FN Thomson Reuters Web of Science™ VR 1.0 PT J AU Wang, LP Koblinsky, CJ Howden, S AF Wang, LP Koblinsky, CJ Howden, S TI Annual and intra-annual sea level variability in the region of the Kuroshio Extension from TOPEX/POSEIDON and Geosat altimetry SO JOURNAL OF PHYSICAL OCEANOGRAPHY LA English DT Article ID LOW-FREQUENCY VARIABILITY; INTERANNUAL VARIABILITY; NORTH-ATLANTIC; GULF-STREAM; PRECIPITATION; EVAPORATION; ENERGETICS; PACIFIC; SYSTEM; OCEAN AB Using 4.2 years of sea surface height data collected by the TOPEX/POSEIDON altimeter and 2.3 years of data collected by the Geosat altimeter, the authors study the annual, intra-annual, and linear-trend sea level height variability in the region of the Kuroshio Extension. Both the annual and intra-annual variabilities are separated spatially into large (less than or equal to 2000 km), intermediate (similar to 1500 km), and short scales (similar to 800 km). The intermediate rind short-scale annual and intra-annual sea level height fluctuations in both periods have large components with two-dimensional phase propagation. Close correspondents between the characteristic spatial structure of both the intermediate and short-scale annual and intra-annual sea level height fluctuations and major bottom topographic features suggests that bottom topography plays a critical role in the generation of those low-frequency variabilities. On the other hand, large-scale annual variability is primarily a standing oscillation, and bottom topography does not appear to be involved in its generation. The linear trend of the sea level change in the 4.2-yr TOPEX/POSEIDON period suggests that both the northern and the southern recirculations have been weakening considerably in the last 4.2 years, and that there exists a strong introdecadal to decadal sea level height change. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Maryland, Dept Meteorol, NASA, UMD JCESS, College Pk, MD 20742 USA. RP Wang, LP (reprint author), NASA, Goddard Space Flight Ctr, Code 971, Greenbelt, MD 20771 USA. NR 28 TC 16 Z9 16 U1 0 U2 2 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 USA SN 0022-3670 J9 J PHYS OCEANOGR JI J. Phys. Oceanogr. PD APR PY 1998 VL 28 IS 4 BP 692 EP 711 DI 10.1175/1520-0485(1998)028<0692:AAIASL>2.0.CO;2 PG 20 WC Oceanography SC Oceanography GA ZJ548 UT WOS:000073227800011 ER PT J AU Webb, GM Ratkiewicz, R Brio, M Zank, GP AF Webb, GM Ratkiewicz, R Brio, M Zank, GP TI Multidimensional simple waves in gas dynamics SO JOURNAL OF PLASMA PHYSICS LA English DT Article ID PARTIALLY-INVARIANT SOLUTIONS; ISENTROPIC FLOW; LIE SUBGROUPS; EQUATIONS; MAGNETOHYDRODYNAMICS; NONSTATIONARY; VARIABLES; HELICITY; SYSTEMS; FLUID AB A formalism for multidimensional simple waves in gas dynamics using ideas developed by Boillat is investigated. For simple-wave solutions, the physical variables depend on a single function phi(r, t). The wave phase phi(r, t) is implicitly determined by an equation of the form f(phi) = r.n(phi) - lambda(phi)t, where n(phi) denotes the normal to the wave front, lambda is the characteristic speed of the wave mode of Interest, r is the position vector, t is the time, and the function f(phi) determines whether the wave is a cent red (f(phi) = 0) or a non-centred (f(phi) not equal 0) wave. Examples are given of time-dependent vortex waves, shear waves and sound waves in one or two space dimensions. The streamlines for the wave reduce to two coupled ordinary differential equations in which the wave phase phi plays the role of a parameter along: the streamlines. The streamline equations are expressed in Hamiltonian form. The roles of Clebsch variables: Lagrangian variables, Hamiltonian formulations and characteristic surfaces are briefly discussed. C1 Univ Arizona, Lunar & Planetary Lab, Tucson, AZ 85721 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Polish Acad Sci, Space Res Ctr, PL-00716 Warsaw, Poland. Univ Arizona, Dept Math, Tucson, AZ 85721 USA. Univ Delaware, Bartol Res Inst, Newark, DE 19716 USA. RP Webb, GM (reprint author), Univ Arizona, Lunar & Planetary Lab, Tucson, AZ 85721 USA. NR 46 TC 16 Z9 16 U1 0 U2 2 PU CAMBRIDGE UNIV PRESS PI NEW YORK PA 40 WEST 20TH STREET, NEW YORK, NY 10011-4211 USA SN 0022-3778 J9 J PLASMA PHYS JI J. Plasma Phys. PD APR PY 1998 VL 59 BP 417 EP 460 DI 10.1017/S0022377897006375 PN 3 PG 44 WC Physics, Fluids & Plasmas SC Physics GA ZQ743 UT WOS:000073898600002 ER PT J AU Herbell, TP Hull, DR Garg, A AF Herbell, TP Hull, DR Garg, A TI Hot hydrogen exposure degradation of the strength of mullite SO JOURNAL OF THE AMERICAN CERAMIC SOCIETY LA English DT Article AB Near-stoichiometric mullite (3Al(2)O(3) . 2SiO(2)) that contained small amounts of calcium and magnesium was exposed to pure dry hydrogen gas at elevated temperatures, Exposure temperatures were 1050 degrees and 1250 degrees C, and exposure times were up to 500 h, Preferential attack of the aluminosilicate glass that was present it the grain boundaries of the mullite occurred after 125 h at 1250 degrees C. Hydrogen scrubbing off the silica from the glassy grain boundaries and the mullite grains yielded a porous alumina-rich surface. The room-temperature strength increased after short exposure times at 1250 degrees C (up to 125 h) and then decreased by 53% after exposure for 500 h. At 1050 degrees C, all exposure times (25-500 h) decreased the strength. The room-temperature strength of mullite decreased 22% after 500 h in hydrogen at 1050 degrees C, We also observed a rapid 25% strength loss after short exposure times at 1050 degrees C, which was attributed to the calcium/hydrogen-assisted crystallization of the glassy grain-boundary phase. C1 NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. RP Herbell, TP (reprint author), NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. NR 8 TC 6 Z9 6 U1 0 U2 1 PU AMER CERAMIC SOC PI WESTERVILLE PA 735 CERAMIC PLACE, PO BOX 6136, WESTERVILLE, OH 43081-6136 USA SN 0002-7820 J9 J AM CERAM SOC JI J. Am. Ceram. Soc. PD APR PY 1998 VL 81 IS 4 BP 910 EP 916 PG 7 WC Materials Science, Ceramics SC Materials Science GA ZJ248 UT WOS:000073195000012 ER PT J AU Fox, DS AF Fox, DS TI Oxidation behavior of chemically-vapor-deposited silicon carbide and silicon nitride from 1200 degrees to 1600 degrees C SO JOURNAL OF THE AMERICAN CERAMIC SOCIETY LA English DT Article ID SINGLE-CRYSTAL SILICON; SIO2-SI3N4 INTERFACE; PASSIVE OXIDATION; DRY OXYGEN; CVD SI3N4; KINETICS; ENVIRONMENTS; CERAMICS AB The isothermal oxidation of pure CVD SiC and Si3N4 has been studied for 100 h in dry, flowing oxygen from 1200 degrees to 1600 degrees C in an alumina tube furnace. Adherent oxide formed at temperatures to 1550 degrees C. The major crystalline phase in the resulting silica scales was alpha-cristobalite. Parabolic rate constants for SiC were within an order of magnitude of literature values. The oxidation kinetics of Si3N4 in this study were not statistically different from that of SiC. Measured activation energies were 190 kJ/mol for SiC and 186 kJ/mol for Si3N4. Silicon oxynitride did not appear to play a role in the oxidation of Si3N4 under the conditions herein. This is thought to be derived from the presence of ppm levels of sodium impurities in the alumina furnace tube. It is proposed that sodium modifies the silicon oxynitride, rendering it ineffective as a diffusion barrier. Material recession as a function of oxide thickness was calculated and found to be low. Oxidation behavior at 1600 degrees C differed from the lower temperatures in that silica spallation occurred after exposure. C1 NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. RP Fox, DS (reprint author), NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. NR 30 TC 59 Z9 60 U1 2 U2 17 PU AMER CERAMIC SOC PI WESTERVILLE PA 735 CERAMIC PLACE, PO BOX 6136, WESTERVILLE, OH 43081-6136 USA SN 0002-7820 J9 J AM CERAM SOC JI J. Am. Ceram. Soc. PD APR PY 1998 VL 81 IS 4 BP 945 EP 950 PG 6 WC Materials Science, Ceramics SC Materials Science GA ZJ248 UT WOS:000073195000017 ER PT J AU Bhatt, RT Hull, DR AF Bhatt, RT Hull, DR TI Strength-degrading mechanisms for chemically-vapor-deposited SCS-6 silicon carbide fibers in an argon environment SO JOURNAL OF THE AMERICAN CERAMIC SOCIETY LA English DT Article ID SELF-DIFFUSION; POLYCRYSTALLINE AB The room-temperature tensile strengths of chemically-vapor-deposited SCS-6 silicon carbide fibers were measured after 1 to 400 h heat treatments in 0.1 MPa of argon at temperatures up to 2100 degrees C. The fibers heat-treated for 1 h above 1400 degrees C and those heat-treated for 400 h above 1300 degrees C showed strength degradation. Scanning and transmission electron microscopic examination of the degraded fibers showed formation of a recrystallization region within the outer zone of the SiC sheath and the growth of SiC particles in the carbon-rich surface coating. The activation energy for the growth of the recrystallization region was similar to 370 kJ/mol. The tensile strength of the fibers was found to vary as an inverse function of the recrystallized zone thickness. C1 USA, Prop Directorate, Res Lab, Lewis Res Ctr, Cleveland, OH 44135 USA. NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. RP USA, Prop Directorate, Res Lab, Lewis Res Ctr, Cleveland, OH 44135 USA. NR 18 TC 9 Z9 10 U1 0 U2 0 PU WILEY-BLACKWELL PI HOBOKEN PA 111 RIVER ST, HOBOKEN 07030-5774, NJ USA SN 0002-7820 EI 1551-2916 J9 J AM CERAM SOC JI J. Am. Ceram. Soc. PD APR PY 1998 VL 81 IS 4 BP 957 EP 964 PG 8 WC Materials Science, Ceramics SC Materials Science GA ZJ248 UT WOS:000073195000019 ER PT J AU Mansur, MH Tischler, MB AF Mansur, MH Tischler, MB TI An empirical correction for improving off-axes response in flight mechanics helicopter models SO JOURNAL OF THE AMERICAN HELICOPTER SOCIETY LA English DT Article; Proceedings Paper CT AGARD Flight Vehicle Integration Panel Symposium on Advances in Rotorcraft Technology CY MAY 27-30, 1996 CL OTTAWA, CANADA AB Historically, component-type flight mechanics simulation models of helicopters have been unable to satisfactorily predict the roll response to pitch stick input and the pitch response to roll stick input off-axes responses. In the study presented here, simple first-order low-pass filtering of the elemental lift and drag forces was considered as a means of improving the correlation. The method was applied to a blade-element model of the AH-64 Apache, and responses of the modified model were compared with flight data in hover and forward flight. Results indicate that significant improvement in the off-axes responses can be achieved in hover. In forward flight, however, the best correlation in the longitudinal and lateral off-axes responses required different values of the filter time constant for each axis. A compromise value was selected and was shown to result in good overall improvement in the off-axes responses. The paper describes both the method and the model used for its implementation, and presents results obtained at hover and in forward flight. C1 USA, Aeroflightdynam Directorate, Aviat Res Dev & Engn Ctr, Aviat & Missile Command,Ames Res Ctr, Moffett Field, CA 94035 USA. RP Mansur, MH (reprint author), USA, Aeroflightdynam Directorate, Aviat Res Dev & Engn Ctr, Aviat & Missile Command,Ames Res Ctr, MS 211-2, Moffett Field, CA 94035 USA. NR 20 TC 9 Z9 9 U1 0 U2 3 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 APR PY 1998 VL 43 IS 2 BP 94 EP 102 PG 9 WC Engineering, Aerospace SC Engineering GA ZL899 UT WOS:000073484700001 ER PT J AU Baker, DJ Rogers, C AF Baker, DJ Rogers, C TI Analysis and tests of reinforced carbon-epoxy/foam-core sandwich panels with cutouts SO JOURNAL OF THE AMERICAN HELICOPTER SOCIETY LA English DT Article; Proceedings Paper CT 52nd Annual Forum of the American-Helicopter-Society CY JUN 04-06, 1996 CL WASHINGTON, D.C. SP Amer Helicopter Soc AB The results of a structurally-efficient minimum-gage shear-panel ape presented. The shear-panel design is based on an Integrally stiffened syntactic-foam stabilized-skin concept with an all-bias-ply tape construction for the skins. The panels considered in the study were designed to be buckling resistant up to 100 lbs/in. of shear load and to have an ultimate strength of 300 lbs/in. The experimental buckling strength of the reinforced panels is 83 to 90 percent of the predicted buckling strength based on a linear buckling analysis. The maximum experimental deflection exceeds the maximum deflection predicted by a nonlinear analysis by approximately one panel thickness. The failure strength of the reinforced panels was two and a half to four times the buckling strength. This efficient shear-panel design concept exceeds the required ultimate strength requirement of 300 lbs/in. by over 100 percent. C1 NASA, Struct Mech Branch, Vehicle Technol Ctr, ARL,Langley Res Ctr, Hampton, VA 23681 USA. Bell Helicopter Textron Inc, Ft Worth, TX 76101 USA. RP Baker, DJ (reprint author), NASA, Struct Mech Branch, Vehicle Technol Ctr, ARL,Langley Res Ctr, Hampton, VA 23681 USA. NR 4 TC 1 Z9 1 U1 0 U2 0 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 APR PY 1998 VL 43 IS 2 BP 120 EP 132 PG 13 WC Engineering, Aerospace SC Engineering GA ZL899 UT WOS:000073484700004 ER PT J AU Colello, GD Grivet, C Sellers, PJ Berry, JA AF Colello, GD Grivet, C Sellers, PJ Berry, JA TI Modeling of energy, water, and CO2 flux in a temperate grassland ecosystem with SiB2: May-October 1987 SO JOURNAL OF THE ATMOSPHERIC SCIENCES LA English DT Article; Proceedings Paper CT FIFE Symposium at the Annual Meeting of the American-Meteorological-Society CY 1996 CL ATLANTA, GA SP Amer Meteorol Soc, FIFE ID GENERAL-CIRCULATION MODEL; SURFACE PARAMETERIZATION SIB2; TERRESTRIAL CARBON METABOLISM; FIELD EXPERIMENT FIFE; SENSIBLE HEAT FLUXES; STOMATAL CONDUCTANCE; LAND-SURFACE; TALLGRASS PRAIRIE; ATMOSPHERIC CO2; CANOPY PHOTOSYNTHESIS AB The Simple Biosphere Model, version 2 (SiB2), was designed for use within atmospheric general circulation models as a soil-vegetation-atmosphere transfer scheme that includes CO2 flux prediction. A stand-alone version of SiB2 was used to simulate a grassland at Station 16 of the First ISLSCP Field Experiment (FIFE) located near Manhattan, Kansas, for a period of 142 days of the 1987 growing season. Modeled Values of soil temperature and moisture were initialized, using field measurements from the soil profile, and thereafter updated solely by model calculations. The model was driven by half-hourly atmospheric observations and regular observations of canopy biophysics. This arrangement was intended to mimic model forcing in a GCM. Three model Versions are compared: (i) a Control run using parameter values taken from look-up tables used for running the Colorado State University GCM; (ii) a Tuned run with many adjustments to optimize SiB2 to this ecosystem; and (iii) a Calibrated run, which calibrated the Control Version soil to the local site and incorporated two important changes from the Tuned version. Modeled fluxes of latent heat, sensible heat, soil heat, net radiation, and net site CO2 were compared to over 800 half-hourly observations; modeled surface and deep soil temperatures compared to 6500 observations; and three layers of modeled soil water content compared to 15 measurements of the soil water profile. Statistical methods were used to analyze these results. In the absence of water stress all three versions accurately simulated photosynthesis and canopy conductance. However, during episodes of drought, only the Tuned and Calibrated versions accurately simulated physiological control of canopy fluxes. The largest errors were encountered in the simulation of soil respiration. These were traced to problems predicting water content and temperature in the soil profile. These results highlight the need for improved simulation of soil biophysics to obtain accurate estimates of net CO2 balance. The accuracy of the Tuned version was improved by changes that (i) allowed water extraction by roots from all soil layers, (ii) matched the soil texture specification to the site, and (iii) calibrated the expressions used for diffusion of water and heat within the soil profile. C1 Carnegie Inst Sci, Dept Plant Biol, Stanford, CA 94305 USA. NASA, Goddard Space Flight Ctr, Biospher Sci Branch, Atmospheres Lab, Greenbelt, MD 20771 USA. RP Berry, JA (reprint author), Carnegie Inst Sci, Dept Plant Biol, Stanford, CA 94305 USA. EM gcolello@mendelbio.com RI Berry, Joseph/B-8211-2009; Young, Kristina/M-3069-2014 OI Berry, Joseph/0000-0002-5849-6438; NR 74 TC 52 Z9 61 U1 0 U2 12 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 USA SN 0022-4928 EI 1520-0469 J9 J ATMOS SCI JI J. Atmos. Sci. PD APR 1 PY 1998 VL 55 IS 7 BP 1141 EP 1169 DI 10.1175/1520-0469(1998)055<1141:MOEWAC>2.0.CO;2 PG 29 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA ZF369 UT WOS:000072890600005 ER PT J AU Bosilovich, MG Sun, WY AF Bosilovich, MG Sun, WY TI Monthly simulation of surface layer fluxes and soil properties during FIFE SO JOURNAL OF THE ATMOSPHERIC SCIENCES LA English DT Article; Proceedings Paper CT FIFE Symposium at the Annual Meeting of the American-Meteorological-Society CY 1996 CL ATLANTA, GEORGIA SP Amer Meteorol Soc, FIFE ID BIOSPHERE MODEL SIB; LAND-SURFACE; PRAIRIE GRASSLAND; MOISTURE FLUXES; BOUNDARY-LAYER; UNITED-STATES; PARAMETERIZATION; SENSITIVITY; EVAPORATION; PREDICTION AB Global change and regional climate experiments with atmospheric numerical models rely on the parameterization of the surface boundary in order to evaluate impact on society and agriculture. In this paper, several surface modeling strategies have been examined in order to test their ability to simulate for a period of one month, and hence, their impact on short-term and regional climate modeling. The interaction between vegetation and soil models is also discussed. The resolution of a multiple-level soil model, the method of computing moisture availability, the Force-Restore Method, and vegetation parameterization were studied by comparing model-simulated soil temperature, soil moisture, and surface energy budget with observations and intercomparison of the simulations. The increase of model soil resolution improved both the simulation of daytime ground heat Bur and latent heat. Evaporation from the soil surface with more coarse resolution soil was larger than the higher resolution simulation, but transpiration and the simulation of soil water were similar for each case. The Alpha method of moisture availability allowed less soil evaporation under stressed conditions than the Beta method. The soil water became larger than the observations, and more transpiration occurred. The Force-Restore Method simulations produced reasonable results, when coupled with the vegetation model. Eliminating the vegetation model from several of the previous cases, however, produced significant variability between different soil models. It is possible that this variability could affect long-term GCM sensitivity simulations. C1 NASA, Goddard Space Flight Ctr, Univ Space Res Assoc, Greenbelt, MD 20771 USA. Purdue Univ, Dept Earth & Atmospher Sci, W Lafayette, IN 47907 USA. RP Bosilovich, MG (reprint author), NASA, Goddard Space Flight Ctr, Univ Space Res Assoc, Greenbelt, MD 20771 USA. RI Bosilovich, Michael/F-8175-2012 NR 41 TC 10 Z9 11 U1 0 U2 0 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 APR 1 PY 1998 VL 55 IS 7 BP 1170 EP 1184 DI 10.1175/1520-0469(1998)055<1170:MSOSLF>2.0.CO;2 PG 15 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA ZF369 UT WOS:000072890600006 ER PT J AU Strebel, DE Landis, DR Huemmrich, KF Newcomer, JA Meeson, BW AF Strebel, DE Landis, DR Huemmrich, KF Newcomer, JA Meeson, BW TI The FIFE data publication experiment SO JOURNAL OF THE ATMOSPHERIC SCIENCES LA English DT Article; Proceedings Paper CT FIFE Symposium at the Annual Meeting of the American-Meteorological-Society CY 1996 CL ATLANTA, GEORGIA SP Amer Meteorol Soc, FIFE ID SYSTEM AB The First ISLSCP Field Experiment (FIFE) provided an opportunity to test the concept of data publication for long-term access to valuable scientific data. In analogy with the procedures used in research publication, the FIFE Information System and NASA's Pilot Land Data System adapted the functions performed by authors, editors, and publishers to an information management environment. Procedures and standards were developed to organize, quality check, document, and review data and associated supporting information for publication on a series of five CD-ROM volumes. The CD-ROM series has been successfully published and is in widespread use in the scientific community. The preliminary indications are that this publication will pass the "20-year test" recommended by a committee of the National Research Council for preserving global change data. It is concluded that the data publication approach, using near-permanent distributable publication units like CD-ROMs, is an important addition to the tools for ensuring the survival of large scientific datasets over long periods. C1 Versar Inc, Columbia, MD 21045 USA. NASA, Goddard Space Flight Ctr, Hughes STX, Greenbelt, MD 20771 USA. RP Strebel, DE (reprint author), Versar Inc, 9200 Rumsey Rd, Columbia, MD 21045 USA. NR 16 TC 6 Z9 6 U1 0 U2 1 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 APR 1 PY 1998 VL 55 IS 7 BP 1277 EP 1283 DI 10.1175/1520-0469(1998)055<1277:TFDPE>2.0.CO;2 PG 7 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA ZF369 UT WOS:000072890600014 ER PT J AU Juday, RD AF Juday, RD TI Generalized Rayleigh quotient approach to filter optimization SO JOURNAL OF THE OPTICAL SOCIETY OF AMERICA A-OPTICS IMAGE SCIENCE AND VISION LA English DT Article ID SPATIAL LIGHT-MODULATOR; PATTERN-RECOGNITION; NOISE RATIO; PHASE; DEVICES; TARGET; SIGNAL AB Through the Rayleigh quotient (the ratio of intensity of a filter to different objects) we may generalize a great number of metrics used in optical pattern recognition. The Rayleigh quotient has been optimized in linear digital system under the constraint of unit-energy filters. In optical pattern recognition at least two considerations violate the conditions under which the quotient has been digitally optimized: the noise background of the measurement invokes nonlinearity, and the filters are constrained other than to unit energy. I show a solution that optimizes the ration of biased measurements, subject to constraining filter values to arbitrary subsets of the complex plane. Previous solutions are discussed as special cases. A metric's numerator and denominator may now both include the objects' phase. (C) 1998 Optical Society of America. C1 NASA, Automat Robot & Simulat Div, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. RP Juday, RD (reprint author), NASA, Automat Robot & Simulat Div, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. NR 16 TC 14 Z9 14 U1 0 U2 0 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 APR PY 1998 VL 15 IS 4 BP 777 EP 790 DI 10.1364/JOSAA.15.000777 PG 14 WC Optics SC Optics GA ZD744 UT WOS:000072719100002 ER PT J AU Gokcen, T Park, CS Newfield, ME Fletcher, DG AF Gokcen, T Park, CS Newfield, ME Fletcher, DG TI Computational simulation of emission spectra from shock-layer flows in an arcjet facility 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 AB This paper reports computational comparisons with experimental studies of a nonequilibrium blunt-body shock-layer now in a high-enthalpy arcjet wind tunnel at NASA Ames Research Center, The experimental data include spatially resolved emission spectra of radiation emanating from a shock layer formed in front of a flat-faced cylinder model. Multitemperature nonequilibrium codes are used to compute the conical nozzle now, supersonic jet, and shock-layer now. A line-of-sight (LOS) radiation code is employed to predict the spectra from the computed flowfield. Computed LOS emission intensities are directly compared with the experimental data at several axial locations along the stagnation streamline, Various LOS-averaged flow properties, such as vibrational and rotational temperatures, and species number densities, deduced from the experimental spectra, are compared with computed results. Comparisons provide an assessment of thermochemical equilibration processes in an arcjet shock layer. C1 NASA, Ames Res Ctr, Thermosci Inst, Moffett Field, CA 94035 USA. NASA, Ames Res Ctr, Reacting Flow Environm Branch, Moffett Field, CA 94035 USA. RP Gokcen, T (reprint author), NASA, Ames Res Ctr, Thermosci Inst, Moffett Field, CA 94035 USA. NR 13 TC 6 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 0887-8722 J9 J THERMOPHYS HEAT TR JI J. Thermophys. Heat Transf. PD APR-JUN PY 1998 VL 12 IS 2 BP 180 EP 189 DI 10.2514/2.6343 PG 10 WC Thermodynamics; Engineering, Mechanical SC Thermodynamics; Engineering GA ZG837 UT WOS:000073045000008 ER PT J AU Park, CS Newfield, ME Fletcher, DG Gokcen, T Sharma, SP AF Park, CS Newfield, ME Fletcher, DG Gokcen, T Sharma, SP TI Spectroscopic emission measurements within the blunt-body shock layer in an arcjet flow 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 AB In the present study, radiation emanating from the freestream and shock-layer now over a 15.24-cm-diam, nat-faced cylinder model was measured in the NASA Ames Research Center's 20-MW Arcjet Facility. The test gas was a mixture of argon and air. Spatially resolved emission spectra were obtained over a 200- to 890-nm wavelength range using a charged-coupled device camera (1024 x 256 array) attached to a spectrograph. The optical system was calibrated using tungsten and deuterium radiation sources. Analytical tools were used to determine the following line-of-sight-averaged thermodynamic properties from the calibrated spectra: 1) rotational temperature of the freestream and 2) rotational, vibrational, electronic temperatures, and species number densities within the shock layer. An analysis was performed to estimate the uncertainty bounds of the determined properties. C1 NASA, Ames Res Ctr, Thermosci Inst, Moffett Field, CA 94035 USA. NASA, Ames Res Ctr, Reacting Flow Environm Branch, Moffett Field, CA 94035 USA. RP Park, CS (reprint author), NASA, Ames Res Ctr, Thermosci Inst, Moffett Field, CA 94035 USA. NR 11 TC 16 Z9 16 U1 0 U2 0 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 APR-JUN PY 1998 VL 12 IS 2 BP 190 EP 197 DI 10.2514/2.6344 PG 8 WC Thermodynamics; Engineering, Mechanical SC Thermodynamics; Engineering GA ZG837 UT WOS:000073045000009 ER PT J AU Bose, D Candler, GV AF Bose, D Candler, GV TI Advanced model of nitric oxide formation in hypersonic flows SO JOURNAL OF THERMOPHYSICS AND HEAT TRANSFER LA English DT Article ID ULTRAVIOLET ROCKET EXPERIMENTS; N-2+O->NO+N REACTION; NONEQUILIBRIUM; SURFACES; DYNAMICS; (3)A'' AB A model for nitric oxide (NO) formation in low-density hypersonic flows is presented. The thermal nonequilibrium reaction rates, reactant energy removal rates, and product energy disposal rates are based on a quasiclassical trajectory analysis of the Zeldovich reactions, At hypersonic now conditions, the newly obtained reaction rate for the second Zeldovich reaction is approximately an order of magnitude larger than the commonly used rate. The rate of this reaction is a weak function of the reactant internal energy, but it produces vibrationally excited NO molecules that result in an elevated NO vibrational temperature, A flowfield model that includes these effects is proposed, and a computational fluid dynamics method is used to simulate the BSUV1 and BSUV2 flight experiments. The new model generally improves the agreement with the spectrally resolved radiation data; however, it appears that there are additional mechanisms that preferentially remove the highly excited NO molecules. C1 Univ Minnesota, Dept Aerosp Engn & Mech, Army High Performance Comp Res Ctr, Minneapolis, MN 55455 USA. RP Bose, D (reprint author), NASA, Ames Res Ctr, Thermosci Inst, Moffett Field, CA 94035 USA. NR 25 TC 6 Z9 7 U1 1 U2 2 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 APR-JUN PY 1998 VL 12 IS 2 BP 214 EP 222 DI 10.2514/2.6324 PG 9 WC Thermodynamics; Engineering, Mechanical SC Thermodynamics; Engineering GA ZG837 UT WOS:000073045000012 ER PT J AU Miyoshi, K AF Miyoshi, K TI Lubrication by diamond and diamondlike carbon coatings 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 FILMS; FRICTION; WEAR AB Regardless of environment (ultrahigh vacuum, humid air, dry nitrogen, or water), ion-beam-deposited diamondlike carbon (DLC) and nitrogen-ion-implanted, chemical-vapor-deposited (CVD) diamond films had low steady-state coefficients of friction (<0.1) and low wear rates (less than or equal to 1O(-6) mm(3)/N . m). These films can be used as effective wear-resistant, self-lubricating coatings regardless of environment. On the other hand, as-deposited, fine-grain CVD diamond films; polished, coarse-grain CVD diamond films; and polished and then fluorinated, coarse-grain CVD diamond films can be used as effective wear-resistant, self-lubricating coatings in humid air, in dry nitrogen, and in water, but they had a high coefficient of friction and a high wear rate in ultrahigh vacuum. The polished, coarse-grain CVD diamond film revealed an extremely low wear rate, far less than 10(-10) mm(3)/N . m, in water. C1 NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. RP NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. NR 28 TC 10 Z9 10 U1 1 U2 5 PU ASME PI NEW YORK PA TWO PARK AVE, NEW YORK, NY 10016-5990 USA SN 0742-4787 EI 1528-8897 J9 J TRIBOL-T ASME JI J. Tribol.-Trans. ASME PD APR PY 1998 VL 120 IS 2 BP 379 EP 384 DI 10.1115/1.2834437 PG 6 WC Engineering, Mechanical SC Engineering GA ZH630 UT WOS:000073130900035 ER PT J AU Hah, C Rabe, DC Sullivan, TJ Wadia, AR AF Hah, C Rabe, DC Sullivan, TJ Wadia, AR TI Effects of inlet distortion on the flow field in a transonic compressor rotor SO JOURNAL OF TURBOMACHINERY-TRANSACTIONS OF THE ASME LA English DT Article; Proceedings Paper CT 41st International Gas Turbine and Aeroengine Congress and Exhibition CY JUN 10-13, 1996 CL BIRMINGHAM, ENGLAND ID AXIAL COMPRESSOR; HIGH-THROUGHFLOW; UNSTEADY-FLOW; STAGE AB The effects of circumferential distortions in inlet total pressure on the flow field in a low-aspect-ratio, high-speed, high-pressure-ratio, transonic compressor rotor are investigated in this paper. The flow field was studied experimentally and numerically with and without inlet total pressure distortion. Total pressure distortion was created by screens mounted upstream from the rotor inlet. Circumferential distortions of eight periods per revolution were investigated at two different rotor speeds. The unsteady blade surface pressures were measured with miniature pressure transducers mounted in the blade. The flow fields with and without inlet total pressure distortion were analyzed numerically by solving steady and unsteady forms of the Reynolds-averaged Navier-Stokes equations. Steady three-dimensional viscous flow calculations were performed for the flow without inlet distortion while unsteady three-dimensional viscous flow calculations were used for the flow with inlet distortion. For the time-accurate calculation, circumferential and radial variations of the inlet total pressure were used as a time-dependent inflow boundary condition. A second-order implicit scheme was used for the time integration. The experimental measurements and the numerical analysis are highly complementary for this study because of the extreme complexity of the flow field. The current investigation shows that inlet flow distortions travel through the rotor blade passage and are convected into the following stator. At a high rotor speed where the flow is transonic, the passage shock was found to oscillate by as much as 20 percent of the blade chord, and very strong interactions between the unsteady passage shock and the blade boundary layer were observed. This interaction increases the effective blockage of the passage, resulting in an increased aerodynamic loss and a reduced stall margin. The strong interaction between the passage shock and the blade boundary layer increases the peak aerodynamic loss by about one percent. C1 NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. GE, Aircraft Engines, Cincinnati, OH 45215 USA. RP Hah, C (reprint author), NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. NR 33 TC 17 Z9 19 U1 1 U2 4 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 APR PY 1998 VL 120 IS 2 BP 233 EP 246 PG 14 WC Engineering, Mechanical SC Engineering GA ZJ899 UT WOS:000073264900004 ER PT J AU Giel, PW Thurman, DR Van Fossen, GJ Hippensteele, SA Boyle, RJ AF Giel, PW Thurman, DR Van Fossen, GJ Hippensteele, SA Boyle, RJ TI Endwall heat transfer measurements in a transonic turbine cascade SO JOURNAL OF TURBOMACHINERY-TRANSACTIONS OF THE ASME LA English DT Article; Proceedings Paper CT 41st International Gas Turbine and Aeroengine Congress and Exhibition CY JUN 10-13, 1996 CL BIRMINGHAM, ENGLAND ID TURBULENCE; BLADES AB Turbine blade endwall heat transfer measurements are presented for a range of Reynolds and Mach numbers. Data were obtained for Reynolds numbers based on inlet conditions of 0.5 and 1.0 x 10(6), for isentropic exit Mach numbers of 1.0 and 1.3, and for free-stream turbulence intensities of 0.25 and 7.0 percent. Tests were conducted in a linear cascade at the NASA Lewis Transonic Turbine Blade Cascade Facility. The rest article was a turbine rotor with 136 deg of turning and ail axial chord of 12.7 cm. The large scale allowed for very detailed measurements of both flow field and surface phenomena. The intent of the work is to provide benchmark quality data for CFD code and model verification. The flow field in the cascade is highly three dimensional as a result of thick boundary layers at the test section inlet. Endwall heat transfer data were obtained using a steady-state liquid crystal technique. C1 NYMA Inc, Engn Serv Div, Brookpark, OH 44142 USA. USA, Res Lab, NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. NASA, Lewis Res Ctr, Internal Fluid Mech Div, Cleveland, OH 44135 USA. RP Giel, PW (reprint author), NYMA Inc, Engn Serv Div, Brookpark, OH 44142 USA. NR 28 TC 26 Z9 27 U1 0 U2 1 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 APR PY 1998 VL 120 IS 2 BP 305 EP 313 PG 9 WC Engineering, Mechanical SC Engineering GA ZJ899 UT WOS:000073264900012 ER PT J AU Jones, WR Paciorek, KJL Lin, WH Masuda, SR Nakahara, JH AF Jones, WR Paciorek, KJL Lin, WH Masuda, SR Nakahara, JH TI Evaluation of degradation inhibitors in poly(hexafluoropropeneoxide) fluids SO LUBRICATION ENGINEERING 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 additives; ferrous alloys; lubricant degradation/stability ID PERFLUOROPOLYALKYLETHER OIL; PERFLUOROALKYL ETHERS; PERFLUOROPOLYETHERS; TEMPERATURES; STABILITY; STEEL; FEF3 AB The action of various alloys - 440C steel, M-50 steel, Pyrowear 675, Cronidur 30 and Ti (4Al, 4Mn) - and the effect of degradation inhibitors mono-and diphospha-s-triazines, diphosphate-traazacyclooctatetreane, phosphate esters, phosphate/diester rust inhibiting mixtures, and a phosphine were evaluated in two poly (hexafluoropropene oxide) fluids (143AC and 16256). The degradation promoting action of the ferrous alloys in 16256 fluid were comparable and the Ti (4Al, 4Mn) alloy was significantly more detrimental. The overall rating of the additives was phosphates>phosphate/diester mixture>phosphine greater than or equal to 2phospha-s-triazines. The 16256 fluid was less responsive to additive inhibition than 143AC. Phosphate esters were fully effective over 24-hour exposure in the 16256/440C steel and the 16256/Ti (4Al, 4Mn) systems at 330 degrees C. In general, the phosphine was less effective in the presence of ferrous alloys than the phosphates and phospha-s-triazines. C1 NASA Lewis Res Ctr, Cleveland, OH 44135 USA. Lubricating Specialties Co, Vernon, CA 90058 USA. RP Jones, WR (reprint author), NASA Lewis Res Ctr, Cleveland, OH 44135 USA. NR 23 TC 0 Z9 0 U1 0 U2 0 PU SOC TRIBOLOGISTS & LUBRICATION ENGINEERS PI PARK RIDGE PA 840 BUSSE HIGHWAY, PARK RIDGE, IL 60068 USA SN 0024-7154 J9 LUBR ENG JI Lubric. Eng. PD APR PY 1998 VL 54 IS 4 BP 16 EP 20 PG 5 WC Engineering, Mechanical SC Engineering GA ZG629 UT WOS:000073023000001 ER PT J AU Johnson, SW Rice, SD Moles, DA AF Johnson, SW Rice, SD Moles, DA TI Effects of submarine mine tailings disposal on juvenile yellowfin sole (Pleuronectes asper): A laboratory study SO MARINE POLLUTION BULLETIN LA English DT Article DE yellowfin sole; Pleuronectes asper; Alaska; mine tailings ID BODY-SIZE; SEDIMENTS; PREDATION; GROWTH; IMPACT; OIL AB Behaviour, survival, and growth studies were conducted in the laboratory on juvenile yellowfin sole (Pleuronectes asper) exposed to mine tailings produced by a pilot plant for a gold mine near Juneau, Alaska. Fish avoided fresh tailings in favour of natural marine sediment (control) and weathered tailings (75 years old). Only when fresh tailings were covered with 2 cm of control sediment did fish prefer control and fresh tailings equally Survival of fish was similar (p = 0.66) for fish held on all test sediments. Fish held on fresh tailings for 60 d grew significantly (p = 0.013) less than control fish during the first, but not the second, month. Avoidance or short-term reductions in flatfish growth may occur from submarine disposal of tailings. Rapid burial of tailings in areas with high natural sedimentation (e.g., large river mouths) may accelerate recovery of the sea floor. Published by Elsevier Science Ltd. C1 Natl Marine Fisheries Serv, Alaska Fisheries Sci Ctr, Auke Bay Lab, Juneau, AK 99801 USA. RP Natl Marine Fisheries Serv, Alaska Fisheries Sci Ctr, Auke Bay Lab, 11305 Glacier Highway, Juneau, AK 99801 USA. NR 31 TC 11 Z9 11 U1 1 U2 4 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0025-326X EI 1879-3363 J9 MAR POLLUT BULL JI Mar. Pollut. Bull. PD APR PY 1998 VL 36 IS 4 BP 278 EP 287 DI 10.1016/S0025-326X(97)00181-1 PG 10 WC Environmental Sciences; Marine & Freshwater Biology SC Environmental Sciences & Ecology; Marine & Freshwater Biology GA ZU636 UT WOS:000074217900013 ER PT J AU Mossi, KM Selby, GV Bryant, RG AF Mossi, KM Selby, GV Bryant, RG TI Thin-layer composite unimorph ferroelectric driver and sensor properties SO MATERIALS LETTERS LA English DT Article DE piezoelectric device; ferroelectric; optic; displacement; optical sensor; poled ceramic wafers; PZT; actuator; THUNDER AB Tests were conducted on 13 different configurations of a new class of piezoelectric devices called THUNDER (thin-layer composite unimorph ferroelectric driver and sensor). These configurations consisted of a combination of 1, 3, 5, 7, and 9 layers of 25.4 mu m thick aluminum as backing material, with and without a top layer of 25.4 mu m aluminum. All of these configurations used the same piezoelectric ceramic wafer (PZT-5A) with dimensions of 5.08 X 3.81 X 0.018 cm. The above configurations were tested at two stages of the manufacturing process: before and after re-poling. The parameters measured included frequency, driving voltage, displacement, capacitance, and radius of curvature. An optic sensor recorded the displacement at a fixed voltage (100-400 V peak-to-peak), over a predetermined frequency range (1-1000 Hz). These displacement measurements were performed using a computer that controlled the process of activating and measuring the displacement of the device. A parameter cu was defined which can be used to predict which configuration will produce the most displacement for a free standing device. (C) 1998 Elsevier Science B.V. C1 Face Int Corp, Norfolk, VA 23508 USA. Old Dominion Univ, Dept Mech Engn, Norfolk, VA 23529 USA. NASA, Langley Res Ctr, Hampton, VA 23681 USA. RP Mossi, KM (reprint author), Face Int Corp, 427 W 35th St, Norfolk, VA 23508 USA. NR 25 TC 89 Z9 90 U1 1 U2 5 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0167-577X J9 MATER LETT JI Mater. Lett. PD APR PY 1998 VL 35 IS 1-2 BP 39 EP 49 DI 10.1016/S0167-577X(97)00214-0 PG 11 WC Materials Science, Multidisciplinary; Physics, Applied SC Materials Science; Physics GA ZK443 UT WOS:000073321400008 ER PT J AU Bickler, D AF Bickler, D TI Roving ever Mars SO MECHANICAL ENGINEERING LA English DT Article C1 Jet Prop Lab, Pasadena, CA 91109 USA. RP Bickler, D (reprint author), Jet Prop Lab, Pasadena, CA 91109 USA. NR 0 TC 5 Z9 5 U1 0 U2 0 PU ASME-AMER SOC MECHANICAL ENG PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017 USA SN 0025-6501 J9 MECH ENG JI Mech. Eng. PD APR PY 1998 VL 120 IS 4 BP 74 EP 77 PG 4 WC Engineering, Mechanical SC Engineering GA ZD590 UT WOS:000072701800028 ER PT J AU Cho, PS Lee, S Marks, RJ Oh, SH Sutlief, SG Phillips, MH AF Cho, PS Lee, S Marks, RJ Oh, SH Sutlief, SG Phillips, MH TI Optimization of intensity modulated beams with volume constraints using two methods: Cost function minimization and projections onto convex sets SO MEDICAL PHYSICS LA English DT Article DE beam intensity modulation; optimization; dose-volume constraint; convex set; cost function ID RADIATION-THERAPY; RADIOTHERAPY; DISTRIBUTIONS; LIMITATIONS; RESTORATION; WEIGHTS; IMAGES AB For accurate prediction of normal tissue tolerance, it is important that the volumetric information of dose distribution be considered. However, in dosimetric optimization of intensity modulated beams, the dose-volume factor is usually neglected. In this paper we describe two methods of volume-dependent optimization for intensity modulated beams such as those generated by computer-controlled multileaf collimators, The first method uses a volume sensitive penalty function in which fast simulated annealing is used for cost function minimization (CFM). The second technique is based on the theory of projections onto convex sets (POCS) in which the dose-volume constraint is replaced by a limit on integral dose. The ability of the methods to respect the dose-volume relationship was demonstrated by using a prostate example involving partial volume constraints to the bladder and the rectum. The volume sensitive penalty function used in the CFM method can be easily adopted by existing optimization programs. The convex projection method can find solutions in much shorter time with minimal user interaction. (C) 1998 American Association of Physicists in Medicine. [S0094-2405(98)01004-9]. C1 Univ Washington, Dept Radiat Oncol, Seattle, WA 98195 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ Washington, Dept Elect Engn, Seattle, WA 98195 USA. NeoPath Inc, Redmond, WA 98052 USA. RP Cho, PS (reprint author), Univ Washington, Dept Radiat Oncol, Seattle, WA 98195 USA. NR 33 TC 70 Z9 70 U1 0 U2 1 PU AMER INST PHYSICS PI WOODBURY PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 USA SN 0094-2405 J9 MED PHYS JI Med. Phys. PD APR PY 1998 VL 25 IS 4 BP 435 EP 443 DI 10.1118/1.598218 PG 9 WC Radiology, Nuclear Medicine & Medical Imaging SC Radiology, Nuclear Medicine & Medical Imaging GA ZH764 UT WOS:000073145300005 PM 9571609 ER PT J AU Evans, JW Evans, JY Lall, P Cornford, SL AF Evans, JW Evans, JY Lall, P Cornford, SL TI Thermomechanical failures in microelectronic interconnects SO MICROELECTRONICS AND RELIABILITY LA English DT Article AB Thermomechanical Fatigue failures are an important class of failures in microelectronic interconnect structures. Thermomechanical stresses arise from differences in the coefficients of thermal expansion of the various materials comprising a microelectronics circuit. Polymer dielectrics and adhesives have larger coefficients of expansion than metal conductors. Dielectrics and adhesives may also exhibit large anisotropy in the coefficient of expansion, producing significant thermomechanical stresses in vias or other metal interconnect structures. During ambient thermal cycling or operational power dissipation, cyclic stresses are induced, which cause fatigue failures. The basic elements of thermomechanical fatigue behavior of microelectronic interconnect structures, such as lines and vias, are presented in this paper. In addition, a case study illustrating many of the concepts is presented for a complex 3-D interconnect. (C) 1998 Elsevier Science Ltd. All rights reserved. C1 Ajou Univ, Inst Adv Engn, Dept Syst Engn, Kyonggi Do 449800, South Korea. Korea Univ, Dept Ind Engn, Seoul 136701, South Korea. Motorola Corp, Adv Mfg Technol, Boca Raton, FL USA. CALTECH, Jet Prop Lab, Reliabil Engn Sect, Pasadena, CA USA. RP Evans, JW (reprint author), Ajou Univ, Inst Adv Engn, Dept Syst Engn, Yong In Complex,POB 25, Kyonggi Do 449800, South Korea. NR 12 TC 8 Z9 8 U1 0 U2 1 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0026-2714 J9 MICROELECTRON RELIAB JI Microelectron. Reliab. PD APR PY 1998 VL 38 IS 4 BP 523 EP 529 DI 10.1016/S0026-2714(97)00226-6 PG 7 WC Engineering, Electrical & Electronic; Nanoscience & Nanotechnology; Physics, Applied SC Engineering; Science & Technology - Other Topics; Physics GA ZM946 UT WOS:000073592200005 ER PT J AU Lynn, BH Tao, WK Wetzel, PJ AF Lynn, BH Tao, WK Wetzel, PJ TI A study of landscape-generated deep moist convection SO MONTHLY WEATHER REVIEW LA English DT Article ID MESOSCALE HEAT FLUXES; NUMERICAL SIMULATIONS; ATMOSPHERIC FLOW; BOUNDARY-LAYER; SURFACE FLUXES; SOIL-MOISTURE; SQUALL LINES; LAND-USE; MODEL; PRECIPITATION AB A two-dimensional version of a cloud-resolving model was used to study the generation of deep moist convection over heterogeneous landscapes. Alternating patches of dry and wet soil were simulated for various profiles of background wind. Results suggested a significant, systematic impact of patch length and background wind on moist convection. Rainfall occurred most intensely along sea-breeze-like fronts, which formed at patch boundaries. Total accumulated rainfall-as the average over simulations with the same patch size but with different background wind profiles-was largest for a patch length of 128 km. This patch length was similar in size to a local radius of deformation (r(o) = HN/omega). The deposition of rainfall generated a much different distribution of soil moisture after one day of model simulation. This new distribution, however, was far from equilibrium, as the landscape still consisted of a number of wet and dry soil patches. The cloud structure of moist convection was also examined using a cloud classification technique. The greatest percentage of rainfall that occurred from deep clouds (which had "roots" in the middle troposphere) was also obtained over patches with length similar to r(o). The results suggest the need to account for the triggering of moist convection by land surface heterogeneity in regional-and global-scale atmospheric models. It is also necessary to include the impact of patch size on cloud type. Moreover, because the distribution of soil moisture patches evolves over time in response to background atmospheric conditions. further study is suggested to gain a more full understanding of local-scale feedbacks between moist convection and soil moisture. C1 NASA, Goddard Space Flight Ctr, Mesoscale Atmospher Proc Branch, Greenbelt, MD 20771 USA. Columbia Univ, Ctr Climate Syst Res, New York, NY USA. RP Lynn, BH (reprint author), NASA, Goddard Space Flight Ctr, Mesoscale Atmospher Proc Branch, Bldg 22,Code 912, Greenbelt, MD 20771 USA. NR 51 TC 50 Z9 50 U1 1 U2 4 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 APR PY 1998 VL 126 IS 4 BP 928 EP 942 DI 10.1175/1520-0493(1998)126<0928:ASOLGD>2.0.CO;2 PG 15 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA ZF765 UT WOS:000072930900006 ER PT J AU Stone, M Gabrieli, JDE Stebbins, GT Sullivan, EV AF Stone, M Gabrieli, JDE Stebbins, GT Sullivan, EV TI Working and strategic memory deficits in schizophrenia SO NEUROPSYCHOLOGY LA English DT Article ID CEREBRAL BLOOD-FLOW; DORSOLATERAL PREFRONTAL CORTEX; STRUCTURED CLINICAL INTERVIEW; FRONTAL-LOBE LESIONS; PARKINSONS-DISEASE; COGNITIVE DEFICITS; NEUROPSYCHOLOGICAL DEFICITS; INDIVIDUAL-DIFFERENCES; TEMPORAL-ORDER; DYSFUNCTION AB Working memory and its contribution to performance on strategic memory tests in schizophrenia were studied. Patients (n = 18) and control participants (it = 15), all men, received tests of immediate memory (forward digit span), working memory (listening, computation, and backward digit span), and long-term strategic (free recall, temporal order, and self-ordered pointing) and nonstrategic (recognition) memory. Schizophrenia patients performed worse on all tests. Education. verbal intelligence, and immediate memory capacity did not account for deficits in working memory in schizophrenia patients. Reduced working memory capacity accounted for group differences in strategic memory but not in recognition memory. Working memory impairment may be central to the profile of impaired cognitive performance in schizophrenia and is consistent with hypothesized frontal lobe dysfunction associated with this disease. Additional medial-temporal dysfunction may account for the recognition memory deficit. C1 Stanford Univ, Dept Psychol, Stanford, CA 94305 USA. Rush Presbyterian St Lukes Med Ctr, Dept Neurol Sci, Chicago, IL 60612 USA. Stanford Univ, Sch Med, Dept Psychiat & Behav Sci, Stanford, CA 94305 USA. RP Stone, M (reprint author), NASA, Ames Res Ctr, Mail Stop 262-4, Moffett Field, CA 94035 USA. EM mstone@mail.arc.nasa.gov FU NIA NIH HHS [5 F32 AG05616]; NIMH NIH HHS [MH30854] NR 81 TC 113 Z9 114 U1 0 U2 3 PU AMER PSYCHOLOGICAL ASSOC PI WASHINGTON PA 750 FIRST ST NE, WASHINGTON, DC 20002-4242 USA SN 0894-4105 J9 NEUROPSYCHOLOGY JI Neuropsychology PD APR PY 1998 VL 12 IS 2 BP 278 EP 288 PG 11 WC Psychology, Clinical; Neurosciences; Psychology SC Psychology; Neurosciences & Neurology GA ZD795 UT WOS:000072725200011 PM 9556774 ER PT J AU Bardeen, W Duncan, A Eichten, E Hockney, G Thacker, H AF Bardeen, W Duncan, A Eichten, E Hockney, G Thacker, H TI Resolving exceptional configurations SO NUCLEAR PHYSICS B-PROCEEDINGS SUPPLEMENTS LA English DT Article; Proceedings Paper CT XVth International Symposium on Lattice Field Theory (Lattice 97) CY JUL 22-26, 1997 CL EDINBURGH, SCOTLAND SP Cray Res, Silicon Graph, Hitachi, Inst Phys, UK Particle Phys & Astron Res Council, Univ Edinburgh ID WILSON FERMIONS; LATTICE QCD; U(1) PROBLEM; LIMIT AB In lattice QCD with Wilson fermions, exceptional configurations arise in the quenched approximation at small quark mass. The origin of these large previously uncontrolled lattice artifacts is identified. A simple well-defined procedure (MQA) is presented which removes the artifacts while preserving the correct continuum limit. C1 Fermilab Natl Accelerator Lab, Batavia, IL 60510 USA. Univ Pittsburgh, Dept Phys & Astron, Pittsburgh, PA 15260 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ Virginia, Dept Phys, Charlottesville, VA 22901 USA. RP Fermilab Natl Accelerator Lab, POB 500, Batavia, IL 60510 USA. EM tony@dectony.phyast.pitt.edu; eichten@fnal.gov; thacker@virginia.edu NR 17 TC 8 Z9 8 U1 0 U2 0 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0920-5632 EI 1873-3832 J9 NUCL PHYS B-PROC SUP JI Nucl. Phys. B-Proc. Suppl. PD APR PY 1998 VL 63 BP 141 EP 146 DI 10.1016/S0920-5632(97)00705-6 PG 6 WC Physics, Particles & Fields SC Physics GA ZG230 UT WOS:000072980200017 ER PT J AU Ning, CZ Bischoff, S Koch, SW Harkness, GK Moloney, JV Chow, WW AF Ning, CZ Bischoff, S Koch, SW Harkness, GK Moloney, JV Chow, WW TI Microscopic modeling of vertical-cavity surface-emitting lasers: many-body interaction, plasma heating, and transverse dynamics SO OPTICAL ENGINEERING LA English DT Article DE bloch equations; vertical-cavity surface-emitting lasers (VCSELs); plasma heating; mode dynamics ID SEMICONDUCTOR MICROCAVITY LASERS; GAIN; AMPLIFIERS; MODES AB A microscopic theory for the interaction between semiconductor quantum-well structures and laser fields based on the semiconductor Bloch equations is applied to vertical-cavity surface-emitting lasers (VCSELs) with the inclusion of plasma heating. The semiconductor Bloch equations are reduced to a set of equations for the first and second moments of the carrier distribution functions. Plasma heating and many-body effects are then studied by solving this set of equations in steady state under the approximation of a single transverse and longitudinal mode. The transverse-and longitudinal-mode dynamics of VCSELs is analyzed by solving the full space-time-dependent problem. (C) 1998 Society of Photo-Optical instrumentation Engineers. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Univ Marburg, Fachbereich Phys, D-35032 Marburg, Germany. Univ Marburg, Zentrum Mat Wissensch, D-35032 Marburg, Germany. Univ Arizona, Arizona Ctr Math Sci, Tucson, AZ 85721 USA. Sandia Natl Labs, Albuquerque, NM 87185 USA. RP Ning, CZ (reprint author), NASA, Ames Res Ctr, Mail Stop T27A-1, Moffett Field, CA 94035 USA. RI Ning, C. Z./D-4699-2009 OI Ning, C. Z./0000-0003-4583-8889 NR 22 TC 5 Z9 5 U1 0 U2 0 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 APR PY 1998 VL 37 IS 4 BP 1175 EP 1181 DI 10.1117/1.602032 PG 7 WC Optics SC Optics GA ZG374 UT WOS:000072995200015 ER PT J AU Cady, SL AF Cady, SL TI Astrobiology: A new frontier for 21st century paleontologists SO PALAIOS LA English DT Editorial Material ID MARS C1 NASA, Ames Res Ctr, Space Sci Microscopy Lab, SETI Inst, Washington, DC USA. RP Cady, SL (reprint author), NASA, Ames Res Ctr, Space Sci Microscopy Lab, SETI Inst, Washington, DC USA. NR 9 TC 6 Z9 6 U1 0 U2 2 PU SEPM-SOC SEDIMENTARY GEOLOGY PI TULSA PA 1731 E 71ST STREET, TULSA, OK 74136-5108 USA SN 0883-1351 J9 PALAIOS JI Palaios PD APR PY 1998 VL 13 IS 2 BP 95 EP 97 DI 10.2307/3515482 PG 3 WC Geology; Paleontology SC Geology; Paleontology GA ZG391 UT WOS:000072997100002 PM 11542813 ER PT J AU Thompson, RJ Turchette, QA Carnal, O Kimble, HJ AF Thompson, RJ Turchette, QA Carnal, O Kimble, HJ TI Nonlinear spectroscopy in the strong-coupling regime of cavity QED SO PHYSICAL REVIEW A LA English DT Article ID PHASE-SENSITIVE DETECTION; ONE-ATOM MASER; OPTICAL CAVITY; QUANTUM FLUCTUATIONS; PHOTON STATISTICS; 2-STATE ATOMS; FIELD; MODE; VACUUM; BISTABILITY AB nonlinear spectroscopic investigation of a strongly coupled atom-cavity system is presented. A two-field pump-probe experiment is employed to study nonlinear structure as the average number of intracavity atoms is varied from (N) over bar approximate to 4.2 to (N) over bar approximate to 0.8. Nonlinear effects are observed for as few as 0.1 intracavity pump photons. A detailed semiclassical simulation of the atomic beam experiment gives reasonable agreement with the data for (N) over bar greater than or equal to 2 atoms. The simulation procedure accounts for fluctuations in atom-field coupling which have important effects on both the linear and nonlinear probe transmission spectra. A discrepancy between the simulations and the experiments is observed for small numbers of atoms ((N) over bar less than or equal to 1). Unfortunately, it is difficult to determine if this discrepancy is a definitive consequence of the quantum nature of the atom-cavity coupling or a result of the severe technical complications of the experiment. C1 CALTECH, Norman Bridge Lab Phys, Pasadena, CA 91125 USA. RP Thompson, RJ (reprint author), CALTECH, Jet Prop Lab, M-C 298-100, Pasadena, CA 91109 USA. NR 58 TC 33 Z9 33 U1 0 U2 6 PU AMERICAN PHYSICAL SOC PI COLLEGE PK PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA SN 1050-2947 J9 PHYS REV A JI Phys. Rev. A PD APR PY 1998 VL 57 IS 4 BP 3084 EP 3104 DI 10.1103/PhysRevA.57.3084 PG 21 WC Optics; Physics, Atomic, Molecular & Chemical SC Optics; Physics GA ZJ698 UT WOS:000073243700103 ER PT J AU Ramaty, R Kozlovsky, B Lingenfelter, R AF Ramaty, R Kozlovsky, B Lingenfelter, R TI Cosmic rays, nuclear gamma rays and the origin of the light elements SO PHYSICS TODAY LA English DT Article ID BORON; STARS; CLOUD; ORION AB Recent observations of Li, Be and B abundances in halo stars formed in the early Galaxy shed new light on the source of cosmic rays, suggesting acceleration from the ejecta of supernovae. C1 Tel Aviv Univ, IL-69978 Tel Aviv, Israel. Univ Calif San Diego, San Diego, CA 92103 USA. RP Ramaty, R (reprint author), NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. NR 34 TC 27 Z9 27 U1 0 U2 1 PU AMER INST PHYSICS PI MELVILLE PA CIRCULATION & FULFILLMENT DIV, 2 HUNTINGTON QUADRANGLE, STE 1 N O 1, MELVILLE, NY 11747-4501 USA SN 0031-9228 J9 PHYS TODAY JI Phys. Today PD APR PY 1998 VL 51 IS 4 BP 30 EP 35 DI 10.1063/1.882257 PG 6 WC Physics, Multidisciplinary SC Physics GA ZF498 UT WOS:000072903500006 ER PT J AU Kondo, Y McCluskey, GE AF Kondo, Y McCluskey, GE TI Frank Bradshaw Wood - Obituary SO PHYSICS TODAY LA English DT Biographical-Item C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Lehigh Univ, Bethlehem, PA 18015 USA. RP Kondo, Y (reprint author), NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. NR 1 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 0031-9228 J9 PHYS TODAY JI Phys. Today PD APR PY 1998 VL 51 IS 4 BP 90 EP 90 DI 10.1063/1.882222 PG 1 WC Physics, Multidisciplinary SC Physics GA ZF498 UT WOS:000072903500019 ER PT J AU Breus, TK Pimenov, KY Izakov, MN Krymskii, AM Luhmann, JG Kliore, AJ AF Breus, TK Pimenov, KY Izakov, MN Krymskii, AM Luhmann, JG Kliore, AJ TI Conditions in the Martian ionosphere/atmosphere from a comparison of a thermospheric model with radio occultation data SO PLANETARY AND SPACE SCIENCE LA English DT Article ID MAGNETIC-FIELD; MARS; IONOSPHERE; TEMPERATURE; ATMOSPHERE; VENUS AB In this paper a possibility to find out some effect of dipole-like intrinsic magnetic field on the plasma scale height at altitudes 180-240 km in the Martian ionosphere, that is above the topside boundary of the chemically controlled region predicted by existing models of the magnetic field-free ionosphere, is examined. It is assumed that the effect could be detected if the relationship between plasma and neutral atmosphere scale heights which is expected under the photochemical equilibrium conditions in the multicomponent atmosphere remains valid at altitude region 180-240 km. The plasma scale heights assessed from the data collected during the Mariner 9 and Viking 1 sessions are statistically analyzed and its trends with the solar zenith angle and F-10.7 flux are evaluated A half of statistically averaged scale height presented as a function of the solar zenith angle (SZA) and F-10.7 flux is compared with the neutral atmosphere scale heights, calculated from the model of Izakov and Roste (1996) for the corresponding SZA and F-10.7 fluxes. Since the conditions for the radio occultation experiments during the Mariner 9 and Viking 1 sessions are different a ratio of assessed plasma scale height to the appropriate neutral atmosphere scale height suits better for comparison than the average scale heights itself does. Employing such ratios the effect of dust content within the lower atmosphere on the thermal balance within the topside atmosphere at altitude 180-200 km is estimated. (C) 1998 Elsevier Science Ltd. All rights reserved. C1 Russian Acad Sci, Space Res Inst, Moscow 117810, Russia. Rostov State Univ, Rostov On Don 344104, Russia. Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA. CALTECH, Jet Prop Lab, Pasadena, CA USA. RP Breus, TK (reprint author), Russian Acad Sci, Space Res Inst, Moscow 117810, Russia. NR 21 TC 15 Z9 17 U1 0 U2 0 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0032-0633 J9 PLANET SPACE SCI JI Planet Space Sci. PD APR PY 1998 VL 46 IS 4 BP 367 EP 376 DI 10.1016/S0032-0633(97)00168-2 PG 10 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZQ708 UT WOS:000073895100003 ER PT J AU Goolish, EM Evans, R Okutake, K Max, R AF Goolish, EM Evans, R Okutake, K Max, R TI Chamber volume requirements for reproduction of the zebrafish Danio rerio SO PROGRESSIVE FISH-CULTURIST LA English DT Article ID BRACHYDANIO-RERIO; VERTEBRATE; BIOLOGY AB The zebrafish or zebra danio Danio (=Brachydanio) rerio has recently become a major vertebrate model for the study of developmental biology, neurobiology, and molecular genetics. As a result, most research universities have now invested considerable resources in the construction of large zebrafish facilities. A key element in the design of these facilities is maximizing the efficiency of available space. Here we report on the effects of aquarium chamber volume on the reproduction of zebrafish, with the objective of identifying the minimal volume required for normal egg production. Six adults (two males and four females) were tested in chamber volumes of 500, 400, 300, 200, and 100 mL. Results were compared with those from a control volume of 3.5 L. Eggs were removed from the test chambers after spawning and incubated in petri dishes at 28 degrees C. Total egg production, percent of eggs hatching, and larval length at 96 h postfertilization were used to evaluate breeding success. Compared with the control, egg production was not significantly affected by reduced aquaria volumes of 500, 400, and 300 mi,. However, mean egg production from a test volume of 200 mt was only 48% of the control egg production (P < 0.05), and at a test volume of 100 mt, egg production was reduced to 26% of the control value (P < 0.005). Percent egg hatch and 96-h larval length were not affected at any test volume. C1 NASA, Lockheed Martin Engn & Sci Co, Space Stn Biol Res Project, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Goolish, EM (reprint author), NASA, Lockheed Martin Engn & Sci Co, Space Stn Biol Res Project, Ames Res Ctr, T20G, Moffett Field, CA 94035 USA. EM egoolish@mail.arc.nasa.gov NR 14 TC 20 Z9 20 U1 0 U2 8 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 APR PY 1998 VL 60 IS 2 BP 127 EP 132 DI 10.1577/1548-8640(1998)060<0127:CVRFRO>2.0.CO;2 PG 6 WC Fisheries SC Fisheries GA ZM982 UT WOS:000073596000008 ER PT J AU Beichman, CA Chester, TJ Cutri, R Lonsdale, CJ Kirkpatrick, D Smith, HE Skrutskie, M AF Beichman, CA Chester, TJ Cutri, R Lonsdale, CJ Kirkpatrick, D Smith, HE Skrutskie, M TI The discovery of a low-redshift, red quasar in the 2MASS prototype survey SO PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF THE PACIFIC LA English DT Article ID ENERGY-DISTRIBUTIONS; DUST; POPULATION; EVOLUTION; BRIGHT; QSOS AB A prototype camera designed to test the observing and data reduction techniques for the 2 Micron All Sky Survey (2MASS) has been used to search for extremely red objects. Selection criteria based on the combination of near-IR and visible light observations help separate the vast majority of ordinary stars from more exotic objects. Visible spectroscopic observations for objects selected using these criteria in an area of just a few tenths of a square degree has resulted in the discovery of a quasar with a redshift of 0.147. The number of quasars expected at K(s) in the 2MASS survey based on typical quasar colors and on the surface density of optically selected samples is similar to 0.17 deg(-2). The 2MASS survey will result in a sample of quasars relatively unbiased by the presence of dust and will allow a reliable determination of whether there is a significant population of quasars with internal dust absorption. C1 CALTECH, Jet Prop Lab, Ctr Infrared Proc & Anal, Pasadena, CA 91109 USA. Univ Calif San Diego, La Jolla, CA 92093 USA. Univ Massachusetts, Amherst, MA 01003 USA. RP Beichman, CA (reprint author), CALTECH, Jet Prop Lab, Ctr Infrared Proc & Anal, Pasadena, CA 91109 USA. NR 23 TC 10 Z9 10 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 1427 E 60TH ST, CHICAGO, IL 60637-2954 USA SN 0004-6280 J9 PUBL ASTRON SOC PAC JI Publ. Astron. Soc. Pac. PD APR PY 1998 VL 110 IS 746 BP 367 EP 373 DI 10.1086/316145 PG 7 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZH807 UT WOS:000073149600001 ER PT J AU Patterson, J Richman, H Kemp, J Mukai, K AF Patterson, J Richman, H Kemp, J Mukai, K TI Rapid oscillations in cataclysmic variables. XIII. WZ Sagittae revisited SO PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF THE PACIFIC LA English DT Article ID X-RAY-EMISSION; DWARF NOVA; OUTBURST; SPECTRA; TIME; SGE AB We report new observations of the dwarf nova WZ Sagittae, showing the return of the 27.87 s oscillation in 1995/1996 high-speed optical light curves. As was true in 1978, the main peak of the power spectrum generally occurred at 27.87 or 25.96 s, with the signals sometimes simultaneously present. Weak transient signals were also seen at 28.20 and 29.69 s. An ASCA X-ray observation showed a significant peak at 27.86 +/- 0.01 s in the 2-6 keV band, which appeared to establish the star's membership as a "DQ Herculis star," in which accretion onto the white dwarf is channeled by a strong magnetic field. The X-ray period is most likely the true white dwarf spin period. However, we certainly do not understand the distribution of power among these various signals of slightly different period. This puzzling multiperiodic structure remains an impediment to full acceptance of WZ Sge as a DQ Her star The star's soft X-ray orbital light curve shows a strong but transient energy-dependent dip around orbital phase 0.7, which is probably due to absorption by an extended gas cloud in which the mass-transfer stream strikes the disk. C1 Columbia Univ, Dept Astron, New York, NY 10027 USA. NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. RP Patterson, J (reprint author), Columbia Univ, Dept Astron, 550 W 120th St, New York, NY 10027 USA. NR 30 TC 60 Z9 60 U1 0 U2 1 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 APR PY 1998 VL 110 IS 746 BP 403 EP 414 DI 10.1086/316152 PG 12 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZH807 UT WOS:000073149600005 ER PT J AU Beichman, CA Chester, TJ Skrutskie, M Low, FJ Gillett, F AF Beichman, CA Chester, TJ Skrutskie, M Low, FJ Gillett, F TI Characteristics of the 2MASS prototype survey SO PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF THE PACIFIC LA English DT Article ID STARS AB The 2 Micron All Sky Survey (2MASS) will catalog over 100,000,000 individual objects, the vast majority of which will be stars of spectral type K and Inter. For many projects it will be important to develop techniques to identify interesting objects within this data set. The combination of near-IR and visible light observations will be a powerful tool for finding objects from brown dwarfs to dust-enshrouded quasars. This paper describes prototype hardware and software systems used as part of the preparation for the 2MASS survey. Three years of observations with prototype systems have produced a database of more than 1 million objects. A companion paper describes the comparison of these data with optical plate material and visible spectroscopic observations resulting in the discovery of a quasar with a redshift of 0.147. C1 CALTECH, Jet Prop Lab, Ctr Infrared Proc & Anal, Pasadena, CA 91125 USA. Univ Massachusetts, Amherst, MA 01003 USA. Univ Arizona, Steward Observ, Tucson, AZ 85721 USA. RP Beichman, CA (reprint author), CALTECH, Jet Prop Lab, Ctr Infrared Proc & Anal, Pasadena, CA 91125 USA. NR 10 TC 33 Z9 33 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 1427 E 60TH ST, CHICAGO, IL 60637-2954 USA SN 0004-6280 J9 PUBL ASTRON SOC PAC JI Publ. Astron. Soc. Pac. PD APR PY 1998 VL 110 IS 746 BP 480 EP 489 DI 10.1086/316144 PG 10 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZH807 UT WOS:000073149600013 ER PT J AU Francis, PN Hignett, P Macke, A AF Francis, PN Hignett, P Macke, A TI The retrieval of cirrus cloud properties from aircraft multi-spectral reflectance measurements during EUCREX'93 SO QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY LA English DT Article DE aircraft measurements; cirrus radiative properties; ice crystal shape; solar radiation ID ICE CRYSTALS; RADIATIVE PROPERTIES; SCATTERING PROPERTIES; OPTICAL-THICKNESS; PHASE; LIGHT; EVOLUTION AB We present details of a scheme for retrieving cirrus cloud optical thickness and effective particle size from nadir-viewing reflectance measurements. Two near-infrared wavelengths are used, one with negligible ice absorption (1.04 mu m) and one with significant ice absorption (1.55 mu m). Four ice crystal shapes are used in the scheme: ice spheres, hexagonal columns, hexagonal plates and randomized polycrystals. We highlight the sensitivity of the retrievals to the shape of the phase function, which follows from the particular ice crystal shape assumed. Five aircraft-based retrievals are presented, all cases occurring during the 1993 intensive field campaign of the European Cloud Radiation Experiment (EUCREX'93). The retrieved effective sizes are compared with the in situ measurements taken from the same cases. In these comparisons, account has to be taken of the fact that (a) in situ replicator data indicate that the presence of small (<100 mu m) ice crystals can have a significant effect on the effective crystal size, and (b) the measured crystal sizes consistently show a systematic decrease with height in all cases, the effective sizes at cloud base being typically two or three times larger than at cloud top. Taking these considerations into account, we conclude that the assumption of polycrystals gives the most consistent agreement with the in situ measurements. C1 Meteorol Res Flight, Meteorol Off, DERA, Farnborough GU14 0LX, Hants, England. NASA, Goddard Inst Space Studies, Greenbelt, MD USA. RP Francis, PN (reprint author), Meteorol Res Flight, Meteorol Off, DERA, Bldg Y46,, Farnborough GU14 0LX, Hants, England. RI Francis, Peter/H-9352-2013 OI Francis, Peter/0000-0002-5869-803X NR 36 TC 54 Z9 54 U1 0 U2 0 PU ROYAL METEOROLOGICAL SOC PI READING PA 104 OXFORD ROAD, READING, BERKS, ENGLAND RG1 7LJ SN 0035-9009 J9 Q J ROY METEOR SOC JI Q. J. R. Meteorol. Soc. PD APR PY 1998 VL 124 IS 548 BP 1273 EP 1291 DI 10.1002/qj.49712454812 PN B PG 19 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA ZT322 UT WOS:000074073200011 ER PT J AU Pawson, S Langematz, U Radek, G Schlese, U Strauch, P AF Pawson, S Langematz, U Radek, G Schlese, U Strauch, P TI The Berlin troposphere-stratosphere-mesosphere GCM: Sensitivity to physical parametrizations SO QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY LA English DT Article DE gravity-wave drag; middle atmosphere; radiation; Rayleigh friction; troposphere-stratosphere interaction ID GENERAL-CIRCULATION MODEL; GRAVITY-WAVE DRAG; WEATHER PREDICTION MODELS; MIDDLE ATMOSPHERE MODEL; ZONAL MEAN CIRCULATION; INTERANNUAL VARIABILITY; ECMWF MODEL; NORTHERN-HEMISPHERE; PLANETARY-WAVES; FLOW AB The sensitivity of a troposphere-stratosphere-mesosphere general-circulation model to changes in the radiation transfer and subgrid-scale drag parametrizations is investigated. The large interannual variability of the middle atmospheric circulation necessitated a methodological approach. A set of 1260-day, perpetual-January integrations was performed; this enabled significant signals to be extracted from the model variability at a reasonable cost. A Rayleigh-friction scheme was used for the mesospheric drag. Reducing its strength led to changes in the zonal-mean structure of the model which resembled the leading mode of variability. Increasing its depth led to significant changes throughout the stratosphere and extending Into the troposphere. Including the diurnal cycle induced no significant changes in the zonal-mean state below the stratopause. Radiation-transfer calculations are not performed fully every time-step; decreasing the frequency of computation from 2 to 12 hours caused marked changes in the mean structure and variability. Including a topographic gravity-wave drag parametrization (TGWD) restored the zonal-mean structure of the 2-hour radiation frequency in the lower stratosphere at the expense of changes in both the temporal variability and the planetary-wave structures. The sensitivity to the frequency of radiation calculations arose from the highly coupled nature of tropical cloud-radiation interactions: the modified structure of the upper tropospheric divergence led to changes in the Rossby-wave source term in the extratropics. The major conclusions are: (1) the natural variability must be properly included in interpretations of the model sensitivity; (2) the adequacy of the tropospheric simulation can profoundly affect the stratosphere; (3) changes in the mesospheric drag can modify the tropospheric circulation; and (4) deficiencies in one parametrization (in this case radiation transfer) can be compensated by other changes (TGWD), but such 'improvements' may not apply to all aspects of the simulation. C1 Free Univ Berlin, D-1000 Berlin, Germany. Deutsch Klimarechenzentrum, Hamburg, Germany. RP Pawson, S (reprint author), NASA, Goddard Space Flight Ctr, Code 916, Greenbelt, MD 20771 USA. EM pawson@polska.gsfc.nasa.gov RI Pawson, Steven/I-1865-2014 OI Pawson, Steven/0000-0003-0200-717X NR 58 TC 25 Z9 25 U1 0 U2 0 PU ROYAL METEOROLOGICAL SOC PI READING PA 104 OXFORD ROAD, READING, BERKS, ENGLAND RG1 7LJ SN 0035-9009 J9 Q J ROY METEOR SOC JI Q. J. R. Meteorol. Soc. PD APR PY 1998 VL 124 IS 548 BP 1343 EP 1371 DI 10.1256/smsqj.54815 PN B PG 29 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA ZT322 UT WOS:000074073200015 ER PT J AU Kouveliotou, C AF Kouveliotou, C TI Finally resolved: The puzzle of gamma bursts SO RECHERCHE LA French DT Article ID RAY BURSTS C1 NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. RP Kouveliotou, C (reprint author), NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. NR 14 TC 0 Z9 0 U1 0 U2 0 PU SOC ED SCIENTIFIQUES PI PARIS 06 PA 57 RUE DE SEINE, 75280 PARIS 06, FRANCE SN 0029-5671 J9 RECHERCHE JI Recherche PD APR PY 1998 IS 308 BP 48 EP 52 PG 5 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA ZF186 UT WOS:000072872300017 ER PT J AU Roger, JC Vermote, EF AF Roger, JC Vermote, EF TI A method to retrieve the reflectivity signature at 3.75 mu m from AVHRR data SO REMOTE SENSING OF ENVIRONMENT LA English DT Article ID DIFFERENCE VEGETATION INDEX; LAND SURFACE-TEMPERATURE; ATMOSPHERIC WATER-VAPOR; SEA-SURFACE; SENEGALESE SAHEL; WINDOW; EMISSIVITY; IDENTIFICATION; CALIBRATION; RESOLUTION AB Global monitoring of land surface properties has primarily relied on the AVHRR red and near-infrared channels through use of the NDVI. The AVHRR Channel 3, centered at 3.75 mu m, has been shown to be sensitive to vegetation on a local scale. A method so separate the reflected and emitted components in this channel has been developed. The 3.75-mu m reflectivity is computed by subtracting the thermal contribution from the total signal and dividing the remaining signal component by atmospheric transmission and solar irradiance. The thermal contribution is estimated by using thermal infrared Channels 4 and 5 as well as NDVI to estimate infrared surface emissivities. The atmospheric transmission is computed with MODTRAN2 and uses integrated water vapor derived from the Split Window Technique. The formula derived are validated over ocean using sun glint observations and land using the FIFE-87 data set. Despite the uncertainties inherent to the procedure we adopted quantitative use of the derived reflectance at 3.75 mu m appears possible. Published by Elsevier Science Inc., 1998. C1 Univ Maryland, Dept Geog, College Pk, MD 20742 USA. RP Vermote, EF (reprint author), NASA, Goddard Space Flight Ctr, Code 923, Greenbelt, MD 20771 USA. RI Vermote, Eric/K-3733-2012 NR 38 TC 25 Z9 26 U1 0 U2 2 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 APR PY 1998 VL 64 IS 1 BP 103 EP 114 DI 10.1016/S0034-4257(97)00173-9 PG 12 WC Environmental Sciences; Remote Sensing; Imaging Science & Photographic Technology SC Environmental Sciences & Ecology; Remote Sensing; Imaging Science & Photographic Technology GA ZB754 UT WOS:000072504400009 ER PT J AU Brasunas, JC Cushman, GM AF Brasunas, JC Cushman, GM TI A simple scanning mirror mechanism for a Fourier transform spectrometer SO REVIEW OF SCIENTIFIC INSTRUMENTS LA English DT Article AB We present a simple scanning mirror mechanism for a Fourier transform spectrometer, consisting of a voice coil actuator, a ball-bearing slide, and a single cube corner mirror or retroreflector. The use of a single cube corner reduces significantly the sensitivity of the Fourier transform spectrometer to the tilt of its moving mirror, enabling the simple mechanism. With simple velocity feedback using a linear velocity transducer, we achieve a scan speed stability of 2%-5% (root-mean-square) for scan speeds from 40 to 440 mu m/s for a travel of 2.2 cm, corresponding to a spectral resolution of 0.06 cm(-1). Fringe amplitude stability is about 5%. This scan mechanism was operated at standard temperature and pressure, but the relatively minute amount of lubricant in the ball-bearing slide may indicate possible operation under vacuum and/or cryogenic conditions. (C) 1998 American Institute of Physics. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Hughes STX Corp, Lanham, MD 20706 USA. RP Brasunas, JC (reprint author), NASA, Goddard Space Flight Ctr, Code 693, Greenbelt, MD 20771 USA. RI brasunas, john/I-2798-2013 NR 6 TC 1 Z9 1 U1 2 U2 3 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 APR PY 1998 VL 69 IS 4 BP 1637 EP 1641 DI 10.1063/1.1148820 PG 5 WC Instruments & Instrumentation; Physics, Applied SC Instruments & Instrumentation; Physics GA ZJ144 UT WOS:000073183900013 ER PT J AU Koppel, LN Marshall, JR AF Koppel, LN Marshall, JR TI A miniature metal-ceramic x-ray source for spacecraft instrumentation SO REVIEW OF SCIENTIFIC INSTRUMENTS LA English DT Article AB Definitive mineralogical identification of materials with x-ray diffraction and fluorescence on remote planetary probes requires the development of a rugged miniature x-ray source that complies with the mass, power, thermal, and electrical management constraints imposed by space missions. Conventional x-ray tubes are generally fragile, glass-envelope designs with heat-sensitive seals. They are too brittle and bulky for planetary missions, and usually require cumbersome and power-consuming cooling systems. Here we describe the development of a novel, rugged miniature x-ray source employing a ceramic BeO substrate upon which a metal target material is deposited. Conventional thermionic emission and high-voltage acceleration of electrons to strike the metal target material produce an x-ray yield comparable to conventional x-ray tubes. Thermal management of the x-ray source is achieved with the excellent heat transport properties of the BeO target substrate coupled with a passive heatpipe. (C) 1998 American Institute of Physics. C1 Oryx Technol Corp, Fremont, CA 94538 USA. NASA, Ames Res Ctr, SETI Inst, Moffett Field, CA 94035 USA. RP Koppel, LN (reprint author), Oryx Technol Corp, Fremont, CA 94538 USA. NR 7 TC 4 Z9 4 U1 1 U2 2 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 APR PY 1998 VL 69 IS 4 BP 1893 EP 1897 DI 10.1063/1.1148860 PG 5 WC Instruments & Instrumentation; Physics, Applied SC Instruments & Instrumentation; Physics GA ZJ144 UT WOS:000073183900056 PM 11542818 ER PT J AU Krainsky, IL Lesny, GG AF Krainsky, IL Lesny, GG TI Simple device for monitoring secondary electron emission of materials in the pulse mode SO REVIEW OF SCIENTIFIC INSTRUMENTS LA English DT Article AB A simple device for simultaneously measuring the secondary electron emission coefficient a and the primary current in the pulse mode has been built. It allows convenient monitoring of these parameters for either conductive or insulating materials. C1 NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. RP Krainsky, IL (reprint author), NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. NR 3 TC 5 Z9 5 U1 1 U2 4 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 APR PY 1998 VL 69 IS 4 BP 1916 EP 1917 DI 10.1063/1.1149170 PG 2 WC Instruments & Instrumentation; Physics, Applied SC Instruments & Instrumentation; Physics GA ZJ144 UT WOS:000073183900061 ER PT J AU Chang, ES Deming, D AF Chang, ES Deming, D TI Accurate determination of electron densities in active and quiescent prominences: The mid-infrared advantage SO SOLAR PHYSICS LA English DT Article ID HYDROGEN LINES; PROFILES; SPECTRUM; MICRONS AB We have analyzed all lines in the MIR (8 to 20 micron) spectra of a quiescent and two time-frames of an active prominence. In the quiescent prominence, in addition to those lines found by Zirker (1985), we have identified a higher excitation hydrogen line and two helium recombination lines. Accounting for instrumental broadening, we can further separate out the Doppler and the Stark contributions to the line width. The former yields maximum temperatures of 6200 K, 34 000 K and 12 000 K and the latter electric field strengths of 7, 17, and 10 V cm(-1) for the above prominences, respectively. We show that these electric fields when divided by 2.2 are equal to the normal electric field in Holtsmark's quasi-static Stark broadening theory. Hence, we obtain electron densities of N-e=2.4(0.3), 9.1(1.2), and 5.5(0.6) in units of 10 cm(-3) respectively. Using the same assumptions as made by Zirker, namely, (1) the strongest line (7-6) is optically thin, (2) the population of the lower level (n = 6) is determined by direct radiative recombination and photo-ionization, (3) the equality of proton and electron densities, and (4) the thickness of the prominence is at least 10(8) cm, we derive a new inequality, N-e less than or equal to 1.83 x 10(8)T(0.75)e(-2195/T). Substituting our maximum temperatures into the right-hand side, we find upper bound N-e values of 9, 43, and 30 in the same units as above. These upper bound values are comfortably higher than our measurement, unlike those of Zirker's derived from the same set of assumptions. We have also observed the helium recombination spectrum which has been postulated by Tandberg-Hanssen as one of three possible ways of equilibrating the triplet/singlet ratio. Surprisingly, it is present in the quiescent as well as in the active prominence. We show that no meaningful values can be found for the turbulent velocities by combining the helium with the hydrogen line widths. C1 Univ Massachusetts, Dept Phys & Astron, Amherst, MA 01003 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Chang, ES (reprint author), Univ Massachusetts, Dept Phys & Astron, Amherst, MA 01003 USA. NR 31 TC 7 Z9 7 U1 0 U2 0 PU KLUWER ACADEMIC PUBL PI DORDRECHT PA SPUIBOULEVARD 50, PO BOX 17, 3300 AA DORDRECHT, NETHERLANDS SN 0038-0938 J9 SOL PHYS JI Sol. Phys. PD APR PY 1998 VL 179 IS 1 BP 89 EP 114 DI 10.1023/A:1005098011886 PG 26 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZH383 UT WOS:000073103000006 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 111358 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 20770 USA. Goddard Space Flight Ctr, Greenbelt, MD 20770 USA. RP Hoyt, DV (reprint author), Hughes STX, 7701 Greenbelt Rd, Greenbelt, MD 20770 USA. NR 11 TC 281 Z9 288 U1 0 U2 14 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 APR PY 1998 VL 179 IS 1 BP 189 EP 219 DI 10.1023/A:1005007527816 PG 31 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZH383 UT WOS:000073103000012 ER PT J AU Steigman, G Hata, N Felten, JE AF Steigman, G Hata, N Felten, JE TI Non-BBN constraints on the key cosmological parameters SO SPACE SCIENCE REVIEWS LA English DT Review DE baryon-to-photon ratio; universal matter density; Hubble parameter ID DARK-MATTER MODELS; BIG-BANG NUCLEOSYNTHESIS; DEUTERIUM ABUNDANCE; GALAXY CLUSTERS; BARYON CONTENT; AGE; EVOLUTION; CONSTANT; SPECTRUM; CONFLICT AB Since the baryon-to-photon ratio eta(10) is in some doubt at present, we ignore the constraints on eta(10) from big bang nucleosynthesis (BBN) and fit the three key cosmological parameters (h, Ohm(m), eta(10)) to four other observational constraints: Hubble parameter (h(o)), age of the universe (t(o)), cluster gas (baryon) fraction (f(o) f(G)h(3/2)), and effective shape parameter (Gamma(o)). We consider open and flat CDM models and flat Lambda CDM models, testing goodness of fit and drawing confidence regions by the Delta chi(2) method. CDM models with Omega(M) = 1 (SCDM models) are accepted only because we allow a large error on h(o), permitting h < 0.5. Open CDM models are accepted only for Omega(M) greater than or similar to 0.4. Lambda CDM models give similar results. In all of these models, large eta(10)(greater than or similar to 6) is favored strongly over small eta(10)(less than or similar to 2), supporting reports of low deuterium abundances on some QSO lines of sight, and suggesting that observational determinations of primordial He-4 may be contaminated by systematic errors. Only if we drop the crucial Gamma(o) constraint are much lower values of Ohm(M) and eta(10) permitted. C1 Ohio State Univ, Dept Phys, Columbus, OH 43210 USA. Ohio State Univ, Dept Astron, Columbus, OH 43210 USA. Inst Adv Study, Princeton, NJ 08540 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Ohio State Univ, Dept Phys, 174 W 18th Ave, Columbus, OH 43210 USA. NR 51 TC 4 Z9 4 U1 0 U2 0 PU SPRINGER PI DORDRECHT PA VAN GODEWIJCKSTRAAT 30, 3311 GZ DORDRECHT, NETHERLANDS SN 0038-6308 EI 1572-9672 J9 SPACE SCI REV JI Space Sci. Rev. PD APR PY 1998 VL 84 IS 1-2 BP 31 EP 42 DI 10.1023/A:1005030125733 PG 12 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 112AU UT WOS:000075472200004 ER PT J AU Mahaffy, PR Donahue, TM Atreya, SK Owen, TC Niemann, HB AF Mahaffy, PR Donahue, TM Atreya, SK Owen, TC Niemann, HB TI Galileo probe measurements of D/H and He-3/He-4 in Jupiter's atmosphere SO SPACE SCIENCE REVIEWS LA English DT Review ID LOCAL INTERSTELLAR CLOUD; HIGH DEUTERIUM ABUNDANCE; MASS-SPECTROMETER; GAS-COMPOSITION; SOLAR; HELIUM; RATIO; ULYSSES; WATER; SWICS AB The Galileo Probe Mass Spectrometer measurements in the atmosphere of Jupiter give D/H = (2.6 +/- 0.7) x 10(-5) He-3/He-4 = (1.66 +/- 0.05) x 10(-4) These ratios supercede earlier results by Niemann et al. (1996) and are based on a reevaluation of the instrument response at high count rates and a more detailed study of the contributions of different species to the mass peak at 3 amu. The D/H ratio is consistent with Voyager and ground based data and recent spectroscopic and solar wind (SW) values obtained from the Infrared Spectroscopic Observatory (1SO) and Ulysses. The He-3/He-4 ratio is higher than that found in meteoritic gases (1.5 +/- 0.3) x 10(-4). The Galileo result for D/H when compared with that for hydrogen in the local interstellar medium (1.6 +/- 0.12) x 10(-5) implies a small decrease in D/H in this part of the universe during the past 4.55 billion years. Thus, it tends to support small values of primordial D/H - in the range of several times 10(-5) rather than several times 10(-4). These results are also quite consistent with no change in (D + He-3)/H during the past 4.55 billion years in this part of our galaxy. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Michigan, Dept Atmospher Ocean & Space Sci, Ann Arbor, MI 48109 USA. Univ Hawaii, Inst Astron, Honolulu, HI 96822 USA. RP NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RI Mahaffy, Paul/E-4609-2012 NR 32 TC 140 Z9 140 U1 2 U2 8 PU SPRINGER PI DORDRECHT PA VAN GODEWIJCKSTRAAT 30, 3311 GZ DORDRECHT, NETHERLANDS SN 0038-6308 EI 1572-9672 J9 SPACE SCI REV JI Space Sci. Rev. PD APR PY 1998 VL 84 IS 1-2 BP 251 EP 263 DI 10.1023/A:1005091806594 PG 13 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 112AU UT WOS:000075472200026 ER PT J AU Rosi, M Bauschlicher, CW Chertihin, GV Andrews, L AF Rosi, M Bauschlicher, CW Chertihin, GV Andrews, L TI The vibrational frequencies of CaO2, ScO2, and TiO2: a comparison of theoretical methods SO THEORETICAL CHEMISTRY ACCOUNTS LA English DT Article DE harmonic frequencies; density functional theory; coupled cluster singles and doubles ID GAUSSIAN-BASIS SETS; COUPLED-CLUSTER THEORY; ORBITAL BASIS-SETS; THIRD-ROW ATOMS; MOLECULAR WAVEFUNCTIONS; ELECTRON CORRELATION; CORRELATION-ENERGY; INFRARED-SPECTRA; WAVE-FUNCTIONS; 1ST-ROW AB The vibrational frequencies of several states of CaO2, ScO2, and TiO2 are computed using density functional theory (DFT), the Hartree-Fock approach, second-order Moller-Plesset perturbation theory (MP2), and the complete-active-space self-consistent-field theory. Three different functionals are used in the DFT calculations, including two hybrid functionals. The coupled cluster singles and doubles approach including the effect of connected triples, determined using perturbation theory, is applied to selected stales. The Becke-Perdew 86 functional appears to be the most cost-effective method of choice, although even this functional does not perform well for one stale of CaO2. The MP2 approach is significantly inferior to the DFT approaches. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Univ Virginia, Dept Chem, Charlottesville, VA 22901 USA. Univ Perugia, Dept Chem, I-06100 Perugia, Italy. RP Bauschlicher, CW (reprint author), NASA, Ames Res Ctr, STC-230-3, Moffett Field, CA 94035 USA. RI Rosi, Marzio/L-5748-2015 OI Rosi, Marzio/0000-0002-1264-3877 NR 36 TC 31 Z9 31 U1 1 U2 12 PU SPRINGER VERLAG PI NEW YORK PA 175 FIFTH AVE, NEW YORK, NY 10010 USA SN 1432-881X J9 THEOR CHEM ACC JI Theor. Chem. Acc. PD APR PY 1998 VL 99 IS 2 BP 106 EP 112 DI 10.1007/s002140050311 PG 7 WC Chemistry, Physical SC Chemistry GA ZL817 UT WOS:000073474500006 ER PT J AU Bozzolo, G Ferrante, J AF Bozzolo, G Ferrante, J TI Modelling of thin films via a semiempirical method SO THIN SOLID FILMS LA English DT Article; Proceedings Paper CT 5th European Vacuum Conference (EVC 5) / 10th International Conference on Thin Films (ICTF 10) CY SEP 23-27, 1996 CL UNIV SALAMANCA, SALAMANCA, SPAIN SP Spanish Vacuum Soc, Int Union Vacuum Sci Technol & Applicat, Vacuum Sci & Thin Film Div HO UNIV SALAMANCA DE thin films; semiempirical method; BFS (Bozzolo-Ferrante-Smith) method ID NI(110); GROWTH; AU AB Computer modelling of atomic processes on surfaces and bulk materials has seen great progress in the last decade due to the advent of semiempirical methods. In this work, we extend the scope of these techniques to deal with thin films, an area where the progress in large scale atomistic modelling lags behind similar process in bulk alloy design and surface structure analysis. These techniques rely on solid theoretical background and provide the computational economy that allows for the treatment of complex problems. We discuss one of these techniques, the BFS (Bozzolo-Ferrante-Smith) method for alloys, and illustrate its application to the problem of thin film formation. In particular, we show modelling results on the formation of binary and ternary films of Ni and Al with either Ti or Cr alloying additions. Differences and similarities with the corresponding ternary bulk alloys are discussed. Radical changes in layer-by-layer composition are observed in both cases. While Ti additions induce the formation of a particular ternary phase close to the (110) surface, Cr additions result in the formation of an alpha-Cr precipitate close to the surface in addition to the changes in surface composition. (C) 1998 Elsevier Science S.A. C1 Ohio Aerosp Inst, Cleveland, OH 44142 USA. NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. RP Bozzolo, G (reprint author), Ohio Aerosp Inst, 22800 Cedar Point Rd, Cleveland, OH 44142 USA. NR 9 TC 0 Z9 0 U1 0 U2 1 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 APR 1 PY 1998 VL 317 IS 1-2 BP 1 EP 5 DI 10.1016/S0040-6090(97)00651-2 PG 5 WC Materials Science, Multidisciplinary; Materials Science, Coatings & Films; Physics, Applied; Physics, Condensed Matter SC Materials Science; Physics GA ZX454 UT WOS:000074517700002 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 Ballistic-electron-emission microscopy and spectroscopy of metal/GaN interfaces SO APPLIED PHYSICS LETTERS LA English DT Article ID GAN AB Ballistic-electron-emission microscopy (BEEM) spectroscopy and imaging have been applied to the Au/GaN interface. In contrast to previous BEEM measurements, spectra yield a Schottky barrier height of 1.04 eV that agrees well with the highest values measured by conventional methods. A second threshold is observed in the spectra at about 0.2 V above the first threshold. Imaging of the Au/GaN interface reveals transmission in nearly all areas, although the magnitude is small and varies by an order of magnitude. BEEM of other GaN material shows no transmission in any areas. (C) 1998 American Institute of Physics. 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 13 TC 3 Z9 3 U1 1 U2 5 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 MAR 30 PY 1998 VL 72 IS 13 BP 1590 EP 1592 DI 10.1063/1.121124 PG 3 WC Physics, Applied SC Physics GA ZE124 UT WOS:000072760100023 ER PT J AU Tippelt, A Jahnke, L Poralla, K AF Tippelt, A Jahnke, L Poralla, K TI Squalene-hopene cyclase from Methylococcus capsulatus (Bath): a bacterium producing hopanoids and steroids SO BIOCHIMICA ET BIOPHYSICA ACTA-LIPIDS AND LIPID METABOLISM LA English DT Article DE triterpene; hopanoid; squalene-hopene cyclase; (Methylococcus capsulatus) ID ENCODING LANOSTEROL SYNTHASE; CELL-FREE SYSTEM; SACCHAROMYCES-CEREVISIAE; OXIDOSQUALENE CYCLASE; ZYMOMONAS-MOBILIS; MOLECULAR-CLONING; ESCHERICHIA-COLI; METHYL STEROL; ACTIVE-SITE; GENE AB We report the cloning and characterisation of the Methylococcus capsulatus shc gene, which encodes the squalene-hopene cyclase (SHC). This enzyme catalyses the complex cyclization of squalene to the pentacyclic triterpene skeleton of hopanoids and represents the key reaction in this biosynthesis. Using a combination of PCR amplification and DNA hybridization, two overlapping 2.6 kb PstI and 3.3 kb SalI DNA fragments were cloned bearing a 1962 bp open reading frame encoding a 74 kDa protein with 654 amino acids and a predicted isoelectric point at about pH 6.3. The deduced amino acid sequence of the M. capsulatus shc gene showed significant similarity to known prokaryotic SHCs and to a lesser degree to the related eukaryotic oxidosqualene cyclases (OSCs). Like other triterpene cyclases, the M. capsulatus SHC contains seven so-called QW-motifs as well as an aspartate-rich domain. The recombinant M. capsulatus SHC was expressed in Escherichia coli and in vitro activity of the recombinant cyclase was demonstrated using crude cell-free lysate or solubilized membrane preparation. The cyclization products hop-22-ene and hopan-22-ol (diplopterol) were identified by GC and GC-MS. (C) 1998 Elsevier Science B.V. C1 Univ Tubingen, D-72076 Tubingen, Germany. NASA, Ames Res Ctr, Exobiol Branch, Moffett Field, CA 94035 USA. RP Poralla, K (reprint author), Univ Tubingen, Morgenstelle 28, D-72076 Tubingen, Germany. EM poralla@uni.tuebingen.de NR 50 TC 34 Z9 34 U1 0 U2 9 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0005-2760 J9 BBA-LIPID LIPID MET JI Biochim. Biophys. Acta-Lipids Lipid Metab. PD MAR 30 PY 1998 VL 1391 IS 2 BP 223 EP 232 DI 10.1016/S0005-2760(97)00212-9 PG 10 WC Biochemistry & Molecular Biology; Biophysics SC Biochemistry & Molecular Biology; Biophysics GA ZJ224 UT WOS:000073191900010 PM 9555026 ER PT J AU Ratcliff, JT Bercovici, D Schubert, G Kroenke, LW AF Ratcliff, JT Bercovici, D Schubert, G Kroenke, LW TI Mantle plume heads and the initiation of plate tectonic reorganizations SO EARTH AND PLANETARY SCIENCE LETTERS LA English DT Article DE mantle plumes; Pacific Plate; flood basalts; Ontong Java Plateau; plate tectonics; movement; viscosity; numerical analysis; CFD ID FLOOD BASALTS; PACIFIC PLATE; SURFACE PLATES; FRACTURE-ZONE; CONVECTION; VISCOSITY; RECONSTRUCTIONS; DYNAMICS; MODEL; FLUID AB We present results of numerical simulations which examine the plausibility of a reorganization of plate motions brought about by the interaction of a hot, low-viscosity plume head with the underside of a tectonic plate. A numerical model of highly viscous fluid flow driven by thermal buoyancy is employed to examine the interaction of mantle plumes with surface plates in a two-dimensional cartesian geometry. Plate-like boundary conditions applied to the upper surface consist of a large active plate with fixed speed plus a smaller passive plate whose speed and direction of motion are permitted to react to tractions induced by the underlying mantle how (driven by the active plate). The passive plate is also subject to applied end-loads intended to simulate incipient subduction. The mantle plume is initiated with a hot patch on the lower boundary, and viscosity varies with temperature following an Arrhenius rheology. The calculations, performed with fixed aspect ratio (4 x 1) and fixed Rayleigh number (Ra = 10(6), where Ra refers to the strength of the starting plume), were found to depend on three parameters: the strength of the viscosity variation, the size of the applied end-load, and the speed of the active plate. These calculations indicate that plate motions can be sharply influenced by the lubricating effects of mantle plume heads even to the point of causing a reversal in the direction of plate motion. (C) 1998 Elsevier Science B.V. All rights reserved. C1 Univ Calif Los Angeles, Dept Earth & Space Sci, Los Angeles, CA 90095 USA. Univ Hawaii, Sch Ocean & Earth Sci & Technol, Dept Geol & Geophys, Honolulu, HI 96822 USA. Univ Calif Los Angeles, Inst Geophys & Planetary Phys, Los Angeles, CA 90095 USA. RP Ratcliff, JT (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr,MS 238-332, Pasadena, CA 91109 USA. EM todd.ratcliff@jp.nasa.gov RI Bercovici, David/B-1676-2008; Wright, Dawn/A-4518-2011 OI Wright, Dawn/0000-0002-2997-7611 NR 39 TC 14 Z9 14 U1 0 U2 3 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0012-821X J9 EARTH PLANET SC LETT JI Earth Planet. Sci. Lett. PD MAR 30 PY 1998 VL 156 IS 3-4 BP 195 EP 207 DI 10.1016/S0012-821X(98)00016-8 PG 13 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA ZL370 UT WOS:000073426100006 ER PT J AU Ricca, A Bauschlicher, CW AF Ricca, A Bauschlicher, CW TI Accurate heats of formation for PHn, PHn+, and PHn- SO CHEMICAL PHYSICS LETTERS LA English DT Article ID GAUSSIAN-BASIS SETS; CORRELATED MOLECULAR CALCULATIONS; COUPLED-CLUSTER THEORY; WAVE-FUNCTIONS; ELECTRON CORRELATION; BOND-ENERGIES; 1ST-ROW AB Accurate heats of formation are computed for PHn and PHn+, for n = 1-3, and for PHn-, for n = 1-2. The geometries and vibrational frequencies are determined at the B3LYP level of theory. The energetics are determined at the CCSD(T) level of theory. Basis set limit values are obtained by extrapolation. Spin-orbit effects are taken from experiment. The temperature dependence of the heat of formation, heat capacity, and entropy are computed for the temperature range 300 to 4000 K and fit to a polynomial. (C) 1998 Elsevier Science B.V. C1 Stanford Univ, Dept Chem Engn, Stanford, CA 94305 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Ricca, A (reprint author), Stanford Univ, Dept Chem Engn, Stauffer III,381 North South Mall, Stanford, CA 94305 USA. NR 28 TC 11 Z9 11 U1 0 U2 0 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 MAR 27 PY 1998 VL 285 IS 5-6 BP 455 EP 458 DI 10.1016/S0009-2614(97)01468-1 PG 4 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA ZF809 UT WOS:000072935400025 ER PT J AU Karpinsky, OG Shelimova, LE Kretova, MA Fleurial, JP AF Karpinsky, OG Shelimova, LE Kretova, MA Fleurial, JP TI An x-ray study of the mixed-layered compounds of (GeTe)(n)(Sb2Te3)(m) homologous series SO JOURNAL OF ALLOYS AND COMPOUNDS LA English DT Article DE X-ray diffraction; crystal structure; germanium; tellurium AB Single crystals of the Ge2Sb2Te5 (phase D), GeSb2Te4 (phase B) and GeSb4Te7 (phase C) ternary mixed-layered compounds have been investigated by X-ray diffraction. A dependence of the (c/N) average distance between two adjacent atomic layers (N is the number of layers per unit cell) on the cation-to-anion ratio for the ternary phases and the GrTe and Sb2Te3 binary compounds has been analyzed. It is found that the dependence is linear. Based on the dependence, the c lattice parameters were also calculated for other members of the (GeTe)(n) (Sb2Te3)(m) homologous series in the quasi-binary GeTe-Sb2Te3 system for which experimental data were not reported, The GeSb2Te4 (B) crystal structure was determined using an automatic diffractometer 'Syntex P (1) over bar'. The results obtained indicate that Gr and Sb atoms are statistically distributed in octahedral interstices to form mixed-cation layers. The Ge3Sb2Te6 (A) compound with 33-layer structure (c=6.2234(5) nm) and Ge4Sb2Te7 (F) one with 39-layer structure (c=7.279(1) nm) have been found in the GeTe-Sb2Te3 system by X-ray diffraction. The Ge4Sb2Te7 compound is present as a miner admixture to the A phase. (C) 1998 Elsevier Science S.A. C1 AA Baikov Met Inst, Moscow 117911, Russia. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Shelimova, LE (reprint author), AA Baikov Met Inst, Leninskii Prospect 49, Moscow 117911, Russia. NR 28 TC 62 Z9 62 U1 3 U2 26 PU ELSEVIER SCIENCE SA PI LAUSANNE PA PO BOX 564, 1001 LAUSANNE, SWITZERLAND SN 0925-8388 J9 J ALLOY COMPD JI J. Alloy. Compd. PD MAR 27 PY 1998 VL 268 IS 1-2 BP 112 EP 117 DI 10.1016/S0925-8388(97)00625-7 PG 6 WC Chemistry, Physical; Materials Science, Multidisciplinary; Metallurgy & Metallurgical Engineering SC Chemistry; Materials Science; Metallurgy & Metallurgical Engineering GA ZH125 UT WOS:000073075200021 ER PT J AU Rind, D AF Rind, D TI Latitudinal temperature gradients and climate change SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Review ID SEA-SURFACE TEMPERATURE; ATMOSPHERIC CARBON-DIOXIDE; LAST GLACIAL MAXIMUM; MIDDLE PLIOCENE CLIMATE; ICE CORE RECORDS; NORTH-ATLANTIC; UNITED-STATES; JOINT INVESTIGATIONS; PLEISTOCENE CLIMATE; MODEL SENSITIVITY AB The effects of a change in the latitudinal sea surface temperature gradient are investigated in several GCM experiments. Sea surface temperatures are increased/decreased in the tropics and polar regions,; with little change in the global average surface air temperature. Then the experiments are repeated with colder/warmer conditions globally. Expectations generated from these runs are compared with the resulting climate changes in a doubled CO2 experiment and show overall agreement. Results show that the latitudinal temperature gradient governs the Hadley cell intensity, eddy energy properties; and eddy transports other than latent heat. The global mean temperature governs moisture and cloud cover, Hadley cell extent, and total rainfall. The degree of tropical and subtropical moisture changes depend on both the latitudinal gradient and the mean temperature. The Aleutian low is particularly sensitive to gradient changes, while the Icelandic low (and therefore the Greenland ice core region) is not, possibly due to orographically induced constraints in the North Atlantic. The results are then compared with paleoclimate evidence to deduce what has happened to latitudinal gradients and climate in the past. It is estimated that low-latitude temperature gradients similar to today's may have occurred in the Mesozoic and in the Little Ice Age; reduced gradients were more likely in the Pliocene, Eocene, Younger Dryas, and Last Glacial Maximum. At higher latitudes, warm climates likely had reduced temperature gradients, and cold climates increased gradients. Observed equator to pole gradients were increased in the 1980s relative to the 1950s, and the simulated climate changes consistent with observations include warming of Alaska and Asia, drying in the subtropics, and moisture variability in the United States. Assignment of causes to past latitudinal gradient changes is problematic due to uncertainties concerning CO2 and ocean heat transports, but tentative conclusions based on this analysis support the likelihood of a future, higher-CO2 climate exhibiting a large low-latitude gradient and ample precipitation at middle latitudes. C1 NASA, Goddard Space Flight Ctr, Inst Space Studies, New York, NY 10025 USA. RP Rind, D (reprint author), NASA, Goddard Space Flight Ctr, Inst Space Studies, 2880 Broadway, New York, NY 10025 USA. EM drind@giss.nasa.gov NR 111 TC 107 Z9 107 U1 2 U2 25 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 MAR 27 PY 1998 VL 103 IS D6 BP 5943 EP 5971 DI 10.1029/97JD03649 PG 29 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA ZD911 UT WOS:000072737800002 ER PT J AU Choi, W Grant, WB Park, JH Lee, KM Lee, H Russell, JM AF Choi, W Grant, WB Park, JH Lee, KM Lee, H Russell, JM TI Role of the quasi-biennial oscillation in the transport of aerosols from the tropical stratospheric reservoir to midlatitudes SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID HALOGEN OCCULTATION EXPERIMENT; GENERAL-CIRCULATION; OZONE; CLIMATOLOGY AB The temporal evolution of the stratospheric aerosol distribution in the tropical stratospheric reservoir after the eruption of Mount Pinatubo was observed from 1992 to 1995 by the HALOE instrument on the UARS satellite. Since the spatial gradient of aerosol loading is large at the boundaries of the tropical stratospheric reservoir due to the volcanic aerosols, the effect of the meridional circulation on the distribution is seen clearly. The mechanism for dispersal of aerosol in the lower stratosphere from the tropics into midlatitudes strongly depends on the phase of the equatorial zonal wind. The time-latitude crosssections of the normalized distribution of aerosol on isentropic surfaces are used to observe the equatorial variation as well as change in meridional dispersal during the quasibiennial period. Observed tropical stratospheric winds are used with a simple analytical dynamical model to examine transport processes of tracers from the tropics during several phases of the quasibiennial oscillation (QBO) from 1992 to 1995. The Lagrangian meridional circulation in the tropics is consistent with the vertical and meridional velocities correlated with the QBO in the zonal wind. We find that vertical motion plays a crucial role in vertical and subsequent meridional transport. The pattern of meridional divergence derived from the vertical velocity is closely related to the observed HALOE aerosol distributions and their temporal development in the equatorial region. The westerly (easterly) shear phase of the QBO is associated with sinking (rising) motions at the equator and subsequent poleward (equatorward) transport in the lower stratosphere. C1 NASA, Langley Res Ctr, Div Atmospher Sci, Hampton, VA 23681 USA. Kyungpook Natl Univ, Dept Astron & Atmospher Sci, Taegu 702701, South Korea. Hampton Univ, Dept Phys, Ctr Atmospher Sci, Hampton, VA 23668 USA. Seoul Natl Univ, Dept Atmospher Sci, Seoul, South Korea. RP Grant, WB (reprint author), NASA, Langley Res Ctr, Div Atmospher Sci, MS 401A, Hampton, VA 23681 USA. EM wchoi@plaza.snu.ac.kr; w.b.grant@larc.nasa.gov RI Grant, William/B-8311-2009 OI Grant, William/0000-0002-1439-3285 NR 30 TC 22 Z9 24 U1 0 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD MAR 27 PY 1998 VL 103 IS D6 BP 6033 EP 6042 DI 10.1029/97JD03118 PG 10 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA ZD911 UT WOS:000072737800007 ER PT J AU Doran, JC Hubbe, JM Liljegren, JC Shaw, WJ Collatz, GJ Cook, DR Hart, RL AF Doran, JC Hubbe, JM Liljegren, JC Shaw, WJ Collatz, GJ Cook, DR Hart, RL TI A technique for determining the spatial and temporal distributions of surface fluxes of heat and moisture over the Southern Great Plains Cloud and Radiation Testbed SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID PARAMETERIZATION SIB2; STOMATAL CONDUCTANCE; ATMOSPHERIC GCMS; BOUNDARY-LAYER; LAND; MODEL; PHOTOSYNTHESIS; EXCHANGE; PROJECT; CLIMATE AB Land surface parameterization schemes such as the Simple Biosphere Model (SiB2) have found considerable use in climate simulation models, where they provide lower boundary conditions in the form of surface sensible and latent heat fluxes. A methodology is described to apply models of this type at high resolution, using data from the Department of Energy's Cloud and Radiation Testbed in Oklahoma and Kansas, to determine the spatial variations of heat fluxes over the domain and to determine area-weighted flux averages for use in single-column model studies. Data from a dense array of meteorological instruments are interpolated to provide the wind, temperature, vapor pressure, radiation, and precipitation values needed by SiB2. The state of the vegetation is characterized through the use of the normalized difference vegetation index determined from satellites. The performance of the SiB2 model is evaluated by comparing its predictions with flux data from seven Bowen ratio stations over a B-month period. No tuning of the model parameters for individual sites was allowed during the simulation period. Although there is significant scatter in the results, the performance of the model was generally good, accounting for over 60% of the variance in sensible heat fluxes and over 80% of the variance in latent heat fluxes'. The model was therefore used to prepare "flux maps" for the study area. These maps show large contrasts in sensible and latent heat fluxes associated primarily with differences in vegetation cover and soil moisture over the site. The differences in vegetation, in turn, result from the planting of large areas with winter wheat, which leaves some regions nearly devoid of actively growing vegetation in midsummer, while other areas are still covered with thriving crops or naturally occurring vegetation. Implications for determining large-area averages of fluxes from a limited number of measurement sites are discussed. C1 Pacific NW Lab, Richland, WA 99352 USA. NASA, Goddard Space Flight Ctr, Biospher Sci Branch, Greenbelt, MD 20771 USA. Argonne Natl Lab, Div Environm Res, Argonne, IL 60439 USA. Iowa State Univ, IPRT, Ctr Nondestruct Evaluat, Ames, IA 50011 USA. RP Doran, JC (reprint author), Pacific NW Lab, POB 999,MSIN K9-30, Richland, WA 99352 USA. EM jc_doran@pnl.gov; jm_hubbe@pnl.gov; jim@ultra1.cnde.iastate.edu; will.shaw@pnl.gov; jcollatz@biome.gsfc.nasa.gov; cook@anler.er.anl.gov; hart@anler.er.anl.gov RI collatz, george/D-5381-2012 NR 23 TC 27 Z9 30 U1 0 U2 2 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD MAR 27 PY 1998 VL 103 IS D6 BP 6109 EP 6121 DI 10.1029/97JD03427 PG 13 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA ZD911 UT WOS:000072737800014 ER PT J AU Myneni, RB Tucker, CJ Asrar, G Keeling, CD AF Myneni, RB Tucker, CJ Asrar, G Keeling, CD TI Interannual variations in satellite-sensed vegetation index data from 1981 to 1991 SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID HIGH-RESOLUTION RADIOMETER; HEAT-BALANCE; SNOW COVER; AVHRR DATA; DATA SET; TEMPERATURE; CLASSIFICATION; CO2; DESERT; MODEL AB Normalized difference vegetation index (NDVI) data processed from measurements of advanced very high resolution radiometers (AVHRR) onboard the afternoon-viewing NOAA series satellites (NOAA 7, 9, and 11) were analyzed for spatial and temporal patterns comparable to those observed in atmospheric CO2, near-surface air temperature, and sea surface temperature (SST) data during the 1981-1991 time period. Two global data sets of NDVI were analyzed for consistency: (1) the land segment of the joint NOAA/NASA Earth Observing System AVHRR Pathfinder data set and (2) the Global Inventory Monitoring and Modeling Studies AVHRR NDVI data set. The impact of SST events was found to be confined mostly to the tropical latitudes but was generally dominant enough to be manifest in the global NDVI anomaly. The vegetation index anomalies at latitudes north of 45 degrees N were found to exhibit an increasing trend. This linear trend corresponds to a 10% increase in seasonal NDVI amplitude over a 9 year period (1981-1990). During the same time period, annual amplitude in the record of atmosphere CO2 measured at Point Barrow, Alaska, was reported to have increased by about 14%. The increase in vegetation index data between years was especially consistent through the spring and early summer time periods. When this increase was translated into an advance in the:timing of spring green-up, the measure (8 +/- 3 days) was similar to the recently published estimate of about 7 days in the advance of the midpoint of CO2 drawdown between spring and summer at Point Barrow, Alaska. The geographical distribution of the increase in vegetation activity was consistent with the reported patterns in springtime warming and decline of snow cover extent over the northern hemisphere land area. C1 Boston Univ, Dept Geog, Boston, MA 02215 USA. NASA, Mission Planet Earth, Washington, DC 20546 USA. Scripps Inst Oceanog, La Jolla, CA 92093 USA. NASA, Goddard Space Flight Ctr, Biospher Sci Branch, Greenbelt, MD 20771 USA. RP Myneni, RB (reprint author), Boston Univ, Dept Geog, 675 Commonwealth Ave, Boston, MA 02215 USA. EM rmyneni@crsa.bu.edu RI Myneni, Ranga/F-5129-2012 NR 41 TC 180 Z9 221 U1 1 U2 23 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 MAR 27 PY 1998 VL 103 IS D6 BP 6145 EP 6160 DI 10.1029/97JD03603 PG 16 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA ZD911 UT WOS:000072737800017 ER PT J AU Leblanc, T McDermid, IS Hauchecorne, A Keckhut, P AF Leblanc, T McDermid, IS Hauchecorne, A Keckhut, P TI Evaluation of optimization of lidar temperature analysis algorithms using simulated data SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID MIDDLE ATMOSPHERE; RAYLEIGH LIDAR; GRAVITY-WAVES; VALIDATION; CLIMATOLOGY; RETRIEVALS; INVERSIONS; ISAMS AB Temperature lidar data have been simulated in order to test the Jet Propulsion Laboratory (JPL) SO3ANL version 3.2 and Service d'Aeronomie du Centre National de la Recherche Scientifique (CNRS/SA) TEMPER version 2.1 lidar temperature analysis software. Assuming known atmospheric temperature-pressure-density profiles, theoretical raw-photons lidar profiles have been calculated using the actual characteristics of two JPL lidar instruments, located at the Table Mountain Facility (TMF) in California and the Mauna Loa Observatory (MLO), Hawaii, and the CNRS/SA Rayleigh lidar, located at the Observatoire de Haute-Provence (OHP) in France. The simulations were performed for an initial climatological profile taken from the CIRA-86 model and for various profiles derived from this model including realistic atmospheric disturbances. Comparisons between the original and retrieved temperature profiles revealed errors of several kelvins for both the JPL and the CNRS/SA programs. By varying parameters in the simulation, it was possible to determine both the source and the magnitude of these errors. Once identified, the errors were corrected, and the analysis programs were optimized, leading to new operational versions of these programs (SO3ANL version 3.6 and TEMPER version 2.2), An accurate accounting of the temperature lidar analysis errors, before and after this work, is presented. C1 CALTECH, Jet Prop Lab, Table Mt Facil, Wrightwood, CA 92397 USA. CNRS, Serv Aeron, F-91371 Verrieres Le Buisson, France. RP Leblanc, T (reprint author), CALTECH, Jet Prop Lab, Table Mt Facil, Wrightwood, CA 92397 USA. EM leblanc@tmf.jpl.nasa.gov; mcdermid@tmf.jpl.nasa.gov RI Hauchecorne, Alain/A-8489-2013; OI Hauchecorne, Alain/0000-0001-9888-6994 NR 26 TC 57 Z9 58 U1 2 U2 6 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD MAR 27 PY 1998 VL 103 IS D6 BP 6177 EP 6187 DI 10.1029/97JD03494 PG 11 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA ZD911 UT WOS:000072737800019 ER PT J AU Pardo, JR Cernicharo, J Pagani, L AF Pardo, JR Cernicharo, J Pagani, L TI Ground-based spectroscopic observations of atmospheric ozone from 142 to 359 GHz in southern Europe SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID MESOSPHERIC OZONE; MICROWAVE RADIOMETRY; UPPER-STRATOSPHERE; DIURNAL-VARIATIONS; MIDDLE ATMOSPHERE; WATER-VAPOR AB During different periods of time between 1991 and 1996 we have achieved ground-based observations of rotational lines of atmospheric ozone using two different ground-based radio telescopes located in southern Europe: the 30 meters IRAM radio telescope at Pico Veleta (latitude 37:04:05.60 degrees N, longitude 3:23:58.10 degrees W, altitude 2850 m) and POM-2 at Plateau de Pure, (Hautes Alpes, France, latitude 44:38:02.00 degrees N, longitude 5:54:28.50 degrees E, altitude 2550 m). A total of eight different ozone lines have been observed with frequencies in the range 142-359 GHz. Several back-end spectrometers were able to analyze the incoming signal with very different frequency resolutions and total spectral coverage. This has allowed us to retrieve information about the vertical profile of ozone over a relatively wide range of altitudes. The retrieval itself has been achieved by means of a nonlinear least squares fit of the observed line profile, taking into account the spectroscopic, observational, and instrumental parameters of the different observations. A comparison between the ozone amounts retrieved fr om observations of different ozone lines in winter and summertime is given separately. Ozone amounts obtained from the different instruments and ozone lines are consistent. C1 NASA, Goddard Inst Space Studies, New York, NY 10025 USA. CSIC, IEM, Dept Fis Mol, E-28006 Madrid, Spain. Observ Paris, DEMIRM, URA 336 CNRS, F-75014 Paris, France. Natl Astron Observ, Madrid, Spain. RP Pardo, JR (reprint author), NASA, Goddard Inst Space Studies, 2880 Broadway, New York, NY 10025 USA. EM jpardo@giss.nasa.gov; cerni@astro.iem.csic.es; pagani@mesioa.obspm.fr NR 37 TC 2 Z9 2 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD MAR 27 PY 1998 VL 103 IS D6 BP 6189 EP 6202 DI 10.1029/97JD03628 PG 14 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA ZD911 UT WOS:000072737800020 ER PT J AU Hansen, J Cairns, B Druyan, L Jiang, X Miller, R Tegen, I AF Hansen, J Cairns, B Druyan, L Jiang, X Miller, R Tegen, I TI Forcings and chaos in interannual to decadal climate change (vol 102, pg 679, 1997) SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Correction C1 NASA, Goddard Inst Space Studies, New York, NY 10025 USA. Columbia Univ, Dept Appl Phys, New York, NY 10027 USA. Columbia Univ, Ctr Climate Syst Res, New York, NY 10027 USA. RP Cairns, B (reprint author), NASA, Goddard Inst Space Studies, New York, NY 10025 USA. RI Miller, Ron/E-1902-2012 NR 1 TC 0 Z9 0 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 MAR 27 PY 1998 VL 103 IS D6 BP 6247 EP 6247 DI 10.1029/98JD00342 PG 1 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA ZD911 UT WOS:000072737800028 ER PT J AU Davidson, K Ishibashi, K Corcoran, MF AF Davidson, K Ishibashi, K Corcoran, MF TI The relationship between two periodicities observed in Eta Carinae SO NEW ASTRONOMY LA English DT Article DE stars : individual : Eta Carinae; Binaries : general; Binaries : spectroscopic; X-rays : stars ID COROTATING INTERACTION REGIONS; CYCLE AB An 85-day periodicity in the X-ray emission of Eta Carinae has been reported, while spectrocopic events recur with a period of 5.5 years (Corcoran et al., 1997 [Natur, 390, 587]; Damineli, 1996 [ApJ, 460, L49]). If the hot X-rays are produced by colliding winds in a 5.5-year binary system, then the interval of 85 days between X-ray flares is likely to represent pulsation or rotation of the primary star, or conceivably the orbit of a third object. In a broad class of models, the 85-day recurrence interval is predicted to lengthen drastically in 1998 after the two stars pass periastron. If this effect does occur, then it can give information about the nature of the system. If it does not, then specific types of models are ruled out. (C) 1998 Elsevier Science B.V. C1 Univ Minnesota, Dept Astron, Minneapolis, MN 55455 USA. NASA, High Energy Astrophys Lab, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Davidson, K (reprint author), Univ Minnesota, Dept Astron, 116 Church St SE, Minneapolis, MN 55455 USA. NR 11 TC 16 Z9 16 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 MAR 27 PY 1998 VL 3 IS 4 BP 241 EP 245 DI 10.1016/S1384-1076(98)00008-6 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZY774 UT WOS:000074658200001 ER PT J AU Davis, CH Kluever, CA Haines, BJ AF Davis, CH Kluever, CA Haines, BJ TI Elevation change of the southern Greenland ice sheet SO SCIENCE LA English DT Article ID SEA-LEVEL CHANGE; SATELLITE ALTIMETRY; GROWTH; RETRACKING AB Seasat and Geosat satellite altimeter measurements for the Greenland ice sheet (south of 72 degrees N latitude) show that surface elevations above 2000 meters increased at an average rate of only 1.5 +/- 0.5 centimeters per year from 1978 to 1988. In contrast, elevation changes varied regionally from -15 to +18 centimeters per year, seasonally by +/-15 centimeters, and interannually by +/-8 centimeters. The average growth rate is too small to determine if the Greenland ice sheet is undergoing a long-term change due to a warmer polar climate. C1 Univ Missouri, Dept Elect Engn, Kansas City, MO 64110 USA. Univ Missouri, Dept Mech & Aerosp Engn, Kansas City, MO 64110 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Davis, CH (reprint author), Univ Missouri, Dept Elect Engn, 5605 Troost Ave, Kansas City, MO 64110 USA. NR 26 TC 58 Z9 58 U1 0 U2 4 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 MAR 27 PY 1998 VL 279 IS 5359 BP 2086 EP 2088 DI 10.1126/science.279.5359.2086 PG 5 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA ZE274 UT WOS:000072775600040 ER PT J AU Bauschlicher, CW Rosi, M AF Bauschlicher, CW Rosi, M TI Differentiating between H and F or H and CN on C(111) or Si(111) surfaces SO JOURNAL OF PHYSICAL CHEMISTRY B LA English DT Article ID GAUSSIAN-BASIS SETS; ATOMS AB Molecule-surface interaction energies are computed at the B3LYP level of theory. The C(111) and Si(111) surfaces, with H, F, or CN covalently bonded to the surface, are studied. The incoming molecule simulates the tip of a probe that should be able to differentiate between the atoms or molecules on the surface. A Sc-tipped probe molecule yields a larger difference for the probe-surface H versus probe-surface F interaction energies than our previously studied. electron-rich pyridine (C(5)H(5)N) and (CH(3))(3)PO probes. However, it is not always possible to differentiate between the surface H and F atoms because the Sc probe interacts too strongly with the neighboring surface atoms. The difference in the probe-H and probe-F interaction energies is smaller for Si(111) than C(111), making it more difficult to differentiate between these two atoms on Si(111). The larger lattice constant for Si(111) significantly reduces the surface atom-surface atom interaction energy as well as the probe-neighbor interaction energies. This means that the H/CN system, which is not practical for C(111) due to the CN-CN repulsion, is possible for Si(111). The difference in the probe-H and probe-CN interaction energies is very large for the H/CN data storage system, making this the best system studied to date. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Univ Perugia, Dept Chem, I-06100 Perugia, Italy. RP Bauschlicher, CW (reprint author), NASA, Ames Res Ctr, STC-230-3, Moffett Field, CA 94035 USA. RI Rosi, Marzio/L-5748-2015 OI Rosi, Marzio/0000-0002-1264-3877 NR 11 TC 6 Z9 6 U1 0 U2 2 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA SN 1520-6106 J9 J PHYS CHEM B JI J. Phys. Chem. B PD MAR 26 PY 1998 VL 102 IS 13 BP 2403 EP 2405 DI 10.1021/jp9734742 PG 3 WC Chemistry, Physical SC Chemistry GA ZF505 UT WOS:000072904200016 ER PT J AU Kolb, EW Riotto, A Tkachev, II AF Kolb, EW Riotto, A Tkachev, II TI GUT baryogenesis after preheating: numerical study of the production and decay of X-bosons SO PHYSICS LETTERS B LA English DT Article ID INFLATIONARY UNIVERSE; BARYON ASYMMETRY AB We perform a fully non-linear calculation of the production of supermassive Grand Unified Theory (GUT) X bosons during preheating, taking into account the fact that they are unstable with a decay width Gamma(X). We show that parametric resonance does not develop if Gamma(X) is larger than about 10(-2)m(X). We compute the nonthermal number density of superheavy bosons produced in the preheating phase and demonstrate that the observed baryon asymmetry may be explained by GUT baryogenesis after preheating if Gamma(X) is smaller than about 10(-3)m(X). (C) 1998 Published by Elsevier Science B.V. C1 NASA, Fermi Natl Accelerator Lab, Fermilab Astrophys Ctr, Batavia, IL 60510 USA. Univ Chicago, Dept Astron & Astrophys, Enrico Fermi Inst, Chicago, IL 60637 USA. CERN, Div Theory, CH-1211 Geneva, Switzerland. Purdue Univ, Dept Phys, W Lafayette, IN 47907 USA. Russian Acad Sci, Inst Nucl Res, Moscow 117312, Russia. RP Kolb, EW (reprint author), NASA, Fermi Natl Accelerator Lab, Fermilab Astrophys Ctr, Batavia, IL 60510 USA. EM rocky@rigolelto.fnal.gov; riotto@nxth04.cern.ch; tkachev@physics.purdue.edu NR 24 TC 71 Z9 71 U1 2 U2 2 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0370-2693 J9 PHYS LETT B JI Phys. Lett. B PD MAR 26 PY 1998 VL 423 IS 3-4 BP 348 EP 354 DI 10.1016/S0370-2693(98)00134-8 PG 7 WC Astronomy & Astrophysics; Physics, Nuclear; Physics, Particles & Fields SC Astronomy & Astrophysics; Physics GA ZM231 UT WOS:000073517800019 ER PT J AU Burke, PJ Schoelkopf, RJ Prober, DE Skalare, A Karasik, BS Gaidis, MC McGrath, WR Bumble, B LeDuc, HG AF Burke, PJ Schoelkopf, RJ Prober, DE Skalare, A Karasik, BS Gaidis, MC McGrath, WR Bumble, B LeDuc, HG TI Spectrum of thermal fluctuation noise in diffusion and phonon cooled hot-electron mixers SO APPLIED PHYSICS LETTERS LA English DT Article ID SUPERCONDUCTING MIXERS; BOLOMETER MIXER; MICROBOLOMETER; BANDWIDTH AB A systematic study of the intermediate frequency noise bandwidth of Nb thin-film superconducting hot-electron bolometers is presented. We have measured the spectrum of the output noise as well as the conversion efficiency over a very broad intermediate frequency range (from 0.1 to 7.5 GHz) for devices varying in length from 0.08 mu m to 3 mu m. Local oscillator and rf signals from 8 to 40 GHz were used. For a device of a given length, the spectrum of the output noise and the conversion efficiency behave similarly for intermediate frequencies less than the gain bandwidth, in accordance with a simple thermal model for both the mixing and thermal fluctuation noise. For higher intermediate frequencies the conversion efficiency decreases; in contrast, the noise decreases but has a second contribution which dominates at higher frequency. The noise bandwidth is larger than the gain bandwidth, and the mixer noise is low, between 120 and 530 K (double side band). (C) 1998 American Institute of Physics. C1 Yale Univ, Dept Appl Phys, New Haven, CT 06520 USA. Yale Univ, Dept Phys, New Haven, CT 06520 USA. CALTECH, Jet Prop Lab, Ctr Space Microelect Technol, Pasadena, CA 91109 USA. RP Burke, PJ (reprint author), CALTECH, MS114-36, Pasadena, CA 91109 USA. RI Schoelkopf, Robert/J-8178-2012; Gaidis, Michael/D-3327-2013; Burke, Peter/F-3308-2010; Karasik, Boris/C-5918-2011 NR 16 TC 6 Z9 6 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 MAR 23 PY 1998 VL 72 IS 12 BP 1516 EP 1518 DI 10.1063/1.121044 PG 3 WC Physics, Applied SC Physics GA ZD085 UT WOS:000072649900037 ER PT J AU Elson, RAW Grillmair, CJ Forbes, DA Rabban, M Williger, GM Brodie, JP AF Elson, RAW Grillmair, CJ Forbes, DA Rabban, M Williger, GM Brodie, JP TI HST imaging of the globular clusters in the Fornax cluster: NGC 1379 SO MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY LA English DT Article DE galaxies, clusters, individual, Fornax; galaxies, elliptical and lenticular, cD; galaxies, individual, NGC 1379; galaxies, star clusters ID LOCAL GROUP; ELLIPTICAL GALAXIES; VIRGO ELLIPTICALS; PHOTOMETRY; DISTANCE AB We present B and I photometry for similar to 300 globular cluster candidates in NGC 1379, an EO galaxy in the Fornax cluster. Our data are from both Hubble Space Telescope (HST) and ground-based observations, The HST photometry (B only) is essentially complete and free of foreground/background contamination to similar to 2 mag fainter than the peak of the globular cluster luminosity function. Fitting a Gaussian to the luminosity function, we find [B] = 24.95 +/- 0.30 and sigma(B) = 1.55 +/- 0.21. We estimate the total number of globular clusters to be 436 +/- 30. To a radius of 70 arcsec we derive a moderate specific frequency, S-N = 3.5 +/- 0.4. At radii r similar to 3-6 kpc the surface density profile of the globular cluster system is indistinguishable from that of the underlying galaxy light, At r less than or similar to 2.5 kpc the profile of the globular cluster system flattens, and at r less than or similar to 1 kpc, the number density appears to decrease. The (B - I) colour distribution of the globular clusters (from ground-based data) is similar to that for Milky Way globulars, once corrected for background contamination, It shows no evidence for bimodality or for the presence of a population with [Fe/H] greater than or similar to -0.5. Unlike in the case of larger, centrally located cluster ellipticals, neither mergers nor a multiphase collapse are required to explain the formation of the NGC 1379 globular cluster system. We stress the importance of corrections for background contamination in ground-based samples of this kind: the area covered by a globular cluster system (with radius similar to 30 kpc) at the distance of the Virgo or Fornax cluster contains greater than or similar to 200 background galaxies unresolved from the ground, with magnitudes comparable to brighter globular clusters at that distance. The colour distribution of these galaxies is strongly peaked slightly bluer than the peak of a typical globular cluster distribution. Such contamination can thus create the impression of skewed colour distributions, or even of bimodality, where none exists. C1 Univ Cambridge, Inst Astron, Cambridge CB3 0HA, England. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ Birmingham, Sch Phys & Astron, Birmingham B15 2TT, W Midlands, England. Univ Calif Santa Cruz, Lick Observ, Santa Cruz, CA 95064 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Elson, RAW (reprint author), Univ Cambridge, Inst Astron, Madingley Rd, Cambridge CB3 0HA, England. EM elson@ast.cam.ac.uk; carl@grandpa.jpl.nasa.gov; forbes@star.sr.bham.ac.uk; mrabban@ucolick.org; williger@tejut.gsfc.nasa.gov; brodie@ucolik.org NR 35 TC 13 Z9 13 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 MAR 21 PY 1998 VL 295 IS 1 BP 240 EP 250 DI 10.1046/j.1365-8711.1998.29511307.x PG 11 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZF497 UT WOS:000072903400027 ER PT J AU Godon, P Livio, M Lubow, S AF Godon, P Livio, M Lubow, S TI Spiral shocks in accretion discs SO MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY LA English DT Letter DE accretion, accretion discs; hydrodynamics; stars, individual, IP Peg; novae, cataclysmic variables ID WAVE-PROPAGATION; BINARY-SYSTEMS; DISKS AB We perform two-dimensional numerical calculations of the tidal interaction between the companion star and the disc around the primary in a cataclysmic variable system with parameters appropriate for the eclipsing dwarf nova binary IP Peg. We show that a spiral shock pattern is indeed obtained. We find, however, that it is impossible to reproduce the two-armed spiral that has been recently observed in IP Peg for realistic discs. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Space Telescope Sci Inst, Baltimore, MD 21218 USA. RP Godon, P (reprint author), CALTECH, Jet Prop Lab, 480 Oak Grove Dr,MS 238-332, Pasadena, CA 91109 USA. NR 24 TC 15 Z9 15 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 MAR 21 PY 1998 VL 295 IS 1 BP L11 EP L14 DI 10.1046/j.1365-8711.1998.29510584.x PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZF497 UT WOS:000072903400003 ER PT J AU Vander Wal, RL Jensen, KA AF Vander Wal, RL Jensen, KA TI Laser-induced incandescence: excitation intensity SO APPLIED OPTICS LA English DT Article ID ETHYLENE DIFFUSION FLAMES; SOOT-VOLUME FRACTION; FLICKERING METHANE; DIAGNOSTICS; SCATTERING; PARTICLES AB Assumptions of theoretical laser-induced incandescence (LII) models along with possible effects of high-intensity laser light on soot aggregates and the constituent primary particles are discussed in relation to selection of excitation laser fluence. Ex situ visualization of laser-heated soot by use of transmission electron microscopy reveals significant morphological changes (graphitization) induced by pulsed laser heating. Pulsed laser transmission measurements within a premixed laminar sooting flame suggest that soot vaporization occurs for laser fluences greater than 0.5 J/cm(2) at 1064 nm. Radial LII intensity profiles at different axial heights in a laminar ethylene gas jet diffusion flame reveal a wide range of signal levels depending on the laser fluence that is Varied over an eight fold range. Results of double-pulse excitation experiments in which a second laser pulse heats in situ the same soot that was heated by a prior laser pulse are detailed. These two-pulse measurements suggest varying degrees of soot structural change for fluences below and above a vaporization threshold of 0.5 J/cm(2) at 1064 nm. Normalization of the radial-resolved LII signals based on integrated intensities, however, yields selfsimilar profiles. The self-similarity suggests robustness of LII for accurate relative measurement of soot volume fraction despite the morphological changes induced in the soot, variations in soot aggregate and primary particle size, and local gas temperature. Comparison of LII intensity profiles with soot volume fractions (f(v)) derived by light extinction validates LII for quantitative determination of f(v), upon calibration for laser fluences ranging from 0.09 to 0.73 J/cm(2). (C) 1998 Optical Society of America. C1 Nyma Inc, Brook Pk, OH 44142 USA. Univ Chicago, Dept Engn, Chicago, IL 60607 USA. RP Jensen, KA (reprint author), NASA, Lewis Res Ctr, Natl Ctr Micrograv Res, MS 110-3,21000 Brookpk Rd, Cleveland, OH 44135 USA. NR 28 TC 57 Z9 57 U1 0 U2 4 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 MAR 20 PY 1998 VL 37 IS 9 BP 1607 EP 1616 DI 10.1364/AO.37.001607 PG 10 WC Optics SC Optics GA ZB681 UT WOS:000072496900027 PM 18268755 ER PT J AU Malkan, MA Stecker, FW AF Malkan, MA Stecker, FW TI An empirically based calculation of the extragalactic infrared background SO ASTROPHYSICAL JOURNAL LA English DT Article DE diffuse radiation; infrared, galaxies; infrared, general ID MICRON GALAXY SAMPLE; LUMINOSITY FUNCTION; IRAS GALAXIES; RADIATION; FIELDS; LIMITS; Z=2.5 AB Using the excellent observed correlations among various infrared wave bands with 12 and 60 mu m luminosities, we calculate the 2-300 mu m spectra of galaxies as a function of luminosity. We then use 12 mu m and 60 mu m galaxy luminosity functions derived from IRAS data, together with recent data on the redshift evolution of galaxy emissivity, to derive a new, empirically based infrared background spectrum from stellar and dust emission in galaxies. Our best estimate for the infrared background is of order 2-3 nW m(-2) sr(-1) with a peak around 200 mu m reaching similar to 6-8 nW m(-2) sr(-1). Our empirically derived background spectrum is fairly hat in the mid-infrared, as opposed to spectra based on modeling with discrete temperatures that exhibit a pronounced "valley" in the mid-infrared. We also derive a conservative lower limit to the infrared background that is more than a factor of 2 lower than our derived flux. C1 Univ Calif Los Angeles, Dept Phys & Astron, Los Angeles, CA 90095 USA. NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. RP Univ Calif Los Angeles, Dept Phys & Astron, Los Angeles, CA 90095 USA. EM malkan@bonnie.astro.ucla.edu; stecker@lheavx.gsfc.nasa.gov RI Stecker, Floyd/D-3169-2012 NR 32 TC 129 Z9 129 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 MAR 20 PY 1998 VL 496 IS 1 BP 13 EP 16 DI 10.1086/305384 PN 1 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZE341 UT WOS:000072782900003 ER PT J AU Ulvestad, JS Roy, AL Colbert, EJM Wilson, AS AF Ulvestad, JS Roy, AL Colbert, EJM Wilson, AS TI A subparsec radio jet or disk in NGC 4151 SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies, individual (NGC 4151); galaxies, jets; galaxies, Seyfert; radio continuum, galaxies ID HOPKINS-ULTRAVIOLET-TELESCOPE; PARSEC-SCALE STRUCTURE; SEYFERT-GALAXIES; VLBI OBSERVATIONS; GALACTIC NUCLEI; ACTIVE GALAXIES; LINE REGION; NGC-4151; EXPANSION; EMISSION AB We have imaged the classical Seyfert galaxy NGC 4151 with the VLBA at wavelengths of 6 and 18 cm, achieving resolutions of similar or equal to 2 and 5 mas (similar or equal to 0.16 and 0.40 pc), respectively. At 18 cm, four radio components, spread over similar or equal to 0." 5 (similar or equal to 40 pc) are detected. The eastermmost pair comprises a bright component elongated in position angle similar or equal to 20 degrees (component E) and an extension to the northeast (component Fl which curves into position angle similar or equal to 75 degrees, similar to that of the 3." 5 (280 pc) scale radio jet and the narrow-line region. At the higher resolution achieved at 6 cm, component E is found to be a linear radio source with a length of similar to 13 mas (1.0 pc). This source has a length/width ratio of greater than or similar to 4, and therefore fulfills one of the classical criteria for a radio jet, but its radio luminosity is only similar to 10(38) ergs s(-1), several orders of magnitude less than the parsec-scale jets in radio galaxies. It is also misaligned by similar or equal to 55 degrees from the arcsecond-scale radio jet. Possible reasons for the misalignment include deflection by the inner narrow-line region, buoyancy forces, and a change in the plane of the accretion disk presumably responsible for jet collimation. We also discuss an alternative interpretation, in which component E is a disk or torus viewed edge-on and emitting flat-spectrum, possibly thermal, radio emission. Component E appears to be the only part of the radio emission that contains a significant flat-spectrum component, and we favor identification of the central, brightest, unresolved subcomponent of E as the ultraviolet (UV) and optical nucleus. In order to reconcile the much smaller column density of H I toward the nucleus found by Lyman absorption than by 21 cm absorption measurements, we argue that a similar or equal to 0.01 pc thick gas disk surrounds the nucleus and is ionized out to a radius of similar or equal to 2 pc. The large 21 cm absorption column observed then results from off-nuclear radio components shining through the outer, neutral part of this disk. The flat spectrum of the nuclear radio source may indicate synchrotron self-absorption or free-free absorption by the inner, ionized part of the accretion disk. Interestingly, the apparent nuclear source and a radio subcomponent similar or equal to 0.2 pc to the southeast align precisely perpendicular to the arcsec-scale radio jet, suggesting that they may outline the large-scale structure of the accretion disk responsible for jet collimation. Comparison of the 18 cm image with the European VLBI network image acquired by Harrison et al. in 1984 provides upper limits of 0.14c and 0.25c for the apparent speeds of the radio components at distances of 7 and 36 pc, respectively, from the galaxy nucleus. C1 Natl Radio Astron Observ, Socorro, NM 87801 USA. NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. Space Telescope Sci Inst, Baltimore, MD 21218 USA. Univ Maryland, Dept Astron, College Pk, MD 20742 USA. RP Ulvestad, JS (reprint author), Natl Radio Astron Observ, POB O, Socorro, NM 87801 USA. EM julvesta@nrao.edu; aroy@nrao.edu; colbert@lheamail.gsfc.nasa.gov; wilson@astro.umd.edu NR 40 TC 37 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 MAR 20 PY 1998 VL 496 IS 1 BP 196 EP 202 DI 10.1086/305382 PN 1 PG 7 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZE341 UT WOS:000072782900016 ER PT J AU Terashima, Y Ptak, A Fujimoto, R Itoh, M Kunieda, H Makishima, K Serlemitsos, PJ AF Terashima, Y Ptak, A Fujimoto, R Itoh, M Kunieda, H Makishima, K Serlemitsos, PJ TI An ASCA observation of M51 (NGC 5194): Iron K emission from an obscured active galactic nucleus SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies, individual (M51); galaxies, nuclei; X-rays, galaxies ID X-RAY-SPECTRUM; GALAXIES; REFLECTION; NGC-5195; NGC-6552; DISK AB We present an ASCA observation of the nearby spiral galaxy M51 (NGC 5194). We detected hard X-ray emission with a photon index of similar to 1.4 and a luminosity of L-x similar to 1.1 x 10(40) ergs s(-1) in the 2-10 keV band (assuming a distance of 9.6 Mpc). A strong fluorescent iron K line (equivalent width similar to 900 eV) was detected at 6.4 keV in the X-ray spectra. Such an intense iron line is characteristic of Seyfert 2 galaxies and strongly suggests the presence of a heavily obscured active galactic nucleus (AGN). However, the X-ray image is extended even at energies above 2 keV. From the strong iron line and the extended hard X-ray image we speculate that the AGN is obscured by matter with a hydrogen column density more than several times 10(23) cm(-2) and that the observed 2-10 keV X-ray flux is not dominated by emission from the AGN but rather by other components, such as low-mass X-ray binaries, which typically dominate the X-ray emission of normal spiral galaxies. Emission lines from O K, Ne K, Fe L, Mg K and Si K were detected in the soft energy spectra, which indicate the presence of hot gas. The soft component is well represented by a Raymond-Smith thermal plasma model (with kT similar to 0.4 keV), which suggests a lower iron abundance (<0.1 solar) than other elements (similar to 0.1-0.4 solar), or by a two temperature (kT similar to 0.3 keV and kT similar to 0.8 keV) model with similar to 0.1 solar abundance, which is reminiscent of the X-ray-emitting gas in starburst galaxies. C1 Nagoya Univ, Fac Sci, Dept Phys, Chikusa Ku, Nagoya, Aichi 46401, Japan. NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. Univ Maryland, College Pk, MD 20742 USA. Inst Space & Astronaut Sci, Kanagawa 229, Japan. Kobe Univ, Fac Human Dev, Nada Ku, Kobe, Hyogo 657, Japan. Univ Tokyo, Dept Phys, Bunkyo Ku, Tokyo 113, Japan. RP Nagoya Univ, Fac Sci, Dept Phys, Chikusa Ku, Nagoya, Aichi 46401, Japan. NR 42 TC 30 Z9 30 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 MAR 20 PY 1998 VL 496 IS 1 BP 210 EP 215 DI 10.1086/305367 PN 1 PG 6 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZE341 UT WOS:000072782900018 ER PT J AU in't Zand, JJM Baykal, A Strohmayer, TE AF in't Zand, JJM Baykal, A Strohmayer, TE TI Recent X-ray measurements of the accretion-powered pulsar 4U 1907+09 SO ASTROPHYSICAL JOURNAL LA English DT Article DE accretion, accretion disks; binaries, general; pulsars, individual (4U 1907+09); stars, neutron; X-rays, stars ID QUASI-PERIODIC OSCILLATIONS; MAGNETIC NEUTRON STARS; TIMING EXPLORER; DISK ACCRETION; CENTAURUS X-3; VELA X-1; DISCOVERY; PERFORMANCE; GX-301-2; TORQUE AB X-ray observations of the accreting X-ray pulsar 4U 1907 + 09 obtained during 1996 February with the Proportional Counter Array onboard the Rossi X-Ray Timing Explorer (RXTE) have made possible the first measurement of the intrinsic pulse period (P-pulse) since 1984: P-pulse = 440.341(-0.017)(+0.012) s. 4U pulse 1907 + 09 is in a binary system with a blue supergiant. The orbital parameters have been solved, which enables us to correct a measurement of P-pulse obtained in 1990 with Ginga for orbital delay effects. Thus, three spin-down rates can be extracted from four pulse periods obtained in 1983, 1984, 1990, and 1996. These are equal to within 8% to a value of (P) over dot(pulse) = +0.225 s yr(-1). This suggests that the pulsar has perhaps been in a monotonous spin-down mode since its discovery in 1983. Furthermore, the RXTE observations showed transient similar to 18 s oscillations during a flare that lasted about 1 hr. These oscillations could be interpreted as Keplerian motion of an accretion disk near the magnetospheric radius. This, and the notion that the corotation radius is much larger than any conceivable value for the magnetospheric radius (because of the long spin period), renders it unlikely that this pulsar spins near equilibrium, as is suspected for other slowing accreting X-ray pulsars. We suggest as an alternative that the frequent occurrence of a retrograde transient accretion disk may be consistently slowing the pulsar down. Further observations of flares could provide more evidence of this. C1 Space Res Org Netherlands, NL-3584 CA Utrecht, Netherlands. Middle E Tech Univ, Dept Phys, TR-06531 Ankara, Turkey. NASA, Goddard Space Flight Ctr, Lab High Energy Astron, Greenbelt, MD 20771 USA. RP Space Res Org Netherlands, Sorbonnelaan 2, NL-3584 CA Utrecht, Netherlands. EM jeanz@sron.ruu.nl; altan@astroa.physics.metu.edu.tr; stroh@lheamail.gsfc.nasa.gov NR 43 TC 52 Z9 52 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 MAR 20 PY 1998 VL 496 IS 1 BP 386 EP 394 DI 10.1086/305362 PN 1 PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZE341 UT WOS:000072782900034 ER PT J AU Ayres, TR Simon, T Stern, RA Drake, SA Wood, BE Brown, A AF Ayres, TR Simon, T Stern, RA Drake, SA Wood, BE Brown, A TI The coronae of moderate-mass giants in the Hertzsprung gap and the clump SO ASTROPHYSICAL JOURNAL LA English DT Article DE stars, coronae; ultraviolet, stars; X-rays, stars ID X-RAY-SPECTRA; CHROMOSPHERICALLY ACTIVE STARS; COOL STARS; ULTRAVIOLET-SPECTRA; EXTREME-ULTRAVIOLET; ROTATIONAL MODULATION; ROSAT OBSERVATIONS; OUTER ATMOSPHERES; OXYGEN ABUNDANCES; COMAE-BERENICES AB We have used the Roentgensatellit (ROSAT), the Extreme Ultraviolet Explorer (EUVE), and the Hubble Space Telescope (HST) to measure X-ray and ultraviolet emissions of moderate-mass (similar to 2-3 M-.) giants in the Hertzsprung gap (spectral types early F to mid-G) and the post-helium flash "clump" (similar to G8-K0). Our motivation was to document the evolution of hot coronae (T > 10(6) K) along the post-main-sequence trajectories traveled by such stars in order to gain insight concerning the "X-ray deficiency" of the F-G0 giants and the strong braking of stellar rotation at the red edge of the Hertzsprung gap. With few exceptions, Hertzsprung gap and clump giants observed by ROSAT PSPC show hot (T similar to 10(7) K) coronal energy distributions, regardless of any X-ray deficiency. EUVE spectra of gap star 31 Com (G0 III) indicate a broad coronal emission measure hump at similar to 10(7.2) K, while the active clump giant beta Ceti (K0 III) displays a sharp peak at similar to 10(6.8) K, as seen previously in the mixed clump/gap binary Capella (alpha Aur: G8 III + G0 III). The gap giants v Peg (F8 III) and 24 UMa (G4 III) have EUV emissions of intermediate temperature (similar to 10(7.0) K). The stars 31 Com, psi(3) Psc (G0 III), and beta Cet exhibit redshifted transition zone (TZ: similar to 10(5) K) lines in HST GHRS spectra, as reported earlier in Procyon (alpha CMi: F5 IV-V) and Capella G0. Such redshifts on the Sun are thought to signify flows in magnetic loops. beta Cas (F2 III)-a rare soft coronal source among the gap stars-displays blueshifts of C IV and O IV], although emissions at cooler and hotter temperatures are near the photospheric velocity. The remarkably broad line profiles of the fastest rotating gap giants suggest that the 10(5) K "subcoronal" emission zones extend to h similar to R-star above the photosphere, about 50 scale heights. In contrast to the TZ line redshifts, the upper chromospheric emissions (e.g., Mg II and Si III) of 31 Com and psi(3) Psc have blueshifted cores. Blue-asymmetric peaks in the solar Mg II lines are thought to indicate dynamical heating in the chromosphere. Observations of the H I Ly alpha feature of 31 Com taken 9 months apart reveal striking profile changes, reminiscent of those noted previously in the Ly alpha blue peak of the Capella G0 star. We used the far-ultraviolet diagnostics, in combination with ROSAT X-ray photometry and EUVE high-excitation line strengths, to constrain physical models of the stellar outer atmospheres. Quasi-static magnetic loops can simulate the empirical coronal emission measures of the giant stars, but the inferred pressures for sensible loop lengths conflict with direct measurements of subcoronal densities. Furthermore, the high rate of emission at similar to 10(5) K cannot be explained by thermal conduction down the legs of hot quasi-static loops. On the other hand, the possible existence of elongated (l similar to R-star) emission structures on the gap giants leads to a speculative scenario to explain the X-ray deficiency. It is based on the increased importance of the dynamical filling phase ("explosive evaporation") of the loop life cycle; conductive cooling, yielding TZ emissions at the footpoints, when the heating is interrupted; and the possibility for transitions between "hot" and "cool" energy balance solutions owing to dynamical suspension and centrifugal trapping of the cooling gas. The long loops might represent a vestigial global "magnetosphere" inherited from the main-sequence phase, which ultimately is disrupted near similar to G0 by the deepening convective envelope and growth of a more solar-like dynamo. Coronal emissions might be boosted temporarily as the X-ray deficiency is removed but soon would be quenched by wind braking previously inhibited by the magnetospheric "dead zone.". C1 Univ Colorado, Ctr Astrophys & Space Astron, Boulder, CO 80309 USA. Univ Hawaii, Inst Astron, Honolulu, HI 96822 USA. Lockheed Martin Solar & Astrophys Lab, Dept H1 12, Palo Alto, CA 94304 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Colorado, Joint Inst Lab Astrophys, Boulder, CO 80309 USA. RP Univ Colorado, Ctr Astrophys & Space Astron, Campus Box 389 CASA, Boulder, CO 80309 USA. EM ayres@vulcan.colorado.edu; simon@hubble.ifa.hawaii.edu; stern@sag.space.lockheed.com; drake@lheavx.gsfc.nasa.gov; wood@marmot.colorado.edu; ab@echidna.colorado.edu NR 90 TC 54 Z9 54 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 MAR 20 PY 1998 VL 496 IS 1 BP 428 EP 448 DI 10.1086/305347 PN 1 PG 21 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZE341 UT WOS:000072782900037 ER PT J AU Reimer, O Menn, W Hof, M Simon, M Davis, AJ Labrador, AW Mewaldt, RA Schindler, SM Barbier, LM Christian, ER Krombel, KE Mitchell, JW Ormes, JF Streitmatter, RE Golden, RL Stochaj, SJ Webber, WR Rasmussen, IL AF Reimer, O Menn, W Hof, M Simon, M Davis, AJ Labrador, AW Mewaldt, RA Schindler, SM Barbier, LM Christian, ER Krombel, KE Mitchell, JW Ormes, JF Streitmatter, RE Golden, RL Stochaj, SJ Webber, WR Rasmussen, IL TI The cosmic-ray He-3/He-4 ratio from 200 MeV per nucleon(-1) to 3.7 GeV per nucleon(-1) SO ASTROPHYSICAL JOURNAL LA English DT Article DE acceleration of particles; balloons; cosmic rays; nuclear reactions, nucleosynthesis, abundances ID FRAGMENTATION CROSS-SECTIONS; RELATIVISTIC NUCLEI; CARBON TARGETS; ENERGY-RANGE; ELASTIC-SCATTERING; GEV-C; HELIUM; HYDROGEN; PROTONS; HE-3 AB The abundances of cosmic-ray helium isotopes between 0.2 and 3.7 GeV nucleon(-1) were measured by the Isotope Matter Antimatter Experiment (IMAX) during a flight from Lynn Lake, Manitoba, Canada on 1992 July 16-17. The IMAX balloon-borne magnetic spectrometer realized a direct measurement of the charge, the velocity, and the rigidity of cosmic rays using plastic scintillators, a high-resolution time-of-flight system, and two silica-aerogel Cerenkov counters in conjunction with a drift chamber/multiwire proportional chamber tracking system. About 75,000 helium isotopes are identified by their mass using the velocity versus magnetic rigidity technique. The measured He-3/He-4 ratios are corrected to the top of the atmosphere, and a comparison with previous data is given. The observed isotopic composition is found to be generally consistent with the predictions of a standard leaky box model of cosmic-ray transport in the Galaxy. C1 Univ Gesamthsch Siegen, D-57068 Siegen, Germany. CALTECH, Pasadena, CA 91125 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. New Mexico State Univ, Las Cruces, NM 88003 USA. Danish Space Res Inst, DK-2100 Copenhagen, Denmark. RP Reimer, O (reprint author), Max Planck Inst Extraterr Phys, D-85740 Garching, Germany. RI Christian, Eric/D-4974-2012; Reimer, Olaf/A-3117-2013 OI Christian, Eric/0000-0003-2134-3937; Reimer, Olaf/0000-0001-6953-1385 NR 69 TC 28 Z9 28 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 MAR 20 PY 1998 VL 496 IS 1 BP 490 EP 502 DI 10.1086/305358 PN 1 PG 13 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZE341 UT WOS:000072782900042 ER PT J AU Wachter, S Smale, AP AF Wachter, S Smale, AP TI Optical studies of the transient dipping X-ray sources X1755-338 and X1658-298 in quiescence SO ASTROPHYSICAL JOURNAL LA English DT Article DE stars, individual (V4134 Sagittarii, V2134 Ophiuchi); stars, variables, other; X-rays, stars ID MXB 1659-29; BLACK-HOLE; MASS; SPECTROSCOPY; BINARIES; A0620-00; SPECTRUM; DIPS AB We have studied the optical counterparts of X1755-338 and X1658-298 in their X-ray "off" states, The first observations of X1755-338 in quiescence show that the counterpart, V4134 Sgr, has faded by more than 3.5 mag in V, If the mass donor in the system is an MO V star, as implied by the period, our upper limits on the brightness of the counterpart suggest that it is more distant than 4 kpc. We observed V2134 Oph, the optical counterpart of X1658-298, on several occasions in 1997 April/May and found the source only similar to 1 mag fainter than when it is X-ray bright, Contemporaneous X-ray data confirm that the source remains in the quiescent state during our optical observations. Our optical light curve, folded on the 7.1 hr orbital period, does not show any modulation across the binary cycle. It is possible that the absence of detectable X-ray emission, despite the indication for an accretion disk and activity in the system, is related to a structure in the disk that permanently obscures the central X-ray source. The optical properties of V2134 Oph are unique among the known X-ray transients. C1 Univ Washington, Dept Astron, Seattle, WA 98195 USA. NASA, Goddard Space Flight Ctr, Univ Space Res Assoc, Greenbelt, MD 20771 USA. RP Wachter, S (reprint author), Univ Washington, Dept Astron, Box 351580, Seattle, WA 98195 USA. NR 28 TC 10 Z9 10 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 MAR 20 PY 1998 VL 496 IS 1 BP L21 EP L24 DI 10.1086/311242 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZE343 UT WOS:000072783100006 ER PT J AU Boda, WL Campbell, JA Yang, C Hargens, AR AF Boda, WL Campbell, JA Yang, C Hargens, AR TI Comparison of upright gait with supine bungee-cord gait SO FASEB JOURNAL LA English DT Meeting Abstract C1 NASA, Ames Res Ctr, Gravitat Res Branch, Moffett Field, CA 94035 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU FEDERATION AMER SOC EXP BIOL PI BETHESDA PA 9650 ROCKVILLE PIKE, BETHESDA, MD 20814-3998 USA SN 0892-6638 J9 FASEB J JI Faseb J. PD MAR 20 PY 1998 VL 12 IS 5 SU S MA 5547 BP A958 EP A958 PN 2 PG 1 WC Biochemistry & Molecular Biology; Biology; Cell Biology SC Biochemistry & Molecular Biology; Life Sciences & Biomedicine - Other Topics; Cell Biology GA 121HD UT WOS:000076006501930 ER PT J AU Campbell, JA Sanchez, E Yang, C Mitsui, I Murthy, G Schwandt, D Fechner, KP Ballard, RE Watenpaugh, DE Hargens, AR AF Campbell, JA Sanchez, E Yang, C Mitsui, I Murthy, G Schwandt, D Fechner, KP Ballard, RE Watenpaugh, DE Hargens, AR TI MRI evaluation of spinal length and vertebral body angle during loading with a spinal compression harness SO FASEB JOURNAL LA English DT Meeting Abstract C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Vet Adm Palo Alto Hlth Care Syst, Diagnost Radiol Ctr, Palo Alto, CA 94304 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU FEDERATION AMER SOC EXP BIOL PI BETHESDA PA 9650 ROCKVILLE PIKE, BETHESDA, MD 20814-3998 USA SN 0892-6638 J9 FASEB J JI Faseb J. PD MAR 20 PY 1998 VL 12 IS 5 SU S MA 5480 BP A946 EP A946 PN 2 PG 1 WC Biochemistry & Molecular Biology; Biology; Cell Biology SC Biochemistry & Molecular Biology; Life Sciences & Biomedicine - Other Topics; Cell Biology GA 121HD UT WOS:000076006501864 ER PT J AU Clarke, MSF Stowe, RP Feeback, DL AF Clarke, MSF Stowe, RP Feeback, DL TI Modulation of cholesterol-dependent plasma membrane order after microgravity exposure. SO FASEB JOURNAL LA English DT Meeting Abstract C1 NASA, JSC, Univ Space Res Assoc, Houston, TX 77058 USA. Univ Texas, Med Branch, Dept Pathol, Galveston, TX 77550 USA. NASA, JSC, Life Sci Res Labs, Houston, TX 77058 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU FEDERATION AMER SOC EXP BIOL PI BETHESDA PA 9650 ROCKVILLE PIKE, BETHESDA, MD 20814-3998 USA SN 0892-6638 J9 FASEB J JI Faseb J. PD MAR 20 PY 1998 VL 12 IS 5 SU S MA 5556 BP A959 EP A959 PN 2 PG 1 WC Biochemistry & Molecular Biology; Biology; Cell Biology SC Biochemistry & Molecular Biology; Life Sciences & Biomedicine - Other Topics; Cell Biology GA 121HD UT WOS:000076006501940 ER PT J AU Hashemi, BB Hatton, JP Schmitt, D Sams, CF AF Hashemi, BB Hatton, JP Schmitt, D Sams, CF TI Rearrangement of the cytoskeletal architecture and polarization of T-cells inhibited in microgravity culture during space flight. SO FASEB JOURNAL LA English DT Meeting Abstract C1 ETSS, F-67065 Strasbourg, France. NASA, Lyndon B Johnson Space Ctr, Life Sci Res Labs, Houston, TX 77058 USA. NR 0 TC 2 Z9 2 U1 0 U2 0 PU FEDERATION AMER SOC EXP BIOL PI BETHESDA PA 9650 ROCKVILLE PIKE, BETHESDA, MD 20814-3998 USA SN 0892-6638 J9 FASEB J JI Faseb J. PD MAR 20 PY 1998 VL 12 IS 5 SU S MA 3640 BP A626 EP A626 PN 2 PG 1 WC Biochemistry & Molecular Biology; Biology; Cell Biology SC Biochemistry & Molecular Biology; Life Sciences & Biomedicine - Other Topics; Cell Biology GA 121HD UT WOS:000076006500022 ER PT J AU Heeke, DS White, MP Mele, GD Hanifin, JP Brainard, GC Rollag, MD Winget, CM Holley, DC AF Heeke, DS White, MP Mele, GD Hanifin, JP Brainard, GC Rollag, MD Winget, CM Holley, DC TI Light-emitting-diode (LED) light is similar to cool white fluorescent (CWF) light in suppressing pineal melatonin and maintaining retinal function and morphology in the rat. SO FASEB JOURNAL LA English DT Meeting Abstract C1 San Jose State Univ, San Jose, CA 95192 USA. Thomas Jefferson Univ, Jefferson Med Coll, Philadelphia, PA 19107 USA. Uniformed Serv Univ Hlth Sci, Bethesda, MD 20814 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU FEDERATION AMER SOC EXP BIOL PI BETHESDA PA 9650 ROCKVILLE PIKE, BETHESDA, MD 20814-3998 USA SN 0892-6638 J9 FASEB J JI Faseb J. PD MAR 20 PY 1998 VL 12 IS 5 SU S MA 6413 BP A1108 EP A1108 PN 2 PG 1 WC Biochemistry & Molecular Biology; Biology; Cell Biology SC Biochemistry & Molecular Biology; Life Sciences & Biomedicine - Other Topics; Cell Biology GA 121HD UT WOS:000076006502797 ER PT J AU McCormick, S Whitson, P McIntire, L AF McCormick, S Whitson, P McIntire, L TI The effect of shear stress on PGHS1 and PGHS2 protein levels in HUVECs SO FASEB JOURNAL LA English DT Meeting Abstract C1 NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. Rice Univ, Houston, TX 77005 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU FEDERATION AMER SOC EXP BIOL PI BETHESDA PA 9650 ROCKVILLE PIKE, BETHESDA, MD 20814-3998 USA SN 0892-6638 J9 FASEB J JI Faseb J. PD MAR 20 PY 1998 VL 12 IS 5 SU S MA 3728 BP A641 EP A641 PN 2 PG 1 WC Biochemistry & Molecular Biology; Biology; Cell Biology SC Biochemistry & Molecular Biology; Life Sciences & Biomedicine - Other Topics; Cell Biology GA 121HD UT WOS:000076006500110 ER PT J AU Moran, MM Eyestone, ME Hoban-Higgins, TM Fuller, CA Wade, CE AF Moran, MM Eyestone, ME Hoban-Higgins, TM Fuller, CA Wade, CE TI Body mass, food and water intake of aged rats in response to centrifugation. SO FASEB JOURNAL LA English DT Meeting Abstract C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Univ Calif Davis, Chron Accelerat Res Unit, Davis, CA 95616 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU FEDERATION AMER SOC EXP BIOL PI BETHESDA PA 9650 ROCKVILLE PIKE, BETHESDA, MD 20814-3998 USA SN 0892-6638 J9 FASEB J JI Faseb J. PD MAR 20 PY 1998 VL 12 IS 5 SU S MA 5554 BP A959 EP A959 PN 2 PG 1 WC Biochemistry & Molecular Biology; Biology; Cell Biology SC Biochemistry & Molecular Biology; Life Sciences & Biomedicine - Other Topics; Cell Biology GA 121HD UT WOS:000076006501939 ER PT J AU Syrkin, NJ Mele, GD Winger, CM Holley, DC AF Syrkin, NJ Mele, GD Winger, CM Holley, DC TI Light-emitting diodes (LED) and cool white fluorescent (CWF) light have similar effects on the circadian system of the rat. SO FASEB JOURNAL LA English DT Meeting Abstract C1 San Jose State Univ, Dept Biol Sci, San Jose, CA 95192 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU FEDERATION AMER SOC EXP BIOL PI BETHESDA PA 9650 ROCKVILLE PIKE, BETHESDA, MD 20814-3998 USA SN 0892-6638 J9 FASEB J JI Faseb J. PD MAR 20 PY 1998 VL 12 IS 5 SU S MA 4339 BP A748 EP A748 PN 2 PG 1 WC Biochemistry & Molecular Biology; Biology; Cell Biology SC Biochemistry & Molecular Biology; Life Sciences & Biomedicine - Other Topics; Cell Biology GA 121HD UT WOS:000076006500724 ER PT J AU Ueno, T Ballard, RE Shuer, LM Cantrell, JH Yost, WT Hargens, AR AF Ueno, T Ballard, RE Shuer, LM Cantrell, JH Yost, WT Hargens, AR TI Postural effects on intracranial pressure as assessed noninvasively. SO FASEB JOURNAL LA English DT Meeting Abstract C1 NASA, Ames Res Ctr, Gravitat Res Branch, Moffett Field, CA 94035 USA. Stanford Med Ctr, Stanford, CA 94305 USA. NASA, Langley Res Ctr, Hampton, VA 23665 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU FEDERATION AMER SOC EXP BIOL PI BETHESDA PA 9650 ROCKVILLE PIKE, BETHESDA, MD 20814-3998 USA SN 0892-6638 J9 FASEB J JI Faseb J. PD MAR 20 PY 1998 VL 12 IS 5 SU S MA 5550 BP A958 EP A958 PN 2 PG 1 WC Biochemistry & Molecular Biology; Biology; Cell Biology SC Biochemistry & Molecular Biology; Life Sciences & Biomedicine - Other Topics; Cell Biology GA 121HD UT WOS:000076006501934 ER PT J AU Wade, CE Moran, MM Eyestone, ME Hoban-Higgins, TM Fuller, CA AF Wade, CE Moran, MM Eyestone, ME Hoban-Higgins, TM Fuller, CA TI Altered renal handling of urea and sodium in old and young rats in response to 14 days of centrifugation SO FASEB JOURNAL LA English DT Meeting Abstract C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Univ Calif Davis, Davis, CA 95616 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU FEDERATION AMER SOC EXP BIOL PI BETHESDA PA 9650 ROCKVILLE PIKE, BETHESDA, MD 20814-3998 USA SN 0892-6638 J9 FASEB J JI Faseb J. PD MAR 20 PY 1998 VL 12 IS 5 SU S MA 5553 BP A959 EP A959 PN 2 PG 1 WC Biochemistry & Molecular Biology; Biology; Cell Biology SC Biochemistry & Molecular Biology; Life Sciences & Biomedicine - Other Topics; Cell Biology GA 121HD UT WOS:000076006501936 ER PT J AU Kidd, C AF Kidd, C TI On rainfall retrieval using polarization-corrected temperatures SO INTERNATIONAL JOURNAL OF REMOTE SENSING LA English DT Article ID MICROWAVE AB This paper describes a technique for the delineation and retrieval of rainfall from passive microwave data using the polarization-corrected temperature (PCT) algorithm. The main advantage of the technique is its ability to reduce the effect of background surface emissivities making it possible to delineate areas of rainfall over varying surface types. This ability is most important when attempting to retrieve rainfall over coastal areas with emissivity signatures from sea, land and combinations of these two. This paper outlines the formula;ion of polarization-corrected temperatures, and its use with data from the Special Sensor Microwave/Imager. Central to the success of the technique is the appropriate assignment of values to two key variables: One effecting the calculation of the polarization-corrected temperature, the other the threshold of the rain/no-rain boundary. A method is examined whereby both variables are generated from the analysis of the data. The technique is applied to one year of data over the United Kingdom to examine the dependence of these variables on the seasonal cycle. Initial results indicate that the technique is good at delineating rainfall and adjusting for seasonal fluctuations in the background surface temperature. However, retrieval of rainfall rates from the PCT using a constant relationship is less promising due to differences in cloud structure affecting the PCT to rain-rate conversion. C1 Univ Bristol, Dept Geog, Ctr Remote Sensing, Bristol BS8 1SS, Avon, England. RP Kidd, C (reprint author), NASA, Goddard Space Flight Ctr, Univ Space Res Assoc, Code 912, Greenbelt, MD 20771 USA. RI Kidd, Christopher/H-9910-2014 NR 15 TC 34 Z9 34 U1 0 U2 5 PU TAYLOR & FRANCIS LTD PI LONDON PA ONE GUNPOWDER SQUARE, LONDON EC4A 3DE, ENGLAND SN 0143-1161 J9 INT J REMOTE SENS JI Int. J. Remote Sens. PD MAR 20 PY 1998 VL 19 IS 5 BP 981 EP 996 DI 10.1080/014311698215829 PG 16 WC Remote Sensing; Imaging Science & Photographic Technology SC Remote Sensing; Imaging Science & Photographic Technology GA ZJ052 UT WOS:000073174700011 ER PT J AU Hegg, DA Kaufman, YJ AF Hegg, DA Kaufman, YJ TI Measurements of the relationship between submicron aerosol number and volume concentration SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID CLOUD-CONDENSATION-NUCLEI; SULFATE AEROSOL; LIGHT-SCATTERING; ALBEDO; SUPERSATURATION; PARTICLE; MODEL; CCN AB The relationship between aerosol number concentration and volume, or mass, concentration is a key linkage for the impact of aerosols on cloud albedo and thus climate forcing. Furthermore, this relationship is important in interpreting aerosol remote retrievals by satellites. We report here aircraft data, primarily from the TARFOX (Tropospheric Aerosol Radiative Forcing Experiment) study, which suggest a general linear relationship between aerosol number and mass concentration in the effective cloud condensation nucleus (CCN) size range (diameter >0.1 mu m) for the locations examined. Limited data on the relationship between aerosol number concentration and chemical composition are also presented, which show a preferential dependence of effective CCN number concentration on sulfate mass. However, an implicit dependence on organic mass is also suggested. C1 Univ Washington, Dept Atmospher Sci, Seattle, WA 98195 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Hegg, DA (reprint author), Univ Washington, Dept Atmospher Sci, Box 351640, Seattle, WA 98195 USA. EM deanhegg@atmos.washington.edu; kaufman@climate.gsfc.nasa.gov NR 23 TC 23 Z9 23 U1 1 U2 6 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD MAR 20 PY 1998 VL 103 IS D5 BP 5671 EP 5678 DI 10.1029/97JD03652 PG 8 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA ZC819 UT WOS:000072621300003 ER PT J AU Manney, GL Bird, JC Donovan, DP Duck, TJ Whiteway, JA Pal, SR Carswell, AI AF Manney, GL Bird, JC Donovan, DP Duck, TJ Whiteway, JA Pal, SR Carswell, AI TI Modeling ozone laminae in ground-based Arctic wintertime observations using trajectory calculations and satellite data SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID POLAR VORTEX CONDITIONS; STRATOSPHERE; ATMOSPHERE; LIDAR; AEROSOL AB Reverse-trajectory calculations initialized with ozone. observed by the Upper Atmosphere Research Satellite Microwave Limb Sounder (MLS) provide high-resolution ozone profiles for comparison with lidar and ozonesonde observations from the Arctic Stratospheric Observatory facility near Eureka in the Canadian Arctic (similar to 80 degrees N) 86 degrees W) By statistical measures, calculated profiles show a small average improvement over MLS profiles in the agreement of small-scale structure with that in ground-based observations throughout the stratosphere, and a larger (although still modest) and more consistent improvement in the lower stratosphere. Nearly all of the calculated profiles initialized with daily gridded MLS data show some improvement in the lower stratosphere. Even in cases where overall agreement between profiles is mediocre, there are frequently one or more individual features in the calculated profiles that strongly resemble laminae in the ground-based observations. Differential advection of ozone by the large-scale winds. leads to lamination in three distinct ways. Filamentation results in lamination throughout the stratosphere, with comparable features arising from initializations with gridded MLS data and with potential vorticity/theta-space reconstructions of MLS data (reconstructed (RC) fields). Laminae also form in the middle and lower stratosphere in conjunction with intrusions into the vortex; while calculations initialized with RC fields produce laminae, the agreement of structure calculated using gridded MLS initialization data with ground-based observations is distinctly better. Inside the lower stratospheric vortex, laminae form by advection of local features in the MLS initialization fields; RC-initialized calculations fail to produce any significant features since these local ozone variations are not strongly correlated with potential vorticity. That local features observed by MLS are needed to produce laminae resembling those in independent ground-based observations at Eureka indicates that both datasets are capturing real atmospheric features. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Ctr Res Earth & Space Technol, Lidar Lab, N York, ON M3J 3K1, Canada. York Univ, Dept Phys & Astron, N York, ON M3J 3K1, Canada. Univ Coll Wales, Dept Phys, Aberystwyth SY23 3BZ, Dyfed, Wales. RP Manney, GL (reprint author), CALTECH, Jet Prop Lab, Mail Stop 183-701, Pasadena, CA 91109 USA. EM manney@mls.jpl.nasa.gov NR 32 TC 33 Z9 33 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 MAR 20 PY 1998 VL 103 IS D5 BP 5797 EP 5814 DI 10.1029/97JD03449 PG 18 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA ZC819 UT WOS:000072621300013 ER PT J AU Orsolini, YJ Manney, GL Engel, A Ovarlez, J Claud, C Coy, L AF Orsolini, YJ Manney, GL Engel, A Ovarlez, J Claud, C Coy, L TI Layering in stratospheric profiles of long-lived trace species: Balloon-borne observations and modeling SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID ARCTIC POLAR VORTEX; LAMINATED STRUCTURE; OZONE PROFILES; EASOE; WINTER AB A series of balloon flights conducted in March 1993 from Aire-sur-Adour, in southern France, aimed at making in situ measurements of a variety of trace gases in the polar vortex during a dynamically active period. Meteorological analyses indicate that the balloons were launched when the vortex edge was passing aloft. These mid latitude balloon flights revealed coincident layering in long-lived tropospheric source gases such as nitrous oxide, methane and halocarbons as well. as in ozone and water vapor. At low altitudes, well-resolved laminations appeared clearly in all these gases. A layer of mid latitude air, enriched in trace gases, was detected at the highest sampled level, near 15 mbar, inducing a pronounced reversal in the profiles of tropospheric source gases. Using global meteorological analyses, trace constituent data derived from the UARS observations and high-resolution advection models, fine-scale distributions of ozone, nitrous oxide, methane, and halocarbons have been constructed. The calculations show qualitatively how such profile reversal arises near 15 mbar, when a filament of air enriched in trace gases is drawn into the outer portion of the vortex. Very high resolution calculations furthermore provide reasonable quantitative agreement between predicted tracer mixing ratios and in situ balloon-borne measurements. C1 Meteo France, Ctr Natl Rech Meteorol, F-31057 Toulouse, France. CNRS, Lab Meteorol Dynam, Paris, France. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Goethe Univ Frankfurt, Inst Meteorol & Geophys, D-6000 Frankfurt, Germany. CALTECH, Jet Prop Lab, Pasadena, CA USA. RP Orsolini, YJ (reprint author), Meteo France, Ctr Natl Rech Meteorol, 42 Ave G Coriolis, F-31057 Toulouse, France. EM yvan.orsolini@meteo.fr RI Engel, Andreas/E-3100-2014; OI Engel, Andreas/0000-0003-0557-3935; Claud, Chantal/0000-0001-7613-9525 NR 25 TC 25 Z9 25 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 MAR 20 PY 1998 VL 103 IS D5 BP 5815 EP 5825 DI 10.1029/97JD03131 PG 11 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA ZC819 UT WOS:000072621300014 ER PT J AU Staehelin, J Renaud, A Bader, J McPeters, R Viatte, P Hoegger, B Bugnion, V Giroud, M Schill, H AF Staehelin, J Renaud, A Bader, J McPeters, R Viatte, P Hoegger, B Bugnion, V Giroud, M Schill, H TI Total ozone series at Arosa (Switzerland): Homogenization and data comparison SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID STRATOSPHERIC OZONE; TRENDS AB Five Dobson and two Brewer spectrophotometers were used for total ozone observations at Arosa, beginning in 1926 and providing the world's longest Series. In this paper we present the results of our attempts to provide a homogeneous series and discuss the data quality problems of the record. From the mid-1950s to 1992, Dobson instrument D15 was calibrated by the statistical Langley plot method. In 1986 the calibration of another Dobson spectrometer at Arosa (D101) was changed by the intercomparison with the primary world Dobson instrument (D83). A statistical model based on simultaneous measurements of D101 and D15 of the period from 1987 to 1990 was used to obtain a total ozone series in Line with the primary Dobson spectrophotometer, including a correction for an optical disalignment problem of D15. The series of D101 from 1990 to 1995 was corrected on the basis of data from the Dobson intercomparisons of 1990 and 1995 and comparisons with other total ozone measurements of Brewer and Dobson spectrophotometers at Arosa. A transfer function between Dobson and Brewer spectrophotometric measurements of Arosa is presented, and total ozone measurements of Arosa are compared with version 7 daily overpass data of the satellite instrument the total ozone mapping spectrometer (TOMS) which operated on board Nimbus 7 from autumn 1978 to spring 1993. Available information allowing us to track back the total ozone measurements of Arosa to the measurements of the primary Dobson spectrometer reveal that the total ozone series of Arosa fluctuated no more than approximately 1% against D83 in the period from 1978 to 1995. Average shift of Arosa total ozone data against the TOMS instrument was -1.12 (+/-0.1)% over the lifetime of the TOMS instrument. C1 ETH Honggerberg, Inst Atmospher Sci, CH-8093 Zurich, Switzerland. Aerol Stn, CH-1530 Payerne, Switzerland. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. GeoSol, CH-4052 Basel, Switzerland. RP Staehelin, J (reprint author), ETH Honggerberg, Inst Atmospher Sci, CH-8093 Zurich, Switzerland. EM staehelin@atmos.umnw.ethz.ch RI McPeters, Richard/G-4955-2013 OI McPeters, Richard/0000-0002-8926-8462 NR 57 TC 72 Z9 73 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 MAR 20 PY 1998 VL 103 IS D5 BP 5827 EP 5841 DI 10.1029/97JD02402 PG 15 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA ZC819 UT WOS:000072621300015 ER PT J AU Hsieh, ST Lillywhite, HB Ballard, RE Hargens, AR AF Hsieh, ST Lillywhite, HB Ballard, RE Hargens, AR TI Cardiovascular responses of snakes to gravitational gradients SO FASEB JOURNAL LA English DT Meeting Abstract C1 NASA, Ames Res Ctr, Gravitat Res Branch, Moffett Field, CA 94035 USA. Univ Calif Berkeley, Berkeley, CA 94720 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU FEDERATION AMER SOC EXP BIOL PI BETHESDA PA 9650 ROCKVILLE PIKE, BETHESDA, MD 20814-3998 USA SN 0892-6638 J9 FASEB J JI Faseb J. PD MAR 17 PY 1998 VL 12 IS 4 SU S MA 1935 BP A333 EP A333 PN 1 PG 1 WC Biochemistry & Molecular Biology; Biology; Cell Biology SC Biochemistry & Molecular Biology; Life Sciences & Biomedicine - Other Topics; Cell Biology GA 121HC UT WOS:000076006401932 ER PT J AU Liang, MTC Arnaud, SB Whalen, R Breit, G Cleek, T Navidi, M AF Liang, MTC Arnaud, SB Whalen, R Breit, G Cleek, T Navidi, M TI High salt diets, bone strength and mineral content of mature femur after skeletal unloading. SO FASEB JOURNAL LA English DT Meeting Abstract C1 Bowling Green State Univ, Bowling Green, OH 43403 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU FEDERATION AMER SOC EXP BIOL PI BETHESDA PA 9650 ROCKVILLE PIKE, BETHESDA, MD 20814-3998 USA SN 0892-6638 J9 FASEB J JI Faseb J. PD MAR 17 PY 1998 VL 12 IS 4 SU S MA 1433 BP A246 EP A246 PN 1 PG 1 WC Biochemistry & Molecular Biology; Biology; Cell Biology SC Biochemistry & Molecular Biology; Life Sciences & Biomedicine - Other Topics; Cell Biology GA 121HC UT WOS:000076006401430 ER PT J AU Lopez, V Clegg, MS Globus, RK Keen, CL AF Lopez, V Clegg, MS Globus, RK Keen, CL TI Zinc deficiency induces apoptosis in primary rat osteoblasts SO FASEB JOURNAL LA English DT Meeting Abstract C1 Univ Calif Davis, Dept Nutr, Davis, CA 95616 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU FEDERATION AMER SOC EXP BIOL PI BETHESDA PA 9650 ROCKVILLE PIKE, BETHESDA, MD 20814-3998 USA SN 0892-6638 J9 FASEB J JI Faseb J. PD MAR 17 PY 1998 VL 12 IS 4 SU S MA 2014 BP A346 EP A346 PN 1 PG 1 WC Biochemistry & Molecular Biology; Biology; Cell Biology SC Biochemistry & Molecular Biology; Life Sciences & Biomedicine - Other Topics; Cell Biology GA 121HC UT WOS:000076006402009 ER PT J AU Smith, SM Block, G Rice, BL Davis-Street, JE Lane, HW AF Smith, SM Block, G Rice, BL Davis-Street, JE Lane, HW TI A food frequency questionnaire (FFQ) for use during space flight: A ground-based evaluation. SO FASEB JOURNAL LA English DT Meeting Abstract C1 NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. Univ Calif Berkeley, Berkeley, CA 94720 USA. RI Block, Gladys/E-3304-2010 NR 0 TC 0 Z9 0 U1 0 U2 0 PU FEDERATION AMER SOC EXP BIOL PI BETHESDA PA 9650 ROCKVILLE PIKE, BETHESDA, MD 20814-3998 USA SN 0892-6638 J9 FASEB J JI Faseb J. PD MAR 17 PY 1998 VL 12 IS 4 SU S MA 3057 BP A526 EP A526 PN 1 PG 1 WC Biochemistry & Molecular Biology; Biology; Cell Biology SC Biochemistry & Molecular Biology; Life Sciences & Biomedicine - Other Topics; Cell Biology GA 121HC UT WOS:000076006403053 ER PT J AU Takamata, A Ito, T Yaegashi, K Takamiya, H Maegawa, Y Itoh, T Morimoto, T Greenleaf, JE AF Takamata, A Ito, T Yaegashi, K Takamiya, H Maegawa, Y Itoh, T Morimoto, T Greenleaf, JE TI Effect of heat acclimation on body fluid regulation in older subjects. SO FASEB JOURNAL LA English DT Meeting Abstract C1 Kyoto Prefectural Univ Med, Dept Physiol, Kyoto 602, Japan. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. NR 0 TC 0 Z9 0 U1 0 U2 2 PU FEDERATION AMER SOC EXP BIOL PI BETHESDA PA 9650 ROCKVILLE PIKE, BETHESDA, MD 20814-3998 USA SN 0892-6638 J9 FASEB J JI Faseb J. PD MAR 17 PY 1998 VL 12 IS 4 SU S MA 725 BP A125 EP A125 PN 1 PG 1 WC Biochemistry & Molecular Biology; Biology; Cell Biology SC Biochemistry & Molecular Biology; Life Sciences & Biomedicine - Other Topics; Cell Biology GA 121HC UT WOS:000076006400730 ER PT J AU Copi, CJ Olive, KA Schramm, DN AF Copi, CJ Olive, KA Schramm, DN TI Implications of a primordial origin for the dispersion in D/H in quasar absorption systems SO PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA LA English DT Article ID BIG-BANG NUCLEOSYNTHESIS; DEUTERIUM ABUNDANCE; INFLATIONARY UNIVERSE; BARYOGENESIS; DENSITY; FLUCTUATIONS; GENERATION; MECHANISM; COMPLEX; LIGHT AB We explore the difficulties with a primordial origin of variations of D/H in quasar absorption systems. In particular we examine options such as a very large-scale inhomogeneity in the baryon content of the universe. We show that very large-scale (much larger than 1 Mpc) isocurvature perturbations are excluded by current cosmic microwave background observations, Smaller-scale ad hoc perturbations (similar to 1 Mpc) still may lead to a large dispersion in primordial abundances but are subject to other constraints. C1 Univ Chicago, Ctr Astron & Astrophys, Chicago, IL 60637 USA. Case Western Reserve Univ, Cleveland, OH 44106 USA. Univ Minnesota, Sch Phys & Astron, Minneapolis, MN 55455 USA. Fermi Natl Accelerator Lab, NASA, Fermilab Astrophys Ctr, Batavia, IL 60510 USA. RP Olive, KA (reprint author), Univ Chicago, Ctr Astron & Astrophys, 5640 S Ellis Ave, Chicago, IL 60637 USA. NR 27 TC 6 Z9 6 U1 0 U2 0 PU NATL ACAD SCIENCES PI WASHINGTON PA 2101 CONSTITUTION AVE NW, WASHINGTON, DC 20418 USA SN 0027-8424 J9 P NATL ACAD SCI USA JI Proc. Natl. Acad. Sci. U. S. A. PD MAR 17 PY 1998 VL 95 IS 6 BP 2758 EP 2760 DI 10.1073/pnas.95.6.2758 PG 3 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA ZC589 UT WOS:000072596200011 PM 9501162 ER PT J AU Tessler, A Riggs, HR Freese, CE Cook, GM AF Tessler, A Riggs, HR Freese, CE Cook, GM TI An improved variational method for finite element stress recovery and a posteriori error estimation SO COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING LA English DT Article ID PATCH RECOVERY; SHEAR AB A new variational formulation is presented which serves as a foundation for an improved finite element stress recovery and a posteriori error estimation. In the case of stress predictions, interelement discontinuous stress fields from finite element solutions are transformed into a C-1-continuous stress field with C-0-continuous stress gradients. These enhanced results are ideally suited for error estimation since the stress gradients can be used to assess equilibrium satisfaction. The approach is employed as a post-processing step in finite element analysis. The variational statement used herein combines discrete-least squares, penalty-constraint, and curvature-control functionals, thus enabling automated recovery of smooth stresses and stress gradients. The paper describes the mathematical foundation of the method and presents numerical examples including stress recovery in two-dimensional structures and built-up aircraft components, and error estimation for adaptive mesh refinement procedures. (C) 1998 Elsevier Science S.A. C1 NASA, Langley Res Ctr, Computat Struct Branch, Hampton, VA 23681 USA. Univ Hawaii Manoa, Dept Civil Engn, Honolulu, HI 96822 USA. USA, Res Lab, Mat Directorate, Watertown, MA USA. George Washington Univ, NASA, Langley Res Ctr, Hampton, VA USA. RP Tessler, A (reprint author), NASA, Langley Res Ctr, Computat Struct Branch, Hampton, VA 23681 USA. RI Tessler, Alexander/A-4729-2009 NR 24 TC 18 Z9 18 U1 0 U2 3 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 MAR 16 PY 1998 VL 155 IS 1-2 BP 15 EP 30 DI 10.1016/S0045-7825(97)00135-7 PG 16 WC Engineering, Multidisciplinary; Mathematics, Interdisciplinary Applications; Mechanics SC Engineering; Mathematics; Mechanics GA ZJ008 UT WOS:000073170300002 ER PT J AU Liu, WT Tang, WQ Polito, PS AF Liu, WT Tang, WQ Polito, PS TI NASA scatterometer provides global ocean-surface wind fields with more structures than numerical weather prediction SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article AB The major differences between monthly-mean ocean-surface wind fields derived from the observations of the National Aeronautics and Space Administration (NASA) Scatterometer (NSCAT) and produced by the operational numerical weather prediction (NWP) model of the European Center for Medium-Range Weather Forecasts are found in coastal and equatorial regions, where the sharp changes are smoothed over in NWP products; these wind differences are explained to be the result of the superior spatial resolution of NSCAT winds. Objective interpolation of NSCAT data alleviates errors caused by the uneven satellite sampling and retains greater energy content of NSCAT winds at high wavenumbers. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Liu, WT (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. RI Polito, Paulo/F-3040-2013 OI Polito, Paulo/0000-0003-2217-3853 NR 10 TC 111 Z9 114 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 MAR 15 PY 1998 VL 25 IS 6 BP 761 EP 764 DI 10.1029/98GL00544 PG 4 WC Geosciences, Multidisciplinary SC Geology GA ZD051 UT WOS:000072645900001 ER PT J AU Rosen, P Werner, C Fielding, E Hensley, S Buckley, S Vincent, P AF Rosen, P Werner, C Fielding, E Hensley, S Buckley, S Vincent, P TI Aseismic creep along the San Andreas Fault northwest of Parkfield, CA measured by radar interferometry SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID CENTRAL CALIFORNIA; SURFACE DEFORMATION; EARTHQUAKE AB ERS-1 radar images acquired 14 months apart studied by differential radar interferometry show the wide-area distribution of aseismic creep along the fault segment northwest of Parkfield, California. A sharp discontinuity in the interferometric phase of less than 2 cm equivalent line-of-sight displacement extends over 80 km in the differential interferogram, coincident with the mapped trace of the active San Andreas fault and consistent with the expected and measured fault motion. Although patterns of strain associated with the transition from locked to creeping are not clearly identifiable, a decrease in creep displacement from northwest to southeast along the fault is visible. The observations are in agreement with a model of elastic deformation constrained by in situ data that supports a maximum expected deformation signature of 10 mm across the image. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Rosen, P (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. RI Fielding, Eric/A-1288-2007 OI Fielding, Eric/0000-0002-6648-8067 NR 19 TC 28 Z9 28 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 MAR 15 PY 1998 VL 25 IS 6 BP 825 EP 828 DI 10.1029/98GL50495 PG 4 WC Geosciences, Multidisciplinary SC Geology GA ZD051 UT WOS:000072645900017 ER PT J AU Hashimoto, K Matsumoto, H Murata, T Kaiser, ML Bougeret, JL AF Hashimoto, K Matsumoto, H Murata, T Kaiser, ML Bougeret, JL TI Comparison of AKR simultaneously observed by the GEOTAIL and WIND spacecraft SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID TERRESTRIAL KILOMETRIC RADIATION; PROPAGATION; RADIO AB AKR dynamic spectra observed with the GEOTAIL Plasma Wave Instrument (PWI) and the WIND WAVES investigation are compared. GEOTAIL was in the near earth orbit of 10 - 50 R-E until February and 10 - 30 R-E after March 1995. WIND was in near-earth orbits of a few to 75 R-E in November - December 1994, and was mainly in a 'halo' orbit of about 200 R-E between Earth and the sun in 1995. The comparison is made for the following two cases, (a) both satellites are in the near-earth orbits, and (b) when GEOTAIL was in the near-earth orbits and WIND was in the 'halo' orbit. The observations are compared with ray tracing to explain the results. Most observations are explained in terms of AKR source locations around 21-22 MLT, but some cannot be explained unless the source locations are assumed to be extended to around 19 MLT during substorms. C1 Kyoto Univ, Ctr Radio Atmospher Sci, Kyoto 6110011, Japan. Observ Paris, F-92195 Meudon, France. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Ehime Univ, Matsuyama, Ehime 790, Japan. RP Hashimoto, K (reprint author), Kyoto Univ, Ctr Radio Atmospher Sci, Kyoto 6110011, Japan. 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 MAR 15 PY 1998 VL 25 IS 6 BP 853 EP 856 DI 10.1029/98GL00385 PG 4 WC Geosciences, Multidisciplinary SC Geology GA ZD051 UT WOS:000072645900024 ER PT J AU Liemohn, MW Khazanov, GV Kozyra, JU AF Liemohn, MW Khazanov, GV Kozyra, JU TI Banded electron structure formation in the inner magnetosphere SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID CENTRAL PLASMA SHEET; MODEL; SUBSTORM AB Banded electron structures in energy-time spectrograms have been observed in the inner magnetosphere concurrent with a sudden relaxation of geomagnetic activity. In this study, the formation of these banded structures is considered with a global, bounce-averaged model of electron transport, and it is concluded that this structure is a natural occurrence when plasma sheet electrons are captured on closed drift paths near the Earth followed by an extended period of quiet time for more than a day. These bands do not appear unless there is capture of plasma sheet electrons; convection along open drift paths making one pass around the Earth do not have time to develop this feature. The separation of high-energy bands from the injected population due to the preferential advection of the gradient-curvature drift creates spikes in the energy distribution above a keV, which overlap to form a series of bands in energy. The lowest band is the bulk of the injected population in the sub-keV energy range. Using the Kp history for an observed banded structure event, a cloud of plasma sheet electrons is captured and the formation of their distribution function is examined. C1 NASA, George C Marshall Space Flight Ctr, Space Sci Lab, Huntsville, AL 35812 USA. Univ Alaska Fairbanks, Inst Geophys, Dept Phys, Fairbanks, AK 99775 USA. Univ Michigan, Space Phys Res Lab, Ann Arbor, MI 48109 USA. RP Liemohn, MW (reprint author), NASA, George C Marshall Space Flight Ctr, Space Sci Lab, Mail Code ES-83, Huntsville, AL 35812 USA. RI Liemohn, Michael/H-8703-2012 OI Liemohn, Michael/0000-0002-7039-2631 NR 11 TC 14 Z9 14 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 MAR 15 PY 1998 VL 25 IS 6 BP 877 EP 880 DI 10.1029/98GL00411 PG 4 WC Geosciences, Multidisciplinary SC Geology GA ZD051 UT WOS:000072645900030 ER PT J AU Jackman, CH Considine, DB Fleming, EL AF Jackman, CH Considine, DB Fleming, EL TI A global modeling study of solid rocket aluminum oxide emission effects on stratospheric ozone SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID IMPACT AB Recent laboratory measurements [Molina st al. 1997] have indicated that the heterogeneous chlorine activation reaction ClONO2 + HCl --> HNO3 + Cl-2 has a reaction probability of about 0.02 on aluminum oxide particles (alumina). Since alumina is among those substances emitted by solid rocket motors (SRMs), we have assessed the heterogeneous chemical impact of SRM-emitted alumina on stratospheric ozone using the Goddard Space Flight Center two-dimensional photochemistry and transport model. Historical launch rates of the Space Shuttle, Titan III, and Titan IV rockets were used in time-dependent and steady-state model calculations. Variations in the temporal ozone decreases reflected the fluctuation in launch rate frequency. The annually averaged global total ozone (AAGTO) is computed to decrease by 0.025% by the year 1997. About one-third of this AAGTO change results from the SRM-emitted alumina while about two-thirds is due to SRM-emitted hydrogen chloride. C1 NASA, Goddard Space Flight Ctr, Atmospher Chem & Dynam Branch, Greenbelt, MD 20771 USA. Univ Maryland, Joint Ctr Earth Syst Sci, College Pk, MD 20742 USA. Space Applicat Corp, Vienna, VA USA. RP Jackman, CH (reprint author), NASA, Goddard Space Flight Ctr, Atmospher Chem & Dynam Branch, Code 916, Greenbelt, MD 20771 USA. RI Jackman, Charles/D-4699-2012 NR 20 TC 23 Z9 23 U1 2 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 MAR 15 PY 1998 VL 25 IS 6 BP 907 EP 910 DI 10.1029/98GL00403 PG 4 WC Geosciences, Multidisciplinary SC Geology GA ZD051 UT WOS:000072645900038 ER PT J AU Jiang, YB Yung, YL Douglass, AR Tung, KK AF Jiang, YB Yung, YL Douglass, AR Tung, KK TI The standard deviation of column ozone from the zonal mean SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID PLANETARY-WAVES; NORTHERN; TRENDS; CYCLE AB The standard deviation of column ozone from the zonal mean (COSDZ) provides a measure of the longitudinal inhomogeneity in ozone and dynamical wave activities in the atmosphere. Using the Total Ozone Mapping Spectrometer (TOMS) data, we obtain latitude-season maps of COSDZ that are representative of a dynamically quiet year (1987) and a dynamically active year (1992). The spatial and temporal patterns of COSDZ show considerable similarity to the standard deviation of the 50 mb geopotential heights from the zonal mean We point out that the simulation of this quantity by three-dimensional (3-D) models could provide a sensitive check of wave activities in the stratosphere that are responsible for ozone transport. Comparison between the observed COSDZ and the simulations of the GSFC 3-D model of ozone reveals major discrepancies between data and model in the tropical stratosphere. C1 NASA, Goddard Space Flight Ctr, Atmospheres Lab, Greenbelt, MD 20771 USA. Univ Washington, Dept Appl Math, Seattle, WA 98195 USA. CALTECH, Div Geol & Planetary Sci, Pasadena, CA 91125 USA. RP Jiang, YB (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. EM ybj@mercu1.gps.caltech.edu RI Douglass, Anne/D-4655-2012 NR 17 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 MAR 15 PY 1998 VL 25 IS 6 BP 911 EP 914 DI 10.1029/98GL00329 PG 4 WC Geosciences, Multidisciplinary SC Geology GA ZD051 UT WOS:000072645900039 ER PT J AU Beyerle, G Schafer, HJ Neuber, R Schrems, O McDermid, IS AF Beyerle, G Schafer, HJ Neuber, R Schrems, O McDermid, IS TI Dual wavelength lidar observation of tropical high-altitude cirrus clouds during the ALBATROSS 1996 campaign SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID STRATOSPHERE; SCATTERING; AIR AB Dual wavelength aerosol lidar observations of tropical high-altitude cirrus clouds were performed during the ALBATROSS 1996 campaign aboard the research vessel "POLARSTERN" on the Atlantic ocean in October-November 1996. On the basis of 57 hours of night-time observations between 23.5 degrees N and 23.5 degrees S we find in 72% of the altitude profiles indications of the presence of cirrus cloud layers. This percentage drops to 32% at subtropical latitudes (23.5 degrees-30 degrees) based on 15 hours of data. About one-half of the subtropical and tropical cirrus layers are subvisual with an optical depth of less than 0.03 at a wavelength of 532 nm. In general the clouds exhibit high spatial and temporal variability on scales of a few tens of meters vertically and a few hundred meters horizontally. No clouds are observed above the tropopause An abrupt change in the relation between the color ratios of the parallel and perpendicular backscatter coefficients at about 240 K is interpreted in terms of changes of particle shape and/or size distribution. At temperatures between 195 and 255 K only a small fraction of the observations are consistent with the presence of small particles with dimensions of less than 0.1 mu m. C1 CALTECH, Jet Prop Lab, Table Mt Facil, Wrightwood, CA 92397 USA. Alfred Wegener Inst Polar & Marine Res, D-27515 Bremerhaven, Germany. Alfred Wegener Inst Polar & Marine Res, D-14401 Potsdam, Germany. RP Beyerle, G (reprint author), CALTECH, Jet Prop Lab, Table Mt Facil, POB 367, Wrightwood, CA 92397 USA. RI Neuber, Roland/B-4923-2014; OI Neuber, Roland/0000-0001-7382-7832; Beyerle, Georg/0000-0003-1215-2418 NR 16 TC 14 Z9 14 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 MAR 15 PY 1998 VL 25 IS 6 BP 919 EP 922 DI 10.1029/98GL00491 PG 4 WC Geosciences, Multidisciplinary SC Geology GA ZD051 UT WOS:000072645900041 ER PT J AU Li, XF Sui, CH Adamec, D Lau, KM AF Li, XF Sui, CH Adamec, D Lau, KM TI Impacts of precipitation in the upper ocean in the western Pacific warm pool during TOGA-COARE SO JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS LA English DT Article ID MIXED-LAYER; EQUATORIAL PACIFIC; TROPICAL OCEAN; HEAT; CIRCULATION; VARIABILITY; TEMPERATURE; SALINITY; MODELS AB An ocean mixed-layer model with a modified Kraus-Turner parameterization scheme is used to investigate the impacts of precipitation in the upper ocean in the western Pacific warm pool during Tropical Ocean Global Atmosphere-Coupled Ocean-Atmosphere Response Experiment (TOGA-COARE). Heat and salt budgets calculated in the upper ocean indicate local balance between surface forcing and the ocean response. Thus the mixed-layer model captures the dominant processes governing heat and salt variability. The model responses are analyzed and compared with the observed upper ocean in three distinctive layers determined by Monin-Obukhov length scales. In the top layer (the top 5 m), about 90% of the surface buoyancy flux is absorbed, and strong diurnal and intraseasonal variations are excited. The second layer, 5-20 m, contains intraseasonal variability that is characterized by nearly neutral stratification during strong westerly wind events, strong thermal stratification during clear-sky days, and strong saline stratification during heavy precipitation. The dominant effect of precipitation is to generate a stable stratification and to form a barrier layer. The third layer, 20-50 m, has intraseasonal variations due to mixing during westerly wind events. Heavy precipitation amplifies mixed-layer temperature fluctuations by a cycle of strong surface cooling and entrainment warming through the following processes. Heavy precipitation causes a shallower mixed layer and a larger cooling rate. Surface temperature drops rapidly, and the upper ocean becomes thermally unstable. The salinity maintains a-weak density stability, which causes strong entrainment warming. Surface freshwater flux is the key factor controlling saline structure when advection is excluded. However, experiments without the entrainment process show a significant bias toward a lower salinity, indicating that the entrainment process must be properly treated in the model to prevent a biased trend. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Space Applicat Corp, Vienna, VA USA. RP Li, XF (reprint author), NASA, Goddard Space Flight Ctr, Code 913, Greenbelt, MD 20771 USA. RI Li, Xiaofan/F-5605-2010; Li, Xiaofan/G-2094-2014; OI SUI, CHUNG-HSIUNG/0000-0003-2842-5660 NR 27 TC 24 Z9 25 U1 0 U2 6 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA J9 J GEOPHYS RES-OCEANS JI J. Geophys. Res.-Oceans PD MAR 15 PY 1998 VL 103 IS C3 BP 5347 EP 5359 DI 10.1029/97JC03420 PG 13 WC Oceanography SC Oceanography GA ZB957 UT WOS:000072525300002 ER PT J AU Fukumori, I Raghunath, R Fu, LL AF Fukumori, I Raghunath, R Fu, LL TI Nature of global large-scale sea level variability in relation to atmospheric forcing: A modeling study SO JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS LA English DT Article ID GENERAL-CIRCULATION MODEL; DATA ASSIMILATION; SATELLITE ALTIMETRY; OCEAN CIRCULATION; PACIFIC-OCEAN; WORLD OCEAN; WIND-STRESS; SURFACE; FLUCTUATIONS AB The relation between large-scale sea level variability and ocean circulation is studied using a numerical model. A global primitive equation model of the ocean is forced by daily winds and climatological heat fluxes corresponding to the period from January 1992 to January 1994. The physical nature of sea level's temporal variability from periods of days to a year is examined on the basis of spectral analyses of model results and comparisons with satellite altimetry and tide gauge measurements. The study elucidates and diagnoses the inhomogeneous physics of sea level change in space and frequency domain. At midlatitudes, large-scale sea level variability is primarily due to steric changes associated with the seasonal heating and cooling cycle of the surface layer. In comparison, changes in the tropics and high latitudes are mainly wind driven. Wind-driven variability exhibits a strong latitudinal dependence in itself. Wind-driven changes are largely baroclinic in the tropics but barotropic at higher latitudes. Baroclinic changes are dominated by the annual harmonic of the first baroclinic mode and is largest off the equator; variabilities associated with equatorial waves are smaller in comparison. Wind-driven barotropic changes exhibit a notable enhancement over several abyssal plains in the Southern Ocean, which is likely due to resonant planetary wave modes in basins semienclosed by discontinuities in potential vorticity. Otherwise, barotropic sea level changes are typically dominated by high frequencies with as much as half the total variance in periods shorter than 20 days, reflecting the frequency spectra of wind stress curl. Implications of the findings with regards to analyzing observations and data assimilation are discussed. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Fukumori, I (reprint author), CALTECH, Jet Prop Lab, Mail Stop 300-323,4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 41 TC 119 Z9 122 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 MAR 15 PY 1998 VL 103 IS C3 BP 5493 EP 5512 DI 10.1029/97JC02907 PG 20 WC Oceanography SC Oceanography GA ZB957 UT WOS:000072525300011 ER PT J AU Hammond, TG Goda, FO Navar, GL Campbell, WC Majewski, RR Galvan, DL Pontillon, F Kaysen, JH Goodwin, TJ Paddock, SW Verroust, PJ AF Hammond, TG Goda, FO Navar, GL Campbell, WC Majewski, RR Galvan, DL Pontillon, F Kaysen, JH Goodwin, TJ Paddock, SW Verroust, PJ TI Membrane potential mediates H+-ATPase dependence of "degradative pathway" endosomal fusion SO JOURNAL OF MEMBRANE BIOLOGY LA English DT Article DE kidney; flow cytometry; endosomal trafficking; yolk sac; energy transfer ID CELL-SURFACE; RAT-KIDNEY; V-ATPASE; YOLK-SAC; PROTEINS; VESICLES; TRANSPORT; GP330; SYNAPTOBREVIN; POPULATIONS AB In some epithelial cell lines, the uptake and degradation of proteins is so pronounced as to be regarded as a specialized function known as "degradative endocytosis." The endosomal pathways of the renal proximal tubule and the visceral yolk sac share highly specialized structures for "degradative endocytosis." These endosomal pathways also have a unique distribution of their H+-ATPase, predominantly in the subapical endosomal pathway. Previous studies provide only indirect evidence that H+-ATPases participate in endosomal fusion events: formation of vesicular intermediates between early and late endosomes is H+-ATPase dependent in baby hamster kidney cells, and H+-ATPase subunits bind fusion complex proteins in detergent extracts of fresh rat brain. To determine directly whether homotypic endosomal fusion is H+-ATPase dependent, we inhibited v-type H+-ATPase during flow cytometry and cuvette-based fusion assays reconstituting endosomal fusion in vitro. We report that homotypic fusion in subapical endosomes derived from rat renal cortex, and immortalized visceral yolk sac cells in culture, is inhibited by the v-type H+-ATPase specific inhibitor bafilomycin Al. Inhibition of fusion by H+-ATPase is mediated by the membrane potential as collapsing the pH gradient with nigericin had no effect on homotypic endosomal fusion, while collapsing the membrane potential with valinomycin inhibited endosomal fusion. Utilizing an in vitro reconstitution assay this data provides the first direct evidence for a role of v-type Hc-ATPase in mammalian homotypic endosomal fusion. C1 Tulane Univ, Sch Med, Tulane Environm Astrobiol Ctr, New Orleans, LA 70112 USA. New Orleans Vet Affairs Med Ctr, New Orleans, LA 70112 USA. Univ Wisconsin, Dept Med, Madison, WI USA. Univ Wisconsin, Sinai Samaritan Med Ctr, Cell Biol Lab, Milwaukee, WI USA. Hop Tenon, INSERM, U64, Paris, France. NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. Univ Wisconsin, Dept Biol Mol, Madison, WI USA. Univ Wisconsin, Howard Hughes Med Inst, Madison, WI USA. RP Hammond, TG (reprint author), Tulane Univ, Sch Med, Tulane Environm Astrobiol Ctr, 1430 Tulane Ave, New Orleans, LA 70112 USA. FU NCRR NIH HHS [R21 RR12645]; NIDDK NIH HHS [DK46117] NR 41 TC 18 Z9 18 U1 0 U2 1 PU SPRINGER PI NEW YORK PA 233 SPRING ST, NEW YORK, NY 10013 USA SN 0022-2631 EI 1432-1424 J9 J MEMBRANE BIOL JI J. Membr. Biol. PD MAR 15 PY 1998 VL 162 IS 2 BP 157 EP 167 DI 10.1007/s002329900353 PG 11 WC Biochemistry & Molecular Biology; Cell Biology; Physiology SC Biochemistry & Molecular Biology; Cell Biology; Physiology GA ZC175 UT WOS:000072548300008 PM 9538509 ER PT J AU Cordero, EC Nathan, TR Echols, RS AF Cordero, EC Nathan, TR Echols, RS TI An analytical study of ozone feedbacks on Kelvin and Rossby-gravity waves: Effects on the QBO SO JOURNAL OF THE ATMOSPHERIC SCIENCES LA English DT Article ID QUASI-BIENNIAL OSCILLATION; GENERAL-CIRCULATION MODEL; PLANETARY-WAVES; DIMENSIONAL MODEL; EQUATORIAL WAVES; STRATOSPHERE; PARAMETERIZATION; STABILITY AB An equatorial beta-plane model of the middle atmosphere is used to analytically examine the effects of radiative cooling and ozone heating on the spatial and temporal evolution of the quasi-biennial oscillation (QBO). Under the assumption that the diabatic heating is weak and the background fields of wind, temperature, and ozone are slowly varying, a perturbation analysis yields expressions describing the vertical spatial modulation of Kelvin and Rossby-gravity waves in the presence of ozone. These expressions show that wave-induced changes in the diabatic heating arising from the advection of basic-stare ozone reduce the local radiative damping rate by up to 15% below 35 km. In a one-dimensional model of the QBO, eddy ozone heating increases the amplitude of the zonal wind QBO by 1-2 m s(-1) and increases the oscillation period by about two months. The significance of these results to the observed QBO is discussed. C1 Univ Calif Davis, Dept Land Air & Water Resources, Atmospher Sci Program, Davis, CA USA. Univ Calif Santa Cruz, Dept Phys, Santa Cruz, CA 95064 USA. RP Cordero, EC (reprint author), NASA, Goddard Space Flight Ctr, Code 916, Greenbelt, MD 20771 USA. RI Nathan, Terrence/F-5958-2011 NR 38 TC 7 Z9 7 U1 1 U2 1 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 MAR 15 PY 1998 VL 55 IS 6 BP 1051 EP 1062 DI 10.1175/1520-0469(1998)055<1051:AASOOF>2.0.CO;2 PG 12 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA ZB373 UT WOS:000072465500009 ER PT J AU Brewer, WD Bird, RK Wallace, TA AF Brewer, WD Bird, RK Wallace, TA TI Titanium alloys and processing for high speed aircraft SO MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING LA English DT Article; Proceedings Paper CT Conference on Thermomechanical Processing and Metallurgy of Titanium Alloys CY JUL 07-11, 1997 CL UNIV WOLLONGONG, WOLLONGONG, AUSTRALIA SP Asian Off Aerosp Res & Dev, USAF, Off Sci Res HO UNIV WOLLONGONG DE Ti alloys; processing techniques; research AB Commercially available titanium alloys as well as emerging titanium alloys with limited or no production experience are being considered for a variety of applications to high speed commercial aircraft structures. A number of government and industry programs are underway to improve the performance of promising alloys by chemistry and/or processing modifications and to identify appropriate alloys and processes for specific aircraft structural applications. This paper discusses some results to date of NASA sponsored research on the effects of heat treatment, service temperatures from -54 to +177 degrees C, and selected processing on the mechanical properties of several candidate beta and alpha-beta titanium alloys. Included are beta alloys Timetal 21S, LCB, Beta-C, Beta-CEZ and Ti-10-2-3 and alpha-beta alloys Ti-62222, Ti-6242S, Timetal 550, Ti-62S, SP-700 and Corona-X. The emphasis is on strength and toughness properties of rolled sheet product and on the superplastic properties and processing of the materials. (C) 1998 Elsevier Science S.A. All rights reserved. C1 NASA, Langley Res Ctr, Met Mat Branch, Hampton, VA 23681 USA. RP Brewer, WD (reprint author), NASA, Langley Res Ctr, Met Mat Branch, 2 W Reid St, Hampton, VA 23681 USA. NR 6 TC 76 Z9 87 U1 2 U2 22 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 MAR 15 PY 1998 VL 243 IS 1-2 BP 299 EP 304 DI 10.1016/S0921-5093(97)00818-6 PG 6 WC Nanoscience & Nanotechnology; Materials Science, Multidisciplinary; Metallurgy & Metallurgical Engineering SC Science & Technology - Other Topics; Materials Science; Metallurgy & Metallurgical Engineering GA ZH762 UT WOS:000073145100043 ER PT J AU Lei, JF Will, HA AF Lei, JF Will, HA TI Thin-film thermocouples and strain-gauge technologies for engine applications SO SENSORS AND ACTUATORS A-PHYSICAL LA English DT Article DE engine applications; strain gauges; thin-film thermocouples AB Advanced thin-film sensor techniques that can provide accurate surface strain and temperature measurements are being developed at NASA Lewis Research Center. These sensors are needed to provide minimally intrusive characterization of advanced materials (such as ceramics and composites) and structures (such as components for Space Shuttle main engine, high-speed civil transport, and general aviation aircraft) in hostile, high-temperature environments, and for validation of design codes. This paper presents two advanced thin-film sensor technologies: strain gauges and thermocouples. These sensors are sputter deposited directly onto the test articles and are only a few micrometers thick; the surface of the test article is not structurally altered and there is minimal disturbance of the gas flow over the surface. The strain gauges are palladium-13% chromium based and the thermocouples are platinum-13% rhodium versus platinum. The fabrication techniques of these thin-film sensors in a class 1000 cleanroom at the NASA Lewis Research Center are described. Their demonstration on a variety of engine materials, including superalloys, ceramics, and advanced ceramic matrix composites, in several hostile, high-temperature test environments is discussed. (C) 1998 Elsevier Science S.A. C1 NASA, Lewis Res Ctr, Army Res Lab, Cleveland, OH 44135 USA. RP Lei, JF (reprint author), NASA, Lewis Res Ctr, Army Res Lab, Cleveland, OH 44135 USA. NR 17 TC 52 Z9 56 U1 2 U2 20 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 MAR 15 PY 1998 VL 65 IS 2-3 BP 187 EP 193 PG 7 WC Engineering, Electrical & Electronic; Instruments & Instrumentation SC Engineering; Instruments & Instrumentation GA ZD246 UT WOS:000072666000016 ER PT J AU Amir, Y Wool, A AF Amir, Y Wool, A TI Optimal availability quorum systems: Theory and practice SO INFORMATION PROCESSING LETTERS LA English DT Article DE quorum systems; distributed computing; fault tolerance; replication ID MANAGING REPLICATED DATA; MUTUAL EXCLUSION; ALGORITHM AB Quorum systems serve as a basic tool providing a uniform and reliable way to achieve coordination in a distributed system. They are useful for distributed and replicated databases, name servers, mutual exclusion, and distributed access control and signatures. The un-availability of a quorum system is the probability of the event that no live quorum exists in the system. When such an event occurs the service is completely halted. The un-availability is widely accepted as the measure by which quorum systems are evaluated. In this paper we characterize the optimal availability quorum system in the general case, when the failure probabilities may take any value in the range 0 < p(i) < 1. Then we deal with the practical scenario in which the failure probabilities are unknown, but can be estimated. We give a robust and efficient algorithm that calculates a near optimal quorum system based on the estimated failure probabilities. (C) 1998 Elsevier Science B.V. C1 Lucent Technol, Bell Labs, Murray Hill, NJ 07974 USA. Johns Hopkins Univ, Dept Comp Sci, Baltimore, MD 21218 USA. NASA, Ctr Excellence Space Data & Informat Sci, Washington, DC USA. Weizmann Inst Sci, Dept Appl Math & Comp Sci, IL-76100 Rehovot, Israel. RP Amir, Y (reprint author), Lucent Technol, Bell Labs, 700 Mt Ave, Murray Hill, NJ 07974 USA. EM yash@research.bell-labs.com RI Amir, Yair/A-3261-2010; Wool, Avishai/K-6185-2013 OI Wool, Avishai/0000-0002-8371-4759 NR 25 TC 18 Z9 21 U1 1 U2 1 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0020-0190 J9 INFORM PROCESS LETT JI Inf. Process. Lett. PD MAR 13 PY 1998 VL 65 IS 5 BP 223 EP 228 DI 10.1016/S0020-0190(98)00017-9 PG 6 WC Computer Science, Information Systems SC Computer Science GA ZK288 UT WOS:000073304200001 ER PT J AU Frank, J Gent, IP Walsh, T AF Frank, J Gent, IP Walsh, T TI Asymptotic and finite size parameters for phase transitions: Hamiltonian circuit as a case study SO INFORMATION PROCESSING LETTERS LA English DT Article DE analysis of algorithms; computational complexity; phase transitions; constrainedness; finite size scaling C1 Univ Strathclyde, Dept Comp Sci, Glasgow G1 1XH, Lanark, Scotland. NASA, Ames Res Ctr, Caelum Res Corp, Moffett Field, CA 94035 USA. RP Gent, IP (reprint author), Univ Strathclyde, Dept Comp Sci, Glasgow G1 1XH, Lanark, Scotland. RI Walsh, Toby/Q-9043-2016; OI Walsh, Toby/0000-0003-2998-8668; Gent, Ian/0000-0002-5604-7006 NR 16 TC 5 Z9 5 U1 1 U2 1 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0020-0190 J9 INFORM PROCESS LETT JI Inf. Process. Lett. PD MAR 13 PY 1998 VL 65 IS 5 BP 241 EP 245 DI 10.1016/S0020-0190(97)00222-6 PG 5 WC Computer Science, Information Systems SC Computer Science GA ZK288 UT WOS:000073304200004 ER PT J AU Albee, AL Palluconi, FD Arvidson, RE AF Albee, AL Palluconi, FD Arvidson, RE TI Mars global surveyor mission: Overview and status SO SCIENCE LA English DT Article AB The Mars Global Surveyor (MGS) spacecraft achieved a 45-hour elliptical orbit at Mars on 11 September 1997 after an 11-month cruise from Earth, The mission is acquiring high-quality global observations of the martian surface and atmosphere and of its magnetic and gravitational fields. These observations will continue for one martian year. C1 CALTECH, Pasadena, CA 91125 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Washington Univ, St Louis, MO 63130 USA. RP Albee, AL (reprint author), CALTECH, Pasadena, CA 91125 USA. NR 2 TC 94 Z9 97 U1 2 U2 11 PU AMER ASSOC ADVANCEMENT SCIENCE PI WASHINGTON PA 1200 NEW YORK AVE, NW, WASHINGTON, DC 20005 USA SN 0036-8075 J9 SCIENCE JI Science PD MAR 13 PY 1998 VL 279 IS 5357 BP 1671 EP 1672 DI 10.1126/science.279.5357.1671 PG 2 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA ZB612 UT WOS:000072490000042 PM 9497277 ER PT J AU Keating, GM Bougher, SW Zurek, RW Tolson, RH Cancro, GJ Noll, SN Parker, JS Schellenberg, TJ Shane, RW Wilkerson, BL Murphy, JR Hollingsworth, JL Haberle, RM Joshi, M Pearl, JC Conrath, BJ Smith, MD Clancy, RT Blanchard, RC Wilmoth, RG Rault, DF Martin, TZ Lyons, DT Esposito, PB Johnston, MD Whetzel, CW Justus, CG Babicke, JM AF Keating, GM Bougher, SW Zurek, RW Tolson, RH Cancro, GJ Noll, SN Parker, JS Schellenberg, TJ Shane, RW Wilkerson, BL Murphy, JR Hollingsworth, JL Haberle, RM Joshi, M Pearl, JC Conrath, BJ Smith, MD Clancy, RT Blanchard, RC Wilmoth, RG Rault, DF Martin, TZ Lyons, DT Esposito, PB Johnston, MD Whetzel, CW Justus, CG Babicke, JM TI The structure of the upper atmosphere of Mars: In situ accelerometer measurements from Mars global surveyor SO SCIENCE LA English DT Article ID GENERAL-CIRCULATION; THERMOSPHERES; POLAR; VENUS; MODEL AB The Mars Global Surveyor (MGS) z-axis accelerometer has obtained over 200 vertical structures of thermospheric density, temperature, and pressure, ranging from 110 to 170 kilometers, compared to only three previous such vertical structures. In November 1997 a regional dust storm in the Southern Hemisphere triggered an unexpectedly large thermospheric response at mid-northern latitudes, increasing the altitude of thermospheric pressure surfaces there by as much as 8 kilometers and indicating a strong global thermospheric response to a regional dust storm. Throughout the MGS mission, thermospheric density bulges have been detected on opposite sides of the planet near 90 degrees E and 90 degrees W, in the vicinity of maximum terrain heights. This wave 2 pattern may be caused by topographically-forced planetary waves propagating up from the lower atmosphere. C1 George Washington Univ, NASA, Langley Res Ctr, Hampton, VA 23681 USA. Univ Arizona, Tucson, AZ 85721 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Space Sci Inst, Boulder, CO 80309 USA. Comp Sci Corp, Huntsville, AL 35824 USA. RP Keating, GM (reprint author), George Washington Univ, NASA, Langley Res Ctr, MS 269, Hampton, VA 23681 USA. RI Joshi, Manoj/C-1795-2008; Smith, Michael/C-8875-2012; Bougher, Stephen/C-1913-2013 OI Joshi, Manoj/0000-0002-2948-2811; Bougher, Stephen/0000-0002-4178-2729 NR 37 TC 156 Z9 158 U1 2 U2 13 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 MAR 13 PY 1998 VL 279 IS 5357 BP 1672 EP 1676 DI 10.1126/science.279.5357.1672 PG 5 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA ZB612 UT WOS:000072490000043 ER PT J AU Acuna, MH Connerney, JEP Wasilewski, P Lin, RP Anderson, KA Carlson, CW McFadden, J Curtis, DW Mitchell, D Reme, H Mazelle, C Sauvaud, JA d'Uston, C Cros, A Medale, JL Bauer, SJ Cloutier, P Mayhew, M Winterhalter, D Ness, NF AF Acuna, MH Connerney, JEP Wasilewski, P Lin, RP Anderson, KA Carlson, CW McFadden, J Curtis, DW Mitchell, D Reme, H Mazelle, C Sauvaud, JA d'Uston, C Cros, A Medale, JL Bauer, SJ Cloutier, P Mayhew, M Winterhalter, D Ness, NF TI Magnetic field and plasma observations at Mars: Initial results of the Mars global surveyor mission SO SCIENCE LA English DT Article ID SOLAR-WIND INTERACTION; SPECTROMETER MEASUREMENTS; MARTIAN MAGNETOSPHERE; BOW SHOCK; ELECTRON; VENUS; IONOSPHERE; BOUNDARY; PLANETS; DAYSIDE AB The magnetometer and electron reflectometer investigation (MAG/ER) on the Mars Global Surveyor spacecraft has obtained magnetic field and plasma observations throughout the near-Mars environment, from beyond the influence of Mars to just above the surface (at an altitude of similar to 100 kilometers). The solar wind interaction with Mars is in many ways similar to that at Venus and at an active comet, that is, primarily an ionospheric-atmospheric interaction. No significant planetary magnetic field of global scale has been detected to date (<2 X 10(21) Gauss-cubic centimeter), but here the discovery of multiple magnetic anomalies of small spatial scale in the crust of Mars is reported. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA. Univ Calif Berkeley, Dept Phys, Berkeley, CA 94720 USA. Ctr Etud Spatiale Rayonnements, F-31209 Toulouse, France. Graz Univ, A-8010 Graz, Austria. Austrian Acad Sci, Space Res Inst, A-8010 Graz, Austria. Rice Univ, Dept Space Phys & Astron, Houston, TX 77005 USA. Natl Sci Fdn, Arlington, VA 22230 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ Delaware, Bartol Res Inst, Newark, DE 19716 USA. RP Acuna, MH (reprint author), NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RI connerney, john/I-5127-2013; OI Bauer, Siegfried/0000-0003-4213-2047 NR 47 TC 417 Z9 430 U1 6 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 MAR 13 PY 1998 VL 279 IS 5357 BP 1676 EP 1680 DI 10.1126/science.279.5357.1676 PG 5 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA ZB612 UT WOS:000072490000044 ER PT J AU Smith, DE Zuber, MT Frey, HV Garvin, JB Head, JW Muhleman, DO Pettengill, GH Phillips, RJ Solomon, SC Zwally, HJ Banerdt, WB AF Smith, DE Zuber, MT Frey, HV Garvin, JB Head, JW Muhleman, DO Pettengill, GH Phillips, RJ Solomon, SC Zwally, HJ Banerdt, WB TI Topography of the northern hemisphere of Mars from the Mars orbiter laser altimeter SO SCIENCE LA English DT Article ID RADIO OCCULTATION MEASUREMENTS; MARINER-9; DICHOTOMY; VOLCANISM; IMPACT; ATMOSPHERE AB The first 18 tracks of laser altimeter data across the northern hemisphere of Mars from the Mars Global Surveyor spacecraft show that the planet at latitudes north of 50 degrees is exceptionally flat; slopes and surface roughness increase toward the equator. The polar layered terrain appears to be a thick ice-rich formation with a non-equilibrium planform indicative of ablation near the periphery. Slope relations suggest that the northern Tharsis province was uplifted in the past. A profile across Ares Vallis channel suggests that the discharge through the chan nel was much greater than previously estimated. The martian atmosphere shows significant 1-micrometer atmospheric opacities, particularly in low-lying areas such as Valles Marineris. C1 NASA, Earth Sci Directorate, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. MIT, Cambridge, MA 02139 USA. Brown Univ, Providence, RI 02912 USA. CALTECH, Pasadena, CA 91125 USA. Washington Univ, St Louis, MO 63130 USA. Carnegie Inst Washington, Dept Terr Magnetism, Washington, DC 20015 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. NASA, Terr Phys Lab, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Smith, DE (reprint author), NASA, Earth Sci Directorate, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. NR 45 TC 163 Z9 164 U1 3 U2 6 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 MAR 13 PY 1998 VL 279 IS 5357 BP 1686 EP 1692 DI 10.1126/science.279.5357.1686 PG 7 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA ZB612 UT WOS:000072490000046 PM 9497281 ER PT J AU Christensen, PR Anderson, DL Chase, SC Clancy, RT Clark, RN Conrath, BJ Kieffer, HH Kuzmin, RO Malin, MC Pearl, JC Roush, TL AF Christensen, PR Anderson, DL Chase, SC Clancy, RT Clark, RN Conrath, BJ Kieffer, HH Kuzmin, RO Malin, MC Pearl, JC Roush, TL TI Results from the Mars global surveyor thermal emission spectrometer SO SCIENCE LA English DT Article ID GREAT DUST STORMS; SOUTH POLAR-CAP; SNC METEORITES; ATMOSPHERE; VIKING; CLOUDS AB The Thermal Emission Spectrometer spectra of low albedo surface materials suggests that a four to one mixture of pyroxene to plagioclase, together with about a 35 percent dust component provides the best fit to the spectrum. Qualitative upper limits can be placed on the concentration of carbonates (<10 percent), olivine (<10 percent), clay minerals (<20 percent), and quartz (<5 percent) in the limited regions observed. Limb observations in the northern hemisphere reveal low-lying dust hazes and detached water-ice clouds at altitudes up to 55 kilometers. At an aerocentric longitude of 224 degrees a major dust storm developed in the Noachis Terra region, The south polar cap retreat was similar to that observed by Viking. C1 Arizona State Univ, Tempe, AZ 85287 USA. Univ Colorado, Goleta, CA 93017 USA. US Geol Survey, Denver, CO 80225 USA. Cornell Univ, Ithaca, NY 14850 USA. US Geol Survey, Flagstaff, AZ 86001 USA. VI Vernadskii Inst Geochem & Analyt Chem, Moscow 117975, Russia. Malin Space Sci Syst, San Diego, CA USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Santa Barbara Remote Sensing, Goleta, CA 93017 USA. RP Christensen, PR (reprint author), Arizona State Univ, Tempe, AZ 85287 USA. EM phil.christensen@asu.edu NR 30 TC 156 Z9 157 U1 0 U2 3 PU AMER ASSOC ADVANCEMENT SCIENCE PI WASHINGTON PA 1200 NEW YORK AVE, NW, WASHINGTON, DC 20005 USA SN 0036-8075 J9 SCIENCE JI Science PD MAR 13 PY 1998 VL 279 IS 5357 BP 1692 EP 1698 DI 10.1126/science.279.5357.1692 PG 7 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA ZB612 UT WOS:000072490000047 PM 9497282 ER PT J AU Thummel, HT AF Thummel, HT TI Theoretical study on X-H, -O, -OH, -NO, -ONO, and -NO(2) (X = CH(3), t-C(4)H(9), C(13)H(21)) SO JOURNAL OF PHYSICAL CHEMISTRY A LA English DT Article ID BOND-DISSOCIATION ENERGIES; GAUSSIAN-BASIS SETS; CIS-METHYL NITRITE; ELECTRON CORRELATION; INTERNAL-ROTATION; MICROWAVE-SPECTRA; DIAMOND SURFACE; ALKYL NITRITES; PLASMA; NITROMETHANE AB Theoretical studies are reported for conformational energies and bond energies of compounds X-H, X-O, X-OH, X-NO, X-NO(2) X-ONO, XO-NO, and XN(O)-O with X = CH(3), tert-butyl, and C(13)H(21), which are templates for a radical sire of a hydrogen-terminated diamond C(111) surface. All structures are fully optimized using density functional theory (DFT) based on the B3LYP functional. For X = CH(3) calibration calculations are done in detail using the coupled-cluster approach (CCSD(T)) and do support use of the B3LYP functional for rotational barriers and bond energies. Bond energies X-O and X-OH for X = tert-butyl are close to those computed for X = C(13)H(21), but bond energies X-NO, X-NO(2), X-ONO, and XO-NO differ by 5-11 kcal/mol and show that the effect of second nearest neighbors of the surface is significant in these cases. Combining the trends observed for the small cluster models yields our best values for adsorption energies, on an active site of hydrogenated C(111): Bond energies, decrease in the sequence C-EI (98 kcal/ mol) > C-OH(95 kcal/mol) > C-O (94 kcal/mol) > trans C-ONO (53 kcal/mol) > C-NO(2) (53 kcal/mol) > cis C-ONO (45 kcal/mol) > C-NO (30 kcal/mol). Dissociation energies of cis CO-NO and trans CO-NO are small (26 kcal/mol, 33 kcal/mol). All barriers computed for internal rotation along C-N and C-O are less than 1 kcal/mol, which shows that the rotation of adsorbed species is essentially free. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Thummel, HT (reprint author), NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. NR 66 TC 7 Z9 7 U1 1 U2 4 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA SN 1089-5639 J9 J PHYS CHEM A JI J. Phys. Chem. A PD MAR 12 PY 1998 VL 102 IS 11 BP 2002 EP 2008 DI 10.1021/jp971873r PG 7 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA ZC830 UT WOS:000072622400017 ER PT J AU Saeki, T Anraku, K Orito, S Ormes, J Imori, M Kimbell, B Makida, Y Matsumoto, H Matsunaga, H Mitchell, J Motoki, M Nishimura, J Nozaki, M Otoba, M Sanuki, T Streitmatter, R Suzuki, J Tanaka, K Ueda, I Yajima, N Yamagami, T Yamamoto, A Yoshida, T Yoshimura, K AF Saeki, T Anraku, K Orito, S Ormes, J Imori, M Kimbell, B Makida, Y Matsumoto, H Matsunaga, H Mitchell, J Motoki, M Nishimura, J Nozaki, M Otoba, M Sanuki, T Streitmatter, R Suzuki, J Tanaka, K Ueda, I Yajima, N Yamagami, T Yamamoto, A Yoshida, T Yoshimura, K TI A new limit on the flux of cosmic antihelium SO PHYSICS LETTERS B LA English DT Article DE cosmic-ray; antihelium; antimatter; Universe ID NUMBER DOMAIN-STRUCTURE; NUCLEI; SEARCH AB A very sensitive search for cosmic-ray antihelium was performed using data obtained from three scientific flights of the BESS magnetic rigidity spectrometer. We have not observed any antihelium; this places a model-independent upper limit (95% C.L.) on the antihelium flux of 6 x 10(-4) m(-2)sr(-1)s(-1) at the top of the atmosphere in the rigidity region 1 to 16 GV, after correcting for the estimated interaction loss of antihelium in the air and in the instrument. The corresponding upper limit on the <(He)over bar>/He flux ratio is 3.1 x 10(-6), 30 times more stringent than the limits obtained in similar rigidity regions with magnetic spectrometers previous to BESS. (C) 1998 Published by Elsevier Science B.V. C1 Univ Tokyo, Bunkyo Ku, Tokyo 113, Japan. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. New Mexico State Univ, Las Cruces, NM 88003 USA. KEK, High Energy Accelerator Res Org, Tsukuba, Ibaraki 305, Japan. Kobe Univ, Kobe, Hyogo 657, Japan. Inst Space & Astronaut Sci, Sagamihara, Kanagawa 229, Japan. RP Saeki, T (reprint author), Univ Tokyo, Bunkyo Ku, Tokyo 113, Japan. RI MOTOKI, Masakazu/B-4212-2009 NR 31 TC 39 Z9 39 U1 1 U2 2 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0370-2693 J9 PHYS LETT B JI Phys. Lett. B PD MAR 12 PY 1998 VL 422 IS 1-4 BP 319 EP 324 DI 10.1016/S0370-2693(98)00131-2 PG 6 WC Astronomy & Astrophysics; Physics, Nuclear; Physics, Particles & Fields SC Astronomy & Astrophysics; Physics GA ZK629 UT WOS:000073344400043 ER PT J AU Sambruna, RM George, IM Mushotzky, RF Nandra, K Turner, TJ AF Sambruna, RM George, IM Mushotzky, RF Nandra, K Turner, TJ TI ASCA observations of the broad-line radio galaxy 3C 445 SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies, active; galaxies, individual (3C 445); X-rays, galaxies ID ACTIVE GALACTIC NUCLEI; X-RAY-SPECTRA; SEYFERT-GALAXIES; COLD MATTER; DISTRIBUTIONS; SAMPLE AB We present the first high-resolution X-ray observation of the nearby (z = 0.057) broad-line radio galaxy 3C 445 obtained with ASCA in 0.6-10 keV. The earlier detection of the Fe K alpha line is confirmed. The ASCA data are best fitted by a model involving complex absorption (dual absorber), where an intrinsically flat (Gamma similar to 1.3) continuum is seen through two distinct layers of absorption of cold gas with column densities N-H(1) similar to 10(23) cm(-2) and N-H(2) similar to 6 x 10(22) cm(-2), both larger than the column derived from the optical reddening. Fits with this model to the nonsimultaneous ROSAT and ASCA data put tighter constraints on the continuum parameters. With the continuum described by a dual absorber the Fe K alpha line has an EW similar to 270 eV and a width sigma similar to 0.2 keV, implying an origin in neutral gas moving with velocities less than or similar to 35,000 km s(-1). However, the presence of complex absorption in the nucleus of this type 1 active galactic nucleus (AGN) is unexpected in the context of current unification models. A statistically good fit to the ASCA data is also provided by a power-law plus Compton reflection model; however, this model is physically implausible because of the weak (EW similar to 80 eV) Fe line and unrealistically high (similar to 10(46) ergs s(-1)) luminosity inferred. Among BLRGs observed with ASCA, 3C 445 sticks out as a moderately luminous source with an unusually complex spectrum at soft X-rays. C1 NASA, Goddard Space Flight Ctr, NRC, Greenbelt, MD 20771 USA. NASA, Goddard Space Flight Ctr, USRA, Greenbelt, MD 20771 USA. RP Sambruna, RM (reprint author), Penn State Univ, Dept Astron & Astrophys, Davey Lab 525, University Pk, PA 16802 USA. NR 60 TC 32 Z9 32 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 MAR 10 PY 1998 VL 495 IS 2 BP 749 EP 756 DI 10.1086/305324 PN 1 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZD699 UT WOS:000072714200023 ER PT J AU Storzer, H Hollenbach, D AF Storzer, H Hollenbach, D TI Nonequilibrium photodissociation regions with advancing ionization fronts SO ASTROPHYSICAL JOURNAL LA English DT Article DE H II regions; infrared, ISM, lines and bands; ISM, clouds; ISM, molecules ID MOLECULAR-HYDROGEN GAS; ORION-BAR; ULTRAVIOLET-RADIATION; INFRARED RESPONSE; RATE COEFFICIENTS; EMISSION; CO; CLOUDS; EXCITATION; CHEMISTRY AB We have modeled the thermal and chemical structure of photodissociation regions (PDRs) where the interface between the H II region and the neutral cloud (the ionization front IF) is moving with a velocity v(IF) into the PDR. This situation applies, for example, to PDRs associated with photoevaporating clumps, blister H II regions, and expanding H 11 regions. Although the chemical and temperature structure of the PDR achieves a steady state value in the frame of the IF, the chemical and thermal structure of these nonequilibrium models differ from static equilibrium values because of the advection of molecular gas through the PDR toward the IF. We have studied PDRs with hydrogen nucleus densities n ranging from 10(4) to 10(6) cm(-3) and FUV fluxes chi = 10(4)-10(5) times the local average FUV flux, such as is appropriate for many PDRs associated with dense H n regions near O stars. The velocity of the ionization front v(IF) is varied between O and 1 km s(-1), the range predicted for the advance of a D-type ionization front into a photoevaporating PDR. We predict intensities of the [O I] 63 mu m and the [C II] 158 mu m fine-structure lines, the pure rotational H-2 0-0 S(O) 28.22 mu m, S(1) 17.03 mu m, S(2) 12.28 mu m, S(3) 9.67 mu m, S(4) 8.03 mu m, and S(5) 6.91 mu m lines; the H-2 v = 1-0 S(1) and H-2 v = 2-1 S(1) vibrational lines; and the CO 1-0 and 2-1 rotational lines. We find that there is no H/H-2 photodissociation front for models with chi/n less than or equal to 0.2v(IF), where n is in cm(-3) and v(IF) is in km s(-1). The H-2 is rapidly advected to the IF before it can photodissociate. For chi/n > 0.20v(IF) an H/H-2 photodissociation front exists, but the front moves progressively nearer to the cloud surface as chi/n declines. We also find that the nonequilibrium models always have a well-defined C+/CO transition layer, because the CO does not self-shield as effectively as H-2 and the CO photodissociation timescale is shorter than the flow time across the PDR. This layer is, however, shifted slightly nearer to the cloud surface compared to the equilibrium models. The [C II] and [O I] fine-structure line intensities are relatively insensitive to v(IF) in the range studied, because of the relative rapid photodissociation of CO and photoionization of C I. We conclude that nonequilibrium effects have a relatively minor effect on previous analysis of the physical conditions of PDRs based on CO [O I], [C II], and IR continuum intensities. The CO low-J lines can be a factor of 2 stronger compared to the static equilibrium models. The H-2 rotational and vibrational lines can be enhanced by a factor of 3. We consider the Orion Bar PDR and conclude that nonequilibrium effects are probably minor. 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 39 TC 33 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 MAR 10 PY 1998 VL 495 IS 2 BP 853 EP 870 DI 10.1086/305315 PN 1 PG 18 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZD699 UT WOS:000072714200031 ER PT J AU Rubin, RH Martin, PG Dufour, RJ Ferland, GJ Baldwin, JA Hester, JJ Walter, DK AF Rubin, RH Martin, PG Dufour, RJ Ferland, GJ Baldwin, JA Hester, JJ Walter, DK TI Temperature variations and N/O in the Orion Nebula from HST observations SO ASTROPHYSICAL JOURNAL LA English DT Article DE ISM, abundances; ISM, atoms; ISM, H II regions; ISM, individual (Orion Nebula) ID H-II REGIONS; EFFECTIVE COLLISION STRENGTHS; PLANETARY-NEBULAE; RECOMBINATION COEFFICIENTS; CHEMICAL-COMPOSITION; ATOMIC DATA; N-II; O-II; ULTRAVIOLET; ABUNDANCE AB Using the Goddard High Resolution Spectrograph (GHRS) and the Faint Object Spectrograph (FOS) on the Hubble Space Telescope, we measured the flux of the N II] (2s2p(3) (5)S(2) --> 2s(2)2p(2) (3)P(2,1)) lines at lambda(vac) = 2143.45, 2139.68 Angstrom in the Orion Nebula-the first detection of these lines in an H II region. In order to assess the N(+)/O(+) ratio, we also measured the flux of the [O II] (2p(3) (2)P(1/2,3/2)(0) --> 2p(3) (4)S(3/2)(0)) lines at lambda(vac) = 2471.05, 2471.12 Angstrom. In addition, with the FOS, other emission lines were measured in the same aperture in order to assess the average electron temperature and mean-square temperature variation (t(2)) in the N(+) region, as well as the N(+)/O(+) ratio. When we require that the empirically determined values be equal for (N(+)/O(+))(uv) (obtained from the N II] 2142 and [O II] 2471 lines) and (N(+)/O(+))(opt) (obtained from the [N II] 6585 and [O II] 3728 lines), we obtain the following. For the (N(+), O(+)) zone, the average electron density is similar to 7000 cm(-3), the average electron temperature is 9500 K, t(2) = 0.032, and N(+)/O(+) = 0.14. By comparing our FOS observations to predicted fluxes, utilizing our two previous photoionization models, we are able to derive the N/O ratio. There is fairly good agreement between (N/O0)(uv) and (N/O)(opt) as derived from the two models with a range between 0.13 and 0.18. This range also encompasses our model-derived values for (N/O)(ir) (0.17-0.18), which fit the observed far-infrared line ratio [N III] 57 mu m/[O III] 52 mu m. The empirically derived N(+)/O(+) value requires a correction for the possibility that the N(+) and O(+) regions are not identical. Our overall results place the gas-phase Orion N/O ratio in the range 0.13-0.18, which is somewhat higher than solar. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Univ Toronto, Canadian Inst Theoret Astrophys, Toronto, ON M5S 3H8, Canada. Rice Univ, Dept Space Phys & Astron, Houston, TX 77251 USA. Univ Kentucky, Dept Phys & Astron, Lexington, KY 40506 USA. Cerro Tololo Interamer Observ, La Serena, Chile. Arizona State Univ, Dept Phys & Astron, Tempe, AZ 85287 USA. S Carolina State Univ, Orangeburg, SC 29117 USA. RP Rubin, RH (reprint author), NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. OI Ferland, Gary/0000-0003-4503-6333 NR 60 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 J9 ASTROPHYS J JI Astrophys. J. PD MAR 10 PY 1998 VL 495 IS 2 BP 891 EP 904 DI 10.1086/305326 PN 1 PG 14 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZD699 UT WOS:000072714200033 ER PT J AU Mullan, DJ Carpenter, KG Robinson, RD AF Mullan, DJ Carpenter, KG Robinson, RD TI Large variations in the winds of single cool giants: lambda velorum and gamma crucis SO ASTROPHYSICAL JOURNAL LA English DT Article DE line, profiles; stars, mass loss; stars, late-type; ultraviolet, stars ID HYBRID STARS; MASS-LOSS; SUPERGIANTS AB UV spectra of the "noncoronal" single K supergiant lambda Vel and of the single M giant gamma Cru obtained with IUE and the Hubble Space Telescope at various epochs indicate that the profiles of many lines formed in the wind exhibit striking alterations in shape with time. We parameterize the wind profiles in terms of an empirical optical depth tau(emp) by reflecting the red wing about line center and comparing the reflected intensity with that of the blue wing. In the lambda Vel wind the terminal velocity v(infinity) was found to be close to 40 km s(-1) in 1978, 1982, and 1994, but was at least 20 km s(-1) greater in 1990. The faster wind in 1990 also had a total optical depth that was a factor of 2-6 times greater than at the other epochs. C1 Univ Delaware, Bartol Res Inst, Newark, DE 19716 USA. NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, Greenbelt, MD 20771 USA. NASA, Goddard Space Flight Ctr, Astron Program, Comp Sci Corp, Greenbelt, MD 20771 USA. RP Mullan, DJ (reprint author), Univ Delaware, Bartol Res Inst, Newark, DE 19716 USA. RI Carpenter, Kenneth/D-4740-2012 NR 19 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 MAR 10 PY 1998 VL 495 IS 2 BP 927 EP 932 DI 10.1086/305340 PN 1 PG 6 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZD699 UT WOS:000072714200036 ER PT J AU Catelan, M AF Catelan, M TI Is there a difference in luminosity between field and cluster RR Lyrae variables? SO ASTROPHYSICAL JOURNAL LA English DT Article DE globular clusters, individual (NGC 362, M5, M68, M15, M92); stars, horizontal-branch; stars, variables, other ID GALACTIC GLOBULAR-CLUSTERS; BAADE-WESSELINK ANALYSIS; BV PHOTOMETRY; STARS; DISTANCES; METALLICITIES; KINEMATICS; SYSTEM; AGES; M15 AB Recent Hipparcos results have lent support to the idea that RR Lyrae variables in the halo field and in globular clusters differ in luminosity by approximate to 0.2 mag. In this Letter, we study the pulsation properties of RR Lyrae variables in clusters with distances determined via main-sequence fitting to Hipparcos parallaxes for field subdwarfs and compare them with the properties of field variables also analyzed with Hipparcos. We show that the period-temperature distributions for field and cluster variables are essentially indistinguishable, thus suggesting that there is no significant difference in luminosity between them. C1 NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, Greenbelt, MD 20771 USA. RP Catelan, M (reprint author), NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, Code 681, Greenbelt, MD 20771 USA. EM catelan@stars.gsfc.nasa.gov NR 51 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 EI 1538-4357 J9 ASTROPHYS J JI Astrophys. J. PD MAR 10 PY 1998 VL 495 IS 2 BP L81 EP L84 DI 10.1086/311227 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZD700 UT WOS:000072714300004 ER PT J AU James, TS Ivins, ER AF James, TS Ivins, ER TI Predictions of Antarctic crustal motions driven by present-day ice sheet evolution and by isostatic memory of the Last Glacial Maximum SO JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH LA English DT Article ID COMPUTING 3-DIMENSIONAL DEFORMATIONS; DEEP MANTLE VISCOSITY; SEA-LEVEL CHANGE; TRANSANTARCTIC MOUNTAINS; SURFACE LOADS; DRY VALLEYS; SPECTRAL FORMALISM; LATE WISCONSIN; NORTH-AMERICA; EARTH AB Detectable crustal motion and secular rate of change of solid-surface gravity may be produced by the Earth's response to present-day and past ice mass changes in Antarctica. Scenarios of present-day ice mass balance, previously utilized to explore the global geodetic signatures of the Antarctic ice sheet, produce elastic crustal responses that are typically bounded by uplift rates less than or equal to 5 mm/yr, horizontal motion less than or equal to 1 mm/yr, and solid-surface gravity change rates less than or equal to 1 mu Gal/yr. In a restricted locality, one scenario produces uplift rates slightly in excess of 10 mm/yr and correspondingly enhanced horizontal and gravity rates. In contrast, the viscoelastic response to ice mass changes occurring since Last Glacial Maximum (LGM) exceeds 5 mm/yr (uplift) over substantial portions of West Antarctica for a wide range of plausible choices of timing and magnitude of deglaciation and mantle viscosity. Similarly, viscoelastic gravity rate predictions exceed 1 mu Gal/yr (decrease) over large regions, confirming suggestions that a Global Positioning System (GPS) and absolute gravity-based program of crustal monitoring in Antarctica could potentially detect postglacial rebound. A published revision to the CLIMAP model of the Antarctic ice sheet at LGM, herein called the D91 model, features a substantially altered West Antarctic, ice sheet reconstruction. This revision predicts a spatial pattern of present-day crustal motion and surface gravity change that diverges strikingly from CLIMAP-based models. Peak D91 crustal rates, assuming deglaciation begins at 12 kyr and ends at 5 kyr, are around 16 mm/yr (uplift), 2 mm/yr (horizontal), and -2.5 mu Gal/yr(gravity). Tabulated crustal response predictions for selected Antarctic bedrock sites indicate critical localities in the interior of West Antarctica where expected responses are large and D91 predictions differ from CLIMAP-based models by a factor of 2 or more. Observations of the postglacial rebound signal in Antarctica might help constrain Antarctic mass balance and contribution to sea level rise over the past 20,000 years. C1 Geol Survey Canada, Sidney, BC V8L 4B2, Canada. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP James, TS (reprint author), Geol Survey Canada, 9860 W Saanich Rd, Sidney, BC V8L 4B2, Canada. EM james@pgc.nrcan.gc.ca; eri@scn1.jpl.nasa.gov RI James, Thomas/D-9301-2013 OI James, Thomas/0000-0001-7321-047X NR 95 TC 82 Z9 83 U1 1 U2 4 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-9313 EI 2169-9356 J9 J GEOPHYS RES-SOL EA JI J. Geophys. Res.-Solid Earth PD MAR 10 PY 1998 VL 103 IS B3 BP 4993 EP 5017 DI 10.1029/97JB03539 PG 25 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA ZB383 UT WOS:000072466700009 ER PT J AU Bar-Sever, YE Kroger, PM Borjesson, JA AF Bar-Sever, YE Kroger, PM Borjesson, JA TI Estimating horizontal gradients of tropospheric path delay with a single GPS receiver SO JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH LA English DT Article ID INTERFEROMETRY AB We present evidence that modeling troposphere delay gradients in precise Global Positioning System (GPS) geodesy improves the accuracy and precision of the estimated quantities, and that the estimated gradients resemble real atmospheric moisture gradients observed with a water vapor radiometer (WVR). Using a low elevation angle cutoff, combined with a model of the atmospheric delay gradient as a random walk process leads to 19.5% and 15% average improvement in radial and horizontal site position repeatabilities, respectively, relative to a current state-of-the-art estimation strategy that does not model horizontal gradients and imposes high elevation angle cutoff. The agreement between estimated values of zenith wet delay from collocated GPS receivers and WVRs was improved by at least 25%. Merely lowering the elevation angle cutoff improves the repeatability of the radial component of the site's position vector but tends to degrade the repeatability of the horizontal components of the position vector if troposphere gradients are not properly modeled. The estimates of wet delay gradients from a collocated GPS receiver and a WVR at Onsala, Sweden, seem to be correlated over timescales as short as 15 min. The agreement in azimuth between the GPS-based and the WVR-based gradients was at the 10 degrees level, for significant gradients. The GPS was found to under-estimate the magnitude of the gradients by about 60% relative to the WVR-based gradients. The ability to sense atmospheric moisture gradients from a single GPS receiver increases the useful information content from networks of GPS receivers by providing additional spatial information for weather forecasting applications. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Chalmers Univ Technol, Onsala Space Observ, S-43992 Onsala, Sweden. RP Bar-Sever, YE (reprint author), CALTECH, Jet Prop Lab, MS 238-600, Pasadena, CA 91109 USA. EM yeb@cobra.jpl.nasa.gov; ajb@oso.chalmers.se NR 22 TC 157 Z9 170 U1 3 U2 14 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-9313 EI 2169-9356 J9 J GEOPHYS RES-SOL EA JI J. Geophys. Res.-Solid Earth PD MAR 10 PY 1998 VL 103 IS B3 BP 5019 EP 5035 DI 10.1029/97JB03534 PG 17 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA ZB383 UT WOS:000072466700010 ER PT J AU Baloga, SM Glaze, LS Crisp, JA Stockman, SA AF Baloga, SM Glaze, LS Crisp, JA Stockman, SA TI New statistics for estimating the bulk rheology of active lava flows: Puu Oo examples SO JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH LA English DT Article ID MOUNT ETNA; EMPLACEMENT; VOLCANO; CRYSTALLIZATION; HAWAII AB Downstream changes in lava rheology due to cooling, crystallization, and vesiculation have a strong influence on the final length and morphology of a lava flow. Three statistics are proposed to estimate the change in lava rheology with distance along the path of an active flow. These statistics correspond to three separate models of the volumetric flow rate dependence on the thickness of the flow. Each statistic is based on flow dimensions and topographic data that are often available from field measurements or remote sensing. One model assumes an elementary laminar Newtonian flow. A second empirical model often used to describe the flow of complex geologic materials, such as lahars, sediment-laden floods, and debris flows, is also investigated for comparison. A new volume-loss model is also proposed to account for stationary components such as levees and stagnant areas. The three statistics derived from these flow rate models are applied and interpreted for two well-defined lobes from episodes 2 and 18 of the 1983-1984 Puu Oo eruption. The power law dependence of the first two models results only in modest differences in the estimates of theologic change along the flow path. However, the removal of lava from the active flow to construct stationary components produces significant differences in both the magnitude of computed theologic changes and the ability to discern trends in theologic changes along the path of the flow. C1 Proxemy Res, Laytonville, MD 20882 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Baloga, SM (reprint author), Proxemy Res, 20528 Farcroft Lane, Laytonville, MD 20882 USA. EM baloga@denali.gsfc.nasa.gov RI Glaze, Lori/D-1314-2012; Crisp, Joy/H-8287-2016 OI Crisp, Joy/0000-0002-3202-4416 NR 22 TC 21 Z9 21 U1 0 U2 4 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-9313 EI 2169-9356 J9 J GEOPHYS RES-SOL EA JI J. Geophys. Res.-Solid Earth PD MAR 10 PY 1998 VL 103 IS B3 BP 5133 EP 5142 DI 10.1029/97JB03743 PG 10 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA ZB383 UT WOS:000072466700017 ER PT J AU Huang, NE Shen, Z Long, SR Wu, MLC Shih, HH Zheng, QN Yen, NC Tung, CC Liu, HH AF Huang, NE Shen, Z Long, SR Wu, MLC Shih, HH Zheng, QN Yen, NC Tung, CC Liu, HH TI The empirical mode decomposition and the Hilbert spectrum for nonlinear and non-stationary time series analysis SO PROCEEDINGS OF THE ROYAL SOCIETY A-MATHEMATICAL PHYSICAL AND ENGINEERING SCIENCES LA English DT Article DE non-stationary time series; nonlinear differential equations; frequency-time spectrum; Hilbert spectral analysis; intrinsic time scale; empirical mode decomposition ID FREQUENCY SIGNAL ANALYSIS; WIGNER DISTRIBUTION; EL-NINO; WAVES; GEOSAT; TOOL; MOTION; OCEAN; FLOW AB A new method for analysing nonlinear and non-stationary data has been developed. The key part of the method is the 'empirical mode decomposition' method with which any complicated data set can be decomposed into a finite and often small number of 'intrinsic mode functions' that admit well-behaved Hilbert transforms. This decomposition method is adaptive, and, therefore, highly efficient. Since the decomposition is based on the local characteristic time scale of the data, it is applicable to nonlinear and non-stationary processes. With the Hilbert transform, the 'instrinic mode functions' yield instantaneous frequencies as functions of time that give sharp identifications of imbedded structures. The final presentation of the results is an energy-frequency-time distribution, designated as the Hilbert spectrum. In this method, the main conceptual innovations are the introduction of 'intrinsic mode functions' based on local properties of the signal, which makes the instantaneous frequency meaningful; and the introduction of the instantaneous frequencies for complicated data sets, which eliminate the need for spurious harmonics to represent nonlinear and non-stationary signals. Examples from the numerical results of the classical nonlinear equation systems and data representing natural phenomena are given to demonstrate the power of this new method. Classical nonlinear system data are especially interesting, for they serve to illustrate the roles played by the nonlinear and non-stationary effects in the energy-frequency-time distribution. C1 NASA, Lab Hydrospher Proc, Oceans & Ice Branch, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Johns Hopkins Univ, Dept Earth & Planetary Sci, Baltimore, MD 21218 USA. NASA, Lab Hydrospher Proc, Observ Sci Branch, Wallops Flight Facil, Wallops Island, VA 23337 USA. NASA, Atmospheres Lab, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Natl Ocean Serv, NOAA, Silver Spring, MD 20910 USA. Univ Delaware, Coll Marine Studies, Newark, DE 19716 USA. USN, Res Lab, Washington, DC 20375 USA. N Carolina State Univ, Dept Civil Engn, Raleigh, NC 27695 USA. USN, Ctr Surface Warfare, Carderock Div, Bethesda, MD 20084 USA. RP Huang, NE (reprint author), NASA, Lab Hydrospher Proc, Oceans & Ice Branch, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RI Zheng, Quanan/F-9025-2010; Long, Steven/D-7248-2012 NR 64 TC 6275 Z9 8093 U1 74 U2 546 PU ROYAL SOC PI LONDON PA 6-9 CARLTON HOUSE TERRACE, LONDON SW1Y 5AG, ENGLAND SN 1364-5021 EI 1471-2946 J9 P ROY SOC A-MATH PHY JI Proc. R. Soc. A-Math. Phys. Eng. Sci. PD MAR 8 PY 1998 VL 454 IS 1971 BP 903 EP 995 PG 93 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA ZD271 UT WOS:000072668500010 ER PT J AU Bauschlicher, CW Partridge, H AF Bauschlicher, CW Partridge, H TI The Sc+-OH and Sc+-OCH3 bond energies in ScOH+, ScOCH3+, Sc(OH)(2)(+), ScOHOCH3+, and Sc(OCH)(2)(+) SO CHEMICAL PHYSICS LETTERS LA English DT Article ID GAUSSIAN-BASIS SETS; COUPLED-CLUSTER THEORY; ORBITAL BASIS-SETS; MOLECULAR CALCULATIONS; ROW ATOMS; ELECTRON CORRELATION; WAVE-FUNCTIONS; CONTRACTION; 1ST-ROW; SPIN AB The greometries of ScOCH3+, ScOHOCH3+ and Sc(OCH3)(2)(+) have been optimized rind the zero-point energies computed using the B3LYP approach. The Sc+-OH and Sc+-OCH3 bond energies have been computed at the B3LYP and CCSD(T) levels of theory. These results are compared to the previous results for ScOH+ and Sc(OH)(2)(+). The Sc+-OCH3 bond is found to be about 6 kcal/mol weaker than the Sc+-OH bond. The results are compared with experiment and previous theoretical results at the MP2 level. (C) 1998 Elsevier Science B.V. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Bauschlicher, CW (reprint author), NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. NR 22 TC 2 Z9 2 U1 0 U2 0 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 MAR 6 PY 1998 VL 284 IS 5-6 BP 308 EP 312 DI 10.1016/S0009-2614(97)01106-8 PG 5 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA ZF810 UT WOS:000072935500002 ER PT J AU Luo, S Clewley, JD Flanagan, TB Bowman, RC Wade, LA AF Luo, S Clewley, JD Flanagan, TB Bowman, RC Wade, LA TI Further studies of the isotherms of LaNi5-xSnx-H for x=0-0.5 SO JOURNAL OF ALLOYS AND COMPOUNDS LA English DT Article DE hydrogen isotherms; hydride formation; decomposition ID HYDROGEN ABSORPTION; PLATEAU PRESSURES; LANI5-H2 SYSTEM; CALORIMETRY; HYSTERESIS; HYDRIDES; DEGRADATION; ENTHALPIES; STABILITY; BEHAVIOR AB Complete hydrogen isotherms have been measured using highly stoichiometric, activated LaNi5 over a wide temperature range, 373-228 K. Van't Hoff plots for hydride formation and decomposition have been constructed using the isotherms in the low temperature range from 228 to 298 K. The following thermodynamic results are obtained: \Delta H-plat\=15.4 kJ/mol 1/2 H-2 and \Delta S-plat\=54.4 J/K mol 1/2 H-2. These should be regarded as reliable in view of the nearly stoichiometric LaNi5 employed and because utilizing data over a wide, low temperature range avoids problems introduced by degradation of the alloy which can be a factor at higher temperatures due to the inherent instability of the H-containing alloy. It has been observed previously in the LaNi5-H system that the absorption plateau measured with virgin alloys, i.e., before activation, is significantly higher than the subsequent values. This phenomenon was investigated in this research using the LaNi5-xSnx alloys, with x=0, 0.05, 0.10, 0.20, 0.25, 0.32, 0.40 and 0.50. Isotherms for the virgin and activated alloys were measured at 373 K. The difference between the initial plateau pressures for hydride formation and values for activated material decrease with increase of x. An important result is that the initially high plateau pressure for hydride formation for alloys is related to hysteresis because the difference between the plateau pressures before and after activation almost vanishes at a Sn content of x=0.32, where hysteresis itself nearly vanishes. (C) 1998 Elsevier Science S.A. C1 Univ Vermont, Mat Sci Program, Burlington, VT 05405 USA. Univ Vermont, Dept Chem, Burlington, VT 05405 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Luo, S (reprint author), Univ Vermont, Mat Sci Program, Burlington, VT 05405 USA. NR 26 TC 32 Z9 35 U1 0 U2 3 PU ELSEVIER SCIENCE SA PI LAUSANNE PA PO BOX 564, 1001 LAUSANNE, SWITZERLAND SN 0925-8388 J9 J ALLOY COMPD JI J. Alloy. Compd. PD MAR 6 PY 1998 VL 267 IS 1-2 BP 171 EP 181 DI 10.1016/S0925-8388(97)00536-7 PG 11 WC Chemistry, Physical; Materials Science, Multidisciplinary; Metallurgy & Metallurgical Engineering SC Chemistry; Materials Science; Metallurgy & Metallurgical Engineering GA ZE552 UT WOS:000072805000037 ER PT J AU Topaler, MS Allison, TC Schwenke, DW Truhlar, DG AF Topaler, MS Allison, TC Schwenke, DW Truhlar, DG TI Test of trajectory surface hopping against accurate quantum dynamics for an electronically nonadiabatic chemical reaction SO JOURNAL OF PHYSICAL CHEMISTRY A LA English DT Article ID STATE TRANSITION-PROBABILITIES; QUASI-CLASSICAL CALCULATIONS; ROTATIONAL ENERGY-TRANSFER; CROSS-SECTIONS; MOLECULAR-COLLISIONS; CONICAL INTERSECTION; CONVERGED QUANTUM; SCATTERING; SYSTEM; MODEL AB This paper presents the first test of the popular trajectory surface-hopping (TSH) method against accurate three-dimensional quantum mechanics for a reactive system. The system considered is a model system in which an excited atom with an excitation energy of 0.76 eV reacts with or is quenched by the H(2) molecule. The electronically nonadiabatic collisions occur primarily near a conical intersection of an exciplex with a repulsive ground state. The accurate quantal results are calculated using the outgoing wave variational principle in an electronically diabatic representation. Four variants of the TSH method are tested, differing in the criteria for hopping and the component of momentum that is adjusted in order to conserve energy when a hop occurs. Coupling between the ground and excited surface occurs primarily in the vicinity of a conical intersection and is mediated by an exciplex found on the upper surface. We find that the overall TSH quenching probabilities are in good agreement with quantum mechanical results, but the branching ratios between reactive and nonreactive trajectories and many of the state-selected results are poorly reproduced by trajectory calculations. The agreement between trajectory surface hopping and quantal results is on average worse for the relatively more "quantum mechanical" j = 0 initial state and M + H(2) quenching process and better for the relatively more "classical" j = 2 initial state and MH + H' reactive process. We also perform a statistical calculation of overall quenching probability and unimolecular rate of the nonadiabatic decay of the exciplex. We find that only about 10 % of trajectories can be described as "statistical" and that statistical calculation overestimates the total quenching rate significantly. C1 Univ Minnesota, Dept Chem, Minneapolis, MN 55455 USA. Univ Minnesota, Inst Supercomp, Minneapolis, MN 55455 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Truhlar, DG (reprint author), Univ Minnesota, Dept Chem, Minneapolis, MN 55455 USA. RI schwenke, david/I-3564-2013; Truhlar, Donald/G-7076-2015 OI Truhlar, Donald/0000-0002-7742-7294 NR 51 TC 49 Z9 49 U1 1 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 MAR 5 PY 1998 VL 102 IS 10 BP 1666 EP 1673 DI 10.1021/jp9731922 PG 8 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA ZB971 UT WOS:000072526700003 ER PT J AU Dwyer, JH Dwyer, KM Nicholson, LM Sun, P Selzer, RH AF Dwyer, JH Dwyer, KM Nicholson, LM Sun, P Selzer, RH TI Carotid wall thickness and central adiposity in men and women. The Los Angeles Atherosclerosis Study. SO CIRCULATION LA English DT Meeting Abstract C1 CALTECH, Jet Prop Lab, Pasadena, CA USA. Univ So Calif, Los Angeles, CA USA. NR 0 TC 0 Z9 0 U1 0 U2 2 PU LIPPINCOTT WILLIAMS & WILKINS PI PHILADELPHIA PA 227 EAST WASHINGTON SQ, PHILADELPHIA, PA 19106 USA SN 0009-7322 J9 CIRCULATION JI Circulation PD MAR 3 PY 1998 VL 97 IS 8 MA P62 BP 829 EP 829 PG 1 WC Cardiac & Cardiovascular Systems; Peripheral Vascular Disease SC Cardiovascular System & Cardiology GA YY916 UT WOS:000072200800113 ER PT J AU Dwyer, KM Nicholson, LM Sun, P Sun, W Selzer, RH Dwyer, JH AF Dwyer, KM Nicholson, LM Sun, P Sun, W Selzer, RH Dwyer, JH TI Carotid wall thickness and intake of wine, beer and liquor. The Los Angeles Atherosclerosis Study. SO CIRCULATION LA English DT Meeting Abstract C1 Univ So Calif, Los Angeles, CA USA. CALTECH, Jet Prop Lab, Pasadena, CA USA. NR 0 TC 0 Z9 0 U1 0 U2 1 PU LIPPINCOTT WILLIAMS & WILKINS PI PHILADELPHIA PA 227 EAST WASHINGTON SQ, PHILADELPHIA, PA 19106 USA SN 0009-7322 J9 CIRCULATION JI Circulation PD MAR 3 PY 1998 VL 97 IS 8 MA P63 BP 829 EP 829 PG 1 WC Cardiac & Cardiovascular Systems; Peripheral Vascular Disease SC Cardiovascular System & Cardiology GA YY916 UT WOS:000072200800114 ER PT J AU Stecker, FW AF Stecker, FW TI On the origin of the highest energy cosmic rays SO PHYSICAL REVIEW LETTERS LA English DT Article ID CUTOFF; WELL AB We present a new estimate of the photodisintegration of ultrahigh energy cosmic-ray (UHCR) nuclei in intergalactic space. Critical interactions for energy loss and photodisintegration of UHCR nuclei occur with the infrared background radiation (IBR). We have made use of a new determination of the IBR based on IR data and on TeV gamma-ray observations. Our results indicate that a 200 EeV nucleus which started out as Fe can have propagated similar to 100 Mpc though the IBR. It is thus possible that the highest energy cosmic rays observed may be nuclei. C1 NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. RP Stecker, FW (reprint author), NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Code 661, Greenbelt, MD 20771 USA. RI Stecker, Floyd/D-3169-2012 NR 18 TC 31 Z9 31 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 MAR 2 PY 1998 VL 80 IS 9 BP 1816 EP 1817 DI 10.1103/PhysRevLett.80.1816 PG 2 WC Physics, Multidisciplinary SC Physics GA YZ785 UT WOS:000072291400006 ER PT J AU Rajan, N Zorman, CA Mehregany, M DeAnna, R Harvey, R AF Rajan, N Zorman, CA Mehregany, M DeAnna, R Harvey, R TI Performance of 3C-SiC thin films as protective coatings for silicon-micromachined atomizers SO THIN SOLID FILMS LA English DT Article DE silicon carbide thin films; atmospheric pressure chemical vapor deposition; silicon-micromachined fuel atomizers ID GROWTH; SI AB This paper presents a study of the deposition and performance of SC-silicon carbide (3C-SiC) coatings on the flow surfaces of silicon micromachined fuel atomizers. Atmospheric pressure chemical vapor deposition (APCVD) was used to grow 3C-SiC on atomizer features which were fabricated from silicon wafers using deep reactive ion etching (DRIE). The 3C-SiC films were shown to be conformal across high-aspect-ratio atomizer structures which were etched to depths greater than 250 mu m. For tests conducted at pressures up to 690 kPa, the SiC-coated atomizers had wider spray angles, equivalent Sauter Mean Diameters (SMD), and an 11% increase in flow rates when compared to uncoated atomizers. Erosion tests proved that the SiC coating can dramatically increase the service life of silicon fuel atomizers. (C) 1998 Elsevier Science S.A. C1 Case Western Reserve Univ, Dept Elect Engn & Appl Phys, Microfabricat Lab, Cleveland, OH 44106 USA. Parker Hannifin, Gas Turbine Fuel Syst Div, Cleveland, OH 44112 USA. NASA, Lewis Res Ctr, USA, Res Lab, Cleveland, OH 44135 USA. RP Rajan, N (reprint author), Case Western Reserve Univ, Dept Elect Engn & Appl Phys, Microfabricat Lab, Cleveland, OH 44106 USA. OI Zorman, Christian/0000-0001-9773-9351 NR 8 TC 23 Z9 23 U1 0 U2 2 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 MAR 2 PY 1998 VL 315 IS 1-2 BP 170 EP 178 DI 10.1016/S0040-6090(97)00708-6 PG 9 WC Materials Science, Multidisciplinary; Materials Science, Coatings & Films; Physics, Applied; Physics, Condensed Matter SC Materials Science; Physics GA ZV073 UT WOS:000074265800029 ER PT J AU Ramesham, R AF Ramesham, R TI Effect of annealing and hydrogen plasma treatment on the voltammetric and impedance behavior of the diamond electrode SO THIN SOLID FILMS LA English DT Article DE CVD diamond; diamond; hydrogen plasma treatment; annealing; cyclic voltammetry; AC impedance; electrochemistry; plasma processing and deposition; photovoltage ID POLYCRYSTALLINE DIAMOND; THIN-FILMS; RESISTIVITY AB Undoped polycrystalline diamond thin films have been grown on molybdenum substrates by microwave-assisted chemical vapor deposition using a hydrogen and methane gas mixture. Cyclic voltammetric behavior of diamond films has been studied in 0.5 M NaCl solution as a function of annealing in nitrogen gas at 425 degrees C and hydrogen microwave plasma treatments at 800 degrees C. Preliminary voltammetry studies have shown that the annealed diamond film has a high resistivity, and hydrogen microwave plasma-treated diamond has a low resistivity. These treatments have an effect on the extent of the gas evolution reaction either in the anodic or in the cathodic polarization of the diamond electrode. AC impedance and DC linear polarization techniques have provided the data on the increase and decrease in diamond film resistance upon annealing and hydrogen microwave plasma treatment, respectively, which further corroborates the voltammetry studies. These electrochemical measurements may qualitatively suggest that there may be a change in electron affinity characteristics of the diamond surface as a function of various pretreatments, (C) 1998 Elsevier Science S.A. C1 Auburn Univ, Space Power Inst, Auburn, AL 36849 USA. RP Ramesham, R (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 26 TC 26 Z9 27 U1 0 U2 11 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 MAR 2 PY 1998 VL 315 IS 1-2 BP 222 EP 228 DI 10.1016/S0040-6090(97)00592-0 PG 7 WC Materials Science, Multidisciplinary; Materials Science, Coatings & Films; Physics, Applied; Physics, Condensed Matter SC Materials Science; Physics GA ZV073 UT WOS:000074265800037 ER PT J AU Ho, JX Snell, EH Sisk, RC Ruble, JR Carter, DC Owens, SM Gibson, WM AF Ho, JX Snell, EH Sisk, RC Ruble, JR Carter, DC Owens, SM Gibson, WM TI Stationary crystal diffraction with a monochromatic convergent X-ray source and application for macromolecular crystal data collection SO ACTA CRYSTALLOGRAPHICA SECTION D-BIOLOGICAL CRYSTALLOGRAPHY LA English DT Article ID OPTICS; PERFECTION AB A diffraction geometry utilizing convergent X-rays from a polycapillary optic incident on a stationary crystal is described. A mathematical simulation of the resulting diffraction pattern tin terms of spot shape, position and intensity) is presented along with preliminary experimental results recorded from a lysozyme crystal. The effective source coverage factor is introduced to bring the reflection intensities onto the same scale. The feasibility of its application to macromolecular crystal data collection is discussed. C1 NASA, Marshall Space Flight Ctr ES 76, Huntsville, AL 35812 USA. SUNY Albany, Ctr Xray Opt, Albany, NY 12222 USA. RP Ho, JX (reprint author), New Century Pharmaceut Inc, 895 Martin Rd, Huntsville, AL 35824 USA. NR 12 TC 16 Z9 16 U1 0 U2 0 PU MUNKSGAARD INT PUBL LTD PI COPENHAGEN PA 35 NORRE SOGADE, PO BOX 2148, DK-1016 COPENHAGEN, DENMARK SN 0907-4449 J9 ACTA CRYSTALLOGR D JI Acta Crystallogr. Sect. D-Biol. Crystallogr. PD MAR 1 PY 1998 VL 54 BP 200 EP 214 DI 10.1107/S0907444997009013 PN 2 PG 15 WC Biochemical Research Methods; Biochemistry & Molecular Biology; Biophysics; Crystallography SC Biochemistry & Molecular Biology; Biophysics; Crystallography GA ZD256 UT WOS:000072667000004 PM 9761885 ER PT J AU Wincheski, RA Namkung, M AF Wincheski, RA Namkung, M TI New inspection tools for aging aircraft SO AEROSPACE AMERICA LA English DT Editorial Material C1 NASA, Washington, DC 20546 USA. RP Wincheski, RA (reprint author), NASA, Washington, DC 20546 USA. RI Namkung, Min/E-1533-2012 NR 0 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 0740-722X J9 AEROSPACE AM JI Aerosp. Am. PD MAR PY 1998 VL 36 IS 3 BP 27 EP 29 PG 3 WC Engineering, Aerospace SC Engineering GA YZ956 UT WOS:000072312100016 ER PT J AU Tischler, AO AF Tischler, AO TI What happened to flight 800 SO AEROSPACE AMERICA LA English DT Article C1 NASA, Washington, DC 20546 USA. RP Tischler, AO (reprint author), NASA, Washington, DC 20546 USA. NR 0 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 0740-722X J9 AEROSPACE AM JI Aerosp. Am. PD MAR PY 1998 VL 36 IS 3 BP 30 EP 34 PG 5 WC Engineering, Aerospace SC Engineering GA YZ956 UT WOS:000072312100017 ER PT J AU Kube, R Splettstoesser, WR Wagner, W Seelhorst, U Yu, YH Tung, C Beaumier, P Prieur, J Rahier, G Spiegel, P Boutier, A Brooks, TF Burley, CL Boyd, DD Mercker, E Pengel, K AF Kube, R Splettstoesser, WR Wagner, W Seelhorst, U Yu, YH Tung, C Beaumier, P Prieur, J Rahier, G Spiegel, P Boutier, A Brooks, TF Burley, CL Boyd, DD Mercker, E Pengel, K TI HHC aeroacoustic rotor tests in the German-Dutch wind tunnel: Improving physical understanding and prediction codes SO AEROSPACE SCIENCE AND TECHNOLOGY LA English DT Article DE higher harmonic control; rotor aeroacoustic; helicopter vibrations; wind tunnel test techniques; rotor simulation codes AB Within an international research program jointly conducted by the US Army's Aeroflightdynamics Directorate (AFDD), NASA Langley, DNW, ONERA and DLR, the effects of a higher harmonic blade pitch angle variation on the rotor noise and vibrations were intensively studied. The program, denoted with Higher Harmonic Control Aeroacoustic Rotor Tests (HART) comprised both theoretical and experimental activities, the latter ones being represented by a comprehensive wind tunnel test campaign. Besides aeroacoustic measurements it comprised flow visualization tests and flow field measurements which were applied along with optical methods to determine the blade deflections. The measurements were preceded by extensive predictions performed with the analytical models of each organization. Within these simulations different models were used, leading to a very comprehensive theoretical data base. It gave an impression of the rotor codes' uncertainties which were tried to be eliminated by means of the wind tunnel findings. Although these activities yielded general improvements of the simulation codes they demonstrated also that further work is required in order to accurately predict the effects of a higher harmonic blade pitch angle on the rotor noise and vibrations. (C) Elsevier, Paris. C1 DLR, D-38108 Braunschweig, Germany. DLR, D-37073 Gottingen, Germany. NASA, Ames Res Ctr, Aeroflightdynam Directorate, AFDD, Moffett Field, CA 94035 USA. Off Natl Etud & Rech Aerosp, F-92322 Chatillon, France. NASA, Langley Res Ctr, Aeroacoust Branch, FMAD, Hampton, VA 23681 USA. Lockheed Engn & Sci Co, Hampton, VA 23681 USA. Deutsch Niederlandischer Windkanal DNW, NL-8300 AD Emmeloord, Netherlands. RP Kube, R (reprint author), DLR, Lilienthalpl 7, D-38108 Braunschweig, Germany. NR 14 TC 3 Z9 3 U1 0 U2 2 PU GAUTHIER-VILLARS/EDITIONS ELSEVIER PI PARIS PA 23 RUE LINOIS, 75015 PARIS, FRANCE SN 0034-1223 J9 AEROSP SCI TECHNOL JI Aerosp. Sci. Technol. PD MAR-APR PY 1998 VL 2 IS 3 BP 177 EP 190 DI 10.1016/S1270-9638(98)80052-7 PG 14 WC Engineering, Aerospace SC Engineering GA ZV127 UT WOS:000074272100003 ER PT J AU Chanetz, B Benay, R Bousquet, JM Bur, R Pot, T Grasso, F Moss, J AF Chanetz, B Benay, R Bousquet, JM Bur, R Pot, T Grasso, F Moss, J TI Experimental and numerical study of the laminar separation in hypersonic flow SO AEROSPACE SCIENCE AND TECHNOLOGY LA English DT Article DE separation; hypersonic flow; hollow cylinder flare; Navier-Stokes solver; direct-simulation Monte-Carlo solver AB This article is devoted to an experimental and numerical study of shock wave/boundary layer interaction in hypersonic laminar flow (M = 10). The experiment was performed in the ONERA R5Ch wind tunnel on a hollow cylinder hare. The flow stream delivered by the R5Ch wind tunnel produces physical conditions which justify both the theoretical approach using classical Navier-Stokes equations and the approach by Direct Simulation Monte-Carlo. So the aim of this study is to improve the capacity of Navier-Stokes and DSMC codes to predict high Mach number interactions. Pressure and heat flux have been measured at the wall and compared with the results obtained with Navier-Stokes and DSMC codes. Two different meshes have been considered with the three Navier-Stokes codes used. The conclusion is that the codes can give a good evaluation of the physical quantities at the wall. (C) Elsevier, Paris. C1 Off Natl Etud & Rech Aerosp, F-92322 Chatillon, France. Univ Rome La Sapienza, Rome, Italy. NASA, Washington, DC 20546 USA. RP Chanetz, B (reprint author), ONERA, DAFE, 8 Rue Vertugadins, F-92190 Meudon, France. NR 34 TC 8 Z9 9 U1 0 U2 5 PU GAUTHIER-VILLARS/EDITIONS ELSEVIER PI PARIS PA 23 RUE LINOIS, 75015 PARIS, FRANCE SN 0034-1223 J9 AEROSP SCI TECHNOL JI Aerosp. Sci. Technol. PD MAR-APR PY 1998 VL 2 IS 3 BP 205 EP 218 DI 10.1016/S1270-9638(98)80054-0 PG 14 WC Engineering, Aerospace SC Engineering GA ZV127 UT WOS:000074272100005 ER PT J AU Phillips, JG Cane, MA Rosenzweig, C AF Phillips, JG Cane, MA Rosenzweig, C TI ENSO, seasonal rainfall patterns and simulated maize yield variability in Zimbabwe SO AGRICULTURAL AND FOREST METEOROLOGY LA English DT Article DE climate variability; El Nino; Zimbabwe; maize ID EQUATORIAL AB A correlation between ENSO (El Nino/Southern Oscillation) and rainfall in southern Africa has been recognized for at least a decade. This recognition has led to the expectation that ENSO-based climate predictions will have significant applications in agricultural management. This study is an analysis of the potential for using ENSO predictions to reduce risk in agricultural production associated with rainfall variability at the site level. Records of sea-surface temperatures in the equatorial Pacific during November, December and January were used to define El Nino, La Nina and neutral years. Climate data from four sites in four of the five agroecological zones (AEZ) in Zimbabwe were analyzed with respect to ENSO phases and used to drive a maize growth simulation model parameterized for soil conditions typical of each area, using two nitrogen fertilizer treatments and three planting dates. The four sites (Karoi, AEZ II; Gweru, AEZ III; Masvingo, AEZ IV; and Beitbridge, AEZ V) all showed a decrease in seasonal precipitation associated with the El Nino phase, compared to both neutral and La Nina years. At sites in zones II and III, within-season rainfall variability increased for both El Nino and La Nina years relative to neutral years. While average simulated maize yields were generally lowest in El Nino years, variability in rainfall pattern and standard deviation of yields at the site level was high within each ENSO phase, indicating that more precise seasonal climate predictions would be necessary for forecasts to be valuable in crop management decisions in Zimbabwe. However, simulation results point towards the relative importance of predicting favorable cropping seasons as opposed to poor ones with respect to better nitrogen management and yield improvement for the more marginal sites. (C) 1998 Elsevier Science B.V. C1 NASA, Goddard Inst Space Studies, Ctr Climate Syst Res, New York, NY 10025 USA. Columbia Univ, New York, NY 10025 USA. Columbia Univ, Lamont Doherty Earth Observ, Palisades, NY 10964 USA. RP Phillips, JG (reprint author), NASA, Goddard Inst Space Studies, Ctr Climate Syst Res, New York, NY 10025 USA. RI Cane, Mark/I-8086-2012 NR 23 TC 87 Z9 91 U1 2 U2 11 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0168-1923 J9 AGR FOREST METEOROL JI Agric. For. Meteorol. PD MAR PY 1998 VL 90 IS 1-2 BP 39 EP 50 DI 10.1016/S0168-1923(97)00095-6 PG 12 WC Agronomy; Forestry; Meteorology & Atmospheric Sciences SC Agriculture; Forestry; Meteorology & Atmospheric Sciences GA ZK358 UT WOS:000073312400004 ER PT J AU Jongen, T Mompean, G Gatski, TB AF Jongen, T Mompean, G Gatski, TB TI Predicting S-duct flow using a composite algebraic stress model SO AIAA JOURNAL LA English DT Article ID NONEQUILIBRIUM TURBULENT FLOWS; DISSIPATION AB An incompressible composite algebraic stress model is presented that accounts for dissipation rate anisotropies and that is validated against S-duct flow. The component algebraic stress and algebraic, anisotropic dissipation rate models have been developed previously and tested against homogeneous flow. The composite model is developed for integration to the wall and is calibrated against high-Reynolds number plane channel flow data to ensure the correct log-law behavior. The model is validated and analyzed against turbulent how in an S duct. Both predicted mean flow quantities and turbulence statistics are compared with experimental data, as well as with an isotropic eddy viscosity model and an algebraic stress model with an isotropic dissipation rate. The experimentally observed lag between the shear stress vector direction and the mean velocity gradient vector direction is qualitatively predicted. The effects of anisotropic dissipation rate on the production of the dissipation term in the dissipation rate equation and on the scalar functions that multiply the linear and nonlinear terms in the tensor expansion are examined relative to the algebraic stress formulation with an isotropic eddy viscosity. C1 Swiss Fed Inst Technol, Dept Mech Engn, Fluid Mech Lab, CH-1015 Lausanne, Switzerland. NASA, Langley Res Ctr, Aerodynam & Acoust Methods Branch, Hampton, VA 23681 USA. RP Jongen, T (reprint author), Swiss Fed Inst Technol, Dept Mech Engn, Fluid Mech Lab, CH-1015 Lausanne, Switzerland. NR 18 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 0001-1452 J9 AIAA J JI AIAA J. PD MAR PY 1998 VL 36 IS 3 BP 327 EP 335 DI 10.2514/2.400 PG 9 WC Engineering, Aerospace SC Engineering GA YZ480 UT WOS:000072258300004 ER PT J AU Watmuff, JH AF Watmuff, JH TI Detrimental effects of almost immeasurably small freestream nonuniformities generated by wind-tunnel screens 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 FREE-STREAM TURBULENCE; BOUNDARY-LAYER; FLOW AB Measurements are presented that were obtained during the course of a series of how quality improvements to a small stand-alone wind tunnel that has been modified for boundary-layer transition studies. The objective of establishing a Blasius boundary layer with a high degree of spanwise uniformity has been frustrated by the persistence of Klebanoff modes, i.e., weak streamwise vortices within the layer. The vortices originate at the leading edge and appear to be caused by almost immeasurably small nonuniformities in the freestream introduced by the wind-tunnel screens. The vortices cause a spanwise thickening and thinning of the layer. Contours of the background unsteadiness in a spanwise plane through the layer show locally concentrated regions with elevated levels that are associated with the vortices. These contours are used as a sensitive indicator for the how quality improvements. Although far from forming a complete parametric study, the observations should act as a valuable guide for others. For example, spanwise variations in the porosity of the screens were discovered by traversing each screen between a laser and a photo detector. Significant improvement in the spanwise uniformity of the layer was obtained by sorting the screens based on these results. The quantities that are generally agreed upon to define acceptable how quality proved to be inadequate during the final stages of refinement. The background unsteadiness within the layer has been reduced by a factor of 30 compared with the initial configuration. C1 MCAT Inc, Moffett Field, CA 94035 USA. RP Watmuff, JH (reprint author), NASA, Ames Res Ctr, Mail Stop 260-1, Moffett Field, CA USA. NR 26 TC 12 Z9 12 U1 0 U2 2 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0001-1452 J9 AIAA J JI AIAA J. PD MAR PY 1998 VL 36 IS 3 BP 379 EP 386 DI 10.2514/2.374 PG 8 WC Engineering, Aerospace SC Engineering GA YZ480 UT WOS:000072258300011 ER PT J AU Mei, H Agrawal, OP Pai, SS AF Mei, H Agrawal, OP Pai, SS TI Wavelet-based model for stochastic analysis of beam structures SO AIAA JOURNAL LA English DT Article ID PARTIAL-DIFFERENTIAL EQUATIONS; 2-DIMENSIONAL POTENTIAL FLOW; BOUNDARY ELEMENTS; EXPANSION; MULTIPLICATION; ALGORITHMS; SYSTEMS AB A wavelet-based model for stochastic analysis of beam structures is presented. In this model, the random processes representing the stochastic material and geometric properties are treated as stationary Gaussian processes with specified mean and correlation functions. Using the Karhunen-Loeve expansion, the process is represented as a linear sum of orthonormal eigenfunctions with uncorrelated random coefficients. The correlation and the eigenfunctions are approximated as truncated linear sums of compactly supported orthogonal wavelets, and the integral eigenvalue problem is converted to a finite dimensional eigenvalue problem. The energy-principle-based finite element approach is used to obtain the equilibrium and boundary conditions, Neumann expansion of the stiffness matrix is used to write the nodal displacement vector in terms of random coefficients. The expectation operator is applied to the nodal displacements and their squares to obtain the mean and standard deviation of the displacements. Studies show that the results obtained using this method compare well with Monte Carlo and semianalytical techniques. C1 So Illinois Univ, Coll Engn, Carbondale, IL 62901 USA. NASA, Lewis Res Ctr, Struct & Acoust Div, Cleveland, OH 44135 USA. RP Mei, H (reprint author), So Illinois Univ, Coll Engn, Carbondale, IL 62901 USA. NR 32 TC 6 Z9 7 U1 0 U2 1 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 MAR PY 1998 VL 36 IS 3 BP 465 EP 470 DI 10.2514/2.387 PG 6 WC Engineering, Aerospace SC Engineering GA YZ480 UT WOS:000072258300023 ER PT J AU Hwang, DP AF Hwang, DP TI Skin-friction reduction by a micro-blowing technique SO AIAA JOURNAL LA English DT Article C1 NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. RP Hwang, DP (reprint author), NASA, Lewis Res Ctr, 21000 Brookpk Rd, Cleveland, OH 44135 USA. NR 5 TC 1 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 0001-1452 J9 AIAA J JI AIAA J. PD MAR PY 1998 VL 36 IS 3 BP 480 EP 481 DI 10.2514/2.390 PG 2 WC Engineering, Aerospace SC Engineering GA YZ480 UT WOS:000072258300026 ER PT J AU Ribner, HS AF Ribner, HS TI Comment on "experimental study of a normal shock homogeneous turbulence interaction" SO AIAA JOURNAL LA English DT Editorial Material C1 Univ Toronto, Inst Aerosp Studies, Downsview, ON M3H 5T6, Canada. NASA, Langley Res Ctr, Hampton, VA 23681 USA. RP Ribner, HS (reprint author), Univ Toronto, Inst Aerosp Studies, 4925 Dufferin St, Downsview, ON M3H 5T6, Canada. NR 7 TC 6 Z9 6 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 MAR PY 1998 VL 36 IS 3 BP 494 EP 494 DI 10.2514/2.397 PG 1 WC Engineering, Aerospace SC Engineering GA YZ480 UT WOS:000072258300032 ER PT J AU McKay, CP Mellon, MT Friedmann, EI AF McKay, CP Mellon, MT Friedmann, EI TI Soil temperatures and stability of ice-cemented ground in the McMurdo Dry Valleys, Antarctica SO ANTARCTIC SCIENCE LA English DT Article DE climate change; dry valleys; ice-cemented ground; Linnaeus Terrace ID CRYPTOENDOLITHIC MICROBIAL ENVIRONMENT; ROSS DESERT; PERMAFROST; REGION AB Year-round temperature measurements at 1600 m elevation during 1994 in the Asgard Range Antarctica, indicate that the mean annual frost point of the ice-cemented ground, 25 cm below the surface, is -21.7 +/- 0.2 degrees C and the mean annual frost point of the atmosphere is -27.5 +/- 1.0 degrees C. The corresponding mean annual temperatures are -24.9 degrees C and -23.3 degrees C. These results imply that there is a net flux of water vapour from the ice to the atmosphere resulting in a recession of the ice-cemented ground by about 0.4-0.6 mm yr(1). The level of the ice-cemented permafrost is about 12 cm below the level of dry permafrost. The summer air temperatures would have to increase about 7 degrees C for thawing temperatures to just reach the top of the subsurface ice. Either subsurface ice at this location is evaporating over time or there are sporadic processes that recharge the ice and maintain equilibrium over long timescales. C1 NASA, Ames Res Ctr, Div Space Sci, Moffett Field, CA 94035 USA. Florida State Univ, Dept Biol Sci, Tallahassee, FL 32306 USA. RP McKay, CP (reprint author), NASA, Ames Res Ctr, Div Space Sci, Moffett Field, CA 94035 USA. NR 21 TC 59 Z9 61 U1 0 U2 1 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 MAR PY 1998 VL 10 IS 1 BP 31 EP 38 PG 8 WC Environmental Sciences; Geography, Physical; Geosciences, Multidisciplinary SC Environmental Sciences & Ecology; Physical Geography; Geology GA ZE131 UT WOS:000072760800005 PM 11541256 ER PT J AU Bushouse, HA Telesco, CM Werner, MW AF Bushouse, HA Telesco, CM Werner, MW TI The distribution of mid- and far-infrared emission in 10 interacting galaxy systems SO ASTRONOMICAL JOURNAL LA English DT Article DE galaxies, interactions; galaxies, photometry; galaxies, starburst ID BRIGHT SPIRAL GALAXIES; RECENT STAR FORMATION; STRONG RADIO-SOURCES; 1.49 GHZ ATLAS; SEYFERT-GALAXIES; MERGING GALAXIES; LUMINOSITY; CO; PHOTOMETRY; DYNAMICS AB A sample of 10 interacting and merging galaxy systems has been mapped at mid-infrared (10 mu m) and far-infrared (100-160 mu m) wavelengths with spatial resolutions of 4" and 45", respectively, The interacting and merging systems are known to be strong IRAS sources; however, the IRAS dates contain limited information concerning the distribution of infrared emission between the two galaxies in each pair and no information on the distribution within each galaxy. The observations presented here show that in five of the seven paired systems, one galaxy is the dominant or the only infrared source. There is a good correlation between the H alpha and infrared emission levels for these galaxies, indicating that the infrared emission is closely tied to dust heated by young stars. There is also a good spatial correlation between the H alpha, infrared, and radio continuum morphologies of these systems, which further strengthens the belief that the infrared, as well as the radio emission, is associated with regions of active star formation. The 10 mu m emission is concentrated around the nuclei of most of these galaxies, indicating that the highest levels of current star formation activity are also confined to the near-nuclear regions. Some systems, however, show evidence for significant star formation activity throughout the outer disk regions of the galaxies. All the sample galaxies that are bright in the infrared also have optical indications of high levels of star formation or nuclear activity, suggesting that these conditions are necessary in order for a galaxy to exhibit excess infrared emission. C1 Space Telescope Sci Inst, Baltimore, MD 21218 USA. Univ Florida, Dept Astron, Gainesville, FL 32611 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Bushouse, HA (reprint author), Space Telescope Sci Inst, 3700 San Martin Dr, Baltimore, MD 21218 USA. NR 50 TC 24 Z9 24 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5801 S ELLIS AVENUE, CHICAGO, IL 60637 USA SN 0004-6256 J9 ASTRON J JI Astron. J. PD MAR PY 1998 VL 115 IS 3 BP 938 EP 946 DI 10.1086/300255 PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZB173 UT WOS:000072443700008 ER PT J AU Tingay, SJ Jauncey, DL Reynolds, JE Tzioumis, AK King, EA Preston, RA Jones, DL Murphy, DW Meier, DL Van Ommen, TD McCulloch, PM Ellingsen, SP Costa, ME Edwards, PG Lovell, JEJ Nicolson, GD Quick, JFH Kemball, AJ Migenes, V Harbison, P Jones, PA White, GL Gough, RG Ferris, RH Sinclair, MW Clay, RW AF Tingay, SJ Jauncey, DL Reynolds, JE Tzioumis, AK King, EA Preston, RA Jones, DL Murphy, DW Meier, DL Van Ommen, TD McCulloch, PM Ellingsen, SP Costa, ME Edwards, PG Lovell, JEJ Nicolson, GD Quick, JFH Kemball, AJ Migenes, V Harbison, P Jones, PA White, GL Gough, RG Ferris, RH Sinclair, MW Clay, RW TI The subparsec-scale structure and evolution of Centaurus A: The nearest active radio galaxy SO ASTRONOMICAL JOURNAL LA English DT Article DE galaxies, active; galaxies, individual (NGC 5128, Centaurus A, PKS 1322 - 427); techniques, interferometric ID VLBI OBSERVATIONS; RAY-EMISSION; NUCLEUS; NGC-5128; JET AB We present high-resolution VLBI radio images of the closest classical radio galaxy? Centaurus A, including the highest resolution image yet for this source. The images were made from data obtained over a period of approximately 8 yr at the frequencies of 2.3, 3.8, and 8.4 GHz with the Southern Hemisphere VLBI Experiment (SHEVE) array and at 2.3, 8.4, and 22.2 GHz with the Very Long Baseline Array. We give complete details of the data reduction and analysis procedures. The subparsec-scale structure of Cen A is complex, consisting of a bright jet and a fainter counterjet. The bright jet contains components that have subluminal speeds of approximately 0.1c and undergo irregular episodes of rapid internal evolution. The rapid evolution sometimes observed could be interpreted as evidence for an underlying jet flow much faster (> 0.45c) than observed from the proper motion of components (similar to 0.1c). Considering the large-scale morphology of the sourer, the motions and temporal variations in the jet, and the detection of a counterjet, we conclude that the axis of the Cen A jet lies between similar to 50 degrees and similar to 80 degrees to our line of sight. We find that the estimated times of component ejection from the compact core are reasonably coincident with enhancements in hard X-ray intensity and 22 GHz flux density. In the context of the radio galaxy population, Cen A is a low-luminosity FR I-type source and in general has the properties observed in other FR I radio galaxies. Overall, the observations of Cen A presented here, and from other investigations, are consistent with the idea that sources with an FR I appearance are not aligned with our line of sight and have relativistic flow on the subparsec scale. The apparently subluminal subparsec-scale jet components are interpreted as being slow patterns on the relativistic flow. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. CSIRO, Australia Telescope Natl Facil, Epping, NSW 2121, Australia. Univ Tasmania, Dept Phys, Hobart, Tas 7001, Australia. Inst Space & Astronaut Sci, Sagamihara, Kanagawa 229, Japan. Hartebeesthoek Radio Astron Observ, ZA-1740 Krugersdorp, Transvaal, South Africa. Natl Astron Observ, Mitaka, Tokyo 181, Japan. British Aerosp Australia, The Levels, SA 5095, Australia. Univ Western Sydney Nepean, Dept Phys, Kingswood, NSW 2747, Australia. Univ Adelaide, Dept Phys & Math Phys, Adelaide, SA 5005, Australia. RP Tingay, SJ (reprint author), CALTECH, Jet Prop Lab, Mail Stop 238,4800 Oak Grove Dr, Pasadena, CA 91109 USA. RI Tingay, Steven/B-5271-2013; van Ommen, Tas/B-5020-2012; King, Edward/A-1473-2012; Ellingsen, Simon/J-7754-2014; Migenes, Victor/F-3157-2015 OI van Ommen, Tas/0000-0002-2463-1718; King, Edward/0000-0002-6898-2130; Ellingsen, Simon/0000-0002-1363-5457; Migenes, Victor/0000-0002-7990-2191 NR 31 TC 113 Z9 113 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 MAR PY 1998 VL 115 IS 3 BP 960 EP 974 DI 10.1086/300257 PG 15 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZB173 UT WOS:000072443700010 ER PT J AU Geha, MC Holtzman, JA Mould, JR Gallagher, JS Watson, AM Cole, AA Grillmair, CJ Stapelfeldt, KR Ballester, GE Burrows, CJ Clarke, JT Crisp, D Evans, RW Griffiths, RE Hester, JJ Hoessel, JG Scowen, PA Trauger, JT Westphal, JA AF Geha, MC Holtzman, JA Mould, JR Gallagher, JS Watson, AM Cole, AA Grillmair, CJ Stapelfeldt, KR Ballester, GE Burrows, CJ Clarke, JT Crisp, D Evans, RW Griffiths, RE Hester, JJ Hoessel, JG Scowen, PA Trauger, JT Westphal, JA TI Stellar populations in three outer fields of the Large Magellanic Cloud SO ASTRONOMICAL JOURNAL LA English DT Article DE galaxies, stellar content; Magellanic Clouds; stars, evolution ID STAR-FORMATION; CLUSTERS; AGE; PERFORMANCE; CALIBRATION; ISOCHRONES; HISTORY; REGIONS; WFPC2 AB We present Hubble Space Telescope photometry for three fields in the outer disk of the Large Magellanic Cloud (LMC) extending approximately 4 mag below the faintest main-sequence turnoff. We cannot detect any strongly significant differences in the stellar populations of the three fields based on the morphologies of the color-magnitude diagrams, the luminosity functions, and the relative numbers of stars in different evolutionary stages. Our observations therefore suggest similar star formation histories in these regions, although some variations are certainly allowed. The fields are located in two regions of the LMC: one is in the northeast and two are located in the northwest. Under the assumption of a common star formation history, we combine the three fields with ground-based data at the same location as one of the fields to improve statistics for the brightest stars. We compare this stellar population with those predicted from several simple star formation histories suggested in the literature, using a combination of the R-method of Bertelli et al. (1992) and comparisons with the observed luminosity function. The only model we consider that is not rejected by the observations is one in which the star formation rate is roughly constant for most of the LMC's history and then increases by a factor of 3 about 2 Gyr ago. Such a model has roughly equal numbers of stars older and younger than 4 Gyr, and thus is not dominated by young stars. This star formation history, combined with a closed-box chemical evolution model, is consistent with observations that the metallicity of the LMC has doubled in the past 2 Gyr. C1 New Mexico State Univ, Dept Astron, Las Cruces, NM 88003 USA. Australian Natl Univ, Mt Stromlo & Siding Spring Observ, Weston Creek, ACT 2611, Australia. Univ Wisconsin, Dept Astron, Madison, WI 53706 USA. Univ Nacl Autonoma Mexico, Inst Astron, Morelia 58090, Michoacan, Mexico. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ Michigan, Dept Atmospher Ocean & Space Sci, Ann Arbor, MI 48109 USA. Space Telescope Sci Inst, Baltimore, MD 21218 USA. ESA, Dept Space Sci, F-75738 Paris 15, France. Carnegie Mellon Univ, Dept Phys, Pittsburgh, PA 15213 USA. Arizona State Univ, Dept Phys & Astron, Tempe, AZ 85287 USA. CALTECH, Div Geol & Planetary Sci, Pasadena, CA 91125 USA. RP Geha, MC (reprint author), New Mexico State Univ, Dept Astron, Dept 4500,Box 30001, Las Cruces, NM 88003 USA. RI Stapelfeldt, Karl/D-2721-2012; Clarke, John/C-8644-2013; OI Cole, Andrew/0000-0003-0303-3855 NR 30 TC 79 Z9 79 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 MAR PY 1998 VL 115 IS 3 BP 1045 EP 1056 DI 10.1086/300252 PG 12 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZB173 UT WOS:000072443700014 ER PT J AU Fekel, FC Eitter, JJ De Medeiros, JR Kirkpatrick, JD AF Fekel, FC Eitter, JJ De Medeiros, JR Kirkpatrick, JD TI Chromospherically active stars. XVII. The double-lined binary 54 Camelopardalis (AE Lyncis) SO ASTRONOMICAL JOURNAL LA English DT Article DE binaries, spectroscopic; stars, chromospheres ID RS-CANUM-VENATICORUM; SOLAR-TYPE STARS; H-ALPHA; SYSTEMS; LITHIUM; CATALOG; EVOLUTION; CORAVEL; HYADES AB New spectroscopic observations of the double-lined chromospherically active binary 54 Camelopardalis (=AE Lyncis) have been obtained, resulting in improved orbital elements and the determination of the fundamental properties of the system. 54 Cam has a period of 11.06794 days, an eccentricity of 0.125, and a mass ratio of 0.9945. The spectral types are F8 IV-V and G5 IV, positioning the components on opposite sides of the Hertzsprung gap. From a comparison with theoretical evolutionary tracks, the masses are estimated to be 1.60 and 1.59 M. for the G and F stars, respectively, while the radii are 3.7 and 3.2 R.. Only the G star is chromospherically active. 54 Cam is particularly interesting since the F star is the brighter star at blue and red wavelengths, but the G star is slightly more massive and evolved. Both stars appear to be pseudosynchronously rotating, and the orbital and rotational inclinations are aligned. The lithium abundances of the two components are significantly different but consistent with standard theory, supporting the conclusion that both stars are more massive than the lithium-dip stars. C1 Tennessee State Univ, Ctr Automated Space Sci, Nashville, TN 37203 USA. Tennessee State Univ, Ctr Excellence Informat Syst, Nashville, TN 37203 USA. NASA, George C Marshall Space Flight Ctr, Space Sci Lab, Huntsville, AL 35812 USA. Iowa State Univ, Erwin W Fick Observ, Ames, IA 50011 USA. Univ Fed Rio Grande Norte, Dept Fis, BR-59072970 Natal, RN, Brazil. CALTECH, Jet Prop Lab, Ctr Infrared Proc & Anal, Pasadena, CA 91125 USA. RP Fekel, FC (reprint author), Tennessee State Univ, Ctr Automated Space Sci, 330 10th Ave N, Nashville, TN 37203 USA. NR 58 TC 4 Z9 4 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5801 S ELLIS AVENUE, CHICAGO, IL 60637 USA SN 0004-6256 J9 ASTRON J JI Astron. J. PD MAR PY 1998 VL 115 IS 3 BP 1153 EP 1159 DI 10.1086/300260 PG 7 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZB173 UT WOS:000072443700025 ER PT J AU Jacobson, RA AF Jacobson, RA TI The orbits of the inner Uranian satellites from Hubble Space Telescope and Voyager 2 observations SO ASTRONOMICAL JOURNAL LA English DT Article DE planets and satellites, general; planets and satellites, individual (Uranus); solar system, general ID TRACKING DATA; URANUS; SYSTEM AB This article presents revised orbital elements for the 10 small Uranian satellites discovered by the Voyager 2 spacecraft. The elements have been determined from a fit to astrometric observations made with the Hubble Space Telescope and imaging data acquired by Voyager 2. An assessment of the accuracy of the orbits represented by the elements is provided, as are comparisons with orbits found by previous investigators. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Jacobson, RA (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 15 TC 15 Z9 16 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 MAR PY 1998 VL 115 IS 3 BP 1195 EP 1199 DI 10.1086/300263 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZB173 UT WOS:000072443700029 ER PT J AU Bujarrabal, V Alcolea, J Sahai, R Zamorano, J Zijlstra, AA AF Bujarrabal, V Alcolea, J Sahai, R Zamorano, J Zijlstra, AA TI The shock structure in the protoplanetary nebula M 1-92: imaging of atomic and H(2) line emission SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE circumstellar matter; stars : AGB and post-AGB; planetary nebulae : individual : M 1-92; shocks infrared : ISM : lines and bands ID ASPHERICAL PLANETARY-NEBULAE; POINT-SYMMETRICAL NEBULAE; MOLECULAR-HYDROGEN; BIPOLAR NEBULAE; RADIATION-GASDYNAMICS; FOOTPRINT M1-92; JETS; EVOLUTION; OUTFLOW; SIMULATION AB We present HST imaging of continuum (5500 Angstrom) and atomic line (H alpha, [OI] 6300 Angstrom, [SII] 6717 and 6731 Angstrom, and [OIII] 5007 Angstrom) emissions in the protoplanetary nebula M 1-92. Ground based imaging of 2 mu m continuum and H(2) ro-vibrational (S(1) v=1-0 and v=2-1 lines) emission has been also performed. The 5500 Angstrom continuum is due to scattering of the stellar light by grains in a double-lobed structure comparable in extent and total density with the molecular envelope detected at mm wavelengths, which consists of two empty shells with a clear axis of symmetry. On the other hand, the optical line emission comes mainly from two chains of shocked knots placed along the symmetry axis of the nebula and inside those cavities, for which relatively high excitation is deduced (shock velocities of about 200 km s(-1)). The H(2) emission probably comes from more extended regions with representative temperature and density of 1600 K and 6 10(3) cm(-3), intermediate in location and excitation between the atomic line knots and the very cold region detected in CO emission. We argue that the chains of knots emitting in atomic lines correspond to shocks taking place in the post-AGE bipolar flow. The models for interstellar Herbig-Haro objects seem to agree with the observations, at least qualitatively, explaining in particular that the atomic emission from the bipolar flow dominates over that from shocks propagating in the AGE shell. Models developed for protoplanetary nebula dynamics fair, however, to explain the strong concentration of the atomic emission along the symmetry axis. C1 Observ Astron Nacl IGN, E-28800 Alcala De Henares, Spain. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ Complutense Madrid, Fac Ciencias Fis, Dept Astrofis, E-28040 Madrid, Spain. European So Observ, D-85748 Garching, Germany. RP Bujarrabal, V (reprint author), Observ Astron Nacl IGN, Apartado 1143, E-28800 Alcala De Henares, Spain. EM bujarrabal.j.alcolea@oan.es; sahai@lb6.jpl.nasa.gov; jaz@astrax.fis.ucm.es; azijlstr@eso.og RI Zamorano, Jaime/K-7706-2014 OI Zamorano, Jaime/0000-0002-8993-5894 NR 51 TC 52 Z9 52 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 MAR 1 PY 1998 VL 331 IS 1 BP 361 EP 371 PG 11 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZB164 UT WOS:000072442800031 ER PT J AU Gaztanaga, E Bernardeau, F AF Gaztanaga, E Bernardeau, F TI The skewness and kurtosis of the projected density distribution function: validity of perturbation theory SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE cosmic microwave background; dark matter; gravitational lensing; large-scale structure of Universe ID LARGE-SCALE STRUCTURE; APM GALAXY SURVEY; CORRELATION HIERARCHY; STATISTICAL-ANALYSIS; CATALOGS; OBJECTS AB We study the domain of validity of Perturbation Theory (PT), by comparing its predictions for the reduced skewness, s(3), and kurtosis, s(4), Of the projected cosmological density field, with the results of N-body simulations. We investigate models with different linear power spectra and consider as physical applications both angular galaxy catalogues and weak lensing surveys. We first find that the small-angle approximation for the predicted skewness provides a good match to the exact numerical PT results. On the other hand, results from non-linear simulated catalogues agree well with PT results on quasi-linear angular scales, which correspond to scales larger than about 1 deg in the applications we have considered. We also point out that projection effects tend to attenuate the effects of strong non-linearities in the angular skewness and kurtosis. C1 Ctr Etud Saclay, Serv Phys Theor, F-91191 Gif Sur Yvette, France. CSIC, Unidad Nixta, Inst Estudis Espacials Catalunya, E-08034 Barcelona, Spain. NASA, Fermilab Astrophys Ctr, Batavia, IL 60510 USA. RP Bernardeau, F (reprint author), Ctr Etud Saclay, Serv Phys Theor, F-91191 Gif Sur Yvette, France. EM fbernardeau@cea.fr OI Gaztanaga, Enrique/0000-0001-9632-0815 NR 33 TC 38 Z9 38 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 MAR PY 1998 VL 331 IS 3 BP 829 EP 837 PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZD690 UT WOS:000072713100016 ER PT J AU Dolan, JF Hill, RF Boyd, PT Silvis, JM Percival, JW van Citters, GW AF Dolan, JF Hill, RF Boyd, PT Silvis, JM Percival, JW van Citters, GW TI Reprocessed UV pulses from the binary companions of X-ray pulsars SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE binaries : close; stars : individual : HD 77581; stars : neutron; pulsars : individual : 4U 0900-40; ultraviolet : stars; X-rays : stars ID HZ-HERCULIS/HERCULES X-1; VELA X-1; OPTICAL PULSATIONS; NEUTRON STAR; 4U 0900-40; ULTRAVIOLET; SYSTEM; MASS; PERIODICITY; 4U1145-619 AB A search for reprocessed X-rays causing UV pulsations in the companion stars to X-ray pulsars was carried out in a 200 Angstrom wide bandpass centered at 1450 Angstrom using the High Speed Photometer on the Hubble Space Telescope. We observed the systems A0535+26 = HD245770, 4U0900-40 (Vela XR-1)= HD77581, A1118-61 = He3-640, and 4U1145-619 = HD102567. We confirm the existence of reprocessed X-rays reported in 4U0900-40 by Boroson et al. (1996) and give upper limits on the pulsed fraction in our UV bandpass present in the other systems. Archival IUE spectra are consistent with the finding of Boroson et al. that the UV radiation from HD77581 is emitted primarily in resonance emission lines from multiply ionized metals. The existence of two different pulse frequencies (UV and X-ray) in an X-ray binary system makes it dynamically equivalent to a double-lined spectroscopic binary. If the UV pulses are emitted from a site in the primary's outer atmosphere rather than its stellar wind, then the mass of the neutron star can be derived from the orbital phase dependence of the two frequencies. C1 NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, Greenbelt, MD 20771 USA. NASA, Goddard Space Flight Ctr, Hughes STX Corp, Greenbelt, MD 20771 USA. NASA, Goddard Space Flight Ctr, Univ Space Res Assoc, Greenbelt, MD 20771 USA. Univ Wisconsin, Dept Astron, Madison, WI 53706 USA. Univ Wisconsin, Space Astron Lab, Madison, WI 53706 USA. Natl Sci Fdn, Div Astron Sci, Arlington, VA 22230 USA. RP Dolan, JF (reprint author), NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, Greenbelt, MD 20771 USA. EM tejfd@splvin.gsfc.nasa.gov; hill@noether.gsfc.nasa.gov; padi@dragons.gsfc.nasa.gov; silvis@xfiles.gsfc.nasa.gov; jwp@maddog.sal.wisc.edu; gvancitt@notel.nsf.gov RI Boyd, Patricia/D-3274-2012 NR 63 TC 5 Z9 5 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 MAR PY 1998 VL 331 IS 3 BP 1037 EP 1045 PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZD690 UT WOS:000072713100036 ER PT J AU Jones, LR Scharf, C Ebeling, H Perlman, E Wegner, G Malkan, M Horner, D AF Jones, LR Scharf, C Ebeling, H Perlman, E Wegner, G Malkan, M Horner, D TI The WARPS survey. II. The log N log S relation and the X-ray evolution of low-luminosity clusters of galaxies SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies, clusters, general; galaxies, evolution; X-rays, galaxies ID FLUX-LIMITED SAMPLE; REDSHIFT; SPECTRUM; DENSITY AB The strong negative evolution observed in previous X-ray-selected surveys of clusters of galaxies is evidence in favor of hierarchical models of the growth of structure in the universe. A large recent survey has, however, contradicted the low-redshift results, finding no evidence for evolution at z < 0.3. Here we present the first results from an X-ray-selected, flux-and surface brightness-limited deep survey for high-redshift clusters and groups of galaxies based on ROSAT PSPC pointed data. The log N-log S relation of all clusters in this survey is consistent with that of most previous surveys, but it occupies a flux range not previously covered (greater than 6 x 10(-14) ergs cm(-2) s(-1) total flux in the 0.5-2 keV band). At high redshifts (z > 0.3) the cluster luminosities are in the range 4 x 10(43)-2 x 10(44) h(50)(-2) ergs s(-1), the luminosities of poor clusters. The number of high-redshift, low-luminosity clusters is consistent with no evolution of the X-ray luminosity function between redshifts of z approximate to 0.4 and z = 0, and it places a limit of a factor of less than 1.7 (at 90% confidence) on the amplitude of any pure negative density evolution of clusters of these luminosities, in contrast with the factor of approximate to 3 [corresponding to number density evolution proportional to (1 + z)(-2.5)] found in the Einstein Extended Medium-Sensitivity Survey at similar redshifts but higher luminosities. Taken together, these results support hierarchical models in which there is mild negative evolution of the most luminous clusters at high redshift, but little or no evolution of the less luminous but more common optically poor clusters. Models involving preheating of the X-ray gas at an early epoch fit the observations, at least for Omega(0) = 1. C1 Univ Birmingham, Sch Phys & Space Res, Birmingham B15 2TT, W Midlands, England. NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. Univ Hawaii, Inst Astron, Honolulu, HI 96822 USA. Space Telescope Sci Inst, Baltimore, MD 21218 USA. Dartmouth Coll, Dept Phys & Astron, Hanover, NH 03755 USA. Univ Calif Los Angeles, Dept Astron, Los Angeles, CA 90024 USA. RP Jones, LR (reprint author), Univ Birmingham, Sch Phys & Space Res, Birmingham B15 2TT, W Midlands, England. NR 52 TC 99 Z9 99 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 MAR 1 PY 1998 VL 495 IS 1 BP 100 EP 114 DI 10.1086/305283 PN 1 PG 15 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZA394 UT WOS:000072359100008 ER PT J AU Whitney, JH Rood, RT O'Connell, RW D'Cruz, NL Dorman, B Landsman, WB Bohlin, RC Roberts, MS Smith, AM Stecher, TP AF Whitney, JH Rood, RT O'Connell, RW D'Cruz, NL Dorman, B Landsman, WB Bohlin, RC Roberts, MS Smith, AM Stecher, TP TI Analysis of the hot stellar population of the globular cluster omega Centauri SO ASTROPHYSICAL JOURNAL LA English DT Article DE globular clusters, individual (omega Centauri); stars, evolution stars, horizontal-branch; ultraviolet, stars ID HORIZONTAL-BRANCH STARS; PHOTOGRAPHIC PHOTOMETRY; BRIGHT STARS; RED GIANTS; MASS-LOSS; AGE; METALLICITY; ABUNDANCES; MORPHOLOGY; MODELS AB We analyze the far-UV and Stromgren u photometric data of the globular cluster omega Cen presented in an earlier paper. The color-magnitude diagram of the cluster from these two bands shows that omega Cen's horizontal-branch (HE) consists of a group of cooler intermediate blue HE (IBHB) and a group of extreme HE (EHB) stars, together with a large population of post-HE stars. Unexpected features in the diagram are a discontinuity between the EHB and IBHB objects lying at (FUV - 3500)(0) similar to - 1.5, an unusually large population of stars below the EHB, and a number of sources bluer than an infinite temperature blackbody. No adjustment of the assumed reddening or distance modulus parameters satisfactorily explains either the sub-HE or very hot star components observed. The radial distributions of the IBHB and EHB subpopulations are similar after corrections for completeness and crowding are made. This result, as well as the fact that omega Cen's core is not dynamically evolved, implies that dynamical effects are not required for the production of EHB stars in globular clusters. To compare the observations to theory we use Hess diagrams, which describe the density distribution of stars in the color-magnitude diagram. To simulate the known abundance spread in omega Cen, we use image-processing "morphing" techniques to create a composite Hess diagram for [Fe/H] = -2.2, -1.5, and -0.5. We populate the zero-age HE (ZAHB) in our simulations assuming either flat or Gaussian distributions in total stellar mass or, alternatively, distributions in the red giant branch mass-loss efficiency parameter eta in Reimers's formula. Our ZAHB's extend to the lowest possible ZAHB mass as determined by evolving models along the red giant branch with extreme mass-loss rates. Neither flat nor Gaussian distributions in ZAHB mass reproduce the observed HB gap or the sub-HB population. However, the eta distribution models can crudely reproduce the gap as well as the sub-HB population while simultaneously fitting the rest of the HB and post-HB population. C1 Univ Virginia, Dept Astron, Charlottesville, VA 22903 USA. NASA, Goddard Space Flight Ctr, STX Co, Greenbelt, MD 20771 USA. Space Telescope Sci Inst, Baltimore, MD 21218 USA. Natl Radio Astron Observ, Charlottesville, VA 22903 USA. NASA, Astron & Solar Phys Lab, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Whitney, JH (reprint author), Univ Virginia, Dept Astron, POB 3818, Charlottesville, VA 22903 USA. EM jw9w@virginia.edu; rtr@virginia.edu; rwo@virginia.edu; nld2n@virginia.edu; bd4r@virginia.edu; landsman@sorbet.gsfc.nasa.gov; bohlin@fos.stsci.edu; mroberts@nrao.edu; asmith@.uit.gsfc.nasa.gov; stecher@uit.gsfc.nasa.gov NR 65 TC 44 Z9 44 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 MAR 1 PY 1998 VL 495 IS 1 BP 284 EP 296 DI 10.1086/305288 PN 1 PG 13 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZA394 UT WOS:000072359100025 ER PT J AU Kleinman, SJ Nather, RE Winget, DE Clemens, JC Bradley, PA Kanaan, A Provencal, JL Claver, CF Watson, TK Yanagida, K Nitta, A Dixson, JS Wood, MA Grauer, AD Hino, BP Fontaine, G Liebert, J Sullivan, DJ Wickramasinghe, DT Achilleos, N Marar, TMK Seetha, S Ashoka, BN Meistas, E Leibowitz, EM Moskalik, P Krzesinski, J Solheim, JE Bruvold, A O'Donoghue, D Kurtz, DW Warner, B Martinez, P Vauclair, G Dolez, N Chevreton, M Barstow, MA Kepler, SO Giovannini, O Augusteijn, T Hansen, CJ Kawaler, SD AF Kleinman, SJ Nather, RE Winget, DE Clemens, JC Bradley, PA Kanaan, A Provencal, JL Claver, CF Watson, TK Yanagida, K Nitta, A Dixson, JS Wood, MA Grauer, AD Hino, BP Fontaine, G Liebert, J Sullivan, DJ Wickramasinghe, DT Achilleos, N Marar, TMK Seetha, S Ashoka, BN Meistas, E Leibowitz, EM Moskalik, P Krzesinski, J Solheim, JE Bruvold, A O'Donoghue, D Kurtz, DW Warner, B Martinez, P Vauclair, G Dolez, N Chevreton, M Barstow, MA Kepler, SO Giovannini, O Augusteijn, T Hansen, CJ Kawaler, SD TI Understanding the cool DA white dwarf pulsator, G29-38 SO ASTROPHYSICAL JOURNAL LA English DT Article DE stars, individual (G29-38); stars, oscillations; stars, white dwarfs ID WHOLE EARTH TELESCOPE; ASTEROSEISMOLOGY; STARS AB The white dwarfs are promising laboratories for the study of cosmochronology and stellar evolution. Through observations of the pulsating white dwarfs, we can measure their internal structures and compositions, critical to understanding post-main-sequence evolution, along with their cooling rates, which will allow us to calibrate their ages directly. The most important set of white dwarf variables to measure are the oldest of the pulsators, the cool DA variables (DAVs), which have not been explored previously through asteroseismology due to their complexity and instability. Through a time-series photometry data set spanning 10 yr, we explore the pulsation spectrum of the cool DAV, G29 - 38 and find an underlying structure of 19 (not including muitiplet components) normal-mode, probably l = 1 pulsations amidst an abundance of time variability and linear combination modes. Modeling results are incomplete, but we suggest possible starting directions and discuss probable values for the stellar mass and hydrogen layer size. For the first time, we have made sense out of the complicated power spectra of a large-amplitude DA pulsator. We have shown that its seemingly erratic set of observed frequencies can be understood in terms of a recurring set of normal-mode pulsations and their linear combinations. With this result, we have opened the interior secrets of the DAVs to future asteroseismological modeling, thereby joining the rest of the known white dwarf pulsators. C1 New Jersey Inst Technol, Big Bear Solar Observ, Big Bear City, CA 92314 USA. Univ Texas, Dept Astron, Austin, TX 78712 USA. CALTECH, Pasadena, CA 91125 USA. Univ Calif Los Alamos Natl Lab, Los Alamos, NM 87545 USA. Univ Fed Rio Grande Sul, Inst Fis, BR-91501970 Porto Alegre, RS, Brazil. Univ Delaware, Dept Phys & Astron, Sharp Lab, Newark, DE 19716 USA. Natl Opt Astron Observ, Tucson, AZ 85726 USA. Iowa State Univ, Dept Phys & Astron, Ames, IA 50211 USA. Florida Inst Technol, Dept Phys & Space Sci, Melbourne, FL 32901 USA. Univ Arkansas, Dept Phys & Astron, Little Rock, AR 72204 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Univ Montreal, Dept Phys, Montreal, PQ H3C 3J7, Canada. Univ Arizona, Steward Observ, Tucson, AZ 85721 USA. Univ Victoria, Dept Phys, Wellington, New Zealand. Australian Natl Univ, Dept Math, Canberra, ACT, Australia. Indian Space Res Org, Bangalore 560017, Karnataka, India. Inst Theoret Phys & Astron, LT-2600 Vilnius, Lithuania. Tel Aviv Univ, Dept Phys & Astron, IL-69978 Tel Aviv, Israel. Copernicus Astron Ctr, Warsaw, Poland. Cracow Pedagog Univ, Mt Suhora Observ, PL-30084 Krakow, Poland. Univ Tromso, Inst Matemat Realfag, N-9000 Tromso, Norway. Univ Cape Town, Dept Astron, ZA-7700 Rondebosch, Cape Province, South Africa. Observ Midi Pyrenees, F-31400 Toulouse, France. Observ Paris, F-92195 Meudon, France. Univ Leicester, Dept Phys & Astron, Leicester LE1 7RH, Leics, England. European So Observ, Santiago 19, Chile. Univ Colorado, Joint Inst Lab Astrophys, Boulder, CO 80309 USA. RP Kleinman, SJ (reprint author), New Jersey Inst Technol, Big Bear Solar Observ, 40386 N Shore Lane, Big Bear City, CA 92314 USA. RI Achilleos, Nicholas/C-1647-2008; Kepler, S. O. /H-5901-2012; OI Kepler, S. O. /0000-0002-7470-5703; Achilleos, Nicholas/0000-0002-5886-3509; Kawaler, Steven/0000-0002-6536-6367 NR 33 TC 101 Z9 101 U1 1 U2 7 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 MAR 1 PY 1998 VL 495 IS 1 BP 424 EP 434 DI 10.1086/305259 PN 1 PG 11 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZA394 UT WOS:000072359100038 ER PT J AU Gull, TR Lindler, DJ Crenshaw, DM Dolan, JF Hulbert, SJ Kraemer, SB Lundqvist, P Sahu, KC Sollerman, J Sonneborn, G Woodgate, BE AF Gull, TR Lindler, DJ Crenshaw, DM Dolan, JF Hulbert, SJ Kraemer, SB Lundqvist, P Sahu, KC Sollerman, J Sonneborn, G Woodgate, BE TI Space Telescope Imaging Spectrograph near-ultraviolet time-tagged spectra of the Crab Pulsar SO ASTROPHYSICAL JOURNAL LA English DT Article DE dust, extinction; instrumentation, spectrographs; pulsars, individual (Crab Pulsar); supernova remnants; ultraviolet, ISM; ultraviolet, stars ID NEBULA AB We present the spectrum and the pulse profile of the Crab Pulsar in the near-ultraviolet (1600-3200 Angstrom) observed with the Space Telescope Imaging Spectrograph (STIS) during the Hubble Space Telescope (HST) second Servicing Mission Orbital Verification (SMOV) period. The two-dimensional near-ultraviolet Multianode Microchannel Array (NUV MAMA) was used in time-tag mode with a 2" x 2" aperture and the low-dispersion grating, G230L, to obtain a cube with axes of slit position, wavelength, and time. The observation-derived pulse period is consistent with radio measurements, and the pulse profile agrees well with previous NUV broadband measurements by the High Speed Photometer. The pulsar spectrum includes the 2200 Angstrom dust absorption feature, plus several interstellar absorption lines. Dereddening the spectrum using the Savage-Mathis model with E(B - V) = 0.55 +/- 0.05 leads to a good fit to a power law with slope alpha(v) = -0.3 +/- 0.2. The spectra of the main pulse, the interpulse, and the individual rising and falling edges are similar to the total spectrum within the limits of photon statistics. The four pulse profiles produced by breaking the spectrum into 400 Angstrom bins show the pulse profile to be stable across the NUV spectral range. Histogram analysis reveals no evidence for the superpulses seen at radio wavelengths. The interstellar absorption-line equivalent widths of Mg I, Mg II, and Fe II are lower than expected based on the implied H I column density from E(B - V) = 0.5. While several explanations are possible, additional studies will be necessary to narrow the options. C1 Astron & Solar Phys Lab, Greenbelt, MD USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Adv Comp Concepts, Greenbelt, MD USA. Catholic Univ, Greenbelt, MD USA. Space Telescope Sci Inst, Baltimore, MD 21218 USA. Stockholm Observ, SE-13336 Saltsjobaden, Sweden. RP Gull, TR (reprint author), Astron & Solar Phys Lab, Greenbelt, MD USA. RI Gull, Theodore/D-2753-2012; Woodgate, Bruce/D-2970-2012; OI Gull, Theodore/0000-0002-6851-5380; Sollerman, Jesper/0000-0003-1546-6615 NR 20 TC 16 Z9 16 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5801 S ELLIS AVENUE, CHICAGO, IL 60637 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD MAR 1 PY 1998 VL 495 IS 1 BP L51 EP + DI 10.1086/311215 PN 2 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZA395 UT WOS:000072359200013 ER PT J AU Zhang, W Jahoda, K Kelley, RL Strohmayer, TE Swank, JH Zhang, SN AF Zhang, W Jahoda, K Kelley, RL Strohmayer, TE Swank, JH Zhang, SN TI Millisecond oscillations in the persistent and bursting flux of Aquila X-1 during an outburst SO ASTROPHYSICAL JOURNAL LA English DT Article DE stars, individual (Aquila X-1); stars, neutron AB The Rossi X-Ray Timing Explorer observed the soft X-ray transient Aquila X-1 during its outburst in 1997 February and March. We report the discovery of quasi-periodic oscillations (QPOs) in its persistent flux with frequencies in the range of 740-830 Hz, a e-value of over 100, a fractional rms amplitude of 6.8% +/- 0.6%, and nearly coherent oscillations (NCOs) during a type I burst with a frequency of 549 Hz. The frequency of the QPOs in the persistent flux is correlated with the mass accretion rate on a timescale of hours, but not on a timescale of days. This is most likely the manifestation in a single source of the kilohertz QPO puzzle observed among many sources, i.e., on the one hand, individual sources show a correlation between the QPO frequency and the inferred mass accretion rate, and on the other hand, the dozen or so sources with luminosities spanning two decades have essentially the same QPO frequencies. We propose that this multivalued QPO frequency and mass accretion rate correlation indicates the existence of many similar regimes of the accretion disk. These regimes, with a very similar energy spectrum and QPO frequency, are distinguished from each other by the mass accretion rate or the total X-ray flux. The NCOs during the burst can be made almost perfectly coherent by taking into account a large (nu) over dot. This strongly suggests that this frequency is related to the neutron star spin frequency. The large (nu) over dot is attributable to the expansion or contraction of the neutron star photosphere during the burst. C1 NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. NASA, George C Marshall Space Flight Ctr, Univ Space Res Assoc, Huntsville, AL 35812 USA. RP NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. RI Jahoda, Keith/D-5616-2012; Swank, Jean/F-2693-2012; Kelley, Richard/K-4474-2012 NR 10 TC 98 Z9 99 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 MAR 1 PY 1998 VL 495 IS 1 BP L9 EP L12 DI 10.1086/311210 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZA395 UT WOS:000072359200003 ER PT J AU Rukhovets, L van den Dool, HM Barnston, AG AF Rukhovets, L van den Dool, HM Barnston, AG TI Forecast-observation pattern relationships in NCEP medium range forecasts of non-winter Northern Hemisphere 500-mb height fields SO ATMOSPHERE-OCEAN LA English DT Article ID CIRCULATION PATTERNS; SKILL AB Empirical orthogonal function (EOF) and singular value decomposition (SVD) analyses are applied to the Dynamical Extended Range Forecasting 90 (DERF90) dataset to find the most predictable areas and patterns in the non-winter Northern Hemisphere 500-mb height fields. Global 500-mb height forecast and analysis fields covering 4 months of 1990 are used The EOF method is applied to the forecast and analysis fields separately A close correspondence between the forecast and analysis modes is found for 1-day lead time. The correlation relations between these modes rapidly decrease with increasing forecast lead time. At 10-day lead the projections of the forecasts and corresponding analyses onto the strongest Northern Hemisphere EOF mode of the analyses correlate at 0.65, which is which higher than the general forecast-analysis correlation of about 0.20. This particularly predictable mode consists of a Pacific/North America-like pattern. Joint forecast vs. analysis correlation matrices were used to apply the SVD method to forecast and analysis fields. By design, the correlations between the forecast and analysis SVD modes are stronger than between the forecast and analysis EOF modes. Maps of temporal correlations between gridpoint values of analysis fields and the first and second EOF as well as SVD expansion coefficients of the forecast fields (i.e., heterogeneous EOF and SVD correlation maps) are used to find the regions of the best prediction skill. It is shown that the Pacific/North American, western and southeastern Pacific the southern Atlantic and Indian ocean areas have relatively better prediction skill. C1 NOAA, NCEP, Climate Predict Ctr, Washington, DC 20233 USA. RP Rukhovets, L (reprint author), NASA, Goddard Space Flight Ctr, 7501 Forbes Blvd,Suite 200, Seabrook, MD 20706 USA. NR 17 TC 0 Z9 0 U1 1 U2 2 PU CANADIAN METEOROLOGICAL OCEANOGRAPHIC SOC PI OTTAWA PA 150 LOUIS PASTEUR PVT., STE 112, MCDONALD BUILDING, OTTAWA, ONTARIO K1N 6N5, CANADA SN 0705-5900 J9 ATMOS OCEAN JI Atmos.-Ocean PD MAR PY 1998 VL 36 IS 1 BP 55 EP 70 PG 16 WC Meteorology & Atmospheric Sciences; Oceanography SC Meteorology & Atmospheric Sciences; Oceanography GA ZE287 UT WOS:000072776900004 ER PT J AU Bhatia, AK Young, PR AF Bhatia, AK Young, PR TI Atomic data and spectral line intensities for Mg VI SO ATOMIC DATA AND NUCLEAR DATA TABLES LA English DT Article ID ELECTRON-IMPACT EXCITATION; ENERGETIC PARTICLES; SOLAR ATMOSPHERE; CROSS-SECTIONS; COEFFICIENTS; PLASMAS AB Electron collision strengths for Mg VI, calculated in the distorted-wave approximation, are presented for all transitions between the 23 levels of the 2s(2)2p(3), 2s(2)p(3), 2p(5), and 2s(2)2p(2)3s configurations, Radiative data have been calculated utilizing the same four-configuration model of the ion. Proton rates for the transitions between the ground states are also presented. The level balance equations for Mg VI have been solved using these data and comparisons are made with previous results-excellent agreement is found. Theoretical line intensities for the important transitions are presented and compared with lines found in the extreme ultraviolet in a spectrum from the 1989 flight of the Solar EUV Rocket Telescope and Spectrograph. Recent data from the Coronal Diagnostic Spectrometer onboard the Solar and Heliospheric Observatory are also presented. (C) 1998 Academic Press. C1 NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, Greenbelt, MD 20771 USA. Univ Cambridge, Dept Appl Math & Theoret Phys, Cambridge CB3 9EW, England. RP Bhatia, AK (reprint author), NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, Greenbelt, MD 20771 USA. NR 33 TC 7 Z9 7 U1 0 U2 0 PU ACADEMIC PRESS INC PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA SN 0092-640X J9 ATOM DATA NUCL DATA JI Atom. Data Nucl. Data Tables PD MAR PY 1998 VL 68 IS 2 BP 219 EP 239 DI 10.1006/adnd.1997.0766 PG 21 WC Physics, Atomic, Molecular & Chemical; Physics, Nuclear SC Physics GA ZK058 UT WOS:000073280700003 ER PT J AU Frey, MAB Sulzman, FM Oser, H Ruyters, G AF Frey, MAB Sulzman, FM Oser, H Ruyters, G TI Part one: The effects of moderately elevated ambient carbon dioxide levels on human physiology and performance: A joint NASA-ESA-DARA study-overview SO AVIATION SPACE AND ENVIRONMENTAL MEDICINE LA English DT Article C1 NASA, Div Life Sci, Washington, DC 20546 USA. Wright State Univ, Sch Med, Dayton, OH 45435 USA. European Space Agcy, F-75738 Paris, France. Deutsch Agentur Raumfahrtangelegenheiten, Bonn, Germany. RP Frey, MAB (reprint author), NASA, Div Life Sci, Mail Code UL,300 E St SW, Washington, DC 20546 USA. NR 9 TC 2 Z9 3 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 MAR PY 1998 VL 69 IS 3 BP 282 EP 284 PG 3 WC Public, Environmental & Occupational Health; Medicine, General & Internal; Sport Sciences SC Public, Environmental & Occupational Health; General & Internal Medicine; Sport Sciences GA ZB215 UT WOS:000072448300004 PM 9549565 ER PT J AU Stoner, AW Glazer, RA AF Stoner, AW Glazer, RA TI Variation in natural mortality: Implications for queen conch stock enhancement SO BULLETIN OF MARINE SCIENCE LA English DT Article; Proceedings Paper CT International Symposium in Fisheries Ecology CY NOV 20-23, 1996 CL MOTE MARINE LAB, SARASOTA, FLORIDA SP Florida State Univ HO MOTE MARINE LAB ID STROMBUS-GIGAS; JUVENILE; GROWTH; AGGREGATION; PREDATION; GASTROPOD; SIZE; SURVIVORSHIP; POPULATIONS; RECRUITMENT AB Our long-term investigations of mortality and predation in the large, economically significant gastropod Strombus gigas (queen conch) indicate that instantaneous rates of natural mortality (M) in nursery grounds in the Bahamas and the Florida Keys are often higher and more variable than recognized earlier. Wide divergence from a simple size-specific curve of natural mortality was caused by seasonal, interannual, and site-specific sources of variation. In the Florida Keys, mortality rates for 200-mm conch were highest in summer and most stable in the fall, but summer values of M varied interannually from <2.0 to 12.0. Mortality rates for 100-mm conch, often considered ideal in size for field releases, varied from 0.5 to 12.0, depending on site, season, conch density, and deficits in behavior and shell form associated with hatchery rearing. Unlike many marine invertebrates, juvenile queen conch have an inverse density dependence in mortality. Because of the logarithmic relationship between mortality rate and the cost to enhance a stock, it is critical for those involved in stock enhancement to have a realistic understanding of mortality processes and effects and to optimize culture and release strategies for highest possible survival. Specific recommendations are made for queen conch releases. C1 Natl Marine Fisheries Serv, NE Fisheries Sci Ctr, Highlands, NJ 07723 USA. Florida Marine Res Inst, Dept Environm Protect, Marathon, FL 33050 USA. RP Stoner, AW (reprint author), Natl Marine Fisheries Serv, NE Fisheries Sci Ctr, 74 Magruder Rd, Highlands, NJ 07723 USA. NR 51 TC 22 Z9 24 U1 0 U2 6 PU ROSENSTIEL SCH MAR ATMOS SCI PI MIAMI PA 4600 RICKENBACKER CAUSEWAY, MIAMI, FL 33149 USA SN 0007-4977 J9 B MAR SCI JI Bull. Mar. Sci. PD MAR PY 1998 VL 62 IS 2 BP 427 EP 442 PG 16 WC Marine & Freshwater Biology; Oceanography SC Marine & Freshwater Biology; Oceanography GA 132DL UT WOS:000076615000010 ER PT J AU Olla, BL Davis, MW Ryer, CH AF Olla, BL Davis, MW Ryer, CH TI Understanding how the hatchery environment represses or promotes the development of behavioral survival skills SO BULLETIN OF MARINE SCIENCE LA English DT Article; Proceedings Paper CT International Symposium in Fisheries Ecology CY NOV 20-23, 1996 CL MOTE MARINE LAB, SARASOTA, FLORIDA SP Florida State Univ HO MOTE MARINE LAB ID SALMON ONCORHYNCHUS-KISUTCH; JUVENILE COHO SALMON; COD GADUS-MORHUA; ATLANTIC SALMON; PREDATOR-AVOIDANCE; FORAGING BEHAVIOR; FOOD DISTRIBUTION; AGONISTIC BEHAVIOR; RAINBOW-TROUT; BROWN TROUT AB Although great strides have been made in the development of techniques for rearing marine fish, methods for improving survival capabilities following release of these fish into the natural environment have not kept pace. Most responsible for impeding progress has been the lack of adequate knowledge of the complex interactions between a species and the myriad physical and biological factors a hatchery fish faces upon release. Being reared in the psychosensorily deprived environment of a hatchery may lessen the innate capability of fish to carry out the basic survival strategy of all fish: to eat and not be eaten. In this synthesis we focus on some of the key behaviors that play a role in predator avoidance and food acquisition and on how the rearing environment may affect the expression of these behaviors. One of the major causes of mortality in hatchery-reared fish is predation, much of which occurs shortly after release. Available evidence seems to indicate that antipredator behavior in hatchery-reared fish is not fully developed. Possible deficits may also occur in feeding after release, when fish are faced with the shift from hatchery-supplied foods to the capture of live prey. Added to possible hatchery-induced deficits in behavior are the alterations in behavior that may result from the stress of handling and transportation. Behavioral capabilities in hatchery-reared fish can be improved in a number of ways, including exposure to predators err predatory stimuli, alteration of spatial and temporal distribution of food mitigation of rearing and transport stress, and control of the social environment. C1 Oregon State Univ, Hatfield Marine Sci Ctr, Natl Marine Fisheries Serv,Alaska Fisheries Sci C, Fisheries Behav Ecol Program, Newport, OR 97365 USA. RP Olla, BL (reprint author), Oregon State Univ, Hatfield Marine Sci Ctr, Natl Marine Fisheries Serv,Alaska Fisheries Sci C, Fisheries Behav Ecol Program, Newport, OR 97365 USA. RI 平山, 幸恵/G-9307-2012 NR 94 TC 177 Z9 180 U1 5 U2 36 PU ROSENSTIEL SCH MAR ATMOS SCI PI MIAMI PA 4600 RICKENBACKER CAUSEWAY, MIAMI, FL 33149 USA SN 0007-4977 J9 B MAR SCI JI Bull. Mar. Sci. PD MAR PY 1998 VL 62 IS 2 BP 531 EP 550 PG 20 WC Marine & Freshwater Biology; Oceanography SC Marine & Freshwater Biology; Oceanography GA 132DL UT WOS:000076615000016 ER PT J AU Epstein, PR Diaz, HF Elias, S Grabherr, G Graham, NE Martens, WJM Mosley-Thompson, E Susskind, J AF Epstein, PR Diaz, HF Elias, S Grabherr, G Graham, NE Martens, WJM Mosley-Thompson, E Susskind, J TI Biological and physical signs of climate change: Focus on mosquito-borne diseases SO BULLETIN OF THE AMERICAN METEOROLOGICAL SOCIETY LA English DT Article ID INFECTIOUS-DISEASES; DENGUE FEVER; MALARIA; TRANSMISSION; TEMPERATURE; CALIFORNIA; TRENDS; OCEAN; BIODIVERSITY; SIMULATION AB The Intergovernmental Panel on Climate Change concluded that there is "discernible evidence" that humans-through accelerating changes in multiple forcing factors-have begun to alter the earth's climate regime. Such conclusions are based primarily upon so-called "fingerprint" studies, namely the warming pattern in the midtroposphere in the Southern Hemisphere, the disproportionate rise in nighttime and winter temperatures, and the statistical increase in extreme weather events in many nations. All three aspects of climate change and climate variability have biological implications. Detection of climate change has also drawn upon data from glacial records that indicate a general retreat of tropical summit glaciers. Here the authors examine biological (plant and insect) data, glacial findings, and temperature records taken at high-elevation, mountainous regions. It is concluded that, at high elevations, the overall trends regarding glaciers, plants, insect range, and shifting isotherms show remarkable internal consistency, and that there is consistency between model projections and the ongoing changes. There are implications for public health as well as for developing an interdisciplinary approach to the detection of climate change. C1 Harvard Univ, Sch Med, Oliver Wendell Holmes Soc, Ctr Hlth & Global Environm, Boston, MA 02115 USA. NOAA, Environm Res Lab, Climat Diag Ctr, Boulder, CO 80303 USA. Univ Colorado, Boulder, CO 80309 USA. Univ Vienna, Dept Vegetat Ecol & Conservat Biol, A-1010 Vienna, Austria. Scripps Inst Oceanog, Int Res Inst Climat Predict, La Jolla, CA USA. Maastricht Univ, Dept Math, Maastricht, Netherlands. Ohio State Univ, Byrd Polar Res Ctr, Dept Geog, Columbus, OH 43210 USA. NASA, Goddard Space Flight Ctr, Atmospheres Lab, Greenbelt, MD 20771 USA. RP Epstein, PR (reprint author), Harvard Univ, Sch Med, Oliver Wendell Holmes Soc, Ctr Hlth & Global Environm, Room 263,260 Londwood Ave, Boston, MA 02115 USA. EM PEPSTEIN@warren.med.harvard.edu RI Martens, Pim/A-9297-2011 NR 85 TC 99 Z9 107 U1 11 U2 37 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 USA SN 0003-0007 J9 B AM METEOROL SOC JI Bull. Amer. Meteorol. Soc. PD MAR PY 1998 VL 79 IS 3 BP 409 EP 417 DI 10.1175/1520-0477(1998)079<0409:BAPSOC>2.0.CO;2 PG 9 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA ZE363 UT WOS:000072785100002 ER PT J AU Moles, A Norcross, BL AF Moles, A Norcross, BL TI Effects of oil-laden sediments on growth and health of juvenile flatfishes SO CANADIAN JOURNAL OF FISHERIES AND AQUATIC SCIENCES LA English DT Article ID CRUDE-OIL; PLEURONECTES-AMERICANUS; WINTER FLOUNDER; EXXON-VALDEZ; FISH; EXPOSURE; PLATESSA; SPILL AB Juvenile yellowfin sole (Pleuronectes asper), rock sole (Pleuronectes bilineatus), and Pacific halibut (Hippoglossus stenolepis) had reduced growth following 30-90 days of exposure to sediments laden with Alaska North Slope crude oil. Changes in fish health bioindicators after 90 days, i.e., increases in fin erosion, liver lipidosis, gill hyperplasia, and gill parasites, coupled with decreases in macrophage aggregates, occurred at hydrocarbon concentrations (1600 mu g/g) that reduced growth 34-56% among the flatfishes. Chronic hydrocarbon pollution of nearshore nursery sediments could alter growth and health of juvenile flatfishes. Recruitment of juveniles to the fishery may decline because of increased susceptibility to predation and slower growth. C1 NOAA, Auke Bay Lab, Alaska Fisheries Sci Ctr, Natl Marine Fisheries Serv, Juneau, AK 99801 USA. Univ Alaska, Inst Marine Sci, Fairbanks, AK 99775 USA. RP Moles, A (reprint author), NOAA, Auke Bay Lab, Alaska Fisheries Sci Ctr, Natl Marine Fisheries Serv, 11305 Glacier Highway, Juneau, AK 99801 USA. NR 20 TC 32 Z9 33 U1 2 U2 14 PU NATL RESEARCH COUNCIL CANADA PI OTTAWA PA RESEARCH JOURNALS, MONTREAL RD, OTTAWA, ONTARIO K1A 0R6, CANADA SN 0706-652X J9 CAN J FISH AQUAT SCI JI Can. J. Fish. Aquat. Sci. PD MAR PY 1998 VL 55 IS 3 BP 605 EP 610 DI 10.1139/cjfas-55-3-605 PG 6 WC Fisheries; Marine & Freshwater Biology SC Fisheries; Marine & Freshwater Biology GA ZR921 UT WOS:000074029600008 ER PT J AU Pellett, GL Isaac, KM Humphreys, WM Gartrell, LR Roberts, WL Dancey, CL Northam, GB AF Pellett, GL Isaac, KM Humphreys, WM Gartrell, LR Roberts, WL Dancey, CL Northam, GB TI Velocity and thermal structure, and strain-induced extinction of 14 to 100% hydrogen-air counterflow diffusion flames SO COMBUSTION AND FLAME LA English DT Article AB Extensive results from axisymmetric convergent-nozzle and straight-tube opposed jet burners (OJBs) characterized strain-induced extinction of unanchored (free-floating), laminar H-2/N-2-air flames. Parameters included (a) plug-few and parabolic input velocity profiles, (b) jet exit diameters ranging 2.7 to 7.2 mm for nozzles and 1.8 to 10 mm for tubes, (c) various relative jet gaps, and (d) 14 to 100% H-2 in the fuel jet. Extinction, a sudden rupture (blowoff) of the mostly-airside disk flame, occurred as fuel and air flows were slowly increased and a critical radial strain rate was exceeded. The disk flame was restored at much lower flows, unique to H-2 systems. Focusing schlieren, thermocouple, and airside LDV (and PIV) data confirmed the one-dimensional (1-D) character of nozzle-OJB flow fields; axial widths of velocity-and thermal-layers varied as (input strain rate)(-1/2) for both nozzles and tubes. The global approximation of a 1-D applied stress rate (ASR), using average air jet velocity divided by exit diameter, enabled high quality correlations of extinction data with varied H, concentrations, for both nozzles and tubes. Pre-extinction ASRs for nozzles agreed closely with LDV-measured centerline input strain rates; for tubes, however, an empirical factor of 3 produced close agreement. For methane-air extinction, nozzle-OJB ASRs agreed within 4% of independent nozzle and Tsuji burner results. For extinction of 100% H-2-air, an ASR of 5670 1/s compared with 7350, 8140, and 8060 from independent 1-D numerical evaluations using potential-flow inputs; for 50 to 14% H-2 inputs, agreement was much closer. The nozzle-ASR/tube-ASR ratio for extinction was greater than or equal to 3 for <50% H-2 inputs, 2.74 +/- 0.03 for 50 to 100% H-2 inputs, and 2.83 for methane-air. Because these ratios exceeded 2.0, which "accounted" for centerline velocity inputs from parabolic profiles, an additional 3/2 radial strain component was apparent and was supported by the axial velocity gradient measurements. (C) 1998 by The Combustion Institute. C1 NASA, Langley Res Ctr, Aerodynam & Gas Dynam Div, Hampton, VA 23681 USA. Univ Missouri, Rolla, MO 65401 USA. NASA, Langley Res Ctr, Fluid Mech & Acoust Div, Hampton, VA 23681 USA. N Carolina State Univ, Raleigh, NC 27695 USA. Virginia Polytech Inst & State Univ, Blacksburg, VA 24061 USA. NASA, Langley Res Ctr, Div Mat, Hampton, VA 23681 USA. RP Pellett, GL (reprint author), NASA, Langley Res Ctr, Aerodynam & Gas Dynam Div, Hampton, VA 23681 USA. NR 63 TC 28 Z9 29 U1 1 U2 5 PU ELSEVIER SCIENCE INC PI NEW YORK PA 655 AVENUE OF THE AMERICAS, NEW YORK, NY 10010 USA SN 0010-2180 J9 COMBUST FLAME JI Combust. Flame PD MAR PY 1998 VL 112 IS 4 BP 575 EP 592 DI 10.1016/S0010-2180(97)00169-7 PG 18 WC Thermodynamics; Energy & Fuels; Engineering, Multidisciplinary; Engineering, Chemical; Engineering, Mechanical SC Thermodynamics; Energy & Fuels; Engineering GA YQ533 UT WOS:000071397300009 ER PT J AU Vander Wal, RL AF Vander Wal, RL TI Soot precursor carbonization: Visualization using LIF and LII and comparison using bright and dark field TEM SO COMBUSTION AND FLAME LA English DT Article ID LASER-INDUCED INCANDESCENCE; DIFFUSION FLAMES; VOLUME FRACTION AB Comparison between laser-induced fluorescence (LIF) and laser-induced incandescence (LII) images and axial intensity profiles derived from these images of a laminar ethylene-air diffusion flame distinguish the polycyclic aromatic hydrocarbon (PAH) and soot-containing regions along the axial flow streamline. Examination of the temporal evolution of the combined fluorescence plus incandescence signal along the axial streamline reveals the transformation of soot precursor material into solid carbonaceous soot. Bright field transmission electron microscopy (TEM) of thermophoretically sampled material shows soot precursor material and more generally nascent soot particles and their evolution towards solid carbonaceous soot. Corresponding dark field TEM images track the increasing crystallinity of the soot precursor material as carbonization proceeds with increasing integrated temperature-time history within the flame. Both bright and dark field TEM confirm interpretation of the optical signals as reflecting the overall material transformation from soot precursor material toward solid carbonaceous soot. (C) 1998 by The Combustion Institute. C1 NASA, Lewis Res Ctr, USRA, Cleveland, OH 44135 USA. RP Vander Wal, RL (reprint author), NASA, Lewis Res Ctr, USRA, Cleveland, OH 44135 USA. NR 39 TC 58 Z9 58 U1 0 U2 10 PU ELSEVIER SCIENCE INC PI NEW YORK PA 655 AVENUE OF THE AMERICAS, NEW YORK, NY 10010 USA SN 0010-2180 J9 COMBUST FLAME JI Combust. Flame PD MAR PY 1998 VL 112 IS 4 BP 607 EP 616 DI 10.1016/S0010-2180(97)00171-5 PG 10 WC Thermodynamics; Energy & Fuels; Engineering, Multidisciplinary; Engineering, Chemical; Engineering, Mechanical SC Thermodynamics; Energy & Fuels; Engineering GA YQ533 UT WOS:000071397300011 ER PT J AU Jaunky, N Knight, NF Ambur, DR AF Jaunky, N Knight, NF Ambur, DR TI Optimal design of general stiffened composite circular cylinders for global buckling with strength constraints SO COMPOSITE STRUCTURES LA English DT Article ID ANISOTROPIC PLATES; STACKING-SEQUENCE; OPTIMIZATION; PANELS; SHELLS AB A design strategy for optimal design of composite grid-stiffened cylinders subjected to global and local buckling constraints and strength constraints was developed using a discrete optimizer based on a genetic algorithm. An improved smeared stiffener theory was used for the global analysis. Local buckling of skin segments were assessed using a Rayleigh-Ritz method that accounts for material anisotropy. The local buckling of stiffener segments were also assessed. Constraints on the axial membrane strain in the skin and stiffener segments were imposed to include strength criteria in the grid-stiffened cylinder design. Design variables used in this study were the axial and transverse stiffener spacings, stiffener height and thickness, skin laminate stacking sequence and stiffening configuration, where stiffening configuration is a design variable that indicates the combination of axial, transverse and diagonal stiffener in the grid-stiffened cylinder. The design optimization process was adapted to identify the best suited stiffening configurations and stiffener spacings for grid-stiffened composite cylinder with the length and radius of the cylinder, the design in-plane loads and material properties as inputs. The effect of having axial membrane strain constraints in the skin and stiffener segments in the optimization process is also studied for selected stiffening configurations. (C) 1998 Published by Elsevier Science Ltd. All rights reserved. C1 Old Dominion Univ, Dept Aerosp Engn, Norfolk, VA 23529 USA. NASA, Langley Res Ctr, Hampton, VA 23681 USA. RP Jaunky, N (reprint author), Old Dominion Univ, Dept Aerosp Engn, Norfolk, VA 23529 USA. NR 27 TC 38 Z9 45 U1 0 U2 4 PU ELSEVIER SCI LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, OXON, ENGLAND SN 0263-8223 J9 COMPOS STRUCT JI Compos. Struct. PD MAR-APR PY 1998 VL 41 IS 3-4 BP 243 EP 252 DI 10.1016/S0263-8223(98)00020-8 PG 10 WC Materials Science, Composites SC Materials Science GA 121BC UT WOS:000075991400004 ER PT J AU Regnier, S Bocchialini, K Vial, JC Delaboudiniere, JP Thompson, W AF Regnier, S Bocchialini, K Vial, JC Delaboudiniere, JP Thompson, W TI Statistical analysis of solar bright points observed with the SOHO spacecraft SO COMPTES RENDUS DE L ACADEMIE DES SCIENCES SERIE II FASCICULE B-MECANIQUE PHYSIQUE ASTRONOMIE LA French DT Article DE Sun; bright points; magnetic reconnection; coronal heating; power law ID QUIET-SUN; FLARES; NANOFLARES; AVALANCHES AB Bright points, small and short lifetime structures, appear permanently in the atmosphere and could be associated with magnetic reconnections, potential sources of coronal heating. Such structures have been observed with the coronal instruments on-board SOHO and a statistical analysis was carried out in order to find the signature of very small scale structures. (C) Academie des Sciences/Elsevier, Paris. C1 Univ Paris 11, CNRS, Inst Astrophys Spatiale, F-91405 Orsay, France. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Regnier, S (reprint author), Univ Paris 11, CNRS, Inst Astrophys Spatiale, Bat 121, F-91405 Orsay, France. NR 18 TC 1 Z9 1 U1 0 U2 0 PU EDITIONS SCIENTIFIQUES MEDICALES ELSEVIER PI PARIS CEDEX 15 PA 23 RUE LINOIS, 75724 PARIS CEDEX 15, FRANCE SN 1287-4620 J9 CR ACAD SCI II B JI Comptes Rendus Acad. Sci. Ser. II-B PD MAR PY 1998 VL 326 IS 3 BP 211 EP 218 DI 10.1016/S1251-8069(99)89010-1 PG 8 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA ZT815 UT WOS:000074130400010 ER PT J AU Breininger, DR Barkaszi, MJ Smith, RB Oddy, DM Provancha, JA AF Breininger, DR Barkaszi, MJ Smith, RB Oddy, DM Provancha, JA TI Prioritizing wildlife taxa for biological diversity conservation at the local scale SO ENVIRONMENTAL MANAGEMENT LA English DT Article DE biological diversity; endangered species; conservation ID INDIAN-RIVER LAGOON; FLORIDA; HABITAT; NORTHERN; RARITY AB We identified and ranked 108 resident and migratory wildlife taxa on John F. Kennedy Space Center (KSC) that were vulnerable to local, regional, or global extinction. We ranked taxa based on their vulnerability to extinction, their potential role for maintaining faunal integrity, and the relevance of KSC for maintaining their populations in the United States and Florida. Several taxa, not listed by agencies, were vulnerable to regional or global extinction. Many taxa not vulnerable to global extinction were vulnerable to local and regional extinction. Top predators were vulnerable to extinction because of small population size, isolation from other populations, and road mortality. Many taxa were dependent on habitat conditions at different geographic locations so that conservation required greater collaboration among land owners, managers, and researchers at local, regional, and global scales. C1 NASA, Biomed Operat Off, Dynamac Int, Kennedy Space Ctr, FL 32899 USA. RP Breininger, DR (reprint author), NASA, Biomed Operat Off, Dynamac Int, Dyn-2, Kennedy Space Ctr, FL 32899 USA. NR 47 TC 17 Z9 18 U1 2 U2 4 PU SPRINGER VERLAG PI NEW YORK PA 175 FIFTH AVE, NEW YORK, NY 10010 USA SN 0364-152X J9 ENVIRON MANAGE JI Environ. Manage. PD MAR-APR PY 1998 VL 22 IS 2 BP 315 EP 321 DI 10.1007/s002679900107 PG 7 WC Environmental Sciences SC Environmental Sciences & Ecology GA YX163 UT WOS:000072012700015 ER PT J AU McTigue, TA Zimmerman, RJ AF McTigue, TA Zimmerman, RJ TI The use of infauna by juvenile Penaeus aztecus Ives and Penaeus setiferus (Linnaeus) SO ESTUARIES LA English DT Article ID POSTLARVAL BROWN SHRIMP; TEXAS SALT-MARSH; SPECIES DENSITIES; SOUTH-CAROLINA; MACROBENTHOS; SELECTION; PREDATION; SEAGRASS; FOOD; ASSIMILATION AB Penaeus aztecus Ives, the brown shrimp, and Ponaeus setiferus (Linnaeus), the white shrimp, co-occur in Texas salt marshes as juveniles. Although their life cycles are similar, evidence indicates that the species utilize different resources for the primary faunal element of their diets. Prey selection and growth studies have shown that brown shrimp successfully remove infauna from natural sediment Further, a diet of polychaetes, whether alone or in combination with algae, produced growth in the species. Brown shrimp appear to be trophically linked to infaunal populations, thus the structure and dynamics of the benthic community may directly affect local brown shrimp productivity. Areas dominated by surface-dwelling polychaetes as opposed to deep burrowers may provide more accessible foraging opportunities for juvenile brown shrimp. By contrast, white shrimp neither removed infauna nor grew to a significant degree when provided polychaetes or amphipods as food. White shrimp are omnivorous but do not rely on infaunal material to the same extent as brown shrimp. The primary faunal element in the diet of white shrimp has not yet been identified. The dietary differences between the two species may play a role in determining which species dominates in regions with varying marsh accessibility. Although not the only factors influencing penaeid survival and growth, prey choice and availability may greatly affect production and Local success of penaeid populations. C1 Natl Marine Fisheries Serv, Lafayette Off, Lafayette, LA 70504 USA. Natl Marine Fisheries Serv, Galveston Lab, Galveston, TX 77551 USA. RP McTigue, TA (reprint author), Natl Marine Fisheries Serv, Lafayette Off, POB 42451, Lafayette, LA 70504 USA. NR 55 TC 32 Z9 34 U1 0 U2 4 PU ESTUARINE RES FEDERATION PI LAWRENCE PA PO BOX 368, LAWRENCE, KS 66044 USA SN 0160-8347 J9 ESTUARIES JI Estuaries PD MAR PY 1998 VL 21 IS 1 BP 160 EP 175 DI 10.2307/1352554 PG 16 WC Environmental Sciences; Marine & Freshwater Biology SC Environmental Sciences & Ecology; Marine & Freshwater Biology GA ZC528 UT WOS:000072589400012 ER PT J AU Benedetto, S Montorsi, G Divsalar, D Pollara, F AF Benedetto, S Montorsi, G Divsalar, D Pollara, F TI Soft-input soft-output modules for the construction and distributed iterative decoding of code networks SO EUROPEAN TRANSACTIONS ON TELECOMMUNICATIONS LA English DT Article ID TURBO-CODES; ALGORITHM AB Soft-input soft-output building blocks (modules) are presented to construct and iteratively decode in a distributed fashion code networks, a new concept that includes, and generalizes, various forms of concatenated coding schemes. Among the modules, a central role is played by the SISO module (and the underlying algorithm): it consists of a four-port device performing a processing of the sequences of two input probability distributions by constraining them to the code trellis structure. The SISO and other soft-input soft-output modules are employed to construct and decode a variety of code networks, including "turbo codes" and serially concatenated codes with interleavers. C1 Politecn Torino, Dipartimento Elettron, I-10129 Turin, Italy. CALTECH, Jet Prop Lab, Pasadena, CA USA. RP Benedetto, S (reprint author), Politecn Torino, Dipartimento Elettron, Corso Duca degli Abruzzi 24, I-10129 Turin, Italy. EM benedettp@polito.it RI Montorsi, Guido/D-4867-2012; OI benedetto, sergio/0000-0002-7648-5396 NR 29 TC 125 Z9 126 U1 0 U2 6 PU WILEY-BLACKWELL PI MALDEN PA COMMERCE PLACE, 350 MAIN ST, MALDEN 02148, MA USA SN 1124-318X J9 EUR T TELECOMMUN JI Eur. Trans. Telecomm. PD MAR-APR PY 1998 VL 9 IS 2 BP 155 EP 172 DI 10.1002/ett.4460090206 PG 18 WC Telecommunications SC Telecommunications GA ZG291 UT WOS:000072986300005 ER PT J AU Lindner, JL Gilbert, JA AF Lindner, JL Gilbert, JA TI Panoramic modal testing of the space shuttle main engine alternative turbopump inlet bellows liner SO EXPERIMENTAL TECHNIQUES LA English DT Article; Proceedings Paper CT 1996 SEM VIII International Congress on Experimental Mechanics CY JUN 10-13, 1996 CL NASHVILLE, TENNESSEE SP SEM C1 NASA, Struct & Dynam Lab, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. Univ Alabama, CHAMP, Huntsville, AL 35899 USA. RP Lindner, JL (reprint author), NASA, Struct & Dynam Lab, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. NR 3 TC 2 Z9 2 U1 0 U2 1 PU SOC EXPERIMENTAL MECHANICS PI BETHEL PA 7 SCHOOL STREET, BETHEL, CT 06801 USA SN 0732-8818 J9 EXP TECHNIQUES JI Exp. Tech. PD MAR-APR PY 1998 VL 22 IS 2 BP 15 EP 19 DI 10.1111/j.1747-1567.1998.tb02413.x PG 5 WC Engineering, Mechanical; Mechanics; Materials Science, Characterization & Testing SC Engineering; Mechanics; Materials Science GA ZF776 UT WOS:000072932100004 ER PT J AU Wiecek, KC Mehta, RD AF Wiecek, KC Mehta, RD TI Effects of velocity ratio on mixing layer three-dimensionality SO EXPERIMENTAL THERMAL AND FLUID SCIENCE LA English DT Article DE two-stream mixing layers; three-dimensional structure; vortical flow ID STREAMWISE VORTICAL STRUCTURES; 3-DIMENSIONAL EVOLUTION; PLANE; TRANSITION AB Three-dimensionality in transitioning mixing layers, in the form of streamwise vortical structures, is now well established and understood. In the present investigation, the effects of velocity ratio, or more precisely of velocity difference across the layer, on the near-field generation and development of three-dimensionality in two-stream mixing layers have been investigated for the first rime. Detailed time-averaged velocity measurements were obtained using a single rotatable cross-wire probe on fine cross-plane grids at four streamwise locations in the near-field region. The effects of five velocity ratios, ranging from r = 0.5 to 0.9, were investigated by keeping the velocity of one stream constant while varying that of the other. The results indicate that the mixing layer three-dimensionality is strongest for the mixing layer with the lowest velocity ratio. The peak mean streamwise vorticity levels decrease with increasing velocity ratio at all the streamwise locations investigated. However, the rate of decrease is highest at the most upstream station and it decreases with increasing downstream distance. The mean streamwise vorticity contours at the first station shaw that their distribution is quite similar at the different velocity ratios, implying that the generating mechanism and initial disturbance fields remain unchanged with velocity ratio. However, it is conceivable that the amount of stretching in the braid regions due to the spanwise vortical structures is affected by velocity ratio. As the velocity ratio decreases land the velocity difference across the layer increases), stronger spanwise rollers are generated which increase the amount of stretching in the braid regions and hence the streamwise vorticity is amplified. The splitter plate wake has a lasting effect on the three-dimensional structure of the mixing layers at the higher velocity ratios, The presence and effects of the wake are clearly seen in the mean velocity, mean streamwise vorticity and Reynolds stress contours. (C) 1998 Elsevier Science Inc. All rights reserved. C1 NASA, Ames Res Ctr, Fluid Mech Lab, Moffett Field, CA 94035 USA. Stanford Univ, Dept Aeronaut & Astronaut, JIAA, Stanford, CA 94305 USA. RP Mehta, RD (reprint author), NASA, Ames Res Ctr, Fluid Mech Lab, Mail Stop 260-1, Moffett Field, CA 94035 USA. EM rmehta@mail.arc.nasa.gov NR 23 TC 5 Z9 5 U1 0 U2 2 PU ELSEVIER SCIENCE INC PI NEW YORK PA 655 AVENUE OF THE AMERICAS, NEW YORK, NY 10010 USA SN 0894-1777 J9 EXP THERM FLUID SCI JI Exp. Therm. Fluid Sci. PD MAR PY 1998 VL 16 IS 3 BP 165 EP 176 DI 10.1016/S0894-1777(97)10018-8 PG 12 WC Thermodynamics; Engineering, Mechanical; Physics, Fluids & Plasmas SC Thermodynamics; Engineering; Physics GA ZU367 UT WOS:000074190000001 ER PT J AU Caldwell, JL AF Caldwell, JL TI Formal methods technology transfer: A view from NASA SO FORMAL METHODS IN SYSTEM DESIGN LA English DT Article; Proceedings Paper CT 1st International Workshop of the ERCIM Working-Group on Formal Methods for Industrial Critical Systems CY MAR 19, 1996 CL ST HUGHS COLL, OXFORD, ENGLAND SP European Res Consortium Informat & Math HO ST HUGHS COLL DE fault-tolerant systems; industrial application; NASA; PVS; technology transfer AB Since 1988 NASA Langley Research Center has supported a formal methods research program. From its inception, a primary goal of the program has been to transfer formal methods technology into aerospace industries focusing on applications in commercial air transport. The overall program has been described elsewhere. This paper gives an account of the technology transfer strategy and its evolution. C1 NASA, Flight Elect Technol Div, Langley Res Ctr, Hampton, VA 23681 USA. NR 69 TC 2 Z9 2 U1 0 U2 1 PU KLUWER ACADEMIC PUBL PI DORDRECHT PA SPUIBOULEVARD 50, PO BOX 17, 3300 AA DORDRECHT, NETHERLANDS SN 0925-9856 J9 FORM METHOD SYST DES JI Form. Methods Syst. Des. PD MAR PY 1998 VL 12 IS 2 BP 125 EP 137 DI 10.1023/A:1008693709419 PG 13 WC Computer Science, Theory & Methods SC Computer Science GA ZB844 UT WOS:000072513700002 ER PT J AU Tan, LC Fung, SF Kessel, RL Chen, SH Green, JL Eastman, TE AF Tan, LC Fung, SF Kessel, RL Chen, SH Green, JL Eastman, TE TI Inn temperature anisotropies in the Earth's high-latitude magnetosheath: Hawkeye observations SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID PROTON CYCLOTRON INSTABILITY; ION; MAGNETOPAUSE; BETA AB We present here for the first time observations of the inverse correlation between the ion temperature anisotropy and plasma beta in the Earth's high-latitude magnetosheath. Hot proton data with energies of 0.3-8 keV were obtained from magnetosheath passages by the Hawkeye spacecraft which had a polar orbit with an apogee of 20-21 R-E. A newly developed technique has been used to calculate the distribution functions of protons in their non-streaming frame in which their first-order anisotropy is absent. The ion-energy dependence of distribution functions indicates the existence of two hot ion components. Thus the correlation has been examined for each hot ion component separately. We have analyzed three Hawkeye magnetosheath passes during which the magnetosheath's magnetic field was dose to the spacecraft spin plane, so that the two-dimensional Hawkeye sensor can adequately sample temperature anisotropies. Results of our analyses are consistent with the theoretical prediction given by Gary et al. [1994; 1995] that a universal inverse-correlation relationship exists between the temperature anisotropy and plasma beta of hot ions. C1 Univ Maryland, Inst Phys Sci & Technol, College Pk, MD 20742 USA. NASA, Goddard Space Flight Ctr, Space Phys Data Facil, Greenbelt, MD 20771 USA. Raytheon STX Corp, Lanham, MD USA. RP Tan, LC (reprint author), NASA, Goddard Space Flight Ctr, Space Phys Data Facil, Code 632, Greenbelt, MD 20771 USA. EM ltan@nssdca.gsfc.nasa.gov RI Fung, Shing/F-5647-2012 NR 14 TC 17 Z9 17 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 MAR 1 PY 1998 VL 25 IS 5 BP 587 EP 590 DI 10.1029/98GL00306 PG 4 WC Geosciences, Multidisciplinary SC Geology GA ZA533 UT WOS:000072373800003 ER PT J AU Roberts, DA Goldstein, ML AF Roberts, DA Goldstein, ML TI Evidence for a high-latitude origin of lower latitude high-speed wind SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID CORONAL HOLES; INTERPLANETARY MEDIUM; SOLAR ROTATION; FLUCTUATIONS AB Using low-frequency spectra of the wind speed, density, and magnetic field strength, we show that the near-streamer belt solar wind at solar minimum exhibits many harmonics of fundamental frequencies corresponding to 26- and 34-day periods. Nearly all the low-frequency peaks in the spectra can be explained by these harmonics. The 26-day period is that of coronal hole rotation, and the 34-day period is naturally associated with the photospheric rotation period at about 70 degrees S latitude. Thus we find evidence that the wind flow near 25 degrees S comes from a region poleward of 60 degrees S, consistent with magnetic field models. C1 NASA, Goddard Space Flight Ctr, Extraterr Phys Lab, Greenbelt, MD 20771 USA. RP Roberts, DA (reprint author), NASA, Goddard Space Flight Ctr, Extraterr Phys Lab, Greenbelt, MD 20771 USA. RI Roberts, Dana/D-4625-2012; Goldstein, Melvyn/B-1724-2008 NR 13 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 MAR 1 PY 1998 VL 25 IS 5 BP 595 EP 598 DI 10.1029/98GL00332 PG 4 WC Geosciences, Multidisciplinary SC Geology GA ZA533 UT WOS:000072373800005 ER PT J AU Schatten, K Hoyt, D AF Schatten, K Hoyt, D TI Solar cycle 23 forecast update SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID PREDICTION AB Solar activity, although virtually impossible to forecast a month in advance, has succumbed to scientific methods on long time scales, much as climate or seasonal weather predictions are simpler than weekly weather forecasting. Moderately accurate solar activity forecasts on decadal time scales now seem possible. The methods that work fall into a class of prediction techniques called "precursor methods." We utilize solar, interplanetary field, and geomagnetic precursors to update our cycle 23 prediction to provide a mean smoothed sunspot number of 153 +/- 30 and mean smoothed F10.7 cm Radio flux of 200 +/- 30. This is comparable to, but somewhat smaller than, the NOAA SEC panel findings that the next solar cycle would peak at a sunspot number near 160 +/- 30. This paper also provides some discussion relating solar and interplanetary field components to serve as a bridge in interplanetary space, helping to forge Sun-Earth connections. C1 NASA, Goddard Space Flight Ctr, Terr Phys Lab, Greenbelt, MD 20771 USA. Raytheon STX, Lanham, MD USA. RP Schatten, K (reprint author), NASA, Goddard Space Flight Ctr, Terr Phys Lab, Greenbelt, MD 20771 USA. NR 11 TC 9 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 MAR 1 PY 1998 VL 25 IS 5 BP 599 EP 601 DI 10.1029/98GL00303 PG 3 WC Geosciences, Multidisciplinary SC Geology GA ZA533 UT WOS:000072373800006 ER PT J AU Roberts, DA Miller, JA AF Roberts, DA Miller, JA TI Generation of nonthermal electron distributions by turbulent waves near the Sun SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID SUPRATHERMAL TAIL STRENGTHS; IMPULSIVE SOLAR-FLARES; MAGNETOHYDRODYNAMIC TURBULENCE; TRANSITION REGION; WIND; ACCELERATION; CORONA; ION; MODELS; ENERGY AB We present a model for the generation of the nonthermal electron distributions observed in interplanetary space and required in some solar wind acceleration and coronal heating theories. The particles are accelerated by fast mode waves generated by an unspecified mechanism (perhaps reconnection associated with microflares) in the upper chromosphere or lower transition region. The waves interact and cascade to higher wavenumbers where they eventually energize electrons out of an initially Maxwellian distribution. Coulomb collisions limit the number that are accelerated. As the electrons are driven to higher energy they more readily escape from the acceleration site. Escape limits the efficiency of the acceleration at high energies. The distributions do not extend into the ultrarelativistic regime like those generated under solar flare conditions, but do have significant nonthermal tails. C1 NASA, Goddard Space Flight Ctr, Extraterr Phys Lab, Greenbelt, MD 20771 USA. Univ Alabama, Dept Phys, Huntsville, AL 35899 USA. RP Roberts, DA (reprint author), NASA, Goddard Space Flight Ctr, Extraterr Phys Lab, Greenbelt, MD 20771 USA. EM roberts@vayu.gsfc.nasa.gov; miller@mpingo.uah.edu RI Roberts, Dana/D-4625-2012 NR 21 TC 26 Z9 26 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 MAR 1 PY 1998 VL 25 IS 5 BP 607 EP 610 DI 10.1029/98GL00328 PG 4 WC Geosciences, Multidisciplinary SC Geology GA ZA533 UT WOS:000072373800008 ER PT J AU Mischna, MA Bell, JF James, PB Crisp, D AF Mischna, MA Bell, JF James, PB Crisp, D TI Synoptic measurements of Martian winds using the Hubble Space Telescope SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID MARS; MARINER-9 AB We used the Hubble Space Telescope to make wind speed and wind direction measurements of the Martian atmosphere during early northern summer (L-s=97 degrees). Our strategy utilized a series of near-UV images with optimal temporal sampling to track observable cloud features and to determine the direction and speed of cloud motion. Several techniques were used to identify similar features between images, including Fourier transform and cross-correlation. In these measurements, which span 19-75 degrees N lat and 319 degrees E to 135 degrees W ion, we find average wind speeds of 26.2 +/- 10.1 m/s and a range of wind directions from 51 degrees to 162 degrees with an average error of 123 degrees. C1 Cornell Univ, Dept Astron, Ithaca, NY 14853 USA. Univ Toledo, Dept Phys & Astron, Toledo, OH 43606 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91125 USA. RP Mischna, MA (reprint author), Penn State Univ, University Pk, PA 16802 USA. NR 16 TC 9 Z9 9 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 MAR 1 PY 1998 VL 25 IS 5 BP 611 EP 614 DI 10.1029/98GL50358 PG 4 WC Geosciences, Multidisciplinary SC Geology GA ZA533 UT WOS:000072373800009 ER PT J AU Grant, WB Fenn, MA Browell, EV McGee, TJ Singh, UN Gross, MR McDermid, IS Froidevaux, L Wang, PH AF Grant, WB Fenn, MA Browell, EV McGee, TJ Singh, UN Gross, MR McDermid, IS Froidevaux, L Wang, PH TI Correlative stratospheric ozone measurements with the airborne UV DIAL system during TOTE/VOTE SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID GAS EXPERIMENT-II; ABSORPTION CROSS-SECTIONS; TEMPERATURE-DEPENDENCE; AEROSOL; LIDAR; INSTRUMENT; VALIDATION AB The airborne UV differential absorption lidar (DIAL) system participated in the Tropical Ozone Transport Experiment/Vortex Ozone Transport Experiment (TOTE/VOTE) in late 1995/early 1996. This mission afforded the opportunity to compare the DIAL system's stratospheric ozone measuring capability with other remote-sensing instruments through correlative measurements over a latitude range from the tropics to the Arctic. These instruments included ground-based DIAL and space-based stratospheric instruments: HALOE; MLS; and SAGE II. The ozone profiles generally agreed within random error estimates for the various instruments in the middle of the profiles in the tropics, but regions of significant systematic differences, especially near or below the tropopause or at the higher altitudes were also found. The comparisons strongly suggest that the airborne UV DIAL system can play a valuable role as a mobile lower-stratospheric ozone validation instrument. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. NASA, Langley Res Ctr, Div Atmospher Sci, Hampton, VA 23681 USA. Sci Applicat Int Corp, Hampton, VA USA. Hughes STX Corp, Lanham, MD USA. NASA, Langley Res Ctr, Aerosp Elect Syst Div, Hampton, VA 23681 USA. Sci & Technol Corp, Hampton, VA 23666 USA. RP Grant, WB (reprint author), NASA, Langley Res Ctr, Div Atmospher Sci, MS 401A, Hampton, VA 23681 USA. RI Grant, William/B-8311-2009; McGee, Thomas/G-4951-2013 OI Grant, William/0000-0002-1439-3285; NR 22 TC 16 Z9 16 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 MAR 1 PY 1998 VL 25 IS 5 BP 623 EP 626 DI 10.1029/98GL00231 PG 4 WC Geosciences, Multidisciplinary SC Geology GA ZA533 UT WOS:000072373800012 ER PT J AU Mlynczak, MG Zhou, DK AF Mlynczak, MG Zhou, DK TI Kinetic and spectroscopic requirements for the measurement of mesospheric ozone at 9.6 mu m under non-LTE conditions SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID TERRESTRIAL MIDDLE ATMOSPHERE; INFRARED LIMB EMISSION; VIBRATIONAL-RELAXATION; ABSORPTION; OXYGEN AB Radiative emission from transitions involving the vibration-rotation bands of ozone in the 9.6 mu m spectral region is readily detected by limb-scanning instruments on orbiting satellites and such measurements are used to infer the ozone profile in the middle atmosphere. In the terrestrial mesosphere and lower thermosphere these transitions are predicted to depart from local thermodynamic equilibrium (LTE). The occurrence of non-LTE complicates the interpretation of emission measurements in terms of the ozone abundance as the vibrational temperatures must be known a priori or calculated directly as part of the retrieval process. This in turn requires accurate knowledge of various kinetic and spectroscopic parameters used in a statistical equilibrium model to calculate the vibrational temperatures. Through detailed simulations of the forward and inverse retrieval problem we find that in order to achieve retrieved ozone concentrations accurate to 15% the collisional quenching rates must be known to better than 25% accuracy and that the distribution of energy within ozone upon recombination of O and O-2 must be significantly improved. Collisional quenching rates are currently uncertain by more than a factor of 2. C1 NASA, Langley Res Ctr, Hampton, VA 23681 USA. Utah State Univ, Space Dynam Lab, Logan, UT 84322 USA. RP Mlynczak, MG (reprint author), NASA, Langley Res Ctr, Mail Stop 401 B, Hampton, VA 23681 USA. RI Mlynczak, Martin/K-3396-2012 NR 18 TC 18 Z9 19 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 MAR 1 PY 1998 VL 25 IS 5 BP 639 EP 642 DI 10.1029/98GL00092 PG 4 WC Geosciences, Multidisciplinary SC Geology GA ZA533 UT WOS:000072373800016 ER PT J AU Zhou, DK Mlynczak, MG Bingham, GE Wise, JO Nadile, RM AF Zhou, DK Mlynczak, MG Bingham, GE Wise, JO Nadile, RM TI CIRRIS-1A limb spectral measurements of mesospheric 9.6-mu m airglow and ozone SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID MIDDLE ATMOSPHERE; VIBRATIONAL-RELAXATION; MODEL; EMISSIONS; DYNAMICS AB Limb infrared spectral measurements of the 9.6-mu m mesospheric ozone airglow were made by the Cryogenic Infrared Radiance Instrumentation for Shuttle (CIRRIS-1A) during one flight of the space shuttle Discovery (April 28(th) to May 6(th) 1991). A significant difference between ozone nightglow and dayglow is observed. The measured spectrally integrated ozone nu(3) fundamental band radiance profile is used to retrieve the ozone (nu(3) = 1) excited state density. Modeled ozone (nu(3) = 1) vibrational temperatures are used to infer the total ozone density. Night and day ozone abundance profiles inferred from ozone 9.6-mu m infrared spectral emissions and comparisons with photochemical model calculations are reported. The observed ozone abundance is significantly larger than predicted by the photochemical model. C1 Utah State Univ, Space Dyanm Lab, Logan, UT 84341 USA. Phillips Lab, Geophys Directorate, Bedford, MA 01731 USA. NASA, Langley Res Ctr, ASD, Hampton, VA 23681 USA. RP Zhou, DK (reprint author), Utah State Univ, Space Dyanm Lab, Logan, UT 84341 USA. RI Mlynczak, Martin/K-3396-2012 NR 19 TC 19 Z9 19 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 MAR 1 PY 1998 VL 25 IS 5 BP 643 EP 646 DI 10.1029/98GL00236 PG 4 WC Geosciences, Multidisciplinary SC Geology GA ZA533 UT WOS:000072373800017 ER PT J AU Mlynczak, MG Zhou, DK Adler-Golden, SM AF Mlynczak, MG Zhou, DK Adler-Golden, SM TI Kinetic and spectroscopic requirements for the inference of chemical heating rates and atomic hydrogen densities from OH Meinel band measurements SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID EMISSION AB We present the accuracy requirements for specific kinetic and spectroscopic parameters used in modeling populations of vibrationally excited hydroxyl. The requirements are based on simulations of the inference of chemical energy deposition rates and atomic hydrogen densities from satellite observations of the hydroxyl Meinel band emission rates. Improvement in the rate constants which describe the collisional removal of the high-lying upsilon states of OH and the reaction of high-lying upsilon states with atomic oxygen is required in addition to improved specification of the nascent distribution of energy within OH upon reaction of atomic hydrogen and ozone. These improvements are necessary for the interpretation of Meinel band measurements to be made from a new spaceflight experiment in less than 3 years. C1 NASA, Langley Res Ctr, Hampton, VA 23681 USA. Utah State Univ, Space Dynam Lab, Logan, UT 84322 USA. Spectral Sci Inc, Burlington, MA USA. RP Mlynczak, MG (reprint author), NASA, Langley Res Ctr, Mail Stop 401B, Hampton, VA 23681 USA. EM m.g.mlynczak@larc.nasa.gov RI Mlynczak, Martin/K-3396-2012 NR 19 TC 26 Z9 26 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 MAR 1 PY 1998 VL 25 IS 5 BP 647 EP 650 DI 10.1029/98GL00325 PG 4 WC Geosciences, Multidisciplinary SC Geology GA ZA533 UT WOS:000072373800018 ER PT J AU Donnellan, A Webb, FH AF Donnellan, A Webb, FH TI Geodetic observations of the M 5.1 January 29, 1994 Northridge aftershock SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID VELOCITY AB Geodetic observations of the January 29, 1994 M 5.1 aftershock of the Northridge earthquake are consistent with seismic solutions Showing left-lateral Oblique slip on a northeast striking steeply dipping fault. Thirty second solutions of the data from the station showing the maximum observed displacement (35 mm) indicate neither precursory nor immediate post-seismic motion to the aftershock. The aftershock does appear to be superimposed over the longer term Northridge post-seismic deformation field. Inversions of the data yield a potency of 2.6 +/- 0.3 x 10(-3) km(3) slightly higher than that determined by seismic methods. Combining the potency with estimates of rigidity from P- and S-wave velocities yields a moment that is consistent with seismic moment solutions. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP CALTECH, Jet Prop Lab, Mail Stop 238-600,4800 Oak Grove Dr, Pasadena, CA 91109 USA. EM andrea@cobra.jpl.nasa.gov; fhw@cobra.jpl.nasa.gov NR 12 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 EI 1944-8007 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD MAR 1 PY 1998 VL 25 IS 5 BP 667 EP 670 DI 10.1029/98GL50323 PG 4 WC Geosciences, Multidisciplinary SC Geology GA ZA533 UT WOS:000072373800024 ER PT J AU Chang, CL Drobot, AT Papadopoulos, K Wright, KH Stone, NH Gurgiolo, C Winningham, JD Bonifazi, C AF Chang, CL Drobot, AT Papadopoulos, K Wright, KH Stone, NH Gurgiolo, C Winningham, JD Bonifazi, C TI Current-Voltage characteristics of the tethered satellite system: Measurements and uncertainties due to temperature variations SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID TSS-1 AB One of the primary goals of the Tethered Satellite System reflight mission (TSS-1R) is to determine the current-voltage characteristics of the TSS satellite orbiting in the ionosphere. While the collected current was measured directly with high reliability, the satellite potential could only be deduced from a circuit model or from interpretation of measurement data below satellite potentials of 500 Volts. The greatest uncertainty in the circuit model is the value of tether resistance R. We have provided quantitative calibration of the resistance based on instrument data for Vs < 100 Volts. We have reached the important conclusion that the R value in the TSS circuit model is correlated to temperature changes associated with the diurnal cycles along the TSS flight path. We have also applied the calibrated R value in the TSS circuit equation to construct the I-V curves that extend to high voltages. The resulting I-V characteristics are presented with error bounds on satellite potential to indicate the uncertainty associated with the tether resistance determination. The I-V relation exhibits different scalings in the high (> 100 Volts) and low (< 10 Volts) voltage regimes, which indicates a fundamental transition for the current collection physics in the ionospheric plasma surrounding the satellite. C1 Sci Applicat Int Corp, Appl Phys Operat, Mclean, VA 22102 USA. Univ Alabama, Ctr Space Plasma & Aeron Res, Huntsville, AL 35899 USA. NASA, Space Sci Lab, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. Bitterroot Basic Res Inc, Hamilton, MT 59840 USA. SW Res Inst, Space Instrument Div, San Antonio, TX 78228 USA. Agenzia Spaziale Italiana, Rome, Italy. RP Chang, CL (reprint author), Sci Applicat Int Corp, Appl Phys Operat, Mclean, VA 22102 USA. NR 6 TC 4 Z9 5 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 MAR 1 PY 1998 VL 25 IS 5 BP 713 EP 716 DI 10.1029/97GL02981 PG 4 WC Geosciences, Multidisciplinary SC Geology GA ZA533 UT WOS:000072373800036 ER PT J AU Potter, CS Davidson, EA Klooster, SA Nepstad, DC De Negreiros, GH Brooks, V AF Potter, CS Davidson, EA Klooster, SA Nepstad, DC De Negreiros, GH Brooks, V TI Regional application of an ecosystem production model for studies of biogeochemistry in Brazilian Amazonia SO GLOBAL CHANGE BIOLOGY LA English DT Article DE Amazon; biogeochemistry; ecosystem modelling; trace gases; transects ID NDVI DATA SET; NITRIC-OXIDE; TROPICAL SAVANNA; CARBON-DIOXIDE; NITROUS-OXIDE; SOUTH-AMERICA; RAIN-FOREST; SOILS; SATELLITE; CLIMATE AB The degree to which primary production, soil carbon, and trace gas fluxes in tropical forests of the Amazon are limited by moisture availability and other environmental factors was examined using an ecosystem modelling application for the country of Brazil. A regional geographical information system (GIS) serves as the data source of climate drivers, satellite images, land cover, and soil properties for input to the NASA Ames-CASA (Carnegie-Ames-Stanford Approach) model over a 8-km grid resolution. Simulation results lead us to hypothesize that net primary production (NPP) is limited by cloud interception of solar radiation over the humid north-western portion of the region. Peak annual rates for NPP of nearly 1.4 kg C m(-2) year(-1) are localized in the seasonally dry eastern Amazon in areas that we assume are primarily deep-rooted evergreen forest cover. Regional effects of forest conversion on NPP and soil carbon content are indicated in the model results, especially in seasonally dry areas. Comparison of model flux predictions along selected eco-climatic transects reveal moisture, soil, and land use controls on gradients of ecosystem production and soil trace gas emissions (CO2, N2O, and NO). These results are used to formulate a series of research hypotheses for testing in the next phase of regional modelling, which includes recalibration of the light-use efficiency term in NASA-CASA using field measurements of NPP, and refinements of vegetation index and soil property (texture and potential rooting depth) maps for the region. C1 NASA, Ames Res Ctr, Ecosyst Sci Branch, Moffett Field, CA 94035 USA. Woods Hole Res Ctr, Woods Hole, MA 02543 USA. Univ Washington, Coll Forest Resources, Seattle, WA 98195 USA. RP Potter, CS (reprint author), NASA, Ames Res Ctr, Ecosyst Sci Branch, Mail Stop 242-4, Moffett Field, CA 94035 USA. RI Davidson, Eric/K-4984-2013 OI Davidson, Eric/0000-0002-8525-8697 NR 58 TC 65 Z9 68 U1 0 U2 20 PU BLACKWELL SCIENCE LTD PI OXFORD PA P O BOX 88, OSNEY MEAD, OXFORD OX2 0NE, OXON, ENGLAND SN 1354-1013 J9 GLOB CHANGE BIOL JI Glob. Change Biol. PD MAR PY 1998 VL 4 IS 3 BP 315 EP 333 DI 10.1046/j.1365-2486.1998.00154.x PG 19 WC Biodiversity Conservation; Ecology; Environmental Sciences SC Biodiversity & Conservation; Environmental Sciences & Ecology GA ZF050 UT WOS:000072857700008 ER PT J AU Cuzzi, JN Estrada, PR AF Cuzzi, JN Estrada, PR TI Compositional evolution of Saturn's rings due to meteoroid bombardment SO ICARUS LA English DT Review ID PARTICLE EROSION MECHANISMS; OUTER SOLAR-SYSTEM; VOYAGER PHOTOMETRY; REFLECTANCE SPECTROSCOPY; BALLISTIC TRANSPORT; OPTICAL-PROPERTIES; RADIATIVE-TRANSFER; AMORPHOUS-CARBON; PLANETARY RINGS; SATELLITES AB In this paper we address the question of compositional evolution in planetary ring systems subsequent to meteoroid bombardment. The huge surface area to mass ratio of planetary rings ensures that this is an important process, even with current uncertainties on the meteoroid Aux. We develop a new model which includes both direct deposition of extrinsic meteoritic "pollutants" and ballistic transport of the increasingly polluted ring material as impact ejecta. Our study includes detailed radiative transfer modeling of ring particle spectral reflectivities based on refractive indices of realistic constituents. Voyager data have shown that the lower optical depth regions in Saturn's rings (the C ring and Cassini division) have darker and less red particles than the optically thicker A and B rings. These coupled structural-compositional groupings have never been explained; we present and explore the hypothesis that global scale color and compositional differences in the main rings of Saturn arise naturally from extrinsic meteoroid bombardment of a ring system which was initially composed primarily, but not entirely, of water ice. We find that the regional color and albedo differences can be understood if all ring material was initially water ice colored by tiny amounts of intrinsic reddish, plausibly organic, absorber, which then evolved entirely by addition and redistribution of extrinsic, nearly neutrally colored, plausibly carbonaceous material. The regional compositional differences result from different susceptibilities to pollution of regions with very different surface mass density. We further demonstrate that the detailed radial profile of color across the abrupt B ring-C ring boundary can constrain key unknown parameters in the model. We carefully reanalyze and revise meteoroid flux estimates by Cuzzi and Durisen (1990, Icarus 84, 467-501) and estimate the duration of the exposure to extrinsic meteoroid flux of this part of the rings, at least, to be on the order of 10(8) years. This conclusion is easily extended by inference to the Cassini division and its surroundings as well. This geologically young "exposure age" is compatible with time scales estimated elsewhere based on the evolution of ring structure due to ballistic transport and also with other "short time scales" estimated on the grounds of gravitational torques. However, uncertainty in the flux of interplanetary debris and in the ejecta yield may preclude ruling out a ring age as old as the Solar System at this time. (C) 1998 Academic Press. C1 NASA, Ames Res Ctr, Div Space Sci, Moffett Field, CA 94035 USA. Cornell Univ, Dept Astron, Ithaca, NY 14853 USA. RP Cuzzi, JN (reprint author), NASA, Ames Res Ctr, Div Space Sci, Mail Stop 245-3, Moffett Field, CA 94035 USA. EM cuzzi@cosmic.arc.nasa.gov NR 106 TC 97 Z9 97 U1 1 U2 6 PU ACADEMIC PRESS INC ELSEVIER SCIENCE PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA SN 0019-1035 J9 ICARUS JI Icarus PD MAR PY 1998 VL 132 IS 1 BP 1 EP 35 DI 10.1006/icar.1997.5863 PG 35 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZP811 UT WOS:000073790800001 ER PT J AU Rappaport, N AF Rappaport, N TI Ring-ringlet interactions SO ICARUS LA English DT Article DE planetary rings; dynamics ID SMALL SATELLITES; PLANETARY RINGS; NARROW RINGLETS; SATURNS RINGS AB This paper is motivated by the recent discovery of the single-sided shepherding observed in numerical simulations by Hanninen and Salo (1994, Icarus 108, 325-346; 1995, Icarus 117, 435-438) and explained by Goldreich, Rappaport, and Sicardy (1995, Icarus 118, 414-417). It deals with the question of the confinement of the gap's edges. Gravitational perturbations exerted by the narrow ringlet on the gap's edges and the exchange of angular momentum between the ringlet and the gap's edges are studied. These results are applied to the ringlet and gap at 1.470 R-p in Saturn's C ring. We find that if the ringlet's shape is dominated by the m = 1 mode, then its surface density would have to be much smaller than generally thought, otherwise the perturbations exerted on the edges would have been observed in the Voyager data. If the ringlet's eccentricity is forced by the 2:1 Lindblad resonance with Prometheus, as suggested by Goldreich, Rappaport and Sicardy's explanation, then the perturbations exerted by the ringlet on the gap's edges are on the same order of magnitude as those exerted by Prometheus. The torque exerted by the ringlet is able to confine the gap's inner edge, but the flux of angular momentum due to the ringlet perturbations near the outer edge of the gap has the sign opposite to that expected for confinement. This suggests that either the gap's edges are, as the ringlet itself, confined by reversal of the viscous flux of angular momentum or that one or several satellites or big particles located within the gap are responsible for the confinement of its edges. (C) 1998 Academic Press. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Rappaport, N (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 15 TC 6 Z9 6 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 MAR PY 1998 VL 132 IS 1 BP 36 EP 42 DI 10.1006/icar.1997.5875 PG 7 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZP811 UT WOS:000073790800002 ER PT J AU Scheeres, DJ Ostro, SJ Hudson, RS DeJong, EM Suzuki, S AF Scheeres, DJ Ostro, SJ Hudson, RS DeJong, EM Suzuki, S TI Dynamics of orbits close to asteroid 4179 Toutatis SO ICARUS LA English DT Article ID STABILITY ZONES; RADAR IMAGES; SHAPE AB We use a radar-derived physical model of 4179 Toutatis (Hudson and Ostro 1995, Science 270, 84-86) to investigate close-orbit dynamics around that irregularly shaped, non-principal-axis rotator. The orbital dynamics about this body are markedly different than the dynamics about uniformly rotating asteroids. The results of this paper are generally applicable to orbit dynamics about bodies in a non-principal-axis rotation state. The radar results support the hypothesis that Toutatis has a homogeneous density distribution, and we assume a density of 2.5 g/cc. The asteroid's gravity field is computed using a truncated harmonic expansion when outside of its circumscribing sphere and a closed-form expression for the potential field of an arbitrary polyhedron when inside that sphere. The complete equations of motion are time-periodic in the Toutatis-fixed frame due to the complex rotation of the asteroid. The system is Hamiltonian and has all the characteristics of such a system, including conservation of phase volume, but there is no Jacobi constant of the motion and zero velocity surfaces cannot be used to analyze the system's behavior. We also examine some of the close-orbit dynamics with the Lagrange planetary form of the equations of motion. Families of quasi-periodic "frozen orbits" that shaw minimal variations in orbital elements are found to exist very close to the asteroid; some of them are stable and hence can hold natural or artificial satellites. A retrograde family of frozen orbits is especially robust and persists down to semi-major axes of about 2.5 km, comparable to half of Toutatis' longest dimension. We identify families of periodic orbits, which repeat in the Toutatis-fixed frame. Due to the time-periodic nature of the equations of motion, all periodic orbits about Toutatis in its body-fixed frame must be commensurate with the 5.42-day period associated with those equations. Exact calculations of both stable and unstable periodic orbits are made. The sum of surface forces acting on a particle on Toutatis is time-varying, so particles on and in the asteroid are being continually shaken with a period of 5.42 days, perhaps enhancing the uniformity of the regolith distribution. A global map of the gravitational slope reveals that it is surprisingly shallow for such an elongated, irregularly shaped object, averaging 16 degrees globally and less than 35 degrees over 96% of the surface. A global map of tangential accelerations shows no values larger than 0.5 mm/s(2), an average value of 0.2 mm/s(2), and less than 0.25 mm/s(2) over 70% of the surface. A global map of the escape speed for launch normal to the surface shows that quantity to be between 1.2 and 1.8 m/s over most of the surface. Each of these mapped quantities has small periodic variations. We have found trajectories that leave the surface, persist in the region of phase space around a frozen orbit, and then impact the surface after a flight time of more than 100 days. Return orbit durations of years seem possible. Whereas a uniformly rotating asteroid preferentially accumulates non-escaping ejecta on its leading sides, Toutatis accumulates ejecta uniformly over its surface. We render a variety of close orbits in inertial and body-fixed frames. (C) 1998 Academic Press. C1 Iowa State Univ, Dept Aerosp Engn & Engn Mech, Ames, IA 50011 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Washington State Univ, Sch Elect Engn & Comp Sci, Pullman, WA 99164 USA. RP Scheeres, DJ (reprint author), Iowa State Univ, Dept Aerosp Engn & Engn Mech, Ames, IA 50011 USA. NR 20 TC 100 Z9 106 U1 1 U2 7 PU ACADEMIC PRESS INC PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA SN 0019-1035 J9 ICARUS JI Icarus PD MAR PY 1998 VL 132 IS 1 BP 53 EP 79 DI 10.1006/icar.1997.5870 PG 27 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZP811 UT WOS:000073790800004 ER PT J AU Smith, MD AF Smith, MD TI Estimation of a length scale to use with the quench level approximation for obtaining chemical abundances SO ICARUS LA English DT Article DE abundances, atmospheres; Jovian planets, atmosphere ID NEPTUNE ATMOSPHERE; MOIST CONVECTION; GIANT PLANETS; JUPITER; WATER; SATURN; CONSTRAINTS; INHIBITION; NITROGEN; HYDROGEN AB The "quench level" approximation for estimating the observed abundance of chemically reacting species in the presence of convective dynamics states that the chemical reaction is quenched at the level where the time scales for the chemical reaction, t(chem), and for convective dynamics, t(dyn), are equal. The dynamical time constant, t(dyn), can be computed using t(dyn), L-2/K-eddy, where L is a length scale and K-eddy is the vertical eddy diffusion coefficient. Usually K-eddy is left as a free parameter, and lacking any better information, L is taken to be the pressure scale height, H. Here it is shown that an effective length scale L-eff, can be estimated from the e-folding length scales of t(chem) and t(dyn) and the pressure dependence of the equilibrium value of the chemical abundance. The improved accuracy of using L = L-eff instead of L = H is demonstrated by comparing the results of three different mathematical "models" for convective dynamics. The three models are the quench level approximation, a second computation that uses diffusive mixing to describe convection, and a third computation that explicitly integrates the equations of motion and chemical equilibration. Each of the three models uses a different fundamental quantity in describing the strength or efficiency of mixing that depends on the length scale L in a different way. When L = H is used, the three models give three different results, but when L = L-eff is used, results from the three models are virtually identical. The effective length scale, L-eff, is different for different chemical reactions and can be far from a scale height. As an example, for the isotropic enrichment of (D/H) in CH4 over (D/H) in H-2, the effective length scale is L-eff = 0.14H at a typical value of K-eddy = 10(8) cm(2) sec(-1). Using L = 0.14H leads to an enrichment factor of 1.17 on Jupiter compared to 1.21 when L = H is used. (C) 1998 Academic Press. C1 NASA, NRC, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Smith, MD (reprint author), NASA, NRC, Goddard Space Flight Ctr, Code 693, Greenbelt, MD 20771 USA. RI Smith, Michael/C-8875-2012 NR 24 TC 41 Z9 41 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 MAR PY 1998 VL 132 IS 1 BP 176 EP 184 DI 10.1006/icar.1997.5886 PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZP811 UT WOS:000073790800012 ER PT J AU DeCoste, D AF DeCoste, D TI The significance of Kasparov versus DEEP BLUE and the future of computer chess SO ICCA JOURNAL LA English DT Article ID GAME-TREE SEARCH; ALGORITHM AB In this paper we argue that the Garry Kasparov versus DEEP BLUE matches of 1996 and 1997, despite some shortcomings, have had a significant positive impact on computer-chess and artificial-intelligence research. Such matches can be viewed as valuable lessons in how (and how not) to use man-machine competitions to obtain a better focus on applied research and on the development efforts. One of the most important goals is to provide benchmarks (both in terms of development effort and match performance) that more knowledge-intensive (i.e., less brute-force) approaches must surpass to justify their extra complexity. We will briefly summarize some of the latest developments in computer-chess research and highlight how our work on a program called CHESTER tries to build on them to provide such justifications. Using our CHESTER work as an example, we propose a possible shift in emphasis for the computer-chess community: away from tournament performances (nowadays a short-term goal) and more toward treating the chess domain as a valuable testbed for research on emerging large-scale data-mining and machine-learning techniques. The successes of DEEP BLUE, despite legitimate questions of validity and scope, have in some sense freed (and perhaps even compelled) us to refocus on such longer-term goals. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91009 USA. NR 43 TC 1 Z9 1 U1 3 U2 7 PU INTL COMPUTER CHESS ASSN UNIV LIMBURG,DEPT COMPUTER SCI PI MAASTRICHT PA FACULTY GENERAL SCIENCES PO BOX 616, 6200 MAASTRICHT, NETHERLANDS SN 0920-234X J9 ICCA J JI ICCA J. PD MAR PY 1998 VL 21 IS 1 BP 33 EP 43 PG 11 WC Computer Science, Software Engineering SC Computer Science GA ZF685 UT WOS:000072921800003 ER PT J AU Van Baalen, J AF Van Baalen, J TI Meta-Amphion: cost-effective development of high-assurance software generators SO IEEE INTELLIGENT SYSTEMS & THEIR APPLICATIONS LA English DT Editorial Material C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Univ Wyoming, Laramie, WY 82071 USA. RP Van Baalen, J (reprint author), NASA, Ames Res Ctr, MS 269-2 Code IC, Moffett Field, CA 94035 USA. NR 5 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 0885-9000 J9 IEEE INTELL SYST APP JI IEEE Intell. Syst. Appl. PD MAR-APR PY 1998 VL 13 IS 2 BP 12 EP 13 PG 2 WC Computer Science, Artificial Intelligence; Engineering, Electrical & Electronic SC Computer Science; Engineering GA ZF700 UT WOS:000072923300005 ER PT J AU Romanofsky, RR AF Romanofsky, RR TI Correction factor for determining the London penetration depth from strip resonators SO IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY LA English DT Article DE high-temperature superconductors; superconducting materials measurements; superconducting resonators ID INDUCTANCE; FILMS; LINES; RING AB The strip resonator technique is a popular way to measure the temperature (T)-dependent London penetration depth lambda(L)(T) in superconducting thin films, The temperature dependence can provide fundamental information about the superconducting energy gap and hence insight into the pairing mechanism, Since lambda(L)(T) characterizes the film's response to a magnetic field near the surface, it qualifies the suitability of the superconducting film for microwave device applications, There has been much controversy regarding the actual form of the temperature dependency, with some researchers reporting a weak-coupled Bardeen-Cooper-Schriefer (<(BCS)under bar>)-like behavior and others favoring a Gorter-Casimir type fit. This paper shows that the disagreement can be at least partially attributed to a temperature sensitive term traceable to stray susceptance coupled into the resonator, The effect is inherent to the technique, but a simple procedure to compensate for it can be used and is presented here as a correction factor (1 + xi). C1 NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. RP Romanofsky, RR (reprint author), NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. NR 15 TC 3 Z9 3 U1 0 U2 0 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 1051-8223 J9 IEEE T APPL SUPERCON JI IEEE Trans. Appl. Supercond. PD MAR PY 1998 VL 8 IS 1 BP 3 EP 6 DI 10.1109/77.662687 PG 4 WC Engineering, Electrical & Electronic; Physics, Applied SC Engineering; Physics GA ZC985 UT WOS:000072639200001 ER PT J AU Woodard, SE Gell, DA Lay, RR AF Woodard, SE Gell, DA Lay, RR TI Measured spacecraft dynamic effects on atmospheric science instruments SO IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING LA English DT Article DE atmospheric measurements; Halogen Occultation Experiment (HALOE); High Resolution Doppler Image (HRDI); jitter; Microwave Limb Sounder (MLS); spacecraft dynamic response; Upper Atmosphere Research Satellite (UARS); vibration; Wind Imaging Interferometer (WINDII) ID WINDII AB In September 1991, NASA launched the Upper Atmosphere Research Satellite (UARS). In addition to its atmospheric science mission, spacecraft dynamic effects on science measurements mere analyzed. The investigation included two in-flight experiments to determine how each onboard instrument, subsystem, and environmental disturbance contributed to the spacecraft dynamic response and how these disturbances affected science measurements. Three case studies are presented that show the impact of spacecraft dynamic response on science measurements. The case studies have demonstrated that the influence of spacecraft dynamic response needs to be examined in most remote sensing spacecraft that have attitude jitter levels commensurate to instrument pointing requirements. In the first case, correlation of independent atmospheric meridional wind measurements taken by two instruments with the spacecraft dynamic response demonstrated that excessive vibration (exceeding instrument pointing requirements) resulted in wind measurement disagreement. In the second case, solar array disturbances produced a spacecraft response signature on radiometer measurements. The signature explicitly demonstrated that if an instrument has sufficient spatial and temporal resolution, spacecraft dynamic response could impact measurements. In the final case, correlation of an instruments fine sun-sensor data and CO2 measurements demonstrated the effect of temporal and spatial, sampling resolution and active pointing control on science measurements. The sun sensor had a frequency modulated characteristic, due to spacecraft vibration and the periodic scanning of another instrument, which was not present on the CO2 measurements. C1 NASA, Langley Res Ctr, Hampton, VA 23681 USA. Univ Michigan, Ann Arbor, MI 48109 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Woodard, SE (reprint author), NASA, Langley Res Ctr, Hampton, VA 23681 USA. NR 12 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 0196-2892 J9 IEEE T GEOSCI REMOTE JI IEEE Trans. Geosci. Remote Sensing PD MAR PY 1998 VL 36 IS 2 BP 359 EP 367 DI 10.1109/36.662722 PG 9 WC Geochemistry & Geophysics; Engineering, Electrical & Electronic; Remote Sensing; Imaging Science & Photographic Technology SC Geochemistry & Geophysics; Engineering; Remote Sensing; Imaging Science & Photographic Technology GA ZC333 UT WOS:000072566800001 ER PT J AU Grivet-Talocia, S Einaudi, F AF Grivet-Talocia, S Einaudi, F TI Wavelet analysis of a microbarograph network SO IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING LA English DT Article DE adaptive filters; adaptive signal processing; data processing; nonlinear filters; pressure measurement; time-frequency analysis; wavelet transforms ID GRAVITY-WAVES; ATMOSPHERIC-PRESSURE; CONVECTIVE STORMS; DISTURBANCES; TRANSFORM; TIME; DECOMPOSITION; FLUCTUATIONS; VARIABILITY; SIGNALS AB This paper presents a wavelet-based algorithm for the detection, identification, and extraction of gravity waves from atmospheric pressure traces, The main data processing tool is a nonlinear adaptive filter based on the selective reconstruction of a waveform from its wavelet coefficients, The time-frequency localization of the wavelet transform provides an ideal framework for the decomposition of long-period gravity waves (30 min-6 h), which are characterized by a generally broad spectrum and few oscillation cycles, The procedure is iterative and allows the exhaustive processing of all the events present in a fixed time period, The waveform of each disturbance is reconstructed with high accuracy. This minimizes the influence of the data-processing technique on the estimate of horizontal speed and direction of propagation, obtained by maximization of the cross-correlation functions between the reconstructed waveforms at the different stations, The introduction of coherency criteria through the network of seven stations allows us to separate the events into two classes. The first includes the events that propagate with very small distortion through the network, while the second includes less coherent but still highly energetic events, The size of the network and the algorithm developed for the analysis is well suited for the identification and the extraction of those mesoscale disturbances that have a particularly strong influence on the weather as well as on the forecast. C1 Sci Syst & Applicat Inc, Lanham, MD 20706 USA. Politecn Torino, Dipartimento Elettron, I-10129 Turin, Italy. NASA, Goddard Space Flight Ctr, Atmospheres Lab, Greenbelt, MD 20771 USA. RP Grivet-Talocia, S (reprint author), Sci Syst & Applicat Inc, Lanham, MD 20706 USA. EM grivet@polito.it RI Grivet-Talocia, Stefano/M-1480-2015 OI Grivet-Talocia, Stefano/0000-0002-5463-3810 NR 54 TC 7 Z9 7 U1 1 U2 2 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 MAR PY 1998 VL 36 IS 2 BP 418 EP 433 DI 10.1109/36.662727 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 ZC333 UT WOS:000072566800006 ER PT J AU Burke, EJ Gurney, RJ Simmonds, LP O'Neill, PE AF Burke, EJ Gurney, RJ Simmonds, LP O'Neill, PE TI Using a modeling approach to predict soil hydraulic properties from passive microwave measurements SO IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING LA English DT Article DE hydraulic properties; passive microwave; soil; SVAT model; vegetation ID MOISTURE; EMISSION AB A soil water and energy budget model coupled with a microwave emission model (MICRO-SWEAT) was used to predict the diurnal courses of soil surface water content and microwave brightness temperatures during a number of drying cycles on soils of contrasting texture that were either cropped or bare, The parameters describing the soil water retention and conductivity characteristics [saturated hydraulic conductivity, air entry potential, bulk density, and the exponent (b) describing the slope of the water release curve] had a strong influence on the modeled bare-soil microwave brightness temperatures, These parameters were varied until the error between the remotely sensed and modeled brightness temperatures was minimized, leading to their predicted values, These predictions agreed with the measured values to within the experimental error; The modeled brightness temperature for a soybean-covered soil was sensitive to some of the vegetation parameters (particularly to the optical depth), in addition to the soil hydraulic properties, Preliminary findings suggest that, given an independent estimate of the vegetation parameters, it may still be possible to estimate the soil hydraulic properties under a moderate vegetation canopy. C1 Univ Reading, Environm Syst Sci Ctr, Reading RG6 6AL, Berks, England. Univ Reading, Dept Soil Sci, Reading RG6 2DW, Berks, England. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Burke, EJ (reprint author), Inst Hydrol, Wallingford OX10 8BB, Oxon, England. RI O'Neill, Peggy/D-2904-2013 NR 24 TC 49 Z9 50 U1 0 U2 3 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 0196-2892 J9 IEEE T GEOSCI REMOTE JI IEEE Trans. Geosci. Remote Sensing PD MAR PY 1998 VL 36 IS 2 BP 454 EP 462 DI 10.1109/36.662729 PG 9 WC Geochemistry & Geophysics; Engineering, Electrical & Electronic; Remote Sensing; Imaging Science & Photographic Technology SC Geochemistry & Geophysics; Engineering; Remote Sensing; Imaging Science & Photographic Technology GA ZC333 UT WOS:000072566800008 ER PT J AU Karpinskii, OG Shelimova, LE Kretova, MA Fleurial, JP AF Karpinskii, OG Shelimova, LE Kretova, MA Fleurial, JP TI Structural study of ternary layered compounds in the (GeTe)(n)center dot(Bi2Te3)(m) and (GeTe)(n)center dot(Sb2Te3)(m) homologous series SO INORGANIC MATERIALS LA English DT Article AB Layered compounds in the (GeTe)(n).(Bi2Te3)(m) and (GeTe)(n).(Sb2Te3)(m) homologous series (n=1-4, m=1,2) are studied by single-crystal and powder x-ray diffraction. The dependences of the a cell parameter and average atomic-layer thickness c/N on the cation-to-anion ratio are analyzed for the ternary compounds and constituent tellurides. These dependences are used to estimate the lattice parameters of higher members of the (GeTe)(n).(Bi2Te3)(m) and (GeTe)(n).(Sb2Te3)(m) homologous series, for which experimental data are lacking. X-ray diffraction data for Ge3Sb2Te6 (33-layer structure, c=6.2234(5) nm) and Ge4Sb2Te7 (39-layer structure, c=7.279(1) nm) ale reported for the first time. C1 Russian Acad Sci, Baikov Inst Met, Moscow 117334, Russia. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Karpinskii, OG (reprint author), Russian Acad Sci, Baikov Inst Met, Leninskii Pr 49, Moscow 117334, Russia. NR 32 TC 2 Z9 2 U1 1 U2 3 PU MAIK NAUKA/INTERPERIODICA/SPRINGER PI NEW YORK PA 233 SPRING ST, NEW YORK, NY 10013-1578 USA SN 0020-1685 EI 1608-3172 J9 INORG MATER+ JI Inorg. Mater. PD MAR PY 1998 VL 34 IS 3 BP 225 EP 232 PG 8 WC Materials Science, Multidisciplinary SC Materials Science GA ZC245 UT WOS:000072557500010 ER PT J AU Girimaji, SS Balachandar, S AF Girimaji, SS Balachandar, S TI Analysis and modeling of buoyancy-generated turbulence using numerical data SO INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER LA English DT Article ID CONVECTION AB Rayleigh-Bernard convection offers a unique flow situation in which buoyancy-generated turbulence can be studied in isolation, free of the complicating influence of shear production of turbulence. The objective of this paper is to examine and model important aspects of buoyancy-generated turbulence using numerical simulation (DNS) data of Rayleigh-Bernard convection. In particular, we examine the pressure-strain and pressure-temperature gradient correlations, turbulent transport of Reynolds stress, and assumptions pertaining to algebraic modeling of thermal flux and Reynolds stress. Published by Elsevier Science Ltd. C1 NASA, Langley Res Ctr, Inst Comp Applicat Sci & Engn, Hampton, VA 23681 USA. Univ Illinois, Dept Theoret & Appl Mech, Urbana, IL 61801 USA. RP Girimaji, SS (reprint author), NASA, Langley Res Ctr, Inst Comp Applicat Sci & Engn, Hampton, VA 23681 USA. RI Balachandar, Sivaramakrishnan/E-7358-2011 NR 11 TC 16 Z9 18 U1 0 U2 1 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0017-9310 J9 INT J HEAT MASS TRAN JI Int. J. Heat Mass Transf. PD MAR-APR PY 1998 VL 41 IS 6-7 BP 915 EP 929 DI 10.1016/S0017-9310(97)00166-X PG 15 WC Thermodynamics; Engineering, Mechanical; Mechanics SC Thermodynamics; Engineering; Mechanics GA YP687 UT WOS:000071303900008 ER PT J AU Kooi, JW Stern, JA Chattopadhyay, G LeDuc, HG Bumble, B Zmuidzinas, J AF Kooi, JW Stern, JA Chattopadhyay, G LeDuc, HG Bumble, B Zmuidzinas, J TI Low-loss NbTiN films for THz SIS mixer tuning circuits SO INTERNATIONAL JOURNAL OF INFRARED AND MILLIMETER WAVES LA English DT Article DE NbTiN superconducting films; SIS junctions; niobium bandgap AB Recent results at 1 THz using normal-metal tuning circuits have shown that SIS mixers can work well up to twice the gap frequency of the junction material (niobium). However, the performance at 1 THz is limited by the substantial loss in the normal metal films. For better performance superconducting films with a higher gap frequency than niobium and with low RF loss are needed. Niobium nitride has long been considered a good candidate material, but typical NbN films suffer from high RF loss. To circumvent this problem we are currently investigating the RF loss in NbTiN films, a 15K Tc compound superconductor, by incorporating them into quasi-optical slot antenna SIS devices. C1 CALTECH, Pasadena, CA 91125 USA. CALTECH, Jet Prop Lab, Ctr Space Microelect Technol, Pasadena, CA 91108 USA. RP Kooi, JW (reprint author), CALTECH, MS 320-47, Pasadena, CA 91125 USA. NR 5 TC 17 Z9 17 U1 1 U2 4 PU PLENUM PUBL CORP PI NEW YORK PA 233 SPRING ST, NEW YORK, NY 10013 USA SN 0195-9271 J9 INT J INFRARED MILLI JI Int. J. Infrared Millimeter Waves PD MAR PY 1998 VL 19 IS 3 BP 373 EP 383 DI 10.1023/A:1022595223782 PG 11 WC Engineering, Electrical & Electronic; Optics; Physics, Applied SC Engineering; Optics; Physics GA ZD480 UT WOS:000072690200001 ER PT J AU Durante, M Cella, L Furusawa, Y George, K Gialanella, G Grossi, G Pugliese, M Saito, M Yang, TC AF Durante, M Cella, L Furusawa, Y George, K Gialanella, G Grossi, G Pugliese, M Saito, M Yang, TC TI The effect of track structure on the induction of chromosomal aberrations in murine cells SO INTERNATIONAL JOURNAL OF RADIATION BIOLOGY LA English DT Article ID C3H 10T1/2 CELLS; ALPHA-PARTICLES; CHARGED-PARTICLES; MOUSE SPLENOCYTES; DAMAGE; IRRADIATION; TRANSLOCATIONS; TRANSFORMATION; HYBRIDIZATION; INACTIVATION AB Purpose: To measure chromosome aberrations in C3H 10T1/2 mouse fibroblasts using FISH painting at the first mitosis following exposure to 30 keV/mu m hydrogen or neon ions. Materials and methods: Cells in plateau-phase were irradiated with 0.86 MeV protons at the TTT-3 Tandem accelerator in Naples (Italy), or with 400 MeV/n Ne ions at the HIMAC accelerator in Chiba (Japan). Colcemid-blocked cells were harvested at the first mitosis following exposure, and chromosome spreads were hybridized in situ with a fluorescein-labelled composite mouse DNA probe specific for chromosomes 2 and 8. Results: Protons were more efficient than neon ions at the same LET in the induction of chromosome interchanges and breaks. Yields of complex exchanges were similar for both particles at the same dose, but protons produced mostly insertions, while with Ne exposure non-reciprocal exchanges were the most frequent complex-type exchange. Conclusions: Charged particles with the same LET produce different yields of chromosome aberrations, and some observed differences can be explained based on the available track-structure models. C1 Univ Naples Federico II, Dipartimento Sci Fis, I-80126 Naples, Italy. Natl Inst Radiol Sci, Space & Particle Radiat Grp, Inage Ku, Chiba 263, Japan. Krug Life Sci, Houston, TX 77058 USA. NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. RP Durante, M (reprint author), Univ Naples Federico II, Dipartimento Sci Fis, Monte S Angelo,Via Cintia, I-80126 Naples, Italy. RI Durante, Marco/K-1315-2014; OI Cella, Laura/0000-0003-0058-4029; Durante, Marco/0000-0002-4615-553X NR 35 TC 15 Z9 15 U1 0 U2 4 PU TAYLOR & FRANCIS LTD PI LONDON PA ONE GUNPOWDER SQUARE, LONDON EC4A 3DE, ENGLAND SN 0955-3002 J9 INT J RADIAT BIOL JI Int. J. Radiat. Biol. PD MAR PY 1998 VL 73 IS 3 BP 253 EP 262 DI 10.1080/095530098142347 PG 10 WC Biology; Nuclear Science & Technology; Radiology, Nuclear Medicine & Medical Imaging SC Life Sciences & Biomedicine - Other Topics; Nuclear Science & Technology; Radiology, Nuclear Medicine & Medical Imaging GA ZD010 UT WOS:000072641800002 PM 9525253 ER PT J AU Tung, C Kube, R Brooks, TF Rahier, G AF Tung, C Kube, R Brooks, TF Rahier, G TI Prediction and measurement of blade-vortex interaction SO JOURNAL OF AIRCRAFT LA English DT Article; Proceedings Paper CT AIAA/CEAS 1st Joint Aeroacoustics Conference CY JUN 12-15, 1995 CL MUNICH, GERMANY SP AIAA, CEAS AB An extensive quantity of airload measurements was obtained for a pressure-instrumented model of the BO-105 main rotor for a large number of higher harmonic control settings at Duits-Nederlandse Wind Tunnel. The wake geometry, vortex strength, and vortex core size mere also measured through a laser light sheet technique and laser Doppler velocimetry, These results are used to verify the blade-vol tex interaction (BVI) airload prediction methodologies developed by Army Aeroflightdynamics Directorate, Deutsche Forschungsanstalt fur Luft-und Raumfahrt, NASA Langley Research Center, and the Office National d'Etudes et de Recherches Aerospatiales. The comparisons show that an accurate prediction of the blade motion and the wake geometry is the most important aspect of the BVI airload predictions. C1 NASA, Ames Res Ctr, Div Fluid Dynam, Moffett Field, CA 94035 USA. German Aerosp Res Estab, DLR, Inst Flight Mech, Braunschweig, Germany. NASA, Langley Res Ctr, Div Acoust, Hampton, VA 23681 USA. Off Natl Etud & Rech Aerosp, Div Acoust, F-92320 Chatillon, France. RP Tung, C (reprint author), NASA, Ames Res Ctr, Div Fluid Dynam, Moffett Field, CA 94035 USA. NR 17 TC 5 Z9 5 U1 0 U2 2 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 MAR-APR PY 1998 VL 35 IS 2 BP 260 EP 266 DI 10.2514/2.2293 PG 7 WC Engineering, Aerospace SC Engineering GA ZE540 UT WOS:000072803600015 ER PT J AU Gallman, JM Schultz, KJ Spiegel, P Burley, CL AF Gallman, JM Schultz, KJ Spiegel, P Burley, CL TI Effect of wake structure on blade-vortex interaction phenomena: Acoustic prediction and validation SO JOURNAL OF AIRCRAFT LA English DT Article; Proceedings Paper CT AIAA/CEAS 1st Joint Aeroacoustics Conference CY JUN 12-15, 1995 CL MUNICH, GERMANY SP AIAA, CEAS AB The higher harmonic control aeroacoustic rotor test conducted at Duits-Nederlandse Wind Tunnel has made extensive measurements of the rotor aerodynamics, far-field acoustics, wake geometry, and the blade motion for powered descent flight conditions. These measurements have been used to validate and improve the prediction of blade-vortex interaction (BVI) noise. The improvements made to the BVI modeling after the evaluation of the test data are discussed. The effect of these improvements on the acoustic-pressure predictions is shown. These improvements include restructuring the wake, modifying the core size, incorporating the measured blade motion into the calculations, and attempting to improve the dynamic blade response. A comparison of four different implementations of the Ffowcs Williams and Hawkings equation is presented. A common set of aerodynamic input has been used for this comparison. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. DLR, German Aerosp Res Estab, Braunschweig, Germany. Off Natl Etud & Rech Aerosp, F-92320 Chatillon, France. NASA, Langley Res Ctr, Hampton, VA 23681 USA. RP Gallman, JM (reprint author), NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. NR 20 TC 2 Z9 2 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 MAR-APR PY 1998 VL 35 IS 2 BP 267 EP 273 DI 10.2514/2.2294 PG 7 WC Engineering, Aerospace SC Engineering GA ZE540 UT WOS:000072803600016 ER PT J AU Byun, C Guruswamy, GP AF Byun, C Guruswamy, GP TI Aeroelastic computations on wing-body-control configurations on parallel computers SO JOURNAL OF AIRCRAFT LA English DT Article ID FLOWS AB A multizonal capability for aeroelastic computation of complex geometries has been implemented in ENSAERO, an aeroelastic analysis code with Euler/Navier-Stokes now solver, on the IBM SP2 parallel computer. The discipline parallelization is achieved by distributing the fluid, structure, and control domains onto different groups of computational nodes. The fluid domain is further parallelized based on the multizonal method. The coupling between the fluids and structures is obtained by exchanging the interface boundary data at every iteration by using the explicit message passing interface standard library. The performance of the current implementation shows that about 12 computational nodes of the SP2 computer are equivalent to the speed of a single C90 processor. For demonstration purposes, static aeroelastic computations coupled with control surfaces are made for an arrow wing-body-control configuration in the transonic how regime. Computed pressure coefficients for a rigid configuration were compared with the mind-tunnel experiment. The two results show good agreement. Steady aeroelastic simulations are made with and without control surface deflections. The static aeroelastic simulations show that the effect of flexibility is significant on aerodynamic coefficients. It is noted that the flexible wing lowered the sectional lifts compared to the rigid wing. This procedure can be utilized for the fast computational solution of large-scale mind-tunnel models and real configurations that inevitably deform under aerodynamic loads. C1 NASA, Ames Res Ctr, MCAT Inst, Appl Computat Aerodynam Branch, Moffett Field, CA 94035 USA. RP Byun, C (reprint author), NASA, Ames Res Ctr, MCAT Inst, Appl Computat Aerodynam Branch, Moffett Field, CA 94035 USA. NR 19 TC 6 Z9 6 U1 0 U2 0 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0021-8669 J9 J AIRCRAFT JI J. Aircr. PD MAR-APR PY 1998 VL 35 IS 2 BP 288 EP 294 DI 10.2514/2.2297 PG 7 WC Engineering, Aerospace SC Engineering GA ZE540 UT WOS:000072803600019 ER PT J AU Harris, CE Newman, JC Piascik, RS Starnes, JH AF Harris, CE Newman, JC Piascik, RS Starnes, JH TI Analytical methodology for predicting widespread fatigue damage onset in fuselage structure SO JOURNAL OF AIRCRAFT LA English DT Article AB A comprehensive analytical methodology has been developed for predicting the onset of widespread fatigue damage (WFD) in fuselage structure, The determination of the number of flights and operational hours of aircraft service life that are related to the onset of WFD includes analyses for crack initiation, fatigue crack growth, and residual strength. Therefore, the computational capability required to predict analytically the onset of WFD must be able to represent a wide range of crack sizes, from the material (microscale) level to the global (structural-scale) level. The results of carefully conducted teardown examinations of aircraft components indicate that fatigue crack behavior can be represented conveniently by the following three analysis scales: 1) small three-dimensional cracks at the microscale level, 2) through-the-thickness two-dimensional cracks at the local structural level, and 3) long cracks at the global structural level. The computational requirements for each of these three analysis scales are described in this paper. C1 NASA, Langley Res Ctr, Div Mat, Hampton, VA 23681 USA. NASA, Langley Res Ctr, Mech Mat Branch, Hampton, VA 23681 USA. NASA, Langley Res Ctr, Struct Mech Branch, Hampton, VA 23681 USA. RP Harris, CE (reprint author), NASA, Langley Res Ctr, Div Mat, Hampton, VA 23681 USA. NR 51 TC 15 Z9 16 U1 1 U2 1 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0021-8669 J9 J AIRCRAFT JI J. Aircr. PD MAR-APR PY 1998 VL 35 IS 2 BP 307 EP 317 DI 10.2514/2.2301 PG 11 WC Engineering, Aerospace SC Engineering GA ZE540 UT WOS:000072803600022 ER PT J AU Palm, SP Hagan, D Schwemmer, G Melfi, SH AF Palm, SP Hagan, D Schwemmer, G Melfi, SH TI Inference of marine atmospheric boundary layer moisture and temperature structure using airborne lidar and infrared radiometer data SO JOURNAL OF APPLIED METEOROLOGY LA English DT Article ID SEA-SURFACE TEMPERATURE; WATER-VAPOR; SATELLITE DATA; HEAT FLUXES; OCEAN; HUMIDITY; SYSTEM; CONVECTION; AEROSOLS; PROFILES AB A new technique for retrieving near-surface moisture and profiles of mixing ratio and potential temperature through the depth of the marine atmospheric boundary layer (MABL) using airborne lidar and multichannel infrared radiometer data is presented. Data gathered during an extended field campaign over the Atlantic Ocean in support of the Lidar In-space Technology Experiment are used to generate 16 moisture and temperature retrievals that are then compared with dropsonde measurements. The technique utilizes lidar-derived statistics on the height of cumulus clouds that frequently cap the MABL to estimate the lifting condensation level. Combining this information with radiometer-derived sea surface temperature measurements, an estimate of the near-surface moisture fan be obtained to an accuracy of about 0.8 g kg(-1). Lidar-derived statistics on convective plume height and coverage within the MABL are;hen used to infer the profiles of potential temperature and moisture with a vertical resolution of 20 m. The mts accuracy of derived MABL average moisture and potential temperature is better than 1 g kg(-1) and 1 degrees C, respectively. The method relies on the presence of a cumulus-capped MABL, and it was found that the conditions necessary for use of the technique occurred roughly 75% of the time. The synergy of simple aerosol backscatter Lidar and infrared radiometer data also shows promise for the retrieval of MABL moisture and temperature from space. C1 NASA, Goddard Space Flight Ctr, Atmospheres Lab, Greenbelt, MD 20771 USA. Sci Syst & Applicat Inc, Lanham, MD USA. CALTECH, Jet Prop Lab, Pasadena, CA USA. Univ Maryland, Catonsville, MD 21228 USA. RP Palm, SP (reprint author), NASA, Goddard Space Flight Ctr, Atmospheres Lab, Code 912, Greenbelt, MD 20771 USA. EM spp@virl.gsfc.nasa.gov NR 37 TC 12 Z9 12 U1 0 U2 1 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 USA SN 0894-8763 J9 J APPL METEOROL JI J. Appl. Meteorol. PD MAR PY 1998 VL 37 IS 3 BP 308 EP 324 DI 10.1175/1520-0450-37.3.308 PG 17 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA YY532 UT WOS:000072157300005 ER PT J AU Walsh, BM Barnes, NP Di Bartolo, B AF Walsh, BM Barnes, NP Di Bartolo, B TI Branching ratios, cross sections, and radiative lifetimes of rare earth ions in solids: Application to Tm3+ and Ho3+ ions in LiYF4 SO JOURNAL OF APPLIED PHYSICS LA English DT Article ID ROOM-TEMPERATURE; OPTICAL-SPECTRUM; YLF CRYSTALS; LASER; HOLMIUM; ABSORPTION; DYNAMICS; EMISSION; 2-MU-M; YLIF4 AB The measurement of branching ratios, cross sections and radiative lifetimes for rare earth ions in solids is considered, The methods are applied to Tm and Ho in YLF as a test case. De-activation rates for electric dipole and magnetic dipole emission are calculated for many of the lower lying manifolds in Tm:YLF and Ho:YLF in the context of the Judd-Ofelt theory to determine radiative lifetimes. Measured values for the branching ratios as well as the absorption and emission cross sections are also presented for many of the excited state manifolds. From these measurements, a methodology is developed to extract measured values for the radiative lifetimes. These results are compared with the Judd-Ofelt theory as a guide for consistency and for determining the accuracy of the Judd-Ofelt theory in predicting branching ratios and radiative lifetimes. The parameters generated by the methods covered here have potential applications for more accurate modeling of Tm:Ho laser systems. (C) 1998 American Institute of Physics. C1 NASA, Langley Res Ctr, Hampton, VA 23681 USA. Boston Coll, Dept Phys, Chestnut Hill, MA 02167 USA. RP NASA, Langley Res Ctr, MS 474, Hampton, VA 23681 USA. EM b.m.walsh@larc.nasa.gov NR 42 TC 203 Z9 210 U1 9 U2 56 PU AMER INST PHYSICS PI MELVILLE PA 1305 WALT WHITMAN RD, STE 300, MELVILLE, NY 11747-4501 USA SN 0021-8979 EI 1089-7550 J9 J APPL PHYS JI J. Appl. Phys. PD MAR 1 PY 1998 VL 83 IS 5 BP 2772 EP 2787 DI 10.1063/1.367037 PG 16 WC Physics, Applied SC Physics GA YZ942 UT WOS:000072310700055 ER PT J AU Foster, PP Conkin, J Powell, MR Waligora, JM Chhikara, RS AF Foster, PP Conkin, J Powell, MR Waligora, JM Chhikara, RS TI Role of metabolic gases in bubble formation during hypobaric exposures SO JOURNAL OF APPLIED PHYSIOLOGY LA English DT Article DE bubble growth; Doppler ultrasound; inert and noninert dissolved gases; tissue ratio; logistic model; log likelihood; gas kinetics ID DECOMPRESSION-SICKNESS; PROBABILISTIC MODEL; LIKELIHOOD; EXCHANGE; OXYGEN AB Our hypothesis is that metabolic gases play a role in the initial explosive growth phase of bubble formation during hypobaric exposures. Models that account for optimal internal tensions of dissolved gases to predict the probability of occurrence of venous gas emboli were statistically fitted to 426 hypobaric exposures from National Aeronautics and Space Administration tests. The presence of venous gas emboli in the pulmonary artery was detected with an ultrasound Doppler detector. The model fit and parameter estimation were done by using the statistical method of maximum likelihood. The analysis results were as follows. 1) For the model without an input of noninert dissolved gas tissue tension, the log likelihood (in absolute value) was 255.01. 2) When an additional parameter was added to the model to account for the dissolved noninert gas tissue tension, the log likelihood was 251.70. The significance of the additional parameter was established based on the likelihood ratio test (P < 0.012). 3) The parameter estimate for the dissolved noninert gas tissue tension participating in bubble formation was 19.1 kPa (143 mmHg). 4) The additional gas tissue tension, supposedly due to noninert gases, did not show an exponential decay as a function of time during denitrogenation, but it remained constant. 5) The positive sign for this parameter term in the model is characteristic of an outward radial pressure of gases in the bubble. This analysis suggests that dissolved gases other than Na in tissues may facilitate the initial explosive bubble-growth phase. C1 NASA, Lyndon B Johnson Space Ctr, Life Sci Res Labs, Environm Physiol Lab SD3, Houston, TX 77058 USA. NASA, Univ Space Res Assoc, Div Space Life Sci, Houston, TX 77058 USA. Univ Houston Clear Lake, Div Comp & Math, Houston, TX 77058 USA. RP Foster, PP (reprint author), NASA, Lyndon B Johnson Space Ctr, Life Sci Res Labs, Environm Physiol Lab SD3, Houston, TX 77058 USA. NR 24 TC 11 Z9 12 U1 0 U2 0 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 MAR PY 1998 VL 84 IS 3 BP 1088 EP 1095 PG 8 WC Physiology; Sport Sciences SC Physiology; Sport Sciences GA YZ674 UT WOS:000072279000044 PM 9480973 ER PT J AU Abraham, S Dhaka, SK Praveen, KD Nath, N Nagpal, OP Baluja, KL AF Abraham, S Dhaka, SK Praveen, KD Nath, N Nagpal, OP Baluja, KL TI Planetary wave effect on ionospheric absorption SO JOURNAL OF ATMOSPHERIC AND SOLAR-TERRESTRIAL PHYSICS LA English DT Article ID EQUATORIAL WAVES; STRATOSPHERE AB A relationship is examined between quasi-periodic fluctuations in absorption data at ionospheric altitudes and wave perturbations in wind data at tropospheric, stratospheric and lower mesospheric heights at Indian latitudes. The spectral analyses using Maximum Entropy Method (MEM) reveal almost the same band of periodicities in both the parameters. The important band of frequencies of 6-8 days and between 20-25 days in wind data are found to propagate up to mesospheric heights and are well reflected in absorption data. These fluctuations in absorption data are thought to be due to the vertical propagation of Rossby waves on different time scales. The correlation coefficient between absorption and wind data are found to be of the order of 0.5 to 0.75 at 95% confidence level in most of the cases at a lag of 1 to 5 days with lower stratospheric zonal winds. The lag reduces considerably when the correlation coefficient was computed at 60 km altitude using rocket data. Another important finding is that when the QBO is in the easterly phase the long-period band preferably shows a predominance of 20-25 days, while during the westerly phase of the QBO, this band of periods extends to 30-45 days, which is consistently observed in quasi-periodic fluctuations of both absorption and wind data. This may have possible implications of coupling between the stratosphere and mesosphere through the QBO. (C) 1997 Elsevier Science Ltd. All rights reserved. C1 Univ Delhi, Dept Phys & Astrophys, Delhi 110007, India. RP Abraham, S (reprint author), NASA, HSTX, Goddard Space Flight Ctr, Code 975, Greenbelt, MD 20771 USA. RI Dhaka, Surendra /I-2146-2016 OI Dhaka, Surendra /0000-0002-0812-525X NR 20 TC 3 Z9 3 U1 0 U2 0 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 1364-6826 J9 J ATMOS SOL-TERR PHY JI J. Atmos. Sol.-Terr. Phys. PD MAR PY 1998 VL 60 IS 4 BP 441 EP 453 DI 10.1016/S1364-6826(97)00072-2 PG 13 WC Geochemistry & Geophysics; Meteorology & Atmospheric Sciences SC Geochemistry & Geophysics; Meteorology & Atmospheric Sciences GA ZN425 UT WOS:000073644600003 ER PT J AU Ma, Q Tipping, RH AF Ma, Q Tipping, RH TI The distribution of density matrices over potential-energy surfaces: Application to the calculation of the far-wing line shapes for CO2 SO JOURNAL OF CHEMICAL PHYSICS LA English DT Article ID INFRARED-ABSORPTION SPECTRA; WATER CONTINUUM ABSORPTION; ROTATIONAL BANDS; REGION AB Within the formalism developed previously for the calculation of the far-wing line shape for molecular systems, most of the computer resources were used to diagonalize anisotropic potential-energy matrices whose sizes are determined by the number of states included. As this number is increased, one expects the results to converge. However, for some systems of atmospheric interest, e.g., CO2, the convergence is so slow that one is unable to obtain converged results within reasonable computer limitations. In the present paper, a new formalism is presented in which the eigenfunctions of the orientations of the system, not the states themselves, are chosen as the complete set of basis functions in Hilbert space. In this case, the diagonalization procedure is unnecessary and one can include as many states as desired. The main computational task is transformed-from a diagonalization procedure to the carrying out of multidimensional integrations over the continuous orientational variables. In practice, the integrals are approximated by multidimensional summations over discrete values, the number of which is determined by the resolution required so that the approximated integrals are close to their true values. By choosing reasonable resolutions based on the smooth functional behavior of the integrands, one is able to evaluate the required integrations within reasonable computer time. Furthermore, by introducing weighting functions which are the distribution of the density matrices over potential-energy surfaces, one can reduce the multidimensional integrations to two-dimensional ones. The calculation of the weighting functions can also be carried out with reasonable CPU time and furthermore needs only to be done once for a given molecular system at a specified temperature. Using these as input data, the remaining calculations of the line shapes and corresponding absorption for given potential parameters become straightforward. The formalism is applied in the present paper for linear molecular systems and sample calculations for CO2-CO2 and CO2-N-2 are presented. To our knowledge, these are the first, first-principle calculations for the far-wing line shape of CO2 except for the much simpler CO2-rare gas systems. (C) 1998 American Institute of Physics. [S0021-9606(98)01809-1]. C1 Columbia Univ, Dept Appl Phys, New York, NY 10025 USA. NASA, Goddard Space Flight Ctr, Inst Space Studies, New York, NY 10025 USA. Univ Alabama, Dept Phys & Astron, Tuscaloosa, AL 35487 USA. RP Ma, Q (reprint author), Columbia Univ, Dept Appl Phys, 2880 Broadway, New York, NY 10025 USA. NR 24 TC 20 Z9 23 U1 0 U2 0 PU AMER INST PHYSICS PI WOODBURY PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 USA SN 0021-9606 J9 J CHEM PHYS JI J. Chem. Phys. PD MAR 1 PY 1998 VL 108 IS 9 BP 3386 EP 3399 DI 10.1063/1.475774 PG 14 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA YZ048 UT WOS:000072215000003 ER PT J AU Marshak, A Davis, A Wiscombe, W Ridgway, W Cahalan, R AF Marshak, A Davis, A Wiscombe, W Ridgway, W Cahalan, R TI Biases in shortwave column absorption in the presence of fractal clouds SO JOURNAL OF CLIMATE LA English DT Article ID SOLAR-RADIATION ABSORPTION; EXTENDED WATER CLOUDS; STRATOCUMULUS CLOUDS; INHOMOGENEOUS ATMOSPHERES; AIRCRAFT MEASUREMENTS; PARAMETERIZATION; CLIMATE; ALBEDO; MODELS; SATELLITE AB In this paper, the effect of cloud structure on column absorption by water vapor is investigated. Radiative fluxes above and below horizontally inhomogeneous liquid water clouds are computed using an efficient Monte Carlo technique, the independent pixel approximation, and plane-parallel theory. Cloud inhomogeneity is simulated by two related fractal models that use bounded cascades for the horizontal distribution of optical depth. The first ("clumpy") model has constant cloud top and base, hence a constant geometrical thickness but varying extinction; the second ("bumpy") model has constant extinction and cloud base, hence variable cloud-top and geometrical thickness. The spectral range between 0.9 and 1.0 mu m (with strong water vapor absorption and negligible cloud liquid water absorption) is selected for a detailed study, not only of domain-averaged quantities, but also radiation fields. Column-absorption fields are calculated as the difference between the two net fluxes above and below clouds. It is shown that 1) redistribution of cloud liquid water decreases column absorption, that is, plane-parallel absorption is larger than the independent pixel approximation one by 1%-3%; 2) 3D radiative effects enhance column absorption by about 0.6% for the clumpy model and 2% for the bumpy model, that is, Monte Carlo absorption is larger than independent pixel approximation absorption-this effect is most pronounced for the bumpy cloud model at solar zenith angle approximate to 45 degrees; and 3) plane-parallel absorption is larger than 3D Monte Carlo absorption for high solar elevations and nearly equal to it for low solar elevations. Thus, for extended clouds of thickness 1-2 km or less, in an important water vapor absorption band (0.94 mu m), the authors do not find a significant enhancement of cloud absorption due to horizontal inhomogeneity. C1 NASA, Goddard Space Flight Ctr, Climate & Radiat Branch, Greenbelt, MD 20771 USA. RP NASA, Goddard Space Flight Ctr, Climate & Radiat Branch, Code 913, Greenbelt, MD 20771 USA. EM marshak@climate.gsfc.nasa.gov RI Cahalan, Robert/E-3462-2012; Wiscombe, Warren/D-4665-2012; Marshak, Alexander/D-5671-2012 OI Cahalan, Robert/0000-0001-9724-1270; Wiscombe, Warren/0000-0001-6844-9849; NR 46 TC 39 Z9 41 U1 0 U2 4 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 USA SN 0894-8755 EI 1520-0442 J9 J CLIMATE JI J. Clim. PD MAR PY 1998 VL 11 IS 3 BP 431 EP 446 DI 10.1175/1520-0442(1998)011<0431:BISCAI>2.0.CO;2 PG 16 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA ZF338 UT WOS:000072887500008 ER PT J AU Knudsen, DJ Clemmons, JH Wahlund, JE AF Knudsen, DJ Clemmons, JH Wahlund, JE TI Correlation between core ion energization, suprathermal electron bursts, and broadband ELF plasma waves SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID LOWER HYBRID ACCELERATION; KINETIC ALFVEN WAVES; CUSP CLEFT; SATELLITE-OBSERVATIONS; MULTICOMPONENT PLASMA; CYCLOTRON-RESONANCE; SUPRAURORAL REGION; AURORAL IONOSPHERE; TOPSIDE IONOSPHERE; FREQUENCY WAVES AB Observations of the lowest energy or core ions provide a particularly sensitive measure of the early stages of auroral ion energization. Freja satellite observations of 0-20 eV core ions in the topside auroral ionosphere and cusp/cleft show signs of heating within both regions of VLF hiss and broadband ELF plasma waves. However, heating to several eV or more is associated predominantly with the ELF waves. A correlation analysis of wave and core ion data formed from orbital segments shows that, on average, correlations are highest for wave frequencies below several hundred Hz, and less at VLF hiss frequencies. A similar analysis,shows a higher correlation between electron precipitation and ion heating for electron energies below several hundred eV (i.e., the energies associated with suprathermal electron bursts) and a lower correlation above the 1 keV energies associated with auroral inverted-V's. Signs of core ion heating begin to appear when wave power at the O+ gyrofrequency exceeds about 10(-3) (mV m(-1))(2)/Hz, and when the integrated field-aligned electron flux exceeds a few times 10 cm(-2) s(-1) sr(-1). This electron energy flux threshold is at least an order of magnitude lower than previously inferred from earlier studies comparing suprathermal electron fluxes and energetic ions. Almost all observed heating events occur during enhanced or active geomagnetic conditions; i.e., K-p greater than or equal to 4. While the most intense core ion heating is correlated with broadband ELF waves, we also present one example of weak ion heating of a few eV in a region of VLF auroral hiss. C1 Univ Calgary, Dept Phys & Astron, Calgary, AB T2N 1N4, Canada. Swedish Inst Space Phys, Uppsala Div, S-75591 Uppsala, Sweden. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Natl Res Council Canada, Ottawa, ON, Canada. RP Knudsen, DJ (reprint author), Univ Calgary, Dept Phys & Astron, 2500 Univ Dr NW, Calgary, AB T2N 1N4, Canada. EM knud-sen@phys.ucalgary.ca; james.clemmons@aero.org; jwe@irfu.se NR 58 TC 80 Z9 79 U1 1 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 MAR 1 PY 1998 VL 103 IS A3 BP 4171 EP 4186 DI 10.1029/97JA00696 PG 16 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZA782 UT WOS:000072401200021 ER PT J AU Gary, JB Zanetti, LJ Anderson, BJ Potemra, TA Clemmons, JH Winningham, JD Sharber, JR AF Gary, JB Zanetti, LJ Anderson, BJ Potemra, TA Clemmons, JH Winningham, JD Sharber, JR TI Identification of auroral oval boundaries from in situ magnetic field measurements SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID PARTICLE ENVIRONMENT MONITOR; ALIGNED CURRENTS; FREJA; DISTRIBUTIONS; SATELLITE; SYSTEM; STORM; WAVES AB We have conducted an investigation into the relationship between magnetic field fluctuations below 100 Hz observed with the UARS and Freja magnetic field experiments and concluded that increases in this "ac" activity serve as an excellent indicator of the boundaries of large-scale field-aligned current systems. Magnetic field fluctuations in these regions generally correspond to increased electron fluxes at energies below roughly 2 keV. Using a single equatorward boundary crossing as a reference point, the statistical field-aligned current pattern of Iijima and Potemra [1978] for disturbed magnetic conditions can be extrapolated to provide an estimate of the global position of the auroral oval. Real-time in situ magnetic field measurements from high-latitude spacecraft can be used to provide a quick, simple, locator of the equatorward boundaries of the large-scale field-aligned currents, accurate to within +/- 2 degrees in latitude. A proof-of-concept implementation of this technique has been performed using magnetic field data acquired by the Freja spacecraft. Development of the automated detection algorithm, essentially a measurement of the standard deviation of the low-frequency magnetic field measurements, was aided by using UARS magnetic field data. The UARS data were binned by MLT and magnetic latitude for varying Kp conditions and demonstrated observable ac boundaries at all local times and all Kp levels. In a separate statistical study consisting of 96 UARS high-latitude observations, we determined the differences between the observed and estimated equatorward boundaries of the large-scale field-aligned current system for each high-altitude pass. This difference was within 2 deg of latitude in 53 of 96 cases, with 84 of 96 cases within 5 deg. C1 Johns Hopkins Univ, Appl Phys Lab, Laurel, MD 20723 USA. SW Res Inst, San Antonio, TX 78284 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Gary, JB (reprint author), Johns Hopkins Univ, Appl Phys Lab, Johns Hopkins Rd, Laurel, MD 20723 USA. RI Anderson, Brian/I-8615-2012 NR 19 TC 14 Z9 14 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 MAR 1 PY 1998 VL 103 IS A3 BP 4187 EP 4197 DI 10.1029/97JA02395 PG 11 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZA782 UT WOS:000072401200022 ER PT J AU Olsson, A Andersson, L Eriksson, AI Clemmons, J Erlandsson, RE Reeves, G Hughes, T Murphee, JS AF Olsson, A Andersson, L Eriksson, AI Clemmons, J Erlandsson, RE Reeves, G Hughes, T Murphee, JS TI Freja studies of the current-voltage relation in substorm-related events SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID PARTICLE-PRECIPITATION; ELECTRIC-FIELDS; POTENTIAL DIFFERENCE; HIGH-ALTITUDE; AURORA; MODEL; SATELLITE; FLUXES; DISTRIBUTIONS; SURGE AB Field-aligned currents and electrostatic potentials play important roles in the coupling between the magnetosphere and the ionosphere. If one assumes that the ionosphere-magnetosphere potential difference is mainly due to the mirror force, one can use the single particle adiabatic kinetic theory to describe the system. From this theory, a linear relationship j(parallel to)=KV between field-aligned current density j(parallel to) and potential drop V along the same field line can be derived, provided that the potential drop is not too large and not too small. With rare exceptions, observational tests of this relation have mainly concentrated on quiet magnetospheric situations, with acceleration voltages V less than or similar to 5 kV. Here we use observations from the Freja satellite of precipitating auroral electrons at 1.700 km altitude to study substorm related events, with acceleration voltages up to 20 keV. The observations are found to be consistent with a linear current-voltage relation even in these conditions, although with values of the field aligned K lower than previously reported (1-5 x 10(-11) S/m(2)). This can be explained by lower densities and higher characteristic electron energies in the magnetospheric source region of the precipitating electrons. We analyze the data by three different methods, which are all found to be in general agreement. The results are in agreement with a previous study [Olsson et al., 1996 b], where the spectra of precipitating electrons were indirectly infered by inversion of data from the EISCAT incoherent scatter radar, thereby validating the use of radar data for studies of auroral electrons. Comparisons with previous studies are made, emphasizing the dependence of the results on the type of auroral structure and magnetospheric conditions. C1 Swedish Inst Space Phys, Uppsala Div, S-75591 Uppsala, Sweden. Swedish Inst Space Phys, Kiruna Div, S-98128 Kiruna, Sweden. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Johns Hopkins Univ, Appl Phys Lab, Laurel, MD USA. Univ Calif Los Alamos Natl Lab, Los Alamos, NM USA. Natl Res Council Canada, Herzberg Inst Astrophys, Ottawa, ON K1A 0R6, Canada. Univ Calgary, Dept Phys & Astron, Calgary, AB T2N 1N4, Canada. RP Olsson, A (reprint author), Swedish Inst Space Phys, Uppsala Div, S-75591 Uppsala, Sweden. EM ao@irfu.se; laila@irf.se; jhc@leppow.gsfc.nasa.gov; boberlandson@spacemail.jhuapl.edu; reeves@Lanl.gov; hughes@canott.sp-agency.ca; mur-phree@.phys.ucalgary.ca RI Eriksson, Anders/C-2887-2009; Reeves, Geoffrey/E-8101-2011 OI Reeves, Geoffrey/0000-0002-7985-8098 NR 38 TC 32 Z9 32 U1 0 U2 3 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA J9 J GEOPHYS RES-SPACE JI J. Geophys. Res-Space Phys. PD MAR 1 PY 1998 VL 103 IS A3 BP 4285 EP 4301 DI 10.1029/97JA00560 PG 17 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZA782 UT WOS:000072401200029 ER PT J AU Wahlund, JE Eriksson, AI Holback, B Boehm, MH Bonnell, J Kintner, PM Seyler, CE Clemmons, JH Eliasson, L Knudsen, DJ Norqvist, P Zanetti, LJ AF Wahlund, JE Eriksson, AI Holback, B Boehm, MH Bonnell, J Kintner, PM Seyler, CE Clemmons, JH Eliasson, L Knudsen, DJ Norqvist, P Zanetti, LJ TI Broadband ELF plasma emission during auroral energization 1. Slow ion acoustic waves SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID WEAK DOUBLE-LAYERS; KINETIC ALFVEN WAVES; FREJA SATELLITE-OBSERVATIONS; HIGH-LATITUDE IONOSPHERE; OXYGEN CYCLOTRON WAVES; SOLITARY WAVES; MAGNETIZED PLASMA; FIELD LINES; ELECTROSTATIC SHOCKS; POLAR MAGNETOSPHERE AB High-resolution measurements by the Freja spacecraft of broadband extremely low frequency (BB-ELF) emission from de up to the lower hybrid frequency (a few kHz) are reported from regions of transverse ion acceleration (TAI) and broad-energy suprathermal electron bursts (STEB) occuring in the topside ionospheric auroral regions. A gradual transition of the broadband emission occurs near the local O+ cyclotron frequency (f(O+) approximate to 25 Hz) from predominantly electromagnetic below this frequency to mostly electrostatic above this frequency. The emission below 200 Hz often reach amplitudes up to several hundred mV/m and density perturbations (delta n/n) of tens of %. An improved analysis technique is presented, based on the quantity \delta E/(delta n/n)\ versus frequency and applied to the Freja plasma, wave measurements. The method can be used to infer the dispersion relation for the measured emission as well as give estimates of the thermal plasma temperatures. The BB-ELF emission is found to consist partly of plasma waves with an ion Boltzmann response, which is interpreted as originating from the so-called slow ion acoustic wave mode (SIA). This emission is associated with large bulk ion (O+) temperatures of up to 30 eV and low electron temperatures (1-2 eV) and therefore occurs during conditions when T-e/T-i much less than 1. The BB-ELF emissions also contain other wave mode components, which are not equally easy to identify, even though it is reasonably certain that ion acoustic/cyclotron waves are measured. The ion Boltzmann component is characterized by a dominantly perpendicular polarization with respect to the Earth's magnetic field direction and a small magnetic component with amplitudes around 0.1-1 nT. The ion Boltzmann component dominates the lower-frequency part (30-400 Hz) of the BB-ELF emissions. The BB-ELF emission have often an enhanced spectral power when certain waveform signatures, interpreted as solitary kinetic Alfven waves (SKAW), or when large-amplitude electric fields, possibly related to black aurora, are encountered in regions often associated with large-scale auroral density depletions. A scenario where the SKAW provides the original free energy and via the BB-ELF emission causes intense transverse ion heating (TAI) is suggested. C1 Swedish Inst Space Phys, Uppsala Div, S-75591 Uppsala, Sweden. Lockheed Martin Palo Alto Res Lab, Palo Alto, CA 94304 USA. Cornell Univ, Sch Elect Engn, Ithaca, NY 14853 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Swedish Inst Space Phys, Kiruna Div, S-98128 Kiruna, Sweden. Univ Calgary, Dept Phys & Astron, Calgary, AB T2N 1N4, Canada. Swedish Inst Space Phys, Umea Div, Umea, Sweden. Johns Hopkins Univ, Appl Phys Lab, Laurel, MD 20723 USA. RP Wahlund, JE (reprint author), Swedish Inst Space Phys, Kiruna Div, S-98128 Kiruna, Sweden. RI Eriksson, Anders/C-2887-2009 NR 96 TC 96 Z9 97 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 MAR 1 PY 1998 VL 103 IS A3 BP 4343 EP 4375 DI 10.1029/97JA02008 PG 33 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZA782 UT WOS:000072401200033 ER PT J AU Sundaram, AK Fairfield, DH Vassiliadis, D AF Sundaram, AK Fairfield, DH Vassiliadis, D TI The excitation of lower hybrid waves driven by the del B effect in the current sheet SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID NEUTRAL SHEET; PLASMA SHEET; GEOTAIL OBSERVATIONS; DISTANT MAGNETOTAIL; DRIFT INSTABILITY; BOUNDARY; TURBULENCE AB We have investigated the excitation of electrostatic and electromagnetic lower hybrid waves in the magnetic field reversal region of the plasma sheet using a two-fluid approach. We consider a two-dimensional tail configuration that includes the B-x and B-z magnetic field components and examine the nonlocal properties of lower hybrid modes near the weak field region, where the field B-x(z) reverses sign. We have shown that an electrostatic lower hybrid mode is excited by the magnetic field gradient while electromagnetic modes are driven unstable by the combined effects of the magnetic field gradient and the electron fluid drift across the B-x field. We have shown that the electrostatic and electromagnetic lower hybrid modes grow in a few milliseconds and a few tens of milliseconds, respectively, the former for wavelengths shorter than the current sheet width (that is, for k(y) lambda greater than or equal to 1 where lambda is the current sheet width) and the latter for long wavelengths (k(y) lambda much less than 1). C1 NASA, Goddard Space Flight Ctr, Extraterr Phys Lab, Greenbelt, MD 20771 USA. Hughes STX Corp, Greenbelt, MD USA. Univ Space Res Assoc, Greenbelt, MD USA. RP NASA, Goddard Space Flight Ctr, Extraterr Phys Lab, Code 695, Greenbelt, MD 20771 USA. EM ysaks@lepvax.gsfc.nasa.gov NR 18 TC 6 Z9 6 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-9380 EI 2169-9402 J9 J GEOPHYS RES-SPACE JI J. Geophys. Res-Space Phys. PD MAR 1 PY 1998 VL 103 IS A3 BP 4649 EP 4656 DI 10.1029/97JA03087 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZA782 UT WOS:000072401200055 ER PT J AU Goldstein, R Neugebauer, M Clay, D AF Goldstein, R Neugebauer, M Clay, D TI A statistical study of coronal mass ejection plasma flows SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID INTER-PLANETARY SHOCK; COSMIC-RAY DECREASES; SOLAR-WIND; MAGNETIC LOOP; INTERPLANETARY SHOCK; FIELD STRUCTURE; EVENTS; TEMPERATURE; PARTICLE; HELIOS AB This is a report on the results of a statistical study of plasma flow characteristics before, during, and after coronal mass ejections (CMEs) observed by the instruments on board the ISEE3 spacecraft located near Earth's L1 libration point during the period 1978 to 1980. We have used parametric relationships between plasma properties (such as flow speed and proton temperature) to help distinguish between transient flow resulting from CMEs and more quiescent or quasistatic solar wind flows. A superposed epoch analysis of 29 CMEs during the period studied shows that the transient plasma flow, as we have defined it, often begins earlier and extends later than the start and end times of the CMEs based on such criteria as bidirectional flow of suprathermal electrons or energetic protons. Since the bidirectional flow is tied to the magnetic topology of the CME, our results indicate that plasma having transient flow characteristics (as we have defined them) may extend both in front of as well as behind any magnetically closed region within the CME. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Goldstein, R (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr,MS 169-506, Pasadena, CA 91109 USA. EM rgoldstein@jplsp.jpl.nasa.gov; mneugeb@jplsp.jpl.nasa.gov; dclay@jplsp.jpl.nasa.gov NR 34 TC 15 Z9 15 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 MAR 1 PY 1998 VL 103 IS A3 BP 4761 EP 4766 DI 10.1029/97JA03663 PG 6 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZA782 UT WOS:000072401200066 ER PT J AU Gonzalez-Esparza, JA Neugebauer, M Smith, EJ Phillips, JL AF Gonzalez-Esparza, JA Neugebauer, M Smith, EJ Phillips, JL TI Radial evolution of ejecta characteristics and transient shocks: Ulysses in-ecliptic observations SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID CORONAL MASS EJECTIONS; SOLAR-WIND; MAGNETIC CLOUDS; INTERPLANETARY SHOCKS; EVENTS; WAVES; 1-AU; AU AB During its travel to Jupiter, Ulysses detected 25 ejecta and 32 transient forward shocks (TFS), and in the first 3 months after the Jupiter flyby Ulysses detected 9 ejecta and 5 TFS. Half of these ejecta (17) were associated with TFS. We identified the ejecta using bidirectional streaming of suprathermal electrons accompanied by other plasma cloud signatures. This data set of 34 ejecta at low latitudes (+/-10 degrees) complements previous statistical studies of ejecta and TFS within 1 AU and allows us to study their heliocentric evolution from 1 to 5.4 AU. We used solar wind plasma data to analyze dynamic aspects of these events. In general, ejecta associated with TFS and ejecta without shocks had similar characteristics. However: ejecta associated with TFS had fronts propagating faster than the ambient solar wind, while ejecta not associated with shocks had fronts propagating at about the same speed as the ambient solar wind. The ejecta radial width did not present a clear statistical tendency to expand with heliocentric distance, and the ejecta mean flux density did not decrease more quickly than the square of the distance from the Sun. These two results might suggest that the rate of expansion of ejecta from 1 to 5 AU is less than the rate of expansion within 1 AU. However, a limitation of this analysis is the ambiguity of comparing ejecta parameters that can vary depending on different aspects and with heliocentric distance. Only about 40% of the ejecta associated with TFS had leading edges propagating supermagnetosonically with respect to the ambient solar wind. Ejecta with large radial widths were faster than small ejecta. Stronger TFS (higher Mach numbers) were followed by larger ejecta. C1 Univ Nacl Autonoma Mexico, Inst Geofis, Mexico City 04510, DF, Mexico. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. RP Gonzalez-Esparza, JA (reprint author), Univ Nacl Autonoma Mexico, Inst Geofis, Ciudad Univ, Mexico City 04510, DF, Mexico. EM americo@fis-esp.igeofcu.unam.mx; mneugeb@jplsp.jpl.nasa.gov; esmith@jplsp.jpl.nasa.gov; JLPhilli@ems.jsc.nasa.gov RI Gonzalez-Esparza, J. Americo/A-6720-2013 NR 16 TC 8 Z9 8 U1 0 U2 2 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0148-0227 J9 J GEOPHYS RES-SPACE JI J. Geophys. Res-Space Phys. PD MAR 1 PY 1998 VL 103 IS A3 BP 4767 EP 4773 DI 10.1029/97JA03271 PG 7 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZA782 UT WOS:000072401200067 ER PT J AU Allan, BG Holt, M Packard, A AF Allan, BG Holt, M Packard, A TI Simulation of a controlled airfoil with jets SO JOURNAL OF GUIDANCE CONTROL AND DYNAMICS 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 AB Numerical simulations of a two-dimensional airfoil, controlled by an applied moment in pitch and an airfoil controlled by Sets, were investigated, These simulations couple the Reynolds-averaged Navier-Stokes equations and Euler's equations of rigid body motion, along with an active control system, Controllers for both systems were designed to track altitude commands and were evaluated by simulating a closed-loop altitude step response using the coupled system. The airfoil controlled by a pitching moment used an optimal state feedback controller, A closed-loop simulation of the airfoil with an applied moment showed that the trajectories compared very well with quasisteady aerodynamic theory, providing a measure of validation. The airfoil with jets used a controller designed by robust control methods, A linear plant model for this system was identified using open-loop data generated by the nonlinear coupled system. A closed-loop simulation of the airfoil with jets showed good tracking of an altitude command. This simulation also showed oscillations in the control input as a result of dynamics not accounted for in the control design. This research work demonstrates how computational fluid dynamics, coupled with rigid-body dynamics, and a control law can be used to prototype control systems in problematic nonlinear flight regimes. C1 NASA, Langley Res Ctr, Inst Comp Appl Sci & Engn, Hampton, VA 23681 USA. Univ Calif Berkeley, Dept Mech Engn, Berkeley, CA 94720 USA. RP Allan, BG (reprint author), NASA, Langley Res Ctr, Inst Comp Appl Sci & Engn, Hampton, VA 23681 USA. NR 18 TC 0 Z9 0 U1 1 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 MAR-APR PY 1998 VL 21 IS 2 BP 257 EP 263 DI 10.2514/2.4251 PG 7 WC Engineering, Aerospace; Instruments & Instrumentation SC Engineering; Instruments & Instrumentation GA ZA178 UT WOS:000072336800008 ER PT J AU Gawronski, W Parvin, B AF Gawronski, W Parvin, B TI Radiotelescope low-rate tracking using dither SO JOURNAL OF GUIDANCE CONTROL AND DYNAMICS LA English DT Article; Proceedings Paper CT AIAA Guidance, Navigation, and Control Conference CY AUG 11-13, 1997 CL NEW ORLEANS, LOUISIANA SP Amer Inst Aeronaut & Astronaut ID SLIP FRICTION COMPENSATION; STICK-SLIP; MODEL C1 CALTECH, Jet Prop Lab, Av Syst Engn Sect, Pasadena, CA 91109 USA. RP Gawronski, W (reprint author), CALTECH, Jet Prop Lab, Av Syst Engn Sect, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 11 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 0731-5090 J9 J GUID CONTROL DYNAM JI J. Guid. Control Dyn. PD MAR-APR PY 1998 VL 21 IS 2 BP 349 EP 351 DI 10.2514/2.7605 PG 3 WC Engineering, Aerospace; Instruments & Instrumentation SC Engineering; Instruments & Instrumentation GA ZA178 UT WOS:000072336800020 ER PT J AU Choudhury, BJ DiGirolamo, NE AF Choudhury, BJ DiGirolamo, NE TI A biophysical process-based estimate of global land surface evaporation using satellite and ancillary data - I. Model description and comparison with observations SO JOURNAL OF HYDROLOGY LA English DT Article DE evaporation; biophysical model; satellite data ID TROPICAL RAIN-FOREST; SOIL-WATER DEFICITS; CANOPY PHOTOSYNTHESIS; AMAZONIAN FOREST; EVAPOTRANSPIRATION; BALANCE; RADIATION; TRANSPIRATION; VEGETATION; DYNAMICS AB A biophysical process-based model is used to estimate transpiration, soil evaporation and interception over the global land surface for a 24-month period (January 1987 to December 1988). The model parameters are determined from published records, and their geographical distribution has been prescribed according to land use and land cover data. Satellite observations are used to obtain fractional vegetation cover, isothermal net and photosynthetically active radiation, air temperature and vapor pressure deficit. Precipitation and friction velocity are derived as blended products (disaggregated and assimilated data). The calculated seasonal and geographical variations of evaporation, net radiation and soil moisture are in good agreement with field observations, catchment water balance data, and atmospheric water budget analysis; explained variances being greater than 75%. Uncertainties in the estimated evaporation are about 15 and 20%, respectively, for annual and monthly values. (C) 1998 Elsevier Science B.V. All rights reserved. C1 NASA, Goddard Space Flight Ctr, Hydrol Sci Branch Hydrospher Proc, Greenbelt, MD 20771 USA. Sci Syst & Applicat Inc, Lanham, MD 20706 USA. RP Choudhury, BJ (reprint author), NASA, Goddard Space Flight Ctr, Hydrol Sci Branch Hydrospher Proc, Code 974, Greenbelt, MD 20771 USA. NR 95 TC 69 Z9 73 U1 4 U2 15 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0022-1694 J9 J HYDROL JI J. Hydrol. PD MAR PY 1998 VL 205 IS 3-4 BP 164 EP 185 DI 10.1016/S0022-1694(97)00147-9 PG 22 WC Engineering, Civil; Geosciences, Multidisciplinary; Water Resources SC Engineering; Geology; Water Resources GA ZK229 UT WOS:000073298300002 ER PT J AU Choudhury, BJ DiGirolamo, NE Susskind, J Darnell, WL Gupta, SK Asrar, G AF Choudhury, BJ DiGirolamo, NE Susskind, J Darnell, WL Gupta, SK Asrar, G TI A biophysical process-based estimate of global land surface evaporation using satellite and ancillary data - II. Regional and global patterns of seasonal and annual variations SO JOURNAL OF HYDROLOGY LA English DT Article DE global; evaporation; evaporative fraction; transpiration; satellite data ID WATER-BALANCE; RAIN-FOREST; SOIL; EVAPOTRANSPIRATION; TRANSPIRATION; RUNOFF; BASINS; ENERGY; CYCLE AB A process-based biophysical model of evaporation described previously was run using spatially representative data to calculate global fields of monthly total transpiration, soil evaporation and interception for a period of 24 months (January 1987 to December 1988). Solution of the energy balance equation provided net radiation and sensible heat flux, complementing the evaporative flux. The zonally averaged (area weighted 5 degrees latitude bands) values of annual total evaporation and evaporative fraction (ratio of evaporation and net radiation) are in broad agreement with previous estimates. Transpiration was found to be the dominant component of annual total evaporation in 20 out of the 28 latitude bands. partitioning of annual total evaporation over the global land area is calculated to be, 52% transpiration, 28% soil evaporation and 20% interception. Seasonal variations of total evaporation and its components are presented for some specific types of vegetation (e.g., tundra, taiga, rainforest, crop land) and compared with field observations. (C) 1998 Elsevier Science B.V. All rights reserved. C1 NASA, Goddard Space Flight Ctr, Hydrol Sci Branch, Lab Hydrospher Proc, Greenbelt, MD 20771 USA. Sci Syst & Applicat Inc, Lanham, MD 20706 USA. NASA, Goddard Space Flight Ctr, Satellite Data Utilizat Off, Atmospheres Lab, Greenbelt, MD 20771 USA. NASA, Langley Res Ctr, Div Atmospher Sci, Hampton, VA 23681 USA. Analyt Serv & Mat Inc, Hampton, VA 23666 USA. NASA, Earth Observing Syst Off, Washington, DC 20546 USA. RP Choudhury, BJ (reprint author), NASA, Goddard Space Flight Ctr, Hydrol Sci Branch, Lab Hydrospher Proc, Greenbelt, MD 20771 USA. NR 46 TC 41 Z9 43 U1 0 U2 11 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0022-1694 J9 J HYDROL JI J. Hydrol. PD MAR PY 1998 VL 205 IS 3-4 BP 186 EP 204 DI 10.1016/S0022-1694(97)00149-2 PG 19 WC Engineering, Civil; Geosciences, Multidisciplinary; Water Resources SC Engineering; Geology; Water Resources GA ZK229 UT WOS:000073298300003 ER PT J AU Choi, SR Salem, JA Nemeth, NN AF Choi, SR Salem, JA Nemeth, NN TI High-temperature slow crack growth of silicon carbide determined by constant-stress-rate and constant-stress testing SO JOURNAL OF MATERIALS SCIENCE LA English DT Article ID ELEVATED-TEMPERATURES; LIFE PREDICTION; PROPAGATION; STRENGTH; NITRIDE AB High-temperature slow-crack-growth behaviour of hot-pressed silicon carbide was determined using both constant-stress-rate ("dynamic fatigue") and constant-stress ("static fatigue") testing in flexure at 1300 degrees C in air. Slow crack growth was found to be a governing mechanism associated with failure of the material. Four estimation methods such as the individual data, the Weibull median, the arithmetic mean and the median deviation methods were used to determine the slow crack growth parameters. The four estimation methods were in good agreement for the constant-stress-rate testing with a small variation in the slow-crack-growth parameter, n, ranging from 28 to 36. By contrast, the variation in n between the four estimation methods was significant in the constant-stress testing with a somewhat wide range of n=16 to 32. (C) 1998 Chapman & Hall. C1 Cleveland State Univ, Cleveland, OH 44115 USA. NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. RP Choi, SR (reprint author), Cleveland State Univ, Cleveland, OH 44115 USA. NR 19 TC 9 Z9 9 U1 0 U2 1 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 MAR 1 PY 1998 VL 33 IS 5 BP 1325 EP 1332 DI 10.1023/A:1004358516776 PG 8 WC Materials Science, Multidisciplinary SC Materials Science GA YW466 UT WOS:000071938500028 ER PT J AU Tackman, GE Currey, DR Bills, BG James, TS AF Tackman, GE Currey, DR Bills, BG James, TS TI Paleoshoreline evidence for postglacial tilting in Southern Manitoba SO JOURNAL OF PALEOLIMNOLOGY LA English DT Article; Proceedings Paper CT Special Session on Physical Environment and History of the Lake Winnipeg Basin at the Geological-Association-of-Canada Meeting CY MAY 27-29, 1996 CL WINNIPEG, CANADA SP Geol Assoc Canada DE postglacial rebound; Lake Winnipegosis; Dauphin Lake; Lake Agassiz ID RADIOCARBON TIME SCALE; AD 1950-500 BC; CALIBRATION; CORALS; AGES AB Detailed air photo interpretation and four seasons of field mapping and surveying in southern Manitoba have revealed that the once-level paleoshorelines of Lake Winnipegosis and Dauphin Lake and the Burnside shoreline of former Lake Agassiz have been tilted up to the northeast by postglacial differential rebound. Our investigation has also revealed that Lake Winnipegosis has the best preserved paleoshoreline record of any of the large lakes in southern Manitoba, including lakes Winnipeg and Manitoba. This is because northeasterly uptilting shifts the region's lakes to the southwest. Lakes with southern outlets, like Lake Winnipegosis, undergo general regression as the outlet is lowered relative to the rest of the basin. Lakes with northern outlets, like lakes Winnipeg and Manitoba, undergo general transgression as northeasterly uptilting raises the outlet relative to the rest of the basin. Along the northeastern shore of Lake Winnipegosis a staircase of at least 32 abandoned Winnipegosis shorelines exists that is consistent with northeasterly tilting. The Dawson level represents the major mid-Holocene highstand on Lake Winnipegosis. It persisted for about 500 years, peaking at 5290 C-14 yr B.P. (early Dawson) and then falling about 3 m by 4740 C-14 yr B.P. (late Dawson). The early Dawson shoreline is tilted at 13.5 cm km(-1) in a direction N24.3 degrees E. Three other shorelines informally named shoreline 4, shoreline 3, and shoreline 2 are also tilted up to the northeast. Their radiocarbon ages (and slopes in cm km(-1)) are 3330 yr B.P. (2.2), 1510 yr B.P. (1.3), and 1080 yr B.P. (0.7), respectively. On Dauphin Lake shoreline IV is the oldest level mapped for this study. It has a C-14 age of 7910 yr B.P. and is tilted at 21.7 cm km(-1) in a direction N44.4 degrees E. The Id shoreline marks the major mid-Holocene highstand for Dauphin Lake. It peaked at 4640 C-14 yr B.P. followed by a rapid decline of about 1 m to the Ib shoreline, which is dated at 4320 C-14 yr B.P. Id is tilted up at 8.8 cm km(-1) in a direction N53.4 degrees E. The next major shoreline is Ia3 which has a C-14 age of 3020 yr B.P. and is tilted up at 5.3 cm km(-1) in a direction N62.3 degrees E. Tilt directions are significantly more easterly for the Dauphin Lake shorelines than those from Lake Winnipegosis or any of the much older Lake Agassiz shorelines. Taken together, the Winnipegosis and Dauphin isobases indicate that the direction of tilt in southern Manitoba is more complex than a simple uni-directional pattern. The observed pattern of tilting for paleoshorelines in southern Manitoba agrees better with predictions derived from the recently revised loading history model ICE-4G than with those from its predecessor ICE-3G. In general, the calculated tilt based on the ICE-3G load tends to exceed the observed tilt, while ICE-4G tends to underestimate it. Both ice load models appear to disagree most with our observed tilts in this region during the interval before about 9000 cal yr B.P., when deglaciation was proceeding rapidly and the large water load associated with Lake Agassiz covered the region. Because both of these ice load models have been estimated mainly from a global data set of relative sea level curves from marine coast sites, it is not unexpected that model tilts derived from them do not agree well with observations in the North American continental interior. The pattern of postglacial crustal deformation for southern Manitoba described in this paper could be used to further refine ice load models for the North American continental interior. C1 Univ Utah, Limneotecton Lab, Salt Lake City, UT 84112 USA. NASA, Goddard Space Flight Ctr, Geodynam Branch, Greenbelt, MD 20771 USA. Johns Hopkins Univ, Dept Earth & Planetary Sci, Baltimore, MD 21218 USA. Geol Survey Canada, Sidney, BC V8L 4B2, Canada. RP Tackman, GE (reprint author), Univ Utah, Limneotecton Lab, 270 OSH, Salt Lake City, UT 84112 USA. RI Bills, Bruce/C-1156-2008; James, Thomas/D-9301-2013 OI James, Thomas/0000-0001-7321-047X NR 37 TC 12 Z9 13 U1 0 U2 0 PU KLUWER ACADEMIC PUBL PI DORDRECHT PA SPUIBOULEVARD 50, PO BOX 17, 3300 AA DORDRECHT, NETHERLANDS SN 0921-2728 J9 J PALEOLIMNOL JI J. Paleolimn. PD MAR PY 1998 VL 19 IS 3 BP 343 EP 363 PG 21 WC Environmental Sciences; Geosciences, Multidisciplinary; Limnology SC Environmental Sciences & Ecology; Geology; Marine & Freshwater Biology GA ZN647 UT WOS:000073667600011 ER PT J AU Carr, ME AF Carr, ME TI A numerical study of the effect of periodic nutrient supply on pathways of carbon in a coastal upwelling regime SO JOURNAL OF PLANKTON RESEARCH LA English DT Article ID SHORT-TERM VARIABILITY; SIZE-BASED DYNAMICS; PLANKTON FOOD WEBS; SOUTHERN BENGUELA; ANCHOR STATION; NORTHWEST AFRICA; ORGANIC-MATTER; PHYTOPLANKTON; SYSTEM; SIMULATION AB A size-based ecosystem model was modified to include periodic upwelling events and used to evaluate the effect of episodic nutrient supply on the standing stock, carbon uptake, and carbon how into mesozooplankton grazing and sinking flux in a coastal upwelling regime. Two ecosystem configurations were compared: a single food chain made up of net phytoplankton and mesozooplankton (one autotroph and one heterotroph, A1H1), and three interconnected food chains plus bacteria (three autotrophs and four heterotrophs, A3H4). The carbon pathways in the All-Il simulations were under stronger physical control than those of the A3H4 runs, where the small size classes are not affected by frequent upwelling events. In the more complex food web simulations, the microbial pathway determines the total carbon uptake and grazing rates, and regenerated nitrogen accounts for more than half of the total primary production for periods of 20 days or longer between events. By contrast, new production, export of carbon through sinking and mesozooplankton grazing are more important in the A1H1 simulations. In the A3H4 simulations, the turnover time scale of the autotroph biomass increases as the period between upwelling events increases, because of the larger contribution of slow-growing net phytoplankton. The upwelling period was characterized for three upwelling sites from the alongshore wind speed measured by the NASA Scatterometer (NSCAT) and the corresponding model output compared with literature data. This validation exercise for three upwelling sites and a downstream embayment suggests that standing stock, carbon uptake and size fractionation were best supported by the A3H4 simulations, while the simulated sinking fluxes are not distinguishable in the two configurations. C1 CALTECH, Jet Prop Lab MS 300 323, Pasadena, CA 91009 USA. RP Carr, ME (reprint author), CALTECH, Jet Prop Lab MS 300 323, 4800 Oak Grove Dr, Pasadena, CA 91009 USA. NR 49 TC 23 Z9 23 U1 0 U2 4 PU OXFORD UNIV PRESS PI OXFORD PA GREAT CLARENDON ST, OXFORD OX2 6DP, ENGLAND SN 0142-7873 J9 J PLANKTON RES JI J. Plankton Res. PD MAR PY 1998 VL 20 IS 3 BP 491 EP 516 DI 10.1093/plankt/20.3.491 PG 26 WC Marine & Freshwater Biology; Oceanography SC Marine & Freshwater Biology; Oceanography GA ZF441 UT WOS:000072897800007 ER PT J AU Reddy, DR Reddy, ES Moody, RE AF Reddy, DR Reddy, ES Moody, RE TI Aerodynamic shape optimization of a subsonic inlet using three-dimensional Euler computation SO JOURNAL OF PROPULSION AND POWER LA English DT Article AB A design optimization study of a subsonic inlet is presented where the peak Mach number at cruise condition on the inside of the inlet surface is the objective function to be minimized and inlet lip shape parameters are the design variables, The peak Mach number at takeoff, rolling takeoff, static, and crosswind conditions are constrained to an upper limit, The three-dimensional flowfield is predicted by the NPARC computational fluid dynamics code in Euler mode, A GRAPE-(grids about airfoils using Poisson's equation) based three-dimensional grid generator is employed to generate a C-grid around the inlet. Constrained numerical optimization is carried out by interfacing NPARC with the automated design synthesis optimization code, The constrained optimum is obtained by the method of feasible directions, The required gradients for optimization are computed via forward difference scheme. At the baseline (initial) design, takeoff, rolling takeoff, and crosswind conditions have their peak Mach numbers exceeding the upper bounds. However, at the constrained optimum design, only the upper limit on the takeoff peak Mach number is found to be critical with no appreciable change in cruise Mach number. C1 NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. NYMA Inc, Aeromech, Brook Pk, OH 44142 USA. Boeing Co, Prop Technol & Prod Dev, Seattle, WA 98124 USA. RP Reddy, DR (reprint author), NASA, Lewis Res Ctr, 21000 Brookpark Rd,M-S 5-11, Cleveland, OH 44135 USA. NR 27 TC 1 Z9 1 U1 0 U2 1 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0748-4658 J9 J PROPUL POWER JI J. Propul. Power PD MAR-APR PY 1998 VL 14 IS 2 BP 225 EP 233 DI 10.2514/2.5271 PG 9 WC Engineering, Aerospace SC Engineering GA ZB675 UT WOS:000072496300013 ER PT J AU King, MK AF King, MK TI Rocket propulsion strategy based on kinetic energy management SO JOURNAL OF PROPULSION AND POWER LA English DT Article C1 NASA, Washington, DC 20546 USA. RP King, MK (reprint author), NASA, 300 E St SW,Code UG, Washington, DC 20546 USA. NR 1 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 0748-4658 J9 J PROPUL POWER JI J. Propul. Power PD MAR-APR PY 1998 VL 14 IS 2 BP 270 EP 272 DI 10.2514/2.5277 PG 3 WC Engineering, Aerospace SC Engineering GA ZB675 UT WOS:000072496300019 ER PT J AU Devi, VM Benner, DC Smith, MAH Rinsland, CP AF Devi, VM Benner, DC Smith, MAH Rinsland, CP TI Air- and N-2-broadening coefficients and pressure-shift coefficients in the (CO2)-C-12-O-16 laser bands SO JOURNAL OF QUANTITATIVE SPECTROSCOPY & RADIATIVE TRANSFER LA English DT Article; Proceedings Paper CT 4th Conference on Atmospheric Spectroscopy Applications CY SEP 04-06, 1996 CL REIMS, FRANCE SP Int Radiat Commiss ID BROADENED LINEWIDTHS; CO2; ABSORPTION; 10.4-MU-M; INTENSITIES; TRANSITION; TEMPERATURES; FREQUENCIES; NITROGEN; REGION AB In this paper we report the pressure broadening and the pressure-induced line shift coefficients for 46 individual rovibrational lines in both the (CO2)-C-12-O-16 00(0)1-(10(0)0-02(0)0)(I) and 00(0)1-(10(0)0-02(0)0)(II) laser bands (laser band I centered at 960.959 cm(-1) and laser band II centered at 1063.735 cm(-1)) determined from spectra recorded with the McMath-Pierce Fourier transform spectrometer. The results were obtained from analysis of 10 long-path laboratory absorption spectra recorded at room temperature using a multispectrum nonlinear least-squares technique. Pressure effects caused by both air and nitrogen have been investigated. The air-broadening coefficients determined in this study agree well with the values in the 1996 HITRAN database; ratios and standard deviations of the ratios of the present air-broadening measurements to the 1996 HITRAN values for the two laser bands are: 1.005(15) for laser band I and 1.005(14) for laser band II. Broadening by nitrogen is 3 to 4% larger than that of air. The pressure-induced line shift coefficients are found to be transition dependent and different for the P-and R-branch lines with same J " value. No noticeable differences in the shift coefficients caused by air and nitrogen were found. The results obtained are compared with available values previously reported in the literature. (C) 1998 Elsevier Science Ltd. All rights reserved. C1 Coll William & Mary, Dept Phys, Williamsburg, VA 23187 USA. NASA, Langley Res Ctr, Div Atmospher Sci, Hampton, VA 23681 USA. RP Devi, VM (reprint author), Coll William & Mary, Dept Phys, Williamsburg, VA 23187 USA. NR 40 TC 17 Z9 18 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 MAR-MAY PY 1998 VL 59 IS 3-5 BP 137 EP 149 DI 10.1016/S0022-4073(97)00113-1 PG 13 WC Optics; Spectroscopy SC Optics; Spectroscopy GA YR495 UT WOS:000071501000002 ER PT J AU Goldman, A Schoenfeld, VG Stephen, TM Murcray, FJ Rinsland, CP Barbe, A Hamdouni, A Flaud, JM Camy-Peyret, C AF Goldman, A Schoenfeld, VG Stephen, TM Murcray, FJ Rinsland, CP Barbe, A Hamdouni, A Flaud, JM Camy-Peyret, C TI Isotopic ozone in the 5 mu region from high resolution balloon-borne and ground-based FTIR solar spectra SO JOURNAL OF QUANTITATIVE SPECTROSCOPY & RADIATIVE TRANSFER LA English DT Article; Proceedings Paper CT 4th Conference on Atmospheric Spectroscopy Applications CY SEP 04-06, 1996 CL REIMS, FRANCE SP Int Radiat Commiss ID HEAVY OZONE; (OOO)-O-16-O-18-O-16; STRATOSPHERE; SPECTROSCOPY AB High resolution (0.002-0.004 cm(-1)) i.r. solar absorption spectra of the stratosphere obtained during University of Denver balloon flights, and from the ground-based Network for the Detection of Stratospheric Change (NDSC) observatory at Mauna Loa, Hawaii, show numerous spectral features of several isotopic species of O-3, in both the 10 mu and 5 mu regions. Many of the 5 mu lines reported here have not been previously observed in atmospheric spectra. The identification and quantification of the lines proceed by combined analyses of the atmospheric spectra, laboratory spectra of enriched samples, and updated line parameter calculations. (C) 1998 Elsevier Science Ltd. All rights reserved. C1 Univ Denver, Dept Phys, Denver, CO 80208 USA. NASA, Langley Res Ctr, Div Atmospher Sci, Hampton, VA 23681 USA. GSMA, Fac Sci, F-51062 Reims, France. Univ Paris Sud, Lab Photophys Mol, F-91405 Orsay, France. Univ Paris 06, LPMA, F-75252 Paris 05, France. RP Goldman, A (reprint author), Univ Denver, Dept Phys, Denver, CO 80208 USA. NR 15 TC 11 Z9 12 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 MAR-MAY PY 1998 VL 59 IS 3-5 BP 231 EP 244 DI 10.1016/S0022-4073(97)00118-0 PG 14 WC Optics; Spectroscopy SC Optics; Spectroscopy GA YR495 UT WOS:000071501000010 ER PT J AU Ma, Q Tipping, RH Boulet, C AF Ma, Q Tipping, RH Boulet, C TI A far-wing line shape theory which satisfies the detailed balance principle SO JOURNAL OF QUANTITATIVE SPECTROSCOPY & RADIATIVE TRANSFER LA English DT Article; Proceedings Paper CT 4th Conference on Atmospheric Spectroscopy Applications CY SEP 04-06, 1996 CL REIMS, FRANCE SP Int Radiat Commiss ID INFRARED-ABSORPTION SPECTRA; WATER CONTINUUM ABSORPTION; ROTATIONAL BANDS; FORMALISMS; CO2 AB A far-wing line shape theory in which the validity of the detailed balance principle is maintained in each step of the derivation is presented. The role of the total density matrix including the initial correlations is analyzed rigorously. By factoring out the rapidly varying terms in the complex-time development operator in the interaction representation, better approximate expressions can be obtained. As a result, the spectral density, the Fourier transform of the dipole correlation function, can be expressed in terms of line-coupling functions in which two coupled lines are arranged symmetrically and whose frequency detunings are omega - 1/2(omega(ji) + omega(j'i')). Using the approximate detunings omega - omega(ji) results in expressions that do not satisfy the detailed balance principle. However, this principle remains satisfied for the symmetrized spectral density in which not only the coupled lines are arranged symmetrically, but also the initial and final states belonging to the same lines are arranged symmetrically as well. (C) 1998 Elsevier Science Ltd. All rights reserved. C1 Columbia Univ, Dept Appl Phys, New York, NY 10025 USA. NASA, Goddard Space Flight Ctr, Inst Space Studies, New York, NY 10025 USA. Univ Alabama, Dept Phys & Astron, Tuscaloosa, AL 35487 USA. Univ Paris Sud, CNRS UPR 136, Lab Phys Mol & Applicat, F-91405 Orsay, France. RP Ma, Q (reprint author), Columbia Univ, Dept Appl Phys, 2880 Broadway, New York, NY 10025 USA. NR 18 TC 8 Z9 8 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 MAR-MAY PY 1998 VL 59 IS 3-5 BP 245 EP 257 DI 10.1016/S0022-4073(97)00116-7 PG 13 WC Optics; Spectroscopy SC Optics; Spectroscopy GA YR495 UT WOS:000071501000011 ER PT J AU Ma, Q Tipping, RH Birnbaum, G Boulet, C AF Ma, Q Tipping, RH Birnbaum, G Boulet, C TI Sum rules and the symmetry of the memory function in spectral line shape theories SO JOURNAL OF QUANTITATIVE SPECTROSCOPY & RADIATIVE TRANSFER LA English DT Article; Proceedings Paper CT 4th Conference on Atmospheric Spectroscopy Applications CY SEP 04-06, 1996 CL REIMS, FRANCE SP Int Radiat Commiss ID COLLISIONAL REDISTRIBUTION; DENSITY-MATRIX; RADIATION; MOTION AB Starting from the well-known expression between the absorption coefficient and the spectral density F(omega), the Fourier transform of the dipole correlation function, we use a projection operator to average out the degrees of freedom of the bath variables. As a result, F(omega) can be written in terms of a memory function and effects due to initial correlations, all of which are confined to the line space of the absorber molecule. The initial correlations influence the form of the spectral density and are necessary in order to satisfy the principle of detailed balance. There is a relationship between the existence of sum rules and the symmetry of the memory function matrix and the latter depends on the projection operator introduced. In the present case, the matrix of the memory function is asymmetric and only one-sided sum rules are valid. The above conclusions remain true within the binary collision approximation that is applicable to low density gases. Finally, we discuss previously published two-sided sum rules that have been derived using a different projection operator and consequently a different memory function. (C) 1998 Elsevier Science Ltd. All rights reserved. C1 Columbia Univ, Dept Appl Phys, New York, NY 10025 USA. NASA, Goddard Space Flight Ctr, Inst Space Studies, New York, NY 10025 USA. Univ Alabama, Dept Phys & Astron, Tuscaloosa, AL 35487 USA. Natl Inst Stand & Technol, Gaithersburg, MD 20899 USA. Univ Paris Sud, CNRS UPR 136, Lab Phys Mol & Applicat, F-91405 Orsay, France. RP Ma, Q (reprint author), Columbia Univ, Dept Appl Phys, 2880 Broadway, New York, NY 10025 USA. NR 16 TC 13 Z9 13 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 MAR-MAY PY 1998 VL 59 IS 3-5 BP 259 EP 271 DI 10.1016/S0022-4073(97)00115-5 PG 13 WC Optics; Spectroscopy SC Optics; Spectroscopy GA YR495 UT WOS:000071501000012 ER PT J AU Gamache, RR Lynch, R Neshyba, SP AF Gamache, RR Lynch, R Neshyba, SP TI New developments in the theory of pressure-broadening and pressure-shifting of spectral lines of H2O: The complex Robert-Bonamy formalism SO JOURNAL OF QUANTITATIVE SPECTROSCOPY & RADIATIVE TRANSFER LA English DT Article; Proceedings Paper CT 4th Conference on Atmospheric Spectroscopy Applications CY SEP 04-06, 1996 CL REIMS, FRANCE SP Int Radiat Commiss ID ROTATION-VIBRATION LINES; ASYMMETRIC-TOP MOLECULES; RAMAN-Q-BRANCH; WATER-VAPOR LINES; PERTURBER DEPENDENCES; QUADRUPOLE-MOMENTS; CO; HE; COEFFICIENTS; RANGE AB Calculations of the halfwidth and line shift of water vapor perturbed by N-2, O-2, CO2, and H-2 based on a complex implementation of the formalism of Robert and Bonamy are made. The potentials employ the leading terms of the electrostatic potential, a Lennard-Jones (6-12) atom-atom potential, and the induction and dispersion components of the isotropic potential. The dynamics of the collisions are correct to second order in time. The results are compared with measurements and very good agreement is observed for both halfwidths and line shifts. A new feature in this approach is that the real and imaginary components of the S matrix affect both the halfwidth and the line shift. It is shown here that the imaginary parts of the S matrix strongly affect the calculated halfwidths for some of the systems considered. (C) 1998 Elsevier Science Ltd. All rights reserved. C1 Univ Lowell, Dept Environm Earth & Atmospher Sci, Lowell, MA 01854 USA. Columbia Univ, Goddard Inst Space Studies, New York, NY 10025 USA. Univ Puget Sound, Dept Chem, Tacoma, WA 98416 USA. RP Gamache, RR (reprint author), Univ Lowell, Dept Environm Earth & Atmospher Sci, 1 Univ Ave, Lowell, MA 01854 USA. NR 70 TC 68 Z9 68 U1 0 U2 7 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 MAR-MAY PY 1998 VL 59 IS 3-5 BP 319 EP 335 DI 10.1016/S0022-4073(97)00123-4 PG 17 WC Optics; Spectroscopy SC Optics; Spectroscopy GA YR495 UT WOS:000071501000016 ER PT J AU Goldman, A Schoenfeld, WG Goorvitch, D Chackerian, C Dothe, H Melen, F Abrams, MC Selby, JEA AF Goldman, A Schoenfeld, WG Goorvitch, D Chackerian, C Dothe, H Melen, F Abrams, MC Selby, JEA TI Updated line parameters for OH X(2)II-X(2)II (upsilon '',upsilon ') transitions SO JOURNAL OF QUANTITATIVE SPECTROSCOPY & RADIATIVE TRANSFER LA English DT Article; Proceedings Paper CT 4th Conference on Atmospheric Spectroscopy Applications CY SEP 04-06, 1996 CL REIMS, FRANCE SP Int Radiat Commiss ID DIPOLE-MOMENT FUNCTION; ROTATIONAL LINES; MOLECULAR-CONSTANTS; MEINEL SYSTEM; INTENSITIES; EMISSION; BANDS; HE; PROBABILITIES; EXTRAPOLATION AB New spectral line parameters have been generated for the OH (XII)-I-2-(XII)-I-2 transitions for Delta nu = 0.., 6, with nu' = 0.., 10, and J(max) = 49.5. HITRAN type line parameter sets with low intensity cutoffs are provided at 296 and 6000 K. Recent improvements in line intensities and line positions have been incorporated into the calculations. (C) 1998 Elsevier Science Ltd. All rights reserved. C1 Univ Denver, Dept Phys, Denver, CO 80208 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Mei Associates, Lexington, MA 02173 USA. Univ Liege, Inst Astrophys, B-4000 Liege, Belgium. ITT Aerosp, Ft Wayne, IN 46801 USA. Northrop Grumman, Long Isl, NY 11714 USA. RP Goldman, A (reprint author), Univ Denver, Dept Phys, Denver, CO 80208 USA. NR 36 TC 85 Z9 84 U1 1 U2 4 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 MAR-MAY PY 1998 VL 59 IS 3-5 BP 453 EP 469 DI 10.1016/S0022-4073(97)00112-X PG 17 WC Optics; Spectroscopy SC Optics; Spectroscopy GA YR495 UT WOS:000071501000026 ER PT J AU Jacquinet-Husson, N Scott, NA Chedin, A Bonnet, B Barbe, A Tyuterev, VG Champion, JP Winnewisser, M Brown, LR Gamache, R Golovko, VF Chursin, AA AF Jacquinet-Husson, N Scott, NA Chedin, A Bonnet, B Barbe, A Tyuterev, VG Champion, JP Winnewisser, M Brown, LR Gamache, R Golovko, VF Chursin, AA TI The GEISA system in 1996: Towards an operational tool for the second generation vertical sounders radiance simulation SO JOURNAL OF QUANTITATIVE SPECTROSCOPY & RADIATIVE TRANSFER LA English DT Article; Proceedings Paper CT 4th Conference on Atmospheric Spectroscopy Applications CY SEP 04-06, 1996 CL REIMS, FRANCE SP Int Radiat Commiss ID INFRARED-SPECTRA; METHANE; OZONE; COEFFICIENTS; INTENSITIES; PENTAD; BANDS; N-2 AB Since their creation, in 1974, the GEISA (Gestion et Etude des Informations Spectroscopiques Atmospheriques: Management and Study of Atmospheric Spectroscopic Information) database system (more than 730 000 entries between 0 and 22 656 cm(-1), corresponding to 40 molecules and 86 isotopic species, in its 1992 edition) and the associated software have been widely used for forward atmospheric radiative transfer modelling, with the maximum reliability, tractability and efficiency. For the upcoming high spectral resolution sounders like IASI (Infrared Atmospheric Sounding Interferometer) and AIRS (Atmospheric InfraRed Sounder), more complete and accurate laboratory measurements of spectroscopic parameters, presently included in the databases, are required, and more sophisticated theoretical radiative transfer modelling should be developed. Consequently, it is intended to elaborate the GEISA database as an interactive tool, named GEISA/IASI, designed for providing spectroscopic information tailored to the IASI sounding radiative transfer modelling. (C) 1998 Elsevier Science Ltd. All rights reserved. C1 CNRS, Meteorol Dynam Lab, Palaiseau, France. GSMA, Reims, France. LPUB, Dijon, France. JLU, Giessen, Germany. JPL, Pasadena, CA USA. Dept EEAS, Lowell, MA USA. LTS, Tomsk, Russia. RP Jacquinet-Husson, N (reprint author), CNRS, Meteorol Dynam Lab, Palaiseau, France. RI Champion, Jean-Paul/C-3963-2009 NR 34 TC 19 Z9 19 U1 1 U2 2 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 MAR-MAY PY 1998 VL 59 IS 3-5 BP 511 EP 527 DI 10.1016/S0022-4073(97)00131-3 PG 17 WC Optics; Spectroscopy SC Optics; Spectroscopy GA YR495 UT WOS:000071501000030 ER PT J AU Seraji, H AF Seraji, H TI A new class of nonlinear PID controllers with robotic applications SO JOURNAL OF ROBOTIC SYSTEMS LA English DT Article ID MOTION AB This paper introduces a new class of simple nonlinear PID controllers and provides a formal treatment of their stability analysis. These controllers are comprised of a sector-bounded nonlinear gain in cascade with a linear fixed-gain P, PD, PI, or PID controller. Three simple nonlinear gains are proposed: the sigmoidal function, the hyperbolic function, and the piecewise-linear function. The systems to be controlled are assumed to be modeled or approximated by second-order transfer functions, which can represent many robotic applications. The stability of the closed-loop systems incorporating nonlinear P, PD, PI, and PID controllers are investigated using the Popov stability criterion. It is shown that for P and PD controllers, the nonlinear gain is unbounded for closed-loop stability. For PI and PID controllers, simple expressions are derived that relate the controller gains and system parameters to the maximum allowable nonlinear gain for stability. A numerical example is given for illustration. The stability of partially-nonlinear PID controllers is also discussed. Finally, the nonlinear PI controller is implemented as a force controller on a robotic arm and experimental results are presented. These results demonstrate the superior performance of the nonlinear FI controller relative to a fixed-gain PI controller. (C) 1998 John Wiley & Sons, Inc. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Seraji, H (reprint author), CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. NR 8 TC 51 Z9 58 U1 1 U2 5 PU JOHN WILEY & SONS INC PI NEW YORK PA 605 THIRD AVE, NEW YORK, NY 10158-0012 USA SN 0741-2223 J9 J ROBOTIC SYST JI J. Robot. Syst. PD MAR PY 1998 VL 15 IS 3 BP 161 EP 181 DI 10.1002/(SICI)1097-4563(199803)15:3<161::AID-ROB4>3.0.CO;2-O PG 21 WC Robotics SC Robotics GA YZ097 UT WOS:000072220000004 ER PT J AU Pappa, RS James, GH Zimmerman, DC AF Pappa, RS James, GH Zimmerman, DC TI Autonomous modal identification of the space shuttle tail rudder SO JOURNAL OF SPACECRAFT AND ROCKETS LA English DT Article ID EIGENSYSTEM REALIZATION-ALGORITHM AB Autonomous modal identification automates the calculation from experimental data of natural vibration frequencies, damping, and mode shapes of a structure. This technology complements damage detection techniques that use continuous or periodic monitoring of vibration characteristics. The approach incorporates the Eigensystem Realization Algorithm as a data analysis engine and an autonomous supervisor to condense multiple estimates of modal parameters using the consistent-mode indicator and correlation of mode shapes. The procedure was applied to free-decay responses of a Space Shuttle tail rudder and successfully identified the first seven vibration modes of the structure. The final modal parameters are a condensed set of results for 87 individual cases requiring approximately 5 min of computer time on a Unix workstation. C1 NASA, Langley Res Ctr, Struct Dynam Branch, Struct Div, Hampton, VA 23681 USA. Univ Houston, Dept Mech Engn, Houston, TX 77204 USA. RP Pappa, RS (reprint author), NASA, Langley Res Ctr, Struct Dynam Branch, Struct Div, Hampton, VA 23681 USA. NR 10 TC 32 Z9 35 U1 0 U2 4 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 MAR-APR PY 1998 VL 35 IS 2 BP 163 EP 169 DI 10.2514/2.3324 PG 7 WC Engineering, Aerospace SC Engineering GA ZG315 UT WOS:000072989000007 ER PT J AU Woodard, SE AF Woodard, SE TI Orbital and configuration influences on spacecraft dynamic response SO JOURNAL OF SPACECRAFT AND ROCKETS LA English DT Article AB Results of investigating the orbital and configuration influences on the Upper Atmosphere Research Satellite's dynamic response are presented. Orbital influences were due to temperature variation from crossing the Earth's terminator and variation of the solar incident energy as the orbit precessed. During the terminator crossing, the rapid ambient temperature change caused the spacecraft's two flexible appendages to experience thermal elastic bending (thermal snap). The resulting response was dependent on the orientation of the solar array and the solar incident energy. Orbital influences were also due to onboard disturbances, environmental disturbances, and spacecraft configuration changes resulting in dynamic responses that were repeated each orbit. Configuration influences were due to the solar array rotation's changing of the spacecraft modal properties. The orbital and configuration influences produced measurable spacecraft attitude variations as well as modal and amplitude trends in those variations. C1 NASA, Langley Res Ctr, Struct Dynam Branch, Struct Div, Hampton, VA 23681 USA. RP Woodard, SE (reprint author), NASA, Langley Res Ctr, Struct Dynam Branch, Struct Div, MS 230, Hampton, VA 23681 USA. NR 9 TC 5 Z9 5 U1 0 U2 0 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0022-4650 J9 J SPACECRAFT ROCKETS JI J. Spacecr. Rockets PD MAR-APR PY 1998 VL 35 IS 2 BP 177 EP 182 DI 10.2514/2.3326 PG 6 WC Engineering, Aerospace SC Engineering GA ZG315 UT WOS:000072989000009 ER PT J AU Frauenholz, RB Bhat, RS Shapiro, BE Leavitt, RK AF Frauenholz, RB Bhat, RS Shapiro, BE Leavitt, RK TI Analysis of the TOPEX/Poseidon operational orbit: Observed variations and why SO JOURNAL OF SPACECRAFT AND ROCKETS LA English DT Article ID POSEIDON AB Following launch on Aug. 10, 1992, TOPEX/Poseidon began a very successful global study of the Earth's ocean circulation using a combination of dual-frequency radar altimetry and precision orbit determination. The 1336-km nearly circular frozen orbit and 10-day repeat ground track have been closely monitored and accurately controlled using precise mean orbital elements. A new osculating-to-mean conversion technique designed specifically to meet the stringent TOPEX/Poseidon orbit control requirements removes all short and long-periodic geopotential and third-body gravity perturbations acting over 10 days. The most important orbital parameter, mean semimajor axis, demonstrates stability and consistency to 13 cm rms using a 20 x 20 geopotential field. The mean semimajor axis exhibits unique behavior with intervals of either orbital boost or deboost induced by along-track forces of body-fixed origin that change magnitude and direction depending on the satellite yaw-control mode and solar array articulation strategy. Nine orbit maintenance maneuvers, recently augmented by selective use of solar array articulation, have maintained the semimajor axis within +/-5 m of the reference value, thereby keeping the ground track within the +/-1-km equatorial longitude control band. Other orbital parameters remain within required limits without dedicated maneuvers. C1 CALTECH, Jet Prop Lab, Navigation & Flight Mech Sect, Pasadena, CA 91109 USA. Sterling Software Inc, Navigat & Flight Mech Sect, Pasadena, CA 91107 USA. RP CALTECH, Jet Prop Lab, Navigation & Flight Mech Sect, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 36 TC 4 Z9 4 U1 0 U2 0 PU AMER INST AERONAUTICS ASTRONAUTICS PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091-4344 USA SN 0022-4650 EI 1533-6794 J9 J SPACECRAFT ROCKETS JI J. Spacecr. Rockets PD MAR-APR PY 1998 VL 35 IS 2 BP 212 EP 224 DI 10.2514/2.3312 PG 13 WC Engineering, Aerospace SC Engineering GA ZG315 UT WOS:000072989000014 ER PT J AU Maghami, PG AF Maghami, PG TI Efficient jitter analysis for spacecraft SO JOURNAL OF SPACECRAFT AND ROCKETS LA English DT Article C1 NASA, Langley Res Ctr, Guidance & Control Branch, Hampton, VA 23681 USA. RP Maghami, PG (reprint author), NASA, Langley Res Ctr, Guidance & Control Branch, Mail Stop 161, Hampton, VA 23681 USA. NR 5 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 MAR-APR PY 1998 VL 35 IS 2 BP 235 EP 237 DI 10.2514/2.3317 PG 3 WC Engineering, Aerospace SC Engineering GA ZG315 UT WOS:000072989000019 ER PT J AU Easterbrook, S Callahan, J AF Easterbrook, S Callahan, J TI Formal methods for verification and validation of partial specifications: A case study SO JOURNAL OF SYSTEMS AND SOFTWARE LA English DT Article AB This paper describes our work exploring the suitability of formal specification methods for independent verification and validation (IV & V) of software specifications for large, safety-critical systems. An IV & V contractor often has to perform rapid analysis on incomplete specifications, with no control over how those specifications are represented. Lightweight formal methods show significant promise in this context, as they offer a way of uncovering major errors without the burden of full proofs of correctness. We describe a case study of the use of partial formal models for IV & V of the requirements for Fault Detection Isolation and Recovery on the space station. We conclude that the insights gained from formalizing a specification are valuable, and it is the process of formalization, rather than the end product, that is important. It was only necessary to build enough of the formal model to test the properties in which we were interested. Maintenance of fidelity between multiple representations of the same requirements (as they evolve) is still a problem, and deserves further study. (C) 1998 Elsevier Science Inc. C1 NASA, WVU, Software Res Lab, IV&V Facil, Fairmont, WV 26554 USA. RP NASA, WVU, Software Res Lab, IV&V Facil, 100 Univ Dr, Fairmont, WV 26554 USA. EM steve@research.ivv.nasa.gov NR 19 TC 12 Z9 13 U1 0 U2 1 PU ELSEVIER SCIENCE INC PI NEW YORK PA 360 PARK AVE SOUTH, NEW YORK, NY 10010-1710 USA SN 0164-1212 EI 1873-1228 J9 J SYST SOFTWARE JI J. Syst. Softw. PD MAR PY 1998 VL 40 IS 3 BP 199 EP 210 DI 10.1016/S0164-1212(97)00167-2 PG 12 WC Computer Science, Software Engineering; Computer Science, Theory & Methods SC Computer Science GA YX898 UT WOS:000072091600004 ER PT J AU Chao, WC Deng, LT AF Chao, WC Deng, LT TI Tropical intraseasonal oscillation, super cloud clusters, and cumulus convection schemes. Part II: 3D aquaplanet simulations SO JOURNAL OF THE ATMOSPHERIC SCIENCES LA English DT Article ID GENERAL-CIRCULATION MODEL; MADDEN-JULIAN OSCILLATION; LARGE-SCALE ENVIRONMENT; 40-50 DAY OSCILLATION; AQUA PLANET MODEL; 30-60 DAY OSCILLATION; ARAKAWA-SCHUBERT; WESTERN PACIFIC; SEMIPROGNOSTIC TESTS; PRIMITIVE EQUATIONS AB Chao and Lin's work on tropical intraseasonal oscillations, super cloud clusters, and cumulus convection schemes is extended from a 2D model setup to a 3D aquaplanet setup. It is found that super cloud clusters can be simulated in a 3D model and that the 3D setup has more stringent requirements on the cumulus convection scheme than the 2D setup does for a successful simulation of super cloud clusters. Three cumulus convection schemes are compared in experiments simulating super cloud clusters. In the more successful experiments, individual cloud cluster pairs in the meridional direction, once generated near the equator by the cloud cluster tele-induction mechanism, assume a poleward movement while exhibiting weak zonal movement. The combination of two or three successive cloud cluster pairs (i.e., vortex pairs) straddling the equator gives rise to westerly wind burst events of sizable longitudinal range and duration. Thus, the westerly wind burst, as appeared in the model, is really a part of the super cloud cluster structure. The evaporation-surface wind feedback mechanism is found to be unnecessary for the existence of the super cloud clusters. However, it does make the latter more robust. The need for improvement in cumulus parameterization for tropical simulation is discussed. C1 NASA, Goddard Space Flight Ctr, Atmospheres Lab, Greenbelt, MD 20771 USA. Space Applicat Corp, Vienna, Austria. RP Chao, WC (reprint author), NASA, Goddard Space Flight Ctr, Atmospheres Lab, Mail Code 913, Greenbelt, MD 20771 USA. NR 63 TC 30 Z9 33 U1 0 U2 1 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 MAR 1 PY 1998 VL 55 IS 5 BP 690 EP 709 DI 10.1175/1520-0469(1998)055<0690:TIOSCC>2.0.CO;2 PG 20 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA YZ755 UT WOS:000072288400002 ER PT J AU Heifetz, E Alpert, P da Silva, A AF Heifetz, E Alpert, P da Silva, A TI On the parcel method and the baroclinic wedge of instability SO JOURNAL OF THE ATMOSPHERIC SCIENCES LA English DT Article AB The heuristic explanation, suggested by the parcel method, for the baroclinic instability mechanism is reexamined. The parcel method argues that an air parcel displaced within the wedge of instability, that is, between the horizontal and the isentropes, is vertically accelerated by the buoyancy force and hence becomes unstable. However, in the synoptic scale, the buoyancy is balanced by the vertical pressure gradient force perturbation, which is neglected by the parcel method, and thus the parcel acceleration is essentially horizontal. For the unstable Eady normal modes, the horizontally averaged buoyancy work is found to maximize at the steering level and to vanish at the boundaries, but the horizontally averaged parcel kinetic energy growth is minimized at the steering level and maximized at the boundaries. It is shown that the buoyancy work is vertically redistributed by the pressure gradient force perturbation throughout the secondary circulation. The parcel method also assumes that a parcel displaced adiabatically within the wedge of instability finds itself warmer than its new surroundings and thus contributes toward both vertical and meridional positive heat fluxes. However, since the temperature difference between the parcel and the Environment from which it departed cannot be neglected, the slope of the instantaneous displacement is not a sufficient criterion to determine the signs of the heat fluxes. It is shown here that for the Eady normal modes solution, the four combinations of ascending or descending of initially colder or warmer parcels make jointly the vertical heat Bur maximize at the steering level and the meridional heat Aux remain constant with height. C1 Tel Aviv Univ, Dept Geophys & Planetary Sci, IL-69978 Tel Aviv, Israel. NASA, Goddard Space Flight Ctr, Data Assimilat Off, Greenbelt, MD 20771 USA. RP Heifetz, E (reprint author), Tel Aviv Univ, Dept Geophys & Planetary Sci, IL-69978 Tel Aviv, Israel. RI da Silva, Arlindo/D-6301-2012 OI da Silva, Arlindo/0000-0002-3381-4030 NR 7 TC 1 Z9 1 U1 0 U2 0 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 MAR 1 PY 1998 VL 55 IS 5 BP 788 EP 795 DI 10.1175/1520-0469(1998)055<0788:OTPMAT>2.0.CO;2 PG 8 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA YZ755 UT WOS:000072288400007 ER PT J AU Mell, RJ AF Mell, RJ TI Electrically conductive coating materials SO JOURNAL OF THERMAL SPRAY TECHNOLOGY LA English DT News Item C1 George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. NR 1 TC 0 Z9 0 U1 0 U2 0 PU ASM INTERNATIONAL PI MATERIALS PARK PA SUBSCRIPTIONS SPECIALIST CUSTOMER SERVICE, MATERIALS PARK, OH 44073-0002 USA SN 1059-9630 J9 J THERM SPRAY TECHN JI J. Therm. Spray Technol. PD MAR PY 1998 VL 7 IS 1 BP 20 EP 21 PG 2 WC Materials Science, Coatings & Films SC Materials Science GA ZB684 UT WOS:000072497200009 ER PT J AU Ng, D AF Ng, D TI Two-wavelength pyrometry with self-calibration SO JOURNAL OF THERMAL SPRAY TECHNOLOGY LA English DT News Item C1 Lewis Res Ctr, Cleveland, OH 44135 USA. NR 1 TC 0 Z9 0 U1 1 U2 1 PU ASM INTERNATIONAL PI MATERIALS PARK PA SUBSCRIPTIONS SPECIALIST CUSTOMER SERVICE, MATERIALS PARK, OH 44073-0002 USA SN 1059-9630 J9 J THERM SPRAY TECHN JI J. Therm. Spray Technol. PD MAR PY 1998 VL 7 IS 1 BP 20 EP 20 PG 1 WC Materials Science, Coatings & Films SC Materials Science GA ZB684 UT WOS:000072497200008 ER PT J AU Wernet, MP AF Wernet, MP TI Digital particle-image velocimetry enhanced by fuzzy logic SO JOURNAL OF THERMAL SPRAY TECHNOLOGY LA English DT News Item C1 Lewis Res Ctr, Cleveland, OH 44135 USA. NR 2 TC 0 Z9 0 U1 0 U2 0 PU ASM INTERNATIONAL PI MATERIALS PARK PA SUBSCRIPTIONS SPECIALIST CUSTOMER SERVICE, MATERIALS PARK, OH 44073-0002 USA SN 1059-9630 J9 J THERM SPRAY TECHN JI J. Therm. Spray Technol. PD MAR PY 1998 VL 7 IS 1 BP 22 EP 23 PG 2 WC Materials Science, Coatings & Films SC Materials Science GA ZB684 UT WOS:000072497200013 ER PT J AU Meyyappan, M AF Meyyappan, M TI Modeling of GaN hydride vapor phase epitaxy SO JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A-VACUUM SURFACES AND FILMS LA English DT Article ID GROWTH; DEPOSITION; NITRIDE AB A reactor model for the hydride vapor phase epitaxy of GaN is presented. The governing flow, energy, and species conservation equations are solved in two dimensions to examine the growth characteristics as a function of process variables and reactor geometry. The growth rate varies with GaCl composition but is independent of NH3 and H-2 how rates. A change in carrier gas for Ga source from H-2 to N-2 affects the growth rate and uniformity for a fixed reactor configuration. The model predictions are in general agreement with observed experimental behavior. (C) 1998 American Vacuum Society. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Meyyappan, M (reprint author), NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. EM meyya@orbit.arc.nasa.gov NR 13 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 0734-2101 J9 J VAC SCI TECHNOL A JI J. Vac. Sci. Technol. A-Vac. Surf. Films PD MAR-APR PY 1998 VL 16 IS 2 BP 685 EP 688 DI 10.1116/1.581087 PG 4 WC Materials Science, Coatings & Films; Physics, Applied SC Materials Science; Physics GA ZC509 UT WOS:000072587200045 ER PT J AU Mikouchi, T Miyamoto, M McKay, GA AF Mikouchi, T Miyamoto, M McKay, GA TI Mineralogy of Antarctic basaltic shergottite Queen Alexandra Range 94201: Similarities to Elephant Moraine A79001 (Lithology B) martian meteorite SO METEORITICS & PLANETARY SCIENCE LA English DT Article ID CRYSTALLIZATION; ZAGAMI; PETROGENESIS; MAGMA AB Antarctic meteorite QUE 94201 is a new basaltic shergottite that is mainly composed of subequal amounts of maskelynite and pyroxenes (pigeonite and augite) plus abundant merrillite and accessory phases. It also contains impact melt. Complex zoning patterns in QUE 94201 pyroxenes revealed by elemental map analyses using an electron microprobe suggest a crystallization sequence from Mg-rich pigeonite (En(62)Fs(30)Wo(8)) to extremely Fe-rich pigeonite (En(5)Fs(81)Wo(l4)) via {110} Mg-rich augite bands (En(44)Fs(20)Wo(36)) in a single crystal. These textures, along with the abundant plagioclase (maskelynite), indicates single-stage rapid cooling (>5 degrees C/year) of this rock from a supercooled magma. Transition from Mg-rich augite to Fe-rich pigeonite reflects the onset of plagioclase crystallization. Enrichment of late-stage phases in QUE 94201 implies crystallization from an evolved magma and suggests a different parent magma composition from the other basaltic shergottites. Lithology B of EETA79001 basaltic shergottite contains pyroxenes that show complex zoning with augite bands similar to those in QUE 94201 pyroxene, which suggests similar one-stage rapid cooling. Lithology B of EETA79001 also resembles QUE 94201 in its coarse-grained texture of silicates and its high abundance of maskelynite, although QUE 94201 probably crystallized from a more fractionated magma. We also note that some Apollo lunar mare basalts (e.g., 12020 and 12021) have similar mineralogy and petrology to QUE 94201, especially in pyroxene zoning. All these basaltic rocks with complex pyroxene zoning suggest rapid metastable crystallization from supercooled magmas. C1 Univ Tokyo, Grad Sch Sci, Inst Mineral, Tokyo 113, Japan. NASA, Lyndon B Johnson Space Ctr, Planetary Sci Branch SN4, Houston, TX 77058 USA. RP Mikouchi, T (reprint author), Univ Tokyo, Grad Sch Sci, Inst Mineral, Tokyo 113, Japan. EM mikouchi@min.s.u-tokyo.ac.jp NR 34 TC 31 Z9 31 U1 1 U2 5 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 MAR PY 1998 VL 33 IS 2 BP 181 EP 189 PG 9 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA ZF084 UT WOS:000072861000004 ER PT J AU Bruns, TD Szaro, TM Gardes, M Cullings, KW Pan, JJ Taylor, DL Horton, TR Kretzer, A Garbelotto, M Li, Y AF Bruns, TD Szaro, TM Gardes, M Cullings, KW Pan, JJ Taylor, DL Horton, TR Kretzer, A Garbelotto, M Li, Y TI A sequence database for the identification of ectomycorrhizal basidiomycetes by phylogenetic analysis SO MOLECULAR ECOLOGY LA English DT Article DE Agaricales; Aphyllophorales; Boletales; evolution; mitochondrial LrRNA gene; molecular clock ID MITOCHONDRIAL RIBOSOMAL DNA; MYCORRHIZAL FUNGI; RNA GENES; AMPLIFICATION; CONFIDENCE; NUCLEAR; PROBES AB We have assembled a sequence database for 80 genera of Basidiomycota from the Hymenomycete lineage (sensu Swann & Taylor 1993) for a small region of the mitochondrial large subunit rRNA gene. Our taxonomic sample is highly biased toward known ectomycorrhizal (EM) taxa, but also includes some related saprobic species. This gene fragment can be amplified directly from mycorrhizae, sequenced, and used to determine the family or subfamily of many unknown mycorrhizal basidiomycetes. The method is robust to minor sequencing errors, minor misalignments, and method of phylogenetic analysis. Evolutionary inferences are limited by the small size and conservative nature of the gene fragment. Nevertheless two interesting patterns emerge: (i) the switch between ectomycorrhizae and saprobic lifestyles appears to have happened convergently several and perhaps many times; and (ii) at least five independent lineages of ectomycorrhizal fungi are characterized by very short branch lengths. We estimate that two of these groups radiated in the mid-Tertiary, and we speculate that these radiations may have been caused by the expanding geographical range of their host trees during this period. The aligned database, which will continue to be updated, can be obtained from the following site on the WorldWide Web: http://mendel.berkeley.edu/boletus.html. C1 Univ Calif Berkeley, Dept Plant & Microbial Biol, Berkeley, CA 94720 USA. Univ Toulouse 3, CNRS, CESAC, F-31055 Toulouse 4, France. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Indiana Univ, Dept Biol, Bloomington, IN 47405 USA. Univ Calif Santa Barbara, Dept Ecol Evolut & Marine Biol, Santa Barbara, CA 93106 USA. USDA, Forest Serv, Forest Sci Lab, Corvallis, OR 97331 USA. Dept Bot & Plant Pathol, Corvallis, OR 97331 USA. Fox Chase Canc Ctr, Philadelphia, PA 19111 USA. RP Bruns, TD (reprint author), Univ Calif Berkeley, Dept Plant & Microbial Biol, Berkeley, CA 94720 USA. EM boletus@socrates.berkeley.edu OI Taylor, Donald/0000-0002-5985-9210; Horton, Tom/0000-0002-2112-9618 NR 38 TC 207 Z9 219 U1 2 U2 13 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 MAR PY 1998 VL 7 IS 3 BP 257 EP 272 DI 10.1046/j.1365-294X.1998.00337.x PG 16 WC Biochemistry & Molecular Biology; Ecology; Evolutionary Biology SC Biochemistry & Molecular Biology; Environmental Sciences & Ecology; Evolutionary Biology GA ZH549 UT WOS:000073122200001 ER PT J AU Moore, EM Gottesman, ST AF Moore, EM Gottesman, ST TI A neutral hydrogen study of the barred spiral galaxy NGC 3319 SO MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY LA English DT Article DE galaxies, individual, NGC 3319; galaxies, kinematics and dynamics; galaxies, spiral; galaxies, structure; radio lines, galaxies ID HIGH-RESOLUTION OBSERVATIONS; INTERSTELLAR-MEDIUM; SECULAR EVOLUTION; STAR-FORMATION; BARS; KINEMATICS; NGC-3359; DYNAMICS; REGIONS AB Neutral hydrogen line observations of the late-type barred spiral galaxy NGC 3319 are presented. The distribution and kinematics of the galaxy are studied using the Very Large Array,(1) with spatial resolutions between 11 and 50 arcsec, and a channel separation of 10.33 km s(-1). As is typical for late-type galaxies, NGC 3319 is rich in H I, with a gaseous bar and spiral features. Several large, low-density regions are present, and the Hr spiral structure is distorted, especially in the south. The gas distribution is asymmetric and extends significantly further to the south-east due to a long, off-centre tail. Non-circular motions caused by the bar, spiral structure and low-density regions are present in the radial velocity field, complicating the rotation curve analysis. These non-axisymmetric structures cause the values of the position angle and inclination derived from the velocity field to vary across the disc. In addition, beyond a radius of 180 arcsec, the velocity field is severely perturbed on the approaching (southern) side of the galaxy, and the disc becomes non-planar. However, the galaxy does not show the typical 'integral sign' shape of a warped system. We detect a small system approximately 11 arcmin (40 kpc) south of the centre of NGC 3319. It is seen in eight velocity channels and is coincident with a small, resolved object in the Palomar Sky Survey. A tidal interaction between this object and NGC 3319 is the most likely cause of the distorted spiral structure, the H I tail, and the velocity perturbations found in the southern half of the galaxy. Infalling tidal debris from such an event may account for the large, low-density regions found in the disc, several of which show kinematic evidence that suggest they are expanding superstructures. We are unable to determine the corotation radius from the H I velocity field using kinematic methods, but a break in the slope of the abundance gradient places it near the end of the bar. Star formation zones, as determined from an H image of the galaxy, are aligned with H I peaks and, except in the outermost optical disc, occur when the local H I density is in excess of 1.5 x 10(21) cm(-2). C1 Rutgers State Univ, Dept Phys & Astron, Piscataway, NJ 08855 USA. Univ Florida, Dept Astron, Gainesville, FL 32611 USA. RP Moore, EM (reprint author), NASA, Ames Res Ctr, Johnson Controls, Mail Stop 242-4, Moffett Field, CA 94035 USA. NR 33 TC 11 Z9 11 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 MAR 1 PY 1998 VL 294 IS 3 BP 353 EP 372 DI 10.1046/j.1365-8711.1998.01078.x PG 20 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZB395 UT WOS:000072468200003 ER PT J AU Riotto, A AF Riotto, A TI The superhot, superdense, supersymmetric universe SO NUCLEAR PHYSICS B-PROCEEDINGS SUPPLEMENTS LA English DT Article; Proceedings Paper CT 5th International Conference on Supersymmetries in Physics CY MAY 27-31, 1997 CL PHILADELPHIA, PA ID SYMMETRY NON-RESTORATION; HIGH-TEMPERATURE; BARYON ASYMMETRY; MONOPOLE PROBLEM; GAUGE THEORIES; HIGH-DENSITY; CONDENSATION; BREAKING AB In this talk the following question is addressed: are internal symmetries necessarily restored at high temperature in supersymmetric theories? Contrary to the general belief, we argue that the answer is no when systems possess a net background charge. Our findings are exemplified on abelian models, for both cases of global and local symmetries and possible cosmological implications are also discussed. C1 Fermilab Natl Accelerator Lab, NASA, Fermilab Astrophys Ctr, Batavia, IL 60510 USA. RP Fermilab Natl Accelerator Lab, NASA, Fermilab Astrophys Ctr, POB 500, Batavia, IL 60510 USA. NR 27 TC 3 Z9 3 U1 0 U2 0 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0920-5632 EI 1873-3832 J9 NUCL PHYS B-PROC SUP JI Nucl. Phys. B-Proc. Suppl. PD MAR PY 1998 VL 62 BP 253 EP 258 DI 10.1016/S0920-5632(97)00665-8 PG 6 WC Physics, Particles & Fields SC Physics GA ZG188 UT WOS:000072976000029 ER PT J AU Liu, HK Jin, YH Marzwell, NI AF Liu, HK Jin, YH Marzwell, NI TI Advanced ultra-high-capacity optical random access memory and pattern recognition techniques SO OPTICAL ENGINEERING LA English DT Article DE random access memory; optical pattern recognition; holographic lens; Dammann grating; optical pattern classification ID VOLUME HOLOGRAPHIC STORAGE; SYSTEMS AB The architecture and mathematical analysis of a new multichannel multistage holographic optical random access memory (HORAM) architecture and an experimental demonstration of its feasibility are presented. The new HORAM can be used for ultra-high-capacity storage and high-speed random retrieval of information. A two-stage HORAM, using a Dammann grating and a multifocus holographic lens, clearly shows the capability of storing 2000 holographic matched filters. The functional requirements for key optical elements including laser sources, spatial tight modulators, and electro-optical shutters for making a desired practical and compact HORAM are described. The potential extension of the HORAM system for multiple-channel optical pattern recognition, classification, and image restoration are described. (C) 1998 Society of Photo-Optical Instrumentation Engineers. [S0091-3286(98)02503-3]. C1 Univ S Alabama, Dept Elect & Comp Engn, Mobile, AL 36688 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Liu, HK (reprint author), Univ S Alabama, Dept Elect & Comp Engn, Mobile, AL 36688 USA. EM hkliu@jaguar1.usouthal.edu NR 19 TC 2 Z9 4 U1 0 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 MAR PY 1998 VL 37 IS 3 BP 779 EP 788 DI 10.1117/1.601910 PG 10 WC Optics SC Optics GA ZC007 UT WOS:000072530200008 ER PT J AU Black, FO Paloski, WH AF Black, FO Paloski, WH TI Computerized dynamic posturography: What have we learned from space? SO OTOLARYNGOLOGY-HEAD AND NECK SURGERY LA English DT Article; Proceedings Paper CT Symposium on Vestibular Dysfunction - Lessons and Legacies from Space CY SEP 28, 1996 CL WASHINGTON, D.C. SP Amer Acad Otolaryngol Head & Neck Surg, Amer Neurotol Soc, NASA ID POSTURAL CONTROL; VESTIBULAR FUNCTION; ORIENTATION; NYSTAGMUS; STABILITY; DIAGNOSIS; RESPONSES; SUPPORT; LESIONS; STANCE AB Computerized dynamic posturography (CDP) has been under development since 1970, Several reviews summarize key basic and clinical research studies and outline important clinical uses of CDP along with research applications, This report summarizes new information about the otolith control of posture obtained from the study of astronauts, The dynamics of recovery of postural control upon return from orbital flight provide insight to the peripheral vestibular and central nervous system components of vestibular compensation, The dynamics of postural compensation should aid the clinician in the diagnosis and management of imbalance of vestibular origin. C1 Legacy Neurotol Res, Legacy Holladay Pk Med Ctr, Clin Res & Technol Ctr, Portland, OR 97208 USA. NASA, Lyndon B Johnson Space Ctr, Neurosci Lab, Houston, TX 77058 USA. RP Black, FO (reprint author), Legacy Neurotol Res, Legacy Holladay Pk Med Ctr, Clin Res & Technol Ctr, POB 3950, Portland, OR 97208 USA. FU NIDCD NIH HHS [2-RO-1 DC 00205] NR 45 TC 9 Z9 10 U1 0 U2 0 PU SAGE PUBLICATIONS LTD PI LONDON PA 1 OLIVERS YARD, 55 CITY ROAD, LONDON EC1Y 1SP, ENGLAND SN 0194-5998 J9 OTOLARYNG HEAD NECK JI Otolaryngol. Head Neck Surg. PD MAR PY 1998 VL 118 IS 3 SU S BP S45 EP S51 DI 10.1016/S0194-5998(98)70009-9 PN 2 PG 7 WC Otorhinolaryngology; Surgery SC Otorhinolaryngology; Surgery GA ZC414 UT WOS:000072575600010 PM 9525491 ER PT J AU Paloski, WH AF Paloski, WH TI Vestibulospinal adaptation to microgravity SO OTOLARYNGOLOGY-HEAD AND NECK SURGERY LA English DT Article; Proceedings Paper CT Symposium on Vestibular Dysfunction - Lessons and Legacies from Space CY SEP 28, 1996 CL WASHINGTON, D.C. SP Amer Acad Otolaryngol Head & Neck Surg, Amer Neurotol Soc, NASA ID POSTURAL CONTROL; WEIGHTLESSNESS; RESPONSES AB Human balance control is known to be transiently disrupted after spaceflight; however, the mechanisms responsible for postflight postural ataxia are still under investigation, In this report, we propose a conceptual model of vestibulospinal adaptation based on theoretical adaptive control concepts and supported by the results from a comprehensive study of balance control recovery after spaceflight. The conceptual model predicts that immediately after spaceflight the balance control system of a returning astronaut does not expect to receive gravity-induced afferent inputs and that descending vestibulospinal control of balance is disrupted until the central nervous system is able to cope with the newly available vestibular otolith information, Predictions of the model are tested using data from a study of the neurosensory control of balance in astronauts immediately after landing, In that study, the mechanisms of sensorimotor balance control were assessed under normal, reduced, and/or altered (sway-referenced) visual and somatosensory input conditions, We conclude that the adaptive control model accurately describes the neurobehavioral responses to spaceflight and that similar models of altered sensory, motor, or environmental constraints are needed clinically to predict responses that patients with sensorimotor pathologies may have to various visual-vestibular or changing stimulus environments. C1 NASA, Lyndon B Johnson Space Ctr, Life Sci Res Labs, Houston, TX 77058 USA. RP Paloski, WH (reprint author), NASA, Lyndon B Johnson Space Ctr, Life Sci Res Labs, Mail Code SD3, Houston, TX 77058 USA. NR 22 TC 7 Z9 7 U1 0 U2 2 PU SAGE PUBLICATIONS LTD PI LONDON PA 1 OLIVERS YARD, 55 CITY ROAD, LONDON EC1Y 1SP, ENGLAND SN 0194-5998 J9 OTOLARYNG HEAD NECK JI Otolaryngol. Head Neck Surg. PD MAR PY 1998 VL 118 IS 3 SU S BP S39 EP S44 DI 10.1016/S0194-5998(98)70008-7 PN 2 PG 6 WC Otorhinolaryngology; Surgery SC Otorhinolaryngology; Surgery GA ZC414 UT WOS:000072575600009 PM 9525490 ER PT J AU Ross, MD AF Ross, MD TI Synaptic changes in rat maculae in space and medical imaging: The link SO OTOLARYNGOLOGY-HEAD AND NECK SURGERY LA English DT Article; Proceedings Paper CT Symposium on Vestibular Dysfunction - Lessons and Legacies from Space CY SEP 28, 1996 CL WASHINGTON, D.C. SP Amer Acad Otolaryngol Head & Neck Surg, Amer Neurotol Soc, NASA ID COMPUTER GENERATED IMAGERY; VESTIBULAR SYSTEM; 3-D COMPONENTS; WEIGHTLESSNESS; ORGANIZATION AB Two different space life sciences missions (SLS-1 and SLS-2) have demonstrated that the synapses of the hair cells of rat vestibular maculae increase significantly in microgravity. The results also indicate that macular synapses are sensitive to stress, These findings argue that vestibular maculae exhibit neuroplasticity to macroenvironmental and microenvironmental changes. This capability should be clinically re!levant to rehabilitative training and/or pharmacological treatments for vestibular disease. The results of this ultrastructural research also demonstrated that type I and type II hair cells are integrated into the same neuronal circuitry. The findings were the basis for development of three-dimensional reconstruction software to learn details of macular wiring, This software, produced for scientific research, has now been adapted to reconstruct the face and skull directly from computerized tomography scans. In collaboration with craniofacial reconstructive surgeons at Stanford University Medical Center, an effort is under way to produce a virtual environment workbench for complex craniofacial surgery. When completed, the workbench will help surgeons train for and simulate surgery, The methods are patient specific, This research illustrates the value of basic research in leading to unanticipated medical applications. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Ross, MD (reprint author), NASA, Ames Res Ctr, Mail Stop 239-11, Moffett Field, CA 94035 USA. NR 20 TC 3 Z9 3 U1 0 U2 1 PU MOSBY-YEAR BOOK INC PI ST LOUIS PA 11830 WESTLINE INDUSTRIAL DR, ST LOUIS, MO 63146-3318 USA SN 0194-5998 J9 OTOLARYNG HEAD NECK JI Otolaryngol. Head Neck Surg. PD MAR PY 1998 VL 118 IS 3 SU S BP S25 EP S28 DI 10.1016/S0194-5998(98)70004-X PN 2 PG 4 WC Otorhinolaryngology; Surgery SC Otorhinolaryngology; Surgery GA ZC414 UT WOS:000072575600005 PM 9525486 ER PT J AU Short, HD AF Short, HD TI Cardiovascular effects of microgravity: Evolution of understanding SO OTOLARYNGOLOGY-HEAD AND NECK SURGERY LA English DT Article; Proceedings Paper CT Symposium on Vestibular Dysfunction - Lessons and Legacies from Space CY SEP 28, 1996 CL WASHINGTON, D.C. SP Amer Acad Otolaryngol Head & Neck Surg, Amer Neurotol Soc, NASA ID SPACEFLIGHT AB The understanding of cardiovascular effects of spaceflight has evolved throughout the course of the American manned spaceflight program. Originally descriptive in nature, the present understanding is based on empiric measurements of vascular volume, cardiac output, vascular reflexes, and peripheral and central autonomic control, More detailed understanding of cardiovascular effects has allowed us to separate those symptoms from symptoms caused by musculoskeletal or neurovestibular abnormalities. C1 NASA, Lyndon B Johnson Space Ctr, SA Space & Life Sci, Houston, TX 77058 USA. Baylor Coll Med, Houston, TX 77030 USA. RP Short, HD (reprint author), NASA, Lyndon B Johnson Space Ctr, SA Space & Life Sci, Houston, TX 77058 USA. NR 13 TC 1 Z9 1 U1 0 U2 0 PU MOSBY-YEAR BOOK INC PI ST LOUIS PA 11830 WESTLINE INDUSTRIAL DR, ST LOUIS, MO 63146-3318 USA SN 0194-5998 J9 OTOLARYNG HEAD NECK JI Otolaryngol. Head Neck Surg. PD MAR PY 1998 VL 118 IS 3 SU S BP S52 EP S54 DI 10.1016/S0194-5998(98)70010-5 PN 2 PG 3 WC Otorhinolaryngology; Surgery SC Otorhinolaryngology; Surgery GA ZC414 UT WOS:000072575600011 PM 9525492 ER PT J AU James, GK Slevin, JA Dziczek, D McConkey, JW Bray, I AF James, GK Slevin, JA Dziczek, D McConkey, JW Bray, I TI Polarization of Lyman-alpha radiation from atomic hydrogen excited by electron impact from near threshold to 1800 eV SO PHYSICAL REVIEW A LA English DT Article ID GAS RESONANCE RADIATION; NEAR-THRESHOLD; EXCITATION; SCATTERING; NEON; BEAM AB The polarization of Lyman-alpha radiation, produced by electron-impact excitation of atomic hydrogen, has been measured over the extended energy range from near threshold to 1800 eV. Measurements were obtained in a crossed-beam experiment using a silica-reflection linear polarization analyzer in tandem with a vacuum-ultraviolet monochromator to isolate the emitted line radiation. Comparison with various theoretical calculations shows that the present experimental results are in good agreement with theory over the entire range of electron-impact energies and, in particular, are in excellent agreement with theoretical convergent-close-coupling (CCC) calculations performed in the present work. Our polarization data are significantly different from the previous experimental measurements of Ott, Kauppila, and Fite [Phys. Rev. A 1, 1089 (1970)]. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Natl Univ Ireland, Dept Expt Phys, Maynooth, Kildare, Ireland. Univ Windsor, Dept Phys, Windsor, ON N9B 3P4, Canada. Flinders Univ S Australia, Elect Struct Mat Ctr, Adelaide, SA 5001, Australia. Nicholas Copernicus Univ, Inst Phys, PL-87100 Torun, Poland. RP James, GK (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. RI Bray, Igor/B-8586-2009; Dziczek, Dariusz/G-3620-2014 OI Bray, Igor/0000-0001-7554-8044; NR 38 TC 11 Z9 11 U1 0 U2 1 PU AMERICAN PHYSICAL SOC PI COLLEGE PK PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA SN 1050-2947 J9 PHYS REV A JI Phys. Rev. A PD MAR PY 1998 VL 57 IS 3 BP 1787 EP 1797 DI 10.1103/PhysRevA.57.1787 PG 11 WC Optics; Physics, Atomic, Molecular & Chemical SC Optics; Physics GA ZB155 UT WOS:000072441900045 ER PT J AU Jongen, T Mompean, G Gatski, TB AF Jongen, T Mompean, G Gatski, TB TI Accounting for Reynolds stress and dissipation rate anisotropies in inertial and noninertial frames SO PHYSICS OF FLUIDS LA English DT Article ID TURBULENT FLOWS; CLOSURE; CHANNEL; MODELS AB This paper presents a general procedure for including added effects, such as turbulent dissipation rate anisotropies. into algebraic stress formulations in both inertial and noninertial frames of reference. Explicit algebraic stress models, which assume an isotropic turbulent dissipation rate, have been developed previously and extended for application to noninertial frames. Independently, anisotropic dissipation rate models have also been developed. Recently, an algebraic, anisotropic dissipation rate model has been developed and used in conjunction with a full Reynolds stress closure. Unfortunately, in the theoretical formulations used previously for explicit algebraic models, the combination of the algebraic stress and algebraic dissipation rate models only appeared possible for inertial frames. The alternative procedure outlined here remedies this problem and allows for the construction of a composite model for both inertial and noninertial frames. This new composite model formulation is tested in homogeneous shear with and without rotation, and in strongly rotating channel and pipe flows using different types of anisotropic dissipation rate models. (C) 1998 American Institute of Physics. C1 Swiss Fed Inst Technol, Fluid Mech Lab, CH-1015 Lausanne, Switzerland. NASA, Langley Res Ctr, Hampton, VA 23681 USA. RP Swiss Fed Inst Technol, Fluid Mech Lab, CH-1015 Lausanne, Switzerland. NR 20 TC 14 Z9 16 U1 0 U2 3 PU AMER INST PHYSICS PI MELVILLE PA 1305 WALT WHITMAN RD, STE 300, MELVILLE, NY 11747-4501 USA SN 1070-6631 EI 1089-7666 J9 PHYS FLUIDS JI Phys. Fluids PD MAR PY 1998 VL 10 IS 3 BP 674 EP 684 DI 10.1063/1.869593 PG 11 WC Mechanics; Physics, Fluids & Plasmas SC Mechanics; Physics GA YZ949 UT WOS:000072311400015 ER PT J AU Liemohn, MW Khazanov, GC AF Liemohn, MW Khazanov, GC TI Collisionless plasma modeling in an arbitrary potential energy distribution SO PHYSICS OF PLASMAS LA English DT Article ID PARALLEL ELECTRIC-FIELDS; ION-EXOSPHERE; AURORAL ELECTRONS; REGION; DIFFERENCE; PARTICLE; MIRROR; FLUX AB A new technique for calculating a collisionless plasma along a field line is presented. The primary feature of this new ion-exospheric model is that it can handle an arbitrary (including nonmonotonic) potential energy distribution. This was one of the limiting constraints on the existing models in this class, and these constraints are generalized for an arbitrary potential energy composition. The formulation for relating current density to the field-aligned potential as well as formulas for density, temperature, and energy flux calculations are presented for several distribution functions, ranging from a bi-lorentzian with a loss cone to an isotropic Maxwellian. A comparison of these results with previous models shows that the formulation reduces to the earlier models under similar assumptions. (C) 1998 American Institute of Physics. C1 NASA, Space Sci Lab, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. RP Liemohn, MW (reprint author), NASA, Space Sci Lab, George C Marshall Space Flight Ctr, Mail Code ES-83, Huntsville, AL 35812 USA. RI Liemohn, Michael/H-8703-2012 OI Liemohn, Michael/0000-0002-7039-2631 NR 41 TC 13 Z9 13 U1 0 U2 1 PU AMER INST PHYSICS PI WOODBURY PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 USA SN 1070-664X J9 PHYS PLASMAS JI Phys. Plasmas PD MAR PY 1998 VL 5 IS 3 BP 580 EP 589 DI 10.1063/1.872750 PG 10 WC Physics, Fluids & Plasmas SC Physics GA ZA377 UT WOS:000072357400006 ER PT J AU Lamar, JE AF Lamar, JE TI The use and characteristics of vortical flows near a generating aerodynamic surface: A perspective SO PROGRESS IN AEROSPACE SCIENCES LA English DT Review ID LAYER AB A review is given of the various vortical-flowfield studies with which the author has been involved, first with attached then with separated-vortical flows. All these studies have contained the mutual interference of the flowfield on the generating surface. The common element throughout is using experiment to provide insight to formulate analytical or semi-empirical methods in order that an impact be made on the design of flight vehicles. Examples of these methods, along with an estimate from computational fluid dynamics, and experimental results from wind tunnel and flight ale presented. (C) 1998 Elsevier Science Ltd. C1 NASA, Langley Res Ctr, Hampton, VA 23681 USA. RP Lamar, JE (reprint author), NASA, Langley Res Ctr, Hampton, VA 23681 USA. NR 69 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 0376-0421 J9 PROG AEROSP SCI JI Prog. Aeosp. Sci. PD MAR-APR PY 1998 VL 34 IS 3-4 BP 167 EP 217 DI 10.1016/S0376-0421(98)00004-9 PG 51 WC Engineering, Aerospace SC Engineering GA 114ZJ UT WOS:000075638800002 ER PT J AU Eckstein, MP AF Eckstein, MP TI The lower visual search efficiency for conjunctions is due to noise and not serial attentional processing SO PSYCHOLOGICAL SCIENCE LA English DT Article ID GUIDED SEARCH; INTEGRATION; STIMULUS; DISCRIMINATION; SIMILARITY; TASKS; MODEL AB Models of human visual processing start with an initial stage with parallel independent processing of different physical attributes or features (e.g., color; orientation, motion). A second stage in these models is a temporally serial mechanism (visual attention) that combines or binds information across feature dimensions. Evidence for this serial mechanism is based on experimental results for visual search. I conducted a study of visual search accuracy that carefully controlled for low-level effects: physical similarity of target and distractor; element eccentricity, and eye movements. The larger set-size effects in visual search accuracy for briefly flashed conjunction displays, compared with feature displays, are quantitatively predicted by a simple model in which each feature dimension is processed independently with inherent neural noise and information is combined linearly across feature dimensions. The data are not predicted by a temporally serial mechanism or by a hybrid model with temporally serial and noisy processing. The results do not support the idea that a temporally serial mechanism, visual attention, binds information across feature dimensions and show that the conjunction-feature dichotomy is due to the noisy independent processing of features in the human visual system. C1 Cedars Sinai Med Ctr, Dept Med Phys & Imaging, Los Angeles, CA 90048 USA. NASA, Ames Res Ctr, Los Angeles, CA USA. RP Eckstein, MP (reprint author), Cedars Sinai Med Ctr, Dept Med Phys & Imaging, 8700 Beverly Blvd,Davis 6065, Los Angeles, CA 90048 USA. EM miguel@vision.arc.nasa.gov NR 27 TC 151 Z9 153 U1 0 U2 10 PU BLACKWELL PUBLISHERS PI MALDEN PA 350 MAIN STREET, STE 6, MALDEN, MA 02148 USA SN 0956-7976 J9 PSYCHOL SCI JI Psychol. Sci. PD MAR PY 1998 VL 9 IS 2 BP 111 EP 118 DI 10.1111/1467-9280.00020 PG 8 WC Psychology, Multidisciplinary SC Psychology GA 165PY UT WOS:000078531300005 ER PT J AU Gardner, JP AF Gardner, JP TI An extendable galaxy number count model SO PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF THE PACIFIC LA English DT Article ID INFRARED LUMINOSITY FUNCTIONS; HIGH-REDSHIFT GALAXIES; MEDIUM DEEP SURVEY; FAINT GALAXIES; DARK-MATTER; COSMOLOGICAL CONSTANT; SPECTRAL EVOLUTION; DWARF GALAXIES; FIELD GALAXIES; WIDE-FIELD AB I review galaxy number count models and present ncmod, an extendable and general purpose model for comparing and interpreting the results of field galaxy survey data. I develop techniques and software for converting the results of a survey done in one filter into another filter for direct comparison with other surveys. Comparison of the data from surveys that differ greatly in wavelength coverage or sensitivity is of necessity model dependent, but comparison between similar surveys can be done in a relatively model-independent way. I extrapolate existing number counts into the ultraviolet and thermal infrared. The model is used to predict the results of future space missions, including STIS and NICMOS on Hubble space Telescope, Infrared Space Observatory, Space Infrared Telescope Facility, and Next Generation Space Telescope. C1 NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, Greenbelt, MD 20771 USA. RP Gardner, JP (reprint author), NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, Code 681, Greenbelt, MD 20771 USA. EM gardner@harmony.gsfc.nasa.gov NR 90 TC 50 Z9 51 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 MAR PY 1998 VL 110 IS 745 BP 291 EP 305 DI 10.1086/316141 PG 15 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZF860 UT WOS:000072940500008 ER PT J AU Haas, MR Pfister, L AF Haas, MR Pfister, L TI A high-altitude site survey for SOFIA SO PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF THE PACIFIC LA English DT Article ID ATMOSPHERE RESEARCH SATELLITE; TROPOSPHERIC WATER-VAPOR; MICROWAVE LIMB SOUNDER; OCTOBER 1986 FIRE; HIGH-LEVEL CLOUDS; CIRRUS CLOUDS; STRATOSPHERIC AEROSOL; AIRBORNE ASTRONOMY; RELATIVE-HUMIDITY; SAGE-II AB The Stratospheric Observatory for Infrared Astronomy (SOFIA) is a modified Boeing 747-SP equipped with a 2.5 m telescope dedicated to astronomical research. Currently under joint development by the US (NASA) and Germany (DLR), it is scheduled to begin operations in late 2001. The ability of SOFIA to carry out its mission will depend strongly on the meteorological conditions at and above flight altitudes in the vicinity of its home base. The most important meteorological factors are the frequency of high-altitude clouds and the magnitude of the water vapor overburdens. This paper performs a high-altitude site survey by gathering together the best available meteorological data, defining metrics, and evaluating them for a variety of sites. These metrics are found to corroborate past airborne experience and to be consistent with well-known global circulation patterns, convection, and upper tropospheric dynamics. They indicate that I:here are significant variations in the weather at SOFIA flight altitudes. Particularly in summer, some continental US sites are shown to be worse than Hawaii, where high-altitude cirrus clouds and the associated moisture have historically caused significant losses in the amount and quality of the astronomical data collected by NASA's Kuiper Airborne Observatory. SOFIA's planned home base, Moffett Field? CA, is found to have excellent high-altitude weather and to be one of the best continental US sites. C1 NASA, Ames Res Ctr, Div Space Sci, Moffett Field, CA 94035 USA. NASA, Ames Res Ctr, Div Earth Sci, Moffett Field, CA 94035 USA. RP Haas, MR (reprint author), NASA, Ames Res Ctr, Div Space Sci, MS 245-6, Moffett Field, CA 94035 USA. EM haas@cygnus.arc.nasa.gov; pfister@telsci.arc.nasa.gov NR 79 TC 8 Z9 8 U1 0 U2 1 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 MAR PY 1998 VL 110 IS 745 BP 339 EP 364 DI 10.1086/316132 PG 26 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZF860 UT WOS:000072940500012 ER PT J AU Badhwar, GD Cucinotta, FA AF Badhwar, GD Cucinotta, FA TI Depth dependence of absorbed dose, dose equivalent and linear energy transfer spectra of galactic and trapped particles in polyethylene and comparison with calculations of models SO RADIATION RESEARCH LA English DT Article ID COSMIC-RAYS; RADIATION AB A matched set of five tissue-equivalent proportional counters (TEPCs), embedded at the centers of 0 (bare), 3, 5, 8 and 12-inch-diameter polyethylene spheres, were flown on the Shuttle flight STS-81 (inclination 51.65 degrees, altitude similar to 400 km). The data obtained were separated into contributions from trapped protons and galactic cosmic radiation (GCR). From the measured linear energy transfer (LET) spectra, the absorbed dose and dose-equivalent rates were calculated. The results were compared to calculations made with the radiation transport model HZETRN\NUCFRG2, using the GCR free-space spectra, orbit-averaged geomagnetic transmission function and Shuttle shielding distributions. The comparison shows that the model fits the dose rates to a root mean square (rms) error of 5%, and dose-equivalent rates to an rms error of 10%. Fairly good agreement between the LET spectra was found; however, differences are seen at both low and high LET. These differences can be understood as due to the combined effects of chord-length variation and detector response function. These results rule out a number of radiation transport/nuclear fragmentation models. Similar comparisons of trapped-proton dose rates were made between calculations made with the proton transport model BRYNTRN using the AP-8 MIN trapped-proton model and Shuttle shielding distributions. The predictions of absorbed dose and dose-equivalent rates are fairly good. However, the prediction of the LET spectra below similar to 30 keV/mu m shows the need to improve the AP-8 model. These results have strong implications for shielding requirements for an interplanetary manned mission. (C) 1998 by Radiation Research Society. C1 NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. RP Badhwar, GD (reprint author), NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. NR 30 TC 25 Z9 26 U1 0 U2 1 PU RADIATION RESEARCH SOC PI OAK BROOK PA 2021 SPRING RD, STE 600, OAK BROOK, IL 60521 USA SN 0033-7587 J9 RADIAT RES JI Radiat. Res. PD MAR PY 1998 VL 149 IS 3 BP 209 EP 218 DI 10.2307/3579953 PG 10 WC Biology; Biophysics; Radiology, Nuclear Medicine & Medical Imaging SC Life Sciences & Biomedicine - Other Topics; Biophysics; Radiology, Nuclear Medicine & Medical Imaging GA YZ105 UT WOS:000072220800001 PM 9496883 ER PT J AU Schmugge, TJ Jackson, TJ O'Neill, PE Parlange, MB AF Schmugge, TJ Jackson, TJ O'Neill, PE Parlange, MB TI Observations of coherent emissions from soils SO RADIO SCIENCE LA English DT Article ID WATER-CONTENT; MODEL AB Observations of the microwave emissions at 1.413 GHz (L band) and 2.65 GHz (S band) from a silt loam soil exhibited an oscillatory behavior in time as the soil was being irrigated. The oscillations are attributed to interference between reflections from the air-soil interface and the wet soil-dry soil interface as the latter moved down in the soil. The magnitude of the first oscillation at L band was 56 K, and at S band it was 40 K, with oscillation damping out after about three cycles to the brightness temperature expected for the wet soil. The emission was modeled using a coherent model, and the results show qualitative and quantitative agreement with the observations. C1 ARS, Hydrol Lab, USDA, Agr Res Ctr, Beltsville, MD 20705 USA. NASA, Lab Hydrospher Proc, Hydrol Sci Branch, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Johns Hopkins Univ, Dept Geog & Environm Engn, Baltimore, MD 21218 USA. RP Schmugge, TJ (reprint author), ARS, Hydrol Lab, USDA, Agr Res Ctr, Bldg 007,BARC W, Beltsville, MD 20705 USA. RI O'Neill, Peggy/D-2904-2013; Parlange, Marc/A-3403-2015 NR 9 TC 10 Z9 10 U1 0 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0048-6604 J9 RADIO SCI JI Radio Sci. PD MAR-APR PY 1998 VL 33 IS 2 BP 267 EP 272 DI 10.1029/97RS02614 PG 6 WC Astronomy & Astrophysics; Geochemistry & Geophysics; Meteorology & Atmospheric Sciences; Remote Sensing; Telecommunications SC Astronomy & Astrophysics; Geochemistry & Geophysics; Meteorology & Atmospheric Sciences; Remote Sensing; Telecommunications GA ZE395 UT WOS:000072788300010 ER PT J AU Wang, JR Zhan, J Racette, P AF Wang, JR Zhan, J Racette, P TI Multiple aircraft microwave observations of storms over the western Pacific Ocean SO RADIO SCIENCE LA English DT Article ID 183 GHZ; PRECIPITATION RADIOMETER; DEEP CONVECTION; WATER-VAPOR; SIMULATIONS; RETRIEVAL; RADAR; CLOUD; RAINFALL; MODEL AB During the second half (January-February 1993) of the intensive observation phase of the Tropical Ocean Global Atmosphere/Coupled Ocean-Atmosphere Response Experiment (TOGA/COARE), NASA deployed both DC-8 and ER-2 research aircraft in Townsville, Australia. A number of flights were made over the western Pacific Ocean with the objective of studying strong equatorial convection and clouds. A host of microwave radiometers operating in the frequency range of 10-220 GHz were placed on board both aircraft. Many other instruments were also present in both aircraft; among them was a 13.8-GHz radar in the DC-8 aircraft that provides reflectivity profiles of atmospheric hydrometeors essential for the present study. Observations were made by both aircraft on weather systems of convection as well as of cloud radiation. Some of these observations were conducted with both aircraft flying over the same regions at near coincidence but different altitudes. The nearly concurrent microwave radiometric measurements at comparable frequencies from the two aircraft at the altitudes of about 11 and 20 km provide a unique means to examine the properties of hydrometeors associated with storms. Three well-coordinated DC-8 and ER-2 aircraft flights over storms are described below. All of the microwave radiometers and the 13.8-GHz radar functioned normally during these flights. Some radiometers on the ER-2 and the DC-8 aircraft have comparable frequencies; signatures' acquired by these radiometers from these flights are analyzed in detail. It is shown that storm-associated brightness temperature depressions observed at frequencies less than or equal to 90 GHz from two different altitudes are quite comparable. At high frequencies greater than or equal to 150 GHz the brightness temperature depressions observed at 20-km altitude are significantly larger than those observed at 11-km altitude in some portions of the storms. This suggests the presence of hydrometeors in the 11- to 20-km altitude region that effectively scatter radiation at frequencies greater than or equal to 150 GHz. C1 NASA, Lab Hydrospher Proc, Earth Sci Directorate, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Int Database Syst, Falls Church, VA 22043 USA. RP Wang, JR (reprint author), NASA, Lab Hydrospher Proc, Earth Sci Directorate, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. EM wang@sensor.gsfc.nasa.gov; per@meneg.gsfc.nasa.gov NR 29 TC 10 Z9 11 U1 1 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0048-6604 J9 RADIO SCI JI Radio Sci. PD MAR-APR PY 1998 VL 33 IS 2 BP 351 EP 368 DI 10.1029/97RS02221 PG 18 WC Astronomy & Astrophysics; Geochemistry & Geophysics; Meteorology & Atmospheric Sciences; Remote Sensing; Telecommunications SC Astronomy & Astrophysics; Geochemistry & Geophysics; Meteorology & Atmospheric Sciences; Remote Sensing; Telecommunications GA ZE395 UT WOS:000072788300016 ER PT J AU Solheim, F Godwin, JR Westwater, ER Han, Y Keihm, SJ Marsh, K Ware, R AF Solheim, F Godwin, JR Westwater, ER Han, Y Keihm, SJ Marsh, K Ware, R TI Radiometric profiling of temperature, water vapor and cloud liquid water using various inversion methods SO RADIO SCIENCE LA English DT Article AB We have developed a tunable temperature profiler based on a highly stable synthesizer that can observe at multiple frequencies on the shoulder of the 60-GHz atmospheric oxygen feature. We are developing a similar radiometer to obtain the vertical distribution of water vapor by making observations on the pressure-broadened water vapor line from 22 to 29 GHz. Information on cloud liquid water profiles is also contained in these two wave bands. Various mathematical retrieval methods for temperature, water vapor, and cloud liquid water profiles were tested based on these radiometer designs. These include neural networking, Newtonian iteration of statistically retrieved profiles, and Bayesian "most probable" retrievals. On the basis of realistic radiometer errors and performance, very good retrieval capability is demonstrated. The performance of the various retrieval methods are presented and compared. Examples of profile retrievals are also presented. Data were not binned into seasons to reduce computer time; better retrieval results for all methods would be expected with binning. C1 Radiometr Corp, Boulder, CO 80301 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ Corp Atmospher Res, Boulder, CO 80307 USA. Univ Colorado, NOAA, Cooperat Inst Res Environm Sci, Boulder, CO 80309 USA. RP Solheim, F (reprint author), Radiometr Corp, 2898 30th St, Boulder, CO 80301 USA. EM sol-heim@radiometrics.com; yhan@etl.noaa.gov; stephen.j.keihm@ccmail.jpl.nasa.gov; ware@ucar.edu RI Han, Yong/F-5590-2010 OI Han, Yong/0000-0002-0183-7270 NR 6 TC 137 Z9 150 U1 0 U2 2 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0048-6604 J9 RADIO SCI JI Radio Sci. PD MAR-APR PY 1998 VL 33 IS 2 BP 393 EP 404 DI 10.1029/97RS03656 PG 12 WC Astronomy & Astrophysics; Geochemistry & Geophysics; Meteorology & Atmospheric Sciences; Remote Sensing; Telecommunications SC Astronomy & Astrophysics; Geochemistry & Geophysics; Meteorology & Atmospheric Sciences; Remote Sensing; Telecommunications GA ZE395 UT WOS:000072788300018 ER PT J AU Keihm, SJ Marsh, KA AF Keihm, SJ Marsh, KA TI New model-based Bayesian inversion algorithm for the retrieval of wet troposphere path delay from radiometric measurements SO RADIO SCIENCE LA English DT Article ID WATER-VAPOR; MICROWAVE RADIOMETERS; LIQUID AB A new inversion algorithm has been developed for the retrieval of tropospheric wet path delay from microwave radiometer measurements. The algorithm is based on the principle of maximum probability and uses Bayes' theorem to determine the most probable state vector (comprised of discrete height profiles of temperature and water vapor density) for a given set of measurements. The solution probabilities depend both on conformity to apriori statistics and a minimization of residuals between measured observables and observables computed from candidate state vectors. The new algorithm has been compared with standard statistical inversion techniques using simulations based on radiosonde, lidar, and acoustic sounding measurements of atmospheric temperature and water vapor profiles. For clear conditions the results indicate that the nonlinear algorithm produces a factor of 3-5 improvement in path delay retrieval performance, relative to a nonstratified statistical algorithm, when the observational system includes both a water vapor radiometer and a microwave temperature profiler and measurement errors are minimized. The new algorithm is shown to be most useful when applied to radiometric measurements of path delay fluctuations over minute to multihour timescales. Recommended applications include tropospheric calibration systems for radio science experiments such as very long baseline interferometry astrometry and the planned Cassini gravitational wave experiment. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Keihm, SJ (reprint author), CALTECH, Jet Prop Lab, US 246-101,4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 17 TC 3 Z9 4 U1 0 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0048-6604 J9 RADIO SCI JI Radio Sci. PD MAR-APR PY 1998 VL 33 IS 2 BP 411 EP 419 DI 10.1029/97RS02748 PG 9 WC Astronomy & Astrophysics; Geochemistry & Geophysics; Meteorology & Atmospheric Sciences; Remote Sensing; Telecommunications SC Astronomy & Astrophysics; Geochemistry & Geophysics; Meteorology & Atmospheric Sciences; Remote Sensing; Telecommunications GA ZE395 UT WOS:000072788300020 ER PT J AU Tanner, AB AF Tanner, AB TI Development of a high-stability water vapor radiometer SO RADIO SCIENCE LA English DT Article AB Preliminary design details and laboratory test results of a prototype microwave radiometer operating near 20 GHz are presented. Radiometric stability to 10 millikelvin on time scales from 100 to 10,000 s is the goal for the final system. The use of noise diodes as receiver gain calibrators is examined, and test results showing 30 parts per million stability per day in the intercomparison of noise diodes are presented. Temperature control of the radiometer is also examined, and the design of a solid state temperature control system capable of 1 mK stability near room temperature is presented. A new design for a mechanically actuated Dicke switch is also presented. The results of these laboratory developments are applied to a prototype radiometer. Early indications are that design goals are being met in the prototype. Future confirmation of the system's theoretical performance will only be possible with the completion of the final radiometer units. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Tanner, AB (reprint author), CALTECH, Jet Prop Lab, MS 246-101,4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 7 TC 15 Z9 15 U1 2 U2 5 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0048-6604 J9 RADIO SCI JI Radio Sci. PD MAR-APR PY 1998 VL 33 IS 2 BP 449 EP 462 DI 10.1029/97RS02749 PG 14 WC Astronomy & Astrophysics; Geochemistry & Geophysics; Meteorology & Atmospheric Sciences; Remote Sensing; Telecommunications SC Astronomy & Astrophysics; Geochemistry & Geophysics; Meteorology & Atmospheric Sciences; Remote Sensing; Telecommunications GA ZE395 UT WOS:000072788300023 ER PT J AU Cuzzi, JN AF Cuzzi, JN TI Ringside seat SO SCIENCES-NEW YORK LA English DT Article C1 Ames Res Ctr, Mt View, CA 94035 USA. RP Cuzzi, JN (reprint author), Ames Res Ctr, Mt View, CA 94035 USA. NR 0 TC 2 Z9 2 U1 0 U2 0 PU NEW YORK ACAD SCIENCES PI NEW YORK PA 2 E 63RD ST, NEW YORK, NY 10021 USA SN 0036-861X J9 SCIENCES JI Sci.-New York PD MAR-APR PY 1998 VL 38 IS 2 BP 28 EP 33 PG 6 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA ZK933 UT WOS:000073379000017 ER PT J AU Chang, KY Scharton, TD AF Chang, KY Scharton, TD TI Cassini spacecraft force limited vibration testing SO SOUND AND VIBRATION LA English DT Article AB The environmental test program for the Cassini spacecraft included a force-limited vertical-axis random vibration test. The semi-empirical force limit specified in the Cassini spacecraft vibration test procedure was used without any modifications during the test. Acceleration responses at critical locations were monitored in the spacecraft vibration test, but only the total axial force was used in the control loop to notch the input acceleration. The flight limit loads were achieved at a number of critical locations on the spacecraft and the instrument responses were similar to those in the component random vibration tests. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Chang, KY (reprint author), CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. NR 10 TC 2 Z9 3 U1 2 U2 3 PU ACOUSTICAL PUBL INC PI BAY VILLAGE PA 27101 E OVIATT RD PO BOX 40416, BAY VILLAGE, OH 44140 USA SN 0038-1810 J9 SOUND VIB JI Sound Vib. PD MAR PY 1998 VL 32 IS 3 BP 16 EP 20 PG 5 WC Acoustics; Engineering, Mechanical; Mechanics SC Acoustics; Engineering; Mechanics GA ZG393 UT WOS:000072997300004 ER PT J AU Wolpert, DH Knill, E Grossman, T AF Wolpert, DH Knill, E Grossman, T TI Some results concerning off-training-set and IID error for the Gibbs and the Bayes optimal generalizers SO STATISTICS AND COMPUTING LA English DT Article DE Supervised learning; learning curves; off-training-set; Bayes-optimal; Gibbs; IID AB In this paper we analyse the average behaviour of the Bayes-optimal and Gibbs learning algorithms. We do this both for off-training-set error and conventional IID (independent identically distributed) error (for which test sets overlap with training sets). For the IID case we provide a major extension to one of the better known results. We also show that expected IID test set error is a non-increasing function of training set size for either algorithm. On the other hand, as we show, the expected off-training-set error for both learning algorithms can increase with training set size, for non-uniform sampling distributions. We characterize the relationship the sampling distribution must have with the prior for such an increase. We show in particular that for uniform sampling distributions and either algorithm, the expected off-training-set error is a non-increasing function of training set size. For uniform sampling distributions, we also characterize the priors for which the expected error of the Bayes-optimal algorithm stays constant. In addition we show that for the Bayes-optimal algorithm, expected off-training-set error can increase with training set size when the target function is fixed, but if and only if the expected error averaged over all targets decreases with training set size. Our results hold for arbitrary noise and arbitrary loss functions. 0960-3174 (C) 1998 Chapman & Hall. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Univ Calif Los Alamos Natl Lab, CIC 3 Comp Res & Applicat, Los Alamos, NM 87545 USA. Univ Calif Los Alamos Natl Lab, Div Theoret, Los Alamos, NM 87545 USA. Univ Calif Los Alamos Natl Lab, CNLS, Los Alamos, NM 87545 USA. NR 24 TC 0 Z9 0 U1 1 U2 1 PU KLUWER ACADEMIC PUBL PI DORDRECHT PA SPUIBOULEVARD 50, PO BOX 17, 3300 AA DORDRECHT, NETHERLANDS SN 0960-3174 J9 STAT COMPUT JI Stat. Comput. PD MAR PY 1998 VL 8 IS 1 BP 35 EP 54 DI 10.1023/A:1008867009312 PG 20 WC Computer Science, Theory & Methods; Statistics & Probability SC Computer Science; Mathematics GA ZC249 UT WOS:000072557900004 ER PT J AU Doarn, CR Nicogossian, AE Merrell, RC AF Doarn, CR Nicogossian, AE Merrell, RC TI Applications of telemedicine in the United States space program SO TELEMEDICINE JOURNAL LA English DT Article AB Since the beginning of human space flight, NASA has been placing humans in extreme and remote environments. There are many challenges in maintaining humans in outer space, including the provision of life-support systems, radiation shielding, and countermeasures for minimizing the effect of microgravity. Because astronauts are selected for their health, among other factors, disease and illness are minimized. However, it is still of great importance to have appropriate medical care systems in place to address illness and injury should they occur. With the exception of the Apollo program, exploration of space has been limited to missions that are within several hundred miles of the surface of the Earth. At the dawn of the 21st century and the new millennium, human exploration will be focused on operation of the International Space Station (ISS) and preparation for human missions to Mars. These missions will present inherent risks to human health, and, therefore, appropriate plans must be established to address these challenges and risks. Crews of long-duration missions must become more independent from ground controllers. New systems, protocols, and procedures are currently being perfected. Application of emerging technologies in information systems and telecommunications will be critical to inflight medical care. Application of these technologies through telemedicine will provide crew members access to information, noninvasive procedures for assessing health status, and guidance through the integration of sensors, holography, decision-support systems, and virtual environments. These technologies will also serve as a basis to enhance training and medical education. The design of medical care for space flight should lead to a redesign of the practice of medicine on Earth. C1 NASA, Aerosp Med Div, Off Life & Micrograv Sci & Applicat, Washington, DC 20546 USA. Wright State Univ, Sch Med, Dept Community Hlth, Dayton, OH USA. Yale Univ, Sch Med, Dept Surg, New Haven, CT 06510 USA. RP Doarn, CR (reprint author), NASA, Aerosp Med Div, Off Life & Micrograv Sci & Applicat, Code UO,300 E St SW, Washington, DC 20546 USA. NR 15 TC 34 Z9 35 U1 1 U2 9 PU MARY ANN LIEBERT INC PUBL PI LARCHMONT PA 2 MADISON AVENUE, LARCHMONT, NY 10538 USA SN 1078-3024 J9 TELEMED J JI Telemed. J. PD SPR PY 1998 VL 4 IS 1 BP 19 EP 30 DI 10.1089/tmj.1.1998.4.19 PG 12 WC Health Care Sciences & Services SC Health Care Sciences & Services GA 142KT UT WOS:000077200200004 PM 9599070 ER PT J AU Erlebacher, G Hussaini, MY Jackson, TL AF Erlebacher, G Hussaini, MY Jackson, TL TI Nonlinear strong shock interactions: A shock-fitted approach SO THEORETICAL AND COMPUTATIONAL FLUID DYNAMICS LA English DT Article ID WAVE; VORTEX AB This paper addresses nonlinear effects which result from the interaction of shock waves with vortices. A series of experiments are carried out, which involve the interaction of a strong shock wave with a single plane vorticity wave and a randomly distributed wave system. These experiments are first conducted in the linear regime to obtain a mutual verification of theory and computation. They are subsequently extended into the nonlinear regime. A systematic study of the interaction of a plane shock wave and a single vortex is then conducted. Specifically, we investigate the conditions under which nonlinear effects become important, both as a function of shock Mach number, M-1, and incident vortex strength (characterized by its circulation Gamma). The shock Mach number is varied from 2 to 8, while the circulation of the vortex is varied from infinitesimally small values (linear theory) to unity. Budgets of vorticity, dilatation, and pressure are obtained. They indicate that nonlinear effects become more significant as both the shock Mach number and the circulation increase. For Mach numbers equal to 5 and above, the dilatation in the vortex core grows quadratically with circulation. An acoustic wave propagates radially outward from the vortex center. As circulation increases, its upstream-facing front steepens at low Mach numbers, and its downstream-facing front steepens at high Mach numbers. A high Mach number asymptotic expansion of the Rankins-Hugoniot conditions reveals that nonlinear effects dominate both the shock motion and the downstream flow for Gamma M-1 > 1. C1 Florida State Univ, Program Computat Sci & Engn, Tallahassee, FL 32306 USA. NASA, Langley Res Ctr, Inst Comp Applicat Sci & Engn, Hampton, VA 23681 USA. RP Erlebacher, G (reprint author), Florida State Univ, Program Computat Sci & Engn, Tallahassee, FL 32306 USA. NR 33 TC 10 Z9 10 U1 0 U2 0 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 MAR PY 1998 VL 11 IS 1 BP 1 EP 29 DI 10.1007/s001620050078 PG 29 WC Mechanics; Physics, Fluids & Plasmas SC Mechanics; Physics GA ZJ517 UT WOS:000073224000001 ER PT J AU Jongen, T Gatski, TB AF Jongen, T Gatski, TB TI A nem approach to characterizing the equilibrium states of the Reynolds stress anisotropy in homogeneous turbulence SO THEORETICAL AND COMPUTATIONAL FLUID DYNAMICS LA English DT Article ID CHANNEL FLOW; SHEAR-FLOW; CLOSURES; EXPLICIT AB Using representation theory, a system of three scalar invariant relationships for homogeneous turbulence is developed which is equivalent to the general algebraic relationship for the Reynolds stress anisotropy tensor at equilibrium. From these three relations, which account for any additional anisotropy effect, a single scalar, algebraic relationship between three state variables, the turbulent production-to-dissipation rate ratio, a scaled turbulent time scale, and a ratio of mean rotation rate and strain rate invariants, is derived. This provides a unique characterization for all planar homogeneous turbulent fleas. With this result, equilibrium can be predicted based solely on the form of the pressure-strain rate closure model, including both linear and nonlinear models. Consequences of this formulation to the description of two-dimensional inhomogeneous flows and their prediction are also deduced. 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 25 TC 23 Z9 24 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 MAR PY 1998 VL 11 IS 1 BP 31 EP 47 DI 10.1007/s001620050079 PG 17 WC Mechanics; Physics, Fluids & Plasmas SC Mechanics; Physics GA ZJ517 UT WOS:000073224000002 ER PT J AU Dang, QL Margolis, HA Collatz, GJ AF Dang, QL Margolis, HA Collatz, GJ TI Parameterization and testing of a coupled photosynthesis stomatal conductance model for boreal trees SO TREE PHYSIOLOGY LA English DT Article DE black spruce; environmental controls on gas exchange; jack pine ID GENERAL-CIRCULATION MODEL; SIMPLE BIOSPHERE MODEL; ATMOSPHERIC CO2; TRANSPIRATION; FOREST; PRODUCTIVITY; EXCHANGE; CANOPY; SPRUCE AB A coupled photosynthesis-stomatal conductance model was parameterized and tested with branches of black spruce (Picea mariana (Mill.) B.S.P.) and jack pine (Pinus banksiana Lamb.) trees growing in the Northern Study Area of the Boreal Ecosystem-Atmosphere Study (BOREAS) in Manitoba, Canada. Branch samples containing foliage of all age-classes were harvested from a lowland old black spruce (OBS) and an old jack pine (OJP) stand and the responses of photosynthesis (A(n)) and stomatal conductance (g(s)) to temperature, CO2, light, and leaf-to-air vapor pressure difference (VPD) were determined under controlled laboratory conditions at the beginning, middle, and end of the growing season (Intensive Field Campaigns (IFC) 1, 2, and 3, respectively). The parameterized model was then tested against in situ field gas-exchange measurements in a young jack pine (YJP) and an upland black spruce (UBS) stand as well as in the OBS and OJP stands. Parameterization showed that Rubisco capacity (V-max), apparent quantum yield (alpha') and Q(10) for sink limitation were the most crucial parameters for the photosynthesis sub-model and that V-max varied among different measurement series in the laboratory. Verification of the model against the data used to parameterize it yielded correlation coefficients (r) of 0.97 and 0.93 for black spruce and jack pine, respectively, when IFC-specific parameters were used, and 0.77 and 0.87 when IFC-2 parameters were applied to all IFCs. For both measured and modeled g(s), the stomatal conductance sub-model, which linearly relates g(s) to (A(n)h(s))/c(s) (where h(s) and c(s) are relative humidity and CO2 mole fraction at the leaf surface, respectively), had significantly steeper slopes and higher r values when only the VPD response data were used for parameterization than when all of the response data were used for parameterization. Testing the photosynthesis sub-model against upper canopy field data yielded poor results when laboratory estimates of V-max, were used. Use of the mean V-max, estimated for all upper canopy branches measured on a given day improved model performance for jack pine (from a nonsignificant correlation between measured and modeled A(n) to r = 0.45), but not for black spruce (r = 0.45 for both cases). However, when V-max, was estimated for each branch sample individually, the model accurately predicted the 23 to 137% diurnal variation in A(n) for all stands for both the upper and lower canopy. This was true both when all of the other parameters were IFC-specific (r = 0.93 and 0.92 for black spruce and jack pine, respectively) and when only mid-growing season (IFC-2) values were used (r = 0.92 for both species). Branch-specific V-max estimates also permitted accurate prediction of field g(s) (r = 0.75 and 0.89 for black spruce and jack pine, respectively), although parameterization with all of the response data overestimated g(s) in the field, whereas parameterization with only the VPD response data provided unbiased predictions. Thus, after parameterization with the laboratory data, accurately modeling the range of A(n) and g(s) encountered in the field for both black spruce and jack pine was reduced to a single unknown parameter, V-max. C1 Univ Laval, Ctr Rech Biol Forestiere, Fac Foresterie & Geomat, Quebec City, PQ G1K 7P4, Canada. NASA, Goddard Space Flight Ctr, Biospher Sci Branch, Greenbelt, MD 20771 USA. RP Margolis, HA (reprint author), Univ Laval, Ctr Rech Biol Forestiere, Fac Foresterie & Geomat, Quebec City, PQ G1K 7P4, Canada. RI collatz, george/D-5381-2012 NR 41 TC 60 Z9 61 U1 1 U2 7 PU HERON PUBLISHING PI VICTORIA PA 202, 3994 SHELBOURNE ST, VICTORIA, BC V8N 3E2, CANADA SN 0829-318X J9 TREE PHYSIOL JI Tree Physiol. PD MAR PY 1998 VL 18 IS 3 BP 141 EP 153 PG 13 WC Forestry SC Forestry GA ZC611 UT WOS:000072598800001 ER PT J AU Breininger, DR Larson, VL Duncan, BW Smith, RB AF Breininger, DR Larson, VL Duncan, BW Smith, RB TI Linking habitat suitability to demographic success in Florida scrub-jays SO WILDLIFE SOCIETY BULLETIN LA English DT Article DE demography; habitat suitability; landscape patterns; remote sensing; sink; source ID LANDSCAPES AB We quantified relationships among Florida scrub-jay (Aphelocoma coerulescens) demography, density, and habitat suitability (HSI). A HSI map was derived using a HSI model, vegetation, and fire patterns that were mapped from aerial imagery. Family size, reproductive success, and survival data were collected at nests and territories between 1988 and 1993 using colorbanded jays. The ability to predict demographic performance (potential-breeder production minus breeder mortality) using the HSI model was tested at patch (0.1 and 1.0 ha) and territory (5.5 ha) scales. Florida scrub-jays preferred to nest in patches having the highest HSI and had the highest fledgling production in patches with the highest HSI. Yearling production, breeder survival, jay density, and demographic performance were all correlated with HSI. Minor improvements in the ability to predict demographic performance occurred as sampling scale increased from the smallest patch (0.1 ha) to the territory scale (5.5 ha). Population sources (potential-breeder production exceeded breeder mortality) comprised 28% of the habitat within the study site and had inadequate demographic performance to sustain population sinks (breeder mortality exceeded potential-breeder production), which comprised 62% of the habitat, lay densities were not indicators of demographic performance. C1 NASA, Biomed Operat Off, Dynamac Corp, Kennedy Space Ctr, FL 32899 USA. RP Breininger, DR (reprint author), NASA, Biomed Operat Off, Dynamac Corp, DYN-2, Kennedy Space Ctr, FL 32899 USA. NR 31 TC 24 Z9 24 U1 1 U2 7 PU WILDLIFE SOC PI BETHESDA PA 5410 GROSVENOR LANE, BETHESDA, MD 20814-2197 USA SN 0091-7648 J9 WILDLIFE SOC B JI Wildl. Soc. Bull. PD SPR PY 1998 VL 26 IS 1 BP 118 EP 128 PG 11 WC Biodiversity Conservation SC Biodiversity & Conservation GA 106QZ UT WOS:000075141500021 ER PT J AU Cwik, T Katz, DS Zuffada, C Jamnejad, V AF Cwik, T Katz, DS Zuffada, C Jamnejad, V TI The application of scalable distributed memory computers to the finite element modeling of electromagnetic scattering SO INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING LA English DT Article DE finite elements; electromagnetics; parallel computing; scattering; sparse matrices ID PARALLEL COMPUTATION; MATRICES; SYSTEMS AB Large-scale parallel computation can be an enabling resource in many areas of engineering and science if the parallel simulation algorithm attains an appreciable fraction of the machine peak performance, and if undue cost in porting the code or in developing the code for the parallel machine is not incurred. The issue of code parallelization is especially significant when considering unstructured mesh simulations. The unstructured mesh models considered in this paper result from a finite element simulation of electromagnetic fields scattered from geometrically complex objects (either penetrable or impenetrable.) The unstructured mesh must be distributed among the processors, as must the resultant sparse system of linear equations. Since a distributed memory architecture does not allow direct access to the irregularly distributed unstructured mesh and sparse matrix data, partitioning algorithms not needed in the sequential software have traditionally been used to efficiently spread the data among the processors. This paper presents a new method for simulating electromagnetic fields scattered from complex objects; namely, an unstructured finite element code that does not use traditional mesh partitioning algorithms. (C) 1998 John Wiley & Sons, Ltd. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Cwik, T (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr,M-S 168-522, Pasadena, CA 91109 USA. OI Katz, Daniel S./0000-0001-5934-7525 NR 20 TC 3 Z9 3 U1 0 U2 0 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 FEB 28 PY 1998 VL 41 IS 4 BP 759 EP 776 DI 10.1002/(SICI)1097-0207(19980228)41:4<759::AID-NME315>3.0.CO;2-V PG 18 WC Engineering, Multidisciplinary; Mathematics, Interdisciplinary Applications SC Engineering; Mathematics GA YV174 UT WOS:000071796800009 ER PT J AU Ziemke, JR Herman, JR Stanford, JL Bhartia, PK AF Ziemke, JR Herman, JR Stanford, JL Bhartia, PK TI Total ozone UVB monitoring and forecasting: Impact of clouds and the horizontal resolution of satellite retrievals SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID ULTRAVIOLET AB This study compares the horizontal resolution of solar backscatter ultraviolet 2 (SBUV2) total ozone (Omega) fields with those from the new NASA earth probe (EP) and Advanced Earth Observing Satellite (ADEOS) total ozone mapping spectrometer (TOMS) side-scanning photometers. The latter instruments provide high resolution, easily resolving the medium-scale waves (4-7 wavelengths around the Earth at a fixed latitude) that dominate day-to-day midlatitude Omega fluctuations. In contrast, SBUV2 instruments do not, since these devices measure only at nadir (straight downward), yielding similar to 14 measurements daily at a given latitude. This method has consequences not only for global monitoring of Omega and ultraviolet B (UVB, 290-320 nm), but also for short-timescale Omega and UVB predictions in summer because timescales of a few days are coupled to medium horizontal scales (several thousand kilometers) by baroclinic waves that typically force the observed Omega variations. We use a simple Omega prediction model to test the use of Omega fields from TOMS and SBUV instruments and show that the higher zonal resolution from side-scanning TOMS instruments results in sizeable reductions in Omega prediction errors, whereas predictions using SBUV2 Omega are no better than persistence (where tomorrow's Omega is taken to be today's) in the biologically important summer months. Daily variabilities (equivalent to errors in 24-hour persistence forecasting of Omega) in high-resolution TOMS midlatitude ozone during summer are shown to sometimes exceed 50 Dobson units, producing daily changes of 20% or greater in computed ground-level clear-sky UV index. This study demonstrates that even these large daily changes in measured or predicted clear-sky UV are usually smaller than daily UV changes associated with transient clouds. While surface UVB variability is dominated by local cloudiness variations, Omega forecasts can enhance UVB prediction in relatively cloud free regions such as the U.S. desert southwest and in stagnant high-pressure regimes that can persist for 1-2 weeks in summer. Furthermore, as weather forecast models increase in accuracy of forecasted cloudiness, accurate predictions will allow more accurate UVB forecasts for cloud free regions, the locations where they are most needed. Results from the present paper show, however, that high-resolution TOMS-like side-scanning Omega measurements are required for ozone and UVB monitoring and prediction, rather than SBUV-type nadir observations. C1 NASA, Goddard Space Flight Ctr, Chem & Dynam Branch, Greenbelt, MD 20771 USA. Iowa State Univ Sci & Technol, Dept Phys & Astron, Ames, IA 50011 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; herman@tparty.gsfc.nasa.gov; stanford@iastate.edu; bhartia@carioca.gsfc.nasa.gov RI Bhartia, Pawan/A-4209-2016; OI Bhartia, Pawan/0000-0001-8307-9137; Herman, Jay/0000-0002-9146-1632 NR 15 TC 10 Z9 10 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 FEB 27 PY 1998 VL 103 IS D4 BP 3865 EP 3871 DI 10.1029/97JD03324 PG 7 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA YZ481 UT WOS:000072258400011 ER PT J AU Lin, B Wielicki, B Minnis, P Rossow, W AF Lin, B Wielicki, B Minnis, P Rossow, W TI Estimation of water cloud properties from satellite microwave, infrared and visible measurements in oceanic environments 1. Microwave brightness temperature simulations SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID LIQUID WATER; MARINE-ENVIRONMENT; MODEL; RADIATION; SSM/I; ICE; RETRIEVAL; SURFACE; PARAMETERIZATION; PRECIPITATION AB Theoretical calculations are used to examine the spectral characteristics of SSM/I (special sensor microwave/imager) brightness temperature (Tb) values for non-precipitating clouds over oceans. It was found that liquid water path (LWP) and the cloud water temperature (Tw) could be derived simultaneously with a technique using the SSM/I 37-GHz and 85-GHz brightness temperatures. Uncertainties in column water vapor (CWV) are the most important error sources in the estimation of LWP and Tw, while ice particles smaller than 100 mu m in nonprecipitating clouds have a very weak effect (< 1 K) on the Tb values at the relevant SSM/I frequencies. When all SSM/I instrument noise and error sources associated with sea surface temperature, wind speed, and CWV are considered, the biases in LWP from current microwave methods are very small (less than or equal to 0.01 mm) and the standard deviations vary from 0.02 to 0.04 mm. The Tw bias and standard deviation decrease with increasing LWP from about 6 and 8 K, respectively, for clouds with low LWP to < 1 K for LWP > 0.4 mm. For most marine stratocumulus clouds (LWP similar to 0.1 to 0.2 mm) the Tw bias and standard deviation are about 2 and 4 K, respectively, resulting in cloud height errors of similar to 1 to 2 km. The method should yield an improvement in the accuracy of retrieved LWP because it more closely approximates cloud temperature than previous techniques. To use the radiative transfer results, it is necessary to normalize or calibrate them to the observations. This relative calibration using 22-GHz brightness temperatures reveals differences of 2.86 K and -1.93 K for the 37-GHz horizontal and 85-GHz vertical channels, respectively, between the SSM/I observations and the model simulations. In multilayered cloud conditions, this new microwave analysis method, when combined with infrared data should make it possible to determine cloud temperature for an upperlevel ice cloud from the infrared brightness temperatures while simultaneously deriving Tw and LWP for the lower liquid water cloud with the microwave data. C1 NASA, Langley Res Ctr, Hampton, VA 23681 USA. NASA, Goddard Inst Space Studies, New York, NY 10025 USA. RP Lin, B (reprint author), NASA, Langley Res Ctr, Mail Stop 420, Hampton, VA 23681 USA. EM bing@front.larc.nasa.gov; clwbr@giss.nasa.gov RI Rossow, William/F-3138-2015; Minnis, Patrick/G-1902-2010 OI Minnis, Patrick/0000-0002-4733-6148 NR 45 TC 36 Z9 38 U1 0 U2 2 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD FEB 27 PY 1998 VL 103 IS D4 BP 3873 EP 3886 DI 10.1029/97JD02816 PG 14 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA YZ481 UT WOS:000072258400012 ER PT J AU Lin, B Minnis, P Wielicki, B Doelling, DR Palikonda, R Young, DF Uttal, T AF Lin, B Minnis, P Wielicki, B Doelling, DR Palikonda, R Young, DF Uttal, T TI Estimation of water cloud properties from satellite microwave, infrared and visible measurements in oceanic environments 2. Results SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID SOLAR-RADIATION MEASUREMENTS; EFFECTIVE PARTICLE RADIUS; UPPER-AIR OBSERVATIONS; LIQUID WATER; MARINE STRATOCUMULUS; OPTICAL-THICKNESS; PARAMETERIZATION; SURFACE; CLIMATE; PATH AB yA microwave (MW) method for deriving cloud liquid water path (LWP) and cloud water temperature (Tw) is validated by using soundings and results from a visible (VIS) and infrared (IR) retrieval method. The two retrieval methods are combined into a single technique, MVI (microwave, visible, and infrared), to estimate the frequency of multilayered clouds and the effective droplet radius re in water clouds. These techniques were applied to Meteosat and special sensor microwave/imager (SSM/I) data taken during June 1-28, 1992, over the Atlantic Stratocumulus Transition Experiment (ASTEX) region. For low clouds, as identified with the VIS-IR method, Tw on avenge is nearly the same as the VIS-IR cloud-top temperatures (Tc). A negative correlation between LWP and Tc was found for the clouds. For midlevel clouds, Tw is about 8 K warmer than Tc because of either large cloud thicknesses or multilayered clouds. When high clouds are found by the VIS-IR method, Tc is similar to 30 K colder than Tw, indicating that lower-level liquid-water clouds may be detected by the MW method. On the basis of the matched Tw and Tc obsevations, the estimated frequencies of multilayered high, middle, and low clouds are about 36%, 19%, and 0%, respectively, values that are similar to cloud radar measurements. Matched satellite and ground-based radar data show that the MVI technique can separate cloud layers when high ice clouds overlap lower liquid water clouds. The distributions of re for water clouds are about the same for low, middle, and broken clouds with mean and standard deviations of similar to 12 and 10 mu m, respectively. The frequency of large droplets (r(e) > 16 mu m) suggests that drizzle occurs in similar to 30% of the matched Meteosat-SSM/I cloudy conditions. C1 NASA, Langley Res Ctr, Hampton, VA 23681 USA. Analyt Serv & Mat Inc, Hampton, VA 23681 USA. NOAA, Environm Technol Lab, Boulder, CO 80303 USA. Hampton Univ, Ctr Atmospher Sci, Hampton, VA 23668 USA. RP Lin, B (reprint author), NASA, Langley Res Ctr, Mail Stop 420, Hampton, VA 23681 USA. EM bing@front.larc.nasa.gov; doelling@elviso.larc.nasa.gov RI Minnis, Patrick/G-1902-2010 OI Minnis, Patrick/0000-0002-4733-6148 NR 42 TC 32 Z9 33 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 FEB 27 PY 1998 VL 103 IS D4 BP 3887 EP 3905 DI 10.1029/97JD02817 PG 19 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA YZ481 UT WOS:000072258400013 ER PT J AU Koch, D Rind, D AF Koch, D Rind, D TI Beryllium 10 beryllium 7 as a tracer of stratospheric transport SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID VERTICAL TRANSPORT; BE-7; PB-210; MODEL; TROPOSPHERE; AEROSOLS AB We use the ratio between cosmogenic radionuclides beryllium 10 (t(1/2) 1.5 x 10(6) years) and beryllium 7 (t(1/2)=53 days) to study stratospheric transport, particularly the exchange between the tropics and the high latitudes and as an indicator of stratosphere-troposphere exchange. Both tracers are generated steadily, with maximum production occurring at midlatitudes of the stratosphere. During transport away from their source the ratio Be-10/Be-7 increases and thus acts as a clock for air mass age. According to model (GISS GCM) calculations, the tropics is a reservoir of high-ratio air With the high magnitude of Be-10/Be-7 partly a. consequence of air mixed in from higher latitudes. The observations of Dibb et al. [1994] show a vertical maximum in Be-10/Be-7 in the lower arctic stratosphere during the spring of 1989; model results qualitatively reproduce this maximum and suggest that it may result from transport of tropical air to high latitudes during winter. The model ratio values are not so large as in these observations, possibly due to either excessive leakage into the troposphere near the pole or to insufficient transport from the tropical stratosphere to the pole. Beryllium 10 and Be-7 observations, combined with model analysis, can be a useful indicator of transport processes in the troposphere/stratosphere system. C1 NASA, Goddard Inst Space Studies, New York, NY 10025 USA. Columbia Univ, Ctr Climate Syst Res, New York, NY 10027 USA. RP Koch, D (reprint author), NASA, Goddard Inst Space Studies, 2880 Broadway, New York, NY 10025 USA. EM koch@thebes.giss.nasa.gov; drind@giss.nasa.gov NR 23 TC 52 Z9 53 U1 3 U2 10 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 FEB 27 PY 1998 VL 103 IS D4 BP 3907 EP 3917 DI 10.1029/97JD03117 PG 11 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA YZ481 UT WOS:000072258400014 ER PT J AU Jensen, EJ Toon, OB Kinne, S Sachse, GW Anderson, BE Chan, KR Twohy, CH Gandrud, B Heymsfield, A Miake-Lye, RC AF Jensen, EJ Toon, OB Kinne, S Sachse, GW Anderson, BE Chan, KR Twohy, CH Gandrud, B Heymsfield, A Miake-Lye, RC TI Environmental conditions required for contrail formation and persistence SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID NUCLEATION AB The ambient temperatures and humidities required for contrail formation and persistence are determined from in situ measurements during the Subsonic Aircraft: Contrail and Cloud Effects Special Study (SUCCESS) experiment. Ambient temperatures and water vapor concentrations were measured with the meteorological measurement system a laser hygrometer, and a cryogenic hygrometer (all onboard the DC-8). The threshold temperatures are compared with theoretical estimates based on simple models of plume evolution. Observed contrail onset temperatures for contrail formation are shown to be 0-2 K below the liquid-saturation threshold temperature, implying that saturation with respect to liquid water must be reached at some point in the plume evolution. Visible contrails observed during SUCCESS persisted longer than a few minutes only when substantial ambient supersaturations with respect to ice existed over large regions. On some occasions, contrails formed at relatively high temperatures (greater than or equal to -50 degrees C) due to very high ambient supersaturations with respect to ice (of the order of 150%). These warm contrails usually formed in the presence of diffuse cirrus. Water vapor from sublimated ice crystals that entered the engine was probably necessary for contrail formation in some of these cases. At temperatures above about -50 degrees C, contrails can only form if the ambient air is supersaturated with respect to ice, so these contrails should persist and grow. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Univ Colorado, Dept Atmospher Sci, Boulder, CO 80309 USA. Bay Area Environm Res Inst, San Francisco, CA USA. NASA, Langley Res Ctr, Hampton, VA 23665 USA. Natl Ctr Atmospher Res, Boulder, CO 80307 USA. Aerodyne Res Inc, Billerica, MA 01821 USA. RP Jensen, EJ (reprint author), NASA, Ames Res Ctr, MS 245-4, Moffett Field, CA 94035 USA. EM ejensen@sky.arc.nasa.gov RI Heymsfield, Andrew/E-7340-2011 NR 19 TC 45 Z9 45 U1 0 U2 6 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD FEB 27 PY 1998 VL 103 IS D4 BP 3929 EP 3936 DI 10.1029/97JD02808 PG 8 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA YZ481 UT WOS:000072258400016 ER PT J AU Langhoff, SR Bauschlicher, CW Hudgins, DM Sandford, SA Allamandola, LJ AF Langhoff, SR Bauschlicher, CW Hudgins, DM Sandford, SA Allamandola, LJ TI Infrared spectra of substituted polycyclic aromatic hydrocarbons SO JOURNAL OF PHYSICAL CHEMISTRY A LA English DT Article ID INTERPLANETARY DUST PARTICLES; EMISSION FEATURES; CARBONACEOUS CHONDRITES; ELECTRONIC-SPECTRA; MASS-SPECTROMETRY; MICRON EMISSION; ORGANIC-MATTER; NAPHTHALENE; CATIONS; SPECTROSCOPY AB Calculations are carried out using density functional theory (DFT) to determine the harmonic frequencies and intensities of 1-methylanthracene, 9-methylanthracene, 9-cyanoanthracene, 2-aminoanthrocene, acridine, and their positive ions. The theoretical data are compared with matrix-isolation spectra for these species also reported in this work. The theoretical and experimental frequencies and relative intensities for the neutral species are in generally good agreement, whereas the positive ion spectra are only in qualitative agreement. Relative to anthracene, we find that substitution of a. methyl or CN for a hydrogen does not significantly affect the spectrum other than to add the characteristic methyl C-H and C drop N stretches near 2900 and 2200 cm(-1), respectively. However, addition of NH2 dramatically affects the spectrum of the neutral. Not only are the NH2 modes themselves strong, but this electron-withdrawing group induces sufficient partial charge on the ring to give the neutral molecule spectra characteristics of the anthracene cation. The sum of the absolute intensities is about four times larger for 2-aminoanthracene than those for 9-cyanoanthracene. Substituting nitrogen in the ring at the nine position (acridine) does not greatly alter the spectrum compared with anthracene. C1 NASA, Ames Res Ctr, Space Technol Div, Moffett Field, CA 94035 USA. NASA, Ames Res Ctr, Computat Chem Branch, Moffett Field, CA 94035 USA. NASA, Ames Res Ctr, Astrophys Branch, Moffett Field, CA 94035 USA. RP NASA, Ames Res Ctr, Space Technol Div, Mail Stop 230-3, Moffett Field, CA 94035 USA. NR 59 TC 53 Z9 54 U1 1 U2 14 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 FEB 26 PY 1998 VL 102 IS 9 BP 1632 EP 1646 DI 10.1021/jp9731563 PG 15 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA YZ897 UT WOS:000072305400026 PM 11542816 ER PT J AU Ueda, Y Takahashi, T Inoue, H Tsuru, T Sakano, M Ishisaki, Y Ogasaka, Y Makishima, K Yamada, T Ohta, K Akiyama, M AF Ueda, Y Takahashi, T Inoue, H Tsuru, T Sakano, M Ishisaki, Y Ogasaka, Y Makishima, K Yamada, T Ohta, K Akiyama, M TI A population of faint galaxies that contribute to the cosmic X-ray background SO NATURE LA English DT Article ID GAS IMAGING SPECTROMETER; N-LOG S; BOARD ASCA; SPECTRUM; ORIGIN AB The origin of the cosmic X-ray background radiation(1,2) has remained mysterious since its discovery(3) thirty-five years ago. Investigation of its origin has been difficult because instruments have had insufficient resolution to distinguish small, faint sources in the hard X-ray band (above 2 keV) that dominates the background. Until now, only three per cent of the flux in the 2-10 keV band could be attributed to individual sources(4,5). Here we report the results of a survey 100 times more sensitive than previous studies in the 2-10 keV band. We find many faint resolved sources, whose integrated flux accounts for 30 per cent of the X-ray background in this energy range. The average spectrum of the resolved sources is harder than those of nearby bright active galactic nuclei and is dose to the spectrum of the X-ray background radiation. This means that a new dass of sources, with hard X-ray spectra, dominate the sky at photon energies above 2 keV. C1 Inst Space & Astronaut Sci, Kanagawa 229, Japan. Kyoto Univ, Dept Phys, Kyoto 60601, Japan. Tokyo Metropolitan Univ, Dept Phys, Tokyo 19203, Japan. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Tokyo, Dept Phys, Bunkyo Ku, Tokyo 113, Japan. Tohoku Univ, Inst Astron, Sendai, Miyagi 98077, Japan. Kyoto Univ, Dept Astron, Kyoto 60601, Japan. RP Ueda, Y (reprint author), Inst Space & Astronaut Sci, Yoshinodai, Kanagawa 229, Japan. NR 24 TC 67 Z9 67 U1 0 U2 1 PU MACMILLAN MAGAZINES LTD PI LONDON PA PORTERS SOUTH, 4 CRINAN ST, LONDON, ENGLAND N1 9XW SN 0028-0836 J9 NATURE JI Nature PD FEB 26 PY 1998 VL 391 IS 6670 BP 866 EP 868 DI 10.1038/36047 PG 3 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA YZ206 UT WOS:000072230900043 ER PT J AU Zhang, RH Rothstein, LM Busalacchi, AJ AF Zhang, RH Rothstein, LM Busalacchi, AJ TI Origin of upper-ocean warming and El Nino change on decadal scales in the tropical Pacific Ocean SO NATURE LA English DT Article ID NORTH PACIFIC; CLIMATE VARIABILITY; MODEL; PREDICTABILITY; CIRCULATIONS; TEMPERATURE; AMERICA AB The cause of decadal-scale variability in the tropical Pacific Ocean-such as that marked by the 1976-77 shift in the El Nino/Southern Oscillation(1-7)-is poorly understood. Unravelling the mechanism of the recent decade-long warming in the tropical upper ocean is a particularly important challenge, given the link to El Nino variability, but establishing the hypothesized interannual/decadal oceanic connections between middle latitudes and tropics has proved elusive(8). Here we present observational evidence that Pacific upper-ocean warming and decadal changes in the Fl Nino/Southern Oscillation after 1976 may originate from decadal mid-latitude variability, In the middle 1970s the North Pacific Ocean is observed to have undergone a dear phase-transition; a 'see-saw' subsurface temperature anomaly pattern that rotates clockwise around the subtropical gyre. At middle latitudes a subsurface warm anomaly formed in the early 1970s from subducted surface-waters and penetrated through the subtropics and into the tropics, thus perturbing the tropical thermocline and driving the formation of a warm surface-water anomaly that may have influenced El Nino in the 1980s. The identification of this teleconnection of extratropical thermal anomalies to the tropics, through a subsurface ocean "bridge", may enable improved prediction of decadal-scale climate variability. C1 Univ Rhode Isl, Grad Sch Oceanog, Narragansett, RI 02882 USA. NASA, Goddard Space Flight Ctr, Lab Hydrospher Proc, Greenbelt, MD 20771 USA. RP Zhang, RH (reprint author), Univ Rhode Isl, Grad Sch Oceanog, Narragansett, RI 02882 USA. NR 28 TC 146 Z9 161 U1 2 U2 8 PU MACMILLAN MAGAZINES LTD PI LONDON PA PORTERS SOUTH, 4 CRINAN ST, LONDON, ENGLAND N1 9XW SN 0028-0836 J9 NATURE JI Nature PD FEB 26 PY 1998 VL 391 IS 6670 BP 879 EP 883 DI 10.1038/36081 PG 5 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA YZ206 UT WOS:000072230900048 ER PT J AU Kemp, PA AF Kemp, PA TI Microcontroller incorporates eight interrupts SO ELECTRONIC DESIGN LA English DT Article C1 NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. RP Kemp, PA (reprint author), NASA, Lyndon B Johnson Space Ctr, 2101 NASA Rd,1 Mail Code EP6, Houston, TX 77058 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU PENTON PUBL INC PI CLEVELAND PA 1100 SUPERIOR AVE, CLEVELAND, OH 44114-2543 USA SN 0013-4872 J9 ELECTRON DES JI Electron. Des. PD FEB 23 PY 1998 VL 46 IS 4 BP 124 EP + PG 3 WC Engineering, Electrical & Electronic SC Engineering GA YY683 UT WOS:000072173200023 ER PT J AU Sreekumar, P Bertsch, DL Dingus, BL Esposito, JA Fichtel, CE Hartman, RC Hunter, SD Kanbach, G Kniffen, DA Lin, YC Mayer-Hasselwander, HA Michelson, PF von Montigny, C Mucke, A Mukherjee, R Nolan, PL Pohl, M Reimer, O Schneid, E Stacy, JG Stecker, FW Thompson, DJ Willis, TD AF Sreekumar, P Bertsch, DL Dingus, BL Esposito, JA Fichtel, CE Hartman, RC Hunter, SD Kanbach, G Kniffen, DA Lin, YC Mayer-Hasselwander, HA Michelson, PF von Montigny, C Mucke, A Mukherjee, R Nolan, PL Pohl, M Reimer, O Schneid, E Stacy, JG Stecker, FW Thompson, DJ Willis, TD TI Egret observations of the extragalactic gamma-ray emission SO ASTROPHYSICAL JOURNAL LA English DT Article DE diffuse radiation; gamma rays, observations; surveys ID BLACK-HOLES; COSMIC-RAY; X-RAY; RADIATION; GALAXIES; ORIGIN; ASTRONOMY; EVOLUTION; TELESCOPE; SATELLITE AB The all-sky survey in high-energy gamma rays (E > 30 MeV) carried out by EGRET aboard the Compton Gamma Ray Observatory provides a unique opportunity to examine in detail the diffuse gamma-ray emission. The observed diffuse emission has a Galactic component arising from cosmic-ray interactions with the local interstellar gas and radiation, as well as an almost uniformly distributed component that is generally believed to originate outside the Galaxy. Through a careful study and removal of the Galactic diffuse emission, the flux, spectrum, and uniformity of the extragalactic emission are deduced. The analysis indicates that the extragalactic emission is well described by a power-law photon spectrum with an index of -(2.10 +/- 0.03) in the 30 MeV to 100 GeV energy range. No large-scale spatial anisotropy or changes in the energy spectrum are observed in the deduced extragalactic emission. The most likely explanation for the origin of this extragalactic high-energy gamma-ray emission is that it arises primarily from unresolved gamma-ray-emitting blazars. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Space Res Assoc, Greenbelt, MD USA. Univ Utah, Salt Lake City, UT 84112 USA. Max Planck Inst Extraterr Phys, D-37075 Garching, Germany. Hampden Sydney Coll, Hampden Sydney, VA 23943 USA. Stanford Univ, WW Hansen Expt Phys Lab, Stanford, CA 94305 USA. Landessternwarte Heidelberg Konigstuhl, Heidelberg, Germany. Columbia Univ Barnard Coll, New York, NY 10027 USA. Danish Space Res Inst, DK-2800 Lyngby, Denmark. Northrop Grumman Aerosp Corp, Bethpage, NY 11714 USA. Univ New Hampshire, Durham, NH 03428 USA. RP Sreekumar, P (reprint author), NASA, Goddard Space Flight Ctr, Code 660, Greenbelt, MD 20771 USA. RI Nolan, Patrick/A-5582-2009; Hunter, Stanley/D-2942-2012; Thompson, David/D-2939-2012; Stecker, Floyd/D-3169-2012; Reimer, Olaf/A-3117-2013; OI Thompson, David/0000-0001-5217-9135; Reimer, Olaf/0000-0001-6953-1385; Dingus, Brenda/0000-0001-8451-7450 NR 63 TC 634 Z9 636 U1 2 U2 4 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 FEB 20 PY 1998 VL 494 IS 2 BP 523 EP 534 DI 10.1086/305222 PN 1 PG 12 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YZ796 UT WOS:000072292500004 ER PT J AU Wang, QD Gotthelf, EV AF Wang, QD Gotthelf, EV TI ROSAT and ASCA observations of the crab-like supernova remnant N157B in the large magellanic cloud SO ASTROPHYSICAL JOURNAL LA English DT Article DE ISM, individual (N157B); magellanic clouds; supernova remnants; X-rays, ISM ID X-RAY; 30 DORADUS; NOVA REMNANTS; PULSAR; RADIO; ABUNDANCES; EXTINCTION; 30-DORADUS; REGION; STARS AB We report the results of ROSAT and ASCA X-ray observations of the supernova remnant N157B (or 30 Dor B, SNR 0539-69.1) in the Large Magellanic Cloud. For comparison, we also briefly describe the results on SNR 0540-69.3, the only confirmed Crab-like remnant in the Cloud. The X-ray emission from N157B can be decomposed into a bright comet-shaped feature, superposed on a diffuse emission region with a dimension of similar to 20 pc. The flat and nearly featureless spectrum of the remnant is distinctly different from those of young shell-like remnants, suggesting a predominantly Crab-like nature of N157B. Characterized by a power law with an energy slope of similar to 1.5, the spectrum of N157B above similar to 2 keV is, however, considerably steeper than that of SNR 0540-69.3, which has a slope of similar to 1.0. At lower energies, the spectrum of N157B presents marginal evidence for emission lines, which if real most likely arise in hot gas of the diffuse emission region. The hot gas has a characteristic thermal temperature of 0.4-0.7 keV. No significant periodic signal is detected from N157B in the period range of 3 x 10(-3)-2000 s. The pulsed fraction is less than or similar to 9% (99% confidence) in the 2-7 keV range. We discuss the nature of the individual X-ray components. In particular, we suggest that the synchrotron radiation of relativistic particles from a fast-moving (similar to 10(3) km s(-1)) pulsar explains the size, morphology, spectrum, and energetics of the comet-shaped X-ray feature. We infer the age of the remnant as similar to 5 x 10(3) yr. The lack of radio polarization of the remnant may be due to Faraday dispersion by foreground H II gas. C1 Northwestern Univ, Dearborn Observ, Evanston, IL 60208 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Wang, QD (reprint author), Northwestern Univ, Dearborn Observ, 2131 Sheridan Rd, Evanston, IL 60208 USA. NR 37 TC 56 Z9 56 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 FEB 20 PY 1998 VL 494 IS 2 BP 623 EP 635 DI 10.1086/305214 PN 1 PG 13 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YZ796 UT WOS:000072292500012 ER PT J AU Fierro, JM Michelson, PF Nolan, PL Thompson, DJ AF Fierro, JM Michelson, PF Nolan, PL Thompson, DJ TI Phase-resolved studies of the high-energy gamma-ray emission from the Crab, Geminga, and Vela pulsars SO ASTROPHYSICAL JOURNAL LA English DT Article DE gamma rays, observations; pulsars, individual (Crab, Geminga, Vela) ID RAPIDLY SPINNING PULSARS; EGRET OBSERVATIONS; LONG-TERM; RADIATION; TELESCOPE; NEBULA; COMPTON; MODEL; GAPS; GRO AB Using the first 3.5 years of observations from the Energetic Gamma Ray Telescope (EGRET) on board the Compton Gamma Ray Observatory, phase-resolved analyses are performed on the emission from the three brightest high-energy gamma-ray pulsars: Crab, Geminga, and Vela. For each pulsar, it is found that there is detectable high-energy gamma-ray emission above the galactic diffuse background throughout much of the pulsar rotation cycle. A hardness ratio is introduced to characterize the evolution of the spectral index as a function of pulsar phase. While the hardest emission from the Crab and Vela pulsars comes from the bridge region between the two gamma-ray peaks, the hardest emission from Geminga corresponds to the second gamma-ray peak. For all three pulsars, phase-resolved spectra of the pulse profile components reveal that although there is a large variation in the spectral index over the pulsar phase interval, the high-energy spectral turnover, if any, occurs at roughly the same energy in each component. The high-energy gamma-ray emission from the Crab complex appears to include an unpulsed ultrasoft component of spectral index similar to-4.3, which dominates the total emission below 100 MeV. This component is consistent with the expected emission from the tail end of the Crab Nebula synchrotron emission. C1 Stanford Univ, WW Hansen Expt Phys Lab, Stanford, CA 94305 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Fierro, JM (reprint author), Stanford Univ, WW Hansen Expt Phys Lab, Stanford, CA 94305 USA. RI Nolan, Patrick/A-5582-2009; Thompson, David/D-2939-2012 OI Thompson, David/0000-0001-5217-9135 NR 43 TC 121 Z9 121 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 FEB 20 PY 1998 VL 494 IS 2 BP 734 EP 746 DI 10.1086/305219 PN 1 PG 13 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YZ796 UT WOS:000072292500021 ER PT J AU Evans, NR Bohm-Vitense, E Carpenter, K Beck-Winchatz, B Robinson, R AF Evans, NR Bohm-Vitense, E Carpenter, K Beck-Winchatz, B Robinson, R TI Classical cepheid masses: U Aquilae SO ASTROPHYSICAL JOURNAL LA English DT Article DE binaries, spectroscopic; Cepheids; stars, fundamental parameters; stars, individual (U Aquilae) ID RADIATIVE OPACITIES; STELLAR MODELS; LUMINOSITY; STARS; BINARIES; ORBIT AB We have obtained medium-resolution spectra (lambda/Delta lambda similar to 20,000) of the hot binary companion to the classical Cepheid U Aql with the Goddard High Resolution Spectrograph on the Hubble Space Telescope (HST). These have been used to determine the orbital velocity amplitude. Combining this with the orbital velocity amplitude of the Cepheid from the ground-based orbit and the mass of the companion inferred from its spectral type, we measure a mass of the Cepheid of 5.1 +/- 0.7 M.. We discuss the full sample of Cepheids for which we have determined masses with HST (S Mus, V350 Sgr, Y Car, and U Aql) and also SU Cyg (mass from IUE). The HST masses are in agreement with the luminosities predicted by recent evolutionary tracks with moderate overshoot. This comparison, however, may be altered by reassessment of Cepheid distances based on Hipparcos parallaxes. C1 Harvard Smithsonian Ctr Astrophys, Cambridge, MA 02138 USA. Univ Washington, Dept Astron, Seattle, WA 98195 USA. NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, Greenbelt, MD 20771 USA. NASA, Goddard Space Flight Ctr, Comp Sci Corp, Astron Programs, Greenbelt, MD 20771 USA. RP Evans, NR (reprint author), Harvard Smithsonian Ctr Astrophys, 60 Garden St, Cambridge, MA 02138 USA. EM nevans@cfa.harvard.edu; erica@bluemoon.astro.washington.edu; hrscarpenter@tmal.gsfc.nasa.gov; bbeck@bluemoon.astro.washington.edu; hrsrobinson@tma1.gsfc.nasa.gov RI Carpenter, Kenneth/D-4740-2012 NR 28 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 FEB 20 PY 1998 VL 494 IS 2 BP 768 EP 772 DI 10.1086/305242 PN 1 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YZ796 UT WOS:000072292500025 ER PT J AU Linnell, AP Etzel, PB Hubeny, I Olson, EC AF Linnell, AP Etzel, PB Hubeny, I Olson, EC TI A photometric and spectrophotometric study of MR Cygni SO ASTROPHYSICAL JOURNAL LA English DT Article DE binaries, eclipsing; stars, individual (MR Cygni); stars, mass loss; ultraviolet, stars ID LIGHT CURVES; SPECTROSCOPIC OBSERVATIONS; SPECTRUM SYNTHESIS; SYNTHESIS PROGRAM; BINARY STARS; ATMOSPHERES; EVOLUTION; SYSTEMS; MASSES; STREAM AB A self-consistent, physically accurate program suite has been used in an accurate simulation of new spectroscopy and photometry of MR Cygni. Analysis of both the spectroscopic and photometric data used spectrum synthesis techniques and a synthetic photometry augmentation of a light synthesis program package. The theoretical light curves closely fit the observational data. The same self-consistent parameters from the light synthesis solution produced synthetic spectra precisely fitting the observed spectra at all orbital phases. The IRAF-reduced spectroscopy has produced an accurate double-lined radial velocity curve. The derived mass ratio differs greatly from photometric mass ratios in the literature. New UBV photometry closely replicates existing data and indicates photometric stability of the binary system. A synthetic spectrum fitted to IUE data established the primary component T-eff. The light curve solution determined a single set of system parameters used to calculate U, B, and V light curves. We conclude that MR Cygni is a member of the relatively rare class of hot Algol systems defined by Popper. It is likely that mass transfer still is in progress, but there is no evidence, either from orbital period variation or from a bright spot on the mass gainer, for its existence. The lack of H alpha emission in any of our spectra, including one at phase 0.063, suggests a small current rate of mass transfer. The fact that our computationally self-consistent procedure has successfully represented both the photometry and the spectroscopy for a binary system whose components are appreciably distorted demonstrates the overall power of the procedure. C1 Michigan State Univ, Dept Phys & Astron, E Lansing, MI 48824 USA. San Diego State Univ, Dept Astron, San Diego, CA 92182 USA. NASA, Goddard Space Flight Ctr, AURA NOAO, Greenbelt, MD 20771 USA. Univ Illinois, Dept Astron, Urbana, IL 61801 USA. RP Linnell, AP (reprint author), Univ Washington, Dept Astron, Seattle, WA 98195 USA. NR 35 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 FEB 20 PY 1998 VL 494 IS 2 BP 773 EP 782 DI 10.1086/305231 PN 1 PG 10 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YZ796 UT WOS:000072292500026 ER PT J AU Kalus, G Johansson, S Wahlgren, GM Leckrone, DS Thorne, AP Brandt, JC AF Kalus, G Johansson, S Wahlgren, GM Leckrone, DS Thorne, AP Brandt, JC TI Abundance and isotopic composition of platinum in chi Lupi and HR 7775 derived with the help of new laboratory spectra of Pt II SO ASTROPHYSICAL JOURNAL LA English DT Article DE stars, abundances; stars, chemically peculiar; stars, individual(HR 7775); stars, individual ((chi) Lupi) ID PT-II; HYPERFINE-STRUCTURE; ENERGY-LEVELS; B-STAR; SHIFTS; HG AB The platinum isotope anomaly observed in the chemically peculiar HgMn star chi Lupi has been confirmed by analysis with new high-resolution laboratory spectra recorded with the VUV Fourier transform spectrometer at Lund University. The chi Lupi platinum composition is shown to be a mixture of isotopes 196 and 198. Recent observations made with the Hubble Space Telescope Goddard High-Resolution Spectrograph (HST/GHRS) of a similar temperature HgMn star, HR 7775, have also been analyzed: these show that line profiles of Pt II are best fitted by the terrestrial isotopic mixture. Fits of synthetic spectra to the observations yield a logarithmic abundance of platinum of log N(Pt) = +6.05 for chi Lupi and log N(Pt) = +6.50 for HR 7775, on a scale of log N(H) = +12.00. C1 Lund Univ, Dept Phys, S-22100 Lund, Sweden. NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, Greenbelt, MD 20771 USA. Univ London Imperial Coll Sci Technol & Med, Blackett Lab, London SW7 2BZ, England. Univ Colorado, Atmospher & Space Phys Lab, Boulder, CO 80309 USA. RP Kalus, G (reprint author), Lund Univ, Dept Phys, S-22100 Lund, Sweden. EM Gabriele.Kalus@fysik.lu.se; Sveneric.Johansson@fysik.lu.se; spek_glen@garbo.lucas.lu.se; hrsleckrone@hrs.esfc.nasa.gov; a.thorne@ic.ac.uk; brandt@lyrae.colorado.edu NR 33 TC 15 Z9 16 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 FEB 20 PY 1998 VL 494 IS 2 BP 792 EP 798 DI 10.1086/305241 PN 1 PG 7 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YZ796 UT WOS:000072292500028 ER PT J AU Judge, PG Carpenter, KG AF Judge, PG Carpenter, KG TI On chromospheric heating mechanisms of "basal flux" stars SO ASTROPHYSICAL JOURNAL LA English DT Article DE shock waves; stars, chromospheres; stars, interiors; Sun, chromosphere ID COOL STARS; MAGNETIC-STRUCTURE; C-II; ULTRAVIOLET EMISSION; ALPHA-ORIONIS; GIANT STARS; LINES; COMPONENTS; DENSITY; IUE AB Several pieces of evidence have been pieced together over recent years to support the notion that the chromospheric emission measured from stars with convection zones results in part from the upward propagation and dissipation of acoustic waves. One argument, based on a statistical analysis of available UV data of such stars across the H-R diagram, suggests the presence of an omnipresent "basal" level of chromospheric heating, which has been postulated as resulting from nonlinear acoustic wave heating. However, with few exceptions, no studies have been made that test more directly the intrinsically dynamic nature of this shock-heating mechanism. Therefore, in order to search for more direct signatures of such upward-propagating shock waves in lines of C II, we examined Goddard High-Resolution Spectrograph spectra of several evolved stars that have "basal" levels of activity. No evidence is found to support the presence of such waves as a dominant component of the heating mechanism. Instead, behavior reminiscent of the solar transition region is seen, suggesting a magnetic heating mechanism for these stars. We conclude that upward-propagating shock waves do not dominate the observed radiative losses from chromospheres of stars exhibiting typical "basal" behavior, and we suggest that the nonmagnetic origin of the basal components of all convective stars must be called into question. New solar data from the SUMER instrument on SOHO also suggest problems with the acoustic-wave interpretation, although further work is warranted. In the course of this work, we also found a simple explanation for previously noted discrepancies between calculated and observed ratios of C II lines in the spectrum of alpha Ori. C1 Natl Ctr Atmospher Res, High Altitude Observ, Boulder, CO 80307 USA. NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, Greenbelt, MD 20771 USA. RP Judge, PG (reprint author), Natl Ctr Atmospher Res, High Altitude Observ, Pob 3000, Boulder, CO 80307 USA. RI Carpenter, Kenneth/D-4740-2012 NR 43 TC 39 Z9 39 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 FEB 20 PY 1998 VL 494 IS 2 BP 828 EP 839 DI 10.1086/305232 PN 1 PG 12 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YZ796 UT WOS:000072292500034 ER PT J AU Falcke, H Rieke, MJ Rieke, GH Simpson, C Wilson, AS AF Falcke, H Rieke, MJ Rieke, GH Simpson, C Wilson, AS TI Molecular hydrogen and Pa alpha emission in cooling flow galaxies SO ASTROPHYSICAL JOURNAL LA English DT Article DE cooling flows; galaxies, clusters, general; galaxies, elliptical and lenticular, cD; galaxies, ISM; galaxies, jets ID RADIO GALAXIES; LINE; FILAMENTS; GAS AB We present near-infrared spectra that were obtained in order to search for Pa alpha and molecular hydrogen lines in edge-darkened (FR I-type) radio galaxies with bright Ha emission in the redshift range 0.0535 < z < 0.15. We find that all three galaxies in our sample (PKS 0745-191, PKS 1346+26, and PKS 2322-12) associated with strong cooling flows also have strong Pa alpha and H(2) 1-0 S(1) through S(5) emission, while other radio galaxies do not. Together with earlier observations, this confirms the claims that cooling flow galaxies are copious emitters of molecular hydrogen with large H(2) 1-0 S(3)/Pa alpha ratios in the range 0.5-2. The emission is centrally concentrated within the inner few kiloparsecs and could come from warm (T similar or equal to 1000-1500 K) molecular material that is being deposited by the cooling flow. We speculate that the H(2) emission could be related to the interaction between the jets and this molecular gas. C1 Univ Maryland, Dept Astron, College Pk, MD 20742 USA. Univ Arizona, Steward Observ, Tucson, AZ 85721 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Space Telescope Sci Inst, Baltimore, MD USA. RP Falcke, H (reprint author), Max Planck Inst Radioastron, Auf Hugel 69, D-53121 Bonn, Germany. EM hfalcke@astro.umd.edu; mrieke@as.arizona.edu; grieke@as.arizona.edu; bart@fornax.jpl.nasa.gov; wilson@astro.umd.edu RI Falcke, Heino/H-5262-2012 OI Falcke, Heino/0000-0002-2526-6724 NR 23 TC 29 Z9 29 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 FEB 20 PY 1998 VL 494 IS 2 BP L155 EP L158 DI 10.1086/311176 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YZ797 UT WOS:000072292600007 ER PT J AU Nemiroff, RJ Norris, JP Bonnell, JT Marani, GF AF Nemiroff, RJ Norris, JP Bonnell, JT Marani, GF TI Gamma-ray burst spikes could resolve stars SO ASTROPHYSICAL JOURNAL LA English DT Article DE dark matter; gamma rays, bursts; gravitational lensing ID DARK-MATTER; DURATION; DISTRIBUTIONS; SEARCH; ORIGIN AB Gamma-ray bursts (GRBs) vary more rapidly than any other known cosmological phenomena. The lower limits of this variability have not yet been explored. Improvements in detectors would reveal or limit the actual rate of short GRBs. Were microsecond "spike" GRBs to exist and be detectable, they would time-resolve stellar mass objects throughout the universe by their gravitational microlensing effect. Analyzing the time structure of sufficient numbers of GRB spikes would reveal or limit Omega(star), Omega(MACHO), and Omega(baryon). C1 Michigan Technol Univ, Dept Phys, Houghton, MI 49931 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. George Mason Univ, Ctr Earth & Space Res, Fairfax, VA 22030 USA. RP Nemiroff, RJ (reprint author), Michigan Technol Univ, Dept Phys, Houghton, MI 49931 USA. OI Nemiroff, Robert/0000-0002-4505-6599 NR 32 TC 12 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 FEB 20 PY 1998 VL 494 IS 2 BP L173 EP L176 DI 10.1086/311191 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YZ797 UT WOS:000072292600011 ER PT J AU Soffitta, P Tomsick, JA Harmon, BA Costa, E Ford, EC Tavani, M Zhang, SN Kaaret, P AF Soffitta, P Tomsick, JA Harmon, BA Costa, E Ford, EC Tavani, M Zhang, SN Kaaret, P TI Identification of the periodic hard x-ray transient GRO J1849-03 with the x-ray pulsar GS1843-02=X1845-024: A new Be/x-ray binary SO ASTROPHYSICAL JOURNAL LA English DT Article DE pulsars, individual (GS 1843-02); stars, emission-line, Be; stars, neutron X-rays, stars AB We identify the periodic transient hard X-ray source GRO J1849-03 with the transient X-ray pulsar GS 1843-02 = X1845-024 on the basis of the detection of X-ray outbursts from X1845-024 coincident with hard X-ray outbursts of GRO J1849-03. From its spin period of 94.8 s and its orbital period of 241 days, we classify the system as a Be/X-ray binary. C1 CNR, Ist Astrofis Spaziale, I-00044 Frascati, Italy. Columbia Univ, Columbia Astrophys Lab, New York, NY 10027 USA. NASA, George C Marshall Space Flight Ctr, Univ Space Res Assoc, Huntsville, AL 35812 USA. RP Soffitta, P (reprint author), CNR, Ist Astrofis Spaziale, CP 67, I-00044 Frascati, Italy. NR 13 TC 8 Z9 8 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 FEB 20 PY 1998 VL 494 IS 2 BP L203 EP L205 DI 10.1086/311189 PN 2 PG 3 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YZ797 UT WOS:000072292600018 ER PT J AU Torii, K Kinugasa, K Toneri, T Asanuma, T Tsunemi, H Dotani, T Mitsuda, K Gotthelf, EV Petre, R AF Torii, K Kinugasa, K Toneri, T Asanuma, T Tsunemi, H Dotani, T Mitsuda, K Gotthelf, EV Petre, R TI Discovery of a 69 millisecond X-ray pulsar: A compact source in the vicinity of the supernova remnant RCW 103 SO ASTROPHYSICAL JOURNAL LA English DT Article DE pulsars, general; pulsars, individual (AXS J161730-505505); supernova remnants; X-rays, general ID VELOCITIES; MSH-15-52 AB We report a rare discovery of a fast (69 ms) pulsar using X-ray data acquired with the Advanced Satellite for Cosmology and Astrophysics (ASCA). The highly significant detection arises from the serendipitous ASCA X-ray source AXS J161730-505505, located near the young Galactic supernova remnant (SNR) RCW 103. The epoch-folded light curve displays a single asymmetric pulse profile with a pulse fraction of similar to 50%. Spectral fits to the high-energy (i.e., greater than 3.5 keV) source data using a simple absorbed power-law model, assuming the hydrogen column density to the SNR, gives a photon index gamma = 1.6(-0.3)(+0.2) and an unabsorbed flux of similar to 6.4 x 10(-12) ergs cm(-2) s(-1). The extracted source spectrum below 3.5 keV is contaminated by mirror-scattered soft thermal emission from the similar to 9' diameter RCW 103, whose projected center is located just similar to 7' away. If the pulsar is associated with the remnant, the implied neutron star velocity is at the high end of the pulsar velocity distribution for the distance estimates to the remnant but still plausible. We suggest that AXS J161730-505505 is likely a young rotation-powered pulsar with a characteristic spin-down age of similar to 8000 yr. The physical association of the pulsar with RCW 103 and its central source, 1E 161348-5055, remains intriguing. C1 Osaka Univ, Grad Sch Sci, Dept Earth & Space Sci, Osaka 560, Japan. Japan Sci & Technol Corp, CREST, Osaka, Japan. Inst Space & Astronaut Sci, Kanagawa 229, Japan. NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. RP Torii, K (reprint author), Osaka Univ, Grad Sch Sci, Dept Earth & Space Sci, 1-1 Machikaneyama Cho, Osaka 560, Japan. RI Mitsuda, Kazuhisa/C-2649-2008 NR 30 TC 32 Z9 32 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 FEB 20 PY 1998 VL 494 IS 2 BP L207 EP L210 DI 10.1086/311186 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YZ797 UT WOS:000072292600019 ER PT J AU Bremaud, PJ Taupin, F Thompson, AM Chaumerliac, N AF Bremaud, PJ Taupin, F Thompson, AM Chaumerliac, N TI Ozone nighttime recovery in the marine boundary layer: Measurement and simulation of the ozone diurnal cycle at Reunion Island SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID TROPOSPHERIC CHEMISTRY; STRATIFORM CLOUD; SOUTH-ATLANTIC; PHOTOCHEMISTRY; DYNAMICS; ACID; INVERSION; PACIFIC; MODEL; OCEAN AB We describe the diurnal cycle of ozone in the marine boundary layer measured at Reunion Island (21 degrees S, 55 degrees E) in the western part of the Indian Ocean in August-September 1995. Results from a box chemistry model are compared with ozone measurements at Reunion Island. We focus on the peak-to-peak amplitude of ozone concentration, since our measurements show a variation of about 4 parts per billion by volume, which is close to the value obtained by Johnson et al. [1990] during the Soviet-American Gases and Aerosols (SAGA) 1987 Indian Ocean cruise. Different dynamical mechanisms are examined in order to reproduce such a variation. We conclude that the most important one is the exchange between the ozone-rich free troposphere and the ozone-poor boundary layer. This exchange is supposed to be more important during the night than during the day, allowing ozone nighttime recovery. This is the key point of the observed diurnal cycle, since daytime ozone photochemistry is well described by the model. Then we assume an entrainment velocity equal to 1 mm s(-1) during the day and 14 mm s(-1) during the night to closely match our measurements. Topography influences, together with clouds, are presumed to be responsible for this difference between nighttime and daytime entrainment velocities of free tropospheric air into the boundary layer at Reunion Island. Over the open ocean the difference of the turbulent flux of sensible heat between the day and the night explains the strong ozone nighttime recovery observed by us and by Johnson et al. [1990]. C1 Univ Reunion, Lab Phys Atmosphere, F-97715 St Denis, France. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Clermont Ferrand, CNRS, Lab Meteorol Phys, Clermont Ferrand, France. RP Bremaud, PJ (reprint author), Univ Reunion, Lab Phys Atmosphere, 15 Ave Rene Cassin, F-97715 St Denis, France. EM bremaud@univ-reunion.fr; taupin@univ-reunion.fr; thompson@gator1.gsfc.nasa.gov; chaumerl@opgc.univ-bpclermont.fr RI Thompson, Anne /C-3649-2014 OI Thompson, Anne /0000-0002-7829-0920 NR 42 TC 29 Z9 31 U1 1 U2 3 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD FEB 20 PY 1998 VL 103 IS D3 BP 3463 EP 3473 DI 10.1029/97JD01972 PG 11 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA YY455 UT WOS:000072148300010 ER PT J AU Burris, J Heaps, W Gary, B Hoegy, W Lait, L McGee, T Gross, M Singh, U AF Burris, J Heaps, W Gary, B Hoegy, W Lait, L McGee, T Gross, M Singh, U TI Lidar temperature measurements during the Tropical Ozone Transport Experiment (TOTE) Vortex Ozone Transport Experiment (VOTE) mission SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID STRATOSPHERIC TEMPERATURE AB Temperature profiles were acquired on the Tropical Ozone Transport Experiment (TOTE) and Vortex Ozone Transport Experiment (VOTE) flights by the Goddard Airborne Raman Lidar. The objective was to compare the temperature product from this new instrument with those generated by the Jet Propulsion Laboratory's Microwave Temperature Profiler and Goddard Space Flight Center's ground-based Stratospheric Ozone Lidar. Simultaneous measurements were made between the Airborne Raman Lidar and O-3 lidar on three dates; average temperatures differences varied from similar to 0.5 K-5 K over the 16-24 km altitude region. Comparisons between the Microwave Temperature Profiler and Airborne Raman Lidar for all flights (17) during TOTE/VOTE were performed over the same altitude region. The average temperature difference, Airborne Raman Lidar minus Microwave Temperature Profiler, was +2.3 K. In comparing temperatures between the Airborne Raman Lidar and Goddard's Data Assimilation Model, the ARL showed small scale structures not evident in those of the model for altitudes between similar to 16 and 43 km. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. HSTX, Lanham, MD 20706 USA. RP Burris, J (reprint author), NASA, Goddard Space Flight Ctr, Code 916, Greenbelt, MD 20771 USA. EM burris@aeolus.gsfc.nasa.gov; heaps@aeolus.gsfc.nasa.gov; bgary@jplsp.jpl.nasa.gov; hoegy@mite.gsfc.nasa.gov; lait@ertel.gsfc.nasa.gov; mcgee@aeolus.gsfc.nasa.gov; gross@aeolus.gsfc.nasa.gov RI McGee, Thomas/G-4951-2013 NR 9 TC 10 Z9 10 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 FEB 20 PY 1998 VL 103 IS D3 BP 3505 EP 3510 DI 10.1029/97JD03129 PG 6 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA YY455 UT WOS:000072148300013 ER PT J AU Sen, B Toon, GC Osterman, GB Blavier, JF Margitan, JJ Salawitch, RJ Yue, GK AF Sen, B Toon, GC Osterman, GB Blavier, JF Margitan, JJ Salawitch, RJ Yue, GK TI Measurements of reactive nitrogen in the stratosphere SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID IN-SITU MEASUREMENTS; HETEROGENEOUS CHEMISTRY; INSITU MEASUREMENTS; SOLAR-OCCULTATION; SULFATE AEROSOLS; BORNE MEASUREMENTS; CHLORINE RADICALS; DIURNAL-VARIATION; ATMOS EXPERIMENT; NO2 AB We present volume mixing ratio profiles of NO, NO2, HNO2, HNO4, N2O5, and ClNO3 and their composite budget (NOy), from 20 to 39 km, measured remotely in solar occultation by the Jet Propulsion Laboratory MkIV Interferometer during a balloon flight from Fort Sumner, New Mexico (35 degrees N), on September 25, 1993. In general, observed profiles agree well with values calculated using a photochemical steady state model constrained by simultaneous MkIV observations of long-lived precursors and aerosol surface area from the Stratospheric Aerosol and Gas Experiment II. The measured variation of concentrations of NOx (= NO + NO2) and N2O5 between sunrise and sunset reveals the expected similar to 2:1 stoichiometry at all altitudes. Despite relatively good agreement between theory and observation for profiles of NO and HNO3 the observed concentration of NO2 becomes progressively higher than model values below 30 km, with the discrepancy reaching similar to 30% at 22 km. This suggests an incomplete understanding of factors that regulate the NO/NO2 and NO2/HNO3 ratios below 30 km. Observations obtained during September 1990, prior to the June 1991 eruption of Mount Pinatubo, as well as during April 1993 and September 1993 provide a test of our understanding of the affect of aerosol surface area on the NOx/NOy ratio at midlatitudes. The observations reveal a decrease in the NOx/NOy ratio for increasing aerosol surface area that is consistent with the heterogeneous hydrolysis of N2O5 being the dominant sink of NOx between altitudes of 18 and 24 km for the conditions encountered (e.g., surface areas as high as 14 mu m(2) cm(-3) and temperatures from 209 to 219 K). C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. NASA, Langley Res Ctr, Hampton, VA 23665 USA. RP Sen, B (reprint author), CALTECH, Jet Prop Lab, MS 183-301,4800 Oak Grove Dr, Pasadena, CA 91109 USA. EM sen@mark4sun.jpl.nasa.gov RI Salawitch, Ross/B-4605-2009 OI Salawitch, Ross/0000-0001-8597-5832 NR 69 TC 77 Z9 77 U1 0 U2 5 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD FEB 20 PY 1998 VL 103 IS D3 BP 3571 EP 3585 DI 10.1029/97JD02468 PG 15 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA YY455 UT WOS:000072148300019 ER PT J AU Morris, GA Kawa, SR Douglass, AR Schoeberl, MR Froidevaux, L Waters, J AF Morris, GA Kawa, SR Douglass, AR Schoeberl, MR Froidevaux, L Waters, J TI Low-ozone pockets explained SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID ATMOSPHERE RESEARCH SATELLITE; STRATOSPHERE; VALIDATION; UARS; CHEMISTRY; WINDS AB Pockets of low ozone have been observed on numerous occasions in anticyclones at middle to high latitudes in the middle stratosphere. Air masses within the anticyclones at altitudes near 850 K (similar to 32 km) contain similar to 25% less ozone than the surrounding air. Trajectory calculations have revealed that much of the air within the pockets originates in the tropics or subtropics at higher altitudes several weeks earlier. Previous studies have, however, left unanswered a number of questions related to the formation of the low-ozone regions. Using a Lagrangian chemical model with initialization based upon observations from the Upper Atmosphere Research Satellite (UARS), we examine in detail an event in March 1993. Our results demonstrate that the development of the observed ozone pockets can be explained with our current understanding of chemistry and dynamics. The primary mechanism responsible for the development of these low-ozone regions is the isolation of air at high latitudes for periods of time long enough that significant ozone loss toward the local photochemical equilibrium can occur. Such behavior is different from that of the surrounding air masses that move from middle to high latitudes and back again over the course of a few days. The dynamical behavior associated with these latter air masses results in ozone concentrations more consistent with lower-latitude equilibrium values. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. CALTECH, Jet Prop Lab, Pasadena, CA USA. RP Morris, GA (reprint author), Univ Maryland, Joint Ctr Earth Syst Technol, Baltimore, MD 21201 USA. EM morris@zephyr.gsfc.nasa.gov RI Douglass, Anne/D-4655-2012; Kawa, Stephan/E-9040-2012 NR 30 TC 21 Z9 21 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 FEB 20 PY 1998 VL 103 IS D3 BP 3599 EP 3610 DI 10.1029/97JD02513 PG 12 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA YY455 UT WOS:000072148300021 ER PT J AU Gawronski, W Sawicki, JT AF Gawronski, W Sawicki, JT TI Comments on "response errors of non-proportionally lightly damped structures" - Authors' reply SO JOURNAL OF SOUND AND VIBRATION LA English DT Letter C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Cleveland State Univ, Dept Mech Engn, Cleveland, OH 44115 USA. RP Gawronski, W (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 2 TC 0 Z9 0 U1 0 U2 2 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 FEB 19 PY 1998 VL 210 IS 2 BP 285 EP 285 PG 1 WC Acoustics; Engineering, Mechanical; Mechanics SC Acoustics; Engineering; Mechanics GA YZ276 UT WOS:000072237900008 ER PT J AU Navale, V Harpold, D Vertes, A AF Navale, V Harpold, D Vertes, A TI Development and characterization of gas chromatographic columns for the analysis of prebiological molecules in Titan's atmosphere SO ANALYTICAL CHEMISTRY LA English DT Article ID WEIGHT HYDROCARBONS; CAPILLARY COLUMN; NITRILES; GC AB Parametric studies were conducted to design, develop, and integrate three gas chromatographic columns with a miniaturized mass spectrometer to be part of the Cassini-Huygens mission for studying the atmosphere of Saturn's moon Titan, Separation and identification of low-molecular-weight hydrocarbons and nitriles (important prebiological molecules) were carried out on dimethylpolysiloxane (DMPS) and 14% cyanopropylphenyl-86% dimethylpolysiloxane (CPPS-DMPS) column stationary phases, These phases were deposited as thin films on the inner surface of fused silica coated steel capillary columns, The interaction of hydrocarbons and nitriles with these phases was studied under various column inlet pressure and carrier gas flow conditions, The selectivity for nitriles was enhanced by using the CPPS-DMPS phase, On this phase, the modeling number (log M) values varied linearly with the column temperature, Pronounced differences were observed in the order of elution for C(4) hydrocarbons between CPPS-DMPS and DMPS phases, On CPPS-DMPS phase, the retention time decreased as 1,3-butadiene > l-butene > n-butane, whereas on DMPS phase the order was n-butane > 1,3-butadiene > l-butene, With the exception of certain temperature intervals, the retention times of C(4) hydrocarbons predicted by the thermodynamic retention index model were comparable to experimentally determined values, Experimental and modeled retention times for benzene, toluene, and xylene, and nitriles also exhibited good agreement. Resolution of Ct hydrocarbons on low-temperature glassy carbon phase was demonstrated for the first time by our GC/MS studies, Trace quantities of carbon monoxide and methane present in a large volume of N(2) were separated by porous carbon phase, micropacked in steel capillary columns, The selected three GC columns can provide in situ separation of various gas components expected to be present in Titan's atmosphere. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. George Washington Univ, Dept Chem, Washington, DC 20052 USA. RP Navale, V (reprint author), NASA, Goddard Space Flight Ctr, Code 915, Greenbelt, MD 20771 USA. EM Vivek.Navale@gsfc.nasa.gov RI Vertes, Akos/B-7159-2008; Harpold, Dan/I-3345-2013 OI Vertes, Akos/0000-0001-5186-5352; NR 25 TC 11 Z9 11 U1 0 U2 3 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA SN 0003-2700 J9 ANAL CHEM JI Anal. Chem. PD FEB 15 PY 1998 VL 70 IS 4 BP 689 EP 697 DI 10.1021/ac9708598 PG 9 WC Chemistry, Analytical SC Chemistry GA YX684 UT WOS:000072066100004 ER PT J AU Stone, NH Bonifazi, C AF Stone, NH Bonifazi, C TI The TSS-1R mission: Overview and scientific context SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID PLASMA C1 NASA, George C Marshall Space Flight Ctr, Space Sci Lab, Huntsville, AL 35812 USA. Agenzia Spaziale Italiana, Rome, Italy. RP Stone, NH (reprint author), NASA, George C Marshall Space Flight Ctr, Space Sci Lab, ES83, Huntsville, AL 35812 USA. NR 15 TC 23 Z9 23 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 FEB 15 PY 1998 VL 25 IS 4 BP 409 EP 412 DI 10.1029/97GL02980 PG 4 WC Geosciences, Multidisciplinary SC Geology GA YY192 UT WOS:000072122500001 ER PT J AU Thompson, DC Bonifazi, C Gilchrist, BE Williams, SD Raitt, WJ Lebreton, JP Burke, WJ Stone, NH Wright, KH AF Thompson, DC Bonifazi, C Gilchrist, BE Williams, SD Raitt, WJ Lebreton, JP Burke, WJ Stone, NH Wright, KH TI The current-voltage characteristics of a large probe in low Earth orbit: TSS-1R results SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID MISSION AB Measurements of the current collected by the Tethered Satellite System (TSS) satellite as a function of voltage and ambient plasma parameters are presented. The satellite current is found to vary approximately with the square root of the potential from below 10 to nearly 1200 V. The collected current exceeded premission expectations, based on the Parker and Murphy [1967] collection model, by factors of two to three. Possible reasons for discrepancies between the measurements and model are briefly discussed. C1 Utah State Univ, Ctr Atmospher & Space Sci, Logan, UT 84322 USA. Italian Space Agcy, I-00198 Rome, Italy. Univ Michigan, Space Phys Res Lab, Ann Arbor, MI 48109 USA. Stanford Univ, Space Telecommun & Radiosci Lab, Stanford, CA 94305 USA. European Space Agcy, Estec, Dept Space Sci, NL-2200 AG Noordwijk, Netherlands. Phillips Lab, Geophys Directorate, Hanscom AFB, MA USA. NASA, George C Marshall Space Flight Ctr, Space Sci Lab, Huntsville, AL 35812 USA. Univ Alabama, Ctr Space Plasma & Aeron Res, Huntsville, AL 35899 USA. RP Thompson, DC (reprint author), Utah State Univ, Ctr Atmospher & Space Sci, Logan, UT 84322 USA. NR 10 TC 18 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 FEB 15 PY 1998 VL 25 IS 4 BP 413 EP 416 DI 10.1029/97GL02958 PG 4 WC Geosciences, Multidisciplinary SC Geology GA YY192 UT WOS:000072122500002 ER PT J AU Wright, KH Stone, NH Sorensen, J Winningham, JD Gurgiolo, C AF Wright, KH Stone, NH Sorensen, J Winningham, JD Gurgiolo, C TI Observations of reflected ions and plasma turbulence for satellite potentials greater than the ion ram energy SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article AB During the TSS-IR mission, the behavior of the ions flowing from the forward hemisphere of the Tethered Satellite System (TSS) satellite was examined as the potential on the satellite was changed from below to above 5 V. The ram energy of the ambient atomic oxygen ions is similar to 5 eV. For satellite potentials < 5 V, no ions were observed on the ram side of the satellite. When the satellite potential was raised > 5 V, ions were observed to he flowing from the forward region of the satellite. In the region sampled, the ion flux was a few percent of the ambient with energies of similar to 5 eV. The temperature of the outflowing ions was observed to be enhanced, relative to the ambient ionosphere. The net current to the probe package became much more noisy for satellite potentials > 5 V as compared with satellite potentials < 5 V, indicating a more disturbed plasma environment. C1 Univ Alabama, Ctr Space Plasma & Aeron Res, Huntsville, AL 35899 USA. NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. SW Res Inst, Space Instr Div, San Antonio, TX 78228 USA. Bitterroot Basic Res Inc, Hamilton, MT 59840 USA. RP Wright, KH (reprint author), Univ Alabama, Ctr Space Plasma & Aeron Res, Huntsville, AL 35899 USA. NR 5 TC 5 Z9 5 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD FEB 15 PY 1998 VL 25 IS 4 BP 417 EP 420 DI 10.1029/97GL02999 PG 4 WC Geosciences, Multidisciplinary SC Geology GA YY192 UT WOS:000072122500003 ER PT J AU Mariani, F Candidi, M Orsini, S Terenzi, R Agresti, R Musmann, G Rahm, M Acuna, M Panetta, P Ness, NF Neubauer, F AF Mariani, F Candidi, M Orsini, S Terenzi, R Agresti, R Musmann, G Rahm, M Acuna, M Panetta, P Ness, NF Neubauer, F TI Current flow through high-voltage sheaths observed by the TEMAG experiment during TSS-1R SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID SATELLITE AB During the TSS-1R flight, conditions occurred under which very intense currents flowed through the tether wire system. The effect of these currents during the active phases of operation was clearly seen by the TEMAG sensor assembly located on the short, fixed satellite boom. Magnetic signatures appeared on the field components parallel to the boom and to the spin axis with a strong peak when the boom points closer to the ram direction. While a toroidal current flowing on the ram side of the plasma sheath may explain the main features seen by the TEMAG outboard sensor further studies are needed for the physical interpretation of the complex electrodynamic interactions of the TSS-ionosphere system. C1 Univ Roma Tor Vergata, I-00133 Rome, Italy. CNR, Ist Fis Spazio Interplanetario, I-00133 Rome, Italy. Tech Univ Braunschweig, D-3300 Braunschweig, Germany. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Delaware, Bartol Res Inst, Newark, DE 19716 USA. Univ Cologne, D-50923 Cologne, Germany. RP Mariani, F (reprint author), Univ Roma Tor Vergata, I-00133 Rome, Italy. NR 6 TC 4 Z9 4 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 FEB 15 PY 1998 VL 25 IS 4 BP 425 EP 428 DI 10.1029/97GL03045 PG 4 WC Geosciences, Multidisciplinary SC Geology GA YY192 UT WOS:000072122500005 ER PT J AU Winningham, JD Stone, NH Gurgiolo, CA Wright, KH Frahm, RA Bonifazi, CA AF Winningham, JD Stone, NH Gurgiolo, CA Wright, KH Frahm, RA Bonifazi, CA TI Suprathermal electrons observed on the TSS-1R satellite SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article AB Particle measurements up to 27,000 eV were made on the TSS-IR (Tethered Satellite System) satellite. The TSS satellite developed a positive bias due to the Lorentz force. It was the intent that electron measurements on the TSS satellite could be used to track the spacecraft potential and collected current, What was observed was quite different, Accelerated ionospheric electrons were observed to only similar to 70 eV even though larger spacecraft potentials were observed by other diagnostics on the TSS satellite. When observed they agreed with these independent measurements of the potential. In addition to the anticipated accelerated thermals, a suprathermal population of electrons was observed to be centered around 200 eV. This population exhibited a 4 orders-of-magnitude increase in intensity as the spacecraft potential exceeded the O+ ram energy. The disappearance of the accelerated thermals is explained by the observation that the suprathermal flux becomes larger in magnitude, thus hiding the thermals. However the suprathermals cannot be the dominant current carriers if they are the result of a DC process as their calculated current magnitude exceeds that observed. These results are best explained if one assumes an AC acceleration of the suprathermal electrons whose free energy is derived from the differential ((E) over right arrow x (E) over right arrow driven) drift between electrons and ions. C1 SW Res Inst, Instrumentat & Space Res Div, Dept Space Sci, San Antonio, TX 78228 USA. NASA, George C Marshall Space Flight Ctr ES83, Huntsville, AL 35812 USA. Bitterroot Basic Res, Hamilton, MT USA. Univ Alabama, Ctr Space Plasma & Aeron Res, Huntsville, AL 35899 USA. RP Winningham, JD (reprint author), SW Res Inst, Instrumentat & Space Res Div, Dept Space Sci, PO Drawer 28510, San Antonio, TX 78228 USA. NR 11 TC 6 Z9 7 U1 0 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD FEB 15 PY 1998 VL 25 IS 4 BP 429 EP 432 DI 10.1029/97GL03187 PG 4 WC Geosciences, Multidisciplinary SC Geology GA YY192 UT WOS:000072122500006 ER PT J AU Gilchrist, BE Bonifazi, C Bilen, SG Raitt, WJ Burke, WJ Stone, NH Lebreton, JP AF Gilchrist, BE Bonifazi, C Bilen, SG Raitt, WJ Burke, WJ Stone, NH Lebreton, JP TI Enhanced electrodynamic tether currents due to electron emission from a neutral gas discharge: Results from the TSS-1R mission SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID CURRENT COLLECTION; PLASMA CONTACTOR AB During the reflight of the first electrodynamic Tethered Satellite System (TSS-1R) mission, the unplanned separation of the tether at the Orbiter end resulted in the highest tether current during the mission. In the moments just prior to the tether separation with 19.7 km of tether deployed and a generated electromotive force (EMF) of 3482 V, currents reaching approximately 0.97 A were shunted through the tether to the Orbiter electrical ground, which was in contact with the ionosphere primarily through its main engine surfaces. This current level was nearly twice as large as observed during any nominal operating period. As the failure point of the tether entered into the ambient plasma, the current increased to 1.1 A and maintained this level even after the break for approximately 75 s. The principal surprise in these results was that the broken end of the tether, with only a few short strands of copper wire, could support higher currents than the much larger Orbiter conducting surface areas. Analysis of possible current enhancement mechanisms revealed that only a gas-enhanced electrical discharge, providing an electron emission source, was plausible. Ground plasma chamber tests confirmed this analysis. The TSS-1R results thus represent the highest electron current emission from a neutral plasma source yet demonstrated in a space plasma. This is of interest for current collection processes in general and plasma contactor development in particular. C1 Univ Michigan, Space Phys Res Lab, Ann Arbor, MI 48109 USA. Agenzia Spaziale Italiana, I-00198 Rome, Italy. Utah State Univ, Ctr Atmospher & Space Sci, Logan, UT 84322 USA. Phillips Lab, GPSG, Hanscom AFB, MA 01713 USA. NASA, George C Marshall Space Flight Ctr, Space Sci Lab, Huntsville, AL 35812 USA. European Space Agcy, Estec, Dept Space Sci, NL-2200 AG Noordwijk, Netherlands. Univ Michigan, EECS Dept, Radiat Lab, Ann Arbor, MI 48109 USA. RP Gilchrist, BE (reprint author), Univ Michigan, Space Phys Res Lab, 2455 Hayward St, Ann Arbor, MI 48109 USA. RI Bilen, Sven/F-4329-2011 OI Bilen, Sven/0000-0002-5416-7039 NR 19 TC 12 Z9 12 U1 0 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD FEB 15 PY 1998 VL 25 IS 4 BP 437 EP 440 DI 10.1029/97GL03023 PG 4 WC Geosciences, Multidisciplinary SC Geology GA YY192 UT WOS:000072122500008 ER PT J AU Clancy, RT Sandor, BJ AF Clancy, RT Sandor, BJ TI CO2 ice clouds in the upper atmosphere of Mars SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article AB Recent (Sept. 1996-Sept. 1997) observations of Mars submillimeter CO lines from the James Clerk Maxwell Telescope (JCMT) on Mauna Kea, Hawaii surprisingly cold temperatures as typical atmosphere over the 50-80 km altitude region. Measurements of these J=2->3 and J=3->4 rotational transitions of Mars atmospheric (CO)-C-12 provide unique seasonal coverage of global averaged, dayside temperatures within this poorly observed mesosphere of Mars. At solar longitudes (L-s) of 8 degrees, 90 degrees, 150 degrees, and 187 degrees in 1996-97, the mean atmospheric temperature for the 70-80 km (2.0-0.3 mu bars) altitude region is observed to be at or below 120 K, which is only 10-15 K above the vapor saturation temperature for the CO2 Mars atmosphere. Consequently, local CO2 saturation conditions at these altitudes would be likely to exist and, in fact, were observed during the 3 AM descent entry of the Pathfinder spacecraft, on July 4, 1997. We argue that the blue wave clouds imaged from the Pathfinder lander 35-100 minutes prior to sunrise on Sol 39 are evidence of such CO2 ice formation within the 60-100 km altitude region; and that the 4.3 mu m CO2 lines of solar scattered flux, in Mariner 6 and 7 infrared limb spectra of Mars are a direct spectral identification of CO2 ice cloud formation in the dayside Mars mesosphere. Simple considerations of these Pathfinder and Mariner 6 and 7 observations suggest 0.1-0.3 mu m cloud particle radii, and particle number densities of the order 10(2) cm(-3). On the basis of a variety of such day and night time measurements, we assert that the mesosphere of Mars does not exhibit extreme (25 K) diurnal temperature variations as maintained by the Pathfinder meteorology ream; and that it is often substantially colder (> 20 K) than determined from the Viking descent measurements in 1976 due to temporal variations in dust loading of this region. C1 Space Sci Inst, Boulder, CO 80303 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91125 USA. RP Clancy, RT (reprint author), Space Sci Inst, Suite 294,1234 Innovat Dr, Boulder, CO 80303 USA. NR 17 TC 36 Z9 36 U1 0 U2 8 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 FEB 15 PY 1998 VL 25 IS 4 BP 489 EP 492 DI 10.1029/98GL00114 PG 4 WC Geosciences, Multidisciplinary SC Geology GA YY192 UT WOS:000072122500021 ER PT J AU Hintsa, EJ Newman, PA Jonsson, HH Webster, CR May, RD Herman, RL Lait, LR Schoeberl, MR Elkins, JW Wamsley, PR Dutton, GS Bui, TP Kohn, DW Anderson, JG AF Hintsa, EJ Newman, PA Jonsson, HH Webster, CR May, RD Herman, RL Lait, LR Schoeberl, MR Elkins, JW Wamsley, PR Dutton, GS Bui, TP Kohn, DW Anderson, JG TI Dehydration and denitrification in the Arctic polar vortex during the 1995-1996 winter SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID LOWER STRATOSPHERE; CONDENSATION NUCLEI; HYDROGEN BUDGET; NASA ER-2; AIRCRAFT; CLOUD; PARTICLES; NITROGEN; AEROSOL; HNO3 AB Dehydration of more than 0.5 ppmv water was observed between 18 and 19 km (theta similar to 450-465 K) at the edge of the Arctic polar vortex on February 1, 1996. More than half the reactive nitrogen (NO,) had also been removed, with layers of enhanced NO, at lower altitudes. Back trajectory calculations show that air parcels sampled inside the vortex had experienced temperatures as low as 188 K within the previous 12 days, consistent with a small amount of dehydration. The depth of the dehydrated layer (similar to 1 km) and the fact that trajectories passed through the region of ice saturation in one day imply selective growth of a small fraction of particles to sizes large enough (>10 mu m) to be irreversibly removed on this timescale. Over 25% of the Arctic vortex in a 20-30 K range of theta is estimated to have been dehydrated in this event. C1 Harvard Univ, Dept Chem & Biol Chem, Cambridge, MA 02138 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. USN, Postgrad Sch, Dept Meteorol, Monterey, CA 94943 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. NOAA, Climate Monitoring & Diagnost Lab, Boulder, CO 80307 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Hintsa, EJ (reprint author), Harvard Univ, Dept Chem & Biol Chem, Cambridge, MA 02138 USA. RI Newman, Paul/D-6208-2012; Herman, Robert/H-9389-2012 OI Newman, Paul/0000-0003-1139-2508; Herman, Robert/0000-0001-7063-6424 NR 19 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 FEB 15 PY 1998 VL 25 IS 4 BP 501 EP 504 DI 10.1029/98GL00115 PG 4 WC Geosciences, Multidisciplinary SC Geology GA YY192 UT WOS:000072122500024 ER PT J AU Han, J Jaffe, R AF Han, J Jaffe, R TI Energetics and geometries of carbon nanoconic tips SO JOURNAL OF CHEMICAL PHYSICS LA English DT Article ID NANOTUBES; AZULENE; HYDROCARBONS; FULLERENES; ABINITIO; CAGES; HEATS; C-70 AB The density functional theory (DFT), semiempirical molecular orbital calculations, and pi-orbital axis vector (POAV) analysis are used to study the energetics and geometries of carbon nanoconic tips. The tip models are formed by introducing two to five pentagons into a graphene network corresponding to experimentally observed cone angles of 19 to 84 degrees. The calculations show a pronounced energetic preference of (1,1) pentagons over (2,0) pentagons in tip structures, where one pentagon is at hexagonal coordinate (1,1) or (2,0) relative to the other at (0,0). The DFT energies of tips containing (1,1) pentagon pairs are lower than those with (2,0) pairs by 18.0-55.9 kcal/mol. This is attributed to less in-plane and out-of-plane strain being induced by (1,1) pentagon pairs than (2,0) pentagon pairs. The bond lengths, bond singles, torsion angles, and POAV angles are presented and discussed. The isolated pentagon rule is also tested for tip molecules containing two pentagons. The lower tip energy is obtained by increasing (a,a) pentagon separation or by decreasing (b,0) pentagon separation with b > 1. (C) 1998 American Institute of Physics. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Han, J (reprint author), NASA, Ames Res Ctr, T27A-1, Moffett Field, CA 94035 USA. NR 29 TC 29 Z9 29 U1 1 U2 7 PU AMER INST PHYSICS PI WOODBURY PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 USA SN 0021-9606 J9 J CHEM PHYS JI J. Chem. Phys. PD FEB 15 PY 1998 VL 108 IS 7 BP 2817 EP 2823 DI 10.1063/1.475672 PG 7 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA ZW144 UT WOS:000074379300018 ER PT J AU Murtugudde, R Busalacchi, AJ AF Murtugudde, R Busalacchi, AJ TI Salinity effects in a tropical ocean model SO JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS LA English DT Article ID SEA-SURFACE TEMPERATURE; NINO SOUTHERN OSCILLATION; GENERAL-CIRCULATION MODEL; MIXED-LAYER MODEL; FRESH-WATER FLUX; PACIFIC-OCEAN; EQUATORIAL PACIFIC; INDONESIAN THROUGHFLOW; ATLANTIC-OCEAN; SEASONAL CYCLE AB A reduced gravity, primitive equation, ocean general circulation model (GCM) with a variable depth mixed layer and a natural boundary condition for freshwater fluxes is employed to investigate the role of salinity in tropical ocean dynamics and thermodynamics. Surface heat fluxes are computed without any feedback to observations by an advective atmospheric mixed layer (AML) model which is coupled to the ocean GCM. We analyze the differences in the tropical Atlantic, Pacific, and the Indo-Pacific basins between control runs (simulations with complete hydrology) and simulations where (1) precipitation (P) is neglected, (2) salinity effects are neglected, or (3) salinity is held constant in each layer. Salinity contributes to pressure gradient forces, mixed layer processes, and vertical stability/mixing. Setting P = 0 in the tropical Atlantic produces larger sea surface temperature (SST) changes than previously estimated due to the realistic oceanic mixed layer model and surface flux formulation. Neglecting salinity effects leads to a different choice of mixing parameters, which feeds back into model dynamics and thermodynamics. Salinity anomalies produce an asymmetric response across the equator in the Atlantic due to differences in the air-sea interactions. Including salinity effects in the tropical Pacific leads to an improved cold tongue simulation. The result is a reduced SST gradient at the equator which will have significant feedback in a coupled system. The same experiment with a restoring surface heat flux leads to an increased SST gradient, indicating that the surface flux parameterization is crucial for interpreting the role of salinity. The Indonesian throughflow (ITF) is reduced when salinity is neglected or held constant. The NINO3 and NINO4 SST indices are almost identical for the control run and the simulations when climatological P is used. However, associated subsurface temperature differences are larger, and they may play a role on decadal timescales. It is thus shown with a comprehensive set of experiments that even in the tropics, salinity plays an important role in the model dynamics and thermodynamics. C1 NASA, Goddard Space Flight Ctr, Lab Hydrospher Proc, Greenbelt, MD 20771 USA. Univ Maryland, Earth Syst Sci Interdisciplinary Ctr, College Pk, MD 20742 USA. RP Murtugudde, R (reprint author), NASA, Goddard Space Flight Ctr, Lab Hydrospher Proc, Greenbelt, MD 20771 USA. NR 64 TC 111 Z9 111 U1 0 U2 11 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 FEB 15 PY 1998 VL 103 IS C2 BP 3283 EP 3300 DI 10.1029/97JC02438 PG 18 WC Oceanography SC Oceanography GA YY122 UT WOS:000072115500034 ER PT J AU Sunkara, HB Penn, BG Frazier, DO Ramachandran, N AF Sunkara, HB Penn, BG Frazier, DO Ramachandran, N TI Lattice dynamics of colloidal crystals during photopolymerization of acrylic monomer matrix SO JOURNAL OF MATERIALS SCIENCE LA English DT Article ID NONLINEAR PERIODIC STRUCTURES; POLY(METHYL METHACRYLATE); GRAVITATIONAL COMPRESSION; SILICA; MONODISPERSE; SPHERES; LIGHT; DIFFRACTION; MICROSCOPY; COMPOSITE AB The photoinitiated bulk polymerization process, which has been used recently in the manufacture of solid optical diffraction filters, is examined to understand the dynamics of both the crystalline colloidal arrays (CCA) and the host monomer species. Our analysis indicates that volume shrinkage of the monomer, changes in the dielectric properties of the monomer, and inhomogeneities of polymerization reaction rate across the dispersion during the polymerization process, are the major contributors for observed lattice compression and lattice disorder of the CCA of silica spheres in polymerized acrylic/methacrylic ester films. The effect of orientation of photocell with respect to the radiation source on Bragg diffraction of CCA indicated the presence of convective stirring in the thin fluid system during the photopolymerization that deleteriously affects the periodic array structures. To devise reproducible and more efficient optical filters, experimental methods to minimize or eliminate convective instabilities in monomeric dispersions during polymerization are suggested. (C) 1998 Chapman & Hall. C1 DuPont Nylon, Polymer Sci & Engn Technol Ctr, Expt Stn, Wilmington, DE 19880 USA. NASA, George C Marshall Space Flight Ctr, Space Sci Lab, Huntsville, AL 35812 USA. RP Sunkara, HB (reprint author), DuPont Nylon, Polymer Sci & Engn Technol Ctr, Expt Stn, POB 80302, Wilmington, DE 19880 USA. NR 41 TC 4 Z9 4 U1 0 U2 0 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 FEB 15 PY 1998 VL 33 IS 4 BP 887 EP 894 DI 10.1023/A:1004391207264 PG 8 WC Materials Science, Multidisciplinary SC Materials Science GA YU268 UT WOS:000071699300006 ER PT J AU Zhang, J Cui, W Juda, M McCammon, D Kelley, RL Moseley, SH Stahle, CK Szymkowiak, AE AF Zhang, J Cui, W Juda, M McCammon, D Kelley, RL Moseley, SH Stahle, CK Szymkowiak, AE TI Non-ohmic effects in hopping conduction in doped silicon and germanium between 0.05 and 1 K SO PHYSICAL REVIEW B LA English DT Article ID X-RAY SPECTROSCOPY; FIELD-DEPENDENCE; TRANSPORT; BOLOMETERS; ELECTRONS; TEMPERATURES; DETECTORS; 20-MK; NOISE; SI AB We have studied non-Ohmic effects In hopping conduction in moderately compensated ion-implanted Si:P, B (both n- and p-type) and neutron-transmutation-doped Ge:Ga,As over the temperature range 0.05-0.8 K and up to moderately strong electric fields. In the limit of small fields, where the current is proportional to applied voltage, the resistivities of these materials are approximated over a wide temperature range by the model of variable range hopping with a Coulomb gap: rho=rho(o) exp(T-o/T)(1/2). The samples included in this study have characteristic temperatures T-o in the range 1.4-60 K for silicon, and 22-60 K for germanium. We have compared our data to exponential and "hyperbolic-sine" field-effect models of the electrical nonlinearity: rho(E)=rho(0)e(-x) and rho(E)=rho(0)x/sinh(x), where x=eEl/kT, and to an empirical hot-electron model. The exponential field-effect model tends to be a good representation for the samples with high T-o at low T. The sinh model can match the data only at low fields. The hot-electron model fits our data well over a wide range of power in the low-T-o-high-T regime. We discuss the quantitative implications of these results for the application of these materials as thermometers for microcalorimeters optimized for high-resolution spectroscopy. [S0163-1829(98)05208-4]. C1 Univ Wisconsin, Dept Phys, Madison, WI 53706 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Zhang, J (reprint author), Harvard Smithsonian Ctr Astrophys, 60 Garden St, Cambridge, MA 02138 USA. RI Moseley, Harvey/D-5069-2012; Kelley, Richard/K-4474-2012; OI Juda, Michael/0000-0002-4375-9688; Cui, Wei/0000-0002-6324-5772 NR 40 TC 45 Z9 45 U1 1 U2 3 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 FEB 15 PY 1998 VL 57 IS 8 BP 4472 EP 4481 DI 10.1103/PhysRevB.57.4472 PG 10 WC Physics, Condensed Matter SC Physics GA YZ177 UT WOS:000072228000046 ER PT J AU MacGibbon, JH Brandenberger, RH Wichoski, UF AF MacGibbon, JH Brandenberger, RH Wichoski, UF TI Limits on black hole formation from cosmic string loops SO PHYSICAL REVIEW D LA English DT Article ID GRAVITATIONAL-RADIATION; EVOLUTION; PARTICLES; CONSTRAINTS; ANTIPROTONS; UNIVERSE; DENSITY; RELICS; COBE; RAYS AB In theories with cosmic strings, a small fraction of string loops may collapse to form black holes. In this paper, various constraints on such models involving black holes are considered. Hawking radiation from black holes, gamma and cosmic ray flux limits and constraints from the possible formation of stable black hole remnants are reanalyzed. The constraints which emerge from these considerations are remarkably close to those derived from the normalization of the cosmic string model to the cosmic microwave background anisotropies. [S0556-2821(98)05904-9]. C1 NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. Brown Univ, Dept Phys, Providence, RI 02912 USA. RP MacGibbon, JH (reprint author), NASA, Lyndon B Johnson Space Ctr, Code SN3, Houston, TX 77058 USA. NR 62 TC 17 Z9 17 U1 0 U2 0 PU AMERICAN PHYSICAL SOC PI COLLEGE PK PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA SN 0556-2821 J9 PHYS REV D JI Phys. Rev. D PD FEB 15 PY 1998 VL 57 IS 4 BP 2158 EP 2165 DI 10.1103/PhysRevD.57.2158 PG 8 WC Astronomy & Astrophysics; Physics, Particles & Fields SC Astronomy & Astrophysics; Physics GA YY130 UT WOS:000072116300014 ER PT J AU Berera, A Fang, LZ Hinshaw, G AF Berera, A Fang, LZ Hinshaw, G TI Attempt to determine the largest scale of primordial density perturbations in the universe SO PHYSICAL REVIEW D LA English DT Article ID INFLATIONARY UNIVERSE; PHASE-TRANSITIONS; FLUCTUATIONS; CONSTRAINTS; TEMPERATURE; CAUSALITY; NEUTRINO; TOPOLOGY; MATTER; MAPS AB The principle of causality requires that a pure power-law spectrum of cosmological density perturbations possess a super-Hubble suppression scale. We search for evidence of such suppression by performing a three parameter likelihood analysis of the COBE-DMR 4-year sky maps with respect to the amplitude, the spectral index, and the suppression scale. It is found that all suppression scales larger than c/H-0 are consistent with the data, but that scales of order c/H-0 are slightly preferred, at roughly the one-sigma level. Super-Hubble density fluctuations on very large scales (much greater than c/H-0) can only be explained in the context of present theory by a de Sitter expansion phase, whereas those that are "small" (similar to c/H-0) can also be explained within the standard hot big-bang model. Density perturbations originating after any conceivable de Sitter expansion phase or during non-isentropic de Sitter expansion have natural kinematic constraints which could explain a small super-Hubble suppression scale. Standard inflationary cosmology, which is characterized by isentropic de Sitter expansion, generically predicts that the particle horizon should be much larger than the present-day Hubble radius, c/H-0. For such scenarios, a small super-Hubble suppression scale would require the duration of the inflation epoch to be fairly short. Suppression scales smaller than c/H-0 are strongly excluded by the COBE data. [S0556-2821(98)01106-0]. C1 Vanderbilt Univ, Dept Phys & Astron, Nashville, TN 37235 USA. Univ Arizona, Dept Phys, Tucson, AZ 85721 USA. NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, Greenbelt, MD 20771 USA. RP Berera, A (reprint author), Vanderbilt Univ, Dept Phys & Astron, Nashville, TN 37235 USA. NR 31 TC 32 Z9 32 U1 0 U2 0 PU AMERICAN PHYSICAL SOC PI COLLEGE PK PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA SN 0556-2821 J9 PHYS REV D JI Phys. Rev. D PD FEB 15 PY 1998 VL 57 IS 4 BP 2207 EP 2212 DI 10.1103/PhysRevD.57.2207 PG 6 WC Astronomy & Astrophysics; Physics, Particles & Fields SC Astronomy & Astrophysics; Physics GA YY130 UT WOS:000072116300017 ER PT J AU Clark, JS Tarasov, AE Steele, IA Coe, MJ Roche, P Shrader, C Buckley, DAH Larionov, V Larionova, L Lyuty, VM Zaitseva, GV Grunsfeld, J Fabregat, J Parise, R AF Clark, JS Tarasov, AE Steele, IA Coe, MJ Roche, P Shrader, C Buckley, DAH Larionov, V Larionova, L Lyuty, VM Zaitseva, GV Grunsfeld, J Fabregat, J Parise, R TI Long-term variability of the Be/X-ray binary A 0535+26 - I. Optical and UV spectroscopy SO MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY LA English DT Article DE binaries, close; stars, emission-line, Be; pulsars, individual, A 0535 + 26; X-rays, stars ID OSCILLATIONS; DISKS; A0535+26; STARS; OUTBURSTS AB The results of a 7-yr optical and UV spectroscopic study of the high-mass X-ray binary A 0535 + 26 are presented. It was found that throughout the period of the observations the line profile of H alpha showed considerable variability, A correlation between the equivalent width of H alpha and both V-band magnitude and (B-V) colour excess was observed, albeit with considerable scatter present in the data set. A giant X-ray flare in early 1994 was accompanied by a fading in optical and infrared photometric bands, and a reduction in the equivalent width of H alpha. When the star was observed in 1994 September, it was found to have developed a double-peaked H alpha profile, and further observations saw the V/R peak ratio vary cyclically, with a period of similar to 1 yr. If this is identified as a global one-armed oscillation, it becomes the shortest period ever observed in a Be star. The accompanying photometric and spectroscopic observations provide a test of any theory seeking to describe the onset and behaviour of such a density wave. C1 Crimean Astrophys Observ, UK-334413 Nauchny, Crimea, Ukraine. Liverpool John Moores Univ, Astrophys Grp, Liverpool L3 3AF, Merseyside, England. Univ Sussex, Ctr Astron, MAPS, Brighton BN1 9QH, E Sussex, England. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. S African Astron Observ, ZA-7935 Observatory, South Africa. St Petersburg State Univ, Inst Astron, St Petersburg 198904, Russia. Univ Valencia, Dept Math Aplicada & Astron, E-46100 Valencia, Spain. RP Clark, JS (reprint author), Univ Southampton, Dept Phys, Southampton SO17 1BJ, Hants, England. RI Fabregat, Juan/F-9066-2016; OI Fabregat, Juan/0000-0002-5986-9347; Larionova, Liudmila/0000-0002-0274-1481; Larionov, Valeri/0000-0002-4640-4356 NR 30 TC 35 Z9 36 U1 1 U2 1 PU BLACKWELL SCIENCE LTD PI OXFORD PA P O BOX 88, OSNEY MEAD, OXFORD OX2 0NE, OXON, ENGLAND SN 0035-8711 J9 MON NOT R ASTRON SOC JI Mon. Not. Roy. Astron. Soc. PD FEB 11 PY 1998 VL 294 IS 1 BP 165 EP 176 PG 12 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YY312 UT WOS:000072134500017 ER PT J AU Catelan, M Borissova, J Sweigart, AV Spassova, N AF Catelan, M Borissova, J Sweigart, AV Spassova, N TI Bimodality and gaps on globular cluster horizontal branches. II. The cases of NGC 6229, NGC 1851, and NGC 2808 SO ASTROPHYSICAL JOURNAL LA English DT Review DE globular clusters, individual (NGC 6229, NGC 1851, NGC 2808); Hertzsprung-Russell diagram; stars, horizontal-branch; stars, Population II ID RR LYRAE STARS; COLOR-MAGNITUDE DIAGRAM; RED GIANT STARS; CCD-PHOTOMETRY; BLUE STRAGGLERS; VARIABLE-STARS; PHOTOGRAPHIC PHOTOMETRY; EVOLUTIONARY SEQUENCES; OMEGA CENTAURI; MASS-LOSS AB The outer halo globular cluster NGC 6229 has a peculiar horizontal-branch (HE) morphology, with clear indications of a bimodal HE and a "gap" on the blue HE. In this paper, we present extensive synthetic HE simulations to determine whether peculiar distributions in the underlying physical parameters are needed to explain the observed HE morphology. We find that a unimodal mass distribution along the HE can satisfactorily account for the observed HE bimodality, provided the mass dispersion is substantially larger than usually inferred for the Galactic globular clusters. In this case, NGC 6229 should have a well-populated, extended blue tail. A truly bimodal distribution in HE masses can also satisfactorily account for the observed HE morphology, although in this case the existence of an extended blue tail is not necessarily implied. The other two well-known bimodal-HB clusters, NGC 1851 and NGC 2808, are briefly analyzed. While the HE morphology of NGC 1851 can also be reproduced with a unimodal mass distribution assuming a large mass dispersion, the same is not true of NGC 2808, for which a bimodal, and possibly multimodal, mass distribution seems definitely required. The problem of gaps on the blue HE is also discussed. Applying the standard Hawarden and Newell chi(2) test, we find that the NGC 6229 gap is significant at the 99.7% level. However, in a set of 1000 simulations, blue-HE gaps comparable to the observed one are present in similar to 6%-9% of all cases. We employ a new and simple formalism, based on the binomial distribution, to explain the origin of this discrepancy, and conclude that Hawarden's method, in general, substantially overestimates the statistical significance of gaps. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Bulgarian Acad Sci, Astron Inst, BG-1784 Sofia, Bulgaria. RP NASA, Goddard Space Flight Ctr, Code 681, Greenbelt, MD 20771 USA. EM catelan@stars.gsfc.nasa.gov; jura@hmm.bg400.bg; sweigart@bach.gsfc.nasa.gov; neda@center.phys.acad.bg NR 131 TC 88 Z9 88 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 FEB 10 PY 1998 VL 494 IS 1 BP 265 EP 284 DI 10.1086/305200 PN 1 PG 20 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YY520 UT WOS:000072155800023 ER PT J AU Cannizzo, JK AF Cannizzo, JK TI The accretion disk limit cycle mechanism in the black hole X-ray binaries: Toward an understanding of the systematic effects SO ASTROPHYSICAL JOURNAL LA English DT Article DE accretion, accretion disks; binaries, close; black hole physics; stars, individual (A0620-00); X-rays, bursts; X-rays, stars ID DWARF NOVA OUTBURSTS; CATACLYSMIC VARIABLES; PERIODIC VARIABILITY; OPTICAL COUNTERPART; INSTABILITY MODEL; SECONDARY MAXIMA; GAS-DYNAMICS; WHITE-DWARF; TRANSIENTS; QUIESCENCE AB We examine in detail several aspects of the physics of accretion disks that are of possible relevance to the outburst mechanism of the black hole X-ray transients. We adopt the one-dimensional, time-dependent model described in detail by Cannizzo, Chen, and Livio with parameters appropriate for a system such as A0620-00. We investigate (1) the effect of the grid spacing, utilizing a logarithmic radial spacing Delta r proportional to r in addition to the spacing Delta r proportional to r(1/2), (2) the dependence of the local flow speed of gas within the hot part of the disk on radius and time during the time of the cooling wave propagation, (3) the shape of the outburst light curve as a function of the triggering location for the instability, (4) the long-term light curves of outbursts taken from trials in which complete cycles of quiescence and outburst are followed, both including and excluding the effect of evaporation or removal of matter from the inner edge of the disk, and (5) the strength of the self-irradiation of the outer parts of the disk by the X-rays from the inner disk. Our primary findings in each of these areas are that (1) low-resolution runs taking N similar or equal to 20 grid points using the logarithmic spacing produce decay timescales that are artificially slow by factors of similar to 2-3 and slower than exponential; (2) the deviation from steady state within the outer part of the inner hot disk appears to be in accord with the discussion given in Vishniac and Wheeler-far from the transition front, the flow speed is similar to alpha c(s)(h/r), whereas at the interface between the transition front and the cold disk, the flow speed is similar to alpha(s); (3) the outburst-triggering location must be greater than or similar to 100r(inner) for the rise time of the resulting outburst to be as short as is observed in the standard, bright systems; (4) the longterm light curves using the standard model produce frequent outbursts that are triggered near the inner disk edge and that have slow rise times, and the long-term light curves calculated assuming evaporation of matter from the inner disk exhibit outbursts with longer recurrence times and somewhat (but not significantly) shorter rise times; and (5) for a system with parameters relevant to A0620-00, our "standard" system, irradiation is not a dynamically significant effect, in accord with recent results of van Paradijs. 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 662, Greenbelt, MD 20771 USA. EM cannizzo@lheavx.gsfc.nasa.gov NR 85 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 FEB 10 PY 1998 VL 494 IS 1 BP 366 EP 380 DI 10.1086/305210 PN 1 PG 15 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YY520 UT WOS:000072155800029 ER PT J AU Corcoran, MF Petre, R Swank, JH Drake, SA Koyama, K Tsuboi, Y Viotti, R Damineli, A Davidson, K Ishibashi, K White, S Currie, D AF Corcoran, MF Petre, R Swank, JH Drake, SA Koyama, K Tsuboi, Y Viotti, R Damineli, A Davidson, K Ishibashi, K White, S Currie, D TI The ASCA X-ray spectrum of eta Carinae SO ASTROPHYSICAL JOURNAL LA English DT Article DE stars, abundances; stars, individual (eta Carinae); stars, early-type; X-rays, stars ID EMISSION; NEBULA; STARS; SPECTROSCOPY; SHELL; VARIABILITY; ULTRAVIOLET AB We have obtained high signal-to-noise ratio 0.5-10 keV band X-ray spectra of the peculiar, extremely luminous star eta Carinae with the Advanced Satellite for Cosmology and Astrophysics (ASCA) X-ray observatory during Cycle 4 observations in mid-1996. These data comprise the best X-ray spectra to date of the cool source (kT similar to 0.3 keV) surrounding the homunculus and of the hot source (kT similar to 5 keV) associated with eta Car itself. We identify line emission from ions of N, Mg, Si, and S and numerous strong transitions of Fe in a variety of ionization stages, including the first clear identification of a fluorescent Fe line produced by photoionization of cool material by the X-ray continuum from the hot source. The line strengths are consistent with thermal equilibrium models, though abundances of some important elements are nonsolar. Our analysis suggests that Fe is slightly underabundant and S and Si somewhat overabundant. Most importantly, we confirm the high N enrichment derived by Tsuboi et al. from their analysis of a shorter ASCA observation obtained during the performance verification (PV) phase in 1993 August. The O/N abundance ratio derived from the ASCA spectra is consistent with an upper limit from optical/UV spectral analysis (Davidson et al.) and with predictions of evolutionary models for extremely massive stars. Comparison of the Cycle 4 and PV-phase spectra shows that the X-ray luminosity increased by similar to 50% during this 3 year interval. Using the ASCA spectral model as a template, we reevaluate the spectrum of II Car obtained by the Rontgen Satelite (ROSAT) in late 1992 and construct an X-ray light curve for the 1992.4-1996.6 interval. We present spectra from the Intel national Ultraviolet Explorer (IUE) satellite obtained at nearly the same time as the Cycle 4 ASCA spectra and show that the observed X-ray variability is reflected in changes of some important UV spectral features. Our data suggest that the X-ray emission and state of the stellar wind are intimately connected, though the exact mechanism of coupling is not known. We suggest two alternatives: an underlying photospheric change of undetermined origin in eta Car itself, or a collision between a dense stellar wind from eta Car and the wind or photosphere of a companion. C1 NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. Kyoto Univ, Fac Sci, Dept Phys, Sakyo Ku, Kyoto 60601, Japan. CNR, Ist Astrofis Spaziale, I-00044 Frascati, RM, Italy. Univ Sao Paulo, Inst Astron & Geofis, BR-01065970 Sao Paulo, Brazil. Univ Minnesota, Dept Astron, Minneapolis, MN 55455 USA. Univ Maryland, Dept Phys & Astron, College Pk, MD 20742 USA. RP Univ Space Res Assoc, 7501 Forbes Blvd,Suite 206, Seabrook, MD 20706 USA. EM corcoran@barnegat.gsfc.nasa.gov RI Damineli, Augusto/D-8210-2012; Swank, Jean/F-2693-2012 OI Damineli, Augusto/0000-0002-7978-2994; NR 54 TC 38 Z9 38 U1 0 U2 0 PU IOP PUBLISHING LTD PI BRISTOL PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND SN 0004-637X EI 1538-4357 J9 ASTROPHYS J JI Astrophys. J. PD FEB 10 PY 1998 VL 494 IS 1 BP 381 EP 395 DI 10.1086/305190 PN 1 PG 15 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YY520 UT WOS:000072155800030 ER PT J AU Spicer, DS Feldman, U Widing, KG Rilee, M AF Spicer, DS Feldman, U Widing, KG Rilee, M TI The neon-to-magnesium abundance ratio as a tracer of the source region of prominence material SO ASTROPHYSICAL JOURNAL LA English DT Article DE Sun, abundances; Sun, corona; Sun, magnetic fields; Sun, prominences AB A survey of all 1000 spectroheliograms in the Skylab spectroheliograph plate collection was made to identify prominences above the limb and prominence-like features. The Ne/Mg abundance ratios obtained from the measurements have been determined from relative intensities of Ne VI and Mg VI lines at 400 Angstrom of seven prominences and prominence-like features observed above the solar limb. The derived abundance ratios have values intermediate between the photosphere and corona, while none are as low as the ratio of 0.7 expected in the corona, which implies that the material found in prominences is photospheric in origin. The significance of these results for the formation of prominences is briefly discussed. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. USN, Res Lab, EO Hulburt Ctr Space Res, Washington, DC 20735 USA. RP Spicer, DS (reprint author), NASA, Goddard Space Flight Ctr, Code 930, Greenbelt, MD 20771 USA. NR 6 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 FEB 10 PY 1998 VL 494 IS 1 BP 450 EP + DI 10.1086/305203 PN 1 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YY520 UT WOS:000072155800037 ER PT J AU Mendez, M van der Klis, M van Paradijs, J Lewin, WHG Vaughan, BA Kuulkers, E Zhang, W Lamb, FK Psaltis, D AF Mendez, M van der Klis, M van Paradijs, J Lewin, WHG Vaughan, BA Kuulkers, E Zhang, W Lamb, FK Psaltis, D TI Discovery of a second kilohertz quasi-periodic oscillation peak in 4U 1608-52 SO ASTROPHYSICAL JOURNAL LA English DT Article DE accretion, accretion disks; stars, neutron; stars, individual (4U 1608-52); X-rays, stars ID RAY AB Using a new technique to improve the sensitivity to weak quasi-periodic oscillations (QPOs), we discovered a new QPO peak at about 1100 Hz in the March 1996 outburst observations of 4U 1608-52, simultaneous with the similar to 600-900 Hz peak previously reported from these data. The frequency separation between the upper and the lower QPO peaks varied significantly from 232.7 +/- 11.5 Hz on March 3 to 293.1 +/- 6.6 Hz on March 6. This is the first case of a variable kilohertz peak separation in an atoll source. We discuss to what extent this result could be accommodated in beat-frequency models such as proposed for the kilohertz QPOs. We measured the rms fractional amplitude of both QPOs as a function of energy, and we found that the relation is steeper for the lower than for the upper frequency peak. This is the first source where such a difference between the energy spectrum of the two kilohertz QPOs could be measured. C1 Univ Amsterdam, Astron Inst Anton Pannekoek, NL-1098 SJ Amsterdam, Netherlands. Ctr High Energy Astrophys, NL-1098 SJ Amsterdam, Netherlands. Univ Nacl La Plata, Fac Ciencias Astron & Geofis, RA-1900 La Plata, Buenos Aires, Argentina. Univ Alabama, Dept Phys, Huntsville, AL 35899 USA. MIT, Space Res Ctr, Cambridge, MA 02139 USA. CALTECH, Space Radiat Lab, Pasadena, CA 91125 USA. Univ Oxford, Nucl & Astrophys Lab, Oxford OX1 3RH, England. NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. Univ Illinois, Dept Phys, Urbana, IL 61801 USA. Univ Illinois, Dept Astron, Urbana, IL 61801 USA. Harvard Smithsonian Ctr Astrophys, Cambridge, MA 02138 USA. RP Mendez, M (reprint author), Univ Amsterdam, Astron Inst Anton Pannekoek, Kruislaan 403, NL-1098 SJ Amsterdam, Netherlands. RI Mendez, Mariano/C-8011-2012 OI Mendez, Mariano/0000-0003-2187-2708 NR 25 TC 93 Z9 93 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 FEB 10 PY 1998 VL 494 IS 1 BP L65 EP L69 DI 10.1086/311162 PN 2 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YY522 UT WOS:000072156000016 ER PT J AU Sekanina, Z AF Sekanina, Z TI Modeling the diurnal evolution of a dust feature in comet Hale-Bopp (1995 O1) SO ASTROPHYSICAL JOURNAL LA English DT Article DE comets, general; comets, individual (Hale-Bopp 1995 O1) ID EMISSION PATTERN; SPIN VECTOR; MORPHOLOGY; NUCLEUS; TAIL; HALLEY AB A Monte Carlo computer code for simulating dust features in comets is applied to comet Hale-Bopp in order to model the diurnal evolution of a bright jet observed, in late 1997 February, to point in the southwesterly direction from the nucleus. The jet's morphology is closely matched by a model, which is based on the assumption that the ejecta were released nearly continuously from an isolated source on the nucleus surface. The fitted characteristics include the initial direction of the ejecta's motion, the feature's overall dimensions and shape, and its temporal variations during the rotation cycle. In particular, it is found that the relatively faint appendage some 10 "-15 " directly to the south from the nucleus can be identified with the residual ejecta from the previous rotation cycle. No attempt has been made to fit the observed brightness changes, which apparently are affected by variable seeing, especially in daylight. It is suggested that if the system of concentric halos to the south from the nucleus consists of two independent branches, its southwesterly branch can be identified with the ejecta from the same jet that are several rotations old. Modeling of a jet's diurnal evolution presents a powerful tool in our quest for understanding the emission of dust from discrete active regions on cometary nuclei. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Sekanina, Z (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 22 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 FEB 10 PY 1998 VL 494 IS 1 BP L121 EP + DI 10.1086/311147 PN 2 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YY522 UT WOS:000072156000028 ER PT J AU Szapudi, I Szalay, AS AF Szapudi, I Szalay, AS TI A new class of estimators for the N-point correlations SO ASTROPHYSICAL JOURNAL LA English DT Article DE cosmology, theory; galaxies, statistics; large-scale structure of universe; methods, statistical ID ANGULAR-CORRELATION FUNCTIONS; GALAXY CORRELATION-FUNCTION; HIGHER-ORDER STATISTICS; EXTRAGALACTIC OBJECTS; CATALOGS; COUNTS AB A class of improved estimators is proposed for N-point correlation functions of galaxy clustering and for discrete spatial random processes in general. In the limit of weak clustering, the variance of the unbiased estimator converges to the continuum value much faster than with any alternative, and all terms giving rise to a slower convergence exactly cancel. Explicit variance formulae are provided for both Poisson and multinomial point processes using techniques for spatial statistics reported by Ripley. The formalism naturally includes most previously used statistical tools such as N-point correlation functions and their Fourier counterparts, moments of counts in cells, and moment correlators. For all these, and perhaps some other statistics, our estimator provides a straightforward means for efficient edge corrections. C1 Fermi Natl Accelerator Lab, NASA, Fermilab Astrophys Ctr, Batavia, IL 60510 USA. Johns Hopkins Univ, Baltimore, MD 21218 USA. RP Szapudi, I (reprint author), Univ Durham, Dept Phys, South Rd, Durham DH1 3LE, England. NR 30 TC 45 Z9 45 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 FEB 10 PY 1998 VL 494 IS 1 BP L41 EP L44 DI 10.1086/311146 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YY522 UT WOS:000072156000010 ER PT J AU Zhang, SN Yu, W Zhang, W AF Zhang, SN Yu, W Zhang, W TI Spectral state transitions in Aquila X-1: Evidence for "propeller" effects SO ASTROPHYSICAL JOURNAL LA English DT Article DE accretion, accretion disks; binaries, general; stars, individual (Aquila X-1, Centaurus X-4); stars, low-mass, brown dwarfs; stars, neutron ID X-RAY TRANSIENTS; ACCRETING NEUTRON-STAR; QUIESCENCE; FLASHES; BURSTS; MODEL AB Aquila X-l is a soft X-ray transient source and emits type I X-ray bursts. A spectral state transition was observed with RXTE during its outburst decay in 1997 February and March. Its 10-30 keV and 5-10 keV count rate ratio increased suddenly when its luminosity was between 4 and 12 x 10(35) ergs s(-1), assuming a 2.5 kpc distance. Spectral fitting with a model composed of a blackbody and a power-law component showed that its blackbody component decreased and that the power-law component became much harder significantly and simultaneously. We interpret this transition to be caused by the centrifugal barrier, more commonly known as the "propeller" effect. We thus infer that the magnetic field strength of the neutron star is around 1 x 10(8) G, if the neutron star spin period is 1.8 ms. Similarly, we infer the neutron star magnetic field strength in another soft Xray transient Cen X-4 is about 2 x 10(9) G. We also propose a unified scheme for spectral state transitions in soft X-ray transients, from soft high state to hard low state and further to quiescent state. With this scheme accretion onto neutron star may take place even during the propeller regime. C1 NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. Inst High Energy Phys, LCRHEA, Beijing 100039, Peoples R China. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Zhang, SN (reprint author), NASA, George C Marshall Space Flight Ctr, ES-84, Huntsville, AL 35812 USA. NR 37 TC 73 Z9 74 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 FEB 10 PY 1998 VL 494 IS 1 BP L71 EP L74 DI 10.1086/311161 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YY522 UT WOS:000072156000017 ER PT J AU Liu, Y Vinokur, M AF Liu, Y Vinokur, M TI Exact integrations of polynomials and symmetric quadrature formulas over arbitrary polyhedral grids SO JOURNAL OF COMPUTATIONAL PHYSICS LA English DT Article DE quadrature formulas; polyhedral grids; finite-volume method ID FLOW AB This paper is concerned with two important elements in the high-order accurate spatial discretization of finite-volume equations over arbitrary grids. One element is the integration of basis functions over arbitrary domains, which is used in expressing various spatial integrals in terms of discrete unknowns. The other consists of quadrature approximations to those integrals. Only polynomial basis functions applied to polyhedral and polygonal grids are treated here. Nontriangular polygonal faces are subdivided into a union of planar triangular facets, and the resulting triangulated polyhedron is subdivided into a union of tetrahedra. The straight line segment, triangle, and tetrahedron are thus the fundamental shapes that are the building blocks for all integrations and quadrature approximations, Integrals of products up to the fifth order are derived in a unified manner for the three fundamental shapes in terms of the position vectors of vertices, Results are given both in terms of tensor products and products of Cartesian coordinates, The exact polynomial integrals are used to obtain symmetric quadrature approximations of any degree of precision up to five for arbitrary integrals over the three Fundamental domains, Using a coordinate-free formulation, simple and rational procedures are developed to derive virtually. all quadrature formulas, including some previously unpublished Four symmetry groups of quadrature points are introduced to derive Gauss formulas, while their limiting forms are used to derive Lobatto formulas, Representative Gauss and Lobatto formulas are tabulated, The relative efficiency of their application to polyhedral and polygonal grids is detailed, The extension to higher degrees of precision is discussed, (C) 1998 Academic Press. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Liu, Y (reprint author), NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. NR 8 TC 24 Z9 24 U1 0 U2 3 PU ACADEMIC PRESS INC PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA SN 0021-9991 J9 J COMPUT PHYS JI J. Comput. Phys. PD FEB 10 PY 1998 VL 140 IS 1 BP 122 EP 147 DI 10.1006/jcph.1998.5884 PG 26 WC Computer Science, Interdisciplinary Applications; Physics, Mathematical SC Computer Science; Physics GA ZD984 UT WOS:000072745400006 ER PT J AU Fujiwara, S Rosen, PA Tobita, M Murakami, M AF Fujiwara, S Rosen, PA Tobita, M Murakami, M TI Crustal deformation measurements using repeat-pass JERS 1 synthetic aperture radar interferometry near the Izu Peninsula, Japan SO JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH LA English DT Article ID LANDERS EARTHQUAKE; KILAUEA VOLCANO; CALIFORNIA; HAWAII; MODEL AB We have examined the precision of interferometric synthetic aperture radar (SAR) measurements of surface deformation of the Earth using 24-cm wavelength data acquired by the Japanese Earth Resources Satellite 1 (JERS 1) spacecraft, over the Izu Peninsula, Japan. Radar images acquired from 1993 to 1994 were made into 11 independent interferograms. Apparent water vapor signatures with equivalent path delay up to 16 cm preclude reliable estimates of small deformation from only one interferogram. Averaging of interferograms improves the measurement, such that residuals between precise leveling data and corresponding radar observations are less than 1 cm RMS. There is a clear correlation between cloud cover extent on a given day and the spectral power of the water vapor signature in an interferogram formed from the corresponding day's SAR image. Also, several water vapor features associated with local topography are consistent with accumulation of moisture on the windward side of an on-shore flow. Analysis shows that decorrelation in mixed conifer and deciduous forest is a weak function of the time between observations, imposing a roughly constant level of additional decorrelation relative to scatter-stable Urban areas. Furthermore, in high-relief areas, correlation is high when the baseline is tens of meters but drops rapidly with increasing baseline length. With strict control of the interferometric baseline length, adequate correlation in interferograms over very long time periods is possible even in forested, high relief regions. Observed inflation over Ito city is consistent with a localized magma source at depth, suggesting a different mechanism from the previous episode in 1989. C1 Geog Survey Inst, Ibaraki, Osaka 3050811, Japan. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Fujiwara, S (reprint author), Geog Survey Inst, Kitasato 1, Ibaraki, Osaka 3050811, Japan. EM fujiwara@gsi-mc.go.jp; par@parsar.jpl.nasa.gov NR 28 TC 41 Z9 52 U1 0 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-9313 EI 2169-9356 J9 J GEOPHYS RES-SOL EA JI J. Geophys. Res.-Solid Earth PD FEB 10 PY 1998 VL 103 IS B2 BP 2411 EP 2426 DI 10.1029/97JB02382 PG 16 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA YW382 UT WOS:000071929600001 ER PT J AU Purucker, ME Langel, RA Rajaram, M Raymond, C AF Purucker, ME Langel, RA Rajaram, M Raymond, C TI Global magnetization models with a priori information SO JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH LA English DT Article ID OCEANIC PLATEAUS; ANOMALY MAPS; GEOID HEIGHT; MAGSAT DATA; SATELLITE; FIELD; LITHOSPHERE; TOPOGRAPHY; CONTRASTS; SWELLS AB In an effort to explore the possible effects of change in integrated magnetization at the continent-ocean boundary and to account for such effects in modeling, an inverse technique is developed which allows for the inclusion of a priori information in models of global crustal magnetization or susceptibility. This technique accounts for processing effects such as main and external field removal. An a priori model consisting of an ocean-continent magnetic contract, oceanic topography, and remanent magnetization in the Cretaceous quiet zones is constructed using equivalent source dipoles. Previous investigations using similar models utilize only forward modeling procedures. We show how this a priori model can be modified so that the resulting computed field, after removal of spherical harmonics below some specified degree ("main field" removal) and along track filtering ("external field" removal), matches that of the robust POGO-Magsat anomaly map in a least squares sense. The dependence of the final model on the a priori information is also investigated. Between degrees 20 and 60 the final models are found to be almost identical for reasonable a priori conditions. An example from the Gulf of Mexico and surrounding Gulf Coast region serves to illustrate the utility of the technique. High heat flow, > 400 C/km, is observed in much of the Gulf Coast region. The example suggests that the elevated heat flow persists at depth and has elevated the Curie point. C1 NASA, Goddard Space Flight Ctr, Geodynam Branch, Raytheon STX, Greenbelt, MD 20771 USA. Indian Inst Geomagnetism, Bombay 400005, Maharashtra, India. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Purucker, ME (reprint author), NASA, Goddard Space Flight Ctr, Geodynam Branch, Raytheon STX, Code 921, Greenbelt, MD 20771 USA. EM purucker@geomag.gsfs.nasa.gov; langel@usit.net; mita@iigm0.ernet.in; car@orion.jpl.nasa.gov NR 49 TC 28 Z9 33 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-9313 EI 2169-9356 J9 J GEOPHYS RES-SOL EA JI J. Geophys. Res.-Solid Earth PD FEB 10 PY 1998 VL 103 IS B2 BP 2563 EP 2584 DI 10.1029/97JB02935 PG 22 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA YW382 UT WOS:000071929600012 ER PT J AU Jennings, DE Sada, PV AF Jennings, DE Sada, PV TI Water in Betelgeuse and Antares SO SCIENCE LA English DT Article ID ALPHA-ORIONIS; STELLAR SPECTRA; SCORPII; STARS; COOL; DUST; DIAMETERS; EMISSION; SUN; IAB AB Absorption lines of hot water have been identified in the infrared spectra of Betelgeuse (alpha Orionis) and Antares (alpha Scorpii) near 12.3 micrometers (811 to 819 wavenumbers). The water lines originate in the atmospheres of the stars, not in their circumstellar material. The spectra are similar in structure to umbral sunspot spectra. Pure rotation water lines of this type will occur throughout the spectra of cool stars at wavelengths greater than 10 micrometers. From the water spectra, the upper limit for the temperature in the line formation region in both stars is 2800 kelvin, The water column density in both stars is (3 +/- 2) x 10(18) molecules per square centimeter, yielding an abundance relative to atomic hydrogen of n(H-2,O)/n(H) approximate to 10(-7). C1 NASA, Planetary Syst Branch, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Consultoria Astron Monterrey, Garza Garcia 66250, NL, Mexico. RP Jennings, DE (reprint author), NASA, Planetary Syst Branch, Goddard Space Flight Ctr, Code 693, Greenbelt, MD 20771 USA. RI Jennings, Donald/D-7978-2012 NR 35 TC 34 Z9 34 U1 1 U2 3 PU AMER ASSOC ADVANCEMENT SCIENCE PI WASHINGTON PA 1200 NEW YORK AVE, NW, WASHINGTON, DC 20005 USA SN 0036-8075 J9 SCIENCE JI Science PD FEB 6 PY 1998 VL 279 IS 5352 BP 844 EP 847 DI 10.1126/science.279.5352.844 PG 4 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA YW330 UT WOS:000071923500038 PM 9452380 ER PT J AU Bauschlicher, CW AF Bauschlicher, CW TI QCISD(T) and B3LYP can correctly describe the EA of B, Al, and Ga SO INTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY LA English DT Article ID ELECTRON CORRELATION AB The electron affinities (EA) of B, Al, and Ga are determined accurately at the CCSD(T), QCISD(T), and B3LYP levels of theory. The failure of the QCISD(T) and B3LYP methods reported by Jursic is attributed to his treating the wrong state of the ion. (C) 1998 John Wiley & Sons, Inc. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Bauschlicher, CW (reprint author), NASA, Ames Res Ctr, STC-230-3, Moffett Field, CA 94035 USA. NR 10 TC 3 Z9 3 U1 1 U2 5 PU JOHN WILEY & SONS INC PI NEW YORK PA 605 THIRD AVE, NEW YORK, NY 10158-0012 USA SN 0020-7608 J9 INT J QUANTUM CHEM JI Int. J. Quantum Chem. PD FEB 5 PY 1998 VL 66 IS 4 BP 285 EP 286 DI 10.1002/(SICI)1097-461X(1998)66:4<285::AID-QUA4>3.0.CO;2-R PG 2 WC Chemistry, Physical; Mathematics, Interdisciplinary Applications; Physics, Atomic, Molecular & Chemical SC Chemistry; Mathematics; Physics GA YR705 UT WOS:000071522000004 ER PT J AU Grasso, D Riotto, A AF Grasso, D Riotto, A TI On the nature of the magnetic fields generated during the electroweak phase transition SO PHYSICS LETTERS B LA English DT Article ID STRINGS AB In this letter we reanalyse the question of the origin of magnetic fields during the electroweak phase transition. We show that their formation is intimately connected to some semiclassical configurations of the gauge fields, such as electroweak Z-strings and W-condensates. We describe the formation of these semiclassical configurations during a first order phase transition and argue that they might be generated also in the case of a second order phase transition. We suggest that the instability of electroweak strings does not imply the disappearance of the embedded magnetic field. (C) 1998 Elsevier Science B.V. C1 Uppsala Univ, Dept Theoret Phys, S-75108 Uppsala, Sweden. NASA, Fermilab Astrophys Ctr, Fermi Natl Accelerator Lab, Batavia, IL 60510 USA. RP Grasso, D (reprint author), Uppsala Univ, Dept Theoret Phys, Box 803, S-75108 Uppsala, Sweden. RI Grasso, Dario/I-2440-2012 OI Grasso, Dario/0000-0001-7761-7242 NR 18 TC 29 Z9 29 U1 0 U2 0 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0370-2693 J9 PHYS LETT B JI Phys. Lett. B PD FEB 5 PY 1998 VL 418 IS 3-4 BP 258 EP 265 DI 10.1016/S0370-2693(97)01224-0 PG 8 WC Astronomy & Astrophysics; Physics, Nuclear; Physics, Particles & Fields SC Astronomy & Astrophysics; Physics GA ZF843 UT WOS:000072938800004 ER PT J AU Lewis, MS AF Lewis, MS TI Improving on excellence SO AEROSPACE AMERICA LA English DT Editorial Material C1 NASA, Langley Res Ctr, Aviat Safety Program Off, Hampton, VA 23665 USA. RP Lewis, MS (reprint author), NASA, Langley Res Ctr, Aviat Safety Program Off, Hampton, VA 23665 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 FEB PY 1998 VL 36 IS 2 BP 3 EP 3 PG 1 WC Engineering, Aerospace SC Engineering GA YW020 UT WOS:000071887600001 ER PT J AU Osborne, DJ Ng, WF Tweedt, DL AF Osborne, DJ Ng, WF Tweedt, DL TI Studies of secondary flow at endwall of a supersonic compressor cascade SO AIAA JOURNAL 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 AB A combined experimental and numerical study was conducted to investigate the endwall secondary how in a linear supersonic compressor cascade. The experiment was carried out in a supersonic wind tunnel, with Mach and Reynolds numbers (based on the blade chord) of 2.36 and 4.8 X 10(6), respectively. A three dimensional viscous computational fluid dynamics (CFD) calculation was performed to simulate the endwall boundary layer and the three-dimensional secondary flows. The experimental and computational analyses presented are all at the design incidence angle. Experimental measurements include multiple-color surface oil flow visualization applied to the endwall and blade surfaces, blade-to-blade pitot pressure contours at the 90% chordwise position, and upstream and downstream static pressures at the endwall. All of these measurements compare favorably with the CPD calculation. Results from the CFD analysis show that endwall total-pressure losses in this supersonic compressor cascade are a significant contributor to the overall losses and can account for one-third of the overall flowfield loss. C1 Virginia Polytech Inst & State Univ, Dept Mech Engn, Blacksburg, VA 24061 USA. NASA, Lewis Res Ctr, Turbomachinery & Propuls Syst Div, Cleveland, OH 44135 USA. RP Osborne, DJ (reprint author), Virginia Polytech Inst & State Univ, Dept Mech Engn, Blacksburg, VA 24061 USA. RI Ng, Wing/F-2447-2014 NR 12 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 0001-1452 J9 AIAA J JI AIAA J. PD FEB PY 1998 VL 36 IS 2 BP 128 EP 133 DI 10.2514/2.7493 PG 6 WC Engineering, Aerospace SC Engineering GA YU341 UT WOS:000071697800002 ER PT J AU Mankbadi, RR Hixon, R Shih, SH Povinelli, LA AF Mankbadi, RR Hixon, R Shih, SH Povinelli, LA TI Use of linearized enter equations for supersonic jet noise prediction SO AIAA JOURNAL LA English DT Article; Proceedings Paper CT AIAA 34th Aerospace Sciences Meeting and Exhibit CY JAN 15-19, 1996 CL RENO, NEVADA SP Amer Inst Aeronaut & Astronaut ID DEPENDENT BOUNDARY-CONDITIONS; HYPERBOLIC SYSTEMS; SOUND; FIELD; FLOWS AB The use of linearized Euler equations for direct prediction of supersonic jet noise is explored. It is shown that a high-order numerical scheme coupled with proper boundary treatment can produce a stable solution nearly free from reflections. Results are verified against analytical results for sound radiated by instability waves. Applicability of this approach to real jets is explored by taking the inflow disturbances to be random in time and comparing the computed sound field to the experimentally measured one. C1 NASA, Lewis Res Ctr, Inst Computat Mech Propuls, Computat Aeroacoust Grp, Cleveland, OH 44135 USA. NASA, Lewis Res Ctr, Turbomachinery & Propuls Syst Div, Cleveland, OH 44135 USA. RP Mankbadi, RR (reprint author), NASA, Lewis Res Ctr, Inst Computat Mech Propuls, Computat Aeroacoust Grp, Cleveland, OH 44135 USA. NR 37 TC 26 Z9 28 U1 0 U2 6 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 FEB PY 1998 VL 36 IS 2 BP 140 EP 147 DI 10.2514/2.7495 PG 8 WC Engineering, Aerospace SC Engineering GA YU341 UT WOS:000071697800004 ER PT J AU McHugh, PR Knoll, DA Keyes, DE AF McHugh, PR Knoll, DA Keyes, DE TI Application of Newton-Krylov-Schwarz algorithm to low-Mach-number compressible combustion SO AIAA JOURNAL LA English DT Article; Proceedings Paper CT AIAA 34th Aerospace Sciences Meeting and Exhibit CY JAN 15-19, 1996 CL RENO, NEVADA SP Amer Inst Aeronaut & Astronaut ID LINEAR-SYSTEMS; MATRIX C1 Semitool Inc, Thermal Prod Div, Kalispell, MT 59901 USA. Univ Calif Los Alamos Natl Lab, Appl Theoret & Computat Phys Div, Los Alamos, NM 87545 USA. Old Dominion Univ, Dept Comp Sci, Norfolk, VA 23529 USA. NASA, Langley Res Ctr, Inst Comp Applicat Sci & Engn, Hampton, VA 23681 USA. RP McHugh, PR (reprint author), Semitool Inc, Thermal Prod Div, Kalispell, MT 59901 USA. NR 11 TC 4 Z9 4 U1 0 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 FEB PY 1998 VL 36 IS 2 BP 290 EP 292 DI 10.2514/2.7515 PG 3 WC Engineering, Aerospace SC Engineering GA YU341 UT WOS:000071697800024 ER PT J AU Matousek, J Mount, DM Netanyahu, NS AF Matousek, J Mount, DM Netanyahu, NS TI Efficient randomized algorithms for the repeated median line estimator SO ALGORITHMICA LA English DT Article DE repeated median estimator; line fitting; robust estimators; randomized algorithms; computational geometry ID SQUARES REGRESSION; SLOPE SELECTION; TIME; SPACE AB The problem of fitting a straight line to a finite collection of points in the plane is an important problem in statistical estimation. Recently there has been a great deal of interest is robust estimators, because of their lack of sensitivity to outlying data points. The basic measure of the robustness of an estimator is its breakdown point, that is, the fraction (up to 50%) of outlying data points that can corrupt the estimator, One problem with robust estimators is that achieving high breakdown points (near 50%) has proved to be computationally demanding. In this paper we present the best known theoretical algorithm and a practical subquadratic algorithm for computing a 50% breakdown point line estimator, the Siegel or repeated median line estimator. We first present an O(n log n) randomized expected-time algorithm, where la is the number of given points. This algorithm relies, however, on sophisticated data structures. We also present a very simple O(n log(2) n) randomized algorithm for this problem, which uses no complex data structures. We provide empirical evidence that, for many realistic input distributions, the running time of this second algorithm is actually O (n log n) expected time. C1 UNIV MARYLAND, DEPT COMP SCI, COLLEGE PK, MD 20742 USA. UNIV MARYLAND, INST ADV COMP STUDIES, COLLEGE PK, MD 20742 USA. UNIV MARYLAND, CTR AUTOMAT RES, COLLEGE PK, MD 20742 USA. NASA, GODDARD SPACE FLIGHT CTR, CTR EXCELLENCE SPACE DATA & INFORMAT SCI, GREENBELT, MD 20771 USA. RP CHARLES UNIV, DEPT APPL MATH, CR-11800 PRAGUE, CZECH REPUBLIC. NR 37 TC 9 Z9 9 U1 0 U2 0 PU SPRINGER PI NEW YORK PA 233 SPRING ST, NEW YORK, NY 10013 USA SN 0178-4617 EI 1432-0541 J9 ALGORITHMICA JI Algorithmica PD FEB PY 1998 VL 20 IS 2 BP 136 EP 150 DI 10.1007/PL00009190 PG 15 WC Computer Science, Software Engineering; Mathematics, Applied SC Computer Science; Mathematics GA YH868 UT WOS:A1998YH86800002 ER PT J AU Ostgaard, N Stadsnes, J Aarsnes, K Soraas, F Maseide, K Smith, M Sharber, J AF Ostgaard, N Stadsnes, J Aarsnes, K Soraas, F Maseide, K Smith, M Sharber, J TI Simultaneous measurements of X-rays and electrons during a pulsating aurora SO ANNALES GEOPHYSICAE-ATMOSPHERES HYDROSPHERES AND SPACE SCIENCES LA English DT Article DE ionospheric particle precipitation; magnetospheric physics; annual phenomena; energetic particle ID BREMSSTRAHLUNG; ATMOSPHERE AB The PULSAUR II rocket was launched from Andoya Rocket Range at 23.43 UT on 9 February 1994 into a pulsating aurora. In this paper we focus on the observations of precipitating electrons and auroral X-rays. By using models it is possible to deduce the electron energy spectrum from X-ray measurements. Comparisons are made between the deduced electron fluxes and the directly measured electron fluxes on the rocket. We found the shape of the observed and the deduced electron spectra to fit very well, with almost identical e-folding energies in the energy range from 10 keV to similar to 60-80 keV. For the integrated fluxes from 10.8 to 250 keV, we found a discrepancy of 30%. By combining two models, we have found a good method of deducing the electron precipitation from X-ray measurements. The discrepancies between calculations and measurements are in the range of the uncertainties in the measurements. C1 Univ Bergen, Dept Phys, N-5007 Bergen, Norway. Univ Oslo, Dept Phys, N-0316 Oslo, Norway. NASA, Goddard Space Flight Ctr, Extraterr Phys Lab, Greenbelt, MD 20771 USA. SW Res Inst, San Antonio, TX USA. RP Ostgaard, N (reprint author), Univ Bergen, Dept Phys, Allegaten 55, N-5007 Bergen, Norway. NR 23 TC 7 Z9 7 U1 1 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 FEB PY 1998 VL 16 IS 2 BP 148 EP 160 DI 10.1007/s005850050588 PG 13 WC Astronomy & Astrophysics; Geosciences, Multidisciplinary; Meteorology & Atmospheric Sciences SC Astronomy & Astrophysics; Geology; Meteorology & Atmospheric Sciences GA ZB184 UT WOS:000072444800004 ER PT J AU Venkateswaran, K Dohmoto, N Harayama, S AF Venkateswaran, K Dohmoto, N Harayama, S TI Cloning and nucleotide sequence of the gyrB gene of Vibrio parahaemolyticus and its application in detection of this pathogen in shrimp SO APPLIED AND ENVIRONMENTAL MICROBIOLOGY LA English DT Article ID POLYMERASE CHAIN-REACTION; THERMOSTABLE DIRECT HEMOLYSIN; FLUOROGENIC ASSAY; RAPID DETECTION; REACTION AMPLIFICATION; PHYLOGENETIC ANALYSIS; BACTERIA; STRAINS; FOODS; TDH AB Because biochemical testing and 16S rRNA sequence analysis have proven inadequate for the differentiation of Vibrio parahaemolyticus from closely related species, we employed the gyrase B gene (gvrB) as a molecular diagnostic probe. The gyrB genes of V. parahaemolyticus and closely related Vibrio alginolyticus were cloned and sequenced. Oligonucleotide PCR primers were designed for the amplification of a 285-bp fragment from within gyrB specific for V. parahaemolyticus. These primers recognized 117 of 117 reference and wild-type V. parahaemolyticus strains, whereas amplification did not occur when 90 strains of 37 other Vibrio species or 60 strains representing 34 different nonvibrio species were tested. In 100-mu l PCR mixtures, the lower detection limits were 5 CFU for live cells and ii pg for purified DNA. The possible application of gyrB primers for the routine identification of V. parahaemolyticus in food was examined. We developed and tested a procedure for the specific detection of the target organism in shrimp consisting of an 18-h preenrichment followed by PCR amplification of the 285-bp V. parahaemolyticus-specific fragment. This method enabled us to detect an initial inoculum of 1.5 CFU of V. papahaemolyticus cells per g of shrimp homogenate. By this approach, we were able to detect V. parahaemolyticus in all of 27 shrimp samples artificially inoculated with this bacterium. We present here a rapid, reliable, and sensitive protocol for the detection of V. parahaemolyticus in shrimp. C1 Nippon Suisan Kaisha Ltd, Cent Res Lab, Hachioji, Tokyo 192, Japan. Marine Biotechnol Inst, Kamaishi Labs, Kamaishi, Iwate 026, Japan. RP Venkateswaran, K (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. EM kjvenkat@csd.uwm.edu NR 32 TC 107 Z9 135 U1 0 U2 6 PU AMER SOC MICROBIOLOGY PI WASHINGTON PA 1325 MASSACHUSETTS AVENUE, NW, WASHINGTON, DC 20005-4171 USA SN 0099-2240 J9 APPL ENVIRON MICROB JI Appl. Environ. Microbiol. PD FEB PY 1998 VL 64 IS 2 BP 681 EP 687 PG 7 WC Biotechnology & Applied Microbiology; Microbiology SC Biotechnology & Applied Microbiology; Microbiology GA YV746 UT WOS:000071858600048 PM 9464408 ER PT J AU Peele, AG Nugent, KA AF Peele, AG Nugent, KA TI Lobster-eye x-ray optics: a rapid evaluation of the image distribution SO APPLIED OPTICS LA English DT Article ID ARRAYS AB A method for calculating the image distribution for one-dimensional lobster-eye optics is presented. This method gives the image distribution exactly for certain cases and offers improved speed over the method of ray tracing. Examples of the use of the algorithm are given. We show that the algorithm gives the same results as detailed ray-tracing codes. Extension of the method to the two-dimensional case is discussed. (C) 1998 Optical Society of America. C1 Univ Melbourne, Sch Phys, Parkville, Vic 3052, Australia. RP Peele, AG (reprint author), NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. RI Nugent, Keith/J-2699-2012; Nugent, Keith/I-4154-2016 OI Nugent, Keith/0000-0003-1522-8991; Nugent, Keith/0000-0002-4281-3478 NR 9 TC 2 Z9 2 U1 0 U2 2 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 FEB 1 PY 1998 VL 37 IS 4 BP 632 EP 642 DI 10.1364/AO.37.000632 PG 11 WC Optics SC Optics GA YV841 UT WOS:000071868700005 PM 18268634 ER PT J AU Green, RO AF Green, RO TI Spectral calibration requirement for earth-looking imaging spectrometers in the solar-reflected spectrum SO APPLIED OPTICS LA English DT Article AB Earth-looking imaging spectrometers operating in the solar-reflected spectrum measure spectra of the total upwelling radiance for each spatial element in an image. These measurements are used to derive physical parameters of the Earth's surface and atmosphere from the energy, molecular absorption, and constituent scattering characteristics expressed in each spectrum. To achieve these quantitative objectives, the measured spectra must be spectrally, radiometrically, and spatially calibrated. The ubiquitous presence of numerous, strong, narrow atmosphere and solar absorptions in the upwelling spectral radiance in conjunction with the narrow spectral channels of imaging spectrometers forms the basis for a general spectral calibration requirement. In order to determine the requirement for spectral calibration accuracy, a sensitivity analysis has been completed for imaging spectrometers with contiguously sampled spectral channel response functions of 5, 10, and 20 nm full width at half-maximum from 400 to 2500 nm. This sensitivity analysis shows that spectral calibration errors of 10% and 5% cause significant, spectrally distinct errors in the measured radiance throughout the solar-reflected spectrum. These errors result from the sensitivity of the measured radiance to the exact convolution of the narrow channels of imaging spectrometers with the upwelling spectral radiance that contains narrow atmosphere and solar absorptions. These errors are systematic and add directly to the radiometric calibration uncertainty for every spectrum in the image. This analysis establishes that a spectral calibration accuracy approaching 1% of the full width at half-maximum throughput of the spectral response function for both spectral channel position and shape is necessary to suppress these errors in the measured radiance spectrum. (C) 1998 Optical Society of America. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ Calif Santa Barbara, Inst Computat Earth Syst Sci, Santa Barbara, CA 93106 USA. RP Green, RO (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 6 TC 90 Z9 96 U1 0 U2 11 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 FEB 1 PY 1998 VL 37 IS 4 BP 683 EP 690 DI 10.1364/AO.37.000683 PG 8 WC Optics SC Optics GA YV841 UT WOS:000071868700012 PM 18268641 ER PT J AU Sahoo, NK Shapiro, AP AF Sahoo, NK Shapiro, AP TI Process-parameter-dependent optical and structural properties of ZrO2MgO mixed-composite films evaporated from the solid solution SO APPLIED OPTICS LA English DT Article ID ION-ASSISTED DEPOSITION; ATOMIC-FORCE MICROSCOPY; THIN-FILMS; MICROSTRUCTURAL DEVELOPMENT; SPUTTER DEPOSITION; VISIBLE REGION; ZIRCONIA FILMS; BAND-GAP; CONSTANTS; INHOMOGENEITY AB The process-parameter-dependent optical and structural properties of ZrO2MgO mixed-composite material have been investigated. Optical properties were derived from spectrophotometric measurements. By use of atomic force microscopy, x-ray diffraction analysis, and energy-dispersive x-ray (EDX) analysis, the surface morphology, grain size distributions, crystallographic phases, and process-dependent material composition of films have been investigated. EDX analysis made evident the correlation between the oxygen enrichment in the films prepared at a high level of oxygen pressure and the very low refractive index. Since oxygen pressure can be dynamically varied during a deposition process, coatings constructed of suitable mixed-composite thin films can benefit from continuous modulation of the index of refraction. A step modulation approach is used to develop various multilayer-equivalent thin-film devices. C1 NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. BARC, Div Spect, Bombay 40085, Maharashtra, India. RP Sahoo, NK (reprint author), NASA, George C Marshall Space Flight Ctr, Mail Code EB52, Huntsville, AL 35812 USA. NR 65 TC 32 Z9 32 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 FEB 1 PY 1998 VL 37 IS 4 BP 698 EP 718 DI 10.1364/AO.37.000698 PG 21 WC Optics SC Optics GA YV841 UT WOS:000071868700014 PM 18268643 ER PT J AU Schlegel, EM Petre, R Loewenstein, M AF Schlegel, EM Petre, R Loewenstein, M TI ROSAT observations of X-ray-faint S0 galaxies: NGC 1380 SO ASTRONOMICAL JOURNAL LA English DT Article DE galaxies, individual (NGC 1380); X-rays ID PSPC OBSERVATIONS; ELLIPTIC GALAXIES; EMISSION; SAMPLE; ABUNDANCES; DISCOVERY; SPECTRA; MATTER; ASCA; GAS AB We used the ROSAT Position Sensitive Proportional Counter (PSPC) to obtain a 13 ks exposure and the ROSAT HRI to obtain a 42.5 ks exposure of the faint SO galaxy NGC 1380. We show that the PSPC spectrum can be modeled as a thermal spectrum with kT similar to 0.5 keV, which is consistent with emission from a hot interstellar medium. We do not detect any emission from a hard component; the 90% upper limit is consistent with the trend for the scaled-up luminosities of X-ray-emitting point sources. The radial profiles from the PSPC and HRI data support the spectral fitting, because each profile is more sharply concentrated than the optical light (which reflects the stellar distribution), in contrast to other E/SO galaxies. The PSPC radial profile is consistent with emission from a point source, because of the larger point-spread function; the HRI profile reveals the presence of extended hot gas. We also extend the L(X)-L(B) plane, described by Matsumoto et al. in the range 10.8 < log L(B) < 11.3, to log L(B) similar to 10.5. We extend this plane separately for the hard discrete and the soft thermal components and show that the scaling relation for the hard component continues to at least log L(B) similar to 10.5. C1 Smithsonian Astrophys Observ, Cambridge, MA 02138 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Maryland, College Pk, MD 20742 USA. RP Schlegel, EM (reprint author), Smithsonian Astrophys Observ, Mail Stop 4,60 Garden St, Cambridge, MA 02138 USA. NR 45 TC 8 Z9 8 U1 0 U2 0 PU IOP PUBLISHING LTD PI BRISTOL PA DIRAC HOUSE, TEMPLE BACK, BRISTOL BS1 6BE, ENGLAND SN 0004-6256 J9 ASTRON J JI Astron. J. PD FEB PY 1998 VL 115 IS 2 BP 525 EP 534 DI 10.1086/300217 PG 10 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YW535 UT WOS:000071946100014 ER PT J AU Verter, F Rickard, LJ AF Verter, F Rickard, LJ TI Infrared properties of molecular cirrus. I. Photometry of extended sources on IRAS image products SO ASTRONOMICAL JOURNAL LA English DT Article DE infrared radiation; ISM, clouds; ISM, molecules ID HIGH GALACTIC LATITUDE; 100 MICRON CIRRUS; SPECTROSCOPIC ANALYSIS; PHYSICAL CONDITIONS; DUST CLOUD; EMISSION; SEARCH; STARS; GAS; DISTANCES AB We have conducted a survey of IRAS images of the high-latitude molecular cirrus clouds cataloged by Magnani, Blitz, & Mundy. This paper reports the data reduction methods used in our survey and also studies the photometric accuracy that can be achieved for faint extended sources on IRAS image products. The principal topics covered are the modeling and removal of sky backgrounds at high Galactic latitude, and as a function of ecliptic latitude; the relative accuracy of different background models and methods of background removal; the integration of source flux on background-subtracted images; the proper definition of flux error bars, their calculation, and the minimum uncertainties set by the performance of the IRAS detectors; the creation of multiple-wavelength composite images; and the creation of temperature and opacity maps. We find that most error bars quoted for IRAS fluxes in the literature are incorrect. We conclude that the limiting surface brightness to which Sky Flux Plates may be used to study faint extended sources is approximately 0.05 MJy sr(-1). The photometric issues discussed herein are relevant to all IRAS image products, including Sky Flux Plates, co-added images, and the IRAS Sky Survey Atlas (ISSA). We compare the accuracy of data reduction on different products and discuss their relative advantages and disadvantages. We are particularly concerned with the accurate removal of zodiacal backgrounds near the ecliptic plane, a region known as the ISSA Reject Set. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. USN, Res Lab, Washington, DC 20375 USA. RP NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. NR 66 TC 9 Z9 9 U1 0 U2 0 PU IOP PUBLISHING LTD PI BRISTOL PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND SN 0004-6256 EI 1538-3881 J9 ASTRON J JI Astron. J. PD FEB PY 1998 VL 115 IS 2 BP 745 EP 766 DI 10.1086/300199 PG 22 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YW535 UT WOS:000071946100030 ER PT J AU Sloan, GC Little-Marenin, IR Price, SD AF Sloan, GC Little-Marenin, IR Price, SD TI The carbon-rich dust sequence: Infrared spectral classification of carbon stars SO ASTRONOMICAL JOURNAL LA English DT Article DE infrared radiation; stars, carbon ID LOW-RESOLUTION SPECTRA; ASYMPTOTIC GIANT BRANCH; M-MIRA VARIABLES; EMISSION FEATURES; CIRCUMSTELLAR ENVELOPES; CHEMICAL-COMPOSITION; SILICATE EMISSION; OXYGEN-RICH; MASS-LOSS; SHELLS AB We have developed a classification system for the infrared spectral emission from carbon stars, using a sample of 96 bright carbon-rich variables associated with the asymptotic giant branch. In addition to the stellar contribution, most spectra include the 11.2 mu m emission feature from SiC and either a smooth, cool continuum from amorphous carbon or a secondary emission feature at 9.0 mu m. We have identified a carbon-rich dust sequence along which the amorphous carbon component grows while the 9.0 mu m feature declines in strength. Along this spectral sequence, the proportion of Mira variables increases, as does the period of variability, the mass-loss rate, and the thickness of the circumstellar shell. Thus the carbon-rich dust sequence appears to be an evolutionary sequence. One class of spectra shows a particularly strong 9.0 mu m feature, enhanced C/O ratio, and several other unusual properties that suggest a different sequence, perhaps related to J stars. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Wellesley Coll, Whitin Observ, Wellesley, MA 02181 USA. Phillips Lab, GPOB, Bedford, MA 01731 USA. RP Sloan, GC (reprint author), Univ Coll, Australian Def Force Acad, Sch Phys, Canberra, ACT 2600, Australia. EM sloan@ssa1.arc.nasa.gov; ilittle@lucy.wellesley.edu; price@plh.af.mil NR 64 TC 31 Z9 31 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 FEB PY 1998 VL 115 IS 2 BP 809 EP 820 DI 10.1086/300205 PG 12 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YW535 UT WOS:000071946100035 ER PT J AU Haberl, F Angelini, L Motch, C White, NE AF Haberl, F Angelini, L Motch, C White, NE TI X-ray observations of the slowest known Be/X-ray pulsars RX J0146.9+6121 and X Persei SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE stars : emission-line, Be; stars : individual : RX J0146.9+6121, X Persei; stars : neutron; X-rays : stars ID SPECTRUM; X0142+614 AB We present ASCA and ROSAT observations of the Be/X-ray binary pulsars RX J0146.9+6121 and X Persei between 1994 and 1996. Measuring the neutron star spin period and X-ray luminosity of X Persei shows that the episode of low X-ray luminosity and monotonic spin-down since 1978 continued to at least August 1995. ASCA and ROSAT HRI observations of RX J0146.9+6121 detected the pulsar with the longest known neutron star spin period at low luminosities after the X-ray outburst seen by EXOSAT in August 1984. The large spin period decrease seen between 1984 and 1993 has nearly stopped at a period of 1407.3 s in February 1996. We discuss that the X-ray outburst behaviour of X Persei with respect to its Be star phase changes observed in the optical can be caused by an asymmetry in the matter distribution around the Be star. C1 Max Planck Inst Extraterr Phys, D-85748 Garching, Germany. NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. Univ Strasbourg 1, Observ Astron Strasbourg, F-67000 Strasbourg, France. Univ Space Res Assoc, 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 RI White, Nicholas/B-6428-2012 OI White, Nicholas/0000-0003-3853-3462 NR 27 TC 27 Z9 27 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 FEB 1 PY 1998 VL 330 IS 1 BP 189 EP 194 PG 6 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YW755 UT WOS:000071970100028 ER PT J AU Haser, SM Pauldrach, AWA Lennon, DJ Kudritzki, RP Lennon, M Puls, J Voels, SA AF Haser, SM Pauldrach, AWA Lennon, DJ Kudritzki, RP Lennon, M Puls, J Voels, SA TI Quantitative UV spectroscopy of early O stars in the Magellanic Clouds - The determination of the stellar metallicities SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE stars : early type, mass loss; line : profiles; stars : abundances; Magellanic Clouds ID RADIATION-DRIVEN WINDS; HOT LUMINOUS STARS; B-TYPE STARS; WOLF-RAYET STARS; MASS-LOSS RATES; CHEMICAL ABUNDANCES; METAL ABUNDANCES; RESONANCE LINES; GALAXIES; MODELS AB UV spectra of 4 O-stars in the Magellanic Clouds obtained with the Faint Object Spectrograph of the Hubble Space Telescope are analyzed with respect to metallicity. With the stellar parameters T-eff, log g, R*, and the mass loss rates (M) over dot known from optical analyses, the metal abundances including iron group elements are derived in two steps. First, hydrodynamic radiation driven wind NLTE models with metallicity as a free parameter are constructed to fit the observed wind momentum rate and thus, yield a dynamical metallicity. Then, synthetic spectra are computed for different metal abundances and compared to the observed spectra to obtain a spectroscopic metallicity. In general, the results obtained from both methods agree. For the two stars in the Small Magellanic Cloud (NGC 346#3, O3 III(f*) and AV 243, O6 V) metallicities of log z/z(circle dot) = -0.7 and -0.8, respectively, are found. The O3 star shows evidence for CNO-cycled matter in its atmosphere. The metallicity of the two stars in the Large Cloud (Sk-68 degrees 137, O3 III(f*) and Sk-67 degrees 166, O4 If(+)) are constrained to log z/z(circle dot) = -0.3 and -0.1. Because of saturation effects in the cores of the pseudophotospheric metal lines the determination of the LMC metallicity is less reliable. C1 Univ Sternwarte Munchen, D-81679 Munich, Germany. Max Planck Inst Astrophys, D-85748 Garching, Germany. NASA, Goddard Space Flight Ctr, Astrophys Data Facil, Greenbelt, MD 20771 USA. RP Kudritzki, RP (reprint author), Univ Sternwarte Munchen, Scheinerstr 1, D-81679 Munich, Germany. NR 70 TC 59 Z9 59 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 FEB 1 PY 1998 VL 330 IS 1 BP 285 EP 305 PG 21 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YW755 UT WOS:000071970100040 ER PT J AU Yrjola, I Jenniskens, P AF Yrjola, I Jenniskens, P TI Meteor stream activity - VI. A survey of annual meteor activity by means of forward meteor scattering SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE meteors; meteoroids ID RADIANT DISTRIBUTIONS; COMMUNICATION AB The meteor activity of northern hemisphere streams was measured by means of radio forward meteor scatter. In 1994, there were 45 episodes of enhanced activity which were detected again in 1995, at both times on top of a continuous background of sporadic activity. Thirty of these enhancements were identified with known meteor streams by examining their daily variation of rates. For each stream, the radiant, the time of maximum, the duration, and the peak activity are given in units that allow direct comparison with prior results from visual observations. These results further refine models of the near-Earth dust environment and serve to characterise the properties of the current automatic meteor counting system for future use in the search for meteor outbursts. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Jenniskens, P (reprint author), NASA, Ames Res Ctr, Mail Stop 239-4, Moffett Field, CA 94035 USA. NR 66 TC 28 Z9 29 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 FEB PY 1998 VL 330 IS 2 BP 739 EP 752 PG 14 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YY349 UT WOS:000072138200045 ER PT J AU Lagrange, AM Beust, H Mouillet, D Deleuil, M Feldman, PD Ferlet, R Hobbs, L des Etangs, AL Lissauer, JJ McGrath, MA McPhate, JB Spyromilio, J Tobin, W Vidal-Madjar, A AF Lagrange, AM Beust, H Mouillet, D Deleuil, M Feldman, PD Ferlet, R Hobbs, L des Etangs, AL Lissauer, JJ McGrath, MA McPhate, JB Spyromilio, J Tobin, W Vidal-Madjar, A TI The beta Pictoris circumstellar disk XXIV. Clues to the origin of the stable gas SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE stars : individual : beta Pictoris; stars : circumstellar matter; ultraviolet : stars ID INFALLING EVAPORATING BODIES; PROTO-PLANETARY SYSTEM; HST-GHRS OBSERVATIONS; CA-II; GASEOUS COMPONENT; A-STAR; K-LINE; PARAMETERS; MODEL; ELEMENTS AB GHRS high resolution spectra of beta Pictoris were obtained to study the stable gas around this star. Several elements are detected and their abundances measured. Upper limits to the abundances of others are also measured. The data permit improved chemical analysis of the stable gas around beta Pictoris, and yield new and more accurate estimates of the radiation pressure acting on various elements. We first:analyze the data in the framework of a closed-box model. The electron density is evaluated (N-e similar or equal to 10(6) cm(-3)), which in turn implies constraints on the ionization stages of the various elements. The refractory elements in the stable gas have then standard abundances. In contrast, in this model, the lighter elements sulfur and carbon, observed in their neutral form, seem to be depleted. However several arguments, especially the strong radiation pressure, argue against a closed-box hypothesis. We therefore develop hydrodynamical simulations, taking into account the radiation pressure, to reproduce the stable features under three different hypotheses for the origin of the stable gas: stellar ejection, comet evaporation and grain evaporation. They show that a permanent production of gas is needed in order to sustain a stable absorption. In order to reproduce the observed zero velocity of the absorption features a mechanism is also needed to slow down the radial flow of matter. We show that this could be achieved by a colliding ring of neutral hydrogen farther than 0.5 AU from the star. Applied to the FeII lines, the simulations constrain the temperature (T similar or equal to 1500-2000K) and the velocity dispersion (similar or equal to 2 km s(-1)) in the gaseous medium. When applied to CaII and to other UV lines, they test the chemical composition of the parent source of gas, which is found to have standard abundances in refractory elements. The gas production rate is similar or equal to 10(-16) M. yr(-1). This description is the first consistent explanation for these long-lived stable absorptions observed for a large number of lines arising from a variety of energy levels in different chemical elements. It raises the question of the origin of the parent material, together with its composition and dynamics. This realizes a link between this gaseous component and the whole circumstellar system. C1 Univ Grenoble 1, Astrophys Lab, F-38041 Grenoble 9, France. Inst Astrophys, CNRS, F-75014 Paris, France. Univ Chicago, Yerkes Observ, Williams Bay, WI 53191 USA. CNRS, Astron Spatiale Lab, F-13376 Marseille 12, France. Johns Hopkins Univ, Dept Phys & Astron, Baltimore, MD 21218 USA. SUNY Stony Brook, Dept Earth & Space Sci, Astron Program, Stony Brook, NY 11794 USA. NASA, Ames Res Ctr, Div Space Sci, Moffett Field, CA 94035 USA. Anglo Australian Observ, Epping, NSW 2121, Australia. Univ Canterbury, Dept Phys & Astron, Christchurch 1, New Zealand. Space Telescope Sci Inst, Baltimore, MD 21218 USA. RP Lagrange, AM (reprint author), Univ Grenoble 1, Astrophys Lab, BP 53, F-38041 Grenoble 9, France. EM lagrange@obs.ujf-grenoble.fr NR 52 TC 48 Z9 48 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 FEB PY 1998 VL 330 IS 3 BP 1091 EP 1108 PG 18 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YY888 UT WOS:000072197200028 ER PT J AU Mirabel, IF Dhawan, V Chaty, S Rodriguez, LF Marti, J Robinson, CR Swank, J Geballe, TR AF Mirabel, IF Dhawan, V Chaty, S Rodriguez, LF Marti, J Robinson, CR Swank, J Geballe, TR TI Accretion instabilities and jet formation in GRS 1915+105 SO ASTRONOMY & ASTROPHYSICS LA English DT Letter DE accretion, accretion disks : stars : individual : GRS 1915+105; stars : variables; Infrared : stars; radio continuum : stars; X-rays : stars AB We report simultaneous observations in the X-ray, infrared, and radio wavelengths of the galactic superluminal source GRS 1915+105. During episodes of rapid disappearance and follow up replenishment of the inner accretion disk evidenced by the X-ray oscillating flux, we observe the ejection of relativistic plasma clouds in the form of synchrotron flares at infrared and radio wavelengths. The expelled clouds contain very energetic particles with Lorentz factors of similar to 10(3), or more. These ejections can be viewed as small-scale analogs of the more massive ejecta with relativistic bulk motions that have been previously observed in GRS 1915+105. C1 CEA Saclay, Ctr Etud Saclay, Serv Astrophys, DSM,DAPNIA,SAP, F-91191 Gif Sur Yvette, France. Inst Astron & Fis Espacio, RA-1428 Buenos Aires, DF, Argentina. Natl Radio Astron Observ, Socorro, NM 87801 USA. Univ Nacl Autonoma Mexico, Inst Astron, Morelia 58090, Michoacan, Mexico. NASA, George C Marshall Space Flight Ctr, Space Sci Lab, Huntsville, AL 35812 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Joint Astron Ctr, Hilo, HI 96720 USA. RP Mirabel, IF (reprint author), CEA Saclay, Ctr Etud Saclay, Serv Astrophys, DSM,DAPNIA,SAP, F-91191 Gif Sur Yvette, France. RI Swank, Jean/F-2693-2012 NR 14 TC 237 Z9 239 U1 0 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 FEB 1 PY 1998 VL 330 IS 1 BP L9 EP L12 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YW755 UT WOS:000071970100003 ER PT J AU Jacobson, RA AF Jacobson, RA TI The orbit of Phoebe from Earthbased and Voyager observations SO ASTRONOMY & ASTROPHYSICS SUPPLEMENT SERIES LA English DT Article DE ephemerides; planets and satellites, general; planets and satellites, individual, Phoebe AB This article presents the results of a fit of a numerically integrated orbit for the Saturnian satellite Phoebe to Earthbased astrometric observations (from 1904 to 1996) and imaging data acquired by the Voyager 2 spacecraft during its encounter with Saturn. The primary results are the epoch state vector for the integration and a set of mean orbital elements which approximately represent the orbit. An assessment of the quality of the fit and the accuracy of the orbit is also provided. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Jacobson, RA (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 68 TC 20 Z9 24 U1 0 U2 0 PU E D P SCIENCES PI LES ULIS CEDEXA PA 7, AVE DU HOGGAR, PARC D ACTIVITES COURTABOEUF, BP 112, F-91944 LES ULIS CEDEXA, FRANCE SN 0365-0138 J9 ASTRON ASTROPHYS SUP JI Astron. Astrophys. Suppl. Ser. PD FEB PY 1998 VL 128 IS 1 BP 7 EP 17 PG 11 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZA584 UT WOS:000072379200002 ER PT J AU Betlem, H ter Kuile, CR de Lignie, M van't Leven, J Jobse, K Miskotte, K Jenniskens, P AF Betlem, H ter Kuile, CR de Lignie, M van't Leven, J Jobse, K Miskotte, K Jenniskens, P TI Precision meteor orbits obtained by the Dutch Meteor Society - Photographic Meteor Survey (1981-1993) SO ASTRONOMY & ASTROPHYSICS SUPPLEMENT SERIES LA English DT Article DE meteoroids ID STREAM; PERTURBATIONS; PHAETHON; SHOWER AB 359 precisely reduced meteor orbits are presented that are the result of the Dutch Meteor Society's Photographic Meteor Survey in the period 1981 until 1993. Orbits include those of major and minor showers, doubling the number of known precise orbits of some meteor streams. From the spread in solutions of all possible sets of two photographic stations, we derive the measurement uncertainties from which we are able to calculate the intrinsic scatter in the Perseid meteor stream. The new Geminid orbits are compared to those obtained in similar surveys in the 1950's. This first measurement of the rate of change of Geminid orbits over time agrees well with model predictions. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Dutch Meteor Soc, Lederkarper 4, NL-2318 NB Leiden, Netherlands. NR 52 TC 20 Z9 20 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 FEB PY 1998 VL 128 IS 1 BP 179 EP 185 PG 7 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZA584 UT WOS:000072379200014 ER PT J AU Connaughton, V Akerlof, CW Biller, S Boyle, P Buckley, J Carter-Lewis, DA Catanese, M Cawley, MF Fegan, DJ Finley, J Gaidos, J Hillas, AM Lamb, RC Lessard, R McEnery, J Mohanty, G Porter, NA Quinn, J Rose, HJ Schubnell, MS Sembroski, G Srinivasan, R Weekes, TC Wilson, C Zweerink, J AF Connaughton, V Akerlof, CW Biller, S Boyle, P Buckley, J Carter-Lewis, DA Catanese, M Cawley, MF Fegan, DJ Finley, J Gaidos, J Hillas, AM Lamb, RC Lessard, R McEnery, J Mohanty, G Porter, NA Quinn, J Rose, HJ Schubnell, MS Sembroski, G Srinivasan, R Weekes, TC Wilson, C Zweerink, J TI A search for TeV gamma-ray bursts on a 1-second time-scale SO ASTROPARTICLE PHYSICS LA English DT Article DE TeV astronomy; gamma-ray bursts; primordial black holes ID PRIMORDIAL BLACK-HOLES; ASTRONOMY; ENERGIES AB Although atmospheric Cherenkov telescopes have restricted fields of view, their fluence sensitivity warrants a search for gamma-ray burst phenomena. A search for 400 GeV gamma-ray bursts on a 1 s time-scale using archival data taken between 1988 and 1992 with the Whipple Collaboration 10 m reflector is presented. No evidence of such bursts is found. Bursts of TeV gamma rays have been predicted from exotic astrophysical objects such as Primordial Black Holes and Cosmic Strings. An upper limit to the number density of exploding PBH of 3.0 +/- 1.0 x 10(6) pc(-3) yr(-1) is calculated. (C) 1998 Elsevier Science B.V. C1 Harvard Smithsonian Ctr Astrophys, Whipple Observ, Cambridge, MA 02138 USA. Natl Univ Ireland Univ Coll Dublin, Dublin 4, Ireland. Univ Michigan, Ann Arbor, MI 48109 USA. Univ Leeds, Leeds LS2 9JT, W Yorkshire, England. Iowa State Univ, Ames, IA 50011 USA. St Patricks Coll, Maynooth, Kildare, Ireland. Purdue Univ, W Lafayette, IN 47907 USA. RP Connaughton, V (reprint author), NASA, George C Marshall Space Flight Ctr, ES84, Huntsville, AL 35812 USA. EM vc@msfc.nasa.gov RI McEnery, Julie/D-6612-2012 NR 25 TC 18 Z9 18 U1 0 U2 0 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0927-6505 J9 ASTROPART PHYS JI Astropart Phys. PD FEB PY 1998 VL 8 IS 3 BP 179 EP 191 DI 10.1016/S0927-6505(97)00055-8 PG 13 WC Astronomy & Astrophysics; Physics, Particles & Fields SC Astronomy & Astrophysics; Physics GA YX877 UT WOS:000072088700006 ER PT J AU Shi, XD Turner, MS AF Shi, XD Turner, MS TI Expectations for the difference between local and global measurements of the Hubble constant SO ASTROPHYSICAL JOURNAL LA English DT Article DE cosmic microwave background; cosmology, observations; cosmology, theory distance scale ID DARK-MATTER; UNIVERSE; MODELS AB There are irreducible differences between the Hubble constant measured locally and the global value. They are due to density perturbations, a finite sample volume (cosmic variance), and a finite number of objects in the sample (sampling variance). We quantify these differences for a suite of COBE-normalized cold dark matter models that are consistent with the observed large-scale structure. For small samples of objects that only extend to 10,000 km s(-1), the variance can approach 4%. For the largest samples of Type Ia supernovae (SNe Ia), which include about 40 objects and extend to almost 40,000 km s(-1), the variance is 1%-2% and is dominated by sampling variance. Sampling and cosmic variance may be an important consideration in comparing local determinations of the Hubble constant with precision determinations of the global value that will be made from high-resolution maps of cosmic background radiation anisotropy. C1 Univ Calif San Diego, Dept Phys, La Jolla, CA 92093 USA. Univ Chicago, Dept Astron & Astrophys, Chicago, IL 60637 USA. Univ Chicago, Enrico Fermi Inst, Dept Phys, Chicago, IL 60637 USA. NASA, Fermilab Astrophys Ctr, Fermi Natl Accelerator Lab, Batavia, IL 60510 USA. RP Shi, XD (reprint author), Univ Calif San Diego, Dept Phys, La Jolla, CA 92093 USA. NR 17 TC 25 Z9 25 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 FEB 1 PY 1998 VL 493 IS 2 BP 519 EP 522 DI 10.1086/305169 PN 1 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YW232 UT WOS:000071911700002 ER PT J AU Salamon, MH Stecker, FW AF Salamon, MH Stecker, FW TI Absorption of high-energy gamma rays by interactions with extragalactic starlight photons at high redshifts and the high-energy gamma-ray background SO ASTROPHYSICAL JOURNAL LA English DT Article DE diffuse radiation; galaxies, active; galaxies, evolution; gamma rays, bursts; gamma rays, theory ID DAMPED LYMAN-ALPHA; GALAXIES; QUASARS; SYSTEMS; UNIVERSE; LIGHT; DUST; PHOTOIONIZATION; RADIATION; LIMIT AB In this paper, we extend previous work on the absorption of high-energy gamma-rays in intergalactic space by calculating the absorption of 10-500 GeV gamma-rays at high redshifts. This calculation requires the determination of the high-redshift evolution of the intergalactic starlight photon field, including its spectral energy distribution out to frequencies beyond the Lyman limit. To estimate this evolution, we have followed a recent analysis by Fall, Chariot, & Pei, which reproduces the redshift dependence of the star-light background emissivity obtained by the Canada-France Redshift Survey group. We give our results for the gamma-ray opacity as a function of redshift out to a redshift of z = 3. We also give predicted gamma-ray spectra for selected blazars and extend our calculations of the extragalactic gamma-ray background from blazars to an energy of 500 GeV with absorption effects included. Our results indicate that the extragalactic gamma-ray background spectrum from blazars should steepen significantly above 20 GeV, owing to extragalactic absorption. Future observations of a such a steepening would thus provide a test of the blazar origin hypothesis for the gamma-ray background radiation. We also note that our absorption calculations can be used to place limits on the redshifts of gamma-ray bursts; for example, our calculated opacities indicate that the 1994 February 17 burst observed by EGRET most probably originated at z less than or equal to similar to 2. C1 Univ Utah, Dept Phys, Salt Lake City, UT 84112 USA. NASA, High Energy Astrophys Lab, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Salamon, MH (reprint author), Univ Utah, Dept Phys, Salt Lake City, UT 84112 USA. RI Stecker, Floyd/D-3169-2012 NR 49 TC 163 Z9 163 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 FEB 1 PY 1998 VL 493 IS 2 BP 547 EP 554 DI 10.1086/305134 PN 1 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YW232 UT WOS:000071911700006 ER PT J AU Kazanas, D Titarchuk, LG Hua, XM AF Kazanas, D Titarchuk, LG Hua, XM TI The duration photon energy relation of gamma-ray bursts and its interpretations SO ASTROPHYSICAL JOURNAL LA English DT Article DE gamma rays, bursts ID COMPTONIZATION; BATSE AB Fenimore et al. have recently presented a very tight correlation between the spectral and the temporal structure in gamma-ray bursts (GRBs). In particular, they discovered that the durations of the constituent subpulses which make up the time profile of a given GRB have a well-defined power-law dependence of index similar or equal to 0.45 on the energy E of the observed photons. In this paper we present two simple models which can account in a straightforward fashion for the observed correlation. These models involve (1) the impulsive injection of a population of relativistic electrons and their subsequent cooling by synchrotron radiation, and (2) The impulsive injection of monoenergetic high-energy photons in a medium of Thompson depth tau(T) similar to 5 and their subsequent downgrading in energy due to electron scattering. We present arguments for distinguishing between these two models from the existing data. C1 NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. RP Kazanas, D (reprint author), NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. NR 14 TC 21 Z9 21 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 FEB 1 PY 1998 VL 493 IS 2 BP 708 EP 714 DI 10.1086/305131 PN 1 PG 7 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YW232 UT WOS:000071911700019 ER PT J AU Snowden, SL Egger, R Finkbeiner, DP Freyberg, MJ Plucinsky, PP AF Snowden, SL Egger, R Finkbeiner, DP Freyberg, MJ Plucinsky, PP TI Progress on establishing the spatial distribution of material responsible for the 1/4 kev soft X-ray diffuse background local and halo components SO ASTROPHYSICAL JOURNAL LA English DT Article DE diffuse radiation; Galaxy, halo; X-rays, galaxies; X-rays, ISM ID H-I STRUCTURE; INTERSTELLAR-MEDIUM; MOLECULAR CLOUD; GALACTIC HALO; ROSAT; GAS; EMISSION; SPECTRUM; SUPERBUBBLE; REGIONS AB In this paper we present a new look at the distribution of emission responsible for the soft X-ray diffuse background (SXRB) using ROSAT all-sky survey data. This is prompted by the demonstration of the existence of extensive 1/4 keV emission in the Galactic halo that was not considered in the most successful previous model, in which the bulk of the observed 1/4 keV X-rays originated in a Local Hot Bubble (LHB) that surrounds the Sun. The basic distribution can be represented by two angularly varying Galactic components (the LHB and an X-ray halo) and an isotropic extragalactic component. In addition, there are the distinct enhancements of supernova remnants, superbubbles, and clusters of galaxies. Using the negative correlation between the SXRB and DIRBE-corrected IRAS 100 mu m intensity, we find a LHB that is similar to previous models, although it is possibly more limited in extent. The emission of the LHB varies by a factor of similar to 3.3 with direction and produces ROSAT 1/4 keV intensities between similar to 250 and similar to 820 x 10(-6) counts s(-1) arcmin(-2) (typically brighter at higher Galactic latitudes), with inferred emission measures of similar to 0.0018 to 0.0058 cm(-6) pc (assuming thermal ionization equilibrium). The distribution of the emission temperature of the LHB is peaked at 10(6.07) K with a range of +/-12% at FWHM. While this variation is small and is perhaps due to systematic uncertainties in the analysis, there is a suggestion of a cooler region in the anticenter direction consistent with previous studies. We derive halo plus extragalactic intensities that vary from similar to 400 to greater than or similar to 3000 x 10(-6) counts s(-1) arcmin(-2) outside the absorbing gas of the Galactic disk. As the low end of the range is comparable to what is expected for the extragalactic background, this implies that the halo emission varies considerably over the sky, with inferred emission measures ranging from near zero to >0.02 cm(-6) pc. The distribution of emission temperatures in the halo, again derived from thermal equilibrium emission models, peaks near 10(6.02) K and varies over +/-20% at FWHM. C1 Max Planck Inst Extraterr Phys, D-85740 Garching, Germany. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Calif Berkeley, Dept Astron, Berkeley, CA 94720 USA. Harvard Smithsonian Ctr Astrophys, Cambridge, MA 02138 USA. Univ Space Res Assoc, Greenbelt, MD USA. RP Snowden, SL (reprint author), Max Planck Inst Extraterr Phys, D-85740 Garching, Germany. RI Snowden, Steven/D-5292-2012 NR 89 TC 240 Z9 241 U1 0 U2 1 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 FEB 1 PY 1998 VL 493 IS 2 BP 715 EP + DI 10.1086/305135 PN 1 PG 17 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YW232 UT WOS:000071911700020 ER PT J AU Canuto, VM Dubovikov, M AF Canuto, VM Dubovikov, M TI Stellar turbulent convection. I. Theory SO ASTROPHYSICAL JOURNAL LA English DT Article DE convection; diffusion; stars, interiors; turbulence ID REYNOLDS STRESS APPROACH; BOUNDARY-LAYER; COMPRESSIBLE CONVECTION; DYNAMICAL MODEL; DEEP ATMOSPHERE; STARS; SIMULATION; MOMENTS; GIANT; ZONE AB The description of stellar turbulent convection requires a minimum of five coupled, time-dependent, nonlocal, differential equations for the five variables: turbulent kinetic energy, turbulent potential energy, turbulent pressure, convective flux, and energy dissipation. Any fewer number of equations makes the model local. In this paper, we present the following results: 1. We derive the five coupled equations using a new turbulence model. The physical foundations and the turbulence statistics on which the model was tested are discussed. The model is able to reproduce the high Rayleigh number laboratory and direct numerical simulation data corresponding to medium-to-high values of the Peclet number (a measure of the efficiency of convection). 2. One of the major difficulties for any stellar convective model is the description of the low-efficiency, low Pe number region in which the physical timescale is no longer the turbulent timescale but the radiative one. No previous turbulence model has been able to incorporate these multiple timescales within the same framework properly. The present model does. 3. Overshooting is an unsolved problem in stellar structure. Its solution requires not only the above ingredients, but an additional one, a nonlocal model. This is because in the stably stratified region where del - del(ad) < 0, the only source of energy is diffusion, a nonlocal process. We discuss why the expressions used thus far to describe diffusion terms are inadequate. We then present a model that was successfully tested against LES data on the convective planetary boundary layer. 4. We analyze the nonlocal models of Cough and Xiong and discuss the approximations that are required to derive them from the full set of equations. 5. We discuss a model that relates the up/down drafts filling factors found by DNS/LES to the skewness of the velocity field which can be computed from the turbulence model. The results from DNS/LES and this model can thus be cross-checked. 6. We show that the stationary, local limit of the model reproduces recent local models (independently derived) which have been successfully tested against a variety of astrophysical data. 7. We discuss the fact that if the dissipation epsilon is described by a local model with a mixing length I (as done by all authors thus far), the remaining nonlocal equations exhibit divergences which preclude a physical solution to be found. OV results based on this method may be a coincidence since they are arrived at by fine tuning a coefficient. 8. The role of compressibility is discussed. C1 NASA, Goddard Inst Space Studies, New York, NY 10025 USA. RP Canuto, VM (reprint author), NASA, Goddard Inst Space Studies, 2880 Broadway, New York, NY 10025 USA. EM acvmc@nasagiss.giss.nasa.gov NR 65 TC 85 Z9 85 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 FEB 1 PY 1998 VL 493 IS 2 BP 834 EP 847 DI 10.1086/305141 PN 1 PG 14 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YW232 UT WOS:000071911700029 ER PT J AU Titarchuk, L Zannias, T AF Titarchuk, L Zannias, T TI The extended power law as an intrinsic signature for a black hole SO ASTROPHYSICAL JOURNAL LA English DT Article DE accretion, accretion disks; black hole physics; radiation mechanisms, nonthermal; stars, neutron; X-rays, general ID CONVERGING FLUID-FLOW; COMPTON-SCATTERING; ACCRETION DISKS; RADIATION; SPECTRA AB We analyze the exact general relativistic integrodifferential equation of radiative transfer describing the interaction of low-energy photons with a Maxwellian distribution of hot electrons in the gravitational field of a Schwarzschild black hole. We prove that, owing to Comptonization, an initial arbitrary spectrum of low-energy photons unavoidably results in spectra characterized by an extended power-law feature. We examine the spectral index by using both analytical and numerical methods for a variety of physical parameters as such the plasma temperature and the mass accretion rate. The presence of the event horizon as well as the behavior of the null geodesics in its vicinity largely determine the dependence of the spectral index on the flow parameters. We come to the conclusion that the bulk motion of a converging flow is more efficient in upscattering photons than thermal Comptonization, provided that the electron temperature in the flow is of order of a few kilo-electron volts or less. In this case, the spectrum observed at infinity consists of a soft component, which is produced by those input photons that escape after a few scatterings without any significant energy change, and a hard component (described by a power law), which is produced by the photons that underwent significant upscattering. The luminosity of the power-law component is relatively small compared to that of the soft component. For accretion into a black hole, the spectral energy index of the power law is always higher than 1 for plasma temperatures of order of a few kilo-electron volts. This result suggests that the bulk motion Comptonization might be responsible for the power-law spectra seen in the black hole X-ray sources. C1 NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. Univ Michoacana, Inst Fis & Matemat, Morelia 58040, Michoacan, Mexico. George Mason Univ, Inst Computat Sci & Informat, Fairfax, VA 22030 USA. RP Titarchuk, L (reprint author), NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. NR 18 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 FEB 1 PY 1998 VL 493 IS 2 BP 863 EP 872 DI 10.1086/305157 PN 1 PG 10 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YW232 UT WOS:000071911700031 ER PT J AU Cui, W Ebisawa, K Dotani, T Kubota, A AF Cui, W Ebisawa, K Dotani, T Kubota, A TI Simultaneous ASCA and RXTE observations of Cygnus X-1 during its 1996 state transition SO ASTROPHYSICAL JOURNAL LA English DT Article DE binaries, general; stars, individual (Cygnus X-1); X-rays, stars ID X-RAY AB We report results from simultaneous ASCA and RXTE observations of Cygnus X-1 when the source made a rare transition from the hard (=low) state to the soft (=high) state in 1996. These observations together cover a broad energy range similar to 0.7-50 keV with a moderate energy resolution at the iron K band and thus make it possible to disentangle various spectral components. The low-energy spectrum is dominated by an ultrasoft component, which is likely to be the emission from the hottest inner portion of the accretion disk around the black hole. At high energies, the X-ray spectrum can be described by a Comptonized spectrum with a reflection component. The Compton corona, which upscatters soft "seed photons" to produce the hard X-ray emission, is found to have a y-parameter similar to 0.28. The hard X-ray emission illuminates the accretion disk, and the reemitted photons produce the observed "reflection bump." We show that the reflecting medium subtends only a small solid angle (similar to 0.15 x 2 pi but has a large ionization parameter such that iron is ionized up to Fe XXIV-Fe XXVI. The presence of a broad iran line at 6.58 +/- 0.04 keV is also consistent with a highly ionized disk, if we take into account the gravitational and Doppler shift of the line energy. These results imply a geometry of a central corona surrounding the black hole and the reflection occurring in the innermost region of the disk where matter is highly ionized. C1 MIT, Ctr Space Res, Cambridge, MA 02139 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Space Res Assoc, Greenbelt, MD USA. Inst Space & Astronaut Sci, Kanagawa 229, Japan. Univ Tokyo, Dept Phys, Bunkyo Ku, Tokyo 113, Japan. RP Cui, W (reprint author), MIT, Ctr Space Res, Cambridge, MA 02139 USA. NR 27 TC 30 Z9 30 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 FEB 1 PY 1998 VL 493 IS 2 BP L75 EP L78 DI 10.1086/311134 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YW236 UT WOS:000071912100006 ER PT J AU Uchida, KI Sellgren, K Werner, M AF Uchida, KI Sellgren, K Werner, M TI Do the infrared emission features need ultraviolet excitation? SO ASTROPHYSICAL JOURNAL LA English DT Article DE dust, extinction; infrared, ISM, lines and bands; ISM, individual (vdB 133); ISM, molecules; reflection nebulae; stars, individual (HD 195593) ID CARBONACEOUS COMPOSITE QCC; VISUAL REFLECTION NEBULAE; 21 MICRON EMISSION; MILKY-WAY; BANDS; STARS; ISOCAM; IDENTIFICATION; SUPERGIANTS; SPECTRUM AB We present the results of imaging spectroscopy of the reflection nebula vdB 133, obtained with the infrared camera and circular variable filter wheel on the Infrared Space Observatory. Our observations reveal the infrared emission features (IEFs), at 6.2, 7.7, 8.7, 11.3, and 12.7 mu m, and associated 5-15 mu m continuum emission. The stellar system illuminating vdB 133 has the lowest ratio of ultraviolet (shortward of 0.4 mu m) to total flux of any stars demonstrated to date to excite the IEFs and associated continuum emission from adjacent inter-stellar dust, as opposed to circumstellar dust. The low fraction of UV flux from this system poses a problem for existing models for the emission mechanism and emitting material, which all require substantial UV radiation for the excitation of the IEFs and associated continuum. C1 Ohio State Univ, Dept Astron, Columbus, OH 43210 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Uchida, KI (reprint author), Ohio State Univ, Dept Astron, 174 W 18th Ave, Columbus, OH 43210 USA. NR 41 TC 60 Z9 60 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 FEB 1 PY 1998 VL 493 IS 2 BP L109 EP L112 DI 10.1086/311136 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YW236 UT WOS:000071912100015 ER PT J AU Vassiliadis, E Dopita, MA Bohlin, RC Harrington, JP Ford, HC Meatheringham, SJ Wood, PR Stecher, TP Maran, SP AF Vassiliadis, E Dopita, MA Bohlin, RC Harrington, JP Ford, HC Meatheringham, SJ Wood, PR Stecher, TP Maran, SP TI Hubble Space Telescope observations of planetary nebulae in the Magellanic Clouds. VI. Cycles 4 and 5 ultraviolet spectroscopy using the Faint Object Spectrograph SO ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES LA English DT Article DE galaxies, Magellanic Clouds; ISM, abundances; planetary nebulae, general; ultraviolet, ISM ID H-II REGIONS; CENTRAL STARS; OPTICAL SPECTROSCOPY; ANGULAR DIAMETERS; CARBON ABUNDANCE; GASEOUS NEBULAE; STELLAR WINDS; HOT STARS; EXTINCTION; SOLAR AB The Faint Object Spectrograph on board the Hubble Space Telescope (HST) is used to obtain spectra in the wavelength range lambda lambda 1150-4800 of three planetary nebulae in the Small Magellanic Cloud and 10 planetary nebulae in the Large Magellanic Cloud. This sample extends the sample of 12 objects previously observed with HST and reported in the third paper of this series. Observed and dereddened emission-line fluxes are presented. Reddening estimates from the He II lambda 1640/lambda 4686 flux ratio are generally up to 0.2 dex lower than the reddening derived from the Balmer decrement. Nebular temperatures are estimated from the N+ lambda lambda 2138, 2142/lambda lambda 6548, 6583 flux ratio. Nebular densities are calculated from the O IV] complex at lambda 1400, the N IV] lambda lambda 1483, 1487 doublet, and the Si III] lambda lambda 1883, 1892 doublet. Densities calculated using the oxygen lines are comparable to those determined from the optical lines. Densities calculated from the nitrogen lines show a scatter of over 3 dex, which is relatively large compared to the optically derived densities. Three of the five densities derived from the silicon lines are greater than 10,000 cm(-3). The C+2/O+2, Si+2/C+2, and N+2/O+2 ionic abundance ratios are calculated using the available ultraviolet emission features. The C/O and N/O ratios are anticorrelated, which supports the premise that third dredge-up has taken place during the asymptotic giant branch phase. In contrast to the third paper in this series, type I classification does not imply the presence of Si mi emission. Three objects show P Cygni-like line profiles at C IV lambda lambda 1548, 1551, indicative of stellar winds. C1 Inst Astrofis Canarias, E-38200 Tenerife, Spain. Australian Natl Univ, Mt Stromlo & Siding Spring Observ, Inst Adv Studies, Weston Creek, ACT 2611, Australia. Space Telescope Sci Inst, Baltimore, MD 21218 USA. Univ Maryland, Dept Astron, College Pk, MD 20742 USA. Johns Hopkins Univ, Dept Phys & Astron, Baltimore, MD 21218 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Vassiliadis, E (reprint author), Inst Astrofis Canarias, Via Lactea S-N, E-38200 Tenerife, Spain. RI Dopita, Michael/P-5413-2014 OI Dopita, Michael/0000-0003-0922-4986 NR 58 TC 12 Z9 12 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 FEB PY 1998 VL 114 IS 2 BP 237 EP 261 DI 10.1086/313071 PG 25 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YU750 UT WOS:000071750500003 ER PT J AU Feibelman, WA AF Feibelman, WA TI The complex IUE spectrum of the "O VI sequence" planetary nebula NGC 2867 SO ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES LA English DT Article DE planetary nebulae, individual (NGC 2867); ultraviolet, ISM; stars, mass loss ID II FLUORESCENCE LINES; FE-II; ELECTRON TEMPERATURES; ULTRAVIOLET-SPECTRA; GASEOUS NEBULAE; EMISSION-LINES; CENTRAL STARS; C-IV; EXCITATION; RATIOS AB The IUE spectrum of the planetary nebula NGC 2867 and its central star displays a rich variety of emission lines that has not been reported before. Fluxes for more than 80 UV features were determined from low- and high-dispersion spectra. Electron densities of log N-e = 3.4 +/- 0.1 cm(-3) from C III], log N-e = 3.9 +/- 0.2 cm(-3) from [Ne IV], and log N-e = 3.25 +/- 0.2 cm(-3) from O IV] diagnostics were derived. Detection of O VIII lines (I.P. = 871 eV) are thought to require a corona or strong stellar winds, yet no strong P Cygni profiles were observed. Several resonantly excited Fe II lines were identified. C1 NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, Greenbelt, MD 20771 USA. RP Feibelman, WA (reprint author), NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, Code 681, Greenbelt, MD 20771 USA. NR 23 TC 7 Z9 7 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 FEB PY 1998 VL 114 IS 2 BP 263 EP 267 DI 10.1086/313073 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YU750 UT WOS:000071750500004 ER PT J AU Mealey, JB Cohen, MM Jordan, K AF Mealey, JB Cohen, MM Jordan, K TI Effects of map orientation during learning on airport identification SO AVIATION SPACE AND ENVIRONMENTAL MEDICINE LA English DT Article ID MENTAL ROTATION; REPETITION; OBJECTS; IMAGE AB Background: If an observer first learns to recognize an object in a specific orientation, a significant increase in processing time usually occurs when the objects subsequently seen in a different orientation; this phenomenon is called the "misorientation effect." The present study examines how quickly and how accurately human observers discriminate between airport maps that are viewed in orientations other than those in which they were initially learned. Method: Participants were trained to discriminate between two navigation maps that were seen in only one orientation; they subsequently were tested with maps and aerial photographs ai the same airports that were presented in various orientations. Results and Conclusions: There were three principal findings: al discriminative responses to maps of airports were most rapid when the maps were seen in the same orientation as that in which they were initially learned; b) a significant reduction in reaction time (RT) occurred with repeated presentations of the misoriented stimuli; and c) information learned from navigation maps was not sufficient for all observers to recognize aerial photographs of the same airports. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. San Jose State Univ, San Jose, CA 95192 USA. RP Mealey, JB (reprint author), NASA, Ames Res Ctr, Mail Stop 239-11, Moffett Field, CA 94035 USA. NR 22 TC 2 Z9 2 U1 0 U2 2 PU AEROSPACE MEDICAL ASSOC PI ALEXANDRIA PA 320 S HENRY ST, ALEXANDRIA, VA 22314-3579 USA SN 0095-6562 J9 AVIAT SPACE ENVIR MD JI Aviat. Space Environ. Med. PD FEB PY 1998 VL 69 IS 2 BP 104 EP 110 PG 7 WC Public, Environmental & Occupational Health; Medicine, General & Internal; Sport Sciences SC Public, Environmental & Occupational Health; General & Internal Medicine; Sport Sciences GA YV836 UT WOS:000071868200002 PM 9491246 ER PT J AU Fortney, SM Mikhaylov, V Lee, SMC Kobzev, Y Gonzalez, RR Greenleaf, JE AF Fortney, SM Mikhaylov, V Lee, SMC Kobzev, Y Gonzalez, RR Greenleaf, JE TI Body temperature and thermoregulation during submaximal exercise after 115-day spaceflight SO AVIATION SPACE AND ENVIRONMENTAL MEDICINE LA English DT Article ID RESPONSES AB Background: Altered thermoregulation has been reported following spaceflight simulations (bed rest and water immersion) but has never been examined after actual spaceflight. Hypothesis: We tested the null hypothesis that body temperatures and heat loss responses during exercise would be similar before and after spaceflight. Methods: Two male crewmembers of the 115-d Mir 18 mission performed supine submaximal cycle exercise (20 min at 40% and 20 min at 65% of preflight (V) over dot O(2)peak) once at 145-146 d preflight and once at 5 d postflight (R + 5). Results: After flight neither crewmember could complete the exercise protocol, stopping after 28-29 min. The core temperature (Tin, ingestible telemetry pill) at test termination was similar (37.8 degrees C for both subjects) pre-and postflight despite shorter postflight test duration. The slopes or the skin blood flow (laser Doppler)/Tin relationship (subject 1: 396 vs. 214; subject 2: 704 vs. 143% change Perfusion Unit/degrees C), and the sweating rate (dew point hygrometry)/Tin relationship (subject 1: 6.3 vs. 2.0; subject 2: 4.6 vs. 0.7 mg.min(-1).cm(-2).degrees C-1), were both reduced postflight without appreciable change in the Tin thresholds for sweating or skin blood flow. Conclusion: in this preliminary report for two crew members, the sensitivity of the heat loss responses were reduced after long-duration spaceflight, resulting ina faster rate of rise in core temperature. C1 NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. Space Biomed Res Inst, Moscow, Russia. KRUG Life Sci Inc, Houston, TX USA. Gagarin Cosmonaut Training Ctr, Star City, Russia. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. USA, Environm Med Res Inst, Natick, MA 01760 USA. RP Fortney, SM (reprint author), NASA, Lyndon B Johnson Space Ctr, Mail Code SD-3, Houston, TX 77058 USA. NR 23 TC 31 Z9 35 U1 0 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 FEB PY 1998 VL 69 IS 2 BP 137 EP 141 PG 5 WC Public, Environmental & Occupational Health; Medicine, General & Internal; Sport Sciences SC Public, Environmental & Occupational Health; General & Internal Medicine; Sport Sciences GA YV836 UT WOS:000071868200008 PM 9491252 ER PT J AU Hamm, PB Billica, RD Johnson, GS Wear, ML Pool, SL AF Hamm, PB Billica, RD Johnson, GS Wear, ML Pool, SL TI Risk of cancer mortality among the longitudinal study of astronaut health (LSAH) participants SO AVIATION SPACE AND ENVIRONMENTAL MEDICINE LA English DT Article AB Background: The potential for occupational radiation exposures in the U.S. Space Program makes cancer risk a major health concern. Methods: The NASA Medical Operations Branch and KRUG Life Sciences Epidemiology Section at the Johnson Space Center (ISC) investigated the rate of cancer mortality among the astronauts and the comparison participants of the Longitudinal Study of Astronaut Health (LSAH). Medical records are maintained by the JSC Flight Medicine Clinic, JSC Occupational Medicine Clinic, and LSAH. Cause of death data from death certificates were reviewed for cancer mortality, These data were compared with cancer mortality data for the general population residing in the Texas Gulf Coast area. Results: The astronauts had a higher age specific risk of cancer mortality than the comparison group (SMR = 345; 95% Cl = 69.5-756.2), but the difference did not reach statistical significance. Both the astronauts and the comparison group had lower age-specific rates than the general population (SMR = 47, 95% CI 9.6-105.1; SMR = 17, 95% Cl = 3.5-37,9, respectively). C1 KRUG Life Sci, Epidemiol Sect, Houston, TX 77058 USA. NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. RP Hamm, PB (reprint author), KRUG Life Sci, Epidemiol Sect, 1290 Hercules Dr,Suite 120, Houston, TX 77058 USA. NR 7 TC 12 Z9 13 U1 0 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 FEB PY 1998 VL 69 IS 2 BP 142 EP 144 PG 3 WC Public, Environmental & Occupational Health; Medicine, General & Internal; Sport Sciences SC Public, Environmental & Occupational Health; General & Internal Medicine; Sport Sciences GA YV836 UT WOS:000071868200009 PM 9491253 ER PT J AU Levine, DS Greenleaf, JE AF Levine, DS Greenleaf, JE TI Immunosuppression during spaceflight deconditioning SO AVIATION SPACE AND ENVIRONMENTAL MEDICINE LA English DT Review ID IMMUNE-SYSTEM; DURATION MISSIONS; SPACE-FLIGHT; EXERCISE; STRESS; BEREAVEMENT; HYPOGRAVITY; ILLNESS; RISK; HYPERGRAVITY AB Spaceflight results in immunosuppression which is likely due mainly to neurohumoral factors released in response to intermittent stress effects during flight. However, no major non-physiological health problems have been reported during or following spaceflight, but diseases resulting from immunosuppression could occur on long-duration missions and would include bacterial, fungal, and Viral infections in addition to increased incidence of neoplasia and autoimmunity, Pharmacokinetics and pharmacodynamics appear to be altered during spaceflight and, as a consequence, alternative drug administration and dosing procedures will need to be developed. Moderate exercise training enhances immune function, but in-flight exercise may affect immunological parameters and immunity in was not yet ascertained. Hyperosmolality may enhance some immune parameters, and attenuate others especially when associated with dehydration and exercise, reducing In-flight stress may attenuate flight-induced immunosuppression, but pharmacological interventions may be essential to prevent undesirable immune responses which may occur on long-duration missions to Mars. C1 NASA, Ames Res Ctr, Div Life Sci 23911, Lab Human Environm Physiol, Moffett Field, CA 94035 USA. RP Greenleaf, JE (reprint author), NASA, Ames Res Ctr, Div Life Sci 23911, Lab Human Environm Physiol, Moffett Field, CA 94035 USA. NR 66 TC 22 Z9 23 U1 0 U2 4 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 FEB PY 1998 VL 69 IS 2 BP 172 EP 177 PG 6 WC Public, Environmental & Occupational Health; Medicine, General & Internal; Sport Sciences SC Public, Environmental & Occupational Health; General & Internal Medicine; Sport Sciences GA YV836 UT WOS:000071868200015 PM 9491259 ER PT J AU Randall, D Curry, J Battisti, D Flato, G Grumbine, R Hakkinen, S Martinson, D Preller, R Walsh, J Weatherly, J AF Randall, D Curry, J Battisti, D Flato, G Grumbine, R Hakkinen, S Martinson, D Preller, R Walsh, J Weatherly, J TI Status of and outlook for large-scale modeling of atmosphere-ice-ocean interactions in the Arctic SO BULLETIN OF THE AMERICAN METEOROLOGICAL SOCIETY LA English DT Article ID SHALLOW-WATER EQUATIONS; GLOBAL CLIMATE MODEL; GRAVITY-WAVE DRAG; SEA-ICE; THICKNESS DISTRIBUTION; GENERAL-CIRCULATION; NUMERICAL-INTEGRATION; STRATUS CLOUDS; SENSITIVITY; RADIATION AB Arctic air masses have direct impacts on the weather and climatic extremes of midlatitude areas such as central North America. Arctic physical processes pose special and very important problems for global atmospheric models used for climate simulation and numerical weather prediction. At present, the observational database is inadequate to support research aimed at overcoming these problems. Three interdependent Arctic field programs now being planned will help to remedy this situation: SHEBA, which will operate an ice camp in the Arctic for a year; ARM, which will supply instruments for use at the SHEBA ice camp and which will also conduct longer-term measurements near Barrow, Alaska; and FIRE, which will conduct one or more aircraft campaigns, in conjunction with remote-sensing investigations focused on the SHEBA ice camp. This paper provides an introductory overview of the physics of the Arctic from the perspective of large-scale modelers, outlines some of the modeling problems that arise in attempting to simulate these processes, and explains how the data to be provided by the three field programs can be used to test and improve large-scale models. C1 Colorado State Univ, Dept Atmospher Sci, Ft Collins, CO 80523 USA. Univ Colorado, Boulder, CO 80309 USA. Univ Washington, Seattle, WA 98195 USA. Canadian Ctr Climate Modelling & Anal, Victoria, BC, Canada. Natl Ctr Environm Predict, Camp Springs, MD USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Lamont Doherty Geophys Observ, Palisades, NY USA. USN, Res Lab, Stennis Space Ctr, MS 39529 USA. Univ Illinois, Urbana, IL 61801 USA. Natl Ctr Atmospher Res, Boulder, CO 80307 USA. RP Randall, D (reprint author), Colorado State Univ, Dept Atmospher Sci, Ft Collins, CO 80523 USA. RI Grumbine, Robert/B-9865-2008; Hakkinen, Sirpa/E-1461-2012; Battisti, David /A-3340-2013; Flato, Gregory/K-6711-2015; Randall, David/E-6113-2011 OI Battisti, David /0000-0003-4871-1293; Randall, David/0000-0001-6935-4112 NR 111 TC 110 Z9 115 U1 0 U2 10 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 USA SN 0003-0007 J9 B AM METEOROL SOC JI Bull. Amer. Meteorol. Soc. PD FEB PY 1998 VL 79 IS 2 BP 197 EP 219 DI 10.1175/1520-0477(1998)079<0197:SOAOFL>2.0.CO;2 PG 23 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA YZ883 UT WOS:000072303900001 ER PT J AU Fritsch, JM Houze, RA Adler, R Bluestein, H Bosart, L Brown, J Carr, F Davis, C Johnson, RH Junker, N Kuo, YH Rutledge, S Smith, J Toth, Z Wilson, JW Zipser, E Zrnic, D AF Fritsch, JM Houze, RA Adler, R Bluestein, H Bosart, L Brown, J Carr, F Davis, C Johnson, RH Junker, N Kuo, YH Rutledge, S Smith, J Toth, Z Wilson, JW Zipser, E Zrnic, D TI Quantitative precipitation forecasting: Report of the eighth prospectus development team, US Weather Research Program SO BULLETIN OF THE AMERICAN METEOROLOGICAL SOCIETY LA English DT Editorial Material ID POTENTIAL VORTICITY AB Quantitative precipitation forecasting (QPF) is the most important and significant challenge of weather forecasting. Advances in computing and observational technology combined with theoretical advances regarding the chaotic nature of the atmosphere offer the possibility of significant improvement in QPF. To achieve these improvements, this report recommends research focusing on 1) improving the accuracy and temporal and spatial resolution of the rainfall observing system; 2) performing process and climatological studies using the modernized observing system; 3) designing new data-gathering strategies for numerical model initialization; and 4) defining a probabilistic framework for precipitation forecasting and verification. Advances on the QPF problem will require development of advanced ensemble techniques that account for forecast uncertainty, stemming from sampling error and differences in model physics and numerics and development of statistical techniques for using observational data to verify probabilistic QPF in a way that is consistent with the chaotic nature of the precipitation process. C1 Univ Washington, Dept Atmospher Sci, Seattle, WA 98195 USA. Penn State Univ, Dept Meteorol, University Pk, PA 16802 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Oklahoma, Sch Meteorol, Norman, OK 73019 USA. SUNY Albany, Dept Atmospher Sci, Albany, NY 12222 USA. NOAA, ERL, Forecast Syst Lab, Boulder, CO 80303 USA. Natl Ctr Atmospher Res, Boulder, CO 80307 USA. Colorado State Univ, Dept Atmospher Sci, Ft Collins, CO 80523 USA. Natl Ctr Environm Predict, Hydrometeorol Predict Ctr, Camp Springs, MD USA. Princeton Univ, Dept Civil Engn & Operat Res, Princeton, NJ 08544 USA. Natl Ctr Environm Predict, Environm Modeling Ctr, Camp Springs, MD USA. Univ Texas, Dept Meteorol, College Stn, TX USA. Natl Severe Storms Lab, Norman, OK 73069 USA. RP Houze, RA (reprint author), Univ Washington, Dept Atmospher Sci, Box 351640, Seattle, WA 98195 USA. RI Toth, Zoltan/I-6624-2015; Brown, John/D-3361-2015 OI Toth, Zoltan/0000-0002-9635-9194; NR 15 TC 102 Z9 108 U1 0 U2 3 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 USA SN 0003-0007 J9 B AM METEOROL SOC JI Bull. Amer. Meteorol. Soc. PD FEB PY 1998 VL 79 IS 2 BP 285 EP 299 PG 15 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA YZ883 UT WOS:000072303900007 ER PT J AU Southward, RE Thompson, DS Thornton, TA Thompson, DW St Clair, AK AF Southward, RE Thompson, DS Thornton, TA Thompson, DW St Clair, AK TI Enhancement of dimensional stability in soluble fluorinated polyimides via the in situ formation of lanthanum(III)-oxo-polyimide nanocomposites SO CHEMISTRY OF MATERIALS LA English DT Review ID NYLON 6-CLAY HYBRID; SOL-GEL PROCESS; CERAMIC POLYMER COMPOSITES; TRANSPORT PROPERTIES; INORGANIC COMPOSITE; MOLECULAR-STRUCTURE; SWELLING BEHAVIOR; CELLULOSE-ACETATE; CLAY HYBRID; THIN-FILMS AB The synthesis and characterization of composite inorganic-polyimide films is described by adding diaquotris(2,4-pentanedionato)lanthanum(III) to soluble, low dielectric, colorless polyimides formed from 2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride/1,3-bis(3-aminophenoxy)benzene (6FDA/APB), and 6FDA/2,2-bis[4-(4-aminophenoxy]hexafluoropropane (6FDA/BDAF). The [La(acac)(3)(2H(2)O)(2)]-containing polyimide films were thermally treated from 220 to 340 degrees C which resulted in substantial lowering of the linear coefficients of thermal expansion at low metal concentrations (< 4 %) without sacrificing other essential thermal and mechanical properties of the parent polyimide. TEM data are consistent with particle sizes for the lanthanum ion-containing species which are in the nanometer range; thus, the visual clarity of the films was maintained. Refractive index measurements indicate that the films are isotropic. Addition of the lanthanum complex to the poly(amic acid) form of 6FDA/APB and 6FDA/BDAF followed by thermal curing to 300 degrees C yields low molecular weight crazed polyimide films. C1 NASA, Langley Res Ctr, Div Mat, Hampton, VA 23681 USA. Coll William & Mary, Dept Chem, Williamsburg, VA 23185 USA. RP Southward, RE (reprint author), NASA, Langley Res Ctr, Div Mat, Hampton, VA 23681 USA. NR 124 TC 19 Z9 20 U1 2 U2 10 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 FEB PY 1998 VL 10 IS 2 BP 486 EP 494 DI 10.1021/cm970386l PG 9 WC Chemistry, Physical; Materials Science, Multidisciplinary SC Chemistry; Materials Science GA YY440 UT WOS:000072146800008 ER PT J AU Learned-Coughlin, SM Putcha, L Ramanathan, R Venitz, J AF Learned-Coughlin, SM Putcha, L Ramanathan, R Venitz, J TI Pharmacokinetics (PK) of intravenous scopolamine (SCP) in healthy young male and female volunteers. SO CLINICAL PHARMACOLOGY & THERAPEUTICS LA English DT Meeting Abstract C1 Virginia Commonwealth Univ, PK PD Lab, Richmond, VA USA. Krug Life Sci, Dept Pharmacol, Houston, TX USA. NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. NR 0 TC 1 Z9 1 U1 0 U2 1 PU MOSBY-YEAR BOOK INC PI ST LOUIS PA 11830 WESTLINE INDUSTRIAL DR, ST LOUIS, MO 63146-3318 USA SN 0009-9236 J9 CLIN PHARMACOL THER JI Clin. Pharmacol. Ther. PD FEB PY 1998 VL 63 IS 2 MA PIII93 BP 230 EP 230 PG 1 WC Pharmacology & Pharmacy SC Pharmacology & Pharmacy GA ZA963 UT WOS:000072420300372 ER PT J AU Miller, JH Tannehill, JC Lawrence, SL Edwards, TA AF Miller, JH Tannehill, JC Lawrence, SL Edwards, TA TI Parabolized Navier-Stokes code for hypersonic flows in thermo-chemical equilibrium or nonequilibrium SO COMPUTERS & FLUIDS LA English DT Article AB A parabolized Navier-Stokes (PNS) code has been developed to efficiently compute three-dimensional flows in thermo-chemical equilibrium or nonequilibrium. The new code is an extension of NASA's three-dimensional upwind PNS (UPS) code. The chemical, vibrational, and electronic nonequilibrium effects have been incorporated via a loosely-coupled approach. The new code has been used to compute air flows in thermo-chemical equilibrium and nonequilibrium through expanding hypersonic nozzles. The results are in good agreement with existing numerical and experimental results. (C) 1998 Elsevier Science Ltd. All rights reserved. C1 Iowa State Univ, Dept Aerosp Engn & Engn Mech, Ames, IA 50011 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Miller, JH (reprint author), Iowa State Univ, Dept Aerosp Engn & Engn Mech, Ames, IA 50011 USA. NR 44 TC 2 Z9 2 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 FEB PY 1998 VL 27 IS 2 BP 199 EP 215 DI 10.1016/S0045-7930(97)00037-6 PG 17 WC Computer Science, Interdisciplinary Applications; Mechanics SC Computer Science; Mechanics GA ZG192 UT WOS:000072976400004 ER PT J AU Dressler, BO Sharpton, VL Schuraytz, BC AF Dressler, BO Sharpton, VL Schuraytz, BC TI Shock metamorphism and shock barometry at a complex impact structure: Slate Islands, Canada SO CONTRIBUTIONS TO MINERALOGY AND PETROLOGY LA English DT Article ID PLANAR DEFORMATION FEATURES; HEATED ALPHA-QUARTZ; LAKE-SUPERIOR; PRECAMBRIAN ROCKS; BETA-QUARTZ; CONSTRAINTS; QUEBEC AB The Slate Islands archipelago is believed to represent the central uplifted portion of a complex impact structure. Planar microstructures in quartz and feldspars and shock vitrification of rocks are the most common shock metamorphic features encountered. No diaplectic quartz was identified in the exposed rocks, but minor maskelynite is present. Shatter cones occur on all islands of the archipelago suggesting minimum pressures of 4 +/- 2 GPa. The relative frequency of low index planar microstructures of specific, optically determined crystallographic orientations in quartz are correlated with results from shock barometric experiments to estimate peak shock pressures experienced by the exposed target rocks. In general, there is a decrease in shock pressure recorded in the target rocks from about 20-25 GPa in east-central Patterson Island to about 5-10 GPa at the western shore of this island and on Mortimer Island. The shock attenuation gradient is similar to 4.5 GPa/km across this section of the island group. However, the shock attenuation has a roughly concentric plan only over the western part of the archipelago. There is no distinct shock center and there are other deviations from circularity. This is probably the result of: (1) the shock wave not having expanded from a point or spherical source because of the similar to 1.0 to 1.5 km size of the impactor; (2) differential movement of large target rock blocks during the central uplift and crater modification phases of the impact process. The orientation of planar deformation features in quartz appears to be independent of the shock wave direction suggesting that crystal structure exerts the primary control on microstructure development. Based on the results of XRD analyses, residual, post-impact temperatures were high enough to cause annealing of submicroscopic damage in shocked quartz. C1 Lunar & Planetary Inst, Houston, TX 77058 USA. NASA, Lyndon B Johnson Space Ctr, Planetary Sci Branch, Houston, TX 77058 USA. RP Dressler, BO (reprint author), Lunar & Planetary Inst, 3600 Bay Area Blvd, Houston, TX 77058 USA. NR 45 TC 13 Z9 14 U1 1 U2 2 PU SPRINGER VERLAG PI NEW YORK PA 175 FIFTH AVE, NEW YORK, NY 10010 USA SN 0010-7999 J9 CONTRIB MINERAL PETR JI Contrib. Mineral. Petrol. PD FEB PY 1998 VL 130 IS 3-4 BP 275 EP 287 DI 10.1007/s004100050365 PG 13 WC Geochemistry & Geophysics; Mineralogy SC Geochemistry & Geophysics; Mineralogy GA ZC630 UT WOS:000072600800006 ER PT J AU Cady, SL Wenk, HR Sintubin, M AF Cady, SL Wenk, HR Sintubin, M TI Microfibrous quartz varieties: characterization by quantitative X-ray texture analysis and transmission electron microscopy SO CONTRIBUTIONS TO MINERALOGY AND PETROLOGY LA English DT Article ID MICROCRYSTALLINE QUARTZ; VANISHED EVAPORITES; CRYSTAL-STRUCTURE; FLOOD BASALTS; CHALCEDONY; ORIGIN; SILICA; MICROSTRUCTURE; GROWTH; TESTAMENT AB Quantitative X-ray texture analysis was used to identify the fiber elongation direction of microfibrous quartz varieties in materials that contain narrow bands of closely spaced, radially divergent spherulitic fiber bundles. The statistical approach of X-ray texture analysis makes it possible to determine the fiber axis direction even when the maximum divergence angle of fibers within spherulitic fiber bundles diverge +/-20 degrees from a common growth direction. Representative samples of chalcedony [11 (2) over bar 0], quartzine [0001], and pseudochalcedony were selected for additional study with transmission electron microscopy. All varieties of microfibrous quartz were found to contain high concentrations of polysynthetic Brazil twins and domains characterized by a modulated microstructure. Trace element profiles of aluminum and iron concentration were measured by electron microprobe analysis for an agate sample that contains alternating bands of chalcedony [11 (2) over bar 0] and quartzine fibers. The elemental concentration profiles were measured in a direction parallel to the growth direction of microfibrous quartz. Although fibers within the chalcedony bands initially displayed cooperative helical twisting, the fibers became untwisted during the later stages of growth within any one band. The trace element profiles revealed that higher concentrations of aluminum are associated with quartzine and non-twisted [11 (2) over bar 0] fibers, rather than twisted chalcedony [11 (2) over bar 0] fibers. Except for the presence of iron-rich inclusions between quartzine and chalcedony bands, trace concentrations of iron were below the detection limit for the different varieties of microfibrous quartz analyzed. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Univ Calif Berkeley, Dept Geol & Geophys, Berkeley, CA 94720 USA. Catholic Univ Louvain, Lab Algemene Geol, B-3000 Louvain, Belgium. RP Cady, SL (reprint author), NASA, Ames Res Ctr, M-S N239-4, Moffett Field, CA 94035 USA. RI Sintubin, Manuel/A-7734-2012 OI Sintubin, Manuel/0000-0002-5859-8573 NR 35 TC 16 Z9 17 U1 0 U2 14 PU SPRINGER VERLAG PI NEW YORK PA 175 FIFTH AVE, NEW YORK, NY 10010 USA SN 0010-7999 J9 CONTRIB MINERAL PETR JI Contrib. Mineral. Petrol. PD FEB PY 1998 VL 130 IS 3-4 BP 320 EP 335 DI 10.1007/s004100050368 PG 16 WC Geochemistry & Geophysics; Mineralogy SC Geochemistry & Geophysics; Mineralogy GA ZC630 UT WOS:000072600800009 ER PT J AU Schwandt, CS Cygan, RT Westrich, HR AF Schwandt, CS Cygan, RT Westrich, HR TI Magnesium self-diffusion in orthoenstatite SO CONTRIBUTIONS TO MINERALOGY AND PETROLOGY LA English DT Article ID GARNET; PYROXENE; THERMOBAROMETRY; CONSTRAINTS; EVOLUTION; STRONTIUM; OLIVINE; COMPLEX; HISTORY AB Magnesium self-diffusion coefficients were determined experimentally for diffusion parallel to each of the three crystallographic directions in natural orthoenstatite (En(88)FS(12)). Experiments were conducted at 1 atm in CO-CO2 gas mixing furnaces, which provided oxygen fugacities equivalent to the iron-wustite buffer. Diffusion of Mg-25 was induced in polished samples of oriented orthoenstatite using a film of isotopically enriched (MgO)-Mg-25 as the source material. Very short (< 0.15 mu m) diffusional penetration profiles were measured by ion microprobe depth profiling. The diffusion coefficients determined for four temperatures (900, 850, 800, 750 degrees C) provide the activation energies, E-a, and frequency factors, D-o, where D = D-o exp (-E-a/RT) for Mg self-diffusion parallel to each crystallographic direction: a-axis, E-a = 360 +/- 52 kJ/mole and D-o 1.10 x 10(-4) m(2)/s; b-axis, E-a 339 +/- 77 kJ/mole and D-o = 6.93 x 10(-6) m(2)/s and c-axis, E-a = 265 +/- 66 kJ/mole and D-o 4.34 x 10(-9) m(2)/s. In this temperature range, any possible anisotropy of cation diffusion is very small, however the activation energy for diffusion parallel to the c-axis (001) is the lowest and the activation energies for diffusion parallel to the a-axis (100) and b-axis (010) are higher. Application of these diffusion results to the silicate phases of the Lowicz mesosiderite meteorite provides cooling rates for the silicate portion of the meteorite (4-11 degrees C/100 years) that are similar, although slower, to previous estimates. These silicate cooling rates are still several orders of magnitude faster than the cooling rates (0.1 degrees C/10(6) years) for the metal portions. C1 NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. Sandia Natl Labs, Dept Geochem, Albuquerque, NM 87185 USA. RP Schwandt, CS (reprint author), NASA, Lyndon B Johnson Space Ctr, SN4, Houston, TX 77058 USA. EM cschwand@ems.jsc.nasa.gov NR 42 TC 37 Z9 37 U1 0 U2 2 PU SPRINGER VERLAG PI NEW YORK PA 175 FIFTH AVE, NEW YORK, NY 10010 USA SN 0010-7999 J9 CONTRIB MINERAL PETR JI Contrib. Mineral. Petrol. PD FEB PY 1998 VL 130 IS 3-4 BP 390 EP 396 DI 10.1007/s004100050373 PG 7 WC Geochemistry & Geophysics; Mineralogy SC Geochemistry & Geophysics; Mineralogy GA ZC630 UT WOS:000072600800014 ER PT J AU Bell, LD Narayanamurti, V AF Bell, LD Narayanamurti, V TI Ballistic-electron-emission microscopy of semiconductor heterostructures SO CURRENT OPINION IN SOLID STATE & MATERIALS SCIENCE LA English DT Review ID NANOMETER-SCALE; BAND-STRUCTURE; INTERFACE; CONTACTS; SCATTERING; ZNSE; SPECTROSCOPY; RESOLUTION; TRANSPORT; AU/GAAS AB Ballistic-electron-emission microscopy has developed from its beginning as a probe of Schottky barriers into a powerful nanometer-scale method for characterizing semiconductor interfaces and hot-electron transport. Recent applications include band offsets, electron scattering, confined states, interfacial defects, and insulating layers. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ Calif Santa Barbara, Coll Engn, Santa Barbara, CA 93106 USA. RP Bell, LD (reprint author), CALTECH, Jet Prop Lab, M-S 302-231,4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 44 TC 2 Z9 2 U1 1 U2 4 PU CURRENT CHEMISTRY LTD PI LONDON PA 34-42 CLEVELAND STREET, LONDON W1P 6LE, ENGLAND SN 1359-0286 J9 CURR OPIN SOLID ST M JI Curr. Opin. Solid State Mat. Sci. PD FEB PY 1998 VL 3 IS 1 BP 38 EP 44 DI 10.1016/S1359-0286(98)80063-6 PG 7 WC Materials Science, Multidisciplinary; Physics, Applied; Physics, Condensed Matter SC Materials Science; Physics GA ZD578 UT WOS:000072700600006 ER PT J AU Grover, RF Selland, MA McCullough, RG Dahms, TE Wolfel, EE Butterfield, GE Reeves, JT Greenleaf, JE AF Grover, RF Selland, MA McCullough, RG Dahms, TE Wolfel, EE Butterfield, GE Reeves, JT Greenleaf, JE TI beta-adrenergic blockade does not prevent polycythemia or decrease in plasma volume in men at 4300 m altitude SO EUROPEAN JOURNAL OF APPLIED PHYSIOLOGY LA English DT Article DE erythropoietin; red cell volume; blood volume; propranolol; hypoxia ID OXYGEN-TRANSPORT; CHRONIC HYPOXIA; EXERCISE; ACCLIMATIZATION; PROPRANOLOL; SICKNESS; BLOOD AB When humans ascend to high altitude (ALT) their plasma volume (PV) and total blood volume (BV) decrease during the first few days. With continued residence over several weeks, the hypoxia-induced stimulation of erythropoietin increases red cell production which tends to restore BV. Because hypoxia also activates the beta-adrenergic system, which stimulates red blood cell production, we investigated the effect of adrenergic beta-receptor inhibition with propranolol on fluid volumes and the polycythemic response in 11 healthy unacclimatized men (21-33 years old exposed to an ALT of 4300 m (barometric pressure 460 Torr) for 3 weeks on Pikes Peak, Colorado. PV was determined by the Evans blue dye method (PV(EB)), BV by the carbon monoxide method (BV(CO)), red cell volume (RCV) was calculated from hematocrit (Hct) and BV(CO), and serum erythropoietin concentration ([EPO]) and reticulocyte count, were also determined. All determinations were made at sea level and after 9-11 (ALT-10) and 19-20 (ALT-20) days at ALT. At sea level and ALT, six men received propranolol (pro, 240 mg.day(-1)), and five received a placebo (pla). Effective beta-blockade did not modify the mean (SE) maximal values of [EPO] [pla: 24.9 (3.5) vs pro: 24.5 (1.5) mU.ml(-1)] or reticulocyte count [pla: 2.7 (0.7) vs pro: 2.2 (0.5)%]; nor changes in PV(EB) [pla: -15.8 (3.8) vs pro: -19.9 (2.8)%], RCV(CO) [pla: +7.0 (6.7) vs pro: +10.1 (6.1)%], or BV(CO) [pla: -7.3 (2.3) vs pro: -7.1 (3.9)%]. In the absence of weight loss, a redistribution of body water with no net loss is implied. Hence, activation of the beta-adrenergic system did not appear to affect the hypovolemic or polycythemic responses that occurred during 3 weeks at 4300 m ALT in these subjects. C1 NASA, Ames Res Ctr, Gravitat Res Branch 239 11, Moffett Field, CA 94035 USA. Univ Colorado, Hlth Sci Ctr, Cardiovasc Pulm Res Lab, Denver, CO 80262 USA. Palo Alto VA Hlth Care Syst, Aging Study Unit, Palo Alto, CA 94304 USA. St Louis Univ, Sch Med, Dept Anesthesiol, St Louis, MO 63110 USA. NASA, Ames Res Ctr, Lab Human environm Physiol, Moffett Field, CA 94035 USA. RP Greenleaf, JE (reprint author), NASA, Ames Res Ctr, Gravitat Res Branch 239 11, Moffett Field, CA 94035 USA. FU NHLBI NIH HHS [HL-14984, HL-46481] NR 27 TC 25 Z9 26 U1 2 U2 6 PU SPRINGER PI NEW YORK PA 233 SPRING ST, NEW YORK, NY 10013 USA SN 1439-6319 J9 EUR J APPL PHYSIOL JI Eur. J. Appl. Physiol. PD FEB PY 1998 VL 77 IS 3 BP 264 EP 270 DI 10.1007/s004210050331 PG 7 WC Physiology; Sport Sciences SC Physiology; Sport Sciences GA ZB075 UT WOS:000072432800011 PM 9535588 ER PT J AU Zhao, W Newman, JC Sutton, MA Shivakumar, KN Wu, XR AF Zhao, W Newman, JC Sutton, MA Shivakumar, KN Wu, XR TI Stress intensity factors for surface cracks at a hole by a three-dimensional weight function method with stresses from the finite element method SO FATIGUE & FRACTURE OF ENGINEERING MATERIALS & STRUCTURES LA English DT Article DE stress intensity factors; surface cracks; weight function method; stress concentrations AB Stress intensity factors for semielliptical surface cracks emanating from a circular hole are reported in this paper. The three-dimensional weight function method with three-dimensional finite element solutions for the uncracked stress distribution is used for the analysis. Two different loading conditions, i.e. remote tension and wedge loading are considered for a wide range of geometrical parameters. Both single and double surface cracks are studied and compared with other solutions available in the literature. Typical crack opening displacements are also provided. C1 Univ S Carolina, Columbia, SC 29208 USA. NASA, Langley Res Ctr, Hampton, VA 23681 USA. N Carolina A&T State Univ, Greensboro, NC 27410 USA. Inst Aeronaut Mat, Beijing 100095, Peoples R China. RP Zhao, W (reprint author), Univ S Carolina, Columbia, SC 29208 USA. NR 14 TC 11 Z9 11 U1 0 U2 1 PU BLACKWELL SCIENCE LTD PI OXFORD PA P O BOX 88, OSNEY MEAD, OXFORD OX2 0NE, OXON, ENGLAND SN 8756-758X J9 FATIGUE FRACT ENG M JI Fatigue Fract. Eng. Mater. Struct. PD FEB PY 1998 VL 21 IS 2 BP 229 EP 239 DI 10.1046/j.1460-2695.1998.00015.x PG 11 WC Engineering, Mechanical; Materials Science, Multidisciplinary SC Engineering; Materials Science GA YZ806 UT WOS:000072293500010 ER PT J AU Capo, RC Stewart, BW Chadwick, OA AF Capo, RC Stewart, BW Chadwick, OA TI Strontium isotopes as tracers of ecosystem processes: theory and methods SO GEODERMA LA English DT Article; Proceedings Paper CT National Meeting of the Soil-Science-Society-of-America CY 1994 CL SEATTLE, WASHINGTON SP Soil Sci Soc Amer DE strontium; isotopes; biogeochemistry; weathering; soil; eolian; atmosphere ID WEATHERING RATES; PHANEROZOIC TIME; SR ISOTOPES; RIVER-WATER; FORESTED WATERSHEDS; SR-87/SR-86 RATIOS; DUST DEPOSITION; SOUTHERN NEVADA; PACIFIC-OCEAN; SOURCE-AREA AB The strontium (Sr) isotope method can be a powerful tool in studies of chemical weathering and soil genesis, cation provenance and mobility, and the chronostratigrahic correlation of marine sediments. It is a sensitive geochemical tracer, applicable to large-scale ecosystem studies as well as to centimeter-scaled examination of cation mobility within a soil profile. The Sr-87/Sr-86 ratios of natural materials reflect the sources of strontium available during their formation. Isotopically distinct inputs from precipitation, dryfall, soil parent material, and surface or groundwater allow determination of the relative proportions of those materials entering or leaving an ecosystem. The isotopic compositions of labile (soil exchange complex and soil solution) strontium and Sr in vegetation reflect the sources of cations available to plants. Strontium isotopes can be used to track the biogeochemical cycling of nutrient cations such as calcium. The extent of cation contributions from in situ weathering and external additions to soil from dust and rain can also be resolved with this method. In this paper, we review the geochemistry and isotopic systematics of strontium, and discuss the use of this method as a tracer of earth surface processes. (C) 1998 Elsevier Science B.V. C1 Univ Pittsburgh, Dept Geol & Planetary Sci, Pittsburgh, PA 15260 USA. Univ Calif Santa Barbara, Dept Geog, Santa Barbara, CA 93106 USA. Jet Propuls Lab, Pasadena, CA 91009 USA. RP Capo, RC (reprint author), Univ Pittsburgh, Dept Geol & Planetary Sci, Pittsburgh, PA 15260 USA. NR 99 TC 296 Z9 310 U1 9 U2 107 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0016-7061 J9 GEODERMA JI Geoderma PD FEB PY 1998 VL 82 IS 1-3 BP 197 EP 225 DI 10.1016/S0016-7061(97)00102-X PG 29 WC Soil Science SC Agriculture GA ZH112 UT WOS:000073073400009 ER PT J AU Gurnett, DA Kurth, WS Roux, A Bolton, SJ Thomsen, EA Groene, JB AF Gurnett, DA Kurth, WS Roux, A Bolton, SJ Thomsen, EA Groene, JB TI Galileo plasma wave observations near Europa SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID MAGNETOSPHERE; IO AB In this paper we present results from the Galileo plasma wave instrument during the first two flybys of Europa, which occurred on December 19, 1996, and February 20, 1997. Strong whistler-mode noise was observed in the vicinity of Europa during both flybys. Emission at the upper hybrid resonance frequency, f(UH), and a propagation cutoff at the local electron plasma frequency, f(pe), provided measurements of the local electron number density. The electron density measurements show a region of highly disturbed plasma in the vicinity of Europa with density enhancements ranging from about 30 to 100 cm(-3) above the ambient Jovian magnetospheric background, which in both cases was about 80 cm(-3). C1 Univ Iowa, Dept Phys & Astron, Iowa City, IA 52242 USA. UVSQ, CETP, Velizy, France. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Gurnett, DA (reprint author), Univ Iowa, Dept Phys & Astron, Iowa City, IA 52242 USA. OI Kurth, William/0000-0002-5471-6202 NR 19 TC 24 Z9 24 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 FEB 1 PY 1998 VL 25 IS 3 BP 237 EP 240 DI 10.1029/97GL03706 PG 4 WC Geosciences, Multidisciplinary SC Geology GA YV640 UT WOS:000071848000004 ER PT J AU Mihalov, JD Gazis, PR AF Mihalov, JD Gazis, PR TI Interstellar pickup hydrogen observations at large heliocentric distances SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID SOLAR-WIND; UP IONS; HELIOSPHERIC INTERFACE; TERMINATION SHOCK; ACCELERATION; ULYSSES; OXYGEN; PLASMA; HELIUM; GAS AB Possible signatures of interstellar pickup hydrogen have been identified in data from the Pioneer 10 and 11 Ames plasma analyzers at locations out to beyond the orbit of Saturn, and at a wide range of longitudes in the heliosphere, both upstream and downstream in the interstellar wind. These signatures provide an extension of pickup ion observations out to beyond 15 AU heliocentric distance, including near where the maximum pickup hydrogen flux is expected. A depletion of interstellar pickup hydrogen downstream from the Sun in the interstellar flow may be indicated. These signatures are consistent with Ulysses pickup ion measurements. C1 NASA, Planetary Syst Branch, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Mihalov, JD (reprint author), NASA, Planetary Syst Branch, Ames Res Ctr, Mail Stop 245-3, Moffett Field, CA 94035 USA. EM jmihalov@nimrod.arc.nasa.gov; gazis@arwen.arc.nasa.gov NR 25 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 FEB 1 PY 1998 VL 25 IS 3 BP 241 EP 244 DI 10.1029/97GL03785 PG 4 WC Geosciences, Multidisciplinary SC Geology GA YV640 UT WOS:000071848000005 ER PT J AU Fitzenreiter, RJ Ogilvie, KW Chornay, DJ Keller, J AF Fitzenreiter, RJ Ogilvie, KW Chornay, DJ Keller, J TI Observations of electron velocity distribution functions in the solar wind by the WIND spacecraft: High angular resolution strahl measurements SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID HELIOS PLASMA-EXPERIMENT AB The WIND Solar Wind instrument (SWE) includes a sensor especially configured to measure the solar wind strahl. The strahl is the excess electron (greater than or equal to 100 eV) halo component of the solar wind most closely aligned with the magnetic field. Strahl electrons originate in the inner corona and move freely out to 1 A.U., providing information on the state of the corona. Electron data acquired during seven solar rotations show that the electron velocity distributions are most anisotropic and the strahl flux most intense during high speed streams. The strahl angular width is smallest when the solar wind velocity is largest, approximately 5 degrees in width at 600 eV, and becomes much wider when the velocity is low. Coincident with the strahl is a small reverse electron flux which does not form a beam but fills the field of view. This variability of the flux and angular distribution of the strahl and anti-strahl suggests that a pitch angle scattering process may be acting to broaden the strahl and that the anti-strahl may be due to backscattering of the strahl. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Fitzenreiter, RJ (reprint author), NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RI Keller, John/I-5097-2013 NR 11 TC 53 Z9 53 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 FEB 1 PY 1998 VL 25 IS 3 BP 249 EP 252 DI 10.1029/97GL03703 PG 4 WC Geosciences, Multidisciplinary SC Geology GA YV640 UT WOS:000071848000007 ER PT J AU Lu, G Pi, X Richmond, AD Roble, RG AF Lu, G Pi, X Richmond, AD Roble, RG TI Variations of total electron content during geomagnetic disturbances: A model/observation comparison SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID IONOSPHERE; HEMISPHERE; NETWORK AB This paper studies the ionospheric response to the major geomagnetic storm of October 18-19, 1995, using the NCAR TIE-GCM simulations and the global ionospheric maps (GIM) of total electron content (TEC) observations from the worldwide network of Global Positioning System (GPS) receivers. The TIE-GCM results show a good agreement with the GPS-GIM in terms of simulating storm-time TEC disturbances over the polar regions. The model indicates that the increase of electron density in the high-latitude E and lower F regions below 200 km is directly related to the magnetospheric energy input through auroral precipitation to the ionosphere, while the decrease of TEC is mainly due to the increase in O-2 and N-2 densities in the upper F region above 200 km. During the recovery phase, both the TIE-GCM and GPS-GIM reveal a distinct hemispheric asymmetry in the TEC integrated above \50 degrees\ magnetic latitude, with a 20% decrease in the southern (summer-like) hemisphere and a 30% increase in the northern (winter-like) hemisphere. C1 Natl Ctr Atmospher Res, High Altitude Observ, Boulder, CO 80301 USA. CALTECH, Jet Prop Lab, Pasadena, CA USA. RP Lu, G (reprint author), Natl Ctr Atmospher Res, High Altitude Observ, Pob 3000, Boulder, CO 80301 USA. EM ganglu@ncar.ucar.edu RI Lu, Gang/A-6669-2011; OI Richmond, Arthur/0000-0002-6708-1023 NR 12 TC 35 Z9 35 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 FEB 1 PY 1998 VL 25 IS 3 BP 253 EP 256 DI 10.1029/97GL03778 PG 4 WC Geosciences, Multidisciplinary SC Geology GA YV640 UT WOS:000071848000008 ER PT J AU Rodriguez, P Kennedy, EJ Keskinen, MJ Siefring, CL Basu, S McCarrick, M Preston, J Engebretson, M Kaiser, ML Desch, MD Goetz, K Bougeret, JL Manning, R AF Rodriguez, P Kennedy, EJ Keskinen, MJ Siefring, CL Basu, S McCarrick, M Preston, J Engebretson, M Kaiser, ML Desch, MD Goetz, K Bougeret, JL Manning, R TI The WIND-HAARP experiment: Initial results of high power radiowave interactions with space plasmas SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID AURORAL MAGNETOSPHERE; IRREGULARITIES AB Results from the first science experiment with the new HF Active Auroral Research Program (HAARP) in Alaska are reported. The objective was to study the effects of space plasmas on high power radiowave transmission to high altitudes in the magnetosphere. Reception was done by the NASA/WIND satellite. The data suggest that structured space plasmas along the propagation path impose a power law spectrum of fluctuations on the transmitted waves, resembling scintillations. Because the transmitted waves are near ionospheric plasma frequencies, other types of wave-plasma interactions may occur. Such measurements can provide a new diagnostic tool. C1 USN, Res Lab, Washington, DC 20375 USA. USAF, Res Lab, Hanscom AFB, MA 01731 USA. Adv Power Technol Inc, Washington, DC 20037 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20071 USA. Univ Minnesota, Sch Phys & Astron, Minneapolis, MN 55455 USA. Observ Paris, DESPA, F-92195 Meudon, France. RP Rodriguez, P (reprint author), USN, Res Lab, Code 5550, Washington, DC 20375 USA. NR 11 TC 22 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 FEB 1 PY 1998 VL 25 IS 3 BP 257 EP 260 DI 10.1029/98GL00037 PG 4 WC Geosciences, Multidisciplinary SC Geology GA YV640 UT WOS:000071848000009 ER PT J AU Sparling, LC Douglass, AR Schoeberl, MR AF Sparling, LC Douglass, AR Schoeberl, MR TI An estimate of the effect of unresolved structure on modeled ozone loss from aircraft observations of ClO SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID POLAR VORTEX; STRATOSPHERE; DEPLETION; LATITUDE; CHLORINE AB High resolution aircraft observations of ClO are used to estimate how much the local ozone loss rate due to the ClO dimer reaction is underestimated when small scale structure in ClO is not fully resolved. A local resolution error in the ozone loss rate, for a model with grid scale L, is defined in terms of the variance of the observations within data segments of length L. Errors in the northern and southern winter polar regions are similiar in magnitude, and are largest for gridboxes near the vortex edge. At the edge of the Arctic vortex, the resolution error increases linearly from 5-35% as the grid scale increases from 100-500 km. Errors are much smaller inside the vortex where [ClO] greater than or equal to 0.7 ppbv: increasing from 2-10% over the same range of grid scales. C1 Hughes STX, Lanham, MD 20706 USA. NASA, Atmospher Chem & Dynam Branch, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Sparling, LC (reprint author), Hughes STX, Lanham, MD 20706 USA. RI Douglass, Anne/D-4655-2012 NR 10 TC 8 Z9 8 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 FEB 1 PY 1998 VL 25 IS 3 BP 305 EP 308 DI 10.1029/97GL53696 PG 4 WC Geosciences, Multidisciplinary SC Geology GA YV640 UT WOS:000071848000021 ER PT J AU Mishchenko, MI Sassen, K AF Mishchenko, MI Sassen, K TI Depolarization of lidar returns by small ice crystals: An application to contrails SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID NONSPHERICAL PARTICLES; LIGHT-SCATTERING AB Measurements of the lidar linear depolarization ratio delta can be a powerful remote sensing technique for characterizing the microphysics of contrail particles. Since young contrails often consist of relatively small ice crystals, the quantitative interpretation of lidar measurements requires accurate theoretical computations of delta for polydisperse, randomly oriented nonspherical particles with size parameters ranging from zero to at least several tens, thus ruling out most of the currently available numerical techniques. In this paper we use the recently improved T-matrix method and compute delta for polydispersions of randomly oriented ice spheroids, circular cylinders, and Chebyshev particles with sizes typical of young contrails. We show that ice crystals with effective radii as small as several tenths of a micron can already produce delta exceeding 0.5 at visible wavelengths. This may explain the frequent occurrence of large delta values for very young contrails. We also show that observed increases of delta with the contrail's age can be explained either by a rapid increase of the particle size parameter from essentially zero to about 5 or by assuming that the contrail particles originate as perfect spheres and then acquire a certain degree of asphericity. C1 NASA, Goddard Inst Space Studies, New York, NY 10025 USA. Univ Utah, Dept Meteorol, Salt Lake City, UT 84112 USA. RP Mishchenko, MI (reprint author), NASA, Goddard Inst Space Studies, 2880 Broadway, New York, NY 10025 USA. RI Mishchenko, Michael/D-4426-2012 NR 21 TC 96 Z9 95 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 FEB 1 PY 1998 VL 25 IS 3 BP 309 EP 312 DI 10.1029/97GL03764 PG 4 WC Geosciences, Multidisciplinary SC Geology GA YV640 UT WOS:000071848000022 ER PT J AU Paylor, ED AF Paylor, ED TI Satellites and remote sensing SO GEOTIMES LA English DT Article C1 NASA, Off Earth Sci, Washington, DC 20546 USA. RP Paylor, ED (reprint author), NASA, Off Earth Sci, 300 E St SW, Washington, DC 20546 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU AMER GEOLOGICAL INST PI ALEXANDRIA PA 4220 KING ST, ALEXANDRIA, VA 22302-1507 USA SN 0016-8556 J9 GEOTIMES JI Geotimes PD FEB PY 1998 VL 43 IS 2 BP 56 EP 57 PG 2 WC Geosciences, Multidisciplinary SC Geology GA YV281 UT WOS:000071807500060 ER PT J AU Evans, RW Stapelfeldt, KR Peters, DP Trauger, JT Padgett, DL Ballester, GE Burrows, CJ Clarke, JT Crisp, D Gallagher, JS Griffiths, RE Grillmair, C Hester, JJ Hoessel, JG Holtzmann, J Krist, J McMaster, M Meadows, V Mould, JR Ostrander, E Sahai, R Scowen, PA Watson, AM Westphal, J AF Evans, RW Stapelfeldt, KR Peters, DP Trauger, JT Padgett, DL Ballester, GE Burrows, CJ Clarke, JT Crisp, D Gallagher, JS Griffiths, RE Grillmair, C Hester, JJ Hoessel, JG Holtzmann, J Krist, J McMaster, M Meadows, V Mould, JR Ostrander, E Sahai, R Scowen, PA Watson, AM Westphal, J TI Asteroid trails in Hubble Space Telescope WFPC2 images: First results SO ICARUS LA English DT Article DE asteroids; Hubble Space Telescope ID SIZE DISTRIBUTION; FAMILIES AB Careful examination of 28,460 selected Wide Field and Planetary Camera 2 (WFPC2) long exposures from 1994, 1995, and early 1996 has revealed trails of 96 distinct moving objects. They have been reported to the International Astronomical Union's (IAU) Minor Planet Center for their asteroid database and a few have been identified with known asteroids and used to update their orbits. Most of the objects are new, as they are too faint to show up on ground-based surveys. The trails often show a characteristic curvature due to the parallax induced by HST's orbital motion during the exposures. Using ephemerides for HST, the distance to each object can be directly determined from the parallax contribution to the trail shapes, Based on these distances, constraints on the orbits, and photometry of the trails (16 < V < 24), most of the moving objects appear to be small, main-belt asteroids a few km in diameter, A few are known objects-three are potential Mars crossers. Modern wide-field CCD surveys detect asteroids nearly as faint as these(V < 21), but the corresponding absolute magnitudes are uncertain unless their orbits have been established. The detected objects span the absolute magnitude range 13.6 < H < 19.3 (H is the symbol for absolute magnitude, not H-band). Statistics of the detections imply a reservoir of (3.1 +/- 0.6) x 10(5) such asteroids within 25 degrees of the ecliptic. We find that the slope of the cumulative distribution of absolute magnitudes follows a power law N proportional to H(0.2) to N proportional to: H(0.3) over this absolute magnitude range in the three distance ranges defined by the Palomar-Leiden survey. These are significantly shallower slopes than those inferred by the Palomar-Leiden survey or extrapolated from population studies of larger asteroids. (C) 1998 Academic Press. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. CALTECH, Ctr Infrared Proc & Anal, Pasadena, CA 91125 USA. Univ Michigan, Dept Atmospher Ocean & Space Sci, Ann Arbor, MI 48109 USA. Space Telescope Sci Inst, Baltimore, MD 21218 USA. Univ Wisconsin, Dept Astron, Madison, WI 53706 USA. Carnegie Mellon Univ, Dept Phys, Pittsburgh, PA 15213 USA. Arizona State Univ, Dept Phys & Astron, Tempe, AZ 85287 USA. New Mexico State Univ, Dept Astron, Las Cruces, NM 88003 USA. Australian Natl Univ, Mt Stromlo & Siding Spring Observ, Weston, ACT 2611, Australia. Univ Nacl Autonoma Mexico, Inst Astron, Morelia 58090, Michoacan, Mexico. RP Evans, RW (reprint author), CALTECH, Jet Prop Lab, Mail Stop 183-900,4800 Oak Grove Dr, Pasadena, CA 91109 USA. EM rwe@wfpc2-mail.jpl.nasa.gov RI Stapelfeldt, Karl/D-2721-2012; Clarke, John/C-8644-2013 NR 22 TC 8 Z9 8 U1 1 U2 2 PU ACADEMIC PRESS INC ELSEVIER SCIENCE PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA SN 0019-1035 J9 ICARUS JI Icarus PD FEB PY 1998 VL 131 IS 2 BP 261 EP 282 DI 10.1006/icar.1997.5873 PG 22 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZD758 UT WOS:000072720700003 ER PT J AU Na, CY Trafton, LM Barker, ES Stern, SA AF Na, CY Trafton, LM Barker, ES Stern, SA TI A search for new species in Io's extended atmosphere SO ICARUS LA English DT Article ID HUBBLE-SPACE-TELESCOPE; SO2 AB A sensitive search for potential atomic neutrals in Io's extended atmosphere and torus was made using the 2.1-m telescope at McDonald Observatory. Although no new atomic species were detected, our observation put stricter upper limits on many neutral species, thereby providing important insights into understanding Io's surface composition, its volcanic processes, and its atmosphere. The upper limits from our observations are factors of 20 to 50 lower than the upper limits established in 1975 (Trafton, 1976, Astrophys. J., 456, 384-392), These tighter upper limits for the abundance of metal species strongly constrain the oft-proposed sputtering of cosmic-abundance silicates as one of the dominant atmospheric source mechanisms, by implying the depletion of metal species relative to sodium on the surface of Io. (C) 1998 Academic Press. C1 Univ Colorado, Atmospher & Space Phys Lab, Boulder, CO 80309 USA. Univ Texas, Mcdonald Observ, Austin, TX 78712 USA. NASA Headquarters, Washington, DC 20546 USA. SW Res Inst, Boulder, CO 80302 USA. RP Na, CY (reprint author), Univ Colorado, Atmospher & Space Phys Lab, Campus Box 590, Boulder, CO 80309 USA. NR 12 TC 12 Z9 12 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 FEB PY 1998 VL 131 IS 2 BP 449 EP 453 DI 10.1006/icar.1997.5879 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZD758 UT WOS:000072720700015 ER PT J AU Simon, MK AF Simon, Marvin K. TI A New Twist on the Marcum Q-Function and Its Application SO IEEE COMMUNICATIONS LETTERS LA English DT Article AB A new form of the Marcum Q-function is presented that has both computational and analytical advantages. The new form is particularly useful in simplifying and rendering more accurate the analysis of the error probability performance of uncoded and coded partially coherent, differentially coherent, and noncoherent communication systems in the presence of fading. It also enables simple upper and lower bounds to be found analogous to the Chernoff bound on the Gaussian Q-function. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Simon, MK (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. EM marvin.k.simon@jpl.nasa.gov FU National Aeronautics and Space Administration (NASA) FX This work was supported by a contract from the National Aeronautics and Space Administration (NASA). The associate editor coordinating the review of this letter and approving it for publication was Prof. C. D. Georghiades. NR 16 TC 66 Z9 66 U1 0 U2 0 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI PISCATAWAY PA 445 HOES LANE, PISCATAWAY, NJ 08855 USA SN 1089-7798 J9 IEEE COMMUN LETT JI IEEE Commun. Lett. PD FEB PY 1998 VL 2 IS 2 BP 39 EP 41 AR PII S 1089-7798(98)01917-6 DI 10.1109/4234.660797 PG 3 WC Telecommunications SC Telecommunications GA V04VZ UT WOS:000207087200003 ER PT J AU Benedetto, S Divsalar, D Hagenauer, J AF Benedetto, S Divsalar, D Hagenauer, J TI Concatenated coding techniques and iterative decoding: Sailing toward channel capacity SO IEEE JOURNAL ON SELECTED AREAS IN COMMUNICATIONS LA English DT Editorial Material ID CONVOLUTIONAL-CODES C1 Politecn Torino, I-10129 Turin, Italy. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Tech Univ Munich, D-80290 Munich, Germany. RP Benedetto, S (reprint author), Politecn Torino, I-10129 Turin, Italy. NR 12 TC 12 Z9 14 U1 0 U2 1 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI PISCATAWAY PA 445 HOES LANE, PISCATAWAY, NJ 08855-4141 USA SN 0733-8716 J9 IEEE J SEL AREA COMM JI IEEE J. Sel. Areas Commun. PD FEB PY 1998 VL 16 IS 2 BP 137 EP 139 DI 10.1109/JSAC.1998.661101 PG 3 WC Engineering, Electrical & Electronic; Telecommunications SC Engineering; Telecommunications GA YX423 UT WOS:000072038500001 ER PT J AU Benedetto, S Divsalar, D Montorsi, G Pollara, F AF Benedetto, S Divsalar, D Montorsi, G Pollara, F TI Analysis, design, and iterative decoding of double serially concatenated codes with interleavers SO IEEE JOURNAL ON SELECTED AREAS IN COMMUNICATIONS LA English DT Article DE code design; concatenated codes; iterative decoding ID BLOCK-CODES; TRELLIS AB A double serially concatenated code with two interleavers consists of the cascade of an outer encoder, an interleaver permuting the outer codeword bits, a middle encoder, another interleaver permuting the middle codeword bits, and an inner encoder whose input words are the permuted middle codewords, The construction can be generalized to II cascaded encoders separated by h - 1 interleavers, where h > 3. We obtain upper bounds to the average maximum likelihood bit-error probability of double serially concatenated block and convolutional coding schemes, Then, we derive design guidelines for the outer, middle, and inner codes that maximize the interleaver gain and the asymptotic slope of the error probability curves, Finally, we propose a low-complexity iterative decoding algorithm, Comparisons with parallel concatenated convolutional codes, known as "turbo codes," and with the recently proposed serially concatenated convolutional codes are also presented, showing that in some cases, the new schemes offer better performance. C1 Politecn Torino, Dipartimento Elettron, I-10129 Turin, Italy. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Benedetto, S (reprint author), Politecn Torino, Dipartimento Elettron, I-10129 Turin, Italy. RI Montorsi, Guido/D-4867-2012 NR 16 TC 65 Z9 66 U1 0 U2 0 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI PISCATAWAY PA 445 HOES LANE, PISCATAWAY, NJ 08855-4141 USA SN 0733-8716 J9 IEEE J SEL AREA COMM JI IEEE J. Sel. Areas Commun. PD FEB PY 1998 VL 16 IS 2 BP 231 EP 244 DI 10.1109/49.661111 PG 14 WC Engineering, Electrical & Electronic; Telecommunications SC Engineering; Telecommunications GA YX423 UT WOS:000072038500010 ER PT J AU Subramanyam, G Van Keuls, F Miranda, FA AF Subramanyam, G Van Keuls, F Miranda, FA TI A K-band tunable microstrip bandpass filter using a thin-film conductor/ferroelectric/dielectric multilayer configuration SO IEEE MICROWAVE AND GUIDED WAVE LETTERS LA English DT Article DE ferroelectric thin films; K-band frequencies; multilayer structures; tunable bandpass filters ID COPLANAR AB We report on a gold/strontium titanate (Au/SrTiO3) thin-film K-band tunable bandpass filter on a lanthanum aluminate substrate. The two-pole filter has a center frequency of 19 GHz and a 4% bandwidth, Tunability is achieved through the nonlinear temperature dependence and the de electric field dependence of the relative dielectric constant of SrTiO3. A center frequency shift of 0.85 GHz was obtained at 400-V dc bias and 77 K without degrading the insertion loss of the filter. C1 Univ No Iowa, Cedar Falls, IA 50614 USA. NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. RP Subramanyam, G (reprint author), Univ No Iowa, Cedar Falls, IA 50614 USA. NR 10 TC 53 Z9 53 U1 2 U2 2 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 FEB PY 1998 VL 8 IS 2 BP 78 EP 80 DI 10.1109/75.658647 PG 3 WC Engineering, Electrical & Electronic SC Engineering GA YV476 UT WOS:000071828500011 ER PT J AU Yao, XS AF Yao, XS TI Phase-to-amplitude modulation conversion using Brillouin selective sideband amplification SO IEEE PHOTONICS TECHNOLOGY LETTERS LA English DT Article DE Brillouin scattering; coherent detection; heterodyne; homodyne; microwave; microwave photonics; optical amplification; sidebands; signal mixing AB We demonstrate an effective method for converting a phase modulated signal to an amplitude modulated signal by employing the powerful Brillouin selective sideband amplification technique, We further demonstrate several applications of this technique in various photonic systems, including microwave frequency multiplication, photonic microwave signal mixing with gain, microwave harmonic signal up-conversion, and coherent heterodyne signal detection. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Yao, XS (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 7 TC 25 Z9 27 U1 0 U2 5 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 1041-1135 J9 IEEE PHOTONIC TECH L JI IEEE Photonics Technol. Lett. PD FEB PY 1998 VL 10 IS 2 BP 264 EP 266 DI 10.1109/68.655379 PG 3 WC Engineering, Electrical & Electronic; Optics; Physics, Applied SC Engineering; Optics; Physics GA YU018 UT WOS:000071671600028 ER PT J AU Simon, MK Divsalar, D AF Simon, MK Divsalar, D TI Some new twists to problems involving the Gaussian probability integral SO IEEE TRANSACTIONS ON COMMUNICATIONS LA English DT Article DE communication theory ID TRELLIS AB Using an alternate form of the Gaussian probability integral discovered a number of years ago, it is shown that the solution to a number of previously considered communication problems fan be simplified and,in some casts, made more accurate (i.e., exact rather than bounded). These problems include the evaluation of: 1) bit-error probability of uncoded phase-shift keying (PSK) with Costas loop tracking; 2) word-error probability of antipodal modulation in the presence of fading; 3) bit-error probability of coded M-ary PSK (MPSK) over the memoryless fading channel with given channel-state information; 4) conditional symbol-error probability of MPSK in the presence of carrier synchronization error; and 5) average error probability for the binary additive white Gaussian noise (AWGN) intersymbol interference channel, Also obtained is a generalization of this new alternate form to the case of a two-dimensional Gaussian probability integral with arbitrary correlation which can be used to evaluate the symbol-error probability of MPSK with I-Q unbalance. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Simon, MK (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 10 TC 156 Z9 160 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 0090-6778 J9 IEEE T COMMUN JI IEEE Trans. Commun. PD FEB PY 1998 VL 46 IS 2 BP 200 EP 210 DI 10.1109/26.659479 PG 11 WC Engineering, Electrical & Electronic; Telecommunications SC Engineering; Telecommunications GA YX106 UT WOS:000072007000009 ER PT J AU Divsalar, D Simon, MK Raphaeli, D AF Divsalar, D Simon, MK Raphaeli, D TI Improved parallel interference cancellation for CDMA SO IEEE TRANSACTIONS ON COMMUNICATIONS LA English DT Article; Proceedings Paper CT IEEE Communication Theory Workshop CY APR 24-26, 1995 CL SANTA CRUZ, CA SP IEEE DE communication theory; spread spectrum communications ID MULTIPLE-ACCESS CHANNELS; MULTIUSER DETECTORS; OPTIMUM DETECTION; FADING CHANNELS; SYSTEM AB This paper introduces an improved nonlinear parallel interference cancellation scheme for code-division multiple access (CDMA) that significantly reduces the degrading effect on the desired user of interference from the other users thai share the channel, The implementation complexity of the scheme is linear in the number of users and operates on the fact that parallel processing simultaneously removes from each user a part of the interference produced by the remaining users accessing the channel the amount being proportional to their reliability. The parallel processing can be done in multiple stages, The proposed scheme uses tentative decision devices at the multiple stages to produce the most reliably estimated received data for generation and cancellation of user interference. Simulation results are given for a multitude of different situations, in particular, those cases for which the analysis is too complex. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Tel Aviv Univ, Dept Elect Engn Syst, IL-69978 Tel Aviv, Israel. RP Divsalar, D (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. EM dariush@shannon.jpl.nasa.gov; marvin.k.simon@jpl.nasa.gov; danr@eng.tau.ac.il NR 21 TC 496 Z9 520 U1 2 U2 11 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI PISCATAWAY PA 445 HOES LANE, PISCATAWAY, NJ 08855-4141 USA SN 0090-6778 J9 IEEE T COMMUN JI IEEE Trans. Commun. PD FEB PY 1998 VL 46 IS 2 BP 258 EP 268 DI 10.1109/26.659484 PG 11 WC Engineering, Electrical & Electronic; Telecommunications SC Engineering; Telecommunications GA YX106 UT WOS:000072007000014 ER PT J AU Bishop, DF Million, S Nguyen, TM Simon, MK AF Bishop, DF Million, S Nguyen, TM Simon, MK TI Power spectrum of unbalanced NRZ and biphase signals in the presence of data asymmetry SO IEEE TRANSACTIONS ON ELECTROMAGNETIC COMPATIBILITY LA English DT Article ID TELEMETRY AB The impact of data unbalance and asymmetry on the power spectral density of nonreturn-to-zero (NRZ) and biphase baseband modulations is presented. Previously reported results for this problem assumed an incorrect model for the shape and number of elementary pulse shapes that characterize an arbitrary random data stream and thus led to erroneous computations of these power spectra, The purpose of this paper is to provide the correct analytical model and then use it to obtain theoretical power spectrum results that are in full agreement with those obtained from computer simulation. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Teledes Corp, Kirkland, WA 98033 USA. Aerospace Corp, El Segundo, CA 90245 USA. RP Simon, MK (reprint author), CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. NR 10 TC 7 Z9 7 U1 0 U2 0 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 0018-9375 J9 IEEE T ELECTROMAGN C JI IEEE Trans. Electromagn. Compat. PD FEB PY 1998 VL 40 IS 1 BP 55 EP 61 DI 10.1109/15.659520 PG 7 WC Engineering, Electrical & Electronic; Telecommunications SC Engineering; Telecommunications GA YZ169 UT WOS:000072227200007 ER PT J AU Edmonds, LD AF Edmonds, LD TI The influence of spatial variations of diffusion length on charge collected by diffusion from ion tracks SO IEEE TRANSACTIONS ON NUCLEAR SCIENCE LA English DT Article DE charge collection; diffusion; diffusion length; ion track; recombination ID 3-DIMENSIONAL SIMULATION; DEVICES; UPSET AB Charge collected by diffusion from ion tracks in a semiconductor substrate may be influenced by the substrate diffusion length, which is related to recombination losses, A nonuniform spatial distribution of recombination centers results in a nonuniform diffusion length function, A theoretical analysis shows that, excluding some extreme cases, charge collection is insensitive to spatial variations in the diffusion length function, so it is possible to define an effective diffusion length having the property that,collected charge can be approximated by assuming a uniform diffusion length equal to this effective value, Extreme cases that must be excluded are those in which a large number of recombination centers are confined to a narrow region near the substrate boundary. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Edmonds, LD (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 11 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 0018-9499 J9 IEEE T NUCL SCI JI IEEE Trans. Nucl. Sci. PD FEB PY 1998 VL 45 IS 1 BP 30 EP 40 DI 10.1109/23.659552 PG 11 WC Engineering, Electrical & Electronic; Nuclear Science & Technology SC Engineering; Nuclear Science & Technology GA YY213 UT WOS:000072124600003 ER PT J AU McEwan, MJ Scott, GBI Anicich, VG AF McEwan, MJ Scott, GBI Anicich, VG TI Ion-molecule reactions relevant to Titan's ionosphere SO INTERNATIONAL JOURNAL OF MASS SPECTROMETRY LA English DT Article DE Titan; ion-molecule; ionosphere; ICR; SIFT ID ASSOCIATION REACTIONS; LOW-PRESSURE; CYCLOTRON-RESONANCE; FLOW-TUBE; PROTON AFFINITY; GAS-PHASE; ATMOSPHERE; SYSTEM; HC3N; VOYAGER-1 AB Twenty four new ion-molecule reactions are presented for inclusion in the modeling of the ionosphere of Saturn's satellite Titan. Sixteen reactions were re-examined to reduce uncertainties in the previous literature results. In this study we have examined the reactions of N+ and N-2(+) with CH4, C2H2, C2H4, C2H6, HCN, CH2CHCN and HC3N; the reaction of N+ with CH3CN; the reactions of C3H3 with CH4, C2H2, C2H4, C2H6, H-2, HCN, HC3N and CH2CHCN; the reactions of C2N2+ with C2H2; C2H2+ and C2N2; C2H4 with C2H3+, C2H4+, CHCCNH+, and HC5N+; HCNH+ with C2H6; C3H6+ with C3H6; HCN with C2H6+, C3H6+, c-C3N6+ and NO+;N-2 with C2H2+ and C2H5+; C2H4+ and HC3N. The ions selected for this study were derived either from nitrogen, appropriate hydrocarbons or nitriles. The reactant neutrals were selected on the basis of their known presence in Titan's atmosphere. The reaction products are consistent with the expected increase in ion size through ion-molecule reaction processing. Data are also presented for the reactions of 23 ions with molecular nitrogen. Almost all of these ions are unreactive with N-2. (C) 1998 Elsevier Science B.V. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ Canterbury, Dept Chem, Christchurch 1, New Zealand. RP Anicich, VG (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 62 TC 40 Z9 40 U1 0 U2 11 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 FEB PY 1998 VL 172 IS 3 BP 209 EP 219 DI 10.1016/S0168-1176(97)00236-X PG 11 WC Physics, Atomic, Molecular & Chemical; Spectroscopy SC Physics; Spectroscopy GA ZB807 UT WOS:000072510000003 ER PT J AU Wu, H Sachs, RK Yang, TC AF Wu, H Sachs, RK Yang, TC TI Radiation-induced total-deletion mutations in the human hprt gene: a biophysical model based on random walk interphase chromatin geometry SO INTERNATIONAL JOURNAL OF RADIATION BIOLOGY LA English DT Article ID RAY-INDUCED MUTATIONS; PRIMARY HUMAN FIBROBLASTS; POLYMERASE CHAIN-REACTION; HUMAN SKIN FIBROBLASTS; DOUBLE-STRAND BREAKS; IONIZING-RADIATION; MOLECULAR ANALYSIS; MAMMALIAN-CELLS; INDUCED MUTANTS; LOCUS AB Purpose: To develop a biophysical model that explains the sizes of radiation-induced hprt deletions. Methods: Key assumptions: (1) Deletions are produced by two DSB that are closer than an interaction distance at the time of DSB induction; (2) Interphase chromatin is modelled by a biphasic random walk distribution; and (3) Misrejoining of DSB from two separate tracks dominates at low-LET and misrejoining of DSB from a single track dominates at high-LET. Results: The size spectra for radiation-induced total deletions of the hprt gene are calculated. Comparing with the results of Yamada and coworkers for gamma-irradiated human fibroblasts the study finds that an interaction distance of 0.75 mu m will fit both the absolute frequency and the size spectrum of the total deletions. It is also shown that high-LET radiations produce, relatively, more total deletions of sizes below 0.5 Mb. The model predicts an essential gene to be located between 2 and 3 Mb from the hprt locus towards the centromere. Using the same assumptions and parameters as for evaluating mutation frequencies, a frequency of intra-arm chromosome deletions is calculated that is in agreement with experimental data. Conclusions: Radiation-induced total-deletion mutations of the human hprt gene and intrachange chromosome aberrations share a common mechanism for their induction. C1 NASA, Lyndon B Johnson Space Ctr, Radiat Biophys Lab, Houston, TX 77058 USA. Kelsey Seybold Clin, Houston, TX 77058 USA. Univ Calif Berkeley, Dept Math, Berkeley, CA 94720 USA. RP Yang, TC (reprint author), NASA, Lyndon B Johnson Space Ctr, Radiat Biophys Lab, Mail Code SD2, Houston, TX 77058 USA. NR 36 TC 15 Z9 17 U1 1 U2 1 PU INFORMA HEALTHCARE PI LONDON PA TELEPHONE HOUSE, 69-77 PAUL STREET, LONDON EC2A 4LQ, ENGLAND SN 0955-3002 J9 INT J RADIAT BIOL JI Int. J. Radiat. Biol. PD FEB PY 1998 VL 73 IS 2 BP 149 EP 156 PG 8 WC Biology; Nuclear Science & Technology; Radiology, Nuclear Medicine & Medical Imaging SC Life Sciences & Biomedicine - Other Topics; Nuclear Science & Technology; Radiology, Nuclear Medicine & Medical Imaging GA YW954 UT WOS:000071991400004 PM 9489561 ER PT J AU Lakshmi, V AF Lakshmi, V TI Special sensor microwave imager data in field experiments: FIFE-1987 SO INTERNATIONAL JOURNAL OF REMOTE SENSING LA English DT Article ID POLARIZATION DIFFERENCE INDEX; 37 GHZ; SURFACE-TEMPERATURE; VEGETATION INDEX; SSM/I; RAINFALL; OCEANS; SMMR; MOISTURE; MODEL AB Estimation of regional soil moisture is of importance to the hydrological modelling community for validating the accuracy of model predictions and to the climate community for use in regional and global climate models. Soil moisture estimation is done in two ways, viz., estimation using models and estimation using satellite data. Both these methods have to be corroborated using in situ field data. The present paper examines the feasibility of using observations of brightness temperature from the Special Sensor Microwave Imager (SSM/I) for small scale/catchment scale studies. The simulations of the 19 and 37 GHz brightness temperatures are carried out for a period of 13 days between 6 and 21 August 1987. The comparisons between the simulated and the observed brightness temperatures are good and the errors can be explained based on the atmospheric and surface conditions. Sensitivity analysis of the brightness temperatures to leaf area index, soil moisture and soil temperatures shows interesting characteristics. The errors in the simulated brightness temperatures can be explained by variability in the input parameters. This study shows that such an approach holds promise for local and regional studies of the land surface. C1 NASA, Goddard Space Flight Ctr, Gen Sci Corp, Atmospheres Lab, Greenbelt, MD 20771 USA. RP Lakshmi, V (reprint author), NASA, Goddard Space Flight Ctr, Gen Sci Corp, Atmospheres Lab, Code 910-4, Greenbelt, MD 20771 USA. RI Lakshmi, Venkat/I-3078-2016 OI Lakshmi, Venkat/0000-0001-7431-9004 NR 36 TC 8 Z9 9 U1 2 U2 3 PU TAYLOR & FRANCIS LTD PI LONDON PA ONE GUNPOWDER SQUARE, LONDON EC4A 3DE, ENGLAND SN 0143-1161 J9 INT J REMOTE SENS JI Int. J. Remote Sens. PD FEB PY 1998 VL 19 IS 3 BP 481 EP 505 DI 10.1080/014311698216116 PG 25 WC Remote Sensing; Imaging Science & Photographic Technology SC Remote Sensing; Imaging Science & Photographic Technology GA ZA283 UT WOS:000072348000009 ER PT J AU Seraji, H AF Seraji, H TI A unified approach to motion control of mobile manipulators SO INTERNATIONAL JOURNAL OF ROBOTICS RESEARCH LA English DT Article ID CONFIGURATION CONTROL; REDUNDANT MANIPULATORS AB This paper presents a simple on-line approach for motion control of mobile manipulators comprising a manipulator arm mounted on a mobile base. The proposed approach is equally applicable to nonholonomic mobile robots such as rover-mounted manipulators and holonomic mobile robots such as tracked robots and compound manipulators. For wheeled mobile robots, the nonholonomic base constraints are incorporated directly into the task formulation as kinematic constraints. The configuration control approach is extended to exploit the redundancy introduced by the base mobility to perform a set of user-specified additional tasks during the end-effector motion while satisfying the nonholonomic base constraints (if applicable). This approach treats the base nonholonomy and the kinematic redundancy in a unified manner to formulate new task constraints. The computational efficiency of the proposed control scheme makes it particularly suitable for real-time implementation. Two simulation studies are presented to demonstrate the applications of the motion control scheme to a rover-mounted arm (nonholonomic system) and to a tracked robot (holonomic system). C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 18 TC 117 Z9 120 U1 5 U2 20 PU SAGE PUBLICATIONS LTD PI LONDON PA 1 OLIVERS YARD, 55 CITY ROAD, LONDON EC1Y 1SP, ENGLAND SN 0278-3649 EI 1741-3176 J9 INT J ROBOT RES JI Int. J. Robot. Res. PD FEB PY 1998 VL 17 IS 2 BP 107 EP 118 DI 10.1177/027836499801700201 PG 12 WC Robotics SC Robotics GA ZQ304 UT WOS:000073844700001 ER PT J AU Bayard, DS Chiang, RY AF Bayard, DS Chiang, RY TI Identification, uncertainty characterization and robust control synthesis applied to large flexible structures control SO INTERNATIONAL JOURNAL OF ROBUST AND NONLINEAR CONTROL LA English DT Article DE system identification; robust control; plant set; flexible structures ID ALGORITHM; SYSTEMS AB This paper demonstrates an approach to frequency domain identification for the explicit purpose of designing robust H-infinity controllers. The approach transforms raw experimental data into a plant set estimate directly usable by modern robust control design software (e.g., Matlab Robust Control Toolboxes(1,2)). A key issue in control design from raw data is the question of whether the controller will work when applied to the true system. The main feature of this approach is that the resulting controller is guaranteed to work as designed (when applied to the true system) to a prescribed statistical confidence. While the overall methodology addresses key theoretical issues, it has at the same time been specifically designed to support practical implementations. A simulation example is included to demonstrate the overall approach. (C) 1998 John Wiley & Sons, Ltd. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. TRW Co Inc, Redondo Beach, CA 90278 USA. RP Bayard, DS (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 32 TC 3 Z9 4 U1 0 U2 0 PU JOHN WILEY & SONS LTD PI W SUSSEX PA BAFFINS LANE CHICHESTER, W SUSSEX PO19 1UD, ENGLAND SN 1049-8923 J9 INT J ROBUST NONLIN JI Int. J. Robust Nonlinear Control PD FEB PY 1998 VL 8 IS 2 BP 97 EP 112 DI 10.1002/(SICI)1099-1239(199802)8:2<97::AID-RNC321>3.0.CO;2-1 PG 16 WC Automation & Control Systems; Engineering, Electrical & Electronic; Mathematics, Applied SC Automation & Control Systems; Engineering; Mathematics GA YW945 UT WOS:000071990500002 ER PT J AU Zak, M Williams, CP AF Zak, M Williams, CP TI Quantum neural nets SO INTERNATIONAL JOURNAL OF THEORETICAL PHYSICS LA English DT Article AB The capacity of classical neurocomputers is limited by the number of classical degrees of freedom, which is roughly proportional to the size of the computer. By contrast, a hypothetical quantum neurocomputer can implement an exponentially larger number of the degrees of freedom within the same size. In this paper an attempt is made to reconcile the linear reversible structure of quantum evolution with nonlinear irreversible dynamics for neural nets. C1 CALTECH, Jet Prop Lab, Ultracomp Grp, Ctr Space Microelect Technol, Pasadena, CA 91109 USA. RP Zak, M (reprint author), CALTECH, Jet Prop Lab, Ultracomp Grp, Ctr Space Microelect Technol, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 8 TC 16 Z9 17 U1 1 U2 1 PU PLENUM PUBL CORP PI NEW YORK PA 233 SPRING ST, NEW YORK, NY 10013 USA SN 0020-7748 J9 INT J THEOR PHYS JI Int. J. Theor. Phys. PD FEB PY 1998 VL 37 IS 2 BP 651 EP 684 DI 10.1023/A:1026656110699 PG 34 WC Physics, Multidisciplinary SC Physics GA ZG920 UT WOS:000073053300002 ER PT J AU Yuan, D Lucas, JR Holland, DE AF Yuan, D Lucas, JR Holland, DE TI A Landsat MSS time series model and its application in geological mapping SO ISPRS JOURNAL OF PHOTOGRAMMETRY AND REMOTE SENSING LA English DT Article DE geological mapping; image time series; component separation; remote sensing; Landsat MSS ID RELATIVE RADIOMETRIC NORMALIZATION; AVHRR DATA; VEGETATION; COVER AB Although temporal factors in remotely sensed data have long been recognized by remote sensing scientists, studies on the separation of temporal and stable factors have been very limited. Applications of the time-variant characteristics of the data are also limited in the environmental monitoring and change detection fields. The merits and applications of the stable factors in the time-variant historical image data or image time series have not been fully recognized. This paper presents a time-variant model for the historical multitemporal multispectral scanner (MSS) data and a technique for processing the image time series for geological mapping. This model has been successfully applied to the surface geological mapping of a region in central eastern Nevada, USA. (C) 1998 Elsevier Science B.V. All rights reserved. C1 NASA, Commercial Remote Sensing Program, John C Stennis Space Ctr, MS USA. RP Yuan, D (reprint author), NASA, Commercial Remote Sensing Program, John C Stennis Space Ctr, MS USA. NR 26 TC 6 Z9 6 U1 0 U2 0 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0924-2716 J9 ISPRS J PHOTOGRAMM JI ISPRS-J. Photogramm. Remote Sens. PD FEB PY 1998 VL 53 IS 1 BP 39 EP 53 DI 10.1016/S0924-2716(97)00027-0 PG 15 WC Geography, Physical; Geosciences, Multidisciplinary; Remote Sensing; Imaging Science & Photographic Technology SC Physical Geography; Geology; Remote Sensing; Imaging Science & Photographic Technology GA YZ954 UT WOS:000072311900004 ER PT J AU Evans, KF Walter, SJ Heymsfield, AJ Deeter, MN AF Evans, KF Walter, SJ Heymsfield, AJ Deeter, MN TI Modeling of submillimeter passive remote sensing of cirrus clouds SO JOURNAL OF APPLIED METEOROLOGY LA English DT Article ID DISCRETE-DIPOLE APPROXIMATION; MICROWAVE RADIATIVE-TRANSFER; SHAPED ICE CRYSTALS; WATER-VAPOR; WAVE-PROPAGATION; SCATTERING; PRECIPITATION; MICROPHYSICS; SENSITIVITY; RADIOMETER AB The scattering properties of cirrus clouds at submillimeter-wave frequencies are analyzed and characterized in this paper. This study lays a theoretical foundation for using radiometric measurements to investigate and monitor cirrus properties from high-flying aircraft or satellite. The significance of this capability is that it would provide data on the global distribution of cloud ice mass that is currently required to validate climate models. At present, these needs remain unmet by existing and planned observational systems. In this study the brightness temperature depression (Delta T-b) of upwelling radiation due to cirrus clouds is simulated at 150, 220, 340, 500, 630, and 880 GHz. The effects of a range of size distributions, eight ice particle shapes, and different atmospheric profiles are modeled. The atmospheric transmission is high enough in the submillimeter windows to allow upper-tropospheric sensing from space, but absorption by water vapor reduces the sensitivity to lower cirrus clouds in a simply predictable manner. It is shown that frequencies above 500 GH2 have adequate sensitivity to measure cirrus cloud properties. For these higher frequencies, the Delta T-b is closely proportional to ice water path (IWP) for median mass equivalent sphere diameters (D-me) above 125 mu m. The differing sensitivity with frequency allows two channels to determine particle size. A two-channel Bayesian algorithm is developed to assess retrieval accuracy with a Monte Carlo error analysis procedure. Particle shape, size distribution width, and receiver noise are considered as error sources. The rms errors for a nadir view with 630/880 GHz are less than 40% for IWP > 5 g m(-2) and D-me > 100 mu m, while using an oblique viewing angle of 73 degrees results in the same accuracy down to an IWP of 1 g m(-2) (visible optical depth less than 0.1). The two-channel algorithm and error analysis methods are used to show how submillimeter radiometer and millimeter radar measurements may be combined. C1 Univ Colorado, Program Atmospher & Ocean Sci, Boulder, CO 80309 USA. CALTECH, Jet Prop Lab, Pasadena, CA USA. Natl Ctr Atmospher Res, Boulder, CO 80307 USA. RP Evans, KF (reprint author), Univ Colorado, Program Atmospher & Ocean Sci, Campus Box 311, Boulder, CO 80309 USA. RI Heymsfield, Andrew/E-7340-2011; Deeter, Merritt/O-6078-2016 OI Deeter, Merritt/0000-0002-3555-0518 NR 30 TC 74 Z9 75 U1 1 U2 3 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 USA SN 0894-8763 J9 J APPL METEOROL JI J. Appl. Meteorol. PD FEB PY 1998 VL 37 IS 2 BP 184 EP 205 DI 10.1175/1520-0450(1998)037<0184:MOSPRS>2.0.CO;2 PG 22 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA YW748 UT WOS:000071969300005 ER PT J AU Fokianos, K Kedem, B Qin, J Haferman, JL Short, DA AF Fokianos, K Kedem, B Qin, J Haferman, JL Short, DA TI On combining instruments SO JOURNAL OF APPLIED METEOROLOGY LA English DT Article ID RAINFALL; RADAR; PROFILES AB Suppose two instruments I-0 and I-1 measure the same quantity with the same resolution, where it is known that I-0 is more reliable. The second, I-1, is assumed a distortion of I-0 in some sense. A statistical method is outlined where 1) the information from both I-0 and I-1 is combined to increase the reliability of I-0 and 2) the distortion is quantified. An example is given in terms of shipborne precipitation radar and a spaceborne radiometer, both measuring rain rate. C1 Univ Maryland, Dept Math, College Pk, MD 20742 USA. NASA, Goddard Space Flight Ctr, Univ Space Res Assoc, Greenbelt, MD 20771 USA. NASA, Goddard Space Flight Ctr, Atmospheres Lab, Greenbelt, MD 20771 USA. RP Kedem, B (reprint author), Univ Maryland, Dept Math, College Pk, MD 20742 USA. OI Fokianos, Konstantinos/0000-0002-0051-711X NR 16 TC 13 Z9 13 U1 0 U2 0 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 USA SN 0894-8763 J9 J APPL METEOROL JI J. Appl. Meteorol. PD FEB PY 1998 VL 37 IS 2 BP 220 EP 226 DI 10.1175/1520-0450(1998)037<0220:OCI>2.0.CO;2 PG 7 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA YW748 UT WOS:000071969300007 ER PT J AU Melen, F Mahieu, E Zander, R Rinsland, CP Demoulin, P Roland, G Delbouille, L Servais, C AF Melen, F Mahieu, E Zander, R Rinsland, CP Demoulin, P Roland, G Delbouille, L Servais, C TI Vertical column abundances of COF2 above the Jungfraujoch Station, derived from ground-based infrared solar observations SO JOURNAL OF ATMOSPHERIC CHEMISTRY LA English DT Article DE carbonyl fluoride; IR observations; atmospheric composition ID STRATOSPHERIC TRACE GASES; CARBONYL FLUORIDE COF2; BALLOON-BORNE; SPECTRA; OZONE; SF6 AB Total vertical column abundances of carbonyl fluoride (COF2) have been derived from observations made at the International Scientific Station of the Jungfraujoch (ISSJ; altitude 3.58 km, latitude 46.5 degrees N, longitude 8.0 degrees E), Switzerland. A systematic analysis of two microwindows containing lines of the vi band was performed, based on a large set of high resolution infrared solar absorption spectra recorded with Fourier transform spectrometers, from 1985 to 1995. Examination of the whole available database indicates a significant increase of the burden of COF2 during the 1988-1995 period. The average exponential rate and the average linear rate referenced to 1992, calculated from daily mean measurements, are both equal to (4.0 +/- 0.5)% yr(-1) (one sigma error). The results are also evaluated and discussed within the context of seasonal variability and correlation between carbonyl fluoride and hydrogen fluoride (HF) columns above the ISSJ. C1 Univ Liege, Inst Astrophys, B-4000 Liege, Belgium. NASA, Langley Res Ctr, Div Atmospher Sci, Hampton, VA 23665 USA. RP Melen, F (reprint author), Univ Liege, Inst Astrophys, B-4000 Liege, Belgium. OI Mahieu, Emmanuel/0000-0002-5251-0286 NR 21 TC 8 Z9 8 U1 0 U2 2 PU KLUWER ACADEMIC PUBL PI DORDRECHT PA SPUIBOULEVARD 50, PO BOX 17, 3300 AA DORDRECHT, NETHERLANDS SN 0167-7764 J9 J ATMOS CHEM JI J. Atmos. Chem. PD FEB PY 1998 VL 29 IS 2 BP 119 EP 134 DI 10.1023/A:1005847829686 PG 16 WC Environmental Sciences; Meteorology & Atmospheric Sciences SC Environmental Sciences & Ecology; Meteorology & Atmospheric Sciences GA ZF190 UT WOS:000072872700002 ER PT J AU Chou, MD Suarez, MJ Ho, CH Yan, MMH Lee, KT AF Chou, MD Suarez, MJ Ho, CH Yan, MMH Lee, KT TI Parameterizations for cloud overlapping and shortwave single-scattering properties for use in general circulation and cloud ensemble models SO JOURNAL OF CLIMATE LA English DT Article ID RADIATIVE PROPERTIES; SOLAR-RADIATION; WATER CLOUDS; ACCURATE PARAMETERIZATION; CLIMATE MODELS; ABSORPTION; BUDGET; VAPOR; CO2 AB Parameterizations for cloud single-scattering properties and the scaling of optical thickness in a partial cloudiness condition have been developed for use in atmospheric models. Cloud optical properties are parameterized for four broad bands in the solar (or shortwave) spectrum; one in the ultraviolet and visible region and three in the infrared region. The extinction coefficient, single-scattering albedo, and asymmetry factor are parameterized separately for ice and water clouds. Based on high spectral-resolution calculations, the effective single-scattering coalbedo of a broad band is determined such that errors in the fluxes at the top of the atmosphere and at the surface are minimized. This parameterization introduces errors of a few percent in the absorption of shortwave radiation in the atmosphere and at the surface. Scaling of the optical thickness is based on the maximum-random cloud-overlapping approximation, The atmosphere is divided into three height groups separated approximately by the 400- and 700-mb levels. Clouds are assumed maximally overlapped within each height group and randomly overlapped among different groups. The scaling is applied only to the maximally overlapped cloud layers in individual height groups. The scaling as a function of the optical thickness, cloud amount, and the solar zenith angle is derived from detailed calculations and empirically adjusted to minimize errors in the fluxes at the top of the atmosphere and at the surface. Different scaling is used for direct and diffuse radiation. Except for a large solar zenith angle, the error in fluxes introduced by the scaling is only a few percent. In terms of absolute error, it is within a few watts per square meter. C1 NASA, Goddard Space Flight Ctr, Atmospheres Lab, Greenbelt, MD 20771 USA. Univ Space Res Assoc, Columbia, MD USA. Sci Syst & Appl Inc, Seabrook, MD USA. Kangnung Natl Univ, Dept Atmospher & Environm Sci, Kangnung, South Korea. RP Chou, MD (reprint author), NASA, Goddard Space Flight Ctr, Atmospheres Lab, Code 913, Greenbelt, MD 20771 USA. RI Ho, Chang-Hoi/H-8354-2015 NR 22 TC 174 Z9 183 U1 1 U2 7 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 USA SN 0894-8755 J9 J CLIMATE JI J. Clim. PD FEB PY 1998 VL 11 IS 2 BP 202 EP 214 DI 10.1175/1520-0442(1998)011<0202:PFCOAS>2.0.CO;2 PG 13 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA YY523 UT WOS:000072156100006 ER PT J AU Loeb, NG Coakley, JA AF Loeb, NG Coakley, JA TI Inference of marine stratus cloud optical depths from satellite measurements: Does 1D theory apply? SO JOURNAL OF CLIMATE LA English DT Article ID RADIATION; GEOMETRY; FIELDS; REFLECTANCE; RESOLUTION; ALBEDO; BIASES; COVER AB The validity of plane-parallel (1D) radiative transfer theory for cloudy atmospheres is examined by directly comparing calculated and observed visible reflectances for one month of Global Area Coverage Advanced Very High Resolution Radiometer satellite observations of marine stratus cloud layers off the coasts of California, Peru, and Angola. Marine stratus are an excellent testbed, as they arguably are the closest to plane-parallel found in nature. Optical depths in a 1D radiative transfer model are adjusted so that 1D model reflectances match those observed at nadir on a pixel-by-pixel basis. The 1D cloud optical depth distributions are then used in the plane-parallel model to generate reflectance distributions for different sun-earth-satellite viewing geometries. These reflectance distributions are directly compared with the observations. Separate analyses are performed for overcast and broken cloud layers as identified by the spatial coherence method. When 1D reflectances are directly compared with observations at different view angles, relative differences are generally small (less than or similar to 10%) in the backscattering direction for solar zenith angles less than or similar to 60 degrees and show no systematic view angle dependence. In contrast, 1D reflectances increase much more rapidly with view angle than the observed reflectances in the forward-scattering direction. Relative differences in the forward-scattering direction are approximate to 2-3 times larger than in the backscattering direction. At solar zenith angles less than or similar to 60 degrees, the 1D model underestimates observed reflectances at nadir by 20%-30% and overestimates reflectances at the most oblique view angles in the forward scattering direction by 15%-20%. Consequently, when inferred on a pixel-by-pixel basis, nadir-derived cloud optical depths show a systematic increase with solar zenith angle, both for overcast and broken cloud layers, and cloud optical depths decrease with view angle in the forward scattering direction. Interestingly, in the case of broken marine stratocumulus, the common practice of assuming that pixels are overcast when they are not mitigates this bias to some extent, thereby confounding its detection. But even for broken clouds, the bias remains. Because of the nonlinear dependence of cloud albedo on cloud optical depth, errors in cloud optical depth lead to large errors in cloud albedo-and therefore energy budget calculations-regardless of whether cloud layers are overcast or broken. These findings suggest that as a minimum requirement, direct application of the plane-parallel model approximation should be restricted to moderate-high sun elevations and to view angles in the backscattering direction. Based on Monte Carlo simulations, the likely reason for the discrepancies between observed radiances and radiances calculated on the basis of 1D theory is because real clouds have inhomogeneous (i.e., bumpy) tops. C1 Oregon State Univ, Coll Ocean & Atmospher Sci, Corvallis, OR 97331 USA. RP Loeb, NG (reprint author), NASA, Langley Res Ctr, Mail Stop 420, Hampton, VA 23681 USA. NR 44 TC 88 Z9 90 U1 0 U2 5 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 USA SN 0894-8755 J9 J CLIMATE JI J. Clim. PD FEB PY 1998 VL 11 IS 2 BP 215 EP 233 DI 10.1175/1520-0442(1998)011<0215:IOMSCO>2.0.CO;2 PG 19 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA YY523 UT WOS:000072156100007 ER PT J AU Su, CH Sha, YG Lehoczky, SL Liu, HC Fang, R Brebrick, RF AF Su, CH Sha, YG Lehoczky, SL Liu, HC Fang, R Brebrick, RF TI Vapor-phase stoichiometry and heat treatment of CdTe starting material for physical vapor transport SO JOURNAL OF CRYSTAL GROWTH LA English DT Article ID MOLE PERCENT CDTE; PARTIAL PRESSURES; SOLID-SOLUTIONS; THERMODYNAMIC PROPERTIES; MASS FLUX; ZN-TE; SYSTEMS AB Six batches of CdTe, having total amounts of material from 99 to 203 g and gross mole fraction of Te, X-Te, 0.499954-0.500138, were synthesized from pure Cd and Te elements. The vapor-phase stoichiometry of the as-synthesized CdTe batches was determined from the partial pressure of Te-2, P-Te2, using an optical absorption technique. The measured vapor compositions at 870 degrees C were Te-rich for all of the batches with partial pressure ratios of Cd to Te-2, P-Cd/P-Te2, ranging from 0.00742 to 1.92. After the heat treatment of baking under dynamic vacuum at 870 degrees C for 8 min, the vapor-phase compositions moved toward that of the congruent sublimation, i.e. P-Cd/P-Te2 = 2.0, with the measured P-Cd/P-Te2 varying from 1.84 to 3.47. The partial pressure measurements on one of the heat-treated samples also showed that the sample remained close to the congruent sublimation condition over the temperature range 800-880 degrees C. (C) 1998 Elsevier Science B.V. All rights reserved. C1 NASA, George C Marshall Space Flight Ctr, Space Sci Lab, Huntsville, AL 35812 USA. Marquette Univ, Mat Sci & Met Program, Milwaukee, WI 53233 USA. RP Su, CH (reprint author), NASA, George C Marshall Space Flight Ctr, Space Sci Lab, Huntsville, AL 35812 USA. EM ching.hua.su@msfc.nasa.gov NR 21 TC 9 Z9 9 U1 0 U2 0 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0022-0248 J9 J CRYST GROWTH JI J. Cryst. Growth PD FEB PY 1998 VL 183 IS 4 BP 519 EP 524 DI 10.1016/S0022-0248(98)80001-8 PG 6 WC Crystallography; Materials Science, Multidisciplinary; Physics, Applied SC Crystallography; Materials Science; Physics GA YV678 UT WOS:000071851800003 ER PT J AU Croll, A Szofran, FR Dold, P Benz, KW Lehoczky, SL AF Croll, A Szofran, FR Dold, P Benz, KW Lehoczky, SL TI Floating-zone growth of silicon in magnetic fields - II. Strong static axial fields SO JOURNAL OF CRYSTAL GROWTH LA English DT Article ID SI CRYSTAL-GROWTH; SOLIDIFICATION; CONVECTION; THERMOCAPILLARY; MICROGRAVITY; ALLOYS; MELT AB Silicon floating-zone experiments in axial magnetic fields up to 5 T have been performed and the macroscopic and microscopic segregation have been determined. Although the axial segregation is shifted towards the diffusive case with the application of higher fields, a pure diffusion-controlled regime cannot be attained even with fields of 5 T. The deterioration of the radial profiles experienced with smaller fields, due to the separation of the flow field in a quiescent center and a periphery mixed by thermocapillary (Marangoni) convection, can be reduced considerably with higher fields. A complete suppression of dopant striations caused by time-dependent thermocapillary convection is possible with fields of several Tesla. However, the use of high axial magnetic fields can sometimes lead to the appearance of a new type of pronounced dopant striations of oscillatory nature. These striations can be attributed to thermoelectromagnetic convection, caused by the interaction of thermoelectric currents with the magnetic field, and often suggest an annular flow pattern. The fact, that the direction and magnitude of thermocurrents depend on the interface shape, temperature field, and composition, explains the variety of striation patterns obtained, as well as the possibility to grow striation-free crystals. (C) 1998 Elsevier Science B.V. All rights reserved. C1 Univ Freiburg, Inst Kristallog, D-79004 Freiburg, Germany. NASA, Space Sci Lab, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. RP Croll, A (reprint author), Univ Freiburg, Inst Kristallog, Hebelstr 25, D-79004 Freiburg, Germany. RI Croell, Arne/A-2480-2013 OI Croell, Arne/0000-0002-8673-9994 NR 28 TC 57 Z9 60 U1 1 U2 10 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 FEB PY 1998 VL 183 IS 4 BP 554 EP 563 DI 10.1016/S0022-0248(97)00486-7 PG 10 WC Crystallography; Materials Science, Multidisciplinary; Physics, Applied SC Crystallography; Materials Science; Physics GA YV678 UT WOS:000071851800007 ER PT J AU Coriell, SR Chernov, AA Murray, BT McFadden, GB AF Coriell, SR Chernov, AA Murray, BT McFadden, GB TI Step bunching: generalized kinetics SO JOURNAL OF CRYSTAL GROWTH LA English DT Article DE morphological stability; step motion; anisotropic kinetics; shear flow ID MORPHOLOGICAL STABILITY; CRYSTAL-GROWTH; KDP CRYSTALS; VICINAL FACE; FLOW; SURFACES; INSTABILITY; ELECTROMIGRATION; DEPENDENCE; MACROSTEPS AB Our previous model of the effect of a parallel shear flow and anisotropic interface kinetics on the onset of (linear) instability during growth from a supersaturated solution is extended to allow for a kinetic coefficient which is a nonlinear function of the supersaturation and crystallographic orientation. The presence of impurities in the binary solution is also treated, although for typical impurity levels there is no explicit effect of impurities on morphological stability. As previously, a shear flow counter to the step motion enhances stability and a shear flow in the direction of the step motion promotes instability. Instability is enhanced when the kinetic coefficient increases rapidly with supersaturation. Specific calculations are carried out for parameters appropriate to the growth of ADP and KDP from solution. (C) 1998 Elsevier Science B.V. All rights reserved. C1 Natl Inst Stand & Technol, Gaithersburg, MD 20899 USA. Univ Space Res Assoc, Huntsville, AL 35806 USA. NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35806 USA. RP Coriell, SR (reprint author), Natl Inst Stand & Technol, Gaithersburg, MD 20899 USA. EM coriell@nist.gov RI McFadden, Geoffrey/A-7920-2008 OI McFadden, Geoffrey/0000-0001-6723-2103 NR 57 TC 41 Z9 41 U1 0 U2 15 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 FEB PY 1998 VL 183 IS 4 BP 669 EP 682 DI 10.1016/S0022-0248(97)00489-2 PG 14 WC Crystallography; Materials Science, Multidisciplinary; Physics, Applied SC Crystallography; Materials Science; Physics GA YV678 UT WOS:000071851800018 ER PT J AU Wang, AH Wu, ST Suess, ST Poletto, G AF Wang, AH Wu, ST Suess, ST Poletto, G TI Global model of the corona with heat and momentum addition SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID EULERIAN FICE SCHEME; SOLAR-WIND; WHITE-LIGHT; MASS EJECTIONS; MHD FLOWS; STREAMERS; WAVES AB We have been developing a series of global coronal models directed at a better simulation of empirical coronal hole and streamer properties. In a previous study, a volumetric heat source was used to produce a thin current sheet above streamers and high solar wind speed in the coronal hole. This improved the preexisting coronal structure for coronal mass ejection simulations even when not using a polytropic energy equation. Here we report on the addition of a momentum source to the model with volumetric heating and thermal conduction. Most theoretical acceleration models in coronal holes are driven either by thermal pressure or waves (magnetosonic, Alfven, and sonic waves). In the thermal pressure driven models an artificially high effective temperature is assumed. In the wave driven models the force is generally not big enough to accelerate the solar wind as quickly as observed. In the present model, in comparison to earlier calculations [Suess et al., 1996], we reduce the heat source and add momentum. These changes appear to further improve the numerical simulation results in comparison to empirical properties. We have high solar wind speed in the hole without using unrealistic high plasma temperature. We also demonstrates that the deposition height of the momentum addition affects the mass flux. The model still predicts a slow-speed solar wind source in the streamer and high plasma beta at the top of the streamer. C1 Univ Alabama, Ctr Space Plasma & Aeron Res, Huntsville, AL 35899 USA. Univ Alabama, Dept Mech & Aerosp Engn, Huntsville, AL 35899 USA. NASA, Space Sci Lab, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. Osserv Astrofis Arcetri, I-50125 Florence, Italy. RP Univ Alabama, Ctr Space Plasma & Aeron Res, Huntsville, AL 35899 USA. EM wanga@cspar.uah.edu; wus@cspar.uah.edu; steve.suess@msfc.nasa.gov; po-letto@arcetri.astro.it NR 36 TC 68 Z9 71 U1 0 U2 3 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-9380 EI 2169-9402 J9 J GEOPHYS RES-SPACE JI J. Geophys. Res-Space Phys. PD FEB 1 PY 1998 VL 103 IS A2 BP 1913 EP 1922 DI 10.1029/97JA01770 PG 10 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YV622 UT WOS:000071845800003 ER PT J AU Reiner, MJ Fainberg, J Kaiser, ML Stone, RG AF Reiner, MJ Fainberg, J Kaiser, ML Stone, RG TI Type III radio source located by Ulysses/Wind triangulation SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID BURST CHARACTERISTICS; INTERPLANETARY SPACE; MODEL INTERPRETATION; ELECTRONS; WAVES; DENSITY AB Radio triangulation from the widely separated Ulysses and Wind spacecraft is used to reconstruct the trajectory of a type III radio burst in the three-dimensional heliosphere. The derived radio trajectory follows a (Parker) spiral path corresponding to a solar wind speed of similar to 200 km/s and progresses to the south of the ecliptic plane. These remote radio observations also measure the interplanetary plasma density along the path of the radio source. The derived average density-distance scale is very similar to the previously derived RAE density scale, which was determined in a different way. The results of the radio triangulation combined with a drift rate analysis give an average electron exciter speed of similar to 0.3c. The radio source size and the brightness temperature as viewed from Ulysses and Wind are determined and compared as a function of observing frequency. C1 NASA, Extraterr Phys Lab, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Hughes STX, Lanham, MD USA. RP Reiner, MJ (reprint author), NASA, Extraterr Phys Lab, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. NR 22 TC 23 Z9 23 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA J9 J GEOPHYS RES-SPACE JI J. Geophys. Res-Space Phys. PD FEB 1 PY 1998 VL 103 IS A2 BP 1923 EP 1931 DI 10.1029/97JA02646 PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YV622 UT WOS:000071845800004 ER PT J AU Barnes, A AF Barnes, A TI Shape of the heliospheric termination shock: Effects of latitude variations of solar wind dynamic pressure SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID LOCAL INTERSTELLAR-MEDIUM; MOTION; FLUCTUATIONS; HELIOPAUSE; INTERFACE; REGION; MODEL AB We investigate the consequences of internal solar wind latitude variations on the heliospheric termination shock and the flow of the gas beyond the shock. We have developed a simple gasdynamic model, assuming the solar wind to be a steady, axially symmetric radial outflow of gas that passes through a termination shock and flows incompressibly beyond the shock. We ignore any latitude variations external to the heliosphere (i.e., due to the local interstellar medium) by requiring that the stagnation pressure infinitely far away must be spherically symmetric. Analysis of the model leads to three broad conclusions: (1) The shape of the heliospheric shock is qualitatively similar to what one would predict using the "naive" assumption that the heliocentric distance of the shock is proportional to the square root of the scaled solar wind dynamic pressure rho nu(2). (2) However, the existence of an internal latitude dependence of the scaled dynamic pressure requires that the shock must be oblique at some latitudes, and this obliquity produces an outward "bulge" in the shape of the termination shock; this conclusion is completely general, and in particular is true for the case of an oblate shock. (3) For a prolate termination shock the far-downstream flow is deflected toward the equator, and solar wind originating in the poleward half of (say) the northern hemisphere would fill more than half of the volume of the same hemisphere beyond the termination shock; the deflection would be in the opposite sense (poleward) for an oblate termination shock. C1 NASA, Planetary Syst Branch, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Barnes, A (reprint author), NASA, Planetary Syst Branch, Ames Res Ctr, Code 245-3, Moffett Field, CA 94035 USA. EM abarnes@mail.arc.nasa.gov NR 27 TC 11 Z9 11 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 FEB 1 PY 1998 VL 103 IS A2 BP 2015 EP 2019 DI 10.1029/97JA03030 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YV622 UT WOS:000071845800012 ER PT J AU Krasnopolsky, VA AF Krasnopolsky, VA TI Excitation of X rays in comet Hyakutake (C/1996 B2) SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID SELF-CONSISTENT MODEL; ELECTRON-IMPACT; CROSS-SECTIONS; OUTGASSING COMET; FIELDS UPSTREAM; IONIZATION; PARTICLES; HALLEY; ATOMS AB There is great disagreement between current evaluations of the role of bremsstrahlung and line excitation by electron impact and recombination in cometary X rays. To study the problem in detail, we use the exact values of the Roentgen satellite (ROSAT) high-resolution imager and wide-field camera instrument response functions and apply them to all nine exposure intervals in the ROSAT observation of comet Hyakutake to determine X ray two-parameter power law and thermal bremsstrahlung spectra. Thermal bremsstrahlung is a convenient form for two-parameter spectrum and not a physical reality in comets. Then spectral index is alpha = 1.97 +/- 0.18 approximate to 2, spectral temperature is kT = 360 eV, and the exposure-mean photon emission is 3x10(25) ph s(-1) and 1.3x10(16) ergs s(-1) in a range of 90-2000 eV and in an aperture radius of 1.2x10(5) km. The exposure-mean ROSAT spectrum is in excellent agreement with the Extreme Ultarviolet Explorer (EUVE) observation of 7.5x10(24) ph s(-1) in a range of 100-165 eV from comet Hyakutake. Then we follow the same methods as Northrop et al. [1997] to calculate a volume emission rate at the comet brightness maximum and to calculate that from bremsstrahlung with the Vega 2 electron flux. Yet we obtain a much lower emission than Northrop et al., at a level of 0.5% of the observed emission in accordance with results of Krasnopolsky [1996, 1997a] and Bingham et al. [1997]. Electron impacts of molecular, atomic, and ion species in comets produce mostly excitation of the X ray lines C 277 eV and O 525 eV at a level of 2% of the total X ray emission from comet Hyakutake. This value is calculated for the Vega 2 electron flux. The value for the Giotto electron flux is 3x10(-6) of the measured emission. Processes which are responsible for impurity radiation in fusion plasma either are inefficient or produce ultraviolet photons in cometary plasma, and the method of Bingham et al. is inapplicable to excitation of X ray lines in comets. The calculations show that the expected effects of bremsstrahlung and electron impact are very low in cometary X rays. The obtained spectral index alpha = 2 differs significantly from alpha approximate to 5 for scattering of solar X rays by attogram dust. These facts favor charge transfer of heavy solar wind ions as the dominant process of X ray excitation in comet Hyakutake. Charge transfer is not efficient in production of X rays on the Moon and other solid bodies. 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 693, Greenbelt, MD 20771 USA. RI Krasnopolsky, Vladimir/L-5085-2013 NR 31 TC 11 Z9 11 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA J9 J GEOPHYS RES-SPACE JI J. Geophys. Res-Space Phys. PD FEB 1 PY 1998 VL 103 IS A2 BP 2069 EP 2075 DI 10.1029/97JA02924 PG 7 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YV622 UT WOS:000071845800017 ER PT J AU Richardson, IG Mazur, JE Mason, GM AF Richardson, IG Mazur, JE Mason, GM TI A comparison of recurrent energetic ion enhancements observed at Ulysses and at 1 AU by IMP 8 and SAMPEX: Ulysses launch until following the first north polar passage SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID COROTATING INTERACTION REGIONS; HIGH HELIOGRAPHIC LATITUDES; SOLAR-WIND; PARTICLE EVENTS; INTERPLANETARY ACCELERATION; HEAVY-IONS; HELIOSPHERE; DEPENDENCE; NUCLEONS; MISSION AB During the Ulysses mission, the Goddard Space Flight Center instrument on IMP 8 and the University of Maryland low energy ion composition analyzer instrument on SAMPEX observed recurrent MeV/amu ion enhancements in the ecliptic plane at 1 AU. We identify those IMP 8/SAMPEX events related to the recurrent events observed at Ulysses from its launch until mid-1996, following the first passage over the north solar pole, and compare their properties. Two types of recurrent events were present at Earth. Recurrent enhancements of particles streaming sunward from CIRs in the outer heliosphere were observed most clearly at Earth after the Ulysses Jupiter encounter. Most of the CIRs/particle enhancements at Ulysses, even at high heliolatitudes, can be associated with recurrent events/high-speed streams at Earth by considering simple corotation delays. This suggests that the events at high latitudes occurred poleward of equatorward extensions of the polar coronal holes which produced corotating high-speed streams in the ecliptic. The association between events at Ulysses and Earth was less clear in 1996 when there were few major streams from polar coronal hole extensions present near the ecliptic. At the furthest distance of Ulysses from the Sun (5.4 AU), the intensity of similar to 1 MeV/amu ions in CIR-associated events was 1-2 orders of magnitude higher than at Earth. The intensity at Ulysses then declined as the spacecraft moved closer to the Sun and to high latitudes to reach < 0.1% of that at Earth near polar passage. The observations confirm that the decrease in the intensity of corotating events at high latitudes was predominantly due to the changing spacecraft latitude rather than to a temporal decline in the intensity of corotating events throughout the heliosphere. We suggest that some of the north-south asymmetries in the particle events observed by Ulysses at high latitudes may be associated with differences in the solar wind structure and energetic particle events at low latitudes observed at Ulysses and at Earth during the second half of 1991 were associated with solar activity which, over a period of several solar rotations, was largely confined to a limited range in Carrington longitude. C1 NASA, High Energy Astrophys Lab, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Maryland, Dept Astron, College Pk, MD 20742 USA. Univ Maryland, Dept Phys, College Pk, MD 20742 USA. RP Richardson, IG (reprint author), NASA, High Energy Astrophys Lab, Goddard Space Flight Ctr, Code 661, Greenbelt, MD 20771 USA. EM richardson@lheavx.gsfc.nasa.gov; joe_mazur@qmail2.aero.org; mason@sampx3.umd.edu OI Richardson, Ian/0000-0002-3855-3634 NR 56 TC 20 Z9 20 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA J9 J GEOPHYS RES-SPACE JI J. Geophys. Res-Space Phys. PD FEB 1 PY 1998 VL 103 IS A2 BP 2115 EP 2129 DI 10.1029/97JA03064 PG 15 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YV622 UT WOS:000071845800022 ER PT J AU Siegel, R AF Siegel, R TI Transient thermal effects of radiant energy in translucent materials SO JOURNAL OF HEAT TRANSFER-TRANSACTIONS OF THE ASME LA English DT Article DE heat transfer; participating media; radiation; transient ID SEMITRANSPARENT RADIATING LAYER; FLUX BOUNDARY-CONDITION; IN-DEPTH ABSORPTION; HEAT-TRANSFER; COMBINED CONDUCTION; COUPLED CONDUCTION; SCATTERING; GLASS; MEDIA; IGNITION AB When a solid or stationary fluid is translucent, energy can be transferred internally by radiation in addition to heat conduction. Since radiant propagation is very rapid, it can provide energy within a material mere quickly than diffusion by heat conduction. Radiation emitted in a hot material can also be distributed rapidly in the interior The result is that transient temperature responses including radiation can be significantly difference from those by conduction alone. This is important for evaluating the thermal performance of translucent materials that are at elevated temperatures, are in high temperature surroundings, or are subjected to large incident radiation. Detailed transient solutions are necessary to examine heat transfer for forming and tempering of glass windows, evaluating ceramic components and thermal protection coatings, studying highly backscattering heat shields for atmospheric reentry, porous ceramic insulation systems, ignition and flame spread for translucent plastics, removal of ice layers, and other scientific and engineering applications involving heating and forming of optical materials. Radiation effects have been studied less for transients than for steady state because of the additional mathematical and computational complexities, but an appreciable literature has gradually developed. This paper will review the applications, types of conditions, and geometries that have been studied. Results from the literature are used to illustrate typical radiation effects on transient temperatures, and comparisons are made of transient measurements with numerical solutions. C1 NASA, Lewis Res Ctr, Res & Technol Directorate, Cleveland, OH 44135 USA. RP Siegel, R (reprint author), NASA, Lewis Res Ctr, Res & Technol Directorate, Mail Stop 5-9,21000 Brookpk Rd, Cleveland, OH 44135 USA. EM robert.siegel@lerc.nasa.gov NR 99 TC 34 Z9 34 U1 0 U2 6 PU ASME PI NEW YORK PA TWO PARK AVE, NEW YORK, NY 10016-5990 USA SN 0022-1481 EI 1528-8943 J9 J HEAT TRANS-T ASME JI J. Heat Transf.-Trans. ASME PD FEB PY 1998 VL 120 IS 1 BP 4 EP 23 DI 10.1115/1.2830063 PG 20 WC Thermodynamics; Engineering, Mechanical SC Thermodynamics; Engineering GA ZB974 UT WOS:000072527000001 ER PT J AU DeWeese, RT Palazzolo, AB Chinta, M Kascak, A AF DeWeese, RT Palazzolo, AB Chinta, M Kascak, A TI Magnetic thrust bearing concepts: Tests and analyses SO JOURNAL OF INTELLIGENT MATERIAL SYSTEMS AND STRUCTURES LA English DT Article AB The rotor/stater configurations considered are washer-shaped laminate stack (WL), tape-wound laminate stack (TL), U-shaped laminate stack (UL), solid metal (S), and solid wedge pieces. Since preloading reduces rotor vibration, the effects of preloading a WL rotor and TL stator system on the flux density/input current transfer function magnitude and phase are determined from tests. Since eddy currents result in power loss and phase lag, tests are performed on four rotor/stater pairs, i.e., WL/TL, TL/TL, TL/UL, and SIS, to find the one with minimal eddy currents. For SIS; the test results are compared with those obtained from a two-dimensional finite element analysis, for Silicon-Iron and Hiperco-27. Since overhanging the rotor beyond the stator is a common practice, the effect of this on the fringing of magnetic flux is studied using finite element analysis. C1 Texas A&M Univ, Mech Engn Technol Program, College Stn, TX 77843 USA. Texas A&M Univ, Dept Engn Mech, College Stn, TX 77843 USA. NASA, Lewis Res Ctr, USA, Cleveland, OH 44135 USA. RP Chinta, M (reprint author), Texas A&M Univ, Mech Engn Technol Program, College Stn, TX 77843 USA. NR 13 TC 4 Z9 5 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 FEB PY 1998 VL 9 IS 2 BP 81 EP 86 PG 6 WC Materials Science, Multidisciplinary SC Materials Science GA 151CW UT WOS:000077704000001 ER PT J AU Viudez, A Haney, RL Vazquez-Cuervo, J AF Viudez, A Haney, RL Vazquez-Cuervo, J TI The deflection and division of an oceanic baroclinic jet by a coastal boundary: A case study in the Alboran Sea SO JOURNAL OF PHYSICAL OCEANOGRAPHY LA English DT Article ID SYNOPTIC HYDROGRAPHIC OBSERVATIONS; STAGNATION-POINT FLOW; ANTICYCLONIC GYRES; ROTATING FLUID; CIRCULATION; SEPARATION; VORTICITY; TURBULENCE; GIBRALTAR; EDDIES AB An oceanic baroclinic jet impinging on a coastal boundary represents a particular type of ocean-coast interaction. This specific oceanographic phenomenon is an example of the stagnation in line flows occurring in fluid dynamics with three additional features: rotation, stratification, and a sloping boundary. In this study the authors describe the density, vorticity, and deformation characteristics of an oceanic jet impinging on a sloping boundary. The case study corresponds to the impinging process of the Atlantic jet at the African coast (Alboran Sea). In the impinging region, the acceleration field is divergent related to the fact that the magnitude of the deformation is larger than the magnitude of the rotation. It is also found that the stagnation streamsurface does not lie in a vertical plane but tilts in the opposite direction to the tilt of the isopycnals. The how upstream of the stagnation point is characterized by backing, speed convergence, diffluence, and negative streamwise vorticity. The flow past the stagnation point is characterized by veering, speed divergence, confluence, and positive streamwise vorticity. The current can only be considered irrotational in a narrow part of the impinging region. C1 Naval Postgrad Sch, Dept Meteorol, Monterey, CA USA. CALTECH, Jet Prop Lab, Pasadena, CA USA. RP Viudez, A (reprint author), Univ Illes Balears, Dept Fis, E-07071 Palma de Mallorca, Spain. EM DFSAVL4@PS.UIB.ES RI Viudez, Alvaro/A-8201-2008 OI Viudez, Alvaro/0000-0001-7862-9835 NR 81 TC 7 Z9 7 U1 0 U2 0 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 USA SN 0022-3670 J9 J PHYS OCEANOGR JI J. Phys. Oceanogr. PD FEB PY 1998 VL 28 IS 2 BP 289 EP 308 DI 10.1175/1520-0485(1998)028<0289:TDADOA>2.0.CO;2 PG 20 WC Oceanography SC Oceanography GA YY524 UT WOS:000072156200008 ER PT J AU Rothstein, LM Zhang, RH Busalacchi, AJ Chen, D AF Rothstein, LM Zhang, RH Busalacchi, AJ Chen, D TI A numerical simulation of the mean water pathways in the subtropical and tropical Pacific Ocean SO JOURNAL OF PHYSICAL OCEANOGRAPHY LA English DT Article ID TAHITI SHUTTLE EXPERIMENT; UPPER EQUATORIAL PACIFIC; VENTILATED THERMOCLINE; MIXED-LAYER; POTENTIAL VORTICITY; WIND STRESS; MODEL; CIRCULATION; TEMPERATURE; TRITIUM AB A reduced-gravity, primitive-equation, upper-ocean general circulation model is used to study the mean water pathways in the North Pacific subtropical and tropical ocean. The model features an explicit physical representation of the surface mixed layer, realistic basin geometry, observed wind and heat flux forcing, and a horizontal grid-stretching technique and a vertical sigma coordinate to obtain a realistic simulation of the subtropical/tropical circulation. Velocity fields, and isopycnal and trajectory analyses are used to understand the mean flow of mixed layer and thermocline waters between the subtropics and Tropics. Subtropical/tropical water pathways are not simply direct meridional routes; the existence of vigorous zonal current systems obviously complicates the picture. In the surface mixed layer, upwelled equatorial waters flow into the subtropical gyre mainly through the midlatitude western boundary current (the model Kuroshio). There is additionally an interior ocean pathway, through the Subtropical Countercurrent (an eastward flow across the middle of the subtropical gyre), that directly feeds subtropical subduction sites. Below the mixed layer, the water pathways in the subtropical thermocline essentially reflect the anticyclonic gyre circulation where we find that the model subtropical gyre separates into two circulation centers. The surface circulation also features a double-cell pattern, with the poleward cell centered at about 30 degrees N and the equatorward component contained between 15 degrees and 25 degrees N. In addition, thermocline waters that can be traced to subtropical subduction sites move toward the Tropics almost zonally across the basin, succeeding in flowing toward the equator only along relatively narrow north-south conduits. The low-latitude western boundary currents serve as the main southward circuit for the subducted subtropical thermocline water. However, the model does find a direct flow of thermocline water into the Tropics through the ocean interior, confined to the far western Pacific (away from the low-latitude western boundary currents) across 10 degrees N. This interior pathway is found just to the west of a recirculating gyre in and just below the mixed layer in the northeastern Tropics. This equatorward interior flow and a flow that can be traced directly to the western boundary are then swept eastward by the deeper branches of the North Equatorial Countercurrent, finally penetrating to the equator in the central and eastern Pacific. Most of these results are consistent with available observations and recently published theoretical and idealized numerical experiments, although the interior pathway of subtropical thermocline water into the Tropics found in this experiment is not apparent in other published numerical simulations. Potential vorticity dynamics are useful in explaining the pathways taken by subtropical thermocline water as it flows into the Tropics. In particular, a large-scale zonally oriented "island" of homogenous potential vorticity, whose signature is determined by thin isopycnal layers in the central tropical Pacific along about 10 degrees N, is dynamically linked to a circulation that does not how directly from the subtropics to the Tropics. This large-scale potential vorticity feature helps to explain the circuitous pathways of the subducted subtropical thermocline waters as they approach the equator. Consequently, waters must first flow westward to the western boundary north of these closed potential vorticity contours and then mostly move southward through the low-latitude western boundary currents, flow eastward with the North Equatorial Countercurrent, and finally equatorward to join the Equatorial Undercurrent in the thermocline. C1 Univ Rhode Isl, Grad Sch Oceanog, Narragansett, RI 02882 USA. NASA, Goddard Space Flight Ctr, Lab Hydrospher Proc, Greenbelt, MD 20771 USA. Lamont Doherty Earth Observ, Palisades, NY 10964 USA. RP Zhang, RH (reprint author), Univ Rhode Isl, Grad Sch Oceanog, Narragansett, RI 02882 USA. EM zrh@sequan.gso.uri.edu RI Chen, Dake/E-7082-2011 NR 41 TC 70 Z9 75 U1 1 U2 6 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 USA SN 0022-3670 J9 J PHYS OCEANOGR JI J. Phys. Oceanogr. PD FEB PY 1998 VL 28 IS 2 BP 322 EP 343 DI 10.1175/1520-0485(1998)028<0322:ANSOTM>2.0.CO;2 PG 22 WC Oceanography SC Oceanography GA YY524 UT WOS:000072156200010 ER PT J AU Gurocak, HB Peabody, J AF Gurocak, HB Peabody, J TI Design of a robot that walks in any direction SO JOURNAL OF ROBOTIC SYSTEMS LA English DT Article AB In this article the design of a six-legged walking robot is presented. The design consists of two triangular body halves joined by actuators. Each body half has three legs attached to it. By shifting one of the halves with respect to the other the robot can walk in any direction. The design of the robot is explained in detail and a final prototype is presented. (C) 1998 John Wiley & Sons, Inc. C1 Washington State Univ, Mfg Engn Program, Vancouver, WA 98686 USA. NASA, Ames Res Ctr, Sverdrup Technol Inc, Moffett Field, CA 94035 USA. RP Gurocak, HB (reprint author), Washington State Univ, Mfg Engn Program, Vancouver, WA 98686 USA. NR 8 TC 8 Z9 8 U1 0 U2 1 PU JOHN WILEY & SONS INC PI NEW YORK PA 605 THIRD AVE, NEW YORK, NY 10158-0012 USA SN 0741-2223 J9 J ROBOTIC SYST JI J. Robot. Syst. PD FEB PY 1998 VL 15 IS 2 BP 75 EP 83 DI 10.1002/(SICI)1097-4563(199802)15:2<75::AID-ROB2>3.0.CO;2-P PG 9 WC Robotics SC Robotics GA YU962 UT WOS:000071774100002 ER PT J AU Main, M Foltz, D Babinsky, E Bailey, D Frantz, B Pleva, D Baldizzi, M Myers, D Jones, K Spence, M Freeman, K Morehead, A Thomas, J AF Main, M Foltz, D Babinsky, E Bailey, D Frantz, B Pleva, D Baldizzi, M Myers, D Jones, K Spence, M Freeman, K Morehead, A Thomas, J TI Real-time transmission of echocardiographic images over high speed networks: Effects of bandwidth, cell loss ratio and cell error ratio on image quality SO JOURNAL OF THE AMERICAN COLLEGE OF CARDIOLOGY LA English DT Meeting Abstract C1 Cleveland Clin Fdn, Cleveland, OH USA. NASA Lewis, Cleveland, OH USA. Ames Res Ctr, Cleveland, OH USA. Ames Res Ctr, Mt View, CA USA. NR 0 TC 2 Z9 2 U1 0 U2 0 PU ELSEVIER SCIENCE INC PI NEW YORK PA 655 AVENUE OF THE AMERICAS, NEW YORK, NY 10010 USA SN 0735-1097 J9 J AM COLL CARDIOL JI J. Am. Coll. Cardiol. PD FEB PY 1998 VL 31 IS 2 SU A BP 259A EP 259A DI 10.1016/S0735-1097(97)84836-X PG 1 WC Cardiac & Cardiovascular Systems SC Cardiovascular System & Cardiology GA YW305 UT WOS:000071920601100 ER PT J AU Choi, J Aggarwal, MD Wang, WS Penn, BG Frazier, DO AF Choi, J Aggarwal, MD Wang, WS Penn, BG Frazier, DO TI Solid-phase epitaxial growth of organic materials SO JOURNAL OF THE KOREAN PHYSICAL SOCIETY LA English DT Article; Proceedings Paper CT 9th International Meeting on Ferroelectricity (IMF-9) CY AUG 25-29, 1997 CL SEOUL, SOUTH KOREA AB In an effort to utilize the best second-order nonlinearity of 2-methyl-4-nitroaniline (MNA), heteroepitaxial film of this material is grown on organic substrate by solid-phase epitaxial method. Heat treatment at various temperatures and time is performed on this amorphous layer of MNA which is vacuum deposited on benzil and benzil-aniline single crystals. As grown heteroepitaxial film seems to be smooth and transparent surface. Second-harmonic intensity has increased for MNA film on benzil-aniline. C1 Alabama A&M Univ, Dept Phys, Normal, AL 35762 USA. NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. RP Choi, J (reprint author), Alabama A&M Univ, Dept Phys, Normal, AL 35762 USA. NR 8 TC 1 Z9 1 U1 0 U2 0 PU KOREAN PHYSICAL SOC PI SEOUL PA 635-4, YUKSAM-DONG, KANGNAM-KU, SEOUL 135-703, SOUTH KOREA SN 0374-4884 J9 J KOREAN PHYS SOC JI J. Korean Phys. Soc. PD FEB PY 1998 VL 32 SU S BP S1234 EP S1235 PN 3 PG 2 WC Physics, Multidisciplinary SC Physics GA YZ022 UT WOS:000072212300110 ER PT J AU Choi, J Aggarwal, MD Wang, WS Penn, BG Frazier, DO AF Choi, J Aggarwal, MD Wang, WS Penn, BG Frazier, DO TI Binary organic single crystals for nonlinear optical application SO JOURNAL OF THE KOREAN PHYSICAL SOCIETY LA English DT Article; Proceedings Paper CT 9th International Meeting on Ferroelectricity (IMF-9) CY AUG 25-29, 1997 CL SEOUL, SOUTH KOREA ID 2-METHYL-4-NITROANILINE AB An organic binary system benzil:2-methyl-4-nitroaniline(MNA) which takes advantage of thermal stability and high second-order nonlinearity in an effort to find new modified materials for nonlinear optical application is described. This combination improves its processability and mechanical properties. A new design consisting of a self-sealing ampoule has been successfully used to grow bulk crystals of benzil:MNA using the Bridgman-Stockbarger technique. The Vickers hardness is found to be 13 kg/mm(2) with a second-harmonic conversion efficiency of 5 wt% benzil:MNA determined to be 1.5% using a Nd:YAG laser. C1 Alabama A&M Univ, Dept Phys, Normal, AL 35762 USA. NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. RP Choi, J (reprint author), Alabama A&M Univ, Dept Phys, Normal, AL 35762 USA. NR 12 TC 3 Z9 3 U1 0 U2 0 PU KOREAN PHYSICAL SOC PI SEOUL PA 635-4, YUKSAM-DONG, KANGNAM-KU, SEOUL 135-703, SOUTH KOREA SN 0374-4884 J9 J KOREAN PHYS SOC JI J. Korean Phys. Soc. PD FEB PY 1998 VL 32 SU S BP S433 EP S435 PN 2 PG 3 WC Physics, Multidisciplinary SC Physics GA YZ021 UT WOS:000072212200010 ER PT J AU Hah, C Tsung, FL Loellbach, J AF Hah, C Tsung, FL Loellbach, J TI Comparison of two three-dimensional unsteady Navier-Stokes codes applied to a turbine stage flow analysis SO JSME INTERNATIONAL JOURNAL SERIES B-FLUIDS AND THERMAL ENGINEERING LA English DT Article; Proceedings Paper CT International Conference on Fluid Engineering at the JSME Centennial Grand Congress CY JUL 13-16, 1997 CL TOKYO INT FORUM, TOKYO, JAPAN SP JSME, Fluid Engn Div, ASME, Fluids Engn Div, KSME, Thermal Fluids Engn Div HO TOKYO INT FORUM DE Navier-Stokes; calculation; three-dimensional; unsteady; turbine; unstructured; tetrahedral ID EULER EQUATIONS AB A comparison between two numerical flow solution methods, one based on structured grids and the other based on unstructured grids, is made by using both methods to solve for steady and unsteady flowfields in turbomachinery blade rows. Numerical results from the two different methods are compared to each other as well as to available experimental data. Both methods solve the three-dimensional Reynolds-averaged Navier-Stokes equations using the finite volume technique, and can be run in steady-state or time-accurate unsteady modes. The structured solver uses a pressure-based method applied to hexahedral control volumes and a standard two-equation turbulence model, The unstructured solver uses a density-based method applied to tetrahedral control volumes and the one-equation Spalart-Allmaras turbulence objective of the comparison is to assess the current capabilities of the unstructured flow soh er relative to those of a well established structured flow solver, and to establish areas for further development to improve accuracy and economy. C1 NASA, Turbomachinery Div, Lewis Res Ctr, Cleveland, OH 44135 USA. Inst Computat Mech Propuls, Cleveland, OH 44135 USA. RP Hah, C (reprint author), NASA, Turbomachinery Div, Lewis Res Ctr, 21000 Brookpark Rd MS 5-11, Cleveland, OH 44135 USA. NR 17 TC 0 Z9 0 U1 0 U2 0 PU JAPAN SOC MECHANICAL ENGINEERS PI TOKYO PA SHINANOMACHI-RENGAKAN BLDG, SHINANOMACHI 35, SHINJUKU-KU, TOKYO, 160, JAPAN SN 1340-8054 J9 JSME INT J B-FLUID T JI JSME Int. J. Ser. B-Fluids Therm. Eng. PD FEB PY 1998 VL 41 IS 1 BP 200 EP 207 PG 8 WC Thermodynamics; Engineering, Mechanical SC Thermodynamics; Engineering GA ZF982 UT WOS:000072952700027 ER PT J AU Nissen, JA Swanson, DR Geng, ZK Dohm, V Israelsson, UE DiPirro, MJ Lipa, JA AF Nissen, JA Swanson, DR Geng, ZK Dohm, V Israelsson, UE DiPirro, MJ Lipa, JA TI Testing critical point universality along the lambda-line SO LOW TEMPERATURE PHYSICS LA English DT Article; Proceedings Paper CT International Workshop on Low Temperature Microgravity Physics (CWS-97) CY JUL 23-27, 1997 CL CHERNOGOLOVKA, RUSSIA ID CRITICAL-BEHAVIOR; RENORMALIZATION-GROUP; MINIMAL RENORMALIZATION; EPSILON-EXPANSION; HEAT-CAPACITY; 3 DIMENSIONS; 2ND SOUND; HE-4; TRANSITION; VELOCITY AB We are currently building a prototype for a new test of critical-point universality at the lambda transition in He-4, which is to be performed in microgravity conditions. The flight experiment will measure the second-sound velocity as a function of temperature at pressures from 1 to 30 bars in the region close to the lambda line. The critical exponents and other parameters characterizing the behavior of the superfluid density will be determined from the measurements. The microgravity measurements will be quite extensive, probably taking 30 days to complete. In addition to the superfluid density, some measurements of the specific heat will be made using the low-g simulator at the Jet Propulsion Laboratory. The results of the superfluid density and specific heat measurements will be used to compare the asymptotic exponents and other universal aspects of the superfluid density with the theoretical predictions currently established by renormalization group techniques. (C) 1998 American Institute of Physics. C1 Stanford Univ, Stanford, CA 94305 USA. Rhein Westfal TH Aachen, Inst Theoret Phys, D-52056 Aachen, Germany. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Nissen, JA (reprint author), Stanford Univ, Stanford, CA 94305 USA. EM joel@chex.stanford.edu NR 28 TC 6 Z9 6 U1 0 U2 0 PU AMER INST PHYSICS PI WOODBURY PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 USA SN 1063-777X J9 LOW TEMP PHYS+ JI Low Temp. Phys. PD FEB PY 1998 VL 24 IS 2 BP 86 EP 89 DI 10.1063/1.593544 PG 4 WC Physics, Applied SC Physics GA YY569 UT WOS:000072161300006 ER PT J AU Israelsson, UE Lee, MC AF Israelsson, UE Lee, MC TI The NASA/JPL program in microgravity fundamental physics SO LOW TEMPERATURE PHYSICS LA English DT Article; Proceedings Paper CT International Workshop on Low Temperature Microgravity Physics (CWS-97) CY JUL 23-27, 1997 CL CHERNOGOLOVKA, RUSSIA ID LAMBDA-POINT; RENORMALIZATION-GROUP; THERMAL-CONDUCTIVITY; CONFINED HELIUM; HEAT-CAPACITY; HE-4 AB The National Aeronautics and Space Administration (NASA) has been supporting research in microgravity low temperature physics for about 20 years. In the last 10 years, the program has seen significant growth in the number of funded investigations and in the breadth of the research activities being pursued, Currently, flight experiments are being performed exclusively on the Space Shuttle. For the future, a cryogenic Space Station facility is being developed by the Jet Propulsion Laboratory and industrial partners to support the microgravity needs of the international scientific community, The facility will be attached to the Japanese Experiments Module's Exposed Facility and will operate with a 6 month helium cryogen lifetime. Flights of the facility ate planned at 2 year intervals starting in 2003 with each flight accommodating multiple scientific experiments, Capabilities, conceptual designs and development plans for the facility are discussed along with a summary of potential near term flight candidate experiments, (C) 1998 American Institute of Physics. [S1063-777X(98)02402-5]. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. NASA, Micrograv Res Div, Washington, DC 20546 USA. RP Israelsson, UE (reprint author), CALTECH, Jet Prop Lab, Mailstop 79-5,4800 Oak Grove Dr, Pasadena, CA 91109 USA. EM ulf@squid.jpl.nasa.gov; mark.lee@hq.nasa.gov NR 17 TC 0 Z9 0 U1 0 U2 1 PU AMER INST PHYSICS PI WOODBURY PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 USA SN 1063-777X J9 LOW TEMP PHYS+ JI Low Temp. Phys. PD FEB PY 1998 VL 24 IS 2 BP 140 EP 143 DI 10.1063/1.593562 PG 4 WC Physics, Applied SC Physics GA YY569 UT WOS:000072161300019 ER PT J AU Zaretsky, EV AF Zaretsky, EV TI A. Palmgren revisited - A basis for bearing life prediction SO LUBRICATION ENGINEERING LA English DT Article; Proceedings Paper CT 52nd Annual Meeting of the Society-of-Tribologists-and-Lubrication-Engineers CY MAY 18-22, 1997 CL KANSAS CITY, MISSOURI SP Soc Tribologists & Lubricat Engineers DE rolling-element bearings; life prediction methods; dynamic modeling AB Bearing technology-as well as the bearing industry,:began to develop with the invention of the bicycle in the 1850s. At the same time, high-qualify steel was: made possible by the Bessemer process. In 1881, H Hertz published his contact stress analysis. By 1902, R. Stribeck had published his work based on Hertz theory to calculate the maximum load of a radially loaded ball bearing. By 1920, all of the rolling bearing types used today were being manufactured. AISI 52100 bearing steel became the material of choice for these bearings. Beginning in 1918, engineers directed their attention to predicting the lives of these bearings. In 1924, A. Palmgren published a paper outlining his approach to bearing life prediction. This paper was the basis for the Lundberg Palmgren life theory published in 1947. A critical review of the 1924 Palmgren paper is presented here together with a discussion of its effect on bearing life prediction. C1 NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. RP Zaretsky, EV (reprint author), NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. NR 22 TC 13 Z9 13 U1 0 U2 2 PU SOC TRIBOLOGISTS & LUBRICATION ENGINEERS PI PARK RIDGE PA 840 BUSSE HIGHWAY, PARK RIDGE, IL 60068 USA SN 0024-7154 J9 LUBR ENG JI Lubric. Eng. PD FEB PY 1998 VL 54 IS 2 BP 18 EP 24 PG 7 WC Engineering, Mechanical SC Engineering GA YY158 UT WOS:000072119100003 ER PT J AU Burl, MC Asker, L Smyth, P Fayyad, U Perona, P Crumpler, L Aubele, J AF Burl, MC Asker, L Smyth, P Fayyad, U Perona, P Crumpler, L Aubele, J TI Learning to recognize volcanoes on Venus SO MACHINE LEARNING LA English DT Article DE machine learning; pattern recognition; learning from examples; large image databases; data mining; automatic cataloging; detection of natural objects; Magellan SAR; JARtool; volcanoes; Venus; principal components analysis; trainable ID IMAGE; METHODOLOGY; PERFORMANCE; RETRIEVAL; MAGELLAN; SYSTEM AB Dramatic improvements in sensor and image acquisition technology have created a demand for automated tools that can aid in the analysis of large image databases. We describe the development of JARtool, a trainable software system that learns to recognize volcanoes in a large data set of Venusian imagery. A machine learning approach is used because it is much easier for geologists to identify examples of volcanoes in the imagery than it is to specify domain knowledge as a set of pixel-level constraints. This approach can also provide portability to other domains without the need for explicit reprogramming; the user simply supplies the system with a new set of training examples. We show how the development of such a system requires a completely different set of skills than are required for applying machine learning to "toy world" domains. This paper discusses important aspects of the application process not commonly encountered in the "toy world" including obtaining labeled training data, the difficulties of working with pixel data, and the automatic extraction of higher-level features. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ Stockholm, S-10691 Stockholm, Sweden. Univ Calif Irvine, Irvine, CA 92717 USA. Univ Padua, I-35100 Padua, Italy. Brown Univ, Providence, RI 02912 USA. New Mexico Museum Nat Hist & Sci, Albuquerque, NM USA. Microsoft Res, Redmond, WA USA. RP Burl, MC (reprint author), CALTECH, Jet Prop Lab, MS 525-3660,4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 45 TC 38 Z9 38 U1 3 U2 6 PU KLUWER ACADEMIC PUBL PI DORDRECHT PA SPUIBOULEVARD 50, PO BOX 17, 3300 AA DORDRECHT, NETHERLANDS SN 0885-6125 J9 MACH LEARN JI Mach. Learn. PD FEB-MAR PY 1998 VL 30 IS 2-3 BP 165 EP 194 DI 10.1023/A:1007400206189 PG 30 WC Computer Science, Artificial Intelligence SC Computer Science GA ZK607 UT WOS:000073342100003 ER PT J AU Feng, AG McCoy, BJ Munir, ZA Cagliostro, D AF Feng, AG McCoy, BJ Munir, ZA Cagliostro, D TI Wettability of transition metal oxide surfaces SO MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING LA English DT Article DE wettability; contact angles; microscopy AB The wettability of transition metal oxide surfaces (TiO2, ZrO2 and HfO2) by water was investigated by measuring the contact angles using the sessile drop method. The oxide surfaces were prepared by thermal oxidation of polished metal foils of Ti, Zr and I-If which had been polished to different levels of surface roughness. The surfaces were also characterized by optical microscopy, X-ray diffraction (XRD), atomic force microscopy (AFM) and Auger/XPS (AES/ESCA) methods. From the dependence of contact angles on surface roughness for the three investigated oxides, contact angles on Bat surfaces win calculated as 70.7 degrees, 59.9 degrees and 74.0 degrees for TiO2, ZrO2 and HfO2, respectively. These results suggest thar the three oxides do nor provide acceptable waterproofing coatings on silica fibers used for space shuttle thermal insulation. (C) 1998 Elsevier Science S.A. C1 Univ Calif Davis, Dept Chem Engn & Mat Sci, Davis, CA 95616 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Munir, ZA (reprint author), Univ Calif Davis, Dept Chem Engn & Mat Sci, Davis, CA 95616 USA. NR 10 TC 39 Z9 41 U1 3 U2 11 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 FEB PY 1998 VL 242 IS 1-2 BP 50 EP 56 DI 10.1016/S0921-5093(97)00527-3 PG 7 WC Nanoscience & Nanotechnology; Materials Science, Multidisciplinary; Metallurgy & Metallurgical Engineering SC Science & Technology - Other Topics; Materials Science; Metallurgy & Metallurgical Engineering GA ZD887 UT WOS:000072734400008 ER PT J AU Choi, SR Salem, JA AF Choi, SR Salem, JA TI 'Ultra'-fast fracture strength of advanced ceramics at elevated temperatures SO MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING LA English DT Article DE 'ultra'-fast fracture strength; advanced ceramics; slow crack growth; elevated temperature constant stress-rate testing ID HOT-PRESSED SI3N4; SLOW CRACK-GROWTH; SILICON-NITRIDE; FATIGUE BEHAVIOR; FAILURE; PROPAGATION; TOUGHNESS; FLAWS; GLASS AB An attempt was made to determine elevated-temperature, 'ultra'-fast fracture strengths of one alumina, two silicon nitrides and one silicon carbide by using constant stress-rate ('dynamic fatigue') testing with a series of 'ultra'-fast test rates. Of the materials rested, the alumina exhibited a convergence of strength at stress rates below 3.3 x 10(4) MPa s(-1). The strength approached approximately the room-temperature inert strength. By contrast, the silicon nitrides and silicon carbide did not reveal a strength approach: but exhibited elevated-temperature strengths 10 and 20% lower than their respective room-temperature strengths. Although the analytical results imply that the elevated-temperature 'inert' strength of a ceramic material can be obtained by using sufficiently high stress rates, the experimental testing rates were only sufficient to demonstrate convergence for the alumina. (C) 1998 Elsevier Science S.A. C1 NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. Cleveland State Univ, Cleveland, OH 44115 USA. RP Choi, SR (reprint author), NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. NR 38 TC 11 Z9 11 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 FEB PY 1998 VL 242 IS 1-2 BP 129 EP 136 DI 10.1016/S0921-5093(97)00525-X PG 8 WC Nanoscience & Nanotechnology; Materials Science, Multidisciplinary; Metallurgy & Metallurgical Engineering SC Science & Technology - Other Topics; Materials Science; Metallurgy & Metallurgical Engineering GA ZD887 UT WOS:000072734400016 ER PT J AU Goldsby, JC Yun, HM Morscher, GN DiCarlo, JA AF Goldsby, JC Yun, HM Morscher, GN DiCarlo, JA TI Annealing effects on creep of polycrystalline alumina-based fibers SO MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING LA English DT Article DE grain growth; microstructural instability; annealing effects; polycrystalline alumina-based fibers ID PLASTIC-DEFORMATION; AL2O3 AB Continuous-length polycrystalline aluminum oxide-based fibers are being considered as reinforcements for advanced high-temperature composite materials. For these fine-grained fibers, basic issues arise concerning grain growth and microstructural instability during composite fabrication and the resulting effects on the fiber's thermo-mechanical properties. To examine these issues, commercially available Nextel 610 (alumina) and Alter (alumina-silica) fibers were annealed at 1100 and 1300 degrees C for up to 100 h in air. Changes in fiber microstructural fiber tensile creep, and bend stress relaxation (BSR) that occurred with annealing were then determined. BSR tests were also used to compare as-received and annealed fibers to other polycrystalline oxide fibers. Annealing was shown to have a significant effect, particularly on the Alter fiber, and caused it to have increased creep resistance. (C) 1998 Elsevier Science S.A. C1 NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. Cleveland State Univ, Dept Chem Engn, Cleveland, OH 44115 USA. Cleveland State Univ, Dept Mat Sci & Engn, Cleveland, OH 44106 USA. RP Goldsby, JC (reprint author), NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. NR 11 TC 13 Z9 14 U1 1 U2 5 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 FEB PY 1998 VL 242 IS 1-2 BP 278 EP 283 DI 10.1016/S0921-5093(97)00537-6 PG 6 WC Nanoscience & Nanotechnology; Materials Science, Multidisciplinary; Metallurgy & Metallurgical Engineering SC Science & Technology - Other Topics; Materials Science; Metallurgy & Metallurgical Engineering GA ZD887 UT WOS:000072734400032 ER PT J AU Goldin, DS Venneri, SL Noor, AK AF Goldin, DS Venneri, SL Noor, AK TI A new frontier in engineering SO MECHANICAL ENGINEERING LA English DT Article C1 NASA, Washington, DC 20546 USA. Univ Virginia, NASA, Langley Res Ctr, Ctr Adv Computat Technol, Hampton, VA USA. RP Goldin, DS (reprint author), NASA, Washington, DC 20546 USA. NR 0 TC 10 Z9 10 U1 0 U2 0 PU ASME-AMER SOC MECHANICAL ENG PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017 USA SN 0025-6501 J9 MECH ENG JI Mech. Eng. PD FEB PY 1998 VL 120 IS 2 BP 62 EP 69 PG 8 WC Engineering, Mechanical SC Engineering GA YU583 UT WOS:000071732400022 ER PT J AU Halama, G McAdoo, J Liu, H AF Halama, G McAdoo, J Liu, H TI Composite x-ray image assembly for large-field digital mammography with one- and two-dimensional positioning of a focal plane array SO MEDICAL PHYSICS LA English DT Article DE x ray; mammography; CCD; digital; electronic AB To demonstrate the feasibility of a novel large-field digital mammography technique, a 1024 x 1024 pixel Loral charge-coupled device (CCD) focal plane array (FPA) was positioned in a mammographic field with one-and two-dimensional scan sequences to obtain 950 x 1800 pixel and 3600 x 3600 pixel composite images, respectively. These experiments verify that precise positioning of FPAs produced seamless composites and that the CCD mosaic concept has potential for high-resolution, large-field imaging. The proposed CCD mosaic concept resembles a checkerboard pattern with spacing left between the CCDs for the driver and readout electronics. To obtain a complete x-ray image, the mosaic must be repositioned four times, with an x-ray exposure at each position. To reduce the patient dose, a lead shield with appropriately patterned holes is placed between the x-ray source and the patient. The high-precision motorized translation stages and the fiber-coupled-scintillating-screen-CCD sensor assembly were placed in the position usually occupied by the film cassette. Because of the high mechanical precision, seamless composites were constructed from the subimages. This paper discusses the positioning, image alignment procedure, and composite image results. The paper only addresses the formation of a seamless composite image from subimages and will not consider the effects of the lead shield, multiple CCDs, or the speed of motion. (C) 1998 American Association of Physicists in Medicine. C1 NASA, Langley Res Ctr, Hampton, VA 23681 USA. Univ Virginia, Dept Radiol, Charlottesville, VA 22908 USA. RP Halama, G (reprint author), NASA, Langley Res Ctr, MS468, Hampton, VA 23681 USA. FU NCI NIH HHS [CA69043] NR 5 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 0094-2405 J9 MED PHYS JI Med. Phys. PD FEB PY 1998 VL 25 IS 2 BP 172 EP 175 DI 10.1118/1.598177 PG 4 WC Radiology, Nuclear Medicine & Medical Imaging SC Radiology, Nuclear Medicine & Medical Imaging GA YX658 UT WOS:000072063400004 PM 9507476 ER PT J AU Ramasundaram, P Ye, F Bowman, RR Soboyejo, WO AF Ramasundaram, P Ye, F Bowman, RR Soboyejo, WO TI An investigation of toughening in NiAl composites reinforced with yttria-partially stabilized zirconia particles SO METALLURGICAL AND MATERIALS TRANSACTIONS A-PHYSICAL METALLURGY AND MATERIALS SCIENCE LA English DT Article ID INTERMETALLIC ALLOYS; TRANSFORMATION; FRACTURE; PHASE; DEFORMATION; MECHANICS; BEHAVIOR; CERAMICS; SYSTEM AB The results of an investigation of toughening mechanisms in NiAl composites reinforced with yttria-partially stabilized zirconia polycrystals are presented. Different yttria stabilization levels in the zirconia, between 0 and 6 mole pct are employed. It is shown that substantial improvements in fracture toughness are obtained in all the composites reinforced with partially stabilized zirconia particles. The phase contents and microstructures of the composite systems are characterized by X-ray diffraction and transmission electron microscopy (TEM) techniques. Crack tip deformation was also studied using crack tip TEM analysis, and laser Raman spectroscopy was used to estimate the size of the transformation zone. The results show that transformation toughening is significant only in the 2 mole pct yttria-stabilized zirconia composite. Toughening is also shown to occur via slip phenomena within the NiAl grains in the near-tip regions of the composites reinforced with 2, 4, or 6 mole pct yttria-stabilized zirconia particles. C1 Wyman Gordon Co, Houston, TX 77240 USA. NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. MIT, Dept Mech Engn, Cambridge, MA 02139 USA. MIT, Dept Mat Sci & Engn, Cambridge, MA 02139 USA. RP Ramasundaram, P (reprint author), Wyman Gordon Co, Houston, TX 77240 USA. NR 27 TC 12 Z9 12 U1 1 U2 7 PU MINERALS METALS MATERIALS SOC PI WARRENDALE PA 420 COMMONWEALTH DR, WARRENDALE, PA 15086 USA SN 1073-5623 J9 METALL MATER TRANS A JI Metall. Mater. Trans. A-Phys. Metall. Mater. Sci. PD FEB PY 1998 VL 29 IS 2 BP 493 EP 505 DI 10.1007/s11661-998-0130-1 PG 13 WC Materials Science, Multidisciplinary; Metallurgy & Metallurgical Engineering SC Materials Science; Metallurgy & Metallurgical Engineering GA YZ133 UT WOS:000072223600009 ER PT J AU Chen, C Tao, WK Lin, PL Lai, GS Tseng, SF Wang, TCC AF Chen, C Tao, WK Lin, PL Lai, GS Tseng, SF Wang, TCC TI The intensification of the low-level jet during the development of mesoscale convective systems on a mei-yu front SO MONTHLY WEATHER REVIEW LA English DT Article ID MODEL; INSTABILITY; SIMULATION; EQUATION; CHINA; TAMEX; TESTS; SHEAR AB During the period of 21-25 June 1991, a mei-yu front, observed by the post-Taiwan Area Mesoscale Experiment, produced heavy precipitation along the western side of the Central Mountain Range of Taiwan. Several oceanic mesoscale convective systems were also generated in an area extending from Taiwan to Hong Kong. Numerical experiments using the Penn State-NCAR MM5 mesoscale model were used to understand the intensification of the low-level jet (LLJ). These processes include thermal wind adjustment and convective, inertial, and conditional symmetric instabilities. Three particular circulations are important in the development of the mei-yu front. First, there is a northward branch of the circulation that develops across the upper-level jet and is mainly caused by the thermal wind adjustment as air parcels enter an upper-level jet streak. The upper-level divergence associated with this branch of the circulation triggers convection. Second, the southward branch of the circulation, with its rising motion in the frontal region and equatorward sinking motion, is driven by frontal vertical deep convection. The return flow of this circulation at low levels can produce an LLJ through geostrophic adjustment. The intensification of the LLJ is sensitive to the presence of convection. Third, there is a circulation that develops from low to middle levels that has a slantwise rising and sinking motion in the pre-and postfrontal regions, respectively. From an absolute momentum surface analysis, this slantwise circulation is maintained by conditionally symmetric instability located at low levels ahead of the front. The presence of both the LLJ and moisture is an essential ingredient in fostering this conditionally symmetric unstable environment. C1 NASA, Goddard Space Flight Ctr, Mesoscale Atmospher Proc Branch, Atmospheres Lab, Greenbelt, MD 20771 USA. Sci Syst & Applicat Inc, Lanham, MD USA. Natl Cent Univ, Dept Atmospher Phys, Chungli 32054, Taiwan. RP Chen, C (reprint author), NASA, Goddard Space Flight Ctr, Mesoscale Atmospher Proc Branch, Atmospheres Lab, Code 912, Greenbelt, MD 20771 USA. NR 33 TC 20 Z9 26 U1 0 U2 2 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 FEB PY 1998 VL 126 IS 2 BP 349 EP 371 DI 10.1175/1520-0493(1998)126<0349:TIOTLL>2.0.CO;2 PG 23 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA YV136 UT WOS:000071793000005 ER PT J AU Klarmann, J Binns, WR Hink, PL Israel, MH Fishman, GJ Parnell, TA Pendleton, GN AF Klarmann, J Binns, WR Hink, PL Israel, MH Fishman, GJ Parnell, TA Pendleton, GN TI Scintillating optical fibers in astrophysics research SO NUCLEAR PHYSICS B LA English DT Article; Proceedings Paper CT 5th International Conference on Advanced Technology and Particle Physics (ICATPP-5) CY OCT 07-11, 1996 CL COMO, ITALY SP European Phys Soc, Ist Nazl Fis Nucl, Univ Florence, INFN AB This work reports on the use of scintillating optical fibers in two experiments being prepared for space flight. The Advanced Composition Explorer (ACE) [1], to be launched in August 1997, includes the Cosmic Ray Isotope Spectrometer (CRIS) which uses a Scintillating Optical Fiber Trajectory detector (SOFT) for trajectory information. The Scintillating Fiber Telescope for Energetic Radiation (SIFTER) is currently being developed as a high energy gamma ray telescope for a future space mission. It uses scintillating optical fibers distributed throughout the converter material to allow detailed study of the development of the electromagnetic cascade produced by gamma rays. C1 Washington Univ, Dept Phys, St Louis, MO 63130 USA. Washington Univ, McDonnell Ctr Space Sci, St Louis, MO 63130 USA. NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. Univ Alabama, Dept Phys, Huntsville, AL 35899 USA. RP Klarmann, J (reprint author), Washington Univ, Dept Phys, CB 1105,1 Brookings Dr, St Louis, MO 63130 USA. NR 3 TC 1 Z9 1 U1 0 U2 0 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0550-3213 J9 NUCL PHYS B JI Nucl. Phys. B PD FEB PY 1998 SU 61B BP 378 EP 383 DI 10.1016/S0920-5632(97)00590-2 PG 6 WC Physics, Particles & Fields SC Physics GA YN972 UT WOS:000071228400061 ER PT J AU Chen, PC Saha, TT Smith, AM Romeo, R AF Chen, PC Saha, TT Smith, AM Romeo, R TI Progress in very lightweight optics using graphite fiber composite materials SO OPTICAL ENGINEERING LA English DT Article DE lightweight optics; replica optics; composite optics; x-ray optics ID X-RAY MIRRORS; XMM TELESCOPE AB We report progress in the fabrication of very low areal density (<5 kg/m(2)) optical mirrors using space-flight-qualified graphite-fiber-reinforced cyanate ester composite materials. Previous attempts have been thwarted by fiber print-through at the surface. We find that the problem can be successfully overcome if the composite is processed to leave a very thin layer of resin at the surface. Results thus far include replicas with surface microroughness <1 nm rms, midfrequency ripples <3 nm rms, areal density 2 kg/m(2) at 42-cm aperture, and freedom from print-through after vacuum drying and ion milling. The process is being extended to the fabrication of very lightweight meter-class optics for space UV astronomy applications, x-ray optics, and other ground-and space-based applications. (C) 1998 Society of Photo-Optical instrumentation Engineers. C1 Catholic Univ Amer, Dept Phys, Washington, DC 20064 USA. Composite Mirror Applicat Inc, Tucson, AZ 85710 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Chen, PC (reprint author), Catholic Univ Amer, Dept Phys, Washington, DC 20064 USA. NR 23 TC 28 Z9 32 U1 0 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 FEB PY 1998 VL 37 IS 2 BP 666 EP 676 DI 10.1117/1.601866 PG 11 WC Optics SC Optics GA YX568 UT WOS:000072053600039 ER PT J AU Steele, DD Volodin, BL Savina, O Kippelen, B Peyghambarian, N Rockel, H Marder, SR AF Steele, DD Volodin, BL Savina, O Kippelen, B Peyghambarian, N Rockel, H Marder, SR TI Transillumination imaging through scattering media by use of photorefractive polymers SO OPTICS LETTERS LA English DT Article ID HOLOGRAPHY AB We demonstrate the use of a near-infrared-sensitive photorefractive polymer with high efficiency for imaging through scattering media, using an all-optical holographic time gate. Imaging through nine scattering mean free paths is performed at 800 nm with a mode-locked continuous-wave Ti:sapphire laser. (C) 1998 Optical Society of America. OCIS codes: 190.5330, 160.5470, 160.5320, 110.3080. C1 Univ Arizona, Ctr Opt Sci, Tucson, AZ 85721 USA. CALTECH, Beckman Inst, Pasadena, CA 91125 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Steele, DD (reprint author), Univ Arizona, Ctr Opt Sci, Tucson, AZ 85721 USA. RI Kippelen, Bernard/I-4058-2013 OI Kippelen, Bernard/0000-0002-8417-7051 NR 13 TC 28 Z9 28 U1 0 U2 1 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 FEB 1 PY 1998 VL 23 IS 3 BP 153 EP 155 DI 10.1364/OL.23.000153 PG 3 WC Optics SC Optics GA YU188 UT WOS:000071691100003 PM 18084443 ER PT J AU Summers, DP Lerner, N AF Summers, DP Lerner, N TI Ammonia from iron(II) reduction of nitrite and the Strecker synthesis: Do iron(II) and cyanide interfere with each other? SO ORIGINS OF LIFE AND EVOLUTION OF THE BIOSPHERE LA English DT Article ID CARBON-DIOXIDE; EARLY EARTH; ATMOSPHERE; PHOTOCHEMISTRY; OXYGEN; OCEAN; HCN AB The question of whether the production of ammonia, from the reduction of nitrite by iron(II), is compatible with its use in the Strecker synthesis of amino acids, or whether the iron and the cyanide needed for the Strecker synthesis interfere with each other, is addressed. Results show that the presence of iron(II) appears to have little, or no, effect on the Strecker synthesis. The presence of cyanide does interfere with reduction of nitrite, but the reduction proceeds at cyanide/iron ratios of less than 4:1. At ratios of about 2:1 and less there is only a small effect. The reduction of nitrite and the Strecker can be combined to proceed in each other's presence, to yield glycine from a mixture of nitrite, Fe+2, formaldehyde, and cyanide. C1 SETI Inst, Moffett Field, CA 94035 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Summers, DP (reprint author), SETI Inst, M-S 239-4, Moffett Field, CA 94035 USA. NR 22 TC 13 Z9 13 U1 0 U2 3 PU KLUWER ACADEMIC PUBL PI DORDRECHT PA SPUIBOULEVARD 50, PO BOX 17, 3300 AA DORDRECHT, NETHERLANDS SN 0169-6149 J9 ORIGINS LIFE EVOL B JI Orig. Life Evol. Biosph. PD FEB PY 1998 VL 28 IS 1 BP 1 EP 11 DI 10.1023/A:1006510326053 PG 11 WC Biology SC Life Sciences & Biomedicine - Other Topics GA ZB829 UT WOS:000072512200001 PM 11536852 ER PT J AU Begault, DR Wenzel, EM Tran, LL Anderson, MR AF Begault, DR Wenzel, EM Tran, LL Anderson, MR TI Survey of commercial airline pilots' hearing loss SO PERCEPTUAL AND MOTOR SKILLS LA English DT Article AB 64 commercial airline pilots (ages 35-64 yr., Mdn: 53) were surveyed regarding hearing loss and tinnitus. Within specific age groups. the proportions responding positively exceed the corresponding proportions in the general population reported by the National Center for Health Statistics. C1 NASA, Ames Res Ctr, Flight Management & Human Factors Div, Moffett Field, CA 94035 USA. RP Begault, DR (reprint author), NASA, Ames Res Ctr, Flight Management & Human Factors Div, Mail Stop 262-2, Moffett Field, CA 94035 USA. NR 2 TC 5 Z9 6 U1 0 U2 2 PU PERCEPTUAL MOTOR SKILLS PI MISSOULA PA PO BOX 9229, MISSOULA, MT 59807 USA SN 0031-5125 J9 PERCEPT MOTOR SKILL JI Percept. Mot. Skills PD FEB PY 1998 VL 86 IS 1 BP 258 EP 258 PG 1 WC Psychology, Experimental SC Psychology GA ZB568 UT WOS:000072485600045 PM 9530744 ER PT J AU Rhie, JK Hayashi, Y Welage, LS Frens, J Wald, RJ Barnett, JL Amidon, GE Putcha, L Amidon, GL AF Rhie, JK Hayashi, Y Welage, LS Frens, J Wald, RJ Barnett, JL Amidon, GE Putcha, L Amidon, GL TI Drug marker absorption in relation to pellet size, gastric motility and viscous meals in humans SO PHARMACEUTICAL RESEARCH LA English DT Article DE gastric emptying; oral absorption; gastric motility; enteric coated; caffeine; acetaminophen; viscous meal ID GASTROINTESTINAL TRANSIT; ACETAMINOPHEN; VISCOSITY; CAFFEINE; SOLIDS; PLASMA; DOGS AB Purpose. The objective of this study was to evaluate drug marker absorption in relation to the gastric emptying (GE) of 0.7 mm and 3.6 mm enteric coated pellets as a function of viscosity and the underlying gastric motility. Methods. Twelve subjects were evaluated in a 3-way crossover study. 0.7 mm caffeine and 3.6 mm acetaminophen enteric coated pellets were concurrently administered with a viscous caloric meal at the levels of 4000, 6000 and 8000 cP. Gastric motility was simultaneously measured with antral manometry and compared to time events in the plasma profiles of the drug markers. Results. Caffeine, from the 0.7 mm pellets, was observed significantly earlier in the plasma than acetaminophen, from the 3.6 mm pellets, at all levels of viscosity. Motility related size differentiated GE was consistently observed at all viscosity levels, however, less variability was observed with the 4000 cP meal. Specifically, the onset of absorption from the of 3.6 mm pellets correlated with the onset of Phase II fasted state contractions (r = 0.929, p < 0.01). Conclusions, The timeframe of drug marker absorption and the onset of motility events were not altered within the range of viscosities evaluated. Rather, the differences in drug marker profiles from the non-digestible solids were most likely the result of the interaction between viscosity and motility influencing antral flow dynamics. The administration of the two sizes of pellets and a viscous caloric meal with subsequent monitoring of drug marker profiles is useful as a reference to assess the influence of motility patterns on the absorption profile of orally administered agents. C1 Univ Michigan, Coll Pharm, Ann Arbor, MI 48109 USA. Nagoya City Univ, Coll Pharm, Nagoya, Aichi, Japan. Univ Michigan, Hlth Syst, Dept Pharm, Ann Arbor, MI 48109 USA. Pharmacia & Upjohn Inc, Kalamazoo, MI 49001 USA. Univ Michigan, Hlth Syst, Dept Internal Med, Div Gastroenterol, Ann Arbor, MI 48109 USA. Univ Michigan, Sch Med, Ann Arbor, MI 48109 USA. NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. RP Amidon, GL (reprint author), Univ Michigan, Coll Pharm, Ann Arbor, MI 48109 USA. EM glamidon@umich.edu FU NCRR NIH HHS [M01 RR00042] NR 22 TC 13 Z9 13 U1 1 U2 2 PU PLENUM PUBL CORP PI NEW YORK PA 233 SPRING ST, NEW YORK, NY 10013 USA SN 0724-8741 J9 PHARMACEUT RES JI Pharm. Res. PD FEB PY 1998 VL 15 IS 2 BP 233 EP 238 DI 10.1023/A:1011962501270 PG 6 WC Chemistry, Multidisciplinary; Pharmacology & Pharmacy SC Chemistry; Pharmacology & Pharmacy GA ZA124 UT WOS:000072331300012 PM 9523309 ER PT J AU Temkin, A Shertzer, J Bhatia, AK AF Temkin, A Shertzer, J Bhatia, AK TI Extension of the Temkin-Poet model to L > 0 partial waves: The generalized exchange approximation SO PHYSICAL REVIEW A LA English DT Article ID SCATTERING AB The Temkin-Poet (TP) model of electron-hydrogen scattering is here generalized to L>0 partial waves in such a way as to be a clear generalization of the exchange approximation (EA). This generalized exchange approximation (GEA) leads to a pair of coupled partial differential equations (PDE's). Boundary conditions are formulated, and the PDE's are solved by a finite element method program adapted from a previous partial wave calculation of the full problem [Shertzer and Botero, Phys. Rev. A 49, 3673 (1994)]. Calculations are carried out for P-1,P-3 and D-1,D-3 partial waves in the elastic region. Phase shifts are bounded from below, as is rigorously required, by exchange approximate phase shifts. But the GEA can yield resonances: in the elastic region, in addition to the S-1 resonance of the TP model, there is a P-3 resonance whose position and width are in close proximity to the lowest P-3 resonance of the full theory. The GEA distinguishes between singlet and triplet scattering for all L, and it contains inelastic and ionization channels in the appropriate energy regions. It is expected that the GEA will have its greatest utility in the ionization domain, as a nontrivial test of the many recent methods being developed. [S1050-2947(98)09202-6]. C1 NASA, Astron & Solar Phys Lab, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Coll Holy Cross, Dept Phys, Worcester, MA 01610 USA. RP Temkin, A (reprint author), NASA, Astron & Solar Phys Lab, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. NR 20 TC 1 Z9 1 U1 0 U2 0 PU AMERICAN PHYSICAL SOC PI COLLEGE PK PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA SN 1050-2947 J9 PHYS REV A JI Phys. Rev. A PD FEB PY 1998 VL 57 IS 2 BP 1091 EP 1095 DI 10.1103/PhysRevA.57.1091 PG 5 WC Optics; Physics, Atomic, Molecular & Chemical SC Optics; Physics GA YW253 UT WOS:000071913800054 ER PT J AU Ramsey, CR Townsend, LW Tripathi, RK Cucinotta, FA AF Ramsey, CR Townsend, LW Tripathi, RK Cucinotta, FA TI Optical model methods of predicting nuclide production from spallation reactions SO PHYSICAL REVIEW C LA English DT Article ID HEAVY-ION FRAGMENTATION; ABRASION-ABLATION; HYDROGEN TARGETS AB Quantum mechanical optical model methods for calculating isotope production cross sections from the spallation of heavy nuclei by high-energy protons are developed from a modified abrasion-ablation collision formalism. The abrasion step is treated quantum-mechanically as a knockout process which leaves the residual prefragment nucleus in an excited state. In ablation the prefragment deexcites to produce the final fragment. The excitation energies of the prefragments are estimated from a combination of liquid drop and frictional-spectator interaction considerations. Estimates of elemental and isotopic production cross sections are in good agreement with recently published cross section measurements. C1 Univ Tennessee, Dept Nucl Engn, Knoxville, TN 37996 USA. Hampton Univ, Dept Phys, Hampton, VA 23668 USA. NASA, Langley Res Ctr, Hampton, VA 23681 USA. RP Ramsey, CR (reprint author), Univ Tennessee, Dept Nucl Engn, Knoxville, TN 37996 USA. NR 18 TC 6 Z9 6 U1 0 U2 2 PU AMERICAN PHYSICAL SOC PI COLLEGE PK PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA SN 0556-2813 J9 PHYS REV C JI Phys. Rev. C PD FEB PY 1998 VL 57 IS 2 BP 982 EP 985 DI 10.1103/PhysRevC.57.982 PG 4 WC Physics, Nuclear SC Physics GA YY129 UT WOS:000072116200063 PM 11542400 ER PT J AU Bardeen, W Duncan, A Eichten, E Hockney, G Thacker, H AF Bardeen, W Duncan, A Eichten, E Hockney, G Thacker, H TI Light quarks, zero modes, and exceptional configurations SO PHYSICAL REVIEW D LA English DT Article ID LATTICE QCD; WILSON FERMIONS; U(1) PROBLEM; SPECTRUM; MASSES; LIMIT AB In continuum QCD, nontrivial gauge topologies give rise to zero eigenvalues of the massless Dirac operator. In lattice QCD with Wilson fermions, analogs of these zero modes appear as exactly real eigenvalues of the Wilson-Dirac operator, leading to poles in the quark propagator in the vicinity of the critical hopping parameter. It is shown that "exceptional configurations," which arise in the quenched approximation at small quark mass, are the result of the fluctuation of the position of zero mode poles to subcritical values of hopping parameter on particular gauge configurations. We describe a procedure for correcting these lattice artifacts by first isolating the contribution of zero mode poles to the quark propagator and then shifting the subcritical poles to the critical point. This procedure defines a modified quenched approximation in which accurate calculations can be carried out for arbitrarily small quark masses. C1 Fermi Natl Accelerator Lab, Batavia, IL 60510 USA. Univ Pittsburgh, Dept Phys & Astron, Pittsburgh, PA 15260 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ Virginia, Dept Phys, Charlottesville, VA 22901 USA. RP Bardeen, W (reprint author), Fermi Natl Accelerator Lab, POB 500, Batavia, IL 60510 USA. NR 25 TC 54 Z9 54 U1 0 U2 0 PU AMERICAN PHYSICAL SOC PI COLLEGE PK PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA SN 0556-2821 J9 PHYS REV D JI Phys. Rev. D PD FEB 1 PY 1998 VL 57 IS 3 BP 1633 EP 1641 DI 10.1103/PhysRevD.57.1633 PG 9 WC Astronomy & Astrophysics; Physics, Particles & Fields SC Astronomy & Astrophysics; Physics GA YV535 UT WOS:000071834800030 ER PT J AU Yeh, C Bergman, L AF Yeh, C Bergman, L TI Enhanced pulse compression in a nonlinear fiber by a wavelength division multiplexed optical pulse SO PHYSICAL REVIEW E LA English DT Article ID PHASE MODULATION; DISPERSION; WAVEGUIDES; SOLITONS AB A way to compress an optical pulse in a single-mode fiber is presented in this paper. By the use of the cross-phase modulation (CPM) effect caused by the nonlinearity of the optical fiber, a shepherd pulse propagating on a different wavelength beam in a wavelength division multiplexed single-mode fiber system can be used to enhance the pulse compression of a copropagating primary pulse. Although CPM will not cause energy to be exchanged among the beams, the pulse shapes on these beams can be altered significantly. For example, a 1-mW peak power 10-ps primary pulse on a given wavelength beam may be compressed by a factor of as much as 25 when a copropagating 10-ps shepherd pulse of peak power of 49 mW on a different wavelength beam is similarly compressed. Results of a systematic study on this effect are presented in this paper. Furthermore, even when the primary pulse on a given wavelength beam has a peak power of much less than 1 mW, it can still be compressed by the same compression factor-as a copropagating shepherd pulse of peak power much larger than 1 mW on a different wavelength beam as it undergoes compression. Through CPM, copropagating pulses on separate beams appear to share the nonlinear effect induced on any one of the pulses on separate beams. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Yeh, C (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 25 TC 36 Z9 36 U1 0 U2 0 PU AMERICAN PHYSICAL SOC PI COLLEGE PK PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA SN 1063-651X J9 PHYS REV E JI Phys. Rev. E PD FEB PY 1998 VL 57 IS 2 BP 2398 EP 2404 DI 10.1103/PhysRevE.57.2398 PN B PG 7 WC Physics, Fluids & Plasmas; Physics, Mathematical SC Physics GA YY128 UT WOS:000072116100061 ER PT J AU Siregar, E Vinas, AF Goldstein, ML AF Siregar, E Vinas, AF Goldstein, ML TI Coarse-graining and nonlocal processes in proton cyclotron resonant interactions SO PHYSICS OF PLASMAS LA English DT Article ID WAVES AB Coarse-grained information from a hybrid simulation show that previously developed quasifluid equations of state capture some aspects of proton cyclotron resonant interactions for parallel propagation in a low beta plasma. Direct kinetic information is used as a closure for the information exchanged with the higher-order moment quantities. The coarse-graining procedure involves averaging over many proton-inertial lengths and looking at long time scales associated with the wave envelopes. By use of the coarse-graining prior to statistical analysis, the anticorrelations predicted by the equations of state are very high for both the single resonant wave case and for a broadband spectrum centered on a resonant wave. These anticorrelations are also consistent with what one expects from a single particle orbit analysis. A similar analysis, but done without the prior averaging procedures, shows no relevant correlations, and no simple dynamics emerges from the kinetic data in this case. A comparison is made with a model based on quasilinear theory. These results suggest that, in addition to simply taking velocity moments of particle distributions, the proper averaging of kinetic information over space and time scales lying below the range accessible to a fluid model can be essential to its success. (C) 1998 American Institute of Physics. C1 NASA, Goddard Space Flight Ctr, Extraterr Phys Lab, Greenbelt, MD 20771 USA. Space Applicat Corp, Vienna, VA 22180 USA. RP Siregar, E (reprint author), NASA, Goddard Space Flight Ctr, Extraterr Phys Lab, Code 692, Greenbelt, MD 20771 USA. RI Goldstein, Melvyn/B-1724-2008 NR 23 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 1070-664X J9 PHYS PLASMAS JI Phys. Plasmas PD FEB PY 1998 VL 5 IS 2 BP 333 EP 344 DI 10.1063/1.872715 PG 12 WC Physics, Fluids & Plasmas SC Physics GA YV530 UT WOS:000071834300001 ER PT J AU Gehrels, N Paul, J AF Gehrels, N Paul, J TI The new gamma-ray astronomy SO PHYSICS TODAY LA English DT Article ID RADIO C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Saclay Nucl Res Ctr, Gif Sur Yvette, France. RP Gehrels, N (reprint author), NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RI Gehrels, Neil/D-2971-2012 NR 12 TC 8 Z9 8 U1 0 U2 0 PU AMER INST PHYSICS PI WOODBURY PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 USA SN 0031-9228 J9 PHYS TODAY JI Phys. Today PD FEB PY 1998 VL 51 IS 2 BP 26 EP 32 DI 10.1063/1.882139 PG 7 WC Physics, Multidisciplinary SC Physics GA YU713 UT WOS:000071746800014 ER PT J AU Sekanina, Z AF Sekanina, Z TI Evidence for asteroidal origin of the Tunguska object SO PLANETARY AND SPACE SCIENCE LA English DT Article; Proceedings Paper CT International Workshop Tunguska 96 CY JUL 15-17, 1996 CL BOLOGNA, ITALY SP Univ Bologna, Dept Phys, Univ Bologna, Commiss Int Relat, Alessandro Volta Ctr Sci Culture, Emilia Romagna Reg Govt, Giorgio Abetti Astron Observ, Int Sci Fdn, Landau Network Coordinat Ctr, Luigi Negro Fdn, Russian Fdn Basic Res ID COMET SHOEMAKER-LEVY-9; EARTHS ATMOSPHERE; COSMIC BODY; PEEKSKILL METEORITE; FEBRUARY 1; FRAGMENTATION; METEOROIDS; COLLISION; EXPLOSION; JUPITER AB The progress in the understanding of the Tunguska object is reviewed in the light of evidence presented in numerous recent investigations, which appeared following the publication of my 1983 paper on the object's proposed asteroidal nature. The issues addressed extensively in the present review involve: (i) the fundamental characteristics of the event, such as the object's energy, altitude and velocity at the time of: its terminal explosion and the dynamic pressure involved; (ii) the problem of atmospheric fragmentation of very massive impactors and the implications for their ablation and deceleration; (iii) new analysis of the orientation of the Tunguska object's heliocentric orbit based on the best data on the apparent radiant of the fireball's atmospheric trajectory; and (iv) comparison with the findings of other recent investigations, including compositional studies. Also employed in the arguments are the results now available on the impacts of comet Shoemaker-Levy 9's fragments into Jupiter and the findings of a recent comparative study of two huge fireballs (one cometary, one stony, both involving impactors several meters across) observed-with the cameras of the European Network of fireball monitoring. It is concluded that hypotheses based on presumed cometary origin of the Tunguska object encounter unsurmountable difficulties and that the interpretation of the event as a fall of a small stony or carbonaceous asteroid is not only plausible, but virtually certain. (C) 1998 Elsevier Science Ltd. All rights reserved. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Sekanina, Z (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 64 TC 18 Z9 18 U1 0 U2 1 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0032-0633 J9 PLANET SPACE SCI JI Planet Space Sci. PD FEB-MAR PY 1998 VL 46 IS 2-3 BP 191 EP 204 DI 10.1016/S0032-0633(96)00154-7 PG 14 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZN567 UT WOS:000073658800008 ER PT J AU Harris, AW AF Harris, AW TI Evaluation of ground-based optical surveys for near-Earth asteroids SO PLANETARY AND SPACE SCIENCE LA English DT Article; Proceedings Paper CT International Workshop Tunguska 96 CY JUL 15-17, 1996 CL BOLOGNA, ITALY SP Univ Bologna, Dept Phys, Univ Bologna, Commiss Int Relat, Alessandro Volta Ctr Sci Culture, Emilia Romagna Reg Govt, Giorgio Abetti Astron Observ, Int Sci Fdn, Landau Network Coordinat Ctr, Luigi Negro Fdn, Russian Fdn Basic Res AB Near-Earth asteroids (NEAs) pose a long-term hazard to the Earth and its inhabitants as a result of impacts, such as the Tunguska event of 1908, and especially from still larger, although even less frequent events. An evaluation is presented of the ability of ground-based telescope systems to inventory the population of NEAs, as a function of telescope parameters, NEA size and albedo, and duration of the survey. The optimum strategy for surveying appears to be to cover the entire visible sky every month, rather than covering a smaller area of sky to a fainter threshold of detection. An optimally designed and operated system consisting of two or three 1 m telescopes should be able to achieve similar to 75% completeness of survey down to a size of 1 km diameter, in 10 years of operation. To achieve a completeness >90% in the same time would require several telescopes of 2-3m aperture. Achieving near-completeness down to the size of the smallest NEAs capable of causing significant ground damage (similar to 70m diameter) on a timescale of 10 years appears impractical with present technology, however because of the long timescale of events, even present or soon-to-start surveys are likely to discover the next Earth-impacting body before it hits. (C) 1998 Elsevier Science Ltd. All rights reserved. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Harris, AW (reprint author), CALTECH, Jet Prop Lab, MS 183-501, Pasadena, CA 91109 USA. NR 6 TC 17 Z9 17 U1 1 U2 4 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0032-0633 J9 PLANET SPACE SCI JI Planet Space Sci. PD FEB-MAR PY 1998 VL 46 IS 2-3 BP 283 EP 290 DI 10.1016/S0032-0633(97)00036-6 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZN567 UT WOS:000073658800017 ER PT J AU Jacobson, NS Fox, DS Opila, EJ AF Jacobson, NS Fox, DS Opila, EJ TI High temperature oxidation of ceramic matrix composites SO PURE AND APPLIED CHEMISTRY LA English DT Article; Proceedings Paper CT 20th IUPAC Symposium on the Chemistry of Natural Products CY SEP 15-20, 1996 CL CHICAGO, IL SP IUPAC ID CRYSTAL SILICON-CARBIDE; ENVIRONMENTS; CORROSION; POTASSIUM; COATINGS; KINETICS; MULLITE; SODIUM; VAPOR; PHASE AB Ceramic matrix composites are developmental high temperature materials. We focus on composites with SiC matrices, SiC fibers, and BN fiber coatings. High temperature oxidation/corrosion reactions are discussed for each of these constituents. SiC forms a highly protective SiO(2) scale in pure oxygen, but problems arise in complex gas mixtures. These include: SiO(g) formation, Si-O-H(g) formation, impurity enhanced SiO(2) formation, and fluxing of SiO(2 )in molten salts and slags. Refractory oxide coatings may minimize these effects. The major issue with these composites is oxidation of the BN fiber coating. The key reactions here are borosilicate glass formation, potential gettering of oxygen by SiC, and volatilization. We conclude with an oxidation study of an actual composite, which illustrates some of these effects. C1 NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. Cleveland State Univ, NASA Lewis, Cleveland, OH 44115 USA. RP Jacobson, NS (reprint author), NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. RI Jacobson, Nathan/A-9411-2009 NR 24 TC 16 Z9 16 U1 0 U2 8 PU INT UNION PURE APPLIED CHEMISTRY PI RES TRIANGLE PK PA 104 TW ALEXANDER DR, PO BOX 13757, RES TRIANGLE PK, NC 27709-3757 USA SN 0033-4545 J9 PURE APPL CHEM JI Pure Appl. Chem. PD FEB PY 1998 VL 70 IS 2 BP 493 EP 500 DI 10.1351/pac199870020493 PG 8 WC Chemistry, Multidisciplinary SC Chemistry GA ZU823 UT WOS:000074238800045 ER PT J AU Ganapol, BD Johnson, LF Hammer, PD Hlavka, CA Peterson, DL AF Ganapol, BD Johnson, LF Hammer, PD Hlavka, CA Peterson, DL TI LEAFMOD: A new within-leaf radiative transfer model SO REMOTE SENSING OF ENVIRONMENT LA English DT Article ID REFLECTANCE; CANOPY; INDEX AB We describe the construction and verification of a within-leaf radiative transfer model called LEAFMOD (Leaf Experimental Absorptivity Feasibility MODel). In the model, the one-dimensional radiative transfer equation in a slab of leaf material with homogeneous optical properties is solved. When run in the forward mode, LEAFMOD generates an estimate of leaf reflectance and transmittance given the leaf thickness and optical characteristics of the leaf material (i.e., the absorption and scattering coefficients). In the inverse mode, LEAFMOD computes the total within-leaf absorption and scattering coefficient profiles from measured reflectance, transmittance,and leaf thickness. Inversions with simulated data demonstrate that the model appropriately decouples scattering and adsorption within the leaf, producing fresh leaf absorption profiles with peaks at locations corresponding to the major absorption feature for water and chlorophyll. Experiments with empirical input data demonstrate that the amplitude of the fresh leaf absorption coefficient profile in the visible wavebands is correlated with pigment concentrations as determined by wet chemical analyses,and that absorption features in the near-infrared wavebands related to various other biochemical constituents can be identified in a dry-leaf absorption profile. (C) Elsevier Science Inc., 1998. C1 Univ Arizona, Dept Aerosp & Mech Engn, Tucson, AZ 85721 USA. Univ Arizona, Dept Hydrol & Water Resources, Tucson, AZ 85721 USA. NASA, Ecosyst Sci & Technol Branch, Ames Res Ctr, Moffett Field, CA USA. Calif State Univ, Inst Earth Syst Sci & Policy, Monterey Bay, CA USA. RP Ganapol, BD (reprint author), Univ Arizona, Dept Aerosp & Mech Engn, Tucson, AZ 85721 USA. NR 32 TC 60 Z9 66 U1 2 U2 17 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 FEB PY 1998 VL 63 IS 2 BP 182 EP 193 DI 10.1016/S0034-4257(97)00134-X PG 12 WC Environmental Sciences; Remote Sensing; Imaging Science & Photographic Technology SC Environmental Sciences & Ecology; Remote Sensing; Imaging Science & Photographic Technology GA YM346 UT WOS:000071054400009 ER PT J AU Bindschadler, R AF Bindschadler, R TI Monitoring ice sheet behavior from space SO REVIEWS OF GEOPHYSICS LA English DT Review ID SATELLITE RADAR INTERFEROMETRY; SSM/I BRIGHTNESS TEMPERATURES; WEST ANTARCTICA; STREAM-C; PASSIVE MICROWAVE; ALTIMETER RETURN; GREENLAND SUMMIT; SURFACE; TOPOGRAPHY; IMAGERY AB Satellite remote sensing has revolutionized ice sheet research. A variety of instruments sensitive to different parts of the electromagnetic spectrum take what the human eye detects as a flat, white desert and provide data sets rich in scientific information. Image-based maps of ice sheets are becoming commonplace and have become an integral component of field work. More than a pretty picture, the digital character of the satellite data from these instruments has become fundamental to the production of elevation, motion, accumulation, and reflectance data sets. Visible imagery shows the scientist a wealth of features that offer clues to the history and current behavior of the ice sheet. Radar and microwave Imagery provide information from beneath the surface and have been used to estimate snow accumulation rates. Interferometry principles have recently been applied to measure surface topography and ice motion with unparalleled precision. Nonimaging instruments also keep a watchful eye, monitoring the ice sheet for indications of growth or shrinkage. Further expansion of the uses of satellite data is anticipated in the future. C1 NASA, Goddard Space Flight Ctr, Oceans & Ice Branch, Lab Hydrospher Sci, Greenbelt, MD 20771 USA. RP Bindschadler, R (reprint author), NASA, Goddard Space Flight Ctr, Oceans & Ice Branch, Lab Hydrospher Sci, Code 971, Greenbelt, MD 20771 USA. EM bob@igloo.gsfc.nasa.gov NR 86 TC 50 Z9 52 U1 1 U2 7 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 8755-1209 J9 REV GEOPHYS JI Rev. Geophys. PD FEB PY 1998 VL 36 IS 1 BP 79 EP 104 DI 10.1029/97RG02669 PG 26 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA YW045 UT WOS:000071890100003 ER PT J AU Davis-Lunde, K Rudolph, DK Miller, RL Estess, RS AF Davis-Lunde, K Rudolph, DK Miller, RL Estess, RS TI MERMAID Optics System SO SEA TECHNOLOGY LA English DT Article C1 USN, Opt Program, Stennis Space Ctr, MS 39529 USA. USN, Oceanog Off, Stennis Space Ctr, MS 39529 USA. NASA, Earth Syst Sci Off, Stennis Space Ctr, MS USA. RP Davis-Lunde, K (reprint author), USN, Opt Program, Stennis Space Ctr, MS 39529 USA. NR 3 TC 0 Z9 0 U1 0 U2 0 PU COMPASS PUBL INC PI ARLINGTON PA SUITE 1000 1117 N 19 ST, ARLINGTON, VA 22209 USA SN 0093-3651 J9 SEA TECHNOL JI Sea Technol. PD FEB PY 1998 VL 39 IS 2 BP 10 EP + PG 6 WC Engineering, Ocean SC Engineering GA YZ655 UT WOS:000072276800002 ER PT J AU Alexandrov, NM Dennis, JE Lewis, RM Torczon, V AF Alexandrov, NM Dennis, JE Lewis, RM Torczon, V TI A trust-region framework for managing the use of approximation models in optimization SO STRUCTURAL OPTIMIZATION LA English DT Article ID STRUCTURAL SYNTHESIS; DESIGN AB This paper presents an analytically robust, globally convergent approach to managing the use of approximation models of varying fidelity in optimization. By robust global behaviour we mean the mathematical assurance that the iterates produced by the optimization algorithm, started at an arbitrary initial iterate, will converge to a stationary point or local optimizer for the original problem. The approach presented is based on the trust region idea from nonlinear programming and is shown to be provably convergent to a solution of the original high-fidelity problem. The proposed method for managing approximations in engineering optimization suggests ways to decide when the fidelity, and thus the cost, of the approximations might be fruitfully increased or decreased in the course of the optimization iterations. The approach is quite general. We make no assumptions on the structure of the original problem, in particular, no assumptions of convexity and separability, and place only mild requirements on the approximations. The approximations used in the framework can be of any nature appropriate to an application; for instance, they can be represented by analyses, simulations, or simple algebraic models. This paper introduces the approach and outlines the convergence analysis. C1 NASA, Langley Res Ctr, Multidisciplinary Optimizat Branch, Hampton, VA 23681 USA. RP Alexandrov, NM (reprint author), NASA, Langley Res Ctr, Multidisciplinary Optimizat Branch, MS 159, Hampton, VA 23681 USA. RI UF, MDO/G-8720-2012; Dennis, John/A-6910-2008 NR 30 TC 237 Z9 247 U1 0 U2 23 PU SPRINGER PI NEW YORK PA 233 SPRING ST, NEW YORK, NY 10013 USA SN 0934-4373 J9 STRUCT OPTIMIZATION JI Struct. Optim. PD FEB PY 1998 VL 15 IS 1 BP 16 EP 23 DI 10.1007/BF01197433 PG 8 WC Computer Science, Interdisciplinary Applications; Engineering, Multidisciplinary; Mechanics SC Computer Science; Engineering; Mechanics GA YY412 UT WOS:000072144000003 ER PT J AU Alterovitz, SA Johs, B AF Alterovitz, SA Johs, B TI Multiple minima in the ellipsometric error function SO THIN SOLID FILMS LA English DT Article; Proceedings Paper CT 2nd International Conference on Spectroscopic Ellipsometry (ICSE-2) CY MAY 12-15, 1997 CL CHARLESTON, SOUTH CAROLINA DE spectroscopic ellipsometry; multiple minima; dielectric films ID ANGLE SPECTROSCOPIC ELLIPSOMETRY; LAYERS AB A study of the multiple minima problem was performed for a simple case using simulations. The test case was static (usually ex-situ) spectroscopic ellipsometry of thick dielectric films on crystalline silicon substrates taken at high sensitivity conditions near the s-wave antireflection angle-of-incidence (AOI). Analysis of the data was performed using the Levenberg-Marquardt algorithm with the unbiased tan Psi and cos Delta estimator. A large number of minima were observed on both sides of the main minimum, albeit with larger values of the error function. Moreover, data simulated at additional AOIs and/or at additional wavelengths showed an even higher number of minima. Three ways to overcome this problem are suggested: using another estimator, reducing the sensitivity of the data or performing a grid search. (C) 1998 Elsevier Science S.A. C1 NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. JA Woollam Co, Lincoln, NE 68508 USA. RP Alterovitz, SA (reprint author), NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. NR 14 TC 14 Z9 15 U1 1 U2 1 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 FEB PY 1998 VL 313 BP 124 EP 127 DI 10.1016/S0040-6090(97)00784-0 PG 4 WC Materials Science, Multidisciplinary; Materials Science, Coatings & Films; Physics, Applied; Physics, Condensed Matter SC Materials Science; Physics GA ZP520 UT WOS:000073761700021 ER PT J AU Tiwald, TE Thompson, DW Woollam, JA Pepper, SV AF Tiwald, TE Thompson, DW Woollam, JA Pepper, SV TI Determination of the mid-IR optical constants of water and lubricants using IR ellipsometry combined with an ATR cell SO THIN SOLID FILMS LA English DT Article; Proceedings Paper CT 2nd International Conference on Spectroscopic Ellipsometry (ICSE-2) CY MAY 12-15, 1997 CL CHARLESTON, SOUTH CAROLINA DE infrared ellipsometry; Attenuated Total Reflection; lubricants; water AB The mid-IR bulk optical constants for the lubricants Fomblin, Demnum S200, 2001A and Krytox 16256N, as well as water, are determined by infrared ellipsometric analysis using an Attenuated Total Reflection (ATR) cell. The water optical constants closely match those found in other studies. In addition, the real and imaginary parts of the dielectric functions for all the fluids are self-consistent under Kramers-Kronig transformation. (C) 1998 Elsevier Science S.A. C1 Univ Nebraska, Ctr Microelect & Opt Mat Res, Lincoln, NE 68588 USA. Univ Nebraska, Dept Elect Engn, Lincoln, NE 68588 USA. NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. RP Tiwald, TE (reprint author), Univ Nebraska, Ctr Microelect & Opt Mat Res, Lincoln, NE 68588 USA. EM ttiwald@unlgrad1.unl.edu NR 11 TC 27 Z9 27 U1 0 U2 4 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 FEB PY 1998 VL 313 BP 718 EP 721 DI 10.1016/S0040-6090(97)00984-X PG 4 WC Materials Science, Multidisciplinary; Materials Science, Coatings & Films; Physics, Applied; Physics, Condensed Matter SC Materials Science; Physics GA ZP520 UT WOS:000073761700131 ER PT J AU Evans, DM Huang, D McClure, JC Nunes, AC AF Evans, DM Huang, D McClure, JC Nunes, AC TI Arc efficiency of plasma arc welding SO WELDING JOURNAL LA English DT Article AB Are efficiency was measured for variable polarity plasma are welds on 6061 aluminum. It was found to vary from 0.48 to 0.66 and increased with are voltage but decreased with are current. The current and voltage dependence of the various mechanisms for heat transfer from the are to a workpiece are critically examined. Calculations show that radiation from the optically thin are contributes little to the transferred energy, but that heating of the shield gas by convection from the are gas is a significant component of workpiece heating. Experimental values are compared to theory and show approximate agreement. C1 Univ Texas, Dept Met & Mat Engn, El Paso, TX 79968 USA. NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. RP Evans, DM (reprint author), Univ Texas, Dept Met & Mat Engn, El Paso, TX 79968 USA. NR 16 TC 7 Z9 8 U1 0 U2 1 PU AMER WELDING SOC PI MIAMI PA PO BOX 351040, MIAMI, FL 33135 USA SN 0043-2296 J9 WELD J JI Weld. J. PD FEB PY 1998 VL 77 IS 2 BP 53S EP 58S PG 6 WC Metallurgy & Metallurgical Engineering SC Metallurgy & Metallurgical Engineering GA YV874 UT WOS:000071872200020 ER PT J AU Karpinsky, OG Shelimova, LE Kretova, MA Fleurial, JP AF Karpinsky, OG Shelimova, LE Kretova, MA Fleurial, JP TI X-ray study of the nGeTe center dot mBi(2)Te(3) mixed layered tetradymite-like compounds SO JOURNAL OF ALLOYS AND COMPOUNDS LA English DT Article DE X-ray diffraction; crystal structure; germanium; bismuth; tellurium ID HOMOLOGOUS SERIES; PROGRAM SYSTEM AB Single crystals and powders of the ternary mixed layered compounds Ge3Bi2Te6 (phase A), GeBi2Te4 (phase B) and GeBi4Te7 (phase C) have been investigated by X-ray diffraction analysis. The dependencies of the a and c/N parameters of the hexagonal lattices (N is the number of layers per unit cell) on the cation-to-anion ratio for the ternary phases and the GeTe and Bi2Te3 binary compounds have been analyzed. These dependencies were considered to be very close to linear. Based on those results, the lattice parameters were also calculated for other members of the (GeTe)(n)(Bi2Te3)(m) homologous series in the quasi-binary GeTe-Bi2Te3 system for which experimental data were not reported. The GeBi2Te4 and Ge1.5Bi3.5Te5 (D) crystal structures were determined using an automatic diffractometer "Syntex P (1) over bar". Results indicated that Ge and Bi atoms are statistically distributed in octahedral interstices to form mixed-cation layers. In addition to the observed disorder in the cation sublattice, anti-structure defects were also discovered in these compounds. (C) 1998 Elsevier Science S.A. C1 AA Baikov Met Inst, Moscow 117911, Russia. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Shelimova, LE (reprint author), AA Baikov Met Inst, Leninskii Prospect 49, Moscow 117911, Russia. NR 24 TC 27 Z9 27 U1 1 U2 12 PU ELSEVIER SCIENCE SA PI LAUSANNE PA PO BOX 564, 1001 LAUSANNE, SWITZERLAND SN 0925-8388 J9 J ALLOY COMPD JI J. Alloy. Compd. PD JAN 30 PY 1998 VL 265 IS 1-2 BP 170 EP 175 DI 10.1016/S0925-8388(97)00294-6 PG 6 WC Chemistry, Physical; Materials Science, Multidisciplinary; Metallurgy & Metallurgical Engineering SC Chemistry; Materials Science; Metallurgy & Metallurgical Engineering GA ZA255 UT WOS:000072344900029 ER PT J AU Lakshmi, V Wood, EF AF Lakshmi, V Wood, EF TI Diurnal cycles of evaporation using a two-layer hydrological model SO JOURNAL OF HYDROLOGY LA English DT Article DE diurnal cycles; evaporation; two-layer model ID WATER; SOIL; VEGETATION; MOISTURE AB The objective of this paper is to study the variation of evaporation in time and space. A two-layer model for solving energy and water balance is presented. The vertical soil column between the soil surface and the water table is divided into the root zone and the transmission zone. The variable infiltration capacity (VIC) concept is used to introduce a spatially varied distribution of soil moisture in the root zone layer, The soil moisture is distributed uniformly in space in the transmission zone layer. The model is used to simulate the fluxes for the King's Creek catchment in Manhattan, Kansas for a period between June through October 1987 (for the four intensive field campaigns), during which the first ISLSCP (International Satelite Land Surface Climatology Project) field experiment (FIFE) was conducted, The model is calibrated using the observed data during the first intensive field campaign (IFC) and validated over the next three IFCS, The energy and water balance equations are solved to vield the time series of fluxes which are compared to their observed counterparts. The model predicted diurnal variation of the evaporative fluxes and the variation of the fluxes after rainfall events is compared with the observations. The model computed fluxes match fairly well with the observed fluxes. (C) 1998 Elsevier Science B.V. C1 NASA, Goddard Space Flight Ctr, Gen Sci Corp, Greenbelt, MD 20771 USA. Princeton Univ, Dept Civil Engn & Operat Res, Water Resources Program, Princeton, NJ 08544 USA. RP Lakshmi, V (reprint author), NASA, Goddard Space Flight Ctr, Gen Sci Corp, Code 910-4, Greenbelt, MD 20771 USA. RI Lakshmi, Venkat/I-3078-2016; OI Lakshmi, Venkat/0000-0001-7431-9004; Wood, Eric/0000-0001-7037-9675 NR 18 TC 10 Z9 10 U1 1 U2 8 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0022-1694 J9 J HYDROL JI J. Hydrol. PD JAN 30 PY 1998 VL 204 IS 1-4 BP 37 EP 51 DI 10.1016/S0022-1694(97)00108-X PG 15 WC Engineering, Civil; Geosciences, Multidisciplinary; Water Resources SC Engineering; Geology; Water Resources GA YZ756 UT WOS:000072288500003 ER PT J AU Bindschadler, R Vornberger, P AF Bindschadler, R Vornberger, P TI Changes in the West Antarctic ice sheet since 1963 from declassified satellite photography SO SCIENCE LA English DT Article ID STREAM-C; STAGNATION AB Comparison of declassified satellite photography taken in 1963 with more recent satellite imagery reveals that large changes have occurred in the region where an active ice stream enters the Ross Ice Shelf. Ice stream B has widened by 4 kilometers, at a rate much faster than suggested by models, and has decreased in speed by 50 percent. The ice ridge between ice streams B and C has eroded 14 kilometers. These changes, along with changes in the crevassing around Crary Ice Rise, imply that this region's velocity field shifted during this century. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Gen Sci Corp, Laurel, MD 20727 USA. RP Bindschadler, R (reprint author), NASA, Goddard Space Flight Ctr, Code 971, Greenbelt, MD 20771 USA. NR 16 TC 84 Z9 85 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 JAN 30 PY 1998 VL 279 IS 5351 BP 689 EP 692 DI 10.1126/science.279.5351.689 PG 4 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA YU574 UT WOS:000071731500032 ER PT J AU Thorn, RP Monks, PS Stief, LJ Kuo, SC Zhang, ZY Ross, SK Klemm, RB AF Thorn, RP Monks, PS Stief, LJ Kuo, SC Zhang, ZY Ross, SK Klemm, RB TI Photoionization-efficiency spectrum and ionization energy of the cyanomethyl radical CH2CN and products of the N(S-4)+C2H3 reaction SO JOURNAL OF PHYSICAL CHEMISTRY A LA English DT Article ID GAS-PHASE REACTIONS; RATE-CONSTANT; PHOTOELECTRON-SPECTRA; REACTION CHANNELS; ACETONITRILE; THERMOCHEMISTRY; KINETICS; NITROGEN; DIOXIDE; ATOMS AB Photoionization efficiency (PIE) spectra of the CH2CN radical were measured over the wavelength range lambda = 115-130 nm using a discharge-flow-photoionization mass spectrometer coupled to a dispersed synchrotron-radiation source. The cyanomethyl radical was produced by the reaction F + CH3CN --> CH2CN + HF, and the PIE spectrum displayed steplike behavior near threshold, From the half-rise point of the initial step, a value of 10.28(0) +/- 0.01(0) eV was obtained for the adiabatic ionization energy (IE) of CH2CN based on five independent determinations. From a single measurement of the PIE spectrum and threshold for CD2CN, we obtain IE(CD2CN) = 10.24 eV. The experimental result for CH2CN is compared with previous measurements, estimates, and calculations. The present PIMS study of the CH2CN radical provides experimental measurements of the adiabatic ionization energy that are simultaneously the most direct and the must precise available. For the reaction N(S-4) + C2H3, the C2H2N radical product exhibits a PIE spectrum that may include CH2CN along with another species that has a gradual threshold that is at a considerably longer wavelength than the steplike threshold of CH2CN (derived from F + CH3CN). A possible source of this difference is the contribution from higher-energy C2H2N isomers and/or from excited CH2CN, In sharp contrast to the results for the N(S-4) + C2H3 reaction, no signal attributable to an isomer of the C2D2N radical was observed from the N(S-4) + C2H3 reaction, The C2H3N/C2D3N adducts from the N(S-4) + C2H3/C2D3 reactions were also studied. The adduct was observed to be solely CH3CN for the N(S-4) + C2H3 reaction, while for N(S-4) + C2D3, the PIE spectrum appears to include significant contributions from both the lowest-energy isomer CD3CN and one or more higher-energy isomers. C1 NASA, Goddard Space Flight Ctr, Extraterr Phys Lab, Greenbelt, MD 20771 USA. Brookhaven Natl Lab, Upton, NY 11973 USA. RP Klemm, RB (reprint author), NASA, Goddard Space Flight Ctr, Extraterr Phys Lab, Code 690, Greenbelt, MD 20771 USA. RI Monks, Paul/H-6468-2016 OI Monks, Paul/0000-0001-9984-4390 NR 25 TC 22 Z9 22 U1 0 U2 3 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 JAN 29 PY 1998 VL 102 IS 5 BP 846 EP 851 DI 10.1021/jp973164j PG 6 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA YV452 UT WOS:000071825600007 ER PT J AU Ricca, A Bauschlicher, CW AF Ricca, A Bauschlicher, CW TI Accurate heats of formation for SiF(n) and SiF(n)(+), for n=1-4 SO JOURNAL OF PHYSICAL CHEMISTRY A LA English DT Article ID GAUSSIAN-BASIS SETS; QUADRATIC CONFIGURATION-INTERACTION; CORRELATED MOLECULAR CALCULATIONS; DENSITY-FUNCTIONAL THEORY; WAVE-FUNCTIONS; ORBITAL METHODS; MOLLER-PLESSET; HARTREE-FOCK; THERMOCHEMISTRY; ENERGIES AB Accurate beats of formation are computed for SiF(n) and SIF(n)(+), for n = 1 - 4. The vibrational frequencies are determined at the B3LYP level of theory. The energetics are determined at the CCSD(T) level of theory. Basis set limit values an obtained by extrapolation; In those cases where the CCSD(T) calculations become prohibitively large, the basis set extrapolation is performed at the MP2 level, The temperature dependence of the hear of formation, heat capacity, and entropy are computed for the temperature range 300-4000 It and fit to a polynomial. The CCSD(T) bond energies are compared with those obtained at the B3LYP, MP2, G2, and G2MP2 levels of theory. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Bauschlicher, CW (reprint author), NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. NR 37 TC 35 Z9 35 U1 0 U2 1 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 JAN 29 PY 1998 VL 102 IS 5 BP 876 EP 880 DI 10.1021/jp973202z PG 5 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA YV452 UT WOS:000071825600011 ER PT J AU Mesbahi, M AF Mesbahi, M TI On the rank minimization problem and its control applications SO SYSTEMS & CONTROL LETTERS LA English DT Article DE rank minimization under LMI constraints; semi-definite programming; reduced-order output feedback synthesis AB We present several new results on the rank minimization problem over sets which are defined by linear matrix inequalities. We proceed to apply some of these results to propose a computational procedure for determining lower and upper bounds for the minimal-order dynamic output feedback which stabilizes a given linear time-invariant plant. (C) 1998 Elsevier Science B.V. All rights reserved. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Mesbahi, M (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 11 TC 35 Z9 35 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 JAN 29 PY 1998 VL 33 IS 1 BP 31 EP 36 DI 10.1016/S0167-6911(97)00111-4 PG 6 WC Automation & Control Systems; Operations Research & Management Science SC Automation & Control Systems; Operations Research & Management Science GA YX212 UT WOS:000072017600005 ER PT J AU Mishchenko, M Macke, A AF Mishchenko, M Macke, A TI Incorporation of physical optics effects and computation of the Legendre expansion for ray-tracing phase functions involving delta-function transmission SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID LIGHT-SCATTERING; RADIATIVE-TRANSFER; ICE CRYSTALS; T-MATRIX; NONSPHERICAL PARTICLES; SINGLE-SCATTERING; APPROXIMATION AB The standard geometric optics (GO) technique predicts that the phase function for large nonspherical particles with parallel plane facets (e.g., hexagonal ice crystals) should have an infinitesimally narrow delta-function transmission peak caused by rays twice transmitted(refracted) in exactly the forward scattering direction. However, exact T-matrix computations and physical considerations based on the Kirchhoff approximation suggest that this peak is an artifact of GO completely ignoring physical optics effects and must be convolved with the Fraunhofer pattern, thereby producing a phase function component with an angular profile similar to the standard diffraction component. This convolution can be performed with a simple procedure which supplements the standard ray-tracing code and makes the computation of the phase function and its Legendre expansion both more physically realistic and more accurate. C1 NASA, Goddard Inst Space Studies, New York, NY 10025 USA. Inst Meereskunde, Abt Maritime Meteorol, D-24105 Kiel, Germany. RP Mishchenko, M (reprint author), NASA, Goddard Inst Space Studies, 2880 Broadway, New York, NY 10025 USA. EM crmim@giss.nasa.gov; amacke@ifm.uni-kiel.de RI Mishchenko, Michael/D-4426-2012 NR 27 TC 32 Z9 32 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 JAN 27 PY 1998 VL 103 IS D2 BP 1799 EP 1805 DI 10.1029/97JD03121 PG 7 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA YU776 UT WOS:000071753000005 ER PT J AU Nagel, D Herber, A Thomason, LW Leiterer, U AF Nagel, D Herber, A Thomason, LW Leiterer, U TI Vertical distribution of the spectral aerosol optical depth in the Arctic from 1993 to 1996 SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID STRATOSPHERIC AEROSOL; HAZE; PINATUBO; SPITSBERGEN; PHOTOMETER; ATMOSPHERE; CLOUD AB During the period from summer 1993 to spring 1996, 51 profiles of spectral aerosol optical depth were measured with airborne Sun photometers throughout the Arctic. This period was influenced by volcanic aerosols after the Pinatubo eruption and the removal of volcanic material from the stratosphere into the troposphere. By 1996, stratospheric aerosol concentration has decreased to pre-Pinatubo levels. Mean values of aerosol optical depth have changed during the period from 1993 to 1996 from 0.09 to 0.02 at 403 nm and from 0.065 to 0.01 at 1041 nm/1057 nm, respectively. Size spectra of stratospheric aerosol also show the influence of volcanic aerosols. A bimodal distribution was found with main radius modes at 0.1 mu m to 0.3 mu m and 0.75 mu m to 0.9 mu m The typical vertical distribution of tropospheric aerosols in the Arctic in this time period and inferred size spectra are presented. The seasonal change in the spectral aerosol optical depth with a minimum in summer and high values in spring is shown, as well as the high extinction and distinct layering of Arctic haze up into the free troposphere. Size spectra of Arctic haze also change with height and show, in addition to particles with radii smaller than 0.1 mu m, main radius modes between 0.1 mu m and 0.2 mu m and between 1 mu m and 2 mu m. Possible influence of tropospheric aerosols on the radiation balance is also discussed for the spring and summer season. While in summer the influence on the radiation balance of the very small amount of tropo-spheric aerosols is negligible, in spring, haze layers with high extinction can result in a slight warming. C1 Alfred Wegener Inst Polar & Marine Res, D-14473 Potsdam, Germany. Deutsch Wetterdienst, Meteorol Observ Lindenberg, D-15864 Lindenberg, Germany. NASA, Langley Res Ctr, Div Atmospher Sci, Hampton, VA 23665 USA. RP Nagel, D (reprint author), Alfred Wegener Inst Polar & Marine Res, Telegrafenberg A43, D-14473 Potsdam, Germany. EM dnagel@awi-potsdam.de; aherber@awi-potsdam.de OI Thomason, Larry/0000-0002-1902-0840 NR 37 TC 25 Z9 25 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 JAN 27 PY 1998 VL 103 IS D2 BP 1857 EP 1870 DI 10.1029/97JD02678 PG 14 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA YU776 UT WOS:000071753000010 ER PT J AU Zak, M AF Zak, M TI Incompatible stochastic processes and complex probabilities SO PHYSICS LETTERS A LA English DT Article AB The definition of conditional probabilities is based upon the existence of a joint probability, However, a reconstruction of the joint probability from given conditional probabilities imposes certain constraints upon the latter, so that if several conditional probabilities are chosen arbitrarily, the corresponding joint probability may not exist. Such an incompleteness in conditional probabilities can be eliminated by introducing complex probabilities. The physical meaning of the new mathematical formalism, as well as its relation to quantum probabilities, is discussed. (C) 1998 Elsevier Science B.V. 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 7 TC 7 Z9 7 U1 0 U2 0 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0375-9601 J9 PHYS LETT A JI Phys. Lett. A PD JAN 26 PY 1998 VL 238 IS 1 BP 1 EP 7 DI 10.1016/S0375-9601(97)00763-9 PG 7 WC Physics, Multidisciplinary SC Physics GA YY134 UT WOS:000072116700001 ER PT J AU Rubincam, DP AF Rubincam, DP TI Yarkovsky thermal drag on small asteroids and Mars-Earth delivery SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS LA English DT Article ID APPROACHING ASTEROIDS; IMPACT EJECTA; LAGEOS; METEORITES; RADIATION; EVOLUTION; SURFACE; ORIGIN; SIZE; BELT AB There is an optimal size for the delivery of small asteroids from Mars to the Earth by Yarkovsky thermal drag. Basaltic asteroids with radii of about 6 m take on the average 185 million years (Myr) for their semimajor axes to shrink by 0.52 AU, assuming circular orbits and ignoring planetary perturbations and collisions. All other sizes take longer. Bigger objects are slower because they are more massive, and smaller objects are slower because they are more isothermal. These results are based on treating the asteroids as spheres and solving the heat conduction equation using spherical Bessel functions. The small near-Earth asteroids show a concentration of sizes in the thermal drag range; thus some of them may come from Mars as survivors of gravitational mechanisms which eliminate them on the 10 Myr timescale. The possible role of thermal drag in Mars-Earth delivery will remain speculative until it is included in numerical integrations of the orbits of small asteroids. C1 NASA, Goddard Space Flight Ctr, Geodynam Branch, Terr Phys Lab, Greenbelt, MD 20771 USA. RP Rubincam, DP (reprint author), NASA, Goddard Space Flight Ctr, Geodynam Branch, Terr Phys Lab, Code 921, Greenbelt, MD 20771 USA. RI Rubincam, David/D-2918-2012 NR 31 TC 37 Z9 37 U1 1 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 JAN 25 PY 1998 VL 103 IS E1 BP 1725 EP 1732 DI 10.1029/97JE03034 PG 8 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA YU557 UT WOS:000071729800005 ER PT J AU Carr, MH Belton, MJS Chapman, CR Davies, AS Geissler, P Greenberg, R McEwen, AS Tufts, BR Greeley, R Sullivan, R Head, JW Pappalardo, RT Klaasen, KP Johnson, TV Kaufman, J Senske, D Moore, J Neukum, G Schubert, G Burns, JA Thomas, P Veverka, J AF Carr, MH Belton, MJS Chapman, CR Davies, AS Geissler, P Greenberg, R McEwen, AS Tufts, BR Greeley, R Sullivan, R Head, JW Pappalardo, RT Klaasen, KP Johnson, TV Kaufman, J Senske, D Moore, J Neukum, G Schubert, G Burns, JA Thomas, P Veverka, J TI Evidence for a subsurface ocean on Europa SO NATURE LA English DT Article ID GALILEAN SATELLITES; ICE SHELL AB Ground-based spectroscopy of Jupiter's moon Europa, combined with gravity data, suggests that the satellite has an icy crust roughly 150 km thick and a rocky interior(1-4). In addition, images obtained by the voyager spacecraft revealed that Europa's surface is crossed by numerous intersecting ridges and dark bands (called lineae) and is sparsely cratered, indicating that the terrain is probably significantly younger than that of Ganymede and Callisto(5). It has been suggested that Europa's thin outer ice shell might be separated from the moon's silicate interior by a liquid water layer, delayed or prevented from freezing by tidal heating(6-10); in this model, the lineae could be explained by repetitive tidal deformation of the outer ice shell(11-13). However, observational confirmation of a subsurface ocean was largely frustrated by the low resolution (>2 km per pixel) of the Voyager images(14). Here we present high-resolution (54 m per pixel) Galileo spacecraft images of Europa, in which we find evidence for mobile 'icebergs'. The detailed morphology of the terrain strongly supports the presence of liquid water at shallow depths below the surface, either today or at some time in the past. Moreover, lower-resolution observations of much larger regions suggest that the phenomena reported here are widespread. C1 US Geol Survey, Menlo Pk, CA 94025 USA. Natl Opt Astron Observ, Tucson, AZ 85719 USA. SW Res Inst, Boulder, CO 80302 USA. Rand Corp, Santa Monica, CA 90406 USA. Univ Arizona, Lunar & Planetary Lab, Tucson, AZ 85721 USA. Arizona State Univ, Dept Geol, Tempe, AZ 85287 USA. Cornell Univ, Ithaca, NY 14853 USA. Brown Univ, Dept Geol, Providence, RI 02912 USA. Jet Prop Lab, Pasadena, CA 91909 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. DLR, Inst Planetenerkundung, D-12489 Berlin, Germany. Univ Calif Los Angeles, Dept Earth & Space Sci, Los Angeles, CA 90095 USA. RP Carr, MH (reprint author), US Geol Survey, 345 Middlefield Rd, Menlo Pk, CA 94025 USA. EM carr@astmnl.wr.usgs.gov NR 24 TC 258 Z9 265 U1 15 U2 93 PU MACMILLAN MAGAZINES LTD PI LONDON PA PORTERS SOUTH, 4 CRINAN ST, LONDON, ENGLAND N1 9XW SN 0028-0836 J9 NATURE JI Nature PD JAN 22 PY 1998 VL 391 IS 6665 BP 363 EP 365 DI 10.1038/34857 PG 3 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA YT444 UT WOS:000071604200045 PM 9450749 ER PT J AU Pappalardo, RT Head, JW Greeley, R Sullivan, RJ Pilcher, C Schubert, G Moore, WB Carr, MH Moore, JM Belton, MJS Goldsby, DL AF Pappalardo, RT Head, JW Greeley, R Sullivan, RJ Pilcher, C Schubert, G Moore, WB Carr, MH Moore, JM Belton, MJS Goldsby, DL TI Geological evidence for solid-state convection in Europa's ice shell SO NATURE LA English DT Article ID SATELLITES; WATER AB The ice-rich surface of the jovian satellite Europa is sparsely cratered, suggesting that this moon might be geologically active today(1). Moreover, models of the satellite's interior indicate that tidal interactions with Jupiter might produce enough heat to maintain a subsurface liquid water layer(2-5). But the mechanisms of interior heat loss and resurfacing are currently unclear, as is the question of whether Europa has (or had at one time) a liquid water ocean(6,7). Here we report on the morphology and geological interpretation of distinct surface features-pits, domes and spots-discovered in high-resolution images of Europa obtained by the Galileo spacecraft. The features are interpreted as the surface manifestation of diapirs, relatively warm localized ice masses that have risen buoyantly through the subsurface. We find that the formation of the features can be explained by thermally induced solid-state convection within an ice shell, possibly overlying a liquid water layer. Our results are consistent with the possibility that Europa has a liquid water ocean beneath a surface layer of ice, but further tests and observations are needed to demonstrate this conclusively. C1 Brown Univ, Dept Geol Sci, Providence, RI 02912 USA. Arizona State Univ, Dept Geol, Tempe, AZ 85287 USA. NASA Headquarters, Washington, DC 20546 USA. Univ Calif Los Angeles, Inst Geophys & Planetary Phys, Dept Earth & Space Sci, Los Angeles, CA 90095 USA. US Geol Survey, Menlo Park, CA 94025 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Natl Opt Astron Observ, Tucson, AZ 85726 USA. RP Pappalardo, RT (reprint author), Brown Univ, Dept Geol Sci, Providence, RI 02912 USA. NR 29 TC 203 Z9 205 U1 1 U2 25 PU MACMILLAN MAGAZINES LTD PI LONDON PA PORTERS SOUTH, 4 CRINAN ST, LONDON, ENGLAND N1 9XW SN 0028-0836 J9 NATURE JI Nature PD JAN 22 PY 1998 VL 391 IS 6665 BP 365 EP 368 DI 10.1038/34862 PG 4 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA YT444 UT WOS:000071604200046 PM 9450750 ER PT J AU Sullivan, R Greeley, R Homan, K Klemaszewski, J Belton, MJS Carr, MH Chapman, CR Tufts, R Head, JW Pappalardo, R Moore, J Thomas, P AF Sullivan, R Greeley, R Homan, K Klemaszewski, J Belton, MJS Carr, MH Chapman, CR Tufts, R Head, JW Pappalardo, R Moore, J Thomas, P CA Galileo Imaging Team TI Episodic plate separation and fracture infill on the surface of Europa SO NATURE LA English DT Article AB Images obtained by the Voyager spacecraft revealed dark, wedge-shaped bands on Europa that were interpreted as evidence that surface plates, 50-100 km across, moved and rotated relative to each other(1). This implied that they may be mechanically decoupled from the interior by a layer of warm ice or Liquid water(2,3). Here we report similar features seen in higher resolution images (420 metres per pixel) obtained by the Galileo spacecraft that reveal new details of wedge-band formation. In particular, the interior of one dark band shows bilateral symmetry of parallel lineaments and pit complexes which indicates that plate separation occurred in discrete episodes from a central axis. The images also show that this style of tectonic activity involved plates < 10 km across. Although this tectonic style superficially resembles aspects of similar activity on Earth, such as sea-floor spreading and the formation of ice leads in polar seas, there are significant differences in the underlying physical mechanisms: the wedge-shaped bands on Europa most probably formed when lower material (ice or water) rose to fill the fractures that widened in response to regional surface stresses. C1 Cornell Univ, Ithaca, NY 14853 USA. Natl Opt Astron Observ, Tucson, AZ 85719 USA. US Geol Survey, Menlo Pk, CA 94025 USA. SW Res Inst, Boulder, CO 80302 USA. Univ Arizona, Lunar & Planetary Lab, Tucson, AZ 85721 USA. Brown Univ, Dept Geol Sci, Providence, RI 02912 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Arizona State Univ, Dept Geol, Tempe, AZ 85287 USA. RP Sullivan, R (reprint author), Cornell Univ, 308 Space Sci, Ithaca, NY 14853 USA. NR 13 TC 74 Z9 75 U1 2 U2 13 PU MACMILLAN MAGAZINES LTD PI LONDON PA PORTERS SOUTH, 4 CRINAN ST, LONDON, ENGLAND N1 9XW SN 0028-0836 J9 NATURE JI Nature PD JAN 22 PY 1998 VL 391 IS 6665 BP 371 EP 373 DI 10.1038/34874 PG 3 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA YT444 UT WOS:000071604200048 PM 9450752 ER PT J AU Forbes, DA Grillmair, CJ Williger, GM Elson, RAW Brodie, JP AF Forbes, DA Grillmair, CJ Williger, GM Elson, RAW Brodie, JP TI HST imaging of the globular clusters in the Fornax cluster: NGC 1399 and NGC 1404 SO MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY LA English DT Article DE galaxies, clusters, individual, Fornax; galaxies, elliptical and lenticular, cD; galaxies, individual, NGC 1399; galaxies, individual, NGC 1404; galaxies, interactions; galaxies, star clusters ID ELLIPTICAL GALAXIES; LOCAL GROUP; SYSTEM; NGC-1399; PHOTOMETRY; NGC-1404; MATTER; M87 AB The Fornax cluster galaxies NGC 1399 and NGC 1404 are ideal for studying the effects of a cluster environment on globular cluster systems. Here we present new optical imaging of these two galaxies from both the Hubble Space Telescope's Wide Field and Planetary Camera 2 and the Cerro Tololo Inter-American Observatory 1.5-m telescope. The combination of both data sets provides a unique insight on the spatial and colour distribution of globular clusters. From B - I colours, we find that both galaxies have a broad globular cluster metallicity distribution that is inconsistent with a single population. Two Gaussians provide a reasonable representation of the metallicity distribution in each galaxy. The metal-rich subpopulation is more centrally concentrated than the metal-poor one. We show that the radial metallicity gradient can be explained by the changing relative mix of the two globular cluster subpopulations. We derive globular cluster surface density profiles, and find that they are flatter (i.e., more extended) than the underlying starlight. The total number of globular clusters and specific frequency are calculated to be N = 5700 +/- 500, S-N = 11.5 +/- 1.0 for NGC 1399, and N = 725 +/- 145, S-N = 2.0 +/- 0.5 for NGC 1404. Our results are compared with the expectations of globular cluster formation scenarios. C1 Univ Birmingham, Sch Phys & Astron, Birmingham B15 2TT, W Midlands, England. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. MPIA, D-69117 Heidelberg, Germany. NOAO, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Cambridge, Inst Astron, Cambridge CB3 0HA, England. Univ Calif Santa Cruz, Lick Observ, Santa Cruz, CA 95064 USA. RP Forbes, DA (reprint author), Univ Birmingham, Sch Phys & Astron, Birmingham B15 2TT, W Midlands, England. NR 39 TC 58 Z9 58 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 JAN 21 PY 1998 VL 293 IS 3 BP 325 EP 336 DI 10.1046/j.1365-8711.1998.01202.x PG 12 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YU939 UT WOS:000071771800015 ER PT J AU Agrawal, AK Butuk, NK Gollahalli, SR Griffin, D AF Agrawal, AK Butuk, NK Gollahalli, SR Griffin, D TI Three-dimensional rainbow schlieren tomography of a temperature field in gas flows SO APPLIED OPTICS LA English DT Article ID OPTICAL TOMOGRAPHY; MOIRE DEFLECTOMETRY AB We present quantitative rainbow schlieren deflectometry with tomography for measurements of temperature in three-dimensional gas flows. The schlieren apparatus with a continuously graded spectral filter of known transmissivity was used to create color schlieren images of the test media. These images at multiple viewing angles were used to infer beam deflection angles by the medium. The deflection data were used with a tomographic technique to reconstruct the refractive index and thus the temperature field. The temperature distributions obtained by the rainbow schlieren tomography agreed with those measured by a thermocouple probe. This research demonstrates that tomography can be used with full-field schlieren deflectometry to measure quantitatively temperature in asymmetric gas flows. The technique could be used to obtain related properties such as pressure, density, and gas composition. (C) 1998 Optical Society of America. C1 Univ Oklahoma, Sch Aerosp & Mech Engn, Norman, OK 73019 USA. NASA, Lewis Res Ctr, Micrograv Fluid Phys Branch, 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 21 TC 45 Z9 49 U1 2 U2 8 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 JAN 20 PY 1998 VL 37 IS 3 BP 479 EP 485 DI 10.1364/AO.37.000479 PG 7 WC Optics SC Optics GA YR499 UT WOS:000071501400012 PM 18268610 ER PT J AU Bumba, V Garcia, A Jordan, S AF Bumba, V Garcia, A Jordan, S TI Interpreting the growth and destruction of a large long-duration solar active-region complex SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE Sun : magnetic field; Sun : activity; Sun : coronal hole; Sun : flares ID MAGNETIC-FIELDS; ROTATION AB In a companion paper, we show that the large limb flare and coronal mass ejection of July 9, 1982, and other energetic events that followed through September 4, 1982, represent the final phase in the evolution of a large active-region complex (Jordan et al. 1997). In this paper, we review the long-duration evolution of this complex. We begin by showing that, before its final phase, new activity in the form of renewed flux continued to appear for nearly two years, progressively complicating the field topology. Observations suggest that the source of this flux rotated almost as a rigid body. Evidence is presented that, during the final phase of large-scale eruptions, either the connection with the underlying source of flux is broken, or the source itself has changed. After the flare and CME of September 4, 1982, the magnetic field topology of the entire complex was greatly simplified, and the area of former activity was replaced by a large coronal hole. We conclude that this evolution and destruction of a large long-duration active-region complex is a characteristic feature of how the global magnetic field of the Sun changes during the solar cycle. C1 Acad Sci Czech Republic, Inst Astron, CR-25165 Ondrejov, Czech Republic. Univ Coimbra, Astron Observ, P-3040 Coimbra, Portugal. NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, Greenbelt, MD 20771 USA. RP Bumba, V (reprint author), Acad Sci Czech Republic, Inst Astron, CR-25165 Ondrejov, Czech Republic. NR 15 TC 6 Z9 7 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 JAN 20 PY 1998 VL 329 IS 3 BP 1138 EP 1144 PG 7 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YT767 UT WOS:000071643000041 ER PT J AU Roettiger, K Stone, JM Mushotzky, RF AF Roettiger, K Stone, JM Mushotzky, RF TI Anatomy of a mercer: A numerical model of A754 SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies, clusters, individual (A754); galaxies, intergalactic medium; hydrodynamics; methods, numerical; X-rays, galaxies ID X-RAY-CLUSTERS; GALAXY CLUSTERS; WAVELET ANALYSIS; COOLING FLOWS; GAS; SUBSTRUCTURE; SIMULATIONS; ABELL-754; TEMPERATURE; EVOLUTION AB A754 is a well-observed cluster of galaxies (z = 0.054) that exhibits a variety of morphological peculiarities. These include a bar of X-ray emission that is offset significantly from the galaxy distribution, an elongated X-ray surface brightness distribution extending between two distinct peaks in the galaxy distribution, and an extremely nonisothermal and asymmetric intracluster medium temperature morphology. Using these observational constraints, we present a numerical hydro/N-body model of A754 in which two clusters (2.5:1 mass ratio) have merged nearly in the plane of the sky less than 0.5 Gyr ago with an impact parameter of similar to 120 kpc and an impact velocity of similar to 2500 km s(-1) (roughly the escape velocity of the primary cluster). Our models allow us to identify the origin of A754's peculiar X-ray and temperature morphologies, the underlying hydrodynamical processes that shape them, and their future evolution. We make detailed predictions for future high-resolution X-ray spectroscopic observations (e.g., Astro-E). We discuss general properties of our models that will be characteristic of off-axis mergers. In particular, we find significant nonthermal pressure support within the central region that could bias cluster mass estimates. We find significant angular momentum imparted on the gas distribution in the cluster. We find that mixing of the subcluster gas components is an inefficient process, particularly at large radii. Finally, we find that subsequent dark matter-core passages result in an extended relaxation timescale. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Maryland, Dept Astron, College Pk, MD 20742 USA. RP Roettiger, K (reprint author), NASA, Goddard Space Flight Ctr, Code 930, Greenbelt, MD 20771 USA. NR 53 TC 77 Z9 77 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 JAN 20 PY 1998 VL 493 IS 1 BP 62 EP + DI 10.1086/305102 PN 1 PG 14 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YV314 UT WOS:000071810800007 ER PT J AU Turner, TJ George, IM Nandra, K Mushotzky, RF AF Turner, TJ George, IM Nandra, K Mushotzky, RF TI ASCA observations of type 2 Seyfert galaxies. III. Orientation and X-ray absorption SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies, active; galaxies, nuclei; galaxies, Seyfert; X-rays, galaxies ID ACTIVE GALACTIC NUCLEI; BROAD-LINE REGIONS; IONIZING-RADIATION; UNIFIED MODEL; BLACK-HOLE; NGC-1068; DISK; SPECTROPOLARIMETRY; EMISSION; QUASARS AB We discuss the spectral properties of a sample of type 2 Seyfert galaxies based upon the analysis of ASCA data. In this paper, we consider the sources for which the X-ray spectra appear to be dominated by the nuclear continuum, transmitted through a large column of absorbing material. We find that both Seyfert 2 galaxies and narrow emission line galaxies (NELGs) show iron Ka line profiles indicative of reprocessing of nuclear X-rays in a face-on accretion disk. Such line profiles are also observed in Seyfert 1 galaxies. This result is contrary to unification models, which would predict the inner regions of transmitted Seyfert 2 galaxies to be observed edge-on. This raises some questions as to the orientation of the circumnuclear absorber. If the observed differences between Seyfert 1 and 2 galaxies and NELGs are not due to differences in the orientation of the absorbing material, then we suggest that differences in dust composition and grain size, and in the density of the circumnuclear gas, could be of primary importance. C1 NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. RP Turner, TJ (reprint author), NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Code 660, Greenbelt, MD 20771 USA. NR 62 TC 59 Z9 59 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 JAN 20 PY 1998 VL 493 IS 1 BP 91 EP 101 DI 10.1086/305117 PN 1 PG 11 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YV314 UT WOS:000071810800010 ER PT J AU Sahai, R Trauger, JT Watson, AM Stapelfeldt, KR Hester, JJ Burrows, CJ Ballister, GE Clarke, JT Crisp, D Evans, RW Gallagher, JS Griffiths, RE Hoessel, JG Holtzman, JA Mould, JR Scowen, PA Westphal, JA AF Sahai, R Trauger, JT Watson, AM Stapelfeldt, KR Hester, JJ Burrows, CJ Ballister, GE Clarke, JT Crisp, D Evans, RW Gallagher, JS Griffiths, RE Hoessel, JG Holtzman, JA Mould, JR Scowen, PA Westphal, JA TI Imaging of the Egg Nebula (CRL 2688) with WFPC2/HST: A history of age/post-AGB giant branch mass loss SO ASTROPHYSICAL JOURNAL LA English DT Article DE ISM, individual (CRL 2688); ISM, jets and outflows; ISM, structure; reflection nebulae; stars, AGB and post-AGB; stars, mass loss ID RED GIANTS; CRL-2688; DUST; SUBMILLIMETER; EMISSION; STARS; AFGL-2688; ENVELOPE; WINDS; GAS AB The proto-planetary nebula, CRL 2688, has been imaged through a wideband filter centered at 606 nm (F606W) with the Wide Field Planetary Camera 2 onboard the Hubble Space Telescope. CRL 2688 is the prototypical bipolar reflection nebula in which a star is surrounded by a dense, flattened cocoon of dust seen nearly edge-on and starlight escapes preferentially along the polar directions producing a pair of bright nebulosities, one above and one below the equatorial plane. We find a pair of radial "searchlight beams" emerging from within the dusty cocoon which intersect at the position expected for the central star when extrapolated inside the cocoon. The beams are crisscrossed by a large number of roughly round arcs with their center of curvature in the vicinity of the central star. The arcs are not systematically elongated along the polar axis of the nebula, as would be expected in the current model of CRL 2688 where the nebular density decreases with latitude. Our image directly shows the last similar to 13,000 yr history of mass ejection from the central star while it was on the tip of the asymptotic giant branch (AGE). We find that the average surface brightness varies as r(-3.7), implying that the average mass-loss rate or the scattering opacity of the dust grains varies as r(-0.7), i.e., one or both of these parameters have steadily increased with time. The temporal resolution of approximate to 25 yr in our images has provided direct evidence for episodic increases in the mass-loss rate by factors of similar to 2 or more, occurring every 150-450 yr, and lasting over periods of 75-200 yr. These irregularities in the mass-loss rate are roughly spherically symmetric. We have resolved the edges of the searchlight beams, as well as the peculiar structure of the inner region of the nebula (1."5 < radius < 6"). Our data require a new model for CRL 2688 in which the beams result from starlight escaping through a pair of nonuniform annular holes in the dust cocoon which are coaxial with the polar axis of the nebula. The holes have probably been generated by a young (less than 200 yr) high-velocity outflow which streams out through these holes and interacts with the surrounding dense AGE wind to produce the peculiar structure of the inner nebula. The cocoon contains dust grains of size about 0.6 mu m, significantly larger than those in the extended nebula. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Lowell Observ, Flagstaff, AZ 86001 USA. Arizona State Univ, Dept Phys & Astron, Tempe, AZ 85287 USA. Space Telescope Sci Inst, Baltimore, MD 21218 USA. Univ Michigan, Dept Atmospher Ocean & Space Sci, Ann Arbor, MI 48109 USA. Univ Wisconsin, Dept Astron, Madison, WI 53706 USA. Carnegie Mellon Univ, Dept Phys, Pittsburgh, PA 15213 USA. Australian Natl Univ, Mt Stromlo & Siding Spring Observ, Weston, ACT 2611, Australia. CALTECH, Div Geol & Planetary Sci, Pasadena, CA 91125 USA. RP Sahai, R (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. RI Stapelfeldt, Karl/D-2721-2012; Clarke, John/C-8644-2013 NR 41 TC 183 Z9 183 U1 0 U2 4 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 JAN 20 PY 1998 VL 493 IS 1 BP 301 EP + DI 10.1086/305121 PN 1 PG 14 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YV314 UT WOS:000071810800026 ER PT J AU Aptekar, RL Butterworth, PS Cline, TL Frederiks, DD Golenetskii, SV Il'Inskii, VN Mazets, EP Stilwell, DE Terekhov, MM AF Aptekar, RL Butterworth, PS Cline, TL Frederiks, DD Golenetskii, SV Il'Inskii, VN Mazets, EP Stilwell, DE Terekhov, MM TI Hard X-ray bursts from GRO J1744-28. I. Observations by the Konus-Wind and Konus-A experiments SO ASTROPHYSICAL JOURNAL LA English DT Article DE stars, individual (GRO J1744-28); stars, neutron; X-rays, bursts; X-rays, stars ID TRANSIENT AB Observations of hard X-ray bursts from GRO J1744-28 by the Konus-Wind and Konus-A experiments, including the characteristics of the burst light curve and energy spectra, are reported. Observed burst rates display onset, plateau, and decay periods. The average burst strength increases to its highest values by January 20 and then declines. However, an analysis of the burst rate, if corrected for the missed weaker events, shows that the mean time interval between bursts is evidently constant, (T) over bar similar to 29.6 minutes, for the whole period of observation from 1995 December 18 to 1996 March 15. C1 AF Ioffe Phys Tech Inst, St Petersburg 194021, Russia. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Aptekar, RL (reprint author), AF Ioffe Phys Tech Inst, Politekhnicheskaya 26, St Petersburg 194021, Russia. RI Frederiks, Dmitry/C-7612-2014; Aptekar, Raphail/B-3456-2015; Golenetskii, Sergey/B-3818-2015 NR 10 TC 7 Z9 7 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 JAN 20 PY 1998 VL 493 IS 1 BP 404 EP 407 DI 10.1086/305100 PN 1 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YV314 UT WOS:000071810800034 ER PT J AU Aptekar, RL Butterworth, PS Cline, TL Frederiks, DD Golenetskii, SV Il'Inskii, VN Mazets, EP Stilwell, DE Terekhov, MM AF Aptekar, RL Butterworth, PS Cline, TL Frederiks, DD Golenetskii, SV Il'Inskii, VN Mazets, EP Stilwell, DE Terekhov, MM TI Hard X-ray bursts from GRO J1744-28. II. Statistical studies SO ASTROPHYSICAL JOURNAL LA English DT Article DE stars, individual (GRO J1744-28); stars, neutron; X-rays, bursts; X-rays, stars ID TRANSIENT AB Statistical studies of the hard X-ray bursts from GRO J1744-28 observed by the Konus-Wind and Konus-A experiments are presented. It is shown that during the whole period of outburst activity, the intervals of time between successive bursts form a stochastic Markov sequence that is characterized by both the constancy of the mean interval and the existence of a weak negative correlation between two successive intervals. A weak correlation between burst strength and the adjacent intervals is also indicated. C1 AF Ioffe Phys Tech Inst, St Petersburg 194021, Russia. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Aptekar, RL (reprint author), AF Ioffe Phys Tech Inst, Politekhnicheskaya 26, St Petersburg 194021, Russia. RI Frederiks, Dmitry/C-7612-2014; Aptekar, Raphail/B-3456-2015; Golenetskii, Sergey/B-3818-2015 NR 5 TC 1 Z9 1 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5801 S ELLIS AVENUE, CHICAGO, IL 60637 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD JAN 20 PY 1998 VL 493 IS 1 BP 408 EP 411 DI 10.1086/305101 PN 1 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YV314 UT WOS:000071810800035 ER PT J AU Cannizzo, JK AF Cannizzo, JK TI On the M-v(peak) versus orbital period relation for dwarf nova outbursts SO ASTROPHYSICAL JOURNAL LA English DT Article DE accretion, accretion disks; instabilities; novae, cataclysmic variables; stars, individual (SS Cygni) ID X-RAY BINARIES; CATACLYSMIC VARIABLES; ACCRETION DISKS; MODEL; MAGNITUDES; EVOLUTION; DECAY AB We present computations for the accretion disk limit cycle model in an attempt to explain the empirical relation for dwarf nova outbursts between the peak visual absolute magnitude and orbital period found by Warner. For longer period systems one sees intrinsically brighter outbursts. This is accounted for in the limit cycle model by the scaling with radius of the critical surface density Sigma(max) that triggers the dwarf nova outbursts. During the storage phase of the instability, the accretion disk mass must be less than some maximum value, a value that scales with radius and therefore with orbital period. When the instability is triggered and the accumulated mass is redistributed into a quasi-steady state disk in outburst, the resultant peak optical flux from the disk is a measure of the total mass that was stored in quiescence. We compute light curves for a range in outer disk radius (or equivalently, orbital period), and find that our peak values of M-V are within less than 1 mag of the observed relation M-V(peak) = 5.64 - 0.259P(orbital) for 2 less than or similar to P-orbital less than or similar to 8, where P-orbital is in hours. C1 NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. RP Cannizzo, JK (reprint author), NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Code 662, Greenbelt, MD 20771 USA. NR 26 TC 35 Z9 35 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 JAN 20 PY 1998 VL 493 IS 1 BP 426 EP 430 DI 10.1086/305123 PN 1 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YV314 UT WOS:000071810800037 ER PT J AU Gibson, SE Low, BC AF Gibson, SE Low, BC TI A time-dependent three-dimensional magnetohydrodynamic model of the coronal mass ejection SO ASTROPHYSICAL JOURNAL LA English DT Article DE MHD; Sun, corona; Sun, particle emission ID FREE MAGNETIC-FIELDS; SELF-SIMILAR MAGNETOHYDRODYNAMICS; SOLAR MINIMUM CORONA; EQUILIBRIUM; PROMINENCE; TRANSIENTS; FLARES; DISRUPTION; ATMOSPHERE; EVOLUTION AB We present a theoretical magnetohydrodynamic (MHD) model describing the time-dependent expulsion of a three-dimensional coronal mass ejection (CME) out of the solar corona. The model relates the white-light appearance of the CME to its internal magnetic field, which takes the form of a closed bubble, filled with a partly anchored, twisted magnetic flux rope, and embedded in an otherwise open background held. The model is constructed by solving in closed form the time-dependent ideal MHD equations for a gamma = 4/3 polytrope making use of a similarity assumption and the application of a mathematical stretching transformation in order to treat a complex field geometry with three-dimensional variations. The density distribution frozen into the expanding CME magnetic field is obtained. The scattered white light integrated along the line of sight shows the conspicuous three features often associated with CMEs as observed with white-light coronagraphs: a surrounding high-density region, an internal low-density cavity, and a high-density core. We also show how the orientation of this three-dimensional structure relative to the line of sight can give rise to a variety of different geometric appearances in white light. These images generated from a CME model in a realistic geometry offer an opportunity to directly compare theoretical predictions on CME shapes with observations of CMEs in white light. The mathematical methods used in the model construction have general application and are described in the Appendices. C1 Natl Ctr Atmospher Res, High Altitude Observ, Boulder, CO 80307 USA. RP NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, Greenbelt, MD 20771 USA. RI Gibson, Sarah/A-9189-2011 NR 55 TC 186 Z9 187 U1 1 U2 4 PU IOP PUBLISHING LTD PI BRISTOL PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND SN 0004-637X EI 1538-4357 J9 ASTROPHYS J JI Astrophys. J. PD JAN 20 PY 1998 VL 493 IS 1 BP 460 EP 473 DI 10.1086/305107 PN 1 PG 14 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YV314 UT WOS:000071810800041 ER PT J AU Ofman, L Klimchuk, JA Davila, JM AF Ofman, L Klimchuk, JA Davila, JM TI A self-consistent model for the resonant heating of coronal loops: The effects of coupling with the chromosphere SO ASTROPHYSICAL JOURNAL LA English DT Article DE MHD; Sun, chromosphere; Sun, corona; Sun, magnetic fields; waves ID ALFVEN WAVES; SCALING LAWS; RESISTIVE MHD; ACTIVE-REGION; SOLAR CORONA; GLOBAL MODE; ABSORPTION; DRIVEN; EFFICIENCY; LINES AB We present the first model of resonant heating of coronal loops that incorporates the dependence of the loop density on the heating rate. By adopting the quasi-static equilibrium scaling law rho proportional to Q(5/7), where rho is the density and Q is the volumetric heating rate, we are able to approximate the well-known phenomena of chromospheric evaporation and chromospheric condensation, which regulate the coronal density. We combine this scaling law with a quasi-nonlinear MHD model for the resonant absorption of Alfven waves in order to study the spatial and temporal dependence of the heating. We find that the heating is concentrated in multiple resonance layers, rather than in the single layer of previous models, and that these layers drift throughout the loop to heat the entire volume. These newfound properties are in much better agreement with coronal observations. C1 Hughes STX, Greenbelt, MD 20771 USA. NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, Greenbelt, MD 20771 USA. USN, Res Lab, EO Hulburt Ctr Space Res, Washington, DC 20375 USA. RP Ofman, L (reprint author), Hughes STX, Code 682, Greenbelt, MD 20771 USA. RI Klimchuk, James/D-1041-2012 OI Klimchuk, James/0000-0003-2255-0305 NR 37 TC 64 Z9 64 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 JAN 20 PY 1998 VL 493 IS 1 BP 474 EP 479 DI 10.1086/305109 PN 1 PG 6 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YV314 UT WOS:000071810800042 ER PT J AU Groot, PJ Galama, TJ van Paradijs, J Kouveliotou, C Wijers, RAMJ Bloom, J Tanvir, N Vanderspek, R Greiner, J Castro-Tirado, AJ Gorosabel, J von Hippel, T Lehnert, M Kuijken, K Hoekstra, H Metcalfe, N Howk, C Conselice, C Telting, J Rutten, RGM Rhoads, J Cole, A Pisano, DJ Naber, R Schwarz, R AF Groot, PJ Galama, TJ van Paradijs, J Kouveliotou, C Wijers, RAMJ Bloom, J Tanvir, N Vanderspek, R Greiner, J Castro-Tirado, AJ Gorosabel, J von Hippel, T Lehnert, M Kuijken, K Hoekstra, H Metcalfe, N Howk, C Conselice, C Telting, J Rutten, RGM Rhoads, J Cole, A Pisano, DJ Naber, R Schwarz, R TI A search for optical afterglow from GRB 970828 SO ASTROPHYSICAL JOURNAL LA English DT Article DE dust, extinction; galaxies, general; gamma rays, bursts; gamma rays, observations radiation; mechanisms, nonthermal ID GAMMA-RAY BURSTS; PHOTOMETRY; EXTINCTION; ABSORPTION AB We report on the results of R-band observations of the error box of the gamma-ray burst of 1997 August 28 made between 4 hr and 8 days after this burst occurred. No counterpart was found varying by more than 0.2 mag down to R = 23.8. We discuss the consequences of this nondetection for relativistic blast wave models of gamma-ray bursts and the possible effect of redshift on the relation between optical absorption and the low-energy cutoff in the X-ray afterglow spectrum. C1 Univ Amsterdam, Astron Inst Anton Pannekoek, NL-1098 SJ Amsterdam, Netherlands. Ctr High Energy Astrophys, NL-1098 SJ Amsterdam, Netherlands. Univ Alabama, Dept Phys, Huntsville, AL 35899 USA. NASA, Univ Space Res Assoc, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. Univ Cambridge, Inst Astron, Cambridge CB3 0HA, England. CALTECH, Div Phys Math & Astron 105 24, Pasadena, CA 91125 USA. MIT, Ctr Space Res, Cambridge, MA 02139 USA. Astrophys Inst Postdam, Potsdam, Germany. INTA, Lab Astrofis Espacial & Fis Fundamental, E-28080 Madrid, Spain. Univ Wisconsin, Dept Astron, Madison, WI 53706 USA. Sterrewacht Leiden, NL-2300 RA Leiden, Netherlands. Kapteyn Astron Inst, NL-9700 AV Groningen, Netherlands. Univ Durham, Dept Phys, Durham, England. ING Telescopes NFRA, Tenerife 38780, Spain. Natl Opt Astron Observ, Tucson, AZ 85726 USA. RP Groot, PJ (reprint author), Univ Amsterdam, Astron Inst Anton Pannekoek, Kruislaan 403, NL-1098 SJ Amsterdam, Netherlands. RI Conselice, Christopher/B-4348-2013; Howk, Jay/D-2577-2013; 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; Howk, J. Christopher/0000-0002-2591-3792; Hoekstra, Henk/0000-0002-0641-3231 NR 41 TC 103 Z9 104 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 JAN 20 PY 1998 VL 493 IS 1 BP L27 EP L30 DI 10.1086/311125 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YV315 UT WOS:000071810900007 ER PT J AU Noor, AK Needleman, A Peters, JM AF Noor, AK Needleman, A Peters, JM TI Sensitivity analysis for failure and damage in dynamically loaded tensile bars SO COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING LA English DT Article; Proceedings Paper CT Interdisciplinary Symposium on Advances in Computational Mechanics in Honor of Professor John Tinsley Oden CY JAN 12-15, 1997 CL AUSTIN, TX ID DUCTILE FRACTURE; LOCALIZATION; SOLIDS; VOIDS AB A computational procedure is presented for evaluating the sensitivity coefficients of porous viscoplastic solids under dynamic loading conditions. The effects of finite strains, material strain and strain-rate hardening, and the thermal softening due to adiabatic heating are incorporated into the formulation. A critical void volume fraction criterion is used to identify the initiation of failure. The equations of motion emanating from a finite element semi-discretization are integrated using an explicit central difference scheme. First-and second-order sensitivity coefficients of the response quantities (derivatives with respect to various material parameters) are evaluated using a direct differentiation approach in conjunction with an automatic differentiation software facility. Numerical results are presented for tensile specimens subjected to impact loading. Both axisymmetric and plane strain states are considered. The first-and second-order sensitivity coefficients are generated by evaluating the derivatives of the response quantities with respect to various macroscopic and microscopic material parameters. Time histories of the response and sensitivity coefficients, and their spatial distributions at selected times are presented. C1 Univ Virginia, NASA, Langley Res Ctr, Ctr Adv Computat Technol, Hampton, VA 23681 USA. Brown Univ, Div Engn, Providence, RI 02912 USA. RP Noor, AK (reprint author), Univ Virginia, NASA, Langley Res Ctr, Ctr Adv Computat Technol, Hampton, VA 23681 USA. RI Needleman, Alan/A-1879-2008 OI Needleman, Alan/0000-0002-4697-4535 NR 18 TC 9 Z9 9 U1 0 U2 0 PU ELSEVIER SCIENCE SA PI LAUSANNE PA PO BOX 564, 1001 LAUSANNE, SWITZERLAND SN 0045-7825 EI 1879-2138 J9 COMPUT METHOD APPL M JI Comput. Meth. Appl. Mech. Eng. PD JAN 20 PY 1998 VL 151 IS 3-4 BP 461 EP 478 DI 10.1016/S0045-7825(97)00289-2 PG 18 WC Engineering, Multidisciplinary; Mathematics, Interdisciplinary Applications; Mechanics SC Engineering; Mathematics; Mechanics GA YP439 UT WOS:000071276900012 ER PT J AU Cardelino, BH Moore, CE Frazier, DO Musaev, DG Morokuma, K AF Cardelino, BH Moore, CE Frazier, DO Musaev, DG Morokuma, K TI Ab initio calculations on the diacetylene dimer: HCCCC(H)C(H)CCCH SO INTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY LA English DT Article DE diacetylene; dimer; C8H4; ab initio; DFT ID POLYDIACETYLENE FILMS; OPTICAL-PROPERTIES; THIN-FILMS; PHOTODEPOSITION; CRYSTALS; GROWTH; HYPERPOLARIZABILITIES; POLY(DIACETYLENES); POLYMERIZATION; SPECTROSCOPY AB Geometry optimizations were performed for singlet, triplet, and quintet states on the planar structures (in C-2h,, and C-2v, symmetries) of the diacetylene dimer, using restricted open-shell Hartree-Fock (ROHF), unrestricted Hartree-Fock (UHF), and unrestricted hybrid density functional theory (UB3LYP) methods, with 6-31G(d) and 6-311G(d, p) basis sets. The (1)A(g) state of the planar van der Waals dimer is lower in energy than are any covalently bonded dimers. At our best B3LYP/6-311G(d, p) level, the most stable covalently bonded diacetylene dimer is the B-3(u) State in C-2h, symmetry, 11 kcal mol(-1) above the van der Waals dimer, followed by the B-3(2) state in C-2v, symmetry with 13 kcal mol(-1) above the van der Waals dimer. Both structures were confirmed to be local minima. The two diacetylene monomers of these structures are bridged through a single bond and they exhibit a small bend at the neighboring carbons to the bridge, trans to the hydrogens. The B-1(u), and (5)A(g) states in C-2h,, and the B-1(2) and (5)A(1) states in C-2v are between 39 and 43 kcal mol(-1) above the van der Waals dimer. (C) 1998 John Wiley & Sons, Inc. C1 Spelman Coll, Dept Chem, Atlanta, GA 30314 USA. NASA, George C Marshall Space Flight Ctr, Space Sci Lab, Huntsville, AL 35812 USA. Emory Univ, Cherry L Emerson Ctr Sci Computat, Atlanta, GA 30322 USA. RP Cardelino, BH (reprint author), Spelman Coll, Dept Chem, Atlanta, GA 30314 USA. NR 41 TC 10 Z9 10 U1 0 U2 3 PU JOHN WILEY & SONS INC PI NEW YORK PA 605 THIRD AVE, NEW YORK, NY 10158-0012 USA SN 0020-7608 J9 INT J QUANTUM CHEM JI Int. J. Quantum Chem. PD JAN 20 PY 1998 VL 66 IS 3 BP 189 EP 202 DI 10.1002/(SICI)1097-461X(1998)66:3<189::AID-QUA1>3.3.CO;2-H PG 14 WC Chemistry, Physical; Mathematics, Interdisciplinary Applications; Physics, Atomic, Molecular & Chemical SC Chemistry; Mathematics; Physics GA YN134 UT WOS:000071136500001 ER PT J AU Dungan, J AF Dungan, J TI Spatial prediction of vegetation quantities using ground and image data SO INTERNATIONAL JOURNAL OF REMOTE SENSING LA English DT Article ID LEAF-AREA INDEX; LANDSAT THEMATIC MAPPER; REMOTELY SENSED DATA; SATELLITE DATA; MSS DATA; FOREST; MODEL; SIMULATION; GEOSTATISTICS; PHYTOMASS AB A major challenge in Earth system studies is mapping vegetation quantities over large regions. Aspatial regression is typically the empirical method applied to remotely sensed and ground data for the spatial prediction of vegetation variables. Geostatistical methods, such as cokriging and stochastic simulation, have rarely been used for this purpose. A synthetic example was constructed from imaging spectrometer data to allow an objective comparison between regression, cokriging and a new stochastic simulation method. A range of linear relations between ground sample data and image data was represented in the example. The lowest root-mean-square-error was achieved with cokriging until the correlation coefficient (r) between direct and ancillary data exceeded 0.89, at which point regression was the more accurate predictor. Probability-field simulation gave a range of possible realizations, overall less accurate than those from regression but more faithful to the histogram and spatial pattern of the variable to be predicted. The strength of the relation between ground measurements and image data was shown to be a critical factor in choosing a spatial prediction method. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Dungan, J (reprint author), NASA, Ames Res Ctr, JCWS MS 242-4, Moffett Field, CA 94035 USA. RI Dungan, Jennifer/G-9921-2016 OI Dungan, Jennifer/0000-0002-4863-1616 NR 54 TC 42 Z9 45 U1 0 U2 3 PU TAYLOR & FRANCIS LTD PI ABINGDON PA 4 PARK SQUARE, MILTON PARK, ABINGDON OX14 4RN, OXON, ENGLAND SN 0143-1161 J9 INT J REMOTE SENS JI Int. J. Remote Sens. PD JAN 20 PY 1998 VL 19 IS 2 BP 267 EP 285 DI 10.1080/014311698216242 PG 19 WC Remote Sensing; Imaging Science & Photographic Technology SC Remote Sensing; Imaging Science & Photographic Technology GA YW951 UT WOS:000071991100005 ER PT J AU Wamsley, PR Elkins, JW Fahey, DW Dutton, GS Volk, CM Myers, RC Montzka, SA Butler, JH Clarke, AD Fraser, PJ Steele, LP Lucarelli, MP Atlas, EL Schauffler, SM Blake, DR Rowland, FS Sturges, WT Lee, JM Penkett, SA Engel, A Stimpfle, RM Chan, KR Weisenstein, DK Ko, MKW Salawitch, RJ AF Wamsley, PR Elkins, JW Fahey, DW Dutton, GS Volk, CM Myers, RC Montzka, SA Butler, JH Clarke, AD Fraser, PJ Steele, LP Lucarelli, MP Atlas, EL Schauffler, SM Blake, DR Rowland, FS Sturges, WT Lee, JM Penkett, SA Engel, A Stimpfle, RM Chan, KR Weisenstein, DK Ko, MKW Salawitch, RJ TI Distribution of halon-1211 in the upper troposphere and lower stratosphere and the 1994 total bromine budget SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID IN-SITU MEASUREMENTS; NEAR-ULTRAVIOLET SPECTROSCOPY; ATMOSPHERIC CH3BR; MCMURDO STATION; ANTARCTIC OZONE; METHYL-BROMIDE; BRO; CHLORINE; AIR; RADICALS AB We report here on the details of the first, in situ, real-time measurements of H-1211 (CBrClF2) and sulfur hexafluoride (SF6) mixing ratios in the stratosphere up to 20 km. Stratospheric air was analyzed for these gases and others with a new gas chromatograph, flown aboard a National Aeronautics and Space Administration ER-2 aircraft as part of the Airborne Southern Hemisphere Ozone Experiment/Measurements for Assessing the Effects of Stratospheric Aircraft mission conducted in 1994. The mixing ratio of SF6, with its nearly linear increase in the troposphere, was used to estimate the mean age of stratospheric air parcels along the EK-2 flight path. Measurements of H-1211 and mean age estimates were then combined with simultaneous measurements of CFC-11 (CCl3F), measurements of brominated compounds in stratospheric whole air samples, and records of tropospheric organic bromine mixing ratios to calculate the dry mixing ratio of total bromine in the lower stratosphere and its partitioning between organic and inorganic forms. We estimate that the organic bromine-containing species were almost completely photolyzed to inorganic species in the oldest air parcels sampled. Our results for inorganic bromine are consistent with those obtained from a photochemical, steady state model for stratospheric air parcels with CFC-11 mixing ratios greater than 150 ppt. For stratospheric air parcels with CFC-11 mixing ratios less than 50 ppt (mean age greater than or equal to 5 years) we calculate inorganic bromine mixing ratios that are approximately 20% less than the photochemical, steady state model. There is a 20% reduction in calculated ozone loss resulting from bromine chemistry in old air relative to some previous estimates as a result of the lower bromine levels. C1 NOAA, Climate Monitoring & Diagnost Lab, Boulder, CO 80303 USA. Univ Calif Irvine, Dept Chem, Irvine, CA 92717 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. NOAA, Aeron Lab, Boulder, CO 80303 USA. Atmospher & Environm Res Inc, Cambridge, MA 02139 USA. Univ E Anglia, Sch Environm Sci, Norwich NR4 7TJ, Norfolk, England. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Harvard Univ, Dept Chem, Cambridge, MA 02138 USA. Univ Colorado, NOAA, Cooperat Inst Res Environm Sci, Boulder, CO 80309 USA. Monash Univ, Cooperat Res Ctr So Hemisphere Meteorol, Clayton, Vic 3168, Australia. CSIRO, Aspendale, Vic 3195, Australia. Forschungszentrum Julich, Inst Stratosphar Chem, Julich, Germany. Natl Ctr Atmospher Res, Boulder, CO 80307 USA. RP Wamsley, PR (reprint author), NOAA, Climate Monitoring & Diagnost Lab, Boulder, CO 80303 USA. EM paulaw@ophir.com; jelkins@cmdl.noaa.gov; dfahey@al.noaa.gov; m.volk@meteor.uni-frankfurt.de; jbutlter@cmdl.noaa.gov; pjf@atmos.dar.csiro.au; lps@atmos.dar.csiro.au; atlas@acd.ucar.edu; sues@acd.ucar.edu; dblake@onion.oac.uci.edu; rowland@uci.edu; w.sturges@uea.ac.uk; julial@ucar.edu; mpenkett@uea.ac.uk; An.Engel@meteor.uni-frankfurt.de; stimpfle@huarpl.harvard.edu; roland_chan@qmgate.arc.nasa.gov; weisenstein@aer.com; ko@aer.com; rjs@casear.jpl.gov RI Atlas, Elliot/J-8171-2015; Fahey, David/G-4499-2013; Steele, Paul/B-3185-2009; Salawitch, Ross/B-4605-2009; Engel, Andreas/E-3100-2014; Fraser, Paul/D-1755-2012; Ko, Malcolm/D-5898-2015 OI Fahey, David/0000-0003-1720-0634; Steele, Paul/0000-0002-8234-3730; Salawitch, Ross/0000-0001-8597-5832; Engel, Andreas/0000-0003-0557-3935; NR 72 TC 106 Z9 109 U1 0 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 JAN 20 PY 1998 VL 103 IS D1 BP 1513 EP 1526 DI 10.1029/97JD02466 PG 14 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA YR851 UT WOS:000071537300013 ER PT J AU Nair, H Allen, M Froidevaux, L Zurek, RW AF Nair, H Allen, M Froidevaux, L Zurek, RW TI Localized rapid ozone loss in the northern winter stratosphere: An analysis of UARS observations SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID ATMOSPHERE RESEARCH SATELLITE; MICROWAVE LIMB SOUNDER; NIMBUS-7 DATA; MODEL; PHOTOCHEMISTRY; MESOSPHERE; INSTRUMENT; VALIDATION; DEFICIT; SYSTEM AB Observations of low-ozone air pockets forming during northern winter in the middle stratosphere outside the polar vortex provide an opportunity to test models of the photochemistry of ozone at several altitudes, as the trajectories of the associated air parcels are well defined by Lagrangian transport codes over the periods of interest, and vertical profiles of key species, including ozone, are available from instruments aboard the Upper Atmosphere Research Satellite (UARS). We find that a Lagrangian photochemical model, where the chemistry within an isolated parcel of air is simulated as it travels along a specified trajectory, does reproduce the observed formation of low-ozone pockets in the 6-10 mbar altitude range within the measurement uncertainties but overestimates the ozone loss rate at higher altitudes. The rapid ozone loss localized in these pockets is due to the isolation of air at high latitudes (and high solar zenith angles). Thus the low ozone levels are due to a decrease in the odd oxygen production rate and not to an increase in the loss rate by reaction with halogen species, as in the "classical" ozone hole. C1 CALTECH, Div Geol & Planetary Sci, Pasadena, CA 91125 USA. CALTECH, Jet Prop Lab, Div Earth & Space Sci, Pasadena, CA 91109 USA. RP Nair, H (reprint author), Hughes Aircraft Co, Los Angeles, CA 90009 USA. EM han@mercu1.gps.caltech.edu; maa@mercu1.gps.caltech.edu; lu-cien@wilga.jpl.nasa.gov; rwz@rich.jpl.nasa.gov NR 42 TC 13 Z9 13 U1 0 U2 2 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD JAN 20 PY 1998 VL 103 IS D1 BP 1555 EP 1571 DI 10.1029/97JD03072 PG 17 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA YR851 UT WOS:000071537300016 ER PT J AU Considine, DB Dessler, AE Jackman, CH Rosenfield, JE Meade, PE Schoeberl, MR Roche, AE Waters, JW AF Considine, DB Dessler, AE Jackman, CH Rosenfield, JE Meade, PE Schoeberl, MR Roche, AE Waters, JW TI Interhemispheric asymmetry in the 1 mbar O-3 trend: An analysis using an interactive zonal mean model and UARS data SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID NIMBUS-7 SBUV; POLAR VORTEX; OZONE; STRATOSPHERE; VALIDATION AB Trends in O-3 calculated from solar backscattered ultraviolet (SBUV) observations near 1 mbar are more negative at high latitudes in the southern hemisphere than in the northern hemisphere [Hood et al., 1993]. A mechanism is presented that produces an interhemispheric O-3 trend asymmetry similar to the observed asymmetry in the Goddard Space Flight Center dynamically interactive zonal mean model. Upper Atmosphere Research Satellite (UARS) data. are then examined for evidence that the atmospheric trend asymmetry is produced by a similar mechanism. The model O-3 trend asymmetry is mainly due to interhemispheric differences in odd chlorine (Cl-y) partitioning. The asymmetry in Cl-y partitioning is caused primarily by lower amounts of CH4 and NO in the southern hemisphere than the northern hemisphere high latitudes, due to differences in the dynamical behavior of the model hemispheres. Symmetric increases in Cl-y are accompanied by a southern hemisphere increase in ClO that is larger than in the northern hemisphere. Concentrations of CH4 and N2O retrieved by the cryogenic limb array etalon spectrometer aboard UARS during 1992 are lower in the southern hemisphere fall and winter seasons at high latitudes in the upper stratosphere than in the northern hemisphere, favoring higher southern hemisphere ClO values. However, observations of ClO by the microwave limb sounder on UARS do not show consistently higher values in the southern hemisphere compared with the northern hemisphere in 1992, 1993, or 1994. The UARS data therefore do not confirm that a mechanism similar to the model mechanism occurs in the real atmosphere and is the cause of the SBUV O-3 trend asymmetry. C1 Univ Maryland, Dept Meteorol, Joint Ctr Earth Syst Sci, College Pk, MD 20742 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Lockheed Palo Alto Res Labs, Palo Alto, CA 94304 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Gen Sci Corp, Laurel, MD USA. Appl Res Corp, Landover, MD 20785 USA. RP Considine, DB (reprint author), Univ Maryland, Dept Meteorol, Joint Ctr Earth Syst Sci, College Pk, MD 20742 USA. EM dbc@welkin.gsfc.nasa.gov RI Jackman, Charles/D-4699-2012; Dessler, Andrew/G-8852-2012 OI Dessler, Andrew/0000-0003-3939-4820 NR 19 TC 7 Z9 7 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 JAN 20 PY 1998 VL 103 IS D1 BP 1607 EP 1618 DI 10.1029/97JD02363 PG 12 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA YR851 UT WOS:000071537300019 ER PT J AU Jefferson, A Tanner, DJ Eisele, FL Davis, DD Chen, G Crawford, J Huey, JW Torres, AL Berresheim, H AF Jefferson, A Tanner, DJ Eisele, FL Davis, DD Chen, G Crawford, J Huey, JW Torres, AL Berresheim, H TI OH photochemistry and methane sulfonic acid formation in the coastal Antarctic boundary layer SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID NITRIC-OXIDE MEASUREMENTS; MARINE AEROSOL; METHANESULFONIC-ACID; TROPOSPHERIC OH; SULFUR CYCLE; SULFATE; PACIFIC; COLORADO; SAGA-3; SOUTH AB Studies of dimethylsulfide (DMS) oxidation chemistry were conducted at Palmer Station on Anvers Island, Antarctica, during the austral summer of 1993/1994. Part of the study involved gas phase measurements of OH, methane sulfonic acid (MSA), and H2SO4 using a chemical ionization mass spectrometer, as well as measurements of the NO, CO, and O-3 concentrations, Mean 24 hour concentrations from February 16-23 of OH, MSA, and H2SO4 were 1.1 x 10(5), 9.5 x 10(5), and 1.61 x 10(6) molecules cm(-3), respectively. Model calculations of OH compared well with observed levels (e.g., within 30%). The modeling results suggest that the dominant source of OH is from the reaction of O(D-1) with H2O, where O(D-1) is the product of O-3 photolysis, Because of the clean atmospheric environment and predicted low nonmethyl hydrocarbon levels in Antarctica, the dominant OH sink was found to be reaction with CO and CH4. Particulate levels of MSA were higher than could be attributed to condensation of boundary layer (BL) gas phase MSA on to the aerosol surface. Alternate mechanisms for generating MSA in the particle phase were speculated to involve either in-cloud oxidation of dimethylsulfoxide or OH oxidation of DMS in the atmospheric buffer layer above the boundary layer followed by condensation of gas phase MSA on aerosols and transport back to the BL [Davis et al., this issue]. C1 Natl Ctr Atmospher Res, Div Atmospher Chem, Boulder, CO 80307 USA. Deutsch Wetterdienst, MOHp, D-82383 Hohenpeissenberg, Germany. Georgia Inst Technol, Atlanta, GA 30332 USA. US EPA, Air Div, Atlanta, GA 30303 USA. NASA, Goddard Space Flight Ctr, Wallops Isl, VA 23337 USA. RP Jefferson, A (reprint author), Natl Ctr Atmospher Res, Div Atmospher Chem, Boulder, CO 80307 USA. EM ajeff@acd.ucar.edu RI Berresheim, Harald/F-9670-2011; Jefferson, Anne/K-4793-2012; Crawford, James/L-6632-2013 OI Crawford, James/0000-0002-6982-0934 NR 49 TC 102 Z9 104 U1 1 U2 7 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD JAN 20 PY 1998 VL 103 IS D1 BP 1647 EP 1656 DI 10.1029/97JD02376 PG 10 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA YR851 UT WOS:000071537300023 ER PT J AU Rothermel, J Olivier, LD Banta, RM Hardesty, RM Howell, JN Cutten, DR Johnson, SC Menzies, RT Tratt, DM AF Rothermel, J Olivier, LD Banta, RM Hardesty, RM Howell, JN Cutten, DR Johnson, SC Menzies, RT Tratt, DM TI Remote sensing of multi-level wind fields with high-energy airborne scanning coherent Doppler lidar SO OPTICS EXPRESS LA English DT Article ID LASER-RADAR; BACKSCATTER; AEROSOL; WEATHER; SENSOR AB The atmospheric lidar remote sensing groups of NOAA Environmental Technology Laboratory, NASA Marshall Space Flight Center, and Jet Propulsion Laboratory have developed and flown a scanning, 1 Joule per pulse, CO2 coherent Doppler lidar capable of mapping a three-dimensional volume of atmospheric winds and aerosol backscatter in the planetary boundary layer, free troposphere, and lower stratosphere. Applications include the study of severe and non-severe atmospheric flows, intercomparisons with other sensors, and the simulation of prospective satellite Doppler lidar wind profilers. Examples of wind measurements are given for the marine boundary layer and near the coastline of the western United States. (C) 1997 Optical Society of America. C1 NASA, George C Marshall Space Flight Ctr, Global Hydrol & Climate Ctr, Huntsville, AL 35806 USA. NOAA, Environm Res Labs, Environm Technol Lab, Boulder, CO 80303 USA. Univ Alabama, Global Hydrol & Climate Ctr, Huntsville, AL 35806 USA. NASA, Astrion Lab, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Rothermel, J (reprint author), NASA, George C Marshall Space Flight Ctr, Global Hydrol & Climate Ctr, Huntsville, AL 35806 USA. EM jeffry.rothermel@msfc.nasa.gov RI Tratt, David/A-7884-2009; Hardesty, Robert/H-9844-2013; Banta, Robert/B-8361-2008 OI Tratt, David/0000-0002-3942-6848; NR 23 TC 8 Z9 12 U1 1 U2 7 PU OPTICAL SOC AMER PI WASHINGTON PA 2010 MASSACHUSETTS AVE NW, WASHINGTON, DC 20036 USA SN 1094-4087 J9 OPT EXPRESS JI Opt. Express PD JAN 19 PY 1998 VL 2 IS 2 BP 40 EP 50 PG 11 WC Optics SC Optics GA 121ZJ UT WOS:000076045700003 PM 19377577 ER PT J AU Bada, JL Glavin, DP McDonald, GD Becker, L AF Bada, JL Glavin, DP McDonald, GD Becker, L TI A search for endogenous amino acids in martian meteorite ALH84001 SO SCIENCE LA English DT Article ID MURCHISON METEORITE; GENERATION; HYDROLYSIS; MARS AB Trace amounts of glycine, serine, and alanine were detected in the carbonate component of the martian meteorite ALH84001 by high-performance liquid chromatography. The detected amino acids were not uniformly distributed in the carbonate component and ranged in concentration from 0.1 to 7 parts per million. Although the detected alanine consists primarily of the L enantiomer, low concentrations (<0.1 parts per million) of endogenous D-alanine may be present in the ALH84001 carbonates. The amino acids present in this sample of ALH84001 appear to be terrestrial in origin and similar to those in Allan Hills ice, although the possibility cannot be ruled out that minute amounts of some amino acids such as D-alanine are preserved in the meteorite. C1 Univ Calif San Diego, Scripps Inst Oceanog, La Jolla, CA 92093 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ Hawaii, Hawaii Inst Geophys & Planetol, Honolulu, HI 96822 USA. RP Bada, JL (reprint author), Univ Calif San Diego, Scripps Inst Oceanog, La Jolla, CA 92093 USA. EM jbada@ucsd.edu RI Glavin, Daniel/D-6194-2012 OI Glavin, Daniel/0000-0001-7779-7765 NR 38 TC 116 Z9 119 U1 0 U2 14 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 JAN 16 PY 1998 VL 279 IS 5349 BP 362 EP 365 DI 10.1126/science.279.5349.362 PG 4 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA YT158 UT WOS:000071570800041 PM 9430583 ER PT J AU Lacis, AA Chowdhary, J Mishchenko, MI Cairns, B AF Lacis, AA Chowdhary, J Mishchenko, MI Cairns, B TI Modeling errors in diffuse-sky radiation: Vector vs. scalar treatment SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID PLANETARY ATMOSPHERES; MULTIPLE-SCATTERING; FLUXES; LIGHT AB Radiative transfer calculations that utilize the scalar approximation of light produce intensity errors as large as 10% in the case of pure Rayleigh scattering. This modeling error, which arises primarily from second order scattering, is greatly reduced for flux and albedo results because of error cancellation brought about by integration over scattering angle. However, polarized light scattered from an underlying ocean surface, or from atmospheric aerosols, interacts with the pattern of Rayleigh scattered polarization to distort the error cancellation and thus incur larger flux and albedo errors. While addition of scattered radiation from clouds, aerosols or ground surface into the Rayleigh atmosphere tends to reduce the magnitude of scalar approximation intensity errors, the scalar errors in fluxes and albedos are not proportionately reduced, but are actually increased. C1 NASA, Goddard Inst Space Studies, New York, NY 10025 USA. Columbia Univ, New York, NY 10027 USA. SUNY Stony Brook, Stony Brook, NY 11794 USA. RP Lacis, AA (reprint author), NASA, Goddard Inst Space Studies, 2880 Broadway, New York, NY 10025 USA. RI Lacis, Andrew/D-4658-2012; Mishchenko, Michael/D-4426-2012; OI Cairns, Brian/0000-0002-1980-1022 NR 9 TC 67 Z9 70 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 JAN 15 PY 1998 VL 25 IS 2 BP 135 EP 138 DI 10.1029/97GL03613 PG 4 WC Geosciences, Multidisciplinary SC Geology GA YT257 UT WOS:000071581600001 ER PT J AU Oltmans, SJ Lefohn, AS Scheel, HE Harris, JM Levy, H Galbally, IE Brunke, EG Meyer, CP Lathrop, JA Johnson, BJ Shadwick, DS Cuevas, E Schmidlin, FJ Tarasick, DW Claude, H Kerr, JB Uchino, O Mohnen, V AF Oltmans, SJ Lefohn, AS Scheel, HE Harris, JM Levy, H Galbally, IE Brunke, EG Meyer, CP Lathrop, JA Johnson, BJ Shadwick, DS Cuevas, E Schmidlin, FJ Tarasick, DW Claude, H Kerr, JB Uchino, O Mohnen, V TI Trends of ozone in the troposphere SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article AB Using a set of selected surface ozone (nine stations) and ozone vertical profile measurements (from six stations), we have documented changes in tropospheric ozone at a number of locations. From two stations at high northern hemisphere (NH) latitudes there has been a significant decline in ozone amounts throughout the troposphere since the early 1980s. At midlatitudes of the NH where data are the most abundant, on the other hand, important regional differences prevail. The two stations in the eastern United States show that changes in ozone concentrations since the early 1970s have been relatively small. At the two sites in Europe, however, ozone amounts increased rapidly into the mid-1980s, but have increased less rapidly (or in some places not at all) since then. Increases at the Japanese ozonesonde station have been largest in the lower troposphere, but have slowed in the recent decade. The tropics are sparsely sampled but do not show significant changes. Small increases are suggested at southern hemisphere (SH) midlatitudes by the two surface data records. In Antarctica large declines in the ozone concentration are noted in the South Pole data, and like those at high latitudes of the NH, seem to parallel the large decreases in the stratosphere. C1 NOAA, Climate Monitoring & Diagnost Lab, Boulder, CO 80303 USA. ASL Associates, Helena, MT USA. IFU, Garmisch Partenkirchen, Germany. NOAA, ERL, Geophys Fluid Dynam Lab, Princeton, NJ USA. CSIRO, Aspendale, Vic, Australia. CSIR, Stellenbosch, South Africa. Univ Colorado, Cooperat Inst Res Environm Sci, Boulder, CO 80309 USA. Mantech Environm Technol Inc, Res Triangle Pk, NC 27709 USA. Izana Baseline Observ, Tenerife, Spain. NASA, Goddard Space Flight Ctr, Wallops Island, VA 23337 USA. Atmospher Environm Serv, Downsview, ON, Canada. Meteorol Observ, Hohenpeissenberg, Germany. Japan Meteorol Agcy, Tokyo, Japan. SUNY Albany, Albany, NY 12222 USA. RP Oltmans, SJ (reprint author), NOAA, Climate Monitoring & Diagnost Lab, Boulder, CO 80303 USA. RI Meyer, Carl/H-2311-2011; Garmisch-Pa, Ifu/H-9902-2014; Galbally, Ian/E-5852-2011; Cuevas, Emilio/L-2109-2013; OI Meyer, Carl/0000-0002-8062-3712; Galbally, Ian/0000-0003-2383-1360; Cuevas, Emilio/0000-0003-1843-8302; Tarasick, David/0000-0001-9869-0692 NR 15 TC 131 Z9 139 U1 2 U2 16 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 JAN 15 PY 1998 VL 25 IS 2 BP 139 EP 142 DI 10.1029/97GL03505 PG 4 WC Geosciences, Multidisciplinary SC Geology GA YT257 UT WOS:000071581600002 ER EF