of these propellants for future vehicles are outlined using mission study results and the technologies are briefly discussed. C1 NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. Cent Inst Avian Motors, Dept Adv Aviat Engines & Appl Chem, Moscow 111250, Russia. USAF, Res Lab, Propellants Branch, Edwards, CA 93524 USA. RP Palaszewski, B (reprint author), NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. NR 80 TC 25 Z9 27 U1 0 U2 5 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0748-4658 J9 J PROPUL POWER JI J. Propul. Power PD SEP-OCT PY 1998 VL 14 IS 5 BP 641 EP 648 DI 10.2514/2.5356 PG 8 WC Engineering, Aerospace SC Engineering GA 146XB UT WOS:000077457200009 ER PT J AU Fisher, MF AF Fisher, MF TI Propellant management in booster and upper-stage propulsion systems SO JOURNAL OF PROPULSION AND POWER LA English DT Article AB A summary review of some of the technical issues that surround the design of the propulsion systems' for booster and upper stage systems is presented. The work focuses on propellant geyser, slosh, and orientation. A brief description is given with graphics that help the reader to understand the physics of the situation. The most common solutions to these problems are given with their respective advantages and disadvantages. C1 NASA, George C Marshall Space Flight Ctr, Propuls Lab, Huntsville, AL 35812 USA. RP Fisher, MF (reprint author), NASA, George C Marshall Space Flight Ctr, Propuls Lab, Bldg 4666, Huntsville, AL 35812 USA. NR 14 TC 0 Z9 0 U1 0 U2 0 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0748-4658 J9 J PROPUL POWER JI J. Propul. Power PD SEP-OCT PY 1998 VL 14 IS 5 BP 649 EP 656 DI 10.2514/2.5326 PG 8 WC Engineering, Aerospace SC Engineering GA 146XB UT WOS:000077457200010 ER PT J AU McCarty, JP Lyles, GM AF McCarty, JP Lyles, GM TI Quality issues in propulsion SO JOURNAL OF PROPULSION AND POWER LA English DT Article AB In this paper, a high-quality propulsion system is one that has high reliability. Thus, quality is a high probability within tolerance performance or operation. Because failures are out of tolerance performance, the probability that failures will occur is the difference between high- and low-quality systems. Failures can be described at three levels: 1) the system failure (the detectable end of a failure), 2) the failure mode (the failure process), and 3) the failure cause (the start). Failure causes can be evaluated and classified by type. The results of typing night history failures show that most failures are in unrecognized modes and result from human error or noise, that is, failures are when engineers learn how things really work Although the study is based on U.S. launch vehicles, a sampling of failures from other countries indicates that the finding has broad application. The parameters of the design of a propulsion system are not single valued, but have dispersions associated with the manufacturing of parts. Many tests are needed to find failures, if the dispersions are large relative to tolerances, that could contribute to the large number of failures in unrecognized modes. C1 McCarty Grp Inc, Huntsville, AL 35806 USA. NASA, George C Marshall Space Flight Ctr, Adv Space Transportat Off, Huntsville, AL 35812 USA. RP McCarty, JP (reprint author), McCarty Grp Inc, Huntsville, AL 35806 USA. NR 4 TC 0 Z9 0 U1 0 U2 0 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0748-4658 J9 J PROPUL POWER JI J. Propul. Power PD SEP-OCT PY 1998 VL 14 IS 5 BP 664 EP 668 DI 10.2514/2.5328 PG 5 WC Engineering, Aerospace SC Engineering GA 146XB UT WOS:000077457200012 ER PT J AU Hurlbert, E Applewhite, J Nguyen, T Reed, B Zhang, BJ Wang, Y AF Hurlbert, E Applewhite, J Nguyen, T Reed, B Zhang, BJ Wang, Y TI Nontoxic orbital maneuvering and reaction control systems for reusable spacecraft SO JOURNAL OF PROPULSION AND POWER LA English DT Article AB Toxic propellants have a high ground operations cost because of the potential hazards that require extensive safety precautions, particularly for reusable spacecraft. Nontoxic propellants for orbital maneuvering and reaction control systems have received periodic attention since the late 1960s as new reusable vehicles and upgrades to existing vehicles are proposed. This paper discusses the spacecraft requirements that drive propellant selections, the viable candidates for nontoxic propellants, and the system concepts and technologies required. Options for nontoxic propellants are also discussed, which are categorized as monopropellants, storable bipropellants, and cryogenic oxygen-based bipropellants. Monopropellants provide inherently simple systems and are most suited to low total impulse systems. Hydrogen peroxide and kerosene is a promising storable bipropellant in terms of its density, specific impulse, and low toxicity for long-duration spacecraft on-orbit propulsion systems. This combination can be made hypergolic, which renders it a very effective replacement for currently used storable propellants. The hypergolic characteristics of kerosene with additives and high-concentration hydrogen peroxide are presented in detail. Higher-performance liquid oxygen and alcohol or hydrocarbon fuels are advantageous for reusable propulsion systems that emphasize fluid commonality with other spacecraft systems and for human exploration missions where in-situ propellant production is foreseen. The prospects for further research work on all of these propellants are also discussed. C1 NASA, Lyndon B Johnson Space Ctr, Div Energy Syst, Houston, TX 77058 USA. NASA, Lewis Res Ctr, Div Energy Syst, Cleveland, OH 44135 USA. Shanghai Acad Spaceflight Technol, Onboard Propuls Branch, Shanghai 200233, Peoples R China. Shanghai Acad Spaceflight Technol, Res Inst 801, Shanghai 200233, Peoples R China. RP Hurlbert, E (reprint author), NASA, Lyndon B Johnson Space Ctr, Div Energy Syst, Houston, TX 77058 USA. NR 25 TC 15 Z9 15 U1 2 U2 6 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0748-4658 J9 J PROPUL POWER JI J. Propul. Power PD SEP-OCT PY 1998 VL 14 IS 5 BP 676 EP 687 DI 10.2514/2.5330 PG 12 WC Engineering, Aerospace SC Engineering GA 146XB UT WOS:000077457200014 ER PT J AU Brophy, JR Noca, M AF Brophy, JR Noca, M TI Electric propulsion for solar system exploration SO JOURNAL OF PROPULSION AND POWER LA English DT Article AB The use of ion propulsion for deep-space missions will become a reality in 1998 with the night of the ion-propelled, New Millennium Deep Space 1 (DS1) spacecraft, The anticipation of this event is stimulating the call for improved ion propulsion technologies, a trend that is expected to continue. This paper describes the evaluation of possible advanced solar electric propulsion technologies and their potential benefits to projected near-term and midterm solar system exploration missions. The advanced technologies include high-performance derivatives of the DS1 ion propulsion technology, sealed-down DS1 systems, and direct-drive Hall-effect thruster systems. The results of this study indicate that significant near-term benefits can be obtained by the development of improved versions of the DS1 ion propulsion system (IPSs) components. In addition, if the current trend to smaller planetary spacecraft continues, then missions flying these smaller future spacecraft will benefit substantially from the development of scaled-down IPSs that incorporate advanced technologies in the ion engines and the propellant feed systems. The performance of the direct-drive Hall thruster systems is potentially superior to that of all other midterm options, but this technology has the highest development risk. Significantly reduced trip times to small bodies and the outer planets may be possible if technology programs work to retire these risks. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Brophy, JR (reprint author), Boeing Co, 6633 Canoga Ave, Canoga Park, CA 91309 USA. NR 18 TC 30 Z9 30 U1 0 U2 1 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0748-4658 J9 J PROPUL POWER JI J. Propul. Power PD SEP-OCT PY 1998 VL 14 IS 5 BP 700 EP 707 DI 10.2514/2.5332 PG 8 WC Engineering, Aerospace SC Engineering GA 146XB UT WOS:000077457200016 ER PT J AU Wilbur, PJ Rawlin, VK Beattie, JR AF Wilbur, PJ Rawlin, VK Beattie, JR TI Ion thruster development trends and status in the United States SO JOURNAL OF PROPULSION AND POWER LA English DT Article AB The current interest in ion thrusters for near-Earth and deep-space missions has occurred because of long-term development efforts yielding an understanding of the physical phenomena involved in thruster operation and hardware that is suited to a wide range of missions. Features of state-of-the-art thrusters are described in terms of the various physical processes that occur within them. Tradeoffs that must be considered to arrive at thruster designs suited to commercialization are discussed. C1 Colorado State Univ, Dept Mech Engn, Ft Collins, CO 80523 USA. NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. Hughes Space & Commun Co, Plasma Phys Dev & Technol, Torrance, CA 90505 USA. RP Wilbur, PJ (reprint author), Colorado State Univ, Dept Mech Engn, Ft Collins, CO 80523 USA. NR 53 TC 25 Z9 26 U1 1 U2 5 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0748-4658 J9 J PROPUL POWER JI J. Propul. Power PD SEP-OCT PY 1998 VL 14 IS 5 BP 708 EP 715 DI 10.2514/2.5333 PG 8 WC Engineering, Aerospace SC Engineering GA 146XB UT WOS:000077457200017 ER PT J AU Mishchenko, MI Travis, LD AF Mishchenko, MI Travis, LD TI Capabilities and limitations of a current FORTRAN implementation of the T-matrix method for randomly oriented, rotationally symmetric scatterers SO JOURNAL OF QUANTITATIVE SPECTROSCOPY & RADIATIVE TRANSFER LA English DT Article; Proceedings Paper CT 2nd International Workshop on Light Scattering by Non-spherical Particles CY JUN 09-11, 1997 CL HELSINKI, FINLAND ID DISCRETE-DIPOLE APPROXIMATION; LIGHT-SCATTERING; NONSPHERICAL PARTICLES; POLARIZED-LIGHT; COMPUTATIONS AB We describe in detail a software implementation of a current version of the T-matrix method for computing light scattering by polydisperse, randomly oriented, rotationally symmetric particles. The FORTRAN T-matrix codes are publicly available on the World Wide Web at http://www.giss.nasa.gov/similar to crmin. We give all necessary formulas, describe input and output parameters, discuss numerical aspects of T-matrix computations, demonstrate the capabilities and limitations of the codes, and discuss the performance of the codes in comparison with other available numerical approaches. Published by Elsevier Science Ltd. C1 NASA, Goddard Inst Space Studies, New York, NY 10025 USA. RP NASA, Goddard Inst Space Studies, 2880 Broadway, New York, NY 10025 USA. RI Mishchenko, Michael/D-4426-2012 NR 39 TC 446 Z9 452 U1 3 U2 19 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0022-4073 EI 1879-1352 J9 J QUANT SPECTROSC RA JI J. Quant. Spectrosc. Radiat. Transf. PD SEP PY 1998 VL 60 IS 3 BP 309 EP 324 DI 10.1016/S0022-4073(98)00008-9 PG 16 WC Optics; Spectroscopy SC Optics; Spectroscopy GA 112WW UT WOS:000075518500003 ER PT J AU Windhorst, R Ardema, M Bowles, J AF Windhorst, R Ardema, M Bowles, J TI Minimum heating entry trajectories for reusable launch vehicles SO JOURNAL OF SPACECRAFT AND ROCKETS LA English DT Article ID OPERATION AB A finite control volume heat transfer analysis is coupled to a flight-path optimization and integration algorithm for the purpose of calculating conductive heat rates and transient temperature effects within the thermal protection system of a reusable launch vehicle. Results are obtained for three different thermal protection system concepts: tile, blanket, and metallic. The optimization algorithm is based on the energy state approximation and is used to generate optimal entry trajectories minimizing the following three criteria: 1) the thermal energy absorbed at the vehicle surface, 2) the heat load applied to the vehicle, and 3) the thermal energy absorbed by the internal structure. Results indicate that all three trajectories produce comparable peak internal structure temperatures for a given thermal protection system, with the trajectory minimizing the heat load applied to the vehicle producing the lowest peak temperature. However, if the maximum stagnation temperature constraint at the nose of the vehicle is increased from 3000 to 4000 degrees F, the trajectory minimizing the thermal energy absorbed by the internal structure becomes superior. Further, the trajectory with the 4000 degrees F limit gives a peak internal structure temperature 25 degrees F less than the one with the 3000 degrees F limit. C1 Santa Clara Univ, Dept Mech Engn, Santa Clara, CA 95053 USA. NASA, Ames Res Ctr, Syst Anal Branch, Moffett Field, CA 94035 USA. RP Windhorst, R (reprint author), Santa Clara Univ, Dept Mech Engn, Santa Clara, CA 95053 USA. NR 8 TC 7 Z9 8 U1 0 U2 1 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0022-4650 J9 J SPACECRAFT ROCKETS JI J. Spacecr. Rockets PD SEP-OCT PY 1998 VL 35 IS 5 BP 672 EP 682 DI 10.2514/2.3384 PG 11 WC Engineering, Aerospace SC Engineering GA 129WT UT WOS:000076487600013 ER PT J AU Seale, MD Smith, BT Prosser, WH Zalameda, JN AF Seale, MD Smith, BT Prosser, WH Zalameda, JN TI Lamb wave assessment of fiber volume fraction in composites SO JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA LA English DT Article ID MECHANICAL-PROPERTIES AB Among the various techniques available, ultrasonic Lamb waves offer a convenient method of examining composite materials. Since the Lamb wave velocity depends on the elastic properties of a material, an effective tool exists to evaluate composites by measuring the velocity of these waves. Lamb waves can propagate over long distances and are sensitive to the desired in-plane elastic properties of the material. This paper discusses a study in which Lamb waves were used to examine fiber volume fraction variations of approximately 0.40-0.70 in composites. The Lamb wave measurements were compared to fiber volume fractions obtained from acid digestion tests. Additionally, a model to predict the fiber volume fraction from Lamb wave velocity values was evaluated. (C) 1998 Acoustical Society of America. [S0001-4966(98)03809-0] C1 NASA, Langley Res Ctr, Hampton, VA 23681 USA. Coll William & Mary, Dept Phys, Williamsburg, VA 23187 USA. Norfolk Acad, Norfolk, VA 23502 USA. RP Seale, MD (reprint author), NASA, Langley Res Ctr, Mail Stop 231, Hampton, VA 23681 USA. NR 20 TC 12 Z9 12 U1 0 U2 1 PU AMER INST PHYSICS PI WOODBURY PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 USA SN 0001-4966 J9 J ACOUST SOC AM JI J. Acoust. Soc. Am. PD SEP PY 1998 VL 104 IS 3 BP 1399 EP 1403 DI 10.1121/1.424349 PN 1 PG 5 WC Acoustics; Audiology & Speech-Language Pathology SC Acoustics; Audiology & Speech-Language Pathology GA 118WW UT WOS:000075864800028 PM 9745734 ER PT J AU Macke, A Francis, PN AF Macke, A Francis, PN TI The role of ice particle shapes and size distributions in the single scattering properties of cirrus clouds SO JOURNAL OF THE ATMOSPHERIC SCIENCES LA English DT Article ID SOLAR RADIATIVE-TRANSFER; LIGHT-SCATTERING; NONSPHERICAL PARTICLES; OPTICAL-PROPERTIES; CRYSTALS; FIRE; MATRIX; APPROXIMATION; EVOLUTION; CEPEX AB The roles of ice particle size distributions (SDs) and particle shapes in cirrus cloud solar radiative transfer are investigated by analyzing SDs obtained from optical array probe measurements (particle sizes larger than 20-40 mu m) during intensive field observations of the International Cirrus Experiment, the: European Cloud and Radiation Experiment, the First ISCCP Regional Experiment, and the Central Equatorial Pacific Experiment. It is found that the cloud volume extinction coefficient is more strongly correlated with the total number density than with the effective particle size. Distribution-averaged mean single scattering properties are calculated for hexagonal columns, hexagonal plates, and polycrystals at a nonabsorbing (0.5 mu m), moderately absorbing (1.6 mu m), and strongly absorbing (3.0 mu m) wavelength. At 0.5 mu m (1.6 mu m) (3.0 mu m), the spread in the resulting mean asymmetry parameters due to different SDs is smaller than (comparable to) (smaller than) the difference caused by applying different particle shapes to these distributions. From a broadband solar radiative transfer point of view it appears more important to use the correct particle shapes than to average over the correct size distributions. C1 Columbia Univ, Dept Appl Phys, New York, NY 10027 USA. Meteorol Off, Meteorol Res Flight, Farnborough, Hants, England. Natl Ctr Atmospher Res, Boulder, CO 80307 USA. NASA, Bay Area Environm Res Inst, Moffett Field, CA USA. RP Macke, A (reprint author), Univ Kiel, Inst Meereskunde, Dusternbrooker Weg 20, D-24105 Kiel, Germany. RI Francis, Peter/H-9352-2013; OI Francis, Peter/0000-0002-5869-803X; McFarquhar, Greg/0000-0003-0950-0135 NR 41 TC 53 Z9 53 U1 0 U2 3 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 USA SN 0022-4928 J9 J ATMOS SCI JI J. Atmos. Sci. PD SEP 1 PY 1998 VL 55 IS 17 BP 2874 EP 2883 DI 10.1175/1520-0469(1998)055<2874:TROIPS>2.0.CO;2 PG 10 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 115MN UT WOS:000075669100010 ER PT J AU Hissam, DA Zimmerman, F Davis, WM Krotz, P Liaw, YK Oelgoetz, P Sanders, H AF Hissam, DA Zimmerman, F Davis, WM Krotz, P Liaw, YK Oelgoetz, P Sanders, H TI Removable fillers for VPS fabrication of closed channels SO JOURNAL OF THERMAL SPRAY TECHNOLOGY LA English DT News Item C1 George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. Rockwell Int Corp, Dallas, TX USA. RP Hissam, DA (reprint author), George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU ASM INTERNATIONAL PI MATERIALS PARK PA SUBSCRIPTIONS SPECIALIST CUSTOMER SERVICE, MATERIALS PARK, OH 44073-0002 USA SN 1059-9630 J9 J THERM SPRAY TECHN JI J. Therm. Spray Technol. PD SEP PY 1998 VL 7 IS 3 BP 307 EP 308 PG 2 WC Materials Science, Coatings & Films SC Materials Science GA 119WF UT WOS:000075920600007 ER PT J AU Dunham, RS AF Dunham, RS TI Improved nonlinear mathematical model of viscoelasticity SO JOURNAL OF THERMAL SPRAY TECHNOLOGY LA English DT News Item C1 NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. RP Dunham, RS (reprint author), NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU ASM INTERNATIONAL PI MATERIALS PARK PA SUBSCRIPTIONS SPECIALIST CUSTOMER SERVICE, MATERIALS PARK, OH 44073-0002 USA SN 1059-9630 J9 J THERM SPRAY TECHN JI J. Therm. Spray Technol. PD SEP PY 1998 VL 7 IS 3 BP 308 EP 309 PG 2 WC Materials Science, Coatings & Films SC Materials Science GA 119WF UT WOS:000075920600009 ER PT J AU Hause, T Librescu, L Johnson, TF AF Hause, T Librescu, L Johnson, TF TI Thermomechanical load-carrying capacity of sandwich flat panels SO JOURNAL OF THERMAL STRESSES LA English DT Article DE bucking bifurcation; postbuckling; sandwich panel; snap-through AB The study of the nonlinear response of sandwich flat panels exposed to thermomechanical loading systems is the topic of this article. The sandwich structure considered in this article consists of a thick core layer bonded by the face layers, which are assumed to be symmetrically located with respect to the midplane of the overall structure. The loads involved in this analysis consist of biaxial compressive edge loads, a lateral pressure, and a nonuniform temperature field. The effects of the unavoidable initial geometric imperfections and the character of tangential boundary conditions are incorporated, and their implications upon the structural response are explored. In short, the results of this study are intended to provide pertinent information on the thermomechanical load-carrying capacity of flat sandwich structures. C1 Virginia Polytech Inst & State Univ, Dept Engn Sci & Mech, Blacksburg, VA 24061 USA. NASA, Langley Res Ctr, Struct Div, Thermal Struct Branch, Hampton, VA 23665 USA. RP Librescu, L (reprint author), Virginia Polytech Inst & State Univ, Dept Engn Sci & Mech, Blacksburg, VA 24061 USA. EM librescu@vt.edu NR 10 TC 6 Z9 6 U1 0 U2 0 PU TAYLOR & FRANCIS LTD PI LONDON PA ONE GUNPOWDER SQUARE, LONDON EC4A 3DE, ENGLAND SN 0149-5739 J9 J THERM STRESSES JI J. Therm. Stresses PD SEP PY 1998 VL 21 IS 6 BP 627 EP 653 DI 10.1080/01495739808956166 PG 27 WC Thermodynamics; Mechanics SC Thermodynamics; Mechanics GA 123VL UT WOS:000076146100002 ER PT J AU Chamis, CC Gotsis, PK Mital, SK AF Chamis, CC Gotsis, PK Mital, SK TI Meso-mechanics and meso-structures: A matter of scale SO JOURNAL OF THERMOPLASTIC COMPOSITE MATERIALS LA English DT Article AB Meso-mechanics and meso-structures are described in terms of the scales at which they are observed and formulated. Select composite examples are presented to illustrate that meso-mechanics and/or meso-structures are meaningful only when they refer to a specific scale in a hierarchical scale observation/simulation. These examples include different types of composite unit cells, woven fabric unit cells, and progressive fracture as a composite enhanced infrastructure made from reinforced concrete. The results from the select examples indicate that meso-mechanics and meso-structures are elusive terms and depend mainly on the investigators' knowledge and available information. C1 NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. Univ Toledo, Toledo, OH 43606 USA. RP Chamis, CC (reprint author), NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. NR 10 TC 1 Z9 1 U1 1 U2 3 PU TECHNOMIC PUBL CO INC PI LANCASTER PA 851 NEW HOLLAND AVE, BOX 3535, LANCASTER, PA 17604 USA SN 0892-7057 J9 J THERMOPLAST COMPOS JI J. Thermoplast. Compos. Mater. PD SEP PY 1998 VL 11 IS 5 BP 478 EP 490 PG 13 WC Materials Science, Composites SC Materials Science GA 119GR UT WOS:000075888000007 ER PT J AU Herwitz, SR Slye, RE Turton, SM AF Herwitz, SR Slye, RE Turton, SM TI Redefining the ecological niche of a tropical rain forest canopy tree species using airborne imagery: long-term crown dynamics of Toona ciliata SO JOURNAL OF TROPICAL ECOLOGY LA English DT Article DE airborne imaging; canopy trees; crown growth; diameter growth; ecological niches; mortality; pioneer species; survivorship; Toona ciliata ID EMERGENT TREES; PIONEER TREE; GROWTH-RATES; COSTA-RICA; SEED SIZE; MORTALITY; DIVERSITY; RECRUITMENT; PATTERNS; LOWLAND AB Past controlled growth experiments indicate that the seedling and sapling responses of the tropical rainforest canopy tree species Toona ciliata are most consistent with a light-demanding, early successional pioneer. This ecological niche assignment was tested in the mature stage of its life cycle after it achieves a position in the upper canopy. Mortality, survivorship and crown growth rates over the 18-y period 1976-1994 were measured using co-registered repeat airborne stereophotographic coverage of a representative forest stand in northeast Queensland, Australia, where T, ciliata had the fourth highest relative importance in a population of 46 co-occurring canopy tree species. The airborne re-inventory was conducted in a 3.6-ha sample area and limited to only canopy trees. The results were compared with a ground-based inventory of both canopy and subcanopy trees greater than or equal to 10 cm dbh in a 0.5-ha permanent plot. Over the period 1976-1994,, there was no mortality and no evidence of decline among T. ciliata conspecifics having crown areas >60 m(2) and trunk diameters >30 cm. In the 3.6-ha airborne sample area, more than 85% of T. ciliata survivors experienced positive crown growth, in contrast to only 57% of the other co-occurring canopy trees. Toona ciliata's crown growth rates were highest in the 60-80-m(2) crown size class. Upon reaching an upper canopy position, T. ciliata not only persisted as a dominant canopy tree species, but it also achieved some of the largest crown areas (> 100 m(2)). Toona ciliata mortality in the ground-based plot involved mainly subcanopy trees of 10-30 cm dbh that had not yet assumed a canopy position and were not detectable in the aerial stereopairs. Both the crown and dbh growth rates of T. ciliata indicate enhanced vigour in the later stage of its life cycle. Its long-term survivorship and growth patterns are indicative of a persistent canopy tree species that fits the niche of a long-lived, shade-intolerant pioneer. These results demonstrate the usefulness of a long-term airborne database on the life-histories of canopy tree crowns for more clearly defining their ecological niches. C1 Clark Univ, Grad Sch Geog, Worcester, MA 01610 USA. Clark Univ, Dept Biol, Worcester, MA 01610 USA. NASA, Ames Res Ctr, Ecosyst Sci & Technol Branch, Moffett Field, CA 94035 USA. James Cook Univ N Queensland, Sch Trop Environm Studies & Geog, Cairns, Qld 4870, Australia. RP Herwitz, SR (reprint author), Clark Univ, Grad Sch Geog, Worcester, MA 01610 USA. RI Turton, Stephen/F-7585-2012 NR 66 TC 20 Z9 20 U1 0 U2 2 PU CAMBRIDGE UNIV PRESS PI NEW YORK PA 40 WEST 20TH STREET, NEW YORK, NY 10011-4211 USA SN 0266-4674 J9 J TROP ECOL JI J. Trop. Ecol. PD SEP PY 1998 VL 14 BP 683 EP 703 DI 10.1017/S0266467498000480 PN 5 PG 21 WC Ecology SC Environmental Sciences & Ecology GA 139GQ UT WOS:000077020100009 ER PT J AU Chen, LY Hunter, GW Neudeck, PG Knight, D AF Chen, LY Hunter, GW Neudeck, PG Knight, D TI X-ray photoelectron spectroscopy study of the heating effects on Pd/6H-SiC Schottky structure SO JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A-VACUUM SURFACES AND FILMS LA English DT Article; Proceedings Paper CT 44th National Symposium of the American-Vacuum-Society CY OCT 20-24, 1997 CL SAN JOSE, CALIFORNIA SP Amer Vacuum Soc ID INTERFACE; AUGER; XPS AB X-ray photoelectron spectroscopy is used to study the effects of heat treatment on the Pd/6H-SiC Schottky diode structure. After heating the structure at 425 degrees C for 140 h, a very thin surface layer of PdO mixed with SiOx formed on the palladium surface of the Schottky structure. Heat treatment promoted interfacial diffusion and reaction which significantly broadened the interfacial region. In the interfacial region, the palladium concentration decreases with depth, and the interfacial products are PdxSi (x = 1,2,3,4). In the high Pd concentration regions, Pd4Si is the major silicide component while PdSi and Pd,Si are major components in the low Pd concentration region. At the center of the interface, where the total palladium concentration equals that of silicon, the concentrations of palladium associated with various palladium silicides (PdxSi, x = 1,2,3,4) are approximately equal. The surface passivation layer composed of PdO and SiOx may significantly affect the electronic and catalytic properties of the surface of the Schottky diode which plays a major role in gas detection. The electronic properties of the Schottky structure may be dominated by a (Pd + PdxSi)/SiC interface. In order to stabilize the properties of the Schottky structure the surface and interface diffusion and reactions must be controlled. (C) 1998 American Vacuum Society. [S0734-2101(98)04205-5]. C1 NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. RP Chen, LY (reprint author), NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. NR 12 TC 26 Z9 26 U1 0 U2 1 PU AMER INST PHYSICS PI WOODBURY PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 USA SN 0734-2101 J9 J VAC SCI TECHNOL A JI J. Vac. Sci. Technol. A-Vac. Surf. Films PD SEP-OCT PY 1998 VL 16 IS 5 BP 2890 EP 2895 DI 10.1116/1.581436 PG 6 WC Materials Science, Coatings & Films; Physics, Applied SC Materials Science; Physics GA 121MJ UT WOS:000076017300021 ER PT J AU Lindstrom, E AF Lindstrom, E TI The role of the National Aeronautics and Space Administration in major oceanographic research programs SO MARINE TECHNOLOGY SOCIETY JOURNAL LA English DT Editorial Material C1 NASA, Headquarters, Washington, DC 20546 USA. RP Lindstrom, E (reprint author), NASA, Headquarters, Washington, DC 20546 USA. NR 0 TC 1 Z9 1 U1 0 U2 0 PU MARINE TECHNOLOGY SOC INC PI WASHINGTON PA C/O I CLAYION MATTHEWS, 1828 L ST, NW, 9TH FL, WASHINGTON, DC 20036 USA SN 0025-3324 J9 MAR TECHNOL SOC J JI Mar. Technol. Soc. J. PD FAL PY 1998 VL 32 IS 3 BP 88 EP 90 PG 3 WC Engineering, Ocean; Oceanography SC Engineering; Oceanography GA 148LH UT WOS:000077506400012 ER PT J AU Roth, DJ Carney, DV Baaklini, GY Bodis, JR Rauser, RW AF Roth, DJ Carney, DV Baaklini, GY Bodis, JR Rauser, RW TI A novel ultrasonic method for characterizing microstructural gradients in tubular structures SO MATERIALS EVALUATION LA English DT Article DE ultrasonic; microstructure; time-of-flight ID VELOCITY; THICKNESS; COMPOSITES AB Ultrasonic velocity and time-of-flight (TOF) imaging that uses back surface reflections to gage volumetric material quality is highly suited for quantitative characterization of microstructural gradients including those due to pore fraction, density, fiber fraction, and chemical composition variations. However, a weakness of conventional pulse echo ultrasonic velocity and TOF imaging is that the image shows the effects of thickness as well as microstructural variations, unless the part is uniformly thick. This limits this imaging method's usefulness in practical applications. Prior studies have described a pulse echo TOF based ultrasonic imaging method that requires using a single transducer in combination with a reflector plate placed behind samples which, eliminates the effect of thickness variation in the image. In those studies, this method was successful at isolating ultrasonic variations due to material microstructure in plate like samples of silicon nitride, metal matrix composite, and polymer matrix composite. In this study, the method is engineered for inspection of more complexly shaped structures-those having (hollow) tubular or curved geometry. The experimental inspection technique and results are described as applied to a polymer matrix composite "proof of concept" tube that contains machined patches of various depths and an as manufactured monolithic silicon nitride ceramic tube that might be used in "real world" applications. C1 NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. Cleveland State Univ, Cleveland, OH 44115 USA. RP Roth, DJ (reprint author), NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. NR 21 TC 5 Z9 6 U1 0 U2 1 PU AMER SOC NON-DESTRUCTIVE TEST PI COLUMBUS PA 1711 ARLINGATE LANE PO BOX 28518, COLUMBUS, OH 43228-0518 USA SN 0025-5327 J9 MATER EVAL JI Mater. Eval. PD SEP PY 1998 VL 56 IS 9 BP 1053 EP 1061 PG 9 WC Materials Science, Characterization & Testing SC Materials Science GA 121BE UT WOS:000075991600004 ER PT J AU Jenniskens, P AF Jenniskens, P TI Preparing for the return of the storming Leonids SO METEORITICS & PLANETARY SCIENCE LA English DT Editorial Material C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Jenniskens, P (reprint author), NASA, Ames Res Ctr, Mail Stop 239-4, Moffett Field, CA 94035 USA. NR 0 TC 1 Z9 1 U1 0 U2 0 PU METEORITICAL SOC PI FAYETTEVILLE PA DEPT CHEMISTRY/BIOCHEMISTRY, UNIV ARKANSAS, FAYETTEVILLE, AR 72701 USA SN 0026-1114 J9 METEORIT PLANET SCI JI Meteorit. Planet. Sci. PD SEP PY 1998 VL 33 IS 5 BP 955 EP 956 PG 2 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 131BD UT WOS:000076555100002 ER PT J AU McKay, GA Miyamoto, M Mikouchi, T Ogawa, T AF McKay, GA Miyamoto, M Mikouchi, T Ogawa, T TI The cooling history of the Lewis Cliff 86010 angrite as inferred from kirschsteinite lamellae in olivine SO METEORITICS & PLANETARY SCIENCE LA English DT Article ID DOS-REIS METEORITE; DIFFUSION; MG; CA; BODY; AGE AB Olivine in the angritic meteorite Lewis Cliff (LEW) 86010 contains abundant exsolution lamellae of kirschsteinite. Compositional gradients adjacent to the interface in both host and lamellae were formed by diffusion of chemical components into and out of the lamellae during cooling and growth. We have compared these gradients with compositional profiles calculated from diffusion and heat flow equations to estimate the cooling rate and burial depth of the sample. The resulting values for cooling rate and burial depth depend on which values are used for the diffusion rate of Ca in olivine, and how measured diffusivities are extrapolated to the lower temperatures at which the lamellae grew. If the highest diffusion coefficients are used, the cooling rates obtained from seven different lamellae range from 30 to 52 degrees C/year, with an average of 42 degrees C/year, and burial depths (assuming an overburden with a thermal diffusivity typical of solid rock) range from 14 to 17 m, with an average of 15 m. If the lowest reasonable diffusion coefficients are used, the cooling rates range from 1.4 to 2.2 degrees C/year, with an average of 1.7 degrees C/year, and the depths range from 68 to 83 m, with an average of 75 m. For the highest Ca diffusivities, details of the compositional profiles near the olivine/kirschsteinite interface suggest that continuous cooling was greatly accelerated at a temperature near 600-700 degrees C. The simplest physical explanation for such an acceleration is excavation of the sample from its original burial depth by an impact event. If Ca diffusivities are lower, a two-stage cooling history is not required. C1 NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. Univ Tokyo, Grad Sch Sci, Inst Mineral, Bunkyo Ku, Tokyo 113, Japan. Univ Tokyo, Coll Arts & Sci, Meguro Ku, Tokyo 173, Japan. RP McKay, GA (reprint author), NASA, Lyndon B Johnson Space Ctr, SN2, Houston, TX 77058 USA. NR 42 TC 11 Z9 11 U1 1 U2 4 PU METEORITICAL SOC PI FAYETTEVILLE PA DEPT CHEMISTRY/BIOCHEMISTRY, UNIV ARKANSAS, FAYETTEVILLE, AR 72701 USA SN 0026-1114 J9 METEORIT PLANET SCI JI Meteorit. Planet. Sci. PD SEP PY 1998 VL 33 IS 5 BP 977 EP 983 PG 7 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 131BD UT WOS:000076555100004 ER PT J AU Krot, AN Petaev, MI Scott, ERD Choi, BG Zolensky, ME Keil, K AF Krot, AN Petaev, MI Scott, ERD Choi, BG Zolensky, ME Keil, K TI Progressive alteration in CV3 chondrites: More evidence for asteroidal alteration SO METEORITICS & PLANETARY SCIENCE LA English DT Article; Proceedings Paper CT Workshop on Parent Body and Nebular Modification of Chrondritic Materials CY JUL 16-19, 1997 CL UNIV HAWAII, MAUI, HAWAII HO UNIV HAWAII ID ALLENDE CARBONACEOUS CHONDRITE; HIGH-TEMPERATURE CONDENSATION; AQUEOUS ALTERATION; SOLAR NEBULA; REFRACTORY INCLUSIONS; THERMAL METAMORPHISM; DARK INCLUSIONS; VIGARANO TYPE; PARENT BODY; METEORITE AB The oxidized CV3 chondrites can be divided into two major subgroups or lithologies, Ball-like (CV3(oxB)) and Allende-like (CV3(oxA)), in which chondrules, calcium-aluminum-rich inclusions (CAIs) and matrices show characteristic alteration features (Weisberg et al., 1997; Krot et al., 1997d; Kimura and Ikeda, 1997). The CV3(oxB) lithology is present in Bail, Kaba, parts of the Mokoia breccia and, possibly, in Grosnaja and Allan Hills (ALH) 85006. It is characterized by the presence of the secondary low-Ca phyllosilicates (saponite and sodium phlogopite), magnetite, Ni-rich sulfides, fayalite (Fa(>90)), Ca-Fe-rich pyroxenes (Fs(10-50)Wo(45-50)) and andradite. Phyllosilicates replace primary Ca-rich minerals in chondrules and CAIs, which suggests mobilization of Ca during aqueous alteration. Magnetite nodules are replaced to various degrees by fayalite, Ca-Fe-rich pyroxenes and minor andradite. Fayalite veins crosscut fine-grained rims around chondrules and extend into the matrix. Thermodynamic analysis of the observed reactions indicates that they could have occurred at relatively low temperatures (<300 degrees C) in the presence of aqueous solutions. Oxygen isotopic compositions of the coexisting magnetite and fayalite plot close to the terrestrial fractionation line with large Delta(18)O(fyalite-magnetite) fractionation (similar to 20 parts per thousand). We infer that phyllosilicates, magnetite, fayalite, Ca-Fe-rich pyroxenes and andradite formed at relatively low temperatures (<300 degrees C) by fluid-rock interaction in an asteroidal environment. Secondary fayalite and phyllosilicates are virtually absent in chondrules and CAIs in the CV3(oxA) lithology, which is present in Allende and its dark inclusions, Axtell, ALHA81258, ALH 84028, Lewis Cliff(LEW) 86006, and parts of the Mokoia and Vigarano breccias. Instead secondary nepheline, sodalite, and fayalitic olivine are common. Fayalitic olivine in chondrules replaces low-Ca pyroxenes and rims and veins forsterite grains; it also forms coarse lath-shaped grains in matrix. Secondary Ca-Fe-rich pyroxenes are abundant. We infer that the CV3(oxA) lithology experienced alteration at higher temperatures than the CV3(oxB) lithology. The presence of the reduced and CV3(oxA) lithologies in the Vigarano breccia and CV3(oxA) and CV3(oxB) lithologies in the Mokoia breccia indicates that all CV3 chondrites came from one heterogeneously altered asteroid. The metamorphosed clasts in Mokoia (Krot and Hutcheon, 1997) may be rare samples of the hotter interior of the CV asteroid. We conclude that the alteration features observed in the oxidized CV3 chondrites resulted from the fluid-rock interaction in an asteroid during progressive metamorphism of a heterogeneous mixture of ices and anhydrous materials mineralogically similar to the reduced CV3 chondrites. C1 Univ Hawaii Manoa, Sch Ocean & Earth Sci & Technol, Hawaii Inst Geophys & Planetol, Honolulu, HI 96822 USA. Harvard Smithsonian Ctr Astrophys, Cambridge, MA 02138 USA. Univ Calif Los Angeles, Dept Earth & Planetary Sci, Los Angeles, CA 90095 USA. Univ Calif Los Angeles, Inst Geophys & Planetary Phys, Los Angeles, CA 90095 USA. NASA, Earth Sci & Solar Syst Explorat Div, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. Hawaii Ctr Volcanol, Honolulu, HI USA. RP Krot, AN (reprint author), Univ Hawaii Manoa, Sch Ocean & Earth Sci & Technol, Hawaii Inst Geophys & Planetol, Honolulu, HI 96822 USA. EM sasha@pgd.hawaii.edu NR 94 TC 164 Z9 166 U1 1 U2 18 PU METEORITICAL SOC PI FAYETTEVILLE PA DEPT CHEMISTRY/BIOCHEMISTRY, UNIV ARKANSAS, FAYETTEVILLE, AR 72701 USA SN 0026-1114 J9 METEORIT PLANET SCI JI Meteorit. Planet. Sci. PD SEP PY 1998 VL 33 IS 5 BP 1065 EP 1085 PG 21 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 131BD UT WOS:000076555100013 ER PT J AU Pittard, JM Stevens, IR Corcoran, MF Ishibashi, K AF Pittard, JM Stevens, IR Corcoran, MF Ishibashi, K TI The X-ray light curve of Eta Carinae SO MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY LA English DT Letter DE hydrodynamics; binaries : general; stars : early-type; stars : individual : Eta Car; X-rays : stars ID LONG-PERIOD BINARY; EMISSION; SYSTEMS; WINDS AB Following the proposal by Damineli that the central object of Eta Carinae may be an early-type binary, we perform numerical simulations of the X-ray emission from colliding stellar winds. A synthetic light curve has been generated which qualitatively agrees with the recent X-ray variability, and provides further support for the binary model. In particular, the model predicts a rise in the observed X-ray emission towards periastron, followed by a sharp drop and subsequent recovery. This is indeed what is seen in the RXTE light curve, although some problems concerning the X-ray spectrum at periastron still need to be explained. The simulations suggest that the width of the periastron dip will provide strong constraints on the binary and stellar wind properties of the components of Eta Car. C1 Univ Birmingham, Sch Phys & Astron, Birmingham B15 2TT, W Midlands, England. Univ Space Res Assoc, High Energy Astrophys Lab, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Minnesota, Dept Astron, Minneapolis, MN 55455 USA. RP Pittard, JM (reprint author), Univ Birmingham, Sch Phys & Astron, Birmingham B15 2TT, W Midlands, England. EM jmp@star.sr.bham.ac.uk; irs@star.sr.bham.ac.uk; corcoran@barnegat.gsfc.nasa.gov; bish@astro.spa.umn.edu NR 26 TC 50 Z9 50 U1 0 U2 2 PU BLACKWELL SCIENCE LTD PI OXFORD PA P O BOX 88, OSNEY MEAD, OXFORD OX2 0NE, OXON, ENGLAND SN 0035-8711 J9 MON NOT R ASTRON SOC JI Mon. Not. Roy. Astron. Soc. PD SEP 1 PY 1998 VL 299 IS 1 BP L5 EP L9 DI 10.1046/j.1365-8711.1998.01962.x PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 118JG UT WOS:000075834300002 ER PT J AU Globus, A Bauschlicher, CW Han, J Jaffe, RL Levit, C Srivastava, D AF Globus, A Bauschlicher, CW Han, J Jaffe, RL Levit, C Srivastava, D TI Machine phase fullerene nanotechnology SO NANOTECHNOLOGY LA English DT Article; Proceedings Paper CT 5th Foresight Conference on Molecular Nanotechnology CY NOV 05-08, 1997 CL PALO ALTO, CALIFORNIA SP Foresight Inst ID CARBON NANOTUBE BUNDLES; LARGE-SCALE SYNTHESIS; GRAPHITIC CARBON; DYNAMICS; MICROSCOPY; TRANSPORT; CHEMISTRY; TUBULES; GROWTH; ROPES AB Recent advances in fullerene science and technology suggest that it may be possible, in the distant future, to design and build atomically precise programmable machines composed largely of functionalized fullerenes. Large numbers of such machines with appropriate interconnections could conceivably create a material able to react to the environment and repair itself. This paper reviews some of the experimental and theoretical work relating to these materials, sometimes called machine phase, including the fullerene gears and high-density memory recently designed and simulated in our laboratory. C1 NASA, Ames Res Ctr, MRJ Technol Solut Inc, Moffett Field, CA 94035 USA. RP Globus, A (reprint author), NASA, Ames Res Ctr, MRJ Technol Solut Inc, Moffett Field, CA 94035 USA. NR 59 TC 29 Z9 29 U1 0 U2 0 PU IOP PUBLISHING LTD PI BRISTOL PA DIRAC HOUSE, TEMPLE BACK, BRISTOL BS1 6BE, ENGLAND SN 0957-4484 J9 NANOTECHNOLOGY JI Nanotechnology PD SEP PY 1998 VL 9 IS 3 BP 192 EP 199 DI 10.1088/0957-4484/9/3/008 PG 8 WC Nanoscience & Nanotechnology; Materials Science, Multidisciplinary; Physics, Applied SC Science & Technology - Other Topics; Materials Science; Physics GA 126JH UT WOS:000076289800008 ER PT J AU Walch, SP Merkle, RC AF Walch, SP Merkle, RC TI Theoretical studies of diamond mechanosynthesis reactions SO NANOTECHNOLOGY LA English DT Article; Proceedings Paper CT 5th Foresight Conference on Molecular Nanotechnology CY NOV 05-08, 1997 CL PALO ALTO, CALIFORNIA SP Foresight Inst AB Density functional theory methods have been used to examine the interaction of (i) the carbene and C-2 tools With a pair of radical sites on the diamond (111) surface and (ii) the carbene tool with a surface dimer on the reconstructed diamond (100) surface. For the (111) surface, the carbene tool (carbenecyclopropene) is found to bond preferentially to a single radical site (on top site) rather than at a bridged site. This means this tool is not useful for adding a carbon to diamond (111) at this site. The C-2 tool, on the other hand, is found to add a bridged C-2 molecule, through a series of steps which are overall exothermic. The carbene tool can add a carbon to the bridged C-2 molecule, leading to a bridged C-3 molecule perpendicular to the surface, by an overall exothermic series of steps. If another radical site is activated, the C-3 can bend over to a threefold coordinated position, with only a small barrier. Thus, this series of steps can be used to create a threefold coordinated C-3 molecule on the diamond (Ill)surface. For the surface dimer on the reconstructed (100) surface, the carbene tool is found to add with no barrier if the angle between the tool and the surface is allowed to vary or with a 0.09 aJ (13 kcal mol(-1)) barrier for a C-2 upsilon constrained approach. In this case, a bridged site is strongly favored, and the subsequent steps of sequentially breaking the pi and sigma bonds between the tool and added carbon atom are all feasible. Thus, this series of steps can add a bridged C atom to the reconstructed diamond (100) surface. C1 NASA, Ames Res Ctr, Thermosci Inst, Moffett Field, CA 94035 USA. Xerox Corp, Palo Alto Res Ctr, Palo Alto, CA 94304 USA. RP Walch, SP (reprint author), NASA, Ames Res Ctr, Thermosci Inst, MS 230-3, Moffett Field, CA 94035 USA. NR 8 TC 9 Z9 9 U1 0 U2 0 PU IOP PUBLISHING LTD PI BRISTOL PA DIRAC HOUSE, TEMPLE BACK, BRISTOL BS1 6BE, ENGLAND SN 0957-4484 J9 NANOTECHNOLOGY JI Nanotechnology PD SEP PY 1998 VL 9 IS 3 BP 285 EP 296 DI 10.1088/0957-4484/9/3/020 PG 12 WC Nanoscience & Nanotechnology; Materials Science, Multidisciplinary; Physics, Applied SC Science & Technology - Other Topics; Materials Science; Physics GA 126JH UT WOS:000076289800020 ER PT J AU Globus, A Srivastava, D AF Globus, A Srivastava, D TI Special issue featuring papers from 5th Foresight Conference on Molecular Nanotechnology - Introduction SO NANOTECHNOLOGY LA English DT Editorial Material C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Globus, A (reprint author), NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU IOP PUBLISHING LTD PI BRISTOL PA DIRAC HOUSE, TEMPLE BACK, BRISTOL BS1 6BE, ENGLAND SN 0957-4484 J9 NANOTECHNOLOGY JI Nanotechnology PD SEP PY 1998 VL 9 IS 3 BP U3 EP U3 PG 1 WC Nanoscience & Nanotechnology; Materials Science, Multidisciplinary; Physics, Applied SC Science & Technology - Other Topics; Materials Science; Physics GA 126JH UT WOS:000076289800001 ER PT J AU Zheng, Q Susanto, RD Yan, XH Liu, WT Ho, CR AF Zheng, Q Susanto, RD Yan, XH Liu, WT Ho, CR TI Observation of equatorial Kelvin solitary waves in a slowly varying thermocline SO NONLINEAR PROCESSES IN GEOPHYSICS LA English DT Article ID PACIFIC-OCEAN; TRAPPED WAVES; SOLITONS; ALTIMETER; CHANNEL AB TOPEX/POSEIDON (T/P) sea level deviation (SLD) time series from October 3, 1992 to May 15, 1997 combined with upper ocean thermal structures are used to observe the characteristics and analyze the dynamics of equatorial waves in the Pacific Ocean. The evolution of the Kelvin wave propagating along an eastward shoaling thermocline in the equatorial Pacific is investigated. The behavior of this wave as it propagates eastward can be approximately described with the solutions of the perturbed Korteweg-de Vries (PKdV) equation and modified Green's Law. Assuming that the nonlinear term and dispersive term of this equation are balanced, the amplitude increases as the thermocline decreases to the power -3/8. Approaching the eastern Pacific, the nonlinearity increases and the relation changes to the power -9/8. The dispersion relation, and mass and energy conservations are investigated. The results indicate that under a varying thermocline, the nonlinear Kelvin solitary waves indeed exist in the real ocean. C1 Univ Delaware, Grad Coll Marine Studies, Ctr Remote Sensing, Newark, DE 19716 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Natl Taiwan Ocean Univ, Dept Oceanog, Keelung 202, Taiwan. RP Zheng, Q (reprint author), Univ Delaware, Grad Coll Marine Studies, Ctr Remote Sensing, Newark, DE 19716 USA. RI Zheng, Quanan/F-9025-2010 NR 33 TC 5 Z9 5 U1 0 U2 2 PU EUROPEAN GEOPHYSICAL SOCIETY PI KATLENBURG-LINDAU PA MAX-PLANCK-STR 13, 37191 KATLENBURG-LINDAU, GERMANY SN 1023-5809 J9 NONLINEAR PROC GEOPH JI Nonlinear Process Geophys. PD SEP PY 1998 VL 5 IS 3 BP 153 EP 165 PG 13 WC Geochemistry & Geophysics; Meteorology & Atmospheric Sciences SC Geochemistry & Geophysics; Meteorology & Atmospheric Sciences GA 247MT UT WOS:000083225100005 ER PT J AU Grant, WB AF Grant, WB TI New lasers push space-based Lidar SO PHOTONICS SPECTRA LA English DT Article C1 NASA, Div Atmospher Sci, Langley Res Ctr, Hampton, VA 23665 USA. RP Grant, WB (reprint author), NASA, Div Atmospher Sci, Langley Res Ctr, Hampton, VA 23665 USA. RI Grant, William/B-8311-2009 OI Grant, William/0000-0002-1439-3285 NR 0 TC 0 Z9 0 U1 0 U2 0 PU LAURIN PUBL CO INC PI PITTSFIELD PA BERKSHIRE COMMON PO BOX 1146, PITTSFIELD, MA 01202 USA SN 0731-1230 J9 PHOTON SPECTRA JI Photon. Spect. PD SEP PY 1998 VL 32 IS 9 BP 43 EP 44 PG 2 WC Optics SC Optics GA 115NH UT WOS:000075671100017 ER PT J AU Drake, A Wesphal, RV Kennelly, RA Driver, DM AF Drake, A Wesphal, RV Kennelly, RA Driver, DM TI Interferometric skin friction footprint for a tripped boundary layer SO PHYSICS OF FLUIDS LA English DT Article; Proceedings Paper CT 15th Annual Fluid Mechanics Photo Contest at the Meeting of the American-Physical-Society-Division-of-Fluid-Dynamics CY NOV, 1997 CL SAN FRANCISCO, CALIFORNIA SP Amer Phys Soc, Div Fluid Dynam C1 Washington State Univ, Richland, WA USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Drake, A (reprint author), Washington State Univ, Richland, WA USA. NR 0 TC 0 Z9 0 U1 0 U2 1 PU AMER INST PHYSICS PI WOODBURY PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 USA SN 1070-6631 J9 PHYS FLUIDS JI Phys. Fluids PD SEP PY 1998 VL 10 IS 9 BP S5 EP S5 PG 1 WC Mechanics; Physics, Fluids & Plasmas SC Mechanics; Physics GA 114JA UT WOS:000075604300005 ER PT J AU Weislogel, MM Lichter, S AF Weislogel, MM Lichter, S TI Water balloon rupture in low-G SO PHYSICS OF FLUIDS LA English DT Article; Proceedings Paper CT 15th Annual Fluid Mechanics Photo Contest at the Meeting of the American-Physical-Society-Division-of-Fluid-Dynamics CY NOV, 1997 CL SAN FRANCISCO, CALIFORNIA SP Amer Phys Soc, Div Fluid Dynam C1 NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. Northwestern Univ, Evanston, IL 60208 USA. RP Weislogel, MM (reprint author), NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. RI Lichter, Seth/B-7598-2009 NR 0 TC 0 Z9 0 U1 0 U2 3 PU AMER INST PHYSICS PI WOODBURY PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 USA SN 1070-6631 J9 PHYS FLUIDS JI Phys. Fluids PD SEP PY 1998 VL 10 IS 9 BP S4 EP S4 PG 1 WC Mechanics; Physics, Fluids & Plasmas SC Mechanics; Physics GA 114JA UT WOS:000075604300004 ER PT J AU Flasar, FM AF Flasar, FM TI The composition of Titan's atmosphere: a meteorological perspective SO PLANETARY AND SPACE SCIENCE LA English DT Article; Proceedings Paper CT International Symposia Titan's Atmosphere and Surface - Recent Developments at the EGS Scientific Assembly CY APR 23-25, 1997 CL VIENNA, AUSTRIA SP EGS ID ROTOTRANSLATIONAL ABSORPTION-SPECTRA; VOYAGER INFRARED OBSERVATIONS; RADIO-OCCULTATION; HYPOTHESIZED OCEAN; SURFACE; TEMPERATURE; PAIRS; TROPOSPHERE; PHOTOCHEMISTRY; UNCERTAINTIES AB One of the most important and intriguing issues concerning Titan's atmosphere is the methane cycle. Although the broad outline of the breakup of methane by photolytic and catalytic dissociation to produce a suite of more complex hydrocarbons and nitriles (additionally requiring the dissociation of N-2) is understood, several fundamental questions exist, and many details remain obscure. The spatial distribution of stratospheric hydrocarbons and nitriles has been inferred from Voyager thermal infrared spectra, but only at northern spring equinox. The photochemical, radiative, and dynamical processes underlying this distribution ape not well understood. Additionally, methane itself is important both radiatively and (possibly) dynamically in the troposphere. Voyager infrared and radio-occultation measurements place some constraints on the vertical and horizontal distribution of methane, and suggest that it may be supersaturated in the upper troposphere. The presence of convective activity associated with methane condensation is unknown, but recent work indicates that a meager amount of convection (compared to Earth) could be Sufficient to transport heat and methane vertically and account in part for the vertical thermal structure of Titan's troposphere and provide a major source of methane for the stratosphere. The additional measurements provided by Cassini over a four-year period will greatly improve our understanding of these issues. Emphasis in this paper is on the combination of radio occultation measurements and thermal infrared spectra, with their different sensitivities to atmospheric constituents. Published by Elsevier Science Ltd. C1 NASA, Extraterr Phys Lab, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Flasar, FM (reprint author), NASA, Extraterr Phys Lab, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. EM F.M.Flasar@gsfc.nasa.gov RI Flasar, F Michael/C-8509-2012 NR 70 TC 20 Z9 20 U1 0 U2 2 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0032-0633 J9 PLANET SPACE SCI JI Planet Space Sci. PD SEP-OCT PY 1998 VL 46 IS 9-10 BP 1109 EP 1124 DI 10.1016/S0032-0633(97)00182-7 PG 16 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 150AR UT WOS:000077640700005 ER PT J AU Flasar, FM AF Flasar, FM TI The dynamic meteorology of Titan SO PLANETARY AND SPACE SCIENCE LA English DT Article; Proceedings Paper CT International Symposia Titan's Atmosphere and Surface - Recent Developments at the EGS Scientific Assembly CY APR 23-25, 1997 CL VIENNA, AUSTRIA SP EGS ID VOYAGER-1 RADIO-OCCULTATION; GRAVITY-WAVES; ATMOSPHERIC PROFILES; SCALE WAVES; VENUS; TEMPERATURE; MODEL; SUPERROTATION; ROTATION; STRATOSPHERE AB Current understanding of Titan's atmospheric circulation and thermal structure is reviewed. Knowledge of Titan's zonal winds derives from temperatures retrieved from Voyager infrared measurements and geopotential heights retrieved from stellar citation observations. The inferred stratospheric winds are cyclostrophic, like those of Venus. Radiative response times are long in the lower troposphere, but decline to values small compared to a season in the upper stratosphere. Given Titan's effective obliquity of 27 degrees, stratospheric temperatures and zonal winds should vary seasonally, requiring a cross-equatorial Lagrangian circulation to transport angular momentum and heat to maintain the thermal wind balance. Atmospheric waves may play an important role in transporting and depositing angular momentum, but they are as yet constrained by few observations. General circulation models of Titan's winds are still in their infancy, but suggest much of the troposphere must be stably stratified, so that the cyclostrophic zonal winds aloft are isolated from surface drag. The vertical structure of temperature, above the lowest 4 km, is consistent with a radiatively balanced atmosphere. However, moist convection could still be very efficient, and updrafts covering only < 10(-4) of the surface area can balance the flux of sunlight absorbed at the surface. The review concludes with a summary of the meteorological capabilities of the scientific payload of Cassini Huygens, providing observations of winds, temperatures, and composition that should transform one's conceptual understanding of Titan's atmospheric circulation and thermal structure. Published by Elsevier Science Ltd. C1 NASA, Extraterr Phys Lab, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Flasar, FM (reprint author), NASA, Extraterr Phys Lab, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. EM F.M.Flasar@gsfc.nasa.gov RI Flasar, F Michael/C-8509-2012 NR 88 TC 33 Z9 33 U1 1 U2 4 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0032-0633 J9 PLANET SPACE SCI JI Planet Space Sci. PD SEP-OCT PY 1998 VL 46 IS 9-10 BP 1125 EP 1147 DI 10.1016/S0032-0633(97)00223-7 PG 23 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 150AR UT WOS:000077640700006 ER PT J AU Keller, CN Anicich, VG Cravens, TE AF Keller, CN Anicich, VG Cravens, TE TI Model of Titan's ionosphere with detailed hydrocarbon ion chemistry SO PLANETARY AND SPACE SCIENCE LA English DT Article; Proceedings Paper CT International Symposia Titan's Atmosphere and Surface - Recent Developments at the EGS Scientific Assembly CY APR 23-25, 1997 CL VIENNA, AUSTRIA SP EGS ID ORGANIC-MOLECULES; ATMOSPHERE; PHOTOCHEMISTRY AB We have modified the previous model of Keller, Cravens and Gan (1992, J. Geophys. Res. 97, - 12117) of the ionosphere of Titan. The model is a one-dimensional photochemical model and takes into account newly measured gas phase kinetic rates, particularly those of the higher mass hydrocarbons and nitriles. The model neutral atmospheres developed by, Yung er nl. (1984, Astrophys. J. Suppl. 55, 465), Yung,(1987, Icarus 72, 468) and Toublanc et al. (1995, Icarus 113, 2) were used in our model. The current model includes more neutral and ion species and discriminates among the various higher mass hydrocarbon and nitrile ion species. Ion neutral chemistry produces HCNH+ as the single major ion species at the ionospheric peak (an altitude of 1055 km), however, the total density of all the higher mass hydrocarbons is more than that of HCNH+. The higher mass hydrocarbons include such species as : c-C3H3+, C5H5+, and C3H5+. Another important ion species is H2C3N+. Based on this model Mle expect the higher mass channels (e.g. 39 amu, 41 amu, 53 amu, 65 amu, 67 amu, and 69 amu) of the Cassini Ion-Neutral Mass Spectrometer to measure higher densities than previous models have predicted. (C) 1998 Elsevier Science Ltd. All rights reserved. C1 Univ Kansas, Dept Phys & Astron, Lawrence, KS 66045 USA. Univ Jos, Dept Phys, Jos, Nigeria. NASA, Jet Prop Lab, Pasadena, CA 91109 USA. RP Cravens, TE (reprint author), Univ Kansas, Dept Phys & Astron, Lawrence, KS 66045 USA. NR 26 TC 149 Z9 149 U1 0 U2 8 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0032-0633 J9 PLANET SPACE SCI JI Planet Space Sci. PD SEP-OCT PY 1998 VL 46 IS 9-10 BP 1157 EP 1174 DI 10.1016/S0032-0633(98)00053-1 PG 18 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 150AR UT WOS:000077640700008 ER PT J AU Borgarelli, L Im, E Johnson, WTK Scialanga, L AF Borgarelli, L Im, E Johnson, WTK Scialanga, L TI The microwave sensing in the Cassini Mission: the radar SO PLANETARY AND SPACE SCIENCE LA English DT Article; Proceedings Paper CT International Symposia Titan's Atmosphere and Surface - Recent Developments at the EGS Scientific Assembly CY APR 23-25, 1997 CL VIENNA, AUSTRIA SP EGS AB The spacecraft of Cassini Mission has been launched towards Saturn on October 1997 to study the physical structure and chemical composition of Saturn as well as all its moons. To this end many instruments have been mounted on the spacecraft; one of these is the Cassini Radar. Cassini Mission is a cooperative mission between NASA (National Aeronautics and Space Administration), ESA (European Space Agency) and ASI (Agenzia Spaziale Italiana) to acquire scientific knowledge about the Saturnian system. Through many different scientific instruments, the Cassini Radar objective will be to investigate the nature of Titan : its optically opaque atmosphere and surface. Part of the Radar, the Radio Frequency Electronic Subsystem (RFES) has been developed by Alenia Aerospazio while the other parts have been developed from Jet Propulsion Laboratory (JPL). Cassini Radar is a multimode instrument able to operate in altimeter mode (4.25 MHz), an imaging mode (0.85 and 0.425 MHz bandwidth), a scatterometer mode (0.106 MHz bandwidth), and a radiometer mode (100 MHz bandwidth). These modes will be used to acquire images, topographic profiles, backscatter reflection coefficient, and sense brightness temperatures of the surface of Titan. A passive mode, i.e. radiometer, has been implemented to measure Titan's surface emissivity in the ku-band. In the development of such an hardware, designers faced many requirements coming from the "deep space environment" and the specific features of a spacecraft designed to cruise in the Solar System to reach Saturn and its moons. e.g. reduced mass, low available room, low power consumption, severe environmental conditions, specific thermal control and on-ground test accessibility. The structure has been designed to survive high levels of vibrations at high frequencies (pyro-shocks). Thermal design has to withstand wide range of temperature. Design avoids the generation of magnetic fields, which could disturb magnetic sensitive sensor. Electronics have been shielded from natural and artificial radiation, (C) 1998 Elsevier Science Ltd. All rights reserved. C1 Alenia Aerosp, Space Div, I-00131 Rome, Italy. CALTECH, Jet Prop Lab, Radar Sci & Engn Sect, Pasadena, CA 91109 USA. RP Borgarelli, L (reprint author), Alenia Aerosp, Space Div, Via Saccomuro 24, I-00131 Rome, Italy. NR 10 TC 2 Z9 2 U1 0 U2 2 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0032-0633 J9 PLANET SPACE SCI JI Planet Space Sci. PD SEP-OCT PY 1998 VL 46 IS 9-10 BP 1245 EP + DI 10.1016/S0032-0633(98)00065-8 PG 11 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 150AR UT WOS:000077640700015 ER PT J AU Resch, GM Bar-Sever, Y Keihm, SJ Kroger, P Linfield, RP Mahoney, MJ Tanner, A Teitelbaum, LP AF Resch, GM Bar-Sever, Y Keihm, SJ Kroger, P Linfield, RP Mahoney, MJ Tanner, A Teitelbaum, LP TI Atmospheric calibration for precision Doppler tracking of spacecraft SO PLANETARY AND SPACE SCIENCE LA English DT Article; Proceedings Paper CT International Symposia Titan's Atmosphere and Surface - Recent Developments at the EGS Scientific Assembly CY APR 23-25, 1997 CL VIENNA, AUSTRIA SP EGS AB The signals from the Cassini spacecraft that will be used for radio science experiments will be affected by delay fluctuations in the Earth's atmosphere. These fluctuations are dominated by water vapor in the troposphere, and in the case of the gravitational wave experiment (GWE), they are likely to be a limiting error source. A passive remote sensing system, centered around a water vapor radiometer (WVR), has been developed to provide calibrations of water vapor fluctuations during radio science experiments. During the past two years, most of the technical challenges involved in the design of this instrument have been overcome and we are ready to begin implementation. We will discuss the performance that has been demonstrated with the current generation of WVR instrumentation and the general design of the package that will be installed at the Goldstone tracking site. In addition, recent results obtained for a comparison of co-located WVRs and global positioning system (GPS) receivers will be presented. The possibility of using these results to estimate gradients and/or fluctuations in the dry atmosphere will be discussed. (C) 1998 Elsevier Science Ltd. All rights reserved. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Resch, GM (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. EM george.m.resch@jpl.nasa.gov NR 4 TC 2 Z9 2 U1 0 U2 2 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0032-0633 J9 PLANET SPACE SCI JI Planet Space Sci. PD SEP-OCT PY 1998 VL 46 IS 9-10 BP 1257 EP 1261 DI 10.1016/S0032-0633(98)00048-8 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 150AR UT WOS:000077640700016 ER PT J AU Coradini, A Capaccioni, F Drossart, P Semery, A Arnold, G Schade, U Angrilli, F Barucci, MA Bellucci, G Bianchini, G Bibring, JP Blanco, A Blecka, M Bockelee-Morvan, D Bonsignori, R Bouye, M Bussoletti, E Capria, MT Carlson, R Carsenty, U Cerroni, P Colangeli, L Combes, M Combi, M Crovisier, J Dami, M DeSanctis, MC DiLellis, AM Dotto, E Encrenaz, T Epifani, E Erard, S Espinasse, S Fave, A Federico, C Fink, U Fonti, S Formisano, V Hello, Y Hirsch, H Huntzinger, G Knoll, R Kouach, D Ip, WH Irwin, P Kachlicki, J Langevin, Y Magni, G McCord, T Mennella, V Michaelis, H Mondello, G Mottola, S Neukum, G Orofino, V Orosei, R Palumbo, P Peter, G Pforte, B Piccioni, G Reess, JM Ress, E Saggin, B Schmitt, B Stefanovitch, D Stern, A Taylor, F Tiphene, D Tozzi, G AF Coradini, A Capaccioni, F Drossart, P Semery, A Arnold, G Schade, U Angrilli, F Barucci, MA Bellucci, G Bianchini, G Bibring, JP Blanco, A Blecka, M Bockelee-Morvan, D Bonsignori, R Bouye, M Bussoletti, E Capria, MT Carlson, R Carsenty, U Cerroni, P Colangeli, L Combes, M Combi, M Crovisier, J Dami, M DeSanctis, MC DiLellis, AM Dotto, E Encrenaz, T Epifani, E Erard, S Espinasse, S Fave, A Federico, C Fink, U Fonti, S Formisano, V Hello, Y Hirsch, H Huntzinger, G Knoll, R Kouach, D Ip, WH Irwin, P Kachlicki, J Langevin, Y Magni, G McCord, T Mennella, V Michaelis, H Mondello, G Mottola, S Neukum, G Orofino, V Orosei, R Palumbo, P Peter, G Pforte, B Piccioni, G Reess, JM Ress, E Saggin, B Schmitt, B Stefanovitch, D Stern, A Taylor, F Tiphene, D Tozzi, G TI VIRTIS: an imaging spectrometer for the ROSETTA mission SO PLANETARY AND SPACE SCIENCE LA English DT Article; Proceedings Paper CT International Symposia Titan's Atmosphere and Surface - Recent Developments at the EGS Scientific Assembly CY APR 23-25, 1997 CL VIENNA, AUSTRIA SP EGS ID INFRARED SPECTRAL REFLECTANCE; COMET P/WIRTANEN; WATER; EVOLUTION; ICE; HYAKUTAKE; HALLEY; ORIGIN AB The VIRTIS scientific and technical teams will take advantage of their previous experience in the design and development of spectrometers for space applications. Tn fact. the various groups contributing fd the VIRTIS experiment, from Italy, France and Germany, have been deeply involved in the CASSINI mission, with the experiments VIMS and CIRS. The targets of the ROSETTA mission are the most primitive solar system bodies: comets and asteroids. ROSETTA will study in detail a comet nucleus, the prime target of the mission, and will fly by one or two asteroids. The small bodies of the solar system are of great interest for planetary science and their study is crucial to understand the solar system formation. Tn fact it is believed that comets and, to a lesser extent, asteroids underwent a moderate evolution so that they preserve some pristine solar system material. Comets and asteroids are in close relationship with the planetesimals, which formed from the solar nebula 4.6 billion years ago. The global characterisation of one comet nucleus and one or two asteroids will provide basic information on the origin of the solar system and on the interrelation between the solar system and the interstellar dust environment. The ROSETTA mission is designed to obtain the above mentioned scientific goals by. (a) in situ analysis of comet material; (b) long period of remote sensing of the comet. The combination of remote sensing and in situ measurements will increase the scientific return of the mission. In fact, the "in situ" measurements will give relevant "ground-truth" for the remote sensing information, and, in turn, the locally collected data will be interpreted in the appropriate scenario provided by remote sensing investigation. The scientific payload of ROSETTA includes a Visual Infra Red Spectral and Thermal Spectrometer (VIRTIS) among the instrument on board the spacecraft orbiting around the comet. This instrument is fundamental to detect and study the evolution of specific fingerprints-such as the typical spectral bands of minerals and molecules-arising from surface components and from materials dispersed in the coma. Their identification is a primary goal of the ROSETTA mission as it will allow us to identify the nature of the main constituent of the comets. Moreover, the surface thermal evolution during comet approach to Sun is important information that can be obtained by means of spectroscopic observation. The VIRTIS design and its detailed science goals are reported hereafter. (C) 1998 Elsevier Science Ltd. All rights reserved. C1 CNR, Ist Astrofis Spaziale, I-00185 Rome, Italy. Observ Paris, Sect Meudon, Paris, France. DLR, Inst Planeterkundung, Berlin, Germany. CNR, Ist Fis Spazio Interplanetario, I-00185 Rome, Italy. Univ Padua, Dipartimento Ingn Meccan, I-35100 Padua, Italy. Univ Lecce, Dipartimento Fis, I-73100 Lecce, Italy. Osservatorio Astron Capodimonte, I-80131 Naples, Italy. Officine Galileo, Florence, Italy. Osservatorio Astrofis Arcetri, I-50125 Florence, Italy. CNRS, Inst Astrophys Spatiale, F-91405 Orsay, France. Lab Glaciol & Geophys Environm, Grenoble, France. Univ Michigan, Space Phys Res Lab, Ann Arbor, MI 48109 USA. Univ Hawaii, Hawaii Inst Geophys & Planetol, Honolulu, HI 96822 USA. Univ Arizona, Luna Planetary Lab, Tucson, AZ USA. Polish Acad Sci, Warsaw, Poland. NASA, JPL, Pasadena, CA USA. Univ Perugia, I-06100 Perugia, Italy. MPI, Katlenburg, Germany. Univ Oxford, Atmospher Ocean & Planetary Phys Dept, Oxford OX1 2JD, England. So Res Inst, Boulder, CO USA. RP Coradini, A (reprint author), CNR, Ist Astrofis Spaziale, Viale Univ 11, I-00185 Rome, Italy. RI Schmitt, Bernard/A-1064-2009; Combi, Michael/J-1697-2012; Schade, Ulrich/D-9341-2013; OI Tozzi, Gian Paolo/0000-0003-4775-5788; Schmitt, Bernard/0000-0002-1230-6627; Combi, Michael/0000-0002-9805-0078; De Sanctis, Maria Cristina/0000-0002-3463-4437; Dotto, Elisabetta/0000-0002-9335-1656; Bellucci, Giancarlo/0000-0003-0867-8679; Capaccioni, Fabrizio/0000-0003-1631-4314; Irwin, Patrick/0000-0002-6772-384X; Piccioni, Giuseppe/0000-0002-7893-6808; saggin, bortolino/0000-0002-4033-3585 NR 26 TC 56 Z9 57 U1 2 U2 12 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0032-0633 J9 PLANET SPACE SCI JI Planet Space Sci. PD SEP-OCT PY 1998 VL 46 IS 9-10 BP 1291 EP 1304 DI 10.1016/S0032-0633(98)00025-7 PG 14 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 150AR UT WOS:000077640700019 ER PT J AU Simon, MK Alouini, MS AF Simon, MK Alouini, MS TI A unified approach to the performance analysis of digital communication over generalized fading channels SO PROCEEDINGS OF THE IEEE LA English DT Article DE communication channels; differential phase shift keying; digital communication; dispersive channels; diversity methods; fading channels; frequency shift keying; phase shift keying; signal detection ID RADIO PROPAGATION; DIVERSITY; SYSTEMS; MODEL AB Presented here is a unified approach to evaluating the error-rate performance of digital communication systems operating over a generalized fading channel. What enables the unification is the recognition of the desirable form for alternate representations of the Gaussian and Marcum Q-functions that are characteristic of error-probability expressions for coherent, differentially coherent, and noncoherent forms of detection. It is shown that in the largest majority of cases, these error-rate expressions can be put in the form of a single integral with finite limits and an integrand composed of elementary functions, thus readily enabling numerical evaluation. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. CALTECH, Dept Elect Engn, Commun Grp, Pasadena, CA 91125 USA. RP Simon, MK (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 54 TC 407 Z9 419 U1 0 U2 9 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 0018-9219 J9 P IEEE JI Proc. IEEE PD SEP PY 1998 VL 86 IS 9 BP 1860 EP 1877 DI 10.1109/5.705532 PG 18 WC Engineering, Electrical & Electronic SC Engineering GA 110KK UT WOS:000075379800006 ER PT J AU Fuller, T AF Fuller, T TI Exploring the unknown, selected documents in the history of the US civil space program, vol 2, External relationships SO PUBLIC HISTORIAN LA English DT Book Review C1 US Space Command, Peterson AFB, CO USA. RP Fuller, T (reprint author), US Space Command, Peterson AFB, CO USA. NR 1 TC 0 Z9 0 U1 0 U2 0 PU UNIV CALIF PRESS PI BERKELEY PA JOURNALS DEPT 2120 BERKELEY WAY, BERKELEY, CA 94720 USA SN 0272-3433 J9 PUBL HISTORIAN JI Public Hist. PD FAL PY 1998 VL 20 IS 4 BP 108 EP 110 PG 3 WC History SC History GA 141WR UT WOS:000077167700028 ER PT J AU Erickson, EF AF Erickson, EF TI Effects of telluric water vapor on airborne infrared observations SO PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF THE PACIFIC LA English DT Article AB Atmospheric effects on astronomical observations from aircraft are described. The most extensive effects and those most influenced by flight parameters are due to atmospheric water vapor at far-infrared wavelengths. This paper evaluates these effects in terms of observing efficiency for different observing modes. For the anticipated Stratospheric Observatory for infrared Astronomy (SOFIA) program, roughly a 10% reduction in observing time will result from a 1 mu m reduction of the average water vapor overburden. Strategies for maximizing observing efficiency are discussed in the context of SOFIA, operations. C1 NASA, Ames Res Ctr, Div Space Sci, Moffett Field, CA 94035 USA. RP Erickson, EF (reprint author), NASA, Ames Res Ctr, Div Space Sci, MS 245-6, Moffett Field, CA 94035 USA. NR 22 TC 6 Z9 6 U1 0 U2 0 PU ASTRONOMICAL SOC PACIFIC PI SAN FRANCISCO PA 390 ASHTON AVE, SAN FRANCISCO, CA 94112 USA SN 0004-6280 J9 PUBL ASTRON SOC PAC JI Publ. Astron. Soc. Pac. PD SEP PY 1998 VL 110 IS 751 BP 1098 EP 1105 DI 10.1086/316218 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 125CM UT WOS:000076219900012 ER PT J AU Poi, SLC Ruf, CS Keihm, SJ AF Poi, SLC Ruf, CS Keihm, SJ TI Improved 20- to 32-GHz atmospheric absorption model SO RADIO SCIENCE LA English DT Article ID MICROWAVE RADIOMETER; WATER-VAPOR; RADIOSONDE AB An improved model for the absorption of the atmosphere near the 22-GHz water vapor line is presented. The Van Vleck-Weisskopf line shape is used with a simple parameterized version of the model from Liebe et al. [1993] for the water vapor absorption spectra and a scaling of the model from Rosenkranz [1993] for the 20- to 32-GHz oxygen absorption. Radiometric brightness temperature measurements from two sites of contrasting climatological properties, San Diego, California, and West Palm Beach, Florida, were used as ground truth for comparison with in situ radiosonde-derived brightness temperatures under clear-sky conditions. Estimation of the new model's four parameters, related to water vapor line strength, line width and continuum absorption, and far-wing oxygen absorption, was performed using the Newton-Raphson inversion method. Improvements to the water vapor line strength and line width parameters are found to be statistically significant. The accuracy of the new absorption model is estimated to be 3% between 20 and 24 GHz, degrading to 8% near 32 GHz. In addition, the Hill line shape asymmetry ratio was evaluated on several currently used models to show the agreement of the data with Van Vleck-Weisskopf based models and to rule out water vapor absorption models near 22 GHz given by Waters [1976] and Ulaby et al. [1981], which are based on the Gross line shape. C1 Penn State Univ, Commun & Space Sci Lab, University Pk, PA 16802 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Poi, SLC (reprint author), Penn State Univ, Commun & Space Sci Lab, University Pk, PA 16802 USA. RI Ruf, Christopher/I-9463-2012 NR 33 TC 19 Z9 19 U1 1 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0048-6604 J9 RADIO SCI JI Radio Sci. PD SEP-OCT PY 1998 VL 33 IS 5 BP 1319 EP 1333 PG 15 WC Astronomy & Astrophysics; Geochemistry & Geophysics; Meteorology & Atmospheric Sciences; Remote Sensing; Telecommunications SC Astronomy & Astrophysics; Geochemistry & Geophysics; Meteorology & Atmospheric Sciences; Remote Sensing; Telecommunications GA 125UL UT WOS:000076255400005 ER PT J AU Linfield, RP AF Linfield, RP TI Effect of aperture averaging upon tropospheric phase fluctuations seen with a radio antenna SO RADIO SCIENCE LA English DT Article ID WATER-VAPOR; REFRACTIVE-INDEX; OUTER SCALE; INTERFEROMETRY AB The spectrum of tropospheric, phase fluctuations expected for a radio antenna at timescales <100 s on a space to ground link has been calculated. A new feature included in these calculations is the effect of aperture averaging, which causes a reduction in delay fluctuations on timescales less than the antenna wind speed crossing time, similar to D/(8 m/s) (D is the antenna diameter). On timescales less than a few seconds, the Allan deviation sigma(y)(Delta t) proportional to (Delta t)(+1), rather than sigma(y)(Delta t) proportional to (Delta t)(-1/6) without aperture averaging. Calibration of tropospheric phase fluctuations with water vapor radiometers will not be possible: on timescales less than similar to 10 s, due to thermal radiometer noise. However, the tropospheric fluctuation level will be small enough that phase measurements on timescales less than a few seconds will be limited by the stability of frequency standards and/or other nontropospheric effects. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Linfield, RP (reprint author), CALTECH, Jet Prop Lab, 238-600,4800 Oak Grove Dr, Pasadena, CA 91109 USA. EM rpl@logos.jgl.nasa.gov NR 17 TC 5 Z9 5 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0048-6604 J9 RADIO SCI JI Radio Sci. PD SEP-OCT PY 1998 VL 33 IS 5 BP 1353 EP 1359 DI 10.1029/98RS02316 PG 7 WC Astronomy & Astrophysics; Geochemistry & Geophysics; Meteorology & Atmospheric Sciences; Remote Sensing; Telecommunications SC Astronomy & Astrophysics; Geochemistry & Geophysics; Meteorology & Atmospheric Sciences; Remote Sensing; Telecommunications GA 125UL UT WOS:000076255400007 ER PT J AU Green, RO Eastwood, ML Sarture, CM Chrien, TG Aronsson, M Chippendale, BJ Faust, JA Pavri, BE Chovit, CJ Solis, MS Olah, MR Williams, O AF Green, RO Eastwood, ML Sarture, CM Chrien, TG Aronsson, M Chippendale, BJ Faust, JA Pavri, BE Chovit, CJ Solis, MS Olah, MR Williams, O TI Imaging spectroscopy and the Airborne Visible Infrared Imaging Spectrometer (AVIRIS) SO REMOTE SENSING OF ENVIRONMENT LA English DT Review ID SPECTRAL MIXTURE ANALYSIS; ATMOSPHERIC CORRECTIONS; LOSSLESS COMPRESSION; SURFACE-REFLECTANCE; GREEN VEGETATION; DEATH-VALLEY; REMOTE; CANOPY; IMAGES; CALIFORNIA AB Imaging spectroscopy is of growing interest as a new approach to Earth remote sensing. The Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) was the first imaging sensor to measure the solar reflected spectrum from 400 nm to 2500 nm at 10 nm intervals. The calibration accuracy and signal-to-noise of AVIRIS remain unique. The AVIRIS system as well as the science research and applications have evolved significantly in recent years. The initial design and upgraded characteristics of the AVIRIS system are described in terms of the sensor, calibration, data system, and flight operation. This update on the characteristics of AVIRIS provides the context for the science research and applications that use AVIRIS data acquired in the past several years. Recent science research and applications are reviewed spanning investigations of atmospheric correction, ecology and vegetation, geology and soils, inland and coastal waters, the atmosphere, snow and ice hydrology, biomass burning, environmental hazards, satellite simulation and calibration commercial applications, spectral algorithms, human infrastructure, as well as spectral modeling. (C)Elsevier Science Inc., 1998 C1 CALTECH, Jet Prop Lab, Pasadena, CA USA. RP Green, RO (reprint author), JPL Mail Stop 306-438,4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 148 TC 770 Z9 793 U1 15 U2 138 PU ELSEVIER SCIENCE INC PI NEW YORK PA 655 AVENUE OF THE AMERICAS, NEW YORK, NY 10010 USA SN 0034-4257 J9 REMOTE SENS ENVIRON JI Remote Sens. Environ. PD SEP PY 1998 VL 65 IS 3 BP 227 EP 248 DI 10.1016/S0034-4257(98)00064-9 PG 22 WC Environmental Sciences; Remote Sensing; Imaging Science & Photographic Technology SC Environmental Sciences & Ecology; Remote Sensing; Imaging Science & Photographic Technology GA 112ZL UT WOS:000075524700001 ER PT J AU Roberts, DA Gardner, M Church, R Ustin, S Scheer, G Green, RO AF Roberts, DA Gardner, M Church, R Ustin, S Scheer, G Green, RO TI Mapping chaparral in the Santa Monica Mountains using multiple endmember spectral mixture models SO REMOTE SENSING OF ENVIRONMENT LA English DT Article ID MULTISPECTRAL IMAGES; REFLECTANCE SPECTRA; BRAZILIAN AMAZON; VEGETATION; ABUNDANCE; DESERTS; AVIRIS AB A new technique, called multiple endmember spectral mixture analysis (MESMA), was developed and tested in the Santa Monica Mountains, using Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) data acquired in the fall of 1994 to map California chaparral. The technique models remotely measured spectra as linear combinations of pure spectra, called endmembers, while allowing the types and number of endmembers to vary on a per pixel basis. In this manner, vegetation is characterized by a unique set of endmembers as well as by the fractions. Reference endmembers were selected from a library of field and laboratory measured spectra of leaves, canopies, nonphotosynthetic materials (e.g., stems), and soils and used to develop a series of candidate models. Each candidate model was applied to the image, then, on a per pixel basis, assessed in terms of fractions, root mean squared (RMS) error, and residuals. If a model met all criteria, it was listed as a candidate for that pixel. For this study, selection criteria included fractions between -0.01 and 1.01, an RMS less than 0.025 and a residual less than 0.025 in seven or more contiguous bands. A total of 889 two-endmember models were evaluated and used to generate 276 three-endmember models. To facilitate model selection from a large pool of candidates, an optimal set was selected to provide maximal areal coverage. A total of 24 two-endmember and 12 three-endmember models were chosen. These models were used to generate fraction images and vegetation maps showing evergreen and drought deciduous or senesced vegetation. We found that a majority of the image could be modeled as two-endmember models. Three-endmember models provided greater areal coverage, yet provided poorer vegetation discrimination due to an increase in model overlap (two or more model candidates modeling the same pixel). The vegetation maps demonstrate that the technique is capable of discriminating a large number of spectrally distinct types of vegetation while capturing the mosaic-like spatial distribution typical of chaparral. However, additional research is required to fully evaluate the technique and validate the vegetation maps that were produced. (C)Elsevier Science Inc., 1998 C1 Univ Calif Santa Barbara, Dept Geog, Santa Barbara, CA 93106 USA. Univ Calif Davis, Dept Land Air & Water Resources, Davis, CA USA. CALTECH, Jet Prop Lab, Pasadena, CA USA. RP Roberts, DA (reprint author), Univ Calif Santa Barbara, Dept Geog, Ellison Hall 3611, Santa Barbara, CA 93106 USA. EM dar@geog.ucsb.edu NR 31 TC 595 Z9 656 U1 8 U2 82 PU ELSEVIER SCIENCE INC PI NEW YORK PA 655 AVENUE OF THE AMERICAS, NEW YORK, NY 10010 USA SN 0034-4257 J9 REMOTE SENS ENVIRON JI Remote Sens. Environ. PD SEP PY 1998 VL 65 IS 3 BP 267 EP 279 DI 10.1016/S0034-4257(98)00037-6 PG 13 WC Environmental Sciences; Remote Sensing; Imaging Science & Photographic Technology SC Environmental Sciences & Ecology; Remote Sensing; Imaging Science & Photographic Technology GA 112ZL UT WOS:000075524700004 ER PT J AU Painter, TH Roberts, DA Green, RO Dozier, J AF Painter, TH Roberts, DA Green, RO Dozier, J TI The effect of grain size on spectral mixture analysis of snow-covered area from AVIRIS data SO REMOTE SENSING OF ENVIRONMENT LA English DT Article ID LANDSAT THEMATIC MAPPER; MULTISPECTRAL IMAGES; DRY SNOW; RESOLUTION; VEGETATION; ALBEDO AB We developed a technique to improve spectral mixture analysis of snow-covered area in alpine regions through the use of multiple snow endmembers. Snow reflectance in near-infrared wavelengths is sensitive to snow grain size while in visible wavelengths it is relatively insensitive. Snow-covered alpine regions often exhibit large surface grain size gradients due to changes in aspect and elevation. The sensitivity of snow spectral reflectance to grain size translates these grain size gradients into spectral nature of snow must be accounted for by use of multiple snow endmembers of varying grain size. We performed numerical simulations to demonstrate the sensitivity of mixture analysis to grain size for a range of sizes and snow fractions. From Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) data collected over Mammoth Mountain CA on 5 April 1994, a suite of snow image endmembers spanning the imaged region's grain size range were extracted. Mixture models with fixed vegetation, rock, and shade were applied with each snow endmember. For each pixel, the snow fraction estimated by the model with least mixing error (RMS) was chosen to produce an optimal map of subpixel snow-covered area. Results were verified with a high spatial resolution aerial photograph demonstrating equivalent accuracy. Analysis of fraction under/overflow and residuals confirmed mixture analysis sensitivity to grain size gradients. (C) Elsevier Science Inc., 1998 C1 Univ Calif Santa Barbara, Inst Computat Earth Syst Sci, Santa Barbara, CA 93106 USA. Univ Calif Santa Barbara, Dept Geog, Santa Barbara, CA 93106 USA. CALTECH, Jet Prop Lab, Pasadena, CA USA. Univ Calif Santa Barbara, Donald Bren Sch Environm Sci & Management, Santa Barbara, CA 93106 USA. RP Painter, TH (reprint author), Univ Calif Santa Barbara, Inst Computat Earth Syst Sci, 6th Floor Ellison, Santa Barbara, CA 93106 USA. RI Dozier, Jeff/B-7364-2009; Painter, Thomas/B-7806-2016 OI Dozier, Jeff/0000-0001-8542-431X; NR 39 TC 115 Z9 119 U1 1 U2 16 PU ELSEVIER SCIENCE INC PI NEW YORK PA 655 AVENUE OF THE AMERICAS, NEW YORK, NY 10010 USA SN 0034-4257 J9 REMOTE SENS ENVIRON JI Remote Sens. Environ. PD SEP PY 1998 VL 65 IS 3 BP 320 EP 332 DI 10.1016/S0034-4257(98)00041-8 PG 13 WC Environmental Sciences; Remote Sensing; Imaging Science & Photographic Technology SC Environmental Sciences & Ecology; Remote Sensing; Imaging Science & Photographic Technology GA 112ZL UT WOS:000075524700008 ER PT J AU Weissman, PR AF Weissman, PR TI The Oort cloud SO SCIENTIFIC AMERICAN LA English DT Article C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. NASA, Deep Space 4 Champoll Miss, Washington, DC USA. RP Weissman, PR (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 4 TC 2 Z9 2 U1 0 U2 1 PU SCI AMERICAN INC PI NEW YORK PA 415 MADISON AVE, NEW YORK, NY 10017 USA SN 0036-8733 J9 SCI AM JI Sci.Am. PD SEP PY 1998 VL 279 IS 3 BP 84 EP 89 PG 6 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA 111FL UT WOS:000075426600026 ER PT J AU McClain, CR Cleave, ML Feldman, GC Gregg, WW Hooker, SB Kuring, N AF McClain, CR Cleave, ML Feldman, GC Gregg, WW Hooker, SB Kuring, N TI Science quality SeaWiFS data for global biosphere research SO SEA TECHNOLOGY LA English DT Article ID COASTAL C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 35812 USA. RP McClain, CR (reprint author), NASA, Goddard Space Flight Ctr, Greenbelt, MD 35812 USA. RI Hooker, Stanford/E-2162-2012 NR 21 TC 268 Z9 274 U1 2 U2 9 PU COMPASS PUBL INC PI ARLINGTON PA SUITE 1000 1117 N 19 ST, ARLINGTON, VA 22209 USA SN 0093-3651 J9 SEA TECHNOL JI Sea Technol. PD SEP PY 1998 VL 39 IS 9 BP 10 EP 16 PG 7 WC Engineering, Ocean SC Engineering GA 121ZK UT WOS:000076045800002 ER PT J AU Dozier, G Homaifar, A Bryson, S Bikdash, M AF Dozier, G Homaifar, A Bryson, S Bikdash, M TI Artificial potential field-based motion planning/navigation, dynamic constrained optimization and simple genetic hill climbing SO SIMULATION LA English DT Article DE motion planning; navigation; genetic algorithms; artificial potential field; constrained optimization; robot; simple genetic hill climbing; steepest descent hill climbing; NASA; AGIE3 AB In this paper we show a relationship between artificial potential field (APF) based motion planning/navigation, and constrained optimization. We then present a simple genetic hill climbing algorithm (SGHC), which is used to navigate a point robot through an environment using the APF approach. We compare SGHC with steepest descent hill climbing (SDHC). In SDHC, candidate moves are evaluated within a 360-degree radius and the best candidate is selected by the robot. One would think that SGHC would be at a disadvantage; however, the performance of SGHC is comparable with SDHC. SGHC has an advantage in that it is capable of evolving (learning) the appropriate step size as well as the appropriate angle of movement. C1 Auburn Univ, Dept Comp Sci & Engn, Auburn, AL 36849 USA. N Carolina Agr & Tech State Univ, NASA, Ctr Autonomous Control Engn, Greensboro, NC 27411 USA. RP Dozier, G (reprint author), Auburn Univ, Dept Comp Sci & Engn, Auburn, AL 36849 USA. EM gvdozier@eng.auburn.edu; homaifar@ncat.edu; sidney@ncat.edu NR 31 TC 1 Z9 1 U1 0 U2 1 PU SIMULATION COUNCILS INC PI SAN DIEGO PA PO BOX 17900, SAN DIEGO, CA 92117 USA SN 0037-5497 J9 SIMULATION JI Simulation PD SEP PY 1998 VL 71 IS 3 BP 168 EP 181 DI 10.1177/003754979807100303 PG 14 WC Computer Science, Interdisciplinary Applications; Computer Science, Software Engineering SC Computer Science GA 160FE UT WOS:000078219100003 ER PT J AU McClure, JC Singh, VP Lush, GB Clark, E Thompson, G AF McClure, JC Singh, VP Lush, GB Clark, E Thompson, G TI Foil mounted thin-film solar cells for space and terrestrial applications SO SOLAR ENERGY MATERIALS AND SOLAR CELLS LA English DT Article; Proceedings Paper CT International Symposium on H2 Fuel Cell Photovoltaic Systems CY AUG 31-SEP 05, 1998 CL CANCUN, MEXICO DE solar cells; photovoltaics; CdTe; Cds AB The developing photovoltaic market for civilian communications satellites has caused a reassessment of the traditional single-crystal cells used in space. Thin-him cells mounted on metal foil substrates offer considerable weight, manufacturing, and radiation resistance advantages. These same cells can solve the manufacturing problems of glass breakage and temperature uniformity in cells intended for terrestrial applications. This paper describes work on a back-wall CdS/CdTe cell on molybdenum foils. Large grained adherent films of CdTe are formed. A thin interlayer of Cu and Te between the CdTe and the molybdenum formed a low resistance (less than 1 Ohm cm(2)) ohmic contact. The cell is completed with a sputtered indium tin oxide top contact layer and a V-oc of 580 mV was obtained. (C) 1998 Elsevier Science B.V. All rights reserved. C1 Univ Texas, Dept Met & Mat Engn, El Paso, TX 79968 USA. Univ Texas, Dept Elect & Comp Engn, El Paso, TX 79968 USA. NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. RP McClure, JC (reprint author), Univ Texas, Dept Met & Mat Engn, El Paso, TX 79968 USA. NR 8 TC 14 Z9 14 U1 0 U2 3 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0927-0248 J9 SOL ENERG MAT SOL C JI Sol. Energy Mater. Sol. Cells PD SEP PY 1998 VL 55 IS 1-2 BP 141 EP 148 DI 10.1016/S0927-0248(98)00054-3 PG 8 WC Energy & Fuels; Materials Science, Multidisciplinary; Physics, Applied SC Energy & Fuels; Materials Science; Physics GA 119XM UT WOS:000075923700016 ER PT J AU Bhatia, AK Kastner, SO AF Bhatia, AK Kastner, SO TI Opacity in the Si III spectrum SO SOLAR PHYSICS LA English DT Article ID SOLAR TRANSITION REGION; EMISSION-LINE RATIOS; RR-TELESCOPII; APPROXIMATE CALCULATION; C-III; IUE; LIST; STAR; PROMINENCES; TEMPERATURE AB The opacities of the Si III resonance line at 1206.5 Angstrom and component lines of the UV 4 multiplet near 1300 Angstrom are analyzed and re-examined in published spectra, taking account of improved expressions for photon escape probabilities and making use of an intensity/linewidth analysis recently developed. Level populations and line intensities are computed to extend knowledge of the optically thin spectrum to lower densities. Diagnostic diagrams of line ratios are included. Opacities are found to be higher than in previous treatments. C1 NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, Greenbelt, MD 20771 USA. RP Bhatia, AK (reprint author), NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, Greenbelt, MD 20771 USA. NR 34 TC 6 Z9 6 U1 0 U2 0 PU KLUWER ACADEMIC PUBL PI DORDRECHT PA SPUIBOULEVARD 50, PO BOX 17, 3300 AA DORDRECHT, NETHERLANDS SN 0038-0938 J9 SOL PHYS JI Sol. Phys. PD SEP PY 1998 VL 182 IS 1 BP 37 EP 63 DI 10.1023/A:1005057808400 PG 27 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 138CW UT WOS:000076954700003 ER PT J AU Wilson, RM AF Wilson, RM TI A comparison of Wolf's reconstructed record of annual sunspot number with Schwabe's observed record of 'clusters of spots' for the interval of 1826-1868 SO SOLAR PHYSICS LA English DT Article ID MAUNDER MINIMUM AB Samuel Heinrich Schwabe, the discoverer of the sunspot cycle, observed the Sun routinely from Dessau, Germany during the interval of 1826-1868, averaging about 290 observing days per year. His yearly counts of 'clusters of spots' (or, more correctly, the yearly number of newly appearing sunspot groups) provided a simple means for describing the overt features of the sunspot cycle (i.e., the timing and relative strengths of cycle minimum and maximum). In 1848, Rudolf Wolf, a Swiss astronomer, having become aware of Schwabe's discovery, introduced his now familiar 'relative sunspot number' and established an international cadre of observers for monitoring the future behavior of the sunspot cycle and for reconstructing its past behavior (backwards in time to 1818, based on daily sunspot number estimates). While Wolf's reconstruction is complete (without gaps) only from 1849 (hence, the beginning of the modern era), the immediately preceding interval of 1818-1848 is incomplete, being based on an average of 260 observing days per year. In this investigation, Wolf's reconstructed record of annual sunspot number is compared against Schwabe's actual observing record of yearly counts of clusters of spots. The comparison suggests that Wolf may have misplaced (by about 1-2 yr) and underestimated (by about 16 units of sunspot number) the maximum amplitude for cycle 7. If true, then, cycle '7's ascent and descent durations should measure about 5 years each instead of 7 and 3 years, respectively, the extremes of the distributions, and its maximum amplitude should measure about 86 instead of 70. This study also indicates that cycle 9's maximum amplitude is more reliably determined than cycle 8's and that both appear to be of comparable size (about 130 units of sunspot number) rather than being significantly different. Therefore, caution is urged against the indiscriminate use of the pre-modern era sunspot numbers in long-term studies of the sunspot cycle, since such use may lead to specious results. C1 NASA, Marshall Space Flight Ctr, Space Sci Lab, Huntsville, AL 35812 USA. RP Wilson, RM (reprint author), NASA, Marshall Space Flight Ctr, Space Sci Lab, Huntsville, AL 35812 USA. NR 21 TC 25 Z9 25 U1 0 U2 0 PU SPRINGER PI DORDRECHT PA VAN GODEWIJCKSTRAAT 30, 3311 GZ DORDRECHT, NETHERLANDS SN 0038-0938 EI 1573-093X J9 SOL PHYS JI Sol. Phys. PD SEP PY 1998 VL 182 IS 1 BP 217 EP 230 PG 14 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 138CW UT WOS:000076954700014 ER PT J AU Mattes, RA AF Mattes, RA TI Defining spectroscopy SO SPECTROSCOPY LA English DT Letter C1 George C Marshall Space Flight Ctr, Huntsville, AL USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU ADVANSTAR COMMUNICATIONS PI DULUTH PA 131 W FIRST ST, DULUTH, MN 55802 USA SN 0887-6703 J9 SPECTROSCOPY JI Spectroscopy PD SEP PY 1998 VL 13 IS 9 BP 8 EP 8 PG 1 WC Spectroscopy SC Spectroscopy GA 117KU UT WOS:000075781100001 ER PT J AU Van Doornik, DM Winans, GA AF Van Doornik, DM Winans, GA TI Inheritance of allozymes in coho salmon SO TRANSACTIONS OF THE AMERICAN FISHERIES SOCIETY LA English DT Article ID CHINOOK SALMON; PACIFIC-NORTHWEST; GENETIC-BASIS; CHUM SALMON; LOCI; DEHYDROGENASE; VARIABILITY AB We examined allozyme variation in the parents and offspring of 41 crossings of coho salmon Oncorhynchus kisutch. Mendelian inheritance previously unreported for Pacific salmon was confirmed at 11 loci: sAAT-4*, sAH*, ALAT*, EST-1*, beta GALA*, GAPDH-2*, GPI-B2*, sMDH-A1,2*, PEPA*, PEPC*, and PNP-1*. Independent assortment was found for the following locus pairs: ADA-1* and beta GALA*, ALAT* and beta GALA*, ALAT* and EST-1*, EST-1* and beta GALA*, EST-1* and PEPC*, GAPDH-2* and PNP-1*, beta GALA* and GPI-B2*, beta GALA* and sMDH-A1,2*, and beta GALA* and PEPC*. C1 NOAA, Natl Marine Fisheries Serv, NW Fisheries Sci Ctr, Seattle, WA 98112 USA. RP Van Doornik, DM (reprint author), Natl Marine Fisheries Serv, POB 130, Manchester, WA 98353 USA. EM don.vandoornik@noaa.gov NR 29 TC 2 Z9 2 U1 2 U2 2 PU TAYLOR & FRANCIS INC PI PHILADELPHIA PA 325 CHESTNUT ST, SUITE 800, PHILADELPHIA, PA 19106 USA SN 0002-8487 J9 T AM FISH SOC JI Trans. Am. Fish. Soc. PD SEP PY 1998 VL 127 IS 5 BP 833 EP 837 DI 10.1577/1548-8659(1998)127<0833:IOAICS>2.0.CO;2 PG 5 WC Fisheries SC Fisheries GA 142JY UT WOS:000077198200014 ER PT J AU Dwyer, JH Sun, P Kwong-Fu, H Dwyer, KM Selzer, RH AF Dwyer, JH Sun, P Kwong-Fu, H Dwyer, KM Selzer, RH TI Automated intima-media thickness: The Los Angeles atherosclerosis study SO ULTRASOUND IN MEDICINE AND BIOLOGY LA English DT Article DE atherosclerosis; coronary heart disease; cerebrovascular disease; ultrasonography; carotid artery; intima-media thickness; reproducibility ID CORONARY HEART-DISEASE; COLESTIPOL-NIACIN THERAPY; ARTERIAL-WALL THICKNESS; COMMON CAROTID-ARTERY; RISK-FACTORS; COMMUNITIES; ULTRASOUND; REPRODUCIBILITY; VARIABILITY; REDUCTION AB Common carotid artery (CCA) intima-media thickness (IMT) from B-mode ultrasound is a widely used measure of early atherosclerosis. This study evaluated within- and between-sonographer reproducibility of automated edge-tracking IMT using a low-cost mobile scanner. B-mode images of the left and right CCA were acquired on two occasions (interval of 2-14 days) by two sonographers for 38 subjects, aged 31-75 y, Reproduciblity error was measured as the mean absolute difference (MAD +/- SEM) and the standard deviation of differences (SD Delta) between repeated measurements. Within-sonographer (MAD = 0.027 +/- 0.006 mm; SD Delta = 0.044 mm) and between-sonographer errors (MAD = 0.041 +/- 0.008 mm; SD Delta = 0.064) in IMT (mean = 0.74, SD = 0.14) of a single artery were small compared to those of other protocols. Combined averaging across both body positions and arteries I educed intersonographer MAD by 47% (MAD = 0.022 +/- 0.003 mm; SD Delta = 0.029 mm), These data demonstrate that the proposed IMT protocol reduces reproducibility error by more than 50% relative to several protocols used in other major studies. (C) 1998 World Federation for Ultrasound in Medicine & Biology. C1 Univ So Calif, Sch Med, Inst Hlth Promot & Dis Prevent Res, Dept Prevent Med, Los Angeles, CA 90033 USA. CALTECH, NASA, Jet Propuls Lab, Pasadena, CA 91125 USA. RP Dwyer, JH (reprint author), Univ So Calif, Sch Med, Inst Prevent Res, Dept Prevent Med, 1540 Alcazar St,CHP205, Los Angeles, CA 90033 USA. FU NHLBI NIH HHS [HL49910] NR 20 TC 28 Z9 28 U1 0 U2 1 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0301-5629 J9 ULTRASOUND MED BIOL JI Ultrasound Med. Biol. PD SEP PY 1998 VL 24 IS 7 BP 981 EP 987 DI 10.1016/S0301-5629(98)00069-6 PG 7 WC Acoustics; Radiology, Nuclear Medicine & Medical Imaging SC Acoustics; Radiology, Nuclear Medicine & Medical Imaging GA 121TF UT WOS:000076029500005 PM 9809632 ER PT J AU Mattikalli, NM Engman, ET Jackson, TJ Ahuja, LR AF Mattikalli, NM Engman, ET Jackson, TJ Ahuja, LR TI Microwave remote sensing of temporal variations of brightness temperature and near-surface soil water content during a watershed-scale field experiment, and its application to the estimation of soil physical properties SO WATER RESOURCES RESEARCH LA English DT Article ID PARTICLE-SIZE DISTRIBUTION; HYDRAULIC CONDUCTIVITY; ORGANIC-MATTER; RETENTION; MOISTURE; MANAGEMENT; PARAMETERS; DRAINAGE; PREDICT; TEXTURE AB Passive microwave airborne remote sensing was employed to collect daily brightness temperature (T(B)) and near-surface (0-5 cm depth) soil water content (referred to as "soil water content") data during June 10-18, 1992. in the Little Washita watershed, Oklahoma. A comparison of multitemporal data with the soils data revealed a direct correlation between changes in T(B) and soil water content, and soil texture. Regression relationships were developed for the ratio of percent sand to percent clay (RSC) and effective saturated hydraulic conductivity (K(sat)) in terms of T(B) and soil water content change. Validation of results indicated that both RSC and K(sat) can be estimated with adequate accuracy. The relationships are valid for the region with Small variation Of soil organic matter content, soils with fewer macropores, and limiting experimental conditions. However, the findings have potential to employ microwave remote sensing for obtaining quick estimates of soil properties over large areas. C1 NASA, Goddard Space Flight Ctr, Hydrol Sci Branch, Lab Hydrospher Proc, Greenbelt, MD 20771 USA. USDA ARS, Ft Collins, CO 80522 USA. USDA ARS, Beltsville Agr Res Ctr, Hydrol Lab, Beltsville, MD 20705 USA. RP Mattikalli, NM (reprint author), NASA, Goddard Space Flight Ctr, Hydrol Sci Branch, Lab Hydrospher Proc, Code 974, Greenbelt, MD 20771 USA. EM nandish@hydro5.gsfc.nasa.gov NR 39 TC 38 Z9 41 U1 0 U2 11 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0043-1397 J9 WATER RESOUR RES JI Water Resour. Res. PD SEP PY 1998 VL 34 IS 9 BP 2289 EP 2299 DI 10.1029/98WR00553 PG 11 WC Environmental Sciences; Limnology; Water Resources SC Environmental Sciences & Ecology; Marine & Freshwater Biology; Water Resources GA 115PX UT WOS:000075674800017 ER PT J AU Owe, M Van de Griend, AA AF Owe, M Van de Griend, AA TI Comparison of soil moisture penetration depths for several bare soils at two microwave frequencies and implications for remote sensing SO WATER RESOURCES RESEARCH LA English DT Article ID WATER; MODELS AB Microwave brightness temperature measurements were made over three different bare soils at frequencies of 5 GHz (lambda= 6 cm) and 1.67 GHz (lambda = 18 cm) to compare differences in penetration depth according to texture, soil moisture, and wavelength. The soil plots were wetted, and circularly polarized microwave measurements were made during the dry-down cycle. Soil profile temperature and profile moisture content were monitored continuously for the duration of the experiment. Laboratory analyses of soil physical properties such as texture and bulk density were conducted to aid theoretical calculations of the soil dielectric constants. Laboratory measurements of the soil dielectric constants were also made. Two commonly used soil dielectric models were compared. Theoretical values of soil dielectric constant were calculated with the Dobson model and the Wang-Schmugge model, and both compared reasonably well with laboratory measurements and also to values reported in the literature. Calculated soil emissivities derived from the field measurements also compared well with emissivities calculated from both the modeled dielectrics and those measured in the laboratory. Emissivities were compared with the average soil moisture for surface profiles of varying thickness. It was found that the observed effective penetration depth appeared to exceed the theoretically defined values. C1 NASA, Goddard Space Flight Ctr, Hydrol Sci Branch, Greenbelt, MD 20771 USA. Vrije Univ Amsterdam, Inst Earth Sci, NL-1081 HV Amsterdam, Netherlands. RP Owe, M (reprint author), NASA, Goddard Space Flight Ctr, Hydrol Sci Branch, Mail Code 974, Greenbelt, MD 20771 USA. NR 22 TC 26 Z9 26 U1 0 U2 7 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0043-1397 J9 WATER RESOUR RES JI Water Resour. Res. PD SEP PY 1998 VL 34 IS 9 BP 2319 EP 2327 DI 10.1029/98WR01469 PG 9 WC Environmental Sciences; Limnology; Water Resources SC Environmental Sciences & Ecology; Marine & Freshwater Biology; Water Resources GA 115PX UT WOS:000075674800020 ER PT J AU Geerts, B AF Geerts, B TI Mesoscale convective systems in the southeast United States during 1994-95: A survey SO WEATHER AND FORECASTING LA English DT Article ID MIDLATITUDE SQUALL LINE; CLOUD CLUSTERS; PRECIPITATION; COMPLEXES; OKLAHOMA; REGION; RADAR; EVOLUTION; RAIN AB A preliminary survey of mesoscale convective systems (MCSs) in the southeastern United Stares is presented. MCSs are identified and characterized by means of high-resolution, digital, composite radar reflectivity data. Surveys of this kind are needed to give forecasters better guidance in their real-time assessment of MCS evolution, severe weather potential, and quantitative precipitation. The average lifetime and maximum length of the nearly 400 MCSs included in this survey are 9 h and 350 km, respectively. MCSs are more common in the summer months. when small and short-lived MCSs dominate. In winter larger and longer-lived systems occur more frequently. Because cold-season MCSs, which are about half as numerous as warm-season MCSs, are larger in size and duration, the MCS probability at any location is about constant throughout the year. In summer MCSs occur more commonly in the afternoon. approximately in phase with thunderstorm activity, but the amplitude of the diurnal cycle is small compared to that of observed thunderstorms. Some characteristic echo patterns are discussed. C1 Embry Riddle Univ, Prescott, AZ USA. RP Geerts, B (reprint author), NASA, Goddard Space Flight Ctr, Code 912, Greenbelt, MD 20771 USA. EM geerts@agnes.gsfc.nasa.gov NR 42 TC 25 Z9 30 U1 0 U2 4 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 USA SN 0882-8156 J9 WEATHER FORECAST JI Weather Forecast. PD SEP PY 1998 VL 13 IS 3 BP 860 EP 869 DI 10.1175/1520-0434(1998)013<0860:MCSITS>2.0.CO;2 PN 2 PG 10 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 130HD UT WOS:000076513400019 ER PT J AU Christian, JR Karl, DM AF Christian, JR Karl, DM TI Ectoaminopeptidase specificity and regulation in Antarctic marine pelagic microbial communities SO AQUATIC MICROBIAL ECOLOGY LA English DT Article DE aminopeptidase; enzyme specificity; enzyme regulation; Antarctica ID EXOPROTEOLYTIC ACTIVITY; ORGANIC-MATTER; WATERS; AMINOPEPTIDASE; OCEAN; SEAWATER; BACTERIA; IRON; SEA AB Ectoaminopeptidase activities of pelagic marine microbial communities were investigated on several research cruises in the western Antarctic Peninsula region from 1992 to 1994, using the fluorigenic substrate analogue L-leucyl-beta-naphthylamine. K-m values at in situ temperature were comparable to those observed by other investigators for a variety of aquatic environments. Competitive inhibition by dipeptides of a variety of amino acids showed that the aminopeptidases present were broadly specific; no strong tendency toward greater affinity for hydrophobic or hydrophilic amino acids was observed. Seawater cultures (1.0 mu m filtrate) were inoculated with a variety of monomeric organic compounds and incubated for 24 to 72 h prior to activity determination; histidine and phenylalanine were found to consistently inhibit aminopeptidase expression. It is hypothesized that auxotrophy for histidine and phenylalanine may be widespread in these assemblages, giving rise to high levels of constitutive, nonspecific aminopeptidase activity which results in significant respiration of the more common amino acids. Whatever the exact mechanism, aminopeptidase activity is strongly affected by the specific compounds present and not simply by the carbon-to-nitrogen ratio. C1 NASA, Goddard Space Flight Ctr, Univ Space Res Assoc, Greenbelt, MD 20771 USA. Univ Hawaii, Sch Ocean & Earth Sci & Technol, Honolulu, HI 96822 USA. RP Christian, JR (reprint author), NASA, Goddard Space Flight Ctr, Univ Space Res Assoc, Code 970-2, Greenbelt, MD 20771 USA. EM jrc@bluefin.gsfc.nasa.gov NR 45 TC 16 Z9 16 U1 0 U2 4 PU INTER-RESEARCH PI OLDENDORF LUHE PA NORDBUNTE 23, D-21385 OLDENDORF LUHE, GERMANY SN 0948-3055 EI 1616-1564 J9 AQUAT MICROB ECOL JI Aquat. Microb. Ecol. PD AUG 31 PY 1998 VL 15 IS 3 BP 303 EP 310 DI 10.3354/ame015303 PG 8 WC Ecology; Marine & Freshwater Biology; Microbiology SC Environmental Sciences & Ecology; Marine & Freshwater Biology; Microbiology GA 117LY UT WOS:000075783800011 ER PT J AU Covault, C AF Covault, C TI Second X-38 set for flight SO AVIATION WEEK & SPACE TECHNOLOGY LA English DT Article C1 NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. RP Covault, C (reprint author), NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. NR 0 TC 2 Z9 2 U1 0 U2 0 PU MCGRAW HILL INC PI NEW YORK PA 1221 AVENUE OF THE AMERICAS, NEW YORK, NY 10020 USA SN 0005-2175 J9 AVIAT WEEK SPACE TEC JI Aviat. Week Space Technol. PD AUG 31 PY 1998 VL 149 IS 9 BP 58 EP 62 PG 5 WC Engineering, Aerospace SC Engineering GA 115UP UT WOS:000075684300027 ER PT J AU Kivelson, MG Warnecke, J Bennett, L Joy, S Khurana, KK Linker, JA Russell, CT Walker, RJ Polanskey, C AF Kivelson, MG Warnecke, J Bennett, L Joy, S Khurana, KK Linker, JA Russell, CT Walker, RJ Polanskey, C TI Ganymede's magnetosphere: Magnetometer overview SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS LA English DT Article; Proceedings Paper CT Conference on Magnetospheres of the Outer Planets CY MAR 17-21, 1997 CL BOULDER, COLORADO SP NASA, Jet Prop Lab, Galileo Project ID MAGNETIC-FIELD; GALILEO SPACECRAFT; MAGNETOPAUSE; LAYER; IO AB Ganymede presents a unique example of an internally magnetized moon whose intrinsic magnetic field excludes the plasma present at its orbit, thereby forming a magnetospheric cavity. We describe some of the properties of this mini-magnetosphere, embedded in a sub-Alfvenic flow and formed within a planetary magnetosphere. A vacuum superposition model (obtained by adding the internal field of Ganymede to the field imposed by Jupiter) organizes the data acquired by the Galileo magnetometer on four close passes in a useful, intuitive fashion. The last field line that links to Ganymede at both ends extends to similar to 2 Ganymede radii, and the transverse scale of the magnetosphere is similar to 5.5 Ganymede radii. Departures from this simple model arise from currents flowing in the Alfven wings and elsewhere on the magnetopause. The four passes give different cuts through the magnetosphere from which we develop a geometric model for the magnetopause surface as a function of the System Ln location of Ganymede. On one of the passes, Ganymede was located near the center of Jupiter's plasma disk. For this pass we identify probable Kelvin-Helmholtz surface waves on the magnetopause, After entering the relatively low-latitude upstream magnetosphere, Galileo apparently penetrated the region of closed field lines (ones that link to Ganymede at both ends), where we identify predominantly transverse fluctuations at frequencies reasonable for field line resonances. We argue that magnetic field measurements, when combined with flow measurements, show that reconnection is extremely efficient. Downstream reconnection, consequently, may account for heated plasma observed in a distant crossing of Ganymede's wake. We note some of the ways in which Ganymede's unusual magnetosphere corresponds to familiar planetary magnetospheres (viz., the magnetospheric topology and an electron ring current). We also comment on some of the ways in which it differs from familiar planetary magnetospheres (viz., relative stability and predictability of upstream plasma and field conditions, absence of a magnetotail plasma sheet and of a plasmasphere, and probable instability of the ring current). C1 Univ Calif Los Angeles, Inst Geophys & Planetary Phys, Los Angeles, CA 90095 USA. Univ Calif Los Angeles, Dept Earth & Space Sci, Los Angeles, CA 90024 USA. Sci Applicat Int Corp, San Diego, CA 92121 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Kivelson, MG (reprint author), Univ Calif Los Angeles, Inst Geophys & Planetary Phys, Los Angeles, CA 90095 USA. RI Kivelson, Margaret/I-9019-2012 OI Kivelson, Margaret/0000-0003-3859-8581 NR 14 TC 69 Z9 69 U1 0 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0148-0227 J9 J GEOPHYS RES-PLANET JI J. Geophys. Res.-Planets PD AUG 30 PY 1998 VL 103 IS E9 BP 19963 EP 19972 DI 10.1029/98JE00227 PG 10 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 116LP UT WOS:000075726800011 ER PT J AU Kaiser, ML AF Kaiser, ML TI Jovian and terrestrial low-frequency radio bursts: Possible cause of anomalous continuum SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS LA English DT Article; Proceedings Paper CT Conference on Magnetospheres of the Outer Planets CY MAR 17-21, 1997 CL BOULDER, COLORADO SP NASA, Jet Prop Lab, Galileo Project ID NONTHERMAL CONTINUUM; SOLAR-WIND; EMISSIONS; RADIATION; MAGNETOSPHERE; COMPONENT; JUPITER AB Observations by the Ulysses Unified Radio and Plasma Wave instrument show that the most intense portion of the Jovian continuum emission appears to emanate from the planet's bow shock or magnetosheath region. This intense component is highly correlated with the Jovian "type III" or quasi-periodic (QP-15 and QP-40) bursts. I suggest that this intense continuum component may be the unresolved merging of the low-frequency portion of the QP bursts and occasionally the low-frequency extent of broadband kilometric emissions which have been scattered and dispersed in the magnetosheath. A similar, but much less dramatic, effect happens at Earth with the scattering of LF bursts. C1 NASA, Extraterr Phys Lab, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Kaiser, ML (reprint author), NASA, Extraterr Phys Lab, Goddard Space Flight Ctr, Code 695, Greenbelt, MD 20771 USA. NR 19 TC 9 Z9 9 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0148-0227 J9 J GEOPHYS RES-PLANET JI J. Geophys. Res.-Planets PD AUG 30 PY 1998 VL 103 IS E9 BP 19993 EP 19999 DI 10.1029/97JE03369 PG 7 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 116LP UT WOS:000075726800014 ER PT J AU Grun, E Kruger, H Graps, AL Hamilton, DP Heck, A Linkert, G Zook, HA Dermott, S Fechtig, H Gustafson, BA Hanner, MS Horanyi, M Kissel, J Lindblad, BA Linkert, D Mann, I McDonnell, JAM Morfill, GE Polanskey, C Schwehm, G Srama, R AF Grun, E Kruger, H Graps, AL Hamilton, DP Heck, A Linkert, G Zook, HA Dermott, S Fechtig, H Gustafson, BA Hanner, MS Horanyi, M Kissel, J Lindblad, BA Linkert, D Mann, I McDonnell, JAM Morfill, GE Polanskey, C Schwehm, G Srama, R TI Galileo observes electromagnetically coupled dust in the Jovian magnetosphere SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS LA English DT Article; Proceedings Paper CT Conference on Magnetospheres of the Outer Planets CY MAR 17-21, 1997 CL BOULDER, COLORADO SP NASA, Jet Prop Lab, Galileo Project ID GOSSAMER RING; JUPITER; DISCOVERY; DETECTOR; EJECTION; STREAMS; GRAINS AB Measurements of dust coupled to the Jovian magnetosphere have been obtained with the dust detector on board the Galileo spacecraft. We report on data obtained during the first four orbits about Jupiter that had flybys of the Galilean satellites: Ganymede (orbits 1 and 2), Callisto (orbit 3), and Europa (orbit 4). The most prominent features observed are highly time variable dust streams recorded throughout the Jovian system. The impact rate varied by up to 2 orders of magnitude with a 5 and 10 hour periodicity, which shows a correlation with Galileo's position relative to the Jovian magnetic field. Around 20 R-J (Jupiter radius, R-J = 71,492 km) in bound a dip in the impact rate has been found consistently. At the same times, reversals by 180 degrees in impact direction occurred. This behavior can be qualitatively explained by strong coupling of nanometer-sized dust to the Jovian magnetic field. At times of satellite flybys, enhanced rates of dust impacts have been observed, which suggests that all Galilean satellites are sources of ejecta particles. Inside about 20 R-J impacts of micrometer-sized particles have been recorded that could be particles on bound orbits about Jupiter. C1 Max Planck Inst Kernphys, D-69117 Heidelberg, Germany. Univ Florida, Dept Astron, Gainesville, FL 32611 USA. Univ Maryland, Dept Phys, College Pk, MD 20742 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ Colorado, Atmospher & Space Phys Lab, Boulder, CO 80309 USA. Lund Observ, S-22100 Lund, Sweden. Max Planck Inst Aeron, D-37191 Katlenburg Lindau, Germany. Univ Kent, Unit Space Sci & Astrophys, Canterbury CT2 7NR, Kent, England. Max Planck Inst Extraterr Phys, D-85740 Garching, Germany. European Space Technol Ctr, NL-2200 AG Noordwijk, Netherlands. Stanford Univ, Ctr Space Sci & Astrophys, Stanford, CA 94305 USA. NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. RP Grun, E (reprint author), Max Planck Inst Kernphys, Saupfercheckweg 1, D-69117 Heidelberg, Germany. RI Gustafson, Bo/B-9526-2011; OI Horanyi, Mihaly/0000-0002-5920-9226 NR 19 TC 43 Z9 43 U1 0 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0148-0227 J9 J GEOPHYS RES-PLANET JI J. Geophys. Res.-Planets PD AUG 30 PY 1998 VL 103 IS E9 BP 20011 EP 20022 DI 10.1029/98JE00228 PG 12 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 116LP UT WOS:000075726800016 ER PT J AU James, GK Ajello, JM Pryor, WR AF James, GK Ajello, JM Pryor, WR TI The middle ultraviolet-visible spectrum of H-2 excited by electron impact SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS LA English DT Article; Proceedings Paper CT Conference on Magnetospheres of the Outer Planets CY MAR 17-21, 1997 CL BOULDER, COLORADO SP NASA, Jet Prop Lab, Galileo Project ID QUANTUM-DEFECT THEORY; MINIMUM 1-SIGMA-G+ STATES; CROSS-SECTIONS; ENERGY-LEVELS; EMISSION; HYDROGEN; EXCITATION; MOLECULE; CURVES; D-2 AB The electron-impact-induced emission spectrum of H-2 has been measured in the extended wavelength region 175-530 nm at a spectral resolution of 1.7 nm (full width at half maximum). The laboratory spectra observed in the middle ultraviolet (MUV) and visible spectral region are characterized by underlying H-2 (a (3)Sigma(g)(+) --> b (3)Sigma(u)(+)) continuum emission, together with many strong lines assigned to the radiative decay of the gerade singlet states of H-2, and to members of the H Balmer series resulting from dissociative excitation of H-2. Our calibrated MW spectral data, obtained at 14, 19, and 100 eV electron-impact energies, provide absolute emission cross sections of these H-2 lines and will assist in the interpretation of planned Galileo ultraviolet spectrometer observations of Jupiter's aurora in this wavelength region. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ Colorado, Atmospher & Space Phys Lab, Boulder, CO 80303 USA. RP James, GK (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 19 TC 15 Z9 15 U1 0 U2 3 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0148-0227 J9 J GEOPHYS RES-PLANET JI J. Geophys. Res.-Planets PD AUG 30 PY 1998 VL 103 IS E9 BP 20113 EP 20123 DI 10.1029/97JE03692 PG 11 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 116LP UT WOS:000075726800023 ER PT J AU Ajello, J Shemansky, D Pryor, W Tobiska, K Hord, C Stephens, S Stewart, I Clarke, J Simmons, K McClintock, W Barth, C Gebben, J Miller, D Sandel, B AF Ajello, J Shemansky, D Pryor, W Tobiska, K Hord, C Stephens, S Stewart, I Clarke, J Simmons, K McClintock, W Barth, C Gebben, J Miller, D Sandel, B TI Galileo orbiter ultraviolet observations of Jupiter aurora SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS LA English DT Article; Proceedings Paper CT Conference on Magnetospheres of the Outer Planets CY MAR 17-21, 1997 CL BOULDER, COLORADO SP NASA, Jet Prop Lab, Galileo Project ID HUBBLE-SPACE-TELESCOPE; INTERPLANETARY LYMAN-ALPHA; ELECTRON-IMPACT; MOLECULAR-HYDROGEN; UPPER-ATMOSPHERE; JOVIAN AURORA; SOLAR MAXIMUM; BAND SYSTEM; UV AURORA; RESOLUTION AB In 1996 during the first four orbits of the satellite tour the Galileo ultraviolet spectrometer (UVS) (1130-4320 Angstrom) and extreme ultraviolet spectrometer (EUVS) (540-1280 Angstrom) performed near-simultaneous observations of the Jupiter aurora in both the north and south polar regions. These observations are modeled to provide the absolute surface brightness of the aurora from the H-2 Rydberg Systems (B, B', B ", C, D, D' --> X band systems). The spectral distribution and brightness of the EUV aurora are sensitive to H-2 abundance, H-2 temperature, and CH4 abundance. Analysis of the emission spectra indicates that the EUV aurora (800-1200 Angstrom) are produced over a range of altitudes corresponding to slant column abundances of H-2 from 10(16) to 10(20) cm(-2) or greater. The UVS spectra of the far ultraviolet (FUV) from 1130 to 1700 Angstrom are optically thin in H-2, but highly sensitive to the CH4 column abundance and to the secondary electron energy distribution. The slant column abundance of CH4 absorbers found from models of the FUV spectra varied in the range 0 - 10 x 10(16) cm(-2), indicating the presence of both high altitude aurora, at or above the homopause, and deep aurora. The EW spectra show C2H2 absorption bands near 1520 Angstrom. The surface brightness of the aurora from the H-2 Rydberg Systems ranged from 100 to 600 kR and of H Lyman alpha was 60 to 130 kR for a 2000 km wide oval. The total power input to the atmosphere from particle deposition is estimated to be similar to 1 x 10(14) W. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ So Calif, Dept Aerosp Engn, Los Angeles, CA 90089 USA. Univ Colorado, Atmospher & Space Phys Lab, Boulder, CO 80303 USA. CALTECH, Jet Prop Lab, Fed Data Corp, Pasadena, CA 91109 USA. Univ Michigan, Space Phys Res Lab, Ann Arbor, MI 48109 USA. Univ Arizona, Lunar & Planetary Lab, Tucson, AZ 85721 USA. RP Ajello, J (reprint author), CALTECH, Jet Prop Lab, MS 183-601,4800 Oak Grove Dr, Pasadena, CA 91109 USA. EM jajello@jpluvs.ipl.nasa.gov RI Clarke, John/C-8644-2013 NR 54 TC 41 Z9 41 U1 0 U2 3 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0148-0227 J9 J GEOPHYS RES-PLANET JI J. Geophys. Res.-Planets PD AUG 30 PY 1998 VL 103 IS E9 BP 20125 EP 20148 DI 10.1029/98JE00832 PG 24 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 116LP UT WOS:000075726800024 ER PT J AU Pryor, WR Ajello, JM Tobiska, WK Shemansky, DE James, GK Hord, CW Stephens, SK West, RA Stewart, AIF McClintock, WE Simmons, KE Hendrix, AR Miller, DA AF Pryor, WR Ajello, JM Tobiska, WK Shemansky, DE James, GK Hord, CW Stephens, SK West, RA Stewart, AIF McClintock, WE Simmons, KE Hendrix, AR Miller, DA TI Galileo ultraviolet spectrometer observations of Jupiter's auroral spectrum from 1600-3200 angstrom SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS LA English DT Article; Proceedings Paper CT Conference on Magnetospheres of the Outer Planets CY MAR 17-21, 1997 CL BOULDER, COLORADO SP NASA, Jet Prop Lab, Galileo Project ID ELECTRON-IMPACT; EXCITATION; STATE AB In 1996 and 1997 the Galileo Ultraviolet Spectrometer (WS) obtained the first measurements of Jupiter's nightside midultraviolet (MUV) polar auroral spectrum from 1620 to 3231 Angstrom at 13 Angstrom resolution. The reduced polar spectra, after removal of off-axis scattered radiation from the sunlit dayside of Jupiter, contain a spectrum that matches laboratory spectra of the H-2 continuum in the a-b dissociative emission transition. This is the first direct identification of the H-2 a-b transition in astronomy. The a-b emission is excited by electron impact exchange reactions with H-2 that peak in cross section near 15 eV. The emission threshold is at 1216 Angstrom, and the continuum peaks in intensity in the 2000-2500 Angstrom range. Jupiter's observed wavelength-integrated MUV H-2 a-b emissions (1620-3231 Angstrom) have a photon flux similar to 8 times smaller than simultaneously observed wavelength-integrated far-ultraviolet (FUV) H-2 band emissions (1230-1650 Angstrom). Because the FUV H-2 emissions have an emission cross section that peaks at higher energies near 50 eV, this FUV/MUV brightness ratio is diagnostic of the secondary electron energy distribution and is consistent with a "warm" distribution of electrons. C1 Univ Colorado, Atmospher & Space Phys Lab, Boulder, CO 80303 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. CALTECH, Jet Prop Lab, FDC, Pasadena, CA 91109 USA. Univ So Calif, Dept Aerosp Engn, Los Angeles, CA 90089 USA. RP Pryor, WR (reprint author), Univ Colorado, Atmospher & Space Phys Lab, 1234 Innovat Dr, Boulder, CO 80303 USA. NR 21 TC 19 Z9 19 U1 0 U2 2 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0148-0227 J9 J GEOPHYS RES-PLANET JI J. Geophys. Res.-Planets PD AUG 30 PY 1998 VL 103 IS E9 BP 20149 EP 20158 DI 10.1029/98JE00787 PG 10 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 116LP UT WOS:000075726800025 ER PT J AU Prange, R Rego, D Pallier, L Connerney, JEP Zarka, P Queinnec, J AF Prange, R Rego, D Pallier, L Connerney, JEP Zarka, P Queinnec, J TI Detailed study of FUV Jovian auroral features with the post-COSTAR HST faint object camera SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS LA English DT Article; Proceedings Paper CT Conference on Magnetospheres of the Outer Planets CY MAR 17-21, 1997 CL BOULDER, CO SP NASA, Jet Prop Lab, Galileo Project ID HUBBLE-SPACE-TELESCOPE; ULTRAVIOLET AURORA; GIANT PLANETS; LYMAN-ALPHA; JUPITER; ATMOSPHERE; EMISSIONS; MODEL; PRECIPITATION; MORPHOLOGY AB A set of Hubble Space Telescope faint object camera images taken in the Hp bands near 1550 Angstrom is used to infer the morphological properties of the steady state Jovian FUV aurorae. We focus on issues best addressed using the excellent spatial resolution available after correction of the spherical aberration, i.e., those related to high latitude or small auroral features. A thorough comparison of the emission loci with model ovals highlights the improvement of the VIP4 magnetic field model over previous ones at all latitudes. The north-south conjugacy of the main oval is now correctly accounted for, and second-order discrepancies suggest non axially symmetric contributions of external origin. This oval is usually amazingly narrow (down to 80 +/- 50 km) and very bright, although quite variable with time (l00 kR to 1-2 MR, i.e., peak input flux of similar to 10-200 ergs cm(-2) s(-1)). We discuss its structure, in latitude and longitude, and show that it is consistent with precipitation by pitch angle scattering. Fainter concentric narrow ovals are also present on the north polar cap, presumably at the footprint of open field lines. Both polar caps are partly covered by a faint diffuse emission, confined to the afternoon sector in magnetic local time. A bright extended feature, previously identified across the north polar cap along the 160 degrees meridian, might be not a specific auroral feature but rather a region where inner arcs and diffuse polar cap emissions are intensified, maybe by a solar wind driven ionospheric process. Equatorward of the main oval, we identify a belt of moderate emission, attributed to a precipitation process distributed between the Io torus and the distant magnetosphere. Longitudinally confined bright areas lie in the same latitude range and consist of series of short segments of concentric arcs. We also present the discovery of a narrow faint oval at the footprint of Io's orbit. Finally, we confirm that the FUV footprints of the Io flux tube are very small (a few hundreds of kilometers or less), implying an interaction close to lo. The input energy flux in this spots is huge and variable (0.8-5 x 10(11) W). C1 Univ Paris 11, CNRS, Inst Astrophys Spatiale, F-91405 Orsay, France. Inst Astrophys, F-75014 Paris, France. UCL, Dept Phys & Astron, London WC1E 6BT, England. Goddard Space Flight Ctr, Greenbelt, MD 21771 USA. Observ Paris, CNRS, URA 264, DESPA, F-92195 Meudon, France. RP Prange, R (reprint author), Univ Paris 11, CNRS, Inst Astrophys Spatiale, Bat 121, F-91405 Orsay, France. EM prange@ias.fr RI connerney, john/I-5127-2013 NR 35 TC 88 Z9 88 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0148-0227 J9 J GEOPHYS RES-PLANET JI J. Geophys. Res.-Planets PD AUG 30 PY 1998 VL 103 IS E9 BP 20195 EP 20215 DI 10.1029/98JE01128 PG 21 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 116LP UT WOS:000075726800027 ER PT J AU Clarke, JT Ballester, G Trauger, J Ajello, J Pryor, W Tobiska, K Connerney, JEP Gladstone, GR Waite, JH Ben Jaffel, L Gerard, JC AF Clarke, JT Ballester, G Trauger, J Ajello, J Pryor, W Tobiska, K Connerney, JEP Gladstone, GR Waite, JH Ben Jaffel, L Gerard, JC TI Hubble Space Telescope imaging of Jupiter's UV aurora during the Galileo orbiter mission SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS LA English DT Article; Proceedings Paper CT Conference on Magnetospheres of the Outer Planets CY MAR 17-21, 1997 CL BOULDER, COLORADO SP NASA, Jet Prop Lab, Galileo Project ID COMET SHOEMAKER-LEVY-9; H-3+ EMISSIONS; JOVIAN AURORA; POLAR AURORA; MU-M; ULTRAVIOLET; IO; IMAGES; MORPHOLOGY; IMPACT AB Hubble Space Telescope (HST) Wide-Field Planetary Camera 2 (WFPC 2) images of Jupiter's aurora have been obtained close in time with Galileo ultraviolet spectrometer (UVS) spectra and in situ particles, fields, and plasma wave measurements between June 1996 and July 1997, overlapping Galileo orbits G1, G2, G7, G8, and C9. This paper presents HST images of Jupiter's aurora as a first step toward a comparative analysis of the auroral images with the in situ Galileo data. The WFPC 2 images appear similar to earlier auroral images, with the main ovals at similar locations to those observed over the preceding 2 years, and rapidly variable emissions poleward of the main ovals. Further examples have been observed of the equatorward surge of the auroral oval over 140-180 degrees longitude as this region moves from local morning to afternoon. Comparison of the WFPC 2 reference auroral ovals north and south with the VIP4 planetary magnetic field model suggests that the main ovals map along magnetic field lines exceeding 15R(J), and that the Io footprint locations have lead angles of 0-10 degrees from the instantaneous magnetic projection. There was an apparent dawn auroral storm on June 23, 1996, and projections of the three dawn storms imaged with HST to date demonstrate that these appear consistently along the WFPC 2 reference oval. Auroral emissions have been consistently observed from Io's magnetic footprints on Jupiter. Possible systematic variations in brightness are explored, within factor of 6 variations in brightness with time. Images are also presented marked with expected locations of any auroral footprints associated with the satellites Europa and Ganymede, with localized emissions observed at some times but not at other times. C1 Univ Michigan, Dept Atmospher Ocean & Space Sci, Space Phys Res Lab, Ann Arbor, MI 48109 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ Colorado, Atmospher & Space Phys Lab, Boulder, CO 80303 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. SW Res Inst, San Antonio, TX 78228 USA. Inst Astrophys, F-75014 Paris, France. Inst Astrophys, B-4000 Liege, Belgium. RP Clarke, JT (reprint author), Univ Michigan, Dept Atmospher Ocean & Space Sci, Space Phys Res Lab, 2455 Hayward St, Ann Arbor, MI 48109 USA. EM clarke@umich.edu RI Clarke, John/C-8644-2013; connerney, john/I-5127-2013; OI GERARD, Jean-Claude/0000-0002-8565-8746 NR 45 TC 142 Z9 142 U1 1 U2 6 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0148-0227 J9 J GEOPHYS RES-PLANET JI J. Geophys. Res.-Planets PD AUG 30 PY 1998 VL 103 IS E9 BP 20217 EP 20236 DI 10.1029/98JE01130 PG 20 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 116LP UT WOS:000075726800028 ER PT J AU Trauger, JT Clarke, JT Ballester, GE Evans, RW Burrows, CJ Crisp, D Gallagher, JS Griffiths, RE Hester, JJ Hoessel, JG Holtzman, JA Krist, JE Mould, JR Sahai, R Scowen, PA Stapelfeldt, KR Watson, AM AF Trauger, JT Clarke, JT Ballester, GE Evans, RW Burrows, CJ Crisp, D Gallagher, JS Griffiths, RE Hester, JJ Hoessel, JG Holtzman, JA Krist, JE Mould, JR Sahai, R Scowen, PA Stapelfeldt, KR Watson, AM TI Saturn's hydrogen aurora: Wide field and planetary camera 2 imaging from the Hubble Space Telescope SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS LA English DT Article; Proceedings Paper CT Conference on Magnetospheres of the Outer Planets CY MAR 17-21, 1997 CL BOULDER, COLORADO SP NASA, Jet Prop Lab, Galileo Project ID EXTREME ULTRAVIOLET OBSERVATIONS; KILOMETRIC RADIATION; JUPITER AURORA; UPPER-ATMOSPHERE; MAGNETIC-FIELD; RADIO-EMISSION; VOYAGER-1; MAGNETOSPHERE; INSTABILITY; ENCOUNTER AB Wide field and planetary camera 2/Hubble Space Telescope (WFPC2/HST) images of Saturn's far ultraviolet aurora reveal emissions confined to a narrow band of latitudes near Saturn's north and south poles. The aurorae are most prominent in the morning sector with patterns that appear fixed in local time. The geographic distribution and vertical extent of the auroral emissions seen in these images provide the first new observational insights into the physical mechanisms that power Saturn's aurora since the Voyager encounters 17 years ago. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ Michigan, Space Phys Res Lab, Ann Arbor, MI 48109 USA. Space Telescope Sci Inst, Baltimore, MD 21218 USA. Univ Wisconsin, Dept Astron, Madison, WI 53706 USA. Carnegie Mellon Univ, Dept Phys, Pittsburgh, PA 15213 USA. Arizona State Univ, Dept Phys & Astron, Tempe, AZ 85287 USA. New Mexico State Univ, Dept Astron, Las Cruces, NM 88003 USA. Australian Natl Univ, Mt Stromlo & Siding Spring Observ, Weston Creek, ACT 2611, Australia. RP Trauger, JT (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. RI Stapelfeldt, Karl/D-2721-2012; Clarke, John/C-8644-2013 NR 38 TC 59 Z9 59 U1 0 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0148-0227 J9 J GEOPHYS RES-PLANET JI J. Geophys. Res.-Planets PD AUG 30 PY 1998 VL 103 IS E9 BP 20237 EP 20244 DI 10.1029/98JE01324 PG 8 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 116LP UT WOS:000075726800029 ER PT J AU Gao, S Ho, CW Huang, TS Alexander, CJ AF Gao, S Ho, CW Huang, TS Alexander, CJ TI Uranus' magnetic field and particle drifts in its inner magnetosphere SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS LA English DT Article; Proceedings Paper CT Conference on Magnetospheres of the Outer Planets CY MAR 17-21, 1997 CL BOULDER, COLORADO SP NASA, Jet Prop Lab, Galileo Project ID CONVECTION AB Both the Q3 model (dipole and quadrupole) and OCT model (Q3 plus octupole) of Uranus' magnetic field within 5 R-U are expressed in alpha and beta (Euler potentials) coordinate systems. By using the alpha and beta coordinates of magnetic fields, we calculate the drift paths and velocities for the zero second invariant (J = 0) charged particles with different total energies. Many aspects of Uranus' magnetic field are similar to those of Neptune [Ho et al., 1997], such as a warped zero magnetic scalar potential surface and a region of local distorted magnetic field lines that gives rise to a large "open" area on the planetary surface when the field lines are mapped from this region. It is found that the OCT model gives a map of magnetic field coordinates on the planetary surface that better explains the Voyager 2 ultraviolet spectrometer (UVS) data of Herbert and Sandel [1994] than the Q3 model. The grossly distorted alpha and beta contours on the planetary surface may explain the incomplete aurora circles around both magnetic poles, and weak UV emissions are found lying along a belt that coincides remarkably well with the OCT magnetic equator. In addition, tracing of drift paths of J = 0 charged particles shows that the weak emission along the magnetic equator is due to the precipitation of J = 0 particles, or particles with a large equatorial pitch angle. In particular, the low-energy J = 0 particles tend to drift toward a planet in three concentrated regions where UV emissions are observed. C1 Prairie View A&M Univ, Dept Phys, Prairie View, TX 77446 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Gao, S (reprint author), Prairie View A&M Univ, Dept Phys, Prairie View, TX 77446 USA. NR 14 TC 4 Z9 4 U1 0 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0148-0227 J9 J GEOPHYS RES-PLANET JI J. Geophys. Res.-Planets PD AUG 30 PY 1998 VL 103 IS E9 BP 20257 EP 20265 DI 10.1029/98JE00944 PG 9 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 116LP UT WOS:000075726800031 ER PT J AU Huang, TS Ho, CW Alexander, CJ AF Huang, TS Ho, CW Alexander, CJ TI The plasmasphere of Neptune SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS LA English DT Article; Proceedings Paper CT Conference on Magnetospheres of the Outer Planets CY MAR 17-21, 1997 CL BOULDER, COLORADO SP NASA, Jet Prop Lab, Galileo Project ID MAGNETIC-FIELD; MAGNETOSPHERE; MODEL; CONVECTION; AURORA; URANUS AB We examine the plausible existence of Neptune's plasmasphere and study the drift of particles inside it. Using the O8 magnetic field model [Connerney et al., 1991] and assuming a uniform solar wind convection electric field, the plasma convection time and refining time are calculated in a Euler potential coordinate system [Ho et al., 1997]. The plasma density and refilling time at the equilibrium state are first calculated, and the location of the plasmapause is set to be where the refilling time and convection time are equal. The refilling time as a function of ion speed is then recalculated along field lines, and the plasma density and temperature are obtained by directly integrating the local ion distribution function over the range of speeds for which the refilling time is less than the convection time. The density calculated using this model shows sharp drop-offs at approximately 3.25 to 4.5 R-N on the zero magnetic scalar potential surface, a boundary taken to be the plasmapause. Our calculated density compares fairly with the observed density along the Voyager trajectory within about 5 R-N. Ion temperature is also calculated along the field line with results which indicate that high-speed tails of the distribution function might be needed to explain the high observed temperature measured along the Voyager 2 trajectory. Drift trajectories and speeds of 90 degrees pitch angle particles inside the plasmapause are calculated. Particles of energy above tens of eV are gradient drift dominated, and the drift paths of this class of particles are essentially the minimum B contours that are similar to Acuna et al.'s [1993] calculations. Atmospheric precipitation of the J = 0 particles may provide an explanation for the UV emissions, as an alternative to the "monoprecipitation'' suggested by Paranicas and Cheng [1994]. Drifts of low-energy particles are strongly affected by the gravitational and centrifugal forces, and because of the largely tilted dipole and the large higher components of magnetic field, the resultant drift is nonaxisymmetric and quite complicated. C1 Prairie View A&M Univ, Dept Phys, Prairie View, TX 77446 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Huang, TS (reprint author), Prairie View A&M Univ, Dept Phys, Prairie View, TX 77446 USA. NR 22 TC 4 Z9 4 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0148-0227 J9 J GEOPHYS RES-PLANET JI J. Geophys. Res.-Planets PD AUG 30 PY 1998 VL 103 IS E9 BP 20267 EP 20278 DI 10.1029/98JE01129 PG 12 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 116LP UT WOS:000075726800032 ER PT J AU Marshak, A Davis, A Wiscombe, W Cahalan, R AF Marshak, A Davis, A Wiscombe, W Cahalan, R TI Radiative effects of sub-mean free path liquid water variability observed in stratiform clouds SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID MARINE STRATOCUMULUS; TURBULENCE; ALBEDO AB A unique 4-cm-resolution data set of stratocumulus cloud liquid water content (LWC) made possible, for the first time, the generation of credible models of cloud LWC down to centimeter-scales, well below the photon mean free path (mfp) which is typically tens of meters. These models are exploited to study the errors in the usual assumption of LWC homogeneity within three-dimensional (3D) radiative transfer grid boxes, by doing Monte Carlo computations for 30-m cubes resolved down to IO-cm scales. Cloud models with and without vertical variability are compared. We found that vertically homogeneous but horizontally variable cloud structure produces cloud radiation biases of 3-5% relative to the assumption of complete homogeneity. The addition of vertical variability similar to the horizontal variability reduces these biases well below 1%. We therefore conclude that 3D cloud models resolved down to the mfp scale (20-30 m for marine stratocumulus clouds), with an incorrect assumption of homogeneity below that scale are sufficient for modeling radiative properties averaged over mfp and larger scales in both visible and near-infrared spectral regions. This conclusion is restricted to only the overcast cases. C1 NASA, Goddard Space Flight Ctr, Climate & Radiat Branch, Greenbelt, MD 20771 USA. Los Alamos Natl Lab, Space & Remote Sensing Sci Grp, Baltimore, MD USA. RP Marshak, A (reprint author), NASA, Goddard Space Flight Ctr, Climate & Radiat Branch, Mail Code 913, Greenbelt, MD 20771 USA. EM marshak@climate.gsfc.nasa.gov; adavis@lanl.gov; wiscombe@climate.gsfc.nasa.gov; cahalan@clouds.gsfc.nasa.gov RI Cahalan, Robert/E-3462-2012; Wiscombe, Warren/D-4665-2012; Marshak, Alexander/D-5671-2012 OI Cahalan, Robert/0000-0001-9724-1270; Wiscombe, Warren/0000-0001-6844-9849; NR 43 TC 36 Z9 36 U1 0 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD AUG 27 PY 1998 VL 103 IS D16 BP 19557 EP 19567 DI 10.1029/98JD01728 PG 11 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 114ED UT WOS:000075595400010 ER PT J AU Chen, MH Rood, RB Read, WG AF Chen, MH Rood, RB Read, WG TI Upper tropospheric water vapor from GEOS reanalysis and UARS MLS observation SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID MICROWAVE LIMB SOUNDER; RELATIVE-HUMIDITY; SATELLITE-OBSERVATIONS; GLOBAL CLIMATE; CONVECTION; MODEL; FEEDBACK; MOISTURE; PROJECT AB The upper tropospheric water vapor (UTWV) from the reanalysis produced by the Goddard Earth Observing System (GEOS) Data Assimilation System is compared with the retrieved UTWV from the measurements of the Microwave Limb Sounder (MLS) aboard the Upper Atmosphere Research Satellite (UARS). The UTWV from the GEOS reanalysis is in fair agreement with the UTWV retrieved from the UARS MLS observation. Both data sets show high tropical UTWV closely I elated with the tropical deep convection. There is, however, clear evidence of overestimation of UTWV in the GEOS reanalysis, especially for the summer season (July 1992). The GEOS overestimation is more significant after considering the MLS retrieval bias. The reasons for the GEOS overestimation are discussed. I;or interannual variations between 1992 and 1993. the reanalysis and the observation consistently show significant changes in UTWV resulting from sea surface temperature anomalies associated with the El Nino-Southern Oscillation phenomenon. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. CALTECH, Jet Prop Lab, Pasadena, CA USA. RP Chen, MH (reprint author), NASA, Goddard Space Flight Ctr, Code 910-3, Greenbelt, MD 20771 USA. EM mchen@dao.gsfc.nasa.gov RI Rood, Richard/C-5611-2008 OI Rood, Richard/0000-0002-2310-4262 NR 36 TC 8 Z9 8 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD AUG 27 PY 1998 VL 103 IS D16 BP 19587 EP 19594 DI 10.1029/98JD02122 PG 8 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 114ED UT WOS:000075595400013 ER PT J AU Cutten, DR Spinhirne, JD Menzies, RT Bowdle, DA Srivastava, V Pueschel, RF Clarke, AD Rothermel, J AF Cutten, DR Spinhirne, JD Menzies, RT Bowdle, DA Srivastava, V Pueschel, RF Clarke, AD Rothermel, J TI Intercomparison of pulsed lidar data with flight level CW lidar data and modeled backscatter from measured aerosol microphysics near Japan and Hawaii SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID ATMOSPHERIC AEROSOL; CLOUD BACKSCATTER; PACIFIC; WAVELENGTHS AB Aerosol backscatter coefficient data were examined from two nights near Japan and Hawaii undertaken during NASA's Global Backscatter Experiment (GLOBE:) in May-June 1990. During each of these two nights the aircraft traversed different altitudes within a legion of the atmosphere defined by the same set of latitude and longitude coordinates. This provided an ideal opportunity to allow flight level focused continuous wave (CW) lidar backscatter measured at 9.11-mu m wavelength and modeled aerosol backscatter from two aerosol optical counters to be compared with pulsed lidar aerosol backscatter data at 1.06- and 9.25-mu m wavelengths. The best agreement between all sensors was found in the altitude region below 7 km, where backscatter values were moderately high at all three wavelengths. Above this altitude the pulsed lidar backscatter data at 1.06- and 9.25-mu m wavelengths were higher than the flight level data obtained from the CW lidar or derived from the optical counters, suggesting sample volume effects were responsible for this. Aerosol microphysics analysis of data near Japan revealed a strong sea-salt aerosol plume extending upward from the marine boundary layer. On the basis of sample volume differences, it was found that large particles were of different composition compared with the small particles for low backscatter conditions. C1 Univ Alabama, Earth Syst Sci Lab, Global Hydrol & Climate Ctr, Huntsville, AL 35899 USA. Univ Hawaii, Sch Oceanog, Honolulu, HI 96822 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. NASA, George C Marshall Space Flight Ctr, Global Hydrol & Climate Ctr, Huntsville, AL 35806 USA. RP Cutten, DR (reprint author), Univ Alabama, Earth Syst Sci Lab, Global Hydrol & Climate Ctr, Huntsville, AL 35899 USA. EM Dean.Cutten@msfc.nasa.gov; jspin@virl.gsfc.nasa.gov; Robert.Menzies@jpl.nasa.gov; David.Bowdle@msfc.nasa.gov; Vandana.Srivastava@msfc.nasa.gov; rpueschel@mail.arc.nasa.gov; tclarke@soest.hawaii.edu; Jeffry.Rothermel@msfc.nasa.gov NR 15 TC 6 Z9 6 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD AUG 27 PY 1998 VL 103 IS D16 BP 19649 EP 19661 DI 10.1029/98JD01155 PG 13 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 114ED UT WOS:000075595400017 ER PT J AU Ferrare, RA Melfi, SH Whiteman, DN Evans, KD Leifer, R AF Ferrare, RA Melfi, SH Whiteman, DN Evans, KD Leifer, R TI Raman lidar measurements of aerosol extinction and backscattering - 1. Methods and comparisons SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID OPTICAL-PROPERTIES; ATMOSPHERIC AEROSOL; NEPHELOMETER; TROPOSPHERE; AIRBORNE; COUNTER; RATIO AB This paper examines the aerosol backscattering and extinction profiles measured at night by the NASA Goddard Space Flight Center Scanning Raman Lidar (SRL) during the remote cloud sensing (RCS) intensive operations period (IOP) at the Department of Energy Atmospheric Radiation Measurement (ARM) southern Great Plains (SGP) site in April 1994. These lidar data are used to derive aerosol profiles for altitudes between 0.015 and 5 km. Since this lidar detects Raman scattering from nitrogen and oxygen molecules as well as the elastic scattering from molecules and aerosols, it measures both aerosol backscattering and extinction simultaneously, The aerosol extinction/backscattering ratio varied between approximately 30 sr and 75 sr at 351 nm. Aerosol optical thicknesses derived by integrating the lidar profiles of aerosol extinction measured at night between 0.1 and 5 km are found to be about 10-40% lower than those measured by a Sun photometer during the day. This difference is attributed to the contribution by stratospheric aerosols not included in the lidar estimates as well as to diurnal differences in aerosol properties and concentrations. Aerosol profiles close to the surface were acquired by pointing the lidar nearly horizontally. Measurements of aerosol scattering from a tower-mounted nephelometer are found to be 40% lower than lidar measurements of aerosol extinction over a wide range of relative humidities even after accounting for the difference in wavelengths. The reasons for this difference are not clear but may be due to the inability of the nephelometer to accurately measure scattering by large particles. C1 NASA, Langley Res Ctr, Hampton, VA 23681 USA. Univ Maryland Baltimore Cty, Dept Phys, Baltimore, MD 21250 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Maryland Baltimore Cty, Joint Ctr Earth Syst Technol, Baltimore, MD 21250 USA. US DOE, Environm Measurements Lab, New York, NY 10014 USA. RP Ferrare, RA (reprint author), NASA, Langley Res Ctr, Mail Stop 401A,Bldg 1250,Room 132A,21 Langley Blv, Hampton, VA 23681 USA. EM r.ferrare@larc.nasa.gov NR 35 TC 79 Z9 83 U1 0 U2 7 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD AUG 27 PY 1998 VL 103 IS D16 BP 19663 EP 19672 DI 10.1029/98JD01646 PG 10 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 114ED UT WOS:000075595400018 ER PT J AU Ferrare, RA Melfi, SH Whiteman, DN Evans, KD Poellot, M Kaufman, YJ AF Ferrare, RA Melfi, SH Whiteman, DN Evans, KD Poellot, M Kaufman, YJ TI Raman lidar measurements of aerosol extinction and backscattering - 2. Derivation of aerosol real refractive index, single-scattering albedo, and humidification factor using Raman lidar and aircraft size distribution measurements SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID OPTICAL-PROPERTIES; LIGHT-SCATTERING; TROPOSPHERIC AEROSOLS; RELATIVE-HUMIDITY; PARTICLES; RADIOMETER; RADIATION; ABSORPTION; POLLUTION; COUNTER AB Aerosol backscattering and extinction profiles measured by the NASA Goddard Space Flight Center Scanning Raman Lidar (SRL) during the remote cloud sensing (RCS) intensive operations period (IOP) at the Department of Energy Atmospheric Radiation Measurement (ARM) southern Great Plains (SGP) site during two nights in April 1994 are discussed. These profiles are shown to be consistent with the simultaneous aerosol size distribution measurements made by a PCASP (Passive Cavity Aerosol Spectrometer Probe) optical particle counter flown on the University of North Dakota Citation aircraft. We describe a technique which uses both lidar and PCASP measurements to derive the dependence of particle size on relative humidity, the aerosol real refractive index n, and estimate the effective single-scattering albedo omega(0). Values of n ranged between 1.4-1.5 (dry) and 1.37-1.47 (wet); omega(0) varied between 0.7 and 1.0. The single-scattering albedo derived from this technique is sensitive to the manner in which absorbing particles are represented in the aerosol mixture; representing the absorbing particles as an internal mixture rather than the external mixture assumed here results in generally higher values of oo. The lidar measurements indicate that the change in particle size with relative humidity as measured by the PCASP can be represented in the form discussed by Hanel [1976] with the exponent gamma 0.3 +/- 0.05. The variations in aerosol optical and physical characteristics captured in the lidar and aircraft size distribution measurements are discussed in the context of the meteorological conditions observed during the experiment. C1 NASA, Langley Res Ctr, Hampton, VA 23681 USA. Univ Maryland Baltimore Cty, Dept Phys, Baltimore, MD 21250 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Maryland Baltimore Cty, Joint Ctr Earth Syst Technol, Baltimore, MD 21250 USA. Univ N Dakota, Dept Atmospher Sci, Grand Forks, ND 58202 USA. RP Ferrare, RA (reprint author), NASA, Langley Res Ctr, Mail Stop 401A,Bldg 1250,Room 132A,21 Langley Blv, Hampton, VA 23681 USA. EM r.ferrare@larc.nasa.gov NR 55 TC 49 Z9 49 U1 0 U2 5 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD AUG 27 PY 1998 VL 103 IS D16 BP 19673 EP 19689 DI 10.1029/98JD01647 PG 17 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 114ED UT WOS:000075595400019 ER PT J AU Kinne, S Bergstrom, R Toon, OB Dutton, E Shiobara, M AF Kinne, S Bergstrom, R Toon, OB Dutton, E Shiobara, M TI Clear-sky atmospheric solar transmission: An analysis based on FIRE 1991 field experiment data SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID AEROSOL AB We consider explanations for disagreements between models and measurements of clear-sky solar transmission. Data from four cloud-free days during the FIRE 1991 field experiment are studied. Our model simulations of solar broadband fluxes exceed measurements by about 10%. About half of this discrepancy occurs in the near-infrared spectral region. About half of this discrepancy can be linked to the direct irradiance. These deviations suggest (1) model under estimates in near-infrared trace-gas absorption and (2) errors in visible diffuse fluxes. The near-infrared error in other models is generally less than the one associated with our model. Other models suggest more trace-gas absorption. However, variations among models are so large that they swamp current measurement errors such as uncertainties of the water vapor column. The visible diffuse flux error cannot be easily explained. We illustrate that a poor cosine response of solar flux instruments could have contributed. Also, underestimates of aerosol absorption could be a factor. There is clearly a need for measurements and comparisons at high spectral resolution to better quantify the sources of these errors. However, these comparisons will only be fruitful if we have confidence in the accuracy of our models and the accuracy of the data. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. NOAA, Boulder, CO 80303 USA. Bay Area Environm Res, San Francisco, CA 94122 USA. MRI Meteorol Res Inst, Tsukuba, Ibaraki 305, Japan. Univ Colorado, LASP, Boulder, CO 80309 USA. RP Kinne, S (reprint author), NASA, Goddard Space Flight Ctr, Code 923, Greenbelt, MD 20771 USA. EM kinne@spamer.gsfc.nasa.gov NR 14 TC 23 Z9 23 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD AUG 27 PY 1998 VL 103 IS D16 BP 19709 EP 19720 DI 10.1029/98JD01540 PG 12 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 114ED UT WOS:000075595400021 ER PT J AU Manalo-Smith, N Smith, GL Tiwari, SN Staylor, WF AF Manalo-Smith, N Smith, GL Tiwari, SN Staylor, WF TI Analytic forms of bidirectional reflectance functions for application to Earth radiation budget studies SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID NIMBUS-7 ERB; SCANNER MEASUREMENTS; EMISSION MODELS; SATELLITE AB Analytic expressions for the bidirectional reflectance functions are formulated and fit to the Earth Radiation Budget Experiment (ERBE) operational models, which were developed using Nimbus 7 ERB data. The analytic bidirectional reflectance distribution functions (BRDFs) are based on theoretical considerations and are functions of viewing geometry and scene type. The models consist of a Rayleigh scattering term and a term for scattering due to clouds and surface. The darkness of the ocean permits the empirical determination of the Rayleigh component of scattering from the atmosphere. The models have the advantage that they are smooth in terms of view and solar zenith angles and relative solar azimuth angle and satisfy reciprocity. Results are presented for the ERBE scene types. The analytic functions closely model the reflectances in the forward scatter direction, but in the backscatter direction, the analytic models are slightly more limb brightened than the ERBE operational models. The model was also fit to the Dlhopolsky/Cess BRDF for clear ocean, which provides a finer angular resolution than the ERBE BRDFs. The results of this study provide a set of BRDFs for ERBE scene types in terms of a set of simple equations and few coefficients for each scene type. These models can be used for mission planning and interpretation of data from future Earth radiation budget missions such as the Clouds and Earth's Radiant Energy System (CERES). C1 Old Dominion Univ, Dept Mech Engn, Norfolk, VA 23529 USA. NASA, Langley Res Ctr, Div Atmospher Sci, Hampton, VA 23681 USA. RP Manalo-Smith, N (reprint author), Analyt Serv & Mat Inc, 1 Enterprise Pkwy,Suite 300, Hampton, VA 23666 USA. EM n.m.smith@larc.nasa.gov; g.l.smith@larc.nasa.gov; june@mem.odu.edu NR 25 TC 23 Z9 23 U1 1 U2 2 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD AUG 27 PY 1998 VL 103 IS D16 BP 19733 EP 19751 DI 10.1029/98JD00279 PG 19 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 114ED UT WOS:000075595400023 ER PT J AU Mackerras, D Darveniza, M Orville, RE Williams, ER Goodman, SJ AF Mackerras, D Darveniza, M Orville, RE Williams, ER Goodman, SJ TI Global lightning: Total, cloud and ground flash estimates SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID KATHMANDU THUNDERSTORMS; CIRCUIT; RATIO; RADAR AB A worldwide survey of the ratio of cloud flashes to ground flashes in thunderstorms using CGR3 (Cloud-Ground Ratio #3) instruments at sites covering a latitude range from 59.9 degrees N to 27.3 degrees S between 1986 and 1991 inclusive has provided information on the latitudinal variation of total flash density and the ratio of cloud flashes to total flashes. Two surveys of global lightning occurrence using satellites, the Defense Meteorological Satellite Program (DMSP) survey using optical sensors to detect lightning at near local midnight and the Ionospheric Sounding Satellite-b (ISS-b) survey using radio-frequency lightning detection equipment, were used in conjunction with the CGR3 observations to obtain the latitudinal variation of total flash density over each major land mass and each major ocean. These three surveys and other sources provided data on the annual and diurnal variation in lightning occurrence at various latitudes. We have combined the above information in a computational model of global lightning occurrence and have separated total flashes into cloud flash and ground flash components. Using this model, we estimate the global annual number of total flashes to be 2.05 x 10(9) yr(-1), corresponding to a mean rate of 65 s(-1). This estimate is probably low because of inadequate detection of weak cloud flashes. Depending on the assumption made concerning the latitudinal variation of the ratio of cloud flashes to total flashes, the mean rates of occurrence are between about 51 s(-1) and 55 s(-1) fur cloud flashes and between about 10 s(-1) and 14 s(-1) for ground flashes. The uncertainty in these estimates is a factor of 2 in either direction. The calculated global diurnal variation has a peak rate of occurrence of about 1.6 rimes the mean rate at about 1400 universal time (UT) in the northern hemisphere spring and has its lowest rate of about 0.5 times the mean rate at about 0300 UT in the northern hemisphere summer. About 54% of all lightning occurs in the northern hemisphere. The mean global land total flash density is about 8.3 km(-2) yr(-1). This is about 3.4 times the mean global total flash density over oceans. C1 Univ Queensland, Dept Comp Sci & Elect Engn, Brisbane, Qld 4072, Australia. NASA, George C Marshall Space Flight Ctr, Global Hydrol Res Off, Huntsville, AL 35806 USA. Texas A&M Univ, Dept Meteorol, College Stn, TX 77843 USA. MIT, Parsons Lab, Cambridge, MA 02139 USA. RP Mackerras, D (reprint author), Univ Queensland, Dept Comp Sci & Elect Engn, Brisbane, Qld 4072, Australia. EM d.mackerras@mailbox.uq.edu.au; matt@elec.uq.edu.au; orville@ariel.met.tamu.edu; earlew@juliet.ll.mit.edu; steven.goodman@msfc.nasa.gov RI Orville, Richard/G-9866-2012 OI Orville, Richard/0000-0003-0280-7169 NR 47 TC 75 Z9 84 U1 1 U2 11 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X EI 2169-8996 J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD AUG 27 PY 1998 VL 103 IS D16 BP 19791 EP 19809 DI 10.1029/98JD01461 PG 19 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 114ED UT WOS:000075595400027 ER PT J AU Mohiuddin, MA Khulief, YA AF Mohiuddin, MA Khulief, YA TI Modal characteristics of cracked rotors using a conical shaft finite element SO COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING LA English DT Article ID VIBRATION; SYSTEM AB A finite element model of a tapered rotating cracked shaft is developed for modal analysis and dynamic modeling of rotor-bearing systems. The finite shaft element has ten degrees of freedom and accounts for linear tapering. The flexibility compliance due to the crack is computed using fracture mechanics approach. The formulation of the tapered rotating cracked finite element includes shear deformation and rotary inertia. The shape functions are derived and explicit expressions for the element mass, stiffness and gyroscopic matrices are obtained using consistent mass formulation. The generalized eigenvalue problem is defined and numerical solutions are obtained for a wide range of whirl ratios, crack depths and crack locations. Comparisons with other results reported in the literature are presented. (C) 1998 Elsevier Science S.A. All rights reserved. C1 King Fahd Univ Petr & Minerals, Dept Engn Mech, Dhahran 31261, Saudi Arabia. RP Khulief, YA (reprint author), NASA, JPL, Pasadena, CA 91109 USA. NR 19 TC 7 Z9 7 U1 0 U2 2 PU ELSEVIER SCIENCE SA PI LAUSANNE PA PO BOX 564, 1001 LAUSANNE, SWITZERLAND SN 0045-7825 J9 COMPUT METHOD APPL M JI Comput. Meth. Appl. Mech. Eng. PD AUG 25 PY 1998 VL 162 IS 1-4 BP 223 EP 247 DI 10.1016/S0045-7825(97)00345-9 PG 25 WC Engineering, Multidisciplinary; Mathematics, Interdisciplinary Applications; Mechanics SC Engineering; Mathematics; Mechanics GA 120XV UT WOS:000075983700013 ER PT J AU Kalkhoran, IM Smart, MK Wang, FY AF Kalkhoran, IM Smart, MK Wang, FY TI Supersonic vortex breakdown during vortex/cylinder interaction SO JOURNAL OF FLUID MECHANICS LA English DT Article ID WING-TIP VORTICES; NUMERICAL-SIMULATION; NORMAL SHOCK; OBLIQUE; DISTORTION; MODEL AB The head-one interaction of a supersonic streamwise vortex with a circular cylinder reveals a vortex breakdown similar in many ways to that of incompressible vortex breakdown. In particular, the dramatic flow reorganization observed during the interaction resembles the conical vortex breakdown reported by Sarpkaya (1995) at high Reynolds number. In the present study, vortex breakdown is brought about when moderate and strong streamwise vortices encounter the bow shock in front of a circular cylinder at Mach 2.49. The main features of the vortex/cylinder interaction are the formation of a blunt-nosed conical shock with apex far upstream of the undisturbed shock stand-off distance, and a vortex core which responds to passage through the apex of the conical shock by expanding into a turbulent conical flow structure. The geometry of the expanding vortex core as well as the location of the conical shock apex are seen to be strong functions of the incoming vortex strength and the cylinder diameter. A salient feature of the supersonic vortex breakdown is the formation of an entropy-shear layer, which separates an interior subsonic zone containing the burst vortex from the surrounding supersonic flow. In keeping with the well-established characteristics of the low-speed vortex breakdown, a region of reversed flow is observed inside the turbulent subsonic zone. The steady vortex/cylinder interaction flow fields generated in the current study exhibit many characteristics of the unsteady vortex distortion patterns previously observed during normal shock wave/vortex interactions. This similarity of the instantaneous flow structure indicates that the phenomenon previously called vortex distortion by Kalkhoran et al. (1996) is a form of supersonic vortex breakdown. C1 Polytech Univ, Dept Mech Aerosp & Mfg Engn, Brooklyn, NY 11201 USA. NASA, Langley Res Ctr, Hampton, VA 23681 USA. RP Kalkhoran, IM (reprint author), Polytech Univ, Dept Mech Aerosp & Mfg Engn, Brooklyn, NY 11201 USA. RI Smart, Michael/C-8823-2013 NR 26 TC 12 Z9 12 U1 2 U2 3 PU CAMBRIDGE UNIV PRESS PI NEW YORK PA 40 WEST 20TH STREET, NEW YORK, NY 10011-4211 USA SN 0022-1120 J9 J FLUID MECH JI J. Fluid Mech. PD AUG 25 PY 1998 VL 369 BP 351 EP 380 PG 30 WC Mechanics; Physics, Fluids & Plasmas SC Mechanics; Physics GA 122PK UT WOS:000076080500014 ER PT J AU Gulick, VC AF Gulick, VC TI Magmatic intrusions and a hydrothermal origin for fluvial valleys on Mars SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS LA English DT Article ID SMALL MARTIAN VALLEYS; GROUND ICE; EVOLUTION; CHANNELS; HISTORY; LIFE; VOLATILES; METEORITE; CLIMATE; VOLCANO AB Numerical models of Martian hydrothermal systems demonstrate that systems associated with magmatic intrusions greater than several hundred cubic kilometers can provide sufficient groundwater outflow to form the observed fluvial valleys, if subsurface permeability exceeds about 1.0 darcy. Groundwater outflow increases with increasing intrusion volume and subsurface permeability and is relatively insensitive to intrusion depth and subsurface porosity within the range considered here. Hydrothermally-derived fluids can melt through 1 to 2 km thick ice-rich permafrost layers in several thousand years. Hydrothermal systems thus provide a viable alternative to rainfall for providing surface water for valley formation. This mechanism can form fluvial valleys not only during the postulated early warm, wet climatic epoch, but also during more recent epochs when atmospheric conditions did not favor atmospheric cycling of water. The clustered distribution of the valley networks on a given geologic surface or terrain unit of Mars may also be more compatible with localized, hydrothermally-driven groundwater outflow than regional rainfall. Hydrothermal centers on Mars may have provided appropriate environments for the initiation of life or final eases for the long-term persistence of life. C1 New Mexico State Univ, Dept Astron, Las Cruces, NM 88003 USA. NASA, Ames Res Ctr, Div Space Sci, Moffett Field, CA 94035 USA. RP Gulick, VC (reprint author), NASA, Ames Res Ctr, Div Space Sci, Moffett Field, CA 94035 USA. EM vgulick@mail.arc.nasa.gov NR 73 TC 131 Z9 132 U1 2 U2 10 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0148-0227 J9 J GEOPHYS RES-PLANET JI J. Geophys. Res.-Planets PD AUG 25 PY 1998 VL 103 IS E8 BP 19365 EP 19387 DI 10.1029/98JE01321 PG 23 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 138KD UT WOS:000076970300002 ER PT J AU Copp, DL Guest, JE AF Copp, DL Guest, JE TI New insights into Coronae evolution: Mapping on Venus SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS LA English DT Article ID IMPACT CRATER DENSITIES; GLOBAL DISTRIBUTION; VOLCANISM; ORIGIN; MORPHOLOGY; FEATURES; HISTORY; MODELS; RISES; REGIO AB Coronae are geologically and geophysically important features on Venus, because they are thought to contribute to planetary heat loss. It is thus necessary to understand their role in space and time in the evolution of Venus. Detailed mapping of five coronae in Guinevere and Sedna Planitia illustrates that although previous models invoked initial uplift, not all coronae can be explained in such a simple way. We show that the formation of corona annuli can be multistaged and that the position of the annulus does not always coincide with the main topographic ridges and troughs that outline the feature. The magnitude and timing of volcanism are not necessarily the same at each corona, and coronae can have long and complex histories, in contrast with the stratigraphic relations suggested by other workers. We demonstrate that coronae do not all have the same relative ages with respect to adjacent units. These results suggest that corona formation was (is) not confined to a single time period in the history of Venus and that detailed mapping is a reliable method of establishing the relative timing of corona formation. C1 UCL, Univ London Observ, Dept Phys & Astron, Planetary Image Ctr, London NW7 4SD, England. CALTECH, Jet Prop Lab, Pasadena, CA 91125 USA. RP Copp, DL (reprint author), UCL, Univ London Observ, Dept Phys & Astron, Planetary Image Ctr, 33-35 Daws Lane,Mill Hill, London NW7 4SD, England. EM dlc@star.ucl.ac.uk NR 34 TC 22 Z9 22 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0148-0227 J9 J GEOPHYS RES-PLANET JI J. Geophys. Res.-Planets PD AUG 25 PY 1998 VL 103 IS E8 BP 19401 EP 19417 DI 10.1029/97JE03182 PG 17 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 138KD UT WOS:000076970300004 ER PT J AU Sugita, S Schultz, PH Adams, MA AF Sugita, S Schultz, PH Adams, MA TI Spectroscopic measurements of vapor clouds due to oblique impacts SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS LA English DT Article ID OSCILLATOR-STRENGTHS; NEUTRAL CALCIUM; PARAMETERS; ATMOSPHERE; EARTH; LINES AB Vapor clouds generated by oblique impacts were observed spectroscopically. The observations here concentrate on the earliest downrange-moving component, among multiple components of vapor clouds generated by hypervelocity impacts of quartz projectiles into dolomite targets. The spectrum of impact vapor simultaneously exhibits blackbody radiation, molecular band emission, and atomic line emission, but their relative ratios change with time and space. The spectrum of the earliest component is dominated by the line/band emissions. The strong band/line emissions demonstrate the presence of a gas phase. The ratio of line/band emission to blackbody radiation is higher in near-vertical impacts than shallower angle impacts. Ratios of normalized intensities of emission lines indicate that a Boltzmann distribution with an equilibrium temperature ranging from 4000 K to 6000 K approximates well the distribution of calcium atoms in energy levels in the impact vapor. Furthermore, the temperature of impact vapor appears to be controlled by the vertical component of the impact velocity. The degree of self-absorption of a calcium emission line, which comes from vaporized dolomite target, indicates that only a very small mass of impact vapor is involved in the observed atomic radiation process. This observation, as well as the short lifetime and extremely high temperature, suggests that jetting may be the dominant source of the line emissions in the earliest stage vapor component at impact velocities less than 6 km/s. The experimental techniques and analysis methods presented in this study are applicable to other components of impact-generated vapor and will provide new information on vaporization mechanisms in hypervelocity impacts. C1 Brown Univ, Dept Geol Sci, Providence, RI 02912 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Sugita, S (reprint author), Brown Univ, Dept Geol Sci, Box 1846, Providence, RI 02912 USA. NR 38 TC 39 Z9 41 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0148-0227 J9 J GEOPHYS RES-PLANET JI J. Geophys. Res.-Planets PD AUG 25 PY 1998 VL 103 IS E8 BP 19427 EP 19441 DI 10.1029/98JE02026 PG 15 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 138KD UT WOS:000076970300006 ER PT J AU Kubo, S Murakami, T Ishida, M Corbet, RHD AF Kubo, S Murakami, T Ishida, M Corbet, RHD TI ASCA X-ray observations of gamma Cassiopeiae SO PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN LA English DT Article DE line profiles; stars : Be; stars : individual (gamma Cassiopeiae); x-rays : spectra ID SS-CYGNI; TIME VARIABILITY; WHITE-DWARF; EX-HYDRAE; SPECTRUM; QUIESCENCE; OUTBURST; BINARY; CATALOG; STARS AB We present the results of X-ray observations of gamma Cassiopeiae made with the ASCA satellite. Since the discovery of X-ray emission from this system, several possible models for the origin of X-rays have been proposed, including the corona of gamma Gas, itself, a binary neutron-star companion, and a binary white-dwarf companion. However, there has been no clear way to distinguish which, if any, of these models is correct. In this paper we exploit the spectral resolution of the ASCA SIS detectors which, for the first time, enables the iron-line emission from this system to be studied in detail. The line and continuous spectrum of gamma Cas is compared with the X-ray spectra of hot coronae of early type stars, low-mass X-ray binaries, high-mass X-ray binaries, and white-dwarf binaries. The observed properties of rapid fluctuations on timescales down to 10 s and a spectrum with a temperature of 10.6 keV, together with iron line emission, are very similar to those of binary white-dwarf systems. Assuming a white-dwarf binary origin for the X-rays, we estimated the luminosity of this system as a function of the binary separation using recent measurements of the circumstellar environment of gamma Cas. Despite previous arguments that the X-ray luminosity is too large to be accounted for by accretion onto a white dwarf, we find that such a model is, in fact, consistent with the observed properties of the system. C1 Inst Space & Astronaut Sci, Sagamihara, Kanagawa 2298510, Japan. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Inst Space & Astronaut Sci, 3-1-1 Yoshinodai, Sagamihara, Kanagawa 2298510, Japan. EM murakami@astro.isas.ac.jp NR 38 TC 28 Z9 28 U1 0 U2 0 PU OXFORD UNIV PRESS PI OXFORD PA GREAT CLARENDON ST, OXFORD OX2 6DP, ENGLAND SN 0004-6264 EI 2053-051X J9 PUBL ASTRON SOC JPN JI Publ. Astron. Soc. Jpn. PD AUG 25 PY 1998 VL 50 IS 4 BP 417 EP 426 DI 10.1093/pasj/50.4.417 PG 10 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 113HN UT WOS:000075545100006 ER PT J AU Luo, LS AF Luo, LS TI Unified theory of lattice boltzmann models for nonideal gases SO PHYSICAL REVIEW LETTERS LA English DT Article ID NAVIER-STOKES EQUATION; AUTOMATA; FLOWS AB A nonideal gas lattice Boltzmann model is directly derived, in an a priori fashion, from the Enskog equation for dense gases. The model is rigorously obtained by a systematic procedure to discretize the Enskog equation (in the presence of an external force) in both phase space and time. The lattice Boltzmann model derived here is thermodynamically consistent and is free of the defects which exist in previous lattice Boltzmann models for nonideal derived here. C1 NASA, Langley Res Ctr, ICASE, Hampton, VA 23681 USA. RP Luo, LS (reprint author), NASA, Langley Res Ctr, ICASE, MS 403,6 N Dryden St,Bldg 1298, Hampton, VA 23681 USA. RI Luo, Li-Shi/A-4561-2011 OI Luo, Li-Shi/0000-0003-1215-7892 NR 23 TC 197 Z9 202 U1 4 U2 32 PU AMERICAN PHYSICAL SOC PI COLLEGE PK PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA SN 0031-9007 J9 PHYS REV LETT JI Phys. Rev. Lett. PD AUG 24 PY 1998 VL 81 IS 8 BP 1618 EP 1621 DI 10.1103/PhysRevLett.81.1618 PG 4 WC Physics, Multidisciplinary SC Physics GA 112FJ UT WOS:000075483200021 ER PT J AU Goodstein, DL Harter, AW Chui, TCP AF Goodstein, DL Harter, AW Chui, TCP TI Heat capacity of a current carrying superconductor SO PHYSICS LETTERS A LA English DT Article DE superconductivity; heat capacity; Ginzburg-Landau theory AB We present an analysis of the heat capacity of a superconductor carrying a constant applied electric current. We find that the heat capacity diverges with an exponent of 0.5 at a depressed transition temperature. This result is similar to a recent calculation of the heat capacity of superfluid helium under an applied heat current. (C) 1998 Elsevier Science B.V. C1 CALTECH, Pasadena, CA 91125 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Goodstein, DL (reprint author), CALTECH, Pasadena, CA 91125 USA. EM dg@cco.caltech.edu NR 4 TC 2 Z9 2 U1 1 U2 1 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0375-9601 EI 1873-2429 J9 PHYS LETT A JI Phys. Lett. A PD AUG 24 PY 1998 VL 245 IS 5 BP 477 EP 478 DI 10.1016/S0375-9601(98)00474-5 PG 2 WC Physics, Multidisciplinary SC Physics GA 112YN UT WOS:000075522600023 ER PT J AU Carle, GC Kojiro, DR Lasher, LE Valentin, JR AF Carle, GC Kojiro, DR Lasher, LE Valentin, JR TI Hummingbird - The comet surface sampling mission SO ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY LA English DT Meeting Abstract C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. SETI Inst, Mt View, CA 94043 USA. NR 0 TC 0 Z9 0 U1 1 U2 1 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA SN 0065-7727 J9 ABSTR PAP AM CHEM S JI Abstr. Pap. Am. Chem. Soc. PD AUG 23 PY 1998 VL 216 MA 109-ANYL BP U171 EP U171 PN 1 PG 1 WC Chemistry, Multidisciplinary SC Chemistry GA 107WX UT WOS:000075234900451 ER PT J AU Chuang, KC Tytko, SF Galat, KJ Youngs, WJ AF Chuang, KC Tytko, SF Galat, KJ Youngs, WJ TI Configurations of fluorobenzidines and corresponding polyimides SO ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY LA English DT Meeting Abstract C1 NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. Baldwin Wallace Coll, Dept Chem, Berea, OH 44017 USA. Univ Akron, Dept Chem, Akron, OH 44325 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA SN 0065-7727 J9 ABSTR PAP AM CHEM S JI Abstr. Pap. Am. Chem. Soc. PD AUG 23 PY 1998 VL 216 MA 457-POLY BP U137 EP U137 PN 3 PG 1 WC Chemistry, Multidisciplinary SC Chemistry GA 107WZ UT WOS:000075235100457 ER PT J AU Dyall, KG AF Dyall, KG TI Bonding and bending in the actinyls. SO ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY LA English DT Meeting Abstract C1 NASA, Ames Res Ctr, Thermosci Inst, Moffett Field, CA 94035 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA SN 0065-7727 J9 ABSTR PAP AM CHEM S JI Abstr. Pap. Am. Chem. Soc. PD AUG 23 PY 1998 VL 216 MA 421-PHYS BP U781 EP U781 PN 2 PG 1 WC Chemistry, Multidisciplinary SC Chemistry GA 107WY UT WOS:000075235002352 ER PT J AU Dyall, KG AF Dyall, KG TI Efficient and accurate relativistic all-electron approximations. SO ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY LA English DT Meeting Abstract C1 NASA, Ames Res Ctr, Thermosci Inst, Moffett Field, CA 94035 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA SN 0065-7727 J9 ABSTR PAP AM CHEM S JI Abstr. Pap. Am. Chem. Soc. PD AUG 23 PY 1998 VL 216 MA 088-PHYS BP U683 EP U683 PN 2 PG 1 WC Chemistry, Multidisciplinary SC Chemistry GA 107WY UT WOS:000075235002033 ER PT J AU Golub, MA Banks, BA Rutledge, SK Kitral, MC AF Golub, MA Banks, BA Rutledge, SK Kitral, MC TI Fluoropolymer films deposited by argon ion-beam sputtering of polytetrafluoroethylene. SO ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY LA English DT Meeting Abstract C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. Cleveland State Univ, Cleveland, OH 44115 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA SN 0065-7727 J9 ABSTR PAP AM CHEM S JI Abstr. Pap. Am. Chem. Soc. PD AUG 23 PY 1998 VL 216 MA 276-POLY BP U82 EP U82 PN 3 PG 1 WC Chemistry, Multidisciplinary SC Chemistry GA 107WZ UT WOS:000075235100275 ER PT J AU Golub, MA AF Golub, MA TI Fluoropolymer films deposited by rf plasma sputtering of polytetrafluoroethylene using inert gases. SO ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY LA English DT Meeting Abstract C1 NASA, Ames Res Ctr, Lockheed Martin Engn & Sci, Moffett Field, CA 94035 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA SN 0065-7727 J9 ABSTR PAP AM CHEM S JI Abstr. Pap. Am. Chem. Soc. PD AUG 23 PY 1998 VL 216 MA 274-POLY BP U82 EP U82 PN 3 PG 1 WC Chemistry, Multidisciplinary SC Chemistry GA 107WZ UT WOS:000075235100273 ER PT J AU Kojiro, DR Cohen, MJ Wernlund, RF Stimac, RM Takeuchi, N AF Kojiro, DR Cohen, MJ Wernlund, RF Stimac, RM Takeuchi, N TI Exobiology flight experiment advanced GC detectors SO ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY LA English DT Meeting Abstract C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. PCP Inc, W Palm Beach, FL 33409 USA. Glimmerglass Sci & Technol Corp, Utica, NY 13501 USA. ManTech Syst Engn Corp, Fairfax, VA 22033 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA SN 0065-7727 J9 ABSTR PAP AM CHEM S JI Abstr. Pap. Am. Chem. Soc. PD AUG 23 PY 1998 VL 216 MA 206-ANYL BP U199 EP U199 PN 1 PG 1 WC Chemistry, Multidisciplinary SC Chemistry GA 107WX UT WOS:000075234900546 ER PT J AU Ma, H Liu, S Wu, XM Wang, XJ Jen, AKY Levina, G Staub, K Marder, SR AF Ma, H Liu, S Wu, XM Wang, XJ Jen, AKY Levina, G Staub, K Marder, SR TI A versatile approach for the synthesis of side-chain aromatic polyquinolines for E-O devices. SO ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY LA English DT Meeting Abstract C1 Northeastern Univ, Dept Chem, Boston, MA 02115 USA. CALTECH, Beckman Inst, Pasadena, CA 91125 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91125 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA SN 0065-7727 J9 ABSTR PAP AM CHEM S JI Abstr. Pap. Am. Chem. Soc. PD AUG 23 PY 1998 VL 216 MA 604-POLY BP U196 EP U196 PN 3 PG 1 WC Chemistry, Multidisciplinary SC Chemistry GA 107WZ UT WOS:000075235100601 ER PT J AU Marder, SR Barlow, S Beljonne, D Bredas, JL Cumpston, BH Fu, JY Ehrlich, JE Heikal, AA Kogej, T Levin, M McCord-Maughon, D Perry, JW Rockel, H Rumi, M Subramaniam, G Thayumanvan, S Wu, XL AF Marder, SR Barlow, S Beljonne, D Bredas, JL Cumpston, BH Fu, JY Ehrlich, JE Heikal, AA Kogej, T Levin, M McCord-Maughon, D Perry, JW Rockel, H Rumi, M Subramaniam, G Thayumanvan, S Wu, XL TI Design, synthesis and applications of two-photon absorbing organic molecules. SO ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY LA English DT Meeting Abstract C1 CALTECH, Beckman Inst, Pasadena, CA 91125 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ Mons, Ctr Res Mol Elect & Photon, B-7000 Mons, Belgium. RI Bredas, Jean-Luc/A-3431-2008; Perry, Joseph/B-7191-2011 OI Bredas, Jean-Luc/0000-0001-7278-4471; Perry, Joseph/0000-0003-1101-7337 NR 0 TC 1 Z9 1 U1 0 U2 2 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA SN 0065-7727 J9 ABSTR PAP AM CHEM S JI Abstr. Pap. Am. Chem. Soc. PD AUG 23 PY 1998 VL 216 MA 608-POLY BP U197 EP U197 PN 3 PG 1 WC Chemistry, Multidisciplinary SC Chemistry GA 107WZ UT WOS:000075235100605 ER PT J AU Pohorille, A New, MH AF Pohorille, A New, MH TI Extended system molecular dynamics methods for biological systems. SO ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY LA English DT Meeting Abstract C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA SN 0065-7727 J9 ABSTR PAP AM CHEM S JI Abstr. Pap. Am. Chem. Soc. PD AUG 23 PY 1998 VL 216 MA 070-COMP BP U704 EP U704 PN 1 PG 1 WC Chemistry, Multidisciplinary SC Chemistry GA 107WX UT WOS:000075234902092 ER PT J AU Southward, RE Stoakley, DM St Clair, AK AF Southward, RE Stoakley, DM St Clair, AK TI Oxo-metal-polyimide hybrid materials: Alternatives to silica and titania phases using rare earth metal complexes SO ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY LA English DT Meeting Abstract C1 NASA, Langley Res Ctr, Hampton, VA 23681 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA SN 0065-7727 J9 ABSTR PAP AM CHEM S JI Abstr. Pap. Am. Chem. Soc. PD AUG 23 PY 1998 VL 216 MA 459-POLY BP U137 EP U137 PN 3 PG 1 WC Chemistry, Multidisciplinary SC Chemistry GA 107WZ UT WOS:000075235100456 ER PT J AU Baptista, R Horne, K Wade, RA Hubeny, I Long, KS Rutten, RGM AF Baptista, R Horne, K Wade, RA Hubeny, I Long, KS Rutten, RGM TI HST spatially resolved spectra of the accretion disc and gas stream of the nova-like variable UX Ursae Majoris SO MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY LA English DT Article DE accretion, accretion discs; eclipses; binaries : close; stars : individual : UX UMa; novae, cataclysmic variables; ultraviolet : stars ID HOPKINS ULTRAVIOLET TELESCOPE; ECLIPSE MAPPING METHOD; Z-CAMELOPARDALIS; OUTBURST; DWARF; STARS; MAPS AB Time-resolved eclipse spectroscopy of the nova-like variable UXUMa obtained with the HST/FOS on 1994 August and November is analysed with eclipse mapping techniques to produce spatially resolved spectra of its accretion disc and gas stream as a function of distance from the disc centre. The inner accretion disc is characterized by a blue continuum filled with absorption bands and lines, which cross over to emission with increasing disc radius, similar to that reported by Rutten et al. at optical wavelengths. The comparison of spatially resolved spectra at different azimuths reveals a significant asymmetry in the disc emission at ultraviolet (UV) wavelengths, with the disc side closest to the secondary star showing pronounced absorption by an 'iron curtain' and a Balmer jump in absorption. These results suggest the existence of an absorbing ring of cold gas whose density and/or vertical scale increase with disc radius. The spectrum of the infalling gas stream is noticeably different from the disc spectrum at the same radius suggesting that gas overflows through the impactpoint at the disc rim and continues along the stream trajectory, producing distinct emission down to 0.1 R(L1). The spectrum of the uneclipsed Light shows prominent emission lines of Ly alpha; N V lambda 1241, Si IV lambda 1400, C IV lambda 1550, He II lambda 1640, and Mg II lambda 2800, and a UV continuum rising towards longer wavelengths. The Balmer jump appears clearly in emission indicating that the uneclipsed light has an important contribution from optically thin gas. The lines and optically thin continuum emission are most probably emitted in a vertically extended disc chromosphere + wind. The radial temperature profiles of the continuum maps are well described by a steady-state disc model in the inner and intermediate disc regions (R less than or equal to 0.3 R(L1)) There is evidence of an increase in the mass accretion rate from August to November (from (M) over dot = 10(-8.3+/-0.1) to 10(-8.1+/-0.1) M. yr(-1)), in accordance with the observed increase in brightness. Since the UX UMa disc seems to be in a high mass accretion, high-viscosity regime in both epochs, this result suggests that the mass transfer rate of UX UMa varies substantially (similar or equal to 50 per cent) on time-scales of a few months. It is suggested that the reason for the discrepancies between the prediction of the standard disc model and observations is not an inadequate treatment of radiative transfer in the disc atmosphere, but rather the presence of additional important sources of light in the system besides the accretion disc (e.g. optically thin continuum emission from the disc wind and possible absorption by circumstellar cool gas). C1 Univ Fed Santa Catarina, Dept Fis, BR-88040900 Florianopolis, SC, Brazil. Univ St Andrews, Sch Phys & Astron, St Andrews KY16 9SS, Fife, Scotland. Space Telescope Sci Inst, Baltimore, MD 21218 USA. Penn State Univ, Dept Astron & Astrophys, Davey Lab 525, University Pk, PA 16802 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Isaac Newton Grp, E-38780 Santa Cruz De La Palma, Spain. RP Baptista, R (reprint author), Univ Fed Santa Catarina, Dept Fis, Campus Trindade, BR-88040900 Florianopolis, SC, Brazil. EM bap@fsc.ufsc.br; kdhl@st-andrews.ac.uk; wade@astro.psu.edu; hubeny@stars.gsfc.nasa.gov; long@stsci.edu; rgmr@ing.iac.es NR 28 TC 30 Z9 30 U1 0 U2 0 PU WILEY-BLACKWELL PI MALDEN PA COMMERCE PLACE, 350 MAIN ST, MALDEN 02148, MA USA SN 0035-8711 J9 MON NOT R ASTRON SOC JI Mon. Not. Roy. Astron. Soc. PD AUG 21 PY 1998 VL 298 IS 4 BP 1079 EP 1091 DI 10.1046/j.1365-8711.1998.01712.x PG 13 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 117LA UT WOS:000075781700012 ER PT J AU Rind, D AF Rind, D TI Climate change - Just add water vapor SO SCIENCE LA English DT Editorial Material C1 NASA, Goddard Inst Space Studies, New York, NY 10025 USA. RP Rind, D (reprint author), NASA, Goddard Inst Space Studies, New York, NY 10025 USA. NR 9 TC 29 Z9 32 U1 0 U2 5 PU AMER ASSOC ADVANCEMENT SCIENCE PI WASHINGTON PA 1200 NEW YORK AVE, NW, WASHINGTON, DC 20005 USA SN 0036-8075 J9 SCIENCE JI Science PD AUG 21 PY 1998 VL 281 IS 5380 BP 1152 EP 1153 DI 10.1126/science.281.5380.1152 PG 2 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA 113CE UT WOS:000075531200036 ER PT J AU Menzies, RT Tratt, DM Hunt, WH AF Menzies, RT Tratt, DM Hunt, WH TI Lidar In-space Technology Experiment measurements of sea surface directional reflectance and the link to surface wind speed SO APPLIED OPTICS LA English DT Article ID OCEAN COLOR; WATER; SYSTEM AB The dependence of sea surface directional reflectance on surface wind stress suggests a method for deriving surface wind speed from space-based lidar measurements of sea surface backscatter. In particular, lidar measurements in the nadir angle range from 10 degrees to 30 degrees appear to be most sensitive to surface wind-speed variability in the regime below 10 m/s. The Lidar In-space Technology Experiment (LITE) shuttle Lidar mission of September 1994 provided a unique opportunity to measure directional backscatter at selected locations by use of the landmark track maneuver and to measure fixed-angle backscatter from the ocean surfaces on a global scale. During the landmark track maneuver the shuttle orbiter orientation and roll axis are adjusted continuously to maintain the lidar footprint at a fixed location for a duration of similar to 1 min. Several data sets were converted to calibrated reflectance units and compared with a surface reflectance model to deduce surface wind speeds. Comparisons were made with ERS-1 scatterometer data and surface measurements. (C) 1998 Optical Society of America. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Wyle Labs, Hampton, VA 23666 USA. RP Menzies, RT (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. RI Tratt, David/A-7884-2009 OI Tratt, David/0000-0002-3942-6848 NR 32 TC 24 Z9 26 U1 0 U2 3 PU OPTICAL SOC AMER PI WASHINGTON PA 2010 MASSACHUSETTS AVE NW, WASHINGTON, DC 20036 USA SN 0003-6935 J9 APPL OPTICS JI Appl. Optics PD AUG 20 PY 1998 VL 37 IS 24 BP 5550 EP 5559 DI 10.1364/AO.37.005550 PG 10 WC Optics SC Optics GA 110CA UT WOS:000075360700005 PM 18286039 ER PT J AU Auchere, F Boulade, S Koutchmy, S Smartt, RN Delaboudiniere, JP Georgakilas, A Gurman, JB Artzner, GE AF Auchere, F Boulade, S Koutchmy, S Smartt, RN Delaboudiniere, JP Georgakilas, A Gurman, JB Artzner, GE TI The prolate solar chromosphere SO ASTRONOMY & ASTROPHYSICS LA English DT Letter DE Sun : chromosphere; corona ID TELESCOPE AB We present a comparative analysis of the chromospheric solar limb prolateness, using strictly simultaneous H-alpha ground-based observations and Hen space-based observations. The typical prolateness is found to be Delta D/D = 5.5 x 10(-3) in Hen and 1.2 x 10(-3) in H-alpha. The first measurements in the 30.4 nm Hen line over a period of two years, as well as coronal data, are discussed to explore further the origin of the prolateness and its possible consequences. C1 Univ Paris 11, Inst Astrophys Spatiale, F-91405 Orsay, France. Inst Astrophys, F-75014 Paris, France. Natl Solar Observ, Sacramento Peak Observ, Sunspot, NM 88349 USA. Natl Observ, Athens, Greece. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Auchere, F (reprint author), Univ Paris 11, Inst Astrophys Spatiale, Batiment 121, F-91405 Orsay, France. NR 11 TC 16 Z9 16 U1 0 U2 0 PU EDP SCIENCES S A PI LES ULIS CEDEX A PA 17, AVE DU HOGGAR, PA COURTABOEUF, BP 112, F-91944 LES ULIS CEDEX A, FRANCE SN 0004-6361 J9 ASTRON ASTROPHYS JI Astron. Astrophys. PD AUG 20 PY 1998 VL 336 IS 3 BP L57 EP L60 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 118FL UT WOS:000075827700005 ER PT J AU Coustenis, A Salama, A Lellouch, E Encrenaz, T Bjoraker, GL Samuelson, RE de Graauw, T Feuchtgruber, H Kessler, MF AF Coustenis, A Salama, A Lellouch, E Encrenaz, T Bjoraker, GL Samuelson, RE de Graauw, T Feuchtgruber, H Kessler, MF TI Evidence for water vapor in Titan's atmosphere from ISO/SWS data SO ASTRONOMY & ASTROPHYSICS LA English DT Letter DE planets and satellites : Titan; infrared : solar system ID CARBON-MONOXIDE; SATURNS RINGS; MODEL AB The infrared spectrum of Titan around 40 mu m was recorded in the grating mode of the Short Wavelength Spectrometer (SWS) of ISO, with a resolving power of about 1900. Two emission features appear at 43.9 and 39.4 mu m, where pure rotational water lines are expected. Line strengths are about 8 times the 1 sigma statistical noise level. The H2O vertical profile for water suggested by the photochemical model of Lara et al. (1996), rescaled by a factor of about 0.4(-0.2)(+0.3), is compatible with the data. The associated water mole fraction is about 8(-4)(+6) x 10(-9) at an altitude of 400 km (column density of 2.6(-1.6)(+1.9) x 10(14) mol cm(-2) above the surface). The inferred water influx at 700 km in Titan's atmosphere is in the range (0.8-2.8) x 10(6) mol cm(-2)s(-1). C1 Observ Paris, DESPA, F-92195 Meudon, France. ESA, ISO Sci Operat Ctr, E-28080 Madrid, Spain. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. SRON, NL-9700 AV Groningen, Netherlands. RP Coustenis, A (reprint author), Observ Paris, DESPA, F-92195 Meudon, France. EM coustenis@obspm.fr RI Bjoraker, Gordon/D-5032-2012 NR 20 TC 129 Z9 129 U1 1 U2 5 PU EDP SCIENCES S A PI LES ULIS CEDEX A PA 17, AVE DU HOGGAR, PA COURTABOEUF, BP 112, F-91944 LES ULIS CEDEX A, FRANCE SN 0004-6361 J9 ASTRON ASTROPHYS JI Astron. Astrophys. PD AUG 20 PY 1998 VL 336 IS 3 BP L85 EP L89 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 118FL UT WOS:000075827700012 ER PT J AU Palazzi, E Pian, E Masetti, N Nicastro, L Vreeswijk, P Galama, TJ Groot, P Frontera, F Della Valle, M Lidman, C Kouveliotou, C Pizzichini, G van Paradijs, J Pedersen, H Mannucci, F Di Martino, M Diercks, AH Deutsch, EW Amati, L Benetti, S Castro-Tirado, AJ Clasen, J Costa, E Dal Fiume, D Falomo, R Feroci, M Fynbo, J Heise, J in't Zand, JJM Piro, L Robinson, C Tornikoski, M Valtaoja, E Zapatero-Osorio, MR Lamb, D Quashnock, J Van den Berk, D AF Palazzi, E Pian, E Masetti, N Nicastro, L Vreeswijk, P Galama, TJ Groot, P Frontera, F Della Valle, M Lidman, C Kouveliotou, C Pizzichini, G van Paradijs, J Pedersen, H Mannucci, F Di Martino, M Diercks, AH Deutsch, EW Amati, L Benetti, S Castro-Tirado, AJ Clasen, J Costa, E Dal Fiume, D Falomo, R Feroci, M Fynbo, J Heise, J in't Zand, JJM Piro, L Robinson, C Tornikoski, M Valtaoja, E Zapatero-Osorio, MR Lamb, D Quashnock, J Van den Berk, D TI Optical and near-infrared follow-up observations of GRB980329 SO ASTRONOMY & ASTROPHYSICS LA English DT Letter DE gamma-rays : bursts; radiation mechanisms : non thermal ID GAMMA-RAY BURST; STAR-FORMATION; GALAXIES; EMISSION; FIELD AB We imaged the field of GRB980329 in the optical and in the near-infrared starting 20 hours after the event, at the ESO NTT, at the NOT, at the APO and at the TIRGO. In the first night we detect an object of R = 23.6 +/- 0.2 within the BeppoSAX NFI error box at the same position as a transient VLA source proposed as the radio afterglow of this GRB. The source faded by 1.6 +/- 0.5 magnitudes in 2.1 days, similarly to the decays of previous GRB optical afterglows. This transient is likely the optical counterpart of GRB980329. In the near-infrared we detect signal at 2-sigma significance, whose position is only marginally consistent with that of the VLA source. The spectrum of the transient bears the signatures of substantial absorption within the GRB host galaxy. The afterglow energetics are interpreted as synchrotron radiation from an expanding blast wave. C1 CNR, Ist Tecnol & Studio Radiazioni Extraterrestri, I-40129 Bologna, Italy. CNR, Ist Fis Cosm Applicazioni Informat, I-90146 Palermo, Italy. Univ Amsterdam, NL-1098 SJ Amsterdam, Netherlands. Univ Ferrara, Dept Phys, I-44100 Ferrara, Italy. Univ Padua, Dept Astron, I-35122 Padua, Italy. European So Observ, Santiago 19, Chile. NASA, George C Marshall Space Flight Ctr, Univ Space Res Assoc, Huntsville, AL 35812 USA. Univ Alabama, Huntsville, AL 35899 USA. Copenhagen Univ Observ, DK-2100 Copenhagen, Denmark. CNR, Ctr Astron Infrarossa & Studio Mezzo Interstellar, I-50125 Arcetri, Italy. Osservatorio Astron Torino, I-10025 Pino Torinese, Italy. Univ Washington, Dept Astron, Seattle, WA 98195 USA. CNR, Ist Astrofis Spaziale, I-00131 Rome, Italy. Nordic Opt Telescope, La Palma, Canary Island, Spain. Astron Observ Padova, I-35122 Padua, Italy. Inst Phys & Astron, Aarhus, Denmark. Space Res Org Netherlands, NL-3584 CA Utrecht, Netherlands. Metsahovi Radio Observ, Helsinki, Finland. Tuorla Observ, Turku, Finland. Inst Astrofis Canarias, La Laguna, Tenerife, Spain. Univ Chicago, Dept Astron & Astrophys, Chicago, IL 60637 USA. Univ Texas, Mcdonald Observ, Austin, TX 78712 USA. RP Palazzi, E (reprint author), CNR, Ist Tecnol & Studio Radiazioni Extraterrestri, Via Gobetti 101, I-40129 Bologna, Italy. EM eliana@tesre.bo.cnr.it RI Galama, Titus/D-1429-2014; PIRO, LUIGI/E-4954-2013; Nicastro, Luciano/F-5866-2015; Palazzi, Eliana/N-4746-2015; Amati, Lorenzo/N-5586-2015; Groot, Paul/K-4391-2016 OI Galama, Titus/0000-0002-1036-396X; PIRO, LUIGI/0000-0003-4159-3984; Nicastro, Luciano/0000-0001-8534-6788; Amati, Lorenzo/0000-0001-5355-7388; Groot, Paul/0000-0002-4488-726X NR 42 TC 44 Z9 45 U1 0 U2 1 PU EDP SCIENCES S A PI LES ULIS CEDEX A PA 17, AVE DU HOGGAR, PA COURTABOEUF, BP 112, F-91944 LES ULIS CEDEX A, FRANCE SN 0004-6361 J9 ASTRON ASTROPHYS JI Astron. Astrophys. PD AUG 20 PY 1998 VL 336 IS 3 BP L95 EP L99 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 118FL UT WOS:000075827700014 ER PT J AU Cheng, LX Leventhal, M Smith, DM Gehrels, N Tueller, J Fishman, G AF Cheng, LX Leventhal, M Smith, DM Gehrels, N Tueller, J Fishman, G TI Batse all-sky search for transient gamma-ray lines between 300 and 550 keV SO ASTROPHYSICAL JOURNAL LA English DT Article DE gamma rays : observations; line : identification ID POSITRON-ANNIHILATION LINE; CRAB PULSAR SPECTRUM; GALACTIC-CENTER; SMM OBSERVATIONS; NOVA-MUSCAE; FIGARO-II; 1E-1740.7-2942; EMISSION; NEBULA; DISCOVERY AB We present an all-sky search for bright, transient emission lines from 300 to 550 keV in more than two years (1993 December and 1996 March) of data from the Burst And Transient Source Experiment (BATSE) on the Compton Gamma-Ray Observatory. Our approach is sensitive only to events with durations from 0.5-3.0 days. The results show that the gamma-ray sky is very "quiet" in these two years, which is consistent with an earlier search using BATSE data from 1991 to 1993. No transients are observed in the search, and our 3 sigma upper limits are significantly below the fluxes of the two most significant events previously reported from Nova Muscae and 1E 1740.7-2942 by SIGMA. The disagreement between the BATSE data sets and those of SIGMA are quantitatively discussed. C1 Univ Maryland, Dept Astron, College Pk, MD 20742 USA. Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. RP Univ Maryland, Dept Astron, College Pk, MD 20742 USA. RI Gehrels, Neil/D-2971-2012; Tueller, Jack/D-5334-2012 NR 28 TC 9 Z9 9 U1 0 U2 0 PU IOP PUBLISHING LTD PI BRISTOL PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND SN 0004-637X EI 1538-4357 J9 ASTROPHYS J JI Astrophys. J. PD AUG 20 PY 1998 VL 503 IS 2 BP 809 EP 814 DI 10.1086/306012 PN 1 PG 6 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 152KN UT WOS:000077776700028 ER PT J AU Smith, RK Dwek, E AF Smith, RK Dwek, E TI Soft X-ray scattering and halos from dust SO ASTROPHYSICAL JOURNAL LA English DT Article DE dust, extinction; ISM : abundances; novae, cataclysmic variables; stars : individual (Nova Cygni 1992); X-rays : general; X-rays : ISM ID INTERSTELLAR DUST; OPTICAL-PROPERTIES; GRAINS; CARBON; PARTICLES; GRAPHITE; EMISSION AB Small-angle scatterings of X-rays by interstellar dust particles create halos around X-ray sources. The halo intensity and its projected radial distribution around a source can provide important information on the spatial distribution of the dust along the line of sight to the source and on the physical properties of the scattering dust particles. Halos around X-ray point sources have been used by several authors to infer that the scattering dust particles are fluffy in nature, consisting of aggregates of smaller refractory particles with vacuum occupying a significant fraction of their volume. The nature and morphology of interstellar dust particles has recently gained new importance, since huffy, composite dust particles have been suggested as a possible solution to the interstellar carbon "crisis." This crisis results from the discrepancy between the abundance of carbon in the interstellar medium available for creating dust and the significantly larger amount of carbon that must be in dust in order to account for the UV-optical interstellar extinction in the diffuse ISM. Previous studies of X-ray scattering have used the Rayleigh-Gans (RG) approximation to the differential scattering cross section to calculate halo properties. However, the validity of the RG approximation fails for energies below 1 keV. We use the exact Mie solution for the differential scattering cross section and find that, for these energies, the scattering becomes much less efficient than is predicted by the RG approximation. Furthermore, the effects of K and L shell absorption by atoms in the dust become important. The net effect is that the RG approximation systematically and substantially overestimates the intensity of the halo below 1 keV, relative to the Mie solution result. In particular, Mathis and coworkers used the weaker than expected halo intensity observed around Nova Cygni 1992 to conclude that interstellar dust must be fluffy. Using the Mie solution to the scattering intensity and including the effects of absorption, we find that, contrary to the conclusion of Mathis and coworkers, the halo around Nova Cygni 1992 does not require interstellar dust grains to be fluffy in nature and that the data are consistent with scattering from a mixture of bare refractory silicate and carbon grains as well. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Smith, RK (reprint author), Smithsonian Astrophys Observ, High Energy Astrophys Div, 60 Garden St, Cambridge, MA 02138 USA. NR 27 TC 69 Z9 69 U1 0 U2 2 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD AUG 20 PY 1998 VL 503 IS 2 BP 831 EP 842 DI 10.1086/306018 PN 1 PG 12 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 152KN UT WOS:000077776700030 ER PT J AU Smith, MA Robinson, RD Corbet, RHD AF Smith, MA Robinson, RD Corbet, RHD TI A multiwavelength campaign on gamma cassiopeiae. I. The case for surface X-ray flaring SO ASTROPHYSICAL JOURNAL LA English DT Article DE stars : emission-line, Be; stars : flare; stars : individual (gamma Cassiopeiae); ultraviolet : stars; x-rays : stars ID BE-STAR ATMOSPHERES; DYNAMIC PROCESSES; TIME VARIABILITY; LAMBDA-ERIDANI; EMISSION; SPECTRUM; PERSEI; ULTRAVIOLET; PARAMETERS; CONTINUUM AB In 1996 March we obtained simultaneous Rossi X-Ray Timing Explorer RXTE Proportional Counter Array (PCA) and Hubble Space Telescope (HST) Goddard High-Resolution Spectrograph (GHRS) light curves for the B0.5e star gamma Cas in order to compare its X-ray and ultraviolet continuum flux behaviors. The GHRS data set consisted of a nearly continuous sequence of UV spectra covering a 21+ hr interval. Each 40 Angstrom spectrum was centered on the Si IV lambda lambda 1394-1403 lines and registered 8100 counts in each 1 s exposure. Combining spectra and integrating over greater-than 100 continuum pixels allowed us to define a UV continuum light curve binned to 1 minute with a signal-to-noise ratio of a few thousand pixel(-1). We found that the light curve exhibited variations over a time comparable to the rotation period of the star, showing two broad minima 10 hr apart, which had depths of 0.8% and 1.8%. The long-term trends in the UV are anticorrelated with the X-ray fluxes, with the X-rays exhibiting increases of similar to 10% and similar to 40% during times of UV flux minima. The stability of the long-term X-ray variations on gamma Cas is supported by phasing our March data with contemporaneous ASCA data, suggesting a possible period of 1.125 days (or a close alias). We also get agreement of dip patterns for an assumed 1.123 day period by phasing the GHRS continuum flux curve with IUE light curves in various wavelengths from 2 months earlier. We take this as an estimate of the star's rotational period. We conclude that the X-ray emission from gamma Cas probably consists of two components. The first is a slowly varying "basal" flux representing the minimum level seen during any given phase. Superimposed on this are rapid fluctuations ("shots") that have lifetimes ranging from greater-than 10 a to greater-than-or-equal-to 10 minutes. The character of these components varies from one spacecraft orbit to the next, indicating that the emissions are not produced in a truly "stationary" chaotic environment. Moreover, both the number and amplitude of the shots increase during UV minima. The shot profiles are typically symmetric and can have decay times of a few seconds or less. The shots also have a slightly harder flux distribution than the basal component, suggesting that the two emission regions are not cospatial. The time-averaged X-ray spectrum indicates a quasi temperature of similar to 10(8) K, in agreement with earlier studies. We present a picture in which magnetically generated structures on and over the star's surface are responsible for the basal and shot X-ray components. The energies and luminosities of the shots are so high that even the weakest events we measure are comparable in strength to the most luminous flares on cool active stars. Using general cooling relations for a thermal plasma, one finds that the source region for the shots probably have a size scale of less-than-or-equal-to 10(4) km and densities of similar to 10(13-14) cm(-3). From a simple flare model, we find that generally only a small fraction of the shot energy is radiated during the event itself. The remainder of the hot plasma expands to fill a confined volume, possibly a magnetic loop, connected to the original hare site. A collection of these loops may then account for the basal emission. With this model, we estimate that the individual loops have a characteristic density of similar to 10(11) cm(-3) and dimensions of greater than or equal to 0.1R(*). We note that the magnetic interpretation for the shot and basal emission poses several theoretical questions, such as how complex, dynamic fields can exist on a star that does not have a convective envelope. These results suggest that gamma Cas is a member of an arguably new group of hot stars that flare continuously in X-rays. This group may represent an extension of the hotter Bp stars to high values of rotation. C1 Comp Sci Corp, Space Telescope Sci Inst, Baltimore, MD 21218 USA. Catholic Univ Amer, Washington, DC 20064 USA. Goddard Space Flight Ctr, USRA RXTE Project, Greenbelt, MD USA. RP Smith, MA (reprint author), Comp Sci Corp, Space Telescope Sci Inst, 3700 San Martin Dr, Baltimore, MD 21218 USA. EM msmith@nebula.gsfc.nasa.gov NR 62 TC 45 Z9 45 U1 0 U2 2 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD AUG 20 PY 1998 VL 503 IS 2 BP 877 EP 893 DI 10.1086/306006 PN 1 PG 17 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 152KN UT WOS:000077776700034 ER PT J AU Hilchenbach, M Hsieh, KC Hovestadt, D Klecker, B Grunwaldt, H Bochsler, P Ipavich, FM Burgi, A Mobius, E Gliem, F Axford, WI Balsiger, H Bornemann, W Coplan, MA Galvin, AB Geiss, J Gloeckler, G Hefti, S Judge, DL Kallenbach, R Laeverenz, P Lee, MA Livi, S Managadze, GG Marsch, E Neugebauer, M Ogawa, HS Reiche, KU Scholer, M Verigin, MI Wilken, B Wurz, P AF Hilchenbach, M Hsieh, KC Hovestadt, D Klecker, B Grunwaldt, H Bochsler, P Ipavich, FM Burgi, A Mobius, E Gliem, F Axford, WI Balsiger, H Bornemann, W Coplan, MA Galvin, AB Geiss, J Gloeckler, G Hefti, S Judge, DL Kallenbach, R Laeverenz, P Lee, MA Livi, S Managadze, GG Marsch, E Neugebauer, M Ogawa, HS Reiche, KU Scholer, M Verigin, MI Wilken, B Wurz, P TI Detection of 55-80 keV hydrogen atoms of heliospheric origin by CELIAS/HSTOF on Soho SO ASTROPHYSICAL JOURNAL LA English DT Article DE cosmic rays; ISM : atoms; solar wind ID COSMIC-RAY HYDROGEN; ANOMALOUS COMPONENT; OUTER HELIOSPHERE; ACCELERATION; SPECTRA; SHOCK AB The High-Energy Suprathermal Time-of-Flight sensor (HSTOF) of the Charge, Element, and Isotope Analysis System (CELIAS) on the Solar and Heliospheric Observatory (SOHO) near the Lagrangian point L1 is capable of identifying energetic hydrogen atoms (EHAs) between 55 and 80 keV. Between 1996 February 13 and 1997 August 31, near solar minimum, there were 285 "quiet" days when the interplanetary charged-particle flux was low. During these quiet times, HSTOF scanned the apex of the heliosphere once and the antiapex twice. The flux level and time profile, and hence the arrival direction, of the EHAs accumulated during these quiet times are best interpreted as fluxes of EHAs coming from the heliosheath. C1 Max Planck Inst Aeron, D-37189 Katlenburg Lindau, Germany. Univ Arizona, Dept Phys, Tucson, AZ 85721 USA. Max Planck Inst Extraterr Phys, D-85740 Garching, Germany. Univ Bern, Inst Phys, CH-3012 Bern, Switzerland. Univ Maryland, Dept Phys & Astron, College Pk, MD 20742 USA. ARIAS, CH-3012 Bern, Switzerland. Univ New Hampshire, EOS, Durham, NH 03824 USA. Tech Univ Carolo Wilhelmina Braunschweig, Inst Datenverarbeitungsanlagen, D-38023 Braunschweig, Germany. Int Space Sci Inst, CH-3012 Bern, Switzerland. Univ So Calif, Ctr Space Sci, Los Angeles, CA 90089 USA. Inst Space Phys, Moscow, Russia. Jet Prop Lab, Pasadena, CA 91103 USA. RP Max Planck Inst Aeron, D-37189 Katlenburg Lindau, Germany. RI Galvin, Antoinette/A-6114-2013; OI Moebius, Eberhard/0000-0002-2745-6978 NR 27 TC 74 Z9 75 U1 0 U2 0 PU IOP PUBLISHING LTD PI BRISTOL PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND SN 0004-637X EI 1538-4357 J9 ASTROPHYS J JI Astrophys. J. PD AUG 20 PY 1998 VL 503 IS 2 BP 916 EP 922 DI 10.1086/306022 PN 1 PG 7 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 152KN UT WOS:000077776700037 ER PT J AU Goodman, ML AF Goodman, ML TI Quantitative magnetohydrodynamic modeling of the solar transition region SO ASTROPHYSICAL JOURNAL LA English DT Article DE MHD; Sun : magnetic fields; Sun : transition region ID SCALE ELECTRIC CURRENTS; VELOCITY FILTRATION; MIDDLE CHROMOSPHERE; RESISTIVE DISSIPATION; ENERGY-BALANCE; CORONA; DRIVEN; EMISSION; PLASMAS AB The transition region (TR) is assumed to be a collision-dominated plasma. The dissipation and transport of energy in such a plasma is accurately described by the classical transport coefficients, which include the electrical and thermal conductivity, viscosity, and thermoelectric tensors. These tensors are anisotropic and are functions of local values of temperature, density, and magnetic field strength. The transport coefficients are valid for all magnetic field strengths and so may be used to study the physics of weakly as well as strongly magnetized regions of the TR. They may be used in an MHD model to obtain a self-consistent, realistic description of the TR. The physics of kinetic processes is included in the MHD model through the transport coefficients. As a first step in studying heating and cooling processes in the TR in a realistic, quantitative manner, a 1.5 dimensional, steady state MHD model with a specified temperature profile is developed. The momentum equation includes the inertial, pressure, magnetic, and gravitational forces. Ohm's law includes the exact expressions for the electrical conductivity and thermoelectric tensors. It is found that the contribution of the dissipation of large-scale electric currents to in situ heating of the TR is negligible, but that thermal energy flowing into the TR from the corona can provide the energy required to heat the TR. The possibility that significant in situ heating of the TR takes place through viscous dissipation or small-scale electric current dissipation such as may occur in current sheets or filaments is discussed, although these processes are not described by the model. The importance of thermoelectric and electron pressure gradient effects in Ohm's law, and in determining the electron heat flux, is demonstrated. Results of the model suggest that the force-free approximation is not valid over most of the TR. Justification for assuming that the TR is collision dominated is presented. In particular, a self-consistent calculation of the ratio of the electric field parallel to the magnetic field to the Dreicer electric field yields a value less than or similar to 10(-3), which suggests that anomalous transport processes are not important. The necessity of using a realistic description of transport processes in modeling heating mechanisms in the solar atmosphere is stressed. C1 NASA, Comp Sci Corp, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. NASA, Extraterr Phys Lab, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP NASA, Comp Sci Corp, Goddard Space Flight Ctr, Code 695, Greenbelt, MD 20771 USA. EM goodman@spof02.gsfc.nasa.gov NR 35 TC 10 Z9 10 U1 1 U2 1 PU IOP PUBLISHING LTD PI BRISTOL PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND SN 0004-637X EI 1538-4357 J9 ASTROPHYS J JI Astrophys. J. PD AUG 20 PY 1998 VL 503 IS 2 BP 938 EP 952 DI 10.1086/306013 PN 1 PG 15 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 152KN UT WOS:000077776700039 ER PT J AU Asai, K Dotani, T Nagase, F Ebisawa, K Mukai, K Smale, AP Kotani, T AF Asai, K Dotani, T Nagase, F Ebisawa, K Mukai, K Smale, AP Kotani, T TI ASCA observation of the supersoft X-ray source CAL 87 SO ASTROPHYSICAL JOURNAL LA English DT Article DE binaries : close; binaries : eclipsing; stars : individual (CAL 87); white dwarfs; X-rays : stars ID GAS IMAGING SPECTROMETER; LARGE MAGELLANIC CLOUD; BINARY; MODELS; LMC AB We have investigated the energy spectrum and the orbital modulation of the supersoft X-ray source CAL 87 using the ASCA satellite. We have detected a deep absorption edge at 0.85(-0.01)(+0.02) keV superposed on a continuum that can be approximated with an absorbed blackbody (kT = 0.05(-0.01)(+0.06) keV). The edge structure may be produced by the highly ionized species of O VIII and O VII. Such deep edge structures from highly ionized heavy elements are expected for X-ray emission from a white dwarf with an envelope of stable hydrogen burning and strongly supports the model that a white dwarf with a large mass accretion rate is involved in the supersoft X-ray sources. Epoch-folding analysis reveals the presence of a partial X-ray eclipse with broad wings at orbital phase 0; the eclipse covers a quarter of the orbital phase and the X-ray flux decreases down to similar to 40% of the out-of-eclipse level. We discuss the possible cause of the partial eclipse, including the extended emission region due to the accretion disk corona, and the X-ray scattering site formed by the gas escaping from the binary system, where the gas is highly ionized by the large X-ray luminosity from the white dwarf. C1 Inst Space & Astronaut Sci, Sagamihara, Kanagawa 2298510, Japan. NASA, High Energy Astrophys Lab, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Inst Phys & Chem Res, RIKEN, Wako, Saitama 3510198, Japan. RP Asai, K (reprint author), Inst Space & Astronaut Sci, 3-1-1 Yoshinodai, Sagamihara, Kanagawa 2298510, Japan. EM asai@astro.isas.ac.jp; dotani@astro.isas.ac.jp; nagase@astro.isas.ac.jp NR 21 TC 10 Z9 10 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD AUG 20 PY 1998 VL 503 IS 2 BP L143 EP L146 DI 10.1086/311547 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 152KQ UT WOS:000077777000010 ER PT J AU Keohane, JW Gotthelf, EV Petre, R AF Keohane, JW Gotthelf, EV Petre, R TI Evidence for proportionate partition between the magnetic field and hot gas in turbulent Cassiopeia A SO ASTROPHYSICAL JOURNAL LA English DT Article DE MHD; supernova remnants; supernovae : individual (Cassiopeia A); techniques : image processing; turbulence; X-rays : ISM ID YOUNG SUPERNOVA-REMNANTS; X-RAY; RADIO; ABSORPTION AB We present a deep X-ray observation of the young Galactic supernova remnant Cassiopeia A, acquired with the ROSAT High Resolution Imager. This high dynamic range (232 ks) image reveals low surface brightness Xray structure that appears qualitatively similar to corresponding radio features. We consider the correlation between the X-ray and radio morphologies and its physical implications. After correcting for the inhomogeneous absorption across the remnant, we performed a point-by-point (4 " resolution) surface brightness comparison between the Xray and radio images. We find a strong (r = 0.75) log-log correlation, implying an overall relationship of log (Sigma(X-ray)) proportional to (2.21 +/- 0.05) x log(Sigma(radio)). This is consistent with proportionate partition land possibly equipartition) between the local magnetic field and the hot gas-implying that Cas A's plasma is fully turbulent and continuously amplifying the magnetic field. C1 NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. RP Keohane, JW (reprint author), Univ Minnesota, Minneapolis, MN 55455 USA. EM jonathan@lheamail.gsf.nasa.gov; gotthelf@gsfc.nasa.gov; petre@lheavx.gsfc.nasa.gov NR 20 TC 10 Z9 10 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD AUG 20 PY 1998 VL 503 IS 2 BP L175 EP L181 DI 10.1086/311541 PN 2 PG 7 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 152KQ UT WOS:000077777000017 ER PT J AU Rho, J Petre, R AF Rho, J Petre, R TI Mixed-morphology supernova remnants SO ASTROPHYSICAL JOURNAL LA English DT Article DE ISM : clouds; ISM : general; shock waves; supernova remnants; X-rays : ISM ID X-RAY; ROSAT OBSERVATIONS; DISCOVERY; W44; EMISSION; 3C-400.2; PULSAR; W51C; W28; CO AB While shell-like, Crab-like, and composite supernova remnants (SNRs) represent well-defined classes, there is another group of SNRs with different X-ray and radio morphologies: shell-like in the radio and centrally filled in the X-ray (with little or no limb brightening). We present the results of a systematic X-ray study of 19 such remnants, using ROSAT and ASCA data. We show that they have physical and environmental properties distinct from the other categories, and we propose that they form a unique class that we term "mixed-morphology" supernova remnants. We found two prominent distinctions of this new class: their dominant X-ray emission mechanism is thermal despite their X-ray morphological similarity to Crab-like SNRs, and their emission arises primarily from swept-up interstellar material, not ejecta. The temperature across each remnant is nearly uniform, and the density and pressure are constant or increase toward the remnant center, contrary to the standard Sedov model. Most of these remnants are interacting with molecular or H I clouds, as indicated in some cases by strong infrared line emission or OH masers. The population represents at least 8% of all Galactic SNRs and as much as 25% of all X-ray-detected Galactic SNRs. This suggests that supernovae often explode in an environment that is conducive to the formation of a mixed-morphology remnant. The two most likely mechanisms for forming these remnants-evaporation of many small interior clouds and interior "fossil radiation" evolved in a denser than normal medium-require a reservoir of material with density higher than the typical intercloud ISM. C1 NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. Ctr Etud Saclay, Serv Astrophys, F-91191 Gif Sur Yvette, France. RP Rho, J (reprint author), NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Code 662, Greenbelt, MD 20771 USA. NR 31 TC 164 Z9 166 U1 2 U2 3 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD AUG 20 PY 1998 VL 503 IS 2 BP L167 EP L170 DI 10.1086/311538 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 152KQ UT WOS:000077777000015 ER PT J AU Strohmayer, TE Zhang, W Swank, JH Lapidus, I AF Strohmayer, TE Zhang, W Swank, JH Lapidus, I TI The long-term stability of oscillations during thermonuclear X-ray bursts: Constraining the binary X-ray mass function SO ASTROPHYSICAL JOURNAL LA English DT Article DE stars : individual (4U 1636-53, 4U 1728-34); stars : neutron; stars : rotation; X-rays : bursts ID ORBITAL PERIOD AB We report on the long-term stability of the millisecond oscillations observed with the Rossi X-Ray Timing Explorer during thermonuclear X-ray bursts from the low-mass X-ray binaries (LMXBs) 4U 1728-34 and 4U 1636-53. We show that bursts from 4U 1728-34 spanning more than 1.5 yr have observed asymptotic oscillation periods that are within 0.2 mu s of each other, well within the magnitude that could be produced by the orbital motion of the neutron star in a canonical LMXB. This stability implies a timescale to change the oscillation period of more than 23,000 yr in this system and suggests a highly stable process, such as stellar rotation, as the mechanism producing the oscillations. For 4U 1636-53, which has an orbital period of 3.8 hr, we show that the offsets in the asymptotic oscillation periods from three different bursts can be consistently interpreted as due to the orbital velocity of the neutron star with v sin i/c approximate to 4.25 x 10(-4). An updated optical ephemeris for the epoch of maximum light from V801 Arae would provide a strong test of this interpretation. We discuss the constraints on the X-ray mass function, which in principle can be derived using this technique. C1 NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. Univ Sussex, Ctr Astron, Phys & Astron Subject Grp, CPES, Brighton BN1 9QH, E Sussex, England. RP Strohmayer, TE (reprint author), NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. RI Swank, Jean/F-2693-2012 NR 11 TC 58 Z9 58 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD AUG 20 PY 1998 VL 503 IS 2 BP L147 EP L150 DI 10.1086/311545 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 152KQ UT WOS:000077777000011 ER PT J AU Pearson, RJ Oncley, SP Delany, AC AF Pearson, RJ Oncley, SP Delany, AC TI A scalar similarity study based on surface layer ozone measurements over cotton during the California Ozone Deposition Experiment SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID SAN-JOAQUIN VALLEY; MEAN CONCENTRATION; FLUX; CHEMISTRY; ENTRAINMENT; DYNAMICS; OCEAN; NO AB This paper reports the first power spectra of ozone (O-3) in the surface layer for which the data quality approaches that of high-quality spectra of meteorological properties. These results are employed in a surface layer scalar similarity study involving temperature, moisture, and O-3 measurements over cotton. All data were obtained during the California Ozone Deposition Experiment, in the San Joaquin Valley of California, during July and August, 1991. A detailed comparison of nondimensional scalar power spectra during unstable conditions showed that the three scalars behaved similarly, thereby providing the first completely general test of scalar similarity theory. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Natl Ctr Atmospher Res, Boulder, CO 80307 USA. RP Pearson, RJ (reprint author), NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. EM oncley@ucar.edu; delany@ucar.edu NR 34 TC 16 Z9 16 U1 0 U2 3 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD AUG 20 PY 1998 VL 103 IS D15 BP 18919 EP 18926 DI 10.1029/98JD01479 PG 8 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 112LE UT WOS:000075495500004 ER PT J AU Kent, GS Trepte, CR Skeens, KM Winker, DM AF Kent, GS Trepte, CR Skeens, KM Winker, DM TI LITE and SAGE II measurements of aerosols in the southern hemisphere upper troposphere SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID STRATOSPHERIC AEROSOL; VERTICAL TRANSPORT; OPTICAL-THICKNESS; AIR; DISTRIBUTIONS; WAVELENGTHS; ATMOSPHERE; EXTINCTION; AUSTRALIA; AFRICA AB Two global satellite data sets have been used to characterize the behavior of aerosols in the upper troposphere of the southern hemisphere during the spring season. The first data set was obtained by the Lidar-In-Space Technology Experiment (LITE) during 10 days in September 1994 and provides high-resolution information about aerosol layering and optical characteristics. The second data set was obtained by the Stratospheric Aerosol and Gas Experiment (SAGE) II over the time period 1984-1996 and provides information on the aerosol distribution and longterm climatology. During September, elevated aerosol layers are found to occur within a latitude band between 20 degrees S and 40 degrees S that extends to almost all longitudes. The latitude and altitude distribution and the optical characteristics of the aerosol suggest that a major source is smoke from biomass burning within the southern hemisphere. This conclusion is supported by the results of back-trajectory analyses that show airmasses originating in the region of southern Africa and traveling longitudinally across the Indian Ocean and Australia into the western Pacific Ocean. The dominant source of the smoke is uncertain, but quite possibly some of it may have originated from Brazil, with additions from southern Africa. The aerosol distribution shows strong similarities to published distributions for ozone and carbon monoxide, also believed to have originated from biomass burning. C1 Sci & Technol Corp, Hampton, VA 23666 USA. Sci Applicat Int Corp, Hampton, VA USA. NASA, Langley Res Ctr, Div Atmospher Sci, Hampton, VA 23681 USA. RP Kent, GS (reprint author), Sci & Technol Corp, 101 Res Dr, Hampton, VA 23666 USA. EM kent@arbs9.larc.nasa.gov; c.r.trepte@larc.nasa.gov; Kristi.Skeens@East.Sun.COM; d.m.winker@larc.nasa.gov NR 50 TC 37 Z9 37 U1 0 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD AUG 20 PY 1998 VL 103 IS D15 BP 19111 EP 19127 DI 10.1029/98JD00364 PG 17 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 112LE UT WOS:000075495500016 ER PT J AU May, RD AF May, RD TI Open-path, near-infrared tunable diode laser spectrometer for atmospheric measurements of H2O SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID UPPER-TROPOSPHERIC WATER; SIMULTANEOUS INSITU MEASUREMENTS; LOWER STRATOSPHERE; VAPOR; AIRCRAFT; ER-2; CH4; NO2; NORTHERN; NITROGEN AB A new instrument for in situ measurements of atmospheric water vapor from aircraft platforms has been developed based upon near-infrared turnable diode laser sources operating near 1.37 mu m. The spectrometer features a unique open-path, multipass (Herriott) cell for true in situ monitoring of water vapor concentrations with precision levels exceeding those of existing Lyman alpha and frost point hygrometers. External sampling outside of the aircraft boundary layer minimizes ambiguities in the measured water vapor abundances. Variable spectrum acquisition rates up to 10 Hz provide fast temporal resolution free from sampling or flow rate limitations. In its current configuration the instrument operates from the right wing pod of the NASA ER-2 research aircraft and is optimized for measurements in the upper troposphere and stratosphere (to 20 km). Measurement precision is +/-0.05 ppmv in the stratosphere for a 2-s measurement integration period. The flight-ready instrument weight is 8.2 kg, and power consumption, exclusive of structural heaters, is 7.5 W. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP May, RD (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr,Mail Stop 183-401, Pasadena, CA 91109 USA. EM randy.d.may@jpl.nasa.gov NR 37 TC 109 Z9 109 U1 0 U2 13 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD AUG 20 PY 1998 VL 103 IS D15 BP 19161 EP 19172 DI 10.1029/98JD01678 PG 12 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 112LE UT WOS:000075495500019 ER PT J AU Joiner, J Lee, HT Strow, LL Bhartia, PK Hannon, S Miller, AJ Rokke, L AF Joiner, J Lee, HT Strow, LL Bhartia, PK Hannon, S Miller, AJ Rokke, L TI Radiative transfer in the 9.6 mu m HIRS ozone channel using collocated SBUV-determined ozone abundances SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID OPERATIONAL VERTICAL SOUNDER; TIROS-N; ATMOSPHERIC TRANSMITTANCE; ABSORBING GAS; TEMPERATURE; RETRIEVAL; SATELLITE; INVERSION; TRENDS; MODEL AB We have carried out a detailed analysis of radiative transfer and observational errors for the high-resolution infrared radiation sounder 2 (HIRS2) channel 9 centered in the 9.6 mu m ozone absorption band. Several previous studies have shown significant differences between the total column ozone derived from HIRS2 and the ultraviolet (UV) radiometers. Here we use collocated ozone profiles derived from the solar backscatter ultraviolet (SBUV) spectrometer to isolate errors in HIRS2 channel 9. Radiative transfer in the 9.6 mu m band is complicated because it is affected by atmospheric ozone, temperature, humidity, and the surface skin temperature and emissivity. We examine the accuracy of three fast radiative transfer algorithms. We validate current models for weak water vapor continuum absorption at 9.6 mu m. In addition, we develop a method to correct for errors in older continuum models, in ozone transmittances, and in the channel 9 spectral response function. We also identify errors resulting from the spectral dependence of the surface emissivity and propose a correction method. Using UV-derived reflectivity, we have detected instances where IR cloud-detection and cloud-clearing algorithms have apparently failed. Our results show that if appropriate corrections and quality control are applied, it is possible to compute HIRS2 channel 9 brightness temperatures with an root-mean-square (RMS) accuracy of better than similar to 0.6 K and a bias less than 0.1 K in clear skies and RMS of Getter than similar to 0.9 K and a bias less than 0.1 K in partially cloudy skies. We plan to use the methods described here to improve IR ozone retrieval algorithms. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Res & Data Syst Corp, Greenbelt, MD USA. Univ Maryland Baltimore Cty, Dept Phys, Baltimore, MD 21250 USA. NOAA, NWS, NCEP, Climate Predict Ctr, Camp Springs, MD 20746 USA. Joint Ctr Earth Syst Technol, Baltimore, MD USA. RP Joiner, J (reprint author), NASA, Goddard Space Flight Ctr, Code 910-3, Greenbelt, MD 20771 USA. EM joiner@dao.gsfc.nasa.gov; wd53hl@sun13.wwb.noaa.gov; strow@umbc.edu; bhartia@chapman.gsfc.nasa.gov; hannon@umbc.edu; miller@upair.wwb.noaa.gov; rokke@dao.gsfc.nasa.gov RI Joiner, Joanna/D-6264-2012; Rokke, Laurie/I-5642-2015; Bhartia, Pawan/A-4209-2016 OI Rokke, Laurie/0000-0002-5696-7240; Bhartia, Pawan/0000-0001-8307-9137 NR 62 TC 11 Z9 11 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD AUG 20 PY 1998 VL 103 IS D15 BP 19213 EP 19229 DI 10.1029/98JD01382 PG 17 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 112LE UT WOS:000075495500023 ER PT J AU Reichle, HG Connors, VS Olson, J Thompson, A AF Reichle, HG Connors, VS Olson, J Thompson, A TI MAPS - Preface SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Editorial Material ID CO; H-2 C1 N Carolina State Univ, Dept Marine Earth & Atmospher Sci, Raleigh, NC 27695 USA. NASA, Langley Res Ctr, Hampton, VA 23665 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Reichle, HG (reprint author), N Carolina State Univ, Dept Marine Earth & Atmospher Sci, Box 8208, Raleigh, NC 27695 USA. NR 13 TC 2 Z9 2 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD AUG 20 PY 1998 VL 103 IS D15 BP 19283 EP 19284 DI 10.1029/98JD01108 PG 2 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 112LE UT WOS:000075495500031 ER PT J AU Novelli, PC Connors, VS Reichle, HG Anderson, BE Brenninkmeijer, CAM Brunke, EG Doddridge, BG Kirchhoff, VWJH Lam, KS Masarie, KA Matsuo, T Parrish, DD Scheel, HE Steele, LP AF Novelli, PC Connors, VS Reichle, HG Anderson, BE Brenninkmeijer, CAM Brunke, EG Doddridge, BG Kirchhoff, VWJH Lam, KS Masarie, KA Matsuo, T Parrish, DD Scheel, HE Steele, LP TI An internally consistent set of globally distributed atmospheric carbon monoxide mixing ratios developed using results from an intercomparison of measurements SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID REFERENCE SCALE; CO AB The Measurement of Air Pollution from Satellite (MAPS) instrument measures carbon monoxide (CO) in the middle troposphere from a space platform. In anticipation of the deployment of MAPS aboard the space shuttle. Endeavor for two 10-day missions in 1994, plans were made to prepare a set of correlative measurements which would be used as part of the mission validation program. Eleven laboratories participated in the correlative measurement program by providing NASA with the results of their CO field programs during April and October 1994. Measurements of CO in the boundary layer, while not used in the MAPS validation, provide a picture of CO in the lower troposphere. Because measurements of CO made by different laboratories have been known to differ significantly, all correlative team members participated in an intercomparison of their measurements to define potential differences in techniques and calibration scales. While good agreement was found between some laboratories, there were differences between others. The use of similar analytical techniques and calibration scales did not always provide similar results. The results of the intercomparisons were used to normalize all ground-based measurements to the National Oceanic and Atmospheric Administration/Climate Monitoring and Diagnostics Laboratory CO reference scale. These data provide an internally consistent picture of CO in the lower atmosphere during spring and fall 1994. C1 NOAA, Climate Monitoring & Diagnost Lab, Boulder, CO 80303 USA. NASA, Langley Res Ctr, Hampton, VA 23681 USA. Natl Inst Water & Atmospher Res, Inst Geol & Nucl Sci, Lower Hutt, New Zealand. CSIR, EMATEK, AIM, Stellenbosch, South Africa. Univ Maryland, Dept Meteorol, College Pk, MD 20742 USA. Inst Nacl Pesquisas Espaciais, Sao Paulo, Brazil. Hong Kong Polytech Inst, Dept Civil & Struct Engn, Hong Kong, Peoples R China. Univ Colorado, Cooperat Inst Res Environm Sci, Boulder, CO 80309 USA. Japan Meteorol Agcy, Tokyo, Japan. NOAA, Aeron Lab, Boulder, CO 80303 USA. Fraunhofer Inst Atmosphar Umweltforsch, D-8100 Garmisch Partenkirchen, Germany. CSIRO, Div Atmospher Res, Aspendale, Vic 3195, Australia. RP Novelli, PC (reprint author), NOAA, Climate Monitoring & Diagnost Lab, 325 Broadway,MS R-E-CG1, Boulder, CO 80303 USA. EM pnovelli@cmdl.noaa.gov RI Steele, Paul/B-3185-2009; Parrish, David/E-8957-2010; Brenninkmeijer, Carl/B-6860-2013; Garmisch-Pa, Ifu/H-9902-2014 OI Steele, Paul/0000-0002-8234-3730; Parrish, David/0000-0001-6312-2724; NR 26 TC 52 Z9 53 U1 1 U2 7 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD AUG 20 PY 1998 VL 103 IS D15 BP 19285 EP 19293 DI 10.1029/97JD00031 PG 9 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 112LE UT WOS:000075495500032 ER PT J AU Doddridge, BG Morales-Morales, R Rhoads, KP Merrill, JT Novelli, PC Dickerson, RR Connors, VS Reichle, HG AF Doddridge, BG Morales-Morales, R Rhoads, KP Merrill, JT Novelli, PC Dickerson, RR Connors, VS Reichle, HG TI Ground-based and airborne observations of carbon monoxide during NASA measurements of air pollution from satellite (MAPS) missions SRL-1 and SRL-2 SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID MACE-HEAD; INTERANNUAL VARIABILITY; ATMOSPHERIC CHEMISTRY; SCALE TRANSPORT; ATLANTIC-OCEAN; NORTH-ATLANTIC; TROPOSPHERE; OZONE; MASS; IRELAND AB Surface carbon monoxide (CO) data were acquired continuously at Heimaey, Iceland (63 degrees 24'N, 20 degrees 18'W), Mace Head, Ireland (53 degrees 19'N, 9 degrees 54'W), and Ragged Point, Barbados (13 degrees 15'N, 59 degrees 30'W), during April and October 1994, in support of Measurement of Air Pollution From Satellite (MAPS) Space Radar Laboratory (SRL) missions SRL-1 and SRL-2, respectively, measuring middle tropospheric CO from space. Observed median CO levels from the three surface sites during these two MAPS missions approximate the monthly median for 1994 and are mostly typical of data from prior years. For two of the sites, computed mission isentropic back-trajectory ensemble probability fields are compared to seasonal (March-May and September-November) probability fields for 1994 and 1986-1995. Such comparisons help gauge the representativeness of (1) observed surface air quality at, and (2) isentropic flow to, these sites during the mission periods, in terms of intraseasonal and interannual variability. Results appear consistent with longer-term flow climatological data and confirm the SRL-1 and SRL-2 mission periods are generally representative of the climatology applicable to these sites for the time of year. Lower free troposphere in situ CO data were acquired from an aircraft over the Maryland Eastern Shore, on April 14 and October 3, 4, and 6. During the April flight a nearly linear gradient in CO with pressure from 1000-650 mbar of 225-150 parts per billion by volume (ppbv) was observed. At 650 mbar, CO was quite steady around 150 ppbv; this value compares favorably with the MAPS CO data for the closest 5 degrees x 5 degrees grid box averaged April 13-15 of 105-120 ppbv. During SRL-2 a three flight CO average of 125 ppbv observed at similar to 725 mbar is in good agreement with the closest MAPS 5 degrees x 5 degrees grid box averaged October 3-7 of 90-105 ppbv. A layer of elevated CO at 845-740 mbar, most likely the result of synoptic-scale transport, was observed during the October flights and seen to dissipate with time. The MAPS cloud-filtered second-by-second CO data during concurrent shuttle overflights show temporal structure consistent with the in situ observations, indicating the MAPS weighting function may be capable of discerning features at lower altitudes than thought previously. C1 Univ Maryland, Dept Meteorol, College Pk, MD 20742 USA. Univ Maryland, Dept Chem, College Pk, MD 20742 USA. Univ Rhode Isl, Grad Sch Oceanog, Narragansett, RI 02882 USA. NOAA, Climate Monitoring & Diagnost Lab, Boulder, CO 80303 USA. NASA, Div Atmospher Sci, Langley Res Ctr, Hampton, VA 23665 USA. N Carolina State Univ, Dept Marine Earth & Atmospher Sci, Raleigh, NC 27695 USA. RP Doddridge, BG (reprint author), Univ Maryland, Dept Meteorol, College Pk, MD 20742 USA. EM burce@atmos.umd.edu; raym@atmos.umd.edu; rhoads@atmos.umd.edu; jmerrill@boreas.gso.uri.edu; pnovelli@cmdl.noaa.edu; russ@atmos.umd.edu; vconnors@unity.ncsu.edu; henry_reichle@ncsu.edu RI Dickerson, Russell/F-2857-2010 OI Dickerson, Russell/0000-0003-0206-3083 NR 43 TC 7 Z9 7 U1 0 U2 2 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD AUG 20 PY 1998 VL 103 IS D15 BP 19305 EP 19316 DI 10.1029/97JD01837 PG 12 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 112LE UT WOS:000075495500034 ER PT J AU Pougatchev, NS Jones, NB Connor, BJ Rinsland, CP Becker, E Coffey, MT Connors, VS Demoulin, P Dzhola, AV Fast, H Grechko, EI Hannigan, JW Koike, M Kondo, Y Mahieu, E Mankin, WG Mittermeier, RL Notholt, J Reichle, HG Sen, B Steele, LP Toon, GC Yurganov, LN Zander, R Zhao, Y AF Pougatchev, NS Jones, NB Connor, BJ Rinsland, CP Becker, E Coffey, MT Connors, VS Demoulin, P Dzhola, AV Fast, H Grechko, EI Hannigan, JW Koike, M Kondo, Y Mahieu, E Mankin, WG Mittermeier, RL Notholt, J Reichle, HG Sen, B Steele, LP Toon, GC Yurganov, LN Zander, R Zhao, Y TI Ground-based infrared solar spectroscopic measurements of carbon monoxide during 1994 Measurement of Air Pollution From Space flights SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID VERTICAL-DISTRIBUTION; MIDDLE ATMOSPHERE; TRACE GASES; KITT PEAK; TRANSPORT; OXIDE; CO AB Results of the comparison of carbon monoxide ground-based infrared solar spectroscopic measurements with data obtained during 1994 Measurement of Air Pollution From Space (MAPS) flights are presented. Spectroscopic measurements were performed correlatively with April and October MAPS flights by nine research groups from Belgium, Canada, Germany, Japan, New Zealand, Russia, and the United States. Characterization of the techniques and error analysis were performed. The role of the CO a priori profile used in the retrieval was estimated. In most cases an agreement between spectroscopic and MAPS data is within estimated MAPS accuracy of +/-10%. C1 Christopher Newport Univ, Dept Phys Comp Sci & Engn, Newport News, VA 23606 USA. Natl Inst Water & Atmospher Res, Lauder, New Zealand. Atmospher Environm Serv, Toronto, ON M3H 5T4, Canada. Nagoya Univ, Solar Terr Environm Lab, Aichi 442, Japan. Alfred Wegener Inst Polar & Marine Res, D-14473 Potsdam, Germany. Natl Ctr Atmospher Res, Boulder, CO 80307 USA. Univ Liege, Inst Astrophys, B-4000 Liege, Belgium. CALTECH, Jet Prop Lab, Pasadena, CA 91125 USA. NASA, Langley Res Ctr, Hampton, VA 23681 USA. Russian Acad Sci, Inst Atmospher Phys, Moscow, Russia. Univ Toronto, Dept Phys, Toronto, ON M5S 1A7, Canada. N Carolina State Univ, Dept Marine Earth & Atmospher Sci, Raleigh, NC 27607 USA. CSIRO, Aspendale, Vic 3195, Australia. RP Pougatchev, NS (reprint author), Christopher Newport Univ, Dept Phys Comp Sci & Engn, Newport News, VA 23606 USA. RI Steele, Paul/B-3185-2009; Koike, Makoto/F-4366-2011; Jones, Nicholas/G-5575-2011; Notholt, Justus/P-4520-2016; OI Steele, Paul/0000-0002-8234-3730; Jones, Nicholas/0000-0002-0111-2368; Notholt, Justus/0000-0002-3324-885X; Mahieu, Emmanuel/0000-0002-5251-0286 NR 20 TC 21 Z9 21 U1 0 U2 4 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD AUG 20 PY 1998 VL 103 IS D15 BP 19317 EP 19325 DI 10.1029/97JD02889 PG 9 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 112LE UT WOS:000075495500035 ER PT J AU Christopher, SA Chou, J Welch, RM Kliche, DV Connors, VS AF Christopher, SA Chou, J Welch, RM Kliche, DV Connors, VS TI Satellite investigations of fire, smoke, and carbon monoxide during April 1994 MAPS mission: Case studies over tropical Asia SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID BIOMASS; RADIOMETER; ATMOSPHERE; CHEMISTRY; TRANSPORT; AEROSOL; CO AB During April 9-19, 1994, the Measurement of Air Pollution from Satellites (MAPS) measured free tropospheric carbon monoxide (CO) concentrations on a near-global basis. For these eleven days the global 1 km advanced very high resolution radiometer (AVHRR) Pathfinder data are used to detect fires and smoke over the Indo-Burma region (85 degrees E-110 degrees E; 10 degrees N-30 degrees N). The fire activities are categorized for four major ecosystems that include (1) cropland/natural vegetation mosaic (CNVM), (2) evergreen broadleaf forest (EBF), (3) mixed forest (MFD), and (4) grassland (GL). Using published emission rates between particulate matter and carbon monoxide concentrations from temperate areas, the fire counts along with other information are used to obtain estimates of CO concentrations from the AVHRR data. More than 7000 fires are detected during the study period with 23%, 43%, 24%, and 10% fires in the CNVM, EBF, MFD, and GL ecosystems, respectively. The enhanced CO concentrations over the area of study are either over or downwind of the fires detected by the AVHRR. The preliminary AVHRR estimates of CO concentrations are smaller than the MAPS-measured values by a factor of 4 to 5 for fire counts greater than 200. The differences are attributed to the lack of transport mechanisms and other assumptions in the current model. However, these results show a good potential for using the AVHRR measurements to detect fires and smoke and also to estimate CO concentrations. C1 Univ Alabama, Dept Atmospher Sci, Huntsville, AL 35899 USA. S Dakota Sch Mines & Technol, Inst Atmospher Sci, Rapid City, SD USA. NASA, Langley Res Ctr, Hampton, VA 23665 USA. RP Christopher, SA (reprint author), Univ Alabama, Dept Atmospher Sci, 977 Explorer Blvd, Huntsville, AL 35899 USA. EM sun-dar@atmos.uah.edu RI Christopher, Sundar/E-6781-2011 NR 34 TC 20 Z9 20 U1 1 U2 3 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD AUG 20 PY 1998 VL 103 IS D15 BP 19327 EP 19336 DI 10.1029/97JD01813 PG 10 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 112LE UT WOS:000075495500036 ER PT J AU McElrath, T AF McElrath, T TI Older antenna shown SO AVIATION WEEK & SPACE TECHNOLOGY LA English DT Letter C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP McElrath, T (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU MCGRAW HILL INC PI NEW YORK PA 1221 AVENUE OF THE AMERICAS, NEW YORK, NY 10020 USA SN 0005-2175 J9 AVIAT WEEK SPACE TEC JI Aviat. Week Space Technol. PD AUG 17 PY 1998 VL 149 IS 7 BP 6 EP 6 PG 1 WC Engineering, Aerospace SC Engineering GA 111AJ UT WOS:000075414900007 ER PT J AU Strauss, K AF Strauss, K TI Turned on, even when the meter isn't SO ELECTRONIC DESIGN LA English DT Letter C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Strauss, K (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU PENTON MEDIA, INC PI CLEVELAND PA 1100 SUPERIOR AVE, CLEVELAND, OH 44114-2543 USA SN 0013-4872 J9 ELECTRON DES JI Electron. Des. PD AUG 17 PY 1998 VL 46 IS 19 BP 105 EP 105 PG 1 WC Engineering, Electrical & Electronic SC Engineering GA 112TT UT WOS:000075510800038 ER PT J AU Bauschlicher, CW Langhoff, SR AF Bauschlicher, CW Langhoff, SR TI Infrared spectra of polycyclic aromatic hydrocarbons: methyl substitution and loss of H SO CHEMICAL PHYSICS LA English DT Article ID EMISSION FEATURES; PAHS AB The B3LYP approach, in conjunction with the 4-31G basis set, is used to compute the harmonic frequencies of 1- and 2-methylnaphthalene, 1-, 2-, and 9-methylanthracene, and their cations. The IR spectra of the methyl substituted species are very similar to the parent spectra, except for the addition of the methyl C-H stretch at lower frequency than the aromatic C-H stretch. The loss of a single hydrogen from naphthalene, anthracene, and their cations is shown to have a very small effect on the IR spectra. Loss of a methyl hydrogen from 1- or 2-methylnaphthalene, or their cations, is shown to shift the side group C-H frequencies from below aromatic hydrogen stretching frequencies to above them. The loss of H from 2-methylenenaphthalene shows only a small shift in the side group C-H stretching frequency. (C) 1998 Elsevier Science B.V. All rights reserved. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Bauschlicher, CW (reprint author), NASA, Ames Res Ctr, Mail Stop 230-3, Moffett Field, CA 94035 USA. NR 19 TC 16 Z9 16 U1 0 U2 4 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0301-0104 J9 CHEM PHYS JI Chem. Phys. PD AUG 15 PY 1998 VL 234 IS 1-3 BP 79 EP 86 PG 8 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA 108HW UT WOS:000075261100006 ER PT J AU Bauschlicher, CW AF Bauschlicher, CW TI Infrared spectra of polycyclic aromatic hydrocarbons: nitrogen substitution SO CHEMICAL PHYSICS LA English DT Article ID EMISSION FEATURES; MASS-SPECTROMETRY; IDENTIFICATION; APPROXIMATION; EXCHANGE; ENERGY; DUST AB The B3LYP/4-31G approach is used to compute the harmonic frequencies of substituted naphthalene, anthracene, and their cations. The substitutions include cyano (CN), aminio (NH2), imino (NH), and replacement of a CH group by a nitrogen atom. All unique sites are considered, namely 1 and 2 for naphthalene and 1, 2, and 9 for anthracene, except for the imino, where only 2-iminonaphthalene is studied. The IR spectra of these substituted species are compared with those of the unsubstituted molecules. The addition of a CN group does not significantly affect the spectra except to add the C-N stretching frequency. Replacing a CH group by N has only a small effect on the IR spectra. The addition of the NH2 group dramatically affects the neutral spectra, giving it much of the character of the cation spectra. However, the neutral 2-iminonaphthalene spectra looks more like that of naphthalene than like the 2-aminonaphthalene spectra. (C) 1998 Elsevier Science B.V. All rights reserved. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Bauschlicher, CW (reprint author), NASA, Ames Res Ctr, Mail Stop 230-3, Moffett Field, CA 94035 USA. NR 27 TC 19 Z9 19 U1 0 U2 4 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0301-0104 J9 CHEM PHYS JI Chem. Phys. PD AUG 15 PY 1998 VL 234 IS 1-3 BP 87 EP 94 PG 8 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA 108HW UT WOS:000075261100007 ER PT J AU Parks, G Brittnacher, M Elsen, R McCarthy, M O'Meara, JM Germany, G Spann, J AF Parks, G Brittnacher, M Elsen, R McCarthy, M O'Meara, JM Germany, G Spann, J TI Comparison of dark pixels observed by VIS and UVI: in dayglow images SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID FAR-ULTRAVIOLET DAYGLOW; TRANSIENT DECREASES AB Frank and Sigwarth [1997a] claim that the dark pixels observed in dayglow images obtained by the Earth sensor of the Visible Imaging System (VIS) are due to bombardment of Earth by 20 to 40 ton cosmic snowballs. We have independently studied the VIS data and compared the dark pixels from the VIS images to those obtained from the overlapping images from the Ultraviolet Imager (UVI). We find the occurrence distributions of the dark pixels, single and multiple, from VIS and UVI are nearly identical. The distributions also do not show any altitude dependence. A search for evidence of spacecraft "wobble" motion, whose presence would indicate that the source is external to the camera, has found that pairs of dark pixel clusters are uniformly distributed in orientation and no preference is observed in the wobble direction. Instrument artifacts as the source of the dark pixels is the most likely explanation for these results. The conclusion of this study is that neither VIS nor UVI provide any scientific evidence that the dark pixels are geophysical. C1 Univ Washington, Geophys Program, Seattle, WA 98195 USA. Univ Alabama, CSPAR, Huntsville, AL 35899 USA. NASA, George C Marshall Space Flight Ctr, Space Sci Lab, Huntsville, AL 35812 USA. RP Parks, G (reprint author), Univ Washington, Geophys Program, Box 351650, Seattle, WA 98195 USA. NR 4 TC 8 Z9 8 U1 0 U2 2 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD AUG 15 PY 1998 VL 25 IS 16 BP 3063 EP 3066 DI 10.1029/98GL02108 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 111WT UT WOS:000075462000002 ER PT J AU Reddy, CA Mayr, HG AF Reddy, CA Mayr, HG TI Storm-time penetration to low latitudes of magnetospheric-ionospheric convection and convection-driven thermospheric winds SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID GENERAL-CIRCULATION MODEL; GEOMAGNETIC STORM; ELECTRIC-FIELDS; NOVEMBER 8-9; DYNAMICS; ELECTRODYNAMICS; DISTURBANCES; ATMOSPHERE; MIDDLE; PLASMA AB From DE-2 satellite measurements during two magnetic storms, we show that (i) the magnetospheric convection-driven east-west ion flows of high velocities (1400 m/s) penetrate to magnetic latitudes as low as 30 degrees, with larger velocities (2000-3000 m/s) appearing at 45 degrees 50 degrees latitudes, and (ii) high velocities (300-640 m/s) thermospheric winds appear in association with the : above ion flows. The similarity of the latitude structures and time evolutions of the ion and neutral motions indicates that the zonal winds are driven by ma,magnetospheric-ionospheric convection through ion drag. These velocities of the convection-driven ion flows and winds at such low latitudes are much larger than those reported from observations or predicted by current models. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. VSSC, Space Phys Lab, Trivandrum, Kerala, India. RP Reddy, CA (reprint author), 6-748 Anantha, Trivandrum 695013, Kerala, India. EM carreddy@md3.vsnl.net.in; Mayr@mite.gsfc.nasa.gov NR 30 TC 16 Z9 16 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD AUG 15 PY 1998 VL 25 IS 16 BP 3075 EP 3078 DI 10.1029/98GL02334 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 111WT UT WOS:000075462000005 ER PT J AU Kaiser, ML MacDowall, RJ AF Kaiser, ML MacDowall, RJ TI Jovian radio "bullseyes" observed by Ulysses SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID DECAMETRIC ARCS; GALILEO SPACECRAFT; GANYMEDE; JUPITER; EMISSIONS; BURSTS; MAGNETOSPHERE AB We report the observation of extremely rare semi-bullseye or target-like features in the dynamic spectra of Jupiter obtained in 1991-1994 by the Ulysses Unified Radio and Plasma wave instrument. The emissions lie in the 20-50 kHz band and consist of narrow band (similar to 1-2 kHz) semi-concentric wisps on frequency-time dynamic spectra. The individual wisps correspond to a 4 pi steradian radiated power in the range of tens of kilowatts to more than ten megawatts. The emissions show a tendency to occur in groups every 25-27 days with a spacing between some individual episodes of about 10.5 hours. The 25-27 day periodicity is strongly correlated with solar wind ram pressure at Jupiter. Speculation on the cause of these events includes constructive-destructive interference or diffraction of a previously known radio source viewed through the Io plasma torus, or perhaps radio emission from Ganymede or from the magnetic flux tube threading through Ganymede. C1 NASA, Goddard Space Flight Ctr, Extraterr Phys Lab, Greenbelt, MD 20771 USA. RP Kaiser, ML (reprint author), NASA, Goddard Space Flight Ctr, Extraterr Phys Lab, Code 695, Greenbelt, MD 20771 USA. RI MacDowall, Robert/D-2773-2012 NR 23 TC 3 Z9 3 U1 0 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD AUG 15 PY 1998 VL 25 IS 16 BP 3113 EP 3116 DI 10.1029/98GL02255 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 111WT UT WOS:000075462000015 ER PT J AU Domingue, DL Lane, AL Beyer, RA AF Domingue, DL Lane, AL Beyer, RA TI IUE's detection of tenuous SO2 frost on Ganymede and its rapid time variability SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID MAGNETOSPHERIC ION-BOMBARDMENT; GALILEAN SATELLITES; ABSORPTION-BAND; SPECTRA; EUROPA; REFLECTANCE; SURFACE; OXYGEN; OZONE; NM AB International Ultraviolet Explorer (IUE) observations of Ganymded demonstrate decade length or less temporal variations at a few discreet trailing side longitude regions. The temporal changes are seen in comparisons of IUE spectra from 1984-1986 with new IUE observations from 1996. Variations are observed on the trailing side associated with the new detection of SO2 frost. A distinctive SO2 frost spectral signature at 0.32 mu m is detected in the 1984-1986 spectra of trailing side regions from 2.25 degrees to 285 degrees which are absent in corresponding 1996 measurements. C1 Johns Hopkins Univ, Appl Phys Lab, Laurel, MD 20723 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ Illinois, Urbana, IL 61801 USA. RP Domingue, DL (reprint author), Johns Hopkins Univ, Appl Phys Lab, 11100 Johns Hopkins Rd, Laurel, MD 20723 USA. EM deborah.domingue@jhuapl.edu; arthur.l.lane@jpl.nasa.gov; rossb@astro.uiuc.edu OI Beyer, Ross/0000-0003-4503-3335 NR 26 TC 7 Z9 7 U1 0 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD AUG 15 PY 1998 VL 25 IS 16 BP 3117 EP 3120 DI 10.1029/98GL02386 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 111WT UT WOS:000075462000016 ER PT J AU Hu, H Liu, WT AF Hu, H Liu, WT TI The impact of upper tropospheric humidity from Microwave Limb Sounder on the midlatitude greenhouse effect SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID WATER-VAPOR; RADIATION BUDGET; CLIMATOLOGY; OCEANS; MLS AB This paper presents an analysis of upper tropospheric humidity, as measured by the Microwave Limb Sounder, and the impact of the humidity on the greenhouse effect in the midlatitudes. Enhanced upper tropospheric humidity and an enhanced greenhouse effect occur over the storm tracks in the North Pacific and North Atlantic. In these areas, strong baroclinic activity and the large number of deep convective clouds transport more water vapor to the upper troposphere, and hence increase greenhouse trapping. The greenhouse effect increases with upper tropospheric humidity in areas with a moist upper troposphere (such as areas over storm tracks), but it is not sensitive to changes in upper tropospheric humidity in regions with a dry upper troposphere, clearly demonstrating that there are different mechanisms controlling the geographical distribution of the greenhouse effect in the midlatitudes. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Hu, H (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr,MS 300-323, Pasadena, CA 91109 USA. NR 20 TC 9 Z9 9 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD AUG 15 PY 1998 VL 25 IS 16 BP 3151 EP 3154 DI 10.1029/98GL02252 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 111WT UT WOS:000075462000025 ER PT J AU Bamber, JL Ekholm, S Krabill, W AF Bamber, JL Ekholm, S Krabill, W TI The accuracy of satellite radar altimeter data over the Greenland ice sheet determined from airborne laser data SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article AB The 336 days of the geodetic phase of ERS-1 provides dense coverage, by satellite radar altimetry, of the whole of the Greenland ice sheet. These data have been used to produce a digital elevation model of the ice sheet. The errors present in the altimeter data were investigated via a comparison with airborne laser altimeter data an absolute accuracy typically in the range 2-10 cm +/- 10 cm. Comparison of differences between the radar and laser derived elevations, showed a correlation with surface slope. The difference between the two data sets ranged from 84 cm +/- 79 cm for slopes below 0.1 degrees, to 10.3 m +/- 8.4 m for a slope of 0.7 degrees ( the half power beam-width of the ERS-1 radar altimeter). An explanation for the behaviour of the difference as a function of surface slope is given in terms of the pattern of surface roughness on the ice sheet. C1 Univ Bristol, Sch Geog Sci, Ctr Remote Sensing, Bristol BS8 1SS, Avon, England. Kort & Matrikelstyelsen, Natl Survey & Cadastre, Copenhagen, Denmark. NASA, Goddard Space Flight Ctr, Wallops Flight, Wallops Island, VA 23337 USA. RP Bamber, JL (reprint author), Univ Bristol, Sch Geog Sci, Ctr Remote Sensing, Univ Rd, Bristol BS8 1SS, Avon, England. EM j.l.bamber@bristol.ac.uk; se@kms.min.dk; krabill@osb1.wff.nasa.gov RI Bamber, Jonathan/C-7608-2011 OI Bamber, Jonathan/0000-0002-2280-2819 NR 5 TC 19 Z9 21 U1 1 U2 6 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD AUG 15 PY 1998 VL 25 IS 16 BP 3177 EP 3180 DI 10.1029/98GL01594 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 111WT UT WOS:000075462000032 ER PT J AU Yang, J Ventzek, PLG Sakai, Y Date, H Kitamori, K Tagashira, H Meyyappan, M AF Yang, J Ventzek, PLG Sakai, Y Date, H Kitamori, K Tagashira, H Meyyappan, M TI Simulations of step responses of electronegative radio-frequency capacitively coupled discharges SO JOURNAL OF APPLIED PHYSICS LA English DT Article ID MODULATED HIGH-DENSITY; GLOW-DISCHARGES; GAS-MIXTURES; MONOSILANE; MODEL; FLUID AB The transient response of electronegative radio-frequency glow discharges is important for process control, charge free etching, and highly selective etch applications. The step response of typical electronegative process gases (silane at 1 Torr and chlorine at 100 mTorr) is studied using a drift-diffusion model for silane and a three-moment model for chlorine. The silane simulations include a blocking capacitor whereas the chlorine results do not. For the silane results with a blocking capacitor in series with the plasma, it is found that there are three types of transients. Depending on the final steady-state value of the source rf voltage, the step response can be characterized either by smooth transitions in the number densities of species in the discharge from one steady state to the next, temporary extinction of the discharge or a discharge mode characterized by temporary extinction and reignition of the discharge. In the case of silane definite thresholds separate the phenomena. The step response of the chlorine discharges is always characterized by a smooth transition from one steady state to the next. Smooth transitions from one steady state to the next in the case of step decreases in the source voltage are possible since decrease of the negative ion density in the bulk is controlled by ion-ion recombination. It appears that the temporary extinction of the discharge and natural pulsed steady state is the consequence of how the voltage is divided between the gap and the blocking capacitor during the transient and the fact that the attachment coefficient becomes larger than the ionization coefficient at low values of reduced electric field. (C) 1998 American Institute of Physics. [S0021-8979(98)08716-7] C1 Hokkaido Univ, Dept Elect Engn, Sapporo, Hokkaido 060, Japan. Hokkaido Inst Technol, Dept Elect Engn, Sapporo, Hokkaido 065, Japan. Hokkaido Inst Technol, Dept Ind Engn, Sapporo, Hokkaido 065, Japan. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Ventzek, PLG (reprint author), Motorola Inc, Predict Engn Lab, 3501 Ed Bluestein Blvd, Austin, TX 78721 USA. RI Date, Hiroyuki/A-4040-2012 NR 28 TC 3 Z9 3 U1 0 U2 2 PU AMER INST PHYSICS PI WOODBURY PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 USA SN 0021-8979 J9 J APPL PHYS JI J. Appl. Phys. PD AUG 15 PY 1998 VL 84 IS 4 BP 1848 EP 1858 DI 10.1063/1.368343 PG 11 WC Physics, Applied SC Physics GA 108GL UT WOS:000075257700014 ER PT J AU Hwang, PA Walsh, EJ Krabill, WB Swift, RN Manizade, SS Scott, JF Earle, MD AF Hwang, PA Walsh, EJ Krabill, WB Swift, RN Manizade, SS Scott, JF Earle, MD TI Airborne remote sensing applications to coastal wave research SO JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS LA English DT Article ID SURFACE CONTOUR RADAR; GREENLAND ICE-SHEET; LASER ALTIMETRY; TRANSFORMATION; SPECTRA AB Airborne sensors provide effective coverage of a broad region and are suitable for large-scale experiments. In this paper, two scanning sensors that use the direct ranging technique to measure surface wave displacement are described. On a NASA P-3 aircraft the sensors can complete one run across a 100-km continental shelf in 17 min. A case study is presented using radar-measured, two-dimensional surface topography to derive wave damping due to bottom friction. The results are in good agreement with an analytical model based on a quadratic formulation of bottom shear stress. This study demonstrates that remote sensing measurements can be used for rapid characterization of surface waves on the continental shelf and in coastal regions. Examples illustrated in this paper include the derivation of wavenumber spectra and estimation of the dissipation rate of shoaling ocean swell. C1 USN, Res Lab, Div Oceanog, Stennis Space Ctr, MS 39529 USA. NASA, Lab Hydrosper Proc, Wallops Island, VA 23337 USA. EG&G Serv Inc, Wallops Flight Facil, Wallops Island, VA 23337 USA. Neptune Sci Inc, Reston, VA USA. RP Hwang, PA (reprint author), USN, Res Lab, Div Oceanog, Code 7332, Stennis Space Ctr, MS 39529 USA. NR 18 TC 14 Z9 14 U1 2 U2 4 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA J9 J GEOPHYS RES-OCEANS JI J. Geophys. Res.-Oceans PD AUG 15 PY 1998 VL 103 IS C9 BP 18791 EP 18800 DI 10.1029/98JC00895 PG 10 WC Oceanography SC Oceanography GA 110CZ UT WOS:000075363700029 ER PT J AU Holt, B AF Holt, B TI Introduction to special section: Studies of the ocean surface from the Spaceborne Imaging radar C/X-band SAR experiments SO JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS LA English DT Editorial Material C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Holt, B (reprint author), CALTECH, Jet Prop Lab, MS 300-323,4800 Oak Grove Dr, Pasadena, CA 91109 USA. EM ben@pacific.jpl.nasa.gov NR 5 TC 1 Z9 1 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA J9 J GEOPHYS RES-OCEANS JI J. Geophys. Res.-Oceans PD AUG 15 PY 1998 VL 103 IS C9 BP 18813 EP 18814 DI 10.1029/98JC01618 PG 2 WC Oceanography SC Oceanography GA 110CZ UT WOS:000075363700033 ER PT J AU Hofacker, IL Fekete, M Flamm, C Huynen, MA Rauscher, S Stolorz, PE Stadler, PF AF Hofacker, IL Fekete, M Flamm, C Huynen, MA Rauscher, S Stolorz, PE Stadler, PF TI Automatic detection of conserved RNA structure elements in complete RNA virus genomes SO NUCLEIC ACIDS RESEARCH LA English DT Article ID HEPATITIS-C VIRUS; REV-RESPONSE ELEMENT; 5' NONCODING REGION; SECONDARY STRUCTURE; MESSENGER-RNA; COMPUTER-SIMULATION; INTERNAL INITIATION; TARGET SEQUENCE; GENE-EXPRESSION; PRION PROTEIN AB We propose a new method for detecting conserved RNA secondary structures in a family of related RNA sequences. Our method is based on a combination of thermodynamic structure prediction and phylogenetic comparison. In contrast to purely phylogenetic methods, our algorithm can be used for small data sets of similar to 10 sequences, efficiently exploiting the information contained in the sequence variability. The procedure constructs a prediction only for those parts of sequences that are consistent with a single conserved structure. Our implementation produces reasonable consensus structures without user interference. As an example we have analysed the complete HIV-1 and hepatitis C virus (HCV) genomes as well as the small segment of hantavirus. Our method confirms the known structures in HIV-1 and predicts previously unknown conserved RNA secondary structures in HCV. C1 Univ Vienna, Inst Theoret Chem, A-1090 Vienna, Austria. EMBL, Heidelberg, Germany. Max Delbruck Ctr, Berlin, Germany. CALTECH, Jet Prop Lab, Pasadena, CA USA. Santa Fe Inst, Santa Fe, NM 87501 USA. RP Stadler, PF (reprint author), Univ Vienna, Inst Theoret Chem, Wahringerstr 17, A-1090 Vienna, Austria. EM studla@tbi.univie.ac.at RI Hofacker, Ivo/A-2378-2013; Stadler, Peter F./L-7857-2015; Huynen, Martijn/A-1530-2014; OI Hofacker, Ivo/0000-0001-7132-0800; Stadler, Peter F./0000-0002-5016-5191; Flamm, Christoph/0000-0001-5500-2415 NR 68 TC 89 Z9 91 U1 1 U2 1 PU OXFORD UNIV PRESS PI OXFORD PA GREAT CLARENDON ST, OXFORD OX2 6DP, ENGLAND SN 0305-1048 EI 1362-4962 J9 NUCLEIC ACIDS RES JI Nucleic Acids Res. PD AUG 15 PY 1998 VL 26 IS 16 BP 3825 EP 3836 DI 10.1093/nar/26.16.3825 PG 12 WC Biochemistry & Molecular Biology SC Biochemistry & Molecular Biology GA 110YB UT WOS:000075408200029 PM 9685502 ER PT J AU Anantram, MP Govindan, TR AF Anantram, MP Govindan, TR TI Conductance of carbon nanotubes with disorder: A numerical study SO PHYSICAL REVIEW B LA English DT Article ID TRANSPORT; MICROSCOPY; JUNCTIONS; DEFECTS; DEVICES; CONTACT AB We study the conductance of carbon nanotube wires in the presence of disorder, in the limit of phase-coherent transport. For this purpose, we have developed a simple numerical procedure to compute transmission through carbon nanotubes and related structures. Two models of disorder are considered, weak uniform disorder and isolated strong scatterers. In the case of weak uniform disorder, our simulations show that the conductance is not significantly affected by disorder when the Fermi energy is close to the band center. Further, the transmission around the band center depends on the diameter of these zero band-gap wires. We also find that the calculated small bias conductance as a function of the Fermi energy exhibits a dip when the Fermi energy is close to the second subband minima. In the presence of strong isolated disorder, our calculations show a transmission gap at the band center, and the corresponding conductance is very small. C1 NASA, Ames Res Ctr, Moffett Field, CA 94045 USA. Appl Res Lab, State Coll, PA 16804 USA. RP Anantram, MP (reprint author), NASA, Ames Res Ctr, Mail Stop T27A-1, Moffett Field, CA 94045 USA. EM anant@nas.nasa.gov; tr@nas.nasa.gov NR 32 TC 148 Z9 148 U1 0 U2 10 PU AMER PHYSICAL SOC PI COLLEGE PK PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA SN 1098-0121 EI 1550-235X J9 PHYS REV B JI Phys. Rev. B PD AUG 15 PY 1998 VL 58 IS 8 BP 4882 EP 4887 DI 10.1103/PhysRevB.58.4882 PG 6 WC Physics, Condensed Matter SC Physics GA 117GE UT WOS:000075772500099 ER PT J AU Leon, R Fafard, S Piva, PG Ruvimov, S Liliental-Weber, Z AF Leon, R Fafard, S Piva, PG Ruvimov, S Liliental-Weber, Z TI Tunable intersublevel transitions in self-forming semiconductor quantum dots SO PHYSICAL REVIEW B LA English DT Article ID TIME-RESOLVED PHOTOLUMINESCENCE; RADIATIVE RECOMBINATION; VISIBLE LUMINESCENCE; PHONON BOTTLENECK; BARRIER HEIGHT; BOX SYSTEMS; RELAXATION; ENSEMBLES; WELLS AB Interfacial compositional disordering in In0.6Ga0.4As/GaAs quantum dots has been used to tune their intersublevel energy spacings (Delta E[(i+1-i])). Interdiffusion blueshifted all levels while lowering values for Delta E[(i+1-i]). Rate equation simulations of photoluminescence (PL) spectra estimated relaxation lifetime ratios for intersublevel transitions. A slight trend towards increasing thermalization rates at values Delta E[(i+1-i]) similar to LO phonon energies was found. However, PL measurements showed strong emission from excited states for all Delta E[(i+1-i]) values, which ranged from 53 to 25 meV. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Natl Res Council Canada, Inst Microstruct Sci, Ottawa, ON K1A 0R6, Canada. Univ Calif Berkeley, Lawrence Berkeley Lab, Div Mat Sci, Berkeley, CA 94720 USA. RP Leon, R (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. RI Liliental-Weber, Zuzanna/H-8006-2012 NR 25 TC 73 Z9 73 U1 0 U2 4 PU AMER PHYSICAL SOC PI COLLEGE PK PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA SN 1098-0121 EI 1550-235X J9 PHYS REV B JI Phys. Rev. B PD AUG 15 PY 1998 VL 58 IS 8 BP R4262 EP R4265 DI 10.1103/PhysRevB.58.R4262 PG 4 WC Physics, Condensed Matter SC Physics GA 117GE UT WOS:000075772500018 ER PT J AU Copeland, EJ Grivell, IJ Kolb, EW Liddle, AR AF Copeland, EJ Grivell, IJ Kolb, EW Liddle, AR TI On the reliability of inflation potential reconstruction SO PHYSICAL REVIEW D LA English DT Article ID PERTURBATIONS AB If primordial scalar and tensor perturbation spectra can be inferred from observations of the cosmic background radiation and large-scale structure, then one might hope to reconstruct a unique single-field inflaton potential capable of generating the observed spectra. In this paper we examine conditions under which such a potential can be reliably reconstructed. For it to be possible at all, the spectra must be well fit by a Taylor series expansion. A complete reconstruction requires a statistically significant tensor mode to be measured in the microwave background. We find that the observational uncertainties dominate the theoretical error from use of the slow-roll approximation, and conclude that the reconstruction procedure will never insidiously lead to an irrelevant potential. C1 Univ Sussex, Ctr Theoret Phys, Brighton BN1 9QH, E Sussex, England. Univ Sussex, Ctr Astron, Brighton BN1 9QJ, E Sussex, England. NASA, Fermilab Astrophys Ctr, Fermi Natl Accelerator Lab, Batavia, IL 60510 USA. Univ Chicago, Dept Astron & Astrophys, Chicago, IL 60637 USA. Univ Chicago, Enrico Fermi Inst, Chicago, IL 60637 USA. RP Copeland, EJ (reprint author), Univ Sussex, Ctr Theoret Phys, Brighton BN1 9QH, E Sussex, England. NR 17 TC 21 Z9 21 U1 0 U2 0 PU AMERICAN PHYSICAL SOC PI COLLEGE PK PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA SN 0556-2821 J9 PHYS REV D JI Phys. Rev. D PD AUG 15 PY 1998 VL 58 IS 4 AR 043002 DI 10.1103/PhysRevD.58.043002 PG 8 WC Astronomy & Astrophysics; Physics, Particles & Fields SC Astronomy & Astrophysics; Physics GA 112YC UT WOS:000075521600007 ER PT J AU Lee, S AF Lee, S TI Propagation of extragalactic high energy cosmic and gamma rays SO PHYSICAL REVIEW D LA English DT Article ID INTERGALACTIC INFRARED RADIATION; MICROWAVE BACKGROUND-RADIATION; UNIFICATION SCALE PHYSICS; TOPOLOGICAL DEFECTS; COSMOLOGICAL DISTANCES; RADIO GALAXIES; SPECTRUM; ORIGIN; STRINGS; ABSORPTION AB The observation of air showers from elementary particles with energies exceeding 10(20) eV poses a puzzle to the physics and astrophysics of cosmic rays which is still unresolved. Explaining the origin and nature of these particles is a challenge. In order to constrain production mechanisms and sites, one has to account for the processing of particle spectra by interactions with radiation backgrounds and magnetic fields on the way to the observer. In this paper, I report on an extensive study on the propagation of extragalactic nucleons, gamma-rays, and electrons in the energy range between 10(8) eV and 10(25) eV. We have devised an efficient numerical method to solve the transport equations for cosmic ray spectral evolution. The universal radiation background spectrum in the energy range between similar or equal to 10(-9) eV and similar or equal to 10 eV is considered in the numerical code, including the diffuse radio background, the cosmic microwave background, and the infrared-optical background, as well as a possible extragalactic magnetic field. We apply the code to compute the particle spectra predicted by several models of ultrahigh energy cosmic ray origin. A comparison with the observed fluxes, especially the diffuse gamma-ray background in several energy ranges, allows one to constrain certain classes of models. C1 Univ Chicago, Enrico Fermi Inst, Dept Phys, Chicago, IL 60637 USA. NASA, Fermilab Astrophys Ctr, Fermi Natl Accelerator Lab, Batavia, IL 60510 USA. RP Univ Chicago, Enrico Fermi Inst, Dept Phys, Chicago, IL 60637 USA. NR 95 TC 75 Z9 75 U1 0 U2 0 PU AMER PHYSICAL SOC PI COLLEGE PK PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA SN 2470-0010 EI 2470-0029 J9 PHYS REV D JI Phys. Rev. D PD AUG 15 PY 1998 VL 58 IS 4 AR 043004 DI 10.1103/PhysRevD.58.043004 PG 24 WC Astronomy & Astrophysics; Physics, Particles & Fields SC Astronomy & Astrophysics; Physics GA 112YC UT WOS:000075521600009 ER PT J AU Tinto, M Armstrong, JW AF Tinto, M Armstrong, JW TI Spacecraft Doppler tracking as a narrow-band detector of gravitational radiation SO PHYSICAL REVIEW D LA English DT Article AB We discuss a filtering technique for reducing the frequency fluctuations due to the troposphere, ionosphere, and mechanical vibrations of the ground antenna in spacecraft Doppler tracking searches for gravitational radiation. This method takes advantage of the sinusoidal behavior of the transfer function to the Doppler observable of these noise sources, which displays sharp nulls at selected Fourier components. The non-zero gravitational wave signal remaining at these frequencies makes this Doppler tracking technique the equivalent of a series of narrow-band detectors of gravitational radiation distributed across the low-frequency band. Estimates for the sensitivities achievable with the future Cassini Doppler tracking experiments are presented in the context of gravitational wave bursts, monochromatic signals, and a stochastic background of gravitational radiation. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Tinto, M (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. EM mtinto@pop.jpl.nasa.gov; John.W.Armstrong@jpl.nasa.gov NR 24 TC 8 Z9 8 U1 0 U2 0 PU AMER PHYSICAL SOC PI COLLEGE PK PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA SN 1550-7998 EI 1550-2368 J9 PHYS REV D JI Phys. Rev. D PD AUG 15 PY 1998 VL 58 IS 4 AR 042002 DI 10.1103/PhysRevD.58.042002 PG 8 WC Astronomy & Astrophysics; Physics, Particles & Fields SC Astronomy & Astrophysics; Physics GA 112YC UT WOS:000075521600005 ER PT J AU Tornkvist, O AF Tornkvist, O TI Electroweak origin of cosmological magnetic fields SO PHYSICAL REVIEW D LA English DT Article ID EARLY UNIVERSE; BUBBLE COLLISIONS; PHASE-TRANSITIONS; ELECTRICAL-CONDUCTIVITY; W-CONDENSATION; STRINGS; GENERATION; STABILITY; QCD; INFLATION AB Magnetic fields may have been generated in the electroweak phase transition through spontaneous symmetry breaking or through the subsequent dynamical evolution of semiclassical field configurations. Here I demonstrate explicitly how magnetic fields emerge spontaneously in the phase transition also when no gradients of the Higgs field are present. Using a simple model, I show that no magnetic fields an generated, at least initially, from classical two-bubble collisions in a first-order phase transition. An improved gauge-invariant definition of the electromagnetic field is advocated which is more appropriate in the sense that it never allows electrically neutral fields to serve as sources for the electromagnetic field. In particular, semiclassical configurations of the Z field alone do not generate magnetic fields. The possible generation of magnetic fields in the decay of unstable Z strings is discussed. C1 NASA, Fermilab Astrophys Ctr, Fermi Natl Accelerator Lab, Batavia, IL 60510 USA. RP Univ Cambridge, Dept Appl Math & Theoret Phys, Silver St, Cambridge CB3 9EW, England. EM O.Tornkvist@damtp.cam.ac.uk NR 55 TC 16 Z9 16 U1 0 U2 0 PU AMER PHYSICAL SOC PI COLLEGE PK PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA SN 2470-0010 EI 2470-0029 J9 PHYS REV D JI Phys. Rev. D PD AUG 15 PY 1998 VL 58 IS 4 AR 043501 DI 10.1103/PhysRevD.58.043501 PG 12 WC Astronomy & Astrophysics; Physics, Particles & Fields SC Astronomy & Astrophysics; Physics GA 112YC UT WOS:000075521600011 ER PT J AU Kong, J Cassell, AM Dai, HJ AF Kong, J Cassell, AM Dai, HJ TI Chemical vapor deposition of methane for single-walled carbon nanotubes SO CHEMICAL PHYSICS LETTERS LA English DT Article ID GROWTH; FILAMENTS; FIBERS; TUBES AB We report the synthesis of high-quality single-walled carbon nanotubes (SWNT) by chemical vapor deposition (CVD) of methane at 1000 degrees C on supported Fe(2)O(3) catalysts. The type of catalyst support is found to control the formation of individual or bundled SWNTs. Catalysts supported on crystalline alumina nanoparticles produce abundant individual SWNTs and small bundles. Catalysts supported by amorphous silica particles produce only SWNT bundles. Studies of the ends of SWNTs lead to an understanding of their growth mechanism. Also, we present the results of methane CVD on supported NiO, CoO and NiO/CoO catalysts. (C) 1998 Published by Elsevier Science B.V. All rights reserved. C1 Stanford Univ, Dept Chem, Stanford, CA 94305 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Dai, HJ (reprint author), Stanford Univ, Dept Chem, Stanford, CA 94305 USA. EM hdai@chem.stanford.edu NR 25 TC 653 Z9 681 U1 17 U2 291 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0009-2614 J9 CHEM PHYS LETT JI Chem. Phys. Lett. PD AUG 14 PY 1998 VL 292 IS 4-6 BP 567 EP 574 DI 10.1016/S0009-2614(98)00745-3 PG 8 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA 112EZ UT WOS:000075482300030 ER PT J AU Bhatia, AK Ho, YK AF Bhatia, AK Ho, YK TI Calculations of doubly excited F-1,3(0) states in helium-like systems using Hylleraas functions SO JOURNAL OF PHYSICS B-ATOMIC MOLECULAR AND OPTICAL PHYSICS LA English DT Article ID COMPLEX-COORDINATE CALCULATION; RADIATIVE STABILIZATION; RESONANCES; HE; IONS; PARAMETERS; CAPTURE; 4L4L' AB Doubly excited or Feshbach-type F-1,3(0) resonances in helium-like systems have been calculated using the complex-rotation method. Using Hylleraas-type wavefunctions of up to 1632 terms, we calculate resonance parameters (both resonance positions and widths) below the N = 3 and 4 thresholds of the hydrogenic systems with nuclear charge from Z = 2 to Z = 10. Comparisons are made with the other calculations for Z greater than or equal to 2 in the literature. C1 NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, Greenbelt, MD 20771 USA. Acad Sinica, Inst Atom & Mol Sci, Taipei, Taiwan. RP Bhatia, AK (reprint author), NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, Greenbelt, MD 20771 USA. RI Ho, Yew Kam/F-7912-2012 NR 23 TC 10 Z9 10 U1 0 U2 0 PU IOP PUBLISHING LTD PI BRISTOL PA DIRAC HOUSE, TEMPLE BACK, BRISTOL BS1 6BE, ENGLAND SN 0953-4075 J9 J PHYS B-AT MOL OPT JI J. Phys. B-At. Mol. Opt. Phys. PD AUG 14 PY 1998 VL 31 IS 15 BP 3307 EP 3319 DI 10.1088/0953-4075/31/15/005 PG 13 WC Optics; Physics, Atomic, Molecular & Chemical SC Optics; Physics GA 113RR UT WOS:000075565500005 ER PT J AU Hansen, JE Sato, M Ruedy, R Lacis, A Glascoe, J AF Hansen, JE Sato, M Ruedy, R Lacis, A Glascoe, J TI Global warming - Global climate data and models: A reconciliation SO SCIENCE LA English DT Editorial Material ID TEMPERATURE C1 NASA, Goddard Inst Space Studies, New York, NY 10025 USA. RP Hansen, JE (reprint author), NASA, Goddard Inst Space Studies, New York, NY 10025 USA. RI Lacis, Andrew/D-4658-2012 NR 14 TC 23 Z9 23 U1 0 U2 3 PU AMER ASSOC ADVANCEMENT SCIENCE PI WASHINGTON PA 1200 NEW YORK AVE, NW, WASHINGTON, DC 20005 USA SN 0036-8075 J9 SCIENCE JI Science PD AUG 14 PY 1998 VL 281 IS 5379 BP 930 EP 932 DI 10.1126/science.281.5379.930 PG 3 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA 110ZK UT WOS:000075412700028 ER PT J AU Beck, JG Duvall, TL Scherrer, PH AF Beck, JG Duvall, TL Scherrer, PH TI Long-lived giant cells detected at the surface of the Sun SO NATURE LA English DT Article ID SOLAR; CONVECTION; OSCILLATIONS; DEPTH AB Giant convective cells have been predicted(1) to exist in the Sun. Such cells should span the entire zone unstable to convective motions-now known to cover the outer 29 per cent of the Sun's radius(2)-and could be dredging up the magnetic flux that is thought to be the source of solar activity (sunspots). Several studies(3-5) have failed to detect these giant cells, although there have been hints(6-9) of their existence. We have detected long-lived velocity cells, which we identify as the elusive giant convective cells, extending over 40-50 degrees of longitude but less than 10 degrees of latitude. The large aspect ratio (>4) is surprising (although predicted by one model(10)) and may be a consequence of the Sun's differential rotation, whereby features with a larger extent in latitude are broken up by rotational shear. C1 Stanford Univ, WW Hansen Expt Phys Lab, Stanford, CA 94305 USA. NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, Greenbelt, MD 20771 USA. RP Beck, JG (reprint author), Stanford Univ, WW Hansen Expt Phys Lab, Stanford, CA 94305 USA. RI Duvall, Thomas/C-9998-2012 NR 23 TC 47 Z9 47 U1 0 U2 2 PU MACMILLAN MAGAZINES LTD PI LONDON PA PORTERS SOUTH, 4 CRINAN ST, LONDON, ENGLAND N1 9XW SN 0028-0836 J9 NATURE JI Nature PD AUG 13 PY 1998 VL 394 IS 6694 BP 653 EP 655 DI 10.1038/29245 PG 3 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA 110MD UT WOS:000075384200035 ER PT J AU Garasi, C Loken, C Burns, JO Roettiger, K AF Garasi, C Loken, C Burns, JO Roettiger, K TI Numerical simulations of rotating cooling flows in galaxy cluster environments SO MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY LA English DT Article DE hydrodynamics; instabilities; galaxies : clusters : general; cooling flows ID THERMAL-INSTABILITY; MAGNETOTHERMAL INSTABILITY; MAGNETIC-FIELDS; GAS; RADIO; ACCRETION; ROSAT; STAGE AB We have used 2D numerical simulations to study the evolution of galaxy cluster cooling flows undergoing a rotational perturbation. We show that such rotations in the intracluster medium may arise from cluster/subcluster mergers. Our galaxy cluster initial conditions involve spherically symmetric, steady-state cooling flows with varying mass-dropout strengths. The rotational perturbation serves to break the symmetry for each of the initial cooling flows, resulting in the formation of thin, gaseous disc-like structure extending radially out to similar to 10 kpc. Disc-like structure formed for low mass-dropout strength simulations appears to contain cooling condensations whereas disc-like structure in higher mass-dropout strength simulations appears smooth. This is due to the influence of mass-dropout on the degree of cooling, which serves to reduce the strength of thermal instabilities by the removal of 'cold' gas from the flow. Morphological comparisons of the disc-like structure formed in our simulations are made to structure observed in the X-ray emitting gas of A4059. Comparisons of the gas dynamics within the disc-like structure are also made to the solid-body rotation profile observed from emission-line gas within the central galaxy of Hydra A. The influence of grid effects on the simulations is also discussed. C1 New Mexico State Univ, Dept Astron, Las Cruces, NM 88003 USA. Univ Missouri, Res Off, Columbia, MO 65211 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Missouri, Dept Phys & Astron, Columbia, MO 65211 USA. RP Garasi, C (reprint author), New Mexico State Univ, Dept Astron, Box 30001,Dept 4500, Las Cruces, NM 88003 USA. NR 42 TC 2 Z9 2 U1 0 U2 0 PU BLACKWELL SCIENCE LTD PI OXFORD PA P O BOX 88, OSNEY MEAD, OXFORD OX2 0NE, OXON, ENGLAND SN 0035-8711 J9 MON NOT R ASTRON SOC JI Mon. Not. Roy. Astron. Soc. PD AUG 11 PY 1998 VL 298 IS 3 BP 697 EP 707 DI 10.1046/j.1365-8711.1998.01631.x PG 11 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 114GX UT WOS:000075601700010 ER PT J AU Kastner, SO Bhatia, AK AF Kastner, SO Bhatia, AK TI An intensity/linewidth analysis of opacity: first applications to a solar prominence and He II line profiles SO MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY LA English DT Article DE line, profiles; Sun, atmosphere; Sun, prominences; ultraviolet, stars ID QUIET-SUN; EMISSION; SPECTRUM; PLASMA; SIIII; LIMB AB An analysis is described which can derive optical thicknesses and associated quantities from measured intensities and linewidths using convenient expressions for photon escape probabilities and for opacity-broadened line halfwidths. An associated analysis of the effect of observational errors is provided. The analysis treats intensities and linewidths independently so that internal consistency of results can provide a measure of observational accuracy, which is shown here to be a stringent requirement. As examples, first applications are made to Si II lines in a solar prominence and to some high-resolution observations of the solar Hen 303.78-Angstrom resonance line. C1 NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, Greenbelt, MD 20771 USA. RP Kastner, SO (reprint author), 1-A Ridge Rd, Greenbelt, MD 20770 USA. NR 23 TC 8 Z9 8 U1 1 U2 1 PU BLACKWELL SCIENCE LTD PI OXFORD PA P O BOX 88, OSNEY MEAD, OXFORD OX2 0NE, OXON, ENGLAND SN 0035-8711 J9 MON NOT R ASTRON SOC JI Mon. Not. Roy. Astron. Soc. PD AUG 11 PY 1998 VL 298 IS 3 BP 763 EP 776 DI 10.1046/j.1365-8711.1998.01694.x PG 14 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 114GX UT WOS:000075601700017 ER PT J AU Ohsaka, K Chung, SK Rhim, WK AF Ohsaka, K Chung, SK Rhim, WK TI Specific volumes and viscosities of the Ni-Zr alloys and their correlation with the glass formability of the alloys SO ACTA MATERIALIA LA English DT Article ID NONCONTACT MEASUREMENT TECHNIQUE; ELECTROSTATIC LEVITATOR; LIQUID; HEAT AB The specific volumes and viscosities of the Ni-Zr liquid alloys as a function of temperature are determined by employing a digitizing technique and numerical analysis methods applied to the optical images of the electrostatically levitated liquid alloys. The results show that the specific volume of the NiZr2 alloy is significantly smaller than that of an ideal mixture of the constituent metals, thereby indicating the presence of the associated species in the form of NiZr2. The presence of NiZr2 species can account for the observed properties; the specific volume anomaly above the melting point under a moderate cooling rate and a relatively small undercooling level prior to crystallization. The results also show that the viscosities of the compound forming alloys are larger than those of the eutectic alloys, thereby indicating the presence of the NiZr and NiZr2 species. The associated species are stable and exist at temperatures well above their melting points, it is concluded that a small specific volume or a large viscosity resulting from the presence of the associated species primarily facilitates the glass formation of the Ni-Zr alloys by slowing down the growth of the crystalline phases. (C) 1998 Acm Metallurgica Inc. Published by Elsevier Science Ltd. All rights reserved. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Ohsaka, K (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 11 TC 20 Z9 20 U1 0 U2 6 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 1359-6454 J9 ACTA MATER JI Acta Mater. PD AUG 10 PY 1998 VL 46 IS 13 BP 4535 EP 4542 DI 10.1016/S1359-6454(98)00154-2 PG 8 WC Materials Science, Multidisciplinary; Metallurgy & Metallurgical Engineering SC Materials Science; Metallurgy & Metallurgical Engineering GA 112KN UT WOS:000075494000008 ER PT J AU Moritz, P Wennmacher, A Herbstmeier, U Mebold, U Egger, R Snowden, SL AF Moritz, P Wennmacher, A Herbstmeier, U Mebold, U Egger, R Snowden, SL TI X-ray shadows of the Draco nebula - A new method to determine total hydrogen column densities SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE ISM : atoms; ISM : clouds; dust, extinction; ISM : individual objects : Draco nebula; ISM : molecules; X-rays : ISM ID H-I; ROSAT PSPC; INFRARED CIRRUS; MOLECULAR CLOUD; GALACTIC HALO; URSA MAJOR; SKY SURVEY; DIFFUSE; ABUNDANCES; CALIBRATION AB We have used the ROSAT 1/4 keV all-sky survey together with HI observations to derive the total column density of hydrogen nuclei, N(H), of the Draco nebula [= G91+38 (v(LSR) = -21 km s(-1))], which casts a deep shadow in the soft X-ray background. Adopting a two-component model for the X-ray plasma in which one component is located behind the Draco nebula, the other in front of all the absorbing material (the so-called Local Hot Bubble, LHB), we fit the parameters of the radiation transport equation to the observed X-ray count rates. The optical depth in this equation is derived from H I column densities obtained with the 100-m telescope and the appropriate X-ray absorption cross sections. The solutions obtained by this approach are biased since HI column densities underestimate the absorption in regions where molecular hydrogen is abundant. The bias is avoided by excluding regions with strong X-ray shadowing from the fit and by comparing fits which are obtained on the basis of hydrogen column densities derived from IRAS 100(-) mu m data. We find that the absorbing column densities at the deepest X-ray shadows are up to about 3 10(20) cm(-2) larger than the observed 1-1 I column densities. At the edge towards low galactic latitudes and longitudes, up to 70% of the hydrogen is in molecular form. In other parts of the nebula the molecular abundance is less than or similar to 25%. We also find an approximately constant FIR-emissivity per hydrogen nucleon (H I + 2H(2)) of about 1.0 10(-20) MJy sr(-1) cm(2) This is close to the mean value for the galactic cirrus (0.86 10(-20) MJy sr(-1) cm(2)). In contrast, the FIR-emissivity per H I atom is varying strongly across the nebula. The x(WCO) values (= N(H-2)/W((CO)-C-12)) found in the Draco nebula are typically in the range 0.36 < x(WCO) < 0.52 10(20) cm(-2) (K km s(-1))(-1), similar to other cirrus clouds. We find a very low x(WCO) ratio of 0.17 cm(-2) (K km s(-1))(-1) at the edge of the Draco nebula towards low galactic coordinates where the CO abundance could be altered in a low-velocity shack. Finally, the X-ray emission measure for the distant component of the X-ray emitting plasma is found to be about 5 times larger than that for the LHB, assuming constant plasma temperatures of 10(6.3) K and 10(5.85) K respectively. Since the Draco nebula(distance > 300 pc) is located outside the galactic gas layer, this is evidence of a bright Galactic X-ray corona or an extended coronal hot spot. The intensity of this coronal emission is constant over the observed 7 degrees-field within the uncertainties of our analysis (< 15%). C1 Univ Bonn, Inst Radioastron, D-53121 Bonn, Germany. Univ Cologne, Inst Geophys & Meteorol, D-50923 Cologne, Germany. Max Planck Inst Astron, D-69117 Heidelberg, Germany. Max Planck Inst Extraterr Phys, D-85740 Garching, Germany. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Moritz, P (reprint author), Univ Bonn, Inst Radioastron, Hugel 71, D-53121 Bonn, Germany. RI Snowden, Steven/D-5292-2012 NR 58 TC 15 Z9 15 U1 0 U2 0 PU EDP SCIENCES S A PI LES ULIS CEDEX A PA 17, AVE DU HOGGAR, PA COURTABOEUF, BP 112, F-91944 LES ULIS CEDEX A, FRANCE SN 0004-6361 J9 ASTRON ASTROPHYS JI Astron. Astrophys. PD AUG 10 PY 1998 VL 336 IS 2 BP 682 EP 696 PG 15 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 110RQ UT WOS:000075394500031 ER PT J AU George, IM Turner, TJ Mushotzky, R Nandra, K Netzer, H AF George, IM Turner, TJ Mushotzky, R Nandra, K Netzer, H TI ASCA observations of the ionized gas in the Seyfert galaxy NGC 3783 SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies : active; galaxies : individual (NGC 3783); galaxies : nuclei; galaxies : Seyfert; X-rays : galaxies ID ACTIVE GALACTIC NUCLEI; IMAGING SPECTROMETER; BOARD ASCA; RAY; EMISSION; ABSORPTION; NGC-3783; TELESCOPE; DISK AB We present the results from ASCA observations of NGC 3783 carried out during 1993 and 1996. Variability is observed both between the two epochs and within the individual observations, the latter due to a nonstationary process. We find the spectra at both epochs to contain features due to absorption by ionized material, predominantly due to O VII and O VIII. We find the opacity for such material to decrease by a factor similar to 2 in the similar to 0.7-1.0 keV band between the epochs while the photoionizing flux increases by similar to 25%. By comparison with detailed photoionization models we show that this behavior is inconsistent with that expected from a single zone of photoionized gas. A deficit in the data compared to such models, consistent with excess absorption by O VIII, supports the suggestion that the material consists of two or more zones. Significant Fe K shell emission is also observed during both epochs. We show that this emission is dominated by the asymmetric line profile expected from the innermost regions of the accretion flow. We find no evidence that the Fe emission varied in either shape or equivalent width between the two epochs. C1 NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. Tel Aviv Univ, Raymond & Beverly Sackler Fac Exact Sci, Sch Phys & Astron, IL-69978 Tel Aviv, Israel. Tel Aviv Univ, Raymond & Beverly Sackler Fac Exact Sci, Wise Observ, IL-69978 Tel Aviv, Israel. RP George, IM (reprint author), NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Code 660, Greenbelt, MD 20771 USA. NR 34 TC 38 Z9 38 U1 0 U2 0 PU IOP PUBLISHING LTD PI BRISTOL PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD AUG 10 PY 1998 VL 503 IS 1 BP 174 EP 185 DI 10.1086/305988 PN 1 PG 12 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 152KK UT WOS:000077776400015 ER PT J AU Terashima, Y Kunieda, H Misaki, K Mushotzky, RF Ptak, AF Reichert, GA AF Terashima, Y Kunieda, H Misaki, K Mushotzky, RF Ptak, AF Reichert, GA TI Detection of an iron K emission line from the liner NGC 4579 SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies : individual (NGC 4579); galaxies : nuclei; X-rays : galaxies ID ACTIVE GALACTIC NUCLEI; TYPE-2 SEYFERT-GALAXIES; X-RAY REFLECTION; ASCA OBSERVATIONS; SPIRAL GALAXIES; ALPHA EMISSION; SPECTRUM; DISK; CONTINUUM; BINARIES AB We present the results of an ASCA observation of the LINER NGC 4579. A pointlike X-ray source is detected at the nucleus with a 2-10 keV luminosity of 1.5 x 10(41) ergs s(-1) assuming a distance of 16.8 Mpc. The X-ray spectrum is represented by a combination of a power law with a photon index of similar to 1.7 and a soft thermal component with kT similar to 0.9 keV. An iron K emission line is detected at 6.73 +/- 0.13 keV (rest-frame) with an equivalent width of 490(-190)(+180) eV, and it is statistically significant at greater than 99.9% confidence. The line center energy is consistent with helium-like iron and is significantly higher than 6.4 keV, which is expected from fluorescence by "cold" (or a lower ionization state of) iron. The iron line profile shows no significant red tail in contrast to Seyfert 1 galaxies, although the statistics are limited. The line center energy, the equivalent width, and the profile are consistent with an origin in an ionized accretion disk. However, the large mass accretion rate necessary to ionize the accretion disk is not consistent with the observed luminosity and the normal accretion models. C1 Nagoya Univ, Dept Phys, Chikusa Ku, Nagoya, Aichi 4648602, Japan. NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. RP Terashima, Y (reprint author), Nagoya Univ, Dept Phys, Chikusa Ku, Nagoya, Aichi 4648602, Japan. NR 61 TC 35 Z9 36 U1 0 U2 0 PU IOP PUBLISHING LTD PI BRISTOL PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD AUG 10 PY 1998 VL 503 IS 1 BP 212 EP 218 DI 10.1086/305979 PN 1 PG 7 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 152KK UT WOS:000077776400017 ER PT J AU Vassiliadis, E Dopita, MA Meatheringham, SJ Bohlin, RC Ford, HC Harrington, JP Wood, PR Stecher, TP Maran, SP AF Vassiliadis, E Dopita, MA Meatheringham, SJ Bohlin, RC Ford, HC Harrington, JP Wood, PR Stecher, TP Maran, SP TI Hubble Space Telescope observations of planetary nebulae in the Magellanic Clouds. VII. Cycle 3 and archive narrowband [O III] 500.7 nanometer imaging SO ASTROPHYSICAL JOURNAL LA English DT Article DE Magellanic Clouds; planetary nebulae : general ID INTERNAL DYNAMICS; ANGULAR DIAMETERS; CENTRAL STARS; SMP-83 WS-35; EVOLUTION; IMAGES; RESTORATION; MASS AB We present the continuation of our analysis of narrowband [O III] images, obtained using the Hubble Space Telescope (HST), of planetary nebulae (PNs) in the Magellanic Clouds. Six objects, five in the Large Magellanic Cloud, are observed as part of the General Observer program. An additional 15 objects are retrieved from the HST archive. The majority of the images are obtained prior to the first maintanence and refurbishment mission and are dominated by nebular [O III] 500.7 nm emission: the PN central stars are generally not seen. The raw images are deconvolved using 100 iterations of the Richardson-Lucy image restoration algorithm. The nebular dimensions and morphologies are determined. The nebular dynamical ages are derived using [O III] 500.7 nm expansion velocities from the literature. Using the techniques presented in Paper IV, the measured nebular ages are compared to theoretical evolutionary ages for H-burning and He-burning PN nuclei. Approximately 50% of the PN central stars are He burners in both the Large and Small Magellanic Clouds. C1 Inst Astrofis Canarias, E-38200 La Laguna, Tenerife, Spain. Australian Natl Univ, Mt Stromlo & Siding Spring Observ, Inst Adv Studies, Weston, ACT 2611, Australia. Australian Def Force Acad, Univ Coll, Informat Technol Serv Ctr, Canberra, ACT 2600, Australia. Space Telescope Sci Inst, Baltimore, MD 21218 USA. Johns Hopkins Univ, Dept Phys & Astron, Baltimore, MD 21218 USA. Univ Maryland, Dept Astron, College Pk, MD 20742 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Vassiliadis, E (reprint author), Inst Astrofis Canarias, C Via Lactea S-N, E-38200 La Laguna, Tenerife, Spain. RI Dopita, Michael/P-5413-2014 OI Dopita, Michael/0000-0003-0922-4986 NR 49 TC 20 Z9 20 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD AUG 10 PY 1998 VL 503 IS 1 BP 253 EP 277 DI 10.1086/305969 PN 1 PG 25 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 152KK UT WOS:000077776400022 ER PT J AU Robinson, RD Carpenter, KG Brown, A AF Robinson, RD Carpenter, KG Brown, A TI Goddard high-resolution spectrograph observations of cool low-gravity stars. IV. A comparison of the K5 III stars alpha Tauri and gamma Draconis SO ASTROPHYSICAL JOURNAL LA English DT Article DE stars : chromospheres; stars : individual (alpha Tauri, gamma Draconis); stars : late-type; stars : mass loss; ultraviolet : stars ID HYBRID-CHROMOSPHERE STARS; ORIONIS M2 IAB; GHRS OBSERVATIONS; GIANT STARS; RED GIANTS; EFFECTIVE TEMPERATURES; EXPANDING ENVELOPE; ANGULAR DIAMETERS; OUTER ATMOSPHERES; RESONANCE LINES AB The Goddard High-Resolution Spectrograph (GHRS) has observed the K5 III star a Tau in the 2330 Angstrom region on three separate occasions. These spectra show marked changes with time, with the UV continuum varying by a factor of 2, and with the emission lines changing in flux by 30% or more, with the amount of change dependent upon the opacity of the line. The variations suggests a restructuring of the atmosphere rather than simply a change in the surface area covered by chromospheric material. Surprisingly, there was no detectable change in the chromospheric turbulence on timescales of hours or years. On average, the lower part of the atmosphere was found to be fairly static, with a slight infall of 1-2 km s(-1). At higher altitudes, probed by observation of the stronger Fe rr lines as well as of the O I (UV 2) and Mg II (UV 1) resonance lines, there is evidence for the acceleration of a slow wind, similar to that seen in the M giants gamma Cru and mu Gem. This wind is much less massive than for the later type giants, however, since its effects are seen in only the most optically thick of the Fe II lines. Comparison of the alpha Tau observations with similar data for the K5 VT hybrid star gamma Dra shows remarkable similarity in the photosphere and lower chromosphere. Both stars have pronounced UV continua, identical turbulences and chromospheric densities, and very similar line fluxes and profiles for all lines formed in the lower chromosphere, including C II], Co I, Si II], and Fe II. A deep exposure near 1500 Angstrom also shows the first evidence for hot plasma in the atmosphere of alpha Tau through the detection of the C Iv (UV 1) doublet with a surface flux about 30% of that observed in gamma Dra. Most of the evidence for the stellar wind is in the Mg II (UV 1) and O I (UV 2) resonance Lines. Modeling these lines using the Sobolev with Exact Integration (SEI) radiative transfer code shows that the wind in gamma Dra accelerates faster and reaches a higher terminal velocity than does the wind in alpha Tau. However, the wind turbulent velocity in gamma Dra is only about one-third of the value seen in alpha Tau. We conclude that the observations support the suggestion by Judge & Stencel that the processes that heat the chromosphere are distinct from those that drive the stellar winds. C1 NASA, Goddard Space Flight Ctr, Comp Sci Corp, Greenbelt, MD 20771 USA. NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, Greenbelt, MD 20771 USA. Univ Colorado, CASA, Boulder, CO 80309 USA. RP Robinson, RD (reprint author), NASA, Goddard Space Flight Ctr, Comp Sci Corp, Code 681, Greenbelt, MD 20771 USA. EM robinson@opal.gsfc.nasa.gov; carpenter@tma1.gsfc.nasa.gov RI Carpenter, Kenneth/D-4740-2012 NR 53 TC 34 Z9 34 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD AUG 10 PY 1998 VL 503 IS 1 BP 396 EP 414 DI 10.1086/305971 PN 1 PG 19 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 152KK UT WOS:000077776400037 ER PT J AU Ergun, RE Larson, D Lin, RP McFadden, JP Carlson, CW Anderson, KA Muschietti, L McCarthy, M Parks, GK Reme, H Bosqued, JM D'Uston, C Sanderson, TR Wenzel, KP Kaiser, H Lepping, RP Bale, SD Kellogg, P Bougeret, JL AF Ergun, RE Larson, D Lin, RP McFadden, JP Carlson, CW Anderson, KA Muschietti, L McCarthy, M Parks, GK Reme, H Bosqued, JM D'Uston, C Sanderson, TR Wenzel, KP Kaiser, H Lepping, RP Bale, SD Kellogg, P Bougeret, JL TI Wind spacecraft observations of solar impulsive electron events associated with solar type III radio bursts SO ASTROPHYSICAL JOURNAL LA English DT Article DE Sun : flares; Sun : particle emission; Sun : radiation ID CLUMPY LANGMUIR-WAVES; DENSITY-FLUCTUATIONS; PLASMA; STABILITY; GROWTH AB We present Wind spacecraft observations of solar impulsive electron events associated with locally generated Langmuir waves during solar type III radio bursts. The solar impulsive electrons had energies from similar to 600 eV to greater than 300 keV. Local Langmuir emissions associated with these fluxes generally coincided with the arrival of 2-12 keV electrons. A survey of 27 events over 1 yr shows that there were few occurrences of electron distributions (similar to 96 s averaged) that were unstable to Langmuir waves and none that had a substantial growth rate (>3 x 10(-2) s(-1)) or endured for more than 96 s. Intense solar impulsive electron events that occurred on 1995 April 2 are studied in detail. Marginally stable (plateaued) distributions occasionally coincided with a periods of local Langmuir emissions, but the electron distributions were otherwise stable. These observations suggest that kinetic processes were modifying the electron distribution but also suggest that processes other than one-dimensional quasilinear relaxation were involved. We find that solar impulsive electron distributions were often unstable to oblique waves, such as quasi-electrostatic whistler waves or electromagnetic ion cyclotron waves, suggesting that competition between Langmuir and oblique emissions may be important. There are several other features in the Wind spacecraft solar impulsive electron observations that are noteworthy. Nondispersive flux modulations were visible in many of the events (also visible in the published;ISEE 3 data) in similar to 1-4 keV electrons, suggesting that a local hydromagnetic instability may have accompanied the lowest energy solar impulsive electron fluxes. The Wind data differ from the ISEE 3 data in the energy spectra of the electron events. ISEE 3 recorded few events with only high-energy (>10 keV) electron fluxes, whereas a survey of the Wind events shows a substantially higher ratio of high-energy events. The high-energy events were often associated with solar flares that could not have been magnetically well connected with the satellite. C1 Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA. Univ Washington, Geophys Program, Seattle, WA 98195 USA. Univ Toulouse 3, Ctr Etud Spatiale Rayonnements, F-31029 Toulouse, France. European Space Agcy, European Space Res & Technol Ctr, Dept Space Sci, NL-2200 AG Noordwijk, Netherlands. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ London Queen Mary & Westfield Coll, London E1 4NS, England. Univ Minnesota, Sch Phys & Astron, Minneapolis, MN 55455 USA. Observ Paris, DESPA, URA CNRS 264, LA 324 CNRS, F-92190 Meudon, France. RP Ergun, RE (reprint author), Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA. RI Bale, Stuart/E-7533-2011 OI Bale, Stuart/0000-0002-1989-3596 NR 37 TC 115 Z9 117 U1 0 U2 3 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD AUG 10 PY 1998 VL 503 IS 1 BP 435 EP 445 DI 10.1086/305954 PN 1 PG 11 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 152KK UT WOS:000077776400041 ER PT J AU De Propris, R Eisenhardt, PR Stanford, SA Dickinson, M AF De Propris, R Eisenhardt, PR Stanford, SA Dickinson, M TI The infrared luminosity function of galaxies in the Coma Cluster SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies : luminosity function, mass function; galaxies : clusters : individual (Coma) ID DWARF GALAXIES; FORNAX CLUSTER; POPULATION; MAGNITUDE; EVOLUTION; CATALOG; SAMPLE; FIELD; CORE AB An infrared survey of the central 650 arcmin(2) of the Coma Cluster is used to determine the H-band luminosity function for the cluster. Redshifts are available for all galaxies in the survey with H < 14.5, and for this sample we obtain a good fit to a Schechter function with H* = 11.13 and alpha = -0.78. These luminosity function parameters ale similar to those measured for field galaxies in the infrared, which is surprising considering the very different environmental densities and, presumably, merger histories for field galaxies. For fainter galaxies, we use two independent techniques to correct for field galaxy contamination in the cluster population: the B - R color-magnitude relation and an estimate for the level of background and foreground contamination from the literature. Using either method, we find a steep upturn for galaxies with 14 < H < 16, with slope alpha similar or equal to -1.7. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Lawrence Livermore Natl Lab, Inst Geophys & Planetary Phys, Livermore, CA 94550 USA. Johns Hopkins Univ, Dept Phys & Astron, Baltimore, MD 21218 USA. RP De Propris, R (reprint author), CALTECH, Jet Prop Lab, MS 169-327, Pasadena, CA 91109 USA. EM propris@coma.jpl.nasa.gov; prme@kromos.jpl.nasa.gov; adam@igpp.llnl.gov; med@stsci.edu NR 40 TC 67 Z9 67 U1 0 U2 0 PU IOP PUBLISHING LTD PI BRISTOL PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD AUG 10 PY 1998 VL 503 IS 1 BP L45 EP L48 DI 10.1086/311531 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 152KL UT WOS:000077776500011 ER PT J AU Koerner, DW Ressler, ME Werner, MW Backman, DE AF Koerner, DW Ressler, ME Werner, MW Backman, DE TI Mid-infrared imaging of a circumstellar disk around HR 4796: Mapping the debris of planetary formation SO ASTROPHYSICAL JOURNAL LA English DT Article DE infrared : stars; planetary systems; stars : formation; stars : individual (HR 4796) ID BETA-PICTORIS; DUST DEBRIS; STARS; CONSTRAINTS; HR-4796; MODELS; GAS AB We report the discovery of a circumstellar disk around the young A0 star HR 4796 in thermal infrared imaging carried out at the W. M. Keck Observatory. By fitting a model of the emission from a flat dusty disk to an image at lambda = 20.8 mu m, we derive a disk inclination, i = 72 degrees(-9 degrees)(+6 degrees) from face-on, with the long axis of emission at P.A. 28 degrees +/- 6 degrees. The intensity of emission does not decrease with radius, as expected for circumstellar disks, but increases outward from the star, peaking near both ends of the elongated structure. We simulate this appearance by varying the inner radius in our model and find an inner hole in the disk with radius R-in = 55 +/- 15 AU. This value corresponds to the radial distance of our own Kuiper belt and may suggest a source of dust in the collision of cometesimals. By contrast with the appearance at 20.8 mu m, excess emission at lambda = 12.5 mu m is faint and concentrated at the stellar position. Similar emission is also detected at 20.8 mu m in residual subtraction of the best-fit model from the image. The intensity and ratio of flux densities at the two wavelengths could be accounted for by a tenuous dust component that is confined within a few AU of the star with mean temperature of a few hundred degrees K, similar to that of zodiacal dust in our own solar system. The morphology of dust emission from HR 4796 (age 10 Myr) suggests that its disk is in a transitional planet-forming stage, between that of massive gaseous protostellar disks and more tenuous debris disks such as the one detected around Vega. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ Penn, Philadelphia, PA 19104 USA. Franklin & Marshall Coll, Dept Phys & Astron, Lancaster, PA 17604 USA. RP Koerner, DW (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 22 TC 138 Z9 138 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD AUG 10 PY 1998 VL 503 IS 1 BP L83 EP L87 DI 10.1086/311525 PN 2 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 152KL UT WOS:000077776500020 ER PT J AU Leahy, DA Scott, DM AF Leahy, DA Scott, DM TI Evidence for subsynchronous rotation in HZ Herculis/Hercules X-1 SO ASTROPHYSICAL JOURNAL LA English DT Article DE binaries : eclipsing; pulsars : individual (Hercules X-1); stars : individual (HZ Herculis); stars : neutron; X-rays : stars ID HERCULES-X-1; HERCULIS AB An analysis of the orbit of Hercules X-1 is carried out, including results from recent X-ray and optical studies. Constraints on the binary parameters are given. Since HZ Herculis is required to be inside or filling its critical Roche lobe, no orbital solutions are allowed unless HZ Her's rotation rate is subsynchronous. This is consistent with the observed orbital period derivative. The alternative possibility is that the optical velocity of HZ Her is still not well determined. Assuming that it is correct, new upper and lower limits on the neutron star mass are derived: 1.23 M. < M-x < 1.48 M.. C1 Univ Calgary, Dept Phys, Calgary, AB T2N 1N4, Canada. NASA, George C Marshall Space Flight Ctr, Space Sci Lab, Huntsville, AL 35812 USA. RP Leahy, DA (reprint author), Univ Calgary, Dept Phys, Calgary, AB T2N 1N4, Canada. NR 10 TC 18 Z9 18 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD AUG 10 PY 1998 VL 503 IS 1 BP L63 EP L65 DI 10.1086/311535 PN 2 PG 3 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 152KL UT WOS:000077776500015 ER PT J AU Hook, SJ Cudahy, TJ Kahle, AB Whitbourn, LB AF Hook, SJ Cudahy, TJ Kahle, AB Whitbourn, LB TI Synergy of active and passive airborne thermal infrared systems for surface compositional mapping SO JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH LA English DT Article ID MULTISPECTRAL SCANNER; DEATH-VALLEY; IMAGES; CALIFORNIA; MINERALS; INFORMATION; EMISSIVITY; ROCK AB NASA thermal infrared multispectral scanner (TIMS) and Commonwealth Scientific Industrial Research Organisation mid-infrared airborne CO2 laser spectrometer (MIRACO(2)LAS) data were acquired over the Mount Fitton area, South Australia, in order to evaluate their combined use for geological mapping and mineral exploration. TIMS is a passive, imaging system with six spectral bands in the thermal infrared wavelength region (8-12 mu m), whereas MIRACO(2)LAS is an active, profiling system with similar to 100 spectral bands in the 9-11 mu m spectral range. The TIMS and CO2 laser data (emissivity variations for TIMS and apparent reflectance for MIRACO(2)LAS) were processed to enhance spectral information related to the surface composition. This spectral information was compared with existing geological maps and field emissivity spectra. Known geological units were well discriminated in the TIMS imagery, including a range of quartz-rich and carbonate-rich sedimentary units, as well as several previously unmapped areas of alteration in the carbonate rocks. However, the broadband spectral resolution of TIMS did not allow identification of discrete mineral constituents. In contrast, the high spectral resolution MIRACO(2)LAS data provided diagnostic spectral information about a range of minerals present including quartz, dolomite, talc, and tremolite, albeit, along discrete profiles. The widths of some of these diagnostic spectral features were less than 0.2 mu m wide, which is half the resolution of the TIMS band passes (0.4 mu m). The MIRACO(2)LAS spectra closely matched the shape, location, and depth of spectra of field samples measured by both a field emission spectrometer and a laboratory laser spectrometer. Pure mineral spectra measured by the (bidirectional) laboratory laser spectrometer also closely matched those measured by a conventional laboratory spectrometer measuring directional hemispherical reflectance. These results indicate that future remote thermal infrared systems designed for improved geological mapping and mineral exploration should incorporate both an imager for mapping lithological units and a high spectral resolution profiler for identifying dominant mineral constituents. Recently, a hyperspectral imaging thermal infrared instrument has been developed termed Spatially Enhanced Broadband Array Spectrograph System (SEBASS) [Hackwell and Warren, 1997]. This instrument should allow spectral identification of an entire scene [Gillespie et al., 1997], although the swath width is currently limited to 128 pixels as opposed to the 752 pixels of TIMS after panoramic correction. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. CSIRO, Explorat & Min, N Ryde, NSW 2113, Australia. RP Hook, SJ (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. EM Simon.J.Hook@jpl.nasa.gov; t.cudahy@per.dem.csiro.edu NR 36 TC 6 Z9 6 U1 0 U2 5 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-9313 EI 2169-9356 J9 J GEOPHYS RES-SOL EA JI J. Geophys. Res.-Solid Earth PD AUG 10 PY 1998 VL 103 IS B8 BP 18269 EP 18276 DI 10.1029/98JB01273 PG 8 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 109AU UT WOS:000075299700031 ER PT J AU Garg, A Noebe, RD AF Garg, A Noebe, RD TI Sessile locking and strength enhancement in a solid-solution < 001 > NiAl-0.3Hf single-crystal alloy SO SCRIPTA MATERIALIA LA English DT Article; Proceedings Paper CT Symposium on Defects in Crystals Honoring John Hirth at the TMS Annual Meeting CY FEB 16-19, 1998 CL SAN ANTONIO, TEXAS SP TMS, Electr Magnet & Photon Mat Div, TMS, Struct Mat Div, TMS, Chem & Phy Mat Comm, TMS, Phys Met Comm, TMS, Shaping & Forming Comm, Pacific NW Natl Lab, Washington State Univ, Natl Sci Fdn ID PHASE C1 NASA, Lewis Res Ctr, AYT Corp, Cleveland, OH 44135 USA. RP Garg, A (reprint author), NASA, Lewis Res Ctr, AYT Corp, Cleveland, OH 44135 USA. NR 16 TC 5 Z9 5 U1 0 U2 1 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 1359-6462 J9 SCRIPTA MATER JI Scr. Mater. PD AUG 4 PY 1998 VL 39 IS 4-5 BP 437 EP 443 DI 10.1016/S1359-6462(98)00219-X PG 7 WC Nanoscience & Nanotechnology; Materials Science, Multidisciplinary; Metallurgy & Metallurgical Engineering SC Science & Technology - Other Topics; Materials Science; Metallurgy & Metallurgical Engineering GA 113QQ UT WOS:000075563100010 ER PT J AU Srinivasan, R Savage, MF Daw, MS Noebe, RD Mills, MJ AF Srinivasan, R Savage, MF Daw, MS Noebe, RD Mills, MJ TI Decomposition of a < 111 > and a < 101 > dislocations in hard-oriented NiAl single crystals SO SCRIPTA MATERIALIA LA English DT Article; Proceedings Paper CT Symposium on Defects in Crystals Honoring John Hirth at the TMS Annual Meeting CY FEB 16-19, 1998 CL SAN ANTONIO, TEXAS SP TMS, Electr Magnet & Photon Mat Div, TMS, Struct Mat Div, TMS, Chem & Phy Mat Comm, TMS, Phys Met Comm, TMS, Shaping & Forming Comm, Pacific NW Natl Lab, Washington State Univ, Natl Sci Fdn ID DEFORMATION C1 Ohio State Univ, Dept Mat Sci & Engn, Columbus, OH 43210 USA. Clemson Univ, Dept Phys & Astron, Clemson, SC 29634 USA. NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. RP Srinivasan, R (reprint author), Ohio State Univ, Dept Mat Sci & Engn, 116 W 19Th Ave, Columbus, OH 43210 USA. NR 10 TC 5 Z9 5 U1 1 U2 2 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 1359-6462 J9 SCRIPTA MATER JI Scr. Mater. PD AUG 4 PY 1998 VL 39 IS 4-5 BP 457 EP 464 DI 10.1016/S1359-6462(98)00222-X PG 8 WC Nanoscience & Nanotechnology; Materials Science, Multidisciplinary; Metallurgy & Metallurgical Engineering SC Science & Technology - Other Topics; Materials Science; Metallurgy & Metallurgical Engineering GA 113QQ UT WOS:000075563100013 ER PT J AU Ghaffarian, R AF Ghaffarian, R TI Close the information gap on IC-package reliability SO ELECTRONIC DESIGN LA English DT Editorial Material C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Ghaffarian, R (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU PENTON MEDIA, INC PI CLEVELAND PA 1100 SUPERIOR AVE, CLEVELAND, OH 44114-2543 USA SN 0013-4872 J9 ELECTRON DES JI Electron. Des. PD AUG 3 PY 1998 VL 46 IS 18 BP 71 EP + PG 9 WC Engineering, Electrical & Electronic SC Engineering GA 107FC UT WOS:000075195600014 ER PT J AU King, MK Ross, HD AF King, MK Ross, HD TI Overview of the NASA microgravity combustion program SO AIAA JOURNAL LA English DT Article ID EXTINCTION; DROPLETS; IGNITION AB Recently, three major combustion experiments were carried out in the microgravity environment of the Space Shuttle on the Microgravity Science Laboratory-1 mission. These three efforts entailed a study of laminar soot processes in gaseous diffusion flames, a study of the structure of flame balls at low Lewis numbers, and a study of isolated droplet combustion. Descriptions of these three experiments and their preliminary results appear in the following three papers. The purpose of this paper is to "set the table" for these three papers through a discussion of the importance of microgravity to the study of fundamental combustion phenomena, a presentation of an overview of the current NASA microgravity combustion program, and a brief description (with references to more complete papers) of previous space-based microgravity combustion experiments carried out under the aegis of NASA. C1 NASA, Washington, DC 20546 USA. NASA, Lewis Res Ctr, Micrograv Sci Div, Cleveland, OH 44135 USA. RP King, MK (reprint author), NASA, Code UG,300 E St SW, Washington, DC 20546 USA. NR 79 TC 3 Z9 5 U1 0 U2 0 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0001-1452 J9 AIAA J JI AIAA J. PD AUG PY 1998 VL 36 IS 8 BP 1337 EP 1345 DI 10.2514/2.531 PG 9 WC Engineering, Aerospace SC Engineering GA 105HJ UT WOS:000075066400001 ER PT J AU Urban, DL Yuan, ZG Sunderland, PB Linteris, GT Voss, JE Lin, KC Dai, Z Sun, K Faeth, GM AF Urban, DL Yuan, ZG Sunderland, PB Linteris, GT Voss, JE Lin, KC Dai, Z Sun, K Faeth, GM TI Structure and soot properties of nonbuoyant ethylene/air laminar jet diffusion flames SO AIAA JOURNAL LA English DT Article ID LONG RESIDENCE TIMES; OPTICAL-PROPERTIES; CARBON-MONOXIDE; OVERFIRE SOOT; AIR; PARTICLES; GROWTH; OXIDATION; RATES; MICROGRAVITY AB The structure and soot properties of round, soot-emitting, nonbuoyant, laminar jet diffusion Blames are described, based on long-duration (175-230-s) experiments at microgravity carried out on orbit in the Space Shuttle Columbia. Experimental conditions included ethylene-fueled flames burning in still air at nominal pressures of 50 and 100 kPa and an ambient temperature of 300 K with luminous flame lengths of 49-64 mm. Measurements included luminous flame shapes using color video imaging, soot concentration (volume fraction) distributions using deconvoluted laser extinction imaging, soot temperature distributions using deconvoluted multiline emission imaging, gas temperature distributions at fuel-lean (plume) conditions using thermocouple probes, soot structure distributions using thermophoretic sampling and analysis by transmission electron microscopy, and flame radiation using a radiometer. The present Barnes were larger, and emitted soot more readily, than comparable flames observed during ground-based microgravity experiments due to closer approach to steady conditions resulting from the longer test times and the reduced gravitational disturbances of the space-based experiments. C1 NASA, Lewis Res Ctr, Micrograv Combust Sci Branch, Cleveland, OH 44135 USA. NASA, Lewis Res Ctr, Natl Ctr Micrograv Branch, Cleveland, OH 44135 USA. NASA, Lyndon B Johnson Space Ctr, Astronaut Corps, Houston, TX 77058 USA. Univ Michigan, Dept Aerosp Engn, Ann Arbor, MI 48109 USA. RP Urban, DL (reprint author), NASA, Lewis Res Ctr, Micrograv Combust Sci Branch, Cleveland, OH 44135 USA. OI Ismail, Mostafa/0000-0001-7530-9764; Sunderland, Peter/0000-0002-8262-7100 NR 73 TC 36 Z9 38 U1 0 U2 5 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0001-1452 J9 AIAA J JI AIAA J. PD AUG PY 1998 VL 36 IS 8 BP 1346 EP 1360 DI 10.2514/2.542 PG 15 WC Engineering, Aerospace SC Engineering GA 105HJ UT WOS:000075066400002 ER PT J AU Ronney, PD Wu, MS Pearlman, HG Weiland, KJ AF Ronney, PD Wu, MS Pearlman, HG Weiland, KJ TI Experimental study of flame balls in space: Preliminary results from STS-83 SO AIAA JOURNAL LA English DT Article ID STABILITY AB Results from the Structure Of Flame Balls At Low Lewis-number (SOFBALL) spaceflight experiment conducted on the STS-83/MSL-1 Space Shuttle mission are reported,These are.the first premixed gas combustion experiments to be performed in space. Two of the 15 scheduled tests were successfully completed on this shortened mission. Two different types of mixtures were burned, and both burned much longer than expected based on prior theoretical understanding. From these tests, two new insights were obtained,namely, on the buoyancy-induced drift speed and repulsion of adjacent flame balls due to their mutual interaction. Preliminary results from the STS-94/MSL-1 reflight are also presented and show a remarkable sensitivity of the flame balls to small accelerations resulting from Orbiter attitude control maneuvers. Comparison of experimental results to computational predictions reveals limitations in current models of H-2-O-2 chemistry far very lean mixtures. It is shown how the results of these space experiments may provide an improved understanding of the interactions of the two most important phenomena in combusting materials, namely, chemical reaction and transport processes, in the unequivocally simplest possible configuration. C1 Univ So Calif, Dept Aerosp & Mech Engn, Los Angeles, CA 90089 USA. NASA, Lewis Res Ctr, Micrograv Sci Div, Cleveland, OH 44135 USA. RP Ronney, PD (reprint author), Univ So Calif, Dept Aerosp & Mech Engn, Los Angeles, CA 90089 USA. EM ronney@usc.edu RI Ronney, Paul/B-4007-2009 OI Ronney, Paul/0000-0002-2779-6438 NR 20 TC 49 Z9 51 U1 0 U2 3 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0001-1452 J9 AIAA J JI AIAA J. PD AUG PY 1998 VL 36 IS 8 BP 1361 EP 1368 DI 10.2514/2.553 PG 8 WC Engineering, Aerospace SC Engineering GA 105HJ UT WOS:000075066400003 ER PT J AU Nayagam, V Haggard, JB Colantonio, RO Marchese, AJ Dryer, FL Zhang, BL Williams, FA AF Nayagam, V Haggard, JB Colantonio, RO Marchese, AJ Dryer, FL Zhang, BL Williams, FA TI Microgravity n-heptane droplet combustion in oxygen-helium mixtures at atmospheric pressure SO AIAA JOURNAL LA English DT Article ID ASYMPTOTIC ANALYSIS; CONVECTION; GRAVITY; SOOT AB Results are presented from experiments on the combustion of freely floated n-heptane droplets in helium-oxygen environments conducted in Spacelab onboard the Space Shuttle Columbia during the first launch (STS-83) of the Microgravity Science Laboratory mission in April 1997. During this shortened flight, a total of eight droplets were burned successfully in nominally 300 K oxygen-helium atmospheres having oxygen mole fractions of 25, 30, and 35% at a total pressure of 1 atm.Initial droplet sizes ranged from about 2 to 4 mm.The results demonstrated both radiative and diffusive flame extinction during burning, whereas droplet surface regression followed the d-square law The full. range of possible droplet-burning behaviors was thus observed. The results provide information for testing future theoretical and computational predictions of burning rates, soot and flame characteristics, and extinction conditions. C1 NASA, Lewis Res Ctr, Natl Ctr Micrograv Res, Cleveland, OH 44135 USA. NASA, Lewis Res Ctr, Droplet Combust Expt, Cleveland, OH 44135 USA. Princeton Univ, Dept Mech & Aerosp Engn, Princeton, NJ 08544 USA. Univ Calif San Diego, Dept Appl Mech & Engn Sci, La Jolla, CA 92093 USA. Univ Calif San Diego, Ctr Energy Combust & Res, La Jolla, CA 92093 USA. RP Nayagam, V (reprint author), NASA, Lewis Res Ctr, Natl Ctr Micrograv Res, Cleveland, OH 44135 USA. NR 55 TC 51 Z9 53 U1 2 U2 5 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0001-1452 J9 AIAA J JI AIAA J. PD AUG PY 1998 VL 36 IS 8 BP 1369 EP 1378 DI 10.2514/2.557 PG 10 WC Engineering, Aerospace SC Engineering GA 105HJ UT WOS:000075066400004 ER PT J AU Brentner, KS Farassat, F AF Brentner, KS Farassat, F TI Analytical comparison of the acoustic analogy and Kirchhoff formulation for moving surfaces SO AIAA JOURNAL LA English DT Article ID NOISE AB The Lighthill acoustic analogy, as embodied in the Ffowcs Williams-Hawkings (FW-H) equation, is compared with the Kirchhoff formulation for moving surfaces. A comparison of the two governing equations reveals that the primary advantage of the Kirchhoff formulation(namely, that nonlinear flow effects are included in the surface integration)is also available to the FW-H method if the integration surface used in the FW-H equation is not assumed to be impenetrable. The FW-H equation is analytically superior for aeroacoustics because it is based on the conservation laws of fluid mechanics rather than on the wave equation. Thus, the FW-H equation is valid even if the integration surface is in the nonlinear region. This advantage is demonstrated numerically. With the Kirchhoff approach, substantial errors can result if the integration surface is not positioned in the linear region, and these errors may be hard to identify. Finally, new metrics, based on the Sobolev norm, are introduced that may be used to compare input data for both quadrupole noise calculations and Kirchhoff noise predictions. C1 NASA, Langley Res Ctr, Aerodynam & Acoust Methods Branch, Hampton, VA 23681 USA. NASA, Langley Res Ctr, Aeroacoust Branch, Fluid Mech & Acoust Div, Hampton, VA 23681 USA. RP Brentner, KS (reprint author), NASA, Langley Res Ctr, Aerodynam & Acoust Methods Branch, Hampton, VA 23681 USA. NR 28 TC 131 Z9 156 U1 1 U2 9 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0001-1452 J9 AIAA J JI AIAA J. PD AUG PY 1998 VL 36 IS 8 BP 1379 EP 1386 DI 10.2514/2.558 PG 8 WC Engineering, Aerospace SC Engineering GA 105HJ UT WOS:000075066400005 ER PT J AU Lewellen, DC Lewellen, WS Poole, LR DeCoursey, RJ Hansen, GM Hostetler, CA Kent, GS AF Lewellen, DC Lewellen, WS Poole, LR DeCoursey, RJ Hansen, GM Hostetler, CA Kent, GS TI Large-eddy simulations and lidar measurements of vortex-pair breakup in aircraft wakes SO AIAA JOURNAL LA English DT Article AB Results of large-eddy simulations of an aircraft wake are compared with results from ground-based Lidar measurements made at NASA Langley Research Center during the Subsonic Assessment Near-Field Interaction Flight Experiment held tests. Brief reviews of the design of the field test for obtaining the evolution of wake dispersion behind a Boeing 737 and of the model developed for simulating such wakes are given. Both the measurements and the simulations concentrate on the period from a few seconds to a few minutes after the wake is generated, during which the essentially two-dimensional vortex pair is broken up into a variety of three-dimensional eddies. The model and experiment show similar distinctive breakup eddies induced by the mutual interactions of the vortices, after perturbation by the atmospheric motions. C1 W Virginia Univ, Dept Mech & Aerosp Engn, Morgantown, WV 26506 USA. NASA, Langley Res Ctr, Dept Mech & Aerosp Engn, Hampton, VA 23681 USA. Sci Applicat Int Corp, Hampton, VA 23666 USA. Sci & Technol Corp, Hampton, VA 23666 USA. NASA, Langley Res Ctr, Aerosol Res Branch, Hampton, VA 23681 USA. RP Lewellen, DC (reprint author), W Virginia Univ, Dept Mech & Aerosp Engn, Morgantown, WV 26506 USA. RI Lewellen, David/B-1453-2008 NR 12 TC 10 Z9 10 U1 0 U2 2 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0001-1452 J9 AIAA J JI AIAA J. PD AUG PY 1998 VL 36 IS 8 BP 1439 EP 1445 DI 10.2514/2.535 PG 7 WC Engineering, Aerospace SC Engineering GA 105HJ UT WOS:000075066400013 ER PT J AU Seifert, A Eliahu, S Greenblatt, D Wygnanski, I AF Seifert, A Eliahu, S Greenblatt, D Wygnanski, I TI Use of piezoelectric actuators for airfoil separation control SO AIAA JOURNAL LA English DT Article C1 Tel Aviv Univ, Dept Fluid Mech & Heat Transfer, IL-69978 Tel Aviv, Israel. RP Seifert, A (reprint author), NASA, Langley Res Ctr, MS 170, Hampton, VA 23681 USA. NR 5 TC 66 Z9 67 U1 1 U2 3 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0001-1452 J9 AIAA J JI AIAA J. PD AUG PY 1998 VL 36 IS 8 BP 1535 EP 1537 DI 10.2514/2.549 PG 3 WC Engineering, Aerospace SC Engineering GA 105HJ UT WOS:000075066400026 ER PT J AU Hagstrom, T Goodrich, J AF Hagstrom, T Goodrich, J TI Experiments with approximate radiation boundary conditions for computational aeroacoustics SO APPLIED NUMERICAL MATHEMATICS LA English DT Article DE nonreflecting boundary conditions; aeroacoustics ID EQUATION AB We present a series of numerical experiments on the accuracy of approximate radiation boundary conditions for computational aeroacoustics based on Pade approximants. Our test problem is described by an infinite periodic array of pressure pulses, for which we can independently evaluate the exact solution by numerical quadrature. It is demonstrated that acceptable long time accuracy can be achieved, but only if conditions of high order are employed. As predicted by theory, the order required for a given accuracy is proportional to the time of the simulation. (C) 1998 Elsevier Science B.V. and IMACS. All rights reserved. C1 Univ New Mexico, Dept Math & Stat, Albuquerque, NM 87131 USA. NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. RP Hagstrom, T (reprint author), Univ New Mexico, Dept Math & Stat, Albuquerque, NM 87131 USA. EM hagstrom@math.unm.edu NR 13 TC 6 Z9 6 U1 0 U2 2 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0168-9274 J9 APPL NUMER MATH JI Appl. Numer. Math. PD AUG PY 1998 VL 27 IS 4 BP 385 EP 402 DI 10.1016/S0168-9274(98)00021-X PG 18 WC Mathematics, Applied SC Mathematics GA 107GN UT WOS:000075199100005 ER PT J AU Tsynkov, SV AF Tsynkov, SV TI Numerical solution of problems on unbounded domains. A review SO APPLIED NUMERICAL MATHEMATICS LA English DT Review DE infinite-domain problems; artificial boundary conditions; pseudodifferential equations; difference potentials method; auxiliary problem; boundary equations with projections ID ABSORBING BOUNDARY-CONDITIONS; NAVIER-STOKES EQUATIONS; WAVE-PROPAGATION PROBLEMS; PERFECTLY MATCHED LAYER; LINEARIZED EULER EQUATIONS; TIME-DEPENDENT PROBLEMS; EXTERNAL FLOW PROBLEMS; FINITE-ELEMENT METHOD; ARTIFICIAL BOUNDARY; HYPERBOLIC SYSTEMS AB While numerically solving a problem initially formulated on an unbounded domain, one typically truncates this domain, which necessitates setting the artificial boundary conditions (ABCs) at the newly formed external boundary. The issue of setting the ABCs appears most significant in many areas of scientific computing, for example, in problems originating from acoustics, electrodynamics, solid mechanics, and fluid dynamics. In particular, in computational fluid dynamics (where external problems represent a wide class of important formulations) the proper treatment of external boundaries may have a profound impact on the overall quality and performance of numerical algorithms and interpretation of the results. Most of the currently used techniques for setting the ABCs can basically be classified into two groups. The methods from the first group (global ABCs) usually provide high accuracy and robustness of the numerical procedure but often appear to be fairly cumbersome and (computationally) expensive. The methods from the second group (local ABCs) are, as a rule, algorithmically simple, numerically cheap, and geometrically universal; however, they usually lack accuracy of computations. In this paper we first present an extensive survey and provide a comparative assessment of different existing methods for constructing the ABCs. Then, we describe a new ABCs technique proposed in our recent work and review the corresponding results. This new technique enables one to construct the ABCs that largely combine the advantages relevant to the two aforementioned classes of existing methods. Our approach is based on application of the difference potentials method by Ryaben'kii. This approach allows one to obtain highly accurate ABCs in the form of certain (nonlocal) boundary operator equations. The operators involved are analogous to the pseudodifferential boundary projections first introduced by Calderon and then also studied by Seeley. In spite of the nonlocality, the new boundary conditions are geometrically universal, numerically inexpensive, and easy to implement along with the existing solvers, (C) 1998 Elsevier Science B.V. and IMACS. All rights reserved. C1 NASA, Langley Res Ctr, Hampton, VA 23681 USA. Tel Aviv Univ, Sch Math Sci, IL-69978 Tel Aviv, Israel. RP Tsynkov, SV (reprint author), Tel Aviv Univ, Sch Math Sci, IL-69978 Tel Aviv, Israel. EM tsynkov@math.tau.ac.il NR 253 TC 333 Z9 351 U1 4 U2 52 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0168-9274 EI 1873-5460 J9 APPL NUMER MATH JI Appl. Numer. Math. PD AUG PY 1998 VL 27 IS 4 BP 465 EP 532 DI 10.1016/S0168-9274(98)00025-7 PG 68 WC Mathematics, Applied SC Mathematics GA 107GN UT WOS:000075199100009 ER PT J AU Muscettola, N Nayak, PP Pell, B Williams, BC AF Muscettola, N Nayak, PP Pell, B Williams, BC TI Remote Agent: to boldly go where no AI system has gone before SO ARTIFICIAL INTELLIGENCE LA English DT Article DE autonomous agents; architectures; constraint-based planning; scheduling; execution; reactive systems; diagnosis; recovery; model-based reasoning ID ARCHITECTURE AB Renewed motives for space exploration have inspired NASA to work toward the goal of establishing a virtual presence in space, through heterogeneous fleets of robotic explorers. Information technology, and Artificial Intelligence in particular, will play a central role in this endeavor by endowing these explorers with a form of computational intelligence that we call remote agents. In this paper we describe the Remote Agent, a specific autonomous agent architecture based on the principles of model-based programming, on-board deduction and search, and goal-directed closed-loop commanding, that takes a significant step toward enabling this future. This architecture addresses the unique characteristics of the spacecraft domain that require highly reliable autonomous operations over long periods of time with tight deadlines, resource constraints, and concurrent activity among tightly coupled subsystems. The Remote Agent integrates constraint-based temporal planning and scheduling, robust multi-threaded execution, and model-based mode identification and reconfiguration. The demonstration of the integrated system as an on-board controller for Deep Space One, NASA's first New Millennium mission, is scheduled for a period of a week in mid 1999. The development of the Remote Agent also provided the opportunity to reassess some of Al's conventional wisdom about the challenges of implementing embedded systems, tractable reasoning, and knowledge representation. We discuss these issues, and our often contrary experiences, throughout the paper. (C) 1998 Published by Elsevier Science B.V. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Pell, B (reprint author), NASA, Ames Res Ctr, MS 269-2, Moffett Field, CA 94035 USA. NR 71 TC 203 Z9 215 U1 3 U2 29 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0004-3702 J9 ARTIF INTELL JI Artif. Intell. PD AUG PY 1998 VL 103 IS 1-2 BP 5 EP 47 DI 10.1016/S0004-3702(98)00068-X PG 43 WC Computer Science, Artificial Intelligence SC Computer Science GA 133FU UT WOS:000076676800002 ER PT J AU Landsman, W Bohlin, RC Neff, SG O'Connell, RW Roberts, MS Smith, AM Stecher, TP AF Landsman, W Bohlin, RC Neff, SG O'Connell, RW Roberts, MS Smith, AM Stecher, TP TI The hot stars of old open clusters: M67, NGC 188, and NGC 6791 SO ASTRONOMICAL JOURNAL LA English DT Article DE blue stragglers; open clusters and associations : individual (M67, NGC 188, NGC 6791); ultraviolet emission; white dwarfs ID HORIZONTAL-BRANCH STARS; IRON-GROUP ELEMENTS; ALL-SKY SURVEY; BLUE STRAGGLERS; WHITE-DWARF; CCD PHOTOMETRY; MODEL ATMOSPHERES; PROPER MOTIONS; STELLAR POPULATIONS; ELLIPTIC GALAXIES AB We analyze ultraviolet (similar to 1500 Angstrom) images of the old open clusters M67, NGC 188, and NGC 6791 obtained with the Ultraviolet Imaging Telescope (UIT) during the second flight of the Astro observatory in 1995 March. Twenty stars are detected on the UIT image of M67, including 11 blue stragglers, seven white dwarf candidates, and the yellow giant-white dwarf binary S1040. The ultraviolet photometry of the blue stragglers F90 (S975) and F131 (S1082) suggests that these stars have hot subluminous companions. We present a semiempirical integrated ultraviolet spectrum of M67 and show that the blue stragglers dominate the integrated spectrum at wavelengths shorter than 2600 Angstrom. The number of white dwarfs in M67 is roughly consistent with the number expected from white dwarf cooling models. Eight candidate sdB/sdO stars are detected in NGC 6791, and two are detected in NGC 188. The luminosity range 1.10 < log L/L(.) < 1.27, derived from the ultraviolet photometry of the six sdB candidates, is consistent with theoretical models of metal-rich hot horizontal branch (HB) stars. The fraction of hot HB stars in both NGC 6791 and NGC 188 is about 30%, implying that the integrated spectra of both clusters should show a UV turnup at least as strong as that observed in any elliptical galaxy. C1 NASA, Goddard Space Flight Ctr, STX Corp, Astron & Solar Phys Lab, Greenbelt, MD 20771 USA. Space Telescope Sci Inst, Baltimore, MD 21218 USA. Univ Virginia, Dept Astron, Charlottesville, VA 22903 USA. Natl Radio Astron Observ, Charlottesville, VA 22903 USA. RP Landsman, W (reprint author), NASA, Goddard Space Flight Ctr, STX Corp, Astron & Solar Phys Lab, Code 681, Greenbelt, MD 20771 USA. NR 86 TC 51 Z9 51 U1 0 U2 1 PU IOP PUBLISHING LTD PI BRISTOL PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND SN 0004-6256 J9 ASTRON J JI Astron. J. PD AUG PY 1998 VL 116 IS 2 BP 789 EP 800 DI 10.1086/300449 PG 12 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 115CW UT WOS:000075646800017 ER PT J AU Brandt, JC Heap, SR Beaver, EA Boggess, A Carpenter, KG Ebbets, DC Hutchings, JB Jura, M Leckrone, DS Linsky, JL Maran, SP Savage, BD Smith, AM Trafton, LM Walter, FM Weymann, RJ Snow, M Ake, TB Hogen, RH AF Brandt, JC Heap, SR Beaver, EA Boggess, A Carpenter, KG Ebbets, DC Hutchings, JB Jura, M Leckrone, DS Linsky, JL Maran, SP Savage, BD Smith, AM Trafton, LM Walter, FM Weymann, RJ Snow, M Ake, TB Hogen, RH TI An ultraviolet spectral atlas of 10 lacertae obtained with the Goddard High Resolution Spectrograph on the Hubble Space Telescope SO ASTRONOMICAL JOURNAL LA English DT Article DE atlases; stars : early-type; stars : individual (10 Lacertae) ID INTERSTELLAR ABSORPTION-LINES; O-STARS; MILKY-WAY; B-STARS; CALIBRATION; VELOCITIES AB Observations of the narrow-lined O-type star 10 Lacertae taken with the Goddard High Resolution Spectrograph in 1992 November are presented. The spectra cover the wavelength range 1181-1777 Angstrom with a resolution of 15 km s(-1) and signal-to-noise ratio greater than 100:1. Absorption lines arising in the interstellar medium, the photosphere, and the stellar wind are identified and discussed. C1 Univ Colorado, Atmospher & Space Phys Lab, Boulder, CO 80309 USA. NASA, Astron & Solar Phys Lab, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Calif San Diego, Ctr Astrophys & Space Sci, La Jolla, CA 92093 USA. Ball Aerosp & Technol Corp, Boulder, CO 80306 USA. Dominion Astrophys Observ, Victoria, BC V8X 4M6, Canada. Univ Calif Los Angeles, Dept Phys & Astron, Los Angeles, CA 90095 USA. Joint Inst Lab Astrophys, Boulder, CO 80309 USA. Natl Inst Stand & Technol, Gaithersburg, MD USA. NASA, Space Sci Directorate, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Wisconsin, Dept Astron, Madison, WI 53706 USA. Univ Texas, Mcdonald Observ, Austin, TX 78712 USA. Univ Texas, Dept Astron, Austin, TX 78712 USA. SUNY Stony Brook, Dept Phys & Astron, Stony Brook, NY 11794 USA. Carnegie Inst Washington Observ, Pasadena, CA 91101 USA. Univ Colorado, Atmospher & Space Phys Lab, Boulder, CO 80309 USA. NASA, Sci Program, Comp Sci Corp, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Brandt, JC (reprint author), Univ Colorado, Atmospher & Space Phys Lab, Campus Box 392, Boulder, CO 80309 USA. RI heap, sara/E-2237-2012; Carpenter, Kenneth/D-4740-2012; OI SNOW, MARTIN/0000-0001-9106-1332 NR 48 TC 12 Z9 12 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5801 S ELLIS AVENUE, CHICAGO, IL 60637 USA SN 0004-6256 J9 ASTRON J JI Astron. J. PD AUG PY 1998 VL 116 IS 2 BP 941 EP 971 DI 10.1086/300446 PG 31 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 115CW UT WOS:000075646800034 ER PT J AU Manning, C Spinrad, H Brown, ME Newburn, RL Schlegel, D AF Manning, C Spinrad, H Brown, ME Newburn, RL Schlegel, D TI The photometric growth of two Shoemaker-Levy 9 impact sites on Jupiter SO ASTRONOMICAL JOURNAL LA English DT Article DE comets : individual (Shoemaker-Levy 9); planets and satellites : individual (Jupiter) ID COMET SHOEMAKER-LEVY-9; STRATOSPHERE; DEBRIS; NH3 AB We present our findings on the photometric variability of the impact spots of comet Shoemaker-Levy 9 (SL 9) in the Jovian atmosphere. Extensive imaging and differential photometry of impact spots in the methane band (8950/90 Angstrom) have enabled us to conservatively extract their photometric contribution from that of Jupiter. In this methane band, the SL 9 spots appear brighter than the surrounding Jovian surface because they he above the main concentrations of methane that overlie the cloud tops. Our observations of two well-observed and isolated spots, H and Q1, indicate that spots experience a photometric growth that initially approximates a power law in time of index 0.3 and then appears to level off in the case of the H spot. We consider two explanations for the brightening of spots: (1) the dispersal of high optical depth core regions and (2) the coagulation of dust from the atomized or fragmented cometary ejecta. The former has been rejected because one spot, H, which was disrupted by a cyclonic storm, exhibited no discontinuity in its rate of photometric growth that would correspond to the disruption. We adopt the second as a working hypothesis because the growth of grains is consistent with our observations and has been cited as the cause for the observed changes in the integrated optical depth in the near-IR and the UV. We propose a simple model in which sites for grain nucleation are provided by the chemical interaction of cometary material and the shocked Jovian atmosphere and in which grain growth is restrained by the diminishing availability of raw materials for grain formation on timescales inversely proportional to the original aerosol density. This model, applied to a volumetric power-law distribution of aerosols, can produce an integrated scattering amplitude growth rate closely resembling our observations. C1 Univ Calif Berkeley, Dept Astron, Berkeley, CA 94720 USA. CALTECH, Div Geol & Planetary Sci, Pasadena, CA 91125 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ Durham, Dept Phys, Durham DH1 3LE, England. RP Manning, C (reprint author), Univ Calif Berkeley, Dept Astron, 601 Campbell Hall, Berkeley, CA 94720 USA. NR 9 TC 0 Z9 0 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5801 S ELLIS AVENUE, CHICAGO, IL 60637 USA SN 0004-6256 J9 ASTRON J JI Astron. J. PD AUG PY 1998 VL 116 IS 2 BP 972 EP 980 DI 10.1086/300451 PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 115CW UT WOS:000075646800035 ER PT J AU Dyck, HM van Belle, GT Thompson, RR AF Dyck, HM van Belle, GT Thompson, RR TI Radii and effective temperatures for K and M giants and supergiants. II. SO ASTRONOMICAL JOURNAL LA English DT Article DE stars : fundamental parameters; stars : late-type ID ANGULAR DIAMETERS; MICHELSON INTERFEROMETRY; CATALOG; COOLER; STARS AB We present new interferometric observations for 74 luminous red stars, made in the near-infrared. We show that our 2.2 mu m uniform-disk diameters agree with other near-infrared diameter determinations (lunar occultations and interferometers) for 22 stars measured in common with ours. From our new data, we derive effective temperatures that are compared with our previous work and with comparable observations made by lunar occultations at Kitt Peak. The combined data set yields 91 luminosity class II, II-III, and III stars that have well-determined spectral types spanning the range from about K0 to about M8. There are 83 stars in the sample that define an approximately linear relationship between spectral type and effective temperature for giants, with a dispersion of 192 K at each spectral type. Eight of the stars have temperatures that are roughly 750 K too low for their spectral types. These stars are not known to be at the high-luminosity end of the range of stars observed and are not recognized as binary stars. At present, we have no explanation for their low effective temperatures. We also show that Hipparcos parallaxes, combined with our angular diameters, yield linear radii precise enough to see differences in the average radius between luminosity class II and luminosity class III stars. C1 USN Observ, Dept Astrometry, Navy Prototype Opt Interferometer, Flagstaff, AZ 86001 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ Wyoming, Dept Phys & Astron, Laramie, WY 82071 USA. RP Dyck, HM (reprint author), USN Observ, Dept Astrometry, Navy Prototype Opt Interferometer, Rural Route 14,Box 447, Flagstaff, AZ 86001 USA. EM meldyck@sextans.lowell.edu; gerard@huey.jpl.nasa.gov; thompson@sparky.uwyo.edu NR 21 TC 93 Z9 93 U1 0 U2 3 PU UNIV CHICAGO PRESS PI CHICAGO PA 5801 S ELLIS AVENUE, CHICAGO, IL 60637 USA SN 0004-6256 J9 ASTRON J JI Astron. J. PD AUG PY 1998 VL 116 IS 2 BP 981 EP 986 DI 10.1086/300453 PG 6 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 115CW UT WOS:000075646800036 ER PT J AU Stickel, M Bogun, S Lemke, D Klaas, U Toth, LV Herbstmeier, U Richter, G Assendorp, R Laureijs, R Kessler, MF Burgdorf, M Beichman, CA Rowan-Robinson, M Efstathiou, A AF Stickel, M Bogun, S Lemke, D Klaas, U Toth, LV Herbstmeier, U Richter, G Assendorp, R Laureijs, R Kessler, MF Burgdorf, M Beichman, CA Rowan-Robinson, M Efstathiou, A TI The ISOPHOT far-infrared serendipity north ecliptic pole minisurvey SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE surveys; infrared : galaxies; infrared : general AB The ISOPHOT Serendipity Survey fills the otherwise unused slew time between ISO's fine pointings with measurements in an unexplored wavelength regime near 200 mu m. In order to test point source extraction software, the completeness of the detected objects as well as the astrophysical content we investigate a 1000 square degrees field near the North ecliptic pole, dubbed ISOPHOT Serendipity Minisurvey field. A total of 21 IRAS point sources were detected on the Serendipity slews crossing the field. 19 of these objects are galaxies, one is a planetary nebula and one is an empty field without a bright optical counterpart. The detection completeness is better than 90% for IRAS sources brighter than 2 Jy at 100 mu m and better than 80% for sources brighter than 1.5 Jy. The source detection frequency is about 1 per 40 degrees slew length, in agreement with previous estimations based on galaxy number counts. After the end of the ISO mission, about 4000 point sources are expected to be found in the Serendipity slews. C1 Max Planck Inst Astron, D-69117 Heidelberg, Germany. ESA, Dept Space Sci, Div Astrophys, ISO Sci Operat Ctr, E-28080 Madrid, Spain. Eotvos Lorand Univ, Dept Astron, H-1083 Budapest, Hungary. Astophys Inst Potsdam, D-14482 Potsdam, Germany. CALTECH, Infrared Proc & Anal Ctr, JPL, Pasadena, CA 91125 USA. Univ London Imperial Coll Sci Technol & Med, Blackett Lab, London SW7 2BZ, England. RP Stickel, M (reprint author), Max Planck Inst Astron, Konigstuhl 17, D-69117 Heidelberg, Germany. EM sticker@mpia-hd.mpg.de RI Toth, L. Viktor/C-8667-2017 OI Toth, L. Viktor/0000-0002-5310-4212 NR 6 TC 50 Z9 50 U1 0 U2 0 PU EDP SCIENCES S A PI LES ULIS CEDEX A PA 17, AVE DU HOGGAR, PA COURTABOEUF, BP 112, F-91944 LES ULIS CEDEX A, FRANCE SN 0004-6361 J9 ASTRON ASTROPHYS JI Astron. Astrophys. PD AUG 1 PY 1998 VL 336 IS 1 BP 116 EP 122 PG 7 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 110RP UT WOS:000075394400016 ER PT J AU Baykal, A Swank, JH Strohmayer, T Stark, MJ AF Baykal, A Swank, JH Strohmayer, T Stark, MJ TI Spin-down rate of 1E 2259+586 from RXTE observation SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE accretion, accretion disks; pulsars : individual : 1E 2259+586; X-rays : stars ID X-RAY PULSARS; EXTRAORDINARY; 1E-2259+586; ACCRETION; TORQUE AB We present new X-ray observations of the X-ray pulsar 1E 2259+586, obtained during March 1997, with the Rossi X-Ray Timing Explorer (RXTE). We have measured the pulse frequency derivative (nu) over dot = (-1.08 +/- 0.04) x 10(-14) Hz s(-1) from pulse arrival times obtained in a sequence of 5 observations spread over one month. This (nu) over dot is consistent with the long term spin-down trend. We also found that the observed X-ray luminosity is consistent with that measured at quiescent X-ray flux levels by previous missions. Our observations imply that 1E 2259 +/- 586 was spinning down steadily without exhibiting any stochastic torque noise fluctuations during the month covered by our observations. C1 Middle E Tech Univ, Dept Phys, TR-06531 Ankara, Turkey. NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. RP Baykal, A (reprint author), Middle E Tech Univ, Dept Phys, TR-06531 Ankara, Turkey. RI Swank, Jean/F-2693-2012 NR 22 TC 18 Z9 18 U1 0 U2 2 PU EDP SCIENCES S A PI LES ULIS CEDEX A PA 17, AVE DU HOGGAR, PA COURTABOEUF, BP 112, F-91944 LES ULIS CEDEX A, FRANCE SN 0004-6361 J9 ASTRON ASTROPHYS JI Astron. Astrophys. PD AUG 1 PY 1998 VL 336 IS 1 BP 173 EP 176 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 110RP UT WOS:000075394400021 ER PT J AU Boogert, ACA Helmich, EP van Dishoeck, EF Schutte, WA AF Boogert, ACA Helmich, EP van Dishoeck, EF Schutte, WA TI The gas/solid methane abundance ratio toward deeply embedded protostars SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE ISM : dust, extinction; molecules; abundances; infrared : ISM : lines and bands; stars : individual : NGC 7538 : IRS9, W 33A ID MOLECULAR CLOUDS; ICE ANALOGS; YOUNG STARS; PHASE CO; ABSORPTION; GAS; CHEMISTRY; REGION; LINE; CH4 AB We present the detection of re-vibrational absorption lines of the deformation mode of gaseous CH4 toward the massive protostars W 33A, and NGC 7538 : IRS9, using the SWS spectrometer an board of the Infrared Space Observatory. The observed lines indicate that the CH4 gas is warm (T similar to N 90 K), and has a low abundance (similar to 4 10(-7)). The CH4 ice in these Lines of sight is embedded in a polar matrix (Boogert et al. 1996), and the gas/solid state abundance ratio is low (similar to 0.5). We discuss models for the formation of interstellar CH4. The observations impose strong limitations on time dependent gas phase models, e.g. a low initial CO/C ratio would be required, the CH4 must have been formed and subsequently condensed on the grains within a narrow time window, and an additional mechanism would be necessary to form polar ice mantles. More likely, interstellar CH4 is formed through grain surface reactions at a high CO/C ratio, which explains the low observed CH4 abundance (similar to 10(-6)) the presence of CH4 in a polar ice, the low gas/solid ratio, and the absence of a strong cold CH4 gas component. The observed warm CH4 gas probably has sublimated from the grains in the 'hot core' region surrounding the protostar. C1 Kapteyn Astron Inst, NL-9700 AV Groningen, Netherlands. Leiden Observ, NL-2300 RA Leiden, Netherlands. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Rensselaer Polytech Inst, Dept Phys Appl Phys & Astron, Troy, NY 12180 USA. SRON, NL-9700 AV Groningen, Netherlands. RP Boogert, ACA (reprint author), Kapteyn Astron Inst, POB 800, NL-9700 AV Groningen, Netherlands. EM boog@astro.rug.nl NR 31 TC 53 Z9 53 U1 0 U2 3 PU EDP SCIENCES S A PI LES ULIS CEDEX A PA 17, AVE DU HOGGAR, PA COURTABOEUF, BP 112, F-91944 LES ULIS CEDEX A, FRANCE SN 0004-6361 J9 ASTRON ASTROPHYS JI Astron. Astrophys. PD AUG 1 PY 1998 VL 336 IS 1 BP 352 EP 358 PG 7 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 110RP UT WOS:000075394400039 ER PT J AU Boden, AF Shao, M Van Buren, D AF Boden, AF Shao, M Van Buren, D TI Astrometric observation of MACHO gravitational microlensing SO ASTROPHYSICAL JOURNAL LA English DT Article DE astrometry; dark matter; gravitational lensing ID EVENTS; PARALLAXES; STARS; INTERFEROMETER; TELESCOPE; PLANETS; MASS AB Following previous suggestions of other researchers, this paper discusses the prospects for astrometric observation of MACHO gravitational microlensing events. We derive the expected astrometric observables for a simple microlensing event with either a dark or self-luminous lens and demonstrate that accurate astrometry can determine the lens mass, distance, and proper motion in a very general fashion. In particular, we argue that in limited circumstances ground-based, narrow-angle differential astrometric techniques are sufficient to measure the lens mass directly and other lens properties (distance, transverse motion) by applying an independent model for the source distance and motion. We investigate the sensitivity of differential astrometry in determining lens parameters by Monte Carlo methods and derive a quasi-empirical relationship between astrometric accuracy and mass uncertainty. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Boden, AF (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 41 TC 80 Z9 81 U1 0 U2 2 PU IOP PUBLISHING LTD PI BRISTOL PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND SN 0004-637X EI 1538-4357 J9 ASTROPHYS J JI Astrophys. J. PD AUG 1 PY 1998 VL 502 IS 2 BP 538 EP 549 DI 10.1086/305913 PN 1 PG 12 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 152KF UT WOS:000077776000004 ER PT J AU Sambruna, RM Mushotzky, RF AF Sambruna, RM Mushotzky, RF TI X-ray absorption in the BL Lacertae object PKS 0548-322 SO ASTROPHYSICAL JOURNAL LA English DT Article DE BL Lacertae objects : individual (PKS 0548-322); X-rays : galaxies ID EXTREME-ULTRAVIOLET SPECTRUM; ACTIVE GALACTIC NUCLEI; ROSAT OBSERVATIONS; GALAXIES; BLAZARS; PKS-0548-322; QUASARS; HOT; SKY; GAS AB We report on a high signal-to-noise ASCA spectrum of the nearby (z = 0.069) BL Lacertae object PKS 0548-322, obtained during the performance verification phase of the instrument. Our principal result is the detection of discrete absorption at similar to 0.6 keV. The ASCA flux of the source, F2-10 (kev) similar to 2.8 x 10(-11) ergs cm(-2) s(-1), corresponds to an average intensity state with respect to previous X-ray observations. The ASCA spectrum is well fitted by a convex broken power law plus Galactic column density plus an absorption feature, modeled with either an edge at an observed energy E similar to 0.66 keV and with optical depth tau similar to 0.3 or with a line (notch) at an observed energy E similar to 0.82 keV, width Delta E = 0.1 keV (fixed), and covering fraction f(c) similar to 0.1. The feature is at energies higher than in previous observations, when PKS 0548-322 was slightly brighter. The observed properties of the feature are consistent with absorption by ionized gas with column density N-H(gas) approximate to 10(21) cm-2 and a low ionization parameter (U-x approximate to 0.007), strengthening the conclusion that ionized circumnuclear gas is common in BL Lacs. A very subtle curvature is measured for the underlying ASCA continuum, with steepening Delta Gamma similar to 0.2 above 1.7 keV. However, there is no need for a curved continuum once a detailed photoionization model is fitted to the ASCA data. There is no significant contribution to the 0.6-10 keV ASCA data of PKS 0548 - 322 by the associated optical cluster of galaxies; the upper limit to the intergalactic gas luminosity is L-2-10 kev(IGM) similar to 4 x 10(43) ergs s(-1), about 15% of the BL Lac luminosity. C1 NASA, Goddard Space Flight Ctr, NRC, Greenbelt, MD 20771 USA. Penn State Univ, Dept Astron & Astrophys, University Pk, PA 16802 USA. RP Sambruna, RM (reprint author), NASA, Goddard Space Flight Ctr, NRC, Code 662, Greenbelt, MD 20771 USA. EM rms@latte.astro.psu.edu NR 48 TC 12 Z9 12 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD AUG 1 PY 1998 VL 502 IS 2 BP 630 EP 639 DI 10.1086/305922 PN 1 PG 10 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 152KF UT WOS:000077776000010 ER PT J AU Deeter, JE Scott, DM Boynton, PE Miyamoto, S Kitamoto, S Takahama, S Nagase, F AF Deeter, JE Scott, DM Boynton, PE Miyamoto, S Kitamoto, S Takahama, S Nagase, F TI The 35 day evolution of the Hercules X-1 pulse profile: Ginga observations and their implications SO ASTROPHYSICAL JOURNAL LA English DT Article DE binaries : close; pulsars : general; stars : individual (Hercules X-1); stars : neutron; X-rays : stars ID X-RAY PULSARS; LOW STATE; DAY CYCLE; ORBITAL PERIOD; CENTAURUS X-3; PRE-ECLIPSE; LMC X-4; ACCRETION; VARIABILITY; PRECESSION AB We observed Her X-1 using the Ginga observatory in the spring of 1989 with the primary intention of studying the evolution of the pulse profile through the course of the 35 day X-ray HIGH-LOW cycle in that source. These observations cover 16 separate days in two MAIN HIGH states and in the intervening SHORT HIGH state. We have augmented these data with four additional Ginga observations of Her X-1 taken for other purposes but useful for our study. We present light curves in the 1-37 keV energy band for the seven high states covered by these data together with a representative sample of pulse profiles. The signal-to-noise ratio for these profiles is generally excellent, and collectively they provide a sound base for studying the evolution of the pulse profile. Of particular utility is the 1989 May observation, which for the first time provides extensive coverage of a short high state at high photon counting rate. By combining pulse phase and frequency information from all three high state observations in 1989, we are able to determine the phase alignment of main high and short high pulse profiles with high confidence. We identify components in the Her X-1 pulse profile by their distinctive spectral signatures, and we establish the existence of a definite, repetitive pattern of pulse shape variations tied to the 35 day high-low cycle. Comparing pre-Ginga observations of pulse profiles superposed according to the 35 day phase indicates that this pattern has persisted over the past two decades. Moreover, the pulse phase alignment of the 1989 data allows the identification of components common to the main high and short high pulse profiles. One of the key elements of this pattern is the rapid change in pulse profile that occurs roughly 7 days into each main high state. In examining possible mechanisms for this interval of accelerated evolution, we are led to consider a class of models that involve dynamical changes in accretion flow geometry arising from neutron star obliquity. These models, however, suggest asymmetries in the X-ray illumination of the companion star that may conflict with extensive optical observations of the Her X-1 system. By contrast, kinematic changes in the geometrical aspect of obscuring matter flows near or within the magnetosphere that are tied to accretion disk precession provide a mechanism that may be consistent with observations. C1 Univ Washington, Dept Astron, Seattle, WA 98195 USA. NASA, George C Marshall Space Flight Ctr, Space Sci Lab, Huntsville, AL 35812 USA. Univ Space Res Assoc, Washington, DC USA. Univ Washington, Dept Phys, Seattle, WA 98195 USA. Osaka Univ Hlth & Sports Sci, Kumatori, Osaka 59004, Japan. Osaka Univ, Grad Sch Sci, Dept Earth & Space Sci, Toyonaka, Osaka 560, Japan. Inst Space & Astronaut Sci, Sagamihara, Kanagawa 229, Japan. RP Deeter, JE (reprint author), Univ Washington, Dept Astron, Box 351580, Seattle, WA 98195 USA. NR 73 TC 44 Z9 44 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD AUG 1 PY 1998 VL 502 IS 2 BP 802 EP 823 DI 10.1086/305910 PN 1 PG 22 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 152KF UT WOS:000077776000023 ER PT J AU Hanner, MS Brooke, TY Tokunaga, AT AF Hanner, MS Brooke, TY Tokunaga, AT TI 8-13 micron spectroscopy of young stars SO ASTROPHYSICAL JOURNAL LA English DT Article DE infrared : stars; stars : pre-main-sequence ID T-TAURI STARS; POLYCYCLIC AROMATIC-HYDROCARBONS; HALE-BOPP C/1995-O1; EMISSION FEATURES; CIRCUMSTELLAR DISKS; HERBIG-AE/BE; SPECTRA; SILICATES; CLOUD; SPECTROPHOTOMETRY AB We present 8-13 mu m spectra of 23 young stars acquired with the UKIRT CGS3 spectrometer, including T Tauri, Herbig Ae/Be, and FU Orionis stars. Silicate emission and absorption features can generally be matched with the Trapezium emissivity, by employing simple models to account for optical depth effects. Two Herbig Ae/Be objects, LkH alpha 208 and LkH alpha 198, have emission features that peak at 9.3 mu m These spectra can be adequately fitted with the Trapezium emissivity and a variable optical depth model, plus a hydrocarbon component. A different emissivity peaking at shorter wavelength is not ruled out; however, it is not a necessary conclusion from the observed spectra. Two absorption sources appear to require a narrower emissivity profile. The 11.2 mu m peak of crystalline olivine observed in comets is not seen in our YSO spectra, to a limit of 5% for emission sources and 15% for absorption profiles. Aromatic hydrocarbon emission is frequently present in our sample of Herbig Ae/Be stars and is also seen in the T Tauri stars SU Aurigae (G2 III) and DK Tau (K7). Five objects were observed at higher spectral resolution (R similar to 200) to search for spectral structure in the 11 mu m region; the aromatic hydrocarbon band at 11.2 mu m is resolved into two components at 11.22 and 11.06 mu m in LkH alpha 198 and SU Aur. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ Hawaii, Inst Astron, Honolulu, HI 96822 USA. RP Hanner, MS (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr,MS 183-501, Pasadena, CA 91109 USA. EM msh@scn1.jpl.nasa.gov; tyb@scn2.jpl.nasa.gov; tokunaga@galileo.ifa.hawaii.edu NR 35 TC 54 Z9 54 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD AUG 1 PY 1998 VL 502 IS 2 BP 871 EP 882 DI 10.1086/305939 PN 1 PG 12 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 152KF UT WOS:000077776000028 ER PT J AU Wolff, CL AF Wolff, CL TI Linear r-mode oscillations in a differentially rotating star SO ASTROPHYSICAL JOURNAL LA English DT Article DE stars : oscillations; stars : rotation; Sun : oscillations; Sun : rotation ID SOLAR; CONVECTION; SUN AB Differential rotation of a stellar envelope lifts the degeneracy of r-mode rotation rates and can prohibit some modes. It also reduces the physical distinction between the two branches of r-modes: slow (retrograde) and fast (geostrophic). One mode in each branch is dominated by a given spherical harmonic (l, m), and, for increasing rotational shear in the star, their characteristics approach each other until both modes simultaneously cease to exist. Only about half of the 60 r-modes with l less than or equal to 5 and a given radial harmonic can survive as global, linear modes in the Sun. Each of these has at least 70%, and typically 90%, of its energy in a single toroidal component of motion. Among solar survivors are all modes where \m\ = l>1. All results apply to linear, adiabatic oscillations of a spherical fluid shell exhibiting steady, axisymmetric rotation, Omega(r, theta). Since terms similar to Omega(2) are small in the Sun, spheroidal motions are neglected. A generalization of classical perturbation theory was used to treat "perturbations" of large size and to avoid the need for special treatment of oscillation frequencies that are zero or degenerate. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Wolff, CL (reprint author), NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. EM wolff@gsfc.nasa.gov NR 29 TC 14 Z9 14 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD AUG 1 PY 1998 VL 502 IS 2 BP 961 EP 967 DI 10.1086/305934 PN 1 PG 7 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 152KF UT WOS:000077776000036 ER PT J AU Judge, PG Hansteen, V Wikstol, O Wilhelm, K Schuhle, U Moran, T AF Judge, PG Hansteen, V Wikstol, O Wilhelm, K Schuhle, U Moran, T TI Evidence in support of the "nanoflare" picture of coronal heating from SUMER data SO ASTROPHYSICAL JOURNAL LA English DT Article DE Sun : chromosphere; Sun : corona; Sun : flares; Sun : transition region ID UNRESOLVED FINE-STRUCTURES; SOLAR TRANSITION REGION; RADIOMETRIC CALIBRATION; TEMPERATURE REGION; TELESCOPE; SOHO; SPECTROMETER; ATMOSPHERE; SPECTRUM; CHROMOSPHERE AB We study high signal-to-noise profiles of O Iv emission lines obtained using the SUMER instrument on SOHO. Data for the quiet Sun obtained close to the disk center and at the solar limb were acquired. After careful data processing in which disk data were analyzed differentially against limb data, we find a systematic correlation between a density-sensitive emission-line ratio and Doppler shift across the same emission-line profiles. While unidentified blended lines cannot be completely discounted, the data suggest that the effects of such blends are small. Based on theoretical results in an earlier paper, we argue that if wave motions are responsible for the observed behavior, then the data reveal evidence for compressive waves propagating downward from the corona to the chromosphere. This analysis naturally lends support to the dominance of the "nanoflare" mechanism for coronal heating over other theories that invoke upward wave propagation, but other mechanisms capable of generating downward-propagating waves cannot be discounted. If, instead, steady flows are the cause of the observed behavior, such as return flows from spicules, then they must be such that the density is higher in the downflowing plasma. While these particular data do not allow us to discriminate between waves or steady flows, additional data from SOHO should be able to address this problem. This work required and achieved very accurate wavelength calibrations (better than 1/5 of a pixel on the detectors), taking SUMER close to its observational capabilities. We therefore present the elements of the analysis and calibration of SUMER data that may be of interest to other users. C1 Natl Ctr Atmospher Res, High Altitude Observ, Boulder, CO 80307 USA. Univ Oslo, Inst Theoret Astrophys, N-0315 Oslo, Norway. Max Planck Inst Aeron, D-37191 Katlenburg Lindau, Germany. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Judge, PG (reprint author), Natl Ctr Atmospher Res, High Altitude Observ, POB 3000, Boulder, CO 80307 USA. NR 35 TC 35 Z9 35 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD AUG 1 PY 1998 VL 502 IS 2 BP 981 EP 996 DI 10.1086/305915 PN 1 PG 16 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 152KF UT WOS:000077776000038 ER PT J AU Groot, PJ Galama, TJ Vreeswijk, PM Wijers, RAMJ Pian, E Palazzi, E van Paradijs, J Kouveliotou, C in't Zand, JJM Heise, J Robinson, C Tanvir, N Lidman, C Tinney, C Keane, M Briggs, M Hurley, K Gonzalez, JF Hall, P Smith, MG Covarrubias, R Jonker, PG Casares, J Masetti, N Frontera, F Feroci, M Piro, L Costa, E Smith, R Jones, B Windridge, D Bland-Hawthorn, J Veilleux, S Garcia, M Brown, WR Stanek, KZ Castro-Tirado, AJ Gorosabel, J Greiner, J Jager, K Bohm, A Fricke, KJ AF Groot, PJ Galama, TJ Vreeswijk, PM Wijers, RAMJ Pian, E Palazzi, E van Paradijs, J Kouveliotou, C in't Zand, JJM Heise, J Robinson, C Tanvir, N Lidman, C Tinney, C Keane, M Briggs, M Hurley, K Gonzalez, JF Hall, P Smith, MG Covarrubias, R Jonker, PG Casares, J Masetti, N Frontera, F Feroci, M Piro, L Costa, E Smith, R Jones, B Windridge, D Bland-Hawthorn, J Veilleux, S Garcia, M Brown, WR Stanek, KZ Castro-Tirado, AJ Gorosabel, J Greiner, J Jager, K Bohm, A Fricke, KJ TI The rapid decay of the optical emission from GRB 980326 and its possible implications SO ASTROPHYSICAL JOURNAL LA English DT Article DE gamma rays : bursts; gamma rays : observations; radiation mechanisms : nonthermal ID GAMMA-RAY BURST; ASTRONOMY SATELLITE; ACCELERATION AB We report the discovery of the optical counterpart to GRB 980326. Its rapid optical decay can be characterized by a power law with exponent -2.10 +/- 0.13 and a constant underlying source at R-c = 25.5 +/- 0.5. Its optical colors 2.1 days after the burst imply a spectral slope of -0.66 +/- 0.70. The gamma-ray spectrum as observed with BATSE shows that it is among the 4% softest bursts ever recorded. We argue that the rapid optical decay may be a reason for the nondetection of some low-energy afterglows of GRBs. C1 Univ Amsterdam, Astron Inst Anton Pannekoek, NL-1098 SJ Amsterdam, Netherlands. Natl Inst Nucl & High Energy Phys, Ctr High Energy Astrophys, NL-1098 SJ Amsterdam, Netherlands. Univ Cambridge, Inst Astron, Cambridge CB3 0HA, England. CNR, I-40129 Bologna, Italy. Univ Alabama, Dept Phys, Huntsville, AL 35899 USA. Univ Space Res Assoc, Washington, DC USA. NASA, MSFC, Huntsville, AL 35812 USA. SRON, Utrecht, Netherlands. European So Observ, Santiago 19, Chile. Anglo Australian Observ, Epping, NSW 2121, Australia. Cerro Tololo Interamer Observ, La Serena, Chile. Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA. Univ Toronto, Dept Astron, Toronto, ON M5S 3H8, Canada. Inst Astrofis Canarias, Tenerife, Spain. CNR, Ist Astrofis Spaziale, I-00133 Rome, Italy. Univ Wales, Cardiff CF1 3NS, S Glam, Wales. Univ Bristol, Bristol, Avon, England. Univ Maryland, Dept Astron, College Pk, MD 20742 USA. Ctr Astrophys, Cambridge, MA 02138 USA. INTA, LAEFF, E-28080 Madrid, Spain. CSIC, Inst Astrofis Andalucia, E-18080 Granada, Spain. Astrophys Inst Potsdam, D-14482 Potsdam, Germany. Univ Sternwarte Gottingen, D-37083 Gottingen, Germany. RP Groot, PJ (reprint author), Univ Amsterdam, Astron Inst Anton Pannekoek, Kruislaan 403, NL-1098 SJ Amsterdam, Netherlands. RI Gonzalez, Jean-Francois/B-7189-2008; Galama, Titus/D-1429-2014; PIRO, LUIGI/E-4954-2013; Palazzi, Eliana/N-4746-2015; Groot, Paul/K-4391-2016 OI Gonzalez, Jean-Francois/0000-0001-9423-6062; Galama, Titus/0000-0002-1036-396X; PIRO, LUIGI/0000-0003-4159-3984; Wijers, Ralph/0000-0002-3101-1808; Palazzi, Eliana/0000-0002-8691-7666; Jones, Bryn/0000-0002-4679-5625; Masetti, Nicola/0000-0001-9487-7740; Groot, Paul/0000-0002-4488-726X NR 45 TC 66 Z9 68 U1 0 U2 1 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD AUG 1 PY 1998 VL 502 IS 2 BP L123 EP L127 DI 10.1086/311509 PN 2 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 152KH UT WOS:000077776200007 ER PT J AU Weaver, KA Yaqoob, T AF Weaver, KA Yaqoob, T TI On the evidence for extreme gravity effects in MCG -6-30-15 SO ASTROPHYSICAL JOURNAL LA English DT Article DE black hole physics; galaxies : active; galaxies : individual (MCG-6-30-15); line : profiles; X-rays : galaxies ID BLACK-HOLE; GALAXY MCG-6-30-15; DISK; FLUORESCENCE; VARIABILITY; SPECTRUM; LINE AB We examine the unusual Fe-K alpha Line profile in MCG -6-30-15 observed by ASCA during a deep minimum in the source intensity. The intense red wing and depressed blue wing of the line have been interpreted as evidence for extreme gravitational redshifts in terms of emission from within 6 gravitational radii of a black hole. We find that the data do not uniquely support this interpretation and can be equally well explained by occultation of the continuum source and the putative line-emitting accretion disk, which we offer as an alternative hypothesis. Two problems with previous modeling were that the equivalent width of the Line during the deep minimum was required to be unusually large (greater than 1 keV) and the line intensity was thought to increase as the source became dim. The occultation model does not suffer from these problems. Our results serve to highlight the hazards of overinterpreting observational results that have low statistical significance to the extent that theoretical implications can become generally accepted when the data do not provide a strong case for them. C1 Johns Hopkins Univ, Dept Phys & Astron, Bloomberg Ctr, Baltimore, MD 21218 USA. NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. RP Weaver, KA (reprint author), Johns Hopkins Univ, Dept Phys & Astron, Bloomberg Ctr, Baltimore, MD 21218 USA. NR 20 TC 19 Z9 19 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD AUG 1 PY 1998 VL 502 IS 2 BP L139 EP L142 DI 10.1086/311497 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 152KH UT WOS:000077776200010 ER PT J AU Simpson, J Halverson, J Pierce, H Morales, C Iguchi, T AF Simpson, J Halverson, J Pierce, H Morales, C Iguchi, T TI Eyeing the eye: Exciting early stage science results from TRMM SO BULLETIN OF THE AMERICAN METEOROLOGICAL SOCIETY LA English DT Editorial Material C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Commun Res Lab, Kashima, Japan. RP Simpson, J (reprint author), NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. NR 0 TC 13 Z9 14 U1 0 U2 1 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 USA SN 0003-0007 J9 B AM METEOROL SOC JI Bull. Amer. Meteorol. Soc. PD AUG PY 1998 VL 79 IS 8 BP 1711 EP 1711 PG 1 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 114DH UT WOS:000075593500002 ER PT J AU Pawson, S Fiorino, M AF Pawson, S Fiorino, M TI A comparison of reanalyses in the tropical stratosphere. Part 1: Thermal structure and the annual cycle SO CLIMATE DYNAMICS LA English DT Article ID SYSTEM; FORECASTS AB An intercomparison of the thermal structure and the annual cycle in the tropical lower stratosphere of two reanalysis datasets is presented. These are from the National Centers for Environmental Prediction (NCEP)/National Center for Atmospheric Research (NCAR) and the European Centre for Medium Range Weather Forecasts (ECMWF Re-Analysis: ERA). Generally, the ERA data are coldest and in better agreement with radiosonde observations; this is particularly apparent at 100 hPa where there is also a strong geographic bias, the maximum differences (more than 4 K) occurring over the southern Pacific and the Indian Ocean, with much smaller (sometimes reversed) differences over land. The NCEP temperatures are biased towards satellite-derived values, while the ERA data resolve the low tropopause temperatures much better. The lower ERA temperatures have important implications for the cross-tropopause exchange of water vapor. The meridional-height structure of the annual cycles agree quite well, but the amplitude in the ERA data is about 50% stronger than in NCEP at 70 hPa (in better agreement with previous studies) and weaker at lower pressures. As in previous studies, an anticorrelation is found between the tropical and extratropical temperatures of the reanalyses. The mean meridional flow at the equator is northward all year at all stratospheric levels in the NCEP data, implying a mass transport from the Southern to the Northern Hemisphere; in the ERA data the expected annual cycle (flow from summer to winter) is reproduced with very small annual mean exchange. C1 Free Univ Berlin, Inst Meteorol, D-1000 Berlin, Germany. Univ Calif Lawrence Livermore Natl Lab, Program Climate Model Diag & Intercomparison, Livermore, CA USA. RP Pawson, S (reprint author), NASA, Goddard Space Flight Ctr, USRA, Code 916, Greenbelt, MD 20771 USA. EM pawson@polska.gsfc.nasa.gov RI Fiorino, Michael/N-4150-2014; Pawson, Steven/I-1865-2014 OI Fiorino, Michael/0000-0002-2819-8157; Pawson, Steven/0000-0003-0200-717X NR 28 TC 53 Z9 53 U1 0 U2 0 PU SPRINGER VERLAG PI NEW YORK PA 175 FIFTH AVE, NEW YORK, NY 10010 USA SN 0930-7575 J9 CLIM DYNAM JI Clim. Dyn. PD AUG PY 1998 VL 14 IS 9 BP 631 EP 644 DI 10.1007/s003820050246 PG 14 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 108VU UT WOS:000075287100002 ER PT J AU Stothers, RB AF Stothers, RB TI Far reach of the tenth century Eldgja eruption, Iceland SO CLIMATIC CHANGE LA English DT Article ID GREENLAND ICE CORE; VOLCANIC-ERUPTIONS AB At the end of Iceland's settlement period in the 10th century, a great basalt fissure eruption known as Eldgja (Fire Chasm) occurred near the southern settlements and destroyed a portion of them. This lava outpouring was one of the two largest terrestrial fissure eruptions of the last 11 centuries. Historical documents from Iceland, western Europe, and the Middle East are used to trace the eruption's possible climatic and demographic consequences. The cloud of aerosols from the eruption, traversing northern Europe, dimmed and reddened the Sun. There followed a very cold winter, famine, and a widespread disease epidemic during the next year and, again, 5 to 7 years after the eruption, probably as a result of the long-lived stratospheric aerosol veil. Convergent lines of evidence point to 934 as the year of the eruption. Accordingly, it becomes possible to date within a year a prominent acid horizon in ice laid down in central Greenland and, tentatively, to interpret some critical events and dates in early Icelandic history. C1 NASA, Goddard Space Flight Ctr, Inst Space Studies, New York, NY 10025 USA. RP Stothers, RB (reprint author), NASA, Goddard Space Flight Ctr, Inst Space Studies, 2880 Broadway, New York, NY 10025 USA. NR 66 TC 27 Z9 29 U1 0 U2 5 PU KLUWER ACADEMIC PUBL PI DORDRECHT PA SPUIBOULEVARD 50, PO BOX 17, 3300 AA DORDRECHT, NETHERLANDS SN 0165-0009 J9 CLIMATIC CHANGE JI Clim. Change PD AUG PY 1998 VL 39 IS 4 BP 715 EP 726 DI 10.1023/A:1005323724072 PG 12 WC Environmental Sciences; Meteorology & Atmospheric Sciences SC Environmental Sciences & Ecology; Meteorology & Atmospheric Sciences GA 123PA UT WOS:000076132500006 ER PT J AU Davidson, EA Potter, CS Schlesinger, P Klooster, SA AF Davidson, EA Potter, CS Schlesinger, P Klooster, SA TI Model estimates of regional nitric oxide emissions from soils of the southeastern United States SO ECOLOGICAL APPLICATIONS LA English DT Article DE agriculture; air pollution; fertilizer use and management; modeling NO emissions from soils; nitric oxide emissions from soils; nitrogen fertilization in agriculture; ozone; soil emission of NO; southeastern United States; tropospheric ozone precursors; sources ID NITROUS-OXIDE; FIELD-MEASUREMENTS; RURAL SITE; AGRICULTURAL SOILS; NORTH-CAROLINA; NOX EMISSIONS; DATA SET; FOREST; OZONE; ECOSYSTEMS AB Efforts to reduce tropospheric ozone (O(3)) pollution in the southeastern United States by reducing emissions of volatile organic compounds have had only modest success, and attention is now being drawn to sources of nitrogen oxide (NO(x)), which is the other major precursor of photochemical production of O(3). Emissions of nitric oxide (NO) from the soils of this region are poorly known. In this study, we adapt the CASA model of terrestrial-ecosystem productivity and trace-gas emissions to make spatially gridded, monthly estimates of NO emissions from soils for a nine-state region of the southeastern United States. Gridded input data layers to the model include temperature, precipitation, solar surface radiation, soil texture, land cover, fertilizer sales by county, and normalized-difference vegetation index. Total. N gas emissions are modeled as proportional to the rates of gross N mineralization and fertilizer N input. The relative proportional emissions of NO, N(2)O, and N(2) are determined by soil water content. The model estimates 126 x 10(9) g NO-N/yr emitted from soils for the entire nine-state area. Agricultural soils emit two-thirds of the total but cover only similar to 17% of the land area. Highest NO emissions occur along the cultivated Mississippi River corridor, southern Alabama-Georgia, and the Carolina coastal plain. Simulated emissions fall within the range of commonly reported values for temperate forests and cultivated fields, and the regional estimates are probably accurate within a factor of 2. Compared to NO(x) emissions from industrial, transportation, and utility sectors, soil emissions are similar to 10% of total regional emissions. However, the soil source could be a significant fraction of local NO(x) in rural agricultural areas, where emissions from fertilized fields usually range from 300 to 900 mg NO-N . m(-2).yr(-1). Fertilizer management could be an effective O(3)-abatement strategy in some rural agricultural areas, although this possibility and general uncertainties in the soil source of NO should not be grounds to delay other O(3)-abatement strategies for the much larger, nonsoil NO(x) sources in the region. C1 Woods Hole Res Ctr, Woods Hole, MA 02543 USA. NASA, Ames Res Ctr, Ecosyst Sci Branch, Moffett Field, CA 94035 USA. RP Davidson, EA (reprint author), Woods Hole Res Ctr, POB 296, Woods Hole, MA 02543 USA. RI Davidson, Eric/K-4984-2013 OI Davidson, Eric/0000-0002-8525-8697 NR 56 TC 25 Z9 25 U1 1 U2 12 PU ECOLOGICAL SOC AMER PI WASHINGTON PA 1990 M STREET NW, STE 700, WASHINGTON, DC 20036 USA SN 1051-0761 J9 ECOL APPL JI Ecol. Appl. PD AUG PY 1998 VL 8 IS 3 BP 748 EP 759 PG 12 WC Ecology; Environmental Sciences SC Environmental Sciences & Ecology GA 107PZ UT WOS:000075219300017 ER PT J AU Ryer, CH Olla, BL AF Ryer, CH Olla, BL TI Shifting the balance between foraging and predator avoidance: the importance of food distribution for a schooling pelagic forager SO ENVIRONMENTAL BIOLOGY OF FISHES LA English DT Article DE fish behavior; risk balancing; swimming speed; walleye pollock; shoaling; Theragra chalcogramma ID POLLOCK THERAGRA-CHALCOGRAMMA; JUVENILE WALLEYE POLLOCK; EASTERN BERING SEA; ATLANTIC SALMON; VERTICAL-DISTRIBUTION; FEEDING MOTIVATION; FISH PREDATORS; SHOALING FISH; MARINE FISH; RISK AB It is widely held that when predator avoidance conflicts with other activities, such as feeding, avoidance of predators often takes precedence. In this study, we examine how predation risk and food distribution interact to influence the schooling behavior and swimming speed of foraging juvenile walleye pollock, Theragra chalcogramma. Fish were acclimated to either spatially and temporally clumped, or spatially and temporally dispersed food for 3 weeks. Fish were then monitored while feeding in the absence and presence of predatory sablefish, Anoplopoma fimbrin. Fish foraging for clumped food swam rapidly in a loose school when predators were absent, but swam more slowly and adopted more cohesive schooling in the presence of predators, trading-off foraging opportunity for decreased vulnerability to predators. Fish foraging for dispersed food swam about slowly and did not engage in cohesive schooling in either the absence or presence of predators. These fish accepted greater predation risk in order to continue foraging, suggesting that the cost of schooling, in terms of decreased foraging opportunity, was greater when food was dispersed than when it was clumped. This lower responsiveness to predators among fish receiving dispersed food demonstrates that predator avoidance does not always take precedence over other activities, but rather, that a balance is maintained between predator avoidance and feeding, which shifts as food distribution changes. C1 Oregon State Univ, Hatfield Marine Sci Ctr, Natl Marine Fisheries Serv, Alaska Fisheries Sci Ctr, Newport, OR 97365 USA. RP Ryer, CH (reprint author), Oregon State Univ, Hatfield Marine Sci Ctr, Natl Marine Fisheries Serv, Alaska Fisheries Sci Ctr, Newport, OR 97365 USA. NR 52 TC 31 Z9 32 U1 1 U2 10 PU KLUWER ACADEMIC PUBL PI DORDRECHT PA SPUIBOULEVARD 50, PO BOX 17, 3300 AA DORDRECHT, NETHERLANDS SN 0378-1909 J9 ENVIRON BIOL FISH JI Environ. Biol. Fishes PD AUG PY 1998 VL 52 IS 4 BP 467 EP 475 DI 10.1023/A:1007433014921 PG 9 WC Ecology; Marine & Freshwater Biology SC Environmental Sciences & Ecology; Marine & Freshwater Biology GA 109KG UT WOS:000075321100008 ER PT J AU Hill, RW Chien, SA Fayyad, KV AF Hill, RW Chien, SA Fayyad, KV TI Goal-driven automation of a deep space communications station: a case study in knowledge engineering for plan generation and execution SO EXPERT SYSTEMS LA English DT Article DE artificial intelligence; planning and scheduling; architecture AB This paper describes the application of Artificial Intelligence techniques for plan generation, plan execution, and plan monitoring to automate a Deep Space Communication Station. This automation allows a communication station to respond to a set of tracking goals by appropriately reconfiguring the communications hardware and software to provide the requested communications services. In particular this paper describes: (I) the overall automation architecture, (2) the plan generation and execution monitoring AI technologies used and implemented software components, and (3) the knowledge engineering process and effort required for automation. This automation was demonstrated in February 1995, at the DSS13 Antenna Station in Goldstone, CA on a series of Voyager tracks and the technologies demonstrated are being transferred to the operational Deep Space Network stations.(1) C1 CALTECH, Jet Prop Lab, Pasadena, CA 91125 USA. RP Hill, RW (reprint author), CALTECH, Jet Prop Lab, Pasadena, CA 91125 USA. EM steve.chien@jpl.nasa.gov NR 25 TC 0 Z9 0 U1 0 U2 1 PU WILEY-BLACKWELL PI MALDEN PA COMMERCE PLACE, 350 MAIN ST, MALDEN 02148, MA USA SN 0266-4720 J9 EXPERT SYST JI Expert Syst. PD AUG PY 1998 VL 15 IS 3 BP 141 EP 156 PG 16 WC Computer Science, Artificial Intelligence; Computer Science, Theory & Methods SC Computer Science GA 120CU UT WOS:000075937800001 ER PT J AU Nelson, RF Gregoire, TG Oderwald, RG AF Nelson, RF Gregoire, TG Oderwald, RG TI The effects of fixed-area plot width on forest canopy height simulation SO FOREST SCIENCE LA English DT Article DE underestimation bias; stem density AB Mapped-stand data which includes tree location and mensuration data may be used to simulate the height characteristics of a forest canopy in a computer. The dimensions of the rectangular, fixed-area ground plot which is used to collect the tree location and mensuration data can profound ly affect the accuracy of the resultant computer reconstruction of forest cane py heights. Thin fixed-area plots result in forest canopy height constructs (i.e., canopy height models, or CHMs) which are shorter and less dense than the actual forest stand. Ninety-nine 0.405 ha forest stands in the southeastern and south central United States were analyzed. For each stand, a top-of-canopy height model was generated for the entire stand on a 0.25 m x 0.25 m grid. The mean canopy height and the canopy density of the simulated stand was calculated. A Monte Carlo simulator established randomly located sample plots of varying plot width (1 m to 20 m) at three different sampling intensities (1%, 5%, and 10% of stand area) in the mapped stand. The trees selected on any particular plot were used to generate a CHM, and the sample mean canopy height and canopy density were compared with the corresponding stand values. Samples collected using 1 m wide plots resulted in height models which underestimated average canopy height and canopy closure with deviations greater than 5% of the stand value, 95-100% of the time. The underestimation results from the construction of top-of-canopy architecture based on measurements of crowns belonging on ly to trees whose boles are with in the plot. This construction technique omits crowns extending over the plot belonging to tree boles located off the plot. Thinner plots tend to miss more of the trees which support the canopy over the plot. For the 99 stands considered in this study, ground plot widths on the order of 6 to 8 m were required in order to acquire ground data which could be used to accurately model forest canopy height characteristics. The minimum ground plot width required to produce an accurate height model decreased with increasing stem density; a plot width of 4 m, for instance, may be used at stem densities of similar to 2000 stems ha(-1). C1 NASA, Goddard Space Flight Ctr, Biospher Sci Branch, Greenbelt, MD 20771 USA. Virginia Polytech Inst & State Univ, Coll Forestry & Wildlife Resources, Blacksburg, VA 24061 USA. RP Nelson, RF (reprint author), NASA, Goddard Space Flight Ctr, Biospher Sci Branch, Code 923, Greenbelt, MD 20771 USA. RI Nelson, Ross/H-8266-2014 NR 4 TC 8 Z9 8 U1 0 U2 3 PU SOC AMER FORESTERS PI BETHESDA PA 5400 GROSVENOR LANE, BETHESDA, MD 20814 USA SN 0015-749X J9 FOREST SCI JI For. Sci. PD AUG PY 1998 VL 44 IS 3 BP 438 EP 444 PG 7 WC Forestry SC Forestry GA 109YW UT WOS:000075352800011 ER PT J AU Schwandt, CS McKay, GA AF Schwandt, CS McKay, GA TI Rare earth element partition coefficients from enstatite/melt synthesis experiments SO GEOCHIMICA ET COSMOCHIMICA ACTA LA English DT Article ID REE AB Enstatite (En(80)Fs(19)Wo(01)) was synthesized from a hypersthene normative basaltic melt doped at the same time with La, Ce, Nd, Sm, Eu, Dy, Er, Yb, and Lu. The rare earth element concentrations were measured in both the basaltic glass by EMPA and the enstatite by SIMS. Rare earth element concentrations in the glass were determined by electron microprobe analysis with uncertainties less than two percent relative. Rare earth element concentrations in enstatite were determined by secondary ion mass spectrometry with uncertainties less than five percent relative. The resulting rare earth element partition signature for enstatite is similar to previous calculated and composite low-Ca pigeonite signatures, but is better defined and differs in several details. First, the enstatite LREE signature is steeper than for pigeonite. Second, the signature has a negative Eu anomaly which relates to oxygen fugacity and third, the dependence of the partition coefficients on alumina content is linked to crystal structural constraints. Copyright (C) 1998 Elsevier Science Ltd. C1 Lockheed Martin Sci Engn Anal & Test, Houston, TX 77058 USA. NASA, Johnson Space Ctr, Houston, TX 77058 USA. RP Schwandt, CS (reprint author), Lockheed Martin Sci Engn Anal & Test, Houston, TX 77058 USA. NR 14 TC 45 Z9 46 U1 3 U2 10 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0016-7037 J9 GEOCHIM COSMOCHIM AC JI Geochim. Cosmochim. Acta PD AUG PY 1998 VL 62 IS 16 BP 2845 EP 2848 DI 10.1016/S0016-7037(98)00233-6 PG 4 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 139TP UT WOS:000077046000009 ER PT J AU Michelsen, HA Manney, GL Gunson, MR Rinsland, CP Zander, R AF Michelsen, HA Manney, GL Gunson, MR Rinsland, CP Zander, R TI Correlations of stratospheric abundances of CH4 and N2O derived from ATMOS measurements SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID TRANSPORT; TRACERS; SPACE; O-3 AB ATMOS measurements made over a wide range of altitudes and latitudes demonstrate compact correlations between mixing ratios of CH4 and N2O. Tight but distinct correlations are observed for the tropics, the springtime Arctic vortex, and the extra-tropics/extra-vortex regions, indicating dynamical isolation between these regions. Little variability is apparent in correlations between [CH4] and [N2O] from measurements made in different years (1992, 1993, and 1994), seasons (March/April and November), and hemispheres. C1 AER Inc, San Ramon, CA 94583 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ Liege, Inst Astrophys & Geophys, B-4000 Liege, Belgium. NASA, Langley Res Ctr, Hampton, VA 23665 USA. RP Michelsen, HA (reprint author), AER Inc, 2682 Bishop Dr,Ste 120, San Ramon, CA 94583 USA. NR 22 TC 53 Z9 53 U1 0 U2 3 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD AUG 1 PY 1998 VL 25 IS 15 BP 2777 EP 2780 DI 10.1029/98GL01977 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 108WZ UT WOS:000075289900005 ER PT J AU Herman, RL Scott, DC Webster, CR May, RD Moyer, EJ Salawitch, RJ Yung, YL Toon, GC Sen, B Margitan, JJ Rosenlof, KH Michelsen, HA Elkins, JW AF Herman, RL Scott, DC Webster, CR May, RD Moyer, EJ Salawitch, RJ Yung, YL Toon, GC Sen, B Margitan, JJ Rosenlof, KH Michelsen, HA Elkins, JW TI Tropical entrainment time scales inferred from stratospheric N2O and CH4 observations SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID ABSORPTION AB Simultaneous in situ measurements of N2O and CH4 were made with a tunable diode laser spectrometer (ALIAS II) aboard the Observations from the Middle Stratosphere (OMS) balloon platform from New Mexico, Alaska, and Brazil during 1996 and 1997. We find different compact relationships of CH4 with N2O in the tropics and extra-tropics because mixing is slow between these regions. Transport into the extra-tropics from the tropics or the polar vortex leads to deviations from the normal compact relationship. We use measured N2O and CH4 and a simple model to quantify entrainment of mid-latitude stratospheric air into the tropics. The entrainment time scale is estimated to be 16 (+17, -8) months for altitudes between 20 and 28 km. The fraction of tropical air entrained from the extratropical stratosphere is 50% (+18%, -30%) at 20 km, increasing to 78% (+11%, -19%) at 28 km. C1 CALTECH, Div Geol & Planetary Sci, Pasadena, CA 91125 USA. CALTECH, Jet Prop Lab, Pasadena, CA USA. Natl Ocean & Atmospher Adm, Aeron Lab, Boulder, CO USA. Atmospher & Environm Res Inc, San Ramon, CA USA. Natl Ocean & Atmospher Adm, Climate Monitoring & Diagnost Lab, Boulder, CO USA. RP Herman, RL (reprint author), CALTECH, Div Geol & Planetary Sci, Pasadena, CA 91125 USA. EM rherman@gps.caltech.edu RI Salawitch, Ross/B-4605-2009; Herman, Robert/H-9389-2012; Rosenlof, Karen/B-5652-2008 OI Salawitch, Ross/0000-0001-8597-5832; Herman, Robert/0000-0001-7063-6424; Rosenlof, Karen/0000-0002-0903-8270 NR 25 TC 44 Z9 44 U1 0 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD AUG 1 PY 1998 VL 25 IS 15 BP 2781 EP 2784 DI 10.1029/98GL02109 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 108WZ UT WOS:000075289900006 ER PT J AU Brinksma, EJ Meijer, YJ Connor, BJ Manney, GL Bergwerff, JB Bodeker, GE Boyd, IS Liley, JB Hogervorst, W Hovenier, JW Livesey, NJ Swart, DPJ AF Brinksma, EJ Meijer, YJ Connor, BJ Manney, GL Bergwerff, JB Bodeker, GE Boyd, IS Liley, JB Hogervorst, W Hovenier, JW Livesey, NJ Swart, DPJ TI Analysis of record-low ozone values during the 1997 winter over Lauder, New Zealand SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article AB Record-low ozone (O-3) column densities (with a minimum of 222 DU) were observed over the Lauder NDSC (Network for the Detection of Stratospheric Change) station (45 degrees S, 170 degrees E) in August 1997. Possible causes are examined using height-resolved O-3 measurements over Lauder, and high-resolution reverse trajectory maps of O-3 (initialised with Microwave Limb Sounder measurements) and of potential vorticity. The analysis shows that O-3 poor air originated from two regions: Below the 550 K isentrope (similar to 22 km) subtropical air was observed, while between 600 and 1000 K (similar to 25 - 33.5 km) the polar vortex tilted over Lauder for several days. A rapid recovery of the O-3 column density was observed later, due to an O-3 rich polar vortex filament moving over Lauder between 18 and 24 km, while simultaneously the O-3 poor higher vortex moved away. C1 Vrije Univ Amsterdam, Fac Phys & Astron, Dept Phys & Astron, NL-1081 HV Amsterdam, Netherlands. Natl Inst Publ Hlth & Environm, Air Res Lab, RIVM, NL-3720 BA Bilthoven, Netherlands. Natl Inst Water & Atmospher Res Ltd, Lauder, New Zealand. CALTECH, Jet Propuls Lab, Pasadena, CA USA. RP Brinksma, EJ (reprint author), Vrije Univ Amsterdam, Fac Phys & Astron, Dept Phys & Astron, De Boelelaan 1081, NL-1081 HV Amsterdam, Netherlands. EM ellen@nat.vu.nl RI Bodeker, Greg/A-8870-2008; OI Bodeker, Greg/0000-0003-1094-5852; Liley, Ben/0000-0002-8844-7928 NR 13 TC 15 Z9 16 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD AUG 1 PY 1998 VL 25 IS 15 BP 2785 EP 2788 DI 10.1029/98GL52218 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 108WZ UT WOS:000075289900007 ER PT J AU Delworth, TL Mehta, VM AF Delworth, TL Mehta, VM TI Simulated interannual to decadal variability in the tropical and sub-tropical North Atlantic SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID OCEAN-ATMOSPHERE MODEL AB The dominant pattern of tropical and subtropical North Atlantic sea surface temperature (SST) anomalies simulated in the GFDL coupled ocean-atmosphere model is identified and compared to observations. The spatial pattern and temporal variability of that pattern resemble observational results. On interannual time scales it is shown that anomalous surface heat fluxes, consistent with variations in the intensity of the subtropical high pressure system in the atmosphere and the associated Northeasterly Trade winds, appear to be the most important process for generating this SST pattern. This relationship is also true on decadal time scales, although the relative role of oceanic heat advection is somewhat larger than on the interannual time scales. C1 NOAA, Geophys Fluid Dynam Lab, Princeton, NJ 08542 USA. Univ Maryland, NASA, Joint Ctr Earth Syst Sci, Dept Meteorol, College Pk, MD 20742 USA. RP Delworth, TL (reprint author), NOAA, Geophys Fluid Dynam Lab, Princeton, NJ 08542 USA. EM td@gfdl.gov; mehta@atmos.umd.edu RI Delworth, Thomas/C-5191-2014 NR 9 TC 14 Z9 14 U1 0 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD AUG 1 PY 1998 VL 25 IS 15 BP 2825 EP 2828 DI 10.1029/98GL02188 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 108WZ UT WOS:000075289900017 ER PT J AU Bale, SD Kellogg, PJ Larson, DE Lin, RP Goetz, K Lepping, RP AF Bale, SD Kellogg, PJ Larson, DE Lin, RP Goetz, K Lepping, RP TI Bipolar electrostatic structures in the shock transition region: Evidence of electron phase space holes SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID BOW SHOCK; COLLISIONLESS; WAVES AB We present observations of intense, bipolar, electrostatic structures in the transition region of the terrestrial bow shock from the Wind spacecraft. The electric field signatures are on the order of a tenth of a,millisecond in duration and greater than 100 mV/m in amplitude. The measured electric field is generally larger on the smaller dipole antenna, indicating a small spatial size. We compare the potential on the two dipole antennas with a model of antenna response to a Gaussian potential profile. This result agrees with a spatial scale determined by convection and gives a characteristic scale size of 2 - 7 lambda(d). We interpret the observations as small scale convecting unipolar potential structures, consistent with simulations of electron phase space holes and discuss the results in the context of electron thermalization at strong collisionless shocks. C1 Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA. Univ Minnesota, Sch Phys & Astron, Minneapolis, MN 55455 USA. NASA, Goddard Space Flight Ctr, Extraterr Phys Lab, Greenbelt, MD 20771 USA. Univ Calif Berkeley, Dept Phys, Berkeley, CA 94720 USA. Observ Paris, DESPA, F-92195 Meudon, France. RP Bale, SD (reprint author), Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA. EM bale@ssl.berkeley.edu RI Bale, Stuart/E-7533-2011 OI Bale, Stuart/0000-0002-1989-3596 NR 13 TC 167 Z9 169 U1 0 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD AUG 1 PY 1998 VL 25 IS 15 BP 2929 EP 2932 DI 10.1029/98GL02111 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 108WZ UT WOS:000075289900043 ER PT J AU Jordanova, VK Farrugia, CJ Quinn, JM Thorne, RM Ogilvie, KW Lepping, RP Lu, G Lazarus, AJ Thomsen, MF Belian, RD AF Jordanova, VK Farrugia, CJ Quinn, JM Thorne, RM Ogilvie, KW Lepping, RP Lu, G Lazarus, AJ Thomsen, MF Belian, RD TI Effect of wave-particle interactions on ring current evolution for January 10-11, 1997: Initial results SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID ION-CYCLOTRON WAVES; MAGNETOSPHERE; ELECTRON AB We simulate the ring current evolution during the magnetic storm caused by Earth passage of the January 1997 magnetic cloud. Compared to previous studies, we include for the first time energy diffusion caused by wave-particle interactions. The modeled Dst index agrees reasonably well with the measured one, corrected for magnetopause currents and currents induced in the solid Earth. We compare H+ distributions calculated from our model with those measured by the HYDRA instrument on the POLAR spacecraft and find that: a) the agreement between theory and data at large L shells (L>5.5) is very good; b) although the agreement at low L shells is improved when scattering by EMIC waves is included, the result is not entirely satisfactory, suggesting that either transport in a more realistic magnetospheric electric field or additional loss processes should be considered. C1 Univ New Hampshire, Ctr Space Sci, Durham, NH 03824 USA. Univ Calif Los Alamos Natl Lab, Los Alamos, NM 87545 USA. MIT, Ctr Space Res, Cambridge, MA 02139 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Natl Ctr Atmospher Res, High Altitude Observ, Boulder, CO 80307 USA. Univ Calif Los Angeles, Dept Atmospher Sci, Los Angeles, CA 90095 USA. RP Jordanova, VK (reprint author), Univ New Hampshire, Ctr Space Sci, Durham, NH 03824 USA. RI Lu, Gang/A-6669-2011; OI Jordanova, Vania/0000-0003-0475-8743 NR 18 TC 48 Z9 49 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD AUG 1 PY 1998 VL 25 IS 15 BP 2971 EP 2974 DI 10.1029/98GL00649 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 108WZ UT WOS:000075289900054 ER PT J AU Baker, DN Pulkkinen, TI Li, X Kanekal, SG Ogilvie, KW Lepping, RP Blake, JB Callis, LB Rostoker, G Singer, HJ Reeves, GD AF Baker, DN Pulkkinen, TI Li, X Kanekal, SG Ogilvie, KW Lepping, RP Blake, JB Callis, LB Rostoker, G Singer, HJ Reeves, GD TI A strong CME-related magnetic cloud interaction with the Earth's magnetosphere: ISTP observations of rapid relativistic electron acceleration on May 15, 1997 SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID RADIATION BELT; ENERGIZATION; INSTRUMENT AB A geoeffective magnetic cloud impacted the Earth early on 15 May 1997. The cloud exhibited strong initial southward interplanetary magnetic field (B(z)similar to-25 nT), which caused intense substorm activity and an intense geomagnetic storm (Dst similar to-170 nT). SAMPEX data showed that relativistic electrons (E greater than or equal to 1.0 MeV) appeared suddenly deep in the magnetosphere at L=3 to 4. These electrons were not directly "injected" from higher altitudes (i.e., from the magnetorail), nor did they come from an interplanetary source. The electron increase was preceded (for similar to 2 hrs) by remarkably strong low-frequency wave activity as seen by CANOPUS ground stations and by the GOES-8 spacecraft at geostationary orbit. POLAR/CEPPAD measurements support the result that high-energy electrons suddenly appeared deep in the magnetosphere. Thus, these new multi-point data suggest that strong magnetospheric waves can quickly and efficiently accelerate electrons to multi-MeV energies deep in the radiation belts on timescales of tens of minutes. C1 Univ Colorado, Atmospher & Space Phys Lab, Boulder, CO 80303 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Aerospace Corp, Los Angeles, CA 90009 USA. Langley Res Ctr, Hampton, VA 23681 USA. Univ Alberta, Edmonton, AB T6G 2J1, Canada. NOAA, Space Environm Ctr, Boulder, CO 80302 USA. Univ Calif Los Alamos Natl Lab, Los Alamos, NM 87545 USA. RP Baker, DN (reprint author), Univ Colorado, Atmospher & Space Phys Lab, 1234 Innovat Dr, Boulder, CO 80303 USA. RI Reeves, Geoffrey/E-8101-2011; Pulkkinen, Tuija/D-8403-2012 OI Reeves, Geoffrey/0000-0002-7985-8098; Pulkkinen, Tuija/0000-0002-6317-381X NR 17 TC 95 Z9 99 U1 0 U2 5 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD AUG 1 PY 1998 VL 25 IS 15 BP 2975 EP 2978 DI 10.1029/98GL01134 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 108WZ UT WOS:000075289900055 ER PT J AU Dempsey, DL Burch, JL Huddleston, MM Pollock, CJ Waite, JH Wuest, M Moore, TE Shelley, EG AF Dempsey, DL Burch, JL Huddleston, MM Pollock, CJ Waite, JH Wuest, M Moore, TE Shelley, EG TI Reflected solar wind ions and downward accelerated ionospheric ions during the January 1997 magnetic cloud event SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID MAGNETOSPHERE; DYNAMICS AB On January 11, 1997, at 03:40:00 UT, while Polar was traveling up the dusk flank toward apogee, two ion instruments, TIDE and TIMAS, detected upflowing H+ with an energy/pitch-angle dispersion resembling an ionospheric reflection of freshly injected solar wind ions. In the same region of space, TIDE and TIMAS observed cold beams of O+ and H+ traveling down the field line with equal bulk velocities. We interpret these ion signatures as concurrent observations of mirrored solar wind ions and downward accelerated ionospheric ions. By 03:42:00, an energy/pitch-angle dispersion of downward moving ions at very low energies was clearly evident in the TIDE data. This additional signature is interpreted as an indication of reconnection on the same field line in the southern hemisphere. We explain this unique combination of plasma distributions in terms of high-latitude reconnection and magnetic field line convection during northward-IMF conditions associated with the January 1997 magnetic cloud event. C1 SW Res Inst, Div 15, San Antonio, TX 78228 USA. NASA, Goddard Space Flight Ctr, Extraterr Phys Lab, Interplanetary Phys Branch, Greenbelt, MD 20771 USA. Lockheed Martin Adv Technol Ctr, Dept H111, Palo Alto, CA 94304 USA. Rice Univ, Houston, TX 77251 USA. RP Dempsey, DL (reprint author), SW Res Inst, Div 15, 6200 Culebra,Bldg 178, San Antonio, TX 78228 USA. RI Moore, Thomas/D-4675-2012 OI Moore, Thomas/0000-0002-3150-1137 NR 14 TC 3 Z9 3 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD AUG 1 PY 1998 VL 25 IS 15 BP 2979 EP 2982 DI 10.1029/98GL00334 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 108WZ UT WOS:000075289900056 ER PT J AU Christon, SP Cohen, CS Gloeckler, G Eastman, TE Galvin, AB Ipavich, FM Ko, YK Lui, ATY Lundgren, RA McEntire, RW Roelof, EC Williams, DJ AF Christon, SP Cohen, CS Gloeckler, G Eastman, TE Galvin, AB Ipavich, FM Ko, YK Lui, ATY Lundgren, RA McEntire, RW Roelof, EC Williams, DJ TI Concurrent observations of solar wind oxygen by Geotail in the magnetosphere and Wind in interplanetary space SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID AMPTE CCE; IONS; SPECTROMETER; ULYSSES; CARBON; SWICS AB We present an initial report on the first direct, concurrent measurements of solar wind oxygen (O) charge state variations inside and outside Earth's magnetosphere. On 10-11 Jan 1997 a magnetic cloud, with a spatial scale of at least similar to 100 R-E engulfed the magnetosphere. At similar to 1200 UT on 10 Jan 1997, the Wind/SWICS ion charge-state spectrometer, at similar to 90 R-E upstream of Earth, detected an increase in the solar wind O charge state ratio Gamma(0) = (O+7 + O+8) / O+6 at similar to 0.5-30 keV/e which persisted until similar to 2400 UT on 10 Jan 1997. After similar to 1110 UT on 10 Jan 1997, Geotail was in and near the mid-afternoon to dusk magnetosphere. The similar to 9.4-210 keV/e Gamma(0) value from the Geotail/STICS spectrometer showed a longer-term, gradual increase over similar to 8-10 hr. Then, after similar to 0600 UT on 11 Jan 1997, Wind observed a Gamma(0) decrease at a high speed solar wind stream onset. About 6 hr later Gamma(0) decreased promptly at Geotail during a plasma sheet substorm injection. Both instances are long durations compared to nominal 3-hr substorm time-scales. C1 Univ Maryland, Dept Phys, College Pk, MD 20742 USA. CALTECH, SRL, Pasadena, CA 91125 USA. Plasmas Int, Silver Spring, MD 20910 USA. Johns Hopkins Univ, Appl Phys Lab, Laurel, MD 20725 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Maryland, IPST, College Pk, MD 20742 USA. RP Christon, SP (reprint author), Univ Maryland, Dept Phys, College Pk, MD 20742 USA. RI Galvin, Antoinette/A-6114-2013; OI Christon, Stephen/0000-0003-1770-2458 NR 13 TC 5 Z9 5 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD AUG 1 PY 1998 VL 25 IS 15 BP 2987 EP 2990 DI 10.1029/98GL01408 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 108WZ UT WOS:000075289900058 ER PT J AU Laakso, H Fairfield, DH Russell, CT Clemmons, JH Singer, HJ Giles, BL Lepping, RP Mozer, FS Pfaff, RF Tsuruda, K Wygant, JR AF Laakso, H Fairfield, DH Russell, CT Clemmons, JH Singer, HJ Giles, BL Lepping, RP Mozer, FS Pfaff, RF Tsuruda, K Wygant, JR TI Field-line resonances triggered by a northward IMF turning SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID KELVIN-HELMHOLTZ INSTABILITY; ELECTRIC-FIELD; MAGNETOSPHERE; MAGNETOPAUSE; ISEE-1; WAVES AB A sudden northward rotation of the IMF observed by IMP 8 near the bow shock at 21:22 UT on January 10, 1997, triggered surface waves and fast mode waves at the flanks of the duskside magnetosphere, as observed by GEOTAIL instruments. The power spectral density of these Raves peaked in the frequency range where field-line resonances were observed by the POLAR satellite in the region L = 6.6-10.2.. The oscillation periods of the observed field-line resonances were L-dependent with two distinct peaks which may be explained by increased heavy ion content at those field lines. The ULF waves also caused enhanced low-energy ion fluxes from the ionosphere. C1 Finnish Meteorol Inst, FIN-00101 Helsinki, Finland. Aerospace, Los Angeles, CA USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. NASA, George C Marshall Space Flight Ctr, Space Sci Lab, Huntsville, AL 35812 USA. Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA. Univ Calif Los Angeles, Inst Geophys & Planetary Phys, Los Angeles, CA 90095 USA. NOAA RESE, Space Environm Ctr, Boulder, CO 80303 USA. Inst Space & Astronaut Sci, Sagamihara, Kanagawa 299, Japan. Univ Minnesota, Sch Phys & Astron, Minneapolis, MN 55455 USA. RP Laakso, H (reprint author), Finnish Meteorol Inst, FIN-00101 Helsinki, Finland. RI Pfaff, Robert/F-5703-2012; OI Pfaff, Robert/0000-0002-4881-9715; Clemmons, James/0000-0002-5298-5222; Russell, Christopher/0000-0003-1639-8298 NR 14 TC 9 Z9 10 U1 0 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD AUG 1 PY 1998 VL 25 IS 15 BP 2991 EP 2994 DI 10.1029/98GL51034 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 108WZ UT WOS:000075289900059 ER PT J AU Osherovich, VA Fainberg, J Stone, RG Fitzenreiter, R Vinas, AF AF Osherovich, VA Fainberg, J Stone, RG Fitzenreiter, R Vinas, AF TI Measurements of polytropic index in the January 10-11, 1997 magnetic cloud observed by WIND SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID ULYSSES OBSERVATIONS; SHOCK; LOOP AB The polytropic index gamma is a key parameter in the modeling of interplanetary magnetic clouds. In contrast to other models, the self-similar model of Osherovich et al [1993a] suggested gamma < 1 in clouds. The first measurements [Osherovich et al, 1993b] showed that gamma approximate to gamma e = 0.4 - 0.5 in magnetic clouds demonstrating the dominant role of electrons over protons (Te/Tp approximate to 6-7 at 1 AU). For the January 10-11, 1997 cloud observed by WIND, we found that the polytropric relation T-e= FNegamma c-1 is valid with gamma e = 0.52 +/- 0.04 and F = 1.97 10(5) +/- 0.12 10(5) (cgs units) over the number density range 1 < Ne < 10 cm(-3). The constant F is half the value found for other clouds studied at 1 AU, while gamma e is essentially the same. We believe that the small value of F should be attributed to a later stage of the self-similar evolution of this cloud as compared to other clouds studied previously at 1 AU. C1 NASA, Goddard Space Flight Ctr, Hughes STX, Greenbelt, MD 20771 USA. NASA, Goddard Space Flight Ctr, Extraterr Phys Lab, Greenbelt, MD 20771 USA. RP Osherovich, VA (reprint author), NASA, Goddard Space Flight Ctr, Hughes STX, Code 692, Greenbelt, MD 20771 USA. NR 20 TC 15 Z9 15 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD AUG 1 PY 1998 VL 25 IS 15 BP 3003 EP 3006 DI 10.1029/98GL00547 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 108WZ UT WOS:000075289900062 ER PT J AU Laakso, H Fairfield, DH Collier, MR Opgenoorth, H Phan, TD Sibeck, DG Giles, BL Singer, HJ Lepping, RP Lin, RP Mozer, FS Pfaff, RF Tsuruda, K Wygant, JR AF Laakso, H Fairfield, DH Collier, MR Opgenoorth, H Phan, TD Sibeck, DG Giles, BL Singer, HJ Lepping, RP Lin, RP Mozer, FS Pfaff, RF Tsuruda, K Wygant, JR TI Oscillations of magnetospheric boundaries driven by IMF rotations SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID BOW SHOCK; DAYSIDE MAGNETOPAUSE; MOTION AB The arrival of the magnetic cloud on January 10, 1997, 01:05 UT, was preceded by a 12-hour interval of increased fluctuations in the IMF orientation, which drove boundary oscillations in the magnetosphere. The GEOTAIL spacecraft, initially located near the dawnside magnetopause, experienced multiple crossings of the magnetopause; at the geosynchronous distance, GOES 9 observed weak perturbations associated with these oscillations. During this time, the POLAR spacecraft, encountered the dense high-latitude boundary layer, followed by several rapid encounters with the tenuous lobe. The boundary between the mantle and the lobe was observed to be thin as the crossings lasted only 30 seconds. The source of these boundary oscillations is magnetosheath pressure variations produced by rapid IMF directional changes. C1 Finnish Meteorol Inst, FIN-00101 Helsinki, Finland. NASA, Goddard Space Flight Ctr, Extraterr Phys Lab, Greenbelt, MD 20771 USA. NASA, George C Marshall Space Flight Ctr, Space Sci Lab, Huntsville, AL 35812 USA. Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA. Johns Hopkins Univ, Appl Phys Lab, Laurel, MD 20723 USA. NOAA RESE, Space Environm Ctr, Boulder, CO 80302 USA. Inst Space & Astronaut Sci, Sagamihara, Kanagawa 299, Japan. Univ Minnesota, Sch Phys & Astron, Minneapolis, MN 55455 USA. Inst Rymdfysik, Uppsala, Sweden. RP Laakso, H (reprint author), Finnish Meteorol Inst, POB 503, FIN-00101 Helsinki, Finland. RI Sibeck, David/D-4424-2012; Pfaff, Robert/F-5703-2012; Collier, Michael/I-4864-2013 OI Pfaff, Robert/0000-0002-4881-9715; Collier, Michael/0000-0001-9658-6605 NR 11 TC 12 Z9 12 U1 0 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD AUG 1 PY 1998 VL 25 IS 15 BP 3007 EP 3010 DI 10.1029/98GL50916 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 108WZ UT WOS:000075289900063 ER PT J AU Russell, CT Fedder, JA Slinker, SP Zhou, XW Le, G Luhmann, JG Fenrich, FR Chandler, MO Moore, TE Fuselier, SA AF Russell, CT Fedder, JA Slinker, SP Zhou, XW Le, G Luhmann, JG Fenrich, FR Chandler, MO Moore, TE Fuselier, SA TI Entry of the POLAR spacecraft into the polar cusp under northward IMF conditions SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID INTERPLANETARY MAGNETIC-FIELD; LATITUDE BOUNDARY-LAYER; RECONNECTION; INSTRUMENT; ANGLE AB On May 29, 1996 from 0200 to 0800 UT the solar wind dynamic pressure was high ranging from 6 to 8 nPa and the interplanetary field was almost due northward, ranging from 10 to 15 nT in BZ GSM. Even at apogee the POLAR spacecraft should not have entered the magnetosheath according to recent scaling laws. However, the magnetic field was greatly depressed below the value expected indicating the presence of significant plasma energy density throughout the high latitude magnetosphere surrounding the cusp. The presence of this plasma is confirmed by the plasma instrumentation on board the spacecraft. While the entry into this nearly stagnant plasma was gradual, the exit on to polar cap field lines was abrupt. We interpret these observations in terms of the post-cusp reconnection of the strongly northward interplanetary magnetic field. C1 Univ Calif Los Angeles, Inst Geophys, Los Angeles, CA 90095 USA. Univ Calif Los Angeles, Inst Geophys & Planetary Phys, Los Angeles, CA 90095 USA. George Mason Univ, Inst Computat Sci & Informat, Fairfax, VA 22030 USA. USN, Res Lab, Div Plasma Phys, Washington, DC 20375 USA. Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA. NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Lockheed Martin, Palo Alto, CA USA. RP Russell, CT (reprint author), Univ Calif Los Angeles, Inst Geophys, Los Angeles, CA 90095 USA. RI Le, Guan/C-9524-2012; Moore, Thomas/D-4675-2012; OI Le, Guan/0000-0002-9504-5214; Moore, Thomas/0000-0002-3150-1137; Russell, Christopher/0000-0003-1639-8298 NR 18 TC 32 Z9 32 U1 0 U2 2 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD AUG 1 PY 1998 VL 25 IS 15 BP 3015 EP 3018 DI 10.1029/98GL00355 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 108WZ UT WOS:000075289900065 ER PT J AU Germany, GA Parks, GK Ranganath, H Elsen, R Richards, PG Swift, W Spann, JF Brittnacher, M AF Germany, GA Parks, GK Ranganath, H Elsen, R Richards, PG Swift, W Spann, JF Brittnacher, M TI Analysis of auroral morphology: Substorm precursor and onset on January 10, 1997 SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID PRECIPITATION AB We study the dynamics of the poleward and equatorward boundaries of the auroral oval in response to the solar wind IMF on January 10, 1997 using global auroral images obtained by the Ultraviolet Imager (UVI) on Polar. A neural network algorithm is used to perform an automated morphological analysis. Poleward and equatorward boundaries identified by the algorithm exhibit clear equatorward motion during the substorm growth phase associated with the southward turning of the IMF. At substorm expansive phase onset, the high latitude edge of the oval expands poleward while the low latitude edge in the midnight sector shows continued expansion for several minutes after onset. C1 Univ Alabama, Ctr Space Plasma & Aeron Res, Huntsville, AL 35899 USA. Univ Washington, Geophys Program, Seattle, WA 98195 USA. Univ Alabama, Dept Comp Sci, Huntsville, AL 35899 USA. NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. RP Germany, GA (reprint author), Univ Alabama, Ctr Space Plasma & Aeron Res, TH S131, Huntsville, AL 35899 USA. NR 10 TC 18 Z9 20 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD AUG 1 PY 1998 VL 25 IS 15 BP 3043 EP 3046 DI 10.1029/98GL01220 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 108WZ UT WOS:000075289900072 ER PT J AU Tsurutani, BT Arballo, JK Lakhina, GS Ho, CM Ajello, J Pickett, JS Gurnett, DA Lepping, RP Peterson, WK Rostoker, G Kamide, Y Kokubun, S AF Tsurutani, BT Arballo, JK Lakhina, GS Ho, CM Ajello, J Pickett, JS Gurnett, DA Lepping, RP Peterson, WK Rostoker, G Kamide, Y Kokubun, S TI The January 10, 1997 auroral hot spot, horseshoe aurora and first substorm: A CME loop? SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID PLASMA AB The January 10, 1997 interplanetary high-speed stream and the resultant first substorm (similar to 0332 to 0334 UT onset) is studied. A 47 minute interval of relatively intense southward interplanetary magnetic field (IMF) (B-S = 4 to 8 nT)bounded by two tangential discontinuities (TDs) is identified between the interplanetary shock and the magnetic cloud. The two discontinuities arrive at the magnetopause at similar to 0219 and similar to 0302 UT. The IMF B-S event served primarily to transfer solar wind energy to the magnetosphere/magnetotail, as no substorm expansion phase occurred during the event. The eventual energy release was in the form of a large substorm expansion phase which occurred after (similar to 15-17 min.) a second IMF northward turning (after the end of the B-S interval). The interplanetary B-S event came after a prolonged northward IMF interval. During the initial part of the B-S event, both polar cap Sun- Earth aligned arcs formed (part of a theta aurora) and an auroral hot spot along the main are took place. Later, during the B-S interval, an aurora in the shape of a horseshoe developed at lower (60 degrees) latitudes (an oval with a gap in the noon sector). The dawnside portion of the horseshoe aurora became much brighter than the duskside with increasing time. The dawnside polar cap boundary layer (PCBL) broadband waves were well correlated with low energy ion fluxes (H+ He++, O+) during the event. It is speculated that this IMF B-S structure may be an outer loop of the CME coming from the Sun. Another similar loop is identified just adjacent to the cloud. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ Iowa, Dept Phys & Astron, Iowa City, IA 52242 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Lockheed Space Sci Lab, Palo Alto, CA USA. Univ Alberta, Dept Phys, Edmonton, AB T6G 2M7, Canada. Nagoya Univ, Solar Terr Environm Lab, Toyakawa, Aichi 442, Japan. Indian Inst Geomagnetism, Bombay 400005, Maharashtra, India. RP Tsurutani, BT (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. RI Lakhina, Gurbax /C-9295-2012; Peterson, WK/A-8706-2009; OI Peterson, WK/0000-0002-1513-6096; Lakhina, Gurbax /0000-0002-8956-486X NR 10 TC 29 Z9 29 U1 0 U2 2 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD AUG 1 PY 1998 VL 25 IS 15 BP 3047 EP 3050 DI 10.1029/98GL01304 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 108WZ UT WOS:000075289900073 ER PT J AU Hargens, AR Mubarak, SJ AF Hargens, AR Mubarak, SJ TI Current concepts in the pathophysiology, evaluation, and diagnosis of compartment syndrome SO HAND CLINICS LA English DT Article ID INTERSTITIAL FLUID PRESSURE; MUSCLE; COMPRESSION AB This article reviews present knowledge of the pathophysiology, evaluation, and diagnosis of acute compartment syndromes. A compartment syndrome exists when edema or blood accumulates within a confined osseofacial space such that intramuscular pressure is elevated at a sufficient magnitude and time to reduce capillary perfusion and to risk tissue viability. Compartment syndromes are usually characterized by the six so-called Ps: high pressure, pain (especially with passive stretch), paresthesia, paresis, pink skin color, and pulse (distal pulse present). Intramuscular pressure thresholds for decompression fasciotomy range between 30 to 50 mm Hg, depending on clinical signs and systemic blood pressure. However, time factors are also important and usually are incompletely known in most cases of acute compartment syndrome. Recent development of miniature transducer-tipped catheters and the future development of noninvasive techniques may provide accurate recordings of intramuscular pressure in patients with acute compartment syndromes. C1 NASA, Ames Res Ctr, Gravitat Res Branch 239 11, Moffett Field, CA 94035 USA. Univ Calif San Diego, Dept Orthopaed, La Jolla, CA 92093 USA. Childrens Hosp, Orthopaed Programs, San Diego, CA USA. RP Hargens, AR (reprint author), NASA, Ames Res Ctr, Gravitat Res Branch 239 11, Moffett Field, CA 94035 USA. NR 29 TC 52 Z9 52 U1 0 U2 4 PU W B SAUNDERS CO PI PHILADELPHIA PA INDEPENDENCE SQUARE WEST CURTIS CENTER, STE 300, PHILADELPHIA, PA 19106-3399 USA SN 0749-0712 J9 HAND CLIN JI Hand Clin. PD AUG PY 1998 VL 14 IS 3 BP 371 EP + PG 14 WC Orthopedics SC Orthopedics GA 119MG UT WOS:000075899800006 PM 9742417 ER PT J AU Klein, AG Hall, DK Riggs, GA AF Klein, AG Hall, DK Riggs, GA TI Improving snow cover mapping in forests through the use of a canopy reflectance model SO HYDROLOGICAL PROCESSES LA English DT Article DE snow cover; remote sensing; forest canopy ID LANDSAT THEMATIC MAPPER; RED-INFRARED SCATTERGRAMS; TERRESTRIAL MATERIALS; ATMOSPHERIC WINDOW; OPTICAL-PROPERTIES; SPECTRAL ALBEDO; RESOLUTION; EMISSIVITY AB MODIS, the moderate resolution imaging spectroradiometer, will be launched in 1998 as part of the first earth observing system (EOS) platform. Global maps of land surface properties, including snow cover, will be created from MODIS imagery. The MODIS snow-cover mapping algorithm that will be used to produce daily maps of global snow cover extent at 500 m resolution is currently under development. With the exception of cloud cover, the largest limitation to producing a global daily snow cover product using MODIS is the presence of a forest canopy, A Landsat Thematic Mapper (TM) time-series of the southern Boreal Ecosystem-Atmosphere Study (BOREAS) study area in Prince Albert National Park, Saskatchewan, was used to evaluate the performance of the current MODIS snow-cover mapping algorithm in varying forest types. A snow reflectance model was used in conjunction with a canopy reflectance model (GeoSAIL) to model the reflectance of a snow-covered forest stand. Using these coupled models, the effects of varying forest type, canopy density, snow grain size and solar illumination geometry on the performance of the MODIS snow-cover mapping algorithm were investigated. Using both the TM images and the reflectance models, two changes to the current MODIS snow-cover mapping algorithm are proposed that will improve the algorithm's classification accuracy in forested areas. The improvements include using the normalized difference snow index and normalized difference vegetation index in combination to discriminate better between snow-covered and snow-free forests. A minimum albedo threshold of 10% in the visible wavelengths is also proposed. This will prevent dense forests with very low visible albedos from being classified incorrectly as snow. These two changes increase the amount of snow mapped in forests on snow-covered TM scenes, and decrease the area incorrectly identified as snow on non-snow-covered TM scenes. (C) 1998 John Wiley & Sons, Ltd. C1 NASA, Goddard Space Flight Ctr, Hydrol Sci Branch, Lab Hydrospher Proc, Greenbelt, MD 20771 USA. RP Klein, AG (reprint author), NASA, Goddard Space Flight Ctr, Hydrol Sci Branch, Lab Hydrospher Proc, Mail Code 974, Greenbelt, MD 20771 USA. RI Hall, Dorothy/D-5562-2012 NR 46 TC 175 Z9 189 U1 5 U2 26 PU JOHN WILEY & SONS LTD PI W SUSSEX PA BAFFINS LANE CHICHESTER, W SUSSEX PO19 1UD, ENGLAND SN 0885-6087 J9 HYDROL PROCESS JI Hydrol. Process. PD AUG-SEP PY 1998 VL 12 IS 10-11 BP 1723 EP 1744 DI 10.1002/(SICI)1099-1085(199808/09)12:10/11<1723::AID-HYP691>3.0.CO;2-2 PG 22 WC Water Resources SC Water Resources GA 116TF UT WOS:000075740100015 ER PT J AU Cochran, AL Vilas, F AF Cochran, AL Vilas, F TI The changing spectrum of Vesta: Rotationally resolved spectroscopy of pyroxene on the surface SO ICARUS LA English DT Article ID SPACE-TELESCOPE IMAGES; ASTEROID 4-VESTA AB Moderate spectral resolution observations of the 505-nm Fe2+ pyroxene feature in the reflectance spectrum of Vesta were acquired across the complete surface of the asteroid. The feature is consistently centered at 506.54 nm, suggesting an augite (high-calcium) composition. Variations in the equivalent width of the feature correlate with topographically high terrain on Vesta's surface, and could be due to the presence of another material (possibly olivine), or particle size variations, or both. (C) 1998 Academic Press. C1 Univ Texas, Austin, TX 78712 USA. NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. RP Cochran, AL (reprint author), Univ Texas, Austin, TX 78712 USA. EM anita@zinfandel.as.utexas.edu NR 9 TC 27 Z9 27 U1 0 U2 0 PU ACADEMIC PRESS INC PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA SN 0019-1035 J9 ICARUS JI Icarus PD AUG PY 1998 VL 134 IS 2 BP 207 EP 212 DI 10.1006/icar.1998.5952 PG 6 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 117AP UT WOS:000075757800002 ER PT J AU Ogilvie, KW Coplan, MA McFadden, LA AF Ogilvie, KW Coplan, MA McFadden, LA TI Sodium near the tail of comet Giacobini-Zinner SO ICARUS LA English DT Article DE abundances; atmospheres; comets; comets; composition; surfaces; comets ID ION COMPOSITION; P/GIACOBINI-ZINNER; ENCOUNTER; SOLAR AB In September 1985, the International Cometary Explorer (ICE) Spacecraft passed through the plasma tail of Comet Giacobini-Zinner at a distance of 7800 km downstream from the nucleus. The relative velocity between comet and spacecraft was 21 km/s, and instruments aboard the spacecraft made magnetic field, energetic particle, and ion composition measurements. The composition measurements showed the presence of water group and CO+ ions, as well as an appreciable, but localized flux of ions having M/Q = 24 +/- 1 adjacent to the edges of the plasma tail. These ions were tentatively identified by M. A. Coplan et al. (1987, J. Geophys. Res. 92, 39-46) as either C-2(+) or Na+. Motivated by recent observations of neutral sodium in the tail of Comet Hale-Bopp (G. Cremonese et al., 1997, Astrophys. J. Lett. 490, L199), the Giacobini-Zinner composition data have been reexamined, particularly with regard to the spatial distribution of the M/Q = 24 +/- 1 ions, now identified as Na+. This conclusion along with other observations of neutral sodium in comets clearly show that there are a variety of sources Of sodium in comets. (C) 1998 Academic Press. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Maryland, Inst Phys Sci & Technol, College Pk, MD 20742 USA. Univ Maryland, Dept Astron, College Pk, MD 20742 USA. RP Ogilvie, KW (reprint author), NASA, Goddard Space Flight Ctr, Code 690, Greenbelt, MD 20771 USA. RI McFadden, Lucy-Ann/I-4902-2013 OI McFadden, Lucy-Ann/0000-0002-0537-9975 NR 27 TC 5 Z9 5 U1 0 U2 0 PU ACADEMIC PRESS INC PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA SN 0019-1035 J9 ICARUS JI Icarus PD AUG PY 1998 VL 134 IS 2 BP 249 EP 252 DI 10.1006/icar.1998.5953 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 117AP UT WOS:000075757800006 ER PT J AU Chyba, CF Ostro, SJ Edwards, BC AF Chyba, CF Ostro, SJ Edwards, BC TI Radar detectability of a subsurface ocean on Europa SO ICARUS LA English DT Article ID RONNE ICE SHELF; GALILEAN SATELLITES; DIELECTRIC-PROPERTIES; JUPITER; ANTARCTICA; GANYMEDE; CALLISTO; TEMPERATURE; MICROWAVE; EVOLUTION AB A spacecraft in orbit around Jupiter's moon Europa can use ice penetrating radar to probe for a possible liquid water ocean beneath Europe's surface ice and to characterize other important subsurface structure. Consideration of available constraints on the properties of Europa's ice, possible subsurface temperature gradients, and possible impurities in the ice places an upper limit of about 10 km on the depth to which an ocean might be detectable with an orbiting radar. (C) 1998 Academic Press. C1 Univ Arizona, Lunar & Planetary Lab, Tucson, AZ 85721 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Los Alamos Natl Lab, Los Alamos, NM 87544 USA. RP Chyba, CF (reprint author), SETI Inst, 2035 Landings Dr, Mountain View, CA 94043 USA. EM chyba@lpl.arizona.edu NR 74 TC 63 Z9 63 U1 0 U2 9 PU ACADEMIC PRESS INC ELSEVIER SCIENCE PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA SN 0019-1035 J9 ICARUS JI Icarus PD AUG PY 1998 VL 134 IS 2 BP 292 EP 302 DI 10.1006/icar.1998.5961 PG 11 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 117AP UT WOS:000075757800010 ER PT J AU Duncan, MJ Lissauer, JJ AF Duncan, MJ Lissauer, JJ TI The effects of post-main-sequence solar mass loss on the stability of our planetary system SO ICARUS LA English DT Article DE stability; celestial mechanics; planetary orbits ID EVOLUTION; BEHAVIOR AB We present the results of extensive long-term integrations of systems of planets with orbits initially identical to subsets of the planets within our Solar System, but with the Sun's mass decreased relative to the masses of the planets, For systems based on the giant planets, we find an approximate power-law correlation between the time elapsed until a pair of planetary orbits cross and the solar-to-planetary-mass ratio, provided that this ratio is less than or similar to 0.4 times its current value, However, deviations from this relationship at larger ratios suggest that this correlation may not be useful in predicting the lifetime of the current system. Detailed simulations of the evolution of planetary orbits through the solar mass loss phase at the end of the Sun's main-sequence lifetime suggest that the orbits of those terrestrial planets that survive the Sun's red giant phase are likely to remain stable for (possibly much) longer than a billion years and those of the giant planets are likely to remain stable for (possibly much) more than ten billion years. Pluto is likely to escape from its current 2:3 mean-motion resonance with Neptune within a few billion years beyond the Sun's main sequence lifetime if subject only to gravitational forces; its prognosis is likely to be even poorer when nongravitational forces are included. Implications for the effects of stellar mass loss on the stability of other planetary systems are discussed. (C) 1998 Academic Press. C1 Queens Univ, Dept Phys, Kingston, ON K7L 3N6, Canada. NASA, Ames Res Ctr, Div Space Sci, Moffett Field, CA 94035 USA. SUNY Stony Brook, Astron Program, Stony Brook, NY 11794 USA. RP Duncan, MJ (reprint author), Queens Univ, Dept Phys, Kingston, ON K7L 3N6, Canada. NR 14 TC 98 Z9 98 U1 0 U2 0 PU ACADEMIC PRESS INC PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA SN 0019-1035 J9 ICARUS JI Icarus PD AUG PY 1998 VL 134 IS 2 BP 303 EP 310 DI 10.1006/icar.1998.5962 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 117AP UT WOS:000075757800011 ER PT J AU Rabinowitz, DL AF Rabinowitz, DL TI Size and orbit dependent trends in the reflectance colors of earth-approaching asteroids SO ICARUS LA English DT Article ID ORDINARY CHONDRITE METEORITES; PHOTOMETRIC STANDARD STARS; CELESTIAL EQUATOR; BELT; OBJECTS; COMETS AB New observations show that reflectance colors of Earth-approaching asteroids depend on their sizes and orbits. Most bodies larger than similar to 2 lan have reddish colors similar to common main-belt asteroids of spectral type S. Smaller bodies, and those that may have recently migrated from the main belt, have relatively neutral spectra in the 0.5- to 0.8-mu m wavelength range, These trends may result from the action of "space-weathering," recently proposed to explain similar spectral variations on the surfaces of S-type asteroids and the disparity between the colors of ordinary chondrite meteorites and their probable main-belt parents. (C) 1998 Academic Press. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Rabinowitz, DL (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. EM davidr@slam.jpl.nasa.gov NR 25 TC 27 Z9 27 U1 0 U2 0 PU ACADEMIC PRESS INC ELSEVIER SCIENCE PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA SN 0019-1035 J9 ICARUS JI Icarus PD AUG PY 1998 VL 134 IS 2 BP 342 EP 346 DI 10.1006/icar.1998.5951 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 117AP UT WOS:000075757800014 ER PT J AU Reddy, CJ Deshpande, MD Cockrell, CR Beck, FB AF Reddy, CJ Deshpande, MD Cockrell, CR Beck, FB TI Fast RCS computation over a frequency band using method of moments in conjunction with asymptotic waveform evaluation technique SO IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION LA English DT Article DE moment methods; radar cross sections ID PARAMETER-ESTIMATION; EFFICIENCY; INCREASE AB The method of moments (MoM) in conjunction with the asymptotic waveform evaluation (AWE) technique is applied to obtain the radar cross section (RCS) of an arbitrarily shaped three-dimensional (3-D) perfect electric conductor (PEC) body over a frequency band. The electric field integral equation (EFIE) is solved using MoM to obtain the equivalent surface current on the PEC body. In the AWE technique, the equivalent surface current is expanded in a Taylor's series around a frequency in the desired frequency band. The Taylor series coefficients are then matched via the Pade approximation to a rational function. Using the rational function, the surface current is obtained at any frequency within the frequency range, which is in turn used to calculate the RCS of the 3-D PEC body, A rational function approximation is also obtained using the model-based parameter estimation (MBPE) method and compared with the Pade approximation. Numerical results for a square plate, a cube, and a sphere are presented over a frequency bandwidth. Good agreement between the AWE and the exact solution over the bandwidth is observed. C1 Hampton Univ, Dept Elect Engn, Sch Engn & Technol, Hampton, VA 23668 USA. ViGYAN Inc, Hampton, VA 23666 USA. NASA, Langley Res Ctr, Hampton, VA 23681 USA. RP Reddy, CJ (reprint author), Hampton Univ, Dept Elect Engn, Sch Engn & Technol, Hampton, VA 23668 USA. NR 13 TC 78 Z9 100 U1 0 U2 3 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 0018-926X J9 IEEE T ANTENN PROPAG JI IEEE Trans. Antennas Propag. PD AUG PY 1998 VL 46 IS 8 BP 1229 EP 1233 DI 10.1109/8.718579 PG 5 WC Engineering, Electrical & Electronic; Telecommunications SC Engineering; Telecommunications GA 116JU UT WOS:000075721800014 ER PT J AU Tumer, K Ramanujam, N Ghosh, J Richards-Kortum, R AF Tumer, K Ramanujam, N Ghosh, J Richards-Kortum, R TI Ensembles of radial basis function networks for spectroscopic detection of cervical precancer SO IEEE TRANSACTIONS ON BIOMEDICAL ENGINEERING LA English DT Article DE cancer; fluorescence spectroscopy; multivariate statistical analysis; neural network ID LASER-INDUCED FLUORESCENCE; DIAGNOSIS; TISSUE AB The mortality related to cervical cancer can be substantially reduced through early detection and treatment. However, current detection techniques, such as Pap smear and colposcopy, fail to achieve a concurrently high sensitivity and specificity. lit vivo fluorescence spectroscopy is a technique which quickly, noninvasively and quantitatively probes the biochemical and morphological changes that occur in precancerous tissue. A multivariate statistical algorithm was used to extract clinically useful information from tissue spectra acquired from 361 cervical sites from 95 patients at 337-, 380-, and 460-nm excitation wavelengths, The multivariate statistical analysis was also employed to reduce the number of fluorescence excitation-emission wave-length pairs required to discriminate healthy tissue samples from precancerous tissue samples. The use of connectionist methods such as multilayered perceptrons, radial basis function (RBF) networks, and ensembles of such networks was investigated. RBF ensemble algorithms based on fluorescence spectra potentially provide automated and near real-time implementation of precancer detection in the hands of nonexperts. The results are more reliable, direct, and accurate than those achieved by either human experts or multivariate statistical algorithms. C1 Univ Texas, Biomed Engn Program, Austin, TX 78712 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Univ Penn, Sch Med, Johnson Res Fdn, Dept Biochem & Biophys, Philadelphia, PA 19104 USA. Univ Texas, Dept Elect & Comp Engn, Austin, TX 78712 USA. RP Richards-Kortum, R (reprint author), Univ Texas, Biomed Engn Program, Austin, TX 78712 USA. EM kortum@mail.utexas.edu RI Richards-Kortum, Rebecca/P-4074-2014 OI Richards-Kortum, Rebecca/0000-0003-2347-9467 NR 32 TC 51 Z9 52 U1 0 U2 0 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 0018-9294 J9 IEEE T BIO-MED ENG JI IEEE Trans. Biomed. Eng. PD AUG PY 1998 VL 45 IS 8 BP 953 EP 961 DI 10.1109/10.704864 PG 9 WC Engineering, Biomedical SC Engineering GA 104HH UT WOS:000075008300001 PM 9691570 ER PT J AU Shakeri, M Pattipati, KR Raghavan, V Patterson-Hine, A AF Shakeri, M Pattipati, KR Raghavan, V Patterson-Hine, A TI Optimal and near-optimal algorithms for multiple fault diagnosis with unreliable tests SO IEEE TRANSACTIONS ON SYSTEMS MAN AND CYBERNETICS PART C-APPLICATIONS AND REVIEWS LA English DT Article DE Lagrangian relaxation; M-best diagnoses; multiple fault diagnosis (MFD); NP-completeness; set covering ID SET-COVERING PROBLEMS; MODEL AB In this paper, we consider the problem of constructing optimal and near-optimal multiple fault diagnosis (MFD) in bipartite systems with unreliable (imperfect) tests, It is known that exact computation of conditional probabilities for MFD is NP-hard. The novel feature of our diagnostic algorithms is the use of Lagrangian relaxation and subgradient optimization methods to provide 1) near-optimal solutions for the MFD problem and 2) upper bounds for an optimal branch-and-bound algorithm. The proposed method is illustrated using several examples. Computational results indicate the following. 1) Our algorithm has superior computational performance to the existing algorithms (approximately three orders of magnitude improvement over the algorithm in [3]), 2) Near-optimal algorithm generates the most likely candidates with a very high accuracy. 3) Our algorithm can find the most likely candidates in systems,vith as many as 1000 faults. C1 Mathworks Inc, Natick, MA 01760 USA. Univ Connecticut, Dept Elect & Syst Engn, Storrs, CT 06269 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Shakeri, M (reprint author), Mathworks Inc, Natick, MA 01760 USA. NR 20 TC 30 Z9 41 U1 0 U2 2 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 1094-6977 J9 IEEE T SYST MAN CY C JI IEEE Trans. Syst. Man Cybern. Part C-Appl. Rev. PD AUG PY 1998 VL 28 IS 3 BP 431 EP 440 DI 10.1109/5326.704583 PG 10 WC Computer Science, Artificial Intelligence; Computer Science, Cybernetics; Computer Science, Interdisciplinary Applications SC Computer Science GA 104JF UT WOS:000075010400010 ER PT J AU Beratan, KK Anderson, R AF Beratan, KK Anderson, R TI The use of Landsat Thematic Mapper data for mapping and correlation of Quaternary geomorphic surfaces in the southern Whipple Mountains, California SO INTERNATIONAL JOURNAL OF REMOTE SENSING LA English DT Article ID EASTERN MOJAVE DESERT; WEST-CENTRAL ARIZONA; ROCK-VARNISH; SONORAN DESERT; MANGANESE; FUNGI; IDENTIFICATION; ACCUMULATION; EVOLUTION; MINERALS AB Alluvial geomorphic surfaces in the southern Whipple Mountains (south-eastern California) were mapped using Landsat Thematic Mapper (TM) data. Surfaces can readily be classified as young, intermediate or old in terms of stages of development. Spectral and textural information contained in these data are interpretable in terms of source rock composition, degree of desert pavement formation and drainage patterns, which are among the most important criteria used in field-based classification. Thus, classification and mapping of geomorphic surfaces based on image analysis is directly comparable to maps produced from field-based observations, potentially providing information about climate and neotectonics. C1 Univ Pittsburgh, Dept Geol & Planetary Sci, Pittsburgh, PA 15260 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Beratan, KK (reprint author), Univ Pittsburgh, Dept Geol & Planetary Sci, Pittsburgh, PA 15260 USA. NR 38 TC 7 Z9 7 U1 0 U2 2 PU TAYLOR & FRANCIS LTD PI LONDON PA ONE GUNPOWDER SQUARE, LONDON EC4A 3DE, ENGLAND SN 0143-1161 J9 INT J REMOTE SENS JI Int. J. Remote Sens. PD AUG PY 1998 VL 19 IS 12 BP 2345 EP 2359 DI 10.1080/014311698214767 PG 15 WC Remote Sensing; Imaging Science & Photographic Technology SC Remote Sensing; Imaging Science & Photographic Technology GA 112PK UT WOS:000075502900009 ER PT J AU Hause, T Librescu, L Camarda, CJ AF Hause, T Librescu, L Camarda, CJ TI Postbuckling of anisotropic flat and doubly-curved sandwich panels under complex loading conditions SO INTERNATIONAL JOURNAL OF SOLIDS AND STRUCTURES LA English DT Article ID GEOMETRIC IMPERFECTIONS; VIBRATION AB A study of the postbuckling behavior of geometrically imperfect anisotropic sandwich doubly-curved and flat panels subjected to a system of compressive edge loads and a lateral pressure is presented. The study is carried out in the context of the weak core sandwich shell model whose superior structural performance as compared to those of the strong core sandwich or standard laminated structures has resulted in its increased use in the design of advanced flight vehicles. A detailed investigation of the influence played by a number of kinematical and physical parameters as well as by the character of tangential boundary conditions on the load carrying capacity of sandwich structures is performed and pertinent conclusions are outlined. (C) 1998 Elsevier Science Ltd. All rights reserved. C1 Virginia Polytech Inst & State Univ, Dept Engn Sci & Mech, Blacksburg, VA 24061 USA. NASA, Langley Res Ctr, Hampton, VA 23681 USA. RP Librescu, L (reprint author), Virginia Polytech Inst & State Univ, Dept Engn Sci & Mech, Blacksburg, VA 24061 USA. NR 16 TC 26 Z9 26 U1 0 U2 2 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0020-7683 J9 INT J SOLIDS STRUCT JI Int. J. Solids Struct. PD AUG PY 1998 VL 35 IS 23 BP 3007 EP 3027 DI 10.1016/S0020-7683(97)00360-0 PG 21 WC Mechanics SC Mechanics GA ZR785 UT WOS:000074013500001 ER PT J AU Poosanaas, P Dogan, A Thakoor, S Uchino, K AF Poosanaas, P Dogan, A Thakoor, S Uchino, K TI Influence of sample thickness on the performance of photostrictive ceramics SO JOURNAL OF APPLIED PHYSICS LA English DT Article AB Ferroelectric materials with high photovoltaic properties are of interest for new optical devices such as photostrictive ceramic actuators. However, fabrication of these devices requires development of materials exhibiting high photovoltage and photocurrent. In pursuit of these high performance photostrictive materials, the present research examines the influence of illumination intensity, degree of polarization, and sample thickness on the photostrictive response of WO3 doped lanthanum-modified lead zirconate titanate (Pb, La)(Zr, Ti)O-3 ceramics prepared by oxide mixing process. A model for calculating the optimum sample thickness for maximum photostrictive response is proposed. This model agrees well with experimental results, and should be useful in designing photostrictive devices. (C) 1998 American Institute of Physics. [S0021-8979(98)02215-4]. C1 Penn State Univ, Mat Res Lab, Int Ctr Actuators & Transducers, University Pk, PA 16802 USA. Anadolu Univ, Dept Ceram Engn, Eskisehir, Turkey. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Poosanaas, P (reprint author), Penn State Univ, Mat Res Lab, Int Ctr Actuators & Transducers, University Pk, PA 16802 USA. NR 12 TC 59 Z9 60 U1 2 U2 31 PU AMER INST PHYSICS PI WOODBURY PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 USA SN 0021-8979 J9 J APPL PHYS JI J. Appl. Phys. PD AUG 1 PY 1998 VL 84 IS 3 BP 1508 EP 1512 DI 10.1063/1.368216 PG 5 WC Physics, Applied SC Physics GA 108YT UT WOS:000075294600059 ER PT J AU Clarke, MSF Bamman, MM Feeback, DL AF Clarke, MSF Bamman, MM Feeback, DL TI Bed rest decreases mechanically induced myofiber wounding and consequent wound-mediated FGF release SO JOURNAL OF APPLIED PHYSIOLOGY LA English DT Article DE human; skeletal muscle; atrophy; sarcolemma; mechanical ID FIBROBLAST GROWTH-FACTOR; SKELETAL-MUSCLE ATROPHY; HEAVY-CHAIN ISOFORMS; RAT SOLEUS MUSCLE; PLASMA-MEMBRANES; NERVOUS-SYSTEM; CELLS; IMMOBILIZATION; SPACEFLIGHT; EXERCISE AB Using a terrestrial model of spaceflight (i.e., bed rest), we investigated the amount of myofiber wounding and fibroblast growth factor (FGF) release that occurs during unloading. Myofiber wounding was determined by serum levels of the creatine kinase MM (CKMM) isoform before and after bed rest. Serum levels of both acidic FGF (aFGF) and basic FGF were also determined. A second group of subjects was treated in an identical fashion except that they underwent a resistive exercise program during bed rest. Bed rest alone caused significant (P < 0.05; n. = 7) reductions in post-bed-rest serum levels of both CKMM and aFGF, which were paralleled by a significant (P < 0.05; n = 7) decrease in myofiber size. In contrast, bed rest plus resistive exercise resulted in significant (P < 0.05; n = 7) increases in post-bed-rest serum levels of both CKMM and aFGF, which were paralleled by inhibition of the atrophic response. These results suggest that mechanically induced, myofiber wound-mediated FGF release may play an important role in the etiology of unloading-induced skeletal muscle atrophy. C1 Univ Space Res Assoc, Div Space Life Sci, Houston, TX 77058 USA. NASA, Lyndon B Johnson Space Ctr, Life Sci Res Labs, Houston, TX 77058 USA. Univ Alabama, Dept Human Studies, Birmingham, AL 35294 USA. RP Clarke, MSF (reprint author), Univ Space Res Assoc, Div Space Life Sci, 3600 Bay Area Blvd, Houston, TX 77058 USA. NR 62 TC 10 Z9 11 U1 0 U2 1 PU AMER PHYSIOLOGICAL SOC PI BETHESDA PA 9650 ROCKVILLE PIKE, BETHESDA, MD 20814 USA SN 8750-7587 J9 J APPL PHYSIOL JI J. Appl. Physiol. PD AUG PY 1998 VL 85 IS 2 BP 593 EP 600 PG 8 WC Physiology; Sport Sciences SC Physiology; Sport Sciences GA 114CV UT WOS:000075592300030 PM 9688737 ER PT J AU Mack, GW Yang, R Hargens, AR Nagashima, K Haskell, A AF Mack, GW Yang, R Hargens, AR Nagashima, K Haskell, A TI Influence of hydrostatic pressure gradients on regulation of plasma volume after exercise SO JOURNAL OF APPLIED PHYSIOLOGY LA English DT Article DE colloid osmotic pressure; capillary exchange; fluid shift ID ATRIAL-NATRIURETIC-PEPTIDE; TRAINING-INDUCED HYPERVOLEMIA; CAPILLARY PRESSURES; GRADED-EXERCISE; SKELETAL-MUSCLE; BLOOD-VOLUME; ALBUMIN; HUMANS; VASOPRESSIN; EXPANSION AB The impact of posture on the immediate recovery of intravascular fluid and protein after intense exercise was determined in 14 volunteers. Forces which govern fluid and protein movement in muscle interstitial fluid pressure (P-ISF), interstitial colloid osmotic pressure (COPi), and plasma colloid osmotic pressure (COPi) were measured before and after exercise in the supine or upright position. During exercise, plasma volume (PV) decreased by 5.7 +/- 0.7 and 7.0 +/- 0.5 ml/kg body weight in the supine and upright posture, respectively. During recovery, PV returned to its baseline value within 30 min regardless of posture. PV fell below this level by 60 and 120 min in the supine and upright posture, respectively (P < 0.05). Maintenance of PV in the upright position was associated with a decrease in systolic blood pressure, an increase in COPp (from 25 +/- 1 to 27 +/- 1 mmHg; P < 0.05), and an increase in P-ISF (from 5 +/- 1 to 6 +/-: 2 mmHg), whereas COPi was unchanged. Increased PISF indicates that the hydrostatic pressure gradient favors fluid movement into the vascular space. However, retention of the recaptured fluid in the plasma is promoted only in the upright posture because of increased COPi. C1 Yale Univ, Sch Med, John B Pierce Fdn Lab, New Haven, CT 06519 USA. Yale Univ, Sch Med, Dept Epidemiol & Publ Hlth, New Haven, CT 06519 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Mack, GW (reprint author), Yale Univ, Sch Med, John B Pierce Fdn Lab, 290 Congress Ave, New Haven, CT 06519 USA. FU NHLBI NIH HHS [HL-20634, HL-39818] NR 24 TC 22 Z9 22 U1 0 U2 2 PU AMER PHYSIOLOGICAL SOC PI BETHESDA PA 9650 ROCKVILLE PIKE, BETHESDA, MD 20814 USA SN 8750-7587 J9 J APPL PHYSIOL JI J. Appl. Physiol. PD AUG PY 1998 VL 85 IS 2 BP 667 EP 675 PG 9 WC Physiology; Sport Sciences SC Physiology; Sport Sciences GA 114CV UT WOS:000075592300038 PM 9688745 ER PT J AU Hooker, SB Aiken, J AF Hooker, SB Aiken, J TI Calibration evaluation and radiometric testing of field radiometers with the SeaWiFS Quality Monitor (SQM) SO JOURNAL OF ATMOSPHERIC AND OCEANIC TECHNOLOGY LA English DT Article ID OCEAN AB One of the goals of calibration and validation programs supporting ocean color satellites is to produce water-leaving radiances with an uncertainty of 5% in clear-water regions. This objective requires field instruments with a calibration and measurement capability that is on the order of 1%. The Sea-viewing Wide Field-of-view Sensor (SeaWiFS) Project, in collaboration with the National Institute of Standards and Technology, has developed a portable illumination source with three temperature-stabilized internal monitors designed to provide a stable light field for checking the optical stability of radiometers used to measure the in situ optical properties of seawater. This device is called the SeaWiFS Quality Monitor (SQM). A recent field evaluation during an extensive research cruise indicates the SQM has the following capabilities: (a) the SQM can be used to track the stability of field radiometers at less than the 1% level in terms of the radiometric response of the instruments-on average 0.30% (+/-0.15%) for radiance sensors and 0.58% (+/-0.20%) for irradiance sensors: (b) the SQM light field is sufficiently stable to allow for a sensitive measure and, thus, modeling of changes in the radiometric detectors; (cf based on the radiometers used during the field evaluation, daily SQM measurements are needed to resolve the temporal changes in the response of the sensors; and (d) SQM performance, in terms of the generated light field and the SQM internal monitors, is very stable and decayed only by approximately 0.60% during the course of the 36-day deployment with most of the decay attributed to a change in the operating voltage of one of the lamps. C1 NASA, Goddard Space Flight Ctr, Lab Hydrospher Proc, Greenbelt, MD 20771 USA. Plymouth Marine Lab, Plymouth, Devon, England. RP Hooker, SB (reprint author), NASA, Goddard Space Flight Ctr, Lab Hydrospher Proc, Greenbelt, MD 20771 USA. RI Hooker, Stanford/E-2162-2012 NR 10 TC 16 Z9 16 U1 0 U2 2 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 USA SN 0739-0572 J9 J ATMOS OCEAN TECH JI J. Atmos. Ocean. Technol. PD AUG PY 1998 VL 15 IS 4 BP 995 EP 1007 DI 10.1175/1520-0426(1998)015<0995:CEARTO>2.0.CO;2 PG 13 WC Engineering, Ocean; Meteorology & Atmospheric Sciences SC Engineering; Meteorology & Atmospheric Sciences GA 107WK UT WOS:000075233800012 ER PT J AU Johnson, BC Shaw, PS Hooker, SB Lynch, D AF Johnson, BC Shaw, PS Hooker, SB Lynch, D TI Radiometric and engineering performance of the SeaWiFS Quality Monitor (SQM): A portable light source for field radiometers SO JOURNAL OF ATMOSPHERIC AND OCEANIC TECHNOLOGY LA English DT Article ID STANDARD LAMPS AB A portable and stable source of radiant flux, the Sea-viewing Wide Field-of-view Sensor (SeaWiFS) Quality Monitor (SQM), was developed as a field instrument for use in experiments away from the calibration laboratory such as those encountered during oceanographic cruises. The SQM monitors the radiometric stability of radiance and irradiance sensors during these field experiments; a companion paper gives results acquired during the third Atlantic Meridional Transect cruise. In conjunction with laboratory calibration sources, the SQM can be used to transfer the calibration to the field experiment. Two independent lamp assemblies generate three flux levels, and me lamps are operated at constant current using active control. The exit aperture of the SQM is large and homogeneous in radiance. The SQM was designed to approximate a Lambertian radiator. An internal heater provides operational stability and decreased warmup intervals, which minimizes lamp hours. Temperature-controlled silicon photodiodes with colored-glass filters monitor the stability of the SQM, which is better than 1%. These independent monitors, which are integrated with the SQM, provide information on the Aux from the SQM and can be used to normalize the output from the field radiometers during the experiment. Three reference devices, or fiducials, which are designed to mimic the optical surfaces of the held radiometers but are not functioning detector units, are used in place of the field radiometers to produce baseline monitor signals. The front surface of the fiducial is protected when not in use and kept clean during the field experiment. The monitor signals acquired using the fiducials provide additional information on the radiometric stability of the SQM. A kinematically designed mounting ring is used on both the field radiometers and the fiducials to ensure the devices being tested view the same part of the exit aperture each time they are used. C1 NIST, Opt Technol Div, Gaithersburg, MD 20899 USA. NASA, Goddard Space Flight Ctr, Lab Hydrospher Proc, Greenbelt, MD 20771 USA. Reyer Corp, New Market, MD USA. RP Johnson, BC (reprint author), NIST, Opt Technol Div, Bldg 221,Rm B208, Gaithersburg, MD 20899 USA. RI Hooker, Stanford/E-2162-2012 NR 12 TC 11 Z9 11 U1 0 U2 1 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 USA SN 0739-0572 J9 J ATMOS OCEAN TECH JI J. Atmos. Ocean. Technol. PD AUG PY 1998 VL 15 IS 4 BP 1008 EP 1022 DI 10.1175/1520-0426(1998)015<1008:RAEPOT>2.0.CO;2 PG 15 WC Engineering, Ocean; Meteorology & Atmospheric Sciences SC Engineering; Meteorology & Atmospheric Sciences GA 107WK UT WOS:000075233800013 ER PT J AU Clothiaux, EE Mace, GG Ackerman, TP Kane, TJ Spinhirne, JD Scott, VS AF Clothiaux, EE Mace, GG Ackerman, TP Kane, TJ Spinhirne, JD Scott, VS TI An automated algorithm for detection of hydrometeor returns in micropulse lidar data SO JOURNAL OF ATMOSPHERIC AND OCEANIC TECHNOLOGY LA English DT Article ID CLOUD; RADAR AB A cloud detection algorithm for a low power micropulse lidar is presented that attempts to identify all of the significant power returns from the vertical column above the lidar at all times, The main feature of the algorithm is construction of lidar power return profiles during periods of clear sky against which cloudy-sky power returns are compared. This algorithm supplements algorithms designed to detect cloud-base height in that the tops of optically thin clouds are identified and it provides an alternative approach to algorithms that identify significant power returns by analysis of changes in the slope of the backscattered powers with height. The cloud-base heights produced by the current algorithm during nonprecipitating periods are comparable with the results of a cloud-base height algorithm applied to the same data. Although an objective validation of algorithm performance on high, thin cirrus is lacking because of no truth data, the current algorithm produces few false positive and false negative classifications as determined through manual comparison of the original photoelectron count data to the final cloud mask image. C1 Penn State Univ, Dept Meteorol, University Pk, PA 16802 USA. Penn State Univ, Dept Elect Engn, University Pk, PA 16802 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Clothiaux, EE (reprint author), Penn State Univ, Dept Meteorol, 503 Walker Bldg, University Pk, PA 16802 USA. RI Scott, Vibart/B-5086-2013 NR 10 TC 34 Z9 34 U1 1 U2 4 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 USA SN 0739-0572 J9 J ATMOS OCEAN TECH JI J. Atmos. Ocean. Technol. PD AUG PY 1998 VL 15 IS 4 BP 1035 EP 1042 DI 10.1175/1520-0426(1998)015<1035:AAAFDO>2.0.CO;2 PG 8 WC Engineering, Ocean; Meteorology & Atmospheric Sciences SC Engineering; Meteorology & Atmospheric Sciences GA 107WK UT WOS:000075233800015 ER PT J AU Ye, B Del Genio, AD Lo, KKW AF Ye, B Del Genio, AD Lo, KKW TI CAPE variations in the current climate and in a climate change SO JOURNAL OF CLIMATE LA English DT Article ID TROPICAL ATMOSPHERE; BOUNDARY-LAYER; OCEAN; SURFACE; MODELS; CLOUDS; ENVIRONMENT; EQUILIBRIUM; SENSITIVITY; TEMPERATURE AB Observed variations of convective available potential energy (CAPE) in the current climate provide one useful rest of the performance of cumulus parameterizations used in general circulation models (GCMs). It is found that frequency distributions of tropical Pacific CAFE, as well as the dependence of CAFE on surface wet-bulb potential temperature (Theta(w)) simulated by the Goddard Institute for Space Studies's GCM, agree well with that observed during the Australian Monsoon Experiment period, CAFE variability in the current climate greatly overestimates climatic changes in basinwide CAFE in the tropical Pacific in response to a 2 degrees C increase in sea surface temperature (SST) in the GCM because of the different physics involved. In the current climate, CAFE variations in space and time are dominated by regional changes in boundary layer temperature and moisture, which in turn are controlled by SST patterns and large-scale motions. Geographical thermodynamic structure variations in the middle and upper troposphere are smaller because of the canceling effects of adiabatic cooling and subsidence warming in the rising and sinking branches of the Walker and Hadley circulations. In a forced equilibrium global climate change, temperature change is fairly well constrained by the change in the moist adiabatic lapse rate and thus the upper troposphere warms to a greater extent than the surface. For this reason, climate change in CAFE is better predicted by assuming that relative humidity remains constant and that the temperature changes according to the moist adiabatic lapse rate change of a parcel with 80% relative humidity lifted from the surface. The moist adiabatic assumption is not symmetrically applicable to a warmer and colder climate: In a warmer regime moist convection determines the tropical temperature structure, but when the climate becomes colder the effect of moist convection diminishes and the large-scale dynamics and radiative processes become relatively important. Although a prediction based on the change in moist adiabat marches the GCM simulation of climate change averaged over the tropical Pacific basin, it does not match the simulation regionally because small changes in the general circulation change the local boundary layer relative humidity by 1%-2%. Thus, the prediction of regional climate change in CAFE is also dependent on subtle changes in the dynamics. C1 Columbia Univ, Dept Earth & Environm Sci, New York, NY 10025 USA. NASA, Goddard Inst Space Studies, New York, NY 10025 USA. Sci Syst & Applicat Inc, New York, NY USA. RP Ye, B (reprint author), Columbia Univ, Dept Earth & Environm Sci, 2880 Broadway, New York, NY 10025 USA. RI Del Genio, Anthony/D-4663-2012 OI Del Genio, Anthony/0000-0001-7450-1359 NR 37 TC 32 Z9 36 U1 0 U2 7 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 USA SN 0894-8755 J9 J CLIMATE JI J. Clim. PD AUG PY 1998 VL 11 IS 8 BP 1997 EP 2015 DI 10.1175/1520-0442-11.8.1997 PG 19 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 111CT UT WOS:000075420300010 ER PT J AU Christy, JR Spencer, RW Lobl, ES AF Christy, JR Spencer, RW Lobl, ES TI Analysis of the merging procedure for the MSU daily temperature time series SO JOURNAL OF CLIMATE LA English DT Article ID AIR-TEMPERATURE; RADIOSONDE VALIDATION; SURFACE-TEMPERATURE; SATELLITE; TRENDS; PRECISION; VARIABILITY; ANOMALIES; PACIFIC; LAYER AB The merging procedure utilized to generate homogeneous time series of three deep-layer atmospheric temperature products from the nine microwave sounding units (MSUs) is described. A critically important aspect in the process is determining and removing the bias each instrument possesses relative to a common base (here being NOAA-6). Special attention is given to the lower-tropospheric layer and the calculation of the bias of the NOAA-9 MSU and its rather considerable impact on the trend of the overall time series. We show that the bias is best calculated by a direct comparison between NOAA-6 and NOAA-9, though there other possible methods available, and is determined to be +0.50 degrees C. Spurious variations of individual MSUs due to orbital drift and/or cyclic variations tied to the annual cycle are also identified and eliminated. In general, intersatellite biases for the three instruments that form the backbone of the time series (MSUs on NOAA-6, -10 and -12) are known to within 0.01 degrees C. After slight modifications in the treatment of the bias, drift-error, and cyclic fluctuations, the authors produced a time series in which the decadal trend is +0.03 degrees C warmer than previously reported for the lower troposphere. Because they are of much higher precision, the midtropospheric and lower-stratospheric products are only slightly affected by alterations to procedures applied in this study. Recent suggestions that spurious jumps were present in the lower-tropospheric time series of earlier versions of the MSU data based on SST comparisons are addressed. Using independent comparisons of different satellites, radiosondes, and night marine air temperatures, no indication is found of the presence of these "spurious" jumps. C1 Univ Alabama, ESSL, GHCC, Huntsville, AL 35899 USA. NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. Univ Alabama, ESSL, GHCC, Huntsville, AL 35899 USA. RP Christy, JR (reprint author), Univ Alabama, ESSL, GHCC, Huntsville, AL 35899 USA. NR 28 TC 106 Z9 109 U1 0 U2 5 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 USA SN 0894-8755 J9 J CLIMATE JI J. Clim. PD AUG PY 1998 VL 11 IS 8 BP 2016 EP 2041 DI 10.1175/1520-0442-11.8.2016 PG 26 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 111CT UT WOS:000075420300011 ER PT J AU Palosz, W AF Palosz, W TI Diffusive gas losses from silica glass ampoules at elevated temperatures SO JOURNAL OF CRYSTAL GROWTH LA English DT Article ID VITREOUS SILICA; HYDROGEN AB Changes in the pressure of hydrogen, helium and neon due to diffusion through the wall of silica crystal growth ampoules at elevated temperatures were determined experimentally. We show that, while both He- and Ne-losses closely follow the conventional model of diffusive gas permeation through the wall, hydrogen losses, particularly at low fill pressures, can be much larger. This is interpreted in terms of the high solubility of hydrogen in silica glasses. (C) 1998 Elsevier Science B.V. All rights reserved. C1 NASA, George C Marshall Space Flight Ctr, Univ Space Res Assoc, Space Sci Lab, Huntsville, AL 35812 USA. RP Palosz, W (reprint author), NASA, George C Marshall Space Flight Ctr, Univ Space Res Assoc, Space Sci Lab, ES75, Huntsville, AL 35812 USA. EM witold.palosz@msfc.nasa.gov NR 20 TC 6 Z9 6 U1 0 U2 0 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0022-0248 J9 J CRYST GROWTH JI J. Cryst. Growth PD AUG PY 1998 VL 191 IS 4 BP 897 EP 903 DI 10.1016/S0022-0248(98)00251-6 PG 7 WC Crystallography; Materials Science, Multidisciplinary; Physics, Applied SC Crystallography; Materials Science; Physics GA 115WE UT WOS:000075688600040 ER PT J AU Ipavich, FM Galvin, AB Lasley, SE Paquette, JA Hefti, S Reiche, KU Coplan, MA Gloeckler, G Bochsler, P Hovestadt, D Grunwaldt, H Hilchenbach, M Gliem, F Axford, WI Balsiger, H Burgi, A Geiss, J Hsieh, KC Kallenbach, R Klecker, B Lee, MA Managadze, GG Marsch, E Mobius, E Neugebauer, M Scholer, M Verigin, MI Wilken, B Wurz, P AF Ipavich, FM Galvin, AB Lasley, SE Paquette, JA Hefti, S Reiche, KU Coplan, MA Gloeckler, G Bochsler, P Hovestadt, D Grunwaldt, H Hilchenbach, M Gliem, F Axford, WI Balsiger, H Burgi, A Geiss, J Hsieh, KC Kallenbach, R Klecker, B Lee, MA Managadze, GG Marsch, E Mobius, E Neugebauer, M Scholer, M Verigin, MI Wilken, B Wurz, P TI Solar wind measurements with SOHO: The CELIAS/MTOF proton monitor SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID CHARGE; SYSTEM AB The proton monitor, a small subsensor in the Charge, Element, and Isotope Analysis System/Mass Time-of-Flight (CELIAS/MTOF) experiment on the SOHO spacecraft, was designed to assist in the interpretation of measurements from the high mass resolution main MTOF sensor. In this paper we demonstrate that the proton monitor data may be used to generate reasonably accurate values of the solar wind proton bulk speed, density, thermal speed, and north/south flow direction, Correlation coefficients based on comparison with the solar wind measurements from the SWE instrument on the Wind spacecraft range from 0.87 to 0.99. On the basis of the initial 12 months of observations, we find that the proton momentum flux is almost invariant with respect to the bulk speed, confirming a previously published result. We present observations of two interplanetary shock events, and of an unusual solar wind density depletion. This large density depletion, and the correspondingly large drop in the solar wind ram pressure, may have been the cause of a nearly simultaneous large increase in the flux of relativistic magnetospheric electrons observed at geosynchronous altitudes by the GOES 9 spacecraft. Extending our data set with a 10-year time span from the OMNIWeb data set, we find an average frequency of about one large density depletion per year; The origin of these events is unclear; of the 10 events identified, 3 appear to be corotating and at least 2 are probably CME related. The rapidly available, comprehensive data coverage from SOHO allows the production of near-real time solar wind parameters that are now accessible on the World Wide Web. C1 Univ Maryland, Dept Phys, College Pk, MD 20742 USA. Univ Bern, Inst Phys, CH-3012 Bern, Switzerland. Tech Univ Braunschweig, Inst Datenverarbeitungsanlagen, D-38023 Braunschweig, Germany. Max Planck Inst Extraterr Phys, D-85470 Garching, Germany. Max Planck Inst Aeron, D-37189 Katlenburg Lindau, Germany. Univ Arizona, Dept Phys, Tucson, AZ 85721 USA. Univ New Hampshire, EOS, Durham, NH 03824 USA. Moscow Space Res Inst, Moscow 117810, Russia. CALTECH, Jet Prop Lab, Pasadena, CA 91103 USA. RP Ipavich, FM (reprint author), Univ Maryland, Dept Phys, College Pk, MD 20742 USA. EM ipavich@umtof.umd.edu; bochsler@soho.unibe.ch; gruenwaldt@linax1.dnet.gwdg.de; gliem@ida.ing.tu-bs.de; hsieh@soliton.physics.arizona.edu; bek@mpens.mpe-garching.mpg.de; gmanagad@esoc.bitnet; mneugeb@jplsp.jpl.nasa.gov RI Galvin, Antoinette/A-6114-2013 NR 11 TC 47 Z9 47 U1 0 U2 2 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA J9 J GEOPHYS RES-SPACE JI J. Geophys. Res-Space Phys. PD AUG 1 PY 1998 VL 103 IS A8 BP 17205 EP 17213 DI 10.1029/97JA02770 PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 107BV UT WOS:000075186700001 ER PT J AU Aellig, MR Grunwaldt, H Bochsler, P Wurz, P Hefti, S Kallenbach, R Ipavich, FM Axford, WI Balsiger, I Burgi, A Coplan, MA Galvin, AB Geiss, J Gliem, F Gloeckler, G Hilchenbach, M Hovestadt, D Hsieh, EC Klecker, B Lee, MA Livi, S Managadze, GG Marsch, E Mobius, E Neugebauer, M Reiche, KU Scholer, M Verigin, MI Wilken, B AF Aellig, MR Grunwaldt, H Bochsler, P Wurz, P Hefti, S Kallenbach, R Ipavich, FM Axford, WI Balsiger, I Burgi, A Coplan, MA Galvin, AB Geiss, J Gliem, F Gloeckler, G Hilchenbach, M Hovestadt, D Hsieh, EC Klecker, B Lee, MA Livi, S Managadze, GG Marsch, E Mobius, E Neugebauer, M Reiche, KU Scholer, M Verigin, MI Wilken, B TI Iron freeze-in temperatures measured by SOHO/CELIAS/CTOF SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID SOLAR-WIND; IONIZATION; ULYSSES; CHARGE; SWICS; HOLE AB The CELIAS particle experiment on SOHO contains the Charge Time Of Flight (CTOF) mass spectrometer which measures the ionic and elemental composition of minor ions in the solar wind. In this paper we present iron freeze-in temperatures derived with a time resolution of 5 min. They indicate that some of the filamentary structures of the inner corona observed in Ha! survive in the interplanetary medium as far as 1 AU. C1 Univ Bern, Inst Phys, CH-3012 Bern, Switzerland. Max Planck Inst Aeron, D-37189 Lindau, Germany. Max Planck Inst Extraterr Phys, D-85740 Garching, Germany. Univ Maryland, Dept Phys & Astron, College Pk, MD 20742 USA. Univ Maryland, IPST, College Pk, MD 20742 USA. Univ Arizona, Dept Phys, Tucson, AZ 85721 USA. Univ New Hampshire, Inst Study Earth Oceans & Space, Durham, NH 03824 USA. Russian Acad Sci, Inst Space Res, Moscow V71, Russia. CALTECH, Jet Prop Lab, Pasadena, CA 91103 USA. RP Aellig, MR (reprint author), Univ Bern, Inst Phys, Sidlerstr 5, CH-3012 Bern, Switzerland. RI Galvin, Antoinette/A-6114-2013 NR 12 TC 25 Z9 25 U1 0 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA J9 J GEOPHYS RES-SPACE JI J. Geophys. Res-Space Phys. PD AUG 1 PY 1998 VL 103 IS A8 BP 17215 EP 17222 DI 10.1029/98JA00588 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 107BV UT WOS:000075186700002 ER PT J AU Sanderson, TR Lin, RP Larson, DE McCarthy, MP Parks, GK Bosqued, JM Lormant, N Ogilvie, K Lepping, RP Szabo, A Lazarus, AJ Steinberg, JT Hoeksema, JT AF Sanderson, TR Lin, RP Larson, DE McCarthy, MP Parks, GK Bosqued, JM Lormant, N Ogilvie, K Lepping, RP Szabo, A Lazarus, AJ Steinberg, JT Hoeksema, JT TI Wind observations of the influence of the Sun's magnetic field on the interplanetary medium at 1 AU SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID HELIOSPHERIC CURRENT SHEET; PLASMA; SPACECRAFT; CYCLE AB We combine data from several instruments on the Wind spacecraft with ground-based observations of the position of the heliospheric current sheet for the first 2.5 years of the mission, which covers the period from the end of solar cycle 22, through solar minimum, and into the start of cycle 23. We use data from the three-dimensional (3-D) plasma instrument (3DP), magnetometer (MFI), and Solar Wind Experiment (SWE). We examine the energetic ion and electron increases associated with corotating interaction regions (CIR) and relate them to the position and shape of the current sheet. The characteristics of the energetic particle increases associated with the observed CIRs change several times during the mission. We identify these periods and find that we can relate these particle signatures of the CIRs to the plasma conditions which themselves depend upon the changing tilt and warp of the current sheet. We examine the additional increases associated with magnetic clouds and impulsive solar flares that were observed at irregular intervals during the mission. We show how the Sun's magnetic field influences the interplanetary medium at 1 AU, as variations in the shape and inclination of the source surface current sheet propagate out to 1 AU. We identify the three major sources of these variations, (1) the long-term, slowly varying tilt of the current sheet with a timescale of the solar cycle, (2) the medium-term small but significant annual movement of the position of the Earth relative to the current sheet due to the inclination of the plane of the ecliptic with respect to the heliographic equator, and (3) the short-term warps and bulges which come and go due to the appearance of active regions, lasting only a few solar rotations. C1 European Space Agcy, European Space Res & Technol Ctr, Dept Space Sci, NL-2220 AG Noordwijk, Netherlands. CNRS, Ctr Etud Spatiale Rayonnements, F-31029 Toulouse, France. Stanford Univ, Ctr Space Sci & Astrophys, Stanford, CA 94305 USA. Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA. Univ Washington, Dept Geophys, Seattle, WA 98195 USA. NASA, Goddard Space Flight Ctr, Extraterr Phys Lab, Greenbelt, MD 20771 USA. MIT, Ctr Space Res, Cambridge, MA 02139 USA. RP Sanderson, TR (reprint author), European Space Agcy, European Space Res & Technol Ctr, Dept Space Sci, Keplerlaan 1,Postbus 299, NL-2220 AG Noordwijk, Netherlands. EM tsanders@estec.esa.nl; boblin@ssl.berkelet.edu; davin@sunspot.ssl.berkeley.edu; mmccarthy@geophys.washington.edu; parks@geophys.washington.edu; jean-michel.bosqued@cesr.cnes.fr; nicolas.lormant@cesr.cnes.fr; kwo@lep692.gsfc.nasa.gov; rpl@leprp11.gsfc.nasa.gov; asz@lepas2.gsfc.nasa.gov; ajl@space.mit.edu; jts@space.mit.edu; thoeksema@solar.stanford.edu NR 22 TC 18 Z9 18 U1 1 U2 2 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA J9 J GEOPHYS RES-SPACE JI J. Geophys. Res-Space Phys. PD AUG 1 PY 1998 VL 103 IS A8 BP 17235 EP 17247 DI 10.1029/97JA02884 PG 13 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 107BV UT WOS:000075186700004 ER PT J AU Janoo, L Farrugia, CJ Torbert, RB Quinn, JM Szabo, A Lepping, RP Ogilvie, KW Lin, RP Larson, D Scudder, JD Osherovich, VA Steinberg, JT AF Janoo, L Farrugia, CJ Torbert, RB Quinn, JM Szabo, A Lepping, RP Ogilvie, KW Lin, RP Larson, D Scudder, JD Osherovich, VA Steinberg, JT TI Field and flow perturbations in the October 18-19, 1995, magnetic cloud SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID EARTHS MAGNETOPAUSE; WIND SPACECRAFT; SOLAR-WIND; DISCONTINUITIES; RECONNECTION; PLASMA AB We examine magnetic field and plasma perturbations in the October 18-19, 1995, magnetic cloud. Besides the front boundary, the 3-s-averaged magnetic field measurements made by the Magnetic Field Investigation on the Global Geospace Mission spacecraft Wind reveal a further 15 clear magnetic field directional discontinuities (DDs) with field rotations >15 degrees, each lasting for similar to 1 min. A number of these DDs are clustered near the trailing edge of the cloud. Using 3-s resolution proton data from the Three Dimensional Plasma and Energetic Particle Experiment on Wind, we find that these DDs are accompanied by perturbations in the flow. We find that except for the front boundary, which is a clear tangential discontinuity, all the others are rotational. Across the DDs the bulk flow speed is sometimes enhanced and sometimes depressed. Changes in proton temperature across the DDs suggest a more elaborate structure, for example, a reconnection layer. In a search for large-scale regularities, we apply minimum variance analysis to determine the normals to contiguous 1-hour-long stretches of the cloud data and find that there are large-scale structures ordering the field and the how for the first 21 hour of cloud data. Thus we identify three coherent segments of several hours' duration each with a well-defined normal, but the normals to the individual segments are very different from each other. In particular, one segment in the cloud B-z < 0 phase is almost orthogonal to another segment in the B-z > 0 phase. The normals to the DDs within a given segment are closely aligned with the normal to that segment. For the last 6 hours of cloud data, no coherent structure was found since no reliable normals could be determined, Studying flow anisotropies of electrons in the energy range 0.1 - 100 keV and changes in intensity in the >1 keV electrons, Larson et al. [1997] inferred several instances of disconnection of cloud field lines from the Sun, which were attributed to reconnection between adjacent bundles of cloud field lines. Our results are supportive of this interpretation. Furthermore, our results suggest the presence of detailed substructure in, and/or large distortions of, the magnetic cloud which reached 1 AU on October 18-19, 1995. C1 Univ New Hampshire, Inst Study Earth Oceans & Space, Durham, NH 03824 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA. Univ Iowa, Dept Phys & Astron, Iowa City, IA 52240 USA. MIT, Ctr Space Res, Cambridge, MA 02139 USA. RP Janoo, L (reprint author), Univ New Hampshire, Inst Study Earth Oceans & Space, Durham, NH 03824 USA. RI Scudder, Jack/D-8417-2013 OI Scudder, Jack/0000-0001-7975-5630 NR 25 TC 27 Z9 28 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA J9 J GEOPHYS RES-SPACE JI J. Geophys. Res-Space Phys. PD AUG 1 PY 1998 VL 103 IS A8 BP 17249 EP 17259 DI 10.1029/97JA03173 PG 11 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 107BV UT WOS:000075186700005 ER PT J AU Farrugia, CJ Scudder, JD Freeman, MP Janoo, L Lu, G Quinn, JM Arnoldy, RL Torbert, RB Burlaga, LF Ogilvie, KW Lepping, RP Lazarus, AJ Steinberg, JT Gratton, FT Rostoker, G AF Farrugia, CJ Scudder, JD Freeman, MP Janoo, L Lu, G Quinn, JM Arnoldy, RL Torbert, RB Burlaga, LF Ogilvie, KW Lepping, RP Lazarus, AJ Steinberg, JT Gratton, FT Rostoker, G TI Geoeffectiveness of three wind magnetic clouds: A comparative study SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID CORONAL MASS EJECTIONS; GEOMAGNETIC STORMS; IONOSPHERIC CONVECTION; EARTH PASSAGE; Y-COMPONENT; FIELD; MAGNETOSPHERE; MAGNETOPAUSE; SHOCK; DST AB We compare the large-scale goemagnetic response to the three magnetic clouds observed by Wind in October 1995 (OCT95), May 1996 (MAY96), and January 1997 (JAN97), studying specifically storm and substorm activity, and other global effects due to untypically large and variable solar wind dynamic pressures. Since the temporal profiles of the interplanetary parameters of the three clouds resemble one another closely, the comparison is meaningful. Using the integrated Poynting flux into the magnetosphere as a rough measure of energy input into the magnetosphere, we find relative energy inputs to be OCT95:JAN97:MAY96 = 22:11:4, with most of the accumulation in the 3-day periods occurring during passage of the B-z < 0 cloud phase. The peak Dst ring current indices, corrected for magnetopause currents, were in the ratio -138:-87:-38, and hence OCT95 caused a major, JAN97 a moderate, and MAY96 a weak storm. The empirical criterion derived from studies near solar maximum that a solar wind dawn-dusk electric field greater than or equal to 5 m V m(-1) lasting for at least 3 hours is necessary and sufficient to generate major storms does not hold for JAN97. Storm main phase onset coincides with cloud arrival in all three cases. The number of substorm onsets during the cloud periods were OCT95:JAN97:MAY96 = 5:3:2, with peak AL values in the ratio -1180:-1750:570. The dayside magnetosphere was variably compressed, the largest amplitude of variation being on JAN97, where the dynamic pressure change spanned 2 orders of magnitude. MAY96 showed the least variation. The interaction of the individual clouds with the faster trailing flows had two major effects on the magnetosphere: (1) a compression of the cavity during passage of the B-z > 0 cloud phase and the leading edge of the fast stream; and (2) a weakening of the control of the cloud field on magnetosheath flow during the B-z > 0 cloud phase. In summary we find that under most of the aspects considered, OCT95 is the most geoeffective. The buffetting of the magnetospheric cavity by dynamic pressure changes was, however, strongest on JAN97. The profound differences in the magnetospheric response elicited by the clouds is found to be due to the amplitude, duration and rapidity of change of the relevant interplanetary parameters. At present, interplanetary monitors are indispensable for understanding the geomagnetic response to interplanetary structures. C1 Univ New Hampshire, Inst Study Earth Oceans & Space, Durham, NH 03820 USA. Univ Iowa, Dept Phys & Astron, Iowa City, IA 52240 USA. British Antarctic Survey, Cambridge CB3 0ET, England. Natl Ctr Atmospher Res, High Altitude Observ, Boulder, CO 80307 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. MIT, Cambridge, MA 02139 USA. Univ Buenos Aires, Inst Fis Plasma, RA-1428 Buenos Aires, DF, Argentina. RP Farrugia, CJ (reprint author), Univ New Hampshire, Inst Study Earth Oceans & Space, Morse Hall, Durham, NH 03820 USA. RI Lu, Gang/A-6669-2011; Scudder, Jack/D-8417-2013 OI Scudder, Jack/0000-0001-7975-5630 NR 51 TC 33 Z9 33 U1 0 U2 3 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA J9 J GEOPHYS RES-SPACE JI J. Geophys. Res-Space Phys. PD AUG 1 PY 1998 VL 103 IS A8 BP 17261 EP 17278 DI 10.1029/98JA00886 PG 18 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 107BV UT WOS:000075186700006 ER PT J AU Baker, DN Pulkkinen, TI Li X Kanekal, SG Blake, JB Selesnick, RS Henderson, MG Reeves, GD Spence, HE Rostoker, G AF Baker, DN Pulkkinen, TI Li, X Kanekal, SG Blake, JB Selesnick, RS Henderson, MG Reeves, GD Spence, HE Rostoker, G TI Coronal mass ejections, magnetic clouds, and relativistic magnetospheric electron events: ISTP SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID ENERGETIC PARTICLE; SOLAR; INSTRUMENT AB The role of high-speed solar wind streams in driving relativistic electron acceleration within the Earth's magnetosphere during solar activity minimum conditions has been well documented. The rising phase of the new solar activity,cycle (cycle 23) commenced in 1996, and there have recently been a number of coronal mass ejections (CMEs) and related "magnetic clouds" at 1 AU. As these CME/cloud systems interact with the Earth's magnetosphere, some events produce substantial enhancements in the magnetospheric energetic particle population while others do not. This paper compares and contrasts relativistic electron signatures observed by the POLAR, SAMPEX, Highly Elliptical Orbit, and geostationary orbit spacecraft during two magnetic cloud events: May 27-29, 1996, and January 10-11, 1997. Sequences were observed in each case in which the interplanetary magnetic field was first strongly southward and then rotated northward. In both cases, there were large solar wind density enhancements toward the end of the cloud passage at 1 AU. Strong energetic electron acceleration was observed in the January event, but not in the May event. The relative geoeffectiveness for these two cases is assessed, and it is concluded that large induced electric fields (partial derivative B/partial derivative t) caused in situ acceleration of electrons throughout the outer radiation zone during the January 1997 event. C1 Univ Colorado, Atmospher & Space Phys Lab, Boulder, CO 80303 USA. Finnish Meteorol Inst, FIN-00101 Helsinki, Finland. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Boston Univ, Ctr Space Phys, Boston, MA 02215 USA. Univ Alberta, Dept Phys, Edmonton, AB T6G 2J1, Canada. RP Baker, DN (reprint author), Univ Colorado, Atmospher & Space Phys Lab, Boulder, CO 80303 USA. RI Spence, Harlan/A-1942-2011; Reeves, Geoffrey/E-8101-2011; Pulkkinen, Tuija/D-8403-2012; Henderson, Michael/A-3948-2011 OI Reeves, Geoffrey/0000-0002-7985-8098; Pulkkinen, Tuija/0000-0002-6317-381X; Henderson, Michael/0000-0003-4975-9029 NR 28 TC 130 Z9 138 U1 1 U2 13 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0148-0227 J9 J GEOPHYS RES-SPACE JI J. Geophys. Res-Space Phys. PD AUG 1 PY 1998 VL 103 IS A8 BP 17279 EP 17291 DI 10.1029/97JA03329 PG 13 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 107BV UT WOS:000075186700007 ER PT J AU Collier, MR Slavin, JA Lepping, RP Ogilvie, K Szabo, A Laakso, H Taguchi, S AF Collier, MR Slavin, JA Lepping, RP Ogilvie, K Szabo, A Laakso, H Taguchi, S TI Multispacecraft observations of sudden impulses in the magnetotail caused by solar wind pressure discontinuities: Wind and IMP 8 SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID INTERPLANETARY MAGNETIC-FIELD; NEAR-EARTH MAGNETOTAIL; DISTANT MAGNETOTAIL; AVERAGE CONFIGURATION; GEOMAGNETIC TAIL; SPACECRAFT; ISEE-3; LOBE; MAGNETOPAUSE; SHAPE AB Two upstream solar wind pressure discontinuities that were associated with storm sudden commencements have been examined to determine their effect on the geomagnetic tail lobe field. During the two events, occurring on March 9, 1995, and August 17, 1995, the Wind spacecraft was located in the upstream region monitoring the solar wind, and the IMP 8 spacecraft was in the geomagnetic tail lobe observing the tail response. The two events occurred during periods with northward or weak southward interplanetary magnetic field. In each case, the data suggest that the magnetic field in the tail lobe increased in magnitude directly in response to the external solar wind pressure increase. It is shown that a simple model in which a uniform magnetic field is compressed by a step function constriction accurately predicts characteristic timescales, which are of the order of a couple minutes, and the magnetic field profiles. The inferred flaring angles are consistent with model predictions, and the changes in the flaring angle across the discontinuities correspond to expectations based on changes in the subsolar magnetopause position and tail width. Overall, the results of this study indicate that the magnetotail maintains an approximate MHD equilibrium even as it responds rapidly to interplanetary pressure discontinuities. C1 NASA, Goddard Space Flight Ctr, Extraterr Phys Lab, Greenbelt, MD 20771 USA. Finnish Meteorol Inst, FIN-00101 Helsinki, Finland. Univ Electrocommun, Dept Elect Engn, Chofu, Tokyo 182, Japan. RP Collier, MR (reprint author), NASA, Goddard Space Flight Ctr, Extraterr Phys Lab, Greenbelt, MD 20771 USA. RI Slavin, James/H-3170-2012; Collier, Michael/I-4864-2013 OI Slavin, James/0000-0002-9206-724X; Collier, Michael/0000-0001-9658-6605 NR 40 TC 34 Z9 36 U1 1 U2 2 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA J9 J GEOPHYS RES-SPACE JI J. Geophys. Res-Space Phys. PD AUG 1 PY 1998 VL 103 IS A8 BP 17293 EP 17305 DI 10.1029/97JA02870 PG 13 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 107BV UT WOS:000075186700008 ER PT J AU Lui, ATY Williams, DJ McEntire, RW Ohtani, S Zanetti, LJ Bristow, WA Greenwald, RA Newell, PT Christon, SP Mukai, T Tsuruda, K Yamamoto, T Kokubun, S Matsumoto, H Kojima, H Murata, T Fairfield, DH Lepping, RP Samson, JC Rostoker, G Reeves, GD Rodger, AL Singer, HJ AF Lui, ATY Williams, DJ McEntire, RW Ohtani, S Zanetti, LJ Bristow, WA Greenwald, RA Newell, PT Christon, SP Mukai, T Tsuruda, K Yamamoto, T Kokubun, S Matsumoto, H Kojima, H Murata, T Fairfield, DH Lepping, RP Samson, JC Rostoker, G Reeves, GD Rodger, AL Singer, HJ TI Multipoint study of a substorm on February 9, 1995 SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID PLASMA SHEET; MAGNETOSPHERE; FLOWS; WIND AB An extended interval of strong northward interplanetary magnetic field (IMF) was observed by the Wind spacecraft located at an upstream distance of similar to 193 R-E from February 8-10, 1995, with a brief break of southward IMF from 0200 to 0400 UT on February 9. This brief interval of southward IMF led to an isolated substorm of moderate intensity (similar to 500 nT) with expansion phase starting at similar to 0431 UT. This substorm may be triggered by the northward turning of the IMF since its onset time matched well with the time expected for the arrival of the northward turning of the IMF at Earth. The substorm activities were monitored by 11 spacecraft in space (Wind, IMP 8, Geotail, six geosynchronous satellites, one DMSP satellite, and Freja) and two networks of ground stations (Canopus and SuperDARN) covering both the northern and southern hemispheres. The extensive coverage of this event provides us with results (1) showing some unusual characteristics possibly related to the isolated nature of the substorm and (2) revealing some surprising features difficult to reconcile with the traditional substorm model. In the first category is unusually long duration of the growth phase and the long time delay between substorm expansion onset and particle injection onset at the geosynchronous orbit. In the second category is new evidence for multiple particle acceleration sites during substorm expansion and for sunward flow during the late expansion phase of a substorm being unrelated to a single acceleration site (X line) moving from the near-Earth tail to the more distant tail. We also present observations which show the possible optical signature on the ground of bursty bulk flows in the magnetotail. C1 Johns Hopkins Univ, Appl Phys Lab, Laurel, MD 20723 USA. Univ Maryland, Dept Phys & Astron, College Pk, MD 20742 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Inst Space & Astronaut Sci, Kanagawa 229, Japan. Nagoya Univ, Solar Terr Environm Lab, Aichi 442, Japan. Kyoto Univ, Radio Atmospher Sci Ctr, Kyoto, Japan. Univ Alberta, Dept Phys, Edmonton, AB T6G 2M7, Canada. Los Alamos Natl Lab, Los Alamos, NM USA. British Antarctic Survey, Cambridge CB3 0ET, England. NOAA, Space Environm Ctr, Boulder, CO 80303 USA. RP Johns Hopkins Univ, Appl Phys Lab, Johns Hopkins Rd, Laurel, MD 20723 USA. RI Reeves, Geoffrey/E-8101-2011; Ohtani, Shinichi/E-3914-2016 OI Reeves, Geoffrey/0000-0002-7985-8098; Ohtani, Shinichi/0000-0002-9565-6840 NR 28 TC 11 Z9 11 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-9380 EI 2169-9402 J9 J GEOPHYS RES-SPACE JI J. Geophys. Res-Space Phys. PD AUG 1 PY 1998 VL 103 IS A8 BP 17333 EP 17343 DI 10.1029/97JA02632 PG 11 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 107BV UT WOS:000075186700011 ER PT J AU Tsurutani, BT Lakhina, GS Ho, CM Arballo, JK Galvan, C Boonsiriseth, A Pickett, JS Gurnett, DA Peterson, WK Thorne, RM AF Tsurutani, BT Lakhina, GS Ho, CM Arballo, JK Galvan, C Boonsiriseth, A Pickett, JS Gurnett, DA Peterson, WK Thorne, RM TI Broadband plasma waves observed in the polar cap boundary layer: Polar SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID HYBRID DRIFT INSTABILITY; AURORAL FIELD LINES; LOW-FREQUENCY WAVES; DAYSIDE MAGNETOPAUSE; DIFFUSION-PROCESSES; TURBULENCE; FLUCTUATIONS; ACCELERATION; INSTRUMENT; REGIONS AB Polar observations indicate the presence of intense broadband plasma waves nearly all of the time (96% occurrence frequency in this study) near the apogee of the Polar trajectory (similar to 6-8 R-E). The region of wave activity bounds the dayside (0500 to 1800 LT) polar cap magnetic fields, and we thus call these waves polar cap boundary layer (PCBL) waves. The waves are spiky signals spanning a broad frequency range from similar to 10(1) to 2 x 10(4) Hz. The waves have a rough power law spectral shape. The wave magnetic component has on average a f(-2.7) frequency dependence and appears to have an upper frequency cutoff of similar to(6-7) x 10(3) Hz, which is the electron cyclotron frequency. The electric component has on average a f(-2.2) frequency dependence and extends up to similar to 2 x 10(4) Hz. The frequency dependences of the waves and the amplitude ratios of B'/E' indicate a possible mixture of obliquely propagating electromagnetic whistler mode waves plus electrostatic waves. There are no clear intensity peaks in either the magnetic or electric spectra which can identify the plasma instability responsible for the generation of the PCBL waves. The wave character (spiky nature, frequency dependence and admixture of electromagnetic and electrostatic components) and intensity are quite similar to those of the low-latitude boundary layer (LLBL) waves detected at and inside the low-latitude dayside magnetopause. Because of the location of the PCBL waves just inside the polar cap magnetic field lines, it is natural to assume that these waves are occurring on the same magnetic field lines as the LLBL waves, but at lower altitudes. Because of the similar wave intensities at both locations and the occurrence at all local times, we rule out an ionospheric source. We also find a magnetosheath origin improbable. The most likely scenario is that the waves are locally generated by field-aligned currents or current gradients. We find a strong relationship between the presence of ionospheric and magnetosheath ions and the waves near the noon sector. These waves may thus be responsible for ion heating observed near the cusp region. Antisunward convection of these freshly accelerated oxygen ions over the polar cap during intense wave events (occurring during southward B-z events) might lead to enhanced plasma sheet O+ population. For magnetic storm intervals this mechanism would lead to a natural delay between the main phase onset and the appearance of oxygen ions in the ring-current. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Indian Inst Geomagnetism, Bombay, Maharashtra, India. Univ Iowa, Dept Phys & Astron, Iowa City, IA 52242 USA. Lockheed Space Sci Lab, Palo Alto, CA 94304 USA. Univ Calif Los Angeles, Dept Atmospher Sci, Los Angeles, CA 90024 USA. RP Tsurutani, BT (reprint author), CALTECH, Jet Prop Lab, MS 169-506,4800 Oak Grove Dr, Pasadena, CA 91109 USA. RI Lakhina, Gurbax /C-9295-2012; Peterson, WK/A-8706-2009 OI Peterson, WK/0000-0002-1513-6096 NR 42 TC 23 Z9 23 U1 0 U2 3 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA J9 J GEOPHYS RES-SPACE JI J. Geophys. Res-Space Phys. PD AUG 1 PY 1998 VL 103 IS A8 BP 17351 EP 17366 DI 10.1029/97JA03063 PG 16 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 107BV UT WOS:000075186700013 ER PT J AU Chang, SW Scudder, JD Sigwarth, JB Frank, LA Maynard, NC Burke, WJ Peterson, WK Shelley, EG Friedel, R Blake, JB Greenwald, RA Lepping, RP Sofko, GJ Villain, JP Lester, M AF Chang, SW Scudder, JD Sigwarth, JB Frank, LA Maynard, NC Burke, WJ Peterson, WK Shelley, EG Friedel, R Blake, JB Greenwald, RA Lepping, RP Sofko, GJ Villain, JP Lester, M TI A comparison of a model for the theta aurora with observations from Polar, wind, and SuperDARN SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID MAGNETOSPHERIC BOUNDARY-LAYER; PLANETARY MAGNETIC-FIELD; ELECTRIC-FIELD; PLASMA SHEET; ENERGETIC PARTICLE; BIRKELAND CURRENTS; CAP ARCS; MAGNETOPAUSE; NORTHWARD; QUIET AB A model is presented according to which theta auroral arcs form after southward turnings of interplanetary magnetic field (IMF) and/or large variations in IMF B-y, following prolonged periods of northward IMF or very small B-z, with \B-y\ greater than or similar to \B-z\. The arcs start on the dawnside (duskside) of the auroral oval and drift duskward (dawnward) across the polar cap for positive (negative) B-y in the northern hemisphere and conversely in the southern hemisphere. After the theta aurora has formed, changes in IMF B-y or B-z readjust the merging configuration and continue the auroral pattern. The transpolar arcs are on closed magnetic field lines that bifurcate two open sections of the polar cap and map to the outer plasma sheet. Four theta auroral events were studied using data from the ISTP/GGS Polar and Wind spacecraft and the ground-based SuperDARN radars. Observations that are correctly predicted by our model include the following: (1) The formation and evolution of theta auroras observed by the visible imaging system are closely related to the IMF patterns measured by the Wind magnetic field investigation. (2) Both electrons and ions in the transpolar are and poleward part of the nightside auroral oval exhibit similar spectral characteristics, identified from the data acquired with Hydra and the comprehensive energetic particle and pitch angle distribution experiment. The low-energy electrons show counterstreaming distributions, consistent with their being on closed field lines that magnetically connect to the boundary plasma sheet in the magnetotail. (3) Ion composition measurements obtained from the toroidal imaging mass-angle spectrograph show cold plasma outflows from the ionosphere and hot, isotropic magnetospheric ions in the two regions, also indicating transpolar arcs are on closed field lines. (4) Large scale polar cap convection inferred by SuperDARN observations is well correlated with IMF patterns. (5) Plasma convection in the transpolar arcs, inferred from the electric field instrument and the magnetic field investigation measurements, is sunward. C1 Univ Iowa, Dept Phys & Astron, Iowa City, IA 52242 USA. Mission Res Corp, Nashua, NH 03062 USA. Phillips Lab, GPSM, Bedford, MA 01731 USA. Lockheed Martin Space Sci Lab, Dept H1 11, Palo Alto, CA 94304 USA. Max Planck Inst Aeron, D-37189 Katlenburg Lindau, Germany. Aerospace Corp, Los Angeles, CA 90009 USA. Johns Hopkins Univ, Appl Phys Lab, Laurel, MD 20723 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Saskatchewan, Inst Space & Atmospher Studies, Saskatoon, SK S7N 0W0, Canada. CNRS, Lab Phys & Chim Environm, F-45071 Orleans, France. RP Chang, SW (reprint author), Univ Iowa, Dept Phys & Astron, Iowa City, IA 52242 USA. RI Friedel, Reiner/D-1410-2012; Scudder, Jack/D-8417-2013; Peterson, WK/A-8706-2009 OI Friedel, Reiner/0000-0002-5228-0281; Scudder, Jack/0000-0001-7975-5630; Peterson, WK/0000-0002-1513-6096 NR 59 TC 46 Z9 47 U1 0 U2 2 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA J9 J GEOPHYS RES-SPACE JI J. Geophys. Res-Space Phys. PD AUG 1 PY 1998 VL 103 IS A8 BP 17367 EP 17390 DI 10.1029/97JA02255 PG 24 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 107BV UT WOS:000075186700014 ER PT J AU Hirahara, M Horwitz, JL Moore, TE Germany, GA Spann, JE Peterson, WK Shelley, EG Chandler, MO Giles, BL Craven, PD Pollock, CJ Gurnett, DA Pickett, JS Persoon, AM Scudder, JD Maynard, NC Mozer, FS Brittnacher, MJ Nagai, T AF Hirahara, M Horwitz, JL Moore, TE Germany, GA Spann, JE Peterson, WK Shelley, EG Chandler, MO Giles, BL Craven, PD Pollock, CJ Gurnett, DA Pickett, JS Persoon, AM Scudder, JD Maynard, NC Mozer, FS Brittnacher, MJ Nagai, T TI Relationship of topside ionospheric ion outflows to auroral forms and precipitation, plasma waves, and convection observed by Polar SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID SUPRATHERMAL O+ IONS; KILOMETRIC RADIATION; HIGH-ALTITUDE; FIELD LINES; CYCLOTRON RESONANCE; DE-1 ALTITUDES; SOURCE REGION; HIGH-LATITUDE; ACCELERATION; INSTRUMENT AB The POLAR satellite often observes upflowing ionospheric ions (UFIs) in and near the auroral oval on southern perigee (similar to 5000 km altitude) passes. We present the UFI features observed by the thermal ion dynamics experiment (TIDE) and the toroidal imaging mass angle spectrograph (TIMAS) in the dusk-dawn sector under two different geomagnetic activity conditions in order to elicit their relationships with auroral forms, wave emissions, and convection pattern from additional POLAR instruments. During the active interval, the ultraviolet imager (UVI) observed a bright discrete aurora on the duskside after the substorm onset and then observed a small isolated aurora form and diffuse auroras on the dawnside during the recovery phase. The UFIs showed clear conic distributions when the plasma wave instrument (PWI) detected strong broadband wave emissions below similar to 10 Hz, while no significant auroral activities were observed by UVI. At higher latitudes, the low-energy UFI conics gradually changed to the polar wind component with decreasing intensity of the broadband emissions. V-shaped auroral kilometric radiation (AKR) signatures observed above similar to 200 kHz by PWI coincided with the region where the discrete aurora and the UFI beams were detected. The latitude of these features was lower than that of the UFI conics. During the observations of the UFI beams and conics, the lower-frequency fluctuations observed by the electric field instrument were also enhanced, and the convection directions exhibited large fluctuations. It is evident that large electrostatic potential drops produced the precipitating electrons and discrete auroras, the UFI beams, and the AKR, which is also supported by the energetic plasma data from HYDRA. Since the intense broadband emissions were also observed with the UFIs, the ionospheric ions could be energized transversely before or during the parallel acceleration due to the potential drops. C1 Univ Alabama, Ctr Space Plasma Aeron & Astrophys Res, Huntsville, AL 35899 USA. Univ Washington, Geophys Program, Seattle, WA 98195 USA. NASA, George C Marshall Space Flight Ctr, Space Sci Lab, Huntsville, AL 35812 USA. Tokyo Inst Technol, Meguro Ku, Tokyo 152, Japan. Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA. Mission Res Corp, Nashua, NH USA. Univ Iowa, Dept Phys & Astron, Iowa City, IA 52242 USA. SW Res Inst, Instrumentat & Space Res Div, San Antonio, TX 78228 USA. Lockheed Martin Space Phys Lab, Palo Alto, CA 94304 USA. RP Hirahara, M (reprint author), Rikkyo Univ, Coll Sci, Dept Phys, Toshima Ku, 3-34-1 Nishi Ikebukuro, Tokyo 171, Japan. RI Moore, Thomas/D-4675-2012; Scudder, Jack/D-8417-2013; Peterson, WK/A-8706-2009 OI Moore, Thomas/0000-0002-3150-1137; Scudder, Jack/0000-0001-7975-5630; Peterson, WK/0000-0002-1513-6096 NR 83 TC 13 Z9 13 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA J9 J GEOPHYS RES-SPACE JI J. Geophys. Res-Space Phys. PD AUG 1 PY 1998 VL 103 IS A8 BP 17391 EP 17410 DI 10.1029/97JA02668 PG 20 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 107BV UT WOS:000075186700015 ER PT J AU Wilson, RM Hathaway, DH Reichmann, EJ AF Wilson, RM Hathaway, DH Reichmann, EJ TI Estimating the size and timing of maximum amplitude for cycle 23 from its early cycle behavior SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID SUNSPOT CYCLE AB On the basis of the lowest observed smoothed monthly mean sunspot number, cycle 23 appears to have conventionally begun in May 1996, in conjunction with the first appearance of a new cycle, high-latitude spot group. Such behavior, however, is considered rather unusual, since, previously (based on the data-available cycles 12-22), the first appearance of a new cycle, high-latitude spot group has always preceded conventional onset by at least 3 months. Furthermore, accepting May 1996 as the official start for cycle 23 poses a dilemma regarding its projected size and timing of maximum amplitude. Specifically, from the maximum-minimum and amplitude-period relationships we infer that cycle 23 should be above average in size and a fast riser, with maximum amplitude occurring before May 2000 (being in agreement with projections for cycle 23 based on precursor information), yet from its initial languid rate of rise (during the first 6 months of the cycle) we infer that it should be below average in size and a slow riser, with maximum amplitude occurring after May 2000. The dilemma vanishes, however, when we use a slightly later-occurring onset. For example, using August 1996, a date associated with a local secondary minimum prior to the rapid rise that began shortly thereafter tin early 1997), we infer that the cycle 23 rate of rise is above that for the mean of cycles 1-22, the mean of cycles 10-22 (the modern era cycles), the mean of the modern era "fast risers," and the largest of the modern era "slow risers" (i.e.., cycle 20), thereby suggesting that cycle 23 will be both fast rising and above average in size, peaking before August 2000. Additionally, presuming cycle 23 to be a well-behaved fast-rising cycle (regardless of whichever onset date is used), we also infer that its maximum amplitude likely will measure about 144.0 +/- 28.8 (from the general behavior found for the bulk of modern era fast risers; i.e., 5 of 7 have had their maximum amplitude to lie within 20% of the mean curve for modern era fast risers). It is apparent, then, that sunspot number growth during 1998 will prove crucial for correctly establishing the size and shape of cycle 23. C1 NASA, George C Marshall Space Flight Ctr, Space Sci Lab, Huntsville, AL 35812 USA. RP Wilson, RM (reprint author), NASA, George C Marshall Space Flight Ctr, Space Sci Lab, ES82 98-036, Huntsville, AL 35812 USA. NR 21 TC 18 Z9 19 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA J9 J GEOPHYS RES-SPACE JI J. Geophys. Res-Space Phys. PD AUG 1 PY 1998 VL 103 IS A8 BP 17411 EP 17418 DI 10.1029/98JA01434 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 107BV UT WOS:000075186700016 ER PT J AU Chotoo, K Collier, MR Galvin, AB Hamilton, DC Gloeckler, G AF Chotoo, K Collier, MR Galvin, AB Hamilton, DC Gloeckler, G TI Extended solar wind helium distribution functions in high-speed streams SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID VELOCITY DISTRIBUTION; ION; ELECTRON; SPACECRAFT; PARTICLES; HYDROGEN; PLASMAS; TAILS AB The extended velocity distribution function for solar wind doubly charged helium (He(+2)) has been systematically studied for seven high-speed streams occurring in the first 7 months of 1995, near solar minimum. The two instruments, suprathermal ion composition spectrometer (STICS) and high mass resolution spectrometer (MASS), used in this study are both part of the SMS experiment on board the Wind spacecraft. The helium distributions were fit over the speed range nu/nu(sw) approximate to 0.8-1.6 constituting similar to 7.5 thermal widths and 5 orders of magnitude in phase space density, where nu(sw) is the proton solar wind speed. The distributions are reasonably well fit by kappa functions with values of kappa ranging from 3.4 to 5.8, although there may be systematic deviations from a perfect kappa function over the 5 orders of magnitude in phase space density. This is the first study that characterizes the extended helium distribution functions using kappa functions in the high-speed solar wind. C1 Univ Maryland, Dept Phys, College Pk, MD 20742 USA. NASA, Goddard Space Flight Ctr, Extraterr Phys Lab, Greenbelt, MD 20771 USA. Univ Maryland, Dept Phys, College Pk, MD 20742 USA. RP Chotoo, K (reprint author), Univ Maryland, Dept Phys, College Pk, MD 20742 USA. RI Galvin, Antoinette/A-6114-2013; Collier, Michael/I-4864-2013 OI Collier, Michael/0000-0001-9658-6605 NR 37 TC 7 Z9 7 U1 0 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0148-0227 J9 J GEOPHYS RES-SPACE JI J. Geophys. Res-Space Phys. PD AUG 1 PY 1998 VL 103 IS A8 BP 17441 EP 17445 DI 10.1029/98JA01173 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 107BV UT WOS:000075186700019 ER PT J AU Sittler, EC Burlaga, LF AF Sittler, EC Burlaga, LF TI Electron temperatures within magnetic clouds between 2 and 4 AU: Voyager 2 observations SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID WIND THERMAL ELECTRONS; SOLAR-WIND; NONLINEAR EVOLUTION; FLUX ROPES; PLASMA; MAGNETOSPHERE AB We have performed an analysis of Voyager 2 plasma electron observations within magnetic clouds between 2 and 4 AU identified by Burlaga ann Behannon [1982]. The analysis has been confined to three of the magnetic clouds identified by Burlaga and Behannon that had high-quality data. The general properties of the plasma electrons within a magnetic cloud are that (1) the moment electron temperature anticorrelates with the electron density within the cloud, (2) the ratio T(e)/T(p) tends to be >1, and (3) on average, T(e)/T(p) approximate to 7.0. All three results are consistent with previous electron observations within magnetic clouds. Detailed analyses of the core and halo populations within the magnetic clouds show no evidence of either an anticorrelation between the core temperature T(C) and the electron density N(e) or an anticorrelation between the halo temperature T(H) and the electron density. Within the magnetic clouds the halo component can contribute more than 50% of the electron pressure. The anticorrelation of T(e) relative to N(e) can be traced to the density of the halo component relative to the density of the core component. The core electrons dominate the electron density. When the density goes up, the halo electrons contribute less to the electron pressure, so we get a lower T(e). When the electron density goes down, the halo electrons contribute more to the electron pressure, and T(e) goes up. We find a relation between the electron pressure and density of the form P(e) = alpha N(e)(gamma) with gamma approximate to 0.5. C1 NASA, Goddard Space Flight Ctr, Extraterr Phys Lab, Greenbelt, MD 20771 USA. RP Sittler, EC (reprint author), NASA, Goddard Space Flight Ctr, Extraterr Phys Lab, Code 692,Greenbelt Rd, Greenbelt, MD 20771 USA. EM burlaga@lepvax.gsfc.nasa.gov; u2ecs@lepecs.gsfc.nasa.gov NR 27 TC 20 Z9 20 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0148-0227 J9 J GEOPHYS RES-SPACE JI J. Geophys. Res-Space Phys. PD AUG 1 PY 1998 VL 103 IS A8 BP 17447 EP 17454 DI 10.1029/98JA01289 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 107BV UT WOS:000075186700020 ER PT J AU Nose, M Iyemori, T Sugiura, M Slavin, JA Hoffman, RA Winningham, JD Sato, N AF Nose, M Iyemori, T Sugiura, M Slavin, JA Hoffman, RA Winningham, JD Sato, N TI Electron precipitation accompanying Pc 5 pulsations observed by the DE satellites and at a ground station SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID FIELD LINE RESONANCES; LOCAL TIME ASYMMETRY; MAGNETIC PULSATIONS; ALFVEN WAVES; MAGNETOSPHERE; IONOSPHERE; REGIONS; EXCITATION; BEHAVIOR; SECTOR AB Using data from the polar orbiting Dynamic Explorer (DE) -1 and -2 satellites and a ground-based station, we investigated electron precipitation phenomena accompanying Pc 5 pulsations. DE-2 observed oscillatory disturbances in the magnetic and electric fields in the upper ionosphere at the geomagnetic footprint of the high altitude region in which transverse Pc 5 pulsations were detected by DE-1. DE-2 observed electrons precipitating into the ionosphere with energies of several keV to several tens of keV, These electrons were accelerated in the direction of the ambient magnetic field. When Pc 5 pulsations in the H-component and periodic variations of cosmic radio noise absorption (CNA pulsations) were observed at Syowa Station, DE-2 which was in geomagnetic conjunction with Syowa Station also observed oscillatory disturbances in the magnetic and electric fields. These oscillatory disturbances are caused by small-scale field-aligned currents each with. width of 0.5 degrees-1.4 degrees invariant latitude. This suggests that Pc 5 pulsations have a small-scale resonance structure in the radial direction. The resonance structure has a small scale comparable to the ion acoustic gyroradius, then kinetic Alfven waves having electric fields parallel to the ambient magnetic field can arise. The parallel electric field generates a field-aligned potential drop of about 3-5 kV. Electrons accelerated by these kinetic Alfven waves would cause CNA pulsations, the phase of which leads that of the B-component of the Pc 5 pulsations by 90 degrees in the southern hemisphere. This is consistent with the observations at Syowa Station. C1 Kyoto Univ, Fac Sci, Kyoto 6068502, Japan. Tokai Univ, Sci & Technol Res Inst, Tokyo 1510063, Japan. NASA, Extraterr Phys Lab, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. SW Res Inst, San Antonio, TX 78284 USA. Natl Inst Polar Res, Tokyo 1738515, Japan. RP Nose, M (reprint author), Kyoto Univ, Fac Sci, Kyoto 6068502, Japan. RI Slavin, James/H-3170-2012; Nose, Masahito/B-1900-2015 OI Slavin, James/0000-0002-9206-724X; Nose, Masahito/0000-0002-2789-3588 NR 48 TC 22 Z9 22 U1 0 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA J9 J GEOPHYS RES-SPACE JI J. Geophys. Res-Space Phys. PD AUG 1 PY 1998 VL 103 IS A8 BP 17587 EP 17604 DI 10.1029/98JA01187 PG 18 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 107BV UT WOS:000075186700032 ER PT J AU Taguchi, S Slavin, JA Lepping, RP AF Taguchi, S Slavin, JA Lepping, RP TI Traveling compression regions in the midtail: Fifteen years of IMP 8 observations SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID PLASMA SHEET INSTABILITIES; MAGNETOTAIL FLUX ROPES; ISEE-3 OBSERVATIONS; GEOMAGNETIC-ACTIVITY; GEOTAIL OBSERVATIONS; EARTHS MAGNETOTAIL; TAIL; SIGNATURES; PRESSURE AB The characteristics of traveling compression regions (TCRs) in the midtail lobes near expansion-phase onsets have been analyzed utilizing the data set returned by the IMP 8 magnetic field investigation between 1973 and 1990. Examination of the 15 years for which we have the AL index led to the identification of 565 isolated substorm events with expansion phases for which IMP 8 was in the tail lobes and returned magnetic field measurements. For 31 of the 565 events a typical TCR variation was observed at IMP 8. These TCR perturbations have been previously studied in the ISEE 3 distant tail measurements and consist of a field compression during which B-Z increases and then decreases after peaking, although B-Z may not reach a positive value in many cases. For 59 of the substorms a field compression was seen at IMP 8 during which the B-Z peak before the field maximum is lacking, i.e., the B-Z just decreases rapidly, and the variation is unipolar. These 90 (31 plus 59) substorms occurred in the region for X=-26 to -38 R-E \Y\ less than or equal to 15 R-E and Z(N) less than or equal to 20 R-E all in the solar wind aberrated GSM coordinate system. The "unipolar B-Z compression region" has a phase of flat B-Z preceding the sharp southward tilting interval. The typical timescale of this phase is 60-100 s. We interpret this flat B-Z phase as a field compression created by the rapid growth of the plasmoid bulge in the Z dimension underneath IMP 8 just prior to the plasmoid being ejected tailward. The fractional occurrence frequency of the TCRs observed in our substorm database for each year was calculated by dividing the number of the substorms producing TCRs by all of the IMP 8 lobe substorm events for each year. This ratio tends to be high (maximum 41.7%) in the years of low sunspot number, and low (minimum 7.7%) in the years of high sunspot number. For years when the occurrence ratio is low, the TCRs are observed primarily within \Y\ = 10 R-E When the occurrence ratio is high, the TCRs are found across a wider region in Y with a peak in the premidnight. These results suggest that the plasmoid formation is controlled by solar cycle related parameters in such a manner that the near-Earth neutral line occurs at a wider region in the dawn-dusk direction for the years of low sunspot number. C1 Univ Electrocommun, Dept Elect Engn, Tokyo 182, Japan. NASA, Extraterr Phys Lab, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Taguchi, S (reprint author), Univ Electrocommun, Dept Elect Engn, Tokyo 182, Japan. RI Slavin, James/H-3170-2012 OI Slavin, James/0000-0002-9206-724X NR 25 TC 20 Z9 20 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA J9 J GEOPHYS RES-SPACE JI J. Geophys. Res-Space Phys. PD AUG 1 PY 1998 VL 103 IS A8 BP 17641 EP 17650 DI 10.1029/98JA01206 PG 10 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 107BV UT WOS:000075186700035 ER PT J AU Kamide, Y Baumjohann, W Daglis, IA Gonzalez, WD Grande, M Joselyn, JA McPherron, RL Phillips, JL Reeves, EGD Rostoker, G Sharma, AS Singer, HJ Tsurutani, BT Vasyliunas, VM AF Kamide, Y Baumjohann, W Daglis, IA Gonzalez, WD Grande, M Joselyn, JA McPherron, RL Phillips, JL Reeves, EGD Rostoker, G Sharma, AS Singer, HJ Tsurutani, BT Vasyliunas, VM TI Current understanding of magnetic storms: Storm-substorm relationships SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Review ID CORONAL MASS EJECTA; GREAT GEOMAGNETIC STORMS; SOLAR-WIND; RING-CURRENT; SEMIANNUAL VARIATION; PLASMA SHEET; CURRENT DISRUPTION; DECLINING PHASE; FIELD LINES; MAGNETOSPHERE AB This paper attempts to summarize the current understanding of the storm/substorm relationship by clearing up a considerable amount of controversy and by addressing the question of how solar wind energy is deposited into and is dissipated in the constituent elements that are critical to magnetospheric and ionospheric processes during magnetic storms. (1) Four mechanisms are identified and discussed as the primary causes of enhanced electric fields in the interplanetary medium responsible for geomagnetic storms. It is pointed out that in reality, these four mechanisms, which are not mutually exclusive, but interdependent, interact differently from event to event. Interplanetary coronal mass ejections (ICMEs) and corotating interaction regions (CIRs) are found to be the primary phenomena responsible for the main phase of geomagnetic storms. The other two mechanisms, i.e., HILDCAA (high-intensity, long-duration continuous auroral electrojet activity) and the so-called Russell-McPherron effect, work to make the ICME and CIR phenomena more geoeffective. The solar cycle dependence of the various sources in creating magnetic storms has yet to be quantitatively understood. (2) A serious controversy exists as to whether the successive occurrence of intense substorms plays a direct role hn the energization of ring current particles or whether the enhanced electric field associated with southward IMF enhances the effect of substorm expansions. While most of the Dst variance during magnetic storms can be solely reproduced by changes in the large-scale electric field in the solar wind and the residuals are uncorrelated with substorms, recent satellite observations of the ring current constituents during the main phase of magnetic storms show the importance of ionospheric ions. This implies that ionospheric ions, which are associated with the frequent occurrence of intense substorms, are accelerated upward along magnetic field lines, contributing to the energy density of the storm-time ring current. An apparently new controversy regarding the relative importance of the two processes is thus created. It is important to identify the role of substorm occurrence in the large-scale enhancement of magnetospheric convection driven by solar wind electric fields. (3) Numerical schemes for predicting geomagnetic activity indices on the basis of solar/solar wind/interplanetary magnetic field parameters continue to be upgraded, ensuring reliable techniques for forecasting magnetic storms under real-time conditions. There is a need to evaluate the prediction capability of geomagnetic indices on the basis of physical processes that occur during storm time substorms. (4) It is crucial to differentiate between storms and nonstorm time substorms in terms of energy transfer/conversion processes, i.e., mechanical energy from the solar wind, electromagnetic energy in the magnetotail, and again, mechanical energy of particles in the plasma sheet, ring current, and aurora. To help answer the question of the role of substorms in energizing ring current particles, it is crucial to find efficient magnetospheric processes that heat ions up to some minimal energies so that they can have an effect on the strength of the storm time ring current. (5) The question of whether the Dst index is an accurate and effective measure of the storm time ring current is also controversial. In particular, it is demonstrated that the dipolarization effect associated with substorm expansion acts to reduce the Dst magnitude, even though the ring current may still be growing. C1 Nagoya Univ, Solar Terr Environm Lab, Toyokawa 442, Japan. Max Planck Inst Extraterr Phys, D-85740 Garching, Germany. Natl Observ Athens, Inst Ionospher & Space Res, Penteli 15236, Greece. Rutherford Appleton Lab, Didcot OX11 0QX, Oxon, England. Inst Pesquisas Espaciais, Sao Paulo, Brazil. NOAA, Space Environm Ctr, Boulder, CO 80303 USA. Univ Calif Los Angeles, Dept Geophys & Planetary Phys, Los Angeles, CA 90024 USA. NASA, Johnson Space Flight Ctr, Houston, TX 77059 USA. Univ Calif Los Alamos Natl Lab, Los Alamos, NM 87545 USA. Univ Alberta, Dept Phys, Edmonton, AB T6G 2J1, Canada. Univ Maryland, Dept Astron, College Pk, MD 20742 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Max Planck Inst Aeron, D-37189 Katlenburg Lindau, Germany. RP Kamide, Y (reprint author), Nagoya Univ, Solar Terr Environm Lab, Toyokawa 442, Japan. EM kamide@stelab.nagoya-u.ac.jp; bj@mpe-garching.mpg.dr; daglis@creator.space.noa.gr; gonzalez@dge.inpe.br; M.Grande@rl.ac.uk; jjoselyn@sec.noaa.gov; rmcpherron@igpp.ucla.edu; JLPhilli@ems.jsc.gov; reeves@lanl.gov; rostoker@space.ualberta.ca; ssh@avl.umd.edu; hsinger@sec.noaa.gov; btsurutani@jplsp.jpl.nasa.gov; vasyliunas@linaxl.mpae.gwdg.de RI Baumjohann, Wolfgang/A-1012-2010; Daglis, Ioannis/L-6100-2013; Reeves, Geoffrey/E-8101-2011; Grande, Manuel/C-2242-2013 OI Baumjohann, Wolfgang/0000-0001-6271-0110; Daglis, Ioannis/0000-0002-0764-3442; Reeves, Geoffrey/0000-0002-7985-8098; Grande, Manuel/0000-0002-2233-2618 NR 153 TC 200 Z9 202 U1 3 U2 36 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA J9 J GEOPHYS RES-SPACE JI J. Geophys. Res-Space Phys. PD AUG 1 PY 1998 VL 103 IS A8 BP 17705 EP 17728 DI 10.1029/98JA01426 PG 24 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 107BV UT WOS:000075186700040 ER PT J AU Baker, DN Pulkkinen, TI Hesse, M McPherron, RL AF Baker, DN Pulkkinen, TI Hesse, M McPherron, RL TI A quantitative assessment of energy storage and release in the earth's magnetotail SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Editorial Material ID DISTANT TAIL; AURORAL OVAL; SUBSTORMS; FIELD; GEOTAIL; ISEE-3; MODEL C1 Univ Colorado, Atmospher & Space Phys Lab, Boulder, CO 80303 USA. Finnish Meteorol Inst, Helsinki 500101, Finland. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Calif Los Angeles, Dept Geophys & Planetary Phys, Los Angeles, CA 90024 USA. RP Baker, DN (reprint author), Univ Colorado, Atmospher & Space Phys Lab, Campus Box 590, Boulder, CO 80303 USA. RI Hesse, Michael/D-2031-2012; Pulkkinen, Tuija/D-8403-2012 OI Pulkkinen, Tuija/0000-0002-6317-381X NR 18 TC 0 Z9 0 U1 0 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA J9 J GEOPHYS RES-SPACE JI J. Geophys. Res-Space Phys. PD AUG 1 PY 1998 VL 103 IS A8 BP 17733 EP 17734 DI 10.1029/98JA01478 PG 2 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 107BV UT WOS:000075186700042 ER PT J AU Boness, DJ Craig, MP Honigman, L Austin, S AF Boness, DJ Craig, MP Honigman, L Austin, S TI Fostering behavior and the effect of female density in Hawaiian monk seals, Monachus schauinslandi SO JOURNAL OF MAMMALOGY LA English DT Article DE Monachus schauinslandi; Hawaiian monk seals; fostering; non-offspring nursing; maternal care; density effects; pinnipeds ID NORTHERN ELEPHANT SEAL; BAT MATERNITY COLONIES; HARBOR SEAL; PHOCA-VITULINA; ALLOPARENTAL CARE; BUBALUS-BUBALIS; WATER-BUFFALO; GREY SEAL; ADOPTION; MOTHER AB Frequent nursing of pups by non-filial females (fostering) has been reported in Hawaiian monk seals (Monachus schauinslandi) at French Frigate Shoals in the Northwestern-Hawaiian Islands. We present data on the occurrence of fostering at Laysan Island, NWHI, and compare spatial patterns and behavior of seals at Laysan Island and East Island, French Frigate Shoals, to investigate the importance of density in frequency of fostering. Fostering was common at Laysan Island; 53% of 17 females nursed pups other than their own for some part of their lactation period. This level of fostering was significantly less than that at East Island, where ca. 90% of females fostered pups in 2 separate years (n = 30 in 1987 and 10 in 1989). Density of females was significantly lower at Laysan Island than East Island (0.5 versus 1.5 femaIes/1,000 m(2)), and nearest female neighbors were significantly farther away (58 versus 27 m) at Laysan Island. Stage of lactation at which fostering started, the total duration of foster care and the duration of fostering episodes did not differ between colonies. However, mean number of pups fostered per female at the denser colony (2.3 pups, East Island) was greater than at the less dense colony (1.3 pups, Laysan Island). No difference occurred between islands in relative frequency of aggressive interactions between females, which are known to result in females exchanging pups. High female density does appear to increase fostering frequency but not through female-female aggression as expected. Instead, high density increases the likelihood that separated females and pups will encounter another potential partner before reuniting. C1 Smithsonian Inst, Natl Zool Pk, Dept Zool Res, Washington, DC 20008 USA. NOAA, Natl Marine Fisheries Serv, Honolulu, HI 96822 USA. RP Boness, DJ (reprint author), Smithsonian Inst, Natl Zool Pk, Dept Zool Res, Washington, DC 20008 USA. NR 49 TC 27 Z9 28 U1 2 U2 12 PU AMER SOC MAMMALOGISTS PI PROVO PA BRIGHAM YOUNG UNIV, DEPT OF ZOOLOGY, PROVO, UT 84602 USA SN 0022-2372 J9 J MAMMAL JI J. Mammal. PD AUG PY 1998 VL 79 IS 3 BP 1060 EP 1069 DI 10.2307/1383115 PG 10 WC Zoology SC Zoology GA 114TJ UT WOS:000075624900037 ER PT J AU Gaier, JR Hardebeck, WC Bunch, JRT Davidson, ML Beery, DB AF Gaier, JR Hardebeck, WC Bunch, JRT Davidson, ML Beery, DB TI Effect of intercalation in graphite epoxy composites on the shielding of high energy radiation SO JOURNAL OF MATERIALS RESEARCH LA English DT Article AB The half-thickness and mass absorption coefficient of 13.0 keV x-rays, 46.5 keV gamma-rays, and 1.16 MeV beta(-) particles have been measured for pristine, bromine intercalated, and iodine monobromide intercalated pitch-based graphite fiber composites. Since these materials have been proposed to replace aluminum structures in spacecraft, the results were compared to aluminum. Pristine graphite epoxy composites were found to have about 4.0 times the half-thickness, and 40% of the mass absorption of aluminum for ionizing radiation. Bromine intercalation improved performance to 90% of the half-thickness, and 1.7 times the mass absorption coefficient of aluminum. Iodine monobromide extended the performance to 70% of the half-thickness and 3.0 times the mass absorption of aluminum. Thus, intercalation not only makes up the deficiency conventional composites have in shielding components from ionizing radiation, but actually confers advantages in mass and thickness over aluminum. The beta(-) particle shielding of all the materials tested was found to be very effective. The shielding of all of the materials was found to have nearly the same mass absorption coefficient of 17.8 +/- 0.9 cm(2)/g. Inelastic scattering processes were found to be important in beta(-) particle shielding; however, the extent of inelastic scattering and thus the distribution of energies of the transmitted electrons did not vary with material. C1 NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. Manchester Coll, N Manchester, IN 46962 USA. RP Gaier, JR (reprint author), NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. NR 5 TC 4 Z9 9 U1 0 U2 3 PU MATERIALS RESEARCH SOCIETY PI WARRENDALE PA 506 KEYSTONE DR, WARRENDALE, PA 15086 USA SN 0884-2914 J9 J MATER RES JI J. Mater. Res. PD AUG PY 1998 VL 13 IS 8 BP 2297 EP 2301 DI 10.1557/JMR.1998.0320 PG 5 WC Materials Science, Multidisciplinary SC Materials Science GA 104AC UT WOS:000074989200037 ER PT J AU Toth, RA AF Toth, RA TI Water vapor measurements between 590 and 2582 cm(-1): Line positions and strengths SO JOURNAL OF MOLECULAR SPECTROSCOPY LA English DT Article ID TRANSITION FREQUENCIES; (H2O)-O-16; SPECTRA; CM-1; REGION; H2O AB This study involves measurements of (H2O)-O-16, (H2O)-O-17, and (H2O)-O-18 vapor spectra for the region between 590 and 2582 cm(-1) The parameters derived from the data include line positions, energy levels, and linestrengths. The study involves high-resolution line-position measurements with samples at room temperature in the (000)-(000), (010)-(010), and (010)-(000) bands. The experimental frequencies were used along with microwave, far-infrared, and hot water emission measurements in an analysis to obtain high-accuracy rotational energy level values in the (000), and (010) vibrational states of (H2O)-O-16 for J less than or equal to 20. The experimental linestrengths were fitted by least squares to a model in which the dipole moment was represented as a series expansion containing up to 19 dipole moment matrix elements. The measurements in this work were more extensive than reported in prior studies by this author for the (010)-(000) band. (C) 1998 Academic Press. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Toth, RA (reprint author), CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. NR 19 TC 101 Z9 102 U1 1 U2 8 PU ACADEMIC PRESS INC ELSEVIER SCIENCE PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA SN 0022-2852 J9 J MOL SPECTROSC JI J. Mol. Spectrosc. PD AUG PY 1998 VL 190 IS 2 BP 379 EP 396 DI 10.1006/jmsp.1998.7611 PG 18 WC Physics, Atomic, Molecular & Chemical; Spectroscopy SC Physics; Spectroscopy GA 103JB UT WOS:000075153100021 ER PT J AU Schwenke, DW AF Schwenke, DW TI New H2O rovibrational line assignments SO JOURNAL OF MOLECULAR SPECTROSCOPY LA English DT Article C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Schwenke, DW (reprint author), NASA, Ames Res Ctr, MS230-3, Moffett Field, CA 94035 USA. RI schwenke, david/I-3564-2013 NR 2 TC 15 Z9 16 U1 0 U2 2 PU ACADEMIC PRESS INC PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA SN 0022-2852 J9 J MOL SPECTROSC JI J. Mol. Spectrosc. PD AUG PY 1998 VL 190 IS 2 BP 397 EP 402 DI 10.1006/jmsp.1998.7603 PG 6 WC Physics, Atomic, Molecular & Chemical; Spectroscopy SC Physics; Spectroscopy GA 103JB UT WOS:000075153100022 ER PT J AU Perrone, JA Stone, LS AF Perrone, JA Stone, LS TI Emulating the visual receptive-field properties of MST neurons with a template model of heading estimation SO JOURNAL OF NEUROSCIENCE LA English DT Article DE self-motion perception; navigation; optic flow; gaze stabilization; monkey; vision ID OPTIC FLOW STIMULI; SUPERIOR TEMPORAL AREA; PURSUIT EYE-MOVEMENTS; MACAQUE MONKEY; SELF-MOTION; EXPANSION CONTRACTION; FUNCTIONAL-PROPERTIES; RESPONSE SELECTIVITY; TRACKING NEURONS; NEURAL NETWORK AB We have proposed previously a computational neural-network model by which the complex patterns of retinal image motion generated during locomotion (optic flow) can be processed by specialized detectors acting as templates for specific instances of self-motion. The detectors in this template model respond to global optic flow by sampling image motion over a large portion of the visual field through networks of local motion sensors with properties similar to those of neurons found in the middle temporal (MT) area of primate extrastriate visual cortex. These detectors, arranged within cortical-like maps, were designed to extract self-translation (heading) and self-rotation, as well as the scene layout (relative distances) ahead of a moving observer. We then postulated that heading from optic flow is directly encoded by individual neurons acting as heading detectors within the medial superior temporal (MST) area. Others have questioned whether individual MST neurons can perform this function because some of their receptive-field properties seem inconsistent with this role. To resolve this issue, we systematically compared MST responses with those of detectors from two different configurations of the model under matched stimulus conditions. We found that the characteristic physiological properties of MST neurons can be explained by the template model. We conclude that MST neurons are well suited to support self-motion estimation via a direct encoding of heading and that the template model provides an explicit set of testable hypotheses that can guide future exploration of MST and adjacent areas within the superior temporal sulcus. C1 Univ Waikato, Dept Psychol, Hamilton, New Zealand. NASA, Human Informat Proc Res Branch, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Perrone, JA (reprint author), Univ Waikato, Dept Psychol, Private Bag 3105, Hamilton, New Zealand. NR 66 TC 63 Z9 66 U1 1 U2 1 PU SOC NEUROSCIENCE PI WASHINGTON PA 11 DUPONT CIRCLE, NW, STE 500, WASHINGTON, DC 20036 USA SN 0270-6474 J9 J NEUROSCI JI J. Neurosci. PD AUG 1 PY 1998 VL 18 IS 15 BP 5958 EP 5975 PG 18 WC Neurosciences SC Neurosciences & Neurology GA 103RN UT WOS:000074971800036 PM 9671682 ER PT J AU Merkle, LA Layne, CS Bloomberg, JJ Zhang, JJ AF Merkle, LA Layne, CS Bloomberg, JJ Zhang, JJ TI Using factor analysis to identify neuromuscular synergies during treadmill walking SO JOURNAL OF NEUROSCIENCE METHODS LA English DT Article DE coordination; electromyography; factor analysis; neuromuscular synergies ID GAIT; PATTERNS AB Neuroscientists are often interested in grouping variables to facilitate understanding of a particular phenomenon. Factor analysis is a powerful statistical technique that groups variables into conceptually meaningful clusters, but remains underutilized by neuroscience researchers presumably due to its complicated concepts and procedures. This paper illustrates an application of factor analysis to identify coordinated patterns of whole-body muscle activation during treadmill walking. Ten male subjects walked on a treadmill (6.4 km/h) for 20 a during which surface electromyographic (EMG) activity was obtained from the left side sternocleidomastoid, neck extensors, erector spinae, sind right side biceps femoris, rectus femoris, tibialis anterior, and medial gastrocnemius. Factor analysis revealed 65% of the variance of seven muscles sampled aligned with two orthogonal factors, labeled 'transition control' and 'loading'. These two factors describe coordinated patterns of muscular activity across body segments that would not be evident by evaluating individual muscle patterns. The results show that factor analysis can be effectively used to explore relationships among muscle patterns across all body segments to increase understanding of the complex coordination necessary for smooth and efficient locomotion. We encourage neuroscientists to consider using factor analysis to identify coordinated patterns of neuromuscular activation that would be obscured using more traditional EMG analyses. (C) 1998 Elsevier Science B.V. All rights reserved. C1 NASA, Lyndon B Johnson Space Ctr, Neurosci Lab, Houston, TX 77058 USA. Univ Houston, Dept Hlth & Human Performance, Houston, TX 77204 USA. RP Merkle, LA (reprint author), NASA, Lyndon B Johnson Space Ctr, Neurosci Lab, Mail Code NL-37, Houston, TX 77058 USA. NR 17 TC 36 Z9 37 U1 1 U2 6 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0165-0270 J9 J NEUROSCI METH JI J. Neurosci. Methods PD AUG 1 PY 1998 VL 82 IS 2 BP 207 EP 214 DI 10.1016/S0165-0270(98)00054-5 PG 8 WC Biochemical Research Methods; Neurosciences SC Biochemistry & Molecular Biology; Neurosciences & Neurology GA 113LV UT WOS:000075553200011 PM 9700694 ER PT J AU Oliker, L Biswas, R AF Oliker, L Biswas, R TI PLUM: Parallel load balancing for adaptive unstructured meshes SO JOURNAL OF PARALLEL AND DISTRIBUTED COMPUTING LA English DT Article ID GRIDS AB Mesh adaption is a powerful tool for efficient unstructured-grid computations but causes load imbalance among processors on a parallel machine. We present a novel method called PLUM to dynamically balance the processor workloads with a global view. This paper describes the implementation and integration of all major components within our dynamic load balancing strategy for adaptive grid calculations. Mesh adaption, repartitioning, processor assignment, and remapping are critical components of the framework that must be accomplished rapidly and efficiently so as not to cause a significant overhead to the numerical simulation. A data redistribution model is also presented that predicts the remapping cost on the SP2. This model is required to determine whether the gain from a balanced workload distribution offsets the cost of data movement. Results presented in this paper demonstrate that PLUM is an effective dynamic load balancing strategy which remains viable on a large number of processors. (C) 1998 Academic Press. C1 NASA, Ames Res Ctr, Adv Comp Sci Res Inst, Moffett Field, CA 94035 USA. NASA, Ames Res Ctr, MRJ Technol Solut, Moffett Field, CA 94035 USA. RP Oliker, L (reprint author), NASA, Ames Res Ctr, Adv Comp Sci Res Inst, Mail Stop T27A-1, Moffett Field, CA 94035 USA. EM oliker@riacs.edu; rbiswas@nas.nasa.gov NR 35 TC 49 Z9 52 U1 0 U2 3 PU ACADEMIC PRESS INC ELSEVIER SCIENCE PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA SN 0743-7315 EI 1096-0848 J9 J PARALLEL DISTR COM JI J. Parallel Distrib. Comput. PD AUG 1 PY 1998 VL 52 IS 2 BP 150 EP 177 DI 10.1006/jpdc.1998.1469 PG 28 WC Computer Science, Theory & Methods SC Computer Science GA 120NE UT WOS:000075961800004 ER PT J AU Kar, K Chakravarti, S Ray, A Sarkar, S AF Kar, K Chakravarti, S Ray, A Sarkar, S TI Half-lives and presupernova weak interaction rates for nuclei away from the stability line SO JOURNAL OF PHYSICS G-NUCLEAR AND PARTICLE PHYSICS LA English DT Article; Proceedings Paper CT International Workshop on Physics with Radioactive Nuclear Beams CY JAN 12-17, 1998 CL PURI, INDIA SP Saha Inst Nucl Phys, Variable Energy Cyclotron Ctr, Calcutta, India, Govt India, Dept Sci & Technol ID BETA-DECAY; DISTRIBUTIONS; STARS AB A detailed model for the calculation of B-decay rates of the fp shell nuclei for situations prevailing in presupernova and collapse phases of evolution of the core of massive stars leading to supernova explosion has been extended for electron-capture rates. It can also be used to determine the half-lives of neutron-rich nuclei in the fp/fpg shell. The model uses an averaged Gamow-Teller (GT) strength function, but it can also use the experimental log ft values and GT strength function from (n,p) reaction studies wherever available. The calculated rate includes contributions from each of the low-lying excited states of the mother including some specific resonant states ('back resonance') having large GT matrix elements. C1 Saha Inst Nucl Phys, Calcutta 700064, W Bengal, India. Visva Bharati Univ, Dept Phys, Santiniketan 731235, W Bengal, India. Tata Inst Fundamental Res, Bombay 400005, Maharashtra, India. Univ Calif Santa Barbara, Inst Theoret Phys, Santa Barbara, CA 93106 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Ananda Mohan Coll, Calcutta 700009, W Bengal, India. RP Kar, K (reprint author), Saha Inst Nucl Phys, 1-AF Bidhannagar, Calcutta 700064, W Bengal, India. NR 11 TC 4 Z9 4 U1 0 U2 1 PU IOP PUBLISHING LTD PI BRISTOL PA DIRAC HOUSE, TEMPLE BACK, BRISTOL BS1 6BE, ENGLAND SN 0954-3899 J9 J PHYS G NUCL PARTIC JI J. Phys. G-Nucl. Part. Phys. PD AUG PY 1998 VL 24 IS 8 BP 1641 EP 1645 DI 10.1088/0954-3899/24/8/045 PG 5 WC Physics, Nuclear; Physics, Particles & Fields SC Physics GA 109MG UT WOS:000075325900045 ER PT J AU Ogbuji, LUJT AF Ogbuji, LUJT TI Subparabolic oxidation behavior of silicon carbide at 1300 degrees C SO JOURNAL OF THE ELECTROCHEMICAL SOCIETY LA English DT Article ID HIGH-TEMPERATURE OXIDATION; SI3N4; DIFFUSION; KINETICS; OXYGEN; CERAMICS; MODEL AB The phenomenon of subparabolic oxide growth rate, more the rule than the exception in the oxidation of silica formers, is examined in light of data sets acquired in SiC oxidation experiments at 1300 degrees C. Negative deviation from parabolic kinetics is shown to correlate with oxide crystallinity. The data sets were analyzed to ascertain the predominant and contributing growth laws, and tested with models that describe the overall kinetics as combinations of the familiar growth laws. C1 NASA, Lewis Res Ctr Grp, SETAR Team, Cleveland, OH 44135 USA. RP Ogbuji, LUJT (reprint author), NASA, Lewis Res Ctr Grp, SETAR Team, Cleveland, OH 44135 USA. NR 26 TC 6 Z9 6 U1 1 U2 4 PU ELECTROCHEMICAL SOC INC PI PENNINGTON PA 65 SOUTH MAIN STREET, PENNINGTON, NJ 08534 USA SN 0013-4651 J9 J ELECTROCHEM SOC JI J. Electrochem. Soc. PD AUG PY 1998 VL 145 IS 8 BP 2876 EP 2882 DI 10.1149/1.1838728 PG 7 WC Electrochemistry; Materials Science, Coatings & Films SC Electrochemistry; Materials Science GA 104BE UT WOS:000074991700040 ER PT J AU Angelovici, MM Bryant, RG Northam, GB Roberts, AS AF Angelovici, MM Bryant, RG Northam, GB Roberts, AS TI Carbon/ceramic microcomposites, preparation and properties SO MATERIALS LETTERS LA English DT Article DE carbon-carbon; carbon-ceramic; microcomposites; thermo-oxidative stability ID CARBON-CARBON COMPOSITES; OXIDATION BEHAVIOR; ADDITIVES AB Carbon-carbon and carbon-ceramic microcomposites were molded by using thermoplastic polyimide coated carbon and ceramic powders. The effect of particle size powders and different processes of hot pressing were examined. A 53 MPa flexural strength and a 10 Cpa flexural modulus were obtained for 2.15 g/cc density microcomposites. Thermo-oxidative stability of carbon microcomposites with three combinations of B4C/SiC additives were compared with original carbon-carbon microcomposites. The oxidative stability of the carbon/B4C/SiC composites was extended up to 1000 degrees C. After exposure to flowing air at 700 degrees C for 100 h, the weight lost of the carbon-ceramic composites was only 4%, attributed to boron oxide evaporation. There is a degradation of the mechanical and physical properties of carbon-carbon and carbon-ceramic composites after carbonization and graphitization. This degradation is slowed down by B4C/SiC additives. (C) 1998 Elsevier Science B.V. All rights reserved. C1 Old Dominion Univ, Dept Mech Engn, Norfolk, VA 23529 USA. NASA, Langley Res Ctr, Hampton, VA 23681 USA. RP Angelovici, MM (reprint author), Old Dominion Univ, Dept Mech Engn, Norfolk, VA 23529 USA. NR 12 TC 10 Z9 15 U1 0 U2 4 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0167-577X J9 MATER LETT JI Mater. Lett. PD AUG PY 1998 VL 36 IS 5-6 BP 254 EP 265 DI 10.1016/S0167-577X(98)00053-6 PG 12 WC Materials Science, Multidisciplinary; Physics, Applied SC Materials Science; Physics GA 103YG UT WOS:000074985000005 ER PT J AU Vorontsov, SV Jefferies, SM Duval, TL Harvey, JW AF Vorontsov, SV Jefferies, SM Duval, TL Harvey, JW TI Acoustic interferometry of the solar atmosphere: p-modes with frequencies near the 'acoustic cut-off' SO MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY LA English DT Article DE techniques : interferometric; Sun : activity; Sun : atmosphere; Sun : oscillations ID OSCILLATIONS; SUN AB High-frequency p-mode intensity data, obtained from the South Pole in 1987, 1988, 1990 and 1994, show a sharp variation in the phase-shift function and in the frequency spacings near 5.5 mHz. Using a simple theoretical model, we demonstrate that this behaviour is caused by an acoustic resonance in the atmosphere between the excitation source and the upper reflection level. We discuss the diagnostic properties of this resonance, which is sensitive to the acoustic reflectivity of the solar atmosphere and to the location and parity of the excitation source. When applied to the solar data, our model indicates that the average acoustic reflectivity increases with increasing solar activity. The model also shows that the acoustic source has composite parity and is located within one pressure scaleheight of the base of the photosphere. C1 Univ London Queen Mary & Westfield Coll, Astron Unit, London E1 4NS, England. Inst Phys Earth B, Moscow 123810, Russia. Univ Delaware, Bartol Res Inst, Newark, DE 19716 USA. NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, Greenbelt, MD 20771 USA. Natl Opt Astron Observ, Natl Solar Observ, Tucson, AZ 85726 USA. RP Vorontsov, SV (reprint author), Univ London Queen Mary & Westfield Coll, Astron Unit, Mile End Rd, London E1 4NS, England. NR 17 TC 7 Z9 7 U1 0 U2 0 PU BLACKWELL SCIENCE LTD PI OXFORD PA P O BOX 88, OSNEY MEAD, OXFORD OX2 0NE, OXON, ENGLAND SN 0035-8711 J9 MON NOT R ASTRON SOC JI Mon. Not. Roy. Astron. Soc. PD AUG 1 PY 1998 VL 298 IS 2 BP 464 EP 470 DI 10.1046/j.1365-8711.1998.01630.x PG 7 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 120EH UT WOS:000075941500019 ER PT J AU Israel, GL Angelini, L Campana, S Giommi, P Stella, L White, NE AF Israel, GL Angelini, L Campana, S Giommi, P Stella, L White, NE TI The discovery of 12-min X-ray pulsations from 1WGA J1958.2+3232 SO MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY LA English DT Article DE stars : individual : 1WGA J1958.2+3232; novae, cataclysmic variables; pulsars : general; stars : rotation; X-rays : stars ID SMALL-MAGELLANIC-CLOUD; INTERMEDIATE POLAR; X0142+614; PULSARS; SYSTEM; BINARY; PERIOD AB During a systematic search for periodic signals in a sample of ROSAT PSPC (0.1-2.4 keV) light curves, we have discovered similar to 12-min large-amplitude X-ray pulsations in 1WGA J1958.2+3232, an X-ray source which lies close to the Galactic plane. The energy spectrum is well fitted by a power law with a photon index of 0.8, corresponding to an X-ray flux level of similar to 10(-12) erg cm(-2) s(-1). The source is probably a long-period, low-luminosity X-ray pulsar, similar to X Per, or an intermediate polar. C1 Osservatorio Astron Roma, I-00040 Rome, Italy. NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. Univ Space Res Assoc, Greenbelt, MD USA. Osserv Astron Brera, I-23807 Merate, Lecco, Italy. ASI, SAX Sci Data Ctr, I-00198 Rome, Italy. RP Israel, GL (reprint author), Osservatorio Astron Roma, Vicolo Osserv 2, I-00040 Rome, Italy. RI White, Nicholas/B-6428-2012; OI White, Nicholas/0000-0003-3853-3462; Campana, Sergio/0000-0001-6278-1576; giommi, paolo/0000-0002-2265-5003; Israel, GianLuca/0000-0001-5480-6438 NR 27 TC 17 Z9 17 U1 0 U2 0 PU BLACKWELL SCIENCE LTD PI OXFORD PA P O BOX 88, OSNEY MEAD, OXFORD OX2 0NE, OXON, ENGLAND SN 0035-8711 J9 MON NOT R ASTRON SOC JI Mon. Not. Roy. Astron. Soc. PD AUG 1 PY 1998 VL 298 IS 2 BP 502 EP 506 DI 10.1046/j.1365-8711.1998.01653.x PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 120EH UT WOS:000075941500023 ER PT J AU Willacy, K Millar, TJ AF Willacy, K Millar, TJ TI Desorption processes and the deuterium fractionation in molecular clouds SO MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY LA English DT Article DE molecular processes; ISM : abundances; ISM : clouds; ISM : molecules ID DENSE INTERSTELLAR CLOUDS; RAY-INDUCED DESORPTION; GAS-PHASE CHEMISTRY; GRAIN MANTLES; DEPLETION; MODELS; H-2; CORES AB Several processes have been suggested as ways of returning accreted grain mantles to the gas, thus preventing the total removal of molecules from the gas phase in dark quiescent clouds. We attempt to distinguish between them by considering not only the calculated gas-phase abundances, but also the ratio of the abundances of deuterated species to non-deuterated species. We find that the D/H ratio in molecules is relatively model-independent, but that desorption due to the formation of H-2 on grains gives the best overall agreement with the observations. C1 Univ Manchester, Inst Sci & Technol, Dept Phys, Manchester M60 1QD, Lancs, England. RP Willacy, K (reprint author), CALTECH, Jet Prop Lab, MS 169-327, Pasadena, CA 91109 USA. OI Millar, Tom/0000-0001-5178-3656 NR 26 TC 65 Z9 65 U1 0 U2 1 PU BLACKWELL SCIENCE LTD PI OXFORD PA P O BOX 88, OSNEY MEAD, OXFORD OX2 0NE, OXON, ENGLAND SN 0035-8711 J9 MON NOT R ASTRON SOC JI Mon. Not. Roy. Astron. Soc. PD AUG 1 PY 1998 VL 298 IS 2 BP 562 EP 568 DI 10.1046/j.1365-8711.1998.01648.x PG 7 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 120EH UT WOS:000075941500029 ER PT J AU Charnley, SB AF Charnley, SB TI The chemical signature of magnetohydrodynamic waves in molecular clouds SO MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY LA English DT Letter DE MHD; molecular processes; ISM : clouds; ISM : molecules ID DENSE INTERSTELLAR CLOUDS; STAR FORMATION; DARK CLOUDS; DEUTERIUM; CHEMISTRY; MODEL; FRACTIONATION; DISSIPATION; DEUTERATION; IONIZATION AB By considering the propagation of low-amplitude magnetohydrodynamic waves in partially ionized plasmas, it is shown that the ion-neutral drift (ambipolar diffusion) induced by the waves can have specific effects on the molecular chemistry of cold material. The chemistry occurring in gas swept by Alfven waves is described and it is shown that this leads to spatial variations in the deuterium fractionation ratios of, for example, HCO+ and N2H+, on spatial scales of a few hundredths of a parsec, depending upon the fractional ionization of the ambient medium. The possibility of detecting interstellar Alfven waves by molecular spectroscopy and their effect of producing small-scale chemical abundance gradients in molecular clouds are briefly discussed. C1 Univ Calif Berkeley, Dept Astron, Berkeley, CA 94720 USA. NASA, Div Space Sci, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Charnley, SB (reprint author), Univ Calif Berkeley, Dept Astron, 601 Campbell Hall, Berkeley, CA 94720 USA. RI Charnley, Steven/C-9538-2012 NR 38 TC 9 Z9 9 U1 0 U2 0 PU BLACKWELL SCIENCE LTD PI OXFORD PA P O BOX 88, OSNEY MEAD, OXFORD OX2 0NE, OXON, ENGLAND SN 0035-8711 J9 MON NOT R ASTRON SOC JI Mon. Not. Roy. Astron. Soc. PD AUG 1 PY 1998 VL 298 IS 2 BP L25 EP L28 DI 10.1046/j.1365-8711.1998.01757.x PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 120EH UT WOS:000075941500001 ER PT J AU Jusem, JC Atlas, R AF Jusem, JC Atlas, R TI Diagnostic evaluation of vertical motion forcing mechanisms by using Q-vector partitioning SO MONTHLY WEATHER REVIEW LA English DT Article ID SECONDARY CIRCULATIONS; MODEL; FRONTOGENESIS; EQUATION; CYCLONE AB Q-vector partitioning has proven to be a useful tool for the understanding of the frictionless, adiabatic processes responsible for the generation of synoptic-scale vertical motion in the extratropical atmosphere. Partitioning of Q into components parallel and normal to the isotherms on an isobaric surface is standard practice in studies dealing with vertical motion and frontogenesis. This paper is concerned with vertical motion only and examines the consequences of projecting Q onto isohypses, instead of isotherms, on an isobaric surface. Specifically, the Q vector is partitioned in the natural coordinate system that follows the geostrophic wind. The novelty with this partitioning is that it naturally leads to the evaluation of different vertical motion forcing mechanisms, among which are those related to flow curvature and to confluence or diffluence. This evaluation is illustrated by applying the new Q-vector partition to a gridded analysis of a real weather situation. An important conclusion is that the thermal advection by horizontal geostrophic shear is as significant to the forcing of vertical motion as the geostrophic confluence/diffluence. While this result has previously been obtained in the study of frontal dynamics, this is the first application of this finding to the synoptic scale. C1 NASA, Goddard Space Flight Ctr, Atmospheres Lab, Data Assimilat Off, Greenbelt, MD 20771 USA. RP Atlas, R (reprint author), NASA, Goddard Space Flight Ctr, Atmospheres Lab, Data Assimilat Off, Code 910-4, Greenbelt, MD 20771 USA. EM atlas@dao.gsfc.nasa.gov RI Atlas, Robert/A-5963-2011 OI Atlas, Robert/0000-0002-0706-3560 NR 22 TC 16 Z9 21 U1 0 U2 1 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 USA SN 0027-0644 J9 MON WEATHER REV JI Mon. Weather Rev. PD AUG PY 1998 VL 126 IS 8 BP 2166 EP 2184 DI 10.1175/1520-0493(1998)126<2166:DEOVMF>2.0.CO;2 PG 19 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 110TN UT WOS:000075396600007 ER PT J AU Todling, R Cohn, SE Sivakumaran, NS AF Todling, R Cohn, SE Sivakumaran, NS TI Suboptimal schemes for retrospective data assimilation based on the fixed-lag Kalman smoother SO MONTHLY WEATHER REVIEW LA English DT Article ID ATMOSPHERIC DATA ASSIMILATION; FILTER; MODEL AB The fixed-lag Kalman smoother was proposed recently by S. E. Cohn et al. as a framework for providing retrospective data assimilation capability in atmospheric reanalysis projects. Retrospective data assimilation refers to the dynamically consistent incorporation of data observed well past each analysis time into each analysis. Like the Kalman filter, the fixed-lag Kalman smoother requires statistical information that is not available in practice and involves an excessive amount of computation if implemented by brute Force, and must therefore be approximated sensibly to become feasible for operational use. In this article the performance of suboptimal retrospective data assimilation systems (RDASs) based on a variety of approximations to the optimal fixed-lag Kalman smoother is evaluated. Since the fixed-lag Kalman smoother formulation employed in this work separates naturally into a (Kalman) filter portion and an optimal retrospective analysis portion, two suboptimal strategies are considered: (i) viable approximations to the Kalman filter portion coupled with the optimal retrospective analysis portion, and (ii) viable approximations to both portions. These two strategies are studied in the context of a linear dynamical model and observing system, since it is only under these circumstances that performance can be evaluated exactly. A shallow water model, linearized about an unstable basic flow, is used for this purpose. Results indicate that retrospective data assimilation can be successful even when simple filtering schemes are used, such as one resembling current operational statistical analysis schemes. In this case, however, online adaptive tuning of the forecast error covariance matrix is necessary. The performance of this RDAS is similar to that of the Kalman filter itself. More sophisticated approximate filtering algorithms, such as ones employing singular values/vectors of the propagator or eigenvalues/vectors of the error covariances, as a way to account For error covariance propagation, lead to even better RDAS performance. Approximating both the filter and retrospective analysis portions of the RDAS is also shown to be an acceptable approach in some cases. C1 NASA, Goddard Space Flight Ctr, Data Assimilat Off, Univ Space Res Assoc, Greenbelt, MD 20771 USA. RP Todling, R (reprint author), NASA, Goddard Space Flight Ctr, Data Assimilat Off, Univ Space Res Assoc, Code 910-3, Greenbelt, MD 20771 USA. RI Cohn, Stephen/K-1954-2012 OI Cohn, Stephen/0000-0001-8506-9354 NR 36 TC 19 Z9 19 U1 0 U2 0 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 USA SN 0027-0644 J9 MON WEATHER REV JI Mon. Weather Rev. PD AUG PY 1998 VL 126 IS 8 BP 2274 EP 2286 DI 10.1175/1520-0493(1998)126<2274:SSFRDA>2.0.CO;2 PG 13 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 110TN UT WOS:000075396600013 ER PT J AU Aprile, E Egorov, V Giboni, KL Kozu, T Xu, F Doke, T Kikuchi, J Kashiwagi, T Fishman, GJ Rehage, R Trice, D AF Aprile, E Egorov, V Giboni, KL Kozu, T Xu, F Doke, T Kikuchi, J Kashiwagi, T Fishman, GJ Rehage, R Trice, D TI The electronics read out and data acquisition system for a liquid xenon time projection chamber as a balloon-borne Compton telescope SO NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT LA English DT Article ID TPC AB A 10 l liquid xenon time projection chamber with a drift gap of 7 cm, was developed for imaging cosmic gamma-rays in the energy band 0.3-10 MeV. It was used for the first time as a balloon-borne instrument in two recent flights from Palestine, TX. The detector uses both the ionization and the primary scintillation signals produced by gamma-ray interactions in the liquid for an accurate measurement of the three spatial coordinates and for the energy deposition in each interaction. With this information, the arrival direction of gamma-rays fully absorbed in the liquid xenon after one or more Compton scatterings can then be reconstructed. Here we describe the electronics readout system used for the initial balloon flights of the LXeTPC operating as a Compton telescope. Data from the laboratory and cosmic gamma-ray sources acquired with this custom-designed system are presented. (C) 1998 Elsevier Science B.V. All rights reserved. C1 Columbia Univ, Astrophys Lab, New York, NY 10027 USA. Waseda Univ, Adv Res Ctr Sci & Engn, Tokyo 162, Japan. Kanagawa Univ, Fac Engn, Yokohama, Kanagawa 221, Japan. NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. RP Aprile, E (reprint author), Columbia Univ, Astrophys Lab, New York, NY 10027 USA. NR 7 TC 28 Z9 28 U1 0 U2 1 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0168-9002 J9 NUCL INSTRUM METH A JI Nucl. Instrum. Methods Phys. Res. Sect. A-Accel. Spectrom. Dect. Assoc. Equip. PD AUG 1 PY 1998 VL 412 IS 2-3 BP 425 EP 436 DI 10.1016/S0168-9002(98)00480-X PG 12 WC Instruments & Instrumentation; Nuclear Science & Technology; Physics, Nuclear; Physics, Particles & Fields SC Instruments & Instrumentation; Nuclear Science & Technology; Physics GA 116AB UT WOS:000075697800023 ER PT J AU Drachman, RJ AF Drachman, RJ TI A general overview of positron collision physics SO NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS LA English DT Article; Proceedings Paper CT Workshop on Low Energy Positron and Positronium Physics CY JUL 15-18, 1997 CL UNIV NOTTINGHAM, NOTTINGHAM, ENGLAND HO UNIV NOTTINGHAM DE positrons; positronium; antimatter; resonances; annihilation ID HYDROGEN SCATTERING; BOUND-STATES; ATOM SCATTERING; ANNIHILATION; RESONANCES; THRESHOLD; MOLECULES; NONEXISTENCE; ELECTRONS; HELIUM AB I will give a brief history of the field of positronics, both experimental and theoretical, emphasizing what I consider to be the most interesting techniques, results, and processes that have been studied. These include positron and positronium scattering and annihilation in simple and complex systems, positronium formation, resonances, and bound states. Annihilation in astrophysical context will also be mentioned. It will he evident that some of the same questions that engaged the earliest workers in the field are still unanswered, but others have been brilliantly treated and largely resolved. A brief discussion about the future of the subject concludes the overview. Published by Elsevier Science B.V. C1 NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, Greenbelt, MD 20771 USA. RP Drachman, RJ (reprint author), NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, Code 682, Greenbelt, MD 20771 USA. NR 66 TC 13 Z9 13 U1 0 U2 0 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0168-583X J9 NUCL INSTRUM METH B JI Nucl. Instrum. Methods Phys. Res. Sect. B-Beam Interact. Mater. Atoms PD AUG PY 1998 VL 143 IS 1-2 BP 1 EP 10 DI 10.1016/S0168-583X(98)00212-2 PG 10 WC Instruments & Instrumentation; Nuclear Science & Technology; Physics, Atomic, Molecular & Chemical; Physics, Nuclear SC Instruments & Instrumentation; Nuclear Science & Technology; Physics GA 113UY UT WOS:000075573100002 ER PT J AU Bhatia, AK Drachman, RJ AF Bhatia, AK Drachman, RJ TI Relativistic corrections to the binding energy of Ps(-) SO NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS LA English DT Article; Proceedings Paper CT Workshop on Low Energy Positron and Positronium Physics CY JUL 15-18, 1997 CL UNIV NOTTINGHAM, NOTTINGHAM, ENGLAND HO UNIV NOTTINGHAM DE positron; positronium; positronium ion ID POSITRONIUM NEGATIVE-ION; PHOTODETACHMENT AB Relativistic corrections to the nonrelativistic binding energy of Ps(-), calculated using a Hylleraas-type wave function having up to 615 terms, have been calculated by using the Breit interaction reduced to the large components. The nonrelativistic total energy is lowered by 1.35x10(-5) R-mu. We suggest that the binding energy of Ps(-) be measured by experiments similar to that for H-. Published by Elsevier Science B.V. C1 NASA, Astron & Solar Phys Lab, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Bhatia, AK (reprint author), NASA, Astron & Solar Phys Lab, Goddard Space Flight Ctr, Code 682, Greenbelt, MD 20771 USA. NR 6 TC 15 Z9 15 U1 0 U2 2 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0168-583X J9 NUCL INSTRUM METH B JI Nucl. Instrum. Methods Phys. Res. Sect. B-Beam Interact. Mater. Atoms PD AUG PY 1998 VL 143 IS 1-2 BP 195 EP 198 DI 10.1016/S0168-583X(98)00114-1 PG 4 WC Instruments & Instrumentation; Nuclear Science & Technology; Physics, Atomic, Molecular & Chemical; Physics, Nuclear SC Instruments & Instrumentation; Nuclear Science & Technology; Physics GA 113UY UT WOS:000075573100028 ER PT J AU Hepner, GF Houshmand, B Kulikov, I Bryant, N AF Hepner, GF Houshmand, B Kulikov, I Bryant, N TI Investigation of the integration of AVIRIS and IFSAR for urban analysis SO PHOTOGRAMMETRIC ENGINEERING AND REMOTE SENSING LA English DT Article ID LAND-USE CLASSIFICATION; TM-DATA; VEGETATION; MSS AB Most attempts at urban analysis using remotely sensed imagery lack the capabilities necessary to define the detailed geometry and differentiate the textures of the complex urban landscape. This paper presents a proof-of-concept study of the potential for integrative analysis of Interferometric Synthetic Aperture Radar (IFSAR) and Airborne Visible/infrared imaging Spectrometer (AVIRIS) hyperspectral imagery for a study area in Los Angeles, California. Recent advances in the use of interferometric radar allow the definition of high resolution, three-dimensional (3D) geometry of surface features, topography, and impervious surfaces in urban areas. The radar analysis is enhanced using hyperspectral imagery to mask surfaces adjacent to structures in order to assist in the determination of baseline topography and segmentation of building footprints for improved geometric measurement of the complex urban area. C1 Univ Utah, Dept Geog OSH270, Salt Lake City, UT 84112 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Hepner, GF (reprint author), Univ Utah, Dept Geog OSH270, Salt Lake City, UT 84112 USA. EM george.hepner@geog.utah.edu; bh@athena.jpl.nasa.gov NR 24 TC 37 Z9 37 U1 0 U2 3 PU AMER SOC PHOTOGRAMMETRY PI BETHESDA PA 5410 GROSVENOR LANE SUITE 210, BETHESDA, MD 20814-2160 USA SN 0099-1112 J9 PHOTOGRAMM ENG REM S JI Photogramm. Eng. Remote Sens. PD AUG PY 1998 VL 64 IS 8 BP 813 EP 820 PG 8 WC Geography, Physical; Geosciences, Multidisciplinary; Remote Sensing; Imaging Science & Photographic Technology SC Physical Geography; Geology; Remote Sensing; Imaging Science & Photographic Technology GA 106BE UT WOS:000075109200010 ER PT J AU Bennett, MJ Pope, JK Beavis, D Carroll, JB Chiba, J Chikanian, A Crawford, HJ Cronqvist, M Dardenne, Y Debbe, R Doke, T Engelage, J Greiner, L Hayano, RS Hallman, TJ Heckman, HH Kashiwagi, T Kikuchi, J Kumar, BS Kuo, C Lindstrom, PJ Mitchell, JW Nagamiya, S Nagle, JL Stankus, P Tanaka, KH Welsh, RC Zhan, W AF Bennett, MJ Pope, JK Beavis, D Carroll, JB Chiba, J Chikanian, A Crawford, HJ Cronqvist, M Dardenne, Y Debbe, R Doke, T Engelage, J Greiner, L Hayano, RS Hallman, TJ Heckman, HH Kashiwagi, T Kikuchi, J Kumar, BS Kuo, C Lindstrom, PJ Mitchell, JW Nagamiya, S Nagle, JL Stankus, P Tanaka, KH Welsh, RC Zhan, W CA E878 Collaboration TI Light nuclei production in relativistic Au+nucleus collisions SO PHYSICAL REVIEW C LA English DT Article ID HEAVY-ION COLLISIONS; THERMODYNAMIC MODEL; COALESCENCE; FLOW; SIZE AB We have measured the yields of protons and A = 2-4 nuclei in collisions between 10.8A GeV/c Au beams and targets of Al, Cu, and Au. The data, which cover a broad rapidity range at low transverse momenta, were measured as a function of collision centrality using a focusing beam line spectrometer and a high-rate centrality detector. We investigate the dependence of coalescence parameters on event geometry. The data are compared with the predictions of an RQMD+coalescence model. C1 Yale Univ, AW Wright Nucl Struct Lab, New Haven, CT 06511 USA. Brookhaven Natl Lab, Upton, NY 11973 USA. Univ Calif Los Angeles, Los Angeles, CA 90095 USA. KEK, Tsukuba, Ibaraki, Japan. Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA. Waseda Univ, Sci & Engn Res Inst, Waseda, Japan. Univ Tokyo, Tokyo, Japan. EO Lawrence Berkeley Natl Lab, Berkeley, CA 94720 USA. USRA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Columbia Univ, Nevis Lab, Irvington, NY 10533 USA. Johns Hopkins Univ, Baltimore, MD 21218 USA. RP Bennett, MJ (reprint author), Yale Univ, AW Wright Nucl Struct Lab, New Haven, CT 06511 USA. RI Hayano, Ryugo/F-7889-2012; Kuo, Chaincy/H-9475-2016 OI Hayano, Ryugo/0000-0002-1214-7806; Kuo, Chaincy/0000-0001-7958-8764 NR 29 TC 13 Z9 13 U1 0 U2 0 PU AMERICAN PHYSICAL SOC PI COLLEGE PK PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA SN 0556-2813 J9 PHYS REV C JI Phys. Rev. C PD AUG PY 1998 VL 58 IS 2 BP 1155 EP 1164 DI 10.1103/PhysRevC.58.1155 PG 10 WC Physics, Nuclear SC Physics GA 110BR UT WOS:000075359800057 ER PT J AU Stoev, K Rame, E Leonhardt, T Garoff, S AF Stoev, K Rame, E Leonhardt, T Garoff, S TI The effects of thin films on the hydrodynamics near moving contact lines SO PHYSICS OF FLUIDS LA English DT Article ID SOLID-SURFACE; MICROSCOPIC MODEL; FLUID INTERFACE; STEADY MOVEMENT; DYNAMICS; ANGLES; LIQUIDS; MOTION; DROPS; FLOW AB We explore the effects of thin films on the hydrodynamics of macroscopic fluid bodies spreading over solid surfaces. To examine these effects, we measure the interface shape within microns of moving contact lines and compare those measurements to two asymptotic models in the limit of small capillary number, Ca. One model requires that the films affect the hydrodynamics only in a microscopic region near the contact line and allows the macroscopic meniscus to exhibit a nonzero effective contact angle. The other model describes the film as containing mobile fluid and specifically models the flow as fluid moves into or out of the film as the contact line moves. We examine fluids advancing and receding on wetting and nonwetting surfaces with spontaneously forming (molecular scale) and pre-existing (micron scale) films. Our results emphasize the importance of the mobility of the molecules in these very thin films in determining the hydrodynamics governing the moving contact line. The first model, which describes fluids advancing over dry surfaces, also accounts for the hydrodynamics of liquids advancing over very thin, immobile films. Surprisingly, the same model fails when fluid recedes on a nonwetting surface and no film is present. For mobile pre-existing films, the second model, based on Landau and Levich's theory, accounts for the hydrodynamics in the limit of small Ca. (C) 1998 American Institute of Physics. C1 Carnegie Mellon Univ, Dept Phys, Pittsburgh, PA 15213 USA. Carnegie Mellon Univ, Colloids Polymers & Surfaces Program, Pittsburgh, PA 15213 USA. NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. RP Stoev, K (reprint author), Carnegie Mellon Univ, Dept Phys, Pittsburgh, PA 15213 USA. RI Garoff, Stephen/P-7629-2014 OI Garoff, Stephen/0000-0001-8148-8535 NR 46 TC 19 Z9 19 U1 0 U2 6 PU AMER INST PHYSICS PI WOODBURY PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 USA SN 1070-6631 J9 PHYS FLUIDS JI Phys. Fluids PD AUG PY 1998 VL 10 IS 8 BP 1793 EP 1803 DI 10.1063/1.869700 PG 11 WC Mechanics; Physics, Fluids & Plasmas SC Mechanics; Physics GA 110KD UT WOS:000075379200004 ER PT J AU Speziale, CG Younis, BA Rubinstein, R Zhou, Y AF Speziale, CG Younis, BA Rubinstein, R Zhou, Y TI On consistency conditions for rotating turbulent flows SO PHYSICS OF FLUIDS LA English DT Article ID CLOSURE; MODELS AB Consistency conditions for the prediction of turbulent flows in a rotating frame are examined. It is shown that the dissipation rate should vanish along with the eddy viscosity in the limit of rapid rotations. The latter result is also true when the eddy viscosity is anisotropic and formally follows from the explicit algebraic stress approximation as well as from a phenomenological treatment. The former result has been built into the modeled dissipation rate equation of recent turbulence models where the second result has been violated. In fact, some of these models have the eddy viscosity going to infinity while the dissipation rate vanishes, leading to an inconsistency. For consistency, both of these conditions must be satisfied. The implications of these results for turbulence modeling are thoroughly discussed. (C) 1998 American Institute of Physics. C1 Boston Univ, Dept Mech & Aerosp Engn, Boston, MA 02215 USA. City Univ London, Dept Civil Engn, London EC1V 0HB, England. NASA, Langley Res Ctr, Inst Comp Applicat Sci & Engn, Hampton, VA 23681 USA. IBM Corp, Div Res, TJ Watson Res Ctr, Yorktown Heights, NY 10598 USA. RP Speziale, CG (reprint author), Boston Univ, Dept Mech & Aerosp Engn, Boston, MA 02215 USA. NR 16 TC 22 Z9 22 U1 0 U2 7 PU AMER INST PHYSICS PI WOODBURY PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 USA SN 1070-6631 J9 PHYS FLUIDS JI Phys. Fluids PD AUG PY 1998 VL 10 IS 8 BP 2108 EP 2110 DI 10.1063/1.869727 PG 3 WC Mechanics; Physics, Fluids & Plasmas SC Mechanics; Physics GA 110KD UT WOS:000075379200033 ER PT J AU Morgan, TH Killen, RM AF Morgan, TH Killen, RM TI Production mechanisms for faint but possibly detectable coronae about asteroids SO PLANETARY AND SPACE SCIENCE LA English DT Article ID ATMOSPHERE; EVOLUTION; EMISSION; SURFACE; WATER AB Asteroidal surfaces are exposed to the same processes which create observable exospheres about such refractory, volatile-free surfaces as those of the Moan and Mercury. Are there modest coronae about asteroids? We have chosen to examine this problem for two species, sodium and water vapor. Sodium was chosen because NaD emission is easily observed from the Earth's surface and emissions are observed in the exospheres of both the Moon and Mercury. In addition, the spatial distribution of emission in the sodium D lines about an asteroid would be a direct measure of the velocity distribution of the sodium source, which cannot be measured directly in the case of Mercury or the Moon. This provides a new technique for assessing the possible water content of asteroids. There is now very good evidence that water is present in hydrates and other aqueous alteration products. A detection of an hydroxyl corona about one of these asteroids would be proof of the presence of these aqueous bi-products; the amount of the water production would a direct measure of the water content of the asteroidal regolith. Water-rich asteroids are of course a potential resource and hold important clues to the evolution of the planets. We have calculated the production of sodium and water (hydroxyl) coronae about asteroids due to just two production mechanisms: sputtering and impact vaporization. We find that for realistic assumptions an asteroid with perihelion near 2 AU would have a small (about 3R) OH corona, while the likely sodium coronae would be about half as bright. These emissions will be extremely difficult to detect from the ground, but they may be detectable from space. (C) 1998 Elsevier Science Ltd. All rights reserved. C1 NASA, Res Program Management Div, Washington, DC 20546 USA. SW Res Inst, Instrumentat & Space Sci Div, San Antonio, TX 78228 USA. RP Morgan, TH (reprint author), NASA, Res Program Management Div, Code SR,300E St SW, Washington, DC 20546 USA. EM tom@image1.space.swri.edu RI Morgan, Thomas/I-5943-2013 NR 32 TC 15 Z9 15 U1 0 U2 1 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0032-0633 J9 PLANET SPACE SCI JI Planet Space Sci. PD AUG PY 1998 VL 46 IS 8 BP 843 EP 850 DI 10.1016/S0032-0633(98)00029-4 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 128QZ UT WOS:000076418800002 ER PT J AU Enzian, A Cabot, H Klinger, J AF Enzian, A Cabot, H Klinger, J TI Simulation of the water and carbon monoxide production rates of comet Hale-Bopp using a quasi 3-D nucleus model SO PLANETARY AND SPACE SCIENCE LA English DT Article; Proceedings Paper CT Asteroids, Meteors and Comets Meeting CY JUN, 1996 CL VERSAILLES, FRANCE ID EVOLUTION; ICE; C/1995-O1 AB The activity of comet C/1995 O1 (Hale-Bopp) has been simulated using a multidimensional comet model (Enzian et nl., 1997). In this model the comet nucleus is considered to be formed by a fluffy ice-dust matrix. Heat and gas diffusion inside the rotating nucleus is taken into account in radial and meridional direction. A quasi tri-dimensional solution is obtained through the dependency of the boundary conditions on the hour angle. The ice phase is considered to be amorphous water ice including solid carbon monoxide, both trapped in amorphous water ice and as an independent phase. Comet Hale-Bopp is of particular interest due to its strong activity and the significant CO production at large heliocentric distance. The model results provide a satisfying fit to the observed CO production rates (until perihelion) in the case of an amorphous ice composition and a CO source located below the surface, and not at the surface. During the ACM'96 meeting in June 1996 we predicted that the increase in carbon monoxide production levels off at about 3 AU and that the production rates increase again at about 1.5 AU (inbound). The gas production rates will then reach their maximum slightly after the comet's perihelion: 6 x 10(30) molecules s(-1) for CO and 2 x 10(31) molecules s(-1) for H2O (upper limit for a nucleus with a radius of 20 km). An attempt is made to take an extended H2O source in the coma into account. These predictions were compatible with recent observations of comet Hale-Bopp. (C) 1998 Elsevier Science Ltd. All rights reserved. C1 Univ Grenoble 1, CNRS, Lab Glaciol & Geophys Environm, F-38402 St Martin Dheres, France. RP Enzian, A (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr,M-S 183-601, Pasadena, CA 91109 USA. NR 29 TC 17 Z9 17 U1 0 U2 0 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0032-0633 J9 PLANET SPACE SCI JI Planet Space Sci. PD AUG PY 1998 VL 46 IS 8 BP 851 EP 858 DI 10.1016/S0032-0633(98)00057-9 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 128QZ UT WOS:000076418800003 ER PT J AU Goldstein, RM Goldstein, SJ Kessler, DJ AF Goldstein, RM Goldstein, SJ Kessler, DJ TI Radar observations of space debris SO PLANETARY AND SPACE SCIENCE LA English DT Article ID ORBITAL DEBRIS; EARTH AB Our radar monitoring of small Earth-orbiting debris at NASA's Goldstone Tracking Station has been extended to an altitude of 3200 km. Many of the observed particles lie in clusters; the largest of which appears to be remnants of the West Ford Needles, launched over 3 decades earlier, and originally designed to have reentered the Earth's atmosphere long ago. (C) 1998 Elsevier Science Ltd. All rights reserved. C1 Univ Virginia, Dept Astron, Charlottesville, VA 22903 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Goldstein, RM (reprint author), Univ Virginia, Dept Astron, POB 3818, Charlottesville, VA 22903 USA. NR 14 TC 15 Z9 16 U1 0 U2 3 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0032-0633 J9 PLANET SPACE SCI JI Planet Space Sci. PD AUG PY 1998 VL 46 IS 8 BP 1007 EP 1013 DI 10.1016/S0032-0633(98)00026-9 PG 7 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 128QZ UT WOS:000076418800021 ER EF