FN Thomson Reuters Web of Science™ VR 1.0 PT S AU Lou, Y Kim, Y Edelstein, W Miller, T Romero, G Sato, T Skotnicki, W Tauch, S AF Lou, Y Kim, Y Edelstein, W Miller, T Romero, G Sato, T Skotnicki, W Tauch, S BE Mott, H Boerner, WM TI Current status of the NASA/JPL Airborne Synthetic Aperture Radar (AIRSAR) SO WIDEBAND INTERFEROMETRIC SENSING AND IMAGING POLARIMETRY SE PROCEEDINGS OF THE SOCIETY OF PHOTO-OPTICAL INSTRUMENTATION ENGINEERS (SPIE) LA English DT Proceedings Paper CT Conference on Wideband Interferometric Sensing and Imaging Polarimetry CY JUL 28-29, 1997 CL SAN DIEGO, CA SP Soc Photo Opt Instrumentat Engineers C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Lou, Y (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr,MS 300-243, Pasadena, CA 91109 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU SPIE-INT SOC OPTICAL ENGINEERING PI BELLINGHAM PA 1000 20TH ST, PO BOX 10, BELLINGHAM, WA 98227-0010 USA SN 0277-786X BN 0-8194-2542-7 J9 P SOC PHOTO-OPT INS PY 1997 VL 3120 BP 346 EP 350 DI 10.1117/12.300626 PG 5 WC Engineering, Electrical & Electronic; Remote Sensing; Optics SC Engineering; Remote Sensing; Optics GA BK25W UT WOS:000071632400030 ER PT B AU Cannizzo, JK AF Cannizzo, JK BE Howell, S Kuulkers, E Woodward, C TI Accretion disks in transient systems SO WILD STARS IN THE OLD WEST: PROCEEDINGS OF THE 13TH NORTH AMERICAN WORKSHOP ON CATACLYSMIC VARIABLES AND RELATED OBJECTS SE ASTRONOMICAL SOCIETY OF THE PACIFIC CONFERENCE SERIES LA English DT Proceedings Paper CT Wild Stars in the Old West - 13th North American Workshop on Cataclysmic Variables and Related Objects CY JUN 14-19, 1997 CL GRAND TETON NATL PARK, WY SP Univ Wyoming, Off Res, Univ Wyoming, Dept Phys & Astron, Astronom Soc Pacific AB I review recent advances in our understanding of accretion disks in transient systems - the dwarf novae and the soft X-ray transients. The primary theme will be the ongoing development of theory in response to the observations. The accretion disk limit cycle model appears to provide a unifying framework within which we may begin to understand what is seen in different types of interacting binary stars, and also to constrain parameters which enter into the theory. C1 NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Univ Space Res Assoc, Greenbelt, MD 20771 USA. RP Cannizzo, JK (reprint author), NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Univ Space Res Assoc, Greenbelt, MD 20771 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU ASTRONOMICAL SOC PACIFIC PI SAN FRANCISCO PA 390 ASHTON AVE, SAN FRANCISCO, CA 94112 USA BN 1-886733-57-0 J9 ASTR SOC P PY 1997 VL 137 BP 308 EP 322 PG 15 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA BL74M UT WOS:000076533800030 ER PT B AU Godon, P AF Godon, P BE Howell, S Kuulkers, E Woodward, C TI Edge modes and short period coherent oscillations in cataclysmic variables SO WILD STARS IN THE OLD WEST: PROCEEDINGS OF THE 13TH NORTH AMERICAN WORKSHOP ON CATACLYSMIC VARIABLES AND RELATED OBJECTS SE ASTRONOMICAL SOCIETY OF THE PACIFIC CONFERENCE SERIES LA English DT Proceedings Paper CT Wild Stars in the Old West - 13th North American Workshop on Cataclysmic Variables and Related Objects CY JUN 14-19, 1997 CL GRAND TETON NATL PARK, WY SP Univ Wyoming, Off Res, Univ Wyoming, Dept Phys & Astron, Astronom Soc Pacific AB The non-linear growth of non-axisymmetric instability in thin Keplerian discs is followed numerically, using a two-dimensional spectral code. The instability develops at the inner edge of the disc when it is reflective, corresponding to a rigid accreting white dwarf or neutron star. We assume alpha approximate to 0.1 and a Mach number M = upsilon(phi)/c(s) approximate to 40, and find that the m = 2 mode is the dominant one. Its high Q value (> 10(4)) and its period are characteristic of short period coherent oscillations observed in Cataclysmic Variables. In addition, the period of the mode decreases with increasing a, or equivalently with increasing mass accretion rate, and provides an explanation to the 'banana diagram' of the observed coherent oscillations in the period-intensity plane. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Godon, P (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU ASTRONOMICAL SOC PACIFIC PI SAN FRANCISCO PA 390 ASHTON AVE, SAN FRANCISCO, CA 94112 USA BN 1-886733-57-0 J9 ASTR SOC P PY 1997 VL 137 BP 515 EP 516 PG 2 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA BL74M UT WOS:000076533800093 ER PT B AU Mukai, K Ishida, M Osborne, J Rosen, S Stavroyiannopoulos, D AF Mukai, K Ishida, M Osborne, J Rosen, S Stavroyiannopoulos, D BE Howell, S Kuulkers, E Woodward, C TI RXTE observations of EX Hydrae: 49 views of the eclipse SO WILD STARS IN THE OLD WEST: PROCEEDINGS OF THE 13TH NORTH AMERICAN WORKSHOP ON CATACLYSMIC VARIABLES AND RELATED OBJECTS SE ASTRONOMICAL SOCIETY OF THE PACIFIC CONFERENCE SERIES LA English DT Proceedings Paper CT Wild Stars in the Old West - 13th North American Workshop on Cataclysmic Variables and Related Objects CY JUN 14-19, 1997 CL GRAND TETON NATL PARK, WY SP Univ Wyoming, Off Res, Univ Wyoming, Dept Phys & Astron, Astronom Soc Pacific AB In our RXTE observations of EX Hya, we find that the partial eclipse is flat-bottomed at at spin phase 0.125-0.375, indicating that one emission region is totally eclipsed while a second remains uneclipsed. The implied separation of the two regions is >7000 km; they can be identified with the upper and lower poles of the white dwarf. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Mukai, K (reprint author), NASA, Goddard Space Flight Ctr, Code 660-2, Greenbelt, MD 20771 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU ASTRONOMICAL SOC PACIFIC PI SAN FRANCISCO PA 390 ASHTON AVE, SAN FRANCISCO, CA 94112 USA BN 1-886733-57-0 J9 ASTR SOC P PY 1997 VL 137 BP 554 EP 555 PG 2 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA BL74M UT WOS:000076533800112 ER PT J AU Conlin, C AF Conlin, C TI NASA SO WORKFORCE LA English DT Editorial Material RP Conlin, C (reprint author), NASA,WASHINGTON,DC, USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU ACC COMMUNICATIONS INC PI COSTA MESA PA 245 FISCHER AVE, COSTA MESA, CA 92626 SN 0031-5745 J9 WORKFORCE JI Workforce PD JAN PY 1997 VL 76 IS 1 BP 93 EP 93 PG 1 WC Psychology, Applied; Management SC Psychology; Business & Economics GA WV304 UT WOS:A1997WV30400033 ER PT B AU Heap, SR AF Heap, SR BE Viegas, SM Gruenwald, R DeCarvalho, RR TI Searching for the Gunn-Peterson effect in HeII: GHRS spectroscopy of Q0302-003 SO YOUNG GALAXIES AND QSO ABSORPTION-LINE SYSTEMS SE ASTRONOMICAL SOCIETY OF THE PACIFIC CONFERENCE SERIES LA English DT Proceedings Paper CT Workshop on Young Galaxies and QSO Absorbers CY APR 08-12, 1996 CL SANTOS, BRAZIL SP Univ Sao Paulo, Proreitoria Pesquisa, Conselho Nacl Desenvolvimento Cient & Tecnol, Fdn Ampara Pesquisa Estado Sao Paulo, UNESCO AB The Goddard High Resolution Spectrograph (GHRS) on Hubble has obtained spectra of QSO 0302-003 in an effort to detect and measure HeII Ly alpha absorption from the diffuse intergalactic medium and/or discrete clouds. The GHRS spectra do indeed show strong absorption shortward of the rest-frame wavelength of HeII Ly alpha at 304 Angstrom. The absorption is strong even in the "Dobrzycki - Bechtold void," which suggests that at least some of it originates in the diffuse gas. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Heap, SR (reprint author), NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RI heap, sara/E-2237-2012 NR 0 TC 2 Z9 2 U1 0 U2 0 PU ASTRONOMICAL SOC PACIFIC PI SAN FRANCISCO PA 390 ASHTON AVE, SAN FRANCISCO, CA 94112 USA BN 1-886733-34-1 J9 ASTR SOC P PY 1997 VL 114 BP 87 EP 90 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA BK79S UT WOS:000073421300015 ER PT J AU Pierson, DL Chidambaram, M Heath, JD Mallary, L Mishra, SK Sharma, B Weinstock, GM AF Pierson, DL Chidambaram, M Heath, JD Mallary, L Mishra, SK Sharma, B Weinstock, GM TI Epidemiology of Staphylococcus aureus during space flight SO FEMS IMMUNOLOGY AND MEDICAL MICROBIOLOGY LA English DT Article DE Staphylococcus aureus; DNA fingerprinting; space flight; epidemiology; commensal bacterium ID FIELD GEL-ELECTROPHORESIS; RESTRICTION ENDONUCLEASE ANALYSIS; MOLECULAR EPIDEMIOLOGY; CLONAL RELATIONSHIPS; ESCHERICHIA-COLI; RIBOSOMAL-RNA; GENOMIC DNA; OUTBREAK; PATTERNS; FRAGMENTATION AB Staphylococcus aureus was isolated over 2 years from Space Shuttle mission crewmembers to determine dissemination and retention of bacteria. Samples before and after each mission were from nasal, throat, urine, and feces and from air and surface sampling of the Space Shuttle. DNA fingerprinting of samples by digestion of DNA with SmaI restriction endonuclease followed by pulsed-field gel electrophoresis showed S. aureus from each crewmember had a unique fingerprint and usually only one strain was carried by an individual. There was only one instance of transfer between crewmembers. Strains from interior surfaces after flight matched those of crewmembers, suggesting microbial fingerprinting may have forensic application. C1 UNIV TEXAS,SCH MED,DEPT BIOCHEM & MOL BIOL,HOUSTON,TX 77030. NASA,LYNDON B JOHNSON SPACE CTR,BIOMED OPERAT & RES BRANCH,HOUSTON,TX 77058. NASA,LYNDON B JOHNSON SPACE CTR,KRUG LIFE SCI,HOUSTON,TX 77058. NR 43 TC 13 Z9 15 U1 1 U2 1 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0928-8244 J9 FEMS IMMUNOL MED MIC JI FEMS Immunol. Med. Microbiol. PD DEC 31 PY 1996 VL 16 IS 3-4 BP 273 EP 281 DI 10.1111/j.1574-695X.1996.tb00146.x PG 9 WC Immunology; Infectious Diseases; Microbiology SC Immunology; Infectious Diseases; Microbiology GA WE313 UT WOS:A1996WE31300015 PM 9116646 ER PT J AU Meador, MAB Meador, MA Williams, LL Scheiman, DA AF Meador, MAB Meador, MA Williams, LL Scheiman, DA TI Diels-Alder trapping of photochemically generated dienes with a bismaleimide: A new approach to polyimide synthesis SO MACROMOLECULES LA English DT Article ID TEMPERATURE C1 NASA,LEWIS RES CTR,CLEVELAND,OH 44135. SPELMAN COLL,DEPT CHEM,ATLANTA,GA 30314. NYMA TECHNOL,BROOKPARK,OH 44142. OI Meador, Mary Ann/0000-0003-2513-7372 NR 9 TC 21 Z9 21 U1 0 U2 6 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 SN 0024-9297 J9 MACROMOLECULES JI Macromolecules PD DEC 30 PY 1996 VL 29 IS 27 BP 8983 EP 8986 DI 10.1021/ma960881n PG 4 WC Polymer Science SC Polymer Science GA WB741 UT WOS:A1996WB74100060 ER PT J AU Rind, D Lonergan, P Shah, K AF Rind, D Lonergan, P Shah, K TI Climatic effect of water vapor release in the upper troposphere SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID MIDDLE ATMOSPHERE MODEL; STRATOSPHERE SYSTEM; UV VARIABILITY; QBO AB Water vapor is released into the Goddard Institute for Space Studies (GISS) global climate middle atmosphere model at the locations and cruise altitude of subsonic aircraft. A range of water vapor values is used to simulate not only current and 2015 projected emissions but also to provide larger signal-noise ratios. The results show that aircraft water vapor emissions do not significantly affect the model's climate, either at the surface or in situ. With emissions some 15 times higher than the 2015 projection, a small impact is observed, amounting to a few tenths degrees celsius globally and locally, while with emissions 300 times the 2015 values, a global warming of 1 degrees C results. However, with releases this large, only about 5% actually stays in the atmosphere. The larger emissions increase the specific humidity most in the tropical lower troposphere, partly as a result of increased evaporation due to the global warming; at flight altitudes, relative humidity and cloud cover increase at latitudes of emission, and temperature decreases. Surface warming is relatively independent of latitude, and only a slight longitudinal aircraft footprint is found in the warming for the most extreme experiment. Comparison to increased CO2 experiments of similar magnitude warming shows that the upper tropospheric response is greater in the water vapor release experiments, but the high-latitude surface temperature response is larger with increased CO2 due to more effective cryospheric feedbacks. RP Rind, D (reprint author), NASA, GODDARD SPACE FLIGHT CTR, INST SPACE STUDIES, NEW YORK, NY 10025 USA. NR 18 TC 14 Z9 14 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 DEC 27 PY 1996 VL 101 IS D23 BP 29395 EP 29405 DI 10.1029/96JD02747 PG 11 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA WA693 UT WOS:A1996WA69300001 ER PT J AU Wang, PH Minnis, P McCormick, MP Kent, GS Skeens, KM AF Wang, PH Minnis, P McCormick, MP Kent, GS Skeens, KM TI A 6-year climatology of cloud occurrence frequency from stratospheric aerosol and gas experiment II observations (1985-1990) SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID SAGE-II; TROPOSPHERE EXCHANGE; PINATUBO ERUPTION; CIRRUS CLOUD; DISTRIBUTIONS; CYCLE AB A 6-year climatology of subvisual and opaque cloud occurrence frequencies is established using observations from the Stratospheric Aerosol and Gas Experiment (SAGE) II between 1985 and 1990. The subvisual clouds are observed mostly at high altitudes near the tropopause. The opaque clouds terminate the profiling, reducing the measurement frequency of the SAGE II instrument in the troposphere. With its l-km vertical resolution, the climatology shows many interesting features, including (1) the seasonal expansion and migration behavior of the subvisual and opaque cloud systems; (2) the association of the zonal mean cloud frequency distributions with the tropospheric mean circulation (Hadley and Ferrel cells); (3) the tropical cloud occurrence that follows the equatorial circulation, including the Walker circulation over the Pacific Ocean; and (4) the overall higher cloud occurrence in the northern hemisphere than in the southern hemisphere. The radiative impact of subvisual clouds is estimated to be a 1-W m(-2) reduction in outgoing longwave radiation. The maximum overall effect is a net positive cloud forcing of 0.5-1 W m(-2) in the tropics. During the 1987 El Nino-Southern Oscillation (ENSO), cloud frequency was generally enhanced in the tropics and midlatitudes and reduced in the subtropics and high latitudes. The present study shows a distinct negative correlation between the high-altitude-cloud occurrence and the lower stratospheric water vapor mixing ratio in the tropics, providing intrinsic evidence on the delicate connection between the stratospheric-tropospheric exchange and dehydration processes and the high-altitude cloud activities. C1 NASA, LANGLEY RES CTR, DIV ATMOSPHER SCI, HAMPTON, VA 23681 USA. HAMPTON UNIV, DEPT PHYS, HAMPTON, VA 23668 USA. RP Wang, PH (reprint author), SCI & TECHNOL CORP, 101 RES DR, HAMPTON, VA 23666 USA. RI Minnis, Patrick/G-1902-2010 OI Minnis, Patrick/0000-0002-4733-6148 NR 64 TC 265 Z9 267 U1 1 U2 17 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 DEC 27 PY 1996 VL 101 IS D23 BP 29407 EP 29429 DI 10.1029/96JD01780 PG 23 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA WA693 UT WOS:A1996WA69300002 ER PT J AU Remsberg, EE Bhatt, PP AF Remsberg, EE Bhatt, PP TI Zonal variance of nitric acid vapor as an indicator of meridional mixing in the subtropical lower stratosphere SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID LIMB INFRARED MONITOR; MIDDLE ATMOSPHERE; POLAR VORTICES; WAVE ACTIVITY; TRANSPORT; MODEL; EXCHANGE; TROPICS; MASS AB Several transport scenarios have been advanced in the literature to account for the exchange of tracers between the extratropics and tropics in the lower stratosphere. Each scenario involves a slow, net upward transport at low latitudes and varying degrees of mixing at middle latitudes plus detrainment across a subtropical region of enhanced tracer gradients. In situ observations for differentiating among these scenarios are generally lacking above about 21 km altitude. Existing satellite data sets can provide useful information throughout the lower stratosphere. In particular, we have looked for such exchange by examining time series of the daily zonal variance of the Nimbus 7 limb infrared monitor of the stratosphere distributions of nitric acid vapor (HNO3) mixing ratio. This species is characterized by strong subtropical meridional gradients between about 10 and 100 hPa, which develop in response to extratropical wave activity and any associated mixing processes. The subtropical variance is a measure of that activity, its region of maximum values moving equatorward during late autumn and then relaxing and retreating in late spring. At and below the 45-hPa level there is not a clear maximum of variance at a given latitude, perhaps a result of the secondary circulation that was present during the 1978/1979 winter in response to the easterly phase of the quasi-biennial oscillation cycle. At the 30-hPa and 50-hPa levels, while we find occasions in winter when tongues of subtropical air were transported to higher latitudes, we find no clear evidence for a large-scale transport of extratropical air to lower latitudes through a subtropical region of enhanced gradients. C1 SAIC, HAMPTON, VA 23666 USA. RP Remsberg, EE (reprint author), NASA, LANGLEY RES CTR, DIV ATMOSPHER SCI, MS401B, HAMPTON, VA 23666 USA. NR 32 TC 5 Z9 5 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 DEC 27 PY 1996 VL 101 IS D23 BP 29523 EP 29530 DI 10.1029/96JD02804 PG 8 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA WA693 UT WOS:A1996WA69300010 ER PT J AU Williams, ER Zhang, R AF Williams, ER Zhang, R TI Density of rime in laboratory simulations of thunderstorm microphysics and electrification SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article; Proceedings Paper CT 21st General Assembly of the International-Union-of-Geodesy-and-Geophysics CY 1995 CL BOULDER, CO SP Int Union Geodesy & Geophys ID LIQUID WATER; PRECIPITATION DEVELOPMENT; CHARGING MECHANISMS; GRAUPEL GROWTH; ICE CRYSTALS; PARAMETERS; DROPS; HAIL AB Results from earlier laboratory studies are used to estimate the density of rime ice in laboratory simulations of thunderstorm microphysics and electrification. Comparisons of results in the works of Takahashi [1978], Jayaratne et al. [1983], and Saunders et al. [1991] show that kernel and opaque rime (rho > 0.33 g/cm(-3)) are prevalent in the former study, whereas low-density feather rime (rho < 0.33 g/cm(3)) is prevalent in the latter studies. It is suggested that rime density may affect the charging process by either susceptibility to surface fracture on collision or impact of surface roughness on heat and vapor transfer at the ice surface. C1 CALTECH, JET PROP LAB, PASADENA, CA 91125 USA. RP Williams, ER (reprint author), MIT, PARSONS LAB, ROOM 48-211, CAMBRIDGE, MA 02139 USA. RI Zhang, Renyi/A-2942-2011 NR 37 TC 11 Z9 11 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 DEC 27 PY 1996 VL 101 IS D23 BP 29715 EP 29719 DI 10.1029/96JD03216 PG 5 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA WA693 UT WOS:A1996WA69300033 ER PT J AU Kitamoto, S Mukai, K AF Kitamoto, S Mukai, K TI ASCA observation of Cygnus OB2 association SO PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN LA English DT Article DE stars, individual (Cygnus OB2); stars, X-rays; X-rays, spectra ID X-RAY-EMISSION; DRIVEN STELLAR WINDS; EARLY-TYPE STARS; CYG-OB2 NO 5; HOT STARS; RADIO-EMISSION; ORION NEBULA; MASS-LOSS; LINE; INSTABILITIES AB ASCA observed Cygnus OB2 association on 1993 April 29. Four OB stars (5, 8a, 9, and 12; the designation from Schulte 1958, Astron. Jahresber. 58.12376) were clearly detected. In the X-ray spectra of three stars (5, 8a, and 12), at least two emission lines from Si XIII and S XV were identified. The spectra of three stars (5, 9, and 12) can be simulated using the single thin thermal spectra with temperatures of 1.26 +/- 0.12 keV [(1.46 +/- 0.14) x 10(7) K], 2.46 +/- 0.68 keV [(2.85 +/- 0.79) x 10(7) K], and 0.90 +/- 0.05 keV [(1.04 +/- 0.06) x 10(7) K], respectively. However, the spectrum of 8a, which is statistically the best one, requires two-component thin thermal spectra with temperatures of 0.62 +/- 0.04 keV [(0.72 +/- 0.05) x 10(7) K] and 1.47 +/- 0.10 keV [(1.71 +/- 0.12) x 10(7) K]. The emission measures of the four observed stars are similar to 10(56-57) Cm-3, and their photoelectric absorption column densities are (1-2) x 10(22) H Cm-2. The apparent low metal abundances are suggested in all four stars, if the X-ray emission region is really optically thin. This might be explained by an enrichment of light elements, such as He and N. Another possibility is that the emission region is not really optically thin, and that the line strength is suppressed. C1 NASA, GODDARD SPACE FLIGHT CTR, GREENBELT, MD 20771 USA. RP OSAKA UNIV, FAC SCI, DEPT EARTH & SPACE SCI, 1-1 MACHIKANEYAMA CHO, TOYONAKA, OSAKA 560, JAPAN. NR 48 TC 29 Z9 29 U1 0 U2 0 PU OXFORD UNIV PRESS PI OXFORD PA GREAT CLARENDON ST, OXFORD OX2 6DP, ENGLAND SN 0004-6264 EI 2053-051X J9 PUBL ASTRON SOC JPN JI Publ. Astron. Soc. Jpn. PD DEC 25 PY 1996 VL 48 IS 6 BP 813 EP 818 DI 10.1093/pasj/48.6.813 PG 6 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA WA707 UT WOS:A1996WA70700010 ER PT J AU Hirayama, M Nagase, F Tavani, M Kaspi, VM Kawai, N Arons, J AF Hirayama, M Nagase, F Tavani, M Kaspi, VM Kawai, N Arons, J TI Post-periastron ASCA observation of the PSR B1259-63 system SO PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN LA English DT Article DE pulsars; stars, Be; stars, individual (PSR B1259-63); stars, individual (SS 2883); X-rays, binaries ID X-RAY-EMISSION; PULSAR; RADIO; PSR-1259-63 AB We report on the results of a post-periastron ASCA observation of the PSR B1259-63 system, containing a 48 ms pulsar orbiting a Be star in an eccentric 3.4 yr orbit. The ASCA observation was carried out on 1994 February 28 when the radio pulsar was again visible after a prolonged 40-day radio eclipse near to periastron. The source was clearly detected with an X-ray luminosity (1-10 keV) L(X) of (1.03 +/- 0.09) x 10(34) (d/2 kpc)(2) erg s(-1), where d is the pulsar's distance. The X-ray spectrum is well-represented by a single power-law model of the photon index, alpha = 1.61 +/- 0.06, and a small photoelectric absorption, N-H = (5.6 +/- 0.6) x 10(21) cm(-2). No significant X-ray pulsations were detected, and the upper limit for the pulsed component was estimated to be 15% of the total X-ray flux: assuming sinusoidal modulation. The characteristics of the X-ray emission detected on 1994 February 28 are similar to those detected by ASCA near periastron when the pulsed radio emission from PSR B1259-63 was eclipsed. Our results strongly favor a non-thermal model of X-ray emission driven by synchrotron radiation from relativistic shocked particles in the pulsar wind interacting with the outflow from the Be star companion. C1 UNIV TOKYO, DEPT PHYS, SCH SCI, BUNKYO KU, TOKYO 113, JAPAN. COLUMBIA UNIV, COLUMBIA ASTROPHYS LAB, NEW YORK, NY 10027 USA. CALTECH, JET PROP LAB, IPAC, PASADENA, CA 91125 USA. INST PHYS & CHEM RES, WAKO, SAITAMA 35101, JAPAN. UNIV CALIF BERKELEY, DEPT ASTRON, BERKELEY, CA 94720 USA. UNIV CALIF BERKELEY, DEPT PHYS, BERKELEY, CA 94720 USA. RP INST SPACE & ASTRONAUT SCI, 3-1-1 YOSHINODAI, SAGAMIHARA, KANAGAWA 229, JAPAN. OI Tavani, Marco/0000-0003-2893-1459 NR 23 TC 24 Z9 24 U1 1 U2 1 PU OXFORD UNIV PRESS PI OXFORD PA GREAT CLARENDON ST, OXFORD OX2 6DP, ENGLAND SN 0004-6264 EI 2053-051X J9 PUBL ASTRON SOC JPN JI Publ. Astron. Soc. Jpn. PD DEC 25 PY 1996 VL 48 IS 6 BP 833 EP 840 DI 10.1093/pasj/48.6.833 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA WA707 UT WOS:A1996WA70700013 ER PT J AU Knopp, KJ Christensen, DH Hill, JR AF Knopp, KJ Christensen, DH Hill, JR TI Vertical-cavity surface-emitting lasers with low-ripple optical pump bands SO APPLIED PHYSICS LETTERS LA English DT Article AB We have used multilayer mirror optimization methods to enhance the coupling of pump light into vertical-cavity surface-emitting lasers (VCSELs). With previously reported devices, pump light was coupled into VCSEL cavities through interference notches in the mirror reflectance spectrum. This approach is sensitive to temperature dependent reflectance spectrum shifts. We have created devices with a wide pump-band window of low reflectance. We report the simulation, growth, and optically pumped lasing of such optimized low-ripple VCSELs, Further, broadband pump windows open the possibility of spectrally-bread optical pumps and they eliminate need for costly tunable pump lasers. (C) 1996 American Institute of Physics. C1 NASA,LANGLEY RES CTR,HAMPTON,VA 23665. UNIV COLORADO,DEPT ELECT & COMP ENGN,BOULDER,CO 80309. RP Knopp, KJ (reprint author), NATL INST STAND & TECHNOL,MS 815-04,325 BROADWAY,BOULDER,CO 80303, USA. NR 6 TC 3 Z9 3 U1 1 U2 1 PU AMER INST PHYSICS PI WOODBURY PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 SN 0003-6951 J9 APPL PHYS LETT JI Appl. Phys. Lett. PD DEC 23 PY 1996 VL 69 IS 26 BP 3987 EP 3989 DI 10.1063/1.117846 PG 3 WC Physics, Applied SC Physics GA VY894 UT WOS:A1996VY89400009 ER PT J AU Targ, R Steakley, BC Hawley, JG Ames, LL Forney, P Swanson, D Stone, R Otto, RG Zarifis, V Brockman, P Calloway, RS Klein, SH Robinson, PA AF Targ, R Steakley, BC Hawley, JG Ames, LL Forney, P Swanson, D Stone, R Otto, RG Zarifis, V Brockman, P Calloway, RS Klein, SH Robinson, PA TI Coherent lidar airborne wind sensor .2. Flight-test results at 2 and 10 mu m SO APPLIED OPTICS LA English DT Article ID LASER-RADAR; TURBULENCE; SYSTEMS; 2-MU-M AB The use of airborne laser radar (lidar) to measure wind velocities and to detect turbulence in front of an aircraft in real time can significantly increase fuel efficiency, flight safety, and terminal area capacity. We describe the flight-test results for two coherent lidar airborne shear sensor (CLASS) systems and discuss their agreement with our theoretical simulations. The 10.6-mu m CO2 system (CLASS-10) is a flying brassboard; the 2.02-mu m Tm:YAG solid-state system (CLASS-2) is configured in a lugged, light-weight, high-performance package. Both lidars have shown a wind measurement accuracy of better than 1 m/s. (C) 1996 Optical Society of America. C1 NASA,LANGLEY RES CTR,HAMPTON,VA 23665. MIT,LINCOLN LAB,LEXINGTON,MA 02173. RP Targ, R (reprint author), CTR ADV TECHNOL,LOCKHEED MARTIN,3251 HANOVER ST,PALO ALTO,CA 94304, USA. NR 19 TC 76 Z9 81 U1 2 U2 5 PU OPTICAL SOC AMER PI WASHINGTON PA 2010 MASSACHUSETTS AVE NW, WASHINGTON, DC 20036 SN 0003-6935 J9 APPL OPTICS JI Appl. Optics PD DEC 20 PY 1996 VL 35 IS 36 BP 7117 EP 7127 DI 10.1364/AO.35.007117 PG 11 WC Optics SC Optics GA WD673 UT WOS:A1996WD67300012 PM 21151317 ER PT J AU Heaps, WS Burris, J AF Heaps, WS Burris, J TI Airborne Raman lidar SO APPLIED OPTICS LA English DT Article DE lidar; ozone; remote sensing ID POLAR VORTEX; OZONE; WINTER AB We designed and tested an airborne lidar system using Raman scattering to make simultaneous measurements of methane, water vapor, and temperature in a series of flights on a NASA-operated C-130 aircraft. We present the results for methane detection, which show that the instrument has the requisite sensitivity to atmospheric trace gases. Ultimately these measurements can be used to examine the transport of chemically processed air from within the polar vortex to mid-latitudinal regions and the exchange of stratospheric air between tropical and mid-latitudinal regions. (C) 1996 Optical Society of America. RP Heaps, WS (reprint author), NASA,GODDARD SPACE FLIGHT CTR,ATMOSPHERES LAB,GREENBELT,MD 20771, USA. NR 15 TC 11 Z9 13 U1 0 U2 1 PU OPTICAL SOC AMER PI WASHINGTON PA 2010 MASSACHUSETTS AVE NW, WASHINGTON, DC 20036 SN 0003-6935 J9 APPL OPTICS JI Appl. Optics PD DEC 20 PY 1996 VL 35 IS 36 BP 7128 EP 7135 DI 10.1364/AO.35.007128 PG 8 WC Optics SC Optics GA WD673 UT WOS:A1996WD67300013 PM 21151318 ER PT J AU Fixsen, DJ Cheng, ES Gales, JM Mather, JC Shafer, RA Wright, EL AF Fixsen, DJ Cheng, ES Gales, JM Mather, JC Shafer, RA Wright, EL TI The cosmic microwave background spectrum from the full COBE FIRAS data set SO ASTROPHYSICAL JOURNAL LA English DT Article DE cosmic microwave background; cosmology, observations ID EXPLORER COBE; INSTRUMENT; DESIGN; GALAXY AB We have refined the analysis of the data from the FIRAS (Far-InfraRed Absolute Spectrophotometer) on board the COBE (COsmic Background Explorer). The FIRAS measures the difference between the cosmic microwave background and a precise blackbody spectrum. We find new, tighter upper limits on general deviations from a blackbody spectrum. The rms deviations are less than 50 parts per million of the peak of the cosmic microwave background radiation. For the Comptonization and chemical potential we find \y\ < 15 x 10(-6) and \mu\ < 9 x 10(-5) (95% confidence level [CL]). There are also refinements in the absolute temperature, 2.728 +/- 0.004 K (95% CL), the dipole direction, (l, b) = (264.14 degrees +/- 0.30, 48.26 degrees +/- 0.30) (95% CL), and the amplitude, 3.372 +/- 0.014 mK (95% CL). All of these results agree with our previous publications. C1 UNIV CALIF LOS ANGELES,DEPT PHYS,LOS ANGELES,CA 90095. UNIV CALIF LOS ANGELES,DEPT ASTRON,LOS ANGELES,CA 90095. RP Fixsen, DJ (reprint author), NASA,GODDARD SPACE FLIGHT CTR,APPL RES CORP,CODE 6853,GREENBELT,MD 20771, USA. NR 22 TC 757 Z9 759 U1 3 U2 19 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637 SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD DEC 20 PY 1996 VL 473 IS 2 BP 576 EP 587 DI 10.1086/178173 PN 1 PG 12 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VZ151 UT WOS:A1996VZ15100002 ER PT J AU Scoccimarro, R Frieman, JA AF Scoccimarro, R Frieman, JA TI Loop corrections in nonlinear cosmological perturbation theory .2. Two-point statistics and self-similarity SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies, clusters, general; large-scale structure of universe; methods, numerical ID POWER SPECTRUM; DENSITY FIELDS; EVOLUTION; FLUCTUATIONS; PREVIRIALIZATION; GALAXIES AB We calculate the lowest order nonlinear contributions to the power spectrum, two-point correlation function, and smoothed variance of the density field, for Gaussian initial conditions and scale-free initial power spectra, P(k) similar to k(n). These results extend and, in some cases, correct previous work in the literature on cosmological perturbation theory. Comparing with the scaling behavior observed in N-body simulations, we find that the validity of nonlinear perturbation theory depends strongly on the spectral index n. For n < -1, we find excellent agreement over scales where the variance sigma(2)(R)less than or similar to 10; however, for n greater than or equal to -1, perturbation theory predicts deviations from self-similar scaling (which increase with n) not seen in numerical simulations. This anomalous scaling suggests that the principal assumption underlying cosmological perturbation theory, namely, that large-scale fields can be described perturbatively even when fluctuations are highly nonlinear on small scales, breaks down beyond leading order for spectral indices n greater than or equal to -1. For n < -1, the power spectrum, variance, and correlation function in the scaling regime can be calculated using dimensional regularization. C1 UNIV CHICAGO,ENRICO FERMI INST,CHICAGO,IL 60637. UNIV CHICAGO,DEPT ASTRON & ASTROPHYS,CHICAGO,IL 60637. FERMILAB NATL ACCELERATOR LAB,NASA,FERMILAB ASTROPHYS CTR,BATAVIA,IL 60510. RP Scoccimarro, R (reprint author), UNIV CHICAGO,DEPT PHYS,CHICAGO,IL 60637, USA. NR 44 TC 81 Z9 81 U1 0 U2 1 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637 SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD DEC 20 PY 1996 VL 473 IS 2 BP 620 EP 644 DI 10.1086/178177 PN 1 PG 25 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VZ151 UT WOS:A1996VZ15100006 ER PT J AU McLaughlin, MA Mattox, JR Cordes, JM Thompson, DJ AF McLaughlin, MA Mattox, JR Cordes, JM Thompson, DJ TI Variability of CGRO/EGRET gamma-ray sources SO ASTROPHYSICAL JOURNAL LA English DT Article DE BL Lacertae objects, general; gamma rays, observations; quasars, general; radiation mechanisms, nonthermal AB We have developed a method for quantifying the flux variability of EGRET high-energy gamma-ray sources. We apply this method to all sources in the Second EGRET Catalog except for the one solar flare. Allowing for a small systematic uncertainty, the phase-averaged flux densities of the pulsars are consistent with being nonvariable. Many identified active galactic nuclei are variable, as expected, and it is likely that the apparent nonvariability of some identified active galactic nuclei results from decreased sensitivity to variability at low fluxes and low latitudes. Populations of both variable and nonvariable unidentified sources are found to be in excess at low Galactic latitudes. While low-flux, nonvariable, unidentified sources could result from errors in the Galactic diffuse model, some higher flux, nonvariable, unidentified sources are likely to be Galactic pulsars. The excess of variable, unidentified sources at low latitudes suggests that either pulsars can produce variable gamma rays under special circumstances, or that a new class of Galactic gamma-ray sources exists. C1 UNIV MARYLAND, DEPT ASTRON, COLLEGE PK, MD 20742 USA. UNIV SPACE RES ASSOC, SPACE ASTRON PROGRAM, WASHINGTON, DC USA. NASA, GODDARD SPACE FLIGHT CTR, HIGH ENERGY ASTROPHYS LAB, GREENBELT, MD 20771 USA. RP McLaughlin, MA (reprint author), CORNELL UNIV, DEPT ASTRON, ITHACA, NY 14850 USA. RI Thompson, David/D-2939-2012 OI Thompson, David/0000-0001-5217-9135 NR 10 TC 91 Z9 92 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 DEC 20 PY 1996 VL 473 IS 2 BP 763 EP 772 DI 10.1086/178188 PN 1 PG 10 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VZ151 UT WOS:A1996VZ15100017 ER PT J AU Murphy, RJ Share, GH Grove, JE Johnson, WN Kurfess, JD Purcell, WR McNaronBrown, K Ramaty, R AF Murphy, RJ Share, GH Grove, JE Johnson, WN Kurfess, JD Purcell, WR McNaronBrown, K Ramaty, R TI Limits on nuclear gamma-ray emission from Orion SO ASTROPHYSICAL JOURNAL LA English DT Article DE acceleration of particles; gamma rays, observations; ISM, cosmic rays; stars, abundances ID MOLECULAR CLOUDS; LIGHT-ELEMENTS; COSMIC-RAYS; COMPLEX; LINES; SYSTEM; ORIGIN; WINDS AB The discovery of gamma-ray line emission in the 3-7 MeV range from the Orion complex was recently reported. The observed Compton Telescope (COMPTEL) spectrum suggested that the emission results from the de-excitation of excited states of C-12 and O-16. We report on a search for these lines using the Oriented Scintillation Spectroscopy Experiment (OSSE) on the Compton Gamma Ray Observatory (CGRO) during a 5 week observation in 1995 from April to June. The OSSE detectors were pointed midway between the Orion A and B radio sources in three different viewing configurations. We find no compelling evidence for line emission near 4.4 or 6.1 MeV. The sensitivity of the OSSE measurements is dependent on the widths of the reported C and O lines and on the source location and spatial extent. A point source at the flux level reported by COMPTEL and located on-axis would have been detected by OSSE at similar to 7 sigma and similar to 5 sigma levels of confidence for narrow and broad lines, respectively. A spatially distributed source of the same strength with a distribution following the intense CO emission localized around Orion A and Orion B would have been detected by OSSE at similar to 3.5 sigma and similar to 2.5 sigma, respectively. Thus, these OSSE observations require that any gamma-ray line source must be even more extended to be consistent with the reported COMPTEL intensity. C1 NORTHWESTERN UNIV,DEPT PHYS & ASTRON,EVANSTON,IL 60208. GEORGE MASON UNIV,INST COMPUTAT SCI & INFORMAT,FAIRFAX,VA 22030. NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. RP Murphy, RJ (reprint author), USN,RES LAB,EO HULBURT CTR SPACE RES,CODE 7650,WASHINGTON,DC 20375, USA. RI Johnson, Neil/G-3309-2014 NR 21 TC 10 Z9 10 U1 0 U2 1 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637 SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD DEC 20 PY 1996 VL 473 IS 2 BP 990 EP 997 DI 10.1086/178209 PN 1 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VZ151 UT WOS:A1996VZ15100038 ER PT J AU Ellison, DC Baring, MG Jones, FC AF Ellison, DC Baring, MG Jones, FC TI Nonlinear particle acceleration in oblique shocks SO ASTROPHYSICAL JOURNAL LA English DT Article DE acceleration of particles; cosmic rays; diffusion; hydrodynamics; shock waves ID INTERSTELLAR PICKUP IONS; MONTE-CARLO SIMULATIONS; ALIGNED BEAMS UPSTREAM; WIND TERMINATION SHOCK; EARTHS BOW SHOCK; PARALLEL SHOCKS; HYBRID SIMULATIONS; ASTROPHYSICAL SHOCKS; SUPERNOVA-REMNANTS; ALPHA-PARTICLES AB The solution of the nonlinear diffusive shock acceleration problem, where the pressure of the nonthermal population is sufficient to modify the shock hydrodynamics, is widely recognized as a key to understanding particle acceleration in a variety of astrophysical environments. We have developed a Monte Carlo technique for self-consistently calculating the hydrodynamic structure of oblique, steady state shocks, together with the first-order Fermi acceleration process and associated nonthermal particle distributions. This is the first internally consistent treatment of modified shocks that includes cross-field diffusion of particles. Our method overcomes the injection problem faced by analytic descriptions of shock acceleration and the lack of adequate dynamic range and artificial suppression of cross-held diffusion faced by plasma simulations; it currently provides the most broad and versatile description of collisionless shocks undergoing efficient particle acceleration. We present solutions for plasma quantities and particle distributions upstream and downstream of shocks, illustrating the strong differences observed between nonlinear and test particle cases. It is found that, for strong scattering, there are only marginal differences in the injection efficiency and resultant spectra for two extreme scattering modes, namely large-angle scattering and pitch-angle diffusion, for a wide range of shock parameters, i.e., for nonperpendicular subluminal shocks with held obliquities less than or equal to 75 degrees and de Hoffmann-Teller frame speeds much less than the speed of light. C1 NASA, GODDARD SPACE FLIGHT CTR, HIGH ENERGY ASTROPHYS LAB, GREENBELT, MD 20771 USA. RP Ellison, DC (reprint author), N CAROLINA STATE UNIV, DEPT PHYS, BOX 8202, RALEIGH, NC 27695 USA. NR 68 TC 96 Z9 96 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 DEC 20 PY 1996 VL 473 IS 2 BP 1029 EP 1050 DI 10.1086/178213 PN 1 PG 22 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VZ151 UT WOS:A1996VZ15100042 ER PT J AU Boroson, B Vrtilek, SD McCray, R Kallman, T Nagase, F AF Boroson, B Vrtilek, SD McCray, R Kallman, T Nagase, F TI Pulsations and line profile changes in the ultraviolet spectrum of Hercules X-1: Results from a multiwavelength campaign SO ASTROPHYSICAL JOURNAL LA English DT Article DE binaries, eclipsing; stars, individual (Hercules X-1); ultraviolet, stars; X-rays, stars ID HZ HERCULIS; OPTICAL PULSATIONS; PERIODICITY; UHURU; MASS AB We report simultaneous X-ray and ultraviolet observations of the X-ray binary pulsar Hercules X-l, obtained over nearly half of a 1.7 day binary orbit using the ASCA X-ray telescope and the Goddard High Resolution Spectrograph (GHRS) aboard the Hubble Space Telescope. The GHRS resolved, for the first time, two moving emission components. One feature in the N v lambda lambda 1238.8, 1242.8 doublet is broad (FWHM approximate to 1000 km s(-1)) and the other is narrow (FWHM approximate to 150 km s(-1)). We attribute the broad emission line to the X-ray-illuminated surface of a Keplerian accretion disk and the narrow line to the X-ray-heated atmosphere of the companion star, HZ Her. Near orbital phase phi(orb) = 0.80 (simultaneous with a pre-eclipse X-ray dip), the N v lambda 1242.8 component became stronger than the N v lambda 1238.8 component. Later in the orbit, the blue edge of the broad lines diminished as the approaching side of the accretion disk was occulted by HZ Her. UV continuum pulsations were detected for the first time, with an amplitude approximate to 0.5% of the steady flux. The pulse shapes of the UV continuum and hard X-rays were similar at phi(orb) = 0.83 but not at phi(orb) = 0.56. We found evidence for a stronger pulsation (amplitude approximate to 15%) within a narrow (0.25 Angstrom) segment of the broad 1242.8 Angstrom v component, only at phi(orb) = 0.80. We briefly discuss some implications of these observations for the gas hows in the Her X-l system. C1 UNIV COLORADO,JOINT INST LAB ASTROPHYS,BOULDER,CO 80309. NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. INST SPACE & ASTRONAUT SCI,SAGAMIHARA,KANAGAWA 229,JAPAN. RP Boroson, B (reprint author), CTR ASTROPHYS,60 GARDEN ST,CAMBRIDGE,MA 02138, USA. NR 33 TC 21 Z9 21 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637 SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD DEC 20 PY 1996 VL 473 IS 2 BP 1079 EP 1088 DI 10.1086/178217 PN 1 PG 10 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VZ151 UT WOS:A1996VZ15100046 ER PT J AU Lanz, T Barstow, MA Hubeny, I Holberg, JB AF Lanz, T Barstow, MA Hubeny, I Holberg, JB TI A self-consistent optical, ultraviolet, and extreme-ultraviolet model for the spectrum of the hot white dwarf G191-B2B SO ASTROPHYSICAL JOURNAL LA English DT Article DE stars, abundances; stars, individual (G191-B2B); ultraviolet, stars; white dwarfs ID X-RAY SURVEY; STELLAR ATMOSPHERES; HELIUM; EXOSAT; LEVITATION; ABUNDANCE; HYDROGEN AB The star G191-B2B is one of a number of hot DA white dwarfs whose atmospheres have been found to contain significant quantities of heavy elements, including C, N, O, Si, Fe, and Ni. Several earlier studies have measured their abundances using IUE echelle data in conjunction with synthetic spectra derived from theoretical model atmosphere calculations of varying degrees of sophistication. However, predictions of the EW spectrum based on these observations failed completely to match either its shape or absolute flux level. We present here the results of new non-LTE model calculations including the effects of line blanketing from more than 9 million (mainly Fe and Ni) transitions. For the first time, we are able to find an effective temperature and composition that can consistently match the optical, FUV and EUV data. However, to maintain this agreement below the He II lambda 228 Lyman limit, it is necessary to incorporate additional He II opacity in the form of photospheric, circumstellar or interstellar material. C1 UNIV LEICESTER,DEPT PHYS & ASTRON,LEICESTER LE1 7RH,LEICS,ENGLAND. UNIV ARIZONA,LUNAR & PLANETARY LAB,TUCSON,AZ 85721. RP Lanz, T (reprint author), NASA,GODDARD SPACE FLIGHT CTR,UNIV SPACE RES ASSOC,GREENBELT,MD 20711, USA. NR 42 TC 57 Z9 57 U1 0 U2 1 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637 SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD DEC 20 PY 1996 VL 473 IS 2 BP 1089 EP 1093 DI 10.1086/178218 PN 1 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VZ151 UT WOS:A1996VZ15100047 ER PT J AU Jenniskens, P Blake, DF AF Jenniskens, P Blake, DF TI Crystallization of amorphous water ice in the solar system SO ASTROPHYSICAL JOURNAL LA English DT Article DE comets, general; infrared, ISM, lines and bands; infrared, solar system; methods, laboratory; molecular data; planets and satellites, general ID ASTROPHYSICAL IMPLICATIONS; GLASS-TRANSITION; COMET NUCLEI; LIQUID; GASES; PHASE; SUBLIMATION; KINETICS; RELEASE; SPECTRA AB Electron diffraction studies of vapor-deposited water ice have characterized the dynamical structural changes during crystallization that affect volatile retention in cometary materials. Crystallization is found to occur by nucleation of small domains, while leaving a significant part of the amorphous material in a slightly more relaxed amorphous state that coexists metastably with cubic crystalline ice. The onset of the amorphous relaxation is prior to crystallization and coincides with the glass transition. Above the glass transition temperature, the crystallization kinetics are consistent with the amorphous solid becoming a ''strong'' viscous liquid. The amorphous component can effectively retain volatiles during crystallization if the volatile concentration is similar to 10% or less. For higher initial impurity concentrations, a significant amount of impurities is released during crystallization, probably because the impurities are trapped on the surfaces of micropores. A model for crystallization over long timescales is described that can be applied to a wide range of impure water ices under typical astrophysical conditions if the fragility factor D, which describes the viscosity behavior, can be estimated. RP Jenniskens, P (reprint author), NASA,AMES RES CTR,SPACE SCI MICROSCOPY LAB,MAIL STOP 239-4,MOFFETT FIELD,CA 94035, USA. NR 69 TC 133 Z9 134 U1 2 U2 26 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637 SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD DEC 20 PY 1996 VL 473 IS 2 BP 1104 EP & DI 10.1086/178220 PN 1 PG 11 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VZ151 UT WOS:A1996VZ15100049 PM 11539415 ER PT J AU Kormendy, J Bender, R Ajhar, EA Dressler, A Faber, SM Gebhardt, K Grillmair, C Lauer, TR Richstone, D Tremaine, S AF Kormendy, J Bender, R Ajhar, EA Dressler, A Faber, SM Gebhardt, K Grillmair, C Lauer, TR Richstone, D Tremaine, S TI Hubble Space Telescope spectroscopic evidence for A1x10(9)M(circle dot) black hole in NGC 4549 SO ASTROPHYSICAL JOURNAL LA English DT Article DE black hole physics; galaxies, individual (NGC 4594); galaxies, kinematics and dynamics; galaxies, nuclei ID SOMBRERO GALAXY; STELLAR KINEMATICS; NGC-4594; DISK; MASS; M87; VELOCITIES; NGC-3115; NUCLEUS; SEARCH AB The discovery by Kormendy of a M .similar or equal to 10(9) M. massive dark object (MDO) in NGC 4594 is confirmed with higher resolution spectroscopy from the Canada-France-Hawaii Telescope (CFHT) and the Hubble Space Telescope (HST). CFHT measurements with the Subarcsecond Imaging Spectrograph improve the resolution from sigma*=0.''.40 to 0.'' 27 Gaussian dispersion radius of the point-spread function (PSF). The apparent central velocity dispersion rises from sigma=250+/-7 km s(-1) to sigma=286+/-7 km s(-1). As observed with the COSTAR-corrected HST, the Faint Object Spectrograph, and a 0.'' 21 aperture, sigma=321+/-7 km s(-1) is still higher, and the central rotation curve is very steep. The highest-M . published dynamical model fits the new observations reasonably well when ''observed'' at HST resolution. The spatial resolution has now improved by a factor of similar to 5 since the discovery measurements, and the case for a black hole (BH) has strengthened correspondingly. We confirm that NGC 4594 has a Seyfert spectrum; Her is similar to 5200 km s(-1) wide at zero intensity. However, gas velocities are lower than the circular velocities implied by the stars, so they cannot be used to test the BH case in NGC 4594. The gas may be in a ring, or it may be associated with patchy dust. HST images with the Wide Field and Planetary Camera 2 show dust at some aperture positions. NGC 4594 appears to have a bright point nucleus. However, the central absorption-line strengths are low, consistent with dilution by enough nonthermal light to explain the ''nucleus.'' There is no evidence for a distinct nuclear star cluster. NGC 4594 is similar to M87, which also has a nonthermal nuclear source, and not to M31 and NGC 3115, which have quiescent BHs and nuclear star clusters. C1 UNIV STERNWARTE, D-81679 MUNICH, GERMANY. NATL OPT ASTRON OBSERV, KITT PEAK NATL OBSERV, TUCSON, AZ 85726 USA. CARNEGIE INST WASHINGTON OBSERV, PASADENA, CA 91101 USA. UNIV CALIF SANTA CRUZ, LICK OBSERV, UCO, SANTA CRUZ, CA 95064 USA. UNIV MICHIGAN, DEPT ASTRON, ANN ARBOR, MI 48109 USA. JET PROPULS LAB, PASADENA, CA 91109 USA. UNIV TORONTO, CANADIAN INST THEORET ASTROPHYS, TORONTO, ON M5S 3H8, CANADA. RP Kormendy, J (reprint author), UNIV HAWAII, INST ASTRON, 2680 WOODLAWN DR, HONOLULU, HI 96822 USA. RI Tremaine, Scott/M-4281-2015 OI Tremaine, Scott/0000-0002-0278-7180 NR 24 TC 59 Z9 59 U1 0 U2 0 PU IOP PUBLISHING LTD PI BRISTOL PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD DEC 20 PY 1996 VL 473 IS 2 BP L91 EP + DI 10.1086/310399 PN 2 PG 0 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VZ154 UT WOS:A1996VZ15400008 ER PT J AU Shearer, A Butler, R Redfern, RM Cullum, M Danks, AC AF Shearer, A Butler, R Redfern, RM Cullum, M Danks, AC TI A search for the optical counterpart of the triple pulsar system PSR B1620-26 in M4 SO ASTROPHYSICAL JOURNAL LA English DT Article DE binaries, close; globular clusters, individual (M4); pulsars, individual (PSR B1620-26); techniques, photometric ID GLOBULAR-CLUSTER; PHOTOMETRY; COMPANION AB We have performed photometry in B and V of the field of the triple system PSR B1620-26 in the globular cluster M4. Our images were taken with two two-dimensional imaging photon-counting detectors, which permitted deep exposures td be made without saturation. Photometry of the proposed optical counterpart of the second companion of PSR B1620-26 was obtained, yielding a magnitude V=21.30 +/- 0.08 and a color B - V = 1.32 +/- 0.20. The color index has not been successfully determined previously. These values locate the counterpart on the main sequence of the cluster color-magnitude diagram and lead to a mass determination that is consistent with a 0.48 M. cluster main-sequence star. C1 EUROPEAN SO OBSERV,D-85748 GARCHING,GERMANY. NASA,GODDARD SPACE FLIGHT CTR,HUGHES STX,GREENBELT,MD 20771. RP Shearer, A (reprint author), NATL UNIV IRELAND UNIV COLL GALWAY,DEPT EXPT PHYS,GALWAY,IRELAND. RI Butler, Ray/A-6705-2012; Shearer, Andy/N-7609-2014 OI Butler, Ray/0000-0002-8441-7596; Shearer, Andy/0000-0001-7903-0074 NR 24 TC 9 Z9 9 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637 SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD DEC 20 PY 1996 VL 473 IS 2 BP L115 EP & DI 10.1086/310398 PN 2 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VZ154 UT WOS:A1996VZ15400014 ER PT J AU Stecker, FW deJager, OC Salamon, MH AF Stecker, FW deJager, OC Salamon, MH TI Predicted extragalactic TeV gamma-ray sources SO ASTROPHYSICAL JOURNAL LA English DT Article DE gamma rays, theory; BL Lacertae objects, general; BL Lacertae objects, individual (Markarian 421); quasars, general ID BL LACERTAE OBJECTS; SPECTRAL PROPERTIES; BLAZARS; MARKARIAN-421; RADIATION; MODEL AB We suggest that low-redshift X-ray-selected BL Lacertae objects (XBLs) may be the only extragalactic gamma-ray sources observable at TeV energies. We use simple physical considerations involving synchrotron and Compton component spectra for blazars to suggest why the observed TeV sources are XBLs, whereas mostly radio-selected BL objects (RBLs) and flat spectrum radio quasars (FSRQs) are seen at GeV energies. These considerations indicate that the differences between XBLs and RBLs cannot be explained purely as relativistic jet orientation effects. We note that the only extragalactic TeV sources that have been observed are XBLs and that a nearby RBL with a very hard spectrum in the GeV range has not been seen at TeV energies. We also note that of the 14 BL Lac objects observed by EGRET, 12 are RBLs, whereas only two are XBLs. We give a list of nearby XBLs that we consider to be good candidate TeV sources and predict estimated TeV fluxes for these objects. C1 POTCHEFSTROOM UNIV CHRISTIAN HIGHER EDUC,DEPT PHYS,ZA-2520 POTCHEFSTROOM,SOUTH AFRICA. UNIV UTAH,DEPT PHYS,SALT LAKE CITY,UT 84112. RP Stecker, FW (reprint author), NASA,GODDARD SPACE FLIGHT CTR,HIGH ENERGY ASTROPHYS LAB,GREENBELT,MD 20771, USA. RI Stecker, Floyd/D-3169-2012 NR 33 TC 87 Z9 87 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637 SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD DEC 20 PY 1996 VL 473 IS 2 BP L75 EP L78 DI 10.1086/310407 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VZ154 UT WOS:A1996VZ15400004 ER PT J AU Tavani, M Fruchter, A Zhang, SN Harmon, BA Hjellming, RN Rupen, MP Bailyn, C Livio, M AF Tavani, M Fruchter, A Zhang, SN Harmon, BA Hjellming, RN Rupen, MP Bailyn, C Livio, M TI The dual nature of hard X-ray outbursts from the superluminal X-ray transient source GRO J1655-40 SO ASTROPHYSICAL JOURNAL LA English DT Article DE acceleration of particles; instabilities; MHD; radiation mechanisms, nonthermal; radio continuum, stars; X-rays, stars ID RELATIVISTIC JETS AB We report the results of multiwavelength observations of the superluminal X-ray transient GRO J1655-40 during and following the prominent hard X-ray outburst of 1995 March-April. GRO J1655-40 was monitored continuously by BATSE on board the Compton Gamma Ray Observatory and observed repeatedly in the radio and optical bands from the ground. About a month after the onset of the hard X-ray outburst, GRO J1655-40 was observed twice by the Hubble Space Telescope in 1995 April 25 and 27, with the aim of detecting faint optical emission from ejected plasmoids. Despite the similarity of the hard X-ray emission in 1995 April with previous events in 1994, no radio or optical emission from GRO J1655 -40 related to plasmoids was detected. We conclude that GRO J1655-40 is subject to complex behavior showing radio-loud hard X-ray outbursts with strong radio emission (of flux f(r) greater than or similar to 100 mJy), both from a ''core'' source and from propagating plasmoids (as those in 1994), and radio-quiet hard X-ray outbursts with no detectable radio emission and plasmoid activity (f(r) less than or similar to 0.5 mJy) (as those in 1995). Our results can constrain models of particle acceleration and radiation of relativistic plasmoids. C1 SPACE TELESCOPE SCI INST,BALTIMORE,MD 21218. NASA,UNIV SPACE RES ASSOC,MSFC,HUNTSVILLE,AL 35812. NATL RADIO ASTRON OBSERV,SOCORRO,NM 87801. YALE UNIV,DEPT ASTRON,NEW HAVEN,CT 06520. RP Tavani, M (reprint author), COLUMBIA UNIV,COLUMBIA ASTROPHYS LAB,NEW YORK,NY 10027, USA. NR 25 TC 34 Z9 34 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637 SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD DEC 20 PY 1996 VL 473 IS 2 BP L103 EP & DI 10.1086/310406 PN 2 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VZ154 UT WOS:A1996VZ15400011 ER PT J AU Xu, YC Garcia, E Freiser, BS Bauschlicher, CW AF Xu, YC Garcia, E Freiser, BS Bauschlicher, CW TI Experimental and theoretical studies of FeC7H7+ isomers: Fe+-C7H7 bond energies and isomeric differentiation SO INTERNATIONAL JOURNAL OF MASS SPECTROMETRY AND ION PROCESSES LA English DT Article DE bond energies; FeC7H7+; FTICR; isomeric differentiation ID ION-CYCLOTRON RESONANCE; TRANSFORM MASS-SPECTROMETRY; GAS-PHASE REACTIONS; COLLISION-INDUCED DISSOCIATION; TRANSITION-METAL IONS; PHENYL HALIDES; TROPYLIUM ION; C7H7+ IONS; TOLUENE; SPECTROSCOPY AB Three isomeric structures of Fe(C7H7)(+) presumably, Fe(tropylium)(+), Fe(benzyl)(+), and Fe(tolyl)(+), are studied with Fourier transform ion cyclotron resonance (FTICR) mass spectrometry and by theoretical calculations. Of particular interest is the role of the metal in stabilizing the tolyl ligand, given that the unmetallated tolyl ion, C6H4CH3+, rearranges to benzyl ion on the time scale of the FTICR experiment. Ions with the empirical formula Fe(C7H7)(+) were generated by three synthetic routes: (1) reaction of bare metal Fe+ with cycloheptatriene, (2) reaction of Fe(phenyl)(+) with toluene, and (3) reaction of Fe(benzyne)(+) with methyl iodide. The hypothesis is that these three reactions result in the formation of Fe(tropylium)(+), Fe(benzyl)(+) and Fe(tolyl)(+), respectively. Energy resolved collision-induced dissociation, photodissociation, and selected ion/molecule reactions readily distinguish Fe(tropylium)(+) from the other two structures. Fe(benzyl)(+) and Fe(tolyl)(+), however, are indistinguishable by collision-induced dissociation and photodissociation, but exhibit differences in reactivity with selected reagents. These results indicate that while Fe stabilizes the tolyl ion structure, upon activation the ion can rearrange to the benzyl structure. From photodissociation experiments we infer D degrees(Fe+-benzyl) = 63 +/- 5 kcal mol(-1), D degrees(Fe+-tolyl) = 83 +/- 10 kcal mol(-1), and an upper limit of D degrees(Fe+-cycloheptatrienyl) less than or equal to 129 +/- 5 kcal mol(-1), while ion-molecule reactions yield the lower limits D degrees(Fe+-benzyl) > 55 +/- 5 kcal mol(-1), D degrees(Fe+-tolyl) > 60 +/- 5 kcal mol(-1) and D degrees(Fe+-cycloheptatrienyl) > 73 kcal mol(-1). These results are self-consistent and in general agreement with ab initio calculations which yield D degrees(Fe+-cycloheptatrienyl) = 86.8 kcal mol(-1), D degrees(Fe+-tolyl) = 84.4 kcal mol(-1), and D degrees(Fe+-benzyl) = 69.4 kcal mol(-1). C1 PURDUE UNIV, HC BROWN LAB CHEM, W LAFAYETTE, IN 47907 USA. NASA, AMES RES CTR, MOFFETT FIELD, CA 94035 USA. NR 51 TC 5 Z9 5 U1 0 U2 1 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0168-1176 J9 INT J MASS SPECTROM JI Int. J. Mass Spectrom. Ion Process. PD DEC 20 PY 1996 VL 157 BP 249 EP 263 DI 10.1016/S0168-1176(96)04400-X PG 15 WC Physics, Atomic, Molecular & Chemical; Spectroscopy SC Physics; Spectroscopy GA WB312 UT WOS:A1996WB31200016 ER PT J AU Allen, DJ Kasibhatla, P Thompson, AM Rood, RB Doddridge, BG Pickering, KE Hudson, RD Lin, SJ AF Allen, DJ Kasibhatla, P Thompson, AM Rood, RB Doddridge, BG Pickering, KE Hudson, RD Lin, SJ TI Transport-induced interannual variability of carbon monoxide determined using a chemistry and transport model SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID GENERAL-CIRCULATION MODEL; CONVECTIVE-TRANSPORT; REFERENCE SCALE; MACE HEAD; CO; EMISSIONS; PARAMETERIZATION; INVENTORIES; TROPOSPHERE; ATMOSPHERE AB Transport-induced interannual variability of carbon monoxide (CO) is studied during 1989-1993 using the Goddard chemistry and transport model (GCTM) driven by assimilated data. Seasonal changes in the latitudinal distribution of CO near the surface and at 500 hPa are captured by the model. The annual cycle of CO is reasonably well simulated at sites of widely varying character. Day to day fluctuations in CO due to synoptic waves are reproduced accurately at remote North Atlantic locations. By fixing the location and magnitude of chemical sources and sinks, the importance of transport-induced variability is investigated at CO-monitoring sites. Transport-induced variability can explain 1991-1993 decreases in CO at Mace Head, Ireland, and St, David's Head, Bermuda, as well as 1991-1993 increases in CO at Key Biscayne, Florida, Transport-induced variability does not explain decreases in CO at southern hemisphere locations. The model calculation explains 80-90% of interannual variability in seasonal CO residuals at Mace Head, St. David's Head, and Key Biscayne and at least 50% of variability in detrended seasonal residuals at Ascension Island and Guam. Upper tropospheric interannual variability during October is less than 8% in the GCTM. Exceptions occur off the western coast of South America, where mixing ratios are sensitive to the strength of an upper tropospheric high, and just north of Madagascar, where concentrations are influenced by the strength of offshore flow from Africa. C1 MCNC, ENVIRONM PROGRAMS, RES TRIANGLE PK, NC 27709 USA. GEN SCI CORP, LAUREL, MD 20707 USA. NASA, GODDARD SPACE FLIGHT CTR, ATMOSPHERES LAB, GREENBELT, MD 20771 USA. RP UNIV MARYLAND, DEPT METEOROL, JOINT CTR EARTH SYST SCI, COLLEGE PK, MD 20742 USA. RI Allen, Dale/F-7168-2010; Kasibhatla, Prasad/A-2574-2010; Pickering, Kenneth/E-6274-2012; Rood, Richard/C-5611-2008; Thompson, Anne /C-3649-2014; OI Allen, Dale/0000-0003-3305-9669; Rood, Richard/0000-0002-2310-4262; Thompson, Anne /0000-0002-7829-0920; Kasibhatla, Prasad/0000-0003-3562-3737 NR 62 TC 70 Z9 71 U1 0 U2 3 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X EI 2169-8996 J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD DEC 20 PY 1996 VL 101 IS D22 BP 28655 EP 28669 DI 10.1029/96JD02984 PG 15 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA VZ788 UT WOS:A1996VZ78800004 ER PT J AU Shah, KP Rind, D Lonergan, P AF Shah, KP Rind, D Lonergan, P TI Could high-speed civil transport aircraft impact stratospheric and tropospheric temperatures measured by microwave sounding unit? SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID MIDDLE ATMOSPHERE MODEL; CLIMATE-CHANGE; RADIOSONDE VALIDATION; VARIABILITY; CIRCULATION; PRECISION; ANOMALIES; OZONE AB A radiative transfer postprocessor calculates microwave brightness temperatures Tb from climate experiments investigating supersonic aircraft exhaust impacts with the Global Climate/Middle Atmosphere Model (GCMAM) at the NASA Goddard Institute for Space Studies. Microwave signals from the exhaust-perturbed GCMAM atmospheres are contrasted with observed interannual variability (natural ''noise'') for 1982-1991 as measured by microwave sounding unit (MSU) channels across the lower troposphere, midtroposphere, and lower stratosphere. Exaggerated ozone and water vapor perturbations at supersonic cruise altitudes produce microwave signals easily detected against natural noise. Removal of ozone greenhouse action between 200 and 50 hPa cools all MSU channels with greatest Delta T-b of -8.3 K and signal-to-observed-noise (S/N) ratios above 20 in the lower stratospheric channel. Doubling middle-atmospheric water vapor above 100 hPa cools lower stratospheric T-b values by 1.5 K while warming tropospheric channels, particularly the tropopause channel. Detectable S/N ratios of 2-4 occur over the tropics and subtropics in the lower-to-middle troposphere and lower stratosphere. Realistic ozone and water vapor perturbations are based on the High-Speed Research Program/Atmospheric Effects of Stratospheric Aircraft reports. These realistic stratospheric ozone and water vapor changes produce Delta T-b signals under 0.6 K and negligible S/N ratios. The slight climatic forcings are overwhelmed by natural feedbacks of high and low cloud formation, sea ice formation, and snow coverage. Thus the modeled realistic ozone and water vapor perturbations produce small and conflicting microwave signals, undetectable against natural variability and other sources of anthropogenic climatic forcing. C1 SCI SYST & APPLICAT INC, NEW YORK, NY USA. RP Shah, KP (reprint author), NASA, GODDARD INST SPACE STUDIES, GODDARD SPACE FLIGHT CTR, 2880 BROADWAY, NEW YORK, NY 10025 USA. NR 22 TC 2 Z9 2 U1 1 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD DEC 20 PY 1996 VL 101 IS D22 BP 28711 EP 28721 DI 10.1029/96JD02721 PG 11 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA VZ788 UT WOS:A1996VZ78800008 ER PT J AU Jackman, CH Fleming, EL Chandra, S Considine, DB Rosenfield, JE AF Jackman, CH Fleming, EL Chandra, S Considine, DB Rosenfield, JE TI Past, present, and future modeled ozone trends with comparisons to observed trends SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Review ID SOLAR PROTON EVENTS; HALOGEN OCCULTATION EXPERIMENT; QUASI-BIENNIAL OSCILLATION; TWO-DIMENSIONAL MODEL; PARABOLIC METHOD PPM; MIDDLE ATMOSPHERE; 2-DIMENSIONAL MODEL; UPPER-STRATOSPHERE; PINATUBO AEROSOL; GLOBAL OZONE AB The NASA Goddard Space Flight Center (GSFC) two-dimensional (2-D) model of stratospheric transport and photochemistry has been used to predict ozone changes that have occurred in the past 20 years from anthropogenic chlorine and bromine emissions, solar cycle ultraviolet flux variations, the changing sulfate aerosol abundance due to several volcanic eruptions including the major eruptions of El Chichon and Mount Pinatubo, solar proton events (SPEs); and galactic cosmic rays (GCRs). The same linear regression technique has been used to derive profile and total ozone trends from both measurements and the GSFC model. Derived 2-D model ozone profile trends are similar in shape to the Solar Backscattered Ultraviolet (SBUV) and SBUV/2 trends with highest percentage decreases in the upper stratosphere at the highest latitudes. The general magnitude of the derived 2-D model upper stratospheric negative ozone trend is larger than the trends derived from the observations, especially in the northern hemisphere. The derived 2-D model negative trend in the lower stratosphere at middle northern latitudes is less than the measured trend. The derived 2-D model total ozone trends are small in the tropics and larger at middle and high latitudes, a pattern that is very similar to the Total Ozone Mapping Spectrometer (TOMS) derived trends. The differences between the derived 2-D model and TOMS trends are generally within 1-2% in the northern hemisphere and the tropics. The derived 2-D model trends are generally more in southern middle and high latitudes by 2-4%. Our 2-D model predictions are also compared with the temporal variations in total ozone averaged between 65 degrees S and 65 degrees N over the TOMS observing period (1979-1993). Inclusion of anthropogenic chlorine and bromine increases, solar cycle ultraviolet flux variations, and the changing sulfate aerosol area abundance into our model captures much of the observed TOMS global total ozone changes. The model simulations predict a decrease in ozone of about 4% from 1979 to 1995 due to the chlorine and bromine increases. The changing sulfate aerosol abundances were computed to significantly affect ozone and result in a maximum decrease of about 2.8% in 1992 in the annually averaged almost global total ozone (AAGTO) computed between 65 degrees S and 65 degrees N. Solar ultraviolet flux variations are calculated to provide a moderate perturbation to the AAGTO over the solar cycle by a maximum of +/-0.6% (about 1.2% from solar maximum to minimum). Effects from SPEs are relatively small, with a predicted maximum AAGTO decrease of 0.22% in 1990 after the extremely large events of October 1989. GCRs are computed to cause relatively minuscule variations of a maximum of +/-0.02% in AAGTO over a solar cycle. C1 APPL RES CORP, LANDOVER, MD 20785 USA. GEN SCI CORP, LAUREL, MD 20707 USA. RP Jackman, CH (reprint author), NASA, GODDARD SPACE FLIGHT CTR, ATMOSPHERES LAB, CODE 916, GREENBELT, MD 20771 USA. RI Jackman, Charles/D-4699-2012 NR 105 TC 167 Z9 171 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 DEC 20 PY 1996 VL 101 IS D22 BP 28753 EP 28767 DI 10.1029/96JD03088 PG 15 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA VZ788 UT WOS:A1996VZ78800011 ER PT J AU Stanford, JL Ziemke, JR AF Stanford, JL Ziemke, JR TI A practical method for predicting midlatitude total column ozone from operational forecast temperature fields SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article AB Accurate forecasts of total column ozone (Omega) are important because, among other reasons, forecasts of clear-air biologically important solar ultraviolet (UVB) reaching the Earth's surface are exponentially sensitive to Omega. We present a simple method for predicting Omega using forecast lower stratospheric temperatures and a precalculated lookup table based on ozone climatology from several years of satellite observations. Compared with observations, the simple method gives 1-day forecast Omega errors of similar to 1-2% (similar to 2-3%) in northern (southern) hemisphere summers, comparable with current multivariate UVB forecast models being used by national weather services in several countries. The advantage of the prediction method described here is its simplicity: a convenient lookup table based on ozone climatology is used, without the need for recalculation in each forecast. The method may prove useful for surface UVB forecasts, especially in the biologically important summer seasons of both hemispheres. C1 NASA, GODDARD SPACE FLIGHT CTR, NATL RES COUNCIL, GREENBELT, MD 20771 USA. RP Stanford, JL (reprint author), IOWA STATE UNIV SCI & TECHNOL, DEPT PHYS & ASTRON, AMES, IA 50011 USA. NR 20 TC 9 Z9 9 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD DEC 20 PY 1996 VL 101 IS D22 BP 28769 EP 28773 DI 10.1029/96JD03093 PG 5 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA VZ788 UT WOS:A1996VZ78800012 ER PT J AU Jucks, KW Johnson, DG Chance, KV Traub, WA Salawitch, RJ Stachnik, RA AF Jucks, KW Johnson, DG Chance, KV Traub, WA Salawitch, RJ Stachnik, RA TI Ozone production and loss rate measurements in the middle stratosphere SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID SULFURIC-ACID; UARS DATA; CHLORINE; NITROGEN; BROMINE; CLO; O-3; MESOSPHERE; CHEMISTRY; REDUCTION AB We present the first simultaneous measurements of HOx, NOx, and Cl-x radicals in the middle stratosphere obtained during a balloon flight at 34 degrees N in September 1989, along with calculations from a photochemical model, to show that NO, catalytic cycles dominate loss of ozone (O-3) for altitudes between 24 and 38 km; the observed abundance of ClO is lower than that expected for altitudes above 30 km on the basis of models using recommended rates and cross sections, reducing the relative importance of the Cl-x catalytic cycles for loss of O-3; and removal rates of O-3 derived from observed concentrations of rate limiting HOx, NOx, and Cl-x radicals balance computed production rates for altitudes between 32 and 38 km, a region where ozone is expected to be regulated primarily by photochemical processes. C1 CALTECH, JET PROP LAB, PASADENA, CA 91109 USA. RP Jucks, KW (reprint author), HARVARD SMITHSONIAN CTR ASTROPHYS, 60 GARDEN ST, CAMBRIDGE, MA 02138 USA. RI Salawitch, Ross/B-4605-2009; OI Salawitch, Ross/0000-0001-8597-5832; Chance, Kelly/0000-0002-7339-7577 NR 46 TC 30 Z9 30 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 DEC 20 PY 1996 VL 101 IS D22 BP 28785 EP 28792 DI 10.1029/96JD02739 PG 8 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA VZ788 UT WOS:A1996VZ78800014 ER PT J AU Zheng, J Weinheimer, AJ Ridley, BA Liu, SC Sachse, GW Anderson, BE Collins, JE AF Zheng, J Weinheimer, AJ Ridley, BA Liu, SC Sachse, GW Anderson, BE Collins, JE TI Analysis of small- and large-scale increases of reactive nitrogen observed during the Second Airborne Arctic Stratospheric Expedition SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID AIRCRAFT EXHAUST PLUMES; AASE-II; UPPER TROPOSPHERE; NITRIC-OXIDE; OZONE; PACIFIC; NOX; DISTRIBUTIONS; EASTERN; IMPACT AB An analysis of the data obtained during AASE II was made to characterize small- (delta x < 24 km) and large-scale (30 < delta x < 260 km) increases of reactive nitrogen species. By using the NOx/NOy ratio, the increases were classified into fresh emissions and aged air parcels. The sources of the NOy increases were then assessed by the freshness of the increases and by examining the correlation (or absence thereof) between NOy and other trace species including tracers of various NOx sources: for example, aircraft emissions, lightning, the stratospheric source, and sources in the boundary layer. We found that the majority (43%) of NOy increases in the upper troposphere and lower stratosphere were due to displacement of constant mixing ratio surfaces relative to isobaric flight paths. Aircraft emissions were the second most abundant (17%). The next significant contributor was surface emissions, including fossil fuel combustion and biomass burning. Only two lightning spikes were found, apparently due to the winter season and emphasis on high latitudes in the AASE II experiment. The relative contribution from each source to the increases (or positive variability) represents a measure of the relative source strength. However, it is important to note that our findings on the relative contribution of each source to the NOy increases should not be applied directly to estimating the relative source strength of the ambient or background NOy abundance. Knowledge of the detailed temporal and spatial distribution of the relative contribution of each source is needed. This requires a substantially higher precision for the instruments of tracer gases than those used in this study. C1 NASA, LANGLEY RES CTR, HAMPTON, VA 23681 USA. UNIV COLORADO, COOPERAT INST RES ENVIRONM SCI, BOULDER, CO 80309 USA. NOAA, AERON LAB, BOULDER, CO 80303 USA. SCI & TECHNOL CORP, HAMPTON, VA 23666 USA. RP Zheng, J (reprint author), NATL CTR ATMOSPHER RES, DIV ATMOSPHER CHEM, POB 3000, BOULDER, CO 80307 USA. NR 28 TC 5 Z9 5 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 DEC 20 PY 1996 VL 101 IS D22 BP 28805 EP 28816 DI 10.1029/96JD02034 PG 12 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA VZ788 UT WOS:A1996VZ78800016 ER PT J AU McKay, DS ThomasKeprta, KL Romanek, CS Gibson, EK Vali, H AF McKay, DS ThomasKeprta, KL Romanek, CS Gibson, EK Vali, H TI Evaluating the evidence for past life on Mars - Response SO SCIENCE LA English DT Article ID METEORITE ALH84001; SULFIDE MINERALS; CI CHONDRITES; CARBONATE; CONCRETIONS; CHEMISTRY; SIDERITE; ORIGIN C1 LOCKHEED MARTIN,HOUSTON,TX 77058. UNIV GEORGIA,SAVANNAH RIVER ECOL LAB,AIKEN,SC 29802. RP McKay, DS (reprint author), NASA,LYNDON B JOHNSON SPACE CTR,MAIL CODE SN,HOUSTON,TX 77058, USA. RI Vali, Hojatollah/F-3511-2012 OI Vali, Hojatollah/0000-0003-3464-9943 NR 29 TC 5 Z9 5 U1 1 U2 10 PU AMER ASSOC ADVANCEMENT SCIENCE PI WASHINGTON PA 1200 NEW YORK AVE, NW, WASHINGTON, DC 20005 SN 0036-8075 J9 SCIENCE JI Science PD DEC 20 PY 1996 VL 274 IS 5295 BP 2123 EP 2125 PG 3 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA VY974 UT WOS:A1996VY97400067 ER PT J AU Gibson, EK McKay, DS ThomasKeprta, K Romanek, CS AF Gibson, EK McKay, DS ThomasKeprta, K Romanek, CS TI Evaluating the evidence for past life on Mars - Response SO SCIENCE LA English DT Article ID ALH84001 C1 NASA,LYNDON B JOHNSON SPACE CTR,EARTH SCI & SOLAR SYST EXPLORAT DIV,HOUSTON,TX 77058. LOCKHEED MARTIN,HOUSTON,TX 77058. UNIV GEORGIA,SAVANNAH RIVER ECOL LAB,AIKEN,SC 29802. RP Gibson, EK (reprint author), NASA,LYNDON B JOHNSON SPACE CTR,PLANETARY SCI BRANCH,SN4,HOUSTON,TX 77058, USA. NR 5 TC 3 Z9 3 U1 0 U2 3 PU AMER ASSOC ADVANCEMENT SCIENCE PI WASHINGTON PA 1200 NEW YORK AVE, NW, WASHINGTON, DC 20005 SN 0036-8075 J9 SCIENCE JI Science PD DEC 20 PY 1996 VL 274 IS 5295 BP 2125 EP 2125 PG 1 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA VY974 UT WOS:A1996VY97400068 ER PT J AU Lee, TJ AF Lee, TJ TI Characterization of BrNO2, cis-BrONO, and trans-BrONO. Implications for atmospheric chemistry SO JOURNAL OF PHYSICAL CHEMISTRY LA English DT Article ID GAUSSIAN-BASIS SETS; AB-INITIO CHARACTERIZATION; MOLECULAR CALCULATIONS; NITRYL BROMIDE; ATOMS; KINETICS; NO2; HOBR; CL; THERMOCHEMISTRY AB The titled compounds are investigated using large one-particle basis sets in conjunction with the singles and doubles coupled-cluster method that includes a perturbational estimate of the effects of connected triple excitations, denoted CCSD(T). Accurate geometries, dipole moments, harmonic vibrational frequencies, and IR intensities are determined. Agreement with the available experimental data (which is limited to fundamental vibrational frequencies) is very good except for the Br-N stretching mode in BrNO2. Convincing theoretical and experimental arguments are presented which indicate that the experimental assignment for the Br-N fundamental is in error. Accurate isomerization energies are determined at the CCSD(T) level using spdfg one-particle basis sets. Comparison of ab initio results for the titled compounds with previously published ab initio results from the fluorine and chlorine analogs elucidates several trends involving equilibrium geometries, bonding characteristics, and relative energies. Heats of formation of all three titled compounds are evaluated and used to show that BrNO2 and cis-BrONO are sufficiently thermally stable to exist in the Earth's stratosphere. Possible stratospheric formation and destruction mechanisms are discussed. RP Lee, TJ (reprint author), NASA, AMES RES CTR, MS230-3, MOFFETT FIELD, CA 94035 USA. RI Lee, Timothy/K-2838-2012 NR 39 TC 27 Z9 27 U1 1 U2 7 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA SN 0022-3654 J9 J PHYS CHEM-US JI J. Phys. Chem. PD DEC 19 PY 1996 VL 100 IS 51 BP 19847 EP 19852 DI 10.1021/jp962605g PG 6 WC Chemistry, Physical SC Chemistry GA VZ912 UT WOS:A1996VZ91200016 ER PT J AU Pollney, D Zannias, T AF Pollney, D Zannias, T TI Relativistic self-similar flows SO ANNALS OF PHYSICS LA English DT Article ID SHELL-FOCUSING SINGULARITIES; GAMMA-RAY BURSTS; GRAVITATIONAL COLLAPSE; COSMIC FIREBALLS; OPTICALLY THICK; BLACK-HOLES; FLUID; EQUATIONS; DYNAMICS; WAVES AB A mathematical framework analyzing a class of spherical self-similar hydrodynamical flows on a class of homothetic spherically symmetric background geometries is presented. The analysis covers relativistic flows propagating in the following class of spacetimes: (i) Minkowski spacetime, (ii) the homothetic Bondi-Tolman spacetime, (iii) the spatially flat Friedman-Robertson-Walker cosmologies. After the introduction of the mathematical framework, there follows a detailed investigation of special relativistic flows with the pressure P and density rho obeying P = kp, k a constant 0 less than or equal to k less than or equal to 1. An extensive analysis of the singular and critical points of the differential equations determining the flow is presented. By a combination of analytical and numerical techniques several classes of flows have been constructed. We have found flows describing an oscillation of the medium, as well as flows representing relativistic detonation waves propagating on a medium at rest. In addition, two classes of analytical closed form solutions are given. By invoking the relativistic Rankine-Hugoniot conditions we briefly discuss a way by which two self-similar solutions can be joined across an expanding (or contracting) shock wave. (C) 1996 Academic Press, Inc C1 NATL AUTONOMOUS UNIV MEXICO,INST CIENCIAS NUCL,MEXICO CITY 04510,DF,MEXICO. NASA,GODDARD SPACE FLIGHT CTR,HIGH ENERGY ASTROPHYS LAB,GREENBELT,MD 20771. RP Pollney, D (reprint author), QUEENS UNIV,DEPT PHYS,KINGSTON,ON K7L 3N6,CANADA. NR 52 TC 2 Z9 2 U1 0 U2 1 PU ACADEMIC PRESS INC JNL-COMP SUBSCRIPTIONS PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 SN 0003-4916 J9 ANN PHYS-NEW YORK JI Ann. Phys. PD DEC 15 PY 1996 VL 252 IS 2 BP 241 EP 275 DI 10.1006/aphy.1996.0131 PG 35 WC Physics, Multidisciplinary SC Physics GA VY568 UT WOS:A1996VY56800001 ER PT J AU McPeters, RD Labow, GJ AF McPeters, RD Labow, GJ TI An assessment of the accuracy of 14.5 years of Nimbus 7 TOMS Version 7 ozone data by comparison with the Dobson network SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article AB A Version 7 algorithm and calibration have been applied to the 14.5 year Nimbus 7 TOMS ozone record (1978-1993). The ozone retrieval algorithm has been significantly improved for cloudy conditions and for high solar zenith angles, and the radiative transfer used in the algorithm is more accurate. New calibration techniques have been used that produce a very stable data set even after 1990 when TOMS degradation became significant. TOMS ozone now agrees with average ozone from an ensemble of 30 northern hemisphere ground stations (Dobsons and Brewers) to within +/-1% throughout most of the 14.5 year record. The time-dependent drift relative to Dobson is 0.29% per decade through the end of the data record. There is almost no solar zenith angle dependence in the comparison for angles below about 80 degrees, but data should be used with caution for larger solar zenith angles. There is also a residual total ozone dependence in the TOMS-Dobson difference, of about 1% per 100 DU. C1 HUGHES STX CORP,GREENBELT,MD 20770. RP McPeters, RD (reprint author), NASA,GODDARD SPACE FLIGHT CTR,CODE 916,GREENBELT,MD 20771, USA. RI McPeters, Richard/G-4955-2013 OI McPeters, Richard/0000-0002-8926-8462 NR 11 TC 88 Z9 96 U1 0 U2 4 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD DEC 15 PY 1996 VL 23 IS 25 BP 3695 EP 3698 DI 10.1029/96GL03539 PG 4 WC Geosciences, Multidisciplinary SC Geology GA VY929 UT WOS:A1996VY92900006 ER PT J AU McPeters, RD Hollandsworth, SM Flynn, LE Herman, JR Seftor, CJ AF McPeters, RD Hollandsworth, SM Flynn, LE Herman, JR Seftor, CJ TI Long-term ozone trends derived from the 16-year combined Nimbus 7 Meteor 3 TOMS Version 7 record SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article AB Ozone measurements from the Nimbus 7 TOMS instrument, which operated from November 1978 through early May 1993, have been extended through December 1994 using data from the TOMS instrument on-board the Russian Meteor 3 satellite. Both TOMS data records have recently been recalibrated, and then reprocessed using the Version 7 retrieval algorithm. Long-term trend estimates obtained from a multiple regression analysis show ozone losses in the extended data record similar to those reported in previous studies using Version 6 TOMS and SBUV data, and ground-based Dobson data. Ozone continues to decline through the end of 1994, with the most significant ozone losses occurring in the high southern latitudes during October (-20% per decade) and in the northern mid- to high-latitudes during March/April (-6 to -8% per decade). There is no significant ozone trend in the tropics. Annual-average trends derived from the Nimbus 7 Version 7 data are 0-2.5% per decade less negative than those derived over the same time period using Version 6 data. C1 APPL RES CORP,LANDOVER,MD 20785. SOFTWARE CORP AMER,LANHAM,MD. HUGHES STX,LANHAM,MD. RP McPeters, RD (reprint author), NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771, USA. RI Flynn, Lawrence/B-6321-2009; McPeters, Richard/G-4955-2013 OI Flynn, Lawrence/0000-0001-6856-2614; McPeters, Richard/0000-0002-8926-8462 NR 14 TC 93 Z9 95 U1 0 U2 5 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD DEC 15 PY 1996 VL 23 IS 25 BP 3699 EP 3702 DI 10.1029/96GL03540 PG 4 WC Geosciences, Multidisciplinary SC Geology GA VY929 UT WOS:A1996VY92900007 ER PT J AU Duda, DP Spinhirne, JD AF Duda, DP Spinhirne, JD TI Split-window retrieval of particle size and optical depth in contrails located above horixontally inhomogeneous ice clouds SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID THIN CIRRUS CLOUDS; MU-M WINDOW; EMISSIVITY AB Multichannel radiometer measurements-of a newly formed contrail taken from a NASA ER-2 aircraft over northern Oklahoma during the FIRE Cirrus-II experiment are used in a split-window retrieval of the contrail's particle size and optical depth. The effect of horizontal inhomogeneity in an underlying cirrus layer on the contrail retrieval is studied through the use of multi-dimensional radiative transfer model simulations. Estimates of the contrail's effective radius are significantly smaller (5 - 7 mu m) than those in the underlying cirrus (21 mu m). The effect of horizontal inhomogeneity in the underlying cirrus on contrail particle size and optical depth retrievals is generally smaller than the corresponding effects of particle shape or spectral variations in surface emissivity on the retrievals. The differences in particle size retrievals are 10 percent or less as a result of the inhomogeneity, while they are from 10 to 40 percent for ice cylinders, and range from 1 to 40 percent for ice spheroids. Horizontal inhomogeneity affected the optical depth retrievals by only one or two percent, while surface emissivity variations affected the retrievals by 12 to 24 percent, and particle shape produced differences as large as 9 percent. RP Duda, DP (reprint author), NASA,GODDARD SPACE FLIGHT CTR,UNIV SPACE RES ASSOC,CODE 912,GREENBELT,MD 20771, USA. NR 12 TC 9 Z9 9 U1 0 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD DEC 15 PY 1996 VL 23 IS 25 BP 3711 EP 3714 DI 10.1029/96GL03645 PG 4 WC Geosciences, Multidisciplinary SC Geology GA VY929 UT WOS:A1996VY92900010 ER PT J AU Teitelbaum, LP Keihm, SJ Linfield, RP Mahoney, MJ Resch, GM AF Teitelbaum, LP Keihm, SJ Linfield, RP Mahoney, MJ Resch, GM TI A demonstration of precise calibration of tropospheric delay fluctuations with water vapor radiometers SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID TURBULENCE AB The ability of water vapor radiometers (WVRs) to calibrate changes in tropospheric delay was demonstrated during very long baseline radio interferometer (VLBI) observations at Goldstone, California. WVR measurements reduced the observed VLBI delay variations over a 13 hr period by a factor of approximate to 2.5. When applied to shorter time scales, a approximate to 50% reduction in 100-700 s delay variations was achieved during conditions of high tropospheric activity. Thermal WVR noise precluded calibration of short time scale delay fluctuations during quiet tropospheric conditions. RP Teitelbaum, LP (reprint author), CALTECH,JET PROP LAB,4800 OAK GROVE DR,PASADENA,CA 91109, USA. NR 11 TC 2 Z9 2 U1 0 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD DEC 15 PY 1996 VL 23 IS 25 BP 3719 EP 3722 DI 10.1029/96GL03309 PG 4 WC Geosciences, Multidisciplinary SC Geology GA VY929 UT WOS:A1996VY92900012 ER PT J AU Kim, JH Newchurch, MJ AF Kim, JH Newchurch, MJ TI Climatology and trends of tropospheric ozone over the eastern Pacific Ocean: The influences of biomass burning and tropospheric dynamics SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article AB To study the latitudinal variation of tropospheric ozone over the eastern Pacific Ocean, we derive ozone in the lower troposphere by subtracting TOMS column ozone over the Andes from the ozone column over the eastern Pacific Ocean. The analysis of tropospheric ozone climatology in conjunction with meteorological and biomass-burning data suggests three latitude bands with different characteristics for tropospheric ozone. (1) Air in the latitude range 3 degrees N-7 degrees N experiences persistent upward motion in the middle troposphere over the eastern equatorial Pacific Ocean. This condition results in relatively low ozone amounts in this region. (2) Tropospheric ozone between latitudes 2 degrees N-22 degrees S shows strong seasonal variation that is well correlated with the biomass burning season over southern tropical South America. Persistent subsidence in the middle troposphere and prevailing easterlies over this region provide favorable conditions for enhancing ozone amounts in the lower troposphere. (3) Tropospheric ozone over 23 degrees S-36 degrees S does not appear to be influenced by biomass burning. Regression analysis of deseasonalized tropospheric ozone shows positive trends from 12 degrees S to 23 degrees S and from 2 degrees N to 5 degrees N with essentially zero trends elsewhere. Trends north of the equator are generally smaller and less consistently positive than trends from 12 degrees S-23 degrees S. With tropospheric ozone seasonally in phase in the presence of enabling horizontal and vertical winds, the average increasing trend of +0.9+/-0.3(2 sigma)[%/yr] or +0.14+/-0.04(2 sigma)[DU/yr] between 12 degrees S and 23 degrees S over the 14 years analyzed here is consistent with an increasing biomass-burning source. C1 NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,EARTH SYST SCI DIV,HUNTSVILLE,AL 35812. UNIV ALABAMA,DEPT ATMOSPHER SCI,HUNTSVILLE,AL 35899. NR 17 TC 34 Z9 36 U1 0 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD DEC 15 PY 1996 VL 23 IS 25 BP 3723 EP 3726 DI 10.1029/96GL03615 PG 4 WC Geosciences, Multidisciplinary SC Geology GA VY929 UT WOS:A1996VY92900013 ER PT J AU Shih, TH Zhu, J Lumley, JL AF Shih, TH Zhu, J Lumley, JL TI Calculation of wall-bounded complex flows and free shear flows SO INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS LA English DT Article DE turbulence models; realizability; complex flows ID REYNOLDS-STRESS; TURBULENCE; MODELS AB Various wall-bounded flows with complex geometries and free shear flows have been studied with a newly developed realizable Reynolds stress algebraic equation model. The model development is based on the invariant theory in continuum mechanics. This theory enables us to formulate a general constitutive relation for the Reynolds stresses. Pope (J. Fluid Mech., 72, 331-340 (1975)) was the first to introduce this kind of constitutive relation to turbulence modelling. In our study, realizability is imposed on the truncated constitutive relation to determine the coefficients so that, unlike the standard k-epsilon eddy viscosity model, the present model will not produce negative normal stresses in any situations of rapid distortion. The calculations based on the present model have shown encouraging success in modelling complex turbulent flows. C1 CORNELL UNIV,ITHACA,NY 14853. RP Shih, TH (reprint author), NASA,LEWIS RES CTR,OAI,ICOMP,CTR MODELLING TURBULENCE & TRANSIT,CLEVELAND,OH 44135, USA. NR 22 TC 35 Z9 38 U1 0 U2 3 PU JOHN WILEY & SONS LTD PI W SUSSEX PA BAFFINS LANE CHICHESTER, W SUSSEX, ENGLAND PO19 1UD SN 0271-2091 J9 INT J NUMER METH FL JI Int. J. Numer. Methods Fluids PD DEC 15 PY 1996 VL 23 IS 11 BP 1133 EP 1144 DI 10.1002/(SICI)1097-0363(19961215)23:11<1133::AID-FLD456>3.0.CO;2-A PG 12 WC Computer Science, Interdisciplinary Applications; Mathematics, Interdisciplinary Applications; Mechanics; Physics, Fluids & Plasmas SC Computer Science; Mathematics; Mechanics; Physics GA VW276 UT WOS:A1996VW27600002 ER PT J AU Comiso, JC Kwok, R AF Comiso, JC Kwok, R TI Surface and radiative characteristics of the summer Arctic sea ice cover from multisensor satellite observations SO JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS LA English DT Article ID SYNTHETIC-APERTURE-RADAR; PASSIVE MICROWAVE; MULTIYEAR ICE; OCEAN; CLASSIFICATION; SIGNATURES; MELT AB Accurate quantification and characterization of the Arctic summer ice cover are needed for mass balance, heat flux, and modeling studies in the region. A general assessment of the state and basic characteristics of the ice cover can best be done in summer because it is when the perennial component is fully revealed. The main source of summer ice information has been passive microwave and to a lesser degree active microwave data. However, the emissivity and backscatter of sea ice are abnormal and difficult to resolve during this time period, causing large uncertainties in the interpretation of satellite data. In this study we examined the state of the sea ice cover by using special scanning microwave imager (SSM/I), synthetic aperture radar (SAR), and advanced very high resolution radiometer (AVHRR) satellite data synergistically. The surface and radiative characteristics of the summer ice cover were evaluated in the context of three special events: onset of melt, melt pending, and freeze-up. These events affect the emissivity and backscatter and may alter the albedo and ice structure. Onset of melt is readily detectable and is shown to migrate rapidly to the north in June. Melt pending is not directly observable but is postulated to be the main cause of the decreases in brightness temperatures and large discrepancies between the SSM/I and SAR ice concentration results in many areas. In these areas, SAR and AVHRR results show concentrations near 100%, while the SSM/I data were as low as 70%. During freeze-up the ice signatures are still quite different from those of midwinter ice, but the ice concentrations from SSM/I generally agree well with those from SAR data. Our results show that, generally, the average ice concentration within the pack is usually greater than 90% during the summer, which is substantially larger than that inferred previously from passive microwave data. The use of combined SAR and SSM/I data may also provide melt-pending fraction and first-order estimate of albedo in the Arctic region. C1 CALTECH,JET PROP LAB,PASADENA,CA 91109. RP Comiso, JC (reprint author), NASA,GODDARD SPACE FLIGHT CTR,LAB HYDROSPHER PROC,MC 971,GREENBELT,MD 20771, USA. RI Kwok, Ron/A-9762-2008 OI Kwok, Ron/0000-0003-4051-5896 NR 33 TC 65 Z9 66 U1 2 U2 5 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 J9 J GEOPHYS RES-OCEANS JI J. Geophys. Res.-Oceans PD DEC 15 PY 1996 VL 101 IS C12 BP 28397 EP 28416 DI 10.1029/96JC02816 PG 20 WC Oceanography SC Oceanography GA VY902 UT WOS:A1996VY90200007 ER PT J AU Kwok, R Comiso, JC Cunningham, GF AF Kwok, R Comiso, JC Cunningham, GF TI Seasonal characteristics of the perennial ice cover of the Beaufort Sea SO JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS LA English DT Article ID APERTURE RADAR DATA; PASSIVE MICROWAVE; SUMMER; SIGNATURES; IMAGERY; WEATHER AB By definition, ice which survives the summer is classified as multiyear ice. Thus the area covered by multiyear ice during the winter should be nearly equivalent to the ice area during the previous summer's minima. This condition provides a reasonable criterion for the evaluation of ice concentration and ice type retrieval algorithms using remote-sensing data sets. From special sensor microwave imager (SSM/I) data the NASA Team algorithm estimates the multiyear, first-year, and total ice concentrations during the winter using combinations of the polarization and spectral gradient ratios. The Team algorithm provides only estimates of ice concentration in the summer. From ERS 1 synthetic aperture radar (SAR) data the remarkably stable contrast between multiyear ice and first-year ice in winter provides consistent estimates of multiyear ice concentrations. In the summer, multiyear ice concentration cannot be estimated from SAR or SSM/I data because free water on the surface effectively masks the backscatter and emissivity signature of this ice type. From SAR data a technique which takes advantage of the high backscatter of wind-roughened open water as a discrimination feature is used to estimate the total ice concentration in the summer. With a year-long (January 1992 to January 1993) data set from the Beaufort Sea we found that the multiyear ice concentration estimates from the SAR data are stable and are nearly equivalent to the ice concentration estimated at the end of the previous summer. We contrast this with the variability of the multiyear ice concentration and ice fraction estimates obtained using SSM/I data. The Team algorithm produces ice concentration and multiyear ice estimates which are consistently lower than those from the SAR data. We discuss reasons for these discrepancies and the implications of the higher than previously noted multiyear ice concentrations. C1 NASA,GODDARD SPACE FLIGHT CTR,LAB HYDROSPHER PROC,GREENBELT,MD 20771. RP Kwok, R (reprint author), CALTECH,JET PROP LAB,4800 OAK GROVE DR,PASADENA,CA 91109, USA. RI Kwok, Ron/A-9762-2008 OI Kwok, Ron/0000-0003-4051-5896 NR 26 TC 16 Z9 19 U1 0 U2 3 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 J9 J GEOPHYS RES-OCEANS JI J. Geophys. Res.-Oceans PD DEC 15 PY 1996 VL 101 IS C12 BP 28417 EP 28439 DI 10.1029/96JC02455 PG 23 WC Oceanography SC Oceanography GA VY902 UT WOS:A1996VY90200008 ER PT J AU Bansal, NP AF Bansal, NP TI SiC fiber-reinforced barium aluminosilicate glass-ceramic matrix composites SO MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING LA English DT Article DE Barium aluminosilicate; frictional stress; matrix cracking stress ID INTERFACIAL SHEAR-STRESS; SILICON-CARBIDE FIBERS; MECHANICAL-PROPERTIES; STRENGTH; FRACTURE; FRICTION; CRACKING AB Unidirectional CVD SiC (SCS-6) monofilament reinforced BaO-Al2O3-2SiO(2) (BAS) glass-ceramic matrix composites have been fabricated by a tape lay-up method followed by hot pressing. The glass matrix flows around fibers during hot pressing resulting in nearly fully dense (95-98%) composites. Strong and tough composites having first matrix cracking stress of 250-300 MPa and ultimate flexural strength as high as 900 MPa have been obtained. Composite fracture surfaces showed fiber pullout with no chemical reaction at the fiber/matrix interface. From fiber push out, the fiber/matrix interfacial debond strength and the sliding frictional stress were determined to be 5.9 +/- 1.2 MPa and 4.8 +/- 0.9 MPa, respectively. The fracture surface of an uncoated SiCf(SCS-0)/BAS composite also showed fiber/matrix debonding, fiber pullout, and crack deflection around the fibers implying that the SiC fibers may need no surface coating for reinforcement of the BAS glass-ceramic. Applicability of micromechanical models in predicting the first matrix cracking stress and the ultimate strength of these composites has also been examined. RP Bansal, NP (reprint author), NASA,LEWIS RES CTR,CLEVELAND,OH 44135, USA. NR 35 TC 24 Z9 24 U1 0 U2 4 PU ELSEVIER SCIENCE SA LAUSANNE 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 DEC 15 PY 1996 VL 220 IS 1-2 BP 129 EP 139 DI 10.1016/S0921-5093(96)10434-2 PG 11 WC Nanoscience & Nanotechnology; Materials Science, Multidisciplinary; Metallurgy & Metallurgical Engineering SC Science & Technology - Other Topics; Materials Science; Metallurgy & Metallurgical Engineering GA VZ839 UT WOS:A1996VZ83900016 ER PT J AU Reynolds, CS DiMatteo, T Fabian, AC Hwang, U Canizares, CR AF Reynolds, CS DiMatteo, T Fabian, AC Hwang, U Canizares, CR TI The 'quiescent' black hole in M87 SO MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY LA English DT Letter DE accretion, accretion discs; galaxies, active; galaxies, individual, M87 ID ACTIVE GALACTIC NUCLEI; VIRGO CLUSTER; RADIO-SOURCES; VLBI OBSERVATIONS; IONIZED-GAS; GALAXIES; LUMINOSITY; SPECTRUM; IMAGES; DISK AB It is believed that most giant elliptical galaxies possess nuclear black holes with masses in excess of 10(8) M(.). Bondi accretion from the interstellar medium might then be expected to produce quasar-like luminosities from the nuclei of even quiescent elliptical galaxies. It is a puzzle that such luminosities are not observed. Motivated by this problem, Fabian & Rees have recently suggested that the final stages of accretion in these objects occurs in an advection-dominated mode with a correspondingly small radiative efficiency. Despite possessing a long-known active nucleus and dynamical evidence for a black hole, the low radiative and kinetic luminosities of the core of M87 provide the best illustration of this problem, We examine an advection-dominated model for the nucleus of M87, and show that accretion at the Bondi rate is compatible with the best-known estimates for the core flux from radio through to X-ray wavelengths, The success of this model prompts us to propose that Fanaroff-Riley (FR)I radio galaxies and quiescent elliptical galaxies accrete in an advection-dominated mode whereas FRII-type radio-loud nuclei possess radiatively efficient thin accretion discs. C1 NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. MIT,CTR SPACE RES,CAMBRIDGE,MA 02139. RP Reynolds, CS (reprint author), INST ASTRON,MADINGLEY RD,CAMBRIDGE CB3 0HA,ENGLAND. RI Di Matteo, Tiziana/O-4762-2014 OI Di Matteo, Tiziana/0000-0002-6462-5734 NR 37 TC 87 Z9 87 U1 0 U2 0 PU BLACKWELL SCIENCE LTD PI OXFORD PA P O BOX 88, OSNEY MEAD, OXFORD, OXON, ENGLAND OX2 0NE SN 0035-8711 J9 MON NOT R ASTRON SOC JI Mon. Not. Roy. Astron. Soc. PD DEC 15 PY 1996 VL 283 IS 4 BP L111 EP L116 PG 6 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA WA235 UT WOS:A1996WA23500003 ER PT J AU DellaCorte, C AF DellaCorte, C TI The effect of counterface on the tribological performance of a high temperature solid lubricant composite from 25 to 650 degrees C SO SURFACE & COATINGS TECHNOLOGY LA English DT Article; Proceedings Paper CT 23rd International Conference on Metallurgical Coatings and Thin Films CY APR 22-26, 1996 CL SAN DIEGO, CA SP Amer Vacuum Soc, Vacuum Met & Thin Films Div DE solid lubricant; high temperature; friction; wear; superalloys; ceramics ID COATINGS; SILVER; FILMS AB The effect of counterface selection on the tribological performance of a Ag/BaF2-CaF2 containing composite coating are studied. Ceramic (Al2O3) and metal (Inconel X-750) pins are slid against PS300 (a metal bonded chrome oxide coating with Ag and BaF2/CaF2 lubricant additives) in a pin-on-disk tribometer at 25, 500 and 650 degrees C. Compared to the ceramic counterface, the metal counterface generally exhibited lower friction and wear at 25 degrees C but higher friction and wear at 650 degrees C. Friction coefficients, for example, for the Al2O3/PS300 combination at 25 degrees C were 0.64 compared to 0.23 for the Inconel/PS300 sliding couple. At 650 degrees C the ranking was reversed: the Al2O3/PS300 combination gave a friction coefficient of 0.19 while the friction for the metal counterface increased slightly to about 0.3. Based upon these tribological results and other information found in the literature, it appears that the performance of each counterface/PS300 combination is affected by the ability of the solid lubricant additives to form an adequate transfer film. The effects of surface wettability and tribological compatability are discussed in relation to the observed tribological results. RP DellaCorte, C (reprint author), NASA,LEWIS RES CTR,CLEVELAND,OH 44135, USA. NR 27 TC 67 Z9 71 U1 1 U2 12 PU ELSEVIER SCIENCE SA LAUSANNE PI LAUSANNE PA PO BOX 564, 1001 LAUSANNE, SWITZERLAND SN 0257-8972 J9 SURF COAT TECH JI Surf. Coat. Technol. PD DEC 15 PY 1996 VL 86-7 IS 1-3 BP 486 EP 492 DI 10.1016/S0257-8972(96)02959-3 PN 2 PG 7 WC Materials Science, Coatings & Films; Physics, Applied SC Materials Science; Physics GA WC006 UT WOS:A1996WC00600006 ER PT J AU Knopp, KJ Christensen, DH Hill, JR Masterson, KD AF Knopp, KJ Christensen, DH Hill, JR Masterson, KD TI Thin-film design for enhanced stability of optically pumped vertical-cavity surface-emitting lasers (VCSELs) SO SURFACE & COATINGS TECHNOLOGY LA English DT Article; Proceedings Paper CT 23rd International Conference on Metallurgical Coatings and Thin Films CY APR 22-26, 1996 CL SAN DIEGO, CA SP Amer Vacuum Soc, Vacuum Met & Thin Films Div DE thin-film optimization; VCSEL; vertical cavity; optically pumped ID MIRRORS AB We have employed a novel approach to enhance the optical pump-coupling stability of vertical-cavity surface-emitting lasers (VCSELs). These structures are composed of thin-film semiconductor multilayers and are manufactured entirely by thin-film deposition. In the past, pump light was coupled into VCSEL cavities through the short wavelength interference notches in the reflectance spectrum. However, the steep slope and narrow width of the notches inherently makes pump-coupling sensitive to device temperature. We have employed traditional thin-film optimization to the multilayer etalon to create a low ripple, wideband pump region of low reflectance while maintaining cavity-mode field overlap at the quantum wells. We demonstrate a factor of 2.5 times better stability across a 35 nm spectral range. C1 NASA,LANGLEY RES CTR,HAMPTON,VA 23665. UNIV COLORADO,DEPT ELECT & COMP ENGN,BOULDER,CO 80309. NR 9 TC 1 Z9 1 U1 0 U2 0 PU ELSEVIER SCIENCE SA LAUSANNE PI LAUSANNE PA PO BOX 564, 1001 LAUSANNE, SWITZERLAND SN 0257-8972 J9 SURF COAT TECH JI Surf. Coat. Technol. PD DEC 15 PY 1996 VL 86-7 IS 1-3 BP 783 EP 787 DI 10.1016/S0257-8972(96)03070-8 PN 2 PG 5 WC Materials Science, Coatings & Films; Physics, Applied SC Materials Science; Physics GA WC006 UT WOS:A1996WC00600052 ER PT J AU Jaworske, DA AF Jaworske, DA TI Optical and calorimetric evaluation of Z-93-P and other thermal control coatings SO THIN SOLID FILMS LA English DT Article; Proceedings Paper CT 23rd International Conference on Metallurgical Coatings and Thin Films CY APR 22-26, 1996 CL SAN DIEGO, CA SP Amer Vacuum Soc, Vacuum Met & Thin Films Div DE emissivity; absorptivity; thermal control coatings AB The hemispherical total emissivity of two thermal control coatings, Z-93-P and black anodized aluminum, was calculated from hemispherical total reflectivity measured in the wavelength range of 2 to 40 mu m. These data were compared to hemispherical total emissivity values obtained on the same samples measured in a thermal vacuum chamber with a calorimetric technique. The comparison showed clos agreement in the vicinity of room temperature and above, with differing trends at lower temperatures. RP Jaworske, DA (reprint author), NASA, LEWIS RES CTR, CLEVELAND, OH 44135 USA. NR 6 TC 10 Z9 10 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 DEC 15 PY 1996 VL 290 BP 278 EP 282 DI 10.1016/S0040-6090(96)08969-9 PG 5 WC Materials Science, Multidisciplinary; Materials Science, Coatings & Films; Physics, Applied; Physics, Condensed Matter SC Materials Science; Physics GA WB819 UT WOS:A1996WB81900055 ER PT J AU Dodelson, S AF Dodelson, S TI 3K. The cosmic microwave background radiation - Partridge,RB SO SCIENCE LA English DT Book Review RP Dodelson, S (reprint author), NASA,FERMILAB ASTROPHYS CTR,BATAVIA,IL 60510, USA. NR 1 TC 0 Z9 0 U1 0 U2 4 PU AMER ASSOC ADVANCEMENT SCIENCE PI WASHINGTON PA 1200 NEW YORK AVE, NW, WASHINGTON, DC 20005 SN 0036-8075 J9 SCIENCE JI Science PD DEC 13 PY 1996 VL 274 IS 5294 BP 1847 EP 1848 DI 10.1126/science.274.5294.1847 PG 2 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA VY200 UT WOS:A1996VY20000023 ER PT J AU Gurnett, DA Kurth, WS Roux, A Bolton, SJ Kennel, CF AF Gurnett, DA Kurth, WS Roux, A Bolton, SJ Kennel, CF TI Evidence for a magnetosphere at Ganymede from plasma-wave observations by the Galileo spacecraft SO NATURE LA English DT Article ID TURBULENCE; JUPITER AB ON 27 June 1996 the Galileo spacecraft(1,2) made the first of four planned close fly-bys of Ganymede, Jupiter's largest moon, Here we report measurements of plasma waves and radio emissions, over the frequency range 5 Hz to 5.6 MHz during the first encounter, Intense plasma waves were detected over a region of space nearly four times Ganymede's diameter, which is much larger than would be expected for a simple wake arising from Ganymede's passage through Jupiter's rapidly rotating magnetosphere. The types of waves detected (whistler-mode emissions, upper hybrid waves, electrostatic electron cyclotron waves and escaping radio emission) strongly suggest that Ganymede has a large, extended magnetosphere of its own, The data indicate the presence of a strong (B > 400 nT) magnetic field, and show that Ganymede is surrounded by an ionosphere-like plasma with a maximum electron density of about 100 particles cm(-3) and a scale height of about 1,000 km. C1 UNIV VERSAILLES ST QUENTIN,CTR ETUD ENVIRONM TERR & PLANETAIRES,F-78140 VELIZY VILLACOUBL,FRANCE. CALTECH,JET PROP LAB,PASADENA,CA 91109. UNIV CALIF LOS ANGELES,OFF CHANCELLOR,LOS ANGELES,CA 90095. RP Gurnett, DA (reprint author), UNIV IOWA,DEPT PHYS & ASTRON,IOWA CITY,IA 52242, USA. OI Kurth, William/0000-0002-5471-6202 NR 26 TC 92 Z9 93 U1 0 U2 3 PU MACMILLAN MAGAZINES LTD PI LONDON PA 4 LITTLE ESSEX STREET, LONDON, ENGLAND WC2R 3LF SN 0028-0836 J9 NATURE JI Nature PD DEC 12 PY 1996 VL 384 IS 6609 BP 535 EP 537 DI 10.1038/384535a0 PG 3 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA VX769 UT WOS:A1996VX76900049 ER PT J AU Kivelson, MG Khurana, KK Russell, CT Walker, RJ Warnecke, J Coroniti, FV Polanskey, C Southwood, DJ Schubert, G AF Kivelson, MG Khurana, KK Russell, CT Walker, RJ Warnecke, J Coroniti, FV Polanskey, C Southwood, DJ Schubert, G TI Discovery of Ganymede's magnetic field by the Galileo spacecraft SO NATURE LA English DT Article ID IO AB THE Galileo spacecraft has now passed close to Jupiter's largest moon-Ganymede-on two occasions, the first at an altitude of 838 km, and the second at an altitude of just 264 km. Here we report the discovery during these encounters of an internal magnetic field associated with Ganymede (the only other solid bodies in the Solar System known to have magnetic fields are Mercury, Earth and probably Io(1)), The data are consistent with a Ganymede-centred magnetic dipole tilted by similar to 10 degrees relative to the spin axis, and an equatorial surface-field strength of similar to 750 nT, The magnetic field is strong enough to carve out a magnetosphere with clearly defined boundaries within Jupiter's magnetosphere, Although the observations require an internal field, they do not indicate its source. But the existence of an internal magnetic field should in itself help constrain models of Ganymede's interior. C1 UNIV CALIF LOS ANGELES,DEPT EARTH & SPACE SCI,LOS ANGELES,CA 90095. UNIV CALIF LOS ANGELES,DEPT PHYS,LOS ANGELES,CA 90095. CALTECH,JET PROP LAB,PASADENA,CA 91109. UNIV LONDON IMPERIAL COLL SCI TECHNOL & MED,DEPT PHYS,LONDON SW7 2BZ,ENGLAND. RP Kivelson, MG (reprint author), UNIV CALIF LOS ANGELES,INST GEOPHYS & PLANETARY PHYS,LOS ANGELES,CA 90095, USA. RI Kivelson, Margaret/I-9019-2012; OI Kivelson, Margaret/0000-0003-3859-8581; Russell, Christopher/0000-0003-1639-8298 NR 14 TC 192 Z9 199 U1 1 U2 12 PU MACMILLAN MAGAZINES LTD PI LONDON PA 4 LITTLE ESSEX STREET, LONDON, ENGLAND WC2R 3LF SN 0028-0836 J9 NATURE JI Nature PD DEC 12 PY 1996 VL 384 IS 6609 BP 537 EP 541 DI 10.1038/384537a0 PG 5 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA VX769 UT WOS:A1996VX76900050 ER PT J AU Anderson, JD Lau, EL Sjogren, WL Schubert, G Moore, WB AF Anderson, JD Lau, EL Sjogren, WL Schubert, G Moore, WB TI Gravitational constraints on the internal structure of Ganymede SO NATURE LA English DT Article ID TIDAL DISSIPATION; GALILEAN SATELLITES; GRAVITY-FIELD; TRACKING DATA; JUPITER; MODELS; IO AB BEFORE the arrival of the Galileo spacecraft in the jovian system, there was little information on the interior structure of Jupiter's largest moon, Ganymede. Its mean density (1,940 kg m(-3)), determined by the Pioneer and Voyager spacecraft(1-3), implies a composition that is roughly 60% rock and 40% ice, which could be uniformly mixed or differentiated into a rocky core and icy mantle(4), Here we report measurements by the Galileo spacecraft of Ganymede's overall density and the spherical harmonics, J(2) and C-22, of its gravitational field. These data show clearly that Ganymede has differentiated into a core and mantle. Combined with the recent discovery of an intrinsic magnetic field(5,6), our gravity results suggest that Ganymede has a metallic core of radius 400-1,300 km surrounded by a silicate mantle, which is in turn enclosed by an ice shell similar to 800 km thick. Depending on whether the core is pure iron or an alloy of iron and iron sulphide, it could account for as little as 1.4% or as much as one-third of the total mass, If the ice were stripped away, Ganymede could look much like Io(7) in terms of its size and internal mass distribution. C1 UNIV CALIF LOS ANGELES,INST GEOPHYS & PLANETARY PHYS,DEPT EARTH & SPACE SCI,LOS ANGELES,CA 90095. RP Anderson, JD (reprint author), CALTECH,JET PROP LAB,4800 OAK GROVE DR,PASADENA,CA 91109, USA. NR 24 TC 147 Z9 153 U1 2 U2 17 PU MACMILLAN MAGAZINES LTD PI LONDON PA 4 LITTLE ESSEX STREET, LONDON, ENGLAND WC2R 3LF SN 0028-0836 J9 NATURE JI Nature PD DEC 12 PY 1996 VL 384 IS 6609 BP 541 EP 543 DI 10.1038/384541a0 PG 3 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA VX769 UT WOS:A1996VX76900051 ER PT J AU Schubert, G Zhang, KK Kivelson, MG Anderson, JD AF Schubert, G Zhang, KK Kivelson, MG Anderson, JD TI The magnetic field and internal structure of Ganymede SO NATURE LA English DT Article ID TIDAL DISSIPATION; IO; SURFACE; FLOW; CORE AB BEFORE the recent fly-bys of Ganymede by the Galileo spacecraft, viable models of the internal structure of Jupiter's largest moon ranged from a uniform mixture of rock and ice to a differential body with a rocky core and any icy mantle(1). Analysis of the Doppler shift of radio signals from Galileo has now shown that Ganymede is strongly differentiated with a relatively dense core surrounded by a thick shell of ice(2). Other instruments have revealed that Ganymede has an intrinsic magnetic field(3,4), which is aligned approximately antiparallel to Jupiter's magnetic field. Here we argue that these results imply that Ganymede has an outer silicate core surrounding a liquid (or partially liquid) inner core of iron or iron sulphide, and that the magnetic field is generated by dynamo action within this metallic core. Io also appears to have an intrinsic magnetic field(5,6) (antiparallel to that of Jupiter), implying that it too has a metallic core(7) in which the field is generated either by dynamo action or by magneto-convection. C1 UNIV CALIF LOS ANGELES,INST GEOPHYS & PLANETARY PHYS,LOS ANGELES,CA 90095. UNIV EXETER,DEPT MATH,EXETER EX4 4QJ,DEVON,ENGLAND. CALTECH,JET PROP LAB,PASADENA,CA 91109. RP Schubert, G (reprint author), UNIV CALIF LOS ANGELES,DEPT EARTH & SPACE SCI,LOS ANGELES,CA 90095, USA. RI Kivelson, Margaret/I-9019-2012 OI Kivelson, Margaret/0000-0003-3859-8581 NR 25 TC 77 Z9 81 U1 0 U2 10 PU MACMILLAN MAGAZINES LTD PI LONDON PA 4 LITTLE ESSEX STREET, LONDON, ENGLAND WC2R 3LF SN 0028-0836 J9 NATURE JI Nature PD DEC 12 PY 1996 VL 384 IS 6609 BP 544 EP 545 DI 10.1038/384544a0 PG 2 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA VX769 UT WOS:A1996VX76900052 ER PT J AU Ramsey, BD Apple, JA Austin, RA Dietz, KL Minamitani, T Kolodziejczak, JJ Weisskopf, MC AF Ramsey, BD Apple, JA Austin, RA Dietz, KL Minamitani, T Kolodziejczak, JJ Weisskopf, MC TI A large-area microstrip-gas-counter for X-ray astronomy SO NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT LA English DT Article ID PROPORTIONAL-COUNTERS AB We have developed a large-area coded-mask telescope for hard-X-ray astronomy. The heart of the instrument is an imaging microstrip-gas-counter of active area 30 cm x 30 cm and filled with 2 x 10(5) Pa of xenon + 2% isobutylene. Fabricated on a single sheet of borosilicate glass, 1 mm thick, the microstrip features fine anodes (10 mu m) and interleaved cathodes from which the position sensing is derived. Rear pickup electrodes provide the second coordinate. Full details of the instrument and its performance are presented. A first flight, from a high-altitude balloon, is scheduled for the Spring of 1997. RP Ramsey, BD (reprint author), NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,HUNTSVILLE,AL 35812, USA. NR 8 TC 6 Z9 6 U1 0 U2 0 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0168-9002 J9 NUCL INSTRUM METH A JI Nucl. Instrum. Methods Phys. Res. Sect. A-Accel. Spectrom. Dect. Assoc. Equip. PD DEC 11 PY 1996 VL 383 IS 2-3 BP 424 EP 430 DI 10.1016/S0168-9002(96)00853-4 PG 7 WC Instruments & Instrumentation; Nuclear Science & Technology; Physics, Nuclear; Physics, Particles & Fields SC Instruments & Instrumentation; Nuclear Science & Technology; Physics GA VZ889 UT WOS:A1996VZ88900016 ER PT J AU Bolotnikov, A Ramsey, B AF Bolotnikov, A Ramsey, B TI Purification techniques and purity and density measurements of high-pressure Xe SO NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT LA English DT Article ID ENERGY RESOLUTION; LIQUID XENON AB A xenon gas purification system and simple techniques for purity and density measurements of high-pressure (similar to 60 atm) Xe have been developed. The purification system features two stages. As a first stage of purification an oxisorb and a high-temperature getter are used to purify Xe gas up to a level of that typically required for liquid Xe detectors. As a second stage, a titanium spark purifier is employed to further improve the purity by an order of magnitude. A gridded ionization chamber is used to measure the purity level and density of the xenon. The duration of pulses produced by cosmic muons inside the chamber gives the lower limit of an electron's life time. The capacitance between the mesh and anode, which depends on the dielectric constant of Xe, provides a temperature independent measurement of the density. This work is a part of a development program of high-pressure Xe detectors for hard X-ray and low energy gamma-ray astronomy. RP Bolotnikov, A (reprint author), NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,HUNTSVILLE,AL 35812, USA. NR 19 TC 28 Z9 28 U1 0 U2 0 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0168-9002 J9 NUCL INSTRUM METH A JI Nucl. Instrum. Methods Phys. Res. Sect. A-Accel. Spectrom. Dect. Assoc. Equip. PD DEC 11 PY 1996 VL 383 IS 2-3 BP 619 EP 623 DI 10.1016/S0168-9002(96)00752-8 PG 5 WC Instruments & Instrumentation; Nuclear Science & Technology; Physics, Nuclear; Physics, Particles & Fields SC Instruments & Instrumentation; Nuclear Science & Technology; Physics GA VZ889 UT WOS:A1996VZ88900041 ER PT J AU Preece, RD Briggs, MS Pendleton, GN Paciesas, WS Matteson, JL Band, DL Skelton, RT Meegan, CA AF Preece, RD Briggs, MS Pendleton, GN Paciesas, WS Matteson, JL Band, DL Skelton, RT Meegan, CA TI BATSE observations of gamma-ray burst spectra .3. Low-energy behavior of time-averaged spectra SO ASTROPHYSICAL JOURNAL LA English DT Article DE gamma rays, bursts; methods, data analysis; X-rays, general ID EVOLUTION; EMISSION AB We analyze time-averaged spectra from 86 bright gamma-ray bursts from the first 5 years of the Burst And Transient Source Experiment (BATSE) on board the Compton Gamma Ray Observatory to determine whether the lowest energy data are consistent with a standard spectra form fit to the data at all energies. The BATSE Spectroscopy Detectors have the capability to observe photons as low at 5 keV. Using the gamma-ray burst locations obtained with the BATSE Large Area Detectors, the Spectroscopy Detectors' low-energy response can be modeled accurately. This, together with a postlaunch calibration of the lowest energy Spectroscopy Detector discriminator channel, which can lie in the range 5-20 keV, allows spectral deconvolution over a broad energy range, similar to 5 keV to 2 MeV. The additional coverage allows us to search for evidence of excess emission, or for a deficit, below 20 keV. While no burst has a significant (greater than or equal to 3 sigma) deficit relative to a standard spectra model, we find that 12 bursts have excess low-energy emission, ranging between 1.2 and 5.8 times the model flux, that exceeds 5 sigma in significance. This is evidence for an additional low-energy spectral component in at least some bursts, or for deviations from the power-law spectral form typically used to model gamma-ray bursts at energies below 100 keV. C1 UNIV CALIF SAN DIEGO,CTR ASTROPHYS & SPACE SCI,LA JOLLA,CA 92093. NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,HUNTSVILLE,AL 35812. RP Preece, RD (reprint author), UNIV ALABAMA,DEPT PHYS,HUNTSVILLE,AL 35899, USA. OI Preece, Robert/0000-0003-1626-7335 NR 30 TC 69 Z9 69 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637 SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD DEC 10 PY 1996 VL 473 IS 1 BP 310 EP 321 DI 10.1086/178146 PN 1 PG 12 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VX329 UT WOS:A1996VX32900026 ER PT J AU Burrows, CJ Stapelfeldt, KR Watson, AM Krist, JE Ballester, GE Clarke, JT Crisp, D Gallagher, JS Griffiths, RE Hester, JJ Hoessel, JG Holtzman, JA Mould, JR Scowen, PA Trauger, JT Westphal, JA AF Burrows, CJ Stapelfeldt, KR Watson, AM Krist, JE Ballester, GE Clarke, JT Crisp, D Gallagher, JS Griffiths, RE Hester, JJ Hoessel, JG Holtzman, JA Mould, JR Scowen, PA Trauger, JT Westphal, JA TI Hubble space telescope observations of the disk and jet of HH 30 SO ASTROPHYSICAL JOURNAL LA English DT Article DE accretion, accretion disks; circumstellar matter; dust, extinction; ISM, jets and outflows; stars, individual (HH 30); stars, pre-main-sequence ID YOUNG STELLAR OBJECTS; MODEL SCATTERING ENVELOPES; HL TAURI; CIRCUMSTELLAR DISKS; STARS; GRAINS; CLOUD; DUST AB HH 30 in Taurus has been imaged with the Hubble Space Telescope WFPC2. The images show in reflected light a flared disk with a radius of about 250 AU that obscures the protostar. The disk resembles detailed accretion disk models that constrain its density distribution and show that its inclination is less than 10 degrees. There are bipolar emission-line jets perpendicular to the disk, a very clear demonstration of the standard paradigm for accretion disk and jet systems. However, asymmetries in the light distribution show that the disk has not completely settled into a quasi-equilibrium accretion state, or that some of the observed scattering is from an asymmetric envelope. The emission-line jet itself is resolved into a number of knots with typical lengths and separations of 0 ''.4, much smaller and more numerous than indicated by lower resolution ground-based studies. There are indications of still finer structures in the jet all the way to the resolution limit of 0 ''.1. The knots have proper motions ranging from 100 to 300 km s(-1) and are therefore generated at the surprisingly high rate of about 0.4 knots per jet per year. The jet appears to be collimated within a cone of opening angle 3 degrees and can be seen to within 30 AU of the star. Both single- and multiple-scattering disk models have a range of possible solutions, but by requiring pressure support and temperature equilibrium, a self-consistent model emerges. There is evidence for pressure support because the disk appears to have a Gaussian height profile. The temperature at each point in the disk is determined by the disk geometry, which in turn fixes the temperature in a self-consistent manner. The extinction to the protostar is unknown but constrained to be greater than 24 mag. The optical properties of the scattering grains in the disk are determined and found to imply a large scattering asymmetry, but they seem to follow the interstellar reddening law. The absolute magnitude and colors of the unseen protostar, which has a brightness in the I bandpass of about 0.16 times solar and is very red, are obtained. The disk mass is about 0.006 times solar and has an expected lifetime of about 10(5) yr. C1 EUROPEAN SPACE AGCY,DEPT SPACE SCI,DIV ASTROPHYS,F-75738 PARIS 15,FRANCE. CALTECH,JET PROP LAB,PASADENA,CA 91109. NEW MEXICO STATE UNIV,DEPT ASTRON,LAS CRUCES,NM 88003. UNIV MICHIGAN,DEPT ATMOSPHER & OCEAN SIC,ANN ARBOR,MI 48109. UNIV WISCONSIN,DEPT ASTRON,MADISON,WI 53706. JOHNS HOPKINS UNIV,DEPT ASTRON,BALTIMORE,MD 21218. ARIZONA STATE UNIV,DEPT PHYS & ASTRON,TEMPE,AZ 85287. AUSTRALIAN NATL UNIV,MT STROMLO & SIDING SPRING OBSERV,WODEN,ACT 2611,AUSTRALIA. CALTECH,DIV GEOL & PLANETARY SCI,PASADENA,CA 91125. RP Burrows, CJ (reprint author), SPACE TELESCOPE SCI INST,3700 SAN MARTIN DR,BALTIMORE,MD 21218, USA. RI Stapelfeldt, Karl/D-2721-2012; Clarke, John/C-8644-2013 NR 34 TC 353 Z9 353 U1 0 U2 5 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637 SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD DEC 10 PY 1996 VL 473 IS 1 BP 437 EP & DI 10.1086/178156 PN 1 PG 20 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VX329 UT WOS:A1996VX32900036 ER PT J AU Siarkowski, M Pres, P Drake, SA White, NE Singh, KP AF Siarkowski, M Pres, P Drake, SA White, NE Singh, KP TI Corona(e) of AR Lacertae .2. The spatial structure SO ASTROPHYSICAL JOURNAL LA English DT Article DE binaries, eclipsing; stars, coronae; stars, individual (AR Lacertae); X-rays, stars ID RS-CANUM-VENATICORUM; X-RAY-EMISSION; ACTIVE BINARY-SYSTEMS; VLBI OBSERVATIONS; RADIO-CONTINUUM; TY-PYX; FLARE; STARS; CAPELLA; ALGOL AB The X-ray light curves in the 0.4-1.5 keV and 2-7 keV bands of the RS CVn binary AR Lacertae observed on 1993 June 1-3 over one full orbital cycle with the ASCA satellite have been used to map the spatial structure of AR Lac's coronae. We find that both stars are X-ray active, that the corona of the K-type secondary star appears to be hotter than that of the G-type primary star, that X-ray emission is concentrated on the sides of the stars facing each other, and that there are compact and well-localized regions of enhanced X-ray emission with heights much smaller than the stellar radii. In one class of solutions there are additional extended regions with dimensions similar to or greater then the radii of the underlying stars which may be structures that interconnect the two stars. There are also other acceptable models without extended structures, however our analysis indicates that solutions with extended sources are more probable. Also, about 50% of the X-ray emission is unmodulated and could come from either an extended halo region, from the poles of the larger K star, or from other symmetric or uneclipsed structures in the orbital plane. We compare the coronal structures inferred from the ASCA observations with those inferred using the same technique from an EXOSAT observation of AR Lac made in 1984 and find that there are substantial differences between the coronal structures at these two epochs. For the solution with extended material in the orbital plane, we have derived the rough physical parameters for the X-ray-emitting plasma, using the derived information on the spatial sizes of the various spatial components together with information about the emission measure and temperatures obtained from a simple spectral analysis of the ASCA data. C1 UNIV WROCLAW, INST ASTRON, PL-51622 WROCLAW, POLAND. NASA, GODDARD SPACE FLIGHT CTR, HIGH ENERGY ASTROPHYS LAB, GREENBELT, MD 20771 USA. NASA, GODDARD SPACE FLIGHT CTR, USRA, GREENBELT, MD 20771 USA. RP Siarkowski, M (reprint author), POLISH ACAD SCI, SPACE RES CTR, KOPERNIKA 11, PL-51622 WROCLAW, POLAND. RI White, Nicholas/B-6428-2012 OI White, Nicholas/0000-0003-3853-3462 NR 37 TC 48 Z9 48 U1 0 U2 2 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 DEC 10 PY 1996 VL 473 IS 1 BP 470 EP + DI 10.1086/178159 PN 1 PG 0 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VX329 UT WOS:A1996VX32900039 ER PT J AU Schmelz, JT Saba, JLR Ghosh, D Strong, KT AF Schmelz, JT Saba, JLR Ghosh, D Strong, KT TI Anomalous coronal neon abundances in quiescent solar active regions SO ASTROPHYSICAL JOURNAL LA English DT Article DE Sun, abundances; Sun, activity; Sun, corona ID X-RAY TELESCOPE; ELEMENTAL ABUNDANCES; ENERGETIC PARTICLES; FLARE PLASMAS; ENHANCED NEON; FE-XVII; CALCIUM; YOHKOH; IRON; IONIZATION AB The systematic differences between the solar photospheric and coronal composition are generally thought to be related to the first ionization potential (FIP) of the trace elements. While there are ample data showing that this is a significant factor, there is a growing body of observational evidence that a simple, FIP-based formula is not the whole story for coronal abundances. One of the most troubling problems for the FIP-based models is the apparent abundance variation of high-FIP (>11 eV) elements with respect to one another. We describe abundance variations of (high-FIP) neon relative to (high-FIP) oxygen, and (low-FIP) iron and magnesium, in solar active region observations made by the Flat Crystal Spectrometer on the Solar Maximum Mission. We show that, even in quiescent active regions, Ne/O can vary inconsistently with simple empirical FIP models: it shows values about a factor of 2 both above and below the ''standard'' coronal value of 0.15 obtained from solar energetic particle measurements of long-duration events (Reames). McKenzie & Feldman have recently invoked photoionization of O I by EUV radiation to explain low measurements of the Ne/O abundance ratio. Photoionization by a long-lived bath of soft X-rays and chromospheric evaporation have been suggested as being responsible for the anomalous behavior of neon in flares, but flare conditions should not apply in the quiescent regions of the present study. A complex picture involving the detailed dynamics, geometry, and radiation environment in the differentiation layer(s) may be required to understand coronal composition and its variability. C1 RHODES COLL,DEPT PHYS,MEMPHIS,TN 38112. NASA,GODDARD SPACE FLIGHT CTR,LOCKHEED SOLAR & ASTROPHYS GRP,GREENBELT,MD 20771. LOCKHEED SOLAR & ASTROPHYS GRP,PALO ALTO,CA 94304. RP Schmelz, JT (reprint author), MEMPHIS STATE UNIV,DEPT PHYS,MEMPHIS,TN 38152, USA. NR 46 TC 44 Z9 44 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637 SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD DEC 10 PY 1996 VL 473 IS 1 BP 519 EP 532 DI 10.1086/178163 PN 1 PG 14 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VX329 UT WOS:A1996VX32900043 ER PT J AU Canuto, VM Goldman, I Mazzitelli, I AF Canuto, VM Goldman, I Mazzitelli, I TI Stellar turbulent convection: A self-consistent model SO ASTROPHYSICAL JOURNAL LA English DT Article DE convection; stars, evolution; stars, interiors; Sun, interior; turbulence ID DISTANCE AB We present a self-consistent model for stellar turbulent convection that is similar in spirit to the CM model (Canuto & Mazzitelli 1991) since it accounts for the full spectrum of the turbulent eddies rather than only one eddy, as done in the mixing length theory (MLT). The model differs from the CM model in the treatment of the rate of energy input n(s)(k) from the source that generates the turbulence. In the present model, n(s)(k) is controlled by both the source and the turbulence it ultimately generates, thus ensuring a self-consistent modeling of the turbulence. This improves the CM model in which n(s)(k) was taken to be equal to the growth rate of the linear unstable convective modes. However, since the formulation of a self-consistent treatment is far from simple, we were forced to use a representation of the nonlinear interactions less complete than the one in the CM model. The ensuing equations were solved numerically for a wide range of convective efficiencies. The results are the convective flux, the mean square turbulent velocity, the root mean squared turbulent pressure and the turbulent viscosity. We implemented the model in the ATON stellar structure code and computed the evolution of a solar model. The results are generally similar to those of the CM model and thus quite different from the MLT. The present model requires a smaller overshoot into the upper radiative zone than does the CM model, in accord with recent empirical estimates. Application to Population II stars and comparison with the very metal-poor globular cluster M68 yields an age in the range 11-12 Gyr. This is somewhat younger than the CM age, which in turn is younger than the corresponding MLT age, a result of possible cosmological interest. C1 TEL AVIV UNIV,SACKLER FAC EXACT SCI,SCH PHYS & ASTRON,IL-69978 TEL AVIV,ISRAEL. CNR,IST ASTROFIS SPAZIALE,I-00044 FRASCATI,ITALY. RP Canuto, VM (reprint author), NASA,GODDARD INST SPACE STUDIES,2880 BROADWAY,NEW YORK,NY 10025, USA. NR 30 TC 194 Z9 195 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637 SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD DEC 10 PY 1996 VL 473 IS 1 BP 550 EP 559 DI 10.1086/178166 PN 1 PG 10 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VX329 UT WOS:A1996VX32900046 ER PT J AU Cannizzo, JK AF Cannizzo, JK TI On the relative rates of decay of the optical and soft x-ray fluxes in dwarf nova outbursts SO ASTROPHYSICAL JOURNAL LA English DT Article DE accretion, accretion disks; instabilities; novae, cataclysmic variables; stars, individual (SS Cygni); X-rays, stars ID LONG-TERM BEHAVIOR; SS-CYGNI; ACCRETION DISKS AB We present time-dependent computations utilizing the accretion disk limit cycle instability to model the decay of the flux in dwarf nova outbursts. In particular, we model the optical and 0.1 keV fluxes in an attempt to account for recent findings by Ponman et al. The e-folding decay times of similar to 3 days for the optical and similar to 1 day for the soft X-ray/EUV in an outburst of SS Cygni are naturally accounted for in the model by the action of the cooling front which enacts the transition between the high and low states in the accretion disk. The difference in timescales; between V and EUV stems from the fact that, roughly speaking, the optical Bw: samples the surface area of the hot part of the accretion disk, whereas the EUV samples the mass of the hot part of the accretion disk. RP Cannizzo, JK (reprint author), NASA,GODDARD SPACE FLIGHT CTR,HIGH ENERGY ASTROPHYS LAB,CODE 662,GREENBELT,MD 20771, USA. NR 16 TC 12 Z9 12 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637 SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD DEC 10 PY 1996 VL 473 IS 1 BP L41 EP L44 DI 10.1086/310389 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VX331 UT WOS:A1996VX33100011 ER PT J AU Kashlinsky, A Mather, JC Odenwald, S AF Kashlinsky, A Mather, JC Odenwald, S TI Clustering of the diffuse infrared light from the COBE DIRBE maps: An all-sky survey of C(0) SO ASTROPHYSICAL JOURNAL LA English DT Article DE cosmology, observations; cosmology, theory; diffuse radiation; galaxies, evolution; large-scale structure of the universe ID BACKGROUND-RADIATION; SPECTRUM; EVOLUTION; DUST AB We measure the smoothness of the infrared sky using the COBE DIRBE maps, and obtain interesting limits on the production of the diffuse cosmic infrared background (CIB) light by matter clustered like galaxies. The predicted fluctuations of the CIB with the DIRBE beam size of 0 degrees 7 are of the order of 10%, and the maps are smooth at the level of delta nu I-nu similar to a few nW m(-2) sr(-1) rms from 2.2 to 100 mu m. The lowest numbers are achieved at mid- to far-IR, where the foreground is bright but smooth; they are [C(0)](1/2)less than or equal to(1-1.5) nW m(-2) sr(-1) at lambda=10-100 mu m. If the CIB comes from clustered matter evolving according to typical scenarios, then the smoothness of the maps implies CIB levels less than similar to(10-15) nW m(-2) sr(-1) over this wavelength range. C1 NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. RP Kashlinsky, A (reprint author), NORDITA,BLEGDAMSVEJ 17,DK-2100 COPENHAGEN,DENMARK. NR 33 TC 34 Z9 34 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637 SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD DEC 10 PY 1996 VL 473 IS 1 BP L9 EP & DI 10.1086/310379 PN 2 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VX331 UT WOS:A1996VX33100003 ER PT J AU Smith, DA Neff, SG Bothun, GD Fanelli, MN Offenberg, JD Waller, WH Bohlin, RC OConnell, RW Roberts, MS Smith, AM Stecher, TP AF Smith, DA Neff, SG Bothun, GD Fanelli, MN Offenberg, JD Waller, WH Bohlin, RC OConnell, RW Roberts, MS Smith, AM Stecher, TP TI Ultraviolet imaging of NGC 3310: A merger-driven global starburst SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies, individual (NGC 3310); galaxies, interactions; galaxies, starburst; ultraviolet, galaxies ID SPIRAL GALAXY NGC-3310; H-II REGIONS; SURFACE PHOTOMETRY; TELESCOPE; NGC-628; IMAGES; DUST; M81 AB We present the first far-ultraviolet (FUV; lambda similar to 1500 Angstrom) image of the nearby peculiar SAB(r)bc galaxy NGC 3310. The small 15 '' (945 pc) diameter circumnuclear starburst ring is the most luminous structure, producing 30% of the total observed FUV luminosity. Diffuse emission from the inner disk (20 '' > 0. RP VanSnyder, W (reprint author), CALTECH,JET PROP LAB,MAIL STOP 126-147,4800 OAK GROVE DR,PASADENA,CA 91109, USA. NR 2 TC 0 Z9 0 U1 0 U2 0 PU ASSOC COMPUTING MACHINERY PI NEW YORK PA 1515 BROADWAY, NEW YORK, NY 10036 SN 0098-3500 J9 ACM T MATH SOFTWARE JI ACM Trans. Math. Softw. PD DEC PY 1996 VL 22 IS 4 BP 498 EP 500 DI 10.1145/235815.235825 PG 3 WC Computer Science, Software Engineering; Mathematics, Applied SC Computer Science; Mathematics GA WC467 UT WOS:A1996WC46700010 ER PT J AU Billings, CE AF Billings, CE TI Roger Griffith Green, AFBPsS, FRAeS 1948-1996 - Obituary SO AEROSPACE LA English DT Item About an Individual C1 NASA,AMES RES CTR,WASHINGTON,DC. NR 0 TC 0 Z9 0 U1 0 U2 0 PU ROYAL AERONAUTICAL SOC PI LONDON PA 4 HAMILTON PL, LONDON, ENGLAND W1V OBQ SN 0305-0831 J9 AEROSPACE JI Aerospace PD DEC PY 1996 VL 23 IS 12 BP 30 EP 30 PG 1 GA XL736 UT WOS:A1996XL73600009 ER PT J AU Jackson, B Giammarco, J Lapin, M Schwartz, D AF Jackson, B Giammarco, J Lapin, M Schwartz, D TI NASA streamlines computing environment SO AEROSPACE ENGINEERING LA English DT Article RP Jackson, B (reprint author), NASA,LYNDON B JOHNSON SPACE CTR,CONTROL CTR,SYST DIV,HOUSTON,TX 77058, USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU SOC AUTOMOTIVE ENG INC PI WARRENDALE PA 400 COMMONWEALTH DRIVE, WARRENDALE, PA 15096 SN 0736-2536 J9 AEROSPACE ENG JI Aerosp. Eng. PD DEC PY 1996 VL 16 IS 12 BP 26 EP 27 PG 2 WC Engineering, Aerospace SC Engineering GA VX630 UT WOS:A1996VX63000013 ER PT J AU Rosenzweig, C Phillips, J Goldberg, R Carroll, J Hodges, T AF Rosenzweig, C Phillips, J Goldberg, R Carroll, J Hodges, T TI Potential impacts of climate change on citrus and potato production in the US SO AGRICULTURAL SYSTEMS LA English DT Article ID DRY-MATTER PRODUCTION; SOLANUM-TUBEROSUM-L; SOUR ORANGE TREES; HIGH-TEMPERATURE; HEAT TOLERANCE; YIELD PERFORMANCE; DARK RESPIRATION; WATER DEFICIT; 3 ELEVATIONS; GROWTH AB Potential impacts of global climate change on fruit and vegetable yield in the US were investigated through simulations of citrus and potato. Simulated treatments included combinations of three increased temperature regimes (+1.5, +2.5 and +5.0 degrees C), and estimates of the impact of three levels of atmospheric carbon dioxide (440, 530, and 600 ppm) in addition to control runs representing current climatic conditions. Adaptive planting dates of -28, -14, +14 and +28 days were included in the potato simulations for current and increased temperature regimes. Twenty-two sites were simulated for citrus yields and 12 sites for potato, using climate records from 1951 to 1980. Response surfaces were developed for all combinations of increased temperature and CO2. Results of citrus simulations without CO2-induced yield improvement indicate that production may shift slightly northward in the southern states, but yields may decline in southern Florida and Texas due to excessive heat during the winter. CO2 effects tended to counteract the decline in simulated citrus yields. Fall potato production under current management practices appears vulnerable to an increase in temperature in the northern states; increased CO2 and changes in planting date were estimated to have minimal compensating impacts on simulated potato yields. C1 GODDARD INST SPACE STUDIES,NEW YORK,NY 10025. UNIV CALIF DAVIS,DEPT LAND AIR & WATER RESOURCES,DAVIS,CA 95616. USDA ARS,PROSSER,WA 99350. RP Rosenzweig, C (reprint author), COLUMBIA UNIV,CTR CLIMATE SYST RES,NEW YORK,NY 10025, USA. NR 62 TC 36 Z9 42 U1 2 U2 20 PU ELSEVIER SCI LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, OXON, ENGLAND OX5 1GB SN 0308-521X J9 AGR SYST JI Agric. Syst. PD DEC PY 1996 VL 52 IS 4 BP 455 EP 479 DI 10.1016/0308-521X(95)00059-E PG 25 WC Agriculture, Multidisciplinary SC Agriculture GA VX916 UT WOS:A1996VX91600004 ER PT J AU Lachowicz, JT Chokani, N Wilkinson, SP AF Lachowicz, JT Chokani, N Wilkinson, SP TI Boundary-layer stability measurements in a hypersonic quiet tunnel SO AIAA JOURNAL LA English DT Article AB Hypersonic boundary-layer measurements were conducted over a flared cone in a quiet wind tunnel. The flared cone was tested at a freestream unit Reynolds number of 2.82 x 10(6)/ft in a Mach 6 flow. This Reynolds number provided laminar-to-transitional bow over the model in a low-disturbance environment. Point measurements with a single hat wire using a novel constant voltage anemometry system were used to measure the boundary-layer disturbances. Surface temperature and schlieren measurements were also conducted to characterize the laminar-to-transitional state of the boundary layer and to identify instability modes. Results suggest that the second mode is the dominant mode of instability. The integrated growth rates of the second made compared well with linear stability theory in the linear stability regime. Furthermore, the existence of higher harmonics of the fundamental suggests that nonlinear disturbances are not associated with ''high'' freestream disturbance levels. C1 N CAROLINA STATE UNIV,DEPT AEROSP & MECH ENGN,RALEIGH,NC 27695. RP Lachowicz, JT (reprint author), NASA,LANGLEY RES CTR,FLOW MODELING & CONTROL BRANCH,HAMPTON,VA 23681, USA. NR 20 TC 34 Z9 38 U1 0 U2 2 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 SN 0001-1452 J9 AIAA J JI AIAA J. PD DEC PY 1996 VL 34 IS 12 BP 2496 EP 2500 DI 10.2514/3.13430 PG 5 WC Engineering, Aerospace SC Engineering GA VW746 UT WOS:A1996VW74600006 ER PT J AU Abid, R Morrison, JH Gatski, TB Speziale, CG AF Abid, R Morrison, JH Gatski, TB Speziale, CG TI Prediction of aerodynamic flows with a new explicit algebraic stress model SO AIAA JOURNAL LA English DT Article ID TURBULENT FLOWS C1 ANALYT SERV & MAT INC,HAMPTON,VA 23666. NASA,LANGLEY RES CTR,HAMPTON,VA 23681. BOSTON UNIV,BOSTON,MA 02215. RP Abid, R (reprint author), HIGH TECHNOL CORP,HAMPTON,VA 23666, USA. NR 17 TC 26 Z9 27 U1 0 U2 1 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 SN 0001-1452 J9 AIAA J JI AIAA J. PD DEC PY 1996 VL 34 IS 12 BP 2632 EP 2635 DI 10.2514/3.13451 PG 4 WC Engineering, Aerospace SC Engineering GA VW746 UT WOS:A1996VW74600027 ER PT J AU Engelke, KA Doerr, DF Crandall, CG Convertino, VA AF Engelke, KA Doerr, DF Crandall, CG Convertino, VA TI Application of acute maximal exercise to protect orthostatic tolerance after simulated microgravity (vol 40, pg R837, 1996) SO AMERICAN JOURNAL OF PHYSIOLOGY-REGULATORY INTEGRATIVE AND COMPARATIVE PHYSIOLOGY LA English DT Correction C1 NASA, KENNEDY SPACE CTR, KENNEDY SPACE CTR, FL 32899 USA. UNIV N TEXAS, CTR HLTH SCI, DEPT PHYSIOL, FT WORTH, TX 76107 USA. PHYSIOL RES BRANCH, DIV CLIN SCI, BROOKS AFB, TX 78235 USA. RP Engelke, KA (reprint author), UNIV FLORIDA, DEPT PHYSIOL, GAINESVILLE, FL 32610 USA. NR 1 TC 0 Z9 0 U1 0 U2 1 PU AMER PHYSIOLOGICAL SOC PI BETHESDA PA 9650 ROCKVILLE PIKE, BETHESDA, MD 20814 SN 0363-6119 J9 AM J PHYSIOL-REG I JI Am. J. Physiol.-Regul. Integr. Comp. Physiol. PD DEC PY 1996 VL 271 IS 6 BP U23 EP U23 PG 1 WC Physiology SC Physiology GA WB876 UT WOS:A1996WB87600045 ER PT J AU Wang, N Hunter, TR Benford, DJ Serabyn, E Lis, DC Phillips, TG Moseley, SH Boyce, K Szymkowiak, A Allen, C Mott, B Gygax, J AF Wang, N Hunter, TR Benford, DJ Serabyn, E Lis, DC Phillips, TG Moseley, SH Boyce, K Szymkowiak, A Allen, C Mott, B Gygax, J TI Characterization of a submillimeter high-angular-resolution camera with a monolithic silicon bolometer array for the Caltech submillimeter observatory SO APPLIED OPTICS LA English DT Article DE submillimeter camera; bolometer array; monolithic silicon bolometer ID OPTICS AB We constructed a 24-pixel bolometer camera operating in the 350- and 450-mu m atmospheric windows for the Caltech Submillimeter Observatory (CSO). This instrument uses a monolithic silicon bolometer array that is cooled to approximately 300 mK by a single-shot He-3 refrigerator. First-stage amplification is provided by field-effect transistors at approximately 130 K. The sky is imaged onto the bolometer array by means of several mirrors outside the Dewar and a cold off-axis elliptical mirror inside the cryostat. The beam is defined by cold aperture and field stops, which eliminates the need for any condensing horns. We describe the instrument, present measurements of the physical properties of the bolometer array, describe the performance of the electronics and the data-acquisition system, and demonstrate the sensitivity of the instrument operating at the observatory. Approximate detector noise at 350 mu m is 5 x 10(-15) W/root Hz, referenced to the entrance of the Dewar, and the CSO system noise-equivalent flux density is approximately 4 Jy/root Hz. These values are within a factor of 2.5 of the background limit. (C) 1996 Optical Society of America C1 NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. SWALES & ASSOCIATES INC,BELTSVILLE,MD 20705. RP Wang, N (reprint author), CALTECH,M-S 320-47,PASADENA,CA 91125, USA. RI Benford, Dominic/D-4760-2012; Moseley, Harvey/D-5069-2012 OI Benford, Dominic/0000-0002-9884-4206; NR 12 TC 31 Z9 31 U1 0 U2 0 PU OPTICAL SOC AMER PI WASHINGTON PA 2010 MASSACHUSETTS AVE NW, WASHINGTON, DC 20036 SN 0003-6935 J9 APPL OPTICS JI Appl. Optics PD DEC 1 PY 1996 VL 35 IS 34 BP 6629 EP 6640 DI 10.1364/AO.35.006629 PG 12 WC Optics SC Optics GA VV321 UT WOS:A1996VV32100001 PM 21151241 ER PT J AU Gaither, CC Schmahl, EJ Crannell, CJ Dennis, BR Lang, FL Orwig, LE Hartman, CN Hurford, GJ AF Gaither, CC Schmahl, EJ Crannell, CJ Dennis, BR Lang, FL Orwig, LE Hartman, CN Hurford, GJ TI Quantitative characterization of the x-ray imaging capability of rotating modulation collimators with laser light SO APPLIED OPTICS LA English DT Article DE Fourier transform imaging; imaging systems; laser; applications; optical testing; rotating modulation collimators; x-ray imagers ID RECONSTRUCTION AB We developed a method for making quantitative characterizations of bi-grid rotating modulation collimators (RMC's) that are used in a Fourier transform x-ray imager. With appropriate choices of the collimator spacings, this technique can be implemented with a beam-expanded He-Ne laser to simulate the plane wave produced by a point source at infinity even though the RMC's are diffraction limited at the He-Ne wavelength of 632.8 nm. The expanded beam passes through the grid pairs at a small angle with respect to their axis of rotation, and the modulated transmission through the grids as the RMC's rotate is detected with a photomultiplier tube. In addition to providing a quantitative characterization of the RMC's, the method also produces a measured point response function and provides an end-to-end check of the imaging system. We applied our method to the RMC's on the high-energy imaging device (HEIDI) balloon payload in its preflight configuration. We computed the harmonic ratios of the modulation time profile from the laser measurements and compared them with theoretical calculations, including the diffraction effects on irregular grids. Our results indicate the 25-in. (64-cm) x-ray imaging optics on HEIDI are capable of achieving images near the theoretical limit and are not seriously compromised by imperfections in the grids. (C) 1996 Optical Society of America C1 UNIV MARYLAND,DEPT ASTRON,COLLEGE PK,MD 20742. CATHOLIC UNIV AMER,DEPT PHYS,WASHINGTON,DC 20064. NASA,GODDARD SPACE FLIGHT CTR,FLIGHT DATA SYST BRANCH,GREENBELT,MD 20771. CALTECH,PASADENA,CA 91103. RI Dennis, Brian/C-9511-2012 NR 20 TC 2 Z9 2 U1 0 U2 0 PU OPTICAL SOC AMER PI WASHINGTON PA 2010 MASSACHUSETTS AVE NW, WASHINGTON, DC 20036 SN 0003-6935 J9 APPL OPTICS JI Appl. Optics PD DEC 1 PY 1996 VL 35 IS 34 BP 6714 EP 6726 DI 10.1364/AO.35.006714 PG 13 WC Optics SC Optics GA VV321 UT WOS:A1996VV32100013 PM 21151253 ER PT J AU Hill, RS Cheng, KP Smith, EP Hintzen, PMN Bohlin, RC OConnell, RW Roberts, MS Smith, AM Stecher, TP AF Hill, RS Cheng, KP Smith, EP Hintzen, PMN Bohlin, RC OConnell, RW Roberts, MS Smith, AM Stecher, TP TI UIT: New ultraviolet stellar photometry and surface brightness profiles of the globular cluster M79 (NGC1904) (vol 112, pg 601, 1996) SO ASTRONOMICAL JOURNAL LA English DT Correction, Addition C1 CALIF STATE UNIV FULLERTON,DEPT PHYS,FULLERTON,CA 92634. NASA,GODDARD SPACE FLIGHT CTR,ASTRON & SOLAR PHYS LAB,GREENBELT,MD 20771. UNIV NEVADA,DEPT PHYS & ASTRON,LAS VEGAS,NV 19154. SPACE TELESCOPE SCI INST,BALTIMORE,MD 21218. UNIV VIRGINIA,CHARLOTTESVILLE,VA 22903. NATL RADIO ASTRON OBSERV,CHARLOTTESVILLE,VA 22903. RP Hill, RS (reprint author), NASA,GODDARD SPACE FLIGHT CTR,HUGHES STX CORP,CODE 681,GREENBELT,MD 20771, USA. NR 4 TC 2 Z9 2 U1 0 U2 0 PU AMER INST PHYSICS PI WOODBURY PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 SN 0004-6256 J9 ASTRON J JI Astron. J. PD DEC PY 1996 VL 112 IS 6 BP 2909 EP 2910 DI 10.1086/118230 PG 2 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VX174 UT WOS:A1996VX17400041 ER PT J AU Fleming, TA Snowden, SL Pfeffermann, E Briel, U Greiner, J AF Fleming, TA Snowden, SL Pfeffermann, E Briel, U Greiner, J TI Catalogue and luminosity function of white dwarfs detected in the ROSAT all-sky survey SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE stars, white dwarfs; stars, statistics; X-rays, stars surveys ID X-RAY SURVEY; H-I; ATMOSPHERES AB This paper contains a compilation of all white dwarf stars known to have been detected at soft X-ray wavelengths by the Position Sensitive Proportional Counter onboard ROSAT during the all-sky survey phase of the mission. Out of the similar to 55,000 X-ray sources which have been detected in the ROSAT all-sky survey, only 175 are white dwarfs. Most (161) are of type DA, while there are 8 PG 1159, 3 DAO, and 3 DO stars detected. These numbers are compared to the results of the ROSAT Wide Field Camera survey and the log N - log S relation is used to estimate the completeness of the catalogue. The sky coverage of the ROSAT all-sky survey is used to calculate the X-ray luminosity function of DA white dwarfs. We find that only 10% of hot (i.e. T-eff > 20,000 K) DAs are X-ray luminous (i.e. L(X) > 10(29) ergs s(-1)). We also use this sample to infer that one out of every four DAs are in binary systems with a late-type companion. This work represents the first all-sky X-ray survey of white dwarfs to a uniform sensitivity limit. C1 UNIV ARIZONA, STEWARD OBSERV, TUCSON, AZ 85721 USA. NASA, GODDARD SPACE FLIGHT CTR, USRA, GREENBELT, MD 20771 USA. RP Fleming, TA (reprint author), MAX PLANCK INST EXTRATERR PHYS, D-85740 GARCHING, GERMANY. RI Snowden, Steven/D-5292-2012 NR 46 TC 46 Z9 46 U1 0 U2 1 PU EDP SCIENCES S A PI LES ULIS CEDEX A PA 17, AVE DU HOGGAR, PA COURTABOEUF, BP 112, F-91944 LES ULIS CEDEX A, FRANCE SN 0004-6361 J9 ASTRON ASTROPHYS JI Astron. Astrophys. PD DEC PY 1996 VL 316 IS 1 BP 147 EP 154 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VX773 UT WOS:A1996VX77300022 ER PT J AU Marsden, RG Smith, EJ Cooper, JF Tranquille, C AF Marsden, RG Smith, EJ Cooper, JF Tranquille, C TI Ulysses at high heliographic latitudes: An introduction SO ASTRONOMY & ASTROPHYSICS LA English DT Editorial Material DE Sun: solar wind; Sun: general; interplanetary medium; space vehicles ID HELIOSPHERIC MAGNETIC-FIELD; SOUTH POLAR-REGION; COSMIC-RAY; SOLAR; PARTICLES; SUN AB The unique in situ observations acquired by the scientific instrumentation on board the Ulysses spacecraft have provided, for the first time, a comprehensive, 3-dimensional view of the heliosphere from the solar equator to the poles near solar minimum. Since beginning its journey out of the ecliptic plane in February, 1992, Ulysses has acquired a wealth of truly new observations concerning the particles and fields in the previously unreachable high-latitude regions of the heliosphere. The articles that comprise this special issue are devoted to recent results from the high-latitude passes of Ulysses, including the rapid transit from the southern to the northern hemisphere. This paper serves as an introduction to these articles, and provides a short summary of the major scientific findings from the mission to date. Also included is a description of the various Ulysses data archives and their access. C1 CALTECH, JET PROP LAB, PASADENA, CA USA. NASA, GSFC, SPACE PHYS DATA FACIL, HUGHES STX CORP, GREENBELT, MD USA. RP Marsden, RG (reprint author), EUROPEAN SPACE AGCY, ESTEC, DEPT SPACE SCI, POB 299, NL-2200 AG NOORDWIJK, NETHERLANDS. RI Cooper, John/D-4709-2012 NR 21 TC 23 Z9 23 U1 0 U2 0 PU EDP SCIENCES S A PI LES ULIS CEDEX A PA 17, AVE DU HOGGAR, PA COURTABOEUF, BP 112, F-91944 LES ULIS CEDEX A, FRANCE SN 0004-6361 J9 ASTRON ASTROPHYS JI Astron. Astrophys. PD DEC PY 1996 VL 316 IS 2 BP 279 EP 286 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA WH396 UT WOS:A1996WH39600002 ER PT J AU Forsyth, RJ Balogh, A Horbury, TS Erdos, G Smith, EJ Burton, ME AF Forsyth, RJ Balogh, A Horbury, TS Erdos, G Smith, EJ Burton, ME TI The heliospheric magnetic field at solar minimum: Ulysses observations from pole to pole SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE Sun: magnetic fields; solar wind; interplanetary medium ID INTERACTION REGIONS; HELIOGRAPHIC LATITUDES; SECTOR STRUCTURE; WIND; SOUTHERN; HEMISPHERES; ASYMMETRY; NORTHERN; ROTATION; SCAN AB The fast transit of the Ulysses spacecraft from the south polar regions of the heliosphere to the north polar regions has allowed us to obtain a unique perspective on the configuration and properties of the heliospheric magnetic field at a time of solar minimum activity. We compare the magnetic field in the northern and southern hemispheres and find no evidence of asymmetry in the radial component of the field or in the variances of the field. We find that the magnetic field polarity corresponds to that observed at the Sun. The only difference between the hemispheres is that, while magnetic field lines in the southern hemisphere have a most probable azimuth angle approximately 24 degrees more tightly wound than predicted by the Parker model, those in the northern hemisphere are in good agreement with the model. C1 KFKI, RES INST NUCL & PARTICLE PHYS, H-1525 BUDAPEST 114, HUNGARY. CALTECH, JET PROP LAB, PASADENA, CA 91109 USA. RP Forsyth, RJ (reprint author), UNIV LONDON IMPERIAL COLL SCI TECHNOL & MED, BLACKETT LAB, LONDON SW7 2BZ, ENGLAND. NR 28 TC 98 Z9 98 U1 0 U2 3 PU EDP SCIENCES S A PI LES ULIS CEDEX A PA 17, AVE DU HOGGAR, PA COURTABOEUF, BP 112, F-91944 LES ULIS CEDEX A, FRANCE SN 0004-6361 J9 ASTRON ASTROPHYS JI Astron. Astrophys. PD DEC PY 1996 VL 316 IS 2 BP 287 EP 295 PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA WH396 UT WOS:A1996WH39600003 ER PT J AU Goldstein, BE Neugebauer, M Phillips, JL Bame, S Gosling, JT McComas, D Wang, YM Sheeley, NR Suess, ST AF Goldstein, BE Neugebauer, M Phillips, JL Bame, S Gosling, JT McComas, D Wang, YM Sheeley, NR Suess, ST TI Ulysses plasma parameters: Latitudinal, radial, and temporal variations SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE Sun: solar wind; interplanetary medium ID SOLAR-WIND; HELIOGRAPHIC LATITUDES; SCAN AB Observations by the Ulysses SWOOPS plasma experiment are used to investigate spatial and temporal gradients during the mission, with emphasis on more recent high latitude observations including the recent South Pole to North Pole passage during solar minimum. Compared to lower latitudes, the high latitude solar wind had higher average speed, proton temperature, and momentum flux, and lower number flux density. As the average momentum flux observed in the high speed wind was 21% greater than at the equator, during solar minimum the distance to the heliopause will be comparatively less in the solar equatorial plane than over the poles. The long term temporal gradients of momentum flux over the life of the mission are considerably larger than the latitudinal gradient observed by Ulysses during solar minimum. A modest North-South high latitude asymmetry is observed in the plasma parameters; the velocity is on the average 13 km/s to 24 km/s greater at Northern latitudes than at Southern, and temperature is also higher. The North-South temperature asymmetry is greater than can be explained by the North-South velocity difference and the dependence of solar wind temperature upon speed. The power law dependence of temperature on heliocentric distance, r, at high latitudes is in range r(-0.81to-1.03), where r(-0.81) is the Southern latitude result and r(-1.03) the Northern. The parameter T/n(1/2), where T is temperature and n is proton number density, can be better predicted from speed than can temperature alone. Comparison with calculations based on source models and magnetograph data indicate that the expansion of open coronal field lines close to the Sun was greater in the Southern hemisphere than in the Northern; this anticorrelation with the expansion factor is consistent with previous observational and theoretical work. C1 LOS ALAMOS NATL LAB, LOS ALAMOS, NM 87545 USA. USN, RES LAB, WASHINGTON, DC 20375 USA. NASA, GEORGE C MARSHALL SPACE FLIGHT CTR, HUNTSVILLE, AL 35801 USA. RP CALTECH, JET PROP LAB, 4800 OAK GROVE DR, PASADENA, CA 91109 USA. NR 25 TC 113 Z9 113 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 1432-0746 J9 ASTRON ASTROPHYS JI Astron. Astrophys. PD DEC PY 1996 VL 316 IS 2 BP 296 EP 303 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA WH396 UT WOS:A1996WH39600004 ER PT J AU Suess, ST Smith, EJ Phillips, J Goldstein, BE Nerney, S AF Suess, ST Smith, EJ Phillips, J Goldstein, BE Nerney, S TI Latitudinal dependence of the radial IMF component - Interplanetary imprint SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE Sun; corona; solar wind; magnetic field ID SOLAR-WIND; MAGNETIC-FIELD; 1-AU; APPROXIMATION; MODEL; FLOW AB Ulysses measurements have confirmed that then is no significant gradient with respect to heliomagnetic latitude in the radial component, B-r, of the interplanetary magnetic field. There are two precesses responsible for this observation. In the corona, the plasma beta is much less than 1, except directly above streamers, so both longitudinal and latitudinal (meridional) gradients in field strength will relax, due to the transverse magnetic pressure gradient force, as the solar wind carries magnetic flux away from the Sun. This happens so quickly that the field is essentially uniform by 5 R.. Beyond 10 R., beta > 1 and it is possible for a meridional thermal pressure gradient to redistribute magnetic flux - an effect apparently absent in Ulysses and earlier ICE and IMP data. We discuss this second effect here, showing that its absence is mainly due to the perpendicular part of the anisotropic thermal pressure gradient in the interplanetrtry medium being too small to drive significant meridional transport between the Sun and similar to 4 AU. This is done using a linear analytic estimate of meridional transport. The first effect was discussed in an earlier paper. C1 CALTECH, JET PROP LAB, PASADENA, CA 91109 USA. LOS ALAMOS NATL LAB, LOS ALAMOS, NM 87545 USA. OHIO UNIV, LANCASTER, OH 43130 USA. RP Suess, ST (reprint author), NASA, GEORGE C MARSHALL SPACE FLIGHT CTR, MS ES82, HUNTSVILLE, AL 35812 USA. NR 21 TC 33 Z9 33 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 DEC PY 1996 VL 316 IS 2 BP 304 EP 312 PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA WH396 UT WOS:A1996WH39600005 ER PT J AU Burton, ME Smith, EJ Balogh, A Forsyth, RJ Bame, SJ Phillips, JL Goldstein, BE AF Burton, ME Smith, EJ Balogh, A Forsyth, RJ Bame, SJ Phillips, JL Goldstein, BE TI Ulysses out-of-ecliptic observations of interplanetary shocks SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE shock waves; interplanetary medium ID SOLAR-WIND; INTERACTION REGIONS; WAVES; PLANE; SOUTH; 1-AU AB Interplanetary shocks observed at the Ulysses spacecraft as it traveled from the ecliptic plane to the southern solar pole have been identified and analysed using both magnetic field and plasma measurements. The latitude dependences of various parameters associated with the shocks (beta, theta(BN) and Mach number) have been investigated. The direction of shock propagation of forward and reverse corotating shocks is qualitatively consistent with the global 3-D model of Pizzo [1991] which predicts that forward shocks will propagate equatorward while reverse shocks propagate poleward. The strongest shocks, are observed at mid-latitudes and are from the south polar coronal hole. These shocks are shown to be supercritical in contrast to the lower latitude sub-critical shocks. This change in character of the shocks is likely related to the intensity of the shock-accelerated energetic particles which also peaks in the same latitude range. C1 UNIV LONDON IMPERIAL COLL SCI TECHNOL & MED, BLACKETT LAB, LONDON, ENGLAND. LOS ALAMOS NATL LAB, LOS ALAMOS, NM USA. RP Burton, ME (reprint author), CALTECH, JET PROP LAB, 4800 OAK GROVE DR, PASADENA, CA 91109 USA. NR 25 TC 22 Z9 22 U1 0 U2 2 PU EDP SCIENCES S A PI LES ULIS CEDEX A PA 17, AVE DU HOGGAR, PA COURTABOEUF, BP 112, F-91944 LES ULIS CEDEX A, FRANCE SN 0004-6361 J9 ASTRON ASTROPHYS JI Astron. Astrophys. PD DEC PY 1996 VL 316 IS 2 BP 313 EP 322 PG 10 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA WH396 UT WOS:A1996WH39600006 ER PT J AU GonzalezEsparza, JA Smith, EJ Balogh, A Phillips, JL AF GonzalezEsparza, JA Smith, EJ Balogh, A Phillips, JL TI The quasi-parallel shock wave detected by Ulysses on day 92:109 SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE solar system: interplanetary medium; shock waves; waves ID SOLAR-WIND PLASMA; EARTHS BOW SHOCK; INTERPLANETARY SHOCKS; UPSTREAM; IONS; POPULATIONS; EVOLUTION; PLANE AB On day 92:109, at about 5.4 AU and 9 degrees south, Ulysses detected a strong quasi-parallel shock wave leading an interaction region. We describe this singular event on different temporal scales, placing emphasis on the magnetic field observations. The solar wind preceding the shock presented very unusual long-lived conditions: for about one day the interplanetary magnetic field was closely radially oriented and this was associated with a strong anisotropy in proton temperature (T-P parallel to/T-P < 1). The wave activity in the upstream and downstream regions have the largest spatial extent for any interplanetary shock wave reported before. In the foreshock region we identified 10(-2) Hz waves and continual distributions of backstream ions up to 28.5 hours (greater than or equal to 0.29 AU) ahead of the shock. The downstream region was characterized by large amplitude, low frequency (f less than or equal to 10(-3) Hz), compressive perturbations for about 34 hours. The temporal fluctuations around the shock transition do not allow us to apply the techniques based on the Rankine-Hugoniot relations to infer the shock parameters. C1 UNIV LONDON IMPERIAL COLL SCI TECHNOL & MED, BLACKETT LAB, LONDON SW7 2BZ, ENGLAND. LOS ALAMOS NATL LAB, LOS ALAMOS, NM USA. RP GonzalezEsparza, JA (reprint author), CALTECH, JET PROP LAB, 4800 OAK GROVE DR, MAIL STOP 169-506, PASADENA, CA 91109 USA. RI Gonzalez-Esparza, J. Americo/A-6720-2013 NR 31 TC 4 Z9 4 U1 1 U2 6 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 DEC PY 1996 VL 316 IS 2 BP 323 EP 332 PG 10 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA WH396 UT WOS:A1996WH39600007 ER PT J AU Horbury, TS Balogh, A Forsyth, RJ Smith, EJ AF Horbury, TS Balogh, A Forsyth, RJ Smith, EJ TI The rate of turbulent evolution over the Sun's poles SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE interplanetary medium; solar wind; turbulence ID SOLAR-WIND TURBULENCE; ALFVEN WAVES; MAGNETOHYDRODYNAMIC TURBULENCE; ULYSSES OBSERVATIONS; RADIAL EVOLUTION; MAGNETIC-FIELD; LATITUDES; SPECTRA AB Ulysses magnetic field observations in the polar heliosphere have revealed the presence of a population of turbulent fluctuations on small scales with a power spectral index near 5/3 and its extension to progressively larger scales with solar distance. Using the spectral index - calculated from the second order structure function - as a tracer of the turbulent nature of the fluctuations, the rate of extension of the turbulent regime with distance is measured for both the Northern and Southern polar heliosphere. The evolution is similar in both hemispheres: the exponent of the rate of extension of the turbulent regime with solar distance is + 1.1 +/- 0.1. By comparing of the extent of the turbulent regime in the polar heliosphere with previous measurements of fluctuations near the ecliptic, polar fluctuations are shown to evolve more slowly than those in high speed streams at lower heliolatitudes beyond 0.3 Astronomical Units. Within this distance, however, fluctuations in high speed streams at high and low latitudes probably evolve at the same rate. C1 CALTECH, JET PROP LAB, PASADENA, CA 91109 USA. RP Horbury, TS (reprint author), UNIV LONDON IMPERIAL COLL SCI TECHNOL & MED, BLACKETT LAB, LONDON SW7 2BZ, ENGLAND. NR 32 TC 59 Z9 59 U1 0 U2 1 PU EDP SCIENCES S A PI LES ULIS CEDEX A PA 17, AVE DU HOGGAR, PA COURTABOEUF, BP 112, F-91944 LES ULIS CEDEX A, FRANCE SN 0004-6361 J9 ASTRON ASTROPHYS JI Astron. Astrophys. PD DEC PY 1996 VL 316 IS 2 BP 333 EP 341 PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA WH396 UT WOS:A1996WH39600008 ER PT J AU Tsurutani, BT Ho, CM Sakurai, R Goldstein, BE Balogh, A Phillips, JL AF Tsurutani, BT Ho, CM Sakurai, R Goldstein, BE Balogh, A Phillips, JL TI Symmetry in discontinuity properties at the north and south heliographic poles: Ulysses SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE interplanetary medium; plasmas ID INTERPLANETARY AB A study of directional discontinuities (DDs) that occurred during 4 days of the Ulysses north polar pass wets conducted (461 directional discontinuities total) using magnetic field and plasma data. We find that the total number of directional discontinuities selected by the Tsurutani and Smith (1979) method are the same in the north and south polar regions (within statistical errors) if the radial gradient is taken into account. We also find that tangential discontinuities (TDs) occur at edges of mirror mode structures. Approximately half of these structures are locally unstable. TDs are also associated with interplanetary current sheets, some of which are in regions of positive solar wind velocity gradients. To first order, we find no difference in the number of directional discontinuities, number of TDs, or the types of TDs in the north polar region from the south polar region. C1 UNIV LONDON IMPERIAL COLL SCI TECHNOL & MED, BLACKETT LAB, LONDON SW7 2BZ, ENGLAND. LOS ALAMOS NATL LAB, LOS ALAMOS, NM USA. RP Tsurutani, BT (reprint author), CALTECH, JET PROP LAB, MAIL STOP 169-506, PASADENA, CA 91109 USA. NR 8 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 DEC PY 1996 VL 316 IS 2 BP 342 EP 345 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA WH396 UT WOS:A1996WH39600009 ER PT J AU Ho, CM Tsurutani, BT Sakurai, R Goldstein, BE Balogh, A Phillips, JL AF Ho, CM Tsurutani, BT Sakurai, R Goldstein, BE Balogh, A Phillips, JL TI Interplanetary discontinuities in corotating streams and their interaction regions SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE interplanetary medium; solar wind ID ULYSSES OBSERVATIONS; SOLAR-WIND AB In this study. we investigate the discontinuity properties in the low latitude corotating stream regions which are encountered during Ulysses traveling from the south to north heliographic poles in 1995. Through the occurrence rates of directional discontinuities and tangential discontinuities, we find that there are three different regions around a high speed stream. The leading edge regions of the stream have the occurrence rate about 50 DDs/day and 10 TDs/day. These TDs are mostly associated with HCS crossings. Plasma beta and anisotropy R are relatively low. In the stream velocity peak region, the magnetic field magnitude is low and stable. The occurrence rate of DDs is twice as high as in other two regions, but there are very few or no TDs. The stream trailing regions have similar occurrence rates of DDs and TDs to the leading edge regions. However, the structures of the TDs are significant different. These TDs are mostly found at the edges of mirror-mode structures and with large beta and anisotropy ratios R. C1 UNIV LONDON IMPERIAL COLL SCI TECHNOL & MED, BLACKETT LAB, LONDON SW7 2BZ, ENGLAND. LOS ALAMOS NATL LAB, LOS ALAMOS, NM 87545 USA. RP Ho, CM (reprint author), CALTECH, JET PROP LAB, 4800 OAK GROVE DR, PASADENA, CA 91109 USA. NR 12 TC 7 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 0004-6361 J9 ASTRON ASTROPHYS JI Astron. Astrophys. PD DEC PY 1996 VL 316 IS 2 BP 346 EP 349 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA WH396 UT WOS:A1996WH39600010 ER PT J AU McComas, DJ Hoogeveen, GW Gosling, JT Phillips, JL Neugebauer, M Balogh, A Forsyth, R AF McComas, DJ Hoogeveen, GW Gosling, JT Phillips, JL Neugebauer, M Balogh, A Forsyth, R TI Ulysses observations of pressure-balance structures in the polar solar wind SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE solar wind; Sun: corona; interplanetary medium ID MAGNETIC-FIELD; CORONAL PLUMES; FLUCTUATIONS; STREAMS; PLASMA; HOLES AB Throughout its high-latitude excursion Ulysses has observed several types of solar wind structures. In addition to structures such as Alfven waves, compressional features, and microstreams, the solar wind also contains low contrast pressure-balance structures (PBSs). The PBSs are marked by an anti-correlation of the plasma and field pressures; their signatures are often hidden by the comparatively larger effects of compressions. Previous studies of high-latitude solar wind structures have only shown a few examples of PBSs. In this study we examine Ulysses polar pass solar wind plasma and interplanetary magnetic field data sets to provide the first statistical analyses of high-latitude PBSs. Two independent lines of analysis are pursued: first, we identify 78 PBSs in the data and analyze their average properties compared to the rest of the solar wind; second, we use high pass filtering of the data to separate the pressure balance aspects of the solar wind from the longer period compressional features. While our findings indicate that PBSs occur more frequently at small than at large heliocentric distances, indicating a possible solar origin for these structures, they do not have characteristically different plasma or held properties from that of the rest of the polar solar wind. Such differences would indicate that PBSs are possibly the remnants of differing populations of solar wind source plasma back in the polar corona. Our null result does not support the suggestion that PBSs are the interplanetary signature of polar plumes. C1 CALTECH, JET PROP LAB, PASADENA, CA USA. UNIV LONDON IMPERIAL COLL SCI TECHNOL & MED, LONDON, ENGLAND. RP McComas, DJ (reprint author), LOS ALAMOS NATL LAB, SPACE & ATMOSPHER SCI GRP, NIS-1, MS D466, LOS ALAMOS, NM 87545 USA. NR 26 TC 22 Z9 22 U1 0 U2 1 PU EDP SCIENCES S A PI LES ULIS CEDEX A PA 17, AVE DU HOGGAR, PA COURTABOEUF, BP 112, F-91944 LES ULIS CEDEX A, FRANCE SN 0004-6361 J9 ASTRON ASTROPHYS JI Astron. Astrophys. PD DEC PY 1996 VL 316 IS 2 BP 368 EP 373 PG 6 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA WH396 UT WOS:A1996WH39600013 ER PT J AU Poletto, G Parenti, S Noci, G Livi, S Suess, ST Balogh, A McComas, DJ AF Poletto, G Parenti, S Noci, G Livi, S Suess, ST Balogh, A McComas, DJ TI Searching for coronal plumes in Ulysses observations of the far solar wind SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE Sun: corona; solar wind ID TIME-SERIES ANALYSIS; SPECTRAL-ANALYSIS; POLAR PLUMES; PLASMA; HOLES; SPECTROHELIOGRAMS; STREAMS AB In the past, from the analysis of data acquired by the Hellos spacecrafts within distances less than or equal to 1 AU, some evidence has been found of the presence of coronal plumes in the solar wind. Ulysses observations offer a unique opportunity to search for plume remnants in the polar wind at larger distances. Pressure balanced structures (PBS), which might possibly be a signature of those features, have in fact been recently identified in its data. On the basis of previous work, which detected significant peaks (possibly related to plumes) in power spectra of solar wind parameters, we present here the results from a similar research. However, our analysis does not confirm previous findings, because Fewer spectra bear no evidence of significant periodicities, This result allows for different interpretations, but does not rule out the presence of a typical periodicity in the data. By developing a simple 2-D model for structures traversed by Ulysses? we show how easily, even if they were regularly distributed, the original periodicity may become hardly identifiable in power spectra analyses. We conclude that this is not a viable technique for tracing plumes in the solar wind and we suggest alternative means for an unambiguous identification of these features. C1 UNIV FLORENCE, I-50155 FLORENCE, ITALY. MAX PLANCK INST AERON, KATLENBURG DUHM, GERMANY. NASA, GEORGE C MARSHALL SPACE FLIGHT CTR, HUNTSVILLE, AL 35812 USA. UNIV LONDON IMPERIAL COLL SCI TECHNOL & MED, LONDON, ENGLAND. LOS ALAMOS NATL LAB, LOS ALAMOS, NM USA. RP Poletto, G (reprint author), OSSERV ASTROFIS ARCETRI, LARGO E FERMI 5, I-50155 FLORENCE, ITALY. NR 36 TC 12 Z9 12 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 DEC PY 1996 VL 316 IS 2 BP 374 EP 383 PG 10 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA WH396 UT WOS:A1996WH39600014 ER PT J AU MacDowall, RJ Hess, RA Lin, N Thejappa, G Balogh, A Phillips, JL AF MacDowall, RJ Hess, RA Lin, N Thejappa, G Balogh, A Phillips, JL TI Ulysses spacecraft observations of radio and plasma waves: 1991-1995 SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE plasmas; waves; solar wind; interplanetary medium ID EARTHS BOW SHOCK; SOLAR-WIND; FREQUENCY WAVES; ACOUSTIC-WAVES; LANGMUIR-WAVES; MAGNETIC HOLES; THERMAL NOISE; HEAT-FLUX; BURSTS; EMISSION AB The radio and plasma wave investigation of the Ulysses spacecraft mission provided nearly continuous observations of wave electric fields (less than 1 MHz) and magnetic fields (less than 450 Hz) from spacecraft launch in late 1990 through perihelion in 1995 and beyond. The Ulysses spacecraft reached heliographic latitudes of +/-80 degrees, providing a unique opportunity to study wave activity in fast solar wind emanating from polar coronal holes and to examine the differences relative to waves in the streamer belt. These data led to the discovery that many magnetic field depressions (magnetic holes) are populated by waves at the electron plasma frequency; such phenomena occur much more frequently in high-latitude, fast solar wind. At high latitudes, Ulysses frequently detected the waves conventionary assumed to be ion-acoustic waves; however, the electron-proton temperature ratio at these latitudes is always less than one, suggesting that the waves must be some other mode. Electrostatic and electromagnetic waves at lower frequencies also evidenced marked changes as Ulysses recurrently entered and exited the streamer belt during the ''fast latitude scan'' phase of its orbit. These variations with heliographic latitude, as well as variations with distance from the Sun, are presented and interpreted. C1 HUGHES STX CORP, LANHAM, MD 20706 USA. UNIV MINNESOTA, SCH PHYS & ASTRON, MINNEAPOLIS, MN 55455 USA. UNIV MARYLAND, DEPT ASTRON, COLLEGE PK, MD 20740 USA. UNIV LONDON IMPERIAL COLL SCI TECHNOL & MED, BLACKETT LAB, LONDON SW7 2BZ, ENGLAND. LOS ALAMOS NATL LAB, LOS ALAMOS, NM 87545 USA. RP MacDowall, RJ (reprint author), NASA, GODDARD SPACE FLIGHT CTR, CODE 695, GREENBELT, MD 20771 USA. RI MacDowall, Robert/D-2773-2012 NR 50 TC 12 Z9 14 U1 0 U2 1 PU EDP SCIENCES S A PI LES ULIS CEDEX A PA 17, AVE DU HOGGAR, PA COURTABOEUF, BP 112, F-91944 LES ULIS CEDEX A, FRANCE SN 0004-6361 J9 ASTRON ASTROPHYS JI Astron. Astrophys. PD DEC PY 1996 VL 316 IS 2 BP 396 EP 405 PG 10 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA WH396 UT WOS:A1996WH39600016 ER PT J AU Barrow, CH Hoang, S MacDowall, RJ Lecacheux, A AF Barrow, CH Hoang, S MacDowall, RJ Lecacheux, A TI Kilometre-wave radio observations of solar type III bursts by Ulysses compared with decametre-wave observations from the Earth SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE Sun: radio radiation; corona ID WIND; EMISSION; PLASMA; VISIBILITY; DENSITY AB Observations of solar type III bursts, made at kilometric frequencies by the radio receiver of the Ulysses Unified Radio and Plasma Wave (URAP) investigation, are compared with simultaneous observations, made at decametric frequencies at the Nancay Radio Astronomy Station of the Paris-Meudon Observatory, during the period following the spacecraft encounter with Jupiter until the south solar polar pass. Of the events suitable for study, 57 can be identified in both frequency bands having delay times consistent with prediction based upon geometry and upon the frequency drift between the lowest frequency observed on the ground (25 MHz) and the highest frequency observed by URAP (940 kHz). The good agreement between calculated and measured delay times suggests that the large delay anomalies, reported by Steinberg et al. (1984) sometimes to be in excess of 8 minutes in duration, may be confined to frequencies below the 500 kHz limit studied by these authors and not detectable at 940 kHz with the time resolution of the URAP receiver obtained in this study. There are cases when bursts recorded at Ulysses are not seen at Nancay. This may just be due to the source at 25 MHz being beyond the solar limb and so obscured from the Earth. There are other cases, however, when bursts recorded at the Earth are not seen at Ulysses. Such cases do not appear to be correlated with either the Earth-Sun-Ulysses (ESU) angle or with the heliographic latitude of the spacecraft. As the source region at 940 kHz is large and at a considerable distance from the Sun, some part of it will usually be visible from the spacecraft no matter what the relative positions of the Sun, the source and Ulysses may be; this suggests either that there may sometimes be a low frequency cutoff, inherent to the burst itself somewhere between 940 kHz and 25 MHz, or else that the emission has somehow been occulted. Representative examples are presented and discussed. C1 OBSERV PARIS, DESPA, F-92195 MEUDON, FRANCE. NASA, GODDARD SPACE FLIGHT CTR, GREENBELT, MD 20771 USA. OBSERV PARIS, ARPEGES, F-92195 MEUDON, FRANCE. RP Barrow, CH (reprint author), MAX PLANCK INST AERON, D-37189 KATLENBURG DUHM, GERMANY. RI MacDowall, Robert/D-2773-2012 NR 22 TC 0 Z9 0 U1 0 U2 1 PU EDP SCIENCES S A PI LES ULIS CEDEX A PA 17, AVE DU HOGGAR, PA COURTABOEUF, BP 112, F-91944 LES ULIS CEDEX A, FRANCE SN 0004-6361 J9 ASTRON ASTROPHYS JI Astron. Astrophys. PD DEC PY 1996 VL 316 IS 2 BP 413 EP 424 PG 12 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA WH396 UT WOS:A1996WH39600018 ER PT J AU Lin, NG Kellogg, PJ MacDowall, RJ Tsurutani, BT Ho, CM AF Lin, NG Kellogg, PJ MacDowall, RJ Tsurutani, BT Ho, CM TI Langmuir waves associated with discontinuities in the solar wind: A statistical study SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE solar wind; plasmas; waves ID MIRROR-MODE STRUCTURES; MAGNETIC HOLES AB We have reported previously that short bursts of Langmuir waves are frequently observed in the solar wind in isolated local depressions in the magnetic field magnitude, which are called ''magnetic holes''. The magnetic depression regions are often bounded by directional discontinuities (DDs). To study the relation between the waves and the discontinuities, we have examined 402 magnetic field discontinuities in 11 days of Ulysses data which cover a range of radial distances from the Sun (1.8 to 5.2 AU) and of heliographic latitudes (-1.9 degrees to -80 degrees). It is found that Langmuir waves occur at only similar to 9% of the discontinuities identified. About 75% of the DDs which have waves are associated with magnetic depressions. The waves have a higher occurrence rate at tangential discontinuities with magnetic depressions than at rotational discontinuities with little change in the field magnitude. The results suggest that the reduction in the magnetic field strength (a hole-like structure) is important for the excitation of the observed Langmuir waves. The adiabatic focusing of suprathermal electrons passing through the magnetic holes may be a source of free energy for this process. C1 NASA, GODDARD SPACE FLIGHT CTR, GREENBELT, MD 20771 USA. CALTECH, JET PROP LAB, PASADENA, CA 91109 USA. RP Lin, NG (reprint author), UNIV MINNESOTA, SCH PHYS & ASTRON, MINNEAPOLIS, MN 55455 USA. RI MacDowall, Robert/D-2773-2012 NR 13 TC 14 Z9 15 U1 0 U2 0 PU EDP SCIENCES S A PI LES ULIS CEDEX A PA 17, AVE DU HOGGAR, PA COURTABOEUF, BP 112, F-91944 LES ULIS CEDEX A, FRANCE SN 0004-6361 J9 ASTRON ASTROPHYS JI Astron. Astrophys. PD DEC PY 1996 VL 316 IS 2 BP 425 EP 429 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA WH396 UT WOS:A1996WH39600019 ER PT J AU Bird, MK Patzold, M Edenhofer, P Asmar, SW McElrath, TP AF Bird, MK Patzold, M Edenhofer, P Asmar, SW McElrath, TP TI Coronal radio sounding with Ulysses: Solar wind electron density near 0.1 AU during the 1995 conjunction SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE occultations; Sun: corona ID RANGING MEASUREMENTS; LATITUDE SCAN; SPACECRAFT; CYCLE AB Dual-frequency ranging measurements were recorded for a three-week interval during the 1995 solar conjunction of the Ulysses spacecraft. The unusual occultation geometry resulting from the high inclination Ulysses orbit enabled coronal radio sounding from the solar South Pole to the heliographic equator at solar ray path offsets near 0.1 AU. The electron column density along the line-of-sight between Ulysses and Earth, derived from the differential time delays of ranging signals transmitted simultaneously on S-band and X-band carriers, clearly show the signatures of the polar coronal hole and a streamer belt at low latitudes. The observations are utilized in this work to test models for the heliographic latitude dependence of the electron density in the inner heliosphere. Traditional models for solar activity minimum, whereby the density decreases rather slowly from equator to pole, were found to fare rather poorly in representing the measurements. In contrast, a model based on Ulysses in situ solar wind measurements, when combined with ancillary observations to derive the location of the heliospheric current sheet, was found to provide satisfactory agreement with the radio sounding data. C1 UNIV COLOGNE, INST METEOROL & GEOPHYS, D-50923 COLOGNE, GERMANY. RUHR UNIV BOCHUM, INST HF TECH, D-44780 BOCHUM, GERMANY. CALTECH, JET PROP LAB, PASADENA, CA 91109 USA. RP Bird, MK (reprint author), UNIV BONN, INST RADIOASTRON, HUGEL 71, D-53121 BONN, GERMANY. NR 24 TC 16 Z9 17 U1 0 U2 0 PU EDP SCIENCES S A PI LES ULIS CEDEX A PA 17, AVE DU HOGGAR, PA COURTABOEUF, BP 112, F-91944 LES ULIS CEDEX A, FRANCE SN 0004-6361 J9 ASTRON ASTROPHYS JI Astron. Astrophys. PD DEC PY 1996 VL 316 IS 2 BP 441 EP 448 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA WH396 UT WOS:A1996WH39600022 ER PT J AU Bothmer, V Desai, MI Marsden, RG Sanderson, TR Trattner, KJ Wenzel, KP Gosling, JT Balogh, A Forsyth, RJ Goldstein, BE AF Bothmer, V Desai, MI Marsden, RG Sanderson, TR Trattner, KJ Wenzel, KP Gosling, JT Balogh, A Forsyth, RJ Goldstein, BE TI Ulysses observations of open and closed magnetic field lines within a coronal mass ejection SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE Sun: corona; particle emission; magnetic field; interplanetary medium ID COROTATING INTERACTION REGIONS; STREAM INTERACTION REGIONS; SOLAR ENERGETIC PARTICLES; SOUTH POLAR PASS; HELIOGRAPHIC LATITUDES; INTERPLANETARY SHOCKS; ECLIPTIC-PLANE; WIND; EVENTS; ACCELERATION AB During the rapid passage from the Sun's south to north polar regions, the Ulysses spacecraft encountered in February 1995, at 24 degrees S, a coronal mass ejection (CME) exactly at the time when it crossed from high speed solar wind coronal hole flow into low speed streamer belt flows. We have investigated this CME, which was superimposed on an energetic particle event associated with a corotating interaction region (CIR), using energetic particle, plasma and magnetic field measurements. Ulysses' entry into the CME was accompanied by a strong decrease in the intensity of 1-3 MeV protons. The leading portion of the CME with a helical magnetic flux rope topology characteristic of magnetic clouds apparently consisted of closed magnetic loops as indicated by counterstreaming suprathermal electron fluxes along the interplanetary magnetic field (IMF) and bi-directional streaming 0.4-0.7 MeV ions. In contrast, the absence of counterstreaming electrons and ions, the presence of sunward streaming 0.4-5 MeV ions and sunward bursts of suprathermal electrons at energies from similar to 40 eV up to several 100 eV inside another portion of the CME suggest that here the magnetic field lines were ''open'' i.e., with only one end rooted in the solar corona. These field lines were most likely connected to the reverse shock of a CIR beyond Ulysses. We suggest that 3-dimensional reconnection processes are responsible for the formation of magnetic flux rope CMEs from rising coronal loops leading to open and closed field topologies. C1 EUROPEAN SPACE AGCY, DEPT SPACE SCI, NL-2200 AG NOORDWIJK, NETHERLANDS. LOS ALAMOS NATL LAB, LOS ALAMOS, NM USA. UNIV LONDON IMPERIAL COLL SCI TECHNOL & MED, BLACKETT LAB, LONDON, ENGLAND. CALTECH, JET PROP LAB, PASADENA, CA USA. NR 48 TC 21 Z9 21 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 DEC PY 1996 VL 316 IS 2 BP 493 EP 498 PG 6 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA WH396 UT WOS:A1996WH39600028 ER PT J AU Aprile, E Xu, F Zhou, M Doke, T Kikuchi, J Chupp, EL Dunphy, PP Fishman, G Pendleton, G Masuda, K AF Aprile, E Xu, F Zhou, M Doke, T Kikuchi, J Chupp, EL Dunphy, PP Fishman, G Pendleton, G Masuda, K TI The LXeCAT instrument for gamma-ray astrophysics SO ASTRONOMY & ASTROPHYSICS SUPPLEMENT SERIES LA English DT Article; Proceedings Paper CT 3rd Compton Symposium CY JUN 12-14, 1995 CL MUNICH, GERMANY SP Max Planck Inst Extraterrestr Phys, Garching, Marx Planck Gesell, Deut Agentur Raumfahrtangelegenheiten, Deut Aerosp DE gamma-rays, observations; telescope; space vehicles ID LIQUID XENON TPC; IMAGING TELESCOPE AB The Liquid Xenon Coded Aperture Telescope (LX-eCAT) and its capability to image astrophysical gamma-ray sources in the MeV region is described. The gamma-ray detector is a Liquid Xenon Time Projection Chamber (LXe-TPC) triggered by the primary scintillation light. Effective background rejection is a direct consequence of the intrinsic three-dimensional imaging capability of the LXe-TPC. Initial results with a 10 liter prototype confirm an energy resolution of 6% FWHM, a position resolution of 1 mm RMS and a light triggering efficiency higher than 90% for 1 MeV gamma-rays. C1 COLUMBIA UNIV,COLUMBIA ASTROPHYS LAB,NEW YORK,NY 10027. WASEDA UNIV,ADV RES CTR SCI & ENGN,SHINJUKU KU,TOKYO 162,JAPAN. UNIV NEW HAMPSHIRE,DEPT PHYS,DURHAM,NH 03824. UNIV NEW HAMPSHIRE,INST STUDY EARTH OCEANS & SPACE,DURHAM,NH 03824. NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,HUNTSVILLE,AL 35812. SAITAMA COLL HLTH,PHYS LAB,URAWA,SAITAMA,JAPAN. RP Aprile, E (reprint author), COLUMBIA UNIV,DEPT PHYS,538 W 120TH ST,NEW YORK,NY 10027, USA. NR 11 TC 1 Z9 1 U1 0 U2 0 PU EDITIONS PHYSIQUE PI LES ULIS CEDEX PA Z I DE COURTABOEUF AVE 7 AV DU HOGGAR, BP 112, 91944 LES ULIS CEDEX, FRANCE SN 0365-0138 J9 ASTRON ASTROPHYS SUP JI Astron. Astrophys. Suppl. Ser. PD DEC PY 1996 VL 120 IS 4 SI SI BP C649 EP C652 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA WC063 UT WOS:A1996WC06300146 ER PT J AU Araya, RA Harding, AK AF Araya, RA Harding, AK TI Cylotron line models for the X-ray pulsar A 0535+26 SO ASTRONOMY & ASTROPHYSICS SUPPLEMENT SERIES LA English DT Article; Proceedings Paper CT 3rd Compton Symposium CY JUN 12-14, 1995 CL MUNICH, GERMANY SP Max Planck Inst Extraterrestr Phys, Garching, Marx Planck Gesell, Deut Agentur Raumfahrtangelegenheiten, Deut Aerosp DE X-rays, stars; stars, neutron; line formation; pulsars, PSR A 0535+26 ID MAGNETIC-FIELDS; ABSORPTION; SCATTERING; FEATURES AB The spectrum of the transient X-ray binary pulsar A 0535+26 obtained by OSSE in February 1994 shows an absorption feature at 110 keV but does not confirm a feature at around 55 keV, as previously reported by other instruments. If the 110 keV feature is due to cyclotron scattering at the first harmonic, then the magnetic field required is about 10(13) Gauss, the highest observed in an X-ray pulsar. Conversely, if this strong feature is a second harmonic and the line formation process is such that an extremely weak fundamental results at similar or equal to 55 keV, the estimate of the field strength is halved. We present results of detailed cyclotron line transfer models from two source geometries to explore the theoretical contraints on the line shapes in this source. It is found that while a fundamental harmonic line at similar to 55 keV may be partially filled-in by angle redistribution in cylindrical geometries, the required viewing angles give a second harmonic Line shape inconsistent with the observation. Interpretation of the feature at 110 keV as a first harmonic seen at small angles to the field yields more consistent line shapes. C1 NASA, GODDARD SPACE FLIGHT CTR, HIGH ENERGY ASTROPHYS LAB, GREENBELT, MD 20771 USA. JOHNS HOPKINS UNIV, DEPT PHYS & ASTRON, BALTIMORE, MD 21218 USA. RI Harding, Alice/D-3160-2012 NR 9 TC 3 Z9 3 U1 0 U2 0 PU EDITIONS PHYSIQUE PI LES ULIS CEDEX PA Z I DE COURTABOEUF AVE 7 AV DU HOGGAR, BP 112, 91944 LES ULIS CEDEX, FRANCE SN 0365-0138 J9 ASTRON ASTROPHYS SUP JI Astron. Astrophys. Suppl. Ser. PD DEC PY 1996 VL 120 IS 4 SI SI BP C183 EP C186 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA WC063 UT WOS:A1996WC06300039 ER PT J AU Barret, D Grindlay, JE Bloser, PF Zhang, SN Fishman, GJ Harmon, BA Paciesas, WS Ford, E Kaaret, P Tavani, M AF Barret, D Grindlay, JE Bloser, PF Zhang, SN Fishman, GJ Harmon, BA Paciesas, WS Ford, E Kaaret, P Tavani, M TI BATSE observations of hard X-ray emission from X-ray bursters. Presentation of a CGRO/BATSE investigation and first results SO ASTRONOMY & ASTROPHYSICS SUPPLEMENT SERIES LA English DT Article; Proceedings Paper CT 3rd Compton Symposium CY JUN 12-14, 1995 CL MUNICH, GERMANY SP Max Planck Inst Extraterrestr Phys, Garching, Marx Planck Gesell, Deut Agentur Raumfahrtangelegenheiten, Deut Aerosp DE Galaxy center; gamma-rays, observations; X-ray, bursts; X-rays, stars, ID BLACK-HOLE; EXOSAT OBSERVATIONS; GALACTIC-CENTER; DISCOVERY; SIGMA; BINARIES; NOVA AB We present an on-going BATSE/CGRO investigation devoted to search for hard X-ray emission from Xray bursters with the earth occultation and occultation transform imaging techniques. This is a collaboration between the BATSE team at the NASA/Marshall Space Flight Center, Columbia University and the Harvard Smithsonian Center for Astrophysics. In this paper, we first outline the scientific objectives of our investigation and briefly overview some results obtained within our collaboration. We present preliminary results on two Galactic center X-ray bursters Terzan 2 and GX354-0 for which simultaneous SIGMA data exist and we report on the possible BATSE detection of a hard X-ray outburst from 4U 1705-44. Finally, we discuss on the hard X-ray emission from neutron stars and review the different criteria that have been proposed for distinguishing them from black hole systems on the basis of the properties of their hard X-ray emission. C1 HARVARD SMITHSONIAN CTR ASTROPHYS, CAMBRIDGE, MA 02138 USA. UNIV SPACE RES ASSOC, HUNTSVILLE, AL 35806 USA. NASA, GEORGE C MARSHALL SPACE FLIGHT CTR, HUNTSVILLE, AL 35812 USA. UNIV ALABAMA, DEPT PHYS, HUNTSVILLE, AL 35899 USA. COLUMBIA UNIV, DEPT PHYS, NEW YORK, NY 10027 USA. RP UPS, CNRS, CESR, 9 AV COLONEL ROCHE, BP 4346, TOULOUSE, FRANCE. NR 35 TC 0 Z9 0 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 DEC PY 1996 VL 120 IS 4 SI SI BP C121 EP C127 PG 7 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA WC063 UT WOS:A1996WC06300024 ER PT J AU Bloser, PF Barret, D Grindlay, JE Zhang, SN Harmon, BA Fishman, GJ Paciesas, WS Ford, E Kaaret, P Tavani, M AF Bloser, PF Barret, D Grindlay, JE Zhang, SN Harmon, BA Fishman, GJ Paciesas, WS Ford, E Kaaret, P Tavani, M TI BATSE observations of two X-ray bursters: 4U 1820-30 and 4U 1915-05 SO ASTRONOMY & ASTROPHYSICS SUPPLEMENT SERIES LA English DT Article; Proceedings Paper CT 3rd Compton Symposium CY JUN 12-14, 1995 CL MUNICH, GERMANY SP Max Planck Inst Extraterrestr Phys, Garching, Marx Planck Gesell, Deut Agentur Raumfahrtangelegenheiten, Deut Aerosp DE stars, 4U 1820-30, 4U 1915-05; X-rays, stars; gamma-rays, observations ID CLUSTER NGC 6624; NEUTRON-STARS; DISCOVERY; PERIOD; FLUX AB Using the BATSE instrument on the Compton Gamma Ray Observatory, the X-ray bursters 4U 1820-30 and 4U 1915-05 have been monitored in the hard X-ray band. In four years of data neither source was detected. We derive 2 sigma upper limits on 20-100 keV flux from 4U 1915-05 of 2.6 10(-2) photons cm(-2) s(-1) (90 mCrab) for 1 day integrations and 9.0 10(-3) photons cm(-2) s(-1) (30 mCrab) for 10 day integrations. For 4U 1820-30 the upper limits are 2.4 10(-2) photons cm(-2) s(-1) (80 mCrab) for 1 day integrations and 1.0 10(-2) photons cm(-2) s(-1) (30 mCrab) for 10 day integrations. These limits are not strong enough to constrain spectral models for the sources. The implications of these observations are discussed in light of BATSE results on other bursters. C1 CTR ETUD SPATIALE RAYONNEMENTS,CNRS,UPS,TOULOUSE,FRANCE. UNIV SPACE RES ASSOC,HUNTSVILLE,AL 35806. NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,HUNTSVILLE,AL 35812. UNIV ALABAMA,DEPT PHYS,HUNTSVILLE,AL 35899. COLUMBIA UNIV,DEPT PHYS,NEW YORK,NY 10027. RP Bloser, PF (reprint author), HARVARD SMITHSONIAN CTR ASTROPHYS,60 GARDEN ST,CAMBRIDGE,MA 02138, USA. NR 22 TC 1 Z9 1 U1 0 U2 0 PU EDITIONS PHYSIQUE PI LES ULIS CEDEX PA Z I DE COURTABOEUF AVE 7 AV DU HOGGAR, BP 112, 91944 LES ULIS CEDEX, FRANCE SN 0365-0138 J9 ASTRON ASTROPHYS SUP JI Astron. Astrophys. Suppl. Ser. PD DEC PY 1996 VL 120 IS 4 SI SI BP C275 EP C278 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA WC063 UT WOS:A1996WC06300061 ER PT J AU Bloser, PF Barret, D Grindlay, JE Zhang, SN Harmon, BA Fishman, GJ Paciesas, WS AF Bloser, PF Barret, D Grindlay, JE Zhang, SN Harmon, BA Fishman, GJ Paciesas, WS TI BATSE observations of the ultra-soft X-ray transient 4U 1630-47 SO ASTRONOMY & ASTROPHYSICS SUPPLEMENT SERIES LA English DT Article; Proceedings Paper CT 3rd Compton Symposium CY JUN 12-14, 1995 CL MUNICH, GERMANY SP Max Planck Inst Extraterrestr Phys, Garching, Marx Planck Gesell, Deut Agentur Raumfahrtangelegenheiten, Deut Aerosp DE stars, 4U 1630-47; X-rays, stars AB We have monitored the ultra-soft X-ray transient 4U 1630-47 in the hard X-ray band using the BATSE instrument on the Compton Gamma Ray Observatory. In a detailed analysis of the first year of data (May 1991 to April 1992), we have identified a possible similar to 3.5 sigma detection of a transient event in the light curve from TJD 8380-8410 (May 1991). In images made with the new BATSE occultation imaging technique, this event shows up as an excess consistent with the position of 4U 1630-47 to within the technique's angular resolution (similar to 1 degrees). Lacking independent data, and since the event does not concur with the observed 600 day period of the source, we cannot be certain that the outburst is associated with 4U 1630-47. In addition, we investigate those times during the BATSE data that the ephemeris for 4U 1630-47 does predict activity. Parmar et al. (1995) report the detection of 4U 1630-47 by ROSAT during an observation in September 1992. The source was not detected by BATSE and we derive a 2 sigma upper limit during September 1992 of similar to 2.2 10(-2) photons cm(-2) s(-1), or about 70 mCrab, for 5 day integrations. 600 days later in April 1994, we do find evidence of weak emission from 4U 1630-47 at a level of similar to 15 mCrab, owing to a fortuitous lack of interfering sources and good viewing geometry. We compare these results with previous X-ray observations of the source. C1 UPS,CTR ETUD SPATIALE RAYONNEMENTS,CNRS,TOULOUSE,FRANCE. UNIV SPACE RES ASSOC,HUNTSVILLE,AL 35806. NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,HUNTSVILLE,AL 35812. UNIV ALABAMA,DEPT PHYS,HUNTSVILLE,AL 35899. RP Bloser, PF (reprint author), HARVARD SMITHSONIAN CTR ASTROPHYS,60 GARDEN ST,CAMBRIDGE,MA 02138, USA. NR 18 TC 0 Z9 0 U1 0 U2 0 PU EDITIONS PHYSIQUE PI LES ULIS CEDEX PA Z I DE COURTABOEUF AVE 7 AV DU HOGGAR, BP 112, 91944 LES ULIS CEDEX, FRANCE SN 0365-0138 J9 ASTRON ASTROPHYS SUP JI Astron. Astrophys. Suppl. Ser. PD DEC PY 1996 VL 120 IS 4 SI SI BP C191 EP C195 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA WC063 UT WOS:A1996WC06300041 ER PT J AU Burdyuzha, V Kauts, V Wallyn, P AF Burdyuzha, V Kauts, V Wallyn, P TI Characteristic lines of positronium from sources of annihilation line SO ASTRONOMY & ASTROPHYSICS SUPPLEMENT SERIES LA English DT Article; Proceedings Paper CT 3rd Compton Symposium CY JUN 12-14, 1995 CL MUNICH, GERMANY SP Max Planck Inst Extraterrestr Phys, Garching, Marx Planck Gesell, Deut Agentur Raumfahrtangelegenheiten, Deut Aerosp DE elementary particles; lines, formation; radio lines, general ID INTERSTELLAR-MEDIUM; SCATTERING AB Annihilation processes for low temperatures with necessity go through state of positronium (Ps). The possibility of observation of positronium characteristic lines, which can arise during its formation, is explored. Using the diffuse and point components of 511 keV line from sources in the direction on the Galactic Center, as an example, the fluxes in the L(alpha)(2431 Angstrom), H-alpha(1.3 mu m), P-alpha(3.75 mu m) and radiorecombination lines are estimated. C1 CALTECH,JET PROP LAB,PASADENA,CA 91125. RP Burdyuzha, V (reprint author), RUSSIAN ACAD SCI,PN LEBEDEV PHYS INST,CTR ASTRO SPACE,MOSCOW,RUSSIA. RI Kauts, Vladimir/N-3640-2015; Burdyzha, Vladimir/M-6329-2015 NR 11 TC 0 Z9 0 U1 0 U2 0 PU EDITIONS PHYSIQUE PI LES ULIS CEDEX PA Z I DE COURTABOEUF AVE 7 AV DU HOGGAR, BP 112, 91944 LES ULIS CEDEX, FRANCE SN 0365-0138 J9 ASTRON ASTROPHYS SUP JI Astron. Astrophys. Suppl. Ser. PD DEC PY 1996 VL 120 IS 4 SI SI BP C365 EP C367 PG 3 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA WC063 UT WOS:A1996WC06300082 ER PT J AU Chakrabarti, SK Titarchuk, L Kazanas, D Ebisawa, K AF Chakrabarti, SK Titarchuk, L Kazanas, D Ebisawa, K TI Observational signature of the 'boundary layer' of galactic and extragalactic black holes SO ASTRONOMY & ASTROPHYSICS SUPPLEMENT SERIES LA English DT Article; Proceedings Paper CT 3rd Compton Symposium CY JUN 12-14, 1995 CL MUNICH, GERMANY SP Max Planck Inst Extraterrestr Phys, Garching, Marx Planck Gesell, Deut Agentur Raumfahrtangelegenheiten, Deut Aerosp DE accretion disks; transonic flows; black hole physics; hydrodynamics; radiation mechanisms, Compton and inverse Compton; radiative transfer; X-rays, general ID ACCRETION DISKS; RADIO JETS; COMPTONIZATION; RADIATION; MODELS AB We present spectral properties of an accretion disk model, in which a Keplerian accretion disk is flanked by a sub-Keplerian halo component terminating at a standing shock. The post-shock region (which may be considered to be the boundary layer of a black hole) reprocesses the soft photons emitted from the Keplerian accretion disk. We show that switching of states (from hard to soft and vice versa) could be accomplished by a change in the accretion rate of the Keplerian disk component. Our consideration, for the first time, resolves a long-standing problem of identifying the illusive 'Compton cloud' responsible for the switching of states. C1 TIFR,BOMBAY 400005,MAHARASHTRA,INDIA. GEORGE MASON UNIV,CSI,FAIRFAX,VA 22030. NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. RP Chakrabarti, SK (reprint author), GODDARD SPACE FLIGHT CTR,CODE 665,BOMBAY 400005,MAHARASHTRA,INDIA. NR 21 TC 0 Z9 0 U1 0 U2 0 PU EDITIONS PHYSIQUE PI LES ULIS CEDEX PA Z I DE COURTABOEUF AVE 7 AV DU HOGGAR, BP 112, 91944 LES ULIS CEDEX, FRANCE SN 0365-0138 J9 ASTRON ASTROPHYS SUP JI Astron. Astrophys. Suppl. Ser. PD DEC PY 1996 VL 120 IS 4 SI SI BP C163 EP C166 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA WC063 UT WOS:A1996WC06300034 ER PT J AU Chen, W White, RL Bertsch, D AF Chen, W White, RL Bertsch, D TI Possible detection of pi(0)-decay gamma-ray emission from Cyg OB2 by EGRET SO ASTRONOMY & ASTROPHYSICS SUPPLEMENT SERIES LA English DT Article; Proceedings Paper CT 3rd Compton Symposium CY JUN 12-14, 1995 CL MUNICH, GERMANY SP Max Planck Inst Extraterrestr Phys, Garching, Marx Planck Gesell, Deut Agentur Raumfahrtangelegenheiten, Deut Aerosp DE (stars) circumstellar matter; stars, individual, Cyg X-3; gamma rays, observations; gamma rays, theory; associations, Cyg OB2 ID DRIVEN STELLAR WINDS; MASSIVE STARS; HOT STARS; INSTABILITIES; CYGNUS-X-3 AB We report possible detection of pi(0)-decay radiation from Cyg OB2, a nearby (1.7 kpc) massive OB star association. The EGRET flux (> 100 MeV) maps clearly indicate a point source whose error circle includes both Cyg OB2 and Cyg X-3. We show that Cyg X-3 is unlikely to be the counterpart for the EGRET source, because of the marginal spatial consistency and the lack of the 4.8 hour modulation seen in other high energy emissions from Cyg X-3. If confirmed, this will be the first detection by EGRET of massive stars. C1 UNIV SPACE RES ASSOC,WASHINGTON,DC. SPACE TELESCOPE SCI INST,BALTIMORE,MD 21218. RP Chen, W (reprint author), NASA,GODDARD SPACE FLIGHT CTR,CODE 661,GREENBELT,MD 20771, USA. NR 20 TC 4 Z9 4 U1 0 U2 0 PU EDITIONS PHYSIQUE PI LES ULIS CEDEX PA Z I DE COURTABOEUF AVE 7 AV DU HOGGAR, BP 112, 91944 LES ULIS CEDEX, FRANCE SN 0365-0138 J9 ASTRON ASTROPHYS SUP JI Astron. Astrophys. Suppl. Ser. PD DEC PY 1996 VL 120 IS 4 SI SI BP C423 EP C426 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA WC063 UT WOS:A1996WC06300094 ER PT J AU Chen, W Gehrels, N Diehl, R Hartmann, D AF Chen, W Gehrels, N Diehl, R Hartmann, D TI On the spiral arm interpretation of COMPTEL Al-26 map features SO ASTRONOMY & ASTROPHYSICS SUPPLEMENT SERIES LA English DT Article; Proceedings Paper CT 3rd Compton Symposium CY JUN 12-14, 1995 CL MUNICH, GERMANY SP Max Planck Inst Extraterrestr Phys, Garching, Marx Planck Gesell, Deut Agentur Raumfahrtangelegenheiten, Deut Aerosp DE gamma rays, observations; nucleosynthesis; Galaxy, structure AB The signature of spiral arms has been recognized to leave imprints in the Al-26 source distribution as observed by COMPTEL. We have proposed a spiral arm model based on HII region observations plus the free electron distribution, supplemented by an inner Galaxy component that reflects the evidence for a central bar. We discuss some of the issues concerning this interpretation. C1 UNIV SPACE RES ASSOC, WASHINGTON, DC USA. MAX PLANCK INST EXTRATERR PHYS, D-85740 GARCHING, GERMANY. CLEMSON UNIV, DEPT PHYS & ASTRON, CLEMSON, SC 29634 USA. RP NASA, GODDARD SPACE FLIGHT CTR, CODE 661, GREENBELT, MD 20771 USA. RI Gehrels, Neil/D-2971-2012 NR 9 TC 1 Z9 1 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 DEC PY 1996 VL 120 IS 4 SI SI BP C315 EP C316 PG 2 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA WC063 UT WOS:A1996WC06300070 ER PT J AU Crary, DJ Kouveliotou, C vanParadijs, J vanderHooft, F Scott, DM Zhang, SN Rubin, BC Finger, MH Harmon, BA vanderKlis, M Lewin, WHG AF Crary, DJ Kouveliotou, C vanParadijs, J vanderHooft, F Scott, DM Zhang, SN Rubin, BC Finger, MH Harmon, BA vanderKlis, M Lewin, WHG TI 1100 days of BATSE observations of Cygnus X-1 SO ASTRONOMY & ASTROPHYSICS SUPPLEMENT SERIES LA English DT Article; Proceedings Paper CT 3rd Compton Symposium CY JUN 12-14, 1995 CL MUNICH, GERMANY SP Max Planck Inst Extraterrestr Phys, Garching, Marx Planck Gesell, Deut Agentur Raumfahrtangelegenheiten, Deut Aerosp DE X-rays, stars; stars, Cyg X-1 AB We have examined the power spectral behavior of Cyg X-1 using approximately 1100 days of BATSE data. These data have been searched for correlations between different power spectral features, and for correlations between power spectral features and energy spectral parameters derived from BATSE occultation analysis. C1 UNIV SPACE RES ASSOC,HUNTSVILLE,AL 35806. UNIV ALABAMA,DEPT PHYS,HUNTSVILLE,AL 35899. UNIV AMSTERDAM,ASTRON INST ANTON PANNEKOEK,NL-1098 SJ AMSTERDAM,NETHERLANDS. UNIV AMSTERDAM,CTR HIGH ENERGY ASTROPHYS,NL-1098 SJ AMSTERDAM,NETHERLANDS. NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,HUNTSVILLE,AL 35812. MIT,CAMBRIDGE,MA 02139. RP Crary, DJ (reprint author), NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,NASA CODE ES-84,HUNTSVILLE,AL 35812, USA. NR 4 TC 1 Z9 1 U1 0 U2 0 PU EDITIONS PHYSIQUE PI LES ULIS CEDEX PA Z I DE COURTABOEUF AVE 7 AV DU HOGGAR, BP 112, 91944 LES ULIS CEDEX, FRANCE SN 0365-0138 J9 ASTRON ASTROPHYS SUP JI Astron. Astrophys. Suppl. Ser. PD DEC PY 1996 VL 120 IS 4 SI SI BP C153 EP C154 PG 2 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA WC063 UT WOS:A1996WC06300031 ER PT J AU Daugherty, JK Harding, AK AF Daugherty, JK Harding, AK TI Gamma ray pulsars: Extended polar cap cascades from nearly aligned rotators SO ASTRONOMY & ASTROPHYSICS SUPPLEMENT SERIES LA English DT Article; Proceedings Paper CT 3rd Compton Symposium CY JUN 12-14, 1995 CL MUNICH, GERMANY SP Max Planck Inst Extraterrestr Phys, Garching, Marx Planck Gesell, Deut Agentur Raumfahrtangelegenheiten, Deut Aerosp DE gamma rays, theory; pulsars, general-pulsars, PSR 0833-45 ID RAPIDLY SPINNING PULSARS; ENERGETIC RADIATION; GAPS; MODEL; VELA AB We have used Polar Cap (PC) model simulations of gamma-ray pulsars to derive light curves and spectra for Nearly Aligned Rotators (NARs), as well as a more general class of Single Polar Cap (SPC) models which do not require that the inclination alpha << 1. In these models the observed gamma-rays are due to emission concentrated around the rim of a single PC, and may exhibit either one or two peaks. The interpeak emission seen in several doubly peaked sources is produced above the PC interior. If alpha similar to theta(b), the half-width of the PC gamma-beam, the peak-to-peak phase separation can be as large as similar to 0.4 - 0.5. Our simulation assumes the physics of conventional PC models, in which the gamma-rays emerge from photon-pair cascades initiated by curvature radiation from accelerated PC electrons. Here we also assume that the acceleration extends up to heights of several radii above the neutron star surface. We find that the combined effects of increased PC radii (by factors greater than or similar to 2) and extended acceleration zones solve a major problem with earlier PC models, namely their small beam widths which imply low detection probabilities. We compare our results with observations of the Vela pulsar, for models in which the primary electrons have a uniform surface density over the PC interior with a sharp increase (similar to 3) near the rim. We describe model parameters which reproduce key features of both the Vela light curves and phase-resolved spectra. C1 NASA,GODDARD SPACE FLIGHT CTR,HIGH ENERGY ASTROPHYS LAB,GREENBELT,MD 20771. RP Daugherty, JK (reprint author), UNIV N CAROLINA,DEPT COMP SCI,ASHEVILLE,NC 28804, USA. RI Harding, Alice/D-3160-2012 NR 20 TC 7 Z9 7 U1 0 U2 0 PU EDITIONS PHYSIQUE PI LES ULIS CEDEX PA Z I DE COURTABOEUF AVE 7 AV DU HOGGAR, BP 112, 91944 LES ULIS CEDEX, FRANCE SN 0365-0138 J9 ASTRON ASTROPHYS SUP JI Astron. Astrophys. Suppl. Ser. PD DEC PY 1996 VL 120 IS 4 SI SI BP C107 EP C110 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA WC063 UT WOS:A1996WC06300020 ER PT J AU deJager, OC Harding, AK Sreekumar, P Strickman, M AF deJager, OC Harding, AK Sreekumar, P Strickman, M TI The Crab and Vela gamma ray nebulae SO ASTRONOMY & ASTROPHYSICS SUPPLEMENT SERIES LA English DT Article; Proceedings Paper CT 3rd Compton Symposium CY JUN 12-14, 1995 CL MUNICH, GERMANY SP Max Planck Inst Extraterrestr Phys, Garching, Marx Planck Gesell, Deut Agentur Raumfahrtangelegenheiten, Deut Aerosp DE ISM, individual objects, Crab nebula and Vela SNR; ISM, magnetic fields; gamma rays, observations; gamma rays, theory ID SUPERNOVA REMNANT; HIGH-ENERGY; PULSAR AB COMPTEL/EGRET observations of the Crab unpulsed component indicates that the 1-150 MeV emission is variable with a photon spectrum of the form similar to E(-1.7) exp(-E/25 MeV), which does not connect smoothly with the spectrum outside this interval. This hints at an independent synchrotron emission feature in the Crab Nebula. The flux in the 0.3 - 10 GeV interval is a factor similar to 3 larger than the predicted inverse Compton flux, which indicates that the field in the outer nebula decreases faster than predicted by MHD flow soultions. The OSSE detection of the Vela SNR is (spectrally) consistent with emission from the 1' radius compact nebula. The EGRET upper limit constrains the maximum particle energy in this compact nebula to values below the full polar cap potential drop. However, inverse Compton emission from the Vela X radio nebula is also expected in the EGRET range, leading to a constraint on the radio break frequency and nebular magnetic field strength. C1 NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. POTCHEFSTROOM UNIV CHRISTIAN HIGHER EDUC,SPACE RES UNIT,ZA-2520 POTCHEFSTROOM,SOUTH AFRICA. USN,RES LAB,WASHINGTON,DC 20375. RI Harding, Alice/D-3160-2012 NR 21 TC 2 Z9 2 U1 0 U2 0 PU EDITIONS PHYSIQUE PI LES ULIS CEDEX PA Z I DE COURTABOEUF AVE 7 AV DU HOGGAR, BP 112, 91944 LES ULIS CEDEX, FRANCE SN 0365-0138 J9 ASTRON ASTROPHYS SUP JI Astron. Astrophys. Suppl. Ser. PD DEC PY 1996 VL 120 IS 4 SI SI BP C441 EP C444 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA WC063 UT WOS:A1996WC06300097 ER PT J AU Diehl, R Bennett, K Dupraz, C Knodlseder, J Lichti, G Morris, D Oberlack, U Ryan, J Schonfelder, V Strong, A vonBallmoos, P Winkler, C Chen, W Hartmann, D Prantzos, N AF Diehl, R Bennett, K Dupraz, C Knodlseder, J Lichti, G Morris, D Oberlack, U Ryan, J Schonfelder, V Strong, A vonBallmoos, P Winkler, C Chen, W Hartmann, D Prantzos, N TI Modelling the 1.8 MeV sky: Tracers of massive star nucleosynthesis SO ASTRONOMY & ASTROPHYSICS SUPPLEMENT SERIES LA English DT Article; Proceedings Paper CT 3rd Compton Symposium CY JUN 12-14, 1995 CL MUNICH, GERMANY SP Max Planck Inst Extraterrestr Phys, Garching, Marx Planck Gesell, Deut Agentur Raumfahrtangelegenheiten, Deut Aerosp DE nucleosynthesis; gamma-ray, observations; supernovae; Galaxy, structure ID WOLF-RAYET STARS; GALACTIC DISTRIBUTION; SUPERNOVA-REMNANTS; WHITE-DWARFS; SPIRAL ARMS; MILKY-WAY; GALAXY; EVOLUTION AB COMPTEL, the imaging telescope on the Compton Gamma-Ray Observatory, has mapped the sky in 1.809 MeV gamma-ray Line emission attributed to radioactive Al-26 With an angular resolution of similar or equal to 1 degrees. This allows for the first time correlation studies of spatial distributions determined for different Al-26 candidate-source types with the apparent sky distribution of this radio-isotope. The strengths and weaknesses of different source tracers with respect to massive-star nucleosynthesis of Al-26 are discussed. C1 SRON UTRECHT, NL-3584 UTRECHT, NETHERLANDS. UNIV NEW HAMPSHIRE, CTR SPACE SCI, DURHAM, NH 03824 USA. EUROPEAN SPACE AGCY, ESTEC, DIV ASTROPHYS, NL-2200 AG NOORDWIJK, NETHERLANDS. ECOLE NORMALE SUPER, F-75005 PARIS, FRANCE. CTR ETUD SACLAY, SERV ASTROPHYS, DAPNIA, F-75014 PARIS, FRANCE. INST ASTROPHYS, F-75014 PARIS, FRANCE. CTR ETUD SPATIALE RAYONNEMENTS, F-31029 TOULOUSE, FRANCE. NASA, GODDARD SPACE FLIGHT CTR, UNIV SPACE RES ASSOC, GREENBELT, MD 20771 USA. CLEMSON UNIV, DEPT PHYS & ASTRON, CLEMSON, SC 29634 USA. RP MAX PLANCK INST EXTRATERR PHYS, D-85740 GARCHING, GERMANY. NR 37 TC 1 Z9 1 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 DEC PY 1996 VL 120 IS 4 SI SI BP C321 EP C325 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA WC063 UT WOS:A1996WC06300072 ER PT J AU Dixon, DD Johnson, WN Kurfess, JD Pina, RK Puetter, RC Purcell, WR Tumer, TO Wheaton, WA Zych, AD AF Dixon, DD Johnson, WN Kurfess, JD Pina, RK Puetter, RC Purcell, WR Tumer, TO Wheaton, WA Zych, AD TI Pixon-based deconvolution SO ASTRONOMY & ASTROPHYSICS SUPPLEMENT SERIES LA English DT Article; Proceedings Paper CT 3rd Compton Symposium CY JUN 12-14, 1995 CL MUNICH, GERMANY SP Max Planck Inst Extraterrestr Phys, Garching, Marx Planck Gesell, Deut Agentur Raumfahrtangelegenheiten, Deut Aerosp DE gamma rays, observations; methods, data analysis; techniques, image processing AB We describe a new technique, pixon-based deconvolution, for the reconstruction of images and spectra from low signal-to-noise data. In ''traditional'' techniques, such as Maximum Likelihood (ML) and Maximum Entropy (ME), the model parameters (e.g., pixel size) are considered ''nuisance parameters'', and generally held fixed in the course of deconvolution. Pixon techniques allow the model parameters to change according to the information contained in the data. The pixon model admits only that level of detail which is statistically justified by the data, thus greatly reducing the production of spurious sources and signal correlated residuals, common problems in ML and ME reconstructions. As a result, gains in sensitivity and spatial/energy resolution may be realized. Sample applications to data from OSSE and COMPTEL will be presented. C1 USN,RES LAB,EO HULBURT CTR SPACE RES,WASHINGTON,DC 20375. UNIV CALIF SAN DIEGO,CTR ASTROPHYS & SPACE SCI,LA JOLLA,CA 92093. NORTHWESTERN UNIV,DEPT PHYS & ASTRON,EVANSTON,IL 60208. CALTECH,JET PROP LAB,HIGH ENERGY ASTROPHYS GRP,PASADENA,CA 91109. RP Dixon, DD (reprint author), UNIV CALIF RIVERSIDE,INST GEOPHYS & PLANETARY PHYS,RIVERSIDE,CA 92521, USA. RI Johnson, Neil/G-3309-2014 NR 4 TC 3 Z9 3 U1 0 U2 1 PU EDITIONS PHYSIQUE PI LES ULIS CEDEX PA Z I DE COURTABOEUF AVE 7 AV DU HOGGAR, BP 112, 91944 LES ULIS CEDEX, FRANCE SN 0365-0138 J9 ASTRON ASTROPHYS SUP JI Astron. Astrophys. Suppl. Ser. PD DEC PY 1996 VL 120 IS 4 SI SI BP C683 EP C686 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA WC063 UT WOS:A1996WC06300154 ER PT J AU Durouchoux, P Viaud, P Wallyn, P Mahoney, WA AF Durouchoux, P Viaud, P Wallyn, P Mahoney, WA TI On the Be-7* and Li-7* de-excitation lines as a possible explanation of the gamma-ray feature observed in Nova Muscae 1991 SO ASTRONOMY & ASTROPHYSICS SUPPLEMENT SERIES LA English DT Article; Proceedings Paper CT 3rd Compton Symposium CY JUN 12-14, 1995 CL MUNICH, GERMANY SP Max Planck Inst Extraterrestr Phys, Garching, Marx Planck Gesell, Deut Agentur Raumfahrtangelegenheiten, Deut Aerosp DE gamma rays, theory; black hole physics; line, formation; nuclear reactions; X-ray sources, GRS 1124-68 ID POSITRON-ANNIHILATION; PAIR ANNIHILATION; 1E 1740.7-2942; DISCOVERY; EMISSION AB We consider two different models to explain the gamma-ray feature detected on Nova Muscae 1991: a thermal electron-positron plasma and alpha-alpha reactions. In the first case, a direct fit to the data using the detailed model spectrum developed by Svensson (1983) gives a redshifted line (z = 0.048(-0.027)(+0.017)) coming from a relatively low temperature pair plasma (T similar to 4 10(7) K). In the second case, a Monte Carlo simulation of Be-7* - Li-7* de-excitation lines following Ramaty et al. (1979) (RKL79 hereafter), gives a best fit model with monoenergetic and isotropic alpha particles of similar to 10-25 MeV/nucleon or power-law distributions of isotropic alpha particles with index of similar to 2 to 3. C1 CALTECH,JET PROP LAB,PASADENA,CA 91109. RP Durouchoux, P (reprint author), CTR ETUD SACLAY,DAPNIA,SERV ASTROPHYS,F-91191 GIF SUR YVETTE,FRANCE. NR 22 TC 0 Z9 0 U1 0 U2 0 PU EDITIONS PHYSIQUE PI LES ULIS CEDEX PA Z I DE COURTABOEUF AVE 7 AV DU HOGGAR, BP 112, 91944 LES ULIS CEDEX, FRANCE SN 0365-0138 J9 ASTRON ASTROPHYS SUP JI Astron. Astrophys. Suppl. Ser. PD DEC PY 1996 VL 120 IS 4 SI SI BP C265 EP C268 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA WC063 UT WOS:A1996WC06300059 ER PT J AU Fichtel, C AF Fichtel, C TI EGRET overview: Achievements in the light of expectations SO ASTRONOMY & ASTROPHYSICS SUPPLEMENT SERIES LA English DT Article; Proceedings Paper CT 3rd Compton Symposium CY JUN 12-14, 1995 CL MUNICH, GERMANY SP Max Planck Inst Extraterrestr Phys, Garching, Marx Planck Gesell, Deut Agentur Raumfahrtangelegenheiten, Deut Aerosp DE gamma rays, observations, bursts; Sun, gamma rays; cosmic rays ID GAMMA-RAY EMISSION; PRIMORDIAL BLACK-HOLES; HIGH-ENERGY; EXPERIMENT TELESCOPE; MAGELLANIC CLOUD; LONG-DURATION; RADIATION; GEMINGA; PULSARS; SEARCH AB The Energetic Gamma Ray Experiment Telescope (EGRET) on the Compton Gamma Ray Observatory (CGRO) has over ten times the sensitivity of earlier high- energy gamma-ray telescopes flown in space. It covers the energy range from about 3 10(7) eV to approximately 3 10(10) eV. As anticipated, EGRET has indeed produced exciting and important new results on a broad range of astrophysical topics. Highlights include: (1) the finding of a new class of objects - high energy gamma-ray emitting blazars, (2) the emission of high energy gamma-rays from a gamma ray burst for over an hour, with some gamma rays having energies over a GeV and two having energies over 10 GeV, (3) the observation of seven high energy gamma ray pulsars, (4) the determination with high certainty that cosmic rays are galactic, (5) the detailed mapping of the galactic diffuse radiation and the measurement of the pion bump in the high energy gamma-ray energy spectrum, (6) the absence of microsecond bursts and its implication for certain physics unification theories, (7) the long trapping time of over ten hours for energetic solar particles following a flare, and (8) a measurement of the extragalactic diffuse radiation and its consistency with that expected from AGN emission. RP Fichtel, C (reprint author), NASA,GODDARD SPACE FLIGHT CTR,CODE 660,GREENBELT,MD 20771, USA. NR 40 TC 1 Z9 1 U1 1 U2 1 PU EDITIONS PHYSIQUE PI LES ULIS CEDEX PA Z I DE COURTABOEUF AVE 7 AV DU HOGGAR, BP 112, 91944 LES ULIS CEDEX, FRANCE SN 0365-0138 J9 ASTRON ASTROPHYS SUP JI Astron. Astrophys. Suppl. Ser. PD DEC PY 1996 VL 120 IS 4 SI SI BP C23 EP C29 PG 7 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA WC063 UT WOS:A1996WC06300005 ER PT J AU Finger, MH Wilson, RB Chakrabarty, D AF Finger, MH Wilson, RB Chakrabarty, D TI Reappearance of the X-ray binary pulsar 2S 1417-624 SO ASTRONOMY & ASTROPHYSICS SUPPLEMENT SERIES LA English DT Article; Proceedings Paper CT 3rd Compton Symposium CY JUN 12-14, 1995 CL MUNICH, GERMANY SP Max Planck Inst Extraterrestr Phys, Garching, Marx Planck Gesell, Deut Agentur Raumfahrtangelegenheiten, Deut Aerosp DE accretion, accretion disks; stars, emission-line, Be; pulsars, individual, 2S 1417-624; X-rays, stars AB Renewed activity from the transient X-ray binary pulsar 2S 1417-624 was observed by the BATSE instrument between August 26, 1994 and July 7, 1995. The BATSE observations consist of an initial outburst that lasted over 110 days, and five smaller outbursts which followed. During the initial outburst the pulse shape systematically evolved. We show that this evolution is inconsistent with the pulse profile being entirely determined by the mass accretion rate. We have determined the 2S 1417-624 system orbital parameters by assuming that the accretion torque is correlated with the observed hard X-ray pulsed flux. C1 CALTECH,SPACE RADIAT LAB,PASADENA,CA 91125. RP Finger, MH (reprint author), NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,SPACE SCI LAB,ES84,HUNTSVILLE,AL 35812, USA. NR 9 TC 2 Z9 2 U1 0 U2 0 PU EDITIONS PHYSIQUE PI LES ULIS CEDEX PA Z I DE COURTABOEUF AVE 7 AV DU HOGGAR, BP 112, 91944 LES ULIS CEDEX, FRANCE SN 0365-0138 J9 ASTRON ASTROPHYS SUP JI Astron. Astrophys. Suppl. Ser. PD DEC PY 1996 VL 120 IS 4 SI SI BP C209 EP C212 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA WC063 UT WOS:A1996WC06300045 ER PT J AU Gehrels, N Chen, W AF Gehrels, N Chen, W TI Radial velocity map and line profiles of Al-26 emission from Galactic rotation SO ASTRONOMY & ASTROPHYSICS SUPPLEMENT SERIES LA English DT Article; Proceedings Paper CT 3rd Compton Symposium CY JUN 12-14, 1995 CL MUNICH, GERMANY SP Max Planck Inst Extraterrestr Phys, Garching, Marx Planck Gesell, Deut Agentur Raumfahrtangelegenheiten, Deut Aerosp DE gamma rays, observations; nucleosynthesis; Galaxy, structure; line, profiles ID GALAXY AB Based on our spiral-arm model of the COMPTEL Al-26 map features, the 1.8 MeV line centroid from individual hot spots will be shifted due to Galactic rotation. We present a 21-cm style radial velocity map of our model Al-26 distribution and calculate the model line profiles from some of the candidate spiral arm directions. The INTEGRAL, with its fine energy resolution, will help solve the Al-26 problem by accurately measuring the line centroid and so identifying the true locations of the hot spots, especially in the poorly understood inner Galaxy and Galactic center regions. C1 UNIV SPACE RES ASSOC, WASHINGTON, DC USA. RP NASA, GODDARD SPACE FLIGHT CTR, CODE 661, GREENBELT, MD 20771 USA. RI Gehrels, Neil/D-2971-2012 NR 8 TC 0 Z9 0 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 DEC PY 1996 VL 120 IS 4 SI SI BP C331 EP C334 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA WC063 UT WOS:A1996WC06300074 ER PT J AU Gehrels, N Shrader, CR AF Gehrels, N Shrader, CR TI Status of the Compton Gamma Ray Observatory SO ASTRONOMY & ASTROPHYSICS SUPPLEMENT SERIES LA English DT Article; Proceedings Paper CT 3rd Compton Symposium CY JUN 12-14, 1995 CL MUNICH, GERMANY SP Max Planck Inst Extraterrestr Phys, Garching, Marx Planck Gesell, Deut Agentur Raumfahrtangelegenheiten, Deut Aerosp DE gamma rays, observations; telescopes; astronomical databases, miscellaneous; space vehicles AB The Compton Gamma Ray Observatory and its four experiment packages continue to function in a nearly flawless manner now well into the fourth year of mission operations. We discuss the status of the mission as of the time of this submission and the discuss the prospects of an extended mission lasting into the next century. RP Gehrels, N (reprint author), NASA,GODDARD SPACE FLIGHT CTR,HIGH ENERGY ASTROPHYS LAB,GREENBELT,MD 20771, USA. RI Gehrels, Neil/D-2971-2012 NR 7 TC 2 Z9 2 U1 0 U2 0 PU EDITIONS PHYSIQUE PI LES ULIS CEDEX PA Z I DE COURTABOEUF AVE 7 AV DU HOGGAR, BP 112, 91944 LES ULIS CEDEX, FRANCE SN 0365-0138 J9 ASTRON ASTROPHYS SUP JI Astron. Astrophys. Suppl. Ser. PD DEC PY 1996 VL 120 IS 4 SI SI BP C1 EP C4 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA WC063 UT WOS:A1996WC06300002 ER PT J AU Grindlay, JE Barret, D Bloser, PF Zhang, SN Fishman, GJ Harmon, BA Paciesas, WS AF Grindlay, JE Barret, D Bloser, PF Zhang, SN Fishman, GJ Harmon, BA Paciesas, WS TI BATSE survey for faint transients and black hole candidates SO ASTRONOMY & ASTROPHYSICS SUPPLEMENT SERIES LA English DT Article; Proceedings Paper CT 3rd Compton Symposium CY JUN 12-14, 1995 CL MUNICH, GERMANY SP Max Planck Inst Extraterrestr Phys, Garching, Marx Planck Gesell, Deut Agentur Raumfahrtangelegenheiten, Deut Aerosp DE X-rays, stars; stars, GRO J1849-03, 4U 1630-47; black holes; gamma-rays, observations ID X-RAY-EMISSION AB We describe a project to search for faint X-ray transients that are likely to be black hole candidates (BHCs). Our overall objectives are to better constrain the total number of BHCs in the Galaxy and thus the formation and evolution of such systems. A secondary objective is to better understand the outburst mechanism in X-ray novae and the hard X-ray emission region in these systems. We report preliminary BATSE results for analysis of seven fields centered on known (historical) transients in which we search both for recurrent outbursts (to constrain recurrence times) as well as new sources. Preliminary light curves for each source region have been derived for the full 4 year BATSE data from occultation analysis, and occultation imaging has also been carried out to further constrain source positions. As reported in detail in companion papers, a new faint transient, GRO J1849-03 (cf. Zhang et al.), was discovered in one field, and probable hard X-ray outbursts of the recurrent transient 4U 1630-47 (cf. Bloser et al.) were detected for the first time at hard X-ray energies. Initial results for the remaining fields are discussed, and implications for an extended survey are mentioned. C1 UPS,CTR ETUD SPATIALE RAYONNEMENTS,CNRS,TOULOUSE,FRANCE. UNIV SPACE RES ASSOC,HUNTSVILLE,AL 35806. GEORGE C MARSHALL SPACE FLIGHT CTR,HUNTSVILLE,AL 35812. UNIV ALABAMA,DEPT PHYS,HUNTSVILLE,AL 35899. RP Grindlay, JE (reprint author), HARVARD SMITHSONIAN CTR ASTROPHYS,60 GARDEN ST,CAMBRIDGE,MA 02138, USA. NR 21 TC 0 Z9 0 U1 0 U2 0 PU EDITIONS PHYSIQUE PI LES ULIS CEDEX PA Z I DE COURTABOEUF AVE 7 AV DU HOGGAR, BP 112, 91944 LES ULIS CEDEX, FRANCE SN 0365-0138 J9 ASTRON ASTROPHYS SUP JI Astron. Astrophys. Suppl. Ser. PD DEC PY 1996 VL 120 IS 4 SI SI BP C145 EP C148 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA WC063 UT WOS:A1996WC06300029 ER PT J AU Harding, AK Baring, MG Gonthier, PL AF Harding, AK Baring, MG Gonthier, PL TI Photon splitting in gamma-ray pulsars SO ASTRONOMY & ASTROPHYSICS SUPPLEMENT SERIES LA English DT Article; Proceedings Paper CT 3rd Compton Symposium CY JUN 12-14, 1995 CL MUNICH, GERMANY SP Max Planck Inst Extraterrestr Phys, Garching, Marx Planck Gesell, Deut Agentur Raumfahrtangelegenheiten, Deut Aerosp DE pulsars general; PSR 1509-58; gamma-rays; Theory magnetic fields ID STRONG MAGNETIC-FIELDS; EMISSION; SPECTRA AB Magnetic photon splitting is an exotic QED process which becomes important in fields approaching the quantum critical value of 4.41 10(13) Gauss. Its principal effect is to degrade photon energies below the threshold for magnetic single photon pair production. In this paper, we consider the importance of photon splitting in gamma-ray pulsars, specifically focusing on PSR 1509-58, because of its large spin-down field (B = 3 10(13) Gauss). We present calculations of the splitting attenuation length, including the influence of the dipole field and curved spacetime geometry of a neutron star magnetosphere. Test photons originate at different locations on the neutron star surface, initially propagating parallel to the field lines. It is found that splitting prevents gamma-rays emitted from a polar cap of 5 degrees-10 degrees from escaping the magnetosphere when their energy exceeds about 30-50 MeV in fields similar to 10(13) Gauss. Comparison with attenuation lengths for pair creation indicates that splitting is more important in polar cap models for PSR 1509-58 in the 10-200 MeV range: splitting suppresses the creation of pairs and inhibits escape of any near-surface emission above about 10-20 MeV, depending on polar cap size. General relativistic effects on photon trajectories and on the magnetic field decrease the escape energies significantly. C1 HOPE COLL,DEPT PHYS,HOLLAND,MI 49423. RP Harding, AK (reprint author), NASA,GODDARD SPACE FLIGHT CTR,HIGH ENERGY ASTROPHYS LAB,CODE 661,GREENBELT,MD 20771, USA. RI Harding, Alice/D-3160-2012 NR 23 TC 0 Z9 0 U1 0 U2 0 PU EDITIONS PHYSIQUE PI LES ULIS CEDEX PA Z I DE COURTABOEUF AVE 7 AV DU HOGGAR, BP 112, 91944 LES ULIS CEDEX, FRANCE SN 0365-0138 J9 ASTRON ASTROPHYS SUP JI Astron. Astrophys. Suppl. Ser. PD DEC PY 1996 VL 120 IS 4 SI SI BP C111 EP C114 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA WC063 UT WOS:A1996WC06300021 ER PT J AU Harmon, BA Wilson, CA Tavani, M Zhang, SN Rubin, BC Paciesas, WS Ford, EC Kaaret, P AF Harmon, BA Wilson, CA Tavani, M Zhang, SN Rubin, BC Paciesas, WS Ford, EC Kaaret, P TI Discovery of hard X-ray outbursts from the soft X-ray transient Aquila X-1 SO ASTRONOMY & ASTROPHYSICS SUPPLEMENT SERIES LA English DT Article; Proceedings Paper CT 3rd Compton Symposium CY JUN 12-14, 1995 CL MUNICH, GERMANY SP Max Planck Inst Extraterrestr Phys, Garching, Marx Planck Gesell, Deut Agentur Raumfahrtangelegenheiten, Deut Aerosp DE stars, individual, Aql X-1; X-rays, stars stars, neutron ID BLACK-HOLE CANDIDATES; EMISSION AB We report the BATSE discovery of hard X-ray outbursts from the soft X-ray transient Aquila X-1 (Aql X-1), Aql X-1 is the most prolific of the soft X-ray transient sources and it has been known to produce large outbursts near the Eddington limit in the 1-10 keV energy band. The typical recurrence time of outbursts is about 1 year. Aql X-1 shows type I X-ray bursts during the decay phase of the X-ray outbursts and is believed to contain a neutron star. These characteristics of Aql X-1 make it an ideal system to study time variable hard X-ray emission from accreting neutron stars. BATSE has monitored Aql X-1 continuously since the Compton Observatory mission began in April 1991. Several episodes of hard X-ray emission with durations of weeks to months have been detected in 1991-1994. These episodes are coincident with substantial brightening of the optical counterpart and to a lesser degree with observations of soft X-ray emission by ROSAT, EURECA/WATCH and ASCA. We find fluxes in the 20-100 mCrab range with hard spectra extending to above 100 keV and power law spectral fits yielding photon indices between -2 and -3. C1 COLUMBIA UNIV,COLUMBIA ASTROPHYS LAB,NEW YORK,NY 10027. UNIV SPACE RES ASSOC,HUNTSVILLE,AL 35806. UNIV ALABAMA,DEPT PHYS,HUNTSVILLE,AL 35899. COLUMBIA UNIV,DEPT PHYS,NEW YORK,NY 10027. RP Harmon, BA (reprint author), NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,ES84,HUNTSVILLE,AL 35812, USA. NR 30 TC 1 Z9 1 U1 0 U2 0 PU EDITIONS PHYSIQUE PI LES ULIS CEDEX PA Z I DE COURTABOEUF AVE 7 AV DU HOGGAR, BP 112, 91944 LES ULIS CEDEX, FRANCE SN 0365-0138 J9 ASTRON ASTROPHYS SUP JI Astron. Astrophys. Suppl. Ser. PD DEC PY 1996 VL 120 IS 4 SI SI BP C197 EP C200 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA WC063 UT WOS:A1996WC06300042 ER PT J AU Kanbach, G Bertsch, DL Dingus, BL Esposito, JA Fichtel, CE Fierro, JM Hartman, RC Hunter, SD Kniffen, DA Lin, YC Mattox, JR MayerHasselwander, HA Merck, M Michelson, PF vonMontigny, C Mukherjee, R Nolan, PL Pohl, M Schneid, EJ Sreekumar, P Thompson, DJ Willis, T AF Kanbach, G Bertsch, DL Dingus, BL Esposito, JA Fichtel, CE Fierro, JM Hartman, RC Hunter, SD Kniffen, DA Lin, YC Mattox, JR MayerHasselwander, HA Merck, M Michelson, PF vonMontigny, C Mukherjee, R Nolan, PL Pohl, M Schneid, EJ Sreekumar, P Thompson, DJ Willis, T TI Characteristics of galactic gamma-ray sources in the second EGRET catalog SO ASTRONOMY & ASTROPHYSICS SUPPLEMENT SERIES LA English DT Article; Proceedings Paper CT 3rd Compton Symposium CY JUN 12-14, 1995 CL MUNICH, GERMANY SP Max Planck Inst Extraterrestr Phys, Garching, Marx Planck Gesell, Deut Agentur Raumfahrtangelegenheiten, Deut Aerosp DE gamma-rays, observations ID COS-B AB The second catalog of high-energy gamma-ray sources (> 100 MeV) has been derived from the EGRET all sky survey (Phase 1) and the pointed observations obtained during Phase 2 of the Compton Observatory mission. This catalog uses not only more data but also an improved model of the diffuse galactic gamma-ray background which is essential for the analysis of point sources. 129 sources were detected. They include identified sources (a solar flare, five pulsars, the Large Magellanic Cloud and 51 active galactic nuclei, AGN) as well as sources for which no identification with objects at other wavelengths is yet available. We present a short summary of the 2EG catalog and derive properties of the low galactic latitude population of unidentified gamma-ray sources based on assumptions on their distribution in the Galaxy. The typical luminosity of galactic unidentified sources above 100 MeV must be in the range 6 10(34) to 4 10(35) erg/s in order to be compatible with their observed spatial galactic distribution and the spectrum of their fluxes. C1 NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. HAMPDEN SYDNEY COLL,HAMPDEN SYDNEY,VA 23943. STANFORD UNIV,HANSEN EXPTL PHYS LAB,STANFORD,CA 94305. UNIV SPACE RES ASSOC,GREENBELT,MD 20771. NORTHRUP GRUMMAN CORP,BETHPAGE,NY 11714. UNIV MARYLAND,COLLEGE PK,MD 20742. RP Kanbach, G (reprint author), MPI EXTRATERR PHYS,POSTFACH 1603,D-85740 GARCHING,GERMANY. RI Nolan, Patrick/A-5582-2009; Hunter, Stanley/D-2942-2012; Thompson, David/D-2939-2012 OI Thompson, David/0000-0001-5217-9135 NR 9 TC 3 Z9 3 U1 0 U2 0 PU EDITIONS PHYSIQUE PI LES ULIS CEDEX PA Z I DE COURTABOEUF AVE 7 AV DU HOGGAR, BP 112, 91944 LES ULIS CEDEX, FRANCE SN 0365-0138 J9 ASTRON ASTROPHYS SUP JI Astron. Astrophys. Suppl. Ser. PD DEC PY 1996 VL 120 IS 4 SI SI BP C461 EP C464 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA WC063 UT WOS:A1996WC06300102 ER PT J AU Kniffen, DA Bertsch, DL Dingus, BL Esposito, JA Fichtel, CE Hartman, RC Hunter, SD Kanbach, G Lin, YC MayerHasselwander, HA Merck, M Michelson, PF vonMontigny, C Mucke, A Mukherjee, R Nolan, PL Pohl, M Schneid, E Sreekumar, P Thompson, DJ Willis, TD AF Kniffen, DA Bertsch, DL Dingus, BL Esposito, JA Fichtel, CE Hartman, RC Hunter, SD Kanbach, G Lin, YC MayerHasselwander, HA Merck, M Michelson, PF vonMontigny, C Mucke, A Mukherjee, R Nolan, PL Pohl, M Schneid, E Sreekumar, P Thompson, DJ Willis, TD TI EGRET Observations of the high latitude diffuse radiation SO ASTRONOMY & ASTROPHYSICS SUPPLEMENT SERIES LA English DT Article; Proceedings Paper CT 3rd Compton Symposium CY JUN 12-14, 1995 CL MUNICH, GERMANY SP Max Planck Inst Extraterrestr Phys, Garching, Marx Planck Gesell, Deut Agentur Raumfahrtangelegenheiten, Deut Aerosp DE gamma rays, observations; diffuse radiation ID RAY; TELESCOPE AB The all-sky survey in high energy gamma-rays (E greater than or equal to 30 MeV) carried out with the Energetic Gamma Ray Experiment Telescope (EGRET) on the Compton Gamma Ray Observatory has allowed the first study of the extragalactic diffuse gamma-ray emission since the SAS-2 experiment in 1972-73 (Fichtel et al. 1977; Fichtel et al. 1978). The study reported here covers observations made during the period 16 May 1991 to 4 October 1994. The instrument was designed from the beginning with this as a major objective. Most important is that the instrument background must be kept to a minimum. The amount of material in the path of incoming gamma rays was minimized and the orbit was chosen with these objectives in mind by minimizing the exposure to energetic cosmic rays. Energetic interactions of these high energy particles with the material in an around the instrument is an unwanted background source. The low-inclination low-altitude orbit provided by the Shuttle was a good match to these objectives. The all-sky survey reveals a strong galactic emission that extends well away from the galactic plane making the selection of the region used for analysis critical. We have restricted our analysis to regions at latitudes greater than 30 degrees (absolute). The spectrum obtained is consistent with a power-law distribution in energy with a slope of -2.07 +/- 0.03 and an integrated intensity above 100 MeV of 1.5 10(-5) cm(-2)sr(-1)sec(-1). C1 NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. HAMPDEN SYDNEY COLL,DEPT PHYS,HAMPDEN SYDNEY,VA 23943. STANFORD UNIV,HANSEN EXPT PHYS LAB,STANFORD,CA 94305. MAX PLANCK INST EXTRATERR PHYS,D-85748 GARCHING,GERMANY. NORTHROP GRUMMAN CORP,BETHPAGE,NY 11714. RI Nolan, Patrick/A-5582-2009; Hunter, Stanley/D-2942-2012; Thompson, David/D-2939-2012 OI Thompson, David/0000-0001-5217-9135 NR 10 TC 5 Z9 5 U1 0 U2 0 PU EDITIONS PHYSIQUE PI LES ULIS CEDEX PA Z I DE COURTABOEUF AVE 7 AV DU HOGGAR, BP 112, 91944 LES ULIS CEDEX, FRANCE SN 0365-0138 J9 ASTRON ASTROPHYS SUP JI Astron. Astrophys. Suppl. Ser. PD DEC PY 1996 VL 120 IS 4 SI SI BP C615 EP C617 PG 3 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA WC063 UT WOS:A1996WC06300137 ER PT J AU Knodlseder, J Oberlack, U Diehl, R Chen, W Gehrels, N AF Knodlseder, J Oberlack, U Diehl, R Chen, W Gehrels, N TI Search for 1.809 MeV emission of Al-26 from nearby supernova remnants using COMPTEL SO ASTRONOMY & ASTROPHYSICS SUPPLEMENT SERIES LA English DT Article; Proceedings Paper CT 3rd Compton Symposium CY JUN 12-14, 1995 CL MUNICH, GERMANY SP Max Planck Inst Extraterrestr Phys, Garching, Marx Planck Gesell, Deut Agentur Raumfahrtangelegenheiten, Deut Aerosp DE gamma-rays, observations; nucleosynthesis; supernovae; ISM, supernova remnants ID MASSIVE STARS; LOOP; NUCLEOSYNTHESIS; EXPLOSION AB We report the negative results of our searches in COMPTEL data for 1.809 MeV gamma-ray line emission from four localized regions which contain nearby supernova remnants (SNRs). The upper flux limits (2 sigma) are found to be in the range of 1.4 10(-5) to 2.4 10(-5) photons s(-1) cm(-2). These upper limits do not severely constrain the theoretical Al-26 yields from individual core collapse supernovae due to large uncertainties in the SNR distances and the nature of the progenitor stars. C1 MAX PLANCK INST EXTRATERR PHYS, D-85740 GARCHING, GERMANY. NASA, GODDARD SPACE FLIGHT CTR, GREENBELT, MD 20771 USA. UNIV SPACE RES ASSOC, WASHINGTON, DC USA. RP CTR ETUD SPATIALE RAYONNEMENTS, CNRS, UPS, BP 4346, F-31029 TOULOUSE, FRANCE. RI Gehrels, Neil/D-2971-2012 NR 31 TC 1 Z9 1 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 DEC PY 1996 VL 120 IS 4 SI SI BP C339 EP C342 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA WC063 UT WOS:A1996WC06300076 ER PT J AU Kroeger, RA Strickman, MS Grove, JE Kaaret, P Ford, E Harmon, BA McConnell, M AF Kroeger, RA Strickman, MS Grove, JE Kaaret, P Ford, E Harmon, BA McConnell, M TI Gamma-ray observations of GRO J1655-40 SO ASTRONOMY & ASTROPHYSICS SUPPLEMENT SERIES LA English DT Article; Proceedings Paper CT 3rd Compton Symposium CY JUN 12-14, 1995 CL MUNICH, GERMANY SP Max Planck Inst Extraterrestr Phys, Garching, Marx Planck Gesell, Deut Agentur Raumfahrtangelegenheiten, Deut Aerosp DE X-rays, stars; stars, individual, GRO J1655-40; gamma rays, observations ID NOVA; COMPTONIZATION; MUSCA; LINE AB The bright transient X-ray source GRO J1655-40 = XN Sco 1994 was observed by the OSSE instrument on the Compton Gamma Ray Observatory (GRO). Preliminary results are reported here. The initial outburst from GRO J1655-40 was detected by BATSE on 27 Jul 1994. OSSE observations were made in five separate viewing periods starting between 4 Aug 1994 and 4 Apr 1995. The first, third, and fifth observations are near the peak luminosity. In the second observation, the source flux had dropped by several orders of magnitude and we can only set an upper limit. The fourth observation is a weak detection after the period of maximum outburst. In contrast with other X-ray novae such as GRO J0422 + 32, the spectrum determined by OSSE is consistent with a simple power law over the full range of detection, about 50 - 600 keV. The photon spectral index is in the range of -2.5 to -2.8 in all of the observations. We set an upper limit on fractional rms variation of <5% in the frequency range 0.01 - 60 Hz. No significant narrow or broad line features are observed at any energy. C1 COLUMBIA UNIV,NEW YORK,NY. NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,HUNTSVILLE,AL 35812. UNIV NEW HAMPSHIRE,DURHAM,NH 03824. RP Kroeger, RA (reprint author), USN,RES LAB,CODE 7650,WASHINGTON,DC 20375, USA. NR 21 TC 1 Z9 1 U1 0 U2 0 PU EDITIONS PHYSIQUE PI LES ULIS CEDEX PA Z I DE COURTABOEUF AVE 7 AV DU HOGGAR, BP 112, 91944 LES ULIS CEDEX, FRANCE SN 0365-0138 J9 ASTRON ASTROPHYS SUP JI Astron. Astrophys. Suppl. Ser. PD DEC PY 1996 VL 120 IS 4 SI SI BP C117 EP C120 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA WC063 UT WOS:A1996WC06300023 ER PT J AU Kunz, M Kendziorra, E Kretschmar, P Maisack, M Staubert, R Ulmer, MP Kurfess, JD Wilson, RB AF Kunz, M Kendziorra, E Kretschmar, P Maisack, M Staubert, R Ulmer, MP Kurfess, JD Wilson, RB TI OSSE observations of Hercules X-1 during the main-on state SO ASTRONOMY & ASTROPHYSICS SUPPLEMENT SERIES LA English DT Article; Proceedings Paper CT 3rd Compton Symposium CY JUN 12-14, 1995 CL MUNICH, GERMANY SP Max Planck Inst Extraterrestr Phys, Garching, Marx Planck Gesell, Deut Agentur Raumfahrtangelegenheiten, Deut Aerosp DE pulsars, individual, Her X-1; X-rays, stars ID RAY AB The binary X-ray pulsar Her X-1 has been observed by CGRO-OSSE during its Main-On state in July 1994. The average pulse period is determined. Main-On pulse profiles in the 30-60 keV range for successive binary orbits are compatible with a constant pulse width. A thin thermal bremsstrahlung spectrum is fitted to the phase average data, yielding kT = 15(1) keV. C1 INST ASTRON & ASTROPHYS,D-72076 TUBINGEN,GERMANY. NORTHWESTERN UNIV,EVANSTON,IL 60208. USN,RES LAB,WASHINGTON,DC 20375. NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,HUNTSVILLE,AL 35812. NR 8 TC 1 Z9 1 U1 0 U2 0 PU EDITIONS PHYSIQUE PI LES ULIS CEDEX PA Z I DE COURTABOEUF AVE 7 AV DU HOGGAR, BP 112, 91944 LES ULIS CEDEX, FRANCE SN 0365-0138 J9 ASTRON ASTROPHYS SUP JI Astron. Astrophys. Suppl. Ser. PD DEC PY 1996 VL 120 IS 4 SI SI BP C233 EP C234 PG 2 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA WC063 UT WOS:A1996WC06300051 ER PT J AU Lin, YC Bertsch, DL Dingus, BL Esposito, JA Fichtel, CE Hartman, RC Hunter, SD Kanbach, G Kniffen, DA Mattox, JR MayerHasselwander, HA Michelson, PF vonMontigny, C Mukherjee, R Nolan, PL Schneid, EJ Sreekumar, P Thompson, DJ Willis, TD AF Lin, YC Bertsch, DL Dingus, BL Esposito, JA Fichtel, CE Hartman, RC Hunter, SD Kanbach, G Kniffen, DA Mattox, JR MayerHasselwander, HA Michelson, PF vonMontigny, C Mukherjee, R Nolan, PL Schneid, EJ Sreekumar, P Thompson, DJ Willis, TD TI EGRET observations of BL lacertae objects with redshifts below 0.2 SO ASTRONOMY & ASTROPHYSICS SUPPLEMENT SERIES LA English DT Article; Proceedings Paper CT 3rd Compton Symposium CY JUN 12-14, 1995 CL MUNICH, GERMANY SP Max Planck Inst Extraterrestr Phys, Garching, Marx Planck Gesell, Deut Agentur Raumfahrtangelegenheiten, Deut Aerosp DE BL Lacertae objects, general; gamma rays, observation ID GAMMA-RAY EMISSION; GALAXIES AB In the ''Revised and Updated Catalog of Quasi-Stellar Objects'' of Hewitt & Burbidge (1993), 90 sources are designated as BL Lacertae Objects. 11 of these 90 BL Lac objects have redshifts below 0.1, out of which EGRET has detected 3, while 13 of these 90 BL Lac objects have redshifts between 0.1 and 0.2, out of which EGRET has detected 2 more, during Phase 1 and Phase 2 of the Compton Observatory's viewing programs. There seems to be a duty cycle of about 25% for EGRET to detect a close BL Lac object with redshift below 0.2. For the other close BL Lac objects which EGRET did not detect, co-adding of EGRET data also yields no detectable flux. These EGRET results are discussed in the paper. C1 NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. MAX PLANCK INST EXTRATERR PHYS,D-85748 GARCHING,GERMANY. NORTHROP GRUMMAN CORP,BETHPAGE,NY 11714. HAMPDEN SYDNEY COLL,HAMPDEN SYDNEY,VA 23943. NASA,GODDARD SPACE FLIGHT CTR,UNIV SPACE RES ASSOC,GREENBELT,MD 20771. NASA,GODDARD SPACE FLIGHT CTR,NSA,NRC,GREENBELT,MD 20771. UNIV MARYLAND,ASTRON PROGRAM,COLLEGE PK,MD 20742. RP Lin, YC (reprint author), STANFORD UNIV,WW HANSEN EXPT PHYS LAB,STANFORD,CA 94305, USA. RI Nolan, Patrick/A-5582-2009; Hunter, Stanley/D-2942-2012; Thompson, David/D-2939-2012 OI Thompson, David/0000-0001-5217-9135 NR 12 TC 1 Z9 1 U1 0 U2 0 PU EDITIONS PHYSIQUE PI LES ULIS CEDEX PA Z I DE COURTABOEUF AVE 7 AV DU HOGGAR, BP 112, 91944 LES ULIS CEDEX, FRANCE SN 0365-0138 J9 ASTRON ASTROPHYS SUP JI Astron. Astrophys. Suppl. Ser. PD DEC PY 1996 VL 120 IS 4 SI SI BP C499 EP C502 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA WC063 UT WOS:A1996WC06300109 ER PT J AU Ling, JC Wheaton, WA Mahoney, WA Skelton, RT Radocinski, RG Wallyn, P AF Ling, JC Wheaton, WA Mahoney, WA Skelton, RT Radocinski, RG Wallyn, P TI JPL earth occultation analysis package: Status and data products SO ASTRONOMY & ASTROPHYSICS SUPPLEMENT SERIES LA English DT Article; Proceedings Paper CT 3rd Compton Symposium CY JUN 12-14, 1995 CL MUNICH, GERMANY SP Max Planck Inst Extraterrestr Phys, Garching, Marx Planck Gesell, Deut Agentur Raumfahrtangelegenheiten, Deut Aerosp DE gamma-rays, observations; methods, data analysis AB Sixty-five known cosmic sources are currently being monitored using the JPL Enhanced BATSE Occultation Package (EBOP). Daily source count rates in 16 energy channels along with their corresponding errors, both Poisson and systematic, are now becoming available to the community at the Compton Observatory Science Support Center (COSSC), and at the PI institution at MSFC. In this paper, we describe the EBOP system, it's capabilities and limitations. We also present a sample of source spectra obtained for a Viewing Period and discuss issues related to the processing method and results. C1 UNIV CALIF SAN DIEGO,LA JOLLA,CA 92093. RP Ling, JC (reprint author), CALTECH,JET PROP LAB,4800 OAK GROVE DR,PASADENA,CA 91109, USA. NR 5 TC 3 Z9 3 U1 0 U2 0 PU EDITIONS PHYSIQUE PI LES ULIS CEDEX PA Z I DE COURTABOEUF AVE 7 AV DU HOGGAR, BP 112, 91944 LES ULIS CEDEX, FRANCE SN 0365-0138 J9 ASTRON ASTROPHYS SUP JI Astron. Astrophys. Suppl. Ser. PD DEC PY 1996 VL 120 IS 4 SI SI BP C677 EP C682 PG 6 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA WC063 UT WOS:A1996WC06300153 ER PT J AU Macomb, DJ Shrader, CR AF Macomb, DJ Shrader, CR TI Extending the spectral coverage of unidentified galactic plane gamma-ray sources SO ASTRONOMY & ASTROPHYSICS SUPPLEMENT SERIES LA English DT Article; Proceedings Paper CT 3rd Compton Symposium CY JUN 12-14, 1995 CL MUNICH, GERMANY SP Max Planck Inst Extraterrestr Phys, Garching, Marx Planck Gesell, Deut Agentur Raumfahrtangelegenheiten, Deut Aerosp DE gamma rays, observations ID GEMINGA AB Uncovering the nature of the galactic plane gamma-ray sources has been an important problem in high-energy astrophysics since the publication of the COS-B results. Counterpart searches, the most widely pursued method for understanding these sources, have been largely unsuccessful partly because of the poor spatial resolution of gamma-ray instruments. Often there are either many candidates in a field or none and extrapolating poorly defined source characteristics over many orders of magnitude in energy can make identifying non-gamma-ray counterparts difficult. Some progress can be made by learning as much as possible about these sources at energies directly above and below the 100 MeV-1 GeV range, and then studying adjacent wavelengths. Using this as our approach, we identify ten candidates from the population of unidentified EGRET sources for analysis based upon their 30-100 MeV EGRET flux for COMPTEL analysis and present evidence of two possible detections. C1 UNIV SPACE RES ASSOC,WASHINGTON,DC. RP Macomb, DJ (reprint author), NASA,GODDARD SPACE FLIGHT CTR,HIGH ENERGY ASTROPHYS LAB,CODE 668,GREENBELT,MD 20771, USA. NR 10 TC 0 Z9 0 U1 0 U2 0 PU EDITIONS PHYSIQUE PI LES ULIS CEDEX PA Z I DE COURTABOEUF AVE 7 AV DU HOGGAR, BP 112, 91944 LES ULIS CEDEX, FRANCE SN 0365-0138 J9 ASTRON ASTROPHYS SUP JI Astron. Astrophys. Suppl. Ser. PD DEC PY 1996 VL 120 IS 4 SI SI BP C471 EP C474 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA WC063 UT WOS:A1996WC06300104 ER PT J AU Manandhar, RP Grindlay, JE Thompson, DJ AF Manandhar, RP Grindlay, JE Thompson, DJ TI New EGRET/COMPTEL studies of globular clusters SO ASTRONOMY & ASTROPHYSICS SUPPLEMENT SERIES LA English DT Article; Proceedings Paper CT 3rd Compton Symposium CY JUN 12-14, 1995 CL MUNICH, GERMANY SP Max Planck Inst Extraterrestr Phys, Garching, Marx Planck Gesell, Deut Agentur Raumfahrtangelegenheiten, Deut Aerosp DE pulsars, general; globular clusters, individual NGC 6397; globular clusters, individual NGC 6752; gamma rays, observations ID GAMMA-RAY EMISSION; MILLISECOND PULSARS; ECLIPSING BINARY; UPPER LIMITS; TERZAN-5 AB We present results of our Phase 2 program of observations of two nearby globular clusters, NGC 6397 and NGC 6752, with EGRET and COMPTEL to search for the integrated emission from their populations of millisecond pulsars, LMXBs (in quiescence), and CVs. Upper limits were derived for each cluster that are a factor of 2 more sensitive than in the general cluster survey of Michelson et al. (1994) using EGRET. Our COMPTEL limits are the first reported for the 1-30 MeV band for these clusters and are comparably sensitive to the EGRET limits for an assumed Crab-like spectrum yet can also constrain source spectra if they break at energies below 30 MeV. These limits are better than the COMPTEL limits recently reported for 47 Tuc by O'Flaherty et al. (1995). The lowest upper Limits, for NGC 6397, restrict the integrated luminosity to be below similar to 10(35) ergs s(-1) in either the COMPTEL or EGRET energy bands. A serendipitous source, GRO J1718-60, was detected (4.1 sigma) with EGRET, near (but not coincident with) NGC 6397. Although this source would be consistent with the nearby (1.7 degrees) pulsar J1704-60, the published spindown luminosity is too low for it to be a plausible counterpart. Constraints on the typical gamma-ray luminosity for millisecond pulsars and quiescent LMXBs are derived and discussed. C1 HARVARD SMITHSONIAN CTR ASTROPHYS,CAMBRIDGE,MA 02138. NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. RI Thompson, David/D-2939-2012 OI Thompson, David/0000-0001-5217-9135 NR 33 TC 0 Z9 0 U1 0 U2 0 PU EDITIONS PHYSIQUE PI LES ULIS CEDEX PA Z I DE COURTABOEUF AVE 7 AV DU HOGGAR, BP 112, 91944 LES ULIS CEDEX, FRANCE SN 0365-0138 J9 ASTRON ASTROPHYS SUP JI Astron. Astrophys. Suppl. Ser. PD DEC PY 1996 VL 120 IS 4 SI SI BP C255 EP C260 PG 6 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA WC063 UT WOS:A1996WC06300057 ER PT J AU Mattox, JR Koh, DT Lamb, RC Macomb, DJ Prince, TA Ray, PS AF Mattox, JR Koh, DT Lamb, RC Macomb, DJ Prince, TA Ray, PS TI A search for radio-quiet gamma-ray pulsars in the EGRET data SO ASTRONOMY & ASTROPHYSICS SUPPLEMENT SERIES LA English DT Article; Proceedings Paper CT 3rd Compton Symposium CY JUN 12-14, 1995 CL MUNICH, GERMANY SP Max Planck Inst Extraterrestr Phys, Garching, Marx Planck Gesell, Deut Agentur Raumfahrtangelegenheiten, Deut Aerosp DE pulsars, general; gamma-rays, observations ID GEMINGA AB We are searching for radio-quiet gamma-ray pulsars among the brightest unidentified EGRET point sources. This investigation utilizes the computational resources of the Center for Advanced Computing Research at Caltech to compute Gigapoint power spectra. Multiple frequency derivatives are searched by accelerating event times before computing the Fourier transform. We demonstrate that such a search detects the pulsation of radio-quiet Geminga with 10(-12) significance directly from 6 days of EGRET data. The remaining unidentified EGRET sources have substantially less signal to noise to support a periodicity search, but can be detected with similar to 3 weeks of exposure if the pulsar lightcurve has sufficient harmonic content. Only upper limits have been obtained to date. We demonstrate that the error in transforming EGRET event times to the solar system barycenter caused by the inaccuracy of the EGRET position results in a detection at a frequency and frequency derivative different from the true values, but harmonic power is not lost. C1 CALTECH,PASADENA,CA 91125. IOWA STATE UNIV,AMES,IA 50011. GSFC,GRO SCI SUPPORT CTR,GREENBELT,MD 20771. USN,RES LAB,WASHINGTON,DC 20375. RP Mattox, JR (reprint author), UNIV MARYLAND,DEPT ASTRON,COLLEGE PK,MD 20742, USA. NR 10 TC 6 Z9 6 U1 0 U2 0 PU EDITIONS PHYSIQUE PI LES ULIS CEDEX PA Z I DE COURTABOEUF AVE 7 AV DU HOGGAR, BP 112, 91944 LES ULIS CEDEX, FRANCE SN 0365-0138 J9 ASTRON ASTROPHYS SUP JI Astron. Astrophys. Suppl. Ser. PD DEC PY 1996 VL 120 IS 4 SI SI BP C95 EP C98 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA WC063 UT WOS:A1996WC06300017 ER PT J AU Merck, M Bertsch, DL Dingus, BL Esposito, JA Fichtel, CE Fierro, JM Hartman, RC Hunter, SD Kanbach, G Kniffen, DA Lin, YC MayerHasselwander, HA Michelson, PF vonMontigny, C Mucke, A Mukherjee, R Nolan, PL Pohl, M Schneid, E Sreekumar, P Thompson, DJ Willis, TD AF Merck, M Bertsch, DL Dingus, BL Esposito, JA Fichtel, CE Fierro, JM Hartman, RC Hunter, SD Kanbach, G Kniffen, DA Lin, YC MayerHasselwander, HA Michelson, PF vonMontigny, C Mucke, A Mukherjee, R Nolan, PL Pohl, M Schneid, E Sreekumar, P Thompson, DJ Willis, TD TI Study of the spectral characteristics of unidentified galactic EGRET sources. Are they pulsar-like? SO ASTRONOMY & ASTROPHYSICS SUPPLEMENT SERIES LA English DT Article; Proceedings Paper CT 3rd Compton Symposium CY JUN 12-14, 1995 CL MUNICH, GERMANY SP Max Planck Inst Extraterrestr Phys, Garching, Marx Planck Gesell, Deut Agentur Raumfahrtangelegenheiten, Deut Aerosp DE stars, pulsars; gamma rays, observations ID ENERGY GAMMA-RADIATION; RAY PULSAR AB A spectral study of unidentified galactic EGRET sources was performed. The derived spectra are compared to the spectra of pulsars to test the hypothesis, that a significant fraction of these sources are Geminga like radio-quiet pulsars (Yadigaroglu & Romani 1995). Most of the sources show significantly different spectra than expected under this hypothesis. Of those with spectra consistent with typical pulsar spectra, four are positionally consistent with young spin-powered radio pulsars leaving only very few Geminga type candidates in the sample. C1 NASA,GODDARD SPACE FLIGHT CTR,UNIV SPACE RES ASSOC,GREENBELT,MD 20771. STANFORD UNIV,HANSEN EXPTL PHYS LAB,STANFORD,CA 94305. HAMPDEN SYDNEY COLL,HAMPDEN SYDNEY,VA 23943. NASA,GODDARD SPACE FLIGHT CTR,NAS,NRC,GREENBELT,MD 20771. NORTHROP GRUMMAN AEROSP CORP,BETHPAGE,NY 11714. RP Merck, M (reprint author), MAX PLANCK INST EXTRATERR PHYS,GIESSENBACHSTR 1,D-85740 GARCHING,GERMANY. RI Nolan, Patrick/A-5582-2009; Hunter, Stanley/D-2942-2012; Thompson, David/D-2939-2012 OI Thompson, David/0000-0001-5217-9135 NR 15 TC 8 Z9 8 U1 0 U2 0 PU EDITIONS PHYSIQUE PI LES ULIS CEDEX PA Z I DE COURTABOEUF AVE 7 AV DU HOGGAR, BP 112, 91944 LES ULIS CEDEX, FRANCE SN 0365-0138 J9 ASTRON ASTROPHYS SUP JI Astron. Astrophys. Suppl. Ser. PD DEC PY 1996 VL 120 IS 4 SI SI BP C465 EP C469 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA WC063 UT WOS:A1996WC06300103 ER PT J AU Much, R Harmon, BA Nolan, P Strickman, MS Bennett, K Buccheri, R Diehl, R Fierro, JM Fishman, GJ Grabelsky, DA Grove, JE Hermsen, W Johnson, WN Jung, GV Kinzer, RL Kroeger, RA Kuiper, L Kurfess, JD Lichti, GG Matz, SM McConnell, M Paciesas, WS Purcell, WR Ryan, J Schonfelder, V Steinle, H Strong, A Thompson, DJ Ulmer, MP Varendorff, M Wilson, CA Wilson, RB AF Much, R Harmon, BA Nolan, P Strickman, MS Bennett, K Buccheri, R Diehl, R Fierro, JM Fishman, GJ Grabelsky, DA Grove, JE Hermsen, W Johnson, WN Jung, GV Kinzer, RL Kroeger, RA Kuiper, L Kurfess, JD Lichti, GG Matz, SM McConnell, M Paciesas, WS Purcell, WR Ryan, J Schonfelder, V Steinle, H Strong, A Thompson, DJ Ulmer, MP Varendorff, M Wilson, CA Wilson, RB TI The Crab total gamma-ray emission as seen by CGRO SO ASTRONOMY & ASTROPHYSICS SUPPLEMENT SERIES LA English DT Article; Proceedings Paper CT 3rd Compton Symposium CY JUN 12-14, 1995 CL MUNICH, GERMANY SP Max Planck Inst Extraterrestr Phys, Garching, Marx Planck Gesell, Deut Agentur Raumfahrtangelegenheiten, Deut Aerosp DE gamma rays, observations; ISM, Crab nebula ID PULSARS AB The Compton Gamma-Ray Observatory has completed 4 years of observations comprising a full-sky survey and several deep pointings. The Crab is one of the strongest perma- nent sources in the CGRO energy range (20 keV to 10 GeV). Its total (pulsed and unpulsed) emission is often used as a calibration standard. We present the results of an analysis of data from all four CGRO instruments obtained during contemporaneous Crab observations made during Phase I, II and III between 1991 and 1994. Emphasis is given to the cross-calibration of the four CGRO instruments. C1 MAX PLANCK INST EXTRATERR PHYS,D-85740 GARCHING,GERMANY. SRON,NL-3584 CA UTRECHT,NETHERLANDS. UNIV NEW HAMPSHIRE,CTR SPACE SCI,DURHAM,NH 03857. CNR,IFCAI,I-90139 PALERMO,ITALY. USN,RES LAB,WASHINGTON,DC 20375. NORTHWESTERN UNIV,DEPT PHYS & ASTRON,EVANSTON,IL 60208. UNIV SPACE RES ASSOCIATES,WASHINGTON,DC 20375. STANFORD UNIV,HANSEN EXPT PHYS LAB,STANFORD,CA 94305. NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. NASA,GEORGE C MARSHALL SPACE FLIGHT CTR ES84,HUNTSVILLE,AL 35812. UNIV ALABAMA,DEPT PHYS,HUNTSVILLE,AL 35899. RP Much, R (reprint author), EUROPEAN SPACE AGCY,ESTEC,DIV ASTROPHYS,NL-2200 AG NOORDWIJK,NETHERLANDS. RI Nolan, Patrick/A-5582-2009; Thompson, David/D-2939-2012; Johnson, Neil/G-3309-2014 OI Thompson, David/0000-0001-5217-9135; NR 14 TC 1 Z9 1 U1 0 U2 0 PU EDITIONS PHYSIQUE PI LES ULIS CEDEX PA Z I DE COURTABOEUF AVE 7 AV DU HOGGAR, BP 112, 91944 LES ULIS CEDEX, FRANCE SN 0365-0138 J9 ASTRON ASTROPHYS SUP JI Astron. Astrophys. Suppl. Ser. PD DEC PY 1996 VL 120 IS 4 SI SI BP C703 EP C706 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA WC063 UT WOS:A1996WC06300159 ER PT J AU Nel, HI Arzoumanian, Z Bailes, M Brazier, KTS DAmico, N Esposito, JA Fichtel, CE Fierro, JM Hunter, SD Johnston, S Kanbach, G Kaspi, VM Kniffen, DA Lyne, AG Lin, YC Manchester, RN Mattox, JR MayerHasselwander, HA Merck, M Michelson, PF Nice, DJ Nolan, PL Ramanamurthy, PV Taylor, JH Thompson, DJ Westbrook, C AF Nel, HI Arzoumanian, Z Bailes, M Brazier, KTS DAmico, N Esposito, JA Fichtel, CE Fierro, JM Hunter, SD Johnston, S Kanbach, G Kaspi, VM Kniffen, DA Lyne, AG Lin, YC Manchester, RN Mattox, JR MayerHasselwander, HA Merck, M Michelson, PF Nice, DJ Nolan, PL Ramanamurthy, PV Taylor, JH Thompson, DJ Westbrook, C TI EGRET pulsar upper limits SO ASTRONOMY & ASTROPHYSICS SUPPLEMENT SERIES LA English DT Article; Proceedings Paper CT 3rd Compton Symposium CY JUN 12-14, 1995 CL MUNICH, GERMANY SP Max Planck Inst Extraterrestr Phys, Garching, Marx Planck Gesell, Deut Agentur Raumfahrtangelegenheiten, Deut Aerosp DE gamma-rays, observations; pulsars, general ID GAMMA-RAY PULSARS; RADIO PULSARS AB The 3.5 year database of the Energetic Gamma Ray Experiment Telescope (EGRET) has been surveyed for gamma-ray emission from all known spin-powered pulsars. Using contemporaneous timing solutions, upper limits on pulsed emission were obtained for 350 pulsars. Limits to unpulsed gamma radiation were obtained for all cataloged pulsars. No new detections were found, although there is evidence for localized excesses at the positions of a few of these pulsars. No correlation was however found between E over dot/d(2) and the sources of such unpulsed excesses. A number of models predict the gamma-ray luminosity from pulsars as a function of measurable pulsar parameters. The functional form of models are tested for the six detected pulsars above 100 MeV and we find that the luminosity does not scale with the pulsar parameters as predicted. Furthermore, some flux upper limits contradict the model predictions, which seems to indicate that the current models of gamma-ray pulsars are still incomplete. C1 PRINCETON UNIV,DEPT PHYS,PRINCETON,NJ 08544. MAX PLANCK INST EXTRATERR PHYS,D-85748 GARCHING,GERMANY. UNIV PALERMO,INST FIS,I-40126 BOLOGNA,ITALY. UNIV PALERMO,INST FIS,I-40126 BOLOGNA,ITALY. CNR,INST RADIOASTRON,I-40126 BOLOGNA,ITALY. NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. STANFORD UNIV,WW HANSEN EXPT PHYS LAB,STANFORD,CA 94305. STANFORD UNIV,DEPT PHYS,STANFORD,CA 94305. CSIRO,AUSTRALIA TELESCOPE NATL FACIL,EPPING,NSW 2006,AUSTRALIA. UNIV SYDNEY,RES CTR THEORET ASTROPHYS,SYDNEY,NSW 2006,AUSTRALIA. CALTECH,IPAC,PASADENA,CA 91125. HAMPDEN SYDNEY COLL,DEPT PHYS,HAMPDEN SYDNEY,VA 23943. UNIV MANCHESTER,DEPT PHYS,MACCLESFIELD SK11 9DL,CHESHIRE,ENGLAND. UNIV MARYLAND,ASTRON PROJECT,COLLEGE PK,MD 20740. NATL RADIO ASTRON OBSERV,CHARLOTTESVILLE,VA 22903. RP Nel, HI (reprint author), POTCHEFSTROOM UNIV CHRISTIAN HIGHER EDUC,DEPT PHYS,SPACE SCI UNIT,ZA-2520 POTCHEFSTROOM,SOUTH AFRICA. RI Nolan, Patrick/A-5582-2009; Hunter, Stanley/D-2942-2012; Thompson, David/D-2939-2012 OI Thompson, David/0000-0001-5217-9135 NR 20 TC 2 Z9 2 U1 0 U2 0 PU EDITIONS PHYSIQUE PI LES ULIS CEDEX PA Z I DE COURTABOEUF AVE 7 AV DU HOGGAR, BP 112, 91944 LES ULIS CEDEX, FRANCE SN 0365-0138 J9 ASTRON ASTROPHYS SUP JI Astron. Astrophys. Suppl. Ser. PD DEC PY 1996 VL 120 IS 4 SI SI BP C89 EP C93 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA WC063 UT WOS:A1996WC06300016 ER PT J AU Nolan, PL Fierro, JM Lin, YC Michelson, PF Bertsch, DL Dingus, BL Esposito, JA Fichtel, CE Hartman, RC Hunter, SD vonMontigny, C Mukherjee, R Ramanamurthy, PV Thompson, DJ Kniffen, DA Schneid, E Kanbach, G MayerHasselwander, HA Merck, M AF Nolan, PL Fierro, JM Lin, YC Michelson, PF Bertsch, DL Dingus, BL Esposito, JA Fichtel, CE Hartman, RC Hunter, SD vonMontigny, C Mukherjee, R Ramanamurthy, PV Thompson, DJ Kniffen, DA Schneid, E Kanbach, G MayerHasselwander, HA Merck, M TI EGRET observations of pulsars SO ASTRONOMY & ASTROPHYSICS SUPPLEMENT SERIES LA English DT Article; Proceedings Paper CT 3rd Compton Symposium CY JUN 12-14, 1995 CL MUNICH, GERMANY SP Max Planck Inst Extraterrestr Phys, Garching, Marx Planck Gesell, Deut Agentur Raumfahrtangelegenheiten, Deut Aerosp DE stars, pulsars, general; gamma rays, observations ID ENERGY GAMMA-RADIATION; CRAB PULSAR; RAY PULSAR; NEBULA AB EGRET can now study six pulsars since the recent detection of PSR B1951+32. Careful analysis of the three brightest pulsars shows that gamma rays are emitted through essentially the entire rotation. This calls into question the previous interpretation of the Crab's low-level emission as due entirely to its nebula. The pulse light curves have either well-separated double peaks or very broad peaks which might be resolved into multiple components. The spectra are consistent with power laws over a large portion of the EGRET energy range, and many show a dropoff at a few GeV. C1 NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. HAMPDEN SYDNEY COLL,DEPT PHYS,HAMPDEN SYDNEY,VA 23943. NORTHROP GRUMMAN CORP,BETHPAGE,NY 11714. MAX PLANCK INST EXTRATERR PHYS,D-85748 GARCHING,GERMANY. RP Nolan, PL (reprint author), STANFORD UNIV,HANSEN EXPT PHYS LAB,STANFORD,CA 94305, USA. RI Nolan, Patrick/A-5582-2009; Hunter, Stanley/D-2942-2012; Thompson, David/D-2939-2012 OI Thompson, David/0000-0001-5217-9135 NR 21 TC 5 Z9 5 U1 0 U2 0 PU EDITIONS PHYSIQUE PI LES ULIS CEDEX PA Z I DE COURTABOEUF AVE 7 AV DU HOGGAR, BP 112, 91944 LES ULIS CEDEX, FRANCE SN 0365-0138 J9 ASTRON ASTROPHYS SUP JI Astron. Astrophys. Suppl. Ser. PD DEC PY 1996 VL 120 IS 4 SI SI BP C61 EP C64 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA WC063 UT WOS:A1996WC06300009 ER PT J AU Paciesas, WS Deal, KJ Harmon, BA Zhang, SN Wilson, CA Fishman, GJ AF Paciesas, WS Deal, KJ Harmon, BA Zhang, SN Wilson, CA Fishman, GJ TI Observations of the unusual X-ray source GRS 1915+105 in Aquila SO ASTRONOMY & ASTROPHYSICS SUPPLEMENT SERIES LA English DT Article; Proceedings Paper CT 3rd Compton Symposium CY JUN 12-14, 1995 CL MUNICH, GERMANY SP Max Planck Inst Extraterrestr Phys, Garching, Marx Planck Gesell, Deut Agentur Raumfahrtangelegenheiten, Deut Aerosp DE stars, individual, GRS 1915+105; black holes; X-rays, stars ID TRANSIENT; GRS-1915+105; WATCH AB Interest in the X-ray transient GRS 1915+105 has increased recently as a result of observations of its radio counterpart that showed evidence for superluminal expansion (Mirabel & Rodriguez 1994), the first such detection in a galactic source. BATSE observations indicate that this source first appeared in May 1992 and remains sporadically detectable up to the present time. We present the long-term hard X-ray intensity and spectral history of GRS 1915+105 as observed by BATSE and discuss this in the context of other observations. We also present the results of detailed Earth occultation analysis, which indicates that the initial outburst of GRS 1915+105 showed an unusually extreme degree of variability. C1 NASA, GEORGE C MARSHALL SPACE FLIGHT CTR, SPACE SCI LAB, HUNTSVILLE, AL 35812 USA. UNIV SPACE RES ASSOC, HUNTSVILLE, AL 35806 USA. RP UNIV ALABAMA, DEPT PHYS, HUNTSVILLE, AL 35899 USA. NR 15 TC 0 Z9 0 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 DEC PY 1996 VL 120 IS 4 SI SI BP C205 EP C208 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA WC063 UT WOS:A1996WC06300044 ER PT J AU Ramanamurthy, PV Fichtel, CE Harding, AK Kniffen, DA Sreekumar, P Thompson, DJ AF Ramanamurthy, PV Fichtel, CE Harding, AK Kniffen, DA Sreekumar, P Thompson, DJ TI PSR B0656+14 in relation to other high-energy gamma-ray pulsars SO ASTRONOMY & ASTROPHYSICS SUPPLEMENT SERIES LA English DT Article; Proceedings Paper CT 3rd Compton Symposium CY JUN 12-14, 1995 CL MUNICH, GERMANY SP Max Planck Inst Extraterrestr Phys, Garching, Marx Planck Gesell, Deut Agentur Raumfahrtangelegenheiten, Deut Aerosp DE pulsars, PSR B0656+14; gamma-rays, observations AB Possible evidence has been found for a seventh high energy gamma ray pulsar, PSR B0656+14, pulsating in gamma rays at E greater than or equal to 50 MeV with the same 384.9 ms periodicity as in radio, using the data obtained during April, 1991 to December, 1993 by the Energetic Gamma Ray Experiment Telescope (EGRET) aboard the Compton Gamma Ray Observatory (Ramanamurthy et al. 1996). The pulsar appears to have an efficiency similar to 0.001 in converting its spin-down energy loss rate into high energy gamma-rays at E greater than or equal to 100 MeV. This efficiency is inconsistent with a general trend found for the other six pulsars seen by EGRET. C1 NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. HAMPDEN SYDNEY COLL,DEPT PHYS,HAMPDEN SYDNEY,VA 23943. RI Thompson, David/D-2939-2012; Harding, Alice/D-3160-2012 OI Thompson, David/0000-0001-5217-9135; NR 12 TC 4 Z9 4 U1 0 U2 0 PU EDITIONS PHYSIQUE PI LES ULIS CEDEX PA Z I DE COURTABOEUF AVE 7 AV DU HOGGAR, BP 112, 91944 LES ULIS CEDEX, FRANCE SN 0365-0138 J9 ASTRON ASTROPHYS SUP JI Astron. Astrophys. Suppl. Ser. PD DEC PY 1996 VL 120 IS 4 SI SI BP C115 EP C116 PG 2 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA WC063 UT WOS:A1996WC06300022 ER PT J AU Ramaty, R AF Ramaty, R TI Interstellar gamma-ray lines from low energy cosmic ray interactions SO ASTRONOMY & ASTROPHYSICS SUPPLEMENT SERIES LA English DT Article; Proceedings Paper CT 3rd Compton Symposium CY JUN 12-14, 1995 CL MUNICH, GERMANY SP Max Planck Inst Extraterrestr Phys, Garching, Marx Planck Gesell, Deut Agentur Raumfahrtangelegenheiten, Deut Aerosp DE gamma-rays, theory; Galaxy, abundances; nuclear reactions, nucleosynthesis, abundances ID ORION COMPLEX; LIGHT-ELEMENTS; COMPTEL; ORIGIN; SOLAR; ACCELERATION; ENHANCEMENTS; WINDS; LI AB Evidence for the existence of low energy cosmic rays in the Galaxy comes from the COMPTEL observations of gamma-ray line emission from Orion, and also from light element abundance data which seem to suggest a low energy rather than a relativistic Galactic cosmic ray origin for most of the light elements. The Orion and light isotope data are more consistent with a composition that is depleted in protons and alpha particles than with one which is similar to that of the Galactic cosmic rays. This low energy cosmic ray phenomenon appears to be highly localized in space and time in the Galaxy, and is probably associated with star formation regions similar to Orion. RP NASA, GODDARD SPACE FLIGHT CTR, HIGH ENERGY PHYS LAB, GREENBELT, MD 20771 USA. NR 36 TC 9 Z9 9 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 DEC PY 1996 VL 120 IS 4 SI SI BP C373 EP C380 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA WC063 UT WOS:A1996WC06300084 ER PT J AU Rubin, BC Lei, F Fishman, GJ Finger, MH Harmon, BA Kouveliotou, C Paciesas, WS Pendleton, GN Wilson, RB Zhang, SN AF Rubin, BC Lei, F Fishman, GJ Finger, MH Harmon, BA Kouveliotou, C Paciesas, WS Pendleton, GN Wilson, RB Zhang, SN TI A model of the gamma-ray background on the BATSE experiment SO ASTRONOMY & ASTROPHYSICS SUPPLEMENT SERIES LA English DT Article; Proceedings Paper CT 3rd Compton Symposium CY JUN 12-14, 1995 CL MUNICH, GERMANY SP Max Planck Inst Extraterrestr Phys, Garching, Marx Planck Gesell, Deut Agentur Raumfahrtangelegenheiten, Deut Aerosp DE gamma-rays, observations; methods, data; analysis; diffuse radiation; atmospheric effects AB The BATSE experiment on the Compton Gamma-Ray Observatory is a nearly uninterrupted all-sky monitor in the hard X-ray/gamma-ray energy range. Count rate data continuously transmitted to the ground from Low Earth Orbit (altitude similar to 450 km) is dominated, in the 20-300 keV energy range, by diffuse cosmic background modulated by blocking effects of the Earth. Other background sources include atmospheric gamma-rays and the decay of radionuclides created in cosmic ray and radiation belt trapped particle interactions with the detector. Numerous discrete cosmic sources are also present in these data. In this paper we describe a semi-empirical background model which has been used to reduce the effect of dominant background sources. The use of this model can increase the sensitivity of the experiment to sources observed with the Earth occultation technique; to long period pulsed sources; to analysis of flickering noise; and to transient events. C1 UNIV SPACE RES ASSOC,WASHINGTON,DC. UNIV SOUTHAMPTON,DEPT PHYS,SOUTHAMPTON SO17 1BJ,HANTS,ENGLAND. UNIV ALABAMA,DEPT PHYS,HUNTSVILLE,AL 35899. COMPTON GAMMA RAY OBSERV,SCI SUPPORT CTR,GREENBELT,MD. RP Rubin, BC (reprint author), NASA,GEORGE C MARSHALL SPACE FLIGHT CTR ES 84,HUNTSVILLE,AL 35812, USA. NR 6 TC 1 Z9 1 U1 0 U2 0 PU EDITIONS PHYSIQUE PI LES ULIS CEDEX PA Z I DE COURTABOEUF AVE 7 AV DU HOGGAR, BP 112, 91944 LES ULIS CEDEX, FRANCE SN 0365-0138 J9 ASTRON ASTROPHYS SUP JI Astron. Astrophys. Suppl. Ser. PD DEC PY 1996 VL 120 IS 4 SI SI BP C687 EP C690 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA WC063 UT WOS:A1996WC06300155 ER PT J AU Schneid, EJ Bertsch, DL Dingus, BL Esposito, JA Fichtel, CE Hartman, RC Hunter, SD Kanbach, G Kniffen, DA Lin, YC MayerHasselwander, HA Michelson, PF vonMontigny, C Mukherjee, R Nolan, PL Sreekumar, P Thompson, DJ AF Schneid, EJ Bertsch, DL Dingus, BL Esposito, JA Fichtel, CE Hartman, RC Hunter, SD Kanbach, G Kniffen, DA Lin, YC MayerHasselwander, HA Michelson, PF vonMontigny, C Mukherjee, R Nolan, PL Sreekumar, P Thompson, DJ TI EGRET observations of X-class solar flares SO ASTRONOMY & ASTROPHYSICS SUPPLEMENT SERIES LA English DT Article; Proceedings Paper CT 3rd Compton Symposium CY JUN 12-14, 1995 CL MUNICH, GERMANY SP Max Planck Inst Extraterrestr Phys, Garching, Marx Planck Gesell, Deut Agentur Raumfahrtangelegenheiten, Deut Aerosp DE Sun, flares; Sun, gamma rays ID TELESCOPE; PARTICLES; GRO AB A series of X-class solar hares in the first week of June from the same region of the Sun prompted the action of making the Sun a Target of Opportunity for the Compton Observatory. The high energy capabilities of the EGRET instrument provided an opportunity to investigate the energetic solar hare processes for these flares. During the June 11, 1991 hare, the EGRET spark chamber obtained spectral and temporal measurements of high energy gamma-ray emissions to greater than 1 GeV lasting hours after the initial impulsive phase of the hare. Spectral fits of the spark chamber data allow bremsstrahlung and pion decay contributions to the extended delayed emission to be determined. Spectral fits of the EGRET NaI data for the 1-200 MeV energy range allow the solar line fluences of the 2.23 and 4.43 MeV radiation to be determined for four of the June hares. Another series of X-class flare that occurred in late October 1991 were observed by the EGRET NaI detector and similar analyses were performed. C1 NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. MAX PLANCK INST EXTRATERR PHYS,D-85748 GARCHING,GERMANY. HAMPDEN SYDNEY COLL,HAMPDEN SYDNEY,VA 23943. STANFORD UNIV,WW HANSEN EXPT PHYS LAB,STANFORD,CA 94305. NASA,GODDARD SPACE FLIGHT CTR,UNIV SPACE RES ASSOC,GREENBELT,MD 20771. RP Schneid, EJ (reprint author), NORTHROP GRUMMAN CORP,RES & DEV,MAIL STOP A01-26,BETHPAGE,NY 11714, USA. RI Nolan, Patrick/A-5582-2009; Hunter, Stanley/D-2942-2012; Thompson, David/D-2939-2012 OI Thompson, David/0000-0001-5217-9135 NR 18 TC 2 Z9 2 U1 0 U2 0 PU EDITIONS PHYSIQUE PI LES ULIS CEDEX PA Z I DE COURTABOEUF AVE 7 AV DU HOGGAR, BP 112, 91944 LES ULIS CEDEX, FRANCE SN 0365-0138 J9 ASTRON ASTROPHYS SUP JI Astron. Astrophys. Suppl. Ser. PD DEC PY 1996 VL 120 IS 4 SI SI BP C299 EP C302 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA WC063 UT WOS:A1996WC06300067 ER PT J AU Seifert, H Teegarden, BJ Cline, TL Gehrels, N Hurley, KH Madden, N Owens, A Palmer, DM Pehl, R Ramaty, R AF Seifert, H Teegarden, BJ Cline, TL Gehrels, N Hurley, KH Madden, N Owens, A Palmer, DM Pehl, R Ramaty, R TI Gamma-ray observations with the Transient Gamma-Ray Spectrometer (TGRS) SO ASTRONOMY & ASTROPHYSICS SUPPLEMENT SERIES LA English DT Article; Proceedings Paper CT 3rd Compton Symposium CY JUN 12-14, 1995 CL MUNICH, GERMANY SP Max Planck Inst Extraterrestr Phys, Garching, Marx Planck Gesell, Deut Agentur Raumfahrtangelegenheiten, Deut Aerosp DE gamma rays, bursts; gamma rays, observations; instrumentation, detectors ID SPECTROSCOPY; BURSTS AB The Transient Gamma-Ray Spectrometer (TGRS), a high-resolution germanium detector, was launched aboard the WIND satellite on November 1, 1994. After similar to 2 years and several deep space orbits the spacecraft will eventually be injected into a halo orbit around the Sun-Earth L(1) point. Although TGRS is primarily designed to perform high resolution spectroscopy of gamma-ray bursts (GRBs) and solar flares, it equally well lends itself to the study of transient X-ray sources and, using an on-board passive occulter, the long-term monitoring of steady sources such as the Crab and the Galactic Center. Since launch, TGRS has been working exceedingly well and has proven to be very stable in its performance. TGRS has been detecting on the average similar to 5 GRBs per month and to date has observed three solar flares. Preliminary analysis of our data also indicates that TGRS is indeed sensitive to sources such as the X-ray transient GRO J1655-40, the Crab, and the Galactic Center. C1 UNIV CALIF BERKELEY,BERKELEY,CA 94720. UNIV CALIF BERKELEY,LAWRENCE BERKELEY LAB,BERKELEY,CA 94720. UNIV LEICESTER,LEICESTER LE1 7RH,LEICS,ENGLAND. RP Seifert, H (reprint author), NASA,GODDARD SPACE FLIGHT CTR,USRA,GREENBELT,MD 20771, USA. RI Gehrels, Neil/D-2971-2012 NR 9 TC 1 Z9 1 U1 0 U2 0 PU EDITIONS PHYSIQUE PI LES ULIS CEDEX PA Z I DE COURTABOEUF AVE 7 AV DU HOGGAR, BP 112, 91944 LES ULIS CEDEX, FRANCE SN 0365-0138 J9 ASTRON ASTROPHYS SUP JI Astron. Astrophys. Suppl. Ser. PD DEC PY 1996 VL 120 IS 4 SI SI BP C653 EP C656 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA WC063 UT WOS:A1996WC06300147 ER PT J AU Shrader, CR Wagner, RM Hjellming, RM Starrfield, SG AF Shrader, CR Wagner, RM Hjellming, RM Starrfield, SG TI Reprocessing of hard X-ray emission in X-ray novae SO ASTRONOMY & ASTROPHYSICS SUPPLEMENT SERIES LA English DT Article; Proceedings Paper CT 3rd Compton Symposium CY JUN 12-14, 1995 CL MUNICH, GERMANY SP Max Planck Inst Extraterrestr Phys, Garching, Marx Planck Gesell, Deut Agentur Raumfahrtangelegenheiten, Deut Aerosp DE accretion, accretion disks X-rays, stars; novae; stars, individual (GRO J0422+32, GRO J1655 40) ID IUE OBSERVATIONS; OUTBURST AB Much of the visual and ultraviolet luminosity in X-ray novae is likely to result from reprocessing of X-rays illuminating an accretion disk. During the initial stages of its 1992 outburst, GRO J0422+32 exhibited short-time-scale flickering intense enough to be seen in the individual BATSE LAD detectors with a nominal 1-second time resolution. We obtained photometry with continuous minute sampling during this period, in which short-time-scale flickering as well as hourly trends are evident. In addition, we obtained resolution spectroscopy sampled at 10-minute intervals over a baselines comparable to a binary orbital period. We present results of cross-correlation analysis between the optical and hard X-ray of time-series data sets. No statistically significant time lags can be established. For the more recent X-ray nova GRO 1655 40, we have spectra obtained on separate nights within one weeks time, bracketing an upturn in the BATSE light curve, which exhibited dramatic evolution. C1 OHIO STATE UNIV,DEPT ASTRON,COLUMBUS,OH 43210. NATL RADIO ASTRON OBSERV,SOCORRO,NM 87801. ARIZONA STATE UNIV,DEPT PHYS & ASTRON,TEMPE,AZ 85287. RP Shrader, CR (reprint author), NASA,GODDARD SPACE FLIGHT CTR,HIGH ENERGY ASTROPHYS LAB,GREENBELT,MD 20771, USA. NR 8 TC 0 Z9 0 U1 0 U2 0 PU EDITIONS PHYSIQUE PI LES ULIS CEDEX PA Z I DE COURTABOEUF AVE 7 AV DU HOGGAR, BP 112, 91944 LES ULIS CEDEX, FRANCE SN 0365-0138 J9 ASTRON ASTROPHYS SUP JI Astron. Astrophys. Suppl. Ser. PD DEC PY 1996 VL 120 IS 4 SI SI BP C261 EP C263 PG 3 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA WC063 UT WOS:A1996WC06300058 ER PT J AU Shrader, CR Hartman, RC Webb, JR AF Shrader, CR Hartman, RC Webb, JR TI Probable detection of high-energy gamma-ray emission from OJ 287 during a major optical flare SO ASTRONOMY & ASTROPHYSICS SUPPLEMENT SERIES LA English DT Article; Proceedings Paper CT 3rd Compton Symposium CY JUN 12-14, 1995 CL MUNICH, GERMANY SP Max Planck Inst Extraterrestr Phys, Garching, Marx Planck Gesell, Deut Agentur Raumfahrtangelegenheiten, Deut Aerosp DE galaxies, active; BL Lac objects, individual, OJ 287; gamma rays, observations AB We observed the BL Lac object OJ 287 with the CGRO/EGRET instrument as a target of opportunity triggered by an outburst in its visual intensity. OJ 287 is well known as a high-amplitude variable in the optical and radio domain, and recurrent outburst behavior at nominal 11.6-year intervals have led to speculation that there may be some deterministic mechanism underlying its activity cycle - in any case, it became active during late 1994, approximately 11.8 years subsequent to its previous outburst episode. OJ 287 had been considered an excellent candidate for detection at high-energy gamma-ray energies at earlier stages of the CGRO mission, but previous observations did not lead to a detection. We obtained a marginal detection of the source, which we argue is likely to be real given the precise coincidence with the peak of the optical flare. Temporal and spectral analysis are inconclusive due limited statistics. A broad-band spectral energy distribution for OJ 287 at the time of the flare is presented. C1 UNIV SPACE RES ASSOC,LANHAM,MD 20701. FLORIDA INT UNIV,DEPT PHYS,MIAMI,FL 33199. RP Shrader, CR (reprint author), NASA,GODDARD SPACE FLIGHT CTR,HIGH ENERGY ASTROPHYS LAB,GREENBELT,MD 20771, USA. NR 15 TC 1 Z9 1 U1 0 U2 0 PU EDITIONS PHYSIQUE PI LES ULIS CEDEX PA Z I DE COURTABOEUF AVE 7 AV DU HOGGAR, BP 112, 91944 LES ULIS CEDEX, FRANCE SN 0365-0138 J9 ASTRON ASTROPHYS SUP JI Astron. Astrophys. Suppl. Ser. PD DEC PY 1996 VL 120 IS 4 SI SI BP C599 EP C602 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA WC063 UT WOS:A1996WC06300134 ER PT J AU Sikora, M Sol, H Begelman, MC Madejski, G AF Sikora, M Sol, H Begelman, MC Madejski, G TI Propagation of relativistic jets through dense radiation fields in AGN SO ASTRONOMY & ASTROPHYSICS SUPPLEMENT SERIES LA English DT Article; Proceedings Paper CT 3rd Compton Symposium CY JUN 12-14, 1995 CL MUNICH, GERMANY SP Max Planck Inst Extraterrestr Phys, Garching, Marx Planck Gesell, Deut Agentur Raumfahrtangelegenheiten, Deut Aerosp DE galaxies, jets; galaxies, active; scattering AB We present the results of our studies on radiation drag imposed on both cold and relativistic plasma components in a jet propagating at relativistic speeds through a dense radiation field in AGN. We show that in portions of the jet which are energetically dominated by the magnetic fields, the radiation drag imposed on the jet flow through relativistic electrons/positrons can be dynamically important out to distances on the order of the size of the broad emission Line region. Both Compton forces imposed on electrons/positrons by ambient radiation fields and Compton cooling rates of relativistic particles are calculated by using a radiation tensor formalism. With this method, we were also able to derive several simple analytical formulae allowing quick estimates of dynamical and radiative effects resulting from the interaction of relativistic jets with a variety of external radiation-field distributions. C1 DEPT ASTROPHYS RELATIVISTE & COSMOL,CNRS,UPR 176,MEUDON,FRANCE. UNIV COLORADO,APAS,BOULDER,CO. NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. RP Sikora, M (reprint author), COPERNICUS ASTRON CTR,PL-00716 WARSAW,POLAND. NR 7 TC 0 Z9 0 U1 0 U2 0 PU EDITIONS PHYSIQUE PI LES ULIS CEDEX PA Z I DE COURTABOEUF AVE 7 AV DU HOGGAR, BP 112, 91944 LES ULIS CEDEX, FRANCE SN 0365-0138 J9 ASTRON ASTROPHYS SUP JI Astron. Astrophys. Suppl. Ser. PD DEC PY 1996 VL 120 IS 4 SI SI BP C579 EP C582 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA WC063 UT WOS:A1996WC06300129 ER PT J AU Skibo, JG Ramaty, R Purcell, WR AF Skibo, JG Ramaty, R Purcell, WR TI Implications of the diffuse galactic continuum SO ASTRONOMY & ASTROPHYSICS SUPPLEMENT SERIES LA English DT Article; Proceedings Paper CT 3rd Compton Symposium CY JUN 12-14, 1995 CL MUNICH, GERMANY SP Max Planck Inst Extraterrestr Phys, Garching, Marx Planck Gesell, Deut Agentur Raumfahrtangelegenheiten, Deut Aerosp DE gamma-rays, observations; ISM, cosmic rays, general ID X-RAY-SPECTRA; EMISSION; NUCLEI AB Observations made with Ginga, OSSE and COMPTEL provide evidence that the diffuse galactic continuum emission extends down to similar to 10 keV, and that the spectrum steepens below about several hundred keV. If this emission is electron bremsstrahlung, then a very large power (similar to 10(43) erg s(-1)) is required to maintain the electrons against energy losses to the interstellar medium. This exceeds by an order of magnitude the total power provided by galactic supernovae. We suggest that this power might be derived from the gravitational potential released on the passage of the ISM through galactic spiral arm compressions. Alternatively, the hard X-ray galactic continuum could be the superposition of unresolved point sources such as accreting neutron stars or black holes. C1 NASA,GODDARD SPACE FLIGHT CTR,HIGH ENERGY ASTROPHYS LAB,GREENBELT,MD 20771. NORTHWESTERN UNIV,DEPT PHYS & ASTRON,EVANSTON,IL 60308. RP Skibo, JG (reprint author), USN,RES LAB,EO HULBURT CTR SPACE RES,CODE 7653,4555 OVERLOOK AVE SW,WASHINGTON,DC 20375, USA. NR 26 TC 2 Z9 2 U1 0 U2 0 PU EDITIONS PHYSIQUE PI LES ULIS CEDEX PA Z I DE COURTABOEUF AVE 7 AV DU HOGGAR, BP 112, 91944 LES ULIS CEDEX, FRANCE SN 0365-0138 J9 ASTRON ASTROPHYS SUP JI Astron. Astrophys. Suppl. Ser. PD DEC PY 1996 VL 120 IS 4 SI SI BP C403 EP C406 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA WC063 UT WOS:A1996WC06300089 ER PT J AU Smith, DM Leventhal, M Cavallo, R Gehrels, N Tueller, J Fishman, G AF Smith, DM Leventhal, M Cavallo, R Gehrels, N Tueller, J Fishman, G TI BATSE observations of galactic positron-annihilation radiation SO ASTRONOMY & ASTROPHYSICS SUPPLEMENT SERIES LA English DT Article; Proceedings Paper CT 3rd Compton Symposium CY JUN 12-14, 1995 CL MUNICH, GERMANY SP Max Planck Inst Extraterrestr Phys, Garching, Marx Planck Gesell, Deut Agentur Raumfahrtangelegenheiten, Deut Aerosp DE gamma rays, observations; stars, pulsars, individual, crab pulsar; black hole physics; stars, 1E 1740.7-2942, GRO J0422+32 ID GAMMA-RAY TRANSIENTS; SMM OBSERVATIONS; CRAB-NEBULA; LINE; DIRECTION; SEARCH; SIGMA; NOVA AB We are using the Burst And Transient Source Experiment (BATSE) aboard the Compton Gamma-Ray Observatory to study positron annihilation in the Galaxy. We present upper limits on two bright, transient annihilation events reported by the SIGMA telescope aboard the Granat spacecraft. We also present the results of a search for such events from 1E 1740.7-2942, the Crab, and X-ray nova GRO J0422+32 (Nova Persei) in two years of BATSE data. Finally, we report the first detection of the persistent galactic Center 511 keV line in BATSE data and discuss the potential for mapping studies. C1 NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,HUNTSVILLE,AL 35812. RP Smith, DM (reprint author), UNIV MARYLAND,DEPT ASTRON,COLLEGE PK,MD 20742, USA. RI Gehrels, Neil/D-2971-2012; Tueller, Jack/D-5334-2012 NR 17 TC 0 Z9 0 U1 0 U2 0 PU EDITIONS PHYSIQUE PI LES ULIS CEDEX PA Z I DE COURTABOEUF AVE 7 AV DU HOGGAR, BP 112, 91944 LES ULIS CEDEX, FRANCE SN 0365-0138 J9 ASTRON ASTROPHYS SUP JI Astron. Astrophys. Suppl. Ser. PD DEC PY 1996 VL 120 IS 4 SI SI BP C361 EP C364 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA WC063 UT WOS:A1996WC06300081 ER PT J AU Stacy, JG Kippen, RM Kappadath, SC McConnell, M Morris, D Miller, R Connors, A Hersh, B Ryan, J Macri, J Simpson, G Schonfelder, V Steinle, H vanDijk, R Williams, OR AF Stacy, JG Kippen, RM Kappadath, SC McConnell, M Morris, D Miller, R Connors, A Hersh, B Ryan, J Macri, J Simpson, G Schonfelder, V Steinle, H vanDijk, R Williams, OR TI The response of the CGRO COMPTEL determined from Monte Carlo simulation studies SO ASTRONOMY & ASTROPHYSICS SUPPLEMENT SERIES LA English DT Article; Proceedings Paper CT 3rd Compton Symposium CY JUN 12-14, 1995 CL MUNICH, GERMANY SP Max Planck Inst Extraterrestr Phys, Garching, Marx Planck Gesell, Deut Agentur Raumfahrtangelegenheiten, Deut Aerosp DE instrumentation, detectors; methods, numerical; telescopes; gamma rays, observations AB The COMPTEL collaboration has carried out an extensive series of Monte Carlo simulation studies to examine the response of the Imaging Compton Telescope COMPTEL (energy range 0.8 to 30 MeV) aboard the Compton Observatory. These investigations employed the CERN GEANT Monte Carlo package, using a detailed model of the mass distribution within the COMPTEL experiment. We have derived the absolute efficiency of the COMPTEL experiment as a function of photon energy and incidence angle, and present a comparison of simulation results with pre-launch calibration measurements. Also, we report on a comprehensive study of the types of photon interactions leading to accepted COMPTEL telescope events. We briefly describe a new library of monoenergetic instrument-response functions, individual elements of which can now be combined to produce the response of COMPTEL to an input source of arbitrary spectral shape, for use in scientific analysis. A more detailed, complete report on these simulation studies is currently in preparation and will complement parallel reports on the instrument calibration and performance, and background methods and modeling techniques. C1 NASA,GSFC,USRA,COMPTON OBSERV,SCI SUPPORT CTR,GREENBELT,MD 20771. MAX PLANCK INST EXTRATERR PHYS,D-85740 GARCHING,GERMANY. SRON,NL-3584 CA UTRECHT,NETHERLANDS. EUROPEAN SPACE AGCY,ESTEC,DEPT SPACE SCI,DIV ASTROPHYS,NL-2200 AG NOORDWIJK,NETHERLANDS. RP Stacy, JG (reprint author), UNIV NEW HAMPSHIRE,INST STUDY EARTH OCEANS & SPACE,CTR SPACE SCI,MORSE HALL,DURHAM,NH 03824, USA. NR 6 TC 0 Z9 0 U1 0 U2 0 PU EDITIONS PHYSIQUE PI LES ULIS CEDEX PA Z I DE COURTABOEUF AVE 7 AV DU HOGGAR, BP 112, 91944 LES ULIS CEDEX, FRANCE SN 0365-0138 J9 ASTRON ASTROPHYS SUP JI Astron. Astrophys. Suppl. Ser. PD DEC PY 1996 VL 120 IS 4 SI SI BP C691 EP C694 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA WC063 UT WOS:A1996WC06300156 ER PT J AU Stacy, JG Vestrand, WT Sreekumar, P Bonnell, J Kubo, H Hartman, RC AF Stacy, JG Vestrand, WT Sreekumar, P Bonnell, J Kubo, H Hartman, RC TI First Cycle 4 multiwavelength observations of the gamma-ray quasar PKS 0208-512 SO ASTRONOMY & ASTROPHYSICS SUPPLEMENT SERIES LA English DT Article; Proceedings Paper CT 3rd Compton Symposium CY JUN 12-14, 1995 CL MUNICH, GERMANY SP Max Planck Inst Extraterrestr Phys, Garching, Marx Planck Gesell, Deut Agentur Raumfahrtangelegenheiten, Deut Aerosp DE gamma rays, observations; galaxies, active quasars, individual, PKS 0208-512 AB We present first results of CGRO Cycle 4 multiwavelength observations of the gamma-ray quasar PKS 0208-512. A bright, variable gamma-ray source, PKS 0208-512 has been detected numerous times by the EGRET experiment aboard the CGRO, possessing one of the hardest spectra observed to date. The recent COMPTEL observations of Blom et al. (1995) indicate that PKS 0208-512 may belong to a new class of AGN that hare at MeV energies. During the current CGRO Cycle 4 observing cycle we have obtained observations of PKS 0208-512 at high- and medium-energy gamma-rays with the EGRET and COMPTEL instruments aboard the Compton Observatory, at X-ray energies with ASCA, and at ultraviolet wavelengths with IUE. Preliminary analysis of our first CGRO Cycle 4 multiwavelength observations of PKS 0208-512 indicates a significant softening in the high-energy gamma-ray spectrum of this source, compared to earlier epochs. A possible correlation is also noted in flux variations between simultaneous ultraviolet (IUE) and X-ray (ASCA) measurements of this source. Our multiwavelength observations of PKS 0208-512 will be greatly expanded during the CGRO Cycle 5 in 1996, and our results on 0208-512 will ultimately be included in a larger survey of the gamma-ray properties of flat-spectrum radio quasars toward the region of the South Galactic Pole (see Vestrand et al., these proceedings). C1 UNIV NEW HAMPSHIRE,INST STUDY EARTH OCEANS & SPACE,CTR SPACE SCI,DURHAM,NH 03824. NASA,GODDARD SPACE FLIGHT CTR,HIGH ENERGY ASTROPHYS LAB,GREENBELT,MD 20771. UNIV TOKYO,DEPT PHYS,BUNKYO KU,TOKYO 113,JAPAN. UNIV NEW HAMPSHIRE,EOS,CTR SPACE SCI,DURHAM,NH 03824. RP Stacy, JG (reprint author), NASA,GODDARD SPACE FLIGHT CTR,UNIV SPACE RES ASSOC,COMPTON OBSERV SCI SUPPORT CTR,CODE 6681,GREENBELT,MD 20771, USA. NR 8 TC 1 Z9 1 U1 0 U2 0 PU EDITIONS PHYSIQUE PI LES ULIS CEDEX PA Z I DE COURTABOEUF AVE 7 AV DU HOGGAR, BP 112, 91944 LES ULIS CEDEX, FRANCE SN 0365-0138 J9 ASTRON ASTROPHYS SUP JI Astron. Astrophys. Suppl. Ser. PD DEC PY 1996 VL 120 IS 4 SI SI BP C549 EP C552 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA WC063 UT WOS:A1996WC06300122 ER PT J AU Strickman, M deJager, O Harding, A AF Strickman, M deJager, O Harding, A TI OSSE detection of the Vela synchrotron nebula SO ASTRONOMY & ASTROPHYSICS SUPPLEMENT SERIES LA English DT Article; Proceedings Paper CT 3rd Compton Symposium CY JUN 12-14, 1995 CL MUNICH, GERMANY SP Max Planck Inst Extraterrestr Phys, Garching, Marx Planck Gesell, Deut Agentur Raumfahrtangelegenheiten, Deut Aerosp DE gamma rays, observations; ISM, individual objects, Vela SNR; ISM, supernova remnants ID X-RAY NEBULA; SUPERNOVA REMNANT; PULSAR AB We report on the detection of low energy gamma-rays from the Vela Supernova remnant at the similar to 9 sigma level with the OSSE instrument on CGRO during an observation from 31 August to 20 September 1994. The source has a power law photon spectral index of similar to -1.6 +/- 0.3 in the energy range similar to 0.06 MeV to similar to 0.4 MeV. Contamination by the galactic plane was found to be insignificant. This spectrum is perfectly consistent with an extrapolation of the E(-1.7) spectrum of the similar to 1' radius compact nebula surrounding the Vela Pulsar, as seen between 0.1-25 keV with imaging instruments. C1 POTCHEFSTROOM UNIV CHRISTIAN HIGHER EDUC,DEPT PHYS,SPACE RES UNIT,ZA-2520 POTCHEFSTROOM,SOUTH AFRICA. NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. RP Strickman, M (reprint author), USN,RES LAB,CODE 7650,WASHINGTON,DC 20375, USA. RI Harding, Alice/D-3160-2012 NR 17 TC 1 Z9 1 U1 0 U2 0 PU EDITIONS PHYSIQUE PI LES ULIS CEDEX PA Z I DE COURTABOEUF AVE 7 AV DU HOGGAR, BP 112, 91944 LES ULIS CEDEX, FRANCE SN 0365-0138 J9 ASTRON ASTROPHYS SUP JI Astron. Astrophys. Suppl. Ser. PD DEC PY 1996 VL 120 IS 4 SI SI BP C449 EP C452 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA WC063 UT WOS:A1996WC06300099 ER PT J AU Tavani, M Hermsen, W vanDijk, R Strickman, M Zhang, SN Foster, RS Ray, PS Mattox, J Ulmer, M Purcell, W Coe, M AF Tavani, M Hermsen, W vanDijk, R Strickman, M Zhang, SN Foster, RS Ray, PS Mattox, J Ulmer, M Purcell, W Coe, M TI Monitoring the gamma-ray source 2CG 135+1 and the radio star LSI +61 degrees 303 SO ASTRONOMY & ASTROPHYSICS SUPPLEMENT SERIES LA English DT Article; Proceedings Paper CT 3rd Compton Symposium CY JUN 12-14, 1995 CL MUNICH, GERMANY SP Max Planck Inst Extraterrestr Phys, Garching, Marx Planck Gesell, Deut Agentur Raumfahrtangelegenheiten, Deut Aerosp DE gamma-rays, observations; X-rays, stars; stars, individual, LSI +61 303, 2CG 135+1 ID COS-B; LSI+61-DEGREES-303 AB We report the results of a CGRO multi-instrument series of observations of the unidentified gamma-ray source 2CG 135+1 and of its possible counterpart, the peculiar radio source GT 0236+610 coincident with the Be star LSI +61 degrees 303. Previous observations of 2CG 135+1 are consistent with a positional coincidence of the gamma-ray source with LSI +61 degrees 303. Since January 1994, we continuously monitored the time variable radio source GT 0236+610 with the Green Bank Interferometer. For the first time, gamma-ray observations of 2CG 135+1 can be correlated with an extensive database of radio observations of LSI +61 degrees 303. We present OSSE and COMPTEL data obtained during the period May-June 1994, and BATSE data for the period April 1994-January 1995. We discuss the possible time variability of the gamma-ray emission and spectral properties of 2CG 135+1. Understanding the nature of 2CG 135+1 may be of crucial importance for the interpretation of a class of unidentified and time variable gamma-ray sources in the Galaxy. C1 SRON, NL-3584 CA UTRECHT, NETHERLANDS. UNIV AMSTERDAM, INST ASTRON, NL-1098 SJ AMSTERDAM, NETHERLANDS. USN, RES LAB, WASHINGTON, DC 20375 USA. NASA, GEORGE C MARSHALL SPACE FLIGHT CTR, UNIV SPACE RES ASSOC, HUNTSVILLE, AL 35812 USA. UNIV MARYLAND, DEPT ASTRON, COLLEGE PK, MD 20742 USA. NORTHWESTERN UNIV, DEPT PHYS & ASTRON, EVANSTON, IL 60208 USA. UNIV SOUTHAMPTON, DEPT PHYS, SOUTHAMPTON SO17 1BJ, HANTS, ENGLAND. RP COLUMBIA UNIV, COLUMBIA ASTROPHYS LAB, 538 W 120TH ST, NEW YORK, NY 10027 USA. NR 28 TC 2 Z9 2 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 DEC PY 1996 VL 120 IS 4 SI SI BP C243 EP C248 PG 6 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA WC063 UT WOS:A1996WC06300054 ER PT J AU Tavani, M Grove, JE Purcell, W Hermsen, W Kuiper, L Kaaret, P Ford, E Wilson, RB Finger, M Harmon, BA Zhang, SN Mattox, J Thompson, D Arons, J AF Tavani, M Grove, JE Purcell, W Hermsen, W Kuiper, L Kaaret, P Ford, E Wilson, RB Finger, M Harmon, BA Zhang, SN Mattox, J Thompson, D Arons, J TI High-energy emission from the PSR B1259-63 system near periastron SO ASTRONOMY & ASTROPHYSICS SUPPLEMENT SERIES LA English DT Article; Proceedings Paper CT 3rd Compton Symposium CY JUN 12-14, 1995 CL MUNICH, GERMANY SP Max Planck Inst Extraterrestr Phys, Garching, Marx Planck Gesell, Deut Agentur Raumfahrtangelegenheiten, Deut Aerosp DE gamma-ray, observations; X-ray, stars; pulsars, individual, PSR B1259-63; shock waves ID PULSAR; PSR-1259-63; STARS; RADIO AB We report the results of a CGRO multi-instrument 3-week observation of the binary system containing the 47 ms pulsar PSR B1259-63 orbiting around a Be star companion in a very eccentric orbit. The PSR B1259-63 binary is a unique system for the study of the interaction of a rapidly rotating pulsar with time-variable nebular surroundings. CGRO observed the PSR B1259-63 system in coincidence with its most recent periastron passage (January 3-23, 1994). Unpulsed and nonthermal hard X-ray emission was detected up to 200 keV, with a photon index 1.8+/-0.2 and a flux of similar to 4 mCrab, corresponding to a luminosity of a few x 10(34) erg/s at the distance of 2 kpc. The hard X-ray flux and spectrum detected by CGRO agrees with the X-ray emission measured by simultaneous ASCA observations. EGRET upper limits are significant, and exclude strong inverse Compton cooling in the PSR B1259-63 system. We interpret the observed non-thermal emission as synchrotron radiation of shocked electron/positron pairs of the relativistic pulsar wind interacting with the mass outflow from the Be star. Our results clearly indicate, for the first time in a binary pulsar, that high energy emission can be shock-powered rather than caused by accretion. Furthermore, the PSR B1259-63 system shows that shock acceleration can increase the original energy of pulsar wind particles by a factor greater than or similar to 10, despite the high synchrotron and inverse Compton cooling rates near periastron. We also present results of an extensive search for pulsed gamma-ray emission from PSR B1259-63. The lack of pulsations constrains models of gamma-ray emission from rapidly rotating pulsars. C1 USN,RES LAB,WASHINGTON,DC 20375. NORTHWESTERN UNIV,DEPT PHYS & ASTRON,EVANSTON,IL 60208. SRON,NL-3584 CA UTRECHT,NETHERLANDS. NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,HUNTSVILLE,AL 35812. NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,UNIV SPACE RES ASSOC,HUNTSVILLE,AL 35812. UNIV MARYLAND,DEPT ASTRON,COLLEGE PK,MD 20742. NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. UNIV CALIF BERKELEY,DEPT ASTRON,BERKELEY,CA 94720. RP Tavani, M (reprint author), COLUMBIA UNIV,COLUMBIA ASTROPHYS LAB,NEW YORK,NY 10027, USA. NR 24 TC 2 Z9 2 U1 0 U2 0 PU EDITIONS PHYSIQUE PI LES ULIS CEDEX PA Z I DE COURTABOEUF AVE 7 AV DU HOGGAR, BP 112, 91944 LES ULIS CEDEX, FRANCE SN 0365-0138 J9 ASTRON ASTROPHYS SUP JI Astron. Astrophys. Suppl. Ser. PD DEC PY 1996 VL 120 IS 4 SI SI BP C221 EP C226 PG 6 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA WC063 UT WOS:A1996WC06300048 ER PT J AU Teegarden, BJ Cline, TL Gehrels, N Hurley, KH Owens, A Palmer, D Ramaty, R Seifert, H AF Teegarden, BJ Cline, TL Gehrels, N Hurley, KH Owens, A Palmer, D Ramaty, R Seifert, H TI TGRS occultation analysis of the Galactic center region SO ASTRONOMY & ASTROPHYSICS SUPPLEMENT SERIES LA English DT Article; Proceedings Paper CT 3rd Compton Symposium CY JUN 12-14, 1995 CL MUNICH, GERMANY SP Max Planck Inst Extraterrestr Phys, Garching, Marx Planck Gesell, Deut Agentur Raumfahrtangelegenheiten, Deut Aerosp DE Galaxy, center; gamma rays, observations ID POSITRON-ANNIHILATION RADIATION; 511 KEV LINE; EMISSION; SIGMA AB The TGRS (Transient Gamma-Ray Spectrometer) experiment is a high-resolution germanium detector launched on the WIND satellite on Nov. 1, 1994. Although primarily intended to study gamma-ray bursts and solar flares, TGRS also has the capability of studying slower transients (e.g. X-ray novae) and certain steady sources. We present here preliminary results on the narrow 511 keV annihilation line from the general direction of the Galactic Center. These results were obtained from the TGRS occultation mode. In this mode a lead absorber occults the Galactic Center region for 1/4 of each spacecraft rotation, effectively chopping the signal. Data are presented here for the first 2 months of 1995. We detect the narrow annihilation line from the galactic center with flux = (1.36 +/- 0.2) 10(-3) cm(-2) s(-1), and width (FWHM) = 2.6(+1.0/ -0.3) keV. The data are consistent with a single point source at the galactic center, but a distributed source of extent up to similar to 15 degrees cannot be ruled out. No evidence for temporal variability on time scales longer than 1 month was found. C1 NASA, GODDARD SPACE FLIGHT CTR, USRA, GREENBELT, MD 20771 USA. UNIV CALIF BERKELEY, BERKELEY, CA 94720 USA. UNIV LEICESTER, LEICESTER, MA USA. RI Gehrels, Neil/D-2971-2012 NR 12 TC 0 Z9 0 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 DEC PY 1996 VL 120 IS 4 SI SI BP C283 EP C285 PG 3 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA WC063 UT WOS:A1996WC06300063 ER PT J AU The, LS Leising, MD Kurfess, JD Johnson, WN Hartmann, DH Gehrels, N Grove, JE Purcell, WR AF The, LS Leising, MD Kurfess, JD Johnson, WN Hartmann, DH Gehrels, N Grove, JE Purcell, WR TI CGRO/OSSE observations of the Cassiopeia A SNR SO ASTRONOMY & ASTROPHYSICS SUPPLEMENT SERIES LA English DT Article; Proceedings Paper CT 3rd Compton Symposium CY JUN 12-14, 1995 CL MUNICH, GERMANY SP Max Planck Inst Extraterrestr Phys, Garching, Marx Planck Gesell, Deut Agentur Raumfahrtangelegenheiten, Deut Aerosp DE gamma rays, observations; ISM, individual objects, Cas A; nuclear reactions, nucleosynthesis, abundances ID SUPER-NOVA REMNANTS; RAY-LINE EMISSION; X-RAY; TI-44; SPECTRA; MODELS AB We present all OSSE observations to date of the Cas A supernova remnant. The objectives are to detect the Ti-44 lines, one of which has been reportedly detected by COMPTEL, and the hard X-ray continuum above 40 keV, as indicated by HEAO-A2 measurements. Our best fit flux in each of three Ti-44 lines is (+1.76 +/-(1.51)(1.48)) 10(-5) gamma cm(-2) s(-1) with chi(nu)(2) = 1.01, d.o.f.=1780. The implied Ti-44 mass of similar to 10(-4) M. is compatible with explosive nucleosynthesis calculations. OSSE detected also a continuum below 200 keV at better than 4 sigma confidence level with a flux of similar to 9 10(-4) gamma cm(-2) s(-1) MeV(-1) at 100 keV. This continuum can be fitted equally well with a power law, an exponential, or a thermal bremsstrahlung model. The implied temperature of kT approximate to 35 keV can be interpreted as the emission from the shocked circumstellar matter (CSM) by the primary blastwave of the supernova. Alternatively, the continuum can also be interpreted as bremsstrahlung from accelerated electrons that are also producing the observed radio emission. C1 USN,RES LAB,EO HULBURT CTR SPACE RES,WASHINGTON,DC 20375. NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. NORTHWESTERN UNIV,DEPT PHYS & ASTRON,EVANSTON,IL 60208. RP The, LS (reprint author), CLEMSON UNIV,DEPT PHYS & ASTRON,CLEMSON,SC 29634, USA. RI Gehrels, Neil/D-2971-2012; Johnson, Neil/G-3309-2014 NR 21 TC 14 Z9 14 U1 0 U2 0 PU EDITIONS PHYSIQUE PI LES ULIS CEDEX PA Z I DE COURTABOEUF AVE 7 AV DU HOGGAR, BP 112, 91944 LES ULIS CEDEX, FRANCE SN 0365-0138 J9 ASTRON ASTROPHYS SUP JI Astron. Astrophys. Suppl. Ser. PD DEC PY 1996 VL 120 IS 4 SI SI BP C357 EP C360 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA WC063 UT WOS:A1996WC06300080 ER PT J AU Titarchuk, L Mastichiadis, A Kylafis, ND AF Titarchuk, L Mastichiadis, A Kylafis, ND TI Spherical accretion onto neutron stars and black holes SO ASTRONOMY & ASTROPHYSICS SUPPLEMENT SERIES LA English DT Article; Proceedings Paper CT 3rd Compton Symposium CY JUN 12-14, 1995 CL MUNICH, GERMANY SP Max Planck Inst Extraterrestr Phys, Garching, Marx Planck Gesell, Deut Agentur Raumfahrtangelegenheiten, Deut Aerosp DE accretion; black hole physics; radiation mechanisms, non-thermal; radiative transfer; stars, neutron X-rays, general ID CONVERGING FLUID-FLOW; RADIATION-DOMINATED SHOCK; COMPTON-SCATTERING AB Spectral formation in steady state, spherical accretion onto neutron stars and black holes is examined by solving numerically and analytically the equation of radiative transfer. The photons escape diffusively and their energy gains come from their scattering off thermal electrons in the converging how of the accreting gas. We show that the bulk motion of the flow is more efficient in upscattering photons than thermal Comptonization in the range of non-relativistic electron temperatures. The spectrum observed at infinity is a power law with an exponential turnover at energies of order of the electron rest mass. Especially in the case of accretion into a black hole, the spectral energy power-law index is distributed around 1.5. Because bulk motion near the horizon (1-5 Schwarzschild radii) is most likely a necessary characteristic of accretion into a black hole, we claim that observations of an extended power law up to about m(e)c(2), formed as a result of bulk motion, Comptonization, is a real observational evidence for the existence of an underlying black hole. C1 GEORGE MASON UNIV,CSI,FAIRFAX,VA 22030. MAX PLANCK INST KERNPHYS,D-69029 HEIDELBERG,GERMANY. UNIV CRETE,HELLAS,GREECE. FDN RES & TECHNOL,HELLAS,GREECE. RP Titarchuk, L (reprint author), NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771, USA. RI Kylafis, Nikolaos/C-4555-2011 OI Kylafis, Nikolaos/0000-0003-0928-0996 NR 14 TC 13 Z9 13 U1 0 U2 0 PU EDITIONS PHYSIQUE PI LES ULIS CEDEX PA Z I DE COURTABOEUF AVE 7 AV DU HOGGAR, BP 112, 91944 LES ULIS CEDEX, FRANCE SN 0365-0138 J9 ASTRON ASTROPHYS SUP JI Astron. Astrophys. Suppl. Ser. PD DEC PY 1996 VL 120 IS 4 SI SI BP C171 EP C174 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA WC063 UT WOS:A1996WC06300036 ER PT J AU Tueller, J Gehrels, N Leventhal, M Smith, DM Purcell, WR AF Tueller, J Gehrels, N Leventhal, M Smith, DM Purcell, WR TI High-resolution OSSE scanning observations of the galactic center 511 keV source SO ASTRONOMY & ASTROPHYSICS SUPPLEMENT SERIES LA English DT Article; Proceedings Paper CT 3rd Compton Symposium CY JUN 12-14, 1995 CL MUNICH, GERMANY SP Max Planck Inst Extraterrestr Phys, Garching, Marx Planck Gesell, Deut Agentur Raumfahrtangelegenheiten, Deut Aerosp DE gamma-rays, observations; black hole physics; Galaxy, center ID POSITRON-ANNIHILATION RADIATION; GAMMA-RAY CONTINUUM; SOURCE 1E1740.7-2942; MOLECULAR CLOUD; CENTER REGION; BLACK-HOLE; LINE; 1E-1740.7-2942; EMISSION; 511-KEV AB The distribution of positron-annihilation line emission from the Galactic Center (GC) is arguably the most important gamma-ray line measurement that OSSE can make. After nearly 20 years of observations, the source of the positrons is still unknown. Although OSSE has scanned the GC many times, there are only two scans with the collimator perpendicular to the plane. They show a significant offset from the GC of (-1.36 degrees +/- 0.33 degrees; similar to 4 sigma). The centroid is consistent with the black hole source 1E 1740.7-2942. We have developed a new pointing and background strategy for OSSE to maximize sensitivity to this offset. We have analyzed test data in this mode from a blank section of sky, and found it to be well-behaved; a week of actual GC data in this mode are now in hand. These data should be able to confirm the offset from the GC, but more observations are needed to distinguish a point source from an extended source. C1 UNIV MARYLAND, DEPT ASTRON, COLLEGE PK, MD 20742 USA. NORTHWESTERN UNIV, DEPT PHYS & ASTRON, EVANSTON, IL 60208 USA. RP NASA, GODDARD SPACE FLIGHT CTR, CODE 661, GREENBELT, MD 20771 USA. RI Gehrels, Neil/D-2971-2012; Tueller, Jack/D-5334-2012 NR 30 TC 0 Z9 0 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 DEC PY 1996 VL 120 IS 4 SI SI BP C369 EP C372 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA WC063 UT WOS:A1996WC06300083 ER PT J AU vanderHooft, F Kouveliotou, C vanParadijs, J Rubin, BC Crary, DJ Finger, MH Harmon, BA vanderKlis, M Lewin, WHG Norris, JP Fishman, GJ AF vanderHooft, F Kouveliotou, C vanParadijs, J Rubin, BC Crary, DJ Finger, MH Harmon, BA vanderKlis, M Lewin, WHG Norris, JP Fishman, GJ TI Low-frequency quasi-periodic oscillations in the X-ray transient GRO J1719-24 SO ASTRONOMY & ASTROPHYSICS SUPPLEMENT SERIES LA English DT Article; Proceedings Paper CT 3rd Compton Symposium CY JUN 12-14, 1995 CL MUNICH, GERMANY SP Max Planck Inst Extraterrestr Phys, Garching, Marx Planck Gesell, Deut Agentur Raumfahrtangelegenheiten, Deut Aerosp DE accretion, accretions disks; stars, individual, GRO J1719-24; X-rays, stars ID BLACK-HOLE; BINARIES AB We present the results of an analysis of the time variability of the soft X-ray transient GRO J1719-24 (Nova Oph 1993) as observed with BATSE. Our analysis covers the entire similar to 80 day outburst, beginning with the first detection on September 25, 1993. We obtained power density spectra (PDS) of the data in the 20-100 keV energy band covering the frequency interval 0.002-0.488 Hz. The PDS show a significant quasi-periodic oscillations (QPO) peak whose centroid frequency increased from similar to 0.04 Hz at the onset of the outburst, to similar to 0.3 Hz at the end. Additional noise is present in the PDS which we describe in terms of two components. We find that the evolution of the PDS can be described as a gradual stretching by a factor similar to 7.5 in frequency of the power spectrum. C1 UNIV AMSTERDAM, CTR HIGH ENERGY ASTROPHYS, NL-1098 SJ AMSTERDAM, NETHERLANDS. UNIV SPACE RES ASSOC, HUNTSVILLE, AL 35806 USA. NASA, GEORGE C MARSHALL SPACE FLIGHT CTR, HUNTSVILLE, AL 35812 USA. UNIV ALABAMA, DEPT PHYS, HUNTSVILLE, AL 35899 USA. MIT, CAMBRIDGE, MA 02139 USA. NASA, GODDARD SPACE FLIGHT CTR, GREENBELT, MD 20771 USA. RP UNIV AMSTERDAM, ASTRON INST ANTON PANNEKOEK, KRUISLAAN 403, NL-1098 SJ AMSTERDAM, NETHERLANDS. NR 34 TC 0 Z9 0 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 DEC PY 1996 VL 120 IS 4 SI SI BP C141 EP C144 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA WC063 UT WOS:A1996WC06300028 ER PT J AU Vestrand, WT Stacy, JG Sreekumar, P AF Vestrand, WT Stacy, JG Sreekumar, P TI A CGRO survey of radio quasars near the South Galactic Pole: First results SO ASTRONOMY & ASTROPHYSICS SUPPLEMENT SERIES LA English DT Article; Proceedings Paper CT 3rd Compton Symposium CY JUN 12-14, 1995 CL MUNICH, GERMANY SP Max Planck Inst Extraterrestr Phys, Garching, Marx Planck Gesell, Deut Agentur Raumfahrtangelegenheiten, Deut Aerosp DE gamma rays, observations; galaxies, active; BL Lacertae objects, PKS 2155-304 ID OBJECT PKS 2155-304; GAMMA-RAYS; COMPTEL AB We present the first results from our Cycle 4 program to search for gamma-ray emission from flat-spectrum radio quasars with the EGRET and COMPTEL experiments aboard the Compton Gamma Ray Observatory (CGRO). This program, which was designed to fill in the most severe coverage deficiency in the AGN all-sky survey, has detected several previously unknown gamma-ray sources. Our most exciting new EGRET detection is that of PKS 2155-304, a nearby, bright BL Lac, which is considered by many to be the prototypical Xray selected BL Lac object. The hardness of the PKS 2155-304 photon spectrum and the proximity of the source (z = 0.116) make it an excellent candidate for detection at TeV gamma-ray energies. C1 NASA,GODDARD SPACE FLIGHT CTR,HIGH ENERGY ASTROPHYS LAB,GREENBELT,MD 20771. NR 19 TC 1 Z9 1 U1 0 U2 0 PU EDITIONS PHYSIQUE PI LES ULIS CEDEX PA Z I DE COURTABOEUF AVE 7 AV DU HOGGAR, BP 112, 91944 LES ULIS CEDEX, FRANCE SN 0365-0138 J9 ASTRON ASTROPHYS SUP JI Astron. Astrophys. Suppl. Ser. PD DEC PY 1996 VL 120 IS 4 SI SI BP C521 EP C524 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA WC063 UT WOS:A1996WC06300115 ER PT J AU vonMontigny, C Bertsch, DL Dingus, BL Esposito, JA Fichtel, CE Hartman, RC Hunter, SD Kanbach, G Kniffen, DA Lin, YC Merck, M MayerHasselwander, HA Mukherjee, R Michelson, PF Nolan, PL Piner, G Schneid, E Thompson, DJ AF vonMontigny, C Bertsch, DL Dingus, BL Esposito, JA Fichtel, CE Hartman, RC Hunter, SD Kanbach, G Kniffen, DA Lin, YC Merck, M MayerHasselwander, HA Mukherjee, R Michelson, PF Nolan, PL Piner, G Schneid, E Thompson, DJ TI Preliminary results from EGRET phase 3 observations of the Virgo region SO ASTRONOMY & ASTROPHYSICS SUPPLEMENT SERIES LA English DT Article; Proceedings Paper CT 3rd Compton Symposium CY JUN 12-14, 1995 CL MUNICH, GERMANY SP Max Planck Inst Extraterrestr Phys, Garching, Marx Planck Gesell, Deut Agentur Raumfahrtangelegenheiten, Deut Aerosp DE gamma rays, observations; galaxies, active quasars, individual, 3C 273, 3C 279, ON 231=1219+285; PKS 1222+216 AB During phase 3 of the COMPTON Observatory mission (August 93 - October 94), the Virgo region (containing the quasars 3C 279 and 3C 273) has been observed for a total of about 8 weeks by the EGRET instrument which is sensitive to photons with energies in the range of 30 MeV to about 20 GeV. The quasars 3C 279 and 3C 273 have been detected again. In addition, several more sources have been detected by EGRET during these observations. In this paper preliminary results on 3C 273, 3C 279, 1219+285 and PKS 1222+216 are presented. C1 MAX PLANCK INST EXTRATERR PHYS,D-85740 GARCHING,GERMANY. STANFORD UNIV,HANSEN EXPT PHYS LAB,STANFORD,CA 94305. HAMPDEN SYDNEY COLL,HAMPDEN SYDNEY,VA 23943. NORTHROP GRUMMAN AEROSP CORP,BETHPAGE,NY 11714. UNIV SPACE RES ASSOC,NASA,GFSC,WASHINGTON,DC. NAS,NRC,WASHINGTON,DC. UNIV MARYLAND,DEPT ASTRON,COLLEGE PK,MD 20742. RP vonMontigny, C (reprint author), NASA,GODDARD SPACE FLIGHT CTR,CODE 661,GREENBELT,MD 20771, USA. RI Nolan, Patrick/A-5582-2009; Hunter, Stanley/D-2942-2012; Thompson, David/D-2939-2012 OI Thompson, David/0000-0001-5217-9135 NR 8 TC 1 Z9 1 U1 0 U2 0 PU EDITIONS PHYSIQUE PI LES ULIS CEDEX PA Z I DE COURTABOEUF AVE 7 AV DU HOGGAR, BP 112, 91944 LES ULIS CEDEX, FRANCE SN 0365-0138 J9 ASTRON ASTROPHYS SUP JI Astron. Astrophys. Suppl. Ser. PD DEC PY 1996 VL 120 IS 4 SI SI BP C519 EP C520 PG 2 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA WC063 UT WOS:A1996WC06300114 ER PT J AU Wallyn, P Ling, JC Wheaton, WA Mahoney, WA Radocinski, RG Skelton, RT AF Wallyn, P Ling, JC Wheaton, WA Mahoney, WA Radocinski, RG Skelton, RT TI JPL earth occultation analysis of the Galactic center region during flaring of 1E 1740.7-2942 SO ASTRONOMY & ASTROPHYSICS SUPPLEMENT SERIES LA English DT Article; Proceedings Paper CT 3rd Compton Symposium CY JUN 12-14, 1995 CL MUNICH, GERMANY SP Max Planck Inst Extraterrestr Phys, Garching, Marx Planck Gesell, Deut Agentur Raumfahrtangelegenheiten, Deut Aerosp DE gamma rays, observations; black hole, physics; line, identification; star, 1E 1740.7-2942 ID X-RAY NOVA; ANNIHILATION; DISCOVERY; SIGMA; MUSCA; LINE AB We present preliminary results of a search for flaring of the gamma-ray source 1E 1740.7-2942 above 300 keV using the JPL-EBOP package on BATSE data. We selected two periods, 1-19 October 1991 and 19-20 September 1992, corresponding to SIGMA observations of a transient high energy feature in the spectrum of 1E 1740.7-2942 around 450 keV. For the first period, we find an integrated 300-600 keV flux consistent with SIGMA observation. Below 200 keV, the interpretation is uncertain because of potential source confusion with BATSE. For the second period, the sensitivity of the current JPL-EBOP package does not allow us to put strong constraints on this similar to one-day long flaring although no flux variation above 300 keV is observed during a 13-day period including this event with a one-day one-sigma sensitivity of similar to 10(-3) ph cm(-2) s(-1). C1 UNIV CALIF SAN DIEGO,CTR ASTROPHYS & SPACE SCI,LA JOLLA,CA 92093. RP Wallyn, P (reprint author), CALTECH,JET PROP LAB,4800 OAK GROVE DR,PASADENA,CA 91109, USA. NR 17 TC 0 Z9 0 U1 1 U2 1 PU EDITIONS PHYSIQUE PI LES ULIS CEDEX PA Z I DE COURTABOEUF AVE 7 AV DU HOGGAR, BP 112, 91944 LES ULIS CEDEX, FRANCE SN 0365-0138 J9 ASTRON ASTROPHYS SUP JI Astron. Astrophys. Suppl. Ser. PD DEC PY 1996 VL 120 IS 4 SI SI BP C295 EP C298 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA WC063 UT WOS:A1996WC06300066 ER PT J AU Wheaton, WA Ling, JC Mahoney, WA Radocinski, RG Skelton, RT Wallyn, P AF Wheaton, WA Ling, JC Mahoney, WA Radocinski, RG Skelton, RT Wallyn, P TI Long-term 0.03-1.8 MeV BATSE monitoring of Centaurus A SO ASTRONOMY & ASTROPHYSICS SUPPLEMENT SERIES LA English DT Article; Proceedings Paper CT 3rd Compton Symposium CY JUN 12-14, 1995 CL MUNICH, GERMANY SP Max Planck Inst Extraterrestr Phys, Garching, Marx Planck Gesell, Deut Agentur Raumfahrtangelegenheiten, Deut Aerosp DE gamma rays, observations; galaxies, active galaxy, NGC 5128 AB We report the 0.03 - 1.8 MeV spectra of the nearby radio galaxy Centaurus A (NGC 5128) during 15 Compton Gamma-Ray Observatory viewing periods from 1991 May through 1992 June, using data from the Burst and Transient Source Experiment and the earth-occultation method. During these periods the average of the 45 - 140 keV flux was approximate to 1.5 10(-2) gamma cm(-2) s(-1), with variability of a factor of two or less. The mean flux in the 0.5 - 1.0 MeV range was about 1.5 10(-3) gamma cm(-2) s(-1), with evidence for variability. The spectra obtained during most single viewing periods are adequately represented by power-laws dN/dE = AE(-alpha), with a mean photon index [alpha] = 1.84 +/- 0.08, and RMS variability of at most 0.3. C1 UNIV CALIF SAN DIEGO,CTR ASTROPHYS & SPACE SCI 0111,LA JOLLA,CA 92093. RP Wheaton, WA (reprint author), CALTECH,JET PROP LAB 169 327,4800 OAK GROVE DR,PASADENA,CA 91109, USA. NR 7 TC 0 Z9 0 U1 0 U2 0 PU EDITIONS PHYSIQUE PI LES ULIS CEDEX PA Z I DE COURTABOEUF AVE 7 AV DU HOGGAR, BP 112, 91944 LES ULIS CEDEX, FRANCE SN 0365-0138 J9 ASTRON ASTROPHYS SUP JI Astron. Astrophys. Suppl. Ser. PD DEC PY 1996 VL 120 IS 4 SI SI BP C545 EP C548 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA WC063 UT WOS:A1996WC06300121 ER PT J AU Zhang, SN Harmon, BA Paciesas, WS Fishman, GJ Grindlay, JE Barret, D Tavani, M Kaaret, P Bloser, P Ford, E Titarchuk, L AF Zhang, SN Harmon, BA Paciesas, WS Fishman, GJ Grindlay, JE Barret, D Tavani, M Kaaret, P Bloser, P Ford, E Titarchuk, L TI Low state hard X-ray outburst from the X-ray burster 4U 1608-522 observed by BATSE/CGRO SO ASTRONOMY & ASTROPHYSICS SUPPLEMENT SERIES LA English DT Article; Proceedings Paper CT 3rd Compton Symposium CY JUN 12-14, 1995 CL MUNICH, GERMANY SP Max Planck Inst Extraterrestr Phys, Garching, Marx Planck Gesell, Deut Agentur Raumfahrtangelegenheiten, Deut Aerosp DE stars, individual, 4U 1608-522; X-rays, stars; stars, neutron ID BINARIES AB A hard X-ray (low state) outburst lasting for about 170 days was observed with the Burst and Transient Source Experiment (BATSE) Large Area Detectors (LADs) from the X-ray burster 4U 1608-522 from June to December 1991. During the outburst, the flux slowly varied between 75 mCrab and 150 mCrab. Combined with a near simultaneous observation with the Ginga satellite, the low energy spectrum before the break energy is well determined to be a power law with photon index of about 1.75. The high energy spectrum above the break energy can be fit equally well by either the Sunyaev-Titarchuk (S-T) model or a broken power law model. For the first time, we have determined that a rather intense hard X-ray outburst from a neutron star system is associated with a soft X-ray (< 10 keV) low state and the power law photon spectrum breaks at about 65 keV. C1 NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,HUNTSVILLE,AL 35812. UNIV ALABAMA,DEPT PHYS,HUNTSVILLE,AL 35899. HARVARD SMITHSONIAN CTR ASTROPHYS,CAMBRIDGE,MA 02138. COLUMBIA UNIV,DEPT PHYS,NEW YORK,NY 10027. NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. GEORGE MASON UNIV,CSI,FAIRFAX,VA 22030. RP Zhang, SN (reprint author), UNIV SPACE RES ASSOC,HUNTSVILLE,AL 35806, USA. NR 24 TC 3 Z9 3 U1 0 U2 0 PU EDITIONS PHYSIQUE PI LES ULIS CEDEX PA Z I DE COURTABOEUF AVE 7 AV DU HOGGAR, BP 112, 91944 LES ULIS CEDEX, FRANCE SN 0365-0138 J9 ASTRON ASTROPHYS SUP JI Astron. Astrophys. Suppl. Ser. PD DEC PY 1996 VL 120 IS 4 SI SI BP C279 EP C282 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA WC063 UT WOS:A1996WC06300062 ER PT J AU Zhang, SN Harmon, BA Paciesas, WS Fishman, GJ Finger, MH Robinson, CR Rubin, BC Grindlay, JE Barret, D Tavani, M Kaaret, P Bloser, P Ford, E AF Zhang, SN Harmon, BA Paciesas, WS Fishman, GJ Finger, MH Robinson, CR Rubin, BC Grindlay, JE Barret, D Tavani, M Kaaret, P Bloser, P Ford, E TI Periodic transient hard X-ray emission from GRO 1849-03 SO ASTRONOMY & ASTROPHYSICS SUPPLEMENT SERIES LA English DT Article; Proceedings Paper CT 3rd Compton Symposium CY JUN 12-14, 1995 CL MUNICH, GERMANY SP Max Planck Inst Extraterrestr Phys, Garching, Marx Planck Gesell, Deut Agentur Raumfahrtangelegenheiten, Deut Aerosp DE stars, individual, GRO 1849-03; X-rays, stars ID TIME-SERIES; SPACED DATA AB We have recently discovered periodic transient hard X-ray emission from a source, GRO 1849-03, possibly located in the 5 kpc arm of the galaxy, using archival BATSE data. The source produces hard X-ray outbursts at regular 241 day intervals. Each outburst lasts roughly 13 days, reaching a peak luminosity of 75 mCrab. The spectrum extends to at least 100 keV with a photon power law index of -2.8. We interpret the emission as due to close encounters between a compact object and a companion star in a binary system. C1 NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,HUNTSVILLE,AL 35812. UNIV ALABAMA,DEPT PHYS,HUNTSVILLE,AL 35899. HARVARD SMITHSONIAN CTR ASTROPHYS,CAMBRIDGE,MA 02138. COLUMBIA UNIV,DEPT PHYS,NEW YORK,NY 10027. RP Zhang, SN (reprint author), UNIV SPACE RES ASSOC,HUNTSVILLE,AL 35806, USA. NR 23 TC 2 Z9 2 U1 0 U2 0 PU EDITIONS PHYSIQUE PI LES ULIS CEDEX PA Z I DE COURTABOEUF AVE 7 AV DU HOGGAR, BP 112, 91944 LES ULIS CEDEX, FRANCE SN 0365-0138 J9 ASTRON ASTROPHYS SUP JI Astron. Astrophys. Suppl. Ser. PD DEC PY 1996 VL 120 IS 4 SI SI BP C227 EP C230 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA WC063 UT WOS:A1996WC06300049 ER PT J AU Zhang, SN Harmon, BA Paciesas, WS Fishman, GJ AF Zhang, SN Harmon, BA Paciesas, WS Fishman, GJ TI Deep search for celestial hard X-ray emission by earth occultation with BATSE/CGRO SO ASTRONOMY & ASTROPHYSICS SUPPLEMENT SERIES LA English DT Article; Proceedings Paper CT 3rd Compton Symposium CY JUN 12-14, 1995 CL MUNICH, GERMANY SP Max Planck Inst Extraterrestr Phys, Garching, Marx Planck Gesell, Deut Agentur Raumfahrtangelegenheiten, Deut Aerosp DE gamma-rays, observations; X-rays, stars; galaxies, active, Seyfert ID DISCOVERY AB As an important part of the BATSE/CGRO's Cycle 4 guest investigation effort, the BATSE team, in close collaboration with several guest investigators, have started a program to search for weak persistent emission (less than or similar to 5 mCrab) and transient events (less than or similar to 30 mCrab) from several classes of high energy astrophysical objects which were not previously detected by BATSE, including Seyfert II galaxies, X-ray binary neutron star systems (pulsars and X-ray bursters), black hole candidates and unidentified EGRET and COS-B sources. Earth occultation, occultation transform imaging and epoch folding techniques are used in this search effort. Preliminary results have shown positive detections from sources in most of the above listed classes. The search program and the preliminary results are briefly summarised in this paper. C1 NASA, GEORGE C MARSHALL SPACE FLIGHT CTR, HUNTSVILLE, AL 35812 USA. UNIV ALABAMA, DEPT PHYS, HUNTSVILLE, AL 35899 USA. RP UNIV SPACE RES ASSOC, HUNTSVILLE, AL 35806 USA. NR 16 TC 0 Z9 0 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 DEC PY 1996 VL 120 IS 4 SI SI BP C137 EP C140 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA WC063 UT WOS:A1996WC06300027 ER PT J AU Turner, TJ George, IM Kallman, T Yaqoob, T Zycki, PT AF Turner, TJ George, IM Kallman, T Yaqoob, T Zycki, PT TI Reprocessing models and the Advanced Satellite for Cosmology and Astrophysics spectrum of Markarian 290 SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies, individual (Markarian 290); galaxies, nuclei; radiation mechanisms, thermal; radiative transfer; X-rays, galaxies ID ACTIVE GALACTIC NUCLEI; X-RAY OBSERVATIONS; COLD MATTER; SEYFERT-GALAXIES; WARM ABSORBERS; ABSORPTION; MCG-6-30-15; REFLECTION; EMISSION; DISK AB We present the results from a 40 ks Advanced Satellite for Cosmology and Astrophysics observation of the Seyfert 1 galaxy Mrk 290. The source is found to have a complex spectral form, with emission and absorption features caused by oxygen and iron superimposed on an underlying power-law continuum with photon index similar to 1.9 Mrk 290 is also found to exhibit significant flux-correlated spectral variability, predominantly below 2 keV, on a timescale of similar to 5 x 10(4) s. The relatively strong spectral features observed in this source make it an interesting case to use for an investigation of models for reprocessing of the X-ray continuum by ionized material. We consider ionized reprocessors based on the XSTAR photoionization code for geometries in and out of the line of sight. Models in either geometry provide a vast improvement over a simple absorbed power-law model. The warm absorber/emitter model provides a good explanation of the overall spectral shape, with a column density of N-H,N-z* similar to 8 x 10(21) cm(-2) of ionized material (ionization parameter xi = 24) most likely within similar to 10(17) cm of the central source. While the data do not allow us to unambiguously determine the origin of the spectral variability, it is consistent with a drop of similar to 25% in flux accompanied by a proportional drop in the ionization state of the warm absorber. The intense K alpha line of equivalent width similar to 500 eV present in the source can be modeled as a broad Gaussian of FWHM similar to 0.5 keV, or by a line profile expected from the inner regions of a relativistic accretion disk inclined at similar to 30 degrees. In both cases, the rest-frame line energy is consistent with weakly ionized iron and cannot be explained by the warm emitter. An ionized reflector can also model the overall spectral shape, yielding xi(ref) similar to 80, although it has some difficulty simultaneously fitting both the iron K alpha line and the soft X-ray spectral features. This model offers no simple explanation for the observed spectral variability, and the intensity of the reflected component is greater than that expected from a semi-infinite slab illuminated by an isotropic source. A hybrid model featuring reprocessing in both the warm absorber/emitter and reflector may be the most realistic scenario. In this case, the preferred fit models the soft X-ray regime (and spectral variability) with the warm absorber/emitter and the iron K alpha line with a weakly ionized reflector (xi less than or similar to 20). C1 NICOLAUS COPERNICUS ASTRON CTR,PL-00716 WARSAW,POLAND. RP Turner, TJ (reprint author), NASA,GODDARD SPACE FLIGHT CTR,HIGH ENERGY ASTROPHYS LAB,CODE 660,GREENBELT,MD 20771, USA. NR 39 TC 8 Z9 8 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637 SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD DEC 1 PY 1996 VL 472 IS 2 BP 571 EP 581 DI 10.1086/178088 PN 1 PG 11 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VW210 UT WOS:A1996VW21000014 ER PT J AU Fich, M Terebey, S AF Fich, M Terebey, S TI IRAS observations of the outer galaxy .1. Discrete sources and large-scale (diffuse) emission SO ASTROPHYSICAL JOURNAL LA English DT Article DE dust, extinction; Galaxy, structure; H II regions; infrared, ISM, continuum; surveys ID H-II REGIONS; INFRARED-EMISSION; INTERSTELLAR-MEDIUM; PLANETARY-NEBULAE; MOLECULAR CLOUDS; POINT SOURCES; STARS; DUST; CATALOG; GAS AB The infrared emission in two fields of the outer Galaxy is analyzed using the IRAS image data. We present a census of discrete (but extended) IRAS sources, identified from the 60 mu m images. This sample can be used to characterize the properties of typical star-forming regions. We distinguish class A sources (Galactic star-forming regions) from other Galactic objects on the basis of their flux density distributions. However, our class A sources have different infrared colors than other star formation groups (young stellar objects [YSOs] and ultracompact H II regions), as measured by the IRAS Point Source Catalogue. The class A colors, in particular the high 12 mu m/25 mu m ratio, are similar to the color sequence found by Boulanger et al. for the O-star-excited California Nebula. They are also similar to the colors measured, on IRAS image products, for larger ''classical'' H II regions embedded in large molecular clouds. The similar infrared colors suggest that most class A sources are larger, lower density regions that sample a variety of local radiation held strengths. The infrared colors of class A sources are also found to match the colors of normal spiral galaxies. This suggests that a close correspondence exists between the physical conditions in outer Galaxy star-forming regions and normal spiral galaxies. The discrete sources have been carefully measured on IRAS Coadd images, and detailed comparisons are made with the results from other IRAS data products, especially with the Point Source Catalog (PSC). Great care has been taken to investigate the uncertainties associated with these measurements, and these results may be useful for other studies that make use of IRAS image products. Information from these measurements is combined with larger scale IRAS images to investigate the relative contributions of different components of the outer Galaxy to the total mid- and far-infrared emission. At 60 and 100 mu m, the diffuse emission (i.e., infrared cirrus) dominates the emission from the discrete sources, which include all possible sites of star formation. C1 CALTECH,JET PROP LAB,INFRARED PROC & ANAL CTR 10022,PASADENA,CA 91125. RP Fich, M (reprint author), UNIV WATERLOO,DEPT PHYS,GUELPH WATERLOO PROGRAM GRAD WORK PHYS,WATERLOO,ON N2L 3G1,CANADA. NR 50 TC 21 Z9 21 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637 SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD DEC 1 PY 1996 VL 472 IS 2 BP 624 EP 642 DI 10.1086/178093 PN 1 PG 19 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VW210 UT WOS:A1996VW21000019 ER PT J AU Cassen, P Woolum, DS AF Cassen, P Woolum, DS TI Radiatively damped density waves in optically thick protostellar disks SO ASTROPHYSICAL JOURNAL LA English DT Article DE accretion, accretion disks; circumstellar matter; hydrodynamics stars, formation; waves ID PRIMORDIAL SOLAR NEBULA; ACCRETION DISKS; PROPAGATION; EVOLUTION; PHYSICS AB The redistribution of angular momentum and mass in circumstellar disks by spiral density waves is governed by processes that dissipate the waves. Dissipation is usually attributed to unspecified nonlinear processes or an ad hoc viscosity. In this paper, we examine dissipation by radiative losses associated with the cyclic compression and expansion of disk material by the density waves. We consider linear, discrete modes in optically thick disks and use a simplified treatment of the radiative losses in order to assess the parameter dependences and importance of radiative damping. Wave action conservation principles are generalized to describe the effect of dissipation (by any means) and the consequent coupling of wave and disk energy and momenta. A relation is derived (in the WKBJ limit) between radial mass transport of disk: material and the azimuthally averaged dissipation rate. A wave amplitude equation is similarly derived, which describes the radial evolution of wave angular momentum, and therefore the radial deposition of angular momentum in the disk. Associated with the equation is a characteristic damping length, proportional to the cooling time from the base state temperature times the radial wave speed, and a factor that depends weakly on optical depth. The damping length is used to define, in terms of the disk base state temperature and surface density, regimes of strong and weak radiative damping. Waves in warm disks may be damped close to the resonances at which they are excited, while waves in cold disks can propagate to distances at which other dissipative mechanisms may dominate. It is found that the boundary between these regimes cuts across values that are thought to have characterized the primitive solar nebula. Thus both strong and weak radiative damping may be encountered in circumstellar disks in general. C1 CALIF STATE UNIV FULLERTON,DEPT PHYS,FULLERTON,CA 92634. RP Cassen, P (reprint author), NASA,AMES RES CTR,PLANETARY SYST SCI BRANCH,MOFFETT FIELD,CA 94035, USA. NR 23 TC 23 Z9 23 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637 SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD DEC 1 PY 1996 VL 472 IS 2 BP 789 EP 799 DI 10.1086/178107 PN 1 PG 11 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VW210 UT WOS:A1996VW21000033 ER PT J AU Sada, PV McCabe, GH Bjoraker, GL Jennings, DE Reuter, DC AF Sada, PV McCabe, GH Bjoraker, GL Jennings, DE Reuter, DC TI C-13-ethane in the atmospheres of Jupiter and Saturn SO ASTROPHYSICAL JOURNAL LA English DT Article DE infrared, solar system; molecular processes; planets and satellites, individual (Jupiter, Saturn) ID RADIO OCCULTATION MEASUREMENTS; FOURIER-TRANSFORM; C-12-C-13 RATIO; ETHANE; SPECTRA; BAND; IDENTIFICATION; SPECTROSCOPY; ABUNDANCES; C-13H4 AB High-resolution C-12- and C-13-ethane spectra of Jupiter and Saturn were acquired with the McMath-Pierce 60 inch (1.5 m) Telescope and Celeste, Goddard Space Flight Center's cryogenic grating spectrometer, in 1995 November and December. A relative abundance ratio C-12/C-13 of 91(-13)(+26) for Jupiter and 99(-23)(+43) for Saturn was derived from the measurements. These nearly terrestrial values suggest little or no fractionation of carbon isotopes in the atmospheres of Jupiter and Saturn. A weighted average of the available C-12/C-13 ratios for the outer planets yields 88+/-7, thus presenting no evidence for change in the carbon isotopic ratio between the presolar nebula and the present atmospheres of the outer planets. RP Sada, PV (reprint author), NASA,GODDARD SPACE FLIGHT CTR,PLANETARY SYST BRANCH,CODE 6932,GREENBELT,MD 20771, USA. RI Bjoraker, Gordon/D-5032-2012; Jennings, Donald/D-7978-2012 NR 29 TC 21 Z9 21 U1 0 U2 1 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637 SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD DEC 1 PY 1996 VL 472 IS 2 BP 903 EP 907 DI 10.1086/178120 PN 1 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VW210 UT WOS:A1996VW21000046 ER PT J AU Bernstein, MP Sandford, SA Allamandola, LJ AF Bernstein, MP Sandford, SA Allamandola, LJ TI Hydrogenated polycyclic aromatic hydrocarbons and the 2940 and 2850 wavenumber (3.40 and 3.51 micron) infrared emission features SO ASTROPHYSICAL JOURNAL LA English DT Article DE H II regions; infrared, ISM, lines and bands; ISM, molecules; molecular processes; planetary nebulae, general ID IRAS SOURCES; SPECTROSCOPY; MOLECULES; SPECTRUM; NGC-7027; NEBULAE; CATIONS AB The 3150-2700 cm(-1) (3.17-3.70 mu m) range of the spectra of a number of Ar-matrix-isolated PAHs containing excess H atoms (H-n-PAHs) are presented. This region covers features produced by aromatic and aliphatic C-H stretching vibrations as well as overtone and combination bands involving lower lying fundamentals. The aliphatic C-H stretches in molecules of this type having low to modest excess H coverage provide excellent fits to a number of the weak emission features superposed on the plateau between 3080 and 2700 cm(-1) (3.25 and 3.7 mu m) in the spectra of many planetary nebulae, reflection nebulae, and H II regions. Higher H coverage is implied for a few objects. We compare these results in context with the other suggested identifications of the emission features in the 2950-2700 cm(-1) (3.39-3.70 mu m) region and briefly discuss their astrophysical implications. RP Bernstein, MP (reprint author), NASA,AMES RES CTR,ASTROPHYS BRANCH,MAIL STOP 245-6,MOFFETT FIELD,CA 94035, USA. NR 24 TC 85 Z9 85 U1 0 U2 2 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637 SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD DEC 1 PY 1996 VL 472 IS 2 BP L127 EP L130 DI 10.1086/310376 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VW211 UT WOS:A1996VW21100016 PM 11541245 ER PT J AU Heckler, AF Kolb, EW AF Heckler, AF Kolb, EW TI Searching for stellar mass black holes in the solar neighborhood SO ASTROPHYSICAL JOURNAL LA English DT Article DE accretion, accretion disks; black hole physics; dark matter; galaxy, halo; galaxy, solar neighborhood ID DARK-MATTER; ACCRETION AB We propose a search strategy for isolated stellar mass black holes in the solar neighborhood using information from the Sloan Digital Sky Survey. Accretion of the interstellar medium onto an isolated black hole is expected to result in a blended, thermal synchrotron spectrum, roughly flat from the optical to the far-infrared. We find that the Sloan Survey will be sensitive to isolated black holes in the range 1-100 M. out to a few hundred parsecs. We find that multiband photometry can distinguish black holes from field stars, with black holes having colors similar to QSOs. The holes may then be isolated from QSOs because they have a featureless spectrum with no emission lines. The Sloan Survey will likely find hundreds of objects that meet these criteria, and to reduce the number of candidates we suggest other selection criteria such as infrared observations and proper-motion measurements. If no black hole candidates are found in this survey, important limits can be placed on the local density of black holes and the halo fraction in black holes. RP Heckler, AF (reprint author), FERMILAB NATL ACCELERATOR LAB,NASA,FERMILAB ASTROPHYS CTR,BATAVIA,IL 60510, USA. RI Heckler, Andrew/A-7291-2010 OI Heckler, Andrew/0000-0001-5494-7855 NR 21 TC 10 Z9 10 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637 SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD DEC 1 PY 1996 VL 472 IS 2 BP L85 EP L88 DI 10.1086/310362 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VW211 UT WOS:A1996VW21100006 ER PT J AU Landsman, JB Sweigart, AV Bohlin, RC Neff, SG OConnell, RW Roberts, MS Smith, AM Stecher, TP AF Landsman, JB Sweigart, AV Bohlin, RC Neff, SG OConnell, RW Roberts, MS Smith, AM Stecher, TP TI Ultraviolet imagery of NGC 6752: A test of extreme horizontal branch models SO ASTROPHYSICAL JOURNAL LA English DT Article DE globular clusters, individual (NGC 6752); stars, horizontal-branch; ultraviolet, stars ID GLOBULAR-CLUSTERS; ELLIPTIC GALAXIES; PHOTOMETRY; NGC-6752; STARS AB We present a 1620 Angstrom image of the nearby globular cluster NGC 6752 obtained with the Ultraviolet Imaging Telescope (UIT) during the Astro-2 mission of the Space Shuttle Endeavour in 1995 March. An ultraviolet-visible color-magnitude diagram (CMD) is derived for 216 stars matched with the visible photometry of Buonanno et al. This CMD provides a nearly complete census of the hot horizontal-branch (HB) population with good temperature and luminosity discrimination for comparison with theoretical tracks. The observed data show good agreement with the theoretical zero-age horizontal branch (ZAHB) of Sweigart for an assumed reddening of E(B-V) = 0.05 and a distance modulus of 13.05. The observed HB luminosity width is in excellent agreement with the theoretical models and supports the single-star scenario for the origin of extreme horizontal branch (EHB) stars. However, only four stars can be identified as post-EHB stars, whereas almost three times this many are expected from the HB number counts. If this effect is not a statistical anomaly, then some noncanonical effect may be decreasing the post-EHB lifetime. The recent noncanonical models of Sweigart, which have helium-enriched envelopes due to mixing along the red giant branch, cannot explain the deficit of post-EHB stars, but might be better able to explain their luminosity distribution. C1 SPACE TELESCOPE SCI INST,BALTIMORE,MD 21218. UNIV VIRGINIA,DEPT ASTRON,CHARLOTTESVILLE,VA 22903. NATL RADIO ASTRON OBSERV,CHARLOTTESVILLE,VA 22903. RP Landsman, JB (reprint author), NASA,GODDARD SPACE FLIGHT CTR,ASTRON & SOLAR PHYS LAB,HUGHES STX CORP,CODE 681,GREENBELT,MD 20771, USA. NR 26 TC 27 Z9 27 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637 SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD DEC 1 PY 1996 VL 472 IS 2 BP L93 EP & DI 10.1086/310368 PN 2 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VW211 UT WOS:A1996VW21100008 ER PT J AU Tarn, TJ Xi, N Bejczy, AK AF Tarn, TJ Xi, N Bejczy, AK TI Path-based approach to integrated planning and control for robotic systems SO AUTOMATICA LA English DT Article DE robot control; event-based motion planning; task-level control; system integration; intelligent ID MANIPULATORS AB Our newly developed event-based planning and control theory is applied to robotic systems. It introduces a suitable action or motion reference variable other than time, but directly related to the desired and measurable system output, called event. Here the event is the length of the path tracked by a robot. It enables the construction of an integrated planning and control system where planning becomes a real-time closed-loop process. The path-based integration planning and control scheme is exemplified by a single-arm tracking problem. Time and energy optimal motion plans combined with nonlinear feedback control are derived in closed form. To the best of our knowledge, this closed-form solution was not obtained before. The equivalence of path-based and time-based representations of nonlinear feedback control is shown, and an overall system stability criterion has also been obtained. The application of event-based integrated planning and control provides the robotic systems the capability to cope with unexpected and uncertain events in real time, without the need for replanning. The theoretical results are illustrated and verified by experiments. Copyright (C) 1996 Elsevier Science Ltd. C1 CALTECH, JET PROP LAB, PASADENA, CA 91109 USA. RP WASHINGTON UNIV, CTR ROBOT & AUTOMAT,CAMPUS BOX 1040,CUPPLES 2, ROOM 103, 1 BROOKINGS DR, ST LOUIS, MO 63130 USA. NR 29 TC 38 Z9 39 U1 1 U2 3 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0005-1098 EI 1873-2836 J9 AUTOMATICA JI Automatica PD DEC PY 1996 VL 32 IS 12 BP 1675 EP 1687 DI 10.1016/S0005-1098(96)80004-5 PG 13 WC Automation & Control Systems; Engineering, Electrical & Electronic SC Automation & Control Systems; Engineering GA WE358 UT WOS:A1996WE35800005 ER PT J AU Rosekind, MR Gander, PH Gregory, KB Smith, RM Miller, DL Oyung, R Webbon, LL Johnson, JM AF Rosekind, MR Gander, PH Gregory, KB Smith, RM Miller, DL Oyung, R Webbon, LL Johnson, JM TI Managing fatigue in operational settings .1. Physiological considerations and countermeasures SO BEHAVIORAL MEDICINE LA English DT Article DE alertness; circadian rhythms; fatigue countermeasures; performance; safety; sleep ID SLEEP AB The authors consider three aspects of managing fatigue in the workplace. They provide a brief overview of important scientific finding related to sleep and circadian physiology that establish the psychobiological foundation of fatigue. Their major focus is on the relevance of these findings to operational settings. In addition, they provide examples to describe practical fatigue countermeasures that can be used in operational settings. C1 SAN JOSE STATE UNIV FDN,SAN JOSE,CA. STERLING SOFTWARE,PALO ALTO,CA. RP Rosekind, MR (reprint author), NASA,AMES RES CTR,FLIGHT MANAGEMENT & HUMAN FACTORS DIV,FATIGUE COUNTERMEASURES PROGRAM,MS 262,MOFFETT FIELD,CA 94035, USA. NR 40 TC 29 Z9 31 U1 0 U2 2 PU HELDREF PUBLICATIONS PI WASHINGTON PA 1319 EIGHTEENTH ST NW, WASHINGTON, DC 20036-1802 SN 0896-4289 J9 BEHAV MED JI Behav. Med. PD WIN PY 1996 VL 21 IS 4 BP 157 EP 165 PG 9 WC Behavioral Sciences; Psychiatry SC Behavioral Sciences; Psychiatry GA UG885 UT WOS:A1996UG88500001 PM 8731492 ER PT J AU Rosekind, MR Gander, PH Gregory, KB Smith, RM Miller, DL Oyung, R Webbon, LL Johnson, JM AF Rosekind, MR Gander, PH Gregory, KB Smith, RM Miller, DL Oyung, R Webbon, LL Johnson, JM TI Managing fatigue in operational settings .2. An integrated approach SO BEHAVIORAL MEDICINE LA English DT Article DE aviation; fatigue; healthcare professions; scheduling AB The six domains that must be addressed in managing fatigue in operational settings are identified and examples of how the aviation industry is dealing with the problems in each domain are given. Challenges facing healthcare providers in managing fatigue are also discussed. C1 SAN JOSE STATE UNIV FDN,SAN JOSE,CA. STERLING SOFTWARE,PALO ALTO,CA. RP Rosekind, MR (reprint author), NASA,AMES RES CTR,MOFFETT FIELD,CA 94035, USA. NR 7 TC 13 Z9 14 U1 0 U2 0 PU HELDREF PUBLICATIONS PI WASHINGTON PA 1319 EIGHTEENTH ST NW, WASHINGTON, DC 20036-1802 SN 0896-4289 J9 BEHAV MED JI Behav. Med. PD WIN PY 1996 VL 21 IS 4 BP 166 EP 170 PG 5 WC Behavioral Sciences; Psychiatry SC Behavioral Sciences; Psychiatry GA UG885 UT WOS:A1996UG88500002 PM 8731493 ER PT J AU Vernikos, J AF Vernikos, J TI Human physiology in space SO BIOESSAYS LA English DT Article ID BED REST; BONE-FORMATION; SPACEFLIGHT; SYSTEM; MICROGRAVITY; FLIGHT; WEIGHTLESSNESS; RESPONSES; REFLEX; TISSUE AB The universality of gravity (1g) in our daily lives makes it difficult to appreciate its importance in morphology and physiology. Bone and muscle support systems were created, cellular pumps developed, neurons organised and receptors and transducers of gravitational force to biologically relevant signals evolved under 1g gravity. Spaceflight provides the only microgravity environment where systematic experimentation can expand our basic understanding of gravitational physiology and perhaps provide new insights into normal physiology and disease processes. These include the surprising extent of our body's dependence on perceptual information, and understanding the effect and importance of forces generated within the body's weightbearing structures such as muscle and bones. Beyond this exciting prospect is the importance of this work towards opening the solar system for human exploration. Although both appear promising, we are only just beginning to taste what lies ahead. RP Vernikos, J (reprint author), NASA,WASHINGTON,DC 20546, USA. NR 50 TC 46 Z9 48 U1 1 U2 10 PU COMPANY OF BIOLOGISTS LTD PI CAMBRIDGE PA BIDDER BUILDING CAMBRIDGE COMMERCIAL PARK COWLEY RD, CAMBRIDGE, CAMBS, ENGLAND CB4 4DL SN 0265-9247 J9 BIOESSAYS JI Bioessays PD DEC PY 1996 VL 18 IS 12 BP 1029 EP 1037 DI 10.1002/bies.950181215 PG 9 WC Biochemistry & Molecular Biology; Biology SC Biochemistry & Molecular Biology; Life Sciences & Biomedicine - Other Topics GA VX691 UT WOS:A1996VX69100014 PM 8976162 ER PT J AU Morris, PA Domeier, M Stephens, J AF Morris, PA Domeier, M Stephens, J TI Notes on the occurrence and depth distribution of the bat ray in the Southern California Bight, with comments on the effect of trawl size on estimates of abundance SO CALIFORNIA FISH AND GAME LA English DT Article ID MYLIOBATIS-CALIFORNICA; ELKHORN SLOUGH RP Morris, PA (reprint author), NATL MARINE FISHERIES SERV,501 W OCEAN BLVD,SUITE 4470,LONG BEACH,CA 90802, USA. NR 13 TC 1 Z9 1 U1 0 U2 0 PU CALIF FISH AND GAME EDITOR PI SACRAMENTO PA 1416 NINTH ST, SACRAMENTO, CA 95814 SN 0008-1078 J9 CALIF FISH GAME JI Calif. Fish Game PD WIN PY 1996 VL 82 IS 1 BP 48 EP 53 PG 6 WC Fisheries; Zoology SC Fisheries; Zoology GA VU975 UT WOS:A1996VU97500003 ER PT J AU Sterling, T Merkey, P Savarese, D AF Sterling, T Merkey, P Savarese, D TI Improving application performance on the HP/Convex Exemplar SO COMPUTER LA English DT Article AB The Earth and space sciences community faces rich computational challenges ranging from static, regular, and embarrassingly parallel to dynamic, unstructured, and tightly coupled. This problem domain requires highly scalable systems exhibiting broad generality, efficiency, and programmability. These capabilities are appearing in the emerging scalable shared memory cache-coherent architectures like that of the HP/Convex Exemplar SPP-1000. The goal of this class of architecture is to make scientific programming as easy and efficient as it is on vector supercomputers. The authors describe the Exemplar's architecture, whose global system organization comprises up to 16 multiprocessors interconnected by four SCI (Scalable Coherent Interface) ring networks. They then present the findings from four applications: the piecewise parabolic method, a finite-element method for unstructured meshes, a tree code for the n-body problem, and a particle-in-cell code. The authors present application performance data derived after the Exemplar at Goddard Space Flight Center went into production use. These studies expose the operational properties of the Exemplar and determine its suitability for Earth and space sciences applications. The testing reveals that global cache coherence can be used effectively to simplify programming and data migration. However, the basic problem of locality sensitivity still demands direct programmer involvement to achieve effective system behavior. The question of whether message-passing or shared memory programming models are better remains open. C1 CALTECH,JET PROP LAB,HIGH PERFORMANCE COMP SYST GRP,PASADENA,CA 91125. UNIV MARYLAND,COLLEGE PK,MD 20742. NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. RP Sterling, T (reprint author), CALTECH,CTR ADV COMP RES,MAIL CODE 158-79,12000 E CALIF BLVD,PASADENA,CA 91125, USA. NR 8 TC 3 Z9 3 U1 0 U2 0 PU IEEE COMPUTER SOC PI LOS ALAMITOS PA 10662 LOS VAQUEROS CIRCLE, PO BOX 3014, LOS ALAMITOS, CA 90720-1264 SN 0018-9162 J9 COMPUTER JI Computer PD DEC PY 1996 VL 29 IS 12 BP 50 EP & DI 10.1109/MC.1996.546609 PG 7 WC Computer Science, Hardware & Architecture; Computer Science, Software Engineering SC Computer Science GA VX483 UT WOS:A1996VX48300014 ER PT J AU Wasfy, TM Noor, AK AF Wasfy, TM Noor, AK TI Modeling and sensitivity analysis of multibody systems using new solid, shell and beam elements SO COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING LA English DT Article ID DYNAMIC ANALYSIS; FLEXIBLE BEAMS; RECURSIVE FORMULATION; LARGE DISPLACEMENT; TRANSIENT ANALYSIS; LOOP SYSTEMS; MANIPULATORS; MECHANISMS; ROTATIONS; MOTIONS AB A computational procedure is presented for predicting the dynamic response and evaluating the sensitivity coefficients of large, flexible multibody systems consisting of beams, shells and solids undergoing arbitrary spatial motions. The sensitivity coefficients measure the sensitivity of the dynamic response to variations in the material, geometric and external force parameters of the system. The four key components of the procedure are: a) new beam, shell and solid elements with the Cartesian coordinates selected as degrees of freedom and with continuous inter-element slopes; b) a corotational frame approach used in conjunction with a total Lagrangian formulation; c) semi-explicit temporal integration for generating the dynamic response; and d) direct differentiation approach for evaluating the sensitivity coefficients. The nonlinear interactions between the elastic and the large rigid body motions are naturally incorporated in the present formulation. The effectiveness of the procedure is demonstrated through numerical examples, including an articulated space structure consisting of beams, shells and revolute joints. C1 UNIV VIRGINIA, NASA, LANGLEY RES CTR, CTR ADV COMPUTAT TECHNOL, HAMPTON, VA 23681 USA. NR 46 TC 27 Z9 28 U1 0 U2 2 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 DEC 1 PY 1996 VL 138 IS 1-4 BP 187 EP 211 DI 10.1016/S0045-7825(96)01113-9 PG 25 WC Engineering, Multidisciplinary; Mathematics, Interdisciplinary Applications; Mechanics SC Engineering; Mathematics; Mechanics GA VY459 UT WOS:A1996VY45900006 ER PT J AU Hosni, YA Safford, R Barth, TS Osborne, D Stomayor, T AF Hosni, YA Safford, R Barth, TS Osborne, D Stomayor, T TI Knowledge based quality system in support of space shuttle operations SO COMPUTERS & INDUSTRIAL ENGINEERING LA English DT Article; Proceedings Paper CT 18th International Conference on Computers and Industrial Engineering (ICC&IE 95) CY OCT 25-27, 1995 CL SHANGHAI, PEOPLES R CHINA SP Comp & Ind Engn, Chinese Mech Engn Soc DE statistical process control; continuous improvement; expert system; space shuttle AB In an attempt to use statistical variable data for process improvement at Kennedy Space Center (KSC), statistical quality control is being introduced in the shop floor for use by technicians and engineers. An Expert System is proposed to support this effort. The system has a component for process improvement, which uses a process capability index to suggest continuos process improvement to reduce cost and duration of the process. C1 NASA,KSC,OPERAT ANAL OFF,WASHINGTON,DC. RP Hosni, YA (reprint author), UNIV CENT FLORIDA,ORLANDO,FL 32816, USA. NR 10 TC 0 Z9 0 U1 1 U2 2 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, ENGLAND OX5 1GB SN 0360-8352 J9 COMPUT IND ENG JI Comput. Ind. Eng. PD DEC PY 1996 VL 31 IS 3-4 BP 767 EP 773 DI 10.1016/S0360-8352(96)00239-2 PG 7 WC Computer Science, Interdisciplinary Applications; Engineering, Industrial SC Computer Science; Engineering GA VU109 UT WOS:A1996VU10900044 ER PT J AU Tang, YY Noor, AK Xu, K AF Tang, YY Noor, AK Xu, K TI Assessment of computational models for thermoelectroelastic multilayered plates SO COMPUTERS & STRUCTURES LA English DT Article ID LAMINATED PIEZOELECTRIC PLATES; 3-DIMENSIONAL SOLUTIONS; ACTUATORS; ELEMENTS; SENSORS; DESIGN; PANELS AB A study is made of the accuracy of the steady-state (static) thermoelectroelastic response of multilayered hybrid composite plates predicted by five modeling approaches, based on two-dimensional plate theories. The plates consist of a combination of fibre-reinforced and piezothermoelastic layers. The standard of comparison is taken to be the exact three-dimensional thermoelectroelastic solutions, and the quantities compared include gross response characteristics (e.g. strain energy components, and average through-the-thickness displacements); detailed, through-the-thickness distributions of displacements and stresses; and sensitivity coefficients of the response quantities (derivatives of the response quantities with respect to material parameters of the plate). The modeling approaches considered include first-order theory; third-order theory; discrete-layer theory (with piecewise linear variation of the in-plane displacements, temperature and electric potential, in the thickness direction); and two predictor-corrector procedures. Both procedures use first-order theory in the predictor phase, but differ in the elements of the computational model being adjusted in the corrector phase. The first procedure adjusts the transverse shear stiffnesses of the plate and the second procedure corrects the functional dependence of the displacements on the thickness coordinate. The corrected quantities are then used in conjunction with the three-dimensional equations to obtain better estimates for the different response quantities and their sensitivity coefficients. Numerical results are presented for nine-layer plates consisting of eight graphite epoxy layers and one piezothermoelastic layer, subjected to transverse mechanical loading, temperature change and electric potential. Based on the numerical studies conducted, the second predictor-corrector approach appears to be the most accurate among the five modeling approaches considered. For multilayered hybrid composite plates, the detailed response quantities, and sensitivity coefficients obtained by this approach are shown to be in close agreement with the exact three-dimensional thermoelectroelastic solutions for a wide range of the thickness parameter. Published by Elsevier Science Ltd. C1 UNIV VIRGINIA,NASA,LANGLEY RES CTR,CTR ADV COMPUTAT TECHNOL,HAMPTON,VA 23681. NR 18 TC 65 Z9 65 U1 0 U2 2 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, ENGLAND OX5 1GB SN 0045-7949 J9 COMPUT STRUCT JI Comput. Struct. PD DEC PY 1996 VL 61 IS 5 BP 915 EP 933 DI 10.1016/0045-7949(96)00037-5 PG 19 WC Computer Science, Interdisciplinary Applications; Engineering, Civil SC Computer Science; Engineering GA VN443 UT WOS:A1996VN44300012 ER PT J AU Sogard, SM Olla, BL AF Sogard, SM Olla, BL TI Diel patterns of behavior in juvenile walleye pollock, Theragra chalcogramma SO ENVIRONMENTAL BIOLOGY OF FISHES LA English DT Article DE fish behavior; vertical distribution; activity; schooling ID EASTERN BERING SEA; VERTICAL-DISTRIBUTION; FISH; FOOD; ABUNDANCE; ALASKA; LIGHT; FACILITATION; THERMOCLINES; PREDATOR AB In laboratory experiments, we contrasted the behavior of juvenile walleye pollock under dark and light conditions, comparing group cohesion, activity levels, vertical distribution, and movement into cold water when the water column was thermally stratified. At night the fish displayed a tendency for movement into the upper water column and were less active, with groups more dispersed than during the day. Time spent in cold water under stratified conditions did not differ between day and night. These results are interpreted relative to the potential ecological benefits and costs of particular behaviors, and their application in designing effective sampling surveys of juvenile abundances. RP Sogard, SM (reprint author), OREGON STATE UNIV,HATFIELD MARINE SCI CTR,NATL MARINE FISHERIES SERV,ALASKA FISHERIES SCI CTR,NEWPORT,OR 97365, USA. NR 35 TC 26 Z9 26 U1 1 U2 7 PU KLUWER ACADEMIC PUBL PI DORDRECHT PA SPUIBOULEVARD 50, PO BOX 17, 3300 AA DORDRECHT, NETHERLANDS SN 0378-1909 J9 ENVIRON BIOL FISH JI Environ. Biol. Fishes PD DEC PY 1996 VL 47 IS 4 BP 379 EP 386 DI 10.1007/BF00005051 PG 8 WC Ecology; Marine & Freshwater Biology SC Environmental Sciences & Ecology; Marine & Freshwater Biology GA VV176 UT WOS:A1996VV17600005 ER PT J AU Murphy, KD Virgin, LN Rizzi, SA AF Murphy, KD Virgin, LN Rizzi, SA TI Experimental snap-through boundaries for acoustically excited, thermally buckled plates SO EXPERIMENTAL MECHANICS LA English DT Article ID EQUATION AB This paper presents some recent experimental results on the dynamic snap-through behavior of a clamped, rectangular plate subject to thermal loading and intense acoustic excitation, The likelihood of snap-through oscillations is characterized in terms of boundaries separating regions of snap-through and no snap-through in the parameter space, Two scenarios are considered, First, using tonal inputs, the regions of snap-through are mapped in the sound pressure level-input frequency domain ((SPL, omega) plane). Second, random acoustic inputs are used, and the effect of varying the overall sound pressure level and frequency bandwidth are investigated ((SPL, omega(centar)<(omega)over bar>) plane). Several nonlinear characteristics are evident and discussed. C1 DUKE UNIV,DEPT MECH ENGN,DURHAM,NC 27703. NASA,LANGLEY RES CTR,STRUCT ACOUST BRANCH,HAMPTON,VA 23681. RP Murphy, KD (reprint author), UNIV NEBRASKA,DEPT MECH ENGN,LINCOLN,NE 68588, USA. NR 14 TC 21 Z9 21 U1 1 U2 6 PU SOC EXPERIMENTAL MECHANICS PI BETHEL PA 7 SCHOOL STREET, BETHEL, CT 06801 SN 0014-4851 J9 EXP MECH JI Exp. Mech. PD DEC PY 1996 VL 36 IS 4 BP 312 EP 317 DI 10.1007/BF02328572 PG 6 WC Materials Science, Multidisciplinary; Mechanics; Materials Science, Characterization & Testing SC Materials Science; Mechanics GA VW708 UT WOS:A1996VW70800003 ER PT J AU Lehner, DL Richter, AG Matthys, DR Gilbert, JA AF Lehner, DL Richter, AG Matthys, DR Gilbert, JA TI Characterization of the panoramic annular lens SO EXPERIMENTAL MECHANICS LA English DT Article AB The panoramic annular lens (PAL) consists of a single piece of glass, with spherical surfaces, that produces a flat annular image of the entire 360-deg surround of the optical axis of the lens. This paper describes the attributes of the PAL and shows that the lens maps elements from object to image space via a constant aspect ratio polar mapping. A panoramic video system (PVS) is described to illustrate how the characterization can be applied in experimental mechanics for cavity inspection and measurement. C1 NORTHWESTERN UNIV,DEPT PHYS,EVANSTON,IL 60208. MARQUETTE UNIV,DEPT PHYS,MILWAUKEE,WI 53233. UNIV ALABAMA,DEPT AEROSP ENGN,HUNTSVILLE,AL 35899. RP Lehner, DL (reprint author), NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,OPT FABRICAT BRANCH,HUNTSVILLE,AL 35812, USA. NR 7 TC 7 Z9 7 U1 0 U2 3 PU SOC EXPERIMENTAL MECHANICS PI BETHEL PA 7 SCHOOL STREET, BETHEL, CT 06801 SN 0014-4851 J9 EXP MECH JI Exp. Mech. PD DEC PY 1996 VL 36 IS 4 BP 333 EP 338 DI 10.1007/BF02328575 PG 6 WC Materials Science, Multidisciplinary; Mechanics; Materials Science, Characterization & Testing SC Materials Science; Mechanics GA VW708 UT WOS:A1996VW70800006 ER PT J AU Lei, JF Castelli, MG Androjna, D Blue, C Blue, R Lin, RY AF Lei, JF Castelli, MG Androjna, D Blue, C Blue, R Lin, RY TI Comparison testings between two high-temperature strain measurement systems SO EXPERIMENTAL MECHANICS LA English DT Article AB An experimental evaluation was conducted at NASA Lewis Research Center to compare and contrast the performance of a newly developed resistance strain gage, the PdCr temperature-compensated wire strain gage, to that of a conventional high-temperature extensometry, The evaluation of the two strain measurement systems was conducted through the application of various thermal and mechanical loading spectra using a high-temperature thermomechanical uniaxial testing system equipped with quartz lamp heating. The purpose of the testing was not only to compare and contrast the two strain sensors but also to investigate the applicability of the PdCr strain gage to the testing environment typically employed when characterizing the high-temperature mechanical behavior of structural materials, Strain measurement capabilities to 800 degrees C were investigated with a nickel base superalloy IN100 substrate material, and application to titanium matrix composite (TMC) materials was examined with the SCS-6/Ti-15-3 [0](8) system, PdCr strain gages installed by three attachment techniques-namely, flame spraying, spot welding and rapid infrared joining-were investigated. C1 NASA,LEWIS RES CTR,NYMA INC,CLEVELAND,OH 44135. NASA,LEWIS RES CTR,GILCREST,CLEVELAND,OH 44135. UNIV CINCINNATI,DEPT MAT SCI & ENGN,CINCINNATI,OH 45221. RP Lei, JF (reprint author), NASA,LEWIS RES CTR,CLEVELAND,OH 44135, USA. NR 5 TC 3 Z9 3 U1 0 U2 3 PU SOC EXPERIMENTAL MECHANICS PI BETHEL PA 7 SCHOOL STREET, BETHEL, CT 06801 SN 0014-4851 J9 EXP MECH JI Exp. Mech. PD DEC PY 1996 VL 36 IS 4 BP 430 EP 435 DI 10.1007/BF02328588 PG 6 WC Materials Science, Multidisciplinary; Mechanics; Materials Science, Characterization & Testing SC Materials Science; Mechanics GA VW708 UT WOS:A1996VW70800019 ER PT J AU Furuya, M Chao, BF AF Furuya, M Chao, BF TI Estimation of period and Q of the Chandler wobble SO GEOPHYSICAL JOURNAL INTERNATIONAL LA English DT Article DE atmospheric angular momentum; Chandler wobble; period; polar motion; Q-factor ID POLAR MOTION; EXCITATION AB The period P and Q-value of the Chandler wobble are two fundamental functionals of the Earth's internal physical properties and global geodynamics. We revisit the problem of the estimation of P and Q, using 10.8 yr of modern polar motion as well as contemporary atmospheric angular momentum (AAM) data. We make full use of the knowledge that AAM is a major broad-band excitation source for the polar motion. We devise two optimization criteria under the assumption that, after removal of coherent seasonal and long-period signals, the non-AAM excitation is uncorrelated with the AAM. The procedures lead to optimal estimates for P and Q. Our best estimates, judging from comprehensive sets of Monte Carlo simulations, are P = 433.7 +/- 1.8 (1 sigma) days, Q = 49 with a 1 sigma range of (35, 100). In the process we also obtain (as a by-product) an estimate of roughly 0.8 for a 'mixing ratio' of the inverted-barometer (IB) effect in the AAM pressure term, indicating that the ocean behaves nearly as IB in polar motion excitation on temporal scales from months to years C1 NASA,GODDARD SPACE FLIGHT CTR,TERR PHYS LAB,GREENBELT,MD 20771. RP Furuya, M (reprint author), UNIV TOKYO,DEPT EARTH & PLANETARY PHYS,TOKYO 113,JAPAN. RI Furuya, Masato/E-1296-2011; Chao, Benjamin Fong/N-6156-2013 OI Furuya, Masato/0000-0002-5638-5048; NR 30 TC 33 Z9 36 U1 0 U2 0 PU BLACKWELL SCIENCE LTD PI OXFORD PA OSNEY MEAD, OXFORD, OXON, ENGLAND OX2 0EL SN 0956-540X J9 GEOPHYS J INT JI Geophys. J. Int. PD DEC PY 1996 VL 127 IS 3 BP 693 EP 702 DI 10.1111/j.1365-246X.1996.tb04047.x PG 10 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA VY056 UT WOS:A1996VY05600011 ER PT J AU Wu, DL Waters, JW AF Wu, DL Waters, JW TI Satellite observations of atmospheric variances: A possible indication of gravity waves SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID MIDDLE ATMOSPHERE; POLAR VORTEX; CLIMATOLOGY; VARIABILITY AB The Microwave Limb Sounder (MCS) on the Upper Atmosphere Research Satellite has now produced the first global maps of small-scale variances in the middle atmosphere. Initial analyses are presented here that suggest these variances are due to gravity waves, and the technique used to extract gravity wave information from saturated radiance measurements is described. Observations at 30-80km altitudes show that the variances of horizontal scales less than similar to 100km are strongly correlated with upper tropospheric convection, surface topography and stratospheric jetstreams. MLS monthly averages during solstice periods suggest that the normalized variance amplitude grows exponentially with height in the stratosphere, and saturates in the mesosphere as expected from wave breaking and dissipation at these altitudes. RP Wu, DL (reprint author), CALTECH,JET PROP LAB,4800 OAK GROVE DR,MAIL STOP 183-701,PASADENA,CA 91109, USA. RI Wu, Dong/D-5375-2012 NR 24 TC 116 Z9 117 U1 2 U2 7 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD DEC 1 PY 1996 VL 23 IS 24 BP 3631 EP 3634 DI 10.1029/96GL02907 PG 4 WC Geosciences, Multidisciplinary SC Geology GA VW859 UT WOS:A1996VW85900029 ER PT J AU Randerson, JT Thompson, MV Malmstrom, CM Field, CB Fung, IY AF Randerson, JT Thompson, MV Malmstrom, CM Field, CB Fung, IY TI Substrate limitations for heterotrophs: Implications for models that estimate the seasonal cycle of atmospheric CO2 SO GLOBAL BIOGEOCHEMICAL CYCLES LA English DT Article ID HIGH-RESOLUTION RADIOMETER; NDVI DATA SET; NITROGEN DYNAMICS; CARBON-DIOXIDE; LITTER DECOMPOSITION; ORGANIC-MATTER; PRIMARY PRODUCTIVITY; PHOSPHORUS DYNAMICS; VEGETATION INDEX; AIR-TEMPERATURE AB We examine the sensitivity of the seasonal cycle of heterotrophic respiration to model estimates of litterfall seasonality, herbivory, plant allocation, tissue chemistry, and land use. As a part of this analysis, we compare heterotrophic respiration models based solely on temperature and soil moisture controls (zero-order models) with models that depend on available substrate as well (first-order models). As indicators of regional and global CO2 exchange, we use maps of monthly global net ecosystem production, growing season net flux (GSNF), and simulated atmospheric CO2 concentrations from an atmospheric tracer transport model. In one first-order model, CASA, variations on the representation of the seasonal flow of organic matter from plants to heterotrophs can increase global GSNF as much as 60% (5.7 Pg C yr(-1)) above estimates obtained from a zero-order model. Under a new first-order scheme that includes separate seasonal dynamics for leaf litterfall, fine root mortality, coarse woody debris, and herbivory, we observe an increase in GSNF of 8% (0.7 Pg C yr(-1)) over that predicted by the zero-order model. The increase in seasonality of CO2 exchange in first-order models reflects the dynamics of labile litter fractions; specifically, the rapid decomposition of a pulse of labile leaf and fine root litter that enters the heterotrophic community primarily from the middle to the end of the growing season shifts respiration outside the growing season. From the perspective of a first-order model, we then explore the consequences of land use change and winter temperature anomalies on the amplitude of the seasonal cycle of atmospheric CO2. Agricultural practices that accelerate decomposition may drive a long-term increase in the amplitude, independent of human impacts on plant production. Consideration of first-order litter decomposition dynamics may also help explain year-to-year variation in the amplitude. C1 UNIV VICTORIA,SCH EARTH & OCEAN SCI,VICTORIA,BC VSW 2Y2,CANADA. STANFORD UNIV,DEPT BIOL SCI,STANFORD,CA 94305. STANFORD UNIV,DEPT PLANT BIOL,STANFORD,CA 94305. NASA,GODDARD INST SPACE STUDIES,NEW YORK,NY 10025. RP Randerson, JT (reprint author), CARNEGIE INST WASHINGTON,DEPT PLANT BIOL,290 PANAMA ST,STANFORD,CA 94305, USA. NR 91 TC 63 Z9 65 U1 1 U2 16 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 SN 0886-6236 J9 GLOBAL BIOGEOCHEM CY JI Glob. Biogeochem. Cycle PD DEC PY 1996 VL 10 IS 4 BP 585 EP 602 DI 10.1029/96GB01981 PG 18 WC Environmental Sciences; Geosciences, Multidisciplinary; Meteorology & Atmospheric Sciences SC Environmental Sciences & Ecology; Geology; Meteorology & Atmospheric Sciences GA VV175 UT WOS:A1996VV17500003 ER PT J AU Hou, TH Wilkinson, SP Johnston, NJ Pater, RH Schneider, TL AF Hou, TH Wilkinson, SP Johnston, NJ Pater, RH Schneider, TL TI Processing and properties of IM7/LARC(TM)-RP46 polyimide composites SO HIGH PERFORMANCE POLYMERS LA English DT Article AB LARC(TM)-RP46 resin system is a PMR type polyimide and is prepared by replacing methylenedianiline in the PMR-15 composition with 3,4'-oxydianiline. This resin system retains the same processing characteristics as PMR-15 but also offers enhanced fracture toughness. Rheological measurements were conducted on pre-imidized LARC(TM)-RP46 moulding powder subjected to various ramp and hold temperature schemes. Adequate flow properties were found with theoretical (formulated) molecular weight less than or equal to 1500 g mol(-1). Critical transition temperatures for optimizing the process cycle were identified. They included the resin softening point, the imidization reaction peak, the isomerization reaction peak and the gelation point. Utilizing this information, 1.72 x 10(6) Pa (250 psi) cure cycles were designed for B-staged (dry) and unstaged (wet) prepregs. Composite laminates were fabricated which exhibited excellent consolidation and a void content below 0.1-0.2% as measured by image analysis. IM7/LARC(TM)-RP46 exhibited higher composite mechanical properties than IM7/PMR-15. Short-beam shear strength, flexural strength and flexural modulus were measured at room temperature, 93, 150 and 177 degrees C. Composite engineering properties were also obtained including longitudinal tension, logitudinal compression, interlaminar shear, short block compression, open hole compression (OHC) and compression strength after impact (CAI). Excellent longitudinal tensile and compressive strengths were obtained and the CAI strength was 40% higher than that for PMR-15. Over 80% retention of all RT strength were noted at 177 degrees C. C1 LOCKHEED ENGN & SCI CO,HAMPTON,VA 23666. COLL WILLIAM & MARY,WILLIAMSBURG,VA 23518. NASA,LANGLEY RES CTR,HAMPTON,VA 23681. ROHR INC,R&D,RIVERSIDE,CA. NR 17 TC 18 Z9 20 U1 0 U2 6 PU IOP PUBLISHING LTD PI BRISTOL PA DIRAC HOUSE, TEMPLE BACK, BRISTOL, ENGLAND BS1 6BE SN 0954-0083 J9 HIGH PERFORM POLYM JI High Perform. Polym. PD DEC PY 1996 VL 8 IS 4 BP 491 EP 505 DI 10.1088/0954-0083/8/4/002 PG 15 WC Polymer Science SC Polymer Science GA WB675 UT WOS:A1996WB67500002 ER PT J AU Hinkley, JA Jensen, BJ AF Hinkley, JA Jensen, BJ TI Crosslinking in phenylethynyl-terminated polyimides SO HIGH PERFORMANCE POLYMERS LA English DT Article ID NETWORKS; POLYMERS AB Stress relaxation of cured phenylethynyl-terminated polyimides was used to estimate their equilibrium rubbery moduli. The corresponding concentrations of elastically effective chains derived from classical rubber elasticity theory were less than one-fifth what would be expected if every chain end participated in a crosslink. A model is proposed to allow the calculation of the average crosslink functionalities. C1 NASA,LANGLEY RES CTR,COMPOSITES & POLYMERS BRANCH,HAMPTON,VA 23681. NR 13 TC 23 Z9 24 U1 1 U2 6 PU IOP PUBLISHING LTD PI BRISTOL PA DIRAC HOUSE, TEMPLE BACK, BRISTOL, ENGLAND BS1 6BE SN 0954-0083 J9 HIGH PERFORM POLYM JI High Perform. Polym. PD DEC PY 1996 VL 8 IS 4 BP 599 EP 605 DI 10.1088/0954-0083/8/4/008 PG 7 WC Polymer Science SC Polymer Science GA WB675 UT WOS:A1996WB67500008 ER PT J AU Bryant, RG AF Bryant, RG TI LaRC(TM)-SI: A soluble aromatic polyimide SO HIGH PERFORMANCE POLYMERS LA English DT Article AB LaRC(TM)-SI (NASA Langley Research Center-Soluble polylmide) is a wholly aromatic, high-performance thermoplastic with a unique combination of physical, mechanical and adhesive properties. LaRC(TM)-SI is synthesized from equimolar amounts of the dianhydrides 4,4'-oxydiphthalic anhydride (ODPA) and 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA); 3,4'-oxydianiline (3,4'-ODA) and phthalic anhydride (PA) as an endcapping reagent. The most unique property of LaRC(TM)-SI is its initial solubility in conventional high-boiling aprotic solvents. However, when exposed to temperatures above its softening point of 250 degrees C it becomes insoluble yet retains its melt processability. This allows LaRC(TM)-SI to be solution processed as both a polyamic acid and a polyimide. In addition to this solubility characteristic and high softening point, LaRC(TM)-SI is extremely tough and fracture resistant with G(1c) and K-1c values of 4.6 kJ m(-2) and 4.4 MN m(-3/2) respectively. As a melt extruded film, LaRC(TM)-SI has been used asa hot melt adhesive to bond titanium and aluminium with lap shear strengths for titanium and cleavage strengths for aluminium exceeding 43 MPa and 16.9 MPa respectively at 23 degrees C. C1 NASA,LANGLEY RES CTR,HAMPTON,VA 23681. NR 16 TC 34 Z9 35 U1 0 U2 6 PU IOP PUBLISHING LTD PI BRISTOL PA DIRAC HOUSE, TEMPLE BACK, BRISTOL, ENGLAND BS1 6BE SN 0954-0083 J9 HIGH PERFORM POLYM JI High Perform. Polym. PD DEC PY 1996 VL 8 IS 4 BP 607 EP 615 DI 10.1088/0954-0083/8/4/009 PG 9 WC Polymer Science SC Polymer Science GA WB675 UT WOS:A1996WB67500009 ER PT J AU Chang, ATC Foster, JL Hall, DK AF Chang, ATC Foster, JL Hall, DK TI Effects of forest on the snow parameters derived from microwave measurements during the Boreas Winter Field Campaign SO HYDROLOGICAL PROCESSES LA English DT Article; Proceedings Paper CT 53rd Eastern Snow Conference CY MAY, 1996 CL WILLIAMSBURG, VA DE forest; snow parameters; microwave measurements; BOREAS; snow water equivalent ID WATER EQUIVALENT; MOUNTAIN BASIN; SATELLITE DATA; SMMR DATA; ALASKA; REMOTE AB Passive microwave data have been used to infer the areal snow water equivalent (SWE) with some success. However, the accuracy of these retrieved SWE values have not been well determined for heterogeneous vegetated regions. The Boreal Ecosystem-Atmosphere Study (BOREAS) Winter Field Campaign (WFC), which took place in February 1994, provided the opportunity to study in detail the effects of boreal forests on snow parameter retrievals. Preliminary results reconfirmed the relationship between microwave brightness temperature and snow water equivalent. The pronounced effect of forest cover on SWE retrieval was studied. A modified vegetation mixing algorithm is proposed to account for the forest cover. The relationship between the microwave signature and observed snowpack parameters matches results from this model. RP Chang, ATC (reprint author), NASA, GODDARD SPACE FLIGHT CTR, HYDROL SCI BRANCH, LAB HYDROSPHER PROC, GREENBELT, MD 20771 USA. RI Hall, Dorothy/D-5562-2012 NR 31 TC 49 Z9 53 U1 2 U2 11 PU WILEY-BLACKWELL PI MALDEN PA COMMERCE PLACE, 350 MAIN ST, MALDEN 02148, MA USA SN 0885-6087 J9 HYDROL PROCESS JI Hydrol. Process. PD DEC PY 1996 VL 10 IS 12 BP 1565 EP 1574 DI 10.1002/(SICI)1099-1085(199612)10:12<1565::AID-HYP501>3.0.CO;2-5 PG 10 WC Water Resources SC Water Resources GA WG090 UT WOS:A1996WG09000003 ER PT J AU Nolan, MC Asphaug, E Melosh, HJ Greenberg, R AF Nolan, MC Asphaug, E Melosh, HJ Greenberg, R TI Impact craters on asteroids: Does gravity or strength control their size? SO ICARUS LA English DT Article ID FRAGMENTATION; SIMULATIONS AB The formation of kilometer-size craters on asteroids is qualitatively different from the formation of meter-size (laboratory- and weapons-scale) craters on Earth. A numerical hydrocode model is used to examine the outcomes of various-size cratering impacts into spheres and half-spaces. A shock wave fractures the target in advance of the crater excavation flow; thus, for impactors larger than 100 m, impacting at typical asteroid impact velocities, target tensile strength is irrelevant to the impact outcome. This result holds whether the target is initially intact or a ''rubble pile,'' even ignoring the effects of gravity. Because of the shock-induced fracture, crater excavation is controlled by gravity at smaller sizes than would otherwise be predicted. Determining the strength-gravity transition by comparing the physical strength of the material to the force of gravity will not work, because strength is eliminated by the shock wave. (C) 1996 Academic Press, Inc. C1 UNIV ARIZONA,LUNAR & PLANETARY LAB,TUCSON,AZ 85721. NASA,AMES RES CTR,MOFFETT FIELD,CA 94035. RI Nolan, Michael/H-4980-2012 OI Nolan, Michael/0000-0001-8316-0680 NR 27 TC 47 Z9 47 U1 0 U2 4 PU ACADEMIC PRESS INC JNL-COMP SUBSCRIPTIONS PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 SN 0019-1035 J9 ICARUS JI Icarus PD DEC PY 1996 VL 124 IS 2 BP 359 EP 371 DI 10.1006/icar.1996.0214 PG 13 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA WC129 UT WOS:A1996WC12900001 ER PT J AU Yeomans, DK Yau, KK Weissman, PR AF Yeomans, DK Yau, KK Weissman, PR TI The impending appearance of comet Tempel-Tuttle and the Leonid meteors SO ICARUS LA English DT Article ID MOTION AB Using the available observations in 1699, 1865-1866, and 1965, an orbit has been recomputed for periodic comet 55P/Tempel-Tuttle, the parent body of the Leonid meteors. The comet's motion was numerically integrated back in time for two millennia and ephemerides were computed for each perihelion return. Chinese observations of the comet in 1366 are well represented, and possible (but not definite) observations of the comet in October 1234 and January 1035 have been identified. The Leonid meteors have been observed since AD 902. Prior to the eighth century, no Leonid meteors should have been visible because the comet's orbit passed too far outside that of the Earth. By using previously recorded accounts of the Leonid meteor showers and storms as a guide, predictions for the forthcoming Leonid displays in November of 1996-1999 are provided. The 1998 and 1999 events hold the most promise for an impressive Leonid meteor display, although there seems little likelihood that the great storms of 1833 and 1966 will be repeated at this apparition. (C) 1996 Academic Press, Inc. RP Yeomans, DK (reprint author), CALTECH,JET PROP LAB,PASADENA,CA 91125, USA. NR 37 TC 71 Z9 74 U1 0 U2 0 PU ACADEMIC PRESS INC JNL-COMP SUBSCRIPTIONS PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 SN 0019-1035 J9 ICARUS JI Icarus PD DEC PY 1996 VL 124 IS 2 BP 407 EP 413 DI 10.1006/icar.1996.0218 PG 7 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA WC129 UT WOS:A1996WC12900005 ER PT J AU Liou, JC Zook, HA Dermott, SF AF Liou, JC Zook, HA Dermott, SF TI Kuiper belt dust grains as a source of interplanetary dust particles SO ICARUS LA English DT Article ID POYNTING-ROBERTSON DRAG; RESTRICTED 3-BODY PROBLEM; SHORT-PERIOD COMETS; SOLAR-SYSTEM; ASTEROIDAL DUST; ZODIACAL DUST; DISCOVERY; RING; RESONANCES; CAPTURE AB The recent discovery of the so-called Kuiper belt objects has prompted the idea that these objects produce dust grains that may contribute significantly to the interplanetary dust population. In this paper, the orbital evolution of dust grains, of diameters 1 to 9 mu m, that originate in the region of the Kuiper belt is studied by means of direct numerical integration. Gravitational forces of the Sun and planets, solar radiation pressure, as well as Poynting-Robertson drag and solar wind drag are included. The interactions between charged dust grains and solar magnetic field are not considered in the model. Because of the effects of drag forces, small dust grains will spiral toward the Sun once they are released from their large parent bodies. This motion leads dust grains to pass by planets as well as encounter numerous mean motion resonances associated with planets. Our results show that about 80% of the Kuiper belt grains are ejected from the Solar System by the giant planets, while the remaining 20% of the grains evolve all the way to the Sun. Surprisingly, the latter dust grains have small orbital eccentricities and inclinations when they cross the orbit of the Earth. This makes them behave more like asteroidal than cometary-type dust particles. This also enhances their chances of being captured by the Earth and makes them a possible source of the collected interplanetary dust particles; in particular, they represent a possible source that brings primitive/organic materials from the outer Solar System to the Earth. When collisions with interstellar dust grains are considered, however, Kuiper belt dust grains around 9 mu m appear likely to be collisionally shattered before they can evolve toward the inner part of the Solar System. The collision destruction can be applied to Kuiper belt grains up to about 50 mu m. Therefore, Kuiper belt dust grains within this range may not be a significant part of the interplanetary dust complex in the inner Solar System. (C) 1996 Academic Press, Inc. C1 UNIV FLORIDA, DEPT ASTRON, GAINESVILLE, FL 32611 USA. RP Liou, JC (reprint author), NASA, LYNDON B JOHNSON SPACE CTR, SN3, HOUSTON, TX 77058 USA. NR 47 TC 68 Z9 69 U1 1 U2 1 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 DEC PY 1996 VL 124 IS 2 BP 429 EP 440 DI 10.1006/icar.1996.0220 PG 12 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA WC129 UT WOS:A1996WC12900007 ER PT J AU Vilas, F Sykes, MV AF Vilas, F Sykes, MV TI Are low-albedo asteroids thermally metamorphosed? SO ICARUS LA English DT Article ID CCD REFLECTANCE SPECTRA; OUTER-BELT; WATER; SPECTROPHOTOMETRY; HYDRATION; BODIES; AL-26; IRON AB Arguments have been made that the surfaces of the C-, G-, B-, and F-class asteroids have been thermally metamorphosed at temperatures ranging from 600 to 1000 degrees C (Hiroi, T., C. M. Pieters, M. E. Zolensky, and M. E. Lipschutz 1993. Science 261, 1016-1018). These arguments are based on similarities between the strength of a UV/blue absorption feature and the general spectral shape from 1.0 to 2.5 mu m in spectra of these asteroids and spectra of three CI/CM carbonaceous chondrites showing compositional signs of thermal metamorphism. Many of these asteroids exhibit a spectral feature centered at 0.7 mu m associated with the presence of iron-bearing phyllosilicates, products of an aqueous alteration process. This feature vanishes in the spectra of CM2 carbonaceous chondrite samples heated to temperatures greater than or equal to 400 degrees C, contradicting the conclusion that the surface material of these asteroids was last heated to higher temperatures. The presence and distribution of this spectral feature among the low-albedo asteroids places some constraints on the thermal environment in the early Solar System. A weak correlation of the presence of this feature with asteroid diameter suggests that the asteroid heating that occurred shortly after their formation was due to a mechanism having a dependency on both heliocentric distance and size. (C) 1996 Academic Press, Inc. C1 UNIV ARIZONA,STEWARD OBSERV,TUCSON,AZ 85721. RP Vilas, F (reprint author), NASA,LYNDON B JOHNSON SPACE CTR SN3,HOUSTON,TX 77058, USA. NR 39 TC 26 Z9 26 U1 0 U2 0 PU ACADEMIC PRESS INC JNL-COMP SUBSCRIPTIONS PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 SN 0019-1035 J9 ICARUS JI Icarus PD DEC PY 1996 VL 124 IS 2 BP 483 EP 489 DI 10.1006/icar.1996.0224 PG 7 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA WC129 UT WOS:A1996WC12900011 ER PT J AU Buratti, BJ Hiller, JK Wang, M AF Buratti, BJ Hiller, JK Wang, M TI The lunar opposition surge: Observations by Clementine SO ICARUS LA English DT Article ID OUTER PLANET SATELLITES; COHERENT BACKSCATTER; PHOTOMETRY; DISK AB The Clementine mission to the Moon in 1994 provided the first multispectral observations of the lunar opposition surge below a few degrees. The brightness of the Moon increases more than 40% between solar phase angles of 4 degrees and 0 degrees. The opposition effect exhibits a small wavelength dependence: the surge is similar to 3-4% larger at 0.41 mu m than at 1.00 mu m. This result suggests that the principal cause of the lunar opposition surge is shadow hiding, while coherent backscatter, if present, makes only a minor contribution. The amplitude of the effect depends significantly on terrain: the surge is about 10% greater in the lunar highlands. This difference is attributed to textural variations between the two terrains. The Clementine measurements provide a new basis for deriving spectral geometric albedos, phase integrals, and Bond albedos. A value of 0.11 +/- 0.01 was found for the lunar bolometric Band albedo. This value is at the low end of the historical published values, but not as low as the recent result of 0.080 +/- 0.002. (C) 1996 Academic Press, Inc. RP Buratti, BJ (reprint author), CALTECH,JET PROP LAB,4800 OAK GROVE DR,MS 183-501,PASADENA,CA 91109, USA. NR 37 TC 75 Z9 77 U1 0 U2 2 PU ACADEMIC PRESS INC JNL-COMP SUBSCRIPTIONS PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 SN 0019-1035 J9 ICARUS JI Icarus PD DEC PY 1996 VL 124 IS 2 BP 490 EP 499 DI 10.1006/icar.1996.0225 PG 10 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA WC129 UT WOS:A1996WC12900012 ER PT J AU Taylor, LA Patchen, A Taylor, DHS Chambers, JG McKay, DS AF Taylor, LA Patchen, A Taylor, DHS Chambers, JG McKay, DS TI X-ray digital imaging petrography of lunar mare soils: Modal analyses of minerals and glasses SO ICARUS LA English DT Article ID REFLECTANCE; PETROLOGY AB It is essential that accurate modal (i.e., volume) percentages of the various mineral and glass phases in lunar soils be used for addressing and resolving the effects of space weathering upon reflectance spectra, as well as for their calibration such data are also required for evaluating the resource potential of lunar minerals far use at a lunar base. However, these data are largely tacking. Particle-counting information for lunar soils, originally obtained to study formational processes, does not provide these necessary data, including the percentages of minerals locked in multi-phase lithic fragments and fused-soil particles, such as agglutinates. We have developed a technique for modal analyses, sensu stricto, of lunar soils, using digital imaging of X-ray maps obtained with an energy-dispersive spectrometer mounted on an electron microprobe. A suite of nine soils (90 to 150 mu m size fraction) from the Apollo 11, 12, 15, and 17 mare sites was used for this study. This is the first collection of such modal data on soils from all Apollo mare sites. The abundances of free-mineral fragments in the mare soils are greater for immature and submature soils than for mature soils, largely because of the formation of agglutinitic glass as maturity progresses. In considerations of resource utilization at a lunar base, the best; lunar soils to use for mineral benefication (i.e., most free-mineral fragments) have maturities near the immature/submature boundary (I-s/FeO congruent to 30), not the mature soils with their complications due to extensive agglutination. The particle data obtained from the nine mare sons confirm the generalizations for lunar soils predicted by L. A. Taylor and D. S. McKay. (C) 1996 Academic Press, Inc. C1 NASA, LYNDON B JOHNSON SPACE CTR, HOUSTON, TX 77058 USA. RP Taylor, LA (reprint author), UNIV TENNESSEE, PLANETARY GEOSCI INST, KNOXVILLE, TN 37996 USA. NR 53 TC 53 Z9 54 U1 1 U2 7 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 DEC PY 1996 VL 124 IS 2 BP 500 EP 512 DI 10.1006/icar.1996.0226 PG 13 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA WC129 UT WOS:A1996WC12900013 PM 11539387 ER PT J AU Krasnopolsky, VA Mumma, MJ Bjoraker, GL Jennings, DE AF Krasnopolsky, VA Mumma, MJ Bjoraker, GL Jennings, DE TI Oxygen and carbon isotope ratios in Martian carbon dioxide: Measurements and implications for atmospheric evolution SO ICARUS LA English DT Article ID MARS VOLATILE EVOLUTION; SNC METEORITES; THERMAL STRUCTURE; ESCAPE; WATER; CO2; FRACTIONATION; IMPACTS; SPECTRA; CLIMATE AB Our measurements of high-resolution spectra of Mars at 3.7 and 8 mu m revealed 200 lines of (OCO)-O-16-C-12-O-17, (OCO)-O-16-C-12-O-18, and (OCO)-O-16-C-13-O-18 isotopes. Among them are 38 lines which are absent in spectroscopic databases, Eighty lines of the three isotopes with closely equivalent widths were chosen to determine the oxygen and carbon isotope ratios in CO2. A radiation transfer code which coupled the reflected solar and thermal radiation was developed, This code divided the atmosphere into 30 layers and the Voigt profile of each line in each layer into 60 intervals. This results in a determination of the atmospheric pressure P-0 = 7.4 +/- 0.4 mbar and the isotope ratios O-18/O-17 = 0.914 +/- 0.04 and C-13/C-12 = 0.94 +/- 0.15 scaled to CO2 in the Earth's atmosphere. Scaling to SMOW gives O-18/O-17 = 0.93 +/- 0.04; assuming the same initial isotope ratio on Mars and Earth, we find that O-18/O-16 = 0.87 +/- 0.08 in CO2 on Mars. Oxygen and carbon isotope fractionation factors of 0.774 and 0.891 in the escape processes were calculated using individual heights of homopauses for different species. Oxygen and carbon isotope ratios are determined by the present water amount, the regolith-atmosphere-cap reservoir of CO2, the carbonate abundance, the initial abundance of CO2, and losses of H2O and CO2 by escape processes. Two processes affect the carbon isotope ratio in the atmosphere: formation of carbonates and sputtering of CO2. This ratio was calculated as a function of the CO2 sputtering after the end of impact erosion of the atmosphere at 0.8 byr. A weighted-mean value of C-13/C-12 = 0.97 +/- 0.05 (scaled to PDB) for three measurements in the martian atmosphere and determinations of the carbon isotope ratio in carbonates of the SNC meteorites require CO2 escape by sputtering to be smaller than 10 mbar. The oxygen isotope ratio could be depleted in water early in the history of Mars by water-silicate equilibrium; this does not contradict the isotopic composition of the SNC meteorites, Fractionation with CO2 and loss of CO2 by impact erosion depleted heavy oxygen in water as well. We calculated delta(18)O approximate to -70 parts per thousand in water vapor for preferred values of the initial CO2 of 7.5 bars, water escape of 30 m, and the present water ice reservoir of 500 m, Taking into account uncertainities of these values by a factor of 2-3, the expected minimum value of delta(18)O in water vapor is close to -110 parts per thousand and does not agree with some recent determinations. Heavy oxygen in CO2 should either be equal to that in water vapor (in the case of photochemical mixing) or exceed that in water vapor by 90 parts per thousand (in the case of thermodynamic equilibrium). Currently the calculated values of delta(18)O may serve as a guide to measured values which show large scatter and uncertainties. (C) 1996 Academic Press, Inc. RP NASA, GODDARD SPACE FLIGHT CTR, EXTRATERR PHYS LAB, CODE 693, GREENBELT, MD 20771 USA. RI Bjoraker, Gordon/D-5032-2012; Jennings, Donald/D-7978-2012; mumma, michael/I-2764-2013; Krasnopolsky, Vladimir/L-5085-2013 NR 55 TC 25 Z9 26 U1 0 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 EI 1090-2643 J9 ICARUS JI Icarus PD DEC PY 1996 VL 124 IS 2 BP 553 EP 568 DI 10.1006/icar.1996.0230 PG 16 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA WC129 UT WOS:A1996WC12900017 ER PT J AU Sato, M Travis, LD Kawabata, K AF Sato, M Travis, LD Kawabata, K TI Photopolarimetry analysis of the Venus atmosphere in polar regions SO ICARUS LA English DT Article ID VOLCANIC ACTIVITY; LIGHT-SCATTERING; PIONEER-VENUS; CLOUDS; POLARIZATION; MISSIONS; ACID AB An analysis of linear polarization in the north and south polar regions of Venus observed by the Pioneer Venus orbiter during the first 2820 days of its mission has been performed to find microphysical properties of the submicrometer particles and to investigate the temporal variation of the optical thickness of the haze layer. The search for the best values of the physical properties and vertical distribution of the haze particles is based on minimization of the RMS discrepancy between the computed theoretical polarization and observed polarization, under the assumption that the variation of the observed polarization is due to the temporal variation of the optical thickness of the haze layer. This approach allows us to use a simple model which can explain well general features of the angular distribution of polarization for a large number of maps at wavelengths 935, 550, and 365 nm. We find that in the north polar region the haze particles have effective radius 0.25 +/- 0.05 mu m, effective variance 0.25 +/- 0.05, and real part of the refractive index 1.435 +/- 0.02 at wavelength 550 mm. In the south polar region, the haze particles have effective radius 0.29 +/- 0.02 mu m, effective variance 0.25 +/- 0.03, and real part of the refractive index 1.45 +/- 0.02 at wavelength 550 mm. Temporal variations of optical thickness of the haze particles in both polar regions seem to exhibit short-period quasi-oscillation features and our present analysis suggests some correlation between the variation in optical thickness of the haze layer in the north and south polar regions. (C) 1996 Academic Press, Inc. C1 SCI UNIV TOKYO,DEPT PHYS,SHINJUKU KU,TOKYO 162,JAPAN. RP Sato, M (reprint author), NASA,GODDARD INST SPACE STUDIES,SSAI,2880 BROADWAY,NEW YORK,NY 10025, USA. NR 52 TC 23 Z9 23 U1 0 U2 0 PU ACADEMIC PRESS INC JNL-COMP SUBSCRIPTIONS PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 SN 0019-1035 J9 ICARUS JI Icarus PD DEC PY 1996 VL 124 IS 2 BP 569 EP 585 DI 10.1006/icar.1996.0231 PG 17 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA WC129 UT WOS:A1996WC12900018 ER PT J AU Smith, MD Conrath, BJ Pearl, JC Ustinov, EA AF Smith, MD Conrath, BJ Pearl, JC Ustinov, EA TI Retrieval of atmospheric temperatures in the Martian planetary boundary layer using upward-looking infrared spectra SO ICARUS LA English DT Article ID RADIO OCCULTATION MEASUREMENTS; MARS; MARINER-9; SPECTROSCOPY; TOPOGRAPHY; MOISTURE; PROFILES; CLOUDS AB We present an algorithm for the retrieval of temperature in the planetary boundary layer (lowest few kilometers) of the martian atmosphere using upward-looking infrared spectra from a Mars lander. Temperature profiles retrieved from an orbiting or passing spacecraft do not have adequate vertical resolution to provide significant information within the planetary boundary layer. By using spectra taken from a surface lander looking upward toward zenith, and by transforming to a vertical coordinate that ''stretches out'' the atmosphere just above the surface where the contribution to the observed radiation peaks, we find that an efficient algorithm can be formulated with adequate vertical resolution to successfully retrieve temperature profiles that exhibit the major features of the diurnal cycle of planetary boundary layer temperatures. We expect that this technique can be extended to simultaneously retrieve the opacity, and possibly the scattering properties, of atmospheric aerosols as well. Although no upward-looking martian infrared spectra yet exist, demonstration of the abilities of a lander-based infrared spectrometer is important for the planning of future missions to Mars. (C) 1996 Academic Press, Inc. C1 CORNELL UNIV,DEPT ASTRON,ITHACA,NY 14853. RP Smith, MD (reprint author), NASA,GODDARD SPACE FLIGHT CTR,NRC,CODE 693,GREENBELT,MD 20771, USA. RI Smith, Michael/C-8875-2012; Ustinov, Eugene/D-1350-2015 OI Ustinov, Eugene/0000-0003-0227-4286 NR 35 TC 6 Z9 6 U1 1 U2 2 PU ACADEMIC PRESS INC JNL-COMP SUBSCRIPTIONS PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 SN 0019-1035 J9 ICARUS JI Icarus PD DEC PY 1996 VL 124 IS 2 BP 586 EP 597 DI 10.1006/icar.1996.0232 PG 12 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA WC129 UT WOS:A1996WC12900019 ER PT J AU Smith, MD Conrath, BJ Gautier, D AF Smith, MD Conrath, BJ Gautier, D TI Dynamical influence on the isotopic enrichment of CH3D in the outer planets SO ICARUS LA English DT Article ID EFFECTIVE TEMPERATURE; MOIST CONVECTION; ENERGY-BALANCE; SOLAR-SYSTEM; HYDROGEN; JUPITER; WATER; ATMOSPHERES; ABUNDANCE; VOYAGER-2 AB We investigate the influence of atmospheric dynamics on the isotopic enrichment factor of monodeuterated methane, f(z) = (D/H)(CH4)/(D/H)(H2), in the outer planets. We explore the influence of dynamics using three classes of models. In the first two, we briefly discuss the simple approaches that have previously been used to account for dynamics in the determination of f(z). We discuss the strengths and limitations of these approximations. Then, we combine the best portions of the first two models to produce a third model that we feel more realistically describes mixing on the outer planets. Using different limiting assumptions about convective vertical velocities inside the outer planets, we place rough upper and lower limits on possible values of the isotopic enrichment factor at a pressure level of 1 bar for each planet. We find that the isotopic enrichment factor in the observable regions of the outer planets is sensitive to the dynamical model and parameters that are assumed, and thus a measured value of f(z) in the upper, observable levels of the atmosphere could constrain the dynamical regime at deeper levels. (C) 1996 Academic Press C1 OBSERV PARIS,DESPA,F-92195 MEUDON,FRANCE. RP Smith, MD (reprint author), NASA,GODDARD SPACE FLIGHT CTR,NRC,CODE 693,GREENBELT,MD 20771, USA. RI Smith, Michael/C-8875-2012 NR 24 TC 16 Z9 16 U1 0 U2 1 PU ACADEMIC PRESS INC JNL-COMP SUBSCRIPTIONS PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 SN 0019-1035 J9 ICARUS JI Icarus PD DEC PY 1996 VL 124 IS 2 BP 598 EP 607 DI 10.1006/icar.1996.0233 PG 10 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA WC129 UT WOS:A1996WC12900020 ER PT J AU Noll, KS Geballe, TR Knacke, RF Pendleton, YJ AF Noll, KS Geballe, TR Knacke, RF Pendleton, YJ TI Titan's 5 mu m spectral window: Carbon monoxide and the albedo of the surface SO ICARUS LA English DT Article ID VOYAGER INFRARED OBSERVATIONS; ATMOSPHERE; ABUNDANCE; CALLISTO; VARIABILITY; REGION; SEAS; CO AB We have measured the spectrum of Than near 5 mu m and have found it to be dominated by absorption from the carbon monoxide 1-0 vibration-rotation band. The position of the band edge allows us to constrain the abundance of CO in the atmosphere and/or the location of the reflecting layer in the atmosphere. In the most likely case, 5 mu m radiation is reflected from the surface and the mole fraction of CO in the atmosphere is qCO = 10(-5)(+10) ppm, significantly lower than previous estimates for tropospheric CO. The albedo of the reflecting layer is approximately 0.07(-0.01)(+0.02) in the 5 mu m continuum outside the CO band, The 5 mu m albedo is consistent with a surface of mixed ice and silicates similar to the icy Galilean satellites, Organic solids formed in simulated Titan conditions can also produce Similar albedos at 5 mu m. (C) 1996 Academic Press, Inc. C1 JOINT ASTRON CTR,HILO,HI 96720. PENN STATE UNIV,ERIE,PA 16563. NASA,AMES RES CTR,MOFFETT FIELD,CA 94035. RP Noll, KS (reprint author), SPACE TELESCOPE SCI INST,3700 SAN MARTIN DR,BALTIMORE,MD 21218, USA. RI Noll, Keith/C-8447-2012 NR 39 TC 32 Z9 32 U1 0 U2 0 PU ACADEMIC PRESS INC JNL-COMP SUBSCRIPTIONS PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 SN 0019-1035 J9 ICARUS JI Icarus PD DEC PY 1996 VL 124 IS 2 BP 625 EP 631 DI 10.1006/icar.1996.0236 PG 7 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA WC129 UT WOS:A1996WC12900023 PM 11539388 ER PT J AU Horn, LJ Showalter, MR Russell, CT AF Horn, LJ Showalter, MR Russell, CT TI Detection and behavior of Pan wakes in Saturn's A ring SO ICARUS LA English DT Article ID RADIO OCCULTATION; ENCKE GAP; PLANETARY RINGS; SATELLITE WAKES; VOYAGER-1; FEATURES; MOONLET; EDGES AB Six previously unseen Pan wakes are found interior and exterior to the Encke gap in Saturn's A ring, one in the Voyager 2 photopolarimeter (PPS) stellar occultation data and five in the Voyager 1 radio science (RSS) earth occultation data. Pan orbits at the center of the Encke gap and maintains it. Originally it was hypothesized that a wake would be completely damped by the time it reached a longitude of 360 degrees relative to Pan. However, five of the six newly detected wakes are at longitudes in excess of 360 degrees and are a result of earlier encounters with Pan. The sixth is the first detection of the RSS outer Pan wake, The new PPS inner wake is at a longitude of 389.8 degrees. The new RSS inner wakes are at longitudes of 519.4 degrees +/- 1.6 degrees and 879.4 degrees +/- 1.6 degrees. The RSS outer wakes are at longitudes of 200.6 degrees +/- 1.6 degrees, 560.6 degrees +/- 1.6 degrees, and 920.6 degrees +/- 1.6 degrees. Because of the time needed for a wake to develop after encountering Pan, the higher order wakes (longitude >360 degrees) can be more prominent than their lower order counterparts which are superimposed at the same location. The radial dispersion behavior of the Pan wakes are characterized using a Burg autoregressive power spectral algorithm. The wake radial wavelength behavior is compared to a simple model which ignores collisions and self-gravity, The four wakes with longitudes below 360 degrees show an average deviation of 0-3% from the predicted wavelengths, indicative of the strength of collective effects. The detection of Pan wakes at longitudes greater than 360 degrees demonstrates that wakes persist for much longer than originally hypothesized and may interact with one another, The presence and characteristics of these wakes will provide an important test of kinetic theory models. (C) 1996 Academic Press, Inc. C1 STANFORD UNIV,CTR RADAR ASTRON,STANFORD,CA 94305. UNIV CALIF LOS ANGELES,INST GEOPHYS & PLANETARY PHYS,LOS ANGELES,CA 90024. RP Horn, LJ (reprint author), CALTECH,JET PROP LAB,4800 OAK GROVE DR,M-S 183-501,PASADENA,CA 91109, USA. NR 19 TC 13 Z9 13 U1 0 U2 0 PU ACADEMIC PRESS INC JNL-COMP SUBSCRIPTIONS PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 SN 0019-1035 J9 ICARUS JI Icarus PD DEC PY 1996 VL 124 IS 2 BP 663 EP 676 DI 10.1006/icar.1996.0240 PG 14 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA WC129 UT WOS:A1996WC12900027 ER PT J AU Anderson, JD Jurgens, RF Lau, EL Slade, MA AF Anderson, JD Jurgens, RF Lau, EL Slade, MA TI Shape and orientation of mercury from radar ranging data SO ICARUS LA English DT Article ID HARMONIC-ANALYSIS; TOPOGRAPHY; MASS; MARS AB If Mercury's radius is expanded in Legendre functions to the second degree and order, the systematic error in radar ranging can be reduced significantly. We interpret the expansion coefficients in terms of a best-fit ellipsoid displaced with respect to the center of mass in the equatorial plane, The ellipsoid's principal axes are rotated in the equatorial plane such that the long axis is aligned with cartographic longitude 15.3 degrees +/- 2.9 degrees (west). The pole location is consistent with the IAU pole, normal to Mercury's orbital plane. There is a significant equatorial ellipticity (a - b)/a = (540 +/- 54) x 10(-6). The center of figure is offset from the center of mass (C.F.-C.M.) by 640 +/- 78 m in the equatorial plane in the direction of cartographic longitude 319.5 degrees +/- 6.9 degrees. The magnitude of the equatorial center of figure offset implies an excess crustal thickness of 12 km or less, comparable to the Moon's excess. By comparing the equatorial ellipticity with the Mariner 10 gravity coefficient <(C)over bar (22)> and assuming Airy isostatic compensation, we conclude that Mercury's crustal thickness is in the range from 100 to 300 km. (C) 1996 Academic Press, Inc. C1 UNIV CALIF LOS ANGELES,INST GEOPHYS & PLANETARY PHYS,DEPT EARTH & SPACE SCI,LOS ANGELES,CA 90095. RP Anderson, JD (reprint author), CALTECH,JET PROP LAB,4800 OAK GROVE DR,PASADENA,CA 91109, USA. NR 29 TC 38 Z9 39 U1 0 U2 0 PU ACADEMIC PRESS INC JNL-COMP SUBSCRIPTIONS PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 SN 0019-1035 J9 ICARUS JI Icarus PD DEC PY 1996 VL 124 IS 2 BP 690 EP 697 DI 10.1006/icar.1996.0242 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA WC129 UT WOS:A1996WC12900029 ER PT J AU Dobrovolskis, AR AF Dobrovolskis, AR TI Inertia of any polyhedron SO ICARUS LA English DT Article ID GEOMETRIC-PROPERTIES; CHAOTIC ROTATION; OBJECTS; PHOBOS AB Simple formulae are given for the surface area, volume, center of mass, moments of inertia, and principal axes of any homogeneous polyhedron. These can easily be combined with algorithms for the gravitational held of such polyhedra. A FORTRAN version of our code (available from the author) is used to compare digital models of Phobos at different resolutions. The results indicate that a surface resolution of about 10 degrees is adequate to characterize the inertial properties of a small satellite or asteroid within a few percent, comparable to the systematic uncertainty for Phobos. This accuracy scales as the square of the resolution. (C) 1996 Academic Press, Inc. RP Dobrovolskis, AR (reprint author), UNIV CALIF SANTA CRUZ,NASA,AMES RES CTR,MOFFETT FIELD,CA 94035, USA. NR 22 TC 28 Z9 28 U1 0 U2 0 PU ACADEMIC PRESS INC JNL-COMP SUBSCRIPTIONS PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 SN 0019-1035 J9 ICARUS JI Icarus PD DEC PY 1996 VL 124 IS 2 BP 698 EP 704 DI 10.1006/icar.1996.0243 PG 7 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA WC129 UT WOS:A1996WC12900030 ER PT J AU Chien, S Govindjee, A Wang, XM Estlin, T Hill, R AF Chien, S Govindjee, A Wang, XM Estlin, T Hill, R TI Integrating hierarchial task-network and operator-based planning techniques to automate operations of communications antennas SO IEEE EXPERT-INTELLIGENT SYSTEMS & THEIR APPLICATIONS LA English DT Article C1 UNIV SO CALIF,DEPT COMP SCI,LOS ANGELES,CA 90089. RP Chien, S (reprint author), CALTECH,JET PROP LAB,AI GRP,TECH STAFF,PASADENA,CA 91125, USA. NR 0 TC 1 Z9 1 U1 0 U2 2 PU IEEE COMPUTER SOC PI LOS ALAMITOS PA 10662 LOS VAQUEROS CIRCLE, PO BOX 3014, LOS ALAMITOS, CA 90720-1264 SN 0885-9000 J9 IEEE EXPERT JI IEEE Expert-Intell. Syst. Appl. PD DEC PY 1996 VL 11 IS 6 BP 9 EP 11 PG 3 WC Computer Science, Artificial Intelligence; Engineering, Electrical & Electronic SC Computer Science; Engineering GA VV647 UT WOS:A1996VV64700006 ER PT J AU Nixon, RH Kemeny, SE Pain, B Staller, CO Fossum, ER AF Nixon, RH Kemeny, SE Pain, B Staller, CO Fossum, ER TI 256X256 CMOS active pixel sensor camera-on-a-chip SO IEEE JOURNAL OF SOLID-STATE CIRCUITS LA English DT Article; Proceedings Paper CT 1996 International Solid-State Circuits Conference (ISSCC) CY FEB 08-10, 1996 CL SAN FRANCISCO, CA ID IMAGE AB A CMOS imaging senses is described that uses active pixel sensor (APS technology and permits the integration of the detector array with on-chip timing, control, and signal chain electronics, This sensor technology has been used to implement a CMOS APS camera-on-a-chip. The camera-on-a-chip features a 256 x 256 APS sensor integrated on a CMOS chip with the timing and control circuits, and signal-conditioning to enable random-access, low power (similar to 5 mW) operation, and low read noise (13 e(-) rms). The chip features simple power supplies, fast readout rates, and a digital interface for commanding the sensor, as well as for programming the window-of-interest readout and exposure times, Excellent imaging has been demonstrated with the APS camera-om-a-chip, and the measured performance indicates that this technology will be competitive with charge-coupled devices (CCD's) in many applications. C1 CALTECH,JET PROP LAB,CTR SPACE MICROELECT TECHNOL,PASADENA,CA 91109. NR 7 TC 88 Z9 98 U1 0 U2 5 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 SN 0018-9200 J9 IEEE J SOLID-ST CIRC JI IEEE J. Solid-State Circuit PD DEC PY 1996 VL 31 IS 12 BP 2046 EP 2050 DI 10.1109/4.545830 PG 5 WC Engineering, Electrical & Electronic SC Engineering GA VX902 UT WOS:A1996VX90200028 ER PT J AU Wang, N Komisarek, K Dominek, A Hann, RE AF Wang, N Komisarek, K Dominek, A Hann, RE TI Mixed-field hybrid FEM/BEM formulation for two-dimensional TE radiation and scattering by resistive strips SO IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION LA English DT Letter AB In this letter, a new mixed-field, hybrid finite-element method (FEM) (E-field)/BEM (H-field) formulation is presented for modeling the two-dimensional (2-D) radiation and scattering from scatterers comprised with inhomogeneous materials including resistive cards and perfectly electrically conducting (PEG) strips for the TE polarization. Using the usual H-field formulation leads to the requirement for the use of special gap element. And the E-field formulation will result in a much more cumbersome BEM integral, The new mixed-field formulation retains the simplicity of scalar formulation and is useful for a problem which cannot he treated elegantly with existing approach, The new formulation has been implemented into a 2-D FEM/BEM computer code, Numerical results obtained compare well to previously published results. C1 NASA,COMPUTAT MAT LAB,DIV MAT,CLEVELAND,OH 44111. RP Wang, N (reprint author), OHIO STATE UNIV,ELECTROSCI LAB,DEPT ELECT ENGN,COLUMBUS,OH 43212, USA. NR 7 TC 0 Z9 0 U1 0 U2 0 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 SN 0018-926X J9 IEEE T ANTENN PROPAG JI IEEE Trans. Antennas Propag. PD DEC PY 1996 VL 44 IS 12 BP 1640 EP 1641 DI 10.1109/8.546250 PG 2 WC Engineering, Electrical & Electronic; Telecommunications SC Engineering; Telecommunications GA VX892 UT WOS:A1996VX89200015 ER PT J AU Budka, TP Waclawik, SD Rebeiz, GM AF Budka, TP Waclawik, SD Rebeiz, GM TI A coaxial 0.5-18 GHz near electric field measurement system for planar microwave circuits using integrated probes SO IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES LA English DT Article AB This paper reports on the basic theory of operation and experimental results obtained from an electric field imaging system for planar microwave circuits that employs the method of modulated scattering with monolithically integrated probes. The low-cost system is capable of mapping the normal and tangential electric field intensities and electrical phase delays above reciprocal microwave circuits in the frequency range of 0.5-18 GHz with a spatial electric field resolution of better than 100 mu m. Monolithic probes incorporating silicon Schottky diodes integrated with electrically small dipole and monopole antenna scatterers on a 40-mu m-thick high-resistivity silicon substrate are used. Electric field intensity and electrical phase delay images are presented for a 55-Omega coplanar waveguide line (CPW), a three-turn microstrip meander line at 8.8, 11.7, and 13.4 GHz, a microstrip coupled-line directional coupler at 10 GHz, and a microstrip patch antenna at 12.85 GHz, The results demonstrate that the modulated scattering technique is a valuable low-cost tool for microwave circuit diagnostics. C1 UNIV MICHIGAN,DEPT ELECT ENGN & COMP SCI,ANN ARBOR,MI 48109. UNIV MICHIGAN,NASA,CTR SPACE TERAHERTZ TECHNOL,ANN ARBOR,MI 48109. NR 15 TC 38 Z9 38 U1 0 U2 0 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 SN 0018-9480 J9 IEEE T MICROW THEORY JI IEEE Trans. Microw. Theory Tech. PD DEC PY 1996 VL 44 IS 12 BP 2174 EP 2184 DI 10.1109/22.556445 PN 1 PG 11 WC Engineering, Electrical & Electronic SC Engineering GA VZ138 UT WOS:A1996VZ13800007 ER PT J AU Yook, JG Katehi, LPB Simons, RN Shalkhauser, KA AF Yook, JG Katehi, LPB Simons, RN Shalkhauser, KA TI Experimental and theoretical study of parasitic leakage/resonance in a K/KA-band MMIC package SO IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES LA English DT Article; Proceedings Paper CT 40th Successive Annual IEEE MTT-S International Microwave Symposium/Exhibition - Bridging the Spectrum CY JUN 18-20, 1996 CL SAN FRANCISCO, CA SP IEEE MTT Soc AB In this paper, electromagnetic (EM) leakage and spurious resonances in a K/Ka-Band (18-40 GHz) MMIC hermetic package designed for a phase shifter chip are studied using the finite element method (FEM) and the numerical simulation results are compared with the measured data. Both the measured and calculated data indicate several spurious resonances in the 18-24 GHz region and the origin of this phenomenon is identified by virtue of the modeling capability of the FEM, Moreover, the effect of de bias lines, bond wires, shielding, and the asymmetry of the package on electrical performance are closely examined. In addition, the effect of adding a resistive coating to the inside surface of the package lid and also the use of dielectric packaging materials with very high loss tangent are studied in view of the suppression of the spurious resonances, Finally, design guidelines for the improved package are presented. C1 NASA,LEWIS RES CTR,NYMA GRP,CLEVELAND,OH 44135. RP Yook, JG (reprint author), UNIV MICHIGAN,DEPT ELECT ENGN & COMP SCI,RADIAT LAB,ANN ARBOR,MI 48109, USA. NR 11 TC 7 Z9 7 U1 0 U2 1 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 SN 0018-9480 J9 IEEE T MICROW THEORY JI IEEE Trans. Microw. Theory Tech. PD DEC PY 1996 VL 44 IS 12 BP 2403 EP 2410 DI 10.1109/22.554569 PN 2 PG 8 WC Engineering, Electrical & Electronic SC Engineering GA VZ141 UT WOS:A1996VZ14100017 ER PT J AU Johnston, A AF Johnston, A TI Awards chairman's comments SO IEEE TRANSACTIONS ON NUCLEAR SCIENCE LA English DT Editorial Material RP Johnston, A (reprint author), CALTECH,JET PROP LAB,PASADENA,CA 91125, USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 SN 0018-9499 J9 IEEE T NUCL SCI JI IEEE Trans. Nucl. Sci. PD DEC PY 1996 VL 43 IS 6 BP 2535 EP 2535 PN 1 PG 1 WC Engineering, Electrical & Electronic; Nuclear Science & Technology SC Engineering; Nuclear Science & Technology GA WC903 UT WOS:A1996WC90300003 ER PT J AU Cross, JR AF Cross, JR TI Dr John W. Winslow - In memoriam SO IEEE TRANSACTIONS ON NUCLEAR SCIENCE LA English DT Item About an Individual RP Cross, JR (reprint author), CALTECH,JET PROP LAB,PASADENA,CA 91125, USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 SN 0018-9499 J9 IEEE T NUCL SCI JI IEEE Trans. Nucl. Sci. PD DEC PY 1996 VL 43 IS 6 BP 2536 EP 2536 PN 1 PG 1 WC Engineering, Electrical & Electronic; Nuclear Science & Technology SC Engineering; Nuclear Science & Technology GA WC903 UT WOS:A1996WC90300004 ER PT J AU Buehler, M HolmesSiedle, A Caines, C Carmichael, C Martin, D AF Buehler, M HolmesSiedle, A Caines, C Carmichael, C Martin, D TI Stacked p-FET dosimeter for the STRV-2 MWIR detector SO IEEE TRANSACTIONS ON NUCLEAR SCIENCE LA English DT Article; Proceedings Paper CT 33rd Annual IEEE International Nuclear and Space Radiation Effects Conference CY JUL 15-19, 1996 CL RENAISSANCE ESMERALD CONFERENCE RESORT, INDIAN WELLS, CA SP IEEE NPSS, Def Nucl Agcy, Sandia Natl Labs, Phillips Labs, NASA, Goddard Space Flight Lab, Jet Prop Lab HO RENAISSANCE ESMERALD CONFERENCE RESORT AB A stacked p-FET dosimeter consisting of a RADMON mother chip with three p-FETs and multiplexer and an attached RADFET has been developed for the STRV-2/MWIR detector. Calibration of the dosimeter, using an Am-241 source, indicates that the RADFET is about 20 times more sensitive to radiation than the RADMON. This dosimeter is expected to measure radiation dose from rads to Megarads. C1 RADIAT EXPT & MONITORS,OXFORD OX8 1PD,ENGLAND. DEF RES AGCY,DEPT SPACE,FARNBOROUGH GU14 6TD,HANTS,ENGLAND. HALCYON MICROELECT INC,IRWINDALE,CA. RP Buehler, M (reprint author), CALTECH,JET PROP LAB,MICRODEVICES LAB,4800 OAK GROVE DR,PASADENA,CA 91109, USA. NR 5 TC 3 Z9 4 U1 0 U2 1 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 SN 0018-9499 J9 IEEE T NUCL SCI JI IEEE Trans. Nucl. Sci. PD DEC PY 1996 VL 43 IS 6 BP 2679 EP 2686 DI 10.1109/23.556853 PN 1 PG 8 WC Engineering, Electrical & Electronic; Nuclear Science & Technology SC Engineering; Nuclear Science & Technology GA WC903 UT WOS:A1996WC90300025 ER PT J AU Dyer, CS Watson, CJ Peerless, CL Sims, AJ Barth, J AF Dyer, CS Watson, CJ Peerless, CL Sims, AJ Barth, J TI Measurements of the radiation environment from CREDO-II on STRV & APEX SO IEEE TRANSACTIONS ON NUCLEAR SCIENCE LA English DT Article; Proceedings Paper CT 33rd Annual IEEE International Nuclear and Space Radiation Effects Conference CY JUL 15-19, 1996 CL RENAISSANCE ESMERALD CONFERENCE RESORT, INDIAN WELLS, CA SP IEEE NPSS, Def Nucl Agcy, Sandia Natl Labs, Phillips Labs, NASA, Goddard Space Flight Lab, Jet Prop Lab HO RENAISSANCE ESMERALD CONFERENCE RESORT AB The Cosmic Radiation Environment and Dosimetry experiments (CREDO) have now been operational in complementary orbits onboard the Advanced Photovoltaics & Electronics Experiment Spacecraft and Space Technology Research Vehicle since the summer of 1994 enabling extensive comparisons of measured dose and linear energy transfer (LET) spectra with the standard environment models. Measurements have been made at a range of shielding depths and detailed spacecraft models are employed. Significant discrepancies are seen for the outer-belt electron component which shows large time variations. Shielding effects are shown to be highly significant for both dose and LET spectra. Even allowing for this the measured LET spectra are somewhat below the predictions for solar minimum. C1 NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. RP Dyer, CS (reprint author), DEF RES AGCY,DEPT SPACE,FARNBOROUGH GU14 6TD,HANTS,ENGLAND. RI Sims, Andrew/B-7001-2012 OI Sims, Andrew/0000-0002-9553-7278 NR 9 TC 7 Z9 9 U1 0 U2 0 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 SN 0018-9499 J9 IEEE T NUCL SCI JI IEEE Trans. Nucl. Sci. PD DEC PY 1996 VL 43 IS 6 BP 2751 EP 2757 DI 10.1109/23.556862 PN 1 PG 7 WC Engineering, Electrical & Electronic; Nuclear Science & Technology SC Engineering; Nuclear Science & Technology GA WC903 UT WOS:A1996WC90300034 ER PT J AU Edmonds, L Swift, G Johnston, A AF Edmonds, L Swift, G Johnston, A TI Non-destructive measurements for CMOS devices using charge-collection techniques SO IEEE TRANSACTIONS ON NUCLEAR SCIENCE LA English DT Article; Proceedings Paper CT 33rd Annual IEEE International Nuclear and Space Radiation Effects Conference CY JUL 15-19, 1996 CL RENAISSANCE ESMERALD CONFERENCE RESORT, INDIAN WELLS, CA SP IEEE NPSS, Def Nucl Agcy, Sandia Natl Labs, Phillips Labs, NASA, Goddard Space Flight Lab, Jet Prop Lab HO RENAISSANCE ESMERALD CONFERENCE RESORT ID SEU AB Results of an experiment providing initial validation of the use of charge-collection spectroscopy to measure the over-layer and epitaxial thickness and substrate diffusion length are given for several CMOS SRAM test devices. RP Edmonds, L (reprint author), CALTECH,JET PROP LAB,PASADENA,CA 91109, USA. NR 7 TC 4 Z9 4 U1 0 U2 0 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 SN 0018-9499 J9 IEEE T NUCL SCI JI IEEE Trans. Nucl. Sci. PD DEC PY 1996 VL 43 IS 6 BP 2833 EP 2842 DI 10.1109/23.556874 PN 1 PG 10 WC Engineering, Electrical & Electronic; Nuclear Science & Technology SC Engineering; Nuclear Science & Technology GA WC903 UT WOS:A1996WC90300046 ER PT J AU Adolphsen, JW Barth, JL Gee, GB AF Adolphsen, JW Barth, JL Gee, GB TI First observation of proton induced power MOSFET burnout in space: The CRUX experiment on APEX SO IEEE TRANSACTIONS ON NUCLEAR SCIENCE LA English DT Article; Proceedings Paper CT 33rd Annual IEEE International Nuclear and Space Radiation Effects Conference CY JUL 15-19, 1996 CL RENAISSANCE ESMERALD CONFERENCE RESORT, INDIAN WELLS, CA SP IEEE NPSS, Def Nucl Agcy, Sandia Natl Labs, Phillips Labs, NASA, Goddard Space Flight Lab, Jet Prop Lab HO RENAISSANCE ESMERALD CONFERENCE RESORT AB Ground testing has shown that power MOSFETs are susceptible to burnout when irradiated with heavy ions and protons. Satellite data from the Cosmic Ray Upset Experiment (CRUX) demonstrate that single event burnouts (SEBs) on 100-volt and 200-volt power MOSFETs can and do occur in space. Few SEBs occurred on the 100-volt devices, all at L(1) > 3. The 200-volt devices experienced many SEBs at L < 3 when drain-to-source voltage (V-D-S) was greater than 85% of maximum rated voltage. CRUX flight lot devices were ground tested with protons. The SEE rates calculated with the cross-sections from the ground tests show close agreement with the measured rates. C1 NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. SES INC,GREENBELT,MD. RP Adolphsen, JW (reprint author), UNISYS INC,GREENBELT,MD, USA. NR 12 TC 7 Z9 12 U1 0 U2 2 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 SN 0018-9499 J9 IEEE T NUCL SCI JI IEEE Trans. Nucl. Sci. PD DEC PY 1996 VL 43 IS 6 BP 2921 EP 2926 DI 10.1109/23.556886 PN 1 PG 6 WC Engineering, Electrical & Electronic; Nuclear Science & Technology SC Engineering; Nuclear Science & Technology GA WC903 UT WOS:A1996WC90300058 ER PT J AU Nichols, DK Coss, JR Miyahira, TF Schwartz, HR AF Nichols, DK Coss, JR Miyahira, TF Schwartz, HR TI Heavy ion and proton induced single event transients in comparators SO IEEE TRANSACTIONS ON NUCLEAR SCIENCE LA English DT Article; Proceedings Paper CT 33rd Annual IEEE International Nuclear and Space Radiation Effects Conference CY JUL 15-19, 1996 CL RENAISSANCE ESMERALD CONFERENCE RESORT, INDIAN WELLS, CA SP IEEE NPSS, Def Nucl Agcy, Sandia Natl Labs, Phillips Labs, NASA, Goddard Space Flight Lab, Jet Prop Lab HO RENAISSANCE ESMERALD CONFERENCE RESORT AB This paper presents a display of heavy-ion- and proton-induced single event transients for three comparators. The transient vital signs are serious: low LET threshold, very high voltage amplitude and extended pulse duration (microsecs.) RP Nichols, DK (reprint author), CALTECH,JET PROP LAB,4800 OAK GROVE DR,PASADENA,CA 91109, USA. NR 2 TC 38 Z9 41 U1 0 U2 1 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 SN 0018-9499 J9 IEEE T NUCL SCI JI IEEE Trans. Nucl. Sci. PD DEC PY 1996 VL 43 IS 6 BP 2960 EP 2967 DI 10.1109/23.556892 PN 1 PG 8 WC Engineering, Electrical & Electronic; Nuclear Science & Technology SC Engineering; Nuclear Science & Technology GA WC903 UT WOS:A1996WC90300064 ER PT J AU LaBel, KA Gates, MM Moran, AK Kim, HS Seidleck, CM Marshall, P Kinnison, J Carkhuff, B AF LaBel, KA Gates, MM Moran, AK Kim, HS Seidleck, CM Marshall, P Kinnison, J Carkhuff, B TI Radiation effect characterization and test methods of single-chip and multi-chip stacked 16Mbit DRAMs SO IEEE TRANSACTIONS ON NUCLEAR SCIENCE LA English DT Article; Proceedings Paper CT 33rd Annual IEEE International Nuclear and Space Radiation Effects Conference CY JUL 15-19, 1996 CL RENAISSANCE ESMERALD CONFERENCE RESORT, INDIAN WELLS, CA SP IEEE NPSS, Def Nucl Agcy, Sandia Natl Labs, Phillips Labs, NASA, Goddard Space Flight Lab, Jet Prop Lab HO RENAISSANCE ESMERALD CONFERENCE RESORT AB This paper presents radiation effects characterization performed by the NASA Goddard Space Flight Center (GSFC) on spaceflight candidate 16Mbit DRAMs. This includes heavy ion, proton, and Co60 irradiations on single-chip devices as well as proton irradiation of a stacked DRAM module. Lastly, a discussion of test methodology is undertaken. C1 JACKSON & TULL,SEABROOK,MD 20736. HUGHES STX,SEABROOK,MD 20736. RP LaBel, KA (reprint author), NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771, USA. NR 9 TC 5 Z9 5 U1 0 U2 1 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 SN 0018-9499 J9 IEEE T NUCL SCI JI IEEE Trans. Nucl. Sci. PD DEC PY 1996 VL 43 IS 6 BP 2974 EP 2981 DI 10.1109/23.556894 PN 1 PG 8 WC Engineering, Electrical & Electronic; Nuclear Science & Technology SC Engineering; Nuclear Science & Technology GA WC903 UT WOS:A1996WC90300066 ER PT J AU Johnston, AH Lee, CI Rax, BG AF Johnston, AH Lee, CI Rax, BG TI Enhanced damage in bipolar devices at low dose rates: Effects at very low dose rates SO IEEE TRANSACTIONS ON NUCLEAR SCIENCE LA English DT Article; Proceedings Paper CT 33rd Annual IEEE International Nuclear and Space Radiation Effects Conference CY JUL 15-19, 1996 CL RENAISSANCE ESMERALD CONFERENCE RESORT, INDIAN WELLS, CA SP IEEE NPSS, Def Nucl Agcy, Sandia Natl Labs, Phillips Labs, NASA, Goddard Space Flight Lab, Jet Prop Lab HO RENAISSANCE ESMERALD CONFERENCE RESORT ID FIELD OXIDES; INTERFACE AB The effect of very low dose rate irradiation is investigated for several linear bipolar devices that are sensitive to enhanced low dose-rate damage, including one device with super-beta input transistors. New results are included at 0.001 and 0.002 rad(Si)/s. Irradiations at elevated temperature at high dose rate are compared with room temperature irradiation at very low dose rate. Possible mechanisms for enhanced damage are discussed. RP Johnston, AH (reprint author), CALTECH,JET PROP LAB,4800 OAK GROVE DR,PASADENA,CA, USA. NR 13 TC 39 Z9 46 U1 0 U2 0 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 SN 0018-9499 J9 IEEE T NUCL SCI JI IEEE Trans. Nucl. Sci. PD DEC PY 1996 VL 43 IS 6 BP 3049 EP 3059 DI 10.1109/23.556904 PN 1 PG 11 WC Engineering, Electrical & Electronic; Nuclear Science & Technology SC Engineering; Nuclear Science & Technology GA WC903 UT WOS:A1996WC90300076 ER PT J AU Lee, CI Johnston, AH Tang, WC Barnes, CE Lyke, J AF Lee, CI Johnston, AH Tang, WC Barnes, CE Lyke, J TI Total dose effects on microelectromechanical systems (MEMS): Accelerometers SO IEEE TRANSACTIONS ON NUCLEAR SCIENCE LA English DT Article; Proceedings Paper CT 33rd Annual IEEE International Nuclear and Space Radiation Effects Conference CY JUL 15-19, 1996 CL RENAISSANCE ESMERALD CONFERENCE RESORT, INDIAN WELLS, CA SP IEEE NPSS, Def Nucl Agcy, Sandia Natl Labs, Phillips Labs, NASA, Goddard Space Flight Lab, Jet Prop Lab HO RENAISSANCE ESMERALD CONFERENCE RESORT AB Microelectromechanical sensors, ADXL50 and XMMAS40G accelerometers which are fabricated with surface micromachining techniques are characterized for their total dose radiation response. Different failure mechanisms were observed when the sensor element or the whole device was irradiated. C1 USAF,PHILLIPS LAB,KIRTLAND AFB,NM 87117. RP Lee, CI (reprint author), CALTECH,JET PROP LAB,4800 OAK GROVE DR,PASADENA,CA, USA. NR 6 TC 37 Z9 38 U1 2 U2 7 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 SN 0018-9499 J9 IEEE T NUCL SCI JI IEEE Trans. Nucl. Sci. PD DEC PY 1996 VL 43 IS 6 BP 3127 EP 3132 DI 10.1109/23.556915 PN 1 PG 6 WC Engineering, Electrical & Electronic; Nuclear Science & Technology SC Engineering; Nuclear Science & Technology GA WC903 UT WOS:A1996WC90300087 ER PT J AU Lee, CI Rax, BG Johnston, AH AF Lee, CI Rax, BG Johnston, AH TI Total dose hardness assurance techniques for new generation COTS devices SO IEEE TRANSACTIONS ON NUCLEAR SCIENCE LA English DT Article; Proceedings Paper CT 33rd Annual IEEE International Nuclear and Space Radiation Effects Conference CY JUL 15-19, 1996 CL RENAISSANCE ESMERALD CONFERENCE RESORT, INDIAN WELLS, CA SP IEEE NPSS, Def Nucl Agcy, Sandia Natl Labs, Phillips Labs, NASA, Goddard Space Flight Lab, Jet Prop Lab HO RENAISSANCE ESMERALD CONFERENCE RESORT AB Hardness assurance techniques and total dose radiation characterization data for new generation linear and COTS devices from various manufacturers are presented. A bipolar op amp showed more degradation at high dose rate than at low dose rate, which is opposite to the behavior of many other bipolar linear devices. New generation low-power op amps showed more degradation in electrical parameters with total power supply voltage of 3V than at higher voltages. Minimum operating voltage is an important characterization parameter for newer low-power linear circuit designs. RP Lee, CI (reprint author), CALTECH,JET PROP LAB,4800 OAK GROVE DR,PASADENA,CA 91109, USA. NR 10 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 SN 0018-9499 J9 IEEE T NUCL SCI JI IEEE Trans. Nucl. Sci. PD DEC PY 1996 VL 43 IS 6 BP 3145 EP 3150 DI 10.1109/23.556918 PN 1 PG 6 WC Engineering, Electrical & Electronic; Nuclear Science & Technology SC Engineering; Nuclear Science & Technology GA WC903 UT WOS:A1996WC90300090 ER PT J AU Rax, BG Lee, CI Johnston, AH Barnes, CE AF Rax, BG Lee, CI Johnston, AH Barnes, CE TI Total dose and proton damage in optocouplers SO IEEE TRANSACTIONS ON NUCLEAR SCIENCE LA English DT Article; Proceedings Paper CT 33rd Annual IEEE International Nuclear and Space Radiation Effects Conference CY JUL 15-19, 1996 CL RENAISSANCE ESMERALD CONFERENCE RESORT, INDIAN WELLS, CA SP IEEE NPSS, Def Nucl Agcy, Sandia Natl Labs, Phillips Labs, NASA, Goddard Space Flight Lab, Jet Prop Lab HO RENAISSANCE ESMERALD CONFERENCE RESORT AB Radiation damage fi om gamma rays and protons is investigated for two types of optocouplers with different physical configurations. Far more damage occurs from protons because of displacement damage, which reduces the photoresponse of the phototransistor and causes severe degradation in LED light output for one of the two device type. The other device type was far more resistant to radiation, primarily because it used a shorter wavelength LED that was relatively unaffected by protons. RP Rax, BG (reprint author), CALTECH,JET PROP LAB,4800 OAK GROVE DR,PASADENA,CA 91109, USA. NR 10 TC 45 Z9 51 U1 0 U2 1 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 SN 0018-9499 J9 IEEE T NUCL SCI JI IEEE Trans. Nucl. Sci. PD DEC PY 1996 VL 43 IS 6 BP 3167 EP 3173 DI 10.1109/23.556921 PN 1 PG 7 WC Engineering, Electrical & Electronic; Nuclear Science & Technology SC Engineering; Nuclear Science & Technology GA WC903 UT WOS:A1996WC90300093 ER PT J AU Edmonds, LD AF Edmonds, LD TI SEU cross sections derived from a diffusion analysis SO IEEE TRANSACTIONS ON NUCLEAR SCIENCE LA English DT Article ID CHARGE; SIMULATION; COLLECTION; DEVICES; UPSET AB A simple theoretical prediction of single-event upset (SEU) cross section versus linear energy transfer (LET) is derived from a diffusion analysis, and the result is compared to some real device curves, It was found that at least some real device curves show two regimes, One regime (high-LET) is characterized by a very good fit to the theoretical prediction, and the other (low-LET) is characterized by a very bad fit, The existence of a high-LET regime provides additional credibility for the increasingly popular postulate that diffusion has an important effect on the shape of the cross-sectional curve. RP Edmonds, LD (reprint author), CALTECH,JET PROP LAB,PASADENA,CA 91109, USA. NR 15 TC 20 Z9 21 U1 0 U2 0 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 SN 0018-9499 J9 IEEE T NUCL SCI JI IEEE Trans. Nucl. Sci. PD DEC PY 1996 VL 43 IS 6 BP 3207 EP 3217 DI 10.1109/23.552719 PN 2 PG 11 WC Engineering, Electrical & Electronic; Nuclear Science & Technology SC Engineering; Nuclear Science & Technology GA WC905 UT WOS:A1996WC90500002 ER PT J AU Pisharody, SA Fisher, JW Abraham, MA AF Pisharody, SA Fisher, JW Abraham, MA TI Supercritical water oxidation of solid particulates SO INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH LA English DT Article ID KINETICS AB In the application of supercritical water oxidation (SCWO) to the treatment of aqueous solid wastes, particle size will be an important processing parameter. The particle size will impact feed preparation requirements such as slurry concentration, pumping requirements, and, in terms of the destruction of the solid particles, rate of reaction and reactor size. To address these issues, an experimental research program was undertaken to evaluate the effect of particle size on the reaction kinetics in SCWO of solid particulates (wheat straw and cellulose particles in this case). The experiments also included evaluation of the effects of temperature, pressure, dissolution period followed by a longer particle reaction period. Empirically based mathematical relationships were developed that can be used for SCWO system design. C1 NASA,AMES RES CTR,MOFFETT FIELD,CA 94035. UNIV TULSA,DEPT CHEM ENGN,TULSA,OK 74104. NR 13 TC 13 Z9 13 U1 0 U2 5 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 SN 0888-5885 J9 IND ENG CHEM RES JI Ind. Eng. Chem. Res. PD DEC PY 1996 VL 35 IS 12 BP 4471 EP 4478 DI 10.1021/ie960269k PG 8 WC Engineering, Chemical SC Engineering GA VX324 UT WOS:A1996VX32400012 ER PT J AU Lou, JZ Ferraro, R AF Lou, JZ Ferraro, R TI A parallel three-dimensional incompressible Navier-Stokes solver with a parallel multigrid kernel SO INTERNATIONAL JOURNAL OF HIGH SPEED COMPUTING LA English DT Article DE parallel Navier-Stokes solver; multigrid methods; projection method ID 2ND-ORDER PROJECTION METHOD; FLOWS AB The development and applications of a parallel, time-dependent, three-dimensional incompressible Navier-Stokes flow solver and a parallel multigrid elliptic kernel are described. The flow solver is based on a second-order projection method applied to a staggered finite-difference grid. The multigrid algorithms implemented in the parallel elliptic kernel, which is used by the flow solver, are V-cycle and full V-cycle schemes. A grid-partition strategy is used in the parallel implementations of both the flow solver and the multigrid kernel on all fine and coarse grids. Numerical experiments and parallel performance measurements show the parallel solver package is numerically stable, physically robust and computationally efficient. Both the multigrid kernel and the flow solver scale well to a large number of processors on Intel Paragon and Gray T3D/T3E for two- and three-dimensional problems with moderate granularity. The solver package has been carefully designed and implemented so that it can be easily adapted to solve a variety of interesting scientific and engineering flow problems. The code is portable to parallel computers that support MPI, PVM and NX for interprocessor communications. RP Lou, JZ (reprint author), CALTECH,JET PROP LAB,PASADENA,CA 91109, USA. NR 14 TC 0 Z9 0 U1 0 U2 0 PU WORLD SCIENTIFIC PUBL CO PTE LTD PI SINGAPORE PA JOURNAL DEPT PO BOX 128 FARRER ROAD, SINGAPORE 9128, SINGAPORE SN 0129-0533 J9 INT J HIGH SPEED COM JI Int. J. High Speed Comput. PD DEC PY 1996 VL 8 IS 4 BP 319 EP 346 DI 10.1142/S0129053396000185 PG 28 WC Computer Science, Theory & Methods SC Computer Science GA XN205 UT WOS:A1996XN20500002 ER PT J AU Lau, CL Peckham, GE Suttie, RA Jarnot, RF AF Lau, CL Peckham, GE Suttie, RA Jarnot, RF TI Characterization of MLS 1/f noise parameters SO INTERNATIONAL JOURNAL OF REMOTE SENSING LA English DT Article AB Optimal filters provide minimum variance interpolation and smoothing of noisy data, but the form of the noise power spectrum must be known for their design. We analyse data from the Microwave Limb Sounder (MLS) experiment onboard the Upper Atmosphere Research Satellite (UARS) to quantify parameters describing the noise spectra. MLS views space as part of its calibration sequence providing regular samples of the radiometer output. From these samples we determine breakpoint frequencies at which the spectral power density of the low frequency l/f noise is equal to that of the white noise. Breakpoint frequencies were in the range from 0.005 to 0.02 Hz for the 90 filter channels of the MLS. A method was developed to distinguish between l/f noise and systematic disturbances caused by cyclic changes in the operating environment as the spacecraft traverses its orbit. C1 CALTECH,JET PROP LAB,PASADENA,CA 91109. RP Lau, CL (reprint author), HERIOT WATT UNIV,DEPT PHYS,EDINBURGH EH14 4AS,MIDLOTHIAN,SCOTLAND. NR 4 TC 3 Z9 3 U1 0 U2 0 PU TAYLOR & FRANCIS LTD PI LONDON PA ONE GUNPOWDER SQUARE, LONDON, ENGLAND EC4A 3DE SN 0143-1161 J9 INT J REMOTE SENS JI Int. J. Remote Sens. PD DEC PY 1996 VL 17 IS 18 BP 3751 EP 3759 PG 9 WC Remote Sensing; Imaging Science & Photographic Technology SC Remote Sensing; Imaging Science & Photographic Technology GA VW804 UT WOS:A1996VW80400014 ER PT J AU Philander, SGH Gu, D Halpern, D Lambert, G Lau, NC Li, T Pacanowski, RC AF Philander, SGH Gu, D Halpern, D Lambert, G Lau, NC Li, T Pacanowski, RC TI Why the ITCZ is mostly north of the equator SO JOURNAL OF CLIMATE LA English DT Article ID SEA-SURFACE TEMPERATURE; RADIATION BUDGET EXPERIMENT; STRATIFORM CLOUDINESS; SEASONAL CYCLE; PACIFIC-OCEAN; MODEL; EARTH; MAINTENANCE; CIRCULATION; VARIABILITY AB Although the distribution of sunshine is symmetrical about the equator, the earth's climate is not. Climatic asymmetries are prominent in the eastern tropical Pacific and Atlantic Oceans where the regions of maximum sea surface temperature, convective cloud cover, and rainfall are north of the equator. This is the result of two sets of factors: interactions between the ocean and atmosphere that are capable of converting symmetry into asymmetry, and the geometries of the continents that determine in which longitudes the interactions are effective and in which hemisphere the warmest waters and the intertropical convergence zone are located. The ocean-atmosphere interactions are most effective where the thermocline is shallow because the winds can readily affect sea surface temperatures in such regions. The thermocline happens to shoal in the eastern equatorial Pacific and Atlantic, but not in the eastern Indian Ocean, because easterly trade winds prevail over the tropical Atlantic and Pacific whereas monsoons, with a far larger meridional component, are dominant over the Indian Ocean. That is how the global distribution of the continents, by determining the large-scale wind patterns, causes climatic asymmetries to be prominent in some bands of longitude but not others. The explanation for asymmetries that favor the Northern rather than Southern Hemisphere with the warmest waters and the ITCZ involves the details of the local coastal geometries: the bulge of western Africa to the north of the Gulf of Guinea and the slope of the western coast of the Americas relative to meridians. Low-level stratus clouds over cold waters are crucial to the maintenance of the asymmetries. C1 CALTECH,JET PROP LAB,PASADENA,CA. PRINCETON UNIV,NOAA,GEOPHYS FLUID DYNAM LAB,PRINCETON,NJ 08542. RP Philander, SGH (reprint author), PRINCETON UNIV,ATMOSPHER & OCEAN SCI PROGRAM,PRINCETON,NJ 08542, USA. NR 35 TC 268 Z9 281 U1 5 U2 57 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 SN 0894-8755 J9 J CLIMATE JI J. Clim. PD DEC PY 1996 VL 9 IS 12 BP 2958 EP 2972 DI 10.1175/1520-0442(1996)009<2958:WTIIMN>2.0.CO;2 PN 1 PG 15 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA WF071 UT WOS:A1996WF07100003 ER PT J AU Nigam, S Chao, Y AF Nigam, S Chao, Y TI Evolution dynamics of tropical ocean-atmosphere annual cycle variability SO JOURNAL OF CLIMATE LA English DT Article ID SEA-SURFACE TEMPERATURE; EASTERN EQUATORIAL PACIFIC; GENERAL-CIRCULATION MODEL; LATENT-HEAT FLUX; SEASONAL CYCLE; INTERANNUAL VARIABILITY; INDIAN-OCEAN; SIMULATION AB The structure of ocean-atmosphere annual cycle variability is extracted from the revised Comprehensive Ocean-Atmosphere Data Set SSTs, surface winds, and the latent heat (LH) and net shortwave (SW) surface fluxes using the covariance-based rotated principal component analysis method. The coupled annual cycle variability is concisely described using two modes that are in temporal quadrature. The first, peaking in June/July (and Dec/Jan), represents monsoonal flow onto Indochina, Central America, and western Africa. The second mode peaks in September/October and March/April when it represents the extreme phases of the SST annual cycle in the eastern oceans. Analysis of the surface momentum balance in the Pacific cold tongue core shows the equatorial flow, and in particular the zonal wind, to be dynamically consistent with the SST gradient during both the cold tongue's nascent (Jun/Jul) and mature (Sep/Oct) phases; the dynamical consistency improves when the impact of nearsurface static stability variation on horizontal momentum dissipation is also considered. Evolution structure of the extracted annual cycle, moreover, shows the easterly wind tendency to lead SST cooling in the off-coastal zone. Taken together, these findings suggest that the Pacific cold tongue westward expansion results from local interaction of the zonal wind and zonal SST gradient, as encapsulated in the proposed ''westward expansion hypothesis''-a simple analytic model of which is also presented. Although positive LH flux tendency leads SST cooling in the off-coastal zone, its modest magnitude (similar to 5 W m(-2)/mo) indicates that its direct impact on SSTs, while additive, is secondary to the impact of equatorial upwelling. Comparison of the open ocean and coastal annual evolutions reveals that the northward expansion of the Pacific cold tongue likely results from the positive feedback between coastal meridional winds and the upwelled meridional SST gradient, but suggests that the reason for the nonobservance of equatorially antisymmetric SSTs is the counter LH-flux impact northward of the equator. The comparatively modest SST annual cycle in the northern equatorial Indian Ocean is forced by the Asian-monsoon-driven (i.e., nonlocally forced) surface winds through coastal upwelling along the Somali coast and from the monsoon-cloudiness-impacted net SW surface flux and wind-speed-influence LH flux in the off-coastal sector. C1 CALTECH,JET PROP LAB,DIV EARTH & SPACE SCI,PASADENA,CA 91109. RP Nigam, S (reprint author), UNIV MARYLAND,DEPT METEOROL,3433 COMP & SPACE SCI BLDG,COLLEGE PK,MD 20742, USA. RI Nigam, Sumant/A-8338-2009 NR 29 TC 31 Z9 33 U1 0 U2 3 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 SN 0894-8755 J9 J CLIMATE JI J. Clim. PD DEC PY 1996 VL 9 IS 12 BP 3187 EP 3205 DI 10.1175/1520-0442(1996)009<3187:EDOTOA>2.0.CO;2 PN 1 PG 19 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA WF071 UT WOS:A1996WF07100015 ER PT J AU Sud, YC Walker, GK Kim, JH Liston, GE Sellers, PJ Lau, WKM AF Sud, YC Walker, GK Kim, JH Liston, GE Sellers, PJ Lau, WKM TI Biogeophysical consequences of a tropical deforestation scenario: A GCM simulation study SO JOURNAL OF CLIMATE LA English DT Article ID GENERAL-CIRCULATION MODEL; SIMPLE BIOSPHERE MODEL; LAND-SURFACE; CUMULUS PARAMETERIZATION; AMAZONIAN DEFORESTATION; ATMOSPHERIC CIRCULATION; CLIMATE CHANGE; PRECIPITATION; SENSITIVITY; ALBEDO AB Two 3-year (1979-1982) integrations were carried out with a version of the GLA GCM that contains the Simple Biosphere Model (SiB) for simulating land-atmosphere interactions. The control case used the usual SIE vegetation cover (comprising 12 vegetation types), while its twin, the deforestation case, imposed a scenario in which all tropical rainforests were entirely replaced by grassland. Except for this difference, all other initial and prescribed boundary conditions were kept identical in both integrations. An intercomparison of the integrations shows that tropical deforestation decreases evapotranspiration and increases land surface outgoing longwave radiation and sensible heat flux, thereby warming and drying the planetary boundary layer. This happens despite the reduced absorption of solar radiation due to higher surface albedo of the deforested land. produces significant and robust local as well as global climate changes. The local effect includes significant changes (mostly reductions) in precipitation and diabatic heating, while the large-scale effect is to weaken the Hadley circulation but invigorate the southern Ferrel cell, drawing larger air mass from the indirect polar cells. decreases the surface stress (drag force) owing to reduced surface roughness of deforested land, which in turn intensifies winds in the planetary boundary layer, thereby affecting the dynamic structure of moisture convergence. The simulated surface winds are about 70% stronger and are accompanied by significant changes in the power spectrum of the annual cycle of surface and PBL winds and precipitation. Our results broadly confirm several findings of recent tropical deforestation simulation experiments. In addition, some global-scale climatic influences of deforestation not identified in earlier studies are delineated. C1 GEN SCI CORP, LAUREL, MD USA. APPL RES CORP, LANDOVER, MD 20785 USA. UNIV SPACE RES ASSOC, WASHINGTON, DC USA. NASA, GODDARD SPACE FLIGHT CTR, BIOSPHER SCI BRANCH, GREENBELT, MD 20771 USA. RP Sud, YC (reprint author), NASA, GODDARD SPACE FLIGHT CTR, ATMOSPHERES LAB, CLIMATE & RADIAT BRANCH, GREENBELT, MD 20771 USA. RI Lau, William /E-1510-2012 OI Lau, William /0000-0002-3587-3691 NR 57 TC 69 Z9 74 U1 2 U2 14 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 DEC PY 1996 VL 9 IS 12 BP 3225 EP 3247 DI 10.1175/1520-0442(1996)009<3225:BCOATD>2.0.CO;2 PN 2 PG 23 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA WF072 UT WOS:A1996WF07200003 ER PT J AU Sherman, LL Taylor, AC Green, LL Newman, PA Hou, GW Korivi, VM AF Sherman, LL Taylor, AC Green, LL Newman, PA Hou, GW Korivi, VM TI First- and second-order aerodynamic sensitivity derivatives via automatic differentiation with incremental iterative methods SO JOURNAL OF COMPUTATIONAL PHYSICS LA English DT Article ID STRATEGY AB The straightforward automatic-differentiation and the hand-differentiated incremental iterative methods are interwoven to produce a hybrid scheme that captures some of the strengths of each strategy. With this compromise, discrete aerodynamic sensitivity derivatives are calculated with the efficient incremental iterative solution algorithm of the original flow code. Moreover, the principal advantage of automatic differentiation is retained (i.e., all complicated source code for the derivative calculations is constructed quickly with accuracy). The basic equations for second-order sensitivity derivatives are presented, which results in a comparison of four different methods. Each of these four schemes for second-order derivatives requires that large systems are solved first for the first-order derivatives and, in all but one method, for the first-order adjoint variables. Of these latter three schemes, two require no solutions of large systems thereafter. For the other two for which additional systems are solved, the equations and solution procedures are analogous to those for the first-order derivatives. From a practical viewpoint, implementation of the second-order methods is feasible only with software tools such as automatic differentiation, because of the extreme complexity and large number of terms. First- and second-order sensitivities are calculated accurately for two airfoil problems, including a turbulent-flow example. In each of these two sample problems, three dependent variables (coefficients of lift, drag, and pitching-moment) and six independent variables (three geometric-shape and three flow-condition design variables) are considered. Several different procedures are tested, and results are compared on the basis of accuracy, computational time, and computer memory. For first-order derivatives, the hybrid incremental iterative scheme obtained with automatic differentiation is competitive with the best hand-differentiated method. Furthermore, it is at least two to four times faster than central finite differences, without an overwhelming penalty in computer memory. (C) 1996 Academic Press, Inc. C1 OLD DOMINION UNIV, DEPT MECH ENGN, NORFOLK, VA 23529 USA. NASA, LANGLEY RES CTR, MULTIDISCIPLINARY DESIGN OPTIMIZAT BRANCH, HAMPTON, VA 23665 USA. NR 30 TC 49 Z9 51 U1 0 U2 2 PU ACADEMIC PRESS INC ELSEVIER SCIENCE 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 DEC PY 1996 VL 129 IS 2 BP 307 EP 331 DI 10.1006/jcph.1996.0252 PG 25 WC Computer Science, Interdisciplinary Applications; Physics, Mathematical SC Computer Science; Physics GA WC625 UT WOS:A1996WC62500005 ER PT J AU Liou, MS AF Liou, MS TI A sequel to AUSM: AUSM(+) SO JOURNAL OF COMPUTATIONAL PHYSICS LA English DT Article ID DIFFERENCE-SCHEMES; CONSERVATION-LAWS; EQUATIONS; FLOWS AB While enjoying demonstrated improvement in accuracy, efficiency, and robustness over existing schemes, the advection upstream splitting method (AUSM) has been found to have deficiencies in some cases. This paper describes recent progress toward improving the AUSM. We show that the improved scheme, termed AUSM(+), features the following properties: (1) exact resolution of 1D contact and shock discontinuities, (2) positivity preserving of scalar quantity such as the density, (3) free of ''carbuncle phenomenon,'' (4) free of oscillations at the slowly moving shock, (5) algorithmic simplicity, and (6) easy entension to treat other hyperbolic systems. In this paper, we lay out a general construction for the AUSM(+) scheme and prove its heretofore unreported mathematical properties. Especially a CFL-like condition for positivity-preserving property is derived. This positivity-preserving proves to be tightly related to the capability of calculating strong rarefaction and near vacuum flows. Finally, results of numerical tests on many problems are given to confirm the capability and improvements on a variety of problems including those failed by other well-known schemes. (C) 1996 Academic Press, Inc. RP NASA, LEWIS RES CTR, INTERNAL FLUID MECH DIV, CLEVELAND, OH 44135 USA. NR 32 TC 366 Z9 409 U1 4 U2 14 PU ACADEMIC PRESS INC ELSEVIER SCIENCE PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA SN 0021-9991 EI 1090-2716 J9 J COMPUT PHYS JI J. Comput. Phys. PD DEC PY 1996 VL 129 IS 2 BP 364 EP 382 DI 10.1006/jcph.1996.0256 PG 19 WC Computer Science, Interdisciplinary Applications; Physics, Mathematical SC Computer Science; Physics GA WC625 UT WOS:A1996WC62500009 ER PT J AU Pines, V Chait, A Zlatkowski, M AF Pines, V Chait, A Zlatkowski, M TI Anomaly in dendritic growth data - Effect of density change upon solidification SO JOURNAL OF CRYSTAL GROWTH LA English DT Letter AB We examine recent dendritic growth data obtained by Glicksman and co-workers [M.E. Glicksman, M.B. Koss and E.A. Winsa, Phys. Rev. Lett. 73 (1994) 573; M.E. Glicksman, M.B. Koss, L.T. Bushnell, J.C. LaCombe and E.A. Winsa, ISIJ Int. 35 (1995) 1216; MRS Fall Meeting, Symp. P, Boston, MA, 1995, in press: M.E. Glicksman, M,B. Koss, L.T. Bushnell and J.C. LaCombe, in: Modelling of Casting, Welding and Advanced Solidification Processes VII, Eds. M. Cross and J. Campbell, (The Minerals, Metals and Materials Society, 1995); private communication] in microgravity. These authors have pointed out an anomaly in the data, when compared with theoretical predictions, In particular, a systematic deviation of the growth Peclet number from an Ivantsov's theory was noted at the intermediate supercooling range. This work considers effects due to density change upon solidification. This requires a careful reexamination of the definition of material parameters, and an evaluation of effects due to the solidification-induced fluid flow (''Stefan wind''). A consistent application of carefully obtained material parameters clearly eliminates the discrepancy between the theory and experimental data. However, the effect of fluid flow due to the solid-melt density change is shown to be of minor importance to the particular experiment and material under consideration. We conclude hy presenting an Ivantsov's theory modified for the wall proximity effect and corrected for density change upon solidification that matches the entire range of supercooling levels used in Glicksman's experiments. C1 NASA,LEWIS RES CTR,COMP MAT LAB,CLEVELAND,OH 44135. CASE WESTERN RESERVE UNIV,DEPT PHYS,CLEVELAND,OH 44106. NR 12 TC 14 Z9 14 U1 0 U2 2 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 DEC PY 1996 VL 169 IS 4 BP 798 EP 802 DI 10.1016/S0022-0248(96)00667-7 PG 5 WC Crystallography; Materials Science, Multidisciplinary; Physics, Applied SC Crystallography; Materials Science; Physics GA VZ771 UT WOS:A1996VZ77100028 ER PT J AU Shieh, LS Wang, WM Sunkel, JW AF Shieh, LS Wang, WM Sunkel, JW TI Design of PAM and PWM controllers for sampled-data interval systems SO JOURNAL OF DYNAMIC SYSTEMS MEASUREMENT AND CONTROL-TRANSACTIONS OF THE ASME LA English DT Article ID DIGITAL REDESIGN; LINEAR-SYSTEMS; DISCRETE AB In this paper, we address two issues: digital redesign of a continuous-time interval system using an interval chebyshev quadrature approximation method; and translation of the newly digitally redesigned pulse-amplitude modulated (PAM) controller into art equivalent pulse-width modulated (PWM) controller via a second-order Taylor-series approximation method. Using this new interval digital redesign technique, the dynamic states of the digitally controlled sampled-data interval system are able to closely match those of the original analogously controlled continuous-time uncertain system. Three illustrative examples are provided to demonstrate the effectiveness of the proposed methods. C1 NASA,LYNDON B JOHNSON SPACE CTR,NAVIGAT CONTROL & AERONAUT DIV,HOUSTON,TX 77058. RP Shieh, LS (reprint author), UNIV HOUSTON,DEPT ELECT & COMP ENGN,HOUSTON,TX 77204, USA. NR 28 TC 8 Z9 8 U1 2 U2 2 PU ASME-AMER SOC MECHANICAL ENG PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017 SN 0022-0434 J9 J DYN SYST-T ASME JI J. Dyn. Syst. Meas. Control-Trans. ASME PD DEC PY 1996 VL 118 IS 4 BP 673 EP 682 DI 10.1115/1.2802342 PG 10 WC Automation & Control Systems; Instruments & Instrumentation SC Automation & Control Systems; Instruments & Instrumentation GA VZ437 UT WOS:A1996VZ43700004 ER PT J AU Younis, BA Gatski, TB Speziale, CG AF Younis, BA Gatski, TB Speziale, CG TI Assessment of the SSG pressure-strain model in free turbulent jets with and without swirl SO JOURNAL OF FLUIDS ENGINEERING-TRANSACTIONS OF THE ASME LA English DT Article ID REYNOLDS; CLOSURE AB Data from free turbulent jets both with and without swirl are used to assess the performance of the pressure-strain model of Speziale, Sarkar and Gatski, which is quadratic in the Reynolds stresses. Comparative predictions are also obtained with the two versions of the Launder, Reece and Rodi model, which are linear in the same terms. All models are used as part of a complete second-order closure based on the solution of differential transport equations for each nonzero component of <(u(i)u(j))over bar> together with an equation for the scalar energy dissipation rate. For nonswirling jets, the quadratic model underestimates the measured spreading rare of the plane jet but yields a better prediction for the axisymmetric case without resolving the plane jet/round jet anomaly. For the swirling axisymmetric jet, the same model accurately reproduces the effects of swirl on both the mean flow and the turbulence structure in sharp contrast with the linear models which yield results that are in serious error. The reasons for these differences are discussed. C1 NASA,LANGLEY RES CTR,HAMPTON,VA 23681. BOSTON UNIV,DEPT AEROSP & MECH ENGN,BOSTON,MA 02215. RP Younis, BA (reprint author), CITY UNIV LONDON,DEPT CIVIL ENGN,LONDON EC1V 0HB,ENGLAND. NR 27 TC 11 Z9 11 U1 2 U2 3 PU ASME-AMER SOC MECHANICAL ENG PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017 SN 0098-2202 J9 J FLUID ENG-T ASME JI J. Fluids Eng.-Trans. ASME PD DEC PY 1996 VL 118 IS 4 BP 800 EP 809 DI 10.1115/1.2835512 PG 10 WC Engineering, Mechanical SC Engineering GA WD487 UT WOS:A1996WD48700027 ER PT J AU Kuang, D Schutz, BE Watkins, MM AF Kuang, D Schutz, BE Watkins, MM TI On the structure of geometric positioning information in GPS measurements SO JOURNAL OF GEODESY LA English DT Article AB The geometric information from observables of the Global Positioning System is analyzed through the eigenvectors of the normal matrix in the positioning estimation problem. The relationship among observability, bias absorption and loss of information in differencing measurements is addressed. Some general conclusions for point positioning and relative positioning problems are drawn from analytic inference and supported by numerical simulations. C1 UNIV TEXAS,CTR SPACE RES,AUSTIN,TX 78712. CALTECH,JET PROP LAB,PASADENA,CA 91109. NR 9 TC 16 Z9 16 U1 0 U2 0 PU SPRINGER VERLAG PI NEW YORK PA 175 FIFTH AVE, NEW YORK, NY 10010 SN 0949-7714 J9 J GEODESY JI J. Geodesy PD DEC PY 1996 VL 71 IS 1 BP 35 EP 43 DI 10.1007/s001900050073 PG 9 WC Geochemistry & Geophysics; Remote Sensing SC Geochemistry & Geophysics; Remote Sensing GA WE852 UT WOS:A1996WE85200005 ER PT J AU Tsyganenko, NA Stern, DP AF Tsyganenko, NA Stern, DP TI Modeling the global magnetic field of the large-scale Birkeland current systems SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID ALIGNED CURRENTS; MAGNETOMETER DATA; ELECTRIC-FIELD; TAIL CURRENT; MAGNETOSPHERE; MAGNETOPAUSE; SHEET AB Quantitative models are developed for representing the global distribution of the average magnetic field produced by the region 1 and 2 Birkeland current systems. The problem is solved in four following steps: (1) constructing a realistic hit-dependent model of the Birkeland current sheets, based on the formalism of Euler potentials, (2) numerically computing their field at a large number of points within the modeling region, (3) finding a best-fit analytical approximation for that field, and (4) adding a current-free shielding held which confines the Birkeland held within the model magnetopause. At low altitudes the model field-aligned currents reach the ionosphere along eccentric ovals, which fit the observed region I and 2 zones of Iijima and Potemra, and they continue there as horizontal currents. At larger distances the nightside region I currents map to the plasma sheet boundary layer and are then diverted toward the tail flanks, while currents in the dawn-dusk and dayside sectors connect directly to the higher-latitude magnetopause. The region 2 current closes azimuthally near the equator, forming a spread-out partial ring current system. The described approach allows a great flexibility in the geometry of the Birkeland currents, making it feasible to infer their properties from spacecraft data. RP Tsyganenko, NA (reprint author), NASA,GODDARD SPACE FLIGHT CTR,EXTRATERR PHYS LAB,HUGHES STX CORP,CODE 695,GREENBELT,MD 20771, USA. RI Tsyganenko, Nikolai/J-7377-2012 OI Tsyganenko, Nikolai/0000-0002-5938-1579 NR 26 TC 389 Z9 395 U1 0 U2 12 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 SN 0148-0227 J9 J GEOPHYS RES JI J. Geophys. Res-Space Phys. PD DEC 1 PY 1996 VL 101 IS A12 BP 27187 EP 27198 DI 10.1029/96JA02735 PG 12 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VW423 UT WOS:A1996VW42300044 ER PT J AU Kuznetsova, MM Hesse, M Winske, D AF Kuznetsova, MM Hesse, M Winske, D TI Ion dynamics in a hybrid simulation of magnetotail reconnection SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID GEOMAGNETIC TAIL; MAGNETIC RECONNECTION; PARTICLE ORBITS; BOUNDARY-LAYER; CURRENT SHEETS; PLASMA SHEET; NEUTRAL LINE; COLLISIONLESS RECONNECTION; EARTHS MAGNETOTAIL; MHD FIELDS AB The 2 1/2-dimensional hybrid simulations are carried out to investigate self-consistent ion dynamics in time-dependent magnetic reconnection. The system dimensions 25 R(E)X 5 R(E) are able to accommodate large-scale structures associated with magnetotail reconnection. The simulations are started with two ion populations: hot ions forming the thin current sheet self-consistent with the initial equilibrium two-dimensional tail-like magnetic configuration and cold lobe ions with initially uniform density and temperature. The evolution of the initially stable system is triggered by superposition of a spatially localized resistivity. We find ion acceleration and formation of non-Maxwellian multicomponent ion distributions as predicted by test particle studies. Fine features, such as layers of counterstreaming ions, are found in the distributions of the initially cold lobe ions. The hot current sheet ''source'', however gives rather smeared ''output distributions'' due to significant spatial overlapping of ion populations with different histories. We find that ions, which are strongly accelerated in the close vicinity of the reconnection site, contribute little to the equilibrium current before reconnection is initiated. Ions, which significantly contribute to the equilibrium current, are either ejected earthward or carried away inside the released plasmoid without significant energy gain during a single ''impulsive'' interaction with the reconnection fields, Multiple encounters of the acceleration region and quasi-Fermi acceleration of ions trapped between the mirroring earthward boundary and the growing normal magnetic field are found. The simulations also show effective heating of initially cold background ions in the plasma sheet behind the released plasmoid. The tailward speed of energetic ions flowing around the plasmoid along reconnected lobe field lines exceeds the speed of plasmoid. The ions which contribute to these beams are part of the hot population and initially reside in the current sheet. These results match spacecraft observations prior to plasmoid arrival. C1 LOS ALAMOS NATL LAB,DIV APPL THEORET PHYS,LOS ALAMOS,NM 87545. NASA,GODDARD SPACE FLIGHT CTR,ELECTRODYNAM BRANCH,GREENBELT,MD 20771. RI Hesse, Michael/D-2031-2012; Kuznetsova, Maria/F-6840-2012 NR 56 TC 24 Z9 24 U1 0 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 SN 0148-0227 J9 J GEOPHYS RES JI J. Geophys. Res-Space Phys. PD DEC 1 PY 1996 VL 101 IS A12 BP 27351 EP 27373 DI 10.1029/96JA02622 PG 23 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VW423 UT WOS:A1996VW42300056 ER PT J AU Pulkkinen, TI Tsyganenko, NA AF Pulkkinen, TI Tsyganenko, NA TI Testing the accuracy of magnetospheric model field line mapping SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID MAGNETIC-FIELD; QUANTITATIVE MODELS; GEOMAGNETIC-FIELD; CURRENT SHEET; TAIL; MAGNETOTAIL; PARAMETERS AB We present a new method to test the statistical accuracy of field-aligned mappings by using a large magnetospheric data set and apply the method to the Tsyganenko [1989] model. The obtained errors in the field-aligned mappings are generally small in the auroral Bone outside the midnight sector but become larger on the nightside and within the polar cap. The model tail field is overstretched near midnight and the model field lines flare out toward the flanks and toward high Z values too much. The results also imply that there is a shear layer between the plasma sheet and lobe that could be indicative of the region I field-aligned current system. The large-scale mapping properties suggest that the magnetotail field is asymmetric with respect to the noon-midnight meridian: the model better represents the evening-sector field configuration, whereas the morning-sector model field lines map too far down the tail. C1 NASA,GODDARD SPACE FLIGHT CTR,HUGHES STX CORP,GREENBELT,MD 20771. RP Pulkkinen, TI (reprint author), FINNISH METEOROL INST,POB 503,FIN-00101 HELSINKI,FINLAND. RI Tsyganenko, Nikolai/J-7377-2012; Pulkkinen, Tuija/D-8403-2012 OI Tsyganenko, Nikolai/0000-0002-5938-1579; Pulkkinen, Tuija/0000-0002-6317-381X NR 23 TC 21 Z9 22 U1 0 U2 4 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 SN 0148-0227 J9 J GEOPHYS RES JI J. Geophys. Res-Space Phys. PD DEC 1 PY 1996 VL 101 IS A12 BP 27431 EP 27442 DI 10.1029/96JA02489 PG 12 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VW423 UT WOS:A1996VW42300061 ER PT J AU Connerney, JEP Acuna, MH Ness, NF AF Connerney, JEP Acuna, MH Ness, NF TI Octupole model of Jupiters magnetic field from Ulysses observations SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID MAGNETOSPHERE; ENVIRONMENT; PRESSURE; FLYBY AB A spherical harmonic model of the planetary magnetic field of Jupiter is obtained from the Ulysses encounter observations. The magnetic field in the Jovian magnetosphere is represented using a degree and order 3 spherical harmonic for the planetary (''internal'') field, and an explicit model of the magnetodisc for the field (''external'') due to distributed currents. The model is obtained by partial solution of the underdetermined inverse problem using generalized inverse techniques. Dipole, quadrupole, and a subset of the octupole spherical harmonic coefficients are determined and compared with those obtained using Voyager and Pioneer observations. The model requires a-less intense magnetodisc current, in early 1992, compared with that observed during the Voyager 1 encounter in 1979 and the Pioneer encounters of 1973 and 1974. C1 UNIV DELAWARE,BARTOL RES INST,NEWARK,DE 19716. RP Connerney, JEP (reprint author), NASA,GODDARD SPACE FLIGHT CTR,EXTRATERR PHYS LAB,GREENBELT,MD 20771, USA. RI connerney, john/I-5127-2013; OI connerney, jack/0000-0001-7478-6462 NR 23 TC 8 Z9 8 U1 0 U2 2 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 SN 0148-0227 J9 J GEOPHYS RES JI J. Geophys. Res-Space Phys. PD DEC 1 PY 1996 VL 101 IS A12 BP 27453 EP 27458 DI 10.1029/96JA02869 PG 6 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VW423 UT WOS:A1996VW42300064 ER PT J AU Cole, KD AF Cole, KD TI Particle dynamics in a spatially varying electric field - Comment SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article RP Cole, KD (reprint author), NASA,GODDARD SPACE FLIGHT CTR,CODE 910 4,GREENBELT,MD 20771, USA. NR 5 TC 0 Z9 0 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 SN 0148-0227 J9 J GEOPHYS RES JI J. Geophys. Res-Space Phys. PD DEC 1 PY 1996 VL 101 IS A12 BP 27459 EP 27460 DI 10.1029/96JA01606 PG 2 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VW423 UT WOS:A1996VW42300065 ER PT J AU Ratkiewicz, R Barnes, A Molvik, GA Spreiter, JR Stahara, SS AF Ratkiewicz, R Barnes, A Molvik, GA Spreiter, JR Stahara, SS TI Heliospheric termination shock motion due to fluctuations in the solar wind upstream conditions: Spherically symmetric model SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID DISTANCE; SCHEMES AB Large-scale fluctuations in the solar wind plasma upstream of the heliospheric termination shock (TS) will cause inward and outward motions of the shock. Using numerical techniques, we extend an earlier strictly one-dimensional (planar) analytic gasdynamic model [Barnes, 1993] to spherical symmetry to investigate the features of global behavior of shock motion. Our starting point is to establish a steady numerical solution of the gasdynamic equations describing the interaction between the solar wind and the interstellar medium. We then introduce disturbances of the solar wind dynamic pressure at an inner boundary and follow the subsequent evolution of the system, especially the motion of the termination shock. Our model solves spherically symmetric gasdynamic equations as an initial-boundary value problem. The equations in conservative form are solved using a fully implicit total variation diminishing (TVD) upwind scheme with Roe-type Riemann solver. Boundary conditions are given by the solar wind parameters on an inner spherical boundary, where they are allowed to vary with time for unsteady calculations and by a constant pressure (roughly simulating the effect of the local interstellar medium) on an outer boundary. We find that immediately after the interaction, the shock moves with speeds given by the earlier analogous analytic models. However, as the termination shock propagates, it begins to slow down, seeking a new equilibrium position. In addition, the disturbance transmitted through the TS, either a shock or rarefaction wave, will encounter the outer boundary and be reflected back. The reflected signal will encounter the TS, causing it to oscillate. The phenomenon may be repeated for a number of reflections, resulting in a ''ringing'' of the outer heliosphere. C1 NAI,WOODBRIDGE,CA 95258. CTR SPACE RES,PL-00716 WARSAW,POLAND. STANFORD UNIV,STANFORD,CA 94305. RMA AEROSP INC,MOUNTAIN VIEW,CA 94043. RP Ratkiewicz, R (reprint author), NASA,AMES RES CTR,MS 245-3,MOFFETT FIELD,CA 94035, USA. NR 28 TC 13 Z9 13 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 SN 0148-0227 J9 J GEOPHYS RES JI J. Geophys. Res-Space Phys. PD DEC 1 PY 1996 VL 101 IS A12 BP 27483 EP 27497 DI 10.1029/96JA02233 PG 15 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VW423 UT WOS:A1996VW42300069 ER PT J AU Richardson, IG Cane, HV AF Richardson, IG Cane, HV TI Particle flows observed in ejecta during solar event onsets and their implication for the magnetic field topology SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID FLIGHT-CENTER INSTRUMENTS; ENERGETIC PARTICLES; INTERPLANETARY SHOCKS; GEOMAGNETIC STORMS; COMPOUND STREAMS; CLOUDS; WIND; MAGNETOSPHERE; EVOLUTION; AU AB We investigate the magnetic field topology of ejecta (the interplanetary manifestations of solar mass ejections) by using observations of energetic particle anisotropies made by the Goddard Space Flight Center instruments on the ISEE 3, Hellos 1, and Hellos 2 spacecraft at less than or equal to 1 AU from the Sun. In particular, we investigate particle flows observed following the onsets of 39 solar energetic particle events which occurred when the observing spacecraft was located in a preexisting ejecta. To infer when the spacecraft was located in an ejecta, we examine a wide range of indicators of the presence of ejecta including magnetic cloud signatures, bidirectional energetic ion flows, bidirectional solar wind electron heat fluxes, and depressed proton plasma temperatures. We find that inside ejecta, the particle arrival direction in the ecliptic plane varies widely from event to event, with at least 30% of the events showing flows from the east of the Sun. In contrast, in 60 similar events observed outside ejecta, the particle arrival directions are consistent with flows from the Sun along near-Parker spiral field lines in >90% df cases. We also discuss multiple-spacecraft observations of three particle events which illustrate the contrasting particle flows observed during the same event by spacecraft in different solar wind structures. WC conclude that the observations are consistent with the presence of nonspiral magnetic fields, including looped magnetic field lines connected to the Sun, in at least a subset of ejecta. C1 NASA,GODDARD SPACE FLIGHT CTR,HIGH ENERGY ASTROPHYS LAB,GREENBELT,MD 20771. RP Richardson, IG (reprint author), UNIV TASMANIA,DEPT PHYS,GPO BOX 252C,HOBART,TAS 7001,AUSTRALIA. OI Richardson, Ian/0000-0002-3855-3634 NR 34 TC 37 Z9 37 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 SN 0148-0227 J9 J GEOPHYS RES JI J. Geophys. Res-Space Phys. PD DEC 1 PY 1996 VL 101 IS A12 BP 27521 EP 27532 DI 10.1029/96JA02643 PG 12 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VW423 UT WOS:A1996VW42300071 ER PT J AU LengyelFrey, D Hess, RA MacDowall, RJ Stone, RG Lin, N Balogh, A Forsyth, R AF LengyelFrey, D Hess, RA MacDowall, RJ Stone, RG Lin, N Balogh, A Forsyth, R TI Ulysses observations of whistler waves at interplanetary shocks and in the solar wind SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID INSTABILITIES; ELECTRONS AB This study of whistler wave emission observed by the Ulysses Unified Radio and Plasma Wave (URAP) experiment between 1 and 5 AU is a complement to previous studies of whistler waves observed by the Hellos spacecraft between 0.3 and 1 AU. The Hellos spacecraft continuously detected a background of whistlers close to the Sun, and this background was found to decrease in intensity with larger heliocentric distance. Ulysses plasma wave observations confirm this trend. Within a heliocentric distance of approximately 2 AU, whistler waves are routinely observed. Beyond about 3 AU the waves are usually observed only downstream of interplanetary shocks. Moreover, whistler waves are routinely observed within about 2 AU at all heliographic latitudes of the Ulysses trajectory (-80 degrees to +80 degrees). The combined observations from the Hellos and Ulysses spacecraft suggest that whistler emission is always present in the solar wind, although at larger heliocentric distances the wave amplitudes are often below the thresholds of the URAP instrument. Observations throughout the first 5 years of the Ulysses mission show a clear correlation of whistler emission intensity with magnetic field strength, or gyrofrequency, such that increases in wave intensities coincide with increases in gyrofrequency. This correlation is especially evident in observations of interplanetary shocks and high-speed streams. A possible cause of this correlation is increased whistler wave growth due to enhanced electron temperature anisotropies in regions of compressed magnetic field. A shift of the background whistler spectrum as a function of gyrofrequency could account for the observed decrease in whistler amplitudes with increasing heliocentric distance. C1 NASA, GODDARD SPACE FLIGHT CTR, GREENBELT, MD 20771 USA. JOHNS HOPKINS SCH MED, DIV ONCOL, BALTIMORE, MD 21287 USA. UNIV MINNESOTA, SCH PHYS & ASTRON, MINNEAPOLIS, MN 55455 USA. NASA, GODDARD SPACE FLIGHT CTR, EXTRATERR PHYS LAB, GREENBELT, MD 20771 USA. RP LengyelFrey, D (reprint author), UNIV LONDON IMPERIAL COLL SCI TECHNOL & MED, BLACKETT LAB, PRINCE CONSORT RD, LONDON, ENGLAND. RI MacDowall, Robert/D-2773-2012 NR 26 TC 28 Z9 28 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 SN 0148-0227 J9 J GEOPHYS RES JI J. Geophys. Res-Space Phys. PD DEC 1 PY 1996 VL 101 IS A12 BP 27555 EP 27564 DI 10.1029/96JA00548 PG 10 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VW423 UT WOS:A1996VW42300075 ER PT J AU Stribling, T Roberts, DA Goldstein, ML AF Stribling, T Roberts, DA Goldstein, ML TI The evolution of Alfvenic perturbations in a three-dimensional MHD model of the inner heliospheric current sheet region SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID SOLAR-WIND TURBULENCE; MEAN MAGNETIC-FIELD; MAGNETOHYDRODYNAMIC TURBULENCE; SPATIAL TRANSPORT; SPECTRAL TRANSFER; STREAM STRUCTURE; RESISTIVE INSTABILITIES; CONVECTIVE STRUCTURES; FLOWING PLASMA; FLUCTUATIONS AB We investigate an idealized model of the evolution of magnetohydrodynamic (MHD) scale velocity and magnetic field fluctuations in the equatorial region of the inner heliosphere at solar minimum. In this model a three-dimensional current sheet is constructed from a sheared magnetic field embedded between two velocity sheer layers. Simulations of the incompressible MHD equations are used to study the evolution of a variety of perturbations to this configuration. We also perform a linear stability; analysis using the solutions of the Orr-Sommerfeld and related equations for the current sheet model. From simulations in which the model is perturbed with small amplitude Alfven waves, we find that the perturbing velocity and magnetic fields become decorrelated in the region of velocity and magnetic shear during the linear evolution of the fluid instability. This result and similar results for large amplitude perturbations agree qualitatively with previous two-dimensional simulations and with observations made by the Hellos spacecraft at current sheet crossings between 0.3 and 1 AU and gives further evidence that shear-driven fluid instabilities provide a mechanism for the destruction of velocity-magnetic field correlation. The simulations also show enhancement of the power in the radial components of the perturbing velocity and magnetic fields in regions where they are sheared, in agreement with observations. We show that the linear evolution of transverse perturbations to the sheared fields gives rise to these radial power enhancements. While these simulations elucidate the three-dimensional evolution of shear flows, they must be extended further to include compression and expansion of the wind. C1 NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. RP Stribling, T (reprint author), NASA,GODDARD SPACE FLIGHT CTR,CODE 692,GREENBELT,MD 20771, USA. RI Roberts, Dana/D-4625-2012; Goldstein, Melvyn/B-1724-2008 NR 54 TC 12 Z9 12 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 SN 0148-0227 J9 J GEOPHYS RES JI J. Geophys. Res-Space Phys. PD DEC 1 PY 1996 VL 101 IS A12 BP 27603 EP 27623 DI 10.1029/96JA02583 PG 21 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VW423 UT WOS:A1996VW42300079 ER PT J AU Tsurutani, B Gonzalez, WD Tang, FM AF Tsurutani, B Gonzalez, WD Tang, FM TI Interplanetary origin of geomagnetic activity in the declining phase of the solar cycle - Reply SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID INTERACTION REGIONS; CORONAL HOLES; WIND; ULYSSES; FLUX C1 CALTECH,PASADENA,CA 91125. CALTECH,JET PROP LAB,PASADENA,CA 91109. RP Tsurutani, B (reprint author), INST NATL PESQUISAS ESPACIAIS,BR-12200 SAO PAULO,BRAZIL. NR 16 TC 0 Z9 0 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 SN 0148-0227 J9 J GEOPHYS RES JI J. Geophys. Res-Space Phys. PD DEC 1 PY 1996 VL 101 IS A12 BP 27631 EP 27633 DI 10.1029/96JA02499 PG 3 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VW423 UT WOS:A1996VW42300081 ER PT J AU Locci, IE Dickerson, RM Garg, A Noebe, RD Whittenberger, JD Nathal, MV Darolia, R AF Locci, IE Dickerson, RM Garg, A Noebe, RD Whittenberger, JD Nathal, MV Darolia, R TI Microstructure and phase stability of single crystal NiAl alloyed with Hf and Zr SO JOURNAL OF MATERIALS RESEARCH LA English DT Article ID OXIDATION AB Six near stoichiometric, NiAl single-crystal alloys, with 0.05-1.5 at.% of Hf and Zr additions plus Si impurities, were microstructurally analyzed in the as-cast, homogenized, and aged conditions. Hafnium-rich interdendritic regions, containing the Heusler phase (Ni2AlHf), were found in all the as-cast alloys containing Hf. Homogenization heat treatments partially reduced these interdendritic segregated regions. Transmission electron microscopy (TEM) observations of the as-cast and homogenized microstructures revealed the presence of a high density of fine Hf (or Zr) and Si-rich precipitates. These were identified as G-phase, Ni(16)X(6)Si(7), or as an orthorhombic NiXSi phase, where X is Hf or Zr. Under these conditions the expected Heusler phase (beta') was almost completely absent. The Si responsible for the formation of the G and NiHfSi phases is the result of molten metal reacting with the Si-containing crucible used during the casting process. Varying the cooling rates after homogenization resulted in the refinement or complete suppression of the G and NiHfSi phases. In some of the alloys studied, long-term aging heat treatments resulted in the formation of Heusler precipitates, which were more stable at the aging temperature and coarsened at the expense of the G-phase. In other alloys, long-term aging resulted in the formation of the NiXSi phase. The stability of the Heusler or NiXSi phases can be traced to the reactive element (Hf or Zr) to silicon ratio, If the ratio is high, then the Heusler phase appears stable after long time aging. If the ratio is low, then the NiHfSi phase appears to be the stable phase. C1 NASA, LEWIS RES CTR, CLEVELAND, OH 44135 USA. NYMA INC, CLEVELAND, OH 44124 USA. GE CO, AIRCRAFT ENGINES, CINCINNATI, OH 45215 USA. RP CASE WESTERN RESERVE UNIV, CLEVELAND, OH 44106 USA. NR 30 TC 27 Z9 28 U1 1 U2 10 PU CAMBRIDGE UNIV PRESS PI NEW YORK PA 32 AVENUE OF THE AMERICAS, NEW YORK, NY 10013-2473 USA SN 0884-2914 EI 2044-5326 J9 J MATER RES JI J. Mater. Res. PD DEC PY 1996 VL 11 IS 12 BP 3024 EP 3038 DI 10.1557/JMR.1996.0384 PG 15 WC Materials Science, Multidisciplinary SC Materials Science GA VX289 UT WOS:A1996VX28900013 ER PT J AU Handschuh, RF Kicher, TP AF Handschuh, RF Kicher, TP TI A method for thermal analysis of spiral bevel gears SO JOURNAL OF MECHANICAL DESIGN LA English DT Article AB A modelling method for analyzing the three-dimensional thermal behavior of spiral bevel gears has been developed. The model surfaces are generated through application of differential geometry to the manufacturing process for face-milled spiral bevel gears. Contact on the gear surface is found by combining tooth contact analysis with three-dimensional Hertzian theory. The tooth contact analysis provides the principle curvatures and orientations of the two surfaces. This information is then used directly in the Hertzian analysis to find the contact size and maximum pressure. Heat generation during meshing is determined as a function of the applied load, sliding velocity, and coefficient of friction. Each of these factors change as the point of contact changes during meshing. A nonlinear finite element program was used to conduct the heat transfer analysis. This program permitted the time- and position-varying boundary conditions, found in operation, to be applied to a one-tooth model. An example model and analytical results are presented. RP Handschuh, RF (reprint author), USA,RES LAB,VEHICLE PROPULS DIRECTORATE,LEWIS RES CTR,CLEVELAND,OH 44135, USA. NR 26 TC 5 Z9 7 U1 3 U2 7 PU ASME-AMER SOC MECHANICAL ENG PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017 SN 1050-0472 J9 J MECH DESIGN JI J. Mech. Des. PD DEC PY 1996 VL 118 IS 4 BP 580 EP 585 DI 10.1115/1.2826932 PG 6 WC Engineering, Mechanical SC Engineering GA WA870 UT WOS:A1996WA87000022 ER PT J AU Ouardi, O Hilico, JC Loete, M Brown, LR AF Ouardi, O Hilico, JC Loete, M Brown, LR TI The hot bands of methane between 5 and 10 mu m SO JOURNAL OF MOLECULAR SPECTROSCOPY LA English DT Article ID TETRAHEDRAL XY4 MOLECULES; DIPOLE-MOMENT; LINE STRENGTHS; NU-2; SPECTROSCOPY; PARAMETERS; (CH4)-C-13; CH4-C-12; SPECTRUM; DYAD AB Experimental line intensities of 1727 transitions arising from nine hot bands in the pentad-dyad system of methane are fitted to first and second order using the effective dipole moment expansion in the polyad scheme. The observed bands are nu(3) - nu(2), nu(3) - nu(4), nu(1) - nu(2), nu(1) - nu(4), 2 nu(4) - nu(4), nu(2) + nu(4) - nu(2), nu(2) + nu(4) - nu(4), 2 nu(2) - nu(2), and 2 nu(2) - nu(4), and the intensities are obtained from long-path spectra recorded with the Fourier transform spectrometer located at Kitt Peak National Observatory. For the second order model, some of the 27 intensity parameters are not linearly independent, and so two methods (extrapolation and effective parameters) are proposed to model the intensities of the hot bands. In order to obtain stable values for three of these parameters, 1206 dyad (nu(4), nu(2)) intensities are refitted simultaneously with the hot band lines. The simultaneous fits to first and second order lead to rms values respectively of 21.5% and 5.0% for the 1727 hot band lines and 6.5% and 3.0% for the 1206 dyad lines. The band intensities of all 10 pentad-dyad hot bands are predicted in units of cm(-2) atm(-1) at 296 K to range from 0.931 (for 2 nu(4) - nu(4)) to 7.67 x 10(-5) (for 2 nu(4) - nu(2)) The total intensities are also estimated to first order for two other hot band systems (octad-pentad and tetradecad-octad) that give rise to weak transitions between 5 and 10 mu m. (C) 1996 Academic Press, Inc. C1 CALTECH,JET PROP LAB,PASADENA,CA 91109. RP Ouardi, O (reprint author), UNIV BOURGOGNE,PHYS LAB,BP 138,F-21004 DIJON,FRANCE. RI ouardi, Okkacha/C-2180-2015 OI ouardi, Okkacha/0000-0001-6970-5330 NR 26 TC 24 Z9 24 U1 1 U2 3 PU ACADEMIC PRESS INC JNL-COMP SUBSCRIPTIONS PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 SN 0022-2852 J9 J MOL SPECTROSC JI J. Mol. Spectrosc. PD DEC PY 1996 VL 180 IS 2 BP 311 EP 322 DI 10.1006/jmsp.1996.0254 PG 12 WC Physics, Atomic, Molecular & Chemical; Spectroscopy SC Physics; Spectroscopy GA VV347 UT WOS:A1996VV34700012 ER PT J AU Wajsowicz, RC AF Wajsowicz, RC TI The response of the Indo-Pacific throughflow to interannual variations in the Pacific wind stress .2. Realistic geometry and ECMWF wind stress anomalies for 1985-89 SO JOURNAL OF PHYSICAL OCEANOGRAPHY LA English DT Article ID DEPTH-INTEGRATED FLOW; INDONESIAN THROUGHFLOW; WORLD OCEAN; SEA-LEVEL; MODEL; CIRCULATION; REFLECTION; BOUNDARY; EASTERN; ISLAND AB The effect of interannual variability in wind stress on the transport between the Pacific and Indian Oceans through the Indonesian archipelago is investigated using a multilevel, numerical, general circulation model (GCM). The experiments are conducted in a spinup, anomaly mode: the GCM is initially at rest with a horizontally uniform stratification typical of tropical oceans. The wind stress anomalies are derived from the European Centre for Medium-Range Weather Forecasts 1000-mb winds for 1985-89. The modeled variability is sensitive to the specification of bottom topography and archipelago geometry. Two model configurations are considered: (i) flat-bottomed with the option of sills within a simplified, idealized archipelago and (ii) realistic bottom topography and a complex archipelago. In the first model, there is northward depth-integrated transport anomaly lasting 2 1/2 years with phase 6 months ahead of the collapse of the equatorial easterlies prior to the 1986-87 El Nino. The peak transport is about 5 Sv (Sv = 10(6) m(3) s(-1)), which is reduced to 3 Sv if shallow sills are present in the archipelago. There follows a southward transport anomaly, peaking al about 6 Sv during the ensuing La Nina. The baroclinic transport is consistent with cold and warm equatorial Rossby waves partially scattered into the archipelago during El Nino and La Nina, respectively. The reduction in depth-integrated throughflow generated by the reduction in southern midlatitude westerlies over 1985-86 results in a distinct signal in the baroclinic transport, and similarly in their increase again over 1988. Contrasting models with open and wholly blocked archipelagos yields heat content differences, measured as the temperature averaged over the upper 300 m, of typically O(0.05 degrees C) in the west equatorial Pacific and O(0.3 degrees C) in the Pacific western boundary layers and Indian Ocean. This suggests that throughflow variations could have implications for the timing of ENSO. In contrast, the second model has a very weak throughflow with peak-to-peak amplitude of only 3 Sv. Its archipelago is a relatively poor transmitter of equatorial waves, and its f/H contours are such that the depth-integrated throughflow is driven in part by the southerly extent of the South Pacific midlatitude wind stress anomalies. However, interestingly, the model still exhibits a decrease in throughflow in excess of 1 Sv prior to the onset of the 1986-87 El Nino due to variations in the southern midlatitude wind stress over the Pacific, which is also accompanied by a signature in the baroclinic transport. Also, contrasting homogeneous and stratified versions of the models demonstrates the importance of JEBAR over direct wind stress forcing of the depth-integrated throughflow. A closed form analytical expression for the transport in terms of an integral over a closed path formed by uniquely defined f/H contours, an island rule, is derived and used to help interpret the results. C1 NASA,GODDARD SPACE FLIGHT CTR,OCEANS & ICE BRANCH,GREENBELT,MD 20771. NR 13 TC 6 Z9 6 U1 0 U2 2 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 SN 0022-3670 J9 J PHYS OCEANOGR JI J. Phys. Oceanogr. PD DEC PY 1996 VL 26 IS 12 BP 2589 EP 2610 DI 10.1175/1520-0485(1996)026<2589:TROTIT>2.0.CO;2 PG 22 WC Oceanography SC Oceanography GA WC962 UT WOS:A1996WC96200003 ER PT J AU Shebalin, JV AF Shebalin, JV TI Absolute equilibrium entropy SO JOURNAL OF PLASMA PHYSICS LA English DT Article ID MAGNETOHYDRODYNAMIC TURBULENCE; DYNAMICS AB The entropy associated with absolute equilibrium ensemble theories of ideal, homogeneous, fluid and magnetofluid turbulence is discussed, and the three-dimensional fluid case is examined in detail. A sigma function is defined, whose minimum value with respect to global parameters is the entropy. A comparison is made between the use of global functions sigma and phase functions H (associated with the development of various H theorems of ideal turbulence). It is shown that the two approaches are complementary, though conceptually different: H theorems show that an isolated system tends to equilibrium, while sigma functions allow the demonstration that entropy never decreases when two previously isolated systems are combined. This provides a more complete picture of entropy in the statistical mechanics of ideal fluids. RP Shebalin, JV (reprint author), NASA,LANGLEY RES CTR,HAMPTON,VA 23681, USA. NR 21 TC 12 Z9 12 U1 0 U2 0 PU CAMBRIDGE UNIV PRESS PI NEW YORK PA 40 WEST 20TH STREET, NEW YORK, NY 10011-4211 SN 0022-3778 J9 J PLASMA PHYS JI J. Plasma Phys. PD DEC PY 1996 VL 56 BP 419 EP 426 PN 3 PG 8 WC Physics, Fluids & Plasmas SC Physics GA WR143 UT WOS:A1996WR14300005 ER PT J AU Ratnakumar, BV Timmerman, P DiStefano, S AF Ratnakumar, BV Timmerman, P DiStefano, S TI Simulation of temperature-compensated voltage limit curves for aerospace Ni-Cd batteries using a first principles' model SO JOURNAL OF POWER SOURCES LA English DT Article DE batteries; nickel; cadmium; voltage limits; temperature; mathematical models ID NICKEL-CADMIUM; PROTON DIFFUSION; DISCHARGE; ELECTRODE; CELL AB Temperature-compensated voltage limits (V/T limits) are routinely used in Low Earth Orbit (LEO) satellites to permit fast charging of the Ni-Cd battery with minimum overcharge and without the problems of thermal runaway during overcharge. The voltage limits are experimentally determined from extensive testing of cells for a proper design of the charge control system to achieve the desired charge/discharge ratio in orbit. Here, we demonstrate the use of first-principles', mathematical models to construct the V/T curves theoretically. The predicted charge/discharge ratios under various orbit conditions such as different states of charge, in-rush currents and temperatures are compared with the experimental data. RP Ratnakumar, BV (reprint author), CALTECH,JET PROP LAB,4800 OAK GROVE DR,PASADENA,CA 91109, USA. NR 23 TC 1 Z9 1 U1 3 U2 3 PU ELSEVIER SCIENCE SA LAUSANNE PI LAUSANNE PA PO BOX 564, 1001 LAUSANNE, SWITZERLAND SN 0378-7753 J9 J POWER SOURCES JI J. Power Sources PD DEC PY 1996 VL 63 IS 2 BP 157 EP 165 DI 10.1016/S0378-7753(96)02444-5 PG 9 WC Chemistry, Physical; Electrochemistry; Energy & Fuels; Materials Science, Multidisciplinary SC Chemistry; Electrochemistry; Energy & Fuels; Materials Science GA WX082 UT WOS:A1996WX08200001 ER PT J AU Westphal, DL Kinne, S Pilewskie, P Alvarez, JM Minnis, P Young, DF Benjamin, SG Eberhard, WL Kropfli, RA Matrosov, SY Snider, JB Uttal, TA Heymsfield, AJ Mace, GG Melfi, SH Starr, DO Soden, JJ AF Westphal, DL Kinne, S Pilewskie, P Alvarez, JM Minnis, P Young, DF Benjamin, SG Eberhard, WL Kropfli, RA Matrosov, SY Snider, JB Uttal, TA Heymsfield, AJ Mace, GG Melfi, SH Starr, DO Soden, JJ TI Initialization and validation of a simulation of cirrus using FIRE-II data SO JOURNAL OF THE ATMOSPHERIC SCIENCES LA English DT Article ID OCTOBER 1986; AIRCRAFT OBSERVATIONS; RADIATIVE PROPERTIES; OPTICAL-PROPERTIES; RAMAN LIDAR; WATER-VAPOR; CLOUDS; ICE; SENSITIVITY; ABSORPTION AB Observations from a wide variety of instruments and platforms are used to validate many different aspects of a three-dimensional mesoscale simulation of the dynamics, cloud microphysics, and radiative transfer of a cirrus cloud system observed on 26 November 1991 during the second cirrus field program of the First International Satellite Cloud Climatology Program (ISCCP) Regional Experiment (FIRE-II) located in southeastern Kansas. The simulation was made with a mesoscale dynamical model utilizing a simplified bulk water cloud scheme and a spectral model of radiative transfer. Expressions for cirrus optical properties for solar and infrared wavelength intervals as functions of ice water content and effective particle radius are modified for the midlatitude cirrus observed during FIRE II and are shown to compare favorably with explicit size-resolving calculations of the optical properties. Rawinsonde. Raman lidar, and satellite data are evaluated and combined to produce a time-height cross section of humidity at the central FIRE-II site for model verification. Due to the wide spacing of rawinsondes and their infrequent release, important moisture features go undetected and are absent in the con ventional analyses. The upper-tropospheric humidities used for the initial conditions were generally less than 50% of those inferred from satellite data, yet over the course of a 24-h simulation the model produced a distribution that closely resembles the large-scale features of the satellite analysis. The simulated distribution and concentration of ice compares favorably wi th data from radar, lidar, satellite, and aircraft. Direct comparison is made between the radiative transfer simulation and data from broadband and spectral sensors and inferred quantities such as cloud albedo, optical depth, and top-of-the atmosphere 11-mu m brightness temperature, and the 6.7-mu m brightness temperature. Comparison is also made with theoretical heating rates calculated using the rawinsonde data and measured ice water size distributions hear the central site. For this case study, and perhaps for most other mesoscale applications, the differences between the observed and simulated radiative quantities are due more to errors in the prediction of ice water content, than to errors in the optical properties or the radiative transfer solution technique. C1 NASA,AMES RES CTR,MOFFETT FIELD,CA 94035. NASA,LANGLEY RES CTR,HAMPTON,VA 23665. NOAA,FSL,BOULDER,CO. NOAA,ETL,BOULDER,CO. NCAR,BOULDER,CO. PENN STATE UNIV,UNIVERSITY PK,PA 16802. NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. PRINCETON UNIV,NOAA,GEOPHYS FLUID DYNAM LAB,PRINCETON,NJ 08542. RP Westphal, DL (reprint author), USN,RES LAB,7 GRACE HOPPER ST,STOP 2,MONTEREY,CA 94943, USA. RI Heymsfield, Andrew/E-7340-2011; Eberhard, Wynn/B-5402-2015; Benjamin, Stan/C-5818-2015; Minnis, Patrick/G-1902-2010 OI Benjamin, Stan/0000-0002-5751-8236; Minnis, Patrick/0000-0002-4733-6148 NR 49 TC 6 Z9 6 U1 0 U2 1 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 SN 0022-4928 J9 J ATMOS SCI JI J. Atmos. Sci. PD DEC 1 PY 1996 VL 53 IS 23 BP 3397 EP 3429 DI 10.1175/1520-0469(1996)053<3397:IAVOAS>2.0.CO;2 PG 33 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA VX673 UT WOS:A1996VX67300001 ER PT J AU Tsay, SC Gabriel, PM King, MD Stephens, GL AF Tsay, SC Gabriel, PM King, MD Stephens, GL TI Spectral reflectance and atmospheric energetics in cirrus-like clouds .2. Applications of a Fourier-Riccati approach to radiative transfer SO JOURNAL OF THE ATMOSPHERIC SCIENCES LA English DT Article ID SOLAR-RADIATION; STRATOCUMULUS CLOUDS; OPTICAL-THICKNESS; ICE CRYSTALS; AIRCRAFT; CLIMATE; EARTH; SATELLITE; SYSTEM; MODIS AB One of the major sources of uncertainty in climate studies is the detection of cirrus clouds and characterization of their radiative properties. Combinations of water vapor absorption channels (e.g., 1.38 mu m), ice-water absorption channels (e.g., 1.64 mu m), and atmospheric window channels (e.g., 11 mu m) in the imager, together with a lidar profiler on future EOS platforms, will contribute to enhancing our understanding of cirrus clouds. The aforementioned spectral channels are used in this study to explore the effects exerted by uncertainties in cloud microphysical properties (e.g., particle size distribution) and cloud morphology on the apparent radiative properties, such as spectral reflectance and heating and cooling rate profiles. As in Part I of our previous study, which establishes the foundations of the Fourier-Riccati method of radiative transfer in inhomogeneous media, cloud extinction and scattering functions are characterized by simple spatial variations with measured and hypothesized microphysics to facilitate our understanding of their radiative properties. Results of this study suggest that (i) while microphysical variations in the scattering and extinction functions of clouds affect the magnitudes of their spectral reflectances, cloud morphology significantly alters the shape of their angular distribution; (ii) spectral reflectances viewed near nadir are least affected by cloud variability; and (iii) cloud morphology can lead to spectral heating and cooling rate profiles that differ substantially from their plane-parallel averaged equivalents. Since there are no horizontal thermal gradients in plane-parallel clouds, it may be difficult to correct for this deficiency. C1 COLORADO STATE UNIV,DEPT ATMOSPHER SCI,FT COLLINS,CO 80523. NASA,GODDARD SPACE FLIGHT CTR,EARTH SCI DIRECTORATE,GREENBELT,MD 20771. RP Tsay, SC (reprint author), NASA,GODDARD SPACE FLIGHT CTR,ATMOSPHERES LAB,CODE 913,GREENBELT,MD 20771, USA. RI King, Michael/C-7153-2011; Tsay, Si-Chee/J-1147-2014 OI King, Michael/0000-0003-2645-7298; NR 31 TC 8 Z9 8 U1 0 U2 0 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 SN 0022-4928 J9 J ATMOS SCI JI J. Atmos. Sci. PD DEC 1 PY 1996 VL 53 IS 23 BP 3450 EP 3467 DI 10.1175/1520-0469(1996)053<3450:SRAAEI>2.0.CO;2 PG 18 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA VX673 UT WOS:A1996VX67300003 ER PT J AU Shibata, K Uchino, O Kamiyama, T McCormick, MP AF Shibata, K Uchino, O Kamiyama, T McCormick, MP TI An estimation of the radiative effect in the stratosphere due to the Pinatubo aerosol SO JOURNAL OF THE METEOROLOGICAL SOCIETY OF JAPAN LA English DT Article ID MT-PINATUBO; VOLCANIC AEROSOLS; MIDDLE ATMOSPHERE; SIZE DISTRIBUTION; ERUPTION; OZONE; CLIMATE; LIDAR; TEMPERATURE; CLOUD AB The global distribution of the Pinatubo aerosol in the stratosphere is constructed for optical thickness at 1 mu m by combining satellite data and lidar data for one year, from June 1991 to June 1992, following the eruption. The distribution, averaged for every two months, is composed of the data from Stratospheric Aerosol and Gas Experiment II between about 70 degrees N and 70 degrees S and the data from other satellites and lidar measurements at high latitudes and in the tropical lower stratosphere. Radiative heating rate due to the Pinatubo aerosol is calculated combining this distribution at 1 mu m with the radiative properties of observed sulfate aerosols. Sulfate aerosol does not absorb substantially but only scatters solar radiation, thereby producing very weak warming of about 0.02 Kday(-1) in the upper stratosphere due to ozone absorption of aerosol-reflected radiation. Terrestrial radiation brings a warming of about 0.1 Kday(-1) to the aerosol layer in low and middle latitudes, and very weak cooling at high latitudes. The net effect is, then, brought about by terrestrial radiation. Stratospheric temperature change is also calculated using a fixed dynamical heating model. In low latitudes, the middle stratospheric temperature rises rapidly by about 2 K during the first 40 days, following which the warming slows down and its axis moves northward to about 15 degrees N. The largest warming of 3 K appears in the axis latitude after 10 months and the second largest warming of 2.9 K at 5 degrees S after 12 months. C1 NASA, LANGLEY RES CTR, DIV ATMOSPHER SCI, HAMPTON, VA 23665 USA. RP Shibata, K (reprint author), METEOROL RES INST, 1-1 NAGAMINE, TSUKUBA, IBARAKI 305, JAPAN. NR 62 TC 5 Z9 5 U1 0 U2 2 PU METEOROLOGICAL SOC JAPAN PI TOKYO PA C/O JAPAN METEOROLOGICAL AGENCY 1-3-4 OTE-MACHI, CHIYODA-KU, TOKYO, 100-0004, JAPAN SN 0026-1165 EI 2186-9057 J9 J METEOROL SOC JPN JI J. Meteorol. Soc. Jpn. PD DEC PY 1996 VL 74 IS 6 BP 763 EP 780 PG 18 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA WK275 UT WOS:A1996WK27500003 ER PT J AU Barnes, NP Rodriguez, WJ Walsh, BM AF Barnes, NP Rodriguez, WJ Walsh, BM TI Ho:Tm:YLF laser amplifiers SO JOURNAL OF THE OPTICAL SOCIETY OF AMERICA B-OPTICAL PHYSICS LA English DT Article ID OPTICAL-SPECTRUM; HOLMIUM YLF; PERFORMANCE; OSCILLATOR; LIYF4; YAG AB A series of models is developed that describes a Ho:Tm laser, and predictions from these models are compared with experimental measurements for a variety of Ho:Tm:YLF amplifiers. Modeling is complicated by the plethora of required parameters needed to describe the dynamics of the Ho:Tm laser system versus the paucity of measured parameters. To remedy this, calculations presented here begin with measured energy levels and a quantum-mechanical model to determine a set of crystal-field parameters that are then used to calculate the energy-transfer parameters. Energy-transfer parameters, which describe the dynamics of energy exchange in the Ho:Tm system, are subsequently used in a rate-equation model to describe the dynamics of the lowest four manifolds of both Ho and Tm. Next, predictions of the rate-equation model are used in an amplifier model, which, among other effects, includes the variation of the pump energy density with the position of the probe beam in the amplifier. Results of the amplifier model are then compared with small-signal gain measurements from a variety of Ho:Tm:YLF laser amplifiers. Finally, the models are used to investigate the ultimate performance of a Ho:Tm:YLF laser amplifier by varying the concentrations of Ho and Tm in addition to the length of the end-pumped device. (C) 1996 Optical Society of America. C1 NORFOLK STATE UNIV,CTR MAT RES,NORFOLK,VA 23504. BOSTON COLL,CHESTNUT HILL,MA 02167. RP Barnes, NP (reprint author), NASA,LANGLEY RES CTR,HAMPTON,VA 23681, USA. NR 27 TC 48 Z9 52 U1 2 U2 4 PU OPTICAL SOC AMER PI WASHINGTON PA 2010 MASSACHUSETTS AVE NW, WASHINGTON, DC 20036 SN 0740-3224 J9 J OPT SOC AM B JI J. Opt. Soc. Am. B-Opt. Phys. PD DEC PY 1996 VL 13 IS 12 BP 2872 EP 2882 DI 10.1364/JOSAB.13.002872 PG 11 WC Optics SC Optics GA WA572 UT WOS:A1996WA57200026 ER PT J AU Brindley, WJ AF Brindley, WJ TI Thermal barrier coatings SO JOURNAL OF THERMAL SPRAY TECHNOLOGY LA English DT Editorial Material C1 NASA,LEWIS RES CTR,CLEVELAND,OH 44135. NR 24 TC 12 Z9 12 U1 1 U2 4 PU ASM INTERNATIONAL PI MATERIALS PARK PA SUBSCRIPTIONS SPECIALIST CUSTOMER SERVICE, MATERIALS PARK, OH 44073-0002 SN 1059-9630 J9 J THERM SPRAY TECHN JI J. Therm. Spray Technol. PD DEC PY 1996 VL 5 IS 4 BP 379 EP 380 DI 10.1007/BF02645266 PG 2 WC Materials Science, Coatings & Films SC Materials Science GA VW042 UT WOS:A1996VW04200001 ER PT J AU Aboudi, J Pindera, MJ Arnold, SM AF Aboudi, J Pindera, MJ Arnold, SM TI Thermoplasticity theory for bidirectionally functionally graded materials SO JOURNAL OF THERMAL STRESSES LA English DT Article ID METAL-MATRIX COMPOSITES; THERMAL RESIDUAL-STRESSES; FINITE-ELEMENT ANALYSIS; INTERFACES; GRADIENTS; FIBER AB A recently developed higher order theory for the thermoelastic response of composite materials with microstructures characterized by arbitrarily nonuniform reinforcement spacing in two directions (i.e., bidirectionally functionally graded materials) is further extended to accommodate the effect of an inelastic response of the constituent phases. This theory circumvents the problematic use of the standard micromechanical approach, based on the concept of a representative volume element, commonly employed in the analysis of functionally graded composites by explicitly coupling the local (microstructural) and global (macrostructural) responses. The theoretical framework is based on volumetric averaging of the various field quantities together with the imposition of boundary and interfacial conditions in an average sense between the subvolumes used to characterize the composite's functionally graded microstructure. Examples are presented that illustrate how the presence of plasticity and microstructure affect the free-edge interlaminar stresses in metal matrix composites and how these stresses and plastic strains can be altered and managed through functionally graded architectures. Furthermore, the results demonstrate the inability of the standard homogenization approach to capture accurately the microstructural effects in the vicinity of the free edge. C1 NASA, LEWIS RES CTR, STRUCT FATIGUE BRANCH, CLEVELAND, OH 44135 USA. RP Aboudi, J (reprint author), UNIV VIRGINIA, DEPT CIVIL ENGN & APPL MECH, CHARLOTTESVILLE, VA 22903 USA. NR 29 TC 17 Z9 18 U1 0 U2 2 PU TAYLOR & FRANCIS INC PI PHILADELPHIA PA 325 CHESTNUT ST, SUITE 800, PHILADELPHIA, PA 19106 USA SN 0149-5739 J9 J THERM STRESSES JI J. Therm. Stresses PD DEC PY 1996 VL 19 IS 9 BP 809 EP 861 DI 10.1080/01495739608946210 PG 53 WC Thermodynamics; Mechanics SC Thermodynamics; Mechanics GA WA152 UT WOS:A1996WA15200003 ER PT J AU Beshears, RD Hediger, L AF Beshears, RD Hediger, L TI Radiographic analysis of the TSS-1R conductive tether SO MATERIALS EVALUATION LA English DT Article RP Beshears, RD (reprint author), NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,NDE BRANCH,HUNTSVILLE,AL 35879, USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU AMER SOC NON-DESTRUCTIVE TEST PI COLUMBUS PA 1711 ARLINGATE LANE PO BOX 28518, COLUMBUS, OH 43228-0518 SN 0025-5327 J9 MATER EVAL JI Mater. Eval. PD DEC PY 1996 VL 54 IS 12 BP 1348 EP 1349 PG 2 WC Materials Science, Characterization & Testing SC Materials Science GA VY281 UT WOS:A1996VY28100002 ER PT J AU Harkness, SD Singh, RK Mueller, C Miranda, FA Cubbage, C AF Harkness, SD Singh, RK Mueller, C Miranda, FA Cubbage, C TI Epitaxial BaxSr1-xTiO3/YBa2Cu3O7 bilayers for tunable microwave applications SO MATERIALS SCIENCE AND ENGINEERING B-SOLID STATE MATERIALS FOR ADVANCED TECHNOLOGY LA English DT Article DE pulsed laser deposition; microwave antennae; superconduction; X-ray diffraction; Rutherford backscattering spectroscopy; atomic force microscopy ID THIN-FILMS AB The feasibility of epitaxial BaxSr1-xTiO3/YBa2Cu3O7 bilayers was studied for tunable microwave antennae applications. Ferroelectric BaxSr1 - xTiO3 (BST) was epitaxially coupled to YBa2Cu3O7 (YBCO) thin films via the pulsed laser deposition technique. Congruent processing parameters were used for the growth of both layers and it was found that the superconducting phase of the YBCO could still be maintained with sufficient post-deposition anneal in oxygen. X-ray diffraction and Rutherford backscattering spectroscopy results indicate that a mosaic structure was formed in the BST layer. Electrical measurements demonstrate the viability of Ba0.5Sr0.5TiO3 thin films as tuning media for YBCO microwave antennae as the relative dielectric constant was measured to be 360 at 77 K, and 50% modulations were achieved with applied fields as small as 4.5 V. Copyright (C) 1996 Elsevier Science S.A. C1 NASA,LEWIS RES CTR,CLEVELAND,OH 44135. RP Harkness, SD (reprint author), UNIV FLORIDA,DEPT MAT SCI & ENGN,GAINESVILLE,FL 32611, USA. NR 8 TC 4 Z9 6 U1 0 U2 0 PU ELSEVIER SCIENCE SA LAUSANNE PI LAUSANNE PA PO BOX 564, 1001 LAUSANNE, SWITZERLAND SN 0921-5107 J9 MAT SCI ENG B-SOLID JI Mater. Sci. Eng. B-Solid State Mater. Adv. Technol. PD DEC 1 PY 1996 VL 41 IS 3 BP 379 EP 382 DI 10.1016/S0921-5107(96)01892-2 PG 4 WC Materials Science, Multidisciplinary; Physics, Condensed Matter SC Materials Science; Physics GA WA875 UT WOS:A1996WA87500015 ER PT J AU Siconolfi, SF Nusynowitz, ML Suire, SS Moore, AD Leig, J AF Siconolfi, SF Nusynowitz, ML Suire, SS Moore, AD Leig, J TI Determining blood and plasma volumes using bioelectrical response spectroscopy SO MEDICINE AND SCIENCE IN SPORTS AND EXERCISE LA English DT Article DE bioimpedance; body fluids; resistance; inductance ID TOTAL-BODY WATER; IMPEDANCE ANALYSIS; FLUID; IMMERSION; POSTURE; REST AB We hypothesized that an electric field (inductance) produced by charged blood components passing through the many branches of arteries and veins could assess total blood Volume (TBV) or plasma volume (PV). Individual (N = 29) electrical circuits (inductors, two resistors, and a capacitor) were determined from bioelectrical response spectroscopy (BERS) using a Hewlett Packard 4284A Precision LCR Meter. Inductance, capacitance, and resistance from the circuits of 19 subjects modeled TBV (sum of PV and computed red cell volume) and PV based on I-125- albumin). Each model (N = 10, cross validation group) had good validity based on 1) mean differences (-2.3 to 1.5%) between the methods that were not significant and less than the propagated errors (+/- 5.2% for TBV and PV), 2) high correlations (r >0.92) with low SEE (<7.7%) between dilution and BERS assessments, and 3) Bland-Altman pairwise comparisons that indicated ''clinical equivalency'' between the methods. Given the limitation of this study (10 validity subjects), we concluded that BERS models accurately assessed TBV and PV. Further evaluations of the models' validities are needed before they are used in clinical or research settings. C1 UNIV TEXAS,MED BRANCH,NUCL MED SECT,GALVESTON,TX 77555. RP Siconolfi, SF (reprint author), NASA,LYNDON B JOHNSON SPACE CTR,SPACE BIOMED RES INST,EXERCISE PHYSIOL LAB,SD5,HOUSTON,TX 77058, USA. NR 27 TC 11 Z9 11 U1 0 U2 0 PU WILLIAMS & WILKINS PI BALTIMORE PA 351 WEST CAMDEN ST, BALTIMORE, MD 21201-2436 SN 0195-9131 J9 MED SCI SPORT EXER JI Med. Sci. Sports Exerc. PD DEC PY 1996 VL 28 IS 12 BP 1510 EP 1516 DI 10.1097/00005768-199612000-00011 PG 7 WC Sport Sciences SC Sport Sciences GA VY081 UT WOS:A1996VY08100011 PM 8970146 ER PT J AU Gonda, SR Yang, TC Richmond, RC Provost, S Wyborski, DL Fitzgerald, WS Svrcek, CD George, KA Fritz, PH AF Gonda, SR Yang, TC Richmond, RC Provost, S Wyborski, DL Fitzgerald, WS Svrcek, CD George, KA Fritz, PH TI Microgravity-based three-dimensional transgenic models. SO MOLECULAR BIOLOGY OF THE CELL LA English DT Meeting Abstract C1 NASA,LYNDON B JOHNSON SPACE CTR,HOUSTON,TX 77058. DARTMOUTH COLL,DARTMOUTH MED SCH,HANOVER,NH 03755. STRATAGENE,LA JOLLA,CA. KRUG,LIFE SCI,HOUSTON,TX. UNIV SPACE RES,HOUSTON,TX. NR 0 TC 0 Z9 0 U1 0 U2 0 PU AMER SOC CELL BIOLOGY PI BETHESDA PA 8120 WOODMONT AVE, STE 750, BETHESDA, MD 20814-2755 USA SN 1059-1524 J9 MOL BIOL CELL JI Mol. Biol. Cell PD DEC PY 1996 VL 7 SU S BP 652 EP 652 PG 1 WC Cell Biology SC Cell Biology GA WB018 UT WOS:A1996WB01800651 ER PT J AU Cockell, CS Squire, B Rothschild, LJ AF Cockell, CS Squire, B Rothschild, LJ TI Excision repair in nature? SO MOLECULAR BIOLOGY OF THE CELL LA English DT Meeting Abstract C1 NASA,AMES RES CTR,ECOSYST SCI & TECHNOL BRANCH,MOFFETT FIELD,CA 94035. NR 0 TC 0 Z9 0 U1 0 U2 0 PU AMER SOC CELL BIOLOGY PI BETHESDA PA 8120 WOODMONT AVE, STE 750, BETHESDA, MD 20814-2755 USA SN 1059-1524 J9 MOL BIOL CELL JI Mol. Biol. Cell PD DEC PY 1996 VL 7 SU S BP 1106 EP 1106 PG 1 WC Cell Biology SC Cell Biology GA WB018 UT WOS:A1996WB01801110 ER PT J AU Williams, SD Rothschild, LJ AF Williams, SD Rothschild, LJ TI Diurnal patterns of RNA synthesis in nature SO MOLECULAR BIOLOGY OF THE CELL LA English DT Meeting Abstract C1 NASA,AMES RES CTR,ECOSYST SCI & TECHNOL BRANCH,MOFFETT FIELD,CA 94035. NR 0 TC 0 Z9 0 U1 0 U2 0 PU AMER SOC CELL BIOLOGY PI BETHESDA PA 8120 WOODMONT AVE, STE 750, BETHESDA, MD 20814-2755 USA SN 1059-1524 J9 MOL BIOL CELL JI Mol. Biol. Cell PD DEC PY 1996 VL 7 SU S BP 3114 EP 3114 PG 1 WC Cell Biology SC Cell Biology GA WB018 UT WOS:A1996WB01803106 ER PT J AU Globus, RK Holmuhamedov, E Lull, JC Lopez, V Doty, SB Moursi, AM Damsky, C AF Globus, RK Holmuhamedov, E Lull, JC Lopez, V Doty, SB Moursi, AM Damsky, C TI Fibronectin is a survival factor for differentiated osteoblasts. SO MOLECULAR BIOLOGY OF THE CELL LA English DT Meeting Abstract C1 UNIV CALIF SAN FRANCISCO,DEPT MED,SAN FRANCISCO,CA 94043. UNIV CALIF SAN FRANCISCO,DEPT STOMATOL,SAN FRANCISCO,CA 94043. UNIV CALIF SAN FRANCISCO,DEPT ANAT,SAN FRANCISCO,CA 94043. NASA,AMES RES CTR,MOFFETT FIELD,CA 94035. HOSP SPECIAL SURG,NEW YORK,NY 10021. NR 0 TC 0 Z9 0 U1 1 U2 1 PU AMER SOC CELL BIOLOGY PI BETHESDA PA 8120 WOODMONT AVE, STE 750, BETHESDA, MD 20814-2755 USA SN 1059-1524 J9 MOL BIOL CELL JI Mol. Biol. Cell PD DEC PY 1996 VL 7 SU S BP 3397 EP 3397 PG 1 WC Cell Biology SC Cell Biology GA WB018 UT WOS:A1996WB01803389 ER PT J AU Tsinganos, K Sauty, C Surlantzis, G Trussoni, E Contopoulos, J AF Tsinganos, K Sauty, C Surlantzis, G Trussoni, E Contopoulos, J TI On the relation of limiting characteristics to critical surfaces in magnetohydrodynamic flows SO MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY LA English DT Article DE MHD; plasmas; Sun, atmosphere; solar wind; stars, mass-loss; ISM, jets and outflows ID NONPOLYTROPIC ASTROPHYSICAL OUTFLOWS; STEADY HYDROMAGNETIC FLOWS; MAGNETICALLY DRIVEN JETS; FLARING STREAMLINES; COLLIMATED WINDS; ACCRETION DISKS; STELLAR WINDS; MHD SOLUTIONS; FIELDS; MODELS AB We investigate the relation between critical surfaces and limiting characteristics or separatrices in the set of magnetohydrodynamic (MHD) differential equations that govern astrophysical flows such as winds, jets, accretion-type inflows, siphon flows in coronal loops, etc. For the particular case of axisymmetric self-similar solutions, we show that, at these critical/separatrix surfaces, the component of the flow velocity that is perpendicular to the directions of axisymmetry and self-similarity equals the slow/fast MHD wave speed in that direction. Our general analysis and claims are fully supported by analytical examples of three broad classes of axisymmetric self-similar solutions for flows in a uniform or spherical gravitational field. For these examples of exact solutions, we plot the various families of characteristics of the MHD partial differential equations. We then find that one member of each family of characteristics is asymptotically tangent to the corresponding separatrix which coincides with a critical surface there. Besides the well-known polytropic cases with constant polytropic index, more general flows with a variable polytropic index are also analysed. C1 FDN RES & TECHNOL HELLAS, GR-71409 IRAKLION, GREECE. OBSERV PARIS, DAEC, F-92195 MEUDON, FRANCE. OSSERV ASTRON TORINO, I-10025 PINO TORINESE, ITALY. NASA, GODDARD SPACE FLIGHT CTR, GREENBELT, MD 20771 USA. RP Tsinganos, K (reprint author), UNIV CRETE, DEPT PHYS, GR-71003 IRAKLION, GREECE. NR 56 TC 34 Z9 34 U1 0 U2 0 PU WILEY-BLACKWELL PI MALDEN PA COMMERCE PLACE, 350 MAIN ST, MALDEN 02148, MA USA SN 0035-8711 J9 MON NOT R ASTRON SOC JI Mon. Not. Roy. Astron. Soc. PD DEC 1 PY 1996 VL 283 IS 3 BP 811 EP 820 PG 10 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VY727 UT WOS:A1996VY72700017 ER PT J AU Wang, YS Tao, WK Simpson, J AF Wang, YS Tao, WK Simpson, J TI The impact of ocean surface fluxes on a TOGA COARE convective system SO MONTHLY WEATHER REVIEW LA English DT Article ID ADVECTION TRANSPORT ALGORITHM; SMALL IMPLICIT DIFFUSION; BULK PARAMETERIZATION; WESTERN PACIFIC; SQUALL LINES; MESOSCALE; LAYER; MODEL; HEAT; SENSITIVITY AB A two-dimensional cloud-resolving model is linked with a TOGA COARE flux algorithm to examine the impact of the ocean surface fluxes on the development of a tropical squall line and its associated precipitation processes. The model results show that the 12-h total surface rainfall amount in the run excluding the surface fluxes is about 80% of that for the run including surface fluxes (domain-averaged rainfall, 3.4 mm). The model results also indicate that latent heat flux or evaporation from the ocean is the most influential factor among the three fluxes (latent heat, sensible heat, and momentum) for the development of the squall system. The average latent and sensible heat fluxes in the convective (disturbed) region are 60 and 11 W m(-2) larger, respectively, than those of the nonconvective (clear) region due to the gust wind speed, a cool pool near the surface, and drier air from downdrafts associated with the convective activity. These results are in good agreement with observations. In addition, sensitivity tests using a simple bulk aerodynamic approximation as well as a Blackadar-type surface flux formulation have predicted much larger latent and sensible heat fluxes than those obtained using the TOGA COARE Aux algorithm. Consequently, much more surface rainfall was simulated using a simple aerodynamic approximation or a Blackadar-type surface flux formulation. The results presented here also suggest that a fine vertical resolution(at least in the lowest model grid point) is needed in order to study the interactive processes between the ocean and convection using a cloud-resolving model. C1 NASA,GODDARD SPACE FLIGHT CTR,ATMOSPHERES LAB,GREENBELT,MD 20771. SCI SYST & APPLICAT INC,GREENBELT,MD. RP Wang, YS (reprint author), NASA,GODDARD SPACE FLIGHT CTR,MESOSCALE ATMOSPHER PROC BRANCH,CODE 912,GREENBELT,MD 20771, USA. NR 41 TC 46 Z9 46 U1 1 U2 1 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 SN 0027-0644 J9 MON WEATHER REV JI Mon. Weather Rev. PD DEC PY 1996 VL 124 IS 12 BP 2753 EP 2763 DI 10.1175/1520-0493(1996)124<2753:TIOOSF>2.0.CO;2 PG 11 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA VZ340 UT WOS:A1996VZ34000006 ER PT J AU Raju, MS AF Raju, MS TI Application of scalar Monte Carlo probability density function method for turbulent spray flames SO NUMERICAL HEAT TRANSFER PART A-APPLICATIONS LA English DT Article ID PDF METHODS; COMBUSTION; FLOWS AB The objective of the present work is twofold: (I) extend the coupled Monte Carlo probability density function (PDF)/computational fluid dynamics (CFD) computations to the modeling of turbulent spray flames, and (2) extend the PDF/SPRAY/CFD module to parallel computing in order to facilitate large-scale combustor computations. In this approach, the mean gas phase velocity and turbulence fields are determined from a standard turbulence model, the joint composition of species and enthalpy from the solution of a modeled PDF transport equation, and a Lagrangian-based dilute spray model is used for the liquid-phase representation. The PDF transport equation is solved by a Monte Carlo method, and the mean gas phase velocity and turbulence fields together with the liquid phase equations are solved by existing state-of-the-art numerical representations. The application of the method to both open as well as confined axisymmetric swirl-stabilized spray flames shows good agreement with the measured data. Preliminary estimates indicate that it is well within reach of today's modern parallel computer to do a realistic gas turbine combustor simulation within a reasonable turnaround time. The article provides complete details of the overall algorithm, parallelization, and other numerical issues related to coupling between the three solvers. RP Raju, MS (reprint author), NYMA INC,NASA,LEWIS RES CTR,2001 AEROSP PKWY,BROOKPARK,OH 44142, USA. NR 19 TC 13 Z9 13 U1 0 U2 0 PU HEMISPHERE PUBL CORP PI BRISTOL PA 1900 FROST ROAD, SUITE 101, BRISTOL, PA 19007-1598 SN 1040-7782 J9 NUMER HEAT TR A-APPL JI Numer. Heat Tranf. A-Appl. PD DEC PY 1996 VL 30 IS 8 BP 753 EP 777 DI 10.1080/10407789608913869 PG 25 WC Thermodynamics; Mechanics SC Thermodynamics; Mechanics GA WB129 UT WOS:A1996WB12900001 ER PT J AU Chen, YS Shang, HM Liaw, P Chen, CP Wang, TS AF Chen, YS Shang, HM Liaw, P Chen, CP Wang, TS TI Combined Eulerian-VOF-Lagrangian method for general gas-liquid flow applications SO NUMERICAL HEAT TRANSFER PART B-FUNDAMENTALS LA English DT Article AB This article summarizes the technical development and validation of a multiphase computational fluid dynamics (CFD) numerical method using a combined volume-of-fluid (VOF)/Lagrangian tracking model to analyze general dispersed multiphase-flow problems with free surfaces. The gas-liquid interfacial mass, momentum, and energy transfer are modeled by continuum surface mechanisms. A high-order TVD scheme is also implemented for capturing sharp interfaces between immiscible phases. The objectives of the present study are to develop and verify the fractional volume-of-fluid cell partitioning approach into a predictor-corrector algorithm, which is suitable for solving fluid flows at all speeds regimes, and to demonstrate the effectiveness of the present approach by simulating benchmark problems including coaxial jet atomization. C1 ENGN SCI INC,HUNTSVILLE,AL 35802. NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,HUNTSVILLE,AL 35816. RP Chen, YS (reprint author), UNIV ALABAMA,DEPT CHEM & MAT ENGN,MAT SCI BLDG,HUNTSVILLE,AL 35899, USA. NR 20 TC 3 Z9 3 U1 0 U2 2 PU HEMISPHERE PUBL CORP PI BRISTOL PA 1900 FROST ROAD, SUITE 101, BRISTOL, PA 19007-1598 SN 1040-7790 J9 NUMER HEAT TR B-FUND JI Numer Heat Tranf. B-Fundam. PD DEC PY 1996 VL 30 IS 4 BP 409 EP 422 DI 10.1080/10407799608915090 PG 14 WC Thermodynamics; Mechanics SC Thermodynamics; Mechanics GA WA595 UT WOS:A1996WA59500002 ER PT J AU Moder, JP Chai, JC Parthasarathy, G Lee, HS Patankar, SV AF Moder, JP Chai, JC Parthasarathy, G Lee, HS Patankar, SV TI Nonaxisymmetric radiative transfer in cylindrical enclosures SO NUMERICAL HEAT TRANSFER PART B-FUNDAMENTALS LA English DT Article ID FINITE-VOLUME METHOD; DISCRETE-ORDINATES METHOD; HEAT-TRANSFER PROCEDURE; IRREGULAR GEOMETRIES; TRANSFER EQUATION; MEDIA AB A finite-volume method for radiative transfer in cylindrical enclosures is presented. Angular redistribution terms in the equation of transfer are avoided by defining radiation directions in terms of angular coordinates measured with respect to Cartesian base vectors; this definition of radiation directions can result in control angles that overlap control-volume faces, depending on the type of spatial and angular grids used in the azimuthal direction. A simple treatment for such control-angle overlaps is presented, which is also applicable to nonorthogonal curvilinear spatial coordinates. A comparison of the present procedure with other similar methods is given. Solutions are presented for axisymmetric transfer through a cylinder and nonaxisymmetric transfer through two- and three-dimensional annular sectors. Results show that the procedure produces reasonable solutions for transparent and participating media in axisymmetric and nonaxisymmetric cylindrical enclosures. C1 TENNESSEE TECHNOL UNIV,DEPT MECH ENGN,COOKEVILLE,TN 38505. UNIV MINNESOTA,DEPT MECH ENGN,MINNEAPOLIS,MN 55455. NASA,LEWIS RES CTR,PROPULS SYST DIV,CLEVELAND,OH 44135. RP Moder, JP (reprint author), NASA,LEWIS RES CTR,DIV INTERNAL FLUID MECH,21000 BROOKPK RD,MS 5-11,CLEVELAND,OH 44135, USA. RI Chai, John/A-3764-2010 NR 23 TC 36 Z9 38 U1 0 U2 2 PU HEMISPHERE PUBL CORP PI BRISTOL PA 1900 FROST ROAD, SUITE 101, BRISTOL, PA 19007-1598 SN 1040-7790 J9 NUMER HEAT TR B-FUND JI Numer Heat Tranf. B-Fundam. PD DEC PY 1996 VL 30 IS 4 BP 437 EP 452 DI 10.1080/10407799608915092 PG 16 WC Thermodynamics; Mechanics SC Thermodynamics; Mechanics GA WA595 UT WOS:A1996WA59500004 ER PT J AU Walter, MR Desmarais, D Farmer, JD Hinman, NW AF Walter, MR Desmarais, D Farmer, JD Hinman, NW TI Lithofacies and biofacies of mid-paleozoic thermal spring deposits in the Drummond Basin, Queensland, Australia SO PALAIOS LA English DT Article ID HYDROTHERMAL VENTS; RHYNIE; LAKE; EVOLUTION; SCOTLAND; ORIGIN; SYSTEM; SITES AB The Devonian, to Carboniferous sinters of the Drummond Basin, Australia, are among the oldest well established examples of fossil subaerial hot springs. Numerous subaerial and subaqueous spring deposits are known from the geological record as a result of the occurrence of economic mineral deposits in, many of them. Some are reported to contain, fossils, but very few have been studied by paleobiologists; they represent an untapped source of paleobiological information on the history of hydrothermal ecosystems. Such systems are of special interest, given the molecular biological evidence that thermophilic bacteria Lie near the root of the tree of extant Life. The Drummond Basin sinters are very closely comparable with modern examples in Yellowstone National Path and elsewhere. Thirteen microfacies are recognisable in the field, ranging from high temperature apparently abiotic geyserite through various forms of stromatolitic sinter probably of cyanobacterial origin to ambient temperature marsh deposits. Microfossils in the stromatolites are interpreted as cyanobacterial sheaths. Herbaceous lycopsids occur in the lower temperature deposits. C1 NASA, AMES RES CTR, PLANETARY BIOL BRANCH, MOFFETT FIELD, CA 94035 USA. UNIV MONTANA, DEPT GEOL, MISSOULA, MT 59812 USA. RP Walter, MR (reprint author), MACQUARIE UNIV, SCH EARTH SCI, N RYDE, NSW 2109, AUSTRALIA. NR 56 TC 79 Z9 80 U1 0 U2 5 PU SEPM-SOC SEDIMENTARY GEOLOGY PI TULSA PA 6128 EAST 38TH ST, STE 308, TULSA, OK 74135-5814 USA SN 0883-1351 J9 PALAIOS JI Palaios PD DEC PY 1996 VL 11 IS 6 BP 497 EP 518 DI 10.2307/3515187 PG 22 WC Geology; Paleontology SC Geology; Paleontology GA VZ279 UT WOS:A1996VZ27900002 PM 11541250 ER PT J AU Abrams, M Bianchi, R Pieri, D AF Abrams, M Bianchi, R Pieri, D TI Revised mapping of lava flows on Mount Etna, Sicily SO PHOTOGRAMMETRIC ENGINEERING AND REMOTE SENSING LA English DT Article ID THERMAL INFRARED IMAGES; THEMATIC MAPPER DATA; TOOL AB Mt. Etna, Sicily, is the most active volcano in Europe, erupting almost constantly. Historical records of eruptions for the last 350 years are accurate; prior to about 1650, the record is increasingly inaccurate and incomplete. Ages for pre-1650 lava flows, reported on recent geologic maps, are in conflict with ages determined from paleomagnetic measurements. Here we report on a different approach used to determine relative ages of Etnean lava flows. Multispectral image data were acquired from aircraft overflights of Etna in 1991. The Thematic Mapper Simulator instrument obtained 12 channels of data in the visible through thermal infrared wavelength regions. Supervised classification of these data allowed us to group Etnean flows into age groups based on their spectral properties. About 90 percent of the classification agrees with the mapped lava flow ages. Our results also generally support the paleomagnetic age determinations for flow ages that disagree with the mapped ages. In addition, several areas were remapped, correcting errors on the published map. C1 CNR,PROGETTO LARA,I-00040 POMEZIA,ROMA,ITALY. RP Abrams, M (reprint author), CALTECH,JET PROP LAB,4800 OAK GROVE DR,MAIL STOP 183-501,PASADENA,CA 91109, USA. NR 18 TC 7 Z9 7 U1 0 U2 4 PU AMER SOC PHOTOGRAMMETRY PI BETHESDA PA 5410 GROSVENOR LANE SUITE 210, BETHESDA, MD 20814-2160 SN 0099-1112 J9 PHOTOGRAMM ENG REM S JI Photogramm. Eng. Remote Sens. PD DEC PY 1996 VL 62 IS 12 BP 1353 EP 1359 PG 7 WC Geography, Physical; Geosciences, Multidisciplinary; Remote Sensing; Imaging Science & Photographic Technology SC Physical Geography; Geology; Remote Sensing; Imaging Science & Photographic Technology GA VV454 UT WOS:A1996VV45400012 ER PT J AU Jansma, PE Lang, HR AF Jansma, PE Lang, HR TI Applications of spectral stratigraphy to upper cretaceous and tertiary rocks in Southern Mexico: Tertiary graben control on volcanism SO PHOTOGRAMMETRIC ENGINEERING AND REMOTE SENSING LA English DT Article ID TECTONICS AB We used spectral stratigraphic techniques to interpret Landsat TM data covering northern Guerrero state in southern Mexico in order to map Upper Cretaceous and Tertiary rocks and to assess the interplay between volcanism and tectonism; results were confirmed in the field. Seven spectral stratigraphic units, each of which corresponds to a distinct lithostratigraphic unit, were delineated. Five consist of terrestrial Upper Cretaceous and Tertiary siliciclastic, volcanic, and volcaniclastic rocks; one contains Mesozoic marine rocks; and one corresponds to Quaternary alluvium. A previously undocumented NNW-trending Tertiary graben was identified in which 2,000 m of lower Tertiary volcanic rocks accumulated, suggesting volcanism coeval with graben subsidence during WSW-ENE regional extension in the early Tertiary Overlap of the western-graben bounding fault by slightly younger lower Tertiary rocks suggests subsidence ended by the close of the early Tertiary. Continued volcanism within the graben during the late Tertiary indicates a long-lived volcanic source region within the subsurface of the NNW-trending structure and localization of younger magmatic activity within a pre-existing zone of crustal weakness. C1 CALTECH,JET PROP LAB,PASADENA,CA 91109. RP Jansma, PE (reprint author), UNIV PUERTO RICO,DEPT GEOL,MAYAGUEZ,PR 00681, USA. NR 33 TC 4 Z9 4 U1 0 U2 1 PU AMER SOC PHOTOGRAMMETRY PI BETHESDA PA 5410 GROSVENOR LANE SUITE 210, BETHESDA, MD 20814-2160 SN 0099-1112 J9 PHOTOGRAMM ENG REM S JI Photogramm. Eng. Remote Sens. PD DEC PY 1996 VL 62 IS 12 BP 1371 EP 1378 PG 8 WC Geography, Physical; Geosciences, Multidisciplinary; Remote Sensing; Imaging Science & Photographic Technology SC Physical Geography; Geology; Remote Sensing; Imaging Science & Photographic Technology GA VV454 UT WOS:A1996VV45400014 ER PT J AU Vasquez, RP AF Vasquez, RP TI X-ray photoemission measurements of La1-xCaxCoO3 (x=0, 0.5) SO PHYSICAL REVIEW B LA English DT Article ID HIGH-TEMPERATURE SUPERCONDUCTORS; CHARGE-TRANSFER SATELLITES; SPIN-STATE TRANSITION; ELECTRONIC-STRUCTURE; PHOTOELECTRON-SPECTRA; SPECTROSCOPY; MAGNETORESISTANCE; LA1-XSRXCOO3; LACOO3 AB X-ray photoemission measurements of the core levels and valence electronic structure of LaCoO3 and La0.5Ca0.5CoO3 high quality epitaxial films are presented. Shifts of the core levels and main valence band features are consistent with a doping-induced change in the chemical potential. Oxygen states are found ro significantly contribute to a peak in the valence band at I eV binding energy, verifying earlier results of cluster calculations. A Fermi level crossing of this same band upon doping is observed, yielding a high Fermi-level density of states. RP CALTECH, JET PROP LAB, CTR SPACE MICROELECT TECHNOL, PASADENA, CA 91109 USA. NR 29 TC 38 Z9 38 U1 0 U2 6 PU AMER PHYSICAL SOC PI COLLEGE PK PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA SN 2469-9950 EI 2469-9969 J9 PHYS REV B JI Phys. Rev. B PD DEC 1 PY 1996 VL 54 IS 21 BP 14938 EP 14941 DI 10.1103/PhysRevB.54.14938 PG 4 WC Physics, Condensed Matter SC Physics GA VY201 UT WOS:A1996VY20100020 ER PT J AU Langel, RA Sabaka, TJ Baldwin, RT Conrad, JA AF Langel, RA Sabaka, TJ Baldwin, RT Conrad, JA TI The near-Earth magnetic field from magnetospheric and quiet-day ionospheric sources and how it is modeled SO PHYSICS OF THE EARTH AND PLANETARY INTERIORS LA English DT Article ID GEOMAGNETIC-FIELD AB Early attempts to model fields from sources in the magnetosphere during magnetically quiet times were unsuccessful, This is attributed to the presence of fields from lithospheric sources and to deficiencies in the data distribution. The availability of data from the Magsat satellite allowed definitive determination of the first-degree field from magnetospheric sources. Temporal variation of those fields on time scales of hours to a few years was implemented by use of a proxy function thought to mimic that variation. The Dst index was chosen as the proxy function, Extension of determination of the first-degree magnetospheric field to earlier times, namely to 1900, is accomplished first by use of the annual average of the aa index as a proxy function and then by use of cubic B-splines as temporal basis functions. The model first-degree field is well correlated with the annual sunspot number, both in its general level changes and in its detailed year-to-year variation. The correlation coefficient of the year-to-year variation of the first-degree, zero order, external term with the annual sunspot number is 0.77 when the external term lags the sunspot number by 2 years. Another extension of the results made possible by the Magsat data is simultaneous determination of a model of the fields from the magnetosphere, the ionosphere, and internal to the Earth. In this case, data from the Magsat and POGO satellites and magnetic observatory hourly mean and annual mean data were analyzed together. Though still in an experimental stage, these models are shown to fit all the data closely and to be able to readily isolate the fields according as the source is in the magnetosphere, ionosphere, or Earth. C1 HUGHES STX CORP,LANHAM,MD 20706. RP Langel, RA (reprint author), NASA,GODDARD SPACE FLIGHT CTR,GEODYNAM BRANCH,GREENBELT,MD 20771, USA. RI Sabaka, Terence/D-5618-2012 NR 40 TC 41 Z9 56 U1 0 U2 1 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0031-9201 J9 PHYS EARTH PLANET IN JI Phys. Earth Planet. Inter. PD DEC PY 1996 VL 98 IS 3-4 BP 235 EP 267 DI 10.1016/S0031-9201(96)03190-1 PG 33 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA WB253 UT WOS:A1996WB25300009 ER PT J AU Whaler, KA Langel, RA AF Whaler, KA Langel, RA TI Minimal crustal magnetizations from satellite data SO PHYSICS OF THE EARTH AND PLANETARY INTERIORS LA English DT Article ID MAGNETIC ANOMALY MAP; MAGSAT DATA; UNITED-STATES; DOWNWARD CONTINUATION; RIDGE-REGRESSION; HARMONIC SPLINES; GLOBAL VECTOR; FIELD; INVERSION; MODELS AB The minimum amplitude crustal magnetization needed to explain Magsat vector anomaly data is found using harmonic splines as basis functions (Shure et al., 1982, Phys. Earth Planet. Inter., 28: 215-229), and choosing a subset of the original basis (Parker and Shure, 1982, Geophys, Res, Lett., 9: 812-815) to represent magnetization. We suggest the optimum model of this type is obtained by associating representers only with north and vertically downwards data points, given the larger uncertainties associated with east-component Magsat data. Following Parker et al, (1987, Rev, Geophys., 25: 17-40) we find a model minimizing the r.m.s. volume integral of magnetization over the magnetized lithosphere. The numerical effort involved in producing a regional- or continental-scale model with given horizontal spatial detail with our method is less than that for an equivalent source dipole model (when the magnetization is not assumed induced), approximately equal to that for an induced magnetization equivalent dipole model, and considerably less than that for a spherical harmonic apparent susceptibility model. The method is demonstrated by producing a solution for two regions-the contiguous USA, for comparison with previously published models, and Africa and its continental margins. Magnetization models fit the data slightly worse than those of the downward-continued anomaly field at the Earth's surface. Comparison of our component of magnetization for the USA in the direction of the core field with the induced magnetization equivalent dipole model of Mayhew (1984, Earth Planet. Sci, Lett., 71: 290-296) is very good. As expected for magnetization either induced by, or frozen remanently in, an approximately dipole field either parallel or antiparallel to the current rotation axis, the east component of magnetization is much smaller than the north and vertically downwards components. We make no assumptions about the relative contributions of remanent and induced magnetization, and the resulting models have a substantial remanent component. However, our models suffer from the severe non-uniqueness common to all magnetization models, whereby magnetization in a uniform (susceptibility and thickness) shell concentric with the Earth's centre owing to any internal magnetic field that is then 'switched off' generates no external magnetic field. C1 NASA,GODDARD SPACE FLIGHT CTR,GEODYNAM BRANCH,GREENBELT,MD 20771. RP Whaler, KA (reprint author), UNIV EDINBURGH,DEPT GEOL & GEOPHYS,W MAINS RD,EDINBURGH EH9 3JW,MIDLOTHIAN,SCOTLAND. NR 57 TC 11 Z9 12 U1 1 U2 3 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0031-9201 J9 PHYS EARTH PLANET IN JI Phys. Earth Planet. Inter. PD DEC PY 1996 VL 98 IS 3-4 BP 303 EP 319 DI 10.1016/S0031-9201(96)03193-7 PG 17 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA WB253 UT WOS:A1996WB25300012 ER PT J AU Carr, LW Chandrasekhara, MS AF Carr, LW Chandrasekhara, MS TI Compressibility effects on dynamic stall SO PROGRESS IN AEROSPACE SCIENCES LA English DT Article ID PITCHING AIRFOIL AB Dynamic stall delay of flow over airfoils rapidly pitching past the static stall angle has been studied by many scientists. However, the effect of compressibility on this dynamic stall behavior has been less comprehensively studied. This review presents a detailed assessment of research performed on this subject, including a historical review of work performed on both aircraft and helicopters, and offers insight into the impact of compressibility on the complex aerodynamic phenomenon known as dynamic stall. It also documents the major effect that compressibility can have on dynamic stall events, and the complete change of physics of the stall process that can occur as free-stream Mach number is increased. Copyright (C) 1996 Elsevier Science Ltd. C1 NASA,AMES RES CTR,FLUID MECH LAB BRANCH,MOFFETT FIELD,CA 94035. USN,POSTGRAD SCH,DEPT AERONAUT & ASTRONAUT,NASA JOINT INST AERONAUT,MONTEREY,CA 93943. RP Carr, LW (reprint author), USA,AVIAT & TROOP COMMAND,AVIAT RES,CTR DEV & ENGN,MOFFETT FIELD,CA 94035, USA. NR 71 TC 35 Z9 35 U1 0 U2 2 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, ENGLAND OX5 1GB SN 0376-0421 J9 PROG AEROSP SCI JI Prog. Aeosp. Sci. PD DEC PY 1996 VL 32 IS 6 BP 523 EP 573 DI 10.1016/0376-0421(95)00009-7 PG 51 WC Engineering, Aerospace SC Engineering GA VY237 UT WOS:A1996VY23700001 ER PT J AU Bonnell, JT Nemiroff, RJ Goldstein, JJ AF Bonnell, JT Nemiroff, RJ Goldstein, JJ TI The Scale of the Universe debate in 1996 SO PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF THE PACIFIC LA English DT Article AB On April 21, 1996, Sidney van den Bergh and Gustav Tammann engaged in a public debate titled ''The Scale of the Universe.'' The arguments they presented focused on recently determined and still controversial values of the Hubble Constant. The program was moderated by John Bahcall, with lectures on the background and history behind humanity's quest for the scale of the Universe given by Owen Gingerich and Virginia Trimble. These introductory lectures along with the arguments presented by the 1996 debaters are recreated in the following papers. This debate was of the same title and held in the same auditorium as the ''Great Debate'' between Heber Curtis and Harlow Shapley in 1920. Here we discuss some of the issues surrounding the organization and inspiration for the 1996 debate, Like the 1920 debate, the 1996 debate was not intended to resolve a disagreement instantly. Instead it is hoped that this debate and the written contributions will stand as educational tools, summarizing the arguments behind today's Hubble Constant controversy, and will help provide a framework for evaluating progress in this field as the century which saw its creation draws to a close. Together with last year's debate, ''The Distance Scale to Gamma Ray Bursts'' (Nemiroff, R. J. 1995, PASP, 107, 1131), these papers may also provide a clue as to how scientists think. C1 NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. SMITHSONIAN INST,NATL AIR & SPACE MUSEUM,ASTROPHYS LAB,WASHINGTON,DC 20560. NR 4 TC 1 Z9 1 U1 0 U2 0 PU ASTRONOMICAL SOC PACIFIC PI SAN FRANCISCO PA 390 ASHTON AVE, SAN FRANCISCO, CA 94112 SN 0004-6280 J9 PUBL ASTRON SOC PAC JI Publ. Astron. Soc. Pac. PD DEC PY 1996 VL 108 IS 730 BP 1065 EP 1067 DI 10.1086/133835 PG 3 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VY121 UT WOS:A1996VY12100001 ER PT J AU Gao, BC AF Gao, BC TI NDWI - A normalized difference water index for remote sensing of vegetation liquid water from space SO REMOTE SENSING OF ENVIRONMENT LA English DT Article ID INFRARED REFLECTANCE; STRESS; AVIRIS; EARTH; MODIS AB The normalized difference vegetation index (NDVI) has been widely used for remote sensing of vegetation for many years. This index uses radiances or reflectances from a red channel around 0.66 mu m and a near-IR channel around 0.86 mu m. The red channel is located in the strong chlorophyll absorption region, while the near-IR channel is located in the high reflectance plateau of vegetation canopies. The two channels sense very different depths through vegetation canopies. In this article, another index, namely, the normalized difference water index (NDWI), is proposed for remote sensing of vegetation liquid water from space. NDWI is defined as (rho(0.86 mu m) - rho(1.24 mu m))/(rho(0.86 mu m) + rho(1.24 mu m)), where rho represents the radiance in reflectance units. Both the 0.86-mu m and the 1.24-mu m channels are located in the high reflectance plateau of vegetation canopies. They sense similar depths through vegetation canopies. Absorption by vegetation liquid water near 0.86 mu m is negligible. Weak liquid absorption at 1.24 mu m is present. Canopy scattering enhances the water absorption. As a result, NDWI is sensitive to changes in liquid water content of vegetation canopies. Atmospheric aerosol scattering effects in the 0.86-1.24 mu m region are weak. NDWI is less sensitive to atmospheric effects than NDVI. NDWI does not remove completely the background soil reflectance effects, similar to NDVI. Because the information about vegetation canopies contained in the 1.24;um channel is very different from that contained in the red channel near 0.66 mu m, NDWI should be considered as an. independent vegetation index. It is complementary to, not a substitute for NDVI. Laboratory-measured reflectance spectra of stacked green leaves, and spectral imaging data acquired with Airborne Visible Infrared Imaging Spectrometer (AVIRIS) over Jasper Ridge in California and the High Plains in northern Colorado, are used to demonstrate the usefulness of NDWI. Comparisons between NDWI and NDVI images are also given. (C) Elsevier Science Inc., 1996. C1 NASA,GODDARD SPACE FLIGHT CTR,JOINT CTR EARTH SYST SCI,GREENBELT,MD 20771. NR 25 TC 1169 Z9 1313 U1 50 U2 324 PU ELSEVIER SCIENCE INC PI NEW YORK PA 655 AVENUE OF THE AMERICAS, NEW YORK, NY 10010 SN 0034-4257 J9 REMOTE SENS ENVIRON JI Remote Sens. Environ. PD DEC PY 1996 VL 58 IS 3 BP 257 EP 266 DI 10.1016/S0034-4257(96)00067-3 PG 10 WC Environmental Sciences; Remote Sensing; Imaging Science & Photographic Technology SC Environmental Sciences & Ecology; Remote Sensing; Imaging Science & Photographic Technology GA VV513 UT WOS:A1996VV51300003 ER PT J AU Gitelson, AA Kaufman, YJ Merzlyak, MN AF Gitelson, AA Kaufman, YJ Merzlyak, MN TI Use of a green channel in remote sensing of global vegetation from EOS-MODIS SO REMOTE SENSING OF ENVIRONMENT LA English DT Article ID ACER-PLATANOIDES L; RED EDGE; SPECTRAL REFLECTANCE; CANOPY REFLECTANCE; LEAF REFLECTANCE; PLANT STRESS; MAPLE LEAVES; CHLOROPHYLL; AUTUMN; INDEX AB Most animals use a ''green'' spectral range to remotely sense the presence and vitality of vegetation. While humans possess the same ability in their eyes, man-made space-borne sensors that sense evolution of global vegetation, have so far used a combination of the red and near infrared channels instead. In this article we challenge this approach, using measurements of reflectance spectra from 400 nm to 750 nm with spectral resolution of 2 nm, with simultaneous determination of pigment concentrations of mature and autumn senescing leaves. We show that, for a wide range of leaf greenness, the maximum sensitivity of reflectance coincides with the red absorption maximum of chlorophyll-a (Chl-a) at 670 nm. However for yellow-green to green leaves (with Chl-a more than 3-5 mu g/cm(2)), the reflectance near 670 nm is not sensitive to chlorophyll concentration because of saturation of the relationship of absorptions versus chlorophyll concentration. Maximum sensitivity of Chl-a concentration for a wide range of its variation (0.3-45 mu g/cm(2)) was found, not surprisingly so, around the green band from 520 nm to 630 nm and also near 700 nm. We found that the inverse of the reflectance in the green band was proportional to Chl-a concentration with correlation r(2) > 0.95. This band will be present on several future satellite sensors with a global view of vegetation (SeaWiFS to be launched in. 1996, Polder on ADEOS-1 also in 1996, and MODIS on EOS in 1998 and 2000). New indexes that use the green channel and are resistant to atmospheric effects are developed. A green NDVI = (rho(nir) - rho(green)/(rho(nir) + rho(green) was tested for a range of Chl-a from 0.3 mu g/cm(2) to 45 mu g/cm(2), and found to have an error in the chlorophyll a derivation at leaf level of less than 3 mu g/cm(2). The new index has wider dynamic range than the NDVI and is, on average, at least five times more sensitive to Chl-a concentration. A green atmospherically resistant vegetation index (GARI), tailored on the concept of ARVI (Kaufman and Tanre, 1992), is developed and is expected to be as resistant to atmospheric effects as ARVI but more sensitive to a wide range of Chl-a concentrations. While NDVI and ARVI are sensitive to vegetation fraction and to rate of absorption of photosynthetic solar radiation, a green vegetation index like GARI should be added to sense the concentration of chlorophyll, to measure the rate of photosynthesis and to monitor plant stress. (C) Elsevier Science Inc., 1996. C1 NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. MOSCOW MV LOMONOSOV STATE UNIV,FAC BIOL,DEPT CELL PHYSIOL & IMMUNOL,MOSCOW,RUSSIA. RP Gitelson, AA (reprint author), BEN GURION UNIV NEGEV,JACOB BLAUSTEIN INST DESERT RES,SEDE BOKER CAMPUS,IL-84993 SEDE BOQER,ISRAEL. RI Gitelson, Anatoly/G-3452-2012 NR 33 TC 494 Z9 578 U1 11 U2 70 PU ELSEVIER SCIENCE INC PI NEW YORK PA 655 AVENUE OF THE AMERICAS, NEW YORK, NY 10010 SN 0034-4257 J9 REMOTE SENS ENVIRON JI Remote Sens. Environ. PD DEC PY 1996 VL 58 IS 3 BP 289 EP 298 DI 10.1016/S0034-4257(96)00072-7 PG 10 WC Environmental Sciences; Remote Sensing; Imaging Science & Photographic Technology SC Environmental Sciences & Ecology; Remote Sensing; Imaging Science & Photographic Technology GA VV513 UT WOS:A1996VV51300006 ER PT J AU Ford, WF Pennline, JA AF Ford, WF Pennline, JA TI Accelerated convergence in Newton's method SO SIAM REVIEW LA English DT Article DE Newton's method; rate of convergence; function sequence AB This note presents a simplified algorithm for achieving acceleration of convergence in Newton's method. RP Ford, WF (reprint author), NASA,LEWIS RES CTR,CLEVELAND,OH 44135, USA. NR 1 TC 24 Z9 26 U1 0 U2 0 PU SIAM PUBLICATIONS PI PHILADELPHIA PA 3600 UNIV CITY SCIENCE CENTER PH#382-9800, PHILADELPHIA, PA 19104-2688 SN 0036-1445 J9 SIAM REV JI SIAM Rev. PD DEC PY 1996 VL 38 IS 4 BP 658 EP 659 DI 10.1137/S0036144594292972 PG 2 WC Mathematics, Applied SC Mathematics GA VW986 UT WOS:A1996VW98600010 ER PT J AU Sutter, B Hossner, LR Ming, DW AF Sutter, B Hossner, LR Ming, DW TI Phosphorus adsorption and desorption properties of Minnesota basalt lunar simulant and lunar glass simulant SO SOIL SCIENCE LA English DT Article ID ANION-EXCHANGE RESIN; PHOSPHATE SORPTION; ELOVICH EQUATION; SOIL-PHOSPHORUS; KINETICS; RELEASE; CATION AB Phosphorus (P) adsorption and desorption characteristics of Minnesota Basalt Lunar Simulant (MBLS) and Lunar Glass Simulant (LGS) were evaluated. Results of P interactions with lunar simulants indicated that mineral and glass components adsorbed between 50 and 70% of the applied P and that between 85 and 100% of the applied P was desorbed. The Extended Freundlich equation best described the adsorption data (r(2) = 0.92), whereas the Raven/Hossner equation best described the desorption data (r(2) = 0.97). Kinetic desorption results indicated that MBLS and LGS released most of their P within 15 h. The expanded Elovich equation fit the data best at shorter times while t/Q(DT) equation had a better fit at longer times. These results indicate that P does not strongly adsorb to the two simulants and that any P that was adsorbed was readily desorbed in the presence of anion exchange resin. This work suggests that multiple small applications of P (10-20 mg P kg(-1)) should be added to the simulants to ensure adequate solution P for plant uptake and efficient use of P fertilizer. C1 NASA,LYNDON B JOHNSON SPACE CTR,EARTH SCI & SOLAR SYST EXPLORAT DIV,HOUSTON,TX 77058. RP Sutter, B (reprint author), TEXAS A&M UNIV,DEPT CROP & SOIL SCI,COLLEGE STN,TX 77843, USA. NR 55 TC 2 Z9 4 U1 2 U2 4 PU WILLIAMS & WILKINS PI BALTIMORE PA 351 WEST CAMDEN ST, BALTIMORE, MD 21201-2436 SN 0038-075X J9 SOIL SCI JI Soil Sci. PD DEC PY 1996 VL 161 IS 12 BP 873 EP 883 DI 10.1097/00010694-199612000-00007 PG 11 WC Soil Science SC Agriculture GA WB173 UT WOS:A1996WB17300007 ER PT J AU Chiang, KT Wallace, TA Clark, RK AF Chiang, KT Wallace, TA Clark, RK TI Dynamic oxidation of a Cu-30vol.%Cr coating on a copper-based alloy SO SURFACE & COATINGS TECHNOLOGY LA English DT Article; Proceedings Paper CT 23rd International Conference on Metallurgical Coatings and Thin Films CY APR 22-26, 1996 CL SAN DIEGO, CA SP Amer Vacuum Soc, Vacuum Met & Thin Films Div DE dynamic oxidation; Cu-Cr coating; LTAVD; Cr2O3 scale ID CU-NB MICROCOMPOSITES; DEPOSITION TECHNOLOGY AB A Cu-30vol.%Cr coaling produced by co-evaporation of Cu and Cr was evaluated is an electric arc-heated wind tunnel. The wind tunnel generated high-velocity, dissociated air containing atomic oxygen. The coating provided good oxidation protection for the copper alloy substrate under dynamic environment at 650-760 degrees C. The oxide morphologies of the coating under dynamic conditions were distinct from those of static oxidation. The atomic oxygen in the gas stream accelerated the oxidative evaporation of Cr metal resulting in the formation of a porous layer of Cu-oxides on the coating surface. Oxidation resistance of the coating derived from a continuous layer of Cr2O3 formed underneath the external Cu-oxides so that the Cr2O3 scale was shielded from the hostile dynamic oxidation/atomic oxygen environment. C1 NASA, LANGLEY RES CTR, HAMPTON, VA 23681 USA. RP Chiang, KT (reprint author), ROCKWELL INT CORP, ROCKETDYNE DIV, CANOGA PK, CA 91303 USA. NR 14 TC 14 Z9 15 U1 0 U2 0 PU ELSEVIER SCIENCE SA LAUSANNE PI LAUSANNE PA PO BOX 564, 1001 LAUSANNE, SWITZERLAND SN 0257-8972 J9 SURF COAT TECH JI Surf. Coat. Technol. PD DEC 1 PY 1996 VL 86 IS 1-3 BP 48 EP 53 DI 10.1016/S0257-8972(96)03028-9 PN 1 PG 6 WC Materials Science, Coatings & Films; Physics, Applied SC Materials Science; Physics GA WB323 UT WOS:A1996WB32300009 ER PT J AU Lee, KN Miller, RA AF Lee, KN Miller, RA TI Development and environmental durability of mullite and mullite/YSZ dual layer coatings for SiC and Si3N4 ceramics SO SURFACE & COATINGS TECHNOLOGY LA English DT Article; Proceedings Paper CT 23rd International Conference on Metallurgical Coatings and Thin Films CY APR 22-26, 1996 CL SAN DIEGO, CA SP Amer Vacuum Soc, Vacuum Met & Thin Films Div DE environmental durability coating; mullite coating; mullite/YSZ coating; silicon-based ceramics ID SILICON-CARBIDE; OXIDATION; VAPOR AB Development of refractory oxide environmental coatings for SiC and Si3N4 ceramics, interaction with simulated combustion environments, and long-term durability under thermal cycling in air are discussed. Mullite coating performance data indicate its ability to limit the molten salt corrosion. Two-layer mullite/YSZ coating showed promise as a barrier coating limiting enhanced silica volatilization by water vapor in a simulated lean-burn combustion environment. The mullite/YSZ dual layer coatings showed excellent resistance to cracking and debonding for 1000 h using 2-h thermal cycles in air at 1200-1300 degrees C. A CVD SiC bond coat developed for Si3N4 dramatically enhanced the adherence of mullite coatings. Contamination of silica scale by alkali and alkali earth metal oxides resulted in enhanced oxidation and pore formation which is an issue for the long-term environmental durability of these coatings. C1 NASA, LEWIS RES CTR, CLEVELAND, OH 44135 USA. NR 16 TC 62 Z9 67 U1 3 U2 27 PU ELSEVIER SCIENCE SA LAUSANNE PI LAUSANNE PA PO BOX 564, 1001 LAUSANNE, SWITZERLAND SN 0257-8972 J9 SURF COAT TECH JI Surf. Coat. Technol. PD DEC 1 PY 1996 VL 86 IS 1-3 BP 142 EP 148 DI 10.1016/S0257-8972(96)03074-5 PN 1 PG 7 WC Materials Science, Coatings & Films; Physics, Applied SC Materials Science; Physics GA WB323 UT WOS:A1996WB32300022 ER PT J AU Baldy, R DeBenedictis, J Johnson, L Weber, E Baldy, M Osborn, B Burleigh, J AF Baldy, R DeBenedictis, J Johnson, L Weber, E Baldy, M Osborn, B Burleigh, J TI Leaf color and vine size are related to yield in a phylloxera-infested vineyard SO VITIS LA English DT Article DE Phylloxera infestation; yield estimation; canopy spectra; chlorophyll; pruning weight ID GRAPE PHYLLOXERA; RED AB The uneven spread of phylloxera infestation and associated vine symptoms in vineyards usually complicates yield estimates and vineyard replacement decisions. In a Cabernet Sauvignon vineyard with AXR#1 rootstock the current season's and following season's yields of 40 vine plots correlated (r greater than or equal to 0.77, p less than or equal to 0.05) with early to midseason leaf and canopy spectra measured in the field, laboratory and remotely with aircraft-borne sensors. C1 UNIV CALIF DAVIS,DEPT ENTOMOL,DAVIS,CA 95616. JCWS INC,NASA,AMES RES CTR,MOFFETT FIELD,CA. UNIV CALIF NAPA,COOPERAT EXTENS,NAPA,CA. GLEN ELEN CARNEROS WINERY,SONOMA,CA. RP Baldy, R (reprint author), CALIF STATE UNIV CHICO,SCH AGR,CHICO,CA 95926, USA. NR 11 TC 20 Z9 20 U1 0 U2 2 PU BUNDESANSTALT ZUCHTUNGS FORSCHUNG KULTURPFLANZEN PI SIEBELDINGEN PA INST REBENZUCHTUNG GEILWEILERHOF, D-76833 SIEBELDINGEN, GERMANY SN 0042-7500 J9 VITIS JI Vitis PD DEC PY 1996 VL 35 IS 4 BP 201 EP 205 PG 5 WC Horticulture SC Agriculture GA WG042 UT WOS:A1996WG04200009 ER PT J AU Launius, RD AF Launius, RD TI Utah, the right place: The official centennial history - Alexander,TG SO WESTERN HISTORICAL QUARTERLY LA English DT Book Review RP Launius, RD (reprint author), NASA,HOUSTON,TX, USA. NR 1 TC 0 Z9 0 U1 0 U2 0 PU WESTERN HISTORY ASSOCIATION PI LOGAN PA UTAH STATE UNIV, UMC 0740, LOGAN, UT 84322 SN 0043-3810 J9 WESTERN HIST QUART JI West. Hist. Q. PD WIN PY 1996 VL 27 IS 4 BP 540 EP 542 DI 10.2307/970565 PG 3 WC History SC History GA VU318 UT WOS:A1996VU31800035 ER PT J AU Gupta, KK Meek, JL AF Gupta, KK Meek, JL TI A brief history of the beginning of the finite element method SO INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING LA English DT Article DE history; finite elements; structural mechanics AB This paper presents summaries of the works of several authors associated with the invention of the analysis technique now referred to as the finite element method. It stresses the notion of first development from which subsequent ideas evolved and gives what is believed to be an accurate record of the historical sequence of published papers in the international literature. C1 UNIV QUEENSLAND,DEPT CIVIL ENGN,ST LUCIA,QLD 4072,AUSTRALIA. RP Gupta, KK (reprint author), NASA,DRYDEN FLIGHT RES CTR,INTEGRATED SYST,EDWARDS AFB,CA, USA. NR 12 TC 9 Z9 10 U1 0 U2 5 PU JOHN WILEY & SONS LTD PI W SUSSEX PA BAFFINS LANE CHICHESTER, W SUSSEX, ENGLAND PO19 1UD SN 0029-5981 J9 INT J NUMER METH ENG JI Int. J. Numer. Methods Eng. PD NOV 30 PY 1996 VL 39 IS 22 BP 3761 EP 3774 DI 10.1002/(SICI)1097-0207(19961130)39:22<3761::AID-NME22>3.3.CO;2-X PG 14 WC Engineering, Multidisciplinary; Mathematics, Interdisciplinary Applications SC Engineering; Mathematics GA VR515 UT WOS:A1996VR51500001 ER PT J AU Shalish, I Gasser, SM Kolawa, E Nicolet, MA Ruiz, RP AF Shalish, I Gasser, SM Kolawa, E Nicolet, MA Ruiz, RP TI Gold metallization for aluminum nitride SO THIN SOLID FILMS LA English DT Article DE gold; metals; aluminium nitride ID ALLOY JOSEPHSON-JUNCTIONS; TI-AU; FILM; STABILITY; BARRIER AB A metallization scheme for gold on AlN is investigated that incorporates three layers sputter-deposited in succession on the AIN substrate, without breaking vacuum: 20 nm of Ti to promote adhesion, a 100 nm thick Ti-Si-N barrier layer, and 230 nm Au. The stability of the scheme was studied after annealing in vacuum up to 800 degrees C for 30 min and at 400 degrees C in Ar ambient for 300 h, using 2 MeV He-4(++) backscattering spectrometry, sheet resistance measurements, and adhesion tests. It is shown that the incorporation of the diffusion barrier prevents the interaction of the Ti from the adhesion layer with the gold layer and thereby preserves the integrity of the metallization scheme. This metallization scheme may be applicable to other substrate materials. C1 CALTECH,PASADENA,CA 91125. CALTECH,JET PROP LAB,PASADENA,CA 91109. RI Shalish, Ilan/B-4487-2008 OI Shalish, Ilan/0000-0002-8053-7339 NR 19 TC 8 Z9 8 U1 1 U2 1 PU ELSEVIER SCIENCE SA LAUSANNE PI LAUSANNE PA PO BOX 564, 1001 LAUSANNE, SWITZERLAND SN 0040-6090 J9 THIN SOLID FILMS JI Thin Solid Films PD NOV 30 PY 1996 VL 289 IS 1-2 BP 166 EP 169 DI 10.1016/S0040-6090(96)08919-5 PG 4 WC Materials Science, Multidisciplinary; Materials Science, Coatings & Films; Physics, Applied; Physics, Condensed Matter SC Materials Science; Physics GA WB265 UT WOS:A1996WB26500029 ER PT J AU Chin, G Senesac, LR Blass, WE Hillman, JJ AF Chin, G Senesac, LR Blass, WE Hillman, JJ TI Stabilizing lead-salt diode lasers: Understanding and controlling chaotic frequency emission SO SCIENCE LA English DT Article ID MULTIMODE LASER; TIME-SERIES; SYSTEM AB lead-salt tunable diode lasers (TDLs) are the only devices currently available that can generate tunable monochromatic radiation at arbitrary wavelengths between 3 and 30 micrometers and are particularly useful for high-resolution spectroscopy over a wide range of spectral regimes. Detailed observations oi TDLs show that the observed instrumental linewidth is actually a temporal average of many narrow (less than 0.5 megahertz) emission ''modes.'' The lime scale characteristic of these ''modes,'' which appear to be of relatively constant intensity, is of the order of a microsecond. The laser's behavior is highly suggestive of a chaotic process, that is, seemingly random excursions of a dynamic variable (frequency) within a bounded range. This report shows experimentally that TDL emissions are indeed chaotic. Furthermore, in a simple and robust fashion, this chaotic behavior has been successfully controlled with the use of recent techniques that take advantage of chaos to produce a narrow band laser output. C1 UNIV TENNESSEE,DEPT PHYS & ASTRON,KNOXVILLE,TN 37996. RP Chin, G (reprint author), NASA,GODDARD SPACE FLIGHT CTR,EXTRATERR PHYS LAB,GREENBELT,MD 20771, USA. RI Blass, William/A-2792-2008; Chin, Gordon/E-1520-2012 NR 21 TC 8 Z9 8 U1 0 U2 0 PU AMER ASSOC ADVANCEMENT SCIENCE PI WASHINGTON PA 1200 NEW YORK AVE, NW, WASHINGTON, DC 20005 SN 0036-8075 J9 SCIENCE JI Science PD NOV 29 PY 1996 VL 274 IS 5292 BP 1498 EP 1501 DI 10.1126/science.274.5292.1498 PG 4 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA VV775 UT WOS:A1996VV77500039 ER PT J AU Zook, HA Grun, E Baguhl, M Hamilton, DP Linkert, G Liou, JC Forsyth, R Phillips, JL AF Zook, HA Grun, E Baguhl, M Hamilton, DP Linkert, G Liou, JC Forsyth, R Phillips, JL TI Solar wind magnetic field bending of Jovian dust trajectories SO SCIENCE LA English DT Article ID JUPITER; EJECTION; GALILEO AB From September 1991 to October 1992, the cosmic dust detector on the Ulysses spacecraft recorded 11 short bursts, or streams, of dust. These dust grains emanated from the jovian system, and their trajectories were strongly affected by solar wind magnetic field forces. Analyses of the on-board measurements of these fields, and of stream approach directions, show that stream-associated dust grain masses are of the order of 10(-18) gram and dust grain velocities exceed 200 kilometers per second. These masses and velocities are, respectively, about 10(3) times less massive and 5 to 10 times faster than earlier reported. C1 MAX PLANCK INST KERNPHYS,D-69029 HEIDELBERG,GERMANY. UNIV MARYLAND,DEPT ASTRON,COLLEGE PK,MD 20742. UNIV LONDON IMPERIAL COLL SCI TECHNOL & MED,BLACKETT LAB,LONDON SW7 2BZ,ENGLAND. LOS ALAMOS NATL LAB,LOS ALAMOS,NM 87545. RP Zook, HA (reprint author), NASA,LYNDON B JOHNSON SPACE CTR,HOUSTON,TX 77058, USA. NR 14 TC 64 Z9 64 U1 0 U2 1 PU AMER ASSOC ADVANCEMENT SCIENCE PI WASHINGTON PA 1200 NEW YORK AVE, NW, WASHINGTON, DC 20005 SN 0036-8075 J9 SCIENCE JI Science PD NOV 29 PY 1996 VL 274 IS 5292 BP 1501 EP 1503 DI 10.1126/science.274.5292.1501 PG 3 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA VV775 UT WOS:A1996VV77500040 PM 8929405 ER PT J AU Rampino, MR AF Rampino, MR TI Late Permian extinctions SO SCIENCE LA English DT Article C1 NASA,GODDARD INST SPACE STUDIES,NEW YORK,NY 10025. RP Rampino, MR (reprint author), NYU,NEW YORK,NY 10003, USA. RI Canfield, Don/C-1735-2012 OI Canfield, Don/0000-0001-7602-8366 NR 3 TC 5 Z9 5 U1 1 U2 1 PU AMER ASSOC ADVANCEMENT SCIENCE PI WASHINGTON PA 1200 NEW YORK AVE, NW, WASHINGTON, DC 20005 SN 0036-8075 J9 SCIENCE JI Science PD NOV 29 PY 1996 VL 274 IS 5292 BP 1551 EP 1551 PG 1 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA VV775 UT WOS:A1996VV77500059 ER PT J AU Smith, GD Jaffe, RL AF Smith, GD Jaffe, RL TI Quantum chemistry study of conformational energies and rotational energy barriers in n-alkanes SO JOURNAL OF PHYSICAL CHEMISTRY LA English DT Article ID ELECTRONIC-STRUCTURE CALCULATIONS; NORMAL-BUTANE; POTENTIAL FUNCTION; INTERNAL-ROTATION; AB-INITIO; ENTHALPY DIFFERENCE; COUPLED CLUSTER; RAMAN-SPECTRA; PENTANE; TRANS AB The gauche energy, the t-g barrier, and the cis barrier in n-butane and n-hexane have been investigated using high-level ab initio electronic structure calculations. CCSD(T)/cc-pVTZ//MP2/6-311G(2df(3)p) calculations yield a gauche energy in n-butane of 0.59 kcal/mol, which after correction for zero-point and thermal vibrational effects is within 0.05 kcal/mol of the values obtained from recent experiments. Calculations at the same level yield t-g and cis barrier energies in n-butane of 3.31 and 5.48 kcal/mol, respectively, supporting the traditional view that the cis barrier in n-butane is much higher than the t-g barrier. We found that torsional potential functions previously parametrized to reproduce the measured low-lying torsional vibrational transitions in the trans and gauche conformers of n-butane and which yield only a small energy difference between the barriers can be modified to reproduce both the spectroscopic data and the large quantum chemistry energy difference between barriers. For the central bond in n-hexane, the gauche energy is about 0.07 kcal/mol lower than the gauche energy in n-butane at the same level of theory. The chain length effect is greater on the barriers, with the t-g and cis barriers being about 0.5 and 0.3 kcal/mol lower, respectively, for the central bond in n-hexane compared to n-butane at the same level of theory. C1 NASA,AMES RES CTR,MOFFETT FIELD,CA 94035. RP Smith, GD (reprint author), UNIV MISSOURI,DEPT CHEM ENGN,COLUMBIA,MO 65211, USA. NR 36 TC 104 Z9 104 U1 3 U2 22 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 SN 0022-3654 J9 J PHYS CHEM-US JI J. Phys. Chem. PD NOV 28 PY 1996 VL 100 IS 48 BP 18718 EP 18724 DI 10.1021/jp960413f PG 7 WC Chemistry, Physical SC Chemistry GA VV354 UT WOS:A1996VV35400011 ER PT J AU LeClair, LR Trajmar, S AF LeClair, LR Trajmar, S TI Electron impact excitation of autoionizing levels of Kr and Xe between the P-2(3/2) and P-2(1/2) ionic limits SO JOURNAL OF PHYSICS B-ATOMIC MOLECULAR AND OPTICAL PHYSICS LA English DT Article ID RYDBERG SERIES; CROSS-SECTIONS; LASER SPECTROSCOPY; STATES; XENON; KRYPTON; AR; COLLISIONS; ATOMS; NS' AB We have observed electrons ejected from autoionizing levels which lie between the P-2(3/2) and P-2(1/2) ionic limits for Kr and Xe. Kinetic energy spectra of the ejected electrons were obtained following electron-impact excitation of the target gases by using time-of-flight spectroscopy in a crossed-beam experiment. Spectral features which correspond to electrons ejected from both odd and even parity autoionizing levels have been identified. Some of the features have kinetic energies of just over 0.1 eV and have been resolved for the first time in an electron-impact experiment. The most intense features at low electron-impact energies come from optically forbidden np' and nd' terms. It was possible to estimate the integral cross section for autoionization by comparing the intensity of the elastically scattered electrons with the intensity of the autoionizing features. For Xe, autoionization from the levels which lie between the ionic limits appears to account for about 67% and 7.6% of the electron-impact ionization cross section at impact energies of 14 and 24 eV, respectively; while for Kr, the fractions are 20% and 2.7% at 16 and 26 eV. RP LeClair, LR (reprint author), CALTECH,JET PROP LAB,PASADENA,CA 91109, USA. NR 23 TC 5 Z9 5 U1 0 U2 3 PU IOP PUBLISHING LTD PI BRISTOL PA TECHNO HOUSE, REDCLIFFE WAY, BRISTOL, ENGLAND BS1 6NX SN 0953-4075 J9 J PHYS B-AT MOL OPT JI J. Phys. B-At. Mol. Opt. Phys. PD NOV 28 PY 1996 VL 29 IS 22 BP 5527 EP 5542 DI 10.1088/0953-4075/29/22/026 PG 16 WC Optics; Physics, Atomic, Molecular & Chemical SC Optics; Physics GA VW566 UT WOS:A1996VW56600026 ER PT J AU LeClair, LR Trajmar, S AF LeClair, LR Trajmar, S TI Absolute inelastic differential electron scattering cross sections for He, Xe, N-2 and CO at near-threshold impact energies for 90 degrees scattering angle SO JOURNAL OF PHYSICS B-ATOMIC MOLECULAR AND OPTICAL PHYSICS LA English DT Article ID DISTORTED-WAVE CALCULATION; INCIDENT ENERGIES; NOBLE-GASES; EXCITATION; HELIUM; STATES; REGION; XENON; N2; H-2 AB An electron time-of-flight (TOF) technique was utilized to obtain absolute differential cross sections for electron impact excitation in He, Xe, N-2 and CO at near-threshold impact energies at 90 degrees scattering angle. These cross sections are more reliable that those obtained from conventional beam-beam scattering measurements using electrostatic spectrometers and can serve as secondary standards for normalizing relative scattering intensities. The results obtained from the TOF measurements are significant also because they fill the gap between cross sections available at very near threshold and intermediate impact energies. RP LeClair, LR (reprint author), CALTECH,JET PROP LAB,PASADENA,CA 91109, USA. NR 47 TC 25 Z9 25 U1 1 U2 5 PU IOP PUBLISHING LTD PI BRISTOL PA TECHNO HOUSE, REDCLIFFE WAY, BRISTOL, ENGLAND BS1 6NX SN 0953-4075 J9 J PHYS B-AT MOL OPT JI J. Phys. B-At. Mol. Opt. Phys. PD NOV 28 PY 1996 VL 29 IS 22 BP 5543 EP 5566 DI 10.1088/0953-4075/29/22/027 PG 24 WC Optics; Physics, Atomic, Molecular & Chemical SC Optics; Physics GA VW566 UT WOS:A1996VW56600027 ER PT J AU Cahalan, RF Wharton, LE Wu, ML AF Cahalan, RF Wharton, LE Wu, ML TI Empirical orthogonal functions of monthly precipitation and temperature over the United States and homogeneous stochastic models SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID CLIMATE AB The monthly mean precipitation and temperature at p = 62 stations over the United States and Canada for N = 91 years (1900-1990) are analyzed in terms of empirical orthogonal functions (EOFs) and their variances. The eigenvalues and eigenfunctions are compared with a succession of stochastic noise models: (1) uncorrelated noise, having eigenvalues depending on the ratio pin, with n = N - 1; (2) homogeneous noise having spatial correlations which are fit to the observations; and (3) homogeneous noise having both spatial and temporal correlations fit to the observations. Individual monthly data for January and July were analyzed as well as a combined data set of all months. The eigenvalue spectra of the homogeneous noise models are found to be in close agreement with the observed spectra even when time correlation is excluded from the model. Time correlations only slightly affect the results for temperature and have less impact for precipitation. The EOF patterns of the noise models contain inhomogeneities due only to the distribution of stations, the common correlation length, and the limited sample but are nevertheless in good agreement with the observed patterns, whose inhomogeneities may also be affected by secular trends and physical inhomogeneities such as orography. The observed EOF eigenvectors also show identifiable deviations from the homogeneous EOFs. Further work will be needed to see if these deviations can be convincingly associated with true physical inhomogeneities. RP Cahalan, RF (reprint author), NASA, GODDARD SPACE FLIGHT CTR, CLIMATE & RADIAT BRANCH, GODDARD LAB ATMOSPHERES, CODE 913, GREENBELT, MD 20771 USA. NR 11 TC 10 Z9 11 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD NOV 27 PY 1996 VL 101 IS D21 BP 26309 EP 26318 DI 10.1029/96JD01611 PG 10 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA VW421 UT WOS:A1996VW42100014 ER PT J AU Fokianos, K Kedem, B Short, DA AF Fokianos, K Kedem, B Short, DA TI Predicting precipitation level SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID LOGISTIC-REGRESSION; PARTIAL LIKELIHOOD; RAINFALL; MODELS AB We present a generalized logistic regression model for the statistical analysis of multicategorical time series. The model is suitably parameterized and partial likelihood inference is proposed for estimation of the unknown parameters. A goodness of fit statistic is derived to judge the quality of fit. The analysis is applied to data from the Tropical Ocean and Global Atmosphere/Coupled Ocean-Atmosphere Response Experiment. C1 UNIV MARYLAND, SYST RES INST, COLLEGE PK, MD 20742 USA. NASA, GODDARD SPACE FLIGHT CTR, ATMOSPHERES LAB, GREENBELT, MD 20771 USA. RP Fokianos, K (reprint author), UNIV MARYLAND, DEPT MATH, COLLEGE PK, MD 20742 USA. OI Fokianos, Konstantinos/0000-0002-0051-711X NR 14 TC 1 Z9 1 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 NOV 27 PY 1996 VL 101 IS D21 BP 26473 EP 26477 DI 10.1029/96JD01386 PG 5 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA VW421 UT WOS:A1996VW42100027 ER PT J AU Edwards, DP Kumer, JB LopezPuertas, M Mlynczak, MG Gopalan, A Gille, JC Roche, A AF Edwards, DP Kumer, JB LopezPuertas, M Mlynczak, MG Gopalan, A Gille, JC Roche, A TI Non-local thermodynamic equilibrium limb radiance near 10 mu m as measured by UARS CLAES SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID VIBRATIONALLY EXCITED OZONE; RADIATIVE-TRANSFER MODEL; MIDDLE ATMOSPHERE; M BANDS; INFRARED BANDS; CO2; STRATOSPHERE; PERFORMANCE; EMISSION; MISSION AB Observations have been made of non-local thermodynamic equilibrium (non-LTE) limb radiance at 923 cm(-1) (10.83 mu m) using the Cryogenic Limb Array Etalon Spectrometer (CLAES) aboard the Upper Atmosphere Research Satellite (UARS). We study the relative contributions from CO2 and O-3 in three CLAES channels and examine the correlation with solar zenith angle. The moderate spectral resolution of CLAES allows us to discriminate the individual radiance contributions of the CO2 isotopic and O-3 hot bands. The analysis shows good agreement between measured and calculated radiances and confirms our previous theoretical modeling of the non-LTE populations of these states. The diurnal variation of the measured emission points to solar dependent mechanisms selectively populating molecular vibrational levels in CO2 and O-3. These processes are shown to affect the limb radiance for limb view tangent heights above about 38 km at the frequencies studied here. The measurements also show further experimental evidence for the excitation of the CO2(nu(3)) mode by the energy transfer from electronically excited O(D-1) through N-2(1). This study is intended as a precursor to the inclusion of these effects in the operational CLAES data analysis. C1 LOCKHEED PALO ALTO RES LABS, PALO ALTO, CA 94304 USA. CSIC, INST ASTROFIS ANDALUCIA, E-18080 GRANADA, SPAIN. NASA, LANGLEY RES CTR, HAMPTON, VA 23665 USA. RP Edwards, DP (reprint author), NATL CTR ATMOSPHER RES, POB 3000, BOULDER, CO 80307 USA. RI Mlynczak, Martin/K-3396-2012; Lopez Puertas, Manuel/M-8219-2013 OI Lopez Puertas, Manuel/0000-0003-2941-7734 NR 31 TC 16 Z9 17 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 NOV 27 PY 1996 VL 101 IS D21 BP 26577 EP 26588 DI 10.1029/96JD02133 PG 12 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA VW421 UT WOS:A1996VW42100036 ER PT J AU Koshak, WJ Solakiewicz, RJ AF Koshak, WJ Solakiewicz, RJ TI On the retrieval of lightning radio sources from time-of-arrival data SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID SYSTEM AB We examine the problem of retrieving three-dimensional lightning locations from radio frequency time-of-arrival (TOA) measurements. Arbitrary antenna locations are considered. By judiciously differencing measurements that are related to the location of the antennas and their excitation times, the problem is converted from the initial spherical nonlinear form to a system of linear equations. In the linear formalism, the source location and time-of-occurrence is viewed geometrically as an intersection of hyperplanes in the four-dimensional Minkowski space (x,y,z,t). The linear equations are solved to obtain explicit analytic expressions for the location and time variables. Retrieval errors are not interpreted with conventional Geometrical Dilution of Precision (GDOP) arguments as discussed by Holmes and Reedy [1951], but with more recent inversion analyses considered by Twomey [1977]. Measurement errors are propagated analytically so that the specific effect of these errors on the solution is clarified, The sensitivity of the solution on the number of antennas used, antenna network geometry, source position, and measurement differencing schemes are discussed in terms of the eigenvalues of the linear system. C1 CHICAGO STATE UNIV, CTR MATH & COMP SCI, CHICAGO, IL 60628 USA. RP Koshak, WJ (reprint author), NASA, GEORGE C MARSHALL SPACE FLIGHT CTR, SPACE SCI LAB, HUNTSVILLE, AL 35812 USA. NR 19 TC 13 Z9 15 U1 3 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 NOV 27 PY 1996 VL 101 IS D21 BP 26631 EP 26639 DI 10.1029/96JD01618 PG 9 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA VW421 UT WOS:A1996VW42100040 ER PT J AU Allen, CC Morris, RV McKay, DS AF Allen, CC Morris, RV McKay, DS TI Oxygen extraction from lunar soils and pyroclastic glass SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS LA English DT Article ID REDUCTION; IRON; MOON; KINETICS AB We have conducted experiments on 16 lunar soils and three lunar pyroclastic glass samples to study the extraction of oxygen, an important resource for a future lunar base. The samples were chosen to span the range of composition,mineralogy, and maturity represented in the Apollo sample collection. Each sample was reduced in flowing hydrogen for 3 hours at 1050 degrees C. The dominant effect was reduction of Fe2+ (as FeO) in minerals and glass to iron metal, with concomitant release of oxygen. Oxygen extraction was strongly correlated with initial Fe2+ abundance. The data and supporting experiments also indicate extraction of oxygen from TiO2 and SiO2. No dependence of oxygen release on sample maturity could be identified. Oxygen was extracted, in decreasing order of efficiency, from ilmenite, agglutinitic and pyroclastic glass, olivine, and pyroxene. The experimental reduction of lunar soil provides a method for assessing the oxygen production potential for sites on the lunar surface from lunar orbit. Our results show that oxygen yield from the regolith can be predicted from knowledge of only one parameter, total iron content. This parameter can be measured from orbit by gamma ray spectrometry or multispectral imaging. These experimental data also support the selection of feedstocks and operating parameters for a lunar oxygen plant. C1 NASA, LYNDON B JOHNSON SPACE CTR, HOUSTON, TX 77058 USA. RP Allen, CC (reprint author), LOCKHEED ENGN & SCI CO, MAIL CODE C23, 2400 NASA RD 1, HOUSTON, TX 77058 USA. NR 39 TC 23 Z9 23 U1 2 U2 5 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 NOV 25 PY 1996 VL 101 IS E11 BP 26085 EP 26095 DI 10.1029/96JE02726 PG 11 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA VU802 UT WOS:A1996VU80200004 ER PT J AU Roush, TL Orenberg, JB AF Roush, TL Orenberg, JB TI Estimated detectability limits of iron-substituted montmorillonite clay on Mars from thermal emission spectra of clay-palagonite physical mixtures SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS LA English DT Article ID REMOTE-SENSING APPLICATIONS; REFLECTANCE SPECTROSCOPY; MU-M; RICH MONTMORILLONITE; SURFACE-COMPOSITION; PLANETARY SURFACES; AQUEOUS ALTERATION; SNC METEORITES; SOIL; MINERALOGY AB The thermal emission properties of two Mars soil analogs, palagonite and iron-substituted montmorillonite clay, and their physical mixtures are presented in the 5 to 25 mu m (2000 to 400 cm(-1)) region. The clay spectrum has both a greater number of spectral features and higher emissivity contrast when compared to the palagonite spectrum. Emissivity peaks located near 8.9, 11.1, and 19.9 mu m (1120, 905, and 505 cm(-1)) and troughs (restsrahlen features) located near 8.8, 9.7, 18.9, and 22.2 mu m in the spectrum of the clay provide the ability to identify the presence of clay when it is physically mixed with the palagonite. In the mixtures studied, when 15 wt% of clay is mixed with 85 wt% palagonite, the 19.9 mu m emissivity peak and the 9.7 mu m reststrahlen trough are readily identifiable, but the 8.9 and 11.1 mu m peaks and the 8.8, 9.3, and 18.9 mu m troughs are only marginally identifiable. This indicates that identification of clays on Mars, using midinfrared data, should rely upon the sensitivity of the 19.9 and 9.7 mu m features to the clays' presence. C1 NASA,AMES RES CTR,PLANETARY SYST BRANCH,MOFFETT FIELD,CA 94035. SAN FRANCISCO STATE UNIV,DEPT CHEM & BIOCHEM,SAN FRANCISCO,CA 94132. RP Roush, TL (reprint author), SAN FRANCISCO STATE UNIV,DEPT GEOSCI,1600 HOLLOWAY AVE,SAN FRANCISCO,CA 94132, USA. NR 55 TC 7 Z9 7 U1 0 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 SN 0148-0227 J9 J GEOPHYS RES-PLANET JI J. Geophys. Res.-Planets PD NOV 25 PY 1996 VL 101 IS E11 BP 26111 EP 26118 DI 10.1029/96JE02863 PG 8 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA VU802 UT WOS:A1996VU80200006 ER PT J AU Golombek, MP Tanaka, KL Franklin, BJ AF Golombek, MP Tanaka, KL Franklin, BJ TI Extension across Tempe Terra, Mars, from measurements of fault scarp widths and deformed craters SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS LA English DT Article ID THARSIS REGION; TECTONIC HISTORY; DISCONTINUITIES; PROVINCE; GRABENS; SYRIA AB Two independent methods, with no common assumptions, have been used to estimate the extension across the heavily deformed Tempe Terra province of the Tharsis region of Mars. One method uses measurements of normal fault scarp width with average scarp slope data for simple grabens and rifts on Mars to estimate the fault throw, which, combined with sparse fault dip data, can be used to estimate extension. Formal uncertainties in this method are only slightly greater than those in other methods, given that the total uncertainty is dominated by the likely uncertainty in the fault dip (assumed to be 60 degrees +/- 15 degrees). Measurement of normal fault scarp widths along two N25 degrees-50 degrees W directed traverses across Tempe Terra both yield about 22 +/- 16 km of extension (or similar to 2% strain across the northern traverse and nearly 3% across the southern one). About three quarters of the extension has occurred during the two main phases of Tharsis-related deformation from Middle/Late Noachian to Early Hesperian and from Late Hesperian to Early Amazonian, with mow extension closer to the center of Tharsis during the first phase. Extension across the region was also determined by measuring the elongation and elongation direction of all ancient Noachian impact craters without ejecta blankets, which predate most of the deformation. Results have been corrected for initial non circularity of craters, established from similar measurements of young (post deformation) impact craters, yielding a statistically significant mean strain of 1.96 +/- 0.35% in a N38 degrees +/- 10 degrees W direction across Tempe Terra (extension of similar to 20 +/- 4, comparable in magnitude and direction to the average result from the scarp measurement method). Both methods indicate an average extension for single normal fault scarps (and shortening across wrinkle ridges for the crater method) of similar to 100 m. The agreement between the results of the two independent methods in overall extension and average single normal fault extension argues that the average scarp slope and fault dip data in the fault scarp width method accurately represent the actual extension across the observed structures. This conclusion supports existing geometric and kinematic models for structural features on Mars. A preliminary estimate of the total circumferential extension around Tharsis (at a radius of similar to 2500 km) is roughly 60 +/- 42 km; total hoop strain is about 0.4% distributed heterogeneously (Tempe Terra is the most highly strained region on Mars). C1 US GEOL SURVEY, BRANCH ASTROGEOL, FLAGSTAFF, AZ 86001 USA. RP Golombek, MP (reprint author), CALTECH, JET PROP LAB, MAIL STOP 183-501, 4800 OAK GROVE DR, PASADENA, CA 91109 USA. NR 28 TC 27 Z9 27 U1 1 U2 2 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0148-0227 J9 J GEOPHYS RES-PLANET JI J. Geophys. Res.-Planets PD NOV 25 PY 1996 VL 101 IS E11 BP 26119 EP 26130 DI 10.1029/96JE02709 PG 12 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA VU802 UT WOS:A1996VU80200007 ER PT J AU Srivastava, SK Krishnakumar, E Fucaloro, AF vanNote, T AF Srivastava, SK Krishnakumar, E Fucaloro, AF vanNote, T TI Cross sections for the production of cations by electron impact on methanol SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS LA English DT Article ID IONIZATION; ATOMS AB Utilizing a crossed electron beam and a molecular beam collision geometry and the single particle counting technique, cross sections for the production of positive ions by electron impact on methanol have been measured for electron impact energies ranging from 0 to 500 eV. Appearance potentials for the various ionic fragments have also been obtained. These potentials are compared with values calculated from the heats of formation for methanol and for neutral and cationic products in order to identify the various channels of dissociation at threshold energies. C1 CLAREMONT MCKENNA COLL,JOINT SCI DEPT,CLAREMONT,CA 91711. RP Srivastava, SK (reprint author), CALTECH,JET PROP LAB,MS 183-601,4800 OAK GROVE DR,PASADENA,CA 91109, USA. NR 21 TC 11 Z9 11 U1 0 U2 5 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 SN 0148-0227 J9 J GEOPHYS RES-PLANET JI J. Geophys. Res.-Planets PD NOV 25 PY 1996 VL 101 IS E11 BP 26155 EP 26160 DI 10.1029/96JE02471 PG 6 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA VU802 UT WOS:A1996VU80200010 ER PT J AU Stoica, I Sultan, F Keyes, D AF Stoica, I Sultan, F Keyes, D TI A hyperbolic model for communication in layered parallel processing environments SO JOURNAL OF PARALLEL AND DISTRIBUTED COMPUTING LA English DT Article ID COMPUTATION; PERFORMANCE AB We introduce a model for communication costs in parallel processing environments, called the hyperbolic model, which generalizes two-parameter dedicated-link models in an analytically simple way. The communication system is modeled as a directed communication graph in which terminal nodes represent the application processes and internal nodes, called communication blocks (CBs), reflect the layered structure of the underlying communication architecture. A CB is characterized by a two-parameter hyperbolic function of the message size that represents the service time needed for processing the message. Rules are given for reducing a communication graph consisting of many CBs to an equivalent two-parameter form, while maintaining a good approximation for the service time. We demonstrate a tight fit of the estimates of the cost of communication based on the model with actual measurements of the communication and synchronization time between end processes. We compare the hyperbolic model with other two-parameter model and, in appropriate limits, show its compatibility with the LogP model. (C) 1996 Academic Press, Inc. C1 NASA, LANGLEY RES CTR, INST COMP APPL SCI & ENGN, HAMPTON, VA 23681 USA. RP Stoica, I (reprint author), OLD DOMINION UNIV, DEPT COMP SCI, NORFOLK, VA 23529 USA. NR 22 TC 2 Z9 2 U1 0 U2 0 PU ACADEMIC PRESS INC ELSEVIER SCIENCE PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA SN 0743-7315 J9 J PARALLEL DISTR COM JI J. Parallel Distrib. Comput. PD NOV 25 PY 1996 VL 39 IS 1 BP 29 EP 45 DI 10.1006/jpdc.1996.0152 PG 17 WC Computer Science, Theory & Methods SC Computer Science GA WA701 UT WOS:A1996WA70100003 ER PT J AU Lee, TJ AF Lee, TJ TI Ab initio characterization of HBrO2 isomers: Implications for stratospheric bromine chemistry SO CHEMICAL PHYSICS LETTERS LA English DT Article ID GAUSSIAN-BASIS SETS; COUPLED-CLUSTER; MOLECULAR CALCULATIONS; ATOMS; HOBR; CONTRACTION; SPECTRA; ENERGY; HO2 AB Equilibrium geometries, dipole moments, harmonic vibrational frequencies, and IR intensities are determined for the BrOOH, HOBrO, and HBrO2 molecules using the CCSD(T) correlation method in conjunction with a TZ2P one-particle basis set. Accurate heats of formation are evaluated using the CCSD(T) method together with spdfg one-particle basis sets. BrOOH is the lowest energy isomer, although HOBrO is predicted to be less than 5 kcal/mol higher in energy. The torsional barrier for trans-BrOOH is 2.9 kcal/mol (0 K), while for cis-BrOOH it is 5.4 kcal/mol. BrOOH is shown to be stable with respect to thermal dissociation and implications for stratospheric bromine chemistry are discussed. RP Lee, TJ (reprint author), NASA, AMES RES CTR, MS230-3, MOFFETT FIELD, CA 94035 USA. RI Lee, Timothy/K-2838-2012 NR 28 TC 17 Z9 17 U1 0 U2 2 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0009-2614 J9 CHEM PHYS LETT JI Chem. Phys. Lett. PD NOV 22 PY 1996 VL 262 IS 5 BP 559 EP 566 DI 10.1016/S0009-2614(96)01178-5 PG 8 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA VU368 UT WOS:A1996VU36800009 ER PT J AU Yao, MW Matthiesen, DH Chait, A AF Yao, MW Matthiesen, DH Chait, A TI Numerical simulation of heat transport and fluid flow in directional crystal growth of GaAs SO NUMERICAL HEAT TRANSFER PART A-APPLICATIONS LA English DT Article ID PHASE-CHANGE PROBLEMS; BRIDGMAN GROWTH; CONVECTION; SEGREGATION; MELT; SOLIDIFICATION; FURNACE AB Recent progress in numerical modeling of the transient heat transport and fluid flow in the GTE GaAs space experiment is reported. The vertical gradient freeze crystal growth system is simulated using a simplified axisymmetric finite element model The enthalpy method is used to model the phase change, and numerical solutions are computed on a fixed grid using the CFD code FIDAP. The numerical results suggest that the shape and melt-back position of the melt-crystal interface are greatly affected by the melting history, therefore making it necessary to model the whole melting and solidification process. The simulated interface evolution far the flight experiment predicts a delay of about 25 min for the actual growth to start after the power reduction begins, which is in good agreement with the experiment. Some numerical issues, such as the advantages and limitations of the fixed domain approach, are also discussed. C1 CASE WESTERN RESERVE UNIV,CLEVELAND,OH 44106. NASA,LEWIS RES CTR,CLEVELAND,OH 44135. RP Yao, MW (reprint author), OHIO AEROSP INST,22800 CEDAR POINT RD,BROOKPARK,OH 44142, USA. NR 25 TC 5 Z9 5 U1 0 U2 0 PU HEMISPHERE PUBL CORP PI BRISTOL PA 1900 FROST ROAD, SUITE 101, BRISTOL, PA 19007-1598 SN 1040-7782 J9 NUMER HEAT TR A-APPL JI Numer. Heat Tranf. A-Appl. PD NOV 22 PY 1996 VL 30 IS 7 BP 685 EP 701 DI 10.1080/10407789608913865 PG 17 WC Thermodynamics; Mechanics SC Thermodynamics; Mechanics GA WA042 UT WOS:A1996WA04200004 ER PT J AU Boering, KA Wofsy, SC Daube, BC Schneider, HR Loewenstein, M Podolske, JR AF Boering, KA Wofsy, SC Daube, BC Schneider, HR Loewenstein, M Podolske, JR TI Stratospheric mean ages and transport rates from observations of carbon dioxide and nitrous oxide SO SCIENCE LA English DT Article ID TROPOSPHERE; EXCHANGE; AIR; N2O; MIDLATITUDES; SPECTROMETER; CONSTITUENTS; SIMULATIONS; AEROSOL; CO2 AB Measurements of stratospheric carbon dioxide (CO2) and nitrous oxide (N2O) concentrations were analyzed to investigate stratospheric transport rates. Temporal variations in tropospheric CO2 were observed to propagate into the stratosphere, showing that tropospheric air enters the lower tropical stratosphere continuously, ascends, and is transported rapidly (in less than 1 month) to both hemispheres. The mean age A of stratospheric air determined from CO2 data is approximately 5 years in the mid-stratosphere. The mean age is mathematically equivalent to a conserved tracer analogous to exhaust from stratospheric aircraft. Comparison of values for A from models and observations indicates that current model simulations likely underestimate pollutant concentrations from proposed stratospheric aircraft by 25 to 100 percent. C1 HARVARD UNIV,DIV ENGN & APPL SCI,CAMBRIDGE,MA 02138. HARVARD UNIV,DEPT EARTH & PLANETARY SCI,CAMBRIDGE,MA 02138. NASA,AMES RES CTR,MOFFETT FIELD,CA 94035. NOAA,CLIMATE MONITORING & DIAGNOST LAB,BOULDER,CO 80303. NR 48 TC 156 Z9 157 U1 8 U2 26 PU AMER ASSOC ADVANCEMENT SCIENCE PI WASHINGTON PA 1200 NEW YORK AVE, NW, WASHINGTON, DC 20005 SN 0036-8075 J9 SCIENCE JI Science PD NOV 22 PY 1996 VL 274 IS 5291 BP 1340 EP 1343 DI 10.1126/science.274.5291.1340 PG 4 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA VU954 UT WOS:A1996VU95400042 ER PT J AU Levine, ER Kimes, DS Sigillito, VG AF Levine, ER Kimes, DS Sigillito, VG TI Classifying soil structure using neural networks SO ECOLOGICAL MODELLING LA English DT Article DE back propagation; neural networks; soil ecosystems; soil structure; soil characterization data ID AGGREGATE AB Various feed forward artificial neural networks (ANNs) with back propagation were tested to classify 3 types of soil structure (granular, blocky, and massive) from 390 soil samples. The samples represented soils falling within the Ustoll taxonomic suborder that are part of the National Cooperative Soil Survey (USDA, NRCS) data base. The best network found to predict soil structure was one with 3 input nodes, 2 hidden nodes, and 3 output nodes with accuracies on the order of 79%. Inputs were percent organic carbon, silt, and clay, Simple perceptrons and simple linear perceptrons, e.g. networks with no hidden nodes (3 --> 3), had accuracies of only 46%. Thus, ANNs are capable of learning soil structure from soil characterization data, and show a greater ability to classify soil structure types than simpler, linear methods. Classification of soil structure from commonly measured quantitative soil parameters is important because of the role structure plays in determining other soil properties, making it a critical component for modeling the soil system. This study shows the potential of artificial neural networks to recognize and learn complex relationships between quantitative soil parameters that can be used to correctly classify soil structure, and allow soil characterization data to be more effectively used for modeling activities. C1 JOHNS HOPKINS UNIV,APPL PHYS LAB,LAUREL,MD 20723. RP Levine, ER (reprint author), NASA,GODDARD SPACE FLIGHT CTR,TERR PHYS LAB,BIOSPHER SCI BRANCH,CODE 923,GREENBELT,MD 20771, USA. NR 24 TC 45 Z9 45 U1 0 U2 3 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0304-3800 J9 ECOL MODEL JI Ecol. Model. PD NOV 21 PY 1996 VL 92 IS 1 BP 101 EP 108 DI 10.1016/0304-3800(95)00199-9 PG 8 WC Ecology SC Environmental Sciences & Ecology GA VL804 UT WOS:A1996VL80400007 ER PT J AU Riotto, A Tornkvist, O Mohapatra, RN AF Riotto, A Tornkvist, O Mohapatra, RN TI Higgs boson mass in models with gauge-mediated supersymmetry breaking SO PHYSICS LETTERS B LA English DT Article ID STANDARD MODEL; PHYSICS AB We present the predictions for the mass M(h) of the lightest Higgs boson in models with gauge-mediated supersymmetry breaking as a function of the SUSY-breaking scale. We include all radiative corrections up to two loops and point out that if the CDF e(+)e(-)gamma gamma event is interpreted in terms of these models, then the lightest Higgs boson should be lighter than 110 GeV. C1 UNIV MARYLAND,DEPT PHYS & ASTRON,COLLEGE PK,MD 20742. RP Riotto, A (reprint author), FERMILAB NATL ACCELERATOR LAB,NASA,FERMILAB ASTROPHYS CTR,BATAVIA,IL 60510, USA. NR 32 TC 19 Z9 19 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 NOV 21 PY 1996 VL 388 IS 3 BP 599 EP 604 DI 10.1016/S0370-2693(96)01186-0 PG 6 WC Astronomy & Astrophysics; Physics, Nuclear; Physics, Particles & Fields SC Astronomy & Astrophysics; Physics GA VU657 UT WOS:A1996VU65700021 ER PT J AU Herring, GC Roberts, WL Brown, MS DeBarber, PA AF Herring, GC Roberts, WL Brown, MS DeBarber, PA TI Temperature measurement by degenerate four-wave mixing with strong absorption of the excitation beams SO APPLIED OPTICS LA English DT Article ID FLAME; OH; SPECTROSCOPY AB We have made simultaneous temperature measurements by degenerate four-wave mixing (DFWM) and absorption spectroscopy of OH in a CH4-air, lifted-diffusion flame. After we corrected the DFWM data for laser beam absorption of as much as 60%, the DFWM-based temperatures were in good agreement with temperatures derived strictly from the absorption data, as well as a one-dimensional reacting flow simulation. C1 N CAROLINA STATE UNIV,DEPT AEROSP & MECH ENGN,RALEIGH,NC 27695. METROLASER,IRVINE,CA 92714. RP Herring, GC (reprint author), NASA,LANGLEY RES CTR,FLUID MECH & ACOUST DIV,HAMPTON,VA 23681, USA. NR 15 TC 5 Z9 5 U1 0 U2 1 PU OPTICAL SOC AMER PI WASHINGTON PA 2010 MASSACHUSETTS AVE NW, WASHINGTON, DC 20036 SN 0003-6935 J9 APPL OPTICS JI Appl. Optics PD NOV 20 PY 1996 VL 35 IS 33 BP 6544 EP 6547 DI 10.1364/AO.35.006544 PG 4 WC Optics SC Optics GA VT736 UT WOS:A1996VT73600012 PM 21127678 ER PT J AU VanderWal, RL AF VanderWal, RL TI Laser-induced incandescence: Detection issues SO APPLIED OPTICS LA English DT Article DE laser-induced incandescence; LII; soot; particle size ID SOOT-VOLUME FRACTION; DIFFUSION FLAMES; DIAGNOSTICS; PARTICLES; SCATTERING; GROWTH AB Theoretical predictions suggest that soot particle size and local gas temperature affect both the spectral intensity and the temporal evolution of laser-induced incandescence. A discussion of both the physical structure and the theoretical absorption models of soot aggregates is presented, suggesting that the soot particle size relevant to laser-induced incandescence (LII) is the primary particle size regardless of whether the primary particle exists individually or is assembled into an aggregate. Experimental results of LII measurements in a laminar gas-jet flame with different signal collection strategies for the LII are presented. These results suggest that (a) signal integration during the laser pulse is essential for minimizing particle size and local temperature bias in the LII signal, (b) signal integration times subsequent to the laser pulse produce a size and local gas-temperature-dependent bias in the LII signal with long integration times more sensitive to these effects, and (c) long wavelength detection produces less of a size and local gas-temperature-dependent bias than short wavelength detection. (C) 1996 Optical Society of America RP VanderWal, RL (reprint author), NASA,LEWIS RES CTR,MS-110-3,21000 BROOKPARK RD,CLEVELAND,OH 44135, USA. NR 32 TC 72 Z9 72 U1 2 U2 6 PU OPTICAL SOC AMER PI WASHINGTON PA 2010 MASSACHUSETTS AVE NW, WASHINGTON, DC 20036 SN 0003-6935 J9 APPL OPTICS JI Appl. Optics PD NOV 20 PY 1996 VL 35 IS 33 BP 6548 EP 6559 DI 10.1364/AO.35.006548 PG 12 WC Optics SC Optics GA VT736 UT WOS:A1996VT73600013 PM 21127679 ER PT J AU Horack, JM Koshut, TM Mallozzi, RS AF Horack, JM Koshut, TM Mallozzi, RS TI The compatibility of Friedmann cosmological models with observed properties of gamma-ray bursts and a large hubble constant SO ASTROPHYSICAL JOURNAL LA English DT Article DE cosmology, theory; distance scale; gamma rays, bursts ID SPACE-TELESCOPE OBSERVATIONS; BRIGHTNESS DISTRIBUTION; STANDARD COSMOLOGY; CEPHEID VARIABLES; GLOBULAR-CLUSTERS; BATSE NUMBER; UNIVERSE; DISTANCE; DENSITY; NUCLEOSYNTHESIS AB The distance scale to cosmic gamma-ray bursts (GRBs) is still uncertain by many orders of magnitude; however, one viable scenario places GRBs at cosmological distances, thereby permitting them to be used as tracers of the cosmological expansion over a significant range of redshifts z. Also, several recent measurements of the Hubble constant H-0 appearing in the referred literature report values of 70-80 km s(-1) Mpc(-1). Although there is significant debate regarding these measurements, we proceed here under the assumption that they are evidence of a large value for H-0. This is done in order to investigate the additional constraints on cosmological models that can be obtained under this hypothesis when combined with the age of the universe and the brightness distribution of cosmological gamma-ray bursts. We show that the range of cosmological models that can be consistent with the GRB brightness distribution, a Hubble constant of 70-80 km s(-1) Mpc(-1), and a minimum age of the universe of 13-15 Gyr is constrained significantly, largely independent of a wide range of assumptions regarding the evolutionary nature of the burst population. Low-density, Lambda > 0 cosmological models with deceleration parameter in the range -1 < q(0) < 0 and density parameter sigma(0) in the range approximate to 0.10-0.25 (Omega(0) approximate to 0.2-0.5) are strongly favored. C1 NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,UNIV SPACE RES ASSOC,HUNTSVILLE,AL 35812. UNIV ALABAMA,DEPT PHYS,HUNTSVILLE,AL 35899. RP Horack, JM (reprint author), NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,SPACE SCI LAB,ES-84,HUNTSVILLE,AL 35812, USA. RI Horack, John/J-6670-2016 NR 38 TC 1 Z9 1 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637 SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD NOV 20 PY 1996 VL 472 IS 1 BP 25 EP 33 DI 10.1086/178038 PN 1 PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VU065 UT WOS:A1996VU06500003 ER PT J AU Feibelman, WA AF Feibelman, WA TI The IUE spectrum of the planetary nebula NGC 6905 SO ASTROPHYSICAL JOURNAL LA English DT Article DE planetary nebulae, individual (NGC 6905); ultraviolet, ISM ID NUCLEI; VELOCITIES; NGC-6905; RATIOS; STARS AB We present results from new IUE high-dispersion and archival low-dispersion spectra of NGC 6905. Ultraviolet emission lines of O VIII and possibly O VII are detected for the first time in NGC 6905. High-excitation lines of C IV, C V, O VI, [Mg V], [Ne III], [Ne IV], [Ne V], [Ar IV], and [Ar V] are also observed. Electron densities and terminal wind velocities are presented. Terminal wind velocities from O V and C IV lines are discussed. Variability (up to approximate to 25%) of the complex split He II lambda 1640 emission may be intrinsic or a function of position angle of the IUE camera entrance aperture. After reextracting the low-dispersion data, no significant changes between 1981 and 1991 were found for the strong O V lambda 1371, C IV lambda 1549, He II lambda 1640, and C III] lambda 1909 emissions. Many weak features not detected before have been identified in the archival low-resolution data. Some comparisons are made with UV spectra of Sand 3 and KPD 0005+6501. Preliminary results indicate O VIII emissions in IUE spectra of NGC 2371-2, NGC 2867, NGC 5189, and NGC 5315, suggesting that these planetary nebulae, together with NGC 6905, RX J2117+3412, and Sand 3, form a new ''O VIII sequence.'' The present work illustrates the need to reexamine older IUE spectra and demonstrates that today's improved data analysis is capable of improving greatly the results reported in earlier publications. RP Feibelman, WA (reprint author), NASA,GODDARD SPACE FLIGHT CTR,ASTRON & SOLAR PHYS LAB,CODE 681,GREENBELT,MD 20771, USA. NR 59 TC 8 Z9 8 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637 SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD NOV 20 PY 1996 VL 472 IS 1 BP 294 EP 307 DI 10.1086/178064 PN 1 PG 14 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VU065 UT WOS:A1996VU06500029 ER PT J AU Buckley, JH Akerlof, CW Biller, S CarterLewis, DA Catanese, M Cawley, MF Connaughton, V Fegan, DJ Finley, JP Gaidos, J Hillas, AM Kartje, JF Konigl, A Krennrich, F Lamb, RC Lessard, R Macomb, DJ Mattox, JR McEnery, JE Mohanty, G Quinn, J Rodgers, AJ Rose, HJ Schubnel, MS Sembroski, GL Smith, PS Weekes, TC Wilson, C Zweerink, J AF Buckley, JH Akerlof, CW Biller, S CarterLewis, DA Catanese, M Cawley, MF Connaughton, V Fegan, DJ Finley, JP Gaidos, J Hillas, AM Kartje, JF Konigl, A Krennrich, F Lamb, RC Lessard, R Macomb, DJ Mattox, JR McEnery, JE Mohanty, G Quinn, J Rodgers, AJ Rose, HJ Schubnel, MS Sembroski, GL Smith, PS Weekes, TC Wilson, C Zweerink, J TI Gamma-ray variability of the BL Lacertae object markarian 421 SO ASTROPHYSICAL JOURNAL LA English DT Article DE gamma rays, observations; BL Lacertae objects, individual (markarian 421) ID ACTIVE GALACTIC NUCLEI; X-RAY; RADIATION; EMISSION; BLAZARS; JETS AB We report on the gamma-ray variability of Mrk 421 at E(gamma) > 300 GeV during the 1995 season, and concentrate on the results of an intense multiwavelength observing campaign in the period April 20 to May 5, which included > 100 MeV gamma-ray, X-ray, extreme-ultraviolet, optical, and radio observations, some of which show evidence for correlated behavior. Rapid variations in the TeV gamma-ray light curve with doubling and decay times of less than or similar to 1 day require a compact emission region and significant Doppler boosting. The TeV data reveal that the gamma-ray emission is best characterized by a succession of rapid flares with a relatively low baseline level of steady emission. C1 UNIV MICHIGAN,RANDALL LAB PHYS,ANN ARBOR,MI 48109. UNIV LEEDS,DEPT PHYS,LEEDS LS2 9JT,W YORKSHIRE,ENGLAND. IOWA STATE UNIV,DEPT PHYS & ASTRON,AMES,IA 50011. ST PATRICKS COLL,DEPT PHYS,MAYNOOTH,KILDARE,IRELAND. NATL UNIV IRELAND UNIV COLL DUBLIN,DEPT PHYS,DUBLIN 4,IRELAND. PURDUE UNIV,DEPT PHYS,W LAFAYETTE,IN 47907. UNIV CHICAGO,DEPT ASTRON & ASTROPHYS,CHICAGO,IL 60637. NASA,GODDARD SPACE FLIGHT CTR,HIGH ENERGY ASTROPHYS LAB,GREENBELT,MD 20771. UNIV SPACE RES ASSOC,ASTROPHYS PROGRAM,GREENBELT,MD. UNIV MARYLAND,DEPT ASTRON,COLLEGE PK,MD 20742. UNIV ARIZONA,STEWARD OBSERV,TUCSON,AZ 85721. RP Buckley, JH (reprint author), HARVARD SMITHSONIAN CTR ASTROPHYS,FRED LAWRENCE WHIPPLE OBSERV,POB 97,AMADO,AZ 85645, USA. NR 44 TC 98 Z9 98 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637 SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD NOV 20 PY 1996 VL 472 IS 1 BP L9 EP L12 DI 10.1086/310352 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VU067 UT WOS:A1996VU06700003 ER PT J AU Lovell, JEJ Reynolds, JE Jauncey, DL Backus, PR McCulloch, PM Sinclair, MW Wilson, WE Tzioumis, AK King, EA Gough, RG Ellingsen, SP Phillips, CJ Preston, RA Jones, DL AF Lovell, JEJ Reynolds, JE Jauncey, DL Backus, PR McCulloch, PM Sinclair, MW Wilson, WE Tzioumis, AK King, EA Gough, RG Ellingsen, SP Phillips, CJ Preston, RA Jones, DL TI PKS 1830-211: A possible compound gravitational lens SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies, distances and redshifts; galaxies, individual (PKS 1830-211); gravitational lensing ID EINSTEIN RING; RADIO-SOURCE; PKS-1830-211; ABSORPTION; IMAGES AB Measurements of the properties of gravitational lenses have the power to tell us what sort of universe we live in. The brightest known radio Einstein ring/gravitational lens PKS 1830-211, while obscured by our Galaxy at optical wavelengths, has recently been shown to contain absorption at the millimeter waveband at a redshift of 0.89. We report the detection of a new absorption feature, most likely due to neutral hydrogen in a second redshift system at z = 0.19. Follow-up VLBI observations have spatially resolved the absorption and reveal it to cover the NE compact component and part of the lower surface brightness ring. This new information, together with existing evidence of the unusual VLBI radio structure and difficulties in modeling the lensing system, points to the existence of a second lensing galaxy along our line of sight and implies that PKS 1830-211 may be a compound gravitational lens. C1 CSIRO,AUSTRALIA TELESCOPE NATL FACIL,EPPING,NSW 2121,AUSTRALIA. SETI INST,MOUNTAIN VIEW,CA 94043. CALTECH,JET PROP LAB,PASADENA,CA 91109. RP Lovell, JEJ (reprint author), UNIV TASMANIA,DEPT PHYS,GPO BOX 252C,HOBART,TAS 7001,AUSTRALIA. RI King, Edward/A-1473-2012; Ellingsen, Simon/J-7754-2014 OI King, Edward/0000-0002-6898-2130; Ellingsen, Simon/0000-0002-1363-5457 NR 22 TC 45 Z9 45 U1 0 U2 1 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637 SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD NOV 20 PY 1996 VL 472 IS 1 BP L5 EP L7 DI 10.1086/310353 PN 2 PG 3 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VU067 UT WOS:A1996VU06700002 ER PT J AU Parker, JW Hill, JK Bohlin, RC OConnell, RW Neff, SG Roberts, MS Smith, AM Stecher, TP AF Parker, JW Hill, JK Bohlin, RC OConnell, RW Neff, SG Roberts, MS Smith, AM Stecher, TP TI Ultraviolet imaging telescope observations of OB stars in the N 11 region of the Large Magellanic Cloud SO ASTROPHYSICAL JOURNAL LA English DT Article DE Magellanic Clouds; open clusters and associations, individual, N 11; stars, early-type; ultraviolet, stars ID ASSOCIATIONS; N-11 AB We present an analysis of far-ultraviolet (FUV; 1300-1800 Angstrom) and optical (U, B, and V) data of the stellar and nebular content of the OB associations LH 9, 10, and 13 in the Large Magellanic Cloud region N 11. The FUV images from the Ultraviolet Imaging Telescope strongly select the hot O and B stars; over 1900 stars were detected in the FUV to a limiting magnitude of m(152) = 17 mag. The resulting FUV photometry combined with optical ground-based data indicate there are approximately 88 confirmed or candidate O stars in the LH 9, 10, and 13 fields alone (in an area of similar to 41 arcmin(2)) and possibly as many as 170-240 O-type stars within the entire 40' diameter field of view. C1 NASA,GODDARD SPACE FLIGHT CTR,HUGHES STX CORP,GREENBELT,MD 20771. SPACE TELESCOPE SCI INST,BALTIMORE,MD 21218. UNIV VIRGINIA,DEPT ASTRON,CHARLOTTESVILLE,VA 22903. NASA,GODDARD SPACE FLIGHT CTR,ASTRON & SOLAR PHYS LAB,GREENBELT,MD 20771. NATL RADIO ASTRON OBSERV,CHARLOTTESVILLE,VA 22903. NR 16 TC 8 Z9 8 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637 SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD NOV 20 PY 1996 VL 472 IS 1 BP L29 EP & DI 10.1086/310350 PN 2 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VU067 UT WOS:A1996VU06700008 ER PT J AU Herbert, CG Bass, RG Watson, KA Connell, JW AF Herbert, CG Bass, RG Watson, KA Connell, JW TI Preparation of poly(arylene ether pyrimidine)s by aromatic nucleophilic substitution reactions SO MACROMOLECULES LA English DT Article ID OXIDE-CONTAINING POLYIMIDES; POLYMER SYNTHESES; SILYLATED DIPHENOLS; POLYETHERS; PHENYLQUINOXALINES); HETEROCYCLE)S AB As part of a continuing effort to prepare novel thermally stable high-performance polymers, poly(arylene ether pyrimidine)s have been prepared with 4,6-bis(4-(trimethylsiloxy)phenyl)pyrimidine and a series of activated bis(aryl fluoride)s using a catalytic amount of cesium fluoride in diphenyl sulfone. These polymers exhibited good thermal stability in both air and helium atmospheres with 10% weight losses in the range 480-540 degrees C. Moderate to high inherent viscosities (eta(inh): 0.40-0.92 dL/g) were recorded, and clear pale yellow flexible fingernail creasable films were solution cast from these samples. A polymer in this series containing a phenylphosphine oxide linkage exhibited good thin film tensile properties and resistance to oxygen plasma. Model reactions with 4,6-bis(4-fluorophenyl)pyrimidine and p-cresol along with studies of this compound's F-19 NMR shift values indicated sufficient capacity of the pyrimidine ring to activate aryl fluorides toward polymerization with bis(phenol)s. The pyrimidine bis(aryl fluoride) monomer was used to prepare a series of polymers with selected bis(phenol)s by potassium carbonate-mediated aromatic nucleophilic substitution reactions. One example containing the fluorene moiety exhibited a high inherent viscosity (eta(inh): 0.80 dL/g); however, only brittle films could be cast from polymers prepared by this approach. C1 VIRGINIA COMMONWEALTH UNIV,DEPT CHEM,RICHMOND,VA 23284. NASA,LANGLEY RES CTR,DIV MAT,HAMPTON,VA 23681. NR 47 TC 24 Z9 24 U1 2 U2 4 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 SN 0024-9297 J9 MACROMOLECULES JI Macromolecules PD NOV 18 PY 1996 VL 29 IS 24 BP 7709 EP 7716 DI 10.1021/ma960741d PG 8 WC Polymer Science SC Polymer Science GA VU066 UT WOS:A1996VU06600011 ER PT J AU Kolb, EW Linde, A Riotto, A AF Kolb, EW Linde, A Riotto, A TI Grand-unified-theory baryogenesis after preheating SO PHYSICAL REVIEW LETTERS LA English DT Article ID INFLATIONARY UNIVERSE; BARYON ASYMMETRY; COSMOLOGY AB At the end of inflation the Universe is frozen in a near zero-entropy state with energy density in a coherent scalar field and must be ''defrosted'' to produce the observed entropy and baryon number. We propose that the baryon asymmetry is generated by the decay of supermassive grand-unified-theory (GUT) bosons produced nonthermally in a preheating phase after inflation. We show that baryogenesis is possible for an inflaton mass of order 10(13) GeV and a GUT Higgs boson mass of order 10(14) GeV, thus solving many drawbacks facing GUT baryogenesis in the old reheating scenario. C1 UNIV CHICAGO, ENRICO FERMI INST, DEPT ASTRON & ASTROPHYS, CHICAGO, IL 60637 USA. STANFORD UNIV, DEPT PHYS, STANFORD, CA 94305 USA. RP FERMILAB NATL ACCELERATOR LAB, NASA, FERMILAB ASTROPHYS CTR, BATAVIA, IL 60510 USA. NR 27 TC 115 Z9 115 U1 2 U2 3 PU AMER PHYSICAL SOC PI COLLEGE PK PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA SN 0031-9007 EI 1079-7114 J9 PHYS REV LETT JI Phys. Rev. Lett. PD NOV 18 PY 1996 VL 77 IS 21 BP 4290 EP 4293 DI 10.1103/PhysRevLett.77.4290 PG 4 WC Physics, Multidisciplinary SC Physics GA VT692 UT WOS:A1996VT69200003 ER PT J AU Baker, ES Connor, TH AF Baker, ES Connor, TH TI Monitoring occupational exposure to cancer chemotherapy drugs SO AMERICAN JOURNAL OF HEALTH-SYSTEM PHARMACY LA English DT Review DE antineoplastic agents; compliance; guidelines; health professions; metabolism; methodology; safety; tests, laboratory; toxicity, environmental; urine levels ID SISTER-CHROMATID EXCHANGES; HANDLING CYTOSTATIC DRUGS; CYTO-TOXIC DRUGS; PHARMACEUTICAL PLANT WORKERS; URINARY THIOETHER EXCRETION; SALMONELLA-MICROSOME TEST; ANTI-NEOPLASTIC DRUGS; ANTINEOPLASTIC DRUGS; CHROMOSOMAL-ABERRATIONS; PHARMACY PERSONNEL AB Reports of the health effects of handling cytotoxic drugs and compliance with guidelines for handling these agents are briefly reviewed, and studies using analytical and biological methods of detecting exposure are evaluated. There is little conclusive evidence of detrimental health effects from occupational exposure to cytotoxic drugs. Work practices have improved since the issuance of guidelines for handling these drugs, but compliance with the recommended practices is still inadequate. Of 64 reports published since 1979 on studies of workers' exposure to these drugs, 53 involved studies of changes in cellular or molecular endpoints (biological markers) and 12 described chemical analyses of drugs or their metabolites in urine (2 involved both, and 2 reported the same study). The primary biological markers used were urine mutagenicity, sister chromatid exchange, and chromosomal aberrations; other studies involved formation of micronuclei and measurements of urinary thioethers. The studies had small sample sizes, and the methods were qualitative, nonspecific, subject to many confounders, and possibly not sensitive enough to detect most occupational exposures. Since none of the currently available biological and analytical methods is sufficiently reliable or reproducible for routine monitoring of exposure in the workplace, further studies using these methods are not recommended; efforts should focus instead on widespread implementation of improved practices for handling cytotoxic drugs. C1 UNIV TEXAS,HLTH SCI CTR,SCH PUBL HLTH,HOUSTON,TX 77225. NASA,HOUSTON,TX. RI Connor, Thomas/B-7937-2011 NR 146 TC 52 Z9 55 U1 0 U2 3 PU AMER SOC HEALTH-SYSTEM PHARMACISTS PI BETHESDA PA 7272 WISCONSIN AVE, BETHESDA, MD 20814 SN 1079-2082 J9 AM J HEALTH-SYST PH JI Am. J. Health-Syst. Pharm. PD NOV 15 PY 1996 VL 53 IS 22 BP 2713 EP 2723 PG 11 WC Pharmacology & Pharmacy SC Pharmacology & Pharmacy GA VT727 UT WOS:A1996VT72700008 PM 8931813 ER PT J AU Trajmar, S Kanik, I AF Trajmar, S Kanik, I TI Electron impact excitation of C-60 adducts fluorescence from C60OH and C60H species SO CHEMICAL PHYSICS LETTERS LA English DT Article ID SPECTRA; C-70 AB An investigation concerning possible visible and UV photon emissions by gas phase C-60 (and C-70) samples under electron impact excitation was carried out in the 180-750 nm spectral region. No emission from the fullerene molecules was observed. However, radiation resembling OH (A(2) Pi --> X(2) Sigma) emission bands and H Balmer series appeared in this region. We assigned these emissions to simultaneous ionization and excitation and subsequent radiative decay of C60OH and C60H adducts (which are present in the fullerene samples). These results reveal an interesting new character of buckyball adducts. RP Trajmar, S (reprint author), CALTECH,JET PROP LAB,4800 OAK GROVE DR,PASADENA,CA 91109, USA. NR 14 TC 8 Z9 8 U1 0 U2 3 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 NOV 15 PY 1996 VL 262 IS 3-4 BP 241 EP 246 DI 10.1016/0009-2614(96)01090-1 PG 6 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA VT117 UT WOS:A1996VT11700011 ER PT J AU Azen, SP Qian, DJ Mack, WJ Sevanian, A Selzer, RH Liu, CR Liu, CH Hodis, HN AF Azen, SP Qian, DJ Mack, WJ Sevanian, A Selzer, RH Liu, CR Liu, CH Hodis, HN TI Effect of supplementary antioxidant vitamin intake on carotid arterial wall intima-media thickness in a controlled clinical trial of cholesterol lowering SO CIRCULATION LA English DT Article DE antioxidants; atherosclerosis; carotid; arteries ID COLESTIPOL-NIACIN THERAPY; CORONARY ATHEROSCLEROSIS; HEART-DISEASE; E CONSUMPTION; RISK; ULTRASOUND; PROGRESSION; MORTALITY; REDUCTION AB Background There is accumulating experimental, epidemiological, and clinical evidence of an association between antioxidant vitamin intake and reduced risk of coronary heart disease. Using data from the Cholesterol Lowering Atherosclerosis Study (CLAS), we explored the association of self-selected supplementary antioxidant vitamin intake on the rate of progression of early preintrusive atherosclerosis. Methods and Results CLAS was an arterial imaging trial in which nonsmoking 40- to 59-year-old men with previous coronary artery bypass graft surgery were randomized to colestipol/niacin plus diet or placebo plus diet. The rate of progression of early preintrusive atherosclerosis was determined in 146 subjects using high-resolution B-mode ultrasound quantification of the distal common carotid artery far wall intima-media thickness (IMT). From the nutritional supplement database, 22 subjects had an on-trial average supplementary vitamin E intake of greater than or equal to 100 IU per day (high users) and 29 subjects had an average on-trial supplementary vitamin C intake of greater than or equal to 250 mg per day (high users). Within the placebo group, less carotid IMT progression was found for high supplementary vitamin E users when compared with low vitamin E users (0.008 versus 0.023 mm/y, P=.03). No effect of vitamin E within the drug group was found. No effect of vitamin C within the drug or placebo group was found. Conclusions Supplementary vitamin E intake appears to be effective in reducing the progression of atherosclerosis in subjects not treated with lipid-lowering drugs while the process is still confined to the arterial wall (early preintrusive atherosclerosis). C1 UNIV SO CALIF,SCH MED,DIV CARDIOL,ATHEROSCLEROSIS RES UNIT,LOS ANGELES,CA 90033. UNIV SO CALIF,SCH MED,STAT CONSULTAT & RES CTR,LOS ANGELES,CA 90033. UNIV SO CALIF,SCH MED,DEPT PREVENT MED,LOS ANGELES,CA 90033. UNIV SO CALIF,SCH MED,DEPT MED,LOS ANGELES,CA 90033. UNIV SO CALIF,SCH MED,DEPT MOL PHARMACOL & TOXICOL,LOS ANGELES,CA 90033. CALTECH,JET PROP LAB,PASADENA,CA. FU NHLBI NIH HHS [R01-HL-45005, R01-HL-49885]; NIA NIH HHS [R01-AG-13860] NR 27 TC 107 Z9 110 U1 0 U2 1 PU AMER HEART ASSOC PI DALLAS PA 7272 GREENVILLE AVENUE, DALLAS, TX 75231-4596 SN 0009-7322 J9 CIRCULATION JI Circulation PD NOV 15 PY 1996 VL 94 IS 10 BP 2369 EP 2372 PG 4 WC Cardiac & Cardiovascular Systems; Peripheral Vascular Disease SC Cardiovascular System & Cardiology GA VT114 UT WOS:A1996VT11400006 PM 8921775 ER PT J AU Wu, DL Waters, JW AF Wu, DL Waters, JW TI Gravity-wave-scale temperature fluctuations seen by the UARS MLS SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID MIDDLE ATMOSPHERE; CLIMATOLOGY; VARIABILITY; WIND AB The Upper Atmosphere Research Satellite (UARS) Microwave Limb Sounder (MLS) has observed small- and meso-scale temperature fluctuations during a special limb-tracking operation. Analysis of late-December 1994 data shows that there exist significant radiance fluctuations with horizontal scales of 10's-100's km associated with upper tropospheric convection and the stratospheric polar vortex. Phase coherence and amplitude growth with height are observed, showing the presence of vertically propagating waves. Variance maps generated for the limb-tracking days further show that the MLS instrument can measure horizontal temperature variations at scales less than 100km in both limb-scanning and limb-tracking observation modes. RP Wu, DL (reprint author), CALTECH,JET PROP LAB,4800 OAK GROVE DR,MAIL STOP 183-701,PASADENA,CA 91109, USA. RI Wu, Dong/D-5375-2012 NR 14 TC 77 Z9 80 U1 1 U2 3 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD NOV 15 PY 1996 VL 23 IS 23 BP 3289 EP 3292 DI 10.1029/96GL02924 PG 4 WC Geosciences, Multidisciplinary SC Geology GA VU346 UT WOS:A1996VU34600002 ER PT J AU Gross, RS Marcus, SL Eubanks, TM Dickey, JO Keppenne, CL AF Gross, RS Marcus, SL Eubanks, TM Dickey, JO Keppenne, CL TI Detection of an ENSO signal in seasonal length-of-day variations SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID AXIAL ANGULAR-MOMENTUM; NINO SOUTHERN-OSCILLATION; OCEAN-ATMOSPHERE MODEL; EL-NINO; EARTHS ROTATION; SPACE GEODESY; CYCLE; BUDGET; CHAOS; FLUCTUATIONS AB Conservation of angular momentum dictates that as the wind-driven axial atmospheric angular momentum changes, so will the length-of-day (LOD). In particular, as the strength of the seasonal zonal winds change, so should the strength of the seasonal LOD signals. Here, observed changes in the strengths of the annual and semiannual LOD signals during 1963-1991 are analyzed and shown to be both significantly correlated (at the 99% significance level) with the Southern Oscillation Index (SOI), and to exhibit trends of comparable magnitude but opposite signs. This reported correlation between the SOI and changes in the amplitude of the seasonal LOD signals demonstrates a linkage between seasonal LOD (and hence seasonal zonal wind) variability and the El Nino / Southern Oscillation (ENSO) phenomenon. Furthermore, this study suggests that observed variations in the amplitudes of the seasonal LOD signals can be used to study changes in the strengths of the seasonal atmospheric zonal winds on interannual to decadal and longer time scales. C1 USN OBSERV,WASHINGTON,DC 20392. RP Gross, RS (reprint author), CALTECH,JET PROP LAB,4800 OAK GROVE DR,MAIL STOP 238-332,PASADENA,CA 91109, USA. OI Marcus, Steven/0000-0002-5763-6961; Eubanks, Thomas Marshall/0000-0001-9543-0414 NR 31 TC 24 Z9 25 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD NOV 15 PY 1996 VL 23 IS 23 BP 3373 EP 3376 DI 10.1029/96GL03260 PG 4 WC Geosciences, Multidisciplinary SC Geology GA VU346 UT WOS:A1996VU34600023 ER PT J AU Visscher, L Lee, TJ Dyall, KG AF Visscher, L Lee, TJ Dyall, KG TI Formulation and implementation of a relativistic unrestricted coupled-cluster method including noniterative connected triples SO JOURNAL OF CHEMICAL PHYSICS LA English DT Article ID CORRELATED MOLECULAR CALCULATIONS; GAUSSIAN-BASIS SETS; ELECTRON CORRELATION; PERTURBATION-THEORY; QUANTUM-CHEMISTRY; DIFFERENT FORMS; SHELL; ATOMS; HAMILTONIANS; ORBITALS AB The formalism for a relativistic open-shell CCSD(T) method is presented and implemented in a computer program, RELCCSD. The code can be used for calculations with 2- or 4-component relativistic reference wave functions and allows a full inclusion of the spin-orbit coupling. The code is interfaced to the MOLFDIR program system, We illustrate its use with nb initio calculations of the fine structure splittings of Cl, FO, ClO, O-2(+), and O-2(-). The triples correction is found to make a large contribution to the Cl atom splitting, which is within 23 cm(-1), of the experimental value. The molecular results are within 4 cm(-1) of the experimental values where these are available, The value for FO is predicted to be -195+/-4 cm(-1), in good agreement with experiment. (C) 1996 American Institute of Physics. C1 UNIV GRONINGEN, PHYS CHEM LAB, NL-9747 AG GRONINGEN, NETHERLANDS. UNIV GRONINGEN, CTR MAT SCI, NL-9747 AG GRONINGEN, NETHERLANDS. NASA, AMES RES CTR, MOFFETT FIELD, CA 94035 USA. NASA, AMES RES CTR, THERMOSCI INST, MOFFETT FIELD, CA 94035 USA. RI Visscher, Lucas/A-3523-2010; Lee, Timothy/K-2838-2012 OI Visscher, Lucas/0000-0002-7748-6243; NR 48 TC 143 Z9 143 U1 1 U2 10 PU AMER INST PHYSICS PI MELVILLE PA CIRCULATION & FULFILLMENT DIV, 2 HUNTINGTON QUADRANGLE, STE 1 N O 1, MELVILLE, NY 11747-4501 USA SN 0021-9606 J9 J CHEM PHYS JI J. Chem. Phys. PD NOV 15 PY 1996 VL 105 IS 19 BP 8769 EP 8776 DI 10.1063/1.472655 PG 8 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA VT102 UT WOS:A1996VT10200029 ER PT J AU Graber, HC Thompson, DR Carande, RE AF Graber, HC Thompson, DR Carande, RE TI Ocean surface features and currents measured with synthetic aperture radar interferometry and HF radar SO JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS LA English DT Article ID SPIN-OFF EDDIES; PREDICTIONS; FLORIDA; MODEL AB This paper describes the results of the first quantitative comparison between high-resolution ocean surface current fields extracted from interferometric synthetic aperture radar (INSAR) measurements and those from an high-frequency (HF) ocean surface current radar (OSCR) system. Data from each of these radar systems along with supporting measurements from shipboard and buoy-mounted sensors were collected during the High-Resolution Remote Sensing Experiment (High-Res) on June 20, 1993, on the continental shelf off the coast of Cape Hatteras, North Carolina. Both components of the surface current were obtained from the INSAR system at roughly 10-m resolution from two orthogonal flight legs over the region separated in time by about 30 min. The OSCR system measured two-dimensional surface current vectors at about 1-km resolution over this same region, while the USNS Bartlett was collecting hydrographic samples and near-surface current measurements. Two-dimensional wave spectra as well as meteorological and additional current measurements were collected at two buoys within the experimental area. We discuss in the paper two techniques for eliminating the effect of surface wave motion on the INSAR current estimates. One method relies on some knowledge of the local wind and wave field and the use of a microwave scattering model. The other method makes use of a few in situ current measurements spaced at different range locations across the INSAR image. Using either of these techniques, we find that the agreement between the INSAR and OSCR current estimates is generally very good. Furthermore, the INSAR current and magnitude imagery show the presence of undulating surface features where abrupt changes in the current speed and direction occurred. The ship surveys indicate that these features were caused by the collision of water masses of different density. We show for the first time in this paper a high-resolution, area-extensive vector surface current map derived from the INSAR of the two-dimensional flow in the vicinity of these features. Our results demonstrate convincingly that high-resolution oceanic surface current vectors can be derived from INSAR current measurements and that these measurements may be very beneficial for detailed studies of the dynamics of small-scale surface features in regions of strong current divergences or shears. C1 JOHNS HOPKINS UNIV,APPL PHYS LAB,LAUREL,MD. CALTECH,JET PROP LAB,PASADENA,CA. RP Graber, HC (reprint author), UNIV MIAMI,ROSENSTIEL SCH MARINE & ATMOSPHER SCI,4600 RICKENBACKER CAUSEWAY,MIAMI,FL 33149, USA. NR 32 TC 63 Z9 65 U1 1 U2 6 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 SN 0148-0227 J9 J GEOPHYS RES-OCEANS JI J. Geophys. Res.-Oceans PD NOV 15 PY 1996 VL 101 IS C11 BP 25813 EP 25832 DI 10.1029/96JC02241 PG 20 WC Oceanography SC Oceanography GA VT419 UT WOS:A1996VT41900016 ER PT J AU Wolfenden, A Oliver, KA Singh, M AF Wolfenden, A Oliver, KA Singh, M TI Measurements of elastic and anelastic properties of reaction-formed silicon carbide ceramics SO JOURNAL OF MATERIALS SCIENCE LA English DT Article ID MELT INFILTRATION; ALLOYS AB The piezoelectric ultrasonic composite oscillator technique (PUCOT) was used to measure dynamic Young's modulus, damping, strain amplitude, and the strain-amplitude dependence of damping on three reaction-formed silicon carbide (RFSC) specimens. The data were compared with results found on NC 203 SiC. The temperatures used to conduct the tests ranged from 595-1049 degrees C, and this information complemented data collected earlier. The main results are as follows: the modulus for RFSC specimens decreases with increasing temperature over a range of approximately 350-260 GPa from room temperature to 1049 degrees C, the modulus for NC203 ranges from 450-415 GPa over the same temperature range, and damping of RFSCs is independent of strain amplitude and has little temperature dependence. C1 NASA,LEWIS RES CTR,NYMA INC,CLEVELAND,OH 44135. RP Wolfenden, A (reprint author), TEXAS A&M UNIV,DEPT MECH ENGN,COLLEGE STN,TX 77843, USA. NR 13 TC 6 Z9 7 U1 1 U2 1 PU CHAPMAN HALL LTD PI LONDON PA 2-6 BOUNDARY ROW, LONDON, ENGLAND SE1 8HN SN 0022-2461 J9 J MATER SCI JI J. Mater. Sci. PD NOV 15 PY 1996 VL 31 IS 22 BP 6073 EP 6076 DI 10.1007/BF01152161 PG 4 WC Materials Science, Multidisciplinary SC Materials Science GA VU993 UT WOS:A1996VU99300031 ER PT J AU Choi, SR Salem, JA AF Choi, SR Salem, JA TI Preloading technique in dynamic fatigue testing of ceramics: Effect of preloading on strength variation SO JOURNAL OF MATERIALS SCIENCE LETTERS LA English DT Article C1 NASA,LEWIS RES CTR,CLEVELAND,OH 44135. RP Choi, SR (reprint author), CLEVELAND STATE UNIV,CLEVELAND,OH 44115, USA. NR 5 TC 1 Z9 1 U1 0 U2 0 PU CHAPMAN HALL LTD PI LONDON PA 2-6 BOUNDARY ROW, LONDON, ENGLAND SE1 8HN SN 0261-8028 J9 J MATER SCI LETT JI J. Mater. Sci. Lett. PD NOV 15 PY 1996 VL 15 IS 22 BP 1963 EP 1965 DI 10.1007/BF00274350 PG 3 WC Materials Science, Multidisciplinary SC Materials Science GA VU992 UT WOS:A1996VU99200013 ER PT J AU Stevens, IR Corcoran, MF Willis, AJ Skinner, SL Pollock, AMT Nagase, F Koyama, K AF Stevens, IR Corcoran, MF Willis, AJ Skinner, SL Pollock, AMT Nagase, F Koyama, K TI ASCA observations of gamma(2) Velorum (WC8+O9I): The variable X-ray spectrum of colliding winds SO MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY LA English DT Article DE binaries, general; stars, early-type; stars, individual, gamma(2) Velorum; stars, mass-loss; stars, Wolf-Rayet; X-rays, stars ID STELLAR WINDS; BINARY-SYSTEMS; MASS-LOSS; EVOLUTIONARY SCENARIO; OB STARS; EMISSION; ABUNDANCES; V444-CYGNI; MODEL AB We present an analysis of two observations of the nearby Wolf-Rayet (WR) + O-star binary system y(2) Velorum with the Advanced Satellite for Cosmology and Astrophysics (ASCA). These observations were taken at orbital phases phi = 0.4 and 0.5, when the O star is close to being in front of the WR star. At phase phi = 0.5, y(2) Vel is approximately four times more luminous in X-rays than it is at phi = 0.4. We fit the X-ray spectra using simple combinations of absorbed Raymond-Smith emission models. We find evidence of a cool (kT similar to 0.3 keV) and a hot (kT similar to 1.3 keV) component in each spectrum. The hotter component suffers from variable absorption which suggests that it originates in a localized region between the two stars. Between phi = 0.4 and 0.5 the absorbing column for this hotter component drops by a factor of 3 which accounts for most of the corresponding increase in flux. These observations are interpreted in terms of a colliding-wind model. The collision between the winds from the O star and the WR star generates a region of hot X-ray-emitting gas. When the WR star is in front, the dense WR wind effectively absorbs all the X-ray flux from the wind collision. However, when the O star is in front the more diffuse wind of the O star allows substantially more flux from the wind collision to escape. Our ASCA data confirm the colliding-wind origin for the hard X-ray emission from y(2) Vel, first identified from ROSAT data by Willis, Schild & Stevens. At phi = 0.5 the emergent luminosity is L(x) similar to 3.9 x 10(32) erg s(-1). We also use hydrodynamic models of colliding winds to calculate synthetic X-ray spectra for y(2) Vel, which we then fit to the ASCA spectra. This allows us to determine fundamental stellar wind parameters for both stellar components from the X-ray spectra. In particular, we determine a mass loss for the WC8 star of similar to 3 x 10(-5) M. yr(-1), a value 3 times lower than that determined by radio observations. The consequences of this are discussed. We consider that we are definitely seeing colliding-wind emission and also show the great potential for X-ray spectroscopy in determining fundamental wind parameters of WR (and other hot luminous) stars. C1 NASA, GODDARD SPACE FLIGHT CTR, LHEA, USRA, GREENBELT, MD 20771 USA. UNIV LONDON UNIV COLL, DEPT PHYS & ASTRON, LONDON WC1E 6BT, ENGLAND. UNIV COLORADO, JOINT INST LAB ASTROPHYS, BOULDER, CO 80309 USA. COMP & SCI CO LTD, SHEFFIELD S10 3GS, S YORKSHIRE, ENGLAND. INST SPACE & ASTRONAUT SCI, SAGAMIHARA, KANAGAWA 229, JAPAN. KYOTO UNIV, DEPT PHYS, SAKYO KU, KYOTO 60601, JAPAN. RP UNIV BIRMINGHAM, SCH PHYS & SPACE RES, BIRMINGHAM B15 2TT, W MIDLANDS, ENGLAND. NR 50 TC 63 Z9 63 U1 0 U2 0 PU OXFORD UNIV PRESS PI OXFORD PA GREAT CLARENDON ST, OXFORD OX2 6DP, ENGLAND SN 0035-8711 EI 1365-2966 J9 MON NOT R ASTRON SOC JI Mon. Not. Roy. Astron. Soc. PD NOV 15 PY 1996 VL 283 IS 2 BP 589 EP 605 PG 17 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VT962 UT WOS:A1996VT96200020 ER PT J AU Barthel, PD Arnaud, KA AF Barthel, PD Arnaud, KA TI Anomalous radio-loudness of Cygnus A and other powerful radio galaxies SO MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY LA English DT Article DE galaxies, active; intergalactic medium; infrared, galaxies; radio continuum, galaxies ID X-RAY OBSERVATIONS; LINE-EMITTING GAS; VLA OBSERVATIONS; FRII RADIOGALAXIES; COMPLETE SAMPLE; COOLING FLOW; 3C 295; CLUSTERS; REDSHIFT; QUASARS AB The nearby, extremely powerful radio galaxy Cygnus A stands out as having an atypically low far-infrared/radio luminosity ratio. It is demonstrated that in objects displaying such a low ratio the radio-loudness is anomalously high, which fact is connected to these objects inhabiting dense X-ray haloes. The enhanced radio emission is most likely due to strong radiation losses in the dense environment, It must be concluded that radio luminosity is not a good measure of AGN power. C1 NASA,GODDARD SPACE FLIGHT CTR,HIGH ENERGY ASTROPHYS LAB,GREENBELT,MD 20771. UNIV MARYLAND,DEPT ASTRON,COLLEGE PK,MD 20742. RP Barthel, PD (reprint author), KAPTEYN ASTRON INST,POB 800,NL-9700 AV GRONINGEN,NETHERLANDS. NR 46 TC 70 Z9 70 U1 0 U2 0 PU BLACKWELL SCIENCE LTD PI OXFORD PA OSNEY MEAD, OXFORD, OXON, ENGLAND OX2 0EL SN 0035-8711 J9 MON NOT R ASTRON SOC JI Mon. Not. Roy. Astron. Soc. PD NOV 15 PY 1996 VL 283 IS 2 BP L45 EP L49 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VT962 UT WOS:A1996VT96200004 ER PT J AU Dvali, G Riotto, A AF Dvali, G Riotto, A TI Gauge-mediated curvature of the flat directions during preheating SO PHYSICS LETTERS B LA English DT Article ID PARTICLE-PRODUCTION; SUPERSYMMETRIC TECHNICOLOR; COSMOLOGICAL PROBLEMS; ENTROPY CRISIS; INFLATION; BREAKING; UNIVERSE; BARYOGENESIS; SUPERGRAVITY; MODELS AB Usually one expects the inflaton field to be coupled to some gauge-charged particles allowing for its decay during reheating. Such particles then play the role of messengers for the gauge-mediated supersymmetry breaking during and (shortly) after the inflation and radiatively induce soft masses to all other D-flat directions. We show that during the preheating stage this gauge-mediated soft masses are typically much greater than the Hubble parameter during inflation. The dramatic role is played by the supersymmetry (SUSY) breaking due to the parametric resonance effect, which ensures that the inflaton predominantly decays into the bosons and not the fermions. The difference in the Fermi-Bose occupation numbers results in the large gauge-mediated soft masses, which determine the post-inflationary evolution of the flat directions, suggesting that non-thermal phase transitions mediated by gauge messengers may play a crucial role in the Affleck-Dine mechanism for the generation of the baryon asymmetry. C1 FERMILAB NATL ACCELERATOR LAB,NASA,FERMILAB ASTROPHYS CTR,BATAVIA,IL 60510. RP Dvali, G (reprint author), CERN,DIV THEORY,CH-1211 GENEVA,SWITZERLAND. NR 45 TC 7 Z9 7 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 NOV 14 PY 1996 VL 388 IS 2 BP 247 EP 252 DI 10.1016/S0370-2693(96)01139-2 PG 6 WC Astronomy & Astrophysics; Physics, Nuclear; Physics, Particles & Fields SC Astronomy & Astrophysics; Physics GA VU294 UT WOS:A1996VU29400006 ER PT J AU Chipot, C Jaffe, R Maigret, B Pearlman, DA Kollman, PA AF Chipot, C Jaffe, R Maigret, B Pearlman, DA Kollman, PA TI Benzene dimer: A good model for pi-pi interactions in proteins? A comparison between the benzene and the toluene dimers in the cas phase and in an aqueous solution SO JOURNAL OF THE AMERICAN CHEMICAL SOCIETY LA English DT Article ID AROMATIC AROMATIC INTERACTIONS; MOLECULAR-DYNAMICS; FREE-ENERGY; NUCLEIC-ACIDS; FORCE-FIELD; ABINITIO CALCULATION; CHARGE-TRANSFER; LIQUID WATER; SIMULATION; BINDING AB We have investigated the relative orientational preference of two benzene and two toluene molecules in a vacuum and in water, by means of free energy calculations. The gas-phase simulations reveal that, whereas the T-shaped benzene dimer is 0.78 kcal/mol lower in free energy than its stacked homologue, the sandwich arrangement of the toluene dimer is preferred over the T-shaped structure by 0.18 kcal/mol. MP2/TZP ab initio binding energies, evaluated for both dimers, were found to be consistent with the molecular mechanical estimates, hence suggesting that the van der Waals and the electrostatic contributions to the macromolecular force field employed herein are well balanced. We further note that our results agree quite nicely with the experimental binding energies of Neusser and Krause, obtained from breakdown measurements. The tendency witnessed in the gas phase is magnified in an aqueous solution, with differences in free energy between the T-shaped and the sandwich arrangements of the benzene and the toluene dimers equal to -1.47 and 1.12 kcal/mol, respectively. The calculated association constants and osmotic second virial coefficients also correlate reasonably well with the experimental data of Tucker and Christian. The conflict between the orientational preferences of the benzene and the toluene dimers is suggestive that trends in ''pi-pi'' interactions in proteins should be rationalized by other factors than simple electrostatic/dispersion considerations. The analysis of Phe-Phe pairs in protein crystallographic structures sheds light on the influence of both sterical hindrances and ancillary interactions between the aromatic moities and neighboring functional groups on the orientational preference of the phenyl rings. C1 NASA,AMES RES CTR,COMPUTAT CHEM BRANCH,MOFFETT FIELD,CA 94035. UNIV HENRI POINCARE NANCY 1,URA CNRS 510,CHIM THEOR LAB,F-54506 VANDOEUVRE NANCY,FRANCE. VERTEX PHARMACEUT INC,CAMBRIDGE,MA 02139. RP Chipot, C (reprint author), UNIV CALIF SAN FRANCISCO,DEPT PHARMACEUT CHEM,SAN FRANCISCO,CA 94143, USA. NR 72 TC 274 Z9 276 U1 2 U2 32 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 SN 0002-7863 J9 J AM CHEM SOC JI J. Am. Chem. Soc. PD NOV 13 PY 1996 VL 118 IS 45 BP 11217 EP 11224 DI 10.1021/ja961379l PG 8 WC Chemistry, Multidisciplinary SC Chemistry GA VT466 UT WOS:A1996VT46600029 ER PT J AU Smith, DM Leventhal, M Cavallo, R Gehrels, N Tueller, J Fishman, G AF Smith, DM Leventhal, M Cavallo, R Gehrels, N Tueller, J Fishman, G TI All-sky search for transient sources near 0.5 MeV with the burst and transient source experiment (BATSE) SO ASTROPHYSICAL JOURNAL LA English DT Article DE Galaxy, center; gamma rays, bursts; gamma rays, observations line, identification; surveys ID GALACTIC-CENTER REGION; BACKSCATTERED ANNIHILATION RADIATION; GAMMA-RAY TRANSIENTS; NOVA-MUSCAE 1991; 511 KEV LINE; BLACK-HOLE; OSSE OBSERVATIONS; SMM OBSERVATIONS; MOLECULAR CLOUD; CRAB-NEBULA AB We present a search for bright, transient emission lines near 0.5 MeV in nearly two years of data from the Burst and Transient Source Experiment (BATSE) on the Compton Gamma-Ray Observatory. Such features have been reported from black hole candidates Nova Muscae and 1E 1740.7-2942 and from the Crab, lasting for approximate to 1 day. Our survey covers the whole sky and is sensitive to events with durations from 0.5-3.0 day. No transients are observed, and the systematic errors are low enough that the upper limits are significantly below the fluxes of the two most significant events previously reported. C1 NASA, GODDARD SPACE FLIGHT CTR, GREENBELT, MD 20771 USA. NASA, GEORGE C MARSHALL SPACE FLIGHT CTR, HUNTSVILLE, AL 35812 USA. RP Smith, DM (reprint author), UNIV MARYLAND, DEPT ASTRON, COLLEGE PK, MD 20742 USA. RI Gehrels, Neil/D-2971-2012; Tueller, Jack/D-5334-2012 NR 41 TC 15 Z9 15 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 NOV 10 PY 1996 VL 471 IS 2 BP 783 EP 795 DI 10.1086/178006 PN 1 PG 13 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VR611 UT WOS:A1996VR61100019 ER PT J AU Padgett, DL AF Padgett, DL TI Atmospheric parameters and iron abundances of low-mass pre-main-sequence stars in nearby star formation regions SO ASTROPHYSICAL JOURNAL LA English DT Review DE ISM, abundances; stars, abundances; stars, pre-main-sequence; turbulence ID T-TAURI STARS; X-RAY SOURCES; HIGH-RESOLUTION SPECTROSCOPY; RHO-OPHIUCHI CLOUD; CHEMICAL EVOLUTION; LITHIUM ABUNDANCES; DARK CLOUD; OPEN CLUSTERS; B-STARS; SOLAR NEIGHBORHOOD AB High-resolution echelle spectra have been obtained for low-mass pre-main-sequence stars in the Taurus-Auriga, Orion, Chamaeleon, Ophiuchus, and other star formation regions. Using temperature-sensitive individual metallic line ratios, new effective temperatures are determined for a sample of 30 G and K pre-main-sequence stars in nearby star-forming clouds to an accuracy of +/-200 K or better in most cases. Comparison of these values with previous spectral classifications using low-resolution spectra reveals occasional large discrepancies in spectral type. Microturbulences derived for 23 ''weak line'' T Tauri stars range as high as 3.1 +/- 0.4 km s(-1). The mean microturbulent velocity of the sample is 1.6 +/- 0.6 km s(-1). Using these new effective temperatures and microturbulences, iron abundances have been determined for 30 pre-main-sequence stars in several northern and southern sky star-formation regions. By determining the mean [Fe/H] for at least five stars in each cloud, bulk metallicities have been derived for the Taurus-Auriga, Orion, Chamaeleon, and Ophiuchus molecular clouds. [Fe/H] is approximately solar in all the regions surveyed. RP Padgett, DL (reprint author), CALTECH,JET PROP LAB,CTR INFRARED PROC & ANAL,4800 OAK GROVE DR,MC 100-22,PASADENA,CA 91109, USA. NR 110 TC 65 Z9 66 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637 SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD NOV 10 PY 1996 VL 471 IS 2 BP 847 EP 866 DI 10.1086/178012 PN 1 PG 20 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VR611 UT WOS:A1996VR61100025 ER PT J AU Linnell, AP Hubeny, I AF Linnell, AP Hubeny, I TI A spectrum synthesis and light synthesis program for binary stars with optically thick accretion disks SO ASTROPHYSICAL JOURNAL LA English DT Article DE accretion, accretion disks; binaries, eclipsing; techniques, spectroscopic ID CATACLYSMIC VARIABLES; BETA LYRAE; MODEL; IMAGES AB We have completed a new program that calculates both synthetic spectra and synthetic light curves for binary systems that contain a standard model optically thick accretion disk. Our initial model is physically and geometrically simple. It is capable of substantial elaboration. By basing both synthetic light curves and synthetic spectra on a single self-consistent model, we anticipate useful tests of systems for which both types of data are available. Alternatively, explicit simulations now become possible for systems for which only light curves or only spectra are available. C1 NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. RP Linnell, AP (reprint author), MICHIGAN STATE UNIV,DEPT PHYS & ASTRON,E LANSING,MI 48824, USA. NR 43 TC 47 Z9 47 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637 SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD NOV 10 PY 1996 VL 471 IS 2 BP 958 EP 966 DI 10.1086/178022 PN 1 PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VR611 UT WOS:A1996VR61100035 ER PT J AU DSilva, S Duvall, TL Jefferies, SM Harvey, JW AF DSilva, S Duvall, TL Jefferies, SM Harvey, JW TI Helioseismic tomography SO ASTROPHYSICAL JOURNAL LA English DT Article DE Sun, interior; Sun, oscillations ID TIME-DISTANCE HELIOSEISMOLOGY; DYNAMICAL OSCILLATION; MAGNETIC-FIELDS; CONVECTIVE ZONE; PROPULSION; STAR AB ''Helioseismic tomography'' is a method using observations to construct slices of the Sun's internal structure. It is based on a reduction of observations to time-distance surfaces and hypersurfaces. We present a procedure for measuring time-distance surfaces and hypersurfaces, and thereby a method of studying localized inhomogeneities in the interior of the Sun, such as abnormalities in the sound speed (e.g., a thermal shadow, Parker 1987a), or local subsurface flows, or magnetic fields. We also present a simulation of measuring time-distance surfaces and illustrate how to measure the size of an inhomogeneity, its location in depth, and the deviation of its sound speed compared to its local surroundings. C1 NASA,GODDARD SPACE FLIGHT CTR,ASTRON & SOLAR PHYS LAB,GREENBELT,MD 20771. UNIV DELAWARE,BARTOL RES INST,NEWARK,DE 19716. RP DSilva, S (reprint author), NATL OPT ASTRON OBSERV,NATL SOLAR OBSERV,TUCSON,AZ 85726, USA. RI Duvall, Thomas/C-9998-2012 NR 11 TC 21 Z9 21 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637 SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD NOV 10 PY 1996 VL 471 IS 2 BP 1030 EP 1043 DI 10.1086/178030 PN 1 PG 14 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VR611 UT WOS:A1996VR61100043 ER PT J AU Pearson, JC Muller, HSP AF Pearson, JC Muller, HSP TI The submillimeter wave spectrum of isotopic methyl cyanide SO ASTROPHYSICAL JOURNAL LA English DT Article DE ISM, molecules; line identification; methods, laboratory; molecular processes; radio lines, ISM ID ROTATIONAL SPECTRUM; MICROWAVE-SPECTRA; CH3CN; ORION; GHZ; SPECTROSCOPY; CONSTANTS; CORES; HOT AB The laboratory submillimeter wave rotational spectrum of the (CH3CN)-C-13, (CH3CN)-C-13, and (CH3CN)-N-15 isotopomers of methyl cyanide has been observed in natural abundance in the 294 to 607 GHz region. The maximum J and K values are 34 and 14, respectively. Fifteen additional CH3CN transitions up to K = 21 were also measured. The transitions of all four species are fitted to a symmetric top Hamiltonian, and the rotation and distortion constants are determined. The N-14 quadrupole and spin rotation coupling constants are also calculated and presented. Suggested values for many other parameters, which could not be directly determined from the isotope spectra, are calculated from the normal species values and isotope relationships. The determined and calculated constants should predict the spectrum of the three isotopomers to well over 1 THz accurately enough for astronomical assignments. RP Pearson, JC (reprint author), CALTECH,JET PROP LAB,4800 OAK GROVE DR,MAIL STOP 183-301,PASADENA,CA 91109, USA. OI Mueller, Holger/0000-0002-0183-8927 NR 26 TC 18 Z9 18 U1 1 U2 2 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637 SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD NOV 10 PY 1996 VL 471 IS 2 BP 1067 EP 1072 DI 10.1086/178034 PN 1 PG 6 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VR611 UT WOS:A1996VR61100047 ER PT J AU Charpinet, S Fontaine, G Brassard, P Dorman, B AF Charpinet, S Fontaine, G Brassard, P Dorman, B TI The potential of asteroseismology for hot, subdwarf B stars: A new class of pulsating stars? SO ASTROPHYSICAL JOURNAL LA English DT Article DE stars, interiors; stars, oscillations; subdwarfs ID DA WHITE-DWARFS; ZZ-CETI STARS; THERMAL-CONDUCTIVITIES; HORIZONTAL-BRANCH; RADIATIVE FORCES; DENSE MATTER; OB-STARS; ATMOSPHERES; MODELS; ABUNDANCES AB We present key sample results of a systematic survey of the pulsation properties of models of hot B subdwarfs. We use equilibrium structures taken from detailed evolutionary sequences of solar metallicity (Z = 0.02) supplemented by grids of static envelope models of various metallicities (Z = 0.02, 0.04, 0.06, 0.08, and 0.10). We consider all pulsation modes with l = 0, 1, 2, and 3 in the 80-1500 s period window, the interval currently most suitable for fast photometric detection techniques. We establish that significant driving is often present in hot B subdwarfs and is due to an opacity bump associated with heavy-element ionization. We find that models with Z greater than or equal to 0.04 show low radial order unstable modes; both radial and nonradial (p, f, and g) pulsations are excited. The unstable models have T-eff less than or similar to 30,000 K and log g less than or similar to 5.7, depending somewhat on the metallicity. We emphasize that metal enrichment need only occur locally in the driving region. On this basis, combined with the accepted view that local enrichments and depletions of metals are commonplace in the envelopes of hot B subdwarfs, we predict that some of these stars should show luminosity variations resulting from pulsational instabilities. C1 NASA,GODDARD SPACE FLIGHT CTR,ASTRON & SOLAR PHYS LAB,GREENBELT,MD 20771. RP Charpinet, S (reprint author), UNIV MONTREAL,DEPT PHYS,CP 6128,SUCC CTR VILLE,MONTREAL,PQ H3C 3J7,CANADA. OI Charpinet, Stephane/0000-0002-6018-6180 NR 37 TC 98 Z9 98 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637 SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD NOV 10 PY 1996 VL 471 IS 2 BP L103 EP L106 DI 10.1086/310335 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VR612 UT WOS:A1996VR61200008 ER PT J AU Langer, WD Castets, A Lefloch, B AF Langer, WD Castets, A Lefloch, B TI The IRAS 2 and IRAS 4 outflows and star formation in NGC 1333 SO ASTROPHYSICAL JOURNAL LA English DT Article DE ISM, individual (NGC 1333); ISM, jets and outflows; ISM, molecules; stars, formation ID NGC-1333 AB We report the first detection of the western bow shock component from IRAS 2 in NGC 1333 along with observations of previously detected shocks and outflow winds from this source and those from IRAS 4. We compare the shock and outflow distributions from these two young stellar objects (YSOs), and the locations of other YSOs, with the overall distribution of the dense molecular gas in the star-forming core using high spatial resolution observations of CS (J = 2 --> 1, 3 --> 2, and 5 --> 4) emission made with the Institut de Radio Astronomie Millimetrique 30 m antenna. These comparisons provide a new picture of the morphology and dynamics of the star-forming core of NGC 1333. The CS maps show (1) a large cavity with many YSOs just at the inner edge of the cavity, (2) a dense, compressed shell at 8 km s(-1); and (3) a gas layer at 7 km s(-1) probably located inside the cavity. We find that the IRAS 2 and IRAS 4 outflows impact different gas layers as indicated by the spatial association of the red- and blueshifted lobes, and that IRAS 2 is located near the front edge of the CS shell. The burst of star formation that has shaped NGC 1333 is occurring in the compressed shell traced by CS and now appears to be in a late evolutionary stage. C1 OBSERV GRENOBLE,ASTROPHYS LAB,F-38041 GRENOBLE 9,FRANCE. IRAM,E-18012 GRANADA,SPAIN. RP Langer, WD (reprint author), CALTECH,JET PROP LAB,4800 OAK GROVE DR,MS 169-506,PASADENA,CA 91109, USA. NR 9 TC 32 Z9 32 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637 SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD NOV 10 PY 1996 VL 471 IS 2 BP L111 EP & DI 10.1086/310337 PN 2 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VR612 UT WOS:A1996VR61200010 ER PT J AU Lauer, TR Tremaine, S Ajhar, EA Bender, R Dressler, A Faber, SM Gebhardt, K Grillmaier, CJ Kormendy, J Richstone, D AF Lauer, TR Tremaine, S Ajhar, EA Bender, R Dressler, A Faber, SM Gebhardt, K Grillmaier, CJ Kormendy, J Richstone, D TI Hubble Space Telescope observations of the double nucleus of NGC 4486B SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies, nuclei; galaxies, photometry; galaxies, structure ID M31 AB Hubble Space Telescope WFPC2 images show that the low-luminosity elliptical galaxy companion to M87, NGC 4486B, has a double nucleus that resembles the one discovered in M31. The NGC 4486B nucleus comprises two peaks separated by similar to 0.''15 or 12 pc. Neither peak is coincident with the galaxy photocenter, which falls between them. The nuclear morphology is independent of color; thus, the double structure is not likely to arise from dust absorption. It is also unlikely that the peaks are a binary stellar system (such as an ongoing merger of the nucleus of a less luminous system with the nucleus of NGC 4486B), since the decay timescale is short (<10(8) yr) and the present environment of NGC 4486B should inhibit mergers. We suggest that the nuclear morphology of NGC 4486B may be explained by the eccentric-disk model of Tremaine, which was originally advanced to account for the central structure of M31. This model requires that NGC 4486B contains a central massive dark object, which is suggested by the spectroscopic observations of Kormendy et al. The eccentric disk might be related to the symmetric disk seen at larger radii. C1 UNIV TORONTO,CANADIAN INST THEORET ASTROPHYS,CIAR,COSMOL PROGRAM,TORONTO,ON M5S 3H8,CANADA. UNIV STERNWARTE,D-81679 MUNICH,GERMANY. CARNEGIE INST WASHINGTON OBSERV,PASADENA,CA 91101. UNIV CALIF SANTA CRUZ,LICK OBSERV,BOARD STUDIES ASTRON & ASTROPHYS,SANTA CRUZ,CA 95064. UNIV MICHIGAN,DEPT ASTRON,ANN ARBOR,MI 48109. CALTECH,JET PROP LAB,PASADENA,CA 91109. UNIV HAWAII,INST ASTRON,HONOLULU,HI 96822. RP Lauer, TR (reprint author), NATL OPT ASTRON OBSERV,KITT PEAK NATL OBSERV,POB 26732,TUCSON,AZ 85726, USA. RI Tremaine, Scott/M-4281-2015 OI Tremaine, Scott/0000-0002-0278-7180 NR 13 TC 63 Z9 63 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637 SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD NOV 10 PY 1996 VL 471 IS 2 BP L79 EP & DI 10.1086/310344 PN 2 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VR612 UT WOS:A1996VR61200002 ER PT J AU Loewenstein, M Mushotzky, RF AF Loewenstein, M Mushotzky, RF TI The mass of Abell 1060 and AWM 7 from spatially resolved X-ray spectroscopy: Variations in baryon fraction SO ASTROPHYSICAL JOURNAL LA English DT Article DE cosmology, dark matter; galaxies, clusters, individual (AWM 7, Abell 1060) ID POOR CLUSTERS; COOLING FLOWS; HYDRA-I; GALAXIES AB Using X-ray temperature and surface brightness profiles of the hot intracluster medium (ICM) derived from ACA (Astro-D) and ROSAT observations, we place constraints on the dark matter (DM) and baryon fraction distributions in the poor clusters Abell 1060 (A1060) and AWM 7. Although their total mass distributions are similar, AWM 7 has twice the baryon fraction of A1060 in the best-fit models. The functional form of the DM distribution is ill determined; however, mass models where the baryon fractions in A1060 and AWM 7 significantly overlap are excluded. Such variations in baryon fraction are not predicted by standard models and imply that some mechanism in addition to gravity plays a major role in organizing matter on cluster scales. RP Loewenstein, M (reprint author), NASA, GODDARD SPACE FLIGHT CTR, HIGH ENERGY ASTROPHYS LAB, CODE 662, GREENBELT, MD 20771 USA. NR 30 TC 26 Z9 26 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 NOV 10 PY 1996 VL 471 IS 2 BP L83 EP L86 DI 10.1086/310342 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VR612 UT WOS:A1996VR61200003 ER PT J AU Naya, JE Barthelmy, SD Bartlett, LM Gehrels, N Leventhal, M Parsons, A Teegarden, BJ Tueller, J AF Naya, JE Barthelmy, SD Bartlett, LM Gehrels, N Leventhal, M Parsons, A Teegarden, BJ Tueller, J TI Detection of high-velocity Al-26 towards the Galactic Centre SO NATURE LA English DT Article ID GAMMA-RAY LINE; CENTER REGION; EMISSION; RADIATION; PLANE; MAP AB THEORY predicts(1) that radioactive Al-26 (which has a half-life of 0.72 Myr) is released into the interstellar medium by nova and supernova explosions, from the winds of massive stars in the Wolf-Rayet phase, and from less-massive giant stars in very late stages of the asymptotic giant branch phase. Observations of 1,809-keV gamma-ray emission line from Al-26 can therefore be used as a tracer of Galactic nucleosynthesis during the past million years(2,3). The irregularity of the emission in the plane of the Galaxy(4-7) suggests that the dominant sources are likely to be massive stars and supernovae; the other predicted sources are older, and therefore expected to be distributed more uniformly. Here we report the detection of the 1,809-keV emission line from the direction of the Galactic Centre, and we show that the line width is approximately three times that expected(8,9) from the effect of Doppler broadening due to Galactic rotation. The high velocities inferred from the line width favour an origin of the Al-26 in supernovae or Wolf-Rayet stars. Moreover, the fact that the Al-26 has maintained such high velocities is difficult to reconcile with our current understanding of the propagation of material in the interstellar medium. C1 UNIV SPACE RES ASSOC, SEABROOK, MD 20706 USA. UNIV MARYLAND, DEPT ASTRON, COLLEGE PK, MD 20742 USA. RP Naya, JE (reprint author), NASA, GODDARD SPACE FLIGHT CTR, GREENBELT, MD 20771 USA. RI Gehrels, Neil/D-2971-2012; Tueller, Jack/D-5334-2012; Barthelmy, Scott/D-2943-2012; Parsons, Ann/I-6604-2012 NR 26 TC 65 Z9 65 U1 0 U2 1 PU NATURE PUBLISHING GROUP PI LONDON PA MACMILLAN BUILDING, 4 CRINAN ST, LONDON N1 9XW, ENGLAND SN 0028-0836 J9 NATURE JI Nature PD NOV 7 PY 1996 VL 384 IS 6604 BP 44 EP 46 DI 10.1038/384044a0 PG 3 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA VR219 UT WOS:A1996VR21900047 ER PT J AU Casani, EK Alkalai, L AF Casani, EK Alkalai, L TI Success criteria and risk management for the new millennium program SO ACTA ASTRONAUTICA LA English DT Article AB The National Aeronautics and Space Administration (NASA) New Millennium Program (NMP) is a technology development and validation program that will Right-validate advanced, new technologies with space flight applications. NMP's purpose is twofold. First, it will develop technologies that will enable future spacecraft to be smaller, more capable and reliable, and to be launched more frequently. Second, it will validate the technologies in flight to reduce the risks to future science missions that fly these technologies for the first time. To measure the program's success, NMP has devised a set of criteria that stresses the relevance of technologies selected for flight validation to NASA's 21st-century science mission needs. Also, NMP has instituted a 'risk management' policy, where, through a combination of adequate resources and early risk assessment and risk mitigation plans for the technologies, the overall risk of the NMP flights can be rendered acceptable. (C) 1997 Published by Elsevier Science Ltd. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Casani, EK (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr,M-S 180-404, Pasadena, CA 91109 USA. NR 2 TC 0 Z9 0 U1 0 U2 0 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0094-5765 J9 ACTA ASTRONAUT JI Acta Astronaut. PD NOV-DEC PY 1996 VL 39 IS 9-12 BP 669 EP 675 DI 10.1016/S0094-5765(97)00048-9 PG 7 WC Engineering, Aerospace SC Engineering GA V2865 UT WOS:000168745900005 ER PT J AU Hayduk, RJ Scott, WS Walberg, GD Butts, JJ Starr, RD AF Hayduk, RJ Scott, WS Walberg, GD Butts, JJ Starr, RD TI NASA's Small Spacecraft Technology Initiative "Clark" spacecraft SO ACTA ASTRONAUTICA LA English DT Article AB The Small Satellite Technology Initiative (SSTI) is a National Aeronautics and Space Administration (NASA) program to demonstrate smaller, high technology satellites constructed rapidly and less expensively. Under SSTI, NASA funded the development of "Clark," a high technology demonstration satellite to provide 3-m resolution panchromatic and 15-m resolution multispectral images, as well as collect atmospheric constituent and cosmic x-ray data. The 690-lb. satellite, to be launched in early 1997, will be in a 476 km, circular, sun-synchronous polar orbit. This paper describes the program objectives, the technical characteristics of the sensors and satellite, image processing, archiving and distribution. Data archiving and distribution will be performed by NASA Stennis Space Center and by the EROS Data Center, Sioux Falls, South Dakota, USA. (C) 1997 Published by Elsevier Science Ltd. C1 NASA Headquarters, Washington, DC 20003 USA. RP Hayduk, RJ (reprint author), NASA Headquarters, 300 E St SW, Washington, DC 20003 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0094-5765 J9 ACTA ASTRONAUT JI Acta Astronaut. PD NOV-DEC PY 1996 VL 39 IS 9-12 BP 677 EP 686 DI 10.1016/S0094-5765(97)00049-0 PG 10 WC Engineering, Aerospace SC Engineering GA V2865 UT WOS:000168745900006 ER PT J AU Eisenman, A Liebe, CC AF Eisenman, A Liebe, CC TI Operation and performance of a second generation, solid state, star tracker, the ASC SO ACTA ASTRONAUTICA LA English DT Article AB The Advanced Stellar Compass (ASC) is a second generation star tracker, consisting of a CCD camera and its associated microcomputer. The ASC operates by matching the star images acquired by the camera with its internal star catalogs. An initial attitude acquisition (solving the lost in space problem) is performed, and successively, the attitude of the camera is calculated in celestial coordinates by averaging the position of a large number of star observations for each image. Key parameters of the ASC for the Orsted satellite and Astrid II satellite versions are: mass as low as 900 g, power consumption as low as 5.5 W, relative attitude angle errors less than 1.4 arcseconds in declination, and 13 arcseconds in roll, RMS, as measured at the Mauna Kea, HI observatories of the University of Hawaii in June 1996. (C) 1997 Published by Elsevier Science Ltd. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Eisenman, A (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 13 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 0094-5765 J9 ACTA ASTRONAUT JI Acta Astronaut. PD NOV-DEC PY 1996 VL 39 IS 9-12 BP 697 EP 705 DI 10.1016/S0094-5765(97)00051-9 PG 9 WC Engineering, Aerospace SC Engineering GA V2865 UT WOS:000168745900008 ER PT J AU Birnbaum, MM AF Birnbaum, MM TI Spacecraft attitude control using star field trackers SO ACTA ASTRONAUTICA LA English DT Article AB This paper describes a "maturing" class of attitude sensors used to determine spacecraft attitude with respect to the celestial sphere. During the past fifteen years, the design direction of attitude sensors has turned towards star field trackers and away from single-star trackers. The focus of this paper is on the description of the principles of operation and processes by which these star field trackers recognize and track a desired star field. (C) 1997 Published by Elsevier Science Ltd. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Birnbaum, MM (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 14 TC 17 Z9 18 U1 0 U2 2 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0094-5765 J9 ACTA ASTRONAUT JI Acta Astronaut. PD NOV-DEC PY 1996 VL 39 IS 9-12 BP 763 EP 773 DI 10.1016/S0094-5765(97)00060-X PG 11 WC Engineering, Aerospace SC Engineering GA V2865 UT WOS:000168745900017 ER PT J AU Alkalai, L AF Alkalai, L TI Advanced flight computing technologies for validation by NASA's New Millennium Program SO ACTA ASTRONAUTICA LA English DT Article AB The New Millennium Program (NMP) consists of a series of Deep-Space and Earth Orbiting missions that are technology-driven, in contrast to the more traditional science-driven space exploration missions of the past. These flights are designed to validate technologies that will enable a new era of low-cost highly miniaturized and highly capable spaceborne applications in the new millennium. In addition to the series of flight projects managed by separate flight teams, the NMP technology initiatives are managed by the following six focused technology programs: Microelectronics Systems, Autonomy, Telecommunications, Instrument Technologies and Architectures, In-Situ Instruments and Micro-electromechanical Systems, and Modular and Multifunctional Systems. Each technology program is managed as an Integrated Product Development Team (IPDT) of government, academic, and industry partners. In this paper, we will describe elements of the technology roadmap proposed by the NUT Microelectronics IPDT. Moreover, we will relate the proposed technology roadmap to existing NASA technology development programs, such as the Advanced Flight Computing (AFC) program, and the Remote Exploration and Experimentation (REE) program, which constitute part of the on-going NASA technology development pipeline. We will also describe the Microelectronics Systems technologies that have been accepted as part of the first New Millennium Deep-Space One spacecraft, which is an asteroid fly-by mission scheduled for launched in July 1998. (C) 1997 Published by Elsevier Science Ltd. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Alkalai, L (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 8 TC 2 Z9 2 U1 0 U2 1 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0094-5765 J9 ACTA ASTRONAUT JI Acta Astronaut. PD NOV-DEC PY 1996 VL 39 IS 9-12 BP 785 EP 797 DI 10.1016/S0094-5765(97)00062-3 PG 13 WC Engineering, Aerospace SC Engineering GA V2865 UT WOS:000168745900019 ER PT J AU Wall, J Fang, WC AF Wall, J Fang, WC TI Electronics brain design for advanced microspacecraft SO ACTA ASTRONAUTICA LA English DT Article AB A brief history of NASA robotic spacecraft computing architectures is given. Changing needs driving changes in features (10x reduction in cost, various increases in capability, 10x to 100x reduction in power, mass and volume) for spacecraft computing are discussed. An architecture which addresses these changes is proposed. Finally, future directions of exploration for this spacecraft computing architecture are considered. (C) 1997 Published by Elsevier Science Ltd. C1 CALTECH, Jet Prop Lab, Adv Comp Resources Grp, Pasadena, CA 91109 USA. RP Wall, J (reprint author), CALTECH, Jet Prop Lab, Adv Comp Resources Grp, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 9 TC 0 Z9 0 U1 0 U2 0 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0094-5765 EI 1879-2030 J9 ACTA ASTRONAUT JI Acta Astronaut. PD NOV-DEC PY 1996 VL 39 IS 9-12 BP 815 EP 822 DI 10.1016/S0094-5765(97)00065-9 PG 8 WC Engineering, Aerospace SC Engineering GA V2865 UT WOS:000168745900022 ER PT J AU Lam, B AF Lam, B TI Portable end-to-end ground system for low-cost mission support SO ACTA ASTRONAUTICA LA English DT Article AB This paper presents a revolutionary architecture of the end-to-end ground system to reduce overall mission support costs. The present ground system of the Jet Propulsion Laboratory (JPL) is costly to operate, maintain, deploy, reproduce, and document. In the present climate of shrinking NASA budgets, this proposed architecture takes on added importance as it should dramatically reduce all of the above costs. Currently, the ground support functions (i.e., receiver, tracking, ranging, telemetry, command, monitor and control) are distributed among several subsystems that are housed in individual rack-mounted chassis. These subsystems can be integrated into one portable laptop system using established MultiChip Module (MCM) packaging technology and object-based software libraries. The large scale integration of subsystems into a small portable system connected to the World Wide Web (WWW) will greatly reduce operations, maintenance and reproduction costs. Several of the subsystems can be implemented using Commercial Off-The-Shelf (COTS) products further decreasing non-recurring engineering costs. The inherent portability of the system will open up new ways for using the ground system at the "point-of-use" site as opposed to maintaining several large centralized stations. This eliminates the propagation delay of the data to the Principal Investigator (PI), enabling the capture of data in real-time and performing multiple tasks concurrently from any location in the world. Sample applications are to use the portable ground system in remote areas or mobile vessels for real-time correlation of satellite data with earth-bound instruments; thus, allowing near real-time feedback and control of scientific instruments. This end-to-end portable ground system will undoubtedly create opportunities for better scientific observation and data acquisition. (C) 1997 Published by Elsevier Science Ltd. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Lam, B (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 7 TC 1 Z9 1 U1 0 U2 0 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0094-5765 J9 ACTA ASTRONAUT JI Acta Astronaut. PD NOV-DEC PY 1996 VL 39 IS 9-12 BP 909 EP 915 DI 10.1016/S0094-5765(97)00075-1 PG 7 WC Engineering, Aerospace SC Engineering GA V2865 UT WOS:000168745900032 ER PT J AU Metzger, RM AF Metzger, RM TI The New Millennium Program: Fast-track procurements SO ACTA ASTRONAUTICA LA English DT Article AB The National Aeronautics and Space Administration's (NASA's) New Millennium Program (NMP) has embarked on a technology flight-validation demonstration program to enable the kinds of missions that NASA envisions for the 21st century. Embedded in this program is the concept of rapid mission development supported by a fast-track procurement process. This process begins with the decision to initiate a procurement very early in the program along with the formation of a technical acquisition team. A close working relationship among the team members is essential to avoiding delays and developing a clear acquisition plan. The request for proposal (RFP) that is subsequently issued seeks a company with proven capabilities, so that the time allotted for responses from proposers and the length of proposals they submit can be shortened. The fast-track procurement process has been demonstrated during selection of NMP's industrial partners and has been proven to work. (C) 1997 Published by Elsevier Science Ltd. C1 CALTECH, Jet Prop Lab, New Millennium Program, Pasadena, CA 91109 USA. RP Metzger, RM (reprint author), CALTECH, Jet Prop Lab, New Millennium Program, 4800 Oak Grove Dr,M-S 180-404, Pasadena, CA 91109 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0094-5765 J9 ACTA ASTRONAUT JI Acta Astronaut. PD NOV-DEC PY 1996 VL 39 IS 9-12 BP 943 EP 950 DI 10.1016/S0094-5765(97)00080-5 PG 8 WC Engineering, Aerospace SC Engineering GA V2865 UT WOS:000168745900036 ER PT J AU Dunphy, J Peterson, JC Salcedo, JJ AF Dunphy, J Peterson, JC Salcedo, JJ TI Integrated design systems - Capturing, reusing and optimizing design methods in New Millennium SO ACTA ASTRONAUTICA LA English DT Article AB An important goal of New Millennium is to research new methods of performing spacecraft and mission design. We have completed the first phase of our effort on how to make design tools such as analysis programs more available. We are now embarking with Stanford University on discovering methods to allow more project history and knowledge to be automatically captured and reused and with Ames Research Center on how to use virtual reality to enhance the visualization of new missions before any hardware exists. We are also trying to capture the design process in an electronic form so that computer aided optimization may lead to a vastly greater search of the possible designs which meet the design requirements. (C)1997 Published by Elsevier Science Ltd. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Dunphy, J (reprint author), CALTECH, Jet Prop Lab, MS 525-3660,4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 0 TC 1 Z9 2 U1 0 U2 0 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0094-5765 J9 ACTA ASTRONAUT JI Acta Astronaut. PD NOV-DEC PY 1996 VL 39 IS 9-12 BP 1011 EP 1020 DI 10.1016/S0094-5765(97)00088-X PG 10 WC Engineering, Aerospace SC Engineering GA V2865 UT WOS:000168745900044 ER PT J AU Wang, M Lele, SK Moin, P AF Wang, M Lele, SK Moin, P TI Computation of quadrupole noise using acoustic analogy SO AIAA JOURNAL LA English DT Article ID TRAILING EDGE NOISE; SOUND AB Acoustic analogy computations of vortex shedding noise were carried out in the context of a two-dimensional, low-Mach-number laminar how past a NACA 0012 airfoil at chord Reynolds number of 10(4). The incompressible Navier-Stokes equations were solved numerically to give an approximate description of the near-field flow dynamics and the acoustic source functions. The radiated far-field noise was computed based on Curie's extension to the Lighthill analogy, This study emphasizes an accurate evaluation of the Reynolds stress quadrupoles in the presence of an extensive wake. An effective method for separating the physical noise source from spurious boundary contributions caused by eddies crossing a permeable computational boundary is presented. The effect of retarded-time variations across the source region is also examined. Computational solutions confirm that the quadrupole noise is weak compared with the noise due to lift and drag dipoles when the freestream Mach number is small. The techniques developed in this study are equally applicable to hows in which the volume quadrupoles act as a prominent noise source. C1 STANFORD UNIV,DEPT AERONAUT & ASTRONAUT,STANFORD,CA 94305. STANFORD UNIV,DEPT MECH ENGN,STANFORD,CA 94305. RP Wang, M (reprint author), STANFORD UNIV,NASA,AMES RES CTR,MS 202A-1,MOFFETT FIELD,CA 94035, USA. RI Wang, Meng/C-1622-2012 NR 23 TC 42 Z9 44 U1 0 U2 4 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 SN 0001-1452 J9 AIAA J JI AIAA J. PD NOV PY 1996 VL 34 IS 11 BP 2247 EP 2254 DI 10.2514/3.13387 PG 8 WC Engineering, Aerospace SC Engineering GA VQ108 UT WOS:A1996VQ10800004 ER PT J AU Wissink, AM Lyrintzis, AS Strawn, RC AF Wissink, AM Lyrintzis, AS Strawn, RC TI Parallelization of a three-dimensional flow solver for Euler rotorcraft aerodynamics predictions SO AIAA JOURNAL LA English DT Article ID NAVIER-STOKES EQUATIONS; HELICOPTER ROTORS; FLOWFIELD; HOVER AB An approach for parallelizing the three-dimensional Euler/Navier-Stokes rotorcraft computational fluid dynamics flow solver transonic unsteady rotor Navier-Stokes (TURNS) is introduced, Parallelization is performed using a domain decomposition technique that is developed for distributed-memory parallel architectures, Communication between the subdomains on each processor is performed via message passing in the form of message passing interface subroutine calls, The most difficult portion of the TURNS algorithm to implement efficiently in parallel is the implicit time step using the lower-upper symmetric Gauss-Seidel (LU-SGS) algorithm, Two modifications of LU-SGS are proposed to improve the parallel performance, First, a previously introduced Jacobi-like method called data-parallel lower upper relaxation (DP-LUR) is used, Second, a new hybrid method is introduced that combines the Jacobi sweeping approach in DP-LUR for interprocessor communications and the symmetric Gauss-Seidel algorithm in LU-SGS for on-processor computations, The parallelized TURNS code with the modified implicit operator is implemented on two distributed-memory multiprocessor, the IBM SP2 and Thinking Machines: CM-5, and used to compute the three-dimensional quasisteady and unsteady flowfield of a helicopter rotor in forward flight. Good parallel speedups with a low: percentage of communication are exhibited by the code, The proposed hybrid algorithm requires less CPU time than DP-LUR while maintaining comparable parallel speedups and communication costs, Execution rates found on the IBM SP2 are impressive; on 114 processors of the SP2, the solution time of both quasisteady and unsteady calculations is reduced by a factor of al,out 12 over a single processor of the Gray C-90. C1 UNIV MINNESOTA,DEPT ENGN & MECH,MINNEAPOLIS,MN 55455. PURDUE UNIV,SCH AERONAUT & ASTRONAUT,W LAFAYETTE,IN 47907. RP Wissink, AM (reprint author), NASA,AMES RES CTR,MCAT INC,MAIL STOP 258-1,MOFFETT FIELD,CA 94035, USA. NR 29 TC 9 Z9 9 U1 0 U2 0 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 SN 0001-1452 J9 AIAA J JI AIAA J. PD NOV PY 1996 VL 34 IS 11 BP 2276 EP 2283 DI 10.2514/3.13391 PG 8 WC Engineering, Aerospace SC Engineering GA VQ108 UT WOS:A1996VQ10800008 ER PT J AU Joslin, RD AF Joslin, RD TI Simulation of three-dimensional symmetric and asymmetric instabilities in attachment-line boundary layers SO AIAA JOURNAL LA English DT Article ID TRANSITION; STABILITY RP Joslin, RD (reprint author), NASA,LANGLEY RES CTR,FLUID MECH & ACOUST DIV,HAMPTON,VA 23681, USA. NR 18 TC 9 Z9 9 U1 0 U2 0 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 SN 0001-1452 J9 AIAA J JI AIAA J. PD NOV PY 1996 VL 34 IS 11 BP 2432 EP 2434 DI 10.2514/3.13415 PG 3 WC Engineering, Aerospace SC Engineering GA VQ108 UT WOS:A1996VQ10800031 ER PT J AU Gartenberg, E Scott, MA Martinson, SD AF Gartenberg, E Scott, MA Martinson, SD TI Transition detection with deposited hot films in cryogenic tunnels SO AIAA JOURNAL LA English DT Article C1 NASA,LANGLEY RES CTR,AERODYNAM MEASUREMENT BRANCH,HAMPTON,VA 23681. NASA,LANGLEY RES CTR,ACOUST OPT & CHEM MEASUREMENT BRANCH,HAMPTON,VA 23681. RP Gartenberg, E (reprint author), OLD DOMINION UNIV,DEPT MECH ENGN,NORFOLK,VA 23529, USA. NR 12 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 SN 0001-1452 J9 AIAA J JI AIAA J. PD NOV PY 1996 VL 34 IS 11 BP 2434 EP 2436 DI 10.2514/3.13416 PG 3 WC Engineering, Aerospace SC Engineering GA VQ108 UT WOS:A1996VQ10800032 ER PT J AU Bammidipati, S Stewart, GD Elliott, JR Gokoglu, SA Purdy, MJ AF Bammidipati, S Stewart, GD Elliott, JR Gokoglu, SA Purdy, MJ TI Chemical vapor deposition of carbon on graphite by methane pyrolysis SO AICHE JOURNAL LA English DT Article ID CERAMIC COMPOSITES; KINETICS; PRESSURE; SILICON; DECOMPOSITION; DEPENDENCE AB Chemical vapor deposition (CVD) of carbon by methane pyrolysis onto a nonporous graphite rod was studied experimentally in a hot-wall, laminar-flow reactor and theoretically by finite-element modeling. Reactor pressure ranged from 10 to 40 torr, control temperature from 1,000 to 1,100 degrees C, and methane was diluted with H-2, Ar, or N-2. The average residence time ranged from 1 to 50 s. A combination of experimental measurement and numerical modeling was used to accurately characterize fluid and thermal fields inside the reactor. Tractable numerical models were developed for the CVD of carbon with gas-phase chemical reaction mechanisms based on accepted kinetic expressions. Simpler mechanisms were reduced from ones based on a more extensive list of intermediate reactions by systematic comparison to experimental data. A simplified but rational model is recommended based on the best fit to experimental data at various flow rates and pressures. The study indicates that axial dispersion plays a significant role and the pressure fall-off effect for rate coefficients of unimolecular decomposition reactions must be taken into account. C1 UNIV AKRON,DEPT CHEM ENGN,AKRON,OH 44326. NASA,LEWIS RES CTR,CLEVELAND,OH 44135. BF GOODRICH CO,BRECKSVILLE,OH 44141. RI Elliott, J. Richard/K-2544-2016 NR 25 TC 19 Z9 19 U1 1 U2 7 PU AMER INST CHEMICAL ENGINEERS PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017 SN 0001-1541 J9 AICHE J JI AICHE J. PD NOV PY 1996 VL 42 IS 11 BP 3123 EP 3132 DI 10.1002/aic.690421112 PG 10 WC Engineering, Chemical SC Engineering GA VR595 UT WOS:A1996VR59500011 ER PT J AU Ku, YTE Montgomery, LD Webbon, BW AF Ku, YTE Montgomery, LD Webbon, BW TI Hemodynamic and thermal responses to head and neck cooling in men and women SO AMERICAN JOURNAL OF PHYSICAL MEDICINE & REHABILITATION LA English DT Article DE thermoregulation; life support; thermal stress; rheoencephalography ID TEMPERATURE AB Personal cooling systems are used to alleviate symptoms of multiple sclerosis and to prevent increased core temperature during daily activities. The objective of this study was to determine the operating characteristics and the physiologic changes produced by short term use of one commercially available thermal control system. A Life Support Systems, Inc. Mark VII portable cooling system and a liquid cooling helmet were used to cool the head and neck regions of 12 female and 12 male subjects (25-55 yr) in this study. The healthy subjects, seated in an upright position at normal room temperature (similar to 21 degrees C), were tested for 30 min with the liquid cooling garment operated at its maximum cooling capacity. Electrocardiograms and scalp and intracranial blood flows were recorded periodically during each test sequence. Scalp, right and left ear, and oral temperatures and cooling system parameters were logged every 5 min. Scalp, right and left ear canal, and oral temperatures were all significantly (P < 0.05) reduced by 30 min of head and neck cooling. Oral temperatures decreased approximately 0.2-0.6 degrees C after 30 min and continued to decrease further (similar to 0.1-0.2 degrees C) for a period of similar to 10 min after removal of the cooling helmet. Intracranial blood flow decreased significantly (P < 0.05) during the first 10 min of the cooling period, Both right and left ear temperatures in the women were significantly lower than those of the men during the cooling period. These data indicate that head and neck cooling may be used to reduce core temperature to that needed for symptomatic relief of both male and female multiple sclerosis patients. This study quantifies the operating characteristics of one liquid cooling garment as an example of the information needed to compare the efficiency of other garments operated under different test conditions. RP Ku, YTE (reprint author), NASA,AMES RES CTR,MAIL STOP 239-15,MOFFETT FIELD,CA 94035, USA. NR 18 TC 14 Z9 14 U1 0 U2 1 PU WILLIAMS & WILKINS PI BALTIMORE PA 351 WEST CAMDEN ST, BALTIMORE, MD 21201-2436 SN 0894-9115 J9 AM J PHYS MED REHAB JI Am. J. Phys. Med. Rehabil. PD NOV-DEC PY 1996 VL 75 IS 6 BP 443 EP 450 DI 10.1097/00002060-199611000-00008 PG 8 WC Rehabilitation; Sport Sciences SC Rehabilitation; Sport Sciences GA WA783 UT WOS:A1996WA78300007 PM 8985108 ER PT J AU Cady, SL Wenk, HR Downing, KH AF Cady, SL Wenk, HR Downing, KH TI HRTEM of microcrystalline opal in chert and porcelanite from the Monterey Formation, California SO AMERICAN MINERALOGIST LA English DT Article ID TRANSMISSION ELECTRON-MICROSCOPY; LOW-TRIDYMITE; SILICA DIAGENESIS; CRYSTAL-STRUCTURE; TEMBLOR RANGE; PHASE; SHALE; TRANSFORMATION; CRISTOBALITE; CT AB Microcrystalline opal was investigated using low-dose transmission electron microscopy (TEM) methods to identify microstructural characteristics and possible phase-transformation mechanisms that accommodate silica diagenesis. High-resolution TEM (HRTEM) revealed that microcrystalline opal in opal-CT chert (>90 wt% silica) and opal-CT porce-lanite (50-90 wt% silica) from the Miocene Monterey Formation of California displays various amounts of structural disorder and coherent and incoherent lamellar intergrowths. Species of microfibrous opal identified by HRTEM in early-formed opal-CT chert include length-slow opal-C and unidimensionally disordered length-slow opal-CT (''lussatite''). These fibers often display a microstructure characterized by an aperiodic distribution of highly strained domains that separate ordered domains located at discrete positions along the direction of the fiber axes. Microfibrous opal occurs as several types of fiber-aggregation forms. TEM revealed that the siliceous matrix in later-formed opal-CT porcelanite consists of equidimensional, nanometer-size opal-CT crystallites and lussatite fibers. Pseudo-orthorhombic tridymite (PO-2) was identified by HRTEM in one sample of opal-CT porcelanite. Burial diagenesis of chert and porcelanite results in the precipitation of opal-C and the epitaxial growth of opal-C domains on opal-CT substrates. Diagenetic maturation of lussatite was identified by TEM in banded opal-CT-quartz chert to occur as a result of solid-state ordering. The primary diagenetic silica phase transformations between noncrystalline opal, microcrystalline opal, and quartz occur predominantly by a series of dissolution-precipitation reactions. However, TEM showed that in banded opal-CT-quartz chert, the epitaxial growth of quartz on microfibrous opal enhances the rate of silica diagenesis. C1 UNIV CALIF BERKELEY,DEPT GEOL & GEOPHYS,BERKELEY,CA 94720. UNIV CALIF BERKELEY,LAWRENCE BERKELEY NATL LAB,DIV LIFE SCI,BERKELEY,CA 94720. RP Cady, SL (reprint author), NASA,AMES RES CTR,MOFFETT FIELD,CA 94035, USA. NR 82 TC 15 Z9 18 U1 1 U2 6 PU MINERALOGICAL SOC AMER PI WASHINGTON PA 1130 17TH ST NW SUITE 330, WASHINGTON, DC 20036 SN 0003-004X J9 AM MINERAL JI Am. Miner. PD NOV-DEC PY 1996 VL 81 IS 11-12 BP 1380 EP 1395 PG 16 WC Geochemistry & Geophysics; Mineralogy SC Geochemistry & Geophysics; Mineralogy GA WE455 UT WOS:A1996WE45500011 ER PT J AU Bada, JL McDonald, GD AF Bada, JL McDonald, GD TI Detecting amino acids on Mars SO ANALYTICAL CHEMISTRY LA English DT Article ID ELECTROPHORESIS; BIOMOLECULES; ENANTIOMERS; ATMOSPHERE; METEORITE; MICROCHIP; ORIGINS C1 NASA,SPECIALIZED CTR RES & TRAINING EXOBIOL,WASHINGTON,DC. CORNELL UNIV,PLANETARY STUDIES LAB,ITHACA,NY 14853. RP Bada, JL (reprint author), UNIV CALIF SAN DIEGO,SCRIPPS INST OCEANOG,LA JOLLA,CA 92093, USA. NR 28 TC 21 Z9 21 U1 0 U2 2 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 SN 0003-2700 J9 ANAL CHEM JI Anal. Chem. PD NOV 1 PY 1996 VL 68 IS 21 BP A668 EP A673 PG 6 WC Chemistry, Analytical SC Chemistry GA VQ157 UT WOS:A1996VQ15700003 PM 11541467 ER PT J AU Moller, KD Warren, JB Heaney, JB Kotecki, C AF Moller, KD Warren, JB Heaney, JB Kotecki, C TI Cross-shaped bandpass filters for the near- and mid-infrared wavelength regions SO APPLIED OPTICS LA English DT Article DE infrared filters; bandpass filters produced by photolithography AB A photolithographic process has been used to form cross-shaped patterns in 3-mu m-thick nickel foils. Patterns with cross arm dimensions in the 10-20-mu m range, and with periodicities in the 16-26-mu m range, yield self-resonant bandpass filters for wavelengths in the 20-25-mu m region. Transmittances as high as 80% were achieved with center wavelength-to-bandwidth ratios (lambda(R)/Delta lambda) of similar to 5. We present a simple empirical formula that relates the wavelength of peak transmittance, or resonant frequency, with cross dimensions and periodicity. (C) 1996 Optical Society of America C1 BROOKHAVEN NATL LAB,DIV INSTRUMENTAT,UPTON,NY 11973. NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. RP Moller, KD (reprint author), NEW JERSEY INST TECHNOL,DEPT PHYS,NEWARK,NJ 07102, USA. NR 6 TC 16 Z9 16 U1 0 U2 1 PU OPTICAL SOC AMER PI WASHINGTON PA 2010 MASSACHUSETTS AVE NW, WASHINGTON, DC 20036 SN 0003-6935 J9 APPL OPTICS JI Appl. Optics PD NOV 1 PY 1996 VL 35 IS 31 BP 6210 EP 6215 DI 10.1364/AO.35.006210 PG 6 WC Optics SC Optics GA VP971 UT WOS:A1996VP97100017 PM 21127642 ER PT J AU Barth, AJ Reichert, GA Filippenko, AV Ho, LC Shields, JC Mushotzky, RF Puchnarewicz, EM AF Barth, AJ Reichert, GA Filippenko, AV Ho, LC Shields, JC Mushotzky, RF Puchnarewicz, EM TI The ultraviolet spectrum of the liner NGC 4579 SO ASTRONOMICAL JOURNAL LA English DT Article ID ACTIVE GALACTIC NUCLEI; X-RAY; GALAXIES; EMISSION; QUASARS; ORIGIN; HYPOTHESIS; CONTINUUM; SHOCKS; MODELS AB We present a Hubble Space Telescope ultraviolet spectrum of the LINER nucleus of NGC 4579, spanning the wavelength range 1160-3270 Angstrom. The data reveal a low-excitation spectrum of narrow (FWHM approximate to 1200 km s(-1)) and broad (FWHM approximate to 6600 km s(-1)) emission lines, which provide new diagnostics of the physical conditions within the emission-line regions, A featureless ultraviolet continuum is detected unambiguously, with f(n)u proportional to nu(-1.0) over the range 1300-2200 Angstrom and nu(-2.4) over 2200-3000 Angstrom. The 2200 Angstrom continuum flux is a factor of 3.3 lower than the value reported by Maoz et al, (1995) based on an HST image taken 19 months earlier; this is the first time that UV variability has been discovered in a LINER. The predictions of fast shock models are incompatible with the narrow-line spectrum, because the high-excitation lines produced in fast shocks are weak or absent in NGC 4579, Models of a single slab of gas photoionized by a power-law spectrum do not reproduce the observed line ratios well either, and it appears that the narrow-line region cannot be characterized by a unique value of the ionization parameter, We argue that the narrow-line region is photoionized by the central UV/X-ray source, and that more sophisticated photoionization calculations, incorporating the effects of density and/or ionization stratification and different continuum shapes, can yield results in better agreement with the data. (C) 1996 American Astronomical Society. C1 NASA, GODDARD SPACE FLIGHT CTR, GREENBELT, MD 20771 USA. HARVARD SMITHSONIAN CTR ASTROPHYS, CAMBRIDGE, MA 02138 USA. UCL, MULLARD SPACE SCI LAB, DORKING RH5 6NT, SURREY, ENGLAND. RP Barth, AJ (reprint author), UNIV CALIF BERKELEY, DEPT ASTRON, 601 CAMPBELL HALL, BERKELEY, CA 94720 USA. OI Barth, Aaron/0000-0002-3026-0562 NR 49 TC 42 Z9 42 U1 0 U2 1 PU IOP PUBLISHING LTD PI BRISTOL PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND SN 0004-6256 J9 ASTRON J JI Astron. J. PD NOV PY 1996 VL 112 IS 5 BP 1829 EP 1838 DI 10.1086/118145 PG 10 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VQ496 UT WOS:A1996VQ49600007 ER PT J AU Struck, C Appleton, PN Borne, KD Lucas, RA AF Struck, C Appleton, PN Borne, KD Lucas, RA TI Hubble Space Telescope imaging of dust lanes and cometary structures in the inner disk of the Cartwheel ring galaxy SO ASTRONOMICAL JOURNAL LA English DT Article ID HIGH-VELOCITY CLOUDS; STAR-FORMATION; DENSITY WAVE; MODELS AB We have obtained high-resolution B and I-band Hubble Space Telescope (HST) images of the Cartwheel ring galaxy which provide unprecedented views of the structure and color of the two rings and spokes, Here, we focus on the imaging results for the central regions of the Cartwheel, its inner ring and spokes. Prior to these observations there was surprisingly little evidence for gas and star formation within the inner ring. The images clearly resolve a network of obscuring dust lanes in this region, including a prominent dust circle that defines the inner edge of the inner ring. There is also evidence for luminous, kiloparsec-sized, cometary structures in the inner ring which are suggestive of massive dense clouds traveling supersonically through the ambient gas. These cometary structures are bounded by sharp dust lanes, and when corrected for the light from the inner ring are quite blue (0.445 degrees) coronal streamers with enhanced white-light emission. These streamers are located along a neutral line that separates the weak, old-cycle polar field from the weak, new-cycle high-latitude magnetic field of opposite polarity. C1 LOCKHEED PALO ALTO RES LABS,LOCKHEED MARTIN SOLAR & ASTROPHYS LAB,PALO ALTO,CA 94304. CATHOLIC UNIV AMER,DEPT PHYS,WASHINGTON,DC 20064. RP Guhathakurta, M (reprint author), NASA,GODDARD SPACE FLIGHT CTR,CODE 682,GREENBELT,MD 20771, USA. NR 9 TC 15 Z9 15 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637 SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD NOV 1 PY 1996 VL 471 IS 1 BP L69 EP & DI 10.1086/310316 PN 2 PG 6 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VP224 UT WOS:A1996VP22400018 ER PT J AU Neufeld, DA Hollenbach, DJ AF Neufeld, DA Hollenbach, DJ TI Free-free emission from accretion shocks SO ASTROPHYSICAL JOURNAL LA English DT Article DE radio continuum, stars; shock waves; stars, formation; stars, pre-main-sequence ID PROTOSTELLAR DISKS; COLLAPSE AB Shocks associated with the supersonic infall of matter onto a protostellar disk are sources of potentially detectable radio free-free emission: a protostar of mass approximate to 1.5[D/(100 p)]M. is sufficient to generate an 8.4 GHz flux of 100 mu Jy from its protostellar disk when viewed face-on at a distance D. The free-free emission from an accretion shock is a good diagnostic of the mass of the protostar, which determines the area of the optically thick free-free emission from the shocked surface of the inner disk. Accretion shocks are a possible explanation of recent observations of the source NGC 1333 IRAS 4, in which the measured fluxes at 4.8 and 8.4 GHz exceed the values expected for circumstellar dust emission alone. The accretion shock explanation requires the presence in this source of a protostar of mass 3.5-4 M., a value that is consistent with the observed bolometric luminosity only if accretion through the disk is nonsteady and only if the protostellar luminosity lies substantially below its main-sequence value, as indeed is predicted by theoretical models for the evolution of pre-main-sequence stars. We also discuss an alternative model in which the observed free-free emission arises in shocks produced by circumstellar winds impacting dense circumstellar material. C1 NASA,AMES RES CTR,MOFFETT FIELD,CA 94035. RP Neufeld, DA (reprint author), JOHNS HOPKINS UNIV,DEPT PHYS & ASTRON,CHARLES & 34TH ST,BALTIMORE,MD 21218, USA. NR 8 TC 24 Z9 24 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637 SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD NOV 1 PY 1996 VL 471 IS 1 BP L45 EP L48 DI 10.1086/310328 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VP224 UT WOS:A1996VP22400012 ER PT J AU Sion, EM Cheng, FH Huang, M Hubeny, I Szkody, P AF Sion, EM Cheng, FH Huang, M Hubeny, I Szkody, P TI The cooling white dwarf in VW Hydri after normal outburst and superoutburst: HST evidence of a sustained accretion belt SO ASTROPHYSICAL JOURNAL LA English DT Article DE novae, cataclysmic variables; stars, individual (VW Hydri); white dwarfs ID NOVA AB Hubble Faint Object Spectrograph (FOS) observations of VW Hyi one day after the end of a normal dwarf nova outburst reveal a heated white dwarf with deep, broad Ly alpha, narrow metallic absorption features, and evidence of a hotter Keplerian-broadened component manifested in quiescence as a broad continuum hump. Our best reduced chi(2) fit to the data reveals (1) a DAZQ white dwarf with T-eff = 22,500 +/- 500 K, log g = 8, and photospheric abundances C = 0.5 solar, N = 5.0 solar, 0 = 2.0 solar, Si = 0.2 solar, Fe = 0.5 solar, with all other metals being 0.3 solar, and (2) a rapidly spinning accretion belt with V-rot, = 3350 km s(-1), T-belt = 26,000 +/- 1000 K, log g = 6.0, and a fractional belt area of approximately 11%. Our earlier FOS spectrum obtained 10 days after superoutburst reveals a cooler DAZQ white dwarf (20,500 +/- 1000 K), relatively fewer metal abundances, and a smaller fractional area (3%) for the accretion belt. Thus, 1 day after a normal outburst, the white dwarf is approximate to y2000 K hotter, the accretion belt fractional area is a factor of 3 greater, the accretion belt temperature appears to be cooler than at 10 days post-superoutburst, and the accreted atmosphere has relatively higher metal abundances. Finally, the accretion belt maintained during quiescence may provide a natural explanation for the 14 s soft X-ray oscillations, requires a deeper source of heating (compression and shear mixing), and implies a lower limit to the viscous spin-down timescale of 10 days. C1 UNIV SCI & TECHNOL CHINA,CTR ASTROPHYS,HEFEI 230026,PEOPLES R CHINA. NASA,GODDARD SPACE FLIGHT CTR,ASTRON & SOLAR PHYS LAB,GREENBELT,MD 20771. UNIV WASHINGTON,DEPT ASTRON,SEATTLE,WA 98195. RP Sion, EM (reprint author), VILLANOVA UNIV,DEPT ASTRON & ASTROPHYS,VILLANOVA,PA 19085, USA. NR 13 TC 39 Z9 39 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637 SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD NOV 1 PY 1996 VL 471 IS 1 BP L41 EP L44 DI 10.1086/310318 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VP224 UT WOS:A1996VP22400011 ER PT J AU Thompson, DJ Bertsch, DL Dingus, BL Esposito, JA Etienne, A Fichtel, CE Friedlander, DP Hartman, RC Hunter, SD Kendig, DJ Mattox, JR McDonald, LM Mukherjee, R Ramanamurthy, PV Sreekumar, P vonMontigny, C Fierro, JM Jones, BB Lin, YC Michelson, PF Nolan, PL Tompkins, W Willis, TD Kanbach, G MayerHasselwander, HA Merck, M Pohl, M Kniffen, DA Schneid, EJ AF Thompson, DJ Bertsch, DL Dingus, BL Esposito, JA Etienne, A Fichtel, CE Friedlander, DP Hartman, RC Hunter, SD Kendig, DJ Mattox, JR McDonald, LM Mukherjee, R Ramanamurthy, PV Sreekumar, P vonMontigny, C Fierro, JM Jones, BB Lin, YC Michelson, PF Nolan, PL Tompkins, W Willis, TD Kanbach, G MayerHasselwander, HA Merck, M Pohl, M Kniffen, DA Schneid, EJ TI Supplement to the second EGRET catalog of high-energy gamma-ray sources SO ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES LA English DT Article DE catalogs; galaxies, active; gamma rays, observations ID RADIO-SOURCES AB This supplement extends the second EGRET catalog of high-energy gamma-ray sources (see recent paper by Thompson et al.), incorporating data from 1993 September to 1994 October. The second catalog contained 129 sources, based on data from 1991 April to 1993 September. An additional 28 sources are found, including three new identifications of active galactic nuclei. C1 STANFORD UNIV,WW HANSEN EXPT PHYS LAB,STANFORD,CA 94305. STANFORD UNIV,DEPT PHYS,STANFORD,CA 94305. MAX PLANCK INST EXTRATERR PHYS,D-85748 GARCHING,GERMANY. HAMPDEN SYDNEY COLL,DEPT PHYS,HAMPDEN SYDNEY,VA 23943. NORTHROP GRUMMAN CORP,BETHPAGE,NY 11714. RP Thompson, DJ (reprint author), NASA,GODDARD SPACE FLIGHT CTR,CODE 661,GREENBELT,MD 20771, USA. RI Nolan, Patrick/A-5582-2009; Hunter, Stanley/D-2942-2012; Thompson, David/D-2939-2012; OI Thompson, David/0000-0001-5217-9135; Dingus, Brenda/0000-0001-8451-7450 NR 24 TC 119 Z9 122 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637 SN 0067-0049 J9 ASTROPHYS J SUPPL S JI Astrophys. J. Suppl. Ser. PD NOV PY 1996 VL 107 IS 1 BP 227 EP 237 DI 10.1086/192362 PG 11 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA WF467 UT WOS:A1996WF46700011 ER PT J AU Phillips, TR Maluendes, S Green, S AF Phillips, TR Maluendes, S Green, S TI Collisional excitation of H2O by H-2 molecules SO ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES LA English DT Article DE molecular data; molecular processes ID INTERSTELLAR WATER; HYDROGEN; GHZ; TRANSITION; H2O-H-2; RATES; RATIO; ROTOR AB Using accurate theoretical rigid-rotor interaction potential for H2O-H-2 and accurate coupled channel molecular scattering calculations, rates have been obtained for excitation of para- and ortho-H2O out of the lowest, j = 0, 1, and 2, rotational levels owing to collisions with para- and ortho-H-2 at kinetic temperatures from 20 to 140 It. Excitation by para-H-2 is not too different from excitation by He atoms, with most rates being within a factor of 1-3 larger, but excitation by ortho-H-2 is significantly different, with some rates an order of magnitude larger than rates for excitation by He atoms. C1 IBM CORP,ALMADEN RES CTR,SAN JOSE,CA 95120. NASA,GODDARD SPACE FLIGHT CTR,INST SPACE STUDIES,NEW YORK,NY 10025. RP Phillips, TR (reprint author), SCI SYST APPLICAT INC,NEW YORK,NY 10025, USA. NR 21 TC 86 Z9 86 U1 0 U2 1 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637 SN 0067-0049 J9 ASTROPHYS J SUPPL S JI Astrophys. J. Suppl. Ser. PD NOV PY 1996 VL 107 IS 1 BP 467 EP 474 DI 10.1086/192372 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA WF467 UT WOS:A1996WF46700021 ER PT J AU Bhatia, AK Doschek, GA AF Bhatia, AK Doschek, GA TI Atomic data and spectral line intensities for Fe XI SO ATOMIC DATA AND NUCLEAR DATA TABLES LA English DT Article ID CROSS-SECTIONS; EXCITATION AB Electron impact collision strengths and spontaneous radiative decay rates are calculated for Fe XI. The data pertain to the 48 levels of the configurations 3s(2)3p(4), 3s3p(5), 3s(2)3p(3)3d, and 3p(6). Collision strengths are calculated at three incident electron energies, 8.0, 16.0, and 24.0 Ry. Relative spectral line intensities are calculated for all astrophysically important transitions. These are obtained by computing the excitation rate coefficients, i.e., the collision strengths integrated over a Maxwellian electron distribution, and then solving the equations of detailed balance for the populations of the 48 energy levels, assuming a collisional excitation model and an electron temperature of 1.3 x 10(6) K. This temperature is typical for Fe XI when formed in equilibrium by collisional ionization and recombination. Using the excitation rate coefficients and the radiative decay rates, level populations are computed for several electron densities and are given in this paper. We also investigate the effects of proton excitation and solar radiative excitation on the level populations and line intensities. Finally, the calculated relative line intensities are compared with experimental solar intensities where available. (C) 1996 Academic Press, Inc. C1 USN,RES LAB,EO HULBURT CTR SPACE RES,WASHINGTON,DC 20375. RP Bhatia, AK (reprint author), NASA,GODDARD SPACE FLIGHT CTR,ASTRON & SOLAR PHYS LAB,GREENBELT,MD 20771, USA. NR 24 TC 42 Z9 42 U1 0 U2 0 PU ACADEMIC PRESS INC JNL-COMP SUBSCRIPTIONS PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 SN 0092-640X J9 ATOM DATA NUCL DATA JI Atom. Data Nucl. Data Tables PD NOV PY 1996 VL 64 IS 2 BP 183 EP 222 DI 10.1006/adnd.1996.0021 PG 40 WC Physics, Atomic, Molecular & Chemical; Physics, Nuclear SC Physics GA VZ367 UT WOS:A1996VZ36700002 ER PT J AU Vernikos, J Ludwig, DA Ertl, AC Wade, CE Keil, L OHara, D AF Vernikos, J Ludwig, DA Ertl, AC Wade, CE Keil, L OHara, D TI Effect of standing or walking on physiological changes induced by head down bed rest: Implications for spaceflight SO AVIATION SPACE AND ENVIRONMENTAL MEDICINE LA English DT Article ID DOWN TILT; EXERCISE; RESPONSES; POSTURE; FLUID AB Background/Hypothesis: To simulate exposure to microgravity and to determine the effectiveness of intermittent exposure to passive and active +1 Gz force (head-to-foot) in preventing head-down bed rest (HDBR) deconditioning, 4 d of 6 degrees HDBR were used. Methods: Volunteers were 9 males, 30-50 yr, who performed periodic standing or controlled walking for 2 or 4 h . d(-1) in 15-min bouts, one bout per hour, or remained in a continuous HDBR control condition (0 Gz). Results: Standing 4 h (S4) completely prevented, and standing 2 h (S2) partially prevented, decreases in post-HDBR orthostatic tolerance (survival rates with 30 min of upright tilt at 60 degrees). Walking, both 2 h (W2) and 4 fi (W4), and S4 attenuated decreases in peak oxygen uptake compared to 0 Gz. Compared to 0 Ct, both S4 and W4 attenuated plasma volume loss during HDBR. Urinary Ca2+ excretion increased over time with HDBR; the quadratic trend for urinary Ca2+, however, was attenuated with W2 and W4. Conclusions We concluded that various physiological systems benefit differentially from passive +1 Gz or activity in +1 Gz and, in addition to the duration of the stimulus, the number of exposures to postural stimuli may be an important moderating factor. C1 NASA, AMES RES CTR, DIV LIFE SCI, MOFFETT FIELD, CA 94035 USA. UNIV N CAROLINA, GREENSBORO, NC 27412 USA. VANDERBILT UNIV, MED CTR, NASHVILLE, TN 37240 USA. NR 37 TC 56 Z9 61 U1 0 U2 3 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 NOV PY 1996 VL 67 IS 11 BP 1069 EP 1079 PG 11 WC Public, Environmental & Occupational Health; Medicine, General & Internal; Sport Sciences SC Public, Environmental & Occupational Health; General & Internal Medicine; Sport Sciences GA VP505 UT WOS:A1996VP50500010 PM 8908346 ER PT J AU Crump, WJ Levy, BJ Billica, RD AF Crump, WJ Levy, BJ Billica, RD TI A field trial of the NASA telemedicine instrument pack in a family practice SO AVIATION SPACE AND ENVIRONMENTAL MEDICINE LA English DT Article ID HEALTH-CARE AB Background: Previous studies of telemedicine applications have demonstrated that the technology is effective but inefficient. Little attention has been directed to the primary care portion of the connection, especially the use of the medical peripheral devices. This study used a telemedicine testbed that simulates a rural practice environment to describe the effectiveness and efficiency of the NASA Telemedicine Instrument Pack, a small self-contained system of medical peripheral devices. Method: This study was an 8-week field trial of a suitcase-sized pack containing a fundus camera, flexible nasopharyngoscope, dermatology macrolens, light source, and video monitor. The pack was first studied in specialty clinics and then was used in a family practice office connected to the consultant node by digital lines. Evaluations were obtained from technicians, patients, and consultants. Results: During 20 video clinic sessions, 59 patients with 38 different diagnoses were examined. The ear, nose, and throat portion of the exam was effective, with some decrement in cole: and clarity with compression of the signal. The eye portion was marginally effective, limited by a field of view that was too narrow and also by rigorous technician requirements. The skin exam was largely unacceptable primarily because the macrolens did not meet the requirements for color or clarity prior to compression of the signal. Conclusions: Subsequent design efforts for medical peripheral devices for telemedicine use will require significant modifications to ''off the shelf'' equipment to be effective and efficient. A family practice telemedicine testbed provides the appropriate environment for such field trials. C1 NASA,LYNDON B JOHNSON SPACE CTR,MED OPERAT,HOUSTON,TX 77058. RP Crump, WJ (reprint author), UNIV TEXAS,MED BRANCH,DEPT FAMILY MED,301 UNIV BLVD,GALVESTON,TX 77555, USA. NR 24 TC 13 Z9 13 U1 0 U2 3 PU AEROSPACE MEDICAL ASSOC PI ALEXANDRIA PA 320 S HENRY ST, ALEXANDRIA, VA 22314-3579 SN 0095-6562 J9 AVIAT SPACE ENVIR MD JI Aviat. Space Environ. Med. PD NOV PY 1996 VL 67 IS 11 BP 1080 EP 1085 PG 6 WC Public, Environmental & Occupational Health; Medicine, General & Internal; Sport Sciences SC Public, Environmental & Occupational Health; General & Internal Medicine; Sport Sciences GA VP505 UT WOS:A1996VP50500011 PM 8908347 ER PT J AU Solomon, JA Watson, AB AF Solomon, JA Watson, AB TI Cinematica: A system for calibrated, Macintosh-driven displays from within Mathematica SO BEHAVIOR RESEARCH METHODS INSTRUMENTS & COMPUTERS LA English DT Article AB Cinematica is a minimal system for producing calibrated grayscale movies on an Apple Macintosh computer from within the Mathematica programming environment. It makes use of the ISR Video Attenuator and the Video Toolbox software library developed by Denis Pelli. By design, Cinematica provides a very low-level interface to the display routine. Display instructions take the form of a list of pairs (image index, colormap index). The philosophy is that programming is much easier in Mathematica than in C, so we reserve the complexity for Mathematica. A few simple examples are provided. C1 NASA,AMES RES CTR,MOFFETT FIELD,CA 94035. RP Solomon, JA (reprint author), INST OPHTHALMOL,BATH ST,LONDON EC1V 9EL,ENGLAND. NR 3 TC 6 Z9 6 U1 0 U2 0 PU PSYCHONOMIC SOC INC PI AUSTIN PA 1710 FORTVIEW RD, AUSTIN, TX 78704 SN 0743-3808 J9 BEHAV RES METH INSTR JI Behav. Res. Methods Instr. Comput. PD NOV PY 1996 VL 28 IS 4 BP 607 EP 610 DI 10.3758/BF03200550 PG 4 WC Psychology, Mathematical; Psychology, Experimental SC Psychology GA VV855 UT WOS:A1996VV85500013 PM 11541042 ER PT J AU Fu, LL Smith, RD AF Fu, LL Smith, RD TI Global ocean circulation from satellite altimetry and high-resolution computer simulation SO BULLETIN OF THE AMERICAN METEOROLOGICAL SOCIETY LA English DT Article ID GENERAL-CIRCULATION; DATA ASSIMILATION; GULF-STREAM; GEOSAT; SEA; TOPEX/POSEIDON; MODEL; ATLANTIC; MONSOON; PACIFIC AB The sea surface elevation relative to the geoid, a dynamic boundary condition for the three-dimensional oceanic pressure field, is being determined over the global ocean every 10 days by a precision radar altimeter aboard the TOPEX/POSEIDON satellite. This is the most accurate altimeter data stream to date for the study of the ocean general circulation and its variability. The authors compare results from 2 years (October 1992-0ctober 1994) of the satellite observations to computer simulations for the same period using a state-of-the-art ocean general circulation model driven by realistic winds from an atmospheric weather-prediction model. The average horizontal resolution of the model is 1/5 degrees (varying from 30 km at the equator to 6 km at the polar latitudes), the highest for a global simulation performed to date. Comparisons of the mean circulation, the mesoscale variability, the amplitude, and phase of the annual cycle, as well as intraseasonal and interannual changes show that the simulations and observations agree fairly well over a broad range of temporal and spatial scares. However, the sea level variance produced by the model is generally less than the observation by a factor of 2, primarily in the eddy-rich regions. Comparison of wavenumber spectra indicates that even higher spatial resolution is needed to fully resolve the mesoscale eddies. The absolute dynamic topography determined from either the data or the model has an error on the order of 10 cm at wavelengths larger than 2000 km. Geoid errors are the limiting factor for the utility of the altimeter data at smaller scales. Heat flux forcing is a key factor in determining the simulated annual cycle of the ocean Improved agreement with the observation is achieved when the model is driven by heat flux forcing instead of being nudged to sea surface temperature climatology The temporal evolution of the intraseasonal fluctuations at mid- and high latitudes as well as the interannual variability of the tropical oceans, both are primarily wind driven, is simulated fairly well by the model. C1 LOS ALAMOS NATL LAB,LOS ALAMOS,NM. RP Fu, LL (reprint author), CALTECH,JET PROP LAB,4800 OAK GROVE DR,PASADENA,CA 91109, USA. NR 46 TC 92 Z9 94 U1 3 U2 6 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 SN 0003-0007 J9 B AM METEOROL SOC JI Bull. Amer. Meteorol. Soc. PD NOV PY 1996 VL 77 IS 11 BP 2625 EP 2636 DI 10.1175/1520-0477(1996)077<2625:GOCFSA>2.0.CO;2 PG 12 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA VW729 UT WOS:A1996VW72900001 ER PT J AU Charlock, TP Alberta, TL AF Charlock, TP Alberta, TL TI The CERES/ARM/GEWEX experiment (CAGEX) for the retrieval of radiative fluxes with satellite data SO BULLETIN OF THE AMERICAN METEOROLOGICAL SOCIETY LA English DT Article ID WATER-VAPOR; SURFACE RADIATION; BUDGET EXPERIMENT; SOLAR-RADIATION; ATMOSPHERIC ABSORPTION; INFRARED RADIANCES; SEASONAL-VARIATION; RAMAN LIDAR; CLOUD; EARTH AB Results from a temporally intensive, limited area, radiative transfer model experiment are on-line for investigating the vertical profile of shortwave and longwave radiative fluxes from the surface to the top of the atmosphere (TOA). The CERES/ARM/GEWEX Experiment (CAGEX) Version 1 provides a record of fluxes that have been computed with a radiative transfer code; the atmospheric sounding, aerosol, and satellite-retrieved cloud data on which the computations have been based; and surface-based measurements of radiative fluxes and cloud properties from ARM for comparison. The computed broadband fluxes at TOA show considerable scatter when compared with fluxes that are inferred empirically from narrowband operational satellite data. At the surface, LW fluxes computed with an alternate sounding dataset compare well with pyrgeometer measurements. In agreement with earlier work, the authors find that the calculated SW surface insolation is larger than the measurements for clear-sky and total-sky conditions. This experiment has been developed to test retrievals of radiative fluxes and the associated forcings by clouds, aerosols, surface properties, and water vapor. Collaboration is sought; the goal is to extend the domain of meteorological conditions for which such retrievals can be done accurately. CAGEX Version 1 covers April 1994. Subsequent versions will (a) at first span the same limited geographical area with data from October 1995, (b) then expand to cover a significant fraction of the GEWEX Continental-Scale International Project region for April 1996 through September 1996, and (c) eventually be used in a more advanced form to validate CERES. C1 ANALYT SERV & MAT INC,HAMPTON,VA 23666. RP Charlock, TP (reprint author), NASA,LANGLEY RES CTR,MAIL STOP 420,HAMPTON,VA 23681, USA. NR 61 TC 86 Z9 87 U1 0 U2 2 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 SN 0003-0007 J9 B AM METEOROL SOC JI Bull. Amer. Meteorol. Soc. PD NOV PY 1996 VL 77 IS 11 BP 2673 EP 2683 DI 10.1175/1520-0477(1996)077<2673:TCEFTR>2.0.CO;2 PG 11 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA VW729 UT WOS:A1996VW72900004 ER PT J AU Qiu, ZP Elishakoff, I Starnes, JH AF Qiu, ZP Elishakoff, I Starnes, JH TI The bound set of possible eigenvalues of structures with uncertain but non-random parameters SO CHAOS SOLITONS & FRACTALS LA English DT Article AB In this study, a new, deterministic method is discussed for estimating the maximum, or least favorable frequency, and the minimum, or best favorable frequency, of structures with uncertain but non-random parameters. The favorable bound estimate is actually a set in eigenvalue space rather than a single vector. The obtained optimum estimate is the smallest calculable set which contains the uncertain system eigenvalues. This kind of eigenvalue problem involves uncertain but non-random interval stiffness and mass matrices. If one views the deviation amplitude of the interval matrix as a perturbation around the nominal value of the interval matrix, one can solve the generalized eigenvalue problem of the uncertain but non-random interval matrices. By applying the interval extension matrix perturbation formulation, the interval perturbation approximating formula is presented for evaluating interval eigenvalues of uncertain but non-random interval stiffness and mass matrices. A perturbation method is developed which allows one to calculate eigenvalues of an uncertain but non-random interval matrix pair that always contains the system's true stiffness and mass matrices. Inextensive computational effort is a characteristic of the presented method. A numerical example illustrates the application of the proposed method. Copyright (C) 1996 Elsevier Science Ltd. C1 FLORIDA ATLANTIC UNIV, DEPT MECH ENGN, BOCA RATON, FL 33431 USA. NASA, LANGLEY RES CTR, HAMPTON, VA 23664 USA. RP Qiu, ZP (reprint author), DALIAN UNIV TECHNOL, RES INST ENGN MECH, DALIAN 116023, PEOPLES R CHINA. NR 14 TC 19 Z9 25 U1 0 U2 1 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0960-0779 J9 CHAOS SOLITON FRACT JI Chaos Solitons Fractals PD NOV PY 1996 VL 7 IS 11 BP 1845 EP 1857 DI 10.1016/S0960-0779(96)00041-0 PG 13 WC Mathematics, Interdisciplinary Applications; Physics, Multidisciplinary; Physics, Mathematical SC Mathematics; Physics GA VY596 UT WOS:A1996VY59600006 ER PT J AU Buyevich, YA Webbon, BW AF Buyevich, YA Webbon, BW TI Bubble formation at a submerged office in reduced gravity SO CHEMICAL ENGINEERING SCIENCE LA English DT Article DE bubble formation; gas injection; reduced gravity AB We consider gas injection through a circular plate orifice into an ideally wetting liquid which results in the successive detachment of bubbles, each of which is regarded as a separate entity. At normal gravity and at relatively low gas dow rates, the growing bubble is modelled as a spherical segment that touches the orifice perimeter during the whole time of its evolution. If the gas flow rate exceeds a certain threshold value, a second stage of the detachment takes place that follows the first spherical segment stage. In this second stage, a nearly cylindrical stem forms at the orifice that lengthens as the bubble rises above the plate, and this stems feeds an almost spherical gas envelope situated at the stem upper end. At high gas how rates, bubble shape resembles that of a mushroom, and its upper envelope continues to grow until the gas supplied through the stem is completely cut off. This second stage always develops when gravity is sufficiently low, irrespective of the gas dow rate. There are two major factors that determine the moment of bubble detachment: the buoyancy force and a force due to the momentum flowing into the bubble with the injected gas. The buoyancy force dominates the process at normal gravity whereas the inflowing momentum force plays the key role under negligible gravity conditions. As gravity fluctuates, the interplay of these forces drastically influences bubble growth and detachment. At sufficiently low gravity, the bubble formation frequency is proportional to gas flow rate whereas the bubble detachment volume is independent of gas dow rate. At normal and moderately reduced gravity conditions, when the gas how rate grows, bubble formation frequency slightly decreases and bubble detachment volume increases almost linearly. Effects of other parameters, such as the orifice radius, gas and liquid densities and surface tension coefficient are discussed. Copyright (C) 1996 Elsevier Science Ltd RP Buyevich, YA (reprint author), NASA,AMES RES CTR,MOFFETT FIELD,CA 94035, USA. NR 18 TC 27 Z9 28 U1 1 U2 9 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, ENGLAND OX5 1GB SN 0009-2509 J9 CHEM ENG SCI JI Chem. Eng. Sci. PD NOV PY 1996 VL 51 IS 21 BP 4843 EP 4857 DI 10.1016/0009-2509(96)00323-5 PG 15 WC Engineering, Chemical SC Engineering GA VM905 UT WOS:A1996VM90500009 ER PT J AU Bauschlicher, CW AF Bauschlicher, CW TI The dissociation energies of FeF, FeCl, and FeBr and their positive ions SO CHEMICAL PHYSICS LA English DT Article ID GAUSSIAN-BASIS SETS; COUPLED-CLUSTER THEORY; CORRELATED MOLECULAR CALCULATIONS; ORBITAL BASIS-SETS; BINDING-ENERGIES; ELECTRON CORRELATION; TRANSITION-METALS; WAVE-FUNCTIONS; HARTREE-FOCK; ROW ATOMS AB Accurate dissociation energies are computed for FeF, FeCl, and FeBr and their positive ions using the coupled cluster approach in a large basis set and a correction based on CuCl, where then are accurate experimental results for comparison. While the computed IP for FeCl agrees with the recent experimental appearance potential, our best estimate for D-0 is significantly larger then the recent experimental determination. Our best estimates for the D, values of FeF, FeCl, and FeBr are 4.91 +/- 0.14, 3.73 +/- 0.14 eV, and 3.09 +/- 0.21 eV, respectively, and 4.51 +/- 0.14, 3.51 +/- 0.14, and 2.72 +/- 0.21 eV for the positive ions. The results obtained using B3LYP functional are in reasonable agreement with those obtained at higher levels of theory. RP Bauschlicher, CW (reprint author), NASA,AMES RES CTR,STC-230-3,MOFFETT FIELD,CA 94035, USA. NR 39 TC 31 Z9 31 U1 1 U2 3 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0301-0104 J9 CHEM PHYS JI Chem. Phys. PD NOV 1 PY 1996 VL 211 IS 1-3 BP 163 EP 169 DI 10.1016/0301-0104(96)00223-6 PG 7 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA VR360 UT WOS:A1996VR36000013 ER PT J AU Bauschlicher, CW AF Bauschlicher, CW TI The B(H-2)(n)-H-2 binding energies, for n=0-3 SO CHEMICAL PHYSICS LETTERS LA English DT Article ID WAVE-FUNCTIONS; BASIS-SETS; COMPLEXES; DIMER AB The complete basis set limit B-H-2 dissociation energy (D-e) is determined to be 133 cm(-1). This is in good agreement with the estimate made by Alexander. The optimal structures for B(H-2)(n)(n = 1-3) have the H-2 bond axes aligned with the open-shell B 2p orbital to maximize the B to H-2 sigma* donation. The H-2 bond midpoints and B atom all lie in a plane. For n = 4, the analogous structure is slightly above the most stable isomer, which adds an H-2 molecule above one pair of H-2 molecules in B(H-2)(3). This non-planar B(H-2)(4) structure is that recently deduced from the B-H-2 and H-2-H-2 potentials. The computed H-2 binding energies for n = 2-4 are between about 150 and 170 cm(-1) and are expected to be 5-10 cm(-1) too small. RP Bauschlicher, CW (reprint author), NASA, AMES RES CTR, STC-230-3, MOFFETT FIELD, CA 94035 USA. NR 16 TC 1 Z9 1 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 NOV 1 PY 1996 VL 261 IS 6 BP 637 EP 643 DI 10.1016/0009-2614(96)01002-0 PG 7 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA VP786 UT WOS:A1996VP78600006 ER PT J AU Stebbins, RT Bender, PL Folkner, WM AF Stebbins, RT Bender, PL Folkner, WM TI LISA data acquisition SO CLASSICAL AND QUANTUM GRAVITY LA English DT Article; Proceedings Paper CT Symposium on Fundamental Physics in Space (STEP, LISA and Other Space Projects) CY OCT 16-19, 1995 CL IMPERIAL COLL, LONDON, ENGLAND SP Imperial Coll, Phys Dept, Astrophys Grp, ESA, NASA, Ctr Natl Etudes Spatiales, Brit Natl Space Ctr, Particle Phys & Astron Res Council HO IMPERIAL COLL AB The method for measuring changes in the lengths of the three arms for the LISA gravitational-wave detector is described. Accurate phase measurements are required on signals with Doppler shifts of about I MHz for the two main arms of the interferometer, and up to 15 MHz for the third arm. This is accomplished by shifting the signal frequencies down to near 100 kHz, filtering and then timing zero crossings of the signals. The basic methods for correcting for the laser phase noise and for phase noise in the ultra-stable oscillators used to derive various radio frequencies are described briefly. The corrections are made on the spacecraft, before the data are telemetred to the ground. C1 CALTECH,JET PROP LAB,PASADENA,CA 91109. RP Stebbins, RT (reprint author), UNIV COLORADO,JOINT INST LAB ASTROPHYS,CB 440,BOULDER,CO 80309, USA. RI Stebbins, Robin/G-5009-2013 NR 4 TC 5 Z9 5 U1 0 U2 0 PU IOP PUBLISHING LTD PI BRISTOL PA TECHNO HOUSE, REDCLIFFE WAY, BRISTOL, ENGLAND BS1 6NX SN 0264-9381 J9 CLASSICAL QUANT GRAV JI Class. Quantum Gravity PD NOV PY 1996 VL 13 IS 11A SU S BP A285 EP A289 DI 10.1088/0264-9381/13/11A/038 PG 5 WC Astronomy & Astrophysics; Physics, Multidisciplinary; Physics, Particles & Fields SC Astronomy & Astrophysics; Physics GA VW313 UT WOS:A1996VW31300038 ER PT J AU Swanson, PN AF Swanson, PN TI Mini-STEP: A minimal satellite test of the equivalence principle experiment SO CLASSICAL AND QUANTUM GRAVITY LA English DT Article; Proceedings Paper CT Symposium on Fundamental Physics in Space (STEP, LISA and Other Space Projects) CY OCT 16-19, 1995 CL IMPERIAL COLL, LONDON, ENGLAND SP Imperial Coll, Phys Dept, Astrophys Grp, ESA, NASA, Ctr Natl Etudes Spatiales, Brit Natl Space Ctr, Particle Phys & Astron Res Council HO IMPERIAL COLL AB The Mini-STEP concept was conceived from a desire by NASA to reduce the cost of the satellite test of the equivalence principle (STEP) experiment below that of the already downsized Quick STEP concept. The goal was for the total cost, including payload, spacecraft, launch vehicle, reserves and operations, to be in the $50 million range. Stanford University and the Jet Propulsion Laboratory studied this simplified STEP concept between March and June 1995. A similar concept was developed in parallel by the European Space Agency (ESA) as an alternative to the M3 STEP mission. RP Swanson, PN (reprint author), CALTECH,JET PROP LAB,4800 OAK GROVE DR,PASADENA,CA 91109, USA. NR 0 TC 1 Z9 2 U1 0 U2 0 PU IOP PUBLISHING LTD PI BRISTOL PA TECHNO HOUSE, REDCLIFFE WAY, BRISTOL, ENGLAND BS1 6NX SN 0264-9381 J9 CLASSICAL QUANT GRAV JI Class. Quantum Gravity PD NOV PY 1996 VL 13 IS 11A SU S BP A143 EP A147 DI 10.1088/0264-9381/13/11A/019 PG 5 WC Astronomy & Astrophysics; Physics, Multidisciplinary; Physics, Particles & Fields SC Astronomy & Astrophysics; Physics GA VW313 UT WOS:A1996VW31300019 ER PT J AU Dybowski, C Gaffney, EJ Sayir, A Rabinowitz, MJ AF Dybowski, C Gaffney, EJ Sayir, A Rabinowitz, MJ TI Solid-state C-13 and Si-29 MAS NMR spectroscopy of silicon carbide SO COLLOIDS AND SURFACES A-PHYSICOCHEMICAL AND ENGINEERING ASPECTS LA English DT Article DE magic-angle spinning; NMR spectroscopy; silicon carbide AB The solid-state NMR spectroscopy of bulk and powdered silicon carbide, silicon carbide fibers, and materials fabricated with silicon carbide fibers is discussed. Specifically, the NMR spectroscopy of fiber mats indicates that the fabrication process produces silicon-carbon oxides and certain structural changes that are evident as small shifts of the resonances. C1 NASA,LEWIS RES CTR,CLEVELAND,OH 44135. RP Dybowski, C (reprint author), UNIV DELAWARE,DEPT CHEM & BIOCHEM,NEWARK,DE 19716, USA. NR 13 TC 10 Z9 10 U1 1 U2 3 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0927-7757 J9 COLLOID SURFACE A JI Colloid Surf. A-Physicochem. Eng. Asp. PD NOV 1 PY 1996 VL 118 IS 1-2 BP 171 EP 181 DI 10.1016/0927-7757(96)03735-1 PG 11 WC Chemistry, Physical SC Chemistry GA VR157 UT WOS:A1996VR15700016 ER PT J AU Fayyad, U PiatetskyShapiro, G Smyth, P AF Fayyad, U PiatetskyShapiro, G Smyth, P TI The KDD process for extracting useful knowledge from volumes of data SO COMMUNICATIONS OF THE ACM LA English DT Article C1 GTE LABS INC,WALTHAM,MA 02254. UNIV CALIF IRVINE,IRVINE,CA 92717. CALTECH,JET PROP LAB,PASADENA,CA 91125. RP Fayyad, U (reprint author), MICROSOFT CORP,RES,REDMOND,WA 98052, USA. NR 6 TC 471 Z9 507 U1 5 U2 40 PU ASSOC COMPUTING MACHINERY PI NEW YORK PA 1515 BROADWAY, NEW YORK, NY 10036 SN 0001-0782 J9 COMMUN ACM JI Commun. ACM PD NOV PY 1996 VL 39 IS 11 BP 27 EP 34 DI 10.1145/240455.240464 PG 8 WC Computer Science, Hardware & Architecture; Computer Science, Software Engineering; Computer Science, Theory & Methods SC Computer Science GA VR306 UT WOS:A1996VR30600009 ER PT J AU Fayyad, U Haussler, D Stolorz, P AF Fayyad, U Haussler, D Stolorz, P TI Mining scientific data SO COMMUNICATIONS OF THE ACM LA English DT Article ID HIDDEN MARKOV-MODELS; DIGITIZED POSS-II; DNA C1 CALTECH,JET PROP LAB,TECH GRP,PASADENA,CA 91125. UNIV CALIF SANTA CRUZ,SANTA CRUZ,CA 95064. NR 13 TC 49 Z9 53 U1 1 U2 5 PU ASSOC COMPUTING MACHINERY PI NEW YORK PA 1515 BROADWAY, NEW YORK, NY 10036 SN 0001-0782 J9 COMMUN ACM JI Commun. ACM PD NOV PY 1996 VL 39 IS 11 BP 51 EP 57 DI 10.1145/240455.240471 PG 7 WC Computer Science, Hardware & Architecture; Computer Science, Software Engineering; Computer Science, Theory & Methods SC Computer Science GA VR306 UT WOS:A1996VR30600013 ER PT J AU Patnaik, SN Gendy, AS Hopkins, DA Berke, L AF Patnaik, SN Gendy, AS Hopkins, DA Berke, L TI Weight minimization of flight components SO COMPUTERS & STRUCTURES LA English DT Article ID STRUCTURAL DESIGN AB Minimizing the weight of structural components of the Space Station launched onto orbit in a space shuttle can save cost, reduce the number of space shuttle missions and facilitate on-orbit fabrication. Traditional manual design of such components, although feasible, cannot represent a minimum weight condition. At NASA Lewis Research Center, a design capability called CometBoards (which is an acronym for comparative evaluation test bed of optimization and analysis routines for the design of structures) has been developed especially for the design optimization of such flight components of the Space Station-a spacer structure and a support system-illustrating the capability of CometBoards. These components are designed for loads and behavior constraints that arise from a variety of flight accelerations and maneuvers. The optimization process using CometBoards reduced the weights of the components by one third from those obtained with traditional manual design. This paper presents a brief overview of the design code CometBoards; and a description of the Space Station components, their design environments, behavior limitations and attributes of their optimum designs. Published by Elsevier Science Ltd C1 NASA,LEWIS RES CTR,CLEVELAND,OH 44135. RP Patnaik, SN (reprint author), OHIO AEROSP INST,CLEVELAND,OH 44142, USA. NR 48 TC 2 Z9 2 U1 0 U2 0 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, ENGLAND OX5 1GB SN 0045-7949 J9 COMPUT STRUCT JI Comput. Struct. PD NOV PY 1996 VL 61 IS 4 BP 597 EP 616 DI 10.1016/0045-7949(95)00443-2 PG 20 WC Computer Science, Interdisciplinary Applications; Engineering, Civil SC Computer Science; Engineering GA VJ669 UT WOS:A1996VJ66900002 ER PT J AU Danielson, KT Noor, AK Green, JS AF Danielson, KT Noor, AK Green, JS TI Computational strategies for tire modeling and analysis SO COMPUTERS & STRUCTURES LA English DT Article ID SHAPE-ANALYSIS; ALGORITHMS AB Computational strategies are presented for the modeling and analysis of tires in contact with pavement. A procedure is introduced for the simple and accurate determination of tire cross-sectional geometric characteristics from a digitally scanned image. Three new strategies for reducing the computational effort in the finite element solution of tire-pavement contact are also presented. These strategies take advantage of the observation that footprint loads do not usually stimulate a significant tire response away from the pavement contact region. The finite element strategies differ in their level of approximation and required amount of computer resources. The effectiveness of the strategies is demonstrated by numerical examples of frictionless and frictional contact of the Space Shuttle orbiter nose-gear tire. Both an in-house research code and a commercial finite element code are used in the numerical studies. Published by Elsevier Science Ltd C1 MORAVIAN COLL,DEPT COMP SCI,BETHLEHEM,PA 18018. RP Danielson, KT (reprint author), UNIV VIRGINIA,NASA,LANGLEY RES CTR,CTR ADV COMPUTAT TECHNOL,HAMPTON,VA 23681, USA. NR 43 TC 16 Z9 19 U1 0 U2 3 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, ENGLAND OX5 1GB SN 0045-7949 J9 COMPUT STRUCT JI Comput. Struct. PD NOV PY 1996 VL 61 IS 4 BP 673 EP 693 DI 10.1016/0045-7949(96)00051-X PG 21 WC Computer Science, Interdisciplinary Applications; Engineering, Civil SC Computer Science; Engineering GA VJ669 UT WOS:A1996VJ66900009 ER PT J AU Hellings, RW AF Hellings, RW TI Gravitational wave detectors in space SO CONTEMPORARY PHYSICS LA English DT Review AB In the next few years, we expect to see the beginning of a new branch of astronomy-gravitational wave astronomy. Space detectors, especially, will soon have the sensitivity to see the tiny changes in distance between separated masses that are produced by gravitational waves in Einstein's theory of General Relativity. One such space detector, named OMEGA, has been proposed to NASA as a future medium sized Explorer mission. This detector would be formed from six small miniprobes that are launched into high circular Earth orbit, two miniprobes at each of the vertices of a million-kilometre equilateral triangle. The probes track each other with lasers. By subtracting the measurements of the armlengths, a fine Michelson interferometer can be formed that will detect changes in distance of less than one picometre at time scales around 1000s. At this sensitivity, OMEGA will be able to detect gravitational waves from known galactic binary stars and from possible events involving the massive black holes that are expected to reside in the nuclei of many galaxies. C1 HARVEY MUDD COLL,DEPT PHYS,CLAREMONT,CA 91711. RP Hellings, RW (reprint author), CALTECH,JET PROP LAB,4800 OAK GROVE DR,PASADENA,CA 91109, USA. NR 4 TC 3 Z9 3 U1 0 U2 0 PU TAYLOR & FRANCIS LTD PI LONDON PA ONE GUNPOWDER SQUARE, LONDON, ENGLAND EC4A 3DE SN 0010-7514 J9 CONTEMP PHYS JI Contemp. Phys. PD NOV-DEC PY 1996 VL 37 IS 6 BP 457 EP 469 DI 10.1080/00107519608217536 PG 13 WC Physics, Multidisciplinary SC Physics GA VY600 UT WOS:A1996VY60000004 ER PT J AU McDonald, PV Basdogan, C Bloomberg, JJ Layne, CS AF McDonald, PV Basdogan, C Bloomberg, JJ Layne, CS TI Lower limb kinematics during treadmill walking after space flight: Implications for gaze stabilization SO EXPERIMENTAL BRAIN RESEARCH LA English DT Article DE walking; kinematics; stability; variability; space flight ID HEAD STABILIZATION; HUMAN LOCOMOTION AB We examined the lower limb joint kinematics observed during pre- and postflight treadmill walking performed by seven subjects from three Space Shuttle flights flown between March 1992 and February 1994. Basic temporal characteristics of the gait patterns, such as stride time and duty cycle, showed no significant changes after flight. Evaluation of phaseplane variability across the gait cycle suggests that postflight treadmill walking is more variable than preflight, but the response throughout the course of a cycle is joint dependent and, furthermore, the changes are subject dependent. However, analysis of the phaseplane variability at the specific locomotor events of heel strike and toe off indicated statistically significant postflight increases in knee variability at the moment of heel strike and significantly higher postflight hip joint variability at the moment of toe off. Nevertheless, the observation of component-specific variability was not sufficient to cause a change in the overall lower limb joint system stability, since there was no significant change in an index used to evaluate this at both toe off and heel strike. The implications of the observed lower limb kinematics for head and gaze control during locomotion are discussed in light of a hypothesized change in the energy attenuation capacity of the musculoskeletal system in adapting to weightlessness. C1 SO METHODIST UNIV, DEPT MECH ENGN, DALLAS, TX 75275 USA. NASA, LYNDON B JOHNSON SPACE CTR, SPACE BIOMED RES INST, HOUSTON, TX 77058 USA. RP McDonald, PV (reprint author), KRUG LIFE SCI, 1290 HERCULES DR, SUITE 120, HOUSTON, TX 77058 USA. RI Basdogan, Cagatay /H-5192-2011 OI Basdogan, Cagatay /0000-0002-6382-7334 NR 31 TC 37 Z9 37 U1 1 U2 3 PU SPRINGER PI NEW YORK PA 233 SPRING ST, NEW YORK, NY 10013 USA SN 0014-4819 J9 EXP BRAIN RES JI Exp. Brain Res. PD NOV PY 1996 VL 112 IS 2 BP 325 EP 334 PG 10 WC Neurosciences SC Neurosciences & Neurology GA VU120 UT WOS:A1996VU12000016 PM 8951400 ER PT J AU Bell, JH McLachlan, BG AF Bell, JH McLachlan, BG TI Image registration for pressure-sensitive paint applications SO EXPERIMENTS IN FLUIDS LA English DT Article AB Pressure-sensitive paint (PSP) data are generally derived by ratioing two images of a PSP-coated wind tunnel model. One image is taken at a known ''wind-off'' reference pressure while the other is taken at the test condition, in order to factor out the effects of nonuniform illumination and paint thickness. However, airloads on the model cause it to move during testing with respect to both the camera and the illumination source used to excite the PSP. Thus, the raw PSP images must be aligned, or registered, by means of a spatial transform. Once a proper ratioed image is obtained, image coordinates must be related to model coordinates so that pressure data can be obtained at the desired points on the model. This article compares several transforms used for image registration, and demonstrates the use of the projective equation of photogrammetry to relate model to image coordinates. An application in a small-scale wind tunnel test is shown, demonstrating mapping of pressure data to the three-dimensional model surface. RP Bell, JH (reprint author), NASA,AMES RES CTR,DESIGN CYCLE TECHNOL BRANCH,MAIL STOP 227-2,MOFFETT FIELD,CA 94035, USA. NR 17 TC 25 Z9 26 U1 0 U2 3 PU SPRINGER VERLAG PI NEW YORK PA 175 FIFTH AVE, NEW YORK, NY 10010 SN 0723-4864 J9 EXP FLUIDS JI Exp. Fluids PD NOV PY 1996 VL 22 IS 1 BP 78 EP 86 DI 10.1007/BF01893308 PG 9 WC Engineering, Mechanical; Mechanics SC Engineering; Mechanics GA VY588 UT WOS:A1996VY58800008 ER PT J AU Eick, MJ Grossl, PR Golden, DC Sparks, DL Ming, DW AF Eick, MJ Grossl, PR Golden, DC Sparks, DL Ming, DW TI Dissolution of a lunar basalt simulant as affected by pH and organic anions SO GEODERMA LA English DT Article DE lunar simulant; basalt; organic acids; dissolution ID AQUEOUS-SOLUTIONS; LABRADORITE FELDSPAR; SURFACE-CHEMISTRY; KINETICS; ACIDS; MECHANISM; MINERALS; QUARTZ; ALBITE; 25-DEGREES-C AB The dissolution of a lunar simulant (MLS-I) basalt was examined at 298 K; pH 3, 5, and 7; and in the presence of citrate and oxalate anions. The basalt was mined from an abandoned quarry in Duluth, Minnesota. The relative abundance of minerals in the basalt are plagioclase > pyroxene > olivine > ilmenite. The chemical composition and mineralogy of the basalt most closely resembles Apollo Il Mare soil, For most of the experiments the order of major ion release (Mg, Ca, Fe, Al, and Si) from the MLS-1 basalt was controlled by the solubility of its mineral components. The amount of major ion release followed the order Fe approximate to Mg > Si > Al > Ca. Deviations in this release order were related to the effect of the treatments on the quantity of MLS-1 basalt dissolved and the precipitation of secondary minerals, For the pH experiments dissolution followed a two-stage process. The first stage was characterized by a rapid rate of release of the major ions into solution, followed by a slower, more linear rate during the second stage. Rate coefficients were calculated from the linear portions of the rate curves and were inversely related to pH, The first stage was attributed to the dissolution of ultrafine particles created during the sample grinding process. During the second stage, dissolution occurred on the larger mineral surfaces, at higher energy sites (i,e. dislocations, twinning planes, fluid inclusions, etc), For the organic anion experiments, dissolution followed a one-stage parabolic process. Dissolution was greater in the presence of the citrate anion compared to the oxalate anion and decreased with a decrease in concentration, It is proposed that the organic anions accelerate the dissolution of the MLS-1 basalt through chemisorption and subsequent disruption of metal-oxygen bonds. The rate-limiting step of the reaction involves the diffusion of the cation-organic complex formed at thr mineral surface. C1 UTAH STATE UNIV,DEPT PLANTS SOILS & BIOMETEOROL,LOGAN,UT 84322. UNIV DELAWARE,DEPT PLANT & SOIL SCI,NEWARK,DE 19717. NASA,LYNDON B JOHNSON SPACE CTR,HOUSTON,TX 77058. RP Eick, MJ (reprint author), LOUISIANA STATE UNIV,CTR AGR,LOUISIANA AGR EXPT STN,DEPT AGRON,BATON ROUGE,LA 70803, USA. NR 47 TC 22 Z9 27 U1 3 U2 6 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0016-7061 J9 GEODERMA JI Geoderma PD NOV PY 1996 VL 74 IS 1-2 BP 139 EP 160 DI 10.1016/S0016-7061(96)00055-9 PG 22 WC Soil Science SC Agriculture GA VU899 UT WOS:A1996VU89900008 ER PT J AU Chao, Y Gangopadhyay, A Bryan, FO Holland, WR AF Chao, Y Gangopadhyay, A Bryan, FO Holland, WR TI Modeling the Gulf Stream system: How far from reality? SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID NORTH-ATLANTIC; OCEAN CIRCULATION; WORLD OCEAN; RESOLUTION; TRANSPORT AB Analyses of a primitive equation ocean model simulation of the Atlantic Ocean circulation at 1/6 degrees horizontal resolution are presented with a focus on the Gulf Stream region. Among many successful features of this simulation, this letter describes the Gulf Stream separation from the coast of North America near Cape Hatteras, meandering of the Gulf Stream between Cape Hatteras and the Grand Banks, and the vertical structure of temperature and velocity associated with the Gulf Stream. These results demonstrate significant improvement in modeling the Gulf Stream system using basin- to global-scale ocean general circulation models. Possible reasons responsible for the realistic Gulf Stream simulation are discussed, contrasting the major differences between the present model configuration and those of previous eddy-resolving studies. C1 NATL CTR ATMOSPHER RES,BOULDER,CO 80307. RP Chao, Y (reprint author), CALTECH,JET PROP LAB,4800 OAK GROVE DR,PASADENA,CA 91109, USA. RI Bryan, Frank/I-1309-2016 OI Bryan, Frank/0000-0003-1672-8330 NR 14 TC 38 Z9 38 U1 0 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD NOV 1 PY 1996 VL 23 IS 22 BP 3155 EP 3158 DI 10.1029/96GL03003 PG 4 WC Geosciences, Multidisciplinary SC Geology GA VQ924 UT WOS:A1996VQ92400022 ER PT J AU Ross, RJ Otterman, J Starr, DO Elliott, WP Angell, JK Susskind, J AF Ross, RJ Otterman, J Starr, DO Elliott, WP Angell, JK Susskind, J TI Regional trends of surface and tropospheric temperature and evening-morning temperature difference in northern latitudes: 1973-93 SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID AIR-TEMPERATURE AB Trends for the 21-year period 1973-1993 of temperatures at the surface and in the troposphere were analyzed from radiosonde observations in eight north-latitude regions. The seasonal consistency of the surface and tropospheric trends of temperature and evening-morning temperature difference was examined for these regions. In most seasons the surface temperature trends were positive in Eurasia and western N. America but were negative in central N. America and eastern Canada. The regions with sizable and statistically significant surface temperature trends usually had significant tropospheric trends up to 500 mb and sometimes to 300 mb. An exception was central Asia, where the strong warming was confined below 850 mb. The significant tropospheric trends showed a tendency to de crease in magnitude with height. Trends of the evening minus morning temperature difference were also analyzed in two sectors, Canada and Russia, where the radiosonde launches occurred at 5am and pm +/-2hrs. Trends were fairly consistent in sign between the surface and lower troposphere in both sectors and up to 300 mb over Canada. Most Canadian trends were significant and represented a decreasing range between evening and morning temperatures. Significant Russian trends were primarily in summer. C1 NASA,GODDARD SPACE FLIGHT CTR,ATMOSPHERES LAB,GREENBELT,MD 20771. RP Ross, RJ (reprint author), NOAA,AIR RESOURCES LAB,1315 E WEST HWY,SILVER SPRING,MD 20910, USA. NR 9 TC 19 Z9 20 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD NOV 1 PY 1996 VL 23 IS 22 BP 3179 EP 3182 DI 10.1029/96GL03076 PG 4 WC Geosciences, Multidisciplinary SC Geology GA VQ924 UT WOS:A1996VQ92400028 ER PT J AU Randall, CE Rusch, DW Olivero, JJ Bevilacqua, RM Poole, LR Lumpe, JD Fromm, MD Hoppel, KW Hornstein, JS Shettle, EP AF Randall, CE Rusch, DW Olivero, JJ Bevilacqua, RM Poole, LR Lumpe, JD Fromm, MD Hoppel, KW Hornstein, JS Shettle, EP TI An overview of POAM II aerosol measurements at 1.06 mu m SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID STRATOSPHERIC AEROSOL; OZONE AB We present aerosol measurements by the Polar Ozone and Aerosol Measurement (POAM) II instrument, from November 1993 through February 1996. Aerosol extinction profiles are in good agreement with coincident SAGE II measurements from 15 to 24 km. Extinction is continuing to decline since the eruption of Mt. Pinatubo. Seasonal variation in extinction in both hemispheres is examined on constant ground-referenced and tropopause-referenced altitude surfaces. Aerosol extinction peaks in the winter in the north outside the vortex. This also appears to occur in the south, but cannot be followed throughout the winter since FOAM II measurements occur entirely inside the vortex at this time. A summer maximum at 19 km and above in the south is observed when the extinction ratio outside the vortex is plotted at a constant tropopause-referenced altitude. This is not true for the north. We conclude that in late spring in the south FOAM II is sampling low extinction, vortex-processed air, or that an unidentified mechanism operates in the south, but not in the north. Signatures of polar stratospheric clouds (PSCs) are prevalent in the southern hemisphere data. PSCs are also observed in the northern hemisphere, but much less frequently. Evidence of enhanced diabatic descent in the polar vortex in both hemispheres is observed at 500 and 600 K. At 400 K the distinction between extinction ratios inside and outside the vortex in early winter is not as clear as at higher altitudes. C1 EMBRY RIDDLE AERONAUT UNIV,DAYTONA BEACH,FL 32114. USN,RES LAB,WASHINGTON,DC 20375. NASA,LANGLEY RES CTR,HAMPTON,VA 23681. CPI,FAIRFAX,VA 22031. RP Randall, CE (reprint author), UNIV COLORADO,ATMOSPHER & SPACE PHYS LAB,CAMPUS BOX 392,BOULDER,CO 80309, USA. RI Fromm, Michael/F-4639-2010; Randall, Cora/L-8760-2014 OI Randall, Cora/0000-0002-4313-4397 NR 13 TC 16 Z9 16 U1 1 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD NOV 1 PY 1996 VL 23 IS 22 BP 3195 EP 3198 DI 10.1029/96GL02921 PG 4 WC Geosciences, Multidisciplinary SC Geology GA VQ924 UT WOS:A1996VQ92400032 ER PT J AU Manney, GL Santee, ML Froidevaux, L Waters, JW Zurek, RW AF Manney, GL Santee, ML Froidevaux, L Waters, JW Zurek, RW TI Polar vortex conditions during the 1995-96 arctic winter: Meteorology and MLS ozone SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID STRATOSPHERE; TRANSPORT AB The 1995-96 northern hemisphere (NH) winter stratosphere was colder than in any of the previous 17 winters, with lower stratospheric temperatures continuously below the type 1 (primarily HNO3) polar stratospheric cloud (PSC) threshold for over 2 1/2 months. Upper tropospheric ridges in late Feb and early Mar 1996 led to the lowest observed NH lower stratospheric temperatures, and the latest observed NH temperatures below the type 2 (water ice) PSC threshold. Consistent with the unusual cold and chemical processing on PSCs, UARS MLS observed a greater decrease in lower stratospheric ozone (O-3) in 1995-96 than in any of the previous 4 NH winters. O-3 decreased throughout the vortex over an altitude range nearly as large as that typical of the southern hemisphere (SH). The decrease between late Dec 1995 and early Mar 1996 was similar to 2/3 of that over the equivalent SH period. As in other NH winters, temperatures in 1996 rose above the PSC threshold before the spring equinox, ending chemical processing in the NH vortex much earlier than is usual in the SH. A downward trend in column O-3 above 100 hPa during Jan and Feb 1996 appears to be related to the lower stratospheric O-3 depletion. RP Manney, GL (reprint author), CALTECH,JET PROP LAB,MAIL STOP 183-701,PASADENA,CA 91109, USA. NR 11 TC 63 Z9 63 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD NOV 1 PY 1996 VL 23 IS 22 BP 3203 EP 3206 DI 10.1029/96GL02453 PG 4 WC Geosciences, Multidisciplinary SC Geology GA VQ924 UT WOS:A1996VQ92400034 ER PT J AU Santee, ML Manney, GL Read, WG Froidevaux, L Waters, JW AF Santee, ML Manney, GL Read, WG Froidevaux, L Waters, JW TI Polar vortex conditions during the 1995-96 Arctic winter: MILS ClO and HNO3 SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID STRATOSPHERIC CIO; MLS OBSERVATIONS; OZONE; DEPLETION AB Microwave Limb Sounder (MLS) measurements of lower stratospheric ClO and HNO3 during the 1995-96 Arctic winter are presented. The 1995-96 Arctic winter was both colder and more persistently cold than usual, leading to an enhancement in lower stratospheric ClO of greater magnitude, vertical extent, and duration than previously observed in the Arctic. Vortex concentrations of HNO3 in mid-December were large due to diabatic descent. Trajectory calculations indicate that localized severe depletions of gas-phase HNO3 in mid-February and early March did not arise from entrainment of midlatitude air into the vortex and were therefore probably related to polar stratospheric cloud (PSC) formation. A strong correlation between temperature and gas-phase HNO3 was evident, consistent with recurring PSC condensation and evaporation cycles. RP Santee, ML (reprint author), CALTECH,JET PROP LAB,MAIL STOP 183-701,4800 OAK GROVE DR,PASADENA,CA 91109, USA. NR 12 TC 47 Z9 47 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD NOV 1 PY 1996 VL 23 IS 22 BP 3207 EP 3210 DI 10.1029/96GL02454 PG 4 WC Geosciences, Multidisciplinary SC Geology GA VQ924 UT WOS:A1996VQ92400035 ER PT J AU Ho, CM Mannucci, AJ Lindqwister, UJ Pi, X Tsurutani, BT AF Ho, CM Mannucci, AJ Lindqwister, UJ Pi, X Tsurutani, BT TI Global ionosphere perturbations monitored by the worldwide GPS network SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID TOTAL ELECTRON-CONTENT; F-REGION; STORM; NORTHERN AB For the first time, measurements from the Global Positioning System (GPS) worldwide network are employed to study the global ionospheric total electron content (TEC) changes during a magnetic storm (November 26, 1994). These measurements are obtained from more than 60 world-wide GPS stations which continuously receive dual-frequency signals. Based on the delays of the signals, we have generated high resolution global ionospheric maps (GIM) of TEC at 15 minute intervals. Using a differential method comparing storm time maps with quiet time maps, we find that significant TEC increases (the positive effect) are the major feature in the winter hemisphere during this storm (the maximum percent change relative to quiet times is about 150%). During this particular storm, there is almost no negative phase. A traveling ionospheric disturbance (TID) event is identified that propagates from the northern subauroral region to lower latitudes (down to about 30 degrees N) at a speed of similar to 460 m/s. This TID is coincident with significant increases in the TEC around the noon sector. We also find that another strong TEC enhancement occurs in the pre-dawn sector in the northern hemispheric subauroral latitudes, in the beginning of the storm main phase. This enhancement then spreads into almost the entire nightside. The nighttime TEC increase in the subauroral region is also noted in the southern hemisphere, but is less significant. These preliminary results indicate that the differential mapping method, which is based on GPS network measurements, appears to be a powerful tool for studying the global pattern and evolution process of the entire ionospheric perturbation. RP Ho, CM (reprint author), CALTECH,JET PROP LAB,4800 OAK GROVE DR,PASADENA,CA 91109, USA. RI Mannucci, Anthony/A-1349-2007 OI Mannucci, Anthony/0000-0003-2391-8490 NR 20 TC 111 Z9 125 U1 3 U2 9 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD NOV 1 PY 1996 VL 23 IS 22 BP 3219 EP 3222 DI 10.1029/96GL02763 PG 4 WC Geosciences, Multidisciplinary SC Geology GA VQ924 UT WOS:A1996VQ92400038 ER PT J AU Keim, ER Fahey, DW DelNegro, LA Woodbridge, EL Gao, RS Wennberg, PO Cohen, RC Stimpfle, RM Kelly, KK Hintsa, EJ Wilson, JC Jonsson, HH Dye, JE Baumgardner, D Kawa, SR Salawitch, RJ Proffitt, MH Loewenstein, M Podolske, JR Chan, KR AF Keim, ER Fahey, DW DelNegro, LA Woodbridge, EL Gao, RS Wennberg, PO Cohen, RC Stimpfle, RM Kelly, KK Hintsa, EJ Wilson, JC Jonsson, HH Dye, JE Baumgardner, D Kawa, SR Salawitch, RJ Proffitt, MH Loewenstein, M Podolske, JR Chan, KR TI Observations of large reductions in the NO/NOy ratio near the mid-latitude tropopause and the role of heterogeneous chemistry SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID IN-SITU MEASUREMENTS; LOWER STRATOSPHERE; SUPERSONIC AIRCRAFT; INSITU MEASUREMENTS; REACTIVE NITROGEN; REMOVAL; OH; AEROSOLS; EMISSION; RADICALS AB During the 1993 NASA Stratospheric Photochemistry, Aerosols and Dynamics Expedition (SPADE), anomalously low nitric oxide (NO) was found in a distinct sunlit layer located above the mid-latitude tropopause. The presence of a significant amount of reactive nitrogen (NOy) in the layer implies the systematic removal of NO, which Is without precedent in stratospheric irt situ observations. Large increases in measured chlorine monoxide (ClO) and the hydroperoxyl radical (HO2) also were observed in the layer. Heterogeneous reaction rate constants of chlorine nitrate (ClONO2) with hydrogen chloride (HCl) and H2O to form nitric acid (HNO3) on sulfate aerosol are enhanced in the NO removal layer by local increases in H2O and aerosol surface area. The associated conversion of NOx (= NO + NO2) to HNO3 is the most likely cause of the observed low NO and NOx/NOy values and high ClO values. C1 UNIV COLORADO,COOPERAT INST RES ENVIRONM SCI,BOULDER,CO 80309. HARVARD UNIV,DEPT CHEM,CAMBRIDGE,MA 02138. NATL CTR ATMOSPHER RES,BOULDER,CO 80307. NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. CALTECH,JET PROP LAB,PASADENA,CA 91109. NASA,AMES RES CTR,MOFFETT FIELD,CA 94035. UNIV DENVER,DEPT ENGN,DENVER,CO 80208. RP Keim, ER (reprint author), NOAA,AERON LAB,325 BROADWAY,BOULDER,CO 80303, USA. RI Salawitch, Ross/B-4605-2009; Cohen, Ronald/A-8842-2011; Wennberg, Paul/A-5460-2012; Kawa, Stephan/E-9040-2012; Gao, Ru-Shan/H-7455-2013; Fahey, David/G-4499-2013 OI Salawitch, Ross/0000-0001-8597-5832; Cohen, Ronald/0000-0001-6617-7691; Fahey, David/0000-0003-1720-0634 NR 21 TC 32 Z9 35 U1 0 U2 4 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD NOV 1 PY 1996 VL 23 IS 22 BP 3223 EP 3226 DI 10.1029/96GL02593 PG 4 WC Geosciences, Multidisciplinary SC Geology GA VQ924 UT WOS:A1996VQ92400039 ER PT J AU Suess, ST Smith, EJ AF Suess, ST Smith, EJ TI Latitudinal dependence of the radial IMF component: Coronal imprint SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID HELIOSPHERIC MAGNETIC-FIELD; MASS EJECTIONS; WHITE-LIGHT; SOLAR-WIND; MODEL AB Measurements by Ulysses have confirmed that there is no significant gradient with respect to heliomagnetic latitude in the radial component, B-r, of the interplanetary magnetic field. In the corona, the plasma beta is << 1, except directly above streamers, so longitudinal and latitudinal gradients in field strength will relax due to the transverse magnetic pressure gradient force as the solar wind carries magnetic flux away from the Sun. This happens quickly enough so that the field is essentially uniform by 5 - 10 R., apparently remaining so as it is carried to beyond 1 AU. Here, we illustrate the coronal relaxation with a qualitative physical argument and by reference to a detailed MHD simulation. C1 CALTECH,JET PROP LAB,PASADENA,CA 91109. RP Suess, ST (reprint author), NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,MAIL STOP 82,HUNTSVILLE,AL 35812, USA. NR 17 TC 52 Z9 52 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD NOV 1 PY 1996 VL 23 IS 22 BP 3267 EP 3270 DI 10.1029/96GL02908 PG 4 WC Geosciences, Multidisciplinary SC Geology GA VQ924 UT WOS:A1996VQ92400050 ER PT J AU Forsyth, RJ Balogh, A Smith, EJ Murphy, N McComas, DJ AF Forsyth, RJ Balogh, A Smith, EJ Murphy, N McComas, DJ TI The underlying magnetic field direction in Ulysses observations of the southern polar heliosphere - Reply SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article C1 JET PROP LAB,PASADENA,CA 91109. LOS ALAMOS NATL LAB,LOS ALAMOS,NM 87545. RP Forsyth, RJ (reprint author), UNIV LONDON IMPERIAL COLL SCI TECHNOL & MED,BLACKETT LAB,LONDON SW7 2BZ,ENGLAND. NR 5 TC 0 Z9 0 U1 0 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD NOV 1 PY 1996 VL 23 IS 22 BP 3281 EP 3282 DI 10.1029/96GL02381 PG 2 WC Geosciences, Multidisciplinary SC Geology GA VQ924 UT WOS:A1996VQ92400055 ER PT J AU Davies, AG AF Davies, AG TI Io's volcanism: Thermo-physical models of silicate lava compared with observations of thermal emission SO ICARUS LA English DT Article ID ERUPTION; FLOWS; VENUS; MAGMA; EARTH; MOON AB Analyses of thermal infrared outbursts from the jovian satellite Io indicate that at least some of these volcanic events are due to silicate lava. Analysis of the January 9, 1990 outburst indicates that this was an active eruption consisting of a large lava flow (with mass eruption rate of order 10(5) m(3) sec(-1)) and a sustained area at silicate liquidus temperatures. This is interpreted as a series of fire fountains along a rift zone. A possible alternative scenario is that of an overflowing lava lake with extensive fire fountaining. The January 9, 1990 event is unique as multispectral observations with respect to time were obtained. In this paper, a model is presented for the thermal energy lost by active and cooling silicate lava flows and lakes on Io. The model thermal emission is compared with Earth-based observations and Voyager IRIS data. The model (a) provides an explanation of the thermal anomalies on Io's surface; (b) provides constraints on flow behavior and extent and infers some how parameters; and (c) determines flow geometry and change in flow size with time, and the temperature of each part of the flow or lava lake surface as a function of its age. Models of heat output from active lava flows or inactive but recently emplaced lava flows or overturning lava lakes alone are unable to reproduce the observations. If the January 9, 1990 event is the emplacement of a lava how, the equivalent of 27 such events per year would yield a volume of material sufficient, if uniformly distributed, to resurface all of Io at a rate of 1 cm/year. (C) 1996 Academic Press, Inc. RP Davies, AG (reprint author), CALTECH,JET PROP LAB,4800 OAK GROVE DR,PASADENA,CA 91109, USA. NR 39 TC 72 Z9 72 U1 0 U2 4 PU ACADEMIC PRESS INC JNL-COMP SUBSCRIPTIONS PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 SN 0019-1035 J9 ICARUS JI Icarus PD NOV PY 1996 VL 124 IS 1 BP 45 EP 61 DI 10.1006/icar.1996.0189 PG 17 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA WE896 UT WOS:A1996WE89600004 ER PT J AU Pollack, JB Hubickyj, O Bodenheimer, P Lissauer, JJ Podolak, M Greenzweig, Y AF Pollack, JB Hubickyj, O Bodenheimer, P Lissauer, JJ Podolak, M Greenzweig, Y TI Formation of the giant planets by concurrent accretion of solids and gas SO ICARUS LA English DT Article ID ROSSELAND OPACITY TABLES; SOLAR NEBULA; COMET P/HALLEY; PLANETESIMALS; EVOLUTION; JUPITER; DISKS; ACCUMULATION; INSTABILITY; VELOCITIES AB New numerical simulations of the formation of the giant planets are presented, in which for the first time both the gas and planetesimal accretion rates are calculated in a self-consistent, interactive fashion. The simulations combine three elements: (1) three-body accretion cross sections of solids onto an isolated planetary embryo, (2) a stellar evolution code for the planet's gaseous envelope, and (3) a planetesimal dissolution code within the envelope, used to evaluate the planet's effective capture radius and the energy deposition profile of accreted material. Major assumptions include: The planet is embedded in a disk of gas and small planetesimals with locally uniform initial surface mass density, and planetesimals are not allowed to migrate into or out of the planet's feeding zone. All simulations are characterized by three major phases. During the first phase, the planet's mass consists primarily of solid material. The planetesimal accretion rate, which dominates that of gas, rapidly increases owing to runaway accretion, then decreases as the planet's feeding zone is depleted. During the second phase, both solid and gas accretion rates are small and nearly independent of time. The third phase, marked by runaway gas accretion, starts when the solid and gas masses are about equal. It is engendered by a strong positive feedback on the gas accretion rates, driven by the rapid contraction of the gaseous envelope and the rapid expansion of the outer boundary, which depends on the planet's total mass. The overall evolutionary time scale is generally determined by the length of the second phase. The actual rates at which the giant planets accreted small planetesimals is probably intermediate between the constant rates assumed in most previous studies and the highly variable rates used here. Within the context of the adopted model of planetesimal accretion, the joint constraints of the time scale for dissipation of the solar nebula and the current high-Z masses of the giant planets lead to estimates of the initial surface density (sigma(init)) of planetesimals in the outer region of the solar nebula. The results show that sigma(init) approximate to 10 g cm(-2) near Jupiter's orbit and that sigma(init) proportional to a(-2), where a is the distance from the Sun. These values are a factor of 3 to 4 times as high as that of the ''minimum-mass'' solar nebula at Jupiter's distance and a factor of 2 to 3 times as high at Saturn's distance. The estimates for the formation time of Jupiter and Saturn are 1 to 10 million years, whereas those for Uranus fall in the range 2 to 16 million years. These estimates follow from the properties of our Solar System and do not necessarily apply to giant planets in other planetary systems. (C) 1996 Academic Press, Inc. C1 NASA, AMES RES CTR, DIV SPACE SCI, MOFFETT FIELD, CA 94035 USA. UNIV CALIF SANTA CRUZ, UNIV CALIF OBSERV, LICK OBSERV, SANTA CRUZ, CA 95064 USA. SUNY STONY BROOK, DEPT EARTH & SPACE SCI, ASTRON PROGRAM, STONY BROOK, NY 11794 USA. TEL AVIV UNIV, DEPT GEOPHYS & PLANETARY SCI, IL-69978 RAMAT AVIV, ISRAEL. NR 47 TC 1431 Z9 1442 U1 8 U2 55 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 NOV PY 1996 VL 124 IS 1 BP 62 EP 85 DI 10.1006/icar.1996.0190 PG 24 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA WE896 UT WOS:A1996WE89600005 ER PT J AU Mitchell, DL Ostro, SJ Hudson, RS Rosema, KD Campbell, DB Velez, R Chandler, JF Shapiro, II Giorgini, JD Yeomans, DK AF Mitchell, DL Ostro, SJ Hudson, RS Rosema, KD Campbell, DB Velez, R Chandler, JF Shapiro, II Giorgini, JD Yeomans, DK TI Radar observations of asteroids 1 Ceres, 2 Pallas, and 4 Vestal SO ICARUS LA English DT Article ID SPECKLE INTERFEROMETRY; IMAGES; SHAPE; POLE; SURFACE; SCATTERING; ALBEDO; SIZE; MARS; METEORITES AB Asteroids 1 Ceres, 2 Pallas, and 4 Vesta were observed with the 13-cm Arecibo radar and the 3.5-cm Goldstone radar during several apparitions between 1981 and 1995, These observations help to characterize the objects' surface properties. Echoes from Cere;: and Pallas are similar to 95% polarized (mu(C) = sigma(SC/)sigma(OC) approximate to 0.05) in the sense expected for specular (mirror) reflection yet broadly distributed in Doppler frequency, thus revealing surfaces that are smoother than the Moon at decimeter scales but much rougher (rms slopes > 20 degrees) on larger scales. Slopes on Ceres appear to be somewhat higher when viewed with the 3.5-cm wavelength, a trend that is observed for the terrestrial planets and the Moon, In contrast, echoes from Vesta are significantly depolarized, indicating substantial near-surface complexity at scales near 13 cm (mu(C) = 0.24 +/- 0.04) and 3.5 cm (mu(C) = 0.32 +/- 0.04), which is probably a consequence of Vesta's relatively strong basaltic surface material and may be a signature of large impact features inferred to be present on the surface. The low radar albedos of Ceres (<(sigma)over cap>(OC) = 0.042 +/- 0.006) and Pallas (<(sigma)over cap>(OC) = 0.075 +/- 0.011) are in the range expected for surfaces with a carbonaceous chondrite mineralogy. Pallas' distinctly higher albedo implies a similar to 35% higher surface density, which could result from a lower regolith porosity and/or a higher specific gravity (zero-porosity density), Given a porosity of 45%, the specific gravities of the surface materials on Ceres and Pallas would be similar to 2.3 and similar to 3.0 g cm(-3), respectively, which would be consistent with (1) the presence of an additional silicate component on Pallas' surface (as inferred from spectroscopic observations) and (2) recent mass estimates, which suggest a higher mean (volume-averaged) density for Pallas than for Ceres. (C) 1996 Academic Press, Inc. C1 WASHINGTON STATE UNIV,SCH ELECT ENGN & COMP SCI,PULLMAN,WA 99164. CORNELL UNIV,NATL ASTRON & IONOSPHERE CTR,ITHACA,NY 14853. NATL ASTRON & IONOSPHERE CTR,ARECIBO OBSERV,ARECIBO,PR 00613. HARVARD SMITHSONIAN CTR ASTROPHYS,CAMBRIDGE,MA 02138. RP Mitchell, DL (reprint author), CALTECH,JET PROP LAB,4800 OAK GROVE DR,PASADENA,CA 91109, USA. NR 78 TC 34 Z9 34 U1 1 U2 6 PU ACADEMIC PRESS INC JNL-COMP SUBSCRIPTIONS PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 SN 0019-1035 J9 ICARUS JI Icarus PD NOV PY 1996 VL 124 IS 1 BP 113 EP 133 DI 10.1006/icar.1996.0193 PG 21 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA WE896 UT WOS:A1996WE89600008 ER PT J AU Kryszczynska, A Colas, F Berthier, J Michalowski, T Pych, W AF Kryszczynska, A Colas, F Berthier, J Michalowski, T Pych, W TI CCD photometry of seven asteroids: New spin axis and shape determinations SO ICARUS LA English DT Article ID MAIN BELT ASTEROIDS; PHOTOELECTRIC PHOTOMETRY; LIGHTCURVE OBSERVATIONS; POLE AB New photometric observations of 31 Euphrosyne, 76 Freia, 196 Philomela, 218 Bianca, 291 Alice, 376 Geometria, and 5702 Morando carried out at Pic du Midi Observatory (France) and in Ostrowik (Poland) in 1994 are presented. The preliminary pole and shape determinations of 218, 291, and 376 are presented. New lightcurves of 31 and 196 allowed us to recalculate values for its poles, shapes, and sidereal periods. The first lightcurve of 5702 allowed us to estimate its synodical period. (C) 1996 Academic Press, Inc. C1 BUR LONGITUDES,F-75014 PARIS,FRANCE. CALTECH,JET PROP LAB,PASADENA,CA 91109. UNIV WARSAW,ASTRON OBSERV,PL-00478 WARSAW,POLAND. RP Kryszczynska, A (reprint author), ADAM MICKIEWICZ UNIV POZNAN,ASTRON OBSERV,SLONECZNA 36,PL-60286 POZNAN,POLAND. NR 27 TC 11 Z9 11 U1 0 U2 1 PU ACADEMIC PRESS INC JNL-COMP SUBSCRIPTIONS PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 SN 0019-1035 J9 ICARUS JI Icarus PD NOV PY 1996 VL 124 IS 1 BP 134 EP 140 DI 10.1006/icar.1996.0194 PG 7 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA WE896 UT WOS:A1996WE89600009 ER PT J AU Durisen, RH Bode, PW Dyck, SG Cuzzi, JN Dull, JD White, JC AF Durisen, RH Bode, PW Dyck, SG Cuzzi, JN Dull, JD White, JC TI Ballistic transport in planetary ring systems due to particle erosion mechanisms .3. Torques and mass loading by meteoroid impacts SO ICARUS LA English DT Article ID DENSE COLLISIONAL SYSTEMS; SATURNS RINGS; NUMERICAL SIMULATIONS; DUST DATA; BOMBARDMENT; EVOLUTION AB The bombardment of planetary rings by meteoroids has several important consequences for ring structure. In earlier papers, we studied ballistic transport, the net radial transport of mass and angular momentum due to exchanges of meteoroid impact ejecta. Several additional mechanisms which can affect ring structure are introduced by the systematic deposition of meteoroid mass and angular momentum and other nonconservative processes. We refer to these collectively as ''direct'' effects of meteoroids. They include the mass deposition itself, radial drifts due to mass loading and/or loss of ejecta angular momentum, and radial drifts due to torques caused by asymmetric absorption of the meteoroids. In this paper, we calculate deposition rates and radial drifts for Saturn's rings as a function of ring radius and optical depth. We then include them in our ballistic transport code and examine their influence on simulations of the B ring inner-edge region. In all cases, we find that, of the three direct meteoroid effects, it is the radial drifts due to mass loading or angular momentum loss which dominate the additional contributions. For input parameters which give the best fit to structures actually observed near the inner B ring edge, the direct effects are relatively negligible, except for a secular inward drift of the edge and an additional constraint on the allowable range of various uncertain physical input parameters. Our conclusions in earlier papers about the ability of ballistic transport to explain many of the characteristic inner-edge structures are unaffected. Although locally unimportant, the radial drifts due to mass loading can cause major portions of Saturn's ring system to fall into Saturn within a Solar System lifetime. The problem is most severe for the C ring, which should drift into Saturn in approximately a few x 10(8) years. (C) 1996 Academic Press, Inc. C1 MAX PLANCK INST EXTRATERR PHYS,D-85740 GARCHING,GERMANY. MIT,DEPT PHYS,CAMBRIDGE,MA 02139. NASA,AMES RES CTR,DIV SPACE SCI,MOFFETT FIELD,CA 94035. MIDDLE TENNESSEE STATE UNIV,DEPT PHYS & ASTRON,MURFREESBORO,TN 37132. RP Durisen, RH (reprint author), INDIANA UNIV,DEPT ASTRON,BLOOMINGTON,IN 47405, USA. NR 37 TC 18 Z9 18 U1 0 U2 0 PU ACADEMIC PRESS INC JNL-COMP SUBSCRIPTIONS PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 SN 0019-1035 J9 ICARUS JI Icarus PD NOV PY 1996 VL 124 IS 1 BP 220 EP 236 DI 10.1006/icar.1996.0200 PG 17 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA WE896 UT WOS:A1996WE89600015 ER PT J AU Vilas, F Larson, SM Stockstill, KR Gaffey, MJ AF Vilas, F Larson, SM Stockstill, KR Gaffey, MJ TI Unraveling the zebra: Clues to the Iapetus dark material composition SO ICARUS LA English DT Article ID SOLAR-SYSTEM; SPECTRAL REFLECTANCE; ASTEROIDS; LAPETUS; SPECTROPHOTOMETRY; BELT; PHOTOMETRY; ORIGIN; MATTER; SATURN AB A linear mixing model has been used to separate the high-resolution visible/near-infrared reflectance spectrum of the Iapetus dark material from the spectra of the leading and trailing sides of Iapetus. A distinct absorption feature centered at 0.67 mu m is apparent in the spectrum. A slight inflection covering 0.4 to 0.6 mu m and a change in slope near 0.73 mu m suggesting the lower wavelength edge of an absorption are also present. These absorption features are attributed to the (6)A(1) --> T-4(2)(G) and (6)A(1)--> T-4(1)(G) charge transfer transitions in minerals such as goethite and hematite that are products of the aqueous alteration of anhydrous silicates. We confirm the strong, positive spectral slope attributed to organic material. (C) 1996 Academic Press, Inc. C1 UNIV ARIZONA,LUNAR & PLANETARY LAB,TUCSON,AZ 85721. LUNAR & PLANETARY INST,HOUSTON,TX 77058. RENSSELAER POLYTECH INST,DEPT EARTH & ENVIRONM SCI,TROY,NY 14853. RP Vilas, F (reprint author), NASA,LYNDON B JOHNSON SPACE CTR,SN3,HOUSTON,TX 77058, USA. NR 35 TC 28 Z9 28 U1 0 U2 0 PU ACADEMIC PRESS INC JNL-COMP SUBSCRIPTIONS PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 SN 0019-1035 J9 ICARUS JI Icarus PD NOV PY 1996 VL 124 IS 1 BP 262 EP 267 DI 10.1006/icar.1996.0202 PG 6 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA WE896 UT WOS:A1996WE89600017 ER PT J AU Mellon, MT AF Mellon, MT TI Limits on the CO2 content of the Martian polar deposits SO ICARUS LA English DT Article ID THERMAL-CONDUCTIVITY; SUMMER TEMPERATURES; TERRESTRIAL PLANETS; LAYERED DEPOSITS; WATER-VAPOR; GROUND ICE; EARLY MARS; EVOLUTION; HISTORY; STABILITY AB It has recently been suggested that large quantities of CO2 could be sequestered within the martian polar deposits as CO2 ice or CO2 clathrate hydrate, stabilized against sublimation by a non-porous overburden of water ice. I investigate the phase stability of CO2-bearing polar ices and place limits on the quantity of CO? that can be sequestered. The magnitude of this limitation follows from CO2-bearing ices having thermal conductivities on the order of 5 to 6 times smaller than that of water ice, producing a higher geothermal gradient. Results indicate that only under favorable, and probably unrealistic, conditions an upper limit of 112 mbar of CO2 can be sequestered as CO2 clathrate or 254 mbar as CO2 ice in the north polar deposit. More realistic conditions will limit CO2 to no more than a few 10s of mbar. In either case, less CO2 is also allowed and none is required by existing observations. The south polar deposit probably consists of a similar composition, but thinner deposits make placing limits difficult. Limited quantities of CO2 in the polar regions primarily implies that large amounts of CO2 are not released at high obliquity, reducing the magnitude of periodic climate change. In addition, climate-evolution models that predict large CO2-bearing caps at present should be rejected, favoring models that do not predict extensive CO2-bearing ice deposits. (C) 1996 Academic Press, Inc. RP Mellon, MT (reprint author), NASA,AMES RES CTR,MOFFETT FIELD,CA 94035, USA. RI Mellon, Michael/C-3456-2016 NR 63 TC 65 Z9 65 U1 0 U2 7 PU ACADEMIC PRESS INC JNL-COMP SUBSCRIPTIONS PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 SN 0019-1035 J9 ICARUS JI Icarus PD NOV PY 1996 VL 124 IS 1 BP 268 EP 279 DI 10.1006/icar.1996.0203 PG 12 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA WE896 UT WOS:A1996WE89600018 ER PT J AU Hillier, J Helfenstein, P Veverka, J AF Hillier, J Helfenstein, P Veverka, J TI Latitude variations of the polar caps on Ganymede SO ICARUS LA English DT Article ID BIDIRECTIONAL REFLECTANCE SPECTROSCOPY; PHOTOMETRIC ANALYSIS; CALLISTO AB We have modeled Ganymede's polar regions as a frost layer overlying typical non-polar materials using a two-layer photometric model. The optical depth of the overlying layer is found to increase from a few tenths at the cap boundary to more than four at the poles. Such an increase is consistent with the predictions of Johnson's (1985) sputtering model but not with those of thermal migration models of the formation of Ganymede's polar caps. If the frost forms a distinct layer, it must be physically thin-on the order of millimeters or less-particularly near the cap boundary. Therefore, the mechanism responsible for its formation must be ongoing since impact gardening would destroy such a thin layer on short time scales. Interestingly, the photometric properties of the layer are similar to those of the surface of Europa. (C) 1996 Academic Press, Inc. C1 CORNELL UNIV,CTR RADIOPHYS & SPACE RES,ITHACA,NY 14853. RP Hillier, J (reprint author), CALTECH,JET PROP LAB,4800 OAK GROVE DR,MS 183-501,PASADENA,CA 91109, USA. NR 17 TC 8 Z9 8 U1 1 U2 2 PU ACADEMIC PRESS INC JNL-COMP SUBSCRIPTIONS PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 SN 0019-1035 J9 ICARUS JI Icarus PD NOV PY 1996 VL 124 IS 1 BP 308 EP 317 DI 10.1006/icar.1996.0206 PG 10 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA WE896 UT WOS:A1996WE89600021 ER PT J AU Hanner, MS Lynch, DK Russell, RW Hackwell, JA Kellogg, R Blaney, D AF Hanner, MS Lynch, DK Russell, RW Hackwell, JA Kellogg, R Blaney, D TI Mid-infrared spectra of comets P/Borrelly, P/Faye, and P/Schaumasse SO ICARUS LA English DT Article ID SILICATE EMISSION FEATURE; TELESCOPE; OLIVINE; DUST AB A 10 mu m silicate emission feature has been discovered in the spectra of comets P/Borrelly and P/Faye at R similar to 1.5 AU. These are the first short period comets in which silicate emission has definitely been detected. The broad emission features are about 25% above the continuum. No emission feature was present in the spectrum of P/Schaumasse; it is possible that the nucleus of P/Schaumasse was directly detected. If all of the observed flux originated from the nucleus, then the effective radius is about 3 km; the observed color temperature is consistent with a rapidly rotating nucleus. We present models that show how the shape of the silicate feature can depend on the way in which silicate and absorbing material are mixed in the grains. (C) 1996 Academic Press, Inc. C1 AEROSP CORP,LOS ANGELES,CA 90009. RP Hanner, MS (reprint author), CALTECH,JET PROP LAB,MS 183-501,PASADENA,CA 91109, USA. NR 20 TC 34 Z9 35 U1 0 U2 2 PU ACADEMIC PRESS INC JNL-COMP SUBSCRIPTIONS PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 SN 0019-1035 J9 ICARUS JI Icarus PD NOV PY 1996 VL 124 IS 1 BP 344 EP 351 DI 10.1006/icar.1996.0209 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA WE896 UT WOS:A1996WE89600024 ER PT J AU Shieh, LS Wang, WM Sunkel, JW AF Shieh, LS Wang, WM Sunkel, JW TI Digital redesign of cascaded analogue controllers for sampled-data interval systems SO IEE PROCEEDINGS-CONTROL THEORY AND APPLICATIONS LA English DT Article DE digital redesign; cascaded system; observer; sampled-data systems; uncertain systems ID STABILITY AB The paper presents a new method for the digital redesign of cascaded analogue controllers for continuous-time parametric interval systems. The bilinear and inverse-bilinear approximation method is developed to carry out discretisation of the predesigned cascaded analogue controller, taking into account intersample behaviour and implementation errors. A dual concept of the proposed digital redesign method is utilised to construct a new pseudodigital observer such that the estimated states of the digitally redesigned digital observer closely match those of the original continuous-time observer at the sampling instants, Using the newly digitally redesigned observer based controllers, the resulting dynamic states of the digitally controlled cascaded sampled-data interval systems are able to closely match those of the original analogously controlled cascaded continuous-time parametric interval systems. C1 NASA,LYNDON B JOHNSON SPACE CTR,AEROSCI & FLIGHT MECH DIV,HOUSTON,TX 77058. RP Shieh, LS (reprint author), UNIV HOUSTON,DEPT ELECT & COMP ENGN,HOUSTON,TX 77204, USA. NR 30 TC 14 Z9 14 U1 0 U2 1 PU IEE-INST ELEC ENG PI HERTFORD PA MICHAEL FARADAY HOUSE SIX HILLS WAY STEVENAGE, HERTFORD, ENGLAND SG1 2AY SN 1350-2379 J9 IEE P-CONTR THEOR AP JI IEE Proc.-Control Theory Appl. PD NOV PY 1996 VL 143 IS 6 BP 489 EP 498 DI 10.1049/ip-cta:19960820 PG 10 WC Automation & Control Systems; Engineering, Electrical & Electronic; Instruments & Instrumentation SC Automation & Control Systems; Engineering; Instruments & Instrumentation GA WE405 UT WOS:A1996WE40500002 ER PT J AU Mathews, GJ AF Mathews, GJ TI Visualizing space science data in 3D SO IEEE COMPUTER GRAPHICS AND APPLICATIONS LA English DT Article RP Mathews, GJ (reprint author), NASA,GODDARD SPACE FLIGHT CTR,NATL SPACE SCI DATA CTR,MAILSTOP 633,GREENBELT,MD 20771, USA. NR 4 TC 1 Z9 1 U1 0 U2 0 PU IEEE COMPUTER SOC PI LOS ALAMITOS PA 10662 LOS VAQUEROS CIRCLE, PO BOX 3014, LOS ALAMITOS, CA 90720-1264 SN 0272-1716 J9 IEEE COMPUT GRAPH JI IEEE Comput. Graph. Appl. PD NOV PY 1996 VL 16 IS 6 BP 6 EP 9 DI 10.1109/38.544066 PG 4 WC Computer Science, Software Engineering SC Computer Science GA VP677 UT WOS:A1996VP67700002 ER PT J AU Million, S Shah, B Hinedi, S AF Million, S Shah, B Hinedi, S TI Comparison of two maximal ratio combining techniques in antenna arraying SO IEEE TRANSACTIONS ON COMMUNICATIONS LA English DT Article ID SPACE AB When signals from a user (fixed or mobile) are received at multiple antennas, the signals can be arrayed to increase the signal-to-noise ratio (SNR) of the received signal. This article describes two maximal ratio combining techniques referred to as full spectrum combining (FSC) and complex symbol combining (CSC), and then compares them in terms of the achievable arraying gain. Although the performance of these techniques is derived for the case of binary phase shift keying (BPSK) signalling in an additive white Gaussian noise channel, the analytical techniques here are applicable to other modulations and channels. The paper also addresses the use of symbol SNR degradation and symbol SNR loss as system performance measures. It is shown that degradation and loss are equal at weak signal levels but degradation is a lower bound for loss when the signal is strong. RP Million, S (reprint author), CALTECH,JET PROP LAB,4800 OAK GROVE DR,PASADENA,CA 91109, USA. NR 7 TC 0 Z9 1 U1 0 U2 1 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 SN 0090-6778 J9 IEEE T COMMUN JI IEEE Trans. Commun. PD NOV PY 1996 VL 44 IS 11 BP 1599 EP 1609 DI 10.1109/26.544477 PG 11 WC Engineering, Electrical & Electronic; Telecommunications SC Engineering; Telecommunications GA VU309 UT WOS:A1996VU30900027 ER PT J AU Hooker, SB Brown, JW AF Hooker, SB Brown, JW TI Dipole rings and vortex interactions of the Brazil current SO IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING LA English DT Article ID GULF-STREAM RINGS; WARM-CORE RING; COALESCENCE; DYNAMICS; MEXICO AB A reexamination of satellite-derived sea surface temperature imagery reveals many examples of Brazil Current rings, both warm and cold, in dipole configurations, The dynamical significance of the dipole model is established by considering the interaction of a cold (cyclonic) eddy with a warm (anticyclonic) ring. The ring is shown to exist as a dipole for about 60 days, or two rotation periods based on its original rotation rate of approximately 12 degrees per day, The observed interaction of the dipole ring with a solitary (or monopole) cold eddy is complicated, but results in the two vortices coalescing, The latter point is particularly important, since coalescence between two eddies with opposing vorticities cannot occur if they are both monopole - one of them has to be a dipole, After coalescence, the rotation of the dipole ring temporarily reverses due to the addition of cyclonic vorticity, but the original rotation of the dipole is reestablished after an adjustment phase. C1 UNIV MIAMI, ROSENSTIEL SCH MARINE & ATMOSPHER SCI, MPO, MIAMI, FL 33149 USA. RP NASA, GODDARD SPACE FLIGHT CTR, LAB HYDROSPHER PROC, OCEANS & ICE BRANCH, CODE 971, GREENBELT, MD 20771 USA. RI Hooker, Stanford/E-2162-2012 NR 20 TC 5 Z9 5 U1 0 U2 1 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI PISCATAWAY PA 445 HOES LANE, PISCATAWAY, NJ 08855-4141 USA SN 0196-2892 EI 1558-0644 J9 IEEE T GEOSCI REMOTE JI IEEE Trans. Geosci. Remote Sensing PD NOV PY 1996 VL 34 IS 6 BP 1323 EP 1330 DI 10.1109/36.544561 PG 8 WC Geochemistry & Geophysics; Engineering, Electrical & Electronic; Remote Sensing; Imaging Science & Photographic Technology SC Geochemistry & Geophysics; Engineering; Remote Sensing; Imaging Science & Photographic Technology GA VW814 UT WOS:A1996VW81400004 ER PT J AU Kiely, AB Dolinar, SJ McEliece, RJ Ekroot, LL Lin, W AF Kiely, AB Dolinar, SJ McEliece, RJ Ekroot, LL Lin, W TI Trellis decoding complexity of linear block codes SO IEEE TRANSACTIONS ON INFORMATION THEORY LA English DT Article; Proceedings Paper CT 32nd Annual Allerton Conference on Communication, Control, and Computing CY OCT, 1994 CL ALLERTON, IL DE trellis decoding; block codes; decoding complexity; minimal trellises; dimension/length profiles ID GENERALIZED HAMMING WEIGHTS; BCH CODES AB In this partially tutorial paper, we examine minimal trellis representations of linear block codes and analyze several measures of trellis complexity: maximum state and edge dimensions, total span length, and total vertices, edges and mergers. We obtain bounds on these complexities as extensions of well-known dimension/length profile (DLP) bounds, Codes meeting these bounds minimize all the complexity measures simultaneously; conversely, a code attaining the bound for total span length, vertices, or edges, must likewise attain it for all the others, We define a notion of ''uniform'' optimality that embraces different domains of optimization, such as different permutations of a code or different codes with the same parameters, and we give examples of uniformly optimal codes and permutations, We also give some conditions that identify certain cases when no code or permutation can meet the bounds, In addition to DLP-based bounds, we derive new inequalities relating one complexity measure to another, which can be used in conjunction with known. bounds on one measure to imply bounds on the others, As an application, we infer new bounds on maximum state and edge complexity and on total vertices and edges from bounds on span lengths. C1 CALTECH,DEPT ELECT ENGN,PASADENA,CA 91109. RP Kiely, AB (reprint author), CALTECH,JET PROP LAB,4800 OAK GROVE DR,PASADENA,CA 91109, USA. NR 28 TC 19 Z9 19 U1 0 U2 0 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 SN 0018-9448 J9 IEEE T INFORM THEORY JI IEEE Trans. Inf. Theory PD NOV PY 1996 VL 42 IS 6 BP 1687 EP 1697 DI 10.1109/18.556665 PN 1 PG 11 WC Computer Science, Information Systems; Engineering, Electrical & Electronic SC Computer Science; Engineering GA WB184 UT WOS:A1996WB18400003 ER PT J AU McManus, JW Bynum, WL AF McManus, JW Bynum, WL TI Design and analysis techniques for concurrent blackboard systems SO IEEE TRANSACTIONS ON SYSTEMS MAN AND CYBERNETICS PART A-SYSTEMS AND HUMANS LA English DT Article AB This paper gives a Formal Model for Blackboard Systems that provides a consistent method for describing a blackboard system, The Formal Model describes the basic components of a blackboard system and how the components interact, A set of blackboard system design tools has been developed and validated for implementing systems that are expressed using the Formal Model, The tools are used to test and refine a proposed blackboard system design before the design is implemented, The set of blackboard system design tools consists of a Knowledge Source Organizer, a Knowledge Source Input/Output Connectivity Analyzer, a validated Blackboard System Simulation Model, and a Blackboard system Code Generator. The lack of design and analysis tools has hindered the full realization of the concurrency inherent in the blackboard problem-solving model, Use of a centralized control mechanism and knowledge source contention in accessing the blackboard have restricted the concurrency possible in previous systems, Using the design, simulation, and analysis tools, a fast, efficient, and powerful concurrent object-oriented blackboard system has been developed. C1 COLL WILLIAM & MARY,DEPT COMP SCI,WILLIAMSBURG,VA 23187. RP McManus, JW (reprint author), NASA,LANGLEY RES CTR,HAMPTON,VA 23665, USA. NR 28 TC 8 Z9 11 U1 1 U2 1 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 SN 1083-4427 J9 IEEE T SYST MAN CY A JI IEEE Trans. Syst. Man Cybern. Paart A-Syst. Hum. PD NOV PY 1996 VL 26 IS 6 BP 669 EP 680 DI 10.1109/3468.541328 PG 12 WC Computer Science, Cybernetics; Computer Science, Theory & Methods SC Computer Science GA VP078 UT WOS:A1996VP07800001 ER PT J AU Chatterji, GB Sridhar, B AF Chatterji, GB Sridhar, B TI Discrete range clustering using Monte Carlo methods SO IEEE TRANSACTIONS ON SYSTEMS MAN AND CYBERNETICS PART A-SYSTEMS AND HUMANS LA English DT Article ID OPTIMIZATION; GUIDANCE; FLIGHT AB For automatic obstacle avoidance guidance during rotorcraft low altitude flight a reliable model of the nearby environment is needed. Such a model may be constructed by applying surface fitting techniques to the dense range map obtained by active sensing using radars. However, for covertness passive sensing techniques using electro-optic sensors is desirable. As opposed to the dense range map obtained via active sensing, passive sensing algorithms produce reliable range at sparse locations and, therefore, surface fitting techniques to fill the gaps in the range measurement are not directly applicable. Both, for automatic guidance and as a display for aiding the pilot, these discrete ranges need to be grouped into sets which correspond to objects in the nearby environment. The focus of this paper is on using Monte Carlo methods for clustering range points into meaningful groups. We compare three different approaches and present results of application of these algorithms to an image sequence acquired by onboard cameras during a helicopter flight, Starting with an initial grouping, these algorithms are iteratively applied with a new group creation algorithm to determine the optimal number of groups and the optimal group membership, The results indicate that the Simulated Annealing methods do not offer any significant advantage over the basic Monte Carlo method for this discrete optimization problem. C1 NASA, AMES RES CTR, AFF BRANCH, MOFFETT FIELD, CA 94035 USA. RP Chatterji, GB (reprint author), STERLING SOFTWARE INC, PALO ALTO, CA 94303 USA. NR 17 TC 0 Z9 0 U1 0 U2 0 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI PISCATAWAY PA 445 HOES LANE, PISCATAWAY, NJ 08855-4141 USA SN 1083-4427 EI 1558-2426 J9 IEEE T SYST MAN CY A JI IEEE Trans. Syst. Man Cybern. Paart A-Syst. Hum. PD NOV PY 1996 VL 26 IS 6 BP 832 EP 837 DI 10.1109/3468.541342 PG 6 WC Computer Science, Cybernetics; Computer Science, Theory & Methods SC Computer Science GA VP078 UT WOS:A1996VP07800015 ER PT J AU Bayard, DS AF Bayard, DS TI Stable direct adaptive periodic control using only plant order knowledge SO INTERNATIONAL JOURNAL OF ADAPTIVE CONTROL AND SIGNAL PROCESSING LA English DT Article ID NONMINIMUM-PHASE SYSTEMS; TIME-INVARIANT PLANTS; EXCITATION AB The main contribution of this paper is to put stability requirements for convergence of direct adaptive periodic controllers on an equal footing with requirements for indirect adaptive periodic control as set forth by Lozano. The resulting stability condition is simply that the plant order is known a priori. No other prior plant knowledge is used (e.g. relative degree, high-frequency gain, etc.) and persistent excitation is not required. More importantly, no assumption or knowledge is required as to whether the plant is minimum or non-minimum phase. A numerical example is given to demonstrate the method and some guidelines are given for improving the adaptive transient response. RP Bayard, DS (reprint author), CALTECH,JET PROP LAB,4800 OAK GROVE DR,PASADENA,CA 91109, USA. NR 27 TC 3 Z9 4 U1 0 U2 0 PU JOHN WILEY & SONS LTD PI W SUSSEX PA BAFFINS LANE CHICHESTER, W SUSSEX, ENGLAND PO19 1UD SN 0890-6327 J9 INT J ADAPT CONTROL JI Int. J. Adapt. Control Signal Process. PD NOV-DEC PY 1996 VL 10 IS 6 BP 551 EP 570 DI 10.1002/(SICI)1099-1115(199611)10:6<551::AID-ACS398>3.0.CO;2-I PG 20 WC Automation & Control Systems; Engineering, Electrical & Electronic SC Automation & Control Systems; Engineering GA VZ068 UT WOS:A1996VZ06800002 ER PT J AU Bousman, WS McQuillen, JB Witte, LC AF Bousman, WS McQuillen, JB Witte, LC TI Gas-liquid flow patterns in microgravity: Effects of tube diameter, liquid viscosity and surface tension SO INTERNATIONAL JOURNAL OF MULTIPHASE FLOW LA English DT Article DE microgravity; two-phase flow; flow patterns ID DISPERSED BUBBLE AB Two-phase gas-liquid how experiments have been developed for use on NASA microgravity aircraft to allow for high speed measurement of void fraction, liquid film thickness and pressure drop as well as high-speed photography of the flow features. Numerous experiments were conducted in order to determine the effect of liquid and gas superficial velocities, tube diameter, liquid viscosity and surface tension on the occurrence of flow patterns in microgravity. The transition from bubble to slug dow was found to be affected by tube diameter for air-water and by changes in liquid viscosity and surface tension. The transition from slug to annular flow was not significantly affected by changes in tube diameter, liquid viscosity or surface tension. Void fraction based transition models were developed to predict microgravity flow patterns. Weber number based transition models were also evaluated. Copyright (C) 1996 Elsevier Science Ltd. C1 NASA,LEWIS RES CTR,CLEVELAND,OH 44135. UNIV HOUSTON,DEPT MECH ENGN,HOUSTON,TX 77204. RP Bousman, WS (reprint author), UNIV HOUSTON,DEPT CHEM ENGN,HOUSTON,TX 77204, USA. NR 18 TC 41 Z9 43 U1 2 U2 10 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, ENGLAND OX5 1GB SN 0301-9322 J9 INT J MULTIPHAS FLOW JI Int. J. Multiph. Flow PD NOV PY 1996 VL 22 IS 6 BP 1035 EP 1053 DI 10.1016/0301-9322(96)00023-7 PG 19 WC Mechanics SC Mechanics GA VT440 UT WOS:A1996VT44000001 ER PT J AU Brady, MP Brindley, WJ Smialek, JL Locci, IE AF Brady, MP Brindley, WJ Smialek, JL Locci, IE TI The oxidation and protection of gamma titanium aluminides SO JOM-JOURNAL OF THE MINERALS METALS & MATERIALS SOCIETY LA English DT Article ID TI-AL-O; INTERMETALLIC ALLOYS; CYCLIC OXIDATION; BASE ALLOYS; COATINGS; BEHAVIOR; PHASE; RESISTANCE; SYSTEM; SI AB The excellent density-specific properties of the gamma class of titanium aluminides make them attractive for intermediate-temperature (600-850 degrees C) aerospace applications. The oxidation and embrittlement resistance of these alloys is superior to that of the alpha(2) and orthorhombic classes of titanium aluminides. However, since gamma alloys form an intermixed Al2O3/TiO2 scale in air rather than the desired continuous Al2O3 scale, oxidation resistance is inadequate at the high end of this temperature range (i.e., greater than 750-800 degrees C). For applications at such temperatures, an oxidation-resistant coating will be needed; however, a major drawback of the oxidation-resistant coatings currently available is severe degradation in fatigue life by the coating. A new class of oxidation-resistant coatings based in the Ti-Al-Cr system offers the potential for improved fatigue life. RP Brady, MP (reprint author), NASA,LEWIS RES CTR,MS 106-1,21000 BROOK PK RD,CLEVELAND,OH 44135, USA. RI Brady, Michael/A-8122-2008 OI Brady, Michael/0000-0003-1338-4747 NR 78 TC 194 Z9 196 U1 2 U2 27 PU MINERALS METALS MATERIALS SOC PI WARRENDALE PA 420 COMMONWEALTH DR, WARRENDALE, PA 15086 SN 1047-4838 J9 JOM-J MIN MET MAT S JI JOM-J. Miner. Met. Mater. Soc. PD NOV PY 1996 VL 48 IS 11 BP 46 EP 50 PG 5 WC Materials Science, Multidisciplinary; Metallurgy & Metallurgical Engineering; Mineralogy; Mining & Mineral Processing SC Materials Science; Metallurgy & Metallurgical Engineering; Mineralogy; Mining & Mineral Processing GA VW147 UT WOS:A1996VW14700009 ER PT J AU Cler, D Lamb, M Farokhi, S Taghavi, R Hazlewood, R AF Cler, D Lamb, M Farokhi, S Taghavi, R Hazlewood, R TI Application of pressure-sensitive paint in supersonic nozzle research SO JOURNAL OF AIRCRAFT LA English DT Article AB An experimental study was conducted to evaluate the pressure-sensitive paint (PSP) technique as a means of obtaining global surface pressure distribution on the inside surface of a supersonic nozzle at NASA Langley Research Center, In this experiment, the PSP technique was used to measure the surface pressure distribution for several configurations of a convergent-divergent nozzle, which was also instrumented with a densely packed array of pressure taps. The PSP and pressure tap data were obtained simultaneously for each configuration of the nozzle, at several nozzle pressure ratios, to determine the effects of supersonic cavity-ramp vortex generators on the nozzle now and performance, Results from the PSP data agreed very well with the pressure tap data and indicated that a pair of counter-rotating vortices were shed from the cavity vortex generator, The presence of these streamwise vortices caused a delay in the formation of the shock wave inside the nozzle. RP Cler, D (reprint author), NASA,LANGLEY RES CTR,RES FACIL BRANCH,HAMPTON,VA 23681, USA. NR 17 TC 4 Z9 4 U1 0 U2 0 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 SN 0021-8669 J9 J AIRCRAFT JI J. Aircr. PD NOV-DEC PY 1996 VL 33 IS 6 BP 1109 EP 1114 DI 10.2514/3.47064 PG 6 WC Engineering, Aerospace SC Engineering GA VW162 UT WOS:A1996VW16200011 ER PT J AU LeeRausch, EM Batina, JT AF LeeRausch, EM Batina, JT TI Wing flutter computations using an aerodynamic model based on the Navier-Stokes equations SO JOURNAL OF AIRCRAFT LA English DT Article ID AIRFOILS AB The flutter characteristics of the first AGARD standard aeroelastic configuration for dynamic response, Wing 445.6, are studied using an unsteady Navier-Stokes algorithm to investigate a previously noted discrepancy between Euler flutter characteristics and experimental data. The algorithm, which is a three-dimensional, implicit, upwind Euler/Navier-Stokes code (CFL3D Version 2.1), was previously modified for the time-marching, aeroelastic analysis of wings using the unsteady Euler equations, These modifications include the incorporation of a deforming mesh algorithm and the addition of the structural equations of motion for their simultaneous time integration with the governing flow equations. The aeroelastic method is extended and evaluated for applications that use aerodynamics based on the Navier-Stokes equations, A bl ief description of the aeroelastic method and time-marching calculations are presented that verify this method for Navier-Stokes calculations. A linear stability analysis and a time-marching aeroelastic analysis are used to determine the flutter characteristics of the isolated 45-deg swept-back wing, Effects of fluid viscosity, structural damping, and number of modes in the structural model are investigated, For the linear stability analysis, the unsteady generalized aerodynamic forces of the wing are computed for a range of reduced frequencies using the pulse transfer-function approach, The flutter characteristics of the wing are determined using these unsteady generalized aerodynamic forces in a traditional velocity-incremental damping (V-g) analysis, This stability analysis is used to determine the flutter characteristics of the wing at freestream Mach numbers of 0.96 and 1.141, using the generalized aerodynamic forces generated by solving the Euler equations and the Navier-Stokes equations. Time-marching aeroelastic calculations are performed at a freestream Mach number of 1.141 using the Euler and Navier-Stokes equations to compare with the linear V-g flutter analysis method. The V-g analysis, which is used in conjunction with the time-marching analysis, indicates that the fluid viscosity has a significant effect on the supersonic flutter boundary for this wing, whereas the structural damping and number of modes in the structural model have a lesser effect. C1 NASA,LANGLEY RES CTR,DIV STRUCT,AEROELEAST BRANCH,HAMPTON,VA 23681. NR 32 TC 43 Z9 44 U1 0 U2 3 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 SN 0021-8669 J9 J AIRCRAFT JI J. Aircr. PD NOV-DEC PY 1996 VL 33 IS 6 BP 1139 EP 1147 DI 10.2514/3.47068 PG 9 WC Engineering, Aerospace SC Engineering GA VW162 UT WOS:A1996VW16200015 ER PT J AU Gee, K Murman, SM Schiff, LB AF Gee, K Murman, SM Schiff, LB TI Computation of F/A-18 tail buffet SO JOURNAL OF AIRCRAFT LA English DT Article AB The aerodynamic loads that cause tail buffet on the F/A-18 fighter aircraft were analyzed using computational fluid dynamics (CFD). The half-body aircraft geometry was modeled using an overset grid system, which included the fuselage, wing, wing leading-edge extension (LEX), deflected wing leading-edge flap, inlet geometry, and vertical and horizontal tails, Time-accurate solutions with and without the LEX fence were obtained at an high-angle-of-attack flight condition, Time histories of the surface pressures on the rigid vertical tail were computed, The vertical tail root bending moment and side force time histories were obtained from the surface pressure distributions, Power spectral density analysis of the time histories were computed, Results were compared with experimental data from subscale and full-scale wind-tunnel tests, The current grid system yielded results that agree quite well with experimental data, The CFD solution predicted the unsteady rms pressure coefficient, the peak power, and the favorable effect of the LEX fence on these quantities. These results indicated that current CFD methods can be used to predict tail buffet and can be a useful tool for analyzing similar problems in aircraft design. RP Gee, K (reprint author), NASA,AMES RES CTR,MCAT INST,M-S 258-1,MOFFETT FIELD,CA 94035, USA. NR 21 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 SN 0021-8669 J9 J AIRCRAFT JI J. Aircr. PD NOV-DEC PY 1996 VL 33 IS 6 BP 1181 EP 1189 DI 10.2514/3.47073 PG 9 WC Engineering, Aerospace SC Engineering GA VW162 UT WOS:A1996VW16200020 ER PT J AU Sutliff, DL Envia, E AF Sutliff, DL Envia, E TI Inlet acoustic mode measurements using a continuously rotating rake - Comment SO JOURNAL OF AIRCRAFT LA English DT Article RP Sutliff, DL (reprint author), NASA,LEWIS RES CTR,2100 BROOKPK RD,CLEVELAND,OH 44135, USA. NR 3 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 SN 0021-8669 J9 J AIRCRAFT JI J. Aircr. PD NOV-DEC PY 1996 VL 33 IS 6 BP 1212 EP 1214 DI 10.2514/3.47083 PG 3 WC Engineering, Aerospace SC Engineering GA VW162 UT WOS:A1996VW16200030 ER PT J AU McGaughey, G Zipser, EJ Spencer, RW Hood, RE AF McGaughey, G Zipser, EJ Spencer, RW Hood, RE TI High-resolution passive microwave observations of convective-systems over the Tropical Pacific Ocean SO JOURNAL OF APPLIED METEOROLOGY LA English DT Article ID PHYSICAL PRECIPITATION RETRIEVAL; VERTICAL VELOCITY EVENTS; CLOUD-RADIATION MODEL; INNER CORE STRUCTURE; SATELLITE MEASUREMENTS; 183 GHZ; RAINFALL; MESOSCALE; RADIOMETER; ALGORITHM AB This paper presents high-resolution passive microwave measurements obtained in the western Pacific warm pool region. These measurements represent the most comprehensive such observations of convection over the tropical oceans to date, and were obtained from the Advanced Microwave Precipitation Radiometer (AMPR) aboard the NASA ER-2 during the Tropical Ocean and Global Atmosphere Coupled Ocean-Atmosphere Re sponse Experiment. The AMPR measures linearly polarized radiation at 10.7, 19.35, 37.1, and 85.5 GHz. Nadir brightness temperature scatterplots suggest that the three lower frequencies respond primarily to emission/absorption processes. Strong ice scattering is relatively rare, as absolute magnitudes of the ice-scattering signature do not approach those measured in strong convection over land. This is apparently related to the reported weaker updraft velocities over tropical oceans, which would create and suspend relatively smaller graupel or hail particles in the upper cloud. Observations within stratiform regions suggest that approximately 220 K is the minimum 85.5-GHz brightness temperature associated with ice scattering in regions of stratiform precipitation. In agreement with Other studies using high-resolution data, the relationships between data at the lower frequencies and the 85.5-GHz data exhibit considerable scatter. Traces through a hurricane eyewall and a squall line reveal the tilt of these convective systems away from the vertical. It is suggested that this observed tilt of convective lines is responsible, in part, for the finding that warm 10.7-GHz brightness temperatures (showing heavy rain at low levers) and cold 85.5-GHz brightness temperatures (showing large optical depth of ice particles aloft) are not consistently collocated. Observations of heavily raining clouds with little ice above or nearby are also presented, but it is shown that the heaviest rain rates are associated with ice scattering aloft. The AMPR data are averaged to a 24-km resolution, in order to simulate a satellite footprint of that scale. Brightness temperature relationships become more linear, though the scatter is not significantly reduced. The effects of nonhomogeneous beamfilling are obvious. A description of brightness temperature variability within the simulated satellite footprint is also presented. Similar descriptions could be used to develop a beamfilling correction to increase the accuracy of microwave rain-rate retrievals over the tropical oceans. C1 TEXAS A&M UNIV,DEPT METEOROL,COLLEGE STN,TX 77843. NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,EARTH SCI & APPLICAT DIV,HUNTSVILLE,AL 35812. NR 52 TC 33 Z9 35 U1 0 U2 2 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 SN 0894-8763 J9 J APPL METEOROL JI J. Appl. Meteorol. PD NOV PY 1996 VL 35 IS 11 BP 1921 EP 1947 DI 10.1175/1520-0450(1996)035<1921:HRPMOO>2.0.CO;2 PG 27 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA VV053 UT WOS:A1996VV05300001 ER PT J AU FritschYelle, JM Whitson, PA Bondar, RL Brown, TE AF FritschYelle, JM Whitson, PA Bondar, RL Brown, TE TI Subnormal norepinephrine release relates to presyncope in astronauts after spaceflight SO JOURNAL OF APPLIED PHYSIOLOGY LA English DT Article DE orthostatic hypotension; adrenergic ID ATHEROSCLEROTIC CORONARY-ARTERIES; BLOOD-PRESSURE; HEART-RATE; RESPONSES; ESTROGEN; GENDER; WOMEN; HUMANS; MEN; HYPERTENSION AB Postflight orthostatic intolerance is experienced by virtually all astronauts but differs greatly in degree of severity. We studied cardiovascular responses to upright posture in 40 astronauts before and after spaceflights lasting up to 16 days. We separated individuals according to their ability to remain standing without assistance for 10 min on landing day. Astronauts who could not remain standing on landing day had significantly smaller increases in plasma norepinephrine levels with standing than did those who could remain standing (105 +/- 41 vs. 340 +/- 62 pg/ml; P = 0.05). In addition, they had significantly lower standing peripheral vascular resistance (23 +/- 3 vs. 34 +/- 3 mmHg . l(-1). min; P = 0.02) and greater decreases in systolic (-28 +/- 4 vs. -11 +/- 3 mmHg; P = 0.002) and diastolic (-14 +/- 7 vs. 3 +/- 2 mmHg; P = 0.0003) pressures. The presyncopal group also had significantly lower supine (16 +/- 1 vs. 21 +/- 2 mmHg . l(-1). min; P = 0.04) and standing (23 +/- 2 vs. 32 +/- 2 mmHg . l(-1). min; P = 0.038) vascular resistance, supine (66 +/- 2 vs. 73 +/- 2 mmHg; P = 0.008) and standing (69 +/- 4 vs. 77 +/- 2 mmHg; P = 0.007) diastolic pressure, and supine (109 +/- 3 vs. 114 +/- 2 mmHg; P = 0.05) and standing (99 +/- 4 vs. 108 +/- 3 mmHg; P = 0.006) systolic pressures before Eight. This is the first study to clearly document these differences among presyncopal and nonpresyncopal astronauts after spaceflight and also offer the possibility of preflight prediction of postflight susceptibility. These results clearly point to hypoadrenergic responsiveness, possibly centrally mediated, as a contributing factor in postflight orthostatic intolerance. They may provide insights into autonomic dysfunction in Earthbound patients. C1 KRUG LIFE SCI,HOUSTON,TX 77058. RYERSON POLYTECH UNIV,CTR ADV TECHNOL EDUC,TORONTO,ON M5B 2K3,CANADA. RP FritschYelle, JM (reprint author), NASA,LYNDON B JOHNSON SPACE CTR,CARDIOVASC LAB,DIV MED SCI,SD3,HOUSTON,TX 77058, USA. NR 33 TC 185 Z9 187 U1 3 U2 6 PU AMER PHYSIOLOGICAL SOC PI BETHESDA PA 9650 ROCKVILLE PIKE, BETHESDA, MD 20814 SN 8750-7587 J9 J APPL PHYSIOL JI J. Appl. Physiol. PD NOV PY 1996 VL 81 IS 5 BP 2134 EP 2141 PG 8 WC Physiology; Sport Sciences SC Physiology; Sport Sciences GA VT205 UT WOS:A1996VT20500038 PM 8941538 ER PT J AU Miller, NJ Grebowsky, JM Hoegy, WR Mahajan, KK AF Miller, NJ Grebowsky, JM Hoegy, WR Mahajan, KK TI A comparison of ionization densities determined from spacecraft and incoherent scatter radar data SO JOURNAL OF ATMOSPHERIC AND TERRESTRIAL PHYSICS LA English DT Article ID ATMOSPHERE EXPLORER-C AB By comparing direct measurements taken from onboard Atmosphere Explorer spacecraft (AE), in eccentric orbit, with incoherent scatter radar (ISR) measurements taken from the ground, we illustrate both the merits and the difficulties involved in such comparisons. Five altitude profiles of ionization determined from AE, in near coincidence with ground stations making ISR measurements, compared favorably with the ISR data so long as the AE measurements were properly analyzed for the effects of variations in latitude and solar zenith angle along the spacecraft orbit. Copyright (C) 1996 Elsevier Science Ltd C1 NATL PHYS LAB,NEW DELHI 110012,INDIA. RP Miller, NJ (reprint author), NASA,GODDARD SPACE FLIGHT CTR,ATMOSPHERES LAB,GREENBELT,MD 20771, USA. RI Grebowsky, Joseph/I-7185-2013 NR 20 TC 0 Z9 0 U1 0 U2 1 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, ENGLAND OX5 1GB SN 0021-9169 J9 J ATMOS TERR PHYS JI J. Atmos. Terr. Phys. PD NOV PY 1996 VL 58 IS 15 BP 1735 EP 1740 DI 10.1016/0021-9169(95)00200-6 PG 6 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA UZ367 UT WOS:A1996UZ36700008 ER PT J AU Jin, Y Rossow, WB Wylie, DP AF Jin, Y Rossow, WB Wylie, DP TI Comparison of the climatologies of high-level clouds from HIRS and ISCCP SO JOURNAL OF CLIMATE LA English DT Article ID SEA-SURFACE TEMPERATURE; GENERAL-CIRCULATION MODEL; CIRRUS CLOUDS; RADIATIVE PROPERTIES; CLIMATE; SENSITIVITY; RADIANCES; RETRIEVAL; FIELDS; SERIES AB Comparison of individually matched analyses of high-level cloudiness from the High-Resolution infrared Sounder(HIRS) CO2-slicing analysis and the International Satellite Cloud Climatology Project (ISCCP) analysis of satellite data for 4 months shows that the former reports about 0.12 more high-level clouds than the latter. Almost all of the difference in high-level cloud amounts occurs as differences of thin cirrus, defined by infrared emissivity epsilon < 0.5 or tau(vis) < 1.3, consistent with a previous comparison of Stratospheric Aerosol and Gas Experiment II and ISCCP. Some of this difference may be caused by the large field of view of the HIRS instrument. Over oceans the differences in cirrus cloud amounts are caused by the higher sensitivity of the HIRS analysis to optically thin clouds, aided by a small high bias of the sea surface temperatures used in the HIRS cloud detection step. Over land the higher detection sensitivity of the HIRS analysis was partially offset by the effect of large low biases in the surface temperatures used in the HIRS cloud detection step, most especially over high mountainous terrains. From these two datasets the authors conclude that about one-third of the earth is covered by high-level clouds (tops above the 440-mb level) and more than two-thirds of these clouds are cirrus, defined as those clouds that have a net radiative heating effect (i.e., infrared epsilon < 0.84 or tau(vis) < 3.6). About half of all cirrus clouds are optically very thin (epsilon < 0.5 or tau(vis) < 1.3). Optically thicker (tau(vis) > 3.6) high-level clouds appear to be more frequently associated with each other than with cirrus. Notable concentrations of cirrus in the Tropics mark regions of frequent deep convective activity. However, there are also prominent features associated with the subtropical jet streams. In midlatitudes, cirrus concentrations occur in the oceanic cyclone tracks, but they are even larger over major mountain complexes. Although the quantitative uncertainties of both datasets are large in the polar regions, the agreements and disagreements between them can be explained by the presence of large amounts of cirrus over both polar regions. C1 COLUMBIA UNIV,DEPT GEOSCI,NEW YORK,NY. UNIV WISCONSIN,CTR SPACE SCI & ENGN,MADISON,WI. RP Jin, Y (reprint author), NASA,GODDARD INST SPACE STUDIES,2880 BROADWAY,NEW YORK,NY 10025, USA. RI Rossow, William/F-3138-2015 NR 45 TC 75 Z9 80 U1 1 U2 5 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 SN 0894-8755 J9 J CLIMATE JI J. Clim. PD NOV PY 1996 VL 9 IS 11 BP 2850 EP 2879 DI 10.1175/1520-0442(1996)009<2850:COTCOH>2.0.CO;2 PG 30 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA VX838 UT WOS:A1996VX83800013 ER PT J AU Lin, B Rossow, WB AF Lin, B Rossow, WB TI Seasonal variation of liquid and ice water path in nonprecipitating clouds over oceans SO JOURNAL OF CLIMATE LA English DT Article ID PROBABILITY-DISTRIBUTION FUNCTIONS; GENERAL-CIRCULATION MODEL; MARINE STRATOCUMULUS; RADIATIVE PROPERTIES; INFRARED RADIANCES; SATELLITE; MICROWAVE; CIRRUS; RETRIEVAL; PRECIPITATION AB Seasonal variations of liquid and ice water paths (LWP and IWP) in nonprecipitating clouds over oceans are estimated for 4 months by combining the International Satellite Cloud Climatology Project (ISCCP) and Special Sensor Microwave/Imager (SSM/I) data. The ISCCP data are used to separate clear/cloudy skies and warm/ cold clouds and to determine cloud optical thickness, cloud-top temperature, and sea surface temperature. SSM/ I data are used to separate precipitating and nonprecipitating clouds and to determine LWP. About 93% of all clouds are nonprecipitating clouds, and about half of nonprecipitating clouds are warm (cloud-top temperature > 0 degrees C). The average LWP for warm nonprecipitating clouds is about 6 mg cm(-2). The values of total water path obtained from the ISCCP values of optical thickness for cold nonprecipitating clouds are larger than the LWP values from SSM/I, which the authors explain in terms of IWP. The average IWP for cold nonprecipitating clouds is about 7 mg cm(-2), with LWP being about 5 mg cm(-2). Tropical and cold hemisphere clouds have higher IWP values (around 10 mg cm(-2)) than those in warm hemispheres; whereas LWP values for warm nonprecipitating clouds vary little with latitude or season. Ice fractions, IWP/(LWP + IWP), in cold nonprecipitating clouds increase systematically with decreasing cloud-top temperatures, reaching 50% at about -15 degrees C but ranging from about -5 degrees to -10 degrees C in the northern midlatitudes in autumn and the Tropics year-round to about -25 degrees C in the southern midlatitudes in summer. The ratio of IWP to LWP in cold nonprecipitating clouds reaches almost 3 in the northern midlatitudes in autumn and falls as low as 0.6 in the southern midlatitudes in spring-summer Combining warm and cold nonprecipitating clouds gives a global ratio of IWP to LWP that is about 0.7 over oceans. C1 COLL WILLIAM & MARY,WILLIAMSBURG,VA. NASA,GODDARD INST SPACE STUDIES,NEW YORK,NY 10025. RI Rossow, William/F-3138-2015 NR 61 TC 52 Z9 55 U1 0 U2 4 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 SN 0894-8755 J9 J CLIMATE JI J. Clim. PD NOV PY 1996 VL 9 IS 11 BP 2890 EP 2902 DI 10.1175/1520-0442(1996)009<2890:SVOLAI>2.0.CO;2 PG 13 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA VX838 UT WOS:A1996VX83800015 ER PT J AU Carpenter, MH Gottlieb, D AF Carpenter, MH Gottlieb, D TI Spectral methods on arbitrary grids SO JOURNAL OF COMPUTATIONAL PHYSICS LA English DT Article ID ELEMENT METHOD; EQUATIONS; DYNAMICS AB Stable and spectrally accurate numerical methods are constructed on arbitrary grids for partial differential equations, These new methods are equivalent to conventional spectral methods but do not rely on specific grid distributions. Specifically, we show how to implement Legendre Galerkin, Legendre collocation, and Laguerre Galerkin methodology on arbitrary grids. (C) 1996 Academic Press, Inc. C1 BROWN UNIV,DIV APPL MATH,PROVIDENCE,RI 02912. RP Carpenter, MH (reprint author), NASA,LANGLEY RES CTR,AERODYNAM & ACOUST METHODS BRANCH,HAMPTON,VA 23681, USA. NR 9 TC 55 Z9 55 U1 0 U2 4 PU ACADEMIC PRESS INC JNL-COMP SUBSCRIPTIONS PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 SN 0021-9991 J9 J COMPUT PHYS JI J. Comput. Phys. PD NOV PY 1996 VL 129 IS 1 BP 74 EP 86 DI 10.1006/jcph.1996.0234 PG 13 WC Computer Science, Interdisciplinary Applications; Physics, Mathematical SC Computer Science; Physics GA VT313 UT WOS:A1996VT31300006 ER PT J AU Palosz, W Grasza, K Gillies, D Jerman, G AF Palosz, W Grasza, K Gillies, D Jerman, G TI Growth of cadmium-zinc telluride crystals by controlled seeding ''contactless'' physical vapor transport SO JOURNAL OF CRYSTAL GROWTH LA English DT Article ID PHASE-SEPARATION; MICROSCOPY; CDTE AB Bulk crystals of cadmium-zinc telluride, 23 mm in diameter and up to 45 grams in weight were grown. Controlled seed formation procedure was used to limit the number of grains in the crystal. Most uniform distribution of ZnTe in the crystals was obtained using excess (Cd + Zn) pressure in the ampoule. C1 POLISH ACAD SCI,INST PHYS,WARSAW,POLAND. RP Palosz, W (reprint author), NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,ES75,HUNTSVILLE,AL 35812, USA. NR 10 TC 14 Z9 14 U1 1 U2 2 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 NOV PY 1996 VL 169 IS 1 BP 20 EP 26 DI 10.1016/0022-0248(96)00375-2 PG 7 WC Crystallography; Materials Science, Multidisciplinary; Physics, Applied SC Crystallography; Materials Science; Physics GA VQ726 UT WOS:A1996VQ72600003 ER PT J AU Plott, CR Porter, DP AF Plott, CR Porter, DP TI Market architectures and institutional testbedding: An experiment with space station pricing policies SO JOURNAL OF ECONOMIC BEHAVIOR & ORGANIZATION LA English DT Article DE design; experiments; market structure; pricing; auctions RP Plott, CR (reprint author), CALTECH,JET PROP LAB,4800 OAK GROVE DR,PASADENA,CA 91125, USA. NR 7 TC 17 Z9 17 U1 0 U2 3 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0167-2681 J9 J ECON BEHAV ORGAN JI J. Econ. Behav. Organ. PD NOV PY 1996 VL 31 IS 2 BP 237 EP 272 DI 10.1016/S0167-2681(96)00893-1 PG 36 WC Economics SC Business & Economics GA WL434 UT WOS:A1996WL43400007 ER PT J AU Mattikalli, NM Richards, KS AF Mattikalli, NM Richards, KS TI Estimation of surface water quality changes in response to land use change: Application of the export coefficient model using remote sensing and geographical information system SO JOURNAL OF ENVIRONMENTAL MANAGEMENT LA English DT Article DE nitrogen concentration; land use change; fertilizer usage; export coefficient model; remote sensing; geographical information system (GIS) ID UNITED-KINGDOM; CLASSIFICATION; INTEGRATION; BRITAIN AB A trend of increasing solute (i.e. nitrogen and phosphorus) concentrations in surface water has been observed in the recent past. Solute concentrations have often exceeded the World Health Organization directives on the quality of drinking water. In predominantly rural watersheds of developed countries, increasing solute concentrations have been attributed to agricultural intensification (i.e. land use change) and increased fertilizer usage. This paper presents an approach based on remote sensing and Geographical Information System (GIS) to estimate and hindcast water quality changes using historical land use data for a watershed in eastern England. The water quality, as indexed by the nitrogen loading, was estimated using the export coefficient model. The model calculates solute loading at the outlet of a watershed using land use data, fertilizer application rates and export coefficients. Historical land use data were derived from a variety of sources including maps, aerial photographs and remotely-sensed Landsat and SPOT satellite images. Export coefficients indicate the proportion of the total nutrient lost to the surface water, and determine the amount of nutrient loading from various land use types. Export coefficients for various land use classes were compiled from literature. A GIS was necessary to store, manipulate and analyse large volumes of land use data, and to carry out land use change analysis. A number of special GIS routines were developed to carryout the model computations automatically. Results demonstrated that the model estimates nitrogen loading with an acceptable degree of accuracy. Analysis showed an overall increase of nitrogen loading from 1931-1984, after which it remained steady. Experiments were carried out to identify the separate effects of land use and fertilizer application on the nitrogen loading. The export coefficient model operating in a GIS has significant potential for the rapid estimation of surface water quality using land use data derived from remotely sensed satellite images. (C) 1996 Academic Press Limited C1 UNIV CAMBRIDGE, DEPT GEOG, CAMBRIDGE CB2 3EN, ENGLAND. RP Mattikalli, NM (reprint author), NASA, GODDARD SPACE FLIGHT CTR, LAB HYDROSPHER PROC, HYDROL SCI BRANCH, CODE 974, GREENBELT, MD 20771 USA. NR 45 TC 79 Z9 99 U1 10 U2 47 PU ACADEMIC PRESS LTD- ELSEVIER SCIENCE LTD PI LONDON PA 24-28 OVAL RD, LONDON NW1 7DX, ENGLAND SN 0301-4797 EI 1095-8630 J9 J ENVIRON MANAGE JI J. Environ. Manage. PD NOV PY 1996 VL 48 IS 3 BP 263 EP 282 DI 10.1006/jema.1996.0077 PG 20 WC Environmental Sciences SC Environmental Sciences & Ecology GA VR226 UT WOS:A1996VR22600005 ER PT J AU Gitschlag, GR AF Gitschlag, GR TI Migration and diving behavior of Kemp's ridley (Garman) sea turtles along the US southeastern Atlantic coast SO JOURNAL OF EXPERIMENTAL MARINE BIOLOGY AND ECOLOGY LA English DT Article DE diving behavior; Kemp's ridley; migration; sea turtle ID STREAM FRONTAL EDDY; CARETTA-CARETTA; MOVEMENTS; VICINITY; FLORIDA; SHELF AB Three Kemp's ridley (Lepidochelys kempii, Garman) sea turtles were tracked with satellite and radio/sonic telemetry from release points along the Georgia coast beginning in October 1991. The movement demonstrated by these turtles was consistent with seasonal, coastal migration. Radio-tagged juveniles travelled south from Georgia to Florida a distance of 120 and 202 km during 41 and 29 days of monitoring, respectively. Submergence duration was significantly longer at night than during the day for one of two juvenile turtles. A nesting-sized Kemp's ridley tracked via satellite telemetry from October 1991 to July 1992 made longer dives than the radio tagged juveniles, but the percent submergence time was very similar, 94% and 95%, respectively. Seasonal and day-night differences in average submergence duration were significant for the satellite tracked turtle, and longer dives occurred at night throughout all seasons. In spring, average submergence duration was shorter. From mid-November to mid-March the primary overwintering grounds of the nesting-sized ridley sea turtle were within approximately 40 km of the Atlantic coast between Cape Canaveral and Stuart, Florida. During late spring and early summer, coastal South Carolina was the preferred habitat of this individual. RP Gitschlag, GR (reprint author), NATL MARINE FISHERIES SERV, SE FISHERIES CTR, GALVESTON LAB, 4700 AVE U, GALVESTON, TX 77551 USA. NR 47 TC 18 Z9 23 U1 1 U2 14 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0022-0981 J9 J EXP MAR BIOL ECOL JI J. Exp. Mar. Biol. Ecol. PD NOV 1 PY 1996 VL 205 IS 1-2 BP 115 EP 135 DI 10.1016/S0022-0981(96)02602-0 PG 21 WC Ecology; Marine & Freshwater Biology SC Environmental Sciences & Ecology; Marine & Freshwater Biology GA VU573 UT WOS:A1996VU57300008 ER PT J AU Crooker, NU Burton, ME Siscoe, GL Kahler, SW Gosling, JT Smith, EJ AF Crooker, NU Burton, ME Siscoe, GL Kahler, SW Gosling, JT Smith, EJ TI Solar wind streamer belt structure SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID HELIOSPHERIC CURRENT SHEET; PLANAR MAGNETIC-STRUCTURES; HEAT-FLUX DROPOUTS; PLANETARY SECTOR BOUNDARIES; DIRECTIONAL DISCONTINUITIES; CORONAL STREAMERS; FIELD; ELECTRONS; RECONNECTION; FLUCTUATIONS AB In the course of 2 days in October 1978, ISEE 3 encountered 14 magnetic field reversals, five pronounced and several lesser high-beta regions called ''plasma sheets,'' two distinct entropy regimes, two heat flux dropouts (HFDs), and planar magnetic structure led by a shock wave. The complexity of the interval afforded an excellent opportunity to determine the relationships between these streamer belt structures, their geometry and topology, and the resulting implications for the structure of the heliospheric current sheet (HCS). None of the results of three tests applied to the data support a wavy or folded HCS hypothesis. In particular, a test for true magnetic polarity using primarily heat flux data indicated that the field reversals occurred in a predominantly toward sector with three pockets of true away polarity and three of false away polarity. The results are consistent with a view in which current sheets bound intertwined flux ropes, some of which coil back on themselves, possibly as remnants of transient coronal activity. A comparison between joint occurrences of the various structures showed that the most intense plasma sheets in the interval coincided with true polarity reversals, that nearly every reversal, whether true or false, corresponded to at least a weak plasma sheet, and that plasma sheets occurred within HFD intervals. The plasma sheet/HFD relationship was statistically confirmed in a search for plasma sheets in published HFDs. C1 CALTECH,JET PROP LAB,PASADENA,CA 91109. LOS ALAMOS NATL LAB,LOS ALAMOS,NM 87545. PHILLIPS LAB,GEOPHYS DIRECTORATE,BEDFORD,MA 01731. RP Crooker, NU (reprint author), BOSTON UNIV,CTR SPACE PHYS,725 COMMONWEALTH AVE,BOSTON,MA 02215, USA. NR 40 TC 43 Z9 44 U1 0 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 SN 0148-0227 J9 J GEOPHYS RES JI J. Geophys. Res-Space Phys. PD NOV 1 PY 1996 VL 101 IS A11 BP 24331 EP 24341 DI 10.1029/96JA02412 PG 11 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VQ495 UT WOS:A1996VQ49500001 ER PT J AU GonzalezEsparza, J Smith, EJ AF GonzalezEsparza, J Smith, EJ TI Solar cycle dependence of the solar wind dynamics: Pioneer Voyager, and Ulysses from 1 to 5 AU SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID CORONAL MASS EJECTIONS; HELIOSPHERIC CURRENT SHEET; SMM OBSERVATIONS; LARGE-SCALE; EVOLUTION; VELOCITY; SHOCKS AB Significant differences between Pioneer and Voyager observations were found in solar wind structure between 1 and 6 AU. These disagreements were attributed to temporal effects related to the solar cycle, but no unifying study of Pioneer-Voyager observations was performed. On the basis of maps of large-scale features we unify previous reports of Pioneers 10 and 11, Voyagers 1 and 2, and Ulysses observations from 1 to 5 AU. The five spacecraft traveled from Earth to Jupiter at different phases of the solar sunspot cycle. We compare the observations of solar wind streams, interplanetary shock waves, interaction regions, and magnetic sectors. We find that solar wind dynamics has a very irregular behavior throughout the solar cycle. There are continual transitions between periods of a few solar rotations dominated by slow solar wind, transient events, and irregular patterns of magnetic sectors; and periods of a few solar rotations dominated by interaction regions and well-defined magnetic sectors. These transitions occur at temporal scales of the order of 2-4 solar rotations. It is suggested that these transitions are associated with changes in coronal holes and might be related to the yearly modulation of solar wind speeds. The five spacecraft observed, on average, about 3 to 4 interplanetary shocks per solar rotation period. The 90 percent of the total number of shocks detected by Pioneer 11 were caused by interaction regions. However, between 40 to 55 percent of the total number of shocks detected by the other spacecraft were transient forward shocks. The expansion rate of the CIRs between 1 to 5 AU is about 94 km/s, however, there is a significant diversity in the characteristics of the interaction regions. RP GonzalezEsparza, J (reprint author), CALTECH, JET PROP LAB, 4800 OAK GROVE DR, MAIL STOP 169-501, PASADENA, CA 91109 USA. RI Gonzalez-Esparza, J. Americo/A-6720-2013 NR 40 TC 11 Z9 11 U1 0 U2 2 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 NOV 1 PY 1996 VL 101 IS A11 BP 24359 EP 24371 DI 10.1029/96JA02458 PG 13 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VQ495 UT WOS:A1996VQ49500004 ER PT J AU Huba, JD Bernhardt, PA Ossakow, SL Zalesak, ST AF Huba, JD Bernhardt, PA Ossakow, SL Zalesak, ST TI The Rayleigh-Taylor instability is not damped by recombination in the F region SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID EQUATORIAL SPREAD-F; TURBULENCE AB The collisional Rayleigh-Taylor instability plays a crucial role in explaining the onset and development of equatorial spread F. A number of linear and nonlinear analyses of the instability have been developed for the F region that include recombinative damping. It has been argued that recombination damps the unstable density perturbations and provides a mechanism to suppress the onset of instability or saturate the instability via mode coupling. We show that F region recombination, in fact, does not damp unstable density perturbations relative to the background ionosphere. Recombination acts to reduce the total electron density, both the ambient background and the perturbation, at a rate nu(R). C1 NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. RP Huba, JD (reprint author), USN,RES LAB,DIV PLASMA PHYS,CODE 6790,WASHINGTON,DC 20375, USA. NR 23 TC 21 Z9 21 U1 0 U2 2 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 SN 0148-0227 J9 J GEOPHYS RES JI J. Geophys. Res-Space Phys. PD NOV 1 PY 1996 VL 101 IS A11 BP 24553 EP 24556 DI 10.1029/96JA02527 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VQ495 UT WOS:A1996VQ49500021 ER PT J AU Angelopoulos, V Sergeev, VA Mozer, FS Tsuruda, K Kokubun, S Yamamoto, T Lepping, R Reeves, G FriisChristensen, E AF Angelopoulos, V Sergeev, VA Mozer, FS Tsuruda, K Kokubun, S Yamamoto, T Lepping, R Reeves, G FriisChristensen, E TI Spontaneous substorm onset during a prolonged period of steady, southward interplanetary magnetic field SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID SOLAR-WIND ORIGIN; MAGNETOSPHERIC SUBSTORMS; DISTANT MAGNETOTAIL; PLASMA SHEET; NEAR-EARTH; CONVECTION; GEOTAIL; EVENTS; SATELLITE; ISEE-3 AB We document a clear case of spontaneous substorm onset under conditions of steady southward interplanetary magnetic field on January 22, 1993. The substorm occurred at 0415 UT with an intensification at 0455 UT during an interval of convection bay activity but had most of the features associated with substorms. These features include high-latitude and midlatitude magnetic bays at ground magnetometers, and magnetic field compression and energetic particle injection at geosynchronous altitude. In addition, a plasmoid release was observed in the distant tail plasma sheet by the Geotail spacecraft ata GSM position (-96, 1, -6) R(E). We conclude that spontaneous-onset substorms occur occasionally even during steady convection bay events. Such substorms and ''classical'' substorms progress in a very similar manner, Irrespective of possible differences in their onset mechanism. C1 DANISH METEOROL INST,DK-2100 COPENHAGEN,DENMARK. NAGOYA UNIV,SOLAR TERR ENVIRONM LAB,TOYOKAWA,AICHI 442,JAPAN. NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. LOS ALAMOS NATL LAB,LOS ALAMOS,NM 87545. ST PETERSBURG STATE UNIV,INST PHYS,ST PETERSBURG 198904,RUSSIA. INST SPACE & ASTRONAUT SCI,SAGAMIHARA,KANAGAWA 229,JAPAN. RP Angelopoulos, V (reprint author), UNIV CALIF BERKELEY,SPACE SCI LAB,BERKELEY,CA 94720, USA. RI Reeves, Geoffrey/E-8101-2011; Sergeev, Victor/H-1173-2013 OI Reeves, Geoffrey/0000-0002-7985-8098; Sergeev, Victor/0000-0002-4569-9631 NR 64 TC 13 Z9 13 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 SN 0148-0227 J9 J GEOPHYS RES JI J. Geophys. Res-Space Phys. PD NOV 1 PY 1996 VL 101 IS A11 BP 24583 EP 24598 DI 10.1029/96JA02515 PG 16 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VQ495 UT WOS:A1996VQ49500025 ER PT J AU Yamauchi, M Nilsson, H Eliasson, L Norberg, O Boehm, M Clemmons, JH Lepping, RP Blomberg, L Ohtani, SI Yamamoto, T Mukai, T Terasawa, T Kokubun, S AF Yamauchi, M Nilsson, H Eliasson, L Norberg, O Boehm, M Clemmons, JH Lepping, RP Blomberg, L Ohtani, SI Yamamoto, T Mukai, T Terasawa, T Kokubun, S TI Dynamic response of the cusp morphology to the solar wind: A case study during passage of the solar wind plasma cloud on February 21, 1994 SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID INTERPLANETARY MAGNETIC-FIELD; PARTICLE-PRECIPITATION; ION INJECTIONS; BOUNDARY-LAYER; POLAR CUSP; VIKING; DAYSIDE; MODEL; MAGNETOPAUSE; PRESSURE AB On February 21, 1994, both Geotail and LMP 8 satellites detected an interplanetary plasma cloud with intense interplanetary magnetic field (IMF>50 nT) and high dynamic pressure (> 50 nPa). During this interval the Freja satellite detected intense cusp-like plasma injections in four out of six dayside traversals. The first two traversals are carefully studied, During the first traversal the overall morphology of the ion injection is characterized by a ''multiple-injection'' signature over a wide magnetic local time (MLT) range, whereas it is characterized by a ''single-injection'' signature with narrow injection region at 8 MLT in the second traversal, The solar wind conditions were also quite different between these two periods: while both dynamic and magnetic pressures stayed high during entire period, the dynamic beta was much higher during the first Freja traversal than during the second traversal. Between these two traversals, the cusp plasma injection is detected by the Sondre Stromfjord radar. The radar signature of the plasma injection is identified using the satellite particle data when the satellite and the radar were conjugate (the satellite's footprint was in the radar's field of view.) The cusp position and dynamics observed by the Sondre Stromfjord radar again show a very good correlation to the solar wind condition, especially to the dynamic pressure. The result indicates the following. (1) During southward IMF the cusp morphology differs for conditions of high or low solar wind dynamic pressure. High dynamic pressure widens the cusp (with multiple injections), whereas high magnetic pressure narrows it (with single injection), The effect of the IMF on the cusp locations and morphology becomes dominant only when the dynamic pressure is not very high, (2) Such a morphological difference reflects dynamic pressure more than dynamic beta during southward IMF at least during times of high solar wind dynamic pressure. (3) The cusp morphology responds very quickly to the changes in the solar wind conditions. C1 CALTECH, JET PROP LAB, PASADENA, CA 91109 USA. NASA, GODDARD SPACE FLIGHT CTR, GREENBELT, MD 20771 USA. ROYAL INST TECHNOL, INST PLASMA PHYS, S-10044 STOCKHOLM, SWEDEN. JOHNS HOPKINS UNIV, APPL PHYS LAB, LAUREL, MD 20723 USA. INST SPACE & ASTRONAUT SCI, SAGAMIHARA, KANAGAWA 229, JAPAN. UNIV TOKYO, INST EARTH & PLANETARY PHYS, TOKYO 113, JAPAN. NAGOYA UNIV, SOLAR TERR ENVIRONM LAB, TOYOKAWA, AICHI 442, JAPAN. RI Ohtani, Shinichi/E-3914-2016 OI Ohtani, Shinichi/0000-0002-9565-6840 NR 29 TC 20 Z9 20 U1 0 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0148-0227 J9 J GEOPHYS RES-SPACE JI J. Geophys. Res-Space Phys. PD NOV 1 PY 1996 VL 101 IS A11 BP 24675 EP 24687 DI 10.1029/96JA01873 PG 13 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VQ495 UT WOS:A1996VQ49500031 ER PT J AU Chen, JS Guzik, TG Wefel, JP Pyle, KR Cooper, JF AF Chen, JS Guzik, TG Wefel, JP Pyle, KR Cooper, JF TI Energetic helium isotopes trapped in the magnetosphere SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID ANOMALOUS COSMIC-RAYS; IONIZED HELIUM; RADIATION BELT; PROTONS; CRRES; PARTICLES; HYDROGEN; FLARES AB Helium nuclei have been measured within the magnetosphere (L less than or equal to 6) during the 1990/1991 CRRES mission over an energy range of similar to 40-100 MeV nucleon(-1). The Office of Naval Research 604 instrument resolves helium isotopes with a mass resolution of similar to 0.1 amu. Each helium isotope can be represented by a power law energy spectrum, and the energy spectrum of the He-3 is different from that of He-4; that is, the He-3/He-4 ratio is energy dependent. In the energy range 51-86 MeV/nucleon the He-3/He-4 ratio is 7.4+/-2.6 for L = 1.15-1.3 and 2.2+/-0.6 for L = 1.8-2.15. All observed helium events at L < 2.65 show pitch angle distributions consistent with equatorially trapped ions, whereas the distributions at larger L values are more uniform, within a factor of 2. For 2.15 < L < 6, as L decreases, the He-3/He-4 ratio increases and the helium energy spectrum softens. A possible origin of the geomagnetically trapped helium isotopes at L <2.15 is proton interactions in the residual atmosphere. The CRRES satellite was operational during the large geomagnetic storm on March 24, 1991, and we have divided the analysis into prestorm and poststorm time periods. Following the storm, the magnetosphere became more dynamic, and at L similar to 2.3 an enhanced helium flux was observed. Over the energy range of 51-86 MeV nucleon(-1) both the average He-3 and He-4 fluxes at L = 2.15-2.65 increased by a factor of 6 after the storm relative to the prestorm period, while at L = 1.8-2.15 the average 3He and 4He fluxes decreased by factors of 3 and 11, respectively, following the storm. The implications of these observed results are discussed. C1 LOUISIANA STATE UNIV,DEPT PHYS & ASTRON,BATON ROUGE,LA 70803. UNIV CHICAGO,LAB ASTROPHYS & SPACE RES,CHICAGO,IL 60637. NASA,GODDARD SPACE FLIGHT CTR,HUGHES STX CORP,SPACE PHYS DATA FACIL,GREENBELT,MD 20771. RP Chen, JS (reprint author), BOSTON UNIV,CTR SPACE PHYS,BOSTON,MA 02215, USA. RI Cooper, John/D-4709-2012 NR 48 TC 17 Z9 19 U1 0 U2 2 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 SN 0148-0227 J9 J GEOPHYS RES JI J. Geophys. Res-Space Phys. PD NOV 1 PY 1996 VL 101 IS A11 BP 24787 EP 24799 DI 10.1029/96JA02336 PG 13 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VQ495 UT WOS:A1996VQ49500041 ER PT J AU Sundaram, AK Fairfield, DH AF Sundaram, AK Fairfield, DH TI The tearing instabilities driven by lower hybrid waves in the current sheet SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID NEUTRAL SHEET; DRIFT INSTABILITY; PLASMA SHEET; GEOTAIL OBSERVATIONS; SUBSTORM EXPANSIONS; MAGNETOTAIL; RECONNECTION; BOUNDARY; DYNAMICS; TURBULENCE AB We have investigated the excitation of tearing instabilities driven by lower hybrid waves in the current sheet. Considering a two-dimensional equilibrium, we have shown that lower hybrid waves observed throughout the plasma sheet can cause large anomalous resistivity as a consequence of nonlinear interactions and significantly influence the excitation of tearing mode in the layer, where B-x(z) reverses sign. We have found that the perturbed ponderomotive force gives two new physical effects, one due to current gradients in the inner core of the current sheet (z much less than delta much less than lambda, where lambda is the current sheet width and delta is the thickness of the field reversal layer) and the other due to anomalous resistivity in the outer core (delta much less than z less than or equal to lambda). In the presence of these effects, we have demonstrated that global tearing modes with growth times ranging from fraction of a second to several tens of milliseconds are excited for wave electric fields of order of a few mV/m and scale lengths in the range k(0y)L(z) < 1 or k(0y)L(z) > 1, where k(0y) is the wavenumber of the lower hybrid waves and L(z) is the perturbation scale length. Finally, we have discussed the relevance of this wave-driven mode to the magnetic reconnection and the substorm onset processes. C1 HUGHES STX CORP,GREENBELT,MD. RP Sundaram, AK (reprint author), NASA,GODDARD SPACE FLIGHT CTR,EXTRATERR PHYS LAB,CODE 695,GREENBELT,MD 20771, USA. NR 27 TC 6 Z9 6 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 SN 0148-0227 J9 J GEOPHYS RES JI J. Geophys. Res-Space Phys. PD NOV 1 PY 1996 VL 101 IS A11 BP 24919 EP 24927 DI 10.1029/96JA02543 PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VQ495 UT WOS:A1996VQ49500052 ER PT J AU Dougherty, MK Balogh, A Southwood, DJ Smith, EJ AF Dougherty, MK Balogh, A Southwood, DJ Smith, EJ TI Ulysses assessment of the Jovian planetary field SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID MAGNETIC-FIELD; JUPITER; MAGNETOSPHERE; FLYBY AB The magnetic field measurements made by the Ulysses dual fluxgate/vector helium magnetometer during the day of closest approach to Jupiter in February 1992 are reported. The data are compared to a model which describes the field in terms of an internal spherical harmonic component together with an external current sheet field. The sensitivity of the magnetic field model parameters is examined. It is concluded that the dipole term which best fits the Ulysses closest approach data is lower than that used in most recent models and is closer in value to that found for the Pioneer 11 epoch models. Our favored value of the dipole term is 4.059 G. The contribution of the external ring current is weaker than that observed during the Voyager epoch, although the sheet is in fact thicker. The lower dipole value is also found to produce a good fit to the Pioneer 11 and Voyager 1 closest approach data sets, and hence there is no evidence for any secular change in the planetary field at Jupiter. C1 CALTECH,JET PROP LAB,PASADENA,CA 91109. RP Dougherty, MK (reprint author), UNIV LONDON IMPERIAL COLL SCI TECHNOL & MED,BLACKETT LAB,PRINCE CONSORT RD,LONDON SW7 2BZ,ENGLAND. NR 19 TC 13 Z9 13 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 SN 0148-0227 J9 J GEOPHYS RES JI J. Geophys. Res-Space Phys. PD NOV 1 PY 1996 VL 101 IS A11 BP 24929 EP 24941 DI 10.1029/96JA02385 PG 13 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA VQ495 UT WOS:A1996VQ49500053 ER PT J AU Papadopoulos, M Garcia, E Tolson, RH AF Papadopoulos, M Garcia, E Tolson, RH TI Global-local observer Markov parameter identification for system realization SO JOURNAL OF GUIDANCE CONTROL AND DYNAMICS LA English DT Article AB The observer/Kalman filter identification method uses general input/output data to compute the Markov parameters of an asymptotically stable observer. A state space realization is subsequently obtained from these estimated Merkov parameters. However, numerical ill-conditioning, data acquisition, and computer memory constraints may Limit the number of measurements that can be processed far Markov parameter estimation. Use of Limited measurements then will reduce spatial information. A global-local version of the observer/Kalman filter identification was therefore developed to overcome this dilemma. This method obtains a local state space realization from a reduced set of measurements. A global state space realization is subsequently obtained from a least squares process on the remaining measurements. A six-degree-of-freedom numerical simulation and experimental data from a frame structure are presented to validate the proposed method. C1 GEORGE WASHINGTON UNIV,DEPT CIVIL MECH & ENVIRONM ENGN,JOINT INST ADVANCEMENT FLIGHT & SCI,HAMPTON,VA 23681. NASA,LANGLEY RES CTR,HAMPTON,VA 23681. RP Papadopoulos, M (reprint author), VANDERBILT UNIV,DEPT MECH ENGN,SMART STRUCT LAB,BOX 1592,STN B,NASHVILLE,TN 37235, USA. NR 8 TC 0 Z9 0 U1 0 U2 2 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 SN 0731-5090 J9 J GUID CONTROL DYNAM JI J. Guid. Control Dyn. PD NOV-DEC PY 1996 VL 19 IS 6 BP 1221 EP 1225 DI 10.2514/3.21775 PG 5 WC Engineering, Aerospace; Instruments & Instrumentation SC Engineering; Instruments & Instrumentation GA VR850 UT WOS:A1996VR85000004 ER PT J AU Whorton, M Buschek, H Calise, AJ AF Whorton, M Buschek, H Calise, AJ TI Homotopy algorithm for fixed order mixed H-2/H-infinity design SO JOURNAL OF GUIDANCE CONTROL AND DYNAMICS LA English DT Article ID INFINITY AB Recent developments in the held of robust multivariable control have merged the theories of H-infinity and H-2 control. This mixed H-2/H-infinity compensator formulation allows design for nominal performance by H-2 norm minimization while guaranteeing robust stability to unstructured uncertainties by constraining the H-infinity norm. A key difficulty associated with mixed H-2/H-infinity compensation is compensator synthesis. A homotopy algorithm is presented for synthesis of fixed order mixed H-2/H-infinity compensators. Numerical results are presented for a four disk flexible structure to evaluate the efficiency of the algorithm. C1 GEORGIA INST TECHNOL,SCH AEROSP ENGN,ATLANTA,GA 30332. RP Whorton, M (reprint author), NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,ED12 PRECIS POINTING CONTROL SYST,HUNTSVILLE,AL 35812, USA. NR 19 TC 8 Z9 8 U1 0 U2 0 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 SN 0731-5090 J9 J GUID CONTROL DYNAM JI J. Guid. Control Dyn. PD NOV-DEC PY 1996 VL 19 IS 6 BP 1262 EP 1269 DI 10.2514/3.21781 PG 8 WC Engineering, Aerospace; Instruments & Instrumentation SC Engineering; Instruments & Instrumentation GA VR850 UT WOS:A1996VR85000010 ER PT J AU Chuang, CH Goodson, TD Ledsinger, LA Hanson, J AF Chuang, CH Goodson, TD Ledsinger, LA Hanson, J TI Optimality and guidance for planar multiple-burn orbit transfers SO JOURNAL OF GUIDANCE CONTROL AND DYNAMICS LA English DT Article ID OPTIMAL LOW-THRUST AB An analysis of the second variation for extremal orbital transfers is presented, as sell as a discussion of a multiple-burn guidance scheme that may be implemented for such transfers. The second variation analysis includes the examination of the conditions for free final time transfers, A continuous burn transfer is shown to have neighboring extremals through these conditions. An implicit guidance scheme is explored, which implements a neighboring optimal feedback guidance strategy to calculate thrust direction and thrust off-times. A new time-to go formulation is introduced, which has improved performance for this transfer. This continuous burn guidance scheme is adapted to multiple-burn transfers. A two-burn guidance problem is simulated. C1 NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,FLIGHT MECH BRANCH,HUNTSVILLE,AL 35812. RP Chuang, CH (reprint author), GEORGIA INST TECHNOL,SCH AEROSP ENGN,ATLANTA,GA 30332, USA. NR 16 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 SN 0731-5090 J9 J GUID CONTROL DYNAM JI J. Guid. Control Dyn. PD NOV-DEC PY 1996 VL 19 IS 6 BP 1310 EP 1316 DI 10.2514/3.21787 PG 7 WC Engineering, Aerospace; Instruments & Instrumentation SC Engineering; Instruments & Instrumentation GA VR850 UT WOS:A1996VR85000016 ER PT J AU Lim, KB Gawronski, W AF Lim, KB Gawronski, W TI Hankel singular values of flexible structures in discrete time SO JOURNAL OF GUIDANCE CONTROL AND DYNAMICS LA English DT Article ID MODEL-REDUCTION; SPACE STRUCTURES AB Approximate analytical expressions for controllability and observability grammian matrices and Hankel singular values of discrete linear time-invariant flexible structures are derived. The diagonal dominance property of the discrete grammians is shown, which results in the invariance of the principal directions. The approximate discrete Hankel singular values converge to the continuous formula with increased sampling Fate, whereas the controllability and observability grammians go to zero and infinity, respectively. The approximate formula is accurate up to frequencies close to the Nyquist. C1 CALTECH,JET PROP LAB,PASADENA,CA 91109. RP Lim, KB (reprint author), NASA,LANGLEY RES CTR,FLIGHY DYNAM & CONTROL DIV,MS 161,HAMPTON,VA 23681, USA. NR 12 TC 28 Z9 28 U1 0 U2 1 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 SN 0731-5090 J9 J GUID CONTROL DYNAM JI J. Guid. Control Dyn. PD NOV-DEC PY 1996 VL 19 IS 6 BP 1370 EP 1377 DI 10.2514/3.21796 PG 8 WC Engineering, Aerospace; Instruments & Instrumentation SC Engineering; Instruments & Instrumentation GA VR850 UT WOS:A1996VR85000025 ER PT J AU Crassidis, JL Markley, FL AF Crassidis, JL Markley, FL TI Sliding mode control using modified Rodrigues parameters SO JOURNAL OF GUIDANCE CONTROL AND DYNAMICS LA English DT Article ID MANEUVERS C1 NASA,GODDARD SPACE FLIGHT CTR,GUIDANCE NAV & CONTROL BRANCH,GREENBELT,MD 20771. RP Crassidis, JL (reprint author), CATHOLIC UNIV AMER,DEPT MECH ENGN,WASHINGTON,DC 20064, USA. NR 6 TC 100 Z9 133 U1 0 U2 5 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 SN 0731-5090 J9 J GUID CONTROL DYNAM JI J. Guid. Control Dyn. PD NOV-DEC PY 1996 VL 19 IS 6 BP 1381 EP 1383 DI 10.2514/3.21798 PG 3 WC Engineering, Aerospace; Instruments & Instrumentation SC Engineering; Instruments & Instrumentation GA VR850 UT WOS:A1996VR85000027 ER PT J AU Smith, SM Wastney, ME Nyquist, LE Chih, CY Wiesmann, H Nillen, JL Lane, HW AF Smith, SM Wastney, ME Nyquist, LE Chih, CY Wiesmann, H Nillen, JL Lane, HW TI Calcium kinetics with microgram stable isotope doses and saliva sampling SO JOURNAL OF MASS SPECTROMETRY LA English DT Article ID HUMAN PARATHYROID-HORMONE; RADIOIMMUNOASSAY AB Studies of calcium kinetics require administration of tracer doses of calcium and subsequent repeated sampling of biological fluids. This study was designed to develop techniques that would allow estimation of calcium kinetics by using small (mu g) doses of isotopes instead of the more common large (mg) doses to minimize tracer perturbation of the system and reduce cost, and to explore the use of saliva sampling as an alternative to blood sampling, Subjects received an oral dose (133 mu g) of Ca-43 and an i.v. dose (7.7 mu g) of Ca-46. Isotopic enrichment in blood, urine, saliva and feces was well above thermal ionization mass spectrometry measurement precision up to 170 h after dosing, Fractional calcium absorptions determined from isotopic ratios in blood, urine and saliva were similar, Compartmental modeling revealed that kinetic parameters determined from serum or saliva data were similar, decreasing the necessity for blood samples, It is concluded from these results that calcium kinetics can be assessed with mu g doses of stable isotopes, thereby reducing tracer costs and with saliva samples, thereby reducing the amount of blood needed. C1 GEORGETOWN UNIV,MED CTR,DEPT NEONATOL,WASHINGTON,DC 20007. NASA,LYNDON B JOHNSON SPACE CTR,PLANETARY SCI BRANCH,HOUSTON,TX 77058. LOCKHEED ENGN & SCI CO,HOUSTON,TX 77058. KRUG LIFE SCI,HOUSTON,TX 77058. RP Smith, SM (reprint author), NASA,LYNDON B JOHNSON SPACE CTR,NUTR BIOCHEM LAB SD3,BIOMED OPERAT & RES BRANCH,2101 NASA RD,HOUSTON,TX 77058, USA. NR 17 TC 17 Z9 17 U1 0 U2 3 PU JOHN WILEY & SONS LTD PI W SUSSEX PA BAFFINS LANE CHICHESTER, W SUSSEX, ENGLAND PO19 1UD SN 1076-5174 J9 J MASS SPECTROM JI J. Mass Spectrom. PD NOV PY 1996 VL 31 IS 11 BP 1265 EP 1270 DI 10.1002/(SICI)1096-9888(199611)31:11<1265::AID-JMS419>3.0.CO;2-J PG 6 WC Biophysics; Chemistry, Organic; Spectroscopy SC Biophysics; Chemistry; Spectroscopy GA VU428 UT WOS:A1996VU42800009 PM 8946733 ER PT J AU Sang, JC Barkatt, A OKeefe, JA AF Sang, JC Barkatt, A OKeefe, JA TI Attenuation of glass dissolution in the presence of natural additives SO JOURNAL OF NON-CRYSTALLINE SOLIDS LA English DT Article ID NUCLEAR WASTE AB The dissolution kinetics of silicate glasses in aqueous environments in systems which included a variety of natural crystalline solids in addition to the glass itself and the aqueous phase are reported. The results demonstrate the possibility of a dramatic decrease in the rate of dissolution of silicate glass in the presence of certain varieties of olivine-based materials. This decrease in dissolution rate was shown to be due to the fact that these additives consist mostly of Mg-based material but also contain minor amounts of Al and Ca. The combined presence of Mg with these minor species affected the corrosion rate of the glass as a whole, including its most soluble components such as boron. This study has potentially important implications to the durability of glasses exposed to natural environments. The results may be relevant to the use of active backfill materials in burial sites for nuclear waste glasses, as well as to better understanding of the environmental degradation of natural and ancient glasses. C1 CATHOLIC UNIV AMER,DEPT CHEM,WASHINGTON,DC 20064. NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. NR 17 TC 4 Z9 4 U1 1 U2 3 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0022-3093 J9 J NON-CRYST SOLIDS JI J. Non-Cryst. Solids PD NOV PY 1996 VL 208 IS 1-2 BP 170 EP 180 DI 10.1016/S0022-3093(96)00495-4 PG 11 WC Materials Science, Ceramics; Materials Science, Multidisciplinary SC Materials Science GA WB294 UT WOS:A1996WB29400018 ER PT J AU Chatterjee, S Gilbert Jr Oliker, L Schreiber, R Sheffler, TJ AF Chatterjee, S Gilbert, JR Oliker, L Schreiber, R Sheffler, TJ TI Algorithms for automatic alignment of arrays SO JOURNAL OF PARALLEL AND DISTRIBUTED COMPUTING LA English DT Article ID DATA-PARALLEL PROGRAMS; MACHINES; COMMUNICATION; GRAPH AB Aggregate data objects (such as arrays) are distributed across the processor memories when compiling a data-parallel language for a distributed-memory machine. The mapping determines the amount of communication needed to bring operands of parallel operations into alignment with each other. A common approach is to break the mapping into two stages: an alignment that maps all the objects to an abstract template, followed by a distribution that maps the template to the processors. This paper describes algorithms for solving the various facets of the alignment problem: axis and stride alignment, static and mobile offset alignment, and replication labeling. We show that optimal axis and stride alignment is NP-complete for general program graphs and give a heuristic method that can explore the space of possible solutions in a number of ways. We show that some of these strategies can give better solutions than a simple greedy approach proposed earlier. We also show how local graph contractions can reduce the size of the problem significantly without changing the best solution. This allows more complex and effective heuristics to be used. We show how to model the static offset alignment problem using linear programming, and we show that loop-dependent mobile offset alignment is sometimes necessary for optimum performance. We describe an algorithm with for determining mobile alignments for objects within do loops. We also identify situations in which replicated alignment is either required by the program itself or can be used to improve performance. We describe an algorithm based on network flow that replicates objects so as to minimize the total amount of broadcast communication in replication. (C) 1996 Academic Press, Inc. C1 XEROX CORP, PALO ALTO RES CTR, PALO ALTO, CA 94304 USA. NASA, AMES RES CTR, ADV COMP SCI RES INST, MOFFETT FIELD, CA 94035 USA. HEWLETT PACKARD CO, HP LABS 3L 5, PALO ALTO, CA 94304 USA. RAMBUS INC, MT VIEW, CA 94040 USA. RP Chatterjee, S (reprint author), UNIV N CAROLINA, DEPT COMP SCI, CAMPUS BOX 3175, SITTERSON HALL, CHAPEL HILL, NC 27599 USA. NR 22 TC 3 Z9 3 U1 0 U2 0 PU ACADEMIC PRESS INC ELSEVIER SCIENCE PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA SN 0743-7315 J9 J PARALLEL DISTR COM JI J. Parallel Distrib. Comput. PD NOV 1 PY 1996 VL 38 IS 2 BP 145 EP 157 DI 10.1006/jpdc.1996.0137 PG 13 WC Computer Science, Theory & Methods SC Computer Science GA WA828 UT WOS:A1996WA82800004 ER PT J AU Wang, LP Koblinsky, CJ AF Wang, LP Koblinsky, CJ TI Annual variability of the subtropical recirculations in the North Atlantic and North Pacific: A Topex/Poseidon study SO JOURNAL OF PHYSICAL OCEANOGRAPHY LA English DT Article ID GULF-STREAM; KUROSHIO EXTENSION; SEASONAL VARIABILITY; SURFACE TRANSPORT; GEOSAT ALTIMETER; INERTIAL RECIRCULATION; SATELLITE ALTIMETRY; TOPEX DATA; MODEL; VELOCITY AB Using sea surface height data collected by Geosat and Topex/Poseidon, the seasonal( annual) gyre circulations in the regions of the Gulf Stream and the Kuroshio Extension were studied. The seasonal gyre circulation is roughly confined to the regions where the annual mean subtropical recirculations exist. Associated with this seasonal gyre circulation, the surface transports of the Kuroshio and the Gulf Stream are found to be maximum in the late fall and minimum in the late spring. Using historical data, the authors demonstrated that these seasonal gyre circulations are mostly confined to the mixed layer. A simple diagnostic calculation of the buoyancy balance associated with the seasonal gyre circulations shows that they are driven primarily by local buoyancy flux (heating and cooling), while contribution from advection by large-scale ocean circulation is negligible. Even though the seasonal gyre circulation is primarily driven by local buoyancy forcing, it is in the opposite sense to that originally proposed by Worthington for the annual mean subtropical recirculation. The buoyancy balance within the study region suggests that dynamics associated with the mean recirculation and the seasonal gyre are fundamentally different. RP Wang, LP (reprint author), NASA,GODDARD SPACE FLIGHT CTR,CODE 971,GREENBELT,MD 20771, USA. NR 41 TC 19 Z9 19 U1 0 U2 1 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 SN 0022-3670 J9 J PHYS OCEANOGR JI J. Phys. Oceanogr. PD NOV PY 1996 VL 26 IS 11 BP 2462 EP 2479 DI 10.1175/1520-0485(1996)026<2462:AVOTSR>2.0.CO;2 PG 18 WC Oceanography SC Oceanography GA VV574 UT WOS:A1996VV57400010 ER PT J AU Vaidyanathan, H Robbins, K Rao, GM AF Vaidyanathan, H Robbins, K Rao, GM TI Effect of KOH concentration and anions on the performance of an Ni-H-2 battery positive plate SO JOURNAL OF POWER SOURCES LA English DT Article DE potassium hydroxide; positive plates; electrodes; nickel; batteries; anionic additives ID NICKEL AB The capacity and voltage behavior of electrochemically impregnated sintered nickel positive plates was examined by galvanostatic charging and discharging in a flooded electrolyte cell. Three different concentrations of potassium hydroxide (KOH) (40%, 31% and 26%) and 31% KOH containing dissolved nitrate, sulfate, or silicate were investigated The end-of-charge voltage at C/10 charge and at 10 degrees C showed the following order: 40% KOH > 31% KOH alone, and in the presence of the anions > 26% KOH. The mid-discharge voltage at C/2 discharge was higher in 26% KOH, almost the same for 31% KOH with and without the added contaminants, and much lower for 40% KOH. The plate capacity was marginally affected by cycling in all cases except for 40% KOH, where the capacity declined after 1000 cycles at 80% depth-of-discharge (DOD). At the end of cycling all the plates tested experienced a weight loss, except in the case of 31% KOH, as a result of active material extrusion. Cyclic voltammetry of miniature electrodes in 31% KOH showed that the cathodic peak potentials are less polarized at -5 degrees C (compared to 25 degrees C) in the presence and absence of silicate. This indicates a slightly higher voltage during discharge in an Ni-H-2 battery. Furthermore, the features of the current-potential profile were practically unchanged in the presence of silicate. C1 NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. RP Vaidyanathan, H (reprint author), COMSAT LABS,CLARKSBURG,MD 20871, USA. NR 14 TC 6 Z9 6 U1 1 U2 4 PU ELSEVIER SCIENCE SA LAUSANNE PI LAUSANNE PA PO BOX 564, 1001 LAUSANNE, SWITZERLAND SN 0378-7753 J9 J POWER SOURCES JI J. Power Sources PD NOV PY 1996 VL 63 IS 1 BP 7 EP 13 DI 10.1016/S0378-7753(96)02435-4 PG 7 WC Chemistry, Physical; Electrochemistry; Energy & Fuels; Materials Science, Multidisciplinary SC Chemistry; Electrochemistry; Energy & Fuels; Materials Science GA VZ791 UT WOS:A1996VZ79100002 ER PT J AU Birkan, MA Myers, RM AF Birkan, MA Myers, RM TI Introduction to arcjets and are heaters: Research status and needs special section SO JOURNAL OF PROPULSION AND POWER LA English DT Editorial Material C1 NASA,LEWIS RES CTR,NYMA INC,CLEVELAND,OH. RP Birkan, MA (reprint author), USAF,OFF SCI RES,WASHINGTON,DC 20330, USA. NR 0 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 SN 0748-4658 J9 J PROPUL POWER JI J. Propul. Power PD NOV-DEC PY 1996 VL 12 IS 6 BP 1010 EP 1010 DI 10.2514/3.51467 PG 1 WC Engineering, Aerospace SC Engineering GA VT426 UT WOS:A1996VT42600002 ER PT J AU Lichon, PG Sankovic, JM AF Lichon, PG Sankovic, JM TI Development and demonstration of a 600-second mission-average I-sp arcjet SO JOURNAL OF PROPULSION AND POWER LA English DT Article AB Recent advanced development has resulted in a 550-h demonstration of a hydrazine arcjet at a mission-average special impulse I,, of greater than 600 s, The laboratory-type arcjet thruster was operated at 1800 W through a flow rate schedule consistent with a flight application, The thruster demonstrated stable, high-efficiency operation for the duration of the test, The development effort leading to the demonstration addressed the operational and life issues associated with achieving high performance, As a result of the development activity, a wide range of performance Has also achieved, Performance levels of greater than 575 s at 1000 W and greater than 675 s at 2000 W were demonstrated. The problems encountered with extending low-power arcjet performance are discussed, Increased thruster component temperatures caused new life issues to be identified, along with low propellant flow rate stability limits, The elevated temperatures caused significant changes in the electrode geometry for a thruster based on the state-of-the-art tungsten anode designs, Three paths to solving the problem were attempted, including lowering the operating temperature through improved heat rejection, mechanical design changes to reduce thermal stresses, and higher strength materials selection, The success of this program provides substantial evidence that an arcjet capable of greater than 600-s mission-average specific impulse will be available in the near term for night qualification and application. C1 NASA,LEWIS RES CTR,CLEVELAND,OH 44135. RP Lichon, PG (reprint author), OLIN AEROSP CO,REDMOND,WA 98073, USA. NR 5 TC 10 Z9 14 U1 0 U2 0 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 SN 0748-4658 J9 J PROPUL POWER JI J. Propul. Power PD NOV-DEC PY 1996 VL 12 IS 6 BP 1018 EP 1025 DI 10.2514/3.24139 PG 8 WC Engineering, Aerospace SC Engineering GA VT426 UT WOS:A1996VT42600004 ER PT J AU Chima, RV AF Chima, RV TI Application of the k-omega turbulence model to quasi-three-dimensional turbomachinery flows SO JOURNAL OF PROPULSION AND POWER LA English DT Article RP Chima, RV (reprint author), NASA,LEWIS RES CTR,M-S 77-6,BROOKPK RD,CLEVELAND,OH 44135, USA. NR 9 TC 10 Z9 10 U1 0 U2 0 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 SN 0748-4658 J9 J PROPUL POWER JI J. Propul. Power PD NOV-DEC PY 1996 VL 12 IS 6 BP 1176 EP 1179 DI 10.2514/3.24159 PG 4 WC Engineering, Aerospace SC Engineering GA VT426 UT WOS:A1996VT42600024 ER PT J AU Mishchenko, MI AF Mishchenko, MI TI Diffuse and coherent backscattering by discrete random media .1. Radar reflectivity, polarization ratios, and enhancement factors for a half-space of polydisperse, nonabsorbing and absorbing spherical particles SO JOURNAL OF QUANTITATIVE SPECTROSCOPY & RADIATIVE TRANSFER LA English DT Article ID RADIATIVE-TRANSFER MODELS; MULTIPLE-SCATTERING; WEAK LOCALIZATION; PLANETARY ATMOSPHERES; LIGHT-SCATTERING; NONSPHERICAL PARTICLES; RAYLEIGH-SCATTERING; SATURNS RINGS; MATRIX; ICE AB It has been demonstrated recently that diffuse, incoherent multiple scattering of electromagnetic waves by media composed of randomly positioned, discrete scattering particles is always accompanied by coherent backscattering and may explain intriguing opposition phenomena observed for some solar system bodies, in particular peculiar characteristics of radar returns from icy satellite surfaces. In this paper, we study theoretically photometric and polarization characteristics of diffuse and coherent backscattering by discrete random media. The cyclical component of the Stokes reflection matrix at exactly the backscattering direction is expressed in terms of the ladder component, and the ladder component is accurately computed by numerically solving the vector radiative transfer equation. We give formulas expressing the radar reflectivity, radar linear and circular polarization ratios, and backscattering enhancement factors in the elements of the Stokes reflection matrix and describe in detail the computational technique used. Assuming that the scattering medium is homogeneous and semi-infinite and that scattering particles are polydisperse spheres, we report the results of a comprehensive theoretical survey of the dependence of the photometric and polarization characteristics of the radar return on the illumination zenith angle and on the particle effective size parameter and real and imaginary parts of the refractive index. Copyright (C) 1996 Elsevier Science Ltd C1 SUNY STONY BROOK,NASA,INST TERR & PLANETARY ATMOSPHERES,NEW YORK,NY 10025. RP Mishchenko, MI (reprint author), SUNY STONY BROOK,NASA,GODDARD INST SPACE STUDIES,2880 BROADWAY,NEW YORK,NY 10025, USA. RI Mishchenko, Michael/D-4426-2012 NR 66 TC 41 Z9 42 U1 0 U2 1 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, ENGLAND OX5 1GB SN 0022-4073 J9 J QUANT SPECTROSC RA JI J. Quant. Spectrosc. Radiat. Transf. PD NOV PY 1996 VL 56 IS 5 BP 673 EP 702 DI 10.1016/S0022-4073(96)00117-3 PG 30 WC Optics; Spectroscopy SC Optics; Spectroscopy GA VV044 UT WOS:A1996VV04400003 ER PT J AU Olynick, DR Henline, WD AF Olynick, DR Henline, WD TI Navier-Stokes heating calculations for benchmark thermal protection system sizing SO JOURNAL OF SPACECRAFT AND ROCKETS LA English DT Article AB A study was carried out to identify, select, and benchmark simulation techniques needed for thermal protection material selection and sizing for reusable launch vehicles. Fully viscous, chemically reacting, Navier-Stokes solutions for the flow around a sphere are generated and compared using three different flow solvers. The effects of grid resolution, algorithm, transport modeling, and surface boundary conditions on the magnitude and convergence of the predicted heat transfer rate are examined. A third-order Van Leer inviscid upwind flux formulation was found to be a good method for surface heat transfer predictions. A number of three-dimensional, chemically reacting, Navier-Stokes flow solutions are generated for the nose of a single-stage-to-orbit rocket at angle of attack. A methodology for thermal protection system material selection is demonstrated. The strong influence of thermal protection system material selection on predicted heat transfer rates and surface temperatures is demonstrated. Further, it is shown that the changes in surface emissivity and catalycity at the interfaces between different thermal protection system concepts can produce large jumps in the predicted surface temperature. These gradients must be accounted for in the thermal protection system and vehicle design process. RP Olynick, DR (reprint author), NASA, AMES RES CTR, REACTING FLOW ENVIRONM BRANCH, MC 230-2, MOFFETT FIELD, CA 94035 USA. NR 31 TC 7 Z9 7 U1 0 U2 1 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 SN 0022-4650 J9 J SPACECRAFT ROCKETS JI J. Spacecr. Rockets PD NOV-DEC PY 1996 VL 33 IS 6 BP 807 EP 814 DI 10.2514/3.26842 PG 8 WC Engineering, Aerospace SC Engineering GA VX930 UT WOS:A1996VX93000008 ER PT J AU Jaworske, DA Jefferies, KS Mason, LS AF Jaworske, DA Jefferies, KS Mason, LS TI Alignment and initial operation of an advanced solar simulator SO JOURNAL OF SPACECRAFT AND ROCKETS LA English DT Article AB A solar simulator utilizing nine 30-kW xenon ape lamps was built to provide radiant power for testing a solar dynamic space power system in a thermal vacuum environment. The advanced solar simulator achieved the following values specific to the solar dynamic system: 1) a subtense angle of 1 deg; 2) the ability to vary solar simulator intensity up to 1.7 kW/m(2); 3) a beam diameter of 4.8 m; and 4) uniformity of illumination on the order of +/-10%. The flexibility of the solar simulator design allows for other potential uses of the facility. RP Jaworske, DA (reprint author), NASA,LEWIS RES CTR,POWER TECHNOL DIV,CLEVELAND,OH 44135, USA. NR 5 TC 2 Z9 2 U1 0 U2 3 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 SN 0022-4650 J9 J SPACECRAFT ROCKETS JI J. Spacecr. Rockets PD NOV-DEC PY 1996 VL 33 IS 6 BP 867 EP 869 DI 10.2514/3.26852 PG 3 WC Engineering, Aerospace SC Engineering GA VX930 UT WOS:A1996VX93000018 ER PT J AU Stassinopoulos, EG Brucker, GJ Adolphsen, JN Barth, J AF Stassinopoulos, EG Brucker, GJ Adolphsen, JN Barth, J TI Radiation-induced anomalies in satellites SO JOURNAL OF SPACECRAFT AND ROCKETS LA English DT Article ID INDUCED UPSETS; SPACE; CRRES; BELT AB Radiation-induced anomalies are discussed and a compilation of known events in semiconductor devices and electronic systems in commercial and government satellites is provided. The various types of anomalies that have been observed and the interactions of space radiation with devices are described. The number of events is limited to those occurring in some government (NASA, National Oceanic and Atmospheric Administration) and commercial spacecraft. In general, manufacturers are reluctant to disclose their failures, and so these sources of events are not readily available. In the case of government spacecraft, anomalies on Department of Defense classified and unclassified satellites are not often reported. Thus, the list of events here is not complete, It represents only the proverbial tip of the iceberg. An important message for satellite designers is to anticipate this environmental threat and provide remedies or safeguards. C1 RADIAT EFFECTS CONSULTANTS,LONG BEACH,NJ 07764. UNISYS,LANHAM,MD 20706. RP Stassinopoulos, EG (reprint author), NASA,GODDARD SPACE FLIGHT CTR,RADIAT PHYS OFF,EARTH SCI DIRECTORATE,CODE 900,GREENBELT,MD 20770, USA. NR 31 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 SN 0022-4650 J9 J SPACECRAFT ROCKETS JI J. Spacecr. Rockets PD NOV-DEC PY 1996 VL 33 IS 6 BP 877 EP 882 DI 10.2514/3.26854 PG 6 WC Engineering, Aerospace SC Engineering GA VX930 UT WOS:A1996VX93000020 ER PT J AU Wessen, RR AF Wessen, RR TI Tradeoffs between science objectives and ground system capability SO JOURNAL OF SPACECRAFT AND ROCKETS LA English DT Article AB The most fundamental objective of all planetary missions is to return data, To accomplish this, a spacecraft is fabricated and built, software is planned and coded, and a ground system is designed and implemented, However, a systems engineering approach to determine how the collection of data drives ground system capabilities has received little attention, A technique by which science objectives can be quantitatively evaluated is defined, For illustrative purposes, it is applied to the Cassini mission, This mission, to be launched in 1997, is an international endeavor designed to orbit Saturn for four years. The results of this system's engineering approach will show which science objectives drive specific ground system capabilities, In addition, this technique can assist system engineers in the selection of the science payload during preproject mission planning, ground system designers during ground system development and implementation, and operations personnel during the mission. RP Wessen, RR (reprint author), CALTECH,JET PROP LAB,4800 OAK GROVE DR,MAIL STOP 301-250D,PASADENA,CA 91109, USA. NR 3 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 SN 0022-4650 J9 J SPACECRAFT ROCKETS JI J. Spacecr. Rockets PD NOV-DEC PY 1996 VL 33 IS 6 BP 883 EP 886 DI 10.2514/3.26855 PG 4 WC Engineering, Aerospace SC Engineering GA VX930 UT WOS:A1996VX93000021 ER PT J AU Barnes, JR Haberle, RM AF Barnes, JR Haberle, RM TI The Martian zonal-mean circulation: Angular momentum and potential vorticity structure in GCM simulations SO JOURNAL OF THE ATMOSPHERIC SCIENCES LA English DT Article ID MARS ATMOSPHERIC DYNAMICS; GENERAL-CIRCULATION; DUST STORMS; MIDDLE ATMOSPHERE; VENUS; MODELS; WINDS AB Analysis of simulations performed with the NASA/Ames Mars GCM shows that under dusty conditions the Northern Hemisphere winter solstice circulation becomes characterized by a zonally averaged state in which the potential vorticity at upper levels is very small outside of high latitudes. The available observational data-in particular the 15-mu m observations obtained by the Viking IRTM during the 1977 winter solstice global dust storm-provide evidence for changes in the Martian circulation that are basically like those found in the GCM. In the Mars GCM simulations for dusty solstice conditions, an extremely intense and approximately angular-momentum-conserving Hadley circulation is responsible for creating the low potential vorticity configuration. This can be contrasted with the Venus-Titan numerical simulations discussed by Allison et al. in which quasi-barotropic eddies appear to be largely responsible for the existence of low potential vorticity in lower and midlatitudes. At a near-equinox season the simulated Mars circulation is greatly weakened in comparison to that for solstice conditions, angular momentum is not approximately conserved by the mean meridional circulation, and potential vorticity increases relatively smoothly away from the equator. C1 NASA,AMES RES CTR,DIV SPACE SCI,MOFFETT FIELD,CA 94035. RP Barnes, JR (reprint author), OREGON STATE UNIV,COLL OCEAN & ATMOSPHER SCI,OCEANOG ADM BLDG 104,CORVALLIS,OR 97331, USA. NR 24 TC 17 Z9 17 U1 1 U2 2 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 SN 0022-4928 J9 J ATMOS SCI JI J. Atmos. Sci. PD NOV 1 PY 1996 VL 53 IS 21 BP 3143 EP 3156 DI 10.1175/1520-0469(1996)053<3143:TMZMCA>2.0.CO;2 PG 14 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA VT966 UT WOS:A1996VT96600009 ER PT J AU Spitale, GC Tribble, A AF Spitale, GC Tribble, A TI ISO activities in space environments SO JOURNAL OF THE INSTITUTE OF ENVIRONMENTAL SCIENCES LA English DT Editorial Material RP Spitale, GC (reprint author), CALTECH,JET PROP LAB,PASADENA,CA 91109, USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU INST ENVIRONMENTAL SCI PI MT PROSPECT PA 940 E NORTHWEST HIGHWAY, MT PROSPECT, IL 60056 SN 1052-2883 J9 J INST ENVIRON SCI JI J. Inst. Environ. Sci. PD NOV-DEC PY 1996 VL 39 IS 6 BP 12 EP 13 PG 2 WC Engineering, Environmental; Environmental Sciences; Instruments & Instrumentation SC Engineering; Environmental Sciences & Ecology; Instruments & Instrumentation GA WA184 UT WOS:A1996WA18400003 ER PT J AU Hirayama, K Glytsis, EN Gaylord, TK Wilson, DW AF Hirayama, K Glytsis, EN Gaylord, TK Wilson, DW TI Rigorous electromagnetic analysis of diffractive cylindrical lenses SO JOURNAL OF THE OPTICAL SOCIETY OF AMERICA A-OPTICS IMAGE SCIENCE AND VISION LA English DT Article ID OPTICAL-ELEMENTS; DESIGN AB A novel two-region formulation of the rigorous electromagnetic boundary element method (BEM) is developed and applied to practical diffractive cylindrical lenses of continuous profile and with discrete levels (32, 8, and 2). The performance of these diffractive lenses is presented for incident waves of TE and TM polarization, for a range of beam profiles, and for normal and nonnormal incidence. An optimum width of the Gaussian beam is determined. The BEM is shown to be accurate and versatile, providing the numerical and graphical results that are needed for analysis and design of diffractive elements. (C) 1996 Optical Society of America. C1 GEORGIA INST TECHNOL,MICROELECT RES CTR,ATLANTA,GA 30332. CALTECH,JET PROP LAB,PASADENA,CA 91109. RP Hirayama, K (reprint author), GEORGIA INST TECHNOL,SCH ELECT & COMP ENGN,ATLANTA,GA 30332, USA. RI Glytsis, Elias/M-5066-2013 NR 19 TC 98 Z9 98 U1 0 U2 3 PU OPTICAL SOC AMER PI WASHINGTON PA 2010 MASSACHUSETTS AVE NW, WASHINGTON, DC 20036 SN 0740-3232 J9 J OPT SOC AM A JI J. Opt. Soc. Am. A-Opt. Image Sci. Vis. PD NOV PY 1996 VL 13 IS 11 BP 2219 EP 2231 DI 10.1364/JOSAA.13.002219 PG 13 WC Optics SC Optics GA VP770 UT WOS:A1996VP77000010 ER PT J AU Mackowski, DW Mishchenko, MI AF Mackowski, DW Mishchenko, MI TI Calculation of the T matrix and the scattering matrix for ensembles of spheres SO JOURNAL OF THE OPTICAL SOCIETY OF AMERICA A-OPTICS IMAGE SCIENCE AND VISION LA English DT Article ID DISCRETE-DIPOLE APPROXIMATION; ABSORPTION CROSS-SECTIONS; ELECTROMAGNETIC SCATTERING; LIGHT-SCATTERING; NONSPHERICAL PARTICLES; COMPOUNDED SPHERES; OBSERVABLES; CLUSTERS AB We present a method for determination of the random-orientation polarimetric scattering properties of an arbitrary, nonsymmetric cluster of spheres. The method is based on calculation of the cluster T matrix, from which the orientation-averaged scattering matrix and total cross sections can be analytically obtained. An efficient numerical method is developed for the T-matrix calculation, which is faster and requires less computer memory than the alternative approach based on matrix inversion. The method also allows calculation of the random-orientation scattering properties of a cluster in a fraction of the time required for numerical quadrature. Numerical results for the random-orientation scattering matrix are presented for sphere ensembles in the form of densely packed clusters and linear chains. (C) 1996 Optical Society of America. C1 SUNY STONY BROOK,STONY BROOK,NY 11794. NASA,GODDARD INST SPACE STUDIES,NEW YORK,NY 10025. RP Mackowski, DW (reprint author), AUBURN UNIV,DEPT MECH ENGN,AUBURN,AL 36849, USA. RI Mackowski, Daniel/K-1917-2013; Mishchenko, Michael/D-4426-2012 NR 27 TC 403 Z9 414 U1 5 U2 29 PU OPTICAL SOC AMER PI WASHINGTON PA 2010 MASSACHUSETTS AVE NW, WASHINGTON, DC 20036 SN 0740-3232 J9 J OPT SOC AM A JI J. Opt. Soc. Am. A-Opt. Image Sci. Vis. PD NOV PY 1996 VL 13 IS 11 BP 2266 EP 2278 DI 10.1364/JOSAA.13.002266 PG 13 WC Optics SC Optics GA VP770 UT WOS:A1996VP77000015 ER PT J AU Stahelin, M Zysset, B Ahlheim, M Marder, SR Bedworth, PV Runser, C Barzoukas, M Fort, A AF Stahelin, M Zysset, B Ahlheim, M Marder, SR Bedworth, PV Runser, C Barzoukas, M Fort, A TI Nonlinear optical properties of push-pull polyenes for electro-optics SO JOURNAL OF THE OPTICAL SOCIETY OF AMERICA B-OPTICAL PHYSICS LA English DT Article ID SIDE-CHAIN POLYMERS; HYPERPOLARIZABILITIES; DERIVATIVES; CHROMOPHORES; MOLECULES AB Improved nonlinear organic chromophores of varying conjugation length with either thiobarbituric acid or 3-dicyanomethylene-2,3-dihydrobenzothiophene-1,1-dioxide (FORON(R) Blue) accepters have been synthesized and investigated for their nonlinear optical properties. Very large quadratic hyperpolarizabilities beta(-2 omega; omega, omega) have been found, up to 25,700 x 10(-48) esu at lambda = 1.91 mu m. In a guest-host polymer very high electro-optic (EO) coefficients, of up to 55 pm/V, have been determined at lambda = 1.31 mu m with 20-wt % chromophore loading. We find good agreement between molecular parameters evaluated by electric-field-induced second-harmonic generation (EFISH) and the measurements of guest-host solid-solid solutions. The latter method is well suited to the determination of the product of dipole moment mu and hyperpolarizability beta quickly and reliably at the wavelength of interest for EO applications without the complications associated with EFISH measurements. (C) 1996 Optical Society of America. C1 SANDOZ HUNINGUE SA,F-68330 HUNINGUE,FRANCE. CALTECH,JET PROP LAB,PASADENA,CA 91109. CALTECH,BECKMAN INST,PASADENA,CA 91125. CNRS UM 046,OPT NONLINEAIRE & OPTOELECT GRP,F-67037 STRASBOURG,FRANCE. RP Stahelin, M (reprint author), UNIV BASEL,INST PHYS,CH-4056 BASEL,SWITZERLAND. NR 23 TC 10 Z9 10 U1 2 U2 3 PU OPTICAL SOC AMER PI WASHINGTON PA 2010 MASSACHUSETTS AVE NW, WASHINGTON, DC 20036 SN 0740-3224 J9 J OPT SOC AM B JI J. Opt. Soc. Am. B-Opt. Phys. PD NOV PY 1996 VL 13 IS 11 BP 2401 EP 2407 DI 10.1364/JOSAB.13.002401 PG 7 WC Optics SC Optics GA VT941 UT WOS:A1996VT94100005 ER PT J AU Priscu, JC Downes, MT McKay, CP AF Priscu, JC Downes, MT McKay, CP TI Extreme supersaturation of nitrous oxide in a poorly ventilated Antarctic lake SO LIMNOLOGY AND OCEANOGRAPHY LA English DT Article ID LOW OXYGEN CONCENTRATIONS; N2O; NITRIFICATION; DENITRIFICATION; BACTERIA; WATER; N-15; PHYTOPLANKTON; DEFICIENCY; SOLUBILITY AB Lake Bonney, a permanently ice-covered Antarctic lake, has a middepth maximum N2O concentration of 41.6 mu M N (>580,000% saturation with respect to the global average mixing ratio of N2O) in its east lobe, representing the highest level vet reported for a natural aquatic system. Atmospheric N2O over the lake was 45% above the global average, indicating that this lake is an atmospheric source of N2O. Apparent N2O production (ANP) was correlated with apparent oxygen utilization (AOU), and denitrification was not detectable, implying that nitrification is the primary source for this gas. The slope of a regression of ANP on AOU revealed that potential N2O production per unit of potential O-2 consumed in the east lobe of Lake Bonney is at least two orders of magnitude greater than reported for the ocean. The maximum yield ratio for N2O [ANP/(NO2- + NO3-)] in Lake Bonney is 26% (i.e. 1 atom of N appears in N2O for every 3.9 atoms appearing in oxidized N), which exceeds previous reports for pelagic systems, being similar to values from reduced sediments. Areal N2O flux from the lake to the atmosphere is >200 times the areal flux reported for oceanic systems; most of this gas apparently enters the atmosphere through a small moat that occupies similar to 3% of the surface of the lake and exists for similar to 10 weeks in summer. C1 NATL INST WATER & ATMOSPHER RES,CHRISTCHURCH,NEW ZEALAND. NASA,AMES RES CTR,DIV SPACE SCI,MOFFETT FIELD,CA 94035. RP Priscu, JC (reprint author), MONTANA STATE UNIV,DEPT BIOL,BOZEMAN,MT 59717, USA. FU NCCDPHP CDC HHS [DPP 88-20591, DPP 91-17907] NR 46 TC 39 Z9 42 U1 1 U2 9 PU AMER SOC LIMNOLOGY OCEANOGRAPHY PI WACO PA 5400 BOSQUE BLVD, STE 680, WACO, TX 76710-4446 SN 0024-3590 J9 LIMNOL OCEANOGR JI Limnol. Oceanogr. PD NOV PY 1996 VL 41 IS 7 BP 1544 EP 1551 PG 8 WC Limnology; Oceanography SC Marine & Freshwater Biology; Oceanography GA WU273 UT WOS:A1996WU27300018 PM 11541224 ER PT J AU Roth, DJ Hendricks, JL Whalen, MF Bodis, JR Martin, K AF Roth, DJ Hendricks, JL Whalen, MF Bodis, JR Martin, K TI Commercial implementation of NASA-developed ultrasonic imaging methods via technology transfer SO MATERIALS EVALUATION LA English DT Article DE ceramics; composites; failure analysis; imaging; nondestructive evaluation; process control; technology transfer; thickness; ultrasonic testing; velocity AB This article describes ultrasonic imaging methods developed and refined by the nondestructive evaluation group at NASA Lewis Research Center and their commercial implementation. The methods are based on the measurement of ultrasonic velocity in a material. Two velocity imaging methods were implemented: thickness based (apparent) velocity and thickness independent reflector plate velocity methods. The article demonstrates capabilities of the commercial implementation. The significance of this technology transfer effort is that (1) the commercial implementation of velocity imaging provides a 100x speed increase in scanning and processing over the laboratory methods developed at Lewis, thus making it applicable in industrial quality control application; and (2) the aerospace and other materials development intensive industries which use extensive ultrasonic inspection for process control and failure analysis will now have an alternative, highly quantitative, and revealing imaging method commercially available. C1 SONIX INC,SPRINGFIELD,VA 22152. CLEVELAND STATE UNIV,CLEVELAND,OH 44115. RP Roth, DJ (reprint author), NASA,LEWIS RES CTR,CLEVELAND,OH 44135, USA. NR 14 TC 2 Z9 2 U1 0 U2 0 PU AMER SOC NON-DESTRUCTIVE TEST PI COLUMBUS PA 1711 ARLINGATE LANE PO BOX 28518, COLUMBUS, OH 43228-0518 SN 0025-5327 J9 MATER EVAL JI Mater. Eval. PD NOV PY 1996 VL 54 IS 11 BP 1305 EP 1309 PG 5 WC Materials Science, Characterization & Testing SC Materials Science GA VT010 UT WOS:A1996VT01000020 ER PT J AU Weaver, ML Kaufman, MJ Noebe, RD AF Weaver, ML Kaufman, MJ Noebe, RD TI Manifestations of dynamic strain aging in soft-oriented NiAl single crystals SO METALLURGICAL AND MATERIALS TRANSACTIONS A-PHYSICAL METALLURGY AND MATERIALS SCIENCE LA English DT Article ID MECHANICAL-PROPERTIES; SERRATED FLOW; ALLOYS; BEHAVIOR; TEMPERATURES; PRESSURE; PURITY; STRESS; STEEL AB The tensile and compressive properties of six NiAl-base single-crystal alloys have been investigated at temperatures between 77 and 1200 K. The normalized critical resolved shear stresses (CRSS/E) and work-hardening rates (theta/E) for these alloys generally decreased with increasing temperature. However, anomalous peaks or plateaus for these properties were observed in conventional purity (CPNiAl), Si-doped (NiAl-Si), C-doped low Si (UF-NiA11), and Mo-doped (NiAl-Mo) alloys at intermediate temperatures (600 to 1000 K). This anomalous behavior was not observed in high-purity, low interstitial material (HP-NiAl). Low or negative strain-rate sensitivities (SRS) also were observed in all six alloys in this intermediate temperature range. Coincident with the occurrence of negative strain-rate sensitivities was the observation of serrated stress-strain curves in the CPNiAl and NiAl-Si alloys. These phenomena have been attributed to dynamic strain aging (DSA). Chemical analysis of the alloys used in this study suggests that the main specie responsible for strain aging in NiAl is C but indicate that residual Si impurities can enhance the strain aging effects. The corresponding dislocation microstructures at low temperatures (300 to 600 K) were composed of well-defined cells. At intermediate temperatures (600 to 900 K), either poorly defined cells or coarse bands of localized slip, reminiscent of the vein structures observed in low-cycle fatigue specimens deformed in the DSA regime, were observed in conventional purity, Si-doped, and in Mo-doped alloys, In contrast, a well-defined cell structure persisted in the low interstitial, high-purity alloy. At elevated temperatures (greater than or equal to 1000 K), more uniformly distributed dislocations and sub-boundaries were observed in all alloys. These observations are consistent with the occurrence of DSA in NiAl single-crystal alloys at intermediate temperatures. C1 FLORIDA STATE UNIV, CTR MAT RES & TECHNOL, TALLAHASSEE, FL 32310 USA. UNIV FLORIDA, DEPT MAT SCI & ENGN, GAINESVILLE, FL 32611 USA. NASA, LEWIS RES CTR, DIV MAT, CLEVELAND, OH 44135 USA. RP FLORIDA A&M UNIV, CTR NONLINEAR & NONEQUILIBRIUM AEROSCI, TALLAHASSEE, FL 32310 USA. RI Kaufman, Michael/A-7737-2012 NR 66 TC 9 Z9 9 U1 0 U2 2 PU SPRINGER PI NEW YORK PA 233 SPRING ST, NEW YORK, NY 10013 USA SN 1073-5623 EI 1543-1940 J9 METALL MATER TRANS A JI Metall. Mater. Trans. A-Phys. Metall. Mater. Sci. PD NOV PY 1996 VL 27 IS 11 BP 3542 EP 3557 DI 10.1007/BF02595446 PG 16 WC Materials Science, Multidisciplinary; Metallurgy & Metallurgical Engineering SC Materials Science; Metallurgy & Metallurgical Engineering GA VT798 UT WOS:A1996VT79800019 ER PT J AU Goller, G Koty, DP Tewari, SN Singh, M Tekin, A AF Goller, G Koty, DP Tewari, SN Singh, M Tekin, A TI Wear and friction behavior of metal impregnated microporous carbon composites SO METALLURGICAL AND MATERIALS TRANSACTIONS A-PHYSICAL METALLURGY AND MATERIALS SCIENCE LA English DT Article ID MATRIX AB Metal-matrix composites have been prepared by pressure-infiltration casting of copper-base alloy melts into microporous carbon preforms. The carbon preforms contained varying proportions of amorphous carbon and graphite. Load dependence of the wear and friction behavior of the composite pins has been examined under ambient conditions against cast-iron plates, using a pin-on-plate reciprocating wear tester. The wear resistance of the composite is significantly improved, as compared with the base alloy. Contrary to the normally expected behavior, the addition of graphite to the amorphous carbon does not reduce the friction coefficient, especially at high loads. The wear and friction behavior of the composites is very sensitive to the size and distribution of the microstructural constituents. C1 TECH UNIV ISTANBUL,DEPT MAT SCI,ISTANBUL,TURKEY. APPL MAT INC,BOISE,ID 83705. NASA,LEWIS RES CTR,NYMA INC,CLEVELAND,OH 44135. RP Goller, G (reprint author), CLEVELAND STATE UNIV,DEPT CHEM ENGN,CLEVELAND,OH 44115, USA. OI Goller, Gultekin/0000-0003-4680-3936 NR 15 TC 5 Z9 11 U1 0 U2 3 PU MINERALS METALS MATERIALS SOC PI WARRENDALE PA 420 COMMONWEALTH DR, WARRENDALE, PA 15086 SN 1073-5623 J9 METALL MATER TRANS A JI Metall. Mater. Trans. A-Phys. Metall. Mater. Sci. PD NOV PY 1996 VL 27 IS 11 BP 3727 EP 3738 DI 10.1007/BF02595464 PG 12 WC Materials Science, Multidisciplinary; Metallurgy & Metallurgical Engineering SC Materials Science; Metallurgy & Metallurgical Engineering GA VT798 UT WOS:A1996VT79800037 ER PT J AU Harris, A AF Harris, A TI ''Tunguska '96'', Bologna, Italy 1996 July 15-17 SO METEORITICS & PLANETARY SCIENCE LA English DT Editorial Material RP Harris, A (reprint author), CALTECH,JET PROP LAB,4800 OAK GROVE DR,PASADENA,CA 91109, USA. NR 4 TC 0 Z9 0 U1 0 U2 0 PU METEORITICAL SOC PI FAYETTEVILLE PA DEPT CHEMISTRY/BIOCHEMISTRY, UNIV ARKANSAS, FAYETTEVILLE, AR 72701 SN 0026-1114 J9 METEORIT PLANET SCI JI Meteorit. Planet. Sci. PD NOV PY 1996 VL 31 IS 6 BP 697 EP 697 PG 1 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA VY468 UT WOS:A1996VY46800003 ER PT J AU Basu, A McKay, DS Morris, RV Wentworth, SJ AF Basu, A McKay, DS Morris, RV Wentworth, SJ TI Anatomy of individual agglutinates from a lunar highland soil SO METEORITICS & PLANETARY SCIENCE LA English DT Article ID VAPOR DEPOSITS; REGOLITH; GLASS AB We report results of our investigation of the relationship between values of I-S/FeO (relative concentration of nanophase Fe-0 divided by total FeO content), glass abundance, total Fe content, and degree of digestion of < 20 mu m clasts for 22 individual agglutinates (250-1000 mu m) from the mature Apollo 16 soil 61181 (I-S/FeO = 82 units in the < 250 mu m fraction). Agglutinates are important products of space weathering on the Moon, and they influence spectral observations at visible and near-IR wavelengths. Values of I-S/FeO for individual agglutinates (250-1000 mu m) within this single soil span a range from 3 to 262 units which is larger than the range observed for all Apollo 16 bulk soils (similar to 0 to 110 units). No correlation was observed between I-S/FeO and glass abundance and FeO concentrations for either agglutinitic glass or whole agglutinate particles under investigation. Our results suggest that the variation in I-S/FeO for agglutinates from a single soil may be in part a consequence of natural mixing processes on the Moon that produce highly-variable environments (with respect to surface exposure) for agglutinate formation and in part to variable kinetics of reactions in an agglutinate melt, which are influenced by a variety of factors including melt composition, temperature, impactor velocity, and quench rate. We cannot exclude but do not see evidence for other processes including addition of exotic agglutinates, micrometeoritic bombardment into compositionally-diverse microtargets, recycling of agglutinates, preferential melting of very fine soil particles, and production of nanophase Fe-0 in amorphous rims of very fine irradiated lunar grains contributing to the observed variation of I-S/FeO. C1 NASA,LYNDON B JOHNSON SPACE CTR,HOUSTON,TX 77058. LOCKHEED MARTIN,HOUSTON,TX 77058. RP Basu, A (reprint author), INDIANA UNIV,DEPT GEOL SCI,BLOOMINGTON,IN 47405, USA. NR 42 TC 5 Z9 6 U1 1 U2 1 PU METEORITICAL SOC PI FAYETTEVILLE PA DEPT CHEMISTRY/BIOCHEMISTRY, UNIV ARKANSAS, FAYETTEVILLE, AR 72701 SN 0026-1114 J9 METEORIT PLANET SCI JI Meteorit. Planet. Sci. PD NOV PY 1996 VL 31 IS 6 BP 777 EP 782 PG 6 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA VY468 UT WOS:A1996VY46800009 ER EF