FN Thomson Reuters Web of Science™ VR 1.0 PT J AU Neveu, CF Stark, LW AF Neveu, CF Stark, LW TI The virtual lens SO PRESENCE-TELEOPERATORS AND VIRTUAL ENVIRONMENTS LA English DT Article AB We describe a new type of feedback display based upon ocular accommodation, called the virtual lens, that maintains a focused projection of a CRT image on the retina independent of changes in accommodation, and that replaces the optical image-processing action of the crystalline lens with an arbitrary computable image transform. We describe some applications of the virtual lens in visual psychophysics and virtual environments. C1 NASA, Ames Res Ctr, Caelum Res Corp, Intelligent Mechanisms Grp, Moffett Field, CA 94035 USA. Univ Calif Berkeley, Neurol & Telerobot Lab, Berkeley, CA 94720 USA. RP Neveu, CF (reprint author), NASA, Ames Res Ctr, Caelum Res Corp, Intelligent Mechanisms Grp, Moffett Field, CA 94035 USA. NR 12 TC 2 Z9 2 U1 0 U2 0 PU M I T PRESS PI CAMBRIDGE PA FIVE CAMBRIDGE CENTER, CAMBRIDGE, MA 02142 USA SN 1054-7460 J9 PRESENCE-TELEOP VIRT JI Presence-Teleoper. Virtual Env. PD AUG PY 1998 VL 7 IS 4 BP 370 EP 381 DI 10.1162/105474698565785 PG 12 WC Computer Science, Cybernetics; Computer Science, Software Engineering SC Computer Science GA 107BP UT WOS:000075186200003 ER PT J AU Feibelman, WA AF Feibelman, WA TI Is the Galactic halo planetary nebula PN G243-37.1 an "O VI sequence" variable object? SO PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF THE PACIFIC LA English DT Article ID SPECTRUM; STARS AB Archival IUE spectra of the Galactic halo planetary nebula PN G243 - 37.1 have been reprocessed by the NEWSIPS routine. The new results show a much richer emission-line spectrum than has previously been reported. Several C III, C IV, O V, and possibly O VI features were detected. P Cygni line profiles could not be identified with certainty. The He II lambda 1640 emission, which is the strongest line in the IUE spectrum and is likely a mixture of stellar and nebular origin, increased in intensity as did the stellar continuum level between observational epochs of 1988 and 1990, which suggests that the object is a variable planetary nebula. A very recent optical spectrum confirms the UV results and suggests that the object underwent a dramatic change, possibly as a result of an episodic mass-loss event. C1 NASA, Astron & Solar Phys Lab, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Feibelman, WA (reprint author), NASA, Astron & Solar Phys Lab, Goddard Space Flight Ctr, Code 681, Greenbelt, MD 20771 USA. NR 16 TC 4 Z9 4 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 AUG PY 1998 VL 110 IS 750 BP 923 EP 933 DI 10.1086/316209 PG 11 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 113WW UT WOS:000075577700008 ER PT J AU Kaiser, ME Bohlin, RC Lindler, DJ Gilliland, RL Argabright, VS Kimble, RA AF Kaiser, ME Bohlin, RC Lindler, DJ Gilliland, RL Argabright, VS Kimble, RA TI STIS signal-to-noise capabilities in the ultraviolet SO PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF THE PACIFIC LA English DT Article AB The Space Telescope Imaging Spectrograph (STIS) was designed as a versatile spectrograph for the Hubble Space Telescope (HST) capable of maintaining or exceeding the spectroscopic capabilities of both the Goddard High Resolution Spectrograph (GHRS) and the Faint Object Spectrograph (FOS)aver the broad bandpass extending from the ultraviolet (115 nm) through the visible (1 mu m) STIS achieves performance gains over the aforementioned first-generation HST instruments primarily through the use of large (1024 x 1024) areal detectors in both the ultraviolet and visible regions of the spectrum. Simultaneous spatial and spectral coverage is provided through long-slit or slitless spectroscopy of extended sources. A substantial spectral multiplexing advantage is achieved for ultraviolet echelle spectroscopy. This paper will focus on the key issue of signal-ronoise ratio (S/N) performance with the STIS ultraviolet detectors. Spectra obtained during the first few months of operation illustrate that high S/N spectra can be obtained while exploiting STIS's multiplexing advantage. From analysis of a single spectrum of GD 153, with count statistics of similar to 165, a S/N of similar to 130 is achieved per spectral resolution element in the far-ultraviolet (FUV) for a flat-fielded spectrum. Without flat-fielding, a S/N of similar to 85 is achieved. In the near-ultraviolet (NUV), a single spectrum of GRW +70 degrees 5824, with count statistics of similar to 200, yields a S/N of similar to 150 per spectral resolution element for the flat-fielded spectrum. Without Aat-fielding, a S/N of similar to 100 is achieved. An even higher SM capability is illustrated through the use of the fixed pattern (FP) split slits in the medium-resolution echelle modes. Observations of ED 28 degrees 4211 yield a SM of similar to 250 and similar to 350 per spectral resolution element over an extended spectral region in the FUV and NUV, respectively. For the same spectral region, the S/N without the application of a flat, or the use of specialized iterative solution, yields a S/N of similar to 205 in the FUV and similar to 290 in the NUV. The corresponding S/N from pure count statistics is similar to 285 in the FUV and similar to 380 in the NW. Selective regions of the ED 28 degrees 4211 echelle spectrum with suitable. count statistics yield ever higher S/Ns. These higher S/Ns of similar to 390 in the FUV and similar to 380 in the NUV, are quoted for narrow spectral regions spanning a small areal extent on the detector and may not reflect the SM capability over the full detector. These results verify that STIS is capable of achieving a S/N in excess of 100:1 per spectral resolution element in both the first-order and echelle modes. C1 Johns Hopkins Univ, Dept Phys & Astron, Baltimore, MD 21218 USA. Space Telescope Sci Inst, Baltimore, MD 21218 USA. Adv Comp Concepts Inc, Potomac, MD 20805 USA. Ball Aerosp & Technol Corp, Boulder, CO 80301 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Kaiser, ME (reprint author), Johns Hopkins Univ, Dept Phys & Astron, Baltimore, MD 21218 USA. NR 14 TC 7 Z9 7 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 AUG PY 1998 VL 110 IS 750 BP 978 EP 990 DI 10.1086/316214 PG 13 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 113WW UT WOS:000075577700010 ER PT J AU Schmugge, T Hook, SJ Coll, C AF Schmugge, T Hook, SJ Coll, C TI Recovering surface temperature and emissivity from thermal infrared multispectral data SO REMOTE SENSING OF ENVIRONMENT LA English DT Article ID HIGH-RESOLUTION RADIOMETER; WINDOW AB In 1992 Thermal Infrared Multispectral Scanner (TIMS) data were acquired front the NASA C-130 aircraft over the Sahelian region of West Africa as part of the Hydrological and Atmospheric Pilot Experiment in the Sahel (HAPEX). TIMS measures the radiation front the surface modified by the atmosphere in six channels located be between 8 min and 12.5 mu m in the thermal infrared. By using a variety of techniques it is possible to extract both the surface temperature and surface emissivity front the areas over which TIMS data were acquired. One such technique was tested with the data aquired during this experiment. Several TIMS images of both the east and Ic;est central sites on 2 and 4 September were processed, mid the spectral behaviors of different land cover types were determined. These included tiger bush, millet, and fallow grassland sites. There was a 5-10 K difference ii the brightness temperature over the six channels Ir;hen significant bare soil was visible. Channels 1-3 (8.2-9.4 mu m) were cooler than the longer wavelength channels (9.6-12.5 mu m), which is characteristic of soils rich in quartz. These differences in brightness were converted to emissivity differences using the max-milt difference (MMD) method. This method relies on an empirical relationship observed between the range of emissivities and the minimum value for the six TIMS channels. The MMD method was applied iteratively to several entire sce,zes for the east central site on the two days with the interesting results that Channel 5 showed very little spatial variation in emissivity and the short wavelength channels observed substantial regions with emissivities of about 0.8 or le.ss. There is excellent reproducibility when the same area is seen in different lines on the same day. However, there are differences when the same area is seen on the two days especially for the low; emissivity values. Some of these differences may be due to soil moisture differences 2-3%, which were observed for the two days. The observed surface temperatures were in good agreement with other measures, for example, vegetation temperatures agreed well with the measured air temperatures. Published by Elsevier Science Inc. C1 USDA ARS, BARC W, Hydrol Lab, Beltsville, MD 20705 USA. CALTECH, Jet Prop Lab, Pasadena, CA USA. Univ Valencia, Fac Phys, Dept Thermodynam, Valencia, Spain. RP Schmugge, T (reprint author), USDA ARS, BARC W, Hydrol Lab, Bldg 007, Beltsville, MD 20705 USA. EM schmugge@hydrolab.arsusda.gov RI Coll, Cesar/I-7373-2015 OI Coll, Cesar/0000-0001-6665-3870 NR 43 TC 96 Z9 104 U1 0 U2 10 PU ELSEVIER SCIENCE INC PI NEW YORK PA 360 PARK AVE SOUTH, NEW YORK, NY 10010-1710 USA SN 0034-4257 J9 REMOTE SENS ENVIRON JI Remote Sens. Environ. PD AUG PY 1998 VL 65 IS 2 BP 121 EP 131 DI 10.1016/S0034-4257(98)00023-6 PG 11 WC Environmental Sciences; Remote Sensing; Imaging Science & Photographic Technology SC Environmental Sciences & Ecology; Remote Sensing; Imaging Science & Photographic Technology GA ZZ767 UT WOS:000074765100001 ER PT J AU Johnson, NL AF Johnson, NL TI Monitoring and controlling debris in space SO SCIENTIFIC AMERICAN LA English DT Article C1 NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. Int Acad Astronaut, Subcomm Space Debris, Paris, France. RP Johnson, NL (reprint author), NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. NR 5 TC 0 Z9 0 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 AUG PY 1998 VL 279 IS 2 BP 62 EP 67 PG 6 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA 101JB UT WOS:000074864900027 ER PT J AU Klimeck, G Lake, R Blanks, DK AF Klimeck, G Lake, R Blanks, DK TI Numerical approximations to the treatment of interface roughness scattering in resonant tunnelling diodes SO SEMICONDUCTOR SCIENCE AND TECHNOLOGY LA English DT Article; Proceedings Paper CT 2nd International Workshop on Surfaces and Interfaces of Mesoscopic Devices CY DEC 07-12, 1997 CL MAUI, HAWAII SP Arizona State Univ, Off Naval Res ID TUNNELING DIODES AB Current calculations for a resonant tunnelling diode which include a self-consistent Born treatment of interface roughness combined with full charge self-consistency are presented. Approximate but more computationally tractable solutions which either ignore the scattering-assisted charge or the real part of the self-energy are compared with the full solution. The coherent tunnelling calculation combined with quantum charge self-consistency provides an accurate estimate of the resonant current. To obtain the same accuracy while including interface roughness scattering for our particular device requires a treatment of both the real and the imaginary parts of the self-energy combined with a fully self-consistent treatment of the scattering-assisted charge. C1 Raytheon TI Syst, Dallas, TX 75243 USA. RP Klimeck, G (reprint author), Jet Propuls Lab, Pasadena, CA 91109 USA. RI Klimeck, Gerhard/A-1414-2012 OI Klimeck, Gerhard/0000-0001-7128-773X NR 12 TC 4 Z9 4 U1 0 U2 1 PU IOP PUBLISHING LTD PI BRISTOL PA DIRAC HOUSE, TEMPLE BACK, BRISTOL BS1 6BE, ENGLAND SN 0268-1242 J9 SEMICOND SCI TECH JI Semicond. Sci. Technol. PD AUG PY 1998 VL 13 IS 8A SU S BP A165 EP A168 DI 10.1088/0268-1242/13/8A/047 PG 4 WC Engineering, Electrical & Electronic; Materials Science, Multidisciplinary; Physics, Condensed Matter SC Engineering; Materials Science; Physics GA 111MY UT WOS:000075442600047 ER PT J AU Menon, M Srivastava, D Saini, S AF Menon, M Srivastava, D Saini, S TI Fullerene-derived molecular electronic devices SO SEMICONDUCTOR SCIENCE AND TECHNOLOGY LA English DT Article; Proceedings Paper CT 2nd International Workshop on Surfaces and Interfaces of Mesoscopic Devices CY DEC 07-12, 1997 CL MAUI, HAWAII SP Arizona State Univ, Off Naval Res ID CARBON NANOTUBES; MICROTUBULES; CLUSTERS; TUBULES; C-60 AB The carbon nanotube junctions have recently emerged as excellent candidates for use as the building blocks in the formation of nanoscale electronic devices. While the simple joint of two dissimilar tubes can be generated by the introduction of a pair of heptagon-pentagon defects in an otherwise perfect hexagonal graphene sheet, more complex joints require other mechanisms. In this work we explore structural and electronic properties of complex three-point junctions of carbon nanotubes using a generalized tight-binding molecular-dynamics scheme. C1 Univ Kentucky, Dept Phys & Astron, Lexington, KY 40506 USA. NASA, Ames Res Ctr, MRJ, Moffett Field, CA 94035 USA. RP Menon, M (reprint author), Univ Kentucky, Dept Phys & Astron, Lexington, KY 40506 USA. NR 15 TC 2 Z9 3 U1 0 U2 1 PU IOP PUBLISHING LTD PI BRISTOL PA DIRAC HOUSE, TEMPLE BACK, BRISTOL BS1 6BE, ENGLAND SN 0268-1242 J9 SEMICOND SCI TECH JI Semicond. Sci. Technol. PD AUG PY 1998 VL 13 IS 8A SU S BP A51 EP A54 DI 10.1088/0268-1242/13/8A/017 PG 4 WC Engineering, Electrical & Electronic; Materials Science, Multidisciplinary; Physics, Condensed Matter SC Engineering; Materials Science; Physics GA 111MY UT WOS:000075442600017 ER PT J AU Smart, MK Kalkhoran, IM Popovic, S AF Smart, MK Kalkhoran, IM Popovic, S TI Some aspects of streamwise vortex behavior during oblique shock wave vortex interaction SO SHOCK WAVES LA English DT Article DE shock wave; shock wave interactions; vortex; vortical interactions ID WING-TIP VORTICES; NUMERICAL-SIMULATION; MACH-3 STREAM; DISTORTION AB An experimental study of the flowfield generated by the interaction of a streamwise vortex having a strong wake-type axial Mach number profile and a two-dimensional oblique shock wave was conducted in a Mach 2.49 flow. The experiments were aimed at investigating the dynamics of supersonic vortex distortion and to study downstream behavior of a streamwise vortex during a strong shock wave/vortex encounter. The experiments involved positioning an oblique shock generator in the form of a two-dimensional wedge downstream of a semi-span, vortex generator wing section so that the wing-tip vortex interacted with the otherwise planar oblique shock wave. Planar laser sheet visualizations of the flowfield indicated an expansion of the vortex core in crossing a spherically blunt-nose shock front. The maximum vortex core diameter occurred at a distance of 12.7 mm downstream of the wedge leading edge where the vortex had a core diameter of more than double its undisturbed value. At distances further downstream the vortex core diameter remained nearly constant, while it appeared to become more diffused at distances far from the wedge leading edge. Measurements of vortex trajectory revealed that the vortex convected in the freestream direction immediately downstream of the bulged-forward shock structure, while it traveled parallel to the wedge surface at distances further downstream. The turbulent distorted vortex structure which formed as a result of the interaction, was found to be sensitive to downstream disturbances in a manner consistent with incompressible vortex breakdown. Physical arguments are presented to relate behavior of streamwise vortices during oblique and normal shock wave interactions. C1 NASA, Langley Res Ctr, Hampton, VA 23665 USA. Polytech Univ, Dept Mech Aerosp & Mfg Engn, Brooklyn, NY 11201 USA. RP Smart, MK (reprint author), NASA, Langley Res Ctr, Hampton, VA 23665 USA. RI Smart, Michael/C-8823-2013 NR 21 TC 11 Z9 11 U1 2 U2 3 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 AUG PY 1998 VL 8 IS 4 BP 243 EP 255 DI 10.1007/s001930050117 PG 13 WC Mechanics SC Mechanics GA 110UW UT WOS:000075400000005 ER PT J AU Schmieder, B Heinzel, P Kucera, T Vial, JC AF Schmieder, B Heinzel, P Kucera, T Vial, JC TI Filament observations with SOHO SUMER/CDS: The behaviour of hydrogen Lyman lines SO SOLAR PHYSICS LA English DT Article ID QUIESCENT PROMINENCES; EMITTED RADIATION; SOLAR; SPECTRUM; SPECTROMETER; OSCILLATIONS; MODELS; LIMB AB On 21 September 1996, a filament close to an area of enhanced network was observed with the Solar Ultraviolet Measurements of Emitted Radiation (SUMER) spectrometer and Coronal Diagnostic Spectrometer (CDS). CDS provided intensity, Doppler shift and linewidth maps of the region in six lines whose temperature range covers 10(4) to 10(6) It. SUMER observations consisted of maps of the region in four hydrogen Lyman lines (L delta, L epsilon, L-6, L-7) and a S VI line (944 Angstrom). In all the Lyman lines we detect a central absorption and an asymmetry in the intensity of the two peaks. First NLTE computations indicate that such reversed Lyman profiles and their absolute intensities can be reproduced with the existing filament models provided that we take into account a prominence-corona transition region (PCTR). We discuss the Lyman lines' asymmetry in terms of macroscopic flows by comparison with the He I line Doppler shifts observed with CDS. C1 Observ Paris, Sect Meudon, URA 2080, F-92195 Meudon, France. Univ Oslo, Inst Theoret Astrophys, N-0315 Oslo, Norway. Astron Inst, CZ-25165 Ondrejov, Czech Republic. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Space Applicat Corp, Vienna, VA USA. Univ Paris 11, CNRS, Inst Astrophys Spatiale, F-91405 Orsay, France. RP Schmieder, B (reprint author), Observ Paris, Sect Meudon, URA 2080, F-92195 Meudon, France. RI Kucera, Therese/C-9558-2012; Heinzel, Petr/G-9014-2014 NR 25 TC 30 Z9 31 U1 0 U2 1 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 AUG PY 1998 VL 181 IS 2 BP 309 EP 326 DI 10.1023/A:1005022003293 PG 18 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 123AY UT WOS:000076104700007 ER PT J AU Hoyt, DV Schatten, KH AF Hoyt, DV Schatten, KH TI Group Sunspot Numbers: A new solar activity reconstruction SO SOLAR PHYSICS LA English DT Article AB In this paper, we construct a time series known as the Group Sunspot Number. The Group Sunspot Number is designed to be more internally self-consistent (i.e., less dependent upon seeing the tiniest spots) and less noisy than the Wolf Sunspot Number. It uses the number of sunspot groups observed, rather than groups and individual sunspots. Daily, monthly, and yearly means are derived from 1610 to the present. The Group Sunspot Numbers use 65 941 observations from 117 observers active before 1874 that were not used by Wolf in constructing his time series. Hence, we have calculated daily values of solar activity on 111 358 days for 1610-1995, compared to 66 168 days for the Wolf Sunspot Numbers. The Group Sunspot Numbers also have estimates of their random and systematic errors tabulated. The generation and preliminary analysis of the Group Sunspot Numbers allow us to make several conclusions: (1) Solar activity before 1882 is lower than generally assumed and consequently solar activity in the last few decades is higher than it has been for several centuries. (2) There was a solar activity peak in 1801 and not 1805 so there is no long anomalous cycle of 17 years as reported in the Wolf Sunspot Numbers. The longest cycle now lasts no more than 15 years. (3) The Wolf Sunspot Numbers have many inhomogeneities in them arising from observer noise and this noise affects the daily, monthly, and yearly means. The Group Sunspot Numbers also have observer noise, but it is considerably less than the noise in the Wolf Sunspot Numbers. The Group Sunspot Number is designed to be similar to the Wolf Sunspot Number, but, even if both indices had perfect inputs, some differences are expected, primarily in the daily values. C1 Hughes STX, Greenbelt, MD USA. Goddard Space Flight Ctr, Greenbelt, MD 20770 USA. RP Hoyt, DV (reprint author), Hughes STX, 7701 Greenbelt Rd, Greenbelt, MD USA. NR 12 TC 277 Z9 282 U1 0 U2 9 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 AUG PY 1998 VL 181 IS 2 BP 491 EP 512 DI 10.1023/A:1005056326158 PG 22 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 123AY UT WOS:000076104700018 ER PT J AU Ocampo, A Friedman, L Logsdon, J AF Ocampo, A Friedman, L Logsdon, J TI Why space science and exploration benefit everyone SO SPACE POLICY LA English DT Article AB As well as providing practical information on Earth-besetting problems, space science and exploration are vital tools for capturing the public imagination and encouraging young people's interest in space. The relatively small scale of some scientific instruments also allows mission participation by developing countries. Citing the work of the UN and various NGOs in promoting study and distribution of space science data, the authors recommend that it be given a higher profile and suggest a number of projects - the Mars drill study in Egypt, refurbishment of a telescope facility in Sri Lanka - involving developing countries that should be followed up, as well as listing ongoing successful projects. The UN is urged to continue its annual workshops on space science (apparently under threat) and to ensure its inclusion in the forthcoming UNISPACE III Conference. (C) 1998 Elsevier Science Ltd. All rights reserved. C1 Planetary Soc, Pasadena, CA 91106 USA. CALTECH, Jet Prop Lab, NASA, Pasadena, CA 91125 USA. George Washington Univ, Inst Space Policy, Washington, DC 20052 USA. RP Friedman, L (reprint author), Planetary Soc, 65 N Catalina Ave, Pasadena, CA 91106 USA. NR 3 TC 1 Z9 1 U1 2 U2 3 PU ELSEVIER SCI LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, OXON, ENGLAND SN 0265-9646 J9 SPACE POLICY JI Space Policy PD AUG PY 1998 VL 14 IS 3 BP 137 EP 143 DI 10.1016/S0265-9646(98)00012-5 PG 7 WC International Relations; Social Sciences, Interdisciplinary SC International Relations; Social Sciences - Other Topics GA 136HK UT WOS:000076853200004 ER PT J AU Li, Y Menard, R Riishojgaard, LP Cohn, SE Rood, RB AF Li, Y Menard, R Riishojgaard, LP Cohn, SE Rood, RB TI A study on assimilating potential vorticity data SO TELLUS SERIES A-DYNAMIC METEOROLOGY AND OCEANOGRAPHY LA English DT Article ID CHEMICAL-CONSTITUENT OBSERVATIONS; EXTENDED KALMAN FILTER; PREDICTION MODELS; NUMERICAL-MODEL; OZONE; INITIALIZATION; STRATOSPHERE; WAVES; FLOWS AB The correlation that exists between the potential vorticity (PV) field and the distribution of chemical tracers such as ozone suggests the possibility of using tracer observations as proxy PV data in atmospheric data assimilation systems. Especially in the stratosphere, there are plentiful tracer observations brit a general lack of reliable wind observations, and the correlation is most pronounced. The issue investigated in this study is how model dynamics would respond to the assimilation of PV data. First. numerical experiments of identical-twin type were conducted with a simple univariate nuding algorithm and a global shallow water model based on PV and divergence ( PV-D model). Ail model fields are successfully reconstructed through the insertion of complete PS' data alone if an appropriate value for the nudging coefficient is used, A simple linear analysis suggests that slow modes are recovered rapidly, at a rate nearly independent of spatial scale. In a more realistic experiment. appropriately scaled total ozone data from the NIMBUS-7 TOMS instrument were assimilated as proxy PV data into the PV-D model over a 10-day period, The resulting model PV field matches the observed total ozone field relatively well on large spatial scales, and the PV, geopotential and divergence fields are dynamically consistent. These results indicate the potential usefulness that tracer observations, as proxy PV data, may offer in a data assimilation system. C1 NASA, Goddard Space Flight Ctr, Data Assimilat Off, Greenbelt, MD 20771 USA. Univ Maryland Baltimore Cty, Joint Ctr Earth Syst Technol, Baltimore, MD 21228 USA. RP Li, Y (reprint author), NASA, Goddard Space Flight Ctr, UMBC, JCET, Code 910-3, Greenbelt, MD 20771 USA. RI Cohn, Stephen/K-1954-2012; Rood, Richard/C-5611-2008 OI Cohn, Stephen/0000-0001-8506-9354; Rood, Richard/0000-0002-2310-4262 NR 33 TC 6 Z9 6 U1 0 U2 1 PU MUNKSGAARD INT PUBL LTD PI COPENHAGEN PA 35 NORRE SOGADE, PO BOX 2148, DK-1016 COPENHAGEN, DENMARK SN 0280-6495 J9 TELLUS A JI Tellus Ser. A-Dyn. Meteorol. Oceanol. PD AUG PY 1998 VL 50 IS 4 BP 490 EP 506 DI 10.1034/j.1600-0870.1998.t01-2-00008.x PG 17 WC Meteorology & Atmospheric Sciences; Oceanography SC Meteorology & Atmospheric Sciences; Oceanography GA 122MY UT WOS:000076077100008 ER PT J AU Ramesham, R AF Ramesham, R TI Cyclic voltammetric response of boron-doped homoepitaxially grown single crystal and polycrystalline CVD diamond SO SENSORS AND ACTUATORS B-CHEMICAL LA English DT Article DE cyclic voltammetry; boron-doped polycrystalline diamond; boron-doped single crystal diamond; ferri-ferrocyanide; microwave plasma ID THIN-FILM ELECTRODES; CARBON ELECTRODES; GLASSY-CARBON AB Homoepitaxial single crystal and polycrystalline boron-doped CVD diamond films were gown by a microwave plasma process using a methane and hydrogen gas mixture at a pressure of 33 Torr over a Type IIa (orientation: 100) and mechanically damaged, cleaned molybdenum substrate, respectively. Doped diamond was grown on both substrates in a single experiment to maintain constant doping levels in the as-deposited films. Boron-doping of diamond was achieved in situ by using a solid disc source of B2O3. Doped diamond was evaluated for background response in 0.5 M NaCl and 0.5 M HCl solutions by cyclic voltammetry. We have observed a wide potential range over which negligible background current was observed for polycrystalline and single crystal diamond. Decomposition of water occurs electrochemically and evolves O-2 during positive (anodic) polarization and H-2 evolution during negative (cathodic) polarization. All experimental measurements were corrected for uncompensated IR drop and have been compared with the results obtained without the correction for uncompensated IR drop. Scanning electron microscopy has been used to study the morphology of diamond before and after electrochemical characterization and we conclude that the morphology was unchanged. We have investigated the redox kinetics of ferri-ferrocyanide (Fe(CN)(6)(3-) + e(-) < = = > Fe(CN)(6)(4-)) in 0.5 M NaCl solution at the homoepitaxial boron-doped diamond electrode. The reaction is reversible at the diamond electrode, but the redox kinetics is sluggish. The heterogeneous electron transfer rate constant has been determined using the experimental data and COOL algorithm. The rate constant was found to be from 6.62 x 10(-5) to 1.41 x 10(-4) cm s(-1) and the kinetics were considered to be sluggish at the diamond electrode/solution interface. (C) 1998 Published by Elsevier Science S.A. All rights reserved. C1 Auburn Univ, Space Power Inst, Leach Ctr 231, Auburn, AL 36849 USA. RP Ramesham, R (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr,M-S 125-152, Pasadena, CA 91109 USA. EM Rajeshuni.ramesham@jpl.nasa.gov NR 18 TC 15 Z9 16 U1 0 U2 4 PU ELSEVIER SCIENCE SA PI LAUSANNE PA PO BOX 564, 1001 LAUSANNE, SWITZERLAND SN 0925-4005 J9 SENSOR ACTUAT B-CHEM JI Sens. Actuator B-Chem. PD JUL 31 PY 1998 VL 50 IS 2 BP 131 EP 139 DI 10.1016/S0925-4005(98)00214-7 PG 9 WC Chemistry, Analytical; Electrochemistry; Instruments & Instrumentation SC Chemistry; Electrochemistry; Instruments & Instrumentation GA 138GD UT WOS:000076962800006 ER PT J AU Quadrelli, BM Atluri, SN AF Quadrelli, BM Atluri, SN TI Analysis of flexible multibody systems with spatial beams using mixed variational principles SO INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING LA English DT Article DE flexible multibody dynamics; finite rotation; beam finite elements; variational principles ID DYNAMICS AB A general finite element formulation is presented for dynamic analysis of spatial elastic beams, for small strains, in a multi-body configuration The tangent maps associated to the finite rotation vector are used to compute the tangent matrices used to integrate implicitly the equations of motion in descriptor form. A corotational method and a mixed variational method are used to compute the tangent stiffness matrix. The tangent constraint matrices are obtained using consistent linearization of the constraint equations. The tangent inertia matrices, including the gyroscopic and centrifugal terms, are also obtained by using the tangent maps of rotation. The numerical examples analyzed in this paper include: dynamic analysis of flexible beam structures and multi-flexible body systems with open and closed kinematic loops. A comparison with the previous results in the literature shows a very good performance in terms of lime integration step and number of elements used. (C) 1998 John Wiley & Sons, Ltd. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ Calif Los Angeles, Los Angeles, CA 90095 USA. RP Quadrelli, BM (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. EM marco@grover.jpl.nasa.gov RI Atluri, Satya/C-5040-2013 OI Atluri, Satya/0000-0001-6793-9619 NR 16 TC 9 Z9 10 U1 0 U2 1 PU JOHN WILEY & SONS LTD PI W SUSSEX PA BAFFINS LANE CHICHESTER, W SUSSEX PO19 1UD, ENGLAND SN 0029-5981 J9 INT J NUMER METH ENG JI Int. J. Numer. Methods Eng. PD JUL 30 PY 1998 VL 42 IS 6 BP 1071 EP 1090 DI 10.1002/(SICI)1097-0207(19980730)42:6<1071::AID-NME400>3.0.CO;2-F PG 20 WC Engineering, Multidisciplinary; Mathematics, Interdisciplinary Applications SC Engineering; Mathematics GA 101MG UT WOS:000074872300005 ER PT J AU Payne, WA Thorn, RP Nesbitt, FL Stief, LJ AF Payne, WA Thorn, RP Nesbitt, FL Stief, LJ TI Rate constant for the reaction of O(P-3) with IO at T = 298 K SO JOURNAL OF PHYSICAL CHEMISTRY A LA English DT Article ID OZONE DEPLETION; KINETICS; PHOTOLYSIS; RADICALS AB The rate coefficient for the O(P-3) + IO reaction has been measured using the discharge-flow kinetic technique coupled to collision-free mass spectrometric detection at 1 Torr nominal pressure (He). IO is generated by the reaction of O with I-2; IO then decays in the presence of excess atomic oxygen. A one-parameter fitting to a numerical model gives a rate coefficient of (1.5 +/- 0.7) x 10(-10) cm(3) molecule(-1) s(-1) at T=298 K. This result is significantly faster than an earlier estimate but is in good agreement with the only previous study of the reaction which employed laser photolysis combined with absorption spectrophotometry. The present result is compared with those for the reactions O(P-3) + XO and X + IO where X = Cl and Br. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Coppin State Coll, Dept Nat Sci, Baltimore, MD 21216 USA. RP Stief, LJ (reprint author), NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. NR 18 TC 21 Z9 21 U1 0 U2 2 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 JUL 30 PY 1998 VL 102 IS 31 BP 6247 EP 6250 DI 10.1021/jp9811530 PG 4 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA 108QT UT WOS:000075277500009 ER PT J AU Davis, SS AF Davis, SS TI Vibration analysis of rotating machinery using the spectral distribution function SO JOURNAL OF SOUND AND VIBRATION LA English DT Article AB The spectral distribution function is used to characterize the vibration signal of rotating machinery. It is shown to be a more robust indicator than conventional power spectral density estimates, but requires only slightly more computational effort. The method is demonstrated with a model of a defective bearing. The spectral distribution function is applied to practical problems involving seeded helicopter transmission faults and the vibration signal from a ground-based vacuum compressor system. (C) 1998 Academic Press. C1 NASA, Ames Res Ctr, Fluid Mech Lab, Moffett Field, CA 94035 USA. RP Davis, SS (reprint author), NASA, Ames Res Ctr, Fluid Mech Lab, Moffett Field, CA 94035 USA. NR 8 TC 4 Z9 4 U1 0 U2 0 PU ACADEMIC PRESS LTD PI LONDON PA 24-28 OVAL RD, LONDON NW1 7DX, ENGLAND SN 0022-460X J9 J SOUND VIB JI J. Sound Vibr. PD JUL 30 PY 1998 VL 214 IS 5 BP 805 EP 815 DI 10.1006/jsvi.1998.1551 PG 11 WC Acoustics; Engineering, Mechanical; Mechanics SC Acoustics; Engineering; Mechanics GA 105WW UT WOS:000075099200002 ER PT J AU Serabyn, E Shupe, D Figer, DF AF Serabyn, E Shupe, D Figer, DF TI An extraordinary cluster of massive stars near the centre of the Milky Way SO NATURE LA English DT Article ID GALACTIC-CENTER; SPECTRA; GALAXY AB The relative numbers of newborn stars of different masses in a galaxy (the initial mass function) determines whether the galaxy's interstellar gas goes mainly into long-lived low-mass stars, as in the disks of normal spiral galaxies, or into short-lived massive stars, as has been proposed for "starburst" galaxies(1,2). The centre of the Milky Way is not a fully-fledged starburst region, but its star formation rate per unit volume of space is nevertheless roughly a thousand times that of the disk(3,4). It is, however, very difficult to study the initial mass function near the centre, because the dust in the gas clouds obscures the starlight, and the relatively rare young stars are mixed with much more numerous older stars(11). Here we report high-resolution infrared observations of a compact cluster of stars in the central region of our Galaxy. We find approximately 100 young, massive main-sequence stars, several of which seem to be among the most massive in the Galaxy. This cluster may be a weak analogue of the large star clusters in starburst galaxies, which opens the possibility of studying the starburst phenomenon through a local example. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. CALTECH 10022, IPAC, Pasadena, CA 91125 USA. Univ Calif Los Angeles, Dept Phys & Astron, Los Angeles, CA 90095 USA. RP Serabyn, E (reprint author), CALTECH, Jet Prop Lab, MS 171-113,4800 Oak Grove Dr, Pasadena, CA 91109 USA. EM serabyn@tacos.caltech.edu NR 23 TC 77 Z9 78 U1 0 U2 2 PU NATURE PUBLISHING GROUP PI LONDON PA MACMILLAN BUILDING, 4 CRINAN ST, LONDON N1 9XW, ENGLAND SN 0028-0836 J9 NATURE JI Nature PD JUL 30 PY 1998 VL 394 IS 6692 BP 448 EP 451 DI 10.1038/28799 PG 4 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA 105NT UT WOS:000075080400042 ER PT J AU Chou, MD Zhao, WZ Chou, SH AF Chou, MD Zhao, WZ Chou, SH TI Radiation budgets and cloud radiative forcing in the Pacific warm pool during TOGA COARE SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID SEA-SURFACE TEMPERATURE; SOLAR-RADIATION; ATMOSPHERIC ABSORPTION; UNCERTAINTIES; FLUX AB Empirical relationships between the surface radiative fluxes and satellite-measured radiances derived for the Tropical Ocean and Global Atmosphere, Coupled Ocean-Atmosphere Response Experiment (TOGA COARE) radiation sites are applied to compute the shortwave (solar) and longwave (thermal infrared) fluxes over the Pacific warm pool (narrowly defined as the region 10 degrees S-10 degrees N and 135 degrees E-175 degrees E). Even averaged over the entire COARE Intensive Observation Period, November 1992 to February 1993, the net surface radiative heating has a large spatial variation. Regions of minimum shortwave heating, which implies large clouds and strong convection, do not necessarily coincide with regions of maximum sea surface temperature. This indicates that the large-scale atmospheric dynamics, land-sea distribution, and sea surface temperature all play an important role in forcing convection in the warm pool. The total radiative heating (shortwave heating minus longwave cooling) ranges from 125 to 175 W m(-2). The large spatial variation of surface radiative heating in the warm pool, averaged over a period of 4 months, could have a significant impact on the sea surface temperature and oceanic and atmospheric circulations. Partitioning of the shortwave heating between the surface and the atmosphere has been estimated. For the entire warm pool during the COARE Intensive Observation Period, the mean insolation at the top of the atmosphere is 420 W m(-2), and the planetary albedo is similar to 30%. Two thirds (199. W m(-2)) of the total heating of the Earth-atmosphere system (294 W m(-2)) is absorbed at the surface, and one third (95 W m(-2)) is absorbed in the atmosphere, The effect of clouds on the shortwave heating of the atmospheric column is only +9 W m(-2), which is not much different from radiation model calculations. The Earth Radiation Budget Experiment fluxes at the top of the atmosphere in the Pacific warm pool for the period November 1986 to February 1987 are used as proxy for the shortwave heating of the Earth-atmosphere system. C1 NASA, Atmospheres Lab, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Sci Applicat Int Corp, Largo, MD USA. RP Chou, MD (reprint author), NASA, Atmospheres Lab, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. EM chou@climate.gsfc.nasa.gov; zhao@climate.gsfc.nasa.gov; chou@agnes.gsfc.nasa.gov NR 28 TC 12 Z9 12 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 JUL 27 PY 1998 VL 103 IS D14 BP 16967 EP 16977 DI 10.1029/98JD01453 PG 11 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 104BK UT WOS:000074992200007 ER PT J AU Boucher, O Schwartz, SE Ackerman, TP Anderson, TL Bergstrom, B Bonnel, B Chylek, P Dahlback, A Fouquart, Y Fu, Q Halthore, RN Haywood, JM Iversen, T Kato, S Kinne, S Kirkevag, A Knapp, KR Lacis, A Laszlo, I Mishchenko, MI Nemesure, S Ramaswamy, V Roberts, DL Russell, P Schlesinger, ME Stephens, GL Wagener, R Wang, M Wong, J Yang, F AF Boucher, O Schwartz, SE Ackerman, TP Anderson, TL Bergstrom, B Bonnel, B Chylek, P Dahlback, A Fouquart, Y Fu, Q Halthore, RN Haywood, JM Iversen, T Kato, S Kinne, S Kirkevag, A Knapp, KR Lacis, A Laszlo, I Mishchenko, MI Nemesure, S Ramaswamy, V Roberts, DL Russell, P Schlesinger, ME Stephens, GL Wagener, R Wang, M Wong, J Yang, F TI Intercomparison of models representing direct shortwave radiative forcing by sulfate aerosols SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID ANTHROPOGENIC AEROSOLS; MULTIPLE-SCATTERING; SOLAR-RADIATION; CLIMATE MODELS; ATMOSPHERES; ABSORPTION; PARAMETERIZATION; UNCERTAINTY; EXTINCTION; ALGORITHMS AB The importance of aerosols as agents of climate change has recently been highlighted. However, the magnitude of aerosol forcing by scattering of shortwave radiation (direct forcing) is still very uncertain even for the relatively well characterized sulfate aerosol. A potential source of uncertainty is in the model representation of aerosol optical properties and aerosol influences on radiative transfer in the atmosphere. Although radiative transfer methods and codes have been compared in the past, these comparisons have not focused on aerosol forcing (change in net radiative flux at the top of the atmosphere). Here we report results of a project involving 12 groups using 15 models to examine radiative forcing by sulfate aerosol for a wide range of values of particle radius, aerosol optical depth, surface albedo, and solar zenith angle. Among the models that were employed were high and low spectral resolution models incorporating a variety of radiative transfer approximations as well as a line-by-line model. The normalized forcings (forcing per sulfate column burden) obtained with the several radiative transfer models were examined, and the discrepancies were characterized. All models simulate forcings of comparable amplitude and exhibit a similar dependence on input parameters. As expected for a non-light-absorbing aerosol, forcings were negative (cooling influence) except at high surface albedo combined with small solar zenith angle. The relative standard deviation of the zenith-angle-averaged normalized broadband forcing for 15 models was 8% for particle radius near the maximum in this forcing (similar to 0.2 mu m) and at low surface albedo. Somewhat greater model-to-model discrepancies were exhibited at specific solar zenith angles. Still greater discrepancies were exhibited at small particle radii, and much greater discrepancies were exhibited at high surface albedos, at which the forcing changes sign; in these situations, however, the normalized forcing is quite small. Discrepancies among the models arise from inaccuracies in Mie calculations, differing treatment of the angular scattering phase function, differing wavelength and angular resolution, and differing treatment of multiple scattering. These results imply the need for standardized radiative transfer methods tailored to the direct aerosol forcing problem. However, the relatively small spread in these results suggests that the uncertainty in forcing arising from the treatment of radiative forcing of a well-characterized aerosol at well-specified surface albedo is smaller than some of the other sources of uncertainty in estimates of direct forcing by anthropogenic sulfate aerosols and anthropogenic aerosols generally. C1 Univ Lille 1, Opt Atmospher Lab, F-59655 Villeneuve Dascq, France. Ecole Normale Super, CNRS, Meteorol Dynam Lab, Paris, France. Brookhaven Natl Lab, Environm Chem Div, Upton, NY 11973 USA. Penn State Univ, Dept Meteorol, University Pk, PA 16802 USA. Univ Washington, Joint Inst Study Atmosphere & Oceans, Seattle, WA 98195 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Dalhousie Univ, Dept Phys, Atmospher Sci Program, Halifax, NS B3H 3J5, Canada. Norwegian Inst Air Res, Kjeller, Norway. Meteorol Off, Hadley Ctr Climate Predict & Res, Bracknell RG12 2SY, Berks, England. Princeton Univ, NOAA, Geophys Fluid Dynam Lab, Princeton, NJ 08542 USA. Univ Oslo, Dept Geophys, N-0315 Oslo, Norway. Colorado State Univ, Dept Atmospher Sci, Ft Collins, CO 80523 USA. NASA, Goddard Inst Space Studies, New York, NY 10025 USA. Univ Maryland, Dept Meteorol, College Pk, MD 20742 USA. Univ Illinois, Dept Atmospher Sci, Urbana, IL 61801 USA. Brookhaven Natl Lab, Analyt Sci Div, Upton, NY 11973 USA. RP Boucher, O (reprint author), Univ Lille 1, Opt Atmospher Lab, F-59655 Villeneuve Dascq, France. EM boucher@loa.univ-lille1.fr; ses@bnl.gov; ackerman@essc.psu.edu; tadand@atmos.washington.edu; bergstro@sky.arc.nasa.gov; bonnel@loa.univ.lille1.fr; chylek@atm.dal.ca; arne.dahlback@fys.uio.no; fouquart@loa.univ-lille1.fr; qfu@atm.dal.ca; halthore@bnl.gov; jmhaywood@meto.gov.uk; trond.iversen@geofysikk.uio.no; kato@aerosol.larc.nasa.gov; kinne@spamer.gsfc.nasa.gov; alf.kirkevag@geofysikk.uio.no; knapp@cira.colostate.edu; alacis@giss.nasa.gov; laszlo@atmos.umd.edu; mmishchenko@giss.nasa.gov; nemesure@bnl.gov; vr@gfdl.gov; dlroberts@meto.gov.uk; prussell@mail.arc.nasa.gov; schlesin@atmos.uiuc.edu; stephens@langley.atmos.colostate.edu; wagener@bnl.gov; muyin@atm.dal.ca; jwong@atm.dal.ca; fanglin@atmos.uiuc.edu RI Wagener, Richard/B-5445-2008; Laszlo, Istvan/F-5603-2010; Knapp, Kenneth/E-9817-2011; Lacis, Andrew/D-4658-2012; Boucher, Olivier/J-5810-2012; Boucher, Olivier/K-7483-2012; Schwartz, Stephen/C-2729-2008; Wang, Muyin/K-4006-2014; Mishchenko, Michael/D-4426-2012 OI Wagener, Richard/0000-0003-3892-1182; Laszlo, Istvan/0000-0002-5747-9708; Boucher, Olivier/0000-0003-2328-5769; Boucher, Olivier/0000-0003-2328-5769; Schwartz, Stephen/0000-0001-6288-310X; NR 66 TC 102 Z9 102 U1 3 U2 18 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 JUL 27 PY 1998 VL 103 IS D14 BP 16979 EP 16998 DI 10.1029/98JD00997 PG 20 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 104BK UT WOS:000074992200008 ER PT J AU Wenny, BN Schafer, JS DeLuisi, JJ Saxena, VK Barnard, WF Petropavlovskikh, IV Vergamini, AJ AF Wenny, BN Schafer, JS DeLuisi, JJ Saxena, VK Barnard, WF Petropavlovskikh, IV Vergamini, AJ TI A study of regional aerosol radiative properties and effects on ultraviolet-B radiation SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID ANTHROPOGENIC AEROSOLS; SIZE DISTRIBUTIONS; OPTICAL-PROPERTIES; LIGHT-SCATTERING; REFRACTIVE-INDEX; ATLANTIC-OCEAN; UNITED-STATES; IRRADIANCE; UV; OZONE AB A field experiment was conducted in western North Carolina to investigate the relationship between aerosol optical properties and atmospheric transmission. Two research measurement sites in close horizontal proximity but at different altitudes were established to measure the transmission of UV radiation through a slab of atmosphere. An identical set of radiation sensing instruments, including a broadband UV-B radiometer, a direct Sun pyrheliometer, a shadowband radiometer, and a spectral photometer, was placed at both sites, a mountaintop site (Mount Gibbes 35.78 degrees N, 82.29 degrees W, 2004 m elevation) and a valley site;(Black Mountain, North Carolina 35.66 degrees N, 82.38 degrees N, 951 m elevation). Aerosol size distribution sampling equipment was located at the valley site. Broadband solar pseudo-optical depth and aerosol optical depths at 415 nm, 500 nm, and 673 nm were measured for the lowest 1-km layer of the troposphere. The measurements exhibited variations based on an air mass source region as determined by back trajectory analysis. Broadband UV-B transmission through the layer also displayed variations relating to air mass source region. Spectral UV transmission revealed a dependence upon wavelength, with decreased transmission in the UV-B region (300-320 mm) versus UV-A region (320-363.5 mm). UV-B transmission was found to be negatively correlated with aerosol optical depth. Empirical relations were developed to allow prediction of solar noon UV-B transmission if aerosol optical depth at two visible wavelengths (415 and 500 nm) is known. A new method was developed for determining aerosol optical properties from the radiation and aerosol size distribution measurements. The aerosol albedo of single scatter was found to range from 0.75 to 0.93 and the asymmetry factor ranged from 0.63 to 0.76 at 312 nm, which is close to the peak response of human skin to UV radiation. C1 N Carolina State Univ, Dept Marine Earth & Atmospher Sci, Raleigh, NC 27695 USA. NASA, Hughes STX Corp, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. NOAA, Surface Radiat Res Branch, Boulder, CO 80303 USA. US EPA, Atmospher Res & Exposure Assessment Lab, Res Triangle Pk, NC 27111 USA. Univ Colorado, CIRES, Boulder, CO 80303 USA. Harris Corp, Elect Syst Sector, Palm Bay, FL 32935 USA. RP Saxena, VK (reprint author), N Carolina State Univ, Dept Marine Earth & Atmospher Sci, Box 8208, Raleigh, NC 27695 USA. EM saxena@eos.ncsu.edu RI Schafer, Joel/A-3978-2010 NR 61 TC 48 Z9 48 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 JUL 27 PY 1998 VL 103 IS D14 BP 17083 EP 17097 DI 10.1029/98JD01481 PG 15 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 104BK UT WOS:000074992200015 ER PT J AU Torres, O Bhartia, PK Herman, JR Ahmad, Z Gleason, J AF Torres, O Bhartia, PK Herman, JR Ahmad, Z Gleason, J TI Derivation of aerosol properties from satellite measurements of backscattered ultraviolet radiation: Theoretical basis SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID MOUNT-PINATUBO AEROSOLS; TROPOSPHERIC AEROSOLS; DUST; SMOKE; INDEX AB We discuss the theoretical basis of a recently developed technique to characterize aerosols from space. We show that the interaction between aerosols and the strong molecular scattering in the near ultraviolet produces spectral variations of the backscattered radiances that can be used to separate aerosol absorption from scattering effects. This capability allows identification of several aerosol types, ranging from nonabsorbing sulfates to highly UV-absorbing mineral dust, over both land and water surfaces. Two ways of using the information contained in the near-UV radiances are discussed. In the first method, a residual quantity, which measures the departure of the observed spectral contrast from that of a molecular atmosphere, is computed. Since clouds yield nearly zero residues, this method is a useful way of separately mapping the spatial distribution of UV-absorbing and nonabsorbing particles. To convert the residue to optical depth, the aerosol type must be known. The second method is an inversion procedure that uses forward calculations of backscattered radiances for an ensemble of aerosol models. Using a look-up table approach, a set of measurements given by the ratio of backscattered radiance at 340-380 nm and the 380 nm radiance are associated, within the domain of the candidate aerosol models, to values of optical depth and single-scattering albedo. No previous knowledge of aerosol type is required. We present a sensitivity analysis of various error sources contributing to the estimation of aerosol properties by the two methods. C1 Raytheon STX Corp, Lanham, MD USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Sci & Data Syst Inc, Silver Spring, MD 20906 USA. RP Torres, O (reprint author), Hughes STX Corp, 4400 Forbes Blvd, Lanham, MD 20706 USA. EM torres@qhearts.gsfc.nasa.gov RI Gleason, James/E-1421-2012; Torres, Omar/G-4929-2013; Bhartia, Pawan/A-4209-2016; OI Bhartia, Pawan/0000-0001-8307-9137; Herman, Jay/0000-0002-9146-1632 NR 41 TC 564 Z9 582 U1 3 U2 27 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 JUL 27 PY 1998 VL 103 IS D14 BP 17099 EP 17110 DI 10.1029/98JD00900 PG 12 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 104BK UT WOS:000074992200016 ER PT J AU Karcher, B Busen, R Petzold, A Schroder, FP Schumann, U Jensen, EJ AF Karcher, B Busen, R Petzold, A Schroder, FP Schumann, U Jensen, EJ TI Physicochemistry of aircraft-generated liquid aerosols, soot, and ice particles - 2. Comparison with observations and sensitivity studies SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID DIFFERENT SULFUR CONTENTS; CONTRAIL FORMATION; NUCLEATION; FUELS AB Results from a coupled microphysical-chemical-dynamical trajectory box model have been compared to recent in situ observations of particles generated in the wake of aircraft. Sulfur emissions mainly cause the formation of ultrafine volatile particles in young aircraft plumes (mean number radius similar to 5nm). Volatile particle numbers range between 10(16) and 10(17) per kg fuel burnt for average to high fuel sulfur levels, exceeding typical soot emission indices by a factor of 10-100. Model results come into closer agreement;with observations when chemi-ions from fuel combustion are included in the aerosol dynamics. Ice particles (mean number radius < 1 mu m) in young contrails mainly nucleate on.water-activated exhaust aerosols. Homogeneous freezing and soot-induced heterogeneous freezing are competitive processes leading to ice formation, depending on the temperature and level of oxidized sulfur species. There is evidence that soot triggers freezing even for low fuel sulfur contents, suggesting a sulfur-independent water activation pathway. Metal particles emitted by jet engines and entrained ambient aerosols may contribute to the formation of larger (> 1 mu m) crystals. Contrails with larger crystals would also form without soot and sulfur emissions. The lifecycle of cirrus clouds can be modified by exhaust aerosols. C1 DLR, Inst Phys Atmosphare, D-82234 Wessling, Germany. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Karcher, B (reprint author), DLR, Inst Phys Atmosphare, D-82234 Wessling, Germany. EM bernd.kaercher@dlr.de RI Petzold, Andreas/J-2347-2012; Karcher, Bernd/D-5325-2014; OI Petzold, Andreas/0000-0002-2504-1680; Karcher, Bernd/0000-0003-0278-4980; Schumann, Ulrich/0000-0001-5255-6869 NR 37 TC 56 Z9 56 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 JUL 27 PY 1998 VL 103 IS D14 BP 17129 EP 17147 DI 10.1029/98JD01045 PG 19 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 104BK UT WOS:000074992200018 ER PT J AU Leblanc, T McDermid, IS Keckhut, P Hauchecorne, A She, CY Krueger, DA AF Leblanc, T McDermid, IS Keckhut, P Hauchecorne, A She, CY Krueger, DA TI Temperature climatology of the middle atmosphere from long-term lidar measurements at middle and low latitudes SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID PRESSURE MODULATOR RADIOMETER; THERMAL STRUCTURE; MESOPAUSE REGION; SEASONAL-VARIATION; STRATOSPHERE; MESOSPHERE; VARIABILITY; PROFILES; TRENDS; SME AB Long-term measurements from several lidar instruments (Rayleigh and sodium) located at 44.0 degrees N, 40.6 degrees N, 34.4 degrees N, and 19.5 degrees N have been used to develop a new climatology of the middle atmosphere temperature. For each instrument, the measurements on every individual day of the year over the entire long-term record were averaged to build a composite year of temperature profiles. These profiles were then interpolated to provide temperature values at l-km altitude intervals so that the climatology comprises daily temperature values at integer altitudes between 15 and 110 km, depending on the instrument. The climatologies for each lidar were;hen compared to the CIRA-86 model and-to each other. Large differences between the lidar temperatures and the CIRA-86 temperatures are identified and explained. When compared to all instruments, CIRA-86 appears systematically much too cold between 90 and 95 km, by 20 K or more, and possibly 6-8 K too Warm around 80 km, making its use asa reference atmosphere model questionable at these altitudes. The annual and semiannual components of the seasonal variability and the 2- to 33-day period variability were investigated. An annual cycle with 6-7 K amplitude in the upper stratosphere, increasing to 15-20 K at 80 km, is observed at midlatitudes. This cycle is in phase with the solar flux in the stratosphere and in opposite phase in the mesosphere with a very cold summer mesopause at 85 km, in good agreement with previous climatologies. At lower latitudes, a semiannual oscillation propagates downward from 85 to 30 km and is characterized by a stronger first cycle than the second (4 and 2 K amplitude respectively). The 2- to 33-day variability at midlatitudes shows a maximum during winter around 40 km and in the mesosphere. The first peak is associated with planetary wave activity and stratospheric warmings and the second to the occurrence of mesospheric temperature inversions. Finally, sudden seasonal transitions, highly consistent between all instruments, have been observed. In particular, in the early winter midlatitudes a two-step warming of the winter mesosphere between 65 and 85 km as well as a cooling of the lower mesosphere appear to be real climatological events rather than some short-term geophysical or instrumental random variability. C1 CALTECH, Jet Prop Lab, Table Mt Facil, Wrightwood, CA 92397 USA. CNRS, Serv Aeron, F-91371 Verrieres Le Buisson, France. Colorado State Univ, Dept Phys, Ft Collins, CO 80523 USA. RP Leblanc, T (reprint author), CALTECH, Jet Prop Lab, Table Mt Facil, Wrightwood, CA 92397 USA. RI Hauchecorne, Alain/A-8489-2013; OI Hauchecorne, Alain/0000-0001-9888-6994 NR 46 TC 58 Z9 61 U1 1 U2 8 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 JUL 27 PY 1998 VL 103 IS D14 BP 17191 EP 17204 DI 10.1029/98JD01347 PG 14 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 104BK UT WOS:000074992200022 ER PT J AU Moser, RD Rogers, MM Ewing, DW AF Moser, RD Rogers, MM Ewing, DW TI Self-similarity of time-evolving plane wakes SO JOURNAL OF FLUID MECHANICS LA English DT Article ID DIRECT SIMULATION; TURBULENT WAKE; MIXING LAYER AB Direct numerical simulations of three time-developing turbulent plane wakes have been performed. Initial conditions for the simulations were obtained using two realizations of a direct simulation from a turbulent boundary layer at momentum-thickness Reynolds number 670. In addition, extra two-dimensional disturbances were added in two of the cases to mimic two-dimensional forcing. The wakes are allowed to evolve long enough to attain approximate self-similarity, although in the strongly forced case this self-similarity is of short duration. For all three flows, the mass-flux Reynolds number (equivalent to the momentum-thickness Reynolds number in spatially developing wakes) is 2000, which is high enough for a short k(-5/3) range to be evident in the streamwise one-dimensional velocity spectra. The spreading rate, turbulence Reynolds number, and turbulence intensities all increase with forcing (by nearly an order of magnitude for the strongly forced case), with experimental data falling between the unforced and weakly forced cases. The simulation results are used in conjunction with a self-similar analysis of the Reynolds stress equations to develop scalings that approximately collapse the profiles from different wakes. Factors containing the wake spreading rate are required to bring profiles from different wakes into agreement. Part of the difference between the various cases is due to the increased level of spanwise-coherent (roughly two-dimensional) energy in the forced cases. Forcing also has a significant impact on flow structure, with the forced flows exhibiting more organized large-scale structures similar to those observed in transitional wakes. C1 Univ Illinois, Dept Theoret & Appl Mech, Urbana, IL 61801 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. SUNY Buffalo, Dept Mech & Aerosp Engn, Amherst, NY 14260 USA. RP Moser, RD (reprint author), Univ Illinois, Dept Theoret & Appl Mech, Urbana, IL 61801 USA. NR 24 TC 55 Z9 55 U1 0 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 JUL 25 PY 1998 VL 367 BP 255 EP 289 DI 10.1017/S0022112098001426 PG 35 WC Mechanics; Physics, Fluids & Plasmas SC Mechanics; Physics GA 108PL UT WOS:000075274600010 ER PT J AU Gilmore, MS Collins, GC Ivanov, MA Marinangeli, L Head, JW AF Gilmore, MS Collins, GC Ivanov, MA Marinangeli, L Head, JW TI Style and sequence of extensional structures in tessera terrain, Venus SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS LA English DT Review ID MAGELLAN OBSERVATIONS; RESURFACING HISTORY; DIKE EMPLACEMENT; IMPACT CRATERS; CRUSTAL FLOW; TECTONICS; DEFORMATION; EVOLUTION; EARTH; FRACTURES AB Recent studies have focused on the question of the stratigraphic sequence and thus the stages of tessera formation, specifically, if tessera are formed by contractional deformation followed by extensional deformation or vice versa. A major question centers on the interpretation of specific lineaments within tesserae as graben (bounded by faults similar to 60 degrees) or, alternatively, open tension fractures (dipping similar to 90 degrees). We document and assess the origin of extensional structures in tesserae at several locations on Venus, noting the morphology, continuity along strike, parallelism of walls, stratigraphic position and interaction with other structures, and variability due to radar viewing geometry. In each study area, our analyses demonstrate that (1) the extensional structures have variable widths, interior subparallel lineaments, and ramp terminations; (2) ridges and lineaments are continuous across the troughs, where the floors of many of these structures contain the lowered sections of preexisting structures; and (3) intratessera plains are seen to embay ridges and an impact crater is superposed on a ridge and in both cases these features are subsequently deformed by the extensional structures. We conclude that the morphology of these extensional structures is consistent with an origin as graben, not open tension fractures, and that these graben postdate the ridges in each study area. Both the graben and the ridges of the sizes found in our survey can be formed when the brittle crust is of the order of 1 to 10 km thick. To further test the tension fracture model, we examine the conditions of a Venus that could produce tension fractures of the dimension (similar to 1 km width) of extensional structures found in tessera terrain and find that thermal gradients of a minimum of 400 to 1500 K km(-1) (heat flows of 800 to 3000 mW m(-2)) are required for a range of diabase rheologies and strain rates thought typical of Venus during tessera formation. Such a thermal structure would favor partial melting at depths < 1 km. Dike propagation from this region of shallow melting within the tensile stress field would produce vast quantities of volcanism, mitigating against the preservation of the closely associated tension fractures; this volcanism is not observed. Both the amplitude and sign of changes in surface temperature induced by atmospheric warming due to massive outpourings of lava are not consistent with the hotspot model. On the basis of our analysis of tesserae, we conclude that the ridges formed first in response to large-scale contraction of the crust and that the graben formed contemporaneously and largely following this phase as the thickened crust relaxed in a manner to what is predicted and observed for plateau regions on Earth such as Tibet and the Altiplano. C1 Brown Univ, Dept Geol Sci, Providence, RI 02912 USA. Univ G DAnnunzio, Dipartimento Sci, I-65127 Pescara, Italy. Russian Acad Sci, Vernadsky Inst Geochem & Anal Chem, Moscow, Russia. RP Gilmore, MS (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr,Mail Stop 183-335, Pasadena, CA 91109 USA. EM msg@pop.jpl.nasa.gov; Geoffrey_Clark_Collins@brown.edu; ivanov@pggipl.geo.brown.edu; luciam@gotham.sci.unich.it; James_Head_III@brown.edu RI Gilmore, Martha/G-5856-2011 NR 102 TC 31 Z9 31 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 JUL 25 PY 1998 VL 103 IS E7 BP 16813 EP 16840 DI 10.1029/98JE01322 PG 28 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 138KA UT WOS:000076970000004 ER PT J AU Leonard, PJT AF Leonard, PJT TI Astrophysics - The challenge of gamma ray burst observations SO SCIENCE LA English DT Article C1 NASA, Gamma Ray Observ Sci Support Ctr, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Leonard, PJT (reprint author), NASA, Gamma Ray Observ Sci Support Ctr, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. NR 4 TC 1 Z9 1 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 JUL 24 PY 1998 VL 281 IS 5376 BP 525 EP 526 DI 10.1126/science.281.5376.525 PG 2 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA 104KA UT WOS:000075012300027 ER PT J AU Rignot, EJ AF Rignot, EJ TI Fast recession of a West Antarctic glacier SO SCIENCE LA English DT Article ID ICE-SHEET; RETREAT AB Satellite radar interferometry observations of Pine Island Glacier, West Antarctica, reveal that the glacier hinge-line position retreated 1.2 +/- 0.3 kilometers per year between 1992 and 1996, which in turn implies that the ice thinned by 3.5 +/- 0.9 meters per year. The fast recession of Pine Island Glacier, predicted to be a possible trigger for the disintegration of the West Antarctic Ice Sheet, is attributed to enhanced basal melting of the glacier floating tongue by warm ocean waters. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Rignot, EJ (reprint author), CALTECH, Jet Prop Lab, MS 300-235, Pasadena, CA 91109 USA. RI Rignot, Eric/A-4560-2014 OI Rignot, Eric/0000-0002-3366-0481 NR 25 TC 220 Z9 224 U1 1 U2 26 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 JUL 24 PY 1998 VL 281 IS 5376 BP 549 EP 551 DI 10.1126/science.281.5376.549 PG 3 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA 104KA UT WOS:000075012300037 ER PT J AU Wasfy, TM Noor, AK AF Wasfy, TM Noor, AK TI Finite element analysis of flexible multibody systems with fuzzy parameters SO COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING LA English DT Article AB A computational procedure is presented for predicting the dynamic response and evaluating the sensitivity coefficients of flexible multibody systems whose characteristics include fuzzy parameters. Time-histories of the possibility distributions of the response and the sensitivity coefficients are generated. These coefficients measure the sensitivity of the dynamic response to variations in the material, geometric and external force parameters of the system. The five key components of the procedure are: a) a corotational frame approach used in conjunction with a total Lagrangian formulation; b) beam and shell elements with the Cartesian coordinates of the nodes selected as degrees of freedom, and with continuous inter-element slopes; c) use of an approximate method of extension, based on the a-cut representation, called the 'vertex method' for generating the possibility distributions of the desired response quantities and their sensitivity coefficients; d) semi-explicit temporal integration technique for generating the dynamic response; and e) direct differentiation approach for evaluating the sensitivity coefficients. The effectiveness of the procedure and the usefulness of the fuzzy output are demonstrated through numerical examples, including an articulated space structure consisting of beams, shells and revolute joints. Published by Elsevier Science S.A. C1 Univ Virginia, Ctr Adv Computat Technol, NASA, Langley Res Ctr, Hampton, VA 23681 USA. RP Noor, AK (reprint author), Univ Virginia, Ctr Adv Computat Technol, NASA, Langley Res Ctr, Hampton, VA 23681 USA. NR 24 TC 25 Z9 28 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 JUL 23 PY 1998 VL 160 IS 3-4 BP 223 EP 243 DI 10.1016/S0045-7825(97)00297-1 PG 21 WC Engineering, Multidisciplinary; Mathematics, Interdisciplinary Applications; Mechanics SC Engineering; Mathematics; Mechanics GA 106QD UT WOS:000075139600002 ER PT J AU White, NE AF White, NE TI Pulsars - A period of change SO NATURE LA English DT Editorial Material C1 NASA, Goddard Space Flight Ctr, Astrophys Branch, Greenbelt, MD 20771 USA. RP White, NE (reprint author), NASA, Goddard Space Flight Ctr, Astrophys Branch, Code 662, Greenbelt, MD 20771 USA. RI White, Nicholas/B-6428-2012 OI White, Nicholas/0000-0003-3853-3462 NR 7 TC 1 Z9 1 U1 0 U2 0 PU MACMILLAN MAGAZINES LTD PI LONDON PA PORTERS SOUTH, 4 CRINAN ST, LONDON, ENGLAND N1 9XW SN 0028-0836 J9 NATURE JI Nature PD JUL 23 PY 1998 VL 394 IS 6691 BP 323 EP 323 DI 10.1038/28503 PG 1 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA 103QF UT WOS:000074968800023 ER PT J AU Skiles, JW Richardson, CW AF Skiles, JW Richardson, CW TI A stochastic weather generation model for Alaska SO ECOLOGICAL MODELLING LA English DT Article DE ecosystem simulation; weather generator; Alaska ID SOLAR-RADIATION; TEMPERATURE AB A specific problem encountered in ecosystem-level simulation of Arctic ecosystems is the depth and extent of the driving variable record. Often, climate records are of short duration, gathered at locations different from the area to be simulated. or do not contain all the variables required by a given model. This paper addresses this problem for ecosystem simulation in Alaska with the development of a weather generator. The generator, called WGENAL, is based on the WGEN climate generator developed and validated in the 48 conterminous states. Because of the extreme variability of weather in Alaska that is not accommodated by the statistical metrics in the earlier model, a new climate generator was developed. WGENAL generates daily values of precipitation, maximum temperature, minimum temperature, solar radiation, and wind run. Precipitation is generated using a Markov chain-gamma model. A two-parameter gamma distribution is used to generate wind run. Temperatures and solar radiation are generated using procedures developed in the earlier study. Validation of the generator shows it provides adequate diurnal and seasonal weather records for Fairbanks. Other comparisons of synthetic weather with observed weather for sites north of the Brooks Range in Alaska are also within the error of the original data. (C) 1998 Elsevier Science B.V. All rights reserved. C1 NASA, Ames Res Ctr, Johnson Control World Serv, Moffett Field, CA 94035 USA. USDA ARS, Grassland Soil & Water Res Lab, Temple, TX 76502 USA. RP Skiles, JW (reprint author), NASA, Ames Res Ctr, Johnson Control World Serv, Mail Stop 239-20, Moffett Field, CA 94035 USA. NR 22 TC 10 Z9 10 U1 0 U2 0 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0304-3800 J9 ECOL MODEL JI Ecol. Model. PD JUL 22 PY 1998 VL 110 IS 3 BP 211 EP 232 DI 10.1016/S0304-3800(98)00061-1 PG 22 WC Ecology SC Environmental Sciences & Ecology GA 111DE UT WOS:000075421400001 ER PT J AU Larar, AM Hays, PB Drayson, SR AF Larar, AM Hays, PB Drayson, SR TI Global tropospheric and total ozone monitoring with a double-etalon Fabry-Perot interferometer. I. Instrument concept SO APPLIED OPTICS LA English DT Article ID IMAGE PLANE DETECTOR; SATELLITE AB The global distribution of tropospheric ozone (O-3) can be observed from a satellite-based instrument by spectrally isolating the pressure-broadened wings of strong O-3, lines. The Fabry-Perot interferometer (FPI) provides high spectral resolution and high-throughput capabilities that are essential for performing such a measurement. Through proper selection of channel spectral regions, the FPI optimized for tropospheric O-3, measurements can simultaneously observe a stratospheric component and thus the total O-3, column abundance. We present a conceptual instrument design that involves a double-etalon fixed-gap series configuration FPI along with an ultranarrow bandpass filter to achieve single-order operation with an overall spectral resolution of approximately 0.068 cm(-1), sampling the narrow 1054.2-1055.2 cm(-1) spectral region within the strong 9.6-mu m ozone infrared band from a nadir-viewing satellite configuration. (C) 1998 Optical Society of America. C1 NASA, Langley Res Ctr, Div Atmospher Sci, Hampton, VA 23681 USA. Univ Michigan, Dept Atmospher Ocean & Space Sci, Ann Arbor, MI 48109 USA. RP Larar, AM (reprint author), NASA, Langley Res Ctr, Div Atmospher Sci, Mail Stop 401A, Hampton, VA 23681 USA. NR 36 TC 12 Z9 12 U1 0 U2 1 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 JUL 20 PY 1998 VL 37 IS 21 BP 4721 EP 4731 DI 10.1364/AO.37.004721 PG 11 WC Optics SC Optics GA 100RC UT WOS:000074828300026 PM 18285929 ER PT J AU Larar, AM Drayson, SR AF Larar, AM Drayson, SR TI Global tropospheric and total ozone monitoring with a double-etalon Fabry-Perot interferometer. II. Feasibility analysis SO APPLIED OPTICS LA English DT Article ID VERTICAL-DISTRIBUTION; RETRIEVAL AB The feasibility of observing global tropospheric and total ozone (O-3), fields with a double-etalon Fabry-Perot interferometer (FPI) has been assessed. The FPI provides high spectral resolution and high-throughput capabilities that enable observation in pressure-broadened wings of strong O-3, lines while minimizing the impact of undesirable signal contributions (i.e., from the terrestrial surface and interfering species). A retrieval technique has been implemented and is demonstrated for a tropical atmosphere possessing enhanced tropospheric ozone amounts. An error analysis assessing the impact on retrieved O-3, amounts from the most significant uncertainties associated with this particular measurement has been performed, and findings for a tropical atmosphere are presented. Results show the proposed instrumentation to enable a good measurement of absolute ozone amounts and an even better determination of relative changes. (C) 1998 Optical Society of America. C1 NASA, Langley Res Ctr, Div Atmospher Sci, Hampton, VA 23681 USA. Univ Michigan, Dept Atmospher Ocean & Space Sci, Ann Arbor, MI 48109 USA. RP Larar, AM (reprint author), NASA, Langley Res Ctr, Div Atmospher Sci, Mail Stop 401A, Hampton, VA 23681 USA. NR 15 TC 6 Z9 6 U1 0 U2 0 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 JUL 20 PY 1998 VL 37 IS 21 BP 4732 EP 4743 DI 10.1364/AO.37.004732 PG 12 WC Optics SC Optics GA 100RC UT WOS:000074828300027 PM 18285930 ER PT J AU Hoge, FE Wright, CW Kana, TM Swift, RN Yungel, JK AF Hoge, FE Wright, CW Kana, TM Swift, RN Yungel, JK TI Spatial variability of oceanic phycoerythrin spectral types derived from airborne laser-induced fluorescence emissions SO APPLIED OPTICS LA English DT Article ID PASSIVE CORRELATION SPECTROSCOPY; DISSOLVED ORGANIC-MATTER; WATER RAMAN BACKSCATTER; NORTH-ATLANTIC; COLOR MEASUREMENT; SYNECHOCOCCUS; PIGMENTS; PACIFIC AB We report spatial variability of oceanic phycoerythrin spectral types detected by means of a blue spectral shift in airborne laser-induced fluorescence emission. The blue shift of the phycoerythrobilin fluorescence is known from laboratory studies to be induced by phycourobilin chromophore substitution at phycoerythrobilin chromophore sites in some strains of phycoerythrin-containing marine cyanobacteria. The airborne 532-nm laser-induced phycoerythrin fluorescence of the upper oceanic volume showed distinct segregation of cyanobacterial chromophore types in a flight transect from coastal water to the Sargasso Sea in the western North Atlantic. High phycourobilin levels were restricted to the oceanic (oligotrophic) end of the flight transect, in agreement with historical ship findings. These remotely observed phycoerythrin spectral fluorescence shifts have the potential to permit rapid, wide-area studies of the spatial variability of spectrally distinct cyanobacteria, especially across interfacial regions of coastal and oceanic water masses. Airborne laser-induced phytoplankton spectral fluorescence observations also further the development of satellite algorithms for passive detection of phytoplankton pigments. Optical modifications to the NASA Airborne Oceanographic Lidar are briefly described that permitted observation of the fluorescence spectral shifts. (C) 1998 Optical Society of America. C1 NASA, Goddard Space Flight Ctr, Wallops Flight Facil, Wallops Island, VA 23337 USA. Univ Maryland, Horn Point Environm Labs, Cambridge, MD 21613 USA. EG&G Inc, Wallops Flight Facil, Wallops Island, VA 23337 USA. RP Hoge, FE (reprint author), NASA, Goddard Space Flight Ctr, Wallops Flight Facil, Wallops Island, VA 23337 USA. NR 20 TC 19 Z9 20 U1 0 U2 7 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 JUL 20 PY 1998 VL 37 IS 21 BP 4744 EP 4749 DI 10.1364/AO.37.004744 PG 6 WC Optics SC Optics GA 100RC UT WOS:000074828300028 PM 18285931 ER PT J AU Alton, PB Trewhella, M Davies, JI Evans, R Bianchi, S Gear, W Thronson, H Witt, A AF Alton, PB Trewhella, M Davies, JI Evans, R Bianchi, S Gear, W Thronson, H Witt, A TI Resolved 200 mu m images of nearby galaxies - evidence for an extended distribution of cold dust SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE ISM : dust, extinction; galaxies : ISM; infrared : galaxies ID RESOLUTION IRAS MAPS; SPIRAL GALAXIES; H-I; INTERSTELLAR DUST; INFRARED-EMISSION; STAR-FORMATION; LUMINOSITY FUNCTION; MU-M; NGC-6946; DISK AB e present resolved 200 mu m images for 8 nearby galaxies observed with the Infrared Space Observatory (ISO). By comparing the 200 mu m observations with IRAS 60 mu m and 100 mu m data, we find that cold dust becomes more dominant at larger radii. We infer a grain temperature of 18-21 K for this cold component i.e. about 10 K lower than the warm dust detected by IRAS in external spirals. This value is close to theoretical predictions in the literature based on heating by the general interstellar radiation field. A comparison of the 200 mu m images with complementary B-band data also shows that the cold dust is radially more extensive than the stars. The gas-to-dust ratio of external spirals, derived using IRAS fluxes, has been claimed to be about an order of magnitude higher than the value infered for the Galaxy. By analysing the 200 mu m data for our sample, we derive a mean gas-to-dust ratio of similar to 225 which is close to the value in the solar neighborhood (150-300). It is likely that IRAS may have 'overlooked' the vast majority of grains residing in spiral disks. C1 Univ Wales Coll Cardiff, Dept Phys & Astron, Cardiff CF2 3YB, S Glam, Wales. CALTECH, Infrared Proc & Anal Ctr, Pasadena, CA 91125 USA. Univ Chicago, Yerkes Observ, Williams Bay, WI 53191 USA. UCL, Mullard Space Sci Lab, Holmbury RH5 6NT, Surrey, England. NASA Headquarters, Code SR, Washington, DC 20546 USA. SRON, Kapteyn Astron Inst, NL-9700 Groningen, Netherlands. Univ Toledo, Dept Phys & Astron, Toledo, OH 43606 USA. RP Alton, PB (reprint author), Univ Wales Coll Cardiff, Dept Phys & Astron, POB 913, Cardiff CF2 3YB, S Glam, Wales. EM paul.alton@astro.cf.ac.uk NR 71 TC 108 Z9 109 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 JUL 20 PY 1998 VL 335 IS 3 BP 807 EP 822 PG 16 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 103VU UT WOS:000074979200016 ER PT J AU O'Sullivan, C Shearer, A Colhoun, M Golden, A Redfern, M Butler, R Beskin, GM Neizvestny, SI Neustroev, VV Plokhotnichenko, VL Danks, A AF O'Sullivan, C Shearer, A Colhoun, M Golden, A Redfern, M Butler, R Beskin, GM Neizvestny, SI Neustroev, VV Plokhotnichenko, VL Danks, A TI A search for the optical counterpart of PSR B1951+32 in the supernova remnant CTB 80 SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE pulsars : individual : PSR B1951+32; ISM : individual objects : CTB 80 ID X-RAY; FAST PULSARS; EMISSION AB Using time-resolved two-dimensional aperture photometry we have put upper limits on the pulsed emission from two proposed optical counterparts for PSR B1951+32. Our pulsed upper limits of m(upsilon,pulsed) > 23.3, m(b,pulsed) > 24.4, for the first candidate and m(upsilon,pulsed) > 23.6, m(b,pulsed) > 24.3 for the second, make it unlikely that either of these is, in fact, the pulsar. We discuss three further candidates, but also reject these on the basis of timing results. A search of a 5."5 x 5."5 area centred close to these stars failed to find any significant pulsations at the reported pulsar period. C1 Natl Univ Ireland Univ Coll Galway, Dept Phys, Galway, Ireland. Natl Univ Ireland Univ Coll Galway, Ctr Informat Technol, Galway, Ireland. Univ Edinburgh, Dept Math & Stat, Edinburgh EH8 9YL, Midlothian, Scotland. SAO, Karachai Cherkessia, Russia. Goddard Space Flight Ctr, STX, Greenbank, MD USA. RP O'Sullivan, C (reprint author), Natl Univ Ireland Univ Coll Galway, Dept Phys, Galway, Ireland. EM creidhe@physics.ucg.ie RI Neustroev, Vitaly/B-6351-2008; Butler, Ray/A-6705-2012; Shearer, Andy/N-7609-2014 OI Butler, Ray/0000-0002-8441-7596; Shearer, Andy/0000-0001-7903-0074 NR 23 TC 3 Z9 3 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 JUL 20 PY 1998 VL 335 IS 3 BP 991 EP 994 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 103VU UT WOS:000074979200036 ER PT J AU Isliker, H Anastasiadis, A Vassiliadis, D Vlahos, L AF Isliker, H Anastasiadis, A Vassiliadis, D Vlahos, L TI Solar flare cellular automata interpreted as discretized MHD equations SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE chaos; MHD; methods : statistical; Sun : flares ID DRIVEN DISSIPATIVE SYSTEMS; AVALANCHES; NANOFLARES AB We show that the Cellular Automaton (CA) model for Solar flares of Lu and Hamilton (1991) can be understood as the solution to a particular partial differential equation (PDE), which describes diffusion in a localized region in space if a certain instability threshold is met, together with a slowly acting source term. This equation is then compared to the induction equation of MHD, the equation which governs the energy release process in solar flares. The similarities and differences are discussed. We make some suggestions how improved Cellular Automaton models might be constructed on the basis of MHD, and how physical units can be introduced in the existing respective Cellular Automaton models. The introduced formalism of recovering equations from Cellular Automata models is rather general and can be applied to other situations as well. C1 Univ Thessaloniki, Dept Phys, Sect Astrophys Astron & Mech, GR-54006 Salonika, Greece. NASA, Goddard Space Flight Ctr, NASA GSFC USRA, Code 696, Greenbelt, MD 20771 USA. RP Isliker, H (reprint author), Univ Thessaloniki, Dept Phys, Sect Astrophys Astron & Mech, GR-54006 Salonika, Greece. EM isliker@astro.auth.gr; anastasi@astro.auth.gr; vassi@lepgst.gsfc.nasa.gov; vlahos@astro.auth.gr RI Anastasiadis, Anastasios/G-8917-2011; OI Isliker, Heinz/0000-0001-9782-2294 NR 16 TC 32 Z9 32 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 JUL 20 PY 1998 VL 335 IS 3 BP 1085 EP 1092 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 103VU UT WOS:000074979200047 ER PT J AU Dokuchaev, VI Eroshenko, YN Ozernoy, LM AF Dokuchaev, VI Eroshenko, YN Ozernoy, LM TI Gamma-ray bursts from evolved galactic nuclei SO ASTROPHYSICAL JOURNAL LA English DT Article DE binaries : close; black hole physics; galaxies : nuclei; gamma rays : bursts; gravitation ID BLACK-HOLE BINARIES; DENSE STAR-CLUSTERS; NEUTRON-STAR; GRAVITATIONAL-RADIATION; COSMOLOGICAL ORIGIN; COSMIC FIREBALLS; DARK CLUSTERS; EVOLUTION; SYSTEMS; BATSE AB A new cosmological scenario for the origin of gamma-ray bursts (GRBs) is proposed. In our scenario, a highly evolved central core in the dense galactic nucleus is formed, containing a subsystem of compact stellar remnants (CSRs), such as neutron stars and black holes. Those subsystems result from the dynamical evolution of dense central stellar clusters in the galactic nuclei through merging of stars, thereby forming (as has been realized by many authors) the short-lived massive stars and then CSRs. We estimate the rate of random CSR collisions in the evolved galactic nuclei by taking into account, in a procedure similar to that of Quinlan & Shapiro, the dissipative encounters of CSRs, mainly due to radiative losses of gravitational waves, which result in the formation of intermediate short-lived binaries, with further coalescence of the companions to produce GRBs. We also consider how the possible presence of a central supermassive black hole, formed in a highly evolved galactic nucleus, influences the CSR binary formation. This scenario does not postulate ad hoc a required number of tight binary neutron stars in the galaxies. Instead, it gives, for the most realistic parameters of the evolved nuclei, the expected rate of GRBs consistent with the observed one, thereby explaining the GRB appearance as a natural part of the dynamical evolution of galactic nuclei. In addition, this scenario provides an opportunity for a cosmological GRB recurrence, previously considered to be a distinctive feature of GRBs of a local origin only. We also discuss some other observational tests of the proposed scenario. C1 Russian Acad Sci, Inst Nucl Res, Moscow 117312, Russia. George Mason Univ, Dept Phys & Astron, Fairfax, VA 22030 USA. George Mason Univ, Inst Computat Sci & Informat, Fairfax, VA 22030 USA. NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, Greenbelt, MD 20771 USA. RP Dokuchaev, VI (reprint author), Russian Acad Sci, Inst Nucl Res, 60th October Anniversary, Prospect 7A, Moscow 117312, Russia. OI Dokuchaev, Vyacheslav/0000-0003-3657-1051 NR 64 TC 16 Z9 16 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 JUL 20 PY 1998 VL 502 IS 1 BP 192 EP 198 DI 10.1086/305868 PN 1 PG 7 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 151WH UT WOS:000077743300016 ER PT J AU Falcke, H Wilson, AS Simpson, C AF Falcke, H Wilson, AS Simpson, C TI Hubble Space Telescope and VLA observations of Seyfert 2 galaxies: The relationship between radio ejecta and the narrow-line region SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies : Seyfert; galaxies : structure; radio continuum : galaxies ID OPTICAL POSITIONS; ACTIVE GALAXIES; IONIZING-RADIATION; INDIVIDUAL OBJECTS; GALACTIC NUCLEI; IONIZATION CONE; LIMITED SAMPLE; EXTENDED GAS; BRAIDED JETS; NGC-4388 AB We present HST/WFPC2 images, in narrowband filters containing the [O III] lambda 5007 and H alpha + [N II] emission lines and their adjacent continua, of a sample of seven Seyfert 2 galaxies selected because they possess either extended emission-line regions in ground-based observations or a hidden broad-line region in polarized light. Six of the galaxies have also been observed with the VLA in order to obtain radio maps of better quality and angular resolution than those in the literature. We find detailed correspondences between features in the radio and emission-line images, clearly indicating strong interactions between the radio jets and the interstellar medium. Such interactions play a major role in determining the morphology of the NLR, as the radio jets sweep up and compress ambient gas, producing ordered structures with enhanced surface brightness in line emission. In at least three galaxies, namely, Mrk 573, ESO 428-G14, and Mrk 34 (and perhaps also NGC 7212), off-nuclear radio lobes coincide with regions of low gaseous excitation (as measured by the [O III]/(H alpha + [N II]) ratio). In Mrk 573 and NGC 4388, there is a clear trend for low-brightness ionized gas to be of higher excitation. These results may be understood if radio lobes and regions of high emission-line surface brightness are associated with high gas densities, reducing the ionization parameter. [O III]/(H alpha + [N II]) excitation maps reveal bipolar structures that can be interpreted as either the ionization cones expected in the unified scheme or widening, self-excited gaseous outflows. Only NGC 4388 and Mrk 573 show a clearly defined, straight-edged ionization cone. C1 Univ Maryland, Dept Astron, College Pk, MD 20742 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Falcke, H (reprint author), Max Planck Inst Radioastron, Hugel 69, D-53121 Bonn, Germany. EM hfalcke@mpifr-bonn.mpg.de; wilson@astro.umd.edu; bart@fornax.jpl.nasa.gov RI Falcke, Heino/H-5262-2012 OI Falcke, Heino/0000-0002-2526-6724 NR 63 TC 148 Z9 148 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 JUL 20 PY 1998 VL 502 IS 1 BP 199 EP 217 DI 10.1086/305886 PN 1 PG 19 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 151WH UT WOS:000077743300017 ER PT J AU Wojdowski, P Clark, GW Levine, AM Woo, JW Zhang, SN AF Wojdowski, P Clark, GW Levine, AM Woo, JW Zhang, SN TI Quasi-periodic occultation by a precessing accretion disk and other variabilities of SMC X-1 SO ASTROPHYSICAL JOURNAL LA English DT Article DE accretion, accretion disks; binaries : general; galaxies : Magellanic Clouds; pulsars : individual (SMC X-1) ID SMALL MAGELLANIC CLOUD; X-RAY SOURCES; ROSAT OBSERVATIONS; PROPORTIONAL COUNTER; WIND DYNAMICS; TURN-ON; GINGA; HERCULES-X-1; SPECTROSCOPY; DISCOVERY AB We have investigated the variability of the binary X-ray pulsar SMC X-l in data from several X-ray observatories. We confirm the similar to 60 day cyclic variation of the X-ray flux in the long-term monitoring data from the RXTE and CGRO observatories. X-ray light curves and spectra from the ROSAT, Ginga, and ASCA observatories show that the uneclipsed flux varies by as much as a factor of 20 between a high-flux state when 0.71 s pulses are present and a low-flux state when pulses are absent. In contrast, during eclipses when the X-rays consist of radiation scattered from circumsource matter, the fluxes and spectra in the high and low states are approximately the same. These observations prove that the low state of SMC X-1 is not caused by a reduction in the intrinsic luminosity of the source or a spectral redistribution thereof, but rather by a quasi-periodic blockage of the line of sight, most likely by a precessing tilted accretion disk. In each of two observations in the midst of low states a brief increase in the X-ray flux and reappearance of 0.71 s pulses occurred near orbital phase 0.2. A similar brief flux increase near orbital phase 0.2 was observed during a low-state observation that did not have sufficient time resolution to detect 0.71 s pulses. These brief increases result from an opening of the line of sight to the pulsar that may be caused by wobble in the precessing accretion disk. The records of spin-up of the neutron star and decay of the binary orbit are extended during 1991-1996 by pulse-timing analysis of ROSAT, ASCA, and RXTE PCA data. The pulse profiles in various energy ranges from 0.1 to greater than 21 keV are well represented as a combination of a pencil beam and a fan beam. Finally, there is a marked difference between the power spectra of random fluctuations in the high-state data from the RXTE PCA below and above 3.4 keV. In the higher energy range the spectrum has a sharp break at 3.3 Hz, with fitted power-law indices of 0.45 and 1.76 below and above the break. No break is evident in the power spectrum below 3.4 keV, and the fitted power-law index is 0.51. In both spectra there is a positive deviation from the fitted power law around 0.06 Hz that may be quasi-periodic oscillation. C1 MIT, Ctr Space Res, Cambridge, MA 02139 USA. Harvard Smithsonian Ctr Astrophys, Cambridge, MA 02138 USA. NASA, George C Marshall Space Flight Ctr, Univ Space Res Assoc, Huntsville, AL 35812 USA. RP Wojdowski, P (reprint author), MIT, Dept Phys, Cambridge, MA 02139 USA. NR 56 TC 70 Z9 70 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 JUL 20 PY 1998 VL 502 IS 1 BP 253 EP 264 DI 10.1086/305893 PN 1 PG 12 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 151WH UT WOS:000077743300022 ER PT J AU Asakimori, K Burnett, TH Cherry, ML Chevli, K Christ, MJ Dake, S Derrickson, JH Fountain, WF Fuki, M Gregory, JC Hayashi, T Holynski, R Iwai, J Iyono, A Johnson, J Kobayashi, M Lord, J Miyamura, O Moon, KH Nilsen, BS Oda, H Ogata, T Olson, ED Parnell, TA Roberts, FE Sengupta, K Shiina, T Strausz, SC Sugitate, T Takahashi, Y Tominaga, T Watts, JW Wefel, JP Wilczynska, B Wilczynski, H Wilkes, RJ Wolter, W Yokomi, H Zager, E AF Asakimori, K Burnett, TH Cherry, ML Chevli, K Christ, MJ Dake, S Derrickson, JH Fountain, WF Fuki, M Gregory, JC Hayashi, T Holynski, R Iwai, J Iyono, A Johnson, J Kobayashi, M Lord, J Miyamura, O Moon, KH Nilsen, BS Oda, H Ogata, T Olson, ED Parnell, TA Roberts, FE Sengupta, K Shiina, T Strausz, SC Sugitate, T Takahashi, Y Tominaga, T Watts, JW Wefel, JP Wilczynska, B Wilczynski, H Wilkes, RJ Wolter, W Yokomi, H Zager, E TI Cosmic-ray proton and helium spectra: Results from the JACEE experiment SO ASTROPHYSICAL JOURNAL LA English DT Article DE acceleration of particles; balloons; ISM : cosmic rays ID PATH-LENGTH DISTRIBUTION; SHOCK ACCELERATION; EMULSION CHAMBERS; ENERGY-SPECTRA; MAXIMUM ENERGY; PROPAGATION; PRIMARIES; GALAXY AB Measurements of the cosmic-ray hydrogen and helium spectra at energies from 20 to 800 TeV are presented. The experiments were performed on a series of twelve balloon flights, including several long duration Australia to South America and Antarctic circumpolar flights. No clear evidence is seen for a spectral break. Both the hydrogen and the helium spectra are consistent with power laws over the entire energy range, with integral spectral indices 1.80 +/- 0.04 and 1.68(-0.06)(+0.04) for the protons and helium, respectively. The results are fully consistent with expectations based on supernova shock acceleration coupled with a "leaky box" model of propagation through the Galaxy. C1 Kobe Womens Jr Coll, Kobe, Hyogo, Japan. Univ Washington, Dept Phys, Seattle, WA 98195 USA. Louisiana State Univ, Dept Phys & Astron, Baton Rouge, LA 70803 USA. Univ Alabama, Coll Sci, Huntsville, AL 35899 USA. NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. Kobe Univ, Kobe, Hyogo 657, Japan. Kochi Univ, Kochi 780, Japan. Waseda Univ, Tokyo, Japan. Inst Nucl Phys, Krakow, Poland. Okayama Univ, Okayama 700, Japan. Kek Nat Lab High Energy Phys, Tsukuba, Ibaraki 305, Japan. Hiroshima Univ, Hiroshima, Japan. Inst Cosm Ray Res, Tokyo, Japan. Tezukayama Univ, Nara, Japan. RP Asakimori, K (reprint author), Kobe Womens Jr Coll, Kobe, Hyogo, Japan. RI Wilkes, R.Jeffrey/E-6011-2013 NR 49 TC 253 Z9 260 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 JUL 20 PY 1998 VL 502 IS 1 BP 278 EP 283 DI 10.1086/305882 PN 1 PG 6 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 151WH UT WOS:000077743300024 ER PT J AU Godon, P AF Godon, P TI Nonaxisymmetric hydrodynamic instability and subcritical transition to turbulence in the inner region of thin Keplerian disks SO ASTROPHYSICAL JOURNAL LA English DT Article DE accretion, accretion disks; binaries : general; hydrodynamics; instabilities; stars : oscillations; turbulence ID PLANE COUETTE-FLOW; FINITE-AMPLITUDE PERTURBATION; DIFFERENTIALLY ROTATING-DISKS; NON-LINEAR EVOLUTION; ACCRETION DISKS; CATACLYSMIC VARIABLES; RAPID OSCILLATIONS; ANGULAR-MOMENTUM; NUMERICAL-SIMULATION; STREAMWISE VORTICES AB The nonlinear growth of a nonaxisymmetric instability (the Papaloizou-Pringle instability) is followed numerically in thin Keplerian disks with the use of a time-dependent two-dimensional polytropic hybrid Fourier-Chebyshev spectral method of collocation. The nonaxisymmetric instability (a corotation resonance) develops in the inner disk when the inner boundary is rigid (corresponding here to the surface of an accreting compact star). All the modes of the instability have high Q-values and a period of rotation on the order of the Keplerian period at the inner edge of the disk. The high-order modes have growth rates larger than the low-order modes. When the viscosity is large, the higher modes are the first to be damped and saturate at moderate values: the energy is contained in the low-order modes, which dominate the flow. When the viscosity is low, the high-order modes dominate the flow, while the low-order modes do not grow at all: the energy is contained in the higher modes. When the order m and the amplitude a of the unstable mode are high enough (in the present calculations m greater than or similar to 15 and a greater than or similar to 0.3 for alpha = 0.001), the flow undergoes a subcritical transition to turbulence. The turbulence is confined in the inner region of the disk, inside the "resonant cavity," where it sustains itself because of the overreflection of waves (i.e., like the nonaxisymmetric instability itself). Some of the low-order modes are dominant during transient phases of the turbulent flow. The turbulence obtained in this work cannot account for angular momentum transport in the disk. However, the instability provides a new robust mechanism to explain the appearance of short-period oscillations (dwarf nova oscillations and quasi-periodic oscillations) observed in the inner disk of cataclysmic variables and other related systems. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Godon, P (reprint author), Space Telescope Sci Inst, 3700 San Martin Dr, Baltimore, MD 21218 USA. NR 80 TC 7 Z9 7 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 JUL 20 PY 1998 VL 502 IS 1 BP 382 EP 393 DI 10.1086/305887 PN 1 PG 12 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 151WH UT WOS:000077743300032 ER PT J AU Kallman, T Boroson, B Vrtilek, SD AF Kallman, T Boroson, B Vrtilek, SD TI Simultaneous Hubble Space Telescope/Rossi X-Ray Timing Explorer observations of Scorpius X-1 SO ASTROPHYSICAL JOURNAL LA English DT Article DE binaries : close; stars : individual (Scorpius X-1); ultraviolet : stars; X-rays : stars ID ACCRETION DISKS; BLACK-HOLES; EMISSION; IUE; ULTRAVIOLET; ABSORPTION; DISTANCE; CORONAE; SPECTRA; LINES AB Scorpius X-1 is the brightest extrasolar point source of X-rays and may serve as a prototype for low-mass X-ray binaries as a class. It has been suggested that the UV and optical emission arise as a result of reprocessing of X-rays and that a likely site for such reprocessing is an accretion disk around the X-ray source. If UV and optical emission are enhanced by the reprocessing of X-rays, the X-ray variability may be manifest in UV emission. We test this by using high temporal resolution UV data obtained simultaneously with high temporal resolution X-ray data collected by the Goddard High Resolution Spectrograph (GHRS) on the Hubble Space Telescope and by the X-Ray Timing Explorer. We analyze the variability behavior of the UV spectrum and of the X-rays, and we also measure the properties of the emission-line profiles as viewed at high resolution (resolving power similar or equal to 25,000) with the echelle gratings. The variability behavior does not provide direct support for the reprocessing scenario, although the correlated variability between UV and X-rays does not conflict with this hypothesis. Furthermore, the emission-line profiles do not fit with simple models for disk emission lines. C1 NASA, High Energy Astrophys Lab, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Harvard Smithsonian Ctr Astrophys, Cambridge, MA 02138 USA. RP Kallman, T (reprint author), NASA, High Energy Astrophys Lab, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. EM tim@xstar.gsfc.nasa.gov; bboroson@riva.harvard.edu; svrtilek@cfa.harvard.edu NR 49 TC 10 Z9 10 U1 0 U2 0 PU IOP PUBLISHING LTD PI BRISTOL PA DIRAC HOUSE, TEMPLE BACK, BRISTOL BS1 6BE, ENGLAND SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD JUL 20 PY 1998 VL 502 IS 1 BP 441 EP 454 DI 10.1086/305873 PN 1 PG 14 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 151WH UT WOS:000077743300038 ER PT J AU Aschwanden, MJ Schwartz, RA Dennis, BR AF Aschwanden, MJ Schwartz, RA Dennis, BR TI Deconvolution of directly precipitating and trap-precipitating electrons in solar flare hard X-rays. II. Compton Gamma Ray Observatory data analysis SO ASTROPHYSICAL JOURNAL LA English DT Article DE acceleration of particles; radiation mechanisms : nonthermal; Sun : corona; Sun : flares; Sun : X-rays, gamma rays ID OF-FLIGHT DISTANCES; STOCHASTIC ACCELERATION; MAGNETIC RECONNECTION; PARTICLE-ACCELERATION; LOOP; CONFIGURATION; DENSITIES; YOHKOH; DELAYS AB Based on the deconvolution method developed in the first paper of this series, we present here the data analysis of 20-200 keV hard X-ray (HXR) data from the Burst and Transient Source Experiment (BATSE) on board the Compton Gamma Ray Observatory (CGRO) recorded during 103 solar flares in 1991-1995. These are all of the flares simultaneously observed by CGRO with high time resolution (64 ms) and by Yohkoh in hare mode. The deconvolution method takes the measured HXR count rates as function of energy and time, I(epsilon, t), and computes the following self-consistently: the electron injection function n(E, t), the directly precipitating electron flux n(prec)(E, t), the trapped-precipitating flux n(trap)(E, t), the fraction of directly precipitating electrons (q(prec)), the electron time-of-flight distance (l(TOF)), and the electron density at the loss cone site of the trap (n(e)). We find that the electron time-of-flight; distances (l(TOF) = 20.0 +/- 7.3 Mm) inferred with the deconvolution method are fully consistent with those obtained earlier using a Fourier filter method. The trap electron densities (n(e) = 10(10.96+/-0.57) cm(-3)) obtained from deconvolving the e-folding decay times of HXR pulses (according to the trap model of Melrose & Brown) are found to be statistically a factor of 1.5 lower than those inferred from cross-correlation delays. The fraction q(prec) of directly precipitating electrons, measured for the first time here, is found to have a mean (and standard deviation) of q(prec) = 0.42 +/- 0.16. Based on this precipitation fraction, we infer loss cone angles of alpha(0) approximate to 20 degrees-70 degrees and magnetic mirror ratios of R = B-loss/B-inj approximate to 1.2 - 3 (with a median value of R-median = 1.6) between the loss cone site and injection/acceleration site, assuming an isotropic pitch angle distribution at the injection site. The TOF distances and mirror ratios constrain magnetic scale heights in hare loops to lambda(B) = 10-150 Mm. The fact that this two-component model (with free-streaming and trapped electrons) satisfactorily fits the energy-dependent time delays in virtually all flares provides strong evidence that electron time-of-flight differences and collisional scattering times dominate the observed HXR timing, while the injection of electrons appears to be synchronized (independent of energy) and does not reveal the timing of the acceleration process. C1 Univ Maryland, Dept Astron, College Pk, MD 20742 USA. NASA, Hughes STX, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. NASA, Lab Astron & Solar Phys, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Aschwanden, MJ (reprint author), Univ Maryland, Dept Astron, College Pk, MD 20742 USA. RI Dennis, Brian/C-9511-2012 NR 44 TC 37 Z9 37 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 JUL 20 PY 1998 VL 502 IS 1 BP 468 EP 480 DI 10.1086/305891 PN 1 PG 13 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 151WH UT WOS:000077743300040 ER PT J AU Cui, W Barret, D Zhang, SN Chen, W Boirin, L Swank, J AF Cui, W Barret, D Zhang, SN Chen, W Boirin, L Swank, J TI Evolution of Aquila X-1 during the rising phase of its 1998 outburst SO ASTROPHYSICAL JOURNAL LA English DT Article DE accretion, accretion disks; stars : individual (Aquila X-1); stars : neutron; X-rays : stars ID ADVECTION-DOMINATED ACCRETION; X-RAY SOURCES; STARS; BINARIES; OUTFLOWS; PULSARS AB We present results from 16 snapshots of Aquila X-1 with the Rossi X-Ray Timing Explorer during the rising phase of its recent outburst. The observations were carried out at a typical rate of once or twice per day. The source shows interesting spectral evolution during this period. Phenomenologically, it bears remarkable similarities to "atoll" sources. Shortly after the onset of the outburst, the source is seen to be in an "island" state, but with Little X-ray variability. It then appears to have made a rapid spectral transition (on a timescale of less than half a day) to another island state, where it evolves slightly and stays for 4 days. In this state, the observed X-ray flux becomes increasingly variable as the source brightens. Quasi-periodic oscillation (QPO) in the X-ray intensity is detected in the frequency range 670-870 Hz. The QPO frequency increases with the X-ray flux while its fractional rms decreases. The QPO becomes undetectable following a transition to a "banana" state, where the source continues its evolution by moving up and down the banana branch in the color-color diagram as the flux (presumably the mass accretion rate) fluctuates around the peak of the outburst. Throughout the entire period, the power-density spectrum is dominated by very low frequency noises. Little power can be seen above similar to 1 Hz, which is different from typical atoll sources. In the banana state, the overall X-ray variability remains low (with a fractional rms similar to 3%-4%) but roughly constant. The observed X-ray spectrum is soft, with few photons from above similar to 25 keV, implying the thermal origin of the emission. The evolution of both spectral and temporal X-ray properties is discussed in the context of disk-instability models. C1 MIT, Ctr Space Res, Cambridge, MA 02139 USA. Ctr Etud Spatiale Rayonnements, F-31028 Toulouse 4, France. NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. Univ Space Res Assoc, Greenbelt, MD USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Maryland, Dept Astron, College Pk, MD 20742 USA. RP Cui, W (reprint author), MIT, Ctr Space Res, Room 37-571, Cambridge, MA 02139 USA. RI Swank, Jean/F-2693-2012 NR 22 TC 25 Z9 25 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 JUL 20 PY 1998 VL 502 IS 1 BP L49 EP L53 DI 10.1086/311492 PN 2 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 151WJ UT WOS:000077743400011 ER PT J AU Grove, JE Strickman, MS Matz, SM Hua, XM Kazanas, D Titarchuk, L AF Grove, JE Strickman, MS Matz, SM Hua, XM Kazanas, D Titarchuk, L TI Timing noise properties of GRO J0422+32 SO ASTROPHYSICAL JOURNAL LA English DT Article DE accretion, accretion disks; black hole physics; gamma rays : observations; stars : individual (GRO J0422+32) ID BLACK-HOLE CANDIDATES; QUASI-PERIODIC OSCILLATIONS; TRANSIENT NOVA PERSEI; X-RAY SOURCES; CYGNUS X-1; VARIABILITY; STATE AB OSSE observed the transient black hole candidate GRO J0422+32 (XN Persei 92) between 1992 August 11 and 1992 September 17. High time resolution data were obtained in several energy bands over the similar or equal to 35-600 keV range with a timing resolution of 8 ms. Power spectra at energies below 175 keV show substantial low-frequency red noise with a shoulder at a few times 10(-2) Hz, peaked noise with characteristic frequency near 0.2 Hz, and a second shoulder at a few Hz. The frequencies of the shoulders and the peak are independent of energy and source intensity. The complex cross spectrum indicates that photons in the 75-175 keV band lag photons in the 35-60 keV band by a time roughly proportional to the inverse of the Fourier frequency. The maximum lag observed is similar or equal to 300 ms. The power and lag spectra are consistent with the production of the gamma-rays through thermal Comptonization in an extended hot corona with a power-law density profile. C1 USN, Res Lab, EO Hulburt Ctr Space Res, Washington, DC 20375 USA. Northwestern Univ, Evanston, IL 60208 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Grove, JE (reprint author), USN, Res Lab, EO Hulburt Ctr Space Res, Code 7650, Washington, DC 20375 USA. NR 34 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 JUL 20 PY 1998 VL 502 IS 1 BP L45 EP L48 DI 10.1086/311481 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 151WJ UT WOS:000077743400010 ER PT J AU Stapelfeldt, KR Krist, JE Menard, F Bouvier, J Padgett, DL Burrows, CJ AF Stapelfeldt, KR Krist, JE Menard, F Bouvier, J Padgett, DL Burrows, CJ TI An edge-on circumstellar disk in the young binary system HK Tauri SO ASTROPHYSICAL JOURNAL LA English DT Article DE binaries : general; circumstellar matter; stars : individual (HK Tauri); stars : pre-main-sequence ID MAIN-SEQUENCE STARS; PHOTOMETRY; ACCRETION; AURIGA; WFPC2 AB Hubble Space Telescope (HST) images of HK Tauri reveal that the companion star in this 2." 4 (340 AU) pre-main-sequence binary system is an entirely nebulous object at visual wavelengths. HK Tau/c appears as two elongated reflection nebulosities separated by a dark lane. Near-infrared adaptive optics observations made at the Canada-France-Hawaii Telescope show a similar morphology and no directly visible star at lambda less than or equal to 2.2 mu m. HK Tau/c is strikingly similar to scattered light models of an optically thick circumstellar disk seen close to edge-on and to the HST images of KH 30. HK Tau/c is therefore the first disk to be clearly resolved around an individual star in a young binary system. The disk properties have been constrained by fitting model reflection nebulae to the HST images. The disk has a radius of 105 AU, an inclination of about 5 degrees, a scale height of 3.8 AU at r = 50 AU, and is flared. The absence of a point source in the near-IR requires A(v) > 50 mag toward the unseen central star. The thickness of the dark lane establishes a disk mass near 10(-4) M. (similar to 0.1 M-Jupiter) of dust and gas, if the dust grains have interstellar properties and remain fully mixed vertically. With the observed disk radius equal to one-third of the projected separation of the binary, there is a strong possibility that tidal truncation of the circumsecondary disk has occurred in this system. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Space Telescope Sci Inst, Baltimore, MD 21218 USA. Univ Grenoble 1, Astrophys Lab, Observ Grenoble, F-38041 Grenoble, France. CALTECH, IPAC, Pasadena, CA 91125 USA. RP Stapelfeldt, KR (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr,MS 183-900, Pasadena, CA 91109 USA. EM krs@wfpc2-mail.jpl.nasa.gov RI Stapelfeldt, Karl/D-2721-2012 NR 29 TC 159 Z9 159 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 JUL 20 PY 1998 VL 502 IS 1 BP L65 EP L69 DI 10.1086/311479 PN 2 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 151WJ UT WOS:000077743400014 ER PT J AU Storzer, H Hollenbach, D AF Storzer, H Hollenbach, D TI On the [O I] lambda 6300 line emission from the photoevaporating circumstellar disks in the Orion Nebula SO ASTROPHYSICAL JOURNAL LA English DT Article DE ISM : clouds; ISM : individual (Orion Nebula); line : formation; stars : formation ID TRAPEZIUM CLUSTER; OBJECTS; REGIONS; SHOCKS; IMAGES; GAS AB Several of the young stellar objects observed with the Hubble Space Telescope in the Orion Nebula near theta(1)C Ori show disklike structures with sizes r similar to 100 AU, similar to our own planetary system. These disklike shapes appear as dark silhouettes in [O III], [S II], [N II], H alpha, and the continuum but are seen in emission in the [O I] lambda 6300 line. We propose in this Letter that the [O I] emission is emerging from a H/H-2 photodissociation front that lies close to the disk surface. The H/H-2 front lies inside a photodissociation region between the disk surface and an ionization front that typically has a standoff distance of several disk radii from the disk surface. OH is produced efficiently at the warm H/H-2 front by the endothermic chemical reaction O + H-2 --> OH + H. However, OH is also efficiently destroyed by photodissociation caused by FUV photons. Approximately 50% of the photodissociated OH produces electronically excited atomic oxygen in the upper level of the 6300 Angstrom transition, which radiatively decays as intense [O I] lambda 6300 emission. Essentially, broadband FUV photons are absorbed by OH and efficiently converted to lambda 6300 line photons. The theoretically predicted [O I] lambda 6300 emission agrees well with that observed in 182-413 (HST -10), the best-studied object with a clearly resolved disk. The H/H-2 photodissociation front is close to the disk surface of 182-413, and the [O I] line, which peaks at the photodissociation front, thus traces the disk surface. The [O I] emission provides additional evidence in a number of proplyds for the existence of an extended PDR between the disk surface and the ionization front, and the penetration of OH-dissociating FUV photons from the ionization front to the disk surface. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Storzer, H (reprint author), NASA, Ames Res Ctr, MS 245-3, Moffett Field, CA 94035 USA. NR 25 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 JUL 20 PY 1998 VL 502 IS 1 BP L71 EP L74 DI 10.1086/311487 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 151WJ UT WOS:000077743400015 ER PT J AU Khosravi, R Brasseur, GP Smith, AK Rusch, DW Waters, JW Russell, JM AF Khosravi, R Brasseur, GP Smith, AK Rusch, DW Waters, JW Russell, JM TI Significant reduction in the stratospheric ozone deficit using a three-dimensional model constrained with UARS data SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID SOLAR MESOSPHERE EXPLORER; MIDDLE ATMOSPHERE; PHOTOCHEMISTRY; CHLORINE; CLO; OXYGEN; CIRCULATION; TEMPERATURE; SENSITIVITY; SIMULATION AB We present a near-global analysis of the ozone deficit problem by constraining a fully diurnal, three-dimensional, chemical, radiative, transport model of the middle atmosphere with colocated UARS measurements of ClO, NOx, H2O, and CH4. The domain of the study covers a wide range of altitudes (37.4-49.6 km) and latitudes (62.5 degrees S-27.5 degrees N), for the period of January-February 1992. In this domain, the baseline (no constraints with measurements) model temperatures are mostly warmer than U.K. Meteorological Office (UKMO) observations (by up to 5 K), and the baseline O-3 mixing ratios are underestimated by 10 to 25% relative to HALOE measurements. Also, in this domain the model/data discrepancies in concentrations of the ozone-relevant species are as follows: [H2O] and [NOx] are mostly in good agreement, [CH4] is underestimated by 10-60%, and [ClO] is overestimated by 1.3 to 3 times. We find the following: (1) Constraining the model with UKMO temperatures eliminates about 3-10% of the deficit in the 40-48 km altitude range. (2) Constraining the model with observed NOx or H2O (in addition to temperature) has minimal effect on the ozone deficit in most parts of the domain. (3) When the model temperature and ClO profiles are constrained with observations, the deficit is reduced to about 5-15%, bringing the model ozone predictions in the 40 km region to within the uncertainties of HALOE ozone measurements. (4) A 40% reduction in the rate constant of HO2 + O --> OH + O-2, in addition to constraining T, NOx, and ClO, eliminates the deficit in portions of the 40 km region and in the upper stratosphere, but it results in 5-10% excess ozone near the equatorial stratopause. (5) When the model methane profile is constrained with HALOE observations and a 6% HCl + O, channel for the ClO + OH reaction is included in the chemistry, the model ClO abundance agrees well with MLS measurements in most parts of the domain. Further improvement in the ClO abundance can be obtained by decreasing [OH] through reducing the rate constant of the HO2 + O --> OH + O-2 reaction. C1 Natl Ctr Atmospher Res, Boulder, CO 80307 USA. Univ Colorado, Atmospher & Space Phys Lab, Boulder, CO 80309 USA. Hampton Univ, Dept Phys, Hampton, VA 23668 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Khosravi, R (reprint author), Natl Ctr Atmospher Res, Pob 3000, Boulder, CO 80307 USA. EM rashid@ncar.ucar.edu NR 60 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 EI 2169-8996 J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD JUL 20 PY 1998 VL 103 IS D13 BP 16203 EP 16219 DI 10.1029/98JD01084 PG 17 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 100RB UT WOS:000074828200019 ER PT J AU Sugita, T Kondo, Y Nakajima, H Schmidt, U Engel, A Oelhaf, H Wetzel, G Koike, M Newman, PA AF Sugita, T Kondo, Y Nakajima, H Schmidt, U Engel, A Oelhaf, H Wetzel, G Koike, M Newman, PA TI Denitrification observed inside the Arctic vortex in February 1995 SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID TOTAL REACTIVE NITROGEN; POLAR STRATOSPHERIC CLOUD; INDUCED ICE PARTICLES; NITRIC-ACID; ATMOS EXPERIMENT; ANTARCTIC OZONE; NOVEMBER 1994; WATER-VAPOR; AEROSOL; JANUARY AB Balloon-borne in situ measurements of total reactive nitrogen (NO,) and nitrous oxide (N2O) were made from Kiruna (68 degrees N, 21 degrees E), Sweden on February 11, 1995. Ten hours later, N2O was again measured by an infrared spectrometer flown on another balloon launched from Kiruna. Both observations were made inside the polar vortex between 380 K (similar to 14 km) and at least 675 K (similar to 26 km). In the winter of 1994-1995, temperatures at 475 K (similar to 19 km) inside the vortex were extremely low, sometimes lower than ice frost point, especially from mid-December to mid-January. The NOgamma profiles obtained during both the ascent and descent revealed layered structures between 15 and 20 km with mixing ratios ranging from 2.7 to 9.3 parts per billion by volume (ppbv). The observed N2O profiles indicate significant downu ard transport of air due to diabatic cooling in the winter. To quantify the degree of irreversible removal of NOgamma (denitrification) between 12 and 28 km, the unperturbed values of NOgamma (i.e., NOgamma*) were estimated from the observed N2O values using the NOgamma - N2O relationship obtained at midlatitudes by the atmospheric trace molecule spectroscopy ATLAS mission and in situ aircraft and balloon-borne measurements. The largest denitrification was observed at 19 +/- 0.5 km, where the NOgamma values were lower than the NOgamma* values by similar to 10 ppbv, corresponding to a 70% removal of NOgamma In spite of the large uncertainty in NOgamma* the NO, values generally agreed well with the NOgamma* values at similar to 14 km as well as between 23 and 28 km. The relationship between NOgamma and N2O measured between 23 and 28 km agreed with that measured above 40 km at northern midlatitudes in fall, indicating that the air masses sampled at 23-28 km over Kiruna were transported from the midlatitude upper stratosphere followed by the descent inside the vortex. C1 Nagoya Univ, Solar Terr Environm Lab, Aichi 4428507, Japan. Univ Karlsruhe, Forschungszentrum, Inst Meteorol & Klimaforsch, D-76021 Karlsruhe, Germany. Forschungzentrum Julich, Inst Stratosphar Chem, Julich, Germany. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Sugita, T (reprint author), Natl Space Dev Agcy Japan, Earth Observat Res Ctr, Minato Ku, 1-9-9 Roppongi, Tokyo 1060032, Japan. EM sugita@eorc.nasda.go.jp; kondo@stelab.nagoya-u.ac.jp; hide@nies.go.jp; U.Schmidt@meteor.uni-frankfurt.de; An.Engel@meteor.uni-frankfurt.de; oelhaf@imk.fzk.de; wetzel@imk.fzk.de; newman@notus.gsfc.nasa.gov RI Koike, Makoto/F-4366-2011; Kondo, Yutaka/D-1459-2012; Newman, Paul/D-6208-2012; Wetzel, Gerald/A-7065-2013; Oelhaf, Hermann/A-7895-2013; Engel, Andreas/E-3100-2014; OI Newman, Paul/0000-0003-1139-2508; Engel, Andreas/0000-0003-0557-3935; Sugita, Takafumi/0000-0002-0508-7040 NR 59 TC 39 Z9 40 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 JUL 20 PY 1998 VL 103 IS D13 BP 16221 EP 16233 DI 10.1029/98JD01083 PG 13 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 100RB UT WOS:000074828200020 ER PT J AU Cebula, RP DeLand, MT Hilsenrath, E AF Cebula, RP DeLand, MT Hilsenrath, E TI NOAA 11 Solar Backscattered Ultraviolet, model 2 (SBUV/2) instrument solar spectral irradiance measurements in 1989-1994 - 1. Observations and long-term calibration SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID MONITOR-SUSIM-EXPERIMENT; NM; SSBUV; SATELLITE; MISSION; FLIGHT; BOARD; INDEX AB Measurements of solar ultraviolet (UV) irradiance are a valuable diagnostic of physical processes in the solar atmosphere and a key component in characterizing the external forcing of the Earth's atmosphere. However, the deleterious effects of solar UV radiation on satellite instrument components have complicated efforts to determine the magnitude of long-term solar variations for almost 30 years. The NOAA 11 Solar Backscatter Ultraviolet, model 2 (SBUV/2) instrument, primarily designed to measure stratospheric ozone, also made daily spectral scan measurements of solar UV irradiance in the 160-405 nm region from February 1989 to October 1994. An onboard calibration system and comparisons with coincident Shuttle SBUV (SSBUV) measurements were used to correct for long-term NOAA 11 instrument sensitivity changes. Time series of the NOAA 1 1 solar irradiance data indicate a long-term accuracy of approximately +/-0.9-2.3% (2 sigma) over the 5.5-year data record. Long-term solar irradiance changes of approximately -3% are observed between 215 and 250 nm, increasing in magnitude to approximately -7% at 200-205 nm. Additional discussion of solar variations observed by NOAA 11 SBUV/2 are presented by DeLand and Cebula [this issue]. C1 Raytheon STX Corp, Lanham, MD 20706 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Cebula, RP (reprint author), Raytheon STX Corp, 4400 Forbes Blvd, Lanham, MD 20706 USA. EM cebula@ssbuv.gsfc.nasa.gov; mdeland@stx.com; hilsenrath@ssbuv.nasa.gov NR 55 TC 22 Z9 23 U1 0 U2 1 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 JUL 20 PY 1998 VL 103 IS D13 BP 16235 EP 16249 DI 10.1029/98JD01205 PG 15 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 100RB UT WOS:000074828200021 ER PT J AU Hahn, I Boyd, STP Bozler, HM Gould, CM AF Hahn, I Boyd, STP Bozler, HM Gould, CM TI Thermodynamic magnetization discontinuity at the A-B transition in superfluid He-3 SO PHYSICAL REVIEW LETTERS LA English DT Article ID PHASE; TEMPERATURES; RESONANCE AB The difference between total thermodynamic magnetizations in the A and B phases of superfluid He-3 was measured at the equilibrium A-B transition temperature over the entire range of applicable magnetic fields at pressures from 0 to 27 bars. We present evidence that dynamic measurements (NMR) only partially account for the thermodynamic magnetization changes in the superfluid. The present experiment also measures the nontrivial strong-coupling correction to the magnetic field coupling strength in the Landau-Ginzburg free energy. C1 Univ So Calif, Dept Phys & Astron, Los Angeles, CA 90089 USA. RP Hahn, I (reprint author), Jet Prop Lab, MS 125-214,4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 14 TC 8 Z9 8 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 JUL 20 PY 1998 VL 81 IS 3 BP 618 EP 621 DI 10.1103/PhysRevLett.81.618 PG 4 WC Physics, Multidisciplinary SC Physics GA 100XJ UT WOS:000074840400031 ER PT J AU Rosakis, AJ Singh, RP Tsuji, Y Kolawa, E Moore, NR AF Rosakis, AJ Singh, RP Tsuji, Y Kolawa, E Moore, NR TI Full field measurements of curvature using coherent gradient sensing: application to thin film characterization SO THIN SOLID FILMS LA English DT Article DE stress; surface defects; surface morphology; X-ray diffraction ID AL-SI; ELECTROMIGRATION; STRESS; METALLIZATION; LAYER; METAL AB This paper introduces coherent gradient sensing (CGS) as an optical, full-field, real-time, non-intrusive and non-contact technique for measurement of curvature and curvature changes in thin film and micro-mechanical structures. The technique is applied to determine components of the curvature tensor field in multilayered thin films deposited on silicon wafers. Curvature field measurements using CGS are compared with average curvatures obtained using high-resolution X-ray diffraction. Finally, examples are presented to demonstrate the capability of CGS in measuring curvature in a variety of thin film and micro-mechanical structures. (C) 1998 Elsevier Science S.A. All rights reserved. C1 CALTECH, Dept Aeronaut, Pasadena, CA 91125 USA. CALTECH, Dept Appl Phys, Pasadena, CA 91125 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Rosakis, AJ (reprint author), CALTECH, Dept Aeronaut, Pasadena, CA 91125 USA. NR 41 TC 60 Z9 64 U1 0 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 JUL 18 PY 1998 VL 325 IS 1-2 BP 42 EP 54 DI 10.1016/S0040-6090(98)00432-5 PG 13 WC Materials Science, Multidisciplinary; Materials Science, Coatings & Films; Physics, Applied; Physics, Condensed Matter SC Materials Science; Physics GA 106AF UT WOS:000075107000009 ER PT J AU Guadagnini, R Schatz, GC Walch, SP AF Guadagnini, R Schatz, GC Walch, SP TI Ab initio and RRKM studies of the reactions of C, CH, and (CH2)-C-1 with acetylene SO JOURNAL OF PHYSICAL CHEMISTRY A LA English DT Article ID NEUTRAL-NEUTRAL REACTIONS; UNSATURATED-HYDROCARBONS; INTERSTELLAR-MOLECULES; THERMAL-DECOMPOSITION; SINGLET METHYLENE; ATOMIC CARBON; RATES; C2H2; ISOMERIZATION; TEMPERATURE AB We present abinitio calculations of geometries, energies, and normal mode frequencies for complexes and saddle points along the minimum energy reaction path for the reaction C + HCCH --> C3H2 --> C3H + H. We also present ab initio calculations along the minimum energy reaction path in the entrance channel for the reactions C + HCCH, CH + BCCH, and (CH2)-C-1 + HCCH. These results and those presented earlier by Walch(1) are used to calculate rate constants for the reactions of C, CH, and (CH2)-C-1 with acetylene, using variational RRKM theory. The rate constants obtained agree well with experimental results for all three reactions. Unimolecular lifetimes for intermediate complexes associated with each reaction path are also presented. Among the more stable C-3 isomers are propargyl and propargylene, which have lifetimes of 25 and 1900 ps, respectively, under thermal reaction conditions. C1 Northwestern Univ, Dept Chem, Evanston, IL 60208 USA. NASA, Inst Thermophys, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Schatz, GC (reprint author), Northwestern Univ, Dept Chem, 2145 Sheridan Rd, Evanston, IL 60208 USA. NR 44 TC 68 Z9 68 U1 3 U2 6 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 JUL 16 PY 1998 VL 102 IS 29 BP 5857 EP 5866 DI 10.1021/jp9811070 PG 10 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA 103HD UT WOS:000075151200017 ER PT J AU Bauschlicher, CW AF Bauschlicher, CW TI Infrared spectra of polycyclic aromatic hydrocarbons: oxygen substitution SO CHEMICAL PHYSICS LA English DT Article ID EMISSION FEATURES; MASS-SPECTROMETRY; IDENTIFICATION; DUST AB The B3LYP/4-31G approach is used to compute the harmonic frequencies of substituted naphthalenes and their cations. The substitution includes hydroxyl (OH), formyl (HC = O), and methylol (-CH2OH), at both the 1 and 2 sites. Also studied is 2-oxonaphthalene (= O). The TR spectra of these substituted species are compared with that of naphthalene. (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 23 TC 10 Z9 10 U1 0 U2 1 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0301-0104 J9 CHEM PHYS JI Chem. Phys. PD JUL 15 PY 1998 VL 233 IS 1 BP 29 EP 34 PG 6 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA ZZ999 UT WOS:000074790600003 ER PT J AU Razouqi, Q Lee, T Ghosh, S AF Razouqi, Q Lee, T Ghosh, S TI A guaranteed-no-cells-dropped buffer management scheme with selective blocking for cell-switching networks SO COMPUTER COMMUNICATIONS LA English DT Article DE queue management; cell loss; buffers; ATM network; large-scale networks; modeling and simulation of networks ID ATM NETWORKS; FUZZY; STRATEGIES; SIMULATION; DESIGN AB Fundamentally, the inclusion of bursty traffic, the desire to achieve a cost-effective network design, i.e. to obtain maximum throughput in a given network while minimizing cell loss, and the limitation of maximum buffer size, derived from basic digital design principles, lends significant importance to the issue of buffer management in cell switching networks including ATM networks. The buffer management literature is rich and includes reports on improved network performance through priority schemes, fixed thresholds, admission control, buffer partitioning, fuzzy thresholds, fuzzy rule-based congestion and admission control, fuzzy policing mechanisms, and a shared memory buffer for all output ports of a switch subject to a delayed pushout scheme. While highly effective, these techniques suffer from two key weaknesses. First, they are susceptible to cell loss owing to buffer overflow. Second, the performance reported for all of these schemes have been obtained for a single switch and, consequently, the results are not necessarily applicable to a realistic cell-switching network consisting of multiple switches. This paper presents a novel scheme-guaranteed-no-cells-dropped (GNCD), that eliminates cell loss owing to buffer overflow. In this approach, the switching node first records the current buffer occupancy and then determines the absolute number of empty slots. It then admits from the input cell-burst from other switches an exact number of cells equal to the number of empty slots. The remainder of the cells are blocked at the sending switch. The computation involved in the decision to admit or refuse entry into the buffer is simple and fast-a key advantage for high-speed networks. Further, buffer overflow is eliminated implying no cell loss-a key potential advantage for specific traffic classes in ATM. Although the fuzzy thresholding-based buffer management scheme holds a significant potential, according to the literature, to effectively reduce cell loss owing to buffer overflow, GNCD achieves in eliminating cell loss owing to buffer overflow completely. Although the fate of a large fraction of the blocked cells, caused by excess traffic, is similar to that in the fuzzy scheme, it is logical to assume that the prevention of cell loss owing to buffer overflow manifests through increased blocking. GNCD includes an effort to reroute the cells, constituting the increased blocking, to their eventual destinations. Clearly, these rerouted cells may incur delays and cause other cells in the network to suffer additional delays. Thus, the absolute current buffer occupancy and the size of the incoming cell-burst constitute the basis for admitting or blocking cells into the buffer. The GNCD scheme is modeled for both: (1) a single, stand-alone switch to facilitate a meaningful comparison with other competing approaches in the literature; and (2) a 50-switch, representative cell-switching network to study its performance under realistic conditions. Both models are simulated, the first on a uniprocessor computer and the second on a testbed consisting of a network of 25 + Pentium workstations under linux, configured as a loosely coupled parallel processor. For the simulation of model i, a representative traffic stimulus, characterized by a two-state, 'on-off Markov chain model and exponentially distributed departures, is utilized. A comparative analysis of the results reveal that the GNCD scheme yields a slightly higher throughput than the fuzzy scheme while ensuring zero cell loss owing to buffer overflow, over a range of values of input cell arrival rates. Performance results also indicate that, contrary to the general expectation that large buffers will enhance throughput and mitigate congestion, the throughput and blocking behavior of the GNCD scheme are unaffected by increasing the buffer capacity beyond a 'critical buffer size'. For the simulation of model 2, the input traffic distribution consists of a total of 1.0-1.5 million cells that are asserted into the network for each experiment, with the video traffic synthesized from an actual movie in MPEG-1, the audio traffic obtained using an ON/OFF model utilizing parameters extracted from an actual voice segment, while the generator for the data traffic utilizes a Markov chain model, subject to traffic shaping. The results corroborate those in model 1 in that, even for a large-scale representative cell-switching network, the throughput is higher and blocking is lower under GNCD than for the fuzzy thresholding approach, over a range of input traffic distributions corresponding to throughputs of 73-91%, although the difference in the throughputs and blocking are negligibly small for both low and high values of input cell arrival rates. At either extremes of the input cell arrival rate values, the behaviors of both GNCD and fuzzy thresholding are similar. However, while the cell loss owing to buffer overflow is nil, the average delay incurred by the cells in the network are higher for GNCD than the fuzzy approach, for the same range of input traffic distributions, by a factor ranging from 1.43 for relatively light input traffic density to 1.92 for moderate input traffic to 0.93 for heavy traffic. This paper notes that GNCD incurs less blocking than the fuzzy scheme and that the fuzzy scheme incurs cell loss through buffer overflow, and argues conservatively that the cells lost through buffer overflow in the fuzzy scheme manifest through increased blocking at the sending switches and that effort must be expended to reroute them to their respective destinations. Under these circumstances, the average delay incurred by the cells in the network is higher for GNCD than the fuzzy scheme by a factor ranging from 2.5 for relatively light input traffic density to 5.72 for moderate input traffic to 1.6 for heavy traffic. (C) 1998 Elsevier Science B.V. C1 Arizona State Univ, Dept Comp Sci & Engn, Tempe, AZ 85287 USA. NASA, Ames Res Ctr, Network Res Grp, Moffett Field, CA 94035 USA. RP Ghosh, S (reprint author), Arizona State Univ, Dept Comp Sci & Engn, Tempe, AZ 85287 USA. NR 32 TC 1 Z9 1 U1 0 U2 0 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0140-3664 J9 COMPUT COMMUN JI Comput. Commun. PD JUL 15 PY 1998 VL 21 IS 10 BP 930 EP 946 DI 10.1016/S0140-3664(98)00161-3 PG 17 WC Computer Science, Information Systems; Engineering, Electrical & Electronic; Telecommunications SC Computer Science; Engineering; Telecommunications GA ZZ337 UT WOS:000074719300007 ER PT J AU Yu, ST Jiang, BN Wu, J Duh, JC AF Yu, ST Jiang, BN Wu, J Duh, JC TI Three-dimensional simulations of Marangoni-Benard convection in small containers by the least-squares finite element method SO COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING LA English DT Article ID SURFACE-TENSION; ASPECT-RATIO; INSTABILITIES; NUMBER; ONSET; FLOWS AB This paper reports a numerical study of the Marangoni-Benard (MB) convection in a planar fluid layer. The least-squares finite element method (LSFEM) is employed to solve the three-dimensional Stokes equations and the energy equation. First, the governing equations are reduced to be first-order by introducing variables such as vorticity and heat fluxes. The resultant first-order system is then cast into a div-curl-gad formulation, and its ellipticity and boundary conditions are illustrated. This numerical approach provides an equal-order discretization for velocity, pressure, vorticity, temperature and heat conduction fluxes. Numerical results reported include the critical Marangoni numbers (M-ac) for the onset of the convection in containers with various aspect ratios, and the planforms of supercritical MB flows. The numerical solutions compared favorably with the experimental results reported by Koschmieder and Prahl. (C) 1998 Elsevier Science S.A. All rights reserved. C1 Wayne State Univ, Detroit, MI 48202 USA. NASA, Lewis Res Ctr, ICOMP, OAI, Cleveland, OH 44135 USA. RP Yu, ST (reprint author), Wayne State Univ, Detroit, MI 48202 USA. NR 26 TC 2 Z9 2 U1 0 U2 1 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 JUL 15 PY 1998 VL 160 IS 1-2 BP 71 EP 88 DI 10.1016/S0045-7825(97)00284-3 PG 18 WC Engineering, Multidisciplinary; Mathematics, Interdisciplinary Applications; Mechanics SC Engineering; Mathematics; Mechanics GA 105CM UT WOS:000075054900005 ER PT J AU Fox, NJ Peredo, M Thompson, BJ AF Fox, NJ Peredo, M Thompson, BJ TI Cradle to grave tracking of the January 6-11, 1997 Sun-Earth connection event SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article AB During the interval January 6-11, 1997, the satellites and ground facilities of the International Solar-Terrestrial Physics (ISTP) "Observatory" tracked a solar eruption from the Sun to the Earth. The resulting Coronal Mass Ejection (CME) took four days to travel through interplanetary space before arriving at Earth, where it caused electromagnetic disturbances and spectacular aurorae. The initial expulsion lifted off the Sun on January 6, the resulting magnetic cloud arrived on January 10, and its effects lasted over 24 hours. The initial solar observations from SOHO were reported on January 7, during an ISTP Science Workshop on Sun-Earth Connection events. This alerted the community to the impending arrival of the CME thereby allowing the event to be monitored in 'real-time' using the wide variety of ISTP instruments. This event provided the first ever end to end tracking of a space storm. Further, it provided a strong pressure pulse of extremely high density resulting in the compression of the magnetopause to within geosynchronous orbit during northward IMF conditions. Here we present an overview of the event and available observations. C1 NASA, GSFC, Raytheon STX Corp, Greenbelt, MD 20771 USA. NASA, GSFC, Space Applicat Corp, Green Bay, WI 20771 USA. RP Fox, NJ (reprint author), NASA, GSFC, Raytheon STX Corp, Greenbelt, MD 20771 USA. RI Thompson, Barbara/C-9429-2012; Fox, Nicola/P-6692-2016 OI Fox, Nicola/0000-0003-3411-4228 NR 7 TC 110 Z9 112 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 JUL 15 PY 1998 VL 25 IS 14 BP 2461 EP 2464 DI 10.1029/98GL01775 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 101UJ UT WOS:000074886300001 ER PT J AU Thompson, BJ Plunkett, SP Gurman, JB Newmark, JS St Cyr, OC Michels, DJ AF Thompson, BJ Plunkett, SP Gurman, JB Newmark, JS St Cyr, OC Michels, DJ TI SOHO/EIT observations of an Earth-directed coronal mass ejection on May 12, 1997 SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID TELESCOPE; MISSION AB An earth-directed coronal mass ejection (CME) was observed on May 12, 1997 by the SOHO Extreme ultraviolet Imaging Telescope (EIT). The CME; originating north of the central solar meridian, was later observed by the Large Angle Spectrometric Coronagraph (LASCO) as a "halo" CME: a bright expanding ring centered about the occulting disk. Beginning at about 04:35 UT, EIT recorded several CME signatures, including dimming regions close to the eruption, post-eruption arcade formation, and a bright wavefront propagating quasi-radially from the source region. Each of these phenomena appear to be associated with the same eruption, and the onset time of these features corresponds with the estimated onset time observed in LASCO. We discuss the correspondence of these features as observed by EIT with the structure of the CME in the LASCO data. C1 NASA, Goddard Space Flight Ctr, Space Applicat Corp, Greenbelt, MD 20771 USA. USN, Res Lab, Univ Space Res Assoc, Washington, DC 20375 USA. USN, Res Lab, Computat Phys Inc, Washington, DC 20375 USA. USN, Res Lab, EO Hulburt Ctr Space Res, Washington, DC 20375 USA. RP Thompson, BJ (reprint author), NASA, Goddard Space Flight Ctr, Space Applicat Corp, Code 682-3, Greenbelt, MD 20771 USA. RI Thompson, Barbara/C-9429-2012 NR 18 TC 400 Z9 409 U1 0 U2 4 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 JUL 15 PY 1998 VL 25 IS 14 BP 2465 EP 2468 DI 10.1029/98GL50429 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 101UJ UT WOS:000074886300002 ER PT J AU Webb, DF Cliver, EW Gopalswamy, N Hudson, HS St Cyr, OC AF Webb, DF Cliver, EW Gopalswamy, N Hudson, HS St Cyr, OC TI The solar origin of the January 1997 coronal mass ejection, magnetic cloud and geomagnetic storm SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID EARTH AB The magnetic cloud and geomagnetic storm on January 10-11, 1997 were associated with a halo-type Coronal Mass Ejection (CME) observed by the SOHO/LASCO coronagraphs near the sun on January 6. We summarize the solar activity related to this CME and the subsequent storm at Earth. This solar activity was remarkably weak and unimpressive. If the wide CME had not been observed, the storm would not have been forecast. Thus this case represents an extreme example of so-called "problem" magnetic storms that lack obvious surface signatures of eruptive solar activity. It supports the view that CMEs involve the destabilization of large-scale coronal structures which may or may not have associated surface activity, and that CMEs, not the surface activity, are the key causal link between solar eruptions and space weather at Earth. C1 USAF, Res Lab, VSBS, Hanscom AFB, MA 01731 USA. NASA, Goddard Space Flight Ctr, CPI, Naval Res Lab, Greenbelt, MD 20771 USA. Inst Space & Astronaut Sci, Sagamihara, Kanagawa 229, Japan. Boston Coll, Inst Sci Res, Newton Ctr, Chestnut Hill, MA 02167 USA. Catholic Univ Amer, Washington, DC USA. Solar Phys Res Corp, Tucson, AZ USA. RP Webb, DF (reprint author), USAF, Res Lab, VSBS, 29 Randolph Rd, Hanscom AFB, MA 01731 USA. RI Gopalswamy, Nat/D-3659-2012 NR 15 TC 61 Z9 63 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 JUL 15 PY 1998 VL 25 IS 14 BP 2469 EP 2472 DI 10.1029/98GL00493 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 101UJ UT WOS:000074886300003 ER PT J AU Berdichevsky, D Bougeret, JL Delaboudiniere, JP Fox, N Kaiser, M Lepping, R Michels, D Plunkett, S Reames, D Reiner, M Richardson, I Rostoker, G Steinberg, J Thompson, B von Rosenvinge, T AF Berdichevsky, D Bougeret, JL Delaboudiniere, JP Fox, N Kaiser, M Lepping, R Michels, D Plunkett, S Reames, D Reiner, M Richardson, I Rostoker, G Steinberg, J Thompson, B von Rosenvinge, T TI Evidence for multiple ejecta: April 7-11, 1997, ISTP Sun-Earth connection event SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID WIND SPACECRAFT; ENERGETIC PARTICLES; MASS EJECTIONS; SHOCKS AB Evidence is presented that the enhanced geomagnetic activity, on April 10-11, 1997, was caused by one of two ejecta that left the Sun at approximate to 14 UT on April 7. This ejecta was not directly detected at the Earth. The evidence for this interpretation is based on WIND spacecraft observations in the solar wind (SW). It is consistent with: (i) measured velocities of the coronal mass ejections from the SOHO coronagraph; (ii) the initial propagation speed of the shock generated in this event, estimation from type II radio burst observations from the WAVES instrument on WIND, and (iii) the time profile of energetic ions observed by EPACT on WIND. This locally unobserved ejecta (moving at 600 to 700 kms(-1)) generated a fast shock which accelerated ions to several tens of MeV/amu. The inferred passage of the first ejecta close to Earth (on April 10 to 11) is based on the observation of an interplanetary shock (IS) ahead of a field and plasma compressional region where the draping of the SW flow and possibly the changes in the direction of the IMF are consistent with a location northward of a faster ejecta. This ejecta was responsible for disturbed SW conditions including approximately ten hours of southward orientation of the interplanetary magnetic field (IMF) and a ram pressure many times above normal. The slower moving ejecta was directed toward Earth and was observed with WIND from about 0550 until 1500 UT on April 11. It had a strong northward IMF and produced density enhancements which elevated the ram pressure to more than four times above normal. C1 NASA, Goddard Space Flight Ctr, Space Applicat Corp, Greenbelt, MD 20771 USA. Observ Paris, DESPA, URA CNRS 264, F-92195 Meudon, France. Univ Paris 11, Inst Astrophis Spatiale, Orsay, France. USN, Res Lab, USRA, Washington, DC USA. Univ Alberta, Dept Phys, Edmonton, AB, Canada. Can Network Sp Res, Edmonton, AB, Canada. MIT, Ctr Space Res, Cambridge, MA 02139 USA. Hughes STX Corp, Greenbelt, MD 20770 USA. USN, Res Lab, Washington, DC 20375 USA. Space Applicat Corp, Greenbelt, MD 20770 USA. RP Berdichevsky, D (reprint author), NASA, Goddard Space Flight Ctr, Space Applicat Corp, MC 690, Greenbelt, MD 20771 USA. RI Thompson, Barbara/C-9429-2012; OI Richardson, Ian/0000-0002-3855-3634 NR 20 TC 30 Z9 30 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 JUL 15 PY 1998 VL 25 IS 14 BP 2473 EP 2476 DI 10.1029/97GL03771 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 101UJ UT WOS:000074886300004 ER PT J AU Plunkett, SP Thompson, BJ Howard, RA Michels, DJ St Cyr, OC Tappin, SJ Schwenn, R Lamy, PL AF Plunkett, SP Thompson, BJ Howard, RA Michels, DJ St Cyr, OC Tappin, SJ Schwenn, R Lamy, PL TI LASCO observations of an Earth-directed coronal mass ejection on May 12, 1997 SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article AB Coronal mass ejections (CMEs) that occur near the center of the solar disk are most likely to impact Earth. Detection of such events as 'halos' in white-light coronagraphs has been somewhat controversial in recent years. We present observations from the LASCO coronagraphs on SOHO that provide convincing evidence of the detection of an Earth-directed CME on May 12, 1997. The event began at about 04:35 UT and propagated outwards from the Sun with a projected speed of around 250 km s(-1). Using some reasonable assumptions about the geometry of the CME, we estimate the true speed to be around 600 km s(-1). The onset of the event in LASCO is coincident (to within measurement uncertainties) with an eruptive event detected in extreme ultraviolet observations of the solar disk by the SOHO EIT. This is the first reported observation of a halo CME at projected distances greater than 10 R-., with a clearly identifiable solar origin. We discuss the possibility that at least some of the enhanced brightness observed by LASCO may be due to a compressional wave propagating in the corona. C1 USN, Res Lab, EO Hulburt Ctr Space Res, Washington, DC 20375 USA. Astron Spatiale Lab, F-13376 Marseille 12, France. Max Planck Inst Aeron, D-37189 Katlenburg Lindau, Germany. Univ Birmingham, Sch Phys & Astron, Birmingham B15 2TT, W Midlands, England. NASA, Goddard Space Flight Ctr, Space Applicat Corp, Greenbelt, MD USA. USN, Res Lab, Computat Phys Inc, Washington, DC USA. USN, Res Lab, Univ Space Res Assoc, Washington, DC USA. RP Plunkett, SP (reprint author), USN, Res Lab, EO Hulburt Ctr Space Res, Washington, DC 20375 USA. RI Thompson, Barbara/C-9429-2012 NR 8 TC 91 Z9 90 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 JUL 15 PY 1998 VL 25 IS 14 BP 2477 EP 2480 DI 10.1029/98GL50307 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 101UJ UT WOS:000074886300005 ER PT J AU Hudson, HS Lemen, JR St Cyr, OC Sterling, AC Webb, DF AF Hudson, HS Lemen, JR St Cyr, OC Sterling, AC Webb, DF TI X-ray coronal changes during halo CMEs SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID SOLAR AB Using the Yohkoh soft X-ray images, we examine the coronal structures associated with "halo" coronal mass ejections (CMEs). These may correspond to events near solar disk center. Starting with a list of eleven confirmed halo CMEs over the time range from December 1996 through May 1997 we find seven with surface features identifiable in soft X-rays, with GOES classifications ranging from A1 to M1.3. These have a characteristic pattern of sigmoid --> arcade development. In each of these events, the pre-flare structure disrupted during the flare, leaving the appearance of compact transient coronal holes. The four remaining events had weak or indistinguishable signatures in the X-ray images. For the events for which we could see well-defined coronal changes, we confirm our previous result that the estimated mass loss inferred from the soft X-ray dimming is a small fraction of typical CME masses [Sterling & Hudson 1997]. C1 Inst Space & Astronaut Sci, Sagamihara, Kanagawa 229, Japan. Lockheed Martin Palo Alto Res Lab, Palo Alto, CA USA. NASA, Goddard Space Flight Ctr, Naval Res Lab, CPI, Greenbelt, MD 20771 USA. Computat Phys Inc, Fairfax, VA 22031 USA. Boston Coll, Inst Sci Res, Chestnut Hill, MA 02167 USA. RP Hudson, HS (reprint author), Inst Space & Astronaut Sci, 3-1-1 Yoshinodai, Sagamihara, Kanagawa 229, Japan. NR 19 TC 124 Z9 126 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 JUL 15 PY 1998 VL 25 IS 14 BP 2481 EP 2484 DI 10.1029/98GL01303 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 101UJ UT WOS:000074886300006 ER PT J AU Gopalswamy, N Hanaoka, Y Kosugi, T Lepping, RP Steinberg, JT Plunkett, S Howard, RA Thompson, BJ Gurman, J Ho, G Nitta, N Hudson, HS AF Gopalswamy, N Hanaoka, Y Kosugi, T Lepping, RP Steinberg, JT Plunkett, S Howard, RA Thompson, BJ Gurman, J Ho, G Nitta, N Hudson, HS TI On the relationship between coronal mass ejections and magnetic clouds SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID RADIO AB We compare the substructures of the 1997 February 07 coronal mass ejection (CME) observed near the Sun with a corresponding event in the interplanetary medium to determine the origin of magnetic clouds (MCs). We find that the eruptive prominence core of the CME observed near the Sun may not directly become a magnetic cloud as suggested by some authors and that it might instead become the "pressure pulse" following the magnetic cloud. We substantiate our conclusions using time of arrival, size and composition estimates of the CME-MC substructures obtained from ground based, SOHO and WIND observations. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Catholic Univ Amer, Dept Phys, Washington, DC 20064 USA. Nobeyama Radio Observ, Nobeyama, Japan. MIT, Cambridge, MA USA. USN, Res Lab, Washington, DC 20375 USA. Space Applicat Corp, Greenbelt, MD USA. Univ Maryland, Dept Phys, College Pk, MD 20742 USA. Lockheed Martin Res Lab, Palo Alto, CA USA. Solar Phys Res Corp, Tucson, AZ USA. RP Gopalswamy, N (reprint author), NASA, Goddard Space Flight Ctr, Code 682-3,Bldg 26,Room G-1, Greenbelt, MD 20771 USA. RI Gopalswamy, Nat/D-3659-2012; Thompson, Barbara/C-9429-2012 NR 16 TC 65 Z9 66 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 JUL 15 PY 1998 VL 25 IS 14 BP 2485 EP 2488 DI 10.1029/98GL50757 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 101UJ UT WOS:000074886300007 ER PT J AU Reiner, MJ Kaiser, ML Fainberg, J Bougeret, JL Stone, RG AF Reiner, MJ Kaiser, ML Fainberg, J Bougeret, JL Stone, RG TI On the origin of radio emissions associated with the January 6-11, 1997, CME SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID CORONAL MASS EJECTIONS; INTERPLANETARY SHOCKS; DENSITY; BURSTS; EVENTS AB Unusual type II radio emissions were generated by an Earth-directed CME that originated at the sun on Jan. 6, 1997. The intensities of the observed radio emissions were significantly higher than for typical type II events, while the source sizes and the overall frequency drift rate were significantly smaller. By introducing a new way of presenting the radio data that inherently reveals the dynamics of the type II radio source, we used these type II radio emissions, observed by the WAVES experiment on Wind, to track this CME through the interplanetary medium (IPM). From an analysis of the observed frequencies, the frequency drift rates and the results of the Wind radio direction finding, we were able to identify specific interplanetary structures such as a CIR that were the probable sources of at least some of the type II radio emissions associated with this event. This is the first time that type II emissions have been traced to specific interplanetary structures. C1 Hughes STX, Lanham, MD 20706 USA. NASA, Goddard Space Flight Ctr, Extraterr Phys Lab, Greenbelt, MD 20771 USA. Observ Paris, DESPA, F-92195 Meudon, France. Observ Meudon, Meudon, France. RP Reiner, MJ (reprint author), Hughes STX, 4400 Forbes Blvd, Lanham, MD 20706 USA. NR 15 TC 46 Z9 46 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 JUL 15 PY 1998 VL 25 IS 14 BP 2493 EP 2496 DI 10.1029/98GL00138 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 101UJ UT WOS:000074886300009 ER PT J AU Hoang, S Maksimovic, M Bougeret, JL Reiner, MJ Kaiser, ML AF Hoang, S Maksimovic, M Bougeret, JL Reiner, MJ Kaiser, ML TI Wind-Ulysses source location of radio emissions associated with the January 1997 Coronal Mass Ejection SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID SPACECRAFT AB We investigate the 3-D source location of interplanetary type II-like radio bursts from observations involving two spacecraft. Uncommon type II radio emissions were observed simultaneously on 8 January 1997 by the Wind and Ulysses spacecraft and are believed to be associated with the Interplanetary Coronal Mass Ejection detected on 6 - 7 January by the LASCO coronagraph on the SOHO spacecraft and on 10 - 11 January by Wind. Ulysses was located about 4.73 AU from the Sun at 25.6 degrees N ecliptic latitude and 45.1 degrees W of Earth, while Wind was in the solar wind upstream of the Earth. The two spacecraft recorded nearly similar intensity time profiles at the common frequency of 196 kHz. By means of radio triangulation, we locate the 3-D source region, inferring it to be strongly deviated by several AU from the expected source between the Sun and Earth towards the solar hemisphere opposite Earth. Strong propagation effects, such as scattering and refraction, are suggested as affecting Ulysses observations (both in apparent source size and direction), being due to the presence of interplanetary overdense structures of various scales. We also de duce the source location from the direction as measured at Wind and the difference of the arrival times as measured at both spacecraft. From this latter approach we find that the source location is closer to Wind than the expected source by similar to 0.2 - 0.4 AU, corresponding to an excess travel time of similar to 0.55 - 1.44 min on the radiation path to Ulysses. The excess delay time is found to be about 2.6 times greater for the fundamental emission than for the harmonic emission, and it is found to vary (approximately) inversely as the decay time of the intensity at Ulysses, presuming the existence of scattering. C1 Observ Paris, CNRS, URA 264, Dept Rech Spatiale, F-92195 Meudon, France. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Hoang, S (reprint author), Observ Paris, CNRS, URA 264, Dept Rech Spatiale, F-92195 Meudon, France. NR 8 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 JUL 15 PY 1998 VL 25 IS 14 BP 2497 EP 2500 DI 10.1029/98GL00571 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 101UJ UT WOS:000074886300010 ER PT J AU Kaiser, ML Reiner, MJ Gopalswamy, N Howard, RA St Cyr, OC Thompson, BJ Bougeret, JL AF Kaiser, ML Reiner, MJ Gopalswamy, N Howard, RA St Cyr, OC Thompson, BJ Bougeret, JL TI Type II radio emissions in the frequency range from 1-14 MHz associated with the April 7, 1997 solar event SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID CORONAL MASS EJECTIONS; INTERPLANETARY SHOCKS; BURSTS AB We present an analysis of radio emissions associated with the April 7, 1997 solar eruptive event. The event consisted of a filament disappearance, a complex two-phase coronal mass ejection (CME), and a C6.9, 2N flare. At the same time, intermittent type II radio emissions in the frequency range 1-10 MHz, corresponding to an altitude range of 2-15 R-., were observed by the Wind/WAVES radio receiver. Using the onset times and inferred heights and speeds of the radio bursts, we considered both a CME-driven shock and a flare-associated blast wave shock as possible causes of the type II radio emissions. We conclude that some of the radio emissions in the WAVES data are associated with each shock. The type II radio emissions associated with the blast wave shock were farther from the sun than any emission of this type that has been reported previously. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Observ Paris, DESPA, F-92195 Meudon, France. USN, Res Lab, Washington, DC 20375 USA. Ratheon STX, Goddard Space Flight Ctr, Greenbelt, MD USA. Catholic Univ, Washington, DC USA. Computat Phys Inc, Fairfax, VA USA. Space Applicat Corp, Vienna, VA USA. RP Kaiser, ML (reprint author), NASA, Goddard Space Flight Ctr, Code 661, Greenbelt, MD 20771 USA. EM kaiser@lepmlk.gsfc.nasa.gov RI Gopalswamy, Nat/D-3659-2012; Thompson, Barbara/C-9429-2012 NR 22 TC 45 Z9 45 U1 1 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 JUL 15 PY 1998 VL 25 IS 14 BP 2501 EP 2504 DI 10.1029/98GL00706 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 101UJ UT WOS:000074886300011 ER PT J AU Collier, MR Slavin, JA Lepping, RP Szabo, A Ogilvie, K AF Collier, MR Slavin, JA Lepping, RP Szabo, A Ogilvie, K TI Timing accuracy for the simple planar propagation of magnetic field structures in the solar wind SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID SPACECRAFT AB Results from a correlation analysis of Wind and IMP 8 magnetometer data for a total of 543 two hour periods covering Jan-Jul 1995 were analyzed to determine that: (1) the timing accuracy Delta tau for advecting solar wind magnetic field structures goes as (d(per)/d(par)).tau(con) where dp,, is the spacecraft separation along the Sun-Earth line, d(per) is the transverse separation, and tau(con) is the predicted convection lag time, (2) "good" correlation time periods (peak correlation coefficient > 0.80) are about twice as likely at solar maximum than at solar minimum, (3) geometry affects timing accuracy more than any propagation of features with respect to the solar wind, and (4) there is a "high" probability (greater than predicted by a Gaussian distribution) of "very bad" (/d(par)Delta tau/d(per)tau(con)/ > 3) timing agreement due to the long tail on the probability distribution. C1 NASA, Goddard Space Flight Ctr, Extraterr Phys Lab, Greenbelt, MD 20771 USA. 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 16 TC 91 Z9 92 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 JUL 15 PY 1998 VL 25 IS 14 BP 2509 EP 2512 DI 10.1029/98GL00735 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 101UJ UT WOS:000074886300013 ER PT J AU Cane, HV Richardson, IG St Cyr, OC AF Cane, HV Richardson, IG St Cyr, OC TI The interplanetary events of January-May, 1997 as inferred from energetic particle data, and their relationship with solar events SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID CORONAL MASS EJECTIONS; SHOCKS AB We use observations from the Goddard particle detectors on IMP 8 to investigate near-Earth interplanetary disturbances and the associated solar events in January-May 1997, We infer the presence of high-speed streams and ejecta (material in the solar wind associated with coronal mass ejections (CMEs) at the Sun) using depressions in the counting rate of >60 MeV/amu particles measured by the anti-coincidence guard. In addition to a sequence of high-speed streams, the guard detected four ejecta. A fifth ejecta (January 10-11), evident in solar wind observations, did not produce a particle decrease. During the study period there were five particle enhancements, indicating the occurrence of energetic CMEs at the Sun. All the particle enhancements were associated with halo CMEs observed by the SOHO LASCO coronagraphs. Five of the total of nine halo CMEs in this period impacted the Earth. None of the other similar to 120 CMEs detected by LASCO did so, Only the four CMEs associated with traditional flare signatures were also associated with >10 MeV particle increases. C1 NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. NASA, Goddard Space Flight Ctr, Naval Res Lab, Computat Phys Inc, Greenbelt, MD 20771 USA. RP Cane, HV (reprint author), NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. OI Richardson, Ian/0000-0002-3855-3634 NR 12 TC 33 Z9 33 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 JUL 15 PY 1998 VL 25 IS 14 BP 2517 EP 2520 DI 10.1029/98GL00494 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 101UJ UT WOS:000074886300015 ER PT J AU Mazur, JE Mason, GM Dwyer, JR von Rosenvinge, TT AF Mazur, JE Mason, GM Dwyer, JR von Rosenvinge, TT TI Solar energetic particles inside magnetic clouds observed with the Wind spacecraft SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID EVENTS AB Solar energetic particles can be used to probe the structure of magnetic clouds. Since impulsive flare particles are accelerated within active regions, their presence inside a magnetic cloud implies that the cloud's magnetic field connects to an active region at the sun. We report on the flexes and composition of low energy ions inside 13 magnetic clouds observed with instrumentation on the Wind spacecraft from November 1994 to February 1997. The STEP subsystem of the EPACT experiment on Wind resolves He-3 and He-4 and the most abundant heavy ion species from similar to 20 keV/nucleon to similar to 1 MeV/nucleon. Using STEP, we are able to measure the energetic particle composition in an energy range previously unexplored in the context of magnetic clouds. We find that when STEP measured significant ion fluxes inside a cloud, they were most likely from impulsive solar flares; this was the case in 4 events. We find that the 1/10/97 magnetic cloud decreased the interplanetary fluxes of similar to 100 keV/nucleon ions by a factor of similar to 10(2); this was probably because the cloud disconnected Wind from the interplanetary particle source beyond 1 AU. In contrast, we observed particles from several impulsive solar flares inside the 10/18/95 event with fluxes similar to 10(3) higher than the fluxes measured inside the 1/10/97 cloud. C1 Aerospace Corp, El Segundo, CA 90245 USA. Univ Maryland, Dept Phys, College Pk, MD 20742 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Mazur, JE (reprint author), Aerospace Corp, M2-259,270 Coral Circle, El Segundo, CA 90245 USA. EM joseph.mazur@aero.org; mason@sampx3.umd.edu; dwyer@umstep.umd.edu; tycho@lhenmoil.gsfc.nasa.gov NR 13 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 JUL 15 PY 1998 VL 25 IS 14 BP 2521 EP 2524 DI 10.1029/98GL00410 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 101UJ UT WOS:000074886300016 ER PT J AU Wurz, P Ipavich, FM Galvin, AB Bochsler, P Aellig, MR Kallenbach, R Hovestadt, D Grunwaldt, H Hilchenbach, M Axford, WI Balsiger, H Burgi, A Coplan, MA Geiss, J Gliem, F Gloeckler, G Hefti, S Hsieh, KC Klecker, B Lee, MA Managadze, GG Marsch, E Mobius, E Neugebauer, M Reiche, KU Scholer, M Verigin, MI Wilken, B AF Wurz, P Ipavich, FM Galvin, AB Bochsler, P Aellig, MR Kallenbach, R Hovestadt, D Grunwaldt, H Hilchenbach, M Axford, WI Balsiger, H Burgi, A Coplan, MA Geiss, J Gliem, F Gloeckler, G Hefti, S Hsieh, KC Klecker, B Lee, MA Managadze, GG Marsch, E Mobius, E Neugebauer, M Reiche, KU Scholer, M Verigin, MI Wilken, B TI Elemental composition of the January 6, 1997, CME SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID SOLAR AB Using solar wind particle data from the CELIAS/MTOF sensor on the SOHO mission, we studied the abundance of the elements O, Ne, Mg, Si, S, Ca, and Fe for the time period around the January 6, 1997, coronal mass ejection event (CME). In the interstream and coronal hole regions before and after this event we found elemental abundances consistent with the expected abundance patterns of the respective flow regimes. However, during the passage of the CME and during the passage of the erupted filament, which followed the CME, we found that the elemental composition differed markedly from the interstream and coronal hole regions before and after this event. During the passage of the CME and the passage of the erupted filament we found a mass-dependent element fractionation, with a monotonic increase toward heavier elements. We observed Si/O and Fe/O abundance ratios of about one half during these time periods, which is significantly higher than for typical solar wind. C1 Univ Bern, Inst Phys, CH-3012 Bern, Switzerland. Univ Maryland, Dept Phys & Astron, College Pk, MD 20742 USA. Univ Maryland, IPST, College Pk, MD 20742 USA. Int Space Sci Inst, CH-3012 Bern, Switzerland. Max Planck Inst Extraterr Phys, D-85740 Garching, Germany. Max Planck Inst Aeron, D-37189 Katlenburg Lindau, Germany. Tech Univ Braunschweig, Inst Datenverarbeitung, D-38023 Braunschweig, Germany. Univ Arizona, Dept Phys, Tucson, AZ 85721 USA. Univ New Hampshire, EOS, Durham, NH 03824 USA. Jet Prop Lab, Pasadena, CA 91103 USA. RP Wurz, P (reprint author), Univ Bern, Inst Phys, Sidlerstr 5, CH-3012 Bern, Switzerland. EM peter.wurz@soho.unibe.ch; ipavich@umdsp.umd.edu; toni.galvin@unh.edu; bochsler@soho.unibe.ch; maellig@soho.unibe.ch; kallenbach@issi.unibe.ch; dih@mpens.mpe-garching.mpg.de; Gruenwaldt@linax1.dnet.gwdg.de; hilchenbach@linax1.mpae.gwdg.de; hbalsiger@phim.unibe.ch; Coplan@umdsp.umd.edu; geiss@issi.unibe.ch; gloeckler@umdsp.umd.edu; hefti@soho.unibe.ch; hsieh@physics.arizona.edu; bek@mpe.mpe-garching.mpg.de; marty.lee@unh.edu; marsch@linax1.dnet.gwdg.de; eberhard.moebius@unh.edu; mneugeb@jplsp.jpl.nasa.gov; reiche@ida.ing.tu-bs.de; scholer@mpe-garching.mpg.de; wilken@linax1.mpae.gwdg.de RI Galvin, Antoinette/A-6114-2013; OI Moebius, Eberhard/0000-0002-2745-6978 NR 10 TC 27 Z9 27 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 JUL 15 PY 1998 VL 25 IS 14 BP 2557 EP 2560 DI 10.1029/98GL50478 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 101UJ UT WOS:000074886300025 ER PT J AU Li, XL Baker, DN Temerin, M Cayton, T Reeves, GD Araki, T Singer, H Larson, D Lin, RP Kanekal, SG AF Li, XL Baker, DN Temerin, M Cayton, T Reeves, GD Araki, T Singer, H Larson, D Lin, RP Kanekal, SG TI Energetic electron injections into the inner magnetosphere during the Jan. 10-11, 1997 magnetic storm SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID MARCH 24; SIMULATION; SAMPEX; SOLAR; SSC AB At the end of the main phase of the Jan. 10-11, 1997 magnetic storm, a rapid enhancement of 0.4-1.6 MeV electrons across L = 4.2-6 was measured by particle detectors on the Solar, Anomalous, and Magnetospheric Particle Explorer (SAMPEX) and three Global Positioning System (GPS) satellites. This enhancement, over two orders of magnitude at L = 4.2-5, occurred around 11:00 UT on Jan. 10, when the AE index reached similar to 2000 nT and when a solar wind pressure pulse arrived. Using data from multiple satellites and ground stations, we determine that the rapid enhancement of 0.4-1.6 MeV electrons in the magnetosphere at L = 4.2-6 was due to a combination of intense substorm activity during the early part of the magnetic storm which produced a source population and the following pressure pulse which quickly energized some of these electrons by moving them into stronger magnetic field. C1 Univ Colorado, LASP, Boulder, CO 80303 USA. Univ Calif Berkeley, SSL, Berkeley, CA 94720 USA. Univ Calif Los Alamos Natl Lab, Los Alamos, NM 87545 USA. Kyoto Univ, Dept Geophys, Kyoto 606, Japan. NOAA, Space Environm Ctr, Boulder, CO 80303 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Hughes STX, Greenbelt, MD USA. RP Li, XL (reprint author), Univ Colorado, LASP, 1234 Innovat Dr, Boulder, CO 80303 USA. RI Reeves, Geoffrey/E-8101-2011 OI Reeves, Geoffrey/0000-0002-7985-8098 NR 15 TC 47 Z9 49 U1 0 U2 4 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 JUL 15 PY 1998 VL 25 IS 14 BP 2561 EP 2564 DI 10.1029/98GL00036 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 101UJ UT WOS:000074886300026 ER PT J AU Spann, JF Brittnacher, M Elsen, R Germany, GA Parks, GK AF Spann, JF Brittnacher, M Elsen, R Germany, GA Parks, GK TI Initial response and complex polar cap structures of the aurora in response to the January 10, 1997 magnetic cloud SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article AB On January 10(th), 1997, a magnetic cloud originating at the Sun was incident on the Earth. The initial disturbance to the magnetosphere, as reflected in the activities of the aurora, was measured by the Ultraviolet Imager on the Polar Spacecraft. During this event we have observed the development of several unusual unique auroral forms that to our knowledge are unexplained in current models and theories. The observations were made on a global scale with unprecedented spatial and temporal resolution. The first activation of the aurora at local noon occurred within minutes of the arrival of the shock at 0107 UT. The substorm onset was observed at 0334 UT. During the intervening time significant polar cap precipitation occurred. C1 NASA, Marshall Space Flight Ctr, Space Sci Lab, Huntsville, AL 35812 USA. Univ Washington, Geophys Program, Dept Geophys, Seattle, WA 98195 USA. Univ Alabama, Ctr Space Plasma & Aeron & Astron Res, Huntsville, AL 35899 USA. RP Spann, JF (reprint author), NASA, Marshall Space Flight Ctr, Space Sci Lab, Mail Code ES83, Huntsville, AL 35812 USA. NR 5 TC 35 Z9 36 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 JUL 15 PY 1998 VL 25 IS 14 BP 2577 EP 2580 DI 10.1029/98GL00647 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 101UJ UT WOS:000074886300030 ER PT J AU Elsen, RK Winglee, RM Spann, JF Germany, GA Brittnacher, M Parks, GK AF Elsen, RK Winglee, RM Spann, JF Germany, GA Brittnacher, M Parks, GK TI The auroral oval boundaries on January 10, 1997: A comparison of global magnetospheric simulations with UVI images SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID FIELD-ALIGNED CURRENTS AB We present a global magnetospheric simulation of the initial period of the January 10-11, 1997 magnetic cloud event. Model magnetospheric boundaries mapped to the ionosphere are compared to UVI images of the auroral oval from 1:00 to 4:30 UT. The convection reversal boundary generally matches the UVI equatorward boundary and is almost always poleward of the boundary separating Region 1 and Region 2 currents. The separatrix between open and closed magnetic field lines matches the poleward boundary of the UVI images well during quiet periods. During dynamic periods when the separatrix moves several degrees in latitude in some sectors, the poleward boundary of the Region 1 currents matches the UVI images better. C1 Univ Washington, Geophys Program, Seattle, WA 98195 USA. NASA, Marshall Space Flight Ctr, Space Sci Lab, Huntsville, AL 35812 USA. Univ Alabama, Ctr Space Plasma & Aeronom Res, Huntsville, AL 35899 USA. RP Elsen, RK (reprint author), Univ Washington, Geophys Program, Box 351650, Seattle, WA 98195 USA. NR 8 TC 13 Z9 13 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 JUL 15 PY 1998 VL 25 IS 14 BP 2585 EP 2588 DI 10.1029/98GL01066 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 101UJ UT WOS:000074886300032 ER PT J AU Ho, CM Mannucci, AJ Lindqwister, UJ Pi, X Tsurutani, BT Sparks, L Iijima, BA Wilson, BD Harris, I Reyes, MJ AF Ho, CM Mannucci, AJ Lindqwister, UJ Pi, X Tsurutani, BT Sparks, L Iijima, BA Wilson, BD Harris, I Reyes, MJ TI Global ionospheric TEC variations during January 10, 1997 storm SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID NETWORK AB The ionospheric storm evolution process was monitored during the January 10, 1997 magnetic cloud event, through measurements of the ionospheric total electron content (TEC) from 150 GPS stations. The first significant response of the ionospheric TEC to the geomagnetic storm was at 0300 UT as an auroral/subauroral enhancement around the Alaskan evening sector. This enhancement then extended to both noon and midnight. Around 0900 UT, the enhancement at noon broke from the subauroral band and moved to lower latitudes. This dayside northern hemisphere enhancement also corresponded to a conjugate geomagnetic latitude enhancement in the southern hemisphere and lasted about 5 hours. At 1500 UT a large middle latitude enhancement appeared over Mexico and the southern US, and persisted until 2200 UT. The enhancement was probably caused by the equatorward neutral wind which pushed the plasma up. On the basis of this assumption, the kinetic energy of the neutral wind which caused the middle latitude enhancement is estimated as similar to 4.1x10(9) Joules. This is about 0.03% of solar wind energy impinging on the magnetosphere and about 3% of the energy deposited on polar cap ionosphere. After 2000 UT, a negative phase gradually became stronger (especially in the southern hemisphere), although the northern subauroral enhancement persisted one more day. The entire ionosphere gradually recovered to normal on January 12. Thus, large middle latitude enhancement, equatorward motion of the dayside enhancement (probably related to a TID), the persistence of the subauroral enhancement, and the conjugate features at both hemispheres are the main characteristics of this storm. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Ho, CM (reprint author), CALTECH, Jet Prop Lab, MS 238-600,4800 Oak Grove Dr, Pasadena, CA 91109 USA. RI Mannucci, Anthony/A-1349-2007 OI Mannucci, Anthony/0000-0003-2391-8490 NR 14 TC 38 Z9 44 U1 1 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 JUL 15 PY 1998 VL 25 IS 14 BP 2589 EP 2592 DI 10.1029/98GL00539 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 101UJ UT WOS:000074886300033 ER PT J AU Villante, U Francia, P Lepidi, S De Lauretis, M Pietropaolo, E Cafarella, L Meloni, A Lazarus, AJ Lepping, RP Mariani, F AF Villante, U Francia, P Lepidi, S De Lauretis, M Pietropaolo, E Cafarella, L Meloni, A Lazarus, AJ Lepping, RP Mariani, F TI Geomagnetic field variations at low and high latitude during the January 10-11, 1997 magnetic cloud SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID MAGNETOSPHERE; PULSATIONS; EXCITATION; PASSAGE AB On Jan. 10-11, 1997 a wide magnetic cloud reached the Earth triggering intense geomagnetic activity. Observations performed at low and very high latitude show that the same features appear simultaneously in correspondence to different changes in the solar wind conditions. In particular, highly polarized modes are simultaneously observed at the same discrete frequencies after the passage of the high density solar wind region following the cloud. SI's and ULF waves polarization are also examined in a wide latitudinal and longitudinal extent. C1 Univ Aquila, Dipartimento Fis, I-67010 Laquila, Italy. Ist Nazl Geofis, I-00143 Rome, Italy. MIT, Ctr Space Res, Cambridge, MA 02139 USA. NASA, Goddard Space Flight Ctr, Extraterr Phys Lab, Greenbelt, MD 20771 USA. Univ Rome 2, Dipartimento Fis, I-00133 Rome, Italy. RP Villante, U (reprint author), Univ Aquila, Dipartimento Fis, Via Vetoio, I-67010 Laquila, Italy. RI De Lauretis, Marcello/E-1550-2011; OI De Lauretis, Marcello/0000-0002-4088-5689; Villante, Umberto/0000-0002-3630-7958; PIETROPAOLO, Ermanno/0000-0002-6633-9846; cafarella, lili/0000-0003-2005-8923 NR 20 TC 25 Z9 25 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 JUL 15 PY 1998 VL 25 IS 14 BP 2593 EP 2596 DI 10.1029/98GL00335 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 101UJ UT WOS:000074886300034 ER PT J AU Ho, CM Tsurutani, BT Lin, N Lanzerotti, LJ Smith, EJ Goldstein, BE Buti, B Lakhina, GS Zhou, XY AF Ho, CM Tsurutani, BT Lin, N Lanzerotti, LJ Smith, EJ Goldstein, BE Buti, B Lakhina, GS Zhou, XY TI A pair of forward and reverse slow-mode shocks detected by Ulysses at similar to 5 AU SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID SPECTRA AB We report the first finding of a pair of forward and reverse slow-mode shocks in the distant heliosphere using plasma and magnetic field data from the Ulysses spacecraft located at 5.3 AU and 90 S heliolatitude. The slow-mode shocks are found to occur in a compressed magnetic field (low plasma) region within a co-rotating interaction region (CIR). We find Mach numbers to be 0.3-0.5 with respect to forward/reverse slow shocks. Across each shock, the solar wind velocities jump by at least 40 km/s. The increases in plasma density and ion temperature accompany a decrease in the magnetic field. The shocks are also found to have velocities of 60 km/s and 115 km/s and thicknesses between 7.5 - 12.6 x 10(4) km (much larger than the ion inertial length, 10(3) km). Low frequency plasma waves are detected by the Ulysses URAP instrument at the slow-mode shock transition regions. However, the waves are not of sufficient amplitude to provide enough anomalous resistivity through wave-particle interactions for shock dissipation. Low energy (similar to 30 - 90 keV) electron enhancements directed along the local magnetic field are also found associated with the slow shocks, indicating the ability of the shocks to accelerate interplanetary particles. This finding imply that more slow shocks might be found in the CIR magnetic compressed regions (where plasma is squeezed out) at large heliospheric distances. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ Minnesota, Sch Phys & Astron, Minneapolis, MN 55455 USA. Lucent Technol, Bell Labs, Murray Hill, NJ 07974 USA. RP Ho, CM (reprint author), CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RI Lakhina, Gurbax /C-9295-2012 NR 18 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 JUL 15 PY 1998 VL 25 IS 14 BP 2613 EP 2616 DI 10.1029/98GL02014 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 101UJ UT WOS:000074886300039 ER PT J AU Whang, YC Larson, D Lin, RP Lepping, RP Szabo, A AF Whang, YC Larson, D Lin, RP Lepping, RP Szabo, A TI Plasma and magnetic field structure of a slow shock: Wind observations in interplanetary space SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID RANKINE-HUGONIOT PROBLEM; MODE SHOCKS; SOLAR-WIND; SHEET BOUNDARY; MAGNETOTAIL AB This paper reports on the observation of an interplanetary slow shock on May 23, 1995 using 3-s plasma and magnetic field data from the Wind spacecraft. Since the time to traverse the shock (similar to 15 s) is much greater than the 3-s temporal resolution of the data, this observation can reveal the plasma and magnetic field structure through the interior of the shock. The 3-s data also provide accurate preshock and postshock conditions immediately outside the shock layer. The flow speeds in the shock frame of reference U-n < a cos Theta on both sides of the shock, U-n1 > C-S1, and U-n2 < C-S2. Here a and C-S are, respectively, the Alfven speed and the slow speed, Theta is the acute angle between the magnetic field vector and the shock normal, and the subscripts 1 and 2 denote the preshock and the postshock conditions. Theta(1) similar to 47 degrees and Theta(2) similar to 39 degrees. The jump conditions B-2/B-1, N-2/N-1, and (T-i + T-e)(2)/(T-i + T-e)(1) of the observational result are in good agreement with the Rankine-Hugoniot solution. The thickness of the shock is of the order of 36 limes of the preshock ion inertial length. C1 Catholic Univ Amer, Dept Mech Engn, Washington, DC 20064 USA. Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Whang, YC (reprint author), Catholic Univ Amer, Dept Mech Engn, Washington, DC 20064 USA. NR 27 TC 14 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 JUL 15 PY 1998 VL 25 IS 14 BP 2625 EP 2628 DI 10.1029/98GL02043 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 101UJ UT WOS:000074886300042 ER PT J AU Mayr, HG Mengel, JG Reddy, CA Chan, KL Porter, HS AF Mayr, HG Mengel, JG Reddy, CA Chan, KL Porter, HS TI Variability of the equatorial oscillations induced by gravity wave filtering SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID QUASI-BIENNIAL OSCILLATION; MIDDLE ATMOSPHERE; SEMIANNUAL OSCILLATION; KELVIN WAVE; ZONAL WIND; MODEL; STRATOSPHERE AB Large variations are observed in the Semi-Annual Oscillation (SAO) and Quasi-Biennial Oscillation (QBO) near the equator that are not well understood. We had shown earlier that small scale gravity waves (GW) can generate these oscillations. Here we demonstrate that GW filtering can also produce the variability. Our model incorporates Hines' Doppler Spread Parameterization (DSP) for GW. In the present version, we employ a larger GW flux and a more realistic description of Newtonian cooling. This model produces a QBO with amplitudes close to 15 m/s at 25 km and periods around 33 months. At higher altitudes, the model produces a SAO with amplitudes varying between 5 and 30 m/s. We interpret these variations in terms of GW filtering by the QBO that produces bear periods between 4 and 8.5 years. To provide better understanding, we present also a case in which the QBO period is virtually locked at 18 months. The SAO amplitude then varies with a regular pattern having a period of 18 months, and the Annual Oscillation (AO) amplitude varies with a period of 36 months. For QBO's with periods of 18 (or 30) months, the phase relationship with the seasonal cycle of solar forcing would tend to synchronize and stabilize the oscillations. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Space Applicat Corp, Vienna, VA USA. Vikram Sarabhai Space Ctr, Trivandrum 695022, Kerala, India. Hong Kong Univ Sci & Technol, Hong Kong, Hong Kong. Furman Univ, Greenville, SC USA. RP Mayr, HG (reprint author), NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. OI Chan, Kwing/0000-0002-6428-1812 NR 27 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 JUL 15 PY 1998 VL 25 IS 14 BP 2629 EP 2632 DI 10.1029/98GL02013 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 101UJ UT WOS:000074886300043 ER PT J AU Hintsa, EJ Boering, KA Weinstock, EM Anderson, JG Gary, BL Pfister, L Daube, BC Wofsy, SC Loewenstein, M Podolske, JR Margitan, JJ Bui, TP AF Hintsa, EJ Boering, KA Weinstock, EM Anderson, JG Gary, BL Pfister, L Daube, BC Wofsy, SC Loewenstein, M Podolske, JR Margitan, JJ Bui, TP TI Troposphere-to-stratosphere transport in the lowermost stratosphere from measurements of H2O, CO2, N2O and O-3 SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID CARBON-DIOXIDE; WATER-VAPOR; NASA ER-2; EXCHANGE; AIRCRAFT; SPADE; OZONE; AIR AB The origin of air in the lowermost stratosphere is investigated with measurements from the NASA ER-2 aircraft. Air with high water vapor mixing ratios was observed in the stratosphere at theta similar to 330-380 K near 40 N in May 1995, indicating the influence of intrusions of tropospheric air. Assuming that observed tracer-tracer relationships reflect mixing lines between tropospheric and stratospheric air masses, we calculate mixing ratios of H2O (12-24 ppmv) and CO2 for the admixed tropospheric air at theta=352-364 K. Temperatures on the 355 K surface at 20-40 N were low enough to dehydrate air to these values. While most ER-2 CO2 data in both hemispheres are consistent with tropical or subtropical air entering the lowermost stratosphere, measurements from May 1995 for theta<362 K suggest that entry of air from the midlatitude upper troposphere can occur in conjunction with mixing processes near the tropopause. C1 Harvard Univ, Dept Chem & Chem Biol, Cambridge, MA 02138 USA. Jet Prop Lab, Pasadena, CA 91109 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Hintsa, EJ (reprint author), Harvard Univ, Dept Chem & Chem Biol, Cambridge, MA 02138 USA. NR 22 TC 71 Z9 75 U1 2 U2 12 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 JUL 15 PY 1998 VL 25 IS 14 BP 2655 EP 2658 DI 10.1029/98GL01797 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 101UJ UT WOS:000074886300050 ER PT J AU Stakes, D McClain, J VanZandt, T McGill, P Begnaud, M AF Stakes, D McClain, J VanZandt, T McGill, P Begnaud, M TI Core hole seismometer development for low-noise seismic data in a long-term seafloor observatory SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID OCEAN-BOTTOM SEISMOMETER; AMBIENT NOISE AB Longstanding problems unique to marine seismology (in contrast to land-based studies) include high levels of environmental noise, unpredictable instrument placement, short measurement duration, and limited numbers of instruments. Traditional instruments are deployed and recovered from a surface ship with no capability to verify data acquisition until the end of the experiment. They are often poorly sited and usually poorly coupled to the seafloor. Experiments have typically been short in duration with only a minimum number of instruments. The result of these logistical problems is high background noise, sparse data recovery (compared to continental stations), and low fidelity data. In an effort to solve many of these problems, we have developed and deployed "corehole seismometers" (1-90 Hz) into small boreholes drilled by an underwater drilling system, using a tethered Remotely Operated Vehicle (ROV). The results are seismic data with a significantly lower background noise level, a lower threshold for recognition of small events, well-oriented (and useable) horizontal seismograms, and a much longer deployment capability. We present new data from these instruments and compare them with data from two types of traditional instruments deployed from a surface ship. These contemporaneous deployments were conducted during 1996 and 1997 in Monterey Bay. C1 Monterey Bay Aquarium Res Inst, Moss Landing, CA 95039 USA. Univ Calif Davis, Dept Geol, Livermore, CA 95616 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Stakes, D (reprint author), Monterey Bay Aquarium Res Inst, 7700 Sandholdt Rd, Moss Landing, CA 95039 USA. NR 13 TC 11 Z9 11 U1 1 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 JUL 15 PY 1998 VL 25 IS 14 BP 2745 EP 2748 DI 10.1029/98GL01937 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 101UJ UT WOS:000074886300073 ER PT J AU Arrigo, KR Worthen, D Schnell, A Lizotte, MP AF Arrigo, KR Worthen, D Schnell, A Lizotte, MP TI Primary production in Southern Ocean waters SO JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS LA English DT Article ID ANTARCTIC PHYTOPLANKTON; ICE EDGE; SEA; IRON; PHOTOSYNTHESIS; GROWTH; ZONE; DISTRIBUTIONS; CHLOROPHYLL; TEMPERATURE AB The Southern Ocean forms a link between major ocean basins, is the site of deep and intermediate water ventilation, and is one of the few areas where macronutrients are underutilized by phytoplankton. Paradoxically, prior estimates of annual primary production are insufficient to support the Antarctic food web. Here we present results from a primary production algorithm based upon monthly climatological phytoplankton pigment concentrations from the coastal zone color scanner (CZCS), Phytoplankton production was forced using monthly temperature profiles and a radiative transfer model that computed changes in photosynthetically usable radiation at each CZCS pixel location. Average daily productivity (g C m(-2) d(-1)) and total monthly production (Tg C month(-1)) were calculated for each of five geographic sectors (defined by longitude) and three ecological provinces (defined by sea ice coverage and bathymetry as the pelagic province, the marginal ice zone, and the shelf). Annual primary production in the Southern Ocean (south of 50 degrees S) was calculated to be 4414 Tg C yr(-1), 4-5 times higher than previous estimates made from in situ data. Primary production was greatest in the month of December (816 Tg C month(-1)) and in the pelagic province (contributing 88.6% of the annual primary production). Because of their small size the marginal ice zone (MIZ) and the shelf contributed only 9.5% and 1.8%, respectively, despite exhibiting higher daily production rates. The Ross Sea was the most productive region, accounting for 28% of annual production. The fourfold increase in the estimate of primary production for the Southern Ocean likely makes the notion of an "Antarctic paradox" (primary production insufficient to support the populations of Southern Ocean grazers, including krill, copepods, microzooplankton, etc.) obsolete. C1 NASA, Goddard Space Flight Ctr, Oceans & Ice Branch, Greenbelt, MD 20771 USA. Univ Wisconsin, Dept Biol & Microbiol, Oshkosh, WI 54901 USA. Sci Syst & Applicat Inc, Lanham, MD 20706 USA. RP Arrigo, KR (reprint author), NASA, Goddard Space Flight Ctr, Oceans & Ice Branch, Code 971-0, Greenbelt, MD 20771 USA. NR 49 TC 248 Z9 259 U1 8 U2 58 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 JUL 15 PY 1998 VL 103 IS C8 BP 15587 EP 15600 DI 10.1029/98JC00930 PG 14 WC Oceanography SC Oceanography GA ZZ547 UT WOS:000074741000005 ER PT J AU D'Amelio, F Wu, LC Fox, RA Daunton, NG Corcoran, ML Polyakov, I AF D'Amelio, F Wu, LC Fox, RA Daunton, NG Corcoran, ML Polyakov, I TI Hypergravity exposure decreases gamma-aminobutyric acid immunoreactivity in axon terminals contacting pyramidal cells in the rat somatosensory cortex: A quantitative immunocytochemical image analysis SO JOURNAL OF NEUROSCIENCE RESEARCH LA English DT Article DE gamma-aminobutyric acid; inhibition; hindlimb; centrifugation; muscle receptors; afferent input; NIH-image ID ACTIVITY-DEPENDENT REGULATION; HINDLIMB REPRESENTATION; GABAERGIC NEURONS; PREMOTOR CORTEX; VISUAL-CORTEX; PRIMATE MOTOR; GABA; DECARBOXYLASE; INHIBITION AB Quantitative evaluation of gamma-aminobutyric acid immunoreactivity (GABA-IR) in the hindlimb representation of the rat somatosensory cortex after 14 days of exposure to hypergravity (hyper-G) was conducted by using computer-assisted image processing, The area of GABA-IR axosomatic terminals apposed to pyramidal cells of cortical layer V was reduced in rats exposed to hyper-G compared with control rats, which were exposed either to rotation alone or to vivarium conditions. Based on previous immunocytochemical and behavioral studies, we suggest that this reduction is due to changes in sensory feedback information from muscle receptors. Consequently, priorities for muscle recruitment are altered at the cortical level, and a new pattern of muscle activity is thus generated. It is proposed that the reduction observed in GABA-IR of the terminal area around pyramidal neurons is the immunocytochemical expression of changes in the activity of GABAergic cells that participate in reprogramming motor outputs to achieve effective movement control in response to alterations in the afferent information. J. Neurosci. Res. 53:135-142, 1998. (C) 1998 Wiley-Liss, Inc. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. San Jose State Univ Fdn, San Jose, CA USA. San Jose State Univ, Dept Psychol, San Jose, CA 95192 USA. RP D'Amelio, F (reprint author), NASA, Ames Res Ctr, Mail Stop 261-3, Moffett Field, CA 94035 USA. NR 36 TC 7 Z9 8 U1 0 U2 1 PU WILEY-BLACKWELL PI HOBOKEN PA 111 RIVER ST, HOBOKEN 07030-5774, NJ USA SN 0360-4012 EI 1097-4547 J9 J NEUROSCI RES JI J. Neurosci. Res. PD JUL 15 PY 1998 VL 53 IS 2 BP 135 EP 142 PG 8 WC Neurosciences SC Neurosciences & Neurology GA ZW699 UT WOS:000074438300002 PM 9671970 ER PT J AU Hou, AY AF Hou, AY TI Hadley circulation as a modulator of the extratropical climate SO JOURNAL OF THE ATMOSPHERIC SCIENCES LA English DT Article ID GENERAL-CIRCULATION; STORM-TRACKS; BASIC STATE; ATMOSPHERE; INSTABILITY; VARIABILITY; FLOW; TROPOSPHERE; EQUATOR; EDDIES AB Studies based on GCM ensemble forecasts have shown that an intensification of the cross-equatorial Hadley circulation associated with a latitudinal displacement of the zonally averaged convective heating in the Tropics can lead to remote warming in the winter high latitudes. This work further investigates this tropical-extratropical connection in a perpetual winter experiment using an idealized GCM without orography to focus on the role of transient eddies, and tests against observations using a multiyear reanalysis produced by the Goddard Earth Observing System-Version 1 (GEOS-1) Data Assimilation System. The GCM results show that the intensification and poleward expansion of the cross-equatorial Hadley cell induced by a tropical heating shift can lead to westerly acceleration in the winter subtropics and enhanced vertical shear of the zonal wind in the subtropics and midlatitudes. The increased baroclinicity outside the Tropics is accompanied by reduced meridional temperature and potential vorticity (PV) gradients, consistent with enhanced PV mixing and increased poleward heat transport by baroclinic eddies. But if the changes in the Hadley cell are such that they produce a deceleration of the zonal wind in the winter subtropics, stronger temperature and PV gradients result in the winter extratropics. The midlatitude response to Hadley acceleration of the subtropical jet is dominated by enhanced power in low-frequency planetary-scale waves that peaks at zonal wavenumber 2 with a period of 40 days. The extent to which this tropical-extratropical connection may be present in nature is tested using the GEOS-1 reanalysis for five austral winters from 1985 to 1989. Results show that the year-to-year variation in the zonally averaged extratropical temperature gradient in austral winters is correlated with the variation in the acceleration of the subtropical zonal wind by the winter Hadley cell. The anomaly correlation coefficients range from 0.80 to 0.92, depending on the statistical test. The positive Hadley acceleration anomaly in the subtropics during the 1988 austral winter is accompanied by stronger than normal zonal wind shears in the subtropics and midlatitudes, a colder troposphere in the midlatitudes, and a warmer pole. The extratropical temperature anomalies are associated with a reduced PV gradient, and the midlatitude geopotential height anomaly shows a spectral peak at wavenumbers 2-3 with periods between 40 and 60 days, similar to the idealized GCM results. The implication of this study is that the Hadley circulation may play a role in modulating the temperature difference between middle and high latitudes by modifying the zonal wind shear in the subtropics and midlatitudes. C1 NASA, Goddard Space Flight Ctr, Atmospheres Lab, Data Assimilat Off, Greenbelt, MD 20771 USA. RP Hou, AY (reprint author), NASA, Goddard Space Flight Ctr, Atmospheres Lab, Data Assimilat Off, Code 910-3, Greenbelt, MD 20771 USA. RI Hou, Arthur/D-8578-2012 NR 34 TC 43 Z9 57 U1 1 U2 12 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 JUL 15 PY 1998 VL 55 IS 14 BP 2437 EP 2457 DI 10.1175/1520-0469(1998)055<2437:HCAAMO>2.0.CO;2 PG 21 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 105PL UT WOS:000075082400004 ER PT J AU Ovryn, B Andrews, JH AF Ovryn, B Andrews, JH TI Phase-shifting laser feedback interferometry SO OPTICS LETTERS LA English DT Article ID OPTICAL FEEDBACK; SEMICONDUCTOR-LASERS; MICROSCOPY AB We have introduced the techniques of phase-shifting interferometry into a laser feedback interference microscope based on a helium-neon laser. With moderate feedback, multiple reflections between the sample and the laser are shown to be negligible, and the interferometer responds sinusoidally with a well-characterized fringe modulation. One can obtain higher signal-to-noise ratios by determining the number of additional terms required for modeling the effect of multiple reflections on the phase and visibility measurements in the high-feedback regime. Changes in optical path length are determined with nanometer precision without phase averaging or lock-in detection. (C) 1998 Optical Society of America. C1 Case Western Reserve Univ, Dept Mech & Aerosp Engn, Cleveland, OH 44106 USA. NASA, Lewis Res Ctr, Natl Ctr Micrograv Res Fluids & Combust, Cleveland, OH 44135 USA. Youngstown State Univ, Dept Phys & Astron, Ctr Photon Induced Proc, Youngstown, OH 44555 USA. RP Case Western Reserve Univ, Dept Mech & Aerosp Engn, Cleveland, OH 44106 USA. NR 19 TC 36 Z9 38 U1 1 U2 5 PU OPTICAL SOC AMER PI WASHINGTON PA 2010 MASSACHUSETTS AVE NW, WASHINGTON, DC 20036 USA SN 0146-9592 EI 1539-4794 J9 OPT LETT JI Opt. Lett. PD JUL 15 PY 1998 VL 23 IS 14 BP 1078 EP 1080 DI 10.1364/OL.23.001078 PG 3 WC Optics SC Optics GA 102VW UT WOS:000074947600004 PM 18087433 ER PT J AU Armstrong, JW Yeh, C Wilson, KE AF Armstrong, JW Yeh, C Wilson, KE TI Earth-to-deep-space optical communications system with adaptive tilt and scintillation correction by use of near-Earth relay mirrors SO OPTICS LETTERS LA English DT Article ID LASER AB Performance of an Earth-to-deep-space optical telecommunications system is degraded by distortion of the beam as it propagates through the turbulent atmosphere. Conventional approaches to correcting distortions, based on natural or artificial guide stars, have practical difficulties or are not adequate for correction of distortions, which are important for Earth-to-deep-space optical links. A beam-relay approach that overcomes these difficulties is discussed. A downward-directed laser near an orbiting relay mirror provides a reference for atmospheric correction. Adaptive optics at the ground station compensate the uplink beam so that after it passes through the atmosphere uplink propagation effects are removed. The orbiting mirror then directs the corrected beam to the distant spacecraft. (C) 1998 Optical Society of America. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Armstrong, JW (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 12 TC 13 Z9 13 U1 0 U2 3 PU OPTICAL SOC AMER PI WASHINGTON PA 2010 MASSACHUSETTS AVE NW, WASHINGTON, DC 20036 USA SN 0146-9592 J9 OPT LETT JI Opt. Lett. PD JUL 15 PY 1998 VL 23 IS 14 BP 1087 EP 1089 DI 10.1364/OL.23.001087 PG 3 WC Optics SC Optics GA 102VW UT WOS:000074947600007 PM 18087436 ER PT J AU Narayan, DJ Langstaff, DP Sinha, MP Birkinshaw, K AF Narayan, DJ Langstaff, DP Sinha, MP Birkinshaw, K TI Microchannel plate electron multiplier calibration using a discrete detector array SO INTERNATIONAL JOURNAL OF MASS SPECTROMETRY LA English DT Article DE detector; ion; MCP; isotope; mass spectrometer ID X-RAY; SPECTROSCOPY AB The performance of a microchannel plate electron multiplier (MCP) is known to vary with time and exposure to ions, the atmosphere, and other factors. Clearly the recognition of deterioration in experimental work is of great importance. In the present work the performance of an MCP is straightforwardly measured using a detector array integrated on a silicon chip and results presented. The objective of this work is not to accurately quantify the MCP gain distribution but rather to find the distribution shape to enable straightforward monitoring of variations in gain distribution and identification of conditions under which essentially all MCP output pulses are recorded. Thus, isotope ratios of high quality can be measured. This work further demonstrates the versatility of a discrete detector array developed at Aberystwyth. It enables straightforward remote monitoring of the MCP performance and is especially valuable in space-borne experiments. (C) Elsevier Science B.V. C1 Univ Wales Aberystwyth, Dept Phys, Ceredigion SY23 3BZ, Wales. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Narayan, DJ (reprint author), Univ Wales Aberystwyth, Dept Phys, Ceredigion SY23 3BZ, Wales. NR 16 TC 4 Z9 4 U1 2 U2 4 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 1387-3806 J9 INT J MASS SPECTROM JI Int. J. Mass Spectrom. PD JUL 13 PY 1998 VL 176 IS 3 BP 161 EP 166 DI 10.1016/S1387-3806(98)14012-5 PG 6 WC Physics, Atomic, Molecular & Chemical; Spectroscopy SC Physics; Spectroscopy GA 111YZ UT WOS:000075467600001 ER PT J AU Bhattacharjee, P AF Bhattacharjee, P TI Cosmic topological defects, highest energy cosmic rays, and the baryon asymmetry of the Universe SO PHYSICAL REVIEW LETTERS LA English DT Article ID STRINGS; BARYOGENESIS; SPECTRUM; NUMBER; FLUX AB It is pointed out that the observed extremely high energy cosmic rays (EHECR) above 10(11) GeV and the observed baryon asymmetry of the Universe (BAU) may have a common origin in baryon number violating decays of supermassive X particles released from cosmic topological defects (TDs) such as cosmic strings and monopoles. The X particles produced by TDs in the recent epochs produce the EHECR, while the BAU is created by X particles released from TDs mainly in the very early Universe. In this scenario the EHECR is predicted to contain baryons as well as antibaryons with a small asymmetry between the two. [S0031-9007(98)06619-8]. C1 NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. Indian Inst Astrophys, Bangalore 560034, Karnataka, India. RP Bhattacharjee, P (reprint author), NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Code 661, Greenbelt, MD 20771 USA. NR 45 TC 16 Z9 16 U1 0 U2 0 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 JUL 13 PY 1998 VL 81 IS 2 BP 260 EP 263 DI 10.1103/PhysRevLett.81.260 PG 4 WC Physics, Multidisciplinary SC Physics GA ZZ635 UT WOS:000074750400005 ER PT J AU Shupe, DL Fang, F Hacking, PB Huchra, JP AF Shupe, DL Fang, F Hacking, PB Huchra, JP TI The local luminosity function at 25 microns SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies : luminosity function, mass function; infrared : galaxies ID GUIDE STAR CATALOG; REDSHIFT SURVEY; IRAS GALAXIES; SAMPLE SELECTION; VELOCITY-FIELD; COUNTS AB The local luminosity function at 25 mu m provides the basis for interpreting the results of deep midinfrared surveys planned or in progress with space astrophysics missions including the Infrared Space Observatory (ISO), Wide-Field Infrared Explorer (WIRE), and Space Infrared Telescope Facility (SIRTF). We have selected a sample of 1458 galaxies from the IRAS Faint Source Survey with a flux density limit of 250 mJy at 25 mu m. The local luminosity function is derived using both parametric and nonparametric maximum likelihood techniques and the classical 1/V-max estimator. Comparison of these results shows that the 1/V-max estimate of the luminosity function is significantly affected by the Local Supercluster. A maximum likelihood fit to the radial density shows no systematic increase that would be caused by density evolution of the galaxy population. The density fit is used to correct the 1/V-max estimate. We also demonstrate the high quality and completeness of our sample by a variety of methods. The luminosity function derived from this sample is compared with previously published estimates, showing the prior estimates to have been strongly affected by the Local Supercluster. Our new luminosity function leads to lower estimates of midinfrared backgrounds and number counts. C1 CALTECH, Jet Propuls Lab, Infrared Proc & Anal Ctr, Pasadena, CA 91125 USA. Ctr Astrophys, Cambridge, MA 02138 USA. RP CALTECH, Jet Propuls Lab, Infrared Proc & Anal Ctr, 100-22, Pasadena, CA 91125 USA. NR 37 TC 39 Z9 39 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 JUL 10 PY 1998 VL 501 IS 2 BP 597 EP 607 DI 10.1086/305825 PN 1 PG 11 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 101DB UT WOS:000074853400016 ER PT J AU Parsons, AM Gehrels, N Paciesas, WS Harmon, BA Fishman, GJ Wilson, CA Zhang, SN AF Parsons, AM Gehrels, N Paciesas, WS Harmon, BA Fishman, GJ Wilson, CA Zhang, SN TI Multiyear BATSE Earth occultation monitoring of NGC 4151 SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies : active; galaxies : individual (NGC 4151); galaxies : Seyfert; gamma rays : observations ID SHORT-TIMESCALE VARIABILITY; ACTIVE GALACTIC NUCLEI; X-RAY; MULTIWAVELENGTH OBSERVATIONS; NGC-4151 AB We report the results of nearly six years of continuous monitoring of the Seyfert galaxy NGC 4151 by the Burst and Transient Source Experiment (BATSE) on the Compton Gamma Ray Observatory (CGRO). Continuous 2154 day (5.9 yr) light curves for NGC 4151 have been derived from Earth occultation analysis of CGRO BATSE data. Fluxes are calculated assuming a cutoff power-law model of the form F(E)= F(E-0)(E/E-0)(-alpha) exp (E-0 - E/E-cutoff). Light curves for the 20-70 and 70-200 keV bands are shown and found to have an average flux of 11 x 10(-3) and 2.3 x 10(-3) photons cm(-2) s(-1), respectively. Evidence for intrinsic source variability is observed with a fractional variation ratio measured at F-var = 0.2 in both the 20-70 and 70-200 keV bands. A systematic difference is found between OSSE 50-150 keV flux measurements of NGC 4151 and simultaneous BATSE flux measurements in the same energy range. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Alabama, Huntsville, AL 35899 USA. NASA, Marshall Space Flight Ctr, Univ Space Res Assoc, Huntsville, AL 35812 USA. RP Parsons, AM (reprint author), NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RI Gehrels, Neil/D-2971-2012; Parsons, Ann/I-6604-2012 NR 21 TC 6 Z9 6 U1 0 U2 1 PU UNIV CHICAGO PRESS PI CHICAGO PA 5801 S ELLIS AVENUE, CHICAGO, IL 60637 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD JUL 10 PY 1998 VL 501 IS 2 BP 608 EP 615 DI 10.1086/305837 PN 1 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 101DB UT WOS:000074853400017 ER PT J AU Catanese, M Akerlof, CW Badran, HM Biller, SD Bond, IH Boyle, PJ Bradbury, SM Buckley, JH Burdett, AM Gordo, JB Carter-Lewis, DA Cawley, MF Connaughton, V Fegan, DJ Finley, JP Gaidos, JA Hall, T Hillas, AM Krennrich, F Lamb, RC Lessard, RW Masterson, C McEnery, JE Mohanty, G Quinn, J Rodgers, AJ Rose, HJ Samuelson, FW Schubnell, MS Sembroski, GH Srinivasan, R Weekes, TC Wilson, CW Zweerink, J AF Catanese, M Akerlof, CW Badran, HM Biller, SD Bond, IH Boyle, PJ Bradbury, SM Buckley, JH Burdett, AM Gordo, JB Carter-Lewis, DA Cawley, MF Connaughton, V Fegan, DJ Finley, JP Gaidos, JA Hall, T Hillas, AM Krennrich, F Lamb, RC Lessard, RW Masterson, C McEnery, JE Mohanty, G Quinn, J Rodgers, AJ Rose, HJ Samuelson, FW Schubnell, MS Sembroski, GH Srinivasan, R Weekes, TC Wilson, CW Zweerink, J TI Discovery of gamma-ray emission above 350 GeV from the BL Lacertae object 1ES 2344+514 SO ASTROPHYSICAL JOURNAL LA English DT Article DE BL Lacertae objects : individual (1ES 2344+514); gamma rays : observations ID ACTIVE GALAXY MARKARIAN-421; TEV PHOTONS; X-RAY; RADIATION; BLAZARS; JET AB We present the discovery of gamma-ray emission greater than 350 GeV from the BL Lacertae (BL Lac) object 1ES 2344+514 with the Whipple Observatory 10 m gamma-ray telescope. This is the third BL Lac object detected at very high energies (VHE, E > 300 GeV), the other two being Markarian 421 (Mrk 421) and Mrk 501. These three active galactic nuclei are all X-ray selected and have the lowest known redshifts of any BL Lac objects currently identified with declination greater than 0 degrees. The evidence for emission from 1ES 2344+514 comes mostly from an apparent flare on 1995 December 20 (UT) during which a 6 sigma excess was detected with an average flux of I(>350 GeV)= 6.6 +/- 1.9 x 10(-11) photons cm(-2) s(-1). This is approximately 63% of the VHE emission from the Crab Nebula, the standard candle in this field. Observations taken between 1995 October and 1996 January, excluding the night of the hare, yield a 4 sigma detection indicating a flux level of I(> 350 GeV) = 1.1 +/- 0.4 x 10(-11) photons cm(-2) s(-1), or about 11% of the VHE Crab Nebula flux. Observations taken between 1996 September and 1997 January on this object did not yield a significant detection of a steady flux or any evidence of flaring activity. The 99.9% confidence level upper limit from these observations is I(>350 GeV)< 8.2 x 10(-12) photons cm(-2) s(-1), 58% of the Crab Nebula flux. The low baseline emission level and variation in the nightly and yearly flux of 1ES 2344+514 are the same as the VHE emission characteristics of Mrk 421 and Mrk 501. C1 Iowa State Univ, Dept Phys & Astron, Ames, IA 50011 USA. Univ Michigan, Randall Lab Phys, Ann Arbor, MI 48109 USA. Tanta Univ, Fac Sci, Dept Phys, Tanta, Egypt. Univ Oxford, Dept Phys, Oxford, England. Univ Leeds, Dept Phys, Leeds LS2 9JT, W Yorkshire, England. Natl Univ Ireland Univ Coll Dublin, Expt Phyd Dept, Dublin 4, Ireland. Washington Univ, Dept Phys, St Louis, MO 63130 USA. St Patricks Coll, Dept Phys, Maynooth, Kildare, Ireland. NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. Purdue Univ, Dept Phys, W Lafayette, IN 47907 USA. CALTECH, Space Radiat Lab, Pasadena, CA 91125 USA. Harvard Smithsonian CfA, Fred Lawrence Whipple Observ, Amado, AZ 85645 USA. RP Catanese, M (reprint author), Iowa State Univ, Dept Phys & Astron, Ames, IA 50011 USA. NR 40 TC 163 Z9 167 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5801 S ELLIS AVENUE, CHICAGO, IL 60637 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD JUL 10 PY 1998 VL 501 IS 2 BP 616 EP 623 DI 10.1086/305857 PN 1 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 101DB UT WOS:000074853400018 ER PT J AU Dwek, E AF Dwek, E TI The evolution of the elemental abundances in the gas and dust phases of the Galaxy SO ASTROPHYSICAL JOURNAL LA English DT Review DE dust, extinction; Galaxy : abundances; Galaxy : evolution; Galaxy : stellar content; ISM : abundances; ISM : general ID GRAIN-GRAIN COLLISIONS; INITIAL MASS FUNCTION; INTER-STELLAR SPACE; WOLF-RAYET STARS; SMALL MAGELLANIC CLOUD; INTERSTELLAR DUST; CHEMICAL EVOLUTION; INFRARED-EMISSION; SOLAR NEIGHBORHOOD; CARBON STARS AB We present models for the evolution of the elemental abundances in the gas and dust phases of the interstellar medium (ISM) of our Galaxy by generalizing standard models for its dynamical and chemical evolution. In these models, the stellar birthrate history is determined by the infall rate of primordial gas and by its functional dependence on the mass surface density of the stars and gas. We adopt a two-component Galaxy consisting of a central bulge and an exponential disk with different infall rates and stellar birthrate histories. Condensation in stellar winds, Type Ia and Type II supernovae, and the accretion of refractory elements onto preexisting grains in dense molecular clouds are the dominant contributors to the abundance of elements locked up in the dust. Grain destruction by sputtering and evaporative grain-grain collisions in supernova remnants are the most important mechanisms that return these elements back to the gas phase. Guided by observations of dust formation in various stellar sources, and by the presence of isotopic anomalies in meteorites, we calculate the production yield of silicate and carbon dust as a function of stellar mass. We find that Type II supernovae are the main source of silicate dust in the Galaxy. Carbon dust is produced primarily by low-mass stars in the similar to 2-5 M-circle dot range. Type Ia SNe can be important sources of metallic iron dust in the ISM. We also analyze the origin of the elemental depletion pattern and find that the observed core + mantle depletion must reflect the efficiency of the accretion process in the ISM. We also find that grain destruction is very efficient, leaving only similar to 10% of the refractory elements in grain cores. Observed core depletions are significantly higher, requiring significant UV, cosmic ray, or shock processing of the accreted mantle into refractory core material. Adopting the current grain destruction lifetimes from Jones et al., we formulate a prescription for its evolution in time. We make a major assumption, that the accretion timescale evolves in a similar fashion, so that the current ratio between these quantities is preserved over time. We then calculate the evolution of the dust abundance and composition at each Galactocentric radius as a function of time. We find that the dust mass is linearly proportional to the ISM metallicity and is equal to about 40% of the total mass of heavy elements in the Galaxy, independent of Galactocentric radius. The derived relation of dust mass with metallicity is compared to the observed Galactic dust abundance gradient, and to the M-dust versus log (O/H) relation that is observed in external dwarf galaxies. The dependence of dust composition on the mass of the progenitor star and the delayed recycling of newly synthesized dust by low-mass stars back to the ISM give rise to variations in the dust composition as a function of time. We identify three distinct epochs in the evolution of the dust composition, characterized by different carbon-to-silicate mass ratios. Two such epochs are represented by the Galaxy and the SMC. The third is characterized by an excess of carbon dust (compared to the Milky Way Galaxy), and should be observed in galaxies or star-forming regions in which the most massive carbon stars are just evolving off the main sequence. Our models provide a framework for the self-consistent inclusion of dust in population synthesis models for various pre-galactic and galactic systems, allowing for the calculation of their UV to far-infrared spectral energy distribution at various stages of their evolution. C1 NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, Greenbelt, MD 20771 USA. RP NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, Code 685, Greenbelt, MD 20771 USA. EM eli.dwek@gsfc.nasa.gov NR 145 TC 348 Z9 348 U1 0 U2 10 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 JUL 10 PY 1998 VL 501 IS 2 BP 643 EP 665 DI 10.1086/305829 PN 1 PG 23 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 101DB UT WOS:000074853400020 ER PT J AU Rots, AH Jahoda, K Macomb, DJ Kawai, N Saito, Y Kaspi, VM Lyne, AG Manchester, RN Backer, DC Somer, AL Marsden, D Rothschild, RE AF Rots, AH Jahoda, K Macomb, DJ Kawai, N Saito, Y Kaspi, VM Lyne, AG Manchester, RN Backer, DC Somer, AL Marsden, D Rothschild, RE TI Rossi X-ray timing explorer absolute timing results for the pulsars B1821-24 and B1509-58 SO ASTROPHYSICAL JOURNAL LA English DT Article DE ISM : general; pulsars : individual (PSR B1509-58, PSR B1821-24); radio continuum : stars; X-rays : stars ID CRAB PULSAR; PSR B1509-58; GAMMA-RAY; VELA; EPHEMERIDES AB Observations with the Rossi X-Ray Timing Explorer and the Jodrell Bank, Parkes, and Green Bank telescopes have enabled us to determine the time delay between radio and X-ray pulses in the two isolated pulsars B1821-24 and B1509-58. For the former we find that the narrow X-ray and radio pulse components are close to being coincident in time, with the radio peak leading by 0.02 period (60 +/- 20 mu s), while the wide X-ray pulse component lags the last of the two wider radio components by about 0.08 period. For the latter pulsar we find, using the standard value for the dispersion measure, that the X-ray pulse lags the radio by about 0.27 period, with no evidence for any energy dependence in the range 2-100 keV. However, uncertainties in the history of the dispersion measure for this pulsar make a comparison to previous results difficult. It is clear that there are no perceptible variations in either the lag or the dispersion measure at timescales of a year or less. C1 NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. RIKEN, Inst Phys & Chem Res, Wako, Saitama 35101, Japan. Inst Space & Astronaut Sci, Sagamihara, Kanagawa 229, Japan. MIT, Dept Phys, Cambridge, MA 02139 USA. MIT, Space Res Ctr, Cambridge, MA 02139 USA. Univ Manchester, Dept Phys, Macclesfield SK11 9DL, Cheshire, England. CSIRO, Australia Telescope Natl Facil, Epping, NSW 2121, Australia. Univ Calif Berkeley, Dept Astron, Berkeley, CA 94720 USA. Univ Calif Berkeley, Radio Astron Lab, Berkeley, CA 94720 USA. Univ Calif San Diego, Ctr Astrophys & Space Sci, San Diego, CA 92093 USA. RP Rots, AH (reprint author), Harvard Smithsonian Ctr Astrophys, MS 81,60 Garden St, Cambridge, MA 02138 USA. RI Jahoda, Keith/D-5616-2012 NR 27 TC 60 Z9 61 U1 0 U2 1 PU UNIV CHICAGO PRESS PI CHICAGO PA 5801 S ELLIS AVENUE, CHICAGO, IL 60637 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD JUL 10 PY 1998 VL 501 IS 2 BP 749 EP 757 DI 10.1086/305836 PN 1 PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 101DB UT WOS:000074853400029 ER PT J AU Airapetian, VS Holman, GD AF Airapetian, VS Holman, GD TI Atmospheric heating and quiescent radio emission in active stars SO ASTROPHYSICAL JOURNAL LA English DT Article DE MHD; radiation mechanisms : nonthermal; radio continuum : stars; stars : activity; stars : late-type; turbulence; X-rays : stars ID X-RAY-EMISSION; RS-CANUM-VENATICORUM; HIGH-RESOLUTION SPECTROGRAPH; OBSERVING STELLAR CORONAE; ALFVEN WAVES; SOLAR-FLARES; MICROWAVE EMISSION; VLBI OBSERVATIONS; BINARY-SYSTEMS; ACCELERATION AB Surveys of magnetically active stars of K to M spectral classes have revealed an interrelationship between their "quiescent" soft X-ray (SXR) and microwave luminosities. While the quiescent SXR emission has a thermal, corona-like nature, the quiescent microwave emission is usually nonthermal gyrosynchrotron radiation. This correlation is discussed in terms of the ability of heating mechanisms to accelerate the required number of electrons to mildly relativistic energies. We analyze the observational signatures of two models involving heating and electron acceleration by electric currents. The first model proposes that the energetic electrons are accelerated by the electric field in classical current sheets within the stellar coronae. The second considers MHD turbulence cascading down to smaller scales in the presence of current sheets, exciting ion-acoustic waves. These waves enhance the heating and particle acceleration in the stellar transition zone. Differences between RS CVn and Sun-like stars are discussed in terms of these models. Explicit expressions for the SXR-microwave relationship are derived and discussed. C1 NASA, Goddard Space Flight Ctr, Astron Program, Comp Sci Corp, Greenbelt, MD 20771 USA. NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, Greenbelt, MD 20771 USA. RP NASA, Goddard Space Flight Ctr, Astron Program, Comp Sci Corp, Code 681,CSC, Greenbelt, MD 20771 USA. RI Holman, Gordon/C-9548-2012 NR 56 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 JUL 10 PY 1998 VL 501 IS 2 BP 805 EP 812 DI 10.1086/305840 PN 1 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 101DB UT WOS:000074853400036 ER PT J AU Imamura, JN Steiman-Cameron, TY AF Imamura, JN Steiman-Cameron, TY TI High-state observations of the eclipsing am herculis object UZ Fornacis SO ASTROPHYSICAL JOURNAL LA English DT Article DE binaries : eclipsing; novae, cataclysmic variables; stars : individual (UZ Fornacis); white dwarfs ID EXO-033319-2554.2; SPECTROSCOPY; ACCRETION; SYSTEM AB We present high-speed optical photometric observations of the eclipsing AM Her object UZ For that were obtained during 1995 February and October at the Cerro Tololo Inter-American Observatory. On both occasions, UZ For was in its high-luminosity state. In 1995 February, UZ had peak visual magnitude m(v) approximate to 15.9 +/- 0.1 mag, which is roughly 0.5-1 mag brighter than previous reports of its high-state brightness level. In 1995 October, UZ For had peak magnitude m(v) approximate to 16.75 +/- 0.25 mag, which is more similar to earlier reports of its high-state brightness level. The 1995 February light curves and eclipses are different in appearance from those for the lower luminosity states of UZ For reported in the literature. The eclipses are, however, similar to those of other AM Her systems, e.g., they are similar in shape to the eclipses of RE 2107-05 (HU Aqr) and to the ultraviolet eclipses of UZ For. The significance of the last statement is that in both of these systems, the accretion stream contributes a significant fraction of the overall luminosity of the system. In the low-luminosity state of UZ For, the accretion hot spot and the white dwarf photosphere dominate the optical emission. Here, we conclude that in the high-luminosity state, the accretion stream makes a significant contribution (and sometimes dominates) the optical emission from UZ For. C1 Univ Oregon, Dept Phys, Eugene, OR 97403 USA. Univ Oregon, Inst Theoret Sci, Eugene, OR 97403 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Imamura, JN (reprint author), Univ Oregon, Dept Phys, Eugene, OR 97403 USA. NR 16 TC 10 Z9 10 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5801 S ELLIS AVENUE, CHICAGO, IL 60637 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD JUL 10 PY 1998 VL 501 IS 2 BP 830 EP 840 DI 10.1086/305822 PN 1 PG 11 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 101DB UT WOS:000074853400039 ER PT J AU Krist, JE Stapelfeldt, KR Burrows, CJ Ballester, GE Clarke, JT Crisp, D Evans, RW Gallagher, JS Griffiths, RE Hester, JJ Hoessel, JG Holtzman, JA Mould, JR Scowen, PA Trauger, JT Watson, AM Westphal, JA AF Krist, JE Stapelfeldt, KR Burrows, CJ Ballester, GE Clarke, JT Crisp, D Evans, RW Gallagher, JS Griffiths, RE Hester, JJ Hoessel, JG Holtzman, JA Mould, JR Scowen, PA Trauger, JT Watson, AM Westphal, JA TI Hubble space telescope WFPC2 imaging of FS Tauri and Haro 6-5B SO ASTROPHYSICAL JOURNAL LA English DT Article DE binaries : visual; circumstellar matter; ISM : jets and outflows; stars : individual (FS Tauri, Haro 6-5B) ID CIRCUMSTELLAR DISKS; YOUNG STARS; EXCITING STARS; OBJECTS; JETS; SPECTROSCOPY; MULTIPLICITY; PHOTOMETRY; COMPLEX AB We have observed the field of FS Tauri (Haro 6-5) with the Wide Field Planetary Camera 2 on the Hubble Space Telescope. Centered on Hare 6-5B and adjacent to the nebulous binary system of FS Tauri A there is an extended complex of reflection nebulosity that includes a diffuse, hourglass-shaped structure. H6-5B, the source of a bipolar jet, is not directly visible but appears to illuminate a compact, bipolar nebula which we assume to be a protostellar disk similar to HH 30. The bipolar jet appears twisted, which explains the unusually broad width measured in ground-based images. We present the first resolved photometry of the FS Tau A components at visual wavelengths. The fluxes of the fainter, eastern component are well matched by a 3360 K blackbody with an extinction of A(v) = 8. For the western star, however, any reasonable, reddened blackbody energy distribution underestimates the K-band photometry by over 2 mag. This may indicate errors in the infrared photometry or errors in our visible measurements due to bright reflection nebulosity very close to the star. The binary was separated by 0." 239 +/- 0." 005 at a position angle of 84 degrees + 1.degrees 5 on 1996 January 25. There is no nebulosity around FS Tau A at the orientation suggested for a disk based on previous, ground-based polarization measurements. C1 Space Telescope Sci Inst, Baltimore, MD 21218 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. European Space Agcy, Div Astrophys, Dept Space Sci, F-75738 Paris 15, France. Univ Michigan, Dept Astron, Ann Arbor, MI 48109 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, ACT 2611, Australia. Univ Nacl Autonoma Mexico, Inst Astron, Morelia 58090, Michoacan, Mexico. CALTECH, Div Geol & Planetary Sci, Pasadena, CA 91125 USA. RP Space Telescope Sci Inst, 3700 San Martin Dr, Baltimore, MD 21218 USA. EM krist@stsci.edu RI Stapelfeldt, Karl/D-2721-2012; Clarke, John/C-8644-2013 NR 33 TC 39 Z9 39 U1 0 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 JUL 10 PY 1998 VL 501 IS 2 BP 841 EP 852 DI 10.1086/305861 PN 1 PG 12 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 101DB UT WOS:000074853400040 ER PT J AU DeForest, CE Gurman, JB AF DeForest, CE Gurman, JB TI Observation of quasi-periodic compressive waves in solar polar plumes SO ASTROPHYSICAL JOURNAL LA English DT Article DE Sun : corona; Sun : solar wind; Sun : UV radiation ID CORONAL HOLES; TELESCOPE AB On 1996 March 7, the Solar and Heliospheric Observatory spacecraft conducted a multi-instrument campaign to observe polar plumes in the south polar coronal hole. Recent time-domain analyses of EUV Imaging Telescope images from that campaign show filamentary substructure in the plumes, on a length scale of similar to 5", which changes on timescales of a few minutes, and coherent quasi-periodic perturbations in the brightness of Fe IX and Fe X line emission at 171 Angstrom from the plumes. The perturbations amount to 10%-20% of the plumes' overall intensity and propagate outward at 75-150 km s(-1), taking the form of wave trains with periods of 10-15 minutes and envelopes of several cycles. We conclude that the perturbations are compressive waves (such as sound waves or slow-mode magnetosonic waves) propagating along-the plumes. Assuming that the waves are sonic yields a mechanical energy flux of 150-400 W m(-2) (1.5-4 x 10(5) ergs cm(-2) s(-1)) in the plumes. C1 NASA, Goddard Space Flight Ctr, SOHO Experimenters Anal Facil, Greenbelt, MD 20771 USA. RP DeForest, CE (reprint author), NASA, Goddard Space Flight Ctr, SOHO Experimenters Anal Facil, Code 6823,Bldg 26,Room G-1, Greenbelt, MD 20771 USA. EM cdeforest@solar.stanford.edu; jgurman@solar.stanford.edu NR 14 TC 276 Z9 277 U1 0 U2 3 PU UNIV CHICAGO PRESS PI CHICAGO PA 5801 S ELLIS AVENUE, CHICAGO, IL 60637 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD JUL 10 PY 1998 VL 501 IS 2 BP L217 EP L220 DI 10.1086/311460 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 101DG UT WOS:000074853900014 ER PT J AU Rodgers, SD Charnley, SB AF Rodgers, SD Charnley, SB TI HNC and HCNn in comets SO ASTROPHYSICAL JOURNAL LA English DT Article DE comets : general; comets : individual (Hale-Bopp 1995 O1, Hyakutake (C/1996 B2)) ID ABUNDANCE RATIO; CHEMISTRY; MODEL; HYAKUTAKE; EMISSION; CORES; WATER; CLOUD AB We use a multifluid hydrodynamical-chemical model of cometary comae to predict the HNC and HCN abundances in comets Hyakutake and Hale-Bopp for a variety of initial parameters. We find, in general, that the presence of methanol in the nuclear ices inhibits the synthesis of HNC from HCN through proton transfer reactions in the coma. For Hale-Bopp, we find that because of the large gas production rates, isomerization of HCN to HNC driven by the impact of fast hydrogen atoms can explain the HNC abundances, and we predict that the HNC/HCN ratio should increase to similar to 18% as the comet approaches perihelion, as observed. For Hyakutake, we find that gas-phase reactions in the coma cannot produce the observed HNC/HCN ratio and so conclude that the observed HNC is either nuclear or is the decay product of an unknown parent. C1 Univ Manchester, Inst Sci & Technol, Dept Phys, Manchester M60 1QD, Lancs, England. NASA, Ames Res Ctr, Moffett Field, CA 94305 USA. RP Rodgers, SD (reprint author), Univ Manchester, Inst Sci & Technol, Dept Phys, POB 88, Manchester M60 1QD, Lancs, England. RI Charnley, Steven/C-9538-2012 NR 36 TC 59 Z9 59 U1 1 U2 2 PU IOP PUBLISHING LTD PI BRISTOL PA DIRAC HOUSE, TEMPLE BACK, BRISTOL BS1 6BE, ENGLAND SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD JUL 10 PY 1998 VL 501 IS 2 BP L227 EP L230 DI 10.1086/311459 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 101DG UT WOS:000074853900016 ER PT J AU Rubin, RH Colgan, SWJ Dufour, RJ Lord, SD AF Rubin, RH Colgan, SWJ Dufour, RJ Lord, SD TI The He+/H+ abundance in the Orion Nebula from infrared space observatory measurements SO ASTROPHYSICAL JOURNAL LA English DT Article DE H II regions; ISM : abundances; ISM : atoms; ISM : individual (Orion Nebula) ID H-II REGIONS; HELIUM ABUNDANCE; LINES AB Using the Short Wavelength Spectrometer on the Infrared Space Observatory, we measured in the Orion Nebula several components of the He I Br alpha transition, the first detections to the best of our knowledge in an H II region, and the H I Br alpha line. A value of He+/H+ = 0.085 +/- 0.003 is inferred from these data and is typical of previous values found for Orion. The IR method to obtain He+/H+ is very insensitive to extinction. The measurement of the weak He I 2.855 mu m (5p P-3 degrees --> 4s S-3) flux permits an assessment of T-e in the He+ region. Its Aux relative to the flux of He I 4.0490 mu m (5g (3)G --> 4f(3)F degrees, 5g (1)G --> 4f(1)F degrees blend) is roughly proportional to T-e (for T-e range applicable to most H II regions and planetary nebulae) and depends little on N-e. From our measured ratio, using N-e = 10(4) cm(-3), T-e is slightly less than 10(4) K. We stress that many IR measurements of a hydrogen line are likely to also include one or more significant helium line contributions. Attributing all of the flux to the stronger H I line will result in underestimates for abundance ratios relative to H+. This has usually not been taken into account in the past when deriving abundances of other ions/elements relative to H. Errors in the velocity and line width inferred may also occur by failure to consider the blended He component. Because the strongest He I lines will generally be on the blue side of their counterpart H I line, interpreting a blended feature as only H I will cause a spurious bias to lower velocities. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Rice Univ, Houston, TX 77251 USA. CALTECH, IPAC, Pasadena, CA 91125 USA. RP Rubin, RH (reprint author), NASA, Ames Res Ctr, MS 245-6, Moffett Field, CA 94035 USA. RI Colgan, Sean/M-4742-2014 NR 22 TC 4 Z9 4 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5801 S ELLIS AVENUE, CHICAGO, IL 60637 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD JUL 10 PY 1998 VL 501 IS 2 BP L209 EP L212 DI 10.1086/311470 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 101DG UT WOS:000074853900012 ER PT J AU Smith, DM Main, D Marshall, E Swank, J Heindl, WA Leventhal, M In'T Zand, JJM Heise, J AF Smith, DM Main, D Marshall, E Swank, J Heindl, WA Leventhal, M In'T Zand, JJM Heise, J TI XTE J1739-302: An unusual new x-ray transient SO ASTROPHYSICAL JOURNAL LA English DT Article DE accretion, accretion disks; stars : neutron; x-rays : stars ID A0535+26 AB A new X-ray transient, designated XTE J1739-302, was discovered with the proportional counter array on the Rossi X-Ray Timing Explorer in data from 1997 August 12. Although it was the brightest source in the Galactic center region while active (about 3.0 x 10(-9) ergs cm(-2) s(-1) from 2 to 25 keV), it was only observed on that one day; it was not detectable 9 days earlier or 2 days later. There is no known counterpart at other wavelengths, and its proximity to the Galactic center will make such an identification difficult due to source confusion and extinction. The X-ray spectrum and intensity suggest a giant outburst of a Be/neutron star binary, although no pulsations were observed and the outburst was shorter than is usual from these systems. C1 Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Calif San Diego, Ctr Astrophys & Space Sci, La Jolla, CA 92093 USA. Univ Maryland, Dept Astron, College Pk, MD 20742 USA. SRON, NL-3584 CA Utrecht, Netherlands. RP Smith, DM (reprint author), Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA. RI Swank, Jean/F-2693-2012 NR 17 TC 34 Z9 34 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5801 S ELLIS AVENUE, CHICAGO, IL 60637 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD JUL 10 PY 1998 VL 501 IS 2 BP L181 EP L184 DI 10.1086/311472 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 101DG UT WOS:000074853900006 ER PT J AU Skarda, JRL Jacqmin, D McCaughan, FE AF Skarda, JRL Jacqmin, D McCaughan, FE TI Exact and approximate solutions to the double-diffusive Marangoni-Benard problem with cross-diffusive terms SO JOURNAL OF FLUID MECHANICS LA English DT Article ID SURFACE-TENSION; CONVECTION; DRIVEN AB We discuss the linear stability of a cross-doubly-diffusive fluid layer with surface tension variation along the free surface. Two limiting cases of the mass flux basic state are considered in the presence of non-zero Soret and Dufour diffusivities. The first case, which has remained largely unexplored, is one where a temperature difference, Delta (T) over bar, and a concentration difference, Delta (C) over bar, are both imposed across the layer. The second case, which has greater significance to thermosolutal systems, is that where the imposed Delta (T) over bar across the layer induces a Delta (C) over bar. We rescale the problem in the absence of buoyancy, which leads to a more concise representation of neutral stability results in and near the limit of zero gravity. We obtain exact solutions for stationary stability in both cases. One important consequence of the exact solutions is the validation of recently published numerical results in the limit of zero gravity. Moreover, the precise location of asymptotes in relevant parameter (Sm-c,Ma(c)) space are computed from exact solutions. Both numerical and exact solutions are used to further examine stability behaviour. We also derive algebraic expressions for stationary stability, oscillatory stability, frequency, and codimension two point from a one-term Galerkin approximation. The one-term solutions qualitatively reflect the stability behaviour of the system over the parameter ranges in our investigation. A practical consequence is that the nature of the stability (oscillatory or stationary) for a given set of parameter values can be determined approximately, without solving the numerical eigenvalue problem. C1 NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. Case Western Reserve Univ, Dept Mech & Aerosp Engn, Cleveland, OH 44135 USA. RP Skarda, JRL (reprint author), NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. NR 24 TC 16 Z9 16 U1 0 U2 5 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 JUL 10 PY 1998 VL 366 BP 109 EP 133 DI 10.1017/S0022112098001220 PG 25 WC Mechanics; Physics, Fluids & Plasmas SC Mechanics; Physics GA 104LY UT WOS:000075017600004 ER PT J AU Hunt, LR Ramakrishna, V Meyer, G AF Hunt, LR Ramakrishna, V Meyer, G TI Stable inversion and parameter variations SO SYSTEMS & CONTROL LETTERS LA English DT Article DE inversion; parameter variations; nonlinear; tracking; guidance ID TRACKING; SYSTEMS AB As part of the process of automatically guiding an aircraft, we have been successful in using stable inversion to compute a desired bounded state trajectory and corresponding bounded control. In addition to this feedforward control, we must also construct a regulator to address modeling errors and disturbances. With respect to modeling errors we find that the stable inversion procedures used are so accurate that the regulator can assume a simple form, say a linear regulator about the desired trajectory. We show that under the appropriate assumptions, the bounded state trajectory and bounded control computed through stable inversion depend continuously on the parameters of the system. This is a consequence of a mathematical result that we prove about the continuous dependence of the "particular solution" of a time varying nonlinear system driven by a bounded input. This is distinct from the usual continuous dependence of the initial value problem for systems. (C) 1998 Elsevier Science B.V. All rights reserved. C1 Univ Texas, Program Electron Engn, Richardson, TX 75083 USA. Univ Texas, Ctr Engn Math, Richardson, TX 75083 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Hunt, LR (reprint author), Univ Texas, Program Electron Engn, EC 33,POB 830688, Richardson, TX 75083 USA. NR 7 TC 10 Z9 10 U1 0 U2 0 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0167-6911 J9 SYST CONTROL LETT JI Syst. Control Lett. PD JUL 10 PY 1998 VL 34 IS 4 BP 203 EP 207 DI 10.1016/S0167-6911(98)00026-7 PG 5 WC Automation & Control Systems; Operations Research & Management Science SC Automation & Control Systems; Operations Research & Management Science GA 104VM UT WOS:000075036800006 ER PT J AU Parthiban, S Lee, TJ AF Parthiban, S Lee, TJ TI Ab initio investigation of the atmospheric molecule bromine nitrate: Equilibrium structure, vibrational spectrum, and heat of formation SO JOURNAL OF CHEMICAL PHYSICS LA English DT Article ID GAUSSIAN-BASIS SETS; COUPLED-CLUSTER; CHLORINE NITRATE; OZONE DEPLETION; CHEMISTRY; ATOMS; DISSOCIATION; CONTRACTION; ENERGIES; KINETICS AB The equilibrium structure, dipole moment, harmonic vibrational frequencies, and infrared intensities of BrONO2 are determined using the CCSD(T) (singles and doubles coupled-cluster theory plus a perturbational estimate of the effects of connected triple excitations) electronic structure method in conjunction with a TZ2P (triple zeta double polarized) basis set. The heat of formation of BrONO2 is predicted (10.1 kcal/mol at 298.15 K) using isodesmic reactions involving ClONO2, HONO2, HOBr, H2O, and HOCl. In addition, we draw attention to the importance of the reaction of O-3 With BrONO2 in relation to ozone layer depletion and stratospheric reservoirs of bromine. (C) 1998 American Institute of Physics. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Parthiban, S (reprint author), NASA, Ames Res Ctr, MS230-3, Moffett Field, CA 94035 USA. RI Lee, Timothy/K-2838-2012 NR 51 TC 17 Z9 17 U1 0 U2 3 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 JUL 8 PY 1998 VL 109 IS 2 BP 525 EP 530 DI 10.1063/1.476589 PG 6 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA 108FM UT WOS:000075255400020 ER PT J AU Khurgin, JB Saif, B Seery, B AF Khurgin, JB Saif, B Seery, B TI Heterodyning scheme employing quantum interference SO APPLIED PHYSICS LETTERS LA English DT Article ID INTERSUBBAND TRANSITIONS; COHERENT CONTROL; GENERATION; SEMICONDUCTORS AB We propose a method of heterodyne detection of far-infrared signals using quantum interference between one- and two-photon absorption. We suggest different implementations of the scheme using multiple quantum well detectors and evaluate its sensitivity. (C) 1998 American Institute of Physics. C1 Johns Hopkins Univ, Dept Elect & Comp Engn, Baltimore, MD 21218 USA. Swales Aerosp, Beltsville, MD 20705 USA. NASA, Goddard Space Flight Ctr, Seebrook, MD 20705 USA. RP Khurgin, JB (reprint author), Johns Hopkins Univ, Dept Elect & Comp Engn, Baltimore, MD 21218 USA. EM jbk@doomsday.ece.jhu.edu RI khurgin, Jacob/A-3278-2010 NR 12 TC 4 Z9 4 U1 0 U2 0 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 JUL 6 PY 1998 VL 73 IS 1 BP 13 EP 15 DI 10.1063/1.121707 PG 3 WC Physics, Applied SC Physics GA 108PT UT WOS:000075275200005 ER PT J AU Ohsaka, K Trinh, EH AF Ohsaka, K Trinh, EH TI Dynamic nucleation of ice induced by a single stable cavitation bubble SO APPLIED PHYSICS LETTERS LA English DT Article ID SONOLUMINESCENCE; WATER; PRESSURE AB Evidence is presented of the dynamic nucleation of ice induced by an isolated stable cavitation bubble in undercooled water. The evidence supports the notion of dynamic nucleation as a result of the freezing point shift due to high pressure pulses associated with a collapsing bubble. It is found that the cavitation bubble requires minimum undercooling, 5 K, to initiate nucleation on ide. This undercooling may be attributed to the temperature rise of the water due to the heat generated by compression of the bubble or the undercooling required for normal ice to nucleate on a high pressure phase. (C) 1998 American Institute of Physics. 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 18 TC 45 Z9 51 U1 2 U2 12 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 JUL 6 PY 1998 VL 73 IS 1 BP 129 EP 131 DI 10.1063/1.121706 PG 3 WC Physics, Applied SC Physics GA 108PT UT WOS:000075275200044 ER PT J AU Quackenbush, SL Work, TM Balazs, GH Casey, RN Rovnak, J Chaves, A duToit, L Baines, JD Parrish, CR Bowser, PR Casey, JW AF Quackenbush, SL Work, TM Balazs, GH Casey, RN Rovnak, J Chaves, A duToit, L Baines, JD Parrish, CR Bowser, PR Casey, JW TI Three closely related herpesviruses are associated with fibropapillomatosis in marine turtles SO VIROLOGY LA English DT Article ID GREEN TURTLE; CUTANEOUS FIBROPAPILLOMAS; CHELONIA-MYDAS AB Green turtle fibropapillomatosis is a neoplastic disease of increasingly significant threat to the survivability of this species. Degenerate PCR primers that target highly conserved regions of genes encoding herpesvirus DNA polymerases were used to amplify a DNA sequence from fibropapillomas and fibromas from Hawaiian and Florida green turtles. All of the tumors tested (n = 23) were found to harbor viral DNA, whereas no viral DNA was detected in skin biopsies from tumor-negative turtles. The tissue distribution of the green turtle herpesvirus appears to be generally limited to tumors where viral DNA was found to accumulate at approximately two to five copies per cell and is occasionally detected, only by PCR, in some tissues normally associated with tumor development. in addition, herpesviral DNA was detected in fibropapillomas from two loggerhead and four olive ridley turtles. Nucleotide sequencing of a 483-bp fragment of the turtle herpesvirus DNA polymerase gene determined that the Florida green turtle and loggerhead turtle sequences are identical and differ from the Hawaiian green turtle sequence by five nucleotide changes, which results in two amino acid substitutions. The olive ridley sequence differs from the Florida and Hawaiian green turtle sequences by 15 and 16 nucleotide changes, respectively, resulting in four amino acid substitutions, three of which are unique to the olive ridley sequence. Our data suggest that these closely related turtle herpesviruses are intimately involved in the genesis of fibropapillomatosis. (C) 1998 Academic Press. C1 Cornell Univ, Coll Vet Med, Dept Microbiol & Immunol, Ithaca, NY 14853 USA. Cornell Univ, Coll Vet Med, James A Baker Inst Anim Hlth, Ithaca, NY 14853 USA. Natl Wildlife Hlth Res Ctr, Biol Resources Div, US Geol Survey, Honolulu, HI 96850 USA. NOAA, Natl Marine Fisheries Serv, SW Fisheries Sci Ctr, Honolulu Lab, Honolulu, HI 96822 USA. RP Casey, JW (reprint author), Cornell Univ, Coll Vet Med, Dept Microbiol & Immunol, Ithaca, NY 14853 USA. RI Work, Thierry/F-1550-2015 OI Work, Thierry/0000-0002-4426-9090 NR 19 TC 100 Z9 105 U1 3 U2 11 PU ACADEMIC PRESS INC PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA SN 0042-6822 J9 VIROLOGY JI Virology PD JUL 5 PY 1998 VL 246 IS 2 BP 392 EP 399 DI 10.1006/viro.1998.9207 PG 8 WC Virology SC Virology GA ZY286 UT WOS:000074604900020 PM 9657957 ER PT J AU McEwen, AS Keszthelyi, L Spencer, JR Schubert, G Matson, DL Lopes-Gautier, R Klassen, KP Johnson, TV Head, JW Geissler, P Fagents, S Davies, AG Carr, MH Breneman, HH Belton, MJS AF McEwen, AS Keszthelyi, L Spencer, JR Schubert, G Matson, DL Lopes-Gautier, R Klassen, KP Johnson, TV Head, JW Geissler, P Fagents, S Davies, AG Carr, MH Breneman, HH Belton, MJS TI High-temperature silicate volcanism on Jupiter's moon Io SO SCIENCE LA English DT Article ID GALILEAN SATELLITES; INTERNAL STRUCTURE; TOPOGRAPHY; SPECTRA; SYSTEM AB Infrared wavelength observations of lo by the Galileo spacecraft show that at Least 12 different vents are erupting lavas that are probably hotter than the highest temperature basaltic eruptions on Earth today. In at least one case, the eruption near Pillan Patera, two independent instruments on Galileo show that the lava temperature must have exceeded 1700 kelvin and may have reached 2000 kelvin. The most likely explanation is that these lavas are ultramafic (magnesium-rich) silicates, and this idea-is supported by the tentative identification of magnesium-rich orthopyroxene in Lava flows associated with these high-temperature hot spots. C1 Univ Arizona, Lunar & Planetary Lab, Tucson, AZ 85711 USA. Lowell Observ, Flagstaff, AZ 86001 USA. Univ Calif Los Angeles, Dept Earth & Space Sci, Los Angeles, CA 90095 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Brown Univ, Dept Geol Sci, Providence, RI 02912 USA. Arizona State Univ, Dept Geol, Tempe, AZ 85287 USA. US Geol Survey, Menlo Park, CA 94025 USA. Natl Opt Astron Observ, Tucson, AZ 85719 USA. RP McEwen, AS (reprint author), Univ Arizona, Lunar & Planetary Lab, Tucson, AZ 85711 USA. EM mcewen@lplarizona.edu RI Fagents, Sarah/B-3983-2014; Lopes, Rosaly/D-1608-2016 OI Lopes, Rosaly/0000-0002-7928-3167 NR 40 TC 128 Z9 130 U1 0 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 JUL 3 PY 1998 VL 281 IS 5373 BP 87 EP 90 DI 10.1126/science.281.5373.87 PG 4 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA ZZ009 UT WOS:000074685800043 PM 9651251 ER PT J AU Weiler, EJ AF Weiler, EJ TI Let's share the excitement of science SO NATURE LA English DT Letter C1 NASA, Astron Search Origins & Planetary Syst, Washington, DC 20546 USA. RP Weiler, EJ (reprint author), NASA, Astron Search Origins & Planetary Syst, Code S, Washington, DC 20546 USA. NR 1 TC 0 Z9 0 U1 0 U2 0 PU MACMILLAN MAGAZINES LTD PI LONDON PA PORTERS SOUTH, 4 CRINAN ST, LONDON, ENGLAND N1 9XW SN 0028-0836 J9 NATURE JI Nature PD JUL 2 PY 1998 VL 394 IS 6688 BP 10 EP 10 DI 10.1038/27748 PG 1 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA ZY030 UT WOS:000074579600015 ER PT J AU Hunley, JD AF Hunley, JD TI Comparative history of rocket development at Peenemunde in Germany and at the Jet Propulsion Laboratory in the USA from 1932 to 1945 SO ACTA ASTRONAUTICA LA English DT Article RP Hunley, JD (reprint author), NASA, Dryden Flight Res Ctr, Hist Off, Washington, DC 20546 USA. NR 0 TC 1 Z9 1 U1 0 U2 0 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0094-5765 J9 ACTA ASTRONAUT JI Acta Astronaut. PD JUL PY 1998 VL 43 IS 1-2 BP 61 EP 62 DI 10.1016/S0094-5765(97)00039-8 PG 2 WC Engineering, Aerospace SC Engineering GA 116RU UT WOS:000075739000016 ER PT J AU Li, D Robinson, MB Rathz, TJ Williams, G AF Li, D Robinson, MB Rathz, TJ Williams, G TI Liquidus temperatures and solidification behavior in the copper-niobium system SO ACTA MATERIALIA LA English DT Article; Proceedings Paper CT Workshop on Coupled Property Issues in Integrated Microstructures CY APR, 1997 CL MONTEREY, CALIFORNIA SP Inst Mech & Mat, Acta Metallurg Inc ID CU-NB ALLOYS; STRENGTH AB The copper-niobium phase diagram has been under active debate; thus, a corroboratory experimental study is needed. In this investigation, the melts of Cu-Nb alloys at compositions ranging from 5 to 86 wt% Nb were processed in different environments and solidified at relatively low cooling rates of 50-75 degrees C/s to determine liquidus temperatures and to study solidification behavior. For all samples processed under very clean conditions, only Nb dendrites in a Cu matrix were observed; while in the presence of oxy gen impurities, the alloys containing 5-35 wt% Nb exhibited microstructure of Nb-rich spheroids and Nb dendrites in the Cu matrix. The results obtained from clean conditions are in fair agreement with the Cu-Nb phase diagram having an S-shaped, near-horizontal appearance of the liquidus. The formation of Nb-rich droplets at slow cooling rates is discussed in terms of a stable liquid miscibility gap induced by oxygen. (C) 1998 Acta Metallurgica Inc. C1 NASA, George C Marshall Space Flight Ctr, Space Sci Lab, Huntsville, AL 35812 USA. Univ Alabama, Huntsville, AL 35899 USA. RP Li, D (reprint author), NASA, George C Marshall Space Flight Ctr, Space Sci Lab, Huntsville, AL 35812 USA. EM Delin.Li@msfc.nasa.gov NR 23 TC 7 Z9 8 U1 0 U2 2 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 JUL 1 PY 1998 VL 46 IS 11 BP 3849 EP 3855 DI 10.1016/S1359-6454(98)00063-9 PG 7 WC Materials Science, Multidisciplinary; Metallurgy & Metallurgical Engineering SC Materials Science; Metallurgy & Metallurgical Engineering GA 103GF UT WOS:000075149000017 ER PT J AU Dietz, AJ AF Dietz, AJ TI Boundary-layer receptivity to transient convected disturbances SO AIAA JOURNAL LA English DT Article; Proceedings Paper CT AIAA 28th Fluid Dynamics Conference CY JUN 29-JUL 02, 1997 CL SNOWMASS VILLAGE, COLORADO SP Amer Inst Aeronaut & Astronaut ID TOLLMIEN-SCHLICHTING WAVES; ACOUSTIC-WAVES; EVOLUTION AB Previous work has shown that the boundary layer is receptive to acoustic and convected disturbances in regions where there is a rapid streamwise variation in the mean flow such as at the leading edge or at roughness elements or suction strips. Much of this work involved single-frequency, two-dimensional waves, and further studies are required to determine the effects of the broadband three-dimensional nature of turbulent fluctuations. An experimental investigation of the receptivity of a Blasius boundary layer to transient two-dimensional convected disturbances is presented here. A ribbon located upstream of a Rat plate and aligned parallel to the plate leading edge was used to introduce disturbances into the freestream. Two-dimensional roughness elements distributed on the surface of the plate provided a receptivity site. Measurements of the boundary-layer response to single-frequency waves, pulses, and random noise disturbances are reported. Similar receptivity was measured for each of these disturbance types, showing that the broadband nature of transient disturbances does not affect the receptivity characteristics of the boundary layer and that linear superposition may be used to extend theories for single-frequency disturbances to applications involving broadband disturbances. C1 NASA, Ames Res Ctr, Fluid Mech Lab Branch, Moffett Field, CA 94035 USA. NR 20 TC 9 Z9 10 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 JUL PY 1998 VL 36 IS 7 BP 1171 EP 1177 DI 10.2514/2.528 PG 7 WC Engineering, Aerospace SC Engineering GA 147VB UT WOS:000077516900007 ER PT J AU Cutler, AD AF Cutler, AD TI Specification of model entrance conditions for scramjet testing in vitiated air SO AIAA JOURNAL LA English DT Article AB A systematic method is presented for the specification of ramjet/scramjet test facility air simulant and fuel simulant composition and combustor or engine entrance conditions. An analysis of the governing equations is performed to identify a minimum set of dimensionless variables and dimensionless closure relationships. The enthalpy closure, which relates dimensionless enthalpy to dimensionless pressure, density, and composition, is studied. Best air simulant compositions for typical vitiated air facilities are identified by matching a simplified enthalpy closure relationship fur the simulants to flight. The air simulant compositions so identified are tested in simple calculations of a scramjet combustor and nozzle that assume two-stream, quasi one dimensional Bow and equilibrium chemistry. Results for the new simulation method are compared with results for simulants constituted in the conventional manner and to flight. Detailed effects: of chemical kinetics, which are known to be important in many ramjet/scramjet simulations or in flight, are not considered. C1 George Washington Univ, Joint Inst Advancement Flight Sci, Hampton, VA 23681 USA. NASA, Langley Res Ctr, Hampton, VA 23681 USA. RP Cutler, AD (reprint author), George Washington Univ, Joint Inst Advancement Flight Sci, Hampton, VA 23681 USA. NR 14 TC 0 Z9 0 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 JUL PY 1998 VL 36 IS 7 BP 1200 EP 1207 PG 8 WC Engineering, Aerospace SC Engineering GA 147VB UT WOS:000077516900010 ER PT J AU Knapp, AK Carter, GA AF Knapp, AK Carter, GA TI Variability in leaf optical properties among 26 species from a broad range of habitats SO AMERICAN JOURNAL OF BOTANY LA English DT Article DE absorptance; leaf optics; leaf thickness; light; reflectance; transmittance ID EXTREME-SHADE PLANTS; LEAVES; LIGHT; REFLECTANCE; NEEDLES; TISSUE; SUN AB Leaves from 26 species with growth forms from annual herbs to trees were collected from open, intermediate. and shaded understory habitats in Mississippi and Kansas, USA. Leaf optical properties including reflectance, transmittance, and absorptance in visible and near infrared (MR) wavelengths were measured along with leaf thickness and specific leaf mass (SLM). These leaf properties and internal light scattering have been reported to vary with light availability in studies that have focused on a limited number of species. Our objective was to determine whether these patterns in leaf optics and light availability were consistent when a greater number of species were evaluated. Leaf thickness and SLM varied by tenfold among species sampled. but within-habitat variance was high. Although there was a strong trend toward thicker leaves in open habitats, only SLM was significantly,greater in open vs. understory habitats. in contrast, leaf optical properties were strikingly similar among habitats. Reflectance and reflectance/transmittance in the NIR were used to estimate internal light scattering and there were strong relationships (r(2) > 0.65) between these optical properties and leaf thickness. We concluded that leaf thickness, which did not vary consistently among habitats, was the best predictor of NIR reflectance and internal light scattering. However, because carbon allocation to leaves was lower in understory species (low SLM) yet gross optical properties were similar among all habitats, the energy investment by shade leaves required to achieve optical equivalence with sun leaves was lower. Differences in leaf longevity and growth form within a habitat may help explain the lack of consistent patterns in leaf optics as the number of species sampled increases. C1 Kansas State Univ, Div Biol, Manhattan, KS 66506 USA. NASA, Earth Syst Sci Off, Stennis Space Ctr, MS 39529 USA. RP Knapp, AK (reprint author), Kansas State Univ, Div Biol, Manhattan, KS 66506 USA. RI Knapp, Alan/A-2931-2008 NR 27 TC 89 Z9 95 U1 2 U2 29 PU BOTANICAL SOC AMER INC PI COLUMBUS PA OHIO STATE UNIV-DEPT BOTANY 1735 NEIL AVE, COLUMBUS, OH 43210 USA SN 0002-9122 J9 AM J BOT JI Am. J. Bot. PD JUL PY 1998 VL 85 IS 7 BP 940 EP 946 DI 10.2307/2446360 PG 7 WC Plant Sciences SC Plant Sciences GA 104DQ UT WOS:000074998000006 PM 21684977 ER PT J AU Hanson, B Jones, JH AF Hanson, B Jones, JH TI The systematics of Cr3+ and Cr2+ partitioning between olivine and liquid in the presence of spinel SO AMERICAN MINERALOGIST LA English DT Article ID SILICATE LIQUID; ORTHO-PYROXENE; CHROMIUM; MELTS; COEFFICIENTS; TEMPERATURE; EQUILIBRIUM; CHONDRITES; PRESSURE; ORIGIN AB The partitioning behavior of Cr into olivine in basaltic systems has been parameterized and can now be modeled over a wide range of redox conditions and liquid compositions. The Cr2+/Cr3+ in spinel-saturated experimental systems can be estimated based on a simple model of Cr solubility in basalt. Fe3+ appears to suppress the presence of Cr2+ in basaltic systems. We predict that, in Fe-free systems, all Cr is trivalent at log fO(2) = -3 (i.e., QFM+3 to QFM+4), whereas all Cr is trivalent at approximately Ni NiO(QFM+1) in Fe-bearing systems. Cr2+ predominates under redox conditions 100 nT) was chosen to ensure a proper detection of evens also during times of high activity. Readings of all stations of the northern half of the IMAGE network were employed to check the consistency of the ground signature with the notation of a dual-vortex structure moving in an azimuthal direction. Applying these stringent selection criteria we detected a total of 19 clear TCV events. The statistical properties of our selection resemble the expected characteristics of large-amplitude TCVs. New and unexpected results emerged from the superposed epoch analysis. TCVs tend to form during quiet intervals embedded in moderately active periods. The occurrence of events is not randomly distributed but rather shows a clustering around a few days. These clusters recur once or twice every 27 days. Within a storm cycle they show up five to seven days after the commencement. With regard to solar wind conditions, we see the events occurring in the middle of the IMF sector structure. Large-amplitude TCVs seem to require certain conditions to make solar wind transients 'geoeffective', which have the tendency to recur with the solar rotation period. C1 Geoforschungszentrum Potsdam, D-14473 Potsdam, Germany. Kyoto Univ, Data Ctr Geomagnetism & Space Magnetism, Kyoto 60601, Japan. Univ Tromso, Auroral Observ, N-9037 Tromso, Norway. NASA, Goddard Space Flight Ctr, Electrodynam Branch, Greenbelt, MD 20771 USA. RP Luhr, H (reprint author), Geoforschungszentrum Potsdam, Telegrafenberg, D-14473 Potsdam, Germany. NR 24 TC 10 Z9 10 U1 0 U2 2 PU SPRINGER VERLAG PI NEW YORK PA 175 FIFTH AVE, NEW YORK, NY 10010 USA SN 0992-7689 J9 ANN GEOPHYS-ATM HYDR JI Ann. Geophys.-Atmos. Hydrospheres Space Sci. PD JUL PY 1998 VL 16 IS 7 BP 743 EP 753 DI 10.1007/s00585-998-0743-0 PG 11 WC Astronomy & Astrophysics; Geosciences, Multidisciplinary; Meteorology & Atmospheric Sciences SC Astronomy & Astrophysics; Geology; Meteorology & Atmospheric Sciences GA 107JT UT WOS:000075205200001 ER PT J AU Brasunas, JC Cushman, GM Lakew, B AF Brasunas, JC Cushman, GM Lakew, B TI Artificial diamond as a broadband infrared beam splitter for Fourier transform spectroscopy SO APPLIED OPTICS LA English DT Article AB We show that an artificially grown diamond plate serves as a very broadband beam splitter hom approximately 7 mu m, where the intrinsic diamond absorption becomes important, to the submillimeter region (a 250-mu m wavelength or longer). (C) 1998 Optical Society of America. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Raytheon STX Corp, Greenbelt, MD 20770 USA. RP Brasunas, JC (reprint author), NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RI brasunas, john/I-2798-2013 NR 7 TC 9 Z9 9 U1 1 U2 1 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 JUL 1 PY 1998 VL 37 IS 19 BP 4226 EP 4229 DI 10.1364/AO.37.004226 PG 4 WC Optics SC Optics GA ZW479 UT WOS:000074415100026 PM 18285867 ER PT J AU Vander Wal, RL Ticich, TM Stephens, AB AF Vander Wal, RL Ticich, TM Stephens, AB TI Optical and microscopy investigations of soot structure alterations by laser-induced incandescence SO APPLIED PHYSICS B-LASERS AND OPTICS LA English DT Article ID FLICKERING METHANE; DIFFUSION FLAMES; VOLUME FRACTION; VISUALIZATION; DIAGNOSTICS; PARTICLES AB Understanding the physical process of LII is central to practical implementation and accurate theoretical modelling of LII. The LII dependence upon laser fluence is shown to depend upon detection conditions thereby not providing direct information about the soot temperature or structural changes. Transmission electron microscopy, used to investigate the morphological changes induced in the soot at different laser fluences, shows increasing graphitization of the soot with increasing laser fluence. For laser fluences above 0.45 +/- 0.05 J/cm(2) at 1064 nm, vaporization/fragmentation of soot primary particles and aggregates occurs. Optical measurements are performed using a second laser pulse to probe the effects of these changes upon the LII signal. With the exception of very low fluences, the structural changes induced in the soot lead to a decreased LII intensity produced by the second laser pulse. These two-pulse experiments also show that these changes do not alter the LII signal on timescales less than 1 mu s for fluences below the vaporization threshold. C1 NASA, Lewis Res Ctr, NCMR, Cleveland, OH 44135 USA. Centenary Coll Louisiana, Dept Chem, Shreveport, LA 71134 USA. RP Vander Wal, RL (reprint author), NASA, Lewis Res Ctr, NCMR, MS 110-3,21000 Brookpk Rd, Cleveland, OH 44135 USA. NR 30 TC 56 Z9 57 U1 2 U2 7 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 JUL PY 1998 VL 67 IS 1 BP 115 EP 123 DI 10.1007/s003400050483 PG 9 WC Optics; Physics, Applied SC Optics; Physics GA ZZ425 UT WOS:000074728100019 ER PT J AU Lane, W Smette, A Briggs, F Rao, S Turnshek, D Meylan, G AF Lane, W Smette, A Briggs, F Rao, S Turnshek, D Meylan, G TI H I 21 centimeter absorption in two low-redshift damped Ly alpha systems SO ASTRONOMICAL JOURNAL LA English DT Article DE galaxies : ISM; quasars : absorption lines; quasars : individual (PKS 1127-145, OI 363) ID SAMPLE; GALAXY; GAS AB We report the discovery of two low-redshift H I 21 cm absorbers, one at z = 0.2212 toward the z(em) = 0.630 quasar OI 363 (B0738+313), and the other at z = 0.3127 toward PKS B1127-145 (z(em) =1.187). Both were found during a survey of Mg II-selected systems at redshifts 0.2 < z < 1 using the new UHF-high system at the Westerbork Synthesis Radio Telescope. New Hubble Space Telescope Faint Object Spectrograph observations also identify both systems as damped Ly alpha (DLA) absorbers. By comparing the column density from the DLA line with that from the H I 21 cm line, we calculate the spin temperature, T-s, of the two systems. We find T-s approximate to 1000 K for both these low-redshift absorbers. For the z = 0.3127 system toward PKS B1127-145, two galaxies have been previously identified with emission lines at the absorber redshift by Bergeron & Boisse, with the galaxy at a closer projected distance to the quasar assumed to be responsible for the absorption system. An ESO New Technology Telescope/EFOSC2 spectrum of a third, fainter companion at 3." 9, or 11 h(100)(-1) kpc, from the line of sight of PKS B1127-145 reveals [O III] lambda 4958 and lambda 5007 at z = 0.3121 +/- 0.0003. We consider this object the most likely to be responsible for the 21 cm absorption, as it is much closer to the QSO sight line than the two galaxies identified by Bergeron & Boisse. C1 Kapteyn Astron Inst, NL-9700 AV Groningen, Netherlands. NASA, Goddard Space Flight Ctr, Lab Astron & Space Phys, Greenbelt, MD 20771 USA. Natl Opt Astron Observ, Tucson, AZ 85726 USA. Univ Pittsburgh, Dept Phys & Astron, Pittsburgh, PA 15260 USA. European So Observ, D-85748 Munich, Germany. RP Lane, W (reprint author), Kapteyn Astron Inst, Postbus 800, NL-9700 AV Groningen, Netherlands. NR 18 TC 50 Z9 50 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 JUL PY 1998 VL 116 IS 1 BP 26 EP 30 DI 10.1086/300422 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 104KB UT WOS:000075012500005 ER PT J AU Cornett, RH Dorman, B Smith, EP Fanelli, MA Oegerle, WR Bohlin, RC Neff, SG O'Connell, RW Roberts, MS Smith, AM Stecher, TP AF Cornett, RH Dorman, B Smith, EP Fanelli, MA Oegerle, WR Bohlin, RC Neff, SG O'Connell, RW Roberts, MS Smith, AM Stecher, TP TI Ultraviolet imaging of the z=0.23 cluster Abell 2246 SO ASTRONOMICAL JOURNAL LA English DT Article DE galaxies : clusters : individual (Abell 2246); ultraviolet emission ID NEARBY CLUSTERS; COMA CLUSTER; LUMINOSITY FUNCTION; SURFACE PHOTOMETRY; STELLAR MODELS; STAR FORMATION; GALAXIES; EXTINCTION; EVOLUTION; GRIDS AB We present deep ultraviolet observations of a field containing the cluster Abell 2246 (z = 0.225), which provide far-ultraviolet (FUV) images of some of the faintest galaxies yet observed in that bandpass. Abell 2246 lies within the field of view of Ultraviolet Imaging Telescope (UIT) observations of the quasar HS 1700+64, which accumulated over 7100 s of UIT FUV exposure time during the Astro-2 mission in 1995 March. For objects found on both the far-ultraviolet (FUV) and ground-based V-band images, we obtain FUV (lambda similar to 1520 Angstrom) photometry and V-band photometry, as well as mid-UV (lambda similar to 2490 Angstrom) photometry from UIT Astro-1 observations and ground-based I-band photometry. We find five objects in the images that are probably galaxies at the distance of Abell 2246, with FUV magnitudes [m(FUV)] between 18.6 and 19.6 and V magnitudes between 18.4 and 19.6. We find that their absolute FUV fluxes and colors imply strongly that they are luminous galaxies with significant current star formation, as well as some relatively recent, but not current (>400 Myr ago) star formation. We interpret the colors of these five objects by comparing them with local objects, redshift-corrected template spectra, and stellar population models, finding that they are plausibly matched by 10 Gyr-old population models with decaying star formation, with decay time constants in the range 3 Gyr < tau < 5 Gyr, with an additional color component from a single burst of moderate (similar to 400-500 Myr) age. From derived FUV luminosities we compute current star formation rates. We compare the UV properties of Abell 2246 with those of the Coma Cluster, finding that Abell 2246 has significantly more recent star formation, consistent with the Butcher-Oemler phenomenon. C1 Raytheon STX Corp, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Virginia, Dept Astron, Charlottesville, VA 22903 USA. NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, Greenbelt, MD 20771 USA. Johns Hopkins Univ, Dept Phys & Astron, Baltimore, MD 21218 USA. Space Telescope Sci Inst, Baltimore, MD 21218 USA. Natl Radio Astron Observ, Charlottesville, VA 22903 USA. RP Cornett, RH (reprint author), Raytheon STX Corp, Goddard Space Flight Ctr, Code 681, Greenbelt, MD 20771 USA. RI Oegerle, William/C-9070-2012 NR 36 TC 1 Z9 1 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 JUL PY 1998 VL 116 IS 1 BP 44 EP 54 DI 10.1086/300430 PG 11 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 104KB UT WOS:000075012500008 ER PT J AU Scowen, PA Hester, JJ Sankrit, R Gallagher, JS Ballester, GE Burrows, CJ Clarke, JT Crisp, D Evans, RW Griffiths, RE Hoessel, JG Holtzman, JA Krist, J Mould, JR Stapelfeldt, KR Trauger, JT Watson, AM Westphal, JA AF Scowen, PA Hester, JJ Sankrit, R Gallagher, JS Ballester, GE Burrows, CJ Clarke, JT Crisp, D Evans, RW Griffiths, RE Hoessel, JG Holtzman, JA Krist, J Mould, JR Stapelfeldt, KR Trauger, JT Watson, AM Westphal, JA TI Ionization structure in the 30 Doradus Nebula as seen with Hubble Space Telescope Wide Field Planetary Camera 2 SO ASTRONOMICAL JOURNAL LA English DT Article DE H II regions; ISM : individual (30 Doradus); ISM : structure; Magellanic Clouds ID 30-DORADUS; PHOTOEVAPORATION; CLOUDS; IMAGES; WFPC2 AB Using the Hubble Space Telescope (HST) and Wide Field Planetary Camera 2, we have imaged the central 20 pc of the giant H II region 30 Doradus Nebula in three different emission lines. The images allow us to study the nebula with a physical resolution that is within a factor of 2 of that of typical ground-based observations of Galactic H II regions. We present a gallery of interesting objects within the region studied. These include a tube blown by the wind of a high-velocity star and a discrete H II region around an isolated B star. This small isolated H II region appears to be in the midst of the champagne flow phase of its evolution. Most of the emission within 30 Dor is confined to a thin zone located between the hot interior of the nebula and surrounding dense molecular material. This zone appears to be directly analogous to the photoionized photoevaporative flows that dominate emission from small, nearby H II regions. For example, a column of material protruding from the cavity wall to the south of the main cluster is found to be a direct analog to elephant trunks in M16. Surface brightness profiles across this structure are very similar to surface brightness profiles taken at ground-based resolution across the head of the largest column in M16. The dynamical effects of the photoevaporative flow can be seen as well. An arcuate feature located above this column and a similar feature surrounding a second nearby column are interpreted as shocks in which the photoevaporative flow stagnates against the high-temperature gas that fills the majority of the nebula. The ram pressure in the photoevaporative flow, derived from thermal pressure at the surface of the column, is found to balance with the pressure in the interior of the nebula derived from previous X-ray observations. By analogy with the comparison of ground-based and HST images of M16, we infer that the same sharply stratified structure seen in HST images of M16 almost certainly underlies the observed structure in 30 Doradus, which is a crucial case because it allows us to bridge the gap between nearby H II regions and the giant H II regions seen in distant galaxies. The real significance of this result is that it demonstrates that the physical understanding gained from detailed study of photoevaporative interfaces in nearby H II regions can be applied directly to interpretation of giant H II regions. Stated another way, interpretation of observations of giant H II regions must account for the fact that this emission arises not from expansive volumes of ionized gas but instead from highly localized and extremely sharply stratified physical structures. C1 Arizona State Univ, Dept Phys & Astron, Tempe, AZ 85287 USA. Univ Wisconsin, Dept Astron, Madison, WI 53706 USA. Univ Michigan, Dept Atmospher Ocean & Space Sci, Ann Arbor, MI 48109 USA. Space Telescope Sci Inst, Baltimore, MD 21218 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91125 USA. Carnegie Mellon Univ, Dept Phys, Pittsburgh, PA 15213 USA. New Mexico State Univ, Dept Astron, Las Cruces, NM 88003 USA. Australian Natl Univ, Mt Stromlo & Siding Spring Observ, Weston, ACT 2611, Australia. Univ Nacl Autonoma Mexico, Inst Astron, Morelia 58090, Michoacan, Mexico. CALTECH, Div Geol & Planetary Sci, Pasadena, CA 91125 USA. RP Scowen, PA (reprint author), Arizona State Univ, Dept Phys & Astron, Box 871504, Tempe, AZ 85287 USA. RI Stapelfeldt, Karl/D-2721-2012; Clarke, John/C-8644-2013 NR 20 TC 43 Z9 43 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 JUL PY 1998 VL 116 IS 1 BP 163 EP 179 DI 10.1086/300411 PG 17 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 104KB UT WOS:000075012500017 ER PT J AU Parker, JW Hill, JK Cornett, RH Hollis, J Zamkoff, E Bohlin, RC O'Connell, RW Neff, SG Roberts, MS Smith, AM Stecher, TP AF Parker, JW Hill, JK Cornett, RH Hollis, J Zamkoff, E Bohlin, RC O'Connell, RW Neff, SG Roberts, MS Smith, AM Stecher, TP TI Ultraviolet imaging telescope observations of the magellanic clouds SO ASTRONOMICAL JOURNAL LA English DT Article DE Magellanic Clouds; open clusters and associations : general; stars : early-type; stars : luminosity function, mass function; ultraviolet emission ID INITIAL MASS FUNCTION; WOLF-RAYET STARS; STELLAR CONTENT; OB ASSOCIATIONS; LUMINOSITY FUNCTIONS; PHOTOMETRY; LMC; GALAXIES; FIELD; SUPERBUBBLE AB We present wide-field far-ultraviolet (FUV; 1300-1800 Angstrom) images of the Large and Small Magellanic Clouds (LMC, SMC). These data were obtained by the Ultraviolet Imaging Telescope (UIT) during the Astro-1 (1990 December 1-10) and Astro-2 (1995 March 2-18) missions; the images provide an extensive FUV mosaic of the SMC and contain numerous regions in the LMC, covering a wide range of stellar densities and current star formation activity. A total of 47 LMC/Lucke-Hodge and 37 SMC/Hodge OB associations are completely or partially included in the observed fields. FUV data can identify the hottest OB stars more easily than can optical photometry, and these stars dominate the ionizing flux, which is correlated to the observed H-alpha flux of the associated H II regions. Of the H II regions in the catalog of Davies, Elliott and Meaburn (DEM), the UIT fields completely or partially include 102 DEM regions in the LMC and 74 DEM regions in the SMC. We present a catalog of FUV magnitudes derived from point-spread function photometry for 37,333 stars in the LMC (the UIT FUV magnitudes for 11,306 stars in the SMC were presented recently by Cornett et al), with a completeness limit of m(UV) is-approximate-to 15 mag and a detection limit of m(UV) is-approximate-to 17.5. The average uncertainty in the photometry is similar-to-0.1 mag. The full catalog with astrometric positions, photometry, and other information is also available from publicly accessible astronomical data archives. We divide the catalog into field stars and stars that are in DEM regions. We analyze each of these two sets of stars independently, comparing the composite UV luminosity function of our data with UV magnitudes derived from stellar evolution and atmosphere models in order to derive the underlying stellar formation parameters. We find a most probable initial mass function (IMF) slope for the LMC field stars of gamma= -180+0.09. The statistical signficance of this single slope for the LMC field stars is extremely high, though we also find some evidence for a field star IMF slope of gamma is-similar-to -1.4, roughly equal to the Salpeter slope. However, in the case of the stars in the DEM regions (the stars in all the regions were analyzed together as a single group), we find three IMF slopes of roughly equal likelihood: gamma = -1.0, -1.6, and -2.0. No typical age for the field stars is found in our data for time periods up to a continuous star formation age of 500 Myr, which is the maximum age consistent with the completeness limit magnitude of the catalog's luminosity function. The best age for the collection of cluster stars was found to be t(0) = 3.4 +/- 1.9 Myr; this is consistent with the age expected for a collection of OB stars from many different clusters. C1 SW Res Inst, Boulder, CO 80302 USA. NASA, Goddard Space Flight Ctr, Raytheon STX Corp, Code 681, Greenbelt, MD 20771 USA. Space Telescope Sci Inst, Baltimore, MD 21218 USA. Univ Virginia, Dept Astron, Charlottesville, VA 22903 USA. NASA, Goddard Space Flight Ctr, Lab Astron & Solar Phys, Code 681, Greenbelt, MD 20771 USA. Natl Radio Astron Observ, Charlottesville, VA 22903 USA. RP Parker, JW (reprint author), SW Res Inst, Suite 426,1050 Walnut St, Boulder, CO 80302 USA. NR 65 TC 52 Z9 52 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 JUL PY 1998 VL 116 IS 1 BP 180 EP 208 DI 10.1086/300419 PG 29 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 104KB UT WOS:000075012500018 ER PT J AU Bally, J Sutherland, RS Devine, D Johnstone, D AF Bally, J Sutherland, RS Devine, D Johnstone, D TI Externally illuminated young stellar environments in the Orion Nebula: Hubble space telescope Planetary Camera and ultraviolet observations SO ASTRONOMICAL JOURNAL LA English DT Article DE ISM : individual (Orion Nebula); stars : formation; stars : pre-main-sequence ID HERBIG-HARO OBJECTS; TRAPEZIUM-CLUSTER; HIGH-SPEED; SPHERICAL CLOUDS; HOT GAS; PHOTODISSOCIATION REGIONS; INTERSTELLAR CLOUDS; CIRCUMSTELLAR DISK; M42; NGC-1976 AB We present new 0." 05 resolution (22 AU) narrowband Hubble Space Telescope Planetary Camera images of externally illuminated young stellar objects embedded in the Orion Nebula. We also present 0."02 resolution (9 AU) UV images of seven externally illuminated protostellar environments and the first UV spectra that cover the spectral range between 1400 and 3000 Angstrom. We discuss 43 objects for which the angular resolution has been improved over previous data by more than a factor of 2. These young stellar objects are either embedded inside the Orion Nebula and externally illuminated by the Trapezium stars or located in front of the nebula and seen in silhouette. The visibility of young stars surrounded by diffuse matter is dominated by intense line emission from ionization fronts (IFs) propagating into material photoablated from circumstellar disks by soft UV radiation. Near the Trapezium stars, the electron density at these Ifs is around 10(5) to 10(6) cm(-3) and the radial intensity profiles of emission lines decrease roughly as r(-3), consistent with an approximately constant-velocity diverging flow with an r(-2) density profile. However, some radial intensity profiles are better fitted with an exponential function. Low ionization fraction near the IF and the heating and acceleration of the photoablation flow can explain deviations from the r(-3) intensity profiles. Many young stars located within 30 " of theta(1) Ori C are surrounded by concentric arcs of [O III] and H alpha emission located 0." 5 to 3 " from the IF facing theta(1) Ori C. These arcs may trace bow shocks formed by the interaction of the expanding photoablation flow with the fast stellar wind from theta(1) Ori C. The [O III] emission may be enhanced by UV radiation from theta(1) Ori C, thermal conduction, and/or turbulent mixing of weakly shocked, photoablated gas with the thermalized shocked stellar wind. About 30% of the bright externally illuminated young stellar objects contain dark regions seen in silhouette against background nebular emission in H alpha and the forbidden transitions of common ions that may trace circumstellar protoplanetary disks. In some sources, the regions seen in silhouette in H alpha and ionic transitions are bright in the 6300 Angstrom [O I] line. Most externally illuminated young stellar objects have dusty tails pointing radially away from the source of ionizing photons. Tails have an average length of 500 AU, independent of the projected distance from theta(1) Ori C, are limb-brightened in emission lines, and are sometimes seen in silhouette against background nebular light, indicating that they contain large column densities of gas and dust. We discuss a variety of tail formation mechanisms and conclude that initial conditions probably play a key role in their formation. The large fraction of young stellar objects with extended circumstellar structure, the mass limits on this structure, and the estimated mass-loss rates are combined to produce an estimate for the photoionization age of the Orion Nebula. The derived photoionization age of the Orion Nebula is less than 10(5) yr and possibly as short as 10(4) yr. C1 Univ Colorado, Dept Astrophys & Planetary Sci, Boulder, CO 80309 USA. Univ Colorado, Ctr Astrophys & Space Astron, Boulder, CO 80309 USA. Australian Natl Univ, Astrophys Theory Ctr, Canberra, ACT 0200, Australia. Australian Natl Univ, Mt Stromlo & Siding Spring Observ, Canberra, ACT 0200, Australia. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Toronto, Canadian Inst Theoret Astrophys, Toronto, ON M5S 3H8, Canada. RP Bally, J (reprint author), Univ Colorado, Dept Astrophys & Planetary Sci, Boulder, CO 80309 USA. NR 76 TC 146 Z9 146 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 JUL PY 1998 VL 116 IS 1 BP 293 EP 321 DI 10.1086/300399 PG 29 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 104KB UT WOS:000075012500028 ER PT J AU Hester, JJ Stapelfeldt, KR Scowen, PA AF Hester, JJ Stapelfeldt, KR Scowen, PA TI Hubble Space Telescope Wide Field Planetary Camera 2 observations of HH 1-2 SO ASTRONOMICAL JOURNAL LA English DT Article DE ISM : individual (HH 1-2); ISM : jets and outflows; shock waves; stars : formation ID HERBIG-HARO OBJECT-1; BOW-SHOCK; NUMERICAL SIMULATIONS; PROTOSTELLAR JETS; HIGH-RESOLUTION; PROPER MOTIONS; EMISSION-LINES; MODELS; PERFORMANCE; COMPLEX AB We present Hubble Space Telescope Wide Field Planetary Camera 2 images of the bipolar Herbig-Haro complex HH 1-2 in three emission lines (H alpha, [S II], and [O III]) and one continuum band (F702W). In addition to showing the complex morphology of these objects, the WFPC2 data allow us to resolve the cooling and recombination regions behind radiative shocks. This provides important diagnostics for the properties of the shocks present, including information about the direction of shock propagation and the postshock cooling length. The HH 1 jet can be interpreted as a series of bow shocks, consistent with models of the propagation of a pulsed jet. Evidence is seen both of the interaction of the jet with its surroundings and of internal shocks between knots. Large knot complexes are spaced with a period of around 15 yr, while internal structure within these complexes have characteristic separations corresponding to about 3.5 yr. Two knots at the base of the HH 1 jet point away from the main jet and do not line up with the outflow source at VLA 1. These may be associated with an outflow from a third source within the VLA 1/2 region. The HH 1 complex consists of multiple bow shocks that, at least in part, trace variations in jet direction with time. The misalignment between the direction of the visible HH 1 jet and the jet currently reaching the HH 1 bow shock are direct evidence of such variations. Arches on the west side of HH 1 are smooth, faint, display high excitation, and have well-resolved postshock cooling regions. Shoulders on the east side of HH 1 are bright, low excitation, and fragmented. This asymmetry is the result of a significant difference in the density and velocity of preshock material on either side of HH 1 and can be understood if the HH 1 jet is currently striking the edge of its own outflow cavity. The HH 1 knot F bow shock shows a gap in the [O III] at its apex where the shock is fast enough to ionize beyond O++ and the cooling time is long enough for material to how out of the region before cooling. A nested double bow shock structure at this location may be the result of an incoming knot in a clumpy jet that is just overtaking its decelerated predecessor. Features located between VLA 1 and the HH 1 bow shock probably arise as a broader wind from VLA 1 encounters structure along the wall of the outflow cavity. HH 2 has an extremely complex structure, but on a feature-by-feature basis much of the physical structure of HH 2 can be understood, leading to a consistent overall description of the object. The HH 2 jet is currently encountering dense ambient gas. The working surface of the jet is seen as bright, high-ionization emission in the central region of the complex. This emission shows a clumpy appearance due largely to the short cooling lengths behind shocks driven into dense material. The larger bow shock accompanying the jet working surface can be traced as well. Flanking the working surface are several locations where a momentum-driven shell is fragmenting as a result of hydrodynamic and thermal instabilities that arise as it, too, runs into dense ambient material. The dense obstacle being encountered by HH 2 is localized. Fossil bow shocks and "splatter" from the jet can be observed moving around this obstacle on either side of HH 2, giving the object its "indented" appearance. As in HH 1, a broader wind accompanies the HH 2 jet. Interaction of this wind with ambient material is responsible for a number of features in HH 2, including the knot seen farthest from the outflow source. C1 Arizona State Univ, Dept Phys & Astron, Tempe, AZ 85287 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Hester, JJ (reprint author), Arizona State Univ, Dept Phys & Astron, Box 871504,Tyler Mall, Tempe, AZ 85287 USA. RI Stapelfeldt, Karl/D-2721-2012 NR 39 TC 48 Z9 49 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 JUL PY 1998 VL 116 IS 1 BP 372 EP 395 DI 10.1086/300396 PG 24 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 104KB UT WOS:000075012500033 ER PT J AU Jurgens, RF Rojas, F Slade, MA Standish, EM Chandler, JF AF Jurgens, RF Rojas, F Slade, MA Standish, EM Chandler, JF TI Mercury radar ranging data from 1987 to 1997 SO ASTRONOMICAL JOURNAL LA English DT Article DE ephemerides; planets and satellites : individual (Mercury) AB This is a brief report on radar ranging data to the subradar point on Mercury. This report makes available 10 years of such data, from 1987 to 1997. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Harvard Smithsonian Ctr Astrophys, Cambridge, MA 02138 USA. RP Jurgens, RF (reprint author), CALTECH, Jet Prop Lab, Mail Stop 238-420, Pasadena, CA 91109 USA. NR 2 TC 1 Z9 1 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 JUL PY 1998 VL 116 IS 1 BP 486 EP 488 DI 10.1086/300439 PG 3 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 104KB UT WOS:000075012500044 ER PT J AU Ward, WR Hahn, JM AF Ward, WR Hahn, JM TI Dynamics of the trans-Neptune region: Apsidal waves in the Kuiper belt SO ASTRONOMICAL JOURNAL LA English DT Article DE celestial mechanics, stellar dynamics; comets : general; minor planets, asteroids ID OUTER SOLAR-SYSTEM; SHORT-PERIOD COMETS; ORIGINAL DISTRIBUTION; SECULAR RESONANCES; SATURNS RINGS; STABLE ORBITS; TIME SCALES; DISK; ACCRETION; ASTEROIDS AB The role of apsidal density waves propagating in a primordial trans-Neptune disk (i.e., Kuiper belt) is investigated. It is shown that Neptune launches apsidal waves at its secular resonance near 40 AU that propagate radially outward, deeper into the particle disk. The wavelength of apsidal waves is considerably longer than waves that might be launched at Lindblad resonances, because the pattern speed, g(s), resulting from the apsis precesssion of Neptune is much slower than its mean motion, Omega(s). If the early Kuiper belt had a sufficient surface density, sigma, the disk's wave response to Neptune's secular perturbation would have spread the disturbing torque radially over a collective scale lambda(*) approximate to r(2 mu(d)Omega/\r dg/dr\)(1/2), where mu(d) = pi sigma r(2)/(1 M.) and Omega(r) and g(r) are respectively the mean motion and precession frequency of the disk particles. This results in considerably smaller eccentricities at resonance than had the disk particles been treated as noninteracting test particles. Consequently, particles are less apt to be excited into planet-crossing orbits, implying that the erosion timescales reported by earlier test-particle simulations of the Kuiper belt may be underestimated. It is also shown that the torque the disk exerts upon the planet (due to its gravitational attraction for the disk's spiral wave pattern) damps the planet's eccentricity and further inhibits the planet's ability to erode the disk. C1 Lunar & Planetary Inst, Houston, TX 77058 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Ward, WR (reprint author), Lunar & Planetary Inst, 3600 Bay Area Blvd, Houston, TX 77058 USA. NR 41 TC 29 Z9 29 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 JUL PY 1998 VL 116 IS 1 BP 489 EP 498 DI 10.1086/300398 PG 10 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 104KB UT WOS:000075012500045 ER PT J AU Ma, C Arias, EF Eubanks, TM Fey, AL Gontier, AM Jacobs, CS Sovers, OJ Archinal, BA Charlot, P AF Ma, C Arias, EF Eubanks, TM Fey, AL Gontier, AM Jacobs, CS Sovers, OJ Archinal, BA Charlot, P TI The International Celestial Reference Frame as realized by very long baseline interferometry SO ASTRONOMICAL JOURNAL LA English DT Article DE astrometry; catalogs; quasars : general; radio continuum; reference systems; techniques : interferometric ID RADIO REFERENCE FRAME; LINE INTERFEROMETRY; SYSTEM; EARTH; PRECESSION; GRADIENTS; NUTATION; GEODESY; DELAY; VLBI AB A quasi-inertial reference frame is defined based on the radio positions of 212 extragalactic sources distributed over the entire sky. The positional accuracy of these sources is better than about 1 mas in both coordinates. The radio positions are based upon a general solution for all applicable dual-frequency 2.3 and 8.4 GHz Mark III very long baseline interferometry data available through the middle of 1995, consisting of 1.6 million pairs of group delay and phase delay rate observations. Positions and details are also given for an additional 396 objects that either need further observation or are currently unsuitable for the definition of a high-accuracy reference frame. The final orientation of the frame axes has been obtained by a rotation of the positions into the system of the International Celestial Reference System and is consistent with the FK5 J2000.0 optical system, within the limits of the link accuracy. The resulting International Celestial Reference Frame has been adopted by the International Astronomical Union as the fundamental celestial reference frame, replacing the FK5 optical frame as of 1998 January 1. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Observ Astron La Plata, RA-1900 La Plata, Argentina. Observ Naval Buenos Aires, Buenos Aires, DF, Argentina. USN Observ, Washington, DC 20392 USA. Observ Paris, CNRS, URA 1125, F-75014 Paris, France. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Ma, C (reprint author), NASA, Goddard Space Flight Ctr, Code 926, Greenbelt, MD 20771 USA. RI Ma, Chopo/D-4751-2012; OI Eubanks, Thomas Marshall/0000-0001-9543-0414 NR 42 TC 443 Z9 450 U1 2 U2 6 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 JUL PY 1998 VL 116 IS 1 BP 516 EP 546 DI 10.1086/300408 PG 31 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 104KB UT WOS:000075012500048 ER PT J AU Grillmair, CJ Faber, SM Lauer, TR Hester, JJ Lynds, CR O'Neil, EJ Scowen, PA AF Grillmair, CJ Faber, SM Lauer, TR Hester, JJ Lynds, CR O'Neil, EJ Scowen, PA TI The nuclear region of M51 imaged with the HST Planetary Camera (vol 113, pg 225, 1997) SO ASTRONOMICAL JOURNAL LA English DT Correction C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. UCO, Lick Observ, Santa Cruz, CA USA. Kitt Peak Natl Observ, Tucson, AZ 85726 USA. Arizona State Univ, Dept Phys & Astron, Tempe, AZ 85287 USA. RP Grillmair, CJ (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 1 TC 1 Z9 1 U1 0 U2 1 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 JUL PY 1998 VL 116 IS 1 BP 547 EP 547 DI 10.1086/300391 PG 1 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 104KB UT WOS:000075012500049 ER PT J AU Mayer-Hasselwander, HA Bertsch, DL Dingus, BL Eckart, A Esposito, JA Genzel, R Hartman, RC Hunter, SD Kanbach, G Kniffen, DA Lin, YC Michelson, PF Mucke, A von Montigny, C Mukherjee, R Nolan, PL Pohl, M Reimer, O Schneid, EJ Sreekumar, P Thompson, DJ AF Mayer-Hasselwander, HA Bertsch, DL Dingus, BL Eckart, A Esposito, JA Genzel, R Hartman, RC Hunter, SD Kanbach, G Kniffen, DA Lin, YC Michelson, PF Mucke, A von Montigny, C Mukherjee, R Nolan, PL Pohl, M Reimer, O Schneid, EJ Sreekumar, P Thompson, DJ TI High-energy gamma-ray emission from the Galactic Center SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE ISM : clouds; ISM : general; Galaxy : center; gamma rays : observations ID SGR-A-ASTERISK; ACCRETING BLACK-HOLE; DARK MATTER; SAGITTARIUS-A; MOLECULAR GAS; GALAXY; SPECTRUM; DEFICIT; DENSITY; EGRET AB The EGRET instrument on the Compton Gamma-Ray Observatory has observed the Galactic Center (GC) region with good coverage at a number of epochs. A strong excess of emission is observed, peaking at energies > 500 MeV in an error circle of 0.2 degree radius including the position l = 0 degrees and b = 0 degrees. The close coincidence of this excess with the GC direction and the fact that it is the strongest emission maximum within 15 degrees from the GC is taken as compelling evidence for the source's location in the GC region. The history of the emission intensity, observed over 5 years, leaves room for possible time variation; however, it does not provide evidence. The angular extent of the excess appears only marginally compatible with the signature expected for a single compact object. The emission therefore may stem from one or more compact objects or may originate from diffuse interactions within 85 pc from the center of the Galaxy at 8.5 kpc distance. The spatial distribution of the emission does not correlate with the details of the CO-line surveys. Thus, in spite of the existence of a strong emission peak, earlier conclusions based on an apparent 'gamma-ray deficit', postulating the masses of the 'wide-line' clouds in the GC area to be an order of magnitude lower than indicated by naive CO interpretation, are supported. However, the total gas mass in the Nuclear Bulge (NB) derived from the gamma-ray emission is found to be in agreement with the mass which in recent studies has been derived from molecular-line and FIR surveys. The gamma-ray emission spectrum is peculiar and different from the spectrum of the large-scale galactic diffuse emission. A diffuse emission scenario requires an enhanced and peculiar Cosmic Ray (CR) spectrum as suggested for the electrons in the 'Radio Arc'. A compact sources model hints at an origin in pulsars. While the spectrum suggests middle-aged pulsars like Vela, too many are required to produce the observed flux. The only detected very young pulsar, the Crab pulsar, has an incompatible spectrum. However, it is not proven that the Crab spectrum is characteristic for all young pulsars: thus, a single or a few very young pulsars (at the GC not detectable in radio emission), provided their gamma-ray emission is larger than that of the Crab pulsar by a factor of 13, are likely candidates. Alternatively, more exotic scenarios, related to the postulated central black hole or dark matter (neutralino) annihilation, may be invoked. C1 Max Planck Inst Extraterr Phys, D-85748 Garching, Germany. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Utah, Salt Lake City, UT 84112 USA. Hampden Sydney Coll, Dept Phys & Astron, Hampden Sydney, VA 23943 USA. Stanford Univ, Dept Phys, Stanford, CA 94305 USA. Stanford Univ, WW Hansen Expt Phys Lab, Stanford, CA 94305 USA. Landessternwarte Konigstuhl, D-69117 Heidelberg, Germany. Columbia Univ, Columbia Astrophys Lab, New York, NY 10027 USA. Columbia Univ Barnard Coll, New York, NY 10027 USA. Danish Space Res Inst, DK-2100 Copenhagen O, Denmark. Northrop Grumman Corp, Bethpage, NY 11714 USA. RP Mayer-Hasselwander, HA (reprint author), Max Planck Inst Extraterr Phys, D-85748 Garching, Germany. EM HRM@MPE.MPG.DE RI Nolan, Patrick/A-5582-2009; Hunter, Stanley/D-2942-2012; Thompson, David/D-2939-2012; Reimer, Olaf/A-3117-2013 OI Thompson, David/0000-0001-5217-9135; Reimer, Olaf/0000-0001-6953-1385 NR 62 TC 166 Z9 166 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 JUL 1 PY 1998 VL 335 IS 1 BP 161 EP 172 PG 12 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZZ318 UT WOS:000074717400023 ER PT J AU Queloz, D Allain, S Mermilliod, JC Bouvier, J Mayor, M AF Queloz, D Allain, S Mermilliod, JC Bouvier, J Mayor, M TI The rotational velocity of low-mass stars in the Pleiades cluster SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE stars : activity; stars : evolution; stars : pre-main sequence; Galaxy : open clusters and associations : Pleiades ID MAIN-SEQUENCE STARS; SOLAR-TYPE STARS; X-RAY-EMISSION; K-DWARFS; CONVECTION; EVOLUTION; BRAKING AB We present new v sin i measurements for 235 low-mass stars in the Pleiades. The differential rotational broadening has been resolved for all the stars in our sample. These results, combined with previously published measurements, provide a complete and unbiased rotation data set for stars in the mass range from 0.6 to 1.2M(.). Applying a numerical inversion technique on the v sin i distributions, we derive the distributions of equatorial velocities for low-mass Pleiades members. We find that half of the Pleiades dwarfs with a mass between 0.6 to 1 M-. have rotation rates lower than 10 km s(-1). Comparison of the rotational distributions of low-mass members between IC 2602/2391 (approximate to 35 Myr) and the Pleiades (approximate to 100 Myr) suggests that G dwarfs behave like solid-bodies and follow Skumanich's law during this time span. However, comparison between Pleiades and older clusters -M34 (approximate to 200 Myr) and Hyades (approximate to 600 Myr)- indicates that the braking of slow rotators on the early main sequence is weaker than predicted by an asymptotical Skumanich's law. This strongly supports the view that angular momentum tapped in the radiative core of slow rotators on the zero age main sequence (ZAMS) resurfaces into the convective envelope between Pleiades and Hyades age. For the G-dwarfs, we derive a characteristic coupling time scale between the core and the envelope of about 100-200 Myr, which accounts for the observed evolution of surface rotation from the ZAMS to the Hyades. The relationship between rotation and coronal activity in the Pleiades is in agreement with previous observations in other clusters and field stars. We show that the Rossby diagram provides an excellent description of the X-ray activity for all stars in the mass domain studied. The Pleiades data for slow and moderate rotators fills the gap between the X-ray-rotation correlation found for slow rotators and the X-ray "saturation plateau" observed for young fast rotators. The transition between increasing X-ray flux with rotation and X-ray saturation is observed at log(P/tau) = 0.8 +/- 0.1. These results strengthen the hypothesis that the "saturation" of the angular momentum loss process depends on the stellar mass. C1 Observ Geneva, CH-1290 Sauverny, Switzerland. Univ Grenoble 1, Observ Grenoble, Astrophys Lab, F-38041 Grenoble 09, France. Univ Lausanne, Inst Astron, CH-1290 Chavannes Bois, Switzerland. RP Queloz, D (reprint author), CALTECH, Jet Prop Lab, Mail Stop 306-473,4800 Oak Grove Dr, Pasadena, CA 91109 USA. EM Didier.Queloz@obs.unige.ch NR 63 TC 147 Z9 148 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 JUL 1 PY 1998 VL 335 IS 1 BP 183 EP 198 PG 16 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZZ318 UT WOS:000074717400026 ER PT J AU Aulanier, G Demoulin, P van Driel-Gesztelyi, L Mein, P DeForest, C AF Aulanier, G Demoulin, P van Driel-Gesztelyi, L Mein, P DeForest, C TI 3-D magnetic configurations supporting prominences - II. The lateral feet as a perturbation of a twisted flux-tube SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE magnetic fields; Sun : chromosphere; Sun : magnetic fields; Sun : prominences; Sun : filaments ID QUIESCENT PROMINENCES; SOLAR PROMINENCES; ELECTRON-DENSITY; FINE-STRUCTURE; CURRENT SHEETS; FIELD VECTOR; RECONNECTION; FLARES; MODEL; FILAMENTS AB In a previous paper we have shown that a twisted flux-tube is the most probable magnetic configuration supporting prominences. The model interprets many observations in a natural way (in particular the magnetic measurements in prominences and the chirality properties). Moreover, prominence feet appear as a direct consequence of the parasitic polarities present in the filament channel. Here we investigate further the link between feet and parasitic polarities by modelling explicitly these polarities. We show that the prominence lateral feet appear naturally, above secondary photospheric inversion lines and we describe the morphological change of feet as parasitic polarities evolve. This approach is applied to an observed filament in Her with the MSDP on the German VTT (Tenerife) where SOHO/MDI magnetograms are available. We show that the shape of the prominence is defined by the distribution of the dips in the computed magnetic configuration. Then we analyse the topology of the magnetic field using the quasi-separatrix layers (QSLs) method. We describe the basic changes in the topology as the parasitic polarities evolve, in particular how the configuration pass from an OX to an OF topology. We find a correspondance between the computed QSLs and some of the chromospheric brightenings, observed around the feet of filaments in the y line (Ca II, 8542 Angstrom). It confirms the deduced magnetic configuration and shows that energy release is present at a low level in the complex topology of the filament configuration. C1 Observ Paris, Meudon Sect, DASOP, URA 2080 CNRS, F-95195 Meudon, France. Konkoly Observ Budapest, H-1525 Budapest, Hungary. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Observ Paris, Meudon Sect, DASOP, URA 2080 CNRS, F-95195 Meudon, France. OI Demoulin, Pascal/0000-0001-8215-6532 NR 44 TC 76 Z9 76 U1 1 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 1432-0746 J9 ASTRON ASTROPHYS JI Astron. Astrophys. PD JUL 1 PY 1998 VL 335 IS 1 BP 309 EP 322 PG 14 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZZ318 UT WOS:000074717400043 ER PT J AU Ratkiewicz, R Barnes, A Molvik, GA Spreiter, JR Stahara, SS Vinokur, M Venkateswaran, S AF Ratkiewicz, R Barnes, A Molvik, GA Spreiter, JR Stahara, SS Vinokur, M Venkateswaran, S TI Effect of varying strength and orientation of local interstellar magnetic field on configuration of exterior heliosphere: 3D MHD simulations SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE solar wind; ISM : magnetic fields; magnetic fields; MHD; plasmas; shock waves ID SOLAR-WIND; FLOW DOWNSTREAM; TERMINAL SHOCK; HELIOPAUSE AB The aim of this paper is to present the effects of varying magnitude and orientation of the local interstellar magnetic field on the heliospheric boundary region (the region between the termination shock and the bow shock containing the heliopause). Other effects such as interstellar neutrals, cosmic rays and the asymmetry of the solar wind caused by its heliolatitude dependence are disregarded. We calculate the shape and structure of the heliospheric boundary region for different interstellar Alfvenic Mach numbers and various inclination angles between Very Local InterStellar Medium (VLISM) velocity and magnetic field vectors using a fully three-dimensional MHD computational analysis. The new results show the asymmetry of this region for inclination angles 0 degrees < alpha < 90 degrees and are in agreement with the Newtonian approximation theory (Fahr et al. 1986, 1988) concerning trends in the heliopause orientation and location. Unlike the NA model which only qualitatively indicates the effects of the VLISM magnetic field on the heliospheric boundary region the present 3D MHD calculations reveal fully the nature of these effects by capturing all discontinuities including the termination shock, heliopause and bow shock. The numerical scheme employed in this study is fully implicit and conservative, using a Poe-type Riemann solver in a generalized coordinate system. C1 Space Res Ctr, PL-00716 Warsaw, Poland. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. NAI, Woodbridge, CA 95258 USA. Stanford Univ, Stanford, CA 94305 USA. RMA Aerosp Inc, Mt View, CA 94043 USA. RP Ratkiewicz, R (reprint author), Space Res Ctr, Bartycka 18A, PL-00716 Warsaw, Poland. NR 34 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 JUL 1 PY 1998 VL 335 IS 1 BP 363 EP 369 PG 7 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZZ318 UT WOS:000074717400048 ER PT J AU Moehler, S Landsman, W Napiwotzki, R AF Moehler, S Landsman, W Napiwotzki, R TI Hot UV bright stars in globular clusters SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE stars : Post-AGB; globular clusters : individual : NGC 2808, NGC 6121, NGC 6723, NGC 6752; ultraviolet : stars ID PHOTOMETRY; M4; SPECTROSCOPY; PARAMETERS; GIANT AB We have obtained medium-resolution spectra of seven UV-bright stars discovered on images of four southern globular clusters obtained with the Ultraviolet Imaging Telescope (UIT). Effective temperatures, surface gravities and helium abundances are derived from LTE and non-LTE model atmosphere fits. Three of the stars have sdO spectra, including M4-Y453 (T-eff = 58800 K, log g = 5.15), NGC 6723-III60 (T-eff = 40600 K, log g = 4.46) and NGC 6752-B2004 (T-eff = 37000 K, log g = 5.25). All seven stars lie along either post-extended horizontal branch (EHB) or post-early AGE evolutionary tracks. The post-early AGE stars show solar helium abundances, while the post-EHB stars are helium deficient, similar to their EHB progenitors. C1 Univ Erlangen Nurnberg, Astron Inst, Dr Remeis Sternwarte, D-96049 Bamberg, Germany. Space Telescope Sci Inst, Baltimore, MD 21218 USA. NASA, GSFC, Raytheon STX, Greenbelt, MD 20770 USA. RP Univ Erlangen Nurnberg, Astron Inst, Dr Remeis Sternwarte, Sternwartstr 7, D-96049 Bamberg, Germany. NR 41 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 1432-0746 J9 ASTRON ASTROPHYS JI Astron. Astrophys. PD JUL PY 1998 VL 335 IS 2 BP 510 EP 516 PG 7 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 101MX UT WOS:000074873700018 ER PT J AU Haberl, F Angelini, L Motch, C AF Haberl, F Angelini, L Motch, C TI RXTE observations of RX J0146.9+6121: a new X-ray outburst of the Be/X-ray pulsar SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE stars : emission-line, Be; stars : individual : RX J0146.9+6121; stars : neutron; X-rays : stars ID SPECTRUM; PERSEI AB RXTE observations of the Be/X-ray binary pulsar RXJ0146.9+6121 in July 1997 revealed the begin of a new Xray outburst, the second observed after its discovery in August 1984 by EXOSAT. The flux increased by nearly a factor of five within one week reaching 3.2 10(-10) erg cm(-2) s(-1). The corresponding X-ray luminosity for a distance of 2.5 kpc is an order of magnitude brighter than the level observed between 1994 and 1996 by ASCA and ROSAT. The neutron star spin period was measured to 1404.2 +/- 1.2 s indicating the start of a spin-up phase as expected for increased matter accretion onto the neutron star during outburst. A combined spectral analysis of ASCA and RXTE data revealed an exponential cutoff in the power-law spectrum at 4 keV. C1 Max Planck Inst Extraterr Phys, D-85748 Garching, Germany. NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. Univ Space Res Assoc, F-67000 Strasbourg, France. Univ Strasbourg 1, Astron Observ, F-67000 Strasbourg, France. RP Haberl, F (reprint author), Max Planck Inst Extraterr Phys, Giessenbachstr, D-85748 Garching, Germany. EM fwh@mpe-garching.mpg.de NR 11 TC 14 Z9 14 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 JUL PY 1998 VL 335 IS 2 BP 587 EP 590 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 101MX UT WOS:000074873700029 ER PT J AU Fink, U Hicks, MD Fevig, RA Collins, J AF Fink, U Hicks, MD Fevig, RA Collins, J TI Spectroscopy of 46P/Wirtanen during its 1997 apparition SO ASTRONOMY & ASTROPHYSICS LA English DT Letter DE comet spectrophotometry; Wirtanen; production rates; dust ID COMET; HALLEY AB Comet 46P/Wirtanen was observed during five observing runs around its perihelion passage from 1997 January 28 to June 02. The spectra acquired extend from 5200 to 10000 Angstrom at spectral resolutions of 12 Angstrom and 18 Angstrom. A total of 16 spectral averages, each comprising about 30 minutes of integration time, were obtained. The production rate of H2O near perihelion averaged 2.7 x 10(28) molecules/sec. The continuum strength Af rho was 129 cm while the production rates respectively of the parents of C-2, CN and NH2 were 5.7, 3.2 and 5.6 x 10(25) molecules/sec. Our estimated error for all these quantities is 20%. The production rate ratios relative to water can be compared to our larger sample of comets (Fink & Hicks 1996) with the following results: the C-2 and CN abundance ratios are slightly below average but the NH2 ratio is definitely enhanced putting P/Wirtanen among the top few comets in that category. Its Af rho/H2O ratio is very close but slightly below the median of our comet sample. Reduced to 1 AU P/Wirtanen ranks near the 40% level of our ordered list of the H2O production rates of 20 comets. If the production rate of water is combined with P/Wirtanen's estimated radius of 0.6 km, it implies that virtually the whole surface area of the comet is active. Our measured Af rho values combined with those obtained by photometry yield a fairly tight heliocentric activity dependence of r(-3.8) with no pre-post perihelion asymmetry. This agrees well with the general heliocentric brightness dependence of Jupiter family comets. Taking all this data together, P/Wirtanen appears to be a rather typical member of the Jupiter family of comets. C1 Univ Arizona, Lunar & Planetary Lab, Tucson, AZ 85721 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Fink, U (reprint author), Univ Arizona, Lunar & Planetary Lab, Tucson, AZ 85721 USA. EM uwefink@lpl.arizona.edu NR 22 TC 23 Z9 23 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 JUL PY 1998 VL 335 IS 2 BP L37 EP L45 PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 101MX UT WOS:000074873700003 ER PT J AU Shearer, A Golden, A Harfst, S Butler, R Redfern, RM O'Sullivan, CMM Neustroev, VV Plokhotnichenko, VL Cullum, M Danks, A AF Shearer, A Golden, A Harfst, S Butler, R Redfern, RM O'Sullivan, CMM Neustroev, VV Plokhotnichenko, VL Cullum, M Danks, A TI Possible pulsed optical emission from Geminga SO ASTRONOMY & ASTROPHYSICS LA English DT Letter DE pulsars : individual (Geminga) techniques : 2-d photon-counting detectors ID ENERGY GAMMA-RADIATION AB We present optical data which suggests that G ", the optical counterpart of the gamma-ray pulsar Geminga, possibly pulses in B with a period of 0.237 seconds. The similarity between the optical pulse shape and the gamma-ray light curve indicates that a large fraction of the optical emission is non-thermal in origin - contrary to recent suggestions based upon the total optical flux. The derived magnitude of the pulsed emission is m(B) = 26.0 +/- 0.4. Whilst it is not possible to give an accurate figure for the pulsed fraction (due to variations in the sky background) we can give an 1 sigma upper limit of m(B) approximate to 27 for the unpulsed fraction. C1 Natl Univ Ireland Univ Coll Galway, Ctr Informat Technol, Galway, Ireland. Natl Univ Ireland Univ Coll Galway, Dept Phys, Galway, Ireland. SAO, Karacajevo Cerkesija, Russia. European So Observ, D-8046 Garching, Germany. Goddard Space Flight Ctr, STX, Greenbank, MD USA. RP Natl Univ Ireland Univ Coll Galway, Ctr Informat Technol, Galway, Ireland. EM andy.shearer@ucg.ie RI Neustroev, Vitaly/B-6351-2008; Butler, Ray/A-6705-2012; Shearer, Andy/N-7609-2014 OI Butler, Ray/0000-0002-8441-7596; Shearer, Andy/0000-0001-7903-0074 NR 35 TC 37 Z9 37 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 1432-0746 J9 ASTRON ASTROPHYS JI Astron. Astrophys. PD JUL 1 PY 1998 VL 335 IS 1 BP L21 EP L24 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZZ318 UT WOS:000074717400006 ER PT J AU Hughes, SMG Han, MS Hoessel, J Freedman, WL Kennicutt, RC Mould, JR Saha, A Stetson, PB Madore, BF Silberman, NA Harding, P Ferrarese, L Ford, H Gibson, BK Graham, JA Hill, R Huchra, J Illingworth, GD Phelps, R Sakai, S AF Hughes, SMG Han, MS Hoessel, J Freedman, WL Kennicutt, RC Mould, JR Saha, A Stetson, PB Madore, BF Silberman, NA Harding, P Ferrarese, L Ford, H Gibson, BK Graham, JA Hill, R Huchra, J Illingworth, GD Phelps, R Sakai, S TI The Hubble Space Telescope Extragalactic Distance Scale Key Project. X. The Cepheid distance to NGC 7331 SO ASTROPHYSICAL JOURNAL LA English DT Article DE Cepheids; galaxies : distances and redshifts; galaxies : individual (NGC 7331); galaxies : photometry ID H-II REGIONS; PERIOD-LUMINOSITY RELATION; VELOCITY-WIDTH RELATION; SPIRAL GALAXIES; METALLICITY DEPENDENCE; MAGELLANIC CLOUD; NEARBY GALAXIES; CCD PHOTOMETRY; DISCOVERY; CALIBRATION AB The distance to NGC 7331 has been derived from Cepheid variables observed with the Hubble Space Telescope (HST) WFPC2, as part of the Extragalactic Distance Scale Key Project. Multiepoch exposures in F555W (similar to V) and F814W (similar to I), with photometry derived independently from DoPHOT and DAOPHOT/ALLFRAME programs, were used to detect a total of 13 reliable Cepheids, with periods between 11 and 42 days. The relative distance moduli between NGC 7331 and the LMC, derived from the V and I magnitudes, imply an extinction to NGC 7331 of A(v) = 0.47 +/- 0.15 mag and an extinction-corrected distance modulus to NGC 7331 of 30.89 +/- 0.14 (random), equivalent to a distance of 15.1(-0.9)(+1.0) Mpc. There are additional systematic uncertainties in the distance modulus of +/-0.12 mag resulting from the calibration of the Cepheid period-luminosity relation and a systematic offset of +0.05 +/- 0.04 mag if the metallicity correction inferred from the M101 results of Kennicutt et al. are applied. C1 Royal Greenwich Observ, Cambridge CB3 0EZ, England. Univ Wisconsin, Madison, WI 53706 USA. Carnegie Inst Washington Observ, Pasadena, CA 91101 USA. Univ Arizona, Steward Observ, Tucson, AZ 85721 USA. Australian Natl Univ, Mt Stromlo & Siding Spring Observ, Canberra, ACT, Australia. Natl Opt Astron Observ, Tucson, AZ 85726 USA. Dominion Astrophys Observ, Victoria, BC V8X 4M6, Canada. CALTECH, Ctr Infrared Proc & Anal, NASA, Extragalact Database, Pasadena, CA 91125 USA. CALTECH, Palomar Observ, Pasadena, CA 91125 USA. Johns Hopkins Univ, Dept Phys & Astron, Baltimore, MD 21218 USA. Carnegie Inst Washington, Dept Terr Magnetism, Washington, DC 20015 USA. NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, Greenbelt, MD 20771 USA. Harvard Smithsonian Ctr Astrophys, Cambridge, MA 02138 USA. Univ Calif Santa Cruz, Lick Observ, Santa Cruz, CA 95064 USA. CALTECH, Jet Prop Lab, Ctr Infrared Proc & Anal, Pasadena, CA 91125 USA. RP Hughes, SMG (reprint author), Royal Greenwich Observ, Madingley Rd, Cambridge CB3 0EZ, England. EM hughes@ast.cam.ac.uk; mhan@malachi.gsfc.nasa.gov; hoessel@uwfpc.astro.wisc.edu; wendy@ociw.edu; robk@as.arizona.edu; jrm@merlin.anu.edu.au; saha@noao.edu; peter.stetson@hia.nrc.ca; barry@ipac.caltech.edu; nancys@ipac.caltech.edu; harding@as.arizona.edu; lff@astro.caltech.edu; ford@stsci.edu; gibson@mso.anu.edu.au; graham@jag.ciw.edu; hill@esa.nascom.nasa.gov; huchra@cfa.harvard.edu; gdi@ucolick.org; phelps@ociw.edu; shoko@ipac.caltech.edu RI Gibson, Brad/M-3592-2015 OI Gibson, Brad/0000-0003-4446-3130 NR 73 TC 53 Z9 53 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5801 S ELLIS AVENUE, CHICAGO, IL 60637 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD JUL 1 PY 1998 VL 501 IS 1 BP 32 EP 53 DI 10.1086/305808 PN 1 PG 22 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZZ946 UT WOS:000074785300004 ER PT J AU Arnaud, KA Mushotzky, RF AF Arnaud, KA Mushotzky, RF TI A dusty X-ray absorber in the Perseus Cluster? SO ASTROPHYSICAL JOURNAL LA English DT Article DE cooling flows; galaxies : clusters : individual (Perseus); X-rays : galaxies ID COOLING FLOWS; CROSS-SECTIONS; EMITTING GAS; COLD CLOUDS; EMISSION; NGC-1275; ABUNDANCES; DISCOVERY; TELESCOPE; GALAXIES AB We have analyzed 0.35-7.5 keV X-ray spectra of the center of the Perseus Cluster collected using the Broad Band X-Ray Telescope (BBXRT) on the Astro-l mission. These spectra are particularly useful for examining the nature of the X-ray absorber in cooling flows because of BBXRT's sensitivity between 0.35 and 1.0 keV. We confirm that there is X-ray absorption above that expected from gas in our own Galaxy. Furthermore, the absorbing medium is deficient in helium. However, the energy of the oxygen K edge is consistent with neutral material (at the redshift of the cluster), yet is not consistent with any ionized state of oxygen. It is not possible to completely ionize helium and have oxygen neutral, so the apparent helium deficiency cannot be due to ionization. We propose that the X-ray absorption is due to dust grains that have condensed out of a medium in which helium remains ionized. This model satisfies all the observational constraints, but it is difficult to understand theoretically. C1 NASA, High Energy Phys Lab, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Maryland, Dept Astron, College Pk, MD 20742 USA. RP Arnaud, KA (reprint author), NASA, High Energy Phys Lab, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. NR 45 TC 17 Z9 17 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5801 S ELLIS AVENUE, CHICAGO, IL 60637 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD JUL 1 PY 1998 VL 501 IS 1 BP 119 EP 125 DI 10.1086/305801 PN 1 PG 7 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZZ946 UT WOS:000074785300011 ER PT J AU Brainerd, JJ Preece, RD Briggs, MS Pendleton, GN Paciesas, WS AF Brainerd, JJ Preece, RD Briggs, MS Pendleton, GN Paciesas, WS TI Using BATSE observations to test the Compton attenuation spectral theory of cosmological gamma-ray bursts SO ASTROPHYSICAL JOURNAL LA English DT Article DE gamma-rays : bursts; methods : statistical; radiation mechanisms : nonthermal; X-rays : bursts ID HIGH-ENERGY EMISSION; EVOLUTION; MODEL AB The Compton attenuation theory provides an explanation for the characteristic spectral energy possessed by gamma-ray bursts. It makes several predictions that can be tested with current data, two of which are the characteristic shape of the spectrum and the presence of an X-ray excess. We have performed these tests by fitting the Compton attenuation spectral model to 25 gamma-ray bursts from the BATSE 3B catalog. Minimizing chi(2) with four free parameters, we find values of chi(2) with the same level of significance as the values found for the best-fitting four-parameter models of previous studies. The X-ray upturn makes the chi(2) for the Compton attenuation spectrum smaller than for a comparison spectrum that is a power law over the X-ray energy band. The values of the free parameters derived from the model fits are physically meaningful, and each describes the spectrum over a different frequency band. The absence of a correlation between z and the energy in the comoving frame of the peak of the nu F-nu curve provides support for the model's physical validity. A model tit to a gamma-ray burst's spectrum between 5 and 100 keV gives the redshift of the source; we typically find values of z between 1 and 5. The spread in z are consistent with the spread of redshifts for a broad luminosity function, but the large values require source evolution. Additional tests of the theory are available with current experiments and will be possible with several planned and proposed experiments. C1 NASA, George C Marshall Space Flight Ctr, Space Sci Lab, Huntsville, AL 35812 USA. RP Brainerd, JJ (reprint author), NASA, George C Marshall Space Flight Ctr, Space Sci Lab, ES-84, Huntsville, AL 35812 USA. OI Preece, Robert/0000-0003-1626-7335 NR 36 TC 18 Z9 18 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5801 S ELLIS AVENUE, CHICAGO, IL 60637 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD JUL 1 PY 1998 VL 501 IS 1 BP 325 EP 338 DI 10.1086/305786 PN 1 PG 14 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZZ946 UT WOS:000074785300027 ER PT J AU Falconer, DA Moore, RL Porter, JG Hathaway, DH AF Falconer, DA Moore, RL Porter, JG Hathaway, DH TI Network coronal bright points: Coronal heating concentrations found in the solar magnetic network SO ASTROPHYSICAL JOURNAL LA English DT Article DE Sun : corona; Sun : magnetic fields; Sun : UV radiation ID FIELDS AB We examine the magnetic origins of coronal heating in quiet regions by combining SOHO/EIT Fe XII coronal images and Kitt Peak magnetograms. Spatial filtering of the coronal images shows a network of enhanced structures on the scale of the magnetic network in quiet regions. Superposition of the filtered coronal images on maps of the magnetic network extracted from the magnetograms shows that the coronal network does indeed trace and stem from the magnetic network. Network coronal bright points, the brightest features in the network lanes, are found to have a highly significant coincidence with polarity dividing lines (neutral lines) in the network and are often at the feet of enhanced coronal structures that stem from the network and reach out over the cell interiors. These results indicate that, similar to the close linkage of neutral-line core fields with coronal heating in active regions (shown in previous work), low-lying core fields encasing neutral lines in the magnetic network often drive noticeable coronal heating both within themselves (the network coronal bright points) and on more extended field lines rooted around them. This behavior favors the possibility that active core fields in the network are the main drivers of the heating of the bulk of the quiet corona, on scales much larger than the network lanes and cells. C1 NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. RP Falconer, DA (reprint author), NASA, George C Marshall Space Flight Ctr, Code ES82, Huntsville, AL 35812 USA. NR 13 TC 36 Z9 37 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5801 S ELLIS AVENUE, CHICAGO, IL 60637 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD JUL 1 PY 1998 VL 501 IS 1 BP 386 EP 396 DI 10.1086/305805 PN 1 PG 11 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZZ946 UT WOS:000074785300032 ER PT J AU Harris, MJ Teegarden, BJ Cline, TL Gehrels, N Palmer, DM Ramaty, R Seifert, H AF Harris, MJ Teegarden, BJ Cline, TL Gehrels, N Palmer, DM Ramaty, R Seifert, H TI Transient Gamma-Ray Spectrometer measurements of the positron annihilation spectrum from the Galactic center SO ASTROPHYSICAL JOURNAL LA English DT Article DE Galaxy : center; gamma rays : observations ID 511 KEV LINE; FRACTION AB We have obtained spectra of the Galactic center at energies of 400-600 keV from high-resolution data acquired by the Transient Gamma-Ray Spectrometer Ge detector on board the WIND mission during 1995-1997. The data were obtained using an on-board occulter and are relatively free from systematics and backgrounds. Analysis of the spectra reveals a well-resolved electron-positron annihilation line at 511 keV and the associated continuum due to annihilation via positronium formation. Measurements of the line width and the continuum-to-line ratio allow some constraints to be placed on the interstellar sites where annihilation occurs. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Space Res Assoc, Greenbelt, MD USA. RP Harris, MJ (reprint author), NASA, Goddard Space Flight Ctr, Code 661, Greenbelt, MD 20771 USA. EM harris@tgrs2.gsfc.nasa.gov RI Gehrels, Neil/D-2971-2012 NR 17 TC 37 Z9 37 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 JUL 1 PY 1998 VL 501 IS 1 BP L55 EP L58 DI 10.1086/311429 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZZ948 UT WOS:000074785500013 ER PT J AU Lacy, JH Faraji, H Sandford, SA Allamandola, LJ AF Lacy, JH Faraji, H Sandford, SA Allamandola, LJ TI Unraveling the 10 micron "silicate" feature of protostars: The detection of frozen interstellar ammonia SO ASTROPHYSICAL JOURNAL LA English DT Article DE comets : general; ISM : abundances; ISM : clouds; ISM : molecules; infrared : ISM : lines and bands ID ABSORPTION FEATURES; INFRARED-SPECTROSCOPY; MONOCEROS R2/IRS-3; MOLECULAR CLOUDS; SPECTRA; BAND; ICES; ABUNDANCE; METHANOL AB We present infrared spectra of four embedded protostars in the 750-1230 cm(-1) (13.3-8.1 mu m) range. For NGC 7538 IRS 9, a new band is reported at 1110 cm(-1) (9.01 mu m), and several others may be present near 785, 820, 900, 1030, and 1075 cm(-1) (12.7, 12.2, 11.1, 9.71, and 9.30 mu m). The band at 1110 cm(-1) is attributed to frozen NH3. Its position and width imply that the NH3 is frozen in a polar, H2O-rich interstellar ice component. The NH3/H2O ice ratio inferred for NGC 7538 IRS 9 is 0.1, making NH3 as important a component as CH3OH and CO2 in the polar ices along this line of sight. At these concentrations, hydrogen bonding between the NH3 and H2O can account for much of the enigmatic low-frequency wing on the 3240 cm(-1) (3.09 mu m) H2O interstellar ice band. The strength of the implied NH3 deformation fundamental at 1624 cm(-1) (6.158 mu m) can also account for the absorption at this position reported by ISO. C1 Univ Texas, Dept Astron, Austin, TX 78712 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Univ Texas, Dept Astron, RLM 15308, Austin, TX 78712 USA. EM ssandford@maii.arc.nasa.gov NR 40 TC 66 Z9 66 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 JUL 1 PY 1998 VL 501 IS 1 BP L105 EP L109 DI 10.1086/311452 PN 2 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZZ948 UT WOS:000074785500023 PM 11542938 ER PT J AU Mannucci, F Thompson, D Beckwith, SVW Williger, GM AF Mannucci, F Thompson, D Beckwith, SVW Williger, GM TI Infrared emission-line galaxies associated with damped Ly alpha and strong metal absorber redshifts SO ASTROPHYSICAL JOURNAL LA English DT Article DE cosmology : observations; early universe; galaxies : formation; infrared : galaxies ID ABSORPTION SYSTEMS; STAR FORMATION; OBJECT; IDENTIFICATION AB Eighteen candidates for emission-line galaxies were discovered in a narrowband infrared survey that targeted the redshifts of damped Ly alpha or metal lines in the spectra of quasars. The presence of emission lines is inferred from the photometric magnitudes in narrowband and broadband interference filters, corresponding to H alpha at redshifts of 0.89 (six objects) and 2.4 (10 objects) and to [O II] lambda 3727 at a redshift of 2.3 (two objects). Most of the candidates are small, resolved objects that are compatible with galaxies at the redshifts of the damped Ly alpha absorbers. Because a similar survey, targeted at the redshifts of quasars themselves, uncovered only one emission-line galaxy in a larger volume, the results imply substantial clustering of young galaxies or a formation within filaments or sheets whose locations are indicated by the redshifts of strong Ly alpha line absorption along the lines of sight to more distant quasars. C1 CNR, Ctr Astron Infrarossa & Studio Mezzo Interstellar, Florence, Italy. Max Planck Inst Astron, D-69117 Heidelberg, Germany. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Mannucci, F (reprint author), CNR, Ctr Astron Infrarossa & Studio Mezzo Interstellar, Florence, Italy. EM filippo@arcetri.astro.it; djt@mpia-hd.mpg.de; svwb@mpia-hd.mpg.de; williger@tejut.gsfc.nasa.gov NR 33 TC 34 Z9 34 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5801 S ELLIS AVENUE, CHICAGO, IL 60637 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD JUL 1 PY 1998 VL 501 IS 1 BP L11 EP L15 DI 10.1086/311448 PN 2 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZZ948 UT WOS:000074785500003 ER PT J AU McKernan, B Yaqoob, T AF McKernan, B Yaqoob, T TI Occultation mapping of the central engine in the active galaxy MCG -6-30-15 SO ASTROPHYSICAL JOURNAL LA English DT Article DE accretion, accretion disks; black hole physics; galaxies : active; galaxies : individual (MCG -6-30-15); X-rays : galaxies ID MASSIVE BLACK-HOLE; X-RAY VARIABILITY; GALACTIC NUCLEI; POWER SPECTRUM; MCG-6-30-15; DISK; LUMINOSITY; AMPLITUDE; ASCA AB The colossal power output of active galactic nuclei (AGNs) is believed to be fueled by the accretion of matter onto a supermassive black hole. This central accreting region of AGNs has hitherto been spatially unresolved, and its structure therefore unknown. Here we propose that a previously reported "deep minimum" in the X-ray intensity of the AGN MCG -6-30-15 was due to a unique X-ray occultation event and that it probes structure of the central engine on scales smaller than 10(14) crn, or 1.4 x 10(-7) arcsec. This resolution is more than a factor of similar to 3 x 10(6) greater than is possible with current X-ray optics. The data are consistent with a bright central sourer surrounded by a less intense ring, which we identify with the inner edge of an accretion disk. These may be the first direct measurements of the spatial structure and geometry of the accreting black hole system in an active galaxy. We estimate a mass lower limit for sub-Eddington accretion of 3.1 x 10(5) M-.. If the ring of Xray emission is identified with the inner edge of an accretion disk, we get mass upper limits of 1.9 x 10(8) and 9.1 x 10(8) M-. for a nonrotating and maximally rotating black hole, respectively. We point out that our occultation interpretation is controversial in the sense that X-ray variability in AGNs is normally attributed to intrinsic physical changes in the X-ray emission region, such as disk or coronal instabilities. C1 Univ Leeds, Dept Phys & Astron, Leeds LS2 9JT, W Yorkshire, England. NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. RP McKernan, B (reprint author), Natl Univ Ireland Univ Coll Dublin, Dept Expt Phys, Dublin 4, Ireland. NR 26 TC 41 Z9 41 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5801 S ELLIS AVENUE, CHICAGO, IL 60637 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD JUL 1 PY 1998 VL 501 IS 1 BP L29 EP L32 DI 10.1086/311457 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZZ948 UT WOS:000074785500007 ER PT J AU Parise, RA Bohlin, RC Neff, SG O'Connell, RW Roberts, MS Maran, SP Smith, AM Stecher, TP AF Parise, RA Bohlin, RC Neff, SG O'Connell, RW Roberts, MS Maran, SP Smith, AM Stecher, TP TI Ultraviolet Imaging Telescope observations of the horizontal branch in M13 SO ASTROPHYSICAL JOURNAL LA English DT Article DE globular clusters : individual (M13); stars : horizontal-branch; ultraviolet : stars ID GLOBULAR-CLUSTERS; STARS; M3 AB Images of the globular cluster M13 were obtained with the Ultraviolet Imaging Telescope (UIT) during the Astro-2 Spacelab mission. A total of 488 stars are detected in the UIT B5 filter centered at 1620 Angstrom. Of an uncrowded sample of 247 stars, 232 are well correlated with ground-based Johnson V photometry, which was provided by K. Montgomery (1995, private communication). A color-magnitude diagram, constructed from the (m(1620) - V) color index and the m(1620) magnitude, shows a well-populated, blue horizontal branch extending to a temperature in excess of 35,000 K. A King plot of radial density distribution is satisfied by an exponential of index alpha = 3.0, which is consistent with Laget et al. Recent evolutionary models by Sweigart that include the effects of helium mixing into the hydrogen envelope of horizontal-branch stars, in addition to the latest canonical models, are considered when discussing the extreme blue horizontal-branch morphology. An offset toward a higher luminosity of stars near the zero-age horizontal branch in the 4.1 < log T-eff < 4.3 region is also discussed. C1 NASA, Goddard Space Flight Ctr, Comp Sci Corp, Greenbelt, MD 20771 USA. Space Telescope Sci Inst, Baltimore, MD 21218 USA. NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, Greenbelt, MD 20771 USA. Univ Virginia, Dept Astron, Charlottesville, VA 22903 USA. Natl Radio Astron Observ, Charlottesville, VA 22903 USA. NASA, Goddard Space Flight Ctr, Space Sci Directorate, Greenbelt, MD 20771 USA. RP Parise, RA (reprint author), NASA, Goddard Space Flight Ctr, Comp Sci Corp, Code 686 9, Greenbelt, MD 20771 USA. NR 30 TC 6 Z9 6 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 JUL 1 PY 1998 VL 501 IS 1 BP L67 EP L71 DI 10.1086/311432 PN 2 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZZ948 UT WOS:000074785500016 ER PT J AU Ptak, A Yaqoob, T Mushotzky, R Serlemitsos, P Griffiths, R AF Ptak, A Yaqoob, T Mushotzky, R Serlemitsos, P Griffiths, R TI X-ray variability as a probe of advection-dominated accretion in low-luminosity active galactic nuclei SO ASTROPHYSICAL JOURNAL LA English DT Article DE accretion, accretion disks; galaxies : active; X-rays : galaxies ID BLACK-HOLES; GALAXIES; NGC-3628; EMISSION; M81 AB As a class, LINERs and low-luminosity active galactic nuclei (LLAGNs) tend to show little or no significant short-term variability (i.e., with timescales less than a day). This is a marked break from the trend of increased variability in Seyfert 1 galaxies with decreased luminosity. We propose that this difference is due to the lower accretion rate in LINERs and LLAGNs, which is probably causing the accretion flow to be advection-dominated. This results in a larger characteristic size for the X-ray-producing region than is the case in "normal" AGNs. Short-term variability may be caused by a localized instability or occultation events, but we note that such events would likely be accompanied by broadband spectral changes. Since the advection-dominated accretion flow (ADAF) is more compact in a Kerr metric, it is possible that the X-ray emission from ADAFs around rotating black holes would be more variable than X-ray emission from ADAFs in a Schwarzschild metric. Similar variability arguments also apply to other wavelengths, and accordingly multiwavelength monitoring of LLAGNs could serve, to "map" the ADAF regions. C1 Carnegie Mellon Univ, Dept Phys, Pittsburgh, PA 15213 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Ptak, A (reprint author), Carnegie Mellon Univ, Dept Phys, Wean Hall, Pittsburgh, PA 15213 USA. RI Ptak, Andrew/D-3574-2012 NR 32 TC 73 Z9 73 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5801 S ELLIS AVENUE, CHICAGO, IL 60637 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD JUL 1 PY 1998 VL 501 IS 1 BP L37 EP L40 DI 10.1086/311444 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZZ948 UT WOS:000074785500009 ER PT J AU Sweigart, AV Catelan, M AF Sweigart, AV Catelan, M TI The second-parameter effect in metal-rich globular clusters SO ASTROPHYSICAL JOURNAL LA English DT Article DE globular clusters : individual (NGC 6388, NGC 6441); stars : evolution; stars : horizontal-branch; stars : variables : other ID RR-LYRAE STARS; METALLICITIES; KINEMATICS; ABUNDANCE; VARIABLES; AGE AB Recent Hubble Space Telescope observations have found that the horizontal branches (HBs) in the metal-rich globular clusters NGC 6388 and NGC 6441 slope upward with decreasing B - V. Such a slope is not predicted by canonical HE models and cannot be produced by either a greater cluster age or enhanced mass loss along the red giant branch (RGB). The peculiar HE morphology in these clusters may provide an important clue for understanding the second-parameter effect. We have carried out extensive evolutionary calculations and numerical simulations in order to explore three noncanonical scenarios for explaining the sloped HBs in NGC 6388 and NGC 6441: (1) a high cluster helium abundance scenario, in which the HE evolution is characterized by long blue loops; (2) a rotation scenario, in which internal rotation during the RGB phase increases the HE core mass; and (3) a helium-mixing scenario, in which deep mixing on the RGB enhances the envelope helium abundance. All three of these scenarios predict sloped HBs with anomalously bright RR Lyrae variables. We compare this prediction with the properties of the two known RR Lyrae variables in NGC 6388. Additional observational tests of these scenarios are suggested. C1 NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, Greenbelt, MD 20771 USA. RP Sweigart, AV (reprint author), NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, Code 681, Greenbelt, MD 20771 USA. NR 38 TC 71 Z9 71 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5801 S ELLIS AVENUE, CHICAGO, IL 60637 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD JUL 1 PY 1998 VL 501 IS 1 BP L63 EP L66 DI 10.1086/311443 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZZ948 UT WOS:000074785500015 ER PT J AU Snowden, SL AF Snowden, SL TI The calibration of the ROSAT HRI particle background SO ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES LA English DT Article DE instrumentation, detectors; space vehicles; X-rays, general ID DIFFUSE; PSPC AB A calibration for the particle background (PB) of the ROSAT High Resolution Imager (HRI) is presented. It is found that the PB rate is temporally a relatively stable function of the subsatellite geographic position and that the average master veto (MV) signal of the Position Sensitive Proportional Counter is a good template of that function. By determining the general correlation between the average MV signal and PB rate as a function of time and scaling the general correlation by an individual observation's light curve, an accurate PB model for that observation can be produced. Detector maps for the distribution of PB events and the distribution of exposure (including vignetting, detector artifacts, and quantum efficiency variations) are also presented. The maps were created from Earth-block data collected throughout the mission. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Snowden, SL (reprint author), NASA, Goddard Space Flight Ctr, Code 662, Greenbelt, MD 20771 USA. RI Snowden, Steven/D-5292-2012 NR 20 TC 24 Z9 24 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 JUL PY 1998 VL 117 IS 1 BP 233 EP 247 DI 10.1086/313113 PG 15 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 101DK UT WOS:000074854200008 ER PT J AU Ludwig, DA Krock, LP Doerr, DA Convertino, VA AF Ludwig, DA Krock, LP Doerr, DA Convertino, VA TI Mediating effect of onset rate on the relationship between +Gz and LBNP tolerance and cardiovascular reflexes SO AVIATION SPACE AND ENVIRONMENTAL MEDICINE LA English DT Article ID BODY NEGATIVE-PRESSURE; ARTERIAL BLOOD-PRESSURE; VALSALVA MANEUVER; VAGAL BAROREFLEX; ACCELERATION; RESPONSES; REST; STRESS; DEVICE AB Introduction: Research attempting to establish a relationship between human response to lower body negative pressure (LBNP) and +Gz acceleration has in general, disregarded the moderating effects of negative pressure and +Gz onset rates. Many of the past studies designed to examine the relationship between lower body decompression and +Gz acceleration tolerances have also ignored the problem of differences in body position typically encountered during LBNP and +Gz testing (supine LBNP vs. seated +Gz). Methods:There were 17 male subjects (24-34 yr) who were tested in a seated LBNP chamber and received 3 pressure onset rates of 0.067, 0.33, and 2.0 mm Hg.s(-1). Relaxed acceleration tolerance was assessed on a 6.1-m centrifuge using three gradual onset rates of 0.01, 0.05, and 0.2 +Gz.s(-1). LBNP and +Gz tolerances were subjected to principle components (factor) analysis, and the resulting factors correlated with variables derived from autonomic reflex control tests (Valsalva and carotid-cardiac baroreflex responsiveness) and height. Results: The factor model suggested a two-dimensional solution consisting of an acceleration factor and an orthostatic factor. The general pattern of the factor loadings indicates the relationship between tolerances of the two forms of orthostatic stress (acceleration and LBNP) is a function of how fast each stress is delivered. The correlation between LBNP tolerance and acceleration tolerance increases as LBNP onset rate is increased, or +Gz onset rate is decreased. Height was highly correlated (-0.71) and carotid-cardiac baroreflex responsiveness moderately correlated (0.54) with general orthostatic tolerance. Valsalva measures of autonomic reflex control had low correlations with general orthostatic tolerance (<0.30). Conclusions:Although both LBNP and +Gz exposure can lead to eventual loss of consciousness, syncopal events associated with intolerance to either stress are a function of somewhat different cardiovascular mechanisms. There are however, specific situations where LBNP may constitute a viable substitute for +Gz. C1 Univ N Carolina, Dept Math Sci, Greensboro, NC 27412 USA. Armstrong Lab, Hypertens Med Div, Brooks AFB, TX 78235 USA. NASA, KSC, Biomed Operat Off, Kennedy Space Ctr, FL USA. Armstrong Lab, Div Clin Sci, Brooks AFB, TX USA. RP Ludwig, DA (reprint author), Univ N Carolina, Dept Math Sci, 383 Bryan Bldg, Greensboro, NC 27412 USA. NR 35 TC 11 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 JUL PY 1998 VL 69 IS 7 BP 630 EP 638 PG 9 WC Public, Environmental & Occupational Health; Medicine, General & Internal; Sport Sciences SC Public, Environmental & Occupational Health; General & Internal Medicine; Sport Sciences GA ZZ731 UT WOS:000074761500003 PM 9681368 ER PT J AU Moles, A AF Moles, A TI Sensitivity of ten aquatic species to long-term crude oil exposure SO BULLETIN OF ENVIRONMENTAL CONTAMINATION AND TOXICOLOGY LA English DT Article ID SALMON C1 Natl Marine Fisheries Serv, Auke Bay Lab, NOAA, Juneau, AK 99801 USA. RP Moles, A (reprint author), Natl Marine Fisheries Serv, Auke Bay Lab, NOAA, 11305 Glacier Highway, Juneau, AK 99801 USA. NR 10 TC 17 Z9 17 U1 1 U2 9 PU SPRINGER VERLAG PI NEW YORK PA 175 FIFTH AVE, NEW YORK, NY 10010 USA SN 0007-4861 J9 B ENVIRON CONTAM TOX JI Bull. Environ. Contam. Toxicol. PD JUL PY 1998 VL 61 IS 1 BP 102 EP 107 PG 6 WC Environmental Sciences; Toxicology SC Environmental Sciences & Ecology; Toxicology GA ZX044 UT WOS:000074474600015 PM 9657837 ER PT J AU Carter, GA Seal, MR Haley, T AF Carter, GA Seal, MR Haley, T TI Airborne detection of southern pine beetle damage using key spectral bands SO CANADIAN JOURNAL OF FOREST RESEARCH-REVUE CANADIENNE DE RECHERCHE FORESTIERE LA English DT Article ID PLANT STRESS; REFLECTANCE; CHLOROPHYLL; WAVEBANDS; IMAGERY AB Damage by the southern pine beetle (SPB) (Dendroctonus frontalis Zimm.) occurs frequently in the southeastern United States and can result in tree death over large areas. A new technique for detection of SPB activity was tested for shoaleaf pine (Pinus echinata Mill.) in the Caney Creek Wilderness, Ouachita National Forest, Arkansas. Digital images with l-m pixel resolution were acquired from a light aircraft in 6- to 10-nm bandwidths centered at wavelengths of 675, 698, and 840 nm. The 675-nm band was selected to yield a maximum contrast between yellow or brown versus green foliage. The 698-nm band was selected based on its high sensitivity to leaf chlorophyll content to enable detection of less severe chlorosis in more recently damaged trees. The 840-nm band was used as a reference band that is not sensitive to chlorophyll. Images acquired within each band were calibrated to percent reflectance based on the known reflectances of a gray scale placard-located on the ground. Individual trees with yellow to brown foliage were easily located in the 675- and 698-nm images. Milder chlorosis in more recently damaged pines was detected by a normalized difference vegetation index (NDVI) that was derived from 698- and 840-nm reflectances. Although statistically significant, the contrast of recently infested trees versus undamaged trees was generally visually poor in NDVI or color composite images. This was apparently a result of the inherent variability in leaf chlorophyll content throughout the forest. The increased reflectance near 700 nm characteristic of recent damage likely would be resolved more easily in pine plantations of low species diversity. Images of a NDVI that was based on 675- and 840-nm reflectances produced the strongest contrast between heavily damaged and undamaged trees. C1 NASA, Earth Syst Sci Off, Stennis Space Ctr, MS 39529 USA. Space Remote Sensing Ctr, Inst Technol Dev, Stennis Space Ctr, MS 39529 USA. US Forest Serv, Pineville, LA 71360 USA. RP Carter, GA (reprint author), NASA, Earth Syst Sci Off, Stennis Space Ctr, MS 39529 USA. NR 22 TC 10 Z9 10 U1 1 U2 4 PU NATL RESEARCH COUNCIL CANADA PI OTTAWA PA RESEARCH JOURNALS, MONTREAL RD, OTTAWA, ONTARIO K1A 0R6, CANADA SN 0045-5067 J9 CAN J FOREST RES JI Can. J. For. Res.-Rev. Can. Rech. For. PD JUL PY 1998 VL 28 IS 7 BP 1040 EP 1045 DI 10.1139/cjfr-28-7-1040 PG 6 WC Forestry SC Forestry GA 139XM UT WOS:000077056600010 ER PT J AU Zak, M AF Zak, M TI Non-Lipschitz approach to quantum mechanics SO CHAOS SOLITONS & FRACTALS LA English DT Article AB An attempt to reconcile quantum mechanics with Newton's laws represented by the non-Lipschitz formalism has been made. As a proof-of-concept, a line of equally spaced atoms was studied. It appeared that enforcement of atom incompressibility required relaxation of the Lipschitz condition at the points of contact. This, in turn, led to fractional powers and discreteness of values of the basic parameters including energy and action, and finally, to the uncertainty relationship between positions and velocities. In addition to that, the relaxation of the Lipschitz condition caused instability of velocity with respect to small changes of the atom position, and that introduced an element of randomness in the system behavior. It was shown that the only model for the probability evolution which incorporates all the new properties of the motions is the Schrodinger equation. This means that quantum mechanics can be derived from Newton's laws if an unnecessary mathematical restriction-the Lipschitz condition-is removed from the mathematical formalism. Non-local properties of the model, as well as spin-effects and relativistic corrections are discussed. (C) 1998 Elsevier Science Ltd. All rights reserved. C1 CALTECH, Jet Prop Lab, Ctr Space Microelect Technol, Pasadena, CA 91109 USA. RP Zak, M (reprint author), CALTECH, Jet Prop Lab, Ctr Space Microelect Technol, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 9 TC 4 Z9 4 U1 0 U2 0 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0960-0779 J9 CHAOS SOLITON FRACT JI Chaos Solitons Fractals PD JUL PY 1998 VL 9 IS 7 BP 1183 EP 1198 DI 10.1016/S0960-0779(97)00136-7 PG 16 WC Mathematics, Interdisciplinary Applications; Physics, Multidisciplinary; Physics, Mathematical SC Mathematics; Physics GA 112PZ UT WOS:000075504300014 ER PT J AU Bryson, S AF Bryson, S TI Three-dimensional visuazlization for everyone SO COMPUTERS IN PHYSICS LA English DT Article C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Bryson, S (reprint author), NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. NR 4 TC 0 Z9 0 U1 0 U2 0 PU AMER INST PHYSICS PI WOODBURY PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 USA SN 0894-1866 J9 COMPUT PHYS JI Comput. Phys. PD JUL-AUG PY 1998 VL 12 IS 4 BP 346 EP 351 DI 10.1063/1.168694 PG 6 WC Computer Science, Interdisciplinary Applications; Physics, Multidisciplinary; Physics, Mathematical SC Computer Science; Physics GA 114MX UT WOS:000075614200015 ER PT J AU Wood, SJ Paloski, WH Reschke, MF AF Wood, SJ Paloski, WH Reschke, MF TI Spatial coding of eye movements relative to perceived earth and head orientations during static roll tilt SO EXPERIMENTAL BRAIN RESEARCH LA English DT Article DE spatial coding; saccades; tilt; perception; adaption; human ID PERCEPTION; ROTATION; PLANE AB This purpose of this study was to examine the spatial coding of eye movements during static roll tilt (up to +/-45 degrees) relative to perceived earth and head orientations. Binocular videographic recordings obtained in darkness from eight subjects allowed us to quantify the mean deviations in gaze trajectories along both horizontal and vertical coordinates relative to the true earth and head orientations. We found that both variability and curvature of gaze trajectories increased with roll tilt. The trajectories of eye movements made along the perceived earth-horizontal (PEH) were more accurate than movements along the perceived head-horizontal (PHH). The trajectories of both PEH and PHH saccades tended to deviate in the same direction as the head tilt. The deviations in gaze trajectories along the perceived earth-vertical (PEV) and perceived head-vertical (PHV) were both similar to the PHH orientation, except that saccades along the PEV deviated in the opposite direction relative to the head tilt. The magnitude of deviations along the PEV, PHH, and Pi-IV corresponded to perceptual overestimations of roll tilt obtained from verbal reports. Both PEV gaze trajectories and perceptual estimates of tilt orientation were different following clockwise rather than counterclockwise tilt rotation; however, the PEH gaze trajectories were less affected by the direction of tilt rotation. Our results suggest that errors in gaze trajectories along PEV and perceived head orientations increase during roll tilt in a similar way to perceptual errors of tilt orientation. Although PEH and PEV gaze trajectories became nonorthogonal during roll tilt, we conclude that the spatial coding of eye movements during roll tilt is overall more accurate for the perceived earth reference frame than for the perceived head reference frame. C1 KRUG Life Sci, Neurosci Lab, Houston, TX USA. RP Wood, SJ (reprint author), NASA, Lyndon B Johnson Space Ctr, Life Sci Med Res Labs, Mail Code SD3, Houston, TX 77058 USA. NR 20 TC 15 Z9 15 U1 0 U2 0 PU SPRINGER VERLAG PI NEW YORK PA 175 FIFTH AVE, NEW YORK, NY 10010 USA SN 0014-4819 J9 EXP BRAIN RES JI Exp. Brain Res. PD JUL PY 1998 VL 121 IS 1 BP 51 EP 58 DI 10.1007/s002210050436 PG 8 WC Neurosciences SC Neurosciences & Neurology GA ZY025 UT WOS:000074579100007 PM 9698190 ER PT J AU Chai, AT Zhang, NL AF Chai, AT Zhang, NL TI Experimental study of Marangoni-Benard convection in a liquid layer induced by evaporation SO EXPERIMENTAL HEAT TRANSFER LA English DT Article AB Marangoni-Benard instability and convection in Evaporating liquid layers have been studied experimentally through flow visualization and temperature profile measurement. Benard cells have been observed in an evaporating Chin liquid layer whether it is heated, adiabatic, or cooled from below. This experimental study has revealed a different mechanism from the traditional Rayleigh-Benard and Marangoni-Benard instabilities and convections, which require a negative temperature gradient in the thin liquid layer. Evaporation rate and enthalpy of evaporation have been found to be important parameters of instability and convection in an evaporating liquid layer. A modified form of Marangoni number, Ma*, is proposed and its critical values, Ma(c)*, for alcohol and Freon-113 evaporating layers are determined experimentally. A quantitative comparison between Ma* and the traditional Marangoni number, Ma, shows that Ma* is an adequate indicator of the stability status in evaporating liquid layers. C1 NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. RP Chai, AT (reprint author), NASA, Lewis Res Ctr, Mail Stop 500-102, Cleveland, OH 44135 USA. NR 18 TC 34 Z9 35 U1 0 U2 7 PU TAYLOR & FRANCIS INC PI PHILADELPHIA PA 325 CHESTNUT ST, SUITE 800, PHILADELPHIA, PA 19106 USA SN 0891-6152 J9 EXP HEAT TRANSFER JI Exp. Heat Transf. PD JUL-SEP PY 1998 VL 11 IS 3 BP 187 EP 205 DI 10.1080/08916159808946561 PG 19 WC Thermodynamics; Engineering, Mechanical SC Thermodynamics; Engineering GA 122WA UT WOS:000076093400001 ER PT J AU Silbert, MN Moltedo, AD Clements, PJ AF Silbert, MN Moltedo, AD Clements, PJ TI An experimental technique to determine the shock effects of gravity SO EXPERIMENTAL TECHNIQUES LA English DT Article C1 Salisbury State Univ, Dept Phys, Salisbury, MD 21801 USA. Salisbury State Univ, Richard A Henson Sch Sci & Technol, Salisbury, MD 21801 USA. NASA, GSFC, Wallops Flight Facil, Wallops Island, VA USA. RP Silbert, MN (reprint author), Salisbury State Univ, Dept Phys, Salisbury, MD 21801 USA. NR 3 TC 0 Z9 0 U1 2 U2 2 PU SOC EXPERIMENTAL MECHANICS PI BETHEL PA 7 SCHOOL STREET, BETHEL, CT 06801 USA SN 0732-8818 J9 EXP TECHNIQUES JI Exp. Tech. PD JUL-AUG PY 1998 VL 22 IS 4 BP 29 EP 31 DI 10.1111/j.1747-1567.1998.tb02335.x PG 3 WC Engineering, Mechanical; Mechanics; Materials Science, Characterization & Testing SC Engineering; Mechanics; Materials Science GA 106LF UT WOS:000075130200008 ER PT J AU Al-Ammar, K Agrawal, AK Gollahalli, SR Griffin, D AF Al-Ammar, K Agrawal, AK Gollahalli, SR Griffin, D TI Application of rainbow schlieren deflectometry for concentration measurements in an axisymmetric helium jet SO EXPERIMENTS IN FLUIDS LA English DT Article AB The rainbow schlieren deflectometry technique was used to measure oxygen concentrations in a laminar, isothermal helium jet discharged vertically into ambient air. The concentration distributions were inferred from the color schlieren image by taking into consideration the sampling interval and noise in measurements, especially near the jet center. Excellent quantitative agreement was reached between measurements from schlieren and a continuous sampling probe. This work demonstrates the capability of the schlieren technique for providing accurate, spatially-resolved, nonintrusive, full-field of view measurements of species concentration in an isothermal binary system. Because the basic quantity measured is the refractive index, the present schlieren technique can be extended for quantitative measurements of other scalar flow properties related to the refractive index. C1 Univ Oklahoma, Sch Aerosp & Mech Engn, Norman, OK 73019 USA. NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. RP Agrawal, AK (reprint author), Univ Oklahoma, Sch Aerosp & Mech Engn, Norman, OK 73019 USA. RI Agrawal, Ajay/B-5304-2010 NR 18 TC 32 Z9 32 U1 0 U2 2 PU SPRINGER VERLAG PI NEW YORK PA 175 FIFTH AVE, NEW YORK, NY 10010 USA SN 0723-4864 J9 EXP FLUIDS JI Exp. Fluids PD JUL PY 1998 VL 25 IS 2 BP 89 EP 95 DI 10.1007/s003480050211 PG 7 WC Engineering, Mechanical; Mechanics SC Engineering; Mechanics GA 106KT UT WOS:000075129000001 ER PT J AU Bejda, AJ Phelan, BA AF Bejda, AJ Phelan, BA TI Can scales be used to sex winter flounder, Pleuronectes americanus? SO FISHERY BULLETIN LA English DT Article C1 NOAA, Natl Marine Fisheries Serv, NE Fisheries Sci Ctr, James J Howard Marine Sci Lab, Highlands, NJ 07732 USA. RP Bejda, AJ (reprint author), NOAA, Natl Marine Fisheries Serv, NE Fisheries Sci Ctr, James J Howard Marine Sci Lab, Highlands, NJ 07732 USA. NR 22 TC 1 Z9 1 U1 0 U2 0 PU NATL MARINE FISHERIES SERVICE SCIENTIFIC PUBL OFFICE PI SEATTLE PA 7600 SAND POINT WAY NE BIN C15700, SEATTLE, WA 98115 USA SN 0090-0656 J9 FISH B-NOAA JI Fish. Bull. PD JUL PY 1998 VL 96 IS 3 BP 621 EP 623 PG 3 WC Fisheries SC Fisheries GA 106ZP UT WOS:000075181600019 ER PT J AU Benedix, GK McCoy, TJ Keil, K Bogard, DD Garrison, DH AF Benedix, GK McCoy, TJ Keil, K Bogard, DD Garrison, DH TI A petrologic and isotopic study of winonaites: Evidence for early partial melting, brecciation, and metamorphism SO GEOCHIMICA ET COSMOCHIMICA ACTA LA English DT Article ID IIICD IRON-METEORITES; NOBLE-GASES; ORDINARY CHONDRITES; SILICATE INCLUSIONS; ACHONDRITES; MINERALOGY; ORIGIN; CLASSIFICATION; EVOLUTION; BEARING AB We have conducted detailed petrologic, chemical, and isotopic studies of winonaites to ascertain the genesis of this group of meteorites. Winonaites have reduced mineral compositions and mineralogy, and oxygen isotopic compositions distinct from primitive achondrite groups other than silicate inclusions in IAB and IIICD irons. However, winonaites differ from IAB and IIICD irons in that they lack the metallic matrices of the latter and consist mostly of silicates. On the basis of these criteria, Winona, Mount Morris (Wisconsin), Tierra Blanca, Pontlyfni, Y-74025, Y-75300, Y-8005, and QUE 94535 are winonaites and Y-75305 and Y-75261 may be winonaites. Winonaites are fine- to medium-grained, mostly equigranular rocks. Pondyfni and Mount Morris (Wisconsin) contain what appear to be relict chondrules. Several winonaites contain mm-sized areas that differ substantially in grain size and/or silicate mineralogy from the surrounding matrix. Fe,Ni-FeS veins are common in many winonaites. Mineral compositions are intermediate between E and H chondrites, and reduced sulfides are observed in low-FeO winonaites. Bulk major element compositions are roughly chondritic, although REE elements are fractionated. The Ar-39-Ar-40 ages of three winonaites range from greater than or equal to 4.40 Ga (Mount Morris, Wisconsin) to 4.54 Ga (Pontlyfni). Cosmic-ray exposure ages are similar to 20-80 Ma. Trapped noble gases in these winonaites resemble those in enstatite chondrites. We suggest that the winonaites formed from a chondritic precursor material unlike that of known chondrites in mineral and oxygen isotopic compositions, and this material may have been heterogeneous in composition. Extensive heating caused metamorphism and partial melting of both Fe,Ni-FeS and silicate material. Impact brecciation during cooling mixed lithologies with different thermal histories, and subsequent metamorphism produced recrystallization, grain growth, and reduction of mafic silicates. The Ar-39-Ar-40 ages indicate that cooling may have been more rapid than observed in IAB irons, although later resetting may have occurred. Copyright (C) 1998 Elsevier Science Ltd. C1 Univ Hawaii Manoa, Sch Ocean & Earth Sci & Technol, Hawaii Inst Geophys & Planetol, Honolulu, HI 96822 USA. Smithsonian Inst, Natl Museum Nat Hist, MRC, Dept Mineral Sci, Washington, DC 20560 USA. NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. RP Benedix, GK (reprint author), NASA, Ames Res Ctr, MS 245-3, Moffett Field, CA 94035 USA. OI Benedix, Gretchen/0000-0003-0990-8878 NR 65 TC 66 Z9 66 U1 0 U2 4 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 JUL PY 1998 VL 62 IS 14 BP 2535 EP 2553 DI 10.1016/S0016-7037(98)00166-5 PG 19 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 121TY UT WOS:000076031100011 ER PT J AU Garrison, JL Katzberg, SJ Hill, MI AF Garrison, JL Katzberg, SJ Hill, MI TI Effect of sea roughness on bistatically scattered range coded signals from the Global Positioning System SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article AB A series of aircraft experiments was performed using a specialized GPS receiver and a nadir-oriented left hand circularly polarized antenna. This apparatus received reflections of the GPS signals from water surfaces under a variety of sea states. The cross-correlation between the reflected signal and a reference pseudo-random noise code was recorded as a function of the relative time delay. The shape of this function showed a dependence on the roughness of the reflecting surface. This dependence generally followed that predicted by theory for bistatic scattering of range-coded signals. Use of this information as a remote sensing technique for the determination of sea state is discussed. C1 NASA, Langley Res Ctr, Hampton, VA 23681 USA. Harvard Univ, Cambridge, MA 02138 USA. RP Garrison, JL (reprint author), NASA, Langley Res Ctr, Hampton, VA 23681 USA. NR 13 TC 100 Z9 113 U1 1 U2 9 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 JUL 1 PY 1998 VL 25 IS 13 BP 2257 EP 2260 DI 10.1029/98GL51615 PG 4 WC Geosciences, Multidisciplinary SC Geology GA ZZ145 UT WOS:000074700200003 ER PT J AU Fung, SF Tan, LC AF Fung, SF Tan, LC TI Time correlation of low-altitude relativistic trapped electron fluxes with solar wind speeds SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID MAGNETOSPHERE AB We present the results from a study of time correlation between the low-altitude relativistic trapped electron fluxes and the solar wind speeds. Our trapped electron observations in the energy range of 0.19-3.2.MeV were obtained by the OHZORA spacecraft in an altitude range of 350-850 km, near a solar minimum period (1984-87), The solar wind data with a 5-minute time resolution were obtained from IMP-8 observations. Linear correlation analyses between the two data sets have been performed for relative time lags varying from 12 minutes to 60 days. The 2.5-day, 13-day, 27-day and 54-day correlation peaks previously reported for energetic electrons near geosynchronous orbits are clearly seen in our results. However, the use of higher time resolution solar wind data than in previous studies allows correlation analyses to be performed at shorter time lags. We report here that correlation at shorter time lags (< 10 hrs) exists and that while such correlation is stronger than those observed at longer lag times, it can not be entirely attributed to storm or substorm injections. The correlation is also found to decrease with drift shell magnetic equatorial radii, r(t). In addition, local-time and radial variations in the responses of different drift shells to solar wind speed enhancements indicate that the energetic electron population enters the inner magnetosphere predominantly through the midnight sector. C1 NASA, Goddard Space Flight Ctr, Space Phys Data Facil, Greenbelt, MD 20771 USA. Raytheon STX Corp, Lanham, MD USA. RP Fung, SF (reprint author), NASA, Goddard Space Flight Ctr, Space Phys Data Facil, Code 632, Greenbelt, MD 20771 USA. RI Fung, Shing/F-5647-2012 NR 25 TC 19 Z9 19 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 JUL 1 PY 1998 VL 25 IS 13 BP 2361 EP 2364 DI 10.1029/98GL01717 PG 4 WC Geosciences, Multidisciplinary SC Geology GA ZZ145 UT WOS:000074700200030 ER PT J AU Buti, B Jayanti, V Vinas, AF Ghosh, S Goldstein, ML Roberts, DA Lakhina, GS Tsurutani, BT AF Buti, B Jayanti, V Vinas, AF Ghosh, S Goldstein, ML Roberts, DA Lakhina, GS Tsurutani, BT TI Nonlinear evolution of Alfvenic wave packets SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID SOLAR-WIND AB Alfven waves are a ubiquitous feature of the solar wind. One approach to studying the evolution of such waves has been to study exact solutions to approximate evolution equations. Here we compare soliton solutions of the Derivative Nonlinear Schrodinger evolution equation (DNLS) to solutions of the compressible MHD equations. We find that the soliton solutions of the DNLS equation are not stable solutions of Hall-MHD - they evolve and dissipate with time..Although such solitons may serve as approximate initial conditions to the Hall-MHD equations, they are not stationary solutions. This may account for the absence of soliton-like wave forms in the free-flowing solar wind. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. NASA, Goddard Space Flight Ctr, Univ Space Res Assoc, Greenbelt, MD 20771 USA. Space Applicat Corp, Largo, MD USA. RP Buti, B (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. RI Lakhina, Gurbax /C-9295-2012; Roberts, Dana/D-4625-2012; Goldstein, Melvyn/B-1724-2008; OI Lakhina, Gurbax /0000-0002-8956-486X NR 18 TC 20 Z9 20 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 JUL 1 PY 1998 VL 25 IS 13 BP 2377 EP 2380 DI 10.1029/98GL01688 PG 4 WC Geosciences, Multidisciplinary SC Geology GA ZZ145 UT WOS:000074700200034 ER PT J AU Bowman, KP Hoppel, K Swinbank, R AF Bowman, KP Hoppel, K Swinbank, R TI Stationary anomalies in stratospheric meteorological data sets SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID ASSIMILATION AB Several northern hemisphere stratospheric meteorological data sets are shown to contain stationary anomalies. We consider four possible explanations for the anomalies: 1) real stationary-wave features; 2) biases in the analysis and assimilation methods; 3) errors in data input into the analysis and assimilation systems; and 4) tidal signals that are undersampled in the daily analyses. Because the easter:ly flow in the summer stratosphere is not consistent with stationary waves and the anomalies are present in multiple analyses. we conclude that the anomalies are a combination of biases in the input data and tidal signals that are aliased to zero frequency by daily sampling. Because the anomalies are large, they can have significant impacts on many applications of the data, including trajectories and chemical transport calculations. C1 Texas A&M Univ, Dept Meteorol, College Stn, TX 77842 USA. USN, Res Lab, Ctr Remote Sensing, Washington, DC 20375 USA. Univ Space Res Assoc, NASA, Goddard Space Flight Ctr, Data Assimilat Off, Greenbelt, MD 20771 USA. RP Bowman, KP (reprint author), Texas A&M Univ, Dept Meteorol, College Stn, TX 77842 USA. RI Bowman, Kenneth/A-1345-2012 OI Bowman, Kenneth/0000-0002-2667-8632 NR 12 TC 11 Z9 11 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 JUL 1 PY 1998 VL 25 IS 13 BP 2429 EP 2432 DI 10.1029/98GL01716 PG 4 WC Geosciences, Multidisciplinary SC Geology GA ZZ145 UT WOS:000074700200047 ER PT J AU Johnson, AE Hebert, M AF Johnson, AE Hebert, M TI Control of polygonal mesh resolution for 3-D computer vision SO GRAPHICAL MODELS AND IMAGE PROCESSING LA English DT Article DE polygonal mesh; surface simplification; multiresolution modeling; shape approximation; 3-D computer vision ID OBJECT RECOGNITION AB A common representation in 3-D computer vision is the polygonal surface mesh because meshes can model objects of arbitrary shape and are easily constructed from sensed 3-D data. The resolution of a surface mesh is the overall spacing between vertices that comprise the mesh. Because sensed 3-D points are often unevenly distributed, the resolution of a surface mesh is often poorly defined. We present an algorithm that transforms a mesh with an uneven spacing between vertices into a mesh with a more even spacing between vertices, thus improving its definition of resolution, In addition, we show how the algorithm can be used to control the resolution of surface meshes, making them amenable to multiresolution approaches in computer vision. The structure of our algorithm is modeled on iterative mesh simplification algorithms common in computer graphics; however, the individual steps in our algorithm are designed specifically to control mesh resolution. An even spacing between vertices is generated by applying a sequence of local edge operations that promote uniform edge lengths while preserving mesh shape. To account for polyhedral objects, we introduce an accurate shape change measure that permits edge operations along sharp creases. By locally bounding the total change in mesh shape, drastic changes in global shape are prevented. We show results from many 3-D sensing domains including computed tomography, range imaging, and digital elevation map construction. (C) 1998 Academic Press. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Carnegie Mellon Univ, Inst Robot, Pittsburgh, PA 15213 USA. RP Johnson, AE (reprint author), CALTECH, Jet Prop Lab, Mail Stop 107-102,4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 25 TC 21 Z9 21 U1 0 U2 0 PU ACADEMIC PRESS INC PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA SN 1077-3169 J9 GRAPH MODEL IM PROC JI Graph. Models Image Process. PD JUL PY 1998 VL 60 IS 4 BP 261 EP 285 DI 10.1006/gmip.1998.0474 PG 25 WC Computer Science, Software Engineering SC Computer Science GA ZY042 UT WOS:000074580800002 ER PT J AU Morris, RV AF Morris, RV TI Goldenrod pigments and the occurrence of hematite and possibly goethite in the Olympus-Amazonis region of Mars SO ICARUS LA English DT Article DE Mars; hematite; goethite; reflectance spectroscopy; palagonite ID HAWAIIAN PALAGONITIC SOIL; IMPACT MELT; IRON-OXIDES; HYDROTHERMAL ALTERATION; MAGNETIC-PROPERTIES; MINERALOGY; MOSSBAUER; SPECTRA; ROCKS; REFLECTANCE AB The spectral properties of the Olympus-Amazonis region of Mars were reproduced using laboratory mixtures of palagonitic tephra and goldenrod pigments, which are blends of well-crystalline hematite and goethite. Laboratory spectra for pure pigments and mixtures were obtained at similar to 140 and similar to 305 K to bracket the temperature range of the martian surface. The best fit to the martian surface spectrum was obtained with a mixture of palagonitic tephra and 2.5% BLS12, a goldenrod pigment with 44% of its iron atoms associated with hematite and 56% with goethite (determined from Mossbauer spectroscopy). Although goethite is the major phase, the positions of reflectivity maximum and minimum near 750 and 860 nm, respectively, are determined by the hematite component at both temperatures. Spectrally, the presence of goethite is recognized by increased reflectivity between similar to 400 and 550 nm and, particularly at low temperatures, lowered reflectivity between similar to 1000 and 1300 nm compared to spectra of mixtures containing only hematite. Although the presence of goethite is consistent with the martian spectrum, the presence of the mineralogy is equivocal because other ferric-bearing phases (e.g., maghemite, lepidocrocite, akaganeite, schwertmannite, jarosite, and nontronite) have similar spectral characteristics, making definitive identification difficult. Thus, our results show that spectral data for Olympus-Amazonis, which are hematitic based on positions of spectral features, permit the presence of comparable proportions of other ferric-bearing phases. Weathering products in addition to hematite, such as goethite from oxidative and hydrolytic weathering or jarosite and/or schwertmannite from acid-sulfate weathering, may be present but spectrally masked by hematite. (C) 1998 Academic Press. C1 NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. Dual Inc, Houston, TX 77058 USA. RP Morris, RV (reprint author), NASA, Lyndon B Johnson Space Ctr, Code SN3, Houston, TX 77058 USA. EM richard.v.morris1@jsc.nasa.gov NR 50 TC 28 Z9 28 U1 4 U2 13 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 JUL PY 1998 VL 134 IS 1 BP 1 EP 10 DI 10.1006/icar.1998.5939 PG 10 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 108VF UT WOS:000075285800001 ER PT J AU Lissauer, JJ Espresate, J AF Lissauer, JJ Espresate, J TI Resonant satellite torques on low optical depth particulate disks I. Analytic development SO ICARUS LA English DT Article ID COLLISIONAL SIMULATIONS; LINDBLAD RESONANCES; RINGS AB We investigate the torque exerted by a satellite on an annulus centered at a mean motion resonance. The annulus is made of noninteracting (test) particles uniformly distributed in semimajor axis. We obtain an analytic expression for the time evolution of the angular momentum of the annulus. We find that in the linear approximation, the net torque on the disk equals that obtained by P. Goldreich and S, Tremaine (1978, Icarus 34, 240-253) for a fluid disk in quasi-steady state. The same torque is obtained for disks of particles initially on circular orbits as for disks of particles on moderately eccentric orbits with periapses uniformly distributed in longitude. Poisson demonstrated that no secular torque can be obtained in the restricted three-body problem. As the satellite pumps up the eccentricity of a particle's orbit, it also changes the particle's semimajor axis in such a way that eventually the torque is reversed. The period and amplitude for this interchange of angular momentum with the satellite depends on the distance from resonance, being larger the closer the particle is to the resonance. The width of the annulus over which the bulk of the torque is exerted shrinks as time increases. Our linear analysis allows arbitrarily large eccentricities for particles near resonance, which is clearly unphysical. The torque in a nondissipative disk is limited in time by nonlinear effects of the interaction close to resonance. We present quantitative estimates of where in semimajor axis, and when in time, the linear approximation breaks down. (C) 1998 Academic Press C1 NASA, Ames Res Ctr, Div Space Sci, Moffett Field, CA 94035 USA. SUNY Stony Brook, Astron Program, Stony Brook, NY 11794 USA. Inst Astron, Circuito Exterior,Ciudad Univ, Mexico City 04510, DF, Mexico. RP Lissauer, JJ (reprint author), NASA, Ames Res Ctr, Div Space Sci, MS 245-3, Moffett Field, CA 94035 USA. NR 14 TC 8 Z9 8 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 JUL PY 1998 VL 134 IS 1 BP 155 EP 162 DI 10.1006/icar.1998.5922 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 108VF UT WOS:000075285800009 ER PT J AU Calhoun, CC AF Calhoun, CC TI Applying Independent Verification and Validation to the Automatic Test Equipment life cycle SO IEEE AEROSPACE AND ELECTRONIC SYSTEMS MAGAZINE LA English DT Article C1 NASA Ames, Independent Verificat & Validat Facil, Fairmont, WV 26554 USA. RP Calhoun, CC (reprint author), NASA Ames, Independent Verificat & Validat Facil, 100 Univ Dr, Fairmont, WV 26554 USA. NR 7 TC 2 Z9 2 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 0885-8985 J9 IEEE AERO EL SYS MAG JI IEEE Aerosp. Electron. Syst. Mag. PD JUL PY 1998 VL 13 IS 7 BP 37 EP 41 DI 10.1109/62.690866 PG 5 WC Engineering, Aerospace; Engineering, Electrical & Electronic SC Engineering GA 101UG UT WOS:000074886100012 ER PT J AU Interrante, V Grosch, C AF Interrante, V Grosch, C TI Visualizing 3D flow SO IEEE COMPUTER GRAPHICS AND APPLICATIONS LA English DT Article C1 NASA, Inst Comp Applicat Sci & Engn, Langley Res Ctr, Hampton, VA 23681 USA. Old Dominion Univ, Norfolk, VA USA. RP NASA, Inst Comp Applicat Sci & Engn, Langley Res Ctr, Mail Stop 403, Hampton, VA 23681 USA. EM interran@icase.edu NR 8 TC 41 Z9 42 U1 0 U2 4 PU IEEE COMPUTER SOC PI LOS ALAMITOS PA 10662 LOS VAQUEROS CIRCLE, PO BOX 3014, LOS ALAMITOS, CA 90720-1314 USA SN 0272-1716 EI 1558-1756 J9 IEEE COMPUT GRAPH JI IEEE Comput. Graph. Appl. PD JUL-AUG PY 1998 VL 18 IS 4 BP 49 EP 53 DI 10.1109/38.689664 PG 5 WC Computer Science, Software Engineering SC Computer Science GA ZW528 UT WOS:000074420000014 ER PT J AU Kenwright, DN Haimes, R AF Kenwright, DN Haimes, R TI Automatic vortex core detection SO IEEE COMPUTER GRAPHICS AND APPLICATIONS LA English DT Article ID FLOW C1 NASA, Ames Res Ctr, MRJ Technol Solut, Data Anal Grp, Moffett Field, CA 94035 USA. MIT, Dept Aeronaut & Astronaut, Cambridge, MA 02139 USA. RP NASA, Ames Res Ctr, MRJ Technol Solut, Data Anal Grp, MST27A-2, Moffett Field, CA 94035 USA. EM davidk@nas.nasa.gov NR 9 TC 16 Z9 17 U1 0 U2 2 PU IEEE COMPUTER SOC PI LOS ALAMITOS PA 10662 LOS VAQUEROS CIRCLE, PO BOX 3014, LOS ALAMITOS, CA 90720-1314 USA SN 0272-1716 EI 1558-1756 J9 IEEE COMPUT GRAPH JI IEEE Comput. Graph. Appl. PD JUL-AUG PY 1998 VL 18 IS 4 BP 70 EP 74 DI 10.1109/38.689668 PG 5 WC Computer Science, Software Engineering SC Computer Science GA ZW528 UT WOS:000074420000018 ER PT J AU Uselton, SP AF Uselton, SP TI ExVis and wind tunnel experiment data SO IEEE COMPUTER GRAPHICS AND APPLICATIONS LA English DT Article C1 NASA, Ames Res Ctr, MRJ Technol Solut, Moffett Field, CA 94035 USA. RP NASA, Ames Res Ctr, MRJ Technol Solut, MST27A-1, Moffett Field, CA 94035 USA. EM uselton@nas.nasa.gov NR 7 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 0272-1716 EI 1558-1756 J9 IEEE COMPUT GRAPH JI IEEE Comput. Graph. Appl. PD JUL-AUG PY 1998 VL 18 IS 4 BP 75 EP 77 DI 10.1109/38.689669 PG 3 WC Computer Science, Software Engineering SC Computer Science GA ZW528 UT WOS:000074420000019 ER PT J AU Sasidhar, K Alkalai, L Chatterjee, A AF Sasidhar, K Alkalai, L Chatterjee, A TI Testing NASA's 3D-stack MCM space flight computer SO IEEE DESIGN & TEST OF COMPUTERS LA English DT Article AB Advanced packaging technologies pose major testing challenges fcr complex designs. The authors present test strategies used in the space flight computer designed for NASA's Deep Space-1 mission. C1 Georgia Inst Technol, Sch Elect & Comp Engn, Atlanta, GA 30332 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Chatterjee, A (reprint author), Georgia Inst Technol, Sch Elect & Comp Engn, 777 Atlantic Dr, Atlanta, GA 30332 USA. NR 9 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 0740-7475 J9 IEEE DES TEST COMPUT JI IEEE Des. Test Comput. PD JUL-SEP PY 1998 VL 15 IS 3 BP 44 EP 55 DI 10.1109/54.706032 PG 12 WC Computer Science, Hardware & Architecture; Engineering, Electrical & Electronic SC Computer Science; Engineering GA 111MG UT WOS:000075440800008 ER PT J AU Sengupta, D Jandhyala, V Kim, S Fang, W Malin, J Apostolakis, P Hseih, KC Chang, YC Chuang, SL Bandara, S Gunapala, S Feng, M Michielssen, E Stillman, G AF Sengupta, D Jandhyala, V Kim, S Fang, W Malin, J Apostolakis, P Hseih, KC Chang, YC Chuang, SL Bandara, S Gunapala, S Feng, M Michielssen, E Stillman, G TI Redshifting and broadening of quantum-well infrared photodetector's response via impurity-free vacancy disordering SO IEEE JOURNAL OF SELECTED TOPICS IN QUANTUM ELECTRONICS LA English DT Article DE absolute response; dark current characteristics; focal plane array; impurity-free vacancy disordering; peak response wavelength; quantum efficiency; quantum-well infrared photodetectors; rapid thermal annealing; red shift ID GAAS SUPER-LATTICE; MULTIQUANTUM WELLS; DETECTORS; GAAS/ALGAAS; ABSORPTION; SUPERLATTICES AB The partial intermixing of the well and barrier materials offers unique opportunities to shift locally the bandgap of quantum-well (QW) structures. We have demonstrated red-shifting and broadening of the wavelength responses of bound-to-continuum GaAs and InP based quantum-well infrared photodetectors (QWIP's) after growth via impurity-free vacancy disordering (IFVD). A comprehensive set of experiments is conducted on QWIP's fabricated from both as-grown and multiple-quantum-web (MQW) structures, Compared to the as-grown detector, the peak spectral responses of the disordered detectors were shifted to longer wavelengths. The peak absolute response of the disordered GaAs based QWIP is lower by almost a Factor of four, However, the responsivity characteristics of the disordered InP based QWIP show no major degradation. In general, with the spectral broadening taken into account, the overall performance of the disordered QWIP's has not dropped significantly. Thus, the postgrowth control of the QW composition profiles by impurity-free vacancy disordering offers unique opportunities to fine tune various aspects of a photodetector's response. Theoretical calculations of the absorption coefficient spectrum are in excellent agreement with the experimental data. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Ansoft Corp, Pittsburgh, PA 15219 USA. Univ Illinois, Dept Elect & Comp Engn, Urbana, IL 61801 USA. Univ Illinois, Dept Phys, Urbana, IL 61801 USA. RP Sengupta, D (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. RI Chang, Yia-Chung/F-4239-2011 NR 37 TC 14 Z9 14 U1 0 U2 6 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 1077-260X J9 IEEE J SEL TOP QUANT JI IEEE J. Sel. Top. Quantum Electron. PD JUL-AUG PY 1998 VL 4 IS 4 BP 746 EP 757 DI 10.1109/2944.720488 PG 12 WC Engineering, Electrical & Electronic; Optics; Physics, Applied SC Engineering; Optics; Physics GA 124HY UT WOS:000076177400022 ER PT J AU Ji, Y Inagaki, K Shibata, O Karasawa, Y AF Ji, Y Inagaki, K Shibata, O Karasawa, Y TI Receive mode of optical signal processing multibeam array antennas SO IEEE MICROWAVE AND GUIDED WAVE LETTERS LA English DT Article DE antenna arrays; optical signal processing; receiving antennas AB A receive mode of the optical processing array antennas is presented in this letter. In this receive mode, the transmitting radio frequency (RF) signals generated by optical processor will be shifted as local oscillator (LO) signals, and the received RF beams will be discriminated in the downconverted intermediate frequency (IF) frequency domain by a mixer array between optical processor and antenna elements. A proof-of-concept experiment for a two-beam and four-element array antenna is demonstrated, and the received IF power distributions for each beam have very good agreement with the calculated antenna patterns. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. ATR, Adapt Commun Res Labs, Kyoto 61902, Japan. Kokusai Denshin Denwa Co Ltd, R&D Labs, Kamifukuoka, Saitama 356, Japan. RP Ji, Y (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 7 TC 17 Z9 19 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 1051-8207 J9 IEEE MICROW GUIDED W JI IEEE Microw. Guided Wave Lett. PD JUL PY 1998 VL 8 IS 7 BP 251 EP 253 DI 10.1109/75.701382 PG 3 WC Engineering, Electrical & Electronic SC Engineering GA ZV050 UT WOS:000074263300003 ER PT J AU Sorace, R Lee, E Baldauf, J Heffernan, P AF Sorace, R Lee, E Baldauf, J Heffernan, P TI Analysis of solar degradation to TDRS S-band phased array antenna SO IEEE TRANSACTIONS ON AEROSPACE AND ELECTRONIC SYSTEMS LA English DT Article AB A study of the distribution of gain-to-noise-temperature (G/T) values for the Tracking and Data Relay Satellite (TDRS) satellite is described. The statistics of the G/T values are determined by a Monte Carlo simulation of the orbital geometry of the sun and moon, and the gain and noise temperature calculations is included. The results and their underlying assumptions are described.A study of the distribution of gain-to-noise-temperature (G/T) values for the Tracking and Data Relay Satellite (TDRS) satellite is described. The statistics of the G/T values are determined by a Monte Carlo simulation of the orbital geometry of the sun and moon, and the gain and noise temperature calculations is included. The results and their underlying assumptions are described. C1 Hughes Space & Commun Co, Los Angeles, CA 90009 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Sorace, R (reprint author), Hughes Space & Commun Co, POB 92919, Los Angeles, CA 90009 USA. NR 6 TC 1 Z9 1 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 0018-9251 J9 IEEE T AERO ELEC SYS JI IEEE Trans. Aerosp. Electron. Syst. PD JUL PY 1998 VL 34 IS 3 BP 947 EP 954 DI 10.1109/7.705900 PG 8 WC Engineering, Aerospace; Engineering, Electrical & Electronic; Telecommunications SC Engineering; Telecommunications GA 106DA UT WOS:000075113400022 ER PT J AU Nevels, RD Arndt, GD Raffoul, GW Carl, JR Pacifico, A AF Nevels, RD Arndt, GD Raffoul, GW Carl, JR Pacifico, A TI Microwave catheter design SO IEEE TRANSACTIONS ON BIOMEDICAL ENGINEERING LA English DT Article DE arrhythmia; catheter ablation; electrocardiology; microwave ID VENTRICULAR-TACHYCARDIA; ABLATION; ANTENNAS; ENERGY AB A microwave antenna system for transcatheter ablation of cardiac tissue is investigated. A numerical model based on the finite-difference time-domain method incorporating a Gaussian pulse excitation has been constructed and frequency domain electric and magnetic fields are obtained through Fourier transformation. Results are presented for a coaxial line fed monopole catheter which is modified by the successive inclusion of a Teflon sheath outer coating, a terminating disk at the tip of the antenna, a sleeve choke, and a high dielectric constant cylinder surrounding the monopole antenna. The effects of these design features are characterized in terms of specific absorption rate (SAR) and return loss (RL), Numerical calculations are confirmed by comparing with the RL measurement of a Teflon-coated monopole containing a disk and choke. C1 Texas A&M Univ, Dept Elect Engn, College Stn, TX 77843 USA. NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. Houston Methodist Hosp, Houston, TX 79030 USA. RP Nevels, RD (reprint author), Texas A&M Univ, Dept Elect Engn, College Stn, TX 77843 USA. NR 23 TC 47 Z9 49 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 0018-9294 J9 IEEE T BIO-MED ENG JI IEEE Trans. Biomed. Eng. PD JUL PY 1998 VL 45 IS 7 BP 885 EP 890 DI 10.1109/10.686796 PG 6 WC Engineering, Biomedical SC Engineering GA ZV032 UT WOS:000074261500009 PM 9644897 ER PT J AU Cooper, RA Fletcher-Shaw, TL Robertson, RN AF Cooper, RA Fletcher-Shaw, TL Robertson, RN TI Model reference adaptive control of heart rate during wheelchair ergometry SO IEEE TRANSACTIONS ON CONTROL SYSTEMS TECHNOLOGY LA English DT Article DE adaptive control; disability; ergometry; modeling; system identification; wheelchair ID DYNAMICS; EXERCISE; VENTILATION AB This study used parametric methods to identify a model of the wheelchair user's heart rate response to changes in physical workload while on a wheelchair dynamometer. A model reference adaptive control (MRAC) algorithm was developed based upon the results of the system identification process. Based upon the subject's maximum speed, ten random levels from zero to maximal speed were selected to form a tracking input vector. Two autoregressive models with exogenous inputs were developed using a stepwise regression-based algorithm. Analysis of variance results imply that the model development and model validation groups were different. Linear regression was used to compare the model predicted heart rates with recorded heart rates for the validation group. Predicted heart rates from both models were significantly correlated with the data recorded from the validation group. The simulation for all subjects converged for all three inputs. The application of indirect model reference adaptive control appears to be feasible for controlling heart rate kinetics of people with paraplegia or tower limb impairments during wheelchair propulsion on a computer-controlled wheelchair dynamometer. C1 Univ Pittsburgh, Sch Engn, Sch Hlth & Rehabil Sci Mech Engn & Bioengn, Dept Rehabil Sci,Human Engn Res Labs 151R1, Pittsburgh, PA 15206 USA. Univ Pittsburgh, Sch Engn, Sch Hlth & Rehabil Sci Mech Engn & Bioengn, Dept Technol, Pittsburgh, PA 15206 USA. Univ Pittsburgh, Med Ctr, Dept Orthopaed Surg, Div Phys Med & Rehabil, Pittsburgh, PA 15206 USA. Vet Adm Med Ctr, Pittsburgh, PA 15206 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Calif State Univ Sacramento, Dept Hlth & Phys Educ, Sacramento, CA 95819 USA. RP Cooper, RA (reprint author), Univ Pittsburgh, Sch Engn, Sch Hlth & Rehabil Sci Mech Engn & Bioengn, Dept Rehabil Sci,Human Engn Res Labs 151R1, Pittsburgh, PA 15206 USA. NR 19 TC 14 Z9 14 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 JUL PY 1998 VL 6 IS 4 BP 507 EP 514 DI 10.1109/87.701345 PG 8 WC Automation & Control Systems; Engineering, Electrical & Electronic SC Automation & Control Systems; Engineering GA ZV216 UT WOS:000074282000006 ER PT J AU Ranson, KJ Collatz, GJ Diner, DJ Kahle, AB Salomonson, VV AF Ranson, KJ Collatz, GJ Diner, DJ Kahle, AB Salomonson, VV TI EOS AM-1 platform, instruments, and scientific data SO IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING LA English DT Editorial Material C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Ranson, KJ (reprint author), NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RI collatz, george/D-5381-2012; Ranson, Kenneth/G-2446-2012 OI Ranson, Kenneth/0000-0003-3806-7270 NR 0 TC 5 Z9 5 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 JUL PY 1998 VL 36 IS 4 BP 1039 EP 1041 PG 3 WC Geochemistry & Geophysics; Engineering, Electrical & Electronic; Remote Sensing; Imaging Science & Photographic Technology SC Geochemistry & Geophysics; Engineering; Remote Sensing; Imaging Science & Photographic Technology GA ZZ760 UT WOS:000074764400001 ER PT J AU Kaufman, YJ Herring, DD Ranson, KJ Collatz, GJ AF Kaufman, YJ Herring, DD Ranson, KJ Collatz, GJ TI Earth Observing System AM1 mission to earth SO IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING LA English DT Article DE Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) aerosol; anthropogenic forcing; atmospheric chemistry; biomass burning; carbon cycle; carbon dioxide; climate; climate change; clouds; Clouds and Earth's Radiant Energy System (CERES); Earth Observing System (EOS)-AM1; earth science; global change; global warming; greenhouse gas; land use; Measurements Of Pollution In The Troposphere (MOPITT); Moderate Resolution Imaging Spectroradiometer (MODIS); Multi-angle Imaging SpectroRadiometer (MISR); phytoplankton; predictive computer models; radiation budget; remote sensing; sea surface temperature; troposphere; vegetation ID ATMOSPHERIC CO2; EXPORT PRODUCTION; IRON; RISE AB In 1998, NASA launches EOS-AM1, the first of a series of the Earth Observing System (EOS) satellites. EOS will monitor the evolution of the state of the earth for 18 years, starting with the morning observations of EOS-AM1 (10:30 a.m. equatorial crossing time). An integrated view of the earth, as planned by EOS, is needed to study the interchange of energy, moisture, and carbon between the lands, oceans, and atmosphere. The launch of EOS-AM1 and other international satellites marks a new phase of climate and global change research. Both natural and anthropogenic climate change have been studied for more than a century. It is now recognized that processes that vary rapidly in time and space-e.g, aerosol, clouds, land use, and exchanges of energy and moisture-must be considered to adequately explain the temperature record and predict future climate change. Frequent measurements with adequate resolution, as only possible from spacecraft, are key tools in such an effort. The versatile and highly accurate EOS-AM1 data, together with previous satellite records, as well as data from the Advanced Earth Observing System (ADEOS) (I and II), Tropical Rainfall Measuring Mission (TRMM), Sea-viewing Wide Field-of-view Sensor (SeaWiFS), Along Track Scanning Radiometer (ATSR), Medium Resolution Imaging Spectrometer (MERIS), Environmental Satellite (ENVISAT), EOS-PM1, Land Remote-Sensing Satellite (Landsat), and ground-based networks is expected to revolutionize the way scientists look at climate change. This article introduces the EOS-AM1 mission and the special issue devoted to it. Following a brief historical perspective for an insight into the purpose and objectives of the mission, we shall summarize the characteristics of the five instruments onboard EOS-AM1. Specifically, we concentrate on the innovative elements of these five instruments and provide examples of the science issues that require this type of data. These examples show the importance of collecting data simultaneously from each of the five EOS-AM1 sensors for studying rapidly varying processes and parameters. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Kaufman, YJ (reprint author), NASA, Goddard Space Flight Ctr, Code 913, Greenbelt, MD 20771 USA. EM dherring@climate.gsfc.nasa.gov RI collatz, george/D-5381-2012; Ranson, Kenneth/G-2446-2012 OI Ranson, Kenneth/0000-0003-3806-7270 NR 41 TC 73 Z9 77 U1 1 U2 10 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 JUL PY 1998 VL 36 IS 4 BP 1045 EP 1055 DI 10.1109/36.700989 PG 11 WC Geochemistry & Geophysics; Engineering, Electrical & Electronic; Remote Sensing; Imaging Science & Photographic Technology SC Geochemistry & Geophysics; Engineering; Remote Sensing; Imaging Science & Photographic Technology GA ZZ760 UT WOS:000074764400002 ER PT J AU Butler, JJ Barnes, RA AF Butler, JJ Barnes, RA TI Calibration strategy for the Earth Observing System (EOS)-AM1 platform SO IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING LA English DT Article DE calibration; Earth Observing System (EOS); radiometry; reflectance; remote sensing ID PREFLIGHT; SENSORS AB The Earth Observing System (EOS) is an international, 18-year program in global remote sensing of the earth comprising multiple instruments flown on several satellite platforms. The first EOS platform, AM1, scheduled for launch in 1998, includes five instruments designed to make radiometric and reflectance measurements of the earth over a wavelength range extending from the visible to the thermal infrared, The goal of the EOS-AM1 platform and instruments is to advance the scientific understanding of the earth in the areas of clouds, aerosols, radiative balance, terrestrial and oceanic characterization, and the carbon cycle, In order to achieve this goal, the EOS-AM1 instruments must produce state-of-the-art accurate, precise, and consistent radiance and reflectance measurements over their five-year lifetimes, In addition, the production of continuous remote-sensing data from multiple instruments on several platforms requires that the remote-sensing measurements of the AMI platform be radiometrically tied to the measurements made by instruments on successive platforms. This is achieved through careful prelaunch and postlaunch instrument calibration, cross-calibration, and level 1B data validation (i.e,, vicarious calibration). This paper presents an overview of the calibration, cross-calibration, and level 1B data validation strategy for the AM1 platform. C1 NASA, Goddard Space Flight Ctr, Terr Phys Lab, Greenbelt, MD 20771 USA. SAIC Gen Sci Corp, Laurel, MD 20707 USA. RP Butler, JJ (reprint author), NASA, Goddard Space Flight Ctr, Terr Phys Lab, Greenbelt, MD 20771 USA. RI Butler, James/D-4188-2013 NR 21 TC 38 Z9 40 U1 1 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 JUL PY 1998 VL 36 IS 4 BP 1056 EP 1061 DI 10.1109/36.700990 PG 6 WC Geochemistry & Geophysics; Engineering, Electrical & Electronic; Remote Sensing; Imaging Science & Photographic Technology SC Geochemistry & Geophysics; Engineering; Remote Sensing; Imaging Science & Photographic Technology GA ZZ760 UT WOS:000074764400003 ER PT J AU Yamaguchi, Y Kahle, AB Tsu, H Kawakami, T Pniel, M AF Yamaguchi, Y Kahle, AB Tsu, H Kawakami, T Pniel, M TI Overview of Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) SO IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING LA English DT Article DE Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) Earth Observing System (EOS); remote sensing AB The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) is a research facility instrument provided by the Ministry of International Trade and Industry (MITI), Tokyo, Japan to be launched on NASA's Earth Observing System morning (EOS-AM1) platform in 1998, ASTER has three spectral bands in the visible near-infrared (VNIR), six bands in the shortwave infrared (SWIR), and five bands in the thermal infrared (TIR) regions, with 15-, 30-, and 90-m ground resolution, respectively. The VNIR subsystem has one backward-viewing band for stereoscopic observation in the along-track direction. Because the data will have wide spectral coverage and relatively high spatial resolution, we will be able to discriminate a variety of surface materials and reduce problems in some lower resolution data resulting from mixed pixels. ASTER will, for the first time, provide high-spatial resolution multispectral thermal infrared data from orbit and the highest spatial resolution surface spectral reflectance temperature and emissivity data of all of the EOS-AM1 instruments. The primary science objective of the ASTER mission is to improve understanding of the local- and regional-scale processes occurring on or near the earth's surface and lower atmosphere, including surface-atmosphere interactions. Specific areas of the science investigation include the following: 1) land surface climatology; 2) vegetation and ecosystem dynamics; 3) volcano monitoring; 4) hazard monitoring; 5) aerosols and clouds; 6) carbon cycling in the marine ecosystem; 7) hydrology; 8) geology and soil; and 9) land surface and land cover change. There are three categories of ASTER data: a global map, regional monitoring data sets, and local data sets to be obtained for requests from individual investigators. The ASTER instrument will have a limited (8%) duty cycle. Prioritization of data acquisition requests will be based on such factors as data category, user category, and science discipline. C1 Nagoya Univ, Dept Earth & Planetary Sci, Chikusa Ku, Nagoya, Aichi 46401, Japan. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Earth Remote Sensing Data Anal Ctr, Chuo Ku, Tokyo 104, Japan. RP Yamaguchi, Y (reprint author), Nagoya Univ, Dept Earth & Planetary Sci, Chikusa Ku, Nagoya, Aichi 46401, Japan. RI Namikawa, Laercio/C-5559-2013 OI Namikawa, Laercio/0000-0001-7847-1804 NR 10 TC 437 Z9 456 U1 4 U2 61 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 JUL PY 1998 VL 36 IS 4 BP 1062 EP 1071 DI 10.1109/36.700991 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 ZZ760 UT WOS:000074764400004 ER PT J AU Diner, DJ Beckert, JC Reilly, TH Bruegge, CJ Conel, JE Kahn, RA Martonchik, JV Ackerman, TP Davies, R Gerstl, SAW Gordon, HR Muller, JP Myneni, RB Sellers, PJ Pinty, B Verstraete, MM AF Diner, DJ Beckert, JC Reilly, TH Bruegge, CJ Conel, JE Kahn, RA Martonchik, JV Ackerman, TP Davies, R Gerstl, SAW Gordon, HR Muller, JP Myneni, RB Sellers, PJ Pinty, B Verstraete, MM TI Multi-angle Imaging SpectroRadiometer (MISR) - Instrument description and experiment overview SO IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING LA English DT Article DE earth; remote sensing ID HEMISPHERICAL REFLECTANCE; CANOPY REFLECTANCE; AVHRR DATA; SATELLITE; AEROSOL; CLOUD; MODEL; SURFACE; NADIR; PHOTOSYNTHESIS AB The Multi-angle Imaging SpectroRadiometer (MISR) instrument is scheduled for launch aboard the first of the Earth Observing System (EOS) spacecraft, EOS-AM1. MISR will provide global, radiometrically calibrated, georectified, and spatially coregistered imagery at nine discrete viewing angles and four visible/near-infrared spectral bands. Algorithms specifically developed to capitalize on this measurement strategy will be used to retrieve geophysical products for studies of clouds, aerosols, and surface radiation. This paper provides an overview of the as-built instrument characteristics and the application of MISR to remote sensing of the earth. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Penn State Univ, Dept Meteorol, University Pk, PA 16802 USA. Univ Arizona, Inst Atmospher Phys, Tucson, AZ 85721 USA. Los Alamos Natl Lab, Nonproliferat & Int Secur, Los Alamos, NM 87545 USA. Univ Miami, Dept Phys, Coral Gables, FL 33124 USA. Univ London Univ Coll, Dept Geomat Engn, London WC1E 6BT, England. Boston Univ, Dept Geog, Boston, MA 02215 USA. NASA, Johnson Space Ctr, Houston, TX 77058 USA. EC Joint Res Ctr, Space Applicat Inst, I-21020 Ispra, VA, Italy. RP Diner, DJ (reprint author), CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. EM djd@jord.jpl.nasa.gov RI Davies, Roger/D-4296-2009; Kahn, Ralph/D-5371-2012; Myneni, Ranga/F-5129-2012; OI Davies, Roger/0000-0002-2991-0409; Kahn, Ralph/0000-0002-5234-6359; Verstraete, Michel/0000-0003-0968-8721 NR 61 TC 480 Z9 490 U1 3 U2 43 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI PISCATAWAY PA 445 HOES LANE, PISCATAWAY, NJ 08855-4141 USA SN 0196-2892 J9 IEEE T GEOSCI REMOTE JI IEEE Trans. Geosci. Remote Sensing PD JUL PY 1998 VL 36 IS 4 BP 1072 EP 1087 DI 10.1109/36.700992 PG 16 WC Geochemistry & Geophysics; Engineering, Electrical & Electronic; Remote Sensing; Imaging Science & Photographic Technology SC Geochemistry & Geophysics; Engineering; Remote Sensing; Imaging Science & Photographic Technology GA ZZ760 UT WOS:000074764400005 ER PT J AU Barnes, WL Pagano, TS Salomonson, VV AF Barnes, WL Pagano, TS Salomonson, VV TI Prelaunch characteristics of the Moderate Resolution Imaging Spectroradiometer (MODIS) on EOS-AM1 SO IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING LA English DT Article DE calibration; image sensors; optical spectroscopy; radiometry; remote sensing; space technology ID WATER-VAPOR; SPECTROMETER DATA; REMOTE; CLOUD AB The Moderate Resolution Imaging Spectroradiometer (MODIS), with 36 bands and 0.25-, 0.5-, and 1.0-km geometric instantaneous-fields-of-view (GIFOV's) at nadir, has completed system level testing and has been integrated onto the Earth Observing System (EOS)-AM1 spacecraft, which is slated for launch in 1998, Raytheon Santa Barbara Remote Sensing (SBRS), Goleta, Ck, the MODIS developer, has performed extensive characterization and calibration measurements that have demonstrated a system that meets or exceeds most of NASA's demanding requirements. Based on this demonstrated capability, the MODIS Science Team, an international group of 28 land, ocean, atmosphere, and calibration remote-sensing scientists, has commenced delivery of algorithms that will routinely calculate 42 MODIS standard data products postlaunch, These products range from atmospheric aerosols, snow cover, and land and water surface temperature to leaf area index, ocean chlorophyll concentration, and sea ice extent, to name just a few. A description of the Science Team, including members' research interests and descriptions of their MODIS algorithms, can be found at the MODIS homepage (http://Itpwww.gsfc.nasa.gov/MODIS/MODIS.html). The MODIS system level testing included sufficient measurements in both ambient and thermal-vacuum environments to both demonstrate specification compliance and enable postlaunch implementation of radiometric calibration algorithms. The latter will include calculations to account for changes in response versus scan angle, response versus temperature, and response linearity. The system level tests also included performance verification of the onboard calibration systems, including the solar diffuser stability monitor (SDSM), the blackbody (BB), and the spectral radiometric calibration assembly (SRCA), which will enable monitoring of MODIS performance postlaunch, Descriptions of these subsystems are also on the MODIS homepage. C1 NASA, Goddard Space Flight Ctr, Earth Sci Directorate, Greenbelt, MD 20771 USA. Raytheon Santa Barbara Remote Sensing, Goleta, CA 93117 USA. RP Barnes, WL (reprint author), NASA, Goddard Space Flight Ctr, Earth Sci Directorate, Greenbelt, MD 20771 USA. EM wbarnes@neptune.gsfc.nasa.gov; vsalomon@pop900.gsfc.nasa.gov NR 17 TC 512 Z9 531 U1 4 U2 28 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 JUL PY 1998 VL 36 IS 4 BP 1088 EP 1100 DI 10.1109/36.700993 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 ZZ760 UT WOS:000074764400006 ER PT J AU Gillespie, A Rokugawa, S Matsunaga, T Cothern, JS Hook, S Kahle, AB AF Gillespie, A Rokugawa, S Matsunaga, T Cothern, JS Hook, S Kahle, AB TI A temperature and emissivity separation algorithm for Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) images SO IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING LA English DT Article DE algorithms; emission; image analysis; infrared imaging; remote sensing; temperature measurement ID LAND-SURFACE-TEMPERATURE; SEA-SURFACE; INFRARED IMAGES; SCANNER DATA; WINDOW; SATELLITE; MODEL AB The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) scanner on NASA's Earth Observing System (EOS)-AM1 satellite (launch scheduled for 1998) will collect five bands of thermal infrared (TIR) data with a noise equivalent temperature difference (NE Delta T) of less than or equal to 0.3 K to estimate surface temperatures and emissivity spectra, especially over land, where emissivities are not known in advance, Temperature/emissivity separation (TES) is difficult because there are five measurements but six unknowns. Various approaches have been used to constrain the extra degree of freedom, ASTER's TES algorithm hybridizes three established algorithms, first estimating the normalized emissivities and then calculating emissivity band ratios, An empirical relationship predicts the minimum emissivity from the spectral contrast of the ratioed values, permitting recovery of the emissivity spectrum. TES uses an iterative approach to remove reflected sky irradiance. Based on numerical simulation, TES should he able to recover temperatures within about +/-1.5 K and emissivities within about +/-0.015, Validation using airborne simulator images taken over playas and ponds in central Nevada demonstrates that, with proper atmospheric compensation, it is possible to meet the theoretical expectations, The main sources of uncertainty in the output temperature and emissivity images are the empirical relationship between emissivity values and spectral contrast, compensation for reflected sky irradiance, and ASTER's precision, calibration, and atmospheric compensation. C1 Univ Washington, Dept Geol Sci, Seattle, WA 98195 USA. Univ Tokyo, Fac Engn, Bunkyo Ku, Tokyo 113, Japan. Geol Survey Japan, Tsukuba, Ibaraki 305, Japan. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Univ Washington, Dept Geol Sci, Seattle, WA 98195 USA. EM alan@rad.geology.washington.edu NR 48 TC 620 Z9 683 U1 9 U2 80 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI PISCATAWAY PA 445 HOES LANE, PISCATAWAY, NJ 08855-4141 USA SN 0196-2892 EI 1558-0644 J9 IEEE T GEOSCI REMOTE JI IEEE Trans. Geosci. Remote Sensing PD JUL PY 1998 VL 36 IS 4 BP 1113 EP 1126 DI 10.1109/36.700995 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 ZZ760 UT WOS:000074764400008 ER PT J AU Wielicki, BA Barkstrom, BR Baum, BA Charlock, TP Green, RN Kratz, DP Lee, RB Minnis, P Smith, GL Wong, TM Young, DF Cess, RD Coakley, JA Crommelynck, DAH Donner, L Kandel, R King, MD Miller, AJ Ramanathan, V Randall, DA Stowe, LL Welch, RM AF Wielicki, BA Barkstrom, BR Baum, BA Charlock, TP Green, RN Kratz, DP Lee, RB Minnis, P Smith, GL Wong, TM Young, DF Cess, RD Coakley, JA Crommelynck, DAH Donner, L Kandel, R King, MD Miller, AJ Ramanathan, V Randall, DA Stowe, LL Welch, RM TI Clouds and the Earth's Radiant Energy System (CERES): Algorithm overview SO IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING LA English DT Article DE algorithms; clouds; meteorology; radiation monitoring ID RADIATION BUDGET EXPERIMENT; SURFACE RADIATION; SATELLITE DATA; SOLAR-RADIATION; CIRRUS CLOUDS; CLIMATE; PARAMETERIZATION; ERBE; ABSORPTION; FLUXES AB The Clouds and the Earth's Radiant Energy System (CERES) is part of NASA's Earth Observing System (EOS), CERES objectives include the following. 1) For climate change analysis, provide a continuation of the Earth Radiation Budget Experiment (ERBE) record of radiative fluxes at the top-of-the-atmosphere (TOA), analyzed using the same techniques as the existing ERBE data. 2) Double the accuracy of estimates of radiative fluxes at TOA and the earth's surface; 3) Provide the first long-term global estimates of the radiative fluxes within the earth's atmosphere. 4) Provide cloud property estimates collocated in space and time that are consistent with the radiative fluxes from surface to TOA, In order to accomplish these goals, CERES uses data from a combination of spaceborne instruments: CERES scanners, which are an improved version of the ERBE broadband radiometers, and collocated cloud spectral imager data on the same spacecraft. The CERES cloud and radiative flux data products should prove extremely useful in advancing the understanding of cloud-radiation interactions, particularly cloud feedback effects on the earth's radiation balance, For this reason, the CERES data should be fundamental to our ability to understand, detect, and predict global climate change, CERES results should also be very useful for studying regional climate changes associated with deforestation, desertification anthropogenic aerosols, and El Nino/Southern Oscillation events. This overview summarizes the Release 2 version of the planned CERES data products and data analysis algorithms. These algorithms are a prototype for the system that will produce the scientific data required for studying the role of clouds and radiation in the earth's climate system. This release will produce a data processing system designed to analyze the first CERES data, planned for launch on Tropical Rainfall Measuring Mission (TRMM) in November 1997, followed by the EOS morning (EOS-AM1) platform in 1998. C1 NASA, Langley Res Ctr, Div Atmospher Sci, Hampton, VA 23681 USA. Virginia Polytech Inst & State Univ, Blacksburg, VA 24061 USA. SUNY Stony Brook, Stony Brook, NY 11790 USA. Oregon State Univ, Corvallis, OR 97331 USA. Inst Royal Meteorol, B-1180 Brussels, Belgium. Natl Ocean & Atmospher Adm, Geophys Fluid Dynam Lab, Princeton, NJ 08542 USA. Ecole Polytech, Meteorol Dynam Lab, F-91128 Palaiseau, France. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. NOAA, Natl Ctr Environm Predict, NWS, Washington, DC 20233 USA. Univ Calif San Diego, Scripps Inst Oceanog, La Jolla, CA 92093 USA. Colorado State Univ, Ft Collins, CO 80521 USA. NOAA, Natl Environm Satellite Data & Informat Serv, Washington, DC 20233 USA. Univ Alabama, Huntsville, AL 35807 USA. RP Wielicki, BA (reprint author), NASA, Langley Res Ctr, Div Atmospher Sci, Hampton, VA 23681 USA. EM b.a.wielicki@larc.nasa.gov RI King, Michael/C-7153-2011; Randall, David/E-6113-2011; Baum, Bryan/B-7670-2011; Minnis, Patrick/G-1902-2010 OI King, Michael/0000-0003-2645-7298; Randall, David/0000-0001-6935-4112; Baum, Bryan/0000-0002-7193-2767; Minnis, Patrick/0000-0002-4733-6148 NR 59 TC 160 Z9 161 U1 4 U2 17 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI PISCATAWAY PA 445 HOES LANE, PISCATAWAY, NJ 08855-4141 USA SN 0196-2892 J9 IEEE T GEOSCI REMOTE JI IEEE Trans. Geosci. Remote Sensing PD JUL PY 1998 VL 36 IS 4 BP 1127 EP 1141 DI 10.1109/36.701020 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 ZZ760 UT WOS:000074764400009 ER PT J AU Guenther, B Godden, GD Xiong, XX Knight, EJ Qiu, SY Montgomery, H Hopkins, MM Khayat, MG Hao, ZD AF Guenther, B Godden, GD Xiong, XX Knight, EJ Qiu, SY Montgomery, H Hopkins, MM Khayat, MG Hao, ZD TI Prelaunch algorithm and data format for the Level 1 calibration products for the EOS-AM1 Moderate Resolution Imaging Spectroradiometer (MODIS) SO IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING LA English DT Article AB The Moderate Resolution Imaging Spectroradiometer (MODIS) radiometric calibration product (Level 1B) is described for the thermal emissive and reflective solar bands. A band-integrated radiance is produced for all measurements. A reflectance factor product is also produced for the reflected solar band measurements, Specific sensor design characteristics are identified to assist in understanding how the calibration algorithm software product is designed. The product file format is summarized, and the location for the current file format is provided. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Phys Applicat Inc, Vienna, VA 22182 USA. Sci Syst & Applicat Inc, Lanham, MD 20706 USA. Res & Data Syst Corp, Greenbelt, MD 20770 USA. Computat Phys Applicat Inc, Columbia, MD 21042 USA. Gen Sci Corp, Laurel, MD 20707 USA. RP Guenther, B (reprint author), NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. NR 10 TC 80 Z9 85 U1 1 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 JUL PY 1998 VL 36 IS 4 BP 1142 EP 1151 DI 10.1109/36.701021 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 ZZ760 UT WOS:000074764400010 ER PT J AU Thome, K Arai, K Hook, S Kieffer, H Lang, H Matsunaga, T Ono, A Palluconi, F Sakuma, H Slater, P Takashima, T Tonooka, H Tsuchida, S Welch, RM Zalewski, E AF Thome, K Arai, K Hook, S Kieffer, H Lang, H Matsunaga, T Ono, A Palluconi, F Sakuma, H Slater, P Takashima, T Tonooka, H Tsuchida, S Welch, RM Zalewski, E TI ASTER preflight and inflight calibration and the validation of level 2 products SO IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING LA English DT Article DE Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) algorithm validation; geometric calibration; radiometric calibration; vicarious calibration ID REFLECTANCE AB This paper describes the preflight and inflight calibration approaches used for the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER), The system is a multispectral, high-spatial resolution sensor on the Earth Observing System's (EOS)-AM1 platform, Preflight calibration of ASTER uses well-characterized sources to provide calibration and preflight round-robin exercises to understand biases between the calibration sources of ASTER and other EOS sensors. These round-robins rely on well-characterized, ultra-stable radiometers, An experiment held in Yokohama, Japan, showed that the output from the source used for the visible and near-infrared (VNIR) subsystem of ASTER may be underestimated by 1.5%, but this is still within the 4% specification for the absolute, radiometric calibration of these bands. Inflight calibration will rely on vicarious techniques and onboard blackbodies and lamps. Vicarious techniques include ground-reference methods using desert and water sites. A recent joint field campaign gives confidence that these methods currently provide absolute calibration to better than 5%, and indications are that uncertainties less than the required 4% should be achievable at launch. The EOS-AM1 platform will also provide a spacecraft maneuver that will allow ASTER to see the moon, allowing further characterization of the sensor. A method for combining the results of these independent calibration results is presented. The paper also describes the plans for validating the Level 2 data products from ASTER, These plans rely heavily upon field campaigns using methods similar to those used for the ground-reference, vicarious calibration methods. C1 Univ Arizona, Ctr Opt Sci, Tucson, AZ 85721 USA. Saga Univ, Fac Sci Engn, Saga 840, Japan. Jet Prop Lab, Pasadena, CA 91109 USA. US Geol Survey, Flagstaff, AZ 86001 USA. Geol Survey Japan, Tsukuba, Ibaraki 305, Japan. Natl Res Lab Metrol, Tsukuba, Ibaraki 305, Japan. NASDA, Earth Observat Res Ctr, Tokyo 106, Japan. Ibaraki Univ, Hitachi, Ibaraki 316, Japan. Univ Alabama, Huntsville, AL 35807 USA. RP Thome, K (reprint author), Univ Arizona, Ctr Opt Sci, Tucson, AZ 85721 USA. RI Thome, Kurtis/D-7251-2012 NR 38 TC 31 Z9 34 U1 1 U2 9 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 JUL PY 1998 VL 36 IS 4 BP 1161 EP 1172 DI 10.1109/36.701023 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 ZZ760 UT WOS:000074764400012 ER PT J AU Lee, RB Barkstrom, BR Bitting, HC Crommelynck, DAH Paden, J Pandey, DK Priestley, KJ Smith, GL Thomas, S Thornhill, KL Wilson, RS AF Lee, RB Barkstrom, BR Bitting, HC Crommelynck, DAH Paden, J Pandey, DK Priestley, KJ Smith, GL Thomas, S Thornhill, KL Wilson, RS TI Prelaunch calibrations of the Clouds and the Earth's Radiant Energy System (CERES) tropical rainfall measuring mission and Earth Observing System morning (EOS-AM1) spacecraft thermistor bolometer sensors SO IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING LA English DT Article DE calibration; climate; longwave; radiometry; shortwave ID RADIOMETERS AB The Clouds and the Earth's Radiant Energy System (CERES) spacecraft scanning thermistor bolometer sensors measure earth radiances in the broadband shortwave solar (0.3-5.0 mu m) and total (0.3-->100 mu m) spectral bands as well as in the 8-12-mu m water vapor window spectral band. On November 27, 1997, the launch of the Tropical Rainfall Measuring Mission (TRMM) spacecraft placed the first set of CERES sensors into orbit, and 30 days later, the sensors initiated operational measurements of the earth radiance fields, In 1998, the Earth Observing System morning (EOS-AM1) spacecraft will place the second and third sensor sets into orbit. The prelaunch CERES sensors' count conversion coefficients (gains and zero-radiance offsets) were determined in vacuum ground facilities. The gains were tied radiometrically to the International Temperature Scale of 1990 (ITS-90), The gain determinations included the spectral properties (reflectance, transmittance, emittance, etc.) of both the sources and sensors as well as the in-field-of-view (FOV) and out-of-FOV sensor responses. The resulting prelaunch coefficients for the TRMM and EOS-AM1 sensors are presented. Inflight calibration systems and on-orbit calibration approaches are described, which are being used to determine the temporal stabilities of the sensors' gains and offsets from prelaunch calibrations through on-orbit measurements. Analyses of the TRMM prelaunch and on-orbit calibration results indicate that the sensors have retained their ties to ITS-90 at accuracy levels better than +/-0.3% between the 1995 prelaunch and 1997 on-orbit calibrations. C1 NASA, Langley Res Ctr, Div Atmospher Sci, Hampton, VA 23681 USA. TRW Space & Elect Grp, Adv Technol Div, Redondo Beach, CA 90278 USA. Inst Royal Meteorol, B-1180 Brussels, Belgium. Sci Applicat Int Corp, Hampton, VA 23665 USA. Virginia Polytech Inst & State Univ, Dept Mech Engn, Thermal Radiat Lab, Blacksburg, VA 24061 USA. RP Lee, RB (reprint author), NASA, Langley Res Ctr, Div Atmospher Sci, Hampton, VA 23681 USA. NR 24 TC 58 Z9 59 U1 2 U2 5 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 JUL PY 1998 VL 36 IS 4 BP 1173 EP 1185 DI 10.1109/36.701024 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 ZZ760 UT WOS:000074764400013 ER PT J AU Bruegge, CJ Duval, VG Chrien, NL Korechoff, RP Gaitley, BJ Hochberg, EB AF Bruegge, CJ Duval, VG Chrien, NL Korechoff, RP Gaitley, BJ Hochberg, EB TI MISR prelaunch instrument calibration and characterization results SO IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING LA English DT Article DE calibration; image sensors; testing AB Each of the nine cameras that compose the Multiangle Imaging SpectroRadiometer (MISR) has been rigorously tested, characterized, and calibrated. Requirements on these tests include a 3% (1 sigma) radiometric calibration requirement, spectral response function determination of both the in- and out-of-band regions, and distortion mapping. The latter test determines the relative look-angle to the ground corresponding to each focal plane detector element. This is established to within one-tenth of the instantaneous field-of-view. Most of the performance testing was done on the cameras as they completed assembly. This was done to take advantage of the serial delivery of the hardware, minimize the required size of the thermal-vacuum facilities, and allow testing to occur early in the schedule allocated for the hardware build. This proved to be an effective strategy, as each of the test objectives was met, Additional testing as an integrated instrument included verification of the data packetization, camera pointing, and clearances of the fields-of-view. Results of these studies have shown that the MISR cameras are of high quality and will meet the needs of the MISR science community. Highly accurate calibration data are on-hand and available for conversion of camera output to radiances. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Bruegge, CJ (reprint author), CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. NR 18 TC 29 Z9 29 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 JUL PY 1998 VL 36 IS 4 BP 1186 EP 1198 DI 10.1109/36.701025 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 ZZ760 UT WOS:000074764400014 ER PT J AU Thome, K Palluconi, F Takashima, T Masuda, K AF Thome, K Palluconi, F Takashima, T Masuda, K TI Atmospheric correction of ASTER SO IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING LA English DT Article DE Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) atmospheric correction; lookup table ID SURFACE REFLECTANCE FACTORS; EMERGENT RADIATION; SATELLITE; TEMPERATURE; CHANNELS; ALGORITHM; RETRIEVAL; FIELD AB An atmospheric correction algorithm for operational use for the high-spatial resolution, Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) is presented. The correction is a straightforward approach relying on inputs from other satellite sensors to determine the atmospheric characteristics of the scene to be corrected. Methods for the solar reflective and thermal infrared (TIR) are presented separately. The solar-reflective approach uses a lookup table (LUT) based on output from a Gauss-Seidel iteration radiative transfer code. A method to handle adjacency effects is included that relies on model output, assuming a checkerboard surface. An example of a numerical simulation shows that the effect of a land surface on the radiance over the ocean is stronger just off the coastal zone and decreases exponentially with increasing distance from the land. A typical numerical simulation is performed over the Tsukuba lake area in Japan. The TIR approach relies on the radiative transfer code Moderate Resolution Atmospheric Radiance and Transmittance Model (MODTRAN), The code is run for a given set of atmospheric conditions for multiple locations in the scene for several representative elevations. Pixel-by-pixel radiances are then found using spatial interpolation, Sensitivity analysis of the methods indicate that the results of the atmospheric correction,will be limited by the accuracies of the input parameters. C1 Univ Arizona, Remote Sensing Grp, Ctr Opt Sci, Tucson, AZ 85721 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. NASDA, Earth Observat Res Ctr, Minato Ku, Tokyo 106, Japan. Meteorol Res Inst, Tsukuba, Ibaraki 305, Japan. RP Thome, K (reprint author), Univ Arizona, Remote Sensing Grp, Ctr Opt Sci, Tucson, AZ 85721 USA. EM kurt.thome@opt-sci.arizona.edu RI Thome, Kurtis/D-7251-2012 NR 49 TC 65 Z9 72 U1 1 U2 8 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 JUL PY 1998 VL 36 IS 4 BP 1199 EP 1211 DI 10.1109/36.701026 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 ZZ760 UT WOS:000074764400015 ER PT J AU Martonchik, JV Diner, DJ Kahn, RA Ackerman, TP Verstraete, ME Pinty, B Gordon, HR AF Martonchik, JV Diner, DJ Kahn, RA Ackerman, TP Verstraete, ME Pinty, B Gordon, HR TI Techniques for the retrieval of aerosol properties over land and ocean using multiangle imaging SO IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING LA English DT Article DE aerosols; algorithms; remote sensing ID REFLECTANCE FACTOR DISTRIBUTIONS; OPTICAL-PROPERTIES; SATELLITE IMAGERY; AVHRR DATA; ATMOSPHERE; RADIOMETER; SCATTERING; RADIANCE; HARDWOOD; CANOPY AB Aerosols are believed to play a direct role in the radiation budget of earth, but their net radiative effect is not well established, particularly on regional scales, Whether aerosols heat or cool a given location depends on their composition and column amount and on the surface albedo, information that is not routinely available, especially over land. Obtaining global information on aerosol and surface radiative characteristics, over both ocean and land, is a task of the Multi-angle Imaging SpectroRadiometer (MISR), an instrument to be launched in 1998 on the Earth Observing System (EOS)-AM1 platform. Three algorithms are described that will be implemented to retrieve aerosol properties globally using MISR data. Because of the large volume of data to be processed on a daily basis, these algorithms rely on lookup tables of atmospheric radiative parameters and predetermined aerosol mixture models to expedite the radiative transfer (RT) calculations. Over oceans, the "dark water" algorithm is used, taking full advantage of the nature of the MISR data. Over land, a choice of algorithms is made, depending on the surface types within a scene-dark water bodies, heavily vegetated areas, or high-contrast terrain. The retrieval algorithms are tested on simulated MISR data, computed using realistic aerosol and surface reflectance models. The results indicate that aerosol optical depth can be retrieved with an accuracy of 0.05 or 10%, whichever is greater, and some information can be obtained about the aerosol chemical and physical properties. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Penn State Univ, Dept Meteorol, University Pk, PA 16802 USA. Commiss European Communities, Joint Res Ctr, Space Applicat Inst, I-21020 Ispra, VA, Italy. Univ Miami, Dept Phys, Coral Gables, FL 33124 USA. RP Martonchik, JV (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. RI Kahn, Ralph/D-5371-2012; OI Kahn, Ralph/0000-0002-5234-6359; Verstraete, Michel/0000-0003-0968-8721 NR 47 TC 233 Z9 240 U1 2 U2 22 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 JUL PY 1998 VL 36 IS 4 BP 1212 EP 1227 DI 10.1109/36.701027 PG 16 WC Geochemistry & Geophysics; Engineering, Electrical & Electronic; Remote Sensing; Imaging Science & Photographic Technology SC Geochemistry & Geophysics; Engineering; Remote Sensing; Imaging Science & Photographic Technology GA ZZ760 UT WOS:000074764400016 ER PT J AU Justice, CO Vermote, E Townshend, JRG Defries, R Roy, DP Hall, DK Salomonson, VV Privette, JL Riggs, G Strahler, A Lucht, W Myneni, RB Knyazikhin, Y Running, SW Nemani, RR Wan, ZM Huete, AR van Leeuwen, W Wolfe, RE Giglio, L Muller, JP Lewis, P Barnsley, MJ AF Justice, CO Vermote, E Townshend, JRG Defries, R Roy, DP Hall, DK Salomonson, VV Privette, JL Riggs, G Strahler, A Lucht, W Myneni, RB Knyazikhin, Y Running, SW Nemani, RR Wan, ZM Huete, AR van Leeuwen, W Wolfe, RE Giglio, L Muller, JP Lewis, P Barnsley, MJ TI The Moderate Resolution Imaging Spectroradiometer (MODIS): Land remote sensing for global change research SO IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING LA English DT Article DE Earth Observing System Moderate Resolution Imaging Spectroradiometer (EOS-MODIS); global change; monitoring; satellite remote sensing ID CHANGE-VECTOR ANALYSIS; BIDIRECTIONAL REFLECTANCE; SURFACE-TEMPERATURE; VEGETATION INDEX; AVHRR DATA; DATA SET; MULTITEMPORAL SPACE; SATELLITE DATA; COVER CHANGE; SNOW COVER AB The first Moderate Resolution Imaging Spectroradiometer (MODIS) instrument is planned for launch by NASA in 1998. This instrument will provide a new and improved capability for terrestrial satellite remote sensing aimed at meeting the needs of global change research, The MODIS standard products will provide new and improved tools for moderate resolution land surface monitoring, These higher order data products have been designed to remove the burden of certain common types of data processing from the user community and meet the more general needs of global-to-regional monitoring, modeling, and assessment. The near-daily coverage of moderate resolution data from MODIS, coupled with the planned increase in high-resolution sampling from Landsat 7, will provide a powerful combination of observations, The full potential of MODIS will be realized once a stable and well-calibrated time-series of multispectral data has been established. In this paper the proposed MODIS standard products for land applications are described along with the current plans for data quality assessment and product validation. C1 Univ Virginia, Charlottesville, VA 22903 USA. Univ Maryland, College Pk, MD 20742 USA. Res & Data Syst Corp, Greenbelt, MD 20770 USA. Boston Univ, Boston, MA 02215 USA. Univ Montana, Missoula, MT 59801 USA. Univ Calif Santa Barbara, Santa Barbara, CA 93106 USA. Univ Arizona, Tucson, AZ 85721 USA. NASA, Goddard Space Flight Ctr, Raytheon STX, Greenbelt, MD 20771 USA. Sci Syst & Applicat Inc, Lanham, MD 20706 USA. UCL, London WC1E 6BT, England. Univ Coll Swansea, Swansea SA2 8PP, W Glam, Wales. RP Justice, CO (reprint author), Univ Virginia, Charlottesville, VA 22903 USA. EM justice@kratmos.gsfc.nasa.gov RI van Leeuwen, Willem/A-6547-2008; Lewis, Philip/C-1588-2008; Lucht, Wolfgang/G-2180-2011; Privette, Jeffrey/G-7807-2011; Hall, Dorothy/D-5562-2012; Wolfe, Robert/E-1485-2012; Vermote, Eric/K-3733-2012; Myneni, Ranga/F-5129-2012; Huete, Alfredo/C-1294-2008 OI Lewis, Philip/0000-0002-8562-0633; Lucht, Wolfgang/0000-0002-3398-8575; Privette, Jeffrey/0000-0001-8267-9894; Wolfe, Robert/0000-0002-0915-1855; Huete, Alfredo/0000-0003-2809-2376 NR 89 TC 651 Z9 705 U1 11 U2 109 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI PISCATAWAY PA 445 HOES LANE, PISCATAWAY, NJ 08855-4141 USA SN 0196-2892 J9 IEEE T GEOSCI REMOTE JI IEEE Trans. Geosci. Remote Sensing PD JUL PY 1998 VL 36 IS 4 BP 1228 EP 1249 DI 10.1109/36.701075 PG 22 WC Geochemistry & Geophysics; Engineering, Electrical & Electronic; Remote Sensing; Imaging Science & Photographic Technology SC Geochemistry & Geophysics; Engineering; Remote Sensing; Imaging Science & Photographic Technology GA ZZ760 UT WOS:000074764400017 ER PT J AU Esaias, WE Abbott, MR Barton, I Brown, OB Campbell, JW Carder, KL Clark, DK Evans, RH Hoge, FE Gordon, HR Balch, WM Letelier, R Minnett, PJ AF Esaias, WE Abbott, MR Barton, I Brown, OB Campbell, JW Carder, KL Clark, DK Evans, RH Hoge, FE Gordon, HR Balch, WM Letelier, R Minnett, PJ TI An overview of MODIS capabilities for ocean science observations SO IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING LA English DT Article ID SEA-SURFACE TEMPERATURE; ZONE COLOR SCANNER; ATMOSPHERIC CORRECTION; NATURAL FLUORESCENCE; CHLOROPHYLL-A; PHYTOPLANKTON PIGMENTS; INFRARED MEASUREMENTS; IMAGING SPECTROMETER; RADIOMETER DATA; GLOBAL OCEAN AB The Moderate Resolution Imaging Spectroradiometer (MODIS) will add a significant new capability for investigating the 70% of the earth's surface that is covered by oceans, in addition to contributing to the continuation of a decadal scale time series necessary for climate change assessment in the oceans. Sensor capabilities of particular importance for improving the accuracy of ocean products include high SNR and high stability for narrower spectral bands, improved onboard radiometric calibration and stability monitoring, and improved science data product algorithms. Spectral bands for resolving solar-stimulated chlorophyll fluorescence and a split window in the 4-mu m region for SST will result in important new global ocean science products for biology and physics. MODIS will return full global data at 1-km resolution. The complete suite of Levels 2 and 3 ocean products is reviewed, and many areas where MODIS data are expected to make significant, new contributions to the enhanced understanding of the oceans' role in understanding climate change are discussed. In providing a highly complementary and consistent set of observations of terrestrial, atmospheric, and ocean observations, MODIS data will provide important new information on the interactions between earth's major components. C1 Goddard Space Flight Ctr, Oceans & Ice Branch, Greenbelt, MD 20777 USA. Oregon State Univ, Sch Oceanog, Corvallis, OR 97331 USA. CSIRO, Marine Labs, Hobart, Tas 7001, Australia. Univ Miami, Rosenstiel Sch Marine & Atmospher Sci, Div Meteorol & Phys Oceanog, Miami, FL 33149 USA. NASA, MPTE, Washington, DC 20546 USA. Univ S Florida, Dept Oceanog, Tampa, FL 33620 USA. NOAA, Ocean Res & Applicat Div, Camp Springs, MD 20746 USA. NASA, Goddard Space Flight Ctr, Wallops Flight Facil, Wallops Island, VA 23337 USA. Univ Miami, Dept Phys, Coral Gables, FL 33149 USA. Bigelow Lab Ocean Sci, Boothbay Harbor, ME 04575 USA. RP Esaias, WE (reprint author), Goddard Space Flight Ctr, Oceans & Ice Branch, Code 971, Greenbelt, MD 20777 USA. EM wayne.esaias@gsfc.nasa.gov RI Letelier, Ricardo/A-6953-2009; Brown, Otis/C-7188-2015 OI Letelier, Ricardo/0000-0003-3376-4026; Brown, Otis/0000-0003-3111-1507 NR 99 TC 258 Z9 268 U1 2 U2 31 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 JUL PY 1998 VL 36 IS 4 BP 1250 EP 1265 DI 10.1109/36.701076 PG 16 WC Geochemistry & Geophysics; Engineering, Electrical & Electronic; Remote Sensing; Imaging Science & Photographic Technology SC Geochemistry & Geophysics; Engineering; Remote Sensing; Imaging Science & Photographic Technology GA ZZ760 UT WOS:000074764400018 ER PT J AU Martonchik, JV Diner, DJ Pinty, B Verstraete, MM Myneni, RB Knyazikhin, Y Gordon, HR AF Martonchik, JV Diner, DJ Pinty, B Verstraete, MM Myneni, RB Knyazikhin, Y Gordon, HR TI Determination of land and ocean reflective, radiative, and biophysical properties using multiangle imaging SO IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING LA English DT Article DE algorithms; reflection; remote sensing; vegetation ID BIDIRECTIONAL REFLECTANCE; ATMOSPHERIC TRANSFER; FACTOR DISTRIBUTIONS; VEGETATION CANOPIES; ALBEDO; PHOTOSYNTHESIS; TRANSPIRATION; SCATTERING; RADIANCE; SURFACES AB Knowledge of the directional and hemispherical reflectance properties of natural surfaces, such as soils and vegetation canopies, is essential for classification studies and canopy model inversion. The Multi-angle Imaging SpectroRadiometer (MISR), an instrument to be launched in 1998 onboard the EOS-AM1 platform, will make global observations of the earth's surface at 1.1-km spatial resolution, with the objective of determining the atmospherically corrected reflectance properties of most of the land surface and the tropical ocean. The algorithms to retrieve surface directional reflectances, albedos, and selected biophysical parameters using MISR data are described. Since part of the MISR data analyses includes an aerosol retrieval, it is assumed that the optical properties of the atmosphere (i.e., aerosol characteristics) have been determined well enough to accurately model the radiative transfer process. The core surface retrieval algorithms are tested on simulated MISR data, computed using realistic surface reflectance and aerosol models, and the sensitivity of the retrieved directional and hemispherical reflectances to aerosol type and column amount is illustrated. Included is a summary list of the MISR surface products. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Commiss European Communities, Joint Res Ctr, Space Applicat Inst, I-21020 Ispra, VA, Italy. Boston Univ, Dept Geog, Boston, MA 02215 USA. Univ Miami, Dept Phys, Coral Gables, FL 33124 USA. RP Martonchik, JV (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. EM jvm@jord.jpl.nasa.gov RI Myneni, Ranga/F-5129-2012; OI Verstraete, Michel/0000-0003-0968-8721 NR 40 TC 106 Z9 108 U1 1 U2 8 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 JUL PY 1998 VL 36 IS 4 BP 1266 EP 1281 DI 10.1109/36.701077 PG 16 WC Geochemistry & Geophysics; Engineering, Electrical & Electronic; Remote Sensing; Imaging Science & Photographic Technology SC Geochemistry & Geophysics; Engineering; Remote Sensing; Imaging Science & Photographic Technology GA ZZ760 UT WOS:000074764400019 ER PT J AU Welch, R Jordan, T Lang, H Murakami, H AF Welch, R Jordan, T Lang, H Murakami, H TI ASTER as a source for topographic data in the late 1990's SO IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING LA English DT Article DE Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) digital elevation model; terrain mapping ID SYSTEM AB Topography is a fundamental earth characteristic that can be measured for studies of the land surface, The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) onboard the EOS-AM1 platform will acquire along-track stereo data for topographic mapping. ASTER is capable of recording 771 digital stereo pairs per day, each covering 60 x 60 km on the ground, at 15-m resolution, with a base-to-height ratio of 0.6, According to present plans, approximately 30 digital elevation models (DEM's), accurate to within +/-7 to +/-50 m (RMSEz) will be produced daily by processing facilities in Japan and the United States, The Land Processes Distributed Active Archive Center (LP-DAAC) at the United States Geological Survey's (USGS's) EROS Data Center (EDC) will emphasize the use of automated stereocorrelation procedures to produce absolute DEM's tied to ground control. During the six-year mission, ASTER has the potential to provide a coherent, digital stereo data set covering all of the earth's land surface. At minimum, ASTER DEM's will augment topographic data from other sources. Results of simulations of ASTER stereo data using existing satellite and aircraft data over validation sites in Huntsville, AL, and Iguala, Mexico, illustrate the value of high-resolution ASTER DEM's and how actual ASTER DEM's will be validated. C1 Univ Georgia, Dept Geog, Ctr Remote Sensing & Mapping Sci, Athens, GA 30602 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Minist Construct, Geol Survey Inst, Tsukuba, Ibaraki 3050811, Japan. RP Welch, R (reprint author), Univ Georgia, Dept Geog, Ctr Remote Sensing & Mapping Sci, Athens, GA 30602 USA. NR 31 TC 57 Z9 62 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 JUL PY 1998 VL 36 IS 4 BP 1282 EP 1289 DI 10.1109/36.701078 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 ZZ760 UT WOS:000074764400020 ER PT J AU Jovanovic, VM Smyth, MM Zong, J Ando, R Bothwell, GW AF Jovanovic, VM Smyth, MM Zong, J Ando, R Bothwell, GW TI MISR photogrammetric data reduction for geophysical retrievals SO IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING LA English DT Article DE calibration; mapping; photogrammetry; rectification AB The theoretical concept, based on modern photogrammetric methods, underlying the design of the Multi-angle Imaging SpectroRadiometer (MISR) science data processing system, responsible for the autonomous and continuous georectification of multiangle imagery, is the subject of this paper. The algorithm partitions effort between the MTSR Science Computing Facility and the Earth Observing System (EOS) Distributed Active Archive Center (DAAC) in a way that minimizes the amount of processing required at the latter location to rectify and map project remotely sensed data online, as it comes from the instrument. The algorithm deals with the following issues: 1) removal of the errors introduced by inaccurate navigation and attitude data; 2) removal of the distortions introduced by surface topography; 3) attainment of a balance between limited hardware resources, huge data volume and processing requirements, and autonomous and nonstop aspects of the production system. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Jovanovic, VM (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 13 TC 14 Z9 14 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 JUL PY 1998 VL 36 IS 4 BP 1290 EP 1301 DI 10.1109/36.701079 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 ZZ760 UT WOS:000074764400021 ER PT J AU Masuoka, E Fleig, A Wolfe, RE Patt, F AF Masuoka, E Fleig, A Wolfe, RE Patt, F TI Key characteristics of MODIS data products SO IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING LA English DT Article DE data processing; image sensors; remote sensing; satellites ID CHANGE-VECTOR ANALYSIS; LAND-COVER CHANGE; MULTITEMPORAL SPACE AB Forty science products totaling 600 GB of storage volume per day will be produced from NASA's Moderate Resolution Imaging Spectroradiometer (MODIS). Eighty-five percent of this data volume is in products that are in the instrument's scan geometry (processing Levels 1 and 2) that are not earth located. Before ordering MODIS data products, users should consider processing level, data formats, product size, and the unique characteristics of MODIS products. Given the data volumes associated with the MODIS Levels 1 and 2 products, the resources required to process them and the issues associated with the scanning geometry of the instrument, users are encouraged to order data products that are earth located, These include Level 3 products, which are produced on fixed global grids and Level 2G products, in which observations and their earth location have been stored in bins of the MODIS global grids. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Masuoka, E (reprint author), NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RI Wolfe, Robert/E-1485-2012 OI Wolfe, Robert/0000-0002-0915-1855 NR 11 TC 57 Z9 58 U1 4 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 JUL PY 1998 VL 36 IS 4 BP 1313 EP 1323 DI 10.1109/36.701081 PG 11 WC Geochemistry & Geophysics; Engineering, Electrical & Electronic; Remote Sensing; Imaging Science & Photographic Technology SC Geochemistry & Geophysics; Engineering; Remote Sensing; Imaging Science & Photographic Technology GA ZZ760 UT WOS:000074764400023 ER PT J AU Wolfe, RE Roy, DP Vermote, E AF Wolfe, RE Roy, DP Vermote, E TI MODIS land data storage, gridding, and compositing methodology: Level 2 grid SO IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING LA English DT Article ID AVHRR DATA; CUBIC CONVOLUTION; RECONSTRUCTION; INTERPOLATION; RADIOMETER; ALGORITHMS; IMAGES; EOS AB The methodology used to store a number of the Moderate Resolution Imaging Spectroradiometer (MODIS) land products is described. The approach has several scientific and data processing advantages over conventional approaches used to store remotely sensed data sets and may be applied to any remote-sensing data set in which the observations are geolocated to subpixel accuracy. The methodology will enable new algorithms to be more accurately developed because important information about the intersection between the sensor observations and the output grid cells are preserved. The methodology will satisfy the very different needs of the MODIS land product generation algorithms, allow sophisticated users to develop their own application-specific MODIS land data sets, and enable efficient processing and reprocessing of MODIS land products. A generic MODIS land gridding and compositing algorithm that takes advantage of the data storage structure and enables the exploitation of multiple observations of the surface more fully than conventional approaches is described. The algorithms are illustrated with simulated MODIS data, and the practical considerations of increased data storage are discussed. C1 NASA, Goddard Space Flight Ctr, Raytheon STX, Greenbelt, MD 20771 USA. Univ Maryland, Dept Geog, College Pk, MD 20742 USA. RP Wolfe, RE (reprint author), NASA, Goddard Space Flight Ctr, Raytheon STX, Code 922, Greenbelt, MD 20771 USA. RI Wolfe, Robert/E-1485-2012; Vermote, Eric/K-3733-2012 OI Wolfe, Robert/0000-0002-0915-1855; NR 32 TC 233 Z9 241 U1 2 U2 20 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 JUL PY 1998 VL 36 IS 4 BP 1324 EP 1338 DI 10.1109/36.701082 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 ZZ760 UT WOS:000074764400024 ER PT J AU Diner, DJ Barge, LM Bruegge, CJ Chrien, TG Conel, JE Eastwood, ML Garcia, JD Hernandez, MA Kurzweil, CG Ledeboer, WC Pignatano, ND Sarture, CM Smith, BG AF Diner, DJ Barge, LM Bruegge, CJ Chrien, TG Conel, JE Eastwood, ML Garcia, JD Hernandez, MA Kurzweil, CG Ledeboer, WC Pignatano, ND Sarture, CM Smith, BG TI The Airborne Multi-angle Imaging SpectroRadiometer (AirMISR): Instrument description and first results SO IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING LA English DT Article DE Earth; remote sensing AB An Airborne Multi-angle Imaging SpectroRadiometer (AirMISR) instrument has been developed to assist in validation of the Earth Observing System (EOS) MISR experiment. Unlike the EOS MISR, which contains nine individual cameras pointed at discrete look angles, AirMISR utilizes a single camera in a pivoting gimbal mount. The AirMISR camera has been fabricated from MISR brassboard and engineering model components and, thus, has similar radiometric and spectral response as the MISE cameras. This paper provides a description of the AirMISR instrument and summarizes the results of engineering flights conducted during 1997. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Diner, DJ (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 4 TC 42 Z9 42 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 0196-2892 J9 IEEE T GEOSCI REMOTE JI IEEE Trans. Geosci. Remote Sensing PD JUL PY 1998 VL 36 IS 4 BP 1339 EP 1349 DI 10.1109/36.701083 PG 11 WC Geochemistry & Geophysics; Engineering, Electrical & Electronic; Remote Sensing; Imaging Science & Photographic Technology SC Geochemistry & Geophysics; Engineering; Remote Sensing; Imaging Science & Photographic Technology GA ZZ760 UT WOS:000074764400025 ER PT J AU Gregg, WW Woodward, RH AF Gregg, WW Woodward, RH TI Improvements in coverage frequency of ocean color: Combining data from SeaWiFS and MODIS SO IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING LA English DT Article DE biology; remote sensing; sea surface AB Large improvements in coverage frequency (daily to four-day) can be expected by combining ocean color data from the Sea-Viewing Wide Field-Of-View Sensor (Sea WiFS) and Moderate Resolution Imaging Spectrometer (MODIS) missions. Results indicated 40-47% increases in global coverage over SeaWifS alone in one day and >100% in low latitudes. The missions are highly complementary for observation of short-term processes. C1 NASA, Goddard Space Flight Ctr, Lab Hydrospher Proc, Greenbelt, MD 20771 USA. Gen Sci Corp, Laurel, MD 20707 USA. RP Gregg, WW (reprint author), NASA, Goddard Space Flight Ctr, Lab Hydrospher Proc, Code 971, Greenbelt, MD 20771 USA. NR 5 TC 17 Z9 18 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 JUL PY 1998 VL 36 IS 4 BP 1350 EP 1353 DI 10.1109/36.701084 PG 4 WC Geochemistry & Geophysics; Engineering, Electrical & Electronic; Remote Sensing; Imaging Science & Photographic Technology SC Geochemistry & Geophysics; Engineering; Remote Sensing; Imaging Science & Photographic Technology GA ZZ760 UT WOS:000074764400026 ER PT J AU Wallett, TM Vaden, KR Freeman, J Qureshi, AH AF Wallett, TM Vaden, KR Freeman, J Qureshi, AH TI Technical characteristics of a novel helical-groove traveling-wave tube structure SO IEEE TRANSACTIONS ON MAGNETICS LA English DT Article; Proceedings Paper CT 7th Joint MMM-Intermag Conference CY JAN 06-09, 1998 CL SAN FRANCISCO, CALIFORNIA DE MAFIA; helix; interaction impedance; helical-groove AB Experimental measurements of the dispersion characteristics of a C-band helix structure were carried out and compared to the dispersion characteristics found from a helix model using the three-dimensional electromagnetic computer code MAFIA. A conceptually novel design comprising a helical thread of the same pitch and inner diameter in a cylindrical waveguide also were calculated with the MAFIA code. The helical-groove structure exhibits a smaller bandwidth but at a much higher frequency range than the traditional helical structure for similar physical dimensions, It is physically more robust in construction. The interaction impedance also compares favorably with those of the conventional structure. C1 NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. Cleveland State Univ, Cleveland, OH 44115 USA. RP Wallett, TM (reprint author), NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. NR 6 TC 1 Z9 2 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 0018-9464 J9 IEEE T MAGN JI IEEE Trans. Magn. PD JUL PY 1998 VL 34 IS 4 BP 1408 EP 1410 DI 10.1109/20.706564 PN 1 PG 3 WC Engineering, Electrical & Electronic; Physics, Applied SC Engineering; Physics GA 101CP UT WOS:000074852300191 ER PT J AU Teter, JP Sendaula, MH Vranish, J Crawford, EJ AF Teter, JP Sendaula, MH Vranish, J Crawford, EJ TI Magnetostrictive linear motor development SO IEEE TRANSACTIONS ON MAGNETICS LA English DT Article; Proceedings Paper CT 7th Joint MMM-Intermag Conference CY JAN 06-09, 1998 CL SAN FRANCISCO, CALIFORNIA DE linear motor; magnetostriction; transient model AB We are currently designing a high force linear motor that utilizes the inchworm principle coupled with multi-phase actuation. The efficient design of a 17 MV force linear motor that utilizes the magnetostrictive material Terfenol-D requires a transient electromechanical model to determine the operating parameters. The model is described and results indicated. It is found that control of the frequency and current inputs are all that is necessary to control the speed and power handling ability of the motor. Resonant operation is discussed along with increased efficiency power actuation schemes. C1 USN, Ctr Surface Warfare, W Bethesda, MD 20817 USA. Temple Univ, Philadelphia, PA 19122 USA. Goddard Space Flight Ctr, Greenbelt, MD 20071 USA. NAVSSES, Philadelphia, PA 19112 USA. RP Teter, JP (reprint author), USN, Ctr Surface Warfare, Code 684, W Bethesda, MD 20817 USA. NR 6 TC 7 Z9 10 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 0018-9464 J9 IEEE T MAGN JI IEEE Trans. Magn. PD JUL PY 1998 VL 34 IS 4 BP 2081 EP 2083 DI 10.1109/20.706805 PN 1 PG 3 WC Engineering, Electrical & Electronic; Physics, Applied SC Engineering; Physics GA 101CP UT WOS:000074852300407 ER PT J AU Maleki, L AF Maleki, L TI Introduction to the special issue on the Dick effect SO IEEE TRANSACTIONS ON ULTRASONICS FERROELECTRICS AND FREQUENCY CONTROL LA English DT Editorial Material C1 JPL, Time & Frequency Syst Res Grp, Pasadena, CA USA. RP Maleki, L (reprint author), JPL, Time & Frequency Syst Res Grp, Pasadena, CA USA. NR 0 TC 6 Z9 6 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 0885-3010 J9 IEEE T ULTRASON FERR JI IEEE Trans. Ultrason. Ferroelectr. Freq. Control PD JUL PY 1998 VL 45 IS 4 BP 876 EP 876 DI 10.1109/TUFFC.1998.710542 PG 1 WC Acoustics; Engineering, Electrical & Electronic SC Acoustics; Engineering GA 107MW UT WOS:000075213900005 PM 18244240 ER PT J AU Santarelli, G Audoin, C Makdissi, A Laurent, P Dick, GJ Clairon, A AF Santarelli, G Audoin, C Makdissi, A Laurent, P Dick, GJ Clairon, A TI Frequency stability degradation of an oscillator slaved to a periodically interrogated atomic resonator SO IEEE TRANSACTIONS ON ULTRASONICS FERROELECTRICS AND FREQUENCY CONTROL LA English DT Article AB Atomic frequency standards using trapped ions or cold atoms work intrinsically in a pulsed mode. Theoretically and experimentally, this mode of operation has been shown to lead to a degradation of the frequency stability due to the frequency noise of the interrogation oscillator. In this paper a physical analysis of this effect has been made by evaluating the response of a two-level atom to the interrogation oscillator phase noise in Ramsey and multi-Rabi interrogation schemes using a standard quantum mechanical approach. This response is then used to calculate the degradation of the frequency stability of a pulsed atomic frequency standard such as an atomic fountain or an ion trap standard. Comparison is made to an experimental evaluation of this effect in the LPTF Cs fountain frequency standard, showing excellent agreement. C1 Observ Paris, BNM, Lab Primaire Temps & Frequences, F-75014 Paris, France. Univ Paris Sud, Lab Horloge Atom, UP CNRS, F-91405 Orsay, France. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Santarelli, G (reprint author), Observ Paris, BNM, Lab Primaire Temps & Frequences, F-75014 Paris, France. EM giorgio.santarelli@obspm.fr NR 12 TC 140 Z9 141 U1 6 U2 15 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 0885-3010 J9 IEEE T ULTRASON FERR JI IEEE Trans. Ultrason. Ferroelectr. Freq. Control PD JUL PY 1998 VL 45 IS 4 BP 887 EP 894 DI 10.1109/58.710548 PG 8 WC Acoustics; Engineering, Electrical & Electronic SC Acoustics; Engineering GA 107MW UT WOS:000075213900007 PM 18244242 ER PT J AU Greenhall, CA AF Greenhall, CA TI A derivation of the long-term degradation of a pulsed atomic frequency standard from a control-loop model SO IEEE TRANSACTIONS ON ULTRASONICS FERROELECTRICS AND FREQUENCY CONTROL LA English DT Article AB The phase of a frequency standard that uses periodic interrogation and control of a local oscillator (LO) is degraded by a long-term random-walk component induced by downconversion of LO noise into the loop passband. The Dick formula for the noise level of this degradation is derived from an explicit solution of an LO control-loop model. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Greenhall, CA (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 8 TC 14 Z9 14 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 0885-3010 J9 IEEE T ULTRASON FERR JI IEEE Trans. Ultrason. Ferroelectr. Freq. Control PD JUL PY 1998 VL 45 IS 4 BP 895 EP 898 DI 10.1109/58.710550 PG 4 WC Acoustics; Engineering, Electrical & Electronic SC Acoustics; Engineering GA 107MW UT WOS:000075213900008 PM 18244243 ER PT J AU Olson, CF AF Olson, CF TI Improving the generalized Hough transform through imperfect grouping SO IMAGE AND VISION COMPUTING LA English DT Article DE object recognition; generalized Hough transform; perceptual grouping ID OBJECT RECOGNITION; PERCEPTUAL ORGANIZATION; IMAGE; VISION AB This paper analyses the improvements that can be gained in the generalized Hough transform method for recognizing objects through the use of imperfect perceptual grouping techniques. In particular, we consider simple grouping techniques that determine pairs of points that are likely to belong to the same object using a criterion based on connectedness in the image edge map. It is shown that such imperfect grouping techniques can considerably improve both the efficiency and accuracy of object recognition. Experiments are described that demonstrate the improvements in performance. (C) 1998 Elsevier Science B.V. All rights reserved. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Olson, CF (reprint author), CALTECH, Jet Prop Lab, Mail Stop 107-102,4800 Oak Grove Dr, Pasadena, CA 91109 USA. EM olson@robotics.jpl.nasa.gov NR 41 TC 15 Z9 15 U1 0 U2 0 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0262-8856 J9 IMAGE VISION COMPUT JI Image Vis. Comput. PD JUL PY 1998 VL 16 IS 9-10 BP 627 EP 634 DI 10.1016/S0262-8856(98)00083-3 PG 8 WC Computer Science, Artificial Intelligence; Computer Science, Software Engineering; Computer Science, Theory & Methods; Engineering, Electrical & Electronic; Optics SC Computer Science; Engineering; Optics GA ZZ764 UT WOS:000074764800004 ER PT J AU Guice, J AF Guice, J TI Looking backward and forward at the Internet SO INFORMATION SOCIETY LA English DT Article DE communication infrastructure; computer networks; history of technology; Internet; social studies of technology; technology forecasting ID TECHNOLOGY; COMPUTERIZATION; CONSTITUENCIES; INSIGHTS AB This article reviews accounts of the origins and growth of the global Internet with an interest in their implications for the future. Many accounts take overly restricted views of technical development. For instance, the Internet is often seen simply as the outgrowth of U.S. Defense Department work and popular enthusiasm. Recent interdisciplinary studies of technology present a more complex picture of how innovations are developed. They high-light technical alternatives, contributions of diverse groups, variety in meanings of technologies, and the overall surprising character of technology development. They suggest that the Internet has multiple origins and numerous particular reasons for its spread. Current discussions of the entry of Internet technologies into consumers' homes and the convergence among computing, media, and telecommunications enterprises represent examples of more complex accounts of technology development. Such accounts will likely provide more powerful bases for policy, management, and design. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Guice, J (reprint author), 1365 Bay Laurel Dr, Menlo Park, CA 94025 USA. NR 81 TC 12 Z9 12 U1 1 U2 2 PU TAYLOR & FRANCIS INC PI PHILADELPHIA PA 325 CHESTNUT ST, SUITE 800, PHILADELPHIA, PA 19106 USA SN 0197-2243 J9 INFORM SOC JI Inf. Soc. PD JUL-SEP PY 1998 VL 14 IS 3 BP 201 EP 211 DI 10.1080/019722498128827 PG 11 WC Information Science & Library Science SC Information Science & Library Science GA 115GL UT WOS:000075655300004 ER PT J AU Fiorini, P Shiller, Z AF Fiorini, P Shiller, Z TI Motion planning in dynamic environments using velocity obstacles SO INTERNATIONAL JOURNAL OF ROBOTICS RESEARCH LA English DT Article ID MOVING OBSTACLES AB This paper presents a method for robot motion planning in dynamic environments. It consists of selecting avoidance maneuvers to avoid static and moving obstacles in the velocity space, based on the current positions and velocities of the robot and obstacles. It is a first-order method, since it does not integrate velocities to yield positions as functions of time. The avoidance maneuvers are generated by selecting robot velocities outside of the velocity obstacles, which represent the set of robot velocities that would result in a collision with a given obstacle that moves at a given velocity, at some future time. To ensure that the avoidance maneuver is dynamically feasible, the set of avoidance velocities is intersected with the set of admissible velocities, defined by the robot's acceleration constraints. Computing new avoidance maneuvers at regular time intervals accounts for general obstacle trajectories. The trajectory from start to goal is computed by searching a tree of feasible avoidance maneuvers, computed at discrete time intervals. An exhaustive search of the tree yields near-optimal trajectories that either minimize distance or motion time. A heuristic search of the tree is applicable to on-line planning. The method is demonstrated for point and disk robots among static and moving obstacles, and for an automated vehicle in an intelligent vehicle highway system scenario. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ Calif Los Angeles, Dept Mech Aerosp & Nucl Engn, Los Angeles, CA 90024 USA. RP Fiorini, P (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. RI Fiorini, Paolo/A-2603-2012 NR 29 TC 397 Z9 431 U1 5 U2 41 PU SAGE PUBLICATIONS INC PI THOUSAND OAKS PA 2455 TELLER RD, THOUSAND OAKS, CA 91320 USA SN 0278-3649 J9 INT J ROBOT RES JI Int. J. Robot. Res. PD JUL PY 1998 VL 17 IS 7 BP 760 EP 772 DI 10.1177/027836499801700706 PG 13 WC Robotics SC Robotics GA ZX985 UT WOS:000074575200006 ER PT J AU Wilkinson, RA AF Wilkinson, RA TI Density relaxation of liquid-vapor critical fluids in Earth's gravity SO INTERNATIONAL JOURNAL OF THERMOPHYSICS LA English DT Article; Proceedings Paper CT 13th Symposium on Thermophysical Properties CY JUN 22-27, 1997 CL UNIV COLORADO, BOULDER, COLORADO SP Amer Soc Mech Engineers, Heat Transfer Div, Standing Comm Thermophys Properties, Natl Inst Stand & Technol, Chem Sci & Technol Lab, Phys & Chem Properties Div HO UNIV COLORADO DE critical point; density; liquid-vapor critical point; sulfur hexafluoride ID CRITICAL-POINT; MICROGRAVITY; SF6 AB Experimental results of the density relaxation of a liquid-vapor critical fluid in Earth's gravity over a temperature regime of severe density stratification are presented. A 10-mm-diameter x 1-mm-thick disk-shaped sample of SF6 was placed in a Twyman-Green phase shifting interferometer with a phase uncertainty of 1/65 of a wavelength over 60 h. Relaxations to equilibrium stratification were observed for a temperature range from 1.0 to 29.6 mK above T-c, where T-c is the critical temperature. The interferometry provided a density distribution history over the full extent of the sample cell. Two types of initial density states were established before stepping to the final temperature (density) states for relaxation: (1) the two-phase state at T-c-50 mK and (2) the equilibrium state at T-c + 100 mK. Upper and lower portions of the cell relaxed differently for these two initial states. For the T-c + 100 mK initial state, relaxation to T < T-c + 3 mK showed an early density overshoot followed by an additional long-time relaxation not seen in the other relaxation sequences. Otherwise, relaxations were faster and increasingly nondiffusive (without a unique exponential description) as the final state became closer to the critical temperature. C1 NASA, Lewis Res Ctr, Micrograv Fluid Phys Branch, Cleveland, OH 44135 USA. RP Wilkinson, RA (reprint author), NASA, Lewis Res Ctr, Micrograv Fluid Phys Branch, Cleveland, OH 44135 USA. NR 16 TC 2 Z9 2 U1 0 U2 0 PU PLENUM PUBL CORP PI NEW YORK PA 233 SPRING ST, NEW YORK, NY 10013 USA SN 0195-928X J9 INT J THERMOPHYS JI Int. J. Thermophys. PD JUL PY 1998 VL 19 IS 4 BP 1175 EP 1183 DI 10.1023/A:1022650011721 PG 9 WC Thermodynamics; Chemistry, Physical; Mechanics; Physics, Applied SC Thermodynamics; Chemistry; Mechanics; Physics GA 143YZ UT WOS:000077286300016 ER PT J AU Bowles, KJ AF Bowles, KJ TI Adjusting the measured weight loss of aged graphite fabric/PMR-15 composites SO JOURNAL OF ADVANCED MATERIALS LA English DT Article AB The purposes of this study is to evaluate the gr growth of the surface damage layer in polymer matrix composites (PMC's) fabricated with graphite fabric reinforcement and to determine the effects of the cut-surface degradation on the overall thermo-oxidative (TOS) stability of these materials. Four important conclusions were made about the TOS behavior of T650-35/PMR-15 fabric-reinforced composites: 1) Three stages of composite weight loss were seen on the plot of weight loss versus aging rime; 2) the depth of the cut-edge damage is related to the composite thickness, 3) the actual weight loss realized by a mechanical test specimen that has had all the aging-induced cut-edge damage removed during the preparation process is significantly less than the weight loss measured using specimens with a high percentage of cut edges exposed to the damaging environment, and 4) an extrapolation of a section of the weight loss curve can be used to obtain a move correct estimate of the actual weight loss after extended periods of aging at elevated temperatures. C1 NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. RP Bowles, KJ (reprint author), NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. NR 8 TC 2 Z9 2 U1 0 U2 0 PU SAMPE PUBLISHERS PI COVINA PA 1161 PARKVIEW DRIVE, COVINA, CA 91722 USA SN 1070-9789 J9 J ADV MATER JI J. Adv. Mater. PD JUL PY 1998 VL 30 IS 3 BP 21 EP 31 PG 11 WC Materials Science, Multidisciplinary SC Materials Science GA 209HW UT WOS:000081043000003 ER PT J AU Sture, S Costes, NC Batiste, SN Lankton, MR AlShibli, KA Jeremic, B Swanson, RA Frank, M AF Sture, S Costes, NC Batiste, SN Lankton, MR AlShibli, KA Jeremic, B Swanson, RA Frank, M TI Mechanics of granular materials at low effective stresses SO JOURNAL OF AEROSPACE ENGINEERING LA English DT Article AB Six displacement-controlled, conventional, drained axisymmetric triaxial experiments on cohesionless granular soil specimens were conducted at very low effective confining stresses in a SPACEHAB module on the Space Shuttle during the STS-79 and STS-89 missions. Three specimens were tested on each mission. The specimens measured 75 mm in diameter by 150 mm long. The average grain size of the subangular Ottawa quartz sand was 0.22 mm. The specimens' relative density for the STS-79 mission was 86.5% (+/- 0.8%); for the STS-89 mission it was 65.0% (+/- 1.0%). The confining stresses in the six experiments were 0.05, 0.52, and 1.30 kPa. Very high friction angles in the range of 47.6 to 70.0 degrees were observed. The dilatancy angles were also unusually high, in the range of 30 to 31 degrees. In spite of the very low effective stresses, high elastic moduli were observed. C1 Univ Colorado, Dept Civil Environm & Architectural Engn, Boulder, CO 80309 USA. NASA, George C Marshall Space Flight Ctr, Space Sci Lab, Huntsville, AL 35812 USA. Univ Colorado, Marshall Space Flight Ctr, Boulder, CO 80309 USA. Clarkson Univ, Dept Civil & Environm Engn, Potsdam, NY 13699 USA. Univ Colorado, Atmospher & Space Phys Lab, Boulder, CO 80309 USA. RP Sture, S (reprint author), Univ Colorado, Dept Civil Environm & Architectural Engn, Campus Box 428, Boulder, CO 80309 USA. EM sture@grieg.colorado.edu NR 9 TC 55 Z9 57 U1 1 U2 15 PU ASCE-AMER SOC CIVIL ENGINEERS PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2398 USA SN 0893-1321 J9 J AEROSPACE ENG JI J. Aerosp. Eng. PD JUL PY 1998 VL 11 IS 3 BP 67 EP 72 DI 10.1061/(ASCE)0893-1321(1998)11:3(67) PG 6 WC Engineering, Aerospace; Engineering, Civil SC Engineering GA ZU205 UT WOS:000074172800001 ER PT J AU Anderson, BH Gibb, J AF Anderson, BH Gibb, J TI Vortex-generator installation studies on steady-state and dynamic distortion SO JOURNAL OF AIRCRAFT LA English DT Article; Proceedings Paper CT AIAA/ASME/SAE/ASEE 32nd Joint Propulsion Conference CY JUL 01-03, 1996 CL LAKE BUENA VISTA, FLORIDA SP Amer Inst Aeronaut & Astronaut, ASME, SAE, ASEE ID VELOCITY AB The theoretical and experimental work carried out under the NASA/MOD joint aeronautical program has shown that computational fluid dynamics (CFD) vortex-generator installation designs successfully managed inlet-duct now distortion and that significant benefits in now unsteadiness at the engine face were also present. The main conclusions to date from the collaborative effort between the NASA Lewis Research Center and the Defence Research Agency in Bedford are as follows: 1) Vortex-generator installations can be designed to be effective over a wide-range of inlet operating conditions using CFD and formal optimization procedures, 2) reductions in steady-state engine face distortion of up to 80% have been measured in the M2129 inlet S-duct using CFD-designed vortex-generator installations, 3) reductions in flow unsteadiness of up to 80% have been measured in the M2129 inlet S-duct using CFD-designed vortex-generator installations, and 4) the reduced Navier-Stokes code RNS3D is a useful tool to design vortex-generator installations to manage engine-face distortions over a wide range of inlet operating conditions. C1 NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. Def Res Agcy, Bedford MK41 6AE, England. RP Anderson, BH (reprint author), NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. NR 17 TC 13 Z9 14 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 JUL-AUG PY 1998 VL 35 IS 4 BP 513 EP 520 DI 10.2514/2.2340 PG 8 WC Engineering, Aerospace SC Engineering GA 107FJ UT WOS:000075196300001 ER PT J AU Wendt, BJ Dudek, JC AF Wendt, BJ Dudek, JC TI Development of vortex generator use for a transitioning high-speed inlet SO JOURNAL OF AIRCRAFT LA English DT Article AB The development of an effective design strategy for surface-mounted vortex generator arrays in a subsonic diffuser is described in this paper. This strategy uses the strengths of both computational and experimental analyses to determine beneficial vortex generator Locations and sizes. A parabolized Navier-Stokes solver, RNS3D, was used to establish proper placement of the vortex generators for reduction in circumferential total pressure distortion. Experimental measurements were used to determine proper vortex generator sizing to minimize total pressure recovery losses associated with vortex generator device drag. The best result achieved a 59% reduction in the distortion index DC60, with a 0.3% reduction in total pressure recovery. C1 Modern Technol Corp, Aerosp Prop Div, Middleburg Hts, OH 44130 USA. NASA, Lewis Res Ctr, Inlet Branch, Cleveland, OH 44135 USA. RP Wendt, BJ (reprint author), Modern Technol Corp, Aerosp Prop Div, 7530 Lucerne Dr,Islander 2,Suite 206, Middleburg Hts, OH 44130 USA. NR 19 TC 7 Z9 8 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 JUL-AUG PY 1998 VL 35 IS 4 BP 536 EP 543 DI 10.2514/2.2357 PG 8 WC Engineering, Aerospace SC Engineering GA 107FJ UT WOS:000075196300004 ER PT J AU Leon, R Lobo, C Clark, A Bozek, R Wysmolek, A Kurpiewski, A Kaminska, M AF Leon, R Lobo, C Clark, A Bozek, R Wysmolek, A Kurpiewski, A Kaminska, M TI Different paths to tunability in III-V quantum dots SO JOURNAL OF APPLIED PHYSICS LA English DT Article ID HIGHLY STRAINED INGAAS; VISIBLE LUMINESCENCE; ISLAND FORMATION; GAAS; SURFACE; GROWTH; LASERS; LAYER; MORPHOLOGY AB Tunability in the concentration and average dimensions of self-farming semiconductor quantum dots (QDs) has been attained. Three of the approaches examined here are: variations with temperature, group V partial pressure and with substrate miscut angle. Thermally activated group III adatom mobilities result in larger diameters and lower concentrations with increasing deposition temperatures. These variations are presented for InGaAs/CaAs and AlInAs/AlGaAs, where striking differences were seen. Tunability in the InGaAs/GaAs QD concentration was also obtained in metalorganic chemical vapor deposition by varying the arsine flow. The latter gave widely varying concentrations and similar sizes. Substrate orientation was found to also be a key factor in island nucleation: Changes in vicinal orientation near (100) can be used to exploit the preferential step edge nucleation at mono and multi-atomic steps, so varying miscut angle (theta(m)) can be used to change island densities and sizes. Anisotropies in island nucleation producing n-dot strings aligned with multiatomic step edges are observed for theta(m)greater than or equal to 0.75 degrees and up to 2 degrees. Quantum mechanical coupling from such island strings result in non-Gaussian shapes in the inhomogeneously broadened photoluminescence peaks. The effects of some of the other morphological differences presented here on the luminescence emission from QD ground states is discussed for InGaAs/GaAs QDs. (C) 1998 American Institute of Physics. C1 Australian Natl Univ, Res Sch Phys Sci, Canberra, ACT 0200, Australia. Univ Warsaw, Inst Expt Phys, PL-00681 Warsaw, Poland. RP Leon, R (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. RI Schaff, William/B-5839-2009; Lobo, Charlene/B-3977-2013; Lobo, Charlene/G-5003-2011 OI Lobo, Charlene/0000-0002-2746-1363; Lobo, Charlene/0000-0002-2746-1363 NR 28 TC 47 Z9 47 U1 0 U2 7 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 JUL 1 PY 1998 VL 84 IS 1 BP 248 EP 254 DI 10.1063/1.368076 PG 7 WC Physics, Applied SC Physics GA 108GP UT WOS:000075258100033 ER PT J AU Kumei, Y Shimokawa, H Katano, H Akiyama, H Hirano, M Mukai, C Nagaoka, S Whitson, PA Sams, CF AF Kumei, Y Shimokawa, H Katano, H Akiyama, H Hirano, M Mukai, C Nagaoka, S Whitson, PA Sams, CF TI Spaceflight modulates insulin-like growth factor binding proteins and glucocorticoid receptor in osteoblasts SO JOURNAL OF APPLIED PHYSIOLOGY LA English DT Article DE bone demineralization; osteoblast; microgravity ID POLYMERASE CHAIN-REACTION; PROSTAGLANDIN E(2); FACTOR-I; IGF-I; EXPRESSION; BONE; PROMOTER; CELLS; GENE; CULTURES AB Rat osteoblasts were cultured for 4 or 5 days during a Space Shuttle mission. After 20-h treatment with 1 alpha,25-dihydroxyvitamin DB, conditioned media were harvested and cellular DNA and/or RNA were fixed on board. The insulin-like growth factor binding protein (IGF BP)-3 levels in the media were three- and tenfold higher than in ground controls on the fourth and fifth flight days, as quantitated by Western ligand blotting and radioimmunoassay, respectively. The increased ICF BP-3 protein levels correlated with two- to threefold elevation of IGF BP-3 mRNA levels, obtained by reverse transcription-polymerase chain reaction. The IGF BP-5 mRNA levels in flight cultures were 33-69% lower than in ground controls. The IGF BP-4 mRNA levels in flight cultures were 75% lower than in ground controls on the fifth day but were not different on the fourth day. The glucocorticoid receptor mRNA. levels in flight cultures were increased by three- to eightfold on the fourth and fifth days compared with levels in ground controls. These data suggest potential mechanisms underlying spaceflight-induced osteopenia. C1 Tokyo Med & Dent Univ, Fac Dent, Dept Biomat Sci, Bunkyo Ku, Tokyo 1138549, Japan. Natl Space Dev Agcy, Tsukuba Space Ctr, Tsukuba, Ibaraki 3050047, Japan. NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. RP Kumei, Y (reprint author), Tokyo Med & Dent Univ, Fac Dent, Dept Biomat Sci, Bunkyo Ku, Yushima 1-5-45, Tokyo 1138549, Japan. NR 31 TC 11 Z9 13 U1 0 U2 3 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 JUL PY 1998 VL 85 IS 1 BP 139 EP 147 PG 9 WC Physiology; Sport Sciences SC Physiology; Sport Sciences GA ZZ038 UT WOS:000074689200020 PM 9655767 ER PT J AU Han, QY Rossow, WB Chou, J Welch, RM AF Han, QY Rossow, WB Chou, J Welch, RM TI Global survey of the relationships of cloud albedo and liquid water path with droplet size using ISCCP SO JOURNAL OF CLIMATE LA English DT Article ID GENERAL-CIRCULATION MODEL; STRATOCUMULUS CLOUDS; STRATIFORM CLOUDS; EFFECTIVE RADIUS; SULFATE AEROSOL; CLIMATE; MICROPHYSICS; RADIATION; SATELLITE; PARAMETERIZATION AB The most common approach used to model the aerosol indirect effect on clouds holds the cloud liquid water path constant, in this case, increasing aerosol concentration increases cloud droplet concentration, decreases cloud droplet size, and increases cloud albedo. The expected decrease in cloud droplet size associated with larger aerosol concentrations has been found to be larger over land than over water and larger in the Northern than in the Southern Hemisphere, but the corresponding cloud albedo increase has not been found. Many previous studies have shown that cloud liquid water path varies with changing cloud droplet size, which may alter the behavior of clouds when aerosols change. This study examines the relationship between geographic and seasonal variations of cloud effective droplet size and cloud albedo, as well as cloud liquid water path, in low-level clouds using international Satellite Cloud Climatology Project data. The results show that cloud albedo increases with decreasing droplet size for most clouds over continental areas and for all optically thicker clouds, bur that cloud albedo decreases with decreasing droplet size for optically thinner clouds over most oceans and the tropical rain forest regions. For almost all clouds, the liquid water path increases with increasing cloud droplet size. C1 Univ Alabama, Global Hydrol & Climate Ctr, Dept Atmospher Sci, Huntsville, AL 35899 USA. NASA, Goddard Inst Space Studies, New York, NY 10025 USA. RP Han, QY (reprint author), Univ Alabama, Dept Atmospher Sci, Global Hydrol & Climate Ctr, 977 Explorer Blvd, Huntsville, AL 35899 USA. EM han@atmos.uah.edu RI Rossow, William/F-3138-2015 NR 53 TC 80 Z9 83 U1 0 U2 2 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 JUL PY 1998 VL 11 IS 7 BP 1516 EP 1528 DI 10.1175/1520-0442(1998)011<1516:GSOTRO>2.0.CO;2 PG 13 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 109MT UT WOS:000075326900002 ER PT J AU Chattopadhyay, K Feth, S Chen, H Burger, A Su, CH AF Chattopadhyay, K Feth, S Chen, H Burger, A Su, CH TI Characterization of semi-insulating CdTe crystals grown by horizontal seeded physical vapor transport SO JOURNAL OF CRYSTAL GROWTH LA English DT Article ID CURRENT TRANSIENT SPECTROSCOPY; DEPENDENT CHARGE MEASUREMENTS; CADMIUM TELLURIDE; MICROGRAVITY CONDITIONS; DEFECT CHEMISTRY; DOPED CDTE; PHOTOLUMINESCENCE; SUBLIMATION; PRESSURE; CDZNTE AB CdTe crystals were grown by horizontal seeded physical vapor transport technique in uncoated and boron nitride coated fused silica ampoules with the source materials near the congruent sublimation condition. The grown crystals were characterized by current-voltage measurements, low-temperature photoluminescence spectroscopy, near IR transmission optical microscopy, spark source mass spectroscopy and chemical etching. The measured resistivities of the crystals were in the high-10(8) Omega cm range. The photoluminescence spectra of the crystal grown in the boron nitride coated ampoule showed similar features previously observed in the CdTe crystals doped with group III elements. Although the crystal was contaminated with boron, the boron nitride coating of the growth ampoule has yielded a single crystal with no inclusions or precipitates. (C) 1998 Published by Elsevier Science B.V. All rights reserved. C1 Fisk Univ, Dept Phys, Ctr Photon Mat & Devices, Nashville, TN 37208 USA. NASA, George C Marshall Space Flight Ctr, Space Sci Lab, Huntsville, AL 35812 USA. RP Burger, A (reprint author), Fisk Univ, Dept Phys, Ctr Photon Mat & Devices, Nashville, TN 37208 USA. RI Feth, Shari/F-6302-2013 OI Feth, Shari/0000-0003-3545-5649 NR 37 TC 16 Z9 16 U1 1 U2 5 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 JUL PY 1998 VL 191 IS 3 BP 377 EP 385 DI 10.1016/S0022-0248(98)00134-1 PG 9 WC Crystallography; Materials Science, Multidisciplinary; Physics, Applied SC Crystallography; Materials Science; Physics GA 104TY UT WOS:000075032500010 ER PT J AU Sengupta, DK Weisman, MB Feng, M Chuang, SL Chang, YC Cooper, L Adesida, I Bloom, I Hsieh, KC Fang, W Malin, JI Curtis, AP Horton, T Stillman, GE Gunapala, SD Bandara, SV Pool, F Liu, JK McKelvey, M Luong, E Hong, W Mumolo, J Liu, HC Wang, WI AF Sengupta, DK Weisman, MB Feng, M Chuang, SL Chang, YC Cooper, L Adesida, I Bloom, I Hsieh, KC Fang, W Malin, JI Curtis, AP Horton, T Stillman, GE Gunapala, SD Bandara, SV Pool, F Liu, JK McKelvey, M Luong, E Hong, W Mumolo, J Liu, HC Wang, WI TI Growth and characterization of n-type GaAs/AlGaAs quantum well infrared photodetector on GaAs-on-Si substrate SO JOURNAL OF ELECTRONIC MATERIALS LA English DT Article DE dark current characteristics; peak response wavelength; rapid thermal annealing; quantum efficiency; quantum well infrared photodetectors (QWIPs) ID MULTIQUANTUM WELL; IMAGING CAMERA; ABSORPTION; DETECTOR; ARRAY AB We present in this article device characteristics of molecular beam epitaxy grown GaAs/AlGaAs quantum well infrared photodetectors (QWIP) on a semiinsulating GaAs substrate and on a GaAs-on-Si substrate grown by metalorganic chemical vapor deposition (MOCVD). Important issues for QWIP application such as dark current, spectral response, and absolute responsivity were measured. We find that the detector structure grown on a GaAs-on-Si substrate exhibits comparable dark current and absolute responsivity and a small blue shift, in the spectral response. This is the first demonstration of long wavelength GaAs/AlGaAs quantum well infrared photodetector using MOCVD grown GaAs-on-Si substrate and the performance is comparable to a similar detector structure grown on a GaAs substrate. C1 Univ Illinois, Dept Mat Sci & Engn, Urbana, IL 61801 USA. Univ Illinois, Dept Phys, Urbana, IL 61801 USA. Univ Illinois, Dept Elect & Comp Engn, Urbana, IL 61801 USA. CALTECH, Jet Prop Lab, Ctr Space Microelect Technol, Pasadena, CA 91109 USA. Natl Res Council Canada, Inst Microstruct Sci, Ottawa, ON K1A 0R6, Canada. Columbia Univ, Dept Elect Engn, New York, NY 11007 USA. RP Sengupta, DK (reprint author), CALTECH, Jet Prop Lab, Ctr Space Microelect Technol, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. RI Chang, Yia-Chung/F-4239-2011 NR 24 TC 2 Z9 2 U1 0 U2 2 PU MINERALS METALS MATERIALS SOC PI WARRENDALE PA 420 COMMONWEALTH DR, WARRENDALE, PA 15086 USA SN 0361-5235 J9 J ELECTRON MATER JI J. Electron. Mater. PD JUL PY 1998 VL 27 IS 7 BP 858 EP 865 DI 10.1007/s11664-998-0110-7 PG 8 WC Engineering, Electrical & Electronic; Materials Science, Multidisciplinary; Physics, Applied SC Engineering; Materials Science; Physics GA 101QX UT WOS:000074880600009 ER PT J AU Gibson, SE Charbonneau, P AF Gibson, SE Charbonneau, P TI Empirical modeling of the solar corona using genetic algorithms SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID MAGNETIC-FIELD; MINIMUM CORONA AB Many remote sensing applications encountered in astronomy and space science involve the solution of nonlinear inverse problems. These are often difficult to solve because of nonlinearities, ill-behaved integration kernels, and amplification of data noise associated with the inversion of the integral operator. In some cases these difficulties are severe enough to warrant repeated evaluations of the forward problem as an alternate approach to formal inversion. Because a forward approach is intrinsically repetitive and time consuming, an efficient and flexible forward technique is required for this avenue to be practical. We show how a forward technique based on a genetic algorithm allows us to fit magnetostatic models of the solar minimum corona to observations in white light to a degree that would otherwise have been computationally prohibitive. In addition, and perhaps equally important, the method also allows the determination of global error estimates on the model parameters defining the best fit solution. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20770 USA. Natl Ctr Atmospher Res, High Altitude Observ, Boulder, CO 80307 USA. RP Gibson, SE (reprint author), NASA, Goddard Space Flight Ctr, Code 682, Greenbelt, MD 20770 USA. RI Gibson, Sarah/A-9189-2011 NR 27 TC 7 Z9 7 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 JUL 1 PY 1998 VL 103 IS A7 BP 14511 EP 14521 DI 10.1029/98JA00676 PG 11 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZY130 UT WOS:000074589300001 ER PT J AU Feldman, WC Barraclough, BL Gosling, JT McComas, DJ Riley, P Goldstein, BE Balogh, A AF Feldman, WC Barraclough, BL Gosling, JT McComas, DJ Riley, P Goldstein, BE Balogh, A TI Ion energy equation for the high-speed solar wind: Ulysses observations SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID HEAT-FLUX; PLASMA; PARAMETERS; HEMISPHERES; TURBULENCE; ELECTRONS; NORTHERN; SOUTHERN; FIELD; WAVES AB Ulysses data in the high-speed solar wind that cover a wide range of latitudes centered on the solar poles were studied to test whether a polytrope law can be used to close the ion energy equation. Three approaches were taken, We determined the correlation between proton temperature and density (1) in the free expansion of the highspeed solar wind between 1.5 and 4.8 AU, (2) in steepened microstreams at high latitudes, and (3) at the edges of the equatorial band of solar wind variability. Strong correlations were observed in all data subsets that are consistent with a single polytrope relation, T(p) = aN(p)((gamma*-1)), where our best estimate gamma* is between 1.5 and 1.7. The best fitting relation T(p) = (2.0 +/- 0.13) x 10(5) N(p)(0.57). C1 Los Alamos Natl Lab, Space & Atmospher Sci Grp, Los Alamos, NM 87544 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ London Imperial Coll Sci Technol & Med, Blackett Lab, London, England. RP Feldman, WC (reprint author), Los Alamos Natl Lab, Space & Atmospher Sci Grp, Mail Stop D466, Los Alamos, NM 87544 USA. EM wfeldman@lanl.gov NR 36 TC 18 Z9 18 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 JUL 1 PY 1998 VL 103 IS A7 BP 14547 EP 14557 DI 10.1029/98JA00963 PG 11 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZY130 UT WOS:000074589300004 ER PT J AU Gary, SP Newbury, JA Goldstein, BE AF Gary, SP Newbury, JA Goldstein, BE TI Lower bound for electron core beta in the solar wind SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID PLASMA DEPLETION LAYER; EARTHS MAGNETOSHEATH; HEAT-FLUX; ION; INSTABILITIES; ULYSSES; TEMPERATURE; ANISOTROPY AB Solar wind electrons, especially under conditions of relatively low speed flow, often can be represented as two bi-Maxwellian components, a cooler, more dense core (denoted by the subscript c) and a hotter, more tenuous halo. Solar wind observations from Ulysses between 1.5 and 2 AU further indicate that the beta for electron core temperatures parallel to the background magnetic field, beta(parallel to c) has a distinct lower bound near 0.1. To seek the cause of this possible constraint, numerical solutions of the full Vlasov linear dispersion equation are used for four heat flux instabilities under a core/halo model with parameters representative of the solar wind near 1 AU. In this model the whistler heat flux instability is the growing mode of lowest threshold at most observed values beta(parallel to c). As beta(parallel to c) decreased, however, the growth of this c mode is reduced, so that at entry small values of this parameter the Alfven heat flux instability or the electron/ion acoustic instability becomes the fastest growing mode. The critical condition corresponding to this transition is calculated as a function of T-parallel to c/T-p (where T-p is the proton temperature) and approximately corresponds to the observed constraint at beta(parallel to c) similar or equal to 0.1. The Alfven and ion acoustic instabilities both resonate with core electrons; the hypothesis is proposed that core beating by these two modes at the critical condition establishes a lower bound on beta(parallel to c). C1 Univ Calif Los Alamos Natl Lab, Los Alamos, NM 87545 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ Calif Los Angeles, Inst Geophys & Planetary Phys, Los Angeles, CA 90095 USA. RP Gary, SP (reprint author), Univ Calif Los Alamos Natl Lab, MS D466, Los Alamos, NM 87545 USA. EM pgary@lanl.gov; newbury@igpp.ucla.edu; bgoldstein@jplsp.jpl.nasa.gov NR 27 TC 7 Z9 7 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 JUL 1 PY 1998 VL 103 IS A7 BP 14559 EP 14566 DI 10.1029/98JA01172 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZY130 UT WOS:000074589300005 ER PT J AU Neugebauer, M Forsyth, RJ Galvin, AB Harvey, KL Hoeksema, JT Lazarus, AJ Lepping, RP Linker, JA Mikic, Z Steinberg, JT von Steiger, R Wang, YM Wimmer-Schweingruber, RF AF Neugebauer, M Forsyth, RJ Galvin, AB Harvey, KL Hoeksema, JT Lazarus, AJ Lepping, RP Linker, JA Mikic, Z Steinberg, JT von Steiger, R Wang, YM Wimmer-Schweingruber, RF TI Spatial structure of the solar wind and comparisons with solar data and models SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID INTERPLANETARY MAGNETIC-FIELD; HELIOSPHERIC CURRENT SHEET; CORONAL STREAMERS; ULYSSES; SPEED; SPACECRAFT; INSTRUMENT; POLE AB Data obtained by instruments on the Ulysses spacecraft during its rapid sweep through >90 degrees of solar latitude, crossing the solar equator in early 1995, were combined with data obtained near Earth by the Wind spacecraft to study the spatial structure of the solar wind and to compare to different models of the interplanetary magnetic field derived from solar observations. Several different source-surface models matched the double sinusoidal structure of the heliospheric current sheet (HCS) but with differences in latitude as great as 21 degrees. The source-surface model that included an interplanetary current sheet gave poorer agreement with observed current-sheet crossings during this period than did the other source-surface models or an MHD model. The differences between the calculated and observed locations of the HCS were minimized when 22 degrees of solar rotation was added to the constant-velocity travel time from the source surface to the spacecraft. The photospheric footpoints of the open field lines calculated from the models generally agreed with observations in the He 10,830 Angstrom line of the locations of coronal holes with the exceptions that (1) in some places, open field lines originated outside the coronal hole boundaries and (2) the models show apparently closed-field regions just inside some coronal hole boundaries. The patterns of mismatches between coronal hole boundaries and the envelopes of open field lines persisted over at least three solar rotations. The highest-speed wind came from the polar coronal holes, with the wind originating deeper within the hole being faster than the wind coming from near the hole boundary. Intermediate and slow streams originated in smaller coronal holes at low latitudes and from open field regions just outside coronal hole boundaries. Although the HCS threaded regions of low speed, low helium abundance, high ionization temperature, and a high ratio of magnesium to oxygen densities (a surplus of an element with low first-ionization potential), there was a great deal of variation in these parameters from one place to another along the HCS. The gradient of speed with latitude varied from 14 to 28 km s(-1) deg(-1). C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ London Imperial Coll Sci Technol & Med, Blackett Lab, London SW7 2BZ, England. Solar Phys Res Corp, Tucson, AZ 85718 USA. Ctr Space Sci & Astron, Stanford, CA 94305 USA. MIT, Ctr Space Res, Cambridge, MA 02139 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Sci Applicat Int Corp, San Diego, CA 92121 USA. Inst Space Sci Inst, CH-3012 Bern, Switzerland. USN, Res Lab, Div Space Sci, Washington, DC 20375 USA. Univ Bern, Inst Phys, CH-3012 Bern, Switzerland. RP Neugebauer, M (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr,MS 169-506, Pasadena, CA 91109 USA. RI Von Steiger, Rudolf/F-6822-2011; Galvin, Antoinette/A-6114-2013 OI Von Steiger, Rudolf/0000-0002-3350-0023; NR 40 TC 167 Z9 168 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 JUL 1 PY 1998 VL 103 IS A7 BP 14587 EP 14599 DI 10.1029/98JA00798 PG 13 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZY130 UT WOS:000074589300008 ER PT J AU Wang, K Thorne, RM Horne, RB Kurth, WS AF Wang, K Thorne, RM Horne, RB Kurth, WS TI Constraints on Jovian plasma properties from a dispersion analysis of unducted whistlers in the warm Io torus SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID PROPAGATION CHARACTERISTICS; DENSITY; JUPITER; MAGNETOSPHERE; VOYAGER-1; MODEL; WAVES AB The dispersion of unducted lightning-generated whistlers observed by Voyager I in the warm torus around density peaks at L = 5.7 and L = 5.9 are analyzed using the HOTRAY code, which incorporates a newly developed diffusive equilibrium density model for the Io torus. Since the wave propagation characteristics are primarily controlled by electron density, a simplified two-ion (H+ and O+) model has been used to simulate wave dispersion. The properties of O+ are adjusted to simulate the electron density variation at low latitudes (less than or equal to 20 degrees), where heavy ions dominate, and a variable Hf component is added to model the electron density at higher latitudes. Both the offset and tilt of the Jovian magnetic dipole are taken into account to determine the electron distribution as a function of System III longitude. The results confirm earlier suggestions that modest therml anisotropies (T-perpendicular to > T-parallel to) Of heavy ions are required to match the observed whistler dispersion. Proton concentrations typically lie in the range 5-10%, with larger values in the outer torus. On the basis of these optimum plasma parameters, the observed upper cutoff frequencies (similar to 6 kHz) imply a minimum electron density of about 8 cm(-3) at high latitudes along field lines that map into the warm torus. This analysis of unducted whistlers indicates that all observed waves originate in the northern hemisphere rather than the southern hemisphere, as assumed in earlier studies of ducted waves. This new result is consistent with optical lightning events, which were only observed in the northern hemisphere by Voyager 1. C1 Univ Calif Los Angeles, Dept Atmospher Sci, Los Angeles, CA 90095 USA. Univ Iowa, Dept Phys & Astron, Iowa City, IA 52242 USA. British Antarctic Survey, Nat Environm Res Council, Madingley Rd, Cambridge CB3 0ET, England. RP Wang, K (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr,M-S 169-506, Pasadena, CA 91109 USA. OI Wang, Kaiti/0000-0003-2165-5922 NR 24 TC 10 Z9 10 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 JUL 1 PY 1998 VL 103 IS A7 BP 14979 EP 14986 DI 10.1029/98JA00964 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZY130 UT WOS:000074589300041 ER PT J AU Wang, K Thorne, RM Horne, RB Kurth, WS AF Wang, K Thorne, RM Horne, RB Kurth, WS TI Cold torus whistlers: An indirect probe of the inner Jovian plasmasphere SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID JUPITER; DENSITY; VOYAGER-1; MODEL AB The dominant features of Jovian whistlers observed by Voyager 1 in the inner cold torus around R-J approximate to 5.3 are studied using the technique of ray tracing with an offset tilted dipole. These whistlers are unducted, and the electron density in the inner plasmasphere plays a controlling role in the access of whistlers to the cold torus. The upper frequency cutoff of inner zone whistlers allows a firm limit to be;placed on the minimum electron density 3-5 cm(-3) at higher latitudes in the inner plasmasphere around L approximate to 5.3, a region where no spacecraft have ever been. Backward ray tracing from the observation location is used to determine the source location at the top of the Jovian atmosphere, and it is shown to be consistent with the latitude of lightning events observed by Voyager 1. C1 British Antarctic Survey, Nat Environm Res Council, Cambridge CB3 0ET, England. Univ Iowa, Dept Phys & Astron, Iowa City, IA 52242 USA. Univ Calif Los Angeles, Dept Atmospher Sci, Los Angeles, CA 90095 USA. RP Wang, K (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr,M-S 169-506, Pasadena, CA 91109 USA. OI Wang, Kaiti/0000-0003-2165-5922 NR 19 TC 5 Z9 5 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 JUL 1 PY 1998 VL 103 IS A7 BP 14987 EP 14994 DI 10.1029/98JA00965 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZY130 UT WOS:000074589300042 ER PT J AU Zimpfer, DJ Shieh, LS Sunkel, JW AF Zimpfer, DJ Shieh, LS Sunkel, JW TI Digitally redesigned pulse-width modulation spacecraft control SO JOURNAL OF GUIDANCE CONTROL AND DYNAMICS LA English DT Article AB A new method is presented for the design of control laws for systems with on-off nonlinear actuators. The new methodology improves the design of control laws for pulse modulated systems by allowing the use of continuous-time, multi input/multi-output design procedures. Discrete-time state feedback control gains are developed from the digital redesign of continuous time feedback gains, based on a geometric series approximation, to closely match the states of the closed-loop hybrid system to those of the original designed closed-loop, continuous time system at each sampling instant. A delay is then incorporated into a pulse-width modulator design to closely match the states of the modulated system to those of the discrete-time, pulse amplitude modulated system. The delay time is improved from previous work to provide a close match between the states for pulse durations of all sizes, in effect matching the states of the pulse-width modulated system to those of the closed-loop, continuous-time system. The new control law design is applied to the problem of attitude control of the Space Shuttle Orbiter with the Hubble Space Telescope deployed on its remote manipulator. C1 Charles Stark Draper Lab Inc, Control & Dynam Syst, Houston, TX 77058 USA. Univ Houston, Houston, TX 77204 USA. NASA, Lyndon B Johnson Space Ctr, Flight Mech & Aerosci Div, Houston, TX 77058 USA. RP Zimpfer, DJ (reprint author), Charles Stark Draper Lab Inc, Control & Dynam Syst, Houston, TX 77058 USA. NR 12 TC 10 Z9 13 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 JUL-AUG PY 1998 VL 21 IS 4 BP 529 EP 534 DI 10.2514/2.4276 PG 6 WC Engineering, Aerospace; Instruments & Instrumentation SC Engineering; Instruments & Instrumentation GA ZZ102 UT WOS:000074695900001 ER PT J AU Ericsson-Jackson, AJ Bainum, PM Xing, GQ AF Ericsson-Jackson, AJ Bainum, PM Xing, GQ TI Application of singular value decomposition method to digitally controlled large orbiting platforms SO JOURNAL OF GUIDANCE CONTROL AND DYNAMICS LA English DT Article; Proceedings Paper CT 1997 AAS/AIAA Astrodynamics Conference CY AUG 04-07, 1997 CL SUN VALLEY, IDAHO SP Amer Astronaut Soc, Amer Inst Aeronaut & Astronaut ID DESIGN AB The dynamics and control for the specific application of a large orbiting flexible thin square plate are considered. The focus is on the utilization of a singular value decomposition (SVD) method to create a stable reduced-order system. By reviewing the system's singular value bounds in the frequency domain one can properly assess stability robustness parameters that are difficult to characterize effectively in a time-domain setting. This system's open-loop singular values were extremely close to zero, denoting singular system matrices. To alleviate this problem with matrix singularity, the SVD method was applied to transform the original systems. The reduction of actuators/sensors is done partially in the physical sense and partially in the mathematical space. Results show that when the SVD method transformation is applied stable controllable closed-loop system matrices can be designed. C1 Howard Univ, Dept Mech Engn, Washington, DC 20059 USA. RP Ericsson-Jackson, AJ (reprint author), NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. NR 13 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 0731-5090 J9 J GUID CONTROL DYNAM JI J. Guid. Control Dyn. PD JUL-AUG PY 1998 VL 21 IS 4 BP 551 EP 557 DI 10.2514/2.4293 PG 7 WC Engineering, Aerospace; Instruments & Instrumentation SC Engineering; Instruments & Instrumentation GA ZZ102 UT WOS:000074695900004 ER PT J AU Oshman, Y Markley, FL AF Oshman, Y Markley, FL TI Minimal-parameter attitude matrix estimation from vector observations SO JOURNAL OF GUIDANCE CONTROL AND DYNAMICS LA English DT Article ID SPACECRAFT ATTITUDE; SYSTEM AB A computationally efficient, sequential method is presented for attitude matrix estimation using gyro and vector measurements. The method is based on a recently introduced, minimal-parameter third-order method for solving the orthogonal matrix differential equation in R-n. In the three-dimensional case, these third order attitude parameters can be interpreted as temporal integrals of the body-frame angular velocity components. A nonlinear algorithm is developed, which uses this minimal set of three parameters to estimate the nine-parameter direction-cosine matrix. Having an extremely simple kinematic equation, these parameters render the resulting estimator highly computationally efficient. An orthogonalization procedure, incorporated into the measurement processing stage, enhances the accuracy and stability of the resulting algorithm, yet retains reasonable simplicity. The performance of the new estimator is demonstrated via a numerical simulation study. C1 NASA, Goddard Space Flight Ctr, Guidance Navigat & Control Ctr, Greenbelt, MD 20771 USA. RP Oshman, Y (reprint author), Technion Israel Inst Technol, Dept Aerosp Engn, IL-32000 Haifa, Israel. NR 25 TC 9 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 JUL-AUG PY 1998 VL 21 IS 4 BP 595 EP 602 DI 10.2514/2.4277 PG 8 WC Engineering, Aerospace; Instruments & Instrumentation SC Engineering; Instruments & Instrumentation GA ZZ102 UT WOS:000074695900010 ER PT J AU Juang, JN Phan, MQ AF Juang, JN Phan, MQ TI Recursive deadbeat controller design SO JOURNAL OF GUIDANCE CONTROL AND DYNAMICS LA English DT Article ID FLEXIBLE SPACE STRUCTURES; GENERALIZED PREDICTIVE CONTROL; 2ND-ORDER DYNAMIC-SYSTEMS; TRANSMISSION ZEROS; IDENTIFICATION; OBSERVER AB A recursive algorithm is presented for the deadbeat predictive control that brings the output response to rest after a few time steps. The main idea is to put together the system identification process and the deadbeat control design into a unified step. It starts with reformulating the conventional multistep output-prediction equation to explicitly include the coefficient matrices to weight past input and output time histories for computation of feedback control force. The formulation thus derived satisfies simultaneously the system identification and the deadbeat control requirements. As soon as the coefficient matrices are identified satisfying the output prediction equation, no further work is required to design a deadbeat controller The method can be implemented recursively just as any typical recursive system identification technique. C1 NASA, Langley Res Ctr, Struct Dynam Branch, Hampton, VA 23681 USA. Princeton Univ, Dept Mech & Aerosp Engn, Princeton, NJ 08544 USA. RP Juang, JN (reprint author), NASA, Langley Res Ctr, Struct Dynam Branch, Hampton, VA 23681 USA. NR 32 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 0731-5090 J9 J GUID CONTROL DYNAM JI J. Guid. Control Dyn. PD JUL-AUG PY 1998 VL 21 IS 4 BP 624 EP 631 DI 10.2514/2.4281 PG 8 WC Engineering, Aerospace; Instruments & Instrumentation SC Engineering; Instruments & Instrumentation GA ZZ102 UT WOS:000074695900014 ER PT J AU Gawronski, W Lim, KB AF Gawronski, W Lim, KB TI Frequency weighting for the H-infinity and H-2 control design of flexible structures SO JOURNAL OF GUIDANCE CONTROL AND DYNAMICS LA English DT Article C1 CALTECH, Jet Prop Lab, Commun Ground Syst Sect, Pasadena, CA 91109 USA. NASA, Langley Res Ctr, Guidance & Control Branch, Hampton, VA 23665 USA. RP Gawronski, W (reprint author), CALTECH, Jet Prop Lab, Commun Ground Syst Sect, MS 238-528, Pasadena, CA 91109 USA. NR 3 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 JUL-AUG PY 1998 VL 21 IS 4 BP 664 EP 666 DI 10.2514/2.4288 PG 3 WC Engineering, Aerospace; Instruments & Instrumentation SC Engineering; Instruments & Instrumentation GA ZZ102 UT WOS:000074695900020 ER PT J AU Anagnostou, EN Krajewski, WF Seo, DJ Johnson, ER AF Anagnostou, Emmanouil N. Krajewski, Witold F. Seo, Dong-Jun Johnson, Edward R. TI MEAN-FIELD RAINFALL BIAS STUDIES FOR WSR-88D SO JOURNAL OF HYDROLOGIC ENGINEERING LA English DT Article AB Real-time radar-rainfall bias adjustment procedures for weather surveillance Doppler radar (WSR-88D) are investigated. Statistical analysis of the mean-field bias is performed on a 2-year record of WSR-88D observations from Tulsa, Okla., and rain gauge measurements from a dense network under the radar umbrella. The analysis shows strong seasonal effect. A data-based Monte Carlo simulation experiment is performed on the same data to quantify the sampling error of estimated bias for varying rain gauge network densities. Simulation results show (1) that the sampling error decreases proportionally to the square of the rain gauge network density; and (2) that the sampling error is higher in the warm season. The performance of three mean-field radar-rainfall bias estimation and prediction algorithms is investigated. The algorithms include the WSR-88D precipitation adjustment procedure, the adaptive error parameter technique, and the maximum likelihood autoregressive model. A Monte Carlo simulation experiment is used to assess the algorithms' error statistics for the two seasons, three accumulation timescales, and two modes of operation (prediction and update). Results show significant seasonal and time-scale effects. C1 [Anagnostou, Emmanouil N.] Univ Space Res Assn, NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. [Anagnostou, Emmanouil N.; Krajewski, Witold F.] Univ Iowa, Iowa Inst Hydr Res, Iowa City, IA 52242 USA. [Seo, Dong-Jun; Johnson, Edward R.] Nat Weather Serv, Ofc Hydro, Silver Spring, MD 20910 USA. [Johnson, Edward R.] Nat Weather Serv, Hydrol Operat Div, Silver Spring, MD 20910 USA. RP Anagnostou, EN (reprint author), Univ Space Res Assn, NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. FU National Oceanic and Atmospheric Administration [NA47WH0495] FX This paper is dedicated by W. F. K. to the memory of Dr. Dah-Syang Lin, friend, colleague, and student who passed away at a young age before realizing his full potential. The writers also acknowledge and appreciate useful discussions with Dr. James A. Smith from Princeton University and Dr. Grzegorz J. Ciach from the Iowa Institute of Hydraulic Research. The study was supported by the National Oceanic and Atmospheric Administration under a Cooperative Agreement No. NA47WH0495 between the Office of Hydrology of the NWS and The University of Iowa Institute of Hydraulic Research. NR 54 TC 52 Z9 52 U1 0 U2 4 PU ASCE-AMER SOC CIVIL ENGINEERS PI RESTON PA 1801 ALEXANDER BELL DR, RESTON, VA 20191-4400 USA SN 1084-0699 J9 J HYDROL ENG JI J. Hydrol. Eng. PD JUL PY 1998 VL 3 IS 3 BP 149 EP 159 DI 10.1061/(ASCE)1084-0699(1998)3:3(149) PG 11 WC Engineering, Civil; Environmental Sciences; Water Resources SC Engineering; Environmental Sciences & Ecology; Water Resources GA V15AM UT WOS:000207774900001 ER PT J AU Lee, HJ Saravanos, DA AF Lee, HJ Saravanos, DA TI The effect of temperature dependent material properties on the response of piezoelectric composite materials SO JOURNAL OF INTELLIGENT MATERIAL SYSTEMS AND STRUCTURES LA English DT Article ID INTELLIGENT STRUCTURES; PLATE; BEAMS AB Analytical formulations for thermopiezoelectric composite materials are extended to account for thermal effects arising from temperature dependent material properties. The updated mechanics also has the inherent capability to capture thermal effects which arise due to coefficient of thermal expansion mismatch and pyroelectric phenomena, providing a comprehensive thermal analysis capability. The thermal effects are represented at the material level through the thermopiezoelectric constitutive equations. These equations are incorporated into a layerwise laminate theory to provide a unified representation of the coupled mechanical, electrical: and thermal response of piezoelectric composite materials. Corresponding finite element equations are derived and implemented for beams and plates to model the active and sensory response of piezoelectric composite laminates. Applications demonstrate the significance of incorporating temperature dependent material properties on the response of piezoelectric composite beams and plates in both active and sensory configurations. C1 NASA, Glenn Res Ctr, Cleveland, OH 44135 USA. Ohio Aerosp Inst, Brook Pk, OH 44142 USA. RP Lee, HJ (reprint author), NASA, Glenn Res Ctr, 21000 Brookpark Rd,Mail Stop 49-8, Cleveland, OH 44135 USA. NR 14 TC 24 Z9 24 U1 0 U2 2 PU TECHNOMIC PUBL CO INC PI LANCASTER PA 851 NEW HOLLAND AVE, BOX 3535, LANCASTER, PA 17604 USA SN 1045-389X J9 J INTEL MAT SYST STR JI J. Intell. Mater. Syst. Struct. PD JUL PY 1998 VL 9 IS 7 BP 503 EP 508 PG 6 WC Materials Science, Multidisciplinary SC Materials Science GA 216UR UT WOS:000081463300002 ER PT J AU Hel-Or, Y Teo, PC AF Hel-Or, Y Teo, PC TI Canonical decomposition of steerable functions SO JOURNAL OF MATHEMATICAL IMAGING AND VISION LA English DT Article DE steerable filters; Lie group theory; transformation groups; canonical coordinates; Jordan decomposition; equivariant basis functions and low-level image processing ID TRANSFORMS; FILTERS AB This paper describes a general mathematical formulation for the problem of constructing steerable functions. The formulation is based on Lie group theory and is thus applicable to transformations which are Lie groups, such as, rotation, translation, scaling, and affine transformation. For one-parameter and Abelian multiparameter Lie transformation groups, a canonical decomposition of all possible steerable functions, derived using the Jordan decomposition of matrices, is developed. It is shown that any steerable function under Lie transformation groups can be described using this decomposition. Finally, a catalog of steerable functions for several common multi-parameter image transformation groups is also provided. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Stanford Univ, Dept Comp Sci, Stanford, CA 94305 USA. RP NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. EM toky@white.Stanford.EDU; teo@white.Stanford.EDU NR 29 TC 15 Z9 15 U1 0 U2 1 PU SPRINGER PI DORDRECHT PA VAN GODEWIJCKSTRAAT 30, 3311 GZ DORDRECHT, NETHERLANDS SN 0924-9907 EI 1573-7683 J9 J MATH IMAGING VIS JI J. Math. Imaging Vis. PD JUL PY 1998 VL 9 IS 1 BP 83 EP 95 DI 10.1023/A:1008274211102 PG 13 WC Computer Science, Artificial Intelligence; Computer Science, Software Engineering; Mathematics, Applied SC Computer Science; Mathematics GA ZX353 UT WOS:000074507000005 ER PT J AU Chen, YS Shang, HM Chen, CP Wang, TS AF Chen, YS Shang, HM Chen, CP Wang, TS TI General numerical model for liquid jet atomization applications SO JOURNAL OF PROPULSION AND POWER LA English DT Article C1 Engn Sci Inc, Huntsville, AL 35802 USA. Univ Alabama, Huntsville, AL 35899 USA. NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. RP Chen, YS (reprint author), Engn Sci Inc, Huntsville, AL 35802 USA. NR 15 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 0748-4658 J9 J PROPUL POWER JI J. Propul. Power PD JUL-AUG PY 1998 VL 14 IS 4 BP 581 EP 584 DI 10.2514/2.7647 PG 4 WC Engineering, Aerospace SC Engineering GA 100HK UT WOS:000074810600025 ER PT J AU Meyer, SA Bershader, D Sharma, SP AF Meyer, SA Bershader, D Sharma, SP TI Resonance broadening measurements of atomic oxygen at 130 nm SO JOURNAL OF QUANTITATIVE SPECTROSCOPY & RADIATIVE TRANSFER LA English DT Article ID VACUUM-ULTRAVIOLET; SPECTROSCOPY; LINES AB Absorption line profiles have been measured for atomic oxygen at 130.49 nm under conditions dominated by resonance broadening. Atomic samples are prepared by dissociating oxygen in a shock tube, and are probed by tunable vacuum u.v. light generated with a Raman-shifted excimer laser. Linewidths calculated with approximate theoretical models are consistent with the current measurements, and limitations of these models are discussed by references to previously reported measurements in noble gases and metallic vapors. To our knowledge, these are the first resonance broadening measurements of atoms which are normally found in diatomics, and thus, have different electron configurations from those studied previously. (C) 1998 Published by Elsevier Science Ltd. All rights reserved. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. SRI Int, Phys Lab, Menlo Park, CA 94025 USA. Stanford Univ, Dept Aeronaut & Astronaut, Stanford, CA 94305 USA. RP Sharma, SP (reprint author), NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. NR 30 TC 1 Z9 1 U1 0 U2 0 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0022-4073 J9 J QUANT SPECTROSC RA JI J. Quant. Spectrosc. Radiat. Transf. PD JUL PY 1998 VL 60 IS 1 BP 53 EP 68 DI 10.1016/S0022-4073(97)00159-3 PG 16 WC Optics; Spectroscopy SC Optics; Spectroscopy GA ZM063 UT WOS:000073501000006 ER PT J AU Goyette, TM Cohen, EA De Lucia, FC AF Goyette, TM Cohen, EA De Lucia, FC TI Pressure broadening of HNO3 by N-2 and O-2: An intercomparison of results in the millimeter wave region SO JOURNAL OF QUANTITATIVE SPECTROSCOPY & RADIATIVE TRANSFER LA English DT Article ID PERTURBER DEPENDENCES; TEMPERATURE; GHZ; SPECTROSCOPY; TRANSITION; LINES AB It is well known that systematic effects make the evaluation of absolute uncertainties in pressure broadening parameters difficult. In many cases, especially in the retrieval of remote sensing information, it is important that these uncertainties be well understood. In response, the pressure broadening of HNO3 by N-2 and O-2 has been studied in the millimeter-wave region by two different methods in two different laboratories. The focus of this work has been on the strong lines near 206 GHz which are used by the Microwave Limb Sounder for measurement of HNO3 in the Earth's atmosphere. (C) 1998 Elsevier Science Ltd. All rights reserved. C1 Ohio State Univ, Dept Phys, Columbus, OH 43210 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP De Lucia, FC (reprint author), Ohio State Univ, Dept Phys, 174 W 18Th Ave, Columbus, OH 43210 USA. NR 13 TC 14 Z9 14 U1 0 U2 1 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0022-4073 J9 J QUANT SPECTROSC RA JI J. Quant. Spectrosc. Radiat. Transf. PD JUL PY 1998 VL 60 IS 1 BP 77 EP 84 DI 10.1016/S0022-4073(97)00157-X PG 8 WC Optics; Spectroscopy SC Optics; Spectroscopy GA ZM063 UT WOS:000073501000008 ER PT J AU Gnoffo, PA Inger, GR AF Gnoffo, PA Inger, GR TI Analytic corrections to computational heating predictions - Accounting for changes in surface catalysis SO JOURNAL OF SPACECRAFT AND ROCKETS LA English DT Article ID AERODYNAMIC CHARACTERISTICS; FLIGHT EXPERIMENT; SCHEMES; CODE AB A new approach for combining the insight afforded by integral boundary-layer analysis with comprehensive (but time-intensive) computational fluid dynamic flowfield solutions of the thin-layer Navier-Stokes equations is described. The approach extracts computationally simulated quantities at the wall and at the boundary-layer edge for inclusion in a postprocessing boundary-layer analysis. It allows a designer at a workstation to address the question, given a single computational solution, "How much does the heating change for a thermal, protection system with catalytic properties different from those used in the original numerical simulation?" Capabilities of this approach for application to reusable launch vehicle design are demonstrated. If the definition of surface catalysis is uncertain early in the design process, results show that fully catalytic wall boundary conditions provide the best baseline for computationally simulated design points. C1 NASA, Langley Res Ctr, Aerothermodynam Branch, Aero & Gasdynam Div, Hampton, VA 23681 USA. Iowa State Univ Sci & Technol, Dept Aerosp Engn & Engn Mech, Ames, IA 50011 USA. RP Gnoffo, PA (reprint author), NASA, Langley Res Ctr, Aerothermodynam Branch, Aero & Gasdynam Div, Hampton, VA 23681 USA. NR 19 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 0022-4650 J9 J SPACECRAFT ROCKETS JI J. Spacecr. Rockets PD JUL-AUG PY 1998 VL 35 IS 4 BP 417 EP 423 DI 10.2514/2.3356 PG 7 WC Engineering, Aerospace SC Engineering GA 109VZ UT WOS:000075346000001 ER PT J AU Wallace, TA Clark, RK Chiang, KT AF Wallace, TA Clark, RK Chiang, KT TI Dynamic oxidation performance of NARloy-Z with Cu-30 volume percent Cr coating SO JOURNAL OF SPACECRAFT AND ROCKETS LA English DT Article ID DEPOSITION TECHNOLOGY AB The copper alloy NARloy-Z (Cu-3Ag-0.5Zr wt%) has good potential for high heat flux structural applications in hypersonic vehicles because of its high thermal conductivity and high temperature strength. However, it is subject to severe oxidation at temperatures where it might be used. ci Cu-30 vol% Cr protective coating produced by low-temperature are vapor deposition was evaluated under dynamic oxidation in an electric are-heated wind tunnel. The emittance of the coating is greater than the emittance of the alloy, and the recombination efficiency of the coating is typical of values encountered with metal alloys and metallic oxides. The coating protects the alloy under dynamic oxidation conditions, with specimens gaining less than 1 mg/cm(2) over a 10-h exposure period. Protection of the alloy from oxidation results from a continuous layer of Cr2O3 that it is partially shielded from the hostile dynamic oxidation/atomic oxygen environment by a layer of CuO. C1 NASA, Langley Res Ctr, Div Mat, Hampton, VA 23681 USA. Boeing Co, Canoga Park, CA 91303 USA. RP Wallace, TA (reprint author), NASA, Langley Res Ctr, Div Mat, Hampton, VA 23681 USA. NR 18 TC 7 Z9 7 U1 0 U2 0 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 JUL-AUG PY 1998 VL 35 IS 4 BP 546 EP 551 DI 10.2514/2.3365 PG 6 WC Engineering, Aerospace SC Engineering GA 109VZ UT WOS:000075346000018 ER PT J AU Gates, MM Lewis, MJ AF Gates, MM Lewis, MJ TI Semiempirical method for predicting single event effect rates due to direct ionization SO JOURNAL OF SPACECRAFT AND ROCKETS LA English DT Article ID CHARGE COLLECTION AB A semiempirical method for predicting on-orbit single event effect rates has been developed, The derivation of this technique circumvents the need for assumptions regarding sensitive volume geometry, the use of the concept of effective linear energy transfer, and sensitive volume dimension input. Prediction results are compared to flight data from the Cosmic Ray Upset Experiment, for which the presented method is shown to compare up to an order of magnitude more closely than previous methods when applied both to flight-lot-specific and to generic ground test data. The utility of this method in performing trade studies also is demonstrated through an application of candidate microprocessors. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Maryland, Dept Aerosp Engn, College Pk, MD 20740 USA. RP Gates, MM (reprint author), NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. NR 16 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 0022-4650 J9 J SPACECRAFT ROCKETS JI J. Spacecr. Rockets PD JUL-AUG PY 1998 VL 35 IS 4 BP 559 EP 564 DI 10.2514/2.3368 PG 6 WC Engineering, Aerospace SC Engineering GA 109VZ UT WOS:000075346000020 ER PT J AU Rabzak, C Pereira, JM Roberts, GD AF Rabzak, C Pereira, JM Roberts, GD TI Adhesively bonded strain gages for extended use at 315 degrees C on polymers SO JOURNAL OF TESTING AND EVALUATION LA English DT Article DE strain gage; physical aging; high temperature; polymer; composites; PMR-15; polyimide AB A unique strain gage and adhesive system was developed for mechanical property measurement of polymers and polymer composites at elevated temperatures. This system overcomes some of the problems encountered in using commercial strain gages and adhesives. An important limitation with typical commercial strain gage adhesives is that they require a post-cure at temperatures substantially higher than the maximum test temperature. The exposure of the specimen to this temperature may affect subsequent results, and in some cases may be higher than the glass transition temperature of the polymer. In addition, while typical commercial strain gages can be used for short times at temperatures up to 370 degrees C, their long-term use is limited to 230 degrees C. This precludes their use for testing some high-temperature polyimides near their maximum-temperature capability. The system that was developed consists of a nonencapsulated, unbacked gage grid that is bonded directly to the polymer using a specially formulated adhesive. The gage is applied after the specimen has been cured, but prior to the normal post-cure cycle. The adhesive was formulated to cure under the specimen post-cure conditions. Special handling, mounting, and electrical connection procedures were developed, and a fixture was designed to calibrate each strain gage after application on the specimen. A variety of tests was conducted to determine the performance characteristics of the gages at elevated temperatures on PMR-15 neat resin and titanium specimens. These tests included static tension, thermal exposure, and creep tests. The gage and adhesive system performed within normal strain gage specifications at 315 degrees C under these conditions. C1 NYMA Inc, Brook Pk, OH 44142 USA. NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. RP Rabzak, C (reprint author), Boeing Aircraft Grp, Seattle, WA 98124 USA. NR 15 TC 1 Z9 1 U1 0 U2 0 PU AMER SOC TESTING MATERIALS PI W CONSHOHOCKEN PA 100 BARR HARBOR DR, W CONSHOHOCKEN, PA 19428-2959 USA SN 0090-3973 J9 J TEST EVAL JI J. Test. Eval. PD JUL PY 1998 VL 26 IS 4 BP 367 EP 375 PG 9 WC Materials Science, Characterization & Testing SC Materials Science GA 102DH UT WOS:000074907700010 ER PT J AU Iseler, L AF Iseler, L TI Piloted simulator investigation of category A civil rotorcraft terminal area cockpit displays SO JOURNAL OF THE AMERICAN HELICOPTER SOCIETY LA English DT Article; Proceedings Paper CT 51st Annual Forum of the American-Helicopter-Society CY MAY 09-11, 1995 CL FT WORTH, TEXAS SP Amer Helicopter Soc AB A piloted simulation experiment was conducted in the NASA Ames Research Center Vertical Motion Simulator as a preliminary investigation of the use of integrated cockpit displays in terminal area operations for Category A civil rotorcraft. Category A is the transport category of rotorcraft which are required to be able to recover from an engine failure and continue flying. A UH-60 Black Hawk model was used for the simulation, with modifications made to the power available to simulate a civil rotorcraft. Hovering backups were flown from a confined area, raised vertiport site to a takeoff decision point (TDP), followed by normal flyout. Pilots flew the task with the standard Black Hawk instrument set or with one of two integrated formats presented on a color, panel-mounted display. Engine failures were randomly inserted slightly before and slightly after the TDP. The pilot was instructed to make a visual landback to the pad when an engine failed prior to reaching the TDP and to continue the flyout when an engine failed after passing through the TDP. Weather conditions were varied from calm, clear conditions to low visibility and ceilings, with crosswinds and turbulence. Evaluations were conducted with seven pilots. Objective and subjective data describing task performance and pilot workload were collected. It was hypothesized that even without the benefit of display assistance, pilots would achieve better performance handling an engine failure by using integrated displays during the ah-engines-operating back up phase prior to the engine failure occurring. As expected, the pilots were able to maintain more precise night path control during the backup with the integrated display. This precise control, in turn, placed the pilot in a better situation from which to handle an engine failure. Pilot recognition of the TDP location was also highly improved with an integrated display. Emergency landbacks, on runs using the integrated display during the backup portion, were all performed within the specified tolerances. Some of the landbacks using the standard instrument set, however, exceeded the adequate performance parameters. Cooper-Harper Handling Qualities Ratings confirmed that pilot workload was reduced and pilots were able to fly more consistently within the desired performance parameters with the integrated display than with the standard instruments and visual cues. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Iseler, L (reprint author), NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. NR 13 TC 0 Z9 0 U1 0 U2 1 PU AMER HELICOPTER SOC INC PI ALEXANDRIA PA 217 N WASHINGTON ST, ALEXANDRIA, VA 22314 USA SN 0002-8711 J9 J AM HELICOPTER SOC JI J. Am. Helicopter Soc. PD JUL PY 1998 VL 43 IS 3 BP 185 EP 194 PG 10 WC Engineering, Aerospace SC Engineering GA 108NA UT WOS:000075271300001 ER PT J AU Kufeld, RM Bousman, WG AF Kufeld, RM Bousman, WG TI High load conditions measured on a UH-60A in maneuvering flight SO JOURNAL OF THE AMERICAN HELICOPTER SOCIETY LA English DT Article; Proceedings Paper CT 51st Annual Forum of the American-Helicopter-Society CY MAY 09-11, 1995 CL FT WORTH, TEXAS SP Amer Helicopter Soc AB Maneuver data obtained under the NASA/Arrny UH60A Airloads Program are examined qualitatively to show the effects of maneuvering flight conditions on rotor loads. Two test conditions have been selected for review based on a comparison of an 68 maneuver conditions flown in the test program. These two conditions were selected because they ranked in the top ten for rotor load severity and show two different types of non-linear aerodynamic behavior, three-dimensional compressibility and dynamic stall, A detailed assessment of the section lift and moment calculated from measured pressures for each condition is used to provide insight into these two phenomenon. C1 USA, NASA, Rotorcraft Div, Ames Res Ctr, Moffett Field, CA 94035 USA. USA, NASA, Rotorcraft Div, US Army Aeroflightdynam Directorate AMCOM, Moffett Field, CA USA. RP Kufeld, RM (reprint author), USA, NASA, Rotorcraft Div, Ames Res Ctr, Moffett Field, CA 94035 USA. NR 11 TC 13 Z9 14 U1 0 U2 1 PU AMER HELICOPTER SOC INC PI ALEXANDRIA PA 217 N WASHINGTON ST, ALEXANDRIA, VA 22314 USA SN 0002-8711 J9 J AM HELICOPTER SOC JI J. Am. Helicopter Soc. PD JUL PY 1998 VL 43 IS 3 BP 202 EP 211 PG 10 WC Engineering, Aerospace SC Engineering GA 108NA UT WOS:000075271300003 ER PT J AU Srinivas, V Chopra, T Nixon, MW AF Srinivas, V Chopra, T Nixon, MW TI Aeroelastic analysis of advanced geometry tiltrotor aircraft SO JOURNAL OF THE AMERICAN HELICOPTER SOCIETY LA English DT Article AB A tiltrotor model is formulated to predict the aeroelastic response and stability of composite-coupled advanced geometry rotors, Advanced geometry rotor blades are modeled with arbitrary sweep, anhedral, pretwist and planform taper variation with span. The effect of advanced geometry blades on the tiltrotor response and whirl flutter stability in airplane mode is studied, Blade tip sweep and tip anhedral increase the flutter speed while forward tip sweep, tip dihedral and planform taper decrease it. C1 Univ Maryland, Dept Aerosp Engn, Alfred Gessow Rotorcraft Ctr, College Pk, MD 20742 USA. USA, Vehicle Struct Directorate, NASA, Langley Res Ctr, Hampton, VA USA. RP Srinivas, V (reprint author), Engn Technol Associates, Madison Hts, MI 48071 USA. NR 8 TC 10 Z9 10 U1 1 U2 2 PU AMER HELICOPTER SOC INC PI ALEXANDRIA PA 217 N WASHINGTON ST, ALEXANDRIA, VA 22314 USA SN 0002-8711 J9 J AM HELICOPTER SOC JI J. Am. Helicopter Soc. PD JUL PY 1998 VL 43 IS 3 BP 212 EP 221 PG 10 WC Engineering, Aerospace SC Engineering GA 108NA UT WOS:000075271300004 ER PT J AU Nixon, MW Kvaternik, RG Settle, TB AF Nixon, MW Kvaternik, RG Settle, TB TI Tiltrotor vibration reduction through higher harmonic control SO JOURNAL OF THE AMERICAN HELICOPTER SOCIETY LA English DT Article; Proceedings Paper CT 53rd Annual Forum of the American-Helicopter-Society CY APR 29-MAY 01, 1997 CL VIRGINIA BEACH, VIRGINIA SP Amer Helicopter Soc AB The results of a joint NASA/Army/Bell Helicopter Textron wind-tunnel investigation which was conducted to assess the potential of higher harmonic control (HHC) for reducing vibrations in tiltrotor aircraft operating in the airplane mode of night and to evaluate the effectiveness of a Bell-developed HHC algorithm called MAVSS (Multipoint Adaptive Vibration Suppression System) are presented. The test was conducted in the Langley Transonic Dynamics Tunnel using an unpowered 1/5-scale semispan aeroelastic model of the V-22 which was modified to incorporate an HHC system employing both the rotor swashplate and the wing flaperon. The effectiveness of the replate and the flaperon acting either singly or in combination in reducing 1P and 3P wing vibrations over a wide range of tunnel airspeeds and rotor rotational speeds was demonstrated. The MAVSS algorithm was found to be robust to variations in tunnel airspeed and rotor speed, requiring only occasional on-line recalculations of the system transfer matrix. HHC had only a small (usually beneficial) effect on blade loads but increased pitch link loads by 25%. No degradation in aeroelastic stability was noted for any of the conditions tested. C1 ARL Vehicle Technol Ctr, Hampton, VA USA. NASA, Langley Res Ctr, Hampton, VA 23665 USA. RP Nixon, MW (reprint author), ARL Vehicle Technol Ctr, Hampton, VA USA. NR 36 TC 5 Z9 5 U1 1 U2 2 PU AMER HELICOPTER SOC INC PI ALEXANDRIA PA 217 N WASHINGTON ST, ALEXANDRIA, VA 22314 USA SN 0002-8711 J9 J AM HELICOPTER SOC JI J. Am. Helicopter Soc. PD JUL PY 1998 VL 43 IS 3 BP 235 EP 245 PG 11 WC Engineering, Aerospace SC Engineering GA 108NA UT WOS:000075271300006 ER PT J AU Hartmann, JW Coverstone-Carroll, VL Williams, SN AF Hartmann, JW Coverstone-Carroll, VL Williams, SN TI Optimal interplanetary spacecraft trajectories via a Pareto genetic algorithm SO JOURNAL OF THE ASTRONAUTICAL SCIENCES LA English DT Article AB A Pareto genetic algorithm is applied to the optimization of low-thrust interplanetary spacecraft trajectories. A multiobjective, nondominated sorting genetic algorithm is developed following existing methodologies. A hybridized scheme is designed integrating the nondominated sorting genetic algorithm with a calculus-of-variations-based trajectory optimization algorithm. "Families" of Pareto optimal trajectories are generated for the cases of Earth-Mars flyby and rendezvous trajectories. A novel trajectory type generated by the genetic algorithm is expanded to develop a series of versatile, high-performance Earth-Mars rendezvous trajectories. C1 Univ Illinois, Urbana, IL 61801 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Hartmann, JW (reprint author), Univ Illinois, Urbana, IL 61801 USA. NR 15 TC 43 Z9 45 U1 0 U2 5 PU AMER ASTRONAUTICAL SOC PI SPRINGFIELD PA 6352 ROLLING MILL PLACE SUITE 102, SPRINGFIELD, VA 22152 USA SN 0021-9142 J9 J ASTRONAUT SCI JI J. Astronaut. Sci. PD JUL-SEP PY 1998 VL 46 IS 3 BP 267 EP 282 PG 16 WC Engineering, Aerospace SC Engineering GA 222TE UT WOS:000081800200003 ER PT J AU Sui, CH Li, X Lau, KM AF Sui, CH Li, X Lau, KM TI Radiative-convective processes in simulated diurnal variations of tropical oceanic convection SO JOURNAL OF THE ATMOSPHERIC SCIENCES LA English DT Article ID MODEL; CLIMATE; PARAMETERIZATION; MECHANISMS AB This paper presents an analysis of the diurnal variation of tropical oceanic convection and its associated energy cycle as simulated by an anelastic cumulus ensemble model. The model includes subgrid turbulence, cloud microphysics, and radiative transfer processes. In two experiments designed to simulate the diurnal cycles in large-scale disturbed (A1) and undisturbed conditions (A4) over the tropical western Pacific warm pool, the model produces diurnal variations that are in general agreement with observations. In A1, a time-independent SST and mean ascending motion are prescribed in the model. The model generates a diurnal cycle with positive (negative) rainfall anomalies during the night (day), and the maximum (minimum) rainfall near 0200 (1300-1400) local time. In A4, a diurnally varying SST is prescribed in the model and the domain-averaged vertical velocity is constrained to be zero. The simulated diurnal variations still have a nocturnal rainfall maximum but with a weaker magnitude and a secondary peak in the afternoon. The model is then used to investigate the radiative effects of clouds that has been suggested as the cause of the nocturnal rainfall maximum by many studies. Two experiments (A2 and A3) are performed with the model, in which a time-independent SST is prescribed and the domain-averaged vertical velocity is constrained to be zero. The only difference between the two experiments is that the cloud-radiation interaction is suppressed in A3. The results show that despite the significant difference in total cloudiness/rainfall due to the difference in mean vertical motion between A2 and A1, and the difference in cloud-radiative forcing between A2 and A3, the simulated diurnal cycles in all three experiments show a dominant nocturnal rainfall maximum. The results support the suggestion by Sui et al. that the nocturnal rainfall maximum is related to more (less) available precipitable water in the night (day) due to the diurnal radiative cooling/heating cycle. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Space Applicat Corp, Vienna, VA USA. RP Sui, CH (reprint author), NASA, Goddard Space Flight Ctr, Code 913, Greenbelt, MD 20771 USA. RI Li, Xiaofan/F-5605-2010; Li, Xiaofan/G-2094-2014; Lau, William /E-1510-2012; OI Lau, William /0000-0002-3587-3691; SUI, CHUNG-HSIUNG/0000-0003-2842-5660 NR 19 TC 147 Z9 154 U1 0 U2 5 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 JUL 1 PY 1998 VL 55 IS 13 BP 2345 EP 2357 DI 10.1175/1520-0469(1998)055<2345:RCPISD>2.0.CO;2 PG 13 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA ZZ230 UT WOS:000074708600007 ER PT J AU Barth, E Zetzsche, C Rentschler, I AF Barth, E Zetzsche, C Rentschler, I TI Intrinsic two-dimensional features as textons SO JOURNAL OF THE OPTICAL SOCIETY OF AMERICA A-OPTICS IMAGE SCIENCE AND VISION LA English DT Article ID TEXTURE SEGREGATION; EARLY VISION; DISCRIMINATION; PERCEPTION; FILTERS; ORIENTATION; CURVATURE; SEGMENTATION; MECHANISMS; LUMINANCE AB We suggest that intrinsic two-dimensional (i2D) features, computationally defined as the outputs of nonlinear operators that model the activity of end-stopped neurons, play a role in preattentive texture discrimination. We first show that for discriminable textures with identical power spectra the predictions of traditional models depend on the type of nonlinearity and fail for energy measures. We then argue that the concept of intrinsic dimensionality, and the existence of end-stopped neurons, can help us to understand the role of the nonlinearities. Furthermore, we show examples in which models without strong i2D selectivity fail to predict the correct ranking order of perceptual segregation. Our arguments regarding the importance of i2D features resemble the arguments of Julesz and co-workers regarding textons such as terminators and crossings. However, we provide a computational framework: that identifies textons with the outputs of nonlinear operators that are selective to i2D features. (C) 1998 Optical Society of America. C1 Inst Med Psychol, D-80336 Munchen, Germany. RP Barth, E (reprint author), NASA, Ames Res Ctr, MS 262-2, Moffett Field, CA 94035 USA. NR 53 TC 26 Z9 26 U1 0 U2 1 PU OPTICAL SOC AMER PI WASHINGTON PA 2010 MASSACHUSETTS AVE NW, WASHINGTON, DC 20036 USA SN 0740-3232 J9 J OPT SOC AM A JI J. Opt. Soc. Am. A-Opt. Image Sci. Vis. PD JUL PY 1998 VL 15 IS 7 BP 1723 EP 1732 DI 10.1364/JOSAA.15.001723 PG 10 WC Optics SC Optics GA ZW701 UT WOS:000074438500001 PM 9656473 ER PT J AU Siegel, R AF Siegel, R TI Temperature distributions in channel walls with translucent thermal barrier coatings SO JOURNAL OF THERMOPHYSICS AND HEAT TRANSFER LA English DT Article ID RADIATION AB Thermal barrier coatings are important for reducing metal temperatures and thermal gradients in high-temperature applications. At elevated temperatures radiative transfer becomes important, and if several hot surfaces view each other, the coated surfaces exchange radiation. Usually in radiative exchange computations, the surfaces are opaque and each has a unique radiating temperature. Some thermal barrier coating materials such as zirconia are partially transparent to thermal radiation. Hence, an exchange involving coated walls is complicated by radiation penetrating into and coming out of each coating. Radiation leaving an area depends on the temperature distribution inside its coating that is unknown and is affected by the exchange process; each area does not have a unique temperature. The analysis here is for a hot transparent gas flowing in a symmetric parallel-plate channel with translucent coatings on the inside. The coatings view each other and exchange radiation. From symmetry the flux leaving each coating equals its incident value. Relations are developed for the temperature distribution within each coating that satisfies zero-net radiation at the coating surface. This differs from having cold surroundings. In that case the net radiation is not zero because there is radiation from the coating to the surroundings. 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 10 TC 7 Z9 9 U1 0 U2 4 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0887-8722 J9 J THERMOPHYS HEAT TR JI J. Thermophys. Heat Transf. PD JUL-SEP PY 1998 VL 12 IS 3 BP 289 EP 296 DI 10.2514/2.6345 PG 8 WC Thermodynamics; Engineering, Mechanical SC Thermodynamics; Engineering GA 100HE UT WOS:000074810100001 ER PT J AU Wang, TS AF Wang, TS TI Delta clipper experimental in-ground effect on base-heating environment SO JOURNAL OF THERMOPHYSICS AND HEAT TRANSFER LA English DT Article; Proceedings Paper CT AIAA 32nd Thermophysics Conference CY JUN 23-25, 1997 CL ATLANTA, GEORGIA SP Amer Inst Aeronaut & Astronaut ID CLUSTERED NOZZLE CONFIGURATION; FLOWFIELD AB A quasitransient in-ground effect method is developed to study the effect of vertical landing on a launch vehicle base-heating environment. This computational methodology is based on a three-dimensional, pressure-based, viscous now, chemically reacting, computational fluid dynamics formulation, Important in-ground base-now physics such as the fountain;jet formation, plume growth, air entrainment, and plume afterburning are captured with the present methodology. Convective and radiative base-heat fluxes are computed for comparison with those of a night test. The influence of the laminar Prandtl number on the convective heat nux is included in this study, A radiative direction-dependency test is conducted using both the discrete ordinate and finite volume methods. Treatment of the plume afterburning is found to be very important for accurate prediction of the base-heat fluxes. Convective and radiative base-heat fluxes predicted by the model using a finite rate chemistry option compared reasonably well with flight-test data. C1 NASA, George C Marshall Space Flight Ctr, Fluid Dynam Anal Branch, Huntsville, AL 35812 USA. RP Wang, TS (reprint author), NASA, George C Marshall Space Flight Ctr, Fluid Dynam Anal Branch, Huntsville, AL 35812 USA. NR 27 TC 6 Z9 6 U1 0 U2 1 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0887-8722 J9 J THERMOPHYS HEAT TR JI J. Thermophys. Heat Transf. PD JUL-SEP PY 1998 VL 12 IS 3 BP 343 EP 349 DI 10.2514/2.6367 PG 7 WC Thermodynamics; Engineering, Mechanical SC Thermodynamics; Engineering GA 100HE UT WOS:000074810100008 ER PT J AU Hall, CA Glakpe, EK Cannon, JN Kerslake, TW AF Hall, CA Glakpe, EK Cannon, JN Kerslake, TW TI Modeling cyclic phase change and energy storage in solar heat receivers SO JOURNAL OF THERMOPHYSICS AND HEAT TRANSFER LA English DT Article; Proceedings Paper CT AIAA 32nd Thermophysics Conference CY JUN 23-25, 1997 CL ATLANTA, GEORGIA SP Amer Inst Aeronaut & Astronaut AB Numerical results pertaining to cyclic melting and freezing of an encapsulated phase-change material (PCM), integrated into a solar heat receiver, have been reported. The cyclic nature of the present problem is relevant to latent heat thermal energy storage systems used to power solar Brayton engines in space. Specifically, a physical and numerical model of the solar heat receiver component of NASA Lewis Research Center's ground test demonstration (GTD) system was developed and results compared with available experimental data. Multiconjugate effects such as the convective now of a low Prandtl number fluid, conduction in the PCM, containment tube, and working fluid conduit were accounted for in the model, An ideal-body thermal radiation model was also included to quantify reradiative effects inside the receiver along with losses through the aperture and receiver shell. A high-temperature eutectic mixture of LiF-CaF2 was used as the PCM and a mixture of He/Xe was used as the working fluid. A modified version of the computer code HOTTube was used to generate results for comparisons with GTD experimental data in both subcooled and two-phase regimes. While qualitative trends were in close agreement for the balanced-orbit modes, excellent quantitative agreement was observed for steady-state modes. C1 Howard Univ, Dept Mech Engn, Coll Engn Architecture & Comp Sci, Washington, DC 20059 USA. NASA, Lewis Res Ctr, Power & Prop Off, Anal & Management Branch, Cleveland, OH 44135 USA. Howard Univ, Dept Chem Engn, Coll Engn Architecture & Comp Sci, Washington, DC 20059 USA. RP Hall, CA (reprint author), Howard Univ, Dept Mech Engn, Coll Engn Architecture & Comp Sci, Washington, DC 20059 USA. NR 21 TC 9 Z9 9 U1 1 U2 6 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0887-8722 J9 J THERMOPHYS HEAT TR JI J. Thermophys. Heat Transf. PD JUL-SEP PY 1998 VL 12 IS 3 BP 406 EP 413 DI 10.2514/2.6352 PG 8 WC Thermodynamics; Engineering, Mechanical SC Thermodynamics; Engineering GA 100HE UT WOS:000074810100016 ER PT J AU Nance, RP Hash, DB Hassan, HA AF Nance, RP Hash, DB Hassan, HA TI Role of boundary conditions in Monte Carlo simulation of microelectromechanical systems SO JOURNAL OF THERMOPHYSICS AND HEAT TRANSFER LA English DT Article; Proceedings Paper CT AIAA 35th Aerospace Science Meeting / Nonlinear Dynamical Systems Symposium CY JAN 06-10, 1997 CL RENO, NEVADA SP Amer Inst Aeronaut & Astronaut, USAF, Off Sci Res, Sandia Natl Labs ID FLOW C1 N Carolina State Univ, Raleigh, NC 27695 USA. NASA, Ames Res Ctr, Thermosci Inst, Moffett Field, CA 94035 USA. RP Nance, RP (reprint author), N Carolina State Univ, Raleigh, NC 27695 USA. NR 8 TC 55 Z9 66 U1 0 U2 4 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0887-8722 J9 J THERMOPHYS HEAT TR JI J. Thermophys. Heat Transf. PD JUL-SEP PY 1998 VL 12 IS 3 BP 447 EP 449 DI 10.2514/2.6358 PG 3 WC Thermodynamics; Engineering, Mechanical SC Thermodynamics; Engineering GA 100HE UT WOS:000074810100021 ER PT J AU Sugimura, J Jones, WR Spikes, HA AF Sugimura, J Jones, WR Spikes, HA TI EHD film thickness in non-steady state contacts SO JOURNAL OF TRIBOLOGY-TRANSACTIONS OF THE ASME LA English DT Article; Proceedings Paper CT 1997 World Tribology Congress CY SEP 08-12, 1997 CL LONDON, ENGLAND SP Soc Tribologists & Lubricat Engineers ID ELASTOHYDRODYNAMIC LUBRICATION; TRANSIENT AB This paper describes a study of EHD film thickness in non-steady state contact conditions. A modification of ultrathin film interferometry is employed which is able to measure both central film thickness and film thickness profiles 50 times a second. Film thickness with two perfluoropolyethers and two mineral base oils are investigated in a number of different types of non-steady state motion, including acceleration/deceleration, stop/start and reciprocation. The results demonstrate a range of transient behaviors of EHD film whose thicknesses deviate from those in steady state conditions. C1 Kyushu Univ, Dept Energy & Mech Engn, Higashi Ku, Fukuoka 81281, Japan. NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. Univ London Imperial Coll Sci Technol & Med, Tribol Sect, London SW7 2BX, England. RP Sugimura, J (reprint author), Kyushu Univ, Dept Energy & Mech Engn, Higashi Ku, Fukuoka 81281, Japan. NR 18 TC 26 Z9 27 U1 0 U2 2 PU ASME-AMER SOC MECHANICAL ENG PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017 USA SN 0742-4787 J9 J TRIBOL-T ASME JI J. Tribol.-Trans. ASME PD JUL PY 1998 VL 120 IS 3 BP 442 EP 452 DI 10.1115/1.2834569 PG 11 WC Engineering, Mechanical SC Engineering GA 102NQ UT WOS:000074930900005 ER PT J AU Suder, KL AF Suder, KL TI Blockage development in a transonic, axial compressor rotor SO JOURNAL OF TURBOMACHINERY-TRANSACTIONS OF THE ASME LA English DT Article; Proceedings Paper CT 42nd International Gas Turbine and Aeroengine Congress and Exhibition CY JUN 02-05, 1997 CL ORLANDO, FLORIDA SP Int Gas Turbine Inst AB A detailed experimental investigation to understand and quantify. the development of blockage in the flow field of a transonic, axial flow compressor rotor (NASA Rotor 37) has been undertaken. Detailed laser anemometer measurements were acquired upstream, within, and downstream of a transonic, axial compressor rotor. operating at 100, 85, 80, and 60 percent of design speed, which provided inlet relative Mach numbers at the blade tip of 1.48, 1.26, 1.18, and 0.89, respectively. The impact of the shock oil the blockage development, pertaining to both the shock/boundary layer interactions and the shock/tip clearance flow interactions, is discussed. The results indicate that for this rotor the blockage in the endwall region is 2-3 times that of the core flow region, and the blockage in the core flow region more than doubles when the shock strength is sufficient to separate the suction surface boundary layer. C1 NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. RP Suder, KL (reprint author), NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. NR 27 TC 37 Z9 42 U1 0 U2 2 PU ASME-AMER SOC MECHANICAL ENG PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017 USA SN 0889-504X J9 J TURBOMACH JI J. Turbomach.-Trans. ASME PD JUL PY 1998 VL 120 IS 3 BP 465 EP 476 PG 12 WC Engineering, Mechanical SC Engineering GA 110DL UT WOS:000075364800012 ER PT J AU Bell, LD Smith, RP McDermott, BT Gertner, ER Pittman, R Pierson, RL Sullivan, GJ AF Bell, LD Smith, RP McDermott, BT Gertner, ER Pittman, R Pierson, RL Sullivan, GJ TI Metal/GaN Schottky barriers characterized by ballistic-electron-emission microscopy and spectroscopy SO JOURNAL OF VACUUM SCIENCE & TECHNOLOGY B LA English DT Article; Proceedings Paper CT 25th Annual Conference on the Physics and Chemistry of Semiconductor Interfaces CY JAN 18-22, 1998 CL SALT LAKE CITY, UTAH ID GAN; STRAIN AB Ballistic-electron-emission microscopy (BEEM) and spectroscopy have been used to characterize the Pd/GaN and Au/GaN interfaces. BEEM spectra yield a Schottky barrier height for Au/GaN of similar to 1.05 eV that agrees well with the highest values measured by conventional methods. For both Pd and An, a second threshold is observed in the spectra at about 0.2-0.3 V above the first threshold. Imaging of these metal/GaN interfaces reveals transmission in nearly all areas, although the magnitude is small and spatially varies. Attempts to perform BEEM measurements on other GaN material have resulted in no detectable transmission in any areas, even at voltages as high as 3.5 V. (C) 1998 American Vacuum Society. C1 CALTECH, Jet Prop Lab, Ctr Space Microelect Technol, Pasadena, CA 91109 USA. Rockwell Int Sci Ctr, Thousand Oaks, CA 91360 USA. RP Bell, LD (reprint author), CALTECH, Jet Prop Lab, Ctr Space Microelect Technol, Pasadena, CA 91109 USA. NR 15 TC 10 Z9 10 U1 0 U2 1 PU AMER INST PHYSICS PI WOODBURY PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 USA SN 1071-1023 J9 J VAC SCI TECHNOL B JI J. Vac. Sci. Technol. B PD JUL-AUG PY 1998 VL 16 IS 4 BP 2286 EP 2290 DI 10.1116/1.590163 PG 5 WC Engineering, Electrical & Electronic; Nanoscience & Nanotechnology; Physics, Applied SC Engineering; Science & Technology - Other Topics; Physics GA 110LN UT WOS:000075381400089 ER PT J AU Davis, RW Fargion, GS May, N Leming, TD Baumgartner, M Evans, WE Hansen, LJ Mullin, K AF Davis, RW Fargion, GS May, N Leming, TD Baumgartner, M Evans, WE Hansen, LJ Mullin, K TI Physical habitat of cetaceans along the continental slope in the north-central and western Gulf of Mexico SO MARINE MAMMAL SCIENCE LA English DT Article DE cetacean; habitat; Gulf of Mexico ID EASTERN TROPICAL PACIFIC; DOLPHIN GRAMPUS-GRISEUS; OF-MEXICO; SEA; CYCLONE; SHELF; EDDY AB The physical habitat of cetaceans found along the continental slope in the north-central and western Gulf of Mexico was characterized from shipboard sighting data, simultaneous hydrographic measurements, and satellite remote sensing. The study area was encompassed by the longitude of the Florida-Alabama border (87.5 degrees W), the southernmost latitude of the Texas-Mexico border (26.0 degrees N), and the 100-m and 2,000-m isobaths. Shipboard surveys were conducted seasonally for two years from April 1992 to May 1994. A total of 21,350 km of transect was visually sampled in an area of 154,621 km(2). Sighting localities of species in the study area were differentiated most clearly with bottom depth. Atlantic spotted dolphins (Stenella frontalis) were consistently found in the shallowest water on the continental shelf and along the shelf break. In addition, the bottom depth gradient (sea floor slope) was less for Atlantic spotted dolphins than for any other species. Bottlenose dolphins (Tursiops truncatus) were found most commonly along the upper slope in water significantly deeper than that for Atlantic sported dolphins. All the other species and species categories were found over deeper bottom depths; these were Risso's dolphins (Grampus griseus), short-finned pilot whales (Globicephala macrorhynchus), pygmy/dwarf sperm whales (Kogia spp.) rough-toothed dolphins (Steno bredanensis), spinner dolphins (Stenella longivostris), sperm whales (Physeter macrocephalus), striped dolphins (Stenella coevuleoalba), Mesoplodon spp., pantropical spotted dolphins (Stenella attenuata), Clymene dolphins (Stenella clymene) and unidentified beaked whales (Ziphiidae). Risso's dolphins and short-finned pilot whales occurred along the upper slope and, as a subgroup, were significantly different from striped dolphins, Mesoplodon spp., pantropical spotted dolphins, Clymene dolphins, and unidentified beaked whales, which occurred in the deepest water. Pygmy/dwarf sperm whales, rough-toothed dolphins, spinner dolphins, and sperm whales occurred at intermediate depths between these two subgroups and overlapped them. C1 Texas A&M Univ, Texas Inst Oceanog, Galveston, TX 77553 USA. NOAA, Natl Marine Fisheries Serv, SE Fisheries Sci Ctr, Stennis Space Ctr, MS 39529 USA. NOAA, Natl Marine Fisheries Serv, SE Fisheries Sci Ctr, Charleston, SC 29412 USA. NOAA, Natl Marine Fisheries Serv, SE Fisheries Sci Ctr, Pascagoula, MS 39568 USA. RP Davis, RW (reprint author), Texas A&M Univ, Texas Inst Oceanog, Galveston, TX 77553 USA. EM davisr@tamug.tamu.edu NR 67 TC 73 Z9 81 U1 1 U2 17 PU SOC MARINE MAMMALOGY PI LAWRENCE PA 1041 NEW HAMPSHIRE ST, LAWRENCE, KS 66044 USA SN 0824-0469 J9 MAR MAMMAL SCI JI Mar. Mamm. Sci. PD JUL PY 1998 VL 14 IS 3 BP 490 EP 507 DI 10.1111/j.1748-7692.1998.tb00738.x PG 18 WC Marine & Freshwater Biology; Zoology SC Marine & Freshwater Biology; Zoology GA ZW533 UT WOS:000074420500004 ER PT J AU Li, D Robinson, MB Rathz, TJ Williams, G AF Li, D Robinson, MB Rathz, TJ Williams, G TI Direct determination of the metastable liquid miscibility gap in undercooled Cu-Co alloys SO MATERIALS LETTERS LA English DT Article DE undercooled melts; liquid separation; miscibility gap; Cu-Co alloys; dispersion microstructure; coarsening ID MELT AB Bulk Cu-Co alloys at compositions ranging from 10 to 80 wt.% Co were highly undercooled using a melt fluxing technique. The metastable liquid separation boundary has been directly determined from the measured temperature-time profiles. It was also calculated using a subregular solution model. The critical point of the miscibility gap was found to be about 80 K below the Liquidus. A droplet-shaped microstructure was observed for all solidified specimens (Cu-10 to 80 wt.% Co), when the melts were undercooled into the metastable miscibility boundary. (C) 1998 Elsevier Science B.V. All rights reserved. C1 NASA, George C Marshall Space Flight Ctr, Space Sci Lab, Huntsville, AL 35812 USA. Univ Alabama, Huntsville, AL 35899 USA. RP Li, D (reprint author), NASA, George C Marshall Space Flight Ctr, Space Sci Lab, Huntsville, AL 35812 USA. EM delin.li@msfc.nasa.gov NR 15 TC 17 Z9 19 U1 1 U2 2 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0167-577X J9 MATER LETT JI Mater. Lett. PD JUL PY 1998 VL 36 IS 1-4 BP 152 EP 156 DI 10.1016/S0167-577X(98)00039-1 PG 5 WC Materials Science, Multidisciplinary; Physics, Applied SC Materials Science; Physics GA ZY510 UT WOS:000074629000030 ER PT J AU Obst, AW Hyer, MW Vaughn, WL AF Obst, AW Hyer, MW Vaughn, WL TI Thermal stresses in coatings on carbon-carbon composites SO MECHANICS OF COMPOSITE MATERIALS AND STRUCTURES LA English DT Article ID CERAMIC-METAL INTERFACES; FINITE-ELEMENT ANALYSIS; RESIDUAL-STRESSES AB A finite-element model for the analysis of thermal stresses in oxidation-protecting coatings on carbon-carbon composites is developed. The model is based on an incremental formulation of the generalized plane deformation theory and allows for temperature-dependent material properties, and the application of coatings at different temperatures. Emphasis is on the determination of stresses in the coatings near a geometric discontinuity, such as the corner radius of a rectangular cross section The model is used to study the St. Venant effect associated with the discontinuity and the effect of the orthotropy of the carbon-carbon substrate on the stresses in the coatings. The importance of using temperature-dependent material properties is demonstrated. C1 Virginia Polytech Inst & State Univ, Dept Engn Sci & Mech, Blacksburg, VA 24061 USA. NASA, Langley Res Ctr, Div Mat, Environm Interact Branch, Hampton, VA USA. RP Hyer, MW (reprint author), Virginia Polytech Inst & State Univ, Dept Engn Sci & Mech, Norris Hall, Blacksburg, VA 24061 USA. NR 32 TC 2 Z9 2 U1 0 U2 0 PU TAYLOR & FRANCIS LTD PI LONDON PA ONE GUNPOWDER SQUARE, LONDON EC4A 3DE, ENGLAND SN 1075-9417 J9 MECH COMPOS MATER ST JI Mech. Compos. Mater. Struct. PD JUL-SEP PY 1998 VL 5 IS 3 BP 203 EP 225 DI 10.1080/10759419808945899 PG 23 WC Materials Science, Multidisciplinary; Materials Science, Characterization & Testing; Materials Science, Composites SC Materials Science GA ZU010 UT WOS:000074152200001 ER PT J AU Krot, AN Petaev, MI Zolensky, ME Keil, K Scott, ERD Nakamura, K AF Krot, AN Petaev, MI Zolensky, ME Keil, K Scott, ERD Nakamura, K TI Secondary calcium-iron-rich minerals in the Bali-like and Allende-like oxidized CV3 chondrites and Allende dark inclusions SO METEORITICS & PLANETARY SCIENCE LA English DT Article ID HIGH-TEMPERATURE CONDENSATION; CARBONACEOUS CHONDRITE; AQUEOUS ALTERATION; SOLAR NEBULA; COMPOSITIONAL CLASSIFICATION; METEORITE; OLIVINE; ORIGIN; RIMS; METAMORPHISM AB We have characterized Ca-Fe-rich silicates (salite-hedenbergite pyroxenes (Fs(10-50)Wo(45-50)), andradite (Ca3Fe2Si3O12), kirschsteinite (CaFeSiO4), and wollastonite (Ca3Si3O9)) in the type I chondrules and matrices in the Ball-like and Allende-like oxidized CV3 chondrites and Allende dark inclusions. In type I chondrules in the Ball-like CV3 chondrites, metal is oxidized to magnetite; magnetite-sulfide nodules are replaced by Ca-Fe-rich pyroxenes with minor andradite and pure fayalite. We infer that Ca-Fe-rich pyroxenes, andradite, fayalite, magnetite, and phyllosilicates (which occur in mesostases) formed at relatively low temperatures (<300 degrees C) in the presence of aqueous solutions. Thermodynamic analysis of phase relations in the Si-Fe-Ca-O-H system and large O isotopic fractionation of the coexisting magnetite and fayalite (similar to 20 parts per thousand) (Krot et al., 1998) are consistent with this interpretation. In type I chondrules in the Allende-like CV3 chondrites and dark inclusions, magnetite-sulfide nodules are replaced by Ca-Fe-rich pyroxenes and ferrous olivine; low-Ca pyroxene and forsterite phenocrysts are rimmed and veined by ferrous olivine. It appear that the Ca-Fe-rich pyroxenes predate formation of ferrous olivine; the latter postdates formation of talc and biopyriboles (Brearley, 1997). The Allende dark inclusions are crosscut by Ca-Fe-pyroxene-andradite veins and surrounded by Ca-rich rims that consist of Ca-Fe-rich pyroxenes, andradite, wollastonite, and kirschsteinite. Calcium-rich veins and rims formed after aggregation and lithification of the dark inclusions. The rimmed dark inclusions show zoned depletion in Ca, which is due to a lower abundance of Ca-Fe-rich pyroxenes close to the rim. Calcium was probably leached from the inclusions and redeposited along their edges. We infer that the Allende-like chondrites and dark inclusions experienced similar aqueous alteration to the Ball-like chondrites and were metamorphosed subsequently, which resulted in loss of aqueous solutions and dehydration of phyllosilicates. We conclude that Ca-Fe-rich silicates in the oxidized CV3 chondrites and Allende dark inclusions are secondary and resulted from aqueous fluid-rock interactions during progressive metamorphism of a heterogeneous mixture of hydrous (ices?) and anhydrous materials; the latter were possibly 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. NASA, Lyndon B Johnson Space Ctr, Earth Sci & Solar Syst Explorat Div, Houston, TX 77058 USA. Kobe Univ, Div Earth & Planetary Sci, Kobe, Hyogo 657, Japan. RP Krot, AN (reprint author), Univ Hawaii Manoa, Sch Ocean & Earth Sci & Technol, Hawaii Inst Geophys & Planetol, Honolulu, HI 96822 USA. EM sasha@kahana.pgd.hawaii.edu NR 71 TC 57 Z9 57 U1 0 U2 12 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 JUL PY 1998 VL 33 IS 4 BP 623 EP 645 PG 23 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 114GV UT WOS:000075601500008 ER PT J AU Bishop, JL Mustard, JF Pieters, CM Hiroi, T AF Bishop, JL Mustard, JF Pieters, CM Hiroi, T TI Recognition of minor constituents in reflectance spectra of Allan Hills 84001 chips and the importance for remote sensing on Mars SO METEORITICS & PLANETARY SCIENCE LA English DT Article ID MARTIAN METEORITE ALH84001; CARBONATES; MINERALS; BANDS AB Reflectance spectra of splits 92 and 271 from the Martian meteorite Allan Hills (ALH) 84001 are presented and analyzed in this paper. Although the visible and infrared spectra of both chips show that the dominant mineralogy is low-Ca pyroxene, the focus here is on identification of the minor constituents. Infrared spectra measured at multiple spots along the surface of chips 92 and 271 show subtle spectroscopic variations due to changes in the low-Ca pyroxene texture and composition and to the presence of secondary minerals. Absorption bands observed near 0.93 and 1.95 mu m are characteristic of low-Ca pyroxene. Strong mid-infrared reststrahlen bands are observed near 9 and 19.5 mu m in all surface spectra, and additional bands near 7, 10.5, 11.4, 17.8, 20.5 and 23 mu m are variable depending on the low-Ca pyroxene texture and the presence of secondary minerals. Selected spectra exhibit carbonate features near 4, 6.4-7.1 and 11.3 mu m. Detailed analysis of these carbonate features indicates the presence of Mg-Fe carbonate, which is consistent with petrographic studies. Many of these spectra with strong carbonate features exhibit a magnetite feature near 17.9 mu m and a shoulder near 20.5 mu m that cannot be uniquely ascribed to one mineral. Spectroscopic identification of the minor carbonate and magnetite minerals in this probable piece of Mars indicates that detection of small amounts of these minerals of possible biological significance will be possible using infrared hyperspectral analyses of the Martian surface. Also of importance for remote sensing on Mars is the result that Mg, Fe and Mg-Fe carbonates in a low-Ca pyroxene matrix should be distinguishable from one another in the spectral region measured by the thermal emmitance spectrometer (TES). C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Brown Univ, Dept Geol Sci, Providence, RI 02912 USA. RP Bishop, JL (reprint author), NASA, Ames Res Ctr, Mail Stop 239-4, Moffett Field, CA 94035 USA. NR 30 TC 22 Z9 22 U1 0 U2 2 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 JUL PY 1998 VL 33 IS 4 BP 693 EP 698 PG 6 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 114GV UT WOS:000075601500015 ER PT J AU Bishop, JL Pieters, CM Hiroi, T Mustard, JF AF Bishop, JL Pieters, CM Hiroi, T Mustard, JF TI Spectroscopic analysis of Martian meteorite Allan Hills 84001 powder and applications for spectral identification of minerals and other soil components on Mars SO METEORITICS & PLANETARY SCIENCE LA English DT Article ID MU-M; REFLECTANCE SPECTROSCOPY; CARBONACEOUS CHONDRITES; SNC METEORITES; THERMAL METAMORPHISM; AQUEOUS ALTERATION; ALH84001; CARBONATES; TEMPERATURE; PYROXENE AB Spectroscopic measurement and analysis of Martian meteorites provide important information about the mineralogy of Mars, as well as necessary ground-truths for deconvolving remote sensing spectra of the Martian surface rocks. The spectroscopic properties of particulate ALH 84001 from 0.3 to 25 mu m correctly identify low-Ca pyroxene as the dominant mineralogy. Absorption bands due to electronic transitions of ferrous iron are observed at 0.94 and 1.97 mu m that are typical for low-Ca pyroxene. A strong, broad water band is observed near 3 mu m that is characteristic of the water band typically associated with pyroxenes. Weaker features near 4.8, 5.2 and 6.2 mu m are characteristic of particulate low-Ca pyroxene and can be distinguished readily from the features due to high-Ca pyroxene and other silicate minerals. The reflectance minimum occurs near 8.6 mu m for the ALH 84001 powder, which is more consistent with high-Ca pyroxene and augite than low-Ca pyroxene. The dominant mid-infrared (IR) spectral features for the ALH 84001 powder are observed near 9 and 19.5 mu m; however, there are multiple features in this region. These mid-IR features are generally characteristic of low-Ca pyroxene but cannot be explained by low-Ca pyroxene alone. Spectral features from 2.5-5 mu m are typically associated, with water, organics and carbonates and have been studied in spectra of the ALH 84001, split 92 powder and ALH 84001, splits 92 and 271 chip surfaces. Weak features have been identified near 3.5 and 4 mu m that are assigned to organic material and carbonates. Another feature is observed at 4.27 mu m in many surface spots and in the powder but has not yet been uniquely identified. Spectroscopic identification of minor organic and carbonate components in this probable piece of Mars suggests that detection of small amounts of organics and carbonates in the Martian surface regolith would also be possible using visible-infrared hyperspectral analyses. Laboratory spectroscopic analysis of Martian meteorites provides a unique opportunity to identify the spectral features of minerals and other components while they are embedded in their natural medium. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Brown Univ, Dept Geol Sci, Providence, RI 02912 USA. RP Bishop, JL (reprint author), NASA, Ames Res Ctr, Mail Stop 239-4, Moffett Field, CA 94035 USA. EM jbishop@mail.arc.nasa.gov NR 73 TC 29 Z9 29 U1 0 U2 5 PU WILEY-BLACKWELL PI MALDEN PA COMMERCE PLACE, 350 MAIN ST, MALDEN 02148, MA USA SN 1086-9379 J9 METEORIT PLANET SCI JI Meteorit. Planet. Sci. PD JUL PY 1998 VL 33 IS 4 BP 699 EP 707 PG 9 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 114GV UT WOS:000075601500016 ER PT J AU Garrison, DH Bogard, DD AF Garrison, DH Bogard, DD TI Isotopic composition of trapped and cosmogenic noble gases in several Martian meteorites SO METEORITICS & PLANETARY SCIENCE LA English DT Article ID RAY PRODUCTION-RATES; SNC METEORITES; ORTHOPYROXENITE ALH84001; SOLAR-WIND; ORIGIN; SHERGOTTITES; NITROGEN; GLASS; EETA-79001; ATMOSPHERE C1 NASA, Lyndon B Johnson Space Ctr, Planetary Sci Branch, Houston, TX 77058 USA. NASA, Lyndon B Johnson Space Ctr, Lockheed Martin Corp, Houston, TX 77058 USA. RP Bogard, DD (reprint author), NASA, Lyndon B Johnson Space Ctr, Planetary Sci Branch, Houston, TX 77058 USA. NR 56 TC 55 Z9 55 U1 0 U2 3 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 JUL PY 1998 VL 33 IS 4 BP 721 EP 736 PG 16 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 114GV UT WOS:000075601500018 ER PT J AU Morris, RV Golden, DC Shelfer, TD Lauer, HV AF Morris, RV Golden, DC Shelfer, TD Lauer, HV TI Lepidocrocite to maghemite to hematite: A pathway to magnetic and hematitic Martian Soil SO METEORITICS & PLANETARY SCIENCE LA English DT Article ID THERMAL-DECOMPOSITION; CHEMICAL-COMPOSITION; MARS; GAMMA-FE2O3; MINERALOGY; RELEVANCE; SPECTRA; ROCKS AB We examined decomposition products of lepidocrocite, which were produced by heating the phase in air at temperatures up to 525 degrees C for 3 and 300 h, by x-ray diffraction (XRD), transmission electron microscopy (TEM), magnetic methods, and reflectance spectroscopy (visible and near-infrared (IR)). Single-crystal lepidocrocite particles dehydroxylated to polycrystalline particles of disordered maghemite that subsequently transformed to polycrystalline particles of hematite. Essentially pure maghemite was obtained at 265 and 223 degrees C for the 3 and 300 h heating experiments, respectively. Its saturation magnetization (J(S)) and mass specific susceptibility are similar to 50 Am-2/kg and similar to 400 x 10(-6) m(3)/kg, respectively. Because hematite is spectrally dominant, spectrally hematitic samples (i.e., a minimum near 860 nm and a maximum near 750 nm) also could be strongly magnetic (J(S) up to similar to 30 Am-2/kg) from the masked maghemite component. Analyses by TEM showed that individual particles are polycrystalline with respect to both maghemite and hematite. The spectrally hematitic and magnetic Mh + Hm particles can satisfy the spectral and magnetic constraints for Martian surface materials over a wide range of values of Mh/(Mh + Hm) either as pure oxide powders or (within limits) as components of multiphase particles. These experiments are consistent with lepidocrocite as the precursor of Mh + Hm assemblages on Mars, but other phases (e.g., magnetite) that decompose to Mh and Hm are also possible precursors. Simulations done with a copy of the Mars Pathfinder magnet array showed that spectrally hematitic Mh + Hm powders having J(S) equal to 20.6 Am-2/kg adhered to all five magnets. C1 NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. Dual Inc, Houston, TX 77058 USA. Etcetera Serv, Houston, TX 77058 USA. Lockheed Martin Space Mission Syst & Serv, Houston, TX 77058 USA. RP Morris, RV (reprint author), NASA, Lyndon B Johnson Space Ctr, Mail Code SN3, Houston, TX 77058 USA. NR 24 TC 25 Z9 25 U1 3 U2 13 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 JUL PY 1998 VL 33 IS 4 BP 743 EP 751 PG 9 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 114GV UT WOS:000075601500020 ER PT J AU Romanek, CS Perry, EC Treiman, AH Socki, RA Jones, JH Gibson, EK AF Romanek, CS Perry, EC Treiman, AH Socki, RA Jones, JH Gibson, EK TI Oxygen isotopic record of silicate alteration in the Shergotty-Nakhla-Chassigny meteorite Lafayette SO METEORITICS & PLANETARY SCIENCE LA English DT Article ID MARS VOLATILE EVOLUTION; SNC METEORITES; AQUEOUS ALTERATION; MARTIAN VOLATILES; STABLE ISOTOPES; ALH84001; CARBONATE; ORIGIN; TEMPERATURE; EETA-79001 AB Samples from a suite of Shergotty-Nakhla-Chassigny (SNC) meteorites were analyzed for their O isotopic ratios by a modified version of the laser fluorination technique. Measured isotopic ratios (O-17/O-16 and O-18/O-16) from bulk samples of the Shergottites, EETA79001, Shergotty and Zagami; the Nakhlite Lafayette; and Chassigny are similar to those reported in the literature, as are those from olivine and pyroxene mineral separates from Lafayette. Iddingsite, a preterrestrial alteration product of Lafayette, was measured for the first time as a separate phase. Oxygen isotopic ratios increase with the percentage of iddingsite in a sample to a maximum delta(18)O of 14.4 parts per thousand for a similar to 90% separate. Based on these measurements, end-member iddingsite has a delta(18)O of 15.6 parts per thousand, which places it among other O-18-enriched secondary phases (carbonate and silica) observed in SNC meteorites. The relatively large difference in delta(18)O between iddingsite and the olivine and pyroxene it replaces (similar to 11 parts per thousand) is typical of low-temperature alteration products. A range of crustal fluid delta(18)O values can be interpreted from the delta(18)O for end-member iddingsite, assuming isotopic equilibrium was achieved during low-temperature hydrous alteration (<100 degrees C; Treiman et al., 1993). The calculated range of values, -15 to 5 parts per thousand, depends on many factors including: (1) the modal mineralogy of iddingsite, (2) potential isotopic exchange among other O-bearing phases such as host silicate and carbonate, and (3) exchange with evolved or exotic O reservoirs on Mars. Despite the lack of constraints, the calculated range is consistent with isotopic exchange, and possibly equilibria, among components of the CO2-carbonate-iddingsite-H2O system at low temperature. The SNC meteorite samples in this study have Delta(17)O values that are indistinguishable from bulk Mars (0.30 parts per thousand), except for a single, small sample of iddingsite that has an anomalous Delta(17)O of similar to 1.4 parts per thousand. While analytical difficulties make isotopic measurements for this sample problematic, the Delta(17)O is similar in direction to Delta(17)O reported for waters extracted from bulk samples of Lafayette (Karlsson et al., 1992). If the Delta(17)O for iddingsite is confirmed, it can be concluded that evolved or exotic fluids on Mars have contributed volatiles to the O reservoir from which iddingsite formed 130 to 700 Ma ago. C1 Univ Georgia, Dept Geol, Aiken, SC 29802 USA. Univ Georgia, Savannah River Ecol Lab, Aiken, SC 29802 USA. No Illinois Univ, Dept Geol, De Kalb, IL 60115 USA. Lunar & Planetary Inst, Houston, TX 77058 USA. Lockheed Martin, Houston, TX 77058 USA. NASA, Johnson Space Ctr, Houston, TX 77058 USA. RP Univ Georgia, Dept Geol, Drawer E, Aiken, SC 29802 USA. EM romanek@srel.edu NR 76 TC 37 Z9 37 U1 1 U2 4 PU WILEY-BLACKWELL PI HOBOKEN PA 111 RIVER ST, HOBOKEN 07030-5774, NJ USA SN 1086-9379 EI 1945-5100 J9 METEORIT PLANET SCI JI Meteorit. Planet. Sci. PD JUL PY 1998 VL 33 IS 4 BP 775 EP 784 PG 10 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 114GV UT WOS:000075601500023 ER PT J AU Cintala, MJ Grieve, RAF AF Cintala, MJ Grieve, RAF TI Scaling impact melting and crater dimensions: Implications for the lunar cratering record SO METEORITICS & PLANETARY SCIENCE LA English DT Review ID GEOMETRIC MODEL; GIANT IMPACTS; STRATIGRAPHY; CHEMISTRY; MECHANICS; ORIENTALE; DEPOSITS; BRECCIA; QUEBEC; MOON AB The dimensions of large craters formed by impact are controlled to a large extent by gravity, whereas the volume of impact melt created during the same event is essentially independent of gravity. This "differential scaling" fosters size-dependent changes in the dynamics of impact-crater and basin formation as well as in the final morphologies of the resulting structures. A variety of such effects can be observed in the lunar cratering record, and some predictions can be made on the basis of calculations of impact melting and crater dimensions. Among them are the following: (1) as event magnitude increases, the volume of melt created relative to that of the crater will grow, and more will be retained inside the rim of the crater or basin. (2) The depth of melting will exceed the depth of excavation at diameters that essentially coincide with both the inflection in the depth-diameter trend and the simple-to-complex transition. (3) The volume of melt will exceed that of the transient cavity at a cavity diameter on the order of the diameter of the Moon; this would arguably correspond to a Moon-melting event. (4) Small lunar craters only rarely display exterior flows of impact melt because the relatively small volumes of melt created can become choked with clasts, increasing the melt's viscosity and chilling it rapidly. Larger craters and basins should suffer little from such a process. (5) Deep melting near the projectile's axis of penetration during larger events will yield a progression in central-structure morphology; with growing event magnitude, this sequence should range from single peaks through multiple peaks to peak rings. (6) The minimum depth of origin of central-peak material should coincide with the maximum depth of melting; the main central peak in a crater the size of Tycho should have had a preimpact depth of close to 15 km. C1 NASA, Johnson Space Ctr, Planetary Sci Branch, Houston, TX 77058 USA. Geol Survey Canada, Ottawa, ON K1A 0E8, Canada. RP Cintala, MJ (reprint author), NASA, Johnson Space Ctr, Planetary Sci Branch, Code SN2, Houston, TX 77058 USA. EM mark.j.cintalal@jsc.nasa.gov NR 113 TC 173 Z9 175 U1 1 U2 9 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 JUL PY 1998 VL 33 IS 4 BP 889 EP 912 PG 24 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 114GV UT WOS:000075601500035 ER PT J AU See, TH Wagstaff, J Yang, V Horz, F McKay, GA AF See, TH Wagstaff, J Yang, V Horz, F McKay, GA TI Compositional variation and mixing of impact melts on microscopic scales SO METEORITICS & PLANETARY SCIENCE LA English DT Article ID SUEVITE BRECCIA; TEKTITES; ORIGIN; CRATER; ROCKS; RIES; METAMORPHISM; HISTORY; GLASSES; GERMANY AB We investigated the compositional characteristics of schlieren-rich, holohyaline impact glasses from Ries, Wabar, and Meteor Crater using a Cameca SX 100 scanning electron microprobe. This instrument is capable of producing detailed maps of major elements at spatial resolutions of <10 mu m. The objective was to characterize the composition of an unusually large number of individual schlieren and to evaluate details of the process that causes melts of lithologically diverse target rocks to mix on scales of micrometers. The Ries and Meteor Crater impacts involved lithologically heterogeneous targets; whereas, Wabar Crater formed in relatively uniform dune sand. Texturally heterogeneous, schlieren-rich glasses from the Ries Crater illustrate that schlieren of highly variable color can be surprisingly similar in composition, as first detailed by Stahle (1972). Consistent with these earlier findings, most schlieren represent mixtures of diverse rock melts; their compositions deviate only subtly from the average melt and do not resemble monomineralic melts nor binary mixtures of major rock-forming minerals. A specific population of schlieren is enriched in mafic elements (Mg, Fe: and Ca), which suggests incomplete homogenization of an amphibolite progenitor. In the case of Wabar Crater, a compositionally simple melt of dune sand mixed with projectile (IIIA iron meteorite) materials, and specific schlieren are variable mixtures of these two progenitors. The optically homogeneous glass from Meteor Crater is compositionally homogeneous as well, which suggests ideal mixing of such diverse lithologies as platform carbonates, sandstone, and a class IIIA iron meteorite. The mixing of projectile and target melts at Wabar and Meteor Crater unambiguously demonstrates that melts initially produced in distinctly different stratigraphic/structural locations will undergo wholesale mixing, if not homogenization. Also, the projectile melts unquestionably formed relatively early in the cratering process, and their dissemination throughout the prospective melt volume, albeit at variable concentration levels, suggests that the entire mixing process may be an early cratering feature. This also follows from the fact that we investigated ballistic melt ejecta, which thereby eliminates all of those mixing processes that may additionally operate during the pooling and generation of massive melt-ponds following gravitational collapse of large, structurally complex craters. Substantial turbulence ranging from field dimensions to microscopic scales seems inescapable to accomplish the observed degree of mixing, yet this is not readily inferred from current models of macroscopic material motions during hypervelocity impact. C1 NASA, Johnson Space Ctr, Planetary Sci Branch, Houston, TX 77058 USA. Lockheed Martin Space Mission Syst & Serv, Houston, TX 77058 USA. RP Horz, F (reprint author), NASA, Johnson Space Ctr, Planetary Sci Branch, SN4, Houston, TX 77058 USA. EM fhorz@ems.jsc.nasa.gov NR 39 TC 21 Z9 21 U1 0 U2 5 PU WILEY-BLACKWELL PI HOBOKEN PA 111 RIVER ST, HOBOKEN 07030-5774, NJ USA SN 1086-9379 EI 1945-5100 J9 METEORIT PLANET SCI JI Meteorit. Planet. Sci. PD JUL PY 1998 VL 33 IS 4 BP 937 EP 948 PG 12 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 114GV UT WOS:000075601500038 ER PT J AU Bell, MS Zolensky, ME Yang, SV AF Bell, MS Zolensky, ME Yang, SV TI Evidence for thermal alteration in the Asuka 881655 chondrite. SO METEORITICS & PLANETARY SCIENCE LA English DT Meeting Abstract C1 Lockheed Martin Earth & Space Sci, Houston, TX 77058 USA. NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. NR 2 TC 0 Z9 0 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 JUL PY 1998 VL 33 IS 4 SU S BP A13 EP A13 PG 1 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 117JK UT WOS:000075778000017 ER PT J AU Benedix, GK Keil, K AF Benedix, GK Keil, K TI Classification of four new Roosevelt County meteorites SO METEORITICS & PLANETARY SCIENCE LA English DT Article; Proceedings Paper CT 61st Annual Meeting of the Meteoritical-Society CY JUL 27-31, 1998 CL TRINITY COLL, DUBLIN, IRELAND SP Meteorit Soc HO TRINITY COLL AB We have classified four new ordinary chondrites from Roosevelt County, New Mexico (RC 091-094) that were found in June and July of 1994 by I. Wilson. They include one H4(S2) and three L5(S4) chondrites. Degree of weathering is variable and ranges from W2-6. C1 Univ Hawaii Manoa, Sch Ocean & Earth Sci & Technol, Hawaii Inst Geophys & Planetol, Honolulu, HI 96822 USA. Univ Hawaii Manoa, Hawaii Ctr Volcanol, Honolulu, HI 96822 USA. RP Benedix, GK (reprint author), NASA, Ames Res Ctr, MS 245-3, Moffett Field, CA 94035 USA. NR 8 TC 0 Z9 0 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 JUL PY 1998 VL 33 IS 4 SU S BP A191 EP A192 PG 2 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 117JK UT WOS:000075778000319 ER PT J AU Benner, LAM Ostro, SJ Rosema, KD Choate, D Giorgini, JD Jurgens, RF Rose, R Slade, MA Thomas, ML Winkler, R Yeomans, DK AF Benner, LAM Ostro, SJ Rosema, KD Choate, D Giorgini, JD Jurgens, RF Rose, R Slade, MA Thomas, ML Winkler, R Yeomans, DK TI Radar observations of asteroid 7822 (1991 CS). SO METEORITICS & PLANETARY SCIENCE LA English DT Meeting Abstract C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. NR 8 TC 0 Z9 0 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 JUL PY 1998 VL 33 IS 4 SU S BP A13 EP A14 PG 2 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 117JK UT WOS:000075778000018 ER PT J AU Blom, RG McHone, JF Crippen, RE AF Blom, RG McHone, JF Crippen, RE TI Possible 770-meter-diameter impact crater detected by satellite, Yemen Arab Republic. SO METEORITICS & PLANETARY SCIENCE LA English DT Meeting Abstract C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Arizona State Univ, Dept Geol, Tempe, AZ 85287 USA. NR 3 TC 0 Z9 0 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 JUL PY 1998 VL 33 IS 4 SU S BP A17 EP A18 PG 2 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 117JK UT WOS:000075778000025 ER PT J AU Bogard, DD Garrison, DH AF Bogard, DD Garrison, DH TI Trapped and radiogenic argon in Martian shergottites. SO METEORITICS & PLANETARY SCIENCE LA English DT Meeting Abstract C1 NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. NR 4 TC 4 Z9 4 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 JUL PY 1998 VL 33 IS 4 SU S BP A19 EP A19 PG 1 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 117JK UT WOS:000075778000028 ER PT J AU Borg, LE Nyquist, LE Wiesmann, H Reese, Y AF Borg, LE Nyquist, LE Wiesmann, H Reese, Y TI Samarium-neodymium-isotopic systematics of the lherzolitic shergottite Lewis Cliff 88516. SO METEORITICS & PLANETARY SCIENCE LA English DT Meeting Abstract ID PETROGENESIS; ALHA77005; LEW88516 C1 Lockheed Martin, Houston, TX 77258 USA. NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. NR 8 TC 5 Z9 5 U1 1 U2 1 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 JUL PY 1998 VL 33 IS 4 SU S BP A20 EP A20 PG 1 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 117JK UT WOS:000075778000030 ER PT J AU Cassen, P Woolum, DS AF Cassen, P Woolum, DS TI Internal temperatures of the solar nebula inferred from astronomical observations of circumstellar disks. SO METEORITICS & PLANETARY SCIENCE LA English DT Meeting Abstract ID T-TAURI STARS C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Calif State Univ Fullerton, Dept Phys, Fullerton, CA 92834 USA. NR 14 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 JUL PY 1998 VL 33 IS 4 SU S BP A28 EP A29 PG 2 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 117JK UT WOS:000075778000047 ER PT J AU Drake, MJ Lowe, JP Righter, K Zuber, MT Clark, PE AF Drake, MJ Lowe, JP Righter, K Zuber, MT Clark, PE TI Uranium in the lunar crust: Implications for lunar origin and evolution. SO METEORITICS & PLANETARY SCIENCE LA English DT Meeting Abstract C1 Univ Arizona, Lunar & Planetary Lab, Tucson, AZ 85721 USA. MIT, Dept Earth Atmospher & Planetary Sci, Cambridge, MA 02139 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. NR 4 TC 0 Z9 0 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 JUL PY 1998 VL 33 IS 4 SU S BP A41 EP A42 PG 2 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 117JK UT WOS:000075778000071 ER PT J AU Gibson, EK Zolensky, ME Lofgren, GE Lindstrom, DJ Morris, RV Schmidt, SD Yang, SV AF Gibson, EK Zolensky, ME Lofgren, GE Lindstrom, DJ Morris, RV Schmidt, SD Yang, SV TI Monahans(1998)H5 chondrite: An unusual meteorite fall with extraterrestrial halite and sylvite. SO METEORITICS & PLANETARY SCIENCE LA English DT Meeting Abstract C1 Lockheed Martin, Houston, TX 77058 USA. Marian Blakemore Planetarium, Midland, TX 79701 USA. NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. NR 0 TC 3 Z9 3 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 JUL PY 1998 VL 33 IS 4 SU S BP A57 EP A58 PG 2 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 117JK UT WOS:000075778000100 ER PT J AU Head, JW Smith, D Zuber, M AF Head, JW Smith, D Zuber, M TI Mars: Assessing evidence for an ancient northern ocean with MOLA data. SO METEORITICS & PLANETARY SCIENCE LA English DT Meeting Abstract C1 Brown Univ, Dept Geol Sci, Providence, RI 02912 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. MIT, Cambridge, MA 02139 USA. NR 1 TC 4 Z9 4 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 JUL PY 1998 VL 33 IS 4 SU S BP A66 EP A66 PG 1 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 117JK UT WOS:000075778000116 ER PT J AU Jones, JH AF Jones, JH TI Uncertainties in modeling core formation. SO METEORITICS & PLANETARY SCIENCE LA English DT Meeting Abstract ID PRESSURE; MANTLE C1 NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. NR 4 TC 2 Z9 2 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 JUL PY 1998 VL 33 IS 4 SU S BP A79 EP A80 PG 2 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 117JK UT WOS:000075778000141 ER PT J AU Lee, P Cassidy, WA Apostolopoulos, D Deans, M Foessel, A Krause, C Parra, J Pedersen, L Schwehr, K Whittaker, WL AF Lee, P Cassidy, WA Apostolopoulos, D Deans, M Foessel, A Krause, C Parra, J Pedersen, L Schwehr, K Whittaker, WL TI Search for meteorites in the Patriot Hills area, Ellsworth Mountains, West Antarctica. SO METEORITICS & PLANETARY SCIENCE LA English DT Meeting Abstract C1 Museo Nacl Hist Nat, Santiago, Chile. Fuerza Aerea Chile, Santiago, Chile. Carnegie Mellon Univ, Inst Robot, Pittsburgh, PA 15213 USA. Univ Pittsburgh, Dept Geol & Planetary Sci, Pittsburgh, PA 15260 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. NR 1 TC 4 Z9 4 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 JUL PY 1998 VL 33 IS 4 SU S BP A92 EP A93 PG 2 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 117JK UT WOS:000075778000167 ER PT J AU McCoy, TJ Dickinson, TL Lofgren, GE AF McCoy, TJ Dickinson, TL Lofgren, GE TI Partial melting of the Indarch (EH4) meteorite: Textural view of melting and melt migration. SO METEORITICS & PLANETARY SCIENCE LA English DT Meeting Abstract ID ORIGIN C1 NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. Natl Sci Fdn, Arlington, VA 22230 USA. Smithsonian Inst, Dept Mineral Sci, MRC 119, Washington, DC 20560 USA. EM mccoy.tim@nmnh.si.edu NR 10 TC 1 Z9 1 U1 0 U2 2 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 JUL PY 1998 VL 33 IS 4 SU S BP A100 EP A101 PG 2 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 117JK UT WOS:000075778000182 ER PT J AU McKay, G Schwandt, C Mikouchi, T AF McKay, G Schwandt, C Mikouchi, T TI Feldspathic glass and silica in Allan Hills 84001. SO METEORITICS & PLANETARY SCIENCE LA English DT Meeting Abstract ID ALH84001 C1 Univ Tokyo, Fac Sci, Inst Mineral, Tokyo 113, Japan. Lockheed Martin, Houston, TX 77058 USA. NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. NR 8 TC 3 Z9 3 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 JUL PY 1998 VL 33 IS 4 SU S BP A102 EP A102 PG 1 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 117JK UT WOS:000075778000184 ER PT J AU Mikouchi, T Miyamoto, M McKay, GA AF Mikouchi, T Miyamoto, M McKay, GA TI Mineralogical characterization of heated "maskelynitized" plagioclase glass in the Zagami Martian meteorite. SO METEORITICS & PLANETARY SCIENCE LA English DT Meeting Abstract C1 NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. Univ Tokyo, Grad Sch Sci, Inst Mineral, Bunkyo Ku, Tokyo 1130033, Japan. NR 7 TC 2 Z9 2 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 JUL PY 1998 VL 33 IS 4 SU S BP A109 EP A109 PG 1 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 117JK UT WOS:000075778000196 ER PT J AU Mikouchi, T McKay, GA Miyamoto, M AF Mikouchi, T McKay, GA Miyamoto, M TI Comparative mineralogy of shocked plagio-clase in Martian and lunar meteorites. SO METEORITICS & PLANETARY SCIENCE LA English DT Meeting Abstract C1 NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. Univ Tokyo, Grad Sch Sci, Inst Mineral, Bunkyo Ku, Tokyo 1130033, Japan. NR 6 TC 2 Z9 2 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 JUL PY 1998 VL 33 IS 4 SU S BP A109 EP A110 PG 2 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 117JK UT WOS:000075778000197 ER PT J AU Mittlefehldt, DW Lindstrom, MM AF Mittlefehldt, DW Lindstrom, MM TI Petrology and geochemistry of lodranite Graves Nunataks 95209. SO METEORITICS & PLANETARY SCIENCE LA English DT Meeting Abstract C1 NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. Lockheed Martin Space Mission Syst & Serv, Houston, TX 77058 USA. NR 5 TC 8 Z9 8 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 JUL PY 1998 VL 33 IS 4 SU S BP A111 EP A111 PG 1 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 117JK UT WOS:000075778000199 ER PT J AU Mittlefehldt, DW Lindstrom, MM AF Mittlefehldt, DW Lindstrom, MM TI Petrology and geochemistry of large metaigneous inclusions from L chondrites. SO METEORITICS & PLANETARY SCIENCE LA English DT Meeting Abstract ID CHONDRULES C1 NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. Lockheed Martin Space Mission Syst & Serv, Houston, TX 77058 USA. NR 6 TC 0 Z9 0 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 JUL PY 1998 VL 33 IS 4 SU S BP A110 EP A111 PG 2 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 117JK UT WOS:000075778000198 ER PT J AU Nuth, JA AF Nuth, JA TI Comparison of non-mass-dependent, chemical, oxygen-isotopic fractionation and reservoir mixing models as applied to materials in the solar nebula. SO METEORITICS & PLANETARY SCIENCE LA English DT Meeting Abstract ID METEORITES C1 NASA, Goddard Space Flight Ctr, Astrochem Branch, Greenbelt, MD 20771 USA. NR 5 TC 0 Z9 0 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 JUL PY 1998 VL 33 IS 4 SU S BP A119 EP A119 PG 1 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 117JK UT WOS:000075778000213 ER PT J AU Sandford, SA Bernstein, MP Swindle, TD AF Sandford, SA Bernstein, MP Swindle, TD TI The trapping of noble gases by the irradiation and warming of interstellar ice analogs. SO METEORITICS & PLANETARY SCIENCE LA English DT Meeting Abstract C1 Univ Arizona, Lunar & Planetary Lab, Tucson, AZ 85721 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. NR 3 TC 7 Z9 7 U1 1 U2 1 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 JUL PY 1998 VL 33 IS 4 SU S BP A135 EP A135 PG 1 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 117JK UT WOS:000075778000246 ER PT J AU Schulte, M AF Schulte, M TI Organic synthesis during aqueous alteration of carbonaceous chondrites: Comparison of CM and CI groups. SO METEORITICS & PLANETARY SCIENCE LA English DT Meeting Abstract C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Washington Univ, Dept Earth & Planetary Sci, St Louis, MO 63130 USA. NR 9 TC 0 Z9 0 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 JUL PY 1998 VL 33 IS 4 SU S BP A137 EP A138 PG 2 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 117JK UT WOS:000075778000251 ER PT J AU Schwandt, CS Horz, F Haynes, G Lofgren, GE AF Schwandt, CS Horz, F Haynes, G Lofgren, GE TI Shock experiments using Homestake Formation as an analog for the carbonate in meteorite Allan Hills 84001. SO METEORITICS & PLANETARY SCIENCE LA English DT Meeting Abstract ID ALH84001 C1 NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. Lockheed Martin Sci Engn Anal & Test, Houston, TX 77058 USA. NR 8 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 JUL PY 1998 VL 33 IS 4 SU S BP A139 EP A139 PG 1 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 117JK UT WOS:000075778000254 ER PT J AU Steele, A Goddard, DT Toporski, JKW Stapleton, D Wynn-Williams, DD McKay, D AF Steele, A Goddard, DT Toporski, JKW Stapleton, D Wynn-Williams, DD McKay, D TI Terrestrial contamination of an Antarctic chondrite. SO METEORITICS & PLANETARY SCIENCE LA English DT Meeting Abstract C1 British Antarctic Survey, Cambridge CB3 0ET, England. Univ Portsmouth, Dept Geol, Portsmouth PO1 2DT, Hants, England. British Nucl Fuels, Res & Technol, Preston PR4 0XJ, Lancs, England. NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. NR 5 TC 2 Z9 2 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 JUL PY 1998 VL 33 IS 4 SU S BP A149 EP A149 PG 1 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 117JK UT WOS:000075778000272 ER PT J AU Symes, SJ Lofgren, GE Lindstrom, DJ AF Symes, SJ Lofgren, GE Lindstrom, DJ TI Crystalline lunar spherules from Apollo 16 regolith breccias. SO METEORITICS & PLANETARY SCIENCE LA English DT Meeting Abstract C1 NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. NR 4 TC 1 Z9 1 U1 0 U2 2 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 JUL PY 1998 VL 33 IS 4 SU S BP A152 EP A153 PG 2 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 117JK UT WOS:000075778000278 ER PT J AU Wang, MS Socki, R Zolensky, ME Lipschutz, ME AF Wang, MS Socki, R Zolensky, ME Lipschutz, ME TI Thermal metamorphism of carbonaceous chondrites: Simulations and reality. SO METEORITICS & PLANETARY SCIENCE LA English DT Meeting Abstract C1 Purdue Univ, W Lafayette, IN 47907 USA. Lockheed Martin Earth & Space Sci, Houston, TX 77058 USA. NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. NR 9 TC 2 Z9 2 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 JUL PY 1998 VL 33 IS 4 SU S BP A161 EP A162 PG 2 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 117JK UT WOS:000075778000295 ER PT J AU Wilson, L Keil, K Love, SG AF Wilson, L Keil, K Love, SG TI Factors controlling the bulk densities of asteroids. SO METEORITICS & PLANETARY SCIENCE LA English DT Meeting Abstract C1 Univ Hawaii, Sch Ocean & Earth Sci & Technol, Hawaii Inst Geophys & Planetol, Honolulu, HI 96822 USA. Univ Lancaster, Div Environm Sci, Lancaster LA1 4YQ, England. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. NR 7 TC 2 Z9 2 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 JUL PY 1998 VL 33 IS 4 SU S BP A168 EP A168 PG 1 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 117JK UT WOS:000075778000307 ER PT J AU Economou, DJ Panagopoulos, TL Meyyappan, M AF Economou, DJ Panagopoulos, TL Meyyappan, M TI Examining scale-up and computer simulation in tool design for 300-mm wafer processing SO MICRO LA English DT Article ID PLASMA REACTOR; MONTE-CARLO; FLOW C1 Univ Houston, Dept Chem Engn, Houston, TX 77004 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Economou, DJ (reprint author), Univ Houston, Dept Chem Engn, Houston, TX 77004 USA. NR 12 TC 4 Z9 5 U1 0 U2 0 PU CANON COMMUNICATIONS INC PI SANTA MONICA PA 3340 OCEAN PARK BLVD, SUITE 1000, SANTA MONICA, CA 90405 USA SN 1081-0595 J9 MICRO JI Micro PD JUL-AUG PY 1998 VL 16 IS 7 BP 101 EP + PG 8 WC Engineering, Electrical & Electronic; Nanoscience & Nanotechnology; Materials Science, Multidisciplinary; Physics, Condensed Matter SC Engineering; Science & Technology - Other Topics; Materials Science; Physics GA 147ZR UT WOS:000077528200043 ER PT J AU Akse, JR Thompson, JO Sauer, RL Atwater, JE AF Akse, JR Thompson, JO Sauer, RL Atwater, JE TI "Reagentless" flow injection determination of ammonia and urea using membrane separation and solid phase basification SO MICROCHEMICAL JOURNAL LA English DT Article ID BIPOLAR AB Flow injection analysis instrumentation and methodology for the determination of ammonia and ammonium ions in an aqueous solution are described. Using in-line solid phase basification beds containing crystalline media, the speciation of ammoniacal nitrogen is shifted toward the un-ionized form, which diffuses in the gas phase across a hydrophobic microporous hollow fiber membrane into a pure-water-containing analytical stream. The two streams flow in a countercurrent configuration on opposite sides of the membrane. The neutral pH of the analytical stream promotes the formation of ammonium cations, which are detected using specific conductance. The methodology provides a lower limit of detection of 10 mu g/L and a dynamic concentration range spanning three orders of magnitude using a 315-mu L sample injection volume. Using immobilized urease to enzymatically promote the hydrolysis of urea to produce ammonia and carbon dioxide, the technique has been extended to the determination of urea. (C) 1998 Academic Press. C1 UMPQUA Res Co, Myrtle Creek, OR 97457 USA. NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. RP Atwater, JE (reprint author), UMPQUA Res Co, POB 609, Myrtle Creek, OR 97457 USA. NR 15 TC 6 Z9 6 U1 2 U2 4 PU ACADEMIC PRESS INC PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA SN 0026-265X J9 MICROCHEM J JI Microchem J. PD JUL PY 1998 VL 59 IS 3 BP 372 EP 382 DI 10.1006/mchj.1998.1636 PG 11 WC Chemistry, Analytical SC Chemistry GA ZZ972 UT WOS:000074787900005 PM 11541740 ER PT J AU Cullings, KW Vogler, DR AF Cullings, KW Vogler, DR TI A 5.8S nuclear ribosomal RNA gene sequence database: applications to ecology and evolution SO MOLECULAR ECOLOGY LA English DT Article DE 5.8S rRNA; DNA database; DNA sequencing PCR ID MOLECULAR EVIDENCE; DNA; PHYLOGENY; ORIGINS; REGION AB We compiled a 5.8S nuclear ribosomal gene sequence database for animals, plants, and fungi using both newly generated and GenBank sequences. We demonstrate the utility of this database as an internal check to determine whether the target organism and not a contaminant has been sequenced, as a diagnostic tool for ecologists and evolutionary biologists to determine the placement of asexual fungi within larger taxonomic groups, and as a tool to help identify fungi that form ectomycorrhizae. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. San Francisco State Univ, Dept Biol, San Francisco, CA 94132 USA. RP Cullings, KW (reprint author), NASA, Ames Res Ctr, Bldg N239,MS 239-4, Moffett Field, CA 94035 USA. NR 26 TC 51 Z9 52 U1 0 U2 3 PU BLACKWELL SCIENCE LTD PI OXFORD PA P O BOX 88, OSNEY MEAD, OXFORD OX2 0NE, OXON, ENGLAND SN 0962-1083 J9 MOL ECOL JI Mol. Ecol. PD JUL PY 1998 VL 7 IS 7 BP 919 EP 923 DI 10.1046/j.1365-294x.1998.00409.x PG 5 WC Biochemistry & Molecular Biology; Ecology; Evolutionary Biology SC Biochemistry & Molecular Biology; Environmental Sciences & Ecology; Evolutionary Biology GA 105RJ UT WOS:000075087100014 PM 9691493 ER PT J AU Sarna, MJ Yerli, SK Muslimov, AG AF Sarna, MJ Yerli, SK Muslimov, AG TI Magnetic activity and evolution of Algol-type stars - II SO MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY LA English DT Article DE binaries, close; stars, evolution; stars, individual, beta Per; stars, individual, U Sge; stars, magnetic fields; X-rays, stars ID X-RAY-EMISSION; LOW-MASS BINARIES; CHEMICAL EVOLUTION; RS CVN; SYSTEMS; BRAKING; EINSTEIN AB We examine the possibility of probing dynamo action in mass-losing stars, components of Algol-type binaries, Our analysis is based on the calculation of nonconservative evolution of these systems, We model the systems U Sge and beta Per where the more massive companion fills its Roche lobe at the main sequence (case AB) and where it has a small helium core (early case B) respectively, We show that to maintain evolution of these systems at the late stages which are presumably driven by stellar 'magnetic braking', an efficient mechanism for producing large-scale surface magnetic fields in the donor star is needed. We discuss the relevance of dynamo operation in the donor star to the accelerated mass transfer during the late stages of evolution of Algol-type binaries. We suggest that the observed X-ray activity in Algol-type systems may be a good indicator of their evolutionary status and internal structure of the mass-losing stellar components. C1 Polish Acad Sci, N Copernicus Astron Ctr, PL-00716 Warsaw, Poland. Univ Sussex, Sch CPES, Phys & Astron Subject Grp, Brighton BN1 9QJ, E Sussex, England. NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. RP Sarna, MJ (reprint author), Polish Acad Sci, N Copernicus Astron Ctr, Ul Bartycka 18, PL-00716 Warsaw, Poland. RI Yerli, Sinan/D-1324-2010 NR 46 TC 10 Z9 10 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 JUL 1 PY 1998 VL 297 IS 3 BP 760 EP 768 DI 10.1046/j.1365-8711.1998.01539.x PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZZ031 UT WOS:000074688400015 ER PT J AU Smith, CC Klypin, A Gross, MAK Primack, JR Holtzman, J AF Smith, CC Klypin, A Gross, MAK Primack, JR Holtzman, J TI Linearizing the observed power spectrum SO MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY LA English DT Article DE cosmology, theory; dark matter; large-scale structure of Universe ID DARK-MATTER MODELS; LARGE-SCALE STRUCTURE; COSMOLOGICAL CONSTANT; REDSHIFT SURVEY; RADIO GALAXIES; FLUCTUATIONS; UNIVERSE; STATISTICS; RADIATION AB Semi-analytic treatment of the power spectrum with the approximation of constant linear bias provides a way to compare cosmological models to a large amount of data, as Peacock & Dodds have shown, By applying the appropriate corrections to the observational power spectrum it is possible to recover the underlying linear power spectrum for any given cosmological model. Using extensive N-body simulations we carefully test and calibrate all important corrections. To demonstrate that the method is applicable to a wide range of cosmological models, we test the standard Omega = 1 cold dark matter (CDM) model, Omega < 1 models that include a cosmological constant (Lambda CDM), and Omega = 1 models with a mixture of cold and hot dark matter (CI-IDM), both with one massive neutrino and two equal mass neutrinos. The Lambda CDM and CHDM models are normalized to COBE and to cluster abundances. Our tests indicate that the improved linear-non-linear mapping recently suggested by Peacock & Dodds for treating CDM-type power spectra works well for a wide range of scale-dependent power spectra. However, we find that the Peacock & Dodds prescription for the recovery of the linear power spectrum from observations, which is often used to test cosmological models, can be misleading because the corrections are model-dependent. A model should not be judged based on the linear spectrum recovered by that procedure, but must be compared with the recovered spectrum for that particular model. When we apply the proper corrections for a given model to the observational power spectrum, we find that no model in our test group recovers the linear power spectrum well for the bias values suggested by Peacock & Dodds between Abell, radio, optical, and IRAS catalogues: b(A) : b(R) : b(O) : b(I) = 4.5 : 1.9 : 1.3 : 1.0, with b(I) = 1.0. The recovered linear Lambda CDM and CHDM power spectra were systematically below their respective linear power spectra using bI = 1.0. When we allow bl to vary (keeping the same bias ratios) we find that: (i) CHDM models give very good fits to observations if optically selected galaxies are slightly biased (b(O) similar to 1.1), (ii) Most Lambda CDM models give worse but acceptable fits if blue galaxies are considerably antibiased (0.6 less than or similar to b(O) less than or similar to 0.9) and fail if optical galaxies are biased. (iii) There is a universal shape of the recovered linear power spectrum of all Lambda CDM models over their entire range of explored wavenumbers, 0.01 less than or similar to k less than or similar to 0.6 h Mpc(-1). For a given bias, recovered linear power spectra of CDM and CHDM models are nearly the same as that of Lambda CDM in the region 0.01 less than or similar to k less than or similar to 0.2 h Mpc(-1) but diverge from this spectrum at higher k. We tabulate the recovered linear spectra, and also the initial linear spectra, for all the models considered. C1 New Mexico State Univ, Dept Astron, Las Cruces, NM 88001 USA. Univ Calif Santa Cruz, Dept Phys, Santa Cruz, CA 95064 USA. NASA, Goddard Space Flight Ctr, Earth & Space Data Comp Div, Greenbelt, MD 20771 USA. RP Smith, CC (reprint author), New Mexico State Univ, Dept Astron, Las Cruces, NM 88001 USA. EM geekus@flash.net; aklypin@nmsu.edu; gross@fozzie.gsfc.nasa.gov; joel@ucolick.org; holtz@nmsu.edu NR 40 TC 20 Z9 20 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 JUL 1 PY 1998 VL 297 IS 3 BP 910 EP 922 DI 10.1046/j.1365-8711.1998.01561.x PG 13 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZZ031 UT WOS:000074688400029 ER PT J AU Knupp, KR Geerts, B Goodman, SJ AF Knupp, KR Geerts, B Goodman, SJ TI Analysis of a small, vigorous mesoscale convective system in a low-shear environment. Part I: Formation, radar echo structure, and lightning behavior SO MONTHLY WEATHER REVIEW LA English DT Article ID MIDLATITUDE SQUALL LINE; UNITED-STATES; MICROPHYSICAL EVOLUTION; FLORIDA CUMULONIMBUS; KINEMATIC STRUCTURE; DOPPLER RADAR; STRATIFORM REGION; DEEP CONVECTION; BOUNDARY-LAYER; CLOUD CLUSTERS AB The evolution of a small, vigorous mesoscale convective system (MCS) over northern Alabama is described using Doppler radar, GOES satellite, surface mesonet, lightning, and sounding data. The MCS formed near noon in a relatively unstable environment having weak synoptic forcing and weak shear. The initiation of separate lines and clusters of deep convection occurred in regions exhibiting cumulus cloud streets, horizontal variations in stratocumulus cloud cover, and variations in inferred soil moisture. MCS growth via merger of storms within clusters and lines, and among the clusters, was accomplished largely through intersection of storm-scale and mesoscale outflow boundaries. The MCS maximum anvil area (similar to 60 000 km(2) at 220 K) and lifetime (8 h) were about 50% that of the typical Great Plains mesoscale convective complex (MCC). Despite its smaller size, this MCS displayed many aspects that typify the mostly nocturnal Great Plains MCS. The precipitation output was highly variable due to the transient nature of the intense convective elements, many of which produced microbursts. The radar measurements documented the formation of a stratiform region along the trailing side of an intense convective line. This stratiform region formed as decaying convective cores coalesced, rather than through advection of precipitation particles directly from the convective region. Combined GOES IR imagery and radar reflectivity analyses within the stratiform region show a sinking anvil cloud top in the presence of increases in the vertical radar reflectivity gradient within the cloud during the maturation of the stratiform region. During its intense developing stages, the MCS generated a peak cloud-to-ground (CG) flash rate of 2400 h(-1), comparable to rates produced by larger MCCs. Early on, positive CG flashes were most prevalent around intense convective core regions exhibiting strong divergence at anvil level. During the latter stages, the emergence of positive CG was coincident with the formation of a prominent radar bright band within the stratiform region. Thus, a bipole was established, but its length was quite short at approximately 50 km, 25%-50% of the distance documented in other MCSs. C1 Univ Alabama, Earth Syst Sci Lab, Huntsville, AL 35899 USA. NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. RP Knupp, KR (reprint author), Univ Alabama, Earth Syst Sci Lab, Huntsville, AL 35899 USA. NR 75 TC 11 Z9 16 U1 1 U2 5 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 JUL PY 1998 VL 126 IS 7 BP 1812 EP 1836 DI 10.1175/1520-0493(1998)126<1812:AOASVM>2.0.CO;2 PG 25 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 102FU UT WOS:000074914400004 ER PT J AU Riishojgaard, LP Cohn, SE Li, Y Menard, R AF Riishojgaard, LP Cohn, SE Li, Y Menard, R TI The use of spline interpolation in semi-Lagrangian transport models SO MONTHLY WEATHER REVIEW LA English DT Article ID ADVECTION SCHEMES; UPSTREAM AB The accuracy of interpolating semi-Lagrangian (SL) discretization methods depends on the choice of the interpolating function. Results from barotropic transport simulations on the sphere are presented, using either bicubic Lagrangian or bicubic spline SL discretization. The spline-based scheme is shown to generate excessively noisy fields in these simulations. The two methods are then tested in a one-dimensional advection problem. The damping and dispersion relations for the schemes are examined. The analysis and numerical experiments suggest that the excessive noise found in the spline-based simulations is a consequence of insufficient damping of the small scales for small and near-integer values of the Courant number. Inspection of the local Courant number for the two-dimensional spline-based simulation confirms this hypothesis. This noise can be controlled by adding a scale-selective diffusion term to the spline-based scheme, while retaining its excellent dispersion characteristics. C1 Univ Maryland Baltimore Cty, Joint Ctr Eath Syst Technol, Baltimore, MD 21250 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Riishojgaard, LP (reprint author), Univ Maryland Baltimore Cty, Joint Ctr Eath Syst Technol, 1000 Hilltop Circle, Baltimore, MD 21250 USA. RI Cohn, Stephen/K-1954-2012 OI Cohn, Stephen/0000-0001-8506-9354 NR 14 TC 4 Z9 5 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 JUL PY 1998 VL 126 IS 7 BP 2008 EP 2016 DI 10.1175/1520-0493(1998)126<2008:TUOSII>2.0.CO;2 PG 9 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 102FU UT WOS:000074914400014 ER PT J AU Gotthelf, EV Vasisht, G AF Gotthelf, EV Vasisht, G TI Discovery of a 7 second anomalous X-ray pulsar in the distant Milky way SO NEW ASTRONOMY LA English DT Article DE pulsars : general; pulsars : individual : AX J1845-0258; X-rays : general; supernova remnants ID MAGNETIZED NEUTRON-STARS; SOFT GAMMA-REPEATERS; RADIO PULSARS; SUPERNOVA REMNANT; BINARY; ACCRETION AB We report the serendipitous discovery of a 7-s X-ray pulsar using data acquired with the Advanced Satellite for Cosmology and Astrophysics (ASCA). The pulsar is detected as an unresolved source located towards a region of the Galactic plane (l,b similar or equal to 29.5,0.08) that coincides with an overdensity of star-formation tracers. The signal suffers tremendous foreground absorption, equivalent to N-H similar or equal to 10(23) cm(-2); the absorption correlates well with a line-of-sight that is tangential to the inner spiral arms and the 4-kpc molecular ring. The pulsar is not associated with any known supernova remnants or other cataloged objects in that direction. The near sinusoidal pulse (period P similar or equal to 6.9712) is modulated at 35% pulsed amplitude, and the steep spectrum is characteristic of hot black-body emission with temperature kT similar to 0.65 keV. We characterize the source as an anomalous X-ray pulsar (AXP). (C) 1998 Elsevier Science B.V. C1 NASA, Goddard Space Flight Ctr, Univ Space Res Assoc, Greenbelt, MD 20771 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Gotthelf, EV (reprint author), NASA, Goddard Space Flight Ctr, Univ Space Res Assoc, Greenbelt, MD 20771 USA. NR 33 TC 56 Z9 57 U1 0 U2 0 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 1384-1092 J9 NEW ASTRON JI New Astron. PD JUL PY 1998 VL 3 IS 5 BP 293 EP 300 DI 10.1016/S1384-1076(98)00014-1 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZZ597 UT WOS:000074746100002 ER PT J AU Griffin, DW AF Griffin, DW TI Gaussian beam intensity flattener SO OPTICAL ENGINEERING LA English DT Article DE lens design; Gaussian beams ID SYSTEM; DESIGN; LENS C1 NASA, Lewis Res Ctr, Micrograv Fluid Phys Branch, Cleveland, OH 44135 USA. RP Griffin, DW (reprint author), NASA, Lewis Res Ctr, Micrograv Fluid Phys Branch, M-S 100-3,21000 Brookpk Rd, Cleveland, OH 44135 USA. EM devon.griffin@lerc.nasa.gov NR 8 TC 5 Z9 5 U1 1 U2 1 PU SPIE - INTERNATIONAL SOCIETY FOR OPTICAL ENGINEERING PI BELLINGHAM PA POB 10, BELLINGHAM, WA 98227-0010 USA SN 0091-3286 J9 OPT ENG JI Opt. Eng. PD JUL PY 1998 VL 37 IS 7 BP 2185 EP 2187 DI 10.1117/1.601712 PG 3 WC Optics SC Optics GA ZZ669 UT WOS:000074754700035 ER PT J AU Patel, DN Reddy, BR Nash-Stevenson, SK AF Patel, DN Reddy, BR Nash-Stevenson, SK TI Spectroscopic and two-photon upconversion studies of Ho3+-doped Lu3Al5O12 SO OPTICAL MATERIALS LA English DT Article DE energy upconversion; holmium; Lu3Al5O12; two-photon excitation; site-selection; fluorescence ID TRANSITION-PROBABILITIES; TRIVALENT HOLMIUM; UP-CONVERSION; ENERGY; GLASSES AB A detailed spectroscopic investigation of Lu3Al5O12 doped with Ho3+ has been performed. Judd-Ofelt intensity parameters are estimated as Omega(2) = 0.172 +/- 0.10 x 10(-20) cm(2), Omega(4) = 2.08 +/- 0.18 x 10(-20) cm(2), and Omega(6) = 1.92 +/- 0.11 x 10(-20) cm(2). Transition probabilities and lifetimes were also estimated. Experimentally, we found that Ho3+ ion occupies more than one type of site in the lattice. Energy upconversion studies were performed under different laser excitation conditions. (C) 1998 Elsevier Science B.V. All rights reserved. C1 Alabama A&M Univ, Dept Phys, Normal, AL 35762 USA. NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. RP Patel, DN (reprint author), Alabama A&M Univ, Dept Phys, Normal, AL 35762 USA. NR 19 TC 35 Z9 37 U1 0 U2 7 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0925-3467 J9 OPT MATER JI Opt. Mater. PD JUL PY 1998 VL 10 IS 3 BP 225 EP 234 DI 10.1016/S0925-3467(97)00177-8 PG 10 WC Materials Science, Multidisciplinary; Optics SC Materials Science; Optics GA ZY485 UT WOS:000074626500007 ER PT J AU Post, RB Welch, RB AF Post, RB Welch, RB TI Dual adaptation of apparent concomitant motion contingent on head rotation frequency SO PERCEPTION & PSYCHOPHYSICS LA English DT Article ID VESTIBULO-OCULAR REFLEX; ADAPTIVE-CHANGES; ORIENTATION; DIRECTION; GAIN AB Perceived movement of a stationary visual stimulus during head motion was measured before and after adaptation intervals during which participants performed voluntary head oscillations while viewing a moving spot. During these intervals, participants viewed the spot stimulus moving alternately in the same direction as the head was moving during either.25- or 2.0-Hz oscillations, and then in the opposite direction as the head at the other of the two frequencies. Postadaptation measures indicated that the visual stimuli were perceived as stationary only if traveling in the same direction as that viewed during adaptation at the same frequency of head motion. Thus, opposite directions of spot motion were perceived as stationary following adaptation depending on head, movement frequency. The results provide an example of the ability to establish dual (or "context-specific") adaptations to altered visual-vestibular feedback. C1 Univ Calif Davis, Dept Psychol, Davis, CA 95616 USA. NASA, Ames Res Ctr, Mtn View, CA USA. RP Post, RB (reprint author), Univ Calif Davis, Dept Psychol, Davis, CA 95616 USA. NR 37 TC 5 Z9 5 U1 0 U2 0 PU PSYCHONOMIC SOC INC PI AUSTIN PA 1710 FORTVIEW RD, AUSTIN, TX 78704 USA SN 0031-5117 J9 PERCEPT PSYCHOPHYS JI Percept. Psychophys. PD JUL PY 1998 VL 60 IS 5 BP 821 EP 825 DI 10.3758/BF03206065 PG 5 WC Psychology; Psychology, Experimental SC Psychology GA ZZ725 UT WOS:000074760900007 PM 9682606 ER PT J AU Ramanathan, R Geary, RS Bourne, DWA Putcha, L AF Ramanathan, R Geary, RS Bourne, DWA Putcha, L TI Bioavailability of intranasal promethazine dosage forms in dogs SO PHARMACOLOGICAL RESEARCH LA English DT Article DE promethazine; pharmacokinetics; dosage forms; intramuscular and intranasal; dogs ID SPACE MOTION SICKNESS; INTRAMUSCULAR PROMETHAZINE; ELECTROCHEMICAL DETECTION; MEDICATIONS; PROGRAM AB Intramuscular promethazine (PMZ) is used aboard the US Space Shuttle to ameliorate symptoms of space motion sickness. Bioavailability after an oral dose of PMZ during space flight is thought to be impaired because of gastrointestinal disturbances associated with weightlessness and space motion sickness. In an attempt to find an alternative dosage form for use in space, we evaluated two intranasal (i.n.) dosage forms of PMZ in dogs for absorption and bioavailability relative to that of an equivalent intramuscular dose. Promethazine (5 mg kg(-1)) was administered as two intranasal dosage forms and as an intramuscular (i.m.) dose to three dogs in a randomised cross-over design. Serial blood samples were taken and analysed for PMZ concentrations and the absorption and bioavailability of PMZ were calculated for the three dosage forms. PMZ absorption from the carboxymethyl cellulose microsphere i.n. dosage form was more rapid and complete than from the myverol cubic gel formulation or from an i.m. injection. Bioavailability of the microsphere formulation was also greater than that of the gel formulation (AUC 3009 vs 1727 ng h ml(-1)). The bioavailability of the two i.n. dosage forms (relative to that of the i.m. injection) were 94% (microsphere) and 54% (gel). The i.n. microsphere formulation of PMZ offers great promise as an effective non-invasive alternative for treating space motion sickness due to its rapid absorption and bioavailability equivalent to the i.m. dose. (C) 1998 The Italian Pharmacological Society. C1 NASA, Lyndon B Johnson Space Ctr, Life Sci Res Labs, Houston, TX 77058 USA. KRUG Life Sci Inc, Houston, TX USA. SW Res Inst, San Antonio, TX USA. Univ Oklahoma, Hlth Sci Ctr, Oklahoma City, OK USA. RP Putcha, L (reprint author), NASA, Lyndon B Johnson Space Ctr, Life Sci Res Labs, Mail Code SD3, Houston, TX 77058 USA. NR 23 TC 8 Z9 9 U1 0 U2 3 PU ACADEMIC PRESS LTD PI LONDON PA 24-28 OVAL RD, LONDON NW1 7DX, ENGLAND SN 1043-6618 J9 PHARMACOL RES JI Pharmacol. Res. PD JUL PY 1998 VL 38 IS 1 BP 35 EP 39 DI 10.1006/phrs.1998.0328 PG 5 WC Pharmacology & Pharmacy SC Pharmacology & Pharmacy GA ZZ919 UT WOS:000074782600002 PM 9697152 ER PT J AU Schimmerling, W Wilson, JW Cucinotta, F Kim, MHY AF Schimmerling, W Wilson, JW Cucinotta, F Kim, MHY TI Evaluation of risk from space radiation with high-energy heavy ion beams SO PHYSICA MEDICA-EUROPEAN JOURNAL OF MEDICAL PHYSICS LA English DT Article DE space research; heavy ions; track structure; Relative Biological Effect (RBE) AB The most challenging radiation in space consists of fully ionized atomic elements with high energy for which only the few lowest energy ions can be stopped in shielding materials. The health risk from exposure to these ions and their secondary radiations generated in shield materials is poorly understood since there are few human data and a systematic study in relevant animal model systems has not been made. The accuracy of risk prediction is described as the major limiting factor in the management of space radiation risk. The expected impact of systematic studies is examined using the limited available biological data and models. Given the limitations of current predictions, models must be developed that are able to incorporate the required fundamental scientific data into accurate risk estimates. The important radiation components that can be provided for laboratory testing are identified. The use of ground-based accelerator beams to simulate space radiation is explained and quantitative scientific constraints on such facilities are derived. Three facilities, one each in the United States, in Germany and in Japan, currently have the partial capability to satisfy these constraints. A facility has been proposed using the Brookhaven National Laboratory Booster Synchrotron in the United States; in conjunction with other on-site accelerators, it will be able to provide the full range of heavy ion beams and energies required. C1 NASA, Washington, DC 20546 USA. NASA, Langley Res Ctr, Hampton, VA 23665 USA. NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. NR 18 TC 4 Z9 4 U1 0 U2 0 PU ELSEVIER SCI LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, OXON, ENGLAND SN 1120-1797 J9 PHYS MEDICA JI Phys. Medica PD JUL PY 1998 VL 14 SU 1 BP 29 EP 38 PG 10 WC Radiology, Nuclear Medicine & Medical Imaging SC Radiology, Nuclear Medicine & Medical Imaging GA 135QF UT WOS:000076813600005 PM 11542638 ER PT J AU Vega, AJ Sui, CH Lau, KM AF Vega, AJ Sui, CH Lau, KM TI Interannual to interdecadal variations of the regionalized surface climate of the United States and relationships to generalized flow parameters SO PHYSICAL GEOGRAPHY LA English DT Article DE climate change; precipitation; temperature; El Nino; southern oscillation; United States climate ID AMERICAN TELECONNECTION PATTERN; PRINCIPAL COMPONENTS; EL-NINO; PRECIPITATION; TEMPERATURE; VARIABILITY; RAINFALL; FREQUENCY; WINTER; ANTICYCLONES AB This analysis attempts to discern primary causes of interannual and interdecadal climate variations for precipitation and temperature regions of the conterminous United States. Varimax rotated principal components analysis of annual climate division data is used in the derivation of nine precipitation and five temperature regions. Each region's time series is examined for underlying linear trends, representing long-term climate change, and tests for variance changes, to determine regional climate variability shifts. The first six precipitation components, representing the entire eastern half of the country and the Northwest, displayed significant temporal increases. Of these, four displayed significant increases in interannual variability through time. For temperature, only the Southwestern region showed a significant change (increase) through time. However, significant reductions in temperature variability were confirmed for three regions. To determine the causes of the derived climate shifts, correlation analysis was performed with various atmospheric teleconnection indices. Precipitation trends are most strongly associated with variations in the Southern Oscillation Index (SOI) at the interannual time scale while interdecadal variations are associated more with variations in the Pacific/North American (PNA) teleconnection. Both interannual and interdecadal variations of regional temperature are most strongly related to the PNA, except for the Southwest, which showed a significant correlation to the SOI. This suggests that El Nino/Southern Oscillation (ENSO) events are the source for much of the precipitation change evident in the eastern and Northwestern United States and temperature change in the Southwest. C1 Clarion Univ Pennsylvania, Dept Anthropol Geog & Earth Sci, Clarion, PA 16214 USA. NASA, Goddard Space Flight Ctr, Atmospheres Lab, Greenbelt, MD 20771 USA. RP Vega, AJ (reprint author), Clarion Univ Pennsylvania, Dept Anthropol Geog & Earth Sci, Clarion, PA 16214 USA. EM avega@clarion.edu RI Lau, William /E-1510-2012; OI Lau, William /0000-0002-3587-3691; SUI, CHUNG-HSIUNG/0000-0003-2842-5660 NR 51 TC 15 Z9 15 U1 0 U2 1 PU TAYLOR & FRANCIS LTD PI ABINGDON PA 4 PARK SQUARE, MILTON PARK, ABINGDON OX14 4RN, OXON, ENGLAND SN 0272-3646 EI 1930-0557 J9 PHYS GEOGR JI Phys. Geogr. PD JUL-AUG PY 1998 VL 19 IS 4 BP 271 EP 291 PG 21 WC Environmental Sciences; Geography, Physical; Geosciences, Multidisciplinary; Meteorology & Atmospheric Sciences SC Environmental Sciences & Ecology; Physical Geography; Geology; Meteorology & Atmospheric Sciences GA 165DC UT WOS:000078503300001 ER PT J AU Ortiz, RM Worthy, GAJ MacKenzie, DS AF Ortiz, RM Worthy, GAJ MacKenzie, DS TI Osmoregulation in wild and captive west Indian manatees (Trichechus manatus) SO PHYSIOLOGICAL ZOOLOGY LA English DT Article ID PLASMA VASOPRESSIN LEVELS; WATER; ALDOSTERONE; ANATOMY; BALANCE; STRESS; DOG AB The ability of West Indian manatees (Trichechus manatus latirostris and Trichechus manatus manatus) to inhabit both freshwater and marine habitats presents an interesting model to study osmoregulation in sirenians. Blood samples were analyzed from manatees held in fresh- and saltwater and from wild animals captured in fresh-, brackish, and saltwater for concentrations of aldosterone, arginine vasopressin, plasma renin activity, Na+, K+, Cl-, and osmolality. Two separate experiments were also conducted on captive animals to evaluate osmoregulatory responses to acute saltwater exposure and freshwater deprivation. Spurious differences were observed in plasma electrolyte and osmolality among the captive and wild groups. Wild brackish water animals exhibited the highest vasopressin concentrations, while wild freshwater manatees had the highest aldosterone levels. A significant correlation between mean vasopressin and osmolality was demonstrated for captive and wild animals. When freshwater animals were acutely exposed to saltwater, osmolality, Na+, and Cl- increased 5.5%, 8.0%, and 14%, respectively, while aldosterone decreased 82.6%. Saltwater animals deprived of freshwater exhibited an almost twofold increase in aldosterone during the deprivation period and a fourfold decrease when freshwater was again provided. Within this group, osmolality increased significantly by 3.4% over the course of the study; however, electrolytes did not change. The lack of consistent differences in electrolyte and osmolality among wild and captive groups suggests that manatees are good osmoregulators regardless of the environment. The high aldosterone levels in wild freshwater animals may indicate a need to conserve Na+, while the high vasopressin levels in wild brackish-water manatees suggest an antidiuretic state to conserve water. Vasopressin levels appear to be osmotically mediated in manatees as in other mammals. C1 Texas A&M Univ, Dept Marine Biol, Physiol Ecol & Bioenerget Lab, Galveston, TX 77551 USA. Texas A&M Univ, Dept Biol, College Stn, TX 77843 USA. RP Ortiz, RM (reprint author), NASA, Ames Res Ctr, MS 239-11, Moffett Field, CA 94035 USA. NR 35 TC 24 Z9 30 U1 1 U2 12 PU UNIV CHICAGO PRESS PI CHICAGO PA 5801 S ELLIS AVENUE, CHICAGO, IL 60637 USA SN 0031-935X J9 PHYSIOL ZOOL JI Physiol. Zool. PD JUL-AUG PY 1998 VL 71 IS 4 BP 449 EP 457 DI 10.1086/515427 PG 9 WC Physiology; Zoology SC Physiology; Zoology GA ZY266 UT WOS:000074602900011 PM 9678505 ER PT J AU Pohorille, A AF Pohorille, A TI Transient cavities in liquids and the nature of the hydrophobic effect SO POLISH JOURNAL OF CHEMISTRY LA English DT Article DE hydrophobic effect; transient cavities; water; hydrocarbon ID DILUTE AQUEOUS-SOLUTION; MONTE-CARLO; COMPUTER-SIMULATIONS; MOLECULAR-DYNAMICS; FREE-ENERGY; WATER; HYDRATION; ENTROPY; THERMODYNAMICS; DEPENDENCE AB The size distributions of transient cavities in water and organic liquids, obtained ii om computer simulations, have provided a new means to analyze the nature of the hydrophobic effect and to evaluate the adequacy of different analytical models of this effect. The poor solubility of non-polar solutes in water is attributed to a low probability of finding in water cavities of atomic and molecular size. It has been shown that water applies more force per unit area of cavity surface than do hydrocarbon liquids. Models that successfully capture the main characteristics of the hydrophobic effect must at least include information about the density and the radial distribution of oxygen atoms in liquid water. One such model, quantitatively accurate for molecular solutes of arbitrary shape, is presented. C1 NASA, Exobiol Branch, Ames Res Ctr, Moffett Field, CA 94035 USA. Univ Calif San Francisco, Dept Pharmaceut Chem, San Francisco, CA 94143 USA. RP Pohorille, A (reprint author), NASA, Exobiol Branch, Ames Res Ctr, MS 239-4, Moffett Field, CA 94035 USA. NR 42 TC 7 Z9 7 U1 1 U2 2 PU POLISH CHEMICAL SOCIETY PI WARSAW PA C/O POLISH ACAD SCIENCES, INST PHYSICAL CHEMISTRY, UL KASPRZAKA 44/52, 01-224 WARSAW, POLAND SN 0137-5083 J9 POL J CHEM JI Pol. J. Chem. PD JUL PY 1998 VL 72 IS 7 SU S BP 1680 EP 1690 PG 11 WC Chemistry, Multidisciplinary SC Chemistry GA 119NL UT WOS:000075902500039 PM 11542255 ER PT J AU Imbriale, WA AF Imbriale, WA TI Introduction to "Electrical Disturbances Apparently of Extraterrestrial Origin" SO PROCEEDINGS OF THE IEEE LA English DT Editorial Material C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Imbriale, WA (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 3 TC 0 Z9 0 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 0018-9219 J9 P IEEE JI Proc. IEEE PD JUL PY 1998 VL 86 IS 7 BP 1507 EP 1509 DI 10.1109/JPROC.1998.681377 PG 3 WC Engineering, Electrical & Electronic SC Engineering GA ZU502 UT WOS:000074204500015 ER PT J AU Kind, RJ Potapczuk, MG Feo, A Golia, C Shah, AD AF Kind, RJ Potapczuk, MG Feo, A Golia, C Shah, AD TI Experimental and computational simulation of in-flight icing phenomena SO PROGRESS IN AEROSPACE SCIENCES LA English DT Review ID HEAT-TRANSFER; ICE ACCRETION; SURFACE-ROUGHNESS; CIRCULAR-CYLINDER; REYNOLDS-NUMBER; CROSS-FLOW AB This paper reviews experimental and computational methods used for simulation of ice accretion on aircraft flying through icing conditions. Such methods were recently reviewed by the AGARD FDP Working Group 20 and the present paper represents a revised and updated version of parts of the Working Group report. To provide essential background, it begins with a brief physical description of the ice accretion process. Experimental simulations must respect certain similarity requirements or scaling laws if they are to be valid; these requirements are discussed in some detail and in the framework of this discussion, physical phenomena are considered in more detail as well. Techniques and ground-based facilities for experimental simulation of ice-accretion phenomena are then reviewed, followed by a review of techniques and facilities used for flight testing in support of aircraft design and certification for flight in icing conditions. Available instruments for required measurements such as droplet size distribution and liquid water content and for in-flight ice detection are briefly described. Computational simulation is becoming increasingly important in aircraft icing work; computational methods are used to simulate ice accretion both with and without ice-protection systems in operation, Computational approaches are outlined and current capabilities are evaluated. Conclusions emerging from the review include the following: rime icing is reasonably well understood and can be adequately simulated for most practical purposes using either experimental or computational methods; some of the physical phenomena known to be important in glaze icing are only poorly understood and there is considerable uncertainty regarding whether or not certain other phenomena are important; consequently, much additional research is required before reduced-scale experimental simulations or computational simulations of glaze icing will be sufficiently accurate and reliable for most practical purposes. Research recommendations are put forward. (C) 1998 Published by Elsevier Science Ltd. All rights reserved. C1 Carleton Univ, Dept Mech & Aerosp Engn, Ottawa, ON K1S 5B6, Canada. NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. INTA, Cent Aerodynam Lab, E-28850 Madrid, Spain. CIRA, I-81043 Capua, CE, Italy. Boeing Commercial Airplane Co, Renton, WA 98055 USA. RP Kind, RJ (reprint author), Carleton Univ, Dept Mech & Aerosp Engn, 31 35 Mackenzie Bldg,1125 Colonel Bt Dr, Ottawa, ON K1S 5B6, Canada. NR 157 TC 38 Z9 46 U1 1 U2 5 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0376-0421 J9 PROG AEROSP SCI JI Prog. Aeosp. Sci. PD JUL-AUG PY 1998 VL 34 IS 5-6 BP 257 EP 345 DI 10.1016/S0376-0421(98)80001-8 PG 89 WC Engineering, Aerospace SC Engineering GA 135XF UT WOS:000076827500001 ER PT J AU Newman, JC AF Newman, JC TI Th emerging of fatigue and fracture mechanics concepts: a historical perspective SO PROGRESS IN AEROSPACE SCIENCES LA English DT Article ID ELASTIC-PLASTIC ANALYSIS; FINITE-ELEMENT ANALYSIS; CRACK-TIP FIELDS; PATH-INDEPENDENT INTEGRALS; ALUMINUM-ALLOYS; TRIAXIALITY PARAMETER; SPECIMEN GEOMETRY; CLOSURE; GROWTH; PROPAGATION AB In this review, some of the technical developments that have occurred during the past 40 years are presented which have led to the merger of fatigue and fracture mechanics concepts. This review is made from the viewpoint of "crack propagation". As methods to observe the "fatigue" process have improved, the formation of fatigue micro-cracks have been observed earlier in life and the measured crack sizes have become smaller. These observations suggest that fatigue damage can now be characterized by "crack size". In parallel, the crack-growth analysis methods, using stress-intensity factors, have also improved. But the effects of material inhomogeneities, crack-fracture mechanisms, and nonlinear behavior must now be included in these analyses. The discovery of crack-closure mechanisms, such as plasticity, roughness, and oxide/corrosion/fretting product debris, and the use of the effective stress-intensity factor range, has provided an engineering tool to predict small- and large-crack-growth rate behavior under service loading conditions. These mechanisms have also provided a rationale for developing new, damage-tolerant materials. This review suggests that small-crack growth behavior should be viewed as typical behavior, whereas large-crack threshold behavior should be viewed as the anomaly. Small-crack theory has unified "fatigue" and "fracture mechanics" concepts; and has bridged the gap between safe-life and durability/damage-tolerance design concepts. (C) 1998 Elsevier Science Ltd. All rights reserved. C1 NASA, Mat & Mech Branch, Langley Res Ctr, Hampton, VA 23665 USA. RP Newman, JC (reprint author), NASA, Mat & Mech Branch, Langley Res Ctr, Hampton, VA 23665 USA. EM j.c.newman.jr@larc.nasa.gov NR 188 TC 61 Z9 65 U1 1 U2 11 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0376-0421 J9 PROG AEROSP SCI JI Prog. Aeosp. Sci. PD JUL-AUG PY 1998 VL 34 IS 5-6 BP 347 EP 390 DI 10.1016/S0376-0421(98)00006-2 PG 44 WC Engineering, Aerospace SC Engineering GA 135XF UT WOS:000076827500002 ER PT J AU Thrower, F Martin, R Heintz, R AF Thrower, F Martin, R Heintz, R TI Survival and growth of two stocks of presmolt Chinook salmon held overwinter in marine net-pens with an artificial freshwater lens SO PROGRESSIVE FISH-CULTURIST LA English DT Article ID ONCORHYNCHUS-KISUTCH; SMOLTIFICATION; SEAWATER AB Two hatchery stocks of juvenile spring chinook salmon Oncorhynchus tshawytscha originating from two southeast Alaska rivers were reared in freshwater to an average size of 8-10 g and placed in marine net-pens with an artificial freshwater lens system (AFLS) at four entry times from mid-September to early November 1987. Overwinter survival to May 1988 averaged 83.6% for Unuk River stock and 76.0% for Chickamin River stock and did not differ significantly in the AFLS among the four entry dates. Survival over 24 h differed significantly when entry was directly into 30 parts per thousand seawater. The 24-h plasma sodium levels in the juveniles challenged to either full-strength seawater or marine net-pens with an AFLS were not useful predictors of overwinter survival. Over winter, both stocks grew significantly better in the AFLS than in freshwater. The AFLS appears to be a cost-effective means of substantially increasing smelt production while minimizing freshwater use. C1 Natl Marine Fisheries Serv, Natl Ocean & Atmospher Adm, Alaska Fisheries Sci Ctr, Auke Bay Lab, Juneau, AK 99801 USA. RP Thrower, F (reprint author), Natl Marine Fisheries Serv, Natl Ocean & Atmospher Adm, Alaska Fisheries Sci Ctr, Auke Bay Lab, 11305 Glacier Highway, Juneau, AK 99801 USA. NR 11 TC 3 Z9 3 U1 0 U2 1 PU AMER FISHERIES SOC PI BETHESDA PA 5410 GROSVENOR LANE SUITE 110, BETHESDA, MD 20814-2199 USA SN 0033-0779 J9 PROG FISH CULT JI Progress. Fish-Cult. PD JUL PY 1998 VL 60 IS 3 BP 200 EP 205 DI 10.1577/1548-8640(1998)060<0200:SAGOTS>2.0.CO;2 PG 6 WC Fisheries SC Fisheries GA 101YN UT WOS:000074896200005 ER PT J AU Schinka, JA Francis, E Hughes, P LaLone, L Flynn, C AF Schinka, JA Francis, E Hughes, P LaLone, L Flynn, C TI Comparative outcomes and costs of inpatient care and supportive housing for substance-dependent veterans SO PSYCHIATRIC SERVICES LA English DT Article ID ALCOHOL; RATES AB Objective: This study examined the differential effectiveness and costs of three weeks of treatment for patients with moderately severe substance dependence assigned to inpatient treatment or to a supportive housing setting. Supportive housing is temporary housing that allows a patient to participate in an intensive hospital-based treatment program. Type and intensity of treatment were generally equivalent for the two groups. Methods: Patients were consecutive voluntary admissions to the substance abuse treatment program of a large metropolitan Veterans Affairs medical center, Patients with serious medical conditions or highly unstable psychiatric disorders were excluded. Patients in supportive housing attended the inpatient program on weekdays from 7:30 a.m. to 5 p.m. They were assessed at baseline and at two-month follow-up. Results: Baseline analyses of clinical, personality, and demographic characteristics revealed no substantive differences between the 62 patients assigned to inpatient treatment and the 36 assigned to supportive housing. The degree of treatment involvement and dropout rates did not differ between groups. Of the 55 inpatients completing treatment, 29 were known to be abstinent at follow-up, and of the 35 supportive housing patients completing treatment, 22 were abstinent, The proportion was similar for both groups, about 70 percent. The cost of a successful treatment for the inpatient group was $9,524. For the supportive housing group, it was $4,291, Conclusions: Given the absence of differential treatment effects between inpatient and supportive housing settings, the use of supportive housing alternatives appears to provide an opportunity for substantial cost savings for VA patients with substance dependence disorders. C1 James A Haley Vet Adm Med Ctr, Psychol Serv 116B, Tampa, FL 33612 USA. NASA, Houston, TX USA. Univ S Florida, Dept Psychiat, Tampa, FL 33620 USA. Univ S Florida, Dept Psychol, Tampa, FL 33620 USA. RP Schinka, JA (reprint author), James A Haley Vet Adm Med Ctr, Psychol Serv 116B, 13000 Bruce B Downs Blvd, Tampa, FL 33612 USA. NR 18 TC 19 Z9 19 U1 0 U2 1 PU AMER PSYCHIATRIC ASSOCIATION PI WASHINGTON PA 1400 K ST NW, WASHINGTON, DC 20005 USA SN 1075-2730 J9 PSYCHIATR SERV JI Psychiatr. Serv. PD JUL PY 1998 VL 49 IS 7 BP 946 EP 950 PG 5 WC Health Policy & Services; Public, Environmental & Occupational Health; Psychiatry SC Health Care Sciences & Services; Public, Environmental & Occupational Health; Psychiatry GA ZX936 UT WOS:000074570300012 PM 9661231 ER PT J AU Corwin, HG Pesenson, I Schmitz, M Kim, DC Bennett, J Madore, BF Mazzarella, JM Helou, G AF Corwin, HG Pesenson, I Schmitz, M Kim, DC Bennett, J Madore, BF Mazzarella, JM Helou, G TI Accurate positions for MCG galaxies SO PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF THE PACIFIC LA English DT Article AB We have measured accurate celestial coordinates for 4741 extragalactic objects, primarily drawn from a list of MCG galaxies with no recently published accurate positions. The standard deviations in the new positions depend slightly on the measurement method but are on the order of 1."0 to 1."2. Standard deviations in the original MCG positions are confirmed to be at the 1.'5-2.'0 level. These new positions were integrated into NED in 1997 December. C1 CALTECH, Jet Prop Lab, Infred Proc & Anal Ctr, Pasadena, CA 91125 USA. RP Corwin, HG (reprint author), CALTECH, Jet Prop Lab, Infred Proc & Anal Ctr, M-S 100-22, Pasadena, CA 91125 USA. NR 18 TC 3 Z9 3 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 JUL PY 1998 VL 110 IS 749 BP 779 EP 783 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZZ513 UT WOS:000074736900002 ER PT J AU Joiner, J Da Silva, AM AF Joiner, J Da Silva, AM TI Efficient methods to assimilate remotely sensed data based on information content SO QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY LA English DT Article DE data assimilation; retrieval techniques; satellite data ID TEMPERATURE; RETRIEVAL; INVERSION; DENSITY AB Two basic approaches have evolved to utilize measurements of radiance (i.e. thermal or scattered solar radiation) by satellite-borne instruments in data assimilation systems: radiances (raw or cloud-corrected) may be assimilated directly, or they may be pre-processed to retrieve geophysical parameters for subsequent assimilation. The retrieval process is often ill-posed, and therefore requires the use of prior information to constrain the solution. For example, temperature and humidity profiles retrieved using radiances from nadir-viewing infrared and microwave sounders often incorporate prior information in the form of climatology or forecasts. The use of prior information presents difficulties when assimilating retrievals. Here we present methods to remove prior information from retrievals in order to achieve a more consistent assimilation of the data. In addition, these methods can be used as a data compression device, which can reduce the amount of computation required by some analysis systems compared with radiance assimilation. The methods are implemented and compared in a one-dimensional assimilation system using simulated data from current and future infrared-temperature profiling instruments. C1 NASA, Goddard Space Flight Ctr, Data Assimilat Off, Greenbelt, MD 20771 USA. RP Joiner, J (reprint author), NASA, Goddard Space Flight Ctr, Data Assimilat Off, Code 910-3, Greenbelt, MD 20771 USA. EM joiner@hera.gsfc.nasa.gov RI da Silva, Arlindo/D-6301-2012; Joiner, Joanna/D-6264-2012 OI da Silva, Arlindo/0000-0002-3381-4030; NR 50 TC 31 Z9 33 U1 1 U2 2 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 JUL PY 1998 VL 124 IS 549 BP 1669 EP 1694 DI 10.1256/smsqj.54914 PN A PG 26 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 108QD UT WOS:000075276200014 ER PT J AU Christian, HJ Latham, J AF Christian, HJ Latham, J TI Satellite measurements of global lightning SO QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY LA English DT Article DE lightning; radiance; satellite measurements ID PRECIPITATION AB The satellite-borne NASA/MSFC Optical Transient Detector provides global distributions of lightning and lightning-stroke radiance. Measurements made during the first year of its operation show that Lightning activity is particularly pronounced over the tropics, much greater over land than over the oceans, and exhibits great seasonal variability. The values of lightning-stroke radiance tend to be greater over the oceans, less when lightning activity is high, and greater in the northern hemisphere winter than summer. C1 NASA, Washington, DC 20546 USA. RP Latham, J (reprint author), Natl Ctr Atmospher Res, MMM Div, Pob 3000, Boulder, CO 80307 USA. NR 11 TC 37 Z9 40 U1 0 U2 5 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 JUL PY 1998 VL 124 IS 549 BP 1771 EP 1773 DI 10.1256/smsqj.54918 PN A PG 3 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 108QD UT WOS:000075276200018 ER PT J AU Broecker, WS Peteet, D Hajdas, I Lin, J Clark, E AF Broecker, WS Peteet, D Hajdas, I Lin, J Clark, E TI Antiphasing between rainfall in Africa's rift valley and north America's great basin SO QUATERNARY RESEARCH LA English DT Article DE Africa; Great Basin; paleoclimate; Lake Victoria; Lake Lahontan; (14)Cages; abrupt climate change ID SOUTHEASTERN NEW-YORK; YOUNGER DRYAS EVENT; LATE PLEISTOCENE; LAHONTAN BASIN; LAST DEGLACIATION; HUDSON HIGHLANDS; NORTHEASTERN USA; GLACIAL EVENTS; LAKE VICTORIA; C-14 AGES AB The beginning of the Bolling-Allerod warm period was marked in Greenland ice by an abrupt rise in delta(18)O, an abrupt drop in dust rain, and an abrupt increase in atmospheric methane content. The surface waters in the Norwegian Sea underwent a simultaneous abrupt warming. At about this time, a major change in the pattern of global rainfall occurred. Lake Victoria (latitude 0 degrees), which prior to this time was dry, was rejuvenated. The Red Sea, which prior to this time was hypersaline, freshened. Lake Lahontan, which prior to this time had achieved its largest size, desiccated. Whereas the chronologic support for the abruptness of the hydrologic changes is firm only for the Red Sea, in keeping with evidence obtained well away from the northern Atlantic in the Santa Barbara Basin and the Cariaco Trench, the onset and end of the millennial-duration climate events were globally abrupt. If so, the proposed Linkage between the size of African closed basin lakes and insolation cycles must be reexamined. (C) 1998 University of Washington. C1 Lamont Doherty Earth Observ, Palisades, NY 10964 USA. NASA, Goddard Inst Space Studies, New York, NY 10025 USA. Lamont Doherty Earth Observ, Palisades, NY 10964 USA. RP Broecker, WS (reprint author), Lamont Doherty Earth Observ, Palisades, NY 10964 USA. RI Hajdas, Irka/C-6696-2011 NR 56 TC 29 Z9 29 U1 1 U2 3 PU ACADEMIC PRESS INC PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA SN 0033-5894 J9 QUATERNARY RES JI Quat. Res. PD JUL PY 1998 VL 50 IS 1 BP 12 EP 20 DI 10.1006/qres.1998.1973 PG 9 WC Geography, Physical; Geosciences, Multidisciplinary SC Physical Geography; Geology GA 110HM UT WOS:000075375400002 ER PT J AU Cucinotta, FA Nikjoo, H Goodhead, DT AF Cucinotta, FA Nikjoo, H Goodhead, DT TI The effects of delta rays on the number of particle-track traversals per cell in laboratory and space exposures SO RADIATION RESEARCH LA English DT Article ID ULTRASOFT X-RAYS; RADIATION ACTION; MAMMARY-GLAND; COSMIC-RAYS; IRRADIATION; MICROBEAM AB It is a common practice to estimate the number of particle-track traversals per cell or cell nucleus as the product of the ion's linear energy transfer (LET) and cell area. This practice ignores the effects of track width due to the lateral extension of delta rays. We make estimates of the number of particle-track traversals per cell, which includes the effects of delta rays using radial cutoffs in the ionization density about an ion's track of 1 mGy and 1 cGy. Calculations for laboratory and space radiation exposures are discussed, and show that the LET approximation provides a large underestimate of the actual number of particle track traversals per cell from high-charge and energy (HZE) ions. In light of the current interest in the mechanisms of radiation action, including signal transduction and cytoplasmic damage, these results should be of interest for radiobiology studies with HZE ions. (C) 1998 by Radiation Research Society. C1 NASA, Lyndon B Johnson Space Ctr, Houston, TX 77508 USA. MRC, Radiat & Genome Stabil Unit, Didcot OX11 0RD, Oxon, England. RP Cucinotta, FA (reprint author), NASA, Lyndon B Johnson Space Ctr, SN 31, Houston, TX 77508 USA. NR 27 TC 79 Z9 81 U1 0 U2 2 PU RADIATION RESEARCH SOC PI LAWRENCE PA 810 E TENTH STREET, LAWRENCE, KS 66044 USA SN 0033-7587 J9 RADIAT RES JI Radiat. Res. PD JUL PY 1998 VL 150 IS 1 BP 115 EP 119 DI 10.2307/3579651 PG 5 WC Biology; Biophysics; Radiology, Nuclear Medicine & Medical Imaging SC Life Sciences & Biomedicine - Other Topics; Biophysics; Radiology, Nuclear Medicine & Medical Imaging GA ZV652 UT WOS:000074327300015 PM 9650608 ER PT J AU Kimes, DS Nelson, RF Skole, DL Salas, WA AF Kimes, DS Nelson, RF Skole, DL Salas, WA TI Accuracies in mapping secondary tropical forest age from sequential satellite imagery SO REMOTE SENSING OF ENVIRONMENT LA English DT Article ID ABANDONED PASTURES; EASTERN AMAZONIA; LAND-USE; DEFORESTATION; VEGETATION; PATTERNS; STOCKS; BRAZIL AB Multitemporal satellite images have been used to differentiate, measure the areal extent of, and determine transitional probabilities among different secondary forest age classes in the tropics. In these studies, temporal gaps in the satellite archive are common doe to difficulties associated with availability of cloud-free data, costs, temporal discontinuities between satellite sensors, etc. In this probability study, examples of multitemporal image sequences with data gaps are considered in order to illustrate error rates associated with estimating the age of secondary tropical forest. Results indicate that on the order of 8-32% of scene pixels may be misclassified with respect to age of land cover transitions which occur within the data gap(s) are ignored. Using secondary forest regeneration rates from the literature, calculations showed that these gap errors caused the above-ground biomass to be over-estimated by 8-23%. the error rates are scene-dependent. The results are presented to flag a potentially significant source of error. (C) Elsevier Science Inc., 1998. C1 NASA, Goddard Space Flight Ctr, Biospher Sci Branch, Greenbelt, MD 20771 USA. Michigan State Univ, Dept Geog, E Lansing, MI 48824 USA. Univ New Hampshire, Complex Syst Res Ctr, Durham, NH 03824 USA. RP Kimes, DS (reprint author), NASA, Goddard Space Flight Ctr, Biospher Sci Branch, Code 923, Greenbelt, MD 20771 USA. RI Nelson, Ross/H-8266-2014 NR 22 TC 32 Z9 33 U1 0 U2 8 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 JUL PY 1998 VL 65 IS 1 BP 112 EP 120 DI 10.1016/S0034-4257(98)00021-2 PG 9 WC Environmental Sciences; Remote Sensing; Imaging Science & Photographic Technology SC Environmental Sciences & Ecology; Remote Sensing; Imaging Science & Photographic Technology GA ZU069 UT WOS:000074158100009 ER PT J AU Balla, RJ Hart, RC AF Balla, RJ Hart, RC TI Spectral brightness and other improvements to the tunable ArF excimer laser SO REVIEW OF SCIENTIFIC INSTRUMENTS LA English DT Article AB We present two oscillator designs and a new amplification design which improves many characteristics of the dual-discharge tube tunable ArF excimer laser. We demonstrate bandwidths from 0.17-11.0 cm(-1) (5-330 GHz) can be selected by appropriate choice of oscillator slit width and diffraction-grating dispersion. Amplification is achieved using three consecutive passes through the discharge tubes. This amplifier design decreases divergence (9 x diffraction limit) and increases output energy (33%), locking efficiency (20%), range of tunability (40%), and spectral brightness (two orders-of-magnitude) when compared to the standard unstable-resonator amplifier. [S0034-6748(98)02207-2] C1 NASA, Langley Res Ctr, Hampton, VA 23681 USA. RP Balla, RJ (reprint author), NASA, Langley Res Ctr, MS 493, Hampton, VA 23681 USA. NR 7 TC 5 Z9 5 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 JUL PY 1998 VL 69 IS 7 BP 2591 EP 2594 DI 10.1063/1.1148985 PG 4 WC Instruments & Instrumentation; Physics, Applied SC Instruments & Instrumentation; Physics GA 108RL UT WOS:000075279200001 ER PT J AU Barzilai, A VanZandt, T Kenny, T AF Barzilai, A VanZandt, T Kenny, T TI Technique for measurement of the noise of a sensor in the presence of large background signals SO REVIEW OF SCIENTIFIC INSTRUMENTS LA English DT Article AB This work reports on a method to measure the instrumental noise of a sensor in the presence of large background signals, based on measuring the coherence and output of two identical sensors exposed to the same input stimulus. The technique can be applied to any sensor characterization problem where there is interest in distinguishing random noise from common-mode noise. The method is demonstrated using geophones, a single-axis seismometer that has been an important sensor for geophysical measurements for decades. Previous experimental work has not published measurements of the geophone's instrumental noise at frequencies near the,geophone's resonance because of the presence of large background seismic signals compared to the predicted instrumental noise, which is a minimum at the geophone's resonant frequency. With this coherence technique, measurements performed in the presence of 1 mu g/root Hz seismic signals showed that the minimum instrumental noise was within a factor of 2 of the predicted minimum noise of 0.6 ng/root Hz. (C) 1998 American Institute of Physics. [S0034-6748(98)02305-3]. C1 Stanford Univ, Dept Mech Engn, Stanford, CA 94305 USA. CALTECH, Jet Prop Lab, Ctr Space Microelect Technol, Pasadena, CA 91109 USA. RP Barzilai, A (reprint author), Stanford Univ, Dept Mech Engn, Stanford, CA 94305 USA. NR 9 TC 12 Z9 13 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 JUL PY 1998 VL 69 IS 7 BP 2767 EP 2772 DI 10.1063/1.1149013 PG 6 WC Instruments & Instrumentation; Physics, Applied SC Instruments & Instrumentation; Physics GA 108RL UT WOS:000075279200030 ER PT J AU Peele, A Zhang, W AF Peele, A Zhang, W TI Lobster-eye all-sky monitors: A comparison of one- and two-dimensional designs SO REVIEW OF SCIENTIFIC INSTRUMENTS LA English DT Article ID ARRAYS AB X-ray all-sky monitors (ASMs) have played a vital role in the development of x-ray astronomy. In order for them to continue to do so ASMs with high sensitivity, broad energy band coverage, and large sky coverage will be required. The best way to achieve these goals is for the next generation of ASMs to have focusing capability. Lobster-eye optics offer a way to construct a focusing ASM and a design is presented for a lobster-eye ASM that offers an order of magnitude increase in sensitivity over previous nonfocusing instruments. Simpler versions of the lobster-eye telescope, based on arrays of flat reflectors in one dimension only, have also been suggested in the past. In this article we compare the one: and two-dimensional (lobster-eye) configurations and conclude that, for intense short-lived phenomena, where the background is negligible, the one-dimensional configuration is optimal, whereas for ultimate sensitivity of background-limited faint sources the two-dimensional configuration is preferred. (C) 1998 American institute of Physics. [S0034-6748(98)01807-3]. C1 NASA, NRC, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Peele, A (reprint author), NASA, NRC, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. NR 9 TC 7 Z9 8 U1 0 U2 1 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 JUL PY 1998 VL 69 IS 7 BP 2785 EP 2793 DI 10.1063/1.1149017 PG 9 WC Instruments & Instrumentation; Physics, Applied SC Instruments & Instrumentation; Physics GA 108RL UT WOS:000075279200034 ER PT J AU Golombek, MP AF Golombek, MP TI The Mars Pathfinder mission SO SCIENTIFIC AMERICAN LA English DT Article C1 CALTECH, Jet Prop Lab, Pathfinder Project Sci Grp, Pasadena, CA 91109 USA. CALTECH, Jet Prop Lab, Experiment Operat Team, Pasadena, CA USA. RP Golombek, MP (reprint author), CALTECH, Jet Prop Lab, Pathfinder Project Sci Grp, Pasadena, CA 91109 USA. NR 4 TC 3 Z9 3 U1 0 U2 3 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 JUL PY 1998 VL 279 IS 1 BP 40 EP 49 PG 10 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA ZW260 UT WOS:000074391600026 ER PT J AU Guattery, S Miller, GL AF Guattery, S Miller, GL TI On the quality of spectral separators SO SIAM JOURNAL ON MATRIX ANALYSIS AND APPLICATIONS LA English DT Article; Proceedings Paper CT 6th Annual ACM-SIAM Symposium on Discrete algorithms (SODA 95) CY 1995 CL SIAM, PHILADELPHIA, PA SP ACM, SIAM HO SIAM DE graph partitioning; spectral partitioning; graph eigenvalues and eigenvectors ID GRAPHS; SUPERCONCENTRATORS; EIGENVECTORS; EXPANDERS; MATRICES AB Computing graph separators is an important step in many graph algorithms. A popular technique for finding separators involves spectral methods. However, there has not been much prior analysis of the quality of the separators produced by this technique; instead it is usually claimed that spectral methods "work well in practice." We present an initial attempt at such an analysis. In particular, we consider two popular spectral separator algorithms and provide counterexamples showing that these algorithms perform poorly on certain graphs. We also consider a generalized definition of spectral methods that allows the use of some specified number of the eigenvectors corresponding to the smallest eigenvalues of the Laplacian matrix of a graph, and we show that if such algorithms use a constant number of eigenvectors, then there are graphs for which they do no better than using only the second smallest eigenvector. Furthermore, using the second smallest eigenvector of these graphs produces partitions that are poor with respect to bounds on the gap between the isoperimetric number and the cut quotient of the spectral separator. Even if a generalized spectral algorithm uses n(epsilon) for 0 < epsilon < 1/4 eigenvectors, there exist graphs for which the algorithm fails to find a separator with a cut quotient within n(1/4-epsilon)-1 of the isoperimetric number. We also introduce some facts about the structure of eigenvectors of certain types of Laplacian and symmetric matrices; these facts provide the basis for the analysis of the counterexamples. Finally, we discuss some developments in spectral partitioning that have occurred since these results first appeared. C1 NASA, ICASE, Langley Res Ctr, Hampton, VA 23681 USA. Carnegie Mellon Univ, Sch Comp Sci, Pittsburgh, PA 15213 USA. RP NASA, ICASE, Langley Res Ctr, Mail Stop 403, Hampton, VA 23681 USA. EM smg@icase.edu; glmiller@cs.cmu.edu NR 29 TC 46 Z9 46 U1 1 U2 1 PU SIAM PUBLICATIONS PI PHILADELPHIA PA 3600 UNIV CITY SCIENCE CENTER, PHILADELPHIA, PA 19104-2688 USA SN 0895-4798 EI 1095-7162 J9 SIAM J MATRIX ANAL A JI SIAM J. Matrix Anal. Appl. PD JUL PY 1998 VL 19 IS 3 BP 701 EP 719 DI 10.1137/S0895479896312262 PG 19 WC Mathematics, Applied SC Mathematics GA ZC450 UT WOS:000072580600007 ER PT J AU Ruzmaikin, A AF Ruzmaikin, A TI Clustering of emerging magnetic flux SO SOLAR PHYSICS LA English DT Article ID SOLAR CONVECTION ZONE; ACTIVE REGIONS; DYNAMO; TUBES; PATTERNS; SUNSPOTS AB Observations show that newly emerging flux tends to appear on the solar surface at sites where there is flux already; this results in clustering of solar activity. Standard dynamo theories do not predict this effect, and the mean field estimated by the theories is too weak to emerge at the surface of the Sun at all. Here a solution of the problem is suggested that involves strong fluctuating fields generated by the dynamo. The magnetic field emerges at the solar surface when the total field (the mean field plus fluctuations) exceeds the threshold for buoyancy. A slowly changing enhancement of the mean field provides a long-living basis ('hump') for emergence of fluctuating fields. The enhancements are gradually destroyed by the solar differential rotation, the stretching time scale of which defines the lifetime of clusters of activity. A simple 2-dimensional model explaining the appearance of persistent clusters of emerging Aux is presented. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Ruzmaikin, A (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 31 TC 30 Z9 30 U1 0 U2 0 PU SPRINGER PI DORDRECHT PA VAN GODEWIJCKSTRAAT 30, 3311 GZ DORDRECHT, NETHERLANDS SN 0038-0938 J9 SOL PHYS JI Sol. Phys. PD JUL PY 1998 VL 181 IS 1 BP 1 EP 12 DI 10.1023/A:1016563632058 PG 12 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 113KL UT WOS:000075550100001 ER PT J AU Dryer, M Andrews, MD Aurass, H Deforest, C Galvin, AB Garcia, H Ipavich, FM Karlicky, M Kiplinger, A Klassen, A Meisner, R Paswaters, SE Smith, Z Tappin, SJ Thompson, BJ Watari, SI Michels, DJ Brueckner, GE Howard, RA Koomen, MJ Lamy, P Mann, G Arzner, K Schwenn, R AF Dryer, M Andrews, MD Aurass, H Deforest, C Galvin, AB Garcia, H Ipavich, FM Karlicky, M Kiplinger, A Klassen, A Meisner, R Paswaters, SE Smith, Z Tappin, SJ Thompson, BJ Watari, SI Michels, DJ Brueckner, GE Howard, RA Koomen, MJ Lamy, P Mann, G Arzner, K Schwenn, R TI The solar minimum active region 7978, its X2.6/1B flare, CME, and interplanetary shock propagation of 9 July 1996 SO SOLAR PHYSICS LA English DT Article ID CORONAL MASS EJECTIONS; MAGNETOHYDRODYNAMIC SIMULATION; DYNAMICAL EVOLUTION; SCINTILLATION; STREAMER; SYSTEM; IPS AB The first X-class flare in four years occurred on 9 July 1996. This X2.6/LB flare reached its maximum at 09:11 UT and was located in active region 7978 (S10 degrees W30 degrees) which was an old-cycle sunspot polarity group. We report the SOHO LASCO/EIT/MDI and SOONSPOT observations before and after this event together with Yohkoh SXT images of the flare, radio observations of the type II shock, and GOES disk-integrated soft X-ray flux during an extended period that included energy build-up in this active region. The LASCO coronagraphs measured a significant coronal mass ejection (CME) on the solar west limb beginning on 8 July at about 09:53 UT. The GOES 8 soft X-ray Aux (0.1-0.8 nm) had started to increase on the previous day from below the A-level background (10(-8) W m(-2)). At the start time of the CME, it was at the mid-B level and continued to climb. This CME is similar to many events which have been seen by LASCO and which are being interpreted as disruption of existing streamers by emerging flux ropes. LASCO and EIT were not collecting data at the time of the X-flare due to a temporary software outage. A larger CME was in progress when the first LASCO images were taken after the flare, Since the first image of the 'big' CME was obtained after the flare's start time, we cannot clearly demonstrate the physical connection of the CME to the flare. However, the LASCO CME data are consistent with an association of the flare and the CME. No eruptive filaments were observed during this event. We used the flare evidence noted above to employ in real time 3 simplified Shock-Time-of-Arrival (STOA) algorithm to estimate the arrival of a weak shock at the WIND spacecraft. We compare this prediction with the plasma and IMF data from WIND and plasma data from the SOHO/CELIAS instrument and suggest that the flare - and possibly the interplanetary consequences of the 'big' CME - was the progenitor of the mild, high-latitude, geomagnetic storm (daily sum of K p = 16+, Ap = 8) on 12 July 1996. We speculate that the shock was attenuated enroute to Earth as a result of interaction with the heliospheric current/plasma sheer. C1 NOAA, Space Environm Ctr, Boulder, CO 80303 USA. Hughes STX NRL, Washington, DC 20375 USA. Inst Astrophys, D-14472 Potsdam, Germany. Stanford Univ, NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Colorado, Boulder, CO 80309 USA. USN, Res Lab, Washington, DC 20375 USA. Univ Birmingham, Birmingham B15 275, W Midlands, England. NASA, Space Applicat Corp, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Commun Res Lab, Tokyo 184, Japan. Astron Spatiale Lab, F-13376 Marseille 12, France. Max Planck Inst Aeron, D-37189 Katlenburg Lindau, Germany. Univ Maryland, College Pk, MD 20742 USA. Astron Inst, Ondrejov Observ, Ondrejov, Czech Republic. Univ Bern, Inst Angew Phys, CH-3012 Bern, Switzerland. Univ Colorado, Denver, CO 80201 USA. SFA Inc, Landover, MD 20785 USA. RP Dryer, M (reprint author), NOAA, Space Environm Ctr, Boulder, CO 80303 USA. RI Galvin, Antoinette/A-6114-2013; Thompson, Barbara/C-9429-2012; Karlicky, Marian/G-9023-2014; xue, yansheng/A-9712-2012 NR 35 TC 33 Z9 33 U1 0 U2 1 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 JUL PY 1998 VL 181 IS 1 BP 159 EP 183 DI 10.1023/A:1016522812668 PG 25 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 113KL UT WOS:000075550100012 ER PT J AU Wang, Y Sakamoto, J Huang, C Surampudi, S Greenbaum, SG AF Wang, Y Sakamoto, J Huang, C Surampudi, S Greenbaum, SG TI Lithium-7 NMR investigation of electrochemical reaction of lithium with SnO SO SOLID STATE IONICS LA English DT Letter DE tin oxide (SnO); lithium-ion anode; Li-7 NMR ID OXIDE AB We report on solid state Li-7 NMR measurements of electrochemically lithiated SnO. At low Li contents (Li/SnO less than or equal to 2), the results are consistent with the formation of amorphous Li2O. For Li/SnO ratio of 4.3, in addition to the amorphous Li2O phase, there are at least two distinct Sn/Li alloy environments which are similar to those observed in a reference Li2.3Sn alloy. However the Li+ environments in a sample with Li/SnO ratio equal to 6.4 and an Li4.4Sn reference alloy differ markedly. The NMR data are thus consistent with the simple model of Li insertion proposed by other groups, involving the formation of Li2O and LixSn alloys (SnO + xLi --> Li2O + Lix-2Sn), at low and intermediate Li contents. At high Li content however, the Lix-2Sn alloy structure is significantly different in the electrochemically lithiated SnO material, compared to that in the reference alloy. (C) 1998 Elsevier Science B.V. All rights reserved. C1 CUNY Hunter Coll, Dept Phys, New York, NY 10021 USA. CALTECH, Jet Prop Lab, Electrochem Technol Grp, Pasadena, CA 91109 USA. RP Greenbaum, SG (reprint author), CUNY Hunter Coll, Dept Phys, New York, NY 10021 USA. NR 7 TC 42 Z9 48 U1 0 U2 17 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0167-2738 J9 SOLID STATE IONICS JI Solid State Ion. PD JUL PY 1998 VL 110 IS 3-4 BP 167 EP 172 DI 10.1016/S0167-2738(98)00147-7 PG 6 WC Chemistry, Physical; Physics, Condensed Matter SC Chemistry; Physics GA 112XN UT WOS:000075520200001 ER PT J AU Jongen, T Gatski, TB AF Jongen, T Gatski, TB TI A new approach to characterizing the equilibrium states of the Reynolds stress anisotropy in homogeneous turbulence (vol 11, pg 31, 1998) SO THEORETICAL AND COMPUTATIONAL FLUID DYNAMICS LA English DT Correction C1 Swiss Fed Inst Technol, Fluid Mech Lab, CH-1015 Lausanne, Switzerland. NASA, Langley Res Ctr, Hampton, VA 23681 USA. RP Jongen, T (reprint author), Swiss Fed Inst Technol, Fluid Mech Lab, CH-1015 Lausanne, Switzerland. NR 1 TC 4 Z9 4 U1 0 U2 1 PU SPRINGER VERLAG PI NEW YORK PA 175 FIFTH AVE, NEW YORK, NY 10010 USA SN 0935-4964 J9 THEOR COMP FLUID DYN JI Theor. Comput. Fluid Dyn. PD JUL PY 1998 VL 12 IS 1 BP 71 EP 72 PG 2 WC Mechanics; Physics, Fluids & Plasmas SC Mechanics; Physics GA 121FC UT WOS:000076001800004 ER PT J AU Buckel, JA Letcher, BH Conover, DO AF Buckel, JA Letcher, BH Conover, DO TI Effects of a delayed onset of piscivory on the size of age-0 bluefish SO TRANSACTIONS OF THE AMERICAN FISHERIES SOCIETY LA English DT Article ID THE-YEAR BLUEFISH; EARLY-LIFE-HISTORY; POMATOMUS-SALTATRIX; COMPENSATORY GROWTH; LARGEMOUTH BASS; SALVELINUS-ALPINUS; FEEDING HISTORY; ARCTIC CHARR; REEF FISH; RECRUITMENT AB Variation in advection or other physical forces may accelerate or delay arrival of young marine fishes into productive nearshore habitats, thereby affecting the length of the available growing season. The bluefish Pomatomus saltatrix is an oceanic spawner whose juvenile stages, upon entry into estuarine waters, become piscivorous and thereby experience greatly increased growth. Size attained during the growing season may therefore be determined by time of arrival into estuarine habitats. We exposed bluefish recently recruited to an estuary to three diet shift treatments in which test fish were fed adult brine shrimp Artemia sp. for 0, 10, or 20 d before they were switched to piscine prey. Bluefish that had a delayed onset of piscivory were smaller after 40 d of growth, indicating that they did not fully compensate for prior periods of slow growth. These bluefish did exhibit immediate moderate growth compensation (about 6% over 10 d) resulting from increased consumption rates, but relatively low growth efficiencies prevented full recovery of their growth losses. Low growth efficiencies may have resulted from an induced developmental handicap or an energetic penalty for prolonged feeding on an Anemia diet. The timing of age-0 bluefish recruitment into estuarine environments can have a lasting influence on size attained during the first growing season. C1 SUNY Stony Brook, Marine Sci Res Ctr, Stony Brook, NY 11794 USA. RP Buckel, JA (reprint author), Natl Marine Fisheries Serv, James J Howard Marine Sci Lab, 74 Magruder Rd, Highlands, NJ 07732 USA. NR 46 TC 18 Z9 18 U1 0 U2 5 PU AMER FISHERIES SOC PI BETHESDA PA 5410 GROSVENOR LANE SUITE 110, BETHESDA, MD 20814-2199 USA SN 0002-8487 J9 T AM FISH SOC JI Trans. Am. Fish. Soc. PD JUL PY 1998 VL 127 IS 4 BP 576 EP 587 DI 10.1577/1548-8659(1998)127<0576:EOADOO>2.0.CO;2 PG 12 WC Fisheries SC Fisheries GA 109XX UT WOS:000075350600005 ER PT J AU Dellacorte, C AF Dellacorte, C TI A new foil air bearing test rig for use to 700 degrees C and 70,000rpm SO TRIBOLOGY TRANSACTIONS LA English DT Article; Proceedings Paper CT 1997 World Tribology Congress CY SEP 08-12, 1997 CL LONDON, ENGLAND SP Soc Tribologists & Lubricat Engineers DE air bearings; adverse environments tribology, high temperatures; compressors; gas turbine engines AB A new test rig has been developed for evaluating foil air bearings at high temperatures and speeds. These bearings are self-acting hydrodynamic air bearings which have been successfully applied to a variety of turbomachinery operating up to 650 degrees C. This unique test rig is capable of measuring bearing torque during start-up, shutdown and high speed operation. Load capacity and general performance characteristics, such as durability, can be measured at temperatures to 700 degrees C and speeds to 70,000 rpm. This paper describes the new test rig and demonstrates its capabilities through the preliminary characterization of several bearings. The bearing performance data from this facility can be used to develop advanced turbomachinery incorporating high temperature oil-free air bearing technology. C1 NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. RP Dellacorte, C (reprint author), NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. NR 2 TC 23 Z9 25 U1 0 U2 3 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 JUL PY 1998 VL 41 IS 3 BP 335 EP 340 DI 10.1080/10402009808983756 PG 6 WC Engineering, Mechanical SC Engineering GA 111LL UT WOS:000075438800004 ER PT J AU Wu, J Yu, ST Jiang, BN AF Wu, J Yu, ST Jiang, BN TI Simulation of two-fluid flows by the least-squares finite element method using a continuum surface tension model SO INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING LA English DT Article DE two fluid flows; free surface; surface tension; finite element; least-squares ID MULTIPHASE FLOWS; HYDRODYNAMICS; CONVECTION; DYNAMICS AB In this paper a numerical procedure for simulating two-fluid flows is presented. This procedure is based on the Volume of Fluid (VOF) method proposed by Hirt and Nichols(1) and the Continuum Surface Force (CSF) model developed by Brackbill et al.(2) In the VOF method fluids of different properties are identified through the use of a continuous held variable (colour function). The colour function assigns a unique constant (colour) to each fluid. The interfaces between different fluids are distinct due to sharp gradients of the colour function. The evolution of the interfaces is captured by solving the convective equation of the colour function. The CSF model is used as a means to treat surface tension effect at the interfaces. Here a modified version of the CSF model, proposed by Jacqmin,(3) is used to calculate the tension force. In the modified version, the force term is obtained by calculating the divergence of a stress tensor defined by the gradient of the colour function. In its analytical form, this stress formulation is equivalent to the original CSF model.(2) Numerically, however, the use of the stress formulation has some advantages over the original CSF model, as it bypasses the difficulty in approximating the curvatures of the interfaces. The least-squares finite element method (LSFEM)(4) is used to discretize the governing equation systems. The LSFEM has proven to be effective in solving incompressible Navier-Stokes equations and pure convection equations, making it an ideal candidate for the present applications. The LSFEM handles all the equations in a unified manner without any additional special treatment such as upwinding or artificial dissipation. Various bench mark tests have been carried out for both two-dimensional planar and axisymmetric flows, including a dam breaking, oscillating and stationary bubbles and a conical liquid sheet in a pressure swirl atomizer. (C) 1998 John Wiley & Sons, Ltd. C1 NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. Ohio Aerosp Inst, Inst Computat Mech Prop, Brookpark, OH USA. RP Wu, J (reprint author), 7 Windy Ridge Lane, New Milford, CT 06776 USA. EM jiewu@i84.net NR 31 TC 17 Z9 18 U1 3 U2 12 PU WILEY-BLACKWELL PI HOBOKEN PA 111 RIVER ST, HOBOKEN 07030-5774, NJ USA SN 0029-5981 EI 1097-0207 J9 INT J NUMER METH ENG JI Int. J. Numer. Methods Eng. PD JUN 30 PY 1998 VL 42 IS 4 BP 583 EP 600 DI 10.1002/(SICI)1097-0207(19980630)42:4<583::AID-NME341>3.0.CO;2-M PG 18 WC Engineering, Multidisciplinary; Mathematics, Interdisciplinary Applications SC Engineering; Mathematics GA ZP719 UT WOS:000073781600001 ER PT J AU Spiess, FN Chadwell, CD Hildebrand, JA Young, LE Purcell, GH Dragert, H AF Spiess, FN Chadwell, CD Hildebrand, JA Young, LE Purcell, GH Dragert, H TI Precise GPS/Acoustic positioning of seafloor reference points for tectonic studies SO PHYSICS OF THE EARTH AND PLANETARY INTERIORS LA English DT Article DE tectonic; GPS; acoustic ID CASCADIA SUBDUCTION ZONE; CRUSTAL DEFORMATION; GEODETIC MEASUREMENTS; SPEED; SOUND; CALIFORNIA; EQUATIONS; SEAWATER; PLATE AB Global networks for crustal strain measurement provide important constraints for studies of tectonic plate motion and deformation. To date, crustal strain measurements have been possible only in terrestrial settings: on continental plates and island sites within oceanic plates. We report the development of technology for horizontal crustal motion determination at seafloor sites, allowing oceanic plates to be monitored where islands are not available. Seafloor crustal monitoring is an important component of global strain measurement because about 70% of the Earth's surface is covered by water, and this region contains most of the tectonic plate boundaries and zones of crustal deformation. Using the Global Positioning System (GPS) satellites and underwater acoustics, we have established a geodetic reference site on the Juan de Fuca plate at 2.6 km depth, approximately 150 km off the northwest coast of North America. We measure the baselines between this site and two terrestrial GPS stations on Vancouver Island, British Columbia. The Juan de Fuca plate site is an appropriate setting to develop seafloor observation methods, since it is a well studied area, easily accessible from west coast Canadian and United States ports. Determination of seafloor motion at this site addresses questions related to convergence between the Juan de Fuca and North American plates across the Cascadia Subduction Zone. At the Juan de Fuca seafloor geodetic reference site, we installed precision acoustic transponders on the seafloor, and measured ranges to them from a sound source at a surface platform (ship or buoy), The platform is equipped with a set of three GPS antennas allowing determination of the sound source position at times of signal transmission and reception. Merging the satellite and acoustic data allows determination of the transponder network location in global reference frame coordinates. Data processing to date suggests repeatabilities of +/-0.8 cm north and +/- 3.9 cm east in the seafloor transponder network position relative to reference points on Vancouver Island. (C) 1998 Elsevier Science B.V. All rights reserved. C1 Univ Calif San Diego, Scripps Inst Oceanog, Marine Phys Lab, San Diego, CA 92093 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Geol Survey Canada, Pacific Geosci Ctr, Sidney, BC V8L 4B2, Canada. RP Spiess, FN (reprint author), Univ Calif San Diego, Scripps Inst Oceanog, Marine Phys Lab, San Diego, CA 92093 USA. NR 34 TC 82 Z9 82 U1 1 U2 8 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0031-9201 J9 PHYS EARTH PLANET IN JI Phys. Earth Planet. Inter. PD JUN 30 PY 1998 VL 108 IS 2 BP 101 EP 112 DI 10.1016/S0031-9201(98)00089-2 PG 12 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 104XA UT WOS:000075040300002 ER PT J AU Wise, SA AF Wise, SA TI Displacement properties of RAINBOW and THUNDER piezoelectric actuators SO SENSORS AND ACTUATORS A-PHYSICAL LA English DT Article DE RAINBOW; THUNDER; high displacement; piezoelectric actuators ID CERAMICS AB The electromechanical displacement properties of two recently developed piezoelectric actuators, referred to as RAINBOW and THUNDER, have been measured and compared. The actuators evaluated in this investigation are fabricated from 2.54 cm diameter PZT-5H and PZT-5A piezoelectric ceramic disks and are produced with the same total device thicknesses and ceramic-to-metal thickness ratios. For the compositions tested, the RAINBOW devices are found to exhibit 10-25% greater free-displacement properties than comparable THUNDER devices. This finding indicates that larger internal stresses are developed during the RAINBOW process, which lead to enhanced amplification of axial displacement. (C) 1998 Elsevier Science S.A. All rights reserved. C1 NASA, Langley Res Ctr, Div Mat, Hampton, VA 23681 USA. RP Wise, SA (reprint author), NASA, Langley Res Ctr, Div Mat, Mail Stop 188B, Hampton, VA 23681 USA. NR 9 TC 96 Z9 100 U1 0 U2 14 PU ELSEVIER SCIENCE SA PI LAUSANNE PA PO BOX 564, 1001 LAUSANNE, SWITZERLAND SN 0924-4247 J9 SENSOR ACTUAT A-PHYS JI Sens. Actuator A-Phys. PD JUN 30 PY 1998 VL 69 IS 1 BP 33 EP 38 DI 10.1016/S0924-4247(97)01745-7 PG 6 WC Engineering, Electrical & Electronic; Instruments & Instrumentation SC Engineering; Instruments & Instrumentation GA ZX446 UT WOS:000074516700007 ER PT J AU McPhaden, MJ Busalacchi, AJ Cheney, R Donguy, JR Gage, KS Halpern, D Ji, M Julian, P Meyers, G Mitchum, GT Niiler, PP Picaut, J Reynolds, RW Smith, N Takeuchi, K AF McPhaden, MJ Busalacchi, AJ Cheney, R Donguy, JR Gage, KS Halpern, D Ji, M Julian, P Meyers, G Mitchum, GT Niiler, PP Picaut, J Reynolds, RW Smith, N Takeuchi, K TI The tropical ocean global atmosphere observing system: A decade of progress SO JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS LA English DT Article ID SEA-SURFACE-TEMPERATURE; EQUATORIAL PACIFIC-OCEAN; NINO-SOUTHERN-OSCILLATION; GENERAL-CIRCULATION MODEL; 1982-1983 EL-NINO; STATISTICAL INTERPOLATION SCHEME; EXPENDABLE BATHYTHERMOGRAPH DATA; NATIONAL-METEOROLOGICAL-CENTER; GEOSAT ALTIMETER OBSERVATIONS; MESOSCALE CONVECTIVE SYSTEMS AB A major accomplishment of the recently completed Tropical Ocean-Global Atmosphere (TOGA) Program was the development of an ocean observing system to support seasonal-to-interannual climate studies. This paper reviews the scientific motivations for the development of that observing system, the technological advances that made it possible, and the scientific advances that resulted from. the availability of a significantly expanded observational database. A primary phenomenological focus of TOGA was interannual variability of the coupled ocean-atmosphere system associated with El Nino and the Southern Oscillation (ENSO). Prior to the start of TOGA, our understanding of the physical processes responsible for the ENSO cycle was limited, our ability to monitor variability in the tropical oceans was primitive, and the capability to predict ENSO was nonexistent. TOGA therefore initiated and/or supported efforts to provide real-time measurements of the following key oceanographic variables: surface winds, sea surface temperature, subsurface temperature, sea level and ocean velocity. Specific in situ observational; programs developed to provide these data sets included the Tropical Atmosphere-Ocean (TAO) array of moored buoys, in the Pacific, a surface drifting buoy program, an island and coastal tide gauge network, and a volunteer observing ship network of expendable bathythermograph measurements. Complementing these in situ efforts were satellite missions which provided near-global coverage of surface winds, sea surface temperature, and sea level. These new TOGA data sets led to fundamental progress in our understanding of the physical processes responsible for ENSO and to the development of coupled ocean-atmosphere models for ENSO prediction. C1 NOAA, Pacific Marine Environm Lab, Seattle, WA 98115 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. NOAA, Natl Ocean Serv, Silver Spring, MD 20910 USA. Inst Francais Rech Sci Dev Cooperat, F-29263 Plouzane, France. NOAA, Aeron Lab, Boulder, CO 80303 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. NOAA, Natl Ctr Environm Predict, Camp Springs, MD 20746 USA. CSIRO, Div Oceanog, Hobart, Tas 7005, Australia. Univ S Florida, Dept Marine Sci, St Petersburg, FL 33701 USA. Univ Calif San Diego, Scripps Inst Oceanog, La Jolla, CA 92093 USA. Bur Meteorol, Res Ctr, Melbourne, Vic 3001, Australia. Hokkaido Univ, Inst Low Temp Sci, Sapporo, Hokkaido 060, Japan. RP McPhaden, MJ (reprint author), NOAA, Pacific Marine Environm Lab, Bldg 3,7600 Sand Point Way NE, Seattle, WA 98115 USA. EM mcphaden@pmel.noaa.gov RI surname, name/A-2183-2010; McPhaden, Michael/D-9799-2016 NR 535 TC 516 Z9 538 U1 4 U2 58 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 JUN 29 PY 1998 VL 103 IS C7 BP 14169 EP 14240 DI 10.1029/97JC02906 PG 72 WC Oceanography SC Oceanography GA ZX085 UT WOS:000074477900002 ER PT J AU Stockdale, TN Busalacchi, AJ Harrison, DE Seager, R AF Stockdale, TN Busalacchi, AJ Harrison, DE Seager, R TI Ocean modeling for ENSO SO JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS LA English DT Article ID TROPICAL PACIFIC-OCEAN; GENERAL-CIRCULATION MODEL; SEA-SURFACE TEMPERATURE; NINO-SOUTHERN-OSCILLATION; NATIONAL-METEOROLOGICAL-CENTER; EQUATORIAL ATLANTIC-OCEAN; PRIMITIVE EQUATION MODEL; 1982-1983 EL-NINO; MERIDIONAL HEAT-TRANSPORT; SHALLOW-WATER SIMULATIONS AB Tropical ocean modeling has played a major part in the development of our knowledge of El Nino-Southern Oscillation (ENSO) during the Tropical Ocean-Global Atmosphere (TOGA) decade. Although the foundations had already been laid, it was only with the impetus from TOGA that tropical ocean modeling was able to develop so extensively. In this paper we discuss the development of the wide range of tropical ocean models in use today,from the simple to the complex; the ways in which their abilities to reproduce different phenomena have been assessed; and the ways in which they are being used to better understand and predict the behavior of the coupled ocean-atmosphere system in the tropics. Ocean model development is far from finished, however. Outstanding issues such as forcing fields, model improvements, testing strategies, and applications are also discussed. There is at least as much work to be done in the next decade as was achieved in the last. C1 European Ctr Medium Range Weather Forecasts, Reading RG2 9AX, Berks, England. NASA, Lab Hydrospher Proc, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. NOAA, Pacific Marine Environm Lab, Seattle, WA 98115 USA. Columbia Univ, Lamont Doherty Earth Observ, Palisades, NY 10964 USA. RP Stockdale, TN (reprint author), European Ctr Medium Range Weather Forecasts, Shinfield Pk, Reading RG2 9AX, Berks, England. RI Harrison, Don/D-9582-2013 NR 294 TC 47 Z9 51 U1 0 U2 3 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 JUN 29 PY 1998 VL 103 IS C7 BP 14325 EP 14355 DI 10.1029/97JC02440 PG 31 WC Oceanography SC Oceanography GA ZX085 UT WOS:000074477900006 ER PT J AU Delecluse, P Davey, MK Kitamura, Y Philander, SGH Suarez, M Bengtsson, L AF Delecluse, P Davey, MK Kitamura, Y Philander, SGH Suarez, M Bengtsson, L TI Coupled general circulation modeling of the tropical Pacific SO JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS LA English DT Article ID OCEAN-ATMOSPHERE INTERACTION; NINO-SOUTHERN OSCILLATION; SEA-SURFACE TEMPERATURE; EL-NINO; INTERANNUAL VARIABILITY; GLOBAL OCEAN; SEASONAL CYCLE; CLIMATE MODEL; UNIFIED VIEW; MONSOON REGIONS AB During the Tropical Ocean-Global Atmosphere (TOGA) program substantial progress was made in the development of coupled general circulation models with regard to representation of the tropical mean state and climate variability. This paper provides a review of the main developments, focusing on the tropical Pacific region. Early coupled general circulation models were relatively crude; with coarse resolution and limited physical parameterizations and poor surface fluxes, the model drift from the observed mean state was often substantial, and their use for investigating climate variability such as El Nino-Southern Oscillation (ENSO) was limited. Improvements in resolution and parameterizations led to rapid progress. Through the TOGA program it has been possible to assess coupled model mean states and variability against high-quality observations, particularly for the tropical Pacific. Both components of the coupled system (ocean and atmosphere) have benefited from an improved understanding of the physics. Coupled experiments have revealed deficiencies in each model component that were concealed in separate forced runs. Several general systematic errors have yet to be eliminated, especially in the east Pacific. The variety of behavior obtained with coupled models provides evidence that more than one mechanism is active in the generation and evolution of ENSO events. There are also indications that interannual variability is linked to the mean structure of the equatorial Pacific. C1 Univ Pierre & Marie Curie, Lab Oceanog Dynam & Cimatol, Unite Mixte Rech CNRS ORSTOM UPMC, F-75005 Paris, France. Meteorol Off, Hadley Ctr, Bracknell RG12 2SY, Berks, England. Meteorol Res Inst, Tsukuba, Ibaraki 305, Japan. Princeton Univ, Program Atmospher & Ocean Sci, Princeton, NJ 08544 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Max Planck Inst Meteorol, D-20146 Hamburg, Germany. RP Delecluse, P (reprint author), Univ Pierre & Marie Curie, Lab Oceanog Dynam & Cimatol, Unite Mixte Rech CNRS ORSTOM UPMC, Case 100,4 Pl Jussieu, F-75005 Paris, France. NR 124 TC 66 Z9 71 U1 0 U2 2 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 JUN 29 PY 1998 VL 103 IS C7 BP 14357 EP 14373 DI 10.1029/97JC02546 PG 17 WC Oceanography SC Oceanography GA ZX085 UT WOS:000074477900007 ER PT J AU Strahan, SE Douglass, AR Nielsen, JE Boering, KA AF Strahan, SE Douglass, AR Nielsen, JE Boering, KA TI The CO2 seasonal cycle as a tracer of transport SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID GENERAL-CIRCULATION MODEL; 3-DIMENSIONAL SIMULATION; LOWER STRATOSPHERE; CARBON-DIOXIDE; DYNAMICS; AIRCRAFT; SYSTEM; OZONE; WINDS; N2O AB CO2 time series in the lower stratosphere have been constructed as a function of latitude and altitude using ER-2 aircraft observations. A seasonally varying signal derived from tropical surface CO2 data was fit to these data in a manner similar to that of Boering et al. [1996]. This analysis shows how the tropospheric CO2 seasonal cycle in air entering the tropical lower stratosphere ascends and gradually loses amplitude. The midlatitude results show that in the 370- to 400-K range the tropical signal is transported poleward rapidly with only a small loss in amplitude. The signal also reaches the midlatitudes rapidly at higher altitudes but with markedly less amplitude. Above similar to 440 K the midlatitude CO2 data best fit a line whose slope is the secular increase in CO2. This observational analysis is used as a basis for diagnosing transport in a CO2 simulation produced using GEOS-1 Data Assimilation System (DAS) winds in an off-line chemistry and transport model. The model is forced at the lowest levels by a 5-year zonal mean CO2 data set derived from surface observations. The analysis of model results as a function of height and latitude determines whether (1) the seasonally varying CO2 cycle forced in the troposphere survives in the tropical lower stratosphere and whether (2) the CO2 cycle in the tropical lower stratosphere propagates realistically to the midlatitudes. We find that the model transports a CO2 seasonal cycle from the surface to the tropical upper troposphere that agrees with the phase and amplitude of tropospheric aircraft measurements. The cycle input into the model tropical lower stratosphere attenuates with height in a reasonable way compared with observations. The phase and amplitude of the cycle transported from the tropics to the midlatitudes agree well with the data up to about 440 K, but above that the model transports more of the tropical signal to the midlatitudes than is suggested by the ER-2 data. Overall, there is remarkable consistency between the model and observations in the upper troposphere/lower stratosphere, which supports the use of assimilated winds in assessments of the effects of aircraft exhaust. C1 Gen Sci Corp, Laurel, MD 20707 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Space Applicat Corp, Vienna, VA 22180 USA. Harvard Univ, Dept Earth & Planetary Sci, Cambridge, MA 02138 USA. RP Strahan, SE (reprint author), Gen Sci Corp, Laurel, MD 20707 USA. EM strahan@prometheus.gsfc.nasa.gov; douglass@persephone.gsfc.nasa.gov; nielsen@twod.gsfc.nasa.gov; kab@io.harvard.edu RI Douglass, Anne/D-4655-2012; Strahan, Susan/H-1965-2012 NR 31 TC 36 Z9 36 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 JUN 27 PY 1998 VL 103 IS D12 BP 13729 EP 13741 DI 10.1029/98JD01143 PG 13 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA ZW708 UT WOS:000074439500004 ER PT J AU Wang, PH Rind, D Trepte, CR Kent, GS Yue, GK Skeens, KM AF Wang, PH Rind, D Trepte, CR Kent, GS Yue, GK Skeens, KM TI An empirical model study of the tropospheric meridional circulation based on SAGE II observations SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID STRATOSPHERIC AEROSOL; GENERAL-CIRCULATION; WATER-VAPOR; EXCHANGE; CLOUD; MASS; TRANSPORT; RADIATION AB This study investigates the tropospheric mean meridional circulation important to the development of opaque clouds and the measurement opportunity of the 1.02-mu m channel of the Stratospheric Aerosol and Gas Experiment (SAGE) II in the troposphere. A simple empirical model is formulated to derive the mean meridional circulation from the 6-year (1985-1990) statistics of the SAGE II tropospheric measurement frequency. The vertical circulation of the model is assumed to be related to the departure field of the zonally averaged SAGE II measurement frequency from the corresponding global mean in a linear fashion. The proportional constant is calibrated with the observed upwelling circulation statistics in the tropics. The obtained model vertical circulation is then used to determine the distribution of meridional velocity according to the continuity equation. The derived model mean circulation features the influence from both the diabatic circulation and the eddy quasi-isentropic transport, with a distinct pattern of material advection into the upper troposphere from both the lower troposphere and the stratosphere. Most significantly, the model circulation is shown to be highly consistent with the observed free tropospheric aerosol and ozone distributions, particularly with their seasonal variations given the aerosol and ozone source regions. This high degree of consistency illustrates the intimate relationship between the large-scale circulation, cloudiness, and the SAGE II tropospheric measurement frequency, and the robust nature of the empirical model despite the model's simplicity. The discussion in relating the model circulation to the conventional Eulerian circulation and the Lagrangian transport, based on isentropic consideration, is also provided. C1 Sci & Technol Corp, Hampton, VA 23666 USA. NASA, Goddard Inst Space Studies, New York, NY 10025 USA. NASA, Langley Res Ctr, Div Atmospher Sci, Hampton, VA 23681 USA. RP Wang, PH (reprint author), Sci & Technol Corp, 101 Res Dr, Hampton, VA 23666 USA. EM wang@arbs3.larc.nasa.gov; cddhr@giss.nasa.gov; c.r.trepte@larc.nasa.gov; kent@arbs9.larc.nasa.gov; g.k.yue@larc.nasa.gov; Kristi.Skeens@East.Sun.COM NR 44 TC 12 Z9 12 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 JUN 27 PY 1998 VL 103 IS D12 BP 13801 EP 13818 DI 10.1029/98JD00204 PG 18 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA ZW708 UT WOS:000074439500009 ER PT J AU Stenchikov, GL Kirchner, I Robock, A Graf, HF Antuna, JC Grainger, RG Lambert, A Thomason, L AF Stenchikov, GL Kirchner, I Robock, A Graf, HF Antuna, JC Grainger, RG Lambert, A Thomason, L TI Radiative forcing from the 1991 Mount Pinatubo volcanic eruption SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Review ID NORTHERN-HEMISPHERE WINTER; AEROSOL-SIZE DISTRIBUTIONS; STRATOSPHERIC AEROSOL; EL-CHICHON; MT-PINATUBO; LIDAR OBSERVATIONS; SULFURIC-ACID; MULTIPLE-SCATTERING; SURFACE-TEMPERATURE; CLIMATE CHANGES AB Volcanic sulfate aerosols in the stratosphere produce significant long-term solar and infrared radiative perturbations in the Earth's atmosphere and at the surface, which cause a response of the climate system. Here we study the fundamental process of the development of this volcanic radiative forcing, focusing on the eruption of Mount Pinatubo in the Philippines on June 15, 1991. We develop a spectral-, space-, and time-dependent set of aerosol parameters for 2 years after the Pinatubo eruption using a combination of SAGE II aerosol extinctions and UARS-retrieved effective radii, supported by SAM II, AVHRR, lidar and balloon observations. Using these data, we calculate the aerosol radiative forcing with the ECHAM4 general circulation model (GCM) for cases with climatological and observed sea surface temperature (SST), as well as with and without climate response. We find that the aerosol radiative forcing is not sensitive to the climate variations caused by SST or the atmospheric response to the aerosols, except in regions with varying dense cloudiness. The solar forcing in the near infrared contributes substantially to the total stratospheric heating. A complete formulation of radiative forcing should include not only changes of net fluxes at the tropopause but also the vertical distribution of atmospheric heating rates and the change of downward thermal and net solar radiative fluxes at the surface. These forcing and aerosol data are available for GCM experiments with any spatial and spectral resolution. C1 Univ Maryland, Dept Meteorol, College Pk, MD 20742 USA. Max Planck Inst Meteorol, Hamburg, Germany. Univ Oxford, Oxford OX1 2JD, England. NASA, Langley Res Ctr, Hampton, VA 23665 USA. RP Univ Maryland, Dept Meteorol, College Pk, MD 20742 USA. EM gera@atmos.umd.edu; kirchner@dkrz.de; robock@envsci.rutgers.edu; graf@dkrz.de; antuna@atmos.umd.edu; d.grainger@phys.canterbury.ac.nz; alambert@eos.ucar.adu; l.w.thomason@larc.nasa.gov RI Grainger, Roy/E-8823-2011; Georgiy, Stenchikov/J-8569-2013; Robock, Alan/B-6385-2016; OI Grainger, Roy/0000-0003-0709-1315; Thomason, Larry/0000-0002-1902-0840 NR 108 TC 177 Z9 183 U1 9 U2 46 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 JUN 27 PY 1998 VL 103 IS D12 BP 13837 EP 13857 DI 10.1029/98JD00693 PG 21 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA ZW708 UT WOS:000074439500012 ER PT J AU Remer, LA Kaufman, YJ AF Remer, LA Kaufman, YJ TI Dynamic aerosol model: Urban/industrial aerosol SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID SIZE DISTRIBUTIONS; UNITED-STATES; OPTICAL-PROPERTIES; BOUNDARY-LAYER; ATLANTIC-OCEAN; EAST-COAST; EXTINCTION; PARTICLES AB Aerosol properties vary with the aerosol type, loading, or atmospheric conditions. We found that a dynamical aerosol model that describes the variability of aerosol properties as a function of aerosol optical thickness can address this issue. Ambient urban/industrial aerosol is measured in the mid-Atlantic region of the United States during the summer of 1993 by automatic Sun/sky radiometers. The volume size distributions inverted from the measured sky radiance represent the entire column of ambient particles. These data depict an aerosol regime in which accumulation mode particle size and volume increases as optical thickness increases. A dynamical aerosol model that is a function of optical thickness is constructed by fitting lognormal functions to the volume size distributions. It accounts for 60% of the variance in the aerosol accumulation mode size distributions. The accumulation mode is represented as a linear combination of two modes: one with volume modal radius 0.11 mu m and the other with modal radius 0.21 mu m. The model is shown to recreate the correct independently measured sky radiance in the backscattering direction and to predict the phase function within model uncertainties of data collected in subsequent years. The model is shown to be unbiased with respect to the time of day and to reproduce the wavelength dependence measured by the independent Sun measurements. The dynamic model has substantially different properties than a "static" continental model except for the limited optical thickness range of 0.0-0.25. C1 NASA, Goddard Space Flight Ctr, Atmospheres Lab, Greenbelt, MD 20711 USA. NASA, Goddard Space Flight Ctr, Sci Syst & Applicat Inc, Greenbelt, MD 20771 USA. RP Remer, LA (reprint author), NASA, Goddard Space Flight Ctr, Sci Syst & Applicat Inc, Code 913, Greenbelt, MD 20771 USA. EM remer@climate.gsfc.nasa.gov; kaufman@climate.gsfc.nasa.gov NR 46 TC 90 Z9 96 U1 2 U2 9 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 JUN 27 PY 1998 VL 103 IS D12 BP 13859 EP 13871 DI 10.1029/98JD00994 PG 13 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA ZW708 UT WOS:000074439500013 ER PT J AU Congeduti, F DeLuisi, J DeFoor, T Thomason, L AF Congeduti, F DeLuisi, J DeFoor, T Thomason, L TI Optical extinction properties of volcanic stratospheric aerosol derived from ground-based lidar and Sun photometer measurements SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID CHICHON ERUPTION CLOUD; EL-CHICHON; CORRELATIVE MEASUREMENTS; SIZE DISTRIBUTIONS; MOUNT-PINATUBO; OCTOBER 1982; MAUNA-LOA; BACKSCATTER; MODEL; MASS AB Measurements of lidar-integrated backscatter and Sun photometer optical thickness made at Mauna Loa, Hawaii (19.5 degrees N), were used to compute the bulk columnar value of the extinction-to-backscatter ratio S-c of stratospheric aerosol during a period of major stratospheric aerosol contamination following the eruption of El Chichon (Mexico, 17.3 degrees N, March-April 1982). Values of S-c were also calculated using observations of integrated backscatter and aerosol optical thickness collected from various sources in the northern midlatitude region. The calculated values of S-c were found to range between 40 and 70 sr at a wavelength of 0.694 mu m during periods when high and moderate stratospheric aerosol concentrations were observed. Variations of S-c with time of approximately 20-30% are noted in the results. Similar S-c results obtained by other investigators are compared with the results of this investigation. Overall, the agreement among the various results was found to be consistent within their uncertainties. Values of S-c were also calculated for the stratospheric aerosol from the eruption of Mount Pinatubo (Philippines, 15 degrees N, June 1991). The Mount Pinatubo results were about 15% lower than the El Chichon results during their early stages. Differences between the El Chichon and the Pinatubo results are within their error bounds. C1 CNR, Ist Fis Atmosfera, I-00044 Frascati, Italy. NOAA, Environm Res Labs, Boulder, CO 80303 USA. NASA, Langley Atmospher Res Ctr, Hampton, VA 23681 USA. RP Congeduti, F (reprint author), CNR, Ist Fis Atmosfera, CP 27, I-00044 Frascati, Italy. EM deluisi@srrb.noaa.gov OI Thomason, Larry/0000-0002-1902-0840 NR 41 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 JUN 27 PY 1998 VL 103 IS D12 BP 13893 EP 13902 DI 10.1029/98JD00942 PG 10 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA ZW708 UT WOS:000074439500015 ER PT J AU Ziemke, JR Chandra, S AF Ziemke, JR Chandra, S TI Comment on "Tropospheric ozone derived from TOMS/SBUV measurements during TRACE A" by J. Fishman et al. SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Editorial Material ID STRATOSPHERIC OZONE; SATELLITE; TROPICS; SCALE C1 NASA, Goddard Space Flight Ctr, Chem & Dynam Branch, Greenbelt, MD 20771 USA. Software Corp Amer, Lanham, MD USA. RP Ziemke, JR (reprint author), NASA, Goddard Space Flight Ctr, Chem & Dynam Branch, Code 916, Greenbelt, MD 20771 USA. EM ziemke@jwocky.gsfc.nasa.gov; chandra@chapman.gsfc.nasa.gov NR 15 TC 9 Z9 9 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 JUN 27 PY 1998 VL 103 IS D12 BP 13903 EP 13906 DI 10.1029/97JD00550 PG 4 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA ZW708 UT WOS:000074439500016 ER PT J AU Blyth, AM Christian, HJ Latham, J AF Blyth, AM Christian, HJ Latham, J TI Corona emission thresholds for three types of hydrometeor interaction in thunderclouds SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article; Proceedings Paper CT 10th International Conference on Atmospheric Electricity (ICAE 10) CY JUN 10-13, 1996 CL OSAKA, JAPAN SP Int Commiss Atmospher Electr, Meterol Soc Japan, Int Union Radio Sci, Inst Electr Engn Japan, Japan Res Grp Electr Discharge, Sci Council Japan, Commemorat Assoc Japan World Expoosit ID RAINDROPS AB Laboratory studies have been conducted of the conditions under which glancing collisions, at relative velocities V characteristic of those occurring in thunderstorms, of three types of hydrometeor pairs of precipitation dimension (such as (1) warm drop pai:rs, (2) supercooled drop pairs, and (3) a supercooled drop and a graupel pellet) produce a corona discharge in an electric field E. In each case, the observed corona is emitted at the tip of an ephemeral liquid filament, of length greater than the dimensions of-the interacting hydrometeors, drawn out during each interaction. For each type of hydrometeor pair, the probability f that corona was produced during an interaction increased steadily from zero for increasing values of E above about 150 kV/m, and was significantly in excess of 50% for values of E = 400 kV/m, which is probably about the maximum ambient value occurring in a thunderstorm. We conclude that if the associated hydrometeors are present in strongly electrified regions of thunderstorms (unlikely for interaction type 1 but manifestly possible for types 2 and 3, corona initiation leading to the production of lightning could result from each of the three types of interaction studied. C1 New Mexico Inst Min & Technol, Dept Phys, Socorro, NM 87801 USA. NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. Natl Ctr Atmospher Res, MMM Div, Boulder, CO 80307 USA. RP Latham, J (reprint author), 1 Grimsditch Barn,Grimsditch Lane, Warrington WA4 4ED, Cheshire, England. NR 8 TC 11 Z9 12 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 JUN 27 PY 1998 VL 103 IS D12 BP 13975 EP 13977 DI 10.1029/97JD02554 PG 3 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA ZW708 UT WOS:000074439500026 ER PT J AU Priscu, JC Fritsen, CH Adams, EE Giovannoni, SJ Paerl, HW McKay, CP Doran, PT Gordon, DA Lanoil, BD Pinckney, JL AF Priscu, JC Fritsen, CH Adams, EE Giovannoni, SJ Paerl, HW McKay, CP Doran, PT Gordon, DA Lanoil, BD Pinckney, JL TI Perennial Antarctic lake ice: An oasis for life in a polar desert SO SCIENCE LA English DT Article AB The permanent ice covers of Antarctic lakes in the McMurdo Dry Valleys develop liquid water inclusions in response to solar heating of internal aeolian-derived sediments. The ice sediment particles serve as nutrient (inorganic and organic)-enriched microzones for the establishment of a physiologically and ecologically complex microbial consortium capable of contemporaneous photosynthesis,.nitrogen fixation, and decomposition. The consortium is capable of physically and chemically establishing and modifying a relatively nutrient- and organic matter-enriched microbial "oasis" embedded in the lake ice cover. C1 Montana State Univ, Dept Biol Sci, Bozeman, MT 59717 USA. Montana State Univ, Dept Civil Engn, Bozeman, MT 59717 USA. Oregon State Univ, Dept Microbiol, Corvallis, OR 97331 USA. Univ N Carolina, Inst Marine Sci, Morehead City, NC 28557 USA. NASA, Ames Res Ctr, Div Space Sci, Moffett Field, CA 94035 USA. Univ Illinois, Chicago, IL 60607 USA. RP Priscu, JC (reprint author), Montana State Univ, Dept Biol Sci, Bozeman, MT 59717 USA. OI Lanoil, Brian/0000-0001-8603-8330 NR 24 TC 231 Z9 250 U1 2 U2 37 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 JUN 26 PY 1998 VL 280 IS 5372 BP 2095 EP 2098 DI 10.1126/science.280.5372.2095 PG 4 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA ZW680 UT WOS:000074435900038 PM 9641910 ER PT J AU Ward, WR Hahn, JM AF Ward, WR Hahn, JM TI Neptune's eccentricity and the nature of the Kuiper belt SO SCIENCE LA English DT Article ID SHORT-PERIOD COMETS; OUTER SOLAR-SYSTEM; DENSITY WAVES; ORBITAL MIGRATION; SATURNS RINGS; ACCRETION; LINDBLAD; ORIGIN; URANUS AB The small eccentricity of Neptune may be a direct consequence of apsidal wave interaction with the trans-Neptune population of debris called the Kuiper belt. The Kuiper belt is subject to resonant perturbations from Neptune, so that the transport of angular momentum by density waves can result in orbital evolution of Neptune as well as changes in the structure of the Kuiper belt. In particular, for a belt eroded out to the vicinity of Neptune's 2:1 resonance at about 48 astronomical units, Neptune's eccentricity can damp to its current value over the age of the solar system if the belt contains slightly more than an earth mass of material out to about 75 astronomical units. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Lunar & Planetary Inst, Houston, TX 77058 USA. RP Ward, WR (reprint author), SW Res Inst, 1050 Walnut St,Suite 429, Boulder, CO 80302 USA. NR 31 TC 8 Z9 8 U1 1 U2 2 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 JUN 26 PY 1998 VL 280 IS 5372 BP 2104 EP 2106 DI 10.1126/science.280.5372.2104 PG 3 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA ZW680 UT WOS:000074435900041 ER PT J AU Ponchak, GE Katehi, LPB AF Ponchak, GE Katehi, LPB TI Measured attenuation of coplanar waveguide on CMOS grade silicon substrates with polyimide interface layer SO ELECTRONICS LETTERS LA English DT Article AB The measured propagation constant of a coplanar waveguide on CMOS grade silicon with a polyimide interface layer is presented. II is shown that the transmission line can have an attenuation comparable to other transmission lines on Si substrates if the proper polyimide thickness is used. C1 NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. Univ Michigan, Ann Arbor, MI 48109 USA. RP NASA, Lewis Res Ctr, MS 54-5,21000 Brookpk Rd, Cleveland, OH 44135 USA. NR 6 TC 22 Z9 24 U1 0 U2 2 PU INST ENGINEERING TECHNOLOGY-IET PI HERTFORD PA MICHAEL FARADAY HOUSE SIX HILLS WAY STEVENAGE, HERTFORD SG1 2AY, ENGLAND SN 0013-5194 EI 1350-911X J9 ELECTRON LETT JI Electron. Lett. PD JUN 25 PY 1998 VL 34 IS 13 BP 1327 EP 1329 DI 10.1049/el:19980840 PG 3 WC Engineering, Electrical & Electronic SC Engineering GA 103AC UT WOS:000074957600039 ER PT J AU Glaze, LS Baloga, SM AF Glaze, LS Baloga, SM TI Dimensions of Pu'u O'o lava flows on Mars SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS LA English DT Article ID ALBA-PATERA; TERRESTRIAL AB Longitudinal thickness profiles are simulated for lava flows on Mars erupted under conditions identical to those of Episodes 2 and 18 of the Pu'u O'o eruption at Kilauea volcano, Hawaii. Three separate approaches are used to estimate the change in the Newtonian viscosity along the length of these flows. The first approach assumes that all parts of the flow are in uniform motion and the volumetric flow rate is conserved at all stations along the flow path. The second approach assumes the same Newtonian flow model but takes advantage of independently acquired advance rate data. The third approach uses a recent model for the conservation of lava volume. This model apportions the flow rate into an active, advancing component and a separate component that is stationary (e.g., levees, stagnant zones, stationary margins). Viscosity changes for all three approaches are compared, with new insights into the theologic changes in the Pu'u O'o flows. The three approaches to flow emplacement are used as a basis for scaling the terrestrial flow thickness profiles to account for the difference in Mars gravity. For the same volumetric effusion rate and identical topography, explicit scaling for the lower gravity affects the initial flow thickness and advance rate. More subtle is the implicit influence of the lower gravity on the viscosity change along the flow path. Differences in viscosity change estimated by all three models are magnified when applied to lava flows on Mars. To illustrate the sensitivity of relative viscosity estimates on the assumed flow rate model, we also estimate viscosity increases for lava flows sit Ascraeus Mons, Elysium Planitia, and Alba Patera. We show that the third model consistently predicts significantly greater increases in viscosity and must be considered when analyzing channelized flows where significant volumes of material have been lost to stagnant margins during emplacement. C1 Proxemy Res, Laytonsville, MD USA. RP Glaze, LS (reprint author), NASA, Goddard Space Flight Ctr, Proxemy Res, Code 921, Greenbelt, MD 20771 USA. RI Glaze, Lori/D-1314-2012 NR 18 TC 15 Z9 15 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 JUN 25 PY 1998 VL 103 IS E6 BP 13659 EP 13666 DI 10.1029/97JE01427 PG 8 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 138JX UT WOS:000076969700003 ER PT J AU Beardmore, AP Mukai, K Norton, AJ Osborne, JP Hellier, C AF Beardmore, AP Mukai, K Norton, AJ Osborne, JP Hellier, C TI The changing X-ray light curves of the intermediate polar FO Aquarii SO MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY LA English DT Article DE accretion, accretion discs; binaries, close; stars, individual, FO Aqr; novae, cataclysmic variables; X-rays, stars ID DQ HERCULIS STARS; CATACLYSMIC VARIABLES; GINGA OBSERVATIONS; ACCRETION DISK; POWER SPECTRA; WHITE-DWARFS; EX HYA; H2215-086; GK; QUIESCENCE AB Comparison of five X-ray observations of the intermediate polar FO Aqr reveals that the morphology of the X-ray light curve changes considerably with time, In particular, power spectra of the 1988 Ginga and 1993 ASCA data reveal strong sideband and orbital variations, whereas the 1990 Ginga observation does not. This suggests that the amount of stream-fed accretion varies with epoch, and the system was accreting predominantly from a disc in 1990, In contrast to other intermediate polars, the X-ray spin-pulse profiles show significant variations between observations, ranging from relatively sinusoidal to sawtooth-shaped at medium energies, During the 1988 and 1990 observations a notch is visible at spin phase zero, due to the presence of an interpulse at phase 0.85, which is absent during the other observations. At lower energies a narrow pulse of emission is seen at spin phase 0.2, We interpret the pulse profile from the 1990 Ginga observation using a model for accretion from a disc on to a dipolar magnetic field, the axis of which is offset from the white dwarf centre by similar to 0.15 white dwarf radii. In order to account for the later occurrence of the hardness-ratio maximum in 1988 and 1993, we suggest that the accretion-rate profile changes so that accretion is favoured along the field lines which trail the magnetic pole. This also accounts for the disappearance of the interpulse and notch in 1993. C1 Univ Keele, Dept Phys, Keele ST5 5BG, Staffs, England. NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. Open Univ, Dept Phys, Milton Keynes MK7 6AA, Bucks, England. Univ Leicester, Dept Phys & Astron, Leicester LE1 7RH, Leics, England. RP Beardmore, AP (reprint author), Univ Keele, Dept Phys, Keele ST5 5BG, Staffs, England. OI Norton, Andrew/0000-0001-7619-8269 NR 56 TC 30 Z9 30 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 JUN 21 PY 1998 VL 297 IS 2 BP 337 EP 347 DI 10.1046/j.1365-8711.1998.01382.x PG 11 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZZ030 UT WOS:000074688300006 ER PT J AU Hellier, C Mukai, K Osborne, JP AF Hellier, C Mukai, K Osborne, JP TI Iron K alpha linewidths in magnetic cataclysmic variables SO MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY LA English DT Article DE accretion, accretion discs; binaries, close; novae, cataclysmic variables; X-rays, stars ID X-RAY-SPECTRUM; AM-HERCULIS; AO PISCIUM; ASCA; POLARS; MODELS; PLASMA AB Following a recent report that AO Pse has broad iron Ka! emission lines we have looked at the ASCA spectra of 15 magnetic cataclysmic variables. We find that half of the systems have Ka! lines broadened by similar to 200 eV, while the remainder have narrow lines. We argue that the Doppler effect is insufficient to explain the finding and propose that the lines originate In accretion columns on the verge of optical thickness. where Compton scattering of resonantly trapped line photons broadens the profile. We suggest that the broadening is a valuable diagnostic of conditions in the accretion column. C1 Univ Keele, Dept Phys, Keele ST5 5BG, Staffs, England. NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. Univ Leicester, Dept Phys & Astron, Leicester LE1 7RH, Leics, England. RP Hellier, C (reprint author), Univ Keele, Dept Phys, Keele ST5 5BG, Staffs, England. NR 25 TC 24 Z9 24 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 JUN 21 PY 1998 VL 297 IS 2 BP 526 EP 530 DI 10.1046/j.1365-8711.1998.01557.x PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZZ030 UT WOS:000074688300026 ER PT J AU Simpson, C AF Simpson, C TI A new look at the isotropy of narrow-line emission in extragalactic radio sources SO MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY LA English DT Article DE galaxies, active; galaxies, nuclei; quasars, emission lines; radio continuum, galaxies ID COMPLETE SAMPLE; GALAXIES; QUASARS; SPECTROPHOTOMETRY; NUCLEI AB We undertake a quantitative investigation, using Monte Carlo simulations, of the amount by which quasars are expected to exceed radio galaxies in optical luminosity in the context of the 'receding torus' model. We compare these simulations with the known behaviour of the [O III] lambda 5007 and [O II] lambda 3727 emission lines and conclude that [O III] is the better indicator of the strength of the underlying non-stellar continuum. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Simpson, C (reprint author), CALTECH, Jet Prop Lab, MS 169-327,4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 21 TC 57 Z9 57 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 JUN 21 PY 1998 VL 297 IS 2 BP L39 EP L43 DI 10.1046/j.1365-8711.1998.01678.x PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZZ030 UT WOS:000074688300003 ER PT J AU Schmid, B Spyak, PR Biggar, SF Wehrli, C Sekler, J Ingold, T Matzler, C Kampfer, N AF Schmid, B Spyak, PR Biggar, SF Wehrli, C Sekler, J Ingold, T Matzler, C Kampfer, N TI Evaluation of the applicability of solar and lamp radiometric calibrations of a precision Sun photometer operating between 300 and 1025 nm SO APPLIED OPTICS LA English DT Article ID IRRADIANCE MEASUREMENTS; WATER-VAPOR; RADIATION; CONSTANT; AEROSOL; REGION; OZONE AB Over a period of 3 years a precision Sun photometer (SPM) operating between 300 and 1025 nm was calibrated four times at three different high-mountain sites in Switzerland, Germany, and the United States by means of the Langley-plot technique. We found that for atmospheric window wavelengths the total error (2 sigma-statistical plus systematic errors) of the calibration constants V-0 (lambda), the SPM voltage in the absence of any attenuating atmosphere, can be kept below 1.6% in the W-A and blue, 0.9% in the mid-visible, and 0.6% in the near-infrared spectral region. For SPM channels within strong water-vapor or ozone absorption bands a modified Langley-plot technique was used to determine V-0 (lambda) with a lower accuracy. Within the same period of time, we calibrated the SPM five times using irradiance standard lamps in the optical labs of the Physikalisch-Meteorologisches Observatorium Davos and World Radiation Center, Switzerland, and of the Remote Sensing Group of the Optical Sciences Center, University of Arizona, Tucson, Arizona. The lab calibration method requires knowledge of the extraterrestrial spectral irradiance. When we refer the standard lamp results to the World Radiation Center extraterrestrial solar irradiance spectrum, they agree with the Langley results within 2% at 6 of 13 SPM wavelengths. The largest disagreement (4.4%) is found for the channel centered at 610 nm. The results of these intercomparisons change significantly when the lamp results are referred to two different extraterrestrial solar irradiance spectra that have become recently available. (C) 1998 Optical Society of America. C1 Univ Bern, Inst Appl Phys, CH-3012 Bern, Switzerland. Univ Arizona, Ctr Opt Sci, Remote Sensing Grp, Tucson, AZ 85721 USA. Phys Meteorol Observ davos, CH-7260 Davos, Switzerland. World Radiat Ctr, CH-7260 Davos, Switzerland. Swiss Ctr Elect & Microtechnol, CH-2007 Neuchatel, Switzerland. RP Schmid, B (reprint author), NASA, Ames Res Ctr, Bay Area Environm Res Inst, MS 245-5, Moffett Field, CA 94035 USA. NR 56 TC 66 Z9 70 U1 0 U2 1 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 JUN 20 PY 1998 VL 37 IS 18 BP 3923 EP 3941 DI 10.1364/AO.37.003923 PG 19 WC Optics SC Optics GA ZT886 UT WOS:000074127900014 PM 18273360 ER PT J AU Haner, DA McGuckin, BT Menzies, RT Bruegge, CJ Duval, V AF Haner, DA McGuckin, BT Menzies, RT Bruegge, CJ Duval, V TI Directional-hemispherical reflectance for Spectralon by integration of its bidirectional reflectance SO APPLIED OPTICS LA English DT Article AB The directional-hemispherical reflectance is obtained for Spectralon, the material chosen for onboard radiometric calibration of the multiangle imaging spectroradiometer, at laser wavelengths of 442, 632.8, and 859.9 nm. With p-and s-polarized incident light and for an angle of incidence of 45 degrees, the bidirectional reflectance distribution function was measured over a polar angle range of 1-85 degrees and a range of azimuthal angles of 0-180 degrees in 10 degrees increments. The resultant directional-hemispherical reflectance is found by integration to be 1.00 +/- 0.01 at 442 nm, 0.953 +/- 0.01 at 632.8 nn, and 0.956 +/- 0.01 at 859.9 nm. The experimental methodology and the data analysis are presented together with a full discussion of the primary experimental errors. (C) 1998 Optical Society of America. C1 Calif State Polytech Univ Pomona, Dept Chem, Pomona, CA 91768 USA. Edinburgh Instruments, Edinburgh, Midlothian, Scotland. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Haner, DA (reprint author), Calif State Polytech Univ Pomona, Dept Chem, Pomona, CA 91768 USA. NR 12 TC 14 Z9 14 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 JUN 20 PY 1998 VL 37 IS 18 BP 3996 EP 3999 DI 10.1364/AO.37.003996 PG 4 WC Optics SC Optics GA ZT886 UT WOS:000074127900024 PM 18273370 ER PT J AU Bohringer, H Tanaka, Y Mushotzky, RF Ikebe, Y Hattori, M AF Bohringer, H Tanaka, Y Mushotzky, RF Ikebe, Y Hattori, M TI An ASCA-ROSAT study of the distant, lensing cluster A 2390 SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE dark matter; gravitational lensing; Galaxies : clusters : individual : A 2390; cooling flows; X-rays : galaxies ID GALAXIES ABELL 2390; X-RAY-ANALYSIS; RICH CLUSTERS; STRAIGHT ARC; MATTER; GAS AB We present the results of a combined study of ASCA and ROSAT observations of the distant cluster Abell 2390. For this cluster gravitational arc as well as weak lensing shear have been previously discovered. We determine the surface brightness profile and the gas density distribution of the cluster from the ROSAT PSPC and HRI data. A combined spatially resolved spectral analysis of the ASCA and ROSAT data show that the temperature distribution of the intracluster medium of A 2390 is consistent with an isothermal temperature distribution in the range 9 to 12 keV except for the central region. Within a radius of 160h(50)(-1) kpc the cooling time is found to be shorter than the Hubble time, implying the presence of a cooling flow. In this central region we find strong evidence for a multi-temperature structure. Detailed analysis of the combined ASCA and ROSAT data yields a self-consistent result for the spectral structure and the surface brightness profile of the cluster with a cooling flow of about 500 - 700 Mo. y(-1) and an age of about 10(10) y. From the constraints on the temperature and density profile of the intracluster gas we determine the gravitational mass profile of the cluster and find a mass of about 2 . 10(15) M. within a radius of 3h(50)(-1) Mpc. A comparison of the projected mass profiles of the cluster shows an excellent agreement between the mass determined from X-ray data and the mass determined from the models for the gravitational are and the weak lensing results. This agreement in this object, as compared to other cases where a larger lensing mass was implied, may probably be due to the fact that A 2390 is more relaxed than most other cases for which gravitational lensing mass and X-ray mass have been compared so far. C1 Max Planck Inst Extraterr Phys, D-85748 Garching, Germany. Inst Space & Astronaut Sci, Kanagawa 229, Japan. NASA, High Energy Astrophys Lab, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Tohoku Univ, Inst Astron, Sendai, Miyagi 980, Japan. RP Bohringer, H (reprint author), Max Planck Inst Extraterr Phys, D-85748 Garching, Germany. NR 42 TC 28 Z9 28 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 JUN 20 PY 1998 VL 334 IS 3 BP 789 EP 798 PG 10 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZY329 UT WOS:000074609500010 ER PT J AU Matt, G Barcaroli, R Belloni, T Beuermann, K Bonnet-Bidaud, JM De Martino, D Done, C Gansicke, BT Guainazzi, M Mouchet, M Mukai, K AF Matt, G Barcaroli, R Belloni, T Beuermann, K Bonnet-Bidaud, JM De Martino, D Done, C Gansicke, BT Guainazzi, M Mouchet, M Mukai, K TI The X-ray emission of the polar BL Hydri SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE stars : novae, cataclysmic variables; X-rays : stars; stars : individual : BL Hydri ID MAGNETIC WHITE-DWARFS; AM-HERCULIS; ACCRETION; RADIATION; SPECTRA; HYI AB We report on the analysis of the ASCA and BeppoSAX X-ray observations of the polar system BL Hyi, per formed in October 94 and September 96, respectively. Emission from both poles is apparent from the folded light curves of both observations; the emission from the second pole varies from cycle to cycle, indicating non-stationary accretion there. The temperature of the post-shock region is estimated to be about 10 keV. Inclusion of both complex absorption and Compton reflection significantly improves the quality of the fit. No soft X-ray component is observed; the BeppoSAX/LECS upper limit to the soft component is in agreement with theoretical expectations for this low magnetic field system. C1 Univ Roma Tre, Dipartimento Fis, I-00146 Roma, Italy. 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 Sternwarte Gottingen, D-37083 Gottingen, Germany. CENS, CEA, DSN, DAPNIA,Serv Astrophys, F-91191 Gif Sur Yvette, France. Osservatorio Astron Capodimonte, I-80131 Naples, Italy. Univ Durham, Dept Phys, Durham DH1 3LE, England. SAX SDC Nuova Telespazio, I-00131 Roma, Italy. Observ Paris, DAEC, Sect Meudon, F-92195 Meudon, France. Univ Dennis Diderot, F-75005 Paris, France. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Matt, G (reprint author), Univ Roma Tre, Dipartimento Fis, Via Vasca Navale 84, I-00146 Roma, Italy. RI Gaensicke, Boris/A-9421-2012; done, chris/D-4605-2016 OI Gaensicke, Boris/0000-0002-2761-3005; done, chris/0000-0002-1065-7239 NR 34 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 0004-6361 J9 ASTRON ASTROPHYS JI Astron. Astrophys. PD JUN 20 PY 1998 VL 334 IS 3 BP 857 EP 862 PG 6 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZY329 UT WOS:000074609500017 ER PT J AU Neuhauser, R Wolk, SJ Torres, G Preibisch, T Stout-Batalha, NM Hatzes, AP Frink, S Wichmann, R Covino, E Alcala, JM Brander, W Walter, FM Sterzik, MF Kohler, R AF Neuhauser, R Wolk, SJ Torres, G Preibisch, T Stout-Batalha, NM Hatzes, AP Frink, S Wichmann, R Covino, E Alcala, JM Brander, W Walter, FM Sterzik, MF Kohler, R TI Optical and X-ray monitoring, Doppler imaging, and space motion of the young star Par 1724 in Orion SO ASTRONOMY & ASTROPHYSICS LA English DT Review DE stars : activity; stars : formation; stars : kinematics; stars : pre-main sequence; stars : individual : Par 1724 ID T-TAURI STARS; MAIN-SEQUENCE EVOLUTION; NEBULA CLUSTER; MEMBERSHIP ANALYSIS; LITHIUM ABUNDANCES; POPULATION STARS; STELLAR-SYSTEMS; PROPER MOTIONS; MASS STARS; V410 TAURI AB We present a detailed study of the young T Tauri star Par 1724, located 15 are min north of the Trapezium cluster in Orion. Our extensive VRI photometric measurements confirm the rotational period to be 5.7 days. Repeated high-resolution spectra show variability in the radial velocity with the same period. A Doppler imaging analysis based on high-S/N high-resolution spectra yields an image showing a pronounced dark feature (spot) at relatively low latitude, which is responsible for most or all of the observed variability. Our high-resolution spectra yield a rotational velocity of v.sin i similar or equal to 71 km s(-1), a surface gravity of log g similar or equal to 3, and a mean heliocentric radial velocity of similar to 23 km s(-1), the latter being consistent with membership to the Orion association. The equivalent width of the lithium 6708 Angstrom line is variable, consistent with rotational modulation. The line is stronger when the spot is on the front side; the lithium abundance observed when the spot is on the back side is consistent with the primordial value. Many ROSAT X-ray observations show that Par 1724 is a strong and variable X-ray source. It has shown one of the most powerful X-ray flares. Our deep infrared imaging at high spatial resolution reveals no physically bound visual companions down to similar to 1 are sec separations and a magnitude difference up to Delta R = 7 mag, and also no companion down to similar to 0.13 arc sec with Delta K = 2.5 mag. We also present the spectral energy distribution of Par 1724 and show that it does not display infrared excess. We estimate the bolometric luminosity to be similar to 49 L., the spectral type to be K0, and the radius to be similar to 9 R.. Although Par 1724 appears to have lost all its circumstellar material, its bolometric luminosity places it very close to the stellar birth-line at an age of only similar to 2.10(5) years, with a mass of similar to 3 M.. According to its present location and 3D space motion (similar to 20 km s(-1) to the north relative to the cluster), Par 1724 may have been ejected from the Trapezium similar to 10(5) yrs ago. We cannot rule out that a close companion is responsible for part of the radial velocity variation, but such a close pair might still have been ejected together depending on the encounter dynamics. Par 1724 appears to be a very young, weak-line run-away T Tauri star moving north relative to the Trapezium, but sharing the Orion radial velocity. C1 Max Planck Inst Extraterr Phys, D-85740 Garching, Germany. Ctr Astrophys, Cambridge, MA 02138 USA. Univ Wurzburg, Astron Inst, D-97074 Wurzburg, Germany. Univ Calif Santa Cruz, Lick Observ, Santa Cruz, CA 95064 USA. Univ Texas, Dept Astron, Austin, TX 78712 USA. Astron Rech Inst, D-69120 Heidelberg, Germany. IUCAA, Poona 411007, Maharashtra, India. Osservatorio Astron Capodimonte, I-80131 Naples, Italy. CALTECH, JPL, IPAC, Pasadena, CA 91125 USA. SUNY Stony Brook, Dept Phys & Astron, Stony Brook, NY 11794 USA. Inst Astron, D-14482 Potsdam, Germany. RP Neuhauser, R (reprint author), Max Planck Inst Extraterr Phys, D-85740 Garching, Germany. EM me@mpe.mpg.de OI Wolk, Scott/0000-0002-0826-9261 NR 119 TC 39 Z9 39 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 JUN 20 PY 1998 VL 334 IS 3 BP 873 EP 894 PG 22 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZY329 UT WOS:000074609500019 ER PT J AU Stecker, FW de Jager, OC AF Stecker, FW de Jager, OC TI Absorption of very high energy gamma-rays by intergalactic infrared radiation: A new determination SO ASTRONOMY & ASTROPHYSICS LA English DT Letter DE gamma-rays : theory; infrared : general; quasars : general; quasars : individual (Markarian 421, Markarian 501) ID FIELDS AB We present a new calculation of the intergalactic gamma-ray pair-production absorption coefficient as a function of both energy and redshift. In reexamining this problem, we make use of a new empirially based calculation (as opposed to previous model calculations) of the intergalactic infrared radiation field (IIRF). We find smaller opacities than those given previously (Stecker & De Jager 1997). We apply our results to the new observations of the flaring gamma-ray spectra of Mrk 421 and Mrk 501, both at a redshift of similar to 0.03. Our new calculations indicate that there should be no significant curvature in the spectra of these sources for energies below 10 TeV, as indicated by recent observations. However, the intrinsic spectra of these sources should be harder by amounts of similar to 0.25 to 0.45 in the spectral index (in the 1-10 TeV range), with an intergalactic absorption cutoff above similar to 20 TeV. C1 NASA, High Energy Astrophys Lab, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Potchefstroom Univ Christian Higher Educ, Dept Phys, Space Res Unit, ZA-2520 Potchefstroom, South Africa. RP Stecker, FW (reprint author), NASA, High Energy Astrophys Lab, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RI Stecker, Floyd/D-3169-2012 NR 21 TC 75 Z9 75 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 JUN 20 PY 1998 VL 334 IS 3 BP L85 EP L87 PG 3 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZY329 UT WOS:000074609500005 ER PT J AU Odenwald, S Newmark, J Smoot, G AF Odenwald, S Newmark, J Smoot, G TI A study of external galaxies detected by the COBE Diffuse Infrared Background Experiment SO ASTROPHYSICAL JOURNAL LA English DT Article DE diffuse radiation; dust, extinction; galaxies, ISM; galaxies, photometry; infrared, galaxies; surveys ID INTERSTELLAR DUST; IRAS OBSERVATIONS; EMISSION; SAMPLE AB A comparison of the COBE1 Diffuse Infrared Background Experiment (DIRBE) all-sky survey with the locations of known galaxies in the IRAS Catalog of Extragalactic Objects and the Center for Astrophysics Catalog of Galaxies led to the detection of as many as 57 galaxies. In this paper, we present the photometric data for these galaxies and an analysis of the seven galaxies that were detected at lambda > 100 mu m. Estimates of the ratio of the mass of the cold dust (CD) component detected at T-d = 20-30 K to a very cold dust (VCD) component with T-d approximate to 10-15 K suggest that between 2%-100% of the cirrus-like CD mass can also exist in many of these galaxies as VCD. In one galaxy, M33, the DIRBE photometry at 240 mu m suggests as much as 26 times as much VCD may be present as compared to the cirrus-like component. Further submillimeter measurements of this galaxy are required to verify such a large population of VCD. We also present 10 galaxies that were detected in the sky region not previously surveyed by IRAS and that can be used to construct a flux-limited all-sky catalog of galaxies brighter than 1000 Jy with a modest completeness limit of about 65%. C1 Raytheon STX, Goddard SFC, Greenbelt, MD 20771 USA. Appl Res Corp, Landover, MD 20785 USA. Univ Calif Berkeley, Lawrence Berkeley Lab, Berkeley, CA 94720 USA. RP Raytheon STX, Goddard SFC, Code 630-0, Greenbelt, MD 20771 USA. NR 37 TC 27 Z9 27 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 JUN 20 PY 1998 VL 500 IS 2 BP 554 EP 568 DI 10.1086/305737 PN 1 PG 15 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZX419 UT WOS:000074513900002 ER PT J AU Tingay, SJ Murphy, DW Edwards, PG AF Tingay, SJ Murphy, DW Edwards, PG TI VLBI observations of southern EGRET identifications. II. VLBA observations and the importance of jet bending in gamma-ray sources SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies, active; galaxies, jets; gamma rays, observations; techniques, interferometric ID EXTRAGALACTIC RADIO-SOURCES; EXTREME SCATTERING EVENT; MILLIARCSECOND STRUCTURE; SUPERLUMINAL MOTION; VLA OBSERVATIONS; COMPLETE SAMPLE; SOURCE CATALOG; QUASARS; BLAZARS; MAPS AB We present VLBI images of six southern hemisphere radio sources that have been identified by EGRET as sources of greater-than-100 MeV gamma-ray emission, PKS 0521-365, PKS 1127-145, PKS 1622-253, PKS 1622-297, PKS 1730-130, and PKS 1908-201. We quantitatively investigate the suggestion of von Montigny et al. that jet bending may be a significant factor affecting the gamma-ray identification of radio-loud fiat-spectrum active galactic nuclei (AGNs), using samples of EGRET-identified and gamma-ray-quiet radio sources. From this investigation, we find evidence to suggest that jet bending properties, as observed in parsec-scale radio jets, are correlated with gamma-ray identification for this class of source. The parsec-scale jets in gamma-ray-quiet AGNs appear to have more and larger bends than do the parsec-scale jets in EGRET-identified AGNs. Caution should be exercised when interpreting these results, however, since we point out that significant, but difficult to quantify, observational biases may also be at work in these samples. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Inst Space & Astronaut Sci, Sagamihara, Kanagawa, Japan. RP Tingay, SJ (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr,MS238-332, Pasadena, CA 91109 USA. EM tingay@hyaa.jpl.nasa.gov; dwm@casa.jpl.nasa.gov; pge@vsop.isas.ac.jp RI Tingay, Steven/B-5271-2013 NR 70 TC 33 Z9 33 U1 1 U2 2 PU UNIV CHICAGO PRESS PI CHICAGO PA 5801 S ELLIS AVENUE, CHICAGO, IL 60637 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD JUN 20 PY 1998 VL 500 IS 2 BP 673 EP 684 DI 10.1086/305759 PN 1 PG 12 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZX419 UT WOS:000074513900013 ER PT J AU Fang, F Shupe, DL Xu, C Hacking, PB AF Fang, F Shupe, DL Xu, C Hacking, PB TI The mid-infrared color-luminosity relation and the local 12 micron luminosity function SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies, luminosity function, mass function; galaxies, photometry; infrared, galaxies ID GALAXY SAMPLE; IRAS GALAXIES; ASTRONOMICAL DATA; REDSHIFT SURVEY; EMISSION; ISOCAM; VELOCITY; FIELD AB We have established a model to systematically estimate the contribution of the mid-IR emission features between 3 and 11.6 mu m to the IRAS in-band fluxes, using the results of Infrared Space Observatory PHT Spectrophotometer observation of 16 galaxies by Lu et al. in 1997. The model is used to estimate more properly the k-corrections for calculating the rest frame 12 and 25 mu m fluxes and luminosities of IRAS galaxies. We have studied the 12-25 mu m color-luminosity relation for a sample of galaxies selected at 25 mu m The color is found to correlate well with the 25 mu m luminosity, the mid-IR luminosity, and the ratio of far-infrared and blue luminosities. The relations with the mid-IR luminosities are more sensitive to different populations of galaxies, while a single relation of the 12-25 mu m color versus the ratio of the far-infrared and blue luminosities applies equally well to these different populations. The luminous and ultraluminous infrared galaxies have redder 12-25 mu m colors than those of the quasars. These relations provide powerful tools to differentiate different populations of galaxies. The local luminosity function at 12 mu m provides the basis for interpreting the results of deep mid-IR surveys planned or in progress with infrared Space Observatory, Wide-Field Infrared Explorer, and Space Infrared Telescope Facility. We have selected a sample of 668 galaxies from the IRAS Faint Source Survey flux density limited at 200 mJy at 12 mu m. A 12 mu m local luminosity function is derived and, for the first time in the literature, effects of density variation in the local universe are considered and corrected in the calculation of the 12 mu m luminosity function. It is also found that the 12 mu m selected sample is dominated by quasars and active galaxies, which therefore strongly affect the 12 mu m luminosity function at high luminosities. The ultraluminous infrared galaxies are relatively rare at 12 mu m compared to a 25 mu m sample. C1 CALTECH 100 22, Jet Prop Lab, Ctr Infrared Proc & Anal, Pasadena, CA 91125 USA. RP Fang, F (reprint author), CALTECH 100 22, Jet Prop Lab, Ctr Infrared Proc & Anal, Pasadena, CA 91125 USA. NR 35 TC 45 Z9 45 U1 2 U2 2 PU UNIV CHICAGO PRESS PI CHICAGO PA 5801 S ELLIS AVENUE, CHICAGO, IL 60637 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD JUN 20 PY 1998 VL 500 IS 2 BP 693 EP 702 DI 10.1086/305761 PN 1 PG 10 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZX419 UT WOS:000074513900015 ER PT J AU Phelps, RL Sakai, S Freedman, WL Madore, BF Saha, A Stetson, PB Kennicutt, RC Mould, JR Ferrarese, L Ford, HC Gibson, BK Graham, JA Han, MS Hoessel, JG Huchra, JP Hughes, SM Illingworth, GD Silbermann, NA AF Phelps, RL Sakai, S Freedman, WL Madore, BF Saha, A Stetson, PB Kennicutt, RC Mould, JR Ferrarese, L Ford, HC Gibson, BK Graham, JA Han, MS Hoessel, JG Huchra, JP Hughes, SM Illingworth, GD Silbermann, NA TI The Hubble Space Telescope Extragalactic Distance Scale Key Project. IX. The discovery of Cepheids in NGC 2090 SO ASTROPHYSICAL JOURNAL LA English DT Article DE Cepheids; galaxies, distances and redshifts; galaxies, individual (NGC 2090); galaxies, photometry ID ABSOLUTE PEAK BRIGHTNESS; NEARBY GALAXIES; CCD PHOTOMETRY; CONSTANT; M100; H(0) AB We report on the discovery of 34 Cepheid variables in NGC 2090, with periods ranging between 5 and 58 days. Apparent V and I period-luminosity relations for Cepheids with P greater than or equal to 10 days have been constructed, assuming a fiducial distance modulus, mu(0), of 18.50 +/- 0.10 mag and a reddening, E(B - V), of 0.10 mag for the Large Magellanic Cloud. Using the ALLFRAME photometry package, an inferred reddening of E(V-I) = 0.09 +/- 0.02 mag (internal error) and a true distance modulus of 30.45 +/- 0.16 (random) +/- 0.16 (systematic) mag for NGC 2090 are found. The corresponding distance is 12.3 +/- 0.9 (random) +/- 0.9 (systematic) Mpc, a value that agrees at the 2.5% level with that derived from an independent analysis using a modified version of the DoPHOT photometry package. C1 Carnegie Inst Washington Observ, Pasadena, CA 91101 USA. CALTECH, IPAC 100 22, Pasadena, CA 91125 USA. Space Telescope Sci Inst, Baltimore, MD 21218 USA. Dominion Astrophys Observ, Victoria, BC V8X 4M6, Canada. Univ Arizona, Steward Observ, Tucson, AZ 85721 USA. Australian Natl Univ, Mt Stromlo & Siding Spring Observ, Inst Adv Studies, Weston, ACT 2611, Australia. Johns Hopkins Univ, Dept Phys & Astron, Baltimore, MD 21218 USA. Carnegie Inst Washington, Dept Terr Magnetism, Washington, DC 20015 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Wisconsin, Dept Astron, Madison, WI 53706 USA. Harvard Smithsonian Ctr Astrophys, Cambridge, MA 02138 USA. Royal Greenwich Observ, Cambridge CB3 0HA, England. Univ Calif Santa Cruz, Lick Observ, Santa Cruz, CA 95064 USA. RP Phelps, RL (reprint author), Carnegie Inst Washington Observ, 813 Santa Barbara St, Pasadena, CA 91101 USA. RI Gibson, Brad/M-3592-2015 OI Gibson, Brad/0000-0003-4446-3130 NR 54 TC 24 Z9 24 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5801 S ELLIS AVENUE, CHICAGO, IL 60637 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD JUN 20 PY 1998 VL 500 IS 2 BP 763 EP 788 DI 10.1086/305766 PN 1 PG 26 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZX419 UT WOS:000074513900020 ER PT J AU Tateyama, CE Kingham, KA Kaufmann, P Piner, BG de Lucena, AMP Botti, LCL AF Tateyama, CE Kingham, KA Kaufmann, P Piner, BG de Lucena, AMP Botti, LCL TI Observations of BL Lacertae from the geodetic VLBI archive of the Washington correlator SO ASTROPHYSICAL JOURNAL LA English DT Article DE BL Lacertae objects, individual (BL Lacertae); galaxies, jets; radio continuum, galaxies; techniques, interferometric ID RELATIVISTIC JETS; RADIO-SOURCES; 3C-345; NUCLEI; MODEL; CORE AB We present maps of BL Lac obtained from geodetic VLBI data from the archive of the Washington correlator. The observations were made from 1996 March to 1996 November, with periods from one experiment to another as short as 1 month. The dominant structure of the maps is given by a superluminal component (C2) moving predominantly at position angle similar to 190 degrees. At the later epochs a new superluminal component (C3) emerges from the core and moves along a trajectory at a higher position angle (200 degrees). We also include maps from observations made in 1995 June and August showing the main component (C2) in the early stages of its evolution, as well as an older component (C1). The position angle of the component C1 is nearly the same as that of the new component C3. The component C2 shows indications of nonradial motion, which is discussed in terms of a helically distorted jet. The best fit was obtained for a half-opening angle of the jet of 2.degrees 6 and an angle of the helical axis to the line of sight of 17 degrees. C1 Univ Sao Paulo, Escola Politecn, Ctr Radio Astron & Aplicacoes Espacias, CRAAE, BR-05424970 Sao Paulo, Brazil. USN Observ, Earth Orientat Dept, Washington, DC 20392 USA. UNICAMP, NUCATE, Ctr Radio Astron & Aplicacoes Espacias, BR-13083592 Campinas, SP, Brazil. Univ Maryland, Dept Astron, College Pk, MD 20742 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. INPE, CRAAE, Radio Observ Espacial Nordeste, Fortaleza, Ceara, Brazil. RP Tateyama, CE (reprint author), Univ Sao Paulo, Escola Politecn, Ctr Radio Astron & Aplicacoes Espacias, CRAAE, CP61548, BR-05424970 Sao Paulo, Brazil. NR 23 TC 22 Z9 22 U1 0 U2 1 PU UNIV CHICAGO PRESS PI CHICAGO PA 5801 S ELLIS AVENUE, CHICAGO, IL 60637 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD JUN 20 PY 1998 VL 500 IS 2 BP 810 EP 815 DI 10.1086/305783 PN 1 PG 6 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZX419 UT WOS:000074513900023 ER PT J AU Harding, AK Muslimov, AG AF Harding, AK Muslimov, AG TI Pulsar X-ray and gamma-ray pulse profiles: Constraint on obliquity and observer angles SO ASTROPHYSICAL JOURNAL LA English DT Article DE gamma rays : theory; pulsars : general; radiation mechanisms : thermal; X-rays : stars ID NEUTRON-STARS; SURFACE-TEMPERATURE; MAGNETIC-FIELD; POLAR CAPS; HOT SPOTS; RADIATION; EMISSION; PSR-0656+14; GAPS AB We model the thermal X-ray profiles of Geminga, Vela, and PSR 0656+14, which have also been detected as gamma-ray pulsars, to constrain the phase space of obliquity and observer angles required to reproduce the observed X-ray pulsed fractions and pulse widths. These geometrical constraints derived from the X-ray light curves are explored for various assumptions about surface temperature distribution and flux anisotropy caused by the magnetized atmosphere. We include curved spacetime effects on photon trajectories and the magnetic field. The observed gamma-ray pulse profiles are double peaked with phase separations of 0.4-0.5 between the peaks. Assuming that the gamma-ray profiles are due to emission in a hollow cone centered on the magnetic pole, we derive the constraints on the phase space of obliquity and observer angles, for different gamma-ray beam sizes, required to produce the observed gamma-ray peak phase separations. We compare the constraints from the X-ray emission to those derived from the observed gamma-ray pulse profiles and find that the overlapping phase space requires both obliquity and observer angles to be smaller than 20 degrees-30 degrees, implying gamma-ray beam opening angles of at most 30 degrees-35 degrees. C1 NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. RP NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Code 661, Greenbelt, MD 20771 USA. EM harding@twinkie.gsfc.nasa.gov; muslimov@lhea1.gsfc.nasa.gov RI Harding, Alice/D-3160-2012 NR 46 TC 24 Z9 24 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 JUN 20 PY 1998 VL 500 IS 2 BP 862 EP 872 DI 10.1086/305763 PN 1 PG 11 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZX419 UT WOS:000074513900029 ER PT J AU Strohmayer, TE Fenimore, EE Murakami, T Yoshida, A AF Strohmayer, TE Fenimore, EE Murakami, T Yoshida, A TI X-ray spectral characteristics of Ginga gamma-ray bursts SO ASTROPHYSICAL JOURNAL LA English DT Article DE gamma rays : bursts; radiation mechanisms : nonthermal; X-rays : bursts ID BATSE OBSERVATIONS; EVOLUTION; SPECTROSCOPY; ABSORPTION; FEATURES; EMISSION; CATALOG; BRIGHT AB We have investigated the spectral characteristics of a sample of bright gamma-ray bursts detected with the gamma-ray burst sensors aboard the satellite Ginga. This instrument employed a proportional and scintillation counter to provide sensitivity to photons in the 2-400 keV region and as such provided a unique opportunity to characterize the largely unexplored X-ray properties of gamma-ray bursts. The photon spectra of the Ginga bursts are well described by a low-energy slope, a bend energy, and a high-energy slope. In the energy range where they can be compared, this result is consistent with burst spectral analyses obtained from the BATSE experiment aboard the Compton Gamma-Ray Observatory. However, below 20 keV we find evidence for a positive spectral number index in approximately 40% of our burst sample, with some evidence for a strong rolloff at lower energies in a few events. There is a correlation (Pearson's r = -0.62) between the low-energy slope and the bend energy. We find that the distribution of spectral bend energies extends below 10 keV. There has been some concern in cosmological models of gamma-ray bursts (GRBs) that the bend energy covers only a small dynamic range. Our result extends the observed dynamic range, and, since we observe bend energies down to the limit of our instrument, perhaps observations have not yet limited the range. The Ginga trigger range was virtually the same as that of BATSE, yet we find a different range of fit parameters. One possible explanation might be that GRBs have two break energies, one often in the 50-500 keV range and the other near 5 keV. Both BATSE and Ginga fit with only a single break energy, so BATSE tends to find breaks near the center of its energy range, and we tend to find breaks in our energy range. The observed ratio of energy emitted in the X-rays relative to the gamma rays can be much larger than a few percent and, in fact, is sometimes larger than unity. The average for our 22 bursts is 24%. We also investigated spectral evolution in two bursts. In these events we find strong evidence for spectral softening as well as a correlation between photon intensity and spectral hardness. We also find that the X-ray signal below 30 keV itself softens in both of these events. There is one example of a strong X-ray excess at low energy. In addition to providing further constraints on gamma-ray burst models, the description provided here of burst spectra down to 2 keV should prove useful to future planned efforts to detect bursts at X-ray energies. C1 Los Alamos Natl Lab, Los Alamos, NM 87545 USA. Inst Space & Astronaut Sci, Kanagawa 229, Japan. RIKEN, Inst Phys & Chem Res, Wako, Saitama 35101, Japan. RP NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Mail Code 666, Greenbelt, MD 20771 USA. EM stroh@pcasrv.gsfc.nasa.gov; efenimore@lanl.gov NR 44 TC 83 Z9 84 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 JUN 20 PY 1998 VL 500 IS 2 BP 873 EP 887 DI 10.1086/305735 PN 1 PG 15 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZX419 UT WOS:000074513900030 ER PT J AU Yaqoob, T AF Yaqoob, T TI Parameter estimation in X-ray astronomy revisited SO ASTROPHYSICAL JOURNAL LA English DT Article DE methods : numerical; methods : statistical; X-rays : general AB The method of obtaining confidence intervals on a subset of the total number of parameters (p) of a model used for fitting X-ray spectra is to perturb the best-fitting model until, for each parameter, a range is found for which the change in the fit statistic is equal to some critical value. This critical value corresponds to the desired confidence level and is obtained from the chi(2) distribution for a degrees of freedom, where q is the number of interesting parameters. With the advent of better energy-resolution detectors, such as those on board ASCA, it has become more common to fit complex models with narrow features, comparable to the instrumental energy resolution. To investigate whether this leads to significant non-Gaussian deviations between data and model, we use simulations based on ASCA data, and we show that the method is still valid in such cases. We also investigate the weak-source limit as well as the case of obtaining upper limits on equivalent widths of weak emission lines and find that, for all practical purposes, the method gives the correct confidence ranges. However, upper limits on emission-line equivalent widths may be overestimated in the extreme Poisson limit. C1 NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. RP Yaqoob, T (reprint author), NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Code 662, Greenbelt, MD 20771 USA. NR 8 TC 17 Z9 17 U1 0 U2 2 PU UNIV CHICAGO PRESS PI CHICAGO PA 5801 S ELLIS AVENUE, CHICAGO, IL 60637 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD JUN 20 PY 1998 VL 500 IS 2 BP 893 EP 898 DI 10.1086/305781 PN 1 PG 6 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZX419 UT WOS:000074513900032 ER PT J AU Krall, J Chen, J Santoro, R Spicer, DS Zalesak, ST Cargill, PJ AF Krall, J Chen, J Santoro, R Spicer, DS Zalesak, ST Cargill, PJ TI Simulation of buoyant flux ropes in a magnetized solar atmosphere SO ASTROPHYSICAL JOURNAL LA English DT Article DE MHD; Sun : atmosphere; Sun : magnetic fields ID CLOUDS; TUBES; EVOLUTION; MAGNETOHYDRODYNAMICS; INSTABILITY; PLASMA; FIELDS; SUN AB Dynamics are investigated for buoyant flux ropes in a gravitationally stratified solar atmosphere using realistic chromosphere and corona parameters. Two-dimensional magnetohydrodynamic simulations of horizontally oriented flux ropes are performed under the approximation that the flux rope remains parallel to the solar surface as it rises. As expected, this motion tends to halt at the chromosphere-corona boundary, where the buoyancy force drops significantly. It is shown that fragmentation of the rising flux rope into multiple flux bundles can be reduced if the flux-rope field lines are sufficiently twisted and that this is consistent with previous results. It is also shown that a weak, vertically oriented ambient magnetic field, (B-a/B-tube)(2) much less than 1, can prevent fragmentation of an untwisted flux tube. A vertical field of sufficient strength, but still "weak," can direct the upward buoyancy-driven flow so that the untwisted flux tube penetrates the chromosphere-corona boundary. C1 USN, Res Lab, Div Plasma Phys, Washington, DC 20375 USA. USN, Res Lab, Washington, DC 20375 USA. NASA, Goddard Space Flight Ctr, Ctr Computat Sci, Greenbelt, MD 20771 USA. Univ London Imperial Coll Sci Technol & Med, London SW7 2BZ, England. RP USN, Res Lab, Div Plasma Phys, Washington, DC 20375 USA. NR 32 TC 17 Z9 17 U1 0 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 JUN 20 PY 1998 VL 500 IS 2 BP 992 EP 1002 DI 10.1086/305754 PN 1 PG 11 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZX419 UT WOS:000074513900041 ER PT J AU Galama, TJ Wijers, RAMJ Bremer, M Groot, PJ Strom, RG De Bruyn, AG Kouveliotou, C Robinson, CR van Paradus, J AF Galama, TJ Wijers, RAMJ Bremer, M Groot, PJ Strom, RG De Bruyn, AG Kouveliotou, C Robinson, CR van Paradus, J TI The 1.4 GHZ light curve of GRB 970508 SO ASTROPHYSICAL JOURNAL LA English DT Article DE gamma rays : bursts; gamma rays : observations; radio continuum : general ID GAMMA-RAY BURST; RADIO COUNTERPART; SEARCH AB We report on Westerbork 1.4 GHz radio observations of the radio counterpart to gamma-ray burst GRB 970508, between 0.80 and 138 days after this event. The 1.4 GHz light curve shows a transition from optically thick to thin emission between 39 and 54 days after the event. We derive the slope p of the spectrum of injected electrons (dN/d gamma(e) proportional to gamma(e)(-p)) in two independent ways, which yield values very close to p = 2.2. This is in agreement with a relativistic dynamically near-adiabatic blast-wave model whose emission is dominated by synchrotron radiation and in which a significant fraction of the electrons cool fast. C1 Univ Amsterdam, Astron Inst Anton Pannekoek, NL-1098 SJ Amsterdam, Netherlands. Ctr High Energy Astrophys, NL-1098 SJ Amsterdam, Netherlands. Univ Cambridge, Inst Astron, Cambridge CB3 0HA, England. Inst Radio Astron Millimetr, F-38406 St Martin Dheres, France. Netherlands Fdn Res Astron, NL-7990 AA Dwingeloo, Netherlands. Kapteyn Astron Inst, NL-9700 AV Groningen, Netherlands. Univ Space Res Assoc, Washington, DC USA. NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. Univ Alabama, Dept Phys, Huntsville, AL 35899 USA. RP Univ Amsterdam, Astron Inst Anton Pannekoek, Kruislaan 403, NL-1098 SJ Amsterdam, Netherlands. RI Galama, Titus/D-1429-2014; Groot, Paul/K-4391-2016; OI Galama, Titus/0000-0002-1036-396X; Groot, Paul/0000-0002-4488-726X; Wijers, Ralph/0000-0002-3101-1808 NR 47 TC 42 Z9 42 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 JUN 20 PY 1998 VL 500 IS 2 BP L101 EP L104 DI 10.1086/311424 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZX422 UT WOS:000074514200007 ER PT J AU Garcia, MR Callanan, PJ Moraru, D McClintock, JE Tollestrup, E Willner, SP Hergenrother, C Robinson, CR Kouveliotou, C van Paradijs, J AF Garcia, MR Callanan, PJ Moraru, D McClintock, JE Tollestrup, E Willner, SP Hergenrother, C Robinson, CR Kouveliotou, C van Paradijs, J TI Power-law decays in the optical counterparts of GRB 970228 and GRB 970508 SO ASTROPHYSICAL JOURNAL LA English DT Article DE gamma rays : bursts ID GAMMA-RAY BURSTS AB We report on R-C- and K-band observations of the optical counterpart to GRB 970508 with the Fred Lawrence Whipple Observatory (FLWO) 1.2 m telescope. Eleven R-C-band observations were obtained on 1997 May 12, and three on May 14. The counterpart clearly faded between the two nights. On May 12 there was no evidence for variability (<9%) on 10-70 minute timescales based on 11 R-c-band observations. On May 19 a 1 hr observation set a limit on the K magnitude of K > 18.6. Comparison of these data points with those obtained by other authors shows that the decay of the optical counterpart can be well fitted by a power law of the form f similar to t(-alpha), where alpha = 1.22 +/- 0.03 with occasional fluctuations superposed. We note that the decay of the optical counterpart to another burst, GRB 970228, can also be well fitted with a power law with exponent alpha = 1.0(-0.5)(+0.2) with occasional fluctuations superposed. These two decay light curves are remarkably similar in form to that predicted by cosmic-fireball models. C1 Ctr Astrophys, Cambridge, MA 02138 USA. Univ Coll, Dept Phys, Cork, Ireland. Univ Arizona, Lunar & Planetary Lab, Tucson, AZ 85721 USA. NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. Univ Space Res Assoc, Huntsville, AL 35812 USA. Univ Amsterdam, Dept Phys, NL-1098 SJ Amsterdam, Netherlands. Univ Alabama, Dept Phys, Huntsville, AL 35899 USA. RP Garcia, MR (reprint author), Ctr Astrophys, 60 Garden St, Cambridge, MA 02138 USA. EM mgarcia@cfa.harvard.edu; paulc@ucc.ie; dmoraru@cfa.harvard.edu; jmcclintock@cfa.harvard.edu; etollestrup@cfa.harvard.edu; swillner@cfa.harvard.edu; chergen@pirl.lpl.arizona.edu; craig.robinson@msfc.nasa.gov; kouveliotou@eagles.msfc.nasa.gov; jvp@astro.uva.nl NR 38 TC 32 Z9 33 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5801 S ELLIS AVENUE, CHICAGO, IL 60637 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD JUN 20 PY 1998 VL 500 IS 2 BP L105 EP L109 DI 10.1086/311403 PN 2 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZX422 UT WOS:000074514200008 ER PT J AU Gates, EI Gyuk, G Holder, GP Turner, MS AF Gates, EI Gyuk, G Holder, GP Turner, MS TI No need for MACHOs in the halo SO ASTROPHYSICAL JOURNAL LA English DT Article DE dark matter; Galaxy : halo; Galaxy : structure ID GALACTIC HALO; DARK-MATTER; BULGE; STARS; MASS AB One interpretation of the more than dozen microlensing events seen in the direction of the LMC is a halo population of 0.5 M. MACHOs that accounts for about half of the mass of the Galaxy. Such an interpretation is not without its problems, and we show that LMC microlensing can be explained by a combination of dark components of the thick disk and spheroid in a viable and detailed model of the Galaxy. In our models, the total mass within 50 kpc is similar to 10(11) M.. about 60% of the value based on halo MACHO models, and the estimate for the lens mass is lower, 0.3 M. versus 0.5 M.. The chemical evolution problems associated with the MACHO progenitors are not resolved. However, since the MACHO distribution does not trace the l/r(2) dark halo, which extends significantly beyond 50 kpc, the total baryon mass fraction of the Galaxy is reduced considerably, which lessens the problem. C1 Adler Planetarium & Astron Museum, Chicago, IL 60605 USA. Univ Chicago, Ctr Astron & Astrophys, Chicago, IL 60637 USA. SISSA, I-34014 Trieste, Italy. Univ Chicago, Enrico Fermi Inst, Dept Phys, Chicago, IL 60637 USA. NASA, Fermilab Astrophys Ctr, Fermi Natl Accelerator Lab, Batavia, IL 60510 USA. RP Gates, EI (reprint author), Adler Planetarium & Astron Museum, Chicago, IL 60605 USA. NR 30 TC 13 Z9 13 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5801 S ELLIS AVENUE, CHICAGO, IL 60637 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD JUN 20 PY 1998 VL 500 IS 2 BP L145 EP L148 DI 10.1086/311406 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZX422 UT WOS:000074514200016 ER PT J AU Lingenfelter, RE Ramaty, R Kozlovsky, B AF Lingenfelter, RE Ramaty, R Kozlovsky, B TI Supernova grains: The source of cosmic-ray metals SO ASTROPHYSICAL JOURNAL LA English DT Article DE cosmic rays; dust, extinction; Galaxy : abundances; Galaxy : evolution; supernovae : general ID LIGHT-ELEMENTS; EVOLUTION; STARS; EMISSION; SN-1987A; NUCLEI; ORIGIN; 1987A; RATES AB We show that the Be abundances in old halo stars formed in the early Galaxy strongly suggest that the refractory cosmic-ray metals, in both the early Galaxy and the present epoch, are accelerated from fresh supernova ejecta rather than from the interstellar medium, as proposed in most current models. To resolve this problem, we suggest that the high-velocity grains formed in supernova ejecta are the injection source for these cosmic rays, including C and O. We show how this cosmic-ray injection source can refute previous arguments against cosmic-ray acceleration from fresh supernova ejecta: the enrichment of the highly refractory elements relative to the volatiles and the similarity of the refractory cosmic-ray source and solar elemental and isotopic abundance ratios. We also show that the cosmic-ray source O abundance may be the direct consequence of the condensation of O as refractory oxides and that the problematic cosmic-ray C-to-O ratio may be understood if a large fraction of the C in the ejecta is in graphite grains. We further show that if the refractory metals are accelerated from fresh ejects, the cosmic-ray source (54)Fe/(56)Fe should be higher than the corresponding solar value. Such a difference is apparent in some recent cosmic-ray measurements, but forthcoming Advanced Composition Explorer results are needed to confirm this finding. C1 Univ Calif San Diego, Ctr Astrophys & Space Sci, La Jolla, CA 92093 USA. NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. Tel Aviv Univ, Sch Phys & Astron, IL-69978 Tel Aviv, Israel. RP Lingenfelter, RE (reprint author), Univ Calif San Diego, Ctr Astrophys & Space Sci, 9500 Gilman Dr, La Jolla, CA 92093 USA. EM rlingenfelter@ucsd.edu; ramaty@gsfc.nasa.gov; benz@wise.tau.ac.il NR 48 TC 42 Z9 42 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 JUN 20 PY 1998 VL 500 IS 2 BP L153 EP L156 DI 10.1086/311402 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZX422 UT WOS:000074514200018 ER PT J AU Zhang, W Strohmayer, TE Swank, JH AF Zhang, W Strohmayer, TE Swank, JH TI Discovery of two simultaneous kilohertz quasi-periodic oscillations in the persistent flux of GX 349+2 SO ASTROPHYSICAL JOURNAL LA English DT Article DE accretion, accretion disks; stars : individual (GX 349+2); stars : neutron; X-rays : stars AB We report the discovery of two simultaneous quasi-periodic oscillations in the persistent flux of GX 349+2 at frequencies 712 +/- 9 and 978 +/- 9 Hz, with rms amplitudes 1.25% +/- 0.34% and 1.34% +/- 0.32%, respectively. During our 152 ks observation with the Rossi X-ray Timing Explorer, GX 342 + 2 was in either the normal branch or the flaring branch with count rates in the nominal 2-60 keV RXTE-PCA band ranging from a low of 8000 counts s(-1) to a high of 15,000 counts s(-1). The kHz QPOs were observed only when the source was at the top of the normal branch, when the count rate was about 8200 counts s(-1) corresponding to a flux of 1.4 x 10(-8) ergs cm(-1) s(-1) in the 2-10 keV band. With this report, now kHz QPOs have been observed in all six Z sources. C1 NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. Univ Space Res Assoc, Washington, DC USA. RP Zhang, W (reprint author), NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. RI Swank, Jean/F-2693-2012 NR 7 TC 27 Z9 27 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5801 S ELLIS AVENUE, CHICAGO, IL 60637 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD JUN 20 PY 1998 VL 500 IS 2 BP L167 EP L169 DI 10.1086/311423 PN 2 PG 3 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZX422 UT WOS:000074514200021 ER PT J AU Zhang, W Smale, AP Strohmayer, TE Swank, JH AF Zhang, W Smale, AP Strohmayer, TE Swank, JH TI Correlation between energy spectral states and fast time variability and further evidence for the marginally stable orbit in 4U 1820-30 SO ASTROPHYSICAL JOURNAL LA English DT Article DE accretion, accretion disks; stars : individual (4U 1820-30); stars : neutron; X-rays : stars ID X-RAY BINARIES; DISCOVERY; GX5-1 AB We report the results from a long-term monitoring data set obtained with the Rossi X-Ray Timing Explorer (RXTE) from the bright globular cluster binary source 4U 1820-30. During this monitoring, the source flux varied from 2.9 x 10(-9) to 8.5 x 10(-9) ergs cm(-2) s-(1) in the 2-10 keV band, which correspond to, respectively, count rates of 1600 and 4500 counts s(-1) in the nominal 2-60 keV RXTE proportional counter array band. Its energy spectral state was observed to encompass both the banana branches and the island state. Kilohertz quasiperiodic oscillations (kHz QPOs) were observed to exist in the upper banana and lower banana branches, as well as in the island state. In particular, we report that the kHz QPOs were present only when the soft color (defined as the flux ratio of the 3.9-5.0 keV band to the 1.7-3.9 keV band) was below 0.78 without regard to the overall count rate and without regard to whether the source is in any one of the three branches or states. Their centroid frequency was well correlated with the overall count rate below 2500 counts s(-1). When the count rate was above 2500 counts s(-1), the QPO frequency was consistent with a constant independent of the overall count rate. We take this as further evidence that the inner edge of the accretion had reached the marginally stable orbit, and therefore the constant 1060 +/ 20 Hz is the marginally stable orbit frequency. C1 NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. RP Zhang, W (reprint author), NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. RI Swank, Jean/F-2693-2012 NR 20 TC 135 Z9 136 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5801 S ELLIS AVENUE, CHICAGO, IL 60637 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD JUN 20 PY 1998 VL 500 IS 2 BP L171 EP L174 DI 10.1086/311418 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZX422 UT WOS:000074514200022 ER PT J AU Ricaud, P Monnier, E Goutail, F Pommereau, JP David, C Godin, S Froidevaux, L Waters, JW Mergenthaler, J Roche, AE Pumphrey, H Chipperfield, MP AF Ricaud, P Monnier, E Goutail, F Pommereau, JP David, C Godin, S Froidevaux, L Waters, JW Mergenthaler, J Roche, AE Pumphrey, H Chipperfield, MP TI Stratosphere over Dumont d'Urville, Antarctica, in winter 1992 SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID ATMOSPHERE RESEARCH SATELLITE; MICROWAVE LIMB SOUNDER; NITRIC-ACID TRIHYDRATE; NITROGEN-DIOXIDE; INTERHEMISPHERIC DIFFERENCES; VOLCANIC AEROSOL; OZONE; CLOUDS; UARS; DISTRIBUTIONS AB We present an analysis of the temporal evolution of stratospheric constituents above the station of Dumont d'Urviile in Antarctica (67 degrees S, 140 degrees E) from August 14 to September 20, 1992. Data sets include temperature profiles and H2O, ClO, O-3, NO2, ClONO2, HNO3, N2O, and CH4 mixing ratios and aerosol extinction coefficients from 46 to 1 hPa measured by the Microwave Limb Sounder (MLS) and the Cryogenic Limb Array Etalon Spectrometer (CLAES) instruments aboard the Upper Atmosphere Research Satellite (UARS). At the station, aerosol extinction coefficients and O-3 profiles are obtained by a lidar together with O-3 profiles provided by sondes. Integrated O-3 and NO2 column amounts are given by a Systeme d'Analyse par Observation Zenithale (SAOZ) spectrometer located at the station. Column O-3 is also provided by the Total Ozone Mapping Spectrometer (TOMS) instrument aboard the NIMBUS 7 satellite, complemented with potential vorticity derived from the U.K. Meteorological Office assimilated data set and temperature fields provided by the European Centre for Medium-Range Weather Forecasts. Time evolution of these measurements is interpreted by comparison with results from the SLIMCAT three-dimensional chemical transport model. We show that the site is near the vortex edge on average and is alternately inside the Vortex or just outside in the region referred to as the "collar" region. There are no observations of polar stratospheric clouds (PSCs) over the station above 46 hPa (similar to 18 km). In fact, PSCs mainly appear over the Palmer Peninsula area at 46 hPa. The rates of change of chemical species are evaluated at 46 hPa when the station is conservatively inside tho vortex collar region. The ozone loss rate is 0.04 ppmv d(-1) (similar to 1.3% d(-1)), which is consistent with other analyses of southern vortex ozone loss rates; chlorine monoxide tends to decrease by 0.03 ppbv d(-1), while chlorine nitrate increases by 0.025 ppGv d(-1). These negative ClO and positive ClONO2 trends are only observed in the collar region of the vortex where 03 amounts are far from near zero, and little denitrification is observed. Loss and production rates as measured by UARS are more pronounced than the ones deduced from the SLIMCAT model, probably because of the moderate model horizontal resolution (3.75 degrees x 3.75 degrees) which is not high enough to resolve the vortex crossings above Dumont d'Urville and which leads to a larger extent of denitrified air than indicated by the UARS data. The analysis also shows activated ClO inside the vortex at 46 hPa, a dehydrated vortex at 46 hPa, and rehydrated above, with no trace of denitrification in the lower stratosphere. Good agreement between coincident measurements of 03 profiles by UARS/MLS, lidar, and sondes is also observed. Finally, the agreement between UARS and SLIMCAT data sets is much better in the middle stratosphere (4.6 hPa) than in the lower stratosphere (46 hPa). C1 Observ Bordeaux, INSU, CNRS, F-33270 Floirac, France. Univ Jussieu, CNRS, Serv Aeron, INSU, F-75252 Paris 05, France. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. CNRS, Serv Aeron, INSU, F-91371 Verrieres Le Buisson, France. Univ Edinburgh, Dept Meteorol, Edinburgh EH9 3JZ, Midlothian, Scotland. Lockheed Martin Adv Technol Ctr, Palo Alto, CA 94304 USA. Univ Cambridge, Dept Chem, Cambridge CB2 1EW, England. RP Ricaud, P (reprint author), Observ Bordeaux, INSU, CNRS, BP 89, F-33270 Floirac, France. EM ricaud@observ.u-bordeaux.fr RI Chipperfield, Martyn/H-6359-2013 OI Chipperfield, Martyn/0000-0002-6803-4149 NR 41 TC 5 Z9 5 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 JUN 20 PY 1998 VL 103 IS D11 BP 13267 EP 13284 DI 10.1029/98JD00689 PG 18 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA ZV631 UT WOS:000074325200015 ER PT J AU Santee, ML Tabazadeh, A Manney, GL Salawitch, RJ Froidevaux, L Read, WG Waters, JW AF Santee, ML Tabazadeh, A Manney, GL Salawitch, RJ Froidevaux, L Read, WG Waters, JW TI UARS Microwave Limb Sounder HNO3 observations: Implications for Antarctic polar stratospheric clouds SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID ATMOSPHERE RESEARCH SATELLITE; NITRIC-ACID CONDENSATION; AIRBORNE LIDAR; SULFURIC-ACID; SULFATE AEROSOLS; OZONE DEPLETION; TEMPERATURE-FLUCTUATIONS; ARCTIC STRATOSPHERE; MIDDLE ATMOSPHERE; PHYSICAL STATE AB We present Microwave Limb Sounder (MLS) measurements of gas-phase HNO3 obtained at the beginning of five southern hemisphere winters: 1992-1996. To investigate the composition of the polar stratospheric clouds (PSCs) that formed in early winter each year, the observed evolution of HNO3 at 465 K is compared against that predicted using nitric acid trihydrate (NAT), nitric acid dihydrate (NAD), and liquid ternary solution models of PSC formation and correlated with temperature histories from three-dimensional back trajectory calculations. The MLS HNO3 observations suggest that the initial composition of PSCs depends on the physical state of the background sulfate aerosols. If the preexisting aerosols are liquid, then the formation of ternary solutions is initiated as the temperature drops below about 192 K, followed by a gradual conversion to NAD after exposure to low temperatures for several days. HNO3 uptake into ternary solutions occurs at higher temperatures, and the conversion to NAD is delayed, under conditions of enhanced aerosol loading from the Mount Pinatubo eruption. If a majority of the background aerosols are frozen, the growth of ternary solutions is inhibited, but formation of a metastable, water-rich, KNO3-containing solid phase characterized by a relatively high HNO3 vapor pressure (type Ic PSC) may occur. In general, MLS HNO3 measurements obtained during early southern winter indicate a strong correspondence between the area of gas-phase HNO3 loss and the area of temperatures below 192 K but only a weak correspondence between the area of gas-phase HNO3 loss and the area of temperatures below 195 K, the value commonly assumed as the threshold for PSC formation. Although temperatures were low enough to maintain NAT PSCs, the MLS data show that they were not forming, at least not over spatial scales comparable to or larger than the similar to 400 x 100 x 5 km MLS field of view. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Santee, ML (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr,Mail Stop 183-701, Pasadena, CA 91109 USA. EM mls@mls.jpl.nasa.gov; taba@sky.arc.nasa.gov RI Salawitch, Ross/B-4605-2009 OI Salawitch, Ross/0000-0001-8597-5832 NR 90 TC 45 Z9 45 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 JUN 20 PY 1998 VL 103 IS D11 BP 13285 EP 13313 DI 10.1029/98JD00365 PG 29 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA ZV631 UT WOS:000074325200016 ER PT J AU Hall, TM Waugh, DW AF Hall, TM Waugh, DW TI Influence of nonlocal chemistry on tracer distributions: Inferring the mean age of air from SF6 SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID STRATOSPHERIC AIR; CARBON-DIOXIDE; TRANSPORT; TROPOSPHERE AB Sulfur hexafluoride (SF6) is nearly inert in the troposphere and stratosphere and has a documented, steady increase in the troposphere due to industrial sources, making it a useful tracer of atmospheric circulation. Studies using SF6 to estimate the mean age of stratospheric air have assumed the influence of mesospheric photochemical destruction is negligible. However, the mean age of an air parcel may be sensitive tp small fractions, of the air that have resided for long times in the upper atmosphere. Here we use two three-dimensional chemical transport models to estimate the influence of mesospheric SF6 loss on mean age inferences in the stratosphere. Because the mechanisms of SF6 loss are uncertain, we perform a number of simulations employing a range of magnitudes of a simple constant mesospheric loss frequency, as well as a range of scenarios for SF6 time variation in the troposphere. Using loss rates producing plausible global Lifetimes of SF6 (1000 to 3000 years), and tropospheric time-variation matching: observations, we find that age; estimates inferred from SF6 mixing ratios may be significantly biased and that the bias is increasing in time. For example, the present-day time lag of SF6 mixing ratio from the troposphere overestimates the mean age by up to 18% at 68 degrees S and 20 km, and up to 65% at 68 degrees S and 30 km, depending on the loss rate and model. Correcting for this bias would bring recent comparisons of modeled and measured mean age closer in line. C1 NASA, Goddard Inst Space Studies, New York, NY 10025 USA. Monash Univ, Cooperat Res Ctr So Hemisphere Meteorol, Clayton, Vic 3168, Australia. RP Hall, TM (reprint author), NASA, Goddard Inst Space Studies, 2880 Broadway, New York, NY 10025 USA. EM thall@giss.nasa.gov; waugh@jhu.edu RI Waugh, Darryn/K-3688-2016 OI Waugh, Darryn/0000-0001-7692-2798 NR 19 TC 24 Z9 24 U1 1 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 JUN 20 PY 1998 VL 103 IS D11 BP 13327 EP 13336 DI 10.1029/98JD00170 PG 10 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA ZV631 UT WOS:000074325200018 ER PT J AU Sandor, BJ Clancy, RT AF Sandor, BJ Clancy, RT TI Mesospheric HOx chemistry from diurnal microwave observations of HO2, O-3, and H2O SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID SATELLITE MEASUREMENTS; UPPER-STRATOSPHERE; MIDDLE ATMOSPHERE; LIMB SOUNDER; OZONE; OH; PHOTOCHEMISTRY; EXPLORER; SPECTROMETER; PROFILES AB Microwave (lambda similar to 1.2 mm) spectral emission line observations of HO2, O-3, and (H2O)-O-18 from the upper stratosphere and mesosphere (45-80 km) were obtained in April 1992, January 1993, and April and December 1996, using the Kitt Peak National Radio Astronomy Observatory (NRAO). Significant improvements to this, the only method for making mesospheric HO2 measurements, have been made with hardware upgrades allowing observation of a stronger emission line than described in previous work. Data analysis has been improved by (1) recalibration of the (primarily astronomical) instrument for atmospheric studies, (2) incorporation of updated laboratory spectroscopic work, and (3) use of an improved photochemical model. Diurnal HO2 data analyses employing 30 min to 2 hour observations show measured HO2 abundances at 50-80 km altitude are 23-47% higher than photochemical model values at mid day, agree with model values prior to 0900 local time (LT), and exceed model mixing ratios by 70-100% immediately after sunset. Coordinated diurnal measurements of mesospheric O-3 find a model O-3 deficit consistent with model underprediction of ozone seen in all comparable data sets. HOa observations are critical to understanding mesospheric chemistry, in that simultaneous model underpredictions of this ozone-destroying species and of ozone place stringent constraints on proposed sources of model error. The ozone model deficit and 0900-1800 HO2 model deficit are simultaneously resolved with a 40% reduction in the rate coefficient k(HO2 + O --> OH + O-2) We review other modeling studies of this rate change, indicating it has negligible effect in the lower stratosphere and improves a diverse set of model results from the upper stratosphere to mesopause. C1 Space Sci Inst, Boulder, CO 80303 USA. CALTECH, Jet Prop Lab, Pasadena, CA USA. RP Sandor, BJ (reprint author), Natl Ctr Atmospher Res, Div Atmospher Chem, Natl Ctr Atmospher Res, POB 3000, Boulder, CO 80307 USA. EM sandor@acd.ucar.edu; clancy@isidis.colorado.edu NR 47 TC 21 Z9 22 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 JUN 20 PY 1998 VL 103 IS D11 BP 13337 EP 13351 DI 10.1029/98JD00432 PG 15 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA ZV631 UT WOS:000074325200019 ER PT J AU Smith, GD Jaffe, RL Yoon, DY AF Smith, GD Jaffe, RL Yoon, DY TI Conformations of 1,2-dimethoxypropane and 5-methoxy-1,3-dioxane: are ab initio quantum chemistry predictions accurate? SO CHEMICAL PHYSICS LETTERS LA English DT Article ID ELECTRONIC-STRUCTURE CALCULATIONS; MOLECULAR-DYNAMICS SIMULATIONS; MODEL MOLECULES; FORCE-FIELD; GAS-PHASE; POLY(OXYETHYLENE) AB High-level ab initio quantum chemistry calculations are shown to predict conformer populations of 1,2-dimethoxypropane and 5-methoxy-1,3-dioxane that are consistent with gas-phase NMR vicinal coupling constant measurements. The conformational energies of the cyclic ether 5-methoxy-1,3-dioxane are found to be consistent with those predicted by a rotational isomeric state (RIS) model based upon the acyclic analog 1,2-dimethosypropane. The quantum chemistry and RIS calculations indicate the presence of strong attractive 1,5 C(H-3)...O electrostatic interactions in these molecules, similar to those found in 1,2-dimethoxyethane. (C) 1998 Published by Elsevier Science B.V. All rights reserved. C1 Univ Utah, Dept Mat Sci & Engn, Salt Lake City, UT 84112 USA. Univ Utah, Dept Chem & Fuels Engn, Salt Lake City, UT 84112 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. IBM Corp, Almaden Res Ctr, San Jose, CA 95120 USA. RP Smith, GD (reprint author), Univ Utah, Dept Mat Sci & Engn, Salt Lake City, UT 84112 USA. NR 23 TC 7 Z9 7 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 JUN 19 PY 1998 VL 289 IS 5-6 BP 480 EP 486 DI 10.1016/S0009-2614(98)00482-5 PG 7 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA ZW236 UT WOS:000074389300010 ER PT J AU Rumsey, CL Biedron, RT Farassat, F Spence, PL AF Rumsey, CL Biedron, RT Farassat, F Spence, PL TI Ducted-fan engine acoustic predictions using a Navier-Stokes code SO JOURNAL OF SOUND AND VIBRATION LA English DT Article ID COMPUTATIONS AB A Navier-Stokes computer code is used to predict one of the ducted-fan engine acoustic modes that results from rotor-wake/stator-blade interaction. A patched sliding-zone interface is employed to pass information between the moving rotor row and the stationary stator row. The code produces averaged aerodynamic results downstream of the rotor that agree well with a widely used average-passage code. The acoustic mode of interest is generated successfully by the code and is propagated well upstream of the rotor; temporal and spatial numerical resolution are fine enough such that attenuation of the signal is small. Two acoustic codes are used to find the far-field noise. Near-field propagation is computed by using Eversman's wave envelope code, which is based on a finite-element model. Propagation to the far field is accomplished by using the Kirchhoff formula for moving surfaces with the results of the wave envelope code as input data. Comparison of measured and computed far-field noise levels show fair agreement in the range of directivity angles where the peak radiation lobes from the inlet are observed. Although only a single acoustic mode is targeted in this study, the main conclusion is a proof-of-concept: Navier-Stokes codes can be used both to generate and propagate rotor-stator acoustic modes forward through an engine, where the results can be coupled to other far-field noise prediction codes. (C) 1998 Academic Press Limited. C1 NASA, Fluid Mech & Acoust Div, Langley Res Ctr, Hampton, VA 23681 USA. Lockheed Martin Engn & Sci Co, Hampton, VA USA. RP Rumsey, CL (reprint author), NASA, Fluid Mech & Acoust Div, Langley Res Ctr, Hampton, VA 23681 USA. NR 36 TC 34 Z9 36 U1 0 U2 3 PU ACADEMIC PRESS LTD PI LONDON PA 24-28 OVAL RD, LONDON NW1 7DX, ENGLAND SN 0022-460X J9 J SOUND VIB JI J. Sound Vibr. PD JUN 18 PY 1998 VL 213 IS 4 BP 643 EP 664 DI 10.1006/jsvi.1998.1519 PG 22 WC Acoustics; Engineering, Mechanical; Mechanics SC Acoustics; Engineering; Mechanics GA ZZ896 UT WOS:000074780400004 ER PT J AU Wasfy, TM Noor, AK AF Wasfy, TM Noor, AK TI Application of fuzzy sets to transient analysis of space structures SO FINITE ELEMENTS IN ANALYSIS AND DESIGN LA English DT Article DE fuzzy set theory; precision structures; deployable structures; space structures; structural dynamics; Coulomb friction; latch joints ID ELEMENT AB An application of fuzzy sets, in conjunction with finite elements, to the transient analysis of a precision-deployable space structure is presented. The structural members are modeled by using beam finite elements, and the structure's latch joint is modeled by using a spring-damper-Coulomb friction element. Two types of transient response simulations are performed: slow transient load-deflection response and transient impulse response. The first simulation is used to evaluate the stiffness and buckling loads at the structure's tip. The second simulation is used to evaluate the structure's natural frequencies, mode shapes and the precision of the final shape. For each simulation the possibility distributions of various response quantities are obtained. Fuzzy sets are used to represent three beam properties, namely: damping coefficient, bending stiffness, and axial stiffness; as well as two joint parameters: Coulomb friction force and damping coefficient. Fuzzy set techniques provide an insight into the range of possible responses associated with the combined selected variations in the system parameters. (C) 1998 Elsevier Science B.V. All rights reserved. C1 Univ Virginia, NASA, Langley Res Ctr, Ctr Adv Computat Technol, Hampton, VA 23681 USA. RP Noor, AK (reprint author), Univ Virginia, NASA, Langley Res Ctr, Ctr Adv Computat Technol, Mail Stop 201, Hampton, VA 23681 USA. NR 20 TC 21 Z9 22 U1 1 U2 4 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0168-874X J9 FINITE ELEM ANAL DES JI Finite Elem. Anal. Des. PD JUN 15 PY 1998 VL 29 IS 3-4 BP 153 EP 171 DI 10.1016/S0168-874X(98)00006-7 PG 19 WC Mathematics, Applied; Mechanics SC Mathematics; Mechanics GA ZZ214 UT WOS:000074707000001 ER PT J AU Carlson, CW Pfaff, RF Watzin, JG AF Carlson, CW Pfaff, RF Watzin, JG TI The Fast Auroral SnapshoT (FAST) mission SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID ALIGNED ELECTRON FLUX; FLICKERING AURORA; WAVES AB The FAST satellite mission investigates plasma processes occurring in the low altitude auroral acceleration region, where magnetic field-aligned currents couple global magnetospheric current systems to the high latitude ionosphere. In the transition region between the hot tenuous magnetospheric plasma and the cold, dense ionosphere, these currents give rise to parallel electric fields, particle beams, plasma heating, and a host of wave-particle interactions. FAST instruments provide observations of plasma particles and fields in this region, with excellent temporal and spatial resolution combined with high quantitative accuracy. The spacecraft data system performs onboard evaluation of the measurements to select data "snapshots" that are stored for later transmission to the ground. New measurements from FAST show that upward and downward current regions in the auroral zone have complementary field and particle features defined by upward and downward directed parallel electric field structures and corresponding electron and ion beams. Direct measurements of wave particle interactions have led to several discoveries, including Debye-scale electric solitary waves associated with the acceleration of upgoing electron beams and ion heating, and the identification of electrons modulated by ion cyclotron waves as the source of flickering aurora. Detailed quantitative measurements of plasma density, plasma waves, and electron distributions associated with auroral kilometric radiation source regions yield a consistent explanation for AKR wave generation. C1 Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Carlson, CW (reprint author), Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA. RI Pfaff, Robert/F-5703-2012 OI Pfaff, Robert/0000-0002-4881-9715 NR 8 TC 201 Z9 205 U1 0 U2 4 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 JUN 15 PY 1998 VL 25 IS 12 BP 2013 EP 2016 DI 10.1029/98GL01592 PG 4 WC Geosciences, Multidisciplinary SC Geology GA ZV204 UT WOS:000074280800001 ER PT J AU Carlson, CW McFadden, JP Ergun, RE Temerin, M Peria, W Mozer, FS Klumpar, DM Shelley, EG Peterson, WK Moebius, E Elphic, R Strangeway, R Cattell, C Pfaff, R AF Carlson, CW McFadden, JP Ergun, RE Temerin, M Peria, W Mozer, FS Klumpar, DM Shelley, EG Peterson, WK Moebius, E Elphic, R Strangeway, R Cattell, C Pfaff, R TI FAST observations in the downward auroral current region: Energetic upgoing electron beams, parallel potential drops, and ion heating SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID BIRKELAND CURRENTS; SHOCKS; MAGNETOSPHERE; FIELDS AB Observations of plasma particles and fields by the FAST satellite find evidence of acceleration of intense upgoing electron beams by quasi-static parallel electric fields. The beam characteristics include a broad energy spectrum with peak energies between 100 eV and 5 keV, perpendicular temperatures less than 1 eV, and fluxes greater than 10(9)/cm(2)sec. Diverging electrostatic shocks associated with the beams have integrated potentials that match the beam energy. These beams are found in regions of downward Birkeland current and account for the total field-aligned current when they are present. The most energetic ion conics in the auroral zone are found coincident with these beams, in agreement with the model for "trapped" conics. The measured particle densities of the electron beams and associated ion conics are approximately equal and typically range from 1 to 10 cm(-3), with no evidence for additional cold density. The beams are seen frequently at altitudes between 2000 and 4000 km in the winter auroral zone. Their probability of occurrence has a strong dependence on season and altitude and is similar to that for upgoing ion beams in the adjacent upward current regions. This similarity suggests that the density and scale height of ionospheric ions play an important role in the formation of both types of beams. C1 Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA. Lockheed Palo Alto Res Labs, Palo Alto, CA 94304 USA. Univ New Hampshire, Durham, NH 03824 USA. Univ Calif Los Alamos Natl Lab, Los Alamos, NM 87545 USA. Univ Calif Los Angeles, IGPP, Los Angeles, CA 90095 USA. Univ Minnesota, Tate Lab Phys, Minneapolis, MN 55455 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Carlson, CW (reprint author), Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA. RI Pfaff, Robert/F-5703-2012; Peterson, WK/A-8706-2009; OI Pfaff, Robert/0000-0002-4881-9715; Peterson, WK/0000-0002-1513-6096; Moebius, Eberhard/0000-0002-2745-6978; Cattell, Cynthia/0000-0002-3805-320X NR 19 TC 221 Z9 220 U1 0 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 JUN 15 PY 1998 VL 25 IS 12 BP 2017 EP 2020 DI 10.1029/98GL00851 PG 4 WC Geosciences, Multidisciplinary SC Geology GA ZV204 UT WOS:000074280800002 ER PT J AU McFadden, JP Carlson, CW Ergun, RE Mozer, FS Temerin, M Peria, W Klumpar, DM Shelley, EG Peterson, WK Moebius, E Kistler, L Elphic, R Strangeway, R Cattell, C Pfaff, R AF McFadden, JP Carlson, CW Ergun, RE Mozer, FS Temerin, M Peria, W Klumpar, DM Shelley, EG Peterson, WK Moebius, E Kistler, L Elphic, R Strangeway, R Cattell, C Pfaff, R TI Spatial structure and gradients of ion beams observed by FAST SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID ELECTROSTATIC SHOCKS; DISTRIBUTIONS; ALTITUDE; ACCELERATION AB High time resolution measurements of ion distributions by the FAST satellite have revealed kilometer scale spatial structure in the low altitude auroral acceleration region. The low altitude edge of the acceleration region appears to contain fingers of potential that extend hundreds of kilometers along B but are only a few to tens of kilometers wide. These fingers of potential do not appear to be strongly correlated with the local current or total potential drop. Gradients in the ion beam energy are found to be consistent with the electric field signatures expected in the quasi-static potential drop model of auroral acceleration. Typical ion beams show gradients of 0.5-1.0 keV/km, with some events as large a 3 keV/km. Integrations of the electric field along the spacecraft velocity are used to calculate parallel potential below FAST and are found to agree well with the ion beam energy for most events. One event is shown where an apparent temporal change in the auroral configuration occurs at the edge of the ion beam producing a disagreement between the beam energy and inferred potential. C1 Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA. Lockheed Palo Alto Res Labs, Palo Alto, CA 94304 USA. Univ New Hampshire, Durham, NH 03824 USA. Univ Calif Los Alamos Natl Lab, Los Alamos, NM 87545 USA. Univ Calif Los Angeles, Los Angeles, CA 90095 USA. Univ Minnesota, Minneapolis, MN 55455 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP McFadden, JP (reprint author), Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA. RI Pfaff, Robert/F-5703-2012; Peterson, WK/A-8706-2009; OI Pfaff, Robert/0000-0002-4881-9715; Peterson, WK/0000-0002-1513-6096; Moebius, Eberhard/0000-0002-2745-6978; Cattell, Cynthia/0000-0002-3805-320X NR 13 TC 63 Z9 63 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 JUN 15 PY 1998 VL 25 IS 12 BP 2021 EP 2024 DI 10.1029/98GL00648 PG 4 WC Geosciences, Multidisciplinary SC Geology GA ZV204 UT WOS:000074280800003 ER PT J AU Ergun, RE Carlson, CW McFadden, JP Mozer, FS Delory, GT Peria, W Chaston, CC Temerin, M Elphic, R Strangeway, R Pfaff, R Cattell, CA Klumpar, D Shelley, E Peterson, W Moebius, E Kistler, L AF Ergun, RE Carlson, CW McFadden, JP Mozer, FS Delory, GT Peria, W Chaston, CC Temerin, M Elphic, R Strangeway, R Pfaff, R Cattell, CA Klumpar, D Shelley, E Peterson, W Moebius, E Kistler, L TI FAST satellite observations of electric field structures in the auroral zone SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID PAIRED ELECTROSTATIC SHOCKS; DOUBLE-LAYERS; ALTITUDE; PARTICLE; DISTRIBUTIONS; MAGNETOSPHERE; ACCELERATION; ION AB Electric field and energetic particle observations by the Fast Auroral Snapshot (FAST) satellite provide convincing evidence of particle acceleration by quasi-static, magnetic-field-aligned (parallel) electric fields in both the upward and downward current regions of the auroral zone. We demonstrate this by comparing the inferred parallel potentials of electrostatic shocks with particle energies. We also report nonlinear electric field structures which may play a role in supporting parallel electric fields. These structures include large-amplitude ion cyclotron waves in the upward current region, and intense, spiky electric fields in the downward current region. The observed structures had substantial parallel components and correlative electron flux modulations. Observations of parallel electric fields in two distinct plasmas suggest that parallel electric fields may be a fundamental particle acceleration mechanism in astrophysical plasmas. C1 Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA. Univ Calif Los Alamos Natl Lab, Los Alamos, NM 87545 USA. Univ Calif Los Angeles, IGPP, Los Angeles, CA 90095 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Minnesota, Tate Lab Phys, Minneapolis, MN 55455 USA. Lockheed Palo Alto Res Labs, Lockheed Martin, Palo Alto, CA 94304 USA. Univ New Hampshire, Durham, NH 03824 USA. RP Ergun, RE (reprint author), Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA. RI Peterson, WK/A-8706-2009; Pfaff, Robert/F-5703-2012; OI Peterson, WK/0000-0002-1513-6096; Pfaff, Robert/0000-0002-4881-9715; Moebius, Eberhard/0000-0002-2745-6978; Cattell, Cynthia/0000-0002-3805-320X NR 24 TC 208 Z9 210 U1 0 U2 4 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 JUN 15 PY 1998 VL 25 IS 12 BP 2025 EP 2028 DI 10.1029/98GL00635 PG 4 WC Geosciences, Multidisciplinary SC Geology GA ZV204 UT WOS:000074280800004 ER PT J AU Mobius, E Tang, L Kistler, LM Popecki, M Lund, EJ Klumpar, D Peterson, W Shelley, EG Klecker, B Hovestadt, D Carlson, CW Ergun, R McFadden, JP Mozer, F Temerin, M Cattell, C Elphic, R Strangeway, R Pfaff, R AF Mobius, E Tang, L Kistler, LM Popecki, M Lund, EJ Klumpar, D Peterson, W Shelley, EG Klecker, B Hovestadt, D Carlson, CW Ergun, R McFadden, JP Mozer, F Temerin, M Cattell, C Elphic, R Strangeway, R Pfaff, R TI Species dependent energies in upward directed ion beams over auroral arcs as observed with FAST TEAMS SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID ACCELERATION; WAVES; IONOSPHERE AB Upward flowing field-aligned ion beams over auroral arcs have been observed with the 3-dimensional ion mass spectrograph TEAMS on FAST. We have performed a statistical study on a sample of 77 ion beams from the auroral campaign in early 1997. All observed beams contain substantial amounts of H+, He+ and O+. A clear ordering of the total energies according to mass is found, with H+ having the lowest and O+ the highest energy. The composition varies significantly from beam to beam, with O+/H+ ratios ranging from = 0.1 to 10. No variation of the energy ratio between species is observed as a function of relative abundance, These results are discussed in the light of earlier observations of higher energies for O(+ )in statistical studies of beams during solar minimum and attempts to explain this behavior in terms of beam instabilities. C1 Univ New Hampshire, Dept Phys, Durham, NH 03824 USA. Univ New Hampshire, Inst Study Earth Oceans & Space, Durham, NH 03824 USA. Lockheed Palo Alto Res Labs, Palo Alto, CA 94304 USA. Max Planck Inst Extraterr Phys, D-85740 Garching, Germany. Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA. Univ Minnesota, Sch Phys & Astron, Minneapolis, MN 55455 USA. Univ Calif Los Alamos Natl Lab, Los Alamos, NM 87545 USA. Univ Calif Los Angeles, Inst Geophys & Planetary Phys, Los Angeles, CA 90024 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Mobius, E (reprint author), Univ New Hampshire, Dept Phys, Durham, NH 03824 USA. RI Peterson, WK/A-8706-2009; Pfaff, Robert/F-5703-2012; OI Peterson, WK/0000-0002-1513-6096; Pfaff, Robert/0000-0002-4881-9715; Moebius, Eberhard/0000-0002-2745-6978; Cattell, Cynthia/0000-0002-3805-320X NR 17 TC 19 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 JUN 15 PY 1998 VL 25 IS 12 BP 2029 EP 2032 DI 10.1029/98GL00381 PG 4 WC Geosciences, Multidisciplinary SC Geology GA ZV204 UT WOS:000074280800005 ER PT J AU Elphic, RC Bonnell, JW Strangeway, RJ Kepko, L Ergun, RE McFadden, JP Carlson, CW Peria, W Cattell, CA Klumpar, D Shelley, E Peterson, W Moebius, E Kistler, L Pfaff, R AF Elphic, RC Bonnell, JW Strangeway, RJ Kepko, L Ergun, RE McFadden, JP Carlson, CW Peria, W Cattell, CA Klumpar, D Shelley, E Peterson, W Moebius, E Kistler, L Pfaff, R TI The auroral current circuit and field-aligned currents observed by FAST SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID CURRENT-VOLTAGE RELATIONSHIP; ELECTRIC-FIELDS; DE-2; IONOSPHERE; REGIONS; ENERGY; MODEL; ARC AB FAST observes signatures of small-scale downward-going current at the edges of the inverted-V regions where the primary (auroral) electrons are found. In the winter pre-midnight auroral zone these downward currents are carried by upward flowing low- and medium-energy (up to several keV) electron beams. FAST instrumentation shows agreement between the current densities inferred from both the electron distributions and gradients in the magnetic field. FAST data taken near apogee (similar to 4000-km altitude) commonly show downward current magnetic field deflections consistent with the observed upward flux of similar to 10(9) electrons cm(-2) s(-1), or current densities of several mu A m(-2). The electron, field-aligned current and electric field signatures indicate the downward currents may be associated with "black aurora" and auroral ionospheric cavities. The field-aligned voltage-current relationship in the downward current region is nonlinear. C1 Univ Calif Los Alamos Natl Lab, Space & Atmospher Sci Grp, Los Alamos, NM 87545 USA. Univ Calif Los Angeles, Inst Geophys & Planetary Phys, Los Angeles, CA 90095 USA. Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA. Univ Minnesota, Minneapolis, MN 55455 USA. Lockheed Martin Palo Alto Res Labs, Palo Alto, CA 94304 USA. Univ New Hampshire, Durham, NH 03824 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Elphic, RC (reprint author), Univ Calif Los Alamos Natl Lab, Space & Atmospher Sci Grp, MS D466, Los Alamos, NM 87545 USA. RI Kepko, Larry/D-7747-2012; Pfaff, Robert/F-5703-2012; Peterson, WK/A-8706-2009; OI Kepko, Larry/0000-0002-4911-8208; Pfaff, Robert/0000-0002-4881-9715; Peterson, WK/0000-0002-1513-6096; Moebius, Eberhard/0000-0002-2745-6978; Cattell, Cynthia/0000-0002-3805-320X NR 20 TC 63 Z9 63 U1 1 U2 4 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 JUN 15 PY 1998 VL 25 IS 12 BP 2033 EP 2036 DI 10.1029/98GL01158 PG 4 WC Geosciences, Multidisciplinary SC Geology GA ZV204 UT WOS:000074280800006 ER PT J AU Pfaff, R Clemmons, J Carlson, C Ergun, R McFadden, J Mozer, F Temerin, M Klumpar, D Peterson, W Shelley, E Moebius, E Kistler, L Strangeway, R Elphic, R Cattell, C AF Pfaff, R Clemmons, J Carlson, C Ergun, R McFadden, J Mozer, F Temerin, M Klumpar, D Peterson, W Shelley, E Moebius, E Kistler, L Strangeway, R Elphic, R Cattell, C TI Initial FAST observations of acceleration processes in the cusp SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID POLAR CUSP; PRECIPITATION; FIELD; DE-1 AB FAST satellite observations during two encounters with the Earth's cusps near 4000 km are presented. In addition to precipitating magnetosheath particles with isotropic pitch angle distributions, the energetic particle data reveal upgoing ion beams, ion conics, downgoing "inverted-V" electron distributions, and very narrow, intense upgoing electron beams. A rich assortment of DC-coupled electric fields and plasma waves accompany these acceleration processes. In one example, steplike injections of magnetosheath ions are correlated with bursts of upgoing ion beams and downgoing electrons, suggesting that the currents associated with these injections set up local electric potential structures that subsequently drive the acceleration processes. The observations underscore the fact that the cusp is not merely a conduit for the passage of magnetosheath particles and fields, but contains a dynamic internal electrical structure that accelerates particles locally and may alter the precipitating magnetosheath particle populations themselves. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA. Lockheed Palo Alto Lab, Palo Alto, CA USA. Univ New Hampshire, Durham, NH 03824 USA. Univ Minnesota, Sch Phys & Astron, Minneapolis, MN 55455 USA. Univ Calif Los Angeles, Inst Geophys & Planetary Phys, Los Angeles, CA 90024 USA. Univ Calif Los Alamos Natl Lab, Los Alamos, NM USA. RP Pfaff, R (reprint author), NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RI Peterson, WK/A-8706-2009; Pfaff, Robert/F-5703-2012; OI Peterson, WK/0000-0002-1513-6096; Pfaff, Robert/0000-0002-4881-9715; Clemmons, James/0000-0002-5298-5222; Moebius, Eberhard/0000-0002-2745-6978; Cattell, Cynthia/0000-0002-3805-320X NR 9 TC 25 Z9 25 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 JUN 15 PY 1998 VL 25 IS 12 BP 2037 EP 2040 DI 10.1029/98GL00936 PG 4 WC Geosciences, Multidisciplinary SC Geology GA ZV204 UT WOS:000074280800007 ER PT J AU Ergun, RE Carlson, CW McFadden, JP Mozer, FS Delory, GT Peria, W Chaston, CC Temerin, M Roth, I Muschietti, L Elphic, R Strangeway, R Pfaff, R Cattell, CA Klumpar, D Shelley, E Peterson, W Moebius, E Kistler, L AF Ergun, RE Carlson, CW McFadden, JP Mozer, FS Delory, GT Peria, W Chaston, CC Temerin, M Roth, I Muschietti, L Elphic, R Strangeway, R Pfaff, R Cattell, CA Klumpar, D Shelley, E Peterson, W Moebius, E Kistler, L TI FAST satellite observations of large-amplitude solitary structures SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID WAVES AB We report observations of "fast solitary waves" that are ubiquitous in downward current regions of the mid-altitude auroral zone. The single-period structures have large amplitudes (up to 2.5 V/m), travel much faster than the ion acoustic speed, carry substantial potentials (up to similar to 100 Volts), and are associated with strong modulations of energetic electron fluxes. The amplitude and speed of the structures distinguishes them from ion-acoustic solitary waves or weak double layers. The electromagnetic signature appears to be that of an positive charge (electron hole) traveling anti-earthward. We present evidence that the structures are in or near regions of magnetic-field-aligned electric fields and propose that these nonlinear structures play a key role in supporting parallel electric fields in the downward current region of the auroral zone. C1 Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA. Univ Calif Los Alamos Natl Lab, Los Alamos, NM 87545 USA. Univ Calif Los Angeles, IGPP, Los Angeles, CA 90095 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Minnesota, Tate Lab Phys, Minneapolis, MN 55455 USA. Lockheed Palo Alto Res Labs, Lockheed Martin, Palo Alto, CA 94304 USA. Univ New Hampshire, Durham, NH 03824 USA. RP Ergun, RE (reprint author), Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA. EM ree@ssl.berkeley.edu; cwc@ssl.berkeley.edu; mcfadden@ssl.berkeley.edu; gdelory@ssl.berkeley.edu; peria@ssl.berkeley.edu; ccc@ssl.berkeley.edu; temerin@ssl.berkeley.edu; ilan@ssl.berkeley.edu; laurent@ssl.berkeley.edu; relphic@lanl.gov; strange@igpp.ucla.edu; rob.pfaff@gsfc.nasa.gov; cattell@belka.spa.umn.edu; klump@agena.space.lookhead.com; moebius@rotor.sr.unh.edu; kistler@rotor.sr.unh.edu RI Peterson, WK/A-8706-2009; Pfaff, Robert/F-5703-2012; OI Peterson, WK/0000-0002-1513-6096; Pfaff, Robert/0000-0002-4881-9715; Moebius, Eberhard/0000-0002-2745-6978; Cattell, Cynthia/0000-0002-3805-320X NR 15 TC 341 Z9 344 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 JUN 15 PY 1998 VL 25 IS 12 BP 2041 EP 2044 DI 10.1029/98GL00636 PG 4 WC Geosciences, Multidisciplinary SC Geology GA ZV204 UT WOS:000074280800008 ER PT J AU McFadden, JP Carlson, CW Ergun, RE Chaston, CC Mozer, FS Temerin, M Klumpar, DM Shelley, EG Peterson, WK Moebius, E Kistler, L Elphic, R Strangeway, R Cattell, C Pfaff, R AF McFadden, JP Carlson, CW Ergun, RE Chaston, CC Mozer, FS Temerin, M Klumpar, DM Shelley, EG Peterson, WK Moebius, E Kistler, L Elphic, R Strangeway, R Cattell, C Pfaff, R TI Electron modulation and ion cyclotron waves observed by FAST SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID POLAR MAGNETOSPHERE AB New observations from the FAST satellite demonstrate strong wave-particle interactions between energetic electrons and H+ EMIC waves in inverted-V arcs. The intense waves are shown to occur in strong upward current regions which contain intense downgoing field-aligned electron fluxes. Electrons near the inverted-V spectral peak have large, factor of 2 to 10, coherent flux modulations at or near the wave frequency. The electron modulations are typically centered at about f(CH+)/2, where f(CH+) is the local H+ cyclotron frequency. The EMIC waves are broadbanded, extending from about 0.3f(CH+) to 0.7f(CH+). These waves also accelerate cold secondary electrons, forming counterstreaming field-aligned electrons at energies up to about 300 eV.In addition, electron modulations at f(CH+) are observed in the density cavities associated with upgoing ion beams. Intense waves at f(CH+) are simultaneously detected and shown to have a magnetic component similar to the EMIC waves. C1 Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA. Lockheed Martin Palo Alto Res Labs, Palo Alto, CA 94304 USA. Univ New Hampshire, Durham, NH 03824 USA. Univ Calif Los Alamos Natl Lab, Los Alamos, NM 87545 USA. Univ Calif Los Angeles, Los Angeles, CA 90095 USA. Univ Minnesota, Minneapolis, MN 55455 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP McFadden, JP (reprint author), Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA. RI Pfaff, Robert/F-5703-2012; Peterson, WK/A-8706-2009; OI Pfaff, Robert/0000-0002-4881-9715; Peterson, WK/0000-0002-1513-6096; Moebius, Eberhard/0000-0002-2745-6978; Cattell, Cynthia/0000-0002-3805-320X NR 8 TC 55 Z9 55 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 JUN 15 PY 1998 VL 25 IS 12 BP 2045 EP 2048 DI 10.1029/98GL00855 PG 4 WC Geosciences, Multidisciplinary SC Geology GA ZV204 UT WOS:000074280800009 ER PT J AU Lund, EJ Mobius, E Tang, L Kistler, LM Popecki, MA Klumpar, DM Peterson, WK Shelley, EG Klecker, B Hovestadt, D Temerin, M Ergun, RE McFadden, JP Carlson, CW Mozer, FS Elphic, RC Strangeway, RJ Cattell, CA Pfaff, RF AF Lund, EJ Mobius, E Tang, L Kistler, LM Popecki, MA Klumpar, DM Peterson, WK Shelley, EG Klecker, B Hovestadt, D Temerin, M Ergun, RE McFadden, JP Carlson, CW Mozer, FS Elphic, RC Strangeway, RJ Cattell, CA Pfaff, RF TI FAST observations of preferentially accelerated He+ in association with auroral electromagnetic ion cyclotron waves SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID FLICKERING AURORA; ELF WAVES; MECHANISM AB The TEAMS instrument on the FAST satellite has detected events in which He+ ions are resonantly accelerated perpendicular to the magnetic field to energies of several keV. The events occur in association with electromagnetic ion cyclotron (EMIC) waves and conic distributions of up to a few hundred eV in H+ and a few keV in O+. Concentrations of Het can be significantly elevated during the events. Our interpretation is that the He+ ions are accelerated through a cyclotron resonance with the waves. This acceleration is similar to a proposed mechanism for selective ion acceleration in impulsive solar flares. C1 Univ New Hampshire, Ctr Space Sci, Durham, NH 03824 USA. Univ New Hampshire, Dept Phys, Durham, NH 03824 USA. Lockheed Martin Palo Alto Res Lab, Palo Alto, CA 94304 USA. Max Planck Inst Extraterr Phys, D-85740 Garching, Germany. Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA. Univ Calif Los Alamos Natl Lab, Los Alamos, NM 87545 USA. Univ Calif Los Angeles, Inst Geophys & Planetary Phys, Los Angeles, CA 90024 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Minnesota, Sch Phys & Astron, Minneapolis, MN 55455 USA. RP Lund, EJ (reprint author), Univ New Hampshire, Ctr Space Sci, Morse Hall, Durham, NH 03824 USA. EM Eric.Lund@unh.edu RI Pfaff, Robert/F-5703-2012; Peterson, WK/A-8706-2009; OI Pfaff, Robert/0000-0002-4881-9715; Peterson, WK/0000-0002-1513-6096; Lund, Eric/0000-0003-1312-9375; Moebius, Eberhard/0000-0002-2745-6978; Cattell, Cynthia/0000-0002-3805-320X NR 19 TC 29 Z9 29 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 JUN 15 PY 1998 VL 25 IS 12 BP 2049 EP 2052 DI 10.1029/98GL00304 PG 4 WC Geosciences, Multidisciplinary SC Geology GA ZV204 UT WOS:000074280800010 ER PT J AU Cattell, C Bergmann, R Sigsbee, K Carlson, C Chaston, C Ergun, R McFadden, J Mozer, FS Temerin, M Strangeway, R Elphic, R Kistler, L Moebius, E Tang, L Klumpar, D Pfaff, R AF Cattell, C Bergmann, R Sigsbee, K Carlson, C Chaston, C Ergun, R McFadden, J Mozer, FS Temerin, M Strangeway, R Elphic, R Kistler, L Moebius, E Tang, L Klumpar, D Pfaff, R TI The association of electrostatic ion cyclotron waves, ion and electron beams and field-aligned currents: FAST observations of an auroral zone crossing near midnight SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID HYDROGEN CYCLOTRON; INSTABILITIES; LINES; H+ AB FAST particle and wave data for a single nightside auroral zone crossing are utilized to examine the free energy source for electrostatic ion cyclotron (EIC) waves. Comparisons of the unstable wave modes, obtained by an electrostatic linear dispersion relation solver, to the observed waves for two intervals with upflowing ion beams and two with upflowing electron beams are consistent with the conclusion that the observed waves near the cyclotron frequencies are EIC which are driven by the electron drift both in the upgoing ion beam regions and in the upgoing electron regions. A limitation is that the drifting bi-Maxwellian model used in the dispersion relation is not a good match to the observed upflowing electron distributions. The observed ion beams do not drive EIC waves; however, the relative drift of the various ion species comprising the ion beam can drive low frequency (1 V/m and often have a magnetic component even above the proton cyclotron frequency (Omega(p)) with amplitudes up to 2nT. Waves with transverse amplitudes greater than 100 mV/m often exhibit large spiky downward pointing field-aligned components with amplitudes that may exceed that of transverse fluctuation. The ratio of electric to magnetic fluctuation amplitude (E-1/B-1) is dose to c. Using the 3 dimensional electric and magnetic field measurements available from FAST it is demonstrated that these waves are in most cases polarized transverse to the ambient magnetic field (B-0) and have linear polarization with wavelengths perpendicular to B(0 )ranging from hundreds of meters to kilometers. Calculations of the Poynting vector associated with these ICWs indicates Poynting fluxes directed downwards along B(0 )for waves below the local ap and generally upwards for waves observed close to and above this frequency with fluxes which may exceed 10% of the total field-aligned electron beam energy flux. C1 Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA. Univ Minnesota, Minneapolis, MN 55455 USA. Univ Calif Los Alamos Natl Lab, Los Alamos, NM 87545 USA. Lockheed Martin Palo Alto Res Labs, Palo Alto, CA 94304 USA. Univ New Hampshire, Durham, NH 03824 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Calif Los Angeles, Inst Geophys & Planetary Phys, Los Angeles, CA 90024 USA. RP Chaston, CC (reprint author), Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA. RI Pfaff, Robert/F-5703-2012; Peterson, WK/A-8706-2009; OI Pfaff, Robert/0000-0002-4881-9715; Peterson, WK/0000-0002-1513-6096; Moebius, Eberhard/0000-0002-2745-6978; Cattell, Cynthia/0000-0002-3805-320X NR 24 TC 16 Z9 16 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 JUN 15 PY 1998 VL 25 IS 12 BP 2057 EP 2060 DI 10.1029/98GL00513 PG 4 WC Geosciences, Multidisciplinary SC Geology GA ZV204 UT WOS:000074280800012 ER PT J AU Ergun, RE Carlson, CW McFadden, JP Mozer, FS Delory, GT Peria, W Chaston, CC Temerin, M Elphic, R Strangeway, R Pfaff, R Cattell, CA Klumpar, D Shelly, E Peterson, W Moebius, E Kistler, L AF Ergun, RE Carlson, CW McFadden, JP Mozer, FS Delory, GT Peria, W Chaston, CC Temerin, M Elphic, R Strangeway, R Pfaff, R Cattell, CA Klumpar, D Shelly, E Peterson, W Moebius, E Kistler, L TI FAST satellite wave observations in the AKR source region SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID AURORAL KILOMETRIC RADIATION; VIKING SATELLITE; GENERATION; FIELD AB The Fast Auroral SnapshoT (FAST) satellite has made observations in the Auroral Kilometric Radiation (AKR) source region with unprecedented frequency and time resolution. We confirm the AKR source is in a density depleted cavity and present examples in which cold electrons appeared to have been nearly evacuated (n(hot) > n(cold)) Electron distributions were depleted at low-energies and up-going ion beams were always present. Source region amplitudes were far greater than previously reported, reaching 2x10(-4) (V/m)(2)/Hz (300 mV/m) in short bursts with bandwidths generally < 1 kHz. Intense emissions were often at the edge of the density cavity. Emissions were near or below the cold plasma electron cyclotron frequency in the source region, and were almost entirely electromagnetic. The \E\/\B\ ratio was constant as a function of frequency and rarely displayed any features that would identify a cold plasma cutoff or resonance. C1 Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA. Univ Calif Los Alamos Natl Lab, Los Alamos, NM 87545 USA. Univ Calif Los Angeles, IGPP, Los Angeles, CA 90095 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Minnesota, Tate Lab Phys, Minneapolis, MN 55455 USA. Lockheed Palo Alto Res Labs, Lockheed Martin, Palo Alto, CA 94304 USA. Univ New Hampshire, Durham, NH 03824 USA. RP Ergun, RE (reprint author), Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA. RI Pfaff, Robert/F-5703-2012; Peterson, WK/A-8706-2009; OI Pfaff, Robert/0000-0002-4881-9715; Peterson, WK/0000-0002-1513-6096; Moebius, Eberhard/0000-0002-2745-6978; Cattell, Cynthia/0000-0002-3805-320X NR 17 TC 140 Z9 141 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 JUN 15 PY 1998 VL 25 IS 12 BP 2061 EP 2064 DI 10.1029/98GL00570 PG 4 WC Geosciences, Multidisciplinary SC Geology GA ZV204 UT WOS:000074280800013 ER PT J AU Strangeway, RJ Kepko, L Elphic, RC Carlson, CW Ergun, RE McFadden, JP Peria, WJ Delory, GT Chaston, CC Temerin, M Cattell, CA Mobius, E Kistler, LM Klumpar, DM Peterson, WK Shelley, EG Pfaff, RE AF Strangeway, RJ Kepko, L Elphic, RC Carlson, CW Ergun, RE McFadden, JP Peria, WJ Delory, GT Chaston, CC Temerin, M Cattell, CA Mobius, E Kistler, LM Klumpar, DM Peterson, WK Shelley, EG Pfaff, RE TI FAST observations of VLF waves in the auroral zone: Evidence of very low plasma densities SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID KILOMETRIC RADIATION SOURCES; RELATIVISTIC DISPERSION; PROPAGATION; GENERATION; REGION AB The Fast Auroral SnapshoT (FAST) explorer frequently observes the auroral density cavity, which is the source region for Auroral Kilometric Radiation (AKR). An important factor in the generation of AKR is the relative abundance of hot and cold electrons within the cavity, since hot electrons introduce relativistic modifications to the wave dispersion. VLF wave-form data acquired by FAST within the auroral density cavity show clear signatures of whistler-mode waves propagating on the resonance cone. This allows us to obtain the electron plasma frequency, and the cavity often has densities < 1 cm(-3). Moreover, the hot electrons can be the dominant electron species, enabling AKR to be generated below the cold electron gyro-frequency. C1 Univ Calif Los Angeles, Inst Geophys & Planetary Phys, Los Angeles, CA 90095 USA. Univ Calif Los Alamos Natl Lab, Los Alamos, NM 87545 USA. Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA. Univ Minnesota, Sch Phys & Astron, Minneapolis, MN 55455 USA. Univ New Hampshire, Inst Study Earth Oceans & Space, Durham, NH 03824 USA. Univ New Hampshire, Dept Phys, Durham, NH 03824 USA. Lockheed Martin Palo Alto Res Lab, Palo Alto, CA 94304 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Strangeway, RJ (reprint author), Univ Calif Los Angeles, Inst Geophys & Planetary Phys, Los Angeles, CA 90095 USA. RI Kepko, Larry/D-7747-2012; Pfaff, Robert/F-5703-2012; Peterson, WK/A-8706-2009; OI Kepko, Larry/0000-0002-4911-8208; Pfaff, Robert/0000-0002-4881-9715; Peterson, WK/0000-0002-1513-6096; Moebius, Eberhard/0000-0002-2745-6978; Cattell, Cynthia/0000-0002-3805-320X NR 13 TC 91 Z9 91 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 JUN 15 PY 1998 VL 25 IS 12 BP 2065 EP 2068 DI 10.1029/98GL00664 PG 4 WC Geosciences, Multidisciplinary SC Geology GA ZV204 UT WOS:000074280800014 ER PT J AU Sigsbee, K Cattell, CA Lysak, RL Carlson, CW Ergun, RE McFadden, JP Mozer, F Elphic, RC Strangeway, RJ Tsuruda, K Yamamoto, T Kokubun, S Fairfield, D Pfaff, R Parks, G Brittnacher, M AF Sigsbee, K Cattell, CA Lysak, RL Carlson, CW Ergun, RE McFadden, JP Mozer, F Elphic, RC Strangeway, RJ Tsuruda, K Yamamoto, T Kokubun, S Fairfield, D Pfaff, R Parks, G Brittnacher, M TI FAST - Geotail correlative studies of magnetosphere ionosphere coupling in the nightside magnetosphere SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID FIELD AB Data from conjunctions between FAST and Geotail were used to examine the physical processes which mediate coupling between the magnetotail at 30 R-E and the nightside auroral zone near 1.5 R-E. During one conjunction, Geotail observed a large scale recovery of the plasma sheet and several partial thinnings. Two of these encounters with the plasma sheet boundary were recorded by Polar at high latitudes on the dawn flank, indicating the global nature of the plasma sheet motions. Wavelet analysis of the FAST and Geotail electric and magnetic field data revealed low frequency waves which may be involved in magnetosphere-ionosphere coupling. A brief electromagnetic pulse with a frequency of 0.9 Hz consistent with the Alfvenic structures discussed by Lysak [1997] was observed by FAST. Oscillations near this frequency were also observed in the Geotail electric field data. Signatures consistent with field line resonances in the frequency range 0.03 to 0.05 Hz were recorded by both FAST and Geotail. This is the first time these types of structures have been observed simultaneously in the auroral zone and the magnetotail. C1 Univ Minnesota, Sch Phys & Astron, Minneapolis, MN 55455 USA. Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA. Univ Calif Los Alamos Natl Lab, Los Alamos, NM USA. Univ Calif Los Angeles, Inst Geophys & Planetary Phys, Los Angeles, CA 90024 USA. Inst Space & Astronaut Sci, Sagamihara, Kanagawa 229, Japan. Nagoya Univ, STELAB, Toyokawa 442, Japan. NASA, Goddard Space Flight Ctr, Extraterr Phys Lab, Greenbelt, MD 20771 USA. Univ Washington, Seattle, WA 98195 USA. RP Sigsbee, K (reprint author), Univ Minnesota, Sch Phys & Astron, Minneapolis, MN 55455 USA. RI Pfaff, Robert/F-5703-2012; OI Pfaff, Robert/0000-0002-4881-9715; Sigsbee, Kristine/0000-0001-8727-380X; Cattell, Cynthia/0000-0002-3805-320X NR 9 TC 7 Z9 7 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 JUN 15 PY 1998 VL 25 IS 12 BP 2077 EP 2080 DI 10.1029/97GL03769 PG 4 WC Geosciences, Multidisciplinary SC Geology GA ZV204 UT WOS:000074280800017 ER PT J AU Peterson, WK Tung, YK Carlson, CW Clemmons, JH Collin, HL Ergun, RE Fuselier, SA Kletzing, CA Klumpar, DM Lennartsson, OW Lepping, RP Maynard, NC McFadden, JP Onsager, TG Peria, WJ Russell, CT Shelley, EG Tang, L Wygant, J AF Peterson, WK Tung, YK Carlson, CW Clemmons, JH Collin, HL Ergun, RE Fuselier, SA Kletzing, CA Klumpar, DM Lennartsson, OW Lepping, RP Maynard, NC McFadden, JP Onsager, TG Peria, WJ Russell, CT Shelley, EG Tang, L Wygant, J TI Simultaneous observations of solar wind plasma entry from FAST and POLAR SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID MAGNETOSPHERE; INSTRUMENT; MISSION AB On November 15, 1996, NASA FAST and POLAR satellites obtained data in the cusp/cleft region for extended intervals. POLAR sampled a narrow range of local times. FAST observed cusp/cleft plasma for more than 5 hours in local time. At 07:51 UT the satellites were in near magnetic conjunction, and the interplanetary magnetic field was steady for an extended interval before this time. We confirm prior observations that show solar wind plasma often enters the magnetosphere over extended regions of local time. For the one hour interval of steady solar wind conditions when POLAR encountered cusp/cleft plasma, irregularly spaced ion injections interspersed with intervals of nearly constant cusp/cleft ion fluxes were observed. The data are consistent with temporal variations in the reconnection rate. At the time of the near conjugate observations the data suggest that solar wind plasma entered the magnetosphere over an extended region of the magnetopause, i.e. not in small discontinuous patches. C1 Lockheed Martin, Palo Alto, CA 94304 USA. Univ Calif Berkeley, Berkeley, CA 94720 USA. Aerosp Corp, El Segundo, CA 90245 USA. Univ Iowa, Iowa City, IA 52242 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Mission Res Corp, Nashua, NH 03060 USA. NOAA, Space Environm Lab, Boulder, CO 80309 USA. Univ Calif Los Angeles, Los Angeles, CA 90024 USA. Univ New Hampshire, Durham, NH 03824 USA. Univ Minnesota, Minneapolis, MN 55455 USA. RP Peterson, WK (reprint author), Lockheed Martin, 3251 Hanover St, Palo Alto, CA 94304 USA. EM pete@spasci.com RI Peterson, WK/A-8706-2009; OI Peterson, WK/0000-0002-1513-6096; Clemmons, James/0000-0002-5298-5222; Kletzing, Craig/0000-0002-4136-3348; Russell, Christopher/0000-0003-1639-8298 NR 18 TC 4 Z9 4 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 JUN 15 PY 1998 VL 25 IS 12 BP 2081 EP 2084 DI 10.1029/98GL00668 PG 4 WC Geosciences, Multidisciplinary SC Geology GA ZV204 UT WOS:000074280800018 ER PT J AU Kistler, LM Mobius, E Klumpar, DM Popecki, MA Tang, L Jordanova, V Klecker, B Peterson, WK Shelley, EG Hovestadt, D Temerin, M Ergun, RE McFadden, JP Carlson, CW Mozer, FS Elphic, RC Strangeway, RJ Cattell, CA Pfaff, RF AF Kistler, LM Mobius, E Klumpar, DM Popecki, MA Tang, L Jordanova, V Klecker, B Peterson, WK Shelley, EG Hovestadt, D Temerin, M Ergun, RE McFadden, JP Carlson, CW Mozer, FS Elphic, RC Strangeway, RJ Cattell, CA Pfaff, RF TI FAST/TEAMS observations of charge exchange signatures in ions mirroring at low altitudes SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID RING CURRENT IONS; ELECTRIC-FIELDS; MAGNETOSPHERE; PROTON; MODEL; CONVECTION; PARTICLES; STORMS AB Using the TEAMS instrument on FAST, we have observed a case in which signatures of the inner edge of the plasma sheet are clearly observed in the energy spectra of ions mirroring at the FAST altitude. That inner edge is dominated by He+. We show that this is the natural composition expected from charge exchange as the ions drift in from the plasma sheet. C1 Univ New Hampshire, Ctr Space Sci, Durham, NH 03824 USA. Univ New Hampshire, Dept Phys, Durham, NH 03824 USA. Lockheed Martin Palo Alto Res Lab, Palo Alto, CA 94304 USA. Max Planck Inst Extraterr Phys, D-85740 Garching, Germany. Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA. Univ Calif Los Alamos Natl Lab, Los Alamos, NM 87545 USA. Univ Calif Los Angeles, Inst Geophys & Planetary Phys, Los Angeles, CA 90024 USA. Univ Minnesota, Sch Phys & Astron, Minneapolis, MN 55455 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Kistler, LM (reprint author), Univ New Hampshire, Ctr Space Sci, Morse Hall, Durham, NH 03824 USA. RI Pfaff, Robert/F-5703-2012; Peterson, WK/A-8706-2009; OI Pfaff, Robert/0000-0002-4881-9715; Peterson, WK/0000-0002-1513-6096; Cattell, Cynthia/0000-0002-3805-320X; Jordanova, Vania/0000-0003-0475-8743 NR 20 TC 11 Z9 11 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 JUN 15 PY 1998 VL 25 IS 12 BP 2085 EP 2088 DI 10.1029/98GL00331 PG 4 WC Geosciences, Multidisciplinary SC Geology GA ZV204 UT WOS:000074280800019 ER PT J AU Woo, R AF Woo, R TI Reply to: "The Pioneer 6 Faraday rotation transients - On the interpretation of coronal Faraday rotation data" by Patzold and Bird SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID HELIOSPHERIC CURRENT SHEET; SOLAR CORONA; STREAMERS C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Woo, R (reprint author), CALTECH, Jet Prop Lab, MS 238-725,4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 14 TC 2 Z9 2 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 JUN 15 PY 1998 VL 25 IS 12 BP 2109 EP 2110 DI 10.1029/98GL01318 PG 2 WC Geosciences, Multidisciplinary SC Geology GA ZV204 UT WOS:000074280800025 ER PT J AU Krasnopolsky, VA AF Krasnopolsky, VA TI Spectroscopic detection of terrestrial deuterium SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID LYMAN-ALPHA; HYDROGEN; THERMOSPHERE; MESOSPHERE; ATMOSPHERE AB Observation of Mars at 1212-1218 Angstrom with the HST Goddard high-resolution spectrograph revealed both Mars' and Earth's D Ly-alpha lines. The telluric line intensity is 17 +/- 4 R (Rayleighs) at 600 km. We construct a model for H-2, H, HD, and D from 85 to 500 km with escape velocities V-H and V-D as the model parameters. D is formed by photolysis of HDO and in reactions of HD with O, O+, and O(D-1). The calculated intensity at solar minimum (F-10.7 cm = 70, T-infinity = 736 K) agrees with the measured value for V-D = 80 +/- 15 cm/s. We applied our model to previous detections of deuterium by means of deuterium absorption cells and ion mass spectrometry. Escapes of H and D are diffusion limited, isotope fractionation factor is 0.88, and deuterium enrichment in the escape processes is ineffective. C1 Catholic Univ Amer, Greenbelt, MD 20771 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Krasnopolsky, VA (reprint author), Catholic Univ Amer, Greenbelt, MD 20771 USA. RI Krasnopolsky, Vladimir/L-5085-2013 NR 24 TC 1 Z9 1 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 JUN 15 PY 1998 VL 25 IS 12 BP 2115 EP 2118 DI 10.1029/98GL01654 PG 4 WC Geosciences, Multidisciplinary SC Geology GA ZV204 UT WOS:000074280800027 ER PT J AU Danilin, MY Sze, ND Ko, MKW Rodriguez, JM Tabazadeh, A AF Danilin, MY Sze, ND Ko, MKW Rodriguez, JM Tabazadeh, A TI Stratospheric cooling and Arctic ozone recovery SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID POLAR VORTEX; HOLE; DEPLETION; AIRCRAFT; AEROSOL; CLONO2; WINTER; HNO3 AB We present sensitivity studies using the AER box model for an idealized parcel in the lower stratosphere at 70 degrees N during winter/spring with different assumed stratospheric coolings and chlorine loadings. Our calculations show that stratospheric cooling could further deplete ozone via increased polar stratospheric cloud (PSC) formation and retard its expected recovery even with the projected chlorine loading decrease. introduce the concept of chlorine-cooling equivalent and show that a 1 K cooling could provide the same local ozone depletion as an Increase of chlorine by 0.4-0.7 ppbv for the scenarios considered. Thus sustained stratospheric cooling could further reduce Arctic ozone content and delay the anticipated ozone recovery in the Northern Hemisphere even with the realization of the Montreal Protocol and its Amendments. C1 Atmospher & Environm Res Inc, Cambridge, MA 02139 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Danilin, MY (reprint author), Atmospher & Environm Res Inc, 840 Mem Dr, Cambridge, MA 02139 USA. RI Rodriguez, Jose/G-3751-2013; Ko, Malcolm/D-5898-2015 OI Rodriguez, Jose/0000-0002-1902-4649; NR 32 TC 18 Z9 19 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 JUN 15 PY 1998 VL 25 IS 12 BP 2141 EP 2144 DI 10.1029/98GL01587 PG 4 WC Geosciences, Multidisciplinary SC Geology GA ZV204 UT WOS:000074280800034 ER PT J AU Pawson, S Labitzke, K Leder, S AF Pawson, S Labitzke, K Leder, S TI Stepwise changes in stratospheric temperature SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID VALIDATION; PRECISION; TRENDS AB Northern hemispheric temperature analyses for the time period July 1964 until June 1997 are used to investigate the long-term changes of the lower and middle stratosphere. Use of annual, hemispheric means removes many of the dynamical effects and allows the thermal structure to be investigated with more certainty. There is a clear cooling over the 33 years considered. It is not well described by a linear trend because of the increased cooling since 1991. These changes are consistent with those derived from independent satellite-based soundings. It is shown that the low temperatures in the 1990s are not well described by a simple statistical model including the linear trend plus the interannual variability for the period 1964/1965-1980/1981, when the stratosphere was relatively undisturbed by volcanic debris and the O-3 changes were small. Possible links between the stratospheric changes reported here and apparent changes in the thermal structure in the 1990s (reported in other studies) are discussed. C1 NASA, GSFC, Univ Space Res Assoc, Greenbelt, MD 20771 USA. Free Univ Berlin, Inst Meteorol, D-12165 Berlin, Germany. RP Pawson, S (reprint author), NASA, GSFC, Univ Space Res Assoc, Code 916, Greenbelt, MD 20771 USA. EM pawson@polska.gsfc.nasa.gov; labitzke@strat01.met.fu-berlin.de; leder@strat01.met.fu-berlin.de RI Pawson, Steven/I-1865-2014 OI Pawson, Steven/0000-0003-0200-717X NR 12 TC 38 Z9 38 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 JUN 15 PY 1998 VL 25 IS 12 BP 2157 EP 2160 DI 10.1029/98GL51534 PG 4 WC Geosciences, Multidisciplinary SC Geology GA ZV204 UT WOS:000074280800038 ER PT J AU Sridhara, SG Clemen, LL Devaty, RP Choyke, WJ Larkin, DJ Kong, HS Troffer, T Pensl, G AF Sridhara, SG Clemen, LL Devaty, RP Choyke, WJ Larkin, DJ Kong, HS Troffer, T Pensl, G TI Photoluminescence and transport studies of boron in 4H SiC SO JOURNAL OF APPLIED PHYSICS LA English DT Article ID SITE-COMPETITION EPITAXY; ELECTRON-PARAMAGNETIC-RESONANCE; NUCLEAR DOUBLE-RESONANCE; GA-BOUND EXCITONS; SILICON-CARBIDE; CLUSTER CALCULATION; DEEP-BORON; ACCEPTOR; CENTERS; FILMS AB Two distinct boron-related centers are known in silicon carbide polytypes, one shallow (ionization energy similar to 300 meV) and the other deep (similar to 650 meV). In this work, 4H SiC homoepitaxial films are intentionally doped with the shallow boron center by controlling the silicon to carbon source gas ratio during chemical vapor deposition, based on site competition epitaxy. The dominance of the shallow boron center for samples grown with a low Si/C ratio, favoring the incorporation of boron onto the silicon sublattice, is verified by the temperature dependent Hall effect, admittance spectroscopy and deep level transient spectroscopy. In these samples a peak near 3838 Angstrom appears in the low temperature photoluminescence spectrum. Further experiments support the identification of this peak with the recombination of a four particle (bound exciton) complex associated with the neutral shallow boron acceptor as follows: (1) The intensity of the 3838 Angstrom peak grows with added boron. (2) Momentum conserving phonon replicas are observed, with energies consistent with other four particle complexes in SiC. (3) With increasing temperature excited states are observed, as for the neutral aluminum and gallium acceptor four particle complexes. However, the intensity of the shallow boron spectrum is quenched at lower temperatures than the corresponding spectra for Al and Ga, and the lineshapes are strongly sample dependent. These results may be related to the unusual configurational and electronic structure of this center inferred from recent spin resonance experiments by other groups. When the Si/C ratio is high, the optical signatures of the deep boron center, nitrogen-boron donor-acceptor pairs and conduction band to neutral acceptor free-to-bound transitions, are observed in the photoluminescence. At T=2K well resolved, detailed nitrogen-boron pair line spectra are observed in addition to the peak due to distant pairs. As the temperature is raised, the donor-acceptor pair spectrum decreases in intensity while the free-to-bound no-phonon peak appears. Extrapolation of the temperature dependence of the free-to-bound peak to T=0 K, after correction for the temperature dependence of the exciton energy gap, leads to the value E-A(B) - E-X = 628 +/- 1 meV, where E-A(B) is the ionization energy of the deep boron center and E-X is the binding energy of the free exciton which, for 4H SiC, can only be estimated at this time. (C) 1998 American Institute of Physics. C1 Univ Pittsburgh, Dept Phys & Astron, Pittsburgh, PA 15260 USA. NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. Cree Res Inc, Durham, NC 27713 USA. Univ Erlangen Nurnberg, Lehrstuhl Angew Phys, D-91058 Erlangen, Germany. RP Sridhara, SG (reprint author), Univ Pittsburgh, Dept Phys & Astron, Pittsburgh, PA 15260 USA. NR 57 TC 85 Z9 86 U1 2 U2 38 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 JUN 15 PY 1998 VL 83 IS 12 BP 7909 EP 7919 DI 10.1063/1.367970 PG 11 WC Physics, Applied SC Physics GA 108GJ UT WOS:000075257500070 ER PT J AU Walsh, EJ Vandemark, DC Friehe, CA Burns, SP Khelif, D Swift, RN Scott, JF AF Walsh, EJ Vandemark, DC Friehe, CA Burns, SP Khelif, D Swift, RN Scott, JF TI Measuring sea surface mean square slope with a 36-GHz scanning radar altimeter SO JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS LA English DT Article ID BACKSCATTER; WAVES; SPECTRUM AB Values of sea surface mean square slope (mss) computed from the backscattered power falloff with incidence angle measured by an airborne 36-GHz scanning radar altimeter are presented. When the mss values are plotted against the 10-m wind speed (extrapolated from the 46- to 110-m aircraft height), for wind speeds up to 7 m s(-1) the values scatter about a curve which is scaled from that obtained by Wu [1990] by a factor of 0.85. Wu's result was a reanalysis of the optical measurements of Cox and Munk [1954]. The offset between the microwave and optical curves is reasonable because one would expect the surface to appear smoother to the microwave wavelength than to the optical. This is unlike the mss values inferred from absolute power measurements at nadir by 14-GHz satellite altimeters, which indicate a higher mss under light wind conditions than the optical measurements indicate. For wind speeds below 7 m s(-1) the peak of the backscattered power distribution is observed at nadir, but for higher speeds the peak shifts off-nadir in the downwind direction. C1 NASA, Goddard Space Flight Ctr, Lab Hydrospher Proc, Observat Sci Branch,Wallops Flight Facil, Wallops Island, VA 23337 USA. Univ Calif Irvine, Dept Mech Engn, Irvine, CA 92717 USA. EG&G Serv Inc, Wallops Flight Facil, Wallops Island, VA 23337 USA. RP Walsh, EJ (reprint author), NOAA, Environm Technol Lab, R-E-ET6,325 Broadway, Boulder, CO 80303 USA. RI Burns, Sean/A-9352-2008 OI Burns, Sean/0000-0002-6258-1838 NR 33 TC 33 Z9 34 U1 0 U2 1 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 JUN 15 PY 1998 VL 103 IS C6 BP 12587 EP 12601 DI 10.1029/97JC02443 PG 15 WC Oceanography SC Oceanography GA ZU093 UT WOS:000074160900001 ER PT J AU Walsh, EJ Hagan, DE Rogers, DP Weller, RA Fairall, CW Friehe, CA Burns, SP Khelif, D Vandemark, DC Swift, RN Scott, JF AF Walsh, EJ Hagan, DE Rogers, DP Weller, RA Fairall, CW Friehe, CA Burns, SP Khelif, D Vandemark, DC Swift, RN Scott, JF TI Observations of sea surface mean square slope under light wind during the Tropical Ocean Global Atmosphere Coupled Ocean-Atmosphere Response Experiment SO JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS LA English DT Article AB Observations of sea surface mean square slope.(mss) were made with a scanning radar altimeter (SRA) from a low-flying research aircraft on a light-wind day during the Tropical Ocean-global Atmosphere Coupled Ocean-Atmosphere Response Experiment. Wind speed (measured at 60- to 90-m height and extrapolated to the 10-m level) and mss were found to be positively correlated, with correlation coefficients in some cases as high as those obtained for wind speed measurements on adjacent aircraft flying wingtip to wingtip with a 100-m lateral separation of their fuselages. The SRA measurements suggest a much larger azimuthal asymmetry in mss at 36 GHz than was observed in the seminal Cox and Munk optical experiment; the SRA measurements showed a crosswind-to-upwind ratio as low as of 0.26 at 1.8 m s(-1) compared to the typical value of 0.8 for Cox and Munk. For higher wind speed the mss becomes more isotropic. The data suggest that waves generated by a wind speed less than 2 m s(-1) are restricted to the downwind direction. The crosswind-to-upwind ratio would probably have been even lower had it not been for an isotropic background mss caused by an assortment of swell. C1 NOAA, Environm Technol Lab, Boulder, CO 80303 USA. NASA, Goddard Space Flight Ctr, Lab Hydrospher Proc, Observat Sci Branch,Wallops Flight Facil, Wallops Island, VA 23337 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ Calif San Diego, Scripps Inst Oceanog, La Jolla, CA 92093 USA. Woods Hole Oceanog Inst, Woods Hole, MA 02543 USA. Univ Calif Irvine, Dept Mech Engn, Irvine, CA 92717 USA. EG&G Serv Inc, Wallops Flight Facil, Wallops Island, VA 23337 USA. RP Walsh, EJ (reprint author), NOAA, Environm Technol Lab, R-E-ET6,325 Broadway, Boulder, CO 80303 USA. RI Burns, Sean/A-9352-2008 OI Burns, Sean/0000-0002-6258-1838 NR 18 TC 6 Z9 6 U1 0 U2 1 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 JUN 15 PY 1998 VL 103 IS C6 BP 12603 EP 12612 DI 10.1029/98JC00780 PG 10 WC Oceanography SC Oceanography GA ZU093 UT WOS:000074160900002 ER PT J AU Walsh, EJ Pinkel, R Hagan, DE Weller, RA Fairall, CW Rogers, DP Burns, SP Baumgartner, M AF Walsh, EJ Pinkel, R Hagan, DE Weller, RA Fairall, CW Rogers, DP Burns, SP Baumgartner, M TI Coupling of internal waves on the main thermocline to the diurnal surface layer and sea surface temperature during the Tropical Ocean Global Atmosphere Coupled Ocean-Atmosphere Response Experiment SO JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS LA English DT Article AB Patterns in sea surface temperature (SST) on 5-km scales were observed from low-flying research aircraft on a light wind day during the Tropical Ocean-Global Atmosphere Coupled Ocean Atmosphere Response Experiment. An inverse trend was observed between the SST and the sea surface mean square slope (mss). However, low correlation coefficients indicate that the dominant process causing the spatial variation of SST under these light wind conditions is neither well controlled by the wind speed nor well monitored by the mss. The SST spatial pattern persisted for at least 1 hour and propagated toward the NE at about 1 m s(-1), a factor of 1.6 faster than the speed of the surface current. Coupling between internal gravity waves propagating on the seasonal thermocline and the diurnal surface layer is examined as a possible explanation for the observed SST variability in space and time. C1 NOAA, Environm Technol Lab, Boulder, CO 80303 USA. Woods Hole Oceanog Inst, Woods Hole, MA 02543 USA. Univ Calif Irvine, Dept Mech Engn, Irvine, CA 92717 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ Calif San Diego, Scripps Inst Oceanog, La Jolla, CA 92093 USA. NASA, Goddard Space Flight Ctr, Lab Hydrospher Proc, Observat Sci Branch, Wallops Island, VA 23337 USA. RP Walsh, EJ (reprint author), NOAA, Environm Technol Lab, R-E-ET6,325 Broadway, Boulder, CO 80303 USA. RI Burns, Sean/A-9352-2008 OI Burns, Sean/0000-0002-6258-1838 NR 26 TC 13 Z9 13 U1 0 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 JUN 15 PY 1998 VL 103 IS C6 BP 12613 EP 12628 DI 10.1029/98JC00894 PG 16 WC Oceanography SC Oceanography GA ZU093 UT WOS:000074160900003 ER PT J AU Kantha, LH Stewart, JS Desai, SD AF Kantha, LH Stewart, JS Desai, SD TI Long-period lunar fortnightly and monthly ocean tides SO JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS LA English DT Article ID EARTHS ROTATION RATE; ALTIMETRY AB Long-period lunar fortnightly (Mf) and monthly (Mm) tides in the global oceans are of particular interest to geophysicists because of their impact on the Earth's rotation, and they are of interest to oceanographers from the point of view of the response characteristics of the global oceans to low-frequency forcing. Long-period tides have long been quite controversial,but precision altimetry is providing an accurate means of measuring and modeling them in the global oceans. Here we describe Mf and Mm tides in the global oceans extracted from a 1 degrees barotropic global hydrodynamic tidal model, which assimilates ocean tides estimated from cycles 10-130 of TOPEX altimetric data by an empirical tide model. The model results enable a better understanding of the energetics of these tides. Compared to the short-period ocean tides, which dissipate a total of roughly 3490 GW of lunisolar gravitational energy, the dissipation rates for Mf and Mm, 0.369 and 0.023 GW, respectively, are quite insignificant from the point of view of the dissipation of tidal energy in the global oceans. Their energy content is also low, 0.381 and 0.049 PJ respectively (compared to 580 PJ in short-period tides). Also compared to the high quality factor Q values for short-period tides (similar to 23 for semidiurnal and similar to 13 for diurnal), the Q values for these tides are 5.9 and 6.2 for Mf and Mm, respectively. The corresponding unassimilated model Q value is 5.8 for both. These Q values correspond to a decay timescale of the order of a period and hence indicate that unlike its response to short-period tidal forcing, the oceanic response to barotropic forcing at these low frequencies is like a heavily damped system. They are also consistent with the low values of Q (similar to 5.5) observed in the global oceans on timescales of several days. The relative potential energy to kinetic energy ratios for Mf and Mm tides (0.59 and 2.91 for assimilated and 0.83 and 3.20 for unassimilated, for Mf and Mm, respectively) are consistent with the dynamics of long-wavelength Rossby waves. At amplitudes of similar to 0.115 ms in universal time, UT1, for both Mf and Mm, the impact of these long-period tides on the length of day fluctuations of the Earth is considerable. C1 Univ Colorado, Dept Aerosp Engn Sci, Boulder, CO 80309 USA. Univ Colorado, Program Atmospher & Ocean Sci, Boulder, CO 80309 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Kantha, LH (reprint author), Univ Colorado, Dept Aerosp Engn Sci, Campus Box 431, Boulder, CO 80309 USA. NR 29 TC 20 Z9 21 U1 1 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 JUN 15 PY 1998 VL 103 IS C6 BP 12639 EP 12647 DI 10.1029/98JC00888 PG 9 WC Oceanography SC Oceanography GA ZU093 UT WOS:000074160900005 ER PT J AU Shuchman, RA Josberger, EG Russel, CA Fischer, KW Johannessen, OM Johannessen, J Gloersen, P AF Shuchman, RA Josberger, EG Russel, CA Fischer, KW Johannessen, OM Johannessen, J Gloersen, P TI Greenland Sea Odden sea ice feature: Intra-annual and interannual variability SO JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS LA English DT Article ID NIMBUS-7 SMMR; MICROWAVE; WINTER; ZONE; MESOSCALE; NORTH; CONVECTION; REDUCTION; WATER; OCEAN AB The "Odden" is a large sea ice feature that forms in the east Greenland Sea that may protrude eastward to 5 degrees E from the main sea ice pack (at about 8 degrees W) between 73 degrees and 77 degrees N. It generally forms at the beginning of the winter season and can cover 300,000 km(2). Throughout the winter the outer edge of the Odden may advance and retreat by several hundred kilometers on timescales of a few days to weeks. Satellite passive microwave observations from 1978 through 1995 provide a continuous record of the spatial and temporal variations of this extremely dynamic phenomenon. Aircraft synthetic aperture radar, satellite passive microwave, and ship observations in the Odden show that the Odden consists of new ice types, rather than older ice types advected eastward from the main pack. The 17-year record shows both strong interannual and intra-annual variations in Odden extent and temporal behavior. For example, in 1983 the Odden was weak, in 1984 the Odden did not occur, and in 1985 the Odden returned late in the season. An analysis of the ice area and extent time series derived from the satellite passive microwave observations along with meteorological data from the International Arctic Buoy Program (IABP) determined the meteorological forcing associated with Odden growth, maintenance, and decay. The key meteorological parameters that are related to the rapid ice formation and decay associated with the Odden are, in order of importance, air temperature, wind speed, and wind direction. Oceanographic parameters must play an important role in controlling Odden formation, but it is not yet possible to quantify this role because of a lack of long-term oceanographic observations. C1 ERIM Int Inc, Ann Arbor, MI 48113 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. European Space Agcy, Estec, European Space Res & Technol Ctr, NL-2200 AG Noordwijk, Netherlands. Nansen Environm & Remote Sensing Ctr, N-5037 Bergen, Norway. Univ Puget Sound, US Geol Survey, Ice & Climate Project, Tacoma, WA 98416 USA. RP Shuchman, RA (reprint author), ERIM Int Inc, POB 134008, Ann Arbor, MI 48113 USA. NR 47 TC 24 Z9 26 U1 0 U2 1 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 JUN 15 PY 1998 VL 103 IS C6 BP 12709 EP 12724 DI 10.1029/98JC00375 PG 16 WC Oceanography SC Oceanography GA ZU093 UT WOS:000074160900010 ER PT J AU Moller, D Frasier, SJ Porter, DL McIntosh, RE AF Moller, D Frasier, SJ Porter, DL McIntosh, RE TI Radar-derived interferometric surface currents and their relationship to subsurface current structure SO JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS LA English DT Article ID SYNTHETIC-APERTURE RADAR; MICROWAVE BACKSCATTER; OCEAN SURFACE; DUAL-FREQUENCY; WAVE; MODULATION; FRONTS; SEA AB Radar-derived ocean surface currents are analyzed in conjunction with in situ acoustic Doppler current profiler (ADCP) measurements. The interferometric measurements were collected by an X-band imaging Doppler radar in a manner analogous to those of along-track interferometric synthetic aperture radar (ATI-SAR). While the advent of ATI-SAR has provided a new, potentially powerful technique for current mapping, the relationship between surface currents and interferometric velocity measurements is not yet clearly understood. This paper presents comparisons between radar-derived and in situ current measurements. To develop a precise method for estimating the surface current from interferometric measurements, the influence of long wave orbital velocities and the influence of Bragg resonant waves are studied. We find that coupling between the orbital velocity and backscattered power (i.e., the modulation transfer function) can bias surface current estimates, potentially by up to 20 cm s(-1) in an upwind viewing orientation. Furthermore, experimental observations verify a cos(2n) (theta/2) analytical model for the directional spreading of Bragg resonant waves. Extending our analysis to include subsurface currents, case studies are presented under varying environmental conditions for which the vertical current structure changes considerably. Analysis of radar imagery yields both radial surface currents and vector subsurface current estimates derived from long wave dispersion characteristics. Combining these with coincident ADCP measurements yields a vertical profile of current. Using these measurement techniques, we make several observations within the upper meter of the ocean. These profiles reveal the sensitivity of X-band interferometric measurements to wind-drift and the near-surface current structure. C1 Univ Massachusetts, Microwave Remote Sensing Lab, Amherst, MA 01003 USA. Johns Hopkins Univ, Appl Phys Lab, Laurel, MD 20723 USA. RP Moller, D (reprint author), Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. RI Frasier, Stephen/H-1536-2015 OI Frasier, Stephen/0000-0003-4287-2889 NR 28 TC 21 Z9 22 U1 1 U2 3 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 JUN 15 PY 1998 VL 103 IS C6 BP 12839 EP 12852 DI 10.1029/98JC00781 PG 14 WC Oceanography SC Oceanography GA ZU093 UT WOS:000074160900018 ER PT J AU Lindstrom, E Bingham, F Kindle, J Saunders, P Wijffels, S AF Lindstrom, E Bingham, F Kindle, J Saunders, P Wijffels, S TI World Ocean Circulation Experiment (WOCE): Pacific results SO JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS LA English DT Editorial Material C1 NASA, Washington, DC 20546 USA. Univ N Carolina, Wilmington, NC 28401 USA. Southampton Oceanog Ctr, Southampton, Hants, England. CSIRO, Div Marine Res, Hobart, Tas, Australia. RP Lindstrom, E (reprint author), NASA, Washington, DC 20546 USA. RI Wijffels, Susan/I-8215-2012 NR 0 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 JUN 15 PY 1998 VL 103 IS C6 BP 12897 EP 12897 DI 10.1029/98JC01611 PG 1 WC Oceanography SC Oceanography GA ZU093 UT WOS:000074160900024 ER PT J AU Wolfenden, A Coan, DA Hebsur, MG AF Wolfenden, A Coan, DA Hebsur, MG TI Investigation of the dynamic Young's modulus and vibration damping for cryomilled NiAl-AlN composites SO JOURNAL OF MATERIALS SCIENCE LA English DT Article ID TEMPERATURE AB Measurements were made of the dynamic Young's modulus (stiffness) and damping for NiAl specimens containing varying amounts of aluminium nitride and prepared by cryomilling. Five specimens of NiAl-AlN were measured at room temperature, each specimen having a different percentage of AIN in the range 1%-30%. Further measurements were made on the 1% and 30% AIN specimens for the temperature range 22-495 degrees C. At room temperature, the Young's modulus of the NiAl-AlN specimens decreased linearly with increasing percentage of AIN. The temperature dependence of Young's modulus for the 1% and 30% AIN specimens was found to be linear. These results were compared with those of typical nickel-based superalloys for a similar temperature range. The damping for all of the NiAl-AlN specimens was of the order of that for other intermetallic com pounds (10(-3)-10(-4)). The study opened up the possibility of NiAl-AlN being a less-expensive and more easily produced alternative to nickel-based superalloys for high-temperature, high-stiffness applications. (C) 1998 Kluwer Academic Publishers. C1 Texas A&M Univ, Dept Mech Engn, College Stn, TX 77843 USA. NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. RP Wolfenden, A (reprint author), Texas A&M Univ, Dept Mech Engn, College Stn, TX 77843 USA. NR 10 TC 1 Z9 1 U1 1 U2 2 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 JUN 15 PY 1998 VL 33 IS 12 BP 3183 EP 3186 DI 10.1023/A:1004360209778 PG 4 WC Materials Science, Multidisciplinary SC Materials Science GA 149DV UT WOS:000077590600025 ER PT J AU Ramasundaram, P Bowman, R Soboyejo, W AF Ramasundaram, P Bowman, R Soboyejo, W TI An investigation of fatigue and fracture in NiAl-Mo composites SO MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING LA English DT Article DE fatigue; fracture; NiAl-Mo composites ID MECHANICAL-PROPERTIES; CRACK DEFLECTION; PHASE; ALLOY; DEFORMATION; TOUGHNESS; CERAMICS; BEHAVIOR; FLOW; CR AB The effects of reinforcement morphology (particulate versus fibers) and particulate volume fraction on the fatigue and fracture behavior of NiAl-Mo composites are discussed. The improved fracture toughness observed in these composites are not associated with improved tensile ductility. The improved fracture toughness levels are explained by quantifying the shielding contributions due to crack trapping mechanisms. Stable crack growth under cyclic loading was observed at room temperature in all the NiAl-Mo composites that were studied. The potential implications of the results are discussed for future composite development. (C) 1998 Elsevier Science S.A. All rights reserved. C1 Wyman Gordon Forgings, Houston, TX 77095 USA. NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. Ohio State Univ, Dept Mat Sci & Engn, Columbus, OH 43210 USA. RP Soboyejo, W (reprint author), Dept Mat Sci & Engn, Room 8-401,77 Massachusetts Ave, Cambridge, MA 02139 USA. NR 27 TC 17 Z9 17 U1 1 U2 1 PU ELSEVIER SCIENCE SA PI LAUSANNE PA PO BOX 564, 1001 LAUSANNE, SWITZERLAND SN 0921-5093 J9 MAT SCI ENG A-STRUCT JI Mater. Sci. Eng. A-Struct. Mater. Prop. Microstruct. Process. PD JUN 15 PY 1998 VL 248 IS 1-2 BP 132 EP 146 DI 10.1016/S0921-5093(98)00503-6 PG 15 WC Nanoscience & Nanotechnology; Materials Science, Multidisciplinary; Metallurgy & Metallurgical Engineering SC Science & Technology - Other Topics; Materials Science; Metallurgy & Metallurgical Engineering GA ZZ400 UT WOS:000074725600016 ER PT J AU Han, J Anantram, MP Jaffe, RL Kong, J Dai, H AF Han, J Anantram, MP Jaffe, RL Kong, J Dai, H TI Observation and modeling of single-wall carbon nanotube bend junctions SO PHYSICAL REVIEW B LA English DT Article AB Single-wall carbon nanotube (SWNT) bends, with diameters from similar to 1.0 to 2.5 nm and bend angles from 18 degrees to 34 degrees, are observed in catalytic decomposition of hydrocarbons at 600-1200 degrees C. An algorithm using molecular dynamics (MD) simulation techniques is developed to model these structures that are considered to be SWNT junctions formed by topological defects (i.e., pentagon-heptagon pairs). The algorithm is used to predict the; tube helicities and defect configurations for bend junctions using the observed tube diameters and bend angles. The number and arrangement of die defects at the junction interfaces are found to depend on the tube helicities and bend angle. The structural and energetic calculations using the Brenner potential show a number of stable junction configurations for each bend angle with the 34 degrees bends being more stable than the others. Tight-binding calculations for local density of state and transmission coefficients are carried out to investigate electrical properties of the bend junctions. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Stanford Univ, Dept Chem, Palo Alto, CA 94053 USA. RP Han, J (reprint author), NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. NR 20 TC 107 Z9 108 U1 0 U2 12 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 JUN 15 PY 1998 VL 57 IS 23 BP 14983 EP 14989 DI 10.1103/PhysRevB.57.14983 PG 7 WC Physics, Condensed Matter SC Physics GA ZV141 UT WOS:000074273500064 ER PT J AU Il'in, KS Ptitsina, NG Sergeev, AV Gol'tsman, GN Gershenzon, EM Karasik, BS Pechen, EV Krasnosvobodtsev, SI AF Il'in, KS Ptitsina, NG Sergeev, AV Gol'tsman, GN Gershenzon, EM Karasik, BS Pechen, EV Krasnosvobodtsev, SI TI Interrelation of resistivity and inelastic electron-phonon scattering rate in impure NbC films SO PHYSICAL REVIEW B LA English DT Article ID THIN METAL-FILMS; PHASE-COHERENCE TIME; WEAK LOCALIZATION; ALUMINUM FILMS; TEMPERATURES; MECHANISMS; DEPENDENCE; TRANSITION AB A complex study of the electron-phonon interaction in thin NbC films with electron mean free path l=2-13 nm gives strong evidence that electron scattering is significantly modified due to the interference between electron-phonon and elastic electron scattering from impurities. The interference T-2 term, which is proportional to the residual resistivity, dominates over the Bloch-Gruneisen contribution to resistivity at low temperatures up to 60 K. The electron energy relaxation rate is directly measured via the relaxation of hot electrons heated by modulated electromagnetic radiation. In the temperature range 1.5-10 K the relaxation rate shows a weak dependence on the electron mean free path and strong temperature dependence similar to T-n, with the exponent n = 2.5-3. This behavior is explained well by the theory of the electron-phonon-impurity interference taking into account the electron coupling with transverse phonons determined from the resistivity data. C1 Moscow State Pedag Univ, Moscow 119435, Russia. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. PN Lebedev Phys Inst, Moscow 117924, Russia. RP Il'in, KS (reprint author), Moscow State Pedag Univ, Moscow 119435, Russia. RI Krasnosvobodtsev, Sergei/M-7977-2015 NR 33 TC 31 Z9 32 U1 1 U2 6 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 JUN 15 PY 1998 VL 57 IS 24 BP 15623 EP 15628 DI 10.1103/PhysRevB.57.15623 PG 6 WC Physics, Condensed Matter SC Physics GA ZY631 UT WOS:000074643000079 ER PT J AU Bauschlicher, CW Ricca, A AF Bauschlicher, CW Ricca, A TI Accurate heats of formation for SF(n), SF(n)(+), and SF(n)(-) for n=1-6 SO JOURNAL OF PHYSICAL CHEMISTRY A LA English DT Article ID GAUSSIAN-BASIS SETS; CORRELATED MOLECULAR CALCULATIONS; CHARGE-TRANSFER REACTIONS; COUPLED-CLUSTER THEORY; ELECTRON-ATTACHMENT; WAVE-FUNCTIONS; ATOMIZATION ENERGIES; SULFUR; ION; THERMOCHEMISTRY AB Accurate heats of formation are computed for SF(n), SF(n)(+), and SF(n)(-), for n = 1-6. The geometries and vibrational frequencies are determined at the B3LYP level of theory. The energetics are determined at the CCSD(T) level of theory. Extrapolation to the basis set limit is discussed. The temperature dependence of the heat of formation, heat capacity, and entropy are computed for the temperature range 300-4000 K and fit to a polynomial. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Stanford Univ, Dept Chem Engn, Stanford, CA 94305 USA. RP Bauschlicher, CW (reprint author), NASA, Ames Res Ctr, STC-230-3, Moffett Field, CA 94035 USA. NR 46 TC 57 Z9 57 U1 0 U2 2 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 JUN 11 PY 1998 VL 102 IS 24 BP 4722 EP 4727 DI 10.1021/jp981084p PG 6 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA ZV246 UT WOS:000074285000042 ER PT J AU Gendreau, KC Barcons, X Fabian, AC AF Gendreau, KC Barcons, X Fabian, AC TI Deep hard X-ray source counts from a fluctuation analysis of ASCA SIS images SO MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY LA English DT Article DE methods : statistical; diffuse radiation; X-rays : general ID N-LOG-S; ROSAT; ORIGIN AB An analysis of the spatial fluctuations in 15 deep ASCA SISO images has been conducted in order to probe the 2-10 keV X-ray source counts down to a flux limit similar to 2 x 10(-14) erg cm-2 s(-1). Special care has been taken in modelling the fluctuations in terms of the sensitivity maps of every one of the 16 regions (5.6 x 5.6 arcmin(2) each) into which the SISO has been divided, by means of ray-tracing simulations with improved optical constants in the X-ray telescope. The very extended 'sidelobes' (extending up to a couple of degrees) exhibited by these sensitivity maps make our analysis sensitive to both faint on-axis sources and brighter off-axis ones, the former being dominant. The source counts in the range (2-12) x 10(-14) erg cm(-2) s(-1) are found to be close to a Euclidean form which extrapolates well to previous results from higher fluxes and are in reasonable agreement with some recent ASCA surveys. However, our results disagree with the deep survey counts by Georgantopoulos et al, The possibility that the source counts flatten to a sub-Euclidean form, as is observed at soft energies in ROSAT data, is only weakly constrained to happen at a flux < 1.8 x 10(-12) erg cm(-2) s(-1) (90 per cent confidence). Down to the sensitivity limit of our analysis, the integrated contribution of the sources the imprint of which is seen in the fluctuations amounts to similar to 35 +/- 13 per cent of the extragalactic 2-10 keV X-ray background. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Cantabria, Inst Fis Cantabria, CSIC, E-39005 Santander, Spain. Univ Cambridge, Inst Astron, Cambridge CB3 0HA, England. RP Gendreau, KC (reprint author), NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RI Barcons, Xavier/L-3335-2014 OI Barcons, Xavier/0000-0003-1081-8861 NR 29 TC 19 Z9 19 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 JUN 11 PY 1998 VL 297 IS 1 BP 41 EP 48 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZW778 UT WOS:000074447400010 ER PT J AU Wilhelm, K Lemaire, P Dammasch, IE Hollandt, J Schuhle, U Curdt, W Kucera, T Hassler, DM Huber, MCE AF Wilhelm, K Lemaire, P Dammasch, IE Hollandt, J Schuhle, U Curdt, W Kucera, T Hassler, DM Huber, MCE TI Solar irradiances and radiances of UV and EUV lines during the minimum of sunspot activity in 1996 SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE Sun : corona; Sun : transition region; Sun : UV radiation; Sun : activity ID QUIET-SUN; RADIATIVE OUTPUT; VARIABILITY; EMISSION; SPECTRUM; FLUXES; SUMER; SOHO AB Full Sun observations in UV and EUV emission lines were performed by SUMER (Solar Ultraviolet Measurements of Emitted Radiation) on SOHO (Solar and Heliospheric Observatory) in 1996. The radiometric pre-flight calibration of SUMER is traceable to a primary radiometric source standard - the electron storage ring BESSY. Based on this calibration, the irradiance values at SOHO and at 1 AU have been obtained for the lines He I (X 584.33 Angstrom), O V ( 629.74 Angstrom), Ne VIII (lambda 770.41 Angstrom), S V (lambda 786.47 Angstrom), O IV (lambda 787.72 Angstrom), S VI (lambda lambda 933.39, 944.52 Angstrom), HI Ly epsilon (lambda 937.80 Angstrom), C III (lambda 977.04 Angstrom), N V (lambda 1238.81 Angstrom), Si I(lambda 1256.52 Angstrom), and C IV (lambda 1548.20 Angstrom). The spatially resolved measurements allowed good estimates to be made of the active region contributions to the irradiance of the quiet Sun. The centre-to-limb radiance variations of these lines have also been obtained from these measurements. For quiet solar conditions, a radiance spectrum was determined for wavelengths from 800 Angstrom to 1500 Angstrom near the centre of the solar disk. C1 Max Planck Inst Aeron, D-37191 Katlenburg Lindau, Germany. Univ Paris 11, Inst Astrophys Spatiale, CNRS, Unite Mixte, F-91405 Orsay, France. Phys Tech Bundesanstalt, D-10587 Berlin, Germany. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. SW Res Inst, Boulder, CO 80302 USA. European Space Agcy, Estec, Dept Space Sci, NL-2200 AG Noordwijk, Netherlands. RP Wilhelm, K (reprint author), Max Planck Inst Aeron, Max Planck Str 2, D-37191 Katlenburg Lindau, Germany. EM Wilhelm@linmpi.mpg.de RI Kucera, Therese/C-9558-2012; Hollandt, Jorg/A-2124-2014 NR 54 TC 91 Z9 92 U1 1 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 JUN 10 PY 1998 VL 334 IS 2 BP 685 EP 702 PG 18 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZW909 UT WOS:000074460500041 ER PT J AU Petitjean, P Surdej, J Smette, A Shaver, P Mucket, J Remy, M AF Petitjean, P Surdej, J Smette, A Shaver, P Mucket, J Remy, M TI HST observations of the QSO pair Q1026-0045A,B SO ASTRONOMY & ASTROPHYSICS LA English DT Letter DE quasars : individual : Q 1026-0045A,B; galaxies : ISM; quasars : absorption lines; galaxies : halo ID ALPHA ABSORPTION-LINES; SYSTEMS; SIZE; SPECTRA; CLOUDS; GAS AB The spatial distribution of the Ly alpha forest is studied using new HST data for the quasar pair Q 1026-0045 A and B at z(em) = 1.438 and 1.520 respectively. The angular separation is 36 arcsec and corresponds to transverse linear separations between lines of sight of similar to 300h(50)(-1) kpc (q(o) = 0.5) over the redshift range 0.833 < z < 1.438. From the observed numbers of coincident and anti-coincident Ly alpha absorption lines, we conclude that, at this redshift, the Ly alpha structures have typical dimensions of similar to 500(50)(-1) kpc, larger than the mean separation of the two lines of sight. The velocity difference, Delta V, between coincident lines is surprisingly small (4 and 8 pairs with Delta V < 50 and 200 km s(-1) respectively). Metal line systems are present at z(abs) = 1.2651 and 1.2969 in A, z(abs) = 0.6320, 0.7090, 1.2651 and 1.4844 in B. In addition we tentatively identify a weak Mg II system at z(abs) = 0.11 in B. It is remarkable that the z(abs) = 1.2651 system is common to both lines of sight. The system at z(abs) = 1.4844 has strong O VI absorption. There is a metal-poor associated system at z(abs) = 1.4420 along the line of sight to A with complex velocity profiler We detect a strong Ly alpha absorption along the line of sight to B redshifted by only 300 km s-(1) relatively to the associated system. It is tempting to interpret this as the presence of a disk of radius larger than 300h(50)(-1) kpc surrounding quasar A. C1 CNRS, Inst Astrophys, F-75014 Paris, France. Observ Paris Meudon, DAEC, CNRS, UA 173, F-92195 Meudon, France. Univ Liege, Inst Astrophys, B-4000 Liege, Belgium. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. European So Observ, D-85748 Garching, Germany. Inst Astrophys, D-14482 Potsdam, Germany. FNRS, Rech, Brussels, Belgium. RP Petitjean, P (reprint author), CNRS, Inst Astrophys, 98 Bis Blvd Arago, F-75014 Paris, France. EM petitjean@iap.fr NR 28 TC 38 Z9 38 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 JUN 10 PY 1998 VL 334 IS 2 BP L45 EP L48 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZW909 UT WOS:000074460500004 ER PT J AU Ferraro, FR Paltrinieri, B Pecci, FF Rood, RT Dorman, B AF Ferraro, FR Paltrinieri, B Pecci, FF Rood, RT Dorman, B TI Multimodal distributions along the horizontal branch SO ASTROPHYSICAL JOURNAL LA English DT Article DE globular clusters : individual (M80, M13, M3); stars : evolution; stars : horizontal-branch; ultraviolet : stars ID GALACTIC GLOBULAR-CLUSTERS; PHOTOGRAPHIC PHOTOMETRY; CCD-PHOTOMETRY; STARS; HALO; MORPHOLOGY; NGC-1904; GIANT; POPULATIONS; ORIGIN AB We report on the Hubble Space Telescope (HST) Wide Field Planetary Camera 2 (WFPC2) U, V, and far-ultraviolet observations of three galactic globular clusters (GGCs), NGC 5272 = M3, NGC 6205 = M13, and NGC 6093 = M80. Two of these clusters (namely, M13 and M80) have horizontal-branch (HB) tails that extend to the helium-burning main sequence, with the hottest stars reaching theoretical effective temperatures above 35,000 K. In both dusters, groups of stars are found to be separated by narrow gaps along the blue HB sequence. These gaps appear at similar locations in the color-magnitude diagrams of the two dusters. While stochastic effects may give rise to variations in the color distribution along the HB, the coincidence of gaps in different clusters effectively rules this out as the primary cause. The comparison among the clusters strongly suggests that there are separate physical processes operating during the earlier red giant phase of evolution to produce mass loss. C1 Osservatorio Astron Bologna, I-40126 Bologna, Italy. Stn Astron Cagliari, I-09012 Capoterra, Italy. Univ Virginia, Dept Astron, Charlottesville, VA 22903 USA. NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, Greenbelt, MD 20771 USA. RP Ferraro, FR (reprint author), Osservatorio Astron Bologna, Via Zamboni 33, I-40126 Bologna, Italy. NR 58 TC 98 Z9 99 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 JUN 10 PY 1998 VL 500 IS 1 BP 311 EP 319 DI 10.1086/305712 PN 1 PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZV139 UT WOS:000074273300026 ER PT J AU Brage, T Judge, PG Aboussaid, A Godefroid, MR Jonsson, P Ynnerman, A Fischer, CF Leckrone, DS AF Brage, T Judge, PG Aboussaid, A Godefroid, MR Jonsson, P Ynnerman, A Fischer, CF Leckrone, DS TI Hyperfine induced transitions as diagnostics of isotopic composition and densities of low-density plasmas SO ASTROPHYSICAL JOURNAL LA English DT Article DE atomic processes; plasmas; radiative transfer ID ELECTRON-IMPACT-EXCITATION; HARTREE-FOCK CALCULATIONS; MAGNESIUM-LIKE IONS; C-III; N-IV; COLLISION STRENGTHS; ALLOWED TRANSITIONS; LINES; PROGRAM; SOLAR AB The J = 0 --> J' = 0 radiative transitions, usually viewed as allowed through two-photon decay, may also be induced by the hyperfine (HPF) interaction in atoms or ions having a nonzero nuclear spin. We compute new and review existing decay rates for the nsnp P-3(J)0 --> nS(2 1)S(J'= 0) transitions in ions of the Be (n = 2) and Mg (n = 3) isoelectronic sequences. The HPF induced decay rates for the J = 0 --> J' = 0 transitions are many orders of magnitude larger than those for the competing two-photon processes, and when present are typically 1 or 2 orders of magnitude smaller than the decay rates of the magnetic quadrupole (J = 2 --> J' = 0) transitions for these ions. Several HPF induced transitions are potentially of astrophysical interest in ions of C, N, Na, Mg, Al, Si, K, Cr, Fe, and Ni. We highlight those cases that may be of particular diagnostic value for determining isotopic abundance ratios and/or electron densities from UV or EUV emission-line data. We present our atomic data in the form of scaling laws so that, given the isotopic nuclear spin and magnetic moment, a simple expression yields estimates for HPF induced decay rates. We examine some UV and EUV solar and nebular data in light of these new results and suggest possible applications for future study. We could not find evidence for the existence of HPF induced lines in the spectra we examined, but we demonstrate that existing data have come close to providing interesting upper limits. For the planetary nebula SMC N2, we derive an upper limit of 0.1 for C-13/C-12 from Goddard High-Resolution Spectrograph data obtained by Clegg. It is likely that more stringent limits could be obtained using newer data with higher sensitivities in a variety of objects. C1 Comp Sci Corp, Cincinnati, OH 45202 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Natl Ctr Atmospher Res, High Altitude Observ, Boulder, CO 80307 USA. Free Univ Brussels, Lab Chim Phys Mol, B-1050 Brussels, Belgium. Vanderbilt Univ, Dept Comp Sci, Nashville, TN 37235 USA. RP Brage, T (reprint author), Univ Lund, Dept Phys, Box 118, S-22100 Lund, Sweden. RI Jonsson, Per/L-3602-2013; OI Jonsson, Per/0000-0001-6818-9637; Brage, Tomas/0000-0003-3985-767X NR 52 TC 60 Z9 61 U1 0 U2 5 PU UNIV CHICAGO PRESS PI CHICAGO PA 5801 S ELLIS AVENUE, CHICAGO, IL 60637 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD JUN 10 PY 1998 VL 500 IS 1 BP 507 EP 521 DI 10.1086/305690 PN 1 PG 15 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZV139 UT WOS:000074273300043 ER PT J AU Peters, GJ Polidan, RS AF Peters, GJ Polidan, RS TI ORFEUS-SPAS II observations of Algol-type interacting binaries SO ASTROPHYSICAL JOURNAL LA English DT Article DE accretion, accretion disks; binaries, close; circumstellar matter; ultraviolet, stars ID ACCRETION DISKS; ELEMENTS AB The first results from ORFEUS-SPAS II observations of five Algol-type binary systems obtained during the shuttle mission STS-80 in 1996 November/December are reported. Single spectra covering 900-1220 Angstrom of AU Mon, Z Vul, U CrB, and TX UMa were acquired with the Berkeley spectrograph. TT Hya was observed at three phases (0.19, 0.63, and 0.95) to study mass flow and to investigate asymmetry in the circumstellar material in the system. O VI was not detected in any of the binaries, which allows us to place an upper limit on T,,, in the high-temperature plasma seen in Algol-type binaries. Circumstellar material, presumably associated with the accretion disk, was detected in Fe III (UV1) in AU Mon. We estimate a particle density in the range 10(8)-10(9) cm(-3) for the region of the disk sampled during the observations. Evidence for mass infall was found in the phase 0.95 spectrum of TT Hya. From the additional (redshifted) absorption in N II (1085 Angstrom) and N I (1135 Angstrom), we find evidence for superionization in this plasma and estimate a lower limit of 10( )(-12)M. yr(-1) for the current infall rate. C1 Univ So Calif, Ctr Space Sci, Los Angeles, CA 90089 USA. NASA, Goddard Space Flight Ctr, Space Sci Directorate, Greenbelt, MD 20771 USA. RP Peters, GJ (reprint author), Univ So Calif, Ctr Space Sci, Los Angeles, CA 90089 USA. EM gjpeters@mucen.usc.edu; Ronald.S.Polidan.1@gsfc.nasa.gov NR 23 TC 13 Z9 13 U1 0 U2 0 PU IOP PUBLISHING LTD PI BRISTOL PA DIRAC HOUSE, TEMPLE BACK, BRISTOL BS1 6BE, ENGLAND SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD JUN 10 PY 1998 VL 500 IS 1 BP L17 EP L20 DI 10.1086/311398 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZV153 UT WOS:000074275000004 ER PT J AU Trinh, EH Thiessen, DB Holt, RG AF Trinh, EH Thiessen, DB Holt, RG TI Driven and freely decaying nonlinear shape oscillations of drops and bubbles immersed in a liquid: Experimental results SO JOURNAL OF FLUID MECHANICS LA English DT Article ID IMMISCIBLE LIQUID; VISCOUS DROPLETS; SURFACE-TENSION; INVISCID DROPS; WATER; FIELD AB Large-amplitude oscillations of drops and bubbles immersed in an immiscible liquid host have been investigated using ultrasonic radiation pressure techniques. Single levitated or trapped drops and bubbles with effective radius between 0.2 and 0.8 cm have been driven into resonant shape oscillations of the first few orders. The direct coupling of driven drop shape oscillations between the axisymmetric l = 6 and l = 3 modes has been documented as well as the interaction between axisymmetric and non-axisymmetric I = 3 and I = 2 modes. Effective resonant energy transfer from higher- to lower-order modes has been observed together with a much less efficient energy transfer in the reverse direction. The first three resonant modes for bubbles trapped in water have also been excited, and mode coupling during driven and free-decaying oscillations has been measured. The evidence gathered thus far indicates that efficient drop resonant coupling between a higher- and a lower-order mode occurs when the characteristic frequency of the latter mode roughly coincides with a harmonic resonance. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Washington State Univ, Dept Phys, Pullman, WA 99164 USA. Boston Univ, Dept Aerosp & Mech Engn, Boston, MA 02215 USA. RP Trinh, EH (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. RI Thiessen, David/A-2731-2011; Holt, Ray/G-5677-2010 NR 37 TC 40 Z9 41 U1 0 U2 8 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 JUN 10 PY 1998 VL 364 BP 253 EP 272 DI 10.1017/S0022112098001153 PG 20 WC Mechanics; Physics, Fluids & Plasmas SC Mechanics; Physics GA ZY343 UT WOS:000074611000011 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 Distribution of rock, metals, and ices in Callisto SO SCIENCE LA English DT Article ID GALILEAN SATELLITES; TIDAL DISSIPATION; ICY SATELLITES; INTERNAL STRUCTURES; GANYMEDE; MODELS; IO; EVOLUTION; MIXTURES AB Radio Doppler data from a single encounter (C3) of the Galileo spacecraft with Callisto, the outermost Galilean moon of Jupiter, indicated that Callisto was probably undifferentiated. Now, similar data from a second encounter (C9) corroborate this conclusion, but more accurate data from a third encounter (C10) indicate that the rock and ice within Callisto have partially, but not completely, separated. Callisto may be differentiated into a rock-metal core less than 25 percent of Callisto's radius, an outer layer of clean ice less than 350 km thick, and a middle layer of mixed rock and ice. Models in which ice and rock are mixed all the way to the center of Callisto are also consistent with the data. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ Calif Los Angeles, Inst Geophys & Planetary Phys, Dept Earth & Space Sci, Los Angeles, CA 90095 USA. RP Anderson, JD (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 39 TC 59 Z9 62 U1 1 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 JUN 5 PY 1998 VL 280 IS 5369 BP 1573 EP 1576 DI 10.1126/science.280.5369.1573 PG 4 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA ZT213 UT WOS:000074061200032 PM 9616114 ER PT J AU Krasnopolsky, VA Mumma, MJ Gladstone, GR AF Krasnopolsky, VA Mumma, MJ Gladstone, GR TI Detection of atomic deuterium in the upper atmosphere of Mars SO SCIENCE LA English DT Article ID INNER SOLAR-SYSTEM; MARTIAN ATMOSPHERE; LYMAN-ALPHA; TERRESTRIAL PLANETS; CHARGE-TRANSFER; WATER; D/H; EVOLUTION; IONS; ABUNDANCE AB High-resolution spectroscopy of Mars' atmosphere with the Hubble Space Telescope revealed the deuterium Lyman alpha line at an intensity of 23 +/- 6 rayleighs. This measured intensity corresponds to HD/H-2 = 1.5 +/- 0.6 x 10(-4), which is smaller by a factor of 11 than HDO/H2O. This indicates that fractionation of HD/H-2 relative to that of HDO/H2O is not kinetically controlled by the rates of formation and destruction of H-2 and HD but is thermodynamically controlled by the isotope exchange HD + H2O <-> HDO + H-2. Molecular hydrogen is strongly depleted in deuterium relative to water on Mars because of the very long lifetime of H-2 (1200 years). The derived isotope fractionation corresponds to an estimate of a planetwide reservoir of water ice about 5 meters thick that is exchangeable with the atmosphere. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Catholic Univ Amer, Dept Phys, Washington, DC 20064 USA. RP Krasnopolsky, VA (reprint author), NASA, Goddard Space Flight Ctr, Code 6902, Greenbelt, MD 20771 USA. RI mumma, michael/I-2764-2013; Krasnopolsky, Vladimir/L-5085-2013 NR 45 TC 70 Z9 69 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 JUN 5 PY 1998 VL 280 IS 5369 BP 1576 EP 1580 DI 10.1126/science.280.5369.1576 PG 5 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA ZT213 UT WOS:000074061200033 PM 9616115 ER PT J AU Harris, AW AF Harris, AW TI Planetary science - Making and braking asteroids SO NATURE LA English DT Editorial Material ID COMET SHOEMAKER-LEVY-9 C1 CALTECH, Jet Prop Lab, Div Earth & Space Sci, Pasadena, CA 91109 USA. RP Harris, AW (reprint author), CALTECH, Jet Prop Lab, Div Earth & Space Sci, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 8 TC 8 Z9 8 U1 0 U2 0 PU MACMILLAN MAGAZINES LTD PI LONDON PA PORTERS SOUTH, 4 CRINAN ST, LONDON, ENGLAND N1 9XW SN 0028-0836 J9 NATURE JI Nature PD JUN 4 PY 1998 VL 393 IS 6684 BP 418 EP 419 DI 10.1038/30857 PG 2 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA ZR842 UT WOS:000074020000026 ER PT J AU Asphaug, E Ostro, SJ Hudson, RS Scheeres, DJ Benz, W AF Asphaug, E Ostro, SJ Hudson, RS Scheeres, DJ Benz, W TI Disruption of kilometre-sized asteroids by energetic collisions SO NATURE LA English DT Article ID IMPACT; FRAGMENTATION; ENCOUNTER AB Recent numerical studies(1-5) suggest that 'rubble-pile' asteroids (gravitationally bound aggregates of collisional debris) are common in the Solar System, and that self-gravitation may equal or exceed material cohesion for planetary bodies as small as several hundred metres. Because analytical scaling relations for impact cratering and disruption(6-8) do not extend to this size regime, where gravity and material strength are both important, detailed simulations are needed to predict how small asteroids evolve through impact, and also to ascertain whether powerful explosions offer a viable defence against bodies headed for a collision with Earth. Here we present simulations, using a smooth-particle hydrodynamics code(9), of energetic impacts into small planetary bodies with internal structure ranging from solid rock to porous aggregate. We find that the outcome of a collision is very sensitive to the configuration of pre-existing fractures and voids in the target. A porous asteroid (or one with deep regolith) damps the propagation of the shock wave from the impactor, sheltering the most distant regions, while greatly enhancing the local deposition of energy. Multiple-component asteroids (such as contact binaries) are also protected, because the shock wave cannot traverse the discontinuity between the components. We conclude that the first impact to significantly fragment an asteroid may determine its subsequent collisional evolution, and that internal structure will greatly influence attempts to disrupt or deflect an asteroid or comet headed towards Earth. C1 Univ Calif Santa Cruz, Dept Earth Sci, Santa Cruz, CA 95064 USA. NASA, Jet Prop Lab 300 233, Pasadena, CA 91109 USA. Washington State Univ, Sch Elect Engn & Comp Sci, Pullman, WA 99164 USA. Iowa State Univ, Dept Aerosp Engn & Engn Mech, Ames, IA 50011 USA. Univ Bern, Inst Phys, CH-3012 Bern, Switzerland. RP Asphaug, E (reprint author), Univ Calif Santa Cruz, Dept Earth Sci, Santa Cruz, CA 95064 USA. NR 24 TC 106 Z9 106 U1 1 U2 9 PU MACMILLAN MAGAZINES LTD PI LONDON PA PORTERS SOUTH, 4 CRINAN ST, LONDON, ENGLAND N1 9XW SN 0028-0836 J9 NATURE JI Nature PD JUN 4 PY 1998 VL 393 IS 6684 BP 437 EP 440 DI 10.1038/30911 PG 4 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA ZR842 UT WOS:000074020000034 ER PT J AU Cerf, NJ AF Cerf, NJ TI Asymmetric quantum cloning machines SO ACTA PHYSICA SLOVACA LA English DT Article AB A family of asymmetric cloning machines for quantum bits and N-dimensional quantum states is introduced. These machines produce two approximate copies of a single quantum state that emerge from two distinct channels. In particular, an asymmetric Pauli cloning machine is defined.that makes two imperfect copies of a quantum bit, while the overall input-to-output operation for each copy is a Pauli channel. A no-cloning inequality is derived, characterizing the impossibility of copying imposed by quantum mechanics. If p and p' are the probabilities of the depolarizing channels associated with the two outputs, the domain in (root p, root p')-space located inside a particular ellipse representing close-to-perfect cloning is forbidden. This ellipse tends to a circle when copying an N-dimensional state with N --> infinity, which has a simple semi-classical interpretation. The symmetric Pauli cloning machines are then used to provide an upper bound on the quantum capacity of the Pauli channel of probabilities p(x), p(y) and p(z). The capacity is proven to be vanishing if (root p(x), root p(y), root p(z)) lies outside an ellipsoid whose pole coincides with the depolarizing channel that underlies the universal cloning machine.:Finally, the tradeoff between the quality of the two copies is shown to result from.a complementarity akin to Heisenberg uncertainty principle. C1 CALTECH, WK Kellogg Radiat Lab, Pasadena, CA 91125 USA. CALTECH, Jet Prop Lab, Informat & Comp Technol Res Sect, Pasadena, CA 91109 USA. Free Univ Brussels, Ctr Nonlinear Phenomena & Complex Syst, B-1050 Brussels, Belgium. RP Cerf, NJ (reprint author), CALTECH, WK Kellogg Radiat Lab, Pasadena, CA 91125 USA. NR 10 TC 54 Z9 54 U1 0 U2 1 PU SLOVAK ACAD SCIENCES INST PHYSICS PI BRATISLAVA PA DUBRAVSKA CESTA 9, 842 28 BRATISLAVA, SLOVAKIA SN 0323-0465 J9 ACTA PHYS SLOVACA JI Acta Phys. Slovaca PD JUN PY 1998 VL 48 IS 3 BP 115 EP 132 PG 18 WC Physics, Multidisciplinary SC Physics GA 103PC UT WOS:000074966200002 ER PT J AU Benson, J Venneri, S AF Benson, J Venneri, S TI With Sam Venneri SO AEROSPACE AMERICA LA English DT Editorial Material C1 NASA Headquarters, Washington, DC 20546 USA. George Washington Univ, Doctoral Program Engn, Washington, DC 20052 USA. NR 0 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 0740-722X J9 AEROSPACE AM JI Aerosp. Am. PD JUN PY 1998 VL 36 IS 6 BP 12 EP 14 PG 3 WC Engineering, Aerospace SC Engineering GA ZQ569 UT WOS:000073881200005 ER PT J AU Hicks, JW AF Hicks, JW TI International efforts scram into flight SO AEROSPACE AMERICA LA English DT Article C1 NASA Dryden, Washington, DC 20546 USA. RP Hicks, JW (reprint author), NASA Dryden, Washington, DC 20546 USA. NR 0 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 0740-722X J9 AEROSPACE AM JI Aerosp. Am. PD JUN PY 1998 VL 36 IS 6 BP 28 EP 33 PG 6 WC Engineering, Aerospace SC Engineering GA ZQ569 UT WOS:000073881200010 ER PT J AU Glymour, C Ford, KM Hayes, PJ AF Glymour, C Ford, KM Hayes, PJ TI Ramon Lull and the infidels SO AI MAGAZINE LA English DT Editorial Material C1 Univ Calif San Diego, San Diego, CA 92103 USA. Carnegie Mellon Univ, Pittsburgh, PA 15213 USA. NASA, Ames Res Ctr, Moffett Field, CA USA. NASA, Ctr Excellence Informat Technol, Washington, DC USA. Univ W Florida, Inst Human & Machine Cognit, Pensacola, FL 32514 USA. RP Glymour, C (reprint author), Univ Calif San Diego, San Diego, CA 92103 USA. NR 0 TC 1 Z9 1 U1 0 U2 1 PU AMER ASSOC ARTIFICIAL INTELL PI MENLO PK PA 445 BURGESS DRIVE, MENLO PK, CA 94025-3496 USA SN 0738-4602 J9 AI MAG JI AI Mag. PD SUM PY 1998 VL 19 IS 2 BP 136 EP 136 PG 1 WC Computer Science, Artificial Intelligence SC Computer Science GA ZW196 UT WOS:000074385300009 ER PT J AU Reda, DC Wilder, MC Mehta, RD Zilliac, G AF Reda, DC Wilder, MC Mehta, RD Zilliac, G TI Measurement of continuous pressure and shear distributions using coating and imaging techniques SO AIAA JOURNAL LA English DT Article; Proceedings Paper CT AIAA 32nd Thermophysics Conference CY JUN 23-25, 1997 CL ATLANTA, GEORGIA SP Amer Inst Aeronaut & Astronaut ID FREE JET IMPINGEMENT AB The pressure-sensitive paint (PSP) method and the shear-sensitive liquid crystal coating (SSLCC) method were sequentially applied to measure the areal pressure and shear stress vector distributions on a planar test surface beneath an inclined, axisymmetric, turbulent impinging jet. The combined results provide the first-ever consolidated measurements of the continuous normal and tangential force distributions beneath a fundamental flowfield. Results indicate that the PSP method can be extended to the measurement of small pressure differences (< similar to 0.1 psig) encountered in low-speed atmospheric flows. Further, these results provide the first demonstration of the capability of the SSLCC method to measure continuous shear stress vector distributions on planar surfaces beneath flowfields where shear vectors of all possible orientations are present. C1 NASA, Ames Res Ctr, Fluid Mech Lab, Moffett Field, CA 94035 USA. RP Reda, DC (reprint author), NASA, Ames Res Ctr, Fluid Mech Lab, Moffett Field, CA 94035 USA. NR 18 TC 18 Z9 19 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 JUN PY 1998 VL 36 IS 6 BP 895 EP 899 DI 10.2514/2.484 PG 5 WC Engineering, Aerospace SC Engineering GA ZQ577 UT WOS:000073882000003 ER PT J AU Lockard, DP Morris, PJ AF Lockard, DP Morris, PJ TI Radiated noise from airfoils in realistic mean flows SO AIAA JOURNAL LA English DT Article; Proceedings Paper CT AIAA 35th Aerospace Science Meeting / Nonlinear Dynamical Systems Symposium CY JAN 06-10, 1997 CL RENO, NEVADA SP Amer Inst Aeronaut & Astronaut, USAF, Off Sci Res, Sandia Natl Labs ID COMPUTATIONAL ACOUSTICS; SCHEMES AB The long-term objective of the research described is to use computational aeroacoustics methodology and parallel computers to increase the understanding of broadband blade noise. In a systematic progression toward simulations of completely realistic configurations and conditions, some simplified problems that address the important features of the flow are investigated. A two dimensional Navier-Stokes code, implemented using the message passing library and Fortran 90 on the IBM SP2, is used to perform the calculations. Results are presented for the interaction of a vortical gust and NACA airfoils, including nonlinear effects. The influence of gust frequency and airfoil thickness is described. A multigrid method is used to obtain converged steady-state solutions before the gust is introduced in a source region inside the domain. C1 Penn State Univ, Dept Aerosp Engn, University Pk, PA 16802 USA. RP Lockard, DP (reprint author), NASA, Langley Res Ctr, MS 128, Hampton, VA 23681 USA. NR 25 TC 30 Z9 32 U1 2 U2 4 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 JUN PY 1998 VL 36 IS 6 BP 907 EP 914 DI 10.2514/2.494 PG 8 WC Engineering, Aerospace SC Engineering GA ZQ577 UT WOS:000073882000005 ER PT J AU Aftosmis, MJ Berger, MJ Melton, JE AF Aftosmis, MJ Berger, MJ Melton, JE TI Robust and efficient Cartesian mesh generation for component-based geometry SO AIAA JOURNAL LA English DT Article AB This work documents a new method for rapid and robust Cartesian mesh generation for component-based geometry. The new algorithm adopts a novel strategy that first intersects the components to extract the wetted surface before proceeding with volume mesh generation in a second phase. The intersection scheme is based on a robust geometry engine that uses adaptive precision arithmetic and automatically and consistently handles geometric degeneracies with an algorithmic tie-breaking routine. The intersection procedure has worst-case computational complexity of O(N log N) and is demonstrated on test cases with up to 121 overlapping and intersecting components, including a variety of geometric degeneracies. The volume mesh generation takes the intersected surface triangulation as input and generates the mesh through cell division of an initially uniform coarse grid. In refining hexagonal cells to resolve the geometry, the new approach preserves the ability to directionally divide cells that are well aligned with local geometry. The mesh generation scheme has linear asymptotic complexity with memory requirements that total approximately 14-17 words/cell. The mesh generation speed is approximately 10(6) cells/minute on a typical engineering workstation. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. NYU, Courant Inst, Dept Computat Sci, New York, NY 10012 USA. RP Aftosmis, MJ (reprint author), NASA, Ames Res Ctr, Code AAC,Mail Stop T27B-2, Moffett Field, CA 94035 USA. NR 27 TC 100 Z9 103 U1 1 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 JUN PY 1998 VL 36 IS 6 BP 952 EP 960 DI 10.2514/2.464 PG 9 WC Engineering, Aerospace SC Engineering GA ZQ577 UT WOS:000073882000011 ER PT J AU Kenner, WS Knight, NE AF Kenner, WS Knight, NE TI Soft lattice truss static polynomial response using energy methods SO AIAA JOURNAL LA English DT Article; Proceedings Paper CT AIAA/ASME/ASCE/AHS/ASC 38th Structures, Structural Dynamics, and Materials Conference CY APR 07-10, 1997 CL KISSIMMEE, FLORIDA SP Amer Inst Aeronaut & Astronaut, ASME, ASCE, AHS, ASC AB A deterministic methodology is presented for developing closed-form deflection equations for two-dimensional and three-dimensional lattice structures. Two types of lattice structures are studied: beams and soft lattices. Castigliano's second theorem, which entails the total strain energy of a structure, is utilized to generate highly accurate results. Derived deflection equations provide new insight into the bending and shear behavior of the two types of lattices, in contrast to classic solutions of similiar lattice truss structures. C1 NASA, Langley Res Ctr, Thermal Struct Branch, Hampton, VA 23681 USA. Old Dominion Univ, Dept Aerosp Engn, Norfolk, VA 23529 USA. RP Kenner, WS (reprint author), NASA, Langley Res Ctr, Thermal Struct Branch, Hampton, VA 23681 USA. NR 15 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 0001-1452 J9 AIAA J JI AIAA J. PD JUN PY 1998 VL 36 IS 6 BP 1100 EP 1104 PG 5 WC Engineering, Aerospace SC Engineering GA ZQ577 UT WOS:000073882000032 ER PT J AU Fritsch-Yelle, JM Leuenberger, UA D'Aunno, DS Rossum, AC Brown, TE Wood, ML Josephson, ME Goldberger, AL AF Fritsch-Yelle, JM Leuenberger, UA D'Aunno, DS Rossum, AC Brown, TE Wood, ML Josephson, ME Goldberger, AL TI An episode of ventricular tachycardia during long-duration spaceflight SO AMERICAN JOURNAL OF CARDIOLOGY LA English DT Article ID HEART-RATE AB An episode of nonsustained ventricular tachycardia was recorded from a crew member during the second month aboard the MIR space station. Although asymptomatic, this cardiac event increases the concern that serious cardiac dysrhythmias may be a limiting factor during long-duration spaceflight. C1 NASA, Lyndon B Johnson Space Ctr, Life Sci Res Lab, Houston, TX 77058 USA. Milton S Hershey Med Ctr, Hershey, PA USA. Penn State Univ, Hershey, PA USA. Univ Texas, Med Branch, Dept Internal Med, Galveston, TX 77550 USA. NASA, Lyndon B Johnson Space Ctr, Kelsey Seybold Clin, Houston, TX 77058 USA. KRUG Life Sci, Houston, TX USA. Beth Israel Deaconess Med Ctr, Div Cardiovasc, Boston, MA USA. Harvard Univ, Sch Med, Boston, MA USA. RP Fritsch-Yelle, JM (reprint author), NASA, Lyndon B Johnson Space Ctr, Life Sci Res Lab, SD3, Houston, TX 77058 USA. NR 5 TC 40 Z9 41 U1 0 U2 2 PU EXCERPTA MEDICA INC PI NEW YORK PA 245 WEST 17TH STREET, NEW YORK, NY 10011 USA SN 0002-9149 J9 AM J CARDIOL JI Am. J. Cardiol. PD JUN 1 PY 1998 VL 81 IS 11 BP 1391 EP + DI 10.1016/S0002-9149(98)00179-9 PG 3 WC Cardiac & Cardiovascular Systems SC Cardiovascular System & Cardiology GA ZR823 UT WOS:000074017900025 PM 9631987 ER PT J AU Eldred, E Yung, LL Eldred, D Roy, RR AF Eldred, E Yung, LL Eldred, D Roy, RR TI Distribution of muscle spindles in a simply structured muscle: Integrated total sensory representation SO ANATOMICAL RECORD LA English DT Article DE capsularis muscle; distribution of muscle spindles; integrated representation of spindle sensitivity; motor unit interaction with spindle representation ID CAT TIBIALIS ANTERIOR; FIBER-TYPE COMPOSITION; MEDIAL GASTROCNEMIUS-MUSCLE; MOTOR-UNIT CONTRACTIONS; CARPI RADIALIS MUSCLE; SPATIAL-DISTRIBUTION; SOLEUS MUSCLE; TENDON ORGANS; INNERVATION PATTERNS; SYNAPSE ELIMINATION AB Background: The distribution of muscle spindles (Sps) in a small muscle of simple architecture, the capsularis at the cat's hip joint, was quantified to reveal the patterns of proprioceptive representation in the transverse and sagittal planes as well as to model the effect a local disturbance in muscle length would have on total Sp discharge. Methods: Locations in serial cross-section; of the 32 and 38 Sps in 2 muscles, I perfused with the hip joint flexed and the other extended, were plotted, and their patterns of integrated sensitivity calculated assuming that (1) the discharge rate of a Sp afferent varies linearly with change in length along the Sp's axis, and (2) that within a local disturbance produced by contraction of a motor unit (MU), lengths decrease either linearly or as the square of the distance from its center. Results: The isomeric pattern of "integrated, total Sp representation on cross-section" showed two peaks of sensitivity in the half of the muscle that had been next to the joint capsule, offset by low representation in a small, central area and along the extensive zone bordering the laterally facing "superficial surface." The equivalent radius of an idealized symmetrical MU territory was estimated from distributions of the few fast, oxidative-glycolytic fibers found in two muscles, and the effect of a MU's contraction on net Sp discharge predicted when the unit was positioned at distinctive sites within the pattern. As an index of Ia and II afferent representation in the sagittal plane, the distribution of the nucleated regions of Sps and the summed lengths of segments of Sp axial bundles and capsules, respectively, within successive l-mm segments of the muscle were graphed. Conclusions: The longitudinal representation and structure of the muscle are not suited for reflex adjustment of differences in length along the muscle. The isomeric pattern of high relief in the transverse plane suggests that in this similar to 0.2 g muscle, the localization of myotatic reflexes might be accommodated but the need for adjustment in activation of MUs seems minimal. This is because the muscle is not compartmentalized, its fibers extend between the muscle's origin and insertion, their angle of pinnation is low, and greater than 90% are of slow type. The distribution of Sps is consistent with gauging length of the entire muscle and hence angulation at the hip joint. (C) 1998 Wiley-Liss, Inc. C1 Univ Calif Los Angeles, Dept Neurobiol, Los Angeles, CA 90095 USA. Univ Calif Los Angeles, Brain Res Inst, Los Angeles, CA 90095 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91125 USA. RP Roy, RR (reprint author), Univ Calif Los Angeles, Brain Res Inst, 405 Hilgard Ave, Los Angeles, CA 90095 USA. EM rrr@ucla.edu NR 73 TC 4 Z9 4 U1 0 U2 1 PU WILEY-LISS PI HOBOKEN PA DIV JOHN WILEY & SONS INC, 111 RIVER ST, HOBOKEN, NJ 07030 USA SN 0003-276X J9 ANAT RECORD JI Anat. Rec. PD JUN PY 1998 VL 251 IS 2 BP 161 EP 172 DI 10.1002/(SICI)1097-0185(199806)251:2<161::AID-AR3>3.0.CO;2-1 PG 12 WC Anatomy & Morphology SC Anatomy & Morphology GA ZQ376 UT WOS:000073855000003 PM 9624445 ER PT J AU Andersen, DT Mckay, CP Wharton, RA AF Andersen, DT Mckay, CP Wharton, RA TI Dissolved gases in perennially ice-covered lakes of the McMurdo dry valleys, Antarctica SO ANTARCTIC SCIENCE LA English DT Article DE Antarctica; dissolved gases; perennially ice-covered lakes; supersaturation ID OXYGEN SUPERSATURATION; PHYSICAL CONTRIBUTIONS; SIMULATION; WATER AB Measurements of dissolved N-2, O-2, Ar, CO2, and CH4 were made in perennially ice-covered Lake Hoare. Results confirm previous reports that O-2 concentrations in the upper water column exceed atmospheric equilibrium and that N-2 and Ar are supersaturated throughout the water column. The mean supersaturation of N-2 was found to be 2.0 (+/-0.37) and Ar was 3.8 (+/-1.1). The ratios of N-2/Ar (20.3 +/- 3.8), and O-2/Ar (22.5 +/- 4.0) at the ice-water interface are consistent with those previously measured, suggesting that bubble formation is the main process for removing gas from the lake. However, the saturations of N-2 and Ar greatly exceed those previously predicted for degassing by bubble formation only at the ice-water interface. The data support the hypothesis that removal of gas by bubbles occurs in the water column to a depth of 11 m in Lake Hoare. CO2 concentration increases from near zero at the ice-water interface to 80-100 times saturation at and below the chemocline at c. 28 m. There is considerable variability in the gas concentrations throughout the water column; samples separated in depth by one metre may vary by more than 50% in gas content. It is likely that this phenomenon results from the lack of turbulent mixing in the water column. Methane (c. 2 mu g 1(-1)) was detected below the chemocline and immediately above the sediment/water interface at a depth of 30 m. Samples from lakes Vanda, Joyce, and Miers, also show supersaturations of O-2, N-2, and Ar at levels similar to levels found in Lake Hoare. C1 NASA, Ames Res Ctr, SETI Inst, Moffett Field, CA 94035 USA. NASA, Ames Res Ctr, Div Space Sci, Moffett Field, CA 94035 USA. Univ Nevada, Desert Res Inst, Reno, NV 89506 USA. RP Andersen, DT (reprint author), NASA, Ames Res Ctr, SETI Inst, MS 245-3, Moffett Field, CA 94035 USA. FU NCI NIH HHS [NCA2-799] NR 27 TC 21 Z9 22 U1 1 U2 5 PU BLACKWELL SCIENCE LTD PI OXFORD PA P O BOX 88, OSNEY MEAD, OXFORD OX2 0NE, OXON, ENGLAND SN 0954-1020 J9 ANTARCT SCI JI Antarct. Sci. PD JUN PY 1998 VL 10 IS 2 BP 124 EP 133 PG 10 WC Environmental Sciences; Geography, Physical; Geosciences, Multidisciplinary SC Environmental Sciences & Ecology; Physical Geography; Geology GA ZU756 UT WOS:000074231400003 PM 11541288 ER PT J AU Reggia, JA Lohn, JD Chou, HH AF Reggia, JA Lohn, JD Chou, HH TI Self-replicating structures: Evolution, emergence, and computation SO ARTIFICIAL LIFE LA English DT Article DE self-replication; cellular automata; genetic algorithms ID CELLULAR-AUTOMATA; REPRODUCTION; COMPUTER AB Since von Neumann's seminal work around 1950, computer scientists and others have studied the algorithms needed to support self-replicating systems. Much of this work has focused on abstract logical machines (automata) embedded in two-dimensional cellular spaces. This research was motivated by the desire to understand the basic information-processing principles underlying self-replication, the potential long-term applications of programmable self-replicating machines, and the possibility of gaining insight into biological replication and the origins of life. We view past research as taking three main directions: early complex universal computer-constructors modeled after Turing machines, qualitatively simpler self-replicating loops, and efforts to view self-replication as an emergent phenomenon. We discuss our recent studies in the latter category showing that self-replicating structures can emerge from nonreplicating components, and that genetic algorithms can be applied to program automatically simple but arbitrary structures to replicate. We also describe recent work in which self-replicating structures are successfully programmed to do useful problem solving as they replicate. We conclude ty identifying some implications and important research directions for the future. C1 Univ Maryland, Dept Comp Sci, College Pk, MD 20742 USA. Univ Maryland, Inst Adv Comp Studies, College Pk, MD 20742 USA. NASA, Ames Res Ctr, Caelum Res Corp, Moffett Field, CA 94035 USA. Inst Genome Res, Rockville, MD 20850 USA. RP Univ Maryland, Dept Comp Sci, AV Williams Bldg, College Pk, MD 20742 USA. EM reggia@cs.umd.edu; jlohn@ptolemy.arc.nasa.gov; hhchou@tigr.org NR 32 TC 15 Z9 15 U1 52 U2 140 PU MIT PRESS PI CAMBRIDGE PA ONE ROGERS ST, CAMBRIDGE, MA 02142-1209 USA SN 1064-5462 EI 1530-9185 J9 ARTIF LIFE JI Artif. Life PD SUM PY 1998 VL 4 IS 3 BP 283 EP 302 DI 10.1162/106454698568594 PG 20 WC Computer Science, Artificial Intelligence; Computer Science, Theory & Methods SC Computer Science GA 231NL UT WOS:000082316600006 PM 9864440 ER PT J AU Magorrian, J Tremaine, S Richstone, D Bender, R Bower, G Dressler, A Faber, SM Gebhardt, K Green, R Grillmair, C Kormendy, J Lauer, T AF Magorrian, J Tremaine, S Richstone, D Bender, R Bower, G Dressler, A Faber, SM Gebhardt, K Green, R Grillmair, C Kormendy, J Lauer, T TI The demography of massive dark objects in galaxy centers SO ASTRONOMICAL JOURNAL LA English DT Article DE dark matter; galaxies, nuclei ID PLANETARY CAMERA OBSERVATIONS; SIGHT VELOCITY DISTRIBUTIONS; CLAIMED BLACK-HOLES; ELLIPTIC GALAXIES; SPHERICAL GALAXIES; SURFACE PHOTOMETRY; M31; PROFILES; MODELS; M87 AB We construct dynamical models for a sample of 36 nearby galaxies with Hubble Space Telescope (HST) photometry and ground-based kinematics. The models assume that each galaxy is axisymmetric, with a two-integral distribution function, arbitrary inclination angle, a position-independent stellar mass-to-light ratio Y, and a central massive dark object (MDO) of arbitrary mass M-.. They provide acceptable fits to 32 of the galaxies for some value of M-. and Y; the four galaxies that cannot be fitted have kinematically decoupled cores. The mass-to-light ratios inferred for the 32 well-fitted galaxies are consistent with the fundamental-plane correlation Y infinity L-0.2, where L is galaxy luminosity. In all but six galaxies the models require at the 95% confidence level an MDO of mass M-. similar to 0.006M(bulge) =0.006YL. Five of the six galaxies consistent with M-. = 0 are also consistent with this correlation. The other (NGC 7332) has a much stronger upper limit on M-.. We predict the second-moment profiles that should be observed at HST resolution for the 32 galaxies that our models describe well. We consider various parameterizations for the probability distribution describing the correlation of the masses of these MDOs with other galaxy properties. One of the best models can be summarized thus: a fraction f similar or equal to 0.97 of early-type galaxies have MDOs, whose masses are well described by a Gaussian distribution in log (M-./M-bulge) of mean -2.28 and standard deviation similar to 0.51. There is also marginal evidence that M-. is distributed differently for "core" and "power law" galaxies, with core galaxies having a somewhat steeper dependence on M-bulge. C1 Univ Toronto, Canadian Inst Theoret Astrophys, Toronto, ON M5S 3H8, Canada. Canadian Inst Adv Res, Cosmol & Grav Program, Toronto, ON, Canada. Univ Michigan, Dept Astron, Ann Arbor, MI 48109 USA. Univ Sternwarte, D-81679 Munchen, Germany. Kitt Peak Natl Observ, Natl Opt Astron Observ, Tucson, AZ 85726 USA. Observ Carnegie Inst Washington, Pasadena, CA 91101 USA. Univ Calif Santa Cruz, Univ Calif Observ, Lick Observ, Board Studies Astron & Astrophys, Santa Cruz, CA 95064 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ Hawaii, Inst Astron, Honolulu, HI 96822 USA. RP Magorrian, J (reprint author), Univ Toronto, Canadian Inst Theoret Astrophys, 60 St George St, Toronto, ON M5S 3H8, Canada. RI Tremaine, Scott/M-4281-2015 OI Tremaine, Scott/0000-0002-0278-7180 NR 65 TC 2377 Z9 2386 U1 3 U2 28 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 JUN PY 1998 VL 115 IS 6 BP 2285 EP 2305 DI 10.1086/300353 PG 21 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZT599 UT WOS:000074104000010 ER PT J AU Kenyon, SJ Brown, DI Tout, CA Berlind, P AF Kenyon, SJ Brown, DI Tout, CA Berlind, P TI Optical spectroscopy of embedded young stars in the Taurus-Auriga molecular cloud SO ASTRONOMICAL JOURNAL LA English DT Article DE ISM, jets and outflows; stars, formation; stars, pre-main-sequence ID HERBIG-HARO OBJECTS; MAGNETOCENTRIFUGALLY DRIVEN FLOWS; SPECTRAL ENERGY-DISTRIBUTIONS; LOW-MASS STARS; MAIN-SEQUENCE EVOLUTION; INTERMEDIATE-MASS; LUMINOSITY FUNCTIONS; LITHIUM ABUNDANCES; STELLAR CLUSTERS; FORBIDDEN-LINE AB This paper describes the first optical spectroscopic survey of Class I sources (also known as embedded sources and protostars) in the Taurus-Auriga dark cloud. We detect 10 of the 24 known Class I sources in the cloud at 5500-9000 Angstrom. All detected Class I sources have strong Ha emission; most also have strong [O I] and [S II] emission. These data - together with high-guality optical spectra of T Tauri stars in the Taurus-Auriga cloud - demonstrate that forbidden emission lines are stronger and more common in Class I sources than in T Tauri stars. Our results also provide a clear discriminant in the frequency of forbidden line emission between weak-emission and classical T Tauri stars. In addition to strong emission lines, three Class I sources have prominent TiO absorption bands. The M-type central stars of these sources mingle with optically visible T Tauri stars in the H-R diagram and lie somewhat below both the birth line for spherical accretion and the deuterium burning sequence for disk accretion. C1 Harvard Smithsonian Ctr Astrophys, Cambridge, MA 02138 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ Cambridge, Inst Astron, Cambridge CB3 0HA, England. Whipple Observ, Amado, AZ 85645 USA. RP Kenyon, SJ (reprint author), Harvard Smithsonian Ctr Astrophys, 60 Garden St, Cambridge, MA 02138 USA. OI Kenyon, Scott/0000-0003-0214-609X NR 79 TC 92 Z9 92 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 JUN PY 1998 VL 115 IS 6 BP 2491 EP 2503 DI 10.1086/300368 PG 13 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZT599 UT WOS:000074104000028 ER PT J AU Meyer, AW Smith, RG Charnley, SB Pendleton, YJ AF Meyer, AW Smith, RG Charnley, SB Pendleton, YJ TI H2O ice in the envelopes of OH/IR stars SO ASTRONOMICAL JOURNAL LA English DT Article DE dust, extinction; infrared radiation; ISM, clouds; stars, late-type ID OH-IR STARS; CIRCUMSTELLAR ENVELOPE; ABSORPTION FEATURES; SPECTROPHOTOMETRY; SPECTRA; GIANTS; EMISSION; MICRONS; MASERS; RADIO AB In an attempt to better understand the conditions under which molecules condense onto grains in the envelopes of evolved stars, we have searched for the presence of H2O ice in the circumstellar envelopes of several evolved (OH/IR) stars. The sample of stars observed was selected on the basis of mass-loss rates, luminosities, and outflow velocities in order to cover a range of physical conditions that might affect the amount of ice present in stellar envelopes. Despite the clear presence of H2O ice around other, previously observed, evolved stars, our search in six OH/IR stars has resulted in only one clear detection, in OH 26.5 + 0.6, and the tentative detection in one other, OH 26.4 - 1.9. We provide column densities or upper limits for the amount of ice that is present on the grains around these stars and explore the possibility that there could be a relationship between (M)over dot(*) or (M)over dot(*)/L-* and the H2O ice column density to explain the observations. C1 NASA, Ames Res Ctr, Div Space Sci, Moffett Field, CA 94035 USA. Univ New S Wales, Univ Coll, Sch Phys, Australian Def Force Acad, Canberra, ACT 2600, Australia. Univ Calif Berkeley, Dept Astron, Berkeley, CA 94720 USA. RP Meyer, AW (reprint author), NASA, Ames Res Ctr, Div Space Sci, MS 245-3, Moffett Field, CA 94035 USA. RI Charnley, Steven/C-9538-2012 NR 37 TC 12 Z9 12 U1 0 U2 1 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 JUN PY 1998 VL 115 IS 6 BP 2509 EP 2514 DI 10.1086/300363 PG 6 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZT599 UT WOS:000074104000030 PM 11542932 ER PT J AU Lefloch, B Castets, A Cernicharo, J Langer, WD Zylka, R AF Lefloch, B Castets, A Cernicharo, J Langer, WD Zylka, R TI Cores and cavities in NGC 1333 SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE ISM : individual objects : NGC 1333; ISM : jets and outflows; ISM : molecules; radio continuum : ISM; radio lines : ISM; stars : formation ID DUST EMISSION; MOLECULAR-HYDROGEN; NGC-1333 IRAS-4; STAR-FORMATION; DARK CLOUDS; HH 7-11; OUTFLOW; REGION; HH7-11; SSV-13 AB We present 1.3 mm continuum and CS J = 5 --> 4 maps at 12" resolution of the NGC1333 star forming region. The area covered is 8' x 6'. The large-scale bolometer and CS maps delineate very nicely the large central cavity together with the cores situated in the surrounding compressed shell. In addition to the four dust cores IRAS4A-B, IRAS2 and SVS13, we discovered two fainter condensations, one of which is not associated with protostellar activity. All protostars are surrounded by extended low-emissivity envelopes and show indications of depletion of molecules onto grains. The continuum emission traces material entrained by the outflows powered by IRAS4A, IRAS2 and SVS13. The CS J = 5 --> 4 is observed in all dust cores. Apart from IRAS4, the CS emission peak is shifted with respect to the dust continuum. The large-scale dust emission mostly comes from material compressed around two cavities, whose walls are detected in the H-2 S(1) v = 1-0 line. These cavities seem to have been excavated by outflows from the neighboring protostars IRAS4 and SVS13, and are now expanding in the ambient medium. Taken together these new data suggest that the large cavity in NGC1333 grows by local action of stars forming in the compressed edge, each producing a local cavity which eventually overlap. C1 CSIC, Inst Estructura Mat, Dept Fis Mol, E-28006 Madrid, Spain. Observ Grenoble, Astrophys Lab, F-38041 Grenoble, France. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ Heidelberg, Inst Theoret Astrophys, D-69121 Heidelberg, Germany. RP Lefloch, B (reprint author), CSIC, Inst Estructura Mat, Dept Fis Mol, Serrano 123, E-28006 Madrid, Spain. EM Bertrand.Lefloch@obs.ujf-grenoble.fr NR 36 TC 62 Z9 62 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 JUN PY 1998 VL 334 IS 1 BP 269 EP 279 PG 11 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZT314 UT WOS:000074072100038 ER PT J AU Miyaji, T Ishisaki, Y Ogasaka, Y Ueda, Y Freyberg, MJ Hasinger, G Tanaka, Y AF Miyaji, T Ishisaki, Y Ogasaka, Y Ueda, Y Freyberg, MJ Hasinger, G Tanaka, Y TI The cosmic X-ray background spectrum observed with ROSAT and ASCA SO ASTRONOMY & ASTROPHYSICS LA English DT Letter DE ISM : bubbles; galaxy : halo; cosmology : diffuse radiation; X-rays : general ID DIFFUSE AB We have made a series of joint spectral fits for two blank fields, the Lockman Hole and the Lynx-3A field, where a significant amount of both ASCA and ROSAT PSPC data exist after thorough screenings. The ASCA SIS, GIS and ROSAT PSPC spectra from these fields have been fitted simultaneously. Comparison at E > 1 keV shows general agreement within 10% in the Lockman Hole data and a 20-30% disagreement in the Lynx-3A data, indicating remaining observation-dependent systematic problems. In both cases, satisfactory fits have been found for the overall 0.1-10 keV spectrum with an extragalactic power-law component (or a broken power-law component with steepening at E < 1 keV), a hard thermal component with plasma temperature of kT(h) approximate to 0.14 keV and a soft thermal component kT(s) approximate to 0.07 keV. C1 Astrophys Inst Potsdam, D-14482 Potsdam, Germany. Max Planck Inst Extraterr Phys, D-85740 Garching, Germany. Tokyo Metropolitan Univ, Hachioji, Tokyo 19203, Japan. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Inst Space & Astronaut Sci, Sagamihara, Kanagawa 229, Japan. RP Miyaji, T (reprint author), Astrophys Inst Potsdam, Sternwarte 16, D-14482 Potsdam, Germany. EM tmiyaji@aip.de NR 17 TC 70 Z9 70 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 JUN PY 1998 VL 334 IS 1 BP L13 EP L16 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZT314 UT WOS:000074072100004 ER PT J AU Tovmassian, HM Mazzarella, JM Tovmassian, GH Stoll, D Tiersch, H AF Tovmassian, HM Mazzarella, JM Tovmassian, GH Stoll, D Tiersch, H TI Far-infrared emission from Shakhbazian Compact Galaxy Groups SO ASTRONOMY & ASTROPHYSICS SUPPLEMENT SERIES LA English DT Article DE infrared, galaxies; galaxies, interactions ID PHOTOMETRIC CATALOG; STAR-FORMATION; INTERACTING GALAXIES; RADIO OBSERVATIONS; IRAS OBSERVATIONS; SPIRAL GALAXIES; MORPHOLOGY; IMAGES; MHZ AB Using the IRAS archives, we searched for far-infrared (FIR) counterparts of Shakhbazian Compact Groups of Galaxies (SCGGs). Reliable IRAS detections are identified at the positions of 24 out of 367 SCGGs; another 10 IRAS sources, located within similar to 2 arcmin of SCGGs, are possibly associated with the corresponding galaxy groups. Some of these sources are not very reliable. Previous work has shown that the fraction of E and SO galaxies in a representative sample of SCGGs is 77%, while E and SO galaxies comprise about 51% of galaxies in Hickson Compact Groups (HCGs). The higher fraction of early Hubble types, combined with their greater distances, explains the low IRAS detection rate of SCGGs (7 - 8%) compared to HCGs (64%). The FIR colors and morphological types of galaxies in the groups suggest that active star formation or Seyfert galaxies may be the main source of the FIR emission in the SCGGs detected by IRAS, perhaps originating as the result of tidal interactions in the dense environments of these groups. C1 Inst Nacl Astrofis Opt & Electr, Puebla 72000, Mexico. CALTECH, Jet Prop Lab, IPAC, Pasadena, CA 91125 USA. Univ Nacl Autonoma Mexico, Inst Astron, Observ Astron Nacl, Ensenada 22860, Baja California, Mexico. Sternwarte Konigsleiten, Munich, Germany. RP Tovmassian, HM (reprint author), Inst Nacl Astrofis Opt & Electr, AP 51 & 216, Puebla 72000, Mexico. EM hrant@inaoep.mx OI Mazzarella, Joseph/0000-0002-8204-8619 NR 63 TC 8 Z9 8 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 JUN PY 1998 VL 130 IS 2 BP 207 EP 214 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZU240 UT WOS:000074176400001 ER PT J AU Dohm, JM Anderson, RC Tanaka, KL AF Dohm, JM Anderson, RC Tanaka, KL TI Planetary mapping - Digital structural mapping of Mars SO ASTRONOMY & GEOPHYSICS LA English DT Article C1 US Geol Survey, Flagstaff, AZ 86001 USA. Jet Prop Lab, Pasadena, CA 91011 USA. RP Dohm, JM (reprint author), US Geol Survey, Flagstaff, AZ 86001 USA. RI Dohm, James/A-3831-2014 NR 19 TC 12 Z9 12 U1 0 U2 1 PU IOP PUBLISHING LTD PI BRISTOL PA DIRAC HOUSE, TEMPLE BACK, BRISTOL BS1 6BE, ENGLAND SN 1366-8781 J9 ASTRON GEOPHYS JI Astron. Geophys. PD JUN PY 1998 VL 39 IS 3 BP 20 EP 22 PG 3 WC Astronomy & Astrophysics; Geochemistry & Geophysics SC Astronomy & Astrophysics; Geochemistry & Geophysics GA ZT881 UT WOS:000074137900012 ER PT J AU Kraemer, SB Crenshaw, DM Filippenko, AV Peterson, BM AF Kraemer, SB Crenshaw, DM Filippenko, AV Peterson, BM TI Evidence for a physically compact narrow-line region in the Seyfert 1 Galaxy NGC 5548 SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies, individual (NGC 5548); galaxies, Seyfert ID ACTIVE GALACTIC NUCLEI; BROAD EMISSION-LINE; INTERSTELLAR GRAINS; OPTICAL-SPECTRUM; EXTENDED GAS; IUE SPECTRA; NGC-5548; VARIABILITY; SIZE; ULTRAVIOLET AB We have combined Hubble Space Telescope/Faint Object Spectrograph and ground-based spectra of the Seyfert 1 galaxy NGC 5548 to study the narrow emission lines over the 1200-10000 Angstrom region. All of the spectra were obtained when the broad emission line and continuum fluxes were at a historically low level, allowing us to determine accurately the contribution of the narrow-line region (NLR) to the emission lines. We have generated multicomponent photoionization models to investigate the relative strength of the high-ionization lines compared to those in Seyfert 2 galaxies and the weakness of the narrow Mg II lambda 2800 line. We present evidence for a high-ionization component of NLR gas that is very close to the nucleus (similar to 1 pc). This component must be optically thin to ionizing radiation at the Lyman edge (i.e., tau(o) approximate to 2.5) to avoid producing [O I] and Mg II in a partially ionized zone. The very high ionization lines (N V, [Ne V], [Fe VII], [Fe x]) are stronger than the predictions of our standard model, and we show that this may be due to supersolar abundances and/or a "blue bump" in the extreme ultraviolet (although recent observations do not support the latter). An outer component of NLR gas (at only similar to 70 pc from the continuum source) is needed to produce the low-ionization lines. We show that the outer component may contain dust, which further reduces the Mg II flux by depletion and by absorption of the resonance photons after multiple scatterings. We show that the majority of the emission in the NLR of NGC 5548 must arise within similar to 70 pc from the nucleus. Thus, the NLR in this Seyfert 1 galaxy is very physically compact, compared to the typical NLR in Seyfert 2 galaxies. C1 Catholic Univ Amer, NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Calif Berkeley, Dept Astron, Berkeley, CA 94720 USA. Ohio State Univ, Dept Astron, Columbus, OH 43210 USA. RP Kraemer, SB (reprint author), Catholic Univ Amer, NASA, Goddard Space Flight Ctr, Code 681, Greenbelt, MD 20771 USA. NR 58 TC 41 Z9 41 U1 0 U2 2 PU UNIV CHICAGO PRESS PI CHICAGO PA 5801 S ELLIS AVENUE, CHICAGO, IL 60637 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD JUN 1 PY 1998 VL 499 IS 2 BP 719 EP 727 DI 10.1086/305683 PN 1 PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZU199 UT WOS:000074172200017 ER PT J AU Johnstone, D Hollenbach, D Bally, J AF Johnstone, D Hollenbach, D Bally, J TI Photoevaporation of disks and clumps by nearby massive stars: Application to disk destruction in the Orion Nebula SO ASTROPHYSICAL JOURNAL LA English DT Article DE accretion, accretion disks; circumstellar matter; H II regions; ISM, general; open clusters and associations, individual (Orion Nebula Cluster) ID TRAPEZIUM-CLUSTER; CIRCUMSTELLAR DISKS; CONSTRAINTS; ACCRETION; ENVELOPES; PROPLYDS; REGIONS; OBJECTS; IMAGES; MODEL AB We present a model for the photoevaporation of circumstellar disks or dense clumps of gas by an external source of ultraviolet radiation. Our model includes the thermal and dynamic effects of 6-13.6 eV far-ultraviolet (FUV) photons and Lyman continuum EUV photons incident upon disks or clumps idealized as spheres of radius r(d) and enclosed mass M*. For sufficiently large values of r(d)/M*, the radiation field evaporates the surface gas and dust. Analytical and numerical approximations to the resulting flows are presented; the model depends on r(d), M*, the flux of FUV and EUV photons, and the column density of neutral gas heated by FUV photons to high temperatures. Application of this model shows that the circumstellar disks (r(d) similar to 10(14)-10(15) cm) in the Orion Nebula ("proplyds") are rapidly destroyed by the external UV radiation field. Close (d less than or similar to 10(17) cm) to theta(1) Ori C, the ionizing EUV photon flux controls the mass-loss rate, and the ionization front (IF) is approximately coincident with the disk surface. Gas evaporated from the cold disk moves subsonically through a relatively thin photodissociation region (PDR) dominated by FUV photons and heated to similar to 1000 K. As the distance from theta(1) Ori C increases, the Lyman continuum flux declines, the PDR thickens, and the IF moves away from the disk surface. At d similar to 3 x 10(17) cm, the thickness of the PDR becomes comparable to the disk radius. Between 3 x 10(17) cm less than or similar to d less than or similar to 10(18) cm, spherical divergence and the resultant pressure gradient in the 10(3) K PDR forms a mildly supersonic (similar to 3-6 km s(-1)) but neutral Parker wind. This wind flows outward until it passes through a shock, beyond which gas moves subsonically through a stationary D-type IF. The IF is moved away from the disk surface to a standoff distance r(IF) greater than or similar to 2.5r(d). In this regime, the mass-loss rate is determined by the incident FUV photon flux and not the ionizing flux. However, at very large distances, d greater than or similar to 10(18) cm, the FUV photon flux drops to values that cannot maintain the disk surface temperature at similar to 10(3) K. As the PDR temperature drops, the pressure of the FUV-powered flow declines with increasing distance from theta(1) Ori C, and again the EUV ionizing photons can penetrate close to the disk surface and dominate the evaporation rate. Radio, H alpha, and [O III] observations of externally illuminated young stellar objects in the Trapezium region are used to determine r(IF) and the projected distances, d(perpendicular to), from theta(1) Ori C. The observed values of r(IF) and d(perpendicular to) are combined with the theory to estimate the disk sizes, mass-loss rates, surface densities, and disk masses for the ensemble of extended sources in the Trapezium cluster. Observations of r(IF), d(perpendicular to), and r(d) in HST 182-413 and a few other sources are used to calibrate parameters of the theory, especially the column of heated PDR gas. The disks have a range in sizes between 14 < log [r(d)/(cm)] < 15.2, mass-loss rates of -7.7 < log [(M)over dot/(M./yr)] < -6.2, surface densities at disk edge 0.7 < log [Sigma(r(d))/(g cm(-2))] < 2.5 which imply disk surface densities at 1 AU from the central, embedded star of 2.8 < log [Sigma/(g cm(-2))] < 3.8 and disk masses of 0.002 < M-d/M. < 0.07. Sigma and M-d scale with the adopted ionization time, t(i), which we take to be 10(5) yr. The inferred Sigma(r(d)) for the ensemble of disks suggest that the initial surface density power law of an individual disk, Sigma proportional to r(-alpha), is bounded by 1 less than or similar to alpha less than or similar to 1.5. C1 Canadian Inst Theoret Astrophys, Toronto, ON M5S 3H8, Canada. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Univ Colorado, Ctr Astrophys & Space Astron, Dept Astrophys & Planetary Sci, Boulder, CO 80309 USA. RP Canadian Inst Theoret Astrophys, 60 St George St, Toronto, ON M5S 3H8, Canada. EM johnstone@cita.utoronto.ca; hollenbach@warped.arc.nasa.gov; bally@nebula.colorado.edu NR 36 TC 285 Z9 285 U1 1 U2 6 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 JUN 1 PY 1998 VL 499 IS 2 BP 758 EP 776 DI 10.1086/305658 PN 1 PG 19 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZU199 UT WOS:000074172200023 ER PT J AU Wilson, CA Finger, MH Harmon, BA Chakrabarty, D Strohmayer, T AF Wilson, CA Finger, MH Harmon, BA Chakrabarty, D Strohmayer, T TI Discovery of the 198 second X-ray pulsar GRO J2058+42 SO ASTROPHYSICAL JOURNAL LA English DT Article DE binaries, close; gamma rays, bursts; pulsars, individual (GRO J2058 + 42); stars, neutron; X-rays, stars ID ACCRETION; BINARIES AB GRO J2058+42, a transient 198 s X-ray pulsar, was discovered by the Burst and Transient Source Experiment (BATSE) on the Compton Gamma Ray Observatory (CGRO) during a "giant" outburst in 1995 September-October. The total flux peaked at about 300 mcrab (20-50 keV) as measured by Earth occultation. The pulse period decreased from 198 to 196 s during the 46 day outburst. The pulse shape evolved over the course of the outburst and exhibited energy-dependent variations. BATSE observed five additional weak outbursts from CRO J2058+42, each with a 2 week duration and a peak-pulsed flux of about 15 mcrab (20-50 keV), that were spaced by about 110 days. An observation of the 1996 November outburst by the Rossi X-Ray Timing Explorer (RXTE) proportional counter array (PCA) localized the source to within a 4' radius error circle (90% confidence) centered on R.A. = 20(h)59.(m)0, decl. = 41 degrees 43' (J2000). Additional shorter outbursts with peak-pulsed fluxes of about 8 mcrab were detected by BATSE halfway between the first four 15 mcrab outbursts. The RXTE All-Sky Monitor detected all eight weak outbursts with approximately equal durations and intensities. GRO J2058+42 is most likely a Be/X-ray binary that appears to outburst at periastron and apastron. No optical counterpart has been identified to date, and no X-ray source was present in the error circle in archival ROSAT observations. C1 NASA, George C Marshall Space Flight Ctr, Space Sci Lab ES 84, Huntsville, AL 35812 USA. MIT, Ctr Space Res, Cambridge, MA 02139 USA. NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Univ Space Res Assoc, Greenbelt, MD 20771 USA. RP Wilson, CA (reprint author), NASA, George C Marshall Space Flight Ctr, Space Sci Lab ES 84, Huntsville, AL 35812 USA. NR 21 TC 15 Z9 15 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5801 S ELLIS AVENUE, CHICAGO, IL 60637 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD JUN 1 PY 1998 VL 499 IS 2 BP 820 EP 827 DI 10.1086/305677 PN 1 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZU199 UT WOS:000074172200028 ER PT J AU Sofia, UJ Jenkins, EB AF Sofia, UJ Jenkins, EB TI Interstellar medium absorption profile spectrograph observations of interstellar neutral argon and the implications for partially ionized gas SO ASTROPHYSICAL JOURNAL LA English DT Review DE atomic processes; ISM, abundances; ultraviolet, ISM ID INTERPLANETARY HYDROGEN DENSITY; PHOTOIONIZATION CROSS-SECTIONS; EXTREME-ULTRAVIOLET EXPLORER; EPSILON-CANIS-MAJORIS; CHARGE-TRANSFER; IONIZATION EQUILIBRIUM; SPECTRAL OBSERVATIONS; OSCILLATOR-STRENGTHS; COPERNICUS-SATELLITE; ELEMENT ABUNDANCES AB We use the absorption features from the resonance transitions of neutral argon at 1048 and 1066 Angstrom to determine interstellar argon abundances or their lower limits toward nine early-type stars. These features were observed with the interstellar medium absorption profile spectrograph (IMAPS) along sight lines with low reddening and low fractional abundances of molecular hydrogen. Four of the sight lines in our sample have reliably measured interstellar Ar abundances, of which three also have good determinations of N(H I). We find that the interstellar Ar is below its solar and B-star abundance with respect to hydrogen toward zeta Pup, gamma(2) Vel, and beta Cen A with (logarithmic) reduction factors D = -0.37 +/- 0.09 dex, D = -0.18 +/- 0.10 dex, and D = -0.61 +/- 0.12 dex, respectively. While Ar can condense onto the surfaces of dust grains in the interiors of dense clouds, it is unlikely that argon atoms are depleted by this process in the low-density lines of sight considered in this study. Instead, we propose that the relatively large photoionization cross section of Ar makes it much easier to hide in its ionized form than H. In regions that are about half ionized, this effect can lower Ar I/H I by -0.11 to -0.96 dex, depending on the energy of the photoionizing radiation and its intensity divided by the local electron density. We apply this interpretation for the condition of the gas in front of beta Cen A, which shows the largest deficiency of Ar. Also, we determine the expected magnitudes of the differential ionizations for He, N, O, Ne, and Ar in the partly ionized, warm gas in the local cloud around our solar system. For the local cloud and others that can be probed by UV studies, the observed Ar I-to-H I ratio may be a good discriminant between two possible alternatives, collisional ionization or photoionization, for explaining the existence of partly ionized regions. C1 NASA, Goddard Space Flight Ctr, Natl Res Council, Greenbelt, MD 20771 USA. Princeton Univ Observ, Princeton, NJ 08544 USA. RP Sofia, UJ (reprint author), Villanova Univ, Dept Astron & Astrophys, Villanova, PA 19085 USA. RI Jenkins, Edward/P-5684-2014 OI Jenkins, Edward/0000-0003-1892-4423 NR 115 TC 105 Z9 105 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5801 S ELLIS AVENUE, CHICAGO, IL 60637 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD JUN 1 PY 1998 VL 499 IS 2 BP 951 EP 965 DI 10.1086/305684 PN 1 PG 15 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZU199 UT WOS:000074172200039 ER PT J AU Guhathakurta, M Fisher, R AF Guhathakurta, M Fisher, R TI Solar wind consequences of a coronal hole density profile: Spartan 201-03 coronagraph and Ulysses observations from 1.15 R-circle dot to 4 AU SO ASTROPHYSICAL JOURNAL LA English DT Article DE solar wind; Sun, corona ID PHYSICAL-PROPERTIES AB Spartan 201 is a small shuttle-launched and -retrieved satellite, whose mission is to study the origins of the solar wind. It carries on board two instruments, the Ultraviolet Coronal Spectrometer and the White-Light Coronagraph. The third mission of the Spartan 201 (1995 September 7-10) spacecraft was to provide a solar context for the in situ particles and fields measurements during the north polar passage of the Ulysses spacecraft. In this Letter, we characterize the physical conditions of the north polar coronal hole as derived from white-light coronal observations by the Spartan 201-03 White-Light Coronagraph, the ground-based K coronameter in Mauna Loa, Hawaii, and Ulysses observations of in situ particles and their velocity. For the first time, we are able to combine in situ and path-integrated measurements in a coronal hole, to yield a consistent electron density (N) profile from the Sun to the Earth and the outer heliosphere. By using the value of N measured by Ulysses (1.8-4 AU), we are able to determine the actual value of N and not just an upper limit in the polar coronal hole, near the Sun. The current N profile suggests that the acceleration of the fast solar wind in a coronal hole is complete by 10-15 R-., much closer to the Sun than had been previously expected. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Catholic Univ Amer, Dept Phys, Washington, DC 20064 USA. RP Guhathakurta, M (reprint author), NASA, Goddard Space Flight Ctr, Code 682, Greenbelt, MD 20771 USA. NR 18 TC 28 Z9 28 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5801 S ELLIS AVENUE, CHICAGO, IL 60637 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD JUN 1 PY 1998 VL 499 IS 2 BP L215 EP + DI 10.1086/311371 PN 2 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZU234 UT WOS:000074175800023 ER PT J AU Marshall, FE Gotthelf, EV Zhang, W Middleditch, J Wang, QD AF Marshall, FE Gotthelf, EV Zhang, W Middleditch, J Wang, QD TI Discovery of an ultrafast X-ray pulsar in the supernova remnant N157B SO ASTROPHYSICAL JOURNAL LA English DT Article DE pulsars, general; pulsars, individual (PSR J0537-6910); supernova remnants X-rays, general AB We present the serendipitous discovery of 16 ms pulsed X-ray emission from the Crab-like supernova remnant N157B in the Large Magellanic Cloud. This is the fastest spinning pulsar associated with a supernova remnant (SNR). Observations with the Rossi X-Ray Timing Explorer (RXTE), centered on the field containing SN 1987A, reveal an X-ray pulsar with a narrow pulse profile. The archival Advanced Satellite for Cosmology and Astrophysics (ASCA) X-ray data confirm this detection and locate the pulsar within 1' of the supernova remnant N157B, 14' from SN 1987A. The pulsar shows evidence of glitch(es)between the 3.5 yr separating the RXTE and ASCA observations; the mean linear spin-down rate is P = 5.126 x 10(-14) s s(-1). The background-subtracted, pulsed emission is similar to other Crab-like pulsars with a power law of photon index similar to 1.6. The characteristic spin-down age (similar to 5000 yr) is consistent with;he previous age estimate of the SNR. The inferred B-field for a rotationally powered pulsar is similar to 1 x 10(12) G. Our result confirms the Crab-like nature of N157B; the pulsar is likely associated with a compact X-ray source revealed by ROSAT HRI observations. C1 NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. Univ Calif Los Alamos Natl Lab, Los Alamos, NM 87545 USA. Northwestern Univ, Dearborn Observ, Evanston, IL 60208 USA. RP Marshall, FE (reprint author), NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. NR 17 TC 109 Z9 109 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5801 S ELLIS AVENUE, CHICAGO, IL 60637 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD JUN 1 PY 1998 VL 499 IS 2 BP L179 EP L182 DI 10.1086/311381 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZU234 UT WOS:000074175800015 ER PT J AU Naya, JE Barthelmy, SD Bartlett, LM Gehrels, N Parsons, A Teegarden, BJ Tueller, J Leventhal, M AF Naya, JE Barthelmy, SD Bartlett, LM Gehrels, N Parsons, A Teegarden, BJ Tueller, J Leventhal, M TI Gamma-ray limits on galactic (60)Fe nucleosynthesis and implications on the origin of the (26)Al emission SO ASTROPHYSICAL JOURNAL LA English DT Article DE Galaxy, abundances; gamma rays, observations; nuclear reactions, nucleosynthesis, abundances; stars, Wolf-Rayet; supernovae, general AB The Gamma-Ray Imaging Spectrometer recently observed the gamma-ray emission from the Galactic center region. We have detected the 1809 keV Galactic (26)Al emission at a significance level of 6.8 sigma but have found no evidence for emission at 1173 and 1332 keV, which is expected from the decay chain of the nucleosynthetic (60)Fe. The isotopic abundances and fluxes are derived for different source distribution models. The resulting abundances are between 2.6 +/- 0.3 and 4.5 +/- 0.7 M. for (26)Al, and a 2 sigma upper limit for (60)Fe is between 1.7 and 3.1 M.. The measured (26)Al emission flux is significantly higher than that derived from the Compton Gamma Ray Observatory COMPTEL 1.8 MeV sky map. This suggests that a fraction of the (26)Al emission may come from extended sources with low surface brightness that are invisible to COMPTEL. We obtain an (60)Fe/(26)Al flux ratio 2 sigma upper limit of 0.14, which is slightly lower than the 0.16 predicted from current nucleosynthesis models assuming that Type II supernovae are the major contributors to the Galactic (26)Al. Since the uncertainties in the predicted fluxes are large (up to a factor of 2), our measurement is still compatible with the theoretical expectations. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Maryland, Dept Astron, College Pk, MD 20742 USA. RP Naya, JE (reprint author), Univ Space Res Assoc, 7501 Forbes Blvd 206, Seabrook, MD 20706 USA. RI Barthelmy, Scott/D-2943-2012; Gehrels, Neil/D-2971-2012; Parsons, Ann/I-6604-2012; Tueller, Jack/D-5334-2012 NR 24 TC 15 Z9 15 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 JUN 1 PY 1998 VL 499 IS 2 BP L169 EP L173 DI 10.1086/311373 PN 2 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZU234 UT WOS:000074175800013 ER PT J AU McNamara, BJ Harrison, TE Mason, PA Templeton, M Heikkila, CW Buckley, T Galvan, E Silva, A Harmon, BA AF McNamara, BJ Harrison, TE Mason, PA Templeton, M Heikkila, CW Buckley, T Galvan, E Silva, A Harmon, BA TI A multiyear light curve of Scorpius X-1 based on Compton Gamma Ray Observatory BATSE spectroscopy detector observations SO ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES LA English DT Article DE gamma rays, observations; stars, individual (Scorpius X-1); X-rays, stars ID TERM X-RAY; BEHAVIOR; ULTRAVIOLET; BINARIES; SPECTRA; SEARCH AB A multiyear light curve of the low mass X-ray binary, Scorpius X-l, is constructed based on the Compton Gamma Ray Observatory Burst and Transient Source Experiment (BATSE) Spectroscopy Detector (SD) data in the nominal energy range of 10-20 keV. A detailed discussion is given of the reduction process of the BATSE/SD data. Corrections to the SD measurements are made for off-axis pointings, spectral and bandpass changes, and differences in the eight SD sensitivities. The resulting 4.4 yr Sco X-l SD light curve is characterized in terms of the timescales over which various types of emission changes occur. This light curve is then compared with Sco X-l light curves obtained by AI iel 5, the BATSE Large Area Detectors (LADs), and the RXTE all-sky monitor (ASM). Coincident temporal coverage by the BATSE/SD and RXTE/ASM allows a direct comparison of the behavior of Sco X-l over a range of high energies to be made. These ASM light curves are then used to discuss model constraints on the Sco X-l system. C1 New Mexico State Univ, Dept Astron, Dept 4500, Las Cruces, NM 88003 USA. NASA, George C Marshall Space Flight Ctr, Space Sci Lab, Huntsville, AL 35899 USA. RP McNamara, BJ (reprint author), New Mexico State Univ, Dept Astron, Dept 4500, Box 30001, Las Cruces, NM 88003 USA. NR 29 TC 6 Z9 6 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 JUN PY 1998 VL 116 IS 2 BP 287 EP 305 DI 10.1086/313101 PG 19 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZV145 UT WOS:000074274000006 ER PT J AU Wang, PH Minnis, P McCormick, MP Kent, GS Yue, GK Young, DF Skeens, KM AF Wang, PH Minnis, P McCormick, MP Kent, GS Yue, GK Young, DF Skeens, KM TI A study of the vertical structure of tropical (20 degrees S-20 degrees N) optically thin clouds from SAGE II observations SO ATMOSPHERIC RESEARCH LA English DT Article; Proceedings Paper CT 12th International Conference on Clouds and Precipitation CY AUG 19-23, 1996 CL ZURICH, SWITZERLAND DE optically thin clouds ID AEROSOL; STRATOSPHERE; LIDAR AB The tropical cloud data obtained by the satellite instrument of the Stratospheric Aerosol and Gas Experiment (SAGE) II from October 1984 to May 1991 have been used to study cloud vertical distribution, including thickness and multilayer structure, and to estimate cloud optical depth. The results indicate that the SAGE-II-observed clouds are generally optically thin clouds, corresponding to a range of optical depth between approximately 8 X 10(-4) and 3 x 10(-1) with a mean of about 0.035, Two-thirds are classified as subvisual cirrus and one-third thin cirrus. Clouds between 2- to 3-km thick occur most frequently. Approximately 30% of the SAGE II cloud measurements are isolated single-layer clouds, while 65% are high clouds contiguous with an underlying opaque cloud that terminates the SAGE II profile. Thin clouds above detached opaque clouds at altitudes greater than 6.5 km occur less often. Only about 3% of the SAGE II single-layer clouds are located above the tropopause, while 58% of the cloud layers never reach the tropopause. More than one-third of the clouds appear at the tropopause. This study also shows that clouds occur more frequently and extend higher above the tropopause over the western Pacific than over the eastern Pacific, especially during northern winter. The uncertainty of the derived results due to the SAGE II sampling constraints, data processing, and cloud characteristics is discussed. (C) 1998 Elsevier Science B.V. All rights reserved. C1 NASA, Langley Res Ctr, Div Atmospher Sci, Hampton, VA 23681 USA. Sci & Technol Corp, Hampton, VA 23666 USA. Hampton Univ, Dept Phys, Hampton, VA 23668 USA. RP Wang, PH (reprint author), NASA, Langley Res Ctr, Div Atmospher Sci, MS 475, Hampton, VA 23681 USA. EM wang@arbs3.nasa.larc.gov RI Minnis, Patrick/G-1902-2010 OI Minnis, Patrick/0000-0002-4733-6148 NR 32 TC 14 Z9 14 U1 0 U2 2 PU ELSEVIER SCIENCE INC PI NEW YORK PA 360 PARK AVE SOUTH, NEW YORK, NY 10010-1710 USA SN 0169-8095 J9 ATMOS RES JI Atmos. Res. PD JUN PY 1998 VL 48 SI SI BP 599 EP 614 PG 16 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA ZY528 UT WOS:000074631000038 ER PT J AU Demartini, EE AF Demartini, EE TI How might recruitment research on coral-reef fishes help manage tropical reef fisheries? SO AUSTRALIAN JOURNAL OF ECOLOGY LA English DT Article; Proceedings Paper CT Joint United-States/Australia Workshop on Recruitment and Population Dynamics of Coral-Reef Fishes (Reefish 95) CY DEC 11, 1995 CL KURANDA, AUSTRALIA SP Australian Dept Ind, Sci & Tourisms Bilateral Sci & Technol Collaborat Program, USA Natl Sci Fdn Int Programs DE ecology; exploitation; life history; movements; size ID GREAT-BARRIER-REEF; LUTJANUS-ADETII CASTELNAU; POPULATION-STRUCTURE; DAMSELFISHES POMACENTRIDAE; PLECTROPOMUS-LEOPARDUS; QUINQUELINEATUS BLOCH; MORTALITY-RATES; AGE VALIDATION; LARVAL SIZE; GROWTH AB 'Ecologic' reef fishes (basic research subjects) and 'Economic' reef fishes (exploited by humans) share fundamental early life-history attributes of small, widely dispersed planktonic eggs, larvae, and (for some species in both groups) pelagic juveniles. These attributes predispose the open populations of species in both groups to limitation resulting from environmentally induced fluctuations in recruitment from planktonic/pelagic to benthic stages. Rates of movement within and among reefs, one of several postrecruitment processes likely to be subject to density-dependent regulation, may differ between Ecologics (mostly small-bodied) and Economics (generally larger-bodied). This is because of differences between species in the two groups in size-related differences in the home ranges of individuals. Existing data, however, neither support the notion that natural growth and mortality rates basically differ between the adults of Ecological and Economic species, nor that the generally larger home ranges of larger-bodied adult Economics are more subject to density-dependent control. Further, the small-bodied young-of-year juveniles of both groups on average probably have similar growth and mortality rates and small individual home ranges that are equivalently affected by density dependence. In conclusion I argue that, because of fundamental similarities in the sizes and durations of planktonic propagules and spawning periodicities, certain Ecologics and Economics may comprise a single recruitment guild. Coefficients of growth and mortality for postsettlement Ecologics also may resemble, and be applied as preliminary proxies for, analogous coefficients for Economic species. The efficacy of management strategies such as harvest refugia may differ for Ecological and Economic species, however, depending on whether the refugia are used to counter growth or recruitment overfishing. C1 NOAA, Natl Marine Fisheries Serv, SW Fisheries Sci Ctr, Honolulu, HI 96822 USA. RP NOAA, Natl Marine Fisheries Serv, SW Fisheries Sci Ctr, 2570 Dole St, Honolulu, HI 96822 USA. NR 57 TC 6 Z9 6 U1 0 U2 6 PU BLACKWELL PUBLISHING ASIA PI CARLTON PA 54 UNIVERSITY ST, P O BOX 378, CARLTON, VICTORIA 3053, AUSTRALIA SN 0307-692X J9 AUST J ECOL JI Aust. J. Ecol. PD JUN PY 1998 VL 23 IS 3 BP 305 EP 310 DI 10.1111/j.1442-9993.1998.tb00735.x PG 6 WC Ecology SC Environmental Sciences & Ecology GA ZU238 UT WOS:000074176200017 ER PT J AU Grindeland, RE AF Grindeland, RE TI Comparison of hypergravity and microgravity effects on rat physiology: An overview SO AVIATION SPACE AND ENVIRONMENTAL MEDICINE LA English DT Editorial Material C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Grindeland, RE (reprint author), NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. NR 7 TC 1 Z9 1 U1 1 U2 1 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 JUN PY 1998 VL 69 IS 6 SU S BP A1 EP A1 PG 1 WC Public, Environmental & Occupational Health; Medicine, General & Internal; Sport Sciences SC Public, Environmental & Occupational Health; General & Internal Medicine; Sport Sciences GA ZT175 UT WOS:000074056700001 PM 10776444 ER PT J AU Martinez, DA Orth, MW Carr, KE Vanderby, R Vasques, M Grindeland, RE Vailas, AC AF Martinez, DA Orth, MW Carr, KE Vanderby, R Vasques, M Grindeland, RE Vailas, AC TI Cortical bone responses to 2G hypergravity in growing rats SO AVIATION SPACE AND ENVIRONMENTAL MEDICINE LA English DT Article ID MATURATION; GRAVITY AB Background: Rat cortical bone adaptation to chronic hypergravity (2G) was studied using young growing male Wistar rats (60 d). Methods: Animals (10 rats) were subjected to chronic hypergravity (14 d) in order to understand the plastic nature of bone under a constant hypergravity stress using a special rodent habitat that was attached to a 12-ft. radius centrifuge. Also, an equal number of stationary controls were housed in a rodent vivarium containing identical cages that were used for centrif ugation. After 14 d of centrifugation, femur bones were excised and prepared for morphological and biochemical measurements. Results: Results showed that 2G had significantly shortened the femurs (3%) and reduced the cortical bone area (13%). In particular, hypergravity induced significant reductions in the thicknesses of cortical bone at the anterior (13%) and medial regions (15%) of the middiaphysis. However, femoral bone density, collagen and calcium concentrations were unaltered. The content of mature, stable bone collagen cross-links hydroxylysylpyridinoline (HP), lysylpyridinoline (LP), were significantly greater in bones from centrifuged animals. Conclusion: Our findings suggest that short term exposure to 2G does not enhance bone formation or induce changes in cortical bone composition, or alter specific gravity. These data also suggest that bone maturation as reflected by collagen crosslinking is upregulated. However, it is undetermined at this time whether the enhanced content of mature bone collagen in the centrifuged rats is a result of either an increased rate of cross-linking or reduction in the degradation of "older collagen." C1 Univ Houston, Dept Biol & Biochem, Connect Tissue Physiol Lab, Houston, TX 77204 USA. Univ Wisconsin, Biodynam Lab, Madison, WI 53706 USA. Univ Wisconsin, Dept Orthopaed Surg, Madison, WI USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Martinez, DA (reprint author), Univ Houston, Dept Biol & Biochem, Connect Tissue Physiol Lab, Houston, TX 77204 USA. RI Martinez, Daniel/A-5825-2008 NR 43 TC 8 Z9 8 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 JUN PY 1998 VL 69 IS 6 SU S BP A17 EP A22 PG 6 WC Public, Environmental & Occupational Health; Medicine, General & Internal; Sport Sciences SC Public, Environmental & Occupational Health; General & Internal Medicine; Sport Sciences GA ZT175 UT WOS:000074056700005 PM 10776448 ER PT J AU Mednieks, MI Hand, AR Grindeland, RE AF Mednieks, MI Hand, AR Grindeland, RE TI Cyclic AMP-receptor responses to hypergravity SO AVIATION SPACE AND ENVIRONMENTAL MEDICINE LA English DT Article ID DEPENDENT PROTEIN-KINASE; RAT; DESENSITIZATION; MYOCARDIUM; MECHANISMS; SYSTEM; SALIVA AB Background: Altered gravity (G) encountered during spaceflight causes physiologic changes in humans and in experimental animals. In addition to weightlessness (0G) in space, sharply increased G forces are exerted on the spacecraft during the lift-off and reentry phases. Previous studies showed major changes in cAMP-associated activity of rat heart muscle after spaceflight, indicating that (hormone) signaling pathways may have been affected. Hypothesis: The present study was designed to test the hypothesis that cAMP-related cellular responses of exocrine glands after simulated hypergravity (centrifugation at 1.7G) differ from the effects of 0G. Methods: A portion of the parotid and lachrymal gland tissue was fixed for morphologic and immunocytochemical study, and another was used for biochemical determinations. A short-term tissue culture was established from each gland to determine the effects of stimulation by norepinephrine. Heart muscle (ventricle) was also studied. Soluble and particulate fraction extracts of tissue homogenates were prepared, photoaffinity labeled with the [P-32]8-N-3-analog of cAMP, proteins separated by electrophoresis and the cAMP-reactive proteins (cARP) identified by autoradiography. Results: Differences were seen in protein banding patterns of the gland extracts and in altered cARP distribution in the 1.7G samples of heart ventricle and exocrine gland tissues, when compared with 1G controls. In the heart, cARP increased in the soluble fraction, while the particulate fraction extract showed no change. In acinar cells of the parotid, labeled cARP had accumulated, but decreased alter stimulation to the level of the 1G controls. Immunogold labeling showed an increased content of amylase in the secretory granules of the 1.7G animals, while morphologic observation revealed few changes in the structure of parotid acinar cells, The response in the lachrymal gland was translocation of an isoform of cARP from the particulate to the cytoplasmic compartment. Conclusions: Changes distinct from those due to 0G, but specific for hyper-G were found in cARP activity, protein synthesis, as well as in an apparent inhibition of regulated secretion. C1 Univ Illinois, Coll Dent, Dept Oral Biol, Chicago, IL 60612 USA. Univ Connecticut, Sch Dent Med, Storrs, CT 06269 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Univ Illinois, Coll Dent, Dept Oral Biol, 801 S Paulina St, Chicago, IL 60612 USA. FU NIDCR NIH HHS [DE 10105] NR 33 TC 2 Z9 2 U1 0 U2 1 PU AEROSPACE MEDICAL ASSOC PI ALEXANDRIA PA 320 S HENRY ST, ALEXANDRIA, VA 22314-3579 USA SN 0095-6562 EI 1943-4448 J9 AVIAT SPACE ENVIR MD JI Aviat. Space Environ. Med. PD JUN PY 1998 VL 69 IS 6 SU S BP A28 EP A36 PG 9 WC Public, Environmental & Occupational Health; Medicine, General & Internal; Sport Sciences SC Public, Environmental & Occupational Health; General & Internal Medicine; Sport Sciences GA ZT175 UT WOS:000074056700007 PM 10776450 ER PT J AU Shellenberger, KE Grindeland, RE Hymer, WC AF Shellenberger, KE Grindeland, RE Hymer, WC TI Rat anterior pituitary hormone cells: Responses to variable gravity SO AVIATION SPACE AND ENVIRONMENTAL MEDICINE LA English DT Article ID GROWTH-HORMONE; PROLACTIN; INSULIN AB Background: While life science data dealing with effects of hypogravity are accumulating, relatively little is known about the effects of hypergravity at the level of either the whole animal or the individual cell. The purpose of this experiment was to compare data collected on cells of anterior pituitaries from animals centrifuged at 2G using an experimental design that was identical to that of a spaceflight experiment performed in 1989. Hypothesis: Centrifugation of the animal at 2G for 14 d alters the function and morphology of cells of the anterior pituitary in subsequent in vitro tests at 1G. Methods: intact rats were centrifuged at twice Earth's gravity for 14 d in a specially designed animal centrifuge as part of the Cosmos 2G study. This study was designed to replicate a previous spaceflight experiment so that direct comparisons between hyper-(centrifugation, 2G) and hypogravity (spaceflight, 0.001G) could be made. Anterior pituitary cells were then evaluated for cell function and morphology in a variety of post-flight tests. Results: Growth hormone cells from centrifuged animals released less bioactive, but not immunoreactive, growth hormone (GH) than cells from noncentrifuged animals. This was also true for GH released in response to provocative stimulation by a synthetic peptide (growth hormone releasing hormone, GHRH) that causes GH release after binding to cell membrane receptors. Cell morphology was also different between cells from centrifuged and control animals; cells in the experimental group were smaller and less granulated. However, another type of hormone-producing cell contained in these preparations, viz. prolactin cells, was not affected by centrifugation. Conclusions: Centrifugation of animals for 14 d alters both the in vitro release of GH and GH cell morphology relative to corresponding controls from non-centrifuged animals. Because prolactin cells are not affected by centrifugation, the response is specific to the GH cell. C1 Penn State Univ, Dept Biochem & Mol Biol, University Pk, PA 16802 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Hymer, WC (reprint author), 3 Althouse Lab, University Pk, PA 16802 USA. NR 28 TC 5 Z9 5 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 JUN PY 1998 VL 69 IS 6 SU S BP A37 EP A44 PG 8 WC Public, Environmental & Occupational Health; Medicine, General & Internal; Sport Sciences SC Public, Environmental & Occupational Health; General & Internal Medicine; Sport Sciences GA ZT175 UT WOS:000074056700008 PM 10776451 ER PT J AU Vasques, M Grindeland, RE Daunton, N Wade, CE AF Vasques, M Grindeland, RE Daunton, N Wade, CE TI Comparison of hyper- and microgravity on rat muscle, organ weights and selected plasma constituents SO AVIATION SPACE AND ENVIRONMENTAL MEDICINE LA English DT Article ID WEIGHTLESSNESS; ATROPHY; BODY AB Background: Centrifugation has been proposed to be one possible countermeasure for the skeletal muscle, organ, hormonal, and plasma chemistry adaptations associated with chronic unloading (e.g., during spaceflight). Hypothesis: Our hypothesis was that there would be a continuum of physiological and morphological responses from zero gravity to hypergravity. Methods: Adult male rats were centrifuged continuously at 2G for 14 d and the weights of limb muscles and organs, and the levels of plasma constituents were compared with the same measurements from rats flown on a 14-d spaceflight (Cosmos 2044). Results: Mean body weights of centrifuge rats did not change, whereas age-matched controls grew 21%. There was a sparing of muscle protein in the centrifuge rats; the absolute weights of predominantly slow muscles in the hindlimb were maintained and the relative weights (expressed relative to body weight and as a percent difference from control) of almost all muscles studied were larger than control. In contrast, spaceflight resulted in a decrease in the relative weights of most extensor, but not flexor, hindlimb muscles studied. Relative organ weights, in general, were elevated in centrifuge rats compared with control rats. Relative organ weights in flight rats were similar to control, except for a decrease in testes weight. Plasma thyroxine and testosterone levels were significantly reduced following flight, whereas only thyroxine was decreased after centrifugation. Centrifugation resulted in a decrease in most other plasma chemistry measurements, whereas flight rats showed no change or an elevation in these measures. Discussion: These data indicate that the physiological responses to micro-and hypergravity are often in the opposite direction, suggesting that in general there is a continuum of physiological and morphological effects from microgravity to 1G to hypergravity. These data further suggest that the imposition of hypergravity conditions on animals that are in a microgravity environment may have a beneficial effect in maintaining some physiological systems at or near control levels. C1 NASA, Ames Res Ctr, Div Life Sci, Moffett Field, CA 94035 USA. NASA, Ames Res Ctr, Bionet, Moffett Field, CA 94035 USA. Univ Calif Los Angeles, Brain Res Inst, Los Angeles, CA 90024 USA. RP Grindeland, RE (reprint author), NASA, Ames Res Ctr, Div Life Sci, Moffett Field, CA 94035 USA. NR 23 TC 22 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 JUN PY 1998 VL 69 IS 6 SU S BP A2 EP A8 PG 7 WC Public, Environmental & Occupational Health; Medicine, General & Internal; Sport Sciences SC Public, Environmental & Occupational Health; General & Internal Medicine; Sport Sciences GA ZT175 UT WOS:000074056700002 PM 10776445 ER PT J AU Wade, CE Keil, LC AF Wade, CE Keil, LC TI Reduction of pituitary AVP and OT contents in rats following spaceflight SO AVIATION SPACE AND ENVIRONMENTAL MEDICINE LA English DT Article ID NOREPINEPHRINE CONTENT; SPACE-FLIGHT; VASOPRESSIN; WEIGHTLESSNESS; COSMOS-1887; METABOLISM; OXYTOCIN; RELEASE; STRESS AB Background: Responses of pituitary concentrations of vasopressin (AVP) and oxytocin (OT) during spaceflight have been variable, possibly due to differences in flight conditions or in age and strain of flight animals. Methods: We reviewed findings of three spaceflights of varying flight and recovery durations in which rats of different ages and strains were used. Male rats ranging in weight from 248-396 g were flown in space for 7-14 d. Flight animals were then compared with vivarium controls and synchronous controls. Parallel ground-based studies (hypergravity gravity and simulated hypogravity) were conducted. Results: Pituitary content of AVP was significantly (p less than or equal to 0.05) decreased by spaceflight (6.3 +/- 0.3 mu g.mg(-1) protein in flight vs. 8.3 +/- 0.5 mu g.mg(-1) protein in vivarium). OT content was also reduced during spaceflight (4.3 +/- 0.2 mu g.mg(-1) protein in flight vs. 6.1 +/- 0.3 mu g.mg(-1) protein in vivarium). Vivarium and synchronous control rats showed no difference in pituitary contents. Flight duration or recovery times did not appear to influence pituitary hormone contents. Strain of rat had an effect on content but not on responses to spaceflight. Age of animals confounded the response to spaceflight: pituitary contents of AVP and OT were not altered in young animals (less than or equal to 60 d old). Hindlimb suspended animals showed no difference in AVP but OT content was decreased. Ground-based exposure to hypergravity (2 G) did not alter content of AVP or OT in young animals. Conclusions: Decreases in pituitary content of AVP and OT with spaceflight may be due to a variety of factors unique to the microgravity environment. Differences between studies may be due in part to differences in size and age of rats used. C1 NASA, Ames Res Ctr, Div Life Sci, Moffett Field, CA 94035 USA. Marine Biol Lab, Woods Hole, MA 02543 USA. RP Wade, CE (reprint author), NASA, Ames Res Ctr, Div Life Sci, MS-239-11, Moffett Field, CA 94035 USA. NR 29 TC 1 Z9 1 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 JUN PY 1998 VL 69 IS 6 SU S BP A53 EP A57 PG 5 WC Public, Environmental & Occupational Health; Medicine, General & Internal; Sport Sciences SC Public, Environmental & Occupational Health; General & Internal Medicine; Sport Sciences GA ZT175 UT WOS:000074056700011 PM 10776454 ER PT J AU Janmey, PA Otey Wade, C Allen AF Janmey, PA Otey Wade, C Allen TI A role for pp125(FAK) in suppression of apoptosis in fibroblasts - Discussion SO BIOLOGICAL BULLETIN LA English DT Editorial Material C1 Brigham & Womens Hosp, Div Expt Med, Boston, MA 02115 USA. Univ Virginia, Sch Med, Dept Anat & Cell Biol, Charlottesville, VA 22908 USA. NASA, Ames Res Ctr, Moffett Field, CA 94965 USA. Northwestern Univ, Sch Med, Dept Cell Mol & Struct Biol, Chicago, IL 60611 USA. Univ Massachusetts, Sch Med, Shrewsbury, MA 01545 USA. Univ N Carolina, Dept Cell Biol & Anat, Chapel Hill, NC 27599 USA. RP Janmey, PA (reprint author), Brigham & Womens Hosp, Div Expt Med, LMRC 302,221 Longwood Ave, Boston, MA 02115 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU MARINE BIOLOGICAL LABORATORY PI WOODS HOLE PA 7 MBL ST, WOODS HOLE, MA 02543 USA SN 0006-3185 J9 BIOL BULL JI Biol. Bull. PD JUN PY 1998 VL 194 IS 3 BP 388 EP 389 PG 2 WC Biology; Marine & Freshwater Biology SC Life Sciences & Biomedicine - Other Topics; Marine & Freshwater Biology GA ZZ709 UT WOS:000074759100049 ER PT J AU McIntire, LV Wagner, JE Papadaki, M Whitson, PA Eskin, SG AF McIntire, LV Wagner, JE Papadaki, M Whitson, PA Eskin, SG TI Effect of flow on gene regulation in smooth muscle cells and macromolecular transport across endothelial cell monolayers SO BIOLOGICAL BULLETIN LA English DT Article; Proceedings Paper CT Workshop on the Cytoskeleton - Mechanical, Physical, and Biological Interactions CY NOV 15-17, 1996 CL MARINE BIOL LAB, WOODS HOLE, MASSACHUSETTS SP Marine Biol Lab, Ctr Adv Studies Space Life Sci, NASA HO MARINE BIOL LAB ID NITRIC-OXIDE SYNTHASE; SHEAR-STRESS; HYPERPLASIA C1 Rice Univ, Inst Biosci & Bioengn, Houston, TX 77251 USA. NASA, Div Med Sci, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. Texas Biotechnol Corp, Dept Cell Biol, Houston, TX 77030 USA. RP McIntire, LV (reprint author), Rice Univ, Inst Biosci & Bioengn, Houston, TX 77251 USA. NR 16 TC 15 Z9 15 U1 0 U2 1 PU MARINE BIOLOGICAL LABORATORY PI WOODS HOLE PA 7 MBL ST, WOODS HOLE, MA 02543 USA SN 0006-3185 J9 BIOL BULL JI Biol. Bull. PD JUN PY 1998 VL 194 IS 3 BP 394 EP 399 DI 10.2307/1543123 PG 6 WC Biology; Marine & Freshwater Biology SC Life Sciences & Biomedicine - Other Topics; Marine & Freshwater Biology GA ZZ709 UT WOS:000074759100052 PM 9664672 ER PT J AU Wisniewski, R AF Wisniewski, R TI Developing large-scale cryopreservation systems for biopharmaceutical products SO BIOPHARM-THE APPLIED TECHNOLOGIES OF BIOPHARMACEUTICAL DEVELOPMENT LA English DT Article ID WATER; TREHALOSE AB Two novel approaches to cryopreservation have spurred the development of large-scale systems for biopharmaceutical products: freezing and thawing using internal heat transfer surfaces and freezing and granulation using volumetric heat transfer. Both have been applied to large volumes of biological solutions. C1 NASA, Ames Res Ctr, Mt View, CA USA. Integrated Biosyst, Benicia, CA USA. EM rwisniewski@mail.arc.nasa.gov NR 31 TC 11 Z9 12 U1 0 U2 1 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 JUN PY 1998 VL 11 IS 6 BP 50 EP + PG 8 WC Biotechnology & Applied Microbiology; Pharmacology & Pharmacy SC Biotechnology & Applied Microbiology; Pharmacology & Pharmacy GA ZT024 UT WOS:000074040000007 ER PT J AU Peteet, D Andreev, A Bardeen, W Mistretta, F AF Peteet, D Andreev, A Bardeen, W Mistretta, F TI Long-term Arctic peatland dynamics, vegetation and climate history of the Pur-Taz region, Western Siberia SO BOREAS LA English DT Article ID NORTHERN; ACCUMULATION; ECOSYSTEMS; TUNDRA; BOG AB Stratigraphic analyses of peal composition, LOI, pollen, spores, macrofossils, charcoal and AMS ages are used to reconstruct the peatland, vegetation and climatic dynamics in the Pur-Taz region of western Siberia over 5000 years (9300-4500 BP). Section stratigraphy shows many changes from shallow lake sediment to different combinations of forested or open sedge, moss, and Equisetum fen and peatland environments. Macrofossil and pollen data indicate that Larix sibirica and Betula pubescens trees were the first to arrive, followed by Picea obovata. The dominance of Picea macrofossils 6000-5000 BP in the Pur-Taz peatland along with regional Picea pollen maxima indicate warmer conditions and movement of the spruce treeline northward at this time. The decline of pollen and macrofossils from all of these tree species in uppermost peals suggests a change in the environment less favorable for their growth, perhaps cooler temperatures and/or less moisture. Of major significance is the evidence for old ages of the uppermost peals in this area of Siberia, suggesting a real lack of peal accumulation in recent millennia or recent oxidation of uppermost peat. C1 NASA, Goddard Inst Space Studies, New York, NY 10025 USA. Lamont Doherty Earth Observ, Palisades, NY 10964 USA. Russian Acad Sci, Inst Geog, Moscow 109017, Russia. Lamont Doherty Earth Observ, Palisades, NY 10964 USA. RP Peteet, D (reprint author), NASA, Goddard Inst Space Studies, 2880 Broadway, New York, NY 10025 USA. RI Andreev, Andrei/J-2701-2015 NR 77 TC 49 Z9 54 U1 2 U2 11 PU SCANDINAVIAN UNIVERSITY PRESS PI OSLO PA PO BOX 2959 TOYEN, JOURNAL DIVISION CUSTOMER SERVICE, N-0608 OSLO, NORWAY SN 0300-9483 J9 BOREAS JI Boreas PD JUN PY 1998 VL 27 IS 2 BP 115 EP 126 PG 12 WC Geography, Physical; Geosciences, Multidisciplinary SC Physical Geography; Geology GA 111ZH UT WOS:000075468500004 ER PT J AU Jasinski, JPP Warner, BG Andreev, AA Aravena, R Gilbert, SE Zeeb, BA Smol, JP Velichko, AA AF Jasinski, JPP Warner, BG Andreev, AA Aravena, R Gilbert, SE Zeeb, BA Smol, JP Velichko, AA TI Holocene environmental history of a peatland in the Lena River valley, Siberia SO CANADIAN JOURNAL OF EARTH SCIENCES LA English DT Article ID BOREAL-FOREST; TREE REGENERATION; QUEBEC; POLLEN; TUNDRA; VEGETATION; SEDIMENTS; PENINSULA; STOMATE; FIRE AB A 3.86 m core of peat and organic lake mud from a polygonal peatland in the Lena River valley of Siberia was radiocarbon dated and analyzed for pollen, plant macrofossils, chrysophyte stomatocysts, stable isotopes, and charcoal. At around 7200 BP, a shallow lake or open-water wetland supported diverse aquatic macrophytes. The site had transformed initially into a richer fen with Carer, Comarum palustris, and Drepanocladus and later a poorer fen with Sphagnum which persisted until around 3000 BP. Fire may have been responsible for silt being blown onto the peatland, which changed the hydrological and geochemical conditions for development of the poor fen. Ice accretion led to an increase in the height of the centre of the polygon and expansion of Sphagnum peatland. O-18 values become progressively more enriched, which reflects more direct input of summer precipitation waters and less groundwater during this period. Finally, the peatland surface was elevated sufficiently to limit water and nutrient supply, thereby allowing Ericaceae and Betula to grow at the coring site. Fire burned the peatland surface and may have exaggerated the extremely slow rate of peat accumulation Fire may also be a factor in maintaining the open Larix dahurica forest in the region today, while climate may be contributing to reducing postfire regeneration. Fire and climate together may be controlling the character and composition of forests near tree line in the Lena River valley of this part of Siberia. C1 Univ Waterloo, Dept Geog, Waterloo, ON N2L 3G1, Canada. NASA, Goddard Inst Space Studies, New York, NY 10025 USA. Univ Waterloo, Dept Earth Sci, Waterloo, ON N2L 3G1, Canada. Queens Univ, Dept Biol, Paleoecol Environm Assessment & Resource Lab, Kingston, ON K7L 3N6, Canada. Russian Acad Sci, Inst Geog, Moscow 109017, Russia. RP Univ Waterloo, Dept Geog, Waterloo, ON N2L 3G1, Canada. EM bwarner@watserv1.uwaterloo.ca RI Smol, John/A-8838-2015; Andreev, Andrei/J-2701-2015 NR 49 TC 24 Z9 25 U1 0 U2 8 PU CANADIAN SCIENCE PUBLISHING, NRC RESEARCH PRESS PI OTTAWA PA 65 AURIGA DR, SUITE 203, OTTAWA, ON K2E 7W6, CANADA SN 0008-4077 EI 1480-3313 J9 CAN J EARTH SCI JI Can. J. Earth Sci. PD JUN PY 1998 VL 35 IS 6 BP 637 EP 648 DI 10.1139/e98-015 PG 12 WC Geosciences, Multidisciplinary SC Geology GA 139UZ UT WOS:000077049200003 ER PT J AU Bellmann, E Shaheen, SE Thayumanavan, S Barlow, S Grubbs, RH Marder, SR Kippelen, B Peyghambarian, N AF Bellmann, E Shaheen, SE Thayumanavan, S Barlow, S Grubbs, RH Marder, SR Kippelen, B Peyghambarian, N TI New triarylamine-containing polymers as hole transport materials in organic light-emitting diodes: Effect of polymer structure and cross-linking on device characteristics SO CHEMISTRY OF MATERIALS LA English DT Article ID ELECTROLUMINESCENT DEVICES; CHARGE-TRANSPORT; BOND FORMATION; COMPLEXES; FILMS; RUCL2(=CHR')(PR(3))(2); AMINATION; CATALYST; HALIDES AB A series of poly(norbornenes) with pendant triarylamine (TPA) groups has been synthesized by ring-opening metathesis polymerization and investigated as hole transport materials in organic two-layer light-emitting diodes (LEDs). Efficient device fabrication through spin casting of the hole transport layer (HTL) was possible, since the polymers exhibited excellent film formation properties. LEDs of the form ITO/poly(norbornene)-TPA/Alq(3)/Mg (ITO = indium tin oxide, Alq(3) = tris(8-quinolinato)aluminum) showed bright green emission with external quantum efficiencies of up to 0.77% (1.30 lm/W) for 20 nm thick HTL films. The length and polarity of the linker between the triarylamine functionality and the polymer backbone were varied systematically. The device performance was found to depend strongly on these structural differences. Substitution of ester groups by less polar ether functionalities greatly enhances external quantum efficiencies, lowers the operating voltage, and improves the stability of the device. Further improvement of the device characteristics is achieved by reducing the length of the alkyl linker. The HTL can be conveniently cross-linked by UV irradiation. Cross-linking was found to decrease device performance. A maximum external quantum efficiency of 0.37% was achieved for an Alq(3)-LED with cross-linked HTL. C1 CALTECH, Div Chem & Chem Engn, Arnold & Mabel Beckman Labs Chem Synthesis, Pasadena, CA 91125 USA. Univ Arizona, Ctr Opt Sci, Tucson, AZ 85721 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. CALTECH, Beckman Inst, Pasadena, CA 91109 USA. RP Grubbs, RH (reprint author), CALTECH, Div Chem & Chem Engn, Arnold & Mabel Beckman Labs Chem Synthesis, Pasadena, CA 91125 USA. RI grubbs, robert/D-4293-2009; Kippelen, Bernard/I-4058-2013; Shaheen, Sean/M-7893-2013; Barlow, Stephen/E-9754-2010 OI grubbs, robert/0000-0002-0057-7817; Kippelen, Bernard/0000-0002-8417-7051; NR 45 TC 170 Z9 170 U1 4 U2 40 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA SN 0897-4756 J9 CHEM MATER JI Chem. Mat. PD JUN PY 1998 VL 10 IS 6 BP 1668 EP 1676 DI 10.1021/cm980030p PG 9 WC Chemistry, Physical; Materials Science, Multidisciplinary SC Chemistry; Materials Science GA ZV160 UT WOS:000074275800029 ER PT J AU Preston, F AF Preston, F TI Not that many transistors SO COMPUTER LA English DT Letter C1 NASA Langley, Hampton, VA 23665 USA. RP Preston, F (reprint author), NASA Langley, Hampton, VA 23665 USA. NR 0 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 0018-9162 J9 COMPUTER JI Computer PD JUN PY 1998 VL 31 IS 6 BP 7 EP 7 PG 1 WC Computer Science, Hardware & Architecture; Computer Science, Software Engineering SC Computer Science GA ZR267 UT WOS:000073957000011 ER PT J AU Kiris, C Kwak, D Benkowski, R AF Kiris, C Kwak, D Benkowski, R TI Incompressible Navier-Stokes calculations for the development of a ventricular assist device SO COMPUTERS & FLUIDS LA English DT Article; Proceedings Paper CT 6th International Symposium on Computational Fluid Dynamics CY SEP, 1995 CL LAKE TAHOE, NEVADA SP Japan Soc Comp Fluid Dynam ID EQUATIONS AB An incompressible flow analysis code, INS3D, has been applied to the development of a mechanical heart assist device. The solution method is based on the artificial compressibility approach and uses an implicit-upwind differencing scheme together with a Gauss-Seidel line relaxation method. The equations are solved in steadily rotating reference frames and the centrifugal and the Coriolis force terms are included as source terms. The resulting computational procedure is validated for liquid rocket engine analysis and applied subsequently to analyze a Ventricular Assist Device (VAD). A new design configuration is developed which includes an inducer upstream of the impeller main blades, and substantial improvement is observed in the performance of the VAD. (C) 1998 Elsevier Science Ltd. All rights reserved. C1 MCAT Inc, NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Micromed Technol, The Woodlands, TX 77380 USA. RP Kiris, C (reprint author), MCAT Inc, NASA, Ames Res Ctr, MS T27B-1, Moffett Field, CA 94035 USA. NR 9 TC 6 Z9 6 U1 0 U2 0 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0045-7930 J9 COMPUT FLUIDS JI Comput. Fluids PD JUN-JUL PY 1998 VL 27 IS 5-6 BP 709 EP 719 DI 10.1016/S0045-7930(97)00049-2 PG 11 WC Computer Science, Interdisciplinary Applications; Mechanics SC Computer Science; Mechanics GA ZT124 UT WOS:000074050800016 ER PT J AU Stone, M Ladd, SL Vaidya, CJ Gabrieli, JDE AF Stone, M Ladd, SL Vaidya, CJ Gabrieli, JDE TI Word-identification priming for ignored and attended words SO CONSCIOUSNESS AND COGNITION LA English DT Article ID SELECTIVE ATTENTION; EXPLICIT MEMORY; UNCONSCIOUS PERCEPTION; SEMANTIC ACTIVATION; FRAGMENT COMPLETION; LEXICAL DECISION; VISUAL MASKING; IMPLICIT; RECOGNITION; AMNESIA AB Three experiments examined contributions of study phase awareness of word identity to subsequent word-identification priming by manipulating visual attention to words at study. In Experiment 1, word-identification priming was reduced for ignored relative to attended words, even though ignored words were identified sufficiently to produce negative priming in thr: study phase. Word-identification priming was also reduced after color naming relative to emotional valence rating (Experiment 2) or word reading (Experiment 3), even though an effect of emotional valence upon color naming (Experiment 2) indicated that words were identified at study. Thus, word-identification priming was reduced even when word identification occurred at study. Word-identification priming may depend on awareness of word identity at the time of study. (C) 1998 Academic Press. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Stanford Univ, Dept Psychol, Stanford, CA 94305 USA. W Valley Coll, Dept Psychol, Saratoga, CA 95070 USA. RP Stone, M (reprint author), NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. FU NIA NIH HHS [5 F32 AG05616] NR 82 TC 33 Z9 33 U1 2 U2 4 PU ACADEMIC PRESS INC PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA SN 1053-8100 J9 CONSCIOUS COGN JI Conscious. Cogn. PD JUN PY 1998 VL 7 IS 2 BP 238 EP 258 DI 10.1006/ccog.1998.0326 PG 21 WC Psychology, Experimental SC Psychology GA 105RF UT WOS:000075086800019 PM 9690028 ER PT J AU Hooker, MW Wise, SA AF Hooker, MW Wise, SA TI On-orbit performance of YBa2Cu3O7-x thick films SO CRYOGENICS LA English DT Article DE high temperature superconductivity; thick films; hybrid circuits; spaceflight; MIDAS ID SUPERCONDUCTIVITY AB Screen-printed thick films of the YBa2Cu3O7-x high-temperature superconductor were integrated into hybrid microelectronics circuits and characterized on orbit as part of the Materials In Devices As Superconductors (MIDAS) space-flight experiment. The experiment operated autonomously for 90 days on the Mir space station and acquired electrical data on the superconductive films at temperatures ranging from 75 to 250 K. This report describes the on-orbit critical transition temperature, T-c, and critical current density, J(c), performance of the YBa2Cu3O7-x thick films and compares the flight data with those obtained during pre- and post-fright testing. The results of this investigation show no significant difference between the space-flight and ground data, indicating that no degradation occurred in the superconductive films due to either vibrational loads experienced during launch or continuous operation in a microgravity environment. (C) 1998 Published by Elsevier Science Ltd. All rights reserved. C1 NASA, Lockheed Martin Engn & Sci Co, Langley Res Ctr, Hampton, VA 23681 USA. RP Hooker, MW (reprint author), NASA, Lockheed Martin Engn & Sci Co, Langley Res Ctr, Mail Stop 188B, Hampton, VA 23681 USA. NR 15 TC 0 Z9 0 U1 0 U2 0 PU ELSEVIER SCI LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, OXON, ENGLAND SN 0011-2275 J9 CRYOGENICS JI Cryogenics PD JUN PY 1998 VL 38 IS 6 BP 665 EP 672 DI 10.1016/S0011-2275(98)00019-8 PG 8 WC Thermodynamics; Physics, Applied SC Thermodynamics; Physics GA ZZ343 UT WOS:000074719900013 ER PT J AU Heymann, M Lin, F Meyer, G AF Heymann, M Lin, F Meyer, G TI Synthesis and viability of minimally interventive legal controllers for hybrid systems SO DISCRETE EVENT DYNAMIC SYSTEMS-THEORY AND APPLICATIONS LA English DT Article DE hybrid systems; safety control synthesis; Zenoness ID DISCRETE-EVENT SYSTEMS AB In this paper, we study the control of Composite Hybrid Machines (CHMs) subject to safety specifications. CHMs are a fairly general class of hybrid systems modeled in modular fashion as the concurrent operation of Elementary Hybrid Machines (EHMs). The formalism has a well-defined synchronous-composition operation that permits the introduction of the controller as a component of the system. The task of a legal (safety) controller is to ensure that the system never exits a set of specified legal configurations. Among the legal controllers, we are particularly interested in designing a minimally-interventive (or minimally-restrictive) one, which interferes in the system's operation only when constraint violation is otherwise inevitable. Thus, a minimally interventive safety controller provides maximum flexibility in embedding additional controllers designed for other control objectives to operate concurrently while eliminating the need to re-investigate or re-verify the legality of the composite controller with respect to the safety specification. We describe in detail an algorithm for controller synthesis and examine the viability of a synthesized controller as related to the possibility of Zenoness, where the system can undergo an unbounded number of transitions in a bounded length of time. C1 Technion Israel Inst Technol, Dept Comp Sci, IL-32000 Haifa, Israel. Wayne State Univ, Dept Elect & Comp Engn, Detroit, MI 48202 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Heymann, M (reprint author), Technion Israel Inst Technol, Dept Comp Sci, IL-32000 Haifa, Israel. EM heymann@cs.technion.ac.il; flin@ece.eng.wayne.edu; gmeyer@mail.arc.nasa.gov NR 38 TC 26 Z9 26 U1 0 U2 0 PU SPRINGER PI DORDRECHT PA VAN GODEWIJCKSTRAAT 30, 3311 GZ DORDRECHT, NETHERLANDS SN 0924-6703 J9 DISCRETE EVENT DYN S JI Discret. Event Dyn. Syst.-Theory Appl. PD JUN PY 1998 VL 8 IS 2 BP 105 EP 135 DI 10.1023/A:1008285600895 PG 31 WC Automation & Control Systems; Operations Research & Management Science; Mathematics, Applied SC Automation & Control Systems; Operations Research & Management Science; Mathematics GA ZX858 UT WOS:000074562500003 ER PT J AU Chestkov, V Baibakov, B Radko, SP Chrambach, A AF Chestkov, V Baibakov, B Radko, SP Chrambach, A TI Separation of viable from radiation-induced apoptotic lymphocytes by free-flow electrophoresis SO ELECTROPHORESIS LA English DT Article DE apoptotic lymphocytes; isolation; free-flow electrophoresis ID PROGRAMMED CELL-DEATH; SODIUM-CHLORIDE; T-CELLS; SUBPOPULATIONS AB A human lymphocyte population undergoing apoptosis in vitro due to gamma-irradiation was fractionated by free-flow electrophoresis in triethanolamine Na-acetate buffers, containing up to 50 mM NaCl, with pH 6.0, 7.2 and 8.5, made isotonic by addition of sucrose. As shown by a flow cytometric analysis of the eluate, the distribution of apoptotic lymphocytes is shifted to the range of higher electrophoretic mobilities relative to that of viable ones at pH 8.5, yielding cell fractions enriched in apoptotic cells by a factor of 3 to 5. The difference in rates of electrophoretic migration observed at a mildly alkaline pH but not at a neutral or mildly acidic one suggests that the surface of apoptotic lymphocytes is more acidic than that of viable ones. C1 NICHD, Macromol Anal Sect, Lab Cellular & Mol Biophys, NIH, Bethesda, MD 20892 USA. NIH, NASA, Ctr Tissue Culture, Bethesda, MD 20892 USA. RP Chrambach, A (reprint author), NICHD, Macromol Anal Sect, Lab Cellular & Mol Biophys, NIH, Bldg 10,Rm 9D50, Bethesda, MD 20892 USA. NR 17 TC 2 Z9 3 U1 1 U2 3 PU WILEY-V C H VERLAG GMBH PI BERLIN PA MUHLENSTRASSE 33-34, D-13187 BERLIN, GERMANY SN 0173-0835 J9 ELECTROPHORESIS JI Electrophoresis PD JUN PY 1998 VL 19 IS 7 BP 1211 EP 1214 DI 10.1002/elps.1150190723 PG 4 WC Biochemical Research Methods; Chemistry, Analytical SC Biochemistry & Molecular Biology; Chemistry GA ZV360 UT WOS:000074296800022 PM 9662185 ER PT J AU Crews, C AF Crews, C TI Let's broaden our view of cloning SO FUTURIST LA English DT Editorial Material C1 NASA, Mid Continent Technol Transfer Ctr, Washington, DC 20546 USA. RP Crews, C (reprint author), 7200 Almeda Rd,310, Houston, TX 77054 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU WORLD FUTURE SOCIETY PI BETHESDA PA 7910 WOODMONT AVE, SUITE 450, BETHESDA, MD 20814 USA SN 0016-3317 J9 FUTURIST JI Futurist PD JUN-JUL PY 1998 VL 32 IS 5 BP 68 EP 68 PG 1 WC Social Issues SC Social Issues GA ZN600 UT WOS:000073662100038 ER PT J AU Burgmann, R Fielding, E Sukhatme, J AF Burgmann, R Fielding, E Sukhatme, J TI Slip along the Hayward fault, California, estimated from space-based synthetic aperture radar interferometry SO GEOLOGY LA English DT Article ID LANDERS EARTHQUAKE AB For 3-5 years following the 1989 M 7.1 Loma Prieta earthquake, creep along the southern Hayward fault, California, slowed or ceased. Slip apparently resumed pre-earthquake rates by 1994 except for a locked similar to 3-km-long segment at the southern fault tip, which had consistently slipped at similar to 9 mm/yr before 1989, We use repeated interferometric synthetic aperture radar (IntSAR) measurements to map active deformation along the Hayward fault while slip rates recovered between 1992 and 1995. If pure strike slip is assumed, then the slip rates estimated from IntSAR range changes between 1992 and 1995 are generally consistent with creepmeter and alignment-array measurements along much of the fault and confirm the temporary locking of the southernmost fault segment. However, along similar to 6 km of the Fremont segment, IntSAR slip estimates appear to be at least twice those measured in the field. Transient vertical slip (northeast side up) of 23 mm/yr near the southern tip of the creep patch could explain this observation. First-order boundary-element models of a vertical frictionless fault in an elastic half-space predict some, but not all, of the inferred vertical slip. C1 Univ Calif Davis, Dept Geol, Livermore, CA 95616 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Burgmann, R (reprint author), Univ Calif Davis, Dept Geol, Livermore, CA 95616 USA. OI Fielding, Eric/0000-0002-6648-8067 NR 27 TC 24 Z9 25 U1 0 U2 1 PU ASSOC ENGINEERING GEOLOGISTS GEOLOGICAL SOCIETY AMER PI COLLEGE STN PA TEXAS A & M UNIV, DEPT GEOLOGY & GEOPHYSICS, COLLEGE STN, TX 77843-3115 USA SN 0091-7613 J9 GEOLOGY JI Geology PD JUN PY 1998 VL 26 IS 6 BP 559 EP 562 DI 10.1130/0091-7613(1998)026<0559:SATHFC>2.3.CO;2 PG 4 WC Geology SC Geology GA ZU542 UT WOS:000074208500020 ER PT J AU Pfaff, R Yamamoto, M Marionni, P Mori, H Fukao, S AF Pfaff, R Yamamoto, M Marionni, P Mori, H Fukao, S TI Electric field measurements above and within a sporadic-E layer SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID RADAR; WAVES AB In-situ DC and wave electric fields were detected above and within a sporadic-E layer by sounding rocket-borne instruments in the presence of quasi-periodic backscatter radar echoes. When analyzed in conjunction with plasma density measurements, the in-situ data reveal complex electrodynamics associated with the sporadic-E layer. The electric field data show: (1) a sinusoidal variation of +/- 3 mV/m between 130-170 km which may be associated with a gravity wave with a horizontal wavelength of similar to 20 km; (2) localized DC electric fields of similar to 20 mV/m associated with narrow (few km) plasma density depletions near 125 km altitude; and (3) a broad spectrum of plasma irregularities, including long wavelength (km-scale) and meter-scale waves. No short-scale plasma waves were observed in-situ above 115 km, despite the fact that simultaneous radar data show echoes originating from altitudes as high as 135 km. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Kyoto Univ, Ctr Radio Atmospher Sci, Kyoto 606, Japan. Commun Res Lab, Tokyo, Japan. RP Pfaff, R (reprint author), NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RI Pfaff, Robert/F-5703-2012 OI Pfaff, Robert/0000-0002-4881-9715 NR 8 TC 31 Z9 31 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 JUN 1 PY 1998 VL 25 IS 11 BP 1769 EP 1772 DI 10.1029/98GL00935 PG 4 WC Geosciences, Multidisciplinary SC Geology GA ZR962 UT WOS:000074033800003 ER PT J AU Yamamoto, M Itsuki, T Kishimoto, T Tsunoda, RT Pfaff, RF Fukao, S AF Yamamoto, M Itsuki, T Kishimoto, T Tsunoda, RT Pfaff, RF Fukao, S TI Comparison of E-region electric fields observed with a sounding rocket and a Doppler radar in the SEEK campaign SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID MIDLATITUDE SPORADIC-E; E IRREGULARITIES; MU RADAR AB This paper describes results from simultaneous measurements of mid-latitude irregularities by a sounding rocket and a Doppler radar. The experiment was conducted on August 26, 1996 as part of the SEEK (Sporadic-E Experiment over Kyushu) campaign in Japan. Electric field observed with a double-probe sensor on the rocket showed very large fluctuations of +/-10 mV/m where irregularity echoes were quite intense. Doppler velocities observed with the radar agreed well with the electric fields. We estimated growth rates of the gradient-drift instability, which showed positive values around the major sporadic-E layer. It was found that, within intense irregularity region with quasi-periodic structures, there were large polarization electric fields that was likely to be associated with spatial structure of the sporadic-E layer. C1 Kyoto Univ, Ctr Radio Atmospher Sci, Uji, Kyoto 611, Japan. SRI Int, Menlo Park, CA 94025 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Yamamoto, M (reprint author), Kyoto Univ, Ctr Radio Atmospher Sci, Uji, Kyoto 611, Japan. RI Pfaff, Robert/F-5703-2012 OI Pfaff, Robert/0000-0002-4881-9715 NR 11 TC 19 Z9 19 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 JUN 1 PY 1998 VL 25 IS 11 BP 1773 EP 1776 DI 10.1029/98GL01055 PG 4 WC Geosciences, Multidisciplinary SC Geology GA ZR962 UT WOS:000074033800004 ER PT J AU Woo, R Habbal, SR AF Woo, R Habbal, SR TI Comment on: "Polar plumes and fine-scale coronal structures - On the interpretation of coronal radio sounding data" by Patzold and Bird SO GEOPHYSICAL RESEARCH LETTERS LA English DT Editorial Material C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Harvard Smithsonian Ctr Astrophys, Cambridge, MA 02178 USA. RP Woo, R (reprint author), CALTECH, Jet Prop Lab, MS 238-725,4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 9 TC 2 Z9 2 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 JUN 1 PY 1998 VL 25 IS 11 BP 1849 EP 1850 DI 10.1029/98GL00842 PG 2 WC Geosciences, Multidisciplinary SC Geology GA ZR962 UT WOS:000074033800023 ER PT J AU Pierce, RB Grant, WB AF Pierce, RB Grant, WB TI Seasonal evolution of Rossby and gravity wave induced laminae in ozonesonde data obtained from Wallops Island, Virginia SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID LOWER STRATOSPHERE AB A method for evaluating the seasonal evolution of ozone laminae using ozonesonde data is discussed. The method uses the correlation between small-scale ozone and potential temperature variations to distinguish between laminae generated by quasi-isentropic filamentation by Rossby waves and by vertical displacements of material surfaces by gravity waves. Data from Wallops Island, Virginia show that Rossby wave induced ozone laminae are most frequently encountered at Wallops during the winter months near 15 km while statistically significant gravity wave induced laminae occur above 15 km during the early winter and at the tropopause from late winter through early spring. C1 NASA, Langley Res Ctr, Div Atmospher Sci, Hampton, VA 23681 USA. RP Pierce, RB (reprint author), NASA, Langley Res Ctr, Div Atmospher Sci, Hampton, VA 23681 USA. RI Pierce, Robert Bradley/F-5609-2010; Grant, William/B-8311-2009 OI Pierce, Robert Bradley/0000-0002-2767-1643; Grant, William/0000-0002-1439-3285 NR 10 TC 35 Z9 35 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 JUN 1 PY 1998 VL 25 IS 11 BP 1859 EP 1862 DI 10.1029/98GL01507 PG 4 WC Geosciences, Multidisciplinary SC Geology GA ZR962 UT WOS:000074033800026 ER PT J AU Grant, WB Pierce, RB Oltmans, SJ Browell, EV AF Grant, WB Pierce, RB Oltmans, SJ Browell, EV TI Seasonal evolution of total and gravity wave induced laminae in ozonesonde data in the tropics and subtropics SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID TROPOSPHERIC OZONE; LOWER STRATOSPHERE; POLAR VORTEX; TRANSPORT AB ECC ozonesonde ozone and potential temperature profile data for several stations from 25.05 degrees S to 19.6 degrees N were processed to look for the type, seasonal behavior, and vertical distribution of the laminar structure in the troposphere and lower stratosphere. The fractions of ozone laminae associated with Rossby and gravity wave induced laminae were determined from correlations between ozone and potential temperature structure. Gravity-wave-induced laminae in the stratosphere were found to be associated with deep convection in the winter months and winds form the southwest in the summer months for the Hilo station, and orographic wave activity for the Pretoria station in September. Mo significant Rossby wave activity was found for these stations. Lower tropospheric laminae of mixed characteristics were found to be prevalent at the Hilo, related to transport from the northeast, and the continental tropical stations in the June-August period, which are associated with biomass burning. C1 NASA, Langley Res Ctr, Div Atmospher Sci, Hampton, VA 23681 USA. NOAA, Climate Monitoring & Diagnost Lab, Boulder, CO 80303 USA. RP Grant, WB (reprint author), NASA, Langley Res Ctr, Div Atmospher Sci, MS 401A, Hampton, VA 23681 USA. RI Pierce, Robert Bradley/F-5609-2010; Grant, William/B-8311-2009 OI Pierce, Robert Bradley/0000-0002-2767-1643; Grant, William/0000-0002-1439-3285 NR 30 TC 18 Z9 18 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 JUN 1 PY 1998 VL 25 IS 11 BP 1863 EP 1866 DI 10.1029/98GL01297 PG 4 WC Geosciences, Multidisciplinary SC Geology GA ZR962 UT WOS:000074033800027 ER PT J AU Solomon, S Portmann, RW Garcia, RR Randel, W Wu, F Nagatani, R Gleason, J Thomason, L Poole, LR McCormick, MP AF Solomon, S Portmann, RW Garcia, RR Randel, W Wu, F Nagatani, R Gleason, J Thomason, L Poole, LR McCormick, MP TI Ozone depletion at mid-latitudes: Coupling of volcanic aerosols and temperature variability to anthropogenic chlorine SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID HETEROGENEOUS CHEMISTRY; ERUPTION; PINATUBO; ACID AB Satellite observations of total ozone at 40-60 degrees N are presented from a variety of instruments over the time period 1979-1997. These reveal record low values in 1992-3 (after Pinatubo) followed by partial but incomplete recovery. The largest post-Pinatubo reductions and longer-term trends occur in spring, providing a critical test for chemical theories of ozone depletion. The observations are shown to be consistent with current understanding of the chemistry of ozone depletion when changes in reactive chlorine and stratospheric aerosol abundances are considered along with estimates of wave-driven fluctuations in stratospheric temperatures derived from global temperature analyses. Temperature fluctuations are shown to make significant contributions to model calculated northern mid-latitude ozone depletion due to heterogeneous chlorine activation on liquid sulfate aerosols at temperatures near 200-210K (depending upon water vapor pressure), particularly after major volcanic eruptions. Future mid-latitude ozone recovery will hence depend not only on chlorine recovery but also on temperature trends and/or variability, volcanic activity, and any trends in stratospheric sulfate aerosol. C1 NOAA, Aeron Lab, Boulder, CO 80303 USA. Natl Ctr Atmospher Res, Boulder, CO 80307 USA. Natl Ctr Environm Predict, Washington, DC 20233 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. NASA, Langley Res Ctr, Aerosol Res Branch, Hampton, VA 23665 USA. Hampton Univ, Dept Phys, Hampton, VA 23665 USA. RP Solomon, S (reprint author), NOAA, Aeron Lab, 325 Broadway,R E AL8, Boulder, CO 80303 USA. RI Portmann, Robert/C-4903-2009; Gleason, James/E-1421-2012; Randel, William/K-3267-2016; OI Portmann, Robert/0000-0002-0279-6087; Randel, William/0000-0002-5999-7162; Thomason, Larry/0000-0002-1902-0840 NR 29 TC 70 Z9 70 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 JUN 1 PY 1998 VL 25 IS 11 BP 1871 EP 1874 DI 10.1029/98GL01293 PG 4 WC Geosciences, Multidisciplinary SC Geology GA ZR962 UT WOS:000074033800029 ER PT J AU Callis, LB Lambeth, JD AF Callis, LB Lambeth, JD TI NOy formed by precipitating electron events in 1991 and 1992: Descent into the stratosphere as observed by ISAMS SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID ATMOSPHERE; MIDDLE AB NOAA 12 precipitating electron data has been examined together with ISAMS observations of nighttime NO2 during electron events in November 1991 and May 1992. Energy deposition calculations suggest the significant formation of NOy during these events near 0.1 mbar and for 60 degrees-80 degrees latitude. ISAMS confirms increases of NO2 from zonally averaged values of approximate to 1-5 ppbv prior to the events to values in excess of 30-40 ppbv with local maxima in excess of 140 ppbv. The increases occur within 2-3 days and are generally consistent with the calculated NOy formation rates due precipitating electrons. ISAMS data indicate the subsequent transport of the NO2 into the stratosphere affecting NO2 mixing ratios below 1 mbar and down to latitudes of approximate to 30 degrees to 40 degrees in both hemispheres. C1 NASA, Langley Res Ctr, Div Atmospher Sci, Hampton, VA 23681 USA. SAIC, Hampton, VA USA. RP Callis, LB (reprint author), NASA, Langley Res Ctr, Div Atmospher Sci, Mail Stop 401B, Hampton, VA 23681 USA. NR 15 TC 39 Z9 40 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 JUN 1 PY 1998 VL 25 IS 11 BP 1875 EP 1878 DI 10.1029/98GL01219 PG 4 WC Geosciences, Multidisciplinary SC Geology GA ZR962 UT WOS:000074033800030 ER PT J AU Rosenfield, JE Considine, DB Schoeberl, MR Browell, EV AF Rosenfield, JE Considine, DB Schoeberl, MR Browell, EV TI The impact of subvisible cirrus clouds near the tropical tropopause on stratospheric water vapor SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID AIRCRAFT AB The radiative impact of subvisible cirrus ice clouds at and just below the tropical tropopause has been studied using a zonally averaged interactive chemistry-radiation-dynamics model. Model runs have been performed with and without the inclusion of the radiative heating of these thin ice clouds, and with and without sedimentation. Near-infrared optical depths of 0.005-0.08 were computed for assumed log-normal size distributions of spherical particles having mode radii of 2-10 mu m. Particles with 6 mu m mode radii have computed scattering ratios of 3-15 at 603 nm, in good agreement with lidar observations. The increased radiative heating of these clouds, 0.1-0.2 K/day, results in temperature increases of 1-2 K and vertical velocity increases of 0.02-0.04 mm/s. As a consequence of the warmer tropopause, lower stratosphere water vapor increases by as much as 1 ppmv. The dehydration resulting from sedimentation was found to be a much smaller effect. C1 NASA, Goddard Space Flight Ctr, Atmospheres Lab, Greenbelt, MD 20771 USA. NASA, Langley Res Ctr, Div Atmospher Sci, Hampton, VA 23665 USA. Gen Sci Corp, Laurel, MD USA. Univ Maryland, Joint Ctr Earth Syst Sci, College Pk, MD 20742 USA. RP Rosenfield, JE (reprint author), NASA, Goddard Space Flight Ctr, Atmospheres Lab, Code 916, Greenbelt, MD 20771 USA. NR 16 TC 56 Z9 56 U1 1 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 JUN 1 PY 1998 VL 25 IS 11 BP 1883 EP 1886 DI 10.1029/98GL01294 PG 4 WC Geosciences, Multidisciplinary SC Geology GA ZR962 UT WOS:000074033800032 ER PT J AU Hagan, D Crisp, D Blavier, JF DiGirolamo, L Ackerman, T AF Hagan, D Crisp, D Blavier, JF DiGirolamo, L Ackerman, T TI Balloon-based measurements of the profile of downwelling shortwave irradiance in the troposphere SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID RADIATION; CLOUDS AB Using a helium plus reversible fluid balloon system as the observing platform, multiple profiles of shortwave irradiance between 4 and 10 km were recently obtained over the Los Angeles basin. Measurements of downwelling hemispheric broadband irradiance were made over a period of six hours in conditions that could be characterized by a midlatitude, summer model atmosphere. These data are described and compared to model computations using a spectrally-resolving, plane parallel, multiple scattering model. The systematic difference between model and observations (10%) at high altitudes is discussed in terms of possible factors that affect the instrument measurement response under cold temperature conditions. The measurements and calculations of downwelling irradiance agree to better than 5% in the lower troposphere. C1 Penn State Univ, Dept Meteorol, University Pk, PA 16802 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ Arizona, Inst Atmospher Phys, Tucson, AZ 85721 USA. RP Hagan, D (reprint author), Penn State Univ, Dept Meteorol, 503 Walker Bldg, University Pk, PA 16802 USA. EM denise@cacsar.jpl.nnsa.gov; dc@crispy.jpl.nasa.gov; blavier@mark4sun.jpl.nasa.gov; larry@air.atmo.arizona.edu; ackerman@cssc.psu.edu NR 14 TC 1 Z9 1 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 JUN 1 PY 1998 VL 25 IS 11 BP 1887 EP 1890 DI 10.1029/98GL01238 PG 4 WC Geosciences, Multidisciplinary SC Geology GA ZR962 UT WOS:000074033800033 ER PT J AU Flocke, F Atlas, E Madronich, S Schauffler, SM Aikin, K Margitan, JJ Bui, TP AF Flocke, F Atlas, E Madronich, S Schauffler, SM Aikin, K Margitan, JJ Bui, TP TI Observations of methyl nitrate in the lower stratosphere during STRAT: Implications for its gas phase production mechanisms SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID PEROXYACETYL NITRATE; ION COMPOSITION; PHOTOCHEMISTRY EXPERIMENT; 2-DIMENSIONAL MODEL; ALKYL NITRATES; TEMPERATURE; RADICALS; PRESSURE AB Methyl nitrate has been measured for the first time in the lower stratosphere at altitudes to 20.5 km during the December 1996 NASA Stratospheric Tracers of Atmospheric Transport (STRAT) deployment. Whole air samples were taken on board the NASA ER2 aircraft and analyzed using gas chromatography/mass spectrometry. Methyl nitrate was present at measurable levels throughout the entire altitude range covered. Taking advantage of the rather simple chemistry in the lower stratosphere compared to the troposphere, and considering the known in-situ photochemical sources for methyl nitrate, the yield of methyl nitrate from the reaction of methyl peroxy radicals with NO was estimated. C1 Natl Ctr Atmospher Res, Div Atmospher Chem, Boulder, CO 80307 USA. NOAA, Aeron Lab, Boulder, CO 80303 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Flocke, F (reprint author), Natl Ctr Atmospher Res, Div Atmospher Chem, POB 3000, Boulder, CO 80307 USA. RI Aikin, Kenneth/I-1973-2013; Madronich, Sasha/D-3284-2015; Atlas, Elliot/J-8171-2015 OI Madronich, Sasha/0000-0003-0983-1313; NR 22 TC 26 Z9 26 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 JUN 1 PY 1998 VL 25 IS 11 BP 1891 EP 1894 DI 10.1029/98GL01417 PG 4 WC Geosciences, Multidisciplinary SC Geology GA ZR962 UT WOS:000074033800034 ER PT J AU Ji, Q Shaw, GE AF Ji, Q Shaw, GE TI On supersaturation spectrum and size distributions of cloud condensation nuclei SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID PARTICLE AB The supersaturation spectra of cloud condensation nuclei (CCN) are sometimes S-shaped and always asymptotically approach a limiting value as supersaturation becomes more than several percent. Such a complex shape can correspond to a bell-shaped size distribution of sub-micron aerosols. We found that an exponential expression N = N-0 (1-exp[-B S-K]) fits measured supersaturation spectra better than the commonly used power law expression N = C S-K, where N is the number concentration of CCN at the supersaturation S, N-0 is the total number concentration of CCN, B, C and K are empirical coefficients. The exponential expression and the power law are related. For example, at S similar to 0%, the exponential expression reduces to the power law, with C similar to N-0 B. The derived size distribution from the exponential expression agrees closely with measured size distributions for laboratory salts, but not for aerosols in polluted airmasses. The disagreement in polluted airmasses suggests that CCN have complex physiochemistry. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Alaska, Inst Geophys, Fairbanks, AK 99775 USA. RP Ji, Q (reprint author), NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. NR 11 TC 13 Z9 14 U1 3 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 JUN 1 PY 1998 VL 25 IS 11 BP 1903 EP 1906 DI 10.1029/98GL01404 PG 4 WC Geosciences, Multidisciplinary SC Geology GA ZR962 UT WOS:000074033800037 ER PT J AU Yang, JY Yu, LS Koblinsky, CJ Adamec, D AF Yang, JY Yu, LS Koblinsky, CJ Adamec, D TI Dynamics of the seasonal variations in the Indian Ocean from TOPEX/POSEIDON sea surface height and an ocean model SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID CIRCULATION; BENGAL; BAY AB Observations from the TOPEX/POSEIDON (T/P) altimeter reveal that the sea level in the Indian Ocean varies strongly with season. Surface undulations propagate eastward along the equator and westward outside the equatorial waveguide. The forcing mechanisms responsible for such variations are investigated in this paper by analyzing T/P data and surface wind-stress forcing, and by using a nonlinear, 2.5-layer, reduced gravity model. Both the data and the model show that Kelvin and Rossby waves forced by the Indian Ocean monsoon are primarily responsible for the seasonal sea-level change in the tropical and the subtropical Indian Ocean. C1 Woods Hole Oceanog Inst, Dept Phys Oceanog, Woods Hole, MA 02543 USA. Univ Maryland, Joint Ctr Earth Syst Sci, College Pk, MD 20742 USA. Univ Maryland, Dept Meteorol, College Pk, MD 20742 USA. NASA, Goddard Space Flight Ctr, Oceans & Ice Branch, Greenbelt, MD 20771 USA. RP Yang, JY (reprint author), Woods Hole Oceanog Inst, Dept Phys Oceanog, Woods Hole, MA 02543 USA. NR 16 TC 23 Z9 23 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 JUN 1 PY 1998 VL 25 IS 11 BP 1915 EP 1918 DI 10.1029/98GL01401 PG 4 WC Geosciences, Multidisciplinary SC Geology GA ZR962 UT WOS:000074033800040 ER PT J AU Prabhakara, C Iacovazzi, R Yoo, JM Dalu, G AF Prabhakara, C Iacovazzi, R Yoo, JM Dalu, G TI Global warming deduced from MSU SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID TEMPERATURE; SATELLITE AB Microwave Sounding Unit (MSU) radiometer observations in Channel 2 (53.74 GHz) made from sequential, sun-synchronous, polar-orbiting NOAA operational satellites have been used to derive global temperature trend for the period 1980 to 1996. Christy et al. (1998) emphasize that they find a tropospheric cooling trend (-0.046 K decade(-1)) from 1979 to 1997 with these MSU data, although their analysis of near nadir measurements yields a near zero trend (0.003 K decade(-1)). Using an independent method to analyze the MSU Ch 2 nadir data separately over global ocean and land, we infer that the temperature trends over both these regions are about 0.11 K decade(-1), during the period 1980 to 1996. This result is in better agreement with trend analyses based on conventional surface data. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Raytheon STX, Greenbelt, MD USA. Ewha Womans Univ, Seoul, South Korea. CNR, Cagliari, Italy. RP Prabhakara, C (reprint author), NASA, Goddard Space Flight Ctr, Code 913, Greenbelt, MD 20771 USA. RI Iacovazzi Jr, Robert/G-3867-2010 NR 7 TC 22 Z9 22 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 JUN 1 PY 1998 VL 25 IS 11 BP 1927 EP 1930 DI 10.1029/98GL01300 PG 4 WC Geosciences, Multidisciplinary SC Geology GA ZR962 UT WOS:000074033800043 ER PT J AU Shemesh, A Peteet, D AF Shemesh, A Peteet, D TI Oxygen isotopes in fresh water biogenic opal - Northeastern US Allerod-Younger Dryas temperature shift SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID GLACIAL TRANSITION; LINSLEY-POND; SEDIMENTS; ATLANTIC; CLIMATE; RECORDS; SILICA; OCEAN AB The first oxygen isotope analysis of biogenic opal from lake sediments, from the Allerod/Younger Dryas transition in a core from Linsley Pond, Connecticut, gives an average estimate of a 6 degrees C drop in temperature during the Younger Dryas. This shift represents temperatures during the bloom season, and may be less than the winter temperature drop. The sharp transition itself, with a duration of about 200 years, suggests that the temperature decrease may have been as large as 12 degrees C. Previous estimates of the Allerod/Younger Dryas temperature shifts are controversial, and range from 3-20 degrees C, suggesting that further interdisciplinary research on the same samples is warranted. C1 Weizmann Inst Sci, Dept Environm Sci & Energy Res, IL-76100 Rehovot, Israel. NASA, Goddard Inst Space Studies, New York, NY 10025 USA. Lamont Doherty Earth Observ, Palisades, NY 10964 USA. RP Shemesh, A (reprint author), Weizmann Inst Sci, Dept Environm Sci & Energy Res, IL-76100 Rehovot, Israel. NR 23 TC 32 Z9 32 U1 0 U2 4 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 JUN 1 PY 1998 VL 25 IS 11 BP 1935 EP 1938 DI 10.1029/98GL01443 PG 4 WC Geosciences, Multidisciplinary SC Geology GA ZR962 UT WOS:000074033800045 ER PT J AU Jensen, BJ Chang, AC AF Jensen, BJ Chang, AC TI Synthesis and characterization of modified phenylethynyl imides SO HIGH PERFORMANCE POLYMERS LA English DT Article AB As an ongoing effort to develop structural adhesives for high-performance aerospace applications, recent work has focused on phenylethynyl terminated imide (PETI) oligomers. The work reported herein involves the synthesis and characterization of a series of phenylethynyl containing oligomers designated LARC(TM) MPEI (modified phenylethynyl imide). These oligomers presumably contain mixtures of linear, branched and star-shaped molecules. The fully imidized polymers exhibited minimum melt viscosities as low as 600 poise at 335 degrees C, significantly lower than equivalent molecular weight linear materials. Ti/Ti lap shear specimens processed at 288 degrees C under 15 psi showed tensile shear strengths as high as similar to 6000 psi and similar to 5200 psi at ambient temperature and 177 degrees C respectively. The chemistry and properties of these new MPEIs are presented and compared with an optimized linear PMI, LARC(TM) PETI-5. C1 NASA, Langley Res Ctr, Hampton, VA 23681 USA. Lockheed Martin Engn & Sci Corp, Hampton, VA 23666 USA. RP Jensen, BJ (reprint author), NASA, Langley Res Ctr, Hampton, VA 23681 USA. NR 13 TC 22 Z9 23 U1 1 U2 4 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 JUN PY 1998 VL 10 IS 2 BP 175 EP 180 DI 10.1088/0954-0083/10/2/002 PG 6 WC Polymer Science SC Polymer Science GA ZW960 UT WOS:000074466300002 ER PT J AU Hou, TH Cano, RJ Jensen, BJ AF Hou, TH Cano, RJ Jensen, BJ TI IM7/LARC (TM) MPEI-1 polyimide composites SO HIGH PERFORMANCE POLYMERS LA English DT Article AB LARC(TM) MPEI-1 (Langley Research Center(TM) modified phenylethynyl imide-1) phenylethynyl containing aromatic polyimide, is based on the reaction of biphenyl dianhydride (BPDA), 3, 4'-oxydianiline (3, 4'-ODA), 1,3-bis(3-aminophenoxy)benzene (APB), 2,4,6-triaminopyrimidine (TAP) and 4-phenylethynyl phthalic anhydride (PEPA), presumably resulting in a mixture of linear, branched and star shaped phenylethynyl containing imides which was evaluated as a matrix for high-performance composites. The poly(amid acid) solution of MPEI-1 in N-methypyrrolidinone was synthesized at 35% and 42% solids. Unidirectional prepreg was fabricated from these solutions and Hercules IM7 carbon fibre utilizing NASA-Langley's multipurpose prepreg machine. The temperature-dependent volatile depletion rates, thermal crystallization behaviour and resin rheology were characterized. Based on this information, a composite moulding cycle was developed which yielded well consolidated, void-free laminates. Composite mechanical properties such as short beam shear strength, longitudinal and transverse flexural strength and flexural modulus, longitudinal tensile strength and notched and unnotched compression strengths were measured at room temperature (RT) and elevated temperatures. These mechanical properties are compared with those of IM7/LARC(TM) PETI-5 composites. C1 NASA, Langley Res Ctr, Hampton, VA 23681 USA. RP Hou, TH (reprint author), NASA, Langley Res Ctr, Hampton, VA 23681 USA. NR 14 TC 16 Z9 16 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 JUN PY 1998 VL 10 IS 2 BP 181 EP 192 DI 10.1088/0954-0083/10/2/003 PG 12 WC Polymer Science SC Polymer Science GA ZW960 UT WOS:000074466300003 ER PT J AU Hou, TH St Clair, TL AF Hou, TH St Clair, TL TI IM7/LARC (TM)-IAX-3 polyimide composites SO HIGH PERFORMANCE POLYMERS LA English DT Article AB LARC(TM)-IAX-3 (Langley Research Center(TM)-improved adhesive experimental resin-3) aromatic polyimide, based on oxydiphthalic anhydride, 3,4'-oxydianiline (3,4'-ODA) and 1,4-phenylenediamine (p-PDA), was evaluated as a matrix for high-performance composites. Four poly(amide acid) solutions in either N-methypyrrolidone or gamma-butyrolactone, end-capped with phthalic anhydride to various theoretical molecular weights, were synthesized. Unidirectional prepreg was fabricated from each of the four resins utilizing NASA-Langley's multipurpose prepreg machine. The temperature-dependent volatile depletion rates, the thermal crystallization behaviour and the resin rheology were characterized. Based on this information, a composite moulding cycle was developed which consistently yielded well consolidated void-free laminate parts. Composite mechanical properties such as short beam shear strength, longitudinal and transverse flexural strength and flexural modulus, longitudinal tensile strength and notched and unnotched compression strengths were measured at room temperature (RT) and elevated temperatures. Similar properties were obtained independent of the carrier solvent used during matrix resin synthesis. These mechanical properties were superior to those previously measured for IM7/LARC(TM) IA and IM7/LARC(TM)-IAX composites. The enhanced mechanical properties were attributed to the substitution of 25% 3,4'-ODA by p-PDA in the LARC(TM)-IA imide backbones. C1 NASA, Langley Res Ctr, Hampton, VA 23681 USA. RP Hou, TH (reprint author), NASA, Langley Res Ctr, Hampton, VA 23681 USA. NR 10 TC 6 Z9 7 U1 1 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 JUN PY 1998 VL 10 IS 2 BP 193 EP 206 DI 10.1088/0954-0083/10/2/004 PG 14 WC Polymer Science SC Polymer Science GA ZW960 UT WOS:000074466300004 ER PT J AU Sprague, AL Roush, TL AF Sprague, AL Roush, TL TI Comparison of laboratory emission spectra with Mercury telescopic data SO ICARUS LA English DT Article DE Mercury's surface composition; Mercury; planetary surfaces; mid-infrared spectroscopy ID REFLECTANCE SPECTRA; PLANETARY SURFACES; THERMAL EMISSION; MU-M; SPECTROSCOPY; ATMOSPHERE; POTASSIUM; BASALT; ROCKS; MOON AB Thermal emission spectra from four locations on Mercury's surface are compared with three new laboratory emission spectra: two spinels (gahnite and magnetite) and one carbonaceous chondrite (Allende), The mineral and meteorite choices were made to investigate previously suggested unique scenarios for the evolution of Mercury's surface. No resemblance of the Mercury data were seen to the measured emission spectra, We also compare Mercury spectra to a selection of inverted reflectance spectra of feldspars, feldspathoids, Apollo 16 lunar breccias, nepheline-bearing alkali syenite, and simple two-component Linear mixes of feldspars and pyroxenes, The Mercury spectra obtained from locations centered near 40 degrees and 45 degrees mercurian longitude and equatorial latitudes are concave upward in shape between 8 and 10 mu m like that of nepheline but the emissivity maxima of the data occur at shorter wavelength than any of the feldspathoids (nepheline, leucite, sodalite). A good match of the wavelength position of Mercury's emissivity maxima is provided by the nepheline-bearing alkali syenite. Comparisons to several feldspars in the plagioclase series, and plagioclase and pyroxene lunar breccia (67031 and 67455), and linear mixing models of plagioclase and pyroxene provide good matches to some features near similar to 120 degrees and similar to 34 degrees mercurian longitude and equatorial latitudes, More conclusive interpretation of these data from Mercury requires laboratory studies of emission spectra obtained specifically for thermal and insolation conditions appropriate for airless bodies, (C) 1998 Academic Press. C1 Univ Arizona, Lunar & Planetary Lab, Tucson, AZ 85721 USA. San Francisco State Univ, Dept Geosci, San Francisco, CA 94132 USA. NASA, Ames Res Ctr, Planetary Syst Branch, Moffett Field, CA 94035 USA. RP Sprague, AL (reprint author), Univ Arizona, Lunar & Planetary Lab, Tucson, AZ 85721 USA. EM sprague@lpl.arizona.edu NR 54 TC 66 Z9 66 U1 2 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 JUN PY 1998 VL 133 IS 2 BP 174 EP 183 DI 10.1006/icar.1998.5929 PG 10 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 102PJ UT WOS:000074932800002 ER PT J AU Edgington, SG Atreya, SK Trafton, LM Caldwell, JJ Beebe, RF Simon, AA West, RA Barnet, C AF Edgington, SG Atreya, SK Trafton, LM Caldwell, JJ Beebe, RF Simon, AA West, RA Barnet, C TI On the latitude variation of ammonia, acetylene, and phosphine altitude profiles on Jupiter from HST Faint Object Spectrograph observations SO ICARUS LA English DT Article ID UPPER-ATMOSPHERE; RATE-CONSTANT; JOVIAN STRATOSPHERE; FOURIER-TRANSFORM; CROSS-SECTIONS; ULTRAVIOLET; PHOTOCHEMISTRY; SATURN; ABUNDANCES; SCATTERING AB Ultraviolet spectra in the spectral region from 160 to 230 nm were taken with the Hubble Space Telescope Faint Object Spectrograph in May 1992. We analyze these data to obtain the altitude distribution of ammonia and its variation with latitude from 6 degrees N to 25 degrees N. Ammonia condenses below the 150-mbar level, above which it departs from saturation due to photolysis. Using a photochemical model, we also derive the value of atmospheric eddy mixing coefficients at the observed latitudes. It is found that the eddy diffusion coefficient varies from 1.5 x 10(4) cm(2) s(-1) at 450 mbar to 4.9 x 10(2) cm(2) s(-1) at 120 mbar. The vertical distribution of ammonia and the eddy diffusion coefficient do not show a large variation with latitude. We also determine an acetylene mixing ratio of (10-30) x 10(-9) near 80 mbar and an upper limit of 1.5 x 10(-7) for the phosphine mixing ratio, if PH3 is mixed uniformly below the 140 mbar level. The existence of particulate haze at low and high latitudes Is also investigated. (C) 1998 Academic Press. C1 Univ Michigan, Dept Atmospher Ocean & Space Sci, Ann Arbor, MI 48109 USA. Univ Texas, Mcdonald Observ, Austin, TX 78712 USA. York Univ, Dept Phys & Astron, N York, ON M35 1P3, Canada. New Mexico State Univ, Dept Astron, Las Cruces, NM 88033 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Edgington, SG (reprint author), Univ Michigan, Dept Atmospher Ocean & Space Sci, Ann Arbor, MI 48109 USA. RI Barnet, Christopher/F-5573-2010; Simon, Amy/C-8020-2012 OI Simon, Amy/0000-0003-4641-6186 NR 68 TC 28 Z9 28 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 JUN PY 1998 VL 133 IS 2 BP 192 EP 209 DI 10.1006/icar.1998.5925 PG 18 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 102PJ UT WOS:000074932800004 ER PT J AU Beer, R Taylor, FW AF Beer, R Taylor, FW TI Comment on "Carbon monoxide in Jupiter after comet Shoemaker-Levy 9," by K.S. Noll, D. Gilmore, R.F. Knacke, M. Womak, C.A. Griffith, and G. Orton SO ICARUS LA English DT Editorial Material C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ Oxford, Oxford, England. RP Beer, R (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 6 TC 2 Z9 2 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 JUN PY 1998 VL 133 IS 2 BP 321 EP 321 DI 10.1006/icar.1998.5923 PG 1 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 102PJ UT WOS:000074932800013 ER PT J AU Christopher, DA Beach, R AF Christopher, DA Beach, R TI Flywheel technology development program for aerospace applications SO IEEE AEROSPACE AND ELECTRONIC SYSTEMS MAGAZINE LA English DT Article DE energy storage; flywheel; power system; attitude control; power peaking; load leveling AB An overview of advanced flywheel development for energy storage in aerospace applications is presented. The advantages offered by this emerging technology are described and the current NASA approach toward developing the technology is presented. C1 NASA, Lewis Res Ctr, Power & Prop Flight Projects Off, Cleveland, OH 44135 USA. NASA, Lewis Res Ctr, Power Technol Div, Cleveland, OH 44135 USA. RP Christopher, DA (reprint author), NASA, Lewis Res Ctr, Power & Prop Flight Projects Off, Mail Stop 301-5,21000 Brookpk Rd, Cleveland, OH 44135 USA. NR 4 TC 35 Z9 42 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 0885-8985 J9 IEEE AERO EL SYS MAG JI IEEE Aerosp. Electron. Syst. Mag. PD JUN PY 1998 VL 13 IS 6 BP 9 EP 14 DI 10.1109/62.683723 PG 6 WC Engineering, Aerospace; Engineering, Electrical & Electronic SC Engineering GA ZR971 UT WOS:000074034700004 ER PT J AU Oswald, JE Koch, T Mehdi, I Pease, A Dengler, RJ Lee, TH Humphrey, DA Kim, M Siegel, PH Frerking, MA Erickson, NR AF Oswald, JE Koch, T Mehdi, I Pease, A Dengler, RJ Lee, TH Humphrey, DA Kim, M Siegel, PH Frerking, MA Erickson, NR TI Planar diode solid-state receiver for 557 GHz with state-of-the-art performance SO IEEE MICROWAVE AND GUIDED WAVE LETTERS LA English DT Article DE planar; receiver; Schottky diode; subharmonic mixer ID WAVE-GUIDE MIXERS; SCHOTTKY AB The design and performance of a subharmonically pumped (SHP) 557-GHz mixer driven by a solid-state local oscillator (LO) are reported. Whisker contacts are not required as both the mixer and LO utilize planar Schottky devices. A measured mixer noise temperature of 2100-K double sideband (DSB) with a conversion loss of 8.9 dB has been achieved at room temperature. The mixer exhibits broad intermediate frequency (IF) bandwidth with measured DSB noise temperatures below 3400 K in the band from 1.5 to 17 GHz. An external 6-18-GHz amplifier has been added to the output of the mixer, and measured receiver noise temperatures below 7300 K have been measured across the IF band. The results are believed to represent state-of-the-art performance for a room-temperature broad-band solid-state receiver at this frequency. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ Massachusetts, Dept Phys & Astron, Amherst, MA 01003 USA. RP Oswald, JE (reprint author), CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. NR 16 TC 14 Z9 14 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 1051-8207 J9 IEEE MICROW GUIDED W JI IEEE Microw. Guided Wave Lett. PD JUN PY 1998 VL 8 IS 6 BP 232 EP 234 DI 10.1109/75.678575 PG 3 WC Engineering, Electrical & Electronic SC Engineering GA ZP365 UT WOS:000073745000007 ER PT J AU Weisbin, CR AF Weisbin, CR TI IPL Rover and Telerobotics Technology Program SO IEEE ROBOTICS & AUTOMATION MAGAZINE LA English DT Editorial Material C1 CALTECH, Jet Prop Lab, Robot & Mars Explorat Technol Program, Pasadena, CA 91109 USA. RP Weisbin, CR (reprint author), CALTECH, Jet Prop Lab, Robot & Mars Explorat Technol Program, MS 180-6030,4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 0 TC 2 Z9 2 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 1070-9932 J9 IEEE ROBOT AUTOM MAG JI IEEE Robot. Autom. Mag. PD JUN PY 1998 VL 5 IS 2 BP 8 EP 10 DI 10.1109/MRA.1998.692335 PG 3 WC Automation & Control Systems; Robotics SC Automation & Control Systems; Robotics GA ZZ285 UT WOS:000074714100004 ER PT J AU Oberg, J AF Oberg, J TI Shuttle-Mir's lessons for the International Space Station SO IEEE SPECTRUM LA English DT Article C1 NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. RP Oberg, J (reprint author), NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. NR 1 TC 1 Z9 2 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 0018-9235 J9 IEEE SPECTRUM JI IEEE Spectr. PD JUN PY 1998 VL 35 IS 6 BP 28 EP 37 DI 10.1109/6.681969 PG 10 WC Engineering, Electrical & Electronic SC Engineering GA ZQ496 UT WOS:000073867900009 ER PT J AU Wasynczuk, O Sudhoff, SD Corzine, KA Tichenor, JL Krause, PC Hansen, IG Taylor, LM AF Wasynczuk, O Sudhoff, SD Corzine, KA Tichenor, JL Krause, PC Hansen, IG Taylor, LM TI A maximum torque per ampere control strategy for induction motor drives SO IEEE TRANSACTIONS ON ENERGY CONVERSION LA English DT Article ID LOSS MINIMIZATION AB In this paper, a new control strategy is proposed which is simple in structure and has the straightforward goal of minimizing the stator current amplitude for a given load torque. It is shown that the resulting induction motor efficiency is reasonably close to optimal and that the approach is insensitive to variations in rotor resistance. Although the torque response is not as fast as in field-oriented control strategies, the response is reasonably fast, In fact, if the mechanical time constant is large relative to the rotor time constant, which is frequently the case, the sacrifice in dynamic performance is insignificant relative to FO strategies. C1 PC Krause & Associates Inc, W Lafayette, IN 47906 USA. NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. RP Wasynczuk, O (reprint author), PC Krause & Associates Inc, W Lafayette, IN 47906 USA. NR 10 TC 61 Z9 76 U1 2 U2 4 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 0885-8969 J9 IEEE T ENERGY CONVER JI IEEE Trans. Energy Convers. PD JUN PY 1998 VL 13 IS 2 BP 163 EP 169 DI 10.1109/60.678980 PG 7 WC Energy & Fuels; Engineering, Electrical & Electronic SC Energy & Fuels; Engineering GA ZQ035 UT WOS:000073814900009 ER PT J AU Greenhall, CA AF Greenhall, CA TI Spectral ambiguity of Allan variance SO IEEE TRANSACTIONS ON INSTRUMENTATION AND MEASUREMENT LA English DT Article DE covariance functions; finite difference methods; Fourier transforms; frequency stability; integral equations; phase noise; spectral analysis; time domain analysis ID FREQUENCY STABILITY; THEOREM AB The phase-noise spectrum determines the Allan variance by a well-known integral formula. It is shown here that unique inversion of this formula is not possible in general because the mapping from spectrum to Allan variance is not one-to-one. A necessary and sufficient condition for two distinct phase spectra to have the same Allan variance is given. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Greenhall, CA (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 11 TC 14 Z9 14 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 0018-9456 J9 IEEE T INSTRUM MEAS JI IEEE Trans. Instrum. Meas. PD JUN PY 1998 VL 47 IS 3 BP 623 EP 627 DI 10.1109/19.744312 PG 5 WC Engineering, Electrical & Electronic; Instruments & Instrumentation SC Engineering; Instruments & Instrumentation GA 166CH UT WOS:000078558300004 ER PT J AU Liu, CM De Lisio, MP Moussessian, A Rutledge, DB AF Liu, CM De Lisio, MP Moussessian, A Rutledge, DB TI Stability of grid amplifiers SO IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES LA English DT Article; Proceedings Paper CT 1997 Topical Symposium on Millimeter Waves CY JUL 07-08, 1997 CL SHONAN VILLAGE CTR, HAYAMA, JAPAN SP USAF, Off Sci Res, IEEE, Microwave Theory & Techn Soc HO SHONAN VILLAGE CTR DE grid amplifiers; quasi-optics; stability AB We present a stability model for quasi-optical grid amplifiers. This model is useful for predicting and suppressing the common-mode oscillations that often occur in amplifier grids. Three stabilization techniques will be discussed. The first technique uses a capacitor to stabilize the grid. The second approach employs resistance to suppress the oscillations, The final technique stabilizes the grid by reducing the on-chip common-mode resistance, allowing greatly increased amplifier efficiencies. Experimental evidence will be presented to confirm the validity of our stability model. C1 Rockwell Int Corp, Rockwell Int Sci Ctr, Thousand Oaks, CA 91385 USA. Univ Hawaii Manoa, Dept Elect Engn, Honolulu, HI 96822 USA. CALTECH, Jet Prop Lab, Radar Sci & Engn Sect, Pasadena, CA 91109 USA. CALTECH, Dept Elect Engn, Pasadena, CA 91125 USA. RP Liu, CM (reprint author), Rockwell Int Corp, Rockwell Int Sci Ctr, Thousand Oaks, CA 91385 USA. NR 10 TC 8 Z9 8 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 0018-9480 J9 IEEE T MICROW THEORY JI IEEE Trans. Microw. Theory Tech. PD JUN PY 1998 VL 46 IS 6 BP 769 EP 774 DI 10.1109/22.681199 PG 6 WC Engineering, Electrical & Electronic SC Engineering GA ZQ886 UT WOS:000073912900008 ER PT J AU Peskov, V Ramsey, BD Fonte, P AF Peskov, V Ramsey, BD Fonte, P TI Breakdown features of various microstrip-type gas counter designs and their improvements SO IEEE TRANSACTIONS ON NUCLEAR SCIENCE LA English DT Article; Proceedings Paper CT 1997 Nuclear Science Symposium CY NOV 09-15, 1997 CL ALBUQUERQUE, NEW MEXICO AB Breakdown mechanisms and spurious pulses, the precursors to some breakdowns, were studied experimentally for both uncoated and coated Microstrip Gas Counters (MSGC's) of different geometries, as well as for MicroGap Counters (MGC's) and for the "Compteur A Trou" (CAT). It was found that in all cases the breakdowns occurred through surface streamers, although the exact mechanism of streamer formation depended on the particular detector design. Based on these studies, new designs of microstrip detectors, in which the role of the substrate was minimized, were elaborated and tested. In some of these detectors, especially with large pitches (>2 mm), gains up to 2-3x10(5) were achieved together with good rate characteristics. The ultimate gain limit in all geometries was still set by spark-inducing streamers which appeared at some critical charge density in the avalanche. To avoid this, and particularly to enhance the performance of small-pitch MSGC's, preamplification structures can be used. Utilizing a parallel plate avalanche chamber as a front end to an MSGC resulted in an overall gain of similar to 10(6), limited in this case only by charge saturation. C1 NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. Univ Coimbra, LIP, P-3000 Coimbra, Portugal. Inst Super Engn Coimbra, P-3000 Coimbra, Portugal. RP Peskov, V (reprint author), NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. RI Fonte, Paulo/B-1842-2008 OI Fonte, Paulo/0000-0002-2275-9099 NR 13 TC 21 Z9 21 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 0018-9499 J9 IEEE T NUCL SCI JI IEEE Trans. Nucl. Sci. PD JUN PY 1998 VL 45 IS 3 BP 244 EP 248 DI 10.1109/23.682387 PG 5 WC Engineering, Electrical & Electronic; Nuclear Science & Technology SC Engineering; Nuclear Science & Technology GA ZU096 UT WOS:000074161200005 ER PT J AU Ivaniouchenkov, I Fonte, P Peskov, V Ferreira-Marques, R Policarpo, A AF Ivaniouchenkov, I Fonte, P Peskov, V Ferreira-Marques, R Policarpo, A TI The high-rate behavior of parallel mesh chambers SO IEEE TRANSACTIONS ON NUCLEAR SCIENCE LA English DT Article; Proceedings Paper CT 1997 Nuclear Science Symposium CY NOV 09-15, 1997 CL ALBUQUERQUE, NEW MEXICO ID PROJECTION CHAMBERS; AVALANCHE CHAMBER; DETECTOR; BREAKDOWN AB Gas counters made from parallel metallic wire meshes have been proposed by Charpak et al. long ago as a preamplifying stage to wire chambers and developed meanwhile by many workers. The concept led to very robust and versatile detectors, having evolved over time to include complex multistep structures. It is known that parallel geometry chambers can stand counting rates at least up to 10(5) Hz/mm(2) without any pulse-height degradation, suggesting their use as high-rate particle detectors. In this work we describe a study of the high-rate behavior of Parallel Mesh Chambers, measuring the maximum count rates achievable for a given avalanche charge and beam cross-section. The different breakdown regimes that appear at high counting rates are described. C1 LIP, Lab Instrumentacao & Fis Expt Particulas, Coimbra, Portugal. Inst Super Engn Coimbra, Coimbra, Portugal. NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. Univ Coimbra, Dept Fis, P-3000 Coimbra, Portugal. RP Ivaniouchenkov, I (reprint author), LIP, Lab Instrumentacao & Fis Expt Particulas, Coimbra, Portugal. RI Fonte, Paulo/B-1842-2008 OI Fonte, Paulo/0000-0002-2275-9099 NR 15 TC 5 Z9 5 U1 1 U2 1 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 0018-9499 J9 IEEE T NUCL SCI JI IEEE Trans. Nucl. Sci. PD JUN PY 1998 VL 45 IS 3 BP 258 EP 262 DI 10.1109/23.682390 PG 5 WC Engineering, Electrical & Electronic; Nuclear Science & Technology SC Engineering; Nuclear Science & Technology GA ZU096 UT WOS:000074161200008 ER PT J AU Hubbard, GS Binder, AB Feldman, W AF Hubbard, GS Binder, AB Feldman, W TI The Lunar Prospector Discovery mission: Mission and measurement description SO IEEE TRANSACTIONS ON NUCLEAR SCIENCE LA English DT Article; Proceedings Paper CT 1997 Nuclear Science Symposium CY NOV 09-15, 1997 CL ALBUQUERQUE, NEW MEXICO AB Lunar Prospector, the first competitively selected planetary mission in NASA's Discovery Program, is described with emphasis on the radiation spectrometer instrumentation and anticipated scientific data return. Scheduled to be launched in January 1998, the mission will conduct a one year orbital survey of the Moon's composition and structure. The suite of five instruments are outlined: neutron spectrometer, alpha particle spectrometer, gamma-ray spectrometer, electron reflectometer and magnetometer. Scientific requirements and measurement approach to detect water/ice to a sensitivity of 50 ppm (hydrogen), measure key elemental constituents, detect radioactive gas release events and accurately map the Moon's gravitational and magnetic fields are given. A brief overview of the programmatic accomplishments in meeting a tightly constrained schedule and budget is also provided. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Univ Calif Los Alamos Natl Lab, Los Alamos, NM 87545 USA. RP Hubbard, GS (reprint author), NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. NR 5 TC 3 Z9 3 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 0018-9499 J9 IEEE T NUCL SCI JI IEEE Trans. Nucl. Sci. PD JUN PY 1998 VL 45 IS 3 BP 880 EP 887 DI 10.1109/23.682655 PG 8 WC Engineering, Electrical & Electronic; Nuclear Science & Technology SC Engineering; Nuclear Science & Technology GA ZU096 UT WOS:000074161200127 ER PT J AU Prigozhin, G Gendreau, K Bautz, M Burke, B Ricker, G AF Prigozhin, G Gendreau, K Bautz, M Burke, B Ricker, G TI The depletion depth of high resistivity X-ray CCDs SO IEEE TRANSACTIONS ON NUCLEAR SCIENCE LA English DT Article; Proceedings Paper CT 1997 Nuclear Science Symposium CY NOV 09-15, 1997 CL ALBUQUERQUE, NM AB We have developed several techniques which allow measurement of the depletion depth of X-ray CCDs used for imaging and spectroscopy in the 0.2 - 10 keV energy band. These methods were developed as part of the calibration program for the AXAF CCD Imaging Spectrometer (ACIS). The depletion depth is a parameter that determines the high-energy detection limit of the CCDs. One technique is based on the analysis of long traces of high energy ionizing particles traveling through the CCD nearly parallel to its surface. Measuring the ratio of the narrow portion of the trace to the broader diffused portion allows one to extract the depletion depth. Two other methods require illumination of the device with a monochromatic X-ray source (radioactive Fe-55, for instance). Analysis of the spectral distribution of the single- and multipixel events yields the depletion depth. By suitable choice of CCD operating voltages we were able to reach a depletion depth of 75 microns with the ACIS devices. We also present a simple analytical technique to calculate the depth of the depletion region in this essentially three dimensional structure. C1 MIT, Ctr Space Res, Cambridge, MA 02139 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. MIT, Lincoln Lab, Lexington, MA 02173 USA. RP MIT, Ctr Space Res, 77 Mass Ave, Cambridge, MA 02139 USA. NR 6 TC 7 Z9 7 U1 0 U2 0 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI PISCATAWAY PA 445 HOES LANE, PISCATAWAY, NJ 08855-4141 USA SN 0018-9499 EI 1558-1578 J9 IEEE T NUCL SCI JI IEEE Trans. Nucl. Sci. PD JUN PY 1998 VL 45 IS 3 BP 903 EP 909 DI 10.1109/23.682658 PG 7 WC Engineering, Electrical & Electronic; Nuclear Science & Technology SC Engineering; Nuclear Science & Technology GA ZU096 UT WOS:000074161200130 ER PT J AU Yoshita, K Tsunemi, H Gendreau, KC Pennington, G Bautz, MW AF Yoshita, K Tsunemi, H Gendreau, KC Pennington, G Bautz, MW TI Direct measurements at the sub-pixel level of the X-ray detection efficiency of the CCD on board the ASCA satellite SO IEEE TRANSACTIONS ON NUCLEAR SCIENCE LA English DT Article; Proceedings Paper CT 1997 Nuclear Science Symposium CY NOV 09-15, 1997 CL ALBUQUERQUE, NEW MEXICO AB We present here a measurement at sub-pixel resolution of the,X-ray detection efficiency of the CCD detector on board the ASCA satellite. A mesh placed in front of the CCD restricted the interaction position of the, X-ray inside the CCD pixel. We clearly show that all the primary charge is collected in one pixel when the X-ray interaction is sufficiently far from the pixel boundary. Conversely, some photo-ionized charge is collected in neighboring pixels when the, X-ray interacts near the pixel boundary. We also obtained the thickness of various elements gate structure, and measure channel stop dimensions. From these data., we can obtain more accurate estimates of the X-ray responsivity of the CCD. C1 Osaka Univ, Toyonaka, Osaka 560, Japan. NASA, GSFC, Greenbelt, MD 20771 USA. Univ Maryland, College Pk, MD 20742 USA. MIT, Cambridge, MA 02139 USA. RP Yoshita, K (reprint author), Osaka Univ, Toyonaka, Osaka 560, Japan. NR 9 TC 30 Z9 30 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 0018-9499 J9 IEEE T NUCL SCI JI IEEE Trans. Nucl. Sci. PD JUN PY 1998 VL 45 IS 3 BP 915 EP 920 DI 10.1109/23.682668 PG 6 WC Engineering, Electrical & Electronic; Nuclear Science & Technology SC Engineering; Nuclear Science & Technology GA ZU096 UT WOS:000074161200132 ER PT J AU Johnston, AH AF Johnston, AH TI Radiation effects in advanced microelectronics technologies SO IEEE TRANSACTIONS ON NUCLEAR SCIENCE LA English DT Article; Proceedings Paper CT 4th European Conference on Radiation and its Effects on Components and Systems (RADECS 97) CY SEP 15-19, 1997 CL CANNES, FRANCE SP Thomson CSF, Aerospatiale Espace & Def, TEMIC Semiconductors, CEA/DAM, Ministere Culture, Sandia Natl Labs ID SINGLE-EVENT UPSET; CHARGE COLLECTION; HIGH-PERFORMANCE; INDUCED LATCHUP; HARD ERRORS; LOW-POWER; SIMULATION; DEVICES; MICROMETER; CIRCUITS AB The pace of device scaling has increased rapidly in recent years. Experimental CMOS devices have been produced with feature sizes below 0.1 mu m, demonstrating that devices with feature sizes between 0.1 and 0.25 mu m will likely be available in mainstream technologies after the year 2000. This paper discusses how the anticipated changes in device dimensions and design are likely to affect their radiation response in space environments. Traditional problems, such as total dose effects, SEU and latchup are discussed, along with new phenomena. The latter include hard errors from heavy ions (microdose and gate-rupture errors), and complex failure modes related to advanced circuit architecture. The main focus of the paper is on commercial devices, which are displacing hardened device technologies in many space applications. However, the impact of device scaling on hardened devices is also discussed. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Johnston, AH (reprint author), CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. NR 61 TC 66 Z9 72 U1 0 U2 8 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 0018-9499 J9 IEEE T NUCL SCI JI IEEE Trans. Nucl. Sci. PD JUN PY 1998 VL 45 IS 3 BP 1339 EP 1354 DI 10.1109/23.685206 PN 3 PG 16 WC Engineering, Electrical & Electronic; Nuclear Science & Technology SC Engineering; Nuclear Science & Technology GA ZU365 UT WOS:000074189800002 ER EF