FN Thomson Reuters Web of Science™ VR 1.0 PT J AU Yang, TC George, K Johnson, AS Durante, M Fedorenko, BS AF Yang, TC George, K Johnson, AS Durante, M Fedorenko, BS TI Biodosimetry results from space flight Mir-18 SO RADIATION RESEARCH LA English DT Article; Proceedings Paper CT Workshop on Space Radiation Damage and Biodosimetry CY SEP 09-10, 1996 CL CTR ADV SPACE STUDIES, HOUSTON, TEXAS HO CTR ADV SPACE STUDIES ID RADIATION; CHROMOSOMES; EXCHANGE; DAMAGE AB Astronauts are classified as radiation workers due to the presence of ionizing radiation in space. For the assessment of health risks, physical dosimetry has been indispensable. However, the change of the location of dosimeters on the crew members, the variation in dose rate with location inside the spacecraft and the unknown biological effects of microgravity can introduce significant uncertainties in estimating exposure. To circumvent such uncertainty, a study on the cytogenetic effects of space radiation in human lymphocytes was proposed and conducted for Mir-18, a 115-day mission. This study used fluorescence in situ hybridization (FISH) with whole-chromosome painting probes to score chromosomal exchanges and the Giemsa staining method to determine the frequency of dicentrics. The growth kinetics of cells and sister chromatid exchanges (SCEs) were examined to ensure that chromosomal aberrations were scored in the first mitosis and were induced primarily by space radiation. Our results showed that the frequency of chromosomal aberrations increased significantly in postflight samples compared to samples drawn prior to flight, and that the frequency of SCEs was similar for both pre- and postflight samples. Based on a dose-response curve for preflight samples exposed to gamma rays, the absorbed dose received by crew members during the mission was estimated to be about 14.75 cSv. Because the absorbed dose measured by physical dosimeters is 5.2 cGy for the entire mission, the RBE is about 2.8. (C) 1997 by Radiation Research Society. C1 NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. Krug Life Sci Inc, Houston, TX 77058 USA. Univ Naples Federico II, Naples, Italy. Minist Publ Hlth Russia, Inst Biomed Problems, Moscow, Russia. RP Yang, TC (reprint author), NASA, Lyndon B Johnson Space Ctr, SD2, Houston, TX 77058 USA. RI Durante, Marco/K-1315-2014 NR 20 TC 48 Z9 50 U1 0 U2 1 PU RADIATION RESEARCH SOC PI OAK BROOK PA 2021 SPRING RD, STE 600, OAK BROOK, IL 60521 USA SN 0033-7587 J9 RADIAT RES JI Radiat. Res. PD NOV PY 1997 VL 148 IS 5 SU S BP S17 EP S23 DI 10.2307/3579712 PG 7 WC Biology; Biophysics; Radiology, Nuclear Medicine & Medical Imaging SC Life Sciences & Biomedicine - Other Topics; Biophysics; Radiology, Nuclear Medicine & Medical Imaging GA YU196 UT WOS:000071691900004 PM 9355852 ER PT J AU Yang, TC Lucas, JN AF Yang, TC Lucas, JN TI Introduction SO RADIATION RESEARCH LA English DT Editorial Material C1 NASA, Lyndon B Johnson Space Ctr, Div Med Sci, Radiat Biophys Lab, Houston, TX 77058 USA. Univ Calif Lawrence Livermore Natl Lab, Livermore, CA 94550 USA. RP Yang, TC (reprint author), NASA, Lyndon B Johnson Space Ctr, Div Med Sci, Radiat Biophys Lab, Houston, TX 77058 USA. NR 0 TC 0 Z9 1 U1 0 U2 0 PU RADIATION RESEARCH SOC PI OAK BROOK PA 2021 SPRING RD, STE 600, OAK BROOK, IL 60521 USA SN 0033-7587 J9 RADIAT RES JI Radiat. Res. PD NOV PY 1997 VL 148 IS 5 SU S BP S1 EP S2 PG 2 WC Biology; Biophysics; Radiology, Nuclear Medicine & Medical Imaging SC Life Sciences & Biomedicine - Other Topics; Biophysics; Radiology, Nuclear Medicine & Medical Imaging GA YU196 UT WOS:000071691900001 ER PT J AU Foster, JL Chang, ATC Hall, DK AF Foster, JL Chang, ATC Hall, DK TI Comparison of snow mass estimates from prototype passive microwave snow algorithm, a revised algorithm and a snow depth climatology SO REMOTE SENSING OF ENVIRONMENT LA English DT Article ID ALBEDO; COVER AB While it is recognized that no single snow algorithm is capable of producing accurate global estimates of snow depth, for research purposes it is useful to test an algorithm's performance in different climatic areas in order to see how it responds to a variety of snow conditions. This study is one of the first to develop separate passive microwave snow algorithms for North American and Eurasia by including parameters that consider the effects of variations in forest cover sand crystal size on microwave brightness temperature. A new algorithm (GSFC 1996) is compared to a prototype algorithm (Chang et al., 1987) and to a snow depth climatology (SDC), which for this study is considered to be a standard reference or baseline. It is shown that the GSFC 1996 algorithm compares much more favorably to the SDC than does the Chang et al. (1987) algorithm. For example, in North American in February there is a 15% difference between the GSFC 1996 algorithm and the SDC, but with the Chang et al. (1987) algorithm the difference is greater than 50%. In Eurasia, also in February, there is only a 1.3% difference between the GSFC 1996 algorithm and the SDC, whereas with the Chang et al. (1987) algorithm the difference is about 20%. As expected, differences tend to be less when the snow cover extent is greater, particularly for Eurasia. The GSFC 1996 algorithm performs better in North America in each month than does the Chang et al. (1987) algorithm. This is also the case in Eurasia, except in April and May when the Chang et al. (1987) algorithm is in closer accord to the SDC than is the GSFC 1996 algorithm. Published by Elsevier Science Inc. RP Foster, JL (reprint author), NASA,GODDARD SPACE FLIGHT CTR,HYDROL SCI BRANCH,LAB HYDROSPHER PROC,CODE 974,GREENBELT,MD 20771, USA. RI Hall, Dorothy/D-5562-2012 NR 19 TC 135 Z9 170 U1 2 U2 13 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 NOV PY 1997 VL 62 IS 2 BP 132 EP 142 DI 10.1016/S0034-4257(97)00085-0 PG 11 WC Environmental Sciences; Remote Sensing; Imaging Science & Photographic Technology SC Environmental Sciences & Ecology; Remote Sensing; Imaging Science & Photographic Technology GA YB441 UT WOS:A1997YB44100002 ER PT J AU Tsurutani, BT Lakhina, GS AF Tsurutani, BT Lakhina, GS TI Some basic concepts of wave-particle interactions in collisionless plasmas SO REVIEWS OF GEOPHYSICS LA English DT Review ID P GRIGG-SKJELLERUP; HYDROMAGNETIC-WAVES; COMET P/HALLEY; VLF EMISSIONS; CHORUS; FREQUENCY; MAGNETOSPHERE; INSTABILITIES; TURBULENCE; BOUNDARY AB The physical concepts of wave-particle interactions in a collisionless plasma are developed from first principles. Using the Lorentz force, starting with the concepts of particle gyromotion, particle mirroring and the loss cone, normal and anomalous cyclotron resonant interactions, pitch angle scattering, and cross-field diffusion are developed. To aid the reader, graphic illustrations are provided. RP Tsurutani, BT (reprint author), CALTECH,JET PROP LAB,4800 OAK GROVE DR,PASADENA,CA 91109, USA. RI Lakhina, Gurbax /C-9295-2012; OI Lakhina, Gurbax /0000-0002-8956-486X NR 50 TC 91 Z9 92 U1 1 U2 7 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 SN 8755-1209 J9 REV GEOPHYS JI Rev. Geophys. PD NOV PY 1997 VL 35 IS 4 BP 491 EP 501 DI 10.1029/97RG02200 PG 11 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA YF774 UT WOS:A1997YF77400005 ER PT J AU Nelson, RM AF Nelson, RM TI Mercury: The forgotten planet SO SCIENTIFIC AMERICAN LA English DT Article RP Nelson, RM (reprint author), CALTECH,JET PROP LAB,4800 OAK GROVE DR,PASADENA,CA, USA. NR 3 TC 1 Z9 1 U1 0 U2 1 PU SCI AMERICAN INC PI NEW YORK PA 415 MADISON AVE, NEW YORK, NY 10017 SN 0036-8733 J9 SCI AM JI Sci.Am. PD NOV PY 1997 VL 277 IS 5 BP 56 EP & PG 8 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA YC293 UT WOS:A1997YC29300023 ER PT J AU Vigouroux, A Pap, JM Delache, P AF Vigouroux, A Pap, JM Delache, P TI Estimating long-term solar irradiance variability: A new approach SO SOLAR PHYSICS LA English DT Article ID FUNDAMENTAL PERIOD; ACTIVITY INDEXES; PERIODICITIES; CYCLE; SUN; LUMINOSITY; 154-DAY; RADIUS; FLARES; TIME AB The detection of solar irradiance variations (both bolometric and at various wavelengths) by satellite-based experiments during the last one and-a-half decades stimulated modeling efforts to help identify their causes and to provide estimates of irradiance data for those time intervals when no satellite observations exist. In this paper we present estimates of the long-term irradiance changes developed with Fourier and wavelet transforms. The month-to-month irradiance variations, after removing the solar cycle related long-term changes, are studied with the cross-correlation technique. Results of the analysis reveal a significant phase shift at 3 months between the full-disk magnetic field strength and total solar and UV irradiance, with irradiance leading the magnetic field variability, In addition to this time delay between the changes in solar irradiance and the magnetic field, a 10-month phase shift has been found between the UV flux at 280 nm and total solar irradiance corrected for sunspot darkening. The existence of these phase shifts suggests the possibility of a coupling between the physical processes taking place below, in, and above the photosphere. C1 Observ Cote Azur, CNRS, UMR 6529, Lab Cassini, F-06304 Nice 04, France. Univ Calif Los Angeles, Div Astron & Astrophys, Los Angeles, CA 90095 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Vigouroux, A (reprint author), Observ Cote Azur, CNRS, UMR 6529, Lab Cassini, BP 229, F-06304 Nice 04, France. NR 36 TC 9 Z9 10 U1 0 U2 0 PU KLUWER ACADEMIC PUBL PI DORDRECHT PA SPUIBOULEVARD 50, PO BOX 17, 3300 AA DORDRECHT, NETHERLANDS SN 0038-0938 J9 SOL PHYS JI Sol. Phys. PD NOV PY 1997 VL 176 IS 1 BP 1 EP 21 DI 10.1023/A:1004951101497 PG 21 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YV050 UT WOS:000071784600001 ER PT J AU Falconer, DA AF Falconer, DA TI A correlation between length of strong-shear neutral lines and total X-ray brightness in active regions SO SOLAR PHYSICS LA English DT Article AB From a sample of 7 MSFC vector magnetograms of active regions and 17 Yohkoh SXT soft X-ray images of these active regions, we have found that the total X-ray brightness of an entire active region is correlated with the total length of neutral lines on which the magnetic field is both strong (>250 G) and strongly sheared (shear angle > 75 degrees) in the same active region. This correlation, if not fortuitous, is additional evidence of the importance of strong-shear strong-field neutral lines to strong heating in active regions. C1 NASA, George C Marshall Space Flight Ctr, Space Sci Lab, Huntsville, AL 35812 USA. RP Falconer, DA (reprint author), NASA, George C Marshall Space Flight Ctr, Space Sci Lab, ES82, Huntsville, AL 35812 USA. NR 4 TC 10 Z9 10 U1 0 U2 0 PU KLUWER ACADEMIC PUBL PI DORDRECHT PA SPUIBOULEVARD 50, PO BOX 17, 3300 AA DORDRECHT, NETHERLANDS SN 0038-0938 J9 SOL PHYS JI Sol. Phys. PD NOV PY 1997 VL 176 IS 1 BP 123 EP 126 DI 10.1023/A:1004989113714 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YV050 UT WOS:000071784600009 ER PT J AU Moore, RL Schmieder, B Hathaway, DH Tarbell, TD AF Moore, RL Schmieder, B Hathaway, DH Tarbell, TD TI 3-D magnetic field configuration late in a large two-ribbon flare SO SOLAR PHYSICS LA English DT Article ID SOLAR-FLARE; ACTIVE-REGION; RECONNECTION; ARCHES; PROMINENCES; ERUPTIONS; NOVEMBER; HELICITY; EVENTS AB We present Ha and coronal X-ray images of the large two-ribbon flare of 25-26 June, 1992 during its long-lasting gradual decay phase. From these observations we deduce that the 3-D magnetic field configuration late in this flare was similar to that at and before the onset of such large eruptive bipolar flares: the sheared core field running under and out of the flare arcade was S-shaped, and at least one elbow of the S looped into the low corona. From previous observations of filament-eruption flares, we infer that such core-field coronal elbows, though rarely observed, are probably a common feature of the 3-D magnetic field configuration late in large two-ribbon flares. The rare circumstance that apparently resulted in a coronal elbow of the core field being visible in H alpha in our flare was the occurrence of a series of subflares low in the core field under the late-phase arcade of the large flare; these subflares probably produced flaring arches in the northern coronal elbow, thereby rendering this elbow visible in H alpha. The observed late-phase 3-D field configuration presented here, together with the recent sheared-core bipolar magnetic field model of Antiochos, Dahlburg, and Klimchuk (1994) and recent Yohkoh SXT observations of the coronal magnetic field configuration at and before the onset of large eruptive bipolar flares, supports the seminal 3-D model for eruptive two-ribbon flares proposed by Hirayama(1974), with three modifications: (1) the preflare magnetic field is closed over the filament-holding core field; (2) the preflare core field has the shape of an S (or backward S) with coronal elbows; (3) a lower part of the core field does not erupt and open, but remains closed throughout hare, and can have prominent coronal elbows. In this picture, the rest of the core field, the upper part, does erupt and open along with the preflare arcade envelope field in which it rides; the flare arcade is formed by reconnection that begins in the middle of the core field at the start of the eruption and progresses from reconnecting closed core field early in the flare to reconnecting 'opened' envelope field late in the flare. C1 NASA, George C Marshall Space Flight Ctr, Space Sci Lab, Huntsville, AL 35812 USA. Observ Paris, Meudon Sect, F-92195 Meudon, France. Lockheed Palo Alto Res Labs, Palo Alto, CA 94304 USA. RP Moore, RL (reprint author), NASA, George C Marshall Space Flight Ctr, Space Sci Lab, ES82, Huntsville, AL 35812 USA. NR 27 TC 24 Z9 25 U1 0 U2 0 PU SPRINGER PI DORDRECHT PA VAN GODEWIJCKSTRAAT 30, 3311 GZ DORDRECHT, NETHERLANDS SN 0038-0938 J9 SOL PHYS JI Sol. Phys. PD NOV PY 1997 VL 176 IS 1 BP 153 EP 169 DI 10.1023/A:1004990817154 PG 17 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YV050 UT WOS:000071784600012 ER PT J AU Hardesty, RE AF Hardesty, RE TI The dictionary of multimedia terms & acronyms SO TECHNICAL COMMUNICATION LA English DT Book Review C1 CALTECH, Jet Prop Lab, Pasadena, CA 91125 USA. RP Hardesty, RE (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91125 USA. NR 1 TC 0 Z9 0 U1 0 U2 0 PU SOC TECHNICAL COMMUNICATION PI ARLINGTON PA 901 NORTH STUART ST, STE 904, ARLINGTON, VA 22203 USA SN 0049-3155 J9 TECH COMMUN JI Tech. Commun. PD NOV PY 1997 VL 44 IS 4 BP 447 EP 449 PG 3 WC Communication SC Communication GA ZE667 UT WOS:000072817800033 ER PT J AU Dickerson, RR Kondragunta, S Stenchikov, G Civerolo, KL Doddridge, BG Holben, BN AF Dickerson, RR Kondragunta, S Stenchikov, G Civerolo, KL Doddridge, BG Holben, BN TI The impact of aerosols on solar ultraviolet radiation and photochemical smog SO SCIENCE LA English DT Article ID NITROGEN-DIOXIDE PHOTOLYSIS; SKY BRIGHTNESS MEASUREMENTS; EASTERN-UNITED-STATES; AIR-POLLUTION; ACTINIC FLUX; ATMOSPHERE; OZONE; TROPOSPHERE; SCATTERING; CLOUDS AB Photochemical smog, or ground-level ozone, has been the most recalcitrant of air pollution problems, but reductions in emissions of sulfur and hydrocarbons may yield unanticipated benefits in air quality. While sulfate and some organic aerosol particles scatter solar radiation back into space and can cool Earth's surface, they also change the actinic flux of ultraviolet (UV) radiation. Observations and numerical models show that UV-scattering particles in the boundary layer accelerate photochemical reactions and smog production, but UV-absorbing aerosols such as mineral dust and soot inhibit smog production. Results could have major implications for the control of air pollution. C1 NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20742. RP Dickerson, RR (reprint author), UNIV MARYLAND,DEPT METEOROL,COLLEGE PK,MD 20742, USA. RI Dickerson, Russell/F-2857-2010; Georgiy, Stenchikov/J-8569-2013; Kondragunta, Shobha/F-5601-2010 OI Dickerson, Russell/0000-0003-0206-3083; Kondragunta, Shobha/0000-0001-8593-8046 NR 54 TC 257 Z9 273 U1 7 U2 68 PU AMER ASSOC ADVANCEMENT SCIENCE PI WASHINGTON PA 1200 NEW YORK AVE, NW, WASHINGTON, DC 20005 SN 0036-8075 J9 SCIENCE JI Science PD OCT 31 PY 1997 VL 278 IS 5339 BP 827 EP 830 DI 10.1126/science.278.5339.827 PG 4 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA YD479 UT WOS:A1997YD47900036 PM 9346474 ER PT J AU Simpson, JO St Clair, AK AF Simpson, JO St Clair, AK TI Fundamental insight on developing low dielectric constant polyimides SO THIN SOLID FILMS LA English DT Article; Proceedings Paper CT 24th International Conference on Metallurgical Coatings and Thin Films (ICMCTF 97) CY APR 21-25, 1997 CL SAN DIEGO, CALIFORNIA SP Amer Vacuum Soc, Vacuum Met & Thin Films Div DE low dielectric constant; polyimides; optical properties; microelectronic devices ID RELATIVE PERMITTIVITY; FLUORINE AB Thermally stable, durable, insulative polyimides are in great demand for the fabrication of microelectronic devices. In this investigation dielectric and optical properties have been studied for several series of aromatic polyimides. The effect of polarizability, fluorine content, and free volume on dielectric constant was examined. In general, minimizing polarizability, maximizing free volume and fluorination all lowered dielectric constants in the polyimides studied. Published by Elsevier Science S.A. C1 NASA, Langley Res Ctr, Hampton, VA 23681 USA. RP Simpson, JO (reprint author), NASA, Langley Res Ctr, Hampton, VA 23681 USA. NR 16 TC 112 Z9 119 U1 3 U2 19 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 OCT 31 PY 1997 VL 308 BP 480 EP 485 DI 10.1016/S0040-6090(97)00481-1 PG 6 WC Materials Science, Multidisciplinary; Materials Science, Coatings & Films; Physics, Applied; Physics, Condensed Matter SC Materials Science; Physics GA YR993 UT WOS:000071553400088 ER PT J AU Brush, LN Grugel, RN AF Brush, LN Grugel, RN TI The effect of an electric current on rod-eutectic solidification in Sn-0.9 wt.% Cu alloys SO MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING LA English DT Article; Proceedings Paper CT Symposium on Microstructural Evolution in Bulk Phases CY DEC 02-05, 1996 CL BOSTON, MA SP Mat Res Soc DE electric current effect; rod-eutectic solidification; Sn-Cu alloy ID INDUCED GROWTH LAYERS; BI-MNBI COMPOSITES; DIRECTIONAL SOLIDIFICATION; MAGNETIC-PROPERTIES; INTERFACE; STABILITY; MELT AB A directionally solidified Sn-0.9 wt.% Cu rod eutectic alloy is subject to sustained electrical current pulses applied parallel to the direction of growth. The current pulses result in disruption of the aligned rod morphology giving rise instead to segments of the rod (Cu6Sn5) phase embedded in the Sn matrix. A model for the directional growth of the eutectic in the presence of an electric current is presented. The model is used to illustrate that electromigration is unimportant in affecting changes in spacings for steady eutectic growth conditions. (C) 1997 Elsevier Science S.A. C1 NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,UNIV SPACE RES ASSOC,HUNTSVILLE,AL 35812. RP Brush, LN (reprint author), UNIV WASHINGTON,DEPT MAT SCI & ENGN,SEATTLE,WA 98195, USA. NR 53 TC 22 Z9 23 U1 0 U2 3 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 OCT 30 PY 1997 VL 238 IS 1 BP 176 EP 181 DI 10.1016/S0921-5093(97)00451-6 PG 6 WC Nanoscience & Nanotechnology; Materials Science, Multidisciplinary; Metallurgy & Metallurgical Engineering SC Science & Technology - Other Topics; Materials Science; Metallurgy & Metallurgical Engineering GA YF946 UT WOS:A1997YF94600022 ER PT J AU Orgel, VB Ball, DW Zehe, MJ AF Orgel, VB Ball, DW Zehe, MJ TI Optimized structures and proton affinities of fluorinated dimethyl ethers: an ab initio study SO THEOCHEM-JOURNAL OF MOLECULAR STRUCTURE LA English DT Article DE proton affinity; ab initio calculations; G2 theory; fluorinated ethers; geometry optimization ID PERFLUOROPOLYETHERS; DEGRADATION; MOLECULES; SURFACE AB Ab initio methods have been used to investigate the proton affinity and the geometry changes upon protonation for the molecules (CH3)(2)O, (CH2F)(2)O, (CHF2)(2)O, and (CF3)(2)O. Geometry optimizations were performed at the MP2/3-21G level, and the resulting geometries were used for single-point energy MP2/6-31G** calculations. The proton affinity calculated for (CH3)(2)O was 7 kJ mol(-1) from the experimental value, within the desired variance of +/- 8 kJ mol(-1) for G2 theory, suggesting that the methodology used in this study is adequate for energy difference considerations. For (CF3)(2)O, the calculated proton affinity of 602 kJ mol(-1) suggests that perfluorinated ether molecules do not act as Lewis bases under normal circumstances, e.g. degradation of commercial lubricants in tribological applications. (C) 1997 Elsevier Science B.V. C1 Cleveland State Univ, Dept Chem, Cleveland, OH 44115 USA. NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. RP Ball, DW (reprint author), Cleveland State Univ, Dept Chem, Cleveland, OH 44115 USA. NR 24 TC 8 Z9 8 U1 0 U2 1 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0166-1280 J9 THEOCHEM-J MOL STRUC JI Theochem-J. Mol. Struct. PD OCT 30 PY 1997 VL 417 IS 3 BP 195 EP 202 DI 10.1016/S0166-1280(96)04923-8 PG 8 WC Chemistry, Physical SC Chemistry GA YM267 UT WOS:000071046500001 ER PT J AU Casey, RN Quackenbush, SL Work, TM Balazs, GH Bowser, PR Casey, JW AF Casey, RN Quackenbush, SL Work, TM Balazs, GH Bowser, PR Casey, JW TI Evidence for retrovirus infections in green turtles Chelonia mydas from the Hawaiian islands SO DISEASES OF AQUATIC ORGANISMS LA English DT Article DE green turtle; reverse transcriptase; retrovirus; fibropapillomatosis; electron microscopy ID CUTANEOUS FIBROPAPILLOMAS; STIZOSTEDION-VITREUM; TUMOR; VIRUS; PARTICLES; WALLEYE; FISH AB Apparently normal Hawaiian green turtles Chelonia mydas and those displaying fibropapillomas were analyzed for infection by retroviruses. Strikingly, all samples were positive for polymerase enhanced reverse transcriptase (PERT) with levels high enough to quantitate by the conventional reverse transcriptase (RT) assay. However, samples of skin, even from asymptomatic turtles, were RT positive, although the levels of enzyme activity in healthy turtles hatched and raised in captivity were much lower than those observed in asymptomatic free-ranging turtles. Turtles with fibropapillomas displayed a broad range of reverse transcriptase activity. Skin and eye fibropapillomas and a heart tumor were further analyzed and shown to have reverse transcriptase activity that banded in a sucrose gradient at 1.17 g ml(-1). The reverse transcriptase activity purified from the heart tumor displayed a temperature optimum of 37 degrees C and showed a preference for Mn2+ over Mg2+. Sucrose gradient fractions of this sample displaying elevated reverse transcriptase activity contained primarily retroviral-sized particles with prominent envelope spikes, when negatively stained and examined by electron microscopy. Sodium dodecylsulfate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis of gradient-purified virions revealed a conserved profile among 4 independent tumors and showed 7 prominent proteins having molecular weights of 116, 83, 51, 43, 40, 20 and 14 kDa. The data suggest that retroviral infections are widespread in Hawaiian green turtles and a comprehensive investigation is warranted to address the possibility that these agents cause green turtle fibropapillomatosis (GTFP). C1 CORNELL UNIV,COLL VET MED,DEPT MICROBIOL & IMMUNOL,ITHACA,NY 14853. US GEOL SURVEY,BIOL RESOURCES DIV,NATL WILDLIFE HLTH CTR,HONOLULU FIELD STN,HONOLULU,HI 96850. NOAA,NATL MARINE FISHERIES SERV,SW FISHERIES SCI CTR,HONOLULU LAB,HONOLULU,HI 96822. RI Work, Thierry/F-1550-2015 OI Work, Thierry/0000-0002-4426-9090 NR 31 TC 31 Z9 34 U1 0 U2 0 PU INTER-RESEARCH PI OLDENDORF LUHE PA NORDBUNTE 23, D-21385 OLDENDORF LUHE, GERMANY SN 0177-5103 J9 DIS AQUAT ORGAN JI Dis. Aquat. Org. PD OCT 28 PY 1997 VL 31 IS 1 BP 1 EP 7 DI 10.3354/dao031001 PG 7 WC Fisheries; Veterinary Sciences SC Fisheries; Veterinary Sciences GA YK736 UT WOS:A1997YK73600001 ER PT J AU Peteet, D DelGenio, A Lo, KKW AF Peteet, D DelGenio, A Lo, KKW TI Sensitivity of northern hemisphere air temperatures and snow expansion to North Pacific sea surface temperatures in the Goddard Institute for Space Studies general circulation model SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID YOUNGER DRYAS EVENT; WESTERN EQUATORIAL PACIFIC; LAST GLACIAL MAXIMUM; ATLANTIC OCEAN; CLIMATE-CHANGE; ICE-SHEET; NORTHWESTERN PACIFIC; SOUTHEASTERN ALASKA; VEGETATION HISTORY; NORTHEASTERN USA AB Circum-Pacific marine and terrestrial records indicate a series of temperature-inferred oscillations during the late glacial. While many previous studies have Probed the role of the North Atlantic in these oscillations, we test the sensitivity of the northern hemisphere air temperatures to North Pacific sea surface temperature (SST) oscillation in the Goddard Institute for Space Studies general circulation model. The effect of a colder North Pacific is to cool air temperatures over North America, as well as parts of Europe and Asia. The colder SSTs result in a large hemispheric response due to the loss of water vapor as a greenhouse gas. The large sensitivity of the northern hemisphere to a North Pacific SST change has implications for the ice age climate as well as the late glacial interval. The results of this experiment provide a rapid mechanism for widespread cooling which has not been previously addressed. C1 LAMONT DOHERTY EARTH OBSERV, PALISADES, NY 10964 USA. RP NASA, GODDARD INST SPACE STUDIES, 2880 BROADWAY, NEW YORK, NY 10025 USA. RI Del Genio, Anthony/D-4663-2012 OI Del Genio, Anthony/0000-0001-7450-1359 NR 77 TC 19 Z9 20 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X EI 2169-8996 J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD OCT 27 PY 1997 VL 102 IS D20 BP 23781 EP 23791 DI 10.1029/97JD01573 PG 11 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA YD175 UT WOS:A1997YD17500001 ER PT J AU Dong, XQ Ackerman, TP Clothiaux, EE Pilewskie, P Han, Y AF Dong, XQ Ackerman, TP Clothiaux, EE Pilewskie, P Han, Y TI Microphysical and radiative properties of boundary layer stratiform clouds deduced from ground-based measurements SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID MARINE STRATOCUMULUS CLOUDS; EXTENDED WATER CLOUDS; NOCTURNAL STRATOCUMULUS; SOLAR-RADIATION; MULTIPLE-SCATTERING; BUDGET EXPERIMENT; STRATUS CLOUD; DOPPLER RADAR; ASTEX; ABSORPTION AB Two methods for retrieving the microphysical and radiative properties of marine and continental boundary layer stratiform clouds from ground-based measurements are implemented. The first method uses measurements of the cloud liquid water path and the cloud nadir radiance at 1 mu m to infer the cloud optical depth, cloud droplet effective radius, and cloud droplet concentration. In the second method a delta 2-stream radiative transfer model is used to retrieve the microphysical and radiative properties of stratiform clouds from measurements of the cloud liquid water path, the cloud geometric thickness, the downward shortwave irradiance at the surface, and atmospheric profiles of temperature, pressure, and relative humidity. In all of the retrievals the cloud droplets are assumed to have a lognormal size distribution with a logarithmic width of 0.35; the cloud droplet modal radius and cloud droplet concentration are free parameters. Data obtained in the Azores and Oklahoma from marine and continental boundary layer stratiform clouds, respectively, are used in the study.-Results of the analysis demonstrated that the retrieved cloud droplet effective radii from the marine clouds (13 mu m) were generally larger than the values from continental clouds (7 mu m), while cloud droplet number concentrations were much less in marine clouds (150 cm(-3)) than in continental clouds (500 cm(-3)). The retrieved cloud droplet effective radius had a strong negative correlation with the cloud droplet concentration. The effects of uncertainties in the measurements, the cloud droplet distribution width, and the Surface albedo on the retrieved properties were evaluated by using the delta 2-stream model. The errors in the retrieved cloud radiative properties were generally less than 5%, while the errors in the retrieved cloud microphysical properties were considerably larger. C1 PENN STATE UNIV, DEPT METEOROL, UNIVERSITY PK, PA 16802 USA. UNIV COLORADO, COOPERAT INST RES ENVIRONM SCI, BOULDER, CO 80303 USA. NASA, AMES RES CTR, ATMOSPHER PHYS RES BRANCH, MOFFETT FIELD, CA 94035 USA. NOAA, ENVIRONM TECHNOL LAB, BOULDER, CO 80303 USA. RI Han, Yong/F-5590-2010; OI Han, Yong/0000-0002-0183-7270; Dong, Xiquan/0000-0002-3359-6117 NR 45 TC 65 Z9 67 U1 0 U2 7 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 OCT 27 PY 1997 VL 102 IS D20 BP 23829 EP 23843 DI 10.1029/97JD02119 PG 15 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA YD175 UT WOS:A1997YD17500006 ER PT J AU Tabazadeh, A Jensen, EJ Toon, OB AF Tabazadeh, A Jensen, EJ Toon, OB TI A model description for cirrus cloud nucleation from homogeneous freezing of sulfate aerosols SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID SULFURIC-ACID AEROSOLS; SUPERCOOLED WATER; LOW-TEMPERATURE; SIMULATIONS; DROPLETS; ICE; SPECTROSCOPY; HUMIDITY; GROWTH; FTIR AB Classical nucleation theory for homogeneous freezing as well as recent laboratory data are used to formulate an algorithm for ice nucleation from an aqueous sulfuric acid solution droplet A new parameterized function is derived from recent thermodynamic data to express the variation of sulfuric acid solution composition with temperature and relative humidity. This function is then used to derive critical ice nucleation parameters from recent laboratory data. The critical nucleation parameters are used in a classical nucleation theory to derive the diffusion activation energy of water molecules in a sulfuric acid solution from the measurements. The derived diffusion activation energy of water molecules in a sulfuric acid solution does not agree with the diffusion activation energy calculated from a viscous flow formulation that is commonly used in classical nucleation rate calculations. Our results show that ice nucleation in a sulfate droplet occurs when the interface energy of ice against the sulfate solution is approximately 17 dyn cm(-1). We calculate that a supersaturation ratio of about 1.3 to 1.5 is required to nucleate ice from an aqueous sulfuric acid solution droplet in the temperature range of about 185 to 240 K. This supersaturation corresponds to a supercooling of a sulfate solution to about 2 to 3 K below the equilibrium condensation point of ice. Simple functions are given for estimating the nucleation point of ice in the upper troposphere. The differences between previous parameterizations and this work are discussed. C1 UNIV COLORADO, ATMOSPHER & SPACE PHYS LAB, BOULDER, CO 80309 USA. RP NASA, AMES RES CTR, MAIL STOP 245-4, MOFFETT FIELD, CA 94035 USA. NR 33 TC 33 Z9 33 U1 0 U2 2 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 OCT 27 PY 1997 VL 102 IS D20 BP 23845 EP 23850 DI 10.1029/97JD01973 PG 6 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA YD175 UT WOS:A1997YD17500007 ER PT J AU Tegen, I Hollrig, P Chin, M Fung, I Jacob, D Penner, J AF Tegen, I Hollrig, P Chin, M Fung, I Jacob, D Penner, J TI Contribution of different aerosol species to the global aerosol extinction optical thickness: Estimates from model results SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID ATMOSPHERIC SEA-SALT; MINERAL DUST; TROPOSPHERIC AEROSOLS; AMAZON BASIN; TRACER MODEL; TRADE WINDS; DISTRIBUTIONS; TRANSPORT; DESERT; CHEMISTRY AB We combine global distributions of aerosol loading resulting from transport models for soil dust:, sulfate, sea salt, and carbonaceous aerosol. From the aerosol distributions we estimate optical thicknesses and compare them with Sun photometer measurements and satellite retrievals: thereby revealing problems with both model results and comparisons with such measurements. Globally, sulfate, dust, and carbonaceous particles appear to contribute equally to the total aerosol optical thickness. Owing to the different optical properties of different aerosol types, aerosol composition should be taken into consideration for estimating the aerosol climate effect as well as for aerosol retrievals from satellite measurements. C1 NASA, GODDARD INST SPACE STUDIES, NEW YORK, NY 10025 USA. UNIV VICTORIA, SCH EARTH & OCEAN SCI, VICTORIA, BC V8W 2Y2, CANADA. ETH ZURICH, DEPT GEOG, DIV CLIMATE RES, ZURICH, SWITZERLAND. HARVARD UNIV, DIV ENGN & APPL SCI, CAMBRIDGE, MA 02138 USA. UNIV MICHIGAN, DEPT ATMOSPHER OCEAN & SPACE SCI, ANN ARBOR, MI 48109 USA. RP COLUMBIA UNIV, DEPT APPL PHYS, 2880 BROADWAY, NEW YORK, NY 10025 USA. RI Chin, Mian/J-8354-2012; Penner, Joyce/J-1719-2012 NR 52 TC 305 Z9 312 U1 4 U2 28 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 OCT 27 PY 1997 VL 102 IS D20 BP 23895 EP 23915 DI 10.1029/97JD01864 PG 21 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA YD175 UT WOS:A1997YD17500011 ER PT J AU Jimenez, J Linan, A Rogers, MM Higuera, FJ AF Jimenez, J Linan, A Rogers, MM Higuera, FJ TI A priori testing of subgrid models for chemically reacting non-premixed turbulent shear flows SO JOURNAL OF FLUID MECHANICS LA English DT Article ID PASSIVE SCALAR; ISOTROPIC TURBULENCE; DIFFUSION FLAMES; MEAN GRADIENT; MIXING LAYER; HEAT RELEASE; SIMULATION; TEMPERATURE; DISSIPATION; PREDICTION AB The beta-assumed-p.d.f. approximation of Cook & Riley (1994) is tested as a subgrid model for the LES computation of non-premixed turbulent reacting flows, in the limit of infinitely fast chemistry, for two plane constant-density turbulent mixing layers with different degrees of intermittency. Excellent results are obtained in the computation of plane-averaged properties, such as product mass fractions and relatively high powers of the temperature, and even of the p.d.f. of the conserved scalar itself. In all these cases the errors are small enough to be useful in practical applications. The analysis is extended to slightly out-of-equilibrium problems, such as the generation of radicals, and formulated in terms of the p.d.f. of the gradient of the mixture fraction. It is shown that the form of the conditional gradient distribution is universal in a wide range of cases, whose limits are established. Within those limits, engineering approximations to the radical concentration are also possible. It is argued that the experiments in this paper are already in the limit of high Reynolds numbers. C1 UNIV POLITECN MADRID, SCH AERONAUT, E-28040 MADRID, SPAIN. NASA, AMES RES CTR, MOFFETT FIELD, CA 94035 USA. RP Jimenez, J (reprint author), STANFORD UNIV, CTR TURBULENT RES, STANFORD, CA 94305 USA. RI jimenez, javier/A-6691-2008 OI jimenez, javier/0000-0003-0755-843X NR 42 TC 76 Z9 77 U1 0 U2 7 PU CAMBRIDGE UNIV PRESS PI NEW YORK PA 32 AVENUE OF THE AMERICAS, NEW YORK, NY 10013-2473 USA SN 0022-1120 J9 J FLUID MECH JI J. Fluid Mech. PD OCT 25 PY 1997 VL 349 BP 149 EP 171 DI 10.1017/S0022112097006733 PG 23 WC Mechanics; Physics, Fluids & Plasmas SC Mechanics; Physics GA YG258 UT WOS:A1997YG25800006 ER PT J AU Trombka, JI Floyd, SR Boynton, WV Bailey, S Bruckner, J Squyres, SW Evans, LG Clark, PE Starr, R Fiore, E Gold, R Goldsten, J McNutt, R AF Trombka, JI Floyd, SR Boynton, WV Bailey, S Bruckner, J Squyres, SW Evans, LG Clark, PE Starr, R Fiore, E Gold, R Goldsten, J McNutt, R TI Compositional mapping with the NEAR X ray gamma ray spectrometer SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS LA English DT Article ID 433-EROS; SPECTROSCOPY AB The X ray/gamma ray spectrometer (XGRS) instrument on board the Near Earth Asteroid Rendezvous (NEAR) spacecraft will map asteroid 433 Eros in the 0.7 keV to 10 MeV energy region, Measurements of the discrete line X ray and gamma ray emissions in this energy domain dan be used to obtain both qualitative and quantitative elemental compositions with sufficient accuracy enable comparison to the major meteorite types. It is believed that Eros is an S-type asteroid, the most common of the near-Earth asteroids, The determination of whether Eros consists of either differentiated or undifferentiated materials is an important objective of this mission. Observations bf Eros during the NEAR mission will contribute significantly to our understanding of the Structure and composition of this asteroid. The NEAR spacecraft was successfully. launched on February 17, 1996. The NEAR XGRS was turned on during the week of April 7, 1996, and all detector systems operated nominally. Background spectra have been obtained. C1 UNIV ARIZONA, LUNAR & PLANETARY LAB, TUCSON, AZ 85721 USA. MAX PLANCK INST CHEM, D-55128 MAINZ, GERMANY. CATHOLIC UNIV AMER, DEPT PHYS, WASHINGTON, DC 20064 USA. COMP SCI CORP, SCI PROGRAMS, LANHAM, MD 20706 USA. JOHNS HOPKINS UNIV, APPL PHYS LAB, LAUREL, MD 20723 USA. CORNELL UNIV, DEPT ASTRON, ITHACA, NY 14853 USA. RP Trombka, JI (reprint author), NASA, GODDARD SPACE FLIGHT CTR, EXTRATERR PHYS LAB, GREENBELT, MD 20771 USA. RI McNutt, Ralph/E-8006-2010 OI McNutt, Ralph/0000-0002-4722-9166 NR 43 TC 36 Z9 36 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0148-0227 J9 J GEOPHYS RES-PLANET JI J. Geophys. Res.-Planets PD OCT 25 PY 1997 VL 102 IS E10 BP 23729 EP 23750 DI 10.1029/97JE00270 PG 22 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA YD533 UT WOS:A1997YD53300006 ER PT J AU Acuna, MH Russell, CT Zanetti, LJ Anderson, BJ AF Acuna, MH Russell, CT Zanetti, LJ Anderson, BJ TI The NEAR magnetic field investigation: Science objectives at asteroid Eros 433 and experimental approach SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS LA English DT Article ID MISSION; PROGRESS AB The NEAR magnetic field investigation is an integrated technical, scientific, and management undertaking that was selected by NASA to achieve the following goals: to coordinate and support the development, calibration, and integration aboard the NEAR spacecraft of the magnetometer facility instrument (MAG), to provide technical assistance to the NEAR project in the area of magnetic cleanliness, and to ensure maximum science data quality. The prime objective of the MAG investigation is to establish the nature of the magnetic field of 433 Eros and any detectable effects of its interaction with the solar wind. The detection of an intrinsic magnetic field would place a strong constraint on the composition and structure of the asteroid's interior and thermal evolution. NEAR magnetometer data will be primarily available through the Johns Hopkins University Applied Physics Laboratory (APL) Science Data Center, http://sd-www.jhuapl.edu/NEAR. The basic building block of the MAG investigation is the facility-class magnetometer instrument flown aboard the NEAR spacecraft [Lohr et at, 1997]. The NEAR MAG was built as a cooperative undertaking between the Laboratory for Extraterrestrial Physics of the Goddard Space Flight Center (GSFC) and APL. GSFC provided the sensors and analog systems, and APL provided the digital processing unit and power converter as well as oversight for test and integration activities on the spacecraft. No booms or appendages were used to place the MAG sensor away from the spacecraft; instead and in analogous fashion to ESA's Giotto spacecraft, the sensor assembly was mounted on the high-gain antenna feed structure. This arrangement results in a minimum detectable magnetic signature of 2-5 nT. C1 JOHNS HOPKINS UNIV, APPL PHYS LAB, LAUREL, MD 20723 USA. UNIV CALIF LOS ANGELES, INST GEOPHYS & PLANETARY PHYS, LOS ANGELES, CA 90024 USA. RP Acuna, MH (reprint author), NASA, GODDARD SPACE FLIGHT CTR, CODE 695, GREENBELT, MD 20771 USA. RI Anderson, Brian/I-8615-2012 NR 26 TC 16 Z9 16 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-PLANET JI J. Geophys. Res.-Planets PD OCT 25 PY 1997 VL 102 IS E10 BP 23751 EP 23759 DI 10.1029/97JE01161 PG 9 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA YD533 UT WOS:A1997YD53300007 ER PT J AU Zuber, MT Smith, DE Cheng, AF Cole, TD AF Zuber, MT Smith, DE Cheng, AF Cole, TD TI The NEAR laser ranging investigation SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS LA English DT Article ID DEIMOS ASTROMETRIC OBSERVATIONS; RADAR IMAGES; ASTEROID-4179 TOUTATIS; CLEMENTINE MISSION; SURFACE-FEATURES; CONTROL NETWORK; 951 GASPRA; NORTH-POLE; SHAPE; PHOBOS AB The objective of the Near-Earth Asteroid Rendezvous (NEAR) laser ranging investigation is to obtain high integrity profiles and grids of topography for use in geophysical, geodetic and geological studies of asteroid 433 Eros. The NEAR laser rangefinder (NLR) will determine the slant range of the NEAR spacecraft to the asteroid surface by measuring precisely the round trip time bf flight of individual laser pulses. Ranges will be converted to planetary radii measured with respect to the asteroid center of mass by subtracting the spacecraft orbit determined from X band Doppler tracking, The principal components of the NLR include a 1064 nm Cr:Nd:YAG laser, a gold-coated aluminum Dall-Kirkham Cassegrain telescope, an enhanced silicon avalanche photodiode hybrid detector, a 480-MHz crystal oscillator, and a digital processing unit. The instrument has a continuous in-flight calibration capability using a fiber-optic delay assembly. The single shot vertical resolution df the NLR is <6 m, and the absolute accuracy of the global grid will be similar to 10 m with respect to the asteroid center of mass. For the current mission orbital scenario, the laser spot size on the surface of Eros will vary from similar to 4-11 m, and-the along-track resolution for the nominal pulse repetition rate of 1 Hz will be approximately comparable to the spot size, resulting in contiguous along-track profiles. The across-track resolution will depend on the orbital mapping scenario, but will likely be <500 m, which will define the spatial resolution of the global topographic model. Planned science investigations include global-scale analyses related to collisional and impact history and internal density distribution that utilize topographic grids as well as spherical harmonic topographic models that will be analyzed jointly with gravity at commensurate resolution: Attempts will be made to detect possible subtle time variations in internal structure that,may be present if Eros is not a Single coherent body, by analysis of low degree and order spherical harmonic coefficients. Local-to regional-scale analyses will utilize high-resolution three-dimensional topographic maps of specific surface structures to address surface geologic processses. Results from the NLR investigation will contribute significantly to understanding the origin, structure, and evolution of Eros and other asteroidal bodies. C1 JOHNS HOPKINS UNIV,APPL PHYS LAB,LAUREL,MD 20723. NASA,GODDARD SPACE FLIGHT CTR,TERR PHYS LAB,GREENBELT,MD 20771. RP Zuber, MT (reprint author), MIT,DEPT EARTH ATMOSPHER & PLANETARY SCI,CAMBRIDGE,MA 02139, USA. NR 61 TC 22 Z9 22 U1 0 U2 3 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 OCT 25 PY 1997 VL 102 IS E10 BP 23761 EP 23773 DI 10.1029/97JE00890 PG 13 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA YD533 UT WOS:A1997YD53300008 ER PT J AU Yeomans, DK Konopliv, AS Barriot, JP AF Yeomans, DK Konopliv, AS Barriot, JP TI The NEAR Radio Science investigations SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS LA English DT Article ID RADAR IMAGES; ASTEROIDS; SHAPE AB The science objectives for the Near-Earth Asteroid Rendezvous (NEAR) Radio Science team include determining the masses of asteroids 253 Mathilde (to within 10%) and 433 Eros (<0.1%). While the NEAR spacecraft is in orbit about Eros, the radiometric spacecraft tracking data, the optical landmark tracking data, and the lidar altimetry measurements will be used to determine the gravity field of Eros. Comparisons of this gravity field with one determined from Eros shape models (assuming constant density) will provide constraints upon the internal structure of this asteroid. In addition, the spin state, principal axes, and moments of inertia will be determined as part of the Radio Science activities. A campaign to meet the radio science objectives will require the close cooperation of the NEAR Navigation, Imaging, and Lidar teams. C1 CNRS,GRP RECH & GEODESIE SPATIALE,DEPT TERR & PLANETARY GEODESY,F-31055 TOULOUSE,FRANCE. RP Yeomans, DK (reprint author), CALTECH,JET PROP LAB,301-150G,PASADENA,CA 91109, USA. NR 22 TC 8 Z9 8 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 OCT 25 PY 1997 VL 102 IS E10 BP 23775 EP 23780 DI 10.1029/96JE02708 PG 6 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA YD533 UT WOS:A1997YD53300009 ER PT J AU Raman, G Taghavi, R AF Raman, G Taghavi, R TI Aeroacoustic characteristics of a rectangular multi-element supersonic jet mixer-ejector nozzle SO JOURNAL OF SOUND AND VIBRATION LA English DT Article ID INSTABILITY WAVES; NOISE; TONES AB This paper provides a unique, detailed evaluation of the acoustics and aerodynamics of a rectangular multi-element supersonic jet mixer-ejector noise suppressor. The performance of such mixer-ejectors is important in aircraft engine applications for noise suppression and thrust augmentation. In contrast to most prior experimental studies on ejectors that reported either aerodynamic of acoustic data, the present work documents both types of data. Information on the mixing, pumping, ejector wall pressure distribution, thrust augmentation and noise suppression characteristics of four simple, multi-element, jet mixer-ejector configurations is presented. The four configurations included the effect of ejector area ratio (AR = ejector cross-sectional area/total primary nozzle area) and the effect of non-parallel ejector walls. The configuration that produced the best noise suppression characteristics has also been studied in detail. The present results show that ejector configurations that produced the maximum pumping (secondary (induced) flow normalized by the primary flow) also exhibited the lowest wall pressures in the inlet region, and the maximum thrust augmentation. When cases having the same total mass flow were compared, one found that noise suppression trends corresponded with those for pumping (per unit secondary area). Surprisingly, the mixing (quantified by the peak Mach number, and flow uniformity) at the ejector exit exhibited no relationship to the noise suppression at moderate primary jet fully expanded M-j (the Mach number that would have been attained under isentropic expansion). However, the noise suppression dependence on the mixing was apparent at M-j = 1.6. The above observations are justified by noting that the mixing at the ejector exit is not a strong factor in determining the radiated noise when noise produced internal to the ejector dominates the noise field outside the ejector. (C) 1997 Academic Press Limited. C1 UNIV KANSAS, DEPT AEROSP ENGN, LAWRENCE, KS 66045 USA. RP Raman, G (reprint author), NASA, LEWIS RES CTR GRP, NYMA INC, EXPT FLUID DYNAM SECT, BROOKPARK, OH 44142 USA. NR 57 TC 8 Z9 8 U1 0 U2 3 PU ACADEMIC PRESS LTD PI LONDON PA 24-28 OVAL RD, LONDON, ENGLAND NW1 7DX SN 0022-460X J9 J SOUND VIB JI J. Sound Vibr. PD OCT 23 PY 1997 VL 207 IS 2 BP 227 EP + DI 10.1006/jsvi.1997.1100 PG 22 WC Acoustics; Engineering, Mechanical; Mechanics SC Acoustics; Engineering; Mechanics GA YD775 UT WOS:A1997YD77500005 ER PT J AU Stolarski, R AF Stolarski, R TI Atmospheric chemistry - A bad winter for Arctic ozone SO NATURE LA English DT Editorial Material RP Stolarski, R (reprint author), NASA,GODDARD SPACE FLIGHT CTR,LAB ATMOSPHERES ATMOSPHER CHEM & DYNAM,GREENBELT,MD 20771, USA. RI Stolarski, Richard/B-8499-2013 OI Stolarski, Richard/0000-0001-8722-4012 NR 2 TC 8 Z9 9 U1 0 U2 1 PU MACMILLAN MAGAZINES LTD PI LONDON PA PORTERS SOUTH, 4 CRINAN ST, LONDON, ENGLAND N1 9XW SN 0028-0836 J9 NATURE JI Nature PD OCT 23 PY 1997 VL 389 IS 6653 BP 788 EP 789 DI 10.1038/39737 PG 2 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA YC148 UT WOS:A1997YC14800029 ER PT J AU Lyth, DH Riotto, A AF Lyth, DH Riotto, A TI Comments on D-term inflation SO PHYSICS LETTERS B LA English DT Article ID ENTROPY CRISIS; COSMIC STRINGS; ANOMALOUS U(1); SUPERSYMMETRY; SUPERGRAVITY; SUPERSTRINGS; COSMOLOGY; BREAKING AB An inflationary stage dominated by a D-term avoids the slow-roll problem of inflation in supergravity and can naturally emerge in theories with a non-anomalous or anomalous U(1) gauge symmetry. In the latter case, however, the scale of inflation as imposed by the COBE normalization is in contrast with the value fixed by the Green-Schwarz mechanism of anomaly cancellation. In this paper we discuss possible solutions to this problem and comment about the fact that the string-loop generated Fayet-Iliopoulos D-term may trigger the presence of global and local cosmic strings at the end of inflation. (C) 1997 Elsevier Science B.V. C1 FERMILAB NATL ACCELERATOR LAB,NASA,FERMILAB ASTROPHYS CTR,BATAVIA,IL 60510. RP Lyth, DH (reprint author), UNIV LANCASTER,SCH PHYS & CHEM,LANCASTER LA1 4YB,ENGLAND. NR 38 TC 48 Z9 48 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 OCT 23 PY 1997 VL 412 IS 1-2 BP 28 EP 34 DI 10.1016/S0370-2693(97)01044-7 PG 7 WC Astronomy & Astrophysics; Physics, Nuclear; Physics, Particles & Fields SC Astronomy & Astrophysics; Physics GA YG530 UT WOS:A1997YG53000005 ER PT J AU Casscells, SW Ahmad, M David, M Clubb, FJ Bearman, GH Willerson, JT AF Casscells, SW Ahmad, M David, M Clubb, FJ Bearman, GH Willerson, JT TI Thermal detection and induction of apoptosis in macrophages of human atherosclerotic plaques SO CIRCULATION LA English DT Meeting Abstract C1 UNIV TEXAS,HOUSTON,TX. TEXAS HEART INST,HOUSTON,TX 77025. NASA,JPL,PASADENA,CA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU AMER HEART ASSOC PI DALLAS PA 7272 GREENVILLE AVENUE, DALLAS, TX 75231-4596 SN 0009-7322 J9 CIRCULATION JI Circulation PD OCT 21 PY 1997 VL 96 IS 8 SU S BP 812 EP 812 PG 1 WC Cardiac & Cardiovascular Systems; Peripheral Vascular Disease SC Cardiovascular System & Cardiology GA YC880 UT WOS:A1997YC88000809 ER PT J AU Dwyer, JH Sun, P Dwyer, KM Barth, JD Selzer, RH AF Dwyer, JH Sun, P Dwyer, KM Barth, JD Selzer, RH TI The Los Angeles Atherosclerosis Study SO CIRCULATION LA English DT Meeting Abstract C1 UNIV SO CALIF,LOS ANGELES,CA. JET PROPULS LAB,PASADENA,CA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU AMER HEART ASSOC PI DALLAS PA 7272 GREENVILLE AVENUE, DALLAS, TX 75231-4596 SN 0009-7322 J9 CIRCULATION JI Circulation PD OCT 21 PY 1997 VL 96 IS 8 SU S BP 1540 EP 1540 PG 1 WC Cardiac & Cardiovascular Systems; Peripheral Vascular Disease SC Cardiovascular System & Cardiology GA YC880 UT WOS:A1997YC88001538 ER PT J AU Dwyer, KM Mellett, L Sun, P Selzer, RH Barth, JD Dwyer, JH AF Dwyer, KM Mellett, L Sun, P Selzer, RH Barth, JD Dwyer, JH TI Carotid wall thickness and years since bilateral oopherectomy. The Los Angeles atherosclerosis study SO CIRCULATION LA English DT Meeting Abstract C1 UNIV SO CALIF,LOS ANGELES,CA 90089. JET PROPULS LAB,PASADENA,CA. NR 0 TC 0 Z9 0 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 OCT 21 PY 1997 VL 96 IS 8 SU S BP 2268 EP 2268 PG 1 WC Cardiac & Cardiovascular Systems; Peripheral Vascular Disease SC Cardiovascular System & Cardiology GA YC880 UT WOS:A1997YC88002257 ER PT J AU Page, MJ Mason, KO McHardy, IM Jones, LR Carrera, FJ AF Page, MJ Mason, KO McHardy, IM Jones, LR Carrera, FJ TI The evolution of QSOs derived from soft X-ray surveys SO MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY LA English DT Article DE surveys; galaxies: active; quasars: general; cosmology: observations; X-rays: galaxies ID ACTIVE GALACTIC NUCLEI; OPTICALLY SELECTED QSOS; DEEP ROSAT SURVEY; LUMINOSITY FUNCTION; COSMOLOGICAL EVOLUTION; PARAMETER-ESTIMATION; ASTRONOMY AB We present a study of the evolution of active galactic nuclei (AGN) selected in Einstein and ROSAT surveys. A total of 748 broad-line AGN are included in the study, including 29 with z > 2. Pure luminosity evolution provides a good description of the evolution for q(0) = 0. For q(0) = 0.5 we find that pure luminosity evolution underpredicts the number of intermediate-redshift (1.4 < z < 2), low-luminosity AGN. Evolution models with strong evolution at high redshift (z > 1.8) are rejected at high confidence levels. Models with no evolution or negative evolution at z >, 1.8 are acceptable. [V-e/V-a] tests, which are model-independent, suggest that at z > 1.8 evolution is negative, i.e., QSO space densities and/or luminosities decline with redshift. Our model luminosity functions predict that broad-line AGN with z < 4 contribute less than 45 per cent of the 1-2 keV X-ray background. We derive a simple expression to correct a two-power-law luminosity function for the spurious evolution caused by the dispersion of X-ray spectral slopes. When the dispersion in AGN spectral slopes is taken into account, we find that the redshift at which evolution stops may be as low as z similar to 1.4 for both q(0) = 0 and q(0) = 0.5. C1 UNIV SOUTHAMPTON, DEPT PHYS, SOUTHAMPTON SO17 1BJ, HANTS, ENGLAND. NASA, GODDARD SPACE FLIGHT CTR, GREENBELT, MD 20771 USA. UNIV CANTABRIA, CSIC, INST FIS CANTABRIA, E-39005 SANTANDER, SPAIN. RP Page, MJ (reprint author), UCL, MULLARD SPACE SCI LAB, HOLMBURY ST MARY, DORKING RH5 6NT, SURREY, ENGLAND. NR 31 TC 42 Z9 42 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 OCT 21 PY 1997 VL 291 IS 2 BP 324 EP 336 PG 13 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YD915 UT WOS:A1997YD91500009 ER PT J AU Meyer, WV Smart, AE Brown, RGW Anisimov, MA AF Meyer, WV Smart, AE Brown, RGW Anisimov, MA TI Photon correlation and scattering: introduction to the feature issue SO APPLIED OPTICS LA English DT Article AB This feature issue of Applied Optics contains 25 research papers on photon correlation and scattering. Many of the papers in this volume were presented at an OSA Topical Meeting that was held 21-24 August 1996 in Capri, Italy. The focus of these papers is research in dynamic light scattering, surface light scattering, photon correlation, laser velocimetry, and their applications to biological, chemical, and physical processes. (C) 1997 Optical Society of America. C1 SHARP LABS EUROPE LTD,OXFORD OX4 4GA,ENGLAND. UNIV NOTTINGHAM,DEPT ELECT & ELECT ENGN,NOTTINGHAM NG7 2RD,ENGLAND. UNIV MARYLAND,INST PHYS SCI & TECHNOL,COLLEGE PK,MD 20742. RP Meyer, WV (reprint author), NASA,LEWIS RES CTR,OHIO AEROSP INST,21000 BROOKPK RD,M-S 105-1,CLEVELAND,OH 44135, USA. NR 15 TC 5 Z9 5 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 OCT 20 PY 1997 VL 36 IS 30 BP 7477 EP 7479 DI 10.1364/AO.36.007477 PG 3 WC Optics SC Optics GA YB133 UT WOS:A1997YB13300001 PM 18264259 ER PT J AU Rogers, RB Meyer, WV Zhu, JX Chaikin, PM Russel, WB Li, M Turner, WB AF Rogers, RB Meyer, WV Zhu, JX Chaikin, PM Russel, WB Li, M Turner, WB TI Compact laser light-scattering instrument for microgravity research SO APPLIED OPTICS LA English DT Article DE static light scattering; dynamic light scattering; hard spheres; microgravity ID HARD COLLOIDAL SPHERES; OPTICAL FIBERS; SINGLE-MODE; MULTIMODE AB NASA has developed a compact laser light-scattering instrument that employs both static and dynamic light-scattering techniques for microgravity research. The first use of this instrument was to study the behavior of colloidal hard spheres in a reduced gravity environment during the Second United States Microgravity Laboratory space shuttle mission. We discuss the instrument design and possible improvements based on our observations of significant differences between hard-sphere behavior in Earth's gravity and microgravity. (C) 1997 Optical Society of America. C1 PRINCETON UNIV,DEPT PHYS,PRINCETON,NJ 08544. PRINCETON UNIV,DEPT CHEM ENGN,PRINCETON,NJ 08544. NASA,LEWIS RES CTR,NYMA INC,CLEVELAND,OH 44135. RP Rogers, RB (reprint author), NASA,LEWIS RES CTR,OHIO AEROSP INST,CLEVELAND,OH 44135, USA. NR 20 TC 10 Z9 10 U1 0 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 OCT 20 PY 1997 VL 36 IS 30 BP 7493 EP 7500 DI 10.1364/AO.36.007493 PG 8 WC Optics SC Optics GA YB133 UT WOS:A1997YB13300003 PM 18264261 ER PT J AU Lant, CT Smart, AE Cannell, DS Meyer, WV Doherty, MP AF Lant, CT Smart, AE Cannell, DS Meyer, WV Doherty, MP TI Physics of hard spheres experiment: a general-purpose light-scattering instrument SO APPLIED OPTICS LA English DT Article DE light scattering; hard sphere; Bragg scattering; dynamic light scattering; quasi-elastic light scattering; crystal growth; microgravity; colloidal crystal AB A general-purpose, multifunction light-scattering instrument has been developed at the NASA Lewis Research Center for Space Shuttle and Space Station colloid crystallization and other microgravity experiments. For a single sample, the instrument can measure two-dimensional Bragg scattering from 0.5 degrees to 60 degrees, dynamic and static light scattering from 10 degrees to 170 degrees, the shear modulus of samples before and after crystallization, and digital color images of the-sample. A carousel positions any one of eight 3-ml samples into the test position for separate experiments. Program challenges and flight results from the STS-83 Space Shuttle mission are discussed. (C) 1997 Optical Society of America. C1 UNIV CALIF SANTA BARBARA,DEPT PHYS,SANTA BARBARA,CA 93106. NASA,LEWIS RES CTR,OHIO AEROSP INST,CLEVELAND,OH 44135. RP Lant, CT (reprint author), ADF CORP,2001 AEROSP PKWY,BROOKPARK,OH 44142, USA. NR 5 TC 13 Z9 13 U1 2 U2 7 PU OPTICAL SOC AMER PI WASHINGTON PA 2010 MASSACHUSETTS AVE NW, WASHINGTON, DC 20036 SN 0003-6935 J9 APPL OPTICS JI Appl. Optics PD OCT 20 PY 1997 VL 36 IS 30 BP 7501 EP 7507 DI 10.1364/AO.36.007501 PG 7 WC Optics SC Optics GA YB133 UT WOS:A1997YB13300004 PM 18264262 ER PT J AU Meyer, WV Cannell, DS Smart, AE Taylor, TW Tin, P AF Meyer, WV Cannell, DS Smart, AE Taylor, TW Tin, P TI Multiple-scattering suppression by cross correlation SO APPLIED OPTICS LA English DT Article DE particle sizing; dynamic light scattering; cross correlation; multiple-scattering suppression; static light scattering ID LIGHT-SCATTERING; SPECTROSCOPY AB We describe a new method for characterizing particles in turbid media by cross correlating the scattered intensity fluctuations at two nearby points in the far field. The cross-correlation function selectively emphasizes single scattering over multiple scattering. The usual dynamic light-scattering capability of inferring particle size from decay rate is thus extended to samples that are so turbid as to be visually opaque. The method relies on single-scattering speckle being physically larger than multiple-scattering speckle. With a suitable optical geometry to select nearby points in the far field or equivalently slightly different scattering wave vectors (of the same magnitude), the multiple-scattering contribution to the cross-correlation function may be reduced and in some cases rendered insignificant. Experimental results demonstrating the feasibility of this approach are presented. (C) 1997 Optical Society of America. C1 UNIV CALIF SANTA BARBARA,DEPT PHYS,SANTA BARBARA,CA 93106. CLEVELAND STATE UNIV,DEPT PHYS,CLEVELAND,OH 44115. RP Meyer, WV (reprint author), NASA,LEWIS RES CTR,OHIO AEROSP INST,MS 105-1,21000 BROOKPK RD,CLEVELAND,OH 44135, USA. NR 15 TC 45 Z9 45 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 OCT 20 PY 1997 VL 36 IS 30 BP 7551 EP 7558 DI 10.1364/AO.36.007551 PG 8 WC Optics SC Optics GA YB133 UT WOS:A1997YB13300010 PM 18264268 ER PT J AU Tin, P Mann, JA Meyer, WV Taylor, TW AF Tin, P Mann, JA Meyer, WV Taylor, TW TI Fiber-optics surface-light-scattering spectrometer SO APPLIED OPTICS LA English DT Article DE surface light scattering; surface tension; viscosity; fiber-optics homodyning ID SPECTROSCOPY AB We have developed a fiber-optics surface-light-scattering spectrometer completely designed with optical fiber components. To the best of our knowledge, this is the first demonstration of a noninvasive measurement of the surface tension and the viscosity of simple liquid-vapor interfaces with a fiber-optics-based sensor system. With this approach we obtain a compact size, a significant increase in the signal-to-noise ratio, and the ability to select from a continuum of wave vectors. (C) 1997 Optical Society of America. C1 CASE WESTERN RESERVE UNIV,DEPT CHEM ENGN,CLEVELAND,OH 44106. CLEVELAND STATE UNIV,DEPT PHYS,CLEVELAND,OH 44115. RP Tin, P (reprint author), NASA,LEWIS RES CTR,OHIO AEROSP INST,MS 105-1,21000 BROOKPK RD,CLEVELAND,OH 44135, USA. NR 9 TC 9 Z9 9 U1 1 U2 3 PU OPTICAL SOC AMER PI WASHINGTON PA 2010 MASSACHUSETTS AVE NW, WASHINGTON, DC 20036 SN 0003-6935 J9 APPL OPTICS JI Appl. Optics PD OCT 20 PY 1997 VL 36 IS 30 BP 7601 EP 7604 DI 10.1364/AO.36.007601 PG 4 WC Optics SC Optics GA YB133 UT WOS:A1997YB13300016 PM 18264274 ER PT J AU Meyer, WV Lock, JA Cheung, HM Taylor, TW Tin, P Mann, JA AF Meyer, WV Lock, JA Cheung, HM Taylor, TW Tin, P Mann, JA TI Hybrid reflection-transmission surface light-scattering instrument with reduced sensitivity to surface sloshing SO APPLIED OPTICS LA English DT Article ID FLUCTUATION SPECTROSCOPY; SPECTROMETER; WAVES AB A hybrid reflection-transmission surface light-scattering instrumental design is presented, examined theoretically, and tested experimentally. The purpose of the design is to reduce the sensitivity of the instrument to vibration in general and surface sloshing in particular while sacrificing Little performance. Traditional optical arrangements and two new optical configurations with varying trade-offs between slosh resistance and instrumental simplicity and accuracy are examined by use of Fourier optics methods. The most promising design was constructed and tested with acetone, ethanol, and water as subject fluids. The test involved backcalculation of the wave number of the capillary wave examined with the known physical parameters for the test fluids. The agreement of the computed wave number was +/-1.4%. (C) 1997 Optical Society of America. C1 CLEVELAND STATE UNIV,DEPT PHYS,CLEVELAND,OH 44115. UNIV AKRON,DEPT CHEM,AKRON,OH 44325. CASE WESTERN RESERVE UNIV,DEPT CHEM ENGN,CLEVELAND,OH 44106. RP Meyer, WV (reprint author), NASA,LEWIS RES CTR,OHIO AEROSP INST,CLEVELAND,OH 44135, USA. NR 17 TC 5 Z9 5 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 OCT 20 PY 1997 VL 36 IS 30 BP 7605 EP 7614 DI 10.1364/AO.36.007605 PG 10 WC Optics SC Optics GA YB133 UT WOS:A1997YB13300017 PM 18264275 ER PT J AU Ulvestad, JS Antonucci, RRJ AF Ulvestad, JS Antonucci, RRJ TI VLA observations of NGC 253: Supernova remnants and H II regions at 1 parsec resolution SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies, individual (NGC 253); galaxies, ISM; galaxies, nuclei; galaxies, starburst; radio continuum, galaxies; supernova remnants ID STARBURST GALAXY NGC-253; HUBBLE-SPACE-TELESCOPE; COMPACT RADIO-SOURCES; 30 DORADUS REGION; HOT-SPOTS; EMISSION; NUCLEUS; DISCOVERY; M82; SCALE AB The edge-on starburst galaxy NGC 253 has been imaged with the VLA at wavelengths ranging from 1.3 to 20 cm, with resolutions between 1 and 15 pc. These images reveal a large number of compact radio sources embedded within the diffuse radio structure in the inner 200 pc of the galaxy. We have identified approximately 64 individual compact radio sources in the galaxy. Of the strongest 17 sources, for which the flux densities are high enough to measure spectral indices with moderately low errors, about half have flat spectra and half have steep spectra; this indicates that perhaps half of the individual radio sources are dominated by thermal radio emission from H II regions. Over an 8 yr timescale, few, if any, of the strongest sources have varied in flux density, with limits of 1%-2% yr(-1) on the rate of decrease. At the highest resolution of 1 pc, a number of radio sources are beginning to be resolved, and at least 15 different sources can be identified within the innermost 20 pc of the galaxy. Individual radio sources have been explored in more detail. The strongest source, 5.79-39.0 (TH2), assumed to be at the nucleus of the galaxy, has a brightness temperature greater than 20,000 K at 22 GHz and greater than 40,000 K at 15 GHz. It is unresolved at the VLA and may be either an active galactic nucleus or a very compact (nonvariable) supernova remnant. A resolved flat-spectrum source, 5.72-40.1 (TH6), is located similar to 20 pc to the southwest. It has an apparent size of 2.4 x 1.2 pc and appears to be an H II region similar to the inner part of 30 Doradus, containing approximately 10(5) M. in stars, as well as similar to 600 M. of ionized gas. Source counts, the lack of variability, and the lack of new sources imply that the radio supernova rate is no more than 0.3 yr(-1), consistent with estimates made in other wave bands. C1 UNIV CALIF SANTA BARBARA,DEPT PHYS,SANTA BARBARA,CA 93107. CALTECH,JET PROP LAB,PASADENA,CA 91125. RP Ulvestad, JS (reprint author), NATL RADIO ASTRON OBSERV,POB O,SOCORRO,NM 87801, USA. NR 56 TC 121 Z9 121 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 OCT 20 PY 1997 VL 488 IS 2 BP 621 EP 641 DI 10.1086/304739 PN 1 PG 21 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YB992 UT WOS:A1997YB99200014 ER PT J AU Netzer, H Turner, TJ AF Netzer, H Turner, TJ TI Soft X-ray lines and gas composition in NGC 1068 SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies, abundances; galaxies, individual (NGC 1068); galaxies, Seyfert; line, formation; X-rays, galaxies ID NGC-1068; ASCA AB Previous X-ray and ultraviolet spectroscopy suggested that the Fe/O abundance ratio in NGC 1068 may be abnormally high. We have tested this suggestion by measuring and modeling the ASCA spectrum of NGC 1068. We have measured some 15 X-ray lines, to an accuracy better than a factor of 2, and modeled the continuum in two different ways. The first assumes that the hard X-ray continuum is the reflection of the nuclear source by two extended, photoionized gas components; a warm (T similar to 1.5 x 10(5) K) gas and a hot (T similar to 3 x 10(6) K) gas. All the observed emission lines are produced in this gas, and there is an additional, extended 0.6-3 keV pure continuum component. The model is similar to the one proposed by Marshall et al. (1993). The second model is a combination of a hard reflected continuum with a soft thermal plasma component. The calculations show that the emission lines in the photoionized gas model are in very good agreement with the observed ones assuming solar metallicity for all elements except for iron, which is more than twice solar, and oxygen, which is less than 0.25 solar. Models with solar oxygen are possible if the 0.5-1 keV continuum is weaker, but they do not explain the magnesium and silicon lines. The thermal model fit requires extremely low metallicity (0.04 solar) for all elements. We discuss these findings and compare them with the ASCA spectra of recently observed starburst galaxies. We argue that the apparent low metallicity of starburst galaxies, as well as of the extended nuclear source in NGC 1068, are inconsistent with galaxy chemical evolution. The explanation for this apparent anomaly is still unknown and may involve nonthermal continuum mechanisms and, in some cases, depletion onto grains. Given the strong H-like and He-like lines, as well as the prominent Fe L emission features, the origin of the soft X-ray lines in this source is more likely photoionized gas. We compare our model with the recent Iwasawa, Fabian, & Matt (1997) paper. We also show that fluorescence lines of low-Z elements in AGNs are likely to be stronger than previously assumed. C1 TEL AVIV UNIV,RAYMOND & BEVERLY SACKLER FAC EXACT SCI,WISE OBSERV,IL-69978 TEL AVIV,ISRAEL. NASA,GODDARD SPACE FLIGHT CTR,HIGH ENERGY ASTROPHYS LAB,GREENBELT,MD 20771. UNIV SPACE RES ASSOC,WASHINGTON,DC. RP Netzer, H (reprint author), TEL AVIV UNIV,RAYMOND & BEVERLY SACKLER FAC EXACT SCI,SCH PHYS & ASTRON,IL-69978 TEL AVIV,ISRAEL. NR 19 TC 31 Z9 31 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 OCT 20 PY 1997 VL 488 IS 2 BP 694 EP 701 DI 10.1086/304743 PN 1 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YB992 UT WOS:A1997YB99200020 ER PT J AU Ramaty, R Kozlovsky, B Lingenfelter, RE Reeves, H AF Ramaty, R Kozlovsky, B Lingenfelter, RE Reeves, H TI Light elements and cosmic rays in the early galaxy SO ASTROPHYSICAL JOURNAL LA English DT Article DE acceleration of particles; cosmic rays; Galaxy, abundances; Galaxy, evolution; nuclear reactions, nucleosynthesis, abundances ID HALO STARS; RELATIVISTIC NUCLEI; CROSS-SECTIONS; CARBON TARGETS; ORION COMPLEX; LOW-ENERGY; BORON; LINES; RATIO; EVOLUTION AB Observations of Be and B in low-metallicity halo stars formed during the first 10(9) yr of Galactic evolution show that cosmic-ray acceleration must have taken place in the early Galaxy. The observed abundances of these elements relative to Fe, which, in the early Galaxy, is almost exclusively produced in Type II supernovae, strongly suggest that the cosmic-ray acceleration is also related to such supernovae with the particles being accelerated out of freshly nucleosynthesized matter before it mixes into the ambient, essentially nonmetallic interstellar medium. The observed abundances require that about 3 x 10(49) to 2 x 10(50) ergs per Type II supernova be imparted to these metallic cosmic rays, depending on whether or not H and He are accelerated along with the metals. The current data, however, are not sufficient to decide whether these cosmic rays are predominantly low energy or high energy. But, in any case, arguments of energetics imply a hard-energy spectrum extending up in energy to at least 50 MeV nucleon(-1). This rules out Be and B production by supernova ejecta without further acceleration. In addition to production by cosmic rays, there must also be significant B-11 production by neutrinos. This argument is driven by the observed B-11/B-10 ratio in meteorites that is very difficult to reproduce by cosmic-ray interactions. Observations of Li-6 and Li in the early Galaxy provide information on the acceleration of nonmetallic cosmic rays out of the interstellar medium. C1 TEL AVIV UNIV, SACKLER FAC EXACT SCI, IL-69978 TEL AVIV, ISRAEL. UNIV CALIF SAN DIEGO, CTR ASTROPHYS & SPACE SCI, LA JOLLA, CA 92093 USA. CEA, DSM, DAPNIA, SERV ASTROPHYS, F-91191 GIF SUR YVETTE, FRANCE. RP NASA, GODDARD SPACE FLIGHT CTR, HIGH ENERGY ASTROPHYS LAB, GREENBELT, MD 20771 USA. NR 63 TC 123 Z9 123 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 OCT 20 PY 1997 VL 488 IS 2 BP 730 EP 748 DI 10.1086/304744 PN 1 PG 19 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YB992 UT WOS:A1997YB99200023 ER PT J AU Dring, AR Linsky, J Murthy, J Henry, RC Moos, W VidalMadjar, A Audouze, J Landsman, W AF Dring, AR Linsky, J Murthy, J Henry, RC Moos, W VidalMadjar, A Audouze, J Landsman, W TI Lyman-alpha absorption and the D/H ratio in the local interstellar medium SO ASTROPHYSICAL JOURNAL LA English DT Article DE ISM, abundance; ISM, bubbles; ISM, clouds; ISM, kinematics and dynamics; ultraviolet, ISM ID DEUTERIUM ABUNDANCE; GHRS OBSERVATIONS; CANIS-MAJORIS; SOLAR-SYSTEM; HST-GHRS; SIRIUS-A; GAS; CLOUDS; ULTRAVIOLET; IONIZATION AB Using the Goddard High Resolution Spectrograph onboard the Hubble Space Telescope, we have observed Ly alpha absorption against stellar chromospheres along six lines of sight, with additional observations of the Mg II H and K lines along five of the lines of sight and Fe II absorption along four of the lines of sight. We found absorption near the projected velocity of the local interstellar cloud (LIC) along three lines of sight. The velocity toward the stars beta Gem and sigma Gem was only marginally consistent with the LIC. The single interstellar component toward 31 Com had a velocity that was inconsistent with the projected LIC velocity. Three of the lines of sight showed a multicomponent velocity structure. For the star epsilon Eri we required an additional hot, low-density component which we have interpreted as a stellar hydrogen wall. The LIC temperatures derived from our data range from 7800 to 9700 K with values of the microturbulence parameter less than 2.0 km s(-1). The measured D/H ratio for the LIC along every sight line is consistent with a value of 1.6 x 10(-5), the best determined value being the beta Cas line of sight with D/H = 1.7 +/- 0.3 x 10(-5). C1 UNIV COLORADO,JOINT INST LAB ASTROPHYS,BOULDER,CO 80309. NATL INST STAND & TECHNOL,BOULDER,CO 80309. INST ASTROPHYS,CTR NATL RECH SPATIALE,F-75014 PARIS,FRANCE. NASA,GODDARD SPACE FLIGHT CTR,HUGHES STX INC,GREENBELT,MD 20771. RP Dring, AR (reprint author), JOHNS HOPKINS UNIV,DEPT PHYS & ASTRON,BALTIMORE,MD 21218, USA. RI Murthy, Jayant/F-4433-2010 NR 50 TC 62 Z9 62 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 OCT 20 PY 1997 VL 488 IS 2 BP 760 EP 775 DI 10.1086/304738 PN 1 PG 16 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YB992 UT WOS:A1997YB99200025 ER PT J AU Scott, DM Finger, MH Wilson, RB Koh, DT Prince, TA Vaughan, BA Chakrabarty, D AF Scott, DM Finger, MH Wilson, RB Koh, DT Prince, TA Vaughan, BA Chakrabarty, D TI Discovery and orbital determination of the transient X-ray pulsar GRO J1750-27 SO ASTROPHYSICAL JOURNAL LA English DT Article DE pulsars, individual (GRO J1750-27); X-rays, stars ID ACCRETION; PULSATIONS AB We report on the discovery and hard X-ray (20-70 keV) observations of the 4.45 s period transient X-ray pulsar GRO J1750-27 with the BATSE all-sky monitor on board CGRO. A relatively faint outburst (<30 mcrab peak) lasting at least 60 days was observed during which the spin-up rate peaked at 38 pHz s(-1) and was correlated with the pulsed intensity. An orbit with a period of 29.8 days was found. The large spin-up rate, spin period, and orbital period together suggest that accretion is occurring from a disk and that the outburst is a ''giant'' outburst typical of a Be/X-ray transient system. No optical counterpart has yet been reported. C1 CALTECH, SPACE RADIAT LAB 22047, PASADENA, CA 91125 USA. MIT, CTR SPACE RES 37561, CAMBRIDGE, MA 02139 USA. RP NASA, GEORGE C MARSHALL SPACE FLIGHT CTR, SPACE SCI LAB ES84, HUNTSVILLE, AL 35812 USA. NR 22 TC 19 Z9 19 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 OCT 20 PY 1997 VL 488 IS 2 BP 831 EP 835 DI 10.1086/304740 PN 1 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YB992 UT WOS:A1997YB99200032 ER PT J AU Lamb, RC Macomb, DJ AF Lamb, RC Macomb, DJ TI Point sources of GeV gamma rays SO ASTROPHYSICAL JOURNAL LA English DT Article DE catalogs; gamma rays, observations; Magellanic Clouds; pulsars, general ID EGRET OBSERVATIONS; EMISSION AB A catalog of gamma-ray sources based on photons with energies greater than 1 GeV has been developed from observations taken by the EGRET instrument of the Compton Gamma Ray Observatory. The data are taken from the 4.5 yr of observation available in the public data archives. We emphasize sources that are detected using the entire database, without regard to any possible transient or variable behavior. Ten of the 57 sources reported here have not previously been reported in the catalogs developed using photons above 100 MeV in energy. Twenty-seven sources have identifications with objects seen at other wavelengths: the Large Magellanic Cloud, five pulsars, and 21 blazars. The remaining 30 sources are classified as unidentified; however, seven may be associated with Galactic supernova remnants and one source may be a Galactic X-ray binary (LSI 61 303). The 30 unidentified sources are distributed nearly uniformly along the Galactic plane and are symmetric about it. Only one of the unidentified sources has a Galactic latitude in excess of 30 degrees, whereas, if the sources were distributed uniformly, similar to 12 would be expected on the basis of the combined EGRET exposure. A scatter plot of the flux from the unidentified sources versus Galactic latitude reveals two rather distinct categories of source: ''bright'' sources with fluxes greater than or equal to 4.0 x 10(-8) photons cm(-2) s(-1) and ''dim'' sources with fluxes of less than 4.0 x 10(-8) photons cm(-2) s(-1). The absence of high-latitude bright sources is striking. The bright unidentified sources have an average Galactic latitude of 2.degrees 7, which is consistent with a Population I distribution at distances of 1-5 kpc. The dim unidentified sources have a broader latitude distribution with an average \b\ = 13.degrees 8, indicating that if they are at the same average distance from the Galactic plane as the bright sources, they are paradoxically approximately 5 times closer than the bright objects on average and therefore roughly 2 orders of magnitude less luminous. C1 NASA,GODDARD SPACE FLIGHT CTR,SCI SUPPORT CTR,GREENBELT,MD 20771. UNIV SPACE RES ASSOC,ASTRON PROGRAM,WASHINGTON,DC. RP Lamb, RC (reprint author), CALTECH,SPACE RADIAT LAB,PASADENA,CA 91125, USA. NR 29 TC 130 Z9 130 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 OCT 20 PY 1997 VL 488 IS 2 BP 872 EP 880 DI 10.1086/304736 PN 1 PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YB992 UT WOS:A1997YB99200037 ER PT J AU Cheng, ES Cottingham, DA Fixsen, DJ Goldin, AB Inman, CA Knox, L Kowitt, MS Meyer, SS Puchalla, JL Ruhl, JE Silverberg, RF AF Cheng, ES Cottingham, DA Fixsen, DJ Goldin, AB Inman, CA Knox, L Kowitt, MS Meyer, SS Puchalla, JL Ruhl, JE Silverberg, RF TI Detection of cosmic microwave background anisotropy by the third flight of the medium-scale anisotropy measurement SO ASTROPHYSICAL JOURNAL LA English DT Article DE balloons; cosmic microwave background; cosmology, observations; infrared, ISM, continuum AB The third flight of the Medium-Scale Anisotropy Measurement (MSAM1), in 1995 June, observed a new strip of sky, doubling the sky coverage of the original MSAM1 data set, MSAM1 observes with a 0.degrees 5 beam size in four bands from 5 to 20 cm(-1). From these four bands we derive measurements of cosmic microwave background radiation (CMBR) anisotropy and interstellar dust emission. Our measurement of dust emission correlates well with the 100 mu m IRAS Sky Survey Atlas; from this comparison we determine an effective emissivity spectral index between 100 mu m and 444 mu m of 1.46 +/- 0.28. Analysis of our measurement of CMBR anisotropy shows that for Gaussian-shaped correlation functions with theta(c) = 0.degrees 3, we place a limit on total rms anisotropy of 2.2 x 10(-5) < Delta T/T < 3.9 x 10(-5) (90% confidence interval, including calibration error). The band-power limits are [delta T] = [l(l + 1)C-1/2 pi](1/2) = 50(-11)(+15) mu K at l = 160, and [delta T] = 65(-13)(+18) mu K at l = 270 (1 sigma calibration error). The corresponding limits with statistical errors only are [delta T] = 50(-9)(+13) mu K and [delta T] = 65(-10)(+14) mu K, respectively. These measurements are consistent with a standard adiabatic cold dark matter model; we statistical discuss constraints on h, n, and the redshift of reionization. C1 NASA,GODDARD SPACE FLIGHT CTR,ASTRON & SOLAR PHYS LAB,APPL RES CORP,GREENBELT,MD 20771. UNIV CHICAGO,CHICAGO,IL 60637. UNIV TORONTO,CANADIAN INST THEORET ASTROPHYS,TORONTO,ON M5S 3H8,CANADA. UNIV CALIF SANTA BARBARA,DEPT PHYS,SANTA BARBARA,CA 93106. RP Cheng, ES (reprint author), NASA,GODDARD SPACE FLIGHT CTR,ASTRON & SOLAR PHYS LAB,GLOBAL SCI & TECHNOL INC,CODE 685-0,GREENBELT,MD 20771, USA. NR 15 TC 30 Z9 30 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 OCT 20 PY 1997 VL 488 IS 2 BP L59 EP L62 DI 10.1086/310923 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YC001 UT WOS:A1997YC00100002 ER PT J AU Goldin, AB Kowitt, MS Cheng, ES Cottingham, DA Fixsen, DJ Inman, CA AF Goldin, AB Kowitt, MS Cheng, ES Cottingham, DA Fixsen, DJ Inman, CA TI Whole-disk observations of Jupiter, Saturn, and Mars in millimeter/submillimeter bands SO ASTROPHYSICAL JOURNAL LA English DT Article DE balloons; cosmic microwave background; infrared, solar system; planets and satellites, individual (Jupiter, Mars, Saturn); radio continuum, solar system ID SUBMILLIMETER; WAVELENGTH; ANISOTROPY AB New balloon-borne observations of whole-disk brightness ratios for Jupiter, Saturn, and Mars are reported in four millimeter/submillimeter bands of bandwidth Delta nu approximate to 1-2 cm(-1). Using the effective planetary radii of Hildebrand et al., we find that TMars/TJupiter = 1.158 +/- 0.015, 1.189 +/- 0.015, 1.470 +- 0.019, and 1.515 +/- 0.019 and T-Saturn/T-Jupiter = 0.833 +/- 0.012, 0.758 +/- 0.010, 0.818 +/- 0.012, and 0.840 +/- 0.012, at nu = 5.7, 9.5, 16.5, and 22.5 cm(-1), respectively. Using models for the brightness temperature of Mars, we also give the whole-disk brightness temperatures for Jupiter and Saturn for the four frequencies. C1 UNIV CHICAGO,ENRICO FERMI INST,CHICAGO,IL 60637. NASA,GLOBAL SCI & TECHNOL INC,ASTRON & SOLAR PHYS LAB,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. NASA,HUGHES STX,ASTRON & SOLAR PHYS LAB,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. UNIV CALIF SANTA BARBARA,DEPT PHYS,SANTA BARBARA,CA 93106. RP Goldin, AB (reprint author), UNIV CHICAGO,DEPT ASTRON & ASTROPHYS,5640 S ELLIS AVE,CHICAGO,IL 60637, USA. NR 13 TC 26 Z9 27 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 OCT 20 PY 1997 VL 488 IS 2 BP L161 EP L164 DI 10.1086/310919 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YC001 UT WOS:A1997YC00100027 ER PT J AU Nandra, K George, IM Mushotzky, RF Turner, TJ Yaqoob, T AF Nandra, K George, IM Mushotzky, RF Turner, TJ Yaqoob, T TI On the dependence of the iron K-line profiles with luminosity in active galactic nuclei SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies, active; galaxies, nuclei; quasars, general; X-rays, galaxies ID MASSIVE BLACK-HOLE; X-RAY CONTINUUM; SPECTRA; QUASARS; ASCA; DISK AB We present evidence for changes in the strength and profile of the iron K alpha line in active galactic nuclei (AGNs), based on X-ray observations with ASCA. There is a clear decrease in the strength of the line with increasing luminosity. This relation is not due solely to radio power, as it persists when only radio-quiet AGNs are considered and therefore cannot be fully explained by relativistic beaming. In addition to the change in strength, the line profile also appears to be different in higher luminosity sources. We discuss these results in terms of a model where the accretion disk becomes ionized as a function of the accretion rate. C1 NAS NRC,WASHINGTON,DC. UNIV SPACE RES ASSOC,WASHINGTON,DC. RP Nandra, K (reprint author), NASA,GODDARD SPACE FLIGHT CTR,HIGH ENERGY ASTROPHYS LAB,CODE 660,GREENBELT,MD 20771, USA. NR 25 TC 79 Z9 79 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 OCT 20 PY 1997 VL 488 IS 2 BP L91 EP L94 DI 10.1086/310937 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YC001 UT WOS:A1997YC00100010 ER PT J AU Nelson, RW Bildsten, L Chakrabarty, D Finger, MH Koh, DT Prince, TA Rubin, BC Scott, DM Vaughan, BA Wilson, RB AF Nelson, RW Bildsten, L Chakrabarty, D Finger, MH Koh, DT Prince, TA Rubin, BC Scott, DM Vaughan, BA Wilson, RB TI On the dramatic spin-up/spin-down torque reversals in accreting pulsars SO ASTROPHYSICAL JOURNAL LA English DT Article DE pulsars, general; pulsars, individual (GX 1-4) ID X-RAY PULSARS; MAGNETIC NEUTRON STARS; DISK ACCRETION; BINARIES AB Dramatic torque reversals between spin-up and: spin-down have been observed in half of the persistent X-ray pulsars monitored by the BATSE all-sky monitor on the Compton Gamma Ray Observatory. Theoretical models developed to explain early pulsar timing data can explain spin-down torques via a disk-magnetosphere interaction if the star nearly corotates with the inner accretion disk. To produce the observed BATSE torque reversals, however, these equilibrium models require the disk to alternate between two mass accretion rates, with (M) over dot(+/-) producing accretion torques of similar magnitude but always of opposite sign. Moreover, in at least one pulsar (GX 1+4) undergoing secular spin-down, the neutron star spins down faster during brief (similar to 20 day) hard X-ray flares-this is opposite the correlation expected from standard theory, assuming that BATSE pulsed flux increases with mass accretion rate. The 10 day to 10 yr intervals between torque reversals in these systems are much longer than any characteristic magnetic or viscous timescale near the inner disk boundary and are more suggestive of a global disk phenomenon. We discuss possible explanations of the observed torque behavior. Despite the preferred sense of rotation defined by the binary orbit, the BATSE observations are surprisingly consistent with an earlier suggestion for GX 1+4: the disks in these systems somehow alternate between episodes of prograde and retrograde rotation. We are unaware of any mechanism that could produce a stable retrograde disk in a binary undergoing Roche lobe overflow, but such flip-flop behavior does occur in numerical simulations of wind-fed systems, One possibility is that the disks in some of these binaries are fed by an X-ray-excited wind. C1 UNIV CALIF BERKELEY,DEPT PHYS,BERKELEY,CA 94720. UNIV CALIF BERKELEY,DEPT ASTRON,BERKELEY,CA 94720. MIT,CTR SPACE RES,CAMBRIDGE,MA 02139. NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,SPACE SCI LAB,HUNTSVILLE,AL 35812. RIKEN,INST PHYS & CHEM RES,COSM RADIAT LAB,WAKO,SAITAMA 35101,JAPAN. RP Nelson, RW (reprint author), CALTECH,SPACE RADIAT LAB,PASADENA,CA 91125, USA. NR 31 TC 54 Z9 54 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 OCT 20 PY 1997 VL 488 IS 2 BP L117 EP L120 DI 10.1086/310936 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YC001 UT WOS:A1997YC00100016 ER PT J AU Weissman, PR Levison, HF AF Weissman, PR Levison, HF TI Origin and evolution of the unusual object 1996 PW: Asteroids from the Oort cloud? SO ASTROPHYSICAL JOURNAL LA English DT Article DE celestial mechanics, stellar dynamics; comets, general; minor planets, asteroids solar; system, formation ID COMET AB The unusual object 1996 PW was discovered on 1996 August 9 by the Near-Earth Asteroid Tracking automated search camera operating from Haleakala in Hawaii. Although asteroidal in appearance, it was soon determined that the object is in a near-parabolic orbit similar to that of a long-period comet. No object that was not an active comet has ever been discovered on such an eccentric orbit. The discovery of 1996 PW prompted us to examine and evaluate its possible origins, including the intriguing possibility that it is an asteroid from the Oort cloud. Current models for the formation of the Oort cloud argue that most of the material there should be from the Uranus-Neptune region and thus cometary, not asteroidal, in composition. We better quantify these models and show that similar to 1% of the Oort cloud population should be asteroids. We find that 1996 PW has almost certainly been a resident of the Oort cloud. However we find it equally likely that 1996 PW is an extinct comet or an asteroid. Although not conclusive, our results represent a significant change in our understanding of the Oort cloud, because they suggest that the ejection process sampled (1) material from as close to the Sun as the asteroid belt in the primordial solar nebula and hence (2) much warmer formation temperatures than previously thought. This diverse sample is preserved in the Oort cloud. C1 SW RES INST, DEPT SPACE SCI, BOULDER, CO 80302 USA. RP CALTECH, JET PROP LAB, DIV EARTH & SPACE SCI, MAIL STOP 183-601, 4800 OAK GROVE DR, PASADENA, CA 91109 USA. NR 31 TC 28 Z9 28 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 OCT 20 PY 1997 VL 488 IS 2 BP L133 EP L136 DI 10.1086/310940 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YC001 UT WOS:A1997YC00100020 ER PT J AU Kursinski, ER Hajj, GA Schofield, JT Linfield, RP Hardy, KR AF Kursinski, ER Hajj, GA Schofield, JT Linfield, RP Hardy, KR TI Observing Earth's atmosphere with radio occultation measurements using the Global Positioning System SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID HEMISPHERE TEMPERATURE TRENDS; STEP-MOUNTAIN COORDINATE; GRAVITY-WAVES; SCIENCE OBSERVATIONS; BOUNDARY-LAYER; CARBON-DIOXIDE; WATER-VAPOR; CLIMATE; MODEL; VENUS AB The implementation of the Global Positioning System (GPS) network of satellites and the development of small, high-performance instrumentation to receive GPS signals have created an opportunity for active remote sounding of the Earth's atmosphere by radio occultation at comparatively low cost. A prototype demonstration of this capability has now been provided by the GPS/MET investigation. Despite using relatively immature technology, GPS/MET has been extremely successful [Ware et al., 1996; Kursinski et al., 1996], although there is still room for improvement. The aim of this paper is to develop a theoretical estimate of the spatial coverage, resolution, and accuracy that can be expected for atmospheric profiles derived from GPS occultations. We consider observational geometry, attenuation, and diffraction in defining the vertical range of the observations and their resolution. We present the first systematic, extensive error analysis of the spacecraft radio occultation technique using a combination of analytical and simulation methods to establish a baseline accuracy for retrieved profiles of refractivity, geopotential, and temperature. Typically, the vertical resolution of the observations ranges from 0.5 km in the lower troposphere to 1.4 km in the middle atmosphere. Results indicate that useful profiles of refractivity can be derived from similar to 60 km altitude to the surface with the exception of regions less than 250 m in vertical extent associated with high vertical humidity gradients. Above the 250 K altitude level in the troposphere, where the effects of water are negligible, sub-Kelvin temperature accuracy is predicted up to similar to 40 km depending on the phase of the solar cycle. Geopotential heights of constant pressure levels are expected to be accurate to similar to 10 m or better between 10 and 20 km altitudes. Below the 250 K level, the ambiguity between water and dry atmosphere refractivity becomes significant, and temperature accuracy is degraded. Deep in the warn troposphere the contribution of water to refractivity becomes sufficiently large for the accurate retrieval of water vapor given independent temperatures from weather analyses [Kursinski et al., 1995]. The radio occultation technique possesses a unique combination of global coverage, high precision, high vertical resolution, insensitivity to atmospheric particulates, and long-term stability. We show here how these properties are well suited for several applications including numerical weather prediction and long-term monitoring of the Earth's climate. C1 AS&T, PALO ALTO, CA 93404 USA. CALTECH, DIV GEOL & PLANETARY SCI, PASADENA, CA 91109 USA. RP Kursinski, ER (reprint author), CALTECH, JET PROP LAB, 4800 OAK GROVE DR, PASADENA, CA 91109 USA. NR 99 TC 582 Z9 621 U1 6 U2 44 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 OCT 20 PY 1997 VL 102 IS D19 BP 23429 EP 23465 DI 10.1029/97JD01569 PG 37 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA YC171 UT WOS:A1997YC17100018 ER PT J AU Rood, RB Douglass, AR Cerniglia, MC Read, WG AF Rood, RB Douglass, AR Cerniglia, MC Read, WG TI Synoptic-scale mass exchange from the troposphere to the stratosphere SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID MESOSCALE CONVECTIVE COMPLEX; DATA ASSIMILATION SYSTEM; POTENTIAL VORTICITY; CUTOFF LOW; 3-DIMENSIONAL SIMULATION; MIDDLE LATITUDES; WATER-VAPOR; OZONE; CLIMATOLOGY; TRANSPORT AB The transport of material between the troposphere and the stratosphere is studied with an off-line chemical transport model which uses winds from a global assimilated meteorological data set. The focus is on the role of rapidly growing synoptic waves in the maintenance of lower stratospheric tracer distributions in the extratropics. Satellite observations are used to establish that the modeled transport represents the observed tracer variability with sufficient accuracy to justify more quantitative analysis. Diabatic trajectory calculations are then used to understand the transport mechanisms in the model. Two rapidly developing surface cyclones are specifically studied and found to have qualitatively different impact on the tracer distribution. A strong storm in the Pacific Ocean perturbs the tropopause region, and because it remains relatively stationary, ultimately has transport characteristics similar to a cutoff low. The explosively developing synoptic wave responsible for the March 1993 blizzard in the eastern United States causes large-scale transport between the troposphere and stratosphere. There are two notable characteristics of the transport associated with the U.S. blizzard: (1) The U.S. blizzard moves across many degrees of latitude. This storm develops in the subtropics, with a high tropopause, and later decays in a subpolar environment where the tropopause is naturally much lower. (2) Diabatic processes are crucial to the long-range transport and ultimate transfer of mass to the stratosphere. The transport studied in connection with the United States requires consideration of the entire life cycle of the storm from subtropical cyclogenesis to subpolar decay. The fact that storms that are similar to the U.S. blizzard are quite common and that the transport is consistent with available tracer observations suggest that the large-scale transport of air from the troposphere to the stratosphere is plausible. Further investigation with more sophisticated models and tracer observations is needed to verify the importance of the modeled transport. C1 CALTECH, JET PROP LAB, PASADENA, CA 91109 USA. SPACE APPLICAT CORP, VIENNA, VA USA. RP Rood, RB (reprint author), NASA, GODDARD SPACE FLIGHT CTR, ATMOSPHERES LAB, GREENBELT, MD 20771 USA. RI Douglass, Anne/D-4655-2012; Rood, Richard/C-5611-2008 OI Rood, Richard/0000-0002-2310-4262 NR 55 TC 28 Z9 29 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 OCT 20 PY 1997 VL 102 IS D19 BP 23467 EP 23485 DI 10.1029/97JD01598 PG 19 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA YC171 UT WOS:A1997YC17100019 ER PT J AU Mickley, LJ Abbatt, JPD Frederick, JE Russell, JM AF Mickley, LJ Abbatt, JPD Frederick, JE Russell, JM TI Response of summertime odd nitrogen and ozone at 17 mbar to Mount Pinatubo aerosol over the southern midlatitudes: Observations from the halogen occultation experiment SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID IN-SITU MEASUREMENTS; STRATOSPHERIC OZONE; 2-DIMENSIONAL MODEL; POTENTIAL IMPACT; SULFATE AEROSOLS; MT-PINATUBO; AASE-II; NO2; CHEMISTRY; AIRCRAFT AB Observations of stratospheric NO, NO2, and O-3 from the Halogen Occultation Experiment (HALOE) are examined over the southern midlatitudes (35 degrees-45 degrees S) in the summers following the eruption of Mount Pinatubo, from early 1992 through mid-1995. The tracers HF and CH4, also observed by HALOE, are used to distinguish between the effects of chemistry and those of transport processes on the distribution of total reactive nitrogen (NOy) and ozone. Results show that at 17 mbar (about 28 km), in parcels of similar photochemical age, the abundances of summertime NO + NO2 (NOx) increased dramatically between 1992 and 1993 and then leveled off in subsequent years. The 1992-1993 increase is coincident in time with a sharp drop in aerosol surface area density as the Pinatubo aerosol cleared the atmosphere and gives evidence of the sensitivity of NOx to sulfate aerosol even at these altitudes, where the cycling of NOy through HNO3 is rapid. Results also show that summertime ozone abundances at 17 mbar declined by nearly 10% between 1992 and 1993 and then, Like NOx, remained about constant for the next three summers. The trend in ozone is opposite in sign to that observed at lower altitudes in the aftermath of the Pinatubo eruption and demonstrates the importance of the NOx catalytic cycles in the ozone loss budget above 26 km. C1 UNIV CHICAGO, DEPT GEOPHYS SCI, CHICAGO, IL 60637 USA. NASA, LANGLEY RES CTR, DIV ATMOSPHER SCI, HAMPTON, VA 23665 USA. RI Mickley, Loretta/D-2021-2012 OI Mickley, Loretta/0000-0002-7859-3470 NR 57 TC 5 Z9 6 U1 0 U2 3 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD OCT 20 PY 1997 VL 102 IS D19 BP 23573 EP 23582 DI 10.1029/97JD01566 PG 10 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA YC171 UT WOS:A1997YC17100026 ER PT J AU Sodupe, M Branchadell, V Rosi, M Bauschlicher, CW AF Sodupe, M Branchadell, V Rosi, M Bauschlicher, CW TI Theoretical study of M+-CO2 and OM+CO systems for first transition row metal atoms SO JOURNAL OF PHYSICAL CHEMISTRY A LA English DT Article ID GAUSSIAN-BASIS SETS; COUPLED-CLUSTER THEORY; ORBITAL BASIS-SETS; CARBON-DIOXIDE; GAS-PHASE; BINDING-ENERGY; MOLECULAR CALCULATIONS; HARTREE-FOCK; STRUCTURAL CHARACTERIZATION; ELECTRON CORRELATION AB The coordination of carbon dioxide to first transition row metal cations and the insertion reaction of the metal into one CO bond of carbon dioxide have been studied theoretically. The geometry and the vibrational frequencies of the M+-CO2 and OM+CO structures have been determined using the hybrid three-parameter B3LYP density functional approach. Binding energies have also been determined at the CCSD(T) level using large basis sets. The linear end-on M+-OCO structure is the most favorable coordination for CO2, due to the electrostatic nature of the bonding, in the inserted OM+CO structures, the bonding arises from the electrostatic interaction between the ground state of OM+ and CO. For the early transition metals (Sc+, Ti+, and V+), the insertion reaction is exothermic and the inserted OM+CO structure is more stable than the Linear M+-OCO isomer, because of the very strong MO+ bond that is formed. C1 NASA,AMES RES CTR,MOFFETT FIELD,CA 94035. UNIV PERUGIA,DEPT CHEM,I-06100 PERUGIA,ITALY. RP Sodupe, M (reprint author), UNIV AUTONOMA BARCELONA,DEPT QUIM,BELLATERRA 08193,BARCELONA,SPAIN. RI Branchadell, Vicenc/D-2446-2009; Sodupe, Mariona/E-9352-2013; Rosi, Marzio/L-5748-2015 OI Branchadell, Vicenc/0000-0003-3480-1669; Sodupe, Mariona/0000-0003-0276-0524; Rosi, Marzio/0000-0002-1264-3877 NR 62 TC 100 Z9 100 U1 2 U2 14 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 SN 1089-5639 J9 J PHYS CHEM A JI J. Phys. Chem. A PD OCT 16 PY 1997 VL 101 IS 42 BP 7854 EP 7859 DI 10.1021/jp9711252 PG 6 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA YB795 UT WOS:A1997YB79500024 ER PT J AU Noor, AK Starnes, JH Peters, JM AF Noor, AK Starnes, JH Peters, JM TI Thermomechanical buckling and postbuckling responses of composite panels with skewed stiffeners SO FINITE ELEMENTS IN ANALYSIS AND DESIGN LA English DT Article DE buckling; composite panels; finite elements; hierarchical sensitivity coefficients; postbuckling; skewed stiffener; thermomechanical loads ID REDUCED BASIS TECHNIQUE AB The results of a detailed study of the buckling and postbuckling responses of composite panels with skewed stiffeners are presented. The panels are subjected to applied edge displacements and temperature changes. A first-order shear-deformation geometrically nonlinear shallow-shell theory that includes the effects of laminated anisotropic material behavior is used to model each section of the stiffeners and the skin. A mixed formulation is used in the analysis with the fundamental unknowns consisting of the generalized displacements and the stress resultants of the panel. The nonlinear displacements, strain energy, transverse shear stresses, transverse shear strain energy density, and their hierarchical sensitivity coefficients are evaluated. The hierarchical sensitivity coefficients measure the sensitivity of the buckling and postbuckling responses to variations in three sets of interrelated parameters; namely, the panel stiffnesses; the effective material properties of the individual layers; and the constituent material parameters (fibers, matrix, interface and interphase). Numerical results are presented for rectangular panels with open section I-stiffeners, subjected to edge shortening and uniform temperature change. The results show the effects of variations in the material properties of the skin and the stiffener on the buckling and postbuckling responses of the panel, as well as on the sensitivity coefficients. (C) Elsevier Science B.V. RP Noor, AK (reprint author), UNIV VIRGINIA,NASA,LANGLEY RES CTR,CTR ADV COMPUTAT TECHNOL,HAMPTON,VA 23681, USA. NR 14 TC 3 Z9 3 U1 0 U2 2 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0168-874X J9 FINITE ELEM ANAL DES JI Finite Elem. Anal. Des. PD OCT 15 PY 1997 VL 27 IS 2 BP 193 EP 214 DI 10.1016/S0168-874X(97)00014-0 PG 22 WC Mathematics, Applied; Mechanics SC Mathematics; Mechanics GA YC490 UT WOS:A1997YC49000004 ER PT J AU LopesGautier, R Davies, AG Carlson, R Smythe, W Kamp, L Soderblom, L Leader, FE Mehlman, R AF LopesGautier, R Davies, AG Carlson, R Smythe, W Kamp, L Soderblom, L Leader, FE Mehlman, R TI Hot spots on Io: Initial results from Galileo's near infrared mapping spectrometer SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article AB The Near-Infrared Mapping Spectrometer on Galileo has monitored the volcanic activity on Io since June 28, 1996. This paper presents preliminary analysis of NIMS thermal data for the first four orbits of the Galileo mission. NIMS has detected 18 new hot spots and 12 others which were previously known to be active. The distribution of the hot spots on Io's surface may not be random, as hot spots surround the two bright, SO2-rich regions of Bosphorus Regio and Colchis Regio. Most hot spots seem to be persistently active from orbit to orbit and 10 of those detected were active in 1979 during the Voyager encounters. We report the distribution of hot spot temperatures and find that they are consistent with silicate volcanism. C1 US GEOL SURVEY,BRANCH ASTROGEOL STUDIES,FLAGSTAFF,AZ 86001. UNIV CALIF LOS ANGELES,INST GEOPHYS & PLANETARY PHYS,LOS ANGELES,CA 90024. RP LopesGautier, R (reprint author), CALTECH,JET PROP LAB,MS 183 601,4800 OAK GROVE DR,PASADENA,CA 91109, USA. RI Lopes, Rosaly/D-1608-2016 OI Lopes, Rosaly/0000-0002-7928-3167 NR 13 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 OCT 15 PY 1997 VL 24 IS 20 BP 2439 EP 2442 DI 10.1029/97GL02662 PG 4 WC Geosciences, Multidisciplinary SC Geology GA YB602 UT WOS:A1997YB60200001 ER PT J AU McEwen, AS Simonelli, DP Senske, DR Klaasen, KP Keszthelyi, L Johnson, TV Geissler, PE Carr, MH Belton, MJS AF McEwen, AS Simonelli, DP Senske, DR Klaasen, KP Keszthelyi, L Johnson, TV Geissler, PE Carr, MH Belton, MJS TI High-temperature hot spots on Io as seen by the Galiloe solid state imaging (SSI) experiment SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID SILICATE VOLCANISM; IMAGES AB High-temperature hot spots on Io have been imaged at similar to 50 km spatial resolution by Garileo's CCD imaging system (SSI). Images were acquired during eclipses (Io in Jupiter's shadow) via the SSI clear filter (similar to 0.4-1.0 mu m), detecting emissions from both small intense hot spots and diffuse extended glows associated with Io's atmosphere and plumes. A total of 13 hot spots have been detected over similar to 70% of Io's surface. Each hot spot falls precisely on a low-albedo feature corresponding to a caldera floor and/or lava flow. The hot-spot temperatures must exceed similar to 700 K for detection by SSI. Observations at wavelengths longer than those available to SSI require that most of these hot spots actually have significantly higher temperatures (similar to 1000 K or higher) and cover small areas. The high-temperature hot spots probably mark the locations of active silicate volcanism, supporting suggestions that the eruption and near-surface movement of silicate magma drives the heat flow and volcanic activity of Io. C1 CORNELL UNIV,ITHACA,NY 14853. CALTECH,JET PROP LAB,PASADENA,CA 91109. US GEOL SURVEY,MENLO PK,CA 94025. NATL OPT ASTRON OBSERV,TUCSON,AZ 85719. RP McEwen, AS (reprint author), UNIV ARIZONA,LUNAR & PLANETARY LAB,TUCSON,AZ 85721, USA. NR 16 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 OCT 15 PY 1997 VL 24 IS 20 BP 2443 EP 2446 DI 10.1029/97GL01956 PG 4 WC Geosciences, Multidisciplinary SC Geology GA YB602 UT WOS:A1997YB60200002 ER PT J AU Davies, AG McEwen, AS LopesGautier, RMC Keszthelyi, L Carlson, RW Smythe, WD AF Davies, AG McEwen, AS LopesGautier, RMC Keszthelyi, L Carlson, RW Smythe, WD TI Temperature and area constraints of the south Volund volcano on Io from the NIMS and SSI instruments during the Galileo G1 orbit SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID SATELLITES; JUPITER; FLOW AB Analysis of data from darkside and eclipse observations of Io by the NIMS and SSI instruments show that the South Volund hot spot is a manifestation of high temperature active silicate volcanism. The NIMS data are fitted with a two temperature model (developed from modelling terrestrial lavas) which yields a better fit to the data than a single temperature fit. The multispectral color temperatures obtained from NIMS are compared with the brightness temperatures obtained from the SSI instrument, and show excellent agreement for the hotter of the two components fitted to the NIMS data. The two components might correspond to a cooled crust which has formed on the surface of an active flow or lava lake, at a temperature of approximately 450 K, and covering an area of about 50 km(2), and a hotter and much smaller component, at a temperature of approximately 1100 K and an area of less than 0.1 km(2). The hot component implies the existence of cracks in the surface crust of a flow or lake through which the hot interior radiates, a hot vent area, or breakouts of lava forming new flow lobes. The ratio of these areas is consistent with the crack-to-crust ratio of some lava flows and lava lakes on Earth. C1 UNIV ARIZONA,LUNAR & PLANETARY LAB,TUCSON,AZ 85721. RP Davies, AG (reprint author), CALTECH,JET PROP LAB,MS 183 601,4800 OAK GROVE DR,PASADENA,CA 91109, USA. RI Lopes, Rosaly/D-1608-2016 OI Lopes, Rosaly/0000-0002-7928-3167 NR 18 TC 40 Z9 40 U1 0 U2 2 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 OCT 15 PY 1997 VL 24 IS 20 BP 2447 EP 2450 DI 10.1029/97GL02310 PG 4 WC Geosciences, Multidisciplinary SC Geology GA YB602 UT WOS:A1997YB60200003 ER PT J AU Blaney, DL Veeder, GJ Matson, DL Johnson, TV Goguen, JD Spencer, JR AF Blaney, DL Veeder, GJ Matson, DL Johnson, TV Goguen, JD Spencer, JR TI Io's thermal anomalies: Clues to their origins from comparison of ground based observations between 1 and 20 mu m SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID SILICATE VOLCANISM; HEAT-FLOW; PHOTOMETRY; RATES AB Io's thermal emission for 1995 from eclipse photometry at 2.2 mu m; broad band radiometry at 4.8 mu m, 8.7 mu m and 20 mu m; and in eclipse imaging between 1.7 and 5 mu m are compared. The variability of thermal emission from Io at wavelengths between 1-5 mu m (Silverstone et al., 1995; Spencer er al., 1997) is in agreement with the expected variability based on the 13 year record presented in Veeder at al. (1994) and Goguen et al. (1996). We conclude that 1995 was typical for Io, in terms of overall observed variability in the volcanic sources. Detailed comparison of data from Goguen et al. on Aug. 24 and Spencer et al. on Aug. 26 provides evidence of a high temperature eruption that produced a larger, cooler region over the course of two days. The observed frequency of occurrence of high temperature events, the linking of high and lower temperature thermal anomalies, and the observed stability of volcanic regions since Voyager suggests that high temperature silicate eruptions could support the entire observed population of cooler temperature anomalies. It may be more productive to consider sulfur flows on Io in the context of remobilization of existing sulfur deposits. C1 LOWELL OBSERV,FLAGSTAFF,AZ 86001. RP Blaney, DL (reprint author), CALTECH,JET PROP LAB,NASA,MS 183 501,4800 OAK GROVE DR,PASADENA,CA 91109, USA. NR 20 TC 6 Z9 6 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 OCT 15 PY 1997 VL 24 IS 20 BP 2459 EP 2462 DI 10.1029/97GL02509 PG 4 WC Geosciences, Multidisciplinary SC Geology GA YB602 UT WOS:A1997YB60200006 ER PT J AU Schenk, PM McEwen, A Davies, AG Davenport, T Jones, K Fessler, B AF Schenk, PM McEwen, A Davies, AG Davenport, T Jones, K Fessler, B TI Geology and topography of Ra Patera, Io, in the voyager era: Prelude to eruption SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID SULFUR FLOWS; VENUS; EMPLACEMENT; VOLCANISM; MARS AB Voyager era stereo images are used to map the geology and topography of Ra Patera (a major active volcanic center and possible site of sulfur eruptions on Io). The summit of Ra Patera reaches only similar to 1 km above the surrounding plains. pre-Voyager-era lava flows occur on slopes of 0.1-0.3 degrees, comparable to the lunar mare. These flows were emplaced at either low viscosities, high eruption rates, or both. A 600-km-long ridged mountain unit (rising to similar to 8 km near Carancho Patera) forms a 60 by 90 km wide plateau similar to 0.5 km high 50 km east of Ra Patera. The new lava flows observed by Galileo flowed around the southern edge of this plateau. C1 UNIV ARIZONA,LUNAR & PLANETARY LAB,TUCSON,AZ 85721. CALTECH,JET PROP LAB,PASADENA,CA. S DAKOTA SCH MINES,RAPID CITY,SD. BROWN UNIV,PROVIDENCE,RI 02912. RP Schenk, PM (reprint author), LUNAR & PLANETARY INST,3600 BAY AREA BLVD,HOUSTON,TX 77058, USA. RI Jones, Kevin/A-7449-2014 OI Jones, Kevin/0000-0002-6386-2623 NR 25 TC 16 Z9 16 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 OCT 15 PY 1997 VL 24 IS 20 BP 2467 EP 2470 DI 10.1029/97GL02688 PG 4 WC Geosciences, Multidisciplinary SC Geology GA YB602 UT WOS:A1997YB60200008 ER PT J AU Carlson, RW Smythe, WD LopesGautier, RMC Davies, AG Kamp, LW Mosher, JA Soderblom, LA Leader, FE Mehlman, R Clark, RN Fanale, FP AF Carlson, RW Smythe, WD LopesGautier, RMC Davies, AG Kamp, LW Mosher, JA Soderblom, LA Leader, FE Mehlman, R Clark, RN Fanale, FP TI The distribution of sulfur dioxide and other infrared absorbers on the surface of Io SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID HUBBLE-SPACE-TELESCOPE; SO2; SPECTRA; LO; ATMOSPHERE; STATE; H2S AB The Galileo Near Infrared Mapping Spectrometer was used to investigate the distribution and properties of sulfur dioxide over the surface of Io, and qualitative results for the anti-Jove hemisphere sue presented here. SO2, existing as a frost, is found almost everywhere, but with spatially variable concentration. The exceptions are volcanic hot spots, where high surface temperatures promote rapid vaporization and can produce SO2-free areas. The pervasive frost, if fully covering the cold surface, has characteristic grain sizes of 30 to 100 mu m, or greater. Regions of greater sulfur dioxide concentrations are found. The equatorial Colchis Regio area exhibits extensive snowfields with large particles (250 to 500 mu m diameter, or greater) beneath smaller particles. A weak feature at 3.15 mu m is observed and is perhaps due to hydroxides, hydrates, or water. A broad absorption in the 1 mu m region, which could be caused by iron-containing minerals, shows a concentration in Io's southern polar region, with an absence in the Pele plume deposition ring. C1 US GEOL SURVEY,FLAGSTAFF,AZ 86001. UNIV CALIF LOS ANGELES,INST GEOPHYS & PLANETARY PHYS,LOS ANGELES,CA 90095. US GEOL SURVEY,DENVER FED CTR,DENVER,CO 80225. UNIV HAWAII,PLANETARY GEOSCI DIV,HONOLULU,HI 96822. RP Carlson, RW (reprint author), CALTECH,JET PROP LAB,MAIL STOP 183-601,4800 OAK GROVE DR,PASADENA,CA 91109, USA. RI Lopes, Rosaly/D-1608-2016 OI Lopes, Rosaly/0000-0002-7928-3167 NR 20 TC 66 Z9 66 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 OCT 15 PY 1997 VL 24 IS 20 BP 2479 EP 2482 DI 10.1029/97GL02609 PG 4 WC Geosciences, Multidisciplinary SC Geology GA YB602 UT WOS:A1997YB60200011 ER PT J AU Escoubet, CP Bosqued, JM Hoffman, RA Berthelier, A Anderson, PC AF Escoubet, CP Bosqued, JM Hoffman, RA Berthelier, A Anderson, PC TI Opposite ion dispersions observed quasi-simultaneously in the polar cusp by the DE-2 and Aureol-3 satellites SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID INTERPLANETARY MAGNETIC-FIELD; LOW-ALTITUDE; PLASMA; IDENTIFICATION; MODEL; IMF AB On 26 August 1982 the satellites Dynamics Explorer 2 (DE-2) and Aureol-3 (A-3) crossed around the same time the southern polar cusp. DE-2 detected the cleft in the prenoon sector (11.5 H MLT) constituted by a poleward ion dispersion with two steps at around 50 and 1.5 keV, respectively. Around 1.5 H MLT eastward, A-3 detected a diffuse ion precipitation, immediately followed by an equatorward dispersion (energy Increases when the latitude increases). The convection pattern detected by DE-2 was directed westward in the cleft with a maximum, around 1600 m/s, centred on the low energy step. The convection velocity measured by A-3 had a component directed poleward where the diffuse ion precipitation was observed and a convection with an equatorward component where the ion dispersion is observed. The IMP-8 IMF data showed a gap at the time of the cusp crossings, however using the IMF-Bz component around that time and the AE index we infer that the IMF-Bz would have been positive during the cusp crossings. We are explaining the observations by the merging of the interplanetary magnetic field with the geomagnetic lobe field lines which produces the dispersion observed at high latitude on A-3 and the low energy step observed by DE-2. At the same time a viscous diffusion on the frontside of the magnetosphere produces the diffuse ion precipitation observed by A-3 and the high energy step observed by DE-2. C1 NASA,GODDARD SPACE FLIGHT CTR,EXTRATERR PHYS LAB,GREENBELT,MD 20771. CNRS,CRPE,F-94107 ST MAUR FOSSES,FRANCE. AEROSP CORP,SETC,LOS ANGELES,CA 90009. CTR ETUD SPATIALE RAYONNEMENTS,F-31029 TOULOUSE,FRANCE. RP Escoubet, CP (reprint author), EUROPEAN SPACE AGCY,ESTEC,DEPT SPACE SCI,POB 299,NL-2200 AG NOORDWIJK,NETHERLANDS. NR 11 TC 7 Z9 7 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 OCT 15 PY 1997 VL 24 IS 20 BP 2487 EP 2490 DI 10.1029/97GL02575 PG 4 WC Geosciences, Multidisciplinary SC Geology GA YB602 UT WOS:A1997YB60200013 ER PT J AU Woo, R Martin, JM AF Woo, R Martin, JM TI Source regions of the slow solar wind SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID DENSITY-FLUCTUATIONS; DOPPLER SCINTILLATION; SUN; CORONA AB While the fast solar wind is generally thought to originate from coronal holes, the source of the slow solar wind is only known to be associated with the highly structured and highly variable streamer belt. There is growing evidence from multiple-station intensity scintillation measurements of solar wind velocity - often referred to as IFS for interplanetary scintillation - that the slow wind originates in localized regions of the solar corona overlying the streamer belt. In this paper, velocity structure in the corona is investigated based on estimates obtained from the power spectra of single-station intensity scintillation measurements. These measurements were conducted with the S-and X-band (13 and 3.6 cm wavelengths, respectively) radio signals of Voyager 2 during its superior conjunctions in 1979 and 1982. Unlike previous studies, simultaneous estimates Of density fluctuation from the same intensify scintillation measurements were available to provide the coronal context for the velocity measurements. Solar eclipse pictures show that with increasing heliocentric distance, coronal streamers taper to narrow extensions or stalks of angular size 1-2 degrees by a few solar radii. Prominent enhancements in density fluctuation characterizing such streamer stalks are found to coincide with the low speed wind measured by Voyager 2, leading to the first observational evidence for streamer stalks as the long sought coronal sources of the slow solar wind. RP Woo, R (reprint author), CALTECH, JET PROP LAB, 4800 OAK GROVE DR, MS 238-725, PASADENA, CA 91109 USA. NR 26 TC 44 Z9 45 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD OCT 15 PY 1997 VL 24 IS 20 BP 2535 EP 2538 DI 10.1029/97GL02598 PG 4 WC Geosciences, Multidisciplinary SC Geology GA YB602 UT WOS:A1997YB60200025 ER PT J AU Serra, YL Rogers, DP Hagan, DE Friehe, CA Grossman, RL Weller, RA Anderson, S AF Serra, YL Rogers, DP Hagan, DE Friehe, CA Grossman, RL Weller, RA Anderson, S TI Atmospheric boundary layer over the central and western equatorial Pacific Ocean observed during COARE and CEPEX SO JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS LA English DT Article ID SURFACE MIXED-LAYER; TOGA-COARE; TURBULENCE STRUCTURE; RESPONSE EXPERIMENT; HEAT-BUDGET; FLUXES; SEA; AIRCRAFT AB The present study is based on aircraft data collected in the western and central equatorial Pacific as a part of the Coupled Ocean-Atmosphere Response Experiment (COARE) and the Central Equatorial Pacific Experiment (CEPEX). The purpose of this discussion is to provide some insight into the coupling of the atmosphere to the ocean in regions of light winds and high humidity, as well as near deep organized convection, and to compare and contrast these climatically important tropical regions. The results presented use both the aerial extent of cold cloud top temperatures and surface layer similarity to highlight the variation of the surface fluxes as a function of convective regimes. A wide range of convective conditions were encountered during the 5 months of COARE and CEPEX, ranging from deep, towering anvils to shallow trade cumuli. The variety of conditions sampled has provided a unique set of turbulence data over open ocean, which are compared to fundamental spectral forms. Results suggest that assumptions regarding surface layer processes based on a large-scale assessment of the convective conditions are likely to be inaccurate, For example, during free convective conditions, where buoyancy production dominates over mechanical production of turbulence in the boundary layer, surface heat and buoyancy fluxes are enhanced for the given wind conditions, compared to those observed for forced convection, due to transport by buoyant plumes. This highlights the importance of considering the effect of the buoyancy flux on the vertical velocity variance in light winds in the parameterization of the surface fluxes. For forced convective conditions, where cloud circulations cause enhanced mechanical turbulence and reduced buoyancy in the boundary layer, surface fluxes are enhanced, as are the scales of turbulent eddies, drawing surface heat and moisture away from the surface. As with buoyant plumes, this process needs to be considered by surface flux parameterizations early enough in the convective process in order to accurately represent the role of the surface in the development of convection. While the temperature of the warm pool region in COARE is found to be largely independent of local conditions measured by the aircraft, we observe thai the warmest temperatures (>30 degrees C) coincide exclusively with the lightest winds, which highlights the importance of wind-driven mixing in determining the thermal structure of the upper ocean. C1 Univ Washington, Dept Atmospher Sci, Seattle, WA 98195 USA. Woods Hole Oceanog Inst, Dept Phys Oceanog, MS 29, Woods Hole, MA 02543 USA. Univ Calif Irvine, Dept Mech Engn, Irvine, CA 92717 USA. Univ Colorado, Dept Astrophys Planetary & Atmospher Sci, Boulder, CO 80309 USA. CALTECH, Jet Prop Lab, MS 183 301, Pasadena, CA 91109 USA. Univ Calif San Diego, Scripps Inst Oceanog, La Jolla, CA 92093 USA. RP Serra, YL (reprint author), Univ Washington, Dept Atmospher Sci, Seattle, WA 98195 USA. RI Serra, Yolande/I-3457-2015 OI Serra, Yolande/0000-0003-3542-1158 NR 31 TC 12 Z9 13 U1 1 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA J9 J GEOPHYS RES-OCEANS JI J. Geophys. Res.-Oceans PD OCT 15 PY 1997 VL 102 IS C10 BP 23217 EP 23237 DI 10.1029/97JC01191 PG 21 WC Oceanography SC Oceanography GA YL698 UT WOS:000070983400022 ER PT J AU Natarajan, P Bloom, JS Sigurdsson, S Johnson, RA Tanvir, NR Groot, PJ Galama, TJ Van Paradijs, J Kouveliotou, C AF Natarajan, P Bloom, JS Sigurdsson, S Johnson, RA Tanvir, NR Groot, PJ Galama, TJ Van Paradijs, J Kouveliotou, C TI The host to gamma-ray burst 970508: a distant dwarf galaxy? SO NEW ASTRONOMY LA English DT Article DE gamma rays : bursts; galaxies : distances and redshifts AB If the optical transient to gamma-ray burst is indeed associated with the 8 May burst and is connected with the z = 0.835 absorption system reported by Metzger et al. (1997) [Natur, 387, 879], then either the GRB originated from an intrinsically very faint galaxy (L less than or equal to 0.01L*) or it occurred at a large distance from a host galaxy (greater than or equal to 25h(70)(-1) kpc); a large offset of GRBs from galaxies would tend to favour the merging neutron star-neutron star (NS-NS) model (Meszaros & Rees, 1993 [ApJ, 405, 278]; Narayan et al., 1997 [ApJL, 395, 83]). Here we show that the properties of a suspected host galaxy, particularly its intrinsic brightness and comoving distance from the transient, can be constrained indirectly using the Mg II absorption features detected in the spectrum of the optical transient (Metzger et al., 1997 [IAUC, 6676]) by examining the galaxies in the vicinity of the optical transient from ground-based and Hubble Space Telescope (HST) images. This is an independent test of the brightness of GRB host galaxies irrespective of distances implied from logN-logP distributions. The spectral lines most likely arise from absorption by very underluminous galaxies; in which case the optical transient has revealed the presence of a population of intermediate-redshift dwarf galaxies. (C) 1997 Elsevier Science B.V. C1 Univ Cambridge, Inst Astron, Cambridge CB3 0HA, England. Univ Amsterdam, Astron Inst Anton Pannekoek, NL-1098 SJ Amsterdam, Netherlands. Univ Alabama, Dept Phys, Huntsville, AL 35899 USA. NASA, George C Marshall Space Flight Ctr, Univ Space Res Assoc, Code ES 84, Huntsville, AL 35812 USA. RP Natarajan, P (reprint author), Univ Cambridge, Inst Astron, Madingley Rd, Cambridge CB3 0HA, England. EM priya@ast.cam.ac.uk; jsbloom@ast.cam.ac.uk; steinn@ast.cam.ac.uk; raj@ast.cam.ac.uk; nrt@ast.cam.ac.uk; paulgr@astro.uva.nl; titus@astro.uva.nl; jvp@astro.uva.nl; kouveliotou@msfc.nasa.gov RI Galama, Titus/D-1429-2014; Groot, Paul/K-4391-2016; OI Galama, Titus/0000-0002-1036-396X; Groot, Paul/0000-0002-4488-726X; Sigurdsson, Steinn/0000-0002-8187-1144 NR 20 TC 14 Z9 15 U1 0 U2 0 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 1384-1076 J9 NEW ASTRON JI New Astron. PD OCT 15 PY 1997 VL 2 IS 5 BP 471 EP 475 DI 10.1016/S1384-1076(97)00033-X PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YW325 UT WOS:000071922600001 ER PT J AU Turner, MS Weinberg, EJ AF Turner, MS Weinberg, EJ TI Pre-big-bang inflation requires fine-tuning SO PHYSICAL REVIEW D LA English DT Article ID HOMOGENEOUS COSMOLOGICAL MODELS; STRING COSMOLOGY; EXPANSION; CONSTANT; FLATNESS AB The pre-big-bang cosmology inspired by superstring theories has been suggested as an alternative to slow-roll inflation. We analyze, in both the Jordan and Einstein frames, the effect of spatial curvature on this scenario and show that too much curvature - of either sign - reduces the duration of the inflationary era to such an extent that the flatness and horizon problems are not solved. Hence, a fine-tuning of initial conditions is required to obtain enough inflation to solve the cosmological problems. [S0556-2821(97)01020-5]. C1 UNIV CHICAGO,ENRICO FERMI INST,DEPT PHYS,CHICAGO,IL 60637. FERMILAB NATL ACCELERATOR LAB,NASA,FERMILAB ASTROPHYS CTR,BATAVIA,IL 60510. COLUMBIA UNIV,DEPT PHYS,NEW YORK,NY 10027. INST ADV STUDY,SCH NAT SCI,PRINCETON,NJ 08540. RP Turner, MS (reprint author), UNIV CHICAGO,ENRICO FERMI INST,DEPT ASTRON & ASTROPHYS,CHICAGO,IL 60637, USA. NR 18 TC 80 Z9 80 U1 0 U2 0 PU AMERICAN PHYSICAL SOC PI COLLEGE PK PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA SN 0556-2821 J9 PHYS REV D JI Phys. Rev. D PD OCT 15 PY 1997 VL 56 IS 8 BP 4604 EP 4609 DI 10.1103/PhysRevD.56.4604 PG 6 WC Astronomy & Astrophysics; Physics, Particles & Fields SC Astronomy & Astrophysics; Physics GA YC321 UT WOS:A1997YC32100017 ER PT J AU Silveira, V Waga, I AF Silveira, V Waga, I TI Cosmological properties of a class of Lambda decaying cosmologies SO PHYSICAL REVIEW D LA English DT Article ID GRAVITATIONAL LENS SURVEY; IA SUPERNOVAE; HUBBLE CONSTANT; UNIVERSE; QUASARS; DIAGRAM; MATTER; ENERGY; MODELS AB We investigate some properties of flat cosmological models with a Lambda term that decreases with time as Lambda proportional to a(-m) (a is the scale factor and m is a parameter 0 less than or equal to m < 3). The models are equivalent to standard cosmology with matter and radiation plus an exotic fluid with the equation of state p(x) = (m/3 - 1)rho(x). We study the effect of the decaying Lambda term on the cosmic microwave background anisotropy and by using a seminumeric method we compute the angular power spectrum (up to l = 20) for different values of m and Omega(m0). We also investigate the constraints imposed on the models by the magnitude-redshift test in which high-redshift type Ia supernovae (SNe Ia) are used as standard candles. We obtain the 95.4%, 90%, and 68% confidence levels on the parameters m and Omega(m0) and compare them with those arising from lensing statistics. Our analysis reveals that the SNe Ia constraints are stronger for low values of m and Omega(m0), while those from lensing statistics are more important for m greater than or similar to 1. Models with Omega(m0)greater than or similar to 0.2 and m greater than or similar to 1.6 are in good agreement with the data.[S0556-2821(97)03620-5]. C1 FERMILAB NATL ACCELERATOR LAB,NASA,FERMILAB ASTROPHYS CTR,BATAVIA,IL 60510. UNIV FED RIO DE JANEIRO,INST FIS,BR-21945970 RIO JANEIRO,BRAZIL. RP Silveira, V (reprint author), UNIV BRASILIA,INT CTR CONDENSED MATTER PHYS,CP 04513,BR-70919970 BRASILIA,DF,BRAZIL. RI Waga, Ioav/B-6288-2014 NR 45 TC 51 Z9 52 U1 0 U2 1 PU AMERICAN PHYSICAL SOC PI COLLEGE PK PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA SN 0556-2821 J9 PHYS REV D JI Phys. Rev. D PD OCT 15 PY 1997 VL 56 IS 8 BP 4625 EP 4632 DI 10.1103/PhysRevD.56.4625 PG 8 WC Astronomy & Astrophysics; Physics, Particles & Fields SC Astronomy & Astrophysics; Physics GA YC321 UT WOS:A1997YC32100020 ER PT J AU Turner, MS White, M AF Turner, MS White, M TI CDM models with a smooth component SO PHYSICAL REVIEW D LA English DT Article ID COLD DARK-MATTER; COSMOLOGICAL CONSTANT; MASS FLUCTUATIONS; BARYON CONTENT; UNIVERSE; INFLATION; CLUSTERS; DENSITY; GALAXIES; FIELDS AB The inflationary prediction of a flat Universe is at odds with current determinations of the matter density (Omega(M) similar or equal to 0.2-0.4). This dilemma can be resolved if a smooth component contributes the remaining energy density (Omega(X) = 1 - Omega(M)). We parametrize the smooth component by its equation of state, p(X) = w rho(X), and show that XCDM with w similar or equal to -0.6, Omega(M) similar or equal to 0.3, and h similar or equal to 0.7 is the best fit to all present cosmological data. Together, the position of the peak in the CMB angular power spectrum and the type Ia supernova magnitude-redshift diagram provide a crucial test of XCDM. [S0556-2821(97)50220-7]. C1 FERMILAB NATL ACCELERATOR LAB,NASA,CTR ASTROPHYS,BATAVIA,IL 60510. UNIV CHICAGO,DEPT ASTRON & ASTROPHYS,CHICAGO,IL 60637. RP Turner, MS (reprint author), UNIV CHICAGO,DEPT PHYS,CHICAGO,IL 60637, USA. RI White, Martin/I-3880-2015 OI White, Martin/0000-0001-9912-5070 NR 68 TC 469 Z9 469 U1 0 U2 3 PU AMERICAN PHYSICAL SOC PI COLLEGE PK PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA SN 0556-2821 J9 PHYS REV D JI Phys. Rev. D PD OCT 15 PY 1997 VL 56 IS 8 BP R4439 EP R4443 PG 5 WC Astronomy & Astrophysics; Physics, Particles & Fields SC Astronomy & Astrophysics; Physics GA YC321 UT WOS:A1997YC32100001 ER PT J AU Kandebo, SW AF Kandebo, SW TI Redefined propulsion tests target HSCT scale-up issues SO AVIATION WEEK & SPACE TECHNOLOGY LA English DT Article RP Kandebo, SW (reprint author), NASA,LEWIS RES CTR,CLEVELAND,OH 44135, USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU MCGRAW HILL INC PI NEW YORK PA 1221 AVENUE OF THE AMERICAS, NEW YORK, NY 10020 SN 0005-2175 J9 AVIAT WEEK SPACE TEC JI Aviat. Week Space Technol. PD OCT 13 PY 1997 VL 147 IS 15 BP 70 EP 73 PG 4 WC Engineering, Aerospace SC Engineering GA YA586 UT WOS:A1997YA58600034 ER PT J AU Kandebo, SW AF Kandebo, SW TI HSCT engine materials moving forward SO AVIATION WEEK & SPACE TECHNOLOGY LA English DT Article RP Kandebo, SW (reprint author), NASA,LEWIS RES CTR,CLEVELAND,OH 44135, USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU MCGRAW HILL INC PI NEW YORK PA 1221 AVENUE OF THE AMERICAS, NEW YORK, NY 10020 SN 0005-2175 J9 AVIAT WEEK SPACE TEC JI Aviat. Week Space Technol. PD OCT 13 PY 1997 VL 147 IS 15 BP 72 EP 73 PG 2 WC Engineering, Aerospace SC Engineering GA YA586 UT WOS:A1997YA58600035 ER PT J AU Turner, TJ George, IM Nandra, K Mushotzky, RF AF Turner, TJ George, IM Nandra, K Mushotzky, RF TI ASCA observations of type 2 Seyfert Galaxies .2. The importance of X-ray scattering and reflection SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies, active; galaxies, nuclei; line, formation; X-rays, galaxies ID ACTIVE GALACTIC NUCLEI; IONIZING-RADIATION; COLD MATTER; NGC-1068; LINE; SPECTROPOLARIMETRY; EMISSION; TORUS AB We discuss the importance of X-ray scattering and Compton reflection in type 2 Seyfert Galaxies, based upon the analysis of ASCA observations of 25 such sources. Consideration of the iron K alpha complex, [O III] line, and X-ray variability suggest that NGC 1068, NGC 4945, NGC 2992, Mrk 3, Mrk 463E, and Mrk 273 are dominated by reprocessed X-rays. We examine the properties of these sources in more detail. We find that the iron K alpha complex contains significant contributions from neutral and high-ionization species of iron. Compton reflection, hot gas and starburst emission all appear to make significant contributions to the observed X-ray spectra. Mrk 3 is the only source in this subsample that does not have a significant starburst contamination. The ASCA spectrum below 3 keV is dominated by hot scattering gas with U-X similar to 5, N-H similar to 4 x 10(23) cm(-2). This material is more highly ionized than the zone of material comprising the warm absorber seen in Seyfert 1 galaxies, but may contain a contribution from shock-heated gas associated with the jet. Estimates of the X-ray scattering fraction cover 0.02%-5%. The spectrum above 3 keV appears to be dominated by a Compton reflection component, although there is evidence that the primary continuum component becomes visible close to similar to 10 keV. RP Turner, TJ (reprint author), NASA,GODDARD SPACE FLIGHT CTR,HIGH ENERGY ASTROPHYS LAB,CODE 660,GREENBELT,MD 20771, USA. NR 49 TC 131 Z9 131 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 OCT 10 PY 1997 VL 488 IS 1 BP 164 EP 173 DI 10.1086/304701 PN 1 PG 10 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YB991 UT WOS:A1997YB99100017 ER PT J AU Gorkavyi, NN Ozernoy, LM Mather, JC Taidakova, T AF Gorkavyi, NN Ozernoy, LM Mather, JC Taidakova, T TI Quasi-stationary states of dust flows under Poynting-Robertson drag: New analytical and numerical solutions SO ASTROPHYSICAL JOURNAL LA English DT Article DE dust, extinction; interplanetary medium; methods, numerical; radiative transfer ID SOLAR-SYSTEM; INTERPLANETARY DUST; PARTICLES; EVOLUTION; EARTH; CLOUD; RING AB The effect of solar or stellar radiation on dust particles' trajectories (the Poynting-Robertson drag) has been studied by a number of authors and applied to interplanetary dust dynamics in numerical computations. Meanwhile, some important features of dust flows can be studied analytically by implementing our novel hydrodynamical approach to use the continuity equation written in the particle's orbital elements as coordinates (Gor'kavyi, Ozernoy, & Mather). By employing this approach and integrating the continuity equation, we are able to find two integrals of motion when the Poynting-Robertson drag dominates the dissipative forces in the dust flow. These integrals of motion enable us to explore basic characteristics of dust flows from any sources in the solar system (such as asteroids, comets, Kuiper belt, etc.) or in another planetary system. In particular, we have reproduced the classical solution n(r)proportional to r(-1) that approximately represents the overall distribution of dust in the solar system. We have also investigated various factors that could be responsible for the deviations of the power-law index in n(r) proportional to r(delta) from delta = -1, including the influences of the orbital characteristics of dust sources, the evaporation of dust particles, as well as mixtures of dust particles of both asteroidal and cometary origin. We have calculated the masses and number densities of asteroidal and cometary components of the zodiacal cloud at different distances from the Sun. C1 GEORGE MASON UNIV, COMPUTAT SCI INST, FAIRFAX, VA 22030 USA. GEORGE MASON UNIV, DEPT PHYS & ASTRON, FAIRFAX, VA 22030 USA. NASA, GODDARD SPACE FLIGHT CTR, ASTRON & SOLAR PHYS LAB, GREENBELT, MD 20771 USA. RP CRIMEAN ASTROPHYS OBSERV, SIMEIZ DEPT, UA-334242 CRIMEA, UKRAINE. NR 20 TC 23 Z9 23 U1 0 U2 1 PU IOP PUBLISHING LTD PI BRISTOL PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND SN 0004-637X EI 1538-4357 J9 ASTROPHYS J JI Astrophys. J. PD OCT 10 PY 1997 VL 488 IS 1 BP 268 EP 276 DI 10.1086/304702 PN 1 PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YB991 UT WOS:A1997YB99100027 ER PT J AU Craig, WW Hailey, CJ Pisarski, RL AF Craig, WW Hailey, CJ Pisarski, RL TI ROSAT observations of the supernova remnant CTB 1 SO ASTROPHYSICAL JOURNAL LA English DT Article DE ISM, individual (CTB 1, G117.7+0.6); supernova remnants; X-rays, ISM ID X-RAY; EMISSION; 3C-400.2 AB We present ROSAT PSPC observations of the supernova remnant CTB 1 (G116.9 +0.2). The remnant is detected for the first time in the X-ray region. The X-ray morphology places the remnant into the class of center-filled remnants with a centrally peaked X-ray emission profile and accompanying optical and radio shells. The emission is consistent with a thermal plasma with T=3 x 10(6) K and absorption N-H = 7 x 10(21) cm(-2). A ''breakout'' along the northeast rim of the remnant is coincident with the position of an X-ray pulsar. A much larger feature appears to be a partial shell which may be associated with a previous supernova remnant that swept the area around CTB 1 clean. The appearance of the remnant is most easily explained by evaporating clouds. Projection effects caused by an asymmetric remnant are discussed as another, less plausible, explanation. C1 NASA,GODDARD SPACE FLIGHT CTR,ASTROPHYS DATA FAC,GREENBELT,MD 20771. RP Craig, WW (reprint author), COLUMBIA UNIV,COLUMBIA ASTROPHYS LAB,538 W 120TH ST,NEW YORK,NY 10027, USA. NR 25 TC 13 Z9 13 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 OCT 10 PY 1997 VL 488 IS 1 BP 307 EP 316 DI 10.1086/304666 PN 1 PG 10 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YB991 UT WOS:A1997YB99100030 ER PT J AU Rubin, BC Finger, MH Scott, DM Wilson, RB AF Rubin, BC Finger, MH Scott, DM Wilson, RB TI Observation of a long-term spin-up trend in 4U 1538-52 SO ASTROPHYSICAL JOURNAL LA English DT Article DE pulsars, individual (4U 1538-52); stars, neutron; stars, rotation; X-rays, stars ID OPTICAL SPECTROSCOPY; GINGA OBSERVATIONS; CENTAURUS X-3; PULSE PERIOD; BINARY; 4U-1538-52; DISCOVERY; SPECTRA AB The high-mass X-ray pulsar 4U 1538-52 has been continually monitored by the BATSE (Burst and Transient Source Experiment) on Compton Gamma-Ray Observatory. These observations permit the construction of long-term pulse frequency and intensity histories. The frequency history reveals that a reversal of the long-term trend in the accretion torque, from spinning down to spinning up, has occurred, probably in 1988. This is the first time a long-term change is known to have occurred for this source. The magnitude of the average \(nu) over dot/nu\ similar to 10(-11) s(-1) over an interval of similar to 5 yr is similar during spin-down and spin-up. Shorter term pulse frequency variations of either sign are also observed. The power density spectrum of fluctuations in angular acceleration is consistent with white noise on timescales from 16 to 1600 days. It can be well fit with a power law with a power-law index of 0.10 +/- 0.21 and white noise strength of (7.6 +/- 1.6) x 10(-21)(Hz s(-1))(2) Hz(-1). These observations are also used to set 95% confidence level lower and upper limits on the rate of orbital period change, -3.9 < P over dot(orb)/ P-orb < 2.1, in units of 10(-6) yr(-1). C1 UNIV ALABAMA,DEPT PHYS,HUNTSVILLE,AL 35899. NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,HUNTSVILLE,AL 35812. RP Rubin, BC (reprint author), RIKEN,INST PHYS & CHEM RES,COSM RADIAT LAB,WAKO,SAITAMA 35101,JAPAN. NR 28 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 OCT 10 PY 1997 VL 488 IS 1 BP 413 EP 418 DI 10.1086/304679 PN 1 PG 6 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YB991 UT WOS:A1997YB99100040 ER PT J AU Brosius, JW Davila, JM Thomas, RJ White, SM AF Brosius, JW Davila, JM Thomas, RJ White, SM TI Coronal magnetography of a solar active region using coordinated SERTS and VLA observations SO ASTROPHYSICAL JOURNAL LA English DT Article DE Sun, activity; Sun, corona; Sun, magnetic fields; Sun, radio radiation; Sun, UV radiation ID STRUCTURES OBSERVING CAMPAIGN; HIGH-SPATIAL-RESOLUTION; X-RAY OBSERVATIONS; QUIET-SUN; PLASMA PROPERTIES; ULTRAVIOLET; MICROWAVE; ARRAY; SPECTROGRAPH; DIAGNOSTICS AB We observed NOAA region 7563 simultaneously with Goddard Space Flight Center's Solar EUV Rocket Telescope and Spectrograph (SERTS) and with the Very Large Array (VLA) on 1993 August 17. SERTS obtained spectra in the 280-420 Angstrom wavelength range, and images in the lines of Mg IX lambda 368.1, Fe XV lambda 284.1, and Fe XVI lambda 335.4. The VLA obtained microwave images at 20 and 6 cm wavelengths. The microwave emission depends upon the coronal temperature, density, column emission measure, and magnetic field, therefore, the coronal magnetic field can be derived when all of these other quantities are measured. Here we demonstrate this approach by using the SERTS data to derive all the relevant plasma parameters and then fitting the radio observations to a magnetic field model in order to determine the magnetic field structure. We used the method of Monsignori-Fossi & Landini and the coronal elemental abundances of Feldman et al. to derive the differential emission measure (DEM) curve for region 7563 from numerous EUV emission lines in spatially averaged SERTS spectra. A similar curve was estimated for each point (i.e., each pixel or each spatial location) in the two-dimensional region by scaling the average DEM curve with corresponding pixel intensities in the Mg IX, Fe XV, and Fe XVI images. We integrated each such DEM over narrow temperature ranges to obtain the column emission measure (GEM) as a function of temperature, CEM(T). We also obtained electron density measurements from EUV line intensity ratios in the spatially averaged spectrum for several ionization stages of iron. These were used to derive a functional relation between density and temperature, n(e)(T). We derived the temperature dependence of the coronal magnetic field [B(T)] at each point in the two-dimensional region by incorporating CEM(T) and n(e)(T) into expressions for the thermal bremsstrahlung and the gyroresonance opacities, and varying B(T) so as to minimize the difference between the calculated and the observed microwave intensities. The resulting calculated 20 and 6 cm microwave intensity images reproduce the observed images very well. We found that thermal bremsstrahlung alone is not sufficient to produce the observed microwave intensities: gyroemission is required. Further, contrary to several earlier studies, we found no evidence for cool, absorbing plasma in the solar corona above the active region. The coronal magnetic fields derived with our method typically exceed the coronal fields extrapolated with a simple potential model, suggesting the presence of coronal electric currents. However, in the diminutive sunspot which dominates the 6 cm emission this difference is relatively small, suggesting that the sunspot magnetic field itself is nearly potential. Although we cannot firmly establish the uniqueness of our solution in this particular case, the method is quite powerful and should be repeated with other similar data sets. Variations in the coronal elemental abundances could affect the determination of the microwave emission mechanism(s), introduce evidence for the presence of cool coronal plasma, and alter the strengths of the derived coronal magnetic fields. C1 UNIV MARYLAND, ASTRON PROGRAM, COLLEGE PK, MD 20742 USA. HUGHES STX CORP, LANHAM, MD 20706 USA. RP Brosius, JW (reprint author), NASA, GODDARD SPACE FLIGHT CTR, ASTRON & SOLAR PHYS LAB, CODE 682, GREENBELT, MD 20771 USA. NR 46 TC 30 Z9 30 U1 0 U2 3 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637 SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD OCT 10 PY 1997 VL 488 IS 1 BP 488 EP 498 DI 10.1086/304673 PN 1 PG 11 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YB991 UT WOS:A1997YB99100048 ER PT J AU Bloom, SD Hartman, RC Terasranta, H Tornikoski, M Valtaoja, E AF Bloom, SD Hartman, RC Terasranta, H Tornikoski, M Valtaoja, E TI Possible new identifications for EGRET sources SO ASTROPHYSICAL JOURNAL LA English DT Article DE BL lacertae objects, individual; galaxies, active; gamma rays, observations; quasars, individual ID EXTRAGALACTIC RADIO-SOURCES AB The majority of the EGRET objects remain either unidentified or questionably identified at other wavelengths. We have conducted a multiwavelength study of several radio sources within or near the error boxes of EGRET unidentified sources at mid-to high Galactic latitude, under the hypothesis that the radio sources are blazars and are thus the best identification candidates for the EGRET objects. We show that one of these radio sources, PMN 0850-121, has a flux of 1.5 Jy at 22 GHz and a nearly flat spectrum up to 230 GHz and that it is thus very likely to be the correct identification for the EGRET source 2EG 50852-1237. C1 HELSINKI UNIV TECHNOL,METSAHOVI RADIO RES STN,SF-02150 ESPOO,FINLAND. RP Bloom, SD (reprint author), NASA,GODDARD SPACE FLIGHT CTR,HIGH ENERGY ASTROPHYS LAB,GREENBELT,MD 20771, USA. NR 11 TC 16 Z9 16 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 OCT 10 PY 1997 VL 488 IS 1 BP L23 EP L26 DI 10.1086/310911 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YB998 UT WOS:A1997YB99800006 ER PT J AU Wang, YM Sheeley, NR Phillips, JL Goldstein, BE AF Wang, YM Sheeley, NR Phillips, JL Goldstein, BE TI Solar wind stream interactions and the wind speed-expansion factor relationship SO ASTROPHYSICAL JOURNAL LA English DT Article DE interplanetary medium; solar wind; Sun, corona; Sun, magnetic fields ID FLUX-TUBE DIVERGENCE; ECLIPTIC-PLANE; CORONAL HOLE; SYSTEM; FIELD; EVOLUTION; FRONTS; FLOWS AB Previous studies have shown that the solar wind speed observed near Earth is inversely correlated with the divergence rate of magnetic flux tubes near the Sun. We test the global validity of this relationship by employing Ulysses wind speed measurements during 1990-1997 as well as inecliptic data for 1976-1997. When the correspondence between wind speeds and expansion factors is adjusted to yield optimal agreement with the high-latitude Ulysses measurements, the model matches the overall patterns of fast and slow wind near the ecliptic but predicts too much very fast wind there. We show how this discrepancy can be resolved by taking account of wind stream interactions, where we apply a crude algorithm based on the propagation times of neighboring wind parcels; the interactions reduce the amount of very fast wind at latitudes where slow wind is present. We also test and reject an alternative model in which the wind speed is assumed to be a function only of angular distance from the heliospheric neutral sheet. C1 NASA,LYNDON B JOHNSON SPACE CTR,HOUSTON,TX 77058. CALTECH,JET PROP LAB,PASADENA,CA 91109. LOS ALAMOS NATL LAB,LOS ALAMOS,NM 87545. RP Wang, YM (reprint author), USN,RES LAB,EO HULBURT CTR SPACE RES,CODE 7672,WASHINGTON,DC 20375, USA. NR 25 TC 54 Z9 54 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 OCT 10 PY 1997 VL 488 IS 1 BP L51 EP & DI 10.1086/310918 PN 2 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YB998 UT WOS:A1997YB99800013 ER PT J AU Saddoughi, SG AF Saddoughi, SG TI Local isotropy in complex turbulent boundary layers at high Reynolds number SO JOURNAL OF FLUID MECHANICS LA English DT Article ID HOMOGENEOUS SHEAR FLOWS; WING BODY JUNCTION; DYNAMICAL MODEL; DEVELOPED TURBULENCE; SPECTRA; UNIVERSALITY; HYPOTHESIS; NOSE; WALL AB To continue our (Saddoughi & Veeravalli 1994) tests of the local-isotropy predictions of Kolmogorov's (1941) universal equilibrium theory in shear flows, we have taken hot-wire measurements of the velocity fluctuations in complex turbulent boundary layers at several Reynolds numbers. We have studied the plane-of-symmetry flow upstream of a 4 ft diameter, 6 ft long circular cylinder placed with its axis vertical in the zero-pressure-gradient turbulent boundary layer of the test-section ceiling in the 80 ft x 120 ft Full-Scale Aerodynamics Facility at NASA Ames Research Center. In the present experiments, the pressure rises strongly as the obstacle is approached and in and near the plane of symmetry of the flow the boundary layer is influenced by the effects of lateral divergence. In addition to the basic mean shear, partial derivative U/partial derivative y, the extra mean strain rates are partial derivative U/partial derivative x, partial derivative V/partial derivative y and partial derivative W/partial derivative z. During our experiments a full-scale F-18 fighter aircraft, set at an angle of attack of 50 degrees, was present in the central region of the working section. To identify the effects of the aircraft on the boundary-layer characteristics upstream of the cylinder, we have also taken measurements when the wind tunnel was empty. It appears that the presence of the aircraft in the wind tunnel usefully increases the magnitude of the mean strain rates, and also significantly increases the large-scale intermittency near the edge of the boundary layer upstream of the cylinder. The maximum values for the parameters that have been found to represent the effects of mean shear on turbulence are S*(= Sq(2)/epsilon) approximate to 22 and S-c*(= S(nu/epsilon)(1/2)) approximate to 0.05, where for the present experiments S = 2(s(ij)s(ij)/2)(1/2). All of the present results are compared with our plane turbulent boundary-layer experiments (Saddoughi & Veeravalli 1994). In the present distorted boundary-layer cases, the maximum Reynolds numbers based on momentum thickness, R-theta, and on the Taylor (1935) microscale, R-lambda, are increased to approximately 510 000 and 2000 respectively. These are the largest attained in laboratory boundary-layer flows: R-theta is of the same order obtained in flight on a typical commercial aircraft or the space shuttle. In general, the current investigations confirm the conclusions of our earlier study. In summary, it is shown again that one decade of locally isotropic inertial subrange requires a ratio of the Kolmogorov to mean-shear timescales, S-c*, of not more than approximately 0.01. In the present non-equilibrium shear layer, this was achieved at a microscale Reynolds number of approximately 2000. C1 STANFORD UNIV, CTR TURBULENCE RES, STANFORD, CA 94305 USA. NASA, AMES RES CTR, MOFFETT FIELD, CA 94035 USA. NR 74 TC 23 Z9 23 U1 1 U2 8 PU CAMBRIDGE UNIV PRESS PI NEW YORK PA 32 AVENUE OF THE AMERICAS, NEW YORK, NY 10013-2473 USA SN 0022-1120 J9 J FLUID MECH JI J. Fluid Mech. PD OCT 10 PY 1997 VL 348 BP 201 EP 245 DI 10.1017/S0022112097006666 PG 45 WC Mechanics; Physics, Fluids & Plasmas SC Mechanics; Physics GA YC692 UT WOS:A1997YC69200008 ER PT J AU Rignot, E Gogineni, SP Krabill, WB Ekholm, S AF Rignot, E Gogineni, SP Krabill, WB Ekholm, S TI Mass balance of North Greenland - Response SO SCIENCE LA English DT Letter C1 UNIV KANSAS,LAWRENCE,KS 66045. NASA,GODDARD SPACE FLIGHT CTR,WALLOPS FLIGHT FACIL,WALLOPS ISL,VA 23337. KORT & MATRIKELSTYRELSEN,DIV GEODET,DK-2400 COPENHAGEN NV,DENMARK. RP Rignot, E (reprint author), CALTECH,JET PROP LAB,4800 OAK GROVE DR,PASADENA,CA 91109, USA. RI Rignot, Eric/A-4560-2014 OI Rignot, Eric/0000-0002-3366-0481 NR 1 TC 3 Z9 3 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 OCT 10 PY 1997 VL 278 IS 5336 BP 209 EP 209 PG 1 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA YA564 UT WOS:A1997YA56400006 ER PT J AU McCord, TB Carlson, RW Smythe, WD Hansen, GB Clark, RN Hibbitts, CA Fanale, FP Granahan, JC Segura, M Matson, DL Johnson, TV Martin, PD AF McCord, TB Carlson, RW Smythe, WD Hansen, GB Clark, RN Hibbitts, CA Fanale, FP Granahan, JC Segura, M Matson, DL Johnson, TV Martin, PD TI Organics and other molecules in the surfaces of Callisto and Ganymede SO SCIENCE LA English DT Article ID GALILEAN SATELLITES; REFLECTANCE SPECTRUM; INTERNAL STRUCTURE; OPTICAL-CONSTANTS; CARBON-DIOXIDE; ICE ANALOGS; MU-M; FROST AB Five absorption features are reported at wavelengths of 3.4, 3.88, 4.05, 4.25, and 4.57 micrometers in the surface materials of the Galilean satellites Callisto and Ganymede from analysis of reflectance spectra returned by the Galileo mission near-infrared mapping spectrometer. Candidate materials include CO2, organic materials (such as tholins containing C=N and C-H), SO2, and compounds containing an SH-functional group; CO2, SO2, and perhaps cyanogen [(CN)(2)] may be present within the surface material itself as collections of a few molecules each. The spectra indicate that the primary surface constituents are water ice and hydrated minerals. C1 CALTECH,JET PROP LAB,PASADENA,CA 91109. US GEOL SURVEY,DENVER,CO 80225. SCI & TECHNOL INT INC,HONOLULU,HI. RP McCord, TB (reprint author), UNIV HAWAII,HAWAII INST GEOPHYS & PLANETOL,HONOLULU,HI 96822, USA. RI Hibbitts, Charles/B-7787-2016 OI Hibbitts, Charles/0000-0001-9089-4391 NR 54 TC 113 Z9 115 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 OCT 10 PY 1997 VL 278 IS 5336 BP 271 EP 275 DI 10.1126/science.278.5336.271 PG 5 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA YA564 UT WOS:A1997YA56400040 PM 9323203 ER PT J AU Paczynski, B Kouveliotou, C AF Paczynski, B Kouveliotou, C TI Gamma-ray astronomy - Bursts make new waves SO NATURE LA English DT Editorial Material C1 NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,UNIV SPACE RES ASSOC,HUNTSVILLE,AL 35812. RP Paczynski, B (reprint author), PRINCETON UNIV,DEPT ASTROPHYS SCI,PRINCETON,NJ 08544, USA. NR 13 TC 4 Z9 4 U1 0 U2 0 PU MACMILLAN MAGAZINES LTD PI LONDON PA PORTERS SOUTH, 4 CRINAN ST, LONDON, ENGLAND N1 9XW SN 0028-0836 J9 NATURE JI Nature PD OCT 9 PY 1997 VL 389 IS 6651 BP 548 EP 549 DI 10.1038/39200 PG 2 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA YA008 UT WOS:A1997YA00800032 ER PT J AU Baugher, AH Espe, MP Goetz, JM Schaefer, J Pater, RH AF Baugher, AH Espe, MP Goetz, JM Schaefer, J Pater, RH TI Cross-linked structures of nadic-end-capped polyimides at 371 degrees C SO MACROMOLECULES LA English DT Article ID DYNAMIC NUCLEAR-POLARIZATION; PMR-15 POLYIMIDE; MAGNETIC-RESONANCE; FREE-RADICALS; C-13 NMR; POLYMERIZATION; CROSSLINKING; BLENDS AB The thermally induced cross-linking of nadic-end-capped polyimides has been studied by a variety of spectroscopic techniques. Two nadic-end-capped polyimides were subjected to 371 degrees C heat treatment for 100 h in order to study cross-linking resulting from elevated temperature. The glass transition temperature of the treated samples increased to greater than 400 degrees C, indicating that both polyimides underwent extensive chemical changes during heat treatment. C-13 spin counts were measured before and after heat treatment by C-13 cross-polarization magic angle spinning nuclear magnetic resonance. Electron spin resonance measurements showed an increase in the concentration of stable free radicals in the treated samples. Dynamic nuclear polarization and electron spin resonance results show that two species of free radicals are present in the treated samples; the first is located on the polymer backbone and the second on the cross-linking network that arises from the reaction of the nadic end-capping groups. On the basis of these results, new cross-linking structures of nadic-end-capped polyimides before and after heat treatment at 371 degrees C are proposed. C1 WASHINGTON UNIV,DEPT CHEM,ST LOUIS,MO 63130. NASA LANGLEY,COMPOSITE & POLYMER MAT BRANCH,HAMPTON,VA 23681. RP Baugher, AH (reprint author), COLL WILLIAM & MARY,DEPT PHYS,WILLIAMSBURG,VA 23187, USA. NR 18 TC 12 Z9 12 U1 1 U2 6 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 SN 0024-9297 J9 MACROMOLECULES JI Macromolecules PD OCT 6 PY 1997 VL 30 IS 20 BP 6295 EP 6301 DI 10.1021/ma961480a PG 7 WC Polymer Science SC Polymer Science GA YA289 UT WOS:A1997YA28900043 ER PT J AU Kinney, WH Kolb, EW Turner, MS AF Kinney, WH Kolb, EW Turner, MS TI Ribbons on the cosmic background radiation sky: A powerful test of a baryon symmetric universe SO PHYSICAL REVIEW LETTERS LA English DT Article ID ANTIMATTER AB If the Universe consists of domains of matter and antimatter, annihilations at domain interfaces leave a distinctive imprint on the cosmic background radiation (CBR) sky. The signature is anisotropies in the form of long, thin ribbons of width Bw theta(W) similar to 0.1 degrees, separated by angle theta(L) similar or equal to 1 degrees(L/100h(-1) Mpc) (L is the characteristic domain size) and with distortion parameter y approximate to 10(-6). Such a pattern could potentially be detected by the high-resolution CBR anisotropy experiments planned for the next decade, and such experiments may finally settle the question of whether or not our Hubble volume is baryon symmetric. C1 UNIV CHICAGO,ENRICO FERMI INST,DEPT ASTRON & ASTROPHYS,CHICAGO,IL 60637. UNIV CHICAGO,DEPT PHYS,CHICAGO,IL 60637. RP Kinney, WH (reprint author), NASA,FERMILAB ASTROPHYS CTR,FERMI NATL ACCELERATOR LAB,BATAVIA,IL 60510, USA. NR 13 TC 17 Z9 17 U1 0 U2 1 PU AMERICAN PHYSICAL SOC PI COLLEGE PK PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA SN 0031-9007 J9 PHYS REV LETT JI Phys. Rev. Lett. PD OCT 6 PY 1997 VL 79 IS 14 BP 2620 EP 2623 DI 10.1103/PhysRevLett.79.2620 PG 4 WC Physics, Multidisciplinary SC Physics GA XZ544 UT WOS:A1997XZ54400006 ER PT J AU Allen, B Caldwell, RR Dodelson, S Knox, L Shellard, EPS Stebbins, A AF Allen, B Caldwell, RR Dodelson, S Knox, L Shellard, EPS Stebbins, A TI Cosmic microwave background anisotropy induced by cosmic strings on angular scales 15' SO PHYSICAL REVIEW LETTERS LA English DT Article ID DOPPLER PEAKS; ACTIVE PERTURBATIONS; COBE AB We have computed an estimate of the angular power spectrum of the cosmic microwave background induced by cosmic strings on angular scales greater than or similar to 15', using a numerical simulation of a cosmic string network and have decomposed this pattern into scalar, vector, and tensor parts. The anisotropies from vector modes dominate except on very small angular scales, and we find no evidence for strong acoustic oscillations in the scalar anisotropy. The anisotropies generated after recombination are even more important than in adiabatic models. The total anisotropy on small scales is inconsistent with current measurements. The calculation has a number of uncertainties, the largest of which is due to finite temporal range. C1 UNIV PENN,DEPT PHYS & ASTRON,PHILADELPHIA,PA 19106. NASA,FERMILAB ASTROPHYS CTR,BATAVIA,IL 60510. CANADIAN INST THEORET ASTROPHYS,TORONTO,ON M5S 3H8,CANADA. UNIV CAMBRIDGE,DEPT APPL MATH & THEORET PHYS,CAMBRIDGE CB3 9EW,ENGLAND. RP Allen, B (reprint author), UNIV WISCONSIN,DEPT PHYS,POB 413,MILWAUKEE,WI 53201, USA. RI Allen, Bruce/K-2327-2012; OI Allen, Bruce/0000-0003-4285-6256; Caldwell, Robert/0000-0001-7490-7463 NR 24 TC 109 Z9 109 U1 0 U2 0 PU AMERICAN PHYSICAL SOC PI COLLEGE PK PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA SN 0031-9007 J9 PHYS REV LETT JI Phys. Rev. Lett. PD OCT 6 PY 1997 VL 79 IS 14 BP 2624 EP 2627 DI 10.1103/PhysRevLett.79.2624 PG 4 WC Physics, Multidisciplinary SC Physics GA XZ544 UT WOS:A1997XZ54400007 ER PT J AU Dine, M Riotto, A AF Dine, M Riotto, A TI An inflaton candidate in gauge mediated supersymmetry breaking SO PHYSICAL REVIEW LETTERS LA English DT Article ID COSMOLOGICAL MODULI PROBLEM; PHYSICS; TECHNICOLOR; UNIVERSE; SCALE AB Inflation requires the presence of fields (inflatons) with very flat potentials. Models of low-energy supersymmetry (SUSY) breaking yield new candidates for the inflaton field. We present a simple model for slow-rollover inflation where the vacuum energy driving inflation is related to the scale of supersymmetry breaking among ordinary particles. This opens the possibility of gaining possible knowledge about SUSY dynamics from measurements of the microwave background. Gravitinos do not pose a cosmological problem, while the moduli problem is ameliorated. C1 NASA,FERMILAB ASTROPHYS CTR,FERMI NATL ACCELERATOR LAB,BATAVIA,IL 60510. RP Dine, M (reprint author), UNIV CALIF SANTA CRUZ,SANTA CRUZ INST PARTICLE PHYS,SANTA CRUZ,CA 95064, USA. NR 32 TC 25 Z9 25 U1 0 U2 0 PU AMERICAN PHYSICAL SOC PI COLLEGE PK PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA SN 0031-9007 J9 PHYS REV LETT JI Phys. Rev. Lett. PD OCT 6 PY 1997 VL 79 IS 14 BP 2632 EP 2635 DI 10.1103/PhysRevLett.79.2632 PG 4 WC Physics, Multidisciplinary SC Physics GA XZ544 UT WOS:A1997XZ54400009 ER PT J AU Nguyen, H AF Nguyen, H TI Electrical properties and adhesion of metal/polymer layered structures for cross-linked polymer electro-optic modulators SO MICROWAVE AND OPTICAL TECHNOLOGY LETTERS LA English DT Article DE electro-optic modulator; cross-linked polymer; optical waveguide; multilayers ID POLYIMIDE AB The electrical properties and adhesive strength of titaninum, copper, and gold have been studied in cross-linked polymer materials using both sputter-deposited surface pbn and shallow ion-implant sources for electro-optic modulators. In particular multilayer metals with Ti/Au interfaces reported by some authors [1-3] are compared in this letter to Ti/Au/Ti and Ti/Au/Cr interfaces containing Ti and Cr layers on top of an Au layer. Also reported are the adhesion strength using a qualitative ''Scotch-tape'' technique for different multilayer metals. It is shown that the Ti/Au/Ti structure has a better adhesive strength than others being considered In this structure, Ti can wet the modified surface and form an interface between Ti and the polymer with good adhesion. We fabricated multilayer test structures, including a functional traveling-wave (TW) electrode on GaAs substrate, to demonstrate the process feasibility and the electrical performance of metals/polymer interconnections. Microwave losses of the TW electrode for different metal layers are also reported. (C) 1997 John Wiley & Sons, Inc. RP Nguyen, H (reprint author), NASA,LEWIS RES CTR,SPACE COMMUN DIV,MAIL STOP 54-8,CLEVELAND,OH 44135, USA. NR 10 TC 2 Z9 2 U1 1 U2 5 PU JOHN WILEY & SONS INC PI NEW YORK PA 605 THIRD AVE, NEW YORK, NY 10158-0012 SN 0895-2477 J9 MICROW OPT TECHN LET JI Microw. Opt. Technol. Lett. PD OCT 5 PY 1997 VL 16 IS 2 BP 66 EP 72 PG 7 WC Engineering, Electrical & Electronic; Optics SC Engineering; Optics GA XW931 UT WOS:A1997XW93100003 ER PT J AU SmithCoggins, R Rosekind, MR Buccino, KR Dinges, DF Moser, RP AF SmithCoggins, R Rosekind, MR Buccino, KR Dinges, DF Moser, RP TI Rotating shiftwork schedules: Can we enhance physician adaptation to night shifts? SO ACADEMIC EMERGENCY MEDICINE LA English DT Article; Proceedings Paper CT SAEM Annual Meeting CY MAY, 1993 CL SAN FRANCISCO, CA SP Soc Acad Emergency Med DE emergency medicine; sleep; shiftwork; circadian rhythm; physician; clinical performance; sleep deprivation ID CIRCADIAN PRINCIPLES; SLEEP-DEPRIVATION; WORK SCHEDULES; PERFORMANCE AB Objectives: To evaluate the effectiveness of a broad, literature-based night shiftwork intervention for enhancement of emergency physicians' (EPs') adaptation to night rotations. Methods: A prospective, double-blind, active placebo-controlled study was conducted on 6 attending physicians in a university hospital ED. Three data sets were collected under the following conditions: baseline, after active placebo intervention, and after experimental intervention. In each condition, data were collected when the physicians worked both night and day shifts. Measurements included ambulatory polysomnographic recordings of the main sleep periods, objective performance tests administered several times during the subjects' shifts, and daily subjective ratings of the subjects' sleep, moods, and intervention use. Results: The subjects slept an average of 5 hr 42 min across all conditions. After night shifts, the subjects slept significantly less than they did after day shifts (5 hr 13 min vs 6 hr 20 min; p < 0.05). The physicians' vigilance reaction times and times for intubation of a mannequin were significantly slower during night shifts than they were during day shifts (p = 0.007 and p < 0.04, respectively), but performances on ECG analysis did not significantly differ between night and day shifts. Mood ratings were significantly more negative during night shifts than they were during day shifts (more sluggish p < 0.04, less motivated p < 0.03, and less clear thinking p < 0.04), The strategies in the experimental intervention were used 85% of the time according to logbook entries. The experimental and active placebo interventions did not significantly improve the physician's performance, or mood on the night shift, although the subjects slept more after both interventions. Conclusions: Although the experimental intervention was successfully implemented, it failed to significantly improve attending physicians' sleep, performance, or mood on night shifts, A decrease in speed of intubation, vigilance reaction times, and subjective alertness was evident each time the physicians rotated through the night shift, These findings plus the limited sleep across all conditions and shifts suggest that circadian-mediated disruptions of waking neurobehavioral functions and sleep deprivation are problems in EPs. C1 NASA,AMES RES CTR,MT VIEW,CA. UNIV PENN,SCH MED,PHILADELPHIA,PA 19104. VA PALO ALTO HLTH CARE SYST,PALO ALTO,CA. RP SmithCoggins, R (reprint author), STANFORD UNIV,SCH MED,DIV EMERGENCY MED,OFF BLDG,X300,STANFORD,CA 94305, USA. FU NIMH NIH HHS [MH44193] NR 22 TC 64 Z9 68 U1 2 U2 8 PU HANLEY & BELFUS INC PI PHILADELPHIA PA 210 S 13TH ST, PHILADELPHIA, PA 19107 SN 1069-6563 J9 ACAD EMERG MED JI Acad. Emerg. Med. PD OCT PY 1997 VL 4 IS 10 BP 951 EP 961 DI 10.1111/j.1553-2712.1997.tb03658.x PG 11 WC Emergency Medicine SC Emergency Medicine GA YA210 UT WOS:A1997YA21000008 PM 9332626 ER PT J AU Chow, JS Zilliac, GG Bradshaw, P AF Chow, JS Zilliac, GG Bradshaw, P TI Mean and turbulence measurements in the near field of a wingtip vortex SO AIAA JOURNAL LA English DT Article ID FLOW AB The rollup of a wingtip vortex, at a Reynolds number based on chord of 4.6 x 10(6), was studied with an emphasis on suction side and very near-wake measurements (up to x/c = 0.678 downstream of the trailing edge). The research was conducted in a 32 x 48 in. (0.81 x 1.22 m), low-speed wind tunnel. The rectangular half-wing model had a semispan of 36 in. (0.91 m), a chord of 48 in. (1.22 m), and a rounded tip. Seven-hole pressure probe measurements of the velocity field surrounding the wingtip showed that a large axial velocity up to 1.77U(infinity) developed in the vortex core. This high a Level of core axial velocity has not been measured previously. Triple-wire probes were used to measure all components of the Reynolds stress tensor. It was determined from correlation measurements that meandering of the vortex was small and did not contribute appreciably to turbulence measurements. The flow was found to be turbulent in the near field (as high as 24% rms velocity), and the turbulence decayed quickly with streamwise distance because of the stabilizing effect of the nearly solid body rotation of the vortex-core mean flow. A streamwise variation of the location of peak levels of turbulence, relative to the core centerline, was also noted. Close to the trailing edge of the wing, peak shear stress levels were measured at the edge of the vortex core, whereas in the most downstream make plane, the peak levels were measured at a radius roughly equal to one-third of the vortex core radius. The Reynolds shear stresses (in Cartesian coordinates) were not aligned with the mean strain rate, indicating that an isotropic-eddy-viscosity-based prediction method cannot fully model the turbulence in the vortex. In cylindrical coordinates, with the origin at the vortex centerline, the radial normal stress was found to be larger than the circumferential component. C1 NASA,AMES RES CTR,FLUID MECH LAB,MOFFETT FIELD,CA 94035. STANFORD UNIV,DEPT MECH ENGN,STANFORD,CA 94305. RP Chow, JS (reprint author), INST DEF ANAL,ALEXANDRIA,VA 22311, USA. NR 18 TC 93 Z9 98 U1 3 U2 14 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 OCT PY 1997 VL 35 IS 10 BP 1561 EP 1567 DI 10.2514/2.1 PG 7 WC Engineering, Aerospace SC Engineering GA XZ320 UT WOS:A1997XZ32000001 ER PT J AU Smart, MK Kalkhoran, IM AF Smart, MK Kalkhoran, IM TI Flow model for predicting normal shock wave induced vortex breakdown SO AIAA JOURNAL LA English DT Article ID WING-TIP VORTICES AB An analytical study of normal shock wave induced vortex breakdown has been undertaken. In this inviscid axisymmetric analysis, the response of supersonic streamwise vortices to imposed normal shocks has been determined by modeling the rotational core of the vortex as a slender, swirling layer. For vortex/shock combinations of increasing strength, the analysis predicts an ever increasing axial velocity deficit in the vortex core. Vortex breakdown is presumed to occur if a vortex/shock combination Leads to how stagnation at the vortex axis. The results of this study indicate that an inverse relationship exists between vortex swirl and freestream Mach number at breakdown. The breakdown limit curve generated using this analysis shows good correlation with established experimental results, indicating that the onset of normal shock wave induced vortex breakdown can be predicted with a relatively simple flow model and without recourse to numerical simulation. Interpretation of same normal shock wave/vortex interaction experiments in light of the predictions suggests that the phenomenon previously known as supersonic vortex distortion is a form of vortex breakdown. C1 POLYTECH INST NEW YORK,DEPT MECH AEROSP & MFG ENGN,BROOKLYN,NY 11201. RP Smart, MK (reprint author), NASA,LANGLEY RES CTR,HYPERSON AIRBREATHING PROP BRANCH,MAIL STOP 168,HAMPTON,VA 23681, USA. RI Smart, Michael/C-8823-2013 NR 17 TC 9 Z9 11 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 OCT PY 1997 VL 35 IS 10 BP 1589 EP 1596 DI 10.2514/2.17 PG 8 WC Engineering, Aerospace SC Engineering GA XZ320 UT WOS:A1997XZ32000005 ER PT J AU Casscells, W Ahmad, M David, M Clubb, F Bearman, G Willerson, JT AF Casscells, W Ahmad, M David, M Clubb, F Bearman, G Willerson, JT TI Thermal localization of inflammation and induction of macrophage apoptosis in human atherosclerotic plaques SO AMERICAN JOURNAL OF CARDIOLOGY LA English DT Meeting Abstract C1 UNIV TEXAS,HLTH SCI CTR,HOUSTON,TX. HERMANN HOSP,HOUSTON,TX. CALTECH,JET PROP LAB,NASA,PASADENA,CA. TEXAS HEART INST,HOUSTON,TX 77025. ST LUKES EPISCOPAL HOSP,HOUSTON,TX 77030. NR 0 TC 0 Z9 0 U1 0 U2 0 PU EXCERPTA MEDICA INC PI NEW YORK PA 245 WEST 17TH STREET, NEW YORK, NY 10011 SN 0002-9149 J9 AM J CARDIOL JI Am. J. Cardiol. PD OCT PY 1997 VL 80 SI 7A BP TCT2 EP TCT2 PG 1 WC Cardiac & Cardiovascular Systems SC Cardiovascular System & Cardiology GA YC885 UT WOS:A1997YC88500002 ER PT J AU Fang, A Pierson, DL Koenig, DW Mishra, SK Demain, AL AF Fang, A Pierson, DL Koenig, DW Mishra, SK Demain, AL TI Effect of simulated microgravity and shear stress on microcin B17 production by Escherichia coli and on its excretion into the medium SO APPLIED AND ENVIRONMENTAL MICROBIOLOGY LA English DT Article AB Production of the antibacterial polypeptide microcin B17 (MccB17) by Escherichia coli ZK650 was inhibited by simulated microgravity. The site of MccB17 accumulation was found to be different, depending on whether the organism was grown in shaking Basks or in rotating bioreactors designed to establish a simulated microgravity environment, In flasks, the accumulation was cellular, but in the reactors, virtually all the microcin was found in the medium, The change from a cellular site to an extracellular one was apparently not a function of gravity, since extracellular production occurred in these bioreactors, irrespective of whether they were operated in the simulated microgravity or normal gravity mode, More probably, excretion is due to the much lower degree of shear stress in the bioreactors, Addition of even a single glass bead to the 50-ml medium volume in the bioreactor created enough shear to change the site of MccB17 accumulation from the medium to the cells. C1 MIT,DEPT BIOL,FERMENTAT MICROBIOL LAB,CAMBRIDGE,MA 02139. KRUG LIFE SCI INC,HOUSTON,TX 77058. NASA,LYNDON B JOHNSON SPACE CTR,HOUSTON,TX 77058. NR 5 TC 39 Z9 43 U1 0 U2 1 PU AMER SOC MICROBIOLOGY PI WASHINGTON PA 1325 MASSACHUSETTS AVENUE, NW, WASHINGTON, DC 20005-4171 SN 0099-2240 J9 APPL ENVIRON MICROB JI Appl. Environ. Microbiol. PD OCT PY 1997 VL 63 IS 10 BP 4090 EP 4092 PG 3 WC Biotechnology & Applied Microbiology; Microbiology SC Biotechnology & Applied Microbiology; Microbiology GA XY723 UT WOS:A1997XY72300056 PM 9327574 ER PT J AU Haeffelin, MPA Mahan, JR Priestley, KJ AF Haeffelin, MPA Mahan, JR Priestley, KJ TI Predicted dynamic electrothermal performance of thermistor bolometer radiometers for Earth radiation budget applications SO APPLIED OPTICS LA English DT Article AB The Earth Radiation Budget Experiment (ERBE) and the Clouds and the Earth's Radiant Energy System (CERES) rely on scanning thermistor bolometer radiometers of a similar design for accomplishing their mission. High-level dynamic electrothermal models of these instruments have been developed on the basis of the Monte Carlo ray-trace, finite-difference, and finite-element methods. The models are capable of simulating the end-to-end response of the ERBE and the CERES instruments to simulated sequences of Earth scenes. Such models will prove useful in the design of future generations of similar instruments, in defining ground-based and in-flight calibration and data-reduction strategies, in the interpretation of flight data, and in understanding data anomalies that might arise after the instruments have been placed in orbit. Two modules that make up the end-to-end model are presented: the optical-thermal radiative module and the thermistor bolometer dynamic electrothermal module. The optics module is used to determine the point-spread function of the optics, which establishes that the instrument has sharply defined footprints on the Earth. Results obtained with the thermistor bolometer dynamic electrothermal module provide valuable insights into the details of channel operation and establish its high level of equivalence. The combination of the two modules allows the point-spread function of the instrument to be determined and reveals the potential of this tool for scanning realistic Earth scenes. (C) 1997 Optical Society of America. C1 VIRGINIA POLYTECH INST & STATE UNIV,BLACKSBURG,VA 24061. NASA,LANGLEY RES CTR,HAMPTON,VA 23681. NR 29 TC 12 Z9 12 U1 0 U2 2 PU OPTICAL SOC AMER PI WASHINGTON PA 2010 MASSACHUSETTS AVE NW, WASHINGTON, DC 20036 USA SN 0003-6935 J9 APPL OPTICS JI Appl. Optics PD OCT 1 PY 1997 VL 36 IS 28 BP 7129 EP 7142 DI 10.1364/AO.36.007129 PG 14 WC Optics SC Optics GA XX496 UT WOS:A1997XX49600006 PM 18264219 ER PT J AU Pohl, M Hartman, RC Jones, BB Sreekumar, P AF Pohl, M Hartman, RC Jones, BB Sreekumar, P TI A spectral study of gamma-ray emitting active galactic nuclei SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE methods: statistical; BL Lacertae objects: general; quasars: general; Gamma-rays: observations ID RADIATION; BLAZARS AB In this paper we present a statistical analysis of the gamma-ray spectra of flat-spectrum radio quasars (FSRQ) compared to those of BL Lacs. The average spectra and possible systematic deviations from power-law behaviour are investigated by summing up the intensity and the power-law fit statistic for both classes of objects. We also compare the time-averaged spectrum to that at the time of gamma-ray outbursts. The spectrum of the average AGN is softer than that of the extragalactic gamma-ray background. It may be that BL Lacs, which on average have a harder spectrum than FSRQs, make up the bulk of the extragalactic background. We also find apparent cut-offs at both low and high energies in the spectra of FSRQs at the time of gamma-ray outbursts. While the cut-off at high energies may have something to do with opacity, the cut-off at low energies may be taken as indication that the gamma-ray emission of FSRQs is not a one component spectrum. C1 NASA, GODDARD SPACE FLIGHT CTR, GREENBELT, MD 20771 USA. STANFORD UNIV, WW HANSEN EXPT PHYS LAB, STANFORD, CA 94305 USA. RP Pohl, M (reprint author), MAX PLANCK INST EXTRATERR PHYS, POSTFACH 1603, D-85740 GARCHING, GERMANY. NR 25 TC 22 Z9 22 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 OCT PY 1997 VL 326 IS 1 BP 51 EP 58 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XZ849 UT WOS:A1997XZ84900010 ER PT J AU Sambruna, RM AF Sambruna, RM TI Soft X-ray properties of flat-spectrum radio quasars SO ASTROPHYSICAL JOURNAL LA English DT Article DE BL Lacertae objects, general; quasars, general; radio continuum, galaxies; X-rays, galaxies ID ACTIVE GALACTIC NUCLEI; BL-LACERTAE OBJECTS; HIGH-REDSHIFT QUASARS; COMPLETE SAMPLE; INFRARED POLARIZATION; ROSAT OBSERVATIONS; LAC OBJECTS; BLAZARS; VARIABILITY; 3C-279 AB We report the soft X-ray properties of 41 flat-spectrum radio quasars (FSRQs), derived by cross-correlating literature blazar samples with the ROSAT PSPC archive of pointed observations. The redshifts of the sources span the range z = 0-3. The 0.1-2.4 keV spectra of FSRQs are well described by a single power law modified by column densities of neutral gas consistent with Galactic values. Spectral flattening/steepening at the lower energies is present in only 4/41 and 2/41 sources, respectively. The ROSAT photon indices of FSRQs span a wide range, 0.5 less than or similar to Gamma less than or similar to 2.5, and have a measurable intrinsic dispersion; only in part is the spread of slopes due to a redshift effect. The rest-frame ROSAT spectral indices of FSRQs are statistically indistinguishable from low-energy peaked BL Lacs and flatter than high-energy peaked BL Lacs, although with several FSRQs having soft X-ray spectra as steep as HBLs. Similarly, while the bulk of FSRQs are intrinsically X-ray brighter than both types of BL Lacs, the X-ray luminosity distributions of the three classes have a large overlap. The ROSAT spectra of 13 FSRQs are steeper than measured with the Einstein IPC (0.3-4.5 keV), indicating a flat tail emerging at approximate to 1-2 keV at rest-frame energies. We find a trend for blazars with stronger optical emission lines to be more gamma-ray-loud and to have flatter X-ray-to-gamma-ray continua, possibly supporting external Compton scattering models as the primary generation mechanisms of the high-energy continuum in these objects. For several FSRQs repeatedly observed with ROSAT on timescales of weeks to years, flux variations not larger than a factor of 2 have been detected, with more typical variability amplitude on the order of 10%-30%, and with no accompanying spectral changes. This appears to be in contrast to the less luminous BL Lacs, which are generally characterized by large-amplitude X-ray flux changes, usually accompanied by correlated spectral variations. RP Sambruna, RM (reprint author), NASA,GODDARD SPACE FLIGHT CTR,CODE 662,GREENBELT,MD 20771, USA. NR 77 TC 57 Z9 58 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 OCT 1 PY 1997 VL 487 IS 2 BP 536 EP 554 DI 10.1086/304640 PN 1 PG 19 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YA040 UT WOS:A1997YA04000006 ER PT J AU Grandi, P Sambruna, RM Maraschi, L Matt, G Urry, CM Mushotzky, RF AF Grandi, P Sambruna, RM Maraschi, L Matt, G Urry, CM Mushotzky, RF TI ROSAT, ASCA, and OSSE observations of the broad-line radio galaxy 3C 120 SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies, individual (3C 120); galaxies, jets; galaxies, nuclei; galaxies, Seyfert; X-rays, galaxies ID X-RAY-SPECTRA; ACTIVE GALACTIC NUCLEI; SEYFERT-GALAXIES; 3C-120; LUMINOSITY; QUASARS; VARIABILITY; BLAZARS; EXOSAT AB We present simultaneous observations of the superluminal radio galaxy 3C 120 performed with the ASCA and GRO (OSSE) satellites in 1994 February-March, as well as an analysis of all the ROSAT archival data. The ASCA spectrum of this object can be described by an absorbed (N-H = 1.6 x 10(21) cm(-2)) power law with a photon index of T-ASCA = 2 and a very broad (sigma > 0.8 keV) intense iron line (EW > 400 eV) at similar to 6 keV. The combined ASCA-OSSE data do not exclude the presence of a narrower (sigma = 0.4 keV) and less intense (EW < 300 eV) iron line plus a hard component, corresponding either to reflection from an accretion disk or to a flatter power law from a jet. However, a single power law plus broad Fe line is preferred from a statistical point of view by the ASCA data. The ROSAT data yield a column density in excess of the Galactic value. The spectral slopes, ranging from Gamma(ROSAT) = 2.5 to 3.3, are steeper than that measured by ASCA, suggesting the presence of a soft excess. The 0.1-2 keV power-law slope is variable and softer at higher intensity. These results show that the combined soft and hard X-ray spectrum of 3C 120 is rather complex. The intrinsic absorption, the soft excess, and the iron line indicate that the X-ray emission from this blazar-like radio galaxy is dominated by a Seyfert-like component, at least in the 0.1-10 keV energy band. The jet contribution, if present, becomes important only at higher energies. C1 NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. OSSERV ASTRON BRERA,I-20121 MILAN,ITALY. UNIV ROMA TRE,DIPARTIMENTO FIS,I-00146 ROME,ITALY. SPACE TELESCOPE SCI INST,BALTIMORE,MD 21218. RP Grandi, P (reprint author), CNR,IST ASTROFIS SPAZIALE,VIA E FERMI 21,I-00044 FRASCATI,ROMA,ITALY. RI Urry, Claudia/G-7381-2011 OI Urry, Claudia/0000-0002-0745-9792 NR 37 TC 38 Z9 38 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 OCT 1 PY 1997 VL 487 IS 2 BP 636 EP 643 DI 10.1086/304630 PN 1 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YA040 UT WOS:A1997YA04000015 ER PT J AU Simpson, JP Colgan, SWJ Cotera, AS Erickson, EF Haas, MR Morris, M Rubin, RH AF Simpson, JP Colgan, SWJ Cotera, AS Erickson, EF Haas, MR Morris, M Rubin, RH TI Infrared observations of G0.18-0.04 SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxy, center; infrared, ISM, continuum; infrared, ISM, lines and bands; ISM, individual (G0.18-0.04) ID GALACTIC-CENTER; PHOTODISSOCIATION REGIONS; RADIO ARC; INTERSTELLAR EXTINCTION; GRATING SPECTROMETER; MOLECULAR CLOUDS; MAGNETIC-FIELD; ORION NEBULA; IRAS SOURCES; QUINTUPLET AB The Galactic center H II region, G0.18-0.04, also known as the ''Sickle,'' is located where the nonthermal ''Arc'' crosses the Galactic plane. The Sickle appears to be the ionized edge of a dense molecular cloud. The source of ionization has been ascribed to both the interaction of the cloud with the magnetic field of the Are and to the hot stars in the adjacent cluster, AFGL 2004, also known as the ''Quintuplet Cluster.'' This paper addresses the relative locations of the stars, the ionized and molecular gas, and the sources of gas excitation and dust heating. The far-infrared forbidden lines of [S III] 18.7 and 33.5 mu m, [Si II] 34.8 mu m, [Ne III] 36.0 mu m, [O III] 51.8 and 88.4 mu m, [N III] 57.3 mu m, [O I] 63.2 and 146 mu m, [C II] 158 mu m, and [N II] 205 mu m and the adjacent continua were observed with NASA's Kuiper Airborne Observatory at 11 positions around G0.18-0.04, including G0.15-0.05, also known as the ''Pistol.'' The beam size was 40 ''-60 ''. The electron density, the ionic abundances, and the ionization structure of the H II region were estimated from the doubly ionized line fluxes. The density and radiation held found in the photodissociation region (PDR) between the H II region and the molecular cloud were estimated from the [C II] and [O I] line fluxes and the far-infrared continuum. The ionization structure and the PDR properties were compared to shell models of H II regions with varying distances from their exciting stars. The agreement of observations and models indicates that the hot stars of AFGL 2004 are the likely source of ionization of the Sickle. Additional hot stars are necessary to ionize the more outlying positions. However, the low ionization and high PDR radiation field of the Pistol imply that it cannot be as close to AFGL 2004 as is indicated by its proximity on the sky. Instead, the Pistol is probably ionized by the luminous blue variable candidate, Pistol Source A. The extinction to the region was estimated from the IRAS low-resolution spectrum of AFGL 2004 and from the distribution of the J, H, and K' magnitudes of previously observed stars in the held. The extinction is fairly uniform, with no apparent enhancement due to the molecular clouds. The strength of Brackett gamma, the 19 mu m lines and continuum, and the IRAS 25 mu m continuum are all consistent with the absence of a dense, foreground molecular cloud. We conclude that the H II region is on the near side of the dense cloud. C1 IPAC, PASADENA, CA 91109 USA. CALTECH, JET PROP LAB, PASADENA, CA 91109 USA. UNIV CALIF LOS ANGELES, DEPT PHYS & ASTRON, LOS ANGELES, CA 90095 USA. RP Simpson, JP (reprint author), NASA, AMES RES CTR, ASTROPHYS BRANCH, MS 245-6, MOFFETT FIELD, CA 94035 USA. RI Colgan, Sean/M-4742-2014 NR 76 TC 30 Z9 30 U1 0 U2 0 PU IOP PUBLISHING LTD PI BRISTOL PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD OCT 1 PY 1997 VL 487 IS 2 BP 689 EP + DI 10.1086/304634 PN 1 PG 0 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YA040 UT WOS:A1997YA04000021 ER PT J AU Copi, CJ AF Copi, CJ TI A stochastic approach to chemical evolution SO ASTROPHYSICAL JOURNAL LA English DT Review DE Galaxy, abundances; Galaxy, evolution; Galaxy, stellar content; nuclear reactions, nucleosynthesis, abundances ID BIG-BANG NUCLEOSYNTHESIS; RED GIANT STARS; GALACTIC EVOLUTION; HALO-STARS; DEUTERIUM ABUNDANCE; NITROGEN ABUNDANCES; SOLAR NEIGHBORHOOD; LITHIUM ABUNDANCES; OXYGEN ABUNDANCES; BARYON DENSITY AB Observations of elemental abundances in the Galaxy have repeatedly shown an intrinsic scatter as a function of time and metallicity. The standard approach to chemical evolution does not attempt to address this scatter in abundances since only the mean evolution is followed. In this work, the scatter is addressed via a stochastic approach to solving chemical evolution models. Three simple chemical evolution scenarios are studied using this stochastic approach: a closed box model, an infall model, and an outflow model. These models are solved for the solar neighborhood in a Monte Carlo fashion. The evolutionary history of one particular region is determined randomly based on the star formation rate and the initial mass function. Following the evolution in an ensemble of such regions leads to the predicted spread in abundances expected, based solely on different evolutionary histories of otherwise identical regions. In this work, 13 isotopes are followed, including the light elements, the CNO elements, a few alpha-elements, and iron. It is found that the predicted spread in abundances for a 10(5) M. region is in good agreement with observations for the alpha-elements. For CN, the agreement is not as good, perhaps indicating the need for more physics input for low-mass stellar evolution. Similarly for the light elements, the predicted scatter is quite small, which is in contradiction to the observations of He-3 in H II regions. The models are tuned for the solar neighborhood so that good agreement with H II regions is not expected. This has important implications for low-mass stellar evolution and on using chemical evolution to determine the primordial light-element abundances in order to test big bang nucleosynthesis. C1 FERMILAB NATL ACCELERATOR LAB,NASA,FERMILAB ASTROPHYS CTR,BATAVIA,IL 60510. RP Copi, CJ (reprint author), UNIV CHICAGO,ENRICO FERMI INST,DEPT PHYS,CHICAGO,IL 60637, USA. NR 112 TC 26 Z9 26 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 OCT 1 PY 1997 VL 487 IS 2 BP 704 EP 718 DI 10.1086/304627 PN 1 PG 15 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YA040 UT WOS:A1997YA04000022 ER PT J AU Titarchuk, L Mastichiadis, A Kylafis, ND AF Titarchuk, L Mastichiadis, A Kylafis, ND TI X-ray spectral formation in a converging fluid flow: Spherical accretion into black holes SO ASTROPHYSICAL JOURNAL LA English DT Article DE accretion, accretion disks; black hole physics; radiation mechanisms, nonthermal; stars, neutron; X-rays, stars ID RADIATION-DOMINATED SHOCK; COMPTON-SCATTERING AB We study Compton upscattering of low-frequency photons in a converging flow of thermal plasma. The photons escape diffusively, and electron scattering is the dominant source of opacity. We solve the equation of radiative transfer in the case of spherical, steady state accretion into black holes numerically and approximately analytically. Unlike previous work on this subject, we consider the inner boundary at a finite radius, and this has a significant effect on the emergent spectrum. It is shown that the bulk motion of the converging flow is more efficient in upscattering photons than thermal Comptonization, provided that the electron temperature in the flow is of order a few keV or less. In this case, the spectrum observed at infinity consists of a soft component coming from input photons that escaped after a few scatterings without any significant energy change and of a power law that extends to high energies and is made of those photons that underwent significant upscattering. The luminosity of the power law is relatively small compared to that of the soft component. The more reflective the inner boundary is, the flatter the power-law spectrum becomes. The spectral energy power-law index for black hole accretion is always higher than 1, and it is approximately 1.5 for high accretion rates. This result tempts us to say that bulk motion Comptonization might be the mechanism behind the power-law spectra seen in black hole X-ray sources. C1 GEORGE MASON UNIV,INST COMPUTAT SCI & INFORMAT,FAIRFAX,VA 22030. MAX PLANCK INST KERNPHYS,D-69029 HEIDELBERG,GERMANY. UNIV CRETE,RETHIMNON,CRETE,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 21 TC 126 Z9 126 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 OCT 1 PY 1997 VL 487 IS 2 BP 834 EP 846 DI 10.1086/304617 PN 1 PG 13 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YA040 UT WOS:A1997YA04000032 ER PT J AU Shrader, CR Wagner, RM Charles, PA Harlaftis, ET Naylor, T AF Shrader, CR Wagner, RM Charles, PA Harlaftis, ET Naylor, T TI The 1993 August minioutburst of GRO J0422+32 SO ASTROPHYSICAL JOURNAL LA English DT Article DE accretion, accretion disks; binaries, close; stars, individual (GRO J0422+32); X-rays, stars ID RAY TRANSIENT J0422+32; PHOTOMETRY; QUIESCENCE; SUPERHUMPS; MASS AB We report on observations of the soft X-ray transient (SXT) GRO J0422+32 made with the ROSAT Position Sensitive Proportional Counter (PSPC) and the ASCA GIS and SIS X-ray imaging spectrometers during its 1993 August outburst. This event occurred approximately one year after the primary outburst of the source and was characterized by an X-ray-to-optical luminosity ratio much smaller than that typically seen in SXT outbursts or in steady, low-mass X-ray binaries. Our X-ray observations with the ROSAT PSPC, spread over 6.2 days and totalling 28.8 ks, combined with our archival analysis of 17 ks of ASCA observations, indicate an approximately 1 mcrab source that turned off and subsequently back on over a 10 day period, with distinct spectral characteristics in each case. In addition to our analysis of the X-ray spectra, we report on optical photometry and spectroscopy bracketing the X-ray observations. It is noteworthy that the optical light curves remain approximately constant, at least in our data's almost daily sampling, during the turning off and turning on sequence seen in the X-rays. Optical spectroscopy reveals large, asymmetric redshifted and blueshifted components in the double-peaked emission lines He II lambda 4686 and H beta lambda 4861, which can be interpreted as evidence for a wind emanating from the secondary. The phasing of these shifts ruled out a wind originating from the disk. On the other hand, the X-ray power illuminating the star seems insufficient for driving such a wind. Comparisons are made with the primary (1992) outburst and decay phase of GRO J0422+32. Implications for X-ray reprocessing scenarios of the production of optical and UV emission and for other possible scenarios, such as advection-dominated accretion, are briefly considered. An upper limit to the quiescent X-ray luminosity is estimated using data acquired during the X-ray ''off'' state. A similarity between the X-ray-to-optical behavior of GRO J0422+32 during this minioutburst and previously documented optical-to-EUV behavior of certain SU Ursae Majoris system outbursts is noted. A physical interpretation of this analogous behavior, suggesting that the hot and cold branches of the S-shaped stability curve may be relatively closely spaced in GRO J0422+32, is offered. C1 OHIO STATE UNIV,DEPT ASTRON,COLUMBUS,OH 43210. UNIV OXFORD,DEPT ASTROPHYS,NUCL PHYS LAB,OXFORD OX1 3RH,ENGLAND. UNIV ST ANDREWS,SCH PHYS & ASTRON,ST ANDREWS KY16 9SS,FIFE,SCOTLAND. UNIV KEELE,DEPT PHYS,KEELE ST5 5BG,STAFFS,ENGLAND. LOWELL OBSERV,FLAGSTAFF,AZ 86001. RP Shrader, CR (reprint author), NASA,GODDARD SPACE FLIGHT CTR,HIGH ENERGY ASTROPHYS LAB,CODE 660-1,GREENBELT,MD 20771, USA. RI Naylor, Tim /A-9465-2015 NR 24 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 OCT 1 PY 1997 VL 487 IS 2 BP 858 EP 866 DI 10.1086/304635 PN 1 PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YA040 UT WOS:A1997YA04000034 ER PT J AU Aschwanden, MJ Bynum, RM Kosugi, T Hudson, HS Schwartz, RA AF Aschwanden, MJ Bynum, RM Kosugi, T Hudson, HS Schwartz, RA TI Electron trapping times and trap densities in solar flare loops measured with Compton and Yohkoh SO ASTROPHYSICAL JOURNAL LA English DT Review DE acceleration of particles; Sun, flares; Sun, X-rays, gamma rays ID HARD X-RAY; PLUS-PRECIPITATION MODEL; OF-FLIGHT MEASUREMENTS; GAMMA-RAY; MAGNETIC LOOPS; INHOMOGENEOUS-MEDIUM; ENERGETIC PARTICLES; TEMPORAL EVOLUTION; CYCLOTRON MASER; RADIO-BURSTS AB We measure energy-dependent time delays of approximate to 20-200 keV hard X-ray (HXR) emission from 78 flares observed simultaneously with the Compton Gamma Ray Observatory and Yohkoh. Fast time structures (less than or equal to 1 s) are filtered out, because their time delays have been identified in terms of electron time-of-flight (TOF) differences from directly precipitating electrons (Aschwanden et al.). For the smooth HXR flux, we find systematic time delays in the range of tau(s) = t(50 keV)-t(200 keV) approximate to -(1... 10) s, With a Sign opposite to TOF delays, i.e., the high-energy HXRs lag the low-energy HXRs. We interpret these time delays of the smooth HXR flux in terms of electron trapping, and we fitted a model of the collisional deflection time t(Defl)(E) proportional to E(3/2)n(e)(-1) to the observed HXR delays in order to infer electron densities n(e)(Trap) in the trap. Independently, we determine the electron density n(e)(SXR) in flare loops from soft X-ray (SXR) peak emission measures EM = integral n(e)(2) dh, using loop width (w) measurements to estimate the column depth dh approximate to w. Comparing the two independent density measurements in HXR and SXR, we find a mean ratio of q(e) = n(e)(Trap)/n(e)(SXR) approximate to 1, with a relatively small scatter by a factor of approximate to 2. Generally, it is likely that the SXR-bright hare loops have a higher density than the trapping regions (when q(e) < 1), but they also are subject to filling factors less than unity (when q(e) > 1). Our measurements provide comprehensive evidence that electron trapping in solar flares is governed in the weak-diffusion limit, i.e., that the trapping time corresponds to the collisional deflection time, while pitch-angle scattering by resonant waves seems not to be dominant in the 20-200 keV energy range. The measurements do not support a second-step acceleration scenario for energies less than or equal to 200 keV. C1 EASTERN OREGON STATE COLL,DEPT PHYS,LA GRANDE,OR 97850. NATL ASTRON OBSERV,MITAKA,TOKYO 181,JAPAN. INST SPACE & ASTRONAUT SCI,SAGAMIHARA,KANAGAWA 229,JAPAN. NASA,GODDARD SPACE FLIGHT CTR,HUGHES STX,GREENBELT,MD 20771. RP Aschwanden, MJ (reprint author), UNIV MARYLAND,DEPT ASTRON,COLLEGE PK,MD 20742, USA. NR 134 TC 58 Z9 58 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 OCT 1 PY 1997 VL 487 IS 2 BP 936 EP 955 DI 10.1086/304633 PN 1 PG 20 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YA040 UT WOS:A1997YA04000041 ER PT J AU Catanese, M Bradbury, SM Breslin, AC Buckley, JH CarterLewis, DA Cawley, MF Dermer, CD Fegan, DJ Finley, JP Gaidos, JA Hillas, AM Johnson, WN Krennrich, F Lamb, RC Lessard, RW Macomb, DJ McEnery, JE Moriarty, P Quinn, J Rodgers, AJ Rose, HJ Samuelson, FW Sembroski, GH Srinivasan, R Weekes, TC Zweerink, J AF Catanese, M Bradbury, SM Breslin, AC Buckley, JH CarterLewis, DA Cawley, MF Dermer, CD Fegan, DJ Finley, JP Gaidos, JA Hillas, AM Johnson, WN Krennrich, F Lamb, RC Lessard, RW Macomb, DJ McEnery, JE Moriarty, P Quinn, J Rodgers, AJ Rose, HJ Samuelson, FW Sembroski, GH Srinivasan, R Weekes, TC Zweerink, J TI Multiwavelength observations of a flare from Markarian 501 SO ASTROPHYSICAL JOURNAL LA English DT Article DE BL Lacertae objects, individual (Markarian 501); gamma rays, observations ID BL LACERTAE OBJECTS; X-RAY OBSERVATIONS; GAMMA-RAYS; SPECTRA; BLAZARS; RADIATION; TELESCOPE; GALAXIES; JET AB We present multiwavelength observations of the BL Lacertae object Markarian 501 (Mrk 501) in 1997 between April 8 and April 19. Evidence of correlated variability is seen in very high energy (VHE; E greater than or similar to 350 GeV) gamma-ray observations taken with the Whipple Observatory gamma-ray telescope, data from the Oriented Scintillation Spectrometer Experiment of the Compton Gamma Ray Observatory, and quick-look results from the All-Sky Monitor of the Rossi X-Ray Timing Explorer, while EGRET did not detect Mrk 501. Short-term optical correlations are not conclusive, but the U-band flux observed with the 1.2 m telescope of the Whipple Observatory was 10% higher than in March. The average energy output of Mrk 501 appears to peak in the 2-100 keV range, which suggests an extension of the synchrotron emission to at least 100 keV, the highest observed in a blazar and similar to 100 times higher than that seen in the other TeV-emitting BL Lac object, Mrk 421. The VHE gamma-ray flux observed during this period is the highest ever detected from this object. The VHE gamma-ray energy output is somewhat lower than the 2-100 keV range, but the variability amplitude is larger. The correlations seen here do not require relativistic beaming of the emission unless the VHE spectrum extends to greater than or similar to 5 TeV. C1 UNIV LEEDS,DEPT PHYS,LEEDS LS2 9JT,W YORKSHIRE,ENGLAND. NATL UNIV IRELAND UNIV COLL DUBLIN,EXPT PHYS DEPT,DUBLIN 4,IRELAND. HARVARD SMITHSONIAN CTR ASTROPHYS,FRED LAWRENCE WHIPPLE OBSERV,AMADO,AZ 85645. ST PATRICKS COLL,DEPT PHYS,MAYNOOTH,KILDARE,IRELAND. USN,RES LAB,EO HULBURT CTR SPACE RES,WASHINGTON,DC 20375. PURDUE UNIV,DEPT PHYS,W LAFAYETTE,IN 47907. CALTECH,SPACE RADIAT LAB,PASADENA,CA 91125. NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. REG TECH COLL,DEPT PHYS SCI,GALWAY,IRELAND. RP Catanese, M (reprint author), IOWA STATE UNIV,DEPT PHYS & ASTRON,AMES,IA 50011, USA. RI Johnson, Neil/G-3309-2014 NR 47 TC 161 Z9 161 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 OCT 1 PY 1997 VL 487 IS 2 BP L143 EP L146 DI 10.1086/310899 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YA042 UT WOS:A1997YA04200010 ER PT J AU Gotthelf, EV Petre, R Hwang, U AF Gotthelf, EV Petre, R Hwang, U TI The nature of the radio-quiet compact X-ray source in supernova remnant RCW 103 SO ASTROPHYSICAL JOURNAL LA English DT Article DE stars, individual (RCW 103, 1E 161348-5055); stars, neutron; supernova remnants; X-rays, stars ID NOVA REMNANTS; EMISSION; RCW-103; DISCOVERY; PULSARS; ASCA AB We consider the nature of the elusive neutron star candidate 1E 161348-5055 using X-ray observations obtained with ASCA. The compact X-ray source is centered on the shell-type Galactic supernova remnant RCW 103 and has been interpreted as a cooling neutron star associated with the remnant. The X-ray spectrum of the remnant shell can be characterized by a nonequilibrium ionization (NEI) thermal model for a shocked plasma of temperature kT similar to 0.3 keV. The spectrum falls off rapidly above 3 keV to reveal a point source in the spectrally resolved images, at the location of 1E 161348-5055. A blackbody model fit to the source spectrum yields a temperature kT = 0.6 keV, with an unabsorbed 0.5-10 keV luminosity of L-X similar to 10(34) ergs s(-1) (for an assumed distance of 3.3 kpc), both of which are at least a factor of 2 higher than predicted by cooling neutron star models. Alternatively, a power-law model for the source continuum gives a steep photon index of alpha similar to 3.2, similar to that of other radio-quiet, hard X-ray point sources associated with supernova remnants. 1E 161348-5055 may be prototypical of a growing class of radio-quiet neutron stars revealed by ASCA; we suggest that these objects account for previously hidden neutron stars associated with supernova remnants. C1 UNIV MARYLAND,COLLEGE PK,MD 20742. RP Gotthelf, EV (reprint author), NASA,GODDARD SPACE FLIGHT CTR,CODE 660-2,GREENBELT,MD 20771, USA. NR 27 TC 46 Z9 46 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 OCT 1 PY 1997 VL 487 IS 2 BP L175 EP & DI 10.1086/310900 PN 2 PG 6 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YA042 UT WOS:A1997YA04200017 ER PT J AU Michalitsianos, AG Falco, EE Munoz, JA Kazanas, D AF Michalitsianos, AG Falco, EE Munoz, JA Kazanas, D TI The detection of the lambda 2175 feature and further analysis of the broad absorption line profile structure in the gravitational lens candidate UM 425 SO ASTROPHYSICAL JOURNAL LA English DT Article DE dark matter; gravitational lensing; quasars, individual (UM 425) ID QUASARS AB We obtained Multiple Mirror Telescope spectra of the gravitational lens candidate UM 425 to compare the redshifts and line profile structures of lens components A and B, which are separated by approximately 6 ''.5. The C IV lambda 1550 emission in both A and B exhibits broad absorption Line (BAL) structure, consistent with the earlier detection of BAL structure in O VI lambda 1033 and N V lambda 1240 that was found with the International Ultraviolet Explorer in component A. Cross-correlation of the spectra of A and B using emission lines of C IV lambda 1550, He II lambda 1640, N III lambda 1750, C III] lambda 1909, and Mg II lambda 2800 reveals a difference in the redshifts of A and B. However, the detailed BAL profile structure found in the spectra of A and B are strikingly similar to one another, which suggests the system is lensed. The spectra of A and B also indicate significant dust extinction, which we base on the presence of the lambda 2175 absorption feature in the rest frame of the QSO (z(QSO) = 1.47). This feature is commonly seen in galactic sources but is not generally observed in QSO spectra. Our spectra show the presence of the lambda 2175 absorption feature in spectra of both images associated with the gravitational lens UM 425. Based upon the strong similarity of BAL profile structure exhibited by UM 425A and UM 425B, particularly the presence of the lambda 2175 dust absorption feature in spectra of both images, we conclude that UM 425 is a gravitational lens. C1 HARVARD SMITHSONIAN CTR ASTROPHYS, CAMBRIDGE, MA 02138 USA. NASA, GODDARD SPACE FLIGHT CTR, HIGH ENERGY PHYS LAB, GREENBELT, MD 20771 USA. RP NASA, GODDARD SPACE FLIGHT CTR, ASTRON & SOLAR PHYS LAB, CODE 680, GREENBELT, MD 20771 USA. NR 10 TC 11 Z9 11 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 OCT 1 PY 1997 VL 487 IS 2 BP L117 EP L120 DI 10.1086/310903 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YA042 UT WOS:A1997YA04200004 ER PT J AU Sahai, R Nyman, LA AF Sahai, R Nyman, LA TI The Boomerang Nebula: The coldest region of the universe? SO ASTROPHYSICAL JOURNAL LA English DT Article DE circumstellar matter; cosmic microwave background; reflection nebulae; stars, AGB and post-AGB; stars, individual (Boomerang Nebula); stars, mass loss ID CARBON STARS; MASS-LOSS; BIPOLAR; EMISSION AB We have discovered absorption of the 3 K microwave background radiation by ultracold CO gas in the Boomerang Nebula, a bipolar reflection nebula illuminated by a star that has recently evolved off the asymptotic giant branch (AGB). During the AGB phase, stars with main-sequence masses of 1-8 M. eject large amounts of matter, affecting their subsequent evolution as well as the chemical and dynamical evolution of the Galaxy. Our new observations of CO and (CO)-C-13 millimeter-wave lines toward the Boomerang Nebula show it to be quite extreme and perhaps unique in its mass-ejection properties. We find that it has been losing mass through a fast (164 km s(-1)) molecular wind at a prodigious rate of 10(-3) M. yr(-1) (a factor of about 10 larger than the highest rates seen in AGB/post-AGB objects until now) for at least approximately 1500 yr. This wind contains ultracold gas at temperatures below the microwave background temperature, making the Boomerang Nebula the coldest place in the universe found so far (excluding laboratories), and confirming an earlier prediction of the existence of such envelopes. The C-12/C-13 ratio is rather low (5), close to the lowest value attainable (3) through equilibrium CNO-cycle nucleosynthesis. The mechanical wind momentum (dM/dt x V-exp) in the Boomerang Nebula exceeds the total radiative momentum (L*/c) by a factor greater than 10(4). The data also show the presence of an inner shell, expanding at 35 km s(-1), which may have resulted from the ejection of a common envelope by a central binary star. C1 ONSALA SPACE OBSERV,S-43992 ONSALA,SWEDEN. EUROPEAN SO OBSERV,SANTIAGO 19,CHILE. RP Sahai, R (reprint author), CALTECH,JET PROP LAB,MS 183-900,PASADENA,CA 91109, USA. NR 19 TC 24 Z9 24 U1 1 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 OCT 1 PY 1997 VL 487 IS 2 BP L155 EP & DI 10.1086/310897 PN 2 PG 6 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YA042 UT WOS:A1997YA04200013 ER PT J AU Wannier, P Penprase, BE Andersson, BG AF Wannier, P Penprase, BE Andersson, BG TI Rotational excitation of CO in the diffuse interstellar medium: Effects of line emission from dense molecular clouds SO ASTROPHYSICAL JOURNAL LA English DT Article DE ISM, clouds; ISM, kinematics and dynamics; ultraviolet, ISM ID WARM NEUTRAL HALOS; CARBON-MONOXIDE; ZETA-OPHIUCHI; DARK CLOUDS; H-I; PERSEUS; CONTINUUM AB We discuss a somewhat neglected interstellar rotational excitation mechanism that may be significant for CO in diffuse gas (n(tot)less than or equal to 300 cm(-3)). Where such gas is found in the vicinity of a dense interstellar cloud, we show that molecular excitation in the diffuse gas may be dominated by spectral line photons emitted by the denser material. We illustrate the mechanism analytically for a simple two-level case and present the numerical results from a multilevel calculation. In all six of six sight lines that we analyze, it is plausible that the observed rotational excitation results from radiative excitation, so there is no compelling evidence that collisions play an important role. Therefore, densities derived under the assumption of purely collisional excitation would give incorrect (too large) values. Line-of-sight analyses of CO excitation can be (and have been) misinterpreted because of neglect of this contribution to radiative excitation. Similar situations can arise whenever there is a small continuum opacity and a large contrast of gas density within, or around, an interstellar cloud. It is a situation in which the often-used Sobolev (or large-scale velocity gradient) approximation simply does not apply. C1 POMONA COLL,CLAREMONT,CA 91711. RP Wannier, P (reprint author), CALTECH,JET PROP LAB,4800 OAK GROVE DR,PASADENA,CA 91109, USA. OI Andersson, B-G/0000-0001-6717-0686 NR 23 TC 13 Z9 13 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 OCT 1 PY 1997 VL 487 IS 2 BP L165 EP L169 DI 10.1086/310885 PN 2 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YA042 UT WOS:A1997YA04200015 ER PT J AU McKinnell, S Pella, JJ Dahlberg, ML AF McKinnell, S Pella, JJ Dahlberg, ML TI Population-specific aggregations of steelhead trout (Oncorhynchus mykiss) in the North Pacific Ocean SO CANADIAN JOURNAL OF FISHERIES AND AQUATIC SCIENCES LA English DT Article ID SALMO-GAIRDNERI; BRITISH-COLUMBIA; SIZE AB The distribution of North American hatchery-origin steelhead (Oncorhynchus mykiss) in the North Pacific Ocean varied by age and hatchery location. Columbia River steelhead were more abundant south of the Aleutian Islands at an earlier age than steelhead from the Georgia Basin (Georgia Strait, Puget Sound, and waters connecting with the open Pacific). Between 1984 and 1989, there were eight independent and coincident recoveries of coded-wire-tagged steelhead, where individuals released from hatcheries as juveniles at similar times and locations were recovered together on the high seas up to 3 years later. A statistical test was developed to determine whether these coincident recoveries should be expected if individual steelhead within populations travelled in the North Pacific in an uncoordinated manner. The overall test suggested that some tagged steelhead populations travelled together in a significantly (P < 0.05) coordinated manner on the high seas. C1 Pacific Biol Stn, Sci Branch, Dept Fisheries & Oceans, Nanaimo, BC V9R 5K6, Canada. Natl Marine Fisheries Serv, Alaska Fisheries Sci Ctr, Auke Bay Lab, Juneau, AK 99801 USA. RP McKinnell, S (reprint author), Pacific Biol Stn, Sci Branch, Dept Fisheries & Oceans, Hammond Bay Rd, Nanaimo, BC V9R 5K6, Canada. NR 36 TC 22 Z9 22 U1 0 U2 3 PU NATL RESEARCH COUNCIL CANADA PI OTTAWA PA RESEARCH JOURNALS, MONTREAL RD, OTTAWA, ONTARIO K1A 0R6, CANADA SN 0706-652X J9 CAN J FISH AQUAT SCI JI Can. J. Fish. Aquat. Sci. PD OCT PY 1997 VL 54 IS 10 BP 2368 EP 2376 DI 10.1139/cjfas-54-10-2368 PG 9 WC Fisheries; Marine & Freshwater Biology SC Fisheries; Marine & Freshwater Biology GA YR664 UT WOS:000071517900014 ER PT J AU Chen, JW Chiu, HY Hwang, WYP AF Chen, JW Chiu, HY Hwang, WYP TI The structure of solitonic quark stars SO CHINESE JOURNAL OF PHYSICS LA English DT Article ID NON-TOPOLOGICAL SOLITONS; BLACK-HOLES AB We show that, through introduction of quantized scalar and fermion fields in curved space-time, generalized mass and Tolman-Oppenheimer-Volkoff (TOV) equations may be obtained as a means of incorporating scalar and fermionic matter fields (such as quark matter or neutron matter). This provides a convenient framework to treat the problem of solitonic quark stars, stars consisting of quark; matter confined to a phase which is separated from the hadronic phase (e.g., neutron matter) by both the volume energy and the surface energy. We demonstrate that solitonic quark stars dominated by the volume energy reduce to quark stars in the conventional sense while those dominated by the surface energy reduce to fermionic soliton stars obtained by T. D. Lee and others. In addition, the Chandrasekhar limit becomes quite arbitrary and the possibility for the existence of quark stars is significantly enhanced, should we allow the surface energy as an important factor for separating the two phases. C1 NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. RP Chen, JW (reprint author), NATL TAIWAN UNIV,DEPT PHYS,TAIPEI 106,TAIWAN. NR 15 TC 0 Z9 0 U1 0 U2 0 PU PHYSICAL SOC REPUBLIC CHINA PI TAIPEI PA CHINESE JOURNAL PHYSICS PO BOX 23-30, TAIPEI 10764, TAIWAN SN 0577-9073 J9 CHINESE J PHYS JI Chin. J. Phys. PD OCT PY 1997 VL 35 IS 5 BP 543 EP 556 PG 14 WC Physics, Multidisciplinary SC Physics GA YA079 UT WOS:A1997YA07900001 ER PT J AU Wang, P Ferraro, RD AF Wang, P Ferraro, RD TI Parallel computation for natural convection SO CONCURRENCY-PRACTICE AND EXPERIENCE LA English DT Article ID LATERALLY HEATED CAVITY; SHALLOW CAVITY; END WALLS; NUMERICAL-SOLUTIONS AB Parallel computation for two-dimensional convective hows in cavities with adiabatic horizontal boundaries and driven by differential heating of the two vertical end walls are investigated using the Intel Paragon, Intel Touchstone Delta, Gray T3D and IBM SP2, The numerical scheme, including a parallel multigrid solver, and domain decomposition techniques for parallel computing are discussed in detail, Performance comparisons are made for the different parallel systems, and numerical results using various numbers of processors are discussed, (C) 1997 by John Wiley & Sons, Ltd. C1 CALTECH,JET PROP LAB,PASADENA,CA 91109. NR 13 TC 2 Z9 2 U1 0 U2 0 PU JOHN WILEY & SONS LTD PI W SUSSEX PA BAFFINS LANE CHICHESTER, W SUSSEX, ENGLAND PO19 1UD SN 1040-3108 J9 CONCURRENCY-PRACT EX JI Concurrency-Pract. Exp. PD OCT PY 1997 VL 9 IS 10 BP 975 EP 987 PG 13 WC Computer Science, Software Engineering; Computer Science, Theory & Methods SC Computer Science GA YF889 UT WOS:A1997YF88900005 ER PT J AU Baroth, E Hartsough, C Wells, G AF Baroth, E Hartsough, C Wells, G TI A review of HP VEE 4.0 SO EE-EVALUATION ENGINEERING LA English DT Software Review RP Baroth, E (reprint author), CALTECH,JET PROP LAB,MEASUREMENT TEST & ENGN SUPPORT SECT,MEASUREMENT TECHNOL CTR,PASADENA,CA 91109, USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU NELSON PUBLISHING PI NOKOMIS PA 2504 NORTH TAMIAMI TRAIL, NOKOMIS, FL 34275-3482 SN 0149-0370 J9 EE-EVAL ENG JI EE-Eval. Eng. PD OCT PY 1997 VL 36 IS 10 BP 57 EP & PG 4 WC Engineering, Electrical & Electronic SC Engineering GA YC353 UT WOS:A1997YC35300007 ER PT J AU Barut, A Madenci, E Britt, VO Starnes, JH AF Barut, A Madenci, E Britt, VO Starnes, JH TI Buckling of a thin, tension-loaded, composite plate with an inclined crack SO ENGINEERING FRACTURE MECHANICS LA English DT Article ID STRESS INTENSITY FACTORS; BEHAVIOR; FRACTURE AB A numerical study of the local buckling and fracture response of a thin composite plate with an inclined crack and subjected to tension is presented. Local buckling of the unsupported edges of the crack occurs due to compressive stresses caused by a Poisson effect in the neighborhood of the crack. The relationship between fracture of a plate with a crack and the local buckling and postbuckling responses of the plate is established through a geometrically nonlinear finite-element analysis in conjunction with concepts from fracture mechanics. The analysis is based on a co-rotational form of the updated Lagrangian formulation that is implemented with a triangular shell element that includes transverse shear deformation effects. The potential energy release rate results are computed for a predetermined radial crack propagation direction that coincides with the location of the maximum stationary strain energy density near the crack tip. The results indicate that the local buckling load increases and the potential energy release rate decreases as the crack orientation changes from a transverse crack to a longitudinal crack aligned with the direction of the applied tension load. The effect of stacking sequence on the local buckling load and on the energy release rate for specific crack orientations is also discussed. (C) 1997 Elsevier Science Ltd. C1 Univ Arizona, Dept Aerosp & Mech Engn, Tucson, AZ 85721 USA. NASA, Langley Res Ctr, Struct Mech Branch, Hampton, VA 23681 USA. RP Madenci, E (reprint author), Univ Arizona, Dept Aerosp & Mech Engn, Tucson, AZ 85721 USA. NR 30 TC 21 Z9 21 U1 1 U2 4 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0013-7944 J9 ENG FRACT MECH JI Eng. Fract. Mech. PD OCT PY 1997 VL 58 IS 3 BP 233 EP 248 DI 10.1016/S0013-7944(97)00064-7 PG 16 WC Mechanics SC Mechanics GA YR746 UT WOS:000071526100006 ER PT J AU Newman, DJ Jackson, DK Bloomberg, JJ AF Newman, DJ Jackson, DK Bloomberg, JJ TI Altered astronaut lower limb and mass center kinematics in downward jumping following space flight SO EXPERIMENTAL BRAIN RESEARCH LA English DT Article DE kinematics; impedance; jumping; posture control; astronaut performance; human ID CANADIAN VESTIBULAR EXPERIMENTS; PROLONGED WEIGHTLESSNESS; POSTURAL CONTROL; RESPONSES; MISSION; MUSCLE; STABILIZATION; ADAPTATION; MECHANICS; STIFFNESS AB Astronauts exposed to the microgravity conditions encountered during space flight exhibit postural and gait instabilities upon return to earth that could impair critical post flight performance. The aim of the present study was to determine the effects of microgravity exposure on astronauts' performance of two-footed jump landings. Nine astronauts from several Space Shuttle missions were tested both preflight and postflight with a series of voluntary, two-footed downward hops from a 30-cm-high step. A video-based, three-dimensional motion-analysis system permitted calculation of body segment positions and joint angular displacements. Phase-plane plots of knee, hip, and ankle angular velocities compared with the corresponding joint angles were used to describe the lower limb kinematics during jump landings. Thp position of the whole-body center of mass (COM) was also estimated in the sagittal plane using an eight-segment body model. Four of nine subjects exhibited expanded phase-plane portraits postflight, with significant increases in peak joint flexion angles and flexion rates following space flight. In contrast, two subjects showed significant contractions of their phase-plane portraits postflight and three subjects showed insignificant overall changes after space flight. Analysis of the vertical COM motion generally supported the joint angle results. Subjects with expanded joint angle phase-plane portraits postflight exhibited larger downward deviations of the COM and longer times from impact to peak deflection, as well as lower upward recovery velocities. Subjects with postflight joint angle phase-plane contraction demonstrated opposite effects in the COM motion. The joint kinematics results indicated the existence of two contrasting response modes due to microgravity exposure. Most subjects exhibited ''compliant'' impact absorption postflight, consistent with decreased limb stiffness and damping, and a reduction in the bandwidth of the postural control system. Fewer subjects showed ''stiff'' behavior after space flight, where contractions in the phase-plane portraits pointed to an increase in control bandwidth. The changes appeared to result from adaptive modifications in the control of lower limb impedance. A simple 2nd-order model of the vertical COM motion indicated that changes in the effective vertical stiffness of the legs can predict key features of the postflight performance. Compliant responses may reflect inflight adaptation due to altered demands on the postural control system in microgravity, while stiff behavior may result from overcompensation postflight for the presumed reduction in limb stiffness inflight. C1 NASA,LYNDON B JOHNSON SPACE CTR,LIFE SCI RES LABS,HOUSTON,TX 77058. RP Newman, DJ (reprint author), MIT,DEPT AERONAUT & ASTRONAUT,77 MASSACHUSETTS AVE,RM 33-119,CAMBRIDGE,MA 02139, USA. NR 32 TC 30 Z9 30 U1 0 U2 4 PU SPRINGER VERLAG PI NEW YORK PA 175 FIFTH AVE, NEW YORK, NY 10010 SN 0014-4819 J9 EXP BRAIN RES JI Exp. Brain Res. PD OCT PY 1997 VL 117 IS 1 BP 30 EP 42 DI 10.1007/PL00005788 PG 13 WC Neurosciences SC Neurosciences & Neurology GA YC451 UT WOS:A1997YC45100003 PM 9386002 ER PT J AU Balaban, CD Palm, DE Shikher, V Searles, RV Keil, LC Severs, WB AF Balaban, CD Palm, DE Shikher, V Searles, RV Keil, LC Severs, WB TI Mechanisms for vasopressin effects on intraocular pressure in anesthetized rats SO EXPERIMENTAL EYE RESEARCH LA English DT Article DE rat; intraocular pressure; arginine vasopressin; intracameral injection; outflow resistance ID DYNAMICS; FLOW AB Continuous intracameral infusions of a balanced salt solution (0.175 mu l min(-1)) have been reported to raise intraocular pressure (IOP) in anesthetized rats. Palm et al. (1995) previously reported that this effect was attenuated significantly by inclusion of arginine-vasopressin (AVP, 10 ng 0.175 mu l(-1)) in the infusate. This study used experimental and computer simulation methods to investigate factors underlying these changes in IOP. First, constant intracameral infusions of artificial cerebrospinal fluid (aCSF) at different fixed rates (0.049-0.35 mu l min(-1)) were used to estimate the outflow resistance. Secondly, IOP responses were measured during an 2 hr intracameral infusion of either aCSF or AVP that was the sum of a small constant component (0.05 mu l min(-1)) and a larger periodic component (0.25 mu l min(-1), cycling for 4 min on, then 4 min off); the mean infusion rate was 0.175 mu l min(-1). As shown previously for 0.175 mu l min(-1) constant infusions, the periodic aCSF infusion induced a significant rise in IOP that was attenuated by AVP administration. Complex demodulation analysis and the estimated gain parameter of a second order transfer function fit to the periodic responses indicated that outflow resistance increased significantly during the infusions in both aCSF and AVP groups, but that the indices of resistance did not differ significantly between aCSF and AVP infused eyes. This finding implies that changes in outflow resistance do not explain the difference in IOP responses to intracameral aCSF and AVP. The two responses differed significantly, though, in damping factors, such that the aCSF responses were considerably more underdamped than the AVP responses. It is hypothesized that aCSF-induced increase in IOP reflects both (1) a small component reflecting increased outflow resistance and (2) a larger non-resistive component. Since the non-resistive component is insensitive to pretreatment with acetazolamide, it is suggested that the aCSF-induced elevation in IOP reflects primarily vascular perfusion changes that are reduced by local vasoconstrictor actions of AVP. The latter mechanism likely maintains vascular perfusion of the globe when intraocular hypertension develops. (C) 1997 Academic Press Limited. C1 PENN STATE UNIV,COLL MED,MILTON S HERSHEY MED CTR,DEPT PHARMACOL,HERSHEY,PA 17033. NASA,AMES RES CTR,MOFFETT FIELD,CA 94035. UNIV PITTSBURGH,INST EYE & EAR,DEPT PHARMACOL,PITTSBURGH,PA 15213. OI Balaban, Carey/0000-0002-3570-3844 NR 25 TC 4 Z9 4 U1 0 U2 0 PU ACADEMIC PRESS LTD PI LONDON PA 24-28 OVAL RD, LONDON, ENGLAND NW1 7DX SN 0014-4835 J9 EXP EYE RES JI Exp. Eye Res. PD OCT PY 1997 VL 65 IS 4 BP 517 EP 531 DI 10.1006/exer.1997.0346 PG 15 WC Ophthalmology SC Ophthalmology GA YA785 UT WOS:A1997YA78500006 PM 9464185 ER PT J AU Badran, B Gerner, FM Ramadas, P Henderson, T Baker, KW AF Badran, B Gerner, FM Ramadas, P Henderson, T Baker, KW TI Experimental results for low-temperature silicon micromachined micro heat pipe arrays using water and methanol as working fluids SO EXPERIMENTAL HEAT TRANSFER LA English DT Article AB An experimental test facility was constructed to test and verify the operation of two parallel arrays of anisotropically micromachined (etched) micro heat pipes (MHPs) on a single crystalline (100) semiconductor silicon wafer. A micro heat pipe is a small-scale device used to transport energy from a heat source to a heat sink in nearly isothermal operation. The individual MHP was an isosceles triangle with a length of 25.4 mm, and a width of 100 am and 260 mu m far the arrays. A 7740 pyrex glass wafer was used to seal the pipe array hermetically. The transparent glass allowed visual inspection of the level of the working fluid filling the pipe array. Two working fluids were tested, pure water and methanol. A Kapton healer was used to supply the heat input, and cooling water flowing through the condenser (to remove the applied heat) was used as a heat sink. Filling charges of 5%, 10%, 20%, 30%, 50%, and 80% were tested The axial temperature drop along the length of the pipe was measured using K-type thermocouples connected to a data acquisition system. Fourier's law was used to calculate the effective thermal conductivity. The results showed a maximum improvement of 11% in effective thermal conductivity at higher power levels. However, the theoretical model predicted an improvement of at least 193%. An optimum fill of 5% was identified. The results are compared to earlier published data of Duncan from Peterson's group at Texas A&M. C1 Univ Cincinnati, Dept Mech Ind & Nucl Engn, Cincinnati, OH 45221 USA. Univ Cincinnati, Dept Elect & Comp Sci, Cincinnati, OH 45221 USA. NASA, Lewis Res Ctr, Thermal Syst Power Technol Div, Cleveland, OH 44135 USA. RP Gerner, FM (reprint author), Univ Cincinnati, Dept Mech Ind & Nucl Engn, POB 210072, Cincinnati, OH 45221 USA. NR 16 TC 27 Z9 27 U1 0 U2 8 PU TAYLOR & FRANCIS INC PI PHILADELPHIA PA 325 CHESTNUT ST, SUITE 800, PHILADELPHIA, PA 19106 USA SN 0891-6152 J9 EXP HEAT TRANSFER JI Exp. Heat Transf. PD OCT-DEC PY 1997 VL 10 IS 4 BP 253 EP 272 DI 10.1080/08916159708946547 PG 20 WC Thermodynamics; Engineering, Mechanical SC Thermodynamics; Engineering GA YT847 UT WOS:000071651000002 ER PT J AU Johnson, SW Carls, MG Stone, RP Brodersen, CC Rice, SD AF Johnson, SW Carls, MG Stone, RP Brodersen, CC Rice, SD TI Reproductive success of Pacific herring, Clupea pallasi, in Prince William Sound, Alaska, six years after the Exxon Valdez oil spill SO FISHERY BULLETIN LA English DT Article ID HARENGUS-PALLASI AB The Exxon Valdez oil spill occurred just prior to the spring migration of Pacific herring, Clupea pallasi, from offshore feeding grounds to nearshore spawning areas in Prince William Sound PWS), Alaska. Most or all of the life stages of herring in PWS may have been exposed to oil after the March 1989 spill. Delayed impacts from the spill were suspected as one possible cause in the unprecedented crash of the adult herring population in 1993 and stimulated studies to assess reproductive success. In spring 1995, mature herring were collected from four sites in PWS and from three uncontaminated sites in southeast Alaska (SE) to determine if reproductive impairment was evident in PWS herring six years after the spill. Herring were artificially spawned and their eggs were reared in a laboratory until hatching. Observed response parameters included fertilization success, hatching times, hatching success, as well as larval viability, swimming ability and spinal abnormalities. Responses of all year classes combined or those restricted to the same year class did not differ significantly between regions (P>0.50); the best and worst responses generally occurred in the SE. Within each site, response of the 1989 year class (most likely impacted by the oil spill in PWS) generally did not differ significantly from any other year class. To verify macroscopic observations, a subset of larvae from the 1989 year class was also inspected microscopically for yolk and pericardial abnormalities, and yolk volume was measured-but no significant regional differences were observed for any of these morphological categories. Based on the parameters examined in this study, evidence of reproductive impairment of Pacific herring in PWS by the spill was not detected in 1995, and the chances of detecting any oil-related effects against natural background variation appeared to be negligible. RP Johnson, SW (reprint author), NOAA,NATL MARINE FISHERIES SERV,ALASKA FISHERIES SCI CTR,AUKE BAY LAB,11305 GLACIER HIGHWAY,JUNEAU,AK 99801, USA. NR 25 TC 6 Z9 6 U1 1 U2 7 PU NATL MARINE FISHERIES SERVICE SCIENTIFIC PUBL OFFICE PI SEATTLE PA 7600 SAND POINT WAY NE BIN C15700, SEATTLE, WA 98115 SN 0090-0656 J9 FISH B-NOAA JI Fish. Bull. PD OCT PY 1997 VL 95 IS 4 BP 748 EP 761 PG 14 WC Fisheries SC Fisheries GA YA863 UT WOS:A1997YA86300010 ER PT J AU Davis, AB Marshak, A Cahalan, RF Wiscombe, WJ AF Davis, AB Marshak, A Cahalan, RF Wiscombe, WJ TI Interactions: Solar and laser beams in stratus clouds, fractals & multifractals in climate & remote-sensing studies SO FRACTALS-COMPLEX GEOMETRY PATTERNS AND SCALING IN NATURE AND SOCIETY LA English DT Article; Proceedings Paper CT Fractal 97 Meeting CY APR 08-11, 1997 CL ESTES PK, CO SP Univ Denver ID FULLY-DEVELOPED TURBULENCE; RADIATIVE-TRANSFER; MARINE STRATOCUMULUS; GENERALIZED DIMENSIONS; ATMOSPHERIC ABSORPTION; STRANGE ATTRACTORS; SCALE-INVARIANCE; CASCADE; MODELS; RAIN AB Recent research on cloud structure and cloud-radiation interaction at NASA's Goddard Space Flight Center is presented as a show case of interdisciplinary work where fractals and multifractals play a central role. Focus has been primarily on stratocumulus because of their first-order effect on the Earth's energy balance (hence the global climate) due to their unusual horizontal extension and persistence. These cloud layers have quasi-flat upper/lower boundaries and appear to be quite uniform but are highly variable inside. The general strategy has been: utilization of spatial statistics of in situ and remotely sensed data pertaining to cloud structure to constrain stochastic cloud models used in turn for radiative transfer simulations where artificial radiation fields are generated; these fields are compared to actual measurements, and so on, until a degree of closure is achieved. The major trends have been: i) computation and understanding of cloud-radiative properties from the large scales of interest to Global Climate Models (over 10(2) km) down to the smallest observable scales (less than 10 m); ii) from predicting the outcome of "ideal" measurements to those of "real" ones with limited accuracy, sampling and averaging; iii) from passive to active remote-sensing methods; and iv) shifting from standard to wavelet-based analysis/modeling techniques. In terms of potential for impact on geophysical research at large, the most important contributions are: a) criteria for and measures of nonstationarity and intermittency in scale-invariant data; b) so-called "bounded" multifractal cascade models having a continuously variable degree of nonstationarity; c) a parameterization of the bulk effect of fractal variability on large-scale planetary albedo; and d) the basic scaling theory of radiative "smoothing" that explains non-trivially related multiple scattering phenomena in both solar-and lidar-based remote sensing. The last item also suggests new methods of observing clouds and new ways of processing cloud radiance data to retrieve physical cloud properties. C1 NASA, Goddard Space Flight Ctr, Climate & Radiat Branch, Greenbelt, MD 20771 USA. RP NASA, Goddard Space Flight Ctr, Climate & Radiat Branch, Code 913, Greenbelt, MD 20771 USA. RI Cahalan, Robert/E-3462-2012; Wiscombe, Warren/D-4665-2012; Marshak, Alexander/D-5671-2012 OI Cahalan, Robert/0000-0001-9724-1270; Wiscombe, Warren/0000-0001-6844-9849; NR 93 TC 8 Z9 8 U1 0 U2 0 PU WORLD SCIENTIFIC PUBL CO PTE LTD PI SINGAPORE PA 5 TOH TUCK LINK, SINGAPORE 596224, SINGAPORE SN 0218-348X EI 1793-6543 J9 FRACTALS JI Fractals-Complex Geom. Patterns Scaling Nat. Soc. PD OCT PY 1997 VL 5 SU S BP 129 EP 166 DI 10.1142/S0218348X97000875 PG 38 WC Mathematics, Interdisciplinary Applications; Multidisciplinary Sciences SC Mathematics; Science & Technology - Other Topics GA YY488 UT WOS:000072151600009 ER PT J AU Khazanov, GV Liemohn, MW Krivorutsky, EN Horwitz, JL AF Khazanov, GV Liemohn, MW Krivorutsky, EN Horwitz, JL TI A model for lower hybrid wave excitation compared with observations by Viking SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID FREQUENCY WAVES; PLASMA; INSTABILITY; LATITUDES; COLLAPSE AB The mechanism of lower hybrid wave (LHW) excitation due to the O+ relative drift in a plasma subjected to low-frequency waves (LFWs) is used for analysis of Viking satellite data far events in the cusp/cleft region. In some cases, such a mechanism leads to LHW energy densities and ion distribution functions close to those observed, suggesting the proposed mechanism is a plausible candidate to explain certain classes of LHW generation events in space plasmas. C1 UNIV ALABAMA,DEPT PHYS,HUNTSVILLE,AL 35899. UNIV ALABAMA,CTR SPACE PLASMA & AERON RES,HUNTSVILLE,AL 35899. RP Khazanov, GV (reprint author), NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,SPACE SCI LAB,EC-83,HUNTSVILLE,AL 35812, USA. RI Liemohn, Michael/H-8703-2012 OI Liemohn, Michael/0000-0002-7039-2631 NR 22 TC 7 Z9 7 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 OCT 1 PY 1997 VL 24 IS 19 BP 2399 EP 2402 DI 10.1029/97GL02389 PG 4 WC Geosciences, Multidisciplinary SC Geology GA XZ212 UT WOS:A1997XZ21200013 ER PT J AU Grun, E Staubach, P Baguhl, M Hamilton, DP Zook, HA Dermott, S Gustafson, BA Fechtig, H Kissel, J Linkert, D Linkert, G Srama, R Hanner, MS Polanskey, C Horanyi, M Lindblad, BA Mann, I McDonnell, JAM Morfill, GE Schwehm, G AF Grun, E Staubach, P Baguhl, M Hamilton, DP Zook, HA Dermott, S Gustafson, BA Fechtig, H Kissel, J Linkert, D Linkert, G Srama, R Hanner, MS Polanskey, C Horanyi, M Lindblad, BA Mann, I McDonnell, JAM Morfill, GE Schwehm, G TI South-North and radial traverses through the interplanetary dust cloud SO ICARUS LA English DT Article ID INTER-STELLAR GRAINS; ZODIACAL DUST; SOLAR-SYSTEM; INTERSTELLAR DUST; ULYSSES; GALILEO; SPACE; PARTICLES; DETECTOR; VELOCITY AB Identical in situ dust detectors are flown on board the Galileo and Ulysses spacecraft. They record impacts of micrometeoroids in the ecliptic plane at heliocentric distances from 0.7 to 5.4 AU and in a plane almost perpendicular to the ecliptic from -79 degrees to +79 degrees ecliptic latitude. The combination of both Ulysses and Galileo measurements yields information about the radial and latitudinal distributions of micron- and submicron-sized dust in the Solar System. Two types of dust particles were found to dominate the dust flux in interplanetary space. Interplanetary micrometeoroids covering a wide mass range from 10(-16) to 10(-6) g are recorded mostly inside 3 AU and at latitudes below 30 degrees. Interstellar grains with masses between 10(-14) and 10(-12) g have been positively identified outside 3 AU near the ecliptic plane and outside 1.8 AU at high ecliptic latitudes (>50 degrees). Interstellar grains move on hyperbolic trajectories through the planetary system and constitute the dominant dust flux (1.5 X 10(-4) m(-2) sec(-1)) in the outer Solar System and at high ecliptic latitudes. To compare and analyze the Galileo and Ulysses data sets, a new model is developed based on J. Geophys. Res. 98, 17029-17048, Divine's (1993, ''five populations of interplanetary meteoroids'' model. Both models describe the interplanetary meteoroid environment in terms of dust populations on distinct orbits. Taking into account the measured velocities and the effect of radiation pressure on small particles (described by the ratio of radiation pressure force to gravity, beta), we define four populations of meteoroids on elliptical orbits and one population on hyperbolic orbit that can fit the micrometeoroid flux observed by Galileo and Ulysses. Micrometeoroids with masses greater than 10(-10) g and negligible radiation pressure (beta = 0) orbit the Sun on low to moderately eccentric orbits and with low inclinations (less than or equal to 30 degrees). Populations of smaller particles with mean masses of 10(-11) g (beta = 0.3), 10(-13) g (beta = 0.8), and 5 X 10(-15) g (beta = 0.3), respectively, have components with high eccentricities and have increasingly wider inclination distributions with decreasing mass. Similarities among the orbit distributions of the small particle populations on bound orbits suggest that all are genetically related and are part of an overall micrometeoroid complex that prevails in the inner Solar System. The high-eccentricity component of the small particle populations may actually be beta-meteoroids which are not well characterized by our measurements. Our modeling suggests further that the interstellar dust flux is not reduced at Ulysses' perihelion distance (1.3 AU) and that it contributes about 30% of the total dust flux observed there. (C) 1997 Academic Press. C1 ESA,ESOC,D-64293 DARMSTADT,GERMANY. MAX PLANCK INST KERNPHYS,D-69117 HEIDELBERG,GERMANY. NASA,LYNDON B JOHNSON SPACE CTR,COLLEGE PK,MD 20742. UNIV FLORIDA,GAINESVILLE,FL 32611. JET PROP LAB,PASADENA,CA 91103. UNIV COLORADO,ATMOSPHER & SPACE PHYS LAB,BOULDER,CO 80309. LUND OBSERV,S-221 LUND,SWEDEN. MAX PLANCK INST AERON,D-37191 KATLENBURG DUHM,GERMANY. UNIV KENT,CANTERBURY CT2 7NR,KENT,ENGLAND. MAX PLANCK INST EXTRATERR PHYS,D-85748 GARCHING,GERMANY. EUROPEAN SPACE AGCY,ESTEC,NL-2200 AG NOORDWIJK,NETHERLANDS. UNIV MARYLAND,COLLEGE PK,MD 20742. RP Grun, E (reprint author), MAX PLANCK INST KERNPHYS,D-69117 HEIDELBERG,GERMANY. RI Gustafson, Bo/B-9526-2011; OI Horanyi, Mihaly/0000-0002-5920-9226 NR 43 TC 65 Z9 65 U1 1 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 OCT PY 1997 VL 129 IS 2 BP 270 EP 288 DI 10.1006/icar.1997.5789 PG 19 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YG943 UT WOS:A1997YG94300002 ER PT J AU Vilas, F Jensen, EA McFadden, LA AF Vilas, F Jensen, EA McFadden, LA TI Extracting spectral information about 253 Mathilde using the NEAR photometry SO ICARUS LA English DT Article ID CCD REFLECTANCE SPECTRA; LOW-ALBEDO ASTEROIDS; GALILEO PHOTOMETRY; IRON; 253-MATHILDE; HYDRATION; OXIDES; WATER; BELT; UV AB The Near Earth Asteroid Rendezvous (NEAR) spacecraft will conduct the first photometric imagery of a C-class asteroid when it flies by 253 Mathilde. An absorption feature seen in ground-based disk-integrated spectra of many C-class asteroids has been attributed to oxidized iron in phyllosilicate minerals of the serpento-chlorite groups. We have designed a method of identifying this absorption feature in the NEAR photometry of Mathilde. A linear mixing model was used to combine two sets of synthetic NEAR photometry created from a spectrum of Mathilde that does not show this feature and the average of nine spectra of other C-class asteroids each having the 0.7-mu m absorption feature. We find that a spatial unit must contain a minimum of 55% material that has a spectrum showing the 0.7-mu m absorption feature for the presence of this material to be spectrally detectable in the NEAR photometric imaging data. (C) 1997 Academic Press. C1 LOCKHEED MARTIN SPACE MISSION SYST & SERV CO, HOUSTON, TX 77058 USA. TEXAS A&M UNIV, DEPT GEOPHYS, COLLEGE STN, TX 77845 USA. UNIV MARYLAND, ASTRON PROGRAM, COLLEGE PK, MD 20742 USA. RP Vilas, F (reprint author), NASA, JOHNSON SPACE CTR SN3, HOUSTON, TX 77058 USA. RI McFadden, Lucy-Ann/I-4902-2013 OI McFadden, Lucy-Ann/0000-0002-0537-9975 NR 39 TC 7 Z9 7 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 J9 ICARUS JI Icarus PD OCT PY 1997 VL 129 IS 2 BP 440 EP 449 DI 10.1006/icar.1997.5792 PG 10 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YG943 UT WOS:A1997YG94300013 ER PT J AU Joshi, MM Haberle, RM Reynolds, RT AF Joshi, MM Haberle, RM Reynolds, RT TI Simulations of the atmospheres of synchronously rotating terrestrial planets orbiting M dwarfs: Conditions for atmospheric collapse and the implications for habitability SO ICARUS LA English DT Article ID GENERAL-CIRCULATION MODEL; EARLY MARS; VENUS; EVOLUTION; CLIMATE; TITAN AB Planets within the habitable zones of M dwarfs are likely to be synchronous rotators; in other words, one side is permanently illuminated while the other side is in perpetual darkness. We present results of three-dimensional simulations of the atmospheres of such planets, and comment on their possible habitability. Near the ground, a thermally direct longitudinal cell exists, transporting heat from the dayside to the nightside. The circulation is three-dimensional, with low-level winds returning mass to the dayside across the polar regions. Aloft, the zonally averaged winds display a pattern of strong superrotation due to these planets' finite (albeit small) rotation rate. With terrestrial values of insolation, a CO2/H2O atmosphere collapses, or condenses on the surface of the darkside, when surface pressure is approximately 30 mb, this value being much lower for a N-2 atmosphere. This temperature contrast is also sensitive to factors such as gravity, planetary radius, and IR optical depth tau. These results question the suitability of the concept of a habitable zone around M dwarfs that is independent of planetary parameters. If CO2 partial pressure is controlled by the carbonate-silicate cycle, we find that these planets should have a minimum surface pressure of 1000-1500 mb of CO2, as this is the minimum pressure needed to support stable liquid water on the darkside at the inner edge of the habitable zone. We finally conclude that planets orbiting M stars can support atmospheres over a large range of conditions and, despite constraints such as stellar activity, are very likely to be habitable. (C) 1997 Academic Press. RP Joshi, MM (reprint author), NASA,AMES RES CTR,DIV SPACE SCI,MS 245 3,MOFFETT FIELD,CA 94035, USA. RI Joshi, Manoj/C-1795-2008 OI Joshi, Manoj/0000-0002-2948-2811 NR 28 TC 170 Z9 174 U1 1 U2 15 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 OCT PY 1997 VL 129 IS 2 BP 450 EP 465 DI 10.1006/icar.1997.5793 PG 16 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YG943 UT WOS:A1997YG94300014 ER PT J AU McKay, CP Martin, SC Griffith, CA Keller, RM AF McKay, CP Martin, SC Griffith, CA Keller, RM TI Temperature lapse rate and methane in Titan's troposphere SO ICARUS LA English DT Article ID VOYAGER-1 RADIO-OCCULTATION; ATMOSPHERE; REANALYSIS; GREENHOUSE; SURFACE; OCEAN AB We have reanalyzed the Voyager radio occultation data for Titan, examining two alternative approaches to methane condensation. In one approach, methane condensation is facilitated by the presence of nitrogen because nitrogen lowers the condensation level of a methane/nitrogen mixture. The resulting enhancement in methane condensation lowers the upper limit on surface relative humidity of methane obtained from the Voyager occultation data from 0.7 to 0.6. We conclude that in this case the surface relative humidity of methane lies between 0.08 and 0.6, with values close to 0.6 indicated. In the other approach, methane is allowed to become supersaturated and reaches 1.4 times saturation in the troposphere. In this case, surface humidities up to 100% are allowed by the Voyage; occultation data, and thus the upper limit must be set by other considerations. We conclude that if supersaturation is included, then the surface relative humidity of methane can be any value greater than 0.08-unless a deep ocean is present, in which case the surface relative humidity is limited to less than 0.85. Again, values close to 0.6 are indicated. Overall, the tropospheric lapse rate on Titan appears to be determined by radiative equilibrium. The lapse rate is everywhere stable against dry convection, but is unstable to moist convection. This finding is consistent with a supersaturated atmosphere in which condensation-and hence moist convection-is inhibited. (C) 1997 Academic Press. C1 NO ARIZONA UNIV,DEPT PHYS & ASTRON,FLAGSTAFF,AZ 86011. RP McKay, CP (reprint author), NASA,AMES RES CTR,DIV SPACE SCI,MOFFETT FIELD,CA 94035, USA. NR 26 TC 37 Z9 37 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 OCT PY 1997 VL 129 IS 2 BP 498 EP 505 DI 10.1006/icar.1997.5751 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YG943 UT WOS:A1997YG94300017 PM 11541736 ER PT J AU Lee, KF Luk, KM Tong, KF Shum, SM Huynh, T Lee, RQ AF Lee, KF Luk, KM Tong, KF Shum, SM Huynh, T Lee, RQ TI Experimental and simulation studies of the coaxially fed U-slot rectangular patch antenna SO IEE PROCEEDINGS-MICROWAVES ANTENNAS AND PROPAGATION LA English DT Article DE rectangular patch antennas; bandwidth widening ID MICROSTRIP AB Experimental and simulation results are presented on the coaxially fed rectangular patch antenna with a U-shaped slot. Experimental results include impedance bandwidth, copolar- and crosspolar-pattern characteristics and gain measurements. Simulation results are obtained mainly through the development of a FDTD code. It is found that the U-slot patch on a foam substrate of about 0.08 lambda thick can be designed to attain 20-30% impedance as well as gain bandwidths without the need of parasitic patches on another layer or on the same layer. The far-field patterns have good copolar and crosspolar characteristics. By altering the patch width or feed position, the wideband characteristic can be changed into a dual-frequency characteristic. Simulation results are in good agreement with measurements. C1 Univ Missouri, Dept Elect Engn, Columbia, MO 65211 USA. City Univ Hong Kong, Hong Kong, Hong Kong. Decibel Prod, Dallas, TX USA. NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. RP Lee, KF (reprint author), Univ Missouri, Dept Elect Engn, Columbia, MO 65211 USA. OI LUK, Kwai Man/0000-0002-5910-9604 NR 9 TC 139 Z9 141 U1 0 U2 10 PU IEE-INST ELEC ENG PI HERTFORD PA MICHAEL FARADAY HOUSE SIX HILLS WAY STEVENAGE, HERTFORD SG1 2AY, ENGLAND SN 1350-2417 J9 IEE P-MICROW ANTEN P JI IEE Proc.-Microw. Antennas Propag. PD OCT PY 1997 VL 144 IS 5 BP 354 EP 358 DI 10.1049/ip-map:19971334 PG 5 WC Engineering, Electrical & Electronic; Telecommunications SC Engineering; Telecommunications GA ZQ529 UT WOS:000073871200013 ER PT J AU Shaeffer, JF Cooper, BA Hom, KW Baucke, RC Talcott, NA AF Shaeffer, JF Cooper, BA Hom, KW Baucke, RC Talcott, NA TI A review of bistatic k-space imaging for electromagnetic prediction codes for scattering and antennas SO IEEE ANTENNAS AND PROPAGATION MAGAZINE LA English DT Review DE multistatic scattering; electromagnetic imaging; k-space; scattering centers AB A bistatic k-space imaging concept for frequency-domain (FD) electromagnetic (EM) computer codes is presented. The concept enables the computation of images without the frequency sweep required for experimental images, resulting in a significant reduction in computational effort. This analytical imaging technique uses bistatic radiation computed from a generalized radiation integral. Images permit physical insight and understanding into how a radiation or scattering pattern is produced, by decomposition of the resultant radiation into contributions from localized scattering centers, or hot spots. Knowledge of these hot spots permits a user to understand and modify the structure to obtain desired features. C1 NASA,LANGLEY RES CTR,HAMPTON,VA 23681. GE CO,ELECT AIRCRAFT ENGINE BUSINESS GRP,CINCINNATI,OH. RP Shaeffer, JF (reprint author), MARIETTA SCI INC,376 POWDER SPRINGS ST,SUITE 240A,MARIETTA,GA 30064, USA. NR 7 TC 5 Z9 5 U1 0 U2 0 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 SN 1045-9243 J9 IEEE ANTENNAS PROPAG JI IEEE Antennas Propag. Mag. PD OCT PY 1997 VL 39 IS 5 BP 21 EP 29 DI 10.1109/74.637104 PG 9 WC Engineering, Electrical & Electronic; Telecommunications SC Engineering; Telecommunications GA YH412 UT WOS:A1997YH41200005 ER PT J AU Heim, PJS Dagenais, M Krainak, MA Leavitt, R AF Heim, PJS Dagenais, M Krainak, MA Leavitt, R TI High-sensitivity semiconductor optically preamplified Q-PPM receiver SO IEEE PHOTONICS TECHNOLOGY LETTERS LA English DT Article DE optical receivers; pulse position modulation; satellite communications; semiconductor optical amplifiers AB An optically preamplified receiver for 980-nm laser intersatellite communications Is reported. A record sensitivity of 330 photons/bit for a semiconductor optically preamplified receiver is obtained at 50 Mb/s with quaternary pulse-position-modulation (Q-PPM). The experimental results are shown to be in excellent agreement with a novel exact calculation of the optically preamplified receiver Q-PPM bit-error rate (BER). Calculated performance based on these results shows that with an improved optical transmitter the receiver attains 1.5 dB higher sensitivity than previously achieved at this wavelength. C1 NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. ARMY RES LAB,ADELPHI,MD 20783. RP Heim, PJS (reprint author), UNIV MARYLAND,DEPT ELECT ENGN,COLLEGE PK,MD 20742, USA. NR 13 TC 1 Z9 1 U1 0 U2 0 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 SN 1041-1135 J9 IEEE PHOTONIC TECH L JI IEEE Photonics Technol. Lett. PD OCT PY 1997 VL 9 IS 10 BP 1394 EP 1396 DI 10.1109/68.623274 PG 3 WC Engineering, Electrical & Electronic; Optics; Physics, Applied SC Engineering; Optics; Physics GA XV977 UT WOS:A1997XV97700032 ER PT J AU Pentakalos, OI Menasce, DA Halem, M Yesha, Y AF Pentakalos, OI Menasce, DA Halem, M Yesha, Y TI Analytical performance modeling of hierarchical mass storage systems SO IEEE TRANSACTIONS ON COMPUTERS LA English DT Article DE mass storage systems; queuing network modeling; mean-value analysis; Unitree central file manager; compression; file abstraction AB Mass storage systems are finding greater use in scientific computing research environments for retrieving and archiving the large volumes of data generated and manipulated by scientific computations. This paper presents a queuing network model that can be used to carry out capacity planning studies of hierarchical mass storage systems. Measurements taken on a Unitree mass storage system and a detailed workload characterization provided the workload intensity and resource demand parameters for the various types of read and write requests. The performance model developed here is based on approximations to multiclass Mean Value Analysis of queuing networks. The approximations were validated through the use of discrete event simulation and the complete model was validated and calibrated through measurements. The resulting model was used to analyze three different scenarios: effect of workload intensity increase, use of file compression at the server and client, and use of file abstractions. C1 GODDARD SPACE FLIGHT CTR,CTR EXCELLENCE SPACE DATA & INFORMAT SCI,GREENBELT,MD 20771. GEORGE MASON UNIV,DEPT COMP SCI,FAIRFAX,VA 22030. NASA,GODDARD SPACE FLIGHT CTR,DIV SPACE DATA & COMP,GREENBELT,MD 20771. RP Pentakalos, OI (reprint author), UNIV MARYLAND BALTIMORE CTY,GREENBELT,MD 20771, USA. NR 25 TC 7 Z9 7 U1 0 U2 0 PU IEEE COMPUTER SOC PI LOS ALAMITOS PA 10662 LOS VAQUEROS CIRCLE, PO BOX 3014, LOS ALAMITOS, CA 90720-1314 SN 0018-9340 J9 IEEE T COMPUT JI IEEE Trans. Comput. PD OCT PY 1997 VL 46 IS 10 BP 1103 EP 1118 DI 10.1109/12.628395 PG 16 WC Computer Science, Hardware & Architecture; Engineering, Electrical & Electronic SC Computer Science; Engineering GA YB648 UT WOS:A1997YB64800005 ER PT J AU YadidPecht, O Fossum, ER AF YadidPecht, O Fossum, ER TI Wide intrascene dynamic range CMOS APS using dual sampling SO IEEE TRANSACTIONS ON ELECTRON DEVICES LA English DT Article AB A CMOS active pixel sensor that achieves wide intrascene dynamic range using dual sampling is reported. A 64 x 64 element prototype sensor with dual output architecture was fabricated using a 1.2-mu m n-well CMOS process with 20.4-mu m pitch photodiode-type active pixels. The sensor achieves an intrascene dynamic range of 109 dB without nonlinear companding. C1 PHOTOBIT,LA CRESCENTA,CA 91214. RP YadidPecht, O (reprint author), CALTECH,JET PROP LAB,4800 OAK GROVE DR,PASADENA,CA 91109, USA. NR 13 TC 122 Z9 125 U1 1 U2 4 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 SN 0018-9383 J9 IEEE T ELECTRON DEV JI IEEE Trans. Electron Devices PD OCT PY 1997 VL 44 IS 10 BP 1721 EP 1723 DI 10.1109/16.628828 PG 3 WC Engineering, Electrical & Electronic; Physics, Applied SC Engineering; Physics GA XX729 UT WOS:A1997XX72900024 ER PT J AU Nakamura, J Pain, B Nomoto, T Nakamura, T Fossum, ER AF Nakamura, J Pain, B Nomoto, T Nakamura, T Fossum, ER TI On-focal-plane signal processing for current-mode active pixel sensors SO IEEE TRANSACTIONS ON ELECTRON DEVICES LA English DT Article ID DYNAMIC CURRENT MIRRORS AB On-focal-plane signal processing for current-mode active pixel sensors (APS), including fixed pattern noise (FPN) suppression and high-resolution analog-to-digital conversion (ADC), is presented. An FPN suppression circuit that removes the offset current variation between pixels by using a combination of an n-type and a p-type current copier cell is described. The FPN suppression circuit exhibits linear transfer characteristics in the input current range from 0 to 30 mu A. On-chip ADC is expected to improve imaging system performance and reliability, while reducing system size, weight, and cost. Operation and performance of a current-mode second-order incremental Delta-Sigma A/D converter with column parallel architecture and for high-resolution and medium-slow-speed applications is presented. A 12-bit resolution with +/-1.5 LSB accuracy at the conversion rate of 5.6 kHz was obtained. The LSB corresponds to less than twelve signal charges of current-mode 10-mu m pixel APS's. Based on the experimental results, a brief description of a possible image sensor with the on-chip signal processing is also described. C1 CALTECH,JET PROP LAB,PASADENA,CA 91109. PHOTOBIT,LA CRESCENTA,CA 91214. RP Nakamura, J (reprint author), OLYMPUS OPT CO LTD,TOKYO 192,JAPAN. NR 20 TC 41 Z9 42 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 0018-9383 J9 IEEE T ELECTRON DEV JI IEEE Trans. Electron Devices PD OCT PY 1997 VL 44 IS 10 BP 1747 EP 1758 DI 10.1109/16.628832 PG 12 WC Engineering, Electrical & Electronic; Physics, Applied SC Engineering; Physics GA XX729 UT WOS:A1997XX72900028 ER PT J AU Zhou, ZM Pain, B Fossum, ER AF Zhou, ZM Pain, B Fossum, ER TI CMOS active pixel sensor with on-chip successive approximation analog-to-digital converter SO IEEE TRANSACTIONS ON ELECTRON DEVICES LA English DT Article ID IR FOCAL-PLANE; CONVERSION; ARRAYS; ADC AB The first CMOS active pixel sensor (APS) with on-chip column-parallel successive-approximation analog-to-digital converter (ADC) is reported. A 64 x 64 element CMOS APS implemented in a 1.2-mu m n-well single-poly, double-metal process with 24-mu m pixel pitch is integrated with a 64 x 1 array of column parallel successive approximation 8-b ADC's. Good image quality was observed. The capacitively-coupled ADC's dissipate approximately 1 mu W-s/ksample and occupy 0.05 mm(2) of chip area. C1 PHOTOBIT, LA CRESCENTA, CA 91214 USA. RP Zhou, ZM (reprint author), CALTECH, JET PROP LAB, 4800 OAK GROVE DR, PASADENA, CA 91109 USA. NR 18 TC 46 Z9 49 U1 1 U2 4 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI PISCATAWAY PA 445 HOES LANE, PISCATAWAY, NJ 08855-4141 USA SN 0018-9383 J9 IEEE T ELECTRON DEV JI IEEE Trans. Electron Devices PD OCT PY 1997 VL 44 IS 10 BP 1759 EP 1763 PG 5 WC Engineering, Electrical & Electronic; Physics, Applied SC Engineering; Physics GA XX729 UT WOS:A1997XX72900029 ER PT J AU Zhou, ZM Pain, B Fossum, ER AF Zhou, ZM Pain, B Fossum, ER TI Frame-transfer CMOS active pixel sensor with pixel pinning SO IEEE TRANSACTIONS ON ELECTRON DEVICES LA English DT Article ID ARCHITECTURES AB The first frame-transfer CMOS active pixel sensor (APS) is reported. The sensor architecture integrates an array of active pixels with an array of passive memory cells. Charge integration amplifier-based readout of the memory cells permits binning of pixels for variable resolution imaging. A 32 x 32 element prototype sensor with 24-mu m pixel pitch was fabricated in 1.2-mu m CMOS and demonstrated. C1 PHOTOBIT, LA CRESCENTA, CA 91214 USA. RP Zhou, ZM (reprint author), CALTECH, JET PROP LAB, 4800 OAK GROVE DR, PASADENA, CA 91109 USA. NR 10 TC 29 Z9 31 U1 1 U2 4 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI PISCATAWAY PA 445 HOES LANE, PISCATAWAY, NJ 08855-4141 USA SN 0018-9383 J9 IEEE T ELECTRON DEV JI IEEE Trans. Electron Devices PD OCT PY 1997 VL 44 IS 10 BP 1764 EP 1768 PG 5 WC Engineering, Electrical & Electronic; Physics, Applied SC Engineering; Physics GA XX729 UT WOS:A1997XX72900030 ER PT J AU Goverdhanam, K Simons, RN Katehi, LPB AF Goverdhanam, K Simons, RN Katehi, LPB TI Coplanar stripline components for high-frequency applications SO IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES LA English DT Article DE band-stop filters; coplanar stripline; discontinuities; FDTD technique; scattering parameters; TRL calibration; uniplanar circuits ID DISCONTINUITIES; ANTENNA AB In this paper, coplanar stripline (CPS) discontinuities such as a narrow transverse slit, a symmetric step, a right-angle bend, and a T-junction are characterized and their performance is parameterized with respect to frequency and geometry, In addition, filter design using coplanar stripline discontinuities has been investigated, Lumped equivalent circuits are presented for some of the discontinuities. The element values are obtained from the measured discontinuity scattering parameters, The experimental results are compared with theoretical data obtained using the finite-difference time-domain (FDTD) technique for validation and show very good agreement. C1 NASA,LEWIS RES CTR,NYMA GRP,CLEVELAND,OH 44135. RP Goverdhanam, K (reprint author), UNIV MICHIGAN,RADIAT LAB,ANN ARBOR,MI 48109, USA. NR 9 TC 39 Z9 39 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 OCT PY 1997 VL 45 IS 10 BP 1725 EP 1729 DI 10.1109/22.641719 PN 1 PG 5 WC Engineering, Electrical & Electronic SC Engineering GA YA625 UT WOS:A1997YA62500008 ER PT J AU Ueng, SK Sikorski, C Ma, KL AF Ueng, SK Sikorski, C Ma, KL TI Out-of-core streamline visualization on large unstructured meshes SO IEEE TRANSACTIONS ON VISUALIZATION AND COMPUTER GRAPHICS LA English DT Article DE streamline visualization; interactive techniques; unstructured meshes; computational fluid dynamics; out-of-core algorithms; memory management; disk management ID GRIDS AB This paper presents an out-of-core approach for interactive streamline construction on large unstructured tetrahedral meshes containing millions of elements. The out-of-core algorithm uses an octree to partition and restructure the raw data into subsets stored into disk flies for fast data retrieval. A memory management policy tailored to the streamline calculations is used such that, during the streamline construction, only a very small amount of data are brought into the main memory on demand. By carefully scheduling computation and data fetching, the overhead of reading data from the disk is significantly reduced and good memory performance results. This out-of-core algorithm makes possible interactive streamline visualization of large unstructured-grid data sets on a single mid-range workstation with relatively low main-memory capacity: 5-15 megabytes. We also demonstrate that this approach is much more efficient than relying on virtual memory and operating system's paging algorithms. C1 Natl Taiwan Ocean Univ, Dept Comp Sci, Chilung, Taiwan. Univ Utah, Dept Comp Sci, Salt Lake City, UT 84112 USA. NASA, Langley Res Ctr, Inst Comp Appl Sci & Engn, Hampton, VA 23861 USA. RP Ueng, SK (reprint author), Natl Taiwan Ocean Univ, Dept Comp Sci, 2 Pei Ning Rd, Chilung, Taiwan. EM skueng@cs.ntou.edu.tw; sikorski@cs.utah.edu; kma@icase.edu NR 20 TC 88 Z9 92 U1 1 U2 7 PU IEEE COMPUTER SOC PI LOS ALAMITOS PA 10662 LOS VAQUEROS CIRCLE, PO BOX 3014, LOS ALAMITOS, CA 90720-1314 USA SN 1077-2626 EI 1941-0506 J9 IEEE T VIS COMPUT GR JI IEEE Trans. Vis. Comput. Graph. PD OCT-DEC PY 1997 VL 3 IS 4 BP 370 EP 380 DI 10.1109/2945.646239 PG 11 WC Computer Science, Software Engineering SC Computer Science GA YP676 UT WOS:000071302800008 ER PT J AU Garg, VK Abhari, RS AF Garg, VK Abhari, RS TI Comparison of predicted and experimental Nusselt number for a film cooled rotating blade SO INTERNATIONAL JOURNAL OF HEAT AND FLUID FLOW LA English DT Article DE film cooling; three-dimensional Navier-Stokes analysis; rotating blade ID HEAT-TRANSFER; TURBINE; HOLES; FLOW AB The predictions from a three-dimensional (3-D) Navier-Stokes code have been compared to the Nusselt number data obtained on a film-cooled, rotating turbine blade. The blade chosen is the ACE rotor with five rows containing 93 film-cooling holes covering the entire span. This is the only film-cooled rotating blade on which experimental heat transfer data are available for the present comparison. Over 2.25 million grid points are used to compute the flow over the blade. Usually, in a film cooling computation on a stationary blade, the computational domain is just one spanwise pitch of the film-cooling holes, with periodic boundary conditions in the span direction. However, for a rotating blade, the computational domain consists of the entire blade span from hub to tip, as well as the tip clearance region. As far as the authors know, the present work is the first comparison of the prediction of surface heat transfer using a 3-D Navier-Stokes code with film injection and the measured heat flux on a fully film-cooled rotating transonic turbine blade. A reasonably good comparison with the measured data is obtained on the suction surface, particularly near the hub section. On the pressure surface, however, the comparison between the data and the prediction is poor. A potential reason for the discrepancy on the pressure surface could be the presence of unsteady effects caused by stator-rotor interaction in the experiments, which are not modeled in the present numerical computations. (C) 1997 by Elsevier Science Inc. C1 OHIO STATE UNIV,DEPT AEROSP ENGN APPL MECH & AVIAT,COLUMBUS,OH 43210. RP Garg, VK (reprint author), NASA,LEWIS RES CTR,AYT CORP,MAIL STOP 5-11,CLEVELAND,OH 44135, USA. NR 32 TC 28 Z9 32 U1 0 U2 0 PU ELSEVIER SCIENCE INC PI NEW YORK PA 655 AVENUE OF THE AMERICAS, NEW YORK, NY 10010 SN 0142-727X J9 INT J HEAT FLUID FL JI Int. J. Heat Fluid Flow PD OCT PY 1997 VL 18 IS 5 BP 452 EP 460 DI 10.1016/S0142-727X(97)00031-3 PG 9 WC Thermodynamics; Engineering, Mechanical; Mechanics SC Thermodynamics; Engineering; Mechanics GA XX872 UT WOS:A1997XX87200002 ER PT J AU Lim, D Seraji, H AF Lim, D Seraji, H TI Configuration control of a mobile dexterous robot: Real-time implementation and experimentation SO INTERNATIONAL JOURNAL OF ROBOTICS RESEARCH LA English DT Article ID REDUNDANT MANIPULATORS AB This article describes the design and implementation of a realtime control system with multiple modes of operation for a mobile, dexterous manipulator: The manipulator under study is a kinematically redundant seven-degree-of-freedom arm from Robotics Research Corporation, mounted on a one-degree-of-freedom motorized platform. The manipulator-plus-platform system has two degrees-of-redundancy for the basic task of end-effector placement and orientation. The redundancy resolution is achieved by accomplishing two additional tasks using the configuration-control technique. The system allows a choice of arm-angle control or collision avoidance for the seventh task, and elbow-angle control or platform placement for the eighth task. In addition, joint-limit avoidance tasks ale automatically invoked when any of the manipulator joints approach their limits. The system is robust to singularities, and the user is capable of assigning weighting factors to end-effector motion, joint-limit avoidance, and redundancy resolution tasks. The motion-control algorithms are executed at 1.1 ms on two MC68040 processors in a VME-bus environment running the VxWorks real-time operating system. The article describes the hardware and software components of the manipulator-control system. Experimental results on real-time control of the Robotics Research arm are also presented. RP Lim, D (reprint author), CALTECH,JET PROP LAB,4800 OAK GROVE DR,PASADENA,CA 91109, USA. NR 16 TC 11 Z9 11 U1 0 U2 0 PU SAGE PUBLICATIONS INC PI THOUSAND OAKS PA 2455 TELLER RD, THOUSAND OAKS, CA 91320 SN 0278-3649 J9 INT J ROBOT RES JI Int. J. Robot. Res. PD OCT PY 1997 VL 16 IS 5 BP 601 EP 618 DI 10.1177/027836499701600502 PG 18 WC Robotics SC Robotics GA YE534 UT WOS:A1997YE53400002 ER PT J AU Li, YW Elishakoff, I Starnes, JH Bushnell, D AF Li, YW Elishakoff, I Starnes, JH Bushnell, D TI Effect of the thickness variation and initial imperfection on buckling of composite cylindrical shells: Asymptotic analysis and numerical results by BOSOR4 and PANDA2 SO INTERNATIONAL JOURNAL OF SOLIDS AND STRUCTURES LA English DT Article ID PROGRAM; DESIGN; PANELS AB This study is an extension of a previous investigation of the combined effect of axisymmetric thickness variation and axisymmetric initial geometric imperfection on buckling of isotropic shells under uniform axial compression. Here the anisotropic cylindrical shells are investigated by means of Koiter's energy criterion. An asymptotic formula is derived which can be used to determine the critical buckling load for composite shells with combined initial geometric imperfection and thickness variation. Results are compared with those obtained by the software packages BOSOR4 and PANDA2. (C) 1997 Elsevier Science Ltd. C1 NASA,LANGLEY RES CTR,HAMPTON,VA 23664. LOCKHEED MISSILES & SPACE CO INC,PALO ALTO,CA 94304. RP Li, YW (reprint author), FLORIDA ATLANTIC UNIV,DEPT MECH ENGN,BOCA RATON,FL 33431, USA. NR 19 TC 24 Z9 25 U1 1 U2 4 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, ENGLAND OX5 1GB SN 0020-7683 J9 INT J SOLIDS STRUCT JI Int. J. Solids Struct. PD OCT PY 1997 VL 34 IS 28 BP 3755 EP 3767 DI 10.1016/S0020-7683(96)00230-2 PG 13 WC Mechanics SC Mechanics GA XX583 UT WOS:A1997XX58300007 ER PT J AU LeBlanc, A Rowe, R Evans, H West, S Shackelford, L Schneider, V AF LeBlanc, A Rowe, R Evans, H West, S Shackelford, L Schneider, V TI Muscle atrophy during long duration bed rest SO INTERNATIONAL JOURNAL OF SPORTS MEDICINE LA English DT Article; Proceedings Paper CT International Workshop on Muscle Research in Space CY OCT 13-16, 1996 CL UNIV BERN, BERN, SWITZERLAND SP Univ Bern, European Space Agency, Natl Space Agencies Canada, CNES, France, DARA, Germany, NASDA, Japan, NASA HO UNIV BERN DE muscle atrophy; bed rest; disuse atrophy; magnetic resonance imaging; microgravity; human C1 BAYLOR COLL MED,HOUSTON,TX 77030. JOHNSON SPACE FLIGHT CTR,HOUSTON,TX. NASA HEADQUARTERS,WASHINGTON,DC. NR 6 TC 26 Z9 26 U1 0 U2 1 PU GEORG THIEME VERLAG PI STUTTGART PA P O BOX 30 11 20, D-70451 STUTTGART, GERMANY SN 0172-4622 J9 INT J SPORTS MED JI Int. J. Sports Med. PD OCT PY 1997 VL 18 SU 4 BP S283 EP S285 DI 10.1055/s-2007-972726 PG 3 WC Sport Sciences SC Sport Sciences GA YF075 UT WOS:A1997YF07500006 PM 9391832 ER PT J AU Chamis, CC Gotsis, PK AF Chamis, CC Gotsis, PK TI Laminate analogy for composites enhanced concrete structures SO JOURNAL OF ADVANCED MATERIALS LA English DT Article AB A new and effective method is described to design composites to repair damage or enhance the overload strength of concrete infrastructures. The method is based on laminate analogy which is derivable from composite mechanics and available in computer codes. It is used to simulate structural sections made from reinforced concrete which are typical in infrastructures as well as select reinforced concrete structures. The structural sections are represented by a number of layers through the thickness where different layers are used for the concrete, for the reinforcing steel in concrete, and for the composite. The reinforced concrete structures are represented with finite elements where the element stiffness parameters are from the structural sections which are represented by the laminate analogy. The load carrying capability of the structure is determined by progressive structural fracture. Results show up to 40 percent improvements for damage and for overload enhancement with relatively small laminate thickness for the structural sections and up to three times for the composite enhanced select structures (arch and dome). C1 NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. RP Chamis, CC (reprint author), NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. NR 6 TC 3 Z9 3 U1 0 U2 0 PU SAMPE PUBLISHERS PI COVINA PA 1161 PARKVIEW DRIVE, COVINA, CA 91722 USA SN 1070-9789 J9 J ADV MATER JI J. Adv. Mater. PD OCT PY 1997 VL 29 IS 1 BP 3 EP 10 PG 8 WC Materials Science, Multidisciplinary SC Materials Science GA YM896 UT WOS:000071112700002 ER PT J AU Hinkley, JA Messier, BC Marchello, JM AF Hinkley, JA Messier, BC Marchello, JM TI Rapid consolidation of unidirectional graphite/thermoplastic ribbon SO JOURNAL OF ADVANCED MATERIALS LA English DT Article ID COMPOSITES AB An inexpensive apparatus was designed to simulate some features of on-the-fly thermal welding in robotic placement of thermoplastic prepreg ribbon. Studies of a polyimide oligomer have shown how ply/ply weld strength depends on weld time, temperature, and pressure. Examination of the data at very short effective times reveals a contribution from wetting amounting to 20 percent of the ultimate strength followed by the expected time((1/4)) behavior. Welding at low pressures produces high levels of intra-ply voids. Pressures up to 1.7 MPa (250 psi) produce more consistent welds and virtually eliminate voids. This has permitted a study of the conditions required for achieving the limiting ply/ply cohesive strength in simulated tow placement. C1 NASA, Langley Res Ctr, Hampton, VA 23665 USA. Old Dominion Univ, Norfolk, VA USA. RP Hinkley, JA (reprint author), NASA, Langley Res Ctr, Hampton, VA 23665 USA. NR 12 TC 1 Z9 1 U1 1 U2 1 PU SAMPE PUBLISHERS PI COVINA PA 1161 PARKVIEW DRIVE, COVINA, CA 91722 USA SN 1070-9789 J9 J ADV MATER JI J. Adv. Mater. PD OCT PY 1997 VL 29 IS 1 BP 43 EP 47 PG 5 WC Materials Science, Multidisciplinary SC Materials Science GA YM896 UT WOS:000071112700008 ER PT J AU Pueschel, RF Hallett, J Strawa, AW Howard, SD Ferry, GV Foster, T Arnott, WP AF Pueschel, RF Hallett, J Strawa, AW Howard, SD Ferry, GV Foster, T Arnott, WP TI Aerosol and cloud particles in tropical cirrus anvil: Importance to radiation balance SO JOURNAL OF AEROSOL SCIENCE LA English DT Article ID SCATTERING SPECTROMETER PROBE; ICE CRYSTALS; CLIMATE; FEEDBACK; PARAMETERIZATION; MICROPHYSICS; CALIBRATION; TROPOSPHERE; TEMPERATURE; EXTINCTION AB With a multi-instrument approach, we determined the particle size spectrum between 20 nm and 1.6 mm diameter in the outflow portions of a convective tropical cloud. The measured particle size spectrum covered approximate to 12 orders of magnitude particle concentration over approximate to 5 orders of magnitude particle size. Within this size interval, the particle spectrum revealed three modes: A cirrus haze nucleus mode, a cirrus haze particle mode, and a cirrus ice particle mode. In the optically active size range D > 0.4 mu m, the particle population inside the cirrus cloud was enhanced above "background" concentrations by almost 4 orders of magnitude The prevalence of submicron particles led to the definition of cirrus haze nuclei which can grow along Kohler curves to radiatively important sizes. While cirrus ice particles carried most of the condensate mass, the cirrus haze particles dominated the surface area. Consequently, the presence of cirrus haze particles tripled extinction across the whole (visible and infrared) spectrum, and enhanced the IR single-scatter albedo of the cloud. (C) 1997 Elsevier Science Ltd. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Univ Nevada, Desert Res Inst, Reno, NV 89506 USA. Symtech Corp, Arlington, VA 22202 USA. Calif Polytech State Univ San Luis Obispo, San Luis Obispo, CA 93407 USA. RP Pueschel, RF (reprint author), NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. NR 42 TC 8 Z9 8 U1 0 U2 3 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0021-8502 J9 J AEROSOL SCI JI J. Aerosol. Sci. PD OCT PY 1997 VL 28 IS 7 BP 1123 EP 1136 DI 10.1016/S0021-8502(97)00022-0 PG 14 WC Engineering, Chemical; Engineering, Mechanical; Environmental Sciences; Meteorology & Atmospheric Sciences SC Engineering; Environmental Sciences & Ecology; Meteorology & Atmospheric Sciences GA YM833 UT WOS:000071106000002 ER PT J AU Noor, AK Starnes, JH Peters, JM AF Noor, AK Starnes, JH Peters, JM TI Curved sandwich panels subjected to temperature gradient and mechanical loads SO JOURNAL OF AEROSPACE ENGINEERING LA English DT Article ID REDUCED BASIS TECHNIQUE; FLAT AB The results of a detailed study of the nonlinear response of curved sandwich panels with composite face sheets, subjected to a temperature gradient through the thickness combined with mechanical loadings, are presented. The analysis is based on a first-order shear-deformation Sanders-Budiansky-type theory, including the effects of large displacements, moderate rotations, transverse shear deformation, and laminated anisotropic material behavior. A mixed formulation is used with the fundamental unknowns consisting of the generalized displacements and the stress resultants of the panel. The nonlinear displacements, strain energy, principal strains, transverse shear stresses, transverse shear strain energy density, and their hierarchical sensitivity coefficients are evaluated. The hierarchical sensitivity coefficients measure the sensitivity of the nonlinear response to variations in the panel parameters, the effective properties of-the face sheet layers and the core, and the micromechanical parameters. Numerical results are presented for cylindrical panels subjected to combined pressure loading, edge shortening or extension, edge shear, and a temperature gradient through the thickness. The results show the effects of variations in the loading and the panel aspect ratio, on the nonlinear response, and its sensitivity to changes in the various panel, effective layer, and micromechanical parameters. RP Noor, AK (reprint author), UNIV VIRGINIA,CTR ADV COMPUTAT TECHNOL,NASA,LANGLEY RES CTR,HAMPTON,VA 23681, USA. NR 23 TC 8 Z9 8 U1 0 U2 0 PU ASCE-AMER SOC CIVIL ENGINEERS PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2398 SN 0893-1321 J9 J AEROSPACE ENG JI J. Aerosp. Eng. PD OCT PY 1997 VL 10 IS 4 BP 143 EP 161 DI 10.1061/(ASCE)0893-1321(1997)10:4(143) PG 19 WC Engineering, Aerospace; Engineering, Civil SC Engineering GA XX522 UT WOS:A1997XX52200002 ER PT J AU Wu, WH Lu, JY Jones, AR Mortley, DG Loretan, PA Bonsi, CK Hill, WA AF Wu, WH Lu, JY Jones, AR Mortley, DG Loretan, PA Bonsi, CK Hill, WA TI Proximate composition, amino acid profile, fatty acid composition, and mineral content of peanut seeds hydroponically grown at elevated CO2 levels SO JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY LA English DT Article DE CELSS; hydroponic; NFT; elevated CO2 levels; peanut ID STORAGE AB Peanut plants (Arachis hypogaea L. cv. Georgia Red) were grown hydroponically using a recirculating nutrient film technique. The effect of CO2 enrichment on nutritive composition of hydroponic peanut seeds was examined at two elevated CO2 levels (700 and 1400 ppm) that simulate potential conditions in National Aeronautics and Space Administration (NASA) Controlled Ecological Life-Support Systems (CELSS) and compared to ambient CO2 condition in hydroponics (the control). Plants were harvested at 97 days after planting, and the seeds were air-dried and analyzed for composition. Percentages of crude protein, crude fat, ash, and carbohydrate of hydroponic peanut seeds were around 30%, 30%, 3%, and 30%, respectively. The major amino acids were aspartic acid, glutamic acid, and arginine. The limiting amino acid of peanut, methionine, was 1.2%. Linoleic acid was the major fatty acid, followed by oleic and palmitic acids. The major mineral elements were K, P, Mg, and Ca. The results showed that certain peanut varieties can be grown hydroponically. The composition of the hydroponically grown peanuts is generally similar to reported peanut composition The nutrient composition was not affected at the elevated CO2 concentrations investigated. C1 TUSKEGEE UNIV,GEORGE WASHINGTON CARVER AGR EXPT STN,NASA,TUSKEGEE,AL 36088. NR 32 TC 12 Z9 13 U1 1 U2 9 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 SN 0021-8561 J9 J AGR FOOD CHEM JI J. Agric. Food Chem. PD OCT PY 1997 VL 45 IS 10 BP 3863 EP 3866 DI 10.1021/jf970077f PG 4 WC Agriculture, Multidisciplinary; Chemistry, Applied; Food Science & Technology SC Agriculture; Chemistry; Food Science & Technology GA YB397 UT WOS:A1997YB39700027 ER PT J AU Brest, CL Rossow, WB Roiter, MD AF Brest, CL Rossow, WB Roiter, MD TI Update of radiance calibrations for ISCCP SO JOURNAL OF ATMOSPHERIC AND OCEANIC TECHNOLOGY LA English DT Article ID CLOUD-CLIMATOLOGY-PROJECT; RADIOMETRIC CALIBRATION; CHANNELS; NOAA-7; SPACECRAFT; SENSORS AB Since July 1983 ISCCP has collected, normalized, and calibrated radiance data (visible and thermal infrared) from the imaging radiometers on the National Oceanic and Atmospheric Administration polar orbiters and from the geostationary satellites GOES, Meteosat, and GMS. Although analyzed by the International Satellite Cloud Climatology Project (ISCCP) to obtain information about clouds, this global radiance dataset also represents a valuable resource for other remote sensing studies. Examination of the 8-yr cloud climatology produced with the first version of the ISCCP calibration revealed artifacts in the global means that coincided with the changes in the afternoon polar orbiters (used as a reference standard), as well as some localized anomalies related to occasional errors in the geostationary normalizations. This paper reports the changes to the ISCCP normalization and calibration procedures (originally reported in Brest and Rossow) that have been made to reduce these artifacts and errors and to produce a revised calibration. The key assumption, made after examining more than 10 years of global data, is that the mean properties of the earth are more nearly constant over this timescale than are the calibration of these radiometers. The authors conclude that the relative calibrations of the radiances used by ISCCP are now uncertain on average by no more than +/-0.01-0.02 absolute, +/-3%-5% relative, for visible (VIS) radiances and +/-1-2 K absolute, +/-0.3%-1.0% relative, for infrared (IR) radiances. The absolute calibration uncertainty is estimated to be about 10% for VIS and 2% for IR. The history of efforts to calibrate the Advanced Very High Resolution Radiometer (AVHRR) points to some lessons important to future spacecraft observations of climate change: Real decadal-scale changes of the earth are much smaller in magnitude than uncertainties in calibration changes and cannot be reliably detected without significant improvements of instrument calibration; infrequent aircraft calibration results for AVHRR with their attendant uncertainties make it difficult to distinguish real interannual variability from short-term calibration changes and suggest that something more will be required to obtain the needed accuracy: and finally, even calibrations based on onboard targets may not be sufficient, given that the authors still find differences in IR calibrations of more than 1 K. These results suggest, in particular, that reliance on one method of calibration for future spacecraft missions is unlikely to reduce calibration uncertainties enough for climate change monitoring. Even with improvements in all of these areas, the relative accuracy attained will only be apparent in the context of a long data record. RP Brest, CL (reprint author), NASA,GODDARD SPACE FLIGHT CTR,INST SPACE STUDIES,SCI SYST & APPLICAT INC,2880 BROADWAY,NEW YORK,NY 10025, USA. RI Rossow, William/F-3138-2015 NR 28 TC 103 Z9 104 U1 0 U2 1 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 SN 0739-0572 J9 J ATMOS OCEAN TECH JI J. Atmos. Ocean. Technol. PD OCT PY 1997 VL 14 IS 5 BP 1091 EP 1109 DI 10.1175/1520-0426(1997)014<1091:UORCFI>2.0.CO;2 PG 19 WC Engineering, Ocean; Meteorology & Atmospheric Sciences SC Engineering; Meteorology & Atmospheric Sciences GA XX162 UT WOS:A1997XX16200008 ER PT J AU Liu, AK Martin, S Kwok, R AF Liu, AK Martin, S Kwok, R TI Tracking of ice edges and ice floes by wavelet analysis of SAR images SO JOURNAL OF ATMOSPHERIC AND OCEANIC TECHNOLOGY LA English DT Article ID OCEAN; MOTION; ZONE AB This paper demonstrates the use of wavelet transforms in the tracking of sequential ice features in the ERS-1 synthetic aperture radar (SAR) imagery, especially in situations where feature correlation techniques fail to yield reasonable results, Examples include the evolution of the St. Lawrence polynya and summer sea ice change in the Beaufort Sea. For the polynya, the evolution of the region of young ice growth surrounding a polynya can be easily tracked by wavelet analysis due to the large backscatter difference between the young and old ice. Also within the polynya, a 2D fast Fourier transform (FFT) is used to identify the extent of the Langmuir circulation region, which is coincident with the wave-agitated frazil ice growth region, where the sea ice experiences its fastest growth. Therefore, the combination of wavelet and FFT analysis of SAR images provides for the large-scale monitoring of different polynya features. For summer ice, previous work shows that this is the most difficult period for ice trackers due to the lack of features on the sea ice cover. The multiscale wavelet analysis shows that this method delineates the detailed flee shapes during this period, so that between consecutive images, the flee translation and rotation can be estimated. C1 UNIV WASHINGTON, SCH OCEANOG, SEATTLE, WA 98195 USA. CALTECH, JET PROP LAB, PASADENA, CA 91109 USA. RP Liu, AK (reprint author), NASA, GODDARD SPACE FLIGHT CTR, OCEANS & ICE BRANCH, CODE 971, GREENBELT, MD 20771 USA. RI Kwok, Ron/A-9762-2008 OI Kwok, Ron/0000-0003-4051-5896 NR 12 TC 30 Z9 30 U1 0 U2 1 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 SN 0739-0572 J9 J ATMOS OCEAN TECH JI J. Atmos. Ocean. Technol. PD OCT PY 1997 VL 14 IS 5 BP 1187 EP 1198 DI 10.1175/1520-0426(1997)014<1187:TOIEAI>2.0.CO;2 PG 12 WC Engineering, Ocean; Meteorology & Atmospheric Sciences SC Engineering; Meteorology & Atmospheric Sciences GA XX162 UT WOS:A1997XX16200015 ER PT J AU Wong, TM Harrison, EF Gibson, GG Denn, FM AF Wong, TM Harrison, EF Gibson, GG Denn, FM TI On the determination of the optimal scan mode sequence for the TRMM CERES instrument SO JOURNAL OF ATMOSPHERIC AND OCEANIC TECHNOLOGY LA English DT Article ID BUDGET EXPERIMENT ERBE; ENERGY SYSTEM CERES; FLUCTUATION STATISTICS; RADIATION; EARTH; CLOUDS; SATELLITE; MISSION AB Clouds and the Earth's Radiant Energy System (CERES) is a NASA spaceborne measurement program for monitoring the radiation environment of the earth-atmosphere system. The first CERES instrument is scheduled to be launched on board the Tropical Rainfall Measuring Mission (TRMM) satellite in late 1997. In addition to gathering traditional cross-track fixed azimuth measurements for calculating monthly mean radiation fields, this single CERES scanner instrument will also be required to collect angular radiance data using a rotating azimuth configuration for developing new angular dependence models (ADMs). Since the TRMM single CERES instrument can only be run in either one of these two configurations at any one time, it will need to be operated in a cyclical pattern between these two scan modes to achieve the intended measurement goals. To minimize the errors in the derived monthly mean radiation field due to missing cross-track scanner measurements during this satellite mission, determination of the optimal scan mode sequence for the TRMM single CERES instrument is carried out. The Earth Radiation Budget Experiment S-4 daily mean cross-truck scanner data product for April and July 1985 and January 1986 is used with a simple temporal sampling scheme to produce simulated daily mean cross-track scanner measurements under different TRMM CERES operational scan mode sequences. Error analysis is performed on the monthly mean radiation fields derived from these simulated datasets. It is found that the best monthly mean result occurred when the cross-track scanner is operated on a ''2 days on and I day off'' mode. This scan mode sequence will effectively allow for 2 consecutive days of cross-track scanner data and 1 day of angular radiance measurement for each 3-day period. The root-mean-square errors for the monthly mean all-sky (clear sky) longwave and shortwave radiation field, due to missing cross-track scanner measurements for this particular case, are expected to be less than 2.5 (0.5) and 5.0 (1.5) W m(-2), respectively. C1 ANALYT SERV & MAT INC,HAMPTON,VA 23666. RP Wong, TM (reprint author), NASA,LANGLEY RES CTR,MS 420,HAMPTON,VA 23681, USA. NR 8 TC 1 Z9 1 U1 1 U2 1 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 SN 0739-0572 J9 J ATMOS OCEAN TECH JI J. Atmos. Ocean. Technol. PD OCT PY 1997 VL 14 IS 5 BP 1230 EP 1236 DI 10.1175/1520-0426(1997)014<1230:OTDOTO>2.0.CO;2 PG 7 WC Engineering, Ocean; Meteorology & Atmospheric Sciences SC Engineering; Meteorology & Atmospheric Sciences GA XX162 UT WOS:A1997XX16200019 ER PT J AU Persson, BJ Taylor, PR Lee, TJ AF Persson, BJ Taylor, PR Lee, TJ TI Ab initio geometry, quartic force field, and vibrational frequencies for P-4 SO JOURNAL OF CHEMICAL PHYSICS LA English DT Article ID MOLECULAR WAVE-FUNCTIONS; ANO BASIS-SETS; 2ND ROW ATOMS; PHOSPHORUS; P4; CLUSTERS; P2; P8 AB We have computed the equilibrium bond length and quartic force field for tetrahedral P-4 using coupled-cluster methods and a variety of extended basis sets. Our calculations include the effect of correlating core, as well as valence, electrons. As with earlier P-4 studies, our computed results show significant differences with current experimental estimates of both bond length and fundamental vibrational frequencies: possible reasons for this disagreement are discussed, with particular reference to the effects of the elevated temperatures used in gas-phase spectroscopic studies of P-4. Our calculated endothermicity relative to two P-2 molecules appears to be well converged with respect to correlation treatment and basis set, but again differs substantially from present experimental values, which we speculate are underestimates. (C) 1997 American Institute of Physics. C1 SAN DIEGO SUPERCOMP CTR, SAN DIEGO, CA 92186 USA. NASA, AMES RES CTR, MOFFETT FIELD, CA 94035 USA. RP Persson, BJ (reprint author), UNIV CALIF SAN DIEGO, DEPT CHEM & BIOCHEM, POB 85608, SAN DIEGO, CA 92186 USA. RI Lee, Timothy/K-2838-2012 NR 24 TC 24 Z9 24 U1 0 U2 2 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 OCT 1 PY 1997 VL 107 IS 13 BP 5051 EP 5057 DI 10.1063/1.474868 PG 7 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA XX840 UT WOS:A1997XX84000032 ER PT J AU Min, W Schubert, S AF Min, W Schubert, S TI The climate signal in regional moisture fluxes: A comparison of three global data assimilation products SO JOURNAL OF CLIMATE LA English DT Article ID CENTRAL UNITED-STATES; BOUNDARY-LAYER; PHYSICAL INITIALIZATION; NASA/DAO REANALYSES; RIVER BASIN; SUMMER; BUDGET; MODEL; HEAT; PRECIPITATION AB This study assesses the quality of estimates of climate variability in moisture flux and convergence from three assimilated datasets: two are reanalysis products generated at the Goddard Data Assimilation Office and the National Centers for Environmental Prediction-National Center for Atmospheric Research, and the third consists of the operational analyses generated at the European Centre for Medium-Range Weather Forecasts (ECMWF). The regions under study (the United States Great Plains, the Indian monsoon region, and Argentina east of the Andes) are characterized by frequent low-level jets and other interannual low-level wind variations tied to the large-scale flow. While the emphasis is on the reanalysis products, the comparison with the operational product is provided to help assess the improvements gained from a fixed analysis system. All three analyses capture the main moisture flux anomalies associated with selected extreme climate (drought and flood) events during the period 1985-93. The correspondence is strongest over the Great Plains and weakest over the Indian monsoon region reflecting differences in the observational coverage. For the reanalysis products, the uncertainties in the lower tropospheric winds is by far the dominant source of the discrepancies in the moisture flux anomalies in the middle latitude regions. Only in the Indian Monsoon region, where interannual variability in the low-level winds is comparatively small, does the moisture bias play a substantial role. In contrast, the comparisons with the operational product show differences in moisture that are comparable to the differences in the wind in all three regions. Compared with the fluxes, the anomalous moisture convergences show substantially larger differences among the three products. The best agreement occurs over the Great Plains region where all three products show vertically integrated moisture convergence during the floods and divergence during the drought with differences in magnitude of about 25%. The reanalysis products, in particular, show good agreement in depicting the different roles of the mean how and transients during the flood and drought periods. Differences between the three products in the other two regions exceed 100% reflecting differences in the low-level jets and the large-scale circulation patterns. The operational product tends to have locally larger amplitude convergence fields, which average out in area-mean budgets: this appears to be at least in part due to errors in the surface pressure fields and aliasing from the higher resolution of the original ECMWF fields. On average, the reanalysis products show higher coherence with each other than with the operational product in the estimates of interannual variability. This result is less clear in the Indian monsoon region where differences in the input observations appear to be an important factor. The agreement in the anomalous convergence patterns is, however, still rather poor even over relatively data-dense regions such as the United States Great Plains. These differences are attributed to deficiencies in the assimilating general circulation model's representations of the planetary boundary layer and orography, and a global observing system incapable of resolving the highly confined low-level winds associated with the climate anomalies. C1 UNIV SPACE RES ASSOC,SEABROOK,MD. NASA,GODDARD SPACE FLIGHT CTR,DATA ASSIMILAT OFF,GREENBELT,MD 20771. NR 60 TC 24 Z9 25 U1 0 U2 1 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 SN 0894-8755 J9 J CLIMATE JI J. Clim. PD OCT PY 1997 VL 10 IS 10 BP 2623 EP 2642 DI 10.1175/1520-0442(1997)010<2623:TCSIRM>2.0.CO;2 PG 20 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA YC705 UT WOS:A1997YC70500014 ER PT J AU Holdeman, JD Liscinsky, DS Oechsle, VL Samuelsen, GS Smith, CE AF Holdeman, JD Liscinsky, DS Oechsle, VL Samuelsen, GS Smith, CE TI Mixing of multiple jets with a confined subsonic crossflow .1. Cylindrical duct SO JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER-TRANSACTIONS OF THE ASME LA English DT Article; Proceedings Paper CT 41st International Gas Turbine and Aeroengine Congress and Exhibition CY JUN 10-13, 1996 CL BIRMINGHAM, ENGLAND ID FLOW; COMBUSTOR AB This paper summarizes NASA-supported experimental and computational results on the mixing of a role of jets with a confined subsonic crossflow in a cylindrical duct. The studies from which these results were excerpted investigated flow and geometric variations typical of the complex three-dimension flowfield in the combustion chambers in gas turbine engines. The principal observations were that the momentum-flux ratio and the number of orifices were significant variables. Jet penetration was critical, and jet penetration decreased as either the number of orifices increased or the momentum-flux ratio decreased. It also appeared that jet penetration remained similar with variations in orifice size, shape, spacing, and momentum-flux ratio when the number of orifices was proportional to the square root of the momentum-flux ratio. In the cylindrical geometry, planar variances are very sensitive to events in the near-wall region, so planar-averages must be considered in context with the distributions. The mass-flow ratios and orifices investigated were often very large (mass-flow ratio > 1 and ratio of orifice area-to-mainstream cross-sectional area up to 0.5), and the axial planes of interest were sometimes near the orifice trailing edge. Three-dimensional flow as a key part of efficient mixing and was observed for all configurations. The results shown also seem to indicate that nonreacting dimensionless scalar profiles can emulate the reacting flow equivalence ratio distribution reasonably well. The results cited suggest that further study may not necessarily lead to a universal ''rule of thumb'' for mixer design for low esr emissions, because optimization will likely require an assessment for a specific application. C1 UNITED TECHNOL RES CTR,E HARTFORD,CT 06108. ALLISON ENGINE CO,INDIANAPOLIS,IN 46206. UNIV CALIF IRVINE,IRVINE,CA 92717. CFD RES CORP,HUNTSVILLE,AL 35805. RP Holdeman, JD (reprint author), NASA,LEWIS RES CTR,CLEVELAND,OH 44135, USA. NR 47 TC 45 Z9 48 U1 0 U2 8 PU ASME-AMER SOC MECHANICAL ENG PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017 SN 0742-4795 J9 J ENG GAS TURB POWER JI J. Eng. Gas. Turbines Power-Trans. ASME PD OCT PY 1997 VL 119 IS 4 BP 852 EP 862 DI 10.1115/1.2817065 PG 11 WC Engineering, Mechanical SC Engineering GA YD474 UT WOS:A1997YD47400012 ER PT J AU Welch, GE AF Welch, GE TI Two-dimensional computational model for wave rotor flow dynamics SO JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER-TRANSACTIONS OF THE ASME LA English DT Article; Proceedings Paper CT 41st International Gas Turbine and Aeroengine Congress and Exhibition CY JUN 10-13, 1996 CL BIRMINGHAM, ENGLAND ID EULER EQUATIONS AB A two-dimensional (theta, z) Navier-Stokes solver for multiport wave rotor flow simulation is described. The finite-volume forms of the unsteady thin-layer Navier-Stokes equations are integrated in time on multiblock grids that represent the stationary inlet and outlet ports and the moving rotor passages of the wave rotor. Computed results are compared with three-port wave rotor experimental data. The model is applied to predict the performance of a planned four-port wave rotor experiment. Two-dimensional flow features that reduce machine performance and influence rotor blade and duct wall thermal loads are identified. RP NASA, LEWIS RES CTR, USA, RES LAB, VEHICLE TECHNOL CTR, CLEVELAND, OH 44135 USA. NR 37 TC 10 Z9 10 U1 0 U2 1 PU ASME PI NEW YORK PA TWO PARK AVE, NEW YORK, NY 10016-5990 USA SN 0742-4795 EI 1528-8919 J9 J ENG GAS TURB POWER JI J. Eng. Gas. Turbines Power-Trans. ASME PD OCT PY 1997 VL 119 IS 4 BP 978 EP 985 DI 10.1115/1.2817086 PG 8 WC Engineering, Mechanical SC Engineering GA YD474 UT WOS:A1997YD47400033 ER PT J AU Piomelli, U Streett, CL Sarkar, S AF Piomelli, U Streett, CL Sarkar, S TI On the computation of sound by large-eddy simulations SO JOURNAL OF ENGINEERING MATHEMATICS LA English DT Article DE turbulent shear layers; large-eddy simulation; subgrid-scale models; acoustic analogy; Lighthill's analogy ID MODEL; FLOWS AB The effect of the small scales on the source term in Lighthill's acoustic analogy is investigated, with the objective of determining the accuracy of large-eddy simulations when applied to studies of flow-generated sound. The distribution of the turbulent quadrupole is predicted accurately if models that take into account the trace of the SGS stresses are used. Its spatial distribution is also correct, indicating that the low-wave-number (or frequency) part of the sound spectrum can be predicted well by LES. Filtering, however, removes the small-scale fluctuations that contribute significantly to the higher derivatives in space and time of Lighthill's stress tensor T-ij. The rms fluctuations of the filtered derivatives are substantially lower than those of the unfiltered quantities. The small scales, however, are not strongly correlated, and are not expected to contribute significantly to the far-field sound; separate modeling of the subgrid-scale density fluctuations might, however, be required in some configurations. C1 Univ Maryland, Dept Mech Engn, College Pk, MD 20742 USA. NASA, Langley Res Ctr, Hampton, VA 23681 USA. Univ Calif San Diego, Dept Appl Mech & Engn Sci, La Jolla, CA 92093 USA. RP Piomelli, U (reprint author), Univ Maryland, Dept Mech Engn, College Pk, MD 20742 USA. NR 21 TC 20 Z9 21 U1 0 U2 4 PU KLUWER ACADEMIC PUBL PI DORDRECHT PA SPUIBOULEVARD 50, PO BOX 17, 3300 AA DORDRECHT, NETHERLANDS SN 0022-0833 J9 J ENG MATH JI J. Eng. Math. PD OCT PY 1997 VL 32 IS 2-3 BP 217 EP 236 DI 10.1023/A:1004236206327 PG 20 WC Engineering, Multidisciplinary; Mathematics, Interdisciplinary Applications SC Engineering; Mathematics GA YM258 UT WOS:000071045600008 ER PT J AU Cole, KD Hoegy, WR AF Cole, KD Hoegy, WR TI The 100 Hz electric fields observed on Pioneer Venus Orbiter and a case against the whistler hypothesis for them - Comment - Reply SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Editorial Material RP Cole, KD (reprint author), NASA,GODDARD SPACE FLIGHT CTR,ATMOSPHERES LAB,GREENBELT,MD 20771, USA. NR 3 TC 1 Z9 1 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 J9 J GEOPHYS RES-SPACE JI J. Geophys. Res-Space Phys. PD OCT 1 PY 1997 VL 102 IS A10 BP 22283 EP 22283 DI 10.1029/97JA01816 PG 1 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XZ208 UT WOS:A1997XZ20800022 ER PT J AU Esler, SL Nelson, ML AF Esler, SL Nelson, ML TI NASA indexing benchmarks: evaluating text search engines SO JOURNAL OF NETWORK AND COMPUTER APPLICATIONS LA English DT Article ID RESOURCE DISCOVERY AB The current proliferation of on-line information resources underscores the requirement for the ability to index collections of information and search and retrieve them in a convenient manner. This study develops criteria for analytically comparing the index and search engines and presents results for a number of freely-available search engines. A product of this research is a tool-kit capable of automatically indexing, searching, and extracting performance statistics from each of the focused search engines. This tool-kit is highly configurable and has the ability to run these benchmark tests against other engines as well. Results demonstrate that the tested search engines can be grouped into two levels. Level one engines are efficient on small-to medium-sized data collections, but show weaknesses when used for collections 100MB or larger. Level two search engines are recommended for data collections up to and beyond 100MB. (C) 1997 Academic Press Limited. C1 NASA, Langley Res Ctr, Hampton, VA 23681 USA. OI Nelson, Michael/0000-0003-3749-8116 NR 12 TC 0 Z9 0 U1 0 U2 0 PU ACADEMIC PRESS LTD PI LONDON PA 24-28 OVAL RD, LONDON NW1 7DX, ENGLAND SN 1084-8045 J9 J NETW COMPUT APPL JI J. Netw. Comput. Appl. PD OCT PY 1997 VL 20 IS 4 BP 339 EP 353 DI 10.1006/jnca.1997.0049 PG 15 WC Computer Science, Hardware & Architecture; Computer Science, Interdisciplinary Applications; Computer Science, Software Engineering SC Computer Science GA ZN423 UT WOS:000073644400002 ER PT J AU Rice, BL Lane, HW AF Rice, BL Lane, HW TI Dietary studies in the joint US-Russian space program (Reprinted from The Digest, vol 31, pg 1-2, 1995) SO JOURNAL OF THE AMERICAN DIETETIC ASSOCIATION LA English DT Reprint AB Metabolic experiments in the joint US-Russian space program involve analysis of food records, which include weighed foods, stable-isotope turnover, and biochemical samples collected before, during, and after the flights. This article describes the methods of monitoring dietary intake for this program. RP Rice, BL (reprint author), KRUG LIFE SCI INC,NUTR BIOCHEM LAB,NASA,LYNDON B JOHNSON SPACE CTR,1290 HERCULES DR,SUITE 120,HOUSTON,TX 77058, USA. NR 1 TC 2 Z9 2 U1 0 U2 0 PU AMER DIETETIC ASSOC PI CHICAGO PA 216 W JACKSON BLVD #800, CHICAGO, IL 60606-6995 SN 0002-8223 J9 J AM DIET ASSOC JI J. Am. Diet. Assoc. PD OCT PY 1997 VL 97 IS 10 SU 2 BP S127 EP S128 DI 10.1016/S0002-8223(97)00746-3 PG 2 WC Nutrition & Dietetics SC Nutrition & Dietetics GA XZ571 UT WOS:A1997XZ57100008 PM 9336572 ER PT J AU Li, JA OBrien, TK Rousseau, CQ AF Li, JA OBrien, TK Rousseau, CQ TI Test and analysis of composite hat stringer pull-off test specimens SO JOURNAL OF THE AMERICAN HELICOPTER SOCIETY LA English DT Article AB Hat stringer pull-off tests were performed to evaluate the delamination failure mechanisms in the flange region for a rod-reinforced hat stringer section. A special test fixture was used to pull the hat off the stringer while reacting the pull-off load through roller supports at both stringer flanges. Microscopic examinations of the failed specimens revealed that failure occurred at the ply termination in the flange area where the flange of the stiffener is built up by adding 451-45 tape plies on the top surface. Test results indicated that the as-manufactured microstructure in the flange region has a strong influence on the delamination initiation and the associated pull-off loads. Finite element models were created for each specimen with a detailed mesh based on micrographs of the critical location. A fracture mechanics approach and a mixed mode delamination criterion were used to predict the onset of delamination and the pull-off load. By modeling the critical local details of each specimen from micrographs, the model was able to accurately predict the hat stringer pull-off loads and replicate the variability in the test results. C1 USA,RES LAB,NASA,LANGLEY RES CTR,HAMPTON,VA. BELL HELICOPTER TEXTRON INC,FT WORTH,TX. NR 10 TC 10 Z9 10 U1 0 U2 3 PU AMER HELICOPTER SOC INC PI ALEXANDRIA PA 217 N WASHINGTON ST, ALEXANDRIA, VA 22314 SN 0002-8711 J9 J AM HELICOPTER SOC JI J. Am. Helicopter Soc. PD OCT PY 1997 VL 42 IS 4 BP 350 EP 357 PG 8 WC Engineering, Aerospace SC Engineering GA YK998 UT WOS:A1997YK99800006 ER PT J AU Siegel, R AF Siegel, R TI Temperature distribution in a composite of opaque and semitransparent spectral layers SO JOURNAL OF THERMOPHYSICS AND HEAT TRANSFER LA English DT Article ID RADIATION AB The analysis of radiative transfer becomes computationally complex for a composite when there are multiple layers and multiple spectral bands. A convenient analytical method is developed for combined radiation and conduction in a composite of alternating semitransparent and opaque layers. The semitransparent layers absorb, scatter, and emit radiation, and spectral properties with large scattering are included. The two-flux method is used, and its applicability is verified by comparison with a basic solution in the literature. The differential equation In the two-flux method is solved by deriving a Green's function. The solution technique is applied to analyze radiation effects in a multilayer zirconia thermal barrier coating with internal radiation shields for conditions in an aircraft engine combustor. The zirconia radiative properties are modeled by two spectral bands. Thin opaque layers within the coating are used to decrease radiant transmission that can degrade the zirconia insulating ability. With radiation shields, the temperature distributions more closely approach the opaque limit that provides the lowest metal wall temperatures. RP Siegel, R (reprint author), NASA,LEWIS RES CTR,21000 BROOK RD,CLEVELAND,OH 44135, USA. NR 10 TC 6 Z9 7 U1 0 U2 3 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 SN 0887-8722 J9 J THERMOPHYS HEAT TR JI J. Thermophys. Heat Transf. PD OCT-DEC PY 1997 VL 11 IS 4 BP 533 EP 539 DI 10.2514/2.6295 PG 7 WC Thermodynamics; Engineering, Mechanical SC Thermodynamics; Engineering GA YA622 UT WOS:A1997YA62200007 ER PT J AU Gupta, RN Moss, JN Price, JM AF Gupta, RN Moss, JN Price, JM TI Assessment of thermochemical nonequilibrium and slip effects for orbital re-entry experiment SO JOURNAL OF THERMOPHYSICS AND HEAT TRANSFER LA English DT Article ID VEHICLE AB Results are provided from a viscous shock layer (VSL) analysis of the re-entry flowfield around the forebody of the Japanese Orbital Re-entry Experiment (OREX) vehicle. This vehicle is a 50-deg spherically blunted cone with a nose radius of 1.35 m and a base diameter of 3.4 m. Calculations are performed for the OREX trajectory from a 105 to 48.4 km altitude range. A seven-species chemical model for air is found adequate for the flowfield analysis. However, for altitudes greater than 84 km, the low-density effects (such as thermal nonequilibrium and slip) must be implemented to accurately predict flight-inferred heat transfer rate data. At altitudes lower than 84 km, a finite surface recombination probability employed in place of a noncatalytic surface enhances the agreement between the calculations and flight data. VSL results are also compared with the direct simulation Monte Carlo predictions at high altitudes (>80 km) and the electron number density data for three altitudes in the OREX trajectory. Overall, the agreement between the flight data and calculated results is quite good. RP Gupta, RN (reprint author), NASA,LANGLEY RES CTR,AERO & GAS DYNAM DIV,HAMPTON,VA 23681, USA. NR 18 TC 4 Z9 6 U1 0 U2 0 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 SN 0887-8722 J9 J THERMOPHYS HEAT TR JI J. Thermophys. Heat Transf. PD OCT-DEC PY 1997 VL 11 IS 4 BP 562 EP 569 DI 10.2514/2.6280 PG 8 WC Thermodynamics; Engineering, Mechanical SC Thermodynamics; Engineering GA YA622 UT WOS:A1997YA62200011 ER PT J AU Hathaway, MD Wood, JR AF Hathaway, MD Wood, JR TI Application of a multi-block CFD code to investigate the impact of geometry modeling on centrifugal compressor flow field predictions SO JOURNAL OF TURBOMACHINERY-TRANSACTIONS OF THE ASME LA English DT Article; Proceedings Paper CT 41st International Gas Turbine and Aeroengine Congress and Exhibition CY JUN 10-13, 1996 CL BIRMINGHAM, ENGLAND AB CFD codes capable of utilizing multi-block grids provide the capability to analyze the complete geometry of centrifugal compressors including, among others, multiple splitter rows, tip clearance, blunt trailing edges, fillets, and slots between moving and stationary surfaces. Attendant with this increased capability is potentially increased grid setup time and more computational overhead-CPU time and memory requirements-with the resultant increase in ''wall clock'' time to obtain a solution. If the increase in ''difficulty'' of obtaining a solution significantly improves the solution from that obtained by modeling the features of the tip clearance flow or the typical bluntness of a centrifugal compressor's trailing edge, then the additional burden is worthwhile. However, if the additional information obtained is of marginal use, then modeling of certain features of the geometry may provide reasonable solutions for designers to make comparative choices when pursuing a new design. In this spirit a sequence of grids were generated to study the relative importance of modeling versus detailed gridding of the tip gap and blunt trailing edge regions of the NASA large low-speed centrifugal compressor for which there is considerable detailed internal laser anemometry data available for comparison. The results indicate: (I) There is no significant difference in predicted tip clearance mass flow rare whether the tip gap is gridded or modeled. (2) Gridding rather than modeling the trailing edge results in better predictions of some flow details downstream of the impeller but otherwise appears to offer no great benefits. (3) The pitchwise variation of absolute flow angle decreases rapidly up to 8 percent impeller radius ratio and much more slowly thereafter. Although some improvements in prediction of flow field details are realized as a result of analyzing the actual geometry there is no clear consensus that any of the grids investigated produced superior results in every case when compared to the measurements. However, if a multi-block code is available, it should be used, as it has the propensity for enabling better predictions than a single block code, which requires modeling of certain geometry features. If a single block code must be used, some guidance is offered for modeling those geometry features that cannot be directly gridded. C1 NASA,LEWIS RES CTR,CLEVELAND,OH 44135. RP Hathaway, MD (reprint author), VEHICLE TECHNOL CTR,CLEVELAND,OH 44135, USA. NR 13 TC 1 Z9 2 U1 2 U2 4 PU ASME-AMER SOC MECHANICAL ENG PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017 SN 0889-504X J9 J TURBOMACH JI J. Turbomach.-Trans. ASME PD OCT PY 1997 VL 119 IS 4 BP 820 EP 830 PG 11 WC Engineering, Mechanical SC Engineering GA YD813 UT WOS:A1997YD81300018 ER PT J AU Blake, L Stallings, ET AF Blake, L Stallings, ET TI Arranging roots: Classification and subject headings for genealogical collections SO LIBRARY RESOURCES & TECHNICAL SERVICES LA English DT Article AB Because genealogical researchers find ancestors by looking for them by place and not subject, the Dewey Decimal Classification (DDC) was not fulfilling the needs of researchers. After investigating possible manipulations of DDC to fit genealogical collections, a new system was developed at Rowan Public Library. The classification system in its entirety is given and the narrative is illustrated with examples. Also given are suggested additions to the Library of Congress Subject Headings to provide geographic orientation. C1 W Virginia Univ, NASA, Facil 4&5, Fairmont, WV 26654 USA. RP Blake, L (reprint author), W Virginia Univ, NASA, Facil 4&5, Fairmont, WV 26654 USA. OI Blake, Linda/0000-0003-0475-4179 NR 8 TC 0 Z9 0 U1 0 U2 0 PU AMER LIBRARY ASSOC PI CHICAGO PA 50 E HURON ST, CHICAGO, IL 60611 USA SN 0024-2527 J9 LIBR RESOUR TECH SER JI Libr. Res. Tech. Serv. PD OCT PY 1997 VL 41 IS 4 BP 335 EP 346 PG 12 WC Information Science & Library Science SC Information Science & Library Science GA YQ482 UT WOS:000071392200004 ER PT J AU Sullivan, RM Stokes, EH AF Sullivan, RM Stokes, EH TI A model for the effusion of water in carbon phenolic composites SO MECHANICS OF MATERIALS LA English DT Article DE carbon phenolic composites; permeability; thermogravimetric analysis; finite element analysis; porous media; moisture diffusion; derivative weight loss AB A model is developed for the effusion of water in phenolic composites as the material is heated to moderate temperatures. The model is developed from the theory of the flow of gases through a porous media coupled with the thermodynamics of the evaporation of water from a condensed, binary mixture. The resulting model accounts for the evaporation of water fr om solid sites in the material to an internal pore network and the subsequent flow of water vapor through the pore network. The mathematical theory is applied by simulating the effusion behavior of water in a thermogravimetric test. The results obtained from the model compared favorably with the thermogravimetric measurements. The results also showed a close correlation between the permeability of the material and the rate of evaporation of water from the solid sites. (C) 1997 Elsevier Science Ltd. C1 SO RES INST,BIRMINGHAM,AL 35211. RP Sullivan, RM (reprint author), NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,STRUCT & DYNAM LAB,MAIL STOP ED24,HUNTSVILLE,AL 35812, USA. NR 16 TC 12 Z9 12 U1 1 U2 13 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0167-6636 J9 MECH MATER JI Mech. Mater. PD OCT PY 1997 VL 26 IS 3 BP 197 EP 207 DI 10.1016/S0167-6636(97)00024-0 PG 11 WC Materials Science, Multidisciplinary; Mechanics SC Materials Science; Mechanics GA YK063 UT WOS:A1997YK06300003 ER PT J AU Sen, S Kaukler, WF Curreri, P Stefanescu, DM AF Sen, S Kaukler, WF Curreri, P Stefanescu, DM TI Dynamics of solid/liquid interface shape evolution near an insoluble particle - An X-ray transmission microscopy investigation SO METALLURGICAL AND MATERIALS TRANSACTIONS A-PHYSICAL METALLURGY AND MATERIALS SCIENCE LA English DT Article ID SOLID LIQUID INTERFACE; ENGULFMENT; FRONT AB In this article, for the first time, in situ and real-time experimental observations of changes in solid/liquid (s/l) interface shape during interactions with a particle or void are reported for metallic systems. Real-time interface shape evolution for both stationary and growing interfaces was observed by use of a state-of-the-art X-ray transmission microscope. Localized interfacial perturbations were studied as a function of the particle or void diameter, the distance between the s/l interface and the particle or void, and the thermal conductivity ratio between the matrix and the particle or void. In particular, the sensitivity of interfacial perturbation to the thermal conductivity ratio is critically analyzed. Analytical predictions of interface shape are compared to the real-time, in situ experimental data. A good agreement between the experimentally observed and predicted interface shapes was found for stationary interfaces. Based on the differences in experimental observations, between a moving and a stationary interface, an alternate hypothesis is suggested to explain the observed kinetics of particle engulfment by a growing interface. C1 NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,MET & ALLOYS GRP,HUNTSVILLE,AL 35812. UNIV ALABAMA,CTR MICROGRAV & MAT RES,HUNTSVILLE,AL 35899. UNIV ALABAMA,SOLIDIFICAT LAB,TUSCALOOSA,AL 35487. RP Sen, S (reprint author), NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,USRA,HUNTSVILLE,AL 35812, USA. RI Stefanescu, Doru/G-8101-2012; OI Stefanescu, Doru M./0000-0001-5544-8396; Kaukler, William/0000-0002-7758-269X NR 15 TC 39 Z9 40 U1 0 U2 6 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 OCT PY 1997 VL 28 IS 10 BP 2129 EP 2135 DI 10.1007/s11661-997-0170-y PG 7 WC Materials Science, Multidisciplinary; Metallurgy & Metallurgical Engineering SC Materials Science; Metallurgy & Metallurgical Engineering GA YA656 UT WOS:A1997YA65600018 ER PT J AU Brandt, WN Fabian, AC Takahashi, K Fujimoto, R Yamashita, A Inoue, H Ogasaka, Y AF Brandt, WN Fabian, AC Takahashi, K Fujimoto, R Yamashita, A Inoue, H Ogasaka, Y TI ASCA spectroscopy of IRAS 23060+0505: penetrating the torus of a type 2 quasar with X-rays SO MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY LA English DT Article DE galaxies, individual, IRAS 23060 + 0505; galaxies, Seyfert; X-rays, galaxies ID GALAXY AB We report on a pointed ASCA observation of the powerful (L-bol approximate to 1.3 x 10(46) erg s(-1)) type 2 infrared luminous galaxy IRAS 23060 + 0505. This galaxy has been the subject of detailed spectroscopic and spectropolarimetric studies which have revealed a hidden broad-line region and have been used to construct a detailed model of the light paths in this source. Our observation detects IRAS 23060 + 0505 in the X-ray band for the first time and complements the optical and infrared studies. We detect hard X-ray emission that can be modelled as a power law with a 2-10 keV luminosity of 1.5 x 10(44) erg 2-1, thereby verifying the existence of an accreting supermassive black hole in IRAS 23060 + 0505. The obscuring torus of IRAS 23060 + 0505 appears to be Compton thin along our line of sight, and we measure a column to the nuclear X-ray source of about 8 x 10(22) cm(-2). Comparison of the X-ray column with the A(V) = 30 +/- 4 mag extinction measurement by Young et al. suggests that the torus may have a dust-to-gas ratio rather similar to that in the interstellar medium of the Milky Way. We also find some evidence for iron K-line emission. The apparent X-ray to bolometric luminosity ratio for IRAS 23060 + 0505 is less than or similar to 1 per cent, a rather low value, and we consider possible explanations for this low ratio. C1 HARVARD SMITHSONIAN CTR ASTROPHYS,CAMBRIDGE,MA 02138. UNIV CAMBRIDGE,INST ASTRON,CAMBRIDGE CB3 0HA,ENGLAND. INST SPACE & ASTRONAUT SCI,SAGAMIHARA,KANAGAWA 229,JAPAN. NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. RI Brandt, William/N-2844-2015 OI Brandt, William/0000-0002-0167-2453 NR 29 TC 48 Z9 48 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 OCT 1 PY 1997 VL 290 IS 4 BP 617 EP 622 PG 6 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YA286 UT WOS:A1997YA28600008 ER PT J AU Gibson, BK Loewenstein, M Mushotzky, RF AF Gibson, BK Loewenstein, M Mushotzky, RF TI Supernovae types Ia/II and intracluster medium enrichment SO MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY LA English DT Article DE nuclear reactions, nucleosynthesis, abundances; supernovae, general; galaxies, elliptical and lenticular, cD; galaxies, evolution; intergalactic medium; X-rays, galaxies ID ABUNDANCES; GALAXY AB We re-examine the respective roles played by supernovae (SNe) Types Ia and II in enriching the intracluster medium (ICM) of galaxy clusters in the light of the recent downward shift of the ASCA abundance ratios of alpha-elements to iron favoured by Ishimaru & Arimoto. Because of this shift, Ishimaru & Arimoto conclude that greater than or similar to 50 per cent of the ICM iron must have originated from within Type Ia SNe progenitors. A point not appreciated in their study, nor in most previous analyses, is the crucial dependence of such a conclusion upon the adopted massive star physics. Employing several alternative Type II SN yield compilations, we demonstrate how uncertainties in the treatment of convection and mass-loss can radically alter our perception of the relative importance of Type Ia and II SNe as ICM polluters. If mass-loss of the form favoured by Maeder or convection of the form favoured by Arnett is assumed, the effect upon the oxygen yields would lead us to conclude that Type Ia SNe play no part in polluting the ICM, in contradiction with Ishimaru & Arimoto. Apparent dichotomies still exist (e.g., the mean ICM neon-to-iron ratio implies a similar to 100 per cent Type II Fe origin, while the mean sulphur ratio indicates a similar to 100 per cent Type Ia origin) that cannot be reconciled with the currently available yield tables. C1 NASA,GODDARD SPACE FLIGHT CTR,HIGH ENERGY PHYS LAB,GREENBELT,MD 20771. RP Gibson, BK (reprint author), AUSTRALIAN NATL UNIV,MT STROMLO & SIDING SPRING OBSERV,WESTON CREEK PO,WESTON,ACT 2611,AUSTRALIA. RI Gibson, Brad/M-3592-2015 OI Gibson, Brad/0000-0003-4446-3130 NR 24 TC 125 Z9 125 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 OCT 1 PY 1997 VL 290 IS 4 BP 623 EP 628 PG 6 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YA286 UT WOS:A1997YA28600009 ER PT J AU Druyan, LM Lonergan, P Cohen, J AF Druyan, LM Lonergan, P Cohen, J TI Case studies of African wave disturbances in gridded analyses SO MONTHLY WEATHER REVIEW LA English DT Article ID EASTERLY WAVES; ATLANTIC; SYSTEM AB African wave disturbances (AWDs), an important trigger of Sahel summer rainfall, are studied using ECMWF gridded datasets for July and August 1987 and 1988. Power spectra of time series of 700-mb meridional winds near Niamey taken from analyses at both 2 degrees x 2.5 degrees and 4 degrees x 5 degrees horizontal resolution are compared to spectra based on Niamey station data. In addition, spatial distributions of meteorological fields at both resolutions are discussed for three case studies, including the synoptic features of several AWDs. Additional examples are presented from GCM simulations at comparable horizontal resolutions, While vertical motion and divergence centers were more extreme at 2 degrees x 2.5 degrees, many of the deduced characteristics of an AWD were similar at both resolutions. The higher-resolution analyses and simulation show a sharp transition across wave troughs between lower-tropospheric convergence (uplift) on the west and divergence (subsidence) on the east for several AWDs. For the two more southerly AWDs analyzed here, uplift associated with the convergence ahead of the trough appears to be displaced to the southwest at midtropospheric altitudes. Twice-daily July-September precipitation at Niamey is weakly, but significantly, correlated with corresponding time series of ECMWF analyzed vertical motion at nearby grid points. C1 NASA,GODDARD INST SPACE STUDIES,SCI SYST & APPLICAT INC,NEW YORK,NY 10025. MIT,DEPT CIVIL & ENVIRONM ENGN,CAMBRIDGE,MA 02139. RP Druyan, LM (reprint author), COLUMBIA UNIV,CTR CLIMATE SYST RES,ARMSTRONG HALL,2880 BROADWAY,NEW YORK,NY 10025, USA. NR 13 TC 13 Z9 13 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 OCT PY 1997 VL 125 IS 10 BP 2520 EP 2530 DI 10.1175/1520-0493(1997)125<2520:CSOAWD>2.0.CO;2 PG 11 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA XZ561 UT WOS:A1997XZ56100008 ER PT J AU Simpson, J Ritchie, E Holland, GJ Halverson, J Stewart, S AF Simpson, J Ritchie, E Holland, GJ Halverson, J Stewart, S TI Mesoscale interactions in tropical cyclone genesis SO MONTHLY WEATHER REVIEW LA English DT Article ID WARM-CORE VORTEX; SCALE VORTICES; EVOLUTION; DYNAMICS; SYSTEMS; REGION AB With the multitude of cloud clusters over tropical oceans, it has been perplexing that so few develop into tropical cyclones. The authors postulate that a major obstacle has been the complexity of scale interactions, particularly those on the mesoscale, which have only recently been observable. While there are well-known climatological requirements, these are by no means sufficient. A major reason for this rarity is the essentially stochastic nature of the mesoscale interactions that precede and contribute to cyclone development. Observations exist for only a few forming cases. In these, the moist convection in the preformation environment is organized into mesoscale convective systems, each of which have associated mesoscale potential vortices in the midlevels. Interactions between these systems may lead to merger, growth to the surface, and development of both the nascent eye and inner rainbands of a tropical cyclone. The process is essentially stochastic, but the degree of stochasticity can be reduced by the continued interaction of the mesoscale systems or by environmental influences. For example a monsoon trough provides a region of reduced deformation radius, which substantially improves the efficiency of mesoscale vortex interactions and the amplitude of the merged vortices. Further, a strong monsoon trough provides a vertical wind shear that enables long-lived midlevel mesoscale vortices that are able to maintain, or even redevelop, the associated convective system. The authors develop this hypothesis by use of a detailed case study of the formation of Tropical Cyclone Oliver observed during TOGA COARE (1993). In this case, two dominant mesoscale vortices interacted with a monsoon trough to separately produce a nascent eye and a major rainband. The eye developed on the edge of the major convective system, and the associated atmospheric warming was provided almost entirely by moist processes in the upper atmosphere, and by a combination of latent heating and adiabatic subsidence in the lower and middle atmosphere. The importance of mesoscale interactions is illustrated further by brief reference to the development of two typhoons in the western North Pacific. C1 USN,POSTGRAD SCH,DEPT METEOROL,MONTEREY,CA 93943. BUR METEOROL RES CTR,MELBOURNE,FL. NOAA,NATL WEATHER SERV,NEXRAD OSF OTB,NORMAN,OK. RP Simpson, J (reprint author), NASA,GODDARD SPACE FLIGHT CTR,EARTH SCI DIRECTORATE,CODE 912,GREENBELT,MD 20771, USA. RI Ritchie, Elizabeth/B-4232-2016 OI Ritchie, Elizabeth/0000-0002-3413-5830 NR 40 TC 144 Z9 162 U1 1 U2 19 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 OCT PY 1997 VL 125 IS 10 BP 2643 EP 2661 DI 10.1175/1520-0493(1997)125<2643:MIITCG>2.0.CO;2 PG 19 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA XZ561 UT WOS:A1997XZ56100015 ER PT J AU Peskov, V Ramsey, BD Kolodziejczak, JJ Fonte, P AF Peskov, V Ramsey, BD Kolodziejczak, JJ Fonte, P TI Feedback and breakdowns in microstrip gas counters SO NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT LA English DT Article ID OPERATION; CHAMBER AB The phenomena of feedback and breakdowns in microstrip gas counters have been studied. Tests have been performed on a wide variety of microstrips of different geometries and substrates in various gas mixtures and at several pressures. In addition, for direct comparison, similar microstrip gas counters without substrates were also investigated. In the case of ''conventional'' microstrip detectors on substrates, it was found that as maximum gains were approached, self-quenched streamers occurred, but that these were present only over a very narrow voltage range after which they rapidly transited to gliding-discharge-type breakdown sparks. For microstrip detectors without substrates, the situation was quite different. At high gains (> similar to 10(4)) they transited from proportional to self-quenched streamer-mode and would operate stably in this mode over a very broad voltage range. When breakdown occurred in these detectors it was through a previously unreported mechanism and at gains, without exception, 5-10 times higher than in their counterparts with substrates. The conclusion of these studies is that the substrate represents the weak link in the chain and should ideally be avoided or at least removed from the high-field regions. In cases where this is not possible, then the multiplication region should be concentrated to the smallest volume around the anodes and maximally suppressed elsewhere. Recipes for achieving this are provided, along with new geometries which permit gas gains in excess of 10(5) to be achieved. C1 NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,HUNTSVILLE,AL 35812. UNIV COIMBRA,LIP,P-3000 COIMBRA,PORTUGAL. INST SUPER INGN COIMBRA,COIMBRA,PORTUGAL. RI Fonte, Paulo/B-1842-2008 OI Fonte, Paulo/0000-0002-2275-9099 NR 36 TC 28 Z9 28 U1 0 U2 3 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 OCT 1 PY 1997 VL 397 IS 2-3 BP 243 EP 260 DI 10.1016/S0168-9002(97)00743-2 PG 18 WC Instruments & Instrumentation; Nuclear Science & Technology; Physics, Nuclear; Physics, Particles & Fields SC Instruments & Instrumentation; Nuclear Science & Technology; Physics GA YA687 UT WOS:A1997YA68700004 ER PT J AU Des Marais, DJ AF Des Marais, DJ TI Isotopic evolution of the biogeochemical carbon cycle during the Proterozoic Eon SO ORGANIC GEOCHEMISTRY LA English DT Article; Proceedings Paper CT Symposium on Organic Geochemistry - Linking the Biosphere and Geosphere at the Annual Meeting of the Geological-Society-of-America CY OCT 27, 1996 CL DENVER, CO SP Geol Soc Amer, Geochem Soc, Organ Geochem Div DE Precambrian; isotopes; carbon; carbon cycle; oxygen; kerogen ID ORGANIC-CARBON; FRACTIONATION; EARTH; SEAWATER; BACTERIA; SULFATE; OXYGEN AB Time-related changes in the Proterozoic sedimentary isotopic record of organic carbon and carbonates are consistent with the following: (1) an increase in the oxidation state of the environment, (2) a transition towards microbial populations dominated by producers and utilizers of O-2 and SO42-, and (3) a relatively minor increase in organic delta(13)C during postdepositional thermal alteration (delta(13)C increased similar to 3 parts per thousand as H/C declined from 0.8 to 0.1). The progressive oxidation of the environment was episodic. For example, between 2.2 and 1.9 Ga, crustal and atmospheric reservoirs of O-2, Fe3+ and SO42- increased relatively rapidly, and this increase was too large to be attributed solely to the declining rate of oxidant consumption by volcanic and hydrothermal fluxes of reduced species. Additional fundamental changes seem to be required in the tectonic style of organic sedimentation and preservation. Episodic changes in both the biogeochemical C cycle and atmospheric O-2 levels during the Proterozoic Eon likely influenced the evolution of Eukarya. (C) 1997 Elsevier Science Ltd. All rights reserved. C1 NASA, Ames Res Ctr, Div Space Sci, Moffett Field, CA 94035 USA. RP NASA, Ames Res Ctr, Div Space Sci, Moffett Field, CA 94035 USA. NR 51 TC 73 Z9 74 U1 2 U2 10 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0146-6380 J9 ORG GEOCHEM JI Org. Geochem. PD OCT-NOV PY 1997 VL 27 IS 5-6 BP 185 EP 193 DI 10.1016/S0146-6380(97)00061-2 PG 9 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA YR796 UT WOS:000071531100002 ER PT J AU Netanyahu, NS Philomin, V Rosenfeld, A Stromberg, AJ AF Netanyahu, NS Philomin, V Rosenfeld, A Stromberg, AJ TI Robust detection of straight and circular road segments in noisy aerial images SO PATTERN RECOGNITION LA English DT Article DE line fitting; circular arc fitting; ordinary least squares; robust estimators; nonlinear regression ID ARC CENTER; REGRESSION; ALGORITHMS; RADIUS; FIT AB This paper treats the problem of detecting straight or circular pieces of road in noisy low-resolution aerial images. it first uses a local operator to detect pixels whose neighborhoods are line-like, and then applies (robust) estimation techniques to find sets of such pixels that lie on or near straight or circular loci. An (unbiased) ordinary least squares estimator cannot handle outlying data even for straight loci; on the other hand, conventional robust techniques for fitting circular arcs are severely affected by digitization effects and the fact that circular road segments are typically short and shallow. We therefore introduce an estimator that is both robust and statistically efficient. We also present a simple ad hoc technique that achieves comparable results and can handle road segments that are either straight or circular. (C) 1997 Pattern Recognition Society. Published by Elsevier Science Ltd. C1 UNIV MARYLAND, CTR AUTOMAT RES, COMP VIS LAB, COLLEGE PK, MD 20742 USA. NASA, GODDARD SPACE FLIGHT CTR, DIV SPACE DATA & COMP, CTR EXCELLENCE SPACE DATA & INFORMAT SCI, GREENBELT, MD 20771 USA. UNIV KENTUCKY, DEPT STAT, LEXINGTON, KY 40506 USA. NR 55 TC 15 Z9 17 U1 0 U2 1 PU ELSEVIER SCI LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, OXON, ENGLAND SN 0031-3203 EI 1873-5142 J9 PATTERN RECOGN JI Pattern Recognit. PD OCT PY 1997 VL 30 IS 10 BP 1673 EP 1686 DI 10.1016/S0031-3203(96)00189-6 PG 14 WC Computer Science, Artificial Intelligence; Engineering, Electrical & Electronic SC Computer Science; Engineering GA YF781 UT WOS:A1997YF78100009 ER PT J AU Gompers, SL AF Gompers, SL TI On to Mars SO PHOTONICS SPECTRA LA English DT Letter RP Gompers, SL (reprint author), NASA,GODDARD SPACE FLIGHT CTR,TERR PHYS LAB,GREENBELT,MD 20771, USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU LAURIN PUBL CO INC PI PITTSFIELD PA BERKSHIRE COMMON PO BOX 1146, PITTSFIELD, MA 01202 SN 0731-1230 J9 PHOTON SPECTRA JI Photon. Spect. PD OCT PY 1997 VL 31 IS 10 BP 12 EP 12 PG 1 WC Optics SC Optics GA YA618 UT WOS:A1997YA61800004 ER PT J AU Riotto, A Tornkvist, O AF Riotto, A Tornkvist, O TI CP-violating solitons in the minimal supersymmetric standard model SO PHYSICAL REVIEW D LA English DT Article ID FINITE-TEMPERATURE; ELECTROWEAK BARYOGENESIS; BREAKING; PHYSICS; STRINGS; MSSM AB We study nontopological and CP-violating static wall solutions in the framework of the minimal supersymmetric standard model. We show that such membranes, characterized by a nontrivial winding of the relative U(1) phase of the two Higgs fields in the direction orthogonal to the wall, exist for small values of the mass of the CP-odd Higgs boson when loop corrections to the Higgs potential are included. Although their present-day existence is excluded by experimental bounds, we argue why they may have existed in the early universe with important cosmological consequences. RP Riotto, A (reprint author), FERMILAB NATL ACCELERATOR LAB,NASA,FERMILAB ASTROPHYS CTR,POB 500,BATAVIA,IL 60510, USA. NR 26 TC 5 Z9 5 U1 0 U2 0 PU AMERICAN PHYSICAL SOC PI COLLEGE PK PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA SN 0556-2821 J9 PHYS REV D JI Phys. Rev. D PD OCT 1 PY 1997 VL 56 IS 7 BP 3917 EP 3923 DI 10.1103/PhysRevD.56.3917 PG 7 WC Astronomy & Astrophysics; Physics, Particles & Fields SC Astronomy & Astrophysics; Physics GA YA573 UT WOS:A1997YA57300013 ER PT J AU Yoshizawa, A Liou, WW Yokoi, N Shih, TH AF Yoshizawa, A Liou, WW Yokoi, N Shih, TH TI Modeling of compressible effects on the Reynolds stress using a Markovianized two-scale method SO PHYSICS OF FLUIDS LA English DT Article ID NON-ISOTROPIC TURBULENCE; FREE SHEAR LAYERS; STATISTICAL-ANALYSIS; MIXING LAYERS; FLOWS; RENORMALIZATION; REPRESENTATION; GROWTH AB Compressibility effects on the Reynolds stress are modeled using a Markovianized two-scale method, These effects occur twofold. One is the effect on the turbulent viscosity, which is expressed in terms of the ratio of the normalized density variance to the squared turbulent Mach number. Another comes from the deviation of the Reynolds stress from a turbulent-viscosity representation, which is written using the Langrange derivative of the mean velocity and the spatial derivatives of the mean density and internal energy. A simple model with the former compressibility effect incorporated is applied to fully developed free-shear layers and is shown to capture the steep decrease in the growth rate with the increasing convective il Mach number. (C) 1997 American Institute of Physics. C1 WESTERN MICHIGAN UNIV, DEPT MECH & AERONAUT ENGN, KALAMAZOO, MI 49008 USA. NASA, LEWIS RES CTR, CTR MODELLING TURBULENCE & TRANSIT, CLEVELAND, OH 44135 USA. RP UNIV TOKYO, INST IND SCI, MINATO KU, ROPPONGI, TOKYO 106, JAPAN. NR 36 TC 10 Z9 10 U1 0 U2 3 PU AMER INST PHYSICS PI MELVILLE PA 1305 WALT WHITMAN RD, STE 300, MELVILLE, NY 11747-4501 USA SN 1070-6631 EI 1089-7666 J9 PHYS FLUIDS JI Phys. Fluids PD OCT PY 1997 VL 9 IS 10 BP 3024 EP 3036 DI 10.1063/1.869412 PG 13 WC Mechanics; Physics, Fluids & Plasmas SC Mechanics; Physics GA XY999 UT WOS:A1997XY99900020 ER PT J AU Rubinstein, R Erlebacher, G AF Rubinstein, R Erlebacher, G TI Transport coefficients in weakly compressible turbulence SO PHYSICS OF FLUIDS LA English DT Article ID DIRECT INTERACTION APPROXIMATION; HYDRODYNAMIC TURBULENCE; INCOMPRESSIBLE FLUIDS; STATISTICAL-ANALYSIS; SHEAR-FLOW AB A theory of transport coefficients in weakly compressible turbulence is derived by applying Yoshizawa's two-scale direct interaction approximation to the compressible equations of motion linearized about a state of incompressible turbulence. The result is a generalization of the eddy viscosity representation of incompressible turbulence. In addition to the usual incompressible eddy viscosity, the calculation generates eddy diffusivities for entropy and pressure, and an effective bulk viscosity acting on the mean flow. The compressible fluctuations also generate an effective turbulent mean pressure and corrections to the speed of sound. Finally, Yoshizawa's two-scale approximation generates terms in the mean flow equations which contain gradients of incompressible turbulence quantities. A preliminary description of these terms is given. (C) 1997 American Institute of Physics. C1 FLORIDA STATE UNIV,PROGRAM COMPUTAT SCI & ENGN,TALLAHASSEE,FL 32306. RP Rubinstein, R (reprint author), NASA,LANGLEY RES CTR,INST COMP APPLICAT SCI & ENGN,HAMPTON,VA 23681, USA. NR 34 TC 7 Z9 7 U1 0 U2 1 PU AMER INST PHYSICS PI WOODBURY PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 SN 1070-6631 J9 PHYS FLUIDS JI Phys. Fluids PD OCT PY 1997 VL 9 IS 10 BP 3037 EP 3057 DI 10.1063/1.869413 PG 21 WC Mechanics; Physics, Fluids & Plasmas SC Mechanics; Physics GA XY999 UT WOS:A1997XY99900021 ER PT J AU Encrenaz, T Drossart, P Carlson, RW Bjoraker, G AF Encrenaz, T Drossart, P Carlson, RW Bjoraker, G TI Detection of H2O in the splash phase of G- and R-impacts from NIMS-Galileo SO PLANETARY AND SPACE SCIENCE LA English DT Article; Proceedings Paper CT International Conference on SL9-Jupiter Collision CY JUL 03-05, 1996 CL MEUDON, FRANCE SP CNRS, INSU, Programme Natl Planetol Observ Paris, CNES ID JUPITER; SHOEMAKER-LEVY-9; SPECTROMETER; ATMOSPHERE; COLLISION; METHANE AB Near-infrared spectra of Jupiter have been recorded from Galileo with the NIMS instrument at the time of the G-and R-impacts. The beginning of the splash phase is observed between 6 and 10 min after the explosion. Two strong emissions are detected, at 3-4 mu m and at 2.7 mu m. The 3-4 mu m emission. due to the CH4 nu(3) band, is attributed to an increase of the stratospheric temperature (T=1000K 9 min after the impact). The 2.7 mu m emission is attributed to H2O. Estimates of the total H2O mass are 0.6-2.9 x 10(12)g and 0.7-13 x 10(11)g for the impacts G and R, respectively, 9 min after the explosion. The main uncertainty in the H2O mass estimate comes from the uncertainty in the temperature of the emitting area. The data show that the H2O formation started in the splash phase, about 7 and 9 min after the explosion for G and R, respectively. No CO was detected, which implies an upper limit of 2 x 10(-4) for the CO2/CO ratio in the G impact, consistent with a temperature lower than 2500K. (C) 1997 Elsevier Science Ltd. All rights reserved. C1 Observ Paris, DESPA, F-92195 Meudon, France. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Encrenaz, T (reprint author), Observ Paris, DESPA, F-92195 Meudon, France. RI Bjoraker, Gordon/D-5032-2012 NR 24 TC 5 Z9 5 U1 0 U2 2 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0032-0633 J9 PLANET SPACE SCI JI Planet Space Sci. PD OCT PY 1997 VL 45 IS 10 BP 1189 EP 1196 DI 10.1016/S0032-0633(97)00025-1 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YT242 UT WOS:000071580100003 ER PT J AU Martin, TZ Orton, GS AF Martin, TZ Orton, GS TI Shoemaker-Levy 9: distribution of radiant energy SO PLANETARY AND SPACE SCIENCE LA English DT Article; Proceedings Paper CT International Conference on SL9-Jupiter Collision CY JUL 03-05, 1996 CL MEUDON, FRANCE SP CNRS, INSU, Programme Natl Planetol Observ Paris, CNES ID COMET SHOEMAKER-LEVY-9; INFRARED OBSERVATIONS; PALOMAR OBSERVATIONS; JUPITER ATMOSPHERE; LIGHT CURVES; FRAGMENT-R; G-IMPACT; COLLISION; DENSITY; BREAKUP AB Multicolor Galileo observations of several SL9 impacts permit derivation of size and temperature information for the fireball phase. Integration of light-curves yields total fireball radiant energy estimates. Event QI has an initial color temperature of 24 000 K. Total radiant fireball energy for G was 8.3 x 10(24) erg. The largest event, L, is estimated to be 10(25) erg. Modelling of total energy radiated during the fallback phase shows a much larger energy release during that period-up to 4x10(26) erg for L. The mass required to provide the equivalent kinetic energy is about 1 x 10(13) g, which is a strong lower limit to initial fragment mass. The fallback energy derived for the R impact is 1x10(25)erg, with the strongest spectral constraints. Fallback energies for H and Q1 are about 4 x 10(25) erg, derived from only two spectral points. The fallback energies extrapolated from the 2.3 mu m lightcurves of the G and K impacts are 7x10(25) and 9x10(25) erg, respectively. Uncertainties of the fallback energies are an order of magnitude. Improvements to these estimates and their uncertainties will derive from the application of more detailed physical models. (C) 1997 Elsevier Science Ltd. All rights reserved. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Martin, TZ (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr,Mail Stop 169-237, Pasadena, CA 91109 USA. NR 31 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 0032-0633 J9 PLANET SPACE SCI JI Planet Space Sci. PD OCT PY 1997 VL 45 IS 10 BP 1287 EP 1298 DI 10.1016/S0032-0633(97)00091-3 PG 12 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YT242 UT WOS:000071580100013 ER PT J AU Bolton, SJ AF Bolton, SJ TI Interpretation of the observed changes in Jupiter's synchrotron radiation during and after the impacts from comet Shoemaker-Levy 9 SO PLANETARY AND SPACE SCIENCE LA English DT Article; Proceedings Paper CT International Conference on SL9-Jupiter Collision CY JUL 03-05, 1996 CL MEUDON, FRANCE SP CNRS, INSU, Programme Natl Planetol Observ Paris, CNES ID RADIO-EMISSION; SL-9; CM; VARIABILITY; FLUX AB The effects of the Shoemaker-Levy 9 collision with Jupiter included an abrupt and impulsive disturbance to Jupiter's inner magnetosphere. A substantial change to the radio emission originating from Jupiter's radiation belts (synchrotron radiation) was reported and confirmed by numerous observers. The major effect on the radiation belts is due to the latitude of the impact sites on Jupiter. The impacts occurred at the footprint of the magnetic field lines connecting Jupiter's inner radiation belts with the planet. Interferometric maps suggest changes may have continued for weeks after the impacts. The reported increases in synthrotron emission indicate substantial changes to the high energy electron population trapped in Jupiter's radiation belts. A number of mechanisms were suggested almost immediately to explain the observed changes: (1) enhanced radial diffusion, (3) shock acceleration and energization of the electron population and (3) pitch angle scattering of the emitting electrons from plasma waves triggered by the comet impacts. A review of the interpretation of the radio data and a discussion of the consistency between the proposed mechanisms and the observations is presented. A complete understanding of the state of the radiation belts before, during and after the impacts has not yet been reached and requires extensive modeling. (C) 1997 Published by Elsevier Science Ltd. All rights reserved. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Bolton, SJ (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 28 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 0032-0633 J9 PLANET SPACE SCI JI Planet Space Sci. PD OCT PY 1997 VL 45 IS 10 BP 1359 EP 1370 DI 10.1016/S0032-0633(97)00129-3 PG 12 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YT242 UT WOS:000071580100018 ER PT J AU Lin, SJ Rood, RB AF Lin, SJ Rood, RB TI An explicit flux-form semi-Lagrangian shallow-water model on the sphere SO QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY LA English DT Article DE computational test cases; conservative advection; numerical techniques ID CONSERVATIVE DIFFERENCE SCHEME; GENERAL-CIRCULATION MODEL; PARABOLIC METHOD PPM; MOISTURE TRANSPORT; FORECAST MODEL; ADVECTION; EQUATIONS; SIMULATIONS; STRATOSPHERE; FORMULATION AB A global shallow-water model based on the flux-form semi-lagrangian scheme is described. The mass-conserving flux-form semi-lagrangian scheme is a multidimensional semi-lagrangian extension of the higher order Godunov-type finite volume schemes (e.g., the piece-wise parabolic method). Unlike the piece-wise parabolic methodology, neither directional splitting nor a Riemann solver is involved. A reverse engineering procedure is introduced to achieve the goal of consistent transport of the absolute vorticity and the mass, and hence, the potential vorticity. Gravity waves are treated explicitly, in a manner that is consistent with the forward-in-time flux-form semi-lagrangian transport scheme. Due to the finite-volume nature of the flux-form semi-lagrangian scheme and the application of the monotonicity constraint, which can be regarded as a subgrid-scale flux parametrization, essentially noise-free solutions are obtained without additional diffusion. Two selected shallow-water test cases proposed by Williamson et al. (1992) and a stratospheric vortex erosion simulation are presented. Discussions on the accuracy and computational efficiency are given based on the comparisons with a Eulerian spectral model and two advective-form semi-implicit semi-lagrangian models. C1 NASA, Goddard Space Flight Ctr, Atmospheres Lab, Assimilat Off, Greenbelt, MD 20771 USA. Univ Maryland Baltimore Cty, Baltimore, MD 21228 USA. RP NASA, Goddard Space Flight Ctr, Atmospheres Lab, Assimilat Off, Greenbelt, MD 20771 USA. EM lin@dao.gsfc.nasa.gov RI Rood, Richard/C-5611-2008 OI Rood, Richard/0000-0002-2310-4262 NR 46 TC 136 Z9 136 U1 4 U2 11 PU WILEY-BLACKWELL PI HOBOKEN PA 111 RIVER ST, HOBOKEN 07030-5774, NJ USA SN 0035-9009 EI 1477-870X J9 Q J ROY METEOR SOC JI Q. J. R. Meteorol. Soc. PD OCT PY 1997 VL 123 IS 544 BP 2477 EP 2498 DI 10.1002/qj.49712354416 PN B PG 22 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA YM118 UT WOS:000071030400015 ER PT J AU Swaminathan, S VanHalle, JY Smidts, C Mosleh, A Bell, S Rudolph, K Mulvihill, RJ Bream, B AF Swaminathan, S VanHalle, JY Smidts, C Mosleh, A Bell, S Rudolph, K Mulvihill, RJ Bream, B TI The Cassini Mission probabilistic risk analysis: comparison of two probabilistic dynamic methodologies SO RELIABILITY ENGINEERING & SYSTEM SAFETY LA English DT Article ID SYSTEMS AB This paper describes a comparison between two dynamic methodologies used in the probabilistic risk analysis (PRA) of the Cassini Mission. The main Cassini PRA was performed by Lockheed Martin. A combination of Monte Carlo algorithms and event-tree logic was used to perform the study. Results were validated using an alternative method, the Discrete Dynamic Event Tree (DDET) methodology. Two major conclusions of the paper are 1) performing a dynamic PRA of large scale 'real-life' systems is feasible and 2) given the same ground rules and assumptions, two dynamic methodologies would give the same results. (C) 1997 Published by Elsevier Science Limited. C1 UNIV MARYLAND,DEPT MAT & NUCL ENGN,COLLEGE PK,MD 20742. MARTIN MARIETTA SYST,DENVER,CO. PRC INC,EL SEGUNDO,CA. NASA,LEWIS RES CTR,CLEVELAND,OH 44135. NR 21 TC 6 Z9 6 U1 0 U2 0 PU ELSEVIER SCI LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, OXON, ENGLAND OX5 1GB SN 0951-8320 J9 RELIAB ENG SYST SAFE JI Reliab. Eng. Syst. Saf. PD OCT PY 1997 VL 58 IS 1 BP 1 EP 14 DI 10.1016/S0951-8320(97)00052-5 PG 14 WC Engineering, Industrial; Operations Research & Management Science SC Engineering; Operations Research & Management Science GA YH119 UT WOS:A1997YH11900001 ER PT J AU Otterman, J Starr, D Brakke, T Davies, R Jacobowitz, H Mehta, A Cheruy, F Prabhakara, C AF Otterman, J Starr, D Brakke, T Davies, R Jacobowitz, H Mehta, A Cheruy, F Prabhakara, C TI Modeling zenith-angle dependence of outgoing longwave radiation: Implication for flux measurements SO REMOTE SENSING OF ENVIRONMENT LA English DT Article ID BAND RADIANCE MEASUREMENTS; NIMBUS-7 ERB DATA; BUDGET EXPERIMENT; SEASONAL-VARIATION; CIRRUS CLOUDS; BROAD-BAND; EARTH; SURFACE; ATMOSPHERE; EMISSION AB As shown in previous studies, outgoing-longwave radiation (OLR) can be in error by similar to 7% when evaluated from directional measurements by applying time-averaged angular distribution models (ADMs) to account for the emission anisotropy. In order to develop an insight into the problem of assessing hemispheric emission from directional measurements, we formulate the directional (monochromatic) greenhouse factor g(d), specified as the ratio of a longwave radiance measured above the atmosphere to that emitted from the surface at the same zenith angle theta(r). The explicit expressions for g(d) involve two atmospheric parameters, the optical thickness and the temperature-profile parameter. Oar analysis indicates that under clear conditions a narrow-band radiance, if measured at theta(v) approximate to 57 degrees in atmospheric windows (low values of optical thickness) and at theta(v) approximate to 47 degrees in absorption bands, determines the hemispheric-average radiance to within about 1%. For broad spectral bands, whether under clear or cloudy (solid cover, or ''randomly scattered'' clouds) conditions, the same finding applies at theta(v) approximate to 50 degrees. Thus, the zenith angle of equivalence theta(eq) varies by about +/-5 degrees for different values of the optical thickness; it varies only slightly for different temperature profiles (even though different temperature profiles produce quite different patterns of radiance us. theta(v), that is, different ADMs apply). Measurements at or near theta(eq) therefore constitute direct assessment of OLR, without resorting to ADMs to adjust for the variations of emission with view angle (anisotropy). The existing OLR data should be reexamined accepting measurements only within the range 45-60 degrees of view zenith angles. (C) Elsevier Science Inc., 1997. C1 UNIV ARIZONA,TUCSON,AZ. NOAA,NESDIS,CAMP SPRINGS,MD. ECOLE POLYTECH,CNRS,METEOROL DYNAM LAB,F-91128 PALAISEAU,FRANCE. RP Otterman, J (reprint author), NASA,GODDARD SPACE FLIGHT CTR,CODE 910-4,GREENBELT,MD 20771, USA. NR 36 TC 9 Z9 9 U1 1 U2 5 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 OCT PY 1997 VL 62 IS 1 BP 90 EP 100 DI 10.1016/S0034-4257(97)00084-9 PG 11 WC Environmental Sciences; Remote Sensing; Imaging Science & Photographic Technology SC Environmental Sciences & Ecology; Remote Sensing; Imaging Science & Photographic Technology GA XV029 UT WOS:A1997XV02900008 ER PT J AU Atwater, JE Dahl, RW Garmon, FC Lunsford, TD Michalek, WF Wheeler, RR AF Atwater, JE Dahl, RW Garmon, FC Lunsford, TD Michalek, WF Wheeler, RR TI Miniature microwave powered steam sterilization chamber SO REVIEW OF SCIENTIFIC INSTRUMENTS LA English DT Article AB A small device for the rapid ultrahigh temperature sterilization of surfaces is described. Microwave power generated by a 2.45 GHz magnetron is delivered via coaxial cable to a silicon carbide block housed within the chamber, Small quantities of water or aqueous hydrogen peroxide. are introduced into the chamber. Upon application of power, the liquid flashes to vapor and superheats producing temperatures to 300 degrees C. The hot vapor permeates the enclosed space and contacts all exposed surfaces. Complete microbial kill of > 10(6) colony forming units of the spore forming thermophile, Bacillus stearothermophilus, has been demonstrated using a variety of temperatures and exposure times in both steady state and thermal pulse modes of operation. (C) 1997 American Institute of Physics. C1 NASA,LYNDON B JOHNSON SPACE CTR,HOUSTON,TX 77058. RP Atwater, JE (reprint author), UMPQUA RES CO,MYRTLE CREEK,OR 97457, USA. NR 6 TC 6 Z9 6 U1 0 U2 0 PU AMER INST PHYSICS PI WOODBURY PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 SN 0034-6748 J9 REV SCI INSTRUM JI Rev. Sci. Instrum. PD OCT PY 1997 VL 68 IS 10 BP 3924 EP 3925 DI 10.1063/1.1148059 PG 2 WC Instruments & Instrumentation; Physics, Applied SC Instruments & Instrumentation; Physics GA YB160 UT WOS:A1997YB16000050 ER PT J AU Aufgang, JB Labrie, D Olson, K Paton, B Simpson, AM Iseler, GW Borshchevsky, A AF Aufgang, JB Labrie, D Olson, K Paton, B Simpson, AM Iseler, GW Borshchevsky, A TI Photoluminescence and infrared transmission spectroscopies of CdGeAs2 SO SEMICONDUCTOR SCIENCE AND TECHNOLOGY LA English DT Article ID BAND-STRUCTURE; SEMICONDUCTORS; SPECTRA AB The first detailed photoluminescence (PL) study of as-grown CdGeAs2 samples obtained from three different sources is presented. The study was carried out in the 5-100 K temperature range and laser excitation densities 0.5-5 W cm(-2) PL spectra collected on samples from all sources showed a PL band near 355 meV which is assigned to an (e, A(0)) transition to the deep native double acceptor 315 meV above the valence band edge. Samples from one source which contained substantially lower levels of oxygen also had about an order of magnitude lower values of absorption coefficient below the band gap and showed also a single PL band in their PL spectra. C1 MIT,LINCOLN LAB,LEXINGTON,MA 02173. CALTECH,JET PROP LAB,PASADENA,CA. RP Aufgang, JB (reprint author), DALHOUSIE UNIV,DEPT PHYS,HALIFAX,NS B3H 3J5,CANADA. NR 21 TC 13 Z9 13 U1 1 U2 3 PU IOP PUBLISHING LTD PI BRISTOL PA DIRAC HOUSE, TEMPLE BACK, BRISTOL, ENGLAND BS1 6BE SN 0268-1242 J9 SEMICOND SCI TECH JI Semicond. Sci. Technol. PD OCT PY 1997 VL 12 IS 10 BP 1257 EP 1264 DI 10.1088/0268-1242/12/10/013 PG 8 WC Engineering, Electrical & Electronic; Materials Science, Multidisciplinary; Physics, Condensed Matter SC Engineering; Materials Science; Physics GA YB052 UT WOS:A1997YB05200012 ER PT J AU Rhodes, EJ Kosovichev, AG Schou, J Scherrer, PH Reiter, J AF Rhodes, EJ Kosovichev, AG Schou, J Scherrer, PH Reiter, J TI Measurements of frequencies of solar oscillations from the MDI Medium-l Program SO SOLAR PHYSICS LA English DT Article ID LINE-PROFILES; ASYMMETRIES; EXCITATION; ROTATION; SPECTRUM; STATE; SUN AB Inversions of solar internal structure employ both the frequencies and the associated uncertainties of the solar oscillation modes as input parameters. In this paper we investigate how systematic errors in these input parameters may affect the resulting inferences of the sun's internal structure. Such systematic errors are likely to arise from inaccuracies in the theoretical models which are used to represent the spectral lines in the observational power spectra, from line blending, from asymmetries in the profiles of these lines, and from other factors. In order to study such systematic effects we have employed two different duration observing runs (one of 60 days and the second of 144 days) obtained with the Medium-l Program of the Michelson Doppler Imager experiment onboard the SOHO spacecraft. This observing program provides continuous observations of solar oscillation modes having angular degrees, l, ranging from 0 to similar to 300. For this study intermediate- and high-degree p-mode oscillations having degrees less than 251 were employed. In the first of our tests we employed two different methods of estimating the modal frequencies and their associated uncertainties from the 144-day observational power spectra. In our second test we also repeated both methods of frequency estimation on the 60-day time series in order to assess the influence of the duration of the observed time series on the computed frequencies and uncertainties. In a third test we investigated the sensitivity of the computed frequencies to the choice of initial-guess, or 'seed' frequencies that are used in the frequency estimation codes. In a fourth test we attempted to investigate the possible systematic frequency errors which are introduced when the observational asymmetry in the p-mode peaks is ignored. We carried out this particular test by fitting simple models of asymmetric line profiles to the peaks in the observational power spectra. We were then able to compute the differences between those frequencies and our previous frequencies which had been obtained using the assumption that all of the observational peaks were symmetric in shape. In order to study the possible influence of the two different frequency estimation methods upon the radial profile of the internal sound speed, we carried out four parallel structural inversions using the different sets and subsets of frequency estimates and uncertainties as computed from the 144-day observing run as inputs. The results of these four inversions confirm the previous finding by the GONG project (Gough et al., 1996) and by the MDI Medium-l Program (Kosovichev et al., 1997) that, in a thin layer just beneath the convection zone, helium appears to be less abundant than predicted by theory. However, differences in our four inverted radial sound speed profiles demonstrate that the currently-available techniques for determining the frequencies of the Medium-l oscillation peaks introduce systematic errors which are large enough to affect the results of the structural inversions. Moreover, based upon the differences in these four inverted sound speed profiles, it appears that the choice of which subset of modes is included in a particular inversion and which modes are not included may also be introducing systematic errors into our current understanding of solar internal structure. Hence, it appears to be very important that consistent sets of modal selection criteria be employed. Finally, at least one of the two frequency estimation codes which we used was not sensitive to changes in the input 'seed' frequencies which were employed as initial guesses for that code. This result allays fears that the difference in the helium abundance between the sun and the reference solar model in the thin layer beneath the convection zone which was mentioned above might have been due to the particular seed frequencies which were employed in the earlier inversions. Since this thin layer may likely be the place where the solar dynamo operates, it will be extremely important to observe any possible evolution of this transition layer throughout the upcoming 11-year activity cycle. C1 Univ So Calif, Dept Phys & Astron, Los Angeles, CA 90089 USA. Jet Propuls Lab, Pasadena, CA 91101 USA. Stanford Univ, WW Hansen Expt Phys Lab, Stanford, CA 94305 USA. Tech Univ Munich, Inst Math, D-80333 Munich, Germany. RP Rhodes, EJ (reprint author), Univ So Calif, Dept Phys & Astron, Los Angeles, CA 90089 USA. NR 28 TC 74 Z9 74 U1 0 U2 0 PU KLUWER ACADEMIC PUBL PI DORDRECHT PA SPUIBOULEVARD 50, PO BOX 17, 3300 AA DORDRECHT, NETHERLANDS SN 0038-0938 J9 SOL PHYS JI Sol. Phys. PD OCT PY 1997 VL 175 IS 2 BP 287 EP 310 PG 24 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YV047 UT WOS:000071784300005 ER PT J AU DeForest, CE Hoeksema, JT Gurman, JB Thompson, BJ Plunkett, SP Howard, R Harrison, RC Hassler, DM AF DeForest, CE Hoeksema, JT Gurman, JB Thompson, BJ Plunkett, SP Howard, R Harrison, RC Hassler, DM TI Polar plume anatomy: Results of a coordinated observation SO SOLAR PHYSICS LA English DT Article ID SOLAR; TELESCOPE; CORONAGRAPH AB On 7 and 8 March 1996, the SOHO spacecraft and several other space- and ground-based observatories cooperated in the most comprehensive observation to date of solar polar plumes. Based on simultaneous data from five instruments, we describe the morphology of the plumes observed over the south pole of the Sun during the SOHO observing campaign. Individual plumes have been characterized from the photosphere to approximately 15 R. yielding a coherent portrait of the features for more quantitative future studies. The observed plumes arise from small (similar to 2-5 arc sec diameter) quiescent, unipolar magnetic flux concentrations, on chromospheric network cell boundaries. They are denser and cooler than the surrounding coronal hole through which they extend, and are seen clearly in both Fe IX and Fe XII emission lines, indicating an ionization temperature between 1.0-1.5 x 10(6) K. The plumes initially expand rapidly with altitude, to a diameter of 20-30 Mm about 30 Mm off the surface. Above 1.2 R., plumes are observed in white light (as 'coronal rays') and extend to above 12 R.. They grow superradially throughout their observed height, increasing their subtended solid angle (relative to disk center) by a factor of similar to 10 between 1.05 R. and 4-5 R., and by a total factor of 20-40 between 1.05 R. and 12 R.. On spatial scales larger than 10 arc sec, plume structure in the lower corona (R < 1.3 R.) is observed to be steady-state for periods of at least 24 hours; however, on spatial scales smaller than 10 arc sec, plume XUV intensities vary by 10-20% (after background subtraction) on a time scale of a few minutes. C1 Stanford Univ, Ctr Space Sci & Astrophys, WH Hansen Expt Phys Lab, Stanford, CA 94305 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Appl Res Corp, Landover, MD USA. USN, Res Lab, EO Hulburt Ctr Space Res, Washington, DC 20375 USA. Rutherford Appleton Lab, Chilton, England. Natl Ctr Atmospher Res, High Altitude Observ, Boulder, CO 80307 USA. RP DeForest, CE (reprint author), Stanford Univ, Ctr Space Sci & Astrophys, WH Hansen Expt Phys Lab, Stanford, CA 94305 USA. RI Thompson, Barbara/C-9429-2012 NR 27 TC 165 Z9 167 U1 1 U2 3 PU KLUWER ACADEMIC PUBL PI DORDRECHT PA SPUIBOULEVARD 50, PO BOX 17, 3300 AA DORDRECHT, NETHERLANDS SN 0038-0938 J9 SOL PHYS JI Sol. Phys. PD OCT PY 1997 VL 175 IS 2 BP 393 EP 410 DI 10.1023/A:1004955223306 PG 18 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YV047 UT WOS:000071784300011 ER PT J AU Wiik, JE Schmieder, B Kucera, T Poland, A Brekke, P Simnett, G AF Wiik, JE Schmieder, B Kucera, T Poland, A Brekke, P Simnett, G TI Eruptive prominence and associated CME observed with SUMER, CDS and LASCO (SOHO) SO SOLAR PHYSICS LA English DT Article ID CORONAL MASS EJECTION; QUIESCENT PROMINENCE; SOLAR AB Observations of an eruptive prominence were obtained on 1 May 1996, with the SUMER and CDS instruments aboard SOHO during the preparatory phase of the Joint Observing Programme JOP12. A coronal mass ejection observed with LASCO is associated temporally and spatially with this prominence. The main objective of JOP12 is to study the dynamics of prominences and the prominence-corona interface. By analysing the spectra of O IV and Si IV lines observed with SUMER and the spectra of 15 lines with CDS, Doppler shifts, temperatures and electron densities (ratio of O IV 1401 to 1399 Angstrom) were derived in different structures of the prominence. The eruptive part of the prominence consists of a bubble (plasmoid) of material already at transition region temperatures with red shifts up to 100 km s(-1) and an electron density of the order of 10(10) cm(-3). The whole prominence was very active. It developed both a large helical loop and several smaller loops consisting of twisted threads or multiple ropes. These may be studied in the SUMER movie (movie 2), The profiles of the SUMER lines show a large dispersion of velocities (+/-50 km s(-1)) and the ratio of the O IV lines indicates a large dispersion in electron density (3 x 10(9) cm(-3) to 3 x 10(11) cm(-3)). The CME observed by LASCO left the corona some tens of minutes before the prominence erupted. This is evidence that the prominence eruptions are probably the result of the removal of the restraining coronal magnetic fields which are in part responsible for the original stability of the prominence. C1 ITA, N-0315 Oslo, Norway. Observ Cote Azur, F-06304 Nice 4, France. Observ Meudon, DASOP, F-92195 Meudon, France. Appl Res Corp, Landover, MD 20785 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Birmingham, Birmingham B15 2TT, W Midlands, England. RP Wiik, JE (reprint author), ITA, POB 1029, N-0315 Oslo, Norway. RI Kucera, Therese/C-9558-2012 NR 32 TC 30 Z9 30 U1 0 U2 0 PU SPRINGER PI DORDRECHT PA VAN GODEWIJCKSTRAAT 30, 3311 GZ DORDRECHT, NETHERLANDS SN 0038-0938 EI 1573-093X J9 SOL PHYS JI Sol. Phys. PD OCT PY 1997 VL 175 IS 2 BP 411 EP 436 DI 10.1023/A:1004925024794 PG 26 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YV047 UT WOS:000071784300012 ER PT J AU Fludra, A Brekke, P Harrison, RA Mason, HE Pike, CD Thompson, WT Young, PR AF Fludra, A Brekke, P Harrison, RA Mason, HE Pike, CD Thompson, WT Young, PR TI Active regions observed in extreme ultraviolet light by the coronal diagnostic spectrometer on SOHO SO SOLAR PHYSICS LA English DT Article ID SOLAR AB We present observations of five active regions made by the Coronal Diagnostic Spectrometer (CDS) on the Solar and Heliospheric Observatory (SOHO). CDS observes the Sun in the extreme ultraviolet range 150-780 Angstrom. Examples of active region loops seen in spectral lines emitted at various temperatures are shown, Several classes of loops are identified: those that are seen in all temperatures up to 2 x 10(6) K; loops seen at 10(6) K but not reaching 1.6 x 10(6) K; those at temperatures 2-4 x 10(5) K and occasionally at 6 x 10(6) K but not reaching 10(6) K. An increasing loop size with temperature and the relationship between the cool and hot structures is discussed. CDS observations reveal the existence of loops and other unresolved structures in active regions at temperatures between 1.5-4 x 10(5) K, which do not have counterparts in lines emitted above 8 x 10(5) K. Bright compact sources only seen in the transition region lines are investigated. These sources can have lifetimes of up to several days and are located in the vicinity of sunspots, We study the variability of active region sources on time scales from 30 sec to several days. We find oscillatory behaviour of He I and O V line intensities in an active region on time scales of 5-10 min. C1 Rutherford Appleton Lab, Dept Space Sci, Didcot OX11 0QX, Oxon, England. Univ Oslo, Inst Theoret Astrophys, N-0315 Oslo, Norway. Univ Cambridge, Dept Appl Math & Theoret Phys, Cambridge CB3 9EW, England. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Fludra, A (reprint author), Rutherford Appleton Lab, Dept Space Sci, Didcot OX11 0QX, Oxon, England. RI Thompson, William/D-7376-2012 NR 21 TC 59 Z9 59 U1 0 U2 0 PU KLUWER ACADEMIC PUBL PI DORDRECHT PA SPUIBOULEVARD 50, PO BOX 17, 3300 AA DORDRECHT, NETHERLANDS SN 0038-0938 J9 SOL PHYS JI Sol. Phys. PD OCT PY 1997 VL 175 IS 2 BP 487 EP 509 DI 10.1023/A:1004933209773 PG 23 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YV047 UT WOS:000071784300016 ER PT J AU Moses, D Clette, F Delaboudiniere, JP Artzner, GE Bougnet, M Brunaud, J Carabetian, C Gabriel, AH Hochedez, JF Millier, F Song, XY Au, B Dere, KP Howard, RA Kreplin, R Michels, DJ Defise, JM Jamar, C Rochus, P Chauvineau, JP Marioge, JP Catura, RC Lemen, JR Shing, L Stern, RA Gurman, JB Neupert, WM Newmark, J Thompson, B Maucherat, A Portier-Fozzani, F Berghmans, D Cugnon, P Van Dessel, EL Gabryl, JR AF Moses, D Clette, F Delaboudiniere, JP Artzner, GE Bougnet, M Brunaud, J Carabetian, C Gabriel, AH Hochedez, JF Millier, F Song, XY Au, B Dere, KP Howard, RA Kreplin, R Michels, DJ Defise, JM Jamar, C Rochus, P Chauvineau, JP Marioge, JP Catura, RC Lemen, JR Shing, L Stern, RA Gurman, JB Neupert, WM Newmark, J Thompson, B Maucherat, A Portier-Fozzani, F Berghmans, D Cugnon, P Van Dessel, EL Gabryl, JR TI EIT observation of the Extreme Ultraviolet Sun SO SOLAR PHYSICS LA English DT Article ID X-RAY TELESCOPE; TRANSITION REGION; YOHKOH; ATMOSPHERE; CORONA; LOOPS; JETS AB The Extreme Ultraviolet Imaging Telescope (EIT) on board the SOHO spacecraft has been operational since 2 January 1996, EIT observes the Sun over a 45 x 45 are min field of view in four emission line groups: FeIX, X, FeXII, FeXV, and HeII. A post launch determination of the instrument flatfield, the instrument scattering function, and the instrument aging were necessary for the reduction and analysis of the data. The observed structures and their evolution in each of the four EUV bandpasses are characteristic of the peak emission temperature of the line(s) chosen for that bandpass. Reports on the initial results of a variety of analysis projects demonstrate the range of investigations now underway: EIT provides new observations of the corona in the temperature range of 1 to 2 MK. Temperature studies of the large-scale coronal features extend previous coronagraph work with low-noise temperature maps. Temperatures of radial, extended, plume-like structures in both the polar coronal hole and in a low latitude decaying active region were found to be cooler than the surrounding material, Active region loops were investigated in detail and found to be isothermal for the low loops but hottest at the loop tops for the large loops. Variability of solar EUV structures, as observed the EIT time sequences, is pervasive and leads to a re-evaluation of the meaning of the term 'quiet Sun'. Intensity fluctuations in a high cadence sequence of coronal and chromospheric images correspond to a Kolmogorov turbulence spectrum. This can be interpreted in terms of a mixed stochastic or periodic driving of the transition region and the base of the corona. No signature of the photospheric and chromospheric waves is found in spatially averaged power spectra, indicating that these waves do not propagate to the upper atmosphere or are channeled through narrow local magnetic structures covering a small fraction of the solar surface. Polar coronal hole observing campaigns have identified an outflow process with the discovery of transient FeXII jets. Coronal mass ejection observing campaigns have identified the beginning of a CME in an FeXII sequence with a near simultaneous filament eruption (seen in absorption), formation of a coronal void and the initiation of a bright outward moving shell as well as the coronal manifestation of a 'Moreton wave'. C1 USN, Res Lab, Washington, DC 20375 USA. Observ Royal Belgique, B-1180 Brussels, Belgium. Univ Paris 11, Inst Astrophys Spatiale, F-91405 Orsay, France. Ctr Spatial Liege, B-4031 Liege, Belgium. Inst Opt Theor & Appl, F-91403 Orsay, France. Lockheed Palo Alto Res Lab, Palo Alto, CA 94304 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. CNRS, Astron Spatiale Lab, F-13012 Marseille, France. RP Moses, D (reprint author), USN, Res Lab, Washington, DC 20375 USA. RI Thompson, Barbara/C-9429-2012 NR 32 TC 262 Z9 269 U1 2 U2 5 PU KLUWER ACADEMIC PUBL PI DORDRECHT PA SPUIBOULEVARD 50, PO BOX 17, 3300 AA DORDRECHT, NETHERLANDS SN 0038-0938 J9 SOL PHYS JI Sol. Phys. PD OCT PY 1997 VL 175 IS 2 BP 571 EP 599 DI 10.1023/A:1004902913117 PG 29 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YV047 UT WOS:000071784300021 ER PT J AU Dere, KP Brueckner, GE Howard, RA Koomen, MJ Korendyke, CM Kreplin, RW Michels, DJ Moses, JD Moulton, NE Socker, DG St Cyr, OC Delaboudiniere, JP Artzner, GE Brunaud, J Gabriel, AH Millier, F Song, XY Chauvineau, JP Marioge, JP Defise, JM Jamar, C Rochus, P Catura, RC Lemen, JR Gurman, JB Neupert, W Clette, F Cugnon, P Van Dessel, EL Lamy, PL Llebaria, A Schwenn, R Simnett, GM AF Dere, KP Brueckner, GE Howard, RA Koomen, MJ Korendyke, CM Kreplin, RW Michels, DJ Moses, JD Moulton, NE Socker, DG St Cyr, OC Delaboudiniere, JP Artzner, GE Brunaud, J Gabriel, AH Millier, F Song, XY Chauvineau, JP Marioge, JP Defise, JM Jamar, C Rochus, P Catura, RC Lemen, JR Gurman, JB Neupert, W Clette, F Cugnon, P Van Dessel, EL Lamy, PL Llebaria, A Schwenn, R Simnett, GM TI EIT and LASCO observations of the initiation of a coronal mass ejection SO SOLAR PHYSICS LA English DT Article ID TELESCOPE; FILAMENT AB We present the first observations of the initiation of a coronal mass ejection (CME) seen on the disk of the Sun. Observations with the EIT experiment on SOHO show that the CME be an in a small volume and was initially associated with slow motions of prominence material and a small brightening at one end of the prominence. Shortly afterward! the prominence was accelerated to about 100 km s(-1) and was preceded by a bright loop-like structure, which surrounded an emission void, that traveled out into the corona at a velocity of 200-400 km s(-1). These three components, the prominence, the dark void, and the bright loops are typical of CMEs when seen at distance in the corona and here are shown to be present at the earliest stages of the CME. The event was later observed to traverse the LASCO coronagraphs fields of view from 1.1 to 30 RE.. Of particular interest is the fact that this large-scale event, spanning as much as 70 deg in latitude, originated in a volume with dimensions of roughly 35" (2.5 x 10(4) km). Further, a disturbance that propagated across the disk and a chain of activity near the limb may also be associated with this event as well as a considerable degree of activity near the west limb. C1 USN, EO Hulburt Ctr Space Res, Res Lab, Washington, DC 20375 USA. Univ Paris 11, Inst Astrophys Spatiale, F-91405 Orsay, France. Inst Opt Theor & Appl, F-91403 Orsay, France. Ctr Spatial Liege, Liege, Belgium. Lockheed Martin Palo Alto Res Lab, Palo Alto, CA 94304 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Observ Royal Belgique, B-1180 Brussels, Belgium. CNRS, Astron Spatiale Lab, F-13012 Marseille, France. Max Planck Inst Aeron, Lindau, Germany. Univ Birmingham, Sch Phys & Space Res, Space Res Grp, Birmingham B15 2TT, W Midlands, England. RP Dere, KP (reprint author), USN, EO Hulburt Ctr Space Res, Res Lab, Washington, DC 20375 USA. NR 14 TC 149 Z9 152 U1 1 U2 3 PU KLUWER ACADEMIC PUBL PI DORDRECHT PA SPUIBOULEVARD 50, PO BOX 17, 3300 AA DORDRECHT, NETHERLANDS SN 0038-0938 J9 SOL PHYS JI Sol. Phys. PD OCT PY 1997 VL 175 IS 2 BP 601 EP 612 DI 10.1023/A:1004907307376 PG 12 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YV047 UT WOS:000071784300022 ER PT J AU Plunkett, SP Brueckner, GE Dere, KP Howard, RA Koomen, MJ Korendyke, CM Michels, DJ Moses, JD Moulton, NE Paswaters, SE St Cyr, OC Socker, DG Wang, D Simnett, GM Bedford, DK Biesecker, DA Eyles, CJ Tappin, SJ Schwenn, R Lamy, PL Llebaria, A AF Plunkett, SP Brueckner, GE Dere, KP Howard, RA Koomen, MJ Korendyke, CM Michels, DJ Moses, JD Moulton, NE Paswaters, SE St Cyr, OC Socker, DG Wang, D Simnett, GM Bedford, DK Biesecker, DA Eyles, CJ Tappin, SJ Schwenn, R Lamy, PL Llebaria, A TI The relationship of green-line transients to white-light coronal mass ejections SO SOLAR PHYSICS LA English DT Article ID TELESCOPE AB We report observations by the Large Angle Spectrometric Coronagraph (LASCO) on the SOHO spacecraft of three coronal green line transients that could be clearly associated with coronal mass elections (CMEs) detected in Thomson-scattered white light. Two of these events, with speeds > 25 km s(-1), may be classified as 'whip-like' transients. They are associated with the core of the white-light CMEs, identified with erupting prominence material, rather than with the leading edge of the CMEs. The third green-line transient has a markedly different appearance and is more gradual than the other two, with a projected outward speed < 10 km s(-1). This event corresponds to the leading edge of a 'streamer blowout' type of CME. A dark void is left behind in the emission-line corona following each of the fast eruptions. Both fast emission-line transients start off as a loop structure rising up from close to the solar surface. We suggest that the driving mechanism for these events may be the emergence of new bipolar magnetic regions on the surface of the Sun, which destabilize the ambient corona and cause an eruption. The possible relationship of these events to recent X-ray observations of CMEs is briefly discussed. C1 NASA, Univ Space Res Assoc, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. USN, EO Hulburt Ctr Space Res, Res Lab, Washington, DC 20375 USA. Univ Birmingham, Sch Phys & Space Res, Birmingham B15 2TT, W Midlands, England. Max Planck Inst Aeron, D-37189 Katlenburg Lindau, Germany. Astron Spatiale Lab, F-13376 Marseille 12, France. RP Plunkett, SP (reprint author), NASA, Univ Space Res Assoc, Goddard Space Flight Ctr, Mail Code 682-3, Greenbelt, MD 20771 USA. NR 22 TC 37 Z9 37 U1 0 U2 0 PU KLUWER ACADEMIC PUBL PI DORDRECHT PA SPUIBOULEVARD 50, PO BOX 17, 3300 AA DORDRECHT, NETHERLANDS SN 0038-0938 J9 SOL PHYS JI Sol. Phys. PD OCT PY 1997 VL 175 IS 2 BP 699 EP 718 DI 10.1023/A:1004981125702 PG 20 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YV047 UT WOS:000071784300027 ER PT J AU Goldsten, JO Mcnutt, RL Gold, RE Gary, SA Fiore, E Schneider, SE Hayes, JR Trombka, JI Floyd, SR Boynton, WV Bailey, S Bruckner, J Squyres, SW Evans, LG Clark, PE Starr, R AF Goldsten, JO Mcnutt, RL Gold, RE Gary, SA Fiore, E Schneider, SE Hayes, JR Trombka, JI Floyd, SR Boynton, WV Bailey, S Bruckner, J Squyres, SW Evans, LG Clark, PE Starr, R TI The X-ray/Gamma-ray Spectrometer on the Near Earth Asteroid Rendezvous mission SO SPACE SCIENCE REVIEWS LA English DT Review ID SPECTROSCOPY AB An X-ray/gamma-ray spectrometer has been developed as part of a rendezvous mission with the near-Earth asteroid, 433 Eros, in an effort to answer fundamental questions about the nature and origin of asteroids and comets. During about 10 months of orbital operations commencing in early 1999, the X-ray/Gamma-ray Spectrometer will develop global maps of the elemental composition of the surface of Eros. The instrument remotely senses characteristic X-ray and gamma-ray emissions to determine composition. Solar excited X-ray fluorescence in the 1 to 10 keV range will be used to measure the surface abundances of Mg, Al, Si, Ca, Ti, and Fe with spatial resolutions down to 2 km. Gamma-ray emissions in the 0.1 to 10 MeV range will be used to measure cosmic-ray excited elements O, Si, Fe, H and naturally radioactive elements K, Th, U to surface depths on the order of 10 cm. The X-ray spectrometer consists of three gas filled proportional counters with a collimated field of view of 5 degrees and an energy resolution of 850 eV @ 5.9 keV. Two sunward looking X-ray detectors monitor the incident solar flux, one of which is the first flight of a new, miniature solid-state detector which achieves 600 eV resolution @ 5.9 keV. The gamma-ray spectrometer consists of a NaI(Tl) scintillator situated within a Bismuth Germanate (BGO) cup, which provides both active and passive shielding to confine the held of view and eliminate the need for a massive and costly boom. New coincidence techniques enable recovery of single and double escape events in the central detector. The NaI(Tl) and BGO detectors achieve energy resolutions of 8.7% and 14%, respectively @ 0.662 MeV. A data processing unit based on an RTX2010 microprocessor provides the spacecraft interface and produces 256-channel spectra for X-ray detectors and 1024-channel spectra for the raw, coincident, and anti-coincident gamma-ray modes. This paper presents a detailed overview of the X-ray/Gamma-ray Spectrometer and describes the science objectives, measurement objectives, instrument design, and shows some results from early in-flight data. C1 Johns Hopkins Univ, Appl Phys Lab, Laurel, MD 20723 USA. NASA, Goddard Space Flight Ctr, Extraterr Phys Lab, Greenbelt, MD 20771 USA. Univ Arizona, Lunar & Planetary Lab, Tucson, AZ 85721 USA. Max Planck Inst Chem, D-55128 Mainz, Germany. Cornell Univ, Dept Astron, Ithaca, NY 14853 USA. Comp Sci Corp, Sci Programs, Lanham, MD 20706 USA. Catholic Univ Amer, Washington, DC 20064 USA. RP Goldsten, JO (reprint author), Johns Hopkins Univ, Appl Phys Lab, Johns Hopkins Rd, Laurel, MD 20723 USA. RI McNutt, Ralph/E-8006-2010 OI McNutt, Ralph/0000-0002-4722-9166 NR 19 TC 36 Z9 36 U1 0 U2 0 PU SPRINGER PI DORDRECHT PA VAN GODEWIJCKSTRAAT 30, 3311 GZ DORDRECHT, NETHERLANDS SN 0038-6308 J9 SPACE SCI REV JI Space Sci. Rev. PD OCT PY 1997 VL 82 IS 1-2 BP 169 EP 216 DI 10.1023/A:1005052720796 PG 48 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YX814 UT WOS:000072082300005 ER PT J AU Cole, TD Boies, MT El-Dinary, AS Cheng, A Zuber, MT Smith, DE AF Cole, TD Boies, MT El-Dinary, AS Cheng, A Zuber, MT Smith, DE TI The Near-Earth Asteroid Rendezvous laser altimeter SO SPACE SCIENCE REVIEWS LA English DT Review ID RANGEFINDER AB In 1999 after a 3-year transit, the Near-Earth Asteroid Rendezvous (NEAR) spacecraft will enter a low-altitude orbit around the asteroid, 433 Eros. Onboard the spacecraft, five facility instruments will operate continuously during the planned one-year orbit at Eros. One of these instruments, the NEAR Laser Rangefinder (NLR), will provide sufficiently high resolution and accurate topographical profiles that when combined with gravity estimates will result with quantitative insight into the internal structure, rotational dynamics, and evolution of Eros. Developed at the Applied Physics Laboratory (APL), the NLR instrument is a direct-detection laser radar using a bistatic arrangement. The transmitter is a gallium arsenide (GaAs) diode-pumped Cr:Nd:YAG (1.064-mu m) laser and the separate receiver uses an extended infrared performance avalanche-photodiode (APD) detector with 7.62-cm clear aperture Dall-Kirkham telescope. The lithium-niobate (LiNbO3) Q-switched transmitter emits 15-ns pulses at 15.3 mJ pulse(-1), permitting reliable NLR operation beyond the required 50-km altitude. With orbital velocity of 5 m s(-1) and a sampling rate of 1 Hz, the NLR spot size provides high spatial sampling of Eros along the orbital direction. Cross-track sampling, determined by the specific orbital geometry with Eros, defines the resolution of the global topographic model; this spacing is expected to be <500 m on the asteroid's surface. Combining the various sources of range errors results with an overall range accuracy of 6 m with respect to Eros' center-of-mass. The NLR instrument design, perfomance, and validation testing is decribed. In addition, data derived from the NLR are discussed. Using altimetry data from the NLR, we expect to estimate the volume of 433 Eros to 0.01% and its mass to 0.0001% accuracies; significantly greater accuracies than ever possible before NEAR. C1 Johns Hopkins Univ, Appl Phys Lab, Dept Space, Laurel, MD 20723 USA. MIT, Dept Earth Atmospher & Planetary Sci, Cambridge, MA 02139 USA. NASA, Terr Phys Lab, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Cole, TD (reprint author), Johns Hopkins Univ, Appl Phys Lab, Dept Space, Johns Hopkins Rd, Laurel, MD 20723 USA. NR 15 TC 16 Z9 16 U1 0 U2 3 PU KLUWER ACADEMIC PUBL PI DORDRECHT PA SPUIBOULEVARD 50, PO BOX 17, 3300 AA DORDRECHT, NETHERLANDS SN 0038-6308 J9 SPACE SCI REV JI Space Sci. Rev. PD OCT PY 1997 VL 82 IS 1-2 BP 217 EP 253 DI 10.1023/A:1005056828065 PG 37 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YX814 UT WOS:000072082300006 ER PT J AU Lohr, DA Zanetti, LJ Anderson, BJ Potemra, TA Hayes, JR Gold, RE Henshaw, RM Mobley, FF Holland, DB AF Lohr, DA Zanetti, LJ Anderson, BJ Potemra, TA Hayes, JR Gold, RE Henshaw, RM Mobley, FF Holland, DB TI NEAR magnetic field investigation, instrumentation, spacecraft magnetics and data access SO SPACE SCIENCE REVIEWS LA English DT Review ID SATELLITE AB The primary objective of the investigation is the search for a body-wide magnetic field of the near Earth asteroid Eros. The Near Earth Asteroid Rendezvous (NEAR) 3-axis fluxgate magnetometer includes a sensor mounted on the high-gain antenna feed structure. The NEAR Magnetic Facility Instrument (MFI) is a joint hardware effort between GSFC and APL. The design and magnetics approach achieved by the NEAR MFI effort entailed low-cost, up-front attention to engineering solutions which did not impact the schedule. The goal of the magnetometer is reliable magnetic field measurements within 5 nT, which necessitates the use of an extensive spacecraft magnetic interference model but is achievable with the full year's orbital data set. Such a goal has been shown viable with recent in-flight calibration data and comparisons to the WIND magnetometer data. The NEAR MFI effort has succeeded in providing magnetic field measurements for the first flight in NASA's Discovery line. C1 Johns Hopkins Univ, Appl Phys Lab, Laurel, MD 20723 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Lohr, DA (reprint author), Johns Hopkins Univ, Appl Phys Lab, Johns Hopkins Rd, Laurel, MD 20723 USA. RI Anderson, Brian/I-8615-2012 NR 20 TC 9 Z9 9 U1 0 U2 0 PU KLUWER ACADEMIC PUBL PI DORDRECHT PA SPUIBOULEVARD 50, PO BOX 17, 3300 AA DORDRECHT, NETHERLANDS SN 0038-6308 J9 SPACE SCI REV JI Space Sci. Rev. PD OCT PY 1997 VL 82 IS 1-2 BP 255 EP 281 DI 10.1023/A:1005089829882 PG 27 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YX814 UT WOS:000072082300007 ER PT J AU Zhu, DM Miller, RA AF Zhu, DM Miller, RA TI Investigation of thermal fatigue behavior of thermal barrier coating systems SO SURFACE & COATINGS TECHNOLOGY LA English DT Article; Proceedings Paper CT 24th International Conference on Metallurgical Coatings and Thin Films (ICMCTF 97) CY APR 21-25, 1997 CL SAN DIEGO, CA SP Amer Vacuum Soc, Vacuum Met & Thin Films Div DE thermal fatigue; thermal barrier coating systems; crack growth AB In the present study, the mechanisms of fatique crack initiation and propagation, and of coating failure under thermal loads that simulate those in diesel engines are investigated. Surface cracks initiate early and grow continuously under thermal low cycle fatique (LCF) and high cycle fatigue (HCF) stresses. It is found that, in the absence of interfacial oxidation, the failure associated with LCF is closely related to coating sintering and creep at high temperatures. Significant LCF and HCF interactions have been observed in the thermal fatigue tests. The fatigue crack growth rate in the ceramic coating strongly depends on the characteristic HCF cycle number. N*(HCF), which is defined as the number of HCF cycles per LCF cycle. The crack growth rate is increased from 0.36 mu m/LCF cycle for a pure LCF test to 2.8 mu m/LCF cycle for a combined LCF and HCF test at N*(HCF) about 20 000, A surface wedging model has been proposed to account for the HCF crack growth in the coating systems. This mechanism predicts that the HCF damage effect increases with heat Bur and thus with increasing surface temperature swine, thermal expansion coefficient and elastic modulus of the ceramic coating. as well as with the HCF interacting depth. Good correlation has been found between the analysis and experimental evidence. (C) 1997 Elsevier Science S.A. C1 NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. RP Zhu, DM (reprint author), NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. NR 19 TC 19 Z9 19 U1 2 U2 12 PU ELSEVIER SCIENCE SA PI LAUSANNE PA PO BOX 564, 1001 LAUSANNE, SWITZERLAND SN 0257-8972 J9 SURF COAT TECH JI Surf. Coat. Technol. PD OCT PY 1997 VL 94-5 IS 1-3 BP 94 EP 101 DI 10.1016/S0257-8972(97)00484-2 PG 8 WC Materials Science, Coatings & Films; Physics, Applied SC Materials Science; Physics GA YL682 UT WOS:000070981000017 ER PT J AU Bozzolo, G Ferrante, J AF Bozzolo, G Ferrante, J TI Alloy surface structure: Computer simulations using the BFS method SO SURFACE REVIEW AND LETTERS LA English DT Article; Proceedings Paper CT 5th International Conference on the Structure of Surfaces (ICSOS-5) CY JUL 08-12, 1996 CL UNIV AIX MARSEILLE, AIX PROVENCE, FRANCE HO UNIV AIX MARSEILLE AB The use of semiempirical methods for modeling ahoy properties has proven to be difficult and limited. The two primary approaches to this modeling, the embedded atom method and the phenomenological method of Miedema, have serious limitations in the range of materials studied and the degree of success in predicting properties of such systems. Recently, a new method has been developed by Bozzolo, Ferrante and Smith (BFS) which has had considerable success in predicting a wide range of alloy properties. In this work, we reference previous BFS applications to surface alloy formation and alloy surface structure, leading to the analysis of binary and ternary Ni-based alloy surfaces. We present Monte Carlo simulation results of thin films of NiAl and Ni-Al-Ti alloys, for a wide range of concentration of the Ti alloying addition. The composition of planes close to the surface as well as bulk features are discussed. C1 Analex Corp, Brook Pk, OH 44142 USA. NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. RP Bozzolo, G (reprint author), Analex Corp, 3001 Aerosp Pkwy, Brook Pk, OH 44142 USA. NR 10 TC 2 Z9 2 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 0218-625X J9 SURF REV LETT JI Surf. Rev. Lett. PD OCT PY 1997 VL 4 IS 5 BP 825 EP 828 DI 10.1142/S0218625X97000845 PG 4 WC Chemistry, Physical; Physics, Condensed Matter SC Chemistry; Physics GA YL958 UT WOS:000071012500005 ER PT J AU Chen, TC Chen, JM Schubert, S AF Chen, TC Chen, JM Schubert, S TI Interannual variation of atmospheric mass and the southern oscillation SO TELLUS SERIES A-DYNAMIC METEOROLOGY AND OCEANOGRAPHY LA English DT Article ID CIRCULATION FEATURES; ANOMALIES AB Two reanalysis datasets, one generated by the Goddard Laboratory for Atmospheres for 1982-1993 and the other generated by the National Centers for Environmental Prediction for 1982-1995, are used to examine the relationship between the Southern Oscillation (SO) and the interannual variation of atmospheric mass. Both reanalyses show that atmospheric mass increases (decreases) during the positive (negative) SO phase. Atmospheric mass consists of dry air and moisture. Since dry mass is conserved, the interannual variation of atmospheric mass results from the variation of water vapor pressure. Thus, global atmospheric hydrological processes are analyzed to illustrate how the SO affects the interannual variation of atmospheric mass. During the positive (negative) SO phase, water vapor is converged (diverged) toward (out of) the central-eastern tropical Pacific [where sea surface temperatures (SSTs) are higher (lower) than normal] to maintain (suppress) cumulus convection in that area. An anomalous east-west Walker circulation straddling the Dateline is driven by the anomalous cumulus convection in this region to create positive (negative) surface pressure anomalies over the western tropical Pacific-Indian Ocean, which result in an increase (decrease) in atmospheric mass. C1 NASA,GODDARD SPACE FLIGHT CTR,ATMOSPHERES LAB,DATA ASSIMILAT OFF,GREENBELT,MD 20771. RP Chen, TC (reprint author), IOWA STATE UNIV SCI & TECHNOL,DEPT GEOL & ATMOSPHER SCI,ATMOSPHER SCI PROGRAM,3010 AGRON HALL,AMES,IA 50011, USA. NR 32 TC 1 Z9 1 U1 0 U2 0 PU MUNKSGAARD INT PUBL LTD PI COPENHAGEN PA 35 NORRE SOGADE, PO BOX 2148, DK-1016 COPENHAGEN, DENMARK SN 0280-6495 J9 TELLUS A JI Tellus Ser. A-Dyn. Meteorol. Oceanol. PD OCT PY 1997 VL 49 IS 5 BP 544 EP 558 DI 10.1034/j.1600-0870.1997.t01-4-00003.x PG 15 WC Meteorology & Atmospheric Sciences; Oceanography SC Meteorology & Atmospheric Sciences; Oceanography GA YG149 UT WOS:A1997YG14900003 ER PT J AU Chen, TC Chen, JM Schubert, S Takacs, LL AF Chen, TC Chen, JM Schubert, S Takacs, LL TI Seasonal variation of global surface pressure and water vapor SO TELLUS SERIES A-DYNAMIC METEOROLOGY AND OCEANOGRAPHY LA English DT Article ID CYCLE AB Previous studies have shown that the seasonal variation of global-mean surface pressure (p(s)) results from variation of global-mean water vapor pressure (p(w)). The current study, employing the global data generated by Version 1 of the Goddard Earth Observing System (GEOS-1) Data Assimilation System, shows that seasonal variations of regional p(s) and p(w) tend to be out of phase (particularly in the subtropics of the two hemispheres) and that the magnitude of the former variation is generally much larger than that of the latter. The seasonal variations of these two quantities are maintained by airmass and water vapor transports by the global divergent circulation, which is driven by the latent heat released by cumulus convection over the water vapor sink, as the ''water mass forcing'' mechanism predicted. Since p(w) and p(s) are used often in depicting the climate system, assessments of climate change in terms of the global-mean and regional variations of these two variables should be interpreted with caution. C1 NASA,GODDARD SPACE FLIGHT CTR,ATMOSPHERES LAB,DATA ASSIMILAT OFF,GREENBELT,MD 20771. RP Chen, TC (reprint author), IOWA STATE UNIV SCI & TECHNOL,DEPT GEOL & ATMOSPHER SCI,ATMOSPHER SCI PROGRAM,3010 AGRON HALL,AMES,IA 50011, USA. NR 11 TC 11 Z9 17 U1 0 U2 0 PU MUNKSGAARD INT PUBL LTD PI COPENHAGEN PA 35 NORRE SOGADE, PO BOX 2148, DK-1016 COPENHAGEN, DENMARK SN 0280-6495 J9 TELLUS A JI Tellus Ser. A-Dyn. Meteorol. Oceanol. PD OCT PY 1997 VL 49 IS 5 BP 613 EP 621 DI 10.1034/j.1600-0870.1997.t01-4-00007.x PG 9 WC Meteorology & Atmospheric Sciences; Oceanography SC Meteorology & Atmospheric Sciences; Oceanography GA YG149 UT WOS:A1997YG14900007 ER PT J AU Lee, TJ Bauschlicher, CW Jayatilaka, D AF Lee, TJ Bauschlicher, CW Jayatilaka, D TI A challenge for density functional theory: the XONO and XNO2 (X=F, Cl, and Br) molecules SO THEORETICAL CHEMISTRY ACCOUNTS LA English DT Article DE density functional theory; hybrid methods; coupled-cluster theory; Cis-XONO (X=F, Cl and Br) molecules and isomers ID GAUSSIAN-BASIS SETS; CORRELATION-ENERGY; ELECTRON-GAS; ROW ATOMS; FONO; APPROXIMATION; CONTRACTION; EXCHANGE; ACCURATE; 1ST-ROW AB The equilibrium geometries, harmonic frequencies, dipole moments, infrared intensities, and relative energies of the cis-XONO, trans-XONO, and XNO2 (X=F, Cl, and Br) have been investigated using four functionals in common use in Kohn-Sham density functional theory (DFT) calculations. Two of the functionals include non-local or gradient correction terms, while the other two also incorporate some exact Hartree-Fock exchange and are labeled hybrid functionals. The quality of the results obtained from the functionals is determined by comparison to previously published high-level coupled-cluster calculations. The hybrid functionals perform better for prediction of the equilibrium geometries, where the two gradient corrected functionals yield qualitatively incorrect molecular structures for cis-FONO and cis-ClONO. None of the functionals perform well in predicting all six harmonic frequencies, showing that the correlation between equilibrium geometries and harmonic frequencies is not as strong for these DFT methods as it is for conventional wavefunction ab initio methods, such as coupled-cluster theory. Results from the various functionals generally come into better agreement with each other and also with the coupled-cluster results moving down the periodic table. C1 UNIV WESTERN AUSTRALIA,DEPT CHEM,NEDLANDS,WA 6907,AUSTRALIA. RP Lee, TJ (reprint author), NASA,AMES RES CTR,MS230-3,MOFFETT FIELD,CA 94035, USA. RI Jayatilaka, Dylan/B-3498-2012; Lee, Timothy/K-2838-2012 OI Jayatilaka, Dylan/0000-0002-3349-5834; NR 29 TC 25 Z9 25 U1 0 U2 0 PU SPRINGER VERLAG PI NEW YORK PA 175 FIFTH AVE, NEW YORK, NY 10010 SN 1432-881X J9 THEOR CHEM ACC JI Theor. Chem. Acc. PD OCT PY 1997 VL 97 IS 1-4 BP 185 EP 194 DI 10.1007/s002140050252 PG 10 WC Chemistry, Physical SC Chemistry GA YC025 UT WOS:A1997YC02500021 ER PT J AU Sliney, HE AF Sliney, HE TI Sliding contact PM212 bearings for service to 700 degrees C SO TRIBOLOGY TRANSACTIONS LA English DT Article; Proceedings Paper CT 52nd Annual Meeting of the Society-of-Tribologists-and-Lubrication-Engineers CY MAY 18-22, 1997 CL KANSAS CITY, MO SP Soc Tribologists & Lubricat Engineers DE composite bearing; self-lubricating bearings; solid lubricated bearings; journal bearings; high temperatures ID STIRLING ENGINE; COMPOSITE; TRIBOLOGY; COATINGS; AIR AB Cylindrical, sliding contact bearings made entirely of the self-lubricating powder metallurgy composite (PM212) or of superalloy shells lined with clad PM212 were tested in an oscillating mode at temperatures fi-om 25 degrees to 700 degrees C. Tests of 100-hour duration or longer were conducted with the journal oscillating +/- 15 degrees at a frequency of 42 cycles/min and at a bearing unit load of 3.45 MPa (500 psi). Shorter duration tests at various unit loads up to 24.2 MPa (3500 psi) were also conducted. In comparison tests, bearings lubricated with PM212 had lower friction and superior antiwear characteristics compared to the baseline unlubricated, superalloy bearings. No galling of PM212-lubricated bearings occurred, while severe surface damage including galling occurred, especially at high loads, during the baseline tests. A heat treatment procedure, which dimensionally stabilizes PM212 and thereby minimizes clearance changes during high temperature bearing operation, is described. RP Sliney, HE (reprint author), NASA,LEWIS RES CTR,CLEVELAND,OH 44135, USA. NR 14 TC 1 Z9 1 U1 0 U2 1 PU SOC TRIBOLOGISTS & LUBRICATION ENGINEERS PI PARK RIDGE PA 840 BUSSE HIGHWAY, PARK RIDGE, IL 60068 SN 0569-8197 J9 TRIBOL T JI Tribol. Trans. PD OCT PY 1997 VL 40 IS 4 BP 579 EP 588 DI 10.1080/10402009708983695 PG 10 WC Engineering, Mechanical SC Engineering GA YE971 UT WOS:A1997YE97100005 ER PT J AU Dellacorte, C Fellenstein, JA AF Dellacorte, C Fellenstein, JA TI The effect of compositional tailoring on the thermal expansion and tribological properties of PS300: A solid lubricant composite coating SO TRIBOLOGY TRANSACTIONS LA English DT Article; Proceedings Paper CT 52nd Annual Meeting of the Society-of-Tribologists-and-Lubrication-Engineers CY MAY 18-22, 1997 CL KANSAS CITY, MO SP Soc Tribologists & Lubricat Engineers DE solid lubricant; surface films/coatings; adverse environments tribology AB This paper describes a research program in which the goal is to alter the thermal expansion coefficient of a composite solid lubricant coating, PS300, by compositional tailoring. PS300 is a plasma-sprayed coating consisting of chrome oxide, silver and barium fluoride/calcium fluoride eutectic in NiCr binder. By adjusting the composition, the thermal expansion coefficient can be altered, and hence chosen, to more closely match a selected substrate preventing coating spallation at extreme temperatures. Thermal expansion coefficients (CTEs) for a variety of compositions were measured from 25 degrees to 800 degrees C using a commercial dilatometer. The CTEs ranged from 7.0 to 13 x 10(-6)/degrees C depending on the binder content. Subsequent tribological testing of a modified composition indicated that friction and wear properties were generally comparable, and for some operating conditions superior, to the original composition. C1 OHIO AEROSP INST,CLEVELAND,OH 44142. RP Dellacorte, C (reprint author), NASA,LEWIS RES CTR,CLEVELAND,OH 44125, USA. NR 7 TC 41 Z9 44 U1 0 U2 5 PU SOC TRIBOLOGISTS & LUBRICATION ENGINEERS PI PARK RIDGE PA 840 BUSSE HIGHWAY, PARK RIDGE, IL 60068 SN 0569-8197 J9 TRIBOL T JI Tribol. Trans. PD OCT PY 1997 VL 40 IS 4 BP 639 EP 642 DI 10.1080/10402009708983703 PG 4 WC Engineering, Mechanical SC Engineering GA YE971 UT WOS:A1997YE97100013 ER PT J AU Sigl, G Schramm, DN Lee, SJ Hill, CT AF Sigl, G Schramm, DN Lee, SJ Hill, CT TI Implications of a possible clustering of highest-energy cosmic rays SO PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA LA English DT Article ID AIR SHOWER ARRAY; MAGNETIC-FIELDS; GAMMA-RAYS; TOPOLOGICAL DEFECTS; BURSTS; SPECTRUM; ORIGIN; SEARCH; ACCELERATION; RADIATION AB Recently, a possible clustering of a subset of observed ultra-high energy cosmic rays above similar or equal to 40 EeV (4 x 10(19) eV) in pairs near the supergalactic plane was reported. We show that a confirmation of this effect would provide information on the origin and nature of these events and, in case of charged primaries, imply interesting constraints on the extragalactic magnetic field. Possible implications for the most common models of ultra-high energy cosmic ray production in the literature are discussed. C1 UNIV CHICAGO,DEPT ASTRON & ASTROPHYS,ENRICO FERMI INST,CHICAGO,IL 60637. NASA,FERMILAB ASTROPHYS CTR,BATAVIA,IL 60510. FERMILAB NATL ACCELERATOR LAB,BATAVIA,IL 60510. NR 51 TC 12 Z9 12 U1 0 U2 0 PU NATL ACAD SCIENCES PI WASHINGTON PA 2101 CONSTITUTION AVE NW, WASHINGTON, DC 20418 SN 0027-8424 J9 P NATL ACAD SCI USA JI Proc. Natl. Acad. Sci. U. S. A. PD SEP 30 PY 1997 VL 94 IS 20 BP 10501 EP 10505 DI 10.1073/pnas.94.20.10501 PG 5 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA XY998 UT WOS:A1997XY99800006 PM 11038576 ER PT J AU Kent, GS Winker, DM Vaughan, MA Wang, PH Skeens, KM AF Kent, GS Winker, DM Vaughan, MA Wang, PH Skeens, KM TI Simulation of Stratospheric Aerosol and Gas Experiment (SAGE) II cloud measurements using airborne lidar data SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID DISTRIBUTIONS; SATELLITE; INVERSION; ALGORITHM AB The Stratospheric Aerosol and Gas Experiment (SAGE) II satellite instrument measures the attenuation due to stratospheric aerosols, gases, and clouds along a tangential path through the atmosphere from the Sun to the satellite instrument. Data from SAGE II and its predecessor, SAGE I, have been used to study and develop climatologies for high altitude cloud. Because these instruments measure the total attenuation on a long optical path and the data are inverted under the assumption of spherical homogeneity in the region of the measurement, interpretation in terms of individual cloud characteristics is difficult. Airborne lidar data, taken on approximately 8000 lan of flight path over the tropical Pacific Ocean, have been used to simulate high altitude SAGE II cloud measurements and their inversion. The lidar data set, not necessarily typical for the region flown over, showed the general presence of patchy cloud with a mean horizontal cloud dimension of 20-25 km and a vertical thickness of 0.6-0.8 km. Use of the lidar data to simulate SAGE II measurements produces cloud extinction values similar in magnitude and distribution to those obtained from SAGE II. These simulations also show the existence of three possible error conditions that may occur as a result of cloud inhomogeneities along the viewing path. In the first error condition, the true altitude of a cloud may be higher than that found as a result of the SAGE II inversion, errors of 1 km or greater occurring in just under 40% of the simulations, mainly at the lower cloud altitudes. In the second error condition, the inverted cloud extinction may differ from the volume averaged extinction along the horizontal ray path, the former often being biased slightly low. In the third error condition, the presence of nonuniform or isolated cloud patches can result in an apparent negative inverted extinction value just below the cloud. Such values were observed in about one third of the simulations. The first two of these errors have been statistically quantified for application to SAGE II cloud data. C1 NASA, LANGLEY RES CTR, DIV ATMOSPHER SCI, HAMPTON, VA 23681 USA. SCI APPLICAT INT CORP, HAMPTON, VA USA. RP SCI & TECHNOL CORP, 101 RES DR, HAMPTON, VA 23666 USA. NR 24 TC 11 Z9 11 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 SEP 27 PY 1997 VL 102 IS D18 BP 21795 EP 21807 DI 10.1029/97JD01390 PG 13 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA XY462 UT WOS:A1997XY46200009 ER PT J AU Prigent, C Rossow, WB Matthews, E AF Prigent, C Rossow, WB Matthews, E TI Microwave land surface emissivities estimated from SSM/I observations SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID CLOUD LIQUID WATER; 37 GHZ DATA; SOIL-MOISTURE; GLOBAL VEGETATION; POLARIZATION DIFFERENCE; AVHRR DATA; SATELLITE; REMOTE; TEMPERATURE; SMMR AB Microwave emissivities of land surfaces are estimated from special sensor microwave/imager (SSM/I) observations by removing the contributions from the atmosphere, clouds, and rain using ancillary satellite data (International Satellite Cloud Climatology Project (ISCCP) and TIROS Operational Vertical Sounder (TOVS) products), In the first step, cloud-free SSM/I observations are isolated with the help of collocated visible/infrared satellite observations (ISCCP data), The cloud-free atmospheric contribution is then calculated from an estimate of the lo cal atmospheric temperature-humidity profile (TOVS retrieval), Finally, with the surface skin temperature derived from IR observations (ISCCP estimate), the surface emissivity is calculated for all the SSM/I channels, As an exploration the method is applied to the SSM/I data for four months in 1991 within the Meteosat observation area. The magnitude and fluctuations of the atmospheric contributions are estimated along with the effect of surface temperature variations, Correspondences between geographical and seasonal patterns of the emissivities and topography, vegetation, flooding, and snow cover are analyzed, The potential for using microwave emissivities to monitor vegetation phenology and surface properties at regional and continental scale is investigated, and the possibility of retrieving atmospheric parameters (water vapor content, cloud Liquid water path, and precipitation) over land is discussed. C1 OBSERV PARIS, CNRS, DEPT RADIOASTRON MILLIMETR, F-75014 PARIS, FRANCE. RP COLUMBIA UNIV, NASA, GODDARD INST SPACE STUDIES, CTR CLIMATE SYST RES, 2880 BROADWAY, NEW YORK, NY 10025 USA. RI Rossow, William/F-3138-2015 NR 64 TC 119 Z9 128 U1 3 U2 9 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 SEP 27 PY 1997 VL 102 IS D18 BP 21867 EP 21890 DI 10.1029/97JD01360 PG 24 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA XY462 UT WOS:A1997XY46200014 ER PT J AU Krotkov, NA Krueger, AJ Bhartia, PK AF Krotkov, NA Krueger, AJ Bhartia, PK TI Ultraviolet optical model of volcanic clouds for remote sensing of ash and sulfur dioxide SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID OZONE MAPPING SPECTROMETER; MOUNT-PINATUBO AEROSOLS; EL-CHICHON; SETTLING VELOCITY; ST-HELENS; PARTICLES; ERUPTIONS; SO2; SCATTERING; ACID AB The total ozone mapping spectrometer (TOMS) instruments have detected every significant volcanic eruption from November 1978 to December 1994 on the Nimbus 7 and Meteor 3 satellites and since July 1996 on the new satellites, TOMS-Earth Probe and ADEOS. We apply a radiative transfer model to simulate the albedos of these fresh eruption clouds to study the limitations of the present algorithm which assumes an absorbing cloud above a scattering atmosphere. The conditions are found to be approximated when the total absorption optical depth is less than 2 (i.e., 100 Dobson units (DU) SO2 at 312 nm or 300 DU SO2 at 317 nm). The spectral dependence of the albedo of a nonabsorbing Rayleigh atmosphere can be specified by only two parameters which are uniquely different when ash or sulfate aerosols are present in the stratosphere. However, the interaction between ash scattering and SO, absorption within a volcanic cloud produces a nonlinear effect at strongly absorbing wavelengths that accounts for overestimation of sulfur dioxide in ash-laden volcanic clouds by the Krueger ct al. [1995] algorithm. Correction of this error requires knowledge of the ash properties. A method for determining two of the ash parameters from the longer TOMS wavelengths is described. Given the altitude of the cloud, surface reflectivity, and an estimate of effective variance of the ash size distribution, the optical thickness and either the effective radius or the index of refraction can be deduced. The ash retrievals are also needed to evaluate the tephra/gas ratio of eruptions and to compare the ash properties of different volcanoes. C1 NASA, GODDARD SPACE FLIGHT CTR, ATMOSPHERES LAB, GREENBELT, MD 20771 USA. RP ST SYST CORP, 4400 FORBES BLVD, LANHAM, MD 20706 USA. RI Krotkov, Nickolay/E-1541-2012; Bhartia, Pawan/A-4209-2016 OI Krotkov, Nickolay/0000-0001-6170-6750; Bhartia, Pawan/0000-0001-8307-9137 NR 36 TC 40 Z9 40 U1 0 U2 5 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 SEP 27 PY 1997 VL 102 IS D18 BP 21891 EP 21904 DI 10.1029/97JD01690 PG 14 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA XY462 UT WOS:A1997XY46200015 ER PT J AU Ristorcelli, JR AF Ristorcelli, JR TI A pseudo-sound constitutive relationship for the dilatational covariances in compressible turbulence SO JOURNAL OF FLUID MECHANICS LA English DT Article ID MIXING LAYERS; SHEAR-FLOW; DISSIPATION; GROWTH; MODEL AB The mathematical consequences of a few simple scaling assumptions regarding the effects of compressibility are explored using a singular perturbation idea and the methods of statistical fluid mechanics. Representations for the pressure-dilatation and dilatational dissipation appearing in single-point moment closures for compressible turbulence are: obtained. The results obtained, in as much as they come from the same underlying procedure, represent a unified development for both dilatational covariances. While the results are expressed in the context of a statistical turbulence closure they provide, with very few phenomenological assumptions, an interesting and clear mathematical model for the 'scalar' effects of compressibility. For homogeneous turbulence with quasi-normal large scales the expressions derived are - in the small turbulent Mach number squared isotropic limit - exact. The expressions obtained contain constants that have a precise physical significance and are defined in terms of integrals of the longitudinal velocity correlation. The pressure-dilatation covariance is found to be a non-equilibrium phenomenon related to the time rate of change of the kinetic energy and internal energy of the turbulence; it is seen to scale with alpha(2)M(t)(2) epsilon(s)[P-k/epsilon - 1](Sk/epsilon(s))(2). Implicit in the scaling is a dependence on the square of a gradient Mach number, Sl/c. A new feature indicated by the analysis is the appearance of the Kolmogorov scaling coefficient, alpha, suggesting that large-scale quantities embodied in the well-established epsilon similar to (u) over tilde(3)/l relationship provide a link to the structural dependence of the effects of compressibility. The expressions for the dilatational dissipation are found to depend on the turbulent Reynolds number and scale as M-t(4)(Sk/epsilon(s))R-4(t)-1. The scalings for the pressure-dilatation are found to produce an excellent collapse of the pressure-dilatation data from direct numerical simulation. RP NASA, LANGLEY RES CTR, INST COMP APPLICAT SCI & ENGN, HAMPTON, VA 23681 USA. NR 59 TC 48 Z9 48 U1 0 U2 1 PU CAMBRIDGE UNIV PRESS PI NEW YORK PA 32 AVENUE OF THE AMERICAS, NEW YORK, NY 10013-2473 USA SN 0022-1120 EI 1469-7645 J9 J FLUID MECH JI J. Fluid Mech. PD SEP 25 PY 1997 VL 347 BP 37 EP 70 DI 10.1017/S0022112097006083 PG 34 WC Mechanics; Physics, Fluids & Plasmas SC Mechanics; Physics GA XZ196 UT WOS:A1997XZ19600003 ER PT J AU Lee, SS AF Lee, SS TI Generalized critical-layer analysis of fully coupled resonant-triad interactions in boundary layers SO JOURNAL OF FLUID MECHANICS LA English DT Article ID OBLIQUE INSTABILITY WAVES; NONLINEAR CRITICAL LAYERS; TRANSITION; FLOWS AB The critical-layer analysis of the nonlinear resonant-triad interaction by Goldstein & Lee (1992) is extended to include viscous effects, A generalized scaling which is valid both for the quasi-equilibrium and non-equilibrium critical-layer analyses in zero-or non-zero-pressure-gradient boundary layers is obtained. A system of partial differential equations which governs the fully coupled non-equilibrium critical-layer dynamics is obtained and it is solved by using a numerical method. Amplitude equations and their viscous limits are also presented. The parametric-resonance growth rate of the non-equilibrium critical-layer solution with finite viscosity is larger than that of the viscous-limit quasi-equilibrium solution. The viscosity delays both the onset of the fully coupled interaction and the ultimate downstream location of the singularity. The difference between the non-equilibrium critical-layer solution and the corresponding quasi-equilibrium critical-layer solution becomes smaller, at least in the parametric resonance region, as the viscosity parameter becomes large. However, the non-equilibrium solution with finite viscosity always ends in a singularity at a finite downstream position unlike the viscous-limit solution. RP Lee, SS (reprint author), NASA, LEWIS RES CTR GRP, NYMA INC, MS 5-9, CLEVELAND, OH 44135 USA. NR 31 TC 6 Z9 6 U1 0 U2 0 PU CAMBRIDGE UNIV PRESS PI NEW YORK PA 32 AVENUE OF THE AMERICAS, NEW YORK, NY 10013-2473 USA SN 0022-1120 J9 J FLUID MECH JI J. Fluid Mech. PD SEP 25 PY 1997 VL 347 BP 71 EP 103 DI 10.1017/S0022112097006617 PG 33 WC Mechanics; Physics, Fluids & Plasmas SC Mechanics; Physics GA XZ196 UT WOS:A1997XZ19600004 ER PT J AU Pope, KO Baines, KH Ocampo, AC Ivanov, BA AF Pope, KO Baines, KH Ocampo, AC Ivanov, BA TI Energy, volatile production, and climatic effects of the Chicxulub Cretaceous/Tertiary impact SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS LA English DT Review ID SHOCK-INDUCED DEVOLATILIZATION; GULF-OF-MEXICO; TERTIARY BOUNDARY; COMET SHOEMAKER-LEVY-9; SULFURIC-ACID; EL-CHICHON; CRATER; EXTINCTION; ERUPTION; DEPOSITS AB A comprehensive analysis of volatiles in the Chicxulub impact strongly supports the hypothesis that impact-generated sulfate aerosols caused over a decade of global cooling, acid rain, and disruption of ocean circulation, which contributed to the mass extinction at the Cretaceous/Tertiary (WT) boundary. The crater size, meteoritic content of the WT boundary clay, and impact models indicate that the Chicxulub crater was formed by a short period comet or an asteroid impact that released 0.7-3.4 x 10(31) ergs of energy. Impact models and experiments combined with estimates of volatiles in the projectile and target rocks predict that over 200 gigatons (Gt) each of SO2 and water vapor, and over 500 Gt of CO2, were globally distributed in the stratosphere by the impact. Additional volatiles may have been produced on a global or regional scale that formed sulfate aerosols rapidly in cooler parts of the vapor plume, causing an early, intense pulse of sulfuric acid rain. Estimates of the conversion rate of stratospheric SO2 and water vapor to sulfate aerosol, based on volcanic production of sulfate aerosols, coupled with calculations of diffusion, coagulation, and sedimentation, demonstrate that the 200 Ct stratospheric SO2 and water vapor reservoir would produce sulfate aerosols for 12 years. These sulfate aerosols caused a second pulse of acid rain that was global. Radiative transfer modeling of the aerosol clouds demonstrates (1) that if the initial rapid pulse of sulfate aerosols was global, photosynthesis may have been shut down for 6 months and (2) that for the second prolonged aerosol cloud, solar transmission dropped 80% by the end of first year and remained 50% below normal for 9 years. As a result, global average surface temperatures probably dropped between 5 degrees and 31 degrees K, suggesting that global near-freezing conditions may have been reached. Impact-generated CO2 caused less than 1 degrees K greenhouse warming and therefore was insignificant compared to the sulfate cooling. The magnitude of sulfate cooling depends largely upon the rate of ocean mixing as surface waters cool, sink, and are replaced by upwelling of deep ocean water. This upwelling apparently drastically altered ocean stratification and circulation, which may explain the global collapse of the delta C-13 gradient between surface and deep ocean waters at the WT boundary. C1 CALTECH,JET PROP LAB,PASADENA,CA 91109. RUSSIAN ACAD SCI,INST DYNAM & GEOSPHERES,MOSCOW,RUSSIA. RP Pope, KO (reprint author), GEO ECO ARC RES,2222 FOOTHILL BLVD,SUITE E-272,LA CANADA FLINTRIDGE,CA 91011, USA. RI Ivanov, Boris/E-1413-2016 OI Ivanov, Boris/0000-0002-9938-9428 NR 130 TC 100 Z9 106 U1 4 U2 30 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 SEP 25 PY 1997 VL 102 IS E9 BP 21645 EP 21664 DI 10.1029/97JE01743 PG 20 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA XY748 UT WOS:A1997XY74800006 PM 11541145 ER PT J AU Lissauer, JJ AF Lissauer, JJ TI It's not easy to make the Moon SO NATURE LA English DT Editorial Material ID ORIGIN RP Lissauer, JJ (reprint author), NASA,AMES RES CTR,DIV SPACE SCI,MOFFETT FIELD,CA 94035, USA. NR 10 TC 6 Z9 6 U1 0 U2 0 PU MACMILLAN MAGAZINES LTD PI LONDON PA PORTERS SOUTH, 4 CRINAN ST, LONDON, ENGLAND N1 9XW SN 0028-0836 J9 NATURE JI Nature PD SEP 25 PY 1997 VL 389 IS 6649 BP 327 EP 328 DI 10.1038/38596 PG 2 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA XX675 UT WOS:A1997XX67500021 ER PT J AU Christy, JR Spencer, RW Braswell, WD AF Christy, JR Spencer, RW Braswell, WD TI How accurate are satellite 'thermometers'? SO NATURE LA English DT Letter C1 NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,HUNTSVILLE,AL 35812. NICHOLS RES CORP,GHCC,HUNTSVILLE,AL 35806. RP Christy, JR (reprint author), UNIV ALABAMA,HUNTSVILLE,AL 35899, USA. NR 0 TC 16 Z9 16 U1 0 U2 3 PU MACMILLAN MAGAZINES LTD PI LONDON PA PORTERS SOUTH, 4 CRINAN ST, LONDON, ENGLAND N1 9XW SN 0028-0836 J9 NATURE JI Nature PD SEP 25 PY 1997 VL 389 IS 6649 BP 342 EP 342 DI 10.1038/38640 PG 1 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA XX675 UT WOS:A1997XX67500035 ER PT J AU Chen, P Blake, GA Gaidis, MC Brown, ER McIntosh, KA Chou, SY Nathan, MI Wiliamson, F AF Chen, P Blake, GA Gaidis, MC Brown, ER McIntosh, KA Chou, SY Nathan, MI Wiliamson, F TI Spectroscopic applications and frequency locking of THz photomixing with distributed-Bragg-reflector diode lasers in low-temperature-grown GaAs SO APPLIED PHYSICS LETTERS LA English DT Article ID STABILIZATION AB A compact, narrow-linewidth, tunable source of THz radiation has been developed for spectroscopy and other high-resolution applications. Distributed-Bragg-reflector (DBR) diode lasers at 850 nm are used to pump a low-temperature-grown GaAs photomixer. Resonant optical feedback is employed to stabilize the center frequencies and narrow the linewidths of the DBR lasers. The heterodyne linewidth full-width at half-maximum of two optically locked DBR lasers is 50 kHz on the 20 ms time scale and 2 MHz over 10 s; free-running DBR lasers have linewidths of 40 and 90 MHz on such time scales. This instrument has been used to obtain rotational spectra of acetonitrile (CH3CN) at 313 GHz. Detection limits of 1x10(-4)Hz(1/2) (noise/total power) have been achieved, with the noise floor dominated by the detector's noise equivalent power. (C) 1997 American Institute of Physics. C1 CALTECH,JET PROP LAB,PASADENA,CA 91109. MIT,LINCOLN LAB,LEXINGTON,MA 02173. UNIV MINNESOTA,DEPT ELECT ENGN,MINNEAPOLIS,MN 55455. RP Chen, P (reprint author), CALTECH,DIV CHEM & CHEM ENGN,M-S 127-72,PASADENA,CA 91125, USA. RI Chen, Pin/B-1112-2008; Gaidis, Michael/D-3327-2013 OI Chen, Pin/0000-0003-1195-9666; NR 9 TC 45 Z9 45 U1 1 U2 4 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 SEP 22 PY 1997 VL 71 IS 12 BP 1601 EP 1603 DI 10.1063/1.119845 PG 3 WC Physics, Applied SC Physics GA XW907 UT WOS:A1997XW90700003 ER PT J AU McGuckin, BT Haner, DA Menzies, RT AF McGuckin, BT Haner, DA Menzies, RT TI Multiangle imaging spectroradiometer: Optical characterization of the calibration panels SO APPLIED OPTICS LA English DT Article ID REFLECTANCE AB The reflectance properties of an engineering model (EM) of the Spectralon panel intended for use within an on-board calibrator (OBC) on the NASA Multiangle Imaging Spectroradiometer (MISR) instrument have been fully characterized with regard to panel uniformity and isotropy in response to three incident laser wavelengths of 442, 632.8, and 859.9 nm. A regional variation in the relative bidirectional reflectance factor (RBRF) across the surface of the EM panel, which contributes to spatial nonuniformity at the +/-2% level, has been measured at all three laser wavelengths. Further, a reflectance anisotropy has been identified. The mechanism causing these departures from the ideal Lambertian surface may originate in the sanding of the Spectralon surface in the final stage of preparation. This supposition is corroborated by measurements made on a pressed polytetrafluoroethylene (PTFE) panel in which a greatly reduced anisotropy in panel REEF is measured. The EM panel RBRF exhibits a deviation from Lambertian characteristics as an off-specular peak in the forward scattering direction. A common crossover point at an angle of reflection of similar to 37 degrees at which the BRF is constant within +/-0.4% far an illumination angle range of theta(i) = 30 degrees-60 degrees is observed at all three wavelengths. Two Spectralon protoflight panels that were fabricated after the EM was studied were also the subject of a uniformity study over part of the area of the Spectralon panels at the 442-nm wavelength. The analysis indicated that the panel uniformity satisfies the +/-0.5% criterion, which indicates improved panel preparation. However, the off-specular peak. in the forward scattering direction was essentially unchanged, with the crossover point at similar to 37 degrees. (C) 1997 Optical Society of America. C1 CALIF STATE POLYTECH UNIV POMONA,DEPT CHEM,POMONA,CA 91768. RP McGuckin, BT (reprint author), CALTECH,JET PROP LAB,4800 OAK GROVE DR,PASADENA,CA 91109, USA. NR 7 TC 9 Z9 9 U1 1 U2 2 PU OPTICAL SOC AMER PI WASHINGTON PA 2010 MASSACHUSETTS AVE NW, WASHINGTON, DC 20036 SN 0003-6935 J9 APPL OPTICS JI Appl. Optics PD SEP 20 PY 1997 VL 36 IS 27 BP 7016 EP 7022 DI 10.1364/AO.36.007016 PG 7 WC Optics SC Optics GA XV502 UT WOS:A1997XV50200043 PM 18259576 ER PT J AU Scoccimarro, R AF Scoccimarro, R TI Cosmological perturbations: Entering the nonlinear regime SO ASTROPHYSICAL JOURNAL LA English DT Article DE cosmology, theory; large-scale structure of the universe; methods, numerical ID LARGE-SCALE STRUCTURE; 3-POINT CORRELATION-FUNCTION; N-BODY SIMULATIONS; POWER SPECTRUM; GRAVITATIONAL-INSTABILITY; ZELDOVICH APPROXIMATION; CORRELATION HIERARCHY; COSMIC FIELDS; EVOLUTION; FLUCTUATIONS AB We consider next-to-leading-order (one-loop) nonlinear corrections to the bispectrum and skewness of cosmological density fluctuations induced by gravitation evolution, focusing on the case of Gaussian initial conditions and scale-free initial power spectra, P(k) proportional to k ''. As has been established by comparison with numerical simulations, leading order (tree-level) perturbation theory describes these quantities at the largest scales. The one-loop perturbation theory provides a tool to probe the transition to the nonlinear regime on smaller scales. In this work, we find that, as a function of spectral index n, the one-loop bispectrum follows a pattern analogous to that of the one-loop power spectrum, which shows a change in behavior at a ''critical index'' n(c) approximate to -1.4, where nonlinear corrections vanish. The tree-level perturbation theory predicts a characteristic dependence of the bispectrum on the shape of the triangle defined by its arguments. For n less than or similar to n(c), one-loop corrections increase this configuration dependence of the leading order contribution; for n greater than or similar to n(c), one-loop corrections tend to cancel the configuration dependence of the tree-level bispectrum, in agreement with known results from n = -1 numerical simulations. A similar situation is shown to hold for the Zeldovich approximation, where n(c) approximate to -1.75. We obtain explicit analytic expressions for the one-loop bispectrum for n = -2 initial power spectra, for both the exact dynamics of gravitational instability and the Zeldovich approximation. We also compute the skewness factor, including local averaging of the density field, for n = -2: S-3(R) = 4.02 + 3.83 sigma(G)(2)(R) for Gaussian smoothing and S-3(R) = 3.86 + 3.18 sigma(TH)(2)(R) for top-hat smoothing, where sigma(2)(R) is the variance of the density field fluctuations smoothed over a window of radius R. A comparison with fully nonlinear numerical simulations implies that, for n < -1, the one-loop perturbation theory can extend our understanding of nonlinear clustering down to scales where the transition to the stable clustering regime begins. C1 UNIV CHICAGO, DEPT PHYS, CHICAGO, IL 60637 USA. UNIV CHICAGO, ENRICO FERMI INST, CHICAGO, IL 60637 USA. FERMILAB NATL ACCELERATOR LAB, NASA, FERMILAB ASTROPHYS CTR, BATAVIA, IL 60510 USA. NR 66 TC 44 Z9 44 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 SEP 20 PY 1997 VL 487 IS 1 BP 1 EP 17 DI 10.1086/304578 PN 1 PG 17 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XY506 UT WOS:A1997XY50600001 ER PT J AU Brainerd, JJ AF Brainerd, JJ TI The cosmological signatures and flux distribution of gamma-ray bursts with a broad luminosity distribution SO ASTROPHYSICAL JOURNAL LA English DT Article DE cosmology, observations; gamma rays, bursts ID BRIGHTNESS DISTRIBUTION; INTENSITY DISTRIBUTION; INTRINSIC LUMINOSITY; TIME DILATION; BATSE; EVOLUTION; MODELS AB Cosmological expansion cannot produce the reported correlations of the gamma-ray burst timescale and spectral energy with peak flux if the burst model reproduces the Burst and Transient Source Experiment (BATSE) 3B peak flux distribution for a nonevolving burst source density. The required ratios of time dilation and redshift factors are only produced by monoluminous models at peal fluxes below the BATSE threshold, and they are never produced by power-law luminosity models. Monoluminous models produce acceptable fits to the peak flux distribution only for very specific combinations of the spectral and cosmological parameters. The redshift of gamma-ray bursts at the BATSE threshold is z approximate to 1.5. Power-law luminosity distribution models proportional to L-beta produce acceptable fits to the data for most values of the spectral parameters when beta < 1.6. In this model, gamma-ray bursts of a given peak flux have a distribution of redshifts, with a maximum redshift of greater than or similar to 3 for peak fluxes near the BATSE threshold and with an average redshift of < 1 for all values of peak flux. This qualitative behavior occurs whenever the luminosity distribution determines the shape of the peak flux distribution, regardless of whether source density evolution occurs. The reported correlations of the burst timescale and the spectral energy with peak flux are systematically 1 standard deviation above the monoluminous model and 1.5-2 standard deviations above the power-law luminosity model. These results suggest that an intrinsic correlation of burst timescale and spectral energy with luminosity is present. Studies of the peak flux distribution for bursts selected by E-peak or the hardness ratio provide a test for this intrinsic correlation. RP Brainerd, JJ (reprint author), UNIV ALABAMA,GEORGE C MARSHALL SPACE FLIGHT CTR,NASA,SPACE SCI LAB,ES-84,HUNTSVILLE,AL 35812, USA. NR 41 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 SEP 20 PY 1997 VL 487 IS 1 BP 96 EP 113 DI 10.1086/304585 PN 1 PG 18 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XY506 UT WOS:A1997XY50600010 ER PT J AU Allen, RJ Knapen, JH Bohlin, R Stecher, TP AF Allen, RJ Knapen, JH Bohlin, R Stecher, TP TI Evidence for the large-scale dissociation of molecular gas in the inner spiral arms of M81 SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies, individual, M81; galaxies, ISM; infrared, galaxies; ISM, clouds; ISM, molecules; radio lines, galaxies ID H-II REGIONS; ULTRAVIOLET IMAGING TELESCOPE; RADIO-CONTINUUM EMISSION; STAR-FORMATION; INFRARED-EMISSION; IONIZED HYDROGEN; NONTHERMAL DISK; CO EMISSION; M51; GALAXIES AB We compare the detailed distributions of H I, H alpha, and 150 nm far-UV (FUV) continuum emission in the spiral arms of M81 at a resolution of 9 '' (linear resolution 150 pc at 3.7 Mpc distance). The bright H alpha emission peaks are always associated with peaks in the FUV emission. The converse is not always true; there are many regions of FUV emission with little corresponding H alpha. The H I and the FUV are always closely associated, in the sense that the H I is often brightest around the edges of the FUV emission. The effects of extinction on the morphology are small, even in the FUV. Extensive FUV emission, often with little corresponding H alpha, indicates the presence of many ''B stars,'' which produce mostly nonionizing UV photons. These FUV photons dissociate a small fraction of an extensive layer of H-2 into H I. The observed morphology can be understood if ''chimneys'' are common in the spiral arms of M81, where holes are blown out of the galactic disk, exposing-the bright H II regions and the corresponding FUV associated with vigorous star formation. These ''naked'' star-forming regions show little obscuration. H-2 is turned into H I by UV photons impinging on the interior surfaces of these chimneys. The intensity of the FUV radiation measured by the Ultraviolet Imaging Telescope can dissociate the underlying H-2 with a typical density of similar to 10 H nuclei cm(-3) to produce the observed amount of H I in the spiral arms of M81. Except for thin surface layers locally heated in these photodissociation regions that are close to the FUV sources, the bulk of the molecular gas in the inner disk of M81 is apparently too cold to produce much (CO)-C-12(1-0) emission. C1 UNIV HERTFORDSHIRE, DEPT PHYS SCI, HATFIELD AL10 9AB, HERTS, ENGLAND. NASA, GODDARD SPACE FLIGHT CTR, GREENBELT, MD 20771 USA. RP Allen, RJ (reprint author), SPACE TELESCOPE SCI INST, 3700 SAN MARTIN DR, BALTIMORE, MD 21218 USA. NR 50 TC 41 Z9 41 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 SEP 20 PY 1997 VL 487 IS 1 BP 171 EP 181 DI 10.1086/304590 PN 1 PG 11 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XY506 UT WOS:A1997XY50600016 ER PT J AU Tompkins, WF Jones, BB Nolan, PL Kanbach, G Ramanamurthy, PV Thompson, DJ AF Tompkins, WF Jones, BB Nolan, PL Kanbach, G Ramanamurthy, PV Thompson, DJ TI EGRET gamma-ray observations of the crab P2/P1 ratio SO ASTROPHYSICAL JOURNAL LA English DT Article DE gamma rays, observations; pulsars, individual (Crab) ID PULSAR; EMISSION; NEBULA AB Recent observations of the Crab pulsar by the Energetic Gamma-Ray Experiment Telescope (EGRET) on the Compton Gamma Ray Observatory show that the high-energy gamma-ray light curve has changed little over the lifetime of the instrument. Previous data collected by SAS 2 and COS B in the years 1972-1982, along with earlier EGRET data, suggested a 14 yr sinusoidal variation in the flux ratio between the first and second peaks. The new data from EGRET indicate that the flux ratio is constant. C1 MAX PLANCK INST EXTRATERR PHYS,D-85748 GARCHING,GERMANY. NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. RP Tompkins, WF (reprint author), STANFORD UNIV,WW HANSEN EXPT PHYS LAB,STANFORD,CA 94305, USA. RI Nolan, Patrick/A-5582-2009; Thompson, David/D-2939-2012 OI Thompson, David/0000-0001-5217-9135 NR 13 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 SEP 20 PY 1997 VL 487 IS 1 BP 385 EP 387 DI 10.1086/304604 PN 1 PG 3 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XY506 UT WOS:A1997XY50600035 ER PT J AU SteimanCameron, TY Scargle, JD Imamura, JN Middleditch, J AF SteimanCameron, TY Scargle, JD Imamura, JN Middleditch, J TI 16 second optical quasi-periodic oscillations in GX 339-4 SO ASTROPHYSICAL JOURNAL LA English DT Article DE black hole physics; stars, individual (GX 339-4); stars, oscillations; X-rays, stars ID BLACK-HOLE CANDIDATE; X-RAY; GX339-4; STATE; GX-339-4 AB We report the results of high-speed optical white-light photometry of the black hole candidate GX 339-4, obtained at the Cerro Tololo Inter-American Observatory during 1996 April. We searched the data for strictly periodic features, quasi-periodic oscillations (QPOs) and aperiodic variability (noise) using Fourier and wavelet techniques. (1) We found a QPO with amplitude 4.5%-6%, frequency f similar to 0.064 Hz, and width Delta f/f similar to 0.3-0.5. The QPO was long-lived in that it was present in all segments of the data, even in sets acquired one day apart. (2) In addition to the 0.064 Hz QPO there are indications of low-amplitude QPOs at f = 0.02, 0.03, 0.08, 0.3, and 3 Hz. None of the features appeared in more than one day of data (except for the 0.08 Hz feature) and none of the features were as strong as the 0.064 Hz QPO, and so they should be taken with some caution. (3) We found power in excess of counting statistics out to frequencies of several hertz on both nights. The origin of this excess power is not clear. C1 UNIV OREGON,INST THEORET SCI,EUGENE,OR 97403. UNIV OREGON,DEPT PHYS,EUGENE,OR 97403. LOS ALAMOS NATL LAB,COMP INFORMAT & COMMUN DIV,LOS ALAMOS,NM 87545. RP SteimanCameron, TY (reprint author), NASA,AMES RES CTR,DIV SPACE SCI,MOFFETT FIELD,CA 94035, USA. NR 25 TC 17 Z9 17 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 SEP 20 PY 1997 VL 487 IS 1 BP 396 EP 401 PN 1 PG 6 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XY506 UT WOS:A1997XY50600037 ER PT J AU Rosenbush, VK Avramchuk, VV Rosenbush, AE Mishchenko, MI AF Rosenbush, VK Avramchuk, VV Rosenbush, AE Mishchenko, MI TI Polarization properties of the Galilean satellites of Jupiter: Observations and preliminary analysis SO ASTROPHYSICAL JOURNAL LA English DT Article DE minor planets, asteroids; planets and satellites, individual (Jupiter); polarization; radiative transfer ID SATURNS RINGS; OPTICAL POLARIMETRY; ENHANCED BACKSCATTERING; REFLECTANCE POLARIMETRY; WEAK LOCALIZATION; OPPOSITION; ASTEROIDS; LIGHT; 64-ANGELINA; DEPENDENCE AB We present new, detailed polarimetric measurements of the Galilean satellites of Jupiter with U, B, V, and R filters at phase angles ranging from 12 degrees to nearly 0 degrees. The polarization phase curves of Io, Europa, and Ganymede in the B, V, and R filters clearly show the presence of the polarization opposition effect in the form of a sharp peak of negative polarization centered at a very small phase angle of 0.degrees 6-0.degrees 7 and superimposed on the regular negative polarization branch. This phase angle is comparable to the width of the spikelike photometric opposition effect observed for Europa, thus indicating that both opposition phenomena are likely to be produced by the coherent backscattering mechanism. The U filter values of \P-min\ for Io and Europa are close to 0.60% and 0.47%, respectively, and exceed the respective BVR values by a factor of almost 2. The BVR polarization for the trailing hemispheres of Io, Europa, and, especially, Ganymede is systematically stronger than for the respective leading hemispheres. For Callisto, the leading hemisphere polarization is significantly stronger than for the trailing hemisphere. The inversion angles for Io, Europa, and Ganymede are nearly wavelength independent and close to 10.degrees 0, 8.degrees 6, and 8.degrees 8, respectively. The inversion angle for the trailing hemisphere of Callisto is also wavelength independent and is in the range of 12 degrees-13 degrees. C1 NASA,GODDARD INST SPACE STUDIES,NEW YORK,NY 10025. NATL ACAD SCI UKRAINE,MAIN ASTRON OBSERV,UA-252650 KIEV 22,UKRAINE. SUNY STONY BROOK,INST TERR & PLANETARY ATMOSPHERES,STONY BROOK,NY 11794. RI Mishchenko, Michael/D-4426-2012 NR 62 TC 56 Z9 56 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 SEP 20 PY 1997 VL 487 IS 1 BP 402 EP 414 DI 10.1086/304584 PN 1 PG 13 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XY506 UT WOS:A1997XY50600038 ER PT J AU Boezio, M Carlson, P Francke, T Weber, N Suffert, M Hof, M Menn, W Simon, M Stephens, SA Bellotti, R Cafagna, F Castellano, M Circella, M DeCataldo, G DeMarzo, C Giglietto, N Spinelli, P Bocciolini, M Papini, P Perego, A Piccardi, S Spillantini, P Basini, G Ricci, M Codino, A Finetti, N Grimani, C Candusso, M Casolino, M DePascale, MP Morselli, A Picozza, P Sparvoli, R Barbiellini, G Bravar, U Schiavon, P Vacchi, A Zampa, N Mitchell, JW Ormes, JF Streitmatter, RE Golden, RL Stochaj, SJ AF Boezio, M Carlson, P Francke, T Weber, N Suffert, M Hof, M Menn, W Simon, M Stephens, SA Bellotti, R Cafagna, F Castellano, M Circella, M DeCataldo, G DeMarzo, C Giglietto, N Spinelli, P Bocciolini, M Papini, P Perego, A Piccardi, S Spillantini, P Basini, G Ricci, M Codino, A Finetti, N Grimani, C Candusso, M Casolino, M DePascale, MP Morselli, A Picozza, P Sparvoli, R Barbiellini, G Bravar, U Schiavon, P Vacchi, A Zampa, N Mitchell, JW Ormes, JF Streitmatter, RE Golden, RL Stochaj, SJ TI The cosmic-ray antiproton flux between 0.62 AND 3.19 GeV measured near solar minimum activity SO ASTROPHYSICAL JOURNAL LA English DT Article DE balloons; cosmic rays; elementary particles; sun, activity ID CAPRICE-RICH DETECTOR; RADIATION; SPECTROMETER; PERFORMANCE; RATIO AB We report on the absolute antiproton flux and the antiproton to proton ratio in the energy range 0.62-3.19 GeV at the top of the atmosphere, measured by the balloon-borne experiment CAPRICE; flown from Lynn Lake, Manitoba, Canada, on 1994 August 8-9. The experiment used the New Mexico State University WiZard/CAPRICE balloon-borne magnet spectrometer equipped with a solid radiator Ring Imaging Cherenkov (RICH) detector and a silicon-tungsten calorimeter for particle identification. This is the first time a RICH is used together with an imaging calorimeter in a balloon experiment, and it allows antiprotons to be clearly identified over the rigidity range 1.2-4 GV. Nine antiprotons were identified in the energy range 0.62-3.19 GeV at the top of the atmosphere. The data were collected over 18 hr at a mean residual atmosphere of 3.9 g cm(-2). The absolute antiproton flux is consistent with a pure secondary production of antiprotons during the propagation of cosmic rays in the Galaxy. C1 CTR RECH NUCL, F-67037 STRASBOURG, FRANCE. UNIV GESAMTHSCH SIEGEN, D-57068 SIEGEN, GERMANY. TATA INST FUNDAMENTAL RES, BOMBAY 400005, MAHARASHTRA, INDIA. UNIV BARI, DIPARTIMENTO FIS, I-70126 BARI, ITALY. IST NAZL FIS NUCL, I-70126 BARI, ITALY. UNIV FLORENCE, DIPARTIMENTO FIS, I-50125 FLORENCE, ITALY. IST NAZL FIS NUCL, I-50125 FLORENCE, ITALY. IST NAZL FIS NUCL, LAB NAZL FRASCATI, I-00044 FRASCATI, ITALY. UNIV PERUGIA, DIPARTIMENTO FIS, I-06100 PERUGIA, ITALY. IST NAZL FIS NUCL, I-06100 PERUGIA, ITALY. UNIV ROME, DIPARTIMENTO FIS, I-00133 ROME, ITALY. IST NAZL FIS NUCL, I-00133 ROME, ITALY. NASA, GODDARD SPACE FLIGHT CTR, GREENBELT, MD 20771 USA. NEW MEXICO STATE UNIV, LAS CRUCES, NM 88003 USA. UNIV TRIESTE, DIPARTIMENTO FIS, I-34147 TRIESTE, ITALY. IST NAZL FIS NUCL, I-34147 TRIESTE, ITALY. RP ROYAL INST TECHNOL, KTH, S-10405 STOCKHOLM, SWEDEN. RI Morselli, Aldo/G-6769-2011; giglietto, nicola/I-8951-2012; Castellano, Marcello/J-3428-2012; Cafagna, Francesco/A-9299-2010; Vacchi, Andrea/C-1291-2010; OI Morselli, Aldo/0000-0002-7704-9553; Boezio, Mirko/0000-0002-8015-2981; giglietto, nicola/0000-0002-9021-2888; Castellano, Marcello/0000-0002-4211-2903; Cafagna, Francesco/0000-0002-7450-4784; Vacchi, Andrea/0000-0003-3855-5856; Bellotti, Roberto/0000-0003-3198-2708; casolino, marco/0000-0001-6067-5104; Sparvoli, Roberta/0000-0002-6314-6117; Picozza, Piergiorgio/0000-0002-7986-3321; Papini, Paolo/0000-0003-4718-2895 NR 37 TC 117 Z9 118 U1 0 U2 4 PU IOP PUBLISHING LTD PI BRISTOL PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND SN 0004-637X EI 1538-4357 J9 ASTROPHYS J JI Astrophys. J. PD SEP 20 PY 1997 VL 487 IS 1 BP 415 EP 423 DI 10.1086/304593 PN 1 PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XY506 UT WOS:A1997XY50600039 ER PT J AU Allen, GE Keohane, JW Gotthelf, EV Petre, R Jahoda, K Rothschild, RE Lingenfelter, RE Heindl, WA Marsden, D Gruber, DE Pelling, MR Blanco, PR AF Allen, GE Keohane, JW Gotthelf, EV Petre, R Jahoda, K Rothschild, RE Lingenfelter, RE Heindl, WA Marsden, D Gruber, DE Pelling, MR Blanco, PR TI Evidence of X-ray synchrotron emission from electrons accelerated to 40 TeV in the supernova remnant Cassiopeia A SO ASTROPHYSICAL JOURNAL LA English DT Article DE acceleration of particles; cosmic rays; ISM, individual (Cassiopeia A); radiation mechanisms, nonthermal; supernova remnants; X-rays, general ID ABUNDANCES; SEARCH; MODEL; MASS AB We present the 2-60 keV spectrum of the supernova remnant Cassiopeia A measured using the Proportional Counter Array and the High Energy X-Ray Timing Experiment on the Rossi X-Ray Timing Explorer satellite. In addition to the previously reported strong emission-line features produced by thermal plasmas, the broadband spectrum has a high-energy ''tail'' that extends to energies at least as high as 120 keV. This tail may be described by a broken power law that has photon indices of Gamma(1) = 1.8(-0.6)(+0.5) and Gamma(2) = 3.04(0.13)(0.15) and a break energy of E-b = 15.9(-0.4)(+0.3) keV. We argue that the high-energy component, which dominates the spectrum above about 10 keV, is produced by synchrotron radiation from electrons that have energies up to at least 40 TeV. This conclusion supports the hypothesis that Galactic cosmic rays are accelerated predominantly in supernova remnants. C1 UNIV CALIF SAN DIEGO,CTR ASTROPHYS & SPACE SCI,LA JOLLA,CA 92093. RP Allen, GE (reprint author), NASA,GODDARD SPACE FLIGHT CTR,HIGH ENERGY ASTROPHYS LAB,NRC,CODE 662,GREENBELT,MD 20771, USA. RI Jahoda, Keith/D-5616-2012 NR 31 TC 123 Z9 124 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 SEP 20 PY 1997 VL 487 IS 1 BP L97 EP L100 DI 10.1086/310878 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XY509 UT WOS:A1997XY50900025 ER PT J AU Cui, W Heindl, WA Swank, JH Smith, DM Morgan, EH Remillard, R Marshall, FE AF Cui, W Heindl, WA Swank, JH Smith, DM Morgan, EH Remillard, R Marshall, FE TI RXTE observations of a new X-ray transient: GRS 1737-31 SO ASTROPHYSICAL JOURNAL LA English DT Article DE binaries, general; stars, individual (GRS 1737-31); X-rays, stars ID GALACTIC RIDGE; IRON LINE; EMISSION; EXOSAT AB We present the results from RXTE observations of a new X-ray transient, GRS 1737-31, near the Galactic center during an outburst. Over a span of 2 weeks, the source was seen to vary significantly on timescales down to a few seconds. The rapid flares in the light curves bear resemblance to those observed for Cygnus X-l, a well-known black hole candidate (BHC). The power-density spectrum is also very typical of BHCs in the hard (or low) state: it is flat below a characteristic break frequency of about 0.03 Hz and becomes roughly a 1/f power law above. The observed X-ray spectrum can be characterized by a simple power law with a photon index of about 1.7 over a broad energy range 2-200 keV, which is remarkably similar to that of Cyg X-l in the hard state. The similarities to Cyg X-l make GRS 1737-31 a likely BHC. However, unlike most transient BHCs, GRS 1737-31 does not seem to reach a ''soft state'' even during an outburst. We discuss this phenomenon in light of the comparison to a class of hard X-ray BHCs, including transients GRO J0422+32, V404 Cyg, and GRO J1719-24, and persistent sources 1E1740.7-2942 and GRS 1758-258. C1 UNIV CALIF SAN DIEGO,CTR ASTROPHYS & SPACE SCI,LA JOLLA,CA 92093. NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. UNIV CALIF BERKELEY,SPACE SCI LAB,BERKELEY,CA 94720. RP Cui, W (reprint author), MIT,SPACE RES CTR,CAMBRIDGE,MA 02139, USA. RI Swank, Jean/F-2693-2012 NR 22 TC 20 Z9 20 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 SEP 20 PY 1997 VL 487 IS 1 BP L73 EP L76 DI 10.1086/310866 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XY509 UT WOS:A1997XY50900019 ER PT J AU Strohmayer, TE Zhang, W Swank, JH AF Strohmayer, TE Zhang, W Swank, JH TI 363 Hz oscillations during the rising phase of bursts from 4U 1728-34: Evidence for rotational modulation SO ASTROPHYSICAL JOURNAL LA English DT Article DE stars, neutron; stars, rotation; X-rays, bursts ID X-RAY-BURSTS; NEUTRON-STARS; SPECTRA; PROPAGATION; FLASHES; MODEL; TIME AB We report a study of the temporal and spectral characteristics of the rising portions of X-ray bursts from 4U 1728-34 observed with the Rossi X-Ray Timing Explorer (RXTE). We find that when oscillations are present during burst rise, their amplitudes systematically decrease as the X-ray burst flux increases, reaching undetectable levels near the burst peaks before eventually increasing again later in the burst. Oscillation amplitudes as high as 43% +/- 12% are measured within the first 0.2 s of burst onset and have pulse shapes consistent with sinusoids. Spectral analysis indicates that the rises are substantially underluminous compared with those at intervals later in the burst with similar measured blackbody temperatures; this argues that the thermonuclear burning is nonuniform during burst rise and spreads to encompass the star in 0.5 s. Thus, rotational modulation of the expanding hot spot should be expected, assuming that the viewing geometry is favorable. We present the results of theoretical calculations of the light curve from a rotating neutron star with such a growing hot spot and show that this model can account for both the observed initial pulsation amplitudes and their subsequent decrease during the rising phase. We argue that these results provide strong evidence in favor of the rotational modulation hypothesis for the millisecond oscillations seen during X-ray bursts with RXTE. RP NASA, GODDARD SPACE FLIGHT CTR, HIGH ENERGY ASTROPHYS LAB, UNIV SPACE RES ASSOC, MAIL CODE 662, GREENBELT, MD 20771 USA. RI Swank, Jean/F-2693-2012 NR 23 TC 99 Z9 98 U1 0 U2 0 PU IOP PUBLISHING LTD PI BRISTOL PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND SN 0004-637X EI 1538-4357 J9 ASTROPHYS J JI Astrophys. J. PD SEP 20 PY 1997 VL 487 IS 1 BP L77 EP L80 DI 10.1086/310880 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XY509 UT WOS:A1997XY50900020 ER PT J AU Solomon, S Borrmann, S Garcia, RR Portmann, R Thomason, L Poole, LR Winker, D McCormick, MP AF Solomon, S Borrmann, S Garcia, RR Portmann, R Thomason, L Poole, LR Winker, D McCormick, MP TI Heterogeneous chlorine chemistry in the tropopause region SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID IN-SITU MEASUREMENTS; LOWER STRATOSPHERE; VOLCANIC AEROSOLS; CIRRUS CLOUDS; SAGE-II; VERTICAL-DISTRIBUTION; CLIMATIC IMPLICATIONS; MIDDLE ATMOSPHERE; HYDROGEN-CHLORIDE; NUMERICAL-MODEL AB Satellite observations of cloud optical depths and occurrence frequencies are used as input to a two-dimensional numerical model of the chemistry and dynamics of the atmosphere to study the effects of heterogeneous reactions on cloud surfaces upon chemical composition and ozone depletion in the tropopause region, Efficient reactions of ClONO2 with HCl and H2O, and of HOCl with HCl, are likely to take place on the surfaces of cirrus clouds [Borrmann et al., 1996] and perturb chlorine chemistry, much as they do on polar stratospheric clouds present at higher altitudes and colder temperatures, Because of the very low predicted background abundances of ClO near the tropopause, such reactions could enhance the local ClO mixing ratios by up to 30-fold at midlatitudes. Substantial perturbations are also predicted for related chemical species (e.g., HCl, HOCl, ClONO2, NO2, HO2) in the midlatitude and tropical tropopause regions due to these heterogeneous reactions. If cirrus clouds occur with sufficient frequency and spatial extent, they could influence not only the chemical composition but also the ozone depletion in the region near the tropopause. Because of variations in observed cloud occurrence frequency and in photochemical and dynamical timescales, the presence of cirrus clouds likely has its largest effect on ozone near the midlatitude tropopause of the northern hemisphere in summer. C1 NASA, LANGLEY RES CTR, AEROSOL RES BRACH, HAMPTON, VA 23665 USA. HAMPTON UNIV, DEPT PHYS, HAMPTON, VA 23665 USA. NATL CTR ATMOSPHER RES, BOULDER, CO 80307 USA. UNIV MAINZ, INST PHYS ATMOSPHARE, D-6500 MAINZ, GERMANY. RP Solomon, S (reprint author), NOAA, AERON LAB, 325 BROADWAY, R-E-AL8, BOULDER, CO 80303 USA. RI Portmann, Robert/C-4903-2009; Borrmann, Stephan/E-3868-2010; OI Portmann, Robert/0000-0002-0279-6087; Thomason, Larry/0000-0002-1902-0840 NR 78 TC 141 Z9 142 U1 1 U2 12 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD SEP 20 PY 1997 VL 102 IS D17 BP 21411 EP 21429 DI 10.1029/97JD01525 PG 19 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA XX380 UT WOS:A1997XX38000017 ER PT J AU Mickley, LJ Abbatt, JPD Frederick, JE Russell, JM AF Mickley, LJ Abbatt, JPD Frederick, JE Russell, JM TI Evolution of chlorine and nitrogen species in the lower stratosphere during Antarctic spring: Use of tracers to determine chemical change SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID HALOGEN OCCULTATION EXPERIMENT; LATE WINTER; OZONE LOSS; CLO; DEHYDRATION; MODEL; PHOTOLYSIS; CHEMISTRY; TRANSPORT; DEPLETION AB Observations of O-3, HCl, NO, and NO2 from the Halogen Occultation Experiment (HALOE) provide a means to investigate chemical change in the lower stratosphere over Antarctica during the first 23 days of October 1992. Two long-lived species also observed by HALOE, HF and CH4, are used as tracers to identify a series of air parcels having similar Cl-y and NOy abundances. The set of parcels chosen using tracer analysis show uniformly low O-3 mixing ratios, less than 1 ppm on the 480 K surface (about 18-20 km). HCl mixing ratios for those parcels with less than 1 ppm of ozone nearly tripled during the time period, and NO + NO2 abundances rose sharply, by a factor of 6 dr 7. These trends in HCl, NO, and NO2 agree qualitatively with model calculations which show that the formation of HCl proceeds quickly when O-3 levels fall so low that (1) the rate of the reaction Cl + O-3 --> ClO + O-2 slows and (2) the rate of the reaction NO + ClO --> NO2 + Cl becomes faster than the rate of the competing reaction NO + O-3 --> NO2 + O-2. Under these conditions, Cl increases at the expense of ClO, and HCl is formed via the reaction Cl + CH4 --> HCl + CH3. Stratospheric chlorine is thus shifted from reactive species to the long-lived, reservoir molecule HCl. The repartitioning of the active chlorine family in favor of HCl halts the processes that destroy ozone and makes available active nitrogen in the form of NO and NO2. The investigation confirms earlier results and validates tracer analysis as a reliable method to probe chemical change in the stratosphere. C1 UNIV CHICAGO, DEPT GEOPHYS SCI, CHICAGO, IL 60637 USA. NASA, LANGLEY RES CTR, DIV ATMOSPHER SCI, HAMPTON, VA 23665 USA. RI Mickley, Loretta/D-2021-2012 OI Mickley, Loretta/0000-0002-7859-3470 NR 38 TC 12 Z9 12 U1 0 U2 2 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD SEP 20 PY 1997 VL 102 IS D17 BP 21479 EP 21491 DI 10.1029/97JD00422 PG 13 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA XX380 UT WOS:A1997XX38000022 ER PT J AU Mazely, TL Friedl, RR Sander, SP AF Mazely, TL Friedl, RR Sander, SP TI Quantum yield of NO3 from peroxyacetyl nitrate photolysis SO JOURNAL OF PHYSICAL CHEMISTRY A LA English DT Article ID N2O5 PHOTOLYSIS; THERMAL-DECOMPOSITION; PAN; CHEMISTRY; NITROGEN AB Peroxyacetyl nitrate (PAN) vapor was photolyzed at 248 nm and the NO3 photoproduct was detected by laser-induced fluorescence. The quantum yield for the production of NO3 was determined by comparison to N2O5 photolysis data taken under identical experimental conditions, Contributions to the observed laser induced fluorescence were found to arise from excited-stare photoproducts such as NO2*. The excited-state fluorescence contributions were investigated, and a data analysis methodology was established to minimize their effects. The average of data collected over a range of total pressures, precursor concentrations, and buffer gases was 0.3 +/- 0.1 for the NO3 quantum yield, where the quoted statistical uncertainty represents two standard deviations. This result, combined with our previously reported value of 0.83 +/- 0.09 for the NO2 quantum yield from the photolysis of PAN, suggests that NO2 and NO3 represent the only nitrogen-containing products in the 248 nm photolysis of PAN. The atmospheric implications of a NO3 producing channel in PAN photolysis are considered. C1 CALTECH,JET PROP LAB,PASADENA,CA 91109. NR 23 TC 19 Z9 19 U1 1 U2 2 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 SN 1089-5639 J9 J PHYS CHEM A JI J. Phys. Chem. A PD SEP 18 PY 1997 VL 101 IS 38 BP 7090 EP 7097 DI 10.1021/jp971298r PG 8 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA XX153 UT WOS:A1997XX15300012 ER PT J AU Das, IS Khavaran, A Krejsa, EA AF Das, IS Khavaran, A Krejsa, EA TI A computational study of contoured plug-nozzle jet noise SO JOURNAL OF SOUND AND VIBRATION LA English DT Article ID SUPERSONIC JETS; MIXING NOISE; FLOWS AB A computational noise study of a scale model of an axisymmetric ideally contoured plug-nozzle (CPN) is presented. The CPN has an exit diameter of 45 mm and the geometrical configuration is such that the jet flow is shockless at the design pressure ratio, zeta(d) = 362. The gas dynamics of the jet flows has been predicted using the NPARC Computational Fluid Dynamics code with the k-epsilon turbulence model. The gas dynamics data are then used to perform the noise computations based on the modified General Electric MGB code. The study covers a range of pressure ratios, 2.0 less than or equal to 4 xi less than or equal to 5.0. The agreement of the computational aeroacoustic results with the reported experimental data is favorable. At the design pressure ratio (shockless flow), the predicted noise levels are within 3 dB. At the off-design pressure ratios (hows with shocks), the theory predicts the noise levels within 5 dB, except at very high frequencies for pressure ratios farthest from the design pressure ratio when deviations up to 8 dB are noted. The computed directivity patterns do not represent the reported experimental trends well. The mechanism of shock formation in the CPN jet flows is noted to be basically different from those in the convergent nozzle and convergent-divergent nozzle jet flows. The computational results indicate consistent noise reduction effectiveness of the CPN relative to the equivalent convergent and convergent-divergent nozzles for all operating pressure ratios. (C) 1997 Academic Press Limited. C1 NYMA,LEWIS RES CTR GRP,CLEVELAND,OH 44135. NASA,LEWIS RES CTR,CLEVELAND,OH 44135. RP Das, IS (reprint author), PENN STATE UNIV,SHARON,PA 16146, USA. NR 51 TC 3 Z9 3 U1 0 U2 1 PU ACADEMIC PRESS LTD PI LONDON PA 24-28 OVAL RD, LONDON, ENGLAND NW1 7DX SN 0022-460X J9 J SOUND VIB JI J. Sound Vibr. PD SEP 18 PY 1997 VL 206 IS 2 BP 169 EP 194 DI 10.1006/jsvi.1997.1038 PG 26 WC Acoustics; Engineering, Mechanical; Mechanics SC Acoustics; Engineering; Mechanics GA XX807 UT WOS:A1997XX80700003 ER PT J AU Karasik, BS Gaidis, MC McGrath, WR Bumble, B LeDuc, HG AF Karasik, BS Gaidis, MC McGrath, WR Bumble, B LeDuc, HG TI Low noise in a diffusion-cooled hot-electron mixer at 2.5 THz SO APPLIED PHYSICS LETTERS LA English DT Article ID BOLOMETER MIXER AB The noise performance of a Nb hot-electron bolometer mixer at 2.5 THz has been investigated. The devices are fabricated from a 12-nm-thick Nb film, and have a 0.30 mu mX0.15 mu m in-plane size, thus exploiting diffusion as the electron cooling mechanism. The rf coupling was provided by a twin-slot planar antenna on an elliptical Si lens. The experimentally measured double sideband noise temperature of the receiver was as low as 2750+/-250 K with an estimated mixer noise temperature of approximate to 900 K. The mixer bandwidth derived from both noise bandwidth and IF impedance measurements was approximate to 1.4 GHz. These results demonstrate the low-noise operation of the diffusion-cooled bolometer mixer above 2 THz. (C) 1997 American Institute of Physics. RP Karasik, BS (reprint author), CALTECH,JET PROP LAB,CTR SPACE MICROELECT TECHNOL,PASADENA,CA 91109, USA. RI Gaidis, Michael/D-3327-2013; Karasik, Boris/C-5918-2011 NR 15 TC 46 Z9 46 U1 0 U2 5 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 SEP 15 PY 1997 VL 71 IS 11 BP 1567 EP 1569 DI 10.1063/1.119967 PG 3 WC Physics, Applied SC Physics GA XV726 UT WOS:A1997XV72600044 ER PT J AU Angelopoulos, V Phan, TD Larson, DE Mozer, FS Lin, RP Tsuruda, K Hayakawa, H Mukai, T Kokubun, S Yamamoto, T Williams, DJ McEntire, RW Lepping, RP Parks, GK Brittnacher, M Germany, G Spann, J Singer, HJ Yumoto, K AF Angelopoulos, V Phan, TD Larson, DE Mozer, FS Lin, RP Tsuruda, K Hayakawa, H Mukai, T Kokubun, S Yamamoto, T Williams, DJ McEntire, RW Lepping, RP Parks, GK Brittnacher, M Germany, G Spann, J Singer, HJ Yumoto, K TI Magnetotail flow bursts: association to global magnetospheric circulation, relationship to ionospheric activity and direct evidence for localization SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID PLASMA SHEET; SIGNATURES; EXPANSION; ONSET AB A series of bursty bulk flow events (BBFs) were observed by GEOTAIL and WIND in the geomagnetotail. IMP8 at the solar wind showed significant energy coupling into the magnetosphere, while the WI instrument on POLAR evidenced significant energy transfer to the ionosphere during two substorms. There was good correlation between BBFs and ionospheric activity observed by UVI even when ground magnetic signatures were absent, suggesting that low ionospheric conductivity at the active sector may be responsible for this observation. During the second substorm no significant flux transport was evidenced past WIND in stark contrast to GEOTAIL and despite the small intersatellite separation ((3.54, 2.88, -0.06) R-E). Throughout the intervals studied there were significant differences in the individual flow bursts at the two satellites, even during longitudinally extended ionospheric activations. We conclude that the half-scale-size of transport-bearing flow bursts is less than 3 R-E. C1 UNIV WASHINGTON,GEOPHYS PROGRAM,SEATTLE,WA 98195. INST SPACE & ASTRONAUT SCI,SAGAMIHARA,KANAGAWA 229,JAPAN. NAGOYA UNIV,SOLAR TERR ENVIRONM LAB,TOYOKAWA 442,JAPAN. NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. JOHNS HOPKINS UNIV,APPL PHYS LAB,LAUREL,MD 20723. NOAA,SPACE ENVIRONM CTR,RESE,BOULDER,CO 80303. NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,HUNTSVILLE,AL 35812. KYUSHU UNIV,FAC SCI 33,DEPT EARTH & PLANETARY SCI,FUKUOKA 81281,JAPAN. UNIV ALABAMA,CSPAR,HUNTSVILLE,AL 35899. RP Angelopoulos, V (reprint author), UNIV CALIF BERKELEY,SPACE SCI LAB,BERKELEY,CA 94720, USA. NR 11 TC 136 Z9 139 U1 0 U2 2 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 SEP 15 PY 1997 VL 24 IS 18 BP 2271 EP 2274 DI 10.1029/97GL02355 PG 4 WC Geosciences, Multidisciplinary SC Geology GA XW963 UT WOS:A1997XW96300003 ER PT J AU Pi, X Mannucci, AJ Lindqwister, UJ Ho, CM AF Pi, X Mannucci, AJ Lindqwister, UJ Ho, CM TI Monitoring of global ionospheric irregularities using the worldwide GPS network SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID F-LAYER IRREGULARITIES; EQUATORIAL SPREAD-F; SCINTILLATION AB A prototype system has been developed to monitor the instantaneous global distribution of ionospheric irregularities, using the worldwide network of Global Positioning System (GPS) receivers. Case studies in this paper indicate that GPS receiver loss of lock of signal tracking may be associated with strong phase fluctuations. It is shown that a network-based GPS monitoring system will enable us to study the generation and evolution of ionospheric :irregularities continuously around the globe under various solar and geophysical conditions, which is particularly suitable for studies of ionospheric storms, and for space weather research and applications. RP Pi, X (reprint author), CALTECH,JET PROP LAB,M-S 238-600,4800 OAK GROVE DR,PASADENA,CA 91109, USA. RI Mannucci, Anthony/A-1349-2007 OI Mannucci, Anthony/0000-0003-2391-8490 NR 15 TC 204 Z9 219 U1 7 U2 15 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 SEP 15 PY 1997 VL 24 IS 18 BP 2283 EP 2286 DI 10.1029/97GL02273 PG 4 WC Geosciences, Multidisciplinary SC Geology GA XW963 UT WOS:A1997XW96300006 ER PT J AU Olson, CF AF Olson, CF TI An approximation algorithm for least median of squares regression SO INFORMATION PROCESSING LETTERS LA English DT Article DE least median of squares regression; approximation algorithms; computational geometry; design of algorithms ID LINES AB Least median of squares (LMS) regression is a robust method to fit equations to observed data (typically in a linear model). This paper describes an approximation algorithm for LMS regression. The algorithm generates a regression solution with median residual no more than twice the optimal median residual. Random sampling is used to provide a simple O(n log(2) n) expected time algorithm in the two-dimensional case that is successful with high probability. This algorithm is also extended to arbitrary dimension d with O(n(d-1) log n) worst-case complexity for fixed d > 2. (C) 1997 Elsevier Science B.V. C1 CORNELL UNIV,DEPT COMP SCI,ITHACA,NY 14853. RP Olson, CF (reprint author), CALTECH,JET PROP LAB,4800 OAK GROVE DR,MS 107-102,PASADENA,CA 91109, USA. NR 12 TC 16 Z9 16 U1 0 U2 2 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0020-0190 J9 INFORM PROCESS LETT JI Inf. Process. Lett. PD SEP 15 PY 1997 VL 63 IS 5 BP 237 EP 241 DI 10.1016/S0020-0190(97)00132-4 PG 5 WC Computer Science, Information Systems SC Computer Science GA YC110 UT WOS:A1997YC11000002 ER PT J AU Leridon, B Febvre, P George, S Feautrier, P McGrath, WR AF Leridon, B Febvre, P George, S Feautrier, P McGrath, WR TI Experimental evidence of Josephson noise in superconductor-insulator-superconductor quasiparticle mixers SO JOURNAL OF APPLIED PHYSICS LA English DT Article ID JUNCTIONS AB Josephson currents have been observed to drain instabilities and decrease the sensitivity of a heterodyne superconductor-insulator-superconductor (SIS) receiver operated at submillimeter wavelengths. A static magnetic field is usually applied on the SIS junction to reduce the magnitude of its critical Josephson currents and enable quasiparticle mixing, We measured the SIS mixer output power at the intermediate frequency (IF) versus the dc bias voltage of an array of two 1 mu m(2) Nb/Al-Al2O3/Nb junctions, We show evidence of additional, magnetic-field-sensitive noise, peaked at the Shapiro steps voltages, which is due to high-frequency Josephson currents converted to the IF by quasiparticle mixing. (C) 1997 American Institute of Physics. C1 OBSERV PARIS,DEMIRM,F-75014 PARIS,FRANCE. OBSERV GRENOBLE,BP53X 414,F-38041 GRENOBLE,FRANCE. CALTECH,JET PROP LAB,PASADENA,CA 91109. NR 13 TC 3 Z9 3 U1 0 U2 1 PU AMER INST PHYSICS PI WOODBURY PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 SN 0021-8979 J9 J APPL PHYS JI J. Appl. Phys. PD SEP 15 PY 1997 VL 82 IS 6 BP 3024 EP 3027 DI 10.1063/1.366160 PG 4 WC Physics, Applied SC Physics GA XX996 UT WOS:A1997XX99600045 ER PT J AU Jain, A AF Jain, A TI Compensating mass matrix potential for constrained molecular dynamics SO JOURNAL OF COMPUTATIONAL PHYSICS LA English DT Article ID CLASSICAL STATISTICAL-MECHANICS; OPERATOR METHOD; ROBOT DYNAMICS; POLYMER-CHAIN; MANIPULATORS; SIMULATION AB Rigid internal constraints are used in molecular models to speed up molecular dynamics (MD) simulations. It is well recognized that statistical averages from such constrained MD simulations differ by a metric tensor-dependent term from similar averages computed using conventional unconstrained MD simulations. Fixman proposed augmenting the standard potential with a compensating term which depends on the metric tensor to nullify the effects of this bias term. However, in the absence of tractable algorithms to compute this compensating tensor potential and its gradient its use has been impractical. This paper derives a new algorithm for computing the compensating potential, as well as its gradient for tree topology molecular systems. The algorithm is quite straightforward and is an extension of the spatial operators based O(N) algorithm that has been recently proposed for constrained dynamics. Indeed, the compensating potential is closely related and computed from the articulated body inertia quantities available from this O(N) algorithm. (C) 1997 Academic Press. RP Jain, A (reprint author), CALTECH,JET PROP LAB,4800 OAK GROVE DR,PASADENA,CA 91109, USA. NR 28 TC 13 Z9 13 U1 2 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 SEP 15 PY 1997 VL 136 IS 2 BP 289 EP 297 DI 10.1006/jcph.1997.5731 PG 9 WC Computer Science, Interdisciplinary Applications; Physics, Mathematical SC Computer Science; Physics GA XZ450 UT WOS:A1997XZ45000005 ER PT J AU Shindell, DT Wong, S Rind, D AF Shindell, DT Wong, S Rind, D TI Interannual variability of the Antarctic ozone hole in a GCM .1. The influence of tropospheric wave variability SO JOURNAL OF THE ATMOSPHERIC SCIENCES LA English DT Article ID MIDDLE ATMOSPHERE MODEL; PLANETARY-WAVES; CIRCULATION; STRATOSPHERE; DEPLETION AB To study the interannual variability of the Antarctic ozone hole, a physically realistic parameterization of the chemistry responsible for severe polar ozone loss has been included in the GISS GCM. The ensuing ozone hole agrees well with observations, as do modeled surface UV increases of up to 42%. The presence of the ozone hole causes a reduction in lower stratospheric solar heating and an increase in upper stratospheric descent and dynamical heating in the model, as expected. Both the degree of ozone depletion and the dynamical response exhibit large interannual variability, however. These variations are driven by differences in the midwinter buildup of tropospheric wave energy in the model, which affect the dynamics globally for several months according to the mechanism detailed herein. Starting by July, strong tropospheric wave activity lends to greater energy reaching the lower stratosphere, and therefore warmer temperatures, than in years with weak wave activity. The warmer temperatures persist throughout the austral spring, resulting in ozone losses that are only similar to 80% of those seen in the years with weaker wave activity. Significant differences also occur in the zonal Hind field, setting up conditions that ultimately affect the propagation of wave energy in the spring. Differences in the propagation of wave energy lead to an October increase in upper stratospheric dynamical heating that is more than three times larger in the years with weak wave activity than in years with strong wave activity. Modeled interannual variations in both upper stratospheric temperatures and ozone loss are of similar magnitude to observations, though the largest observed variations exceed those seen here, indicating that unforced variability likely plays a significant role in addition to periodic forcings such as the QBO. The results are in accord with observational studies showing a strong anticorrelation between the interannual variability of tropospheric wave forcing and of the Antarctic ozone hole, suggesting that midwinter tropospheric wave energy may be the best predictor of the severity of the ozone hole the following spring. C1 COLUMBIA UNIV,CTR CLIMATE SYST RES,NEW YORK,NY. RP Shindell, DT (reprint author), NASA,GODDARD INST SPACE STUDIES,2880 BROADWAY,NEW YORK,NY 10025, USA. RI Shindell, Drew/D-4636-2012 NR 18 TC 31 Z9 31 U1 0 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 SEP 15 PY 1997 VL 54 IS 18 BP 2308 EP 2319 DI 10.1175/1520-0469(1997)054<2308:IVOTAO>2.0.CO;2 PG 12 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA XW339 UT WOS:A1997XW33900005 ER PT J AU Kinne, S Akerman, TP Shiobara, M Uchiyama, A Heymsfield, AJ Miloshevich, L Wendell, J Eloranta, EW Purgold, C Bergstrom, RW AF Kinne, S Akerman, TP Shiobara, M Uchiyama, A Heymsfield, AJ Miloshevich, L Wendell, J Eloranta, EW Purgold, C Bergstrom, RW TI Cirrus cloud radiative and microphysical properties from ground observations and in situ measurements during FIRE 1991 and their application to exhibit problems in cirrus solar radiative transfer modeling SO JOURNAL OF THE ATMOSPHERIC SCIENCES LA English DT Article ID ICE CRYSTALS; OPTICAL-PROPERTIES; SCATTERING; CLIMATE; LIGHT; PARAMETERIZATION; TEMPERATURE; AIRCRAFT; FEEDBACK AB Measurements from the FIRE 1991 cirrus cloud field experiment in the central United States are presented and analyzed. The first part focuses on cirrus microphysical properties. Aircraft 2D-probe in situ data at different cloud altitudes were evaluated for cirrus cases on four different days. Also presented are simultaneous data samples from balloonborne videosondes. Only these balloonsondes could detect the smaller crystals. Their data suggest (at least for midlatitude altitudes below 10 km) that ice crystals smaller than 15 mu m in size are rare and that small ice crystals not detected by 2D-probe measurements are radiatively of minor importance, as overlooked 2D-probe crystals account for about 10% of the total extinction. The second part focuses on the link between cirrus cloud properties and radiation. With cloud microphysical properties from surface remote sensing added to the microphysical data and additional radiation measurements at the surface, testbeds for radiative transfer models were created. To focus on scattering processes, model evaluations were limited to the solar radiative transfer by comparing calculated and measured transmissions of sunlight at the surface. Comparisons under cloud-free conditions already reveal a model bias of about +45 W m(-2) for the hemispheric solar downward broadband flux. This discrepancy, which is (at least in part) difficult to explain. has to be accounted for in comparisons involving clouds. Comparisons under cirrus cloud conditions identify as the major obstacle in cirrus solar radiative transfer modeling the inability of one-dimensional radiative transfer models to account for horizontal inhomogeneities. The successful incorporation of multidimensional radiative transfer effects will depend not only on better models but critically on the ability to measure and to define characteristic inhomogeneity scales of cloud fields. The relative minor error related to the microphysical treatment is in part a reflection of the improved understanding on solar scattering on ice crystals over the last decade and of the available wealth on ice-crystal size and shape data for this study. In absence of this information, uncertainties from microphysical cirrus model assumptions will remain high. C1 PENN STATE UNIV,DEPT METEOROL,UNIVERSITY PK,PA 16802. METEOROL RES INST,TSUKUBA,IBARAKI 305,JAPAN. NATL CTR ATMOSPHER RES,BOULDER,CO 80307. NOAA,BOULDER,CO. UNIV WISCONSIN,DEPT ATMOSPHER SCI,MADISON,WI. NASA,LANGLEY RES CTR,HAMPTON,VA 23665. BAY AREA ENVIRONM RES INST,SAN FRANCISCO,CA. RP Kinne, S (reprint author), NASA,AMES RES CTR,BAY AREA ENVIRONM RES INST,MAILSTOP 245-4,MOFFETT FIELD,CA 94035, USA. RI Heymsfield, Andrew/E-7340-2011 NR 37 TC 44 Z9 44 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 SEP 15 PY 1997 VL 54 IS 18 BP 2320 EP 2344 DI 10.1175/1520-0469(1997)054<2320:CCRAMP>2.0.CO;2 PG 25 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA XW339 UT WOS:A1997XW33900006 ER PT J AU Lopez, RE Turner, MS Gyuk, G AF Lopez, RE Turner, MS Gyuk, G TI Effect of finite nucleon mass on primordial nucleosynthesis SO PHYSICAL REVIEW D LA English DT Article ID BIG-BANG NUCLEOSYNTHESIS; LITHIUM ABUNDANCE; EVOLUTION; UNIVERSE; DWARFS; STARS; HE-3 AB By numerically evaluating five-dimensional phase-space integrals, we have calculated;the small effect of finite nucleon mass on the weak-interaction rates that interconvert protons and neutrons in the early Universe. We have modified the standard code for primordial nucleosynthesis to include these corrections and find a small, systematic increase in the He-4 yield, Delta Y/Y similar or equal to (0.47-0.50)%, depending slightly on the value of the baryon-to-photon ratio eta. The fractional changes in the abundances of D, He-3, and Li-7 range from 0.06 to 2.8% for 10(-11) less than or equal to eta less than or equal to 10(-8). C1 NASA,FERMILAB ASTROPHYS CTR,FERMI NATL ACCELERATOR LAB,BATAVIA,IL 60510. UNIV CHICAGO,ENRICO FERMI INST,DEPT ASTRON & ASTROPHYS,CHICAGO,IL 60637. SISSA,I-34014 TRIESTE,ITALY. RP Lopez, RE (reprint author), UNIV CHICAGO,DEPT PHYS,CHICAGO,IL 60637, USA. NR 37 TC 14 Z9 14 U1 0 U2 0 PU AMERICAN PHYSICAL SOC PI COLLEGE PK PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA SN 0556-2821 J9 PHYS REV D JI Phys. Rev. D PD SEP 15 PY 1997 VL 56 IS 6 BP 3191 EP 3197 DI 10.1103/PhysRevD.56.3191 PG 7 WC Astronomy & Astrophysics; Physics, Particles & Fields SC Astronomy & Astrophysics; Physics GA XY575 UT WOS:A1997XY57500004 ER PT J AU Dodelson, S Kinney, WH Kolb, EW AF Dodelson, S Kinney, WH Kolb, EW TI Cosmic microwave background measurements can discriminate among inflation models SO PHYSICAL REVIEW D LA English DT Article ID TENSOR PERTURBATIONS; DARK-MATTER; COSMOLOGY; ANISOTROPY; UNIVERSE; GRAVITY AB Quantum fluctuations during inflation may be responsible for temperature anisotropies in the cosmic microwave background (CMB). Observations of CMB anisotropies can be used to falsify many currently popular models. In this paper we discuss the prospectus for observations of CMB anisotropies at the accuracy of planned satellite missions to reject currently popular inflation models and to provide some direction for model building. C1 UNIV CHICAGO,DEPT ASTRON & ASTROPHYS,ENRICO FERMI INST,CHICAGO,IL 60637. RP Dodelson, S (reprint author), NASA,FERMILAB ASTROPHYS CTR,FERMI NATL ACCELERATOR LAB,BATAVIA,IL 60510, USA. NR 31 TC 138 Z9 139 U1 0 U2 1 PU AMERICAN PHYSICAL SOC PI COLLEGE PK PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA SN 0556-2821 J9 PHYS REV D JI Phys. Rev. D PD SEP 15 PY 1997 VL 56 IS 6 BP 3207 EP 3215 DI 10.1103/PhysRevD.56.3207 PG 9 WC Astronomy & Astrophysics; Physics, Particles & Fields SC Astronomy & Astrophysics; Physics GA XY575 UT WOS:A1997XY57500006 ER PT J AU Locci, IE Brady, MP MacKay, RA Smith, JW AF Locci, IE Brady, MP MacKay, RA Smith, JW TI Very long term oxidation of Ti-48A1-2Cr-2Nb at 704 degrees C in air SO SCRIPTA MATERIALIA LA English DT Article ID BEHAVIOR; NITROGEN C1 CASE WESTERN RESERVE UNIV, CLEVELAND, OH 44106 USA. NYMA INC, BROOKPARK, OH 44142 USA. RP NASA, LEWIS RES CTR, M-S 106-5, CLEVELAND, OH 44135 USA. RI Brady, Michael/A-8122-2008 OI Brady, Michael/0000-0003-1338-4747 NR 18 TC 13 Z9 13 U1 0 U2 1 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 1359-6462 J9 SCRIPTA MATER JI Scr. Mater. PD SEP 15 PY 1997 VL 37 IS 6 BP 761 EP 766 DI 10.1016/S1359-6462(97)00178-4 PG 6 WC Nanoscience & Nanotechnology; Materials Science, Multidisciplinary; Metallurgy & Metallurgical Engineering SC Science & Technology - Other Topics; Materials Science; Metallurgy & Metallurgical Engineering GA XR926 UT WOS:A1997XR92600007 ER PT J AU Bauschlicher, CW Partridge, H AF Bauschlicher, CW Partridge, H TI The heats of formation of SiCln+, for n=1-4 SO CHEMICAL PHYSICS LETTERS LA English DT Article ID GAUSSIAN-BASIS SETS; CORRELATED MOLECULAR CALCULATIONS; COUPLED-CLUSTER THEORY; WAVE-FUNCTIONS; PHOTOELECTRON-SPECTROSCOPY; ELECTRON CORRELATION; ORBITAL METHODS; MOLLER-PLESSET; THERMOCHEMISTRY; ENERGIES AB The heats of formation of SiCln and SiCln+, for n = 1-4, have been determined using the G2(B3LYP/MP2/CC) approach. The results for the neutral systems are in very good agreement with previous work. High level calibration calculations allow us to refine the G2(B3LYP/MP2/CC) values. While the computed and experimental IPs of SiCl4 agree, the calculations show that the adiabatic TP is about 7 kcal/mol smaller than the accepted value. The temperature dependence of the heat of formation, heat capacity, and entropy are computed for 300 to 4000 K and fit to a polynomial. (C) 1997 Published by Elsevier Science B.V. RP Bauschlicher, CW (reprint author), NASA, AMES RES CTR, MOFFETT FIELD, CA 94035 USA. NR 34 TC 24 Z9 24 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 SEP 12 PY 1997 VL 276 IS 1-2 BP 47 EP 54 DI 10.1016/S0009-2614(97)00843-9 PG 8 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA XX816 UT WOS:A1997XX81600008 ER PT J AU Kaufman, YJ Fraser, RS AF Kaufman, YJ Fraser, RS TI The effect of smoke particles on clouds and climate forcing SO SCIENCE LA English DT Article ID ANTHROPOGENIC SULFATE AEROSOLS; ATMOSPHERIC CHEMISTRY; BIOMASS; ALBEDO; EMISSIONS; RETRIEVAL; CALIBRATION; RADIATION; POLLUTION; TRANSPORT AB Smoke particles from biomass burning can generate forcing of climate by modifying cloud microphysics and reflectance of sunlight. Cloud modification, critical to an understanding of climate change, is uncertain and variable. Satellite data over the Amazon Basin and Cerrado were analyzed for cloud reflectance and droplet size and for smoke concentration. Smoke increased cloud reflectance from 0.35 to 0.35, while reducing droplet size from 14 to 9 micrometers. The regional variability of the smoke effect was correlated to the availability of water vapor. During the 3 months of biomass burning in the dry season, the smoke-cloud forcing of climate was only -2 watts per square meter in this region, much smaller than what can be inferred from model predictions. RP Kaufman, YJ (reprint author), NASA, GODDARD SPACE FLIGHT CTR, LAB ATMOSPHERES 913, GREENBELT, MD 20771 USA. NR 54 TC 264 Z9 274 U1 2 U2 31 PU AMER ASSOC ADVANCEMENT SCIENCE PI WASHINGTON PA 1200 NEW YORK AVE, NW, WASHINGTON, DC 20005 USA SN 0036-8075 J9 SCIENCE JI Science PD SEP 12 PY 1997 VL 277 IS 5332 BP 1636 EP 1639 DI 10.1126/science.277.5332.1636 PG 4 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA XV684 UT WOS:A1997XV68400042 ER PT J AU Bolotnikov, A Ramsey, B AF Bolotnikov, A Ramsey, B TI The spectroscopic properties of high-pressure xenon SO NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT LA English DT Article ID ENERGY RESOLUTION; LIQUID XENON; FLUID XENON; IONIZATION; COLLECTION; DETECTOR; CHARGE AB The density and temperature dependences of the mean energy to form an ion pair, W-value, and the intrinsic energy resolution, Delta E-0, of high-pressure Xe were investigated with a parallel plate ionization chamber. A temperature and pressure independent technique to monitor the density of Xe was used. Changes in both the W-value and Delta E-0 were observed, as a function of temperature between 14 degrees C and 70 degrees C and density between 0.12 and 1.7 g/cm(3), and these were found to correlate with the formation of energy bands in Xe, for the former, and changes in the recombination rate, for the latter. Qualitative analysis of the experimental results is presented. RP Bolotnikov, A (reprint author), NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,HUNTSVILLE,AL 35812, USA. NR 24 TC 51 Z9 51 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 SEP 11 PY 1997 VL 396 IS 3 BP 360 EP 370 DI 10.1016/S0168-9002(97)00784-5 PG 11 WC Instruments & Instrumentation; Nuclear Science & Technology; Physics, Nuclear; Physics, Particles & Fields SC Instruments & Instrumentation; Nuclear Science & Technology; Physics GA XW947 UT WOS:A1997XW94700006 ER PT J AU Naya, JE Jean, P Albernhe, F Barthelmy, SD Bartlett, LM Borrel, V Cordier, B Gehrels, N Lavigne, JM Leleux, P Parsons, A Teegarden, BJ Tueller, J Vedrenne, G vonBallmoos, P AF Naya, JE Jean, P Albernhe, F Barthelmy, SD Bartlett, LM Borrel, V Cordier, B Gehrels, N Lavigne, JM Leleux, P Parsons, A Teegarden, BJ Tueller, J Vedrenne, G vonBallmoos, P TI Neutron induced activity in natural and enriched Ge-70 detectors SO NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT LA English DT Article ID GAMMA-RAY SPECTROSCOPY; ASTROPHYSICAL APPLICATIONS; GERMANIUM DETECTORS; CROSS-SECTIONS; SPECTROMETERS; REDUCTION; GE AB The results of irradiations of isotopically enriched and natural Ge detectors with a neutron beam are presented. The analysis of the gamma-ray lines generated by decay of neutron induced unstable nuclei have provided us with a direct measurement of relevant interaction cross sections. Within a factor of 2, measurements and predictions are in good agreement. These results have important implications for the instrumental background in astrophysical gamma-ray spectrometers using germanium detectors, We confirm the reduction of the beta-background component, which dominates the continuum background in the 0.1-1 MeV energy range, using Ge-70 enriched detectors. We clearly identify beta(+) decays inside the detector as a significant source of continuum background in the 1-4 MeV energy range, This component is about 2 times more intense in Ge-70 enriched detectors than in natural ones. This is mainly due to the enhanced yield of Ge-69 and Ga-68 isotopes. The choice of either natural or Ge-70 enriched as optimum detector material depends on the energies of astrophysical interest. Detectors made of enriched Ge-70 are more appropriate for studies at energies below 1 MeV. For higher energies natural germanium is slightly better. The possibility of rejecting most of beta-background component by applying alternative analysis techniques makes natural Ge an appropriate material for future gamma-ray spectrometers. C1 NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. UNIV SPACE RES ASSOC,SEABROOK,MD 20706. CENS,CEA,SERV ASTROPHYS,F-91191 GIF SUR YVETTE,FRANCE. UNIV CATHOLIQUE LOUVAIN,INST PHYS NUCL,B-1348 LOUVAIN,BELGIUM. RP Naya, JE (reprint author), CTR ETUD SPATIALE RAYONNEMENTS,UPS,CNRS,TOULOUSE,FRANCE. RI Gehrels, Neil/D-2971-2012; Tueller, Jack/D-5334-2012; Barthelmy, Scott/D-2943-2012 NR 15 TC 2 Z9 2 U1 0 U2 1 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0168-9002 J9 NUCL INSTRUM METH A JI Nucl. Instrum. Methods Phys. Res. Sect. A-Accel. Spectrom. Dect. Assoc. Equip. PD SEP 11 PY 1997 VL 396 IS 3 BP 374 EP 382 DI 10.1016/S0168-9002(97)00799-7 PG 9 WC Instruments & Instrumentation; Nuclear Science & Technology; Physics, Nuclear; Physics, Particles & Fields SC Instruments & Instrumentation; Nuclear Science & Technology; Physics GA XW947 UT WOS:A1997XW94700008 ER PT J AU Fixsen, DJ Hinshaw, G Bennett, CL Mather, JC AF Fixsen, DJ Hinshaw, G Bennett, CL Mather, JC TI The spectrum of the cosmic microwave background anisotropy from the combined COBE FIRAS and DMR observations SO ASTROPHYSICAL JOURNAL LA English DT Article DE cosmic microwave background; cosmology, observations ID EXPLORER COBE; RADIOMETER; INSTRUMENT; DESIGN; MAPS AB We analyze the cosmic microwave background (CMB) anisotropy data from the independent COBE FIRAS and DMR observations. We extract the frequency spectrum of the FIRAS signal that has the spatial distribution seen by DMR and show that it is consistent with CMB temperature fluctuations in the radiation well into the Wien region of the spectrum. Conversely, we form a map of the Planckian component of the sky temperature from FIRAS and show that it correlates with the DMR anisotropy map. The rms fluctuations at angular scales of 7 degrees are 48 +/- 14 mu K for the FIRAS data versus 35 +/- 2 mu K for the DMR data and 31 +/- 6 mu K for the combination (1 sigma uncertainties). The consistency of these data, from very different instruments with very different observing strategies, provides compelling support for the interpretation that the signal seen by DMR is, in fact, temperature anisotropy of cosmological origin. The data also limit rms fluctuations in the Compton y parameter, observable via the Sunyaev-Zeldovich effect, to Delta y < 3 x 10(-6) (95% CL) on 7 degrees angular scales. C1 NASA,GODDARD SPACE FLIGHT CTR,ASTRON & SOLAR PHYS LAB,CODE 685,GREENBELT,MD 20771. RP Fixsen, DJ (reprint author), NASA,GODDARD SPACE FLIGHT CTR,HUGHES STX CORP,CODE 685,GREENBELT,MD 20771, USA. NR 21 TC 36 Z9 36 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 SEP 10 PY 1997 VL 486 IS 2 BP 623 EP 628 DI 10.1086/304560 PN 1 PG 6 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XX173 UT WOS:A1997XX17300003 ER PT J AU Pian, E Urry, CM Treves, A Maraschi, L Penton, S Shull, JM Pesce, JE Grandi, P Kii, T Kollgaard, RI Madejski, G Marshall, HL Wamsteker, W Celotti, A Courvoisier, TJL Falomo, R Fink, HH George, IM Ghisellini, G AF Pian, E Urry, CM Treves, A Maraschi, L Penton, S Shull, JM Pesce, JE Grandi, P Kii, T Kollgaard, RI Madejski, G Marshall, HL Wamsteker, W Celotti, A Courvoisier, TJL Falomo, R Fink, HH George, IM Ghisellini, G TI Multiwavelength monitoring of the BL Lacertae object PKS 2155-304 in 1994 May .2. The IUE campaign SO ASTROPHYSICAL JOURNAL LA English DT Article DE BL Lacertae objects, individual (PKS 2155-304); galaxies, active; galaxies, magnetic fields; ultraviolet, galaxies ID LOW-DISPERSION SPECTRA; X-RAY; ULTRAVIOLET OBSERVATIONS; RELATIVISTIC JETS; LAC OBJECTS; VARIABILITY; PKS-2155-304; EXTINCTION; BLAZARS; EMISSION AB PXS 2155-304, the brightest BL Lac object in the ultraviolet sky, was monitored with the International Ultraviolet Explorer satellite at similar to 1 hr time resolution for 10 nearly uninterrupted days in 1994 May. The campaign, which was coordinated with Extreme Ultraviolet Explorer, ROSAT, and ASCA monitoring, along with optical and radio observations from the ground, yielded the largest set of spectra and the richest short-timescale variability Information ever gathered for a blazar at UV wavelengths. The source flared dramatically during the first day, with an increase by a factor of similar to 2.2 in an hour and a half. In subsequent days, the flux maintained a nearly constant level for similar to 5 days, then hared with similar to 35% amplitude for 2 days. The same variability was seen in both short-and long-wavelength IUE light curves, with zero formal lag (less than or similar to 2 hr), except during the rapid initial flare, when the variations were not resolved. Spectral index variations were small and not clearly correlated with flux. The flux variability observed in the present monitoring is so rapid that, for the first time, based on the UV emission alone, the traditional Delta L/Delta t limit indicating relativistic beaming is exceeded. The most rapid variations, under the likely assumption of synchrotron radiation, lead to a lower limit of 1 G on the magnetic field strength in the UV-emitting region. These results are compared with earlier intensive monitoring of PKS 2155 - 304 with IUE in 1991 November, when the UV flux variations had completely different characteristics. C1 INT SCH ADV STUDIES SISSA,I-34014 TRIESTE,ITALY. OSSERV ASTRON BRERA,I-20121 MILAN,ITALY. UNIV COLORADO,JOINT INST LAB ASTROPHYS,BOULDER,CO 80309. CNR,IST ASTROFIS SPAZIALE,I-00044 FRASCATI,ITALY. INST SPACE & ASTRONAUT SCI,SAGAMIHARA,KANAGAWA 229,JAPAN. PENN STATE UNIV,DEPT ASTRON & ASTROPHYS,UNIVERSITY PK,PA 16802. NASA,GODDARD SPACE FLIGHT CTR,HIGH ENERGY ASTROPHYS LAB,CODE 666,GREENBELT,MD 20771. EUREKA SCI INC,OAKLAND,CA 94602. UNIV CAMBRIDGE,INST ASTRON,CAMBRIDGE CB3 0HA,ENGLAND. INTEGRAL SCI DATA CTR,CH-1290 VERSOIX,SWITZERLAND. OSSERV ASTRON PADOVA,I-35122 PADUA,ITALY. MAX PLANCK INST EXTRATERR PHYS,D-85740 GARCHING,GERMANY. OSSERVATORIO ASTRON BRERA,I-22055 MERATE,COMO,ITALY. ESA,IUE OBSERV,E-28080 MADRID,SPAIN. RP Pian, E (reprint author), SPACE TELESCOPE SCI INST,3700 SAN MARTIN DR,BALTIMORE,MD 21218, USA. RI Urry, Claudia/G-7381-2011; OI Urry, Claudia/0000-0002-0745-9792; Falomo, Renato/0000-0003-4137-6541; Pian, Elena/0000-0001-8646-4858 NR 62 TC 33 Z9 33 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 SEP 10 PY 1997 VL 486 IS 2 BP 784 EP 798 DI 10.1086/304537 PN 1 PG 15 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XX173 UT WOS:A1997XX17300015 ER PT J AU Urry, CM Treves, A Maraschi, L Marshall, HL Kii, T Madejski, G Penton, S Pesce, JE Pian, E Celotti, A Fujimoto, R Makino, F Otani, C Sambruna, RM Sasaki, K Shull, JM Smith, PS Takahashi, T Tashiro, M AF Urry, CM Treves, A Maraschi, L Marshall, HL Kii, T Madejski, G Penton, S Pesce, JE Pian, E Celotti, A Fujimoto, R Makino, F Otani, C Sambruna, RM Sasaki, K Shull, JM Smith, PS Takahashi, T Tashiro, M TI Multiwavelength monitoring of the BL Lacertae object PKS 2155-304 in 1994 May .3. Probing the inner jet through multiwavelength correlations SO ASTROPHYSICAL JOURNAL LA English DT Article DE BL Lacertae objects, individual (PKS 2155-304); galaxies, active; galaxies, jets; ultraviolet, galaxies; X-rays, galaxies ID X-RAY; SPECTRAL VARIABILITY; PKS-2155-304; BLAZARS; ULTRAVIOLET; MODEL; EMISSION; ORIGIN; AGN AB In 1994 May, the BL Lac object PKS 2155-304 was observed continuously for similar to 10 days with the International Ultraviolet Explorer and the Extreme Ultraviolet Explorer and for 2 days with ASCA, as well as with ROSAT and with ground-based radio, infrared, and optical telescopes. The light curves show a well-defined X-ray flare followed by a broader, lower amplitude extreme-ultraviolet flare similar to 1 day later and a broad, low-amplitude UV flare similar to 2 days later. X-ray fluxes obtained at three well-separated times the preceding week indicate at least one previous flare of comparable amplitude or perhaps ongoing stochastic X-ray variations, and additional rapid variability was seen at the beginning of the IUE observation, when extremely sharp changes in UV flux occurred. The X-ray flux observed with ASCA flared by a factor of similar to 2 in about half a day and decayed roughly as fast. In contrast, the subsequent UV flare had an amplitude of only similar to 35% and lasted longer than 2 days. Assuming that the X-ray, EUV, and UV events are associated, the lags, the decrease of amplitude with wavelength, and the broadening of the temporal profile with wavelength are all qualitatively as expected for synchrotron emission from an inhomogeneous, relativistic jet. Because of the high quality of the data, we can rule out that the observed flares were caused by either a Fermi-type shock acceleration event or a pair cascade in a homogeneous synchrotron-emitting region. A homogeneous region is still possible if there was an instantaneous (t much less than hours) injection of high-energy electrons that emit first at X-ray energies. Alternatively, the data are consistent with a compression wave or other disturbance crossing a region with stratified particle energy distributions. This kind of situation is expected to occur behind a shock front and/or in an inhomogeneous jet. The present light curves are in sharp contrast to the multiwavelength variability observed in 1991 November, when the amplitude was wavelength independent and the UV lagged the X-rays by less than similar to 3 hr. This means that the origin of rapid multiwavelength variability in this blazar is complex, involving at least two different modes. C1 INT SCH ADV STUDIES SISSA,I-34014 TRIESTE,ITALY. UNIV MILAN,DIPARTIMENTO FIS,I-22100 COMO,ITALY. OSSERV ASTRON BRERA,I-20121 MILAN,ITALY. EUREKA SCI INC,OAKLAND,CA 94602. INST SPACE & ASTRONAUT SCI,SAGAMIHARA,KANAGAWA 229,JAPAN. NASA,GODDARD SPACE FLIGHT CTR,HIGH ENERGY ASTROPHYS LAB,GREENBELT,MD 20771. UNIV COLORADO,JOINT INST LAB ASTROPHYS,BOULDER,CO 80309. UNIV ARIZONA,STEWARD OBSERV,TUCSON,AZ 85721. UNIV TOKYO,SCH SCI,DEPT PHYS,BUNKYO KU,TOKYO 113,JAPAN. UNIV CAMBRIDGE,INST ASTRON,CAMBRIDGE CB3 0HA,ENGLAND. RP Urry, CM (reprint author), SPACE TELESCOPE SCI INST,3700 SAN MARTIN DR,BALTIMORE,MD 21218, USA. RI Tashiro, Makoto/J-4562-2012; Urry, Claudia/G-7381-2011; Otani, Chiko/A-6510-2016; OI Urry, Claudia/0000-0002-0745-9792; Pian, Elena/0000-0001-8646-4858 NR 54 TC 103 Z9 105 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 SEP 10 PY 1997 VL 486 IS 2 BP 799 EP 809 DI 10.1086/304536 PN 1 PG 11 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XX173 UT WOS:A1997XX17300016 ER PT J AU Shrader, CR Singh, KP Barrett, P AF Shrader, CR Singh, KP Barrett, P TI The ultraviolet spectrum of the magnetic cataclysmic variable RX J1802.1+1804 SO ASTROPHYSICAL JOURNAL LA English DT Article DE novae, cataclysmic variables; stars, individual (RX J1802.1+1804); ultraviolet, stars ID AM-HERCULIS; BOWEN FLUORESCENCE; STARS; LINES; IUE AB We observed the counterpart to the X-ray source RX J1802.1 + 1804, an object recently discovered as part of a survey to identify the optical counterparts to ultrasoft X-ray sources in the ROSAT point-source catalog that was subsequently identified as a magnetic cataclysmic variable, with the ultraviolet spectrometers on IUE in low dispersion mode. We report on the results of these observations and interpret our data within the context of other UV spectroscopic studies of magnetic CVs (polars). RX J1802.1 + 1804 is a relatively bright UV source, with a UV-to-optical flux ratio and emission-line spectrum similar to other wen-studied CVs. Our observations insufficiently sample the binary orbit to discern any phase-dependent effects. We found RX J1802.1 + 1804 to have an unusually large He II lambda 2733 emission-line strength, and we have also made probable detections of weaker He II lines at 2511, 3203, and possibly 2386 Angstrom, in addition to the more commonly detected He II at 1640 Angstrom. We suggest that RX J1802.1 + 1804 is thus anomalous in terms of its overall He II emission-line spectrum among the sample. Several lines of O III lambda lambda 3047 and 3133 are apparently detected as well, which is unusual for CVs at the signal-to-noise ratio levels obtainable with IUE long-wavelength spectrograph. Given the seemingly rich spectrum of helium and oxygen emission lines, and the known relationship between He II Ly alpha and the oxygen lines, i.e., the Bowen fluorescence mechanism, we can, in principle, constrain the size and thermodynamics of the emitting region. This analysis suggests that R similar to 10(9) cm and n(e) similar to 10(11) cm(-3). This physical scale is consistent with the line-emission originating in the accretion column rather than in a hot spot on the white dwarf surface. C1 TATA INST FUNDAMENTAL RES, XRAY & GAMMA RAY ASTRON GRP, MUMBAI 400005, INDIA. RP Shrader, CR (reprint author), NASA, GODDARD SPACE FLIGHT CTR, HIGH ENERGY ASTROPHYS LAB, GREENBELT, MD 20771 USA. NR 23 TC 4 Z9 4 U1 0 U2 0 PU IOP PUBLISHING LTD PI BRISTOL PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD SEP 10 PY 1997 VL 486 IS 2 BP 1006 EP 1012 DI 10.1086/304541 PN 1 PG 7 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XX173 UT WOS:A1997XX17300034 ER PT J AU Augusteijn, T Greiner, J Kouveliotou, C VanParadijs, J Lidman, C Blanco, P Fishman, GJ Briggs, MS Kommers, J Rutledge, R Lewin, WHG Henden, AA Luginbuhl, CB Vrba, FJ Hurley, K AF Augusteijn, T Greiner, J Kouveliotou, C VanParadijs, J Lidman, C Blanco, P Fishman, GJ Briggs, MS Kommers, J Rutledge, R Lewin, WHG Henden, AA Luginbuhl, CB Vrba, FJ Hurley, K TI ROSAT position of GRO J1744-28 and search for its near-infrared counterpart SO ASTROPHYSICAL JOURNAL LA English DT Article DE pulsars, individual (GRO J1744-28); stars, neutron; X-rays, stars ID DISCOVERY AB We report the detection with ROSAT of a transient X-ray source at R.A. 17(h)44(m)33.(s)1 and decl. -28 degrees 44'29'' (J2000), which we identify with the transient bursting pulsar GRO J1744-28. We have made K-band observations of the X-ray source at ESO and the US Naval Observatory, Flagstaff Station. A K-band counterpart of this transient previously identified by us on an image taken 1996 February 8 by Bianco et al. is found to be detected during only two (of seven) short exposures of which this image is composed. We cannot definitely reject the reality of this variable object but feel that it is not possible to rule out an instrumental effect. The lack of a persistent K-band counterpart of GRO J1744-28 is consistent with the idea that the low-energy emission from this object is dominated by reprocessing of X-rays in an accretion disk. C1 MAX PLANCK INST EXTRATERR PHYS,D-85740 GARCHING,GERMANY. UNIV SPACE RES ASSOC,COLUMBIA,MD 21044. ASTRON INST ANTON PANNEKOEK,NL-1098 SJ AMSTERDAM,NETHERLANDS. UNIV AMSTERDAM,CTR HIGH ENERGY ASTROPHYS,NL-1009 DB AMSTERDAM,NETHERLANDS. UNIV ALABAMA,DEPT PHYS,HUNTSVILLE,AL 35899. UNIV CALIF SAN DIEGO,CTR ASTROPHYS & SPACE SCI,LA JOLLA,CA 92093. NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,SPACE SCI LAB,HUNTSVILLE,AL 35805. MIT,CTR SPACE RES,CAMBRIDGE,MA 02139. USN OBSERV,FLAGSTAFF STN,FLAGSTAFF,AZ 86002. UNIV CALIF BERKELEY,SPACE SCI LAB,BERKELEY,CA 94720. RP Augusteijn, T (reprint author), EUROPEAN SO OBSERV,CASILLA 19001,SANTIAGO 19,CHILE. NR 46 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 SEP 10 PY 1997 VL 486 IS 2 BP 1013 EP 1018 DI 10.1086/304567 PN 1 PG 6 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XX173 UT WOS:A1997XX17300035 ER PT J AU Wolff, CL AF Wolff, CL TI Large convective events and their aftermath in a rotating star SO ASTROPHYSICAL JOURNAL LA English DT Article DE convection; hydrodynamics; Sun, activity; Sun, interior; Sun, oscillations; Sun, rotation ID R-MODES; SOLAR; IRRADIANCE; SUN AB The 35 most exceptional, deep convective events that have occurred since the year 1750 are identified using F-j, an index of solar activity. The average event lasted 38 days and was followed by several years of lesser eruptions in a repeatable time sequence. This contradicts the common assumption that stellar convection is random. Deep convective events, which have lifetimes comparable to the stellar rotation period, will accumulate a net azimuthal motion relative to the ambient fluid. In the Sun, the rising portion of such an event moves in longitude similar to 1 degrees day(-1) as it partially conserves initial angular momentum. Its kinetic energy, similar to 10(29) J, in azimuthal motion amounts to a pulse that is available to excite global oscillations (r-modes). Following the pulse, signatures of r-modes can be traced for 1000 days in the lesser solar eruptions, which is evidence that the r-modes are causing or modulating convection. A successful, nonlinear model of this is constructed in which magnetic fields play no role. RP Wolff, CL (reprint author), NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771, USA. NR 21 TC 3 Z9 3 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 SEP 10 PY 1997 VL 486 IS 2 BP 1058 EP & DI 10.1086/304540 PN 1 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XX173 UT WOS:A1997XX17300040 ER PT J AU Gotthelf, EV Vasisht, G AF Gotthelf, EV Vasisht, G TI Kes 73: A young supernova remnant with an X-ray-bright, radio-quiet central source SO ASTROPHYSICAL JOURNAL LA English DT Article DE stars, individual (Kesteven 73, 1E 1841-045); stars, neutron; supernova remnants; X-rays, stars ID G27.4+0.0; SPECTRA AB We clarify the nature of the small-diameter supernova remnant (SNR) Kes 73 and its central compact source, 1E 1841-045, using X-ray data acquired with ASCA. We introduce a spatiospectral decomposition technique necessary to disentangle the ASCA spectrum of the compact source from the barely resolved shell-type remnant. The source spectrum (1-8 keV) is characterized by an absorbed power law with a photon index alpha 0 similar or equal to 3.4 and N-H similar or equal to 3.0 x 10(22) cm(-2), possibly nonthermal in nature. This bright X-ray source is likely a slowly spinning pulsar, whose detection is reported in our companion paper. The SNR spectrum is characteristic of a thermal plasma, with kT similar or equal to 0.6 keV and emission lines typical of a young remnant. The element Mg and possibly O and Ne are found to be overabundant, qualitatively suggesting an origin from a massive progenitor. We find that Kes 73 is a young (less than or similar to 2000 yr) Type II/Ib SNR containing a neutron star pulsar spinning anomalously slowly for its age. Kes 73 is yet another member of a growing class of SNRs containing radio-quiet compact sources with a hard spectral signature. C1 CALTECH,MS 105 24,PASADENA,CA 91125. RP Gotthelf, EV (reprint author), NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771, USA. NR 24 TC 51 Z9 51 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 SEP 10 PY 1997 VL 486 IS 2 BP L133 EP & DI 10.1086/310846 PN 2 PG 7 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XX174 UT WOS:A1997XX17400016 ER PT J AU Hill, RJ Dolan, JF Bless, RC Boyd, PT Percival, JW Taylor, MJ vanCitters, GW AF Hill, RJ Dolan, JF Bless, RC Boyd, PT Percival, JW Taylor, MJ vanCitters, GW TI The spectrum of the Large Magellanic Cloud pulsar B0540-69 SO ASTROPHYSICAL JOURNAL LA English DT Article DE pulsars, individual (B0540-69); ultraviolet, stars ID PSR 0540-69; CRAB PULSAR; ULTRAVIOLET; RESOLUTION; EXTINCTION; SUPERNOVA AB A prism spectrum of PSR B0540-69, the 50 ms pulsar in the Large Magellanic Cloud, was obtained with the Faint Object Spectrograph on the Hubble Space Telescope. This is only the second pulsar spectrum that has been observed in the optical. The 2500-5500 Angstrom spectrum shows a smooth continuum with several broad emission lines. The lines are emitted by the extended nebula surrounding B0540-69. Less than 30% of the total flux in the spectrum can be contributed by the synchrotron nebula surrounding the pulsar; the time-averaged emission from the pulsar must be the dominant source of the continuum. The observed spectral index, alpha, of the continuum, where flux density S-nu = K nu(alpha) mu Jy, is -2.5 +/- 0.2 between 2500 and 4500 Angstrom. Using E(B - V) = 0.20 +/- 0.05 gives a de-extincted spectral index alpha(0) = -1.6 +/- 0.4. This intrinsic spectral index is significantly different from that of the Crab pulsar in the optical alpha(0) = 0.11 +/- 0.13, Unless E(B - V) similar to 0.5, the intrinsic spectral index of time-averaged pulsar radiation must vary as much from pulsar to pulsar in the high-frequency regime as it does in the radio. C1 NASA,GODDARD SPACE FLIGHT CTR,HUGHES STX CORP,GREENBELT,MD 20771. UNIV WISCONSIN,DEPT ASTRON,MADISON,WI 53706. UNIV WISCONSIN,SPACE ASTRON LAB,MADISON,WI 53706. NASA,GODDARD SPACE FLIGHT CTR,UNIV SPACE RES ASSOC,GREENBELT,MD 20771. LORAS COLL,DEPT PHYS & ENGN,DUBUQUE,IA 52004. NATL SCI FDN,DIV ASTRON SCI,ARLINGTON,VA 22230. RP Hill, RJ (reprint author), NASA,GODDARD SPACE FLIGHT CTR,ASTRON & SOLAR PHYS LAB,GREENBELT,MD 20771, USA. RI Boyd, Patricia/D-3274-2012 NR 24 TC 20 Z9 20 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 SEP 10 PY 1997 VL 486 IS 2 BP L99 EP & DI 10.1086/310858 PN 2 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XX174 UT WOS:A1997XX17400008 ER PT J AU Mason, GM Mazur, JE Dwyer, JR Reames, DV vonRosenvinge, TT AF Mason, GM Mazur, JE Dwyer, JR Reames, DV vonRosenvinge, TT TI New spectral and abundance features of interplanetary heavy ions in corotating interaction regions SO ASTROPHYSICAL JOURNAL LA English DT Article DE acceleration of particles; cosmic rays; interplanetary medium; solar wind ID SOLAR-WIND; ENERGETIC PARTICLES; ACCELERATION; INSTRUMENT; NUCLEONS; ULYSSES; STREAM; SHOCK AB We have surveyed the composition and energy spectra of heavy ions accelerated in 17 corotating interaction regions (CIRs) during solar minimum conditions between 1992 December and 1995 July. Using new high-sensitivity instruments on WIND and SAMPEX, we are able to cover the energy range from approximately 20 keV nucleon(-1) to greater than 10 MeV nucleon(-1), making it possible to distinguish differing forms of particle spectra. Previous measurements down to about 0.5 MeV nucleon(-1) found exponential energy spectra; however, at the even lower energies studied here, we find that the spectral forms become power laws in kinetic energy per nucleon. At 150 keV nucleon(-1) we find that the C:O and Ne:O ratios depend on solar wind speed. These variations suggest that in addition to the solar wind, other sources of heavy ions contribute to the CIR composition. C1 NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. UNIV MARYLAND,INST PHYS SCI & TECHNOL,COLLEGE PK,MD 20742. RP Mason, GM (reprint author), UNIV MARYLAND,DEPT PHYS,COLLEGE PK,MD 20742, USA. NR 15 TC 50 Z9 50 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 SEP 10 PY 1997 VL 486 IS 2 BP L149 EP L152 DI 10.1086/310845 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XX174 UT WOS:A1997XX17400020 ER PT J AU Vasisht, G Gotthelf, EV AF Vasisht, G Gotthelf, EV TI The discovery of an anomalous X-ray pulsar in the supernova remnant Kes 73 SO ASTROPHYSICAL JOURNAL LA English DT Article DE ISM, individual (Kesteven 73); pulsars, individual (1E 1841-045); stars, magnetic fields; stars, neutron; supernova remnants ID NEUTRON-STARS; BINARY; G27.4+0.0; ACCRETION AB We report the discovery of pulsed X-ray emission from the compact source 1E 1841-045, using data obtained with the Advanced Satellite for Cosmology and Astrophysics. The X-ray source is located in the center of the small-diameter supernova remnant (SNR) Kes 73 and is very likely to be the compact stellar remnant of the supernova that formed Kes 73. The X-rays are pulsed with a period of similar or equal to 11.8 s and a sinusoidal modulation of roughly 30%. We interpret this modulation to be the rotation period of an embedded neutron star, and as such it would be the longest spin period for an isolated neutron star to date. This is especially remarkable since the surrounding SNR is very young, similar to 2000 yr old. We suggest that the observed characteristics of this object are best understood within the framework of a neutron star with an enormous dipolar magnetic field, B similar or equal to 8 x 10(14) G. C1 NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. RP Vasisht, G (reprint author), CALTECH,MS 105 24,PASADENA,CA 91125, USA. NR 34 TC 164 Z9 164 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 SEP 10 PY 1997 VL 486 IS 2 BP L129 EP L132 DI 10.1086/310843 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XX174 UT WOS:A1997XX17400015 ER PT J AU Schmullius, CC Evans, DL AF Schmullius, CC Evans, DL TI Synthetic aperture radar (SAR) frequency and polarization requirements for applications in ecology, geology, hydrology, and oceanography: a tabular status quo after SIR-C/X-SAR SO INTERNATIONAL JOURNAL OF REMOTE SENSING LA English DT Review ID IMAGING RADAR; ERS-1 SAR; FOREST; BIOMASS; CLASSIFICATION; MULTIFREQUENCY AB The Spaceborne Imaging Radar-C, X-Band Synthetic Aperture Radar (SIR-C/X-SAR) was the first multi-frequency and multi-polarization SAR system to be launched into space. SIR-C/X-SAR imaged over 300 sites around the Earth returning 143 terabits of data. There has been a tremendous advancement of knowledge in the field of radar remote sensing accomplished in the last two years, as well as verification of earlier findings since the two successful SIR-C/X-SAR missions. This review article presents the current status of optimal SAR parameters for various key issues within the disciplines of ecology, geology, hydrology, and oceanography. A polarimetric X- and L-band radar is suggested as a result of our review for future SAR sensors. The design of a single frequency, albeit polarimetric, SAR satellite, limits applications, as can be deduced from the tables. C1 CALTECH,JET PROP LAB,PASADENA,CA 91109. RP Schmullius, CC (reprint author), GERMAN AEROSP RES ESTAB DLR,INST RADIO FREQUENCY TECHNOL,POB 1116,D-82230 WESSELING,GERMANY. NR 47 TC 43 Z9 43 U1 0 U2 11 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 SEP 10 PY 1997 VL 18 IS 13 BP 2713 EP 2722 DI 10.1080/014311697217297 PG 10 WC Remote Sensing; Imaging Science & Photographic Technology SC Remote Sensing; Imaging Science & Photographic Technology GA XQ194 UT WOS:A1997XQ19400002 ER PT J AU Schnetzler, CC Bluth, GJS Krueger, AJ Walter, LS AF Schnetzler, CC Bluth, GJS Krueger, AJ Walter, LS TI A proposed volcanic sulfur dioxide index (VSI) SO JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH LA English DT Article ID OZONE MAPPING SPECTROMETER; ERUPTIONS; AEROSOLS AB This paper proposes a volcanic SO2 index (VSI), on the basis of a 15-year satellite sampling of volcanic eruptions. This index is scaled to be compatible with the commonly cited volcanic explosivity index (VEI) used to compare explosive volcanic eruptions. A range of SO2 for each VEI level is proposed so that estimates of SO2 emission can be made from the historic VEI database. Volcanic SO2 from large eruptions can be routinely measured by satellite instruments, and for the smaller eruptions, where the sensitivity of satellite remote sensing is not sufficient, ground-based measurements are becoming more available. At the present time we do not think SO2 can be used to define an accurate climate-perturbation index, as we have both insufficient data on volcanic SO2 and understanding of the volcano-climate relationship. C1 MICHIGAN TECHNOL UNIV, DEPT GEOL, HOUGHTON, MI 49931 USA. NASA, GODDARD SPACE FLIGHT CTR, ATMOSPHERES LAB, GREENBELT, MD 20771 USA. NASA, GODDARD SPACE FLIGHT CTR, EARTH SCI DIRECTORATE, GREENBELT, MD 20771 USA. RP Schnetzler, CC (reprint author), UNIV MARYLAND, DEPT GEOG, COLLEGE PK, MD 20742 USA. NR 21 TC 23 Z9 23 U1 0 U2 3 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-9313 EI 2169-9356 J9 J GEOPHYS RES-SOL EA JI J. Geophys. Res.-Solid Earth PD SEP 10 PY 1997 VL 102 IS B9 BP 20087 EP 20091 DI 10.1029/97JB01142 PG 5 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA XX120 UT WOS:A1997XX12000002 ER PT J AU Warner, RD Wasilewski, PJ AF Warner, RD Wasilewski, PJ TI Magnetic petrology of arc xenoliths from Japan and Aleutian Islands SO JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH LA English DT Article ID MAFIC INCLUSIONS; NORTHEAST JAPAN; ANOMALIES; CRUSTAL; MODEL; ZONE AB Xenoliths from Japan and the Aleutian Islands were studied for the purpose of identifying source rocks with sufficient magnetization to account for positive subduction zone Magsat anomalies. Two types of magnetic lithologies are identified: (1) amphibolites and homblende gabbros containing up to 8.6% titanomagnetite, mostly as large, unoxidized, multidomain crystals, and (2) pyroxene gabbros and metagabbros with up to 20.3% titanomagnetite, usually in association with primary ilmenite. The first type is represented by xenoliths from Ichinomegata, Japan and Adak Island in the Aleutians. The second, restricted to Iki Island, Japan and Kanaga Island, Aleutians, has abundant coarse-grained titanomagnetite which in most samples has been oxidized, producing secondary, trellis-type ilmenite lamellae; a few Iki Island xenoliths show more advanced oxidation. Are xenoliths show 3 orders of magnitude range in natural remanent magnetization and saturation remanence and about 2 orders of magnitude range in magnetic susceptibility. Nearly all Iki Island rocks and many from Ichinomegata and the Aleutians possess induced magnetization 2 A m(-1) and greater, with the expectation of additional magnetization due to viscous remanence at elevated temperature. The TiO2 content of titanomagnetite, together with the presence of appreciable Al2O3 and MgO, ensure that most xenoliths have Curie points between 400 degrees and 550 degrees C. Remanence acquisition curves exhibit a range reflecting varying degrees of magnetic hardening due to oxidation. Correspondingly, each xenolith site groups distinctly on a plot of magnetic hysteresis ratios. This paper indicates that lithologies with total magnetizations of many A m(-1) exist in lower crust are settings. Their volumetric distribution is uncertain based on the limited xenolith population reported herein. C1 NASA, GODDARD SPACE FLIGHT CTR, EXTRATERR PHYS LAB, GREENBELT, MD 20771 USA. RP Warner, RD (reprint author), CLEMSON UNIV, DEPT GEOL SCI, 336 BRACKETT HALL, BOX 341908, CLEMSON, SC 29634 USA. NR 26 TC 11 Z9 11 U1 1 U2 3 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-9313 EI 2169-9356 J9 J GEOPHYS RES-SOL EA JI J. Geophys. Res.-Solid Earth PD SEP 10 PY 1997 VL 102 IS B9 BP 20225 EP 20243 DI 10.1029/97JB01517 PG 19 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA XX120 UT WOS:A1997XX12000011 ER PT J AU Mathews, PM Dehant, V Gipson, JM AF Mathews, PM Dehant, V Gipson, JM TI Tidal station displacements SO JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH LA English DT Article ID INNER CORE DYNAMICS; FORCED NUTATIONS; LOVE NUMBERS; EARTH TIDES; ELLIPTICITY; ROTATION; MANTLE AB Theoretical modeling of the station displacements produced by tidal deformations of the Earth due to lunisolar gravitational forces is a necessary part of the analysis of space geodetic data. To attain the accuracies demanded by the precision of the data, a generalized version of the Love number formalism has to be used wherein the classical Love and Shida numbers are replaced by sets of Love number parameters with values that depend on the frequency of the tidal excitation. This paper presents theoretical expressions for the contributions from the various Love number parameters to the station displacement vector and a scheme for efficient computation of these contributions, taking into account the frequency dependence of these parameters as well as the imaginary parts that are present when the effects of mantle anelasticity are taken into account. A brief discussion of the permanent tide which arises from the zero frequency component of the tide-generating potential is included. C1 OBSERV ROYAL BELGIQUE, B-1180 BRUSSELS, BELGIUM. NASA, GODDARD SPACE FLIGHT CTR, GREENBELT, MD 20771 USA. RP UNIV MADRAS, DEPT THEORET PHYS, MADRAS 600025, TAMIL NADU, INDIA. NR 27 TC 30 Z9 34 U1 0 U2 2 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-9313 EI 2169-9356 J9 J GEOPHYS RES-SOL EA JI J. Geophys. Res.-Solid Earth PD SEP 10 PY 1997 VL 102 IS B9 BP 20469 EP 20477 DI 10.1029/97JB01515 PG 9 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA XX120 UT WOS:A1997XX12000029 ER PT J AU Cohen, SC Freymueller, JT AF Cohen, SC Freymueller, JT TI Deformation of the Kenai Peninsula, Alaska SO JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH LA English DT Article ID WILLIAM-SOUND EARTHQUAKE; CURRENT PLATE MOTIONS; SUBDUCTION ZONE; SOUTHWEST JAPAN; UPLIFT; INVERSION; RELEASE; MODEL AB Crustal deformation on the Kenai Peninsula in southern Alaska has been studied using data obtained from Global Positioning System (GPS) measurements in 1993 and 1995 and leveling observations in 1964, immediately after the Prince William Sound earthquake. This analysis shows that the Kenai Peninsula has experienced as much as similar to 900 mm uplift during the past 3 decades and that the uplift forms an similar to 125 km wide elongate dome with its major axis trending southwest to northeast following the trend of the major tectonic features of the region. The averaged uplift rate between 1964 and 1995 is as high as 30 mm yr(-1), although the current uplift rate may be substantially lower. The GPS measurements cast further doubt on previously suspect tide gauge data for Nikiski, Alaska, which indicated rapid postseismic uplift at this site located in northwest Kenai Peninsula adjacent to Cook Inlet. Examination of the three-dimensional GPS data indicates that the eastern Kenai Peninsula is currently undergoing significant SSE to NNW contraction in response to North American-Pacific Plate convergence. The horizontal velocities are consistent with the predictions of an elastic half-space model for the interseismic deformation. This result, taken in combination with the small changes in uplift between 1993 and 1995, suggests that most of the present deformation is due to steady plate convergence rather than transient postseismic rebound. C1 UNIV ALASKA, INST GEOPHYS, FAIRBANKS, AK 99775 USA. RP Cohen, SC (reprint author), NASA, GODDARD SPACE FLIGHT CTR, GEODYNAM BRANCH, MC 921, GREENBELT, MD 20771 USA. NR 39 TC 29 Z9 29 U1 0 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-9313 EI 2169-9356 J9 J GEOPHYS RES-SOL EA JI J. Geophys. Res.-Solid Earth PD SEP 10 PY 1997 VL 102 IS B9 BP 20479 EP 20487 DI 10.1029/97JB01513 PG 9 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA XX120 UT WOS:A1997XX12000030 ER PT J AU Vodovotz, Y Chinachoti, P AF Vodovotz, Y Chinachoti, P TI Confocal microscopy of bread. SO ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY LA English DT Meeting Abstract C1 NASA,LYNDON B JOHNSON SPACE CTR,HOUSTON,TX 77058. RI Chinachoti, Pavinee/C-8892-2009 NR 0 TC 0 Z9 0 U1 0 U2 0 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 SN 0065-7727 J9 ABSTR PAP AM CHEM S JI Abstr. Pap. Am. Chem. Soc. PD SEP 7 PY 1997 VL 214 BP 2 EP AGFD PN 1 PG 1 WC Chemistry, Multidisciplinary SC Chemistry GA XQ857 UT WOS:A1997XQ85700002 ER PT J AU Dimandja, JMD Valentin, JR Kaljurand, M Phillips, JB AF Dimandja, JMD Valentin, JR Kaljurand, M Phillips, JB TI Maximum entropy deconvolution of overlapped gas chromatographic peaks. SO ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY LA English DT Meeting Abstract C1 NASA,AMES RES CTR,MOFFETT FIELD,CA 94035. ESTONIAN ACAD SCI,INST CHEM,EE-0026 TALLINN,ESTONIA. SO ILLINOIS UNIV,DEPT CHEM & BIOCHEM,CARBONDALE,IL 62901. NR 0 TC 0 Z9 0 U1 0 U2 0 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 SN 0065-7727 J9 ABSTR PAP AM CHEM S JI Abstr. Pap. Am. Chem. Soc. PD SEP 7 PY 1997 VL 214 BP 4 EP ANYL PN 1 PG 2 WC Chemistry, Multidisciplinary SC Chemistry GA XQ857 UT WOS:A1997XQ85700260 ER PT J AU Golub, MA Wydeven, T Johnson, AL AF Golub, MA Wydeven, T Johnson, AL TI On the similarity of plasma-polymerized tetrafluoroethylene and RF plasma-sputtered polytetrafluoroethylene. SO ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY LA English DT Meeting Abstract C1 NASA,AMES RES CTR,MOFFETT FIELD,CA 94035. SURFACE SCI LABS,MT VIEW,CA 94043. NR 0 TC 0 Z9 0 U1 0 U2 0 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 SN 0065-7727 J9 ABSTR PAP AM CHEM S JI Abstr. Pap. Am. Chem. Soc. PD SEP 7 PY 1997 VL 214 BP 6 EP MACR PN 2 PG 1 WC Chemistry, Multidisciplinary SC Chemistry GA XQ859 UT WOS:A1997XQ85901679 ER PT J AU Barlow, S Bublitz, GU Chen, CT BlanchardDesce, M Marder, SR Boxer, SG AF Barlow, S Bublitz, GU Chen, CT BlanchardDesce, M Marder, SR Boxer, SG TI Spectroscopic studies of metallocene-based chromophores. SO ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY LA English DT Meeting Abstract C1 CALTECH,BECKMAN INST,PASADENA,CA 91125. STANFORD UNIV,DEPT CHEM,STANFORD,CA 94305. ECOLE NORMALE SUPER,DEPT CHIM,URA 1679 CNRS,F-75231 PARIS 05,FRANCE. CALTECH,JET PROP LAB,PASADENA,CA 91109. NR 0 TC 0 Z9 0 U1 0 U2 0 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 SN 0065-7727 J9 ABSTR PAP AM CHEM S JI Abstr. Pap. Am. Chem. Soc. PD SEP 7 PY 1997 VL 214 BP 9 EP INOR PN 1 PG 1 WC Chemistry, Multidisciplinary SC Chemistry GA XQ857 UT WOS:A1997XQ85702030 ER PT J AU Kojiro, DR Humphrey, DE Shao, M Takeuchi, N AF Kojiro, DR Humphrey, DE Shao, M Takeuchi, N TI Gas chromatographic detectors for exobiology flight experiments SO ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY LA English DT Meeting Abstract C1 NASA,AMES RES CTR,MOFFETT FIELD,CA 94035. SETI INST,MT VIEW,CA 94043. NORCAL,TMA,RICHMOND,CA 94804. NR 0 TC 0 Z9 0 U1 0 U2 0 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 SN 0065-7727 J9 ABSTR PAP AM CHEM S JI Abstr. Pap. Am. Chem. Soc. PD SEP 7 PY 1997 VL 214 BP 33 EP ANYL PN 1 PG 1 WC Chemistry, Multidisciplinary SC Chemistry GA XQ857 UT WOS:A1997XQ85700289 ER PT J AU West, JP Oglesby, DM Brown, K Upchurch, BT AF West, JP Oglesby, DM Brown, K Upchurch, BT TI Fluorescent pressure sensitive coatings without paint binders. SO ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY LA English DT Meeting Abstract C1 NASA,LANGLEY RES CTR,HAMPTON,VA 23681. NR 0 TC 0 Z9 0 U1 0 U2 0 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 SN 0065-7727 J9 ABSTR PAP AM CHEM S JI Abstr. Pap. Am. Chem. Soc. PD SEP 7 PY 1997 VL 214 BP 85 EP CHED PN 1 PG 1 WC Chemistry, Multidisciplinary SC Chemistry GA XQ857 UT WOS:A1997XQ85700634 ER PT J AU Thayumanavan, S Barlow, S Marder, SR Lee, P Anderson, J Armstrong, NR Jabbour, GE Kawabe, Y Morrell, MM Shaheen, SE Kippelen, B Peyghambarian, N AF Thayumanavan, S Barlow, S Marder, SR Lee, P Anderson, J Armstrong, NR Jabbour, GE Kawabe, Y Morrell, MM Shaheen, SE Kippelen, B Peyghambarian, N TI Derivatives of TPD as hole transport molecules: Design and synthesis SO ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY LA English DT Meeting Abstract C1 CALTECH,BECKMAN INST,PASADENA,CA 91125. CALTECH,JET PROP LAB,PASADENA,CA 91109. UNIV ARIZONA,DEPT CHEM,TUCSON,AZ 85721. UNIV ARIZONA,CTR OPT SCI,TUCSON,AZ 85721. RI Kippelen, Bernard/I-4058-2013; Shaheen, Sean/M-7893-2013 OI Kippelen, Bernard/0000-0002-8417-7051; NR 0 TC 0 Z9 0 U1 0 U2 0 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 SN 0065-7727 J9 ABSTR PAP AM CHEM S JI Abstr. Pap. Am. Chem. Soc. PD SEP 7 PY 1997 VL 214 BP 97 EP ORGN PN 2 PG 1 WC Chemistry, Multidisciplinary SC Chemistry GA XQ859 UT WOS:A1997XQ85900097 ER PT J AU Jensen, BJ Lowther, SE Chang, AC AF Jensen, BJ Lowther, SE Chang, AC TI Blends of LARC(TM) PETI-5 with phenylethynyl containing reactive additives SO ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY LA English DT Meeting Abstract C1 NASA,LANGLEY RES CTR,HAMPTON,VA 23681. LOCKHEED ENGN & SCI CO,HAMPTON,VA 23666. NR 0 TC 0 Z9 0 U1 0 U2 0 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 SN 0065-7727 J9 ABSTR PAP AM CHEM S JI Abstr. Pap. Am. Chem. Soc. PD SEP 7 PY 1997 VL 214 BP 112 EP POLY PN 2 PG 1 WC Chemistry, Multidisciplinary SC Chemistry GA XQ859 UT WOS:A1997XQ85901046 ER PT J AU Thayumanavan, S Staub, K Mendez, J Kustedjo, K Marder, SR AF Thayumanavan, S Staub, K Mendez, J Kustedjo, K Marder, SR TI Design and synthesis of functionalized organic chromophores for electro-optic applications. SO ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY LA English DT Meeting Abstract C1 CALTECH,BECKMAN INST,PASADENA,CA 91125. CALTECH,JET PROP LAB,PASADENA,CA 91109. NR 0 TC 0 Z9 0 U1 0 U2 0 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 SN 0065-7727 J9 ABSTR PAP AM CHEM S JI Abstr. Pap. Am. Chem. Soc. PD SEP 7 PY 1997 VL 214 BP 148 EP ORGN PN 2 PG 2 WC Chemistry, Multidisciplinary SC Chemistry GA XQ859 UT WOS:A1997XQ85900148 ER PT J AU Wilson, MA Pohorille, A AF Wilson, MA Pohorille, A TI Adsorption and solvation of ethanol at the water liquid-vapor interface: A molecular dynamics study. SO ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY LA English DT Meeting Abstract C1 UNIV CALIF SAN FRANCISCO,DEPT PHARMACEUT CHEM,SAN FRANCISCO,CA 94143. NASA,AMES RES CTR,MOFFETT FIELD,CA 94035. NR 0 TC 0 Z9 0 U1 0 U2 1 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 SN 0065-7727 J9 ABSTR PAP AM CHEM S JI Abstr. Pap. Am. Chem. Soc. PD SEP 7 PY 1997 VL 214 BP 156 EP PHYS PN 2 PG 1 WC Chemistry, Multidisciplinary SC Chemistry GA XQ859 UT WOS:A1997XQ85900673 ER PT J AU Pohorille, A Chipot, C AF Pohorille, A Chipot, C TI Molecular dynamics of peptide folding at aqueous interfaces. SO ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY LA English DT Meeting Abstract C1 NASA,AMES RES CTR,MOFFETT FIELD,CA 94035. UNIV CALIF SAN FRANCISCO,DEPT PHARMACEUT CHEM,SAN FRANCISCO,CA 94143. NR 0 TC 0 Z9 0 U1 0 U2 0 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 SN 0065-7727 J9 ABSTR PAP AM CHEM S JI Abstr. Pap. Am. Chem. Soc. PD SEP 7 PY 1997 VL 214 BP 172 EP PHYS PN 2 PG 1 WC Chemistry, Multidisciplinary SC Chemistry GA XQ859 UT WOS:A1997XQ85900689 ER PT J AU Scott, LA Prabhakaran, R Bryant, RG Buchman, A AF Scott, LA Prabhakaran, R Bryant, RG Buchman, A TI Low-velocity wear resistance of LARC(TM)-SI and blends against titanium. SO ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY LA English DT Meeting Abstract C1 OLD DOMINION UNIV,DEPT MECH ENGN & MECH,NORFOLK,VA 23529. NASA,LANGLEY RES CTR,MS 226,HAMPTON,VA 23681. RAFAEL,DEPT 27,IL-31021 HAIFA,ISRAEL. NR 0 TC 0 Z9 0 U1 0 U2 0 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 SN 0065-7727 J9 ABSTR PAP AM CHEM S JI Abstr. Pap. Am. Chem. Soc. PD SEP 7 PY 1997 VL 214 BP 185 EP PMSE PN 2 PG 1 WC Chemistry, Multidisciplinary SC Chemistry GA XQ859 UT WOS:A1997XQ85901447 ER PT J AU Laszlo, B Friedl, RR Sander, SP AF Laszlo, B Friedl, RR Sander, SP TI Kinetics studies of the HO2+CLO reaction SO ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY LA English DT Meeting Abstract C1 CALTECH,JET PROP LAB,PASADENA,CA 91109. NR 0 TC 0 Z9 0 U1 0 U2 0 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 SN 0065-7727 J9 ABSTR PAP AM CHEM S JI Abstr. Pap. Am. Chem. Soc. PD SEP 7 PY 1997 VL 214 BP 198 EP PHYS PN 2 PG 1 WC Chemistry, Multidisciplinary SC Chemistry GA XQ859 UT WOS:A1997XQ85900715 ER PT J AU Nickolaisen, SL Sander, SP AF Nickolaisen, SL Sander, SP TI Temperature dependent kinetics of the CH3O2+Cl AND CH3O2+ClO reactions SO ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY LA English DT Meeting Abstract C1 CALTECH,JET PROP LAB,PASADENA,CA 91109. NR 0 TC 0 Z9 0 U1 1 U2 1 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 SN 0065-7727 J9 ABSTR PAP AM CHEM S JI Abstr. Pap. Am. Chem. Soc. PD SEP 7 PY 1997 VL 214 BP 200 EP PHYS PN 2 PG 1 WC Chemistry, Multidisciplinary SC Chemistry GA XQ859 UT WOS:A1997XQ85900717 ER PT J AU Han, J Jaffe, R AF Han, J Jaffe, R TI Identification of carbon nanoconic tips via quantum mechanical calculation SO ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY LA English DT Meeting Abstract C1 NASA,AMES RES CTR,MOFFETT FIELD,CA 94035. NR 0 TC 0 Z9 0 U1 0 U2 0 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 SN 0065-7727 J9 ABSTR PAP AM CHEM S JI Abstr. Pap. Am. Chem. Soc. PD SEP 7 PY 1997 VL 214 BP 217 EP COMP PN 1 PG 1 WC Chemistry, Multidisciplinary SC Chemistry GA XQ857 UT WOS:A1997XQ85701416 ER PT J AU Simpson, JO Ounaies, Z Young, JA AF Simpson, JO Ounaies, Z Young, JA TI Mechanisms of piezoelectricity in amorphous and semicrystalline polymers: An overview. SO ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY LA English DT Meeting Abstract C1 NASA,LANGLEY RES CTR,COMPOSITE & POLYMERS BRANCH,HAMPTON,VA 23681. UNIV VIRGINIA,DEPT MAT SCI & ENGN,CHARLOTTESVILLE,VA 22903. NASA,LANGLEY RES CTR,NATL RES COUNCIL,HAMPTON,VA 23681. NR 0 TC 0 Z9 0 U1 0 U2 0 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 SN 0065-7727 J9 ABSTR PAP AM CHEM S JI Abstr. Pap. Am. Chem. Soc. PD SEP 7 PY 1997 VL 214 BP 222 EP POLY PN 2 PG 1 WC Chemistry, Multidisciplinary SC Chemistry GA XQ859 UT WOS:A1997XQ85901151 ER PT J AU Beljonne, D Bredas, JL Cumpston, BH Ehrlich, J Erskine, L Heikal, AA Hu, ZY Kogej, T Lee, IYS Marder, SR Perry, JW Rockel, H Thayumanavan, S Wu, XL AF Beljonne, D Bredas, JL Cumpston, BH Ehrlich, J Erskine, L Heikal, AA Hu, ZY Kogej, T Lee, IYS Marder, SR Perry, JW Rockel, H Thayumanavan, S Wu, XL TI Design, synthesis, nonlinear spectroscopy and applications of two-photon absorbing molecules SO ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY LA English DT Meeting Abstract C1 UNIV MONS,CTR RES MOL ELECT & PHOTON,B-7000 MONS,BELGIUM. CALTECH,BECKMAN INST,MOL MAT RESOURCE CTR,PASADENA,CA 91125. CALTECH,JET PROP LAB,PASADENA,CA 91125. RI Bredas, Jean-Luc/A-3431-2008; Perry, Joseph/B-7191-2011 OI Bredas, Jean-Luc/0000-0001-7278-4471; Perry, Joseph/0000-0003-1101-7337 NR 0 TC 0 Z9 0 U1 0 U2 2 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 SN 0065-7727 J9 ABSTR PAP AM CHEM S JI Abstr. Pap. Am. Chem. Soc. PD SEP 7 PY 1997 VL 214 BP 228 EP POLY PN 2 PG 1 WC Chemistry, Multidisciplinary SC Chemistry GA XQ859 UT WOS:A1997XQ85901157 ER PT J AU Jethmalani, JM Sunkara, HB Ford, WT AF Jethmalani, JM Sunkara, HB Ford, WT TI Processing of monomer dispersions of colloidal silica. SO ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY LA English DT Meeting Abstract C1 CALTECH,DEPT CHEM & CHEM ENGN,PASADENA,CA 91125. NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,SPACE SCI LAB,HUNTSVILLE,AL 35812. OKLAHOMA STATE UNIV,DEPT CHEM,STILLWATER,OK 74078. NR 0 TC 0 Z9 0 U1 0 U2 0 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 SN 0065-7727 J9 ABSTR PAP AM CHEM S JI Abstr. Pap. Am. Chem. Soc. PD SEP 7 PY 1997 VL 214 BP 331 EP POLY PN 2 PG 1 WC Chemistry, Multidisciplinary SC Chemistry GA XQ859 UT WOS:A1997XQ85901260 ER PT J AU Krasnopolsky, VA Mumma, MJ Abbott, M Flynn, BC Meech, KJ Yeomans, BK Feldman, PD Cosmovici, CB AF Krasnopolsky, VA Mumma, MJ Abbott, M Flynn, BC Meech, KJ Yeomans, BK Feldman, PD Cosmovici, CB TI Detection of soft x-rays and a sensitive search for noble gases in comet Hale-Bopp (C/1995 O1) SO SCIENCE LA English DT Article ID ONE-ELECTRON CAPTURE; CROSS-SECTIONS; B2 HYAKUTAKE; P/HALLEY; COLLISIONS; IONS; EVOLUTION; HELIUM; SOLAR; EUVE AB An image of comet Hale-Bopp (C/1995 O1) in soft x-rays reveals a central emission offset from the nucleus, as well as an extended emission feature that does not correlate with the dust jets seen at optical wavelengths, Neon was found to be depleted in the cometary ice by more than a factor of 25 relative to solar abundance, which suggests that ices in Hale-Bopp formed at (or later experienced) temperatures higher than 25 kelvin, A helium line emission at a wavelength of 584 angstroms was detected and may be attributable to charge transfer of solar wind alpha particles in the cometary coma, Ionized oxygen and another helium line contribute to an emission observed at 538 angstroms. C1 NASA, GODDARD SPACE FLIGHT CTR, GREENBELT, MD 20771 USA. UNIV CALIF BERKELEY, CTR EXTREME ULTRAVIOLET ASTROPHYS, BERKELEY, CA 94720 USA. UNIV HAWAII, INST ASTRON, HONOLULU, HI 96822 USA. CALTECH, JET PROP LAB, PASADENA, CA 91109 USA. JOHNS HOPKINS UNIV, BALTIMORE, MD 21218 USA. CNR, IST FIS SPAZIO INTERPLANETARIO, I-00044 FRASCATI, ITALY. RP Krasnopolsky, VA (reprint author), CATHOLIC UNIV AMER, WASHINGTON, DC 20064 USA. RI mumma, michael/I-2764-2013; Krasnopolsky, Vladimir/L-5085-2013 NR 55 TC 88 Z9 88 U1 1 U2 2 PU AMER ASSOC ADVANCEMENT SCIENCE PI WASHINGTON PA 1200 NEW YORK AVE, NW, WASHINGTON, DC 20005 USA SN 0036-8075 J9 SCIENCE JI Science PD SEP 5 PY 1997 VL 277 IS 5331 BP 1488 EP 1491 DI 10.1126/science.277.5331.1488 PG 4 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA XV429 UT WOS:A1997XV42900035 PM 9278508 ER PT J AU Manchala, DW Palazzolo, AB Kascak, AF Montague, GT Brown, GV AF Manchala, DW Palazzolo, AB Kascak, AF Montague, GT Brown, GV TI Constrained quadratic programming, active control of rotating mass imbalance SO JOURNAL OF SOUND AND VIBRATION LA English DT Article AB Jet engines may experience severe vibration due to the sudden imbalance caused by blade failure. The current research investigates employment of piezoelectric actuators to suppress this using active vibration control. This requires identification of the source of the vibrations via an expert system, determination of the required phase angles and amplitudes for the correction forces, and application of the desired control signals to the piezoelectric actuators. Correction forces may exceed the physical limitations of the actuators; hence results of ''constrained force'' quadratic programming, least squares and multi-point correction algorithms will be compared. It is demonstrated that simply scaling down the least squares predicted correction forces to satisfy the actuator saturation constraints does not necessarily yield optimal reductions in vibration. In this paper test results are shown for sudden imbalance, and the computational time requirements and balancing effectiveness for the various approaches are compared. (C) 1997 Academic Press Limited. C1 TEXAS A&M UNIV,COLLEGE STN,TX 77843. USA,NASA LEWIS,CLEVELAND,OH 44135. NASA,LEWIS RES CTR,CLEVELAND,OH 44135. RP Manchala, DW (reprint author), XEROX CORP,EL SEGUNDO,CA 90245, USA. NR 26 TC 9 Z9 10 U1 0 U2 4 PU ACADEMIC PRESS LTD PI LONDON PA 24-28 OVAL RD, LONDON, ENGLAND NW1 7DX SN 0022-460X J9 J SOUND VIB JI J. Sound Vibr. PD SEP 4 PY 1997 VL 205 IS 5 BP 561 EP 580 DI 10.1006/jsvi.1996.1030 PG 20 WC Acoustics; Engineering, Mechanical; Mechanics SC Acoustics; Engineering; Mechanics GA XU849 UT WOS:A1997XU84900001 ER PT J AU Nadarajah, A Li, MR Pusey, ML AF Nadarajah, A Li, MR Pusey, ML TI Growth mechanism of the (110) face of tetragonal lysozyme crystals SO ACTA CRYSTALLOGRAPHICA SECTION D-BIOLOGICAL CRYSTALLOGRAPHY LA English DT Article ID ANGLE NEUTRON-SCATTERING; EGG-WHITE LYSOZYME; KINETICS; MICROSCOPY; CONSTANTS; RATES AB The measured macroscopic growth rates of the (110) face of tetragonal lysozyme show an unexpectedly complex dependence on the supersaturation. In earlier studies it has been shown that an aggregate growth unit could account for experimental growth-rate trends. In particular molecular packing and interactions in the growth of the crystal were favored by completion of the helices along the 4(3) axes. In this study the molecular orientations of the possible growth units and the molecular growth mechanism were identified. This indicated that growth was a two-step process: aggregate growth units corresponding to the 4(3) helix are first formed in the bulk solution by stronger intermolecular bonds and then attached to the crystal face by weaker bonds. A more comprehensive analysis of the measured (110) growth rates was also undertaken. They were compared with the predicted growth rates from several dislocation and two-dimensional nucleation growth models, employing tetramer and octamer growth units in polydisperse solutions and monomer units in monodisperse solutions. The calculations consistently showed that the measured growth rates followed the expected model relations with octamer growth units, in agreement with the predictions from the molecular level analyses. C1 UNIV ALABAMA,NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,BIOPHYS BRANCH ES76,HUNTSVILLE,AL 35899. NR 28 TC 38 Z9 41 U1 1 U2 1 PU MUNKSGAARD INT PUBL LTD PI COPENHAGEN PA 35 NORRE SOGADE, PO BOX 2148, DK-1016 COPENHAGEN, DENMARK SN 0907-4449 J9 ACTA CRYSTALLOGR D JI Acta Crystallogr. Sect. D-Biol. Crystallogr. PD SEP 1 PY 1997 VL 53 BP 524 EP 534 DI 10.1107/S0907444997003041 PN 5 PG 11 WC Biochemical Research Methods; Biochemistry & Molecular Biology; Biophysics; Crystallography SC Biochemistry & Molecular Biology; Biophysics; Crystallography GA XW631 UT WOS:A1997XW63100004 PM 15299882 ER PT J AU Wardell, MR Skinner, R Carter, DC Twigg, PD Abrahams, JP AF Wardell, MR Skinner, R Carter, DC Twigg, PD Abrahams, JP TI Improved diffraction of antithrombin crystals grown in microgravity SO ACTA CRYSTALLOGRAPHICA SECTION D-BIOLOGICAL CRYSTALLOGRAPHY LA English DT Article ID INTACT AB Crystals of antithrombin were grown both on earth and in microgravity aboard US Space Shuttle Flight STS-67. The quality of crystals grown in both environments was highly variable and many could not be indexed. The microgravity crystals, however, generally diffracted better, as demonstrated by a novel procedure that estimates the resolution of the Bragg scatter from single diffraction images, without requiring knowledge of the cell dimensions of the crystal. Whereas the best earth-grown crystals never diffracted beyond 3 Angstrom resolution, the best microgravity crystal diffracted to 2.6 Angstrom. The improvement, demonstrated here by a comparison of 23 microgravity and 12 earth-grown crystals, is attributed to better ordered crystal growth in microgravity, although other factors may have contributed also. C1 UNIV CAMBRIDGE,DEPT HAEMATOL,CAMBRIDGE CB2 2QH,ENGLAND. NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,STRUCT BIOL LAB,HUNTSVILLE,AL 35812. MRC,MOL BIOL LAB,CAMBRIDGE CB2 2QH,ENGLAND. RP Wardell, MR (reprint author), WASHINGTON UNIV,SCH MED,DEPT BIOCHEM & MOL BIOPHYS,CAMPUS BOX 8231,660 S EUCLID AVE,ST LOUIS,MO 63110, USA. RI Abrahams, Jan Pieter/G-7287-2016 OI Abrahams, Jan Pieter/0000-0001-8216-1868 NR 9 TC 20 Z9 20 U1 0 U2 0 PU MUNKSGAARD INT PUBL LTD PI COPENHAGEN PA 35 NORRE SOGADE, PO BOX 2148, DK-1016 COPENHAGEN, DENMARK SN 0907-4449 J9 ACTA CRYSTALLOGR D JI Acta Crystallogr. Sect. D-Biol. Crystallogr. PD SEP 1 PY 1997 VL 53 BP 622 EP 625 DI 10.1107/S0907444997003302 PN 5 PG 4 WC Biochemical Research Methods; Biochemistry & Molecular Biology; Biophysics; Crystallography SC Biochemistry & Molecular Biology; Biophysics; Crystallography GA XW631 UT WOS:A1997XW63100020 PM 11541739 ER PT J AU Ford, K Glymour, C Hayes, P AF Ford, K Glymour, C Hayes, P TI On the other hand ... Cognitive prostheses SO AI MAGAZINE LA English DT Editorial Material C1 UNIV CALIF SAN DIEGO,LA JOLLA,CA 92093. CARNEGIE MELLON UNIV,PITTSBURGH,PA 15213. UNIV W FLORIDA,INST HUMAN & MACHINE COGNIT,PENSACOLA,FL 32514. RP Ford, K (reprint author), NASA,AMES RES CTR,MOFFETT FIELD,CA 94035, USA. NR 0 TC 7 Z9 7 U1 0 U2 0 PU AMER ASSOC ARTIFICIAL INTELL PI MENLO PK PA 445 BURGESS DRIVE, MENLO PK, CA 94025-3496 SN 0738-4602 J9 AI MAG JI AI Mag. PD FAL PY 1997 VL 18 IS 3 BP 104 EP 104 PG 1 WC Computer Science, Artificial Intelligence SC Computer Science GA YA211 UT WOS:A1997YA21100011 ER PT J AU Kao, KH Liou, MS AF Kao, KH Liou, MS TI Application of chimera/unstructured hybrid grids for conjugate heat transfer SO AIAA JOURNAL LA English DT Article AB A method is presented that computes the conjugate heat transfer problem using a hybrid overset grid system. The hybrid grids for the fluid and solid structure regions use Chimera overset structured grids and unstructured grids, respectively. The numerical analyses require the flowfield solution and material thermal response to be obtained simultaneously. A continuous transfer of temperature and heat flux is enforced at the interface, which combines the solid structure and the fluid dow regions into an integral system. Numerical results are compared with analytical and experimental data for a flat plate and a C3X cooled turbine cascade. A simplified drum-disk system is also simulated to show the effectiveness of this hybrid grid system. C1 NASA,LEWIS RES CTR,TURBOMACHINERY & PROP SYST DIV,CLEVELAND,OH 44135. RP Kao, KH (reprint author), NASA,LEWIS RES CTR,INST COMPUTAT MECH PROP,MS 5-11,21000 BROOKPK RD,CLEVELAND,OH 44135, USA. NR 23 TC 23 Z9 24 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 SEP PY 1997 VL 35 IS 9 BP 1472 EP 1478 DI 10.2514/2.270 PG 7 WC Engineering, Aerospace SC Engineering GA XU227 UT WOS:A1997XU22700005 ER PT J AU Holst, TL AF Holst, TL TI Numerical solution of the full potential equation using a chimera grid approach SO AIAA JOURNAL LA English DT Article RP Holst, TL (reprint author), NASA,AMES RES CTR,ADV COMPUTAT METHODS BRANCH,MOFFETT FIELD,CA 94035, USA. NR 5 TC 0 Z9 0 U1 0 U2 0 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 SN 0001-1452 J9 AIAA J JI AIAA J. PD SEP PY 1997 VL 35 IS 9 BP 1543 EP 1545 DI 10.2514/2.7483 PG 3 WC Engineering, Aerospace SC Engineering GA XU227 UT WOS:A1997XU22700016 ER PT J AU Howard, SK Smith, BE Gaba, DM Rosekind, MR AF Howard, SK Smith, BE Gaba, DM Rosekind, MR TI Performance of well-rested vs. highly-fatigued residents: A simulator study SO ANESTHESIOLOGY LA English DT Meeting Abstract C1 NASA,AMES RES CTR,PALO ALTO,CA 94304. STANFORD UNIV,VA PALO ALTO,IICS,ANESTHESIA SERV,PALO ALTO,CA 94304. NR 5 TC 4 Z9 5 U1 0 U2 1 PU LIPPINCOTT-RAVEN PUBL PI PHILADELPHIA PA 227 EAST WASHINGTON SQ, PHILADELPHIA, PA 19106 SN 0003-3022 J9 ANESTHESIOLOGY JI Anesthesiology PD SEP PY 1997 VL 87 IS 3 SU S BP A981 EP A981 DI 10.1097/00000542-199709001-00981 PG 1 WC Anesthesiology SC Anesthesiology GA XV636 UT WOS:A1997XV63600981 ER PT J AU Veres, JP Golding, LAR Smith, WA Horvath, D Medvedev, A AF Veres, JP Golding, LAR Smith, WA Horvath, D Medvedev, A TI Flow analysis of the Cleveland Clinic centrifugal pump SO ASAIO JOURNAL LA English DT Article AB An implantable ventricular assist blood pump is being developed by the Cleveland Clinic Foundation in cooperation with the NASA Lewis Research Center. At the nominal design condition, the pump provides blood flow at the rate of 5 L/min at a pressure rise of 100 mmHg and a rotation speed of 3000 RPM. Bench testing of the centrifugal pump in a water/glycerin mixture has provided flow and pressure data at several rotative speeds. A one-dimensional empirically based pump flow analysis computer code developed at NASA Lewis Research Center has been used in the design process to simulate the flow in the primary radial pump stage. The computer model was used to size key impeller and volute geometric parameters that influence pressure rise and flow. Input requirements to the computer model include a simple representation of the pump geometry. The model estimates the flow conditions under design and off-design operating conditions at the impeller leading and trailing edges, and the volute inlet and exit. Output from the computer model is compared to flow and pressure data obtained from bench testing. C1 CLEVELAND CLIN FDN,DEPT BIOMED ENGN,CLEVELAND,OH 44195. RP Veres, JP (reprint author), NASA,LEWIS RES CTR,COMPUTING & INTERDISCIPLINARY SYST OFF,21000 BROOKPARK RD,MS 142-4,CLEVELAND,OH 44135, USA. FU NHLBI NIH HHS [NHLBI-HV-94-25] NR 7 TC 5 Z9 5 U1 0 U2 0 PU LIPPINCOTT-RAVEN PUBL PI PHILADELPHIA PA 227 EAST WASHINGTON SQ, PHILADELPHIA, PA 19106 SN 1058-2916 J9 ASAIO J JI Asaio J. PD SEP-OCT PY 1997 VL 43 IS 5 BP M778 EP M781 PG 4 WC Engineering, Biomedical; Transplantation SC Engineering; Transplantation GA YD658 UT WOS:A1997YD65800090 PM 9360152 ER PT J AU Kogut, A AF Kogut, A TI Spatial correlation between H alpha emission and infrared cirrus SO ASTRONOMICAL JOURNAL LA English DT Article ID MICROWAVE EMISSION; COBE; RADIATION AB Cross-correlation of the DIRBE 100 mu u-m survey with previously published H alpha maps tests correlations between far-infrared dust and the warm ionized interstellar medium in different regions of the sky. A 10 degrees X 12 degrees patch at Galactic latitude b=-21 degrees shows a correlation slope a(0)=0.85+/-0.44 Rayleighs MJy(-1) sr significant at 97% confidence. A set of H alpha images over the north celestial polar cap yields a weaker correlation slope a(0)=0.34+/-0.33 Rayleighs MJy(-1) sr. Combined with observations from microwave anisotropy experiments, the data show roughly similar correlations on angular scales 0.degrees 7 to 90 degrees. Microwave experiments may observe more emission per unit dust emission than are traced by the same structures observed in H alpha. (C) 1997 American Astronomical Society. RP Kogut, A (reprint author), NASA,GODDARD SPACE FLIGHT CTR,ASTRON & SOLAR PHYS LAB,HUGHES STX CORP,CODE 685,GREENBELT,MD 20771, USA. RI Kogut, Alan/D-6293-2012 NR 16 TC 17 Z9 17 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 SEP PY 1997 VL 114 IS 3 BP 1127 EP 1131 DI 10.1086/118543 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XU632 UT WOS:A1997XU63200023 ER PT J AU Cheng, FH Sion, EM Horne, K Hubeny, I Huang, M Vrtilek, SD AF Cheng, FH Sion, EM Horne, K Hubeny, I Huang, M Vrtilek, SD TI HST synthetic spectral analysis of U Gem in early and late quiescence: A heated white dwarf and accretion belt SO ASTRONOMICAL JOURNAL LA English DT Article ID HOPKINS-ULTRAVIOLET-TELESCOPE; HUBBLE-SPACE-TELESCOPE; NOVA VW HYDRI; GEMINORUM; SUPEROUTBURST; ATMOSPHERES; OUTBURSTS AB We have re-examined two archival HST FOS G130H spectra of the prototype dwarf nova U Geminorum obtained during its quiescence 13 days and 70 days after a wide outburst. Using synthetic spectral fitting with two flux-emitting components, a slowly rotating white dwarf photosphere, and a rapidly spinning accretion belt(V-rot sin i=3200 km s(-1)) significantly improves the spectral fit but does not provide a unique solution. We found clear evidence for the cooling of the white dwarf, confirming earlier results, and evidence for the cooling of the accretion belt or gas in Keplerian motion as well. If an accretion belt is really present, then for the white dwarf and belt, respectively, 13 days post-outburst, we find T-wd=37 000+/-400 K and T-belt=45 000+/-2500 K, while at 70 days post outburst, we find T-wd=33 500+/-700 K and T-belt=37 500+/-4000 K. These results are compared with our HST GHRS G160M observations obtained 13 days and 61 days after a narrow outburst of U Gem. (C) 1997 American Astronomical Society. C1 VILLANOVA UNIV,VILLANOVA,PA 19085. UNIV ST ANDREWS,SCH PHYS & ASTRON,ST ANDREWS KY16 9SS,FIFE,SCOTLAND. HARVARD SMITHSONIAN CTR ASTROPHYS,CAMBRIDGE,MA 02138. NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. NR 23 TC 14 Z9 14 U1 0 U2 1 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 SEP PY 1997 VL 114 IS 3 BP 1165 EP 1169 DI 10.1086/118547 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XU632 UT WOS:A1997XU63200027 ER PT J AU BohmVitense, E Evans, NR Carpenter, K Morgan, S BeckWinchatz, B Robinson, R AF BohmVitense, E Evans, NR Carpenter, K Morgan, S BeckWinchatz, B Robinson, R TI The dynamical mass of the beat Cepheid Y Carinae and stellar opacities SO ASTRONOMICAL JOURNAL LA English DT Article ID STARS; LUMINOSITY; MODELS; TABLES; RADII; ORBIT; SCALE AB The beat Cepheid, Y Carinae A, has a B9 V companion, Y Car B, The primary period P-0 of the Cepheid is 3.64 days and the secondary, P-1, is 2.56 days. Its period ratio P-1/P-0 is thus 0.703. Y Car is the only beat Cepheid known to be a binary and thus offers us the unique opportunity to determine the dynamical mass for a beat Cepheid. We have determined its mass by measuring the orbital velocity amplitude of the hot companion Y Car B using the Goddard High-Resolution Spectrograph (GHRS) with the G200M grating on the Hobble Space Telescope. When combined with the ground-based orbital velocity amplitude of the Cepheid and the mass of the companion, the implied mass of the Cephieid is M=3.8+/-1.2 M.. With the Cepheid luminosity given by the period-luminosity relation, this mass, taken at face value, indicates excess mixing in the main sequence progenitor corresponding to convective overshoot by about 0.9 pressure scale height, however, the large error bars prevent a firm conclusion. As shown by Simon the period ratio for beat Cepheids depends sensitively on the opacities. For models calculated with Cox-Tabor opacities the period ratios for beat Cepheids indicate masses between one and two M.. Models calculated with the new Livermore OPAL opacities on the ether hand indicate masses around 4 solar masses. The good agreement of the beat mass with the dynamical mass, determined here for Y Car, provides a confirmation that the OPAL opacities are a significant improvement over the Cox-Tabor (1976) opacities. (C) 1997 American Astronomical Society. C1 HARVARD SMITHSONIAN CTR ASTROPHYS,CAMBRIDGE,MA 02138. NASA,GODDARD SPACE FLIGHT CTR,CODE 681,GREENBELT,MD 20771. UNIV NO IOWA,CEDAR FALLS,IA 50614. NASA,GODDARD SPACE FLIGHT CTR,COMP SCI CORP,GREENBELT,MD 20771. RP BohmVitense, E (reprint author), UNIV WASHINGTON,DEPT ASTRON,BOX 351580,SEATTLE,WA 98195, USA. RI Carpenter, Kenneth/D-4740-2012 NR 38 TC 6 Z9 6 U1 0 U2 0 PU AMER INST PHYSICS PI WOODBURY PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 SN 0004-6256 J9 ASTRON J JI Astron. J. PD SEP PY 1997 VL 114 IS 3 BP 1176 EP 1182 DI 10.1086/118549 PG 7 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XU632 UT WOS:A1997XU63200029 ER PT J AU Tegler, SC Romanishin, W Stone, A Tryka, K Fink, U Fevig, R AF Tegler, SC Romanishin, W Stone, A Tryka, K Fink, U Fevig, R TI Photometry of the Trans-Neptunian Object 1993 SC SO ASTRONOMICAL JOURNAL LA English DT Article ID KUIPER AB We obtained broadband photometry of the Trans-Neptunian Object 1993 SC with the Steward Observatory 1.5-m telescope near Mt. Bigelow, Arizona and the Lunar and Planetary Laboratory CCD on 1996 October 8. 1993 SC exhibited a constant brightness (V=22.67) with a la scatter about the average of 0.06 magnitudes during a five hour interval. In addition, we obtained observations of 1993 SC with the Steward Observatory 2.3-m telescope on Kitt Peak, Arizona during 1995 November 24-27. Once again 1993 SC exhibited a constant brightness (V=22.73) with a 1 sigma scatter about the average of 0.03 magnitude. If 1993 SC has a lightcurve, the amplitude must be at the level of 0.12 magnitude or less. If the obliquity of 1993 SC is near zero degrees, then 1993 SC is spherical with a semi-major to semi-minor axis ratio less than or equal to 1.12. A spherical nature for 1993 SC may be the result of self-gravity exceeding the tensile strength of the material in the interior of 1993 SC. If the obliquity of 1993 SC is large, then 1993 SC could have an irregular shape. The steady intrinsic brightness for 1993 SC suggests that the object has a relatively uniform surface albedo. Our photometry and the assumption of a comet-like albedo (0.04) indicates that the diameter of 1993 SC is similar to 240 km. (C) 1997 American Astronomical Society. C1 UNIV OKLAHOMA,DEPT PHYS & ASTRON,NORMAN,OK 73019. NO ARIZONA UNIV,NASA,SPACEGRANT PROGRAM,FLAGSTAFF,AZ 86011. UNIV ARIZONA,LUNAR & PLANETARY LAB,TUCSON,AZ 85721. RP Tegler, SC (reprint author), NO ARIZONA UNIV,DEPT PHYS & ASTRON,FLAGSTAFF,AZ 86011, USA. OI Tryka, Kimberly/0000-0002-5399-4235 NR 10 TC 13 Z9 13 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 SEP PY 1997 VL 114 IS 3 BP 1230 EP 1233 DI 10.1086/118556 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XU632 UT WOS:A1997XU63200036 ER PT J AU Mottola, S Erikson, A Harris, AW Hahn, G Neukum, G Buie, MW Sears, WD Harris, AW Tholen, DJ Whiteley, RJ Magnusson, P Piironen, J Kwiatkowski, T Borczyk, W Howell, ES Hicks, MD Fevig, R Krugly, YN Velichko, FP Chiorny, VG Gaftonyuk, NM DiMartino, M Pravec, P Sarounova, L Wolf, M Worman, W Davies, JK Schober, HJ Pych, W AF Mottola, S Erikson, A Harris, AW Hahn, G Neukum, G Buie, MW Sears, WD Harris, AW Tholen, DJ Whiteley, RJ Magnusson, P Piironen, J Kwiatkowski, T Borczyk, W Howell, ES Hicks, MD Fevig, R Krugly, YN Velichko, FP Chiorny, VG Gaftonyuk, NM DiMartino, M Pravec, P Sarounova, L Wolf, M Worman, W Davies, JK Schober, HJ Pych, W TI Physical model of near-Earth asteroid 6489 Golevka (1991 JX) from optical and infrared observations SO ASTRONOMICAL JOURNAL LA English DT Article ID BIDIRECTIONAL REFLECTANCE SPECTROSCOPY; MAIN-BELT ASTEROIDS; PHOTOMETRIC GEODESY; 1620-GEOGRAPHOS; LIGHTCURVES; ROTATION; PERIODS; SHAPES; POLES AB In 1995 asteroid 6489 Golevka (1991 JX) had a close encounter with the Earth at a distance of 0.034 AU, providing a good opportunity for a detailed study of a small Solar System object. In this paper we report the results of an extensive international observing campaign aimed at determining Golevka's rotational and physical properties from optical photometry and thermal IR radiometry. From the analysis of photometric light curves we derive a spin axis model whose coordinates are lambda(p) (J2000)=347 degrees+/-10 degrees and beta(p) (J2000)=35 degrees+/-10 degrees. The strict periodicity observed in light curves taken during virtually constant illumination and observing conditions argues against free precession of the spin vector. The rotation is prograde with a sidereal period P-sid=0.25110+/-0.00001 d (6.02640+/-0.00024 hr). The derived ellipsoidal shape model results in a/b=1.4+/-0.2, while not satisfactorily constraining the b/c ratio. No systematic V-R color index variation larger than 0.005 mag (1 sigma) was observed, suggesting a spectrally uniform surface on a hemispheric scale. The integral phase curve is moderately well represented by the H-G parameter system that fails, however, to reproduce the observed opposition spike. We derive mean H, G values of 19.074 +/-0.029 and 0.138+/-0.013, respectively. The application of the more accurate Hapke photometric function produces a better fit and allows us to describe the surface scattering properties in terms of model parameters: <(theta)over bar>=7 degrees+/-7 degrees, g=-0.435+/-0.001, <(omega)over bar>(0)=0.58+/-0.03, h=0.0114+/-0.0004, B-0=0.758+/-0.014. Infrared measurements reveal that the flux at 10.6 mu m is unusually small in view of the object's optical brightness. The combined application of a modified Fast Rotating Thermal Model and of the photometric model suggests that Golevka is a small body with approximate dimensions (0.35x0.25X0.25 Inn) and a very high geometric albedo p(v) similar to 0.6. However, the possible effect of model assumptions on these latter results still has to be explored. (C) 1997 American Astronomical Society. C1 LOWELL OBSERV,FLAGSTAFF,AZ 86001. CALTECH,JET PROP LAB,PASADENA,CA 91109. UNIV HAWAII,INST ASTRON,HONOLULU,HI 96822. ASTRON OBSERV,S-75220 UPPSALA,SWEDEN. ADAM MICKIEWICZ UNIV POZNAN,ASTRON OBSERV,PL-60286 POZNAN,POLAND. UNIV ARIZONA,LUNAR & PLANETARY LAB,TUCSON,AZ 85721. KHARKIV STATE UNIV,ASTRON OBSERV,UA-31022 KHARKOV,UKRAINE. ASTRON OBSERV,UA-334242 SIMEIS,UKRAINE. OSSERV ASTRON TORINO,I-10025 PINO TORINESE,ITALY. ACAD SCI CZECH REPUBL,INST ASTRON,CZ-25165 ONDREJOV,CZECH REPUBLIC. CHARLES UNIV,ASTRON INST,CZ-15000 PRAGUE,CZECH REPUBLIC. MOORHEAD STATE UNIV,DEPT PHYS & ASTRON,MOORHEAD,MN 56563. JOINT ASTRON CTR,HILO,HI 96720. INST ASTRON,A-8010 GRAZ,AUSTRIA. UNIV WARSAW,ASTRON OBSERV,PL-00478 WARSAW,POLAND. RP Mottola, S (reprint author), DLR,INST PLANETARY EXPLORAT,D-12489 BERLIN,GERMANY. RI Pravec, Petr/G-9037-2014 NR 33 TC 26 Z9 26 U1 0 U2 2 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 SEP PY 1997 VL 114 IS 3 BP 1234 EP 1245 DI 10.1086/118557 PG 12 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XU632 UT WOS:A1997XU63200037 ER PT J AU desEtangs, AL Deleuil, M VidalMadjar, A LagrangeHenri, AM Backman, D Lissauer, JJ Ferlet, R Beust, H Mouillet, D AF desEtangs, AL Deleuil, M VidalMadjar, A LagrangeHenri, AM Backman, D Lissauer, JJ Ferlet, R Beust, H Mouillet, D TI HST-GHRS observations of candidate beta Pictoris-like circumstellar gaseous disks SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE stars: circumstellar matter, planetary systems; stars: beta Pictoris; line: formation; ISM: clouds ID STARS; DUST; BODIES; SEARCH; COMETS; RATIO; HR-10; SHELL; LINE; GAS AB We present HST-GHRS observations of four stars in search of beta Pictoris-like circumstellar gaseous disks. We detected gas around HR 10, HR 2174 and 51 Oph at large distances from the stars; this gas is circumstellar since the absorption lines from very excited levels require densities incompatible with those found in the diffuse interstellar medium. The shape of the lines and the Mg II doubler ratio give evidence that clumpy gas is continuously falling onto these stars. Possible interpretations are discussed. C1 CNRS, ASTRON SPATIALE LAB, F-13376 MARSEILLE 12, FRANCE. CERMO, GRP ASTROPHYS GRENOBLE, F-38041 GRENOBLE, FRANCE. FRANKLIN & MARSHALL COLL, DEPT PHYS & ASTRON, LANCASTER, PA 17604 USA. SUNY STONY BROOK, DEPT EARTH & SPACE SCI, ASTRON PROGRAM, STONY BROOK, NY 11794 USA. NASA, AMES RES CTR, DIV SPACE SCI, MOFFETT FIELD, CA 94035 USA. RP desEtangs, AL (reprint author), INST ASTROPHYS, CNRS, 98 BIS BLVD ARAGO, F-75014 PARIS, FRANCE. NR 38 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 SEP PY 1997 VL 325 IS 1 BP 228 EP 236 PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XV265 UT WOS:A1997XV26500027 ER PT J AU Goodman, ML AF Goodman, ML TI Convection driven heating of the solar middle chromosphere by resistive dissipation of large scale electric currents .2. SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE Sun: chromosphere; Sun: magnetic fields; Sun: atmosphere; magnetic fields: plasmas ID SUNS CHROMOSPHERE; BRIGHT POINTS; K-GRAINS; OSCILLATIONS; NETWORK; ATMOSPHERE; DYNAMICS; FIELDS; WAVES AB A generalization of a recently developed MHD model of a proposed heating mechanism for the middle chromosphere is presented. The generalization consists of including the ideal gas equation of state, allowing the temperature to vary with position, and allowing the hydrogen flow velocity to vary with height in a specified manner. These generalizations allow for a self consistent calculation of a temperature profile. The variation of the flow velocity with height generates a component of the inertial force which adds to the vertical gradient of the thermal pressure in supporting the plasma against gravity. This allows for a lower temperature for a given number density. The solutions presented suggest that resistively heated magnetic loops embedded in a much stronger, larger scale potential field, and having horizontal spatial scales of several thousand kilometers provide the thermal energy necessary to heat the middle chromosphere on these spatial scales. For these solutions the temperature is in the range of 6000 - 8700 K, consistent with the temperature range in the middle chromosphere. The magnetic loops have one footpoint region where the field is strongest and directed mainly upward, and where the heating rates per unit mass and volume are small. The field lines extend upward from this region at the base of the middle chromosphere, diverge horizontally, and return to a footpoint region at the base of the middle chromosphere as a weaker, more diffuse, mainly downward directed field. In this footpoint region the heating rates are also small. The heating rates are largest in the middle of the loops. For the magnetic loops considered, the temperature shows little horizontal variation between the footpoint region where the field is strongest and the heating rates are small, and the region where the heating rates are largest. This suggests that large horizontal variations in the net radiative loss from heated magnetic loops may not always be associated with large horizontal variations in temperature. RP NASA, GODDARD SPACE FLIGHT CTR, COMP SCI CORP, CODE 695, GREENBELT, MD 20771 USA. NR 35 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 1432-0746 J9 ASTRON ASTROPHYS JI Astron. Astrophys. PD SEP PY 1997 VL 325 IS 1 BP 341 EP 351 PG 11 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XV265 UT WOS:A1997XV26500039 ER PT J AU Venturi, T Pearson, TJ Barthel, PD Unwin, SC AF Venturi, T Pearson, TJ Barthel, PD Unwin, SC TI The parsec-scale evolution of the superluminal quasar 1642+690 SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE galaxies: active; quasars: general; radio continuum: galaxies; quasars: Q1642+690 ID DOMINATED RADIO-SOURCES; COMPLETE SAMPLE; JET; 3C-345; VLBI AB We present the results of a 6 cm VLBI monitoring program of the core dominated, radio loud quasar 1642+690. 3.6 cm VLBI observations are also presented. The 6 cm observations, carried out in 1986.4, 1988.2, 1992.2 and 1994.7 confirm that the source is variable, both in morphology and in flux density, its changes reflecting a complicated evolution. We propose a few evolutionary scenarios, and favour the interpretation of the superluminal character of 1642+690, with a flow of superluminal components ejected from the core at a very similar high apparent speed, beta(app) similar to 9, in agreement with the first claim of superluminal motion in this source. C1 CALTECH, PASADENA, CA 91125 USA. KAPTEYN ASTRON INST, NL-9700 AV GRONINGEN, NETHERLANDS. CALTECH, JET PROP LAB, PASADENA, CA 91109 USA. RP Venturi, T (reprint author), CNR, IST RADIOASTRON, VIA GOBETTI 101, I-40129 BOLOGNA, ITALY. RI Pearson, Timothy/N-2376-2015; OI Pearson, Timothy/0000-0001-5213-6231; Venturi, Tiziana/0000-0002-8476-6307 NR 21 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 0004-6361 J9 ASTRON ASTROPHYS JI Astron. Astrophys. PD SEP PY 1997 VL 325 IS 2 BP 484 EP 492 PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XX190 UT WOS:A1997XX19000009 ER PT J AU Ortolani, A Maggio, A Pallavicini, R Sciortino, S Drake, JJ Drake, SA AF Ortolani, A Maggio, A Pallavicini, R Sciortino, S Drake, JJ Drake, SA TI The X-ray coronal emission of lambda Andromedae observed with ASCA and ROSAT SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE stars: coronae; stars: late-type; stars: abundances; stars: individual: lambda And; X-rays: stars ID CHROMOSPHERICALLY ACTIVE STARS; RS-CANUM-VENATICORUM; COOL STARS; EXTREME-ULTRAVIOLET; EUV SPECTROSCOPY; AR LACERTAE; BINARIES; SPECTRA; DEFICIENCY; ABSORPTION AB We present an observation of the long-period RS CVn binary lambda And obtained with ASCA. We also discuss a previous observation by ROSAT of the same star, that we have retrieved from the public archive. There was little variation in the quiescent X-ray flux of lambda And between these two observations almost 5 years apart, but they offer different, and in part complementary, views of its corona. The ASCA spectra of lambda And are well described by a 2-T model with a main component at T-1 similar or equal to 0.9 keV and a smaller component at T-2 similar or equal to 3 keV, with EM2/EM1 similar or equal to 0.15. The fitted coronal metallicity is Z similar or equal to 0.1, much lower than solar but consistent within a factor of 2 with the reported photospheric metallicity Z(phot) similar or equal to 0.2 On the contrary, a successful 2-T fit of the ROSAT spectrum yields a cool component at similar or equal to 0.5 keV and a hotter component at similar or equal to 1.4 keV, with EM2/EM1 similar or equal to 2 and Z similar or equal to 0.25. Because of these differences, we were unable to find an acceptable fit to the joint ASCA and ROSAT data. We discuss possible causes for the discrepancy, including spectral time variability, uncertainties in the plasma emission codes and in the instrumental calibration, and limitations in the adopted fitting model. The hydrogen column density toward lambda And, well constrained by ROSAT, is N-H similar or equal to 1 x 10(19) cm(-2), a factor similar to 2 larger than estimated from UV observations from Copernicus and the Hubble Space Telescope. Albeit small, this difference may indicate the presence of substantial ionization of the interstellar medium. C1 OSSERV ASTRON PALERMO, I-90134 PALERMO, ITALY. OSSERV ASTROFIS ARCETRI, I-50125 FLORENCE, ITALY. CTR ASTROPHYS, CAMBRIDGE, MA 02138 USA. NASA, GODDARD SPACE FLIGHT CTR, GREENBELT, MD 20771 USA. RI Maggio, Antonio/P-5700-2015 OI Maggio, Antonio/0000-0001-5154-6108 NR 67 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 SEP PY 1997 VL 325 IS 2 BP 664 EP 676 PG 13 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XX190 UT WOS:A1997XX19000030 ER PT J AU Kniffen, DA Alberts, WCK Bertsch, DL Dingus, BL Esposito, JA Fichtel, CE Foster, RS Hartman, RC Hunter, SD Kanbach, G Lin, YC Mattox, JR MayerHasselwander, HA Michelson, PF vonMontigny, C Mukherjee, R Nolan, PL Paredes, JM Ray, PS Schneid, EJ Sreekumar, P Tavani, M Thompson, DJ AF Kniffen, DA Alberts, WCK Bertsch, DL Dingus, BL Esposito, JA Fichtel, CE Foster, RS Hartman, RC Hunter, SD Kanbach, G Lin, YC Mattox, JR MayerHasselwander, HA Michelson, PF vonMontigny, C Mukherjee, R Nolan, PL Paredes, JM Ray, PS Schneid, EJ Sreekumar, P Tavani, M Thompson, DJ TI EGRET observations of the gamma-ray source 2CG 135+01 SO ASTROPHYSICAL JOURNAL LA English DT Article DE gamma rays, observations ID LSI +61-DEGREES-303; COS-B; PULSAR AB The COS B source 2CG 135+01 has been observed by the EGRET instrument on 10 different occasions during the first similar to 52 months of the Compton Gamma Ray Observatory mission. The source is detected in all but one of the observations. For that one, the exposure was inadequate. The only likely source that is spatially coincident with the gamma-ray position is the radio source GT 0236+610/LS I +61.303 degrees. However, there is no compelling evidence for time variations in the gamma-ray emission associated with the radio outbursts from GT 0236+610. Spectral determinations on a timescale of a few days also give no strong evidence for a spectral variation associated with the radio emission of GT 0236+610. Such fluctuations might be expected based on models involving a compact object in an elliptical binary orbit about a massive star. The search for correlations simultaneous with the 8.4 GHz radio outbursts were supported by coordinated observations with the Madrid Deep Space Network during one of the exposures and by Green Bank Interferometer observations on two others. Although there is some possible variability in the gamma-ray flux, it is not clear that it is related to the radio phasing. C1 NASA, GODDARD SPACE FLIGHT CTR, UNIV SPACE RES ASSOC, GREENBELT, MD 20771 USA. USN, RES LAB, WASHINGTON, DC 20375 USA. MAX PLANCK INST EXTRATERR PHYS, D-85748 GARCHING, GERMANY. STANFORD UNIV, WW HANSEN EXPT PHYS LAB, STANFORD, CA 94305 USA. BOSTON UNIV, DEPT ASTRON, BOSTON, MA 02215 USA. UNIV BARCELONA, DEPT ASTRON & METEOROL, E-08028 BARCELONA, SPAIN. NRL, WASHINGTON, DC 20375 USA. NORTHROP GRUMMAN CORP, BETHPAGE, NY 11714 USA. COLUMBIA UNIV, COLUMBIA ASTROPHYS LAB, NEW YORK, NY 10027 USA. RP Kniffen, DA (reprint author), HAMPDEN SYDNEY COLL, DEPT PHYS & ASTRON, HAMPDEN SYDNEY, VA 23943 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; Tavani, Marco/0000-0003-2893-1459; Paredes, Josep M./0000-0002-1566-9044; Ray, Paul/0000-0002-5297-5278 NR 31 TC 91 Z9 91 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 SEP 1 PY 1997 VL 486 IS 1 BP 126 EP 131 DI 10.1086/304490 PN 1 PG 6 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XT968 UT WOS:A1997XT96800013 ER PT J AU Yi, SY Demarque, P Oemler, A AF Yi, SY Demarque, P Oemler, A TI On the origin of the UV upturn in elliptical galaxies .1. Sensitivity of UV population synthesis to various input parameters SO ASTROPHYSICAL JOURNAL LA English DT Review DE galaxies, abundances; galaxies, elliptical and lenticular, cD; galaxies, evolution; galaxies, stellar content; stars, evolution; stars, interiors; ultraviolet, galaxies ID HORIZONTAL-BRANCH STARS; GALACTIC GLOBULAR-CLUSTERS; LIVERMORE OPAL OPACITIES; EXTENDED GIANT BRANCHES; INITIAL MASS FUNCTION; RR LYRAE STARS; SPECTRAL-SYNTHESIS; RED GIANTS; SPECTROPHOTOMETRIC ATLAS; EVOLUTIONARY SEQUENCES AB We present models of the late stages of stellar evolution intended to explain the ''UV upturn'' phenomenon in elliptical galaxies. Such models are sensitive to values of a number of poorly constrained physical parameters, including metallicity, age, stellar mass loss, helium enrichment, and the distribution of stars on the zero-age horizontal branch (HE). We explore the sensitivity of the results to values of these parameters and reach the following conclusions. Old, metal-rich galaxies, such as giant ellipticals, naturally develop a UV upturn within a reasonable timescale-less than a Hubble time-without the presence of young stars. The most likely stars to dominate the UV flux of such populations are low-mass, core helium-burning (HE and evolved HE) stars. Metal-poor populations produce a higher ratio of UV-to-V flux, owing to opacity effects, but only metal-rich stars develop a UV upturn, in which the flux increases toward shorter UV wavelengths. C1 NASA, GODDARD SPACE FLIGHT CTR, GREENBELT, MD 20771 USA. CARNEGIE INST WASHINGTON OBSERV, PASADENA, CA 91101 USA. RP Yi, SY (reprint author), YALE UNIV, DEPT ASTRON, POB 208101, NEW HAVEN, CT 06520 USA. NR 104 TC 95 Z9 96 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 SEP 1 PY 1997 VL 486 IS 1 BP 201 EP 229 DI 10.1086/304498 PN 1 PG 29 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XT968 UT WOS:A1997XT96800020 ER PT J AU Bergin, EA Langer, WD AF Bergin, EA Langer, WD TI Chemical evolution in preprotostellar and protostellar cores SO ASTROPHYSICAL JOURNAL LA English DT Article DE ISM, molecules; molecular processes; stars, formation; stars, pre-main-sequence ID NEUTRAL-NEUTRAL REACTIONS; DENSE INTERSTELLAR CLOUDS; INTER-STELLAR CLOUDS; MOLECULAR CLOUDS; THERMAL BALANCE; STAR-FORMATION; CHEMISTRY; MODELS; PROTOSTARS; GRAINS AB The chemistry of developing and collapsing low-mass protostellar cores is followed using a chemical code with a time-varying density. Two evolutionary scenarios are represented, gravitational collapse in the presence of magnetic fields and the slow core growth by accretion near equilibrium. The chemical code includes gas-phase reactions and depletion onto grains with both CO and H2O ice mantles. We find that various species will selectively deplete from the gas phase at times that correspond to the middle to late stages of dynamical evolution when the densities are highest. These depletions do not depend in detail on the dynamical solution and should exist for any centrally condensed density profile. Sulfur-bearing molecules are particularly sensitive to the density increase: CS, SO, and C2S show significant depletions both on a strongly bound water mantle and on the weakly bound GO-covered grain surface. In contrast, CO and HCO+ show large depletions only for an H2O grain mantle and remain in the gas phase for models with CO grain mantles. Two species, NH3 and N2H+, do not deplete from the gas phase for the densities considered in our models. We also find that for very high densities, n(H2) > 10(6) cm(-3) depletion becomes important for all molecules. The effects of coupling chemistry and dynamics on the resulting physical evolution are discussed. We compare our results with current high-resolution observations of preprotostellar cores and to more evolved objects and suggest that ratios of the abundances of few species can be used in concert with our models as sensitive discriminators between different stages of core and star formation. C1 CALTECH,JET PROP LAB,PASADENA,CA 91109. RP Bergin, EA (reprint author), HARVARD SMITHSONIAN CTR ASTROPHYS,MS-66,60 GARDEN ST,CAMBRIDGE,MA 02138, USA. NR 40 TC 279 Z9 279 U1 0 U2 4 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637 SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD SEP 1 PY 1997 VL 486 IS 1 BP 316 EP 328 DI 10.1086/304510 PN 1 PG 13 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XT968 UT WOS:A1997XT96800029 ER PT J AU Strohmayer, TE Jahoda, K Giles, AB Lee, U AF Strohmayer, TE Jahoda, K Giles, AB Lee, U TI Millisecond pulsations from a low-mass X-ray binary in the galactic center region SO ASTROPHYSICAL JOURNAL LA English DT Article DE pulsars, general; stars, neutron; stars, rotation; X-rays, bursts ID NEUTRON-STARS; TIMING EXPLORER; G-MODE; BURSTS; OSCILLATIONS AB We report the detection with the proportional counter array (PCA) onboard the Rossi X-Ray Timing Explorer (RXTE) of 589 Hz oscillations during three type I X-ray bursts from a low-mass X-ray binary located in the Galactic center region. The bursts, which occurred on 1996 May 15.814, June 4.612, and June 19.414 UT, were observed serendipitously during routine monitoring observations of GRO J1744-28 by RXTE. The strongest pulsations were observed from the May 15 burst, reaching an amplitude of 18% of the >8 keV flux in this burst. The pulsation amplitudes in each burst are a strong function of photon energy since no signals were detected in the 1-8 keV band, but there were strong detections above 8 keV. The evolution of the X-ray spectrum through each burst is consistent with modest radius expansion. The pulsations are confined to the postcontraction portion of each burst profile, consistent with the oscillations recently reported in a burst from KS 1731-26 and also some bursts from 4U 1728-34. The location of the burster in the 1 degrees (FWHM) PCA held of view is constrained by comparing the count rates in the five independent detectors of the PCA. This analysis strongly excludes GRO J1744-28 as the source of these bursts but does not yet allow a definitive identification of the source with any known burster in the held of view. However, the derived position strongly overlaps that of MXB 1743-29, identifying this source as a strong candidate for the 589 Hz burster. We argue that the observed oscillations are consistent with rotational modulation of the X-ray brightness. C1 TOHOKU UNIV,INST ASTRON,SENDAI,MIYAGI 98077,JAPAN. RP Strohmayer, TE (reprint author), NASA,GODDARD SPACE FLIGHT CTR,HIGH ENERGY ASTROPHYS LAB,GREENBELT,MD 20771, USA. RI Jahoda, Keith/D-5616-2012 NR 24 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 SEP 1 PY 1997 VL 486 IS 1 BP 355 EP 362 DI 10.1086/304522 PN 1 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XT968 UT WOS:A1997XT96800032 ER PT J AU Bell, KR Cassen, PM Klahr, HH Henning, T AF Bell, KR Cassen, PM Klahr, HH Henning, T TI The structure and appearance of protostellar accretion disks: Limits on disk flaring SO ASTROPHYSICAL JOURNAL LA English DT Article DE accretion, accretion disks; radiative transfer; stars, pre-main-sequence ID ANGULAR-MOMENTUM TRANSPORT; PRIMORDIAL SOLAR NEBULA; YOUNG STELLAR OBJECTS; CIRCUMSTELLAR DISKS; VERTICAL STRUCTURE; EVOLUTION; MODELS; CONVECTION; CLOUDS AB Vertical structure models are used to investigate the structure of protostellar, a-law, accretion disks. Conditions investigated cover a range of mass fluxes (10(-9) to 10(-5) M. yr(-1)), viscous efficiencies (alpha = 10(-2) and 10(-4)), and stellar masses (0.5-3 M.). Analytic formulae for midplane temperatures, optical depths, and volume and surface densities are derived and are shown to agree well with numerical results. The temperature dependence of the opacity is shown to be the crucial factor in determining radial trends. We also consider the effect on disk structure of illumination from a uniform field of radiation such as might be expected of a system immersed in a molecular cloud core or other star-forming environment: T-amb = 10, 20, and 100 K. Model results are compared to Hubble Space Telescope observations of HH30 and the Orion proplyds. Disk shape is derived in both the Rosseland mean approximation and as viewed at particular wavelengths (lambda lambda = 0.66, 2.2, 60, 100, 350, and 1000 mu m) In regions where the opacity is an increasing function of temperature (as in the molecular regions where kappa proportional to T-2), th, disk does not flare, but decreases in relative thickness with radius under both Rosseland mean and single wavelength approximations. The radius at which the disk becomes shadowed from central object illumination depends on radial mass how and varies from a few tenths to about 5 au over the range of mass fluxes tested. This suggests that most planet formation occurred in environments unheated by stellar radiation. Viewing the system at any single wavelength increases the apparent flaring of the disk but leaves the shadow radius essentially unchanged. External heating further enhances flaring at large radii, but, except under extreme illumination (100 K), the inner disk will shield the planet-forming regions of all but the lowest mass flux disks from radiation originating near the origin such as from the star or from an FU Orionis outburst. C1 MAX PLANCK SOC,RES UNIT DUST STAR FORMING REG,D-07745 JENA,GERMANY. RP Bell, KR (reprint author), NASA,AMES RES CTR,DIV SPACE SCI,MS 245-3,MOFFETT FIELD,CA 94035, USA. NR 57 TC 203 Z9 203 U1 0 U2 4 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637 SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD SEP 1 PY 1997 VL 486 IS 1 BP 372 EP 387 DI 10.1086/304514 PN 1 PG 16 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XT968 UT WOS:A1997XT96800034 ER PT J AU Carpenter, KG Robinson, RD Johnson, HR Eriksson, K Gustafsson, B Pijpers, FP Querci, F Querci, M AF Carpenter, KG Robinson, RD Johnson, HR Eriksson, K Gustafsson, B Pijpers, FP Querci, F Querci, M TI Hubble Space Telescope spectroscopy of the carbon star TX Piscium SO ASTROPHYSICAL JOURNAL LA English DT Article DE circumstellar matter; stars, carbon; stars, chromospheres; stars, individual (TX Piscium); stars, mass loss; ultraviolet, stars ID MASS-LOSS; ANGULAR DIAMETERS; EVOLVED STARS; CIRCUMSTELLAR ENVELOPES; ULTRAVIOLET-SPECTRA; LUNAR OCCULTATION; OUTER ATMOSPHERE; LOW-GRAVITY; COOL STARS; AGB STARS AB Ultraviolet spectra obtained with the Hubble Space Telescope of the carbon star TX Piscium (HR 9004) are presented, along with analysis providing information on its outer atmosphere, including flow and turbulent velocities, line formation mechanisms, and variations with time. Both thermal (collisionally excited) and fluorescent emission from the chromosphere of the star appear to be formed near the stellar rest velocity, i.e., in a region below that in which the stellar wind is accelerated. Absorption self-reversals in the Mg II emission confirm the presence of an outflowing stellar wind at a mean velocity of about 9-10 km s(-1). Circumstellar absorption features (Mn I and Fe II overlying the Mg II emission indicate a cool shell expanding at about 5-6 km s(-1) relative to the photosphere. The widths (FWHM) of various emission lines indicate that the chromospheric turbulence is at least 16 km s(-1), but that it may increase with altitude to as much as 34 km s(-1). Three hours of integration on the C II] lines are examined for any signs of variability that might indicate the presence of shocks, but no statistically significant variations are seen. A previous identification (in spectra of UU Aur) of an emission line at 2807 Angstrom, seen only in spectra of carbon stars, as belonging to Fe I multiplet UV45 pumped by the C II line at 2325 Angstrom is confirmed by the discovery of an absorption feature corresponding exactly to the wavelength of the pumped transition (Fe I UV13) near 2325 Angstrom. Lines from Fe II UV165, previously seen in solar off-limb spectra and in Goddard High-Resolution Spectrograph spectra of alpha Tau, are clearly present. The normally much stronger Fe II UV32, 62, and 63 multiplets are seen but are weaker relative to both the UV165 lines and the intercombination lines of C II] and Si II] than in alpha Tau. The weakness of these Fe II lines is indicated both by their absolute flux levels and by their narrow, single-peaked profiles, which are in sharp contrast to the broad, double-peaked profiles seen in oxygen-rich cool giant and supergiant stars. The weakness of the Fe II lines and the presence of the Fe I 2807 Angstrom line suggest that the ionization fraction of iron (Fe II/Fe I) is significantly lower in the outer atmospheres of carbon stars. Fluxes in emission lines of Fe II and Mg II are greater than or equal to 2-3 times lower than in a 1984 IUE spectrum of TX Pac, confirming that the latter was obtained at an epoch of unusual UV brightness for the star. The Mg II profiles are heavily mutilated by overlying absorption, even more so than in 1984. The TX Psc profiles are very similar to those seen in the carbon star TW Hor but are dramatically different than those in another carbon star, UU Aur, whose lines show violet wing emission out to much shorter wavelengths than in the other two stars. C1 NASA,GODDARD SPACE FLIGHT CTR,ASTRON PROGRAMS,COMP SCI CORP,GREENBELT,MD 20771. INDIANA UNIV,DEPT ASTRON,BLOOMINGTON,IN 47405. UNIV COPENHAGEN,NIELS BOHR INST ASTRON PHYS & GEOPHYS,DK-2100 COPENHAGEN,DENMARK. ASTRON OBSERV,S-75120 UPPSALA,SWEDEN. AARHUS UNIV,INST PHYS & ASTRON,THEORET ASTROPHYS CTR,DK-8000 AARHUS,DENMARK. OBSERV MIDI PYRENEES,F-31400 TOULOUSE,FRANCE. RP Carpenter, KG (reprint author), NASA,GODDARD SPACE FLIGHT CTR,ASTRON & SOLAR PHYS LAB,CODE 681,GREENBELT,MD 20771, USA. RI Pijpers, Frank/A-1734-2009; Carpenter, Kenneth/D-4740-2012 NR 60 TC 5 Z9 5 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 SEP 1 PY 1997 VL 486 IS 1 BP 457 EP 470 DI 10.1086/304515 PN 1 PG 14 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XT968 UT WOS:A1997XT96800042 ER PT J AU Ford, EC Kaaret, P Chen, K Tavani, M Barret, D Bloser, P Grindlay, J Harmon, BA Paciesas, WS Zhang, SN AF Ford, EC Kaaret, P Chen, K Tavani, M Barret, D Bloser, P Grindlay, J Harmon, BA Paciesas, WS Zhang, SN TI Energy spectra and high-frequency oscillations in 4U 0614+091 SO ASTROPHYSICAL JOURNAL LA English DT Article DE accretion, accretion disks; stars, individual (4U 0614t-091); stars, neutron; X-rays, stars ID X-RAY SOURCES; ACCRETION DISKS; NEUTRON STARS AB We investigate the behavior of the high-frequency quasi-periodic oscillations (QPOs) in 4U 0614+091, combining timing and spectral analyses of RXTE observations. The energy spectra of the source can be described by a power law (alpha similar to 2.8) and a blackbody (kT similar to 1.5 keV), with the blackbody accounting for 10%-20% of the total energy flux. We find a robust correlation of the frequency, v, of the higher frequency QPO near 1 kHz with the flux of the blackbody, F-BB The slope of this correlation, d log v/d log F-BB,, is 0.27-0.37. The source follows the same relation even in observations separated by several months. The QPO frequency does not have a similarly unique correlation with the total flux or the flux of the power-law component. The rms fraction of the higher frequency QPO rises with energy from 6.8% +/- 1.5% (3-5 keV) to 21.3% +/- 4.0% (10-12 keV). For the lower frequency QPO, however, it is consistent with a constant value of 5.4% +/- 0.9%. The results may be interpreted in terms of a beat-frequency model for the production of the high-frequency QPOs. C1 COLUMBIA UNIV,COLUMBIA ASTROPHYS LAB,NEW YORK,NY 10027. CTR ETUD SPATIALE RAYONNEMENTS,F-31028 TOULOUSE 4,FRANCE. HARVARD SMITHSONIAN CTR ASTROPHYS,CAMBRIDGE,MA 02138. UNIV ALABAMA,HUNTSVILLE,AL 35899. NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,UNIV SPACE RES ASSOC,ES 84,HUNTSVILLE,AL 35812. RP Ford, EC (reprint author), COLUMBIA UNIV,DEPT PHYS,538 W 120TH ST,NEW YORK,NY 10027, USA. NR 30 TC 41 Z9 41 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 SEP 1 PY 1997 VL 486 IS 1 BP L47 EP L50 DI 10.1086/310827 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XT969 UT WOS:A1997XT96900012 ER PT J AU Galama, TJ Groot, PJ Strom, RG vanParadijs, J Hurley, K Kouveliotou, C Fishman, GJ Meegan, CA Heise, J intZand, JJM deBruyn, AG Hanlon, LO Bennett, K Telting, JH Rutten, RGM AF Galama, TJ Groot, PJ Strom, RG vanParadijs, J Hurley, K Kouveliotou, C Fishman, GJ Meegan, CA Heise, J intZand, JJM deBruyn, AG Hanlon, LO Bennett, K Telting, JH Rutten, RGM TI Radio and optical follow-up observations and improved interplanetary network position of GRB 970111 SO ASTROPHYSICAL JOURNAL LA English DT Article DE gamma rays, bursts; radio continuum, general ID GAMMA-RAY BURSTS; BATSE OBSERVATIONS; SPECTRA; COUNTERPART; SEARCH; MODELS AB We report on Westerbork 840 MHz and 1.4 and 5 GHz radio observations of the improved Interplanetary Network Wide Field Camera (IPN WFC) error box of the gamma-ray burst GRB 970111, between 26.4 hr and 120 days after the event onset. In the similar to 13 arcmin(2) area defined by the IPN (BATSE and Ulysses) annulus and the published refined BeppoSAX WFC error box, we detected no steady sources brighter than 0.56 mJy (4 sigma) and no varying radio emission, down to 1.0 mJy (4 sigma). We also report on B-, V-, R-, and I-band observations of the error box with the 4.2 m William Herschel Telescope at La Palma. C1 CTR HIGH ENERGY ASTROPHYS,NL-1098 SJ AMSTERDAM,NETHERLANDS. NETHERLANDS FDN RES ASTRON,NL-7990 AA DWINGELOO,NETHERLANDS. UNIV ALABAMA,DEPT PHYS,HUNTSVILLE,AL 35899. UNIV CALIF BERKELEY,SPACE SCI LAB,BERKELEY,CA 94720. UNIV SPACE RES ASSOC,WASHINGTON,DC. NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,CODE ES 84,HUNTSVILLE,AL 35812. SRON,NL-3584 CA UTRECHT,NETHERLANDS. KAPTEYN ASTRON INST,NL-9700 AV GRONINGEN,NETHERLANDS. UNIV DUBLIN TRINITY COLL,DEPT PHYS,DUBLIN 4,IRELAND. EUROPEAN SPACE TECHNOL CTR,DIV ASTROPHYS,DEPT SPACE SCI,NOORDWIJK,NETHERLANDS. NFRA,ING TELESCOPES,TENERIFE 38780,SPAIN. RP Galama, TJ (reprint author), UNIV AMSTERDAM,ASTRON INST ANTON PANNEKOEK,KRUISLAAN 403,NL-1098 SJ AMSTERDAM,NETHERLANDS. RI Galama, Titus/D-1429-2014; Groot, Paul/K-4391-2016 OI Galama, Titus/0000-0002-1036-396X; Groot, Paul/0000-0002-4488-726X NR 40 TC 15 Z9 15 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 SEP 1 PY 1997 VL 486 IS 1 BP L5 EP & DI 10.1086/310822 PN 2 PG 6 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XT969 UT WOS:A1997XT96900002 ER PT J AU Greenhill, LJ Herrnstein, JR Moran, JM Menten, KM Velusamy, T AF Greenhill, LJ Herrnstein, JR Moran, JM Menten, KM Velusamy, T TI A search for H2O maser emission toward active galactic nuclei: Discovery of a nuclear maser source in NGC 3735 SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies, active; galaxies, individual (NGC 3735); galaxies, nuclei; masers ID X-RAY; GALAXIES AB We report the results of a survey for H2O maser emission in the 6(16)-5(23) transition at 1.35 cm wavelength in 29 active galactic nuclei (AGNs). One new maser was detected. The detection rate among objects with recessional velocities <7000 km s(-1) is consistent with rates reported elsewhere for similarly nearby objects (about one in 15). The new maser lies in the edge-on Seyfert 2 galaxy NGC 3735 (inclination 77 degrees) within 10 km s(-1) of the systemic velocity. No other emission has been identified at velocities within +/-500 km s(-1) of the systemic velocity. The maser is coincident with the radio continuum peak of the nucleus at 6 and 3.6 cm wavelengths to within the estimated 1 sigma astrometric uncertainty of 0''.1 (15 pc at a distance of 30 Mpc). C1 CALTECH,JET PROP LAB,PASADENA,CA 91109. RP Greenhill, LJ (reprint author), HARVARD SMITHSONIAN CTR ASTROPHYS,60 GARDEN ST,CAMBRIDGE,MA 02138, USA. NR 26 TC 34 Z9 35 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 SEP 1 PY 1997 VL 486 IS 1 BP L15 EP L18 DI 10.1086/310824 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XT969 UT WOS:A1997XT96900004 ER PT J AU Marcaide, JM Alberdi, A Ros, E Diamond, P Shapiro, II Guirado, JC Jones, DL Mantovani, F PerezTorres, MA Preston, RA Schilizzi, RT Sramek, RA Trigilio, C VanDyk, SD Weiler, KW Whitney, AR AF Marcaide, JM Alberdi, A Ros, E Diamond, P Shapiro, II Guirado, JC Jones, DL Mantovani, F PerezTorres, MA Preston, RA Schilizzi, RT Sramek, RA Trigilio, C VanDyk, SD Weiler, KW Whitney, AR TI Deceleration in the expansion of SN 1993J SO ASTROPHYSICAL JOURNAL LA English DT Article DE circumstellar matter; galaxies, individual (NGC 3031, M81); radio continuum, stars; supernovae, individual (SN 19935); techniques, interferometric ID SUPERNOVA 1993J; CIRCUMSTELLAR INTERACTION; RADIO SUPERNOVAE; IIB SUPERNOVA; X-RAYS; SN-1993J; EMISSION; MODEL; EJECTA; SHELL AB A rarity among supernova, SN 1993J in M81 can be studied with high spatial resolution. Its radio power and distance permit VLBI observations to monitor the expansion of its angular structure. This radio structure was previously revealed to be shell-like and to be undergoing a self-similar expansion at a constant rate. From VLBI observations at wavelengths of 3.6 and 6 cm in the period 6-42 months after explosion, we have discovered that the expansion is decelerating. Our measurement of this deceleration yields estimates of the density profiles of the supernova ejecta and circumstellar material in standard supernova explosion models. C1 INST NACL TECNICA AEROESPACIAL,LAB ASTROFIS ESPACIAL & FIS FUNDAMENTAL,MADRID 28080,SPAIN. CSIC,INST ASTROFIS ANDALUCIA,E-18080 GRANADA,SPAIN. NATL RADIO ASTRON OBSERV,SOCORRO,NM 87801. HARVARD SMITHSONIAN CTR ASTROPHYS,CAMBRIDGE,MA 02138. CALTECH,JET PROP LAB,PASADENA,CA 91109. CNR,IST RADIOASTRON,I-40129 BOLOGNA,ITALY. JOINT INST VLBI EUROPE,NL-7990 AA DWINGELOO,NETHERLANDS. LEIDEN OBSERV,NL-2300 RA LEIDEN,NETHERLANDS. CNR,IST RADIOASTRON,I-96017 NOTO,ITALY. USN,RES LAB,REMOTE SENSING DIV,COD 7214,WASHINGTON,DC 20375. MIT,HAYSTACK OBSERV,WESTFORD,MA 01886. RP Marcaide, JM (reprint author), UNIV VALENCIA,DEPT ASTRON,E-46100 BURJASSOT,SPAIN. OI Ros, Eduardo/0000-0001-9503-4892; Van Dyk, Schuyler/0000-0001-9038-9950 NR 25 TC 52 Z9 52 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 SEP 1 PY 1997 VL 486 IS 1 BP L31 EP & DI 10.1086/310830 PN 2 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XT969 UT WOS:A1997XT96900008 ER PT J AU NoriegaCrespo, A Garnavich, PM Curiel, S Raga, AC Ayala, S AF NoriegaCrespo, A Garnavich, PM Curiel, S Raga, AC Ayala, S TI The proper motions of the warm molecular hydrogen gas in Herbig-Haro 1 SO ASTROPHYSICAL JOURNAL LA English DT Article DE ISM, individual (HH 1); ISM, jets and outflows; ISM, molecules; stars, formation ID HH OBJECTS; BOW SHOCKS; COMPLEX; OUTFLOWS; JET; SPECTROSCOPY; RESOLUTION; KINEMATICS; EMISSION; FLOW AB We have measured the proper motions of three molecular hydrogen (v = 1-0 2.121 mu m) knots in the Herbig-Haro 1 object using a 4.4 yr baseline (1992-1997). The HH 1F knot, which probably corresponds to the tip of the working surface of HH 1, has a proper motion of 0,19 +/- 0.10 (arcsec yr(-1)) and a position angle of 315(-25)(+29) deg. This motion is comparable to that determined in the atomic emission lines of H alpha and [S II] lambda lambda 6717/31, and confirms that the warm molecular H-2 gas is partaking of the same motion as the atomic/ionic gas. C1 JET PROPULS LAB,PASADENA,CA 91125. HARVARD SMITHSONIAN CTR ASTROPHYS,CAMBRIDGE,MA 02138. NATL AUTONOMOUS UNIV MEXICO,INST ASTRON,MEXICO CITY 04510,DF,MEXICO. RP NoriegaCrespo, A (reprint author), CALTECH,CTR INFRARED PROC & ANAL,PASADENA,CA 91125, USA. NR 29 TC 29 Z9 29 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 SEP 1 PY 1997 VL 486 IS 1 BP L55 EP L58 DI 10.1086/310834 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XT969 UT WOS:A1997XT96900014 ER PT J AU Feibelman, WA AF Feibelman, WA TI The greatly expanded IUE spectrum of the planetary nebula NGC 2371-2 and its central star SO ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES LA English DT Article DE line identification; planetary nebulae, individual (NGC 2371-2); ultraviolet, ISM ID O-VI NUCLEUS; LINE LIST; RR-TELESCOPII; SEQUENCE AB Early IUE low-dispersion SWP and LWR spectra have been reexamined by means of refined current data reduction routines. These spectra contain much more information than was reported in 1981. A high-dispersion SWP spectrum was obtained in 1994 from which more than 80 emission and absorption features were identified, and log N-e = 3.0 +/- 0.2 cm(-3) was determined from the C III] F(lambda 1907/lambda 1909) ratio. Electron densities were also derived from the Si III] F(lambda 1883/lambda 1892) and dereddened [Ne IV] F[lambda 1602/(lambda 2422 + lambda 2424)] line ratios. The terminal wind velocity of the C IV P Cyg feature was measured from the low- and high-resolution spectra. Approximately 50 of the strongest Fe VI and Fe V photospheric absorptions are identified. RP Feibelman, WA (reprint author), NASA, GODDARD SPACE FLIGHT CTR, CODE 681, GREENBELT, MD 20771 USA. NR 32 TC 8 Z9 8 U1 0 U2 0 PU IOP PUBLISHING LTD PI BRISTOL PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND SN 0067-0049 EI 1538-4365 J9 ASTROPHYS J SUPPL S JI Astrophys. J. Suppl. Ser. PD SEP PY 1997 VL 112 IS 1 BP 193 EP 197 DI 10.1086/313033 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XV264 UT WOS:A1997XV26400005 ER PT J AU Watenpaugh, DE Breit, GA Ballard, RE Hargens, AR AF Watenpaugh, DE Breit, GA Ballard, RE Hargens, AR TI Monitoring acute whole-body fluid redistribution by changes in leg and neck volumes SO AVIATION SPACE AND ENVIRONMENTAL MEDICINE LA English DT Article ID SIMULATED MICROGRAVITY; BED REST; WEIGHTLESSNESS; SHIFTS; PRESSURE; HUMANS; HEAD AB Background: Acute fluid shifts initiate chronic cardiovascular acclimation to altered posture or gravity. Hypothesis: We hypothesized that neck volume increases with acute lilt from vertical to horizontal and head-down positions, and that neck volume correlates negatively with leg volume during tilling. Methods: Strain gauges measured changes in calf and neck volumes in 9 subjects during the following tilt table protocol: 90 degrees (upright control), 54 degrees, 30 degrees, 12 degrees, 0 degrees (horizontal supine), -6 degrees (head-down tilt), -12 degrees, -6 degrees, 0 degrees, 12 degrees, 30 degrees, 54 degrees, and 90 degrees. Each position was held for 30 s. Results: Tilting from 90 degrees upright to 0 degrees supine increased neck volume 3.09 +/- 0.37% (mean +/- SE); neck volume increased further above upright control to 4.26 +/- 0.39% at -12 degrees head-down tilt. In the calf, tilting produced significant volume decrements of 1.66 +/- 0.36% below 90 degrees control at 0 degrees supine, and 2.03 +/- 0.50% below control at -12 degrees tilt. Neck volume elevation consistently exceeded the absolute magnitude of calf volume reduction at a given tilt angle by a factor of about 1.5, and the two were linearly correlated (r(2) = 0.60). Conclusions: Responses of body segment volumes to till. were practically instantaneous, indicating that venous blood volume translocation accounted for the changes. We conclude that leg and neck volume changes provide a convenient, non-invasive, and sensitive means of assessing acute regional fluid shifts in humans. C1 NASA,AMES RES CTR,GRAVITAT RES BRANCH 239 11,MOFFETT FIELD,CA 94035. NR 21 TC 3 Z9 3 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 SEP PY 1997 VL 68 IS 9 BP 858 EP 862 PG 5 WC Public, Environmental & Occupational Health; Medicine, General & Internal; Sport Sciences SC Public, Environmental & Occupational Health; General & Internal Medicine; Sport Sciences GA XU847 UT WOS:A1997XU84700012 PM 9293356 ER PT J AU Kumfert, G Pothen, A AF Kumfert, G Pothen, A TI Two improved algorithms for envelope and wavefront reduction SO BIT LA English DT Article; Proceedings Paper CT International Linear Algebra Year Workshops CY SEP, 1995-JUN, 1996 CL TOULOUSE, FRANCE SP CERFACS DE envelope reduction; Laplacian matrices; reordering algorithms; spectral methods; Sloan algorithm; sparse matrices; wavefront reduction ID FINITE-ELEMENT GRAPH; SPARSE MATRICES; PROFILE; NODE; EIGENVECTORS; LAPLACIAN AB Two algorithms for reordering sparse, symmetric matrices or undirected graphs to reduce envelope and wavefront are considered. The first is a combinatorial algorithm introduced by Sloan and further developed by Duff, Reid, and Scott; we describe enhancements to the Sloan algorithm that improve its quality and reduce its run time. Our test problems fall into two classes with differing asymptotic behavior of their envelope parameters as a function of the weights in the Sloan algorithm. We describe an efficient O(n log n + m) time implementation of the Sloan algorithm, where n is the number of rows (vertices), and m is the number of nonzeros (edges). On a collection of test problems, the improved Sloan algorithm required, on the average, only twice the time required by the simpler RCM algorithm while improving the mean square wavefront by a factor of three. The second algorithm is a hybrid that combines a spectral algorithm for envelope and wavefront reduction with a refinement step that uses a modified Sloan algorithm. The hybrid algorithm reduces the envelope size and mean square wavefront obtained from the Sloan algorithm at the cost of greater running times. We illustrate how these reductions translate into tangible benefits for frontal Cholesky factorization and incomplete factorization preconditioning. C1 OLD DOMINION UNIV,DEPT COMP SCI,NORFOLK,VA 23529. NASA,LANGLEY RES CTR,ICASE,HAMPTON,VA 23681. OI Pothen, Alex/0000-0002-3421-3325 NR 41 TC 22 Z9 22 U1 0 U2 0 PU BIT FOUNDATION PI COPENHAGEN PA POSTBOX 113, DK-1004 COPENHAGEN, DENMARK SN 0006-3835 J9 BIT JI Bit PD SEP PY 1997 VL 37 IS 3 BP 559 EP 590 DI 10.1007/BF02510240 PG 32 WC Computer Science, Software Engineering; Mathematics, Applied SC Computer Science; Mathematics GA XY696 UT WOS:A1997XY69600005 ER PT J AU Mundy, BC Moser, HG AF Mundy, BC Moser, HG TI Development of early stages of pelagic armorhead Pseudopentaceros wheeleri with notes on juvenile Ps-richardsoni and larval Histiopterus typus (Pisces, Percoidei, Pentacerotidae) SO BULLETIN OF MARINE SCIENCE LA English DT Article ID NORTH PACIFIC-OCEAN; GULF-OF-MEXICO; PERCOMORPH PHYLOGENY; FISHES; PERCIFORMES; MORPHOLOGY; POPULATION; TELEOSTEI; SEAMOUNTS; ATLANTIC AB Two larvae (4.2 and 7.2 mm notochord length (NL)) and 28 juveniles (8.3-15.3 mm standard length (SL)) of the pelagic armorhead Pseudopentaceros wheeleri, are described from surface tows taken near seamounts in the central North Pacific Ocean (29.5-30.5 degrees N, 178-180 degrees E) during February 1985. Diagnostic features of the larvae include dark pigment on all but the posterior 9-20% of the body, a thick, long intestine (preanal length 76.4-76.9% NL), a supraoccipital crest, spiny supraorbital ridges, and preopercular spines. Juveniles are darkly pigmented over the head and body, with a blotched pattern on specimens >11 mm SL. In juveniles, additional large spines are present on the lacrimals, posttemporals, supracleithra, and cleithral lobes. A 7.4-mm SL Histiopterus typus larva from western Australia has similar head spines but strikingly elongated dorsal-and pelvic-fin elements, more evenly distributed pigment, a larger head, and a more compressed body, compared to Ps. wheeleri. Juvenile Ps. wheeleri can be differentiated from juveniles of the other North Pacific pentacerotids, Pentaceros japonicus and Evistias acutirostris, by numbers of fin rays and from the very similar Southern Hemisphere Ps. richardsoni by vertebral count, interpelvic width, and the absence of anterior spines on the supraoccipital crest. All known armorhead juveniles share a distinctive pattern of cranial spines that includes spines on the lacrimals, large spines in laterally projecting supraorbital ridges, and an enlarged, serrated supraoccipital crest, in addition to the spines on the preopercles, opercles, posttemporals, supracleithra, and pterotics found in many percomorph larvae. Pelagic young of Ps. wheeleri were collected only in neuston tows in winter. The neustonic distribution of small pelagic armorhead may contribute to their advection from seamount spawning sites. C1 Natl Marine Fisheries Serv, Honolulu Lab, SW Fisheries Sci Ctr, NOAA, Honolulu, HI 96822 USA. Natl Marine Fisheries Serv, La Jolla Lab, SW Fisheries Sci Ctr, NOAA, La Jolla, CA 92038 USA. RP Mundy, BC (reprint author), Natl Marine Fisheries Serv, Honolulu Lab, SW Fisheries Sci Ctr, NOAA, 2570 Dole St, Honolulu, HI 96822 USA. NR 52 TC 9 Z9 9 U1 0 U2 0 PU ROSENSTIEL SCH MAR ATMOS SCI PI MIAMI PA 4600 RICKENBACKER CAUSEWAY, MIAMI, FL 33149 USA SN 0007-4977 J9 B MAR SCI JI Bull. Mar. Sci. PD SEP PY 1997 VL 61 IS 2 BP 241 EP 269 PG 29 WC Marine & Freshwater Biology; Oceanography SC Marine & Freshwater Biology; Oceanography GA YZ063 UT WOS:000072216600004 ER PT J AU Spyrou, NK Kazanas, D Esteban, EP AF Spyrou, NK Kazanas, D Esteban, EP TI Steadily rotating perfect-fluid gravitating prolate spheroids in Weyl gravity SO CLASSICAL AND QUANTUM GRAVITY LA English DT Article ID CURVES AB It is shown that the equations of hydrodynamics do not admit solutions describing gravitating, incompressible, perfect fluid, prolate spheroids within the context of Weyl gravity, i.e. a theory whose static, spherically symmetric solution admits, besides the usual 1/r potential, an additional linear one, which has been invoked to solve the galactic rotation curve problem without the introduction of 'dark matter'. This extends the similar, recent result obtained by Florides and Spyrou within Newtonian gravity to this alternative gravitational theory. C1 NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. UNIV PUERTO RICO,DEPT PHYS,HUMACAO,PR 00971. RP Spyrou, NK (reprint author), UNIV THESSALONIKI,DEPT ASTRON,GR-54006 THESSALONIKI,MACEDONIA,GREECE. NR 12 TC 2 Z9 2 U1 0 U2 2 PU IOP PUBLISHING LTD PI BRISTOL PA DIRAC HOUSE, TEMPLE BACK, BRISTOL, ENGLAND BS1 6BE SN 0264-9381 J9 CLASSICAL QUANT GRAV JI Class. Quantum Gravity PD SEP PY 1997 VL 14 IS 9 BP 2663 EP 2671 DI 10.1088/0264-9381/14/9/020 PG 9 WC Astronomy & Astrophysics; Physics, Multidisciplinary; Physics, Particles & Fields SC Astronomy & Astrophysics; Physics GA XY769 UT WOS:A1997XY76900019 ER PT J AU Bhat, K Choi, J McCall, SD Aggarwal, MD Cardelino, BH Moore, CE Penn, BG Frazier, DO Sanghadasa, M Barr, TA Laxmeshwar, NB AF Bhat, K Choi, J McCall, SD Aggarwal, MD Cardelino, BH Moore, CE Penn, BG Frazier, DO Sanghadasa, M Barr, TA Laxmeshwar, NB TI Theoretical and experimental study of the second-order polarizabilities of Schiff's bases for nonlinear optical applications SO COMPUTATIONAL MATERIALS SCIENCE LA English DT Article ID MOLECULES AB A series of twenty-four Schiff's bases was synthesized and nonresonant static molecular second order polarizabilities (beta) of these compounds were theoretically calculated and compared with experimental values. The computational method employed obtained: (a) values of polarization Versus static electric fields using a semiempirical Hamiltonian; (b) all tensor elements of beta by performing polynomial fits of the former data, within the finite-field approach. The experimental values were obtained using a modified electric field induced second harmonic generation (EFISH) experiment with 1,4-dioxane as the solvent. The measured quantities were the projection of beta on mu (the permanent dipole moment), relative to MNA (2-methyl-4-nitroaniline). The correlation between the predicted static molecular quantities and their corresponding experimental Values was 0.95 (based on a simple least-squares regression forced through the origin). A factor of 8.7 +/- 0.3 was determined to be the adjustment parameter for Schiff's bases to account for the solvent and dispersion effects at the fundamental wavelength of 1064 nm. (C) 1997 Elsevier Science B.V. C1 ALABAMA A&M UNIV, DEPT PHYS, NORMAL, AL 35762 USA. ATLANTA UNIV CTR, DEPT CHEM, ATLANTA, GA 30314 USA. NASA, GEORGE C MARSHALL SPACE FLIGHT CTR, SPACE SCI LAB, HUNTSVILLE, AL 35812 USA. UNIV ALABAMA, DEPT PHYS, HUNTSVILLE, AL 35899 USA. ISMAIL YUSUF COLL, BOMBAY 400060, MAHARASHTRA, INDIA. NR 25 TC 6 Z9 7 U1 0 U2 0 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0927-0256 EI 1879-0801 J9 COMP MATER SCI JI Comput. Mater. Sci. PD SEP PY 1997 VL 8 IS 4 BP 309 EP 316 DI 10.1016/S0927-0256(97)00043-8 PG 8 WC Materials Science, Multidisciplinary SC Materials Science GA YE051 UT WOS:A1997YE05100003 ER PT J AU Keller, RM Wolfe, SR Chen, JR Rabinowitz, JL Mathe, N AF Keller, RM Wolfe, SR Chen, JR Rabinowitz, JL Mathe, N TI A bookmarking service for organizing and sharing URLs SO COMPUTER NETWORKS AND ISDN SYSTEMS LA English DT Article; Proceedings Paper CT 6th International World Wide Web Conference CY APR 07-11, 1997 CL SANTA CLARA, CA DE bookmarks; personal information organizers; information sharing; adaptive retrieval; Internet-based collaboration ID INFORMATION AB Web browser bookmarking facilities predominate as the method of choice for managing URLs. In this paper, we describe some deficiencies of current bookmarking schemes, and examine an alternative to current approaches. We present WebTagger(TM), an implemented prototype of a personal bookmarking service that provides both individuals and groups with a customizable means of organizing and accessing Web-based information resources. In addition, the service enables users to supply feedback on the utility of these resources relative to their information needs, and provides dynamically-updated ranking of resources based on incremental user feedback. Individuals may access the service from anywhere on the Internet, and require no special software. This service greatly simplifies the process of sharing URLs within groups, in comparison with manual methods involving email. The underlying bookmark organization scheme is more natural and flexible than current hierarchical schemes supported by the major Web browsers, and enables rapid access to stored bookmarks. (C) 1997 Published by Elsevier Science B.V. C1 NASA,AMES RES CTR,CAELUM RES CORP,MOFFETT FIELD,CA 94035. NASA,AMES RES CTR,RECOM TECHNOL INC,MOFFETT FIELD,CA 94035. RP Keller, RM (reprint author), NASA,AMES RES CTR,DIV COMPUTAT SCI,MOFFETT FIELD,CA 94035, USA. NR 23 TC 13 Z9 13 U1 0 U2 1 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0169-7552 J9 COMPUT NETWORKS ISDN JI Comput. Netw. ISDN Syst. PD SEP PY 1997 VL 29 IS 8-13 BP 1103 EP 1114 DI 10.1016/S0169-7552(97)00028-7 PG 12 WC Computer Science, Information Systems; Engineering, Electrical & Electronic; Telecommunications SC Computer Science; Engineering; Telecommunications GA YF263 UT WOS:A1997YF26300024 ER PT J AU Udomkesmalee, S Zhu, DQ Chu, CC AF Udomkesmalee, S Zhu, DQ Chu, CC TI Image processing for planetary limb/terminator extraction SO COMPUTER VISION AND IMAGE UNDERSTANDING LA English DT Article ID EDGE-DETECTION; SEGMENTATION; CURVES AB A novel image segmentation technique for extracting limbs and terminators of planetary bodies is proposed. Conventional edge-based histogramming approaches are employed to trace object boundaries. The limb and terminator bifurcation is achieved by locating the harmonized segment in the two equations representing the 2-D parametrized boundary curve. This technique is quite efficient and robust. Although only spherical (near-spherical) planetary bodies in full view are addressed in detail, the proposed methodology can be extended to accommodate partially viewed and/or arbitrary-shaped objects; formulations for these cases are also given. Real planetary images from Voyager 1 and 2 serve as representative test cases to verify the proposed methodology. (C) 1997 Academic Press. RP CALTECH, JET PROP LAB, 4800 OAK GROVE DR, PASADENA, CA 91109 USA. NR 20 TC 1 Z9 1 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 1077-3142 EI 1090-235X J9 COMPUT VIS IMAGE UND JI Comput. Vis. Image Underst. PD SEP PY 1997 VL 67 IS 3 BP 274 EP 284 DI 10.1006/cviu.1997.0543 PG 11 WC Computer Science, Artificial Intelligence; Engineering, Electrical & Electronic SC Computer Science; Engineering GA XX931 UT WOS:A1997XX93100005 ER PT J AU Messina, P AF Messina, P TI High-performance computers: The next generation .D. SO COMPUTERS IN PHYSICS LA English DT Article C1 CALTECH,JET PROP LAB,PASADENA,CA. RP Messina, P (reprint author), CALTECH,CTR ADV COMP RES,PASADENA,CA 91125, USA. NR 34 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 0894-1866 J9 COMPUT PHYS JI Comput. Phys. PD SEP-OCT PY 1997 VL 11 IS 5 BP 454 EP 466 PG 13 WC Computer Science, Interdisciplinary Applications; Physics, Multidisciplinary; Physics, Mathematical SC Computer Science; Physics GA YB558 UT WOS:A1997YB55800015 ER PT J AU Shen, HW AF Shen, HW TI Using line-integral convolution to visualize dense vector fields SO COMPUTERS IN PHYSICS LA English DT Article RP Shen, HW (reprint author), NASA,MRJ INC,AMES RES CTR,MOFFETT FIELD,CA 94034, USA. NR 5 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 0894-1866 J9 COMPUT PHYS JI Comput. Phys. PD SEP-OCT PY 1997 VL 11 IS 5 BP 474 EP 478 PG 5 WC Computer Science, Interdisciplinary Applications; Physics, Multidisciplinary; Physics, Mathematical SC Computer Science; Physics GA YB558 UT WOS:A1997YB55800017 ER PT J AU Wade, CE Ortiz, RM AF Wade, CE Ortiz, RM TI Urinary excretion of cortisol from rhesus monkeys (Macaca mulatta) habituated to restraint SO CONTEMPORARY TOPICS IN LABORATORY ANIMAL SCIENCE LA English DT Article AB Use of monkeys in research has often required that they be restrained in a chair, However, chair restraint can elicit an initial neuroendocrine stress response, Also, inactivity associated with restraint can induce muscular atrophy, We proposed that prior habituation of monkeys to chair restraint would attenuate these neuroendocrine responses without causing substantial muscle wasting, Four rhesus monkeys (Macaca mulatta) were trained and habituated to a restraint chair specifically designed for spaceflight, During the study, monkeys were placed in metabolic cages for 7 days (prerestraint, Phase I), placed in a chair restraint for 18 days (Phase II), and then returned to their metabolic cages for 5 days (postrestraint, Phase III), Urine was collected between 0700-1100 daily, and measurements of cortisol, creatinine, and electrolyte concentrations were adjusted for hourly excretion rates, Body weights of the monkeys did not change between start of the prerestraint and postrestraint phases (10.3 +/- 0.8 vs, 10.3 +/- 0.9 kg, respectively), During the 3 phases, mean excretion rate of cortisol did not change (24.1 +/- 10.3, 26.7 +/- 7.7, and 19.3 +/- 5.8 mu g/h, respectively), Mean excretion rate of creatinine (37.3 +/- 7.5, 37.5 +/- 12.2, and 36.9 +/- 17.1 mg/h, respectively), Na+ (3.3 +/- 1.2, 3.2 +/- 1.2, 2.2 +/- 1.8 mmol/h, respectively), and K+ (5.3 +/- 1.8, 5.4 +/- 1.6, and 4.3 +/- 2.8 mmol/h, respectively) were also not altered, Lack of an increase in excreted urinary cortisol suggested that prior habituation to chair restraint attenuated neuroendocrine responses reported previously, Also, the chair restraint method used appeared to allow adequate activity, because the monkeys did not have indices of muscle wasting. C1 NASA,AMES RES CTR,LOCKHEED MARTIN,MOFFETT FIELD,CA 94035. RP Wade, CE (reprint author), NASA,AMES RES CTR,DIV LIFE SCI,MS 239-11,MOFFETT FIELD,CA 94035, USA. NR 16 TC 4 Z9 4 U1 0 U2 2 PU AMER ASSOC LABORATORY ANIMAL SCIENCE PI CORDOVA PA 70 TIMBERCREEK DR, SUITE 5, CORDOVA, TN 38018 SN 1060-0558 J9 CONTEMP TOP LAB ANIM JI Contemp. Top. Lab. Anim. Sci. PD SEP PY 1997 VL 36 IS 5 BP 55 EP 57 PG 3 WC Veterinary Sciences; Zoology SC Veterinary Sciences; Zoology GA XZ233 UT WOS:A1997XZ23300027 PM 11540418 ER PT J AU Peterson, E Horz, F Chang, S AF Peterson, E Horz, F Chang, S TI Modification of amino acids at shock pressures of 3.5 to 32 GPa SO GEOCHIMICA ET COSMOCHIMICA ACTA LA English DT Article ID MURCHISON METEORITE; PLANETARY ACCRETION; ORGANIC-MATTER; FULLERENES; IMPACT; METAMORPHISM; CRATER AB Amino acids were subjected to shock impact over a pressure range of 3.5 to 32 GPa both within and without meteoritic mineral matrices. The extent of amino acid destruction, racemization, and conversion to secondary amino acids was examined. Abundances of parent compounds decreased by a factor of 10(3) over this pressure range. Racemization also occurred, but some residual optical activity remained in the amino acids surviving shocks up to 32 GPa. Secondary amino acids formed in the high peak pressure range; those identified were beta-alanine, glycine, alanine, gamma-aminobutyric acid, and beta-aminoisobutyric acid. At 30 GPa, the abundances of these daughter compounds exceeded those of the remaining initial amino acids. As the concomitant effects of high mechanical stress and temperature accompanying shocks cannot be separated in this work, their relative contribution to the observed transformations cannot be estimated. The survival of amino acids in shock experiments suggests that, after formation or emplacement of amino acids in carbonaceous chondrite parent bodies, these objects never experienced impact velocities greater than 5 km/s, which suffices to generate 30 GPa for typical silicate/silicate impacts. These results also provide guidelines for choosing appropriate capture media for interplanetary dust particles on Earth-orbiting platforms. Copyright (C) 1997 Elsevier Science Ltd. C1 NASA, LYNDON B JOHNSON SPACE CTR, EARTH SCI & SOLAR SYST EXPLORAT DIV, HOUSTON, TX 77058 USA. RP Peterson, E (reprint author), NASA, AMES RES CTR, DIV SPACE SCI, MOFFETT FIELD, CA 94035 USA. NR 48 TC 31 Z9 31 U1 1 U2 6 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0016-7037 J9 GEOCHIM COSMOCHIM AC JI Geochim. Cosmochim. Acta PD SEP PY 1997 VL 61 IS 18 BP 3937 EP 3950 DI 10.1016/S0016-7037(97)00192-0 PG 14 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA YC774 UT WOS:A1997YC77400014 PM 11541218 ER PT J AU Paustian, K Levine, E Post, WM Ryzhova, IM AF Paustian, K Levine, E Post, WM Ryzhova, IM TI The use of models to integrate information and understanding of soil C at the regional scale SO GEODERMA LA English DT Article DE simulation modelling; soil organic matter; scaling; spatial aggregation; climate change; remote sensing; GIS ID NET PRIMARY PRODUCTION; LEAF-AREA INDEX; ORGANIC-MATTER; SATELLITE DATA; LAND-USE; CLIMATE-CHANGE; UNITED-STATES; GLOBAL CHANGE; CARBON STORAGE; EXPERIMENTAL FOREST AB Regional analysis of ecosystem properties, including soil C, is a rapidly developing area of research. Regional analyses are being used to quantify existing soil C stocks, predict changes in soil C as a function of changing landuse patterns, and assess possible responses to climate change. The tools necessary for such analyses are simulation models coupled with spatially-explicit databases of vegetation, soils, topography, landuse and climate. A general framework for regional analyses which integrates models with site-specific and spatially-resolved data is described. Two classes of models are currently being used for analyses at regional scales, ecosystem-level models, which were originally designed for local scale studies, and more aggregated 'macro-scale' models developed for continental and global scale applications. A consideration in applying both classes of models is the need to minimize errors associated with aggregating information to apply to coarser spatial and temporal scales. For model input data, aggregation bias is most severe for variables which enter into non-linear model functions, such as soil textural effects on organic matter decomposition and water balance or the temperature response of decomposer organisms. Aggregation of model structure also needs to be considered, particularly for macro-scale models. For example, representations of litter and soil organic matter by only one or two pools may be suitable for representing equilibrium conditions but rates of change will tend to be overestimated for transient-state conditions using highly aggregated models. Geographic soils data, derived from field surveys, are a key component for regional analyses. Issues of data quality and interpretation of soil survey data are discussed in the context of regional analyses of soil C. Areas for further development of data and modeling capabilities, including refining soil C maps, developing spatial databases on landuse and management practices, using remotely sensed data in regional model applications, and linking terrestrial ecosystem models with global climate models, are discussed. (C) 1997 Published by Elsevier Science B.V. C1 NASA,GODDARD SPACE FLIGHT CTR,BIOSPHER SCI BRANCH,GREENBELT,MD 20771. OAK RIDGE NATL LAB,DIV ENVIRONM SCI,OAK RIDGE,TN 37831. MOSCOW MV LOMONOSOV STATE UNIV,DEPT SOIL SCI,MOSCOW 119899,RUSSIA. RP Paustian, K (reprint author), COLORADO STATE UNIV,NAT RESOURCE ECOL LAB,FT COLLINS,CO 80523, USA. RI Post, Wilfred/B-8959-2012; El Husny, Chafic/G-5410-2012; Paustian, Keith/L-7593-2016 NR 128 TC 108 Z9 112 U1 4 U2 34 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0016-7061 J9 GEODERMA JI Geoderma PD SEP PY 1997 VL 79 IS 1-4 BP 227 EP 260 DI 10.1016/S0016-7061(97)00043-8 PG 34 WC Soil Science SC Agriculture GA YE096 UT WOS:A1997YE09600009 ER PT J AU Hinson, DP Flasar, FM Kliore, AJ Schinder, PJ Twicken, JD Herrera, RG AF Hinson, DP Flasar, FM Kliore, AJ Schinder, PJ Twicken, JD Herrera, RG TI Jupiter's ionosphere: Results from the first Galileo radio occultation experiment SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID UPPER-ATMOSPHERE; SCIENCE; THERMOSPHERE; VOYAGER-1; PLANETS AB The Galileo spacecraft passed behind Jupiter on December 8, 1995, allowing the first radio occultation measurements of its ionospheric structure in 16 years. At ingress (24 degrees S, 68 degrees W), the principal peak of electron density is located at an altitude of 900 km above the 1-bar pressure level, with a peak density of 10(5) cm(-3) and a thickness of similar to 200 km. At egress (43 degrees S, 28 degrees W), the main peak is centered near 2000 km altitude, with a peak density of 2x10(4) cm(-3) and a thickness of similar to 1000 km. Two thin layers, possibly forced by upwardly propagating gravity waves, appear at lower altitudes in the ingress profile. This is the first in a two-year series of observations that should help to resolve long-standing questions about Jupiter's ionosphere. C1 NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. CALTECH,JET PROP LAB,PASADENA,CA 91109. CORNELL UNIV,DEPT ASTRON,ITHACA,NY 14853. RP Hinson, DP (reprint author), STANFORD UNIV,CTR RADAR ASTRON,STANFORD,CA 94305, USA. RI Flasar, F Michael/C-8509-2012 NR 24 TC 57 Z9 58 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 SEP 1 PY 1997 VL 24 IS 17 BP 2107 EP 2110 DI 10.1029/97GL01608 PG 4 WC Geosciences, Multidisciplinary SC Geology GA XU257 UT WOS:A1997XU25700001 ER PT J AU Louarn, P Perraut, S Roux, A Gurnett, D Kurth, W Bolton, S AF Louarn, P Perraut, S Roux, A Gurnett, D Kurth, W Bolton, S TI The global plasma environment of Io as inferred from the Galileo plasma wave observations SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID TORUS AB We take advantage of a partial and a total occultation of the jovian radio sources observed during the flyby of Io to characterize the plasma environment of this moon. We show that it presents a strong upstream / downstream asymmetry. A dense plasma structure (n > 5x10(4) cm(-3)) extends far from Io (at least 1000 km) in the wake direction whereas no extended dense region is found upstream. The dense region in the wake could correspond to a the stagnation region of the flow of the corotating plasma. C1 CTR ETUD ENVIRONM TERRESTRES & PLANETAIRES,VELIZY VILLACOUBL,FRANCE. UNIV IOWA,IOWA CITY,IA 52242. CALTECH,JET PROP LAB,PASADENA,CA. RP Louarn, P (reprint author), OBSERV MIDI PYRENEES,14 AV E BELIN,F-31400 TOULOUSE,FRANCE. OI Kurth, William/0000-0002-5471-6202 NR 9 TC 5 Z9 5 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 SEP 1 PY 1997 VL 24 IS 17 BP 2115 EP 2118 DI 10.1029/97GL01850 PG 4 WC Geosciences, Multidisciplinary SC Geology GA XU257 UT WOS:A1997XU25700003 ER PT J AU Bolton, SJ Thorne, RM Gurnett, DA Kurth, WS Williams, DJ AF Bolton, SJ Thorne, RM Gurnett, DA Kurth, WS Williams, DJ TI Enhanced whistler-mode emissions: Signatures of interchange motion in the Io torus SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID PLASMA-WAVE OBSERVATIONS AB During the Galileo inbound pass through the Io torus the plasma wave instrument detected intervals of enhanced whistler-mode emissions. Over two of these intervals in the inner torus (L < 6.5), for which energetic particle data is also available, the flux and pitch angle anisotropy of resonant electrons exhibited a simultaneous enhancement consistent with inward adiabatic transport from a source region in the outer torus. The enhanced electromagnetic emissions are interpreted as a modulation of cyclotron whistler-mode instability above the normal marginally stable state of the plasma. This suggests that the enhanced emissions are a sensitive indicator of rapid inward transport associated with interchange motions in the Io torus. C1 UNIV CALIF LOS ANGELES,DEPT ATMOSPHER SCI,LOS ANGELES,CA 90024. UNIV IOWA,DEPT PHYS & ASTRON,IOWA CITY,IA 52242. JOHNS HOPKINS UNIV,APPL PHYS LAB,LAUREL,MD. RP Bolton, SJ (reprint author), CALTECH,JET PROP LAB,DIV EARTH & SPACE SCI,PASADENA,CA 91109, USA. OI Kurth, William/0000-0002-5471-6202 NR 4 TC 40 Z9 40 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 SEP 1 PY 1997 VL 24 IS 17 BP 2123 EP 2126 DI 10.1029/97GL02020 PG 4 WC Geosciences, Multidisciplinary SC Geology GA XU257 UT WOS:A1997XU25700005 ER PT J AU Thorne, RM Armstrong, TP Stone, S Williams, DJ McEntire, RW Bolton, SJ Gurnett, DA Kivelson, MG AF Thorne, RM Armstrong, TP Stone, S Williams, DJ McEntire, RW Bolton, SJ Gurnett, DA Kivelson, MG TI Galileo evidence for rapid interchange transport in the Io torus SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID JOVIAN MAGNETOSPHERE AB Anomalous plasma signatures were detected by the Galileo particles and fields instruments during the initial transit through the Io torus. These unusual events are characterized by abrupt changes in the magnetic field, enhanced levels of broadband low frequency electromagnetic waves and a pronounced change in both the flux and pitch angle anisotropy of energetic particles. Here we present a coordinated study of one of the events which occurred near 6.03R(J) just after 17:34 UT on December 7, 1995. The available data are consistent with the concept of rapid inward transport, and this is interpreted as the first evidence for the predicted interchange motions in the region exterior to the orbit of Io. Theoretical arguments indicate that the interchanging flux tube is characterized by substantially reduced plasma density, a spatial scale comparable to 10(3) km, and an inward radial velocity comparable to 10(2) km/s. C1 UNIV KANSAS,DEPT PHYS & ASTRON,LAWRENCE,KS 66045. CALTECH,JET PROP LAB,PASADENA,CA 91109. UNIV IOWA,DEPT PHYS & ASTRON,IOWA CITY,IA 52242. UNIV CALIF LOS ANGELES,INST GEOPHYS & PLANETARY PHYS,LOS ANGELES,CA 90095. JOHNS HOPKINS UNIV,APPL PHYS LAB,LAUREL,MD 20723. RP Thorne, RM (reprint author), UNIV CALIF LOS ANGELES,DEPT ATMOSPHER SCI,LOS ANGELES,CA 90095, USA. RI Kivelson, Margaret/I-9019-2012 OI Kivelson, Margaret/0000-0003-3859-8581 NR 14 TC 73 Z9 73 U1 0 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 SEP 1 PY 1997 VL 24 IS 17 BP 2131 EP 2134 DI 10.1029/97GL01788 PG 4 WC Geosciences, Multidisciplinary SC Geology GA XU257 UT WOS:A1997XU25700007 ER PT J AU Barth, CA Hord, CW Stewart, AIF Pryor, WR Simmons, KE McClintock, WE Aiello, JM Naviaux, KL Aiello, JJ AF Barth, CA Hord, CW Stewart, AIF Pryor, WR Simmons, KE McClintock, WE Aiello, JM Naviaux, KL Aiello, JJ TI Galileo ultraviolet spectrometer observations of atomic hydrogen in the atmosphere of Ganymede SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID WATER ICE; SATELLITES; JUPITER; O-2 AB Atomic hydrogen Lyman alpha radiation (121.6 nm) has been measured in emission from the atmosphere of Ganymede with the Galileo ultraviolet spectrometer. An exospheric model with the following parameters has been fit to the observational data: atomic hydrogen density directly above the surface (radius 2634 km) equal to 1.5 x 10(4) atoms cm(-3), scale height 2634 km, exospheric temperature 450 K. A model calculation of the photodissociation of water vapor from surface ice at 146 K is used to obtain the photodissociation rate necessary to supply the hydrogen atoms that are escaping from the exosphere of Ganymede. The calculated escape flux of atomic hydrogen is 7 x 10(8) atoms/cm(2) sec. Two alternate but speculative sources of the atomic hydrogen escaping from Ganymede are photodesorption of water ice by ultraviolet photons in the wavelength range 120.5-186.0 nm and sputtering of water ice by Jupiter's magnetospheric ion plasma. C1 CALTECH,JET PROP LAB,PASADENA,CA 91109. RP Barth, CA (reprint author), UNIV COLORADO,LASP,BOX 590,BOULDER,CO 80309, USA. NR 23 TC 42 Z9 42 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 SEP 1 PY 1997 VL 24 IS 17 BP 2147 EP 2150 DI 10.1029/97GL01927 PG 4 WC Geosciences, Multidisciplinary SC Geology GA XU257 UT WOS:A1997XU25700011 ER PT J AU Frank, LA Paterson, WR Ackerson, KL Bolton, SJ AF Frank, LA Paterson, WR Ackerson, KL Bolton, SJ TI Outflow of hydrogen ions from Ganymede SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID GALILEO SPACECRAFT; WATER ICE; O-2 AB On 6 September 1996 plasma measurements were obtained in the vicinity of Ganymede as the Galileo spacecraft passed by this moon with a closest approach distance of 261 km. Near Ganymede a dense, cold plasma region was found to be embedded in Jupiter's hot plasma sheet. The cold plasmas are hydrogen ions flowing outwards from Ganymede at supersonic speeds. Temperatures and maximum number densities of these ions were about 4 x 10(4) K and 100 /cm(3), respectively. Over Ganymede's polar caps there is strong plasma convection with speeds in the range of 50 km/s, i.e., the flow is not primarily directed parallel to the local magnetic fields. The corresponding potentials across a Ganymede diameter are in excess of 100 kV. The primary source of the hydrogen ions is believed to be the water ices on the surface of Ganymede. However, the anticipated oxygen ion outflow is not present, which implies that the oxygen is left on the moon's surface. The loss of hydrogen from Ganymede's surface is about 3 x 10(9) grams/year. C1 CALTECH,JET PROP LAB,PASADENA,CA 91109. RP Frank, LA (reprint author), UNIV IOWA,DEPT PHYS & ASTRON,VAN ALLEN HALL,IOWA CITY,IA 52242, USA. RI Paterson, William/F-5684-2012 NR 11 TC 35 Z9 35 U1 0 U2 2 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 SEP 1 PY 1997 VL 24 IS 17 BP 2151 EP 2154 DI 10.1029/97GL01744 PG 4 WC Geosciences, Multidisciplinary SC Geology GA XU257 UT WOS:A1997XU25700012 ER PT J AU Kivelson, MG Khurana, KK Coroniti, FV Joy, S Russell, CT Walker, RJ Warnecke, J Bennett, L Polanskey, C AF Kivelson, MG Khurana, KK Coroniti, FV Joy, S Russell, CT Walker, RJ Warnecke, J Bennett, L Polanskey, C TI The magnetic field and magnetosphere of Ganymede SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID GALILEO SPACECRAFT AB Within Jupiter's magnetosphere, Ganymede's magnetic field creates a mini-magnetosphere. We show that the magnetic field measured during Galileo's second pass by Ganymede, with closest approach at low altitude almost directly over the moon's polar cap, can be understood to a large measure in terms of the structure of a vacuum superposition model of a uniform field and a Ganymede-centered dipole field. Departures from the simple model can be attributed principally to magnetopause currents. We show that the orientation of the observed magnetopause normal is qualitatively consistent with expectations from the vacuum superposition model. The magnetopause currents inferred from the inbound boundary crossing are closely related to expected values, and the magnetic structure of the boundary is similar to that observed at the magnetopause of Earth. We use the vacuum magnetic field model to infer the magnetic field near Ganymede's surface, and thereby predict the particle loss cones that should be present along the spacecraft trajectory. By mapping a fraction of the corotation electric field into the polar cap, we determine expected flow velocities near closest approach to Ganymede as a function of reconnection efficiency. We conclude by discussing prospects for measurements on Galileo's remaining passes by Ganymede. C1 UNIV CALIF LOS ANGELES,DEPT EARTH & SPACE SCI,LOS ANGELES,CA 90024. UNIV CALIF LOS ANGELES,DEPT PHYS,LOS ANGELES,CA 90024. CALTECH,JET PROP LAB,PASADENA,CA. RP Kivelson, MG (reprint author), UNIV CALIF LOS ANGELES,INST GEOPHYS & PLANETARY PHYS,LOS ANGELES,CA 90024, USA. RI Kivelson, Margaret/I-9019-2012; OI Kivelson, Margaret/0000-0003-3859-8581; Russell, Christopher/0000-0003-1639-8298 NR 9 TC 70 Z9 70 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 SEP 1 PY 1997 VL 24 IS 17 BP 2155 EP 2158 DI 10.1029/97GL02201 PG 4 WC Geosciences, Multidisciplinary SC Geology GA XU257 UT WOS:A1997XU25700013 ER PT J AU Frank, LA Paterson, WR Ackerson, KL Bolton, SJ AF Frank, LA Paterson, WR Ackerson, KL Bolton, SJ TI Low-energy electron measurements at Ganymede with the Galileo spacecraft: Probes of the magnetic topology SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article AB During the close flyby of Ganymede by the Galileo spacecraft on 6 September 1996 a plasma analyzer was used to obtain comprehensive measurements of the thermal electron plasmas in the vicinity of this moon. Our initial analyses are directed toward the character of energy influxes into Ganymede's polar caps and the pitch angle distributions for warm electrons in the energy range of 70 eV to 4.5 keV. The source of these electrons is Jupiter's plasma sheet within which Ganymede was embedded during the flyby. These electrons were present along the entire trajectory and provide the opportunity to use their pitch angle distributions with respect to the magnetic field in order to investigate the magnetic field topology at Ganymede. Observations of the loss cones for these pitch angle distributions are a simple means of determining whether or not a given magnetic field line intersects the moon's surface. It is found that the observed pitch angle distributions are inconsistent with the current magnetostatic model for the magnetic fields in the vicinity of Ganymede. Thus a major revision of this model is required that accounts for the contributions of the plasma dynamical interaction in order to achieve a more accurate assessment of an intrinsic magnetic moment in the interior of this moon. In addition, the electron energy fluxes into the polar cap at the time of flyby were measured to be about 1 erg/cm(2)-s, or a total of approximately 5 x 10(16) ergs/s over each polar cap available for excitation and ionization of any atmosphere near the moon's surface. C1 CALTECH,JET PROP LAB,PASADENA,CA 91109. RP Frank, LA (reprint author), UNIV IOWA,DEPT PHYS & ASTRON,VAN ALLEN HALL,IOWA CITY,IA 52242, USA. RI Paterson, William/F-5684-2012 NR 3 TC 18 Z9 18 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 SEP 1 PY 1997 VL 24 IS 17 BP 2159 EP 2162 DI 10.1029/97GL01632 PG 4 WC Geosciences, Multidisciplinary SC Geology GA XU257 UT WOS:A1997XU25700014 ER PT J AU Williams, DJ Mauk, BH McEntire, RW Roelof, EC Armstrong, TP Wilken, B Roederer, JG Krimigis, SM Fritz, TA Lanzerotti, LJ Murphy, N AF Williams, DJ Mauk, BH McEntire, RW Roelof, EC Armstrong, TP Wilken, B Roederer, JG Krimigis, SM Fritz, TA Lanzerotti, LJ Murphy, N TI Energetic particle signatures at Ganymede: Implications for Ganymede's magnetic field SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID GALILEO SPACECRAFT AB The second encounter of the Galileo satellite with the Galilean moon Ganymede provided energetic particle measurements showing effects due to the presence of that moon. Jovian corotation signatures, present on approach to and departure from the Ganymede system, suddenly become much smaller when Galileo enters what has been termed Ganymede's magnetosphere. The location of these transitions agrees with magnetopause crossings identified by the magnetometer and plasma wave instruments. In Ganymede's magnetosphere, energetic ion and electron distributions display loss cone signatures whenever the Energetic Particles Detector (EPD) views along the magnetic field line. The loss cone measurements are used to estimate Ganymede's surface magnetic field along the satellite track. The results agree with model projections to Ganymede's polar cap and support the existence of a Ganymede-intrinsic magnetic field. An evolution from Single to double loss cone also occurs with increasing electron energy. C1 UNIV KANSAS,DEPT PHYS & ASTRON,LAWRENCE,KS 66045. BOSTON UNIV,CTR SPACE PHYS,BOSTON,MA 02215. JET PROP LAB,PASADENA,CA 91103. UNIV ALASKA,INST GEOPHYS,FAIRBANKS,AK 99775. BELL LAB INNOVAT,LUCENT TECHNOL,MURRAY HILL,NJ 07974. MPAE,KATLENBURG DUHM,GERMANY. RP Williams, DJ (reprint author), JOHNS HOPKINS UNIV,APPL PHYS LAB,JOHNS HOPKINS RD,LAUREL,MD 20723, USA. RI Mauk, Barry/E-8420-2017; OI Mauk, Barry/0000-0001-9789-3797; Roederer, Juan/0000-0002-8042-5150 NR 3 TC 36 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 SEP 1 PY 1997 VL 24 IS 17 BP 2163 EP 2166 DI 10.1029/97GL01931 PG 4 WC Geosciences, Multidisciplinary SC Geology GA XU257 UT WOS:A1997XU25700015 ER PT J AU Kurth, WS Gurnett, DA Roux, A Bolton, SJ AF Kurth, WS Gurnett, DA Roux, A Bolton, SJ TI Ganymede: A new radio source SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID TERRESTRIAL KILOMETRIC RADIATION; NONTHERMAL CONTINUUM; GALILEO SPACECRAFT; MAGNETOSPHERE; EMISSIONS; EARTH AB Observations by the Galileo plasma wave receiver during the first two flybys of Ganymede revealed that this Jovian moon is the source of narrowband electromagnetic radio waves, making it the only satellite in the solar system known to generate non-thermal radio emissions. The emissions are the result of mode-coupling from electrostatic electron cyclotron emissions near the upper hybrid resonance frequency, similar to non-thermal continuum radiation found at the known magnetized planets. C1 UNIV VERSAILLES, CTR ETUD ENVIRONM TERRESTE & PLANETAIRES, VELIZY VILLACOUBLAY, FRANCE. CALTECH, JET PROP LAB, PASADENA, CA 91109 USA. RP Kurth, WS (reprint author), UNIV IOWA, DEPT PHYS & ASTRON, IOWA CITY, IA 52242 USA. OI Kurth, William/0000-0002-5471-6202 NR 16 TC 24 Z9 24 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD SEP 1 PY 1997 VL 24 IS 17 BP 2167 EP 2170 DI 10.1029/97GL02249 PG 4 WC Geosciences, Multidisciplinary SC Geology GA XU257 UT WOS:A1997XU25700016 ER PT J AU Grun, E Kruger, H Dermott, S Fechtig, H Graps, AL Zook, HA Gustafson, BA Hamilton, DP Hanner, MS Heck, A Horanyi, M Kissel, J Lindblad, BA Linkert, D Linkert, G Mann, I McDonnell, JAM Morfill, GE Polanskey, C Schwehm, G Srama, R AF Grun, E Kruger, H Dermott, S Fechtig, H Graps, AL Zook, HA Gustafson, BA Hamilton, DP Hanner, MS Heck, A Horanyi, M Kissel, J Lindblad, BA Linkert, D Linkert, G Mann, I McDonnell, JAM Morfill, GE Polanskey, C Schwehm, G Srama, R TI Dust measurements in the Jovian magnetosphere SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID JUPITER; GALILEO; DETECTOR; RING AB Dust measurements have been obtained with the dust detector onboard the Galileo spacecraft inside a distance of about 60R(J) from Jupiter (Jupiter radius, R-J = 71, 492 km) during two periods of about 8 days around Galileo's closest approaches to Ganymede on 27 June and on 6 Sept 1996. The impact rate of submicrometer-sized particles fluctuated by a factor of several hundred with a period of about 10 hours, implying that their trajectories are strongly affected by the interaction with the Jovian magnetic field. Concentrations of small dust impacts were detected at the times of Ganymede closest approaches that could be secondary ejecta particles generated upon impact of other particles onto Ganymede's surface. Micrometer-sized dust particles, which could be on bound orbits about Jupiter, are concentrated in the inner Jovian system inside about 20R(J) from Jupiter. C1 UNIV FLORIDA,GAINESVILLE,FL 32611. STANFORD UNIV,CTR SPACE SCI & ASTROPHYS,STANFORD,CA 94305. NASA,LYNDON B JOHNSON SPACE CTR,HOUSTON,TX 77058. UNIV MARYLAND,COLLEGE PK,MD 20742. CALTECH,JET PROP LAB,PASADENA,CA 91109. UNIV COLORADO,ATMOSPHER & SPACE PHYS LAB,BOULDER,CO 80309. LUND OBSERV,S-22100 LUND,SWEDEN. MAX PLANCK INST AERON,D-37191 KATLENBURG DUHM,GERMANY. UNIV KENT,CANTERBURY CT2 7NR,KENT,ENGLAND. MAX PLANCK INST EXTRATERR PHYS,D-85740 GARCHING,GERMANY. EUROPEAN SPACE AGCY,EUROPEAN SPACE RES & TECHNOL CTR,NL-2200 AG NOORDWIJK,NETHERLANDS. RP Grun, E (reprint author), MAX PLANCK INST KERNPHYS,SAUPFERCHECKWEG 1,D-69117 HEIDELBERG,GERMANY. RI Gustafson, Bo/B-9526-2011; OI Horanyi, Mihaly/0000-0002-5920-9226 NR 12 TC 26 Z9 26 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 SEP 1 PY 1997 VL 24 IS 17 BP 2171 EP 2174 DI 10.1029/97GL01593 PG 4 WC Geosciences, Multidisciplinary SC Geology GA XU257 UT WOS:A1997XU25700017 ER PT J AU Zuber, MT Smith, DE AF Zuber, MT Smith, DE TI Topography of the lunar south polar region: Implications for the size and location of permanently shaded areas SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID CLEMENTINE MISSION; MOON; MERCURY; ICE; STABILITY; MARS AB We analyze Clementine altimetry to constrain the size and location of proposed permanently shadowed regions in the vicinity of the lunar south pole. Long and short wavelength topography in the vicinity of the pole, in combination with measurements of depths of well-preserved craters and basins and the lunar topographic power spectrum, have direct bearing on the nature of elevations in the south polar region. A criterion based on geometric considerations and altimetry demonstrates that the existence of permanent shadowing is not very sensitive to the elevation of the south pole. In addition, permanent shadowing cannot be consequence of large structures such as the South Pole-Aitken Basin and/or a 300-km degraded polar basin. Perennially dark regions, if they exist, are most likely associated with craters or other axisymmetric features with diameters of at most 80 km centered at the pole. For structures displaced 2 degrees from the pole the maximum allowable diameter decreases to similar to 30 km. C1 NASA, GODDARD SPACE FLIGHT CTR, TERR PHYS LAB, GREENBELT, MD 20771 USA. RP Zuber, MT (reprint author), MIT, DEPT EARTH ATMOSPHER & PLANETARY SCI, CAMBRIDGE, MA 02139 USA. NR 20 TC 11 Z9 12 U1 0 U2 2 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD SEP 1 PY 1997 VL 24 IS 17 BP 2183 EP 2186 DI 10.1029/97GL02111 PG 4 WC Geosciences, Multidisciplinary SC Geology GA XU257 UT WOS:A1997XU25700020 ER PT J AU Gurevich, GS Krueger, AJ AF Gurevich, GS Krueger, AJ TI Optimization of TOMS wavelength channels for ozone and sulfur dioxide retrievals SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID MAPPING SPECTROMETER AB The wavelengths of the TOMS channels can be optimized to minimize the effects of random measurement errors on simultaneous ozone and sulfur dioxide retrievals. The inversion matrix is extremely sensitive to the spectral position of the channels due to mathematical singularities related to O-3 and SO2 absorption coefficients. None of the current sets of wavelengths in the TOMS instruments are optimal for the low latitude retrievals considered. Minor adjustment of the wavelengths can reduce retrieval errors by more than a factor of two. C1 NASA,GODDARD SPACE FLIGHT CTR,ATMOSPHERES LAB,GREENBELT,MD 20771. RP Gurevich, GS (reprint author), UNIV MARYLAND,DEPT METEOROL,UNIV SPACE RES ASSOC,COLLEGE PK,MD 20742, USA. NR 4 TC 12 Z9 12 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 SEP 1 PY 1997 VL 24 IS 17 BP 2187 EP 2190 DI 10.1029/97GL02098 PG 4 WC Geosciences, Multidisciplinary SC Geology GA XU257 UT WOS:A1997XU25700021 ER PT J AU Wilson, RM AF Wilson, RM TI Downward trends in the frequency of intense Atlantic hurricanes during the past 5 decades - Comment SO GEOPHYSICAL RESEARCH LETTERS LA English DT Editorial Material RP Wilson, RM (reprint author), NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,SPACE SCI LAB,HUNTSVILLE,AL 35812, USA. NR 7 TC 7 Z9 7 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 SEP 1 PY 1997 VL 24 IS 17 BP 2203 EP 2204 DI 10.1029/97GL02108 PG 2 WC Geosciences, Multidisciplinary SC Geology GA XU257 UT WOS:A1997XU25700025 ER PT J AU Watkins, MM Eanes, RJ AF Watkins, MM Eanes, RJ TI Observations of tidally coherent diurnal and semidiurnal variations in the geocenter SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID EARTH AB The center of mass of the Earth, about which a satellite orbits, is determined by the mass distribution of the solid Earth (including the Earth's interior), the oceans, and the atmosphere. The tracking sites, however, are all located on the lithosphere only, and so the network origin will not generally coincide with the center of mass. Changes in the vector offset between these two points, referred to as apparent geocenter motion, are due to global scale movement of mass. In this study we have extended the approach used by space geodetic techniques for determination of tidally coherent nearly diurnal and semidiurnal variations in the Earth's orientation to include geocenter variations due to ocean tides. We demonstrate the weaker observability of nearly diurnal retrograde motions in x and y, and hence the utility of their separation from the other equatorial terms. We find statistically significant terms at the 99.5% level due to O-1, P-1, K-1, and M-2. The solutions, which indicate geocenter motions at the few millimeter level per tide, compare well with predicted values from theoretical ocean tide models and from TOPEX/Poseidon radar altimetry. C1 UNIV TEXAS,CTR SPACE RES,AUSTIN,TX 78712. RP Watkins, MM (reprint author), CALTECH,JET PROP LAB,4800 OAK GROVE DR,MS 238-600,PASADENA,CA 91109, USA. NR 9 TC 20 Z9 21 U1 4 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 SEP 1 PY 1997 VL 24 IS 17 BP 2231 EP 2234 DI 10.1029/97GL52059 PG 4 WC Geosciences, Multidisciplinary SC Geology GA XU257 UT WOS:A1997XU25700033 ER PT J AU Connell, JW Smith, JG Hergenrother, PM AF Connell, JW Smith, JG Hergenrother, PM TI Properties of imide oligomers containing pendent phenylethynyl groups SO HIGH PERFORMANCE POLYMERS LA English DT Article ID POLYIMIDE OLIGOMERS; ANHYDRIDES AB As part of a programme to develop high-performance/high-temperature structural resins for aeronautical applications, imide oligomers containing pendent phenylethynyl groups were prepared, characterized, thermally cured and the cured resins evaluated as films, mouldings, adhesives and composites matrices. lnitially a diamine containing a pendent phenylethynyl group (3,5-diamino-4'-phenylethynylbenzophenone) was prepared and characterized. This compound was used to make amide acid and subsequently imide oligomers containing pendent phenylethynyl groups. In order to control the distance between reactive sites, the concentration of pendent phenylethynyl groups was varied randomly along the oligomer backbone. The amide acid oligomers in N-methyl-2-pyrrolidinone were processed into thin films, adhesive tape, carbon fibre prepreg and also converted into imide powder. After initial screening work was performed on unoriented thin films, imidized powders and neat resin mouldings to assess glass transition temperature, mechanical properties (tensile properties and fracture toughness), melt dow behaviour and processability, one particular formulation was scaled up for more comprehensive evaluation. This imide oligomer containing pendent phenylthynyl groups was fabricated into adhesive and composite specimens under 1.4 MPa for 1 h at 350-371 degrees C. Excellent mechanical properties were obtained at room temperature and 177 degrees C. The properties of this material are compared with those of a material of similar composition and molecular weight containing only terminal phenylethynyl groups. RP Connell, JW (reprint author), NASA,LANGLEY RES CTR,HAMPTON,VA 23681, USA. NR 22 TC 24 Z9 26 U1 3 U2 8 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 SEP PY 1997 VL 9 IS 3 BP 309 EP 321 DI 10.1088/0954-0083/9/3/009 PG 13 WC Polymer Science SC Polymer Science GA XZ207 UT WOS:A1997XZ20700009 ER PT J AU Boston, HG Reddy, VS Cassidy, PE Fitch, JW Stoakley, D StClair, A AF Boston, HG Reddy, VS Cassidy, PE Fitch, JW Stoakley, D StClair, A TI New aromatic diacids containing the trifluoromethyl group and their polyamides SO HIGH PERFORMANCE POLYMERS LA English DT Article AB A series of new fluorinated, high-temperature polymers has been prepared from 1,1,-bis(p-carboxyphenyl)-2,2,2-trifluoroethanol (3FOH). This diacid was synthesized by oxidation of 1,1-di(p-tolyl)-2,2,2-trifluoroethanol, which was obtained from p-bromotoluene and ethyl trifluoroacetate. The 3FOH was also reacted with dimethyl sulphate to yield 1-methoxy-1,1-bis(p-carboxyphenyl)-2,2,2-trifluoroethane (3FM), and with SOCl2 to produce 1-chloro-1,1-bis(p-chloroformylphenyl)-2,2,2-trifluoroethane (3FCl). These two diacids, as the acid chlorides, were polymerized with six aromatic and four aliphatic diamines to produce polyamides which had viscosities ranging from 0.32 to 1.52 dl g(-1), thermal stabilities up to 518 degrees C in nitrogen and glass transition temperatures from 165 degrees C to 337 degrees C. The dielectric constants of these polyamides ranged from 2.64 to 2.99. The 3FM- and 3FCl-containing polyamides were compared with the 6F (hexafluoroisopropylidene) analogues and found to be somewhat less thermally stable and had equal or lower T(g)s. C1 NASA,LANGLEY RES CTR,HAMPTON,VA 23665. RP Boston, HG (reprint author), SW TEXAS STATE UNIV,DEPT CHEM,POLYMER RES GRP,SAN MARCOS,TX 78666, USA. NR 7 TC 0 Z9 0 U1 0 U2 0 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 SEP PY 1997 VL 9 IS 3 BP 323 EP 332 DI 10.1088/0954-0083/9/3/010 PG 10 WC Polymer Science SC Polymer Science GA XZ207 UT WOS:A1997XZ20700010 ER PT J AU Olkin, CB Elliot, JL Hammel, HB Cooray, AR McDonald, SW Foust, JA Bosh, AS Buie, MW Millis, RL Wasserman, LH Dunham, EW Young, LA Howell, RR Hubbard, WB Hill, R Marcialis, RL McDonald, JS Rank, DM Holbrook, JC Reitsema, HJ AF Olkin, CB Elliot, JL Hammel, HB Cooray, AR McDonald, SW Foust, JA Bosh, AS Buie, MW Millis, RL Wasserman, LH Dunham, EW Young, LA Howell, RR Hubbard, WB Hill, R Marcialis, RL McDonald, JS Rank, DM Holbrook, JC Reitsema, HJ TI The thermal structure of Triton's atmosphere: Results from the 1993 and 1995 occultations SO ICARUS LA English DT Article ID NITROGEN; MODEL; CANDIDATES; NEPTUNE; TEMPERATURE; DYNAMICS; CHARON; PLUTO; CYCLE AB This paper presents new results about Triton's atmospheric structure from the analysis of all ground-based stellar occultation data recorded to date, including one single-chord occultation recorded on 1993 July 10 and nine occultation lightcurves from the double-star event on 1995 August 14. These stellar occultation observations made both in the visible and in the infrared have good spatial coverage of Triton, including the first Triton central-flash observations, and are the first data to probe the altitude level 20-100 km on Triton. The small-planet lightcurve model of J. L. Elliot and L. A, Young (1992, Astron. J. 103, 991-1015) was generalized to include stellar flux refracted by the far limb, and then fitted to the data. Values of the pressure, derived from separate immersion and emersion chords, show no significant trends with latitude, indicating that Triton's atmosphere is spherically symmetric at similar to 50-km altitude to within the error of the measurements; however, asymmetry observed in the central flash indicates the atmosphere is not homogeneous at the lowest levels probed (similar to 20-km altitude). From the average of the 1995 occultation data, the equivalent-isothermal temperature of the atmosphere is 47 +/- 1 K and the atmospheric pressure at 1400-km radius (similar to 50-km altitude) is 1.4 +/- 0.1 mu bar. Both of these are not consistent with a model based on Voyager UVS and RSS observations in 1989 (D. F. Strobel, X. Zhu, M. E. Summers, and M. H. Stevens, 1996, Icarus 120, 266-289). The atmospheric temperature from the occultation is 5 K colder than that predicted by the model and the observed pressure is a factor of 1.8 greater than the model. In our opinion, the disagreement in temperature and pressure is probably due to modeling problems at the microbar level, since measurements at this level have not previously been made. Alternatively, the difference could be due to seasonal change in Triton's atmospheric structure. (C) 1997 Academic Press. C1 MIT, DEPT EARTH ATMOSPHER & PLANETARY SCI, CAMBRIDGE, MA 02139 USA. NASA, AMES RES CTR, MOFFETT FIELD, CA 94035 USA. UNIV WYOMING, DEPT PHYS & ASTRON, LARAMIE, WY 82071 USA. UNIV ARIZONA, LUNAR & PLANETARY LAB, TUCSON, AZ 85721 USA. PIMA COMMUNITY COLL, TUCSON, AZ 85709 USA. SETI INST, MT VIEW, CA 94043 USA. UNIV CALIF SANTA CRUZ, LICK OBSERV, SANTA CRUZ, CA 95064 USA. BALL AEROSP SYST GRP, BOULDER, CO 80306 USA. MIT, DEPT PHYS, CAMBRIDGE, MA 02139 USA. LOWELL OBSERV, FLAGSTAFF, AZ 86001 USA. NR 44 TC 18 Z9 18 U1 0 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 SEP PY 1997 VL 129 IS 1 BP 178 EP 201 DI 10.1006/icar.1997.5757 PG 24 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YD817 UT WOS:A1997YD81700012 ER PT J AU Duxbury, NS Brown, RH Anicich, V AF Duxbury, NS Brown, RH Anicich, V TI Condensation of nitrogen: Implications for Pluto and Triton SO ICARUS LA English DT Article ID POLAR CAPS; SURFACE; ICES; TEMPERATURE; BALANCE; CHARON; MODELS; FROST AB We have observed in the laboratory that nitrogen condenses initially as a transparent layer if the deposition rate is less than about 3 mu m/hr. To correlate our laboratory results with the Voyager observations of Triton and ground-based observations of Pluto, me have calculated the nitrogen deposition rates on these bodies. The maximum deposition rate for Pluto (with 40 K icy surface temperature) is calculated to be about 1.65 mu m/hr and for Triton is approximate to 1.38 mu m/hr at 38 K. This implies that nitrogen on these bodies may preferentially condense as a transparent layer. Voyager 2 observations in August 1989 revealed that Triton's northern hemisphere had an overall lower albedo than the southern hemisphere. This was surprising since at that time deposition of fresh Nz frost should have taken place over most of Triton's northern hemisphere (subsolar point was 45 degrees S). In contrast, the subliming southern cap was seen as a bright feature. Our new approach to this problem is based on the combination of the energy balance calculations and the laboratory results. We explain the darker northern hemisphere by the condensation of an initially transparent layer on a dark substrate, which might be dark organics produced by UV photolysis of CH4 ice. The bright southern cap can be a result of N-2 shattering due to the earlier passage of the cubic-hexagonal phase transition fronts. If there is a similar puzzling north/south albedo asymmetry on Pluto, as indicated by two independent sets of observations (hi. W. Buie, D. J. Tholen, and K. Horne, 1992, Icarus 97, 211-227; E. F. Young and R. P. Binzel, 1993, Icarus 102, 134-149), our results offer an explanation for it. We also infer an original grain size of N-2 ice on Triton and, possibly, on Pluto. The role of impurities is discussed. (C) 1997 Academic Press. C1 UNIV ARIZONA,TUCSON,AZ. RP Duxbury, NS (reprint author), CALTECH,JET PROP LAB,4800 OAK GROVE DR,PASADENA,CA 91109, USA. NR 32 TC 7 Z9 7 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 0019-1035 J9 ICARUS JI Icarus PD SEP PY 1997 VL 129 IS 1 BP 202 EP 206 DI 10.1006/icar.1997.5766 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA YD817 UT WOS:A1997YD81700013 ER PT J AU Fiorini, P Seraji, H Long, MK AF Fiorini, P Seraji, H Long, MK TI A PC-based configuration controller for dexterous 7-DOF arms SO IEEE ROBOTICS & AUTOMATION MAGAZINE LA English DT Article; Proceedings Paper CT 1996 IEEE International Conference on Robotics and Automation CY APR 22-28, 1996 CL MINNEAPOLIS, MN SP IEEE, Robot & Automat Soc DE dexterous manipulators; robotic control; PC-based controllers; motion and force control; operator interface ID REDUNDANT MANIPULATORS AB This implementation of a Configuration Controller for a dexterous 7-DOF manipulator on an IBM-compatible personal computer represents a step toward high-performance robotic controllers designed with consumer electronics, The system has the capability for 3D graphical animation of the arm motion, which is performed on a separate single-board computer interfaced to the PC, Several experiments have shown control performance comparable to that obtained with more expensive computing platforms. RP Fiorini, P (reprint author), CALTECH,JET PROP LAB,4800 OAK GROVE DR,PASADENA,CA 91109, USA. RI Fiorini, Paolo/A-2603-2012 NR 15 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 1070-9932 J9 IEEE ROBOT AUTOM MAG JI IEEE Robot. Autom. Mag. PD SEP PY 1997 VL 4 IS 3 BP 30 EP 38 DI 10.1109/100.618021 PG 9 WC Automation & Control Systems; Robotics SC Automation & Control Systems; Robotics GA XY925 UT WOS:A1997XY92500006 ER PT J AU Hunt, LR Meyer, G Su, RJ AF Hunt, LR Meyer, G Su, RJ TI Driven dynamics of time-varying linear systems SO IEEE TRANSACTIONS ON AUTOMATIC CONTROL LA English DT Article DE inversion; output tracking; time-varying; linear ID OUTPUT TRACKING AB Motivated by applications to automatic control of aircraft, we consider the problem of output tracking for time-varying linear systems, The signals to be tracked are bounded on (-infinity, infinity), and our goal is to compute bounded controls and bounded state trajectories that result in the desired tracking. A convolution integral representation for the desired solution is given in the literature, and we show that certain integrability assumptions can be eliminated from the associated results. Despite the fact that our system is time varying and our signals do not necessarily have Fourier transforms in the classical sense, we show that computations can be carried out using ''generalized'' Fourier transforms. We also consider an output tracking problem in which the driven dynamical equation is an ordinary differential equation. C1 NASA, AMES RES CTR, MOFFETT FIELD, CA 94035 USA. UNIV COLORADO, DEPT ELECT & COMP ENGN, BOULDER, CO 80309 USA. RP Hunt, LR (reprint author), UNIV TEXAS, CTR ENGN MATH, RICHARDSON, TX 75083 USA. NR 13 TC 5 Z9 5 U1 0 U2 0 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI PISCATAWAY PA 445 HOES LANE, PISCATAWAY, NJ 08855-4141 USA SN 0018-9286 J9 IEEE T AUTOMAT CONTR JI IEEE Trans. Autom. Control PD SEP PY 1997 VL 42 IS 9 BP 1313 EP 1317 DI 10.1109/9.623100 PG 5 WC Automation & Control Systems; Engineering, Electrical & Electronic SC Automation & Control Systems; Engineering GA XW212 UT WOS:A1997XW21200019 ER PT J AU Arabshahi, P Marks, RJ Oh, S Caudell, TP Choi, JJ Song, BG AF Arabshahi, P Marks, RJ Oh, S Caudell, TP Choi, JJ Song, BG TI Pointer adaptation and pruning of min-max fuzzy inference and estimation SO IEEE TRANSACTIONS ON CIRCUITS AND SYSTEMS II-ANALOG AND DIGITAL SIGNAL PROCESSING LA English DT Article DE adaptive estimation; adaptive systems; fuzzy control; fuzzy sets; fuzzy systems; intelligent systems; knowledge-based systems AB A new technique for adaptation of fuzzy membership functions in a fuzzy inference system is proposed, The painter technique relies upon the isolation of the specific membership functions that contributed to the final decision, followed by the updating of these functions' parameters using steepest descent, The error measure used is thus backpropagated from output to input, through the min and max operators used during the inference stage, This occurs because the operations of min and max are continuous differentiable functions and, therefore, can be placed in a chain of partial derivatives for steepest descent backpropagation adaptation, Interestingly, the partials of min and max act as ''pointers'' with the result that only the function that gave rise to the min or max is adapted; the others are not, To illustrate, let alpha = max [beta(1), beta(2), ..., beta(N)]. Then partial derivative alpha/partial derivative beta(n) = 1 when beta(n) is the maximum and is otherwise zero, We apply this property to the fine tuning of membership functions of fuzzy min-max decision processes and illustrate with an estimation example, The adaptation process can reveal the need for reducing the number of membership functions, Under the assumption that the inference surface is in some sense smooth, the process of adaptation can reveal overdetermination of the fuzzy system in two ways, First, if two membership functions come sufficiently close to each other, they can be fused into a single membership function, Second, if a membership function becomes too narrow, it can be deleted, In both cases, the number of fuzzy IF-THEN rules is reduced, In certain cases, the overall performance of the fuzzy system ran be improved by this adaptive pruning. C1 UNIV WASHINGTON,DEPT ELECT ENGN,SEATTLE,WA 98195. NEOPATH INC,REDMOND,WA 98052. UNIV NEW MEXICO,DEPT ELECT & COMP ENGN,ALBUQUERQUE,NM 87131. BOEING COMP SERV CO,RES & TECHNOL,SEATTLE,WA 98124. RP Arabshahi, P (reprint author), CALTECH,JET PROP LAB,4800 OAK GROVE DR,PASADENA,CA 91109, USA. NR 28 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 1057-7130 J9 IEEE T CIRCUITS-II JI IEEE Trans. Circuits Syst. II-Analog Digit. Signal Process. PD SEP PY 1997 VL 44 IS 9 BP 696 EP 709 DI 10.1109/82.624992 PG 14 WC Engineering, Electrical & Electronic SC Engineering GA XU989 UT WOS:A1997XU98900002 ER PT J AU Tilton, JC Manohar, M AF Tilton, JC Manohar, M TI Preserving radiometric resolution in remotely sensed data with lossy compression SO IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING LA English DT Article DE data acquisition; data compression; image coding; image communication; satellite applications ID IMAGES AB Recent advances in imaging technology make it possible to obtain remotely sensed imagery data of the Earth at high spatial, spectral, and radiometric resolutions, The rate at which the data is collected from these satellites can far exceed the channel capacity of the data downlink. Reducing the data rate to within the channel capacity can often require painful trade-offs in which certain scientific returns are sacrificed for the sake of others, We focus here on the case where radiometric resolution is sacrificed by dropping a specified number of lower order bits (LOB) from each data pixel, To limit the number LOB's dropped, we also compress the remaining bits using lossless compression, We call this approach ''truncation followed by lossless compression'' or TLLC, We then demonstrate the suboptimality of this TLLC approach by comparing it with the direct application of a more effective lossy compression technique based on the JPEG algorithm, This comparison demonstrates that, for a given channel rate, the method based on JPEG lossy compression better preserves radiometric resolution than does TLLC. C1 BOWIE STATE UNIV,DEPT COMP SCI,BOWIE,MD 20715. RP Tilton, JC (reprint author), NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771, USA. NR 11 TC 1 Z9 1 U1 0 U2 0 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 SN 0196-2892 J9 IEEE T GEOSCI REMOTE JI IEEE Trans. Geosci. Remote Sensing PD SEP PY 1997 VL 35 IS 5 BP 1171 EP 1176 DI 10.1109/36.628784 PG 6 WC Geochemistry & Geophysics; Engineering, Electrical & Electronic; Remote Sensing; Imaging Science & Photographic Technology SC Geochemistry & Geophysics; Engineering; Remote Sensing; Imaging Science & Photographic Technology GA XW390 UT WOS:A1997XW39000008 ER PT J AU Yueh, SH Wilson, WJ Li, FK Nghiem, SV Ricketts, WB AF Yueh, SH Wilson, WJ Li, FK Nghiem, SV Ricketts, WB TI Polarimetric brightness temperatures of sea surfaces measured with aircraft K- and Ka-band radiometers SO IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING LA English DT Article DE microwave radiometry; polarimetry; polarization; radiometry; remote sensing; sea surface; wind ID EMISSION; WAVES AB Dual-frequency (19 and 37 GHz), multi-incidence measurements of the Stokes parameters of sea surface microwave emission are reported in this paper, A series of aircraft polarimetric radiometer flights were carried out over the National Data Buoy Center (NDBC) moored buoys deployed off the northern California coast in July and August 1994, Measured radiometric temperatures showed a few Kelvin azimuth modulations in all Stokes parameters with respect to the wind direction, Wind directional signals observed in the 37-GHz channel were similar to those in the 19-GHz channel, This indicates that the wind direction signals in sea surface brightness temperatures have a weak frequency dependence in the range of 19-37 GHz. Harmonic coefficients of the wind direction signals were derived from experimental data versus incidence angle, It was found that the first harmonic coefficients, which are caused by the up and downwind asymmetric surface features, had a small increasing trend with the incidence angle, In contrast, the second harmonic coefficients, caused by the up and crosswind asymmetry, showed significant variations in T-v and U data, with a sign change when the incidence angle increased from 45 degrees to 65 degrees. Besides the first three Stokes parameters, the fourth Stokes parameter, V, which had never been measured before for sea surfaces, was measured using our 19-GHz channel, The Stokes parameter V an odd symmetry just like that of the third Stokes parameter U, and increases with increasing incidence angles, In summary, sea surface features created by surface winds are anisotropic in azimuth direction and modulate all Stokes parameters of sea surface microwave brightness temperatures by as large as a few Kelvin in the range of incidence angles from 45 degrees to 65 degrees applicable to spaceborne observations. RP Yueh, SH (reprint author), CALTECH,JET PROP LAB,4800 OAK GROVE DR,PASADENA,CA 91109, USA. NR 26 TC 46 Z9 52 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 0196-2892 J9 IEEE T GEOSCI REMOTE JI IEEE Trans. Geosci. Remote Sensing PD SEP PY 1997 VL 35 IS 5 BP 1177 EP 1187 DI 10.1109/36.628785 PG 11 WC Geochemistry & Geophysics; Engineering, Electrical & Electronic; Remote Sensing; Imaging Science & Photographic Technology SC Geochemistry & Geophysics; Engineering; Remote Sensing; Imaging Science & Photographic Technology GA XW390 UT WOS:A1997XW39000009 ER PT J AU Jackson, TJ ONeill, PE Swift, CT AF Jackson, TJ ONeill, PE Swift, CT TI Passive microwave observation of diurnal surface soil moisture SO IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING LA English DT Article ID SAMPLING DEPTH; EMISSION; PROFILE AB Microwave radiometers operating at low frequencies are sensitive to surface soil moisture changes, Few studies have been conducted that have involved multifrequency observations at frequencies low enough to measure a significant soil depth and not be attenuated by the vegetation cover. Another unexplored aspect of microwave observations at low frequencies has been the impact of diurnal variations of the soil moisture and temperature on brightness temperature, In this investigation, observations were made using a dual frequency radiometer (1.4 and 2.65 GHz) over bare soil and corn for extended periods in 1994. Comparisons of emissivity and volumetric soil moisture at four depths for bare soils showed that there was a clear correspondence between the 1 cm soil moisture and the 2.65-GHz emissivity and between the 3-5 cm soil moisture and the 1.4-GHz emissivity. which confirms previous studies, Observations during drying and rainfall demonstrate that new and unique information for hydrologic and energy balance studies can be extracted from these data. C1 NASA,GODDARD SPACE FLIGHT CTR,HYDROL SCI BRANCH,LAB HYDROSPHER PROC,GREENBELT,MD 20771. UNIV MASSACHUSETTS,DEPT ELECT & COMP ENGN,AMHERST,MA 01003. RP Jackson, TJ (reprint author), USDA ARS,BELTSVILLE AGR RES CTR,HYDROL LAB,BELTSVILLE,MD 20705, USA. RI O'Neill, Peggy/D-2904-2013 NR 26 TC 56 Z9 56 U1 0 U2 4 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 SN 0196-2892 J9 IEEE T GEOSCI REMOTE JI IEEE Trans. Geosci. Remote Sensing PD SEP PY 1997 VL 35 IS 5 BP 1210 EP 1222 DI 10.1109/36.628788 PG 13 WC Geochemistry & Geophysics; Engineering, Electrical & Electronic; Remote Sensing; Imaging Science & Photographic Technology SC Geochemistry & Geophysics; Engineering; Remote Sensing; Imaging Science & Photographic Technology GA XW390 UT WOS:A1997XW39000012 ER PT J AU Shi, JC Wang, J Hsu, AY ONeill, PE Engman, ET AF Shi, JC Wang, J Hsu, AY ONeill, PE Engman, ET TI Estimation of bare surface soil moisture and surface roughness parameter using L-band SAR image data SO IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING LA English DT Article DE algorithm; soil moisture; surface roughness; synthetic aperture radar (SAR) ID CALIBRATION AB An algorithm based on a fit of the single-scattering Integral Equation Method (IEM) was developed to provide estimation of soil moisture and surface roughness parameter (a combination of rms roughness height and surface power spectrum) from quad-polarized synthetic aperture radar (SAR) measurements, This algorithm was applied to a series of measurements acquired at L-band (1.25 GHz) from both AIRSAR (Airborne Synthetic Aperture Radar operated by the Jet Propulsion Laboratory) and SIR-C (Spaceborne Imaging Radar-C) over a well-managed watershed in southwest Oklahoma, Prior to its application for soil moisture inversion, a good agreement was found between the single-scattering IEM simulations and the L band measurements of SIR-C and AIRSAR over a nide range of soil moisture and surface roughness conditions, The sensitivity of soil moisture variation to the co-polarized signals were then examined under the consideration of the calibration accuracy of various components of SAR measurements. It was found that the two co-polarized backscattering coefficients and their combinations would provide the best input to the algorithm for estimation of soil moisture and roughness parameter, Application of the inversion algorithm to the co-polarized measurements of both AIRSAR and SIR-C resulted in estimated values of soil moisture and roughness parameter for bare and short-vegetated fields that compared favorably with those sampled on the ground. The root-mean-square (rms) errors of the comparison were found to be 3.4% and 1.9 dB for soil moisture and surface roughness parameter, respectively. C1 NASA,GODDARD SPACE FLIGHT CTR,LAB HYDROSPHER PROC,GREENBELT,MD 20771. RP Shi, JC (reprint author), UNIV CALIF SANTA BARBARA,INST COMPUTAT EARTH SYST SCI,SANTA BARBARA,CA 93106, USA. RI O'Neill, Peggy/D-2904-2013 NR 21 TC 243 Z9 294 U1 1 U2 33 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 SN 0196-2892 J9 IEEE T GEOSCI REMOTE JI IEEE Trans. Geosci. Remote Sensing PD SEP PY 1997 VL 35 IS 5 BP 1254 EP 1266 DI 10.1109/36.628792 PG 13 WC Geochemistry & Geophysics; Engineering, Electrical & Electronic; Remote Sensing; Imaging Science & Photographic Technology SC Geochemistry & Geophysics; Engineering; Remote Sensing; Imaging Science & Photographic Technology GA XW390 UT WOS:A1997XW39000016 ER PT J AU Kaufman, YJ Wald, AE Remer, LA Gao, BC Li, RR Flynn, L AF Kaufman, YJ Wald, AE Remer, LA Gao, BC Li, RR Flynn, L TI The MODIS 2.1-mu m channel - Correlation with visible reflectance for use in remote sensing of aerosol SO IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING LA English DT Article DE aerosols; atmosphere correction; remote sensing ID SATELLITE IMAGERY; AVHRR DATA; OPTICAL-PROPERTIES; GREENHOUSE GASES; SULFATE AEROSOLS; RELATIVE ROLES; EOS-MODIS; RETRIEVAL; CLOUD; INSTRUMENT AB A new technique for remote sensing of aerosol over the land and for atmospheric correction of Earth imagery is developed, It is based on detection of dark surface targets in the blue and red channels, as in previous methods, but uses the 2.1-mu m channel, instead of the 3.75 mu m for their detection, ii 2.1-mu m channel is present on ADEOS OCTS and GLI, and planned on EOS-MODIS and EOSP, and a similar 2.2-mu m channel is present on Landsat TM. The advantage of the 2.1-mu m channel over the 3.75-mu m channel is that it is not affected by emitted radiation, The 2.1-mu m channel is transparent to most aerosol types (except dust) and therefore can be used to detect dark surface targets, Correlation between the surface reflection in the blue (0.49 mu m), red (0.66 mu m), and 2.1 mu m is established using atmospherically corrected Landsat TRI and AVIRIS aircraft images collected over the Eastern United States, Maine, and California and spectral data obtained from the ground and Light aircraft near San Diego, CA. Results from a variety of surface covers show that the surface reflectance at 0.49 mu m (rho(0.49)) and 0.66 mu m (rho(0.66)) can he predicted from that at 2.2 mu m (rho(2.2)) within Delta rho = +/-0.006 for rho(2.2) less than or equal to 0.10, using rho(0.49) = rho(2.2)/4 and rho(0.66) = rho(2.2)/2. Error in surface reflectance of 0.006 corresponds to an error in remote sensing of aerosol optical thickness, tau, of Delta tau similar to +/-0.06. These relationships were validated using spectral data taken close to the surface over vegetated areas in a different biome, This method expands application of dark targets for remote sensing of aerosol to brighter, nonforested vegetation, The higher reflection of the surface at 2.2 mu m than that of 3.75 mu m mag even enable remote sensing of dust above surfaces with reflectivity rho(2.2) = 0.15 +/- 0.05. For this reflectivity range the dust radiative effect at 2.2 mu m is small, and the surface reflectance in the blue and red channels can be retrieved. C1 SCI SYST APPLICAT INC,LANHAM,MD 20706. USN,RES LAB,WASHINGTON,DC 20375. UNIV HAWAII,HAWAII INST GEOPHYS & PLANETOL,HONOLULU,HI 96822. RP Kaufman, YJ (reprint author), NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771, USA. NR 38 TC 438 Z9 520 U1 2 U2 46 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 SN 0196-2892 J9 IEEE T GEOSCI REMOTE JI IEEE Trans. Geosci. Remote Sensing PD SEP PY 1997 VL 35 IS 5 BP 1286 EP 1298 DI 10.1109/36.628795 PG 13 WC Geochemistry & Geophysics; Engineering, Electrical & Electronic; Remote Sensing; Imaging Science & Photographic Technology SC Geochemistry & Geophysics; Engineering; Remote Sensing; Imaging Science & Photographic Technology GA XW390 UT WOS:A1997XW39000019 ER PT J AU Katti, RR AF Katti, RR TI The 1997 IEEE International Magnetics Conference (INTERMAG'97) - Hyatt Regency Hotel, New Orleans, Louisiana, April 1-4, 1997 - Introduction SO IEEE TRANSACTIONS ON MAGNETICS LA English DT Editorial Material RP Katti, RR (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 IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 SN 0018-9464 J9 IEEE T MAGN JI IEEE Trans. Magn. PD SEP PY 1997 VL 33 IS 5 BP 2607 EP 2607 PN 1 PG 1 WC Engineering, Electrical & Electronic; Physics, Applied SC Engineering; Physics GA XW564 UT WOS:A1997XW56400002 ER PT J AU Kaneda, N Houshmand, B Itoh, T AF Kaneda, N Houshmand, B Itoh, T TI FDTD analysis of dielectric resonators with curved surfaces SO IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES LA English DT Article DE dielectric resonator; FDTD ID DIFFERENCE TIME-DOMAIN; ANTENNA AB In this paper, the finite-difference time-domain (FDTD) method is applied to calculate the resonant frequency of dielectric resonators (DR's) with curved surface, The contour-path integral FDTD (CFDTD) is modified to deal with the curved surface of the dielectric body while the traditional rectangular cells are maintained, Results are compared with theoretical values and staircase approximation, and show that the present method is more accurate than the staircase approximation. C1 DOSHISHA UNIV,DEPT ELECT ENGN,KYOTO 61003,JAPAN. CALTECH,JET PROP LAB,PASADENA,CA 91109. RP Kaneda, N (reprint author), UNIV CALIF LOS ANGELES,DEPT ELECT ENGN,LOS ANGELES,CA 90095, USA. NR 15 TC 100 Z9 103 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 0018-9480 J9 IEEE T MICROW THEORY JI IEEE Trans. Microw. Theory Tech. PD SEP PY 1997 VL 45 IS 9 BP 1645 EP 1649 DI 10.1109/22.622937 PG 5 WC Engineering, Electrical & Electronic SC Engineering GA XU755 UT WOS:A1997XU75500018 ER PT J AU Harstad, K Bellan, J AF Harstad, K Bellan, J TI Behavior of a polydisperse cluster of interacting drops evaporating in an inviscid vortex SO INTERNATIONAL JOURNAL OF MULTIPHASE FLOW LA English DT Article DE drop clusters; evaporation; polydisperse; multiphase ID FREE SHEAR-LAYER; SPRAY FLAMES; PARTICLE DISPERSION; JET; COMBUSTION; VAPORIZATION; TURBULENCE; SIMULATION; METHANOL; FIELD AB The dynamics and evaporation of polydisperse collections of liquid drops in an axisymmetric, infinite, cylindrical vortex are described using a statistical model. This model describes both the dense regime where inter-particle effects are important and the dilute regime. The initial size distribution is partitioned into size classes and each initial size-class is followed dynamically and thermodynamically using a class-defined, drop-frame coordinate system. Each initial-size-class develops a continuum of sizes as drops centrifuge towards hotter surroundings and evaporate. A separate coordinate system tracks the gas phase. Because larger drops experience larger centrifugal force, they approach the hotter gas faster. However, for appropriate liquid heating times, the large drops might evaporate at a faster rate, and so the size-differentiated centrifugation previously observed and calculated for cold flow situations does not occur. Instead, a radially peaked drop size distribution is developed in the gas vortex. The centrifugal motion forms a drop-free inner vortex core bound by a cylindrical shell containing all the drops. This shell of gas and drops is called the drop cluster. Numerical calculations show that more parameters control dense clusters than dilute clusters; examples of these parametric relations include: (i) the air/liquid mass ratio controls the inner cluster region and the gas vortex, whereas drop size distribution controls the outer region; and (ii) polydispersity increases the maximum mass fraction of the evaporated compound and enhances penetration of the evaporated compound into the surroundings. Except for dilute clusters, the assumption of uniform drop number distribution in the cluster is found to be inappropriate. Instead, the drop size distribution always becomes non-uniform even if the initial size distribution is monodisperse and the initial drop number distribution is uniform. This development of non-uniformity is caused by drops at the cluster peripheries preventing heat conduction/convection to drops in the central cluster. Published by Elsevier Science Ltd. RP Harstad, K (reprint author), CALTECH,JET PROP LAB,4800 OAK GROVE DR,PASADENA,CA 91109, USA. NR 42 TC 12 Z9 12 U1 0 U2 2 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 SEP PY 1997 VL 23 IS 5 BP 899 EP 925 DI 10.1016/S0301-9322(97)00011-6 PG 27 WC Mechanics SC Mechanics GA XM769 UT WOS:A1997XM76900006 ER PT J AU Lee, HJ Saravanos, DA AF Lee, HJ Saravanos, DA TI Generalized finite element formulation for smart multilayered thermal piezoelectric composite plates SO INTERNATIONAL JOURNAL OF SOLIDS AND STRUCTURES LA English DT Article ID COUPLED LAYERWISE ANALYSIS; INTELLIGENT STRUCTURES; GOVERNING EQUATIONS; SENSORS ACTUATORS; VIBRATION CONTROL; BEAMS; SYSTEMS; DESIGN AB Analytical formulations are presented which account for the coupled mechanical, electrical-and thermal response of piezoelectric composite laminates and plate structures. A robust layerwise theory is formulated with the inherent capability to explicitly model the active and sensory response of piezoelectric composite plates having general laminations in thermal environments. Finite element equations are derived and implemented for a bilinear 4-noded plate element. Applications demonstrate the capability to manage thermally induced bending and twisting deformations in symmetric and antisymmetric composite plates with piezoelectric actuators and attain thermal stability. The resultant stresses in the thermal piezoelectric composite laminates are also investigated. Published by Elsevier Science Ltd. C1 OHIO AEROSP INST,BROOKPARK,OH 44142. RP Lee, HJ (reprint author), NASA,LEWIS RES CTR,21000 BROOKPK RD,MAIL STOP 23-3,CLEVELAND,OH 44135, USA. NR 28 TC 71 Z9 81 U1 1 U2 5 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, ENGLAND OX5 1GB SN 0020-7683 J9 INT J SOLIDS STRUCT JI Int. J. Solids Struct. PD SEP PY 1997 VL 34 IS 26 BP 3355 EP 3371 DI 10.1016/S0020-7683(96)00215-6 PG 17 WC Mechanics SC Mechanics GA XV156 UT WOS:A1997XV15600001 ER PT J AU Rossow, VJ AF Rossow, VJ TI Extended-Betz methods for roll-up of vortex sheets SO JOURNAL OF AIRCRAFT LA English DT Article AB The method derived for the roll-up of vortex sheets shed by lifting wings has been extended so that it can be applied to complex wakes that roll up into more than one vortex pair, Although these so-called extended-Betz methods often predict realistic vortex structures that approximate measured ones, the guidelines need to he improved if the predictions are to be reliable enough for such purposes as the assessment of the hazard posed by a wake or for the validation of other theoretical methods. This paper first describes the problem and then considers whether the five vortex invariants for the time-dependent motion of two-dimensionlal vortices can provide improved guidelines. In particular, the vortex invariants are studied to find out if they can be used to determine the initial division of the vortex sheet for separation into multiple vortices, and then possible merger into larger vortices. It is concluded that any refinements of the present forms of the extended-Betz methods to better define the structure of multiple vortex wakes will be very difficult and probably cannot be derived from the. vortex invariants. RP Rossow, VJ (reprint author), NASA,AMES RES CTR,LOW SPEED AERODYNAM BRANCH,M-S 247-2,MOFFETT FIELD,CA 94035, USA. NR 16 TC 6 Z9 6 U1 0 U2 1 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 SN 0021-8669 J9 J AIRCRAFT JI J. Aircr. PD SEP-OCT PY 1997 VL 34 IS 5 BP 592 EP 599 DI 10.2514/2.2234 PG 8 WC Engineering, Aerospace SC Engineering GA YA419 UT WOS:A1997YA41900003 ER PT J AU Kaminer, II Howard, RM Buttrill, CS AF Kaminer, II Howard, RM Buttrill, CS TI Development of closed-loop tail-sizing criteria for a High Speed Civil Transport SO JOURNAL OF AIRCRAFT LA English DT Article ID DESIGN AB A study was conducted to determine the closed-loop tail-sizing criteria for a High Speed Civil Transport using a newly developed integrated aircraft/controller design methodology. The key idea is to cast closed loop requirements as linear matrix inequalities, for which efficient numerical solvers are available, In particular, the effects of certain feedback specifications, and of actuator amplitude and rate constraints on the maximum allowable e.g. travel for a given set of tail sizes are studied, A constant gain slate feedback controller Is designed as a part of the tail-sizing process. C1 NASA,LANGLEY RES CTR,DYNAM & CONTROL BRANCH,HAMPTON,VA 23681. RP Kaminer, II (reprint author), USN,POSTGRAD SCH,DEPT AERONAUT & ASTRONAUT,MONTEREY,CA 93943, USA. NR 14 TC 1 Z9 1 U1 0 U2 0 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 SN 0021-8669 J9 J AIRCRAFT JI J. Aircr. PD SEP-OCT PY 1997 VL 34 IS 5 BP 658 EP 664 DI 10.2514/2.2226 PG 7 WC Engineering, Aerospace SC Engineering GA YA419 UT WOS:A1997YA41900013 ER PT J AU Strawn, RC Oliker, L Biswas, R AF Strawn, RC Oliker, L Biswas, R TI New computational methods for the prediction and analysis of helicopter noise SO JOURNAL OF AIRCRAFT LA English DT Article; Proceedings Paper CT AIAA/CEAS 2nd Joint Aeroacoustics Conference CY MAY 06-08, 1996 CL STATE COLL, PA SP AIAA, CEAS ID SPEED IMPULSIVE NOISE; ROTOR; VORTEX; ACOUSTICS; HOVER AB This paper describes a new methodology to predict and analyze rotorcraft noise, This methodology includes 1) a combined computational fluid dynamics and Kirchhoff scheme for far-field noise predictions, 2) parallel computer implementation of the Kirchhoff integrations, 3) audio and visual rendering of the computed acoustic predictions over large far-field regions, and 4) acoustic tracebacks to the Kirchhoff surface to pinpoint the sources of the rotor noise. This paper describes each method and presents sample results for three test cases, The first case consists of in-plane high-speed impulsive noise, and the other two cases show idealized parallel and oblique blade-vortex interactions, The computed results show good agreement with available experimental data, but convey much more information about the far-field noise propagation, When taken together, these analysis techniques exploit the power of new computer technologies and offer the potential to significantly improve our prediction and understanding of rotorcraft noise. RP Strawn, RC (reprint author), NASA,AMES RES CTR,USA,AEROFLIGHTDYNAM DIRECTORATE,M-S 258-1,MOFFETT FIELD,CA 94035, USA. NR 27 TC 5 Z9 5 U1 1 U2 2 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 SEP-OCT PY 1997 VL 34 IS 5 BP 665 EP 672 DI 10.2514/2.2227 PG 8 WC Engineering, Aerospace SC Engineering GA YA419 UT WOS:A1997YA41900014 ER PT J AU Gatlin, GM McGhee, RJ AF Gatlin, GM McGhee, RJ TI Experimental investigation of semispan model testing techniques (vol 34, pg 500, 1997) SO JOURNAL OF AIRCRAFT LA English DT Correction, Addition RP Gatlin, GM (reprint author), NASA,LANGLEY RES CTR,HAMPTON,VA 23681, USA. NR 1 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 SEP-OCT PY 1997 VL 34 IS 5 BP 696 EP 696 PG 1 WC Engineering, Aerospace SC Engineering GA YA419 UT WOS:A1997YA41900020 ER PT J AU Hilburger, MW Waas, AM Starnes, JH AF Hilburger, MW Waas, AM Starnes, JH TI Modeling the dynamic response and establishing post buckling post snap-thru equilibrium of discrete structures via a transient analysis SO JOURNAL OF APPLIED MECHANICS-TRANSACTIONS OF THE ASME LA English DT Article AB Results of a transient analysis developed to model the dynamic response and establish post-buckling/post snap-thru equilibrium, of discrete structures are presented. Three systems that exhibit unstable buckling characteristics are analyzed. The analysis consisted of first statically loading the structures up to there respective static limit loads. The structure is then perturbed from their critical state and a transient analysis is used to model the ensuing dynamic response, The transient formulation is first applied to two simple one-degree-of-freedom systems consisting of rigid links, springs, dampers, and lumped masses, The first of these systems was an arch with a point load applied at its vertex. This structure admits dynamic snap-thru response when loaded beyond its limit load. The second system was a model of a curved panel under an applied axial end-shortening. This system exhibited dynamic buckling behavior consisting of a large decrease in the resultant axial load when loaded beyond its limit load. The transient analysis was then applied to a finite element model of a cylindrical shell with a cutout under an applied axial compression load to model the dynamics of the global buckling response upon reaching its limit load. The results from this study illustrate the usefulness of the transient analysis in modeling the dynamics of an unstable structural response and establishing equilibrium beyond any points of instability. C1 UNIV MICHIGAN,DEPT AEROSP ENGN,ANN ARBOR,MI 48109. NASA,LANGLEY RES CTR,STRUCT MECH BRANCH,HAMPTON,VA 23665. NR 8 TC 7 Z9 7 U1 1 U2 2 PU ASME-AMER SOC MECHANICAL ENG PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017 SN 0021-8936 J9 J APPL MECH-T ASME JI J. Appl. Mech.-Trans. ASME PD SEP PY 1997 VL 64 IS 3 BP 590 EP 595 DI 10.1115/1.2788933 PG 6 WC Mechanics SC Mechanics GA XZ220 UT WOS:A1997XZ22000020 ER PT J AU Huffman, GJ AF Huffman, GJ TI Estimates of root-mean-square random error for finite samples of estimated precipitation SO JOURNAL OF APPLIED METEOROLOGY LA English DT Article ID TROPICAL RAINFALL; SATELLITE; MODEL AB `The random errors contained in a finite set E of precipitation estimates result from both finite sampling and measurement-algorithm effects. The expected root-mean-square random error associated with the estimated average precipitation in E is shown to be sigma(r) = (r) over bar[(H - p)/pN(I)](1/2), where (r) over bar is the space-time-average precipitation estimate over E, H is a function of the shape of the probability distribution of precipitation (the nondimensional second moment), p is the frequency of nonzero precipitation in E, and N-1 is the number of independent samples in E. All of these quantities are variables of the space-time-average dataset. In practice H is nearly constant and close to the value 1.5 over most of the globe. An approximate form of sigma(r), is derived that accommodates the limitations of typical monthly datasets, then it is applied to the microwave, infrared, and gauge precipitation monthly datasets from the Global Precipitation Climatology Project. As an aid to visualizing differences in sigma for various datasets, a ''quality index'' is introduced. Calibration in a few locations with dense gauge networks reveals that the approximate form is a reasonable first step in estimating sigma(r). C1 SCI SYST & APPLICAT INC,GREENBELT,MD. RP Huffman, GJ (reprint author), NASA,GODDARD SPACE FLIGHT CTR,ATMOSPHERES LAB,CODE 912,GREENBELT,MD 20771, USA. RI Huffman, George/F-4494-2014 OI Huffman, George/0000-0003-3858-8308 NR 11 TC 121 Z9 124 U1 0 U2 10 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 SEP PY 1997 VL 36 IS 9 BP 1191 EP 1201 DI 10.1175/1520-0450(1997)036<1191:EORMSR>2.0.CO;2 PG 11 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA XU624 UT WOS:A1997XU62400006 ER PT J AU Wang, JR Spinhirne, JD Racette, P Chang, LA Hart, W AF Wang, JR Spinhirne, JD Racette, P Chang, LA Hart, W TI The effect of clouds on water vapor profiling from the millimeter-wave radiometric measurements SO JOURNAL OF APPLIED METEOROLOGY LA English DT Article ID MICROWAVE RADIOMETRY; MOISTURE PROFILES; RAMAN LIDAR; RETRIEVAL; CLEAR; GHZ; SURFACE; MODEL AB Simultaneous measurements with the millimeter-wave imaging radiometer (MIR), cloud lidar system (CLS), and the MODIS airborne simulator (MAS) were made aboard the NASA ER-2 aircraft over the western Pacific Ocean on 17-18 January 1993. These measurements were used to study the effects of clouds on water vapor profile retrievals based on millimeter-wave radiometer measurements. The CLS backscatter measurements (at 0.532 and 1.064 mu m) provided information on the heights and a derailed structure of cloud layers; the types of clouds could be positively identified. All 12 MAS channels (0.6-13 mu m) essentially respond to all types of clouds, while the six MIR channels (89-220 GHz) show little sensitivity to cirrus clouds. The radiances from the 12-mu m and O.875-mu m channels of the MAS and the 89-GHz channel of the MIR were used to gauge the performance of the retrieval of water vapor profiles from the MIR observations under cloudy conditions. It was found that, for cirrus and absorptive (liquid) clouds, better than 80% of the retrieval was convergent when one of the three criteria was satisfied; that is, the radiance at 0.875 mu m is less than 100 W cm(-3) sr(-1), or the brightness at 12 mu m is greater than 260 K, or brightness at 89 GHz is less than 770 K (equivalent to cloud liquid water of less than 0.04 g cm(-2)). The range of these radiances for convergent retrieval increases markedly when the condition for convergent retrieval was somewhat relaxed, The algorithm of water vapor profiling from the MIR measurements could not perform adequately over the areas of storm-related clouds that scatter radiation at millimeter wavelengths. C1 FUTURETECH CORP,GAITHERSBURG,MD. SCI SYST & APPLICAT INC,LANHAM,MD. RP Wang, JR (reprint author), NASA,EARTH SCI DIRECTORATE,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771, USA. NR 23 TC 4 Z9 4 U1 0 U2 0 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 SEP PY 1997 VL 36 IS 9 BP 1232 EP 1244 DI 10.1175/1520-0450(1997)036<1232:TEOCOW>2.0.CO;2 PG 13 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA XU624 UT WOS:A1997XU62400010 ER PT J AU Hsu, CS Wurtele, MG Cunningham, GF Woiceshyn, PM AF Hsu, CS Wurtele, MG Cunningham, GF Woiceshyn, PM TI Construction of marine surface pressure fields from scatterometer winds alone SO JOURNAL OF APPLIED METEOROLOGY LA English DT Article ID PLANETARY BOUNDARY-LAYER; QE-II STORM; SATELLITE SCATTEROMETER; SEASAT; IMPACT; MODEL; RESOLUTION; FORECASTS; WEATHER; RANGE AB A series of 6-h, synoptic, gridded, global surface wind fields with a resolution of 100 km was generated using the dataset of dealiased Seasat satellite scatterometer (SASS) winds produced as described by Peteherych et al. This paper is an account of the construction of surface pressure fields from these SASS synoptic wind fields only, as carried out by different methods, and the comparison of these pressure fields with National Centers for Environmental Prediction (NCEP) analyses, with the pressure fields of the European Centre for Medium-Range Weather Forecasts (ECMWF), and with the special analyses of the Gulf of Alaska Experiment. One of the methods vie use to derive the pressure fields utilizes a two-layer planetary boundary layer (PBL) model iterative scheme that relates the geostrophic wind vector to the surface wind vector, surface roughness, humidity, diabatic and baroclinic effects, and secondary flow. A second method involves the assumption of zero two-dimensional divergence, leading to a Poisson equation (the ''balance equation'') in pressure, with the wind held serving as a forcing function. The pressure fields computed from the SASS winds using a two-layer PBL model closely approximate the NCEP and ECMWF fields. In some cases, the PBL-model-derived pressure fields can detect mesoscale features not resolved in either the NCEP or ECMWF analyses. Balanced pressure fields are much smoother and less well resolved than the PBL-model-derived or NCEP fields. Systematic differences between balanced pressure fields and the PBL-model-derived fields are attributed to the neglect of horizontal divergence in the balance equation. The effect of stratification is found to produce a larger impact than secondary how or thermal wind effects on the derived pressure fields. Inclusion of secondary flow tends to weaken both low and high pressure centers, whereas inclusion of stratification intensifies low centers and weakens high centers. C1 UNIV CALIF LOS ANGELES,DEPT ATMOSPHER SCI,LOS ANGELES,CA 90024. RP Hsu, CS (reprint author), CALTECH,JET PROP LAB,4800 OAK GROVE DR,MAIL STOP 300-320,PASADENA,CA 91109, USA. NR 32 TC 15 Z9 15 U1 0 U2 0 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 SEP PY 1997 VL 36 IS 9 BP 1249 EP 1261 DI 10.1175/1520-0450(1997)036<1249:COMSPF>2.0.CO;2 PG 13 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA XU624 UT WOS:A1997XU62400012 ER PT J AU Huang, ZC Mott, DB Shu, PK Zhang, R Chen, JC Wickenden, DK AF Huang, ZC Mott, DB Shu, PK Zhang, R Chen, JC Wickenden, DK TI Optical quenching of photoconductivity in GaN photoconductors SO JOURNAL OF APPLIED PHYSICS LA English DT Article ID DEEP-LEVEL DEFECTS; N-TYPE GAN AB The observation of optical quenching of photoconductivity in GaN photoconductors temperature is reported on. Three prominent quenching bands were found at E-v + 1.44, 1.58, and 2.20 eV, respectively. These levels are related to three hole traps in GaN materials based on a hole trap model to interpret the quenching mechanism. The responsivity was reduced about 12% with an additional He-Ne laser shining on the photoconductor. (C) 1997 American Institute of Physics. C1 UNIV MARYLAND BALTIMORE CTY,DEPT COMP SCI & ELECT ENGN,BALTIMORE,MD 21228. NASA,GODDARD SPACE FLIGHT CTR,SOLID STATE DEVICE DEV BRANCH,GREENBELT,MD 20771. JOHNS HOPKINS UNIV,APPL PHYS LAB,LAUREL,MD 20723. NR 13 TC 32 Z9 34 U1 0 U2 1 PU AMER INST PHYSICS PI WOODBURY PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 SN 0021-8979 J9 J APPL PHYS JI J. Appl. Phys. PD SEP 1 PY 1997 VL 82 IS 5 BP 2707 EP 2709 DI 10.1063/1.366090 PG 3 WC Physics, Applied SC Physics GA XT821 UT WOS:A1997XT82100101 ER PT J AU Moles, A AF Moles, A TI Effect of bacterial kidney disease on saltwater adaptation of coho salmon smolts SO JOURNAL OF AQUATIC ANIMAL HEALTH LA English DT Article ID ONCORHYNCHUS-KISUTCH; SALVELINUS-FONTINALIS; ATLANTIC SALMON; RAINBOW-TROUT; BROOK TROUT; SEAWATER; SURVIVAL; FISH; SMOLTIFICATION; TRANSFORMATION AB Coho salmon Oncorhynchus kisutch with clinical infections of bacterial kidney disease (BKD) had poorer survival in the laboratory after 30 d in salt water (50%) than in freshwater (85%). Osmoregulatory ability of infected fish was better after acclimation in 10 parts per thousand salinity water before transfer to 30 parts per thousand salinity water. Infected fish exercised overnight (3.0 body lengths/s) were unable to survive the seawater challenge, whereas uninfected fish similarly exercised survived with the same plasma Na+ levels as unexercised fish. Because BKD is present in most salmonid stocks, stress of seawater transfers should be minimized through acclimation and reduced exertion. RP Moles, A (reprint author), NATL MARINE FISHERIES SERV,ALASKA FISHERIES SCI CTR,AUKE BAY FISHERIES LAB,11305 GLACIER HIGHWAY,JUNEAU,AK 99801, USA. NR 23 TC 14 Z9 15 U1 1 U2 2 PU AMER FISHERIES SOC PI BETHESDA PA 5410 GROSVENOR LANE SUITE 110, BETHESDA, MD 20814-2199 SN 0899-7659 J9 J AQUAT ANIM HEALTH JI J. Aquat. Anim. Health PD SEP PY 1997 VL 9 IS 3 BP 230 EP 233 DI 10.1577/1548-8667(1997)009<0230:EOBKDO>2.3.CO;2 PG 4 WC Fisheries; Veterinary Sciences SC Fisheries; Veterinary Sciences GA YD449 UT WOS:A1997YD44900010 ER PT J AU Jahn, JM LaBelle, J Sobral, JHA Aggson, TL Hanson, WB AF Jahn, JM LaBelle, J Sobral, JHA Aggson, TL Hanson, WB TI Detection of an equatorial spread-F bubble by ground-based photometers and the San Marco 5 satellite SO JOURNAL OF ATMOSPHERIC AND SOLAR-TERRESTRIAL PHYSICS LA English DT Article; Proceedings Paper CT 9th International Symposium on Equatorial Aeronomy Including the Middle Atmosphere (ISEA) CY MAR 20-24, 1995 CL BALI, INDONESIA SP Kyoto Univ, Radio Atmospher Sci Ctr, Indonesian Natl Inst Aeronaut & Space, Union RadioSci Int, Sci Comm Solar Terr Phys, Int Assoc Meteorol & Atmospher Sci, Int Assoc Geomagnetism & Aeron, Soc Geomagnetism & Earth Planetary & Space Sci ID ELECTRIC-FIELD OBSERVATIONS; PLASMA DEPLETIONS; IRREGULARITIES; DRIFTS; DISTURBANCES; IONOSPHERE; VELOCITY AB In the Fall of 1988, San Marco 5, instrumented with ion density and electric field experiments, made passes through the equatorial F-region in the Brazilian sector, where scanning photometers have been operated at Cachoeira Paulista, Brazil, for many years. We have cross-checked these large data sets and report here on one night of active spread-F with good data from both San Marco 5 and Cachoeira Paulista. As expected, a correlation is observed between airglow bubbles and ion density depletions encountered by San Marco 5. Additional airglow bubbles can be linked to enhanced AC electric field fluctuations, similar to those previously suspected to characterize satellite passes through pinched off spread-F bubbles. These data complement existing airglow-satellite correlations made in other longitude sectors and provide information relevant to the interpretation of satellite and airglow data. (C) 1997 Elsevier Science Ltd. C1 INST NACL PESQUISAS ESPACIAIS,BR-12201 S JOSE CAMPOS,SP,BRAZIL. NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. UNIV TEXAS,CTR SPACE SCI,RICHARDSON,TX 75083. RP Jahn, JM (reprint author), DARTMOUTH COLL,DEPT PHYS & ASTRON,HANOVER,NH 03755, USA. NR 21 TC 8 Z9 8 U1 0 U2 0 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, ENGLAND OX5 1GB SN 1364-6826 J9 J ATMOS SOL-TERR PHY JI J. Atmos. Sol.-Terr. Phys. PD SEP PY 1997 VL 59 IS 13 BP 1601 EP 1609 DI 10.1016/S1364-6826(96)00159-9 PG 9 WC Geochemistry & Geophysics; Meteorology & Atmospheric Sciences SC Geochemistry & Geophysics; Meteorology & Atmospheric Sciences GA XR095 UT WOS:A1997XR09500012 ER PT J AU Laakso, H Maynard, NC Pfaff, RF Aggson, TL Coley, WR Janhunen, P Herrero, FA AF Laakso, H Maynard, NC Pfaff, RF Aggson, TL Coley, WR Janhunen, P Herrero, FA TI Electric field diagnostics of the dynamics of equatorial density depletions SO JOURNAL OF ATMOSPHERIC AND SOLAR-TERRESTRIAL PHYSICS LA English DT Article; Proceedings Paper CT 9th International Symposium on Equatorial Aeronomy Including the Middle Atmosphere (ISEA) CY MAR 20-24, 1995 CL BALI, INDONESIA SP Kyoto Univ, Radio Atmospher Sci Ctr, Indonesian Natl Inst Aeronaut & Space, Union RadioSci Int, Sci Comm Solar Terr Phys, Int Assoc Meteorol & Atmospher Sci, Int Assoc Geomagnetism & Aeron, Soc Geomagnetism & Earth Planetary & Space Sci ID PLASMA DEPLETIONS; SPREAD-F; BUBBLES; IONOSPHERE; IRREGULARITIES; LATITUDE; FLOW AB During its life of 10 months, the San Marco D satellite crossed a large number of plasma density depletion channels in the nightside F-region equatorial ionosphere. In-situ measurements of vector electric fields from San Marco D reveal convection velocity variations inside such channels and thus can be used as diagnostics of the dynamics of these plasma depleted regions. Furthermore, in some cases, the temporal evolution of the channel can be inferred from the measurements. In this paper the electric field data are converted to plasma drift velocities in order to illustrate cases where the plasma how is directed upward or downward in the channel, the channel itself is oriented vertically upward or tilted eastward/westward, or the channel is experiencing a bifurcation or pinching-off process. Although the E x B plasma drift velocities within the depleted channels are commonly a few hundred m s(-1) on some occasions electric fields corresponding to speeds as large as 2-3 km s(-1) have been observed. The implications for such highly supersonic convection are discussed, including the possible constriction of such high-speed depletion channels at higher altitudes. (C) 1997 Elsevier Science Ltd. C1 MISSION RES CORP,NASHUA,NH 03062. NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. UNIV TEXAS,WB HANSON CTR SPACE SCI,RICHARDSON,TX 75083. RP Laakso, H (reprint author), FINNISH METEOROL INST,POB 503,FIN-00101 HELSINKI,FINLAND. RI Pfaff, Robert/F-5703-2012; OI Pfaff, Robert/0000-0002-4881-9715; Coley, William Robin/0000-0003-2047-0002 NR 20 TC 9 Z9 9 U1 0 U2 0 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, ENGLAND OX5 1GB SN 1364-6826 J9 J ATMOS SOL-TERR PHY JI J. Atmos. Sol.-Terr. Phys. PD SEP PY 1997 VL 59 IS 13 BP 1625 EP 1631 DI 10.1016/S1364-6826(96)00161-7 PG 7 WC Geochemistry & Geophysics; Meteorology & Atmospheric Sciences SC Geochemistry & Geophysics; Meteorology & Atmospheric Sciences GA XR095 UT WOS:A1997XR09500014 ER PT J AU Moursi, AM Globus, RK Damsky, CH AF Moursi, AM Globus, RK Damsky, CH TI Interactions between integrin receptors and fibronectin are required for calvarial osteoblast differentiation in vitro SO JOURNAL OF CELL SCIENCE LA English DT Article DE integrin; fibronectin; osteoblast differentiation; fetal rat calvarial osteoblast ID ALKALINE-PHOSPHATASE ACTIVITY; GENE-EXPRESSION; EXTRACELLULAR-MATRIX; BONE-CELLS; SARCOMA CELLS; IN-VITRO; GLUCOCORTICOIDS INHIBIT; SIGNAL-TRANSDUCTION; ADHESION RECEPTORS; RAT OSTEOCLASTS AB We previously showed that anti-fibronectin antibodies or soluble fibronectin fragments containing the central cell-binding domain inhibit formation of mineralized nodules by fetal calvarial osteoblasts in vitro, These findings suggest a critical role for fibronectin in osteoblast differentiation and morphogenesis, In this study we tested the hypothesis that fibronectin's effects on osteogenesis are mediated via direct interactions with integrin receptors for fibronectin on osteoblasts. Immunocytochemical analysis identified the integrin fibronectin receptor alpha 5 beta 1 in fetal rat calvarial tissue and in cultured osteoblasts at all stages of differentiation, Three other integrins, alpha 3 beta 1, alpha 8 beta 1 and alpha v beta 3, which can bind fibronectin, as well as other matrix components, were also identified in tissue and at all stages of cell culture, Immunoprecipitation data showed that alpha 5 beta 1 levels are constant throughout osteoblast differentiation whereas levels of alpha 3 beta 1 and alpha 8 beta 1 decline in mature mineralized cultures, To determine whether integrin fibronectin receptors are required for osteoblast formation of mineralized nodules, we examined the extent of nodule formation in the presence and absence of function-perturbing antiintegrin antibodies, The antibodies were present continuously in cultures beginning at confluence (day 3), and nodule formation was measured at days 10 and 20, An anti-alpha 5 integrin subunit antibody reduced nodule formation to less than 5% of control values at both time points, Inhibition of nodule formation was reversible and did not affect cell attachment and viability, Function-perturbing antibodies against alpha 3 beta 1 and alpha 8 beta 1 also reduced nodule formation, to less than 20% of control values, In contrast, function-perturbing antibodies to alpha v beta 3 and alpha v beta 5 did not affect nodule formation, indicating that the inhibitions noted were indeed specific, To determine the effect of antibody treatment on gene expression, steady-state mRNA expression was examined and found to be suppressed for osteoblast markers alkaline phosphatase and osteocalcin, Together, these results indicate that direct osteoblast interactions with the extracellular matrix are mediated by a select group of integrin receptors that includes alpha 5 beta 1, alpha 3 beta 1 and alpha 8 beta 1. We further conclude that the specific alpha 5 beta 1 fibronectin receptor mediates critical interactions between osteoblasts and fibronectin required for both bone morphogenesis and osteoblast differentiation. C1 UNIV CALIF SAN FRANCISCO,DEPT STOMATOL,SAN FRANCISCO,CA 94143. UNIV CALIF SAN FRANCISCO,DEPT MED,SAN FRANCISCO,CA 94143. UNIV CALIF SAN FRANCISCO,DEPT ANAT,SAN FRANCISCO,CA 94143. NASA,AMES RES CTR,MOFFETT FIELD,CA 94035. FU NIDCR NIH HHS [P50-DE10306, T32 DE0724] NR 47 TC 272 Z9 279 U1 2 U2 12 PU COMPANY OF BIOLOGISTS LTD PI CAMBRIDGE PA BIDDER BUILDING CAMBRIDGE COMMERCIAL PARK COWLEY RD, CAMBRIDGE, CAMBS, ENGLAND CB4 4DL SN 0021-9533 J9 J CELL SCI JI J. Cell Sci. PD SEP PY 1997 VL 110 BP 2187 EP 2196 PN 18 PG 10 WC Cell Biology SC Cell Biology GA YA401 UT WOS:A1997YA40100005 PM 9378768 ER PT J AU Mitchell, TP Blier, W AF Mitchell, TP Blier, W TI The variability of wintertime precipitation in the region of California SO JOURNAL OF CLIMATE LA English DT Article ID CONTERMINOUS UNITED-STATES; SEA-SURFACE TEMPERATURE; SOUTHERN OSCILLATION; NORTHERN-HEMISPHERE; CIRCULATION PATTERNS; PRINCIPAL COMPONENTS; COAST PRECIPITATION; PACIFIC COAST; HEIGHT FIELD; FREQUENCY AB Rotated principal component (RPC) analysis, subject to the varimax criterion and including area weighting, is applied to a 58-yr record (1931-88) of monthly-and seasonal-mean Climatic Division precipitation anomalies for the contiguous United States to document wintertime precipitation variability in the region of California. Rotated principal components (time series) derived from this analysis are related to anomalies of seasonal-mean global sea surface temperature, and monthly mean Northern Hemisphere 500-hPa geopotential height and sea level pressure (SLP). Wintertime seasonal-mean precipitation in California is captured by two RPCs. The first RPC documents coherent precipitation anomalies centered in northern California, Oregon, southern Idaho, and eastern Washington, and explains the largest portion of area-averaged variance of any of the patterns in the decomposition. A second RPC captures coherent precipitation variability in the south coast and southeast desert regions of California, southern Nevada, southern Utah, and northern Arizona. Fluctuations in the first RPC correlate poorly with Pacific Ocean SST anomalies. However, wet winters in the region of the second RPC correlate modestly with simultaneous cool western subtropical Pacific Ocean SST anomalies and weakly with warm SST anomalies over a broad region of the central and eastern tropical Pacific. The spatial scale of the tropical SST correlations and the prominent multidecadal timescale signal of the RPC are consistent with ENSO fluctuations on this timescale influencing southern California precipitation. Consistent with the results of earlier studies, significant correlations are found between California wintertime monthly mean precipitation variability and regional 500-hPa geopotential height and SLP anomalies. Linear regression analysis is used to construct estimates of the total 500-hPa geopotential height and SLP fields (climatology plus anomaly) that are representative of the extreme wet and dry California winter months; these are then compared with the observed conditions in the individual extreme months. Several different Bow patterns appear capable of producing anomalously large monthly precipitation totals in California. C1 NASA,GODDARD SPACE FLIGHT CTR,UNIV SPACE RES ASSOC INC,GREENBELT,MD 20771. UNIV CALIF LOS ANGELES,DEPT ATMOSPHER SCI,LOS ANGELES,CA 90024. NR 60 TC 19 Z9 24 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 SEP PY 1997 VL 10 IS 9 BP 2261 EP 2276 DI 10.1175/1520-0442(1997)010<2261:TVOWPI>2.0.CO;2 PG 16 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA XX482 UT WOS:A1997XX48200009 ER PT J AU Zhang, YC Rossow, WB AF Zhang, YC Rossow, WB TI Estimating meridional energy transports by the atmospheric and oceanic general circulations using boundary fluxes SO JOURNAL OF CLIMATE LA English DT Article ID SEA-SURFACE TEMPERATURE; SOLAR RADIATIVE FLUXES; BROKEN CLOUD FIELDS; LATENT-HEAT FLUXES; TROPICAL PACIFIC; ATLANTIC OCEAN; BALANCE; RADIANCES; EARTH; SENSITIVITY AB The annual-mean meridional energy transport in the atmosphere-ocean system (total transport) is estimated using 4-yr mean net radiative fluxes at the top of the atmosphere (TOA) calculated from the International Satellite Cloud Climatology Project cloud datasets. In addition, the net atmospheric and surface radiative fluxes are calculated. When supplemented by a climatology of the surface latent and sensible heat fluxes, these radiative fluxes are used to derive the separate atmospheric and oceanic energy transports using a surface and planetary energy-balance method. Most previous results are based on direct calculations of the atmospheric energy transport from in situ measurements of horizontal wind velocity, temperature, and humidity in the atmosphere and on inference of oceanic heat transports as the difference between the atmospheric transports and the total energy transport (the planetary energy-balance method). Total, atmospheric, and oceanic energy transports from this study are in good agreement with more recent results (within mutual uncertainties). A detailed assessment is made of the uncertainties in the atmospheric and ocean energy transports that arise from uncertainties in the TOA and surface energy fluxes: the largest uncertainties are associated with the surface radiative and latent heat fluxes. Since the errors in the present method are from different sources and have different geographic distributions, the results of this study complement previous estimates of the atmospheric and oceanic energy transports. Assessment of error sources also suggests that improvement of this type of result is more likely in the near future than for the other methods. Because the radiative fluxes are calculated from physical quantities, the authors can characterize the mean effects of clouds on the atmospheric and oceanic energy transports: 1) cloud effects on the TOA radiation budget reduce hemispheric differences introduced by hemispheric differences of surface properties, 2) the cloud effects on the atmospheric and surface radiation budgets induce hemispheric differences in the heating/cooling of the atmosphere and ocean that require cross-equatorial transports in opposite directions by the atmosphere and ocean, and 3) all other factors held constant, clouds tend to reduce oceanic energy transports and increase atmospheric energy transports. C1 NASA,GODDARD INST SPACE STUDIES,NEW YORK,NY 10025. RP Zhang, YC (reprint author), COLUMBIA UNIV,DEPT APPL PHYS,2880 BROADWAY,NEW YORK,NY 10025, USA. RI Rossow, William/F-3138-2015 NR 59 TC 39 Z9 39 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 SEP PY 1997 VL 10 IS 9 BP 2358 EP 2373 DI 10.1175/1520-0442(1997)010<2358:EMETBT>2.0.CO;2 PG 16 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA XX482 UT WOS:A1997XX48200016 ER PT J AU Chen, MH Rood, RB Takacs, LL AF Chen, MH Rood, RB Takacs, LL TI Impact of a semi-Lagrangian and an Eulerian dynamical core on climate simulations SO JOURNAL OF CLIMATE LA English DT Article ID GRAVITY-WAVE DRAG; GENERAL-CIRCULATION MODELS; FINITE-DIFFERENCE SCHEME; VERSION; TROPOSPHERE; STRATOSPHERE; INTEGRATION; SENSITIVITY; RESOLUTION; PREDICTION AB To assess the impact of dynamical formulation on climate simulations, a semi-Lagrangian and an Eulerian dynamical core have been used for 5-yr climate simulations with the same physical parameterizations. The comparison of the climate simulations is focused on various eddy statistics (the study of time-mean states from the simulations has been published in a previous paper). Significant differences between the two simulations are evident. Generally, the stationary eddy variances are stronger in the semi-Lagrangian simulation while the transient eddy variances are stronger in the Eulerian simulation. Compared to the data assimilated by the Goddard Earth Observing System data assimilation system, the semi-Lagrangian simulation is closer to the assimilation in many aspects than the Eulerian simulation, even though the Eulerian model was used in the data assimilation. The paper shows that rather than corrupting the ability to diagnose model performance with a parallel data assimilation, quantitative rigor can be advanced because the model environment is more controlled. The two dynamical cores have been run for the idealized Held-Suarez tests to help understand the differences found in the climate simulations. The eddy statistics from the Held-Suarez tests are weaker and more diffused in the semi-Lagrangian than the Eulerian core. The transformed Eulerian mean diagnostics reveal that less wave activity propagates from the lower and middle troposphere into the upper troposphere in the semi-Lagrangian core. The residual circulation driven by eddy forcing is weaker in the semi-Lagrangian core than in the Eulerian core. Consequently, the semi-Lagrangian simulation is closer to the radiative equilibrium state than the Eulerian simulation. These diagnostics show that the different treatment of small-scale processes in the model (e.g., diffusion) profoundly impacts the simulation of the general circulation. C1 NASA, GODDARD SPACE FLIGHT CTR, DATA ASSIMILAT OFF, GREENBELT, MD 20771 USA. RI Rood, Richard/C-5611-2008 OI Rood, Richard/0000-0002-2310-4262 NR 39 TC 10 Z9 13 U1 0 U2 1 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 USA SN 0894-8755 J9 J CLIMATE JI J. Clim. PD SEP PY 1997 VL 10 IS 9 BP 2374 EP 2389 DI 10.1175/1520-0442(1997)010<2374:IOASLA>2.0.CO;2 PG 16 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA XX482 UT WOS:A1997XX48200017 ER PT J AU Dong, TZ AF Dong, TZ TI On boundary conditions for acoustic computations in non-uniform mean flows SO JOURNAL OF COMPUTATIONAL ACOUSTICS LA English DT Article ID HYPERBOLIC SYSTEMS AB Many acoustic problems involve acoustic wave radiation to the exterior held. A common approach in numerical simulations is to restrict the computational domain to a finite region with artificial boundaries. The so-called radiation or non-reflecting boundary conditions must be imposed at those artificial boundaries. Most existing non-reflecting boundary conditions are derived for computing disturbances propagating in a known uniform mean flow near the boundaries. In many applications such as the computation of jet noise or turbofan noise, the mean flow at an artificial boundary is non-uniform and unknown. The mean flow also needs to be computed in these cases. Incorrect computation of this mean how at the boundary could directly affect the near field physics as well as the far field acoustics. In the present paper, a set of boundary conditions is proposed which focuses on computing the correct mean solution at an artificial boundary, while still maintaining the non-reflecting feature for the outgoing transient and acoustic waves. C1 NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. RP Dong, TZ (reprint author), NASA, Lewis Res Ctr, Mail Stop 5-9, Cleveland, OH 44135 USA. NR 17 TC 12 Z9 12 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 0218-396X J9 J COMPUT ACOUST JI J. Comput. Acoust. PD SEP PY 1997 VL 5 IS 3 BP 297 EP 315 DI 10.1142/S0218396X97000174 PG 19 WC Acoustics; Mathematics, Interdisciplinary Applications SC Acoustics; Mathematics GA YP476 UT WOS:000071280600004 ER PT J AU Suresh, A Huynh, HT AF Suresh, A Huynh, HT TI Accurate monotonicity-preserving schemes with Runge-Kutta time stepping SO JOURNAL OF COMPUTATIONAL PHYSICS LA English DT Article ID CONSERVATIVE DIFFERENCE SCHEME; ONE-DIMENSIONAL ADVECTION; SHOCK-CAPTURING SCHEMES; EFFICIENT IMPLEMENTATION; ENO SCHEMES; UPWIND METHODS; LAWS AB A new class of high-order monotonicity-preserving schemes for the numerical solution of conservation laws is presented. The interface value in these schemes is obtained by limiting a higher-order polynomial reconstruction. The limiting is designed to preserve accuracy near extrema and to work well with Runge-Kutta time stepping. Computational efficiency is enhanced by a simple test that determines whether the limiting procedure is needed. For linear advection in one dimension, these schemes are shown to be monotonicity-preserving and uniformly high-order accurate. Numerical experiments for advection as well as the Euler equations also confirm their high accuracy, good shock resolution, and computational efficiency. (C) 1997 Academic Press. C1 NASA, LEWIS RES CTR, CLEVELAND, OH 44135 USA. RP NYMA INC, BROOKPARK, OH 44142 USA. NR 25 TC 171 Z9 180 U1 4 U2 9 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 SEP 1 PY 1997 VL 136 IS 1 BP 83 EP 99 DI 10.1006/jcph.1997.5745 PG 17 WC Computer Science, Interdisciplinary Applications; Physics, Mathematical SC Computer Science; Physics GA XU688 UT WOS:A1997XU68800006 ER PT J AU Burlaga, LF Ness, NF AF Burlaga, LF Ness, NF TI Global patterns of heliospheric magnetic field polarities and elevation angles: 1990 through 1995 SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID MERGED INTERACTION REGIONS; VOYAGER-2 OBSERVATIONS; CURRENT SHEET; SECTOR STRUCTURE; SOLAR CORONA; COSMIC-RAYS; ULYSSES; SHOCK AB From 1990 through 1995, Voyager 1 (V1) moved from 39.9 to 61.7 AU in the distant heliosphere at a latitude of approximate to 32 +/- 1 degrees N. During this period of declining solar activity, the latitudinal extent of the sector zone (the region containing sectors and the heliospheric current sheet) was decreasing. From 1990 through 1992, V1 observed both positive and negative magnetic polarities, indicating that it was ja the sector zone. From 1993 through 1995, V1 observed primarily positive magnetic polarities, indicating that it was above the sector zone. The transition in the V1 polarity distribution at the beginning of 1993 implies that the maximum latitudinal extent of the sector zone was then approximate to 32 degrees N; This transition is related to a decrease in the maximum latitudinal extent of the computed neutral line in the solar corona. The ''classic model'' of the neutral line provides a better description of the V1 polarities than the ''radial model.'' The latitudinal extent of the sector zone was nearly constant from the Sun to 50 AU; A similar transition in the polarity distribution was observed at approximate to 30 degrees S by Ulysses in early 1993 within 5 AU, establishing the minimum latitudinal extent of the sector zone at that time. From 1990 through 1995, hear-Earth spacecraft (which were near the solar equatorial plane, in the middle of the sector zone) observed equal amounts of positive and negative polarities. The bimodal two-polarity distributions observed by Voyager 2 Showed an increasing fraction bf negative polarities as it moved from 2.4 degrees N to 15.1 degrees S and from 31.1 to 47.7 AU. The distribution of elevation angles was gaussian both at V1 in the distant heliosphere and near 1 AU during the each of the years from 1990 through 1995. The width of the distribution did not change significantly at V1 from 1986 through 1995, consistent with little (<5 degrees) or no variation with (1) radial distance from 40 to 62 AU, (2) latitude from 31 degrees to 33 degrees, and (3) the solar cycle. The width of the distribution of elevation angles at 1 AU did vary with Solar activity, being 5 degrees greater at solar maximum than at solar minimum, possibly owing to the extreme north-south fields in many ejecta, which are more frequent near solar maximum. C1 UNIV DELAWARE, BARTOL RES INST, NEWARK, DE 19716 USA. RP Burlaga, LF (reprint author), NASA, GODDARD SPACE FLIGHT CTR, EXTRATERR PHYS LAB, CODE 692, GREENBELT, MD 20771 USA. NR 40 TC 17 Z9 17 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 SEP 1 PY 1997 VL 102 IS A9 BP 19731 EP 19742 DI 10.1029/97JA01568 PG 12 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XU866 UT WOS:A1997XU86600001 ER PT J AU Neugebauer, M Goldstein, R Goldstein, BE AF Neugebauer, M Goldstein, R Goldstein, BE TI Features observed in the trailing of interplanetary clouds from coronal mass ejections SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID INTER-PLANETARY SHOCK; COSMIC-RAY DECREASES; SOLAR-WIND; MAGNETIC CLOUDS; PLASMA-EXPERIMENT; LOOP STRUCTURE; EVENTS; RECONNECTION; TOPOLOGY; DISTURBANCES AB ISEE 3 plasma and magnetic field data are used to study features in the trailing regions of interplanetary plasma clouds resulting from coronal mass ejections (CMEs). Approximately one fifth of these events contain periods greater than or equal to 6 hours for which the interplanetary magnetic field is quiet and nearly radial (\B-x\/B > 0.9). Arguments are presented that the association of quiet radial fields with CMEs is a causal relation, rather than coincidence. The quiet radial fields occur in the trailing, rather than the leading, regions of the CMEs, and they coincide with periods of declining solar wind speed. In some cases the radial field period overlaps periods with other CME signatures, while in other cases the radial field interval follows the disappearance of those signatures. Another trailing-region feature exhibited by approximately half the CMEs detected by ISEE 3 is a period of outward propagating Alfven waves. Possible causes of these signatures are discussed. RP Neugebauer, M (reprint author), CALTECH, JET PROP LAB, MS 169-506, 4800 OAK GROVE DR, PASADENA, CA 91109 USA. NR 44 TC 39 Z9 39 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 SEP 1 PY 1997 VL 102 IS A9 BP 19743 EP 19751 DI 10.1029/97JA01651 PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XU866 UT WOS:A1997XU86600002 ER PT J AU Ruzmaikin, A Feynman, J Smith, EJ AF Ruzmaikin, A Feynman, J Smith, EJ TI Turbulence in coronal mass ejections SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID SOLAR-WIND; MAGNETIC CLOUDS AB The magnetic fields measured by the ISEE 3 spacecraft are used to study MHD turbulence within coronal mass ejections (CMEs). The spectral indices of the turbulence inside CMEs are compared with spectral indices found in solar wind undisturbed by CMEs. Irrespective of the CME velocities, the spectra within CMEs are found to differ from those determined for the fast solar wind from coronal holes. Instead, the CME spectra more closely resemble those found in the slow solar wind. Since both CMEs and the plasma sheet are associated with closed magnetic structures in. the solar corona, it appears that the turbulence in the solar wind arising from closed coronal regions is fundamentally different from the turbulence in wind from coronal holes. Helical properties of magnetic fields-within CMEs at different scales are studied. Preliminary results indicate that, in small scales, helical fields are distributed in a random fashion with alternating signs of twisting structures. In addition however. CMEs have large-scale helical structures. In the case of the magnetic cloud of day 302, 1978 this structure is interpreted as a part of the helical structure identified previously by fitting the data to a force-free flux rope configuration. RP Ruzmaikin, A (reprint author), CALTECH,JET PROP LAB,4800 OAK GROVE DR,PASADENA,CA 91109, USA. NR 25 TC 6 Z9 6 U1 1 U2 2 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 J9 J GEOPHYS RES-SPACE JI J. Geophys. Res-Space Phys. PD SEP 1 PY 1997 VL 102 IS A9 BP 19753 EP 19759 DI 10.1029/97JA01558 PG 7 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XU866 UT WOS:A1997XU86600003 ER PT J AU Huterer, D Paularena, KI Szabo, A AF Huterer, D Paularena, KI Szabo, A TI Observation and analysis of selected IMP 8 and WIND bow shock crossings in late 1994 SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID MAGNETIC-FIELD; ORIENTATION; SPACECRAFT; SHAPE AB Nine bow shock crossings from late 1994 are examined using data from the IMP 8 spacecraft as input to the Rankine-Hugoniot (RH) conservation equations. In addition, two crossings from the same time period are examined using WIND spacecraft data. A nonlinear chi-square minimization method is used to obtain the best fit bow shock (BS) normal and speed for each crossing. The shock normals and speeds are also calculated neglecting temperature, as well as using only the magnetic coplanarity and velocity coplanarity techniques. All of the methods generally give mutually consistent results. The orientations of the shock normals are consistent with the nominal bow shock shape. The shocks were expected to move according to a simple ''breathing model in which the bow shock moves inward and outward from Earth according to changes in external solar wind conditions. However, the results show outward motion of the bow shock for all but one of all the crossings considered. Moreover, the direction of motion of the BS depends on the,exact choice of the shock normal so that a slightly different shock normal can give a different sense of motion of the BS. We conclude that the RH equations that we use may be missing some terms which would provide an accurate description of the balance on both sides of the BS. In particular, the BS acceleration at its flanks is not taken into account by these equations. C1 MIT,DEPT PHYS,CAMBRIDGE,MA 02139. MIT,CTR SPACE RES,CAMBRIDGE,MA 02139. NASA,GODDARD SPACE FLIGHT CTR,EXTRATERR PHYS LAB,GREENBELT,MD 20771. HUGHES STX CORP,LANHAM,MD. NR 19 TC 5 Z9 5 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 J9 J GEOPHYS RES-SPACE JI J. Geophys. Res-Space Phys. PD SEP 1 PY 1997 VL 102 IS A9 BP 19761 EP 19772 DI 10.1029/97JA01661 PG 12 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XU866 UT WOS:A1997XU86600004 ER PT J AU Schneider, NM Taylor, MH Crary, FJ Trauger, JT AF Schneider, NM Taylor, MH Crary, FJ Trauger, JT TI On the nature of the lambda(III) brightness asymmetry in the Io torus SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID EXTREME ULTRAVIOLET OBSERVATIONS; MAGNETIC-ANOMALY MODEL; NEUTRAL CLOUD THEORY; PLASMA TORUS; JOVIAN MAGNETOSPHERE; NUMERICAL-SIMULATION; VOYAGER; ENERGY; ENCOUNTER; TRANSPORT AB The optical brightening of the Io torus around lambda(III)similar to 200 degrees has been known for 20 years, but observations have only recently revealed the nature of the asymmetry. We show that the optical asymmetry is due to changes in ion temperature, with little or no change in flux tube content. These results have significant ramifications for magnetospheric transport and torus energy flows. We examine causes of ion temperature variations and demonstrate that existing zero-dimensional energy balance models are inadequate. We develop a more complete model of energy flow in the torus and find that small changes in energy sources result in large changes in ion and electron temperatures and densities. We extend the theory to predict brightness asymmetries at other wavelengths and show that a search for EUV asymmetries at the 30% level can help resolve the torus ''energy crisis.'' ''Neutral Cloud Theory'' predicts an EUV brightness asymmetry of exactly opposite phase to the optical asymmetry, while an unknown electron energy source around lambda(III)similar to 200 degrees could cancel or reverse this EUV asymmetry. C1 CALTECH,JET PROP LAB,PASADENA,CA 91109. RP Schneider, NM (reprint author), UNIV COLORADO,ATMOSPHER & SPACE PHYS LAB,CB 392,BOULDER,CO 80309, USA. OI SCHNEIDER, NICHOLAS/0000-0001-6720-5519 NR 37 TC 23 Z9 23 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 J9 J GEOPHYS RES-SPACE JI J. Geophys. Res-Space Phys. PD SEP 1 PY 1997 VL 102 IS A9 BP 19823 EP 19833 DI 10.1029/97JA00773 PG 11 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XU866 UT WOS:A1997XU86600009 ER PT J AU Phan, TD Larson, D McFadden, J Lin, RP Carlson, C Moyer, M Paularena, KI McCarthy, M Parks, GK Reme, H Sanderson, TR Lepping, RP AF Phan, TD Larson, D McFadden, J Lin, RP Carlson, C Moyer, M Paularena, KI McCarthy, M Parks, GK Reme, H Sanderson, TR Lepping, RP TI Low-latitude dusk flank magnetosheath, magnetopause, and boundary layer for low magnetic shear: Wind observations SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID DAYSIDE MAGNETOPAUSE; EARTHS MAGNETOPAUSE; SUBSOLAR MAGNETOSHEATH; ISEE OBSERVATIONS; ELECTRIC-FIELDS; PLASMA; RECONNECTION; MAGNETOSPHERE; MODEL; MAGNETOTAIL AB We have studied in detail a Wind spacecraft crossing of the low-latitude dusk flank magnetosheath, magnetopause (MP), and the low-latitude boundary layer (LLBL) when the local magnetic shear across the MP was low (<30 degrees) and the interplanetary magnetic field (IMF) was northward. We find that the magnetosheath flow tangential to the MP slows down initially as one moves from the bow shock toward the MP. However, close to the MP this flow speeds up as the MP is approached. The source of flow acceleration is likely to be the magnetic force associated with draping of the field lines around the MP. Magnetic flux pile-up and a plasma depletion layer are also observed next to the flank MP indicating that the level of magnetic flux transfer across the entire dayside low-latitude MP via reconnection is low. The MP is characterized by changes in the plasma properties. The electron parallel temperature is enhanced across the MP and continues to increase across the LLBL, while the perpendicular temperature is constant across the MP. This constancy of the perpendicular temperature suggests that the transfer of plasma takes place across the local MP. In the LLBL, the ion and electron temperatures are well correlated with the density. In addition, the flow direction in a substantial portion of the LLBL is nearly aligned with that in the magnetosheath, and the flow speed tangential to the MP decreases gradually with decreasing LLBL density. The behavior of the particle distributions suggests that the entire LLBL was on closed field lines. In essence, our findings on the topology and on the LLBL plasma characteristics suggest that even in the absence of reconnection at the local low-shear MP, the LLBL is locally coupled to the adjacent magnetosheath. The smooth variations of the plasma parameters with the density are consistent with the LLBL spatial profiles being gradual. This may suggest that diffusion processes play a role in the formation and dynamics of the LLBL. Finally, the magnetic field and the state of the plasma in the plasma sheet adjacent to the flank MP/LLBL appear to be functions of the IMF direction. Thus the IMF may control both the external (magnetosheath) and the internal (plasma sheet) boundary conditions for the flank MP processes. C1 NASA,GODDARD SPACE FLIGHT CTR,EXTRATERR PHYS LAB,GREENBELT,MD 20771. UNIV WASHINGTON,GEOPHYS PROGRAM,SEATTLE,WA 98195. MIT,CTR SPACE RES,CAMBRIDGE,MA 02139. UNIV TOULOUSE 3,CTR ETUD SPATIALE RAYONNEMENTS,F-31062 TOULOUSE,FRANCE. EUROPEAN SPACE TECHNOL CTR,EUROPEAN SPACE AGCY,DEPT SPACE SCI,NL-2200 AG NOORDWIJK,NETHERLANDS. RP Phan, TD (reprint author), UNIV CALIF BERKELEY,SPACE SCI LAB,BERKELEY,CA 94720, USA. NR 48 TC 66 Z9 67 U1 0 U2 2 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 J9 J GEOPHYS RES-SPACE JI J. Geophys. Res-Space Phys. PD SEP 1 PY 1997 VL 102 IS A9 BP 19883 EP 19895 DI 10.1029/97JA01596 PG 13 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XU866 UT WOS:A1997XU86600014 ER PT J AU Sundaram, AK Fairfield, DH AF Sundaram, AK Fairfield, DH TI Stability of resistive MHD tearing and ballooning modes in the tail current sheet SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID NEUTRAL SHEET; MAGNETOTAIL; INSTABILITY; PLASMA; DRIVEN; WAVES; OSCILLATIONS; TURBULENCE; DYNAMICS AB We have analytically investigated the evolution of resistive MHD tearing and ballooning modes by assuming that the dissipation is anomalous in the current sheet region. A generalized technique is diplayed for obtaining the solutions for both these modes near the singular layer, where the B-x(z) field reverses sign. When the perturbation is limited to two dimensions, we have found that the stability of tearing modes is controlled by compressibility and the Lundquist number S, where S is the ratio of anomalous diffusion time to Alfven time. For S much less than 5 x 10(3), the fluid compressibility plays a significant destabilizing role while the normal component B, contributes to a weak stabilization of tearing modes. In the three-dimensional case with k(y) not equal 0 (k(y) being the wavenumber), it is demonstrated that a linear coupling of the pressure gradient and the magnetic field curvature causes the excitation of a new class of unstable tearing and ballooning modes with their growth rates significantly dependent on anomalous resistivity and the Alfvenic frequency. The resistive ballooning modes, excited in the field reversal layer, are shown to enhance the current and the magnetic field gradients in the center of the plasma sheet and thereby provide the source for the excitation of tearing modes with a typical growth time of 5 s. Finally, the relevance of the newly excited modes to recent AMPTE/IRM, GEOS 2, and Geotail results is discussed. C1 HUGHES STX CORP, GREENBELT, MD USA. RP Sundaram, AK (reprint author), NASA, GODDARD SPACE FLIGHT CTR, EXTRATERR PHYS LAB, CODE 695, GREENBELT, MD 20771 USA. NR 28 TC 12 Z9 12 U1 0 U2 2 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 J9 J GEOPHYS RES-SPACE JI J. Geophys. Res-Space Phys. PD SEP 1 PY 1997 VL 102 IS A9 BP 19913 EP 19925 DI 10.1029/97JA01241 PG 13 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XU866 UT WOS:A1997XU86600017 ER PT J AU Tsyganenko, NA AF Tsyganenko, NA TI An empirical model of the substorm current wedge SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID MAGNETIC-FIELD MODEL; MAGNETOSPHERIC SUBSTORMS; CURRENT SYSTEMS; CURRENT SHEET; TAIL; PARAMETERS; EXPANSION; PHASE AB A wedge-shaped current linking the nightside ionosphere and the plasma sheet is believed to be the principal cause of a major reconfiguration of the magnetospheric held on the nightside, observed at the onset of the substorm's explosive phase. No dynamical model of the magnetosphere is complete without this important component; however, no realistic representation for the field of the substorm current wedge has been available so far, in part due to the geometrical complexity of that current system and related computational problems. In this work, a simple and flexible analytical model is proposed for the magnetic field of substorm current wedge. The key element of the mathematical treatment is the vector potential of the field produced by a pair of current loops with a spread-out volume current density. Applying appropriate shift, rotation, and a minor stretching deformation makes it possible to reproduce the desired geometry of the entire system, including field-aligned currents. The current wedge has a variable longitudinal width, and the model is further generalized by including warping effects due to the tilt of Earth's dipole. This model is intended to be used in data-based representations of the magnetic field dynamics in the near magnetosphere and will make it possible to reproduce the fast restructuring of the near-Earth held during the explosive phase of a substorm. RP 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 22 TC 16 Z9 17 U1 0 U2 3 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-9380 EI 2169-9402 J9 J GEOPHYS RES-SPACE JI J. Geophys. Res-Space Phys. PD SEP 1 PY 1997 VL 102 IS A9 BP 19935 EP 19941 DI 10.1029/97JA01904 PG 7 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XU866 UT WOS:A1997XU86600019 ER PT J AU Meriwether, JW Biondi, MA Herrero, FA Fesen, CG Hallenback, DC AF Meriwether, JW Biondi, MA Herrero, FA Fesen, CG Hallenback, DC TI Optical interferometric studies of the nighttime equatorial thermosphere: Enhanced temperatures and zonal wind gradients SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID FABRY-PEROT-INTERFEROMETER; GENERAL-CIRCULATION MODEL; SCALE GRAVITY-WAVES; F-REGION; NEUTRAL WINDS; VERTICAL WINDS; 6300-A NIGHTGLOW; PLASMA DRIFTS; SOLAR MAXIMUM; SPREAD-F AB Fabry-Perot interferometric observations at 630 nm of equatorial thermospheric winds and temperatures in the four cardinal directions and zenith from Arequipa, Peru, during local winter for moderate and high solar fluxes Showed elevated temperatures over the Andes Mountains that persisted;through the night. The difference in temperature between east;and west observations was typically similar to 100 to 200 K for moderate flux values and as high as 400 K at solar maximum. Correlated with these localized heating regions were differences in the zonal thermospheric wind of 50 to 70 m/s for observations to die west and to the east of the Arequipa observatory. Also noted in these periods for the region over the Andes was the increased variance of the temperature values above the measurement error. These effects of increased variability and localized heating were not observed at solar minimum. The lack of a significant local time dependence in the diurnal variation of the temperature enhancements suggests that the origin of the heating cannot be related to the coupling of the electrodynamics of the ionosphere to the thermosphere, Instead the hypothesis is advanced that gravity wave energy from the surface penetrates into the thermosphere, where viscous dissipation causes the heating. Such wave activity would also explain the increased variability of the temperatures for the thermosphere regions over mountainous terrain. C1 UNIV PITTSBURGH,DEPT PHYS & ASTRON,PITTSBURGH,PA 15260. UNIV TEXAS,PHYS PROGRAMS,WB HANSEN CTR SPACE SCI,RICHARDSON,TX 75083. NASA,LASER TRACKING STN,AREQUIPA,PERU. NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20940. RP Meriwether, JW (reprint author), CLEMSON UNIV,DEPT PHYS & ASTRON,206 KINARD LAB,CLEMSON,SC 29634, USA. NR 62 TC 25 Z9 25 U1 0 U2 2 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 J9 J GEOPHYS RES-SPACE JI J. Geophys. Res-Space Phys. PD SEP 1 PY 1997 VL 102 IS A9 BP 20041 EP 20058 DI 10.1029/97JA01463 PG 18 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XU866 UT WOS:A1997XU86600028 ER PT J AU Crassidis, JL Markley, FL AF Crassidis, JL Markley, FL TI New algorithm for attitude determination using global positioning system signals SO JOURNAL OF GUIDANCE CONTROL AND DYNAMICS LA English DT Article ID SPACECRAFT ATTITUDE; VECTOR OBSERVATIONS; GPS AB A novel technique for finding a point-by-point (deterministic) attitude solution of a vehicle using Global Positioning System phase difference measurements is presented. This technique transforms a general cost function into a more numerically efficient form by determining three-dimensional vectors in either the body or reference coordinate system. Covariance relationships for the new algorithm, as well as methods that minimize the general cost function, are also derived. The equivalence of the general cast function and transformed cost function is shown for the case of orthogonal baselines or sight lines. Simulation results are shown that demonstrate the usefulness of the new algorithm and covariance expressions. C1 NASA,GODDARD SPACE FLIGHT CTR,GUIDANCE NAVIGAT & CONTROL BRANCH,GREENBELT,MD 20771. RP Crassidis, JL (reprint author), CATHOLIC UNIV AMER,DEPT ENGN MECH,WASHINGTON,DC 20064, USA. NR 14 TC 42 Z9 43 U1 1 U2 4 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 SEP-OCT PY 1997 VL 20 IS 5 BP 891 EP 896 DI 10.2514/2.4162 PG 6 WC Engineering, Aerospace; Instruments & Instrumentation SC Engineering; Instruments & Instrumentation GA XU125 UT WOS:A1997XU12500007 ER PT J AU Burken, JJ Burcham, FW AF Burken, JJ Burcham, FW TI Flight-test results of propulsion-only emergency control system on MD-11 airplane SO JOURNAL OF GUIDANCE CONTROL AND DYNAMICS LA English DT Article; Proceedings Paper CT AIAA Guidance, Navigation, and Control Conference and Exhibit CY JUL 29-31, 1996 CL SAN DIEGO, CA SP AIAA AB A large, civilian, multiengine transport MD-11 airplane control system was recently modified to perform as an emergency backup controller using engine thrust only The emergency backup system, referred to as the propulsion-controlled aircraft (PCA) system, would be used if a major primary flight control system fails. To allow for longitudinal-and lateral-directional control, the PCA system requires at least two engines and is implemented through software modifications. A flight-test program was conducted to evaluate the PCA system high-altitude flying characteristics and to demonstrate its capacity to perform safe landings, The cruise flight conditions, several low approaches, and four landings without any aerodynamic flight control surface movement were demonstrated; however only one landing is presented, Results that show satisfactory performance of the PCA system in the longitudinal axis are presented. Test results indicate that the lateral-directional axis of the system performed well at high altitude but was sluggish and prone to thermal upsets during landing approaches. Flight-test experiences and test techniques are also discussed, with emphasis on the lateral-directional axis because of the difficulties encountered in flight test. RP Burken, JJ (reprint author), NASA,DRYDEN FLIGHT RES CTR,CONTROLS & DYNAM BRANCH,EDWARDS AFB,CA 93523, USA. NR 10 TC 14 Z9 14 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 SEP-OCT PY 1997 VL 20 IS 5 BP 980 EP 987 DI 10.2514/2.4143 PG 8 WC Engineering, Aerospace; Instruments & Instrumentation SC Engineering; Instruments & Instrumentation GA XU125 UT WOS:A1997XU12500019 ER PT J AU Walsh, BM Barnes, NP DiBartolo, B AF Walsh, BM Barnes, NP DiBartolo, B TI On the distribution of energy between the Tm F-3(4) and Ho I-5(7) manifolds in Tm-sensitized Ho luminescence SO JOURNAL OF LUMINESCENCE LA English DT Article DE energy transfer; rate equations; thulium; holmium; Tm:Ho lasers ID LASER; YAG AB A theory on the distribution of energy between the Tm F-3(4) and Ho I-5(7) manifolds in Tm-sensitized Ho materials is presented. A rate equation approach is utilized to arrive at an expression for the temperature-dependent equilibrium constant, Theta. Experimental support for this calculation is obtained by two different experimental procedures. Approximations used in the theory and the limits of applicability are also discussed. In the course of the development of the theory, a distinction is made between low and high excitation regimes, and criterion for applicability are given. Equations for the fractional population of Tm and Ho ions of the total excited state population in the low excitation density limit are derived in the context of the present theory, which differ from those widely used in the literature. C1 NASA,LANGLEY RES CTR,HAMPTON,VA 23681. RP Walsh, BM (reprint author), BOSTON COLL,DEPT PHYS,CHESTNUT HILL,MA 02167, USA. NR 17 TC 54 Z9 60 U1 1 U2 6 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0022-2313 J9 J LUMIN JI J. Lumines. PD SEP PY 1997 VL 75 IS 2 BP 89 EP 98 DI 10.1016/S0022-2313(97)00110-5 PG 10 WC Optics SC Optics GA XY977 UT WOS:A1997XY97700002 ER PT J AU Schmidt, GA Johnson, ER AF Schmidt, GA Johnson, ER TI Instability in stratified rotating shear flow along ridges SO JOURNAL OF MARINE RESEARCH LA English DT Article ID LOW-FREQUENCY SCATTERING; COASTALLY TRAPPED WAVES; KELVIN-WAVES; TOPOGRAPHY; MODEL AB This paper examines the interaction between continuously stratified horizontal shear flow and topography. It investigates when topography whose slope changes sign (i.e., a ridge or a trench) destabilizes a shear flow. The instabilities have the form of topographic Rossby waves and rely on the background potential vorticity gradient to exist. Barotropic flow is examined in detail for general horizontal shear over stepped topography and the longwave stratified case is examined in the more specific case of linear shear flow over a top-hat ridge profile. In all cases modes are unstable over significant ranges of the relevant parameters. Stationary unstable modes are seen to correspond to points where two opposing waves are brought simultaneously to rest by the shear flow and propagating unstable modes are seen where opposing waves are brought relatively to rest. Another interpretation of the instabilities in terms of resonance between waves of oppositely signed energy is also explored. Although the greatest growth rates for instabilities occur for the fundamental mode (or external Kelvin wave) interactions, for realistic oceanographic parameters the interactions of the slower moving, higher modes are more likely to be important. C1 UNIV LONDON UNIV COLL,DEPT MATH,LONDON WC1E 6BT,ENGLAND. RP Schmidt, GA (reprint author), NASA,GODDARD SPACE FLIGHT CTR,2880 BROADWAY,NEW YORK,NY 10025, USA. RI Schmidt, Gavin/D-4427-2012; Johnson, Edward/A-9414-2008 OI Schmidt, Gavin/0000-0002-2258-0486; Johnson, Edward/0000-0001-7129-8471 NR 21 TC 3 Z9 3 U1 0 U2 0 PU KLINE GEOLOGY LABORATORY PI NEW HAVEN PA YALE UNIV, NEW HAVEN, CT 06520 SN 0022-2402 J9 J MAR RES JI J. Mar. Res. PD SEP PY 1997 VL 55 IS 5 BP 915 EP 933 DI 10.1357/0022240973224201 PG 19 WC Oceanography SC Oceanography GA YH097 UT WOS:A1997YH09700005 ER PT J AU Ponsardin, PL Browell, EV AF Ponsardin, PL Browell, EV TI Measurements of (H2O)-O-16 linestrengths and air-induced broadenings and shifts in the 815-nm spectral region SO JOURNAL OF MOLECULAR SPECTROSCOPY LA English DT Article ID 720-NM WAVELENGTH REGION; WATER-VAPOR; LIDAR MEASUREMENTS; TEMPERATURE; NITROGEN; LASER; LINES; SENSITIVITY; STRENGTHS; PROFILES AB The linestrengths for 40 absorption lines of (H2O)-O-16 water vapor that were located between 813 and 820 nm were measured; most of these lines were selected for their potential usefulness in laser remote measurements of atmospheric humidity using the differential absorption lidar technique. The air-induced pressure-broadening coefficients were also measured for 32 of these lines and the air-induced pressure shift coefficients were measured for 29 lines. These spectroscopic parameters were derived from spectra obtained with an AlGaAs diode laser and two long-path absorption cells. Collisional narrowing effects were observed and were accurately described by a Galatry profile. Comparisons were made with previous experimental work or theoretical calculations as available, (C) 1997 Academic Press. C1 NASA,LANGLEY RES CTR,DIV ATMOSPHER SCI,HAMPTON,VA 23681. RP Ponsardin, PL (reprint author), NASA,LANGLEY RES CTR,SCI APPLICAT INT CORP,HAMPTON,VA 23681, USA. NR 36 TC 47 Z9 47 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 0022-2852 J9 J MOL SPECTROSC JI J. Mol. Spectrosc. PD SEP PY 1997 VL 185 IS 1 BP 58 EP 70 DI 10.1006/jmsp.1997.7354 PG 13 WC Physics, Atomic, Molecular & Chemical; Spectroscopy SC Physics; Spectroscopy GA YD830 UT WOS:A1997YD83000009 ER PT J AU Moody, AB AF Moody, AB TI Non-military navigation by satellites (Reprinted from Journal of Navigation, vol 16, pg 9, 1963) SO JOURNAL OF NAVIGATION LA English DT Reprint RP Moody, AB (reprint author), NASA,WASHINGTON,DC 20546, USA. NR 1 TC 0 Z9 0 U1 0 U2 0 PU CAMBRIDGE UNIV PRESS PI NEW YORK PA 40 WEST 20TH STREET, NEW YORK, NY 10011-4211 SN 0373-4633 J9 J NAVIGATION JI J. Navig. PD SEP PY 1997 VL 50 IS 3 BP 458 EP 461 PG 4 WC Engineering, Marine; Oceanography SC Engineering; Oceanography GA YK677 UT WOS:A1997YK67700028 ER PT J AU Davidson, G AF Davidson, G TI Managing by processes in private and public organizations: scientific management in the information revolution SO JOURNAL OF POST KEYNESIAN ECONOMICS LA English DT Article C1 NASA, Goddard Space Flight Ctr, Mission Operat & Data Syst Directorate, Greenbelt, MD 20771 USA. RP Davidson, G (reprint author), NASA, Goddard Space Flight Ctr, Mission Operat & Data Syst Directorate, Greenbelt, MD 20771 USA. NR 5 TC 0 Z9 0 U1 1 U2 2 PU M E SHARPE INC PI ARMONK PA 80 BUSINESS PARK DR, ARMONK, NY 10504 USA SN 0160-3477 J9 J POST KEYNESIAN EC JI J. Post Keynes. Econ. PD FAL PY 1997 VL 20 IS 1 BP 25 EP 45 PG 21 WC Economics SC Business & Economics GA ZM451 UT WOS:000073541500003 ER PT J AU Millis, MG AF Millis, MG TI Challenge to create the space drive SO JOURNAL OF PROPULSION AND POWER LA English DT Article ID PROPULSION; FORCE AB To travel to our neighboring stars as practically as envisioned by science fiction, breakthroughs in science are required. One of these breakthroughs is to discover a self-contained means of propulsion that requires no propellant. To chart a path toward such a discovery, seven hypothetical space drives are presented to illustrate tbe specific unsolved challenges and associated research objectives toward this ambition. One research objective is to discover a means to asymmetrically interact with the electromagnetic fluctuations of the vacuum. Another is to develop a physics that describes inertia, gravity, or the properties of space-time as a function of electromagnetics that leads to using electromagnetic technology for inducing propulsive forces. Another is to determine if negative mass exists or if its properties can be synthesized, An alternative approach that covers the possibility that negative mass might not exist is to develop a formalism of Mach's principle or reformulate ether concepts to lay a foundation for addressing reaction forces and conservation of momentum with space drives. RP Millis, MG (reprint author), NASA,LEWIS RES CTR,CLEVELAND,OH 44135, USA. NR 21 TC 34 Z9 35 U1 2 U2 5 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 SEP-OCT PY 1997 VL 13 IS 5 BP 577 EP 582 DI 10.2514/2.5215 PG 6 WC Engineering, Aerospace SC Engineering GA XW136 UT WOS:A1997XW13600001 ER PT J AU Carlson, JR AF Carlson, JR TI Applications of algebraic Reynolds stress turbulence models .1. Incompressible flat plate SO JOURNAL OF PROPULSION AND POWER LA English DT Article; Proceedings Paper CT AIAA/ASME/SAE/ASEE 32nd Joint Propulsion Conference CY JUL 01-03, 1996 CL LAKE BUENA VISTA, FL SP Amer Inst Aeronaut & Astronaut, ASME, SAE, ASEE AB The ability of the three-dimensional Navier-Stokes method, PAB3D, to simulate the effect of Reynolds number variation by using nonlinear explicit algebraic Reynolds stress turbulence modeling was assessed, Subsonic bat-plate boundary-layer flow parameters such as law-of-the-wall velocity distributions, local and average skin Friction, skin friction correlation, and shape factors were compared with direct numerical simulation calculations and classical theory at local Reynolds numbers up to 180 x 10(6). Each model displayed slightly different low and high Reynolds number characteristics, but generally compared very well with classical theories and data, No definitive advantage of one explicit algebraic Reynolds stress model over another was observed. RP Carlson, JR (reprint author), NASA,LANGLEY RES CTR,AERO & GASDYNAM DIV,M-S 286,HAMPTON,VA 23681, USA. NR 19 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 SEP-OCT PY 1997 VL 13 IS 5 BP 610 EP 619 DI 10.2514/2.5225 PG 10 WC Engineering, Aerospace SC Engineering GA XW136 UT WOS:A1997XW13600005 ER PT J AU Carlson, JR AF Carlson, JR TI Applications of algebraic Reynolds stress turbulence models .2. Transonic shock-separated afterbody SO JOURNAL OF PROPULSION AND POWER LA English DT Article; Proceedings Paper CT AIAA/ASME/SAE/ASEE 32nd Joint Propulsion Conference CY JUL 01-03, 1996 CL LAKE BUENA VISTA, FL SP Amer Inst Aeronaut & Astronaut, ASME, SAE, ASEE AB The ability of the three-dimensional Navier-Stokes method PAB3D code to simulate the effect of Reynolds number variation using nonlinear explicit algebraic Reynolds stress turbulence modeling was assessed, Surface pressure coefficient distributions and integrated drag predictions on an axisymmetric nozzle afterbody were compared with experimental data at Reynolds numbers from 10 to 130 x 10(6). There was generally good agreement of surface static pressure coefficients between the computational fluid dynamics (CFD) and measurement. The change in pressure coefficient distributions with varying Reynolds number was similar to the experimental data trends, though the CFD slightly overpredicted the effect. The computational sensitivity of viscous modeling and turbulence modeling are shown, Integrated afterbody pressure drag was typically slightly loner than the experimental data, The change in afterbody pressure drag with Reynolds number was small, both experimentally and computationally, even though the shape of the distribution was somewhat modified with the Reynolds number. RP Carlson, JR (reprint author), NASA,LANGLEY RES CTR,AERO & GASDYNAM DIV,M-S 286,HAMPTON,VA 23681, USA. NR 12 TC 4 Z9 4 U1 0 U2 2 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 SEP-OCT PY 1997 VL 13 IS 5 BP 620 EP 628 DI 10.2514/2.5226 PG 9 WC Engineering, Aerospace SC Engineering GA XW136 UT WOS:A1997XW13600006 ER PT J AU Steinetz, BM Adams, ML Bartolotta, PA Darolia, R Olsen, A AF Steinetz, BM Adams, ML Bartolotta, PA Darolia, R Olsen, A TI High-temperature braided rope seals for static sealing applications SO JOURNAL OF PROPULSION AND POWER LA English DT Article; Proceedings Paper CT AIAA/ASME/SAE/ASEE 32nd Joint Propulsion Conference CY JUL 01-03, 1996 CL LAKE BUENA VISTA, FL SP Amer Inst Aeronaut & Astronaut, ASME, SAE, ASEE AB Achieving efficiency and performance goals of advanced aircraft and industrial systems is leading designers to implement high-temperature materials such as ceramics and intermetallics. Generally, these advanced materials are applied selectively in the highest temperature sections of the engine system, including the combustor and high-pressure turbine sections, among others, Thermal strains that result in attaching the low expansion-rate components to high expansion-rate superalloy structures can cause significant life reduction in the components, Seals are being designed to both seal and serve as compliant mounts, allowing for relative thermal growths between high-temperature, but brittle, primary structures and the surrounding support structures. Designers require high-temperature, low-leakage, compliant seals to mitigate thermal stresses, and to control parasitic and cooling airflow between structures. High-temperature braided rope seals are being developed in it variety of configurations to help solve these problems. This paper will describe the types of seals being developed, describe unique test techniques used to assess seal performance, and present leakage dow data under representative pressure, temperature, and scrubbing conditions, Feasibility of the braided rope seals for both an industrial tube seal and a turbine vane seal application is also demonstrated. C1 NASA,LEWIS RES CTR,FATIGUE & FRACTURE BRANCH,CLEVELAND,OH 44135. NASA,LEWIS RES CTR,DEPT MAT ENGN,CLEVELAND,OH 44135. NASA,LEWIS RES CTR,DEMONSTRAT ENGINE SYST DEPT,CLEVELAND,OH 44135. RP Steinetz, BM (reprint author), NASA,LEWIS RES CTR,STRUCT DYNAM BRANCH,21000 BROOK PK RD,M-S 23-3,CLEVELAND,OH 44135, USA. NR 9 TC 6 Z9 7 U1 0 U2 0 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 SN 0748-4658 J9 J PROPUL POWER JI J. Propul. Power PD SEP-OCT PY 1997 VL 13 IS 5 BP 675 EP 682 DI 10.2514/2.5219 PG 8 WC Engineering, Aerospace SC Engineering GA XW136 UT WOS:A1997XW13600013 ER PT J AU Bhatia, AK Kastner, SO AF Bhatia, AK Kastner, SO TI Doppler-profile escape factors and escape probabilities for the cylinder and hemisphere SO JOURNAL OF QUANTITATIVE SPECTROSCOPY & RADIATIVE TRANSFER LA English DT Article ID RATIOS; LINES AB Escape factors have been computed and tabulated for photons emitted within cylinders and hemispheres and absorbed/scattered according to the Doppler-profile function. The mean escape probability for Doppler-profile photons emerging normal to the axis of a cylinder has also been obtained. The assumptions under which these quantities are derived are described. Logistic-function approximations for the three types of escape probability are fitted to the tabulated values. Typographical errors were found and corrected in an earlier expression quoted in the literature. (C) 1997 Elsevier Science Ltd. C1 NASA,GODDARD SPACE FLIGHT CTR,ASTRON & SOLAR PHYS LAB,GREENBELT,MD 20771. NR 12 TC 14 Z9 14 U1 0 U2 0 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 SEP PY 1997 VL 58 IS 3 BP 347 EP 354 DI 10.1016/S0022-4073(97)00033-2 PG 8 WC Optics; Spectroscopy SC Optics; Spectroscopy GA YF747 UT WOS:A1997YF74700003 ER PT J AU Palmer, GE Henline, WD Olynick, DR Milos, FS AF Palmer, GE Henline, WD Olynick, DR Milos, FS TI High-fidelity thermal protection system sizing of reusable launch vehicle SO JOURNAL OF SPACECRAFT AND ROCKETS LA English DT Article; Proceedings Paper CT AIAA 29th Thermophysics Conference CY JUN 19-22, 1995 CL SAN DIEGO, CA SP Amer Inst Aeronaut & Astronaut AB A coupled computational fluid dynamics/in-depth conduction analysis procedure to perform high-fidelity thermal protection system sizing is presented. The thermal environment on the vehicle surface, including radiative equilibrium wall temperature and surface catalycity, is computed using a real-gas, Navier-Stokes flow solver, Based on the computed surface temperatures, a thermal protection system material mapping is performed, Material thickness and overall thermal protection system mass are obtained using an in-depth conduction code, This procedure is used to size the thermal protection system on a lifting-body, single-stage-to-orbit vehicle. C1 NASA,AMES RES CTR,THERMAL PROTECT MAT & SYST BRANCH,MOFFETT FIELD,CA 94035. RP Palmer, GE (reprint author), NASA,AMES RES CTR,REACTING FLOW ENVIRONM BRANCH,MOFFETT FIELD,CA 94035, USA. NR 18 TC 6 Z9 9 U1 0 U2 2 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 SEP-OCT PY 1997 VL 34 IS 5 BP 577 EP 583 DI 10.2514/2.3261 PG 7 WC Engineering, Aerospace SC Engineering GA YA510 UT WOS:A1997YA51000001 ER PT J AU Richards, WL Monaghan, RC AF Richards, WL Monaghan, RC TI Development of a flight article for a hypersonic boundary-layer experiment SO JOURNAL OF SPACECRAFT AND ROCKETS LA English DT Article AB Preparations for a boundary-layer transition experiment to be conducted on a future flight mission of the air-launched Pegasus(R) rocket are underway. The experiment requires a flight-test article called a glove to be attached to the wing of the Mach-8 first-stage booster. A three-dimensional, nonlinear finite element analysis has been performed and significant small-scale laboratory testing has been accomplished to support the design and development of the flight-test glove. Reliance on analyses and laboratory tests has been instrumental in achieving the structural stability and strength requirements for the glove design. Results obtained from the structural analysis and laboratory testing show that all glove components are well within the allowable thermal stress and deformation requirements to satisfy experiment objectives. RP Richards, WL (reprint author), NASA,DRYDEN FLIGHT RES CTR,AEROSTRUCT BRANCH,POB 273,EDWARDS AFB,CA 93523, USA. NR 6 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 SEP-OCT PY 1997 VL 34 IS 5 BP 609 EP 613 DI 10.2514/2.3277 PG 5 WC Engineering, Aerospace SC Engineering GA YA510 UT WOS:A1997YA51000005 ER PT J AU Wang, TS Cornelison, J AF Wang, TS Cornelison, J TI Analysis of flowfields over four-engine DC-X rockets SO JOURNAL OF SPACECRAFT AND ROCKETS LA English DT Article; Proceedings Paper CT AIAA/ASME/SAE/ASEE 32nd Joint Propulsion Conference CY JUL 01-03, 1996 CL LAKE BUENA VISTA, FL SP Amer Inst Aeronaut & Astronaut, ASME, SAE, ASEE ID CLUSTERED NOZZLE CONFIGURATION; BASE FLOWFIELD AB The objective of this study is to validate a computational methodology for the aerodynamic performance of an advanced conical launch vehicle configuration. The computational methodology is based on a three-dimensional, viscous flow, pressure-based computational fluid dynamics formulation. Both wind-tunnel and ascent flight-test data are used for validation. Emphasis is placed on multiple-engine power-on effects. Computational characterization of the base drag in the critical subsonic regime is the focus of the validation effort; until recently, almost no multiple-engine data existed for a conical launch vehicle configuration. Parametric studies using high-order difference schemes are performed for the cold-how tests, whereas grid studies are conducted for the flight tests. The computed vehicle axial force coefficients, forebody, aftbody, and base surface pressures compare favorably with those of tests. The results demonstrate that with adequate grid density and proper distribution, a high-order difference scheme, finite rate afterburning kinetics to model the plume chemistry, and a suitable turbulence model to describe separated flows, plume/air mixing, and boundary layers, computational fluid dynamics is a tool that can be used to predict the low-speed aerodynamic performance for rocket design and operations. C1 NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,FLUID DYNAM ANAL BRANCH,HUNTSVILLE,AL 35812. RP Wang, TS (reprint author), NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,COMPUTAT ANAL TEAM,HUNTSVILLE,AL 35812, USA. NR 25 TC 4 Z9 4 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 SEP-OCT PY 1997 VL 34 IS 5 BP 620 EP 627 DI 10.2514/2.3279 PG 8 WC Engineering, Aerospace SC Engineering GA YA510 UT WOS:A1997YA51000007 ER PT J AU Goracke, BD Levack, DJH Johnson, GW AF Goracke, BD Levack, DJH Johnson, GW TI Tripropellant engine option comparison for single stage to orbit SO JOURNAL OF SPACECRAFT AND ROCKETS LA English DT Article; Proceedings Paper CT AIAA Space Programs and Technologies Conference CY SEP 26-28, 1995 CL HUNTSVILLE, AL SP Amer Inst Aeronaut & Astronaut AB Recent evaluations of main engine options for the single-stage-to-orbit/reusable launch vehicle mission have considered the use of a tripropellant engine to take advantage of its improved fuel density. A wide range of options has been addressed, including configuration, technology level, and design practices, A study was conducted to evaluate engine configurations on a consistent basis of technology level, design practice, and design ground rules. Engine weight and performance of several cycles and cycle variants were determined and then compared on a vehicle dry weight basis to determine the merit of each, A series of bipropellant configurations was also studied under identical ground rules to evaluate the inherent differences due to propellant selection only. The results showed that the three major variants considered, a single-chamber tripropellant, an annular bell tripropellant, and a bipropellant, were nearly identical in terms of overall vehicle performance. C1 NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,HUNTSVILLE,AL 35812. BOEING CO,ADV SYST PROGRAM,CANOGA PK,CA 91309. RP Goracke, BD (reprint author), BOEING CO,ADV CONCEPTS,CANOGA PK,CA 91309, USA. NR 19 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 0022-4650 J9 J SPACECRAFT ROCKETS JI J. Spacecr. Rockets PD SEP-OCT PY 1997 VL 34 IS 5 BP 636 EP 641 DI 10.2514/2.3281 PG 6 WC Engineering, Aerospace SC Engineering GA YA510 UT WOS:A1997YA51000009 ER PT J AU Boltz, FW AF Boltz, FW TI Payload capability of kerosene-fueled mini shuttle SO JOURNAL OF SPACECRAFT AND ROCKETS LA English DT Article ID SSTO ROCKETS; ACCESS; SPACE RP Boltz, FW (reprint author), NASA,AMES RES CTR,AERONAUT DIV,MOFFETT FIELD,CA 94035, USA. NR 12 TC 4 Z9 4 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 SEP-OCT PY 1997 VL 34 IS 5 BP 685 EP 687 DI 10.2514/2.3270 PG 3 WC Engineering, Aerospace SC Engineering GA YA510 UT WOS:A1997YA51000018 ER PT J AU Blanchard, RC Wilmoth, RG Moss, JN AF Blanchard, RC Wilmoth, RG Moss, JN TI Aerodynamic flight measurements and rarefied-flow simulations of Mars entry vehicles SO JOURNAL OF SPACECRAFT AND ROCKETS LA English DT Article RP Blanchard, RC (reprint author), NASA,LANGLEY RES CTR,AEROTHERMODYNAM BRANCH,HAMPTON,VA 23681, USA. NR 8 TC 12 Z9 14 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 SEP-OCT PY 1997 VL 34 IS 5 BP 687 EP 690 DI 10.2514/2.3271 PG 4 WC Engineering, Aerospace SC Engineering GA YA510 UT WOS:A1997YA51000019 ER PT J AU Lin, CY AbdelHamid, T Sherif, JS AF Lin, CY AbdelHamid, T Sherif, JS TI Software-Engineering Process Simulation model (SEPS) SO JOURNAL OF SYSTEMS AND SOFTWARE LA English DT Article ID COST; PRODUCTIVITY; UTILITY AB This paper describes the Software-Engineering Process Simulation (SEPS) model developed at JPL. SEPS is a dynamic simulation model of the software project-development process. It uses the feedback principles of system dynamics to simulate the dynamic interactions among various software life-cycle development activities and management decision-making processes. The model is designed to be a planning tool to examine trade-offs of cost, schedule, and functionality, and to test the implications of different managerial policies on a project's outcome. Furthermore, SEPS will enable software managers to gain a better understanding of the dynamics of software project development and perform postmortem assessments. (C) 1997 Elsevier Science Inc. C1 CALIF STATE UNIV FULLERTON,FULLERTON,CA 92634. CALTECH,JET PROP LAB,PASADENA,CA. USN,POSTGRAD SCH,MONTEREY,CA. NR 22 TC 27 Z9 28 U1 0 U2 2 PU ELSEVIER SCIENCE INC PI NEW YORK PA 655 AVENUE OF THE AMERICAS, NEW YORK, NY 10010 SN 0164-1212 J9 J SYST SOFTWARE JI J. Syst. Softw. PD SEP PY 1997 VL 38 IS 3 BP 263 EP 277 DI 10.1016/S0164-1212(96)00156-2 PG 15 WC Computer Science, Software Engineering; Computer Science, Theory & Methods SC Computer Science GA XK249 UT WOS:A1997XK24900007 ER PT J AU Dausch, DE AF Dausch, DE TI Ferroelectric polarization fatigue in PZT-based RAINBOWs and bulk ceramics SO JOURNAL OF THE AMERICAN CERAMIC SOCIETY LA English DT Article; Proceedings Paper CT Fall Meeting of the American-Ceramic-Society CY OCT 31, 1996 CL SAN ANTONIO, TX SP Amer Ceram Soc ID ZIRCONATE-TITANATE CERAMICS; ELECTRIC FATIGUE; BEHAVIOR; PLZT AB The ferroelectric fatigue behavior of high-displacement reduced and internally biased oxide wafer (RAINBOW) actuators was investigated and compared with that of conventional bulk ceramics. Piezoelectric lead zirconate titanates (PZT-5H and PZT-5A) as well as electrostrictive lead lanthanum zirconate titanate (PLZT 9/65/35) materials were studied. Piezoelectric bulk ceramics experienced a 25% decrease in remanent polarization over 10(8) switching cycles, whereas RAINBOW polarization degraded by 33%-53%. Bulk ceramic and RAINBOW electrostrictors both fatigued only 8%. Bulk ceramics fatigued as a result of reorientation of the polar axes away from the electric-field direction, RAINBOW fatigue was believed to have been caused by degradation at the interface between the oxide and chemically reduced layers. RP Dausch, DE (reprint author), NASA,LANGLEY RES CTR,NATL RES COUNCIL,HAMPTON,VA 23681, USA. NR 15 TC 23 Z9 23 U1 0 U2 5 PU AMER CERAMIC SOC PI WESTERVILLE PA 735 CERAMIC PLACE, PO BOX 6136, WESTERVILLE, OH 43081-6136 SN 0002-7820 J9 J AM CERAM SOC JI J. Am. Ceram. Soc. PD SEP PY 1997 VL 80 IS 9 BP 2355 EP 2360 PG 6 WC Materials Science, Ceramics SC Materials Science GA XX488 UT WOS:A1997XX48800021 ER PT J AU Bansal, NP AF Bansal, NP TI Strong and tough Hi-nicalon-fiber-reinforced celsian-matrix composites SO JOURNAL OF THE AMERICAN CERAMIC SOCIETY LA English DT Article AB Strong, tough, and almost fully dense BN/SiC-coated Hi-Nicalon-fiber-reinforced celsian-matrix composites have been fabricated by impregnation of the fiber tows with the matrix slurry, winding on a drum, stacking the prepreg tapes in the desired orientation, and hot pressing, The monoclinic celsian phase in the matrix was produced in situ, during hot pressing, from a mixed oxide precursor, The unidirectional composites having approximate to 42 vol% of fibers exhibited graceful failure with extensive fiber pullout in three-point bend tests at room temperature, Values of stress and strain at the proportional limit were 435 +/- 35 MPa and 0.27 +/- 0.01%, respectively, and an apparent ultimate strength of 900 +/- 60 MPa was observed, Young's modulus of the composites was 165 +/- 5 GPa. RP Bansal, NP (reprint author), NASA,LEWIS RES CTR,CLEVELAND,OH 44135, USA. NR 14 TC 30 Z9 30 U1 2 U2 2 PU AMER CERAMIC SOC PI WESTERVILLE PA 735 CERAMIC PLACE, PO BOX 6136, WESTERVILLE, OH 43081-6136 SN 0002-7820 J9 J AM CERAM SOC JI J. Am. Ceram. Soc. PD SEP PY 1997 VL 80 IS 9 BP 2407 EP 2409 PG 3 WC Materials Science, Ceramics SC Materials Science GA XX488 UT WOS:A1997XX48800027 ER PT J AU Johnson, KR AF Johnson, KR TI Mars Pathfinder spacecraft, lander, and rover testing in simulated deep space and Mars surface environments SO JOURNAL OF THE INSTITUTE OF ENVIRONMENTAL SCIENCES LA English DT Article DE Mars Pathfinder; thermal vacuum testing; Mars rover; simulated Mars environment AB The Mars Pathfinder (MPF) spacecraft was built and tested at the Jet Propulsion Laboratory during 1995 and 1996. MPF was launched December 4, 1996, and successfully landed on Mars on July 4, 1997. The testing program required that the mission hardware be subjected to both deep space and Mars surface conditions. A series of tests were devised and conducted from January, 1995, to July, 1996, to study the thermal response of the MPF spacecraft to the environmental conditions to which it was to be exposed during the cruise phase (on the way to Mars) and the lander phase (landed on Mars). In addition, several tests were conducted to study the thermal characteristics of the Mars rover, Sojourner, under Mars surface environmental conditions. Several special test fixtures and methods were devised to simulate the required environmental conditions. Creating simulated Mars surface conditions was a challenging undertaking since the Mars surface is subjected to diurnal cycling between -20 degrees C and -85 degrees C, with wind speeds to 20 m/sec, occurring in an 8 torr CO2 atmosphere. This paper describes the MPF test program conducted at JPL to verify the MPF thermal design. RP Johnson, KR (reprint author), CALTECH,JET PROP LAB,4800 OAK GROVE DR,PASADENA,CA 91125, USA. NR 10 TC 0 Z9 0 U1 0 U2 1 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 SEP-OCT PY 1997 VL 40 IS 5 BP 17 EP 26 PG 10 WC Engineering, Environmental; Environmental Sciences; Instruments & Instrumentation SC Engineering; Environmental Sciences & Ecology; Instruments & Instrumentation GA YD824 UT WOS:A1997YD82400004 ER PT J AU Han, D Kim, YS Noz, ME AF Han, D Kim, YS Noz, ME TI Jones-matrix formalism as a representation of the Lorentz group SO JOURNAL OF THE OPTICAL SOCIETY OF AMERICA A-OPTICS IMAGE SCIENCE AND VISION LA English DT Article ID 2-PHOTON QUANTUM OPTICS; GROUP BERRY PHASES; POLARIZATION OPTICS; STATES AB It is shown that the two-by-two Jones-matrix formalism for polarization optics is a six-parameter two-by-two representation of the Lorentz group. The attenuation and phase-shift filters are represented, respectively, by the three-parameter rotation subgroup and the three-parameter Lorentz group for two spatial dimensions and one time dimension. The Lorentz group has another three-parameter subgroup, which is like the two-dimensional Euclidean group. Optical filters that may have this Euclidean symmetry are discussed in detail. It is shown that the Jones-matrix formalism can be extended to some of the nonorthogonal polarization coordinate systems within the framework of the Lorentz-group representation. (C) 1997 Optical Society of America. C1 UNIV MARYLAND,DEPT PHYS,COLLEGE PK,MD 20742. NYU,DEPT RADIOL,NEW YORK,NY 10016. RP Han, D (reprint author), NASA,GODDARD SPACE FLIGHT CTR,CODE 910-1,GREENBELT,MD 20771, USA. NR 37 TC 28 Z9 28 U1 0 U2 1 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 SEP PY 1997 VL 14 IS 9 BP 2290 EP 2298 DI 10.1364/JOSAA.14.002290 PG 9 WC Optics SC Optics GA XT937 UT WOS:A1997XT93700027 ER PT J AU Watson, AB Solomon, JA AF Watson, AB Solomon, JA TI Model of visual contrast gain control and pattern masking SO JOURNAL OF THE OPTICAL SOCIETY OF AMERICA A-OPTICS IMAGE SCIENCE AND VISION LA English DT Article ID VISION MECHANISMS; CORTEX; FREQUENCY; RESPONSES; NEURONS AB We have implemented a model of contrast gain control in human vision that incorporates a number of key features, including a contrast sensitivity function, multiple oriented bandpass channels, accelerating nonlinearities, and a divisive inhibitory gain control pool. The parameters of this model have been optimized through a fit to the recent data that describe masking of a Gabor function by cosine and Gabor masks [J. M. Foley, ''Human luminance pattern mechanisms: masking experiments require a new model,'' J. Opt. Sec. Am. A 11, 1710 (1994)]. The model achieves a good fit to the data. We also demonstrate how the concept of recruitment may accommodate a variant of this model in which excitatory and inhibitory paths have a common accelerating nonlinearity, but which include multiple channels tuned to different levels of contrast [P. C. Teo and D. J. Heeger, ''Perceptual image distortion,'' in Human Vision, Visual Processing, and Digital Display V, B. E. Rogowitz and J. P. Allebach, eds., Proc. SPIE 2179, 127 (1994)]. (C) 1997 Optical Society of America. C1 INST OPHTHALMOL,LONDON EC1V 9EL,ENGLAND. RP Watson, AB (reprint author), NASA,AMES RES CTR,MOFFETT FIELD,CA 94035, USA. NR 25 TC 265 Z9 274 U1 0 U2 8 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 SEP PY 1997 VL 14 IS 9 BP 2379 EP 2391 DI 10.1364/JOSAA.14.002379 PG 13 WC Optics SC Optics GA XT937 UT WOS:A1997XT93700036 PM 9291608 ER PT J AU Eckstein, MP Ahumada, AJ Watson, AB AF Eckstein, MP Ahumada, AJ Watson, AB TI Visual signal detection in structured backgrounds .2. Effects of contrast gain control, background variations, and white noise SO JOURNAL OF THE OPTICAL SOCIETY OF AMERICA A-OPTICS IMAGE SCIENCE AND VISION LA English DT Article ID OBSERVER MODEL; HUMAN-VISION; DISCRIMINATION; MASKING; EFFICIENCY; PERFORMANCE; KNOWLEDGE AB Studies of visual detection of a signal superimposed on one of two identical backgrounds show performance degradation when the background has high contrast and is similar in spatial frequency and/or orientation to the signal. To account for this finding, models include a contrast gain control mechanism that pools activity across spatial frequency, orientation and space to inhibit (divisively) the response of the receptor sensitive to the signal. In tasks in which the observer has to detect a known signal added to one of M different backgrounds due to added visual noise, the main sources of degradation are the stochastic noise in the image and the suboptimal visual processing. We investigate how these two sources of degradation (contrast gain control and variations in the background) interact in a task in which the signal is embedded in one of M locations in a complex spatially varying background (structured background). We use backgrounds extracted from patient digital medical images. To isolate effects of the fixed deterministic background (the contrast gain control) from the effects of the background variations, we conduct detection experiments with three different background conditions: (1) uniform background, (2) a repeated sample of structured background, and (3) different samples of structured background. Results show that human visual detection degrades from the uniform background condition to the repeated background condition and degrades even further in the different backgrounds condition. These results suggest that both the contrast gain control mechanism and the background random variations degrade human performance in detection of a signal in a complex, spatially varying background. A filter model and added white noise are used to generate estimates of sampling efficiencies, an equivalent internal noise, an equivalent contrast-gain-control-induced noise, and an equivalent noise due to the variations in the structured background. (C) 1997 Optical Society of America. C1 CEDARS SINAI MED CTR,DEPT MED PHYS & IMAGING,LOS ANGELES,CA 90048. RP Eckstein, MP (reprint author), NASA,AMES RES CTR,8700 BEVERLY BLVD,DAVIS 6065,LOS ANGELES,CA 90048, USA. FU NHLBI NIH HHS [IRO1HL 53455] NR 45 TC 110 Z9 110 U1 1 U2 8 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 SEP PY 1997 VL 14 IS 9 BP 2406 EP 2419 DI 10.1364/JOSAA.14.002406 PG 14 WC Optics SC Optics GA XT937 UT WOS:A1997XT93700038 PM 9291610 ER PT J AU Ahumada, AJ Beard, BL AF Ahumada, AJ Beard, BL TI Image discrimination models predict detection in fixed but not random noise SO JOURNAL OF THE OPTICAL SOCIETY OF AMERICA A-OPTICS IMAGE SCIENCE AND VISION LA English DT Article; Proceedings Paper CT 1997 Electronic Imaging Conference CY 1997 CL SAN JOSE, CA SP Soc Imaging Sci & Technol, Soc Photo Opt Instrumentat Engineers ID EFFICIENCY AB By means of a two-interval forced-choice procedure, contrast detection thresholds for an aircraft positioned on a simulated airport runway scene were measured with fixed and random white-noise masks. The term fixed noise refers to a constant, or unchanging, noise pattern for each stimulus presentation. The random noise was either the same or different in the two intervals. Contrary to simple image discrimination model predictions, the same random noise condition produced greater mashing than the fixed noise. This suggests that observers seem unable to hold a new noisy image for comparison. Also, performance appeared limited by internal process variability rather than by external noise variability, since similar masking was obtained for both random noise types. (C) 1997 Optical Society of America. C1 UNIV CALIF BERKELEY,SCH OPTOMETRY,BERKELEY,CA 94720. RP Ahumada, AJ (reprint author), NASA,AMES RES CTR,MOFFETT FIELD,CA 94035, USA. FU NEI NIH HHS [EY0-4776] NR 21 TC 17 Z9 17 U1 0 U2 2 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 SEP PY 1997 VL 14 IS 9 BP 2471 EP 2476 PG 6 WC Optics SC Optics GA XT937 UT WOS:A1997XT93700042 PM 9291614 ER PT J AU Tawfik, HH Zimmerman, F AF Tawfik, HH Zimmerman, F TI Mathematical modeling of the gas and powder flow in HVOF systems SO JOURNAL OF THERMAL SPRAY TECHNOLOGY LA English DT Article DE HVOF; model; optimization; parameters; quality AB A mathematical model was developed to describe the gas dynamics and heat-transfer mechanism in the gas/particle flow of high-velocity oxyfuel (HVOF) systems, A numerical solution was carried out using a PC-based computer program, One-dimensional predictions of the temperature and velocity profiles of gas and particles along the axis of flow were obtained to conduct cost-effective parametric studies and quality optimization of thermal spray coatings produced by HVOF systems, The numerical computer model allows for the variation of the HVOF system parameters, such as air/fuel ratio and flow rates, cooling water inlet temperature and flow rate, barrel length, standoff distance, particle size, and gun geometry. Because of the negligible volume of the powder relative to the gas, the gaseous phase was modeled as continuous nonadiabatic, and friction flow with variable specific heats and changing cross-sectional areas of flow, The generalized continuity, momentum, and energy equations with the influence parameters were used to model the gaseous flow regime and predict its thermodynamic properties, Empirical formulas for the mean axial decay of both velocity and temperature in the supersonic jet plume region were generated from published measurements of these parameters using laser Doppler velocimeter and Rayleigh scattering techniques, respectively, The particle drag and heat-transfer coefficients were calculated by empirical formulas in terms of Reynolds, Nusselt, and Prandtl numbers to evaluate both the momentum and heat transferred between the combustion gases and the powder particles, The model predictions showed good agreement with the particle and gas temperature and velocity measurements that are available in the literature. C1 SUNY FARMINGDALE,FARMINGDALE,NY. NASA,MET PROC BRANCH,MAT & PROC LAB,GEORGE C MARSHALL SPACE FLIGHT CTR,HUNTSVILLE,AL 35812. NR 15 TC 18 Z9 19 U1 1 U2 7 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 SEP PY 1997 VL 6 IS 3 BP 345 EP 352 DI 10.1007/s11666-997-0069-6 PG 8 WC Materials Science, Coatings & Films SC Materials Science GA XV737 UT WOS:A1997XV73700042 ER PT J AU Liu, CX Harcombe, PA Knox, RG AF Liu, CX Harcombe, PA Knox, RG TI Effects of prescribed fire on the composition of woody plant communities in southeastern Texas SO JOURNAL OF VEGETATION SCIENCE LA English DT Article DE big thicket region; canonical correspondence analysis; ordination; permutation test; Pinus palustris ID LAKE WALES RIDGE; UNITED-STATES; FOREST VEGETATION; FLORIDA SANDHILL; BIG THICKET; ORDINATION; SUCCESSION; TEMPERATURE; DYNAMICS; SAVANNAS AB The response to prescribed burning of plant communities ranging from dry to wet habitats was monitored using permanent plots sampled from 1989 to 1993. Temporal controls for fire effects were provided by matched sets of plots protected from fire by newly constructed fire breaks. Changes in species composition were studied by ordination of strata of trees (>5 cm DBH), small trees (2 - 5 cm DBH), large saplings (1 - 2 cm DBH), and small saplings and seedlings (50 - 140 cm tall). Results show that changes occurred largely in the small tree stratum, in which xeric species increased in importance. Although there were changes in sapling and seedling strata, no clear direction of change was recognized. Fire had little effect on the tree stratum. Of the seven community types under study, three types, sandhill, upland pine, and upperslope pine-oak, were most strongly affected, as indicated by post-fire change in positions of samples representing these communities in ordination space and reduction in understory species abundance. Samples representing the other four mesic and wet communities showed little or no change in their positions. These short-term results indicate that changes in vegetation resulting from fire were small and were mostly restricted to the dry types in which possible compositional change is expected to occur. This differential effect of fire suggests that the influence of fire is secondary to that of topographical and soil gradients in determining vegetation pattern under current fire regimes. Fire seems to reinforce an overall vegetation gradient controlled by soil in southeastern Texas. C1 RICE UNIV,DEPT ECOL & EVOLUTIONARY BIOL,HOUSTON,TX 77005. TEXAS PARKS & WILDLIFE DEPT,GEOG INFORMAT SYST LAB,AUSTIN,TX 78744. NASA,GODDARD SPACE FLIGHT CTR,BIOSPHER SCI BRANCH,GREENBELT,MD 20771. RI Knox, Robert/E-9657-2011 NR 59 TC 9 Z9 9 U1 1 U2 11 PU OPULUS PRESS UPPSALA AB PI UPPSALA PA BOX 25137, S 752 25 UPPSALA, SWEDEN SN 1100-9233 J9 J VEG SCI JI J. Veg. Sci. PD SEP PY 1997 VL 8 IS 4 BP 495 EP 504 DI 10.2307/3237201 PG 10 WC Plant Sciences; Ecology; Forestry SC Plant Sciences; Environmental Sciences & Ecology; Forestry GA YG040 UT WOS:A1997YG04000004 ER PT J AU LeckeMitchell, KM Mullin, K AF LeckeMitchell, KM Mullin, K TI Floating marine debris in the US Gulf of Mexico SO MARINE POLLUTION BULLETIN LA English DT Article RP SE FISHERIES SCI CTR, NATL MARINE FISHERIES SERV, PO DRAWER 1207, PASCAGOULA, MS 39568 USA. NR 8 TC 12 Z9 12 U1 1 U2 12 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0025-326X EI 1879-3363 J9 MAR POLLUT BULL JI Mar. Pollut. Bull. PD SEP PY 1997 VL 34 IS 9 BP 702 EP 705 DI 10.1016/S0025-326X(97)00027-1 PG 4 WC Environmental Sciences; Marine & Freshwater Biology SC Environmental Sciences & Ecology; Marine & Freshwater Biology GA YF823 UT WOS:A1997YF82300015 ER PT J AU Lai, R Wang, H Chen, YC Block, T Liu, PH Streit, DC Tran, D Barsky, M Jones, W Siegel, P Gaier, T AF Lai, R Wang, H Chen, YC Block, T Liu, PH Streit, DC Tran, D Barsky, M Jones, W Siegel, P Gaier, T TI 155 GHz MMIC LNAs with 12 dB gain fabricated using a high yield InP HEMT MMIC process (Reprinted from Conference Proceedings, 1997 International Conference on Indium Phosphide and Related Materials, pg 241-244, May 1997) SO MICROWAVE JOURNAL LA English DT Reprint ID AMPLIFIER AB A highly robust, high performance 0.1 mu m passivated InGaAs/InAlAs/InP high electron mobility transistor (InP HEMT) MMIC process with frequency capability to 200 GHz and beyond has been developed. This process has demonstrated consistent wafer-to-wafer performance, as well as remarkable uniformity with a wafer average peak transconductance (Gmp) of 1100 mS/mm +/- 44 mS for more than 1000 sites tested over a two-rich (dia) wafer. A D-band InP HEMT MMIC low noise amplifier (LNA) using this process, which has demonstrated 12 dB gain at 155 GHz, is described. This performance represents the highest frequency solid-state amplifier reported to date. C1 JPL MICROWAVE,LIDAR,INTERFEROMETER TECHNOL SECT,PASADENA,CA. RP Lai, R (reprint author), TRW CO INC,ELECT SPACE & TECHNOL DIV,REDONDO BEACH,CA 90278, USA. NR 10 TC 4 Z9 4 U1 0 U2 1 PU HORIZON HOUSE PUBLICATIONS INC PI NORWOOD PA 685 CANTON ST, NORWOOD, MA 02062 SN 0192-6225 J9 MICROWAVE J JI Microw. J. PD SEP PY 1997 VL 40 IS 9 BP 166 EP & PG 5 WC Engineering, Electrical & Electronic; Telecommunications SC Engineering; Telecommunications GA XV881 UT WOS:A1997XV88100023 ER PT J AU Han, J Globus, A Jaffe, R Deardorff, G AF Han, J Globus, A Jaffe, R Deardorff, G TI Molecular dynamics simulations of carbon nanotube-based gears SO NANOTECHNOLOGY LA English DT Article ID CHEMISTRY; TUBULES; BENZENE AB We use a molecular dynamics simulation to investigate the properties and design space of molecular gears fashioned from carbon nanotubes with teeth added via a benzyne reaction known to occur with C-60. Brenner's reactive hydrocarbon potential is used to model interatomic forces within each molecular gear. A Lennard-Jones 6-12 potential or the Buckingham (exp+6) potential plus electrostatic interaction terms are used for intermolecular interactions between gears. A number of gear and gear/shaft configurations are simulated on parallel computers. One gear is powered by forcing the atoms near the end of the nanotube to rotate, and a second gear is allowed to rotate by keeping the atoms near the end of its nanotube constrained to a cylinder. The meshing aromatic gear teeth transfer angular momentum from the powered gear to the driven gear. Results suggest that these gears can operate at up to 50-100 GHz in a vacuum at room temperature. The failure mode involves tooth slip, not bond breaking, so failed gears can be returned to operation by lowering the temperature and/or rotation rate. RP Han, J (reprint author), NASA,AMES RES CTR,MOFFETT FIELD,CA 94035, USA. NR 18 TC 114 Z9 121 U1 1 U2 20 PU IOP PUBLISHING LTD PI BRISTOL PA DIRAC HOUSE, TEMPLE BACK, BRISTOL, ENGLAND BS1 6BE SN 0957-4484 J9 NANOTECHNOLOGY JI Nanotechnology PD SEP PY 1997 VL 8 IS 3 BP 95 EP 102 DI 10.1088/0957-4484/8/3/001 PG 8 WC Nanoscience & Nanotechnology; Materials Science, Multidisciplinary; Physics, Applied SC Science & Technology - Other Topics; Materials Science; Physics GA XW783 UT WOS:A1997XW78300001 ER PT J AU Garg, VK Ameri, AA AF Garg, VK Ameri, AA TI Comparison of two-equation turbulence models for prediction of heat transfer on film-cooled turbine blades SO NUMERICAL HEAT TRANSFER PART A-APPLICATIONS LA English DT Article ID TRANSITION AB A three-dimensional Navier-Stokes code has been used to compute the heat transfer coefficient on two film-cooled turbine blades, namely, the VKI rotor with sir rows of cooling holes, including three rows on the shower head, and the C3X vane with nine rows of holes, including five rows on the shower head. Predictions of heat transfer coefficient at the blade surface using three two-equation turbulence models, specifically, Coakley's q-omega model, Chien's k-epsilon model, and Wilcox's k-omega model with Menter's modifications, have been compared with the experimental data of Camci and Arts [1] for the VKI rotor, and of Hylton et al. [2] for the C3X vane along with predictions using the Baldwin-Lomax (B-L) model taken front Garg and Gaugler [3]. It is found that for the cases considered here the two-equation models predict the blade heat transfer somewhat better than the B-L model except immediately downstream of the film-cooling holes on the suction surface of the VKI rotor, and over most of the suction surface of the C3X vane. However, ail two-equation models require 40% more computer core than the B-L model for solution, and while the q-omega and k-epsilon models need 40% more computer time than the B-L model the k-omega model requires at least 65% more time because of the slower rate of convergence. It is found that lire heat transfer coefficient exhibits a strong spanwise as web as streamwise variation for both blades and all turbulence models. RP Garg, VK (reprint author), NASA,LEWIS RES CTR,AYT CORP,21000 BROOKPARK RD,MAIL STOP 5-11,CLEVELAND,OH 44135, USA. NR 25 TC 31 Z9 34 U1 0 U2 6 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 SEP PY 1997 VL 32 IS 4 BP 347 EP 371 DI 10.1080/10407789708913895 PG 25 WC Thermodynamics; Mechanics SC Thermodynamics; Mechanics GA XY289 UT WOS:A1997XY28900002 ER PT J AU Afzal, RS Yu, AW Zayhowski, TJ Fan, TY AF Afzal, RS Yu, AW Zayhowski, TJ Fan, TY TI Single-mode high-peak-power passively Q-switched diode-pumped Nd:YAG laser SO OPTICS LETTERS LA English DT Article AB We have demonstrated an efficient, compact, passively Q-switched single-mode diode-pumped Nd:YAG laser that uses Cr4+:YAG as a saturable absorber. Linear- and ring-cavity configurations were demonstrated. Pulse energies and widths were, respectively, 1.5 mJ and 3.9 ns for the linear cavity and 2.1 mJ and 12 ns for the ring cavity. (C) 1997 Optical Society of America. C1 MIT,LINCOLN LAB,LEXINGTON,MA 02173. RP Afzal, RS (reprint author), NASA,GODDARD SPACE FLIGHT CTR,CODE 924,GREENBELT,MD 20771, USA. NR 11 TC 47 Z9 53 U1 0 U2 12 PU OPTICAL SOC AMER PI WASHINGTON PA 2010 MASSACHUSETTS AVE NW, WASHINGTON, DC 20036 SN 0146-9592 J9 OPT LETT JI Opt. Lett. PD SEP 1 PY 1997 VL 22 IS 17 BP 1314 EP 1316 DI 10.1364/OL.22.001314 PG 3 WC Optics SC Optics GA XU425 UT WOS:A1997XU42500012 PM 18188224 ER PT J AU Yao, XS AF Yao, XS TI High-quality microwave signal generation by use of Brillouin scattering in optical fibers SO OPTICS LETTERS LA English DT Article ID OSCILLATOR AB An all-optical optoelectronic oscillator is demonstrated in which a novel Brillouin-selective sideband amplification technique is used to provide sufficient gain far the oscillator to start and sustain electro-optic oscillation. Such an oscillator can generate high-frequency, high-spectral-purity, tunable microwave signals in both optical and electrical domains beyond 100 GHz. (C) 1997 Optical Society of America. RP Yao, XS (reprint author), CALTECH,JET PROP LAB,4800 OAK GROVE DR,PASADENA,CA 91109, USA. NR 9 TC 35 Z9 37 U1 3 U2 6 PU OPTICAL SOC AMER PI WASHINGTON PA 2010 MASSACHUSETTS AVE NW, WASHINGTON, DC 20036 SN 0146-9592 J9 OPT LETT JI Opt. Lett. PD SEP 1 PY 1997 VL 22 IS 17 BP 1329 EP 1331 DI 10.1364/OL.22.001329 PG 3 WC Optics SC Optics GA XU425 UT WOS:A1997XU42500017 PM 18188229 ER PT J AU Ciocca, M Ajello, JM Liu, XM AF Ciocca, M Ajello, JM Liu, XM TI Kinetic-energy distribution of D(2p) atoms from analysis of the D Lyman-alpha line profile SO PHYSICAL REVIEW A LA English DT Article ID ELECTRON-IMPACT DISSOCIATION; ULTRAVIOLET EMISSION-SPECTRUM; MOLECULAR-HYDROGEN; CROSS-SECTIONS; EXTREME-ULTRAVIOLET; BETA EMISSION; H-STAR; H-2; DEUTERIUM; EXCITATION AB The kinetic-energy distribution of D(2p) atoms resulting from electron-impact dissociation of D-2 has been measured. A high-resolution vacuum ultraviolet spectrometer was employed for the first measurement of the D Lyman-alpha (D L alpha) emission line profiles at 20- and 100-eV excitation energies. Analysis of the deconvoluted line profile of D L alpha at 100 eV reveals the existence of a narrow line central peak of 29+/-2 m Angstrom full width at half maximum and a broad pedestal wing structure about 190 m Angstrom wide. The wings of the line can be used to determine the fast atom distribution. The wings of D L alpha arise from dissociative excitation of a series of doubly excited states that cross the Franck-Condon region between 23 and 40 eV. The fast atom distribution at 100-eV electron impact energy spans the energy range from 1 to 10 eV with a peak value near 6 eV. Slow D(2p) atoms characterized by a distribution function with peak energy near 100 meV produce the central peak profile, which is nearly independent of the impact energy. The deconvoluted line profiles of the central peak at 20 eV for dissociative excitation of D-2 and H-2 are fitted with an analytical function for use in calibration of space flight instrumentation equipped with a D/H absorption cell. The kinetic-energy and line profile results are compared to similar measurements for H-2. The absolute cross sections for the line center (slow atoms) and wings (fast atoms) and total emission line profile were measured from threshold to 400 eV. Analytical model coefficients are given for the energy dependence of the measured slow atom cross section. C1 UNIV COLORADO,ATMOSPHER & SPACE PHYS LAB,BOULDER,CO 80303. UNIV KENTUCKY,DEPT PHYS & ASTRON,LEXINGTON,KY 40506. RP Ciocca, M (reprint author), CALTECH,JET PROP LAB,4800 OAK GROVE DR,PASADENA,CA 91109, USA. NR 28 TC 4 Z9 4 U1 0 U2 0 PU AMERICAN PHYSICAL SOC PI COLLEGE PK PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA SN 1050-2947 J9 PHYS REV A JI Phys. Rev. A PD SEP PY 1997 VL 56 IS 3 BP 1929 EP 1937 DI 10.1103/PhysRevA.56.1929 PG 9 WC Optics; Physics, Atomic, Molecular & Chemical SC Optics; Physics GA XV840 UT WOS:A1997XV84000035 ER PT J AU Bennett, MJ Beavis, D Carroll, JB Chiba, J Chikanian, A Crawford, HJ Cronqvist, M Dardenne, Y Debbe, R Doke, T Engelage, J Greiner, L Hayano, RS Hallman, TJ Heckman, HH Kashiwagi, T Kikuchi, J Kumar, BS Kuo, C Lindstrom, PJ Mitchell, JW Nagamiya, S Nagle, JL Pope, JK Stankus, P Tanaka, KH Welsh, RC Zhan, W AF Bennett, MJ Beavis, D Carroll, JB Chiba, J Chikanian, A Crawford, HJ Cronqvist, M Dardenne, Y Debbe, R Doke, T Engelage, J Greiner, L Hayano, RS Hallman, TJ Heckman, HH Kashiwagi, T Kikuchi, J Kumar, BS Kuo, C Lindstrom, PJ Mitchell, JW Nagamiya, S Nagle, JL Pope, JK Stankus, P Tanaka, KH Welsh, RC Zhan, W TI Antiproton distributions in Au+nucleus collisions SO PHYSICAL REVIEW C LA English DT Article ID HEAVY-ION COLLISIONS; NUCLEUS-NUCLEUS COLLISIONS; AU+AU COLLISIONS; GEV/C; ANNIHILATION; PARTICLES; TARGETS; MATTER; SI; AL AB Experiment E878 at the BNL-AGS has measured the invariant cross sections of antiprotons produced near p(t)=0 in interactions of 10.8 GeV/c Au beams with targets of Al, Cu, and Au. The data were measured for a wide range of centralities and rapidities using a focusing beamline spectrometer and a high-rate centrality detector. We compare our data with the predictions of simple models and sophisticated transport models to explore the physics of antiproton production and annihilation. C1 BROOKHAVEN NATL LAB,UPTON,NY 11973. UNIV CALIF LOS ANGELES,LOS ANGELES,CA. NATL LAB HIGH ENERGY PHYS,KEK,TSUKUBA,IBARAKI 305,JAPAN. UNIV CALIF BERKELEY,SPACE SCI LAB,BERKELEY,CA 94720. WASEDA UNIV,TOKYO,JAPAN. UNIV TOKYO,TOKYO,JAPAN. UNIV CALIF BERKELEY,LAWRENCE BERKELEY LAB,BERKELEY,CA 94720. NASA,GODDARD SPACE FLIGHT CTR,UNIV SPACE RES ASSOC,GREENBELT,MD 20771. COLUMBIA UNIV,NEVIS LAB,IRVINGTON,NY. JOHNS HOPKINS UNIV,BALTIMORE,MD. RP Bennett, MJ (reprint author), YALE UNIV,AW WRIGHT NUCL STRUCT LAB,NEW HAVEN,CT 06511, USA. RI Hayano, Ryugo/F-7889-2012; Kuo, Chaincy/H-9475-2016 OI Hayano, Ryugo/0000-0002-1214-7806; Kuo, Chaincy/0000-0001-7958-8764 NR 45 TC 17 Z9 17 U1 0 U2 0 PU AMERICAN PHYSICAL SOC PI COLLEGE PK PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA SN 0556-2813 J9 PHYS REV C JI Phys. Rev. C PD SEP PY 1997 VL 56 IS 3 BP 1521 EP 1535 DI 10.1103/PhysRevC.56.1521 PG 15 WC Physics, Nuclear SC Physics GA XW379 UT WOS:A1997XW37900037 ER PT J AU Chen, CX Albergo, S Caccia, Z Costa, S Crawford, HJ Cronqvist, M Engelage, J Greiner, L Guzik, TG Insolia, A Knott, CN Lindstrom, PJ McMahon, M Mitchell, JW Potenza, R Russo, GV Soutoul, A Testard, O Tull, CE Tuve, C Waddington, CJ Webber, WR Wefel, JP AF Chen, CX Albergo, S Caccia, Z Costa, S Crawford, HJ Cronqvist, M Engelage, J Greiner, L Guzik, TG Insolia, A Knott, CN Lindstrom, PJ McMahon, M Mitchell, JW Potenza, R Russo, GV Soutoul, A Testard, O Tull, CE Tuve, C Waddington, CJ Webber, WR Wefel, JP TI Systematics of isotopic production cross sections from interactions of relativistic Ca-40 in hydrogen SO PHYSICAL REVIEW C LA English DT Article ID INTERSTELLAR-MEDIUM; CARBON TARGETS; NUCLEI; CALCIUM; HELIUM; GRAPHITE; ORIGIN; RAYS AB The isotopic production cross sections for Ca-40 projectiles at 357, 565, and 763 MeV/nucleon interacting in a liquid hydrogen target have been measured by the Transport Collaboration at the LBL HISS facility. The systematics of these cross sections are studied, and the results indicate that nuclear structure effects are present in the isotope production process during the relativistic collisions. The newly measured cross sections are also compared with those predicted by semiempirical and parametric formulas, but the predictions do not fully describe the systematics such as the energy dependence. The consequences of the cross section systematics in galactic cosmic ray studies are also discus sed. C1 LOUISIANA STATE UNIV,DEPT PHYS & ASTRON,BATON ROUGE,LA 70803. UNIV CATANIA,DIPARTMENTO FIS,I-95129 CATANIA,ITALY. IST NAZL FIS NUCL,I-95129 CATANIA,ITALY. UNIV CALIF BERKELEY,SPACE SCI LAB,BERKELEY,CA 94720. UNIV MINNESOTA,SCH PHYS & ASTRON,MINNEAPOLIS,MN 55455. UNIV CALIF BERKELEY,LAWRENCE BERKELEY LAB,BERKELEY,CA 94720. NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. CTR ETUD SACLAY,SERV ASTROPHYS,F-91191 GIF SUR YVETTE,FRANCE. NEW MEXICO STATE UNIV,DEPT ASTRON,LAS CRUCES,NM 88003. RI Insolia, Antonio/M-3447-2015; TUVE', Cristina/P-3933-2015 OI Insolia, Antonio/0000-0002-9040-1566; TUVE', Cristina/0000-0003-0739-3153 NR 37 TC 21 Z9 21 U1 0 U2 3 PU AMERICAN PHYSICAL SOC PI COLLEGE PK PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA SN 0556-2813 J9 PHYS REV C JI Phys. Rev. C PD SEP PY 1997 VL 56 IS 3 BP 1536 EP 1543 DI 10.1103/PhysRevC.56.1536 PG 8 WC Physics, Nuclear SC Physics GA XW379 UT WOS:A1997XW37900038 ER PT J AU Sutaria, FK Ray, A AF Sutaria, FK Ray, A TI Neutrino spectroscopy of the early phase of nearby supernovae SO PHYSICAL REVIEW LETTERS LA English DT Article ID ELECTRON-CAPTURE; GRAVITATIONAL COLLAPSE; STRENGTH DISTRIBUTIONS; STARS; CORE AB Neutrino's emitted during stellar core collapse up to their trapping phase carry information about the stage from which the supernova explosion process initiates. The dominant v(e) emission mechanism is by electron capture on free protons and f-p shell nuclei and the spectrum of these neutrinos is a function of the ambient physical conditions within the core as well as the nuclear equation of state. The number of collapse phase v(e) which can be detected by Super-Kamioka and the Sudbury Neutrino Observatory from a supernova within 1 kpc, and their generic energy spectra, are given. C1 NASA,GODDARD SPACE FLIGHT CTR,HIGH ENERGY ASTROPHYS LAB,GREENBELT,MD 20771. RP Sutaria, FK (reprint author), TATA INST FUNDAMENTAL RES,THEORET ASTROPHYS GRP,BOMBAY 400005,MAHARASHTRA,INDIA. NR 18 TC 10 Z9 10 U1 0 U2 1 PU AMERICAN PHYSICAL SOC PI COLLEGE PK PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA SN 0031-9007 J9 PHYS REV LETT JI Phys. Rev. Lett. PD SEP 1 PY 1997 VL 79 IS 9 BP 1599 EP 1602 DI 10.1103/PhysRevLett.79.1599 PG 4 WC Physics, Multidisciplinary SC Physics GA XU057 UT WOS:A1997XU05700005 ER PT J AU Chernov, AA AF Chernov, AA TI Crystals built of biological macromolecules SO PHYSICS REPORTS-REVIEW SECTION OF PHYSICS LETTERS LA English DT Review DE crystallization; proteins; mosaicity; epitaxy ID ATOMIC-FORCE MICROSCOPY; GROWTH-KINETICS; PROTEIN CRYSTALLIZATION; MORPHOLOGICAL STABILITY; GLOBULAR-PROTEINS; VICINAL FACE; LYSOZYME; MICROGRAVITY; SOLUBILITY; NUCLEATION AB A general view is presented on how biological macromolecules dissolved in aqueous solutions build crystals having in mind, first of all, data on protein crystals. It is demonstrated that these crystals are essentially very close to inorganic ones despite their major quantitative difference in properties. The ''trial and error'' mechanism controlling the selection of species during inorganic crystallization seems not to be effective in proteins. Instead, mainly electrostatic recognition of proper attachment sites by molecules located close to the growing surface is expected. Defects in biocrystals are of the same type as in inorganic salts. Mosaicity of the grown biocrystals seriously deteriorate their practical use to reveal molecular structure by X-ray diffraction. The onset of such mosaicity is discussed making use of epitaxy concepts. RP Chernov, AA (reprint author), NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,UNIV SPACE RES ASSOC,4950 CORP DR,SUITE 100,HUNTSVILLE,AL 35806, USA. NR 84 TC 49 Z9 49 U1 2 U2 5 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0370-1573 J9 PHYS REP JI Phys. Rep.-Rev. Sec. Phys. Lett. PD SEP PY 1997 VL 288 IS 1-6 BP 61 EP 75 DI 10.1016/S0370-1573(97)00021-5 PG 15 WC Physics, Multidisciplinary SC Physics GA XZ711 UT WOS:A1997XZ71100004 ER PT J AU Smith, JG Connell, JW Hergenrother, PM AF Smith, JG Connell, JW Hergenrother, PM TI Imide oligomers containing pendent and terminal phenylethynyl groups SO POLYMER LA English DT Article DE imide oligomers; pendent and terminal phenylethynyl groups; high performance high temperature resins ID POLYIMIDE OLIGOMERS AB As part of a programme to develop high performance/high temperature structural resins for aeronautical applications, imide oligomers containing pendent and terminal phenylethynyl groups were prepared, characterized and the cured resins evaluated as adhesives and composite matrix resins. As a means of controlling the molecular weight between reactive sites (i.e. crosslink density), varying amounts of phenylethynyl groups were distributed randomly along the imide oligomer whose calculated number-average molecular weight was 5000 gmol(-1). Upon thermal cure at 350-371 degrees C for 1 h in air, the phenylethynyl group undergoes a complex reaction resulting in chain extension, branching and crosslinking. The products depend upon several factors such as the relative concentration of phenylethynyl groups, molecular mobility of the growing polymer and conformational restrictions and have been postulated to be predominantly highly conjugated polyenes. In general, the cured resins have a favourable combination of properties including good thermal stability, solvent and moisture resistance and good toughness. The amide acid oligomer solutions were processed into thin films, adhesive tape and carbon fibre prepreg. Neat resin plaques were fabricated from imide oligomer powder by compression moulding. The maximum processing pressure was 1.4MPa and the cure temperature varied from 350-371 degrees C for 1 h for the composites, adhesive panels and neat resin mouldings. The properties of the cured imide oligomers containing pendent and terminal phenylethynyl groups are compared with those of cured oligomers of similar composition and molecular weight which contain either terminal or pendent phenylethynyl groups. Published by Elsevier Science Ltd. C1 NASA,LANGLEY RES CTR,DIV MAT,HAMPTON,VA 23681. NR 33 TC 41 Z9 44 U1 1 U2 6 PU ELSEVIER SCI LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, OXON, ENGLAND OX5 1GB SN 0032-3861 J9 POLYMER JI Polymer PD SEP PY 1997 VL 38 IS 18 BP 4657 EP 4665 DI 10.1016/S0032-3861(96)01062-2 PG 9 WC Polymer Science SC Polymer Science GA XN820 UT WOS:A1997XN82000010 ER PT J AU Yu, YH Gmelin, B Splettstoesser, W Philippe, JJ Prieur, J Brooks, TF AF Yu, YH Gmelin, B Splettstoesser, W Philippe, JJ Prieur, J Brooks, TF TI Reduction of helicopter blade-vortex interaction noise by active rotor control technology SO PROGRESS IN AEROSPACE SCIENCES LA English DT Article AB Helicopter blade-vortex interaction noise is one of the most severe noise sources and is very important both in community annoyance and military detection. Research over the decades has substantially improved basic physical understanding of the mechanisms generating rotor blade-vortex interaction noise and also of controlling techniques, particularly using active rotor control technology. This paper reviews active rotor control techniques currently available for rotor blade-vortex interaction noise reduction, including higher harmonic pitch control, individual blade control, and on-blade control technologies. Basic physical mechanisms of each active control technique are reviewed in terms of noise reduction mechanism and controlling aerodynamic or structural parameters sf a blade. Active rotor control techniques using smart structures/materials are discussed, including distributed smart actuators to induce local torsional or flapping deformations. Published by Elsevier Science Ltd. C1 DEUTSCH FORSCH ANSTALT LUFT & RAUMFAHRT DLR,BRAUNSCHWEIG,GERMANY. OFF NATL ETUD & RECH AEROSP,CHATILLON,FRANCE. NASA,LANGLEY RES CTR,HAMPTON,VA 23665. RP Yu, YH (reprint author), AMES RES CTR,AVRDEC,AEROFLIGHTDYNAM DIRECTORATE,MOFFETT FIELD,CA 94035, USA. NR 51 TC 13 Z9 13 U1 1 U2 4 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 SEP-OCT PY 1997 VL 33 IS 9-10 BP 647 EP 687 DI 10.1016/S0376-0421(97)00006-7 PG 41 WC Engineering, Aerospace SC Engineering GA YF229 UT WOS:A1997YF22900003 ER PT J AU Feibelman, WA AF Feibelman, WA TI A reassessment of the IUE emission-line spectrum of the planetary nebula NGC 5189 and its central star SO PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF THE PACIFIC LA English DT Article ID O-VI; C-IV; NUCLEI AB Archival high-and low-dispersion IUE spectra of NGC 5189 and its central star were reexamined. It was found that earlier published results misinterpreted nebular features for stellar emission lines due to incorrect coordinates and/or incorrect pointing of the spacecraft. NGC 5189 has an UV spectrum rich in emission lines of He II, C II], C III, C III], C IV, C V, N III], N IV], O I, O III, O III], O IV], O V, O VI, O VII, O VIII, [Ne III], [Ne IV], [Ne V], [Mg V], [Ar IV], Si III], and Fe II. The data were reextracted and the emission line fluxes were measured. Electron density for C III] and terminal wind velocities from C IV P Cygni profiles were determined. Comparisons of the IUE spectra of NGC 5189 and NGC 6905 show that these objects have very similar characteristics. RP Feibelman, WA (reprint author), NASA,GODDARD SPACE FLIGHT CTR,ASTRON & SOLAR PHYS LAB,CODE 681,GREENBELT,MD 20771, USA. NR 32 TC 4 Z9 4 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 SEP PY 1997 VL 109 IS 739 BP 982 EP 989 DI 10.1086/133970 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XY125 UT WOS:A1997XY12500006 ER PT J AU Chen, DY Engman, ET Brutsaert, W AF Chen, DY Engman, ET Brutsaert, W TI Spatial distribution and pattern persistence of surface soil moisture and temperature over prairie from remote sensing SO REMOTE SENSING OF ENVIRONMENT LA English DT Article ID FIFE; VARIABILITY AB Images remotely sensed aboard aircraft during FIFE, namely, PBMR (microwave) soil moisture and NS001 thermal infrared surface temperature, were mapped on the same coordinate system covering the 20 km x 20 km experimental site. For both kinds of image data, the frequency distributions were close to symmetric, and the area averages compared reasonably well with the ground based measurements. For any image on any given day, the correlation between the remotely sensed values and collocated ground based measurements over the area was usually high in the case of NS001 surface temperature but low in the case of PBMR soil moisture. On the other hand, fit ally given flux station the correlation between the PBMR and gravimetric soil moisture over all available clays was usually high. The correlation pixel by pixel between images of PBMR on different days was generally high. The preservation of the spatial patterns of soil moisture was also evaluated by considering the correlation station by station between ground-based soil moisture measurements on different days; no persistence of spatial pattern was apparent curing wet periods, but a definite pattern gradually established itself toward the end of each drying episode. The spatial patterns of surface temperature revealed by NS001 were not preserved even within a single day. The cross-correlations among the two kinds of images and the vegetation index NDVI were normally poor. This suggests that different time scales were involved in the different processes of vegetation growth, and of the near-surface soil water and energy budgets. (C) Elsevier Science Inc., 1997. C1 NASA,GODDARD SPACE FLIGHT CTR,HYDROL SCI BRANCH,GREENBELT,MD 20771. CORNELL UNIV,SCH CIVIL & ENVIRONM ENGN,ITHACA,NY 14853. RP Chen, DY (reprint author), UNIV MANCHESTER,SCH ENGN,OXFORD RD,MANCHESTER M13 9PL,LANCS,ENGLAND. NR 14 TC 21 Z9 22 U1 7 U2 10 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 SEP PY 1997 VL 61 IS 3 BP 347 EP 360 DI 10.1016/S0034-4257(97)84216-2 PG 14 WC Environmental Sciences; Remote Sensing; Imaging Science & Photographic Technology SC Environmental Sciences & Ecology; Remote Sensing; Imaging Science & Photographic Technology GA XN253 UT WOS:A1997XN25300002 ER PT J AU Imhoff, ML Lawrence, WT Stutzer, DC Elvidge, CD AF Imhoff, ML Lawrence, WT Stutzer, DC Elvidge, CD TI A technique for using composite DMSP/OLS ''city lights'' satellite data to map urban area SO REMOTE SENSING OF ENVIRONMENT LA English DT Article ID BIODIVERSITY AB A thresholding technique was used to convert a prototype ''city lights'' data set from the National Oceanic and Atmospheric Administration's National Geophysical Data Center (NOAA/NGDC) into a map of ''urban areas'' for the continental United States. Thresholding was required to adapt the Defense Meteorological Satellite Program's Operational Linescan System (DMSP/OLS)-based NGDC data set into an urban map because the values reported in the prototype represent a a cumulative percentage lighted for each pixel extracted from hundreds of nighttime cloud-screened orbits, rather than any suitable land-cover classification. The cumulative percentage lighted data could not be used alone because the very high gain of the OLS nighttime photomultiplier configuration can bad to a pixel (2.7 x 2.7 km) appearing ''lighted'' even with very low intensity, nonurban Eight sources. We found that a threshold of greater than or equal to 89% yielded the best results, removing ephemeral light sources and ''blooming'' of light onto water when adjacent to cities while still leaving the dense urban core intact. This approach gave very good results wizen compared with the urban areas as defined by the 1990 U. S. Census; the ''urban'' area from our analysis being only 5% less than that of the Census. The Census was also used to derive population- and housing-density statistics for the continent-wide ''city lights'' analysis; these averaged 1033 persons/km(2) and 426 housing units/km(2), respectively The use of a nighttime sensor to determine the location and estimate the density of population based on light sources has proved feasible in this exploratory effort. However issues concerning the use of census data as a benchmark for evaluating the accuracy of remotely sensed imagery are discussed and potential improvements in the sensor regarding spatial resolution, instrument gain and pointing accuracy are addressed. C1 BOWIE STATE UNIV,BOWIE,MD. UNIV MARYLAND,DEPT GEOG,COLLEGE PK,MD 20742. UNIV NEVADA,DESERT RES INST,RENO,NV 89506. RP Imhoff, ML (reprint author), NASA,GODDARD SPACE FLIGHT CTR,BIOSPHER SCI BRANCH,CODE 923,GREENBELT,MD 20771, USA. RI Elvidge, Christopher/C-3012-2009 NR 18 TC 195 Z9 224 U1 10 U2 67 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 SEP PY 1997 VL 61 IS 3 BP 361 EP 370 PG 10 WC Environmental Sciences; Remote Sensing; Imaging Science & Photographic Technology SC Environmental Sciences & Ecology; Remote Sensing; Imaging Science & Photographic Technology GA XN253 UT WOS:A1997XN25300003 ER PT J AU Sutton, JF AF Sutton, JF TI Current source with matched common mode output impedances SO REVIEW OF SCIENTIFIC INSTRUMENTS LA English DT Article AB A differential current source with matched common mode output impedances is described. Matching impedances reduces common mode-to-differential mode signal conversion, important in the low noise, high resolution measurement of cryogenic temperatures as low as 50 mK. (C) 1997 American Institute of Physics. RP Sutton, JF (reprint author), NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771, USA. NR 3 TC 0 Z9 0 U1 0 U2 0 PU AMER INST PHYSICS PI WOODBURY PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 SN 0034-6748 J9 REV SCI INSTRUM JI Rev. Sci. Instrum. PD SEP PY 1997 VL 68 IS 9 BP 3590 EP 3592 DI 10.1063/1.1148333 PG 3 WC Instruments & Instrumentation; Physics, Applied SC Instruments & Instrumentation; Physics GA XX257 UT WOS:A1997XX25700046 ER PT J AU Walter, M AF Walter, M TI Life on Mars? SO SEARCH LA English DT Article C1 NASA,MARS EXPLORAT PROGRAM,WASHINGTON,DC 20546. RP Walter, M (reprint author), MACQUARIE UNIV,RYDE,AUSTRALIA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU CONTROL PUBL PTY LTD PI DONCASTER PA 14 ARCHERON ST, DONCASTER VIC 3108, AUSTRALIA SN 0004-9549 J9 SEARCH JI Search PD SEP PY 1997 VL 28 IS 8 BP 244 EP 245 PG 2 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA XY630 UT WOS:A1997XY63000034 ER PT J AU Ford, WF Pennline, JA AF Ford, WF Pennline, JA TI An integral SO SIAM REVIEW LA English DT Letter RP Ford, WF (reprint author), NASA,LEWIS RES CTR,CLEVELAND,OH 44135, USA. NR 1 TC 0 Z9 0 U1 0 U2 0 PU SIAM PUBLICATIONS PI PHILADELPHIA PA 3600 UNIV CITY SCIENCE CENTER, PHILADELPHIA, PA 19104-2688 SN 0036-1445 J9 SIAM REV JI SIAM Rev. PD SEP PY 1997 VL 39 IS 3 BP 524 EP 527 PG 4 WC Mathematics, Applied SC Mathematics GA XV918 UT WOS:A1997XV91800016 ER PT J AU Pentakalos, OI Menasce, DA Yesha, Y AF Pentakalos, OI Menasce, DA Yesha, Y TI Pythia and pythia/WK: Tools for the performance analysis of mass storage systems SO SOFTWARE-PRACTICE & EXPERIENCE LA English DT Article DE mass storage systems; object oriented design; workload characterization; graphical user interfaces; performance prediction tool; Tcl/Tk AB The constant growth on the demands imposed on hierarchical mass storage systems creates a need for frequent reconfiguration and upgrading to ensure that the response times and other performance metrics are within the desired service levels, This paper describes the design and operation of two tools, Pythia and Pythia/WK, that assist system managers and integrators in making cost-effective procurement decisions, Pythia automatically buids and solves an analytic model of a mass storage system based on a graphical description of the architecture of the system, and on a description of the workload imposed on the system, The use of a modeling wizard to perform this conversion from a graphical description of a mass storage system to an analytic model makes Pythia unique among analytic performance tools, Pythia/WK uses clustering algorithms to characterize the workload from the log files of the mass storage system, The resulting workload characterization is used as input to Pythia. (C) 1997 by John Whey & Sons, Ltd. C1 GEORGE MASON UNIV,DEPT COMP SCI,FAIRFAX,VA 22030. UNIV MARYLAND BALTIMORE CTY,DEPT ELECT ENGN & COMP SCI,BALTIMORE,MD 21228. RP Pentakalos, OI (reprint author), NASA,GODDARD SPACE FLIGHT CTR,DIV SPACE DATA & COMP,CODE 930,GREENBELT,MD 20771, USA. NR 24 TC 0 Z9 0 U1 0 U2 0 PU JOHN WILEY & SONS LTD PI W SUSSEX PA BAFFINS LANE CHICHESTER, W SUSSEX, ENGLAND PO19 1UD SN 0038-0644 J9 SOFTWARE PRACT EXPER JI Softw.-Pract. Exp. PD SEP PY 1997 VL 27 IS 9 BP 1035 EP 1054 DI 10.1002/(SICI)1097-024X(199709)27:9<1035::AID-SPE116>3.0.CO;2-H PG 20 WC Computer Science, Software Engineering SC Computer Science GA XW083 UT WOS:A1997XW08300003 ER PT J AU Healy, MJ Hare, VW Summers, SH AF Healy, MJ Hare, VW Summers, SH TI Antibody screening of blood donors: Evaluating test results. SO TRANSFUSION LA English DT Meeting Abstract C1 AMES RES CTR,BLOOD SERV,ATLANTA,GA. GEORGIA STATE UNIV,ATLANTA,GA 30303. NR 0 TC 0 Z9 0 U1 0 U2 0 PU AMER ASSOC BLOOD BANKS PI BETHESDA PA 8101 GLENBROOK RD, BETHESDA, MD 20814-2749 SN 0041-1132 J9 TRANSFUSION JI Transfusion PD SEP PY 1997 VL 37 IS 9 SU S BP A26 EP A26 PG 1 WC Hematology SC Hematology GA XW275 UT WOS:A1997XW27500469 ER PT J AU Brody, FC Lafosse, RA Bellue, DG Oram, TD AF Brody, FC Lafosse, RA Bellue, DG Oram, TD TI Operations of the National Weather Service Spaceflight Meteorology Group SO WEATHER AND FORECASTING LA English DT Article ID SUPPORT AB Weather is a significant aspect of most space shuttle launches and landings. The National Weather Service Spaceflight Meteorology Group (SMG) at Johnson Space Center (JSC) in Houston, Texas, provides weather forecasts and advice to support space shuttle operations. SMG has been an integral part of the flight control team in the Mission Control Center at JSC since 1962. Space shuttle weather support is quite complex and specialized, especially compared to more traditional weather forecast operations. SMG forecasts are compared to shuttle weather flight rules to advise the Eight director on launch and landing decisions. Perhaps the most critical aspect of SMG's weather support is the ''90-min forecast'' issued prior to landing, supporting the Mission Control Center's ''go'' or ''no-go'' deorbit burn decision. Once the deorbit burn has occurred, the shuttle must land at the designated landing site at the designated time. SMG's forecast must be precise, accurate, and clearly communicated. Meteorological data acquisition and display is critical for analysis and forecasting, and for briefing the flight control team. Primary systems used are the Meteorological Interactive Data and Display System and the Weather Surveillance Radar-1988 Doppler Principal User Processor. This article describes SMG functions, operations, data acquisition and display systems, and shuttle launch and landing weather forecast scenarios. C1 NASA,LYNDON B JOHNSON SPACE CTR,UNITED SPACE ALLIANCE,HOUSTON,TX 77058. RP Brody, FC (reprint author), NASA,LYNDON B JOHNSON SPACE CTR,SPACEFLIGHT METEOROL GRP,MAIL CODE ZS8,HOUSTON,TX 77058, USA. NR 25 TC 6 Z9 6 U1 0 U2 0 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 SN 0882-8156 J9 WEATHER FORECAST JI Weather Forecast. PD SEP PY 1997 VL 12 IS 3 BP 526 EP 544 DI 10.1175/1520-0434(1997)012<0526:OOTNWS>2.0.CO;2 PN 1 PG 19 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA XX404 UT WOS:A1997XX40400013 ER PT J AU Martin, JML Taylor, PR Lee, TJ AF Martin, JML Taylor, PR Lee, TJ TI The harmonic frequencies of benzene. A case for atomic natural orbital basis sets SO CHEMICAL PHYSICS LETTERS LA English DT Article ID GAUSSIAN-BASIS SETS; TOTAL ATOMIZATION ENERGIES; EXACT EXCHANGE; FORCE-FIELDS; DERIVATIVES; PERFORMANCE; GEOMETRIES; VIBRATIONS; CONSTANTS; CLUSTERS AB The geometry and harmonic force field of benzene have been computed at the CCSD(T) level with basis sets of spdf quality. Two out-of-plane modes, omega(4) and omega(5) (and to a lesser extent omega(17)), exhibit a pathological basis set dependence due to basis set superposition error. Using an atomic natural orbital (ANO) basis set of [4s3p2d1f/4s2p] quality, the best available experimentally derived harmonic frequencies can be reproduced with an RMS error of 6 cm(-1) without any empirical corrections. We strongly recommend the use of ANO basis sets for accurate frequency calculations on unsaturated and aromatic systems. Our best estimate for the equilibrium geometry is r(e)(CC)=1.392(2), r(e)(CH)=1.081 Angstrom. (C) 1997 Published by Elsevier Science B.V. C1 UNIV CALIF SAN DIEGO,SAN DIEGO SUPERCOMP CTR,SAN DIEGO,CA 92186. UNIV CALIF SAN DIEGO,DEPT CHEM & BIOCHEM,SAN DIEGO,CA 92186. NASA,AMES RES CTR,MOFFETT FIELD,CA 94035. RP Martin, JML (reprint author), WEIZMANN INST SCI,DEPT ORGAN CHEM,KIMMELMAN BLDG,ROOM 262,IL-76100 REHOVOT,ISRAEL. RI Lee, Timothy/K-2838-2012; Martin, Jan/A-7457-2008 OI Martin, Jan/0000-0002-0005-5074 NR 34 TC 63 Z9 63 U1 1 U2 4 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0009-2614 J9 CHEM PHYS LETT JI Chem. Phys. Lett. PD AUG 29 PY 1997 VL 275 IS 3-4 BP 414 EP 422 DI 10.1016/S0009-2614(97)00735-5 PG 9 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA XV887 UT WOS:A1997XV88700042 ER PT J AU Kouveliotou, C AF Kouveliotou, C TI Astrophysics - Gamma ray bursts SO SCIENCE LA English DT Editorial Material RP Kouveliotou, C (reprint author), NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,HUNTSVILLE,AL 35812, USA. NR 15 TC 3 Z9 3 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 AUG 29 PY 1997 VL 277 IS 5330 BP 1257 EP 1258 DI 10.1126/science.277.5330.1257 PG 2 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA XT827 UT WOS:A1997XT82700039 ER PT J AU Smrekar, SE Stofan, ER AF Smrekar, SE Stofan, ER TI Corona formation and heat loss on Venus by coupled upwelling and delamination SO SCIENCE LA English DT Article ID MANTLE CONVECTION; TECTONICS; EVOLUTION; SUBDUCTION; VOLCANISM; ORIGIN; MORPHOLOGY; THICKNESS; BOUNDARY; FEATURES AB Coronae are volcanotectonic features that are unique to Venus and are interpreted to be small-scale upwellings. A model in which upwelling causes delamination at the edge of the plume head, along with deformation of a preexisting depleted mantle layer, produced the full range of topographic forms of coronae. If half of the coronae are active, delamination of the lower lithosphere could account for about IO percent of Venus' heat loss, with another 15 percent due to upwelling. Delamination may occur in other geologic environments and could account for some of Venus' heal loss ''deficit.''. RP Smrekar, SE (reprint author), CALTECH,JET PROP LAB,MS 183-501,4800 OAK GROVE DR,PASADENA,CA 91109, USA. NR 48 TC 68 Z9 69 U1 2 U2 5 PU AMER ASSOC ADVANCEMENT SCIENCE PI WASHINGTON PA 1200 NEW YORK AVE, NW, WASHINGTON, DC 20005 SN 0036-8075 J9 SCIENCE JI Science PD AUG 29 PY 1997 VL 277 IS 5330 BP 1289 EP 1294 DI 10.1126/science.277.5330.1289 PG 6 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA XT827 UT WOS:A1997XT82700050 ER PT J AU Ho, YK Bhatia, AK AF Ho, YK Bhatia, AK TI Doubly-excited D-1,D-3 degrees states in helium-like systems SO JOURNAL OF PHYSICS B-ATOMIC MOLECULAR AND OPTICAL PHYSICS LA English DT Article ID RESONANCES; PARAMETERS; THRESHOLD; HE AB Doubly excited or Feshbach-type resonances in helium-like systems have been calculated using the complex-rotation method. Using Hylleraas-type wavefunctions up to 680 terms, we predict resonance parameters (both resonance positions and widths) below the N = 3, 4 thresholds of the hydrogenic systems with the nuclear charge from Z = 2-10. The present results for the lowest D-1,3(o) states in helium below the N = 3 threshold agree well with those of Lindroth. Comparisons are also made with the other calculations for Z > 2 in the literature. C1 NASA,GODDARD SPACE FLIGHT CTR,ASTRON & SOLAR PHYS LAB,GREENBELT,MD 20771. RP Ho, YK (reprint author), ACAD SINICA,INST ATOM & MOL SCI,POB 23-166,TAIPEI,TAIWAN. RI Ho, Yew Kam/F-7912-2012 NR 16 TC 16 Z9 16 U1 0 U2 2 PU IOP PUBLISHING LTD PI BRISTOL PA DIRAC HOUSE, TEMPLE BACK, BRISTOL, ENGLAND BS1 6BE SN 0953-4075 J9 J PHYS B-AT MOL OPT JI J. Phys. B-At. Mol. Opt. Phys. PD AUG 28 PY 1997 VL 30 IS 16 BP 3597 EP 3609 DI 10.1088/0953-4075/30/16/002 PG 13 WC Optics; Physics, Atomic, Molecular & Chemical SC Optics; Physics GA XU539 UT WOS:A1997XU53900002 ER PT J AU Marder, SR Kippelen, B Jen, AKY Peyghambarian, N AF Marder, SR Kippelen, B Jen, AKY Peyghambarian, N TI Design and synthesis of chromophores and polymers for electro-optic and photorefractive applications SO NATURE LA English DT Review ID BOND-LENGTH ALTERNATION; CONJUGATED ORGANIC-MOLECULES; 2ND HARMONIC-GENERATION; THERMAL-STABILITY; POLED-POLYMER; HETEROAROMATIC CHROMOPHORES; 2ND-ORDER NONLINEARITY; POLYIMIDES; SYSTEMS; HYPERPOLARIZABILITIES AB The ability of nonlinear optical materials to transmit, process and store information forms the basis of emerging optoelectronic and photonic technologies. Organic chromophore-containing polymers, in which the refractive Index can be controlled by light or an electric field, are expected to play an Important role. C1 CALTECH,JET PROP LAB,PASADENA,CA 91125. UNIV ARIZONA,CTR OPT SCI,TUCSON,AZ 85721. NORTHEASTERN UNIV,DEPT CHEM,BOSTON,MA 02115. RP Marder, SR (reprint author), CALTECH,BECKMAN INST,PASADENA,CA 91125, USA. RI Jen, Alex/E-5957-2012; Kippelen, Bernard/I-4058-2013 OI Kippelen, Bernard/0000-0002-8417-7051 NR 44 TC 844 Z9 857 U1 17 U2 127 PU MACMILLAN MAGAZINES LTD PI LONDON PA PORTERS SOUTH, 4 CRINAN ST, LONDON, ENGLAND N1 9XW SN 0028-0836 J9 NATURE JI Nature PD AUG 28 PY 1997 VL 388 IS 6645 BP 845 EP 851 DI 10.1038/42190 PG 7 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA XT754 UT WOS:A1997XT75400040 ER PT J AU Liao, XH Rind, D AF Liao, XH Rind, D TI Local upper tropospheric lower stratospheric clear-sky water vapor and tropospheric deep convection SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID LOWER TROPICAL STRATOSPHERE; SATELLITE; CLIMATE; DEHYDRATION; TRANSPORT; HUMIDITY; EXCHANGE; ISCCP; AIR AB Local upper tropospheric and stratospheric water vapor profile retrievals by Stratospheric Aerosol and Gas Experiment II for July 1986-1990 are compared with concurrent International Satellite Cloud Climatology Project deep convective clouds to investigate the possible impact of deep convection on upper level moisture distributions. Results show that at low latitudes, clear-sky water vapor values in the upper troposphere (above 300 mbar level) decrease following the onset of convection, perhaps because of compensatory subsidence. The drying lasts for a few hours and then is interrupted by a moistening trend centered at 6 hours after the convection breaks out, perhaps because of the detrainment of cloud liquid water from the convective tower and spreading anvil clouds. From about 9 hours later the tropical lower stratosphere shows moistening occurring. Largely because of these effects, the tropical lower stratosphere has 20-30% more moisture at sunrise compared to sunset. The later stratospheric moistening has the largest correlation significance with convection as well as the largest sampling number, though the absolute variation is much less than the variation in the troposphere. At northern hemisphere summer middle latitudes, upper tropospheric drying follows moist convection events, without an obvious moistening trend in the upper troposphere and impact in the stratosphere. The results indicate that the relationship between local upper tropospheric moisture and convective events is timescale and latitude dependent. They illustrate the utility of high vertical and temporal resolution data for proper averaging and interpretation of convection and water vapor studies. C1 SCI SYST & APPLICAT INC, NEW YORK, NY USA. RP NASA, GODDARD SPACE FLIGHT CTR, INST SPACE STUDIES, 2880 BROADWAY, NEW YORK, NY 10025 USA. NR 35 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 EI 2169-8996 J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD AUG 27 PY 1997 VL 102 IS D16 BP 19543 EP 19557 DI 10.1029/97JD01258 PG 15 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA XT934 UT WOS:A1997XT93400013 ER PT J AU Campbell, BA Hawke, BR Thompson, TW AF Campbell, BA Hawke, BR Thompson, TW TI Regolith composition and structure in the lunar maria: Results of long-wavelength radar studies SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS LA English DT Article ID MOON; RESOURCES; GEOLOGY; IRON AB Radar measurements at 70-cm and 7.5-m wavelengths provide insight into the structure and composition of the upper 5-100 m of the lunar regolith and crust. We combine high-resolution (3-5 km) 70-cm radar data for the nearside with earlier calibrated full-disk observations at the same wavelength to provide a reasonable estimate of the lunar backscatter coefficient. These data are tested against models for echoes from a buried substrate and Mie scattering from surface and buried rocks. These mechanisms are expected to dominate the 70-cm radar echo, with their relative importance determined by the rock population, regolith depth, substrate roughness, and the loss tangent of the soil. Results indicate that the 70-cm radar echo for the maria comes largely from Mie scattering by rocks buried within the fine soil. Radar scattering from a buried substrate is not likely to greatly affect the observed return. We also compared the 70-cm and 7.5-m radar images to infrared eclipse temperature maps, crater-population age estimates for the maria, and to TiO2 and FeO abundances inferred from Earth based telescopic and Clementine multispectral observations. These data imply that (1) the TiO2 (ilmenite) content of the regolith controls variations in 70-cm depolarized echo strength among mare units, with higher titanium abundance leading to lower echoes; (2) changes in the average 70-cm return for a given TiO2 abundance between maria of different ages do occur, but uncertainties in the current radar data do not allow us to uniquely distinguish between variations in rock population with age and calibration effects; (3) the 7.5-m radar echoes are controlled by the age of the mare basalt flows, with older deposits having a greater degree of fracturing and higher backscatter. Future mapping at 12.6-cm and 70-cm wavelengths will help to resolve some of the issues raised here. C1 UNIV HAWAII,DEPT PLANETARY GEOSCI,HONOLULU,HI 96822. CALTECH,JET PROP LAB,PASADENA,CA 91109. RP Campbell, BA (reprint author), SMITHSONIAN INST,CTR EARTH & PLANETARY STUDIES,MRC 315,WASHINGTON,DC 20560, USA. NR 36 TC 40 Z9 41 U1 0 U2 3 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 AUG 25 PY 1997 VL 102 IS E8 BP 19307 EP 19320 DI 10.1029/97JE00858 PG 14 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA XT617 UT WOS:A1997XT61700003 ER PT J AU Cooper, GW Thiemens, MH Jackson, TL Chang, S AF Cooper, GW Thiemens, MH Jackson, TL Chang, S TI Sulfur and hydrogen isotope anomalies in meteorite sulfonic acids SO SCIENCE LA English DT Article ID MURCHISON METEORITE; CARBONACEOUS CHONDRITES; HYDROCARBONS; MONOSULFIDE; CHEMISTRY; OZONE AB Intramolecular carbon, hydrogen, and sulfur isotope ratios were measured on a homologous series of organic sulfonic acids discovered in the Murchison meteorite. Mass independent sulfur isotope fractionations were observed along with high deuterium/hydrogen ratios. The deuterium enrichments indicate formation of the hydrocarbon portion of these compounds in a low-temperature environment that is consistent with that of interstellar clouds. Sulfur-33 enrichments observed in methanesulfonic acid could have resulted from gas-phase ultraviolet irradiation of a precursor, carbon disulfide, The source of the sulfonic acid precursors may have been the reactive interstellar molecule carbon monosulfide. C1 NASA, AMES RES CTR, MOFFETT FIELD, CA 94035 USA. UNIV CALIF SAN DIEGO, DEPT CHEM & BIOCHEM, LA JOLLA, CA 92093 USA. RP Cooper, GW (reprint author), SETI INST, MS 239-4, MOFFETT FIELD, CA 94035 USA. NR 27 TC 53 Z9 54 U1 1 U2 12 PU AMER ASSOC ADVANCEMENT SCIENCE PI WASHINGTON PA 1200 NEW YORK AVE, NW, WASHINGTON, DC 20005 USA SN 0036-8075 J9 SCIENCE JI Science PD AUG 22 PY 1997 VL 277 IS 5329 BP 1072 EP 1074 DI 10.1126/science.277.5329.1072 PG 3 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA XT033 UT WOS:A1997XT03300026 PM 9262469 ER PT J AU Li, ZJ Friedl, RR Sander, SP AF Li, ZJ Friedl, RR Sander, SP TI Kinetics of the HO2+BrO reaction over the temperature range 233-348 K SO JOURNAL OF THE CHEMICAL SOCIETY-FARADAY TRANSACTIONS LA English DT Article ID ATMOSPHERIC BROMINE; RATE CONSTANTS; HO2; CHEMISTRY; PRESSURE; RADICALS; OZONE; ATOMS; BRO; CLO AB The reaction BrO + HO2 --> products is the rate-limiting step in a key catalytic ozone destruction cycle in the lower stratosphere. In this study a discharge-flow reactor coupled with molecular beam mass spectrometry has been used to study the BrO + HO3 reaction over the temperature range 233-348 K. Rate constants were measured under pseudo-first-order conditions in separate experiments with first HO2 and then BrO in excess in an effort to identify possible complications in the reaction conditions. At 298 K, the rate constant was determined to be (1.73 +/- 0.61) x 10(-11) cm(3) molecule(-1) s(-1) with HO2 in excess and (2.05 +/- 0.64) x 10(-11) cm(3) molecule(-1) s(-1) with BrO in excess. The combined results of the temperature-dependent experiments gave the following fit to the Arrhenius expression: k = (3.13 +/- 0.33) x 10(-12) exp(536 +/- 206/T) where the quoted uncertainties represent two standard deviations. The reaction mechanism is discussed in light of recent ab initio results on the thermochemistry of isomers of possible reaction intermediates. C1 CALTECH,JET PROP LAB,PASADENA,CA 91109. NR 31 TC 24 Z9 27 U1 0 U2 9 PU ROYAL SOC CHEMISTRY PI CAMBRIDGE PA THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON ROAD, CAMBRIDGE, CAMBS, ENGLAND CB4 4WF SN 0956-5000 J9 J CHEM SOC FARADAY T JI J. Chem. Soc.-Faraday Trans. PD AUG 21 PY 1997 VL 93 IS 16 BP 2683 EP 2691 DI 10.1039/a701583f PG 9 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA XQ891 UT WOS:A1997XQ89100011 ER PT J AU Korb, CL Gentry, BM Li, SXF AF Korb, CL Gentry, BM Li, SXF TI Edge technique Doppler lidar wind measurements with high vertical resolution SO APPLIED OPTICS LA English DT Article ID ACCURACY AB We have developed a Doppler lidar system using the edge technique and have made atmospheric lidar wind measurements. Line-of-sight wind profiles with a vertical resolution of 22 m have a standard deviation of 0.40 m/s for a ten-shot average. Day and night lidar measurements of the vector wind have been made for altitudes from 200 to 2000 m. We validated the lidar measurements by comparing them with independent rawinsonde and pilot balloon measurements of wind speed and direction. Good agreement was obtained. The instrumental noise for these data is 0.11 m/s for a 500-shot average, which is in good agreement with the observed minimum value of the standard deviation for the atmospheric measurements. The average standard deviation over 30 mins varied from 1.16 to 0.25 m/s for day and night, respectively. High spatial and temporal resolution lidar profiles of line-of-sight winds clearly show wind shear and turbulent features at the 1-2-m/s level with a high signal-to-noise ratio and demonstrate the potential of the edge-technique lidar for studying turbulent processes and atmospheric dynamics. (C) 1997 Optical Society of America. C1 SCI & ENGN SERV INC,BURTONSVILLE,MD 20866. RP Korb, CL (reprint author), NASA,GODDARD SPACE FLIGHT CTR,ATMOSPHERES LAB,CODE 912,GREENBELT,MD 20771, USA. NR 18 TC 38 Z9 64 U1 7 U2 11 PU OPTICAL SOC AMER PI WASHINGTON PA 2010 MASSACHUSETTS AVE NW, WASHINGTON, DC 20036 SN 0003-6935 J9 APPL OPTICS JI Appl. Optics PD AUG 20 PY 1997 VL 36 IS 24 BP 5976 EP 5983 DI 10.1364/AO.36.005976 PG 8 WC Optics SC Optics GA XR271 UT WOS:A1997XR27100029 PM 18259439 ER PT J AU Gross, MR McGee, TJ Ferrare, RA Singh, UN Kimvilakani, P AF Gross, MR McGee, TJ Ferrare, RA Singh, UN Kimvilakani, P TI Temperature measurements made with a combined Rayleigh-Mie and Raman lidar SO APPLIED OPTICS LA English DT Article DE lidar; Rayleigh, Mie, and Raman backscatter; tropospheric, stratospheric, and mesospheric temperature profiles ID GRAVITY-WAVE ACTIVITY; STRATOSPHERIC TEMPERATURE; MIDDLE ATMOSPHERE; OZONE LIDAR; DYANA CAMPAIGN; PROFILES; AEROSOL; BACKSCATTER; MESOSPHERE; DENSITY AB The NASA Goddard Space Flight Center stratospheric ozone lidar system has the capability of collecting both Rayleigh-Mie and Raman backscatter data simultaneously at a number of wavelengths. Here we report on an improved method by which temperature can be derived from a combination of the Rayleigh-Mie return at 351-nm lidar channels and the Raman nitrogen return at 382-nm lidar channels. We also examine some common techniques by which temperatures are retrieved from lidar data. Finally, we show results obtained in 1995 during two Network for the Detection of Stratospheric Change intercomparison campaigns at Lauder, New Zealand and Mauna Loa, Hawaii. C1 NASA,GODDARD SPACE FLIGHT CTR,ATMOSPHER CHEM & DYNAM BRANCH,GREENBELT,MD 20771. HUGHES STX CORP,LANHAM,MD 20706. NASA,LANGLEY RES CTR,REMOTE SENSING TECHNOL BRANCH,HAMPTON,VA 23681. TECHNOSCI INC,LANHAM,MD 20706. RP Gross, MR (reprint author), UNIV MARYLAND BALTIMORE CTY,JOINT CTR EARTH SYST TECHNOL,BALTIMORE,MD 21228, USA. RI McGee, Thomas/G-4951-2013 NR 34 TC 26 Z9 29 U1 0 U2 2 PU OPTICAL SOC AMER PI WASHINGTON PA 2010 MASSACHUSETTS AVE NW, WASHINGTON, DC 20036 SN 0003-6935 J9 APPL OPTICS JI Appl. Optics PD AUG 20 PY 1997 VL 36 IS 24 BP 5987 EP 5995 DI 10.1364/AO.36.005987 PG 9 WC Optics SC Optics GA XR271 UT WOS:A1997XR27100031 PM 18259441 ER PT J AU Muslimov, A Harding, AK AF Muslimov, A Harding, AK TI Toward the quasi-steady state electrodynamics of a neutron star SO ASTROPHYSICAL JOURNAL LA English DT Article DE MHD; pulsars, general; relativity; stars, neutron ID STRONG MAGNETIC-FIELDS; PULSAR POLAR CAPS; GAMMA-RAY PULSARS; GENERAL-RELATIVITY; CONDENSED MATTER; POTENTIAL DROPS; MODEL; MAGNETOSPHERE; ACCELERATION; FORMULATION AB We consider the electrodynamics of a rotating magnetized neutron star with allowance for the quasisteady state regime of charged particle ejection from the polar cap into the inner magnetosphere. We derive basic equations within the framework of a general relativistic formalism and present the analytic solutions. We demonstrate that the quasi-steady state supply of electrons into the region of open field lines reduces the total power put into the acceleration of primary particles, although the total power corresponding to a steady state solution in general relativity is increased compared to the hat-space solution. Also, we illustrate that temporarily modulated ejection of electrons from the stellar surface results in substantial modulation of an accelerating electric field and charge density along the open field lines. We briefly outline the implications of this effect for the pulsars. RP Muslimov, A (reprint author), NASA,GODDARD SPACE FLIGHT CTR,HIGH ENERGY ASTROPHYS LAB,CODE 661,GREENBELT,MD 20771, USA. RI Harding, Alice/D-3160-2012 NR 46 TC 78 Z9 79 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 AUG 20 PY 1997 VL 485 IS 2 BP 735 EP 746 DI 10.1086/304457 PN 1 PG 12 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XT240 UT WOS:A1997XT24000024 ER PT J AU Lanz, T Hubeny, I Heap, SR AF Lanz, T Hubeny, I Heap, SR TI Non-LTE line-blanketed model atmospheres of hot stars .3. Hot subdwarfs: The sdO star BD +75 degrees 325 SO ASTROPHYSICAL JOURNAL LA English DT Article DE stars, abundances; stars, atmospheres; stars, early-type; stars, fundamental parameters; stars, individual (BD+75 degrees 325); stars, mass-loss ID IRON-GROUP ELEMENTS; HIGH-RESOLUTION SPECTROGRAPH; MASS-LOSS; O-STARS; STELLAR ATMOSPHERES; METAL ABUNDANCES; RADIATIVE FORCES; HELIUM; EVOLUTION; IV AB We have made a detailed comparison of results of spectroscopic analysis using three differents types of model atmospheres: classical non-LTE H-He models; approximate non-LTE line-blanketed models (with only a subset of Fe and Ni lines: those originating from transitions between levels with measured energies); and non-LTE fully blanketed models. The three models were applied to the sdO star ED +75 degrees 325, adopted as a test case. We demonstrate that the effects of line blanketing are very important: the best fit of the observed H and He lines is achieved for T-eff = 58,000 K when using H-He models, T-eff = 55,000 K for approximate non-LTE line-blanketed models, and T-eff = 52,000 K for fully blanketed non-LTE models. Using the high-resolution Goddard High Resolution Spectrograph spectrum of ED +75 degrees 325 and our final fully blanketed model, we have derived reliable abundances of He, C, N, O, Si, Fe, and Ni. We find that ED +75 degrees 325 is an He-enriched star (He/H = 1 by number), whose surface exhibits CNO-cycle products, i.e., N-rich (A(N) = 1.5 x 10(-3) by number, or 4.2 x 10(-3) by mass fraction), and C and O deficient (by factor of about 100 with respect to the solar value). We also find a significant surface depletion of silicon and an enhancement of iron and nickel. We argue that these anomalous abundances reflect some mixing with processed material from the core, with subsequent modification at the surface by diffusion processes. Finally, ED +75 degrees 325 possesses a weak wind. Using a simplified description of the wind, we have derived a preliminary value of the mass loss rate: (M) over dot = 1.5 x 10(-11) M. yr(-1). C1 NASA,GODDARD SPACE FLIGHT CTR,ASTRON & SOLAR PHYS LAB,GREENBELT,MD 20771. NR 41 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 AUG 20 PY 1997 VL 485 IS 2 BP 843 EP 858 DI 10.1086/304455 PN 1 PG 16 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XT240 UT WOS:A1997XT24000034 ER PT J AU Dotani, T Inoue, H Mitsuda, K Nagase, F Negoro, H Ueda, Y Makishima, K Kubota, A Ebisawa, K Tanaka, Y AF Dotani, T Inoue, H Mitsuda, K Nagase, F Negoro, H Ueda, Y Makishima, K Kubota, A Ebisawa, K Tanaka, Y TI ASCA observation of Cygnus X-1 in the soft state: Mass of the compact object SO ASTROPHYSICAL JOURNAL LA English DT Article DE stars, individual (Cygnus X-1); X-rays, general; X-rays, stars ID BURSTING NEUTRON STARS; X-RAY-EMISSION; ACCRETION DISKS; BINARY-SYSTEMS; BLACK-HOLES; LMC X-3; SATELLITE; SPECTRUM; MODEL AB We describe the ASCA observation of the black hole candidate Cyg X-l in the soft state of 1996 May and report the mass estimation of the central object from X-ray spectral analysis. The energy spectrum in 0.7-10 keV can be described by the sum of a power law (Gamma = 2.3 +/- 0.1) and an ultrasoft component; the latter is most probably the emission from an optically thick accretion disk. Through the spectral analysis of the ultrasoft component, we estimated the size of the accretion disk, which is closely related to the Schwarzschild radius and, hence, to the mass of the central object. Taking the general relativistic effects into account, the most probable mass of the compact object is estimated as 12(-1)(+3) M.. This value is independent of, yet consistent with, the mass estimate based on the orbital kinematics information. C1 NASA,GODDARD SPACE FLIGHT CTR,UNIV SPACE RES ASSOC,GREENBELT,MD 20771. SPACE RES ORG NETHERLANDS UTRECHT,NL-3584 CA UTRECHT,NETHERLANDS. UNIV TOKYO,DEPT PHYS,BUNKYO KU,TOKYO 113,JAPAN. RP Dotani, T (reprint author), INST SPACE & ASTRONAUT SCI,3-1-1 YOSHINODAI,SAGAMIHARA,KANAGAWA 229,JAPAN. RI Mitsuda, Kazuhisa/C-2649-2008 NR 29 TC 54 Z9 54 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 AUG 20 PY 1997 VL 485 IS 2 BP L87 EP L90 DI 10.1086/310816 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XT241 UT WOS:A1997XT24100009 ER PT J AU Piner, BG Kingham, KA AF Piner, BG Kingham, KA TI A slower superluminal velocity for the quasar 1156+295 SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies, jets; quasars, individual (1156+295); radio continuum, galaxies ID RADIO; VLBI AB As part of an ongoing effort to observe high-energy gamma-ray blazars with VLBI, we have produced 8 and 2 GHz VLBI images, at 10 epochs spanning the years 1988 to 1996, of the quasar 1156+295. The VLBI data have been taken from the Washington VLBI correlator's geodetic database. We have detected four components and have measured their apparent speeds to be 8.8 +/- 2.3, 5.3 +/- 1.1, 5.5 +/- 0.9, and 3.5 +/- 1.2 h(-1)c from the outermost component inward. (H-0 = 100 h km s(-1) Mpc(-1), q(0) = 0.5 throughout this Letter). These velocities contradict a previously published very high superluminal velocity of 26 h(-1)c for this source. C1 UNIV MARYLAND,DEPT ASTRON,COLLEGE PK,MD 20742. NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD. RP Piner, BG (reprint author), USN OBSERV,EARTH ORIENTAT DEPT,3450 MASSACHUSETTS AVE NW,WASHINGTON,DC 20392, USA. NR 12 TC 18 Z9 18 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 AUG 20 PY 1997 VL 485 IS 2 BP L61 EP L63 DI 10.1086/310820 PN 2 PG 3 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XT241 UT WOS:A1997XT24100003 ER PT J AU Scharf, CA Mushotzky, RF AF Scharf, CA Mushotzky, RF TI The galaxy cluster luminosity-temperature relationship and iron abundances: A measure of formation history? SO ASTROPHYSICAL JOURNAL LA English DT Article DE cosmology, observations; galaxies, clusters, general; X-rays, galaxies ID X-RAY AB Both the X-ray luminosity-temperature (L-T) relationship and the iron abundance distribution of galaxy clusters show intrinsic dispersion. Using a large set of galaxy clusters with measured iron abundances, we find a correlation between abundance and the relative deviation of a cluster from the mean LT relationship. We argue that these observations can be explained by taking into account the range of cluster formation epochs expected in a hierarchical universe. The known relationship of cooling flow mass deposition rate to luminosity and temperature is also consistent with this explanation. From the observed cluster population, we estimate that the oldest clusters formed at z greater than or similar to 2. We propose that the iron abundance of a galaxy cluster can provide a parameterization of its age and dynamical history. RP Scharf, CA (reprint author), NASA,GODDARD SPACE FLIGHT CTR,HIGH ENERGY ASTROPHYS LAB,CODE 662,GREENBELT,MD 20771, USA. NR 28 TC 11 Z9 11 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 AUG 20 PY 1997 VL 485 IS 2 BP L65 EP L68 DI 10.1086/310815 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XT241 UT WOS:A1997XT24100004 ER PT J AU Taam, RE Chen, XM Swank, JH AF Taam, RE Chen, XM Swank, JH TI Rapid bursts from GRS 1915+105 with RXTE SO ASTROPHYSICAL JOURNAL LA English DT Article DE accretion, accretion disks; binaries, close; black hole physics; stars, individual (GRS 1915f105); X-rays, stars ID X-RAY SOURCES; ACCRETION DISKS; BLACK-HOLES; VARIABILITY; INSTABILITY; EVOLUTION; CORONAE AB The light curves of GRS 1915+105 observed with RXTE on 1996 October 15 reveal a wide range of transient activity, including regular bursts with a recurrence time of about 1 minute, irregular bursts, and dips. In contrast to bursts from other sources, a secondary (and a tertiary) weaker burst immediately following the primary burst are observed. Detailed energy spectra indicate that the source softens during the main outburst and successively hardens during the secondary and tertiary bursts. This may imply that the accretion flow has a corona-disk configuration and that the relative contribution of the hot corona decreases during the primary bursts and increases during the secondary and tertiary bursts. The primary burst profile resembles the bursts produced in the time-dependent evolutions of accretion disks, which are thermally and viscously unstable. The secondary burst may reflect an inward shift of the inner edge of the disk, which results in a greater release of gravitational binding energy. C1 UNIV CALIF SANTA CRUZ, UNIV CALIF OBSERV, LICK OBSERV, BOARD STUDIES ASTRON & ASTROPHYS, SANTA CRUZ, CA 95064 USA. NASA, GODDARD SPACE FLIGHT CTR, GREENBELT, MD 20771 USA. RP Taam, RE (reprint author), NORTHWESTERN UNIV, DEPT PHYS & ASTRON, EVANSTON, IL 60208 USA. RI Swank, Jean/F-2693-2012 NR 27 TC 65 Z9 65 U1 0 U2 1 PU IOP PUBLISHING LTD PI BRISTOL PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD AUG 20 PY 1997 VL 485 IS 2 BP L83 EP L86 DI 10.1086/310812 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XT241 UT WOS:A1997XT24100008 ER PT J AU Matthews, E AF Matthews, E TI Global litter production, pools, and turnover times: Estimates from measurement data and regression models SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Review ID SOIL ORGANIC-MATTER; ATMOSPHERIC CO2 CONCENTRATION; TERRESTRIAL CARBON STORAGE; LAST GLACIAL MAXIMUM; COARSE WOODY DEBRIS; TROPICAL FORESTS; CLIMATE-CHANGE; WORLD PATTERNS; LAND-USE; BIOSPHERE AB Systematic and compatible databases to quantify composition, distribution, and turnover times of carbon in global litter were developed and evaluated. The study employs an integrated approach, estimating related litter pools and fluxes using a variety of data-based and model-based techniques. The analysis includes direct estimates and indirect, or proxy, estimates of litter production and pools; steady-state turnover times are estimated from the two. Proxies for litter production include net primary productivity and root respiration-soil respiration relationships. In addition to implementing a suite of regression models, >1100 published measurements of litter components, along with site characteristics, were integrated into a baseline data set and used to estimate litter production and pools. Historically, global estimates of litter production have ranged from 75 to 135 Pg dm/yr; several estimates from this study suggest values in the middle of this range, from 90 to 100 Pg dm/yr. The estimate of aboveground litter production from the compiled measurements, 39 Pg dm/yr, includes mainly forest, woodland, and wooded grassland; other grassland, shrubland, and xeromorphic communities that occupy similar to 25% of the ice-free land surface are unrepresented in the present compilation. Aboveground litter production may be 5-10 Pg dm/yr higher with the inclusion of these ecosystems, and the total, including belowground production, may approach 90-110 Pg dm/year. Two novel production estimates derived from soil-and root-respiration relationships are 93 Pg and 100 Pg dm/yr. These estimates have the major advantage of accounting. for both aboveground and belowground litter; the latter is rarely included and can account for a substantial fraction of total production. Production of coarse woody detritus may add similar to 12 Pg dm/yr to the fine litter total. The global litter pool has previously been estimated at similar to 100 to 400 Pg dm. The fine litter pool estimated here from the measurement compilation is 136 PE dm. Although this partial estimate includes ecosystems covering just under half the ice-free land surface, it encompasses forests and woodlands which have the largest pools. Inclusion of the remaining ecosystems may add similar to 25 Pg, raising the total to similar to 160 Pg dm. An additional similar to 150 PE dm is estimated for the coarse woody detrital pool. Global mean steady state turnover times of litter estimated from the pool and production data range from 1.4 to 3.4 years; mean turnover time from the partial forest/woodland measurement compilation is similar to 5 years, and turnover time for coarse woody detritus is similar to 13 years. By encompassing spatial distribution, composition, and magnitude, along with numerous field measurements, this integrated approach has begun to yield compositional and ecosystem constraints on modeled global and regional litter fields and NPP allocation schemes in ecosystem models. RP COLUMBIA UNIV, CTR CLIMATE SYST RES, NASA, GODDARD INST SPACE STUDIES, 2880 BROADWAY, NEW YORK, NY 10025 USA. NR 105 TC 74 Z9 83 U1 3 U2 48 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X EI 2169-8996 J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD AUG 20 PY 1997 VL 102 IS D15 BP 18771 EP 18800 DI 10.1029/97JD02956 PG 30 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA XT101 UT WOS:A1997XT10100001 ER PT J AU McLinden, CA McConnell, JC Griffoen, E McElroy, CT Pfister, L AF McLinden, CA McConnell, JC Griffoen, E McElroy, CT Pfister, L TI Estimating the wavelength-dependent ocean albedo under clear-sky conditions using NASA ER 2 spectroradiometer measurements SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID SURFACE; MODEL AB The wavelength-dependent albedo along the flight track of a NASA ER 2 high-altitude research aircraft has been estimated under clear-sky conditions in the 300-775 nm spectral range. We have developed an inversion technique to estimate ocean albedo which used nadir radiance measurements obtained during recent ER 2 campaigns. These are used in conjunction with a multiple-scattering radiative transfer model. This method is general and robust in that any type of surface can be handled as long as a functional form for the angular distribution of surface radiance can be specified. Comparisons have been made against a forward, iterative method and differences do not exceed 1% in the visible and were 1-2% in the near UV. Results are presented for clear-sky portions of flights from two ER 2 campaigns. Specular reflection of the sunlight off the ocean surface has been treated using the Cox and Munk statistical approach. Following this, the wavelength-dependent albedo has been estimated at selected points along various ER 2 flights. Furthermore. photolysis coefficients (or J values) for NO2 and NO3 have been calculated at these points so that the effects of accounting for both specular reflection and wavelength dependence on photo chemistry can be assessed. The use of a wavelength-dependent albedo was found to impact J values by as much as 10%. It was also determined that, in most cases, accounting for specular reflection was found to have a minor impact on J values (1-3%), but under certain conditions, differences of up to 7% are possible. C1 ATMOSPHER ENVIRONM SERV, DOWNSVIEW, ON M3H 5T4, CANADA. YORK UNIV, DEPT EARTH & ATMOSPHER SCI, N YORK, ON M3J 1P3, CANADA. NASA, AMES RES CTR, MOFFETT FIELD, CA 94035 USA. RP YORK UNIV, DEPT PHYS & ASTRON, 4700 KEELE ST, N YORK, ON M3J 1P3, CANADA. NR 22 TC 10 Z9 10 U1 0 U2 2 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X EI 2169-8996 J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD AUG 20 PY 1997 VL 102 IS D15 BP 18801 EP 18811 DI 10.1029/97JD01079 PG 11 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA XT101 UT WOS:A1997XT10100002 ER PT J AU Chiou, EW McCormick, MP Chu, WP AF Chiou, EW McCormick, MP Chu, WP TI Global water vapor distributions in the stratosphere and upper troposphere derived from 5.5 years of SAGE II observations (1986-1991) SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID OZONE AB Global distributions of water vapor in the stratosphere and upper troposphere are presented on the basis of similar to 5.5 years (January 1986 to May 1991) of observations from the Stratospheric Aerosol and Gas Experiment II (SAGE II) aboard the Earth Radiation Budget Satellite (ERBS). Tabulations are included for seasonal zonal mean water vapor mixing ratios (in parts per million by volume) with l-km vertical resolution and an altitude range from 6 to 40 km. Several climatological features identified in a previous study [McCormick et al., 1993], based on 3 years of observations, have been confirmed by this study: (1) the existence of a region of minimum water vapor (the hygropause) at all latitude bands; (2) the increase in the distance between the tropopause and the hygropause from 1 km at low latitudes to 4 km at high latitudes; and (3) the appearance of a positive poleward gradient throughout all seasons for fixed altitudes between 20 km and 40 km. The latitudinal variation of water vapor mixing ratio at 20 km is characterized by a symmetric pattern with a minimum occurring at the equator. However, the corresponding variations at 25 and 30 km indicate a shift of the minimum toward the summer hemisphere. For the latitude zones 0 degrees-20 degrees and 20 degrees-40 degrees in both hemispheres, the seasonal variations of the hygropause reveal that the altitude as well as the value of the minimum water vapor mixing ratio remain essentially unchanged from December, January, and February to March, April, and May. During September, October, and November the weakening of the hygropause and the spreading of the region of minimum water vapor to a wider altitude range are identified throughout these low-latitude and midlatitude zones. For the upper troposphere the clear-sky relative humidities at 300 mbar show atypical range of 5-60%, which is consistent with previous findings based on Meteosat 6.3 mu m measurements. In addition, the unique capability of SAGE II observations has provided us with unprecedented vertically resolved moisture information for the upper troposphere. For example, the integrated column water vapor content for the 300- to 100-mbar layer ranges from 0.002 to 0.01 g/cm(2) with larger longitudinal variability in the tropics. The integrated column water vapor content from 500 to 100 mbar is found to be significantly larger in the eastern hemisphere than in the western hemisphere. The corresponding integrated water vapor content at high latitudes increases by a factor of 6 from winter to summer (0.02 g/cm(2) compared with 0.13 g/cm(2)). C1 SCI APPLICAT INT CORP, HAMPTON, VA USA. RP NASA, LANGLEY RES CTR, DIV ATMOSPHER SCI, MAIL STOP 475, HAMPTON, VA 23681 USA. NR 19 TC 40 Z9 40 U1 0 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X EI 2169-8996 J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD AUG 20 PY 1997 VL 102 IS D15 BP 19105 EP 19118 DI 10.1029/97JD01371 PG 14 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA XT101 UT WOS:A1997XT10100024 ER PT J AU Yudin, VA Geller, MA Khattatov, BV Douglass, AR Cerniglia, MC Waters, JW Elson, LS Roche, AE Russell, JM AF Yudin, VA Geller, MA Khattatov, BV Douglass, AR Cerniglia, MC Waters, JW Elson, LS Roche, AE Russell, JM TI A UARS study of lower stratospheric polar processing in the early stages of northern and southern winters SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID ATMOSPHERE RESEARCH SATELLITE; MICROWAVE LIMB SOUNDER; REACTIVE CHLORINE; MLS OBSERVATIONS; JANUARY 1992; AIR; MODEL; OZONE; CLAES; CLO AB UARS data and results from a three-dimensional transport model have been used to compare and contrast the extent of the early stages of chemical processing by polar stratospheric clouds (PSCs) during the 1991-1993 northern and southern hemisphere winters of the Upper Atmosphere Research Satellite (UARS) mission. The modeled location and timing of regions of polar processing agree quite well with the UARS microwave limb sounder (MLS), cryogenic limb array etalon spectrometer (CLAES) and Halogen Occultation Experiment (HALOE) observations in that enhanced ClO concentrations are generally found in sunlit regions of polar-processed air and decreases of ClONO2, and HNO3 accompany low temperatures and high values of the aerosol extinctions inside the vortex. For these winters it is found that there is a period of about 2 weeks during the northern hemisphere early winter where sporadic polar processing takes place. After this a persistent processing region is seen inside the polar vortex, and the vortex fills with polar-processed air in a bit more than 2 weeks from the first persistent PSC occurrence. In the southern hemisphere, polar processing also fills the vortex in a bit over 2 weeks. Estimates of the spectral aerosol measure of the aerosol spectrum from CLAES observations illustrate that PSC particles are seen where cold temperatures occur inside the polar vortex and heterogeneous conversion of chlorine species on PSCs are expected. C1 NASA, GODDARD SPACE FLIGHT CTR, ATMOSPHERES LAB, GREENBELT, MD 20771 USA. NASA, LANGLEY RES CTR, HAMPTON, VA 23665 USA. LOCKHEED PALO ALTO RES LABS, PALO ALTO, CA 94303 USA. CALTECH, JET PROP LAB, PASADENA, CA 91109 USA. RP SUNY STONY BROOK, INST TERR & PLANETARY ATMOSPHERES, STONY BROOK, NY 11794 USA. RI Douglass, Anne/D-4655-2012 NR 40 TC 5 Z9 5 U1 0 U2 2 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X EI 2169-8996 J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD AUG 20 PY 1997 VL 102 IS D15 BP 19137 EP 19148 DI 10.1029/97JD00871 PG 12 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA XT101 UT WOS:A1997XT10100026 ER PT J AU Luo, M Russell, JM Huang, TYW AF Luo, M Russell, JM Huang, TYW TI Halogen Occultation Experiment observations of the quasi-biennial oscillation and the effects of Pinatubo aerosols in the tropical stratosphere SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID INTERANNUAL VARIABILITY; MIDDLE ATMOSPHERE; MOUNT-PINATUBO; TRACE GASES; MT-PINATUBO; OZONE; ERUPTION; MODEL; CIRCULATION; NO2 AB The time series of Halogen Occultation Experiment (HALOE) observed mixing ratios of chemical tracers in the tropical stratosphere (O-3, HCl, HF, CH4, NO2, NO, and H2O) exhibit obvious quasi-biennial oscillatory (QBO) characteristics. The pressure-time cross sections for the QBO signals in the mixing ratios of HCl, HF, CH4, NO, and H2O are presented for the first time. The QBO in O-3 and NO2 exibits similar amplitudes and patterns as observed and analyzed previously. An apparent in-phase relationship between O-3 and NO2 above 4 mbar is noted, which implies that ozone QBO may not be caused by NO2 chemical destruction in the upper stratosphere. During the early time period of the UARS mission (late 1991 to early 1992), the QBOs in most HALOE species are seen to be strongly affected by Pinatubo aerosols. In order to quantitatively define the different aerosol effects (heating Versus chemical) from HALOE data, we calculate the vertical displacements of constant volume mixing ratio surfaces of HALOE-measured species in the tropical lower stratosphere. The time evolutions of the vertical displacements of HCl and NOx (HALOE NO2 + NO) isopleths are seen to approximately follow that of HF. This indicates that the enhanced vertical velocity that acts to uplift the tracer profiles due to aerosol radiative heating is a significant effect. However, because of the uncertainty in the vertical displacement analyses of these tracers from HALOE data, it can only be concluded that changes in HCl and NOx from chemical effects are less than 30% and 80%, respectively. C1 UNIV CALIF IRVINE, DEPT EARTH SYST SCI, IRVINE, CA 92717 USA. HAMPTON UNIV, DEPT PHYS, HAMPTON, VA 23668 USA. NATL CTR ATMOSPHER RES, BOULDER, CO 80307 USA. NASA, LANGLEY RES CTR, DIV ATMOSPHER SCI, HAMPTON, VA 23665 USA. NR 31 TC 19 Z9 22 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X EI 2169-8996 J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD AUG 20 PY 1997 VL 102 IS D15 BP 19187 EP 19198 DI 10.1029/97JD01015 PG 12 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA XT101 UT WOS:A1997XT10100031 ER PT J AU Douglass, AR Rood, RB Kawa, SR Allen, DJ AF Douglass, AR Rood, RB Kawa, SR Allen, DJ TI A three-dimensional simulation of the evolution of the middle latitude winter ozone in the middle stratosphere SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID GENERAL-CIRCULATION MODEL; TRANSPORT; ATMOSPHERE; CHEMISTRY; NITROGEN; CHLORINE; UARS AB Observations of O-3, CH4, and N2O from the Halogen Occultation Experiment (HALOE), the Cryogenic Limb Array Etalon Spectrometer (CLAES), and the Microwave Limb Sounder on the Upper Atmosphere Research Satellite are compared with fields calculated using a three-dimensional global chemistry and transport model which uses winds from a data assimilation system. Model and observations are found to be in generally good agreement for ozone at middle latitudes between 50 and 3 hPa. Much of the horizontal structure in the observed long-lived tracers N2O and CH4 is seen in the model, but the model profile shapes differ systematically from those seen by CLAES (N2O and CH4) and HALOE (CH4). To understand the influence of transport on these comparisons, attention is focused on January and February 1992, when a series of minor warmings impact the ozone and tracer distributions. The model O-3 at 6.8 hPa, which agrees well with observations, is shown to be influenced by transport from the tropics toward middle and high latitudes, which increases O-3, and photochemical processes, through which O-3 is destroyed. However, the model N2O and CH4 mixing ratios at middle latitudes at 6.8 hPa are much greater than observations. Good comparisons between modeled and observed O-3 and poor comparisons between modeled and observed N2O and CH4 are explained by differences in the horizontal transport from the subtropics. Here photochemical processes control the O-3 mixing ratio, and the horizontal winds transport air with realistic ozone mixing ratios to the middle latitudes. For the longer-lived gases, the model mixing ratios in the subtropics far exceed observations, and the horizontal winds transport air with higher than observed mixing ratios to middle latitudes, leading to the poor comparisons. This analysis shows that the photochemical-and transport processes that affect O-3 at middle latitudes during winter are well represented in the model. However, for long-lived tracers, errors in the model subtropics are communicated to middle latitudes by the horizontal winds. C1 NASA, GODDARD SPACE FLIGHT CTR, DATA ASSIMILAT OFF, GREENBELT, MD 20771 USA. RP NASA, GODDARD SPACE FLIGHT CTR, ATMOSPHER CHEM & DYNAM BRANCH, ATMOSPHERES LAB, CODE 916, GREENBELT, MD 20771 USA. RI Allen, Dale/F-7168-2010; Douglass, Anne/D-4655-2012; Kawa, Stephan/E-9040-2012; Rood, Richard/C-5611-2008 OI Allen, Dale/0000-0003-3305-9669; Rood, Richard/0000-0002-2310-4262 NR 43 TC 26 Z9 26 U1 0 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X EI 2169-8996 J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD AUG 20 PY 1997 VL 102 IS D15 BP 19217 EP 19232 DI 10.1029/97JD01043 PG 16 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA XT101 UT WOS:A1997XT10100034 ER PT J AU Seftor, CJ Jaross, G Herman, JR Gu, X Moy, L Taylor, SL Wellemeyer, CG AF Seftor, CJ Jaross, G Herman, JR Gu, X Moy, L Taylor, SL Wellemeyer, CG TI The Meteor 3 total ozone mapping spectrometer version 7 data set: Calibration and analysis SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID INSTRUMENT; HOLE AB The Meteor 3/total ozone mapping spectrometer (TOMS) data set has been reprocessed using the version 7 TOMS total ozone algorithm and a recalibration of the TOMS instrument using in-flight and revised laboratory data. To provide continuity for the analysis of long-term trends, the absolute calibration of Meteor 3/TOMS was adjusted so that the measured radiances closely matched Nimbus 7/TOMS. The residual bias in ozone is less than 1% and shows no significant latitudinal or seasonal dependence. The calibration procedure and the differences between the current and previously used calibrations are discussed. Problems in the Meteor 3/TOMS data set caused by chopper wheel synchronization problems are described, and comparisons of the resulting data with version 7 of the Nimbus 7/TOMS data are presented. C1 NASA, GODDARD SPACE FLIGHT CTR, GREENBELT, MD 20771 USA. RP HUGHES STX CORP, 7701 GREENBELT RD, SUITE 400, GREENBELT, MD 20770 USA. OI Herman, Jay/0000-0002-9146-1632 NR 11 TC 5 Z9 5 U1 0 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X EI 2169-8996 J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD AUG 20 PY 1997 VL 102 IS D15 BP 19247 EP 19256 DI 10.1029/97JD00606 PG 10 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA XT101 UT WOS:A1997XT10100036 ER PT J AU Miller, AJ Flynn, LE Hollandsworth, SM DeLuisi, JJ Petropavlovskikh, IV Tiao, GC Reinsel, GC Wuebbles, DJ Kerr, J Nagatani, RM Bishop, L Jackman, CH AF Miller, AJ Flynn, LE Hollandsworth, SM DeLuisi, JJ Petropavlovskikh, IV Tiao, GC Reinsel, GC Wuebbles, DJ Kerr, J Nagatani, RM Bishop, L Jackman, CH TI Information content of Umkehr and solar backscattered ultraviolet (SBUV) 2 satellite data for ozone trends and solar responses in the stratosphere SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID NIMBUS-7; DEPLETION; LATITUDE AB Within the past few years, several papers have been published which present updated profile ozone trends from the recently revised ground-based Umkehr record [Miller et al., 1995] and the combined Nimbus 7 solar backscattered ultraviolet (SBUV) and NOAA 11 SBUV 2 satellite data record [Hollandsworth et al., 1995; Miller et al., 1996]. Within these papers, however, there has remained an overriding question as to the actual information content of the measurement systems and their ability to detect atmospheric responses. In this paper, we compare the ozone trends and responses to the 11-year solar cycle (derived from model and/or data specifications of these effects) to results of forward model/retrieval algorithm computations through the algorithms. We consider data at northern midlatitudes (30 degrees-50 degrees N) so that we may compare the satellite results with those of the ground-based systems. Our results indicate that the Umkehr data contain only four independent pieces of information in the vertical and that the SBUV system contains five. In particular, we find that consideration should be restricted to the following regions; Umkehr: the sum of Umkehr layers 1-5, and layers 6, 7, and 8+ (the sum of layers 8 and above), SBUV: the sum of layers 1-5, and layers 6, 7, 8, and 9+ (the sum of layers 9 and above). Additionally, we compare the actual trends and solar coefficients derived in these layers for the periods 1968-1991 and 1979-1991 for the Umkehr and SBUV data. Finally, we include within the latter comparisons the stratospheric aerosol and gas experiment (SAGE) I and II results from Wang et al. [1996] and the computations from the ozonesondes. C1 SOFTWARE CORP AMER, LANHAM, MD USA. APPL RES CORP, LANDOVER, MD 20785 USA. NOAA, AIR RESOURCES LAB, ENVIRONM RES LAB, BOULDER, CO 80303 USA. UNIV CHICAGO, GRAD SCH BUSINESS, CHICAGO, IL 60637 USA. UNIV WISCONSIN, DEPT STAT, MADISON, WI 53706 USA. UNIV ILLINOIS, DEPT ATMOSPHER SCI, URBANA, IL 61801 USA. ATMOSPHER ENVIRONM SERV, DOWNSVIEW, ON, CANADA. NASA, GODDARD SPACE FLIGHT CTR, GREENBELT, MD 20771 USA. ALLIED SIGNAL INC, BUFFALO, NY 14210 USA. NOAA, NATL ENVIRONM SATELLITE DATA & INFORMAT SERV, OFF RES & APPLICAT, WASHINGTON, DC 20233 USA. RP NOAA, NATL WEATHER SERV, CLIMATE PREDICT CTR, WASHINGTON, DC 20233 USA. RI Flynn, Lawrence/B-6321-2009; Jackman, Charles/D-4699-2012 OI Flynn, Lawrence/0000-0001-6856-2614; NR 23 TC 18 Z9 18 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X EI 2169-8996 J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD AUG 20 PY 1997 VL 102 IS D15 BP 19257 EP 19263 DI 10.1029/97JD01482 PG 7 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA XT101 UT WOS:A1997XT10100037 ER PT J AU Fishman, J Brackett, VG AF Fishman, J Brackett, VG TI The climatological distribution of tropospheric ozone derived from satellite measurements using version 7 Total Ozone Mapping Spectrometer and Stratospheric Aerosol and Gas Experiment data sets SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID COLUMN OZONE; TOMS; ULTRAVIOLET; POLLUTION; RADIANCES; REGION AB The climatological distribution of tropospheric ozone derived from satellite observations has been updated using the reprocessed version 7 Total Ozone Mapping Spectrometer (TOMS) gridded data. The use of version 7 of the archive has not changed any of the climatological features first identified using earlier archived versions of the TOMS data. In general, however, the absolute values of the amount of ozone in the troposphere are decreased by similar to 5 Dobson units (DU). In areas of persistent marine stratus clouds, the climatological values are decreased by an additional 2-3 DU. RP NASA, LANGLEY RES CTR, DIV ATMOSPHER SCI, SAIC INT, MAIL STOP 401A, HAMPTON, VA 23681 USA. NR 22 TC 59 Z9 63 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X EI 2169-8996 J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD AUG 20 PY 1997 VL 102 IS D15 BP 19275 EP 19278 DI 10.1029/97JD01373 PG 4 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA XT101 UT WOS:A1997XT10100039 ER PT J AU Allison, M AF Allison, M TI Accurate analytic representations of solar time and seasons on Mars with applications to the Pathfinder/Surveyor missions SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID MARTIAN ATMOSPHERE AB Efficient analytic recipes are presented for a moderately accurate, closed-form calculation of the areocentric longitude (Ls), analemmic ''equation of time,'' and solar hour angles on Mars, along with an approximate recovery of the Viking ''Local Lander Time.'' The adopted fit to the fictitious mean sun implies a Mars tropical orbit period of 686.9725(d). RP Allison, M (reprint author), NASA,GODDARD INST SPACE STUDIES,2880 BROADWAY,NEW YORK,NY 10025, USA. NR 23 TC 6 Z9 6 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 AUG 15 PY 1997 VL 24 IS 16 BP 1967 EP 1970 DI 10.1029/97GL01950 PG 4 WC Geosciences, Multidisciplinary SC Geology GA XR464 UT WOS:A1997XR46400001 ER PT J AU Dinelli, BM Lepri, G Carlotti, M Carli, B Mencaraglia, F Ridolfi, M Nolt, IG Ade, PAR AF Dinelli, BM Lepri, G Carlotti, M Carli, B Mencaraglia, F Ridolfi, M Nolt, IG Ade, PAR TI Measurement of the isotopic ratio distribution of (HDO)-O-16 and (H2O)-O-16 in the 20-38 km altitude range from far-infrared spectra SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID STRATOSPHERIC WATER-VAPOR; BALLOON-BORNE; SUBMILLIMETER; H2O; SPECTROSCOPY; ASSIGNMENTS; HDO AB The altitude distribution of the isotopic ratio between (HDO)-O-16 and (H2O)-O-16 in the stratosphere is derived by retrieving the mixing ratio profiles (from 20 km to 38 km of altitude) of the two isotopic species from far-infrared emission spectra. The measurements were made with a balloon-borne Fourier Transform Spectrometer capable of 0.0025 cm(-1) spectral resolution during the IBEX 92 campaign. The retrievals were carried out using the global-fit procedure on a statistically significant number of spectra for each isotope, in the 40-75 cm(-1) spectral region. This measurement determines the D/H ratio in stratospheric water over an altitude range larger than that of previous measurements. The value of the (HDO)-O-16/(H2O)-O-16 ratio, normalized to the standard value, ranges from 0.4 to 0.5 (with a 10% random error) in the altitude range studied and is in good agreement with the values previously measured. C1 UNIV BOLOGNA,DIPARTIMENTO CHIM FIS & INORGAN,I-40136 BOLOGNA,ITALY. CNR,IST RIC ONDE ELETTROMAGNET,I-50127 FLORENCE,ITALY. NASA,LANGLEY RES CTR,HAMPTON,VA 23681. UNIV LONDON QUEEN MARY & WESTFIELD COLL,DEPT PHYS,LONDON E1 4NS,ENGLAND. RP Dinelli, BM (reprint author), IST SPETTROSCOPIA MOL,VIA GOBETTI 101,I-40129 BOLOGNA,ITALY. RI Dinelli, Bianca Maria/C-1212-2015; OI Dinelli, Bianca Maria/0000-0002-1218-0008 NR 27 TC 10 Z9 10 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 AUG 15 PY 1997 VL 24 IS 16 BP 2003 EP 2006 DI 10.1029/97GL02022 PG 4 WC Geosciences, Multidisciplinary SC Geology GA XR464 UT WOS:A1997XR46400010 ER PT J AU Tabazadeh, A Toon, OB Jensen, EJ AF Tabazadeh, A Toon, OB Jensen, EJ TI Formation and implications of ice particle nucleation in the stratosphere SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID SULFATE AEROSOLS; CLOUD FORMATION; TEMPERATURE; ACID; H2SO4/HNO3/H2O AB The classical nucleation theory of homogeneous freezing along with a thermodynamic model of aqueous HNO3 is used to calculate the critical temperatures and compositions at which ice crystals will nucleate from an aqueous HNO3 droplet. Assuming that stratospheric aerosols are composed of aqueous HNO3 near the ice frost point we show that ice particle formation in the stratosphere can only occur if the air mass is cooled to about 2 to 3 K below the equilibrium condensation point of ice. A simple function is given for predicting the nucleation temperature of ice particle formation in the stratosphere from the ambient water vapor concentration. Microphysical calculations show that only fast cooling rates (> 500 K day(-1)) encountered in cold lee waves are rapid enough for nucleating the majority of the background aerosols into ice particles. The likelihood that ice crystals formed in lee waves may result in the subsequent crystallization of HNO3 in the droplets is discussed. The barrier to ice formation by heterogeneous gas phase nucleation is compared to that of homogeneous freezing nucleation. C1 UNIV COLORADO,ATMOSPHER & SPACE PHYS LAB,BOULDER,CO 80309. RP Tabazadeh, A (reprint author), NASA,AMES RES CTR,MS 245-4,MOFFETT FIELD,CA 94035, USA. NR 29 TC 45 Z9 46 U1 0 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 AUG 15 PY 1997 VL 24 IS 16 BP 2007 EP 2010 DI 10.1029/97GL01883 PG 4 WC Geosciences, Multidisciplinary SC Geology GA XR464 UT WOS:A1997XR46400011 ER PT J AU Miller, CE Nickolaisen, SL Francisco, JS Sander, SP AF Miller, CE Nickolaisen, SL Francisco, JS Sander, SP TI The OBrO C((2)A(2))<-X(B-2(1)) absorption spectrum SO JOURNAL OF CHEMICAL PHYSICS LA English DT Article ID GAUSSIAN-BASIS SETS; MOLECULAR CALCULATIONS; CHLORINE PEROXIDE; TRANSITION; KINETICS; ATOMS; DECOMPOSITION; MECHANISM; RADICALS; DIOXIDE AB The highly structured visible absorption spectrum of the bromine dioxide radical, OBrO, has been observed in the 15 500-26 000 cm(-1) region. The spectrum is dominated by a long progression in the Br-O symmetric stretching motion (nu(1)') and a series of short progressions built on the bending mode (nu(2)'); there are no features associated with the excitation of the antisymmetric stretching mode (nu(3)'), The spectrum also contains numerous transitions originating from the (0,1,0) and (1,0,0) vibrational levels of the electronic ground state, X(B-2(1)), A simultaneous fit to all of the observed vibronic features yielded the frequencies nu(1) ''=799.4 cm(-1), nu(2) ''=317.5 cm(-1), omega w(1)=641.5 cm(-1) omega(2)' = 210.7 cm(-1), and a band origin T-0 = 15 863 cm(-1). Franck-Condon simulations combined with ab initio calculations of the four lowest OBrO doubler electronic states identify the spectrum as arising from the C((2)A(2))<--X(B-2(1)) electronic transition. (C) 1997 American Institute of Physics. C1 CALIF STATE UNIV LOS ANGELES,DEPT CHEM & BIOCHEM,LOS ANGELES,CA 90032. PURDUE UNIV,DEPT CHEM,W LAFAYETTE,IN 47907. CALTECH,JET PROP LAB,PASADENA,CA 91109. NR 40 TC 36 Z9 36 U1 0 U2 1 PU AMER INST PHYSICS PI WOODBURY PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 SN 0021-9606 J9 J CHEM PHYS JI J. Chem. Phys. PD AUG 15 PY 1997 VL 107 IS 7 BP 2300 EP 2307 DI 10.1063/1.474606 PG 8 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA XQ332 UT WOS:A1997XQ33200016 ER PT J AU Descour, MR Volin, CE Dereniak, EL Thome, KJ Schumacher, AB Wilson, DW Maker, PD AF Descour, MR Volin, CE Dereniak, EL Thome, KJ Schumacher, AB Wilson, DW Maker, PD TI Demonstration of a high-speed nonscanning imaging spectrometer SO OPTICS LETTERS LA English DT Article ID SIMULTANEOUS ACQUISITION; RECONSTRUCTION AB We report results from a field demonstration of a nonscanning high-speed imaging spectrometer [computed-tomography imaging spectrometer (CTIS)] capable of simultaneously recording spatial and spectral information about a rapidly changing scene. High-speed spectral imaging was demonstrated by collection of spectral and spatial snapshots of a missile in flight. This instrument is based on computed-tomography concepts and operates in the visible spectrum (430-710 nm). Raw image data were recorded at video frame rate (30 frames/s) and an integration time of 2 ms. An iterative reconstruction of the spatial and spectral scene information from each raw image took 10 s. We present representative missile spectral signatures from the missile firing. The accuracy of the high-speed spectrometer is demonstrated by comparison of extended-source static-scene spectra acquired by a nonimaging reference spectrometer with spectra acquired by use of CTIS imaging of the same static scenes. (C) 1997 Optical Society of America. C1 USA,TANK AUTOMOT & ARMAMENTS COMMAND,WARREN,MI 48397. CALTECH,JET PROP LAB,CTR SPACE MICROELECT TECHNOL,PASADENA,CA 91109. RP Descour, MR (reprint author), UNIV ARIZONA,CTR OPT SCI,TUCSON,AZ 85721, USA. RI Thome, Kurtis/D-7251-2012 NR 13 TC 46 Z9 49 U1 0 U2 3 PU OPTICAL SOC AMER PI WASHINGTON PA 2010 MASSACHUSETTS AVE NW, WASHINGTON, DC 20036 SN 0146-9592 J9 OPT LETT JI Opt. Lett. PD AUG 15 PY 1997 VL 22 IS 16 BP 1271 EP 1273 DI 10.1364/OL.22.001271 PG 3 WC Optics SC Optics GA XP167 UT WOS:A1997XP16700023 PM 18185817 ER PT J AU Sikivie, P Tkachev, II Wang, Y AF Sikivie, P Tkachev, II Wang, Y TI Secondary infall model of galactic halo formation and the spectrum of cold dark matter particles on Earth SO PHYSICAL REVIEW D LA English DT Article ID AXION MINICLUSTERS; CP CONSERVATION; INVISIBLE-AXION; COSMIC AXIONS; GALAXIES; EVOLUTION; UNIVERSE; CLUSTERS; ROTATION; SEARCH AB The spectrum of cold dark matter particles on Earth is expected to have peaks in velocity space associated with particles which are falling onto the Galaxy for the first time and with particles which have fallen in and out of the Galaxy only a small number of times in the past. We obtain estimates for the velocity magnitudes and the local densities of the particles in these peaks. To this end we use the secondary infall model of galactic halo formation which we have generalized to take account of the angular momentum of the dark matter particles. The new model is still spherically symmetric and it admits self-similar solutions. In the absence of angular momentum, the model produces flat rotation curves for a large range of values of a parameter epsilon which is related to the spectrum of primordial density perturbations. We find that the presence of angular momentum produces an effective core radius; i.e., it makes the contribution of the halo to the rotation curve go to zero at zero radius. The model provides a detailed description of the large scale properties of galactic halos including their density profiles, their extent, and total mass. We obtain predictions for the kinetic energies of the particles in the velocity peaks and estimates for their local densities as functions of the amount of angular momentum, the age of the Universe, and epsilon. C1 OHIO STATE UNIV,DEPT PHYS,COLUMBUS,OH 43210. RUSSIAN ACAD SCI,INST NUCL RES,MOSCOW 117312,RUSSIA. NASA,FERMILAB ASTROPHYS CTR,FERMILAB,BATAVIA,IL 60510. RP Sikivie, P (reprint author), UNIV FLORIDA,DEPT PHYS,GAINESVILLE,FL 32611, USA. RI Wang, Yun/B-5724-2011 OI Wang, Yun/0000-0002-4749-2984 NR 44 TC 132 Z9 132 U1 0 U2 0 PU AMERICAN PHYSICAL SOC PI COLLEGE PK PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA SN 0556-2821 J9 PHYS REV D JI Phys. Rev. D PD AUG 15 PY 1997 VL 56 IS 4 BP 1863 EP 1878 DI 10.1103/PhysRevD.56.1863 PG 16 WC Astronomy & Astrophysics; Physics, Particles & Fields SC Astronomy & Astrophysics; Physics GA XT856 UT WOS:A1997XT85600006 ER PT J AU Kinney, WH AF Kinney, WH TI Hamilton-Jacobi approach to non-slow-roll inflation SO PHYSICAL REVIEW D LA English DT Article ID COSMOLOGICAL PERTURBATIONS; DENSITY PERTURBATIONS; UNIVERSE SCENARIO; SYMMETRY-BREAKING; HYBRID INFLATION; SCALAR FIELD; FLUCTUATIONS; FLATNESS; DYNAMICS; HORIZON AB I describe a general approach to characterizing cosmological inflation outside the standard slow-roll approximation, based on the Hamilton-Jacobi formulation of scalar field dynamics. The basic idea is to view the equation of state of the scalar held matter as the fundamental dynamical variable, as apposed to the field value or the expansion rate. I discuss how to formulate the equations of motion for scalar and tensor fluctuations in situations where the assumption of slow roll is not valid. I apply the general results to the simple case uf inflation from an ''inverted'' polynomial potential, and to the more complicated case of hybrid inflation. RP Kinney, WH (reprint author), NASA,FERMI NATL ACCELERATOR LAB,FERMILAB ASTROPHYS CTR,BATAVIA,IL 60510, USA. NR 30 TC 61 Z9 61 U1 0 U2 0 PU AMERICAN PHYSICAL SOC PI COLLEGE PK PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA SN 0556-2821 J9 PHYS REV D JI Phys. Rev. D PD AUG 15 PY 1997 VL 56 IS 4 BP 2002 EP 2009 DI 10.1103/PhysRevD.56.2002 PG 8 WC Astronomy & Astrophysics; Physics, Particles & Fields SC Astronomy & Astrophysics; Physics GA XT856 UT WOS:A1997XT85600017 ER PT J AU Keil, W Janka, HT Schramm, DN Sigl, G Turner, MS Ellis, J AF Keil, W Janka, HT Schramm, DN Sigl, G Turner, MS Ellis, J TI Fresh look at axions and SN 1987A SO PHYSICAL REVIEW D LA English DT Article ID NUCLEON SPIN FLUCTUATIONS; NEUTRON-STARS; CP CONSERVATION; INVISIBLE AXION; SUPERNOVA CORES; DIRAC NEUTRINOS; HARMLESS AXION; SN-1987A; CONSTRAINTS; SN1987A AB We reexamine the very stringent limit on the axion mass based on the strength and duration of the neutrino signal from SN 1987A, in the light of new measurements of the axial-vector coupling strength of nucleons, possible suppression of axion emission due to many-body effects, and additional emission processes involving pions. The suppression of axion emission due to nucleon spin fluctuations induced by many-body effects degrades previous limits by a factor of about 2. Emission processes involving thermal pions can strengthen the limits by a factor of 3-4 within a perturbative treatment that neglects saturation of nucleon spin fluctuations. Inclusion of saturation effects, however, tends to make the limits less dependent on pion abundances. The resulting upper limit to the axion mass also depends on the precise couplings of the axion and ranges from 0.5 x 10(-3) eV to 6 x 10(-3) eV, consistent with previous results. C1 UNIV CHICAGO, ENRICO FERMI INST, DEPT ASTRON & ASTROPHYS, CHICAGO, IL 60637 USA. FERMILAB NATL ACCELERATOR LAB, NASA, FERMILAB ASTROPHYS CTR, BATAVIA, IL 60510 USA. RP MAX PLANCK INST ASTROPHYS, KARL SCHWARZCHILD STR 1, D-85740 GARCHING, GERMANY. NR 55 TC 58 Z9 58 U1 0 U2 0 PU AMER PHYSICAL SOC PI COLLEGE PK PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA SN 2470-0010 EI 2470-0029 J9 PHYS REV D JI Phys. Rev. D PD AUG 15 PY 1997 VL 56 IS 4 BP 2419 EP 2432 DI 10.1103/PhysRevD.56.2419 PG 14 WC Astronomy & Astrophysics; Physics, Particles & Fields SC Astronomy & Astrophysics; Physics GA XT856 UT WOS:A1997XT85600065 ER PT J AU Linde, A Riotto, A AF Linde, A Riotto, A TI Hybrid inflation in supergravity SO PHYSICAL REVIEW D LA English DT Article AB We propose a simple realization of hybrid inflation in supergravity. Inflation in this scenario is relatively short, and inflationary density perturbations fall down on large scales, which corresponds to a blue spectrum with n>1. Superheavy strings which are formed after inflation in this scenario produce density perturbations of comparable magnitude. In this mixed perturbation (MP) model one may have microwave anisotropy produced by strings and galaxy formation due to inflationary perturbations. C1 NASA,FERMILAB ASTROPHYS CTR,FERMI NATL ACCELERATOR LAB,BATAVIA,IL 60510. RP Linde, A (reprint author), STANFORD UNIV,DEPT PHYS,STANFORD,CA 94305, USA. NR 15 TC 235 Z9 235 U1 0 U2 0 PU AMERICAN PHYSICAL SOC PI COLLEGE PK PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA SN 0556-2821 J9 PHYS REV D JI Phys. Rev. D PD AUG 15 PY 1997 VL 56 IS 4 BP R1841 EP R1844 PG 4 WC Astronomy & Astrophysics; Physics, Particles & Fields SC Astronomy & Astrophysics; Physics GA XT856 UT WOS:A1997XT85600003 ER PT J AU Atkinson, DH Ingersoll, AP Seiff, A AF Atkinson, DH Ingersoll, AP Seiff, A TI Deep winds on Jupiter as measured by the Galileo probe SO NATURE LA English DT Article ID STABILITY-CRITERION; ZONAL FLOW; PROFILE AB The Doppler Wind Experiment on the Galileo probe provided the first in situ data on wind speeds in Jupiter's atmosphere. Initial analysis(1) of the results indicated that wind speeds increase with depth, rather than decaying to zero below the cloud tops or remaining relatively constant as had previously been assumed(2). But this earlier analysis was subject to several potential sources of error, as highlighted by the fact that wind speeds measured at the cloud tops did not seem to match those inferred from tracking clouds(3) in images obtained by the Voyager spacecraft, Here we report new analyses of the probe data that use a corrected treatment of the timing errors, adopt the measured(4) (rather than predicted) descent trajectory, and incorporate a new calibration of the instrumentation that takes into account the unexpectedly high temperatures encountered by the probe. We determine wind speeds at the cloud tops (700-mbar level) in the range 80-100 m s(-1), in agreement with the results of cloud tracking; the speed increases dramatically between 1 and 4 bar, and then remains nearly constant at similar to 170 m s(-1) down to the 21-bar level. The increase in wind speed implies a latitudinal density gradient of 0.5% per degree in the 1-2 bar altitude range, but whether these winds are driven by internal heat or absorbed sunlight remains uncertain. C1 CALTECH,DIV GEOL & PLANETARY SCI,PASADENA,CA 91125. NASA,AMES RES CTR,SAN JOSE STATE UNIV FDN,MOFFETT FIELD,CA 94035. RP Atkinson, DH (reprint author), UNIV IDAHO,DEPT ELECT ENGN,MOSCOW,ID 83844, USA. NR 22 TC 40 Z9 41 U1 2 U2 6 PU MACMILLAN MAGAZINES LTD PI LONDON PA PORTERS SOUTH, 4 CRINAN ST, LONDON, ENGLAND N1 9XW SN 0028-0836 J9 NATURE JI Nature PD AUG 14 PY 1997 VL 388 IS 6643 BP 649 EP 650 DI 10.1038/41718 PG 2 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA XQ863 UT WOS:A1997XQ86300040 ER PT J AU Seiff, A Blanchard, RC Knight, TCD Schubert, G Kirk, DB Atkinson, D Mihalov, JD Young, RE AF Seiff, A Blanchard, RC Knight, TCD Schubert, G Kirk, DB Atkinson, D Mihalov, JD Young, RE TI Wind speeds measured in the deep jovian atmosphere by the Galileo probe accelerometers SO NATURE LA English DT Article AB The atmosphere of Jupiter has a complex circulation which, until recently, has been observable only at the cloud tops(1,2); the mechanisms driving the winds, and the nature of the interior circulation, remained unknown(3). Recent analyses(4-6) of the radio signal from the Galileo probe, obtained during its descent into the jovian atmosphere, have suggested a vigorous interior circulation below the 4-bar level. Here we report an independent measurement of the winds below the cloud tops, making use of the data obtained by the two accelerometers on the descending probe. We find evidence for two distinct wind regimes, in general agreement with the Doppler radio measurements: a region of wind shear between 1 and 4 bar, where the wind speed increases dramatically with depth; and then a region of constant high-velocity winds down to at least the 17-bar level. C1 SAN JOSE STATE UNIV,DEPT METEOROL,SAN JOSE,CA 95192. NASA,LANGLEY RES CTR,HAMPTON,VA 23665. UNIV CALIF LOS ANGELES,DEPT EARTH & SPACE SCI,LOS ANGELES,CA 90024. UNIV IDAHO,DEPT ELECT ENGN,MOSCOW,ID 83844. RP Seiff, A (reprint author), NASA,AMES RES CTR,MS 245-1,MOFFETT FIELD,CA 94035, USA. NR 10 TC 18 Z9 18 U1 0 U2 5 PU MACMILLAN MAGAZINES LTD PI LONDON PA PORTERS SOUTH, 4 CRINAN ST, LONDON, ENGLAND N1 9XW SN 0028-0836 J9 NATURE JI Nature PD AUG 14 PY 1997 VL 388 IS 6643 BP 650 EP 652 DI 10.1038/41721 PG 3 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA XQ863 UT WOS:A1997XQ86300041 ER PT J AU Page, MJ Mason, KO McHardy, IM Jones, LR Carrera, FJ AF Page, MJ Mason, KO McHardy, IM Jones, LR Carrera, FJ TI The evolution of X-ray-selected narrow-emission-line galaxies SO MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY LA English DT Article DE surveys; galaxies, active; galaxies, evolution; quasars, general; cosmology, observations; X-rays, galaxies ID ROSAT; DEEP AB We examine the cosmological evolution of X-ray-selected narrow-emission-line galaxies (NELGs), using a sample of 35 such objects identified in the combined ROSAT UK Deep Survey and RIXOS. This sample is entirely independent of those previously used to investigate the X-ray evolution of NELGs. We detect evolution which is at a similar rate to the evolution found in the optical luminosity function of blue galaxies. The lack of high-redshift (z > 0.6) NELGs detected in X-ray surveys, and the small, well-defined number of X-ray sources which are not optically identified indicate that the evolution of NELGs is probably not the same as the X-ray evolution of QSOs: NELG evolution is slower than the evolution of QSOs and/or ends at a lower redshift. C1 UNIV SOUTHAMPTON, DEPT PHYS, SOUTHAMPTON SO17 1BJ, HANTS, ENGLAND. NASA, GODDARD SPACE FLIGHT CTR, GREENBELT, MD 20771 USA. UNIV CANTABRIA, INST FIS CANTABRIA, CSIC, E-39005 SANTANDER, SPAIN. RP Page, MJ (reprint author), UCL, MULLARD SPACE SCI LAB, HOLMBURY ST MARY, DORKING RH5 6NT, SURREY, ENGLAND. NR 20 TC 4 Z9 4 U1 0 U2 0 PU WILEY-BLACKWELL PI MALDEN PA COMMERCE PLACE, 350 MAIN ST, MALDEN 02148, MA USA SN 0035-8711 J9 MON NOT R ASTRON SOC JI Mon. Not. Roy. Astron. Soc. PD AUG 11 PY 1997 VL 289 IS 3 BP 693 EP 699 PG 7 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XR490 UT WOS:A1997XR49000022 ER PT J AU Silverberg, RF Cheng, ES Cottingham, DA Fixsen, DJ Inman, CA Kowitt, MS Meyer, SS Page, LA Puchalla, JL Rephaeli, Y AF Silverberg, RF Cheng, ES Cottingham, DA Fixsen, DJ Inman, CA Kowitt, MS Meyer, SS Page, LA Puchalla, JL Rephaeli, Y TI Millimeter/submillimeter search for the Sunyaev-Zeldovich effect in the Coma cluster SO ASTROPHYSICAL JOURNAL LA English DT Article DE balloons; cosmic microwave background; cosmology, observations; galaxies, clusters, general; intergalactic medium ID MICROWAVE BACKGROUND ANISOTROPY; X-RAY; GALAXIES; MILLIMETER; WAVELENGTHS AB Observations from the first flight of the Medium Scale Anisotropy Measurement (MSAM1-92) are analyzed to search for the Sunyaev-Zeldovich (SZ) effect toward the Coma cluster. This balloon-borne instrument uses a 28' FWHM beam and a three-position chopping pattern with a throw of +/-40'. With spectral channels at 5.7, 9.3, 16.5, and 22.6 cm(-1) the observations simultaneously sample the frequency range where the SZ spectral distortion in the intensity transitions from a decrement to an increment and where the fractional intensity change is substantially larger than in the Rayleigh-Jeans region. We set limits on the Comptonization parameter integrated over our antenna pattern, Delta y less than or equal to 8.0 x 10(-5) (2 sigma). For a spherically symmetric isothermal model, this implies a central Comptonization parameter y(0) less than or equal to 2.0 x 10(-4) or a central electron density n(0) greater than or equal to 5.8 x 10(-3) cm(-3) h(50), a result consistent with central densities implied by X-ray brightness measurements and central Comptonization estimates from lower frequency observations of the SZ effect. C1 NASA,GODDARD SPACE FLIGHT CTR,ASTRON & SOLAR PHYS LAB,HUGHES STX CORP,GREENBELT,MD 20771. UNIV CHICAGO,ENRICO FERMI INST,CHICAGO,IL 60637. PRINCETON UNIV,DEPT PHYS,PRINCETON,NJ 08540. UNIV CALIF BERKELEY,CTR PARTICLE ASTROPHYS,BERKELEY,CA 94720. TEL AVIV UNIV,SCH PHYS & ASTRON,IL-69978 TEL AVIV,ISRAEL. RP Silverberg, RF (reprint author), NASA,GODDARD SPACE FLIGHT CTR,ASTRON & SOLAR PHYS LAB,GLOBAL SCI & TECHNOL INC,CODE 685-0,GREENBELT,MD 20771, USA. NR 27 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 AUG 10 PY 1997 VL 485 IS 1 BP 22 EP 25 DI 10.1086/304427 PN 1 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XR037 UT WOS:A1997XR03700002 ER PT J AU Snowden, SL Egger, R Freyberg, MJ McCammon, D Plucinsky, PP Sanders, WT Schmitt, JHMM Trumper, J Voges, W AF Snowden, SL Egger, R Freyberg, MJ McCammon, D Plucinsky, PP Sanders, WT Schmitt, JHMM Trumper, J Voges, W TI ROSAT survey diffuse X-ray background maps .2. SO ASTROPHYSICAL JOURNAL LA English DT Article DE diffuse radiation; galaxy, center; surveys; X-rays, galaxies; X-rays, ISM ID LOCAL INTERSTELLAR-MEDIUM; SCORPIO-CENTAURUS; HALO; PSPC; ENHANCEMENT; EMISSION; GALAXY; MATTER; CLOUDS; STARS AB This paper presents new maps of the soft X-ray background from the ROSAT all-sky survey. These maps represent a significant improvement over the previous version in that (1) the position resolution of the PSPC has been used to improve the angular resolution from similar to 2 degrees to 12', (2) there are six energy bands that divide each of the previous three into two parts, and (3) the contributions of point sources have been removed to a uniform source flux level over most of the sky. These new maps will be available in electronic format later in 1997. In this paper we also consider the bright emission in the general direction of the Galactic center in the 0.5-2.0 keV band, and the apparent absorption trough that runs through it along the Galactic plane. We find that while the northern hemisphere data are confused by emission from Loop I, the emission seen south of the plane is consistent with a bulge of hot gas surrounding the Galactic center (in our simple model, a cylinder with an exponential fall-off of density with height above the plane). The cylinder has a radial extent of similar to 5.6 kpc. The X-ray emitting gas has a scale height of 1.9 kpc, an in-plane electron density of similar to 0.0035 cm(-3), a temperature of similar to 10(6.6) K, a thermal pressure of similar to 28,000 cm(-3) K, and a total luminosity of similar to 2 x 10(39) ergs s(-1) using a collisional ionization equilibrium (CIE) plasma emission model. C1 NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. UNIV SPACE RES ASSOC,WASHINGTON,DC. UNIV WISCONSIN,DEPT PHYS,MADISON,WI 53706. HARVARD SMITHSONIAN CTR ASTROPHYS,CAMBRIDGE,MA 02138. RP Snowden, SL (reprint author), MAX PLANCK INST EXTRATERR PHYS,D-85740 GARCHING,GERMANY. RI Snowden, Steven/D-5292-2012 NR 69 TC 389 Z9 390 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 AUG 10 PY 1997 VL 485 IS 1 BP 125 EP & DI 10.1086/304399 PN 1 PG 17 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XR037 UT WOS:A1997XR03700010 ER PT J AU GutierrezMoreno, A Moreno, H Costa, E Feibelman, WA AF GutierrezMoreno, A Moreno, H Costa, E Feibelman, WA TI Ultraviolet and optical observations of Hen 1213, Hen 1341, and Hen 1761 SO ASTROPHYSICAL JOURNAL LA English DT Article DE binaries, symbiotic; stars, individual (Hen 1213, Hen 1341, Hen 1761); ultraviolet, stars ID SOUTHERN SPECTROPHOTOMETRIC STANDARDS; SYMBIOTIC STARS; PLANETARY-NEBULAE; SPECTRAL TYPES; IUE; EXTINCTION; CATALOG AB We present UV observations of the symbiotic stars Hen 1213, Hen 1341, and Hen 1761, made almost simultaneously with optical observations during 1995; previous optical observations were made during 1987 and 1991. The UV spectrum of Hen 1213 was badly affected by background radiation, and only a rough description of the spectrum could be given here; for this reason, only the observations of Hen 1341 and Hen 1761 are discussed. They have the typical spectra of symbiotic stars, with a late giant component, with many emission lines superimposed. It is found that for both objects the reddening determined from He II lambda 1640/He II lambda 4686 is smaller than that obtained from the Balmer decrement, including optical depth effects. Hen 1341 does not show important variations for the three observing periods. Hen 1761 shows P Cygni profiles for He II lambda 4686 and He I lambda 4471, with expansion velocities of the order of 900 and 600 km s(-1), respectively. The 1991 observations give the lower temperature of the hot component with the larger size of the nebula and the lowest He contents. Rough estimates indicate that the hot component of Hen 1761 is smaller and less luminous than that of Hen 1341. C1 NASA,GODDARD SPACE FLIGHT CTR,ASTRON & SOLAR PHYS LAB,GREENBELT,MD 20771. RP GutierrezMoreno, A (reprint author), UNIV CHILE,DEPT ASTRON,CASILLA 36-D,SANTIAGO,CHILE. NR 28 TC 8 Z9 8 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 AUG 10 PY 1997 VL 485 IS 1 BP 359 EP 369 PN 1 PG 11 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XR037 UT WOS:A1997XR03700036 ER PT J AU Hurley, K Costa, E Feroci, M Frontera, F Cline, T DalFiume, D Orlandini, M Boer, M Mazets, E Aptekar, R Golenetskii, S Terekhov, M AF Hurley, K Costa, E Feroci, M Frontera, F Cline, T DalFiume, D Orlandini, M Boer, M Mazets, E Aptekar, R Golenetskii, S Terekhov, M TI Third interplanetary network localization, time history, fluence, peak flux, and distance lower limit of the 1997 February 28 gamma-ray burst SO ASTROPHYSICAL JOURNAL LA English DT Article DE gamma rays; bursts AB The gamma-ray burst of 1997 February 28 was localized using the arrival time analysis method with the Ulysses, BeppoSAX, and WIND spacecraft. The result is a +/-31.5 '' (3 sigma) wide annulus of possible arrival directions that intersects both the position of the burst determined independently by the BeppoSAX Wide Field Camera and the position of a fading X-ray source detected by the BeppoSAX focusing X-ray telescopes and reduces these source location areas by factors of 7 and 1.5, respectively. The combination of the annulus and the BeppoSAX locations, a 0.76 arcmin square error box, is consistent with that of an optical transient source and an extended object, possibly a galaxy. We also present the time history, peak flux, and fluence of this event, and we derive a model-independent lower limit to the source distance of approximate to 11,000 AU. C1 CNR,IST ASTROFIS SPAZIALE,I-00044 FRASCATI,ITALY. UNIV FERRARA,BOLOGNA,ITALY. IST TECNOL & STUDIO RADIAZ EXTRATERR,BOLOGNA,ITALY. NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. CTR ETUD SPATIALE RAYONNEMENTS,F-31029 TOULOUSE,FRANCE. AF IOFFE PHYS TECH INST,ST PETERSBURG 194021,RUSSIA. RP Hurley, K (reprint author), UNIV CALIF BERKELEY,SPACE SCI LAB,BERKELEY,CA 94720, USA. RI Orlandini, Mauro/H-3114-2014; Aptekar, Raphail/B-3456-2015; Golenetskii, Sergey/B-3818-2015 OI Orlandini, Mauro/0000-0003-0946-3151; NR 22 TC 18 Z9 18 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 AUG 10 PY 1997 VL 485 IS 1 BP L1 EP L3 DI 10.1086/310808 PN 2 PG 3 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XR079 UT WOS:A1997XR07900001 ER PT J AU Jefferies, SM Osaki, Y Shibahashi, H Harvey, JW DSilva, S Duvall, TL AF Jefferies, SM Osaki, Y Shibahashi, H Harvey, JW DSilva, S Duvall, TL TI Sounding the Sun's chromosphere SO ASTROPHYSICAL JOURNAL LA English DT Article DE Sun, atmosphere; waves ID SOLAR OSCILLATIONS; FREQUENCY; REFLECTION AB Time-distance analysis of solar acoustic waves with frequencies above the nominal atmospheric acoustic cutoff frequency (similar to 5.3 mHz) shows partial reflection of the waves at both the Sun's photosphere and a layer located higher in the atmosphere. This result supports recent reports of chromospheric modes. C1 UNIV TOKYO,DEPT ASTRON,BUNKYO KU,TOKYO 113,JAPAN. NATL OPT ASTRON OBSERV,NATL SOLAR OBSERV,TUCSON,AZ 85726. NASA,GODDARD SPACE FLIGHT CTR,ASTRON & SOLAR PHYS LAB,GREENBELT,MD 20771. RP Jefferies, SM (reprint author), UNIV DELAWARE,BARTOL RES INST,NEWARK,DE 19716, USA. RI Duvall, Thomas/C-9998-2012 NR 14 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 AUG 10 PY 1997 VL 485 IS 1 BP L49 EP L52 DI 10.1086/310805 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XR079 UT WOS:A1997XR07900013 ER PT J AU Speziale, CG Gatski, TB AF Speziale, CG Gatski, TB TI Analysis and modelling of anisotropies in the dissipation rate of turbulence SO JOURNAL OF FLUID MECHANICS LA English DT Article ID REYNOLDS-STRESS CLOSURES; PRESSURE STRAIN CORRELATION; ISOTROPIC TURBULENCE; LOCAL ISOTROPY; SHEAR FLOWS; NUMBER AB The modelling of anisotropies in the dissipation rate of turbulence is considered based on an analysis of the exact transport equation for the dissipation rate tenser. An algebraic model is systematically derived using integrity bases methods and tensor symmetry properties. The new model differs notably from all previously proposed models in that it depends nonlinearly on the mean velocity gradients. This gives rise to a transport equation for the scalar dissipation rate that is of the same general form as the commonly used model with one major exception. the coefficient of the production term is dependent on the invariants of both the rotational and irrotational strain rates. The relationship between the new model and other recently proposed models is examined in detail. Some basic tests and applications of the model are also provided alone with a discussion of the implications for turbulence modelling. C1 NASA, LANGLEY RES CTR, HAMPTON, VA 23681 USA. RP Speziale, CG (reprint author), BOSTON UNIV, DEPT AEROSP & MECH ENGN, BOSTON, MA 02215 USA. NR 37 TC 57 Z9 57 U1 0 U2 1 PU CAMBRIDGE UNIV PRESS PI NEW YORK PA 40 WEST 20TH STREET, NEW YORK, NY 10011-4211 SN 0022-1120 J9 J FLUID MECH JI J. Fluid Mech. PD AUG 10 PY 1997 VL 344 BP 155 EP 180 DI 10.1017/S002211209700596X PG 26 WC Mechanics; Physics, Fluids & Plasmas SC Mechanics; Physics GA XT239 UT WOS:A1997XT23900006 ER PT J AU Kleeorin, N Rogachevskii, I Ruzmaikin, A Soward, AM Starchenko, S AF Kleeorin, N Rogachevskii, I Ruzmaikin, A Soward, AM Starchenko, S TI Axisymmetric flow between differentially rotating spheres in a dipole magnetic field SO JOURNAL OF FLUID MECHANICS LA English DT Article ID CONDUCTING INNER-CORE; SPHERICAL-SHELL; GEODYNAMO MODEL; SOLID CORE; OUTER CORE; EARTHS; FLUCTUATIONS; FLUIDS; MANTLE AB Constant-density electrically conducting fluid is confined to a rapidly rotating spherical shell and is permeated by an axisymmetric potential magnetic field with dipole parity; the regions outside the shell are rigid insulators. Slow steady axisymmetric motion is driven by rotating the inner sphere at a slightly slower rate. Linear solutions of the governing magnetohydrodynamic equations are derived in the small Ekman number E-limit for values of the Elsasser number Lambda less than order unity. Attention is restricted to the mainstream outside the Ekman-Hartmann layers adjacent to the inner and outer boundaries. When Lambda much less than E-1/2, MHD effects only lead to small perturbations of the well-known Proudman-Stewartson solution. Motion is geostrophic everywhere except in the E-1/3 shear layer containing the tangent cylinder to the inner sphere; that is embedded in thicker E-2/7 (interior), E-1/4 (exterior) viscous layers in which quasi-geostrophic adjustments are made, When E-1/2 much less than Lambda much less than E-1/3, those quasi-geostrophic layers become thinner (E/Lambda)(1/2) Hartmann layers (inside only when Lambda > O(E-3/7)), across which the geostrophic shear is suppressed with increasing ii; they blend with the E-1/3 Stewartson layer at Lambda = O(E-1/3). When E-1/3 much less than Lambda much less than 1, magnetogeostrophic adjustments are made in a thicker inviscid Lambda-layer. Viscous effects are confined to the shrinking (blended) Hartmann-Stewartson layer; it consists of a column (stump) aligned to the tangent cylinder, attached to the equator, height O((E/Lambda(3))(1/8)) and width O((E-3/Lambda)(1/8)), supporting strong zonal winds. With increasing Lambda the main adjustment to the geostrophic flow occurs at Lambda = O(E-1/2). When E-1/2 much less than Lambda much less than 1, the mainstream analogue to the non-magnetic Proudman solution is a state of rigid rotation, except for large quasi-geostrophic shears in (magnetic-Proudman) layers adjacent to but inside both the tangent cylinder and the equatorial ring of the outer sphere of widths (E-1/2/Lambda)(4) and (E-1/2/Lambda)(4/7) respectively;the former is swallowed up by the Hartmann layer when Lambda greater than or equal to O(E-3/7). C1 HEBREW UNIV JERUSALEM,RACAH INST PHYS,IL-91904 JERUSALEM,ISRAEL. CALTECH,JET PROP LAB,PASADENA,CA 91109. UNIV EXETER,DEPT MATH,EXETER EX4 4QE,DEVON,ENGLAND. GEOPHYS OBSERV BOROK,YAROSLAVL 152742,RUSSIA. RP Kleeorin, N (reprint author), BEN GURION UNIV NEGEV,DEPT MECH ENGN,POB 653,IL-84105 BEER SHEVA,ISRAEL. RI Starchenko, Sergey/H-8792-2016 NR 47 TC 36 Z9 37 U1 0 U2 1 PU CAMBRIDGE UNIV PRESS PI NEW YORK PA 40 WEST 20TH STREET, NEW YORK, NY 10011-4211 SN 0022-1120 J9 J FLUID MECH JI J. Fluid Mech. PD AUG 10 PY 1997 VL 344 BP 213 EP 244 DI 10.1017/S0022112097006034 PG 32 WC Mechanics; Physics, Fluids & Plasmas SC Mechanics; Physics GA XT239 UT WOS:A1997XT23900008 ER PT J AU Bock, Y Wdowinski, S Fang, P Zhang, J Williams, S Johnson, H Behr, J Genrich, J Dean, J vanDomselaar, M Agnew, D Wyatt, F Stark, K Oral, B Hudnut, K King, R Herring, T Dinardo, S Young, W Jackson, D Gurtner, W AF Bock, Y Wdowinski, S Fang, P Zhang, J Williams, S Johnson, H Behr, J Genrich, J Dean, J vanDomselaar, M Agnew, D Wyatt, F Stark, K Oral, B Hudnut, K King, R Herring, T Dinardo, S Young, W Jackson, D Gurtner, W TI Southern California Permanent GPS Geodetic Array: Continuous measurements of regional crustal deformation between the 1992 Landers and 1994 Northridge earthquakes SO JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH LA English DT Review ID GLOBAL POSITIONING SYSTEM; SAN-ANDREAS FAULT; 28 JUNE 1992; PHASE AMBIGUITY RESOLUTION; BASE-LINE INTERFEROMETRY; CURRENT PLATE MOTIONS; LOMA-PRIETA; INTERSEISMIC DEFORMATION; RADAR INTERFEROMETRY; CENTRAL JAPAN AB The southern California Permanent GPS Geodetic Array (PGGA) was established in 1990 across the Pacific-North America plate boundary to continuously monitor crustal deformation. We describe the development of the array and the time series of daily positions estimated for its first 10 sites in the 19-month period between the June 28, 1992 (M-W = 7.3), Landers and January 17, 1994 (M-W = 6.7), Northridge earthquakes. We compare displacement rates at four site locations with those reported by Feigl et al. [1993], which were derived from an independent set of Global Positioning System (GPS) and very long baseline interferometry (VLBI) measurements collected over nearly a decade prior to the Landers earthquake. The velocity differences for three sites 65-100 km from the earthquake's epicenter are of order of 3-5 mm/yr and are systematically coupled with the corresponding directions of coseismic displacement. The fourth site, 300 km from the epicenter, shows no significant velocity difference. These observations suggest large-scale postseismic deformation with a relaxation time of at least 800 days. The statistical significance of our observations is complicated by our incomplete knowledge of the noise properties of the two data sets; two possible noise models fit the PGGA data equally well as described in the companion paper by Zhang et al. [this issue]; the pre-landers data are too sparse and heterogeneous to derive a reliable noise model. Under a fractal white noise model for the PGGA data we find that the velocity differences for all three sites are statistically different at the 99% significance level. A white noise plus flicker noise model results in significance levels of only 94%, 43%, and 88%. Additional investigations of the pre-landers data, and analysis of longer spans of PGGA data, could have an important effect on the significance of these results and will be addressed in future work. C1 US GEOL SURVEY, PASADENA, CA 91106 USA. MIT, DEPT EARTH ATMOSPHER & PLANETARY SCI, CAMBRIDGE, MA 02139 USA. CALTECH, JET PROP LAB, PASADENA, CA 91109 USA. RIVERSIDE CTY FLOOD CONTROL & WATER CONSERV DIST, RIVERSIDE, CA 92502 USA. UNIV CALIF LOS ANGELES, DEPT EARTH & SPACE SCI, LOS ANGELES, CA 90024 USA. RP UNIV CALIF SAN DIEGO, SCRIPPS INST OCEANOG, CECIL H & IDA M GREEN INST GEOPHYS & PLANETARY PH, LA JOLLA, CA 92093 USA. RI Wdowinski, Shimon/A-4118-2008; Jackson, David/A-9828-2008; Hudnut, Kenneth/B-1945-2009; Hudnut, Kenneth/G-5713-2010; Williams, Simon/C-7214-2011 OI Jackson, David/0000-0001-7913-5714; Hudnut, Kenneth/0000-0002-3168-4797; Williams, Simon/0000-0003-4123-4973 NR 108 TC 68 Z9 71 U1 1 U2 4 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-9313 EI 2169-9356 J9 J GEOPHYS RES-SOL EA JI J. Geophys. Res.-Solid Earth PD AUG 10 PY 1997 VL 102 IS B8 BP 18013 EP 18033 DI 10.1029/97JB01379 PG 21 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA XQ830 UT WOS:A1997XQ83000027 ER PT J AU Bedworth, PV Perry, JW Marder, SR AF Bedworth, PV Perry, JW Marder, SR TI The synthesis of a symmetrically substituted alpha-octa(isopentoxy)anthralocyanine SO CHEMICAL COMMUNICATIONS LA English DT Article ID ABSORPTION; NAPHTHALOCYANINE; PHTHALOCYANINE; DERIVATIVES; COMPLEXES AB alpha-Octa(isopentoxy)anthralocyanine has been synthesized and is found to have an unprecedented low-energy Q-band absorption and a low first oxidation potential. C1 CALTECH 13974,BECKMAN INST,PASADENA,CA 91125. CALTECH,JET PROP LAB,PASADENA,CA 91109. RI Perry, Joseph/B-7191-2011 OI Perry, Joseph/0000-0003-1101-7337 NR 13 TC 27 Z9 28 U1 1 U2 5 PU ROYAL SOC CHEMISTRY PI CAMBRIDGE PA THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON ROAD, CAMBRIDGE, CAMBS, ENGLAND CB4 4WF SN 1359-7345 J9 CHEM COMMUN JI Chem. Commun. PD AUG 7 PY 1997 IS 15 BP 1353 EP 1354 DI 10.1039/a703454g PG 2 WC Chemistry, Multidisciplinary SC Chemistry GA XP047 UT WOS:A1997XP04700009 ER PT J AU Leu, MT Keyser, LF Timonen, RS AF Leu, MT Keyser, LF Timonen, RS TI Morphology and surface areas of thin ice films SO JOURNAL OF PHYSICAL CHEMISTRY B LA English DT Article; Proceedings Paper CT Symposium on Physics and Chemistry of Ice 1996 CY AUG 27-31, 1996 CL HANOVER, NH ID HETEROGENEOUS REACTIONS; WATER ICE; HYDROGEN-CHLORIDE; NITRIC-ACID; POROSITIES; NITRATE; HCL AB Thin ice films formed by deposition from the vapor phase in flow-tube reactors have been used to simulate polar stratospheric cloud surfaces in order to obtain laboratory data on uptake and heterogeneous reaction rates. In the present study, ice films are formed in such a reactor, and their surface areas are determined in-situ from BET (Brunauer, Emmett, and Teller) analysis of gas adsorption isotherms. The measured surface areas are found to be strongly dependent on the total mass of ice deposited. The specific surface areas of ices prepared at 77 or 196 K are consistent with previous data obtained by using thicker nonuniform ice films. In a separate apparatus, environmental scanning electron microscopy (ESEM) is used to obtain particle sizes and shapes and to investigate the morphology of the ices prepared on borosilicate, aluminum, and silicon substrates. Ice films on borosilicate substrates are found to comprise micron-sized granules randomly packed in layers. The uptake of HCl in ice films prepared at 196 K using the same now-tube reactor is also measured to be approximately 1 x 10(14) molecules/cm(2) when a partial pressure of HCl of about 5 x 10(-7) Torr is used. Similar to the surface areas, the total uptake is strongly proportional to the mass of ice deposited. The combined evidence suggests that even for thin ice films (1) surface areas are greater than the geometric area of the flow-tube reactor and (2) interaction of pore diffusion with surface reaction should be accounted for in the determination of uptake and heterogeneous reaction rates. RP Leu, MT (reprint author), CALTECH,JET PROP LAB,DIV EARTH & SPACE SCI,PASADENA,CA 91109, USA. NR 21 TC 43 Z9 43 U1 0 U2 4 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 SN 1089-5647 J9 J PHYS CHEM B JI J. Phys. Chem. B PD AUG 7 PY 1997 VL 101 IS 32 BP 6259 EP 6262 DI 10.1021/jp963251w PG 4 WC Chemistry, Physical SC Chemistry GA XP913 UT WOS:A1997XP91300046 ER PT J AU Pearlman, H AF Pearlman, H TI Target and spiral wave patterns in premixed gas combustion SO JOURNAL OF THE CHEMICAL SOCIETY-FARADAY TRANSACTIONS LA English DT Article AB Excitable behaviour occurs in premixed gas combustion. Single and multiple target patterns, rotating spiral waves and spatially disordered and temporally chaotic patterns, reminiscent of chemical turbulence, have been observed experimentally on freely propagating and burner-stabilized premixed gas flames. RP Pearlman, H (reprint author), NASA,LEWIS RES CTR,UNIV SO CALIF,21000 BROOKPARK RD,MS 500-115,CLEVELAND,OH 44135, USA. NR 5 TC 3 Z9 3 U1 0 U2 2 PU ROYAL SOC CHEMISTRY PI CAMBRIDGE PA THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON ROAD, CAMBRIDGE, CAMBS, ENGLAND CB4 4WF SN 0956-5000 J9 J CHEM SOC FARADAY T JI J. Chem. Soc.-Faraday Trans. PD AUG 7 PY 1997 VL 93 IS 15 BP 2487 EP 2490 DI 10.1039/a701506b PG 4 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA XN885 UT WOS:A1997XN88500007 ER PT J AU Mannings, V Koerner, DW Sargent, AI AF Mannings, V Koerner, DW Sargent, AI TI A rotating disk of gas and dust around a young counterpart to beta Pictoris SO NATURE LA English DT Article ID T-TAURI STARS; CIRCUMSTELLAR DISKS; GRAINS; ABSORPTION AB beta Pictoris is the best known example of a main-sequence star encircled by a tenuous disk(1), Optical(2,3) and infrared(4) images of beta Pic suggest that the disk is composed of dust grains which have been interpreted(1) as the debris generated by the disruption of the asteroid-sized remnants of planet-formation processes(5), The star itself is relatively old, with an age in excess of 100 Myr, Here we present high-resolution millimetre-wave images of continuum and molecular-line emission from dust and gas surrounding a much younger star, MWC480: the stellar properties of MWC480 are similar to those of beta Pic, but its age is just 6 Myr, The morphology of the circumstellar material and a comparison with the predictions of kinematic modelling indicate the presence of a rotating disk, gravitationally bound to the star, Moreover, the mass of the disk is greater than the minimum required to form a planetary system like our own(5), We therefore suggest that the disk around the young star MWC480 could be a progenitor of debris disks of the type associated with older stars such as beta Pic, and so holds much promise for the study of both the origin of debris disks and the early stages of the formation of planetary systems. C1 CALTECH,JET PROP LAB,PASADENA,CA 91109. RP Mannings, V (reprint author), CALTECH,DIV PHYS MATH & ASTRON,MS 105-24,PASADENA,CA 91125, USA. NR 27 TC 88 Z9 88 U1 0 U2 2 PU MACMILLAN MAGAZINES LTD PI LONDON PA PORTERS SOUTH, 4 CRINAN ST, LONDON, ENGLAND N1 9XW SN 0028-0836 J9 NATURE JI Nature PD AUG 7 PY 1997 VL 388 IS 6642 BP 555 EP 557 DI 10.1038/41505 PG 3 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA XP722 UT WOS:A1997XP72200040 PM 9252187 ER PT J AU Takahashi, T Feely, RA Weiss, RF Wanninkhof, RH Chipman, DW Sutherland, SC Takahashi, TT AF Takahashi, T Feely, RA Weiss, RF Wanninkhof, RH Chipman, DW Sutherland, SC Takahashi, TT TI Global air-sea flux of CO2: An estimate based on measurements of sea-air pCO(2) difference SO PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA LA English DT Article; Proceedings Paper CT Colloquium on Carbon Dioxide and Climate Change CY NOV 13-15, 1995 CL NATL ACAD SCI, IRVINE, CA HO NATL ACAD SCI ID ATMOSPHERIC CARBON-DIOXIDE; EQUATORIAL PACIFIC; PARTIAL-PRESSURE; NORTH-ATLANTIC; SURFACE WATERS; OCEAN-CIRCULATION; TROPICAL ATLANTIC; EL-NINO; EXCHANGE; MODEL AB Approximately 250,000 measurements made for the pCO(2) difference between surface water and the marine atmosphere, Delta pCO(2), have been assembled for the global oceans. Observations made in the equatorial Pacific during El Nine events have been excluded from the data set, These observations are mapped on the global 4 degrees x 5 degrees grid for a single virtual calendar year (chosen arbitrarily to be 1990) representing a non-El Nino year. Monthly global distributions of Delta pCO(2) have been constructed using an interpolation method based on a lateral advection-diffusion transport equation. The net flux of CO2 across the sea surface has been computed using Delta pCO(2) distributions and CO2 gas transfer coefficients across sea surface. The annual net uptake flux of CO2 by the global oceans thus estimated ranges from 0.60 to 1.34 Gt-C.yr(-1) depending on different formulations used for wind speed dependence on the gas transfer coefficient, These estimates;Ire subject to an error of up to 75% resulting from the numerical interpolation method used to estimate the distribution of Delta pCO(2) over the global oceans, Temperate and polar oceans of the both hemispheres are the major sinks for atmospheric CO2, whereas the equatorial oceans are the major sources for CO2. The Atlantic Ocean is the most important CO2 sink, providing about 60% of the global ocean uptake, while the Pacific Ocean is neutral because of its equatorial source flux being balanced by the sink flux of the temperate oceans, The Indian and Southern Oceans take up about 20% each. C1 NOAA,PACIFIC MARINE ENVIRONM LAB,SEATTLE,WA 98115. UNIV CALIF SAN DIEGO,SCRIPPS INST OCEANOG,LA JOLLA,CA 92093. NOAA,ATLANTIC OCEANOG & METEOROL LAB,MIAMI,FL 33149. NASA,AMES RES CTR,MOFFETT FIELD,CA 94035. RP Takahashi, T (reprint author), COLUMBIA UNIV,LAMONT DOHERTY EARTH OBSERV,PALISADES,NY 10964, USA. NR 74 TC 312 Z9 323 U1 2 U2 38 PU NATL ACAD SCIENCES PI WASHINGTON PA 2101 CONSTITUTION AVE NW, WASHINGTON, DC 20418 SN 0027-8424 J9 P NATL ACAD SCI USA JI Proc. Natl. Acad. Sci. U. S. A. PD AUG 5 PY 1997 VL 94 IS 16 BP 8292 EP 8299 DI 10.1073/pnas.94.16.8292 PG 8 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA XQ124 UT WOS:A1997XQ12400005 PM 11607736 ER PT J AU Ramaty, R Reeves, H Lingenfelter, RE Kozlovsky, B AF Ramaty, R Reeves, H Lingenfelter, RE Kozlovsky, B TI LiBeB: High and low energy cosmic ray production and comparison with nu induced nucleosynthesis in SNII SO NUCLEAR PHYSICS A LA English DT Article; Proceedings Paper CT 4th International Conference on Nuclei in the Cosmos CY JUN 20-27, 1996 CL UNIV NOTRE DAME, NOTRE DAME, IN HO UNIV NOTRE DAME ID EARLY GALAXY; EVOLUTION; NUCLEI; BORON; ISOTOPES; ELEMENTS; MODELS C1 INST ASTROPHYS,F-75014 PARIS,FRANCE. UNIV CALIF SAN DIEGO,LA JOLLA,CA 92093. TEL AVIV UNIV,SACKLER FAC EXACT SCI,IL-69978 TEL AVIV,ISRAEL. RP Ramaty, R (reprint author), NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771, USA. NR 17 TC 0 Z9 0 U1 0 U2 0 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0375-9474 J9 NUCL PHYS A JI Nucl. Phys. A PD AUG 4 PY 1997 VL 621 IS 1-2 BP C47 EP C51 PG 5 WC Physics, Nuclear SC Physics GA XU965 UT WOS:A1997XU96500011 ER PT J AU Sutaria, FK Sheikh, JA Ray, A AF Sutaria, FK Sheikh, JA Ray, A TI Relativistic Mean Field calculations of nuclear properties in early stages of stellar collapse. SO NUCLEAR PHYSICS A LA English DT Article; Proceedings Paper CT 4th International Conference on Nuclei in the Cosmos CY JUN 20-27, 1996 CL UNIV NOTRE DAME, NOTRE DAME, IN HO UNIV NOTRE DAME ID GRAVITATIONAL COLLAPSE; STATE; EQUATION C1 NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. RP Sutaria, FK (reprint author), TATA INST FUNDAMENTAL RES,NAVY NAGAR,HOMI BHABHA RD,BOMBAY 400005,MAHARASHTRA,INDIA. NR 10 TC 2 Z9 2 U1 0 U2 0 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0375-9474 J9 NUCL PHYS A JI Nucl. Phys. A PD AUG 4 PY 1997 VL 621 IS 1-2 BP C375 EP C378 PG 4 WC Physics, Nuclear SC Physics GA XU965 UT WOS:A1997XU96500075 ER PT J AU Turner, MS AF Turner, MS TI Cosmology 1996 SO NUCLEAR PHYSICS A LA English DT Article; Proceedings Paper CT 4th International Conference on Nuclei in the Cosmos CY JUN 20-27, 1996 CL UNIV NOTRE DAME, NOTRE DAME, IN HO UNIV NOTRE DAME ID COLD DARK-MATTER; BIG-BANG NUCLEOSYNTHESIS; LARGE-SCALE STRUCTURE; GRAND-UNIFIED THEORIES; INFLATIONARY UNIVERSE; DEUTERIUM ABUNDANCE; TENSOR PERTURBATIONS; BACKGROUND-RADIATION; BARYON DENSITY; CONSTANT C1 FERMILAB NATL ACCELERATOR LAB,NASA,FERMILAB ASTROPHYS CTR,BATAVIA,IL 60510. RP Turner, MS (reprint author), UNIV CHICAGO,ENRICO FERMI INST,DEPT PHYS,5640 S ELLIS AVE,CHICAGO,IL 60637, USA. NR 79 TC 1 Z9 1 U1 0 U2 0 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0375-9474 J9 NUCL PHYS A JI Nucl. Phys. A PD AUG 4 PY 1997 VL 621 IS 1-2 BP C522 EP C531 PG 10 WC Physics, Nuclear SC Physics GA XU965 UT WOS:A1997XU96500101 ER PT J AU Freeland, RE Bilyeu, GD Veal, GR Steiner, MD Carson, DE AF Freeland, RE Bilyeu, GD Veal, GR Steiner, MD Carson, DE TI Large inflatable deployable antenna flight experiment results SO ACTA ASTRONAUTICA LA English DT Article; Proceedings Paper CT 48th International-Astronautical-Federation Congress on Developing Business CY OCT 04-10, 1997 CL TURIN, ITALY SP Int Astronaut Federat, Int Acad Astronaut, Int Inst Space Law, Assoc Italiana Aeronaut & Astronaut AB Large space-based deployable antenna structures are needed for a variety of applications. However, recent reductions of antenna user resources have resulted in a real need for low-cost, large-size, lightweight,and reliable deployable space antenna structures. Fortunately, a new class of deployable space structures, called "inflatable space structures is under development at L'Garde, Inc. The potential of this new concept was recognized by NASA who selected it for a flight experiment. The objective of the experiment was to develop a large, low-cost inflatable antenna structure and demonstrate its mechanical performance in the space environment. The carrier for this free-flying experiment was the STS-launched and recovered Spartan spacecraft. The experiment hardware consisted of a 14-meter diameter off-set parabolic reflector structure. The Spartan 207/IAE was successfully flown on STS 77, deployed on May 20, 1996 with Spartan recovery on May 21, 1996. The basic antenna structure deployed successfully, but in an uncontrolled manner, that clearly demonstrated the robustness of this new type of space structure. The low cost of the flight antenna structure hardware and the outstanding mechanical packaging demonstrated on orbit clearly validated the potential of this new class of space structure for enabling new, low-cost missions. (C) 1998 International Astronautical Federation. Published by Elsevier Science Ltd. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Freeland, RE (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. OI Steiner, Mark/0000-0001-5656-2924 NR 17 TC 26 Z9 34 U1 5 U2 15 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 AUG-NOV PY 1997 VL 41 IS 4-10 BP 267 EP 277 DI 10.1016/S0094-5765(98)00057-5 PG 11 WC Engineering, Aerospace SC Engineering GA ZX277 UT WOS:000074499200009 ER PT J AU Rayman, MD Lehman, DH AF Rayman, MD Lehman, DH TI Deep Space One: NASA's first deep-space technology validation mission SO ACTA ASTRONAUTICA LA English DT Article; Proceedings Paper CT 48th International-Astronautical-Federation Congress on Developing Business CY OCT 04-10, 1997 CL TURIN, ITALY SP Int Astronaut Federat, Int Acad Astronaut, Int Inst Space Law, Assoc Italiana Aeronaut & Astronaut AB Under development for launch in July 1998, Deep Space One (DS1) is the first flight of NASA's New Millennium Program, chartered to validate selected technologies required for future low-cost space science programs. Advanced technologies chosen for validation on DS1 include solar electric propulsion, high-power solar concentrator arrays, autonomous on-board optical navigation, two low-mass science instrument packages, and several telecommunications and microelectronics devices. Throughout the two year primary mission, the technology payload will be exercised extensively to assess performance so that subsequent flight projects will not have to incur the cost and risk of being the first users of these new capabilities. An important component of the DS1 mission is diagnosing any in-flight anomalies or failures. Although DS1 is driven by the requirements of the technology validation, it also presents an important opportunity to conduct solar system science. During the primary mission, the spacecraft will fly by asteroid 3352 McAuliffe, Mars, and comet P/West-Kohoutek-Ikemura. The two science instruments that are being validated, an integrated infrared/visible/ultraviolet package and a plasma physics package, will be used to collect science data during the cruise and encounters. In addition, a suite of fields and particles sensors included to aid in the quantification of the effects of the solar electric propulsion on the spacecraft and near-space environment will be used for science measurements complementary to those of the plasma instrument. The return of science data will demonstrate that the technologies are compatible with the demands of future scientific missions and will ensure that this rare opportunity to encounter such a variety of solar system targets during a short mission will be fully exploited. (C) 1998 American Institute of Aeronautics and Astronautics, Inc. Published by Elsevier Science Ltd. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Rayman, MD (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 12 TC 11 Z9 11 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 AUG-NOV PY 1997 VL 41 IS 4-10 BP 289 EP 299 DI 10.1016/S0094-5765(98)00073-3 PG 11 WC Engineering, Aerospace SC Engineering GA ZX277 UT WOS:000074499200011 ER PT J AU Mankins, JC AF Mankins, JC TI A fresh look at space solar power: New architectures, concepts and technologies SO ACTA ASTRONAUTICA LA English DT Article; Proceedings Paper CT 48th International-Astronautical-Federation Congress on Developing Business CY OCT 04-10, 1997 CL TURIN, ITALY SP Int Astronaut Federat, Int Acad Astronaut, Int Inst Space Law, Assoc Italiana Aeronaut & Astronaut AB The concept of generating solar power in space for wireless transmission to receivers on the ground has been discussed at some, length during the past three decades. During the first decades of the new century, global demand for electrical power is projected to growth dramatically-perhaps doubling from 12 terawatts to more than 24 terawatts. Achieving this power growth while managing environmental impacts effectively is a crucial international challenge. During 1995-1996, the National Aeronautics and Space Administration (NASA) conducted a far-reaching reexamination of the technologies, systems concepts and terrestrial markets that might be involved in future space solar power (SSP) systems. The principal objective of this "fresh look" study was to determine whether a solar power satellite (SPS) and associated systems could be defined that could deliver energy into terrestrial electrical power grids at prices equal to or below ground alternatives in a variety of markets, do so without major environmental drawbacks, and which could be developed at a fraction of the initial investment projected for the SPS Reference System of the late 1970s. Working with a major focus on emerging nations-the study examined 5 different markets and about 30 different SPS concepts, ranging from the 1979 SPS Reference Concept defined by the US Department of Energy and NASA to very advanced concepts involving technologies which have not yet been validated in the laboratory. Following a preliminary assessment of technical and economic risks and projected costs, 7 SSP system architectures and 4 specific SPS concepts were chosen for examination in greater depth using a comprehensive, end-to-end systems analysis employing a desk-top computer modeling tool that was developed for the study. Several Innovative concepts were defined and a variety of new technology applications considered. A key ground rule to achieve initial cost goals was to avoid wherever possible the design, development, test and evaluation costs associated with SSP-unique infrastructure. Three architectures in particular were identified as promising: a sunsynchronous low Earth orbit (LEO) constellation, a middle Earth orbit (MEO) multiple-inclination constellation, and one or more stand-alone geostationary Earth orbit (GEO) SPS serving single, dedicated ground sites. This paper presents a summary of the results of the "Fresh Look" Study, including architectures, systems concepts and technologies. C1 NASA, Adv Projects Off, Washington, DC 20546 USA. RP Mankins, JC (reprint author), NASA, Adv Projects Off, 300 E St SW, Washington, DC 20546 USA. NR 8 TC 31 Z9 31 U1 1 U2 9 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 AUG-NOV PY 1997 VL 41 IS 4-10 BP 347 EP 359 DI 10.1016/S0094-5765(98)00075-7 PG 13 WC Engineering, Aerospace SC Engineering GA ZX277 UT WOS:000074499200017 ER PT J AU Hubbard, GS Binder, AB Dougherty, TA Cox, SA AF Hubbard, GS Binder, AB Dougherty, TA Cox, SA TI The Lunar Prospector Discovery Mission: A new approach to planetary science SO ACTA ASTRONAUTICA LA English DT Article; Proceedings Paper CT 48th International-Astronautical-Federation Congress on Developing Business CY OCT 04-10, 1997 CL TURIN, ITALY SP Int Astronaut Federat, Int Acad Astronaut, Int Inst Space Law, Assoc Italiana Aeronaut & Astronaut AB Lunar Prospector, the first competitively selected mission in NASA's Discovery Program, will conduct a one year orbital survey of the Moon's composition and structure. To be launched in late 1997, the suite of five instruments will detect water ice to a sensitivity of 50 ppm (hydrogen), measure key elemental constituents, detect gas release events and accurately map the Moon's gravitational and magnetic fields. At a total real year cost of $63M, including launch vehicle and operations, and a development period of less than two years, the mission also demonstrates a new, rapid, cost-effective approach to planetary science investigations. As a joint effort of NASA's Ames Research Center and Lock-heed Martin, Sunnyvale, Lunar Prospector is a model of government-industry cooperation. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Hubbard, GS (reprint author), NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. NR 4 TC 3 Z9 3 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 AUG-NOV PY 1997 VL 41 IS 4-10 BP 585 EP 597 DI 10.1016/S0094-5765(98)00070-8 PG 13 WC Engineering, Aerospace SC Engineering GA ZX277 UT WOS:000074499200040 ER PT J AU Cook, RA Spear, AJ AF Cook, RA Spear, AJ TI Back to Mars: The Mars Pathfinders mission SO ACTA ASTRONAUTICA LA English DT Article; Proceedings Paper CT 48th International-Astronautical-Federation Congress on Developing Business CY OCT 04-10, 1997 CL TURIN, ITALY SP Int Astronaut Federat, Int Acad Astronaut, Int Inst Space Law, Assoc Italiana Aeronaut & Astronaut AB Mars Pathfinder successfully landed on the surface of Mars on July 4, 1997, and ushered in a new era in Mars exploration. This era will feature numerous low cost missions which will perform important science investigations and engage the world's population in the excitement of planetary exploration. Pathfinder has obtained already obtained a set of significant science results relating to Martian geology and geomorphology, mineralogy and geochemistry, magnetic and surface properties, atmospheric properties, and orbital dynamics. In addition, the Sojourner microrover has traversed the area surrounding the lander and has performed several key technology experiments. The Pathfinder mission has also proven to be one of NASA most popular efforts with the general public. The Mars landing event marked a turning point in the use of the Internet when more than 400 million "hits" were received in the first two weeks after landing. The unprecedented level of excitement and interest should. (C) 1998 International Astronautical Federation. Published by Elsevier Science Ltd. C1 CALTECH, Jet Prop Lab, Mars Pathfinder Project, Pasadena, CA 91125 USA. RP Cook, RA (reprint author), CALTECH, Jet Prop Lab, Mars Pathfinder Project, Pasadena, CA 91125 USA. NR 0 TC 0 Z9 0 U1 1 U2 3 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 AUG-NOV PY 1997 VL 41 IS 4-10 BP 599 EP 608 DI 10.1016/S0094-5765(98)00069-1 PG 10 WC Engineering, Aerospace SC Engineering GA ZX277 UT WOS:000074499200041 ER PT J AU Soffen, GA AF Soffen, GA TI Astrobiology from exobiology: Viking and the current Mars probes SO ACTA ASTRONAUTICA LA English DT Article; Proceedings Paper CT 48th International-Astronautical-Federation Congress on Developing Business CY OCT 04-10, 1997 CL TURIN, ITALY SP Int Astronaut Federat, Int Acad Astronaut, Int Inst Space Law, Assoc Italiana Aeronaut & Astronaut C1 NASA, Washington, DC 20546 USA. RP Soffen, GA (reprint author), NASA, Code S,HQ, Washington, DC 20546 USA. NR 0 TC 3 Z9 3 U1 0 U2 4 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 AUG-NOV PY 1997 VL 41 IS 4-10 BP 609 EP 611 DI 10.1016/S0094-5765(98)00055-1 PG 3 WC Engineering, Aerospace SC Engineering GA ZX277 UT WOS:000074499200042 PM 11541152 ER PT J AU Wilhite, AW Shaw, RJ AF Wilhite, AW Shaw, RJ TI HSCT research picks up speed SO AEROSPACE AMERICA LA English DT Article RP Wilhite, AW (reprint author), NASA,LANGLEY RES CTR,HAMPTON,VA 23665, USA. NR 0 TC 3 Z9 4 U1 0 U2 0 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 SN 0740-722X J9 AEROSPACE AM JI Aerosp. Am. PD AUG PY 1997 VL 35 IS 8 BP 24 EP & PG 7 WC Engineering, Aerospace SC Engineering GA XQ973 UT WOS:A1997XQ97300010 ER PT J AU Flatley, T Kolasinski, J Bretthauer, J Luers, P AF Flatley, T Kolasinski, J Bretthauer, J Luers, P TI Networking in space with fiber optics SO AEROSPACE AMERICA LA English DT Article RP Flatley, T (reprint author), NASA,GODDARD SPACE FLIGHT CTR,FLIGHT COMPONENT DEV GRP,GREENBELT,MD 20771, USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 SN 0740-722X J9 AEROSPACE AM JI Aerosp. Am. PD AUG PY 1997 VL 35 IS 8 BP 36 EP 40 PG 5 WC Engineering, Aerospace SC Engineering GA XQ973 UT WOS:A1997XQ97300012 ER PT J AU Librescu, L Hause, T Camarda, CJ AF Librescu, L Hause, T Camarda, CJ TI Geometrically nonlinear theory of initially imperfect sandwich curved panels incorporating nonclassical effects SO AIAA JOURNAL LA English DT Article; Proceedings Paper CT AIAA 37th Structures, Structural Dynamics and Materials Conference CY APR 15-17, 1996 CL SALT LAKE CITY, UT SP AIAA ID COMPOSITE AB A comprehensive geometrically nonlinear theory of initially imperfect doubly curved sandwich shells is developed. The theory encompasses sandwich structures with dissimilar face sheets constructed of laminate composites and with the core modeled as an orthotropic body featuring strong or soft behaviors. The theory includes the dynamic as well as the temperature and moisture effects. As a special case, a range of related applications of the theory of sandwich shells with soft core are presented. These involve the buckling and postbuckling of flat and circular cylindrical shells compressed by uniaxially edge loads, and the influence played in this respect by a number of geometrical and physical parameters is highlighted. Also contained are comparisons of buckling results obtained in the context of the present theoretical model with the ones obtained experimentally, and reasonable agreements are reported. C1 NASA,LANGLEY RES CTR,THERMAL STRUCT BRANCH,HAMPTON,VA 23681. RP Librescu, L (reprint author), VIRGINIA POLYTECH INST & STATE UNIV,DEPT ENGN SCI & MECH,BLACKSBURG,VA 24061, USA. NR 23 TC 18 Z9 18 U1 1 U2 5 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 AUG PY 1997 VL 35 IS 8 BP 1393 EP 1403 DI 10.2514/2.249 PG 11 WC Engineering, Aerospace SC Engineering GA XN776 UT WOS:A1997XN77600017 ER PT J AU Allen, DL Linderman, JK Roy, RR Bigbee, AJ Grindeland, RE Mukku, V Edgerton, VR AF Allen, DL Linderman, JK Roy, RR Bigbee, AJ Grindeland, RE Mukku, V Edgerton, VR TI Apoptosis: a mechanism contributing to remodeling of skeletal muscle in response to hindlimb unweighting SO AMERICAN JOURNAL OF PHYSIOLOGY-CELL PHYSIOLOGY LA English DT Article DE skeletal muscle plasticity; programmed cell death; hindlimb suspension; soleus; myonuclear number ID PROGRAMMED CELL-DEATH; GROWTH FACTOR-I; DNA FRAGMENTATION; INVOLUTION; SURVIVAL; RAT; SYNERGISTS; HORMONE; FIBERS; NUCLEI AB The role of apoptosis in the elimination of myonuclei during hindlimb unloading-induced atrophy and the inhibition of apoptosis in the prevention of muscle atrophy were examined. The number of nuclei demonstrating double-stranded DNA fragmentation seen by terminal deoxynucleotidyl transferase (TDT) histochemical staining, an indicator of apoptosis, was significantly increased after 14 days of suspension. Double staining with TDT and antilaminin immunohistochemistry revealed that some TDT-positive nuclei were within the fiber lamina and were most likely myonuclei. The number of fibers containing morphologically abnormal nuclei was also significantly greater in suspended compared with control rats. Combined treatment with growth hormone and insulin-like growth factor I (GH/IGF-I) and resistance exercise attenuated the increase in TDT-positive nuclei (similar to 26%, P > 0.05) and significantly decreased the number of fibers with morphologically abnormal nuclei. The data suggest that 1) ''programmed nuclear death'' contributes to the elimination of myonuclei and/or satellite cells from atrophying fibers, and 2) GH/IGF-I administration plus muscle loading ameliorates the apoptosis associated with hindlimb unloading. C1 UNIV CALIF LOS ANGELES, SCH MED, CTR HLTH SCI, BRAIN RES INST, LOS ANGELES, CA 90095 USA. UNIV CALIF LOS ANGELES, DEPT PHYSIOL SCI, LOS ANGELES, CA 90095 USA. NASA, AMES RES CTR, MOFFETT FIELD, CA 94035 USA. GENENTECH INC, S SAN FRANCISCO, CA 94080 USA. FU NINDS NIH HHS [NS-16333] NR 37 TC 255 Z9 262 U1 2 U2 8 PU AMER PHYSIOLOGICAL SOC PI BETHESDA PA 9650 ROCKVILLE PIKE, BETHESDA, MD 20814 SN 0363-6143 J9 AM J PHYSIOL-CELL PH JI Am. J. Physiol.-Cell Physiol. PD AUG PY 1997 VL 273 IS 2 BP C579 EP C587 PG 9 WC Cell Biology; Physiology SC Cell Biology; Physiology GA XQ262 UT WOS:A1997XQ26200024 PM 9277355 ER PT J AU Newell, MP KeskiKuha, RAM AF Newell, MP KeskiKuha, RAM TI Bidirectional reflectance distribution function of diffuse extreme ultraviolet scatterers and extreme ultraviolet baffle materials SO APPLIED OPTICS LA English DT Article DE bidirectional reflectance distribution function; BRDF; scatter; extreme ultraviolet; far ultraviolet; ultraviolet; baffle; diffuse; black ID SURFACES; LIGHT AB Bidirectional reflectance distribution function (BRDF) measurements of a number of diffuse extreme ultraviolet (EUV) scatterers and EUV baffle materials have been performed with the Goddard EW scatterometer. BRDF data are presented for white Spectralon SRS-99 at 121.6 nm; the data exhibit a non-Lambertian nature and a total hemispherical reflectance lower than 0.15. Data are also presented for an evaporated Cu black sample, a black Spectralon SRS-02 sample, and a Martin Optical Black sample at wavelengths of 58.4 and 121.6 nm and for angles of incidence of 15 degrees and 45 degrees. Overall Martin Optical Black exhibited the lowest BRDF characteristic, with a total hemispherical reflectance of the order of 0.01 and measured BRDF values as low as 2 x 10(-3) sr(-1). (C) 1997 Optical Society of America. C1 NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. NR 17 TC 5 Z9 5 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 AUG 1 PY 1997 VL 36 IS 22 BP 5471 EP 5475 DI 10.1364/AO.36.005471 PG 5 WC Optics SC Optics GA XN683 UT WOS:A1997XN68300025 PM 18259367 ER PT J AU Greenberg, PS Ku, JC AF Greenberg, PS Ku, JC TI Soot volume fraction imaging SO APPLIED OPTICS LA English DT Article DE tomography; light extinction; flame spectroscopy ID FLAME-GENERATED SOOT; DIFFUSION FLAMES; SCATTERING; ABSORPTION; TOMOGRAPHY; SMOKE; LIGHT; OPTICS AB A technique is described for the determination of soot volume fractions by laser Light extinction measurements. This technique differs from previously reported pointwise methods in that a two-dimensional array (i.e., image) of data is acquired simultaneously. In this fashion the net data rate is increased and allo ws the study of time-dependent phenomena and the investigation of spatial and temporal correlations. A telecentric imaging configuration is employed to provide depth invariant magnification and to permit the specification of the collection angle far scattered light. A method is also employed to suppress undesirable coherent imaging effects. A discussion of the tomographic inversion process is also provided, including the results obtained from numerical simulations. (C) 1997 Optical Society of America. C1 WAYNE STATE UNIV,DETROIT,MI 48202. RP Greenberg, PS (reprint author), NASA,LEWIS RES CTR,CLEVELAND,OH 44135, USA. NR 33 TC 43 Z9 46 U1 0 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 AUG 1 PY 1997 VL 36 IS 22 BP 5514 EP 5522 DI 10.1364/AO.36.005514 PG 9 WC Optics SC Optics GA XN683 UT WOS:A1997XN68300032 PM 18259374 ER PT J AU Brandt, JC Heap, SR Beaver, EA Boggess, A Carpenter, KG Ebbets, DC Hutchings, JB Jura, M Leckrone, DS Linsky, JL Maran, SP Savage, BD Smith, AM Trafton, LM Walter, FM Weymann, RJ Snow, M Randall, CE Tripp, TM Ake, TB Crenshaw, DM Bruhweiler, FC AF Brandt, JC Heap, SR Beaver, EA Boggess, A Carpenter, KG Ebbets, DC Hutchings, JB Jura, M Leckrone, DS Linsky, JL Maran, SP Savage, BD Smith, AM Trafton, LM Walter, FM Weymann, RJ Snow, M Randall, CE Tripp, TM Ake, TB Crenshaw, DM Bruhweiler, FC TI Observations of 3C 273 with the Goddard High Resolution Spectrograph on the Hubble Space Telescope .2. SO ASTRONOMICAL JOURNAL LA English DT Article ID LYMAN-ALPHA CLOUDS; GALACTIC HALO; LOW-REDSHIFT; 3C-273; ABSORPTION; ABUNDANCE; SYSTEMS; SIGHT AB Observations of the quasar 3C 273 taken with the Goddard High Resolution Spectrograph in 1993 November and December are presented here. We have included both the fully-reduced spectra, and spectra combined with our earlier (1991) observations. There are a total of IO new medium resolution exposures covering four wavelength regions: 1164-1201 Angstrom, 1214-1251 Angstrom, 1537-1573 Angstrom, and 1633-1670 Angstrom. We confirm the suggestion of Morris et al. (1991, ApJ, 377, L21) that the galactic Si IV lambda 1393 line is blended with an extragalactic Ly alpha line by observing the Ly beta counterpart to this extragalactic line. We obtain an improved upper limit on the C IV/H I ratio in these weak low redshift Ly alpha absorption systems by coadding the corresponding C IV spectral regions. Improved line profiles for the galactic C IV and N V absorption are also presented and discussed. The improved measurements lead to a downward revision of the galactic C IV column density, log N(C IV) = 14.46+/-0.04. (C) 1997 American Astronomical Society. C1 NASA,GODDARD SPACE FLIGHT CTR,ASTRON & SOLAR PHYS LAB,GREENBELT,MD 20771. UNIV CALIF SAN DIEGO,CTR ASTROPHYS & SPACE SCI,LA JOLLA,CA 92093. BALL AEROSP & TECHNOL CORP,BOULDER,CO 80306. DOMINION ASTROPHYS OBSERV,VICTORIA,BC V8X 4M6,CANADA. UNIV CALIF LOS ANGELES,DEPT PHYS & ASTRON,LOS ANGELES,CA 90095. UNIV COLORADO,JOINT INST LAB ASTROPHYS,BOULDER,CO 80309. NATL INST STAND & TECHNOL,BOULDER,CO 80309. NASA,GODDARD SPACE FLIGHT CTR,SPACE SCI DIRECTORATE,GREENBELT,MD 20771. UNIV WISCONSIN,DEPT AGRON,MADISON,WI 53706. UNIV TEXAS,MCDONALD OBSERV,AUSTIN,TX 78712. UNIV TEXAS,DEPT ASTRON,AUSTIN,TX 78712. SUNY STONY BROOK,STONY BROOK,NY 11794. OBSERV CARNEGIE INST WASHINGTON,PASADENA,CA 91101. UNIV COLORADO,ATMOSPHER & SPACE PHYS LAB,BOULDER,CO 80309. PRINCETON UNIV OBSERV,PRINCETON,NJ 08544. NASA,GODDARD SPACE FLIGHT CTR,COMP SCI CORP,SCI PROGRAMS,GREENBELT,MD 20771. CATHOLIC UNIV AMER,INST ASTROPHYS,WASHINGTON,DC 20064. RP Brandt, JC (reprint author), UNIV COLORADO,ATMOSPHER & SPACE PHYS LAB,CAMPUS BOX 392,BOULDER,CO 80309, USA. RI heap, sara/E-2237-2012; Carpenter, Kenneth/D-4740-2012; Randall, Cora/L-8760-2014 OI Randall, Cora/0000-0002-4313-4397 NR 18 TC 7 Z9 7 U1 0 U2 1 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 AUG PY 1997 VL 114 IS 2 BP 554 EP 564 DI 10.1086/118492 PG 11 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XN548 UT WOS:A1997XN54800007 ER PT J AU Fanelli, MN Collins, N Bohlin, RC Neff, SG OConnell, RW Roberts, MS Smith, AM Stecher, TP AF Fanelli, MN Collins, N Bohlin, RC Neff, SG OConnell, RW Roberts, MS Smith, AM Stecher, TP TI An ultraviolet view of massive star formation in Seyfert host galaxies SO ASTRONOMICAL JOURNAL LA English DT Article ID NARROW-LINE REGION; IMAGING TELESCOPE; IUE OBSERVATIONS; ROCKET ULTRAVIOLET; NEUTRAL HYDROGEN; STARBURST DISK; CO EMISSION; NGC-1068; NGC-4151; PHOTOMETRY AB We present deep vacuum ultraviolet (lambda lambda 1200-3300 Angstrom) imagery of four Seyfert galaxies observed by the Ultraviolet Imaging Telescope (UIT): NGC 1068, NGC 2992, NGC 4151, and Mrk 335. These data have a spatial resolution of similar to 3 '' and a limiting surface brightness of similar to 24.5 mag arcsec(-2). The host galaxies display a diverse range in ultraviolet morphology. NGC 1068 contains multiple components: the central AGN and a population of luminous starburst knots embedded within a bright oval disk. The starburst disk dominates the observed UV luminosity producing 81% of the far-UV (lambda similar to 1500 Angstrom) flux, and 83% of the near-UV (lambda similar to 2500 Angstrom) flux. In contrast to NGC 1068, the unresolved bright nucleus dominates the UV Light distribution in NGC 4151. The disk component produces 19% of the global far-UV flux and 18% of the near-UV flux. The active nucleus in Mrk 335 appears as a point source in both bandpasses; the host galaxy is not detected. NGC 2992, detected at near-UV wavelengths only, displays diffuse, patchy light at the position of the optically-defined disk, but no bright nuclear source. The UIT imagery highlights the contrast between the recently-formed massive star populations in NGC 4151 and NGC 1068. The radial UV surface brightness profile in NGC 4151 is qualitatively similar to the profile shapes observed in a few nearby spiral disks, while the radial profile found for NGC 1068 is distinctly atypical, The large fraction of observed luminosity produced by the disk component in NGC 1068 demonstrates that even at ultraviolet wavelengths, the fractional contribution of an active nucleus to the observed global flux can be small. (C) 1997 American Astronomical Society. C1 NASA, GODDARD SPACE FLIGHT CTR, ASTRON & SOLAR PHYS LAB, GREENBELT, MD 20771 USA. SPACE TELESCOPE SCI INST, BALTIMORE, MD 21218 USA. UNIV VIRGINIA, DEPT ASTRON, CHARLOTTESVILLE, VA 22903 USA. NATL RADIO ASTRON OBSERV, CHARLOTTESVILLE, VA 22903 USA. NR 64 TC 8 Z9 8 U1 0 U2 0 PU IOP PUBLISHING LTD PI BRISTOL PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND SN 0004-6256 EI 1538-3881 J9 ASTRON J JI Astron. J. PD AUG PY 1997 VL 114 IS 2 BP 575 EP + DI 10.1086/118494 PG 1 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XN548 UT WOS:A1997XN54800009 ER PT J AU NoriegaCrespo, A VanBuren, D Cao, Y Dgani, R AF NoriegaCrespo, A VanBuren, D Cao, Y Dgani, R TI A parsec-size bow shock around Betelgeuse SO ASTRONOMICAL JOURNAL LA English DT Article ID IRAS SURVEY DATA; ALPHA-ORIONIS; CIRCUMSTELLAR ENVELOPE; STARS; CO AB We present new high-resolution IRAS (HiRes) images at 60 and 100 mu m of a bow shock or shell with a mean radius of 6' surrounding Betelgeuse (ct Orionis). The outermost section of this structure is at similar to 7' which corresponds to a physical scale of 0.8 pc at a distance of 400 pc. The images were made by applying a relative Burg entropy maximization algorithm to suppress the ringing around bright sources and allow the detection of nearby low surface brightness features. The shell is relatively narrow at 60 mu m (at the 1' HiRes resolution), asymmetric and oriented along the star's direction of motion. We propose that the shell is confined by the ram pressure of the interstellar medium. Using a shell flux of 110 Jy (at 60 mu m) within a radius of 7:5 we estimate mass of 0.14M(.) for the shell. (C) 1997 American Astronomical Society. C1 CALTECH,JET PROP LAB,PASADENA,CA 91125. CALTECH,DIV PHYS MATH & ASTRON,PASADENA,CA 91125. UNIV TEXAS,DEPT ASTRON,AUSTIN,TX 78712. RP NoriegaCrespo, A (reprint author), CALTECH,CTR INFRARED PROC & ANAL,PASADENA,CA 91125, USA. NR 23 TC 41 Z9 41 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 AUG PY 1997 VL 114 IS 2 BP 837 EP 840 DI 10.1086/118517 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XN548 UT WOS:A1997XN54800032 ER PT J AU Goodman, ML AF Goodman, ML TI Convection driven heating of the solar middle chromosphere by resistive dissipation of large scale electric currents SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE Sun, chromosphere; Sun, magnetic fields; MHD ID CORONA TRANSITION REGION; HIGH-RESOLUTION TELESCOPE; MAGNETIC-FIELDS; FINE-STRUCTURE; SPECTROGRAPH OBSERVATIONS; SUNS CHROMOSPHERE; FLUID MOTIONS; ANGSTROM LINE; K-GRAINS; OSCILLATIONS AB A two dimensional, steady state, resistive magnetohydrodynamic (MHD) model with flow is used to support the proposition that a major source of heating for the solar middle chromosphere is resistive dissipation of large scale electric currents driven by a convection electric field. The currents are large scale in that their scale heights range from hundreds of kilometers in the network to thousands of kilometers in the internetwork. The current is carried by protons, and flows orthogonal to the magnetic field in a weakly ionized, strongly magnetized hydrogen plasma. The flow velocity is mainly parallel to the magnetic field. The relatively small component of flow velocity orthogonal to the magnetic field generates a convection electric field which drives the current. The magnetic field is the sum of a loop shaped field, called a magnetic element, and a much stronger, larger scale potential field. All of the heating takes place in the magnetic element. Solutions to the model indicate that magnetic elements with horizontal spatial extents of about one thousand to five thousand kilometers may be confined to, and heat, the middle chromospheric network. Other solutions to the model indicate that magnetic elements with horizontal spatial extents of about ten thousand to thirty thousand kilometers may span and heat the middle chromospheric internetwork, and may be the building blocks of the chromospheric magnetic canopy. It is suggested that the middle chromosphere is highly structured over a wide range of spatial scales determined by the properties of these magnetic elements, and stronger, larger scale potential fields. RP NASA, GODDARD SPACE FLIGHT CTR, COMP SCI CORP, CODE 695, GREENBELT, MD 20771 USA. NR 65 TC 4 Z9 4 U1 0 U2 0 PU EDP SCIENCES S A PI LES ULIS CEDEX A PA 17, AVE DU HOGGAR, PA COURTABOEUF, BP 112, F-91944 LES ULIS CEDEX A, FRANCE SN 1432-0746 J9 ASTRON ASTROPHYS JI Astron. Astrophys. PD AUG PY 1997 VL 324 IS 1 BP 311 EP 323 PG 13 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XR029 UT WOS:A1997XR02900031 ER PT J AU Ortiz, JL Orton, G Moreno, F Molina, A Larson, S YanamandraFisher, P AF Ortiz, JL Orton, G Moreno, F Molina, A Larson, S YanamandraFisher, P TI The Shoemaker-Levy 9 H impact: Some results from the William Herschel Telescope SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE comets, Shoemaker-Levy 9; Jupiter ID COMET SHOEMAKER-LEVY-9; CALAR-ALTO; JUPITER; COLLISION AB We present a CCD lightcurve for the H impact observed at 948 nm by the 4.2-m William Herscher Telescope at La Palma (Spain). We compare the results with other lightcurves at visible and near infrared. There appears to be a common pattern in all the CCD lightcurves: An initial relative maximum is followed by a relative minimum and another maximum. Considering the plume as a superposition of material ejected at various speeds, we suggest the first maximum is likely due to reflected solar light by the plume at its widest phase. The minimum may be due to the disappearance of part of the plume, as the material ejected with vertical velocities lower than 9 km/s descends in its ballistic trajectory and penetrates below the level of solar illumination. The following maximum is most likely due to thermal emission from the reimpacting ejecta (either from the particulates or the gas). The timing of the second maximum and the moment of detection of the plume suggest vertical velocities in the range 9-12 km/s for most of the ejecta, with peak particle concentration at 11 km/s for the L impact, according to our interpretation of Schleicher et al. (1994) lightcurve. The atmospheric level where the visible emission takes place is estimated to be P = 25(-25)(+65) mbar and P = 35(-35)(+30) mbar for the L and H impacts, respectively. C1 CSIC, INST ASTROFIS ANDALUCIA, E-18080 GRANADA, SPAIN. UNIV GRANADA, DEPT FIS APLICADA, GRANADA, SPAIN. UNIV ARIZONA, LUNAR & PLANETARY LAB, TUCSON, AZ 85721 USA. RP Ortiz, JL (reprint author), CALTECH, JET PROP LAB, 4800 OAK GROVE DR, PASADENA, CA 91109 USA. OI Moreno, Fernando/0000-0003-0670-356X NR 23 TC 4 Z9 4 U1 0 U2 0 PU EDP SCIENCES S A PI LES ULIS CEDEX A PA 17, AVE DU HOGGAR, PA COURTABOEUF, BP 112, F-91944 LES ULIS CEDEX A, FRANCE SN 0004-6361 J9 ASTRON ASTROPHYS JI Astron. Astrophys. PD AUG PY 1997 VL 324 IS 1 BP 357 EP 365 PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XR029 UT WOS:A1997XR02900035 ER PT J AU Phillips, KJH Greer, CJ Bhatia, AK Coffey, IH Barnsley, R Keenan, FP AF Phillips, KJH Greer, CJ Bhatia, AK Coffey, IH Barnsley, R Keenan, FP TI Fe XVII X-ray lines in solar coronal and laboratory plasmas SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE atomic data; atomic processes Sun, activity; Sun, flares; Sun, X-rays, gamma rays ID DIELECTRONIC SATELLITE SPECTRA; ELECTRON-IMPACT EXCITATION; NEON-LIKE IONS; ATOMIC DATA; CRYSTAL SPECTROMETER; MAXIMUM-MISSION; RESONANCE LINES; INTENSITIES; EMISSION; TOKAMAK AB Theoretical intensities of the Fe XVII X-ray lines due to transitions 2p(6) - 2p(5)3d (near 15 Angstrom) and 2p(6) - 2p(5)3s (near 17 Angstrom) are presented, and compared with solar flare and active region spectra. The ratio of the 15 Angstrom lines to the 17 Angstrom lines is a function of temperature T-e, but for solar spectra this is not of practical use because of the resonance scattering of the intense 15.015 Angstrom line. Instead we use the ratio of a nearby Fe XVIII line to obtain T-e. We find very satisfactory correspondence between solar spectra and synthetic spectra based on calculated line intensities with appropriately chosen T-e apart from the 15.015 Angstrom line, which is sometimes less intense than its theoretical value, apparently owing to resonance scattering. Spectra emitted by DITE and JET tokamak plasmas with measured T-e and N-e, are also considered. A predicted density variation of the ratio of the Fe XVII lines at 17.051 Angstrom and 17.096 Angstrom is confirmed, and using Abel inversion techniques applied to a sequence of DITE spectra with different radial distances good agreement is found between the theoretical temperature variation of the I(15.015 Angstrom)/I(16.776 Angstrom) line ratio and that derived from these spectra. We conclude that our calculated Fe XVII line intensities are very reliable and may therefore be used in future analysis. C1 QUEENS UNIV BELFAST, DEPT PHYS, BELFAST BT7 1NN, ANTRIM, NORTH IRELAND. NASA, GODDARD SPACE FLIGHT CTR, ASTRON & SOLAR PHYS LAB, GREENBELT, MD 20771 USA. UNIV LEICESTER, DEPT PHYS & ASTRON, LEICESTER LE1 7RH, LEICS, ENGLAND. RP Phillips, KJH (reprint author), RUTHERFORD APPLETON LAB, DIV ASTROPHYS, DIDCOT OX11 0QX, OXON, ENGLAND. NR 47 TC 52 Z9 52 U1 0 U2 3 PU EDP SCIENCES S A PI LES ULIS CEDEX A PA 17, AVE DU HOGGAR, PA COURTABOEUF, BP 112, F-91944 LES ULIS CEDEX A, FRANCE SN 0004-6361 J9 ASTRON ASTROPHYS JI Astron. Astrophys. PD AUG PY 1997 VL 324 IS 1 BP 381 EP 394 PG 14 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XR029 UT WOS:A1997XR02900037 ER PT J AU Harker, D Bregman, J Tielens, AGGM Temi, P Rank, D AF Harker, D Bregman, J Tielens, AGGM Temi, P Rank, D TI The infrared reflection nebula around the embedded sources in S 140 SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE ISM: S 140; stars: S 140 IRS 1; reflection nebulae; dust; infrared: ISM: continuum, lines and bands ID MOLECULAR OUTFLOW SOURCES; S140; CLOUD; EMISSION; REGIONS; POLARIZATION; CLUSTER; GRAINS; IMAGES; RADIO AB We have observed the protostellar system in S 140 at 2.2, 3.1 and 3.45 mu m using a 128x128 InSb array camera with the Lick Observatory 3m telescope. We have developed a simple model of this region which has been used to derive the physical conditions of the dust and gas. IRS 1 is surrounded by a dense dusty disk viewed almost edge-on. Photons leaking out through the poles of the disk illuminate the inner edge of a surrounding shell of molecular gas as seen at locations NW and VLA4. The optical depth at K through the poles of the disk is about 0.22, while A(V)=30 towards IRS1. Analysis of the observed colors and intensities of the NIR light, using Mie scattering theory, reveals that the dust grains in the molecular cloud are somewhat larger than in the general diffuse interstellar medium. Moreover, the incident light has a ''cool'' color temperature, similar or equal to 850-900K, and likely originates from a dust photosphere close to the protostar. There is little H2O ice associated with the dusty disk around IRS1. Most of the 3.1 mu m ice extinction arises instead from cool intervening molecular cloud material. We have also compared our infrared dust observations with millimeter and radio observations of molecular gas associated with this region. The large scale structure observable in the molecular gas is indicative of the interaction between the protostellar wind and the surrounding molecular cloud rather than the geometry of the protostellar disk, We conclude that S 140 is a young blister formed by this outflow on the side of a molecular cloud and viewed edge-on. C1 NASA, AMES RES CTR, MOFFETT FIELD, CA 94035 USA. RP UNIV CALIF SANTA CRUZ, UNIV CALIF OBSERV, LICK OBSERV, SANTA CRUZ, CA 95064 USA. OI Harker, David/0000-0001-6397-9082 NR 35 TC 13 Z9 13 U1 1 U2 1 PU EDP SCIENCES S A PI LES ULIS CEDEX A PA 17, AVE DU HOGGAR, PA COURTABOEUF, BP 112, F-91944 LES ULIS CEDEX A, FRANCE SN 1432-0746 J9 ASTRON ASTROPHYS JI Astron. Astrophys. PD AUG PY 1997 VL 324 IS 2 BP 629 EP 640 PG 12 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XT419 UT WOS:A1997XT41900031 ER PT J AU Xing, XF Hanner, MS AF Xing, XF Hanner, MS TI Light scattering by aggregate particles SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE polarization; scattering; comets: general ID DISCRETE-DIPOLE APPROXIMATION; HALLEY DUST PARTICLES; OPTICAL-PROPERTIES; COSMIC DUST; GRAINS; BACKSCATTERING; WAVELENGTH; DEPENDENCE AB We have investigated scattering properties of aggregates, emphasizing the size of constituent monomers comparable with the wavelength of visible light, in order to model the scattering properties of cometary dust. This has differentiated our study from previous investigations of aggregates in which the size of the monomers was much smaller than the wavelength. For aggregates, the absorption cross sections tend to have less steep slopes towards longer wavelength than a single sphere, typically, C-abs similar to lambda(-1). Consequently aggregates of absorbing material are cooler than the individual monomers, because the aggregates radiate more efficiently in the infrared. The polarization is sensitive to the shape and size of the constituent monomers as well as to the fine structure of the aggregate. Generally aggregates of highly absorbing material produce a strong positive polarization around theta(p) = 90 degrees, but no negative polarization near the backward direction. In contrast, silicate aggregates are the major source of strong negative polarization at larger scattering angles. A mixture of both carbonaceous and silicate aggregates results in a polarization curve which largely matches the observed negative polarization at theta(p) less than or equal to 20 degrees and the maximum peak around theta(p) = 90 degrees for cometary dust. The same mixture also gives a reasonable rise of the phase function toward the backward direction, which is similar to the phase function of cometary dust. Thus, we find that aggregates with constituent monomers a few tenths of a micron in size and with intermediate porosity (approximate to 0.6), similar to chondritic aggregate interplanetary dust particles, are a reasonable analog for cometary dust. RP Xing, XF (reprint author), CALTECH, JET PROP LAB, 4800 OAK GROVE DR, MAIL STOP 183-501, PASADENA, CA 91109 USA. NR 27 TC 70 Z9 71 U1 0 U2 1 PU EDP SCIENCES S A PI LES ULIS CEDEX A PA 17, AVE DU HOGGAR, PA COURTABOEUF, BP 112, F-91944 LES ULIS CEDEX A, FRANCE SN 0004-6361 J9 ASTRON ASTROPHYS JI Astron. Astrophys. PD AUG PY 1997 VL 324 IS 2 BP 805 EP 820 PG 16 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XT419 UT WOS:A1997XT41900053 ER PT J AU Nilsson, K Valtonen, MJ Jones, LR Saslaw, WC Lehto, HJ AF Nilsson, K Valtonen, MJ Jones, LR Saslaw, WC Lehto, HJ TI Optical emission in the radio lobes of Cygnus A SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE galaxies: active; galaxies: individual: Cygnus A; radio continuum: galaxies; accretion: accretion disks ID PHOTOMETRIC STANDARD STARS; ACTIVE GALACTIC NUCLEI; SLINGSHOT EJECTIONS; CELESTIAL EQUATOR; MULTIPLE HOTSPOTS; VLBI-OBSERVATIONS; BLACK-HOLES; GALAXIES; SPECTRA; TELESCOPE AB Deep optical imaging and spectroscopy of stellar objects in the radio lobes of Cygnus A have been carried out. Brighter optical objects close to the radio hotspots are either confirmed or suspected Galactic stars. Very faint optical emission is found coinciding with hotspot D (R similar to 23.1) and hotspot B (V similar to 25.4) The implications of these observations are discussed in the context of a double twin-jet model. In this model the radio lobes are assumed to contain a supermassive black hole each, and the twin jets emanating from the black holes are responsible for the radio emission. Assuming that the compact X-ray sources in the lobes arise from the accretion disks, the level of expected optical emission from the accretion disks is estimated. The present observations can rule out the model if the accretion disk is extensive, but they are not sensitive enough to exclude a truncated accretion disk, such as is expected in the slingshot ejection process. An approximate estimate for the cutoff frequency in hotspot D yields a magnetic field that is close to values obtained by other authors using minimun energy considerations. C1 NASA, GODDARD SPACE FLIGHT CTR, GREENBELT, MD 20771 USA. UNIV SOUTHAMPTON, DEPT PHYS, SOUTHAMPTON SO17 1BJ, HANTS, ENGLAND. UNIV VIRGINIA, DEPT ASTRON, CHARLOTTESVILLE, VA 22903 USA. UNIV CAMBRIDGE, INST ASTRON, CAMBRIDGE CB3 0HA, ENGLAND. RP Nilsson, K (reprint author), UNIV TURKU, TUORLA OBSERV, VAISALANTIE 20, FIN-21500 PIIKKIO, FINLAND. NR 53 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 0004-6361 J9 ASTRON ASTROPHYS JI Astron. Astrophys. PD AUG PY 1997 VL 324 IS 3 BP 888 EP 898 PG 11 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XT422 UT WOS:A1997XT42200017 ER PT J AU Ferraro, FR Paltrinieri, B Pecci, FF Cacciari, C Dorman, B Rood, RT Buonanno, R Corsi, CE Burgarella, D Laget, M AF Ferraro, FR Paltrinieri, B Pecci, FF Cacciari, C Dorman, B Rood, RT Buonanno, R Corsi, CE Burgarella, D Laget, M TI HST observations of blue Straggler stars in the core of the globular cluster M3 SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE globular clusters: individual: M3; stars: population II; stars: blue stragglers ID CCD PHOTOMETRY; PHOTOGRAPHIC PHOTOMETRY; COLLISIONAL ORIGIN; SEQUENCES; POPULATION; GIANT AB The core of the Galactic Globular Cluster M 3 (NGC 5272) has been observed with the WFPC2 through the filters F255W, F336W, F555W, and F814W. Using these observations along with a thorough reanalysis of earlier catalogs, we have produced a catalog of blue straggler stars (BSS) spanning the cluster. Earlier studies and the fainter part of our sample suffer severe selection biases. Our analysis is based on a more reliable bright global sample of 122 BSS. We confirm earlier suggestions that the radial BSS distribution in M 3 is bimodal. It is strongly peaked in the center, has a clear dip 100-200 '' from the center, and rises again at larger radii. The observed distribution agrees with the dynamical model of Sigurdsson et al. (1994) which takes into account both star collisions and merging of primordial binaries for the origin of BSS. The observed luminosity functions of BSS in the inner and outer parts of the cluster are different. Interpreting these using the models of Bailyn & Pinsonneault (1995), we suggest that the BSS in the inner cluster are formed by stellar collisions and those in the outer cluster from merging primordial binaries. C1 STN ASTRON CAGLIARI, I-09012 CAPOTERRA, ITALY. SPACE TELESCOPE SCI INST, BALTIMORE, MD 21218 USA. NASA, GODDARD SPACE FLIGHT CTR, GREENBELT, MD 20771 USA. UNIV VIRGINIA, CHARLOTTESVILLE, VA USA. OSSERV ASTRON ROMA, I-00136 ROME, ITALY. CNRS, ASTRON SPATIALE LAB, F-13012 MARSEILLE, FRANCE. RP Ferraro, FR (reprint author), OSSERVATORIO ASTRON BOLOGNA, VIA ZAMBONI 33, I-40126 BOLOGNA, ITALY. NR 40 TC 114 Z9 116 U1 0 U2 0 PU EDP SCIENCES S A PI LES ULIS CEDEX A PA 17, AVE DU HOGGAR, PA COURTABOEUF, BP 112, F-91944 LES ULIS CEDEX A, FRANCE SN 0004-6361 J9 ASTRON ASTROPHYS JI Astron. Astrophys. PD AUG PY 1997 VL 324 IS 3 BP 915 EP 928 PG 14 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XT422 UT WOS:A1997XT42200020 ER PT J AU Wyrowski, F Walmsley, CM Natta, A Tielens, AGGM AF Wyrowski, F Walmsley, CM Natta, A Tielens, AGGM TI The photon dominated regions associated with NGC 2023 and S 140 SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE ISM: clouds; ISM: molecules; radio lines: ISM; ISM: NGC 2023, S 140 ID REFLECTION NEBULA NGC-2023; MOLECULAR-HYDROGEN EMISSION; PHOTODISSOCIATION REGIONS; RECOMBINATION LINES; ATOMIC CARBON; CLOUD; ORION; EXCITATION; AMMONIA; S140 AB We have used the Effelsberg 100-m telescope to observe the C91 alpha radio recombination line towards the photon-dominated regions associated with NGC 2023 and S 140. This has been supplemented with observations of the (CO)-O-18 (2-1) and (3-2) lines using the 3-m KOSMA telescope. We have analyzed the C91 alpha observations using 1-dimensional homogeneous models in order to derive estimates of the density and ultraviolet radiation field. Towards both sources, our radio line data suggest densities of 10(5) cm(-3) although we have evidence for a drop-off to a value of around 10(4) cm(-3) at offsets of 0.4 pc from the exciting star in NGC 2023. The molecular line data towards NGC 2023 are also consistent with high densities (certainly above 10(4) and probably of order 10(5) cm(-3)). We discuss the influence of clumping on these models and conclude that densities as high as 10(6) cm(-3) are possible in both the molecular and carbon line emitting gas. C1 OSSERV ASTROFIS ARCETRI, I-50125 FLORENCE, ITALY. NASA, AMES RES CTR, MOFFETT FIELD, CA 94035 USA. RP Wyrowski, F (reprint author), UNIV COLOGNE, INST PHYS 1, ZULPICHERSTR 77, D-50937 COLOGNE, GERMANY. NR 55 TC 15 Z9 15 U1 0 U2 1 PU EDP SCIENCES S A PI LES ULIS CEDEX A PA 17, AVE DU HOGGAR, PA COURTABOEUF, BP 112, F-91944 LES ULIS CEDEX A, FRANCE SN 0004-6361 J9 ASTRON ASTROPHYS JI Astron. Astrophys. PD AUG PY 1997 VL 324 IS 3 BP 1135 EP 1144 PG 10 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XT422 UT WOS:A1997XT42200047 ER PT J AU Bellotti, R Cafagna, F Castellano, M Circella, M DeCataldo, G DeMarzo, C Giglietto, N Marangelli, B Raino, A Spinelli, P Brancaccio, M Grandi, M Papini, P Perego, A Piccardi, S Spillantini, P Basini, G Ricci, M Codino, A Finetti, N Grimani, C Bidoli, V Candusso, M Casolino, M DePascale, MP Morselli, A Picozza, P Sparvoli, R Aversa, F Barbiellini, G Boezio, M Colavita, A Fratnik, F Schiavon, P Vacchi, A Zampa, N Mitchell, JW Streitmatter, RE Golden, RL Stochaj, SJ Hof, M Menn, W Simon, M Stephens, SA AF Bellotti, R Cafagna, F Castellano, M Circella, M DeCataldo, G DeMarzo, C Giglietto, N Marangelli, B Raino, A Spinelli, P Brancaccio, M Grandi, M Papini, P Perego, A Piccardi, S Spillantini, P Basini, G Ricci, M Codino, A Finetti, N Grimani, C Bidoli, V Candusso, M Casolino, M DePascale, MP Morselli, A Picozza, P Sparvoli, R Aversa, F Barbiellini, G Boezio, M Colavita, A Fratnik, F Schiavon, P Vacchi, A Zampa, N Mitchell, JW Streitmatter, RE Golden, RL Stochaj, SJ Hof, M Menn, W Simon, M Stephens, SA TI Study of the combined particle identification capability of a transition radiation detector and a silicon imaging calorimeter during the TS93 balloon flight SO ASTROPARTICLE PHYSICS LA English DT Article ID COSMIC-RAY ELECTRONS; POSITRON IDENTIFICATION; NEURAL-NETWORK; PERFORMANCE; SPECTROMETER; PROTOTYPE; SPACE AB The WiZard Collaboration is involved in a program studying the antimatter components of the cosmic rays. A transition radiation detector and a silicon-tungsten calorimeter with imaging capabilities have been built as part of this program. We present the combined performance of these two detectors for positron identification during a balloon flight on September 8, 1993. The flight was dedicated to the measurement of the positron spectrum in the energy range 4-50 GeV and was launched from Ft. Sumner, New Mexico. (C) 1997 Elsevier-Science B.V. C1 UNIV BARI, DIPARTIMENTO FIS, I-70121 BARI, ITALY. UNIV BARI, IST NAZL FIS NUCL, I-70121 BARI, ITALY. UNIV FLORENCE, DIPARTIMENTO FIS, I-50121 FLORENCE, ITALY. UNIV FLORENCE, IST NAZL FIS NUCL, I-50121 FLORENCE, ITALY. IST NAZL FIS NUCL, LAB NAZL FRASCATI, I-00044 FRASCATI, ITALY. UNIV PERUGIA, DIPARTIMENTO FIS, I-06100 PERUGIA, ITALY. UNIV PERUGIA, IST NAZL FIS NUCL, I-06100 PERUGIA, ITALY. UNIV ROMA TOR VERGATA, DIPARTIMENTO FIS, I-00173 ROME, ITALY. UNIV ROMA TOR VERGATA, IST NAZL FIS NUCL, I-00173 ROME, ITALY. NASA, GODDARD SPACE FLIGHT CTR, GREENBELT, MD 20771 USA. NEW MEXICO STATE UNIV, LAS CRUCES, NM 88003 USA. UNIV SIEGEN, D-5900 SIEGEN, GERMANY. TATA INST FUNDAMENTAL RES, BOMBAY 400005, MAHARASHTRA, INDIA. RI Morselli, Aldo/G-6769-2011; giglietto, nicola/I-8951-2012; Castellano, Marcello/J-3428-2012; Cafagna, Francesco/A-9299-2010; Vacchi, Andrea/C-1291-2010; OI Morselli, Aldo/0000-0002-7704-9553; giglietto, nicola/0000-0002-9021-2888; Castellano, Marcello/0000-0002-4211-2903; Cafagna, Francesco/0000-0002-7450-4784; Vacchi, Andrea/0000-0003-3855-5856; Bellotti, Roberto/0000-0003-3198-2708; casolino, marco/0000-0001-6067-5104; SPINELLI, Paolo/0000-0001-6688-8864; Sparvoli, Roberta/0000-0002-6314-6117; Picozza, Piergiorgio/0000-0002-7986-3321; Papini, Paolo/0000-0003-4718-2895; Boezio, Mirko/0000-0002-8015-2981 NR 20 TC 9 Z9 9 U1 1 U2 2 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0927-6505 EI 1873-2852 J9 ASTROPART PHYS JI Astropart Phys. PD AUG PY 1997 VL 7 IS 3 BP 219 EP 230 DI 10.1016/S0927-6505(97)00027-3 PG 12 WC Astronomy & Astrophysics; Physics, Particles & Fields SC Astronomy & Astrophysics; Physics GA XW104 UT WOS:A1997XW10400004 ER PT J AU Dwek, E AF Dwek, E TI Can composite fluffy dust particles solve the interstellar carbon crisis? SO ASTROPHYSICAL JOURNAL LA English DT Article DE dust, extinction; infrared, ISM, continuum; ISM, abundances ID OPTICAL-PROPERTIES; EXTINCTION CURVE; MOLECULAR CLOUDS; SILICATE GRAINS; EMISSION; GRAPHITE; CIRRUS AB Recent observations suggest that the abundance of carbon in the interstellar medium is only similar to 60% of its solar value, and that other heavy elements may be depleted by a similar amount. Furthermore, more than half of the interstellar carbon is observed to be in the gas in the form of C+, leaving less than similar to 40% of the solar carbon abundance available for the dust phase. These observations have created the so-called Interstellar ''carbon crisis,'' since traditional interstellar dust models require about twice that value to be tied up in graphite grains in order to explain the interstellar extinction curve. Recently, in 1996, J. S. Mathis suggested a possible solution to this crisis. In his newly proposed dust model, the majority of the interstellar carbon is contained in composite and fluffy grains that are made up of silicates and amorphous carbon grains, with 45% of their volume consisting of vacuum. Per unit mass, these grains produce more UV extinction and therefore can account for the interstellar extinction curve with about half the carbon required in traditional dust models. This paper presents a detailed assessment of the newly proposed dust model and concludes that it falls short in solving the carbon crisis, and in providing a fit to the UV-optical interstellar extinction curve. It also predicts a far-infrared emissivity in excess of that observed with the COBE/DIRBE and FIRAS instruments from the diffuse interstellar medium. This excess infrared emission is a direct consequence of the lower albedo of the composite fluffy dust particles, compared with that of the traditional Mathis, Rumpl, & Nordsieck mixture of bare silicate and graphite grains. The failure of the new model highlights the interrelationships between the various dust properties and their observational consequences, and the need to satisfy them all simultaneously in any comprehensive interstellar dust model. In light of these problems, this paper examines other possible solutions to the carbon crisis. C1 INST ASTROPHYS SPATIALE,ORSAY,FRANCE. INST ASTROPHYS,F-75014 PARIS,FRANCE. RP Dwek, E (reprint author), NASA,ASTRON & SOLAR PHYS LAB,GODDARD SPACE FLIGHT CTR,CODE 685,GREENBELT,MD 20771, USA. NR 31 TC 56 Z9 57 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 AUG 1 PY 1997 VL 484 IS 2 BP 779 EP 784 DI 10.1086/304370 PN 1 PG 6 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XP941 UT WOS:A1997XP94100022 ER PT J AU Rho, JG Petre, R AF Rho, JG Petre, R TI X-ray imaging and spectroscopy of the supernova remnant CTB 109 and its associated pulsar 1E 2259+586 SO ASTROPHYSICAL JOURNAL LA English DT Article DE ISM, individual (CTB 109); pulsars, individual (PSR 1E 2259+586); supernova remnants; X-rays, ISM ID MOLECULAR CLOUDS; G109.1-1.0; EXTRAORDINARY; SPECTRUM AB We present the results of our analysis of the X-ray spectral structure of the evolved supernova remnant CTB 109 (G109.1-1.0), using data from the ROSAT Position Sensitive Proportional Counter (PSPC) and Broad Band X-Ray Telescope (BBXRT). The deep broadband PSPC image shows the same overall remnant morphology as previous X-ray images but reveals many new details. The remnant appears as a hemispherical shell centered on the X-ray-bright central pulsar 1E 2259 + 586. Despite the substantial improvement in sensitivity of the PSPC image over previous images, no X-ray emission is detected from the western half of the remnant, consistent with the interpretation that the western shock front has been significantly decelerated by a dense molecular cloud. Enhanced emission along the cloud remnant boundary supports this interpretation. Among important new small-scale structures revealed are clumpy substructure within the jetlike lobe running northeastward from the pulsar to the shell, and extended emission, with 2-3 are minute radius, around 1E 2259 + 586. Spatially resolved spectroscopy using the PSPC reveals an overall column density variation across the remnant as well as intrinsic spectral variations. In particular, the spectrum over most of the shell is well fitted by a single-component thermal model, while for the lobe, the northern and southern shell, two thermal components are required, with one having parameter values similar to that found in those regions fitted by a single-component model. We conclude that either the thermal conditions vary within the remnant or there exists a second, distinct gas component in some parts of the remnant. A simultaneous fit to BBXRT and PSPC spectra for part of the interior and shell to the south of the pulsar shows that the plasma there is not in ionization equilibrium. The results of fitting these spectra using nonequilibrium ionization models are ambiguous, however: equally acceptable fits were obtained using models with and without electron-ion equipartition, but with very different parameter values. The best non-equipartition model yields shock temperature T-s = 2 x 10(7) K and ionization parameter n(0) t = 430 cm(-3) yr, suggesting extreme departure from ionization equilibrium, while the best-fit equipartition model indicates conditions near ionization equilibrium, with T-s = 1.8 x 10(6) K and n(0) t = 17,000 cm(-3) yr. The thermal nature of the emission from the lobe is counter to the prediction of the hypothesis that it arises from a precessing jet and contrasts with the nonthermal lobes in SS433/W50. Thus, the lobe in CTB 109 is probably not related to or powered by the central pulsar. The similarity of the lobe spectrum to those of the northern and southern shell segments suggests they are physically related. Together they form a plumelike structure whose morphology and location relative to the molecular cloud suggest that they represent gas from the remnant interior, swept up and reheated by a shock reflected off the molecular cloud, as reproduced in hydrodynamical simulations (see Tenorio-Tagle et al.). A timing analysis of the PSPC data for 1E 2259 + 586 yields a period of 6.978814 +/- 9.4 x 10(-6) s, consistent with a constant (P) over dot. Simultaneous fitting of the pulsar spectra from the PPC, BBXRT, and the ASCA are best modeled by a blackbody (kT = 0.43 keV). The extended emission around 1E 2259 + 586 has an extent of 2'-3' in both the PSPC and ROSAT HRI images. Its nonthermal spectrum suggests that it arises from a synchrotron nebula, although we cannot rule out the possibility of a dust-scattering halo. C1 CTR ETUD SACLAY,CEA,SERV ASTROPHYS,F-91191 GIF SUR YVETTE,FRANCE. NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. NR 43 TC 51 Z9 51 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 AUG 1 PY 1997 VL 484 IS 2 BP 828 EP 843 DI 10.1086/304350 PN 1 PG 16 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XP941 UT WOS:A1997XP94100027 ER PT J AU Holberg, JB Barstow, MA Lanz, T Hubeny, I AF Holberg, JB Barstow, MA Lanz, T Hubeny, I TI Hubble Space Telescope ultraviolet spectroscopy of two hot white dwarfs SO ASTROPHYSICAL JOURNAL LA English DT Article DE stars, abundances; stars, individual (PG 1057+719, REJ 1614-085); ultraviolet, stars; white dwarfs ID ATMOSPHERES AB We have obtained Hubble Space Telescope high-dispersion spectroscopy of two hot white dwarfs using the Goddard High-Resolution Spectrograph. The stars were selected on the basis of EUV flux as examples of H-rich DA stars containing high and low levels of short-wavelength opacity. The high-opacity star, REJ 1614-085, possesses strong features due to C IV, Si IV, and N V. Carbon and silicon in this star are underabundant with respect to the predictions of radiative levitation; nitrogen, however, is superabundant. This is in sharp contrast to the apparently similar DA star GD 394, where silicon is in extreme overabundance. The low-opacity star PG 1057 + 719, as expected, shows no clear evidence of these or any other heavy ions. We find evidence of weak blueshifted components in the REJ 1614-085 C IV and Si IV lines, which may indicate the star is experiencing ongoing mass loss. C1 UNIV LEICESTER,DEPT PHYS & ASTRON,LEICESTER LE1 7RH,LEICS,ENGLAND. UNIV UTRECHT,INST ASTRON,NL-3508 TA UTRECHT,NETHERLANDS. NASA,GODDARD SPACE FLIGHT CTR,UNIV SPACE RES ASSOC,GREENBELT,MD 20711. RP Holberg, JB (reprint author), UNIV ARIZONA,LUNAR & PLANETARY LAB,GOULD SIMPSON BLDG,TUCSON,AZ 85721, USA. NR 24 TC 25 Z9 25 U1 1 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 AUG 1 PY 1997 VL 484 IS 2 BP 871 EP 878 DI 10.1086/304376 PN 1 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XP941 UT WOS:A1997XP94100033 ER PT J AU Dixon, DD Tumer, TO Zych, AD Cheng, LX Johnson, WN Kurfess, JD Pina, RK Puetter, RC Wheaton, WA AF Dixon, DD Tumer, TO Zych, AD Cheng, LX Johnson, WN Kurfess, JD Pina, RK Puetter, RC Wheaton, WA TI Skymapping with OSSE via the mean field annealing pixon technique SO ASTROPHYSICAL JOURNAL LA English DT Article DE gamma rays, observations; techniques, image processing ID BAYESIAN IMAGE-RECONSTRUCTION AB We present progress toward using scanned OSSE observations for mapping and Sky Survey work. To this end, we have developed a technique for detecting pointlike sources of unknown number and location, given that they appear in a background that is relatively featureless or that can be modeled. The technique, based on the newly developed pixon concept and mean field annealing, is described, with sample reconstructions of data from the OSSE Virgo Survey. The results demonstrate the capability of reconstructing source information without any a priori information about the number and/or location of pointlike sources in the field of view. C1 CALTECH, JET PROP LAB, HIGH ENERGY ASTROPHYS GRP, PASADENA, CA 91125 USA. UNIV CALIF RIVERSIDE, INST GEOPHYS & PLANETARY PHYS, RIVERSIDE, CA 92521 USA. UNIV MARYLAND, DEPT ASTRON, COLLEGE PK, MD 20742 USA. USN, RES LAB, EO HULBURT CTR SPACE RES, WASHINGTON, DC 20375 USA. UNIV CALIF SAN DIEGO, CTR ASTROPHYS & SPACE SCI, LA JOLLA, CA 92093 USA. NORTHWESTERN UNIV, DEPT PHYS & ASTRON, EVANSTON, IL 60208 USA. RI Johnson, Neil/G-3309-2014 NR 17 TC 4 Z9 4 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 AUG 1 PY 1997 VL 484 IS 2 BP 891 EP 899 DI 10.1086/304347 PN 1 PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XP941 UT WOS:A1997XP94100035 ER PT J AU Liao, C Smith, SJ Hitz, D Chutjian, A Tayal, SS AF Liao, C Smith, SJ Hitz, D Chutjian, A Tayal, SS TI Electron excitation cross sections for the S-II transitions 3s(2)3p(3) S-4(0)->3s(2)3p(3 2)D(0), P-2(0), and 3s3p(4 4)P SO ASTROPHYSICAL JOURNAL LA English DT Article DE atomic data; atomic processes ID MERGED-BEAMS METHODS; IO PLASMA TORUS; RESONANCE TRANSITIONS; OSCILLATOR-STRENGTHS; ATOMIC DATA; ENERGY-LOSS; LINE AB Experimental and theoretical collisional excitation cross sections are reported for the transitions 3s(2)3p(3) S-4(o) --> 3S(2)3p(3) D-2(o), P-2(o), and 3s3p(4) P-4 in S II. The transition wavelengths (energies) are 6716 Angstrom (1.85 ev), 4069 Angstrom (3.05 eV), and 1256 Angstrom (9.87 eV), respectively. In the experiments, use is made of the energy-loss merged-beams method. The metastable fraction of the S II beam was assessed and minimized. The contribution of elastically scattered electrons was reduced by the use of a lowered solenoidal magnetic field and a modulated radio-frequency voltage on the analyzing plates and by retarding grids to reject the elastically scattered electrons with larger Larmor radii. For each transition, comparisons are made among experiments, the new 19 state R-matrix calculation, and three other close-coupling calculations. C1 CLARK ATLANTA UNIV,DEPT PHYS,ATLANTA,GA 30314. CEA,DEPT RECH FONDAMENTALE MAT CONDENSEE,F-38054 GRENOBLE 9,FRANCE. RP Liao, C (reprint author), CALTECH,JET PROP LAB,4800 OAK GROVE DR,PASADENA,CA 91109, USA. NR 22 TC 12 Z9 12 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 AUG 1 PY 1997 VL 484 IS 2 BP 979 EP 984 DI 10.1086/304375 PN 1 PG 6 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XP941 UT WOS:A1997XP94100041 ER PT J AU Canuto, VM Dubovikov, M AF Canuto, VM Dubovikov, M TI Overshooting: Mixing length yields divergent results SO ASTROPHYSICAL JOURNAL LA English DT Article DE convection; hydrodynamics; stars, evolution; stars, interiors; Sun, evolution; turbulence ID STARS; CONVECTION AB Overshooting (OV) is the signature of the nonlocal nature of convection. To describe the latter, one needs five nonlocal, coupled differential equations to describe turbulent kinetic energies (total K and in the z-direction K-z), potential energy, convective flux, and rate of dissipation epsilon. We show analytically that if epsilon is assumed to be given by the local expression, epsilon = K(3/2)l(-1) (mixing length l = alpha H-p or l = z/a, since the region is small in extent), the remaining differential equations exhibit singularities (divergences) for specific values of a within the range of values usually employed. No solution can be found. Thus, OV results from such an approach are quite accidental, as they stem from an arbitrary fine tuning of a. RP Canuto, VM (reprint author), NASA,GODDARD INST SPACE STUDIES,2880 BROADWAY,NEW YORK,NY 10025, USA. NR 19 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 AUG 1 PY 1997 VL 484 IS 2 BP L161 EP L163 DI 10.1086/310792 PN 2 PG 3 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XP943 UT WOS:A1997XP94300017 ER PT J AU Ferraro, FR Paltrinieri, B Pecci, FF Cacciari, C Dorman, B Rood, RT AF Ferraro, FR Paltrinieri, B Pecci, FF Cacciari, C Dorman, B Rood, RT TI Hubble Space Telescope ultraviolet observations of the cores of M3 and M13 SO ASTROPHYSICAL JOURNAL LA English DT Article DE globular clusters, individual (M3, M13); stars, evolution; stars, horizontal-branch; ultraviolet, stars ID HORIZONTAL-BRANCH MORPHOLOGY; GLOBULAR-CLUSTERS; STARS; PHOTOMETRY; ORIGIN AB We present preliminary results from Hubble Space Telescope (HST)/WFPC2 observations of the central regions of the of the Galactic globular clusters M13 and M3. The clusters are almost identical in most respects, including chemical composition, but there are dramatic differences in both the horizontal-branch (HB) and blue straggler populations. The M13 HE has a long blue tail extending 4.5 mag in V, reaching well below the level of the main-sequence turnoff. M3 has no such feature. M3 and M13 are thus an extreme case of the ''second-parameter problem'' in HB morphology. Also present in the M13 HE are two gaps similar to those seen in the clusters NGC 6752 and NGC 2808. M3 has a specific frequency of blue stragglers 3 times larger than that of M13. Our results imply that neither age nor cluster density, two popular second-parameter candidates, are likely to be responsible for the observed differences. C1 STN ASTRON CAGLIARI,I-09012 CAPOTERRA,ITALY. 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. RP Ferraro, FR (reprint author), OSSERVATORIO ASTRON BOLOGNA,VIA ZAMBONI 33,I-40126 BOLOGNA,ITALY. OI Cacciari, Carla/0000-0001-5174-3179 NR 37 TC 49 Z9 49 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 AUG 1 PY 1997 VL 484 IS 2 BP L145 EP L148 DI 10.1086/310780 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XP943 UT WOS:A1997XP94300013 ER PT J AU Israel, GL Stella, L Angelini, L White, NE Giommi, P Covino, S AF Israel, GL Stella, L Angelini, L White, NE Giommi, P Covino, S TI The discovery of 8.9 second pulsations from the variable X-ray source 2E 0050.1-7247 in the Small Magellanic Cloud SO ASTROPHYSICAL JOURNAL LA English DT Article DE binaries, general; pulsars, individual (2E 0050.1- 7247); stars, emission-line, Be; stars, rotation; X-rays, stars ID SPECTRUM; PULSAR AB During a systematic search for periodic signals in a sample of ROSAT PSPC light curves, we discovered similar to 8.9 s X-ray pulsations in 2E 0050.1-7247, a variable X-ray source in the Small Magellanic Cloud. The source was detected several times between 1979 and 1993 at luminosity levels ranging from similar to 5 x 10(34) ergs s(-1) up to 1.4 x 10(36) ergs s(-1) with both the Einstein IPC and ROSAT PSPC. The X-ray energy spectrum is consistent with a power-law spectrum that steepens as the source luminosity decreases. We revealed a pronounced H alpha activity from at least two B stars in the X-ray error circles. These results strongly suggest that the X-ray pulsar 2E 0050.1-7247 is in a Be-type massive binary. C1 OSSERV ASTRON ROMA,I-00040 MONTE PORZIO CATO,ROME,ITALY. INT CTR RELATIVIST ASTROPHYS,ROME,ITALY. NASA,GODDARD SPACE FLIGHT CTR,HIGH ENERGY ASTROPHYS LAB,GREENBELT,MD 20771. AGENZIA SPAZIALE ITALIANA,SAX SCI DATA CTR,I-00198 ROME,ITALY. OSSERV ASTRON BRERA,I-22055 MERATE,LECCO,ITALY. RP Israel, GL (reprint author), SCUOLA INT SUPER STUDI AVANZATI,VIA BEIRUT 2-4,I-34014 TRIESTE,ITALY. RI White, Nicholas/B-6428-2012 OI White, Nicholas/0000-0003-3853-3462 NR 21 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 AUG 1 PY 1997 VL 484 IS 2 BP L141 EP L144 DI 10.1086/310779 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XP943 UT WOS:A1997XP94300012 ER PT J AU Prange, R Rego, D Pallier, L BenJaffel, L Emerich, C Ajello, J Clarke, JT Ballester, GE AF Prange, R Rego, D Pallier, L BenJaffel, L Emerich, C Ajello, J Clarke, JT Ballester, GE TI Detection of self-reversed Ly alpha lines from the Jovian aurorae with the Hubble Space Telescope SO ASTROPHYSICAL JOURNAL LA English DT Article DE planets and satellites, general; planets and satellites, individual (Jupiter); ultraviolet, solar system ID ELECTRON-IMPACT; PRECIPITATION; RADIATION; EMISSION; SPECTRUM; JUPITER; MEDIA AB We present Ly alpha profiles taken at high spectral resolution (similar to 70 m Angstrom) in the Jovian aurorae, using the Goddard High-Resolution Spectrograph aboard the Hubble Space Telescope, They exhibit a strong central reversal, reminiscent of solar and stellar spectra, This effect was predicted by models as a consequence of radiative transfer effects on photons excited deep in the atmosphere by energetic charged particles from the magnetosphere. However, it had not been detected until these observations, the first detection of a reversed planetary Ly alpha line. The peaks on both sides of the reversal are separated by about 0.1 to 0.15 Angstrom depending on the region, indicating faint and variable atomic hydrogen vertical column densities of about (1-5) x 10(16) cm(-2) above the auroral source. We find that the line profiles are asymmetric, with differences in intensity between the blue and red peaks. The reversals and the nearby H-2 emission lines seem to be tied to the planet's rest frame, whereas the auroral photons may be shifted by as much as a few kilometers per second in either direction. Finally, the auroral profiles display almost symmetric weak wings extending over more than 1.5 Angstrom, possibly because of emission from a superthermal hydrogen population. C1 CNRS,INST ASTROPHYS PARIS,F-75014 PARIS,FRANCE. UNIV MICHIGAN,DEPT ATMOSPHER OCEAN & SPACE SCI,ANN ARBOR,MI 48109. CALTECH,JET PROP LAB,PASADENA,CA 91109. RP Prange, R (reprint author), UNIV PARIS 11,INST ASTROPHYS SPATIALE,CNRS,UMR 120,BATIMENT 121,F-91405 ORSAY,FRANCE. RI Clarke, John/C-8644-2013 NR 33 TC 21 Z9 21 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 AUG 1 PY 1997 VL 484 IS 2 BP L169 EP L173 DI 10.1086/310786 PN 2 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA XP943 UT WOS:A1997XP94300019 ER EF