FN Thomson Reuters Web of Science™ VR 1.0 PT J AU Hartman, RC Webb, JR Marscher, AP Travis, JP Dermer, CD Aller, HD Aller, MF Balonek, TJ Bennett, K Bloom, SD Fujimoto, R Hermsen, W Hughes, P Jenkins, P Kii, T Kurfess, JD Makino, F Mattox, JR vonMontigny, C Ohashi, T Robson, I Ryan, J Sadun, A Schonfelder, V Smith, AG Terasranta, H Tornikoski, M Turner, MJL AF Hartman, RC Webb, JR Marscher, AP Travis, JP Dermer, CD Aller, HD Aller, MF Balonek, TJ Bennett, K Bloom, SD Fujimoto, R Hermsen, W Hughes, P Jenkins, P Kii, T Kurfess, JD Makino, F Mattox, JR vonMontigny, C Ohashi, T Robson, I Ryan, J Sadun, A Schonfelder, V Smith, AG Terasranta, H Tornikoski, M Turner, MJL TI Simultaneous multiwavelength spectrum and variability of 3C 279 from 10(9) to 10(24) Hz SO ASTROPHYSICAL JOURNAL LA English DT Article DE gamma rays, observations; infrared, galaxies; quasars, individual (3C 279); X-rays, galaxies ID ENERGY GAMMA-RADIATION; EXTRAGALACTIC RADIO-SOURCES; RELATIVISTIC JETS; X-RAY; MULTIFREQUENCY OBSERVATIONS; EGRET DETECTION; QUASAR 3C-279; MILLIMETER; TELESCOPE; EMISSION AB Data from a number of monitoring programs have been combined with data from the Compton Gamma Ray Observatory and the Ginga X-ray satellite to construct a spectrum covering nearly 15 decades in frequency during or near the time of the 3C 279 gamma-ray flare observed by EGRET in 1991 June. A much less complete spectrum is presented for 1991 October. Light curves from early 1991 to mid-1992 are presented for radio, millimeter, submillimeter, infrared, optical, and gamma-rays. Although the temporal coverage is incomplete, the only evidence for correlation in variability between the gamma-rays and lower frequencies is a flare in the optical R-band that peaks within similar to 1 day of the maximum in the gamma-ray light curve. The variability shows higher relative amplitude in gamma-rays than in the R band. We present spectral fits to the overall multi-wave band spectrum averaged over the 1991 June flare corresponding to two models: (i) synchrotron self-Compton (SSC) emission from a relativistic jet and (ii) inverse Compton scattering of seed photons originating external to the jet (ECS) by the synchrotron-emitting relativistic electrons in the jet. Either model can fit the observed spectra satisfactorily. The higher amplitude of the gamma-ray variations is as predicted by the SSC model and can be accommodated within the ECS model if the flare is caused by a temporary change in the bulk Lorentz factor of the gamma-ray-emitting plasma. C1 FLORIDA INT UNIV, DEPT PHYS, MIAMI, FL 33199 USA. BOSTON UNIV, DEPT ASTRON, BOSTON, MA 02215 USA. USN, RES LAB, WASHINGTON, DC 20375 USA. UNIV MICHIGAN, DEPT ASTRON, ANN ARBOR, MI 48109 USA. COLGATE UNIV, DEPT PHYS & ASTRON, HAMILTON, NY 13346 USA. EUROPEAN SPACE AGCY, ESTEC, DIV ASTROPHYS, 2200 AG NOORDWIJK, NETHERLANDS. TECHNION ISRAEL INST TECHNOL, ASHER SPACE RES INST, HAIFA, ISRAEL. INST SPACE & ASTRONAUT SCI, SAGAMIHARA, KANAGAWA 229, JAPAN. SRON, 3584 CA UTRECHT, NETHERLANDS. UNIV MARYLAND, DEPT ASTRON, COLLEGE PK, MD 20742 USA. TOKYO METROPOLITAN UNIV, DEPT PHYS, HACHIOJI, TOKYO 19203, JAPAN. JCMT, HILO, HI 96720 USA. UNIV NEW HAMPSHIRE, INST EARTH OCEANS & SPACE, DURHAM, NH 03824 USA. AGNES SCOTT COLL, BRADLEY OBSERV, DECATUR, GA 30030 USA. MAX PLANCK INST EXTRATERR PHYS, W-8046 GARCHING, GERMANY. UNIV FLORIDA, DEPT ASTRON, GAINESVILLE, FL 32611 USA. METSAHOVI RADIO RES STN, SF-02540 KYLMALA, FINLAND. UNIV LEICESTER, DEPT PHYS & ASTRON, LEICESTER LE1 7RH, LEICS, ENGLAND. RP Hartman, RC (reprint author), NASA, GODDARD SPACE FLIGHT CTR, CODE 661, GREENBELT, MD 20771 USA. NR 69 TC 108 Z9 110 U1 0 U2 2 PU IOP PUBLISHING LTD PI BRISTOL PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD APR 20 PY 1996 VL 461 IS 2 BP 698 EP 712 DI 10.1086/177095 PN 1 PG 15 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA UE570 UT WOS:A1996UE57000019 ER PT J AU Sakai, S Madore, BF Freedman, WL AF Sakai, S Madore, BF Freedman, WL TI Tip of the red giant branch distances to galaxies .3. The dwarf galaxy Sextans A SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies, distances and redshifts; galaxies, individual (Sextans A); Hertzsprung-Russell diagram; stars, luminosity function, mass function ID IRREGULAR GALAXIES; RESOLVED GALAXIES; CCD PHOTOMETRY; STARS AB We present color-magnitude diagrams and luminosity functions for 4486 stars in the nearby dwarf galaxy Sextans A, based on VI photometry obtained with the COSMIC CCD prime-focus camera on the Palomar 5 m telescope. We discuss the previous disagreement in the literature over published zero points for multicolor photometry of the resolved stars in Sex A. The new data presented here shed light on and offer a means of resolving these differences. The discontinuity of the I-band red giant branch luminosity function has been measured at I = 21.73 +/- 0.09 mag. Identification of this feature with the tip of the first-ascent red giant branch at M(I) = -4.01 mag yields an independent (Population II) distance-modulus estimate of 25.74 +/- 0.13 mag (1.42 Mpc) to this galaxy. BVRI CCD observations are presented and combined with published data to derive period-luminosity relations for the six previously known Cepheids in Sex A that have periods ranging from 10 to 25 days. A reddening-corrected true (Population I) distance modulus of 25.85 +/- 0.15 mag is derived, which corresponds to a linear distance of 1.48 Mpc. The agreement of these two independent distance determinations is extremely encouraging; together with similar intercomparisons for other nearby galaxies, it would appear that the zero points of the Cepheid and TRGB distance scales agree at the 0.1 mag level (or 5% in distance). The TRGB method appears to be a distance indicator that is of comparable precision and accuracy as Cepheids, which for so long have been unique in this respect. C1 CALTECH,NASA IPAC EXTRAGALACT DATABASE,CTR INFRARED PROC & ANAL,PASADENA,CA 91125. CARNEGIE INST WASHINGTON,CARNEGIE OBSERV,PASADENA,CA 91101. RP Sakai, S (reprint author), CALTECH,JET PROP LAB,MS 100-22,PASADENA,CA 91125, USA. NR 22 TC 144 Z9 145 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 APR 20 PY 1996 VL 461 IS 2 BP 713 EP 723 DI 10.1086/177096 PN 1 PG 11 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA UE570 UT WOS:A1996UE57000020 ER PT J AU Cotera, AS Erickson, EF Colgan, SWJ Simpson, JP Allen, DA Burton, MG AF Cotera, AS Erickson, EF Colgan, SWJ Simpson, JP Allen, DA Burton, MG TI The discovery of hot stars near the Galactic center thermal radio filaments SO ASTROPHYSICAL JOURNAL LA English DT Article DE Galaxy, center; infrared, stars; open clusters and associations, individual (G0.121+0.017); stars, Wolf-Rayet ID WOLF-RAYET STARS; CONTINUUM OBSERVATIONS; INFRARED QUINTUPLET; CENTER ARC; EMISSION; LINE; LUMINOSITY; SPECTRA; CLUSTER; GALAXY AB We report the discovery of a highly unusual cluster of stars at G0.121+0.017 near the Arched (thermal) Filaments, similar to 10' northeast of the Galactic center. H (1.65 mu m) and K' (2.1 mu m) images are used to estimate a distance to the cluster consistent with a Galactic center location. K'-band spectroscopy reveals that the cluster contains 13 stars with Br gamma (2.166 mu m) emission: 12 of these stars also have He I (2.112/3 mu m) emission, and two show fainter He II (2.189 mu m) emission. Based on a spectral comparison with optically classified stars, we suggest the new emission stars are late WN stars. If the classification is correct, the cluster contains similar to 14% of all known Galactic WN stars. Observations of emission-line stars near G0.15-0.05, the ''Pistol,'' are also presented. There are four stars near the Pistol which contain emission lines. Three of these stars differ spectroscopically from the stars in the new cluster; one has a spectrum that is similar to the new cluster stars. Together with the cluster stars, these newly discovered hot young stars provide evidence for recent star formation and the stellar ionization of the thermal radio emission regions in the vicinity of the Galactic center. C1 NASA,AMES RES CTR,MOFFETT FIELD,CA 94035. UNIV CALIF BERKELEY,BERKELEY,CA 94720. ANGLO AUSTRALIAN OBSERV,EPPING,NSW,AUSTRALIA. UNIV NEW S WALES,SCH PHYS,KENSINGTON,NSW 2033,AUSTRALIA. RP Cotera, AS (reprint author), STANFORD UNIV,DEPT APPL PHYS,STANFORD,CA 94305, USA. RI Colgan, Sean/M-4742-2014; OI Burton, Michael/0000-0001-7289-1998 NR 60 TC 136 Z9 137 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 APR 20 PY 1996 VL 461 IS 2 BP 750 EP & DI 10.1086/177099 PN 1 PG 15 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA UE570 UT WOS:A1996UE57000023 ER PT J AU Mould, JR Watson, AM Gallagher, JS Ballester, GE Burrows, CJ Casertano, S Clarke, JT Crisp, D Griffiths, RE Hester, JJ Hoessel, JG Holtzman, JA Scowen, PA Stapelfeldt, KR Trauger, JT Westphal, JA AF Mould, JR Watson, AM Gallagher, JS Ballester, GE Burrows, CJ Casertano, S Clarke, JT Crisp, D Griffiths, RE Hester, JJ Hoessel, JG Holtzman, JA Scowen, PA Stapelfeldt, KR Trauger, JT Westphal, JA TI Far-ultraviolet imaging of the globular cluster NGC 7099 with the second wide-field and planetary camera SO ASTROPHYSICAL JOURNAL LA English DT Article DE globular clusters, individual (NGC 7099); stars, evolution; stars, horizontal-branch; ultraviolet, stars ID BLUE STRAGGLERS; STELLAR POPULATIONS; CORE; EVOLUTION; STARS; PHOTOMETRY; GALAXIES; HALO; M30 AB We have imaged the globular cluster NGC 7099 in the far-UV and visible with WFPC2 on the Hubble Space Telescope. Our far-UV images show a sparsely populated and fully resolved central region. The far-UV to visible color-magnitude diagram of these stars shows a well-defined horizontal branch with no evidence for hot, more evolved descendants. We find one hot horizontal branch star; the center of the cluster harbors four luminous blue stragglers. Far-UV images do not show any singularly steep density gradient at small radii among the horizontal branch stars of this post-core-collapse cluster. C1 NEW MEXICO STATE UNIV,DEPT ASTRON,LAS CRUCES,NM 88003. UNIV WISCONSIN,DEPT ASTRON,MADISON,WI 53706. UNIV MICHIGAN,DEPT ATMOSPHER & OCEAN SCI,ANN ARBOR,MI 48109. SPACE TELESCOPE SCI INST,BALTIMORE,MD 21218. JOHNS HOPKINS UNIV,DEPT ASTRON,BALTIMORE,MD 21218. CALTECH,JET PROP LAB,PASADENA,CA 91109. ARIZONA STATE UNIV,DEPT PHYS & ASTRON,TEMPE,AZ 85287. CALTECH,DIV GEOL & PLANETARY SCI,PASADENA,CA 91125. RP Mould, JR (reprint author), AUSTRALIAN NATL UNIV,INST ADV STUDIES,MT STROMLO & SIDING SPRING OBSERV,PRIVATE BAG,WESTON,ACT 2611,AUSTRALIA. RI Stapelfeldt, Karl/D-2721-2012; Clarke, John/C-8644-2013 NR 30 TC 7 Z9 7 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 APR 20 PY 1996 VL 461 IS 2 BP 762 EP & DI 10.1086/177100 PN 1 PG 6 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA UE570 UT WOS:A1996UE57000024 ER PT J AU Esposito, JA Hunter, SD Kanbach, G Sreekumar, P AF Esposito, JA Hunter, SD Kanbach, G Sreekumar, P TI Egret observations of radio-bright supernova remnants SO ASTROPHYSICAL JOURNAL LA English DT Article DE acceleration of particles; cosmic rays; gamma rays, observations; shock waves; supernova remnants ID SHOCK ACCELERATION; RAY; RADIATION; ENERGY AB The gamma-ray emission associated with radio-bright supernova remnants has been studied using data from the EGRET instrument aboard the Compton Gamma Ray Observatory. Five sources from The Second EGRET Catalog of High-Energy Gamma-Ray Sources are shown to be coincident with supernova remnants. The two strongest pointlike gamma-ray excesses which are coincident with supernova remnants are 2EG J2020+4026 with gamma Cyg and 2EG J0618+2234 with IC 443. The gamma-ray flux, E > 100 MeV, from the region of these two supernova remnants is (12.6 +/- 0.7) x 10(-7) photons cm(-2) s-1 and (5.0 +/- 0.4) x 10-7 photons cm(-2) s(-1), respectively. The differential gamma-ray flux of both supernova remnants is consistent with a single power law, F proportional to E(-alpha), with alpha = 2.07 +/- 0.05 and 1.97 +/- 0.07 for gamma Cyg and IC 443, respectively. A cosmic-ray origin model based on shock acceleration of cosmic rays is consistent with our results suggesting supernova remnants as an acceleration site, and possibly the origin, of Galactic cosmic rays. Other mechanisms to explain the possible gamma-ray emission from supernova remnants are also discussed in the context of the EGRET observations. C1 NASA,GODDARD SPACE FLIGHT CTR,UNIV SPACE RES ASSOC,GREENBELT,MD 20771. MAX PLANCK INST EXTRATERR PHYS,D-85748 GARCHING,GERMANY. RP Esposito, JA (reprint author), NASA,GODDARD SPACE FLIGHT CTR,CODE 661,GREENBELT,MD 20771, USA. RI Hunter, Stanley/D-2942-2012 NR 57 TC 233 Z9 234 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 APR 20 PY 1996 VL 461 IS 2 BP 820 EP 827 DI 10.1086/177104 PN 1 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA UE570 UT WOS:A1996UE57000028 ER PT J AU Dgani, R VanBuren, D NoriegaCrespo, A AF Dgani, R VanBuren, D NoriegaCrespo, A TI Stability analysis of bow shocks SO ASTROPHYSICAL JOURNAL LA English DT Article DE shock waves; stars, mass loss ID DOUBLE STAR SYSTEM; COLLIDING WINDS; GALACTIC-CENTER; BUBBLES AB We present a linear stability analysis of bow shocks created by the interaction of a spherical wind moving with respect to its surrounding medium. The bounding shocks are assumed isothermal and with Mach number M = infinity. Following Soker, we study the evolution of short-wavelength perturbations. We find that the motion is unstable in this limit. Moreover, the ratio of the wind velocity upsilon(w) to the star velocity upsilon* characterizes the stability properties. Bow shocks with fast winds for which upsilon*/upsilon(w) much less than 1 are more stable than bow shocks with slow winds, i.e., upsilon*/upsilon(w) much greater than 1. RP Dgani, R (reprint author), CALTECH,JET PROP LAB,CTR INFRARED PROC & ANAL,100-22,PASADENA,CA 91125, USA. NR 24 TC 39 Z9 39 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637 SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD APR 20 PY 1996 VL 461 IS 2 BP 927 EP 932 DI 10.1086/177114 PN 1 PG 6 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA UE570 UT WOS:A1996UE57000038 ER PT J AU Chick, KM Pollack, JB Cassen, P AF Chick, KM Pollack, JB Cassen, P TI The transport of thermal radiation in a protostellar envelope SO ASTROPHYSICAL JOURNAL LA English DT Article DE methods, numerical; radiative transfer; solar system, formation; stars, atmospheres; stars, pre-main-sequence ID AXISYMMETRICAL DUST CLOUDS; AURIGA MOLECULAR CLOUD; ROTATING PROTOSTARS; INTERSTELLAR CLOUDS; SOLAR NEBULA; YOUNG STARS; MODELS; COLLAPSE; DISKS; CORES AB We present a discrete ordinate solution for gray radiation transport in axisymmetric protostellar envelopes, for the purpose of defining the patterns of interstellar-grain survival during the formation of the solar system. The gray transfer problem is nonlinear because the opacity depends on temperature, with discontinuities at temperatures where various species of dust vaporize. The standard lambda iteration techniques that are required for accurate solutions to the transfer equation tend to be nonconvergent under these conditions. We show that accuracy can be achieved through a relaxation method. We first compare the thermal profiles in spherically symmetric envelopes computed by the discrete ordinate solution with those predicted by the diffusion approximation. The more accurate discrete ordinate solutions tend to yield steeper temperature gradients, and the central vaporized cavity around the protostar is larger than that given by the diffusion approximation. The transport solution is then applied to an axisymmetric model envelope in which the cloud is flattened due to rotation, and in which a wind evacuates the polar regions of the cloud. The resulting cavity beams the emergent intensity in the polar direction. When the cloud is uniformly opaque, the polar cavity enhances the diffusive escape of radiation and globally reduces temperatures in the cloud. Modeled temperature profiles are used to predict the radial distances at which various dust, species survive infall in the cloud. The results indicate that survival boundaries range from within 1 AU for the most refractory solids, to several AU for volatile organics, and that water ice is excluded from within 20-30 AU of the protostar during the collapse phase. We compare dust vaporization due to heating in the cloud with destruction in the accretion shock; based on the test case, heating in the cloud during collapse is potentially more destructive. C1 UNIV CALIF SANTA CRUZ,SANTA CRUZ,CA 95064. RP Chick, KM (reprint author), NASA,AMES RES CTR,DIV SPACE SCI,MS 245-3,MOFFETT FIELD,CA 94035, USA. NR 46 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 APR 20 PY 1996 VL 461 IS 2 BP 956 EP 971 DI 10.1086/177117 PN 1 PG 16 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA UE570 UT WOS:A1996UE57000041 ER PT J AU Jiang, YB Yung, YL Zurek, RW AF Jiang, YB Yung, YL Zurek, RW TI Decadal evolution of the Antarctic ozone hole SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID STRATOSPHERIC POLAR VORTEX; PLANETARY WAVE BREAKING; INSITU ER-2 DATA; SOUTHERN-HEMISPHERE; MAPPING SPECTROMETER; MLS OBSERVATIONS; LATE WINTER; DEPLETION; CHLORINE; TRENDS AB Ozone column amounts obtained by the total ozone mapping spectrometer (TOMS) in the southern polar region are analyzed during late austral winter and spring (days 240-300) for 1980-1991 using area-mapping techniques and area-weighted vortex averages. The vortex here is defined using the -50 PW (1 PVU = 1.0 x 10(-6) K kg(-1) m(2) s(-1)) contour on the 500 K isentropic surface. The principal results are: (1) there is a distinct change after 1985 in the vortex-averaged column ozone depletion rate during September and October, the period of maximum ozone loss, and (2) the vortex-averaged column ozone in late August (day 240) has dropped by 70 Dobson units (DU) in a decade due to the loss in the dark and the dilution effect. The mean ozone depletion rate in the vortex between day 240 and the day of minimum vortex-averaged ozone is about 1 DU d(-1) at the beginning of the decade, increasing to about 1.8 DU d(-1) by 1985, and then apparently saturating thereafter. The vortex-average column ozone during September and October has declined at the rate of 11.3 DU yr(-1) (3.8%) from 1980 to 1987 (90 DU over 8 years) and at a smaller rate of 2 DU yr(-1) (0.9%) from 1987 to 1991 (10 DU over 5 years, excluding the anomalous year 1988). We interpret the year-to-year trend in the ozone depletion rate during the earlier part of the decade as due to the rise of anthropogenic chlorine in the atmosphere. The slower trend at the end of the decade indicates saturation of ozone depletion in the vortex interior, in that chlorine amounts in the mid-1980s were already sufficiently high to deplete most of the ozone in air within the isolated regions of the lower-stratospheric polar vortex. In subsequent years, increases in stratospheric chlorine may have enhanced wintertime chemical loss of ozone in the south polar vortex even before major losses during the Antarctic spring. C1 CALTECH, JET PROP LAB, DIV EARTH & SPACE SCI, PASADENA, CA 91109 USA. RP Jiang, YB (reprint author), CALTECH, DIV GEOL & PLANETARY SCI, PASADENA, CA 91125 USA. NR 71 TC 11 Z9 11 U1 1 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD APR 20 PY 1996 VL 101 IS D4 BP 8985 EP 8999 DI 10.1029/96JD00063 PG 15 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA UG533 UT WOS:A1996UG53300001 PM 11539364 ER PT J AU Elson, LS Read, WG Waters, JW Mote, PW Kinnersley, JS Harwood, RS AF Elson, LS Read, WG Waters, JW Mote, PW Kinnersley, JS Harwood, RS TI Space-time variations in water vapor as observed by the UARS microwave limb sounder SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID 2-DIMENSIONAL MODEL; SOUTHERN-HEMISPHERE; WEATHER; STRATOSPHERE; CLIMATOLOGY; ATMOSPHERE; HUMIDITY; TROPICS; WAVES AB Water vapor in the upper troposphere has a significant impact on the climate system. Difficulties in making accurate global measurements have led to uncertainty in understanding water vapor's coupling to the hydrologic cycle in the lower troposphere and its role in radiative energy balance. The Microwave Limb Sounder (MLS) on the Upper Atmosphere Research Satellite is able to retrieve water vapor concentration in the upper troposphere with good sensitivity and nearly global coverage. An analysis of these preliminary retrievals based on 3 years of observations shows the water vapor distribution to be similar to that measured by other techniques and to model results. The primary MLS water vapor measurements were made in the stratosphere, where this species acts as a conserved tracer under certain conditions. As is the case for the upper troposphere, most of the stratospheric discussion focuses on the time evolution of the zonal mean and zonally varying water vapor. Stratospheric results span a 19-month period and tropospheric results a 36-month period, both beginning in October of 1991. Comparisons with stratospheric model calculations show general agreement, with some differences in the amplitude and phase of long-term variations. At certain times and places, the evolution of water vapor distributions in the lower stratosphere suggests the presence of meridional transport. C1 UNIV EDINBURGH, DEPT METEOROL, EDINBURGH EH9 3JZ, MIDLOTHIAN, SCOTLAND. UNIV WASHINGTON, DEPT APPL MATH, SEATTLE, WA 98195 USA. RP Elson, LS (reprint author), CALTECH, JET PROP LAB, 4800 OAK GROVE DR, M-S 183-701, PASADENA, CA 91109 USA. NR 48 TC 22 Z9 22 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 APR 20 PY 1996 VL 101 IS D4 BP 9001 EP 9015 DI 10.1029/95JD03653 PG 15 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA UG533 UT WOS:A1996UG53300002 ER PT J AU Miller, AJ Hollandsworth, SM Flynn, LE Tiao, GC Reinsel, GC Bishop, L McPeters, RD Planet, WG DeLuisi, JJ Mateer, CL Wuebbles, D Kerr, J Nagatani, RM AF Miller, AJ Hollandsworth, SM Flynn, LE Tiao, GC Reinsel, GC Bishop, L McPeters, RD Planet, WG DeLuisi, JJ Mateer, CL Wuebbles, D Kerr, J Nagatani, RM TI Comparisons of observed ozone trends and solar effects in the stratosphere through examination of ground-based Umkehr and combined solar backscattered ultraviolet (SBUV) and SBUV 2 satellite data SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID NORTHERN-HEMISPHERE AB Within the past year, two 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 er al, 1995]. In this paper we compare the ozone trends and responses to the Ii-year solar cycle (represented by the F10.7 cm radio flux) derived from these two datasets for the period June 1977 to June 1991 (November 1978 to June 1991 for the satellite data), We consider data at northern midlatitudes (30 degrees-50 degrees N) at altitudes between 25 and 45 km derived from these two data sets. In particular, we investigate the effects of spatial sampling differences between the data sets on the derived signals. The trends derived from the two independent data sets are nearly identical at all levels except 35 km, where the Umkehr data indicate a somewhat more negative trend, The trend is approximately zero near 25 km but becomes more negative in the upper stratosphere, reaching nearly -7% per decade in the 40-45 km region, The upper stratospheric decreases are consistent with model results and are associated with the gas-phase chemical effect of chlorofluorocarbons CFC's and other ozone-destroying chemicals [World Meteorological Organization, 1995], The ozone correlations in the two data sets with the F10.7 cm solar flux are similar, with near-zero solar-induced ozone variations in the 25-30 km region and statistically significant in-phase variations at higher altitudes. Estimates of the solar cycle in the ozone time series at 40-45 km from a regression model indicate variations of about 4.5% from solar cycle maximum to minimum. Analysis of the satellite overpass data at the Umkehr station locations shows that the average of the data from the 11 Umkehr stations is a good approximation for the 30 degrees-50 degrees N zonal mean. C1 NOAA, ENVIRONM RES LAB, AIR RESOURCES LAB, BOULDER, CO 80303 USA. SOFTWARE CORP AMERICA, LANHAM, MD 20706 USA. NASA, GODDARD SPACE FLIGHT CTR, APPL RES CORP, GREENBELT, MD 20785 USA. ATMOSPHER ENVIRONM SERV, DOWNSVIEW, ON M3H 5T4, CANADA. NATL ENVIRONM SATELLITE DATA & INFORMAT SERV, OFF RES & APPLICAT, WASHINGTON, DC 20233 USA. UNIV WISCONSIN, DEPT STAT, MADISON, WI 53706 USA. UNIV CHICAGO, GRAD SCH BUSINESS, CHICAGO, IL 60637 USA. UNIV ILLINOIS, DEPT ATMOSPHER SCI, URBANA, IL 61801 USA. ALLIED SIGNAL INC, BUFFALO, NY 14210 USA. RP Miller, AJ (reprint author), NOAA, NATL WEATHER SERV, CLIMATE PREDICT CTR, WASHINGTON, DC 20233 USA. RI Flynn, Lawrence/B-6321-2009; McPeters, Richard/G-4955-2013 OI Flynn, Lawrence/0000-0001-6856-2614; McPeters, Richard/0000-0002-8926-8462 NR 20 TC 24 Z9 24 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD APR 20 PY 1996 VL 101 IS D4 BP 9017 EP 9021 DI 10.1029/96JD00229 PG 5 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA UG533 UT WOS:A1996UG53300003 ER PT J AU Aikin, AC McPeters, RD Miles, T Flynn, LE AF Aikin, AC McPeters, RD Miles, T Flynn, LE TI Intercomparison of UV spectrometer and polarimeter on SMM and stratospheric aerosol and gas experiment II ozone profiles and trends in the lower mesosphere SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID SOLAR MAXIMUM MISSION; TEMPERATURE; INVERSION; LIDAR AB Ozone concentrations obtained with the technique of solar occultation from the Solar Maximum Mission (SMM)/Ultraviolet Spectrometer and Polarimeter (UVSP) and Earth Radiation Budget Satellite (ERBS)/Stratospheric Aerosol and Gas Experiment II (SAGE II) satellite-borne instruments are compared in the latitude regions of 5 degrees to 15 degrees north and south for the lower mesosphere (53-68 km) for 1985-1989, the period when both instruments were operational. The estimated trends are all positive signifying increasing ozone. At 55 lan in the northern region they are 0.60(+/- 0.47)%/year for SAGE II and 2.56(+/-0.61)%/year for SMM/UVSP during the 1985-1989 period. At 60 km the trends are 0.38(+/-1.06)%/year for SAGE II and 1.63(+/-0.56)%/year for SMM/UVSP. Corresponding numbers at 55 km in the southern region are 1.23(+/-0.82)%/year for SAGE II and 2.38(+/-0.62)%/year for SMM/UVSP. At 60 lan the trends are 1.34(+/-1.01)%/year for SAGE II and 2.14(+/-0.56)%/year for SMM/UVSP. At 65 lan, where only SMM/UVSP data are used, estimated trends are 0.92(+/-0.74)%/year in the northern region and 2.59(+/-0.92)%/year in the southern region. Theory predicts that the increase in solar radiation between 1985 and 1989 should enhance ozone by 1.5%. If temperature feedback is included in the model, then ozone is predicted to decrease. These figures are smaller than the observed 5 to 10% increase. A long-term temperature decrease will also contribute to an ozone increase. C1 SOFTWARE CORP AMERICA, LANHAM, MD 20706 USA. HUGHES STX CORP, GREENBELT, MD 20770 USA. RP Aikin, AC (reprint author), NASA, GODDARD SPACE FLIGHT CTR, ATMOSPHERES LAB, CODE 916, GREENBELT, MD 20771 USA. RI Flynn, Lawrence/B-6321-2009; McPeters, Richard/G-4955-2013 OI Flynn, Lawrence/0000-0001-6856-2614; McPeters, Richard/0000-0002-8926-8462 NR 25 TC 2 Z9 3 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 APR 20 PY 1996 VL 101 IS D4 BP 9023 EP 9029 DI 10.1029/95JD02705 PG 7 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA UG533 UT WOS:A1996UG53300004 ER PT J AU Chance, K Traub, WA Johnson, DG Jucks, KW Ciarpallini, P Stachnik, RA Salawitch, RJ Michelsen, HA AF Chance, K Traub, WA Johnson, DG Jucks, KW Ciarpallini, P Stachnik, RA Salawitch, RJ Michelsen, HA TI Simultaneous measurements of stratospheric HOx, NOx, and Cl-x: Comparison with a photochemical model SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID MOLECULE SPECTROSCOPY EXPERIMENT; DIODE-LASER SPECTROMETER; INSITU MEASUREMENTS; HYDROGEN-PEROXIDE; O3; OH; HNO3; SPACELAB-3; CHEMISTRY; HYDROXYL AB We report simultaneous measurements of the stratospheric concentration profiles of OH, HO2, H2O2, H2O, O-3, HNO3, NO2, N2O, HCl, HOCl, and ClO during a midlatitude balloon flight in 1989. Measurements were made over almost an entire diurnal cycle by the Smithsonian Astrophysical Observatory Far-Infrared Spectrometer (FIRS-2) and the Jet Propulsion Laboratory Balloon Microwave Limb Sounder (BMLS). We analyze these measurements using a photochemical model constrained by observations of long-lived gases. Measured HO, species (OH and HO2) and H2O2 show fair agreement with theory throughout the diurnal cycle. Measurements of HNO3 are higher than theory near the concentration peak, while the levels of NO2 are consistent with the model at most altitudes. Measurements of ClO and HOCl are less than predicted concentrations, suggesting a source of HCl in addition to the reaction of Cl with CH4. Possibilities for such a source include a minor HCl + O-2 product channel for the reaction of ClO with OH and a minor HCl + O-3 channel for the reaction of ClO with HO2. C1 CALTECH, JET PROP LAB, PASADENA, CA 91109 USA. HARVARD UNIV, DEPT EARTH & PLANETARY SCI, CAMBRIDGE, MA 02138 USA. RP Chance, K (reprint author), HARVARD SMITHSONIAN CTR ASTROPHYS, 60 GARDEN ST, CAMBRIDGE, MA 02138 USA. RI Salawitch, Ross/B-4605-2009; OI Salawitch, Ross/0000-0001-8597-5832; Chance, Kelly/0000-0002-7339-7577 NR 55 TC 44 Z9 44 U1 1 U2 2 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD APR 20 PY 1996 VL 101 IS D4 BP 9031 EP 9043 DI 10.1029/96JD00064 PG 13 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA UG533 UT WOS:A1996UG53300005 ER PT J AU Sen, B Toon, GC Blavier, JF Fleming, EL Jackman, CH AF Sen, B Toon, GC Blavier, JF Fleming, EL Jackman, CH TI Balloon-borne observations of midlatitude fluorine abundance SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID STRATOSPHERE; CFC-11 AB Volume mixing ratio profiles of fluorine source gases (CF2Cl2, CFCl3, CF2ClCFCl2, CHF2Cl, CF4, and SF6) and reservoir gases (COF2 and KF) have been derived from a series of high-resolution infrared solar spectra recorded by the Jet Propulsion Laboratory MkIV interferometer during a September 1993 balloon flight from Fort Sumner, New Mexico (34 degrees N, 104 degrees W). The total fluorine budget over the 5- to 38-km altitude range has been evaluated by adding these individual measured profiles to modeled predictions for the unmeasured gas COFCl (considered to be at most 6% of the total fluorine budget). The results indicate a steady decrease of total fluorine, with increasing altitude, from a tropospheric value of about 1.82 parts per billion by volume (ppbv) to 1.48 ppbv at 38 km. The latter value, made up entirely of the reservoir species, is commensurate with tropospheric concentrations of fluorine reported in the late 1980s and with time-dependent two-dimensional model predictions (1.45 ppbv). Therefore the ''age'' of the stratospheric air mass estimated from the MkIV fluorine budget is 4-5 years, in agreement with model simulations (approximate to 6 years) and recent ATMOS measurements. C1 NASA, GODDARD SPACE FLIGHT CTR, ATMOSPHERES LAB, GREENBELT, MD 20771 USA. APPL RES CORP, LANDOVER, MD 20785 USA. RP Sen, B (reprint author), CALTECH, JET PROP LAB, 4800 OAK GROVE DR, MS 183-301, PASADENA, CA 91109 USA. RI Jackman, Charles/D-4699-2012 NR 20 TC 39 Z9 39 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 APR 20 PY 1996 VL 101 IS D4 BP 9045 EP 9054 DI 10.1029/96JD00227 PG 10 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA UG533 UT WOS:A1996UG53300006 ER PT J AU Tabazadeh, A Toon, OB AF Tabazadeh, A Toon, OB TI The presence of metastable HNO3/H2O solid phases in the stratosphere inferred from ER 2 data SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID NITRIC-ACID TRIHYDRATE; ANTARCTIC STRATOSPHERE; ARCTIC STRATOSPHERE; POLAR STRATOSPHERES; LIDAR OBSERVATIONS; VAPOR-PRESSURES; CLOUD FORMATION; DENITRIFICATION; AEROSOL; OZONE AB We present data to show that at least some of the observed polar stratospheric cloud (PSC) particles sampled by the ER 2 on January 20, 1989, during the Airborne Arctic Stratospheric Expedition (AASE 1) were composed of a water-rich HNO3/H2O solid phase. The PSC water content derived from the ER 2 data on this day is larger than that of nitric acid trihydrate (NAT), nitric acid dihydrate (NAD) or an aqueous ternary solution of H2SO4/HNO3/H2O. Here, we suggest that these particles were composed of a water-rich metastable HNO3/H2O solid phase and refer to such clouds as Type Ic PSCs, which are different from Type la (crystalline NAT or NAD particles) or Type Ib (aqueous ternary solution droplets) PSCs. Type 1c PSCs could either be crystalline (a higher hydrate of HNO3 and H2O) or amorphous, and the data analysis presented here cannot distinguish between these different solid phases. The observed PSC on this day could have been a mixture of water-rich HNO3-containing solid particles with liquid ternary droplets and/or NAT (NAD) aerosols. However a mixture of cloud particles composed of ternary solution droplets and NAT (NAD) aerosols is inconsistent with the data. A surface adsorption/reaction process occurring on frozen sulfate surfaces is suggested as a formation mechanism for Type Ic PSCs in the stratosphere. A possible mechanism for the formation of large HNO3-containing aerosols (NAT or NAD) starting with Type Ic PSCs is discussed. RP Tabazadeh, A (reprint author), NASA, AMES RES CTR, MAIL STOP 245-4, MOFFETT FIELD, CA 94035 USA. NR 48 TC 54 Z9 54 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD APR 20 PY 1996 VL 101 IS D4 BP 9071 EP 9078 DI 10.1029/96JD00062 PG 8 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA UG533 UT WOS:A1996UG53300009 ER PT J AU Jacobson, MZ Tabazadeh, A Turco, RP AF Jacobson, MZ Tabazadeh, A Turco, RP TI Simulating equilibrium within aerosols and nonequilibrium between gases and aerosols SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID MULTICOMPONENT ATMOSPHERIC AEROSOLS; AMMONIUM-NITRATE; NITRIC-ACID; OSMOTIC COEFFICIENTS; AQUEOUS-SOLUTIONS; DISSOCIATION-CONSTANT; ELECTRODYNAMIC BALANCE; TEMPERATURE-DEPENDENCE; ELECTROLYTE-SOLUTIONS; RELATIVE-HUMIDITY AB A numerical method to solve chemical equilibrium equations and a method of coupling the equilibrium calculations to nonequilibrium growth and evaporation are discussed. The equilibrium program solves any number of equations for gas, aqueous, ionic, and solid equilibrium concentrations over large spatial grids and particle size grids. It also simultaneously computes electrolyte mean mixed activity coefficients and aerosol liquid water content. Mean mixed activity coefficient calculations require mean binary activity coefficient information. Temperature-dependent mean binary activity coefficient polynomials were constructed using mean binary activity coefficient data at 298 K, apparent molal enthalpy data, and apparent molal heat capacity data. The equilibrium solver is mole and charge conserving, requires iteration, but always converges. Solutions to the equilibrium equations are used for two purposes. The first is to estimate surface vapor pressures over particles containing a solution and/or a solid phase. Such vapor pressures are then applied in Sas-aerosol transfer equations. The second is to estimate intraparticle composition and size immediately after gas-aerosol transfer. C1 NASA, AMES RES CTR, MT VIEW, CA 94035 USA. UNIV CALIF LOS ANGELES, DEPT ATMOSPHER SCI, LOS ANGELES, CA 90024 USA. RP Jacobson, MZ (reprint author), STANFORD UNIV, DEPT CIVIL ENGN, TERMAN ENGN CTR, STANFORD, CA 94305 USA. NR 74 TC 95 Z9 98 U1 1 U2 15 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 APR 20 PY 1996 VL 101 IS D4 BP 9079 EP 9091 DI 10.1029/96JD00348 PG 13 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA UG533 UT WOS:A1996UG53300010 ER PT J AU Vukovich, FM Brackett, V Fishman, J Sickles, JE AF Vukovich, FM Brackett, V Fishman, J Sickles, JE TI On the feasibility of using the tropospheric ozone residual for nonclimatological studies on a quasi-global scale SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article AB The tropospheric ozone residual (TOR) was estimated using total ozone mapping spectrometer (TOMS), Stratospheric Aerosol and Gas Experiment (SAGE), and solar backscatter ultraviolet (SBUV) data for nonclimatological periods (i.e., daily values, weekly averages, and monthly averages). The TOR is the difference between the total ozone from TOMS and the stratospheric ozone estimated using either SAGE or SBUV ozone data and the National Meteorological Center tropopause pressure data. Comparison of the TOMS/SAGE TOR with ozonesonde data and with area-averaged surface ozone data for nonclimatological periods was very poor. The month-to-month variations of the TOMS/SBUV TOR, on the other hand, compared very well with the month-to-month variations of the area-averaged surface ozone concentrations, and the day-to-day variations of the tropospheric ozone using ozonesonde data from five stations compared reasonably well with the day-to-day variations of the TOR. However, the RMS difference between the TOMS/SBUV TOR and the tropospheric ozone from ozonesonde data was about 14.4 Dobson units (DU) and the mean difference about 8 DU, though the mean difference was about 1.5 DU at Boulder, Colorado. C1 NASA, LANGLEY RES CTR, CHEM & DYNAM BRANCH, HAMPTON, VA 23665 USA. SCI APPLICAT INT CORP, HAMPTON, VA 23665 USA. US EPA, NATL EXPOSURE RES LAB, RES TRIANGLE PK, NC 27711 USA. RP Vukovich, FM (reprint author), SCI APPLICAT INT CORP, 615 OBERLIN RD, SUITE 300, RALEIGH, NC 27605 USA. NR 13 TC 16 Z9 16 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD APR 20 PY 1996 VL 101 IS D4 BP 9093 EP 9105 DI 10.1029/95JD03230 PG 13 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA UG533 UT WOS:A1996UG53300011 ER PT J AU Khazanov, GV Moore, TE Krivorutsky, EN Horwitz, JL Liemohn, MW AF Khazanov, GV Moore, TE Krivorutsky, EN Horwitz, JL Liemohn, MW TI Lower hybrid turbulence and ponderomotive force effects in space plasmas subjected to large-amplitude low-frequency waves SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID ION-CYCLOTRON WAVES; PARTICLE INTERACTIONS; ALFVEN WAVES; AURORAL-ZONE; ACCELERATION; GENERATION; REGION; GEOS-1 AB It is demonstrated that large-amplitude low-frequency waves (LFW) can generate lower hybrid waves (LHW) in the auroral zone and ring current region. The LHW could then heat the ions. The ion energization due to the LHW may be comparable with that produced by the ponderomotive force of the LFW. C1 UNIV ALABAMA,CTR SPACE PLASMA & AERONOM RES,HUNTSVILLE,AL 35899. UNIV ALABAMA,DEPT PHYS,HUNTSVILLE,AL 35899. UNIV MICHIGAN,SPACE PHYS RES LAB,ANN ARBOR,MI 48109. RP Khazanov, GV (reprint author), NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,SPACE SCI LAB,ES-83,HUNTSVILLE,AL 35812, USA. RI Moore, Thomas/D-4675-2012; Liemohn, Michael/H-8703-2012 OI Moore, Thomas/0000-0002-3150-1137; Liemohn, Michael/0000-0002-7039-2631 NR 26 TC 23 Z9 23 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 APR 15 PY 1996 VL 23 IS 8 BP 797 EP 800 DI 10.1029/96GL00844 PG 4 WC Geosciences, Multidisciplinary SC Geology GA UF439 UT WOS:A1996UF43900002 ER PT J AU Jensen, EJ Toon, OB Pfister, L Selkirk, HB AF Jensen, EJ Toon, OB Pfister, L Selkirk, HB TI Dehydration of the upper troposphere and lower stratosphere by subvisible cirrus clouds near the tropical tropopause SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID STEP AB The extreme dryness of the lower stratosphere is believed to be caused by freeze-drying of air as it enters the stratosphere through the cold tropical tropopause. Previous investigations have been focused on dehydration occurring at the tops of deep convective cloud systems. However, recent observations of a ubiquitous stratiform cirrus cloud layer near the tropical tropopause suggest the possibility of dehydration as air is slowly lifted by large-scale motions. In this study, we have evaluated this possibility using a detailed ice cloud model. Simulations of ice cloud formation in the temperature minima of gravity waves (wave periods of 1 - 2 hours) indicate that large numbers of ice crystals will likely form due to the low temperatures and rapid cooling. As a result, the crystals do not grow larger than about 10 mu m, fallspeeds are no greater than a few cm-s(-1), and little or no precipitation or dehydration occurs. However, ice clouds formed by large-scale vertical motions (with lifetimes of a day or more) should have fewer crystals and more time for crystal sedimentation to occur, resulting in water vapor depletions as large as 1 ppmv near the tropopause. We suggest that gradual lifting near the tropical tropopause, accompanied by formation of thin cirrus, may account for the dehydration. C1 SAN JOSE UNIV FDN,SAN JOSE,CA. SPACE PHYS RES INST,SUNNYVALE,CA. RP Jensen, EJ (reprint author), NASA,AMES RES CTR,MX 245-4,MOFFETT FIELD,CA 94035, USA. RI Selkirk, Henry/H-2021-2012 NR 15 TC 92 Z9 92 U1 1 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 APR 15 PY 1996 VL 23 IS 8 BP 825 EP 828 DI 10.1029/96GL00722 PG 4 WC Geosciences, Multidisciplinary SC Geology GA UF439 UT WOS:A1996UF43900009 ER PT J AU Arking, A Chou, MD Ridgway, WL AF Arking, A Chou, MD Ridgway, WL TI On estimating the effect of clouds on atmospheric absorption based on flux observations above and below cloud level SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article AB Recent attempts to estimate the contribution of clouds to absorption of solar radiation by the atmosphere have been based on the difference between measurements of solar flux at the top of-the-atmosphere, or in the atmosphere above cloud level, and measurements of solar flux at the surface, or in the atmosphere below cloud level. One problem with this approach is that fluxes below cloud level depend on the position of the clouds relative to the sun, which is not the case for measurements above cloud level. For example, at any point in the atmosphere below cloud level, the net downward flux varies considerably, depending on whether or not the clouds block the direct rays of the sun. As a result, the net downward flux above cloud level is generally a maximum for clear-sky conditions, but not so for the net downward flux below cloud level. This effect, if not taken into account, would bias the methods used to infer the contribution of clouds to atmospheric absorption, and lead to an overestimate of the contribution. C1 NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. APPL RES CORP,LANDOVER,MD 20785. JOHNS HOPKINS UNIV,DEPT EARTH & PLANETARY SCI,BALTIMORE,MD 21218. NR 8 TC 26 Z9 26 U1 1 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 APR 15 PY 1996 VL 23 IS 8 BP 829 EP 832 DI 10.1029/96GL00775 PG 4 WC Geosciences, Multidisciplinary SC Geology GA UF439 UT WOS:A1996UF43900010 ER PT J AU Peredo, JC Patterson, GN Fedyunin, YN AF Peredo, JC Patterson, GN Fedyunin, YN TI Domain collapse in grooved magnetic garnet material SO JOURNAL OF APPLIED PHYSICS LA English DT Meeting Abstract C1 CALTECH,JET PROP LAB,PASADENA,CA 91109. BOSTON UNIV,DEPT ELECT COMP & SYST ENGN,BOSTON,MA 02215. NR 2 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 0021-8979 J9 J APPL PHYS JI J. Appl. Phys. PD APR 15 PY 1996 VL 79 IS 8 BP 6642 EP 6642 DI 10.1063/1.361910 PN 2B PG 1 WC Physics, Applied SC Physics GA UG878 UT WOS:A1996UG87800393 ER PT J AU Crago, R Brutsaert, W AF Crago, R Brutsaert, W TI Daytime evaporation and the self-preservation of the evaporative fraction and the Bowen ratio SO JOURNAL OF HYDROLOGY LA English DT Article ID FIFE AB Under certain conditions several ratios of fluxes in the surface energy budget are known to remain relatively constant during the daytime hours. This 'self-preservation' has allowed the use of midday values of the evaporative fraction, EF, multiplied by the daytime total of net radiation minus the ground heat flux, to provide a good estimate of total daytime evaporation. A similar method is discussed, in which the daytime total sensible heat flux is divided by the noon Bowen ratio (beta = (1/EF)-1). Data from the First International Satellite Land Surface Climatology Project (ISLSCP) Field Experiment (FIFE) indicate that the two methods give rather different results. It is shown by propagating uncertainties that the uncertainty in the daytime total evaporation is likely to be smaller with the constant-EF method than with the constant-beta method for beta greater than about -1/2. C1 CORNELL UNIV,SCH CIVIL & ENVIRONM ENGN,ITHACA,NY 14853. NASA,GODDARD SPACE FLIGHT CTR,HYDROL SCI BRANCH,GREENBELT,MD 20771. RP Crago, R (reprint author), UNIV ILLINOIS,DEPT CIVIL & MAT ENGN,M-C 246,842 W TAYLOR ST,CHICAGO,IL 60607, USA. NR 18 TC 103 Z9 109 U1 1 U2 7 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0022-1694 J9 J HYDROL JI J. Hydrol. PD APR 15 PY 1996 VL 178 IS 1-4 BP 241 EP 255 DI 10.1016/0022-1694(95)02803-X PG 15 WC Engineering, Civil; Geosciences, Multidisciplinary; Water Resources SC Engineering; Geology; Water Resources GA UJ144 UT WOS:A1996UJ14400013 ER PT J AU Chou, MD Lee, KT AF Chou, MD Lee, KT TI Parameterizations for the absorption of solar radiation by water vapor and ozone SO JOURNAL OF THE ATMOSPHERIC SCIENCES LA English DT Article ID CLIMATE; MODEL C1 KANGNUNG NATL UNIV,DEPT ATMOSPHER SCI,KANGNUNG,SOUTH KOREA. RP Chou, MD (reprint author), NASA,GODDARD SPACE FLIGHT CTR,CLIMATE & RADIAT BRANCH,ATMOSPHERES LAB,CODE 913,GREENBELT,MD 20771, USA. NR 10 TC 86 Z9 90 U1 2 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 APR 15 PY 1996 VL 53 IS 8 BP 1203 EP 1208 DI 10.1175/1520-0469(1996)053<1203:PFTAOS>2.0.CO;2 PG 6 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA UF709 UT WOS:A1996UF70900009 ER PT J AU Choi, SR Salem, JA AF Choi, SR Salem, JA TI Cyclic fatigue of brittle materials with an indentation-induced flaw system SO MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING LA English DT Article DE cyclic fatigue; static fatigue; indentation-induced flaw; ceramics ID CRACK-PROPAGATION; CERAMIC MATERIALS; ALUMINA; BEHAVIOR AB The ratio of static to cyclic fatigue life, or 'h ratio', was obtained numerically for an indentation flaw system subjected to sinusoidal loading conditions. Emphasis was placed on developing a simple, quick lifetime prediction tool. The solution for the h ratio was compared with experimental static and cyclic fatigue data obtained from as-indented 96 wt.% alumina specimens tested in room-temperature distilled water. C1 CLEVELAND STATE UNIV,CLEVELAND,OH 44115. RP Choi, SR (reprint author), NASA,LEWIS RES CTR,CLEVELAND,OH 44135, USA. NR 17 TC 2 Z9 2 U1 0 U2 2 PU ELSEVIER SCIENCE SA LAUSANNE PI LAUSANNE 1 PA PO BOX 564, 1001 LAUSANNE 1, SWITZERLAND SN 0921-5093 J9 MAT SCI ENG A-STRUCT JI Mater. Sci. Eng. A-Struct. Mater. Prop. Microstruct. Process. PD APR 15 PY 1996 VL 208 IS 1 BP 126 EP 130 DI 10.1016/0921-5093(95)10068-7 PG 5 WC Nanoscience & Nanotechnology; Materials Science, Multidisciplinary; Metallurgy & Metallurgical Engineering SC Science & Technology - Other Topics; Materials Science; Metallurgy & Metallurgical Engineering GA UM130 UT WOS:A1996UM13000017 ER PT J AU Godon, P AF Godon, P TI Accretion disc boundary layers around pre-main-sequence stars SO MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY LA English DT Article DE accretion, accretion discs; methods, numerical; stars, pre-main-sequence ID T-TAURI STARS; FU-ORIONIS; EMISSION AB One-dimensional time-dependent calculations of geometrically thin accretion disc boundary layers in pre-main-sequence stars are carried out for mass-accretion rates in the range M = 5 x 10(-7) to 10(-4) M circle dot yr(-1), alpha = 0.005-0.3 and different inner boundary conditions on the temperature. Two kinds of solution are obtained: those with a distinct thermal boundary layer (BL) component and those without a thermal boundary layer. For M up to approximate to 10(-5) M circle dot yr(-1), and for alpha > alpha(critic) approximate to 0.04, solutions with a thermal BL are obtained. For M approximate to 10(-4) M circle dot yr(-1) or for alpha < alpha(critic), solutions without a thermal BL are obtained. The inner boundary condition F-T = sigma T-eff(4) leads to hotter solutions and higher threshold values alpha(critic), while the no-flux boundary condition dT/dr = 0 leads to cooler solutions. For a very low mass-accretion rate (M approximate to 5 x 10(-7) M circle dot yr(-1)), the temperature in the disc drops below 10(4) K and the ionization front is adjacent to the outer edge of the hot thermal boundary layer. In the vicinity of the ionization front, the medium becomes slightly optically thin. For a very high mass-accretion rate, advection of energy (zeta = L(adv)/L(acc) approximate to 0.1-0.2) from the boundary layer into the inner boundary becomes important, and the boundary layer luminosity is only a fraction of its expected value. RP Godon, P (reprint author), CALTECH,JET PROP LAB,4800 OAK GROVE DR,MS 238-332,PASADENA,CA 91109, USA. NR 35 TC 6 Z9 6 U1 0 U2 0 PU BLACKWELL SCIENCE LTD PI OXFORD PA OSNEY MEAD, OXFORD, OXON, ENGLAND OX2 0EL SN 0035-8711 J9 MON NOT R ASTRON SOC JI Mon. Not. Roy. Astron. Soc. PD APR 15 PY 1996 VL 279 IS 4 BP 1071 EP 1082 PG 12 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA UG553 UT WOS:A1996UG55300006 ER PT J AU Barstow, MA Holberg, JB Hubeny, I Lanz, T Bruhweiler, FC Tweedy, RW AF Barstow, MA Holberg, JB Hubeny, I Lanz, T Bruhweiler, FC Tweedy, RW TI Solving the mystery of the heavy-element opacity in the DA white dwarf GD 394 SO MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY LA English DT Article DE stars, atmospheres; stars, individual, GD 394; white dwarfs ultraviolet, stars; X-rays, stars ID MODEL STELLAR ATMOSPHERES; GRAVITATIONAL REDSHIFT; ULTRAVIOLET-SPECTRUM; MASS; TEMPERATURES; LEVITATION; ACCRETION; EXOSAT AB The white dwarf GD 394 is one of a very small number of bright hot DAs which have detectable quantities of highly ionized heavy elements in their spectra. Whether this material resides in the photosphere of GD 394 or is in the form of a circumstellar shell has been the subject of much debate, with the large discrepancy between the published radial velocity of the star and the measured velocities of the Si III/IV lines having apparently settled the argument in favour of the latter idea. However, GD 394 is also the coolest DA white dwarf in the ROSAT sky survey showing convincing evidence for the presence of absorbing material which strongly suppresses the EUV continuum. This result has reopened the argument about the nature of the silicon lines. From a combined analysis of the IUE, HST and EUVE spectra, coupled with new measurements of the photospheric radial velocity from H alpha data, we have established that the Si III and Si IV lines are indeed photospheric. Furthermore, other heavy elements must be present to account for the EUV opacity, but at levels below the thresholds for detecting absorption lines in either far-UV or EUV bands. C1 UNIV ARIZONA, LUNAR & PLANETARY LAB, TUCSON, AZ 85721 USA. NASA, GODDARD SPACE FLIGHT CTR, UNIV SPACE RES ASSOC, GREENBELT, MD 20771 USA. CATHOLIC UNIV AMER, DEPT PHYS, WASHINGTON, DC 20064 USA. UNIV ARIZONA, STEWARD OBSERV, TUCSON, AZ 85721 USA. RP Barstow, MA (reprint author), UNIV LEICESTER, DEPT PHYS & ASTRON, UNIV RD, LEICESTER LE1 7RH, LEICS, ENGLAND. NR 49 TC 25 Z9 25 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 APR 15 PY 1996 VL 279 IS 4 BP 1120 EP 1136 PG 17 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA UG553 UT WOS:A1996UG55300012 ER PT J AU Kastner, SO Bhatia, AK AF Kastner, SO Bhatia, AK TI The Bowen fluorescence lines: Overview and re-analysis of the observations SO MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY LA English DT Article DE atomic data; line, identification; planetary nebulae, general ID PLANETARY-NEBULAE; CHARGE-TRANSFER; O-III; HM SAGITTAE; ULTRAVIOLET OBSERVATIONS; IUE OBSERVATIONS; CROSS-SECTIONS; SPECTRUM; EXCITATION; MECHANISM AB The present situation with respect to observations and interpretations of the O III Bowen fluorescence lines is examined. Available sets of observations are assembled, and a general analysis and comparison are carried out using intermediate-coupling radiative rates obtained by Froese Fischer (FF) and by Bhatia & Kastner. Some new identifications of the weaker Bowen lines are made, and lines of a third 'Bowen' cascade are discussed. The results show, however, that while the FF rates are supported by some of the observations, the latter are not sufficiently complete to yield definitive interpretations of the longer wavelength Bowen lines, or to verify predicted charge-exchange processes. Consistency of predicted charge-exchange rates has also not yet been achieved, so that improved observations are especially important to obtain. The analysis presented may be useful to observers who plan to obtain a complete Bowen set of observations as defined here. RP Kastner, SO (reprint author), GODDARD SPACE FLIGHT CTR,ASTRON & SOLAR PHYS LAB,1-A RIDGE RD,GREENBELT,MD 20771, USA. NR 59 TC 6 Z9 6 U1 0 U2 1 PU BLACKWELL SCIENCE LTD PI OXFORD PA OSNEY MEAD, OXFORD, OXON, ENGLAND OX2 0EL SN 0035-8711 J9 MON NOT R ASTRON SOC JI Mon. Not. Roy. Astron. Soc. PD APR 15 PY 1996 VL 279 IS 4 BP 1137 EP 1156 PG 20 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA UG553 UT WOS:A1996UG55300013 ER PT J AU Allan, A Horne, K Hellier, C Mukai, K Barwig, H Bennie, PJ Hilditch, RW AF Allan, A Horne, K Hellier, C Mukai, K Barwig, H Bennie, PJ Hilditch, RW TI The spin period of the intermediate polar RX J0558+53 SO MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY LA English DT Article DE binaries, close; stars, individual, RX J0558.0+5353; novae, cataclysmic variables; X-rays, stars AB The newly discovered intermediate polar RX J0558+53 has been reported to have a spin period of 272 s. We find modulations at both 272 and 545 s, implying that the spin period of the white dwarf is twice that previously suggested, Thus, RX J0558+53, along with YY Dra, is unusual in showing a modulation with most of the power at the first harmonic, rather than at the spin frequency. C1 UNIV KEELE,DEPT PHYS,KEELE ST5 5BG,STAFFS,ENGLAND. NASA,GODDARD SPACE FLIGHT CTR,HIGH ENERGY ASTROPHYS LAB,GREENBELT,MD 20721. UNIV STERNWARTE MUNCHEN,W-8000 MUNICH 80,GERMANY. RP Allan, A (reprint author), UNIV ST ANDREWS,SCH PHYS & ASTRON,N HAUGH,ST ANDREWS KY16 9SS,FIFE,SCOTLAND. NR 12 TC 24 Z9 24 U1 0 U2 0 PU BLACKWELL SCIENCE LTD PI OXFORD PA OSNEY MEAD, OXFORD, OXON, ENGLAND OX2 0EL SN 0035-8711 J9 MON NOT R ASTRON SOC JI Mon. Not. Roy. Astron. Soc. PD APR 15 PY 1996 VL 279 IS 4 BP 1345 EP 1348 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA UG553 UT WOS:A1996UG55300030 ER PT J AU Gates, EI Gyuk, G Turner, MS AF Gates, EI Gyuk, G Turner, MS TI Gravitational microlensing and the galactic halo SO PHYSICAL REVIEW D LA English DT Article ID COLD DARK MATTER; MILKY-WAY; ROTATION CURVE; MASS DENSITY; GALAXY; MODEL; UNIVERSE; OBJECTS; BULGE AB By means of extensive galactic modeling we study the implications of the MACHO, EROS, and OGLE microlensing results for the composition of the dark halo of the Galaxy as well as for other properties of the Galaxy. While microlensing toward the LMC most directly probes the halo MACHO mass fraction, microlensing toward the bulge is almost equally important as it strongly constrains the Galactic model. We take the Galaxy to be comprised of luminous and dark disk components, a bulge, and a dark halo consisting of both MACHO's and cold dark matter with each component being described by several observationally motivated parameters. We pare down an initial model space of millions of galactic models to viable models, those which are consistent with the observational data; including rotation curve, local projected mass density, and microlensing rates toward the LMC and bulge. On the basis of a conservative, minimal set of observational constraints an all-MACHO halo cannot yet be excluded, although in most viable models of the Galaxy the halo MACHO fraction is between 0% and 30%, consistent with expectations for a universe whose primary component is cold dark matter. An all-MACHO halo is required to be light, and when data on the local escape velocity and satellite-galaxy proper motions, which probe the extent of the dark halo, are taken into account, models which have a high MACHO mass fraction are ruled out. We also explore the possibility that there are no MACHO's in the halo. Finally, we point out several important tests that could definitively exclude an all-MACHO halo, e.g., evidence that the optical depth for microlensing is less than 1.5 X 10(-7) toward the LMC or greater than 3 X 10(-6) toward the bulge. C1 FERMILAB NATL ACCELERATOR LAB,NASA,FERMILAB ASTROPHYS CTR,BATAVIA,IL 60510. UNIV CHICAGO,DEPT PHYS,CHICAGO,IL 60637. RP Gates, EI (reprint author), UNIV CHICAGO,ENRICO FERMI INST,DEPT ASTRON & ASTROPHYS,CHICAGO,IL 60637, USA. NR 73 TC 55 Z9 55 U1 2 U2 2 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 APR 15 PY 1996 VL 53 IS 8 BP 4138 EP 4176 DI 10.1103/PhysRevD.53.4138 PG 39 WC Astronomy & Astrophysics; Physics, Particles & Fields SC Astronomy & Astrophysics; Physics GA UH722 UT WOS:A1996UH72200004 ER PT J AU Outlaw, RA RezaieSerej, S Allen, WP Latanision, RM AF Outlaw, RA RezaieSerej, S Allen, WP Latanision, RM TI Desulfurization of Ni-based super alloys by combined heating and glow discharge SO SCRIPTA MATERIALIA LA English DT Article ID OXIDE SCALE ADHERENCE; SULFUR; SEGREGATION; ADHESION; ELEMENTS C1 OLD DOMINION UNIV,NORFOLK,VA 23508. UNITED TECHNOL RES CTR,E HARTFORD,CT 06108. MIT,CAMBRIDGE,MA 02139. RP Outlaw, RA (reprint author), NASA,LANGLEY RES CTR,HAMPTON,VA 23681, USA. NR 24 TC 2 Z9 2 U1 0 U2 0 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, ENGLAND OX5 1GB SN 1359-6462 J9 SCRIPTA MATER JI Scr. Mater. PD APR 15 PY 1996 VL 34 IS 8 BP 1315 EP 1321 DI 10.1016/1359-6462(95)00666-4 PG 7 WC Nanoscience & Nanotechnology; Materials Science, Multidisciplinary; Metallurgy & Metallurgical Engineering SC Science & Technology - Other Topics; Materials Science; Metallurgy & Metallurgical Engineering GA TZ629 UT WOS:A1996TZ62900020 ER PT J AU Becker, L Poreda, RJ Bada, JL AF Becker, L Poreda, RJ Bada, JL TI Extraterrestrial helium trapped in fullerenes in the sudbury impact structure SO SCIENCE LA English DT Article ID ION-MOLECULE REACTIONS; CIRCUMSTELLAR CHEMISTRY; ALLENDE METEORITE; ORGANIC-MOLECULES; INTERSTELLAR; CARBON; PARTICLES; DELIVERY; ORIGINS; GASES AB Fullerenes (C-60 and C-70) in the Sudbury impact structure contain trapped helium with a He-3/He-4 ratio of 5.5 x 10(-4) to 5.9 x 10(-4). The He-3/He-4 ratio exceeds the accepted solar wind value by 20 to 30 percent and is higher by an order of magnitude than the maximum reported mantle value, Terrestrial nuclear reactions or cosmic-ray bombardment are not sufficient to generate such a high ratio. The He-3/He-4 ratios in the Sudbury fullerenes are similar to those found in meteorites and in some interplanetary dust particles. The implication is that the helium within the C-60 molecules at Sudbury is of extraterrestrial origin. C1 UNIV CALIF SAN DIEGO,SCRIPPS INST OCEANOG,LA JOLLA,CA 92093. UNIV ROCHESTER,DEPT EARTH & ENVIRONM SCI,ROCHESTER,NY 14627. RP Becker, L (reprint author), NASA,AMES RES CTR,DIV SPACE SCI,MOFFETT FIELD,CA 94035, USA. NR 45 TC 69 Z9 75 U1 0 U2 9 PU AMER ASSOC ADVANCEMENT SCIENCE PI WASHINGTON PA 1200 NEW YORK AVE, NW, WASHINGTON, DC 20005 SN 0036-8075 J9 SCIENCE JI Science PD APR 12 PY 1996 VL 272 IS 5259 BP 249 EP 252 DI 10.1126/science.272.5259.249 PG 4 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA UE729 UT WOS:A1996UE72900036 PM 8602508 ER PT J AU Ackerman, AS Toon, OB AF Ackerman, AS Toon, OB TI Unrealistic desiccation of marine stratocumulus clouds by enhanced solar absorption SO NATURE LA English DT Article ID MIXED LAYER MODEL; AIRCRAFT OBSERVATIONS; DIURNAL-VARIATION; ALBEDO; WATER AB THE absorption of solar radiation by clouds affects the distribution of heat that drives atmospheric and ocean circulations. Many investigators have measured cloud solar absorption values exceeding theoretical estimates, although the discrepancies have been. regarded as inconclusive(1). But more recent measurements indicate that clouds absorb up to three times as much solar energy than conventional theory predicts(2,3). Marine stratocumulus clouds are particularly sensitive to solar absorption because marine boundary-layer mixing is typically driven by cloud radiative processes. Here we present model simulations of a stratocumulus-topped marine boundary layer, incorporating different levels of solar absorption. With conventional absorption, the simulations reproduce observed cloud behaviour. But those with artificially enhanced absorption result in an unrealistic daytime depletion of cloud water, because a reduction in cloud radiative cooling results in decreased boundary-layer mixing. Moreover, we show that it is unlikely that liquid water or any plausible dissolved material can absorb the energy required by the recent measurements of solar absorption. Our results therefore indicate that either enhanced solar absorption occurs only in clouds other than marine stratocumulus, or the enhancement of cloud solar absorption indicated hy recent measurements(2,3) is overestimated. RP Ackerman, AS (reprint author), NASA,AMES RES CTR,MOFFETT FIELD,CA 94035, USA. RI Ackerman, Andrew/D-4433-2012 OI Ackerman, Andrew/0000-0003-0254-6253 NR 27 TC 11 Z9 11 U1 0 U2 2 PU MACMILLAN MAGAZINES LTD PI LONDON PA 4 LITTLE ESSEX STREET, LONDON, ENGLAND WC2R 3LF SN 0028-0836 J9 NATURE JI Nature PD APR 11 PY 1996 VL 380 IS 6574 BP 512 EP 515 DI 10.1038/380512a0 PG 4 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA UE663 UT WOS:A1996UE66300044 ER PT J AU Eisenhardt, PR Armus, L Hogg, DW Soifer, BT Neugebauer, G Werner, MW AF Eisenhardt, PR Armus, L Hogg, DW Soifer, BT Neugebauer, G Werner, MW TI Hubble space telescope observations of the luminous IRAS source FSC 10214+4724: A gravitationally lensed infrared quasar SO ASTROPHYSICAL JOURNAL LA English DT Article DE gravitational lensing; infrared, galaxies; galaxies, individual (FSC 10214+4724) ID ELLIPTICAL GALAXIES; F10214+4724; PHOTOMETRY; EMISSION; NUMBER AB With a redshift of 2.3, the IRAS source FSC 10214+4724 is apparently one of the most luminous objects known in the universe. We present an image of FSC 10214+4724 at 0.8 mu m obtained with the Hubble Space Telescope (HST) WFPC2 Planetary Camera. The source appears as an unresolved (<0.06 '') are 0.7 '' long, with significant substructure along its length. The center of curvature of the are is located near an elliptical galaxy 1.18 '' to the north. An unresolved component 100 times fainter than the are is clearly detected on the opposite side of this galaxy. The most straightforward interpretation is that FSC 10214+4724 is gravitationally lensed by the foreground elliptical galaxy, with the faint component a counterimage of the IRAS source. The brightness of the are in the HST image is then magnified by similar to 100, and the intrinsic source diameter is similar to 0.01 '' (80 pc) at 0.25 mu m rest wavelength. The bolometric luminosity is probably amplified by a smaller factor (similar to 30) as a result of the larger extent expected for the source in the far-infrared. A detailed lensing model is presented that reproduces the observed morphology and relative flux of the are and counterimage and correctly predicts the position angle of the lensing galaxy. The model also predicts reasonable values for the velocity dispersion, mass, and mass-to-light ratio of the lensing galaxy for a wide range of galaxy redshifts. A redshift for the lensing galaxy of similar to 0.9 is consistent with the measured surface brightness profile from the image, as well as with the galaxy's spectral energy distribution. The background lensed source has an intrinsic luminosity similar to 2 x 10(13) L(.) and remains a highly luminous quasar with an extremely large ratio of infrared to optical/ultraviolet luminosity. C1 CALTECH,DIV PHYS MATH & ASTRON,PASADENA,CA 91125. RP Eisenhardt, PR (reprint author), CALTECH,JET PROP LAB,MS 169-327,4800 OAK GROVE DR,PASADENA,CA 91109, USA. OI Hogg, David/0000-0003-2866-9403 NR 38 TC 91 Z9 91 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 APR 10 PY 1996 VL 461 IS 1 BP 72 EP & DI 10.1086/177038 PN 1 PG 13 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA UD646 UT WOS:A1996UD64600005 ER PT J AU George, IM Turner, TJ AF George, IM Turner, TJ TI The X-ray spectrum of the BL Lacertae object EXO 055625-3838.6 SO ASTROPHYSICAL JOURNAL LA English DT Article DE BL Lacertae objects, individual (EXO 055625-3838.6); X-rays, galaxies ID CATALOG AB We report the results from observations of the BL Lac object EXO 055625 - 3838.6 carried out,in the X-ray band using ROSAT and ASCA during 1993 and 1995. These observations provide the first X-ray spectra of the source obtained using image detectors. We find no evidence for dramatic variability within either observation, but find the source to have varied by a factor of similar to 1.5 in intensity between the two epochs. For both epochs we find the spectrum to be well described by a simple power-law model with a (photon) index Gamma similar to 2.5, absorbed by an effective hydrogen column consistent with 21 cm measurements along the line of sight through our Galaxy. EXO 055625 - 3838.6 lies within the error box of the target designated H0557 - 385, similar to 25' south of the Seyfert 1 Galaxy included in the X-ray log N-log S and luminosity function derived from HEAOI data (Piccinotti et al. 1982). However, based upon the results presented here, we suggest the BL Lac object probably did not contribute significantly to earlier hard X-ray observations made using collimated instruments. RP George, IM (reprint author), NASA,GODDARD SPACE FLIGHT CTR,HIGH ENERGY ASTROPHYS LAB,CODE 6602,GREENBELT,MD 20771, USA. NR 24 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 APR 10 PY 1996 VL 461 IS 1 BP 198 EP 201 DI 10.1086/177047 PN 1 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA UD646 UT WOS:A1996UD64600014 ER PT J AU Tielens, AGGM Wooden, DH Allamandola, LJ Bregman, J Witteborn, FC AF Tielens, AGGM Wooden, DH Allamandola, LJ Bregman, J Witteborn, FC TI The infrared spectrum of the Galactic center and the composition of interstellar dust SO ASTROPHYSICAL JOURNAL LA English DT Article DE dust, extinction; Galaxy, center; infrared, ISM, lines and bands; ISM, abundances ID DENSE MOLECULAR CLOUDS; EXTENDED RED EMISSION; TIME-DEPENDENT CHEMISTRY; MU-M; REFLECTION NEBULAE; SIZE DISTRIBUTION; AMORPHOUS-CARBON; MIRA VARIABLES; SPECTROSCOPY; GRAINS AB We have obtained 5-8 mu m spectra of the Galactic center from the Kuiper Airborne Observatory at resolving powers of approximate to 50, approximate to 150, and approximate to 300. These spectra show absorption features at 5.5, 5.8, 6.1, and 6.8 mu m. Together with previously observed features in the 3 mu m region, these features are compared with laboratory spectra of candidate materials. The 3.0 and 6.1 mu m features are due to the OH stretching and bending variations of H2O and are well fitted by water of hydration in silicates (e.g., talc). The 3.0 mu m band is equally well fitted by ice mixtures containing 30% H2O, but such mixtures do not provide a good fit to the observed 6.1 mu m band. The 3.4 and 6.8 mu m features are identified with the CH stretching and deformation modes in CH, and CH, groups in saturated aliphatic hydrocarbons. The 6.1 mu m band shows a short wavelength shoulder centered on 5.8 mu m, attributed to carbonyl (C=O) groups in this interstellar hydrocarbon dust component. Finally, the narrow 5.5 mu m feature is also attributed to carbonyl groups, but in the form of metal carbonyls [e.g., Fe(CO)(4)]. We have derived column densities and abundances along the line of sight toward the Galactic center for the various identified dust components. This analysis shows that hydrocarbon grains contain only 0.08 of the elemental abundance of C and contribute only a relatively minor fraction (0.1) of the total dust volume. Most of the interstellar dust volume is made up of silicates (approximate to 0.6). Small graphite grains, responsible for the 2200 Angstrom bump, account for 0.07 of the total dust volume. The remaining one-quarter of the interstellar dust volume consists of a material(s) without strong IR absorption features. Likely candidates include large graphite grains, diamonds, or amorphous carbon grains, which all have weak or no IR active modes. Finally, various models for the origin of the hydrocarbon dust component of the interstellar dust are discussed. All of them face some problems in explaining the observations, in particular, the absence of the spectroscopic signature of hydrocarbon grains in sources associated with molecular clouds. RP Tielens, AGGM (reprint author), NASA, AMES RES CTR, MS 245-3, MOFFETT FIELD, CA 94035 USA. NR 87 TC 71 Z9 73 U1 0 U2 2 PU IOP PUBLISHING LTD PI BRISTOL PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD APR 10 PY 1996 VL 461 IS 1 BP 210 EP 222 DI 10.1086/177049 PN 1 PG 13 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA UD646 UT WOS:A1996UD64600016 PM 11539170 ER PT J AU Hora, JL Latter, WB AF Hora, JL Latter, WB TI A butterfly in the making: Revealing the near-infrared structure of hubble 12 SO ASTROPHYSICAL JOURNAL LA English DT Article DE infrared, ISM, continuum; infrared, ISM, lines and bands; molecular processes; planetary nebulae, individual (Hubble 12) ID PLANETARY-NEBULA HUBBLE-12; MOLECULAR-HYDROGEN EMISSION; SPECTROSCOPY AB We present deep narrowband near-IR images and moderate resolution spectra of the young planetary nebula Hubble 12. These data are the first to show clearly the complex structure for this important planetary nebula. Images were obtained at lambda = 2.12, 2.16, and 2.26 mu m. The lambda = 2.12 mu m image reveals the bipolar nature of the nebula, as well as complex structure near the central star in the equatorial region. The images show an elliptical region of emission, which may indicate a ring or a cylindrical source structure. This structure is possibly related to the mechanism that is producing the bipolar flow. The spectra show the nature of several distinct components. The central object is dominated by recombination lines of H I and He I. The core is not a significant source of molecular hydrogen emission. The east position in the equatorial region is rich in lines of ultraviolet-excited fluorescent H-2. A spectrum of part of the central region shows strong [Fe II] emission, which might indicate the presence of shocks. C1 NASA,AMES RES CTR,MOFFETT FIELD,CA 94035. RP Hora, JL (reprint author), INST ASTRON,2680 WOODLAWN DR,HONOLULU,HI 96822, USA. OI Hora, Joseph/0000-0002-5599-4650 NR 36 TC 36 Z9 36 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 APR 10 PY 1996 VL 461 IS 1 BP 288 EP & DI 10.1086/177055 PN 1 PG 13 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA UD646 UT WOS:A1996UD64600022 ER PT J AU Sayer, RW Nice, DJ Kaspi, VM AF Sayer, RW Nice, DJ Kaspi, VM TI A search for pulsar companions to OB runaway stars SO ASTROPHYSICAL JOURNAL LA English DT Article DE pulsars, general; pulsars, individual, J2044+4614; stars, binaries, general; stars, early-type ID X-RAY BINARIES; RADIO PULSARS; EVOLUTION; ORIGIN; FREQUENCY AB We have searched for radio pulsar companions to 40 nearby OB runaway stars. Observations were made at 575 and 770 MHz with the NRAO 140 foot (43 m) telescope. The survey was sensitive to long-period pulsars with flux densities of 1 mJy or more. No pulsar companions to OB runaways were discovered. One previously unknown pulsar was discovered, PSR J2044+4614, while observing toward target O star ED +45 degrees 3260. Follow-up timing observations of the pulsar measured its position to high precision, revealing a 9' separation between the pulsar and the target star, unequivocally indicating they are not associated. The pulsar is ordinary, except that its dispersion measure, 315 pc cm(-3), is unusually high given its Galactic longitude, I = 85 degrees. The nondetection of pulsars bound to target stars places an upper limit of 8% (95% confidence) for the fraction of runaway OB stars with pulsar companions detectable via pulsed radio emission by surveys such as ours. Assuming standard models for the pulsar beaming fraction and luminosity function, we conclude most OB runaways do not have pulsar companions. C1 PRINCETON UNIV,DEPT PHYS,PRINCETON,NJ 08544. NATL RADIO ASTRON OBSERV,CHARLOTTESVILLE,VA 22903. CALTECH,JET PROP LAB,IPAC,PASADENA,CA 91125. RP Sayer, RW (reprint author), PRINCETON UNIV,JOSEPH HENRY LABS,PRINCETON,NJ 08544, USA. NR 32 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 APR 10 PY 1996 VL 461 IS 1 BP 357 EP 361 DI 10.1086/177063 PN 1 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA UD646 UT WOS:A1996UD64600030 ER PT J AU Dgani, R VanBuren, D NoriegaCrespo, A AF Dgani, R VanBuren, D NoriegaCrespo, A TI The transverse acceleration instability for bow shocks in the nonlinear regime SO ASTROPHYSICAL JOURNAL LA English DT Article DE hydrodynamics; instabilities; shock waves; stars, individual (alpha Camelopardalis); turbulence ID DOUBLE STAR SYSTEM; STABILITY ANALYSIS; COLLIDING WINDS; ACCRETION LINE AB We continue our study of the stability of thin isothermal bow shocks. We follow the transverse acceleration instability (TAI) found in the linear analysis to the nonlinear regime. We use numerical simulations to solve the nonlinear Euler equations. Indeed, we find that thin isothermal bow shocks are also unstable in the nonlinear regime. The growth rates for the instability are higher for larger values of v*/v(w), where v*, v(w), are the stellar and wind velocities, respectively, as expected from the linear analysis. We apply our results to observations of bow shocks and find that the size of the clumps in alpha Cam is compatible with the TAI if its viscosity is due to turbulence in the mixing layer between the shocked ambient medium fluid and the shocked wind fluid. RP Dgani, R (reprint author), CALTECH,JET PROP LAB,CTR INFRARED PROC & ANAL,PASADENA,CA 91125, USA. NR 17 TC 15 Z9 15 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 APR 10 PY 1996 VL 461 IS 1 BP 372 EP 376 DI 10.1086/177065 PN 1 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA UD646 UT WOS:A1996UD64600032 ER PT J AU Mattox, JR Bertsch, DL Chiang, J Dingus, BL Digel, SW Esposito, JA Fierro, JM Hartman, RC Hunter, SD Kanbach, G Kniffen, DA Lin, YC Macomb, DJ MayerHasselwander, HA Michelson, PF vonMontigny, C Mukherjee, R Nolan, PL Ramanamurthy, PV Schneid, E Sreekumar, P Thompson, DJ Willis, TD AF Mattox, JR Bertsch, DL Chiang, J Dingus, BL Digel, SW Esposito, JA Fierro, JM Hartman, RC Hunter, SD Kanbach, G Kniffen, DA Lin, YC Macomb, DJ MayerHasselwander, HA Michelson, PF vonMontigny, C Mukherjee, R Nolan, PL Ramanamurthy, PV Schneid, E Sreekumar, P Thompson, DJ Willis, TD TI The likelihood analysis of EGRET data SO ASTROPHYSICAL JOURNAL LA English DT Article DE gamma rays, observations; methods, data analysis; methods, statistical ID GAMMA-RAY ASTRONOMY; TELESCOPE; RADIATION AB The use of likelihood for the analysis of high-energy gamma-ray data from the EGRET instrument aboard the Compton Gamma-Ray Observatory is described. Maximum likelihood is used to estimate point-source flux densities, source locations, and background model parameters. The likelihood ratio test is used to determine the significance of point sources. Monte Carlo simulations have been done to confirm the validity of these techniques. C1 NASA,GODDARD SPACE FLIGHT CTR,COMPTON OBSERV,SCI SUPPORT CTR,GREENBELT,MD 20771. NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. UNIV SPACE RES ASSOC,SPACE ASTRON PROGRAM,WASHINGTON,DC. UNIV TORONTO,CITA,TORONTO,ON M5S 1A1,CANADA. CTR ASTROPHYS,CAMBRIDGE,MA 02138. STANFORD UNIV,WW HANSEN EXPTL PHYS LAB,STANFORD,CA 94305. MAX PLANCK INST EXTRATERR PHYS,W-8046 GARCHING,GERMANY. HAMPDEN SYDNEY COLL,HAMPDEN SYDNEY,VA 23943. GRUMMAN AEROSP CORP,BETHPAGE,NY 11714. RI Nolan, Patrick/A-5582-2009; Hunter, Stanley/D-2942-2012; Thompson, David/D-2939-2012 OI Thompson, David/0000-0001-5217-9135 NR 36 TC 548 Z9 549 U1 1 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 APR 10 PY 1996 VL 461 IS 1 BP 396 EP 407 DI 10.1086/177068 PN 1 PG 12 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA UD646 UT WOS:A1996UD64600035 ER PT J AU Miller, JA LaRosa, TN Moore, RL AF Miller, JA LaRosa, TN Moore, RL TI Stochastic electron acceleration by cascading fast mode waves in impulsive solar flares SO ASTROPHYSICAL JOURNAL LA English DT Article DE acceleration of particles; plasmas; Sun, corona; Sun, flares; Sun, particle emission ID RETURN CURRENT SYSTEMS; X-RAY-BURSTS; MAGNETOHYDRODYNAMIC TURBULENCE; FERMI ACCELERATION; BREMSSTRAHLUNG; DISSIPATION; DIFFUSION; EMISSION; SPECTRA; PLASMAS AB We present a model for the acceleration of electrons from thermal to ultrarelativistic energies during an energy release fragment in an impulsive solar flare. Long-wavelength low-amplitude fast mode waves are assumed to be generated during the initial flare energy release (by, for example, large-scale restructuring of the magnetic field). These waves nonlinearly cascade to higher wavenumbers and eventually reach the dissipation range, whereupon they are transit-time damped by electrons in the tail of the thermal distribution. The electrons, in turn, are energized out of the tail and into substantially higher energies. We find that for turbulence energy densities much smaller than the ambient magnetic field energy density and comparable to the thermal particle energy density, and for a wide range of initial wavelengths, a sufficient number of electrons are accelerated to hard X-ray-producing energies on observed timescales. We suggest that MHD turbulence unifies electron and proton acceleration in impulsive solar flares, since a preceding study established that a second MHD mode (the shear Alfven wave) preferentially accelerates protons from thermal to gamma-ray line-producing energies. C1 KENNESAW STATE COLL, DEPT BIOL & PHYS SCI, MARIETTA, GA 30061 USA. NASA, GEORGE C MARSHALL SPACE FLIGHT CTR, SPACE SCI LAB, HUNTSVILLE, AL 35812 USA. RP Miller, JA (reprint author), UNIV ALABAMA, DEPT PHYS, HUNTSVILLE, AL 35899 USA. NR 55 TC 159 Z9 160 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 APR 10 PY 1996 VL 461 IS 1 BP 445 EP 464 DI 10.1086/177072 PN 1 PG 20 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA UD646 UT WOS:A1996UD64600039 ER PT J AU Feldman, U Doschek, GA Behring, WE AF Feldman, U Doschek, GA Behring, WE TI Electron temperature and emission measure determinations of very faint solar flares SO ASTROPHYSICAL JOURNAL LA English DT Article DE Sun, flares; Sun, X-rays, gamma rays ID DIELECTRONIC SATELLITE SPECTRA; HELIUM-LIKE IONS; LINES AB We have studied 28 flares in the X-ray magnitude range of A2-A9 using high-resolution Bragg crystal spectrometer data obtained from instrumentation flown on the Yohkoh spacecraft. Flares in the A-class category can be detected in spectral lines of He-like ions formed at low temperatures. Their average temperature is approximately 5 x 10(6) K, and their emission measure as determined from the S XV resonance line near 5 Angstrom varies between 2 x 10(46) and 1 x 10(48) Cm-3. C1 NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. RP Feldman, U (reprint author), USN,RES LAB,EO HULBURT CTR SPACE RES,CODE 7608,WASHINGTON,DC 20375, USA. NR 16 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 APR 10 PY 1996 VL 461 IS 1 BP 465 EP 471 DI 10.1086/177073 PN 1 PG 7 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA UD646 UT WOS:A1996UD64600040 ER PT J AU Abney, M Epstein, RI AF Abney, M Epstein, RI TI Ekman pumping in compact astrophysical bodies SO JOURNAL OF FLUID MECHANICS LA English DT Article ID SPIN-UP; STRATIFIED FLUID; CLOSE BINARIES; NEUTRON-STARS; SYNCHRONIZATION; CYLINDER; REST; GAS AB We examine the dynamics of a rotating viscous fluid following an abrupt change in the angular velocity of the solid bounding surface. We include the effects of a density stratification and compressibility which are important in astrophysical objects such as neutron stars. We confirm and extend the conclusions of previous studies that stratification restricts the Ekman pumping process to a relatively thin layer near the boundary, leaving much of the interior fluid unaffected. We find that finite compressibility further inhibits Ekman pumping by decreasing the extent of the pumped layer and by increasing the time for spin-up. The results of this paper are important for interpreting the spin period discontinuities ('glitches') observed in rotating neutron stars. C1 FERMILAB NATL ACCELERATOR LAB,NASA,FERMILAB ASTROPHYS CTR,BATAVIA,IL 60510. LOS ALAMOS NATL LAB,LOS ALAMOS,NM 87545. RP Abney, M (reprint author), UNIV CHICAGO,DEPT ASTRON & ASTROPHYS,ENRICO FERMI INST,5640 S ELLIS AVE,CHICAGO,IL 60637, USA. NR 26 TC 21 Z9 21 U1 0 U2 0 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 APR 10 PY 1996 VL 312 BP 327 EP 340 DI 10.1017/S0022112096002030 PG 14 WC Mechanics; Physics, Fluids & Plasmas SC Mechanics; Physics GA UH147 UT WOS:A1996UH14700014 ER PT J AU Cohen, SC AF Cohen, SC TI Time-dependent uplift of the Kenai Peninsula and adjacent regions of south central Alaska since the 1964 Prince William Sound earthquake SO JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH LA English DT Article ID DISLOCATION MODEL; SUBDUCTION ZONES; DEFORMATION; RELEASE; CYCLE AB Leveling, Global Positioning System, very long baseline interferometry, and tide gauge observations indicate that time-dependent uplift has occurred on the Kenai Peninsula and adjacent regions of southern Alaska that subsided coseismically in the 1964 Prince William Sound earthquake. These observations have been critically assessed and used along with seismological and geological information as constraints in various aseismic slip and viscoelastic flow models of crustal deformation. The postseismic uplift rate in most of the region is significantly greater than the expected interseismic average. Some, but not all, of the data indicate that the uplift rate was quite rapid (more than several centimeters per year) in the years immediately following the earthquake and has slowed to a few centimeters per year or less since then. The modeling shows that the uplift can be explained by aseismic slip at depth but riot by viscoelastic flow. The slip at depth since 1964 must have a transient as well as a steady component, since the deduced slip is considerably greater than the roughly 1.5 m expected from North American-Pacific plate convergence since the 1964 event. The minimum amount of slip required to fit the observations comes from an elastic model and is about 2.75 m. Viscoelastic models require more slip, since the dominant effect of viscoelastic howls to produce subsidence in the region that is uplifted. A simple parameterization of the transient component using an amplitude and decay time is adequate to explain the observations. While the parameters deduced from the viscoelastic models have some ambiguity, the viscosity of models that best fit the observations cannot be much less than several times 10(19) Pa s when the thickness of the North American plate is taken to be about 90 km. RP Cohen, SC (reprint author), NASA, GODDARD SPACE FLIGHT CTR, GEODYNAM BRANCH, CODE 921, GREENBELT, MD 20771 USA. NR 27 TC 16 Z9 16 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 APR 10 PY 1996 VL 101 IS B4 BP 8595 EP 8604 DI 10.1029/96JB00175 PG 10 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA UF005 UT WOS:A1996UF00500037 ER PT J AU Gross, RS AF Gross, RS TI Combinations of earth orientation measurements: SPACE94, COMB94, and POLE94 SO JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH LA English DT Article ID ROTATION AB A Kalman filter has been used to combine independent measurements of the Earth's orientation taken by the space-geodetic observing techniques of lunar laser ranging, satellite laser ranging, very long baseline interferometry, and the Global Positioning System. Prior to their combination, the data series were adjusted to have the same bias and rate, the stated uncertainties of the measurements were adjusted, and data points considered to be outliers were deleted. The resulting combination, SPACE94, consists of smoothed, interpolated polar motion and UT1-UTC values spanning October 6.0, 1976, to January 27.0, 1995, at 1-day intervals. The Kalman filter was then used to combine the space-geodetic series comprising SPACE94 with two different, independent series of Earth orientation measurements taken by the technique of optical astrometry. Prior to their combination with SPACE94, the bias, rate and annual term of the optical astrometric series were corrected; the stated uncertainties of the measurements were adjusted, and data points considered to be outliers were deleted. The adjusted optical astrometric series were then combined with SPACE94 in two steps: (1) the Bureau International de l'Heure (BIH) optical astrometric series was combined with SPACE94 to form COMB94, a combined series of smoothed, interpolated polar motion and UT1-UTC values spanning January 20.0, 1962, to January 27.0, 1995, at 5-day intervals, and (2) the International Latitude Service (ILS) optical astrometric series was combined with COMB94 to form POLE94, a combined series of smoothed, interpolated polar motion values spanning January 20, 1900, to January 21, 1995, at 30.4375-day intervals. RP Gross, RS (reprint author), CALTECH, JET PROP LAB, MS 238-332, 4800 OAK GROVE DR, PASADENA, CA 91109 USA. NR 32 TC 40 Z9 40 U1 0 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-9313 EI 2169-9356 J9 J GEOPHYS RES-SOL EA JI J. Geophys. Res.-Solid Earth PD APR 10 PY 1996 VL 101 IS B4 BP 8729 EP 8740 DI 10.1029/96JB00113 PG 12 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA UF005 UT WOS:A1996UF00500047 ER PT J AU Sigl, G AF Sigl, G TI Weak interactions in supernova cores and saturation of nucleon spin fluctuations SO PHYSICAL REVIEW LETTERS LA English DT Article ID NEUTRAL CURRENT INTERACTIONS; DENSE MATTER; HOT; AXIONS; BREMSSTRAHLUNG; NEUTRINOS; EMISSION; STARS AB Extrapolation of perturbative nucleon spin fluctuation rates seems to suggest a strong suppression of weak interactions in supernova cores. We derive a generalized f sum rule for the dynamical spin-density structure function which relates the spin fluctuation rate to the average nuclear interaction energy. For a bremsstrahlung-like structure function profile we show that, instead of strongly decreasing, the neutrino scattering cross section is roughly density independent, and axion emissivities increase somewhat slower than the lowest order rates toward the center of a hot supernova core. C1 FERMILAB NATL ACCELERATOR LAB,NASA,FERMILAB ASTROPHYS CTR,BATAVIA,IL 60510. RP Sigl, G (reprint author), UNIV CHICAGO,ENRICO FERMI INST,DEPT ASTRON & ASTROPHYS,CHICAGO,IL 60637, USA. NR 28 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 APR 8 PY 1996 VL 76 IS 15 BP 2625 EP 2628 DI 10.1103/PhysRevLett.76.2625 PG 4 WC Physics, Multidisciplinary SC Physics GA UE190 UT WOS:A1996UE19000006 ER PT J AU DeMore, WB AF DeMore, WB TI Experimental and estimated rate constants for the reactions of hydroxyl radicals with several halocarbons SO JOURNAL OF PHYSICAL CHEMISTRY LA English DT Article ID HALOGEN-SUBSTITUTED ETHANES; ATMOSPHERIC LIFETIMES; OH RADICALS; KINETICS; METHANES; CH4 AB Relative rate experiments are used to measure rate constants and temperature dependencies of the reactions of OH with CH3F (41), CH2FCl (31), CH2BrCl (30B1), CH2Br2 (30B2), CHBr3 (20B3), CF2BrCHFCl (123aB1 alpha), and CF2ClCHCl2 (122). Rate constants for additional compounds of these types are estimated using an empirical rate constant estimation method which is based on measured rate constants for a wide range of halocarbons. The experimental data are combined with the estimated and previously reported rate constants to illustrate the effects of F, Cl, and Br substitution on OH rate constants for a series of 19 halomethanes and 25 haloethanes. Application of the estimation technique is further illustrated for some higher hydrofluorocarbons (HFCs), including CHF2CF2CF2CF2H (338pcc), CF3CHFCHFCF2CF3 (43-10mee), CF3CH2CH2CF3, (356ffa), CF3CH2CF2CH2CF3 (458mfcf), CF3CH2CHF2 (245fa), and CF3CH2CF2CH3 (365mfc). The predictions are compared with literature data for these compounds. RP DeMore, WB (reprint author), CALTECH,JET PROP LAB,PASADENA,CA 91109, USA. NR 25 TC 76 Z9 76 U1 1 U2 9 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 SN 0022-3654 J9 J PHYS CHEM-US JI J. Phys. Chem. PD APR 4 PY 1996 VL 100 IS 14 BP 5813 EP 5820 DI 10.1021/jp953216+ PG 8 WC Chemistry, Physical SC Chemistry GA UD604 UT WOS:A1996UD60400032 ER PT J AU Hollingsworth, JL Haberle, RM Barnes, JR Brider, AFC Pollack, JB Lee, H Schaeffer, J AF Hollingsworth, JL Haberle, RM Barnes, JR Brider, AFC Pollack, JB Lee, H Schaeffer, J TI Orographic control of storm zones on Mars SO NATURE LA English DT Article ID GENERAL-CIRCULATION MODEL; BAROCLINIC INSTABILITY; ATMOSPHERIC DYNAMICS; MARTIAN ATMOSPHERE; SIMULATIONS; SYSTEMS; TRACKS; FLOW AB Low-pressure cyclones and their accompanying frontal systems in the middle latitudes of the Earth's troposphere develop, travel eastwards and decay preferentially within latitudinally and longitudinally confined geographical regions known as storm zones' These zones can be readily identified in the circulation statistics of terrestrial weather systems(2). Mars, like the Earth, is a rapidly rotating solid planet and has a seasonally varying shallow atmosphere, large-scale orography, and (in a broadly defined context) continental structures(3). Although there are also important differences between the two planets, travelling weather systems do exist on Mars(3). This raises the question of whether storm zones also occur there, and if so, by what mechanisms. Here we report the results of numerical simulations of global atmospheric circulation patterns on Mars, We find that storm zones can exist during the northern winter, and that continental-scale orography (rather than surface thermal contrasts) is the main factor determining the development of these zones. Storm zones on Mars should play an important role in the martian climate cycle(4,5), by influencing the transport of (for example) heat, momentum, water vapour and atmospheric dust(3,6-8) towards the poles. C1 NASA,AMES RES CTR,MOFFETT FIELD,CA 94035. OREGON STATE UNIV,COLL OCEAN & ATMOSPHER SCI,CORVALLIS,OR 97331. SAN JOSE STATE UNIV,DEPT METEOROL,SAN JOSE,CA 95192. STERLING SOFTWARE INC,PALO ALTO,CA 94393. RP Hollingsworth, JL (reprint author), SAN JOSE STATE UNIV FDN,SAN JOSE,CA 95172, USA. NR 26 TC 49 Z9 49 U1 0 U2 4 PU MACMILLAN MAGAZINES LTD PI LONDON PA 4 LITTLE ESSEX STREET, LONDON, ENGLAND WC2R 3LF SN 0028-0836 J9 NATURE JI Nature PD APR 4 PY 1996 VL 380 IS 6573 BP 413 EP 416 DI 10.1038/380413a0 PG 4 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA UD590 UT WOS:A1996UD59000053 ER PT J AU Tegen, I Lacis, AA Fung, I AF Tegen, I Lacis, AA Fung, I TI The influence on climate forcing of mineral aerosols from disturbed soils SO NATURE LA English DT Article ID ATMOSPHERIC DUST AEROSOLS; 3-DIMENSIONAL MODEL; LIGHT-SCATTERING; INDEX AB AEROSOLS influence the global radiation budget(1), and so changes in the atmospheric aerosol load due to either natural causes or human activity will contribute to climate change(2). A large fraction of the mass of tropospheric aerosol is wind-blown mineral dust, and its contribution to radiative forcing can be locally significant(3,22). Model calculations indicate that 50 +/- 20% of the total atmospheric dust mass originates from disturbed soils(4) (those affected by cultivation, deforestation, erosion, and frequent shifts in vegetation due to droughts and rains),Here, using a radiative transfer model embedded in a general circulation model, we find that dust from disturbed soils causes a decrease of the net surface radiation forcing of about 1 W m(-2), accompanied by increased atmospheric heating that may be a significant forcing of atmospheric dynamics. These findings suggest that mineral dust from disturbed soils needs to be included among the climate forcing factors that are influenced by human activities. C1 NASA, GODDARD INST SPACE STUDIES, NEW YORK, NY 10025 USA. UNIV VICTORIA, SCH EARTH & OCEAN SCI, VICTORIA, BC V8W 2Y2, CANADA. RP Tegen, I (reprint author), COLUMBIA UNIV, DEPT APPL PHYS, 2880 BROADWAY, NEW YORK, NY 10025 USA. RI Lacis, Andrew/D-4658-2012 NR 22 TC 590 Z9 622 U1 19 U2 100 PU NATURE PUBLISHING GROUP PI LONDON PA MACMILLAN BUILDING, 4 CRINAN ST, LONDON N1 9XW, ENGLAND SN 0028-0836 J9 NATURE JI Nature PD APR 4 PY 1996 VL 380 IS 6573 BP 419 EP 422 DI 10.1038/380419a0 PG 4 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA UD590 UT WOS:A1996UD59000055 ER PT J AU Bosela, PA Ludwiczak, DR AF Bosela, PA Ludwiczak, DR TI Geometric stiffness effects on data recovery of an idealized mast/blanket model SO COMPUTERS & STRUCTURES LA English DT Article ID SPACE AB The photovoltaic arrays for the international space station consist of a pre-tensioned blanket of solar collectors and a deployable mast. NASA uses the MSC/NASTRAN finite element program for modeling the dynamic response of the structure due to various loading conditions, such as plume impingement during shuttle docking. This finite element program uses the updated stiffness matrix (elastic plus geometric, or initial stress stiffness matrix) in determining the natural frequencies and mode shapes, as well as the dynamic response, of a pre-loaded structure. However, during the data recovery phase, when the moment and shear at the supports, and internal stresses are determined, geometric stiffness effects are neglected, and only the elastic stiffness is used in the calculation. The purpose of this study was to determine whether using the actual displacements, calculated based upon both elastic and geometric stiffness effects, would produce acceptable results in predicting shear and moment if the geometric stiffness effects were later omitted during data recovery. In this study, the PV array was idealized as a cantilever beam with an attached pre-tensioned cable. Static and dynamic analysis were performed, both using and neglecting the geometric stiffness matrix during data recovery. When considering the idealized mast/blanket model, neglecting the geometric stiffness contribution during data recovery led to a 32.2% difference in the vertical (shear) load at the fixed support, and an 8.8% difference in shear at the free end of the beam (compared to the inclusion of geometric stiffness effects in the analysis). The static analysis provided similar results and supported the ''reasonableness'' of the dynamic analysis. Due to the large discrepancies in the predicted stresses which can ocur when geometric stiffness contributions are neglected during data recovery, it should be imperative that when a structure contains pre-loaded elements, the geometric stiffness effects must be fully considered both in the determination of the natural frequencies and mode shapes, as well as in the subsequent calculation of nodal reactions and stresses. C1 NASA,LEWIS RES CTR,DYNAM BRANCH,STRUCT SYST DIV,ENGN DIRECTORATE,CLEVELAND,OH 44135. RP Bosela, PA (reprint author), CLEVELAND STATE UNIV,DEPT ENGN TECHNOL,CLEVELAND,OH 44115, USA. NR 5 TC 0 Z9 0 U1 0 U2 0 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, ENGLAND OX5 1GB SN 0045-7949 J9 COMPUT STRUCT JI Comput. Struct. PD APR 3 PY 1996 VL 59 IS 1 BP 67 EP 79 DI 10.1016/0045-7949(96)00236-2 PG 13 WC Computer Science, Interdisciplinary Applications; Engineering, Civil SC Computer Science; Engineering GA TU232 UT WOS:A1996TU23200007 ER PT J AU Soni, KK LeviSetti, R Shah, S Gentz, S AF Soni, KK LeviSetti, R Shah, S Gentz, S TI SIMS imaging of Al-Li alloy welds SO ADVANCED MATERIALS & PROCESSES LA English DT Article C1 LOCKHEED MARTIN,HUNTSVILLE,AL. NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,HUNTSVILLE,AL 35812. RP Soni, KK (reprint author), UNIV CHICAGO,ENRICO FERMI INST,5640 S ELLIS AVE,CHICAGO,IL 60637, USA. NR 0 TC 4 Z9 4 U1 0 U2 0 PU ASM INTERNATIONAL PI MATERIALS PARK PA SUBSCRIPTIONS SPECIALIST CUSTOMER SERVICE, MATERIALS PARK, OH 44073-0002 SN 0026-0665 J9 ADV MATER PROCESS JI Adv. Mater. Process. PD APR PY 1996 VL 149 IS 4 BP 35 EP 36 PG 2 WC Materials Science, Multidisciplinary SC Materials Science GA UV069 UT WOS:A1996UV06900008 ER PT J AU Ashby, DL AF Ashby, DL TI Effects of lift-enhancing tabs on a two-element airfoil SO AEROSPACE ENGINEERING LA English DT Article RP Ashby, DL (reprint author), NASA,AMES RES CTR,MOFFETT FIELD,CA 94035, USA. NR 0 TC 3 Z9 3 U1 0 U2 0 PU SOC AUTOMOTIVE ENG INC PI WARRENDALE PA 400 COMMONWEALTH DRIVE, WARRENDALE, PA 15096 SN 0736-2536 J9 AEROSPACE ENG JI Aerosp. Eng. PD APR PY 1996 VL 16 IS 4 BP 31 EP 37 PG 7 WC Engineering, Aerospace SC Engineering GA UG192 UT WOS:A1996UG19200016 ER PT J AU Hayder, ME Jayasimha, DN AF Hayder, ME Jayasimha, DN TI Navier-Stokes simulations of jet flows on a network of workstations SO AIAA JOURNAL LA English DT Article AB We study a Navier-Stokes application code on a network of workstations to investigate the computational, communication, and scalability characteristics. This code uses a high-order finite difference scheme to solve for the time-accurate flowfield of a jet using the compressible Navier-Stokes equations. The network of workstations that is used in this study is the Lewis Advanced Cluster Environment (LACE). LACE has 32 nodes connected through various networks-Ethernet, IBM's ALLNODE switch, FDDI, ATM etc. Each node of LACE has an RS6000 processor as its CPU. On the LACE test bed, we study the communication characteristics of different networks and the overheads induced by the PVM message-passing library used for parallelizing the application. We demonstrate that clustering of workstations is effective and has the potential to be computationally competitive with supercomputers at a fraction of the cost. To illustrate this last point, we compare the performance of LACE with the Cray Y-MP. C1 NASA,LEWIS RES CTR,INST COMPUTAT MECH PROP,CLEVELAND,OH 44135. OHIO STATE UNIV,DEPT COMP & INFORMAT SCI,COLUMBUS,OH 43210. NR 16 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 0001-1452 J9 AIAA J JI AIAA J. PD APR PY 1996 VL 34 IS 4 BP 744 EP 749 DI 10.2514/3.13135 PG 6 WC Engineering, Aerospace SC Engineering GA UC611 UT WOS:A1996UC61100013 ER PT J AU Nobari, MRH Tryggvason, G AF Nobari, MRH Tryggvason, G TI Numerical simulations of three-dimensional drop collisions SO AIAA JOURNAL LA English DT Article ID COALESCENCE; FLOWS AB Three-dimensional simulations of the off-axis collisions of two drops are presented. The full Navier-Stokes equations are solved by a front-tracking finite difference method that allows a fully deformable fluid interface and the inclusion of surface tension. Depending on whether the interface between the drops is ruptured or not, the drops either bounce or coalesce For drops that coalesce, the impact parameter, which measures how far the drops are off the symmetry line, determines the eventual outcome of the collision. For small impact parameters the drops coalesce permanently, but for larger impact parameters a grazing collision, where the drops coalesce and then stretch apart again, is observed. The numerically found boundary between coalescing and grazing collisions is compared with experimental observations. C1 NASA, LEWIS RES CTR, INST COMPUTAT MECH PROP, CLEVELAND, OH 44135 USA. RP Nobari, MRH (reprint author), UNIV MICHIGAN, DEPT MECH ENGN, ANN ARBOR, MI 48109 USA. RI Tryggvason, Gretar/H-4445-2011 OI Tryggvason, Gretar/0000-0002-9884-8901 NR 24 TC 40 Z9 42 U1 0 U2 7 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091-4344 USA SN 0001-1452 J9 AIAA J JI AIAA J. PD APR PY 1996 VL 34 IS 4 BP 750 EP 755 DI 10.2514/3.13136 PG 6 WC Engineering, Aerospace SC Engineering GA UC611 UT WOS:A1996UC61100014 ER PT J AU Xu, KM Noor, AK AF Xu, KM Noor, AK TI Three-dimensional analytical solutions for coupled thermoelectroelastic response of multilayered cylindrical shells SO AIAA JOURNAL LA English DT Article ID ACTUATORS AB Analytical three-dimensional solutions are presented for the coupled thermoelectroelastic response of multilayered hybrid composite cylindrical shells. The shells consist of a combination of fiber-reinforced cross-ply and thermoelectroelastic layers. Both the thermoelectroelastic static response and its sensitivity coefficients are evaluated. The sensitivity coefficients measure the sensitivity of the response to variations in the different mechanical, thermal, and piezoelectric material properties of the shells. A linear constitutive model is used, and the material properties are assumed to be independent of the temperature and the electric field. A mixed formulation is used with the fundamental unknowns consisting of the three transverse stress components; the three displacement components; the transverse component of the electric displacement field; the electric potential; the transverse heat-flux component; and the temperature change. Each of the fundamental unknowns is expressed in terms of a double Fourier series in the surface coordinates. A state-space approach is used to generate the static response and to evaluate the sensitivity coefficients. The response and sensitivity coefficients of the shell are obtained by using a modified Frobenius method and a sublayer method. Numerical results are presented showing the effects of variation in the geometric parameters of the shells on the different response quantities and their sensitivity coefficients. C1 NASA,LANGLEY RES CTR,HAMPTON,VA 23681. RP Xu, KM (reprint author), UNIV VIRGINIA,CTR COMPUTAT STRUCT TECHNOL,HAMPTON,VA 23681, USA. NR 21 TC 50 Z9 54 U1 0 U2 2 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 SN 0001-1452 J9 AIAA J JI AIAA J. PD APR PY 1996 VL 34 IS 4 BP 802 EP 812 DI 10.2514/3.13143 PG 11 WC Engineering, Aerospace SC Engineering GA UC611 UT WOS:A1996UC61100021 ER PT J AU LevineWest, M Milman, M Kissil, A AF LevineWest, M Milman, M Kissil, A TI Mode shape expansion techniques for prediction: Experimental evaluation SO AIAA JOURNAL LA English DT Article AB Mode shape expansion techniques fail under four broad categories. Spatial interpolation methods-use geometric information to infer mode shapes at unmeasured locations. Direct methods use the dynamic equations of motion to obtain closed-form solutions to the expanded eigenvectors. These methods can be interpreted as constrained optimization problems. Projection methods use a least-squares formulation that also can be formulated through constrained optimization. Errors methods use a formulation that can account for uncertainties in the measurements and in the prediction. This includes penalty methods and the new expansion techniques based on least-squares minimization techniques with quadratic inequality constraints (LSQI). Some of these expansion techniques are selected herein for evaluation using the full set of experimental data obtained on the microprecision interferometer test bed. Both a pretest and an updated analytical model are considered in the trade study. The robustness of these methods is verified with respect to measurement noise, model deficiency, number of measured degrees of freedom, and accelerometer location. It is shown that the proposed LSQI method has the best performance and can reliably predict mode shapes, even in very adverse situations. C1 CALTECH,JET PROP LAB,AUTOMAT & CONTROL SECT,TECH STAFF,PASADENA,CA 91109. RP LevineWest, M (reprint author), CALTECH,JET PROP LAB,SCI & TECHNOL DEV SECT,4800 OAK GROVE DR,PASADENA,CA 91109, USA. NR 8 TC 18 Z9 21 U1 0 U2 1 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 SN 0001-1452 J9 AIAA J JI AIAA J. PD APR PY 1996 VL 34 IS 4 BP 821 EP 829 DI 10.2514/3.13145 PG 9 WC Engineering, Aerospace SC Engineering GA UC611 UT WOS:A1996UC61100023 ER PT J AU Brown, AM Ferri, AA AF Brown, AM Ferri, AA TI Probabilistic component mode synthesis of nondeterministic substructures SO AIAA JOURNAL LA English DT Article AB Standard methods of structural dynamic analysis assume that the structural characteristics are deterministic. Recognizing that these characteristics are actually statistical in nature, researchers have recently developed a variety of methods that use this information to determine probabilities of a desired response characteristic, such as natural frequency, without using expensive Monte Carlo simulations. One of the problems in these methods is correctly identifying the statistical properties of primitive variables such as geometry, stiffness, and mass. We present a method where the measured dynamic properties of substructures are used instead as the random variables. The residual flexibility method of component mode synthesis is combined with the probabilistic methods to determine the cumulative distribution function of the system eigenvalues. A simple cantilever beam test problem is presented that illustrates the theory. C1 GEORGIA INST TECHNOL,SCH MECH ENGN,ATLANTA,GA 30332. RP Brown, AM (reprint author), NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,STRUCT ANAL DIV,HUNTSVILLE,AL 35812, USA. NR 19 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 0001-1452 J9 AIAA J JI AIAA J. PD APR PY 1996 VL 34 IS 4 BP 830 EP 834 DI 10.2514/3.13146 PG 5 WC Engineering, Aerospace SC Engineering GA UC611 UT WOS:A1996UC61100024 ER PT J AU Huang, PG Bradshaw, P Coakley, TJ AF Huang, PG Bradshaw, P Coakley, TJ TI Reynolds number effects on the prediction of velocity profile in compressible flows - Reply SO AIAA JOURNAL LA English DT Article C1 MCAT INC,SAN JOSE,CA 95127. STANFORD UNIV,DEPT MECH ENGN,STANFORD,CA 94305. RP Huang, PG (reprint author), NASA,AMES RES CTR,M-S 229-1,MOFFETT FIELD,CA 94035, USA. NR 4 TC 0 Z9 0 U1 0 U2 1 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 SN 0001-1452 J9 AIAA J JI AIAA J. PD APR PY 1996 VL 34 IS 4 BP 873 EP 873 DI 10.2514/3.13162 PG 1 WC Engineering, Aerospace SC Engineering GA UC611 UT WOS:A1996UC61100040 ER PT J AU Ferrando, AA Lane, HW Stuart, CA DavisStreet, J Wolfe, RR AF Ferrando, AA Lane, HW Stuart, CA DavisStreet, J Wolfe, RR TI Prolonged bed rest decreases skeletal muscle and whole body protein synthesis SO AMERICAN JOURNAL OF PHYSIOLOGY-ENDOCRINOLOGY AND METABOLISM LA English DT Article DE amino acid transport; hormonal response to bed rest; protein metabolism during simulated microgravity ID RAY ABSORPTIOMETRY DEXA; DORSAL HAND VEIN; CATABOLIC RESPONSE; INVIVO; METABOLISM; HORMONES; KINETICS; SOLEUS; MASS AB We sought to determine the extent to which the loss of lean body mass and nitrogen during inactivity was due to alterations in skeletal muscle protein metabolism. Six male subjects were studied during 7 days of diet stabilization and after 14 days of simulated microgravity (-6 degrees bed rest). Nitrogen balance became more negative (P < 0.03) during the 2nd wk of bed rest. Leg and whole body lean mass decreased after bed rest (P < 0.05). Serum cortisol, insulin, insulin-like growth factor I, and testosterone values did not change. Arteriovenous model calculations based on the infusion of L-[ring-C-13(6)]phenylalanine in five subjects revealed a 50% decrease in muscle protein synthesis (PS; P < 0.03). Fractional PS by tracer incorporation into muscle protein also decreased by 46% (P < 0.05). The decrease in PS was related to a corresponding decrease in the sum of intracellular amino acid appearance from protein breakdown and inward transport. Whole body protein synthesis determined by [N-15]alanine ingestion on six subjects also revealed a 14% decrease (P < 0.01). Neither model-derived nor whole body values for protein breakdown changed significantly. These results indicate that the loss of body protein with inactivity is predominantly due to a decrease in muscle PS and that this decrease is reflected in both whole body and skeletal muscle measures. C1 NASA, LYNDON B JOHNSON SPACE CTR, HOUSTON, TX 77058 USA. UNIV TEXAS, MED BRANCH, DEPT INTERNAL MED, DIV ENDOCRINOL, GALVESTON, TX 77555 USA. RP Ferrando, AA (reprint author), SHRINERS BURNS INST, 815 MARKET ST, GALVESTON, TX 77550 USA. FU NIDDK NIH HHS [DK-33952]; PHS HHS [M01-0073] NR 34 TC 271 Z9 272 U1 1 U2 35 PU AMER PHYSIOLOGICAL SOC PI BETHESDA PA 9650 ROCKVILLE PIKE, BETHESDA, MD 20814 USA SN 0193-1849 J9 AM J PHYSIOL-ENDOC M JI Am. J. Physiol.-Endocrinol. Metab. PD APR PY 1996 VL 270 IS 4 BP E627 EP E633 PG 7 WC Endocrinology & Metabolism; Physiology SC Endocrinology & Metabolism; Physiology GA UE561 UT WOS:A1996UE56100013 PM 8928769 ER PT J AU Biswas, R Flaherty, JE AF Biswas, R Flaherty, JE TI Special issue on adaptive mesh refinement methods for CFD applications - Introduction SO APPLIED NUMERICAL MATHEMATICS LA English DT Editorial Material C1 RENSSELAER POLYTECH INST,DEPT COMP SCI,TROY,NY 12180. RP Biswas, R (reprint author), NASA,AMES RES CTR,RIACS,MAIL STOP T27A-1,MOFFETT FIELD,CA 94035, USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0168-9274 J9 APPL NUMER MATH JI Appl. Numer. Math. PD APR PY 1996 VL 20 IS 4 BP 319 EP 320 DI 10.1016/0168-9274(96)90021-5 PG 2 WC Mathematics, Applied SC Mathematics GA UT823 UT WOS:A1996UT82300001 ER PT J AU Bey, KS Oden, JT Patra, A AF Bey, KS Oden, JT Patra, A TI A parallel hp-adaptive discontinuous Galerkin method for hyperbolic conservation laws SO APPLIED NUMERICAL MATHEMATICS LA English DT Article ID FINITE-ELEMENT METHOD AB This paper describes a parallel adaptive strategy based on discontinuous hp-finite element approximations of linear, scalar, hyperbolic conservation laws. The paper focuses on the development of an effective parallel adaptive strategy for such problems. Numerical experiments suggest that these techniques are highly parallelizable and deliver super-linear rates of convergence, thereby yielding efficiency many times superior to conventional schemes for hyperbolic problems. C1 UNIV TEXAS,TEXAS INST COMPUTAT & APPL MATH,AUSTIN,TX 78712. RP Bey, KS (reprint author), NASA,LANGLEY RES CTR,MAIL STOP 396,HAMPTON,VA 23681, USA. RI Patra, Abani/F-8262-2016 NR 13 TC 31 Z9 32 U1 0 U2 1 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0168-9274 J9 APPL NUMER MATH JI Appl. Numer. Math. PD APR PY 1996 VL 20 IS 4 BP 321 EP 336 DI 10.1016/0168-9274(95)00101-8 PG 16 WC Mathematics, Applied SC Mathematics GA UT823 UT WOS:A1996UT82300002 ER PT J AU Biswas, R Strawn, RC AF Biswas, R Strawn, RC TI Mesh quality control for multiply-refined tetrahedral grids SO APPLIED NUMERICAL MATHEMATICS LA English DT Article ID UNSTRUCTURED MESHES AB A new algorithm for controlling the quality of multiply-refined tetrahedral meshes is presented in this paper. The basic dynamic mesh adaption procedure allows localized grid refinement and coarsening to efficiently capture aerodynamic flow features in computational fluid dynamics problems; however, repeated application of the procedure may significantly deteriorate the quality of the mesh. Results presented show the effectiveness of this mesh quality algorithm and its potential in the area of helicopter aerodynamics and acoustics. C1 NASA,AMES RES CTR,USA,AFDD,MOFFETT FIELD,CA 94035. RP Biswas, R (reprint author), NASA,AMES RES CTR,RIACS,MAIL STOP T27A-1,MOFFETT FIELD,CA 94035, USA. NR 8 TC 4 Z9 4 U1 1 U2 2 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0168-9274 J9 APPL NUMER MATH JI Appl. Numer. Math. PD APR PY 1996 VL 20 IS 4 BP 337 EP 348 DI 10.1016/0168-9274(95)00099-2 PG 12 WC Mathematics, Applied SC Mathematics GA UT823 UT WOS:A1996UT82300003 ER PT J AU Oliger, J Zhu, XL AF Oliger, J Zhu, XL TI Stability and error estimation for component adaptive grid methods SO APPLIED NUMERICAL MATHEMATICS LA English DT Article ID PARTIAL-DIFFERENTIAL EQUATIONS AB Component adaptive grid (GAG) methods for solving hyperbolic partial differential equations (PDEs) are discussed in this paper. Applying recent stability results for a class of numerical methods on uniform grids, the convergence of these methods for linear problems on component adaptive grids is established here. Furthermore, the computational error can be estimated on CAGs using these stability results. Using these estimates, the error can be controlled on CAGs. Thus, the solution can be computed efficiently on CAGs within a given error tolerance. Computational results for time dependent linear problems in one and two space dimensions are presented. C1 NASA,AMES RES CTR,ADV COMP SCI RES INST,MOFFETT FIELD,CA 94035. RP Oliger, J (reprint author), STANFORD UNIV,SCI COMP & COMP MATH PROGRAM,STANFORD,CA 94035, USA. NR 9 TC 5 Z9 5 U1 0 U2 0 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0168-9274 J9 APPL NUMER MATH JI Appl. Numer. Math. PD APR PY 1996 VL 20 IS 4 BP 407 EP 426 DI 10.1016/0168-9274(95)00100-X PG 20 WC Mathematics, Applied SC Mathematics GA UT823 UT WOS:A1996UT82300007 ER PT J AU Mercer, CR Creath, K AF Mercer, CR Creath, K TI Liquid-crystal point-diffraction interferometer for wave-front measurements SO APPLIED OPTICS LA English DT Article DE phase-stepping interferometry; wave-front measurement; common-path interferometer; error reduction; phase-measurement algorithm AB A new instrument, the liquid-crystal point-diffraction interferometer [LCPDI], is developed for the measurement of phase objects. This instrument maintains the compact, robust design of Linnik's point-diffraction interferometer and adds to it a phase-stepping capability for quantitative interferogram analysis. The result is a compact, simple to align, environmentally insensitive interferometer capable of accurately measuring optical wave fronts with very high data density and with automated data reduction. We describe the theory and design of the LCPDI. A focus shift, was measured with the LCPDI, and the results are compared with theoretical results. (C) 1996 Optical Society of America. C1 UNIV ARIZONA,CTR OPT SCI,TUCSON,AZ 85716. RP Mercer, CR (reprint author), NASA,LEWIS RES CTR,CLEVELAND,OH 44135, USA. NR 26 TC 50 Z9 53 U1 1 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 APR 1 PY 1996 VL 35 IS 10 BP 1633 EP 1642 DI 10.1364/AO.35.001633 PG 10 WC Optics SC Optics GA UC179 UT WOS:A1996UC17900008 PM 21085283 ER PT J AU Saha, TT Leviton, DB Glenn, P AF Saha, TT Leviton, DB Glenn, P TI Performance of ion-figured silicon carbide SUMER telescope mirror in the vacuum ultraviolet SO APPLIED OPTICS LA English DT Article DE mirrors; scattering; optical testing; surfaces; vacuum ultraviolet AB Measured and theoretical encircled energy and small-angle scatter of the telescope mirror (SST) of the solar ultraviolet measurements of emitted radiation (SUMER) instrument are compared at the wavelength of 123.6 nm. Mirror performance modeling was accomplished with the Optical Surface Analysis Code software package. The modeling is based on measured mirror-surface figure error data and roughness characteristics covering all important spatial frequencies that affect imaging in the vacuum ultraviolet wavelength region. Mirror-surface errors were measured with a Zygo Mark IV interferometer, Bauer Model 200 Profiler, and WYKO Topo 2-D (two-dimensional) interferometer. Performance of the SST mirror, including encircled energy and small-angle scatter, was also directly measured. A good agreement is found between measured and theoretical encircled energy within 6 arcsec and small-angle scatter up to similar to 50 arcmin from the peak. The 80% encircled energy diameter of the SST mirror is similar to 1.9 arcsec, and the amount of scattered light drops to approximately 1.0 x 10(-10) of peak irradiance (normalized to 1 arcsec(2) in the focal plane) 50 arcmin from the peak. Vacuum ultraviolet performance of the mirror is degraded primarily by midfrequency errors. (C) 1996 Optical Society of America C1 BAUER ASSOC INC,WELLESLEY,MA 02181. RP Saha, TT (reprint author), NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771, USA. NR 21 TC 20 Z9 20 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 APR 1 PY 1996 VL 35 IS 10 BP 1742 EP 1750 DI 10.1364/AO.35.001742 PG 9 WC Optics SC Optics GA UC179 UT WOS:A1996UC17900022 PM 21085297 ER PT J AU Joshi, RP McAdoo, JA AF Joshi, RP McAdoo, JA TI Picosecond dynamic response of nanoscale low-temperature grown GaAs metal-semiconductor-metal photodetectors SO APPLIED PHYSICS LETTERS LA English DT Article ID PHOTODIODES; TRANSPORT; PHONON; BULK AB We have successfully fabricated and tested nanoscale metal-semiconductor-metal (MSM) devices with picosecond temporal response for photomixer applications around 830 nm. Previous reports on nanoscale MSM devices were not at this longer wavelength. The ultrafast response resulted from a low capacitance of about 1 fF, the use of low-temperature grown (LT)-GaAs active layers, and ultrashort finger separations. A two-dimensional (2D) Monte Carlo model provided very accurate predictions of the transient MSM response. Values of the full width at half-maxima photocurrents for the 50 and 100 nm devices were found to be 1.4 and 2 ps, respectively, in keeping with experimental observations. (C) 1996 American Institute of Physics. C1 NASA,LANGLEY RES CTR,DIV AEROSP ELECT SYST,ELECTROOPT BRANCH,HAMPTON,VA 23681. RP Joshi, RP (reprint author), OLD DOMINION UNIV,DEPT ELECT & COMP ENGN,NORFOLK,VA 23529, USA. NR 20 TC 10 Z9 10 U1 0 U2 1 PU AMER INST PHYSICS PI WOODBURY PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 SN 0003-6951 J9 APPL PHYS LETT JI Appl. Phys. Lett. PD APR 1 PY 1996 VL 68 IS 14 BP 1972 EP 1974 DI 10.1063/1.115643 PG 3 WC Physics, Applied SC Physics GA UC483 UT WOS:A1996UC48300031 ER PT J AU Krainsky, IL Mearini, GT Asnin, VM Sun, H Foygel, M Petukhov, AG AF Krainsky, IL Mearini, GT Asnin, VM Sun, H Foygel, M Petukhov, AG TI Auger electron spectroscopy of the hydrogen terminated chemical vapor deposited diamond surface SO APPLIED PHYSICS LETTERS LA English DT Article AB A simultaneous study of Auger spectra and secondary electron emission from the chemical vapor deposited diamond films under extended electron beam exposure is presented. Up to a 1.2 eV increase in energy of the carbon Auger peak accompanied by the decrease of the total secondary electron yield has been found. Exposure to hydrogen has resulted in recovery of the both Auger peak position and secondary yield. First-principles electronic structure calculations have shown that the effect is due to a change in the surface upper-valence band local density of states of the diamond crystal which is dependent on the extent of hydrogen coverage of the surface. (C) 1996 American Institute of Physics. C1 S DAKOTA SCH MINES & TECHNOL, DEPT PHYS, RAPID CITY, SD 57701 USA. RP Krainsky, IL (reprint author), NASA, LEWIS RES CTR, CLEVELAND, OH 44135 USA. NR 20 TC 5 Z9 5 U1 0 U2 1 PU AMER INST PHYSICS PI MELVILLE PA CIRCULATION & FULFILLMENT DIV, 2 HUNTINGTON QUADRANGLE, STE 1 N O 1, MELVILLE, NY 11747-4501 USA SN 0003-6951 EI 1077-3118 J9 APPL PHYS LETT JI Appl. Phys. Lett. PD APR 1 PY 1996 VL 68 IS 14 BP 2017 EP 2019 DI 10.1063/1.115623 PG 3 WC Physics, Applied SC Physics GA UC483 UT WOS:A1996UC48300046 ER PT J AU Hiatt, JR Shabot, MM Phillips, EH Haines, RF Grant, TL AF Hiatt, JR Shabot, MM Phillips, EH Haines, RF Grant, TL TI Telesurgery - Acceptability of compressed video for remote surgical proctoring SO ARCHIVES OF SURGERY LA English DT Article AB Objective: To determine the clinical acceptability of various levels of video compression for remote proctoring of laparoscopic surgical procedures. Design: Observational, controlled study. Setting: Community-based teaching hospital. Participants: Physician and nurse observers. Interventions: Controlled surgical video scenes were subjected to various levels of data compression for digital transmission and display and shown to participant observers. Main Outcome Measures: Clinical acceptability of video scenes after application of video compression. Results: Clinically acceptable video compression was achieved with a 1.25-megabit/second data rate, with the use of odd-screen 43.3:1 Joint Photographic Expert Group compression and a small screen for remote viewing. Conclusion: With proper video compression, remote proctoring of laparoscopic procedures may be performed with standard 1.5-megabit/second telecommunication data lines and services. C1 UNIV CALIF LOS ANGELES,SCH MED,DEPT SURG,LOS ANGELES,CA 90024. NASA,AMES RES CTR,RECOM TECHNOL INC,MOFFETT FIELD,CA 94035. NASA,AMES RES CTR,COMPUTAT SCI DIV,MOFFETT FIELD,CA 94035. RP Hiatt, JR (reprint author), CEDARS SINAI MED CTR,DEPT SURG,DIV GEN SURG,CEDARS SINAI RES INST,SUITE 8215,8700 BEVERLY BLVD,LOS ANGELES,CA 90048, USA. NR 7 TC 16 Z9 16 U1 2 U2 3 PU AMER MEDICAL ASSOC PI CHICAGO PA 515 N STATE ST, CHICAGO, IL 60610 SN 0004-0010 J9 ARCH SURG-CHICAGO JI Arch. Surg. PD APR PY 1996 VL 131 IS 4 BP 396 EP 400 PG 5 WC Surgery SC Surgery GA UD953 UT WOS:A1996UD95300014 PM 8615725 ER PT J AU Schlegel, EM AF Schlegel, EM TI On the early spectroscopic distinction of Type II supernovae SO ASTRONOMICAL JOURNAL LA English DT Article ID LIGHT CURVES; PHOTOMETRIC-OBSERVATIONS; PLATEAU STAGE; NOVA 1979C; MODEL; DISTANCE; SPECTRUM; SN-1987A; RADIO AB This paper considers the possible spectroscopic differences between two subtypes of Type II supernovae (those supernovae with hydrogen in their spectral: the Linears (II-L), which show a linear decline in their light curves, and the Plateaus (II-P), which show a plateau phase in their light curve. The early phases of evolution of the two supernovae are described as well as clues from the literature that indicate, usually indirectly, the physical nature of the spectroscopic differences. A hypothesis is suggested that the early spectroscopic differences at Ha are the spectroscopic differences between these two subtypes, and that the lack of a strong P Cyg profile at Ha predicts a linear light curve. (C) 1996 American Astronomical Society. C1 NASA, GSFC, GREENBELT, MD 20771 USA. NR 55 TC 32 Z9 32 U1 0 U2 0 PU IOP PUBLISHING LTD PI BRISTOL PA DIRAC HOUSE, TEMPLE BACK, BRISTOL BS1 6BE, ENGLAND SN 0004-6256 J9 ASTRON J JI Astron. J. PD APR PY 1996 VL 111 IS 4 BP 1660 EP 1667 DI 10.1086/117905 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA UB962 UT WOS:A1996UB96200018 ER PT J AU Ofman, L Mouradian, Z AF Ofman, L Mouradian, Z TI Are thermal sudden disappearances of prominences driven by resonant absorption of Alfven waves? SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE Sun, prominences; waves; Sun, oscillations; magnetohydrodynamics ID SURFACE-WAVES; OSCILLATION; MODES AB In the present study we propose the resonant absorption of Alfven waves as the heating mechanism that leads to thermal sudden disappearances (DBt) of prominences. The physical parameters of prominence flux tubes are used with the low-beta, linearized, resistive magnetohydrodynamic (MHD) model to calculate the heating times of prominences for a range of wavenumbers. The heating time dependence on the wavenumbers is compared to the measured times for DBt of quiescent prominences and a qualitative agreement is found. We find that present observational evidence is in qualitative agreement with the predictions of the resonant absorption heating mechanism for DBt of prominences. However, more observations of DBt are required to establish the heating mechanism with a higher degree of certainty. C1 NASA, GODDARD SPACE FLIGHT CTR, ASTRON & SOLAR PHYS LAB, GREENBELT, MD 20771 USA. OBSERV PARIS, DASOP, CNRS URA 326, F-92195 MEUDON, FRANCE. RP Ofman, L (reprint author), NASA, GODDARD SPACE FLIGHT CTR, HUGHES STX, GREENBELT, MD 20771 USA. NR 29 TC 11 Z9 11 U1 0 U2 0 PU EDP SCIENCES S A PI LES ULIS CEDEX A PA 17, AVE DU HOGGAR, PA COURTABOEUF, BP 112, F-91944 LES ULIS CEDEX A, FRANCE SN 1432-0746 J9 ASTRON ASTROPHYS JI Astron. Astrophys. PD APR PY 1996 VL 308 IS 2 BP 631 EP 636 PG 6 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA UE747 UT WOS:A1996UE74700036 ER PT J AU HarraMurnion, LK Phillips, KJH Lemen, JR Zarro, DM Greer, CJ Foster, VJ Barnsley, R Coffey, IH Dubau, J Keenan, FP Fludra, A RachlewKallne, E Watanabe, T Wilson, M AF HarraMurnion, LK Phillips, KJH Lemen, JR Zarro, DM Greer, CJ Foster, VJ Barnsley, R Coffey, IH Dubau, J Keenan, FP Fludra, A RachlewKallne, E Watanabe, T Wilson, M TI Helium like sulphur X-ray emission in solar flares and laboratory plasmas SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE atomic data; x-rays, general; sun, flares, x-rays ID DIELECTRONIC SATELLITE SPECTRA; BRAGG CRYSTAL SPECTROMETER; LINE RATIOS; HE-LIKE; RESONANCE LINE; JET TOKAMAK; IONS; EXCITATION; CALCIUM; NICKEL AB Theoretical X-ray spectra of He-like sulphur (S XV) derived from the General Relativistic Atomic Structure Package, the Dirac R-matrix code and other calculations are compared to laboratory spectra obtained from the Alcator C tokamak and JET, and solar flare spectra obtained from the Yohkoh Bragg Crystal Spectrometer (BCS) and with the SMM Flat Crystal Spectrometer. The spectra depend on electron temperature and electron density for plasma densities greater than 10(14) cm(-3). The fits of the derived synthetic spectra to the laboratory spectra at measured density and temperature are in fair agreement. Very good agreement can be achieved with the solar flare spectra, which are in general consistent with the S XV low-density limit, by adjusting temperature. Thus, S XV line spectra can be used to determine the temperatures of relatively weak flares for which diagnostics from higher-temperature ions are unavailable. Using the synthetic spectra, a search for density effects in Yohkoh BCS data at the time of compact flares was made. None was found, so that it can be deduced that for such flares the electron density is less than 10(14) cm(-3). Density estimates are made from emission measures and image sizes using Yohkoh Soft X-ray Telescope data. Research has been carried out with the results of laboratory spectra which indicate a variation of the I(x)lI(y) line intensity ratio across the tokamak minor radius. We have studied various flares which occur at different locations across the solar disk to determine if the same effect exists on the Sun. C1 RUTHERFORD APPLETON LAB, DIV ASTROPHYS, DIDCOT OX11 0QX, OXON, ENGLAND. LOCKHEED PALO ALTO RES LABS, PALO ALTO, CA 94304 USA. NASA, GODDARD SPACE FLIGHT CTR, APPL RES CORP CODE 680, GREENBELT, MD 20771 USA. QUEENS UNIV BELFAST, DEPT PHYS, BELFAST BT7 1NN, ANTRIM, NORTH IRELAND. JET JOINT UNDERTAKING, ABINGDON OX14 3EA, OXON, ENGLAND. OBSERV PARIS, DARC, UPR 176, CNRS, F-92195 MEUDON, FRANCE. ROYAL INST TECHNOL, DEPT PHYS 1, S-10044 STOCKHOLM, SWEDEN. NATL ASTRON OBSERV, MITAKA, TOKYO 181, JAPAN. UNIV LONDON ROYAL HOLLOWAY & BEDFORD NEW COLL, DEPT PHYS, EGHAM TW20 0EX, SURREY, ENGLAND. RP HarraMurnion, LK (reprint author), UNIV BIRMINGHAM, SCH PHYS & SPACE RES, BIRMINGHAM B15 2TT, W MIDLANDS, ENGLAND. OI Harra, Louise/0000-0001-9457-6200 NR 58 TC 11 Z9 11 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 APR PY 1996 VL 308 IS 2 BP 670 EP 684 PG 15 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA UE747 UT WOS:A1996UE74700041 ER PT J AU Schmieder, B Rovira, M Simnett, GM Fontenla, JM TandbergHanssen, E AF Schmieder, B Rovira, M Simnett, GM Fontenla, JM TandbergHanssen, E TI Subflares and surges in AR 2744 during the Solar Maximum Mission SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE Sun, activity; flares; X-rays ID MAGNETIC RECONNECTION; TRANSITION REGION; FLARING ARCHES; FLARES; LINES; FLUX AB Active region NOAA 2744, which was at S25, had its central meridian passage on Oct 23 1980 and was relatively quiet according to H alpha, UV and X-ray observations made by the Solar Maximum Mission (SMM), The region was also observed by the Marshall Space Flight Center (MSFC) vector magnetograph. During its disk passage only subflares and surges were detected. Their locations appeared to be governed by the magnetic topology. On October 21 a miniflare occurred close to the separator between the two main sunspots. On October 22 the emergence of a small region of parasitic polarity in the existing magnetic field appeared to be responsible for three subflares and subsequent surges. We discuss the energy budget for plasmas at temperatures in the 10(4) K, 10(5) K and 10(6) K ranges in the context of surge-trigger mechanisms. On October 21 the energy deposition driving the surges did not produce a high temperature plasma. By October 22 the active region had evolved and the surges were now associated with some high temperature plasma. However, the energy radiated at transition region temperatures would be larger than that estimated in X-rays depending on the dilution factor. This would imply a continuous influx of energy in order to sustain the long duration surge (30 min) rather than a simple, impulsive energy input. If the electron density in the 10(4)-10(5) K plasma is taken as similar to 10(12) cm(-3) the diameter of individual surge loops should only be similar to 40 km. The relevance of our results to (a) reconnection and (b) gradient pressure driven models for surges is discussed. C1 INST ASTRON & FIS ESPACIO, RA-1428 BUENOS AIRES, DF, ARGENTINA. UNIV BIRMINGHAM, BIRMINGHAM B15 2TT, W MIDLANDS, ENGLAND. NCAR, HAO, BOULDER, CO 80027 USA. NASA, GEORGE C MARSHALL SPACE FLIGHT CTR, DIV SPACE SCI, HUNTSVILLE, AL 35812 USA. RP Schmieder, B (reprint author), OBSERV PARIS, MEUDON SECT, URA 326, F-92195 MEUDON, FRANCE. NR 25 TC 12 Z9 12 U1 0 U2 0 PU EDP SCIENCES S A PI LES ULIS CEDEX A PA 17, AVE DU HOGGAR, PA COURTABOEUF, BP 112, F-91944 LES ULIS CEDEX A, FRANCE SN 0004-6361 J9 ASTRON ASTROPHYS JI Astron. Astrophys. PD APR PY 1996 VL 308 IS 3 BP 957 EP 969 PG 13 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA UG914 UT WOS:A1996UG91400031 ER PT J AU Walter, HG Sovers, OJ AF Walter, HG Sovers, OJ TI Precession and nutation from the analysis of positions of extragalactic radio sources SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE astrometry; reference systems ID BASE-LINE INTERFEROMETRY; REFERENCE FRAME AB Corrections to the Earth's precession and nutation have been derived from VLBI observations of extragalactic sources carried out by JPL's Deep Space Network between 1978 and 1994. The analysis is based on the source right ascensions and declinations given in annual position catalogues referring to the J2000.0 equator and equinox. These catalogues result from the reduction of the VLBI observables by adopting the 1976 IAU convention on precession and one of the following nutation models: 1980 IAU Theory of Nutation, ZMOA 1990-2 and KSNRE. Differences of the J2000.0 positions of a source obtained at different epochs suggest the presence of imperfections in the precession and nutation terms. In contrast to the commonly practiced direct solutions, corrections to the luni-solar precession and the 18.6 yr nutations in longitude and obliquity are determined by a least squares fit to the differences of positions of individual sources at different epochs. Using the 1980 IAU and KSNRE models gives sizable, largely similar corrections. The ZMOA 1990-2 model, on the other hand, is characterized by small corrections to the nutation terms. Each of the three data sets associated with one of the nutation models provides a solution in right ascension (RA) as well as in declination (Dec). The Dec solution is self-sufficient, whereas the RA solution requires some a priori knowledge of the precession and nutation quantities that are to be determined. The self-sufficient declination solutions for the 1980 IAU, the ZMOA 1990-2 and the KSNRE models yield almost identical corrections of the luni-solar precession, which are in turn -3.1 +/- 0.2 mas yr(-1), -3.1 +/- 0.1 mas yr(-1) and -3.3 +/- 0.2 mas yr(-1). For the 18.6 yr nutations in longitude and obliquity the IAU and KSNRE models yield -5.4 +/- 1.1 mas, 3.8 +/- 0.3 mas and -6.7 +/- 0.8 mas, 3.3 +/- 0.1 mas, while the ZMOA model gives 0.0 +/- 0.4 mas and 0.5 +/- 0.2 mas, respectively. C1 CALTECH, JET PROP LAB, PASADENA, CA 91109 USA. RP Walter, HG (reprint author), ASTRON RECH INST, MONCHHOFSTR 12-14, D-69120 HEIDELBERG, GERMANY. NR 20 TC 3 Z9 3 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 APR PY 1996 VL 308 IS 3 BP 1001 EP 1008 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA UG914 UT WOS:A1996UG91400036 ER PT J AU Davis, DS Mulchaey, JS Mushotzky, RF Burstein, D AF Davis, DS Mulchaey, JS Mushotzky, RF Burstein, D TI Spectral and spatial analysis of the intragroup medium in the NGC 2300 group SO ASTROPHYSICAL JOURNAL LA English DT Article DE diffuse radiation; galaxies, clusters, individual (NGC 2300); intergalactic medium; X-rays, galaxies ID X-RAY-EMISSION; DARK MATTER; ELLIPTIC GALAXIES; SHELL GALAXIES; COMA CLUSTER; POTENTIALS; MASS AB We report the results of spectral and spatial analysis of three overlapping ROSAT PSPC observations of the NGC 2300 group. Spatial analysis of the co-added fields reveals that the diffuse X-ray gas can be traced to at least 25' (0.33 Mpc, H-0 = 50 km s(-1) Mpc(-1)). The surface brightness of the gas is well fitted with an isothermal King model with a core radius of 4'.28(-0.93)(+1.27) (56.5(-12.3)(+16.8) kpc) and a beta of 0.410(-0.021)(+0.027) The temperature of the gas, as determined from fitting a Raymond-Smith plasma model to the spectral data, is 0.971(-0.08)(+0.11)keV. The additional exposure time obtained allows three different annuli to be fitted. Fitting these different regions constrains any temperature gradient to be less than similar to 0.2 keV. The abundance determined from the X-ray spectrum is also low-less than 0.11 solar. The mass of gas within 0.33 Mpc is 1.25 x 10(12) M., and if the gas is in hydrostatic equilibrium with the potential the total mass within this radius is 1.47 x 10(13) M.. Comparing the mass of the galaxies plus the mass of hot gas to the total mass of the system yields an observed baryonic fraction of 10%-16%. This value is higher than our original analysis, where the form of the gas density profile was fixed at an assumed value. We also discuss the abundance of the diffuse gas and how the evolution of the elliptical galaxy is expected to affect the gas. C1 CARNEGIE INST WASHINGTON OBSERV, PASADENA, CA 91101 USA. NASA, GODDARD SPACE FLIGHT CTR, HIGH ENERGY ASTROPHYS LAB, GREENBELT, MD 20771 USA. ARIZONA STATE UNIV, DEPT PHYS & ASTRON, TEMPE, AZ 85287 USA. RP Davis, DS (reprint author), UNIV ALABAMA, DEPT PHYS & ASTRON, 206 GALLALEE HALL, TUSCALOOSA, AL 35487 USA. NR 38 TC 31 Z9 31 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 APR 1 PY 1996 VL 460 IS 2 BP 601 EP 611 DI 10.1086/176995 PN 1 PG 11 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA UB530 UT WOS:A1996UB53000005 ER PT J AU deJager, OC Harding, AK Strickman, MS AF deJager, OC Harding, AK Strickman, MS TI OSSE detection of gamma rays from the Vela synchrotron nebula SO ASTROPHYSICAL JOURNAL LA English DT Article DE gamma rays, observations; ISM, individual (Gum Nebula); ISM, magnetic fields; pulsars, individual (PSR BO833-45); supernova remnants ID PULSAR AB We report on the detection of low-energy gamma-rays from the Vela supernova remnant at the similar to 9 a level with the Oriented Scintillation Spectrometer Experiment (OSSE) instrument on the Compton Gamma Ray Observatory (CGRO). The source exhibits a hard spectrum consistent with a power law of index -1.6 +/- 0.5 in the energy range 0.061 MeV to similar to 0.4 MeV. Contamination by the galactic plane and other sources was found to be insignificant. This spectrum is quite consistent with an extrapolation of the similar to(-1.7) spectrum of the 1' radius compact nebula as seen between optical and 25 keV with imaging instruments. No spectral break is seen between similar to 1 eV and 0.4 MeV, but several arguments indicate that this spectrum should cut off below 40 MeV. The extension of the nebular synchrotron emission to an energy of at least 0.4 MeV implies electron energies up to greater than or similar to 3 x 10(14) eV, which is a factor 10 below the maximum acceleration energy of 3.5 x 10(15) eV set by the polar cap vacuum potential. Imaging and spectral observations indicate that the energy in particles and magnetic field are close to equipartition in the compact nebula, with a mean field strength of similar to 6 x 10(-5) G. Even though only similar to 0.1% of the spin-down power is radiated as synchrotron photons, the inferred particle pressure in the compact nebula is about half the pulsar ram pressure L/4 pi r(2)c in the compact nebula. The relatively weak field allows electrons to escape to relatively large distances from the pulsar, which may explain why the synchrotron nebula is extended by several degrees. C1 NASA, GODDARD SPACE FLIGHT CTR, HIGH ENERGY ASTROPHYS LAB, GREENBELT, MD 20771 USA. USN, RES LAB, DIV SPACE SCI, WASHINGTON, DC 20375 USA. RP deJager, OC (reprint author), POTCHEFSTROOM UNIV CHRISTIAN HIGHER EDUC, DEPT PHYS, SPACE RES UNIT, POTCHEFSTROOM 2520, SOUTH AFRICA. RI Harding, Alice/D-3160-2012 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 APR 1 PY 1996 VL 460 IS 2 BP 729 EP 734 DI 10.1086/177005 PN 1 PG 6 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA UB530 UT WOS:A1996UB53000015 ER PT J AU Cassinelli, JP Cohen, DH MacFarlane, JJ Drew, JE LynasGray, AE Hubeny, I Vallerga, JV Welsh, BY Hoare, MG AF Cassinelli, JP Cohen, DH MacFarlane, JJ Drew, JE LynasGray, AE Hubeny, I Vallerga, JV Welsh, BY Hoare, MG TI EUVE spectroscopy of beta Canis majoris (B1 II-III) from 500 angstrom to 700 angstrom SO ASTROPHYSICAL JOURNAL LA English DT Article DE ISM, abundances; line, identification; stars, early-type; stars, individual (beta Canis Majoris); stars, oscillations; ultraviolet, stars ID MODEL STELLAR ATMOSPHERES; EFFECTIVE TEMPERATURES; STANDARD STARS; LINE; OPACITIES; WINDS; SIGHT AB Observations of the bright variable star beta CMa (B1 II-III) made with the Extreme Ultraviolet Explorer (EUVE) are presented, We report on the continuous energy distribution, photospheric line identification, and the variability of the star, as well as the physical implications for the structure of the local interstellar medium. The star is one of the strongest EUV sources in the long-wavelength spectrometer of EUVE, and one of only two early-type stars whose photospheric continuum was detected by the EUVE spectrometers. This paper is primarily concerned with the portion of the spectrum that lies between the neutral helium ionization edge at 504 Angstrom and an effective cutoff by interstellar absorption near 700 Angstrom. As in our EUV analysis of the B2 II star epsilon CMa, we found that line-blanketed model atmospheres are not capable of predicting an energy distribution which matches observations in all wavelength regions. Consequently, we derived two set of basic parameters for the star (T-eff = 24,800 K, log g = 3.7; and T-eff = 23,250 K, log g = 3.5), depending whether we accept the measured angular diameter, or require an exact agreement between models and the observed visual flux. For the higher T-eff model, the predicted EUV flux is in agreement with observations, while for the lower T-eff the star's EUV continuum is about 5 times brighter than the predictions. In either case, the star does not show the order of magnitude EUV excess that was seen in epsilon CMa. Neither model fits the data near 2200 Angstrom, and additional photospheric opacity is proposed. The EUVE data also provide information concerning the low-density interstellar medium in the direction of beta CMa. We derive a neutral hydrogen column density of similar to 2 x 10(18) cm(-2) and estimate a fewer limit for the neutral helium column density of 1.4 x 10(18) cm(-2). This indicates that along this sight line much of the hydrogen is ionized while the helium is neutral, The EUVE spectrum shows many strong photospheric absorption features, similar to that of epsilon CMa. Evidence for a stellar wind is seen in the O v 630 Angstrom absorption feature. There is special interest in beta CMa because it is among the brightest of the beta Cephei class of variables, The pulsations in this class of star manifest themselves primarily as periodic effective temperature changes. We find that the semiamplitude of the change is 108(-32)(+31) K for the primary period. This result is consistent with that derived from an analysis of the UV continuum by Beeckmans & Burger (1977), but our 68% confidence limits are significantly smaller than their 1 sigma error bars, The general agreement implies that the pulsations do propagate between the layers where the optical and UV continua are formed and the layers where the EUV continuum forms, which is about six density scale heights higher in static models. The possibility that some pulsational energy deposition could occur within the outer photosphere is discussed. Our observations, taken over two time intervals separated by 70 days, resulted in the detection of the beat phenomenon owing to the three oscillation periods of beta CMa. C1 UNIV WISCONSIN, FUS TECHNOL INST, MADISON, WI 53706 USA. UNIV OXFORD, DEPT ASTROPHYS, OXFORD OX1 3RH, ENGLAND. NASA, GODDARD SPACE FLIGHT CTR, GREENBELT, MD 20771 USA. EUREKA SCI, OAKLAND, CA 94602 USA. UNIV CALIF BERKELEY, SPACE SCI LAB, BERKELEY, CA 94720 USA. MAX PLANCK INST ASTRON, D-69117 HEIDELBERG, GERMANY. RP Cassinelli, JP (reprint author), UNIV WISCONSIN, DEPT ASTRON, 475 N CHARTER ST, MADISON, WI 53706 USA. NR 50 TC 43 Z9 43 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 APR 1 PY 1996 VL 460 IS 2 BP 949 EP 963 DI 10.1086/177023 PN 1 PG 15 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA UB530 UT WOS:A1996UB53000033 ER PT J AU Hathaway, DH AF Hathaway, DH TI Doppler measurements of the sun's meridional flow SO ASTROPHYSICAL JOURNAL LA English DT Article DE hydrodynamics; sun, activity; sun, interior; sun, oscillations ID SOLAR DIFFERENTIAL ROTATION; SPHERICAL HARMONIC-ANALYSIS; STEADY PHOTOSPHERIC FLOWS; MOUNT-WILSON; LIMB-SHIFT; MOTIONS; LINES; CIRCULATION; VELOCITY; FIELDS AB Doppler velocity data obtained with the Global Oscillation Network Group (GONG) instruments in Tucson from 1992 August through 1995 April were analyzed to determine the structure and evolution of the Sun's meridional flow. Individual measurements of the flow were derived from line-of-sight velocity images averaged over 17 minutes to remove the p-mode oscillation signal. Typical flow velocities are poleward at similar to 20 m s(-1), but the results suggest that episodes may occur with much stronger flows. Such variations may help to explain some of the many disparate reports on the strength and structure of the Sun's meridional flow. RP Hathaway, DH (reprint author), NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,MAIL CODE ES82,HUNTSVILLE,AL 35812, USA. NR 30 TC 132 Z9 133 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 APR 1 PY 1996 VL 460 IS 2 BP 1027 EP 1033 DI 10.1086/177029 PN 1 PG 7 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA UB530 UT WOS:A1996UB53000039 ER PT J AU Feldman, U Doschek, GA Behring, WE Phillips, KJH AF Feldman, U Doschek, GA Behring, WE Phillips, KJH TI Electron temperature, emission measure, and X-ray flux in A2 to X2 X-ray class solar flares SO ASTROPHYSICAL JOURNAL LA English DT Article DE sun, flares; sun, X-rays ID DIELECTRONIC SATELLITE SPECTRA; HELIUM-LIKE IONS; ELEMENTAL ABUNDANCES; IRON; LINES AB In this paper we present a statistical analysis of soft X-ray flare class and emission measure as a function of electron temperature determined for the time of maximum flare X-ray flux. The study includes 868 flares of X-ray class A2 to X2. Our work shows that their properties are very different, although large and small flares as seen by the 1-8 Angstrom detector aboard the Geostationary! Operational Environmental Satellite (GOES) records have similar appearances. The peak temperature of intense (major) flares is much higher than the peak temperature of weak (minor) flares. This finding has important implications on the nature of the flare-heating mechanism. For example, if a flare is a collection of elementary bursts, the plasma properties of the elementary-bursts occurring during peak emission of large flares and small flares must be different. Using the relationship between electron temperature and emission measure in solar flares, we provide an estimate of the electron temperature during the peak emission of large stellar flares. C1 NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. RUTHERFORD APPLETON LAB,DIV ASTROPHYS,DIDCOT OX11 0QX,OXON,ENGLAND. RP Feldman, U (reprint author), USN,RES LAB,EO HULBURT CTR SPACE RES,CODE 7608,WASHINGTON,DC 20375, USA. NR 18 TC 74 Z9 74 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 APR 1 PY 1996 VL 460 IS 2 BP 1034 EP 1041 DI 10.1086/177030 PN 1 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA UB530 UT WOS:A1996UB53000040 ER PT J AU Joblin, C Tielens, AGGM Geballe, TR Wooden, DH AF Joblin, C Tielens, AGGM Geballe, TR Wooden, DH TI Variations of the 8.6 and 11.3 mu m emission bands within NGC 1333: Evidence for polycyclic aromatic hydrocarbon cations SO ASTROPHYSICAL JOURNAL LA English DT Article DE dust, extinction; infrared, ISM, lines and bands; ISM, individual (NGC 1333); reflection nebulae ID CARBONACEOUS COMPOSITE QCC; IRAS SOURCES; INFRARED-SPECTRUM; PAH MOLECULES; FEATURES; IONIZATION; IDENTIFICATION; HD-44179; MODEL; DISK AB We have obtained 8-13 mu m spectra of three positions in the IR reflection nebula associated with SVS 3 in NGC 1333. These observations reveal systematic variations in the relative intensities of the IR emission features at 8.6 mu m and 11.3 mu m. In particular, the [8.6]/[11.3] ratio is highest at the position of the exciting star and decreases with increasing angular distance from the star. We attribute these variations to changes in the relative populations of ionized and neutral polycyclic aromatic hydrocarbons (PAHs), driven by the strong far-ultraviolet radiation field near the star. From experiments and quantum chemical theoretical studies, the intrinsic strength of these two bands is known to vary with the charge state of the emitting PAH. We have developed a simple model for the relative intensity of the 8.6 and 11.3 mu m bands taking the charge state of the carrier into account. This model is in good agreement with the data. We point out several observational and experimental tests of this model. C1 NASA, AMES RES CTR, MOFFETT FIELD, CA 94035 USA. JOINT ASTRON CTR, HILO, HI 96720 USA. NR 37 TC 86 Z9 86 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 APR 1 PY 1996 VL 460 IS 2 BP L119 EP L122 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA UB531 UT WOS:A1996UB53100010 ER PT J AU Lu, NY Hoffman, GL Salpeter, EE Houck, JR AF Lu, NY Hoffman, GL Salpeter, EE Houck, JR TI Radio properties and optical identification of two samples of Millijansky radio sources at 1.4 GHz SO ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES LA English DT Article DE galaxies, distances and redshifts; galaxies, photometry; galaxies, structure radio continuum, galaxies; surveys ID GUIDE STAR CATALOG; HIGH-REDSHIFT; CLUSTER ENVIRONMENTS; GALAXY CLUSTERS; 408 MHZ; 1-JY; LUMINOSITY; PHOTOMETRY; POWERFUL; MORPHOLOGIES AB From the 1.4 GHz radio survey of Condon, Dickey, & Salpeter in a region much devoid of rich galaxy clusters at redshifts z less than or similar to 0.4, we selected a ''distant'' sample of 57 radio sources complete to a 1.4 GHz nux density of 35 mJy and a ''nearby'' sample of 36 mostly weaker radio sources which are optically brighter than B similar to 19 mag. Our ultimate goals are( 1) to study the radio, optical, and near-IR properties of those high-redshift(z similar to I), moderate-power radio sources in the distant sample and to compare them with that of more powerful radio sources, and (2) to make a comparison of primarily noncluster radio sources in the nearby sample with a companion survey of radio sources in a pair of rich superclusters at z similar to 0.1. In this first paper of a series, we report our new C-array VLA continuum snapshots at 4.86 GHz and optical R-band CCD imaging photometry for these two samples and tabulate the observational results on individual sources. Some direct sample statistical properties are also discussed in the paper and summarized as follows: (1) The distant sample: (a) the sample median flux density at 1.4 GHz is about 65 mJy. (b) The majority (80%) of the sample sources have a steep spectrum between 1.4 and 4.86 GHz with a spectral index around 0.9. Nineteen (90%) of the 21 sources that are fully resolved at 4.86 GHz (i.e., angular sizes theta greater than or similar to 11 '') have a radio morphology of Fanaroff-Riley (FR) II type. (c) Thirty-seven ( 88%) of the 42 optically imaged sample sources were optically identified to a limiting R-band magnitude of R similar to 23.5 mag. About 15% of the identified radio sources appear to be point sources, and the others are extended galaxies with an appearance similar to nearby elliptical galaxies. (d) Twenty-eight (76%) of the optically identified sources have R > 20 mag, suggesting that these are probably distant (z greater than or similar to 0.8), with a redshift distribution peaking at z similar to 1, where their radio luminosities are about 10 times the break power between the FR I and II classes. (e) We found no strong evidence for the radio and optical axes of the resolved radio sources (i.e., a greater than or similar to 5 '') to be correlated or anticorrelated, nor any evidence for strong clustering around sample radio sources on average. (2) The nearby sample: except for R less than or similar to 15, the sample is dominated by elliptical galaxies with 16 less than or similar to R < 18.5 mag and a spectral index distribution similar to that of the distant sample. Based on the radial distribution of optical objects around each radio source, we found that the average radio source environment becomes richer from that characteristic of galaxy groups for R < 17 mag (z less than or similar to 0.2) to that of galaxy groups to clusters at R greater than or similar to 18 mag(z greater than or similar to 0.3). C1 LAFAYETTE COLL,DEPT PHYS,EASTON,PA 18042. CORNELL UNIV,ITHACA,NY 14853. RP Lu, NY (reprint author), CALTECH,JET PROP LAB,CTR INFRARED PROC & ANAL,MS 100-22,PASADENA,CA 91125, USA. NR 54 TC 5 Z9 5 U1 0 U2 1 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637 SN 0067-0049 J9 ASTROPHYS J SUPPL S JI Astrophys. J. Suppl. Ser. PD APR PY 1996 VL 103 IS 2 BP 331 EP 362 DI 10.1086/192280 PG 32 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA UB981 UT WOS:A1996UB98100002 ER PT J AU Greenleaf, JE Ertl, AC Bernauer, EM AF Greenleaf, JE Ertl, AC Bernauer, EM TI Submaximal exercise Vo(2) and Q(c) during 30-day 6 degrees head-down bed rest with isotonic and isokinetic exercise training SO AVIATION SPACE AND ENVIRONMENTAL MEDICINE LA English DT Article ID PROLONGED RESTRICTED ACTIVITY; MIDDLE-AGED MEN; OXYGEN-UPTAKE; CAPACITY; VOLUME; DOGS AB Background: Maintaining intermediary metabolism is necessary for the health and well-being of astronauts on long-duration spaceflights. While peak oxygen uptake (V over dot O-2) is consistently decreased during prolonged bed rest, submaximal V over dot O-2 is either unchanged or decreased. Methods: Submaximal exercise metabolism (61 +/- 3% peak V over dot O-2) was measured during ambulation (AMB day-2) and on bed rest days 4, 11, and 25 in 19 healthy men (32-42 yr) allocated into no exercise (NOE, N = 5) control, and isotonic exercise (ITE, N = 7) and isokinetic exercise (IKE, N = 7) training groups. Exercise training was conducted supine for two 30-min periods per day for 6 d per week: ITE training was intermittent at 60-90% peak V over dot O-2; IKE training was 10 sets of 5 repetitions of peak knee flexion-extension force at a velocity of 100 degrees s(-1). Cardiac output was measured with the indirect Fick CO2 method, and plasma volume with Evans blue dye dilution. Results: Supine submaximal exercise V over dot O-2 decreased significantly (*p < 0.05) by 10.3%* with ITE and by 7.3%* with IKE; similar to the submaximal cardiac output decrease of 14.5%* (ITE) and 20.3%* (IKE), but different from change in peak V over dot O-2 (+1.4% with ITE and -10.2%* with IKE) and decrease in plasma volume of -3.7% (ITE) and -18.0%* (IKE). Reduction of submaximal V over dot O-2 during bed rest correlated 0.79 (p < 0.01) with submaximal Q over dot (C), but was not related to change in peak V over dot O-2 or plasma volume. Conclusion: Reduction in submaximal oxygen uptake during prolonged bed rest is related to decrease in exercise but not resting cardiac output; perturbations in active skeletal muscle metabolism may be involved. C1 UNIV CALIF DAVIS,HUMAN PERFORMANCE LAB,DAVIS,CA 95616. VANDERBILT UNIV,MED CTR,CTR SPACE PHYSIOL & MED,NASHVILLE,TN. RP Greenleaf, JE (reprint author), NASA,AMES RES CTR,GRAVITAT RES BRANCH 239 11,LAB HUMAN ENVIRONM PHYIOL,MOFFETT FIELD,CA 94035, USA. NR 28 TC 11 Z9 13 U1 0 U2 0 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 APR PY 1996 VL 67 IS 4 BP 314 EP 319 PG 6 WC Public, Environmental & Occupational Health; Medicine, General & Internal; Sport Sciences SC Public, Environmental & Occupational Health; General & Internal Medicine; Sport Sciences GA UB528 UT WOS:A1996UB52800003 PM 8900981 ER PT J AU Elizondo, LL Doerr, DF Sims, MA Hoffler, GW Convertino, VA AF Elizondo, LL Doerr, DF Sims, MA Hoffler, GW Convertino, VA TI Application of USAF G-suit technology for clinical orthostatic hypotension: A case study SO AVIATION SPACE AND ENVIRONMENTAL MEDICINE LA English DT Article ID DIABETIC AUTONOMIC NEUROPATHY; ARTERIAL BLOOD-PRESSURE; BAROREFLEX RESPONSES; VALSALVA MANEUVER; VAGAL BAROREFLEX; REFLEX; REST; EXERCISE AB Introduction: The purpose of this study was to determine the effectiveness of a USAF anti-gravity suit (G-suit) on the stability of a patient with chronic orthostatic hypotension. Methods: A 37-yr-old female with a history of insulin-dependent diabetes mellitus (IDDM) and symptomatic orthostasis was evaluated and the results were compared with those of non-diabetic controls, matched for age, height, and weight. Cardiac vagal tone was assessed by determination of standard deviation of 100 R-R intervals (R-R SD). We assessed the carotid-cardiac baroreflex response by plotting R-R intervals (ms) at each of eight neck pressure steps with their respective carotid distending pressures (mm Hg). Heart rate and blood pressure were recorded in response to the Valsalva maneuver (VM) performed at an expiratory pressure of 30 mmHg to assess integrated baroreflex responses. Blood pressures and heart rate were measured during three 5-min stand tests to assess orthostatic responses: a) without G-suit; b) with noninflated G-suit; and c) with inflated G-suit (50 mm Hg). Results: The IDDM patient had minimal baseline cardiac vagal tone (R-R SD = 8.5 ms) compared with the average response of a control group of 24 subjects with orthostatic stability (R-R SD = 67.2 +/- 7.1 ms). Carotid-cardiac baroreflex response was virtually non-existent in the IDDM patient (Gain = 0.06 ms . mm Hg-1) compared to the control subjects (4.4 +/- 0.8 ms . mm Hg-1). VM responses corroborated the lack of cardiac baroreflex response in the IDDM patient, while blood pressure changes during the VM were similar to those of the controls. Upon standing, the IDDM patient demonstrated severe orthostatic hypotension (90 mm Hg SBP) and tachycardia without the G-suit. The G-suit, with and without pressure, reduced hypotension and tachycardia during standing. Conclusion: These results demonstrate successful application of Air Force technology as a useful alternative to pharmacologic intervention in the treatment of a patient with autonomic dysfunction leading to supine hypertension and orthostatic hypotension. C1 AL AOCY,DIV CLIN SCI,PHYSIOL RES BRANCH,BROOKS AFB,TX 78235. NASA,BIOMED OPERAT OFF,KENNEDY SPACE CTR,FL 32899. JUPITER HOSP,JUPITER,FL. NR 28 TC 4 Z9 5 U1 2 U2 2 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 APR PY 1996 VL 67 IS 4 BP 344 EP 350 PG 7 WC Public, Environmental & Occupational Health; Medicine, General & Internal; Sport Sciences SC Public, Environmental & Occupational Health; General & Internal Medicine; Sport Sciences GA UB528 UT WOS:A1996UB52800009 PM 8900987 ER PT J AU Whitehead, RE AF Whitehead, RE TI NASA must trim aircraft operations SO AVIATION WEEK & SPACE TECHNOLOGY LA English DT Letter RP Whitehead, RE (reprint author), NASA,WASHINGTON,DC 20546, 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 APR 1 PY 1996 VL 144 IS 14 BP 6 EP 6 PG 1 WC Engineering, Aerospace SC Engineering GA UD270 UT WOS:A1996UD27000001 ER PT J AU Manobianco, J Zack, JW Taylor, GE AF Manobianco, J Zack, JW Taylor, GE TI Workstation-based real-time mesoscale modeling designed for weather support to operations at the Kennedy Space Center and Cape Canaveral Air Station SO BULLETIN OF THE AMERICAN METEOROLOGICAL SOCIETY LA English DT Article ID 4-DIMENSIONAL DATA ASSIMILATION; PLANETARY BOUNDARY-LAYER; CUMULUS PARAMETERIZATION; NUMERICAL SIMULATIONS; MARINE CYCLONE; SEA BREEZES; CYCLOGENESIS; SYSTEM; FRONTOGENESIS; ENVIRONMENT AB This paper describes the capabilities and operational utility of a version of the Mesoscale Atmospheric Simulation System (MASS) that has been developed to support operational weather forecasting at the Kennedy Space Center (KSC) and Cape Canaveral Air Station (CCAS). The implementation of local, mesoscale modeling systems at KSC/CCAS is designed to provide detailed short-range (< 24 h) forecasts of winds, clouds, and hazardous weather such as thunderstorms. Short-range forecasting is a challenge for daily operations, and manned and unmanned launches since KSC/CCAS is located in central Florida where the weather during the warm season is dominated by mesoscale circulations like the sea breeze. For this application, MASS has been modified to run on a Stardent 3000 workstation. Workstation-based, real-time numerical modeling requires a compromise between the requirement to run the system fast enough so that the output can be used before expiration balanced against the desire to improve the simulations by increasing resolution and using more detailed physical parameterizations. It is now feasible to run high-resolution mesoscale models such as MASS on local workstations to provide timely forecasts at a fraction of the cost required to run these models on mainframe supercomputers. MASS has been running in the Applied Meteorology Unit (AMU) at KSC/CCAS since January 1994 for the purpose of system evaluation. In March 1995, the AMU began sending real-time MASS output to the forecasters and meteorologists at CCAS, Spaceflight Meteorology Group (Johnson Space Center, Houston, Texas), and the National Weather Service (Melbourne, Florida). However, MASS is not yet an operational system. The final decision whether to transition MASS for operational use will depend on a combination of forecaster feedback, the AMU's final evaluation results, and the life-cycle costs of the operational system. C1 MESO INC, TROY, NY USA. NASA, APPL METEOROL UNIT, KENNEDY SPACE CTR, FL USA. RP ENSCO INC, 445 PINEDA COURT, MELBOURNE, FL 32940 USA. NR 60 TC 29 Z9 30 U1 0 U2 0 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 USA SN 0003-0007 EI 1520-0477 J9 B AM METEOROL SOC JI Bull. Amer. Meteorol. Soc. PD APR PY 1996 VL 77 IS 4 BP 653 EP 672 DI 10.1175/1520-0477(1996)077<0653:WBRTMM>2.0.CO;2 PG 20 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA UG177 UT WOS:A1996UG17700001 ER PT J AU Pohorille, A Cieplak, P Wilson, MA AF Pohorille, A Cieplak, P Wilson, MA TI Interactions of anesthetics with the membrane-water interface SO CHEMICAL PHYSICS LA English DT Article DE anesthetics; membranes; interfaces; molecular dynamics ID MOLECULAR-DYNAMICS SIMULATION; LIQUID VAPOR INTERFACE; LIPID BILAYER; POTENTIAL FUNCTIONS; FORCES AB Although the potency of conventional anesthetics correlates with lipophilicity, an affinity to water also is essential. It was recently found that compounds with very low affinities to water do not produce anesthesia regardless of their lipophilicity. This finding implies that clinical anesthesia might arise because of interactions at molecular sites near the interface of neuronal membranes with the aqueous environment and, therefore, might require increased concentrations of anesthetic molecules at membrane interfaces. As an initial test of this hypothesis, we calculated in molecular dynamics simulations the free energy profiles for the transfer of anesthetic 1,1,2-trifluoroethane and nonanesthetic perfluoroethane across water-membrane and water-hexane interfaces. Consistent with the hypothesis, it was found that trifluoroethane, but not perfluoroethane, exhibits a free energy minimum and, therefore, increased concentrations at both interfaces. The transfer of trifluoroethane from water to the nonpolar hexane or interior of the membrane is accompanied by a considerable, solvent-induced shift in the conformational equilibrium around the C-C bond. C1 NASA,AMES RES CTR,MOFFETT FIELD,CA 94035. RP Pohorille, A (reprint author), UNIV CALIF SAN FRANCISCO,DEPT PHARMACEUT CHEM,SAN FRANCISCO,CA 94143, USA. FU NIGMS NIH HHS [GM47818-01] NR 40 TC 65 Z9 67 U1 0 U2 2 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0301-0104 J9 CHEM PHYS JI Chem. Phys. PD APR 1 PY 1996 VL 204 IS 2-3 BP 337 EP 345 DI 10.1016/0301-0104(95)00292-8 PG 9 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA UD543 UT WOS:A1996UD54300019 PM 11540160 ER PT J AU Paley, MS Armstrong, S Witherow, WK Frazier, DO AF Paley, MS Armstrong, S Witherow, WK Frazier, DO TI Kinetic studies on photodeposition of polydiacetylene thin films from solution: Preliminary determination of the rate law SO CHEMISTRY OF MATERIALS LA English DT Article ID DIACETYLENE AB Preliminary kinetic studies were undertaken on the photodeposition of thin films of a polydiacetylene derivative of 2-methyl-4-nitroaniline from monomer solutions onto quartz substrates, Solutions of the monomer, DAMNA, in 1,2-dichloroethane at various concentrations were irradiated at 364 nm using an argon-ion laser at several intensities. It was found that the rate of polydiacetylene (PDAMNA) film photodeposition varies linearly with UV light intensity and as the square root of monomer concentration. RP Paley, MS (reprint author), NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,SPACE SCI LAB,HUNTSVILLE,AL 35812, USA. NR 8 TC 7 Z9 7 U1 1 U2 1 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 SN 0897-4756 J9 CHEM MATER JI Chem. Mat. PD APR PY 1996 VL 8 IS 4 BP 912 EP 915 DI 10.1021/cm950514a PG 4 WC Chemistry, Physical; Materials Science, Multidisciplinary SC Chemistry; Materials Science GA UF852 UT WOS:A1996UF85200017 ER PT J AU Slingo, JM Sperber, KR Boyle, JS Ceron, JP Dix, M Dugas, B Ebisuzaki, W Fyfe, J Gregory, D Gueremy, JF Hack, J Harzallah, A Inness, P Kitoh, A Lau, WKM McAvaney, B Madden, R Matthews, A Palmer, TN Park, CK Randall, D Renno, N AF Slingo, JM Sperber, KR Boyle, JS Ceron, JP Dix, M Dugas, B Ebisuzaki, W Fyfe, J Gregory, D Gueremy, JF Hack, J Harzallah, A Inness, P Kitoh, A Lau, WKM McAvaney, B Madden, R Matthews, A Palmer, TN Park, CK Randall, D Renno, N TI Intraseasonal oscillations in 15 atmospheric general circulation models: Results from an AMIP diagnostic subproject SO CLIMATE DYNAMICS LA English DT Article ID OUTGOING LONGWAVE RADIATION; 30-60 DAY OSCILLATION; WESTERN PACIFIC; ANGULAR-MOMENTUM; NORTHERN WINTER; CONVECTION; ANOMALIES; CLUSTERS; TROPICS; OCEAN AB The ability of 15 atmospheric general circulation models (AGCM) to simulate the tropical intraseasonal oscillation has been studied as part of the Atmospheric Model Intercomparison Project (AMIP). Time series of the daily upper tropospheric velocity poential and zonal wind, averaged over the equatorial belt, were provided from each AGCM simulation. These data were analyzed using a variety of techniques such as time filtering and space-time spectral analysis to identify eastward and westward moving waves. The results have been compared with an identical assessment of the European Centre for Medium-range Weather Forecasts (ECMWF) analyses for the period 1982-1991. The models display a wide range of skill in simulating the intraseasonal oscillation. Most models show evidence of an eastward propagating anomaly in the velocity potential field, although in some models there is a greater tendency for a standing oscillation, and in one or two the field is rather chaotic with no preferred direction of propagation. Where a model has a clear eastward propagating signal, typical periodicities seem quite reasonable although there is a tendency for the models to simulate shorter periods than in the ECMWF analyses, where it is near 50 days. The results of the space-time spectral analysis have shown that no model has captured the dominance of the intraseasonal oscillation found in the analyses. Several models have peaks at intraseasonal time scales, but nearly all have relatively more power at higher frequencies (<30 days) than the analyses. Most models underestimate the strength of the intraseasonal variability. The observed intraseasonal oscillation shows a marked seasonality in its occurrence with greatest activity during northern winter and spring. Most models failed to capture this seasonality. The interannual variability in the activity of the intraseasonal oscillation has also been assessed, although the AMIP decade is too short to provide any conclusive results. There is a suggestion that, the observed oscillation was suppressed during the strong El Nino of 1982/83, and this relationship has also been reproduced by some models. The relationship between a model's intraseasonal activity, its seasonal cycle and characteristics of its basic climate has been examined. It is clear that those models with weak intraseasonal activity tend also to have a weak seasonal cycle. It is becoming increasingly evident that an accurate description of the basic climate may be a prerequisite for producing a realistic intraseasonal. In particular, models with the most realistic intraseasonal oscillations appear to have precipitation distributions which are better correlated with warm sea surface temperatures. These models predominantly employ convective parameterizations which are closed on buoyancy rather than moisture convergence. C1 LAWRENCE LIVERMORE NATL LAB,PROGRAM CLIMATE MODEL DIAGNOSIS & INTERCOMPARISON,LIVERMORE,CA 94551. METEO FRANCE,ECOLE NATL METEOROL,F-31057 TOULOUSE,FRANCE. CSIRO,DIV ATMOSPHER RES,MORDIALLOC,VIC 3195,AUSTRALIA. NOAA,NMC,CAMP SPRINGS,MD 20746. UNIV VICTORIA,CANADIAN CLIMATE CTR,VICTORIA,BC V8W 2Y2,CANADA. UK METEOROL OFF,HADLEY CTR CLIMATE PREDICT & RES,BRACKNELL RG12 2SY,BERKS,ENGLAND. NATL CTR ATMOSPHER RES,BOULDER,CO 80307. ECOLE NORMALE SUPER,CNRS,METEOROL DYNAM LAB,F-75231 PARIS 05,FRANCE. METEOROL RES INST,TSUKUBA,IBARAKI 305,JAPAN. BUR METEOROL RES CTR,MELBOURNE,VIC 3001,AUSTRALIA. EUROPEAN CTR MEDIUM RANGE WEATHER FORECASTS,READING RG2 9AX,BERKS,ENGLAND. NASA,GODDARD SPACE FLIGHT CTR,DATA ASSIMILAT OFF,GREENBELT,MD 20771. COLORADO STATE UNIV,DEPT ATMOSPHER SCI,FT COLLINS,CO 80523. CALTECH,PASADENA,CA 91125. RP Slingo, JM (reprint author), UNIV READING,DEPT METEOROL,2 EARLEY GATE,READING RG6 6AU,BERKS,ENGLAND. RI Matthews, Adrian/A-6444-2011; Dix, Martin/A-2334-2012; Sperber, Kenneth/H-2333-2012; Randall, David/E-6113-2011; Lau, William /E-1510-2012 OI Matthews, Adrian/0000-0003-0492-1168; Dix, Martin/0000-0002-7534-0654; Randall, David/0000-0001-6935-4112; Lau, William /0000-0002-3587-3691 NR 45 TC 392 Z9 424 U1 2 U2 14 PU SPRINGER VERLAG PI NEW YORK PA 175 FIFTH AVE, NEW YORK, NY 10010 SN 0930-7575 J9 CLIM DYNAM JI Clim. Dyn. PD APR PY 1996 VL 12 IS 5 BP 325 EP 357 DI 10.1007/BF00231106 PG 33 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA UF608 UT WOS:A1996UF60800003 ER PT J AU Rezaeepazhand, J Simitses, GJ Starnes, JH AF Rezaeepazhand, J Simitses, GJ Starnes, JH TI Scale models for laminated cylindrical shells subjected to axial compression SO COMPOSITE STRUCTURES LA English DT Article AB This study investigates problems associated with the design of scaled down models. Such study is important since it provides the necessary scaling laws, and the factors which affect the accuracy of the scale models. For better understanding the applicability of scaled down models in designing laminated composite structures, an analytical investigation was undertaken to assess the feasibility of their use. Employment of similitude theory to establish similarity among structural systems can save considerable expense and time, provided that the proper scaling laws are found and validated. In this study the limitation and acceptable interval of all parameters and corresponding scale factors are investigated. Particular emphasis is placed on the case of buckling of cross-ply cylindrical shells under uniaxial compressive loads. Both complete and partial similarity are discussed. This analytical study indicates that distorted models with a different number of layers and geometries than those of the prototype can predict the behavior of the prototype with good accuracy. However, it is shown that a scaled down model with different material properties than those of the prototype is incapable of predicting the response of the prototype. Copyright (C) 1996 Elsevier Science Ltd. C1 NASA,LANGLEY RES CTR,AIRCRAFT STRUCT BRANCH,HAMPTON,VA 23664. RP Rezaeepazhand, J (reprint author), UNIV CINCINNATI,DEPT AEROSP ENGN & ENGN MECH,CINCINNATI,OH 45221, USA. OI Rezaeepazhand, Jalil/0000-0003-3653-1623 NR 8 TC 22 Z9 26 U1 1 U2 4 PU ELSEVIER SCI LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, OXON, ENGLAND OX5 1GB SN 0263-8223 J9 COMPOS STRUCT JI Compos. Struct. PD APR PY 1996 VL 34 IS 4 BP 371 EP 379 DI 10.1016/0263-8223(95)00154-9 PG 9 WC Materials Science, Composites SC Materials Science GA UT612 UT WOS:A1996UT61200002 ER PT J AU Karaoglan, L Noor, AK AF Karaoglan, L Noor, AK TI Assessment of temporal integration schemes for the sensitivity analysis of frictional contact/impact response of axisymmetric composite structures SO COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING LA English DT Article ID IMPACT AB An assessment is made of three temporal integration schemes for the sensitivity analysis of the frictional contact/impact response of axisymmetric composite structures. The structures considered consist of an arbitrary number of perfectly-bonded homogeneous anisotropic layers. The material of each layer is assumed to be hyperelastic, and the effect of geometric non-linearity is included. Sensitivity coefficients measure the sensitivity of the response to variations in the different material, lamination and geometric parameters of the structure. A displacement finite element model is used for the spatial discretization. Normal contact conditions are incorporated into the formulation by using a perturbed Lagrangian approach with fundamental unknowns consisting of both the nodal displacements and the Lagrange multipliers associated with the contact conditions. The Lagrange multipliers are allowed to be discontinuous at interelement boundaries. Tangential contact conditions are incorporated by using either a penalty method or a Lagrange multiplier technique, in conjunction with the classical Coulomb's friction model. The three temporal integration schemes considered are: the implicit Newmark and Houbolt schemes, and the explicit central difference method. In the case of the implicit methods, the Newton-Raphson iterative technique is used for the solution of the resulting non-linear algebraic equations, and for the determination of the contact region, contact conditions (sliding or sticking), and the contact pressures. Sensitivity coefficients are evaluated by using a direct differentiation approach in conjunction with the incremental equations. Numerical results are presented for the frictional contact of a composite spherical cap impacting a rigid plate, showing the effects of each of the following factors on the accuracy of the predicted response and sensitivity coefficients: (a) incorporating the normal contact conditions, (b) the magnitude of the penalty parameter in the normal direction (for the perturbed Lagrangian method), and (c) the time step size for the response and the sensitivity analyses. C1 UNIV VIRGINIA,CTR COMPUTAT STRUCT TECHNOL,NASA,LANGLEY RES CTR,HAMPTON,VA 23665. NR 21 TC 3 Z9 3 U1 0 U2 2 PU ELSEVIER SCIENCE SA LAUSANNE PI LAUSANNE 1 PA PO BOX 564, 1001 LAUSANNE 1, SWITZERLAND SN 0045-7825 J9 COMPUT METHOD APPL M JI Comput. Meth. Appl. Mech. Eng. PD APR 1 PY 1996 VL 130 IS 3-4 BP 369 EP 393 DI 10.1016/0045-7825(95)00907-8 PG 25 WC Engineering, Multidisciplinary; Mathematics, Interdisciplinary Applications; Mechanics SC Engineering; Mathematics; Mechanics GA UQ978 UT WOS:A1996UQ97800012 ER PT J AU Hall, JV Walton, AL AF Hall, JV Walton, AL TI A case study in pollution markets: Dismal science vs dismal reality SO CONTEMPORARY ECONOMIC POLICY LA English DT Article; Proceedings Paper CT 70th Annual Conference of the Western-Economic-Association-International CY JUL 05-09, 1995 CL SAN DIEGO, CA SP W Econ Assoc Int ID AIR AB Economists long have argued that economic incentives can reduce pollution more efficiently than do narrow regulatory prescriptions, bur this theory has not enjoyed wide application. Southern California experiences the worst air pollution in the United States and has developed the most complex set of regulatory approaches in the world to address the problem. Rising costs and increasing resistance to further regulation led to the Regional Clean Air Incentives Market (RECLAIM) program, which is expected to reduce pollution control costs by about 50 percent over a decade (relative to direct regulation). This paper describes the theoretical advantages of pollution trading, clearly identifies three criteria that acceptable economic incentive-based programs must meet, explains the structure of RECLAIM, and raises issues regarding firm behavior in response to a newly created asset with an initial price of zero. C1 JET PROPULS LAB,SCI RES & TECHNOL PROGRAM,SPACE & EARTH SCI DIRECTORATE,PASADENA,CA. RP Hall, JV (reprint author), CALIF STATE UNIV FULLERTON,INST ECON & ENVIRONM STUDIES,FULLERTON,CA 92634, USA. NR 15 TC 10 Z9 10 U1 0 U2 2 PU WESTERN ECONOMIC ASSOC INT PI HUNTINGTON BEACH PA 7400 CENTER AVE SUITE 109, HUNTINGTON BEACH, CA 92647-3039 SN 0735-0007 J9 CONTEMP ECON POLICY JI Contemp. Econ. Policy PD APR PY 1996 VL 14 IS 2 BP 67 EP 78 PG 12 WC Economics; Public Administration SC Business & Economics; Public Administration GA UD282 UT WOS:A1996UD28200006 ER PT J AU Oren, R Zimmermann, R Terborgh, J AF Oren, R Zimmermann, R Terborgh, J TI Transpiration in upper Amazonia floodplain and upland forests in response to drought-breaking rains SO ECOLOGY LA English DT Article ID SAP FLOW C1 JET PROP LAB, HYDROL SOILS & ECOL GRP, PASADENA, CA 91109 USA. RP Oren, R (reprint author), DUKE UNIV, SCH ENVIRONM, DURHAM, NC 27708 USA. NR 13 TC 48 Z9 51 U1 1 U2 9 PU ECOLOGICAL SOC AMER PI WASHINGTON PA 1990 M STREET NW, STE 700, WASHINGTON, DC 20036 USA SN 0012-9658 J9 ECOLOGY JI Ecology PD APR PY 1996 VL 77 IS 3 BP 968 EP 973 DI 10.2307/2265517 PG 6 WC Ecology SC Environmental Sciences & Ecology GA UC985 UT WOS:A1996UC98500031 ER PT J AU Baroth, E Brunzie, T Hartsough, C McGregor, J AF Baroth, E Brunzie, T Hartsough, C McGregor, J TI More on visual programming data acquisition software tools SO EE-EVALUATION ENGINEERING LA English DT Article RP Baroth, E (reprint author), CALTECH,JET PROP LAB,MEASUREMENT TECHNOL CTR,MEASUREMENT TEST & ENGN SUPPORT SECT,PASADENA,CA 91109, USA. NR 5 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 APR PY 1996 VL 35 IS 4 BP 32 EP & PG 8 WC Engineering, Electrical & Electronic SC Engineering GA UD592 UT WOS:A1996UD59200005 ER PT J AU Volz, MP Mazuruk, K AF Volz, MP Mazuruk, K TI Flow transitions in a rotating magnetic field SO EXPERIMENTS IN FLUIDS LA English DT Article ID CONVECTION; CYLINDER AB Critical Rayleigh numbers have been measured in a liquid metal cylinder of finite height in the presence of a rotating magnetic field. Several different stability regimes were observed, which were determined by the values of the Rayleigh and Hartmann numbers. For weak rotating magnetic fields and small Rayleigh numbers, the experimental observations can be explained by the existence of a single non-axisymmetric meridional roll rotating around the cylinder, driven by the azimuthal component of the magnetic field. The measured dependence of rotational velocity on magnetic field strength is consistent with the existence of laminar flow in this regime. RP Volz, MP (reprint author), NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,SPACE SCI LAB,HUNTSVILLE,AL 35812, USA. NR 21 TC 14 Z9 14 U1 0 U2 0 PU SPRINGER VERLAG PI NEW YORK PA 175 FIFTH AVE, NEW YORK, NY 10010 SN 0723-4864 J9 EXP FLUIDS JI Exp. Fluids PD APR PY 1996 VL 20 IS 6 BP 454 EP 459 PG 6 WC Engineering, Mechanical; Mechanics SC Engineering; Mechanics GA UK450 UT WOS:A1996UK45000007 ER PT J AU Taghavi, R Raman, G AF Taghavi, R Raman, G TI Visualization of supersonic screeching jets using a phase conditioned focusing schlieren system SO EXPERIMENTS IN FLUIDS LA English DT Article AB This study describes a technique that combines the benefits of focusing schlieren and phase conditioning. Focusing schlieren blurs and drops contrast of non-critical features whereas phase conditioning emphasizes periodic flow features, and their combination produces unique results. The supersonic jets that we studied produced an intense tone referred to as screech. The measured screech tone signal was used as input to the phase conditioning circuit that adjusted the strobing light source to the vertical synchronization pulse of a CCD camera. The sharp video images obtained by this technique could either be frozen or continuously swept through one period of screech to acquire a slow motion video record of the jet unsteadiness. Two cases were visualized in this study: first, an underexpanded jet from a convergent rectangular nozzle at various fully expanded Mach numbers. Second, a supersonic jet emerging from a convergent-divergent rectangular nozzle at a design Mach number of 1.4, artificially excited by impingement tones. The results of this study illustrate the usefulness of this system in visualizing oscillatory flows. C1 NYMA INC,NASA,LEWIS RES CTR GRP,EXPTL FLUID DYNAM SECT,BROOKPARK,OH 44142. RP Taghavi, R (reprint author), UNIV KANSAS,DEPT AEROSP ENGN,LAWRENCE,KS 66045, USA. NR 7 TC 4 Z9 4 U1 0 U2 2 PU SPRINGER VERLAG PI NEW YORK PA 175 FIFTH AVE, NEW YORK, NY 10010 SN 0723-4864 J9 EXP FLUIDS JI Exp. Fluids PD APR PY 1996 VL 20 IS 6 BP 472 EP 475 PG 4 WC Engineering, Mechanical; Mechanics SC Engineering; Mechanics GA UK450 UT WOS:A1996UK45000010 ER PT J AU Caillouet, CW Shaver, DJ Teas, WG Nance, JM Revera, DB Cannon, AC AF Caillouet, CW Shaver, DJ Teas, WG Nance, JM Revera, DB Cannon, AC TI Relationship between sea turtle stranding rates and shrimp fishing intensities in the northwestern Gulf of Mexico: 1986-1989 versus 1990-1993 SO FISHERY BULLETIN LA English DT Article ID LEPIDOCHELYS-KEMPI; RIDLEY AB This paper tested the null hypothesis that the statistical relationship between monthly sea turtle (species combined) stranding rates (strandings per 100 km of accessible shoreline) and monthly shrimp fishing intensities (days fished per 100 km(2)) in the northwestern Gulf of Mexico was the same in 1990-93 as in 1986-89. The expectation was that regulations requiring use of turtle excluder devices (TED's) in shrimp trawls during 1990-93 would reduce the incidental catch of sea turtles and thereby diminish or eliminate the statistical relationship between stranding rates and fishing intensities. Significant positive correlations were detected between the log-transformed stranding rates and fishing intensities for shrimping landward of the 20-fathom (36.6-m) contour in 1990-93. The null hypothesis was not rejected; therefore TED regulations did not result in diminishing or eliminating the statistical relationship between sea turtle stranding rates and shrimp fishing intensities in the northwestern Gulf. Various hypotheses were suggested as possible explanations. C1 NATL BIOL SERV,PADRE ISL NATL SEASHORE,US DEPT INTERIOR,CORPUS CHRISTI,TX 78418. NATL MARINE FISHERIES SERV,MIAMI LAB,SE FISHERIES SCI CTR,NOAA,MIAMI,FL 33149. RP Caillouet, CW (reprint author), NATL MARINE FISHERIES SERV,GALVESTON LAB,SE FISHERIES SCI CTR,NOAA,4600 AVE U,GALVESTON,TX 77551, USA. NR 22 TC 23 Z9 26 U1 0 U2 8 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 APR PY 1996 VL 94 IS 2 BP 237 EP 249 PG 13 WC Fisheries SC Fisheries GA UC962 UT WOS:A1996UC96200003 ER PT J AU DeMartini, EE Parrish, FA Ellis, DM AF DeMartini, EE Parrish, FA Ellis, DM TI Barotrauma-associated regurgitation of food: Implications for diet studies of Hawaiian pink snapper, Pristipomoides filamentosus (family Lutjanidae) SO FISHERY BULLETIN LA English DT Article ID STOMACH CONTENTS; FISHES; COD AB Juvenile (128-244 mm fork length) pink snapper, Pristipomoides filamentosus, were caught by hook and line from 60-90 m depths offshore of Kaneohe Bay, windward Oahu, Hawaii, during February-August 1994. About one-half of the 180 specimens were intercepted by scuba divers 15-18 m below the sea surface and individually ''bagged'' live before they were retrieved for the remaining distance to the surface. The other half were retrieved directly by fishing line to the surface (''unbagged''); these latter fish thus remained at a continual risk of prey loss from regurgitation while they were stressed by the full extent of pressure change. The retained stomach contents of bagged and unbagged fish were compared on the basis of volume and type of food and on the size of individual prey items. Bagged samples of juvenile snapper on average retained a 116% (95% CI=70-157%) greater volume of prey than unbagged snapper; bagged snapper also had more types and greater maximum body sizes of prey than did unbagged fish. These results are discussed in terms of designing quantitative diet studies for juvenile snapper and other deep-water physoclistous fishes. RP DeMartini, EE (reprint author), NATL MARINE FISHERIES SERV,HONOLULU LAB,SW FISHERIES SCI CTR,NOAA,2570 DOLE ST,HONOLULU,HI 96822, USA. NR 19 TC 12 Z9 12 U1 0 U2 3 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 APR PY 1996 VL 94 IS 2 BP 250 EP 256 PG 7 WC Fisheries SC Fisheries GA UC962 UT WOS:A1996UC96200004 ER PT J AU Krieger, KJ Sigler, MF AF Krieger, KJ Sigler, MF TI Catchability coefficient for rockfish estimated from trawl and submersible surveys SO FISHERY BULLETIN LA English DT Article AB A bottom-trawl catchability coefficient was estimated for rockfish by comparing trawl catch rates to densities estimated from a manned submersible. A total of 16 comparisons were completed in 1989 and 1991 at depths of 180-283 m. Pacific ocean perch, Sebastes alutus, was the target species and accounted for 72% of the rockfish caught in the trawl. The seafloor area sampled by the trawl was calculated from the distance between the wingtips of the net and the distance the net traveled across the seafloor. The seafloor area sampled from the submersible was calculated from the distance the submersible traveled and the lateral range of visibility. A larger volume of water was sampled from the submersible because counts of rockfish included fish to 7 m above the seafloor, whereas the vertical opening of the trawl was 1.8 m; approximately 50% of the rockfish observed from the submersible were >1.8 m above the seafloor. Even though a larger volume of water was sampled from the submersible, catchability coefficients of 0.97 and 1.27 were estimated for minimum and maximum detection probabilities of rockfish from the submersible. Apparently, rockfish dove or were herded horizontally into the opening of the net. Density estimates of rockfish and other groundfish species are feasible from a submersible, and these estimates can be used to determine bottom-trawl catchability coefficients. RP Krieger, KJ (reprint author), NATL MARINE FISHERIES SERV,AUKE BAY LAB,ALASKA FISHERIES SCI CTR,NOAA,11305 GLACIER HWY,JUNEAU,AK 99801, USA. NR 15 TC 10 Z9 10 U1 0 U2 2 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 APR PY 1996 VL 94 IS 2 BP 282 EP 288 PG 7 WC Fisheries SC Fisheries GA UC962 UT WOS:A1996UC96200007 ER PT J AU Lindstrom, DJ Jones, JH AF Lindstrom, DJ Jones, JH TI Neutron activation analysis of multiple 10-100 mu g glass samples from siderophile element partitioning experiments SO GEOCHIMICA ET COSMOCHIMICA ACTA LA English DT Article; Proceedings Paper CT Workshop on the Formation of the Earths Core CY APR 18-20, 1995 CL MAX PLANCK INST CHEM, MAINZ, GERMANY HO MAX PLANCK INST CHEM ID CU AB Experimental studies of the metal/silicate partitioning of Ir have produced two sets of results differing by a factor of 10(6) (Jones and Drake, 1986; O'Neill et al., 1995). In an attempt to understand this discrepancy, we have performed instrumental neutron activation analyses of multiple glass chips from these siderophile element partitioning experiments. From seven to ten individual chips (similar to 10-100 mu g each) were analyzed from each experimental glass. The major target was Ir, which was detected at concentrations ranging from 690 ppb (ng/g) to less than 1 ppb. Detection limits are less than 10(-13) grams Ir. Almost all of the run products appear to be homogeneous with respect to lithophile elements, but most vary considerably in their Ir concentrations. It appears that most of the experiments analyzed so far contain small amounts of metal in the glass separates. One experiment from Jones and Drake (1983) appears to be homogeneous, but in fact may not be. More recent experiments are definitely not homogeneous, and require the existence of a metallic phase distinctly different from the bulk solid metal or liquid metal/sulfide phases also present in the charges. Iridium contents of the glass in the stirred crucible experiment studied (O'Neill et al., 1996) decreased continuously over a period of several months, even as the oxygen fugacity was increasing, suggesting that the experiment never achieved equilibrium. Iridium contents in multiple samples of the glasses varied over factors of 2 to 3x. Further subdivision of one low-Lr glass did not result in a reduction in the variation of Ir between aliquots. Thus, the variation in Ir concentration appears to remain fairly constant, irrespective of the scale of the sampling. RP Lindstrom, DJ (reprint author), NASA,LYNDON B JOHNSON SPACE CTR,PLANETARY SCI BRANCH,SN4,HOUSTON,TX 77058, USA. NR 22 TC 15 Z9 15 U1 1 U2 2 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, ENGLAND OX5 1GB SN 0016-7037 J9 GEOCHIM COSMOCHIM AC JI Geochim. Cosmochim. Acta PD APR PY 1996 VL 60 IS 7 BP 1195 EP 1203 DI 10.1016/0016-7037(96)00026-9 PG 9 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA UD534 UT WOS:A1996UD53400009 ER PT J AU Wang, Y McDonald, E Amundson, R McFadden, L Chadwick, O AF Wang, Y McDonald, E Amundson, R McFadden, L Chadwick, O TI An isotopic study of soils in chronological sequences of alluvial deposits, Providence Mountains, California SO GEOLOGICAL SOCIETY OF AMERICA BULLETIN LA English DT Article ID RADIOCARBON MEASUREMENTS; CARBON-DIOXIDE; ORGANIC-MATTER; MOJAVE DESERT; UNITED-STATES; C-14 CONTENT; CLIMATE; INDICATORS; CHEMISTRY; PALEOSOLS AB The carbon (C-14 and C-13) and oxygen isotopic composition of pedogenic carbonate was determined for two soil chronosequences on limestone and granitic alluvium in the Providence Mountains area in the Mojave Desert, California, The measured C-14 ages of pedogenic carbonate coating on clasts were interpreted in the light of a diffusion-reaction model developed in our recent studies (Wang et al., 1993a, 1994; Amundson et al., 1994). Several model parameters were fit or constrained by examining the C-14 content of a Pleistocene soil collected prior to atomic weapons testing and by examining the C-14 content of modern washes in the area, Model ages of soil formation calculated from the measured C-14 ages of pedogenic carbonate are in correct relative order as determined by geomorphic evidence, and are also consistent with model ages from the measured C-14 ages of soil organic matter, C-14 model ages suggest that the older geomorphic surfaces we studied are of late Pleistocene age (ca, 47-17 ka) and the younger surfaces formed during the Holocene (ca, 11-4 ka), These age estimates of the geomorphic surfaces are older than the previously assigned ages based on a combination of soil development, geomorphic relationships, and several infrared stimulated luminescence dates, but they are within a few thousand years of these other age estimates, Several possibilities for this discrepancy are evaluated, but no conclusive reason was found, Stable carbon isotopic composition of the soil carbonate indicates either a slight increase in C-4 or CAM (crassulacean acid metabolism) plants or a decrease in plant density in this area during the Holocene, Both the carbon and oxygen isotopic composition of soil carbonates suggests that the climate int the eastern Mojave Desert has, in general, become warmer and drier during the Holocene, The presence of multiple Holocene alluvial deposits, coupled with our C-14 age data, provide additional insights into the climatic fluctuations during the Holocene, We conclude that C-14 dating of pedogenic carbonate laminations is a useful additional tool in Quaternary studies, Further work is needed, however, to reveal the reasons for the discrepancies between this method and other dating techniques. C1 UNIV CALIF BERKELEY,DEPT ENVIRONM POLICY & MANAGEMENT,BERKELEY,CA 94720. UNIV NEW MEXICO,DEPT EARTH & PLANETARY SCI,ALBUQUERQUE,NM 87131. CALTECH,JET PROP LAB,DEPT EARTH SCI,PASADENA,CA 91109. RI Amundson, Ronald /E-2654-2015 NR 56 TC 57 Z9 57 U1 0 U2 6 PU GEOLOGICAL SOC AMERICA PI BOULDER PA PO BOX 9140 3300 PENROSE PLACE, BOULDER, CO 80301 SN 0016-7606 J9 GEOL SOC AM BULL JI Geol. Soc. Am. Bull. PD APR PY 1996 VL 108 IS 4 BP 379 EP 391 DI 10.1130/0016-7606(1996)108<0379:AISOSI>2.3.CO;2 PG 13 WC Geosciences, Multidisciplinary SC Geology GA UE647 UT WOS:A1996UE64700001 ER PT J AU Frey, HV Bills, BG Nerem, RS Roark, JH AF Frey, HV Bills, BG Nerem, RS Roark, JH TI The isostatic state of Martian topography revisited SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID LITHOSPHERIC STRESS; GRAVITY MODEL; MARS GRAVITY; INERTIA AB We present a spatial analysis of free air gravity and topography for Mars using new, higher resolution gravity data and the latest digital elevation data, both represented by spherical harmonics up to degree and order 50 and, separately, for harmonic degrees 4-19. Interpreting the gravity vs gravity-from-topography scatter diagram in terms of isostatic compensation for small regions, we find that most of Mars older than Amazonian is fully compensated at shallow depths (< 50 km). Exceptions to this include the ancient Tempe Terra region and the central portion of the Isidis impact basin (a known mascon). Most Hesperian-age and Amazonian-age volcanic plains not located near Tharsis and Elysium volcanoes are also compensated isostatically at shallow depths, but Amazonian-age plains near the young volcanic constructs, like Olympus Mons and the Tharsis and Elysium volcanoes themselves, are not. Both Olympus Mons and Alba have isostatic compensation depths > 300 km. C1 SCI SYST & APPLICAT INC,LANHAM,MD. RP Frey, HV (reprint author), NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771, USA. RI Bills, Bruce/C-1156-2008 NR 20 TC 8 Z9 8 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 APR 1 PY 1996 VL 23 IS 7 BP 721 EP 724 DI 10.1029/96GL00744 PG 4 WC Geosciences, Multidisciplinary SC Geology GA UD380 UT WOS:A1996UD38000007 ER PT J AU Dong, D Gross, RS Dickey, JO AF Dong, D Gross, RS Dickey, JO TI Seasonal variations of the Earth's gravitational field: An analysis of atmospheric pressure, ocean tidal, and surface water excitation SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID TEMPORAL VARIATIONS; LAGEOS; ROTATION; DEFORMATION; STARLETTE; MODEL AB Monthly mean gravitational field parameters (denoted here as C-even) that represent linear combinations of the primarily even-degree zonal spherical harmonic coefficients of the Earth's gravitational field have been recovered using LAGEOS I data and are compared with those derived from gridded global surface pressure data of the National Meteorological Center (NMC) spanning 1984-1992. The effect of equilibrium ocean tides and surface water variations are also considered. Atmospheric pressure and surface water fluctuations are shown to be the dominant causes of the observed annual C-even variations. Closure with observations is seen at the 1 sigma level when atmospheric pressure, ocean tide and surface water effects are included. Equilibrium ocean tides are shown to be the main source of excitation at the semiannual period with closure at the 1 sigma level seen when both atmospheric pressure and ocean tide effects are included. The inverted barometer (IB) case is shown to give the best agreement with the observation series. The potential of the observed C-even variations for monitoring mass variations in the polar regions of the Earth and the effect of the land-ocean mask in the IB calculation are discussed. RP Dong, D (reprint author), CALTECH,JET PROP LAB,4800 OAK GROVE DR,MS238-332,PASADENA,CA 91109, USA. NR 27 TC 25 Z9 30 U1 2 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 APR 1 PY 1996 VL 23 IS 7 BP 725 EP 728 DI 10.1029/96GL00740 PG 4 WC Geosciences, Multidisciplinary SC Geology GA UD380 UT WOS:A1996UD38000008 ER PT J AU Myneni, RB Los, SO Tucker, CJ AF Myneni, RB Los, SO Tucker, CJ TI Satellite-based identification of linked vegetation index and sea surface temperature anomaly areas from 1982-1990 for Africa, Australia and South America SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID RAINFALL; REFLECTANCE; OSCILLATION; SAHEL; CO2 AB Meteorological satellite data from 1982 to 1990 were used to identify areas of significant association between tropical Pacific sea surface temperature (SST) and remotely sensed normalized difference vegetation index (NDVI) anomalies, here taken as a surrogate for rainfall anomalies. During this period, large areas of arid and semi-arid Africa, Australia and South America experienced NDVI anomalies directly correlated to tropical Pacific SST anomalies. The results are limited by the relatively short time period of analysis. However, they confirm the disruptive effects of large-scale tropical Pacific SST variations on arid and semi-arid continental rainfall patterns in Africa, Australia, and South America, as reported previously. C1 UNIV MARYLAND,DEPT GEOG,GREENBELT,MD. SCI SYST APPLICAT INC,GREENBELT,MD. RP Myneni, RB (reprint author), NASA,GODDARD SPACE FLIGHT CTR,BIOSPHER SCI BRANCH,MAIL CODE 923,GREENBELT,MD 20771, USA. RI Los, Sietse/G-8985-2012; Myneni, Ranga/F-5129-2012; OI Los, Sietse/0000-0002-1325-3555 NR 18 TC 117 Z9 119 U1 0 U2 5 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD APR 1 PY 1996 VL 23 IS 7 BP 729 EP 732 DI 10.1029/96GL00266 PG 4 WC Geosciences, Multidisciplinary SC Geology GA UD380 UT WOS:A1996UD38000009 ER PT J AU Hsu, NC Herman, JR Bhartia, PK Seftor, CJ Torres, O Thompson, AM Gleason, JF Eck, TF Holben, BN AF Hsu, NC Herman, JR Bhartia, PK Seftor, CJ Torres, O Thompson, AM Gleason, JF Eck, TF Holben, BN TI Detection of biomass burning smoke from TOMS measurements SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID SATELLITE DETECTION; BRAZIL AB A 14.5 year gridded data set of tropospheric absorbing aerosol index was derived from the Nimbus-7 Total Ozone Mapping Spectrometer (TOMS) reflectivity difference between 340 and 380 nm channels. Based upon radiative transfer calculations, the reflectivity anomaly between these two UV wavelength channels is very sensitive to smoke and soot aerosols from biomass burning and forest fires, volcanic ash clouds as well as desert mineral dust. We demonstrate the ability of the TOMS instrument to detect and track smoke and soot aerosols generated by biomass burning in South America. TOMS data can clearly distinguish between absorbing particles (smoke and dust) and non-absorbing aerosols (clouds and haze). For South American fires, comparisons of TOMS data are consistent with the limited amount of ground-based observations (Porto Nacional, Brazil) and show generally good agreement with other satellite imagery. TOMS data shows large-scale transport of smoke particulates generated by the burning fires in the South America, which subsequentially advects smoke aerosols as far as the Atlantic Ocean east of Uruguay. C1 NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. RP Hsu, NC (reprint author), HUGHES STX,7701 GREENBELT RD,SUITE 400,GREENBELT,MD 20770, USA. RI ECK, THOMAS/D-7407-2012; Gleason, James/E-1421-2012; Hsu, N. Christina/H-3420-2013; Torres, Omar/G-4929-2013; Bhartia, Pawan/A-4209-2016; Thompson, Anne /C-3649-2014 OI Bhartia, Pawan/0000-0001-8307-9137; Thompson, Anne /0000-0002-7829-0920 NR 15 TC 170 Z9 179 U1 2 U2 9 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD APR 1 PY 1996 VL 23 IS 7 BP 745 EP 748 DI 10.1029/96GL00455 PG 4 WC Geosciences, Multidisciplinary SC Geology GA UD380 UT WOS:A1996UD38000013 ER PT J AU Baumgardner, D Dye, JE Gandrud, B Barr, K Kelly, K Chan, KR AF Baumgardner, D Dye, JE Gandrud, B Barr, K Kelly, K Chan, KR TI Refractive, indices of aerosols in the upper troposphere and lower stratosphere SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article AB A new instrument for simultaneously measuring aerosol diameter from 0.4 - 10 mu m and the refractive index between 1.30 - 1.60 has recently been flown on the NASA ER-2 aircraft during a stratospheric measurement campaign. Average stratospheric refractive indices varied from 1.40 to 1.42 over a latitude range from 70 degrees S to 50 degrees N and from 1.34 to 1.46 over a vertical range from 4 - 20 km. The measured stratospheric refractive indices do not agree well with theoretical predictions and vertical profiles suggest the presence of non-spherical or absorbing particles in the altitude range of 7 - 9 km. C1 NASA,AMES RES CTR,MOFFETT FIELD,CA 94035. NOAA,AERON LAB,BOULDER,CO 80303. RP Baumgardner, D (reprint author), NATL CTR ATMOSPHER RES,POB 3000,BOULDER,CO 80307, USA. NR 17 TC 46 Z9 46 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 APR 1 PY 1996 VL 23 IS 7 BP 749 EP 752 DI 10.1029/96GL00707 PG 4 WC Geosciences, Multidisciplinary SC Geology GA UD380 UT WOS:A1996UD38000014 ER PT J AU Hamill, P Tabazadeh, A Kinne, S Toon, OB Turco, RP AF Hamill, P Tabazadeh, A Kinne, S Toon, OB Turco, RP TI On the growth of ternary system HNO3/H2SO4/H2O aerosol particles in the stratosphere SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID NITRIC-ACID; CLOUDS AB We present a study of the growth of ternary solution (nitric acid, sulfuric acid and water) droplets in the stratosphere. The growth mechanism is heteromolecular condensation in which the particle is assumed to be in equilibrium with environmental water vapor. Model results are in reasonable agreement with the averaged extinction ratio obtained by the SAM II satellite system. C1 NASA, AMES RES CTR, MOFFETT FIELD, CA 94035 USA. UNIV CALIF LOS ANGELES, DEPT ATMOSPHER SCI, LOS ANGELES, CA 90024 USA. RP Hamill, P (reprint author), SAN JOSE STATE UNIV, DEPT PHYS, SAN JOSE, CA 95192 USA. NR 13 TC 5 Z9 5 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD APR 1 PY 1996 VL 23 IS 7 BP 753 EP 756 DI 10.1029/96GL00703 PG 4 WC Geosciences, Multidisciplinary SC Geology GA UD380 UT WOS:A1996UD38000015 ER PT J AU Zhu, Z Song, P Drake, JF Russell, CT Anderson, RR Gurnett, DA Ogilvie, KW Fitzenreiter, RJ AF Zhu, Z Song, P Drake, JF Russell, CT Anderson, RR Gurnett, DA Ogilvie, KW Fitzenreiter, RJ TI The relationship between ELF-VHF waves and magnetic shear at the dayside magnetopause SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID HYBRID DRIFT INSTABILITY; FLUX-TRANSFER EVENTS; EARTHS MAGNETOPAUSE; PLASMA-WAVES; ISEE 1; RECONNECTION AB ELF-VLF waves within the current layer of the dayside magnetopause are studied using ISEE-1 data. The database consists of 272 current layer crossings at the dayside magnetopause from 1977 to 1979. For each crossing, the average intensity of ELF-VLF waves inside the current layer is obtained and the magnetic shear angle across the current layer is calculated from the magnetometer data. It is found that the wave amplitudes (both electric and magnetic fields), after normalization by the average magnetic field strength in the current layer, are proportional to the local magnetic shear angle, i.e. large magnetic shear corresponds to strong wave emission and vice versa. From the dispersion relation of the waves for different shear angles, the phase velocity of the waves increases with the magnetic shear and peaks around 700 Hz to 1 kHz. The dispersion curve of the waves is consistent with that of whistler modes. C1 UNIV MARYLAND, INST PLASMA RES, COLLEGE PK, MD 20742 USA. UNIV CALIF LOS ANGELES, INST GEOPHYS & PLANETARY PHYS, LOS ANGELES, CA 90095 USA. UNIV IOWA, DEPT PHYS & ASTRON, IOWA CITY, IA 52242 USA. NASA, GODDARD SPACE FLIGHT CTR, GREENBELT, MD 20771 USA. RP Zhu, Z (reprint author), NATL CTR ATMOSPHER RES, HIGH ALTITUDE OBSERV, POB 3000, BOULDER, CO 80307 USA. OI Russell, Christopher/0000-0003-1639-8298 NR 21 TC 17 Z9 17 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 APR 1 PY 1996 VL 23 IS 7 BP 773 EP 776 DI 10.1029/96GL00591 PG 4 WC Geosciences, Multidisciplinary SC Geology GA UD380 UT WOS:A1996UD38000020 ER PT J AU Shavers, MR Poston, JW Cucinotta, FA Wilson, JW AF Shavers, MR Poston, JW Cucinotta, FA Wilson, JW TI Dose equivalent near the bone soft tissue interface from nuclear fragments produced by high-energy protons SO HEALTH PHYSICS LA English DT Article DE dose equivalent; tissue, body; radiation risk; protons ID TARGET FRAGMENTS; RISK ASSESSMENT; MOUSE FEMUR; STEM-CELL; RADIATION; MODEL; DISTRIBUTIONS; INACTIVATION; EXPOSURE AB During manned space missions, high-energy nucleons of cosmic and solar origin collide with atomic nuclei of the human body and produce a broad linear energy transfer spectrum of secondary particles, called target fragments, These nuclear fragments are often more biologically harmful than the direct ionization of the incident nucleon, That these secondary particles increase tissue absorbed dose in regions adjacent to the bone-soft tissue interface was demonstrated in a previous publication, To assess radiological risks to tissue near the bone-soft tissue interface, a computer transport model for nuclear fragments produced by high energy nucleons was used in this study to calculate integral linear energy transfer spectra and dose equivalents resulting from nuclear collisions of 1-GeV protons traversing bone and red bone marrow, In terms of dose equivalent averaged over trabecular bone marrow, target fragments emitted from interactions in both tissues are predicted to be at least as important as the direct ionization of the primary protons-twice as important, if recently recommended radiation weighting factors and ''worst-case'' geometry are used, The use of conventional dosimetry (absorbed dose weighted by a linear energy transfer-dependent quality factor) as an appropriate framework for predicting risk from low fluences of high-linear energy transfer target fragments is discussed. C1 NASA, LANGLEY RES CTR, HAMPTON, VA 23681 USA. NR 77 TC 1 Z9 1 U1 0 U2 0 PU LIPPINCOTT WILLIAMS & WILKINS PI PHILADELPHIA PA 530 WALNUT ST, PHILADELPHIA, PA 19106-3621 USA SN 0017-9078 EI 1538-5159 J9 HEALTH PHYS JI Health Phys. PD APR PY 1996 VL 70 IS 4 BP 473 EP 483 DI 10.1097/00004032-199604000-00003 PG 11 WC Environmental Sciences; Public, Environmental & Occupational Health; Nuclear Science & Technology; Radiology, Nuclear Medicine & Medical Imaging SC Environmental Sciences & Ecology; Public, Environmental & Occupational Health; Nuclear Science & Technology; Radiology, Nuclear Medicine & Medical Imaging GA UA703 UT WOS:A1996UA70300003 PM 8617586 ER PT J AU Ohler, TA Nielsen, SS Mitchell, CA AF Ohler, TA Nielsen, SS Mitchell, CA TI Varying plant density and harvest time to optimize cowpea leaf yield and nutrient content SO HORTSCIENCE LA English DT Article DE Vigna unguiculata; bioregenerative life-support system; controlled ecological life-support system; shoot harvest index; yield-efficiency rate; total dietary fiber ID YOUNG GREEN PODS; LIFE-SUPPORT; PHOTOSYNTHESIS; CULTIVARS; SEED AB Plant density and harvest time were manipulated to optimize vegetative (foliar) productivity of cowpea [Vigna unguiculata (L.) Walp,] canopies for future dietary use in controlled ecological life-support systems as vegetables or salad greens. Productivity was measured as total shoot and edible dry weights (DW), edible yield rate [(EYR) grams DW per square meter per day], shoot harvest index [(SHI) grams DW per edible gram DW total shoot], and yield-efficiency rate [(YER) grams DW edible per square meter per day per grams DW nonedible]. Cowpeas were grown in a greenhouse for leaf-only harvest at 14, 28, 42, 56, 84, or 99 plants/m(2) and were harvested 20, 30, 40, or 50 days after planting (PAP). Shoot and edible dry weights increased as plant density and time to harvest increased, A maximum of 1189 g shoot DW/m(2) and 594 g edible DW/m(2) were achieved at an estimated plant density of 85 plants/m(2) and harvest 50 DAP. EYR also increased as plant density and time to harvest increased, An EYR of 11 g . m(-2) day(-1) was predicted to occur at 85 plants/ m(2) and harvest 50 DAP, SHI and YER were not affected by plant density, However, the highest values of SHI (64%) and YER (1.3 g . m(-2)-day(-1). g(-1)) were attained when cowpeas were harvested 20 DAP. The average fat and ash contents [dry-weight basis (dwb)] of harvested leaves remained constant regardless of harvest time. Average protein content increased from 25% DW at 30 DAP to 45% DW at 50 DAP. Carbohydrate content declined from 50% DW at 30 DAP to 45% DW at 50 DAP. Total dietary fiber content (dwb) of the leaves increased from 19% to 26% as time to harvest increased from 20 to 50 days. C1 PURDUE UNIV,NASA,SPECIALIZED CTR RES & TRAINING BIOREGENERAT LIFE,DEPT HORT,W LAFAYETTE,IN 47907. PURDUE UNIV,NASA,SPECIALIZED CTR RES & TRAINING BIOREGENERAT LIFE,DEPT FOOD SCI,W LAFAYETTE,IN 47907. NR 16 TC 5 Z9 5 U1 1 U2 7 PU AMER SOC HORTICULTURAL SCIENCE PI ALEXANDRIA PA 701 NORTH SAINT ASAPH STREET, ALEXANDRIA, VA 22314-1998 SN 0018-5345 J9 HORTSCIENCE JI Hortscience PD APR PY 1996 VL 31 IS 2 BP 193 EP 197 PG 5 WC Horticulture SC Agriculture GA UE308 UT WOS:A1996UE30800004 PM 11539398 ER PT J AU Hansen, CJ Paige, DA AF Hansen, CJ Paige, DA TI Seasonal nitrogen cycles on Pluto SO ICARUS LA English DT Article ID PHASE-COMPOSITION; POLAR CAPS; TRITON; ATMOSPHERE; SURFACE; STABILITY; CHARON; TEMPERATURE; NEPTUNE; MODELS AB A thermal model, developed to predict seasonal nitrogen cycles on Triton, has been modified and applied to Pluto. The model was used to calculate the partitioning of nitrogen between surface frost deposits and the atmosphere, as a function of time for various sets of input parameters. Volatile transport was confirmed to have a significant effect on Pluto's climate as nitrogen moved around on a seasonal time scale between hemispheres, and sublimed into and condensed out of the atmosphere. Pluto's high obliquity was found to have a significant effect on the distribution of frost on its surface. Conditions that would lead to permanent polar caps on Triton were found to lead to permanent zonal frost bands on Pluto. In some instances, frost sublimed from the middle of a seasonal cap outward, resulting in a ''polar bald spot''. Frost which was darker than the substrate did not satisfy observables on Pluto, in contrast to our findings for Triton. Bright frost (brighter than the substrate) came closer to matching observables. Atmospheric pressure varied seasonally. The amplitudes, and to a lesser extent the phase, of the variation depended significantly on frost and substrate properties. Atmospheric pressure was found to be determined both by Pluto's distance from the sun and by the subsolar latitude. In most cases two peaks in atmospheric pressure were observed annually: a greater one associated with the sublimation of the north polar cap just as Pluto receded from perihelion, and a lesser one associated with the sublimation of the south polar cap as Pluto approached perihelion. Our model predicted frost-free dark substrate surface temperatures in the 50 to 60 K range, while frost temperatures typically ranged between 30 to 40 K. Temporal changes in frost coverage illustrated by our results, and changes in the viewing geometry of Pluto from the Earth, may be important for interpretation of ground-based measurements of Pluto's thermal emission. (C) 1996 Academic Press, Inc. C1 UNIV CALIF LOS ANGELES,DEPT EARTH & SPACE SCI,LOS ANGELES,CA 90024. RP Hansen, CJ (reprint author), CALTECH,JET PROP LAB,4800 OAK GROVE DR,PASADENA,CA 91109, USA. NR 51 TC 52 Z9 52 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 APR PY 1996 VL 120 IS 2 BP 247 EP 265 DI 10.1006/icar.1996.0049 PG 19 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA UH038 UT WOS:A1996UH03800001 ER PT J AU Kim, SJ Orton, GS Dumas, C Kim, YH AF Kim, SJ Orton, GS Dumas, C Kim, YH TI Infrared spectroscopy of Jupiter's atmosphere after the A and E impacts of Comet Shoemaker-Levy 9 SO ICARUS LA English DT Article ID FUNDAMENTAL-BAND; H-3(+); H-3+ AB Infrared spectra of Jupiter's atmosphere were obtained with the infrared spectrometer (IRS) on the 1.5-m telescope at the Cerro Tololo Inter-American Observatory (CTIO) during the first 2 days of the impacts of the fragments of Comet Shoemaker-levy 9 (1993e), We monitored 3.51 +/- 0.17 mu m radiation from the impact areas, undisturbed areas, and auroral regions of Jupiter after the A and E impacts, The strong emission of a portion of the P-branch of the nu(3) band of CH4 was detected on the A impact area 4 hr after the impact. H-3(+) emissions are found to be decreased at the A and E impact sites after 4 hr and 10 hr 50 min of the impacts, respectively, compared with undisturbed areas at the same latitude, The temperatures of the southern H-3(+) aurora were normal within the first several hours following the A and E impacts. (C) 1996 Academic Press, Inc. C1 UNIV MARYLAND, DEPT ASTRON, COLLEGE PK, MD 20742 USA. CALTECH, JET PROP LAB, PASADENA, CA 91109 USA. UNIV HAWAII, INST ASTRON, HONOLULU, HI 96822 USA. CHUNGNAM NATL UNIV, DEPT ASTRON & SPACE SCI, TAEJON, SOUTH KOREA. RP Kim, SJ (reprint author), KYUSHU UNIV, KYUNGHEE OBSERV, DEPT ASTRON & SPACE SCI, FUKUOKA 812, JAPAN. RI Kim, Sang Joon/E-2383-2013 NR 21 TC 10 Z9 10 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 APR PY 1996 VL 120 IS 2 BP 326 EP 331 DI 10.1006/icar.1996.0053 PG 6 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA UH038 UT WOS:A1996UH03800005 ER PT J AU DelGenio, AD Zhou, W AF DelGenio, AD Zhou, W TI Simulations of superrotation on slowly rotating planets: Sensitivity to rotation and initial condition SO ICARUS LA English DT Article ID TITANS ATMOSPHERE; MIDDLE ATMOSPHERE; VENUS; DYNAMICS; CIRCULATION; WINDS; MAINTENANCE; OCCULTATION AB We use a simplified terrestrial general circulation model as a nonlinear process model to investigate factors that influence the extent of equatorial superrotation in statically stable atmospheres on slowly rotating planets such as Titan and Venus, The possibility of multiple equilibria is tested by running the same model to equilibrium from vastly different initial conditions, The final state is effectively independent of initial state, reinforcing the impression that equatorial superrotation is inevitable on slowly rotating planets with stable radiative equilibrium structures, Of particular interest is the fact that at Titan rotation, the model equilibrates with strong prograde winds even when initialized with strong retrograde winds, This suggests that reliable remote sensing inferences of latitudinal temperature gradients on Titan can unambiguously be interpreted as evidence for superrotation, We also demonstrate for the first time that significant equatorial superrotation can be produced at Venus' rotation rate in such models, given sufficient numerical precision, The strength of superrotating zonal winds increases with rotation rate in the slowly rotating regime when other parameters are held fixed, However, the efficiency of superrotation relative to the angular momentum of an atmosphere corotating with the solid planet increases with decreasing rotation rate instead, because the Hadley cell strengthens and expands poleward, This allows for the formation of stronger high latitude jets, which ultimately serve as the source for equatorial superrotation via barotropic instability, Estimates of relevant parameter settings for Triton and Pluto tentatively imply that their atmospheres may marginally be in the superrotating regime, but only if temperature decreases with height near the surface. (C) 1996 Academic Press, Inc. C1 SCI SYST & APPLICAT INC,NEW YORK,NY 10025. RP DelGenio, AD (reprint author), NASA,GODDARD INST SPACE STUDIES,NEW YORK,NY 10025, USA. RI Del Genio, Anthony/D-4663-2012 OI Del Genio, Anthony/0000-0001-7450-1359 NR 23 TC 64 Z9 64 U1 0 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 APR PY 1996 VL 120 IS 2 BP 332 EP 343 DI 10.1006/icar.1996.0054 PG 12 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA UH038 UT WOS:A1996UH03800006 ER PT J AU Baron, RL Owen, T Connerney, JEP Satoh, T Harrington, J AF Baron, RL Owen, T Connerney, JEP Satoh, T Harrington, J TI Solar wind control of Jupiter's H-3(+) auroras SO ICARUS LA English DT Article ID ULYSSES ENCOUNTER; RADIO-EMISSION; POLAR AURORA; MU-M; H-3+; MAGNETOSPHERE; TIME; IO; VARIABILITY; ENVIRONMENT AB A program of observations of Jupiter's H-3(+) auroras was conducted during the first 4 months of 1992, a period that spanned the Ulysses encounter. Daily variations of auroral intensity are small in magnitude (similar to 20%) and well correlated with variations in the solar wind ram pressure arriving at Jupiter, A much larger (factor of 3) time variation is observed to occur on a time scale of approximately 2 months. During the first 2 months of observation, the inferred total intrinsic intensity of the northern aurora exceeded that of the southern aurora by a factor of 2. Throughout the latter 2 months, characterized by less intense auroral activity, the intensity of the northern aurora was comparable to that of the southern aurora. (C) 1996 Academic Press, Inc. C1 NASA,GODDARD SPACE FLIGHT CTR,EXTRATERR PHYS LAB,GREENBELT,MD 20771. RP Baron, RL (reprint author), UNIV HAWAII,INST ASTRON,2680 WOODLAWN DR,HONOLULU,HI 96822, USA. RI Harrington, Joseph/E-6250-2011; connerney, john/I-5127-2013 NR 32 TC 53 Z9 53 U1 0 U2 0 PU ACADEMIC PRESS INC JNL-COMP SUBSCRIPTIONS PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 SN 0019-1035 J9 ICARUS JI Icarus PD APR PY 1996 VL 120 IS 2 BP 437 EP 442 DI 10.1006/icar.1996.0063 PG 6 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA UH038 UT WOS:A1996UH03800015 ER PT J AU Gledhill, CT LyczkowskiShultz, J Rademacher, K Kargard, E Crist, G Grace, MA AF Gledhill, CT LyczkowskiShultz, J Rademacher, K Kargard, E Crist, G Grace, MA TI Evaluation of video and acoustic index methods for assessing reef-fish populations SO ICES JOURNAL OF MARINE SCIENCE LA English DT Article; Proceedings Paper CT ICES International Symposium on Fisheries and Plankton Acoustics CY JUN 12-16, 1995 CL MARINE LAB, ABERDEEN, SCOTLAND SP Int Council Explorat Sea, Inst Acoust, Acoust Soc Amer, Soc Francaise Acoust HO MARINE LAB DE fisheries acoustics; reef fish; video camera AB Since 1991, the National Marine Fisheries Service (NMFS) has used a video camera/trap system to assess the relative abundance of reef fishes in the Gulf of Mexico occurring on natural hard-bottom substrata at depths between 9 m and 110 m. The relative index of reef-fish abundance resulting from these annual Gulf-wide surveys is based on counts of fish recorded during a 1 h set of a video camera on the bottom. During the 1993 reef-fish survey, a total of 115 reef sites were sampled with a video camera and fisheries acoustic system. Video data were used to identify fish species distributed above the bottom. Off-bottom fish included snappers (Lutjanidae), groupers (Serranidae), and amberjacks (Seriola spp.), species of interest to commercial and recreational fisheries. Correlation between total off-bottom taxa abundance and volume backscatter was low (r=0.41, n=115). The low correlation may be caused by differences in the area sampled by the video camera and acoustic systems al each site. The low correlation limits the use of acoustic data as an auxiliary variable in a combined video-acoustic estimator. (C) 1996 International Council for the Exploration of the Sea. C1 NATL MARINE FISHERIES SERV,SE FISHERIES SCI CTR,MISSISSIPPI LABS,PASCAGOULA,MS 39568. RP Gledhill, CT (reprint author), UNIV S ALABAMA,DEPT MARINE SCI,MOBILE,AL 36688, USA. NR 3 TC 21 Z9 22 U1 0 U2 5 PU ACADEMIC PRESS LTD PI LONDON PA 24-28 OVAL RD, LONDON, ENGLAND NW1 7DX SN 1054-3139 J9 ICES J MAR SCI JI ICES J. Mar. Sci. PD APR PY 1996 VL 53 IS 2 BP 483 EP 485 DI 10.1006/jmsc.1996.0069 PG 3 WC Fisheries; Marine & Freshwater Biology; Oceanography SC Fisheries; Marine & Freshwater Biology; Oceanography GA UJ679 UT WOS:A1996UJ67900058 ER PT J AU Poggio, AJ Zacharias, RA Pennock, ST Avalle, CA Carney, H AF Poggio, AJ Zacharias, RA Pennock, ST Avalle, CA Carney, H TI NASA B-757 HIRF test series low power on-the-ground tests SO IEEE AEROSPACE AND ELECTRONIC SYSTEMS MAGAZINE LA English DT Article AB The data acquisition phase of a program intended to provide data for the validation of computational, analytical and experimental techniques for the assessment of electromagnetic effects in commercial transports, for the checkout of instrumentation for following test programs, and for the support of protection engineering of airborne systems has been completed. Funded by the NASA Fly-By-Light/Power-By-Wire Program, the initial phase involved on-the-ground electromagnetic measurements using the NASA Boeing 757 and was executed in the LESLI Facility at the USAF Phillips Laboratory. The major participants were LLNL, NASA Langley Research Center, Phillips Laboratory, and UIE, Inc. Measurements were made of the fields coupled into the aircraft interior and signals induced in select structures and equipment under controlled illumination by RF fields. A characterization of the ground was also performed to permit ground effects to be included in forthcoming computer modeling exercises. A series of fly-by experiments were conducted in early 1995 in which the NASA B-757 was flown in the vicinity of a Voice of America station (similar to 25 MHz), a fixed transmitter driving a log periodic array (172 MHz), and an ASRF radar at Wallops Island (430 MHz). In this paper, the overall test program is defined with particular attention to the on-the-ground portion. The test rationale, test layout, and samples of the data are described. Samples of some inferences from the data that will be useful in protection engineering and EM effects mitigation will also be presented. C1 NASA,LANGLEY RES CTR,HAMPTON,VA 23665. RP Poggio, AJ (reprint author), LAWRENCE LIVERMORE NATL LAB,LIVERMORE,CA 94551, USA. NR 3 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 0885-8985 J9 IEEE AERO EL SYS MAG JI IEEE Aerosp. Electron. Syst. Mag. PD APR PY 1996 VL 11 IS 4 BP 27 EP 33 DI 10.1109/62.490221 PG 7 WC Engineering, Aerospace; Engineering, Electrical & Electronic SC Engineering GA UE972 UT WOS:A1996UE97200010 ER PT J AU Mouret, I Calvel, P Allenspach, M Titus, JL Wheatley, CF LaBel, KA Calvet, MC Schrimpf, RD Galloway, KF AF Mouret, I Calvel, P Allenspach, M Titus, JL Wheatley, CF LaBel, KA Calvet, MC Schrimpf, RD Galloway, KF TI Measurement of a cross-section for single-event gate rupture in power MOSFET's SO IEEE ELECTRON DEVICE LETTERS LA English DT Article AB The heavy-ion fluence required to induce Single-Event Gate Rupture (SEGR) in power MOSFET's is measured as a function of the drain bias, V-DS, and as a function of the gate bias, V-GS These experiments reveal the abrupt nature of the SEGR-voltage threshold, In addition, the concepts of cross-section, threshold, and saturation in the SEGR phenomenon are introduced, This experimental technique provides a convenient method to quantify heavy-ion effects in power MOSFET's. C1 AEROSPITIALE,F-71833 LES MUREAUX,FRANCE. ALCATEL ESPACE,F-31037 TOULOUSE,FRANCE. USN,CTR SURFACE WARFARE,CRANE,IN 47522. RR2,DRUMS,PA 18222. NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. RP Mouret, I (reprint author), UNIV ARIZONA,TUCSON,AZ 85721, USA. RI Schrimpf, Ronald/L-5549-2013 OI Schrimpf, Ronald/0000-0001-7419-2701 NR 12 TC 16 Z9 16 U1 0 U2 1 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI PISCATAWAY PA 445 HOES LANE, PISCATAWAY, NJ 08855 USA SN 0741-3106 J9 IEEE ELECTR DEVICE L JI IEEE Electron Device Lett. PD APR PY 1996 VL 17 IS 4 BP 163 EP 165 DI 10.1109/55.485161 PG 3 WC Engineering, Electrical & Electronic SC Engineering GA UC510 UT WOS:A1996UC51000003 ER PT J AU Cwik, T Zuffada, C Jamnejad, V AF Cwik, T Zuffada, C Jamnejad, V TI Modeling three-dimensional scatterers using a coupled finite element - Integral equation formulation SO IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION LA English DT Article ID ELECTROMAGNETIC SCATTERING; REVOLUTION; CYLINDERS; OBJECTS; BODIES AB Finite-element modeling has proven useful for accurately simulating scattered or radiated fields from complex three-dimensional objects whose geometry varies on the scale of a fraction of a wavelength, To practically compute a solution to exterior problems, the domain must be truncated at some finite surface where the Sommerfeld radiation condition is enforced, either approximately or exactly, This paper outlines a method that couples three-dimensional finite-element solutions interior to a bounding surface with an efficient integral equation solution that exactly enforces the Sommerfeld radiation condition, The general formulation and the main features of the discretized problem are first briefly outlined. Results for far and near fields are presented for geometries where an analytic solution exists and compared with exact solutions to establish the accuracy of the model, Results are also presented for objects that do not allow an analytic solution, and are compared with other calculations and/or measurements. RP Cwik, T (reprint author), CALTECH,JET PROP LAB,4800 OAK GROVE DR,PASADENA,CA 91109, USA. NR 15 TC 24 Z9 24 U1 0 U2 0 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 SN 0018-926X J9 IEEE T ANTENN PROPAG JI IEEE Trans. Antennas Propag. PD APR PY 1996 VL 44 IS 4 BP 453 EP 459 DI 10.1109/8.489296 PG 7 WC Engineering, Electrical & Electronic; Telecommunications SC Engineering; Telecommunications GA UD858 UT WOS:A1996UD85800004 ER PT J AU Moreira, FJS Prata, A Thorburn, MA AF Moreira, FJS Prata, A Thorburn, MA TI Minimization of the plane-wave scattering contribution of inverted-Y strut tripods to the noise temperature of reflector antennas SO IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION LA English DT Article ID FEED-SUPPORT STRUTS; PARABOLOIDAL ANTENNAS AB This work is concerned with determining the metallic strut cross section of inverted-Y tripods to minimize the plane-wave scattering contribution to the noise temperature of ground-station reflector antennas and radio telescopes. This is accomplished by numerically optimizing the cross section for minimum ground-noise pickup over the antenna elevation-angle operation range, Advantage is taken of the fact that although the struts' cross-section perimeter can be comparable to the operation wavelength, their electrical lengths are usually long, This allows the struts' scattering characteristics to be determined by solving standard two-dimensional field integral equations. This work concentrates on the top strut of an inverted-Y configuration since it is responsible for the dominant ground noise pickup associated with the plane-wave scattering, Numerical simulations are presented to substantiate this fact and a simple and convenient broadband closed-form representation for the minimum-noise top-strut cross section is derived and tested. C1 CALTECH,JET PROP LAB,PASADENA,CA 91109. RP Moreira, FJS (reprint author), UNIV SO CALIF,DEPT ELECT ENGN ELECTROPHYS,LOS ANGELES,CA 90089, USA. RI Moreira, Fernando/F-3905-2010 OI Moreira, Fernando/0000-0002-9115-9951 NR 11 TC 4 Z9 4 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 0018-926X J9 IEEE T ANTENN PROPAG JI IEEE Trans. Antennas Propag. PD APR PY 1996 VL 44 IS 4 BP 492 EP 499 DI 10.1109/8.489300 PG 8 WC Engineering, Electrical & Electronic; Telecommunications SC Engineering; Telecommunications GA UD858 UT WOS:A1996UD85800008 ER PT J AU Hunt, LR Meyer, G Su, R AF Hunt, LR Meyer, G Su, R TI Noncausal inverses for linear systems SO IEEE TRANSACTIONS ON AUTOMATIC CONTROL LA English DT Article AB Suppose we are to guide a plant with a square transfer matrix through a series of way points. This can be accomplished by output tracking of trajectories which are fitted together in a sufficiently smooth manner, Each segment of each output is prescribed in terms of a polynomial or sine function or the product thereof, Our technique is to compute: 1) a noncausal ''particular solution'' based on the desired trajectory over each segment and the movement from one segment to the next. This ''particular solution'' consists of a ''particular control'' and a ''particular state trajectory;'' 2) a regulator to handle modeling errors, disturbances, etc. We concentrate on the ''particular solution.'' 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, PROGRAM MATH SCI, RICHARDSON, TX 75083 USA. NR 8 TC 91 Z9 94 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 APR PY 1996 VL 41 IS 4 BP 608 EP 611 DI 10.1109/9.489285 PG 4 WC Automation & Control Systems; Engineering, Electrical & Electronic SC Automation & Control Systems; Engineering GA UF703 UT WOS:A1996UF70300016 ER PT J AU Feynman, J Gabriel, SB AF Feynman, J Gabriel, SB TI High-energy charged particles in space at one astronomical unit SO IEEE TRANSACTIONS ON NUCLEAR SCIENCE LA English DT Article ID PROTON FLUENCE MODEL; COSMIC-RAYS AB Single-event effects and many other spacecraft anomalies are caused by positively charged high-energy particles impinging on the vehicle and its component parts. Here, we review the current knowledge of the interplanetary particle environment in the energy ranges that are most important for these effects. State-of-the-art engineering models are described briefly along with comments on the future work required in this field. C1 UNIV SOUTHAMPTON,DEPT AERONAUT & ASTRONAUT,SOUTHAMPTON SO9 5NH,HANTS,ENGLAND. RP Feynman, J (reprint author), CALTECH,JET PROP LAB,4800 OAK GROVE DR,PASADENA,CA 91109, USA. NR 20 TC 21 Z9 21 U1 0 U2 2 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 SN 0018-9499 J9 IEEE T NUCL SCI JI IEEE Trans. Nucl. Sci. PD APR PY 1996 VL 43 IS 2 BP 344 EP 352 DI 10.1109/23.490754 PN 1 PG 9 WC Engineering, Electrical & Electronic; Nuclear Science & Technology SC Engineering; Nuclear Science & Technology GA UJ077 UT WOS:A1996UJ07700003 ER PT J AU Stassinopoulos, EG Brucker, GJ Nakamura, DW Stauffer, CA Gee, GB Barth, JL AF Stassinopoulos, EG Brucker, GJ Nakamura, DW Stauffer, CA Gee, GB Barth, JL TI Solar flare proton evaluation at geostationary orbits for engineering applications SO IEEE TRANSACTIONS ON NUCLEAR SCIENCE LA English DT Article ID FLUENCE MODEL; EVENTS; UPSETS AB This work presents the results of novel analyses of spacecraft solar flare proton measurements for solar cycles 20, 21, and 22. Solar events and cycles were classified and ranked by fluence and frequency of occurrence, and events were characterized by the mean energy of the proton spectral distributions, Spacecraft observations permitted a detailed study of event characteristics, such as special consideration of solar minimum flares and cycle variability. Tables and curves are presented to allow evaluations of potential threats to spacecraft survivability at GEO, particularly for types of flare environments that emulate solar cycle 22. Upsets for major events are calculated for several Bendel A parameter values and shield thicknesses, and effective energy thresholds of events are determined as a function of these variables, Critical fluence levels, required to cause errors, versus A are presented, SEU's (single event upsets) of 93L422 devices on TDRS-1 are evaluated for various shielding conditions, Finally, upset dependencies on A and shield thickness are correlated with event fluences for threshold energies of >30, >50, and >60 MeV. C1 RADIAT EFFECTS CONSULTANTS,W LONG BRANCH,NJ. SES INC,GREENBELT,MD. RP Stassinopoulos, EG (reprint author), NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771, USA. NR 16 TC 17 Z9 17 U1 0 U2 0 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 SN 0018-9499 J9 IEEE T NUCL SCI JI IEEE Trans. Nucl. Sci. PD APR PY 1996 VL 43 IS 2 BP 369 EP 382 DI 10.1109/23.490756 PN 1 PG 14 WC Engineering, Electrical & Electronic; Nuclear Science & Technology SC Engineering; Nuclear Science & Technology GA UJ077 UT WOS:A1996UJ07700005 ER PT J AU Johnston, AH AF Johnston, AH TI The influence of VLSI technology evolution on radiation-induced latchup in space systems SO IEEE TRANSACTIONS ON NUCLEAR SCIENCE LA English DT Article ID 0.25-MU-M CMOS TECHNOLOGY; BULK CMOS; INTEGRATED-CIRCUITS; HEAVY-IONS; P-WELL; DEVICES; PROTON; SINGLE; MODEL; TEMPERATURE AB Changes in technology and device scaling have generally increased the sensitivity of VLSI devices to latchup from single interactions of heavy particles in space, This paper discusses latchup mechanisms, comparing latchup from heavy particles in space with electrically induced latchup, which has been more widely studied, The effects of technology changes and device scaling on latchup susceptibility are discussed as well. Test methods and the interpretation of latchup results are also included, along with predictions of the effects of device evolution and scaling on latchup susceptibility in space. RP Johnston, AH (reprint author), CALTECH,JET PROP LAB,4800 OAK GROVE DR,PASADENA,CA 91109, USA. NR 69 TC 64 Z9 69 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 0018-9499 J9 IEEE T NUCL SCI JI IEEE Trans. Nucl. Sci. PD APR PY 1996 VL 43 IS 2 BP 505 EP 521 DI 10.1109/23.490897 PN 1 PG 17 WC Engineering, Electrical & Electronic; Nuclear Science & Technology SC Engineering; Nuclear Science & Technology GA UJ077 UT WOS:A1996UJ07700016 ER PT J AU Marshall, PW Dale, CJ LaBel, KA AF Marshall, PW Dale, CJ LaBel, KA TI Space radiation effects in high performance fiber optic data links for satellite data management SO IEEE TRANSACTIONS ON NUCLEAR SCIENCE LA English DT Article AB Fiber optic based technologies are relatively new to satellite applications, and are receiving considerable attention for planned applications in NASA, DOD, and commercial space sectors. We review various activities in recent years aimed at understanding and mitigating radiation related risk in deploying fiber based data handling systems on orbit. Before concluding that there are no critical barriers to designing survivable and reliable systems, we analyze several possible types of radiation effects. Particular attention is given to the subject of particle-induced bit errors in InGaAs p-i-n photodiodes, including a discussion of error mitigation and upset rate prediction methods. C1 SFA INC,LANDOVER,MD 20785. NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. RP Marshall, PW (reprint author), USN,RES LAB,WASHINGTON,DC 20375, USA. NR 29 TC 31 Z9 32 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 0018-9499 J9 IEEE T NUCL SCI JI IEEE Trans. Nucl. Sci. PD APR PY 1996 VL 43 IS 2 BP 645 EP 653 DI 10.1109/23.490907 PN 1 PG 9 WC Engineering, Electrical & Electronic; Nuclear Science & Technology SC Engineering; Nuclear Science & Technology GA UJ077 UT WOS:A1996UJ07700026 ER PT J AU LaBel, KA Gates, NM AF LaBel, KA Gates, NM TI Single-event-effect mitigation from a system perspective SO IEEE TRANSACTIONS ON NUCLEAR SCIENCE LA English DT Article ID TRANSIENT AB With the sharp decline in the availability of radiation-hardened devices from manufacturers, as well as the desire to shrink power, weight, and volume of spacecraft systems, the use of devices that are susceptible to single-event effects (SEE's) has become commonplace. We present herein a perspective and user's tool for understanding SEE's and potential system-level mitigation techniques. RP LaBel, KA (reprint author), NASA,GODDARD SPACE FLIGHT CTR,CODE 735-1,GREENBELT,MD 20771, USA. NR 32 TC 18 Z9 18 U1 0 U2 1 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 SN 0018-9499 J9 IEEE T NUCL SCI JI IEEE Trans. Nucl. Sci. PD APR PY 1996 VL 43 IS 2 BP 654 EP 660 DI 10.1109/23.490908 PN 1 PG 7 WC Engineering, Electrical & Electronic; Nuclear Science & Technology SC Engineering; Nuclear Science & Technology GA UJ077 UT WOS:A1996UJ07700027 ER PT J AU Soulas, GC Myers, RM AF Soulas, GC Myers, RM TI Mechanisms of anode power deposition in a low pressure free burning arc SO IEEE TRANSACTIONS ON PLASMA SCIENCE LA English DT Article; Proceedings Paper CT International Workshop on 2nd-Generation Plasma Accelerators CY JUN 26-30, 1995 CL KARDAMYLI, GREECE ID MAGNETOPLASMADYNAMIC THRUSTERS AB Anode power deposition is a dominant power loss mechanism for arcjets and magnetoplasmadynamic (MPD) thrusters. In this study, a free burning arc experiment was operated at pressures and current densities similar to those in arcjets and MPD thrusters in an attempt to identify the physics controlling this loss mechanism. Use of a free burning are-allowed for the isolation of independent variables controlling anode power deposition and provided a convenient and flexible way to cover a broad range of currents, anode surface pressures, and applied magnetic field strengths and orientations using an argon gas. Test results showed that anode power deposition decreased with increasing anode surface pressure up to 6.7 Pa and then became insensitive to pressure. Anode power increased with increasing are current, while the electron number density near the anode surface increased linearly, Anode power also increased with increasing applied magnetic field strength due to an increasing anode fall voltage, Applied magnetic field orientation had an effect only at high currents and low anode surface pressures, when anode power decreased when applied-field lines intercepted the anode surface. The results demonstrated that anode power deposition was dominated by the kinetic energy of the current-carrying electrons acquired over the anode fail region. Furthermore, the results showed that anode power deposition can be reduced by operating at increased anode pressures, reduced are currents, anode current densities, and applied magnetic field strengths, and with magnetic field lines intercepting the anode. RP Soulas, GC (reprint author), NASA, LEWIS RES CTR GRP, NYMA INC, BROOKPARK, OH 44142 USA. NR 43 TC 1 Z9 1 U1 0 U2 3 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 SN 0093-3813 J9 IEEE T PLASMA SCI JI IEEE Trans. Plasma Sci. PD APR PY 1996 VL 24 IS 2 BP 478 EP 486 DI 10.1109/27.510013 PG 9 WC Physics, Fluids & Plasmas SC Physics GA UP870 UT WOS:A1996UP87000024 ER PT J AU Kim, GJ Lee, S Bekey, GA AF Kim, GJ Lee, S Bekey, GA TI Interleaving assembly planning and design SO IEEE TRANSACTIONS ON ROBOTICS AND AUTOMATION LA English DT Article AB The main objective of assembly planning is to determine a sequence of assembling a product with respect to its geometric and resource constraints, Recent strides toward concurrent engineering have called for a tighter integration of assembly planning with design, because often during assembly planning, one realizes that a significant amount of assembly cost can be cut by redesigning the product itself. Instead of ''retroactively'' redesigning a product upon assembly planning, a concurrent engineering platform must allow its users to evaluate designs (e.g,, with regards to assembly sequencing), and ''proactively'' explore different alternatives at various levels of abstractions so that one can zoom in on ''promising'' design paths and design right within the first few design cycles. This paper presents such an integrated system in which assembly planning becomes an essential part of the design exploration process. An algorithm for assembly planning during design for such an environment is developed, Designing for assembly is more effective and correct because, for a particular sequence of assembly, different design alternatives can be created and evaluated. C1 UNIV SO CALIF,DEPT COMP SCI,LOS ANGELES,CA 90089. CALTECH,JET PROP LAB,PASADENA,CA 91109. RP Kim, GJ (reprint author), NIST,MFG SYST INTEGRAT DIV,ENGN DESIGN TECHNOL GRP,GAITHERSBURG,MD 20899, USA. NR 21 TC 9 Z9 9 U1 0 U2 0 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 SN 1042-296X J9 IEEE T ROBOTIC AUTOM JI IEEE Trans. Robot. Autom. PD APR PY 1996 VL 12 IS 2 BP 246 EP 251 DI 10.1109/70.488944 PG 6 WC Automation & Control Systems; Engineering, Electrical & Electronic; Robotics SC Automation & Control Systems; Engineering; Robotics GA UE318 UT WOS:A1996UE31800008 ER PT J AU Tsujikawa, Y Northam, GB AF Tsujikawa, Y Northam, GB TI Effects of hydrogen active cooling on scramjet engine performance SO INTERNATIONAL JOURNAL OF HYDROGEN ENERGY LA English DT Article AB The scramjet engine can be regarded as the most promising one to propel a vehicle at hypersonic speeds to orbit. It simply consists of an external compression inlet, combustor and nozzle. In its analysis, there are most severe difficulties in the analysis of the combustor due to problems such as turbulent diffusion and mixing at supersonic speeds. For the combustor, a two-dimensional flow model with coaxial injection of hydrogen parallel to the air flow is considered. In addition, the effect of active cooling with slush hydrogen, which is a key aspect, has been analyzed. C1 NASA,LANGLEY RES CTR,HAMPTON,VA 23681. RP Tsujikawa, Y (reprint author), UNIV OSAKA PREFECTURE,1-1 GAKUEN CHO,SAKAI,OSAKA 593,JAPAN. NR 8 TC 26 Z9 28 U1 0 U2 9 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, ENGLAND OX5 1GB SN 0360-3199 J9 INT J HYDROGEN ENERG JI Int. J. Hydrog. Energy PD APR PY 1996 VL 21 IS 4 BP 299 EP 304 DI 10.1016/0360-3199(95)00077-1 PG 6 WC Chemistry, Physical; Electrochemistry; Energy & Fuels SC Chemistry; Electrochemistry; Energy & Fuels GA UB236 UT WOS:A1996UB23600007 ER PT J AU Durden, SL Haddad, ZS Morrissey, LA Livingston, GP AF Durden, SL Haddad, ZS Morrissey, LA Livingston, GP TI Classification of radar imagery over boreal regions for methane exchange studies SO INTERNATIONAL JOURNAL OF REMOTE SENSING LA English DT Article AB Airborne synthetic aperture radar (SAR) data acquired over Alaska are used to investigate the ability of SAR to distinguish between land cover classes of differing methane exchange rates. Land cover within the study area is divided into four classes: forest, bog, water, and fen, with fen having the highest methane emission. Accurate classification is achieved using both statistical and neural network techniques applied to fully polarimetric L- and C-band data. Similar classification accuracies are also obtained using non-polarimetric subsets of the data, analogous to data that would be available by combining SAR observations from ERS-1/2, JERS-1 (Fuyo-l), and RADARSAT. Accurate classification of fens, however, is possible only when the non-polarimetric subset includes L-band data. C1 UNIV VERMONT,SCH NAT RESOURCES,BURLINGTON,VT 05405. NASA,AMES RES CTR,JOHNSON CONTROLS WORLD SERV,MOFFETT FIELD,CA 94035. RP Durden, SL (reprint author), CALTECH,JET PROP LAB,4800 OAK GROVE DR,PASADENA,CA 91109, USA. NR 10 TC 4 Z9 5 U1 0 U2 1 PU TAYLOR & FRANCIS LTD PI LONDON PA ONE GUNDPOWDER SQUARE, LONDON, ENGLAND EC4A 3DE SN 0143-1161 J9 INT J REMOTE SENS JI Int. J. Remote Sens. PD APR PY 1996 VL 17 IS 6 BP 1267 EP 1273 PG 7 WC Remote Sensing; Imaging Science & Photographic Technology SC Remote Sensing; Imaging Science & Photographic Technology GA UG095 UT WOS:A1996UG09500012 ER PT J AU Cunningham, TJ AF Cunningham, TJ TI Improvements in GaAs JFETs for deep cryogenic operation SO JOURNAL DE PHYSIQUE IV LA English DT Article; Proceedings Paper CT 2nd European Workshop on Low Temperature Electronics (WOLTE 2) CY JUN 26-28, 1996 CL LOUVAIN, BELGIUM AB Gallium arsenide junction field-effect transistors (GaAs JFETs) can be made immune to carrier freeze-out, making such transistors useful for the readout of detector arrays that operate at 4 K. Typical applications require transistors with very low noise and extremely low leakage current. By using a recently developed etchant for GaAs that is highly isotropic, etched GaAs JFETs have fabricated that have a gently tapered edge. This reduces edge fields, which consequently reduces the edge tunneling current, the dominant source of leakage current at 4 K. JFETs with gate leakage currents below 10(-15) amps have been fabricated. The fabrication technique, including the isotropic etchant is discussed. The leakage current and noise of these JFETs are presented and compared with previous devices using a conventional etch. RP Cunningham, TJ (reprint author), JET PROP LAB,MAIL STOP 300-315,4800 OAK GROVE DR,PASADENA,CA 91109, USA. NR 7 TC 1 Z9 1 U1 0 U2 0 PU EDITIONS PHYSIQUE PI LES ULIS CEDEX PA Z I DE COURTABOEUF AVE 7 AV DU HOGGAR, BP 112, 91944 LES ULIS CEDEX, FRANCE SN 1155-4339 J9 J PHYS IV JI J. Phys. IV PD APR PY 1996 VL 6 IS C3 BP 231 EP 236 DI 10.1051/jp4:1996335 PG 6 WC Physics, Multidisciplinary SC Physics GA UU973 UT WOS:A1996UU97300036 ER PT J AU Southward, RE Thompson, DS Thompson, DW StClair, AK AF Southward, RE Thompson, DS Thompson, DW StClair, AK TI Enhancement of dimensional stability in soluble polyimides via lanthanide(III) acetate additives SO JOURNAL OF ADVANCED MATERIALS LA English DT Article ID CERAMIC POLYMER COMPOSITES; FLUORINATED POLYIMIDES; 2,2'-BIS(TRIFLUOROMETHYL)-4,4'-DIAMINOBIPHENYL; FILMS; NANOCLUSTERS; IRON AB Soluble lanthanide(III) acetate tetrahydrates have been added to dimethylacetamide solutions of the soluble colorless polyimide 6FDA/3,3'-APB formed from 2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride and 1,3-bis(3-amino-phenoxy) benzene to effect the isotropic lowering of the linear coefficient of thermal expansion (CTE) of the resulting polyimide films. Thermal treatment of the doped films generates an inorganic lanthanide phase which consists of particles from 20-40 nm in the bulk of the film and lowers the CTE's up to 12 percent (relative to controls with the same thermal history). The thermal and mechanical properties of the doped polyimide films are retained. The films retain the optical transparency of the parent polyimide. C1 COLL WILLIAM & MARY,DEPT APPL SCI,WILLIAMSBURG,VA 23185. NASA,LANGLEY RES CTR,DIV MAT,HAMPTON,VA 23665. RP Southward, RE (reprint author), COLL WILLIAM & MARY,DEPT CHEM,WILLIAMSBURG,VA 23185, USA. NR 42 TC 7 Z9 8 U1 0 U2 0 PU SAMPE PUBLISHERS PI COVINA PA 1161 PARKVIEW DRIVE, COVINA, CA 91722 SN 1070-9789 J9 J ADV MATER JI J. Adv. Mater. PD APR PY 1996 VL 27 IS 3 BP 2 EP 8 PG 7 WC Materials Science, Multidisciplinary SC Materials Science GA UP064 UT WOS:A1996UP06400001 ER PT J AU Hinkley, JA AF Hinkley, JA TI DSC study of the cure of a phenylethynyl-terminated imide oligomer SO JOURNAL OF ADVANCED MATERIALS LA English DT Article ID RESINS AB A phenylethynyl-terminated imide oligomer with a nominal molecular weight of 5,000 was cur-ed under nitrogen in a differential scanning calorimeter (DSC) and isothermally in sealed pans. The reaction is complex, and cannot be described in terms of a simple order with respect to amount remaining. Its temperature dependence obeys an Arrhenius relationship with an activation energy of 33 kcal/mol (1 cal = 4.18 J). The glass transition temperature of the product continues to advance even when no residual exotherm is detectable. RP Hinkley, JA (reprint author), NASA,LANGLEY RES CTR,COMPOSITES & POLYMERS BRANCH,HAMPTON,VA 23665, USA. NR 14 TC 15 Z9 17 U1 0 U2 1 PU SAMPE PUBLISHERS PI COVINA PA 1161 PARKVIEW DRIVE, COVINA, CA 91722 SN 1070-9789 J9 J ADV MATER JI J. Adv. Mater. PD APR PY 1996 VL 27 IS 3 BP 55 EP 59 PG 5 WC Materials Science, Multidisciplinary SC Materials Science GA UP064 UT WOS:A1996UP06400009 ER PT J AU Pueschel, RF AF Pueschel, RF TI Stratospheric aerosols: Formation, properties, effects SO JOURNAL OF AEROSOL SCIENCE LA English DT Article ID MOUNT-PINATUBO; SULFURIC-ACID; EL-CHICHON; VOLCANIC AEROSOLS; CLOUD FORMATION; SULFATE AEROSOLS; OZONE DEPLETION; NITRIC-ACID; ICE CLOUDS; CLIMATE AB Atmospheric stability in conjunction with a temperature inversion above 10 km pressure altitude, caused by the absorption of solar radiation by ozone, results in an accumulation of aerosol. The major precursor gas of the stratospheric aerosol is sulfur dioxide from volcanic eruptions. Major volcanic eruptions increase stratospheric aerosol surface area and volume by several orders of magnitude. Direct climatic forcing and changes in heterogeneous chemical reaction rates are the consequence. Anthropogenic influence on the stratospheric aerosol loading appears negligible. Soot aerosol from aircraft amounts to only a fraction of 1% of the sulfuric acid aerosol. Current stratospheric soot aerosol loadings are commensurate with emissions from commercial aircraft. Projected fuel consumption of a future supersonic fleet will increase the stratospheric soot aerosol burden by a factor of 2-3. Any effects from this increase will be confined to the northern hemisphere, because inter-hemispheric mixing of stratospheric aerosol is inhibited. Copyright (C) 1996 Elsevier Science Ltd RP Pueschel, RF (reprint author), NASA,AMES RES CTR,MOFFETT FIELD,CA 94035, USA. NR 76 TC 13 Z9 13 U1 0 U2 5 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, ENGLAND OX5 1GB SN 0021-8502 J9 J AEROSOL SCI JI J. Aerosol. Sci. PD APR PY 1996 VL 27 IS 3 BP 383 EP & DI 10.1016/0021-8502(95)00557-9 PG 19 WC Engineering, Chemical; Engineering, Mechanical; Environmental Sciences; Meteorology & Atmospheric Sciences SC Engineering; Environmental Sciences & Ecology; Meteorology & Atmospheric Sciences GA UN409 UT WOS:A1996UN40900003 ER PT J AU Nicholson, SE Lare, AR Marengo, JAP Santos, P AF Nicholson, SE Lare, AR Marengo, JAP Santos, P TI A revised version of Lettau's evapoclimatonomy model SO JOURNAL OF APPLIED METEOROLOGY LA English DT Article ID SURFACE-ENERGY BALANCE; STATES GREAT PLAINS; MONTHLY MEAN WATER; CLIMATONOMIC DESCRIPTION; SENEGALESE SAHEL; RAINFALL; BUDGETS; AFRICA; RUNOFF; AVHRR AB In this paper a revised version of Lettau's evapoclimatonomy model is introduced. Climatonomy is a one-dimensional representation of mean climate, which includes a complete characterization of the surface energy and water balances. The model is fundamentally forced by two input variables: incoming solar radiation and precipitation. All processes related to the ultimate distribution and exchange of the thereby available energy and moisture are parameterized. The goal of this paper is to describe the model's evolution and demonstrate its utility by sketching results of its application to several diverse climate problems in arid and semiarid Africa. Both the original and the revised evapoclimatonomy models are described, their conceptualization to that of more recent land-atmosphere interaction schemes is compared, their components in terms of the ecosystem are interpreted, and the model improvements incorporated in the current version are proposed. Finally, the use of the model in three applications to studies of climate and ecology in the Sahel and Kalahari regions of Africa is illustrated. C1 NASA, GODDARD SPACE FLIGHT CTR, APPL RES CORP, GREENBELT, MD 20771 USA. RP Nicholson, SE (reprint author), FLORIDA STATE UNIV, DEPT METEOROL, B-161, TALLAHASSEE, FL 32306 USA. RI Marengo, Jose /J-9382-2012 OI Marengo, Jose /0000-0002-8154-2762 NR 55 TC 18 Z9 18 U1 1 U2 4 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 USA SN 0894-8763 J9 J APPL METEOROL JI J. Appl. Meteorol. PD APR PY 1996 VL 35 IS 4 BP 549 EP 561 DI 10.1175/1520-0450(1996)035<0549:ARVOLE>2.0.CO;2 PG 13 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA UL926 UT WOS:A1996UL92600004 ER PT J AU Marengo, JA Nicholson, SE Lare, AR Monteny, BA Galle, S AF Marengo, JA Nicholson, SE Lare, AR Monteny, BA Galle, S TI Application of evapoclimatonomy to monthly surface water balance calculations at the HAPEX-Sahel supersites SO JOURNAL OF APPLIED METEOROLOGY LA English DT Article ID CLIMATONOMIC DESCRIPTION; ENERGY BALANCE; CIRCULATION; RAINFALL; DROUGHT AB In this paper a revised version of Lettau's evapoclimatonomy model is used to simulate climate in West Africa. The model is applied specifically to the study sites of the HAPEX-Sahel region in Niger, an international regional experiment to study regional-scale hydrological and energy balances of the Sahel. The model uses monthly means of precipitation, potential evapotranspiration, and solar radiation from the HAPEX-Sahel observations, as well as vegetation and soil parameters adequate for the region. Evapotranspiration, runoff, and soil moisture are determined. Differences are observed between the three vegetation types (guiera, grass, and millet) and between the three supersites. C1 FLORIDA STATE UNIV, DEPT METEOROL, TALLAHASSEE, FL 32306 USA. NASA, GODDARD SPACE FLIGHT CTR, APPL RES CORP, GREENBELT, MD 20771 USA. ORSTOM, HYDROL LAB, F-34032 MONTPELLIER, FRANCE. RI Marengo, Jose /J-9382-2012; Galle, Sylvie/D-4935-2013 OI Marengo, Jose /0000-0002-8154-2762; Galle, Sylvie/0000-0002-3100-8510 NR 41 TC 7 Z9 7 U1 2 U2 3 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 USA SN 0894-8763 J9 J APPL METEOROL JI J. Appl. Meteorol. PD APR PY 1996 VL 35 IS 4 BP 562 EP 573 DI 10.1175/1520-0450(1996)035<0562:AOETMS>2.0.CO;2 PG 12 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA UL926 UT WOS:A1996UL92600005 ER PT J AU Jackson, HW Watkins, JL Chung, S Wagner, P AF Jackson, HW Watkins, JL Chung, S Wagner, P TI Conductive sphere in a radio frequency field: Theory and applications to positioners, heating, and noncontact measurements SO JOURNAL OF APPLIED PHYSICS LA English DT Article ID LEVITATED METAL SPHERE; ABSORPTION; FORCE; POWER AB An electrically conductive spherical sample located in an electromagnetic field excited by rf (radio frequency) current in a system of coaxial coils is treated theoretically. Maxwell's equations are solved exactly and all integrals in the formulas for the fields are evaluated analytically for the case where the sphere is on the axis and the coil system is modeled by a stack of filamentary circular loops. Formulas are also derived for electromagnetic force exerted on the sphere, excess impedance in the coil system due to the presence of the sphere, and power absorbed by the sphere. All integrals in those formulas have been evaluated analytically. Force measurements are presented and they are in excellent agreement with the new theory. A low-power electromagnetic levitator that is accurately described by the theory has been demonstrated and is discussed. Experimental measurements of excess impedance are presented and compared with theory, and those results are used to demonstrate an accurate noncontact method for determining electrical conductivity. Theoretical formulas for power absorption are evaluated numerically and their usefulness in both rf heating and in making noncontact measurements of a number of thermophysical properties of materials is discussed. (C) 1996 American Institute of Physics. C1 CALTECH,JET PROP LAB,PASADENA,CA 91109. NR 16 TC 1 Z9 1 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 APR 1 PY 1996 VL 79 IS 7 BP 3370 EP 3384 DI 10.1063/1.361419 PG 15 WC Physics, Applied SC Physics GA UC073 UT WOS:A1996UC07300002 ER PT J AU Guenther, B Barnes, W Knight, E Barker, J Harnden, J Weber, R Roberto, M Godden, G Montgomery, H Abel, P AF Guenther, B Barnes, W Knight, E Barker, J Harnden, J Weber, R Roberto, M Godden, G Montgomery, H Abel, P TI MODIS calibration: A brief review of the strategy for the at-launch calibration approach SO JOURNAL OF ATMOSPHERIC AND OCEANIC TECHNOLOGY LA English DT Article AB The Moderate-Resolution Imaging Spectroradiometer (MODIS) is a key instrument on the NASA Earth Observing System. It is a multispectral sensor that will be used to track long-term global change in the land, atmosphere, and ocean components of the earth. Major advances are being made with MODIS over previous sensors in the form of improved on-orbit sensor characterization and calibration using a system of onboard calibrators. This article describes those calibrators and provides an early estimate of the expected accuracy for the MODIS calibrated datasets resulting from the use of these calibrators. The focus of the paper is the calibration approach that is being implemented at-launch for the top-of-the-atmosphere data products. C1 RES & DATA SYST CORP,GREENBELT,MD. PHYS APPLICAT INC,VIENNA,AUSTRIA. RP Guenther, B (reprint author), NASA,GODDARD SPACE FLIGHT CTR,TERR PHYS LAB,MAIL CODE 925,GREENBELT,MD 20771, USA. NR 17 TC 54 Z9 56 U1 0 U2 6 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 APR PY 1996 VL 13 IS 2 BP 274 EP 285 DI 10.1175/1520-0426(1996)013<0274:MCABRO>2.0.CO;2 PG 12 WC Engineering, Ocean; Meteorology & Atmospheric Sciences SC Engineering; Meteorology & Atmospheric Sciences GA UG675 UT WOS:A1996UG67500002 ER PT J AU Bruegge, CJ Diner, DJ Duval, VG AF Bruegge, CJ Diner, DJ Duval, VG TI The MISR calibration program SO JOURNAL OF ATMOSPHERIC AND OCEANIC TECHNOLOGY LA English DT Article ID SPECTRALON AB The Multiangle Imaging SpectroRadiometer (MISR) is currently under development for NASA's Earth Observing System. The instrument consists of nine pushbroom cameras, each with four spectral bands in the visible and near-infrared. The cameras point in different view directions to provide measurements from nadir to highly oblique view angles in the along-track plane. Multiple view-angle observations provide a unique resource for studies of clouds, aerosols, and the surface. MISR is built to challenging radiometric and geometric performance specifications. Radiometric accuracy, for example, must be within +/-3%/1 sigma, and polarization insensitivity must be better than +/-1%. An onboard calibrator (OBC) provides monthly updates to the instrument gain coefficients. Spectralon diffuse panels are used within the OBC to provide a uniform target for the cameras to view. The absolute radiometric scale is established both preflight and in orbit through the use of detector standards. During the mission, ground data processing to accomplish radiometric calibration, geometric rectification and registration of the nine view-angle imagery, and geophysical retrievals will proceed in an automated fashion. A global dataset is produced every 9 days. This paper details the preflight characterization of the MISR instrument, the design of the OBC, and the radiance product processing. RP Bruegge, CJ (reprint author), CALTECH,JET PROP LAB,MAIL STOP 169-237,4800 OAK GROVE DR,PASADENA,CA 91109, USA. NR 11 TC 9 Z9 9 U1 0 U2 0 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 APR PY 1996 VL 13 IS 2 BP 286 EP 299 DI 10.1175/1520-0426(1996)013<0286:TMCP>2.0.CO;2 PG 14 WC Engineering, Ocean; Meteorology & Atmospheric Sciences SC Engineering; Meteorology & Atmospheric Sciences GA UG675 UT WOS:A1996UG67500003 ER PT J AU Lee, RB Barkstrom, BR Smith, GL Cooper, JE Kopia, LP Lawrence, RW Thomas, S Pandey, DK Crommelynck, DAH AF Lee, RB Barkstrom, BR Smith, GL Cooper, JE Kopia, LP Lawrence, RW Thomas, S Pandey, DK Crommelynck, DAH TI The Clouds and the Earth's Radiant Energy System (CERES) sensors and preflight calibration plans SO JOURNAL OF ATMOSPHERIC AND OCEANIC TECHNOLOGY LA English DT Article ID RADIATION BUDGET EXPERIMENT; RADIOMETERS; SATELLITE; SCANNER AB The Clouds and the Earth's Radiant Energy System (CERES) spacecraft sensors are designed to measure broadband earth-reflected solar shortwave (0.3-5 mu m) and earth-emitted longwave (5->100 mu m) radiances at the top of the atmosphere as part of the Mission to Planet Earth program. The scanning thermistor bolometer sensors respond to radiances in the broadband shortwave (0.3-5 mu m) and total-wave (0.3->100 mu m) spectral regions, as well as to radiances in the narrowband water vapor window (8-12 mu m) region. The sensors are designed to operate for a minimum of 5 years aboard the NASA Tropical Rainfall Measuring Mission and Earth Observing System AM-1 spacecraft platforms that are scheduled for launches in 1997 and 1998, respectively. The flight sensors and the in-flight calibration systems will be calibrated in a vacuum ground facility using reference radiance sources, tied to the international temperature scale of 1990. The calibrations will be used to derive sensor gains, offsets, spectral responses, and point spread functions within and outside of the field of view. The shortwave, total-wave, and window ground calibration accuracy requirements (1 sigma) are +/-0.8, +/-0.6, and +/-0.3 W m(-2) sr(-1), respectively, while the corresponding measurement precisions are +/-0.5% and +/-1.0% for the broadband longwave and shortwave radiances, respectively. The CERES sensors, in-flight calibration systems, and ground calibration instrumentation are described along with outlines of the preflight and in-flight calibration approaches. C1 SCI APPLICAT INT CORP,HAMPTON,VA. BELGIUM ROYAL METEOROL INST,BRUSSELS,BELGIUM. RP Lee, RB (reprint author), NASA,LANGLEY RES CTR,DIV ATMOSPHER SCI,420,HAMPTON,VA 23681, USA. NR 36 TC 44 Z9 44 U1 0 U2 2 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 APR PY 1996 VL 13 IS 2 BP 300 EP 313 DI 10.1175/1520-0426(1996)013<0300:TCATER>2.0.CO;2 PG 14 WC Engineering, Ocean; Meteorology & Atmospheric Sciences SC Engineering; Meteorology & Atmospheric Sciences GA UG675 UT WOS:A1996UG67500004 ER PT J AU Ono, A Sakuma, F Arai, K Yamaguchi, Y Fujisada, H Slater, PN Thome, KJ Palluconi, FD Kieffer, HH AF Ono, A Sakuma, F Arai, K Yamaguchi, Y Fujisada, H Slater, PN Thome, KJ Palluconi, FD Kieffer, HH TI Preflight and in-flight calibration plan for ASTER SO JOURNAL OF ATMOSPHERIC AND OCEANIC TECHNOLOGY LA English DT Article ID ABSOLUTE CALIBRATION AB Preflight and in-flight radiometric calibration plans are described for the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) that is a multispectral optical imager of high spatial resolution. It is designed for the remote sensing from orbit of land surfaces and clouds, and is expected to be launched in 1998 on NASA's EOS AM-1 spacecraft. ASTER acquires images in three separate spectral regions, the visible and near-infrared (VNIR), the shortwave infrared (SWIR), and the thermal infrared (TIR) with three imaging radiometer subsystems. The absolute radiometric accuracy is required to be better than 4% for VNIR and SWIR radiance measurements and 1 to 3 K, depending on the temperature regions from 200 to 370 K, for TIR temperature measurements. A reference beam is introduced at the entrance pupil of each imaging radiometer to provide the in-fight calibration. Thus, the ASTER instrument includes internal onboard calibration units that comprise incandescent lamps for the VNIR and SWIR and a blackbody radiator for the TIR as reference sources. The calibration reliability of the VNIR and SWIR is enhanced by a dual system of onboard calibration units as well as by high-stability halogen lamps. A ground calibration system of spectral radiances traceable to fixed-point blackbodies is used for the preflight VNIR and SWIR calibration. Because of the possibility of nonuniform contamination effects on the partial-aperture onboard calibration, it is desirable to check their results with respect to other methods. Reflectance- and radiance-based vicarious methods have been developed for this purpose. These, and methods involving in-flight cross-calibration with other sensors are also described. C1 NATL RES LAB METROL,THERMOPHYS METROL DEPT,TSUKUBA,IBARAKI 305,JAPAN. SAGA UNIV,SAGA 840,JAPAN. GEOL SURVEY JAPAN,TSUKUBA,IBARAKI 305,JAPAN. ELECTROTECH LAB,TSUKUBA,IBARAKI 305,JAPAN. CALTECH,JET PROP LAB,PASADENA,CA. US GEOL SURVEY,FLAGSTAFF,AZ 86001. RI Thome, Kurtis/D-7251-2012 NR 32 TC 33 Z9 33 U1 0 U2 5 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 APR PY 1996 VL 13 IS 2 BP 321 EP 335 DI 10.1175/1520-0426(1996)013<0321:PAIFCP>2.0.CO;2 PG 15 WC Engineering, Ocean; Meteorology & Atmospheric Sciences SC Engineering; Meteorology & Atmospheric Sciences GA UG675 UT WOS:A1996UG67500006 ER PT J AU Sellers, PJ Randall, DA Collatz, GJ Berry, JA Field, CB Dazlich, DA Zhang, C Collelo, GD Bounoua, L AF Sellers, PJ Randall, DA Collatz, GJ Berry, JA Field, CB Dazlich, DA Zhang, C Collelo, GD Bounoua, L TI A revised land surface parameterization (SiB2) for atmospheric GCMs .1. Model formulation SO JOURNAL OF CLIMATE LA English DT Article ID SIMPLE BIOSPHERE MODEL; STOMATAL CONDUCTANCE; CANOPY REFLECTANCE; REGIONAL CLIMATE; BOUNDARY-LAYER; PHOTOSYNTHESIS; VEGETATION; RADIATION; TRANSPIRATION; DEFORESTATION AB The formulation of a revised land surface parameterization for use within atmospheric general circulation models (GCMs) is presented. The model(SiB2) incorporates several significant improvements over the first version of the Simple Biosphere model (SIE) described in Sellers et al. The improvements can be summarized as follows: (i) incorporation of a realistic canopy photosynthesis-conductance model to describe the simultaneous transfer of CO2 and water vapor into;and out of the vegetation, respectively; (ii) use of satellite data, as described in a companion paper, Part II, to describe the vegetation phenology; (iii) modification of the hydrological submodel to give better descriptions of baseflows and a more reliable calculation of interlayer exchanges within the soil profile; (iv) incorporation of a ''patchy'' snowmelt treatment, which prevents rapid thermal and surface reflectance transitions when the area-averaged snow cover is low and decreasing. To accommodate the changes in(i) and (ii) above, the original two-layer vegetation canopy structure of SiB1 has been reduced to a single layer in SiB2. The use of satellite data in SiB2 and the performance of SiB2 when coupled to a GCM are described in the two companion papers,Parts II and III. C1 COLORADO STATE UNIV,DEPT ATMOSPHER SCI,FT COLLINS,CO 80523. CARNEGIE INST WASHINGTON,STANFORD,CA 94305. NASA,GODDARD SPACE FLIGHT CTR,USRA,GREENBELT,MD 20771. RP Sellers, PJ (reprint author), NASA,GODDARD SPACE FLIGHT CTR,BIOSPHER SCI BRANCH,CODE 923,GREENBELT,MD 20771, USA. RI Berry, Joseph/B-8211-2009; Randall, David/E-6113-2011; collatz, george/D-5381-2012 OI Berry, Joseph/0000-0002-5849-6438; Randall, David/0000-0001-6935-4112; NR 67 TC 1025 Z9 1174 U1 9 U2 111 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 SN 0894-8755 J9 J CLIMATE JI J. Clim. PD APR PY 1996 VL 9 IS 4 BP 676 EP 705 DI 10.1175/1520-0442(1996)009<0676:ARLSPF>2.0.CO;2 PG 30 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA UJ643 UT WOS:A1996UJ64300002 ER PT J AU Sellers, PJ Los, SO Tucker, CJ Justice, CO Dazlich, DA Collatz, GJ Randall, DA AF Sellers, PJ Los, SO Tucker, CJ Justice, CO Dazlich, DA Collatz, GJ Randall, DA TI A revised land surface parameterization (SiB2) for atmospheric GCMs .2. The generation of global fields of terrestrial biophysical parameters from satellite data SO JOURNAL OF CLIMATE LA English DT Article ID SIMPLE BIOSPHERE MODEL; DIFFERENCE VEGETATION INDEX; CANOPY REFLECTANCE; STOMATAL CONDUCTANCE; CIRCULATION MODELS; PHOTOSYNTHESIS; RADIATION; TRANSPIRATION; AVHRR; CALIBRATION AB The global parameter fields used in the revised Simple Biosphere Model (SiB2) of Sellers et al. are reviewed. The most important innovation over the earlier SiB1 parameter set of Dorman and Sellers is the use of satellite data to specify the time-varying phenological properties of FPAR, leaf area index, and canopy greenness fraction. This was done by processing a monthly 1 degrees by 1 degrees normalized difference vegetation index (NDVI) dataset obtained from Advanced Very High Resolution Radiometer red and near-infrared data. Corrections were applied to the source NDVI dataset to account for (i) obvious anomalies in the data time series, (ii) the effect of variations in solar zenith angle, (iii) data dropouts in cold regions where a temperature threshold procedure designed to screen for clouds also eliminated cold land surface points, and (iv) persistent cloud cover in the Tropics. An outline of the procedures for calculating the land surface parameters from the corrected NDVI dataset is given, and a brief description is provided of source material, mainly derived from in situ observations, that was used in addition to the NDVI data. The datasets summarized in this paper should be superior to prescriptions currently used in most land surface parameterizations in that the spatial and temporal dynamics of key land surface parameters, in particular those related to vegetation, are obtained directly from a consistent set of global-scale observations instead of being inferred from a variety of survey-based land-cover classifications. C1 NASA,GODDARD SPACE FLIGHT CTR,SCI SYST & APPLICAT INC,GREENBELT,MD 20771. UNIV MARYLAND,GLOBAL REMOTE SENSING LAB,COLLEGE PK,MD 20742. COLORADO STATE UNIV,DEPT ATMOSPHER SCI,FT COLLINS,CO 80523. RP Sellers, PJ (reprint author), NASA,GODDARD SPACE FLIGHT CTR,BIOSPHER SCI BRANCH,CODE 923,GREENBELT,MD 20771, USA. RI Randall, David/E-6113-2011; collatz, george/D-5381-2012; Los, Sietse/G-8985-2012; OI Randall, David/0000-0001-6935-4112; Los, Sietse/0000-0002-1325-3555 NR 55 TC 559 Z9 650 U1 3 U2 65 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 SN 0894-8755 J9 J CLIMATE JI J. Clim. PD APR PY 1996 VL 9 IS 4 BP 706 EP 737 DI 10.1175/1520-0442(1996)009<0706:ARLSPF>2.0.CO;2 PG 32 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA UJ643 UT WOS:A1996UJ64300003 ER PT J AU Randall, DA Dazlich, DA Zhang, C Denning, AS Sellers, PJ Tucker, CJ Bounoua, L Los, SO Justice, CO Fung, I AF Randall, DA Dazlich, DA Zhang, C Denning, AS Sellers, PJ Tucker, CJ Bounoua, L Los, SO Justice, CO Fung, I TI A revised land surface parameterization (SiB2) for GCMs .3. The greening of the Colorado State University general circulation model SO JOURNAL OF CLIMATE LA English DT Article ID PLANETARY BOUNDARY-LAYER; LARGE-SCALE ENVIRONMENT; CUMULUS CLOUD ENSEMBLE; ENERGY; SIMULATIONS; VARIABILITY; EQUATIONS; RADIATION; BUDGET; CO2 AB SiB2, the second-generation land-surface parameterization developed by Sellers et al., has been incorporated into the Colorado State University general circulation model and tested in multidecade simulations. The control run uses a ''bucket'' hydrology but employs the same surface albedo and surface roughness distributions as the SiB2 run. Results show that SiB2 leads to a general warming of the continents, as evidenced in the ground temperature, surface air temperature, and boundary-layer-mean potential temperature. The surface sensible heat flux increases and the latent heat flux decreases. This warming occurs virtually everywhere but is most spectacular over Siberia in winter. Precipitation generally decreases over land but increases in the monsoon regions, especially the Amazon basin in January and equatorial Africa and Southeast Asia in July. Evaporation decreases considerably, especially in dry regions such as the Sahara. The excess of precipitation over evaporation increases in the monsoon regions. The precipitable water (vertically integrated water vapor content) generally decreases over land but increases in the monsoon regions. The mixing ratio of the boundary-layer air decreases over nearly all continental areas, however, including the monsoon regions. The average (composite) maximum boundary-layer depth over the diurnal cycle increases in the monsoon regions, as does the average PBL turbulence kinetic energy. The average boundary-layer wind speed also increases over most continental regions. Groundwater content generally increases in rainy regions and decreases in dry regions, so that SiB2 has a tendency to increase its spatial variability. SiB2 leads to a general reduction of cloudiness over land. The net surface longwave cooling of the surface increases quite dramatically over land, in accordance with the increased surface temperatures and decreased cloudiness. The solar radiation absorbed at the ground also increases. SiB2 has modest effects on the simulated general circulation of the atmosphere. Its most important impacts on the model are to improve the simulations of surface temperature and snow cover and to enable the simulation of the net rate of terrestrial carbon assimilation. C1 NASA, GODDARD SPACE FLIGHT CTR, ATMOSPHERES LAB, GREENBELT, MD 20771 USA. STANFORD UNIV, CARNEGIE INST WASHINGTON, PALO ALTO, CA 94304 USA. UNIV MARYLAND, DEPT GEOG, COLLEGE PK, MD 20742 USA. UNIV VICTORIA, SCH EARTH OCEAN SCI, VICTORIA, BC, CANADA. RP Randall, DA (reprint author), UNIV COLORADO, DEPT ATMOSPHER SCI, FT COLLINS, CO 80523 USA. RI Randall, David/E-6113-2011; Los, Sietse/G-8985-2012; Denning, Scott/F-4974-2011; collatz, george/D-5381-2012 OI Randall, David/0000-0001-6935-4112; Denning, Scott/0000-0003-3032-7875; NR 39 TC 98 Z9 111 U1 2 U2 13 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 APR PY 1996 VL 9 IS 4 BP 738 EP 763 DI 10.1175/1520-0442(1996)009<0738:ARLSPF>2.0.CO;2 PG 26 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA UJ643 UT WOS:A1996UJ64300004 ER PT J AU Molod, A Helfand, HM Takacs, LL AF Molod, A Helfand, HM Takacs, LL TI The climatology of parameterized physical processes in the GEOS-1 GCM and their impact on the GEOS-1 data assimilation system SO JOURNAL OF CLIMATE LA English DT Article ID GENERAL-CIRCULATION MODELS; RADIATION BUDGET EXPERIMENT; CLOUD PARAMETERIZATION; SPATIAL VARIABILITY; FLUX MEASUREMENTS; OCEAN; MASS; INTEGRATION; ALGORITHMS; PREDICTION AB The Goddard Earth Observing System(GEOS) General Circulation Model (GCM) is part of the GEOS Data Assimilation System (DAS), which is being developed at the Goddard Data Assimilation Office for the production of climate datasets. This study examines Version 1 of the GEOS GCM by evaluating the quality of the fields that relate most closely to the GCM physical parameterizations and examines the impact of the GCM climate errors on the climate of the DAS assimilated fields. The climate characteristics are evaluated using independent satellite and ground-based data for comparison. The GEOS-1 GCM shows reasonably good agreement with available observations in terms of general global distribution and seasonal cycles. The major biases or systematic errors are a tendency toward a dry tropical atmosphere and an inadequate cloud radiative impact in the extratropics. Other systematic errors are a generally wet subtropical atmosphere, slightly excess precipitation over the continents, and excess cloud radiative effects over the Tropics. There is also an underestimation of surface sensible and latent heat fluxes over the area of maximum flux. The DAS climate characteristics, in general, show better agreement with available observations than the GCM. Four distinct ways that the GCM impacts the DAS have been identified, ranging from a DAS climate with little or no impact from the GCM bias to a DAS climate with a greater bias than the GCM due to a spurious feedback between the GCM and the input data. RP Molod, A (reprint author), NASA, GODDARD SPACE FLIGHT CTR, DATA ASSIMILAT ODD, ATMOSPHERES LAB, CODE 9103, GREENBELT, MD 20771 USA. NR 59 TC 38 Z9 38 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 APR PY 1996 VL 9 IS 4 BP 764 EP 785 DI 10.1175/1520-0442(1996)009<0764:TCOPPP>2.0.CO;2 PG 22 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA UJ643 UT WOS:A1996UJ64300005 ER PT J AU Li, J OBrien, TK AF Li, J OBrien, TK TI Simplified data reduction methods for the ECT test for mode III interlaminar fracture toughness SO JOURNAL OF COMPOSITES TECHNOLOGY & RESEARCH LA English DT Article DE composites; compliance; strain energy release rate; Mode III fracture toughness ID COMPOSITE-MATERIALS; SPECIMEN; DELAMINATION; TORSION AB Simplified expressions for the parameter controlling the load-point compliance and strain energy release rate were obtained for the edge crack torsion (ECT) specimen for Mode III interlaminar fracture toughness. Data reduction methods for Mode III toughness based on the present analysis are proposed. The effect of the transverse shear modulus G(23) On Mode III interlaminar fracture toughness characterization was evaluated. Parameters influenced by the transverse shear modulus were identified. Analytical results indicate that a higher value of G(23) results in a lower load point compliance and lower Mode III toughness estimation. The effect of G(23) on the Mode III toughness using the ECT specimen is negligible when an appropriate initial delamination length is chosen. A conservative estimation of the Mode III toughness can be obtained by assuming G(23) = G(12) for any initial delamination length. RP Li, J (reprint author), NASA,LANGLEY RES CTR,MS 188E,HAMPTON,VA 23681, USA. NR 17 TC 21 Z9 21 U1 0 U2 0 PU AMER SOC TESTING MATERIALS PI W CONSHOHOCKEN PA 100 BARR HARBOR DR, W CONSHOHOCKEN, PA 19428-2959 SN 0884-6804 J9 J COMPOS TECH RES JI J. Compos. Technol. Res. PD APR PY 1996 VL 18 IS 2 BP 96 EP 101 PG 6 WC Materials Science, Composites; Polymer Science SC Materials Science; Polymer Science GA VB878 UT WOS:A1996VB87800004 ER PT J AU Highsmith, AL Ledbetter, FE Nettles, A Russell, SS AF Highsmith, AL Ledbetter, FE Nettles, A Russell, SS TI Low velocity impact damage in filament-wound composite pressure bottles SO JOURNAL OF COMPOSITES TECHNOLOGY & RESEARCH LA English DT Article DE composite material; filament-wound composite; impact; damage; delamination; matrix cracking; fiber fracture; X-ray radiography AB In an effort to better understand the damage that develops in filament-wound composite structures when they are subjected to low velocity impact loads, a series of low velocity impact experiments was performed on small (146 mm (5.75 in.) diameter) filament wound pressure bottles. Three different material systems, IM7/3501-6ATL, IM7/X8553-45, and IM7/977-2, were evaluated. Three impact energy levels, 4.07 J (3.0 ft-lb), 6.78 J (5.0 ft-lb), and 9.49 J (7.0 ft-lb), were applied. Dye penetrant enhanced X-ray radiography was used to assess the damage that resulted from the impact loading. The through-the-thickness location of damage was assessed by means of stereo radiography. The two material systems with toughened epoxy matrices (X8553-45, 977-2) generally developed smaller damage zones than the system with a standard epoxy matrix (3501-6ATL). Two distinct types of fiber fracture were observed. All of the systems exhibited a tendency to develop fiber fracture in the interior helical layers, usually at locations removed from the impact site. Some of the specimens fabricated from the material systems with the toughened epoxy matrices also developed fiber fracture in the exterior hoop layers. This second fiber fracture mode appeared to originate at the point of contact between the impacting tup and the specimen. C1 NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,NONMET MAT BRANCH,HUNTSVILLE,AL 35812. NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,NONDESTRUCT EVALUAT & TRIBOL BRANCH RUSSELL,HUNTSVILLE,AL 35812. RP Highsmith, AL (reprint author), UNIV ALABAMA,DEPT AEROSP ENGN,TUSCALOOSA,AL 35405, USA. NR 19 TC 3 Z9 3 U1 1 U2 2 PU AMER SOC TESTING MATERIALS PI W CONSHOHOCKEN PA 100 BARR HARBOR DR, W CONSHOHOCKEN, PA 19428-2959 SN 0884-6804 J9 J COMPOS TECH RES JI J. Compos. Technol. Res. PD APR PY 1996 VL 18 IS 2 BP 109 EP 117 PG 9 WC Materials Science, Composites; Polymer Science SC Materials Science; Polymer Science GA VB878 UT WOS:A1996VB87800006 ER PT J AU Jiang, BN Wu, J Povinelli, LA AF Jiang, BN Wu, J Povinelli, LA TI The origin of spurious solutions in computational electromagnetics SO JOURNAL OF COMPUTATIONAL PHYSICS LA English DT Article ID FINITE-ELEMENT METHOD; MAXWELL EQUATIONS; TIME-DOMAIN; WAVE-GUIDES; MODES; SCATTERING; WAVEGUIDE; FORMULATION; ELIMINATION; RADIATION AB It is commonly believed that the divergence equations in the Maxwell equations are ''redundant'' for transient and time-harmonic problems, therefore most of the numerical methods in computational electromagnetics solve only two first-order curl equations or the second-order curl-curl equations. This misconception is the true origin of spurious modes and inaccurate solutions in computational electromagnetics. By studying the div-curl system this paper clarifies that the first-order Maxwell equations are not ''overdetermined,'' and the divergence equations must always be included to maintain the ellipticity of the system in the space domain, to guarantee the uniqueness of the solution and the accuracy of the numerical methods, and to eliminate the infinitely degenerate eigenvalue. This paper shows that the common derivation and usage of the second-order curl-curl equations are incorrect and that the solution of Helmholtz equations needs the divergence condition to be enforced on an associated part of the boundary. The div-curl method and the least-squares method introduced in this paper provide rigorous derivation of the equivalent second-order Maxwell equations and their boundary conditions. The node-based least-squares finite element method (LSFEM) is recommended for solving the first-order full Maxwell equations directly. Examples of the numerical solutions by LSFEM are given to demonstrate that the LSFEM is free of spurious solutions. (C) 1996 Academic Press. Inc. RP Jiang, BN (reprint author), NASA, LEWIS RES CTR, INST COMPUTAT MECH PROPULS, CLEVELAND, OH 44135 USA. NR 70 TC 93 Z9 93 U1 0 U2 10 PU ACADEMIC PRESS INC ELSEVIER SCIENCE PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA SN 0021-9991 J9 J COMPUT PHYS JI J. Comput. Phys. PD APR PY 1996 VL 125 IS 1 BP 104 EP 123 DI 10.1006/jcph.1996.0082 PG 20 WC Computer Science, Interdisciplinary Applications; Physics, Mathematical SC Computer Science; Physics GA UD288 UT WOS:A1996UD28800008 ER PT J AU Iollo, A Salas, MD AF Iollo, A Salas, MD TI Contribution to the optimal shape design of two-dimensional internal flows with embedded shocks SO JOURNAL OF COMPUTATIONAL PHYSICS LA English DT Article AB We explore the praticability of optimal shape design for flows modeled by the Euler equations. We define a functional whose minimum represents the optimality condition. The gradient of the functional with respect to the geometry is calculated with the Lagrange multipliers, which are determined by solving a costate equation. The optimization problem is then examined by comparing the performance of several gradient-based optimization algorithms. In this formulation, the flow field can be computed to an arbitrary order of accuracy. Finally, some results for internal flows with embedded shocks are presented, including a case for which the solution to the inverse problem does not belong to the design space. (C) 1996 Academic Press, Inc. C1 NASA, LANGLEY RES CTR, HAMPTON, VA 23681 USA. RP Iollo, A (reprint author), POLITECN TORINO, DIPARTIMENTO INGN AERONAUT & SPAZIALE, I-10129 TURIN, ITALY. NR 14 TC 14 Z9 14 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 0021-9991 J9 J COMPUT PHYS JI J. Comput. Phys. PD APR PY 1996 VL 125 IS 1 BP 124 EP 134 DI 10.1006/jcph.1996.0083 PG 11 WC Computer Science, Interdisciplinary Applications; Physics, Mathematical SC Computer Science; Physics GA UD288 UT WOS:A1996UD28800009 ER PT J AU Watson, WR Jones, MG Tanner, SE Parrott, TL AF Watson, WR Jones, MG Tanner, SE Parrott, TL TI A finite element propagation model for extracting normal incidence impedance in nonprogressive acoustic wave fields SO JOURNAL OF COMPUTATIONAL PHYSICS LA English DT Article AB A propagation model method for extracting the normal incidence impedance of an acoustic material installed as a finite length segment in a wall of a duct carrying a nonprogressive wave field is presented. The method recasts the determination of the unknown impedance as the minimization of the normalized wall pressure error function. A finite element propagation model is combined with a coarse/fine grid impedance plane search technique to extract the impedance of the material. Results are presented for three different materials for which the impedance is known. For each material, the input data required for the prediction scheme were computed from modal theory and then contaminated by random error. The finite element method reproduces the known impedance of each material almost exactly for random errors typical of those found in many measurement environments. Thus, the method developed here provides a means for determining the impedance of materials in a nonprogressive wave environment such as that usually encountered in a commercial aircraft engine and in most laboratory settings. (C) 1996 Academic Press, Inc. C1 LOCKHEED ENGN & SCI CO,DIV RES,HAMPTON,VA 23666. NASA,LANGLEY RES CTR,DIV FLUID MECH & ACOUST,STRUCT ACOUST BRANCH,HAMPTON,VA 23681. RP Watson, WR (reprint author), NASA,LANGLEY RES CTR,DIV FLUID MECH & ACOUST,AERODYNAM & ACOUST METHODS BRANCH,HAMPTON,VA 23681, USA. NR 11 TC 10 Z9 10 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 0021-9991 J9 J COMPUT PHYS JI J. Comput. Phys. PD APR PY 1996 VL 125 IS 1 BP 177 EP 186 DI 10.1006/jcph.1996.0087 PG 10 WC Computer Science, Interdisciplinary Applications; Physics, Mathematical SC Computer Science; Physics GA UD288 UT WOS:A1996UD28800013 ER PT J AU Lou, JZ Ferraro, R AF Lou, JZ Ferraro, R TI A parallel incompressible flow solver package with a parallel multigrid elliptic kernel SO JOURNAL OF COMPUTATIONAL PHYSICS LA English DT Article ID 2ND-ORDER PROJECTION METHOD AB The development and applications of a parallel, time-dependent incompressible Navier-Stokes flow solver and a parallel multigrid elliptic kernel are described. The flow solver is based on a second-order projection method applied to a staggered finite-difference grid. The multigrid algorithms implemented in the parallel elliptic kernel, which is needed by the flow solver, are V-cycle and full V-cycle schemes. A grid-partition strategy is used in the parallel implementations of both the flow solver and the multigrid elliptic kernel on all fine and coarse grids. Numerical experiments and parallel performance tests show the parallel solver package is numerically stable, physically robust, and computationally efficient, Both the multigrid elliptic kernel and the flow solver scale very well to a large number of processors on Intel Paragon and Gray T3D for computations with moderate granularity. The solver package has been carefully designed and coded so that it can be easily adapted to solving a variety of interesting two- and three-dimensional flow problems. The solver package is portable to parallel systems that support MPI, PVM, and NX for interprocessor communications. (C) 1996 Academic Press, Inc. RP Lou, JZ (reprint author), CALTECH,JET PROP LAB,PASADENA,CA 91109, USA. NR 14 TC 9 Z9 9 U1 0 U2 2 PU ACADEMIC PRESS INC JNL-COMP SUBSCRIPTIONS PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 SN 0021-9991 J9 J COMPUT PHYS JI J. Comput. Phys. PD APR PY 1996 VL 125 IS 1 BP 225 EP 243 DI 10.1006/jcph.1996.0090 PG 19 WC Computer Science, Interdisciplinary Applications; Physics, Mathematical SC Computer Science; Physics GA UD288 UT WOS:A1996UD28800016 ER PT J AU Weizer, VG Fatemi, NS AF Weizer, VG Fatemi, NS TI A unique, device-friendly contact system for shallow junction p/n indium phosphide devices SO JOURNAL OF ELECTRONIC MATERIALS LA English DT Article; Proceedings Paper CT 7th International Conference on Indium Phosphide and Related Materials (IPRM 95) CY MAY 09-13, 1995 CL HOKKAIDO UNIV, SAPPORO, JAPAN SP Japan Soc Appl Phys, IEEE Lasers & Electro Opt Soc, IEEE Electron Devices Soc, Inst Electr Informat & Commun Engineers, Optoelectr Ind & Technol Dev Assoc, Res & Dev Assoc Future Electron Devices HO HOKKAIDO UNIV DE Ag/Zn/Ag metallization; InP; interdiffusion; ohmic contacts ID OHMIC CONTACTS; N-INP; RESISTANCE AB We have discovered what appears to be a unique contact system for use on p-type InP. The new contacts provide low resistance contact to p-InP without the violent metallurgical intermixing that would normally take place between the emitter material and the contact metallization during the contact sintering process. With this new contact system, which is composed of a combination of Ag and Zn, it is possible, for the first time, to make low resistance ohmic contact directly to a shallow junction p/n InP device without destroying the device while doing so. Specific contact resistivity values in the low 10(-4) Omega-cm(2) range are readily achieved. After a description of the new system, we suggest possible mechanisms to explain the observed behavior. C1 ESSENTIAL RES INC,CLEVELAND,OH 44135. RP Weizer, VG (reprint author), NASA,LEWIS RES CTR,21000 BROOKPARK RD,CLEVELAND,OH 44135, USA. NR 18 TC 1 Z9 1 U1 0 U2 0 PU MINERALS METALS MATERIALS SOC PI WARRENDALE PA 420 COMMONWEALTH DR, WARRENDALE, PA 15086 SN 0361-5235 J9 J ELECTRON MATER JI J. Electron. Mater. PD APR PY 1996 VL 25 IS 4 BP 755 EP 760 DI 10.1007/BF02666536 PG 6 WC Engineering, Electrical & Electronic; Materials Science, Multidisciplinary; Physics, Applied SC Engineering; Materials Science; Physics GA UE592 UT WOS:A1996UE59200036 ER PT J AU Telesman, J Ghosn, LJ AF Telesman, J Ghosn, LJ TI Fatigue crack growth behavior of PWA 1484 single crystal superalloy at elevated temperatures SO JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER-TRANSACTIONS OF THE ASME LA English DT Article; Proceedings Paper CT 40th International Gas Turbine and Aeroengine Congress and Exhibition CY JUN 05-08, 1995 CL HOUSTON, TX ID STRESS AB A study was done to determine the fatigue clack growth behavior of a PWA 1484 single-crystal nickel-base superalloy in a temperature range of 427 degrees C to 871 degrees C. Two distinctive failure modes were observed which were a function of both temperature and frequency. At lower temperatures and higher frequencies crack growth occurred on the {111} octahedral slip planes at an oblique angle to the loading direction. Higher temperatures and decrease in frequencies favored a Mode I type failure process. The failure mode transitions were explained by invoking arguments based on environmental damage mechanisms. The fatigue crack growth rate data were analyzed using three different crack driving force parameters. The parameters investigated consisted of the Mode I stress intensity parameter corrected for the inclined crack trajectory, and two different octahedral Mode II parameters, which ave based on the calculation of resolved shear stresses on the {111} slip systems. The Mode I Delta K parameter did a fair job in correlating the data but did not collapse it into a single narrow band. The two octahedral crack driving force parameters, Delta K-RSS and a newly proposed Delta K-OCT, collapsed all the data into a single narrow band. In addition to correlating the fatigue crack growth rates, the two octahedral parameters also predicted the {111} planes on which the crack growth took place. C1 CASE WESTERN RESERVE UNIV,CLEVELAND,OH 44135. RP Telesman, J (reprint author), NASA,LEWIS RES CTR,CLEVELAND,OH 44135, USA. NR 11 TC 20 Z9 21 U1 1 U2 14 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 APR PY 1996 VL 118 IS 2 BP 399 EP 405 DI 10.1115/1.2816603 PG 7 WC Engineering, Mechanical SC Engineering GA UJ384 UT WOS:A1996UJ38400023 ER PT J AU Noor, AK AF Noor, AK TI Recent advances in sensitivity analysis for thermomechanical postbuckling of composite panels SO JOURNAL OF ENGINEERING MECHANICS-ASCE LA English DT Article ID REDUCED BASIS TECHNIQUE; PLATES AB Three recent developments in the sensitivity analysis for the thermomechanical postbuckling response of composite panels are reviewed. The three developments are an effective computational procedure for evaluating hierarchical sensitivity coefficients of the various response quantities with respect to the different laminate, layer, and micromechanical characteristics; an application of reduction methods to the sensitivity analysis of the postbuckling response; and an accurate evaluation of the sensitivity coefficients of transverse shear stresses. Sample numerical results are presented to demonstrate the effectiveness of the computational procedures presented. Some of the future directions for research on sensitivity analysis for the thermomechanical postbuckling response of composite and smart structures are outlined. RP Noor, AK (reprint author), UNIV VIRGINIA,NASA,LANGLEY RES CTR,CTR COMPUTAT STRUC TECHNOL,MAIL STOP 369,HAMPTON,VA 23681, USA. NR 20 TC 3 Z9 3 U1 0 U2 0 PU ASCE-AMER SOC CIVIL ENG PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2398 SN 0733-9399 J9 J ENG MECH-ASCE JI J. Eng. Mech.-ASCE PD APR PY 1996 VL 122 IS 4 BP 300 EP 307 DI 10.1061/(ASCE)0733-9399(1996)122:4(300) PG 8 WC Engineering, Mechanical SC Engineering GA UC580 UT WOS:A1996UC58000002 ER PT J AU Hochhaus, L Johnston, JC AF Hochhaus, L Johnston, JC TI Perceptual repetition blindness effects SO JOURNAL OF EXPERIMENTAL PSYCHOLOGY-HUMAN PERCEPTION AND PERFORMANCE LA English DT Article ID TOKEN INDIVIDUATION AB Repetition blindness (RE) may reveal a new limitation on human perceptual processing. Recently, however, researchers have attributed RE to postperceptual processes. The standard rapid serial visual presentation (RSVP) paradigm used in most RE studies is open to such objections. The ''single-frame'' paradigm introduced by J. C. Johnston and B. L. Hale (1984) allowed investigation of RE with minimal memory demands. Participants made a judgment about whether 1 masked target word was the same or different than a posttarget probe. Confidence ratings permitted use of signal detection methods. In the critical condition for RE, a precue of the posttarget word was provided prior to the target stimulus so that the required judgment amounted to whether the target did or did not repeat the precue word. In control treatments, the precue was an unrelated word or a dummy. Results showed that perceptual sensitivity was significantly reduced in the RE condition relative to baseline control conditions. The data showed that RE can be obtained under conditions in which memory problems are minimal and perceptual sensitivity is assessed independently of biases. RE therefore can be a perceptual phenomenon. C1 NASA,AMES RES LABS,AMES,IA. RP Hochhaus, L (reprint author), OKLAHOMA STATE UNIV,DEPT PSYCHOL,STILLWATER,OK 74078, USA. NR 32 TC 54 Z9 56 U1 0 U2 0 PU AMER PSYCHOLOGICAL ASSOC PI WASHINGTON PA 750 FIRST ST NE, WASHINGTON, DC 20002-4242 SN 0096-1523 J9 J EXP PSYCHOL HUMAN JI J. Exp. Psychol.-Hum. Percept. Perform. PD APR PY 1996 VL 22 IS 2 BP 355 EP 366 PG 12 WC Psychology; Psychology, Experimental SC Psychology GA UD667 UT WOS:A1996UD66700007 PM 8934849 ER PT J AU Ryer, CH Olla, BL AF Ryer, CH Olla, BL TI Growth depensation and aggression in laboratory reared coho salmon: The effect of food distribution and ration size SO JOURNAL OF FISH BIOLOGY LA English DT Article DE Oncorhynchus kisutch; growth depensation; growth variation; dominance; aggression; food distribution ID AGONISTIC BEHAVIOR; ATLANTIC SALMON; SALAR L; FISH; VARIABILITY; POPULATIONS; JUVENILES; TROUT AB Groups of recently emerged coho salmon fry Oncorhynchus kisutch were reared for 3 months on food that appeared either asynchronously at a single location (localized) or synchronously and spatially dispersed (dispersed). Groups were further subdivided into those receiving low (1%) or high (3% body weight per day) rations, with five replicate groups for each treatment combination. At low ration there was greater growth depensation, i.e. growth variation, in groups receiving localized as compared to dispersed food. At high ration there was no difference. There was no effect of food distribution upon mean fish weight, but groups receiving high rations had greater mean fish weights than groups receiving low rations. There was no overall difference in the frequency of chasing between any of the treatment combinations. However, in localized food groups, dominants defended positions close to where food entered the tank, giving them greater access than subordinates. In dispersed food groups, while dominants also defended particular areas, this did not result in greater access to food. These results demonstrate that although feeding methodology may not directly influence the frequency of aggressive interactions, Feeding methods which facilitate feud monopolization by dominants can accelerate the growth of these individuals at the expense of subordinates. In aquacultural applications where greater size is desirable, or otherwise selected for, this may result in the unintentional selection fur increased aggressiveness. (C) 1996 The Fisheries Society of the British Isles RP Ryer, CH (reprint author), NOAA,HATFIELD MARINE SCI CTR,NATL MARINE FISHERIES SERV,ALASKA FISHERIES SCI CTR,NEWPORT,OR 97365, USA. NR 21 TC 68 Z9 70 U1 1 U2 5 PU ACADEMIC PRESS LTD PI LONDON PA 24-28 OVAL RD, LONDON, ENGLAND NW1 7DX SN 0022-1112 J9 J FISH BIOL JI J. Fish Biol. PD APR PY 1996 VL 48 IS 4 BP 686 EP 694 DI 10.1006/jfbi.1996.0069 PG 9 WC Fisheries; Marine & Freshwater Biology SC Fisheries; Marine & Freshwater Biology GA UK347 UT WOS:A1996UK34700013 ER PT J AU Matthaeus, WH Ghosh, S Oughton, S Roberts, DA AF Matthaeus, WH Ghosh, S Oughton, S Roberts, DA TI Anisotropic three-dimensional MHD turbulence SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID SOLAR-WIND FLUCTUATIONS; INCOMPRESSIBLE FLUIDS; MAGNETOHYDRODYNAMICS; WAVES AB Direct spectral method simulation of the three-dimensional magnetohydrodynamics (MHD) equations is used to explore anisotropy that develops from initially isotropic fluctuations as a consequence of a uniform applied magnetic field. Spectral and variance anisotropies are investigated in both compressible and incompressible MHD. The nature of the spectral anisotropy is consistent with the model of Shebalin et al. [1983] in which the spectrum broadens in the perpendicular wavenumber direction, the anisotropy being greater for smaller wavenumbers. Here this effect is seen for both incompressible and polytropic compressible MHD. In contrast, the longitudinal (compressive) velocity fluctuations remain isotropic. Variance anisotropy is observed for low plasma beta compressible MHD but not for incompressible MHD. Solar wind observations are qualitatively consistent with both variance and spectral anisotropies of the type discussed here. C1 APPL RES CORP, LANDOVER, MD 20785 USA. UNIV LONDON UNIV COLL, DEPT MATH, LONDON WC1E 6BT, ENGLAND. NASA, GODDARD SPACE FLIGHT CTR, EXTRATERR PHYS LAB, GREENBELT, MD 20771 USA. RP Matthaeus, WH (reprint author), UNIV DELAWARE, BARTOL RES INST, NEWARK, DE 19716 USA. RI Roberts, Dana/D-4625-2012; Oughton, Sean/A-3380-2012 OI Oughton, Sean/0000-0002-2814-7288 NR 32 TC 176 Z9 178 U1 1 U2 3 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0148-0227 J9 J GEOPHYS RES-SPACE JI J. Geophys. Res-Space Phys. PD APR 1 PY 1996 VL 101 IS A4 BP 7619 EP 7629 DI 10.1029/95JA03830 PG 11 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA UD939 UT WOS:A1996UD93900002 ER PT J AU Cairns, IH Fairfield, DH Anderson, RR Paularena, KI Lazarus, AJ AF Cairns, IH Fairfield, DH Anderson, RR Paularena, KI Lazarus, AJ TI Unusual locations of Earth's bow shock on September 24-25, 1987: Mach number effects - Reply SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Letter ID SOLAR-WIND FLOW; MAGNETOPAUSE SHAPE; PLANETS C1 MIT,CTR SPACE RES,CAMBRIDGE,MA 02139. NASA,GODDARD SPACE FLIGHT CTR,EXTRATERR PHYS LAB,GREENBELT,MD 20771. RP Cairns, IH (reprint author), UNIV IOWA,DEPT PHYS & ASTRON,VAN ALLEN HALL,IOWA CITY,IA 52242, USA. NR 17 TC 6 Z9 5 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 SN 0148-0227 J9 J GEOPHYS RES JI J. Geophys. Res-Space Phys. PD APR 1 PY 1996 VL 101 IS A4 BP 7679 EP 7684 DI 10.1029/95JA03710 PG 6 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA UD939 UT WOS:A1996UD93900007 ER PT J AU Fairfield, DH Jones, J AF Fairfield, DH Jones, J TI Variability of the tail lobe field strength SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID SOLAR-WIND CONTROL; MAGNETIC-FIELD; MAGNETOPAUSE SHAPE; PRESSURE; MAGNETOTAIL; CONSISTENT; SHEET AB A large magnetosphere database has been used to study spatial and temporal variations of the geomagnetic tail lobe field strength. The Study uses 12,388 average tail lobe measurements from the region -15 > X > -70 R(E) Obtained from 11 different spacecraft over a 20-year period. The average radial gradient is found to be represented by B = 1659.2/R(1.46) + 7.47 which can be used to eliminate the dependence of individual measurements on distance down the tail. A set of 5562 of the resulting normalized data points is associated with simultaneously measured solar wind dynamic pressure and interplanetary magnetic field (IMF) values which permit the study of relationships of B-lobe With geomagnetic activity and with solar wind parameters bn various timescales. Variations of annual averages of B-lobe and AE exhibit a solar cycle dependence and are very similar to each other and to solar wind dynamic pressure variations. On an hourly time scale, tail lobe field strength normalized to a distance of 30 R(E) is found to depend on both solar wind dynamic pressure, P-sw, and IMF B-z. This dependence can be represented as B-n(2) = -96.5 + 294.5 root P-sw + 2.36 B-IMF(2) sin(2) (theta/2) where theta varies from 0 degrees for northward to 180 degrees for southward. The ability to quantitatively predict average B-lobe given solar wind pressure and IMF B provides a baseline which should be useful in the study of more rapid substorm variations which are due to internal magnetospheric dynamics. C1 HUGHES STX CORP, LANHAM, MD 20706 USA. RP Fairfield, DH (reprint author), NASA, GODDARD SPACE FLIGHT CTR, EXTRATERR PHYS LAB, CODE 695, GREENBELT, MD 20771 USA. NR 24 TC 72 Z9 75 U1 1 U2 5 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 APR 1 PY 1996 VL 101 IS A4 BP 7785 EP 7791 DI 10.1029/95JA03713 PG 7 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA UD939 UT WOS:A1996UD93900014 ER PT J AU Matthews, DL Ruohoniemi, JM Dudeney, JR Farrugia, CF Lanzerotti, LJ FriisChristensen, E AF Matthews, DL Ruohoniemi, JM Dudeney, JR Farrugia, CF Lanzerotti, LJ FriisChristensen, E TI Conjugate cusp-region ULF pulsation responses to the solar wind event of May 23, 1989 SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID FIELD-LINE RESONANCES; PERIOD MAGNETIC PULSATIONS; SMALL-SCALE IRREGULARITIES; HF RADAR OBSERVATIONS; LATITUDE F-REGION; HYDROMAGNETIC-WAVES; MAGNETOSPHERE; IONOSPHERE; EXCITATION; SYSTEM AB We have studied a hydromagnetic wave event in the early noon sector of the cusp region, using HF radar data collected in the southern hemisphere and ground-based magnetic data from both hemispheres, There were three distinct pulsations, which appear to have been driven by changes in the solar wind, beginning with the passage of a powerful interplanetary shock, This shock triggered the first pulsation, a strong ssc, at 1346 UT, It was followed at 1402 UT by a second pulsation, which had a stable dominant frequency of 3.3 mHz and lasted about half an hour. Although this frequency was close to that of the ssc, the new pulsation was clearly differentiated from the ssc by an abrupt 180 degrees change of phase, A further such phase discontinuity at 1434 UT (near noon MLT) marked the start of a third distinct ULF pulsation with a clearly lower frequency of 2.8 mHz, which continued for another half hour, until 1505 UT, and was correlated with the magnitude of the IMF. These latter two pulsations yielded a successful calibration of the radar observations with ground-based magnetometer measurements; the pulsation current systems in the northern and southern hemispheres were found to be highly correlated and conjugate. The 3.3-mHz pulsation was observed over a range of similar to 10 degrees in invariant latitude, and its amplitude showed a strong, broad maximum close to the latitude of the cusp as inferred from an independent radar-satellite analysis of cusp signatures, The zonal E x B motion associated with the pulsation showed a linear latitudinal decrease in phase (25 degrees per degree of latitude) while the meridional motion had nearly constant phase. The longitudinal phase variation corresponded to an m value of similar to 10 with a source at later MLT. We discuss the possibility that the dominant wave activity near 3 mHz in the latter two pulsations was due to a hydromagnetic surface wave at the magnetopause stimulated by the ssc and modified by the forcing action of the solar wind. C1 UNIV MARYLAND,INST PHYS SCI & TECHNOL,COLLEGE PK,MD 20742. JOHNS HOPKINS UNIV,APPL PHYS LAB,LAUREL,MD. BRITISH ANTARCTIC SURVEY,CAMBRIDGE,ENGLAND. NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. AT&T BELL LABS,MURRAY HILL,NJ 07974. DANISH INST FUNDAMENTAL METROL,COPENHAGEN,DENMARK. NR 41 TC 9 Z9 9 U1 1 U2 3 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 SN 0148-0227 J9 J GEOPHYS RES JI J. Geophys. Res-Space Phys. PD APR 1 PY 1996 VL 101 IS A4 BP 7829 EP 7841 DI 10.1029/95JA03470 PG 13 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA UD939 UT WOS:A1996UD93900018 ER PT J AU Mobarry, CM Fedder, JA Lyon, JG AF Mobarry, CM Fedder, JA Lyon, JG TI Equatorial plasma convection from global simulations of the Earth's magnetosphere SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID INTERPLANETARY MAGNETIC-FIELD; BIRKELAND CURRENTS; ALIGNED CURRENTS; NORTHWARD; MODEL; IMF; ALGORITHMS AB The convection of plasma in the closed field region of the Earth's magnetosphere is an important consequence and a diagnostic of the coupling of solar wind momentum and energy into the magnetosphere; In the outer regions the nature of the flow can help to distinguish between different coupling processes; for example, between (1) a global reconnection process between closed geomagnetic held and the interplanetary magnetic field (IMF), or (2) a local diffusive-viscous interaction. In the inner magnetosphere, the convection is responsible for both energization and redistribution of energetic and thermal plasmas. This paper presents the first results for convection of plasma in the closed field magnetosphere derived from a self-consistent, three-dimensional, magnetohydrodynamic simulation model of the Earth's magnetosphere. The results are shown as electric potential patterns in the equatorial plane. The equipotential contours, which are interpreted as plasma streamlines, demonstrate that line reconnection between closed geomagnetic field and the IMF is the dominant coupling process for southward IMF in the parameter range studied. Results are presented from three simulations, that is, southward, northward, and duskward IMF. For the southward IMF case, the quasi-steady cross polar cap electric potential is essentially equal to the bow reconnection voltage. The results show that reconnection on the open/closed magnetic field boundary is important for northward IMF also. In this case, the reconnection process takes place at the two polar cusps, and is an inherently unsteady process even though it leads to a quasi-steady convection potential in the ionosphere. The implications of these results, for the nature of the solar wind magnetosphere coupling, are discussed. Moreover, the convection results are closely related to the polar Birkeland current systems, which are the self-consistent consequences of the coupling process and in turn create the ionospheric convection flow. C1 USN, RES LAB, BEAM PHYS BRANCH, WASHINGTON, DC 20375 USA. DARTMOUTH COLL, DEPT PHYS & ASTRON, HANOVER, NH 03755 USA. SFA INC, LANDOVER, MD 20785 USA. RP Mobarry, CM (reprint author), NASA, GODDARD SPACE FLIGHT CTR, DIV SPACE DATA & COMP, CODE 934, GREENBELT, MD 20771 USA. NR 39 TC 34 Z9 34 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 SN 0148-0227 J9 J GEOPHYS RES JI J. Geophys. Res-Space Phys. PD APR 1 PY 1996 VL 101 IS A4 BP 7859 EP 7874 DI 10.1029/95JA02301 PG 16 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA UD939 UT WOS:A1996UD93900020 ER PT J AU Middleton, EM Chappelle, EW Cannon, TA Adamse, P Britz, SJ AF Middleton, EM Chappelle, EW Cannon, TA Adamse, P Britz, SJ TI Initial assessment of physiological response to UV-B irradiation using fluorescence measurements SO JOURNAL OF PLANT PHYSIOLOGY LA English DT Article; Proceedings Paper CT 1st International Symposium on Vegetation Stress CY JUN 19-21, 1995 CL GSF RES CTR NEUHERBERG, MUNICH, GERMANY SP Botony II, Karlsruhe, NASA Greenbelt, USA, GSF Res Ctr, Munich Neuherberg HO GSF RES CTR NEUHERBERG DE Cucumis sativus; UV-B; fluorescence; cucumber; plant stress ID LASER-INDUCED FLUORESCENCE; CHLOROPHYLL FLUORESCENCE; TRYPTOPHANYL RESIDUES; GREEN PLANTS; INDUCED BLUE; LEAVES; RADIATION; PHOTOSYNTHESIS; CARBOXYLASE; CAROTENOIDS AB Fluorescence emissions obtained by excitation at 280 and 340 nm (280EX 300-520 nm; 340EX 360-800 nm) were used to discriminate physiological change induced by ultraviolet B (UV-B) irradiation in two cucumber (Cucumis sativus L.) cultivars, Poinsett (UV-B sensitive) and Ashley (insensitive). Plants were grown in chambers with controlled spectral irradiation, including biologically effective UV-B irradiation (21 or 0.3 kJ m(-2) d(-1)) provided for 5 days with photosynthetically active radiation (similar to 38 mol m(-2) d(-1)). Differentiating UV-B induced effects and cultivar differences proved more successful with a dimethyl sulfoxide (DMSO) leaf extract than with freshly excised, intact leaves. Poinsett exhibited significantly lower (P less than or equal to 0.01) fluorescence for most wavelengths or spectral ratios, whether excited at 280 or 340 nm. The single dominant UV-A fluorescence peak observed in all 280EX emission spectra (330-350 nm) was shifted in DMSO from 340 to 350 nm m UV-B irradiated plants (with a significantly higher F350/F475 ratio, P less than or equal to 0.001). This could indicate that UV-B irradiation altered the relative amounts of soluble protein invested in enzymes for photosynthesis (e.g., rubisco) versus UV-B protective compounds. In 340EX spectra, UV-B exposed plants also had higher blue/far-red ratios, possibly due to enhanced production of an antioxidant, blue fluorescing compound known to accumulate after UV-B induced degradation of rubisco. In DMSO, this ratio (F450/F730) was linearly related to the total carotenoid/Chl pigment ratio, with qualitatively different responses for the two cultivars. For 340EX spectra, UV-B effects were most successfully discriminated by the far-red peak, alone or included in a ratio with either red or blue fluorescence. UV-B irradiated plants exhibited a significantly lower (P less than or equal to 0.001) far-red peak in DMSO and lower far-red/red fluorescence ratios in both media, indicating loss of chlorophyll. The F730/F680 ratio for DMSO was log-linearly dependent on total chlorophyll content (r(2) = 0.58; P less than or equal to 0.001). Chlorophyll (Chl) a and b were reduced (P less than or equal to 0.01) and the Chl a/b (P less than or equal to 0.05) and carotenoid/Chl (P less than or equal to 0.001) ratios were higher under UV-B irradiation. This experiment provides further evidence that UV-B induced damage includes degradation of Chi and photosynthetic function, while photoprotection involves the antioxidant defense system. C1 UNIV VIRGINIA,DEPT BIOL,CHARLOTTESVILLE,VA 22903. USDA ARS,CLIMATE STRESS LAB,BELTSVILLE,MD 20705. RP Middleton, EM (reprint author), NASA,GODDARD SPACE FLIGHT CTR,TERR PHYS LAB,GREENBELT,MD 20771, USA. RI Strid, Ake/E-5309-2012; OI Strid, Ake/0000-0003-3315-8835; Adamse, Paulien/0000-0002-7490-2424 NR 41 TC 12 Z9 13 U1 0 U2 3 PU GUSTAV FISCHER VERLAG PI STUTTGART PA WOLLGRASWEG 49, D-70599 STUTTGART, GERMANY SN 0176-1617 J9 J PLANT PHYSIOL JI J. Plant Physiol. PD APR PY 1996 VL 148 IS 1-2 BP 69 EP 77 PG 9 WC Plant Sciences SC Plant Sciences GA UL698 UT WOS:A1996UL69800011 ER PT J AU Wang, C Sun, CT Gates, TS AF Wang, C Sun, CT Gates, TS TI Elastic/viscoplastic behavior of fiber-reinforced thermoplastic composites SO JOURNAL OF REINFORCED PLASTICS AND COMPOSITES LA English DT Article AB An elastic/viscoplastic constitutive model was used to characterize the nonlinear and rate dependent behavior of a continuous fiber-reinforced thermoplastic composite. This model was incorporated into a finite element program for analysis of laminated plates and shells. Details on the finite element formulation with the proposed constitutive model were presented. The numerical results were compared with experimental data for uniaxial tension and three-point bending tests of [+/-45 degrees](3), APC-2 lamintes. C1 PURDUE UNIV, SCH AERONAUT & ASTRONAUT, W LAFAYETTE, IN 47907 USA. GM CORP, CTR TECH, WARREN, MI 48090 USA. NASA, LANGLEY RES CTR, HAMPTON, VA 23665 USA. NR 20 TC 9 Z9 10 U1 1 U2 5 PU SAGE PUBLICATIONS LTD PI LONDON PA 1 OLIVERS YARD, 55 CITY ROAD, LONDON EC1Y 1SP, ENGLAND SN 0731-6844 EI 1530-7964 J9 J REINF PLAST COMP JI J. Reinf. Plast. Compos. PD APR PY 1996 VL 15 IS 4 BP 360 EP 377 PG 18 WC Materials Science, Composites; Polymer Science SC Materials Science; Polymer Science GA UH232 UT WOS:A1996UH23200002 ER PT J AU Furrow, KW Loos, AC Cano, RJ AF Furrow, KW Loos, AC Cano, RJ TI Environmental effects on stitched RTM textile composites SO JOURNAL OF REINFORCED PLASTICS AND COMPOSITES LA English DT Article ID HYBRID COMPOSITES; COMPRESSION AB The effects of temperature and humidity cycling on mechanical properties of A54/3501-6 quasi-isotropic textile composites were determined. The composites were resin transfer molded from unstitched, Kevlar 29 stitched, and S-2 glass stitched uniweave fabric preforms. Data presented include photomicrographs, compression strengths and compression-compression fatigue results for environmentally cycled and uncycled composites. After manufacture, microcracks developed around the glass and Kevlar stitching. These microcracks did not grow after environmental cycling. The unstitched material developed microcracks only after cycling. Temperature and humidity cycling reduced the static compression strength of the unstitched and Kevlar stitched uniweave materials nearly 10 percent. Under the same conditions the glass stitched uniweave material lost 3 percent of its baseline strength. Combined temperature and humidity cycling did not affect the fatigue properties of the uniweave materials when the test specimens were dried to their original weights before testing. Temperature cycling at constant 40 percent humidity, resulted in a 5 percent decrease in static compression strength for the unstitched and Kevlar stitched material. Unstitched, glass stitched and Kevlar stitched materials exposed to constant 60 degrees C and 95 percent relative humidity for 80 days and then saturated in 70 degrees C water, lost 17, 7 and 19 percent of their baseline compression strength, respectively. These conditions lowered the fatigue strengths only after saturation. Braided composites including, a stitched 2-D braid, an unstitched 2-D braid and a 3-D braid were also exposed to environmental cycling. The moisture absorption in the AS4/E905L system was lower than the AS4/3501-6 system. Consequently environmental cycling had little effect on the static or fatigue strengths of braided materials. C1 NASA, LANGLEY RES CTR, POLYMER & COMPOSITES BRANCH, HAMPTON, VA 23681 USA. RP Furrow, KW (reprint author), VIRGINIA POLYTECH INST & STATE UNIV, DEPT ENGN SCI & MECH, BLACKSBURG, VA 24061 USA. NR 46 TC 14 Z9 19 U1 1 U2 10 PU SAGE PUBLICATIONS LTD PI LONDON PA 1 OLIVERS YARD, 55 CITY ROAD, LONDON EC1Y 1SP, ENGLAND SN 0731-6844 J9 J REINF PLAST COMP JI J. Reinf. Plast. Compos. PD APR PY 1996 VL 15 IS 4 BP 378 EP 419 PG 42 WC Materials Science, Composites; Polymer Science SC Materials Science; Polymer Science GA UH232 UT WOS:A1996UH23200003 ER PT J AU Mosher, M Light, JS AF Mosher, M Light, JS TI Study of noise on a small-scale hovering tilt rotor SO JOURNAL OF THE AMERICAN HELICOPTER SOCIETY LA English DT Article AB A study of the noise from a small-scale, semi-span test of a hovering tilt rotor is presented, The effect on noise of the tilt rotor fountain and of several tilt rotor configuration changes is examined, Measurements were made of an isolated rotor; rotor and wing; rotor and image plane; and rotor, wing and image plane. This last configuration models a tilt rotor, With a tilt rotor, the wing turns some of the rotor downwash inboard, When the flows meet, some of the flow is forced upward creating a fountain, Some of the fountain is ingested into the rotor disc, Rotor fountain interactions produce very unsteady impulsive noise to the rear of the aircraft. Configuration changes to investigate download reduction included increasing the rotor/wing separation, deflecting the flap, adding the nacelle, adding vortex trapping plates and blowing on the upper surface. These configuration changes produced little or no effect on the noise, although they changed the net download, Increasing the wing span, however, reduced the annoying content of this impulsive noise about 2 dB. RP Mosher, M (reprint author), NASA,AMES RES CTR,MOFFETT FIELD,CA 94035, USA. NR 15 TC 2 Z9 3 U1 0 U2 0 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 APR PY 1996 VL 41 IS 2 BP 27 EP 36 PG 10 WC Engineering, Aerospace SC Engineering GA UG948 UT WOS:A1996UG94800003 ER PT J AU Schroeder, JA AF Schroeder, JA TI Evaluation of simulation motion fidelity criteria in the vertical and directional axes SO JOURNAL OF THE AMERICAN HELICOPTER SOCIETY LA English DT Article ID FLIGHT SIMULATOR AB An evaluation of existing motion fidelity criteria was conducted on the NASA Ames Vertical Motion Simulator Experienced test pilots performed single-axis repositioning tasks in both the vertical and the directional axes using transfer-function approximations of a hovering helicopter. Gain and natural frequency variations were made only in the software filters that attenuate the commands to the simulator motion system. The variations spanned motion response characteristics from nearly full math-model motion to fixed-base. Between configurations, pilots recalibrated their motion response perception by flying the task with full motion. Pilots subjectively rated the motion fidelity of subsequent configurations relative to this full motion case, which was considered the standard for comparison. The results suggested that the existing vertical-axis criterion was accurate for combinations of gain and natural frequency changes. However, if only the gain or the natural frequency was changed, the rated motion fidelity was better than the criterion predicted. In the vertical axis, the objective and subjective results indicated that a larger gain reduction was tolerated than the existing criterion allowed, Significant degradations in performance were noted between the full-vertical motion and no-vertical motion configurations, The limited data collected in the yaw axis revealed that pilots had difficulty in distinguishing among the variations in the pure yaw motion cues, thus indicating that pure yaw motion may be of little importance in hovering flight simulation. RP Schroeder, JA (reprint author), NASA,AMES RES CTR,MOFFETT FIELD,CA 94035, USA. NR 22 TC 9 Z9 9 U1 0 U2 0 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 APR PY 1996 VL 41 IS 2 BP 44 EP 57 PG 14 WC Engineering, Aerospace SC Engineering GA UG948 UT WOS:A1996UG94800005 ER PT J AU Hassan, AA Charles, BD Tadghighi, H AF Hassan, AA Charles, BD Tadghighi, H TI A consistent approach for modeling the aerodynamics of self-generated rotor blade-vortex interactions SO JOURNAL OF THE AMERICAN HELICOPTER SOCIETY LA English DT Article AB A numerical procedure has been developed far the prediction of the three-dimensional unsteady aerodynamic response of a helicopter rotor during self-generated blade-vortex interactions (BVI), Pertinent vortex wake parameters (e.g,, spatial and temporal trajectories, strengths) were computed using the lifting-line rotor/helicopter trim code CAMRAD/JA, In this code, tracking of the near-field BVI vortex-wake segments was accomplished using a new ''box'' technique which involves tracking all tip vortex elements tying inside a user specified box-like domain which encloses the rotor, Unsteady blade surface pressures were then predicted using a modified version (designated FPRBVI) of the full potential rotor code FPR (v2,1), Two approaches were used to model vortex-induced effects in the FPRBVI solver; the efficient surface or ''transpiration'' approach, and the more comprehensive split potential approach, The numerical procedure was used to predict the unsteady aerodynamic response of the one-seventh scale two-bladed AH-IG OLS model rotor and a United Technologies Corporation 17.5% scale four-bladed model rotor during self-generated BVI, Accuracy of the numerical procedure was assessed using wind tunnel data. C1 NASA,LANGLEY RES CTR,HAMPTON,VA 23665. RP Hassan, AA (reprint author), MCDONNELL DOUGLAS HELICOPTER CO,TECH STAFF 5,MESA,AZ, USA. NR 24 TC 1 Z9 1 U1 1 U2 1 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 APR PY 1996 VL 41 IS 2 BP 74 EP 84 PG 11 WC Engineering, Aerospace SC Engineering GA UG948 UT WOS:A1996UG94800007 ER PT J AU Striepe, SA Desai, PN AF Striepe, SA Desai, PN TI Piloted Mars missions using cryogenic and storable propellants SO JOURNAL OF THE ASTRONAUTICAL SCIENCES LA English DT Article ID RADIATION EXPOSURE PREDICTIONS; INTERPLANETARY AB This analysis of piloted long-duration stay Mars missions using a chemical or nuclear thermal propulsion Earth-departure stage, storable-propellant Mars-arrival and departure stages (to avoid propellant boil-off), and an Earth-entry vehicle was conducted for three year segments from 2000 to 2020. This study initially determines the minimum initial mass in low-Earth orbit (IMLEO) missions and then investigates their radiation exposure levels and Mars parking orbit selection. Also, the impact of reducing the outbound (Earth-Mars) transfer time on IMLEO and predicted radiation exposure levels is included. This analysis indicates that a vehicle using an advanced chemical propulsion system (specific impulse, I-sp of 480 s) for Earth departure is feasible throughout 2000-2020 with an IMLEO less than 640 metric tonnes (MT), while an Earth-departure stage using a nuclear thermal propulsion (NTP) system with an I-sp of 925 s is even more appealing with IMLEO's less than 405 MT. Vehicles with 875 and 825 s I-sp Earth-departure stages had only slightly higher IMLEO's than the advanced NTP system (10 and 20 MT higher, respectively). Also, reducing the time spent in space may not always result in a significantly reduced level of radiation exposure, especially if the mission encounter dates are changed to a less favorable period of the solar cycle. RP Striepe, SA (reprint author), NASA, LANGLEY RES CTR, DIV SPACE SYST & CONCEPTS, HAMPTON, VA 23681 USA. NR 14 TC 7 Z9 7 U1 0 U2 1 PU AMER ASTRONAUTICAL SOC PI SPRINGFIELD PA 6352 ROLLING MILL PLACE SUITE 102, SPRINGFIELD, VA 22152 USA SN 0021-9142 J9 J ASTRONAUT SCI JI J. Astronaut. Sci. PD APR-JUN PY 1996 VL 44 IS 2 BP 207 EP 222 PG 16 WC Engineering, Aerospace SC Engineering GA VP494 UT WOS:A1996VP49400005 ER PT J AU Souza, ACA Srivastava, SK AF Souza, ACA Srivastava, SK TI Photoabsorption cross sections derived by the electron energy loss spectroscopy technique for ammonia, methane and acetylene in the photon energy range of 5 to 100 eV SO JOURNAL OF THE BRAZILIAN CHEMICAL SOCIETY LA English DT Article DE photoabsorption; ammonia; methane; acetylene ID CH4; ABSORPTION AB Photoabsorption cross sections for NH3, CH4 and C2H2 were obtained in the photon energy range of 5 to 100 eV (250 and 12.5 nm) by utilizing the electron energy loss spectroscopy (EELS) technique. They are compared with previously reported data. In general, the agreement is good. The present work provides photoabsorption data at wavelengths where no previous measurements have been made. C1 FED UNIV RIO DE JANEIRO, INST QUIM, BR-21949900 RIO DE JANEIRO, BRAZIL. CALTECH, JET PROP LAB, PASADENA, CA 91109 USA. NR 17 TC 2 Z9 2 U1 0 U2 4 PU SOC BRASILEIRA QUIMICA PI SAO PAULO PA CAIXA POSTAL 26037, 05599-970 SAO PAULO, BRAZIL SN 0103-5053 EI 1678-4790 J9 J BRAZIL CHEM SOC JI J. Braz. Chem. Soc. PD APR-JUN PY 1996 VL 7 IS 2 BP 91 EP 95 PG 5 WC Chemistry, Multidisciplinary SC Chemistry GA UJ389 UT WOS:A1996UJ38900003 ER PT J AU Pallix, JB Copeland, RA AF Pallix, JB Copeland, RA TI Measurement of catalytic recombination coefficients on quartz using laser-induced fluorescence SO JOURNAL OF THERMOPHYSICS AND HEAT TRANSFER LA English DT Article ID OXYGEN-ATOM; 2-PHOTON ABSORPTION; NITROGEN; STATES; FLAMES AB Advanced laser-based diagnostics have been developed to examine catalytic effects and atom/surface interactions on thermal protection materials. This study establishes the feasibility of using two photon laser-induced fluorescence for detection of O and N atom loss in a diffusion tube to measure surface catalytic activity. The experimental apparatus is versatile in that it allows fluorescence detection to be used for measuring species selective recombination coefficients and for performing diffusion tube and microwave discharge diagnostics. Many of the potential sources of error in measuring atom recombination coefficients by this method have been identified and taken into account. These include scattered light, detector saturation, sample surface cleanliness, reactor design, gas pressure and composition, and selectivity of the laser probe. Recombination coefficients and their associated errors are reported for N and O atoms on a quartz surface at room temperature. C1 SRI INT,PHYS MOLEC LAB,MENLO PK,CA 94025. RP Pallix, JB (reprint author), NASA,AMES RES CTR,THERMOSCI INST,THERMAL PROTECT MAT & SYST BRANCH,MOFFETT FIELD,CA 94035, USA. RI Copeland, Richard/E-2201-2011 NR 37 TC 6 Z9 6 U1 1 U2 9 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 APR-JUN PY 1996 VL 10 IS 2 BP 224 EP 233 DI 10.2514/3.779 PG 10 WC Thermodynamics; Engineering, Mechanical SC Thermodynamics; Engineering GA UE790 UT WOS:A1996UE79000005 ER PT J AU Gokcen, T AF Gokcen, T TI Effects of freestream nonequilibrium on convective heat transfer to a blunt body SO JOURNAL OF THERMOPHYSICS AND HEAT TRANSFER LA English DT Article AB The axisymmetric Navier-Stokes equations are solved numerically for nonequilibrium airflows over a hemisphere for two sets of conditions. One set corresponds to a wind-tunnel test flow where the freestream is vibrationally excited and dissociated air, and the other corresponds to hypersonic free flight where the freestream is air at atmospheric conditions, Relevant similitude parameters are partially duplicated in the computations as in the wind-tunnel testing of convective heating. A nonequilibrium formulation with a three-temperature thermochemical model has been employed to simulate vibrationally excited and partially dissociated nonequilibrium airflow, Finite catalytic boundary conditions at the surface are implemented, Computations are carried out at enthalpies of 7.2 and 25 MJ/kg, for surface pressures of 0.017 and 0.076 atm, respectively, Computed stagnation point heat transfer is compared with the classical results of Fay and Riddell, and Goulard. The computed results show that successful testing of surface heat transfer in a high-enthalpy tunnel is possible with partial duplication of similitude variables. RP Gokcen, T (reprint author), NASA,AMES RES CTR,THERMOSCI INST,MOFFETT FIELD,CA 94035, USA. NR 16 TC 8 Z9 8 U1 0 U2 1 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 APR-JUN PY 1996 VL 10 IS 2 BP 234 EP 241 DI 10.2514/3.780 PG 8 WC Thermodynamics; Engineering, Mechanical SC Thermodynamics; Engineering GA UE790 UT WOS:A1996UE79000006 ER PT J AU Gupta, RN AF Gupta, RN TI Viscous shock-layer study of thermochemical nonequilibrium SO JOURNAL OF THERMOPHYSICS AND HEAT TRANSFER LA English DT Article ID FLOWS AB A two-temperature, viscous shock-layer (VSL) technique to analyze low-density (slip) effects and vibrational and electronic nonequilibrium for an Ii-species airflow is presented, This formulation employs recently developed physical models, detailed transport and thermodynamic properties, and body and shock-slip conditions for multicomponent mixtures. Presently obtained results reproduce examined reentry flight data acid numerical calculations with a good degree of accuracy over a wide range of conditions, validating its use for the calculation of low-to-high density flows. Detailed stagnation-region calculations along the trajectory of a proposed single-stage-to-orbit vehicle show significant vibrational and electronic nonequilibrium and slip effects at the highest considered altitude of 85 km. The combined effects of thermal nonequilibrium and slip lower the stagnation-point heating by about 24% at this altitude, These effects are negligible on surface quantities at 55 km altitude, At this altitude, however, the chemical nonequilibrium effects lower the stagnation heating obtained from chemical equilibrium calculations by about 21% for the Shuttle-like surface. The results provided here demonstrate the use of the VSL technique as a fast calculation procedure in a conceptual and preliminary design process, requiring sensitivity analysis and rapid reanalysis. RP Gupta, RN (reprint author), NASA,LANGLEY RES CTR,DIV GAS DYNAM,AEROTHERMODYNAM BRANCH,HAMPTON,VA 23681, USA. NR 38 TC 8 Z9 10 U1 1 U2 1 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 APR-JUN PY 1996 VL 10 IS 2 BP 257 EP 266 DI 10.2514/3.801 PG 10 WC Thermodynamics; Engineering, Mechanical SC Thermodynamics; Engineering GA UE790 UT WOS:A1996UE79000009 ER PT J AU Gupta, RN AF Gupta, RN TI Two- and three-dimensional analysis of hypersonic nonequilibrium low-density flows SO JOURNAL OF THERMOPHYSICS AND HEAT TRANSFER LA English DT Article ID SHOCK-LAYER FLOWS; REYNOLDS-NUMBER FLOWS; LONG SLENDER BODIES AB Flowfield results have been obtained for hypersonic, low-density, two- and three-dimensional, nonequilibrium viscous shock-layer flows, Three-dimensional calculations are performed for sphere-cone-shaped bodies at various angles of attack. Recently obtained surface and shock-slip boundary conditions are implemented to account for the low-density effects. These boundary conditions may also be employed with the Navier-Stokes equations with or without a shock-fitting solution technique, A method is suggested for obtaining the input shock shape for the three dimensional nonequilibrium viscous how. This approach gives superior convergence of results, especially under low-density flow conditions, and makes the VSL method self-starting, The analytic algebraic grid implemented with the equations does not add any numerical dissipation. Obtained results show the effect of low density on the surrounding flowfieid and surface quantities for a hypervelocity vehicle. Good agreement is obtained with the available numerical results (including the direct simulation Monte Carlo predictions) and experimental data for the low-density flight conditions. RP Gupta, RN (reprint author), NASA,LANGLEY RES CTR,DIV GAS DYNAM,AEROTHERMODYNAM BRANCH,HAMPTON,VA 23681, USA. NR 33 TC 2 Z9 2 U1 0 U2 1 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 SN 0887-8722 J9 J THERMOPHYS HEAT TR JI J. Thermophys. Heat Transf. PD APR-JUN PY 1996 VL 10 IS 2 BP 267 EP 276 DI 10.2514/3.783 PG 10 WC Thermodynamics; Engineering, Mechanical SC Thermodynamics; Engineering GA UE790 UT WOS:A1996UE79000010 ER PT J AU Perrell, ER Erickson, WD Candler, GV AF Perrell, ER Erickson, WD Candler, GV TI Numerical simulation of nonequilibrium condensation in a hypersonic wind tunnel SO JOURNAL OF THERMOPHYSICS AND HEAT TRANSFER LA English DT Article AB A computational method for calculating supersonic two-dimensional nozzle flows with nonequilibrium phase change is developed, The code uses a fully implicit, finite volume formulation with Steger-Warming flux vector splitting and Jacobi point relaxation. Source terms for finite rate condensation and evaporation are constructed from the classical theories of nucleation and droplet growth, Calculations of the NASA Langley Research Center 8 ft High Temperature Tunnel nozzle are performed and compared with previously reported quasi-one dimensional calculations and experimental data. C1 N CAROLINA STATE UNIV,RALEIGH,NC 27695. NASA,LANGLEY RES CTR,HYPERSON AIRBREATHING PROPULS BRANCH,HAMPTON,VA 23681. NASA,LANGLEY RES CTR,HYPERSON VEHICLES OFF,HAMPTON,VA 23681. UNIV MINNESOTA,DEPT AEROSP ENGN & MECH,MINNEAPOLIS,MN 55455. NR 15 TC 8 Z9 13 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 APR-JUN PY 1996 VL 10 IS 2 BP 277 EP 283 DI 10.2514/3.784 PG 7 WC Thermodynamics; Engineering, Mechanical SC Thermodynamics; Engineering GA UE790 UT WOS:A1996UE79000011 ER PT J AU Lin, EI Stultz, JW Reeve, RT AF Lin, EI Stultz, JW Reeve, RT TI Effective emittance for Cassini multilayer insulation blankets and heat loss near seams SO JOURNAL OF THERMOPHYSICS AND HEAT TRANSFER LA English DT Article AB Thermal performance of Cassini multilayer insulation (MLI) blankets was characterized in thermal vacuum tests. Effective emittance was derived for the standard and high-temperature layups, with or without micrometeoroid protection standoffs, and for a high-performance duo-layup with staggered seams, The all-Kapton(R) layup was shown to have a 19% higher effective emittance than the hybrid Kapton-Mylar(R) layup, and the duo-layup exhibited a dramatic capability of reducing heat dissipation by 2.6 fold. Several different definitions of effective emittance are discussed, and their relations to distinct hardware-MLI configurations and corresponding modeling techniques clarified, Large temperature differences (up to 70 degrees C) were observed between the center and seam of a blanket. Heat losses in the vicinity of seams are quantified, and a major MLI heat loss mechanism elucidated. RP Lin, EI (reprint author), CALTECH,JET PROP LAB,MECH SYST ENGN & RES DIV,TECH STAFF,4800 OAK GROVE DR,PASADENA,CA 91109, USA. NR 4 TC 1 Z9 1 U1 0 U2 1 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 SN 0887-8722 J9 J THERMOPHYS HEAT TR JI J. Thermophys. Heat Transf. PD APR-JUN PY 1996 VL 10 IS 2 BP 357 EP 363 DI 10.2514/3.795 PG 7 WC Thermodynamics; Engineering, Mechanical SC Thermodynamics; Engineering GA UE790 UT WOS:A1996UE79000022 ER PT J AU Zaretsky, EV Poplawski, JV AF Zaretsky, EV Poplawski, JV TI On the accuracy of rolling bearing fatigue life prediction - Discussion SO JOURNAL OF TRIBOLOGY-TRANSACTIONS OF THE ASME LA English DT Editorial Material C1 JV POPLAWSKI & ASSOC,BETHLEHEM,PA. RP Zaretsky, EV (reprint author), NASA,LEWIS RES CTR,CLEVELAND,OH 44135, USA. NR 7 TC 0 Z9 0 U1 0 U2 2 PU ASME-AMER SOC MECHANICAL ENG PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017 SN 0742-4787 J9 J TRIBOL-T ASME JI J. Tribol.-Trans. ASME PD APR PY 1996 VL 118 IS 2 BP 309 EP 310 DI 10.1115/1.2831300 PG 2 WC Engineering, Mechanical SC Engineering GA UH155 UT WOS:A1996UH15500008 ER PT J AU Ekaterinaris, JA Platzer, MF AF Ekaterinaris, JA Platzer, MF TI Numerical investigation of stall flutter SO JOURNAL OF TURBOMACHINERY-TRANSACTIONS OF THE ASME LA English DT Article; Proceedings Paper CT 39th International Gas Turbine and Aeroengine Congress and Exposition CY JUN 13-16, 1994 CL THE HAGUE, NETHERLANDS ID BOUNDARY-LAYERS; TURBULENCE; EQUATIONS; SCHEMES; MODEL AB Unsteady, separated, high Reynolds number flow over an airfoil undergoing oscillatory motion is investigated numerically. The compressible form of the Reynolds-averaged governing equations is solved using a high-order, upwind biased numerical scheme. The turbulent pow region is computed using a one-equation turbulence model. The computed results show that the key to the accurate prediction of the unsteady loads at stall potter conditions is the modeling of the transitional pow region at the leading edge. A simplified criterion for the transition onset is used. The transitional flow region is computed with a modified form of the turbulence model. The computed solution, where the transitional pow region is included, shows that the small laminar/transitional separation bubble forming during the pitch-rep motion has a decisive effect on the near-wall flow and the development of the unsteady loads. Detailed comparisons of computed fully turbulent and transitional flow solutions with experimental data are presented. C1 USN,POSTGRAD SCH,DEPT AERONAUT & ASTRONAUT,MONTEREY,CA 93943. RP Ekaterinaris, JA (reprint author), NASA,AMES RES CTR,NAVY NASA JOINT INST AERONAUT,MOFFETT FIELD,CA 94035, USA. NR 29 TC 12 Z9 12 U1 1 U2 2 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 APR PY 1996 VL 118 IS 2 BP 197 EP 203 DI 10.1115/1.2836626 PG 7 WC Engineering, Mechanical SC Engineering GA UJ511 UT WOS:A1996UJ51100003 ER PT J AU Suder, KL Celestina, ML AF Suder, KL Celestina, ML TI Experimental and computational investigation of the tip clearance flow in a transonic axial compressor rotor SO JOURNAL OF TURBOMACHINERY-TRANSACTIONS OF THE ASME LA English DT Article; Proceedings Paper CT 39th International Gas Turbine and Aeroengine Congress and Exposition CY JUN 13-16, 1994 CL THE HAGUE, NETHERLANDS ID STALL; FIELD AB Experimental and computational techniques are used to investigate tip clearance flows in a transonic axial compressor rotor at design and part-speed conditions. Laser anemometer data acquired in the endwall region are presented for operating conditions near peak efficiency and near stall at 100 percent design speed and at near peak efficiency al 60 percent design speed. The role of the passage shock/leakage vortex interaction in generating endwall blockage is discussed As a result of the shock/vortex interaction at design speed, the radial influence of the tip clearance flow extends to 20 rimes the physical tip clearance height. At part speed in the absence of the shock, the radial extent is only five limes the tip clearance height. Both measurements and analysis indicate that under part-speed operating conditions a second vortex which does not originate from the tip leakage flow, forms in the end-wall region within the blade passage and exits the passage near midpitch. Mixing of the leakage vortex with the primary pow downstream of the rotor at both design and part-speed conditions is also discussed. C1 NASA,LEWIS RES CTR GRP,SVERDRUP TECHNOL INC,CLEVELAND,OH 44135. RP Suder, KL (reprint author), NASA,LEWIS RES CTR,CLEVELAND,OH 44135, USA. NR 19 TC 84 Z9 94 U1 1 U2 14 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 APR PY 1996 VL 118 IS 2 BP 218 EP 229 DI 10.1115/1.2836629 PG 12 WC Engineering, Mechanical SC Engineering GA UJ511 UT WOS:A1996UJ51100006 ER PT J AU Copenhaver, WW Mayhew, ER Hah, C Wadia, AR AF Copenhaver, WW Mayhew, ER Hah, C Wadia, AR TI The effect of tip clearance on a swept transonic compressor rotor SO JOURNAL OF TURBOMACHINERY-TRANSACTIONS OF THE ASME LA English DT Article; Proceedings Paper CT 39th International Gas Turbine and Aeroengine Congress and Exposition CY JUN 13-16, 1994 CL THE HAGUE, NETHERLANDS ID PERFORMANCE; FLOWS AB An experimental and numerical investigation of detailed tip clearance flow structures and their effects on the aerodynamic performance of a modern low-aspect-ratio, high-throughflow, axial transonic fan is presented, Rotor flow fields were investigated at two clearance levels experimentally, at tip clearance to tip blade chord ratios of 0.27 and 1.87 percent, and at four clearance levels numerically, at ratios of zero, 0.27, 1.0, and 1.87 percent. The numerical method seems to calculate the rotor aerodynamics well, with some disagreement in loss calculation which might be improved with improved turbulence modeling and a further refined grid. Both the experimental and the numerical results indicate that the performance of this class of rotors is dominated by the tip clearance flows. Rotor efficiency drops six points when the tip clearance is increased from 0.27 to 1.87 percent, and flow range decreases about 30 percent. No optimum clearance size for the present rotor was indicated. Most of the efficiency change occurs near the tip section, with the interaction between the tip clearance flow and the passage shock becoming much stronger when the tip clearance is increased. In all cases, the shock structure was three dimensional and swept, with the shock becoming normal to the endwall near the shroud. C1 NASA,LEWIS RES CTR,CLEVELAND,OH 44135. GE AIRCRAFT ENGINES,CINCINNATI,OH 45215. RP Copenhaver, WW (reprint author), USAF,WRIGHT LAB,WRIGHT PATTERSON AFB,OH 45433, USA. NR 21 TC 26 Z9 28 U1 1 U2 5 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 APR PY 1996 VL 118 IS 2 BP 230 EP 239 DI 10.1115/1.2836630 PG 10 WC Engineering, Mechanical SC Engineering GA UJ511 UT WOS:A1996UJ51100007 ER PT J AU Lee, YT Hah, C Loellbach, J AF Lee, YT Hah, C Loellbach, J TI Flow analyses in a single-stage propulsion pump SO JOURNAL OF TURBOMACHINERY-TRANSACTIONS OF THE ASME LA English DT Article; Proceedings Paper CT 39th International Gas Turbine and Aeroengine Congress and Exposition CY JUN 13-16, 1994 CL THE HAGUE, NETHERLANDS ID TURBOMACHINERY AB Steady-state analyses of the incompressible flow past a single-stage stator/rotor propulsion pump are presented and compared to experimental data. The purpose of the current study is to validate a numerical method for the design application of a typical propulsion pump and for the acoustic analysis based on predicted flowfields. ii steady multiple-blade row approach is used to calculate the flowfields of the stator and the rotor. The numerical method is based on a fully conservative control-volume technique. The Reynolds-averaged Navier-Stokes equations are solved along with the standard two-equation k - epsilon turbulence model. Numerical results for both mean flow and acoustic properties compare well with measurements in the wake of each blade row. The rotor blade has a thick boundary layer in the last quarter of the chord and the flow separates near the trailing edge. These features invalidate many Euler-prediction results. Due to the dramatic reduction of the turbulent eddy viscosity in the thick boundary layer; the standard k - epsilon model cannot predict the correct local flow characteristics near the rotor trailing edge and in its near wake. Thus, a modification of the turbulence length scale in the turbulence model is applied in the thick boundary layer in response to the reduction of the turbulent eddy viscosity. C1 NASA,LEWIS RES CTR,CLEVELAND,OH 44135. ICOMP,LEWIS RES CTR,CLEVELAND,OH 44135. RP Lee, YT (reprint author), DAVID TAYLOR MODEL BASIN,BETHESDA,MD 20084, USA. NR 24 TC 10 Z9 10 U1 0 U2 0 PU ASME-AMER SOC MECHANICAL ENG PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017 SN 0889-504X J9 J TURBOMACH JI J. Turbomach.-Trans. ASME PD APR PY 1996 VL 118 IS 2 BP 240 EP 248 DI 10.1115/1.2836631 PG 9 WC Engineering, Mechanical SC Engineering GA UJ511 UT WOS:A1996UJ51100008 ER PT J AU Lessels, B AF Lessels, B TI Advanced technology program targets offshore oil and gas SO MATERIALS PERFORMANCE LA English DT Editorial Material RP Lessels, B (reprint author), NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,HUNTSVILLE,AL 35812, USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU NATL ASSN CORROSION ENG PI HOUSTON PA 1440 SOUTH CREEK DRIVE, HOUSTON, TX 77084-4906 SN 0094-1492 J9 MATER PERFORMANCE JI Mater. Perform. PD APR PY 1996 VL 35 IS 4 BP 7 EP & PG 2 WC Materials Science, Characterization & Testing SC Materials Science GA UD958 UT WOS:A1996UD95800002 ER PT J AU Rao, KBS Schuster, H Halford, GR AF Rao, KBS Schuster, H Halford, GR TI Mechanisms of high-temperature fatigue failure in alloy 800H SO METALLURGICAL AND MATERIALS TRANSACTIONS A-PHYSICAL METALLURGY AND MATERIALS SCIENCE LA English DT Article; Proceedings Paper CT Symposium on High Temperature Fracture Mechanisms in Advanced Materials, at the 1994 Fall Meeting of TMS CY OCT 02-06, 1994 CL ROSEMONT, IL SP ASM SMD Flow & Fracture Comm ID STAINLESS-STEEL; CRACK-GROWTH; BEHAVIOR AB The damage mechanisms influencing the axial strain-controlled low-cycle fatigue (LCF) behavior of alloy 800H at 850 degrees C have been evaluated under conditions of equal tension/compression ramp rates (fast-fast (F-F): 4 x 10(-3) s(-1) and slow-slow (S-S): 4 x 10(-5) s(-1)) and asymmetrical ramp rates (fast-slow (F-S): 4 x 10(-3) s(-1) / 4 x 10(-5) s(-1) and slow-fast (S-F): 4 x 10(-5) / 4 x 10(-3) s(-1)) in tension and compression. The fatigue life, cyclic stress response, and fracture modes were significantly influenced by the waveform shape. The fatigue lives displayed by different loading conditions were in the following order: F-F > S-S > F-S > S-F. The fracture mode was dictated by the ramp rate adopted in the tensile direction. The fast ramp rate in the tensile direction led to the occurrence of transgranular crack initiation and propagation, whereas the slow ramp rate caused intergranular initiation and propagation. The time-dependent processes and their synergistic interactions, which were at the basis of observed changes in cyclic stress response and fatigue life, were identified. Oxidation, creep damage, dynamic strain aging, massive carbide precipitation, time-dependent creep deformation, and deformation ratcheting were among the several factors influencing cyclic life. Irrespective of the loading condition, the largest effect on life was exerted by oxidation processes. Deformation ratcheting had its greatest influence on life under asymmetrical loading conditions. Creep damage accumulated the greatest amount during the slow tensile ramp under S-F conditions. C1 INST MAT ENERGY,SYST RES CTR,D-52425 JULICH,GERMANY. NASA,LEWIS RES CTR,STRUCT DIV,CLEVELAND,OH 44135. NR 27 TC 7 Z9 7 U1 1 U2 8 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 APR PY 1996 VL 27 IS 4 BP 851 EP 861 DI 10.1007/BF02649752 PG 11 WC Materials Science, Multidisciplinary; Metallurgy & Metallurgical Engineering SC Materials Science; Metallurgy & Metallurgical Engineering GA UG103 UT WOS:A1996UG10300004 ER PT J AU Song, H Tewari, SN deGroh, HC AF Song, H Tewari, SN deGroh, HC TI Convection during thermally unstable solidification of Pb-Sn in a magnetic field SO METALLURGICAL AND MATERIALS TRANSACTIONS A-PHYSICAL METALLURGY AND MATERIALS SCIENCE LA English DT Article ID DIRECTIONAL DENDRITIC SOLIDIFICATION; THERMOSOLUTAL CONVECTION; NATURAL-CONVECTION; METALLIC ALLOYS; GROWTH; MACROSEGREGATION; STABILITY; TRANSITION; INTERFACE; SYSTEM AB Convection and macrosegregation in directionally solidified hypoeutectic Pb-38 wt pct Sn and hypereutectic Pb-64.5 wt pct Sn have been examined during upward and downward growth. Temperature fluctuations are observed along the length of the melt column during downward growth. With increasing Rayleigh number, these fluctuations change from none, to cyclic, to time periodic having multiple harmonics, and finally to random. At the higher convective driving force of 350 K temperature inversion, the transverse magnetic field decreased convective levels, strong random temperature fluctuations (flows) becoming smaller and periodic. The maximum field of 0.45 T was unable to completely eliminate convection. For the lower convective driving force of 150 K temperature inversion, the 0.05 T magnetic field decreased flows, and at 0.15 T, the field caused a dramatic decrease in the characteristic frequency of the temperature fluctuations, indicating a change in the nature of the flow, the waveform of the temperature fluctuations changing from sinusoidal to a pulsed wave. Temperature fluctuations and time delays between thermocouples were used to estimate flow velocities. Irrespective of the convection in the bulk melt (ahead of the mushy zone), longitudinal macrosegregation occurs only if the interdendritic melt mixes with the bulk melt. C1 NASA,LEWIS RES CTR,CLEVELAND,OH 44135. RP Song, H (reprint author), CLEVELAND STATE UNIV,DEPT CHEM ENGN,CLEVELAND,OH 44115, USA. NR 39 TC 10 Z9 10 U1 0 U2 3 PU MINERALS METALS MATERIALS SOC PI WARRENDALE PA 420 COMMONWEALTH DR, WARRENDALE, PA 15086 SN 1073-5623 J9 METALL MATER TRANS A JI Metall. Mater. Trans. A-Phys. Metall. Mater. Sci. PD APR PY 1996 VL 27 IS 4 BP 1095 EP 1110 DI 10.1007/BF02649778 PG 16 WC Materials Science, Multidisciplinary; Metallurgy & Metallurgical Engineering SC Materials Science; Metallurgy & Metallurgical Engineering GA UG103 UT WOS:A1996UG10300030 ER PT J AU Torres, LFB Waga, I AF Torres, LFB Waga, I TI Decaying Lambda cosmologies and statistical properties of gravitational lenses SO MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY LA English DT Article DE cosmology, theory; gravitational lensing ID INTERGALACTIC MEDIUM; ELLIPTICAL GALAXIES; DARK MATTER; CONSTANT; UNIVERSE; CONSEQUENCES; DENSITY; LIMITS; MODELS; FIELD AB In this paper we investigate the statistical properties of gravitational lenses for models in which a cosmological term decreases with time as Lambda proportional to a(-m), where a is the scale factor, and m is a parameter (0 less than or equal to m < 3). We show that for given low values of the present matter density parameter Omega(m0), there is a wide range of values for m for which the lensing rate is significantly smaller than that in cosmological constant (Lambda) models. We also show that models with low Omega(m0) and m greater than or similar to 1 have a high likelihood of reproducing the observed lens statistics in the Hubble Space Telescope Snapshot Survey (HSTSS). C1 FERMILAB NATL ACCELERATOR LAB,NASA,FERMILAB ASTROPHYS CTR,BATAVIA,IL 60510. RP Torres, LFB (reprint author), FED UNIV RIO DE JANEIRO,INST FIS,BR-21943 RIO JANEIRO,BRAZIL. RI Waga, Ioav/B-6288-2014 NR 62 TC 27 Z9 28 U1 0 U2 0 PU BLACKWELL SCIENCE LTD PI OXFORD PA OSNEY MEAD, OXFORD, OXON, ENGLAND OX2 0EL SN 0035-8711 J9 MON NOT R ASTRON SOC JI Mon. Not. Roy. Astron. Soc. PD APR 1 PY 1996 VL 279 IS 3 BP 712 EP 726 PG 15 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA UF154 UT WOS:A1996UF15400010 ER PT J AU Iwasawa, K Fabian, AC Mushotzky, RF Brandt, WN Awaki, H Kunieda, H AF Iwasawa, K Fabian, AC Mushotzky, RF Brandt, WN Awaki, H Kunieda, H TI The broad iron K emission line in the Seyfert 2 galaxy IRAS 18325-5926 SO MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY LA English DT Article DE accretion, accretion discs; galaxies, active; galaxies, individual, IRAS 18325; 5926; galaxies, Seyfert; X-rays, galaxies ID ACTIVE GALACTIC NUCLEI; X-RAY-SPECTRA; COLD MATTER; UNIFIED MODEL; DISK; REFLECTION AB We report the detection of a very broad iron K alpha emission line in the ASCA X-ray spectrum of the Seyfert 2 galaxy IRAS 18325 - 5926. The line is strong, with an equivalent width EW = 500-800 eV, and its profile is peaked at 6.9 keV and skewed down to 4 keV. The energy of the blue peak of the line is significantly higher than the rest-energy of 6.4 keV seen in many active galaxies, which is expected from an iron K alpha line arising in cold matter. If the breadth and shift of the line energy are caused by Doppler and relativistic effects in a cold accretion disc about a black hole, then the disc has an intermediate inclination, i = 40 degrees-50 degrees. A plausible interpretation for the large equivalent width is a supersolar abundance of iron; this also accounts for the lack of a significant reflection hump. The line profile can also be explained by emission from highly ionized matter very close to the central object. However, the lack of a deep iron K absorption edge in the Ginga spectrum is inconsistent with this interpretation. We verify that fast X-ray variability on a time-scale of 10(4) s is common in this object, using ASCA and ROSAT observations which are partially simultaneous. A study of spectral variability using combined ASCA and ROSAT PSPC data reveals that the X-ray flux change occurred mainly above 1 keV, and suggests a stable, or at least less-variable, component below 1 keV. It should lie outside the nuclear obscuration region. C1 NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. NAGOYA UNIV,DEPT ASTROPHYS,CHIKUSA KU,NAGOYA,AICHI 46401,JAPAN. KYOTO UNIV,DEPT PHYS,SAKYO KU,KYOTO 60601,JAPAN. RP Iwasawa, K (reprint author), UNIV CAMBRIDGE,INST ASTRON,MADINGLEY RD,CAMBRIDGE CB3 0HA,ENGLAND. RI Brandt, William/N-2844-2015 OI Brandt, William/0000-0002-0167-2453 NR 56 TC 45 Z9 45 U1 0 U2 0 PU BLACKWELL SCIENCE LTD PI OXFORD PA OSNEY MEAD, OXFORD, OXON, ENGLAND OX2 0EL SN 0035-8711 J9 MON NOT R ASTRON SOC JI Mon. Not. Roy. Astron. Soc. PD APR 1 PY 1996 VL 279 IS 3 BP 837 EP 846 PG 10 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA UF154 UT WOS:A1996UF15400020 ER PT J AU Yao, XS Maleki, L AF Yao, XS Maleki, L TI Converting light into spectrally pure microwave oscillation SO OPTICS LETTERS LA English DT Article ID DEVICES AB We present theoretical and experimental results for a novel oscillator that converts continuous light energy into stable and spectrally pure microwave signals. This optoelectronic oscillator can generate ultrastable spectrally pure microwave reference frequencies as high as 75 GHz with a phase noise lower than -140 dBc/Hz at 10 kHz, independent of oscillation frequency. (C) 1996 Optical Society of America RP Yao, XS (reprint author), CALTECH,JET PROP LAB,4800 OAK GROVE DR,PASADENA,CA 91109, USA. NR 13 TC 84 Z9 90 U1 2 U2 13 PU OPTICAL SOC AMER PI WASHINGTON PA 2010 MASSACHUSETTS AVE NW, WASHINGTON, DC 20036 SN 0146-9592 J9 OPT LETT JI Opt. Lett. PD APR 1 PY 1996 VL 21 IS 7 BP 483 EP 485 DI 10.1364/OL.21.000483 PG 3 WC Optics SC Optics GA UC298 UT WOS:A1996UC29800013 PM 19865446 ER PT J AU Welch, RB Post, RB AF Welch, RB Post, RB TI Accuracy and adaptation of reaching and pointing in pitched visual environments SO PERCEPTION & PSYCHOPHYSICS LA English DT Article ID PERCEIVED EYE LEVEL; SYSTEMS; FIELD; ROD AB Visually perceived eye level (VPEL) and the ability of subjects to reach with an unseen limb to targets placed at VPEL were measured in a statically pitched visual surround (pitchroom). VPEL was shifted upward and downward by upward and downward room pitch, respectively. Accuracy in reaching to VPEL represented a compromise between VPEL and actual eye level. This indicates that VPEL shifts reflect in part a change in perceived location of objects. When subjects were provided with terminal visual feedback about their reaching, accuracy improved rapidly. Subsequent reaching, with the room vertical, revealed a negative aftereffect (i.e., reaching errors that were opposite those made initially in the pitched room). In a second study, pointing accuracy was assessed for targets located both at VPEL and at other positions. Errors were similar for targets whether located at VPEL or elsewhere. Additionally, pointing responses were restricted to a narrower range than that of the actual target locations. The small size of reaching and pointing errors in both studies suggests that factors other than a change in perceived location are also involved in VPEL shifts. C1 NASA,AMES RES CTR,MT VIEW,CA. UNIV CALIF DAVIS,DAVIS,CA 95616. NR 20 TC 16 Z9 16 U1 0 U2 1 PU PSYCHONOMIC SOC INC PI AUSTIN PA 1710 FORTVIEW RD, AUSTIN, TX 78704 SN 0031-5117 J9 PERCEPT PSYCHOPHYS JI Percept. Psychophys. PD APR PY 1996 VL 58 IS 3 BP 383 EP 389 DI 10.3758/BF03206814 PG 7 WC Psychology; Psychology, Experimental SC Psychology GA UF308 UT WOS:A1996UF30800006 PM 8935899 ER PT J AU Ajello, JM Ahmed, SM Liu, XM AF Ajello, JM Ahmed, SM Liu, XM TI Line profile of H Lyman-beta emission from dissociative excitation of H-2 SO PHYSICAL REVIEW A LA English DT Article ID ELECTRON-IMPACT DISSOCIATION; MOLECULAR-HYDROGEN; CROSS-SECTIONS; BALMER-ALPHA; BAND SYSTEM; DEUTERIUM; TABLE; STAR AB A high-resolution ultraviolet spectrometer was employed for a measurement of the H Lyman-beta (H L(beta)) emission Doppler line profile at 1025.7 Angstrom from dissociative excitation of H-2 by electron impact. Analysis of the deconvolved line profile reveals the existence of a narrow central peak, less than 30 m Angstrom full width at half maximum (FWHM), and a broad pedestal base about 260 m Angstrom FWHM. Analysis of the red wing of the line profile is complicated by a group of Werner and Lyman rotational lines 160-220 m Angstrom from the line center. Analysis of the blue wing of the line profile gives the kinetic-energy distribution. There are two main kinetic-energy components to the H(3p) distribution: (1) a slow distribution with a peak value near 0 eV from singly excited states, and (2) a fast distribution with a peak contribution near 7 eV from doubly excited states. Using two different techniques, the absolute cross section of H L(beta) is found to be 3.2+/-0.8X10(-19) cm(2) at 100-eV electron impact energy. The experimental cross-section and line-profile results can be compared to previous studies of Ha (6563.7 Angstrom) for principal quantum number n=3 and L(alpha) (1215.7 Angstrom) for n=2. RP Ajello, JM (reprint author), CALTECH,JET PROP LAB,4800 OAK GROVE DR,PASADENA,CA 91109, USA. NR 26 TC 10 Z9 10 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 APR PY 1996 VL 53 IS 4 BP 2303 EP 2308 DI 10.1103/PhysRevA.53.2303 PG 6 WC Optics; Physics, Atomic, Molecular & Chemical SC Optics; Physics GA UE921 UT WOS:A1996UE92100056 ER PT J AU Balasubramaniam, R Lacy, CE Woniak, G Subramanian, RS AF Balasubramaniam, R Lacy, CE Woniak, G Subramanian, RS TI Thermocapillary migration of bubbles and drops at moderate values of the Marangoni number in reduced gravity SO PHYSICS OF FLUIDS LA English DT Article ID TEMPERATURE-GRADIENT; GAS BUBBLE; MOTION; MICROGRAVITY AB Experiments were performed on the motion of isolated drops and bubbles in a Dow-Coming silicone oil under the action of an applied temperature gradient in a reduced gravity environment aboard the NASA Space Shuttle in orbit. Images of the interior of the test cell during these experiments were recorded on cine film and later analyzed to obtain data on the migration velocity as a function of size and the applied temperature gradient. The data are presented in scaled form. Predictions available in the case of gas bubbles, and it is found that the scaled velocity decreases with increasing Marangoni number qualitatively as expected even though there are quantitative discrepancies. The scaled velocity also appears to approach a theoretical asymptote predicted in the limit of large values of the Marangroni number for Stokes motion. Finally; sample results from a preliminary experiment on a pair of drops are presented. They display the remarkable feature that a small drop which leads a large drop in a temperature gradient can significantly retard the motion of the large trailing drop while itself moving as though it is virtually unaffected by the presence of the large drop. (C) 1996 American Institute of Physics. C1 CLARKSON UNIV,DEPT CHEM ENGN,POTSDAM,NY 13699. NASA,LEWIS RES CTR,MICROGRAV FLUIDS BRANCH,CLEVELAND,OH 44135. CLARKSON UNIV,DEPT CHEM ENGN,POTSDAM,NY 13699. BERGAKAD FREIBERG,INST FLUIDMECH & FLUIDENERGIEMASCHINEN,O-9200 FREIBERG,GERMANY. NR 20 TC 40 Z9 45 U1 0 U2 10 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 APR PY 1996 VL 8 IS 4 BP 872 EP 880 DI 10.1063/1.868868 PG 9 WC Mechanics; Physics, Fluids & Plasmas SC Mechanics; Physics GA UC218 UT WOS:A1996UC21800004 ER PT J AU Siregar, E Goldstein, ML AF Siregar, E Goldstein, ML TI A Vlasov moment description of cyclotron wave-particle interactions SO PHYSICS OF PLASMAS LA English DT Article ID ION; INSTABILITY; ANISOTROPY; PLASMAS AB A quasifluid formalism designed to capture some effects of cyclotron interactions is presented. Starting from the contractions of exact moments of the Vlasov equation, a closure for cyclotron interactions is achieved by using kinetic information directly. This nonperturbative approach does not require a priori assumptions about zeroth-order particle velocity distributions. The nonlinear coupling between field-aligned particle thermal velocities and transverse cyclotron wave and thermal motions are described by off-diagonal elements of the pressure tenser. These elements are related to the growth and damping of cyclotron wave energy. A functional form for an effective wave-particle momentum transport coefficient is derived from the requirement of consistency between the energy and momentum moment equations, but its specific magnitude and sign, determined by threshold temperature anisotropy levels, must be input from kinetic theory. This effective transport coefficient has a nondefinite sign, reminiscent of the gyroviscous coefficients of classical transport, and is consistent with the time reversibility of the Vlasov equation. A coupled set of cyclotron equations of state for the evolution of the parallel and perpendicular pressures are derived. This formalism provides a connection between known kinetic solutions of cyclotron interactions and fluid plasma equations. (C) 1996 American Institute of Physics. RP Siregar, E (reprint author), NASA,GODDARD SPACE FLIGHT CTR,EXTRATERR PHYS LAB,GREENBELT,MD 20771, USA. RI Goldstein, Melvyn/B-1724-2008 NR 29 TC 7 Z9 7 U1 0 U2 0 PU AMER INST PHYSICS PI WOODBURY PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 SN 1070-664X J9 PHYS PLASMAS JI Phys. Plasmas PD APR PY 1996 VL 3 IS 4 BP 1437 EP 1446 DI 10.1063/1.871733 PG 10 WC Physics, Fluids & Plasmas SC Physics GA UD445 UT WOS:A1996UD44500027 ER PT J AU daRocha, HR Nobre, CA Bonatti, JP Wright, IR Sellers, PJ AF daRocha, HR Nobre, CA Bonatti, JP Wright, IR Sellers, PJ TI A vegetation-atmosphere interaction study for Amazonia deforestation using field data and a 'single column' model SO QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY LA English DT Article DE Amazon rain-forests; convection; deforestation; evapotranspiration; land-surface processes; vegetation ID SIMPLE BIOSPHERE MODEL; TROPICAL DEFORESTATION; REGIONAL CLIMATE; RAIN-FOREST; PARAMETERIZATION; CIRCULATION; SURFACE; RADIATION; IMPACTS; SCHEME AB The recent high deforestation rates in Amazonia have raised the question of how climate, mainly the precipitation patterns, might be affected as pasture land replaces the primary forest. This work initially shows how the dry season soil moisture and water stress in typical Amazonian pasture modifies the energy partitioning at the surface. Low-level moisture convergence is a primary mechanism to trigger convective cloud formation and precipitation. The relationship between moisture convergence and local surface evaporation in generating precipitation in Amazonia is studied utilizing a one-dimensional 'single column' model (SiB-1D). SiB-1D couples a surface-vegetation model (SiB) to a physical parametrization of deep convection (Kuo scheme), radiation, turbulent diffusion and large-scale precipitation. Model simulations for short periods (2 days) show its ability to calculate the Amazonian surface energy-balance components and boundary-layer dynamics when compared with field observations from the Rondonia Boundary-Layer Experiment and the Anglo-Brazilian Amazonian Climate Observation Study. The model was further used to test the sensitivity of the deep convection scheme to a range of typical low-level moisture convergence situations in a second experiment, and a third test investigated the local convective precipitation generated over forest and grass vegetation as a function of available soil moisture. Results showed that the rainfall over forest vegetation appeared to be almost insensitive to soil water stress whereas reduced precipitation was generated over pasture. When available soil water fell below a threshold of 60% the calculated precipitation over the pasture sites rapidly declined. Although these results are confined by the short integration period and the initial atmospheric profiles, they help to strengthen the notion that deforestation reduces evaporation and convective precipitation, especially during the dry season: a result already indicated by some previous general-circulation model experiments. C1 INST HYDROL, WALLINGFORD OX10 8BB, OXON, ENGLAND. NASA, GODDARD SPACE FLIGHT CTR, GREENBELT, MD 20771 USA. NR 42 TC 18 Z9 18 U1 3 U2 8 PU WILEY-BLACKWELL PI MALDEN PA COMMERCE PLACE, 350 MAIN ST, MALDEN 02148, MA USA SN 0035-9009 J9 Q J ROY METEOR SOC JI Q. J. R. Meteorol. Soc. PD APR PY 1996 VL 122 IS 531 BP 567 EP 594 PN A PG 28 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA UK530 UT WOS:A1996UK53000001 ER PT J AU Considine, G Curry, JA AF Considine, G Curry, JA TI A statistical model of drop-size spectra for stratocumulus clouds SO QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY LA English DT Article DE cloud-droplet spectra; microphysics; stratocumulus ID ARCTIC STRATUS CLOUDS; SHORTWAVE RADIATIVE PROPERTIES; CUMULUS CLOUDS; WATER CLOUDS; MICROPHYSICS; SUPERSATURATION; VARIABILITY; TURBULENCE; AEROSOLS; DYNAMICS AB The purpose of this work is to present a simplified model of cloud-droplet spectra that can be used as a tool for interpreting cloud microphysical observations in boundary-layer clouds, and as a way to begin quantifying the couplings between cloud microphysics, dynamics and radiative properties for eventual use in cloud parametrizations. The model is steady-state, ignores nucleation effects, and is formulated to produce horizontally averaged statistics. The major difference between this model and previous work lies in the model assumption that droplet spectra at a given level within a cloud are horizontal averages over a large number of air parcels, each of which can have a different lifting condensation level (LCL). Vertical motions are driven by buoyancy, so that liquid water and vertical velocity are simple functions of height above the LCL. This relationship, treated statistically over a large number of parcels, relates turbulent kinetic energy to horizontally averaged statistics of the droplet spectra. The broadening of droplet spectra is thus directly related to the turbulent kinetic energy within a cloud. In validating the model, results are compared with observations. It is shown that the basic droplet spectra predicted by the model are quite realistic for stratus and stratocumulus. The modelled droplet spectra broaden from cloud base to cloud top as is frequently observed, and the relationship between drop spectrum width and mean radius agrees quite well with observations. C1 UNIV COLORADO,BOULDER,CO 80309. RP Considine, G (reprint author), NASA,LANGLEY RES CTR,MAIL STOP 401B,HAMPTON,VA 23681, USA. NR 35 TC 21 Z9 21 U1 0 U2 3 PU ROYAL METEOROLOGICAL SOC PI READING PA 104 OXFORD ROAD, READING, BERKS, ENGLAND RG1 7LJ SN 0035-9009 J9 Q J ROY METEOR SOC JI Q. J. R. Meteorol. Soc. PD APR PY 1996 VL 122 IS 531 BP 611 EP 634 PN A PG 24 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA UK530 UT WOS:A1996UK53000003 ER PT J AU Zhou, JY Sud, YC Lau, KM AF Zhou, JY Sud, YC Lau, KM TI Impact of orographically induced gravity-wave drag in the GLA GCM SO QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY LA English DT Article DE climate modelling; extended-range forecasting; gravity-wave drag; systematic errors; upper-boundary conditions ID WEATHER PREDICTION MODELS; GENERAL-CIRCULATION; MOMENTUM FLUX; MOUNTAIN WAVE; PARAMETERIZATION; PARAMETRIZATION; DISSIPATION; ATMOSPHERE; TURBULENCE; SCHEME AB The influence of gravity-wave drag (GWD) parametrization has been investigated in the Goddard Laboratory for Atmospheres general-circulation model with the resolution of 4 degrees latitude x 5 degrees longitude in the horizontal and 17 sigma layers in the vertical. The simulations showed several overall beneficial effects in the extended-range forecast as well as the seasonal simulation for both winter and summer conditions. The key results include the following: (1) The mid-latitude westerlies, which were shifted poleward (equatorward) in northern (southern) winter, have been corrected. Consequently, the systematic bias of low (high) sea level pressure over the north (south) polar region has been largely eliminated. (2) There is a significant improvement in the simulation of the winter hemisphere stationary waves; this can be attributed to the GWD induced Rossby-wave propagation. Over the northern Pacific region, as the storm track is simulated better, precipitation distribution improves remarkably. (3) In cooperation with the improved regional zonal-mean flow, an adjustment of the mean meridional circulation is found over the Asian summer-monsoon region, leading to an improvement in the precipitation distribution. (4) Spurious absorption of gravity waves at the model top (10 mb) has been removed by applying an open upper-boundary condition. The vertical propagation of the tropospherical gravity wave into the upper stratosphere and mesosphere over mid-latitudes of the northern hemisphere in winter is consistent with observational studies as well as the middle-atmospheric dynamics. RP Zhou, JY (reprint author), NASA, GODDARD SPACE FLIGHT CTR, APPL RES CORP, 8201 CORP DR, LANDOVER, MD 20785 USA. RI Lau, William /E-1510-2012 OI Lau, William /0000-0002-3587-3691 NR 34 TC 28 Z9 28 U1 0 U2 2 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 APR PY 1996 VL 122 IS 532 BP 903 EP 927 PN B PG 25 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA UT570 UT WOS:A1996UT57000005 ER PT J AU Lau, KM Yang, S AF Lau, KM Yang, S TI The Asian monsoon and predictability of the tropical ocean-atmosphere system SO QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY LA English DT Article DE Asian monsoon; interannual variations; predictability; seasonal prediction; tropical ocean-atmosphere system ID SOUTHERN OSCILLATION; INDIAN MONSOON; ANNUAL CYCLE; PACIFIC; RAINFALL; VARIABILITY; REGIONS; ENSO AB The influence of the Asian monsoon on the predictability of the tropical ocean-atmosphere is studied using long-term records of monsoon rainfall, sea-level pressure, sea surface temperature (SST) and surface wind data. Results indicate that the Asian monsoon plays an important role in mediating interannual variations of SST, surface pressure and surface wind in a quasi-biennial oscillation of the tropical ocean-atmosphere as found in previous studies. During the boreal spring, monsoon-related atmospheric and oceanic anomalies change most rapidly, while the east-west gradients in sea-level pressure and SST across the equatorial Pacific are at a minimum. The so-called 'spring predictability barrier' (SPB) is associated with the phase-locking of interannual anomalies to the annual cycle variation of the tropical ocean-atmosphere. Results suggest that the Asian monsoon defines two climatic states in the tropical ocean-atmosphere system, corresponding to the warm and cold phases of the tropical biennial oscillation. A weak Asian monsoon is associated with enhanced memory for predictions starting from late boreal spring through to summer and with a well-defined SPB for those starting from boreal fall to winter. On the other hand, a strong monsoon is associated with a recovery of memory at long lags (> 4-6 months) from the boreal fall through to the following spring, indicating a partial breakdown or 'tunnelling' effect for the SPB. The above results may be exploited to improve seasonal-to-interannual predictions of the monsoon-ocean-atmosphere system. C1 GEN SCI CORP,LAUREL,MD. RP Lau, KM (reprint author), NASA,GODDARD SPACE FLIGHT CTR,ATMOSPHERES LAB,CODE 913,GREENBELT,MD 20771, USA. RI Yang, Song/B-4952-2009; Lau, William /E-1510-2012 OI Lau, William /0000-0002-3587-3691 NR 24 TC 77 Z9 81 U1 1 U2 5 PU ROYAL METEOROLOGICAL SOC PI READING PA 104 OXFORD ROAD, READING, BERKS, ENGLAND RG1 7LJ SN 0035-9009 J9 Q J ROY METEOR SOC JI Q. J. R. Meteorol. Soc. PD APR PY 1996 VL 122 IS 532 BP 945 EP 957 PN B PG 13 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA UT570 UT WOS:A1996UT57000007 ER PT J AU Sud, YC Lau, WKM AF Sud, YC Lau, WKM TI Variability of summer rainfall over tropical north Africa (1906-92): Observations and modelling - Comment SO QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY LA English DT Article DE climate models; model intercomparison; north Africa; tropical rainfall; Sahel ID DROUGHT; ALBEDO; SAHEL RP Sud, YC (reprint author), NASA,GODDARD SPACE FLIGHT CTR,ATMOSPHERES LAB,GREENBELT,MD 20771, USA. RI Lau, William /E-1510-2012 OI Lau, William /0000-0002-3587-3691 NR 11 TC 16 Z9 16 U1 1 U2 4 PU ROYAL METEOROLOGICAL SOC PI READING PA 104 OXFORD ROAD, READING, BERKS, ENGLAND RG1 7LJ SN 0035-9009 J9 Q J ROY METEOR SOC JI Q. J. R. Meteorol. Soc. PD APR PY 1996 VL 122 IS 532 BP 1001 EP 1006 PN B PG 6 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA UT570 UT WOS:A1996UT57000011 ER PT J AU Edberg, JR AF Edberg, JR TI JPL reenters undersea technology SO SEA TECHNOLOGY LA English DT Article RP Edberg, JR (reprint author), CALTECH,JET PROP LAB,UNDERSEA TECHNOL PROGRAM,4800 OAK GROVE DR,PASADENA,CA 91109, USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU COMPASS PUBL INC PI ARLINGTON PA SUITE 1000 1117 N 19 ST, ARLINGTON, VA 22209 SN 0093-3651 J9 SEA TECHNOL JI Sea Technol. PD APR PY 1996 VL 37 IS 4 BP 23 EP & PG 6 WC Engineering, Ocean SC Engineering GA UG070 UT WOS:A1996UG07000005 ER PT J AU Ho, HS Sondeen, JL Dubick, MA Wade, CE Gunther, RA AF Ho, HS Sondeen, JL Dubick, MA Wade, CE Gunther, RA TI The renal effects of 7.5% NaCl-6% dextran-70 versus lactated Ringer's resuscitation of hemorrhage in dehydrated sheep SO SHOCK LA English DT Article ID HYPERTONIC SALINE; 6-PERCENT DEXTRAN-70; MULTICENTER TRIAL; CONSCIOUS SWINE; SHOCK; NACL; HYPOTENSION; INFUSION; FAILURE; PLASMA AB A small volume of 7.5% NaCl/6% Dextran-70 (HSD) can rapidly expand the plasma volume, but concerns exist regarding its adverse effects on renal function in the dehydrated state, Sheep were thirsted for 4 days (13% plasma volume contraction), and subjected to a fixed-pressure shock model (mean arterial pressure of 50 mmHg for 2 h), followed by resuscitation with either HSD (4 mUkg) or lactated Ringer's solution (LR; 37 mL/kg). Mean arterial pressure was restored to 90%, cardiac output to 125% and 120%, and plasma volume to 78% and 72% of baseline in LR and HSD groups, respectively. Glomerular filtration rate improved to 100% of baseline following HSD compared with 82% following LR, No significant urinary 70,000 molecular weight dextran was observed, suggesting an intact renal glomerular membrane. These data suggest that small volume HSD resuscitation is effective, even with pre-existing dehydration. In addition, renal function is not compromised by HSD resuscitation of hemorrhaged, dehydrated animals. C1 USA,INST SURG RES,MED TRAUMA BRANCH,FT SAM HOUSTON,TX 78234. NASA,AMES RES CTR,DIV LIFE SCI,MOFFETT FIELD,CA 94035. RP Ho, HS (reprint author), UNIV CALIF DAVIS,MED CTR,SCH MED,DEPT SURG,SACRAMENTO,CA 95817, USA. NR 35 TC 9 Z9 9 U1 0 U2 0 PU BIOMEDICAL PRESS PI AUGUSTA PA 1021 15TH ST, BIOTECH PARK STE 9, AUGUSTA, GA 30901 SN 1073-2322 J9 SHOCK JI Shock PD APR PY 1996 VL 5 IS 4 BP 289 EP 297 DI 10.1097/00024382-199604000-00010 PG 9 WC Critical Care Medicine; Hematology; Surgery; Peripheral Vascular Disease SC General & Internal Medicine; Hematology; Surgery; Cardiovascular System & Cardiology GA UE254 UT WOS:A1996UE25400010 PM 8721390 ER PT J AU Lin, JJ Burger, DR AF Lin, JJ Burger, DR TI TPV cell IV curve testing with varying black body emission temperatures, intensities, and cell temperatures SO SOLAR ENERGY MATERIALS AND SOLAR CELLS LA English DT Article AB A TPV GaSb cell was tested as part of the first effort to establish a standard method of characterizing such cells. Cell current/voltage (IV) curves were measured at different cell temperatures using black body radiation at various emission temperatures and intensities. The results of the effects on performance are briefly analyzed and include temperature coefficients, voltage/intensity coefficient, and response to spectral shift. C1 CALTECH,JET PROP LAB,PASADENA,CA 91109. NR 3 TC 1 Z9 1 U1 2 U2 2 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0927-0248 J9 SOL ENERG MAT SOL C JI Sol. Energy Mater. Sol. Cells PD APR PY 1996 VL 40 IS 2 BP 177 EP 181 DI 10.1016/0927-0248(95)00082-8 PG 5 WC Energy & Fuels; Materials Science, Multidisciplinary; Physics, Applied SC Energy & Fuels; Materials Science; Physics GA UM938 UT WOS:A1996UM93800007 ER PT J AU Spickler, PT Benner, DC Russell, JM AF Spickler, PT Benner, DC Russell, JM TI Solar center-to-limb infrared intensity from the halogen occultation experiment SO SOLAR PHYSICS LA English DT Article ID TEMPERATURE AB Data from the Halogen Occultation Experiment (HALOE) provide the first opportunity to examine solar center-to-limb relative intensity measured exoatmospherically at wavelengths from 2.4 to 10 mu m. The data were obtained from limb-to-limb scans across the solar equator on days of very low activity in May 1994. Coefficients for a function describing limb darkening are obtained at eight infrared wavelengths using a nonlinear least-squares fitting technique. Relative intensities produced by the limb-darkening functions are precise to 0.1% (2 sigma). From the limb-darkening coefficients, it is possible to calculate temperature information about the photosphere. At each of the eight HALOE wavelengths, the brightness temperature from the flux, T-b(disk)(lambda), and the temperature as a function of monochromatic optical depth, T(tau(lambda)), are determined and normalized using Kondratyev et al. (1965) and calibrated Pierce (1954) central intensity measurements. The two temperature quantities are compared with the predictions of Vernazza, Avrett, and Loeser's (1976) model M, and in general there is good agreement. The largest differences occur between 2.4 and 3 mu m and suggest that the central intensities used in this spectral region are low. C1 NASA,LANGLEY RES CTR,DIV ATMOSPHER SCI,HAMPTON,VA 23681. RP Spickler, PT (reprint author), COLL WILLIAM & MARY,DEPT PHYS,WILLIAMSBURG,VA 23187, USA. NR 33 TC 5 Z9 5 U1 0 U2 0 PU KLUWER ACADEMIC PUBL PI DORDRECHT PA SPUIBOULEVARD 50, PO BOX 17, 3300 AA DORDRECHT, NETHERLANDS SN 0038-0938 J9 SOL PHYS JI Sol. Phys. PD APR PY 1996 VL 165 IS 1 BP 23 EP 39 DI 10.1007/BF00149088 PG 17 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA UB699 UT WOS:A1996UB69900003 ER PT J AU Hoyt, DV Schatten, KH AF Hoyt, DV Schatten, KH TI How well was the sun observed during the maunder minimum? SO SOLAR PHYSICS LA English DT Article AB In this paper we examine how well the Sun and sunspots were observed during the Maunder Minimum from 1645 to 1715. Recent research has given us the dates of observations by Hevelius, Picard, La Hire, Flamsteed, and about 70 other observers. These specific observations allow a 'lower estimate' of the fraction of the time the Sun was observed to be deduced. It is found that 52.7% of the days have recorded observations. There are additional 12 observers who provide general statements that no sunspots were observed during specific years or intervals despite diligent efforts. Taking these statements to mean, unrealistically, that every day during these intervals was observed, gives an 'upper estimate' of 98% of the days. If the general statements are relaxed by assuming that 100 +/- 50 days per year were actually observed by these diligent observers, than our 'best estimate' is that 68% +/- 7% of the days during the Maunder Minimum were observed. In short, this supports the view that the Maunder Minimum existed and was not an artifact of few observations. Some sunspots are probably still missed in modern compilations, but the existence of a prolonged sunspot minimum would not be threatened by their discovery in future research. Additional support for intense scrutiny of the Sun comes from a report of a white-light flare in 1705 and from the numerous reports of new sunspots entering the disk of the Sun. C1 NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. NR 19 TC 72 Z9 73 U1 0 U2 1 PU KLUWER ACADEMIC PUBL PI DORDRECHT PA SPUIBOULEVARD 50, PO BOX 17, 3300 AA DORDRECHT, NETHERLANDS SN 0038-0938 J9 SOL PHYS JI Sol. Phys. PD APR PY 1996 VL 165 IS 1 BP 181 EP 192 DI 10.1007/BF00149097 PG 12 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA UB699 UT WOS:A1996UB69900012 ER PT J AU Bin, M Gaidis, MC Zmuidzinas, J Phillips, TG Leduc, HG AF Bin, M Gaidis, MC Zmuidzinas, J Phillips, TG Leduc, HG TI THz SIS mixers with normal-metal Al tuning circuits SO SUPERCONDUCTOR SCIENCE & TECHNOLOGY LA English DT Article; Proceedings Paper CT 5th International Superconductive Electronics Conference (ISEC 95) CY SEP 18-21, 1995 CL NAGOYA, JAPAN AB Nb-based superconductor-insulator-superconductor (SIS) mixers with Nb tuning circuits have demonstrated good results up to the Nb gap frequency. Above the gap frequency the performance is expected to degrade quickly because RF loss in Nb becomes significant. In this paper we present the results of an effort to extend Nb-based SIS mixers to THz frequencies by employing lower-loss normal-metal Al wiring and tuning structures. The SIS mixer has two Nb/Al-oxide/Nb junctions connected by an Al microstrip inductor. The direct detection response of the device was measured by a Fourier transform spectrometer. A double-side-band receiver noise temperature of 840 K was obtained at 1042 GHz when the device was operated at 2.5 K. C1 JET PROPULS LAB,PASADENA,CA 91101. RP Bin, M (reprint author), CALTECH,GW DOWNS LAB PHYS,PASADENA,CA 91125, USA. RI Gaidis, Michael/D-3327-2013 NR 9 TC 0 Z9 0 U1 0 U2 0 PU IOP PUBLISHING LTD PI BRISTOL PA TECHNO HOUSE, REDCLIFFE WAY, BRISTOL, ENGLAND BS1 6NX SN 0953-2048 J9 SUPERCOND SCI TECH JI Supercond. Sci. Technol. PD APR PY 1996 VL 9 IS 4A BP A136 EP A139 DI 10.1088/0953-2048/9/4A/035 PG 4 WC Physics, Applied; Physics, Condensed Matter SC Physics GA UF346 UT WOS:A1996UF34600035 ER PT J AU Gaidis, MC Bin, M Miller, D Zmuidzinas, J LeDuc, HG Stern, JA AF Gaidis, MC Bin, M Miller, D Zmuidzinas, J LeDuc, HG Stern, JA TI Characterization of submillimetre quasi-optical twin-slot double-junction SIS mixers SO SUPERCONDUCTOR SCIENCE & TECHNOLOGY LA English DT Article; Proceedings Paper CT 5th International Superconductive Electronics Conference (ISEC 95) CY SEP 18-21, 1995 CL NAGOYA, JAPAN AB We report on the continuing development of submillimetre quasi-optical slot antenna SIS mixers, which use two-junction tuning circuits. Direct and heterodyne Fourier transform spectrometer measurements have been performed to compare device performance with predictions. Demonstrated double-sideband receiver noise temperatures of better than 540 K at 808 GHz make these SIS mixers substantially better than GaAs Schottky receivers for the astronomically important CI and CO transitions near 810 GHz. C1 CALTECH,JET PROP LAB,PASADENA,CA 91109. RP Gaidis, MC (reprint author), CALTECH,GEORGE W DOWNS LAB PHYS,PASADENA,CA 91125, USA. RI Gaidis, Michael/D-3327-2013 NR 4 TC 0 Z9 0 U1 0 U2 0 PU IOP PUBLISHING LTD PI BRISTOL PA TECHNO HOUSE, REDCLIFFE WAY, BRISTOL, ENGLAND BS1 6NX SN 0953-2048 J9 SUPERCOND SCI TECH JI Supercond. Sci. Technol. PD APR PY 1996 VL 9 IS 4A BP A133 EP A135 DI 10.1088/0953-2048/9/4A/034 PG 3 WC Physics, Applied; Physics, Condensed Matter SC Physics GA UF346 UT WOS:A1996UF34600034 ER PT J AU Chamis, CC Murthy, PLN Minnetyan, L AF Chamis, CC Murthy, PLN Minnetyan, L TI Progressive fracture of polymer matrix composite structures SO THEORETICAL AND APPLIED FRACTURE MECHANICS LA English DT Article AB An approach independent of stress intensity factors and fracture toughness parameters has been developed and is described for the computational simulation of progressive fracture of polymer matrix composite structures. The damage stages are quantified based on physics via composite mechanics while the degradation of the structural behavior is quantified via the finite element method. The approach accounts for all types of composite behavior, structures, load conditions, and fracture processes starting from damage initiation, to unstable propagation and to global structural collapse. Results of structural fracture in composite beams, panels, plates, and shells are presented to demonstrate the effectiveness and versatility of this new approach. Parameters and guidelines are identified which can be used as criteria for structural fracture, inspection intervals and retirement for cause. Generalization to structures made of monolithic metallic materials are outlined and lessons learned in undertaking the development of new approaches, in general, are summarized. C1 CLARKSON UNIV,POTSDAM,NY 13676. RP Chamis, CC (reprint author), NASA,LEWIS RES CTR,CLEVELAND,OH 44135, USA. NR 10 TC 14 Z9 14 U1 0 U2 1 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0167-8442 J9 THEOR APPL FRACT MEC JI Theor. Appl. Fract. Mech. PD APR-MAY PY 1996 VL 25 IS 1 BP 1 EP 15 DI 10.1016/0167-8442(96)00002-X PG 15 WC Engineering, Mechanical; Mechanics SC Engineering; Mechanics GA UW032 UT WOS:A1996UW03200001 ER PT J AU Hergenrother, PM AF Hergenrother, PM TI Polymeric materials for high-speed civil transports SO TRENDS IN POLYMER SCIENCE LA English DT Editorial Material C1 NASA,LANGLEY RES CTR,COMPOSITES & POLYMERS BRANCH,HAMPTON,VA 23681. NR 0 TC 11 Z9 12 U1 1 U2 1 PU ELSEVIER SCI LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, OXON, ENGLAND OX5 1GB SN 0966-4793 J9 TRENDS POLYM SCI JI Trends Polym. Sci. PD APR PY 1996 VL 4 IS 4 BP 104 EP 105 PG 2 WC Polymer Science SC Polymer Science GA UF732 UT WOS:A1996UF73200001 ER PT J AU Zaretsky, EV Poplawski, JV Peters, SM AF Zaretsky, EV Poplawski, JV Peters, SM TI Comparison of life theories for rolling-element bearings SO TRIBOLOGY TRANSACTIONS LA English DT Article; Proceedings Paper CT 50th Annual Meeting of STLE CY MAY 14-19, 1995 CL CHICAGO, IL SP STLE DE rolling element bearings; life prediction methods; rolling-contact fatigue; stress analysis ID FATIGUE AB Nearly five decades have passed since G. Lundberg and A. Palmgren published their life theory in 1947 and 1952 and it was adopted as an ANSI/ABMA and ISO standard in 1350 and 1953. Subsequently, many variations and deviations from their life theory have been proposed, the most recent being that of E. Ioannides and T. A. Harris in, 1985. This paper presents a critical analysis comparing the results of different life theories and discussing their implications in the design and analysis of rolling-element bearings. Variations in the stress-life relation and in the critical stress related to bearing life are discussed using stress fields obtained from three-dimensional, finite-element analysis of a ball in a nonconforming race under varying load. The results showed that for a ninth power stress-life exponent the Lundberg-Palmgrem theory best predicts life as exhibited by most air-melted bearing steels. For a 12th power relation reflected by modern bearing steels, a Zaretsky-modified Weibull equation is superior. The assumption of a fatigue-limiting stress distorts the stress-life exponent and overpredicts life. C1 JV POPLAWSKI & ASSOCIATES,BETHLEHEM,PA. RP Zaretsky, EV (reprint author), NASA,LEWIS RES CTR,CLEVELAND,OH 44135, USA. NR 32 TC 32 Z9 36 U1 0 U2 8 PU SOC TRIBOLOGISTS & LUBRICATION ENGINEERS PI PARK RIDGE PA 838 BUSSE HIGHWAY, PARK RIDGE, IL 60068 SN 0569-8197 J9 TRIBOL T JI Tribol. Trans. PD APR PY 1996 VL 39 IS 2 BP 237 EP 247 DI 10.1080/10402009608983525 PG 11 WC Engineering, Mechanical SC Engineering GA UB372 UT WOS:A1996UB37200001 ER PT J AU Zaretsky, EV Poplawski, JV Peters, SM AF Zaretsky, EV Poplawski, JV Peters, SM TI Comparison of life theories for rolling-element bearings SO TRIBOLOGY TRANSACTIONS LA English DT Article ID MAINSHAFT BALL-BEARINGS; ENDURANCE C1 JV POPLAWSKI & ASSOCIATES,BETHLEHEM,PA. RP Zaretsky, EV (reprint author), NASA,LEWIS RES CTR,CLEVELAND,OH 44135, USA. NR 4 TC 10 Z9 11 U1 0 U2 1 PU SOC TRIBOLOGISTS & LUBRICATION ENGINEERS PI PARK RIDGE PA 838 BUSSE HIGHWAY, PARK RIDGE, IL 60068 SN 0569-8197 J9 TRIBOL T JI Tribol. Trans. PD APR PY 1996 VL 39 IS 2 BP 501 EP 503 DI 10.1080/10402009608983560 PG 3 WC Engineering, Mechanical SC Engineering GA UB372 UT WOS:A1996UB37200038 ER PT J AU Lee, TJ Francisco, JS AF Lee, TJ Francisco, JS TI The proton affinity of HOBr SO CHEMICAL PHYSICS LETTERS LA English DT Article ID GAUSSIAN-BASIS SETS; MOLECULAR CALCULATIONS; ATOMS; CONTRACTION AB The proton affinity (PA) of HOBr is determined to be 161.5 +/- 1.0 kcal/mol (298.15 K). The single and double coupled-cluster method that includes a perturbational estimate of the effects of connected triple excitations, denoted CCSD(T), was used in conjunction with large spdfg atomic natural orbital basis sets to arrive at this value. The PA of HOBr is 7.0 kcal/mol larger than a recent prediction for HOCl. The most stable form of protonated HOBr is H2OBr+ with HOBrH+ determined to be 17.4 +/- 1.0 kcal/mol (298.15 K) higher in energy. C1 PURDUE UNIV, DEPT CHEM, W LAFAYETTE, IN 47907 USA. PURDUE UNIV, DEPT EARTH & ATMOSPHER SCI, W LAFAYETTE, IN 47907 USA. RP Lee, TJ (reprint author), NASA, AMES RES CTR, MS230-3, MOFFETT FIELD, CA 94035 USA. RI Lee, Timothy/K-2838-2012 NR 20 TC 12 Z9 12 U1 0 U2 0 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0009-2614 J9 CHEM PHYS LETT JI Chem. Phys. Lett. PD MAR 29 PY 1996 VL 251 IS 5-6 BP 400 EP 404 DI 10.1016/0009-2614(96)00112-1 PG 5 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA UF733 UT WOS:A1996UF73300022 ER PT J AU Chertihin, GV Saffel, W Yustein, JT Andrews, L Neurock, M Ricca, A Bauschlicher, CW AF Chertihin, GV Saffel, W Yustein, JT Andrews, L Neurock, M Ricca, A Bauschlicher, CW TI Reactions of laser-ablated iron atoms with oxygen molecules in condensing argon. Infrared spectra and density functional calculations of iron oxide product molecules SO JOURNAL OF PHYSICAL CHEMISTRY LA English DT Article ID GAUSSIAN-BASIS SETS; VIBRATIONAL ANALYSIS; MATRIX REACTIONS; METAL ATOMS; GAS-PHASE; FEO; PHOTOOXIDATION; PENTACARBONYL; SPECTROSCOPY; MONOXIDE AB Reaction of laser-ablated Fe atoms with oxygen molecules in a condensing argon stream produced FeO, FeO2, FeO3, FeO4, Fe2O, Fe2O2, and Fe2O4 molecules, which are identified from oxygen isotopic shifts and multiplets in matrix infrared spectra. The Fe + O-2 reaction gives symmetrical bent, symmetrical cyclic, and asymmetrical bent FeO2 isomeric products with triplet, triplet, and quartet isotopic absorptions, respectively, using statistically mixed O-16,18(2) as the reagent. The major reaction product symmetrical bent OFeO iron dioxide molecule (150 +/- 10 degrees) is characterized by stretching fundamentals at 945.8 and 797.1 cm(-1), and the asymmetric bent FeOO form exhibits a 1204.5 cm(-1) absorption. The cyclic isomer Fe(O-2) produced spontaneously during annealing in solid argon absorbs at 956.0 cm(-1). Oxygen and iron isotopic absorptions show that FeOFe is a symmetrical bent (140 +/- 10 degrees) molecule. Rhombic Fe2O2 absorbs at 517.4 cm(-1). Evidence is presented for isomers of FeO3, FeO4, and Fe2O4. Density functional theory was used to calculate energies, structures, and frequencies for product molecules to support their identification. C1 UNIV VIRGINIA,DEPT CHEM,CHARLOTTESVILLE,VA 22901. UNIV VIRGINIA,DEPT CHEM ENGN,CHARLOTTESVILLE,VA 22901. NASA,AMES RES CTR,MOFFETT FIELD,CA 94035. NR 76 TC 141 Z9 141 U1 3 U2 25 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 SN 0022-3654 J9 J PHYS CHEM-US JI J. Phys. Chem. PD MAR 28 PY 1996 VL 100 IS 13 BP 5261 EP 5273 DI 10.1021/jp953198w PG 13 WC Chemistry, Physical SC Chemistry GA UC398 UT WOS:A1996UC39800017 ER PT J AU Perry, JW Lee, LY Bohorquez, M Wu, XL AF Perry, JW Lee, LY Bohorquez, M Wu, XL TI Optical limiting materials using photoinduced charge transfer SO ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY LA English DT Meeting Abstract C1 CALTECH,JET PROP LAB,PASADENA,CA 91109. CALTECH,BECKMAN INST,PASADENA,CA 91125. DRAKE UNIV,DEPT CHEM,DES MOINES,IA 50311. RI Perry, Joseph/B-7191-2011 OI 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 MAR 24 PY 1996 VL 211 BP 11 EP POLY PN 2 PG 1 WC Chemistry, Multidisciplinary SC Chemistry GA UA485 UT WOS:A1996UA48501238 ER PT J AU Youngman, PW Fitch, JW Cassidy, PE AF Youngman, PW Fitch, JW Cassidy, PE TI Synthesis and characterization of poly(ether ketone)s containing phosphorus and fluorine. SO ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY LA English DT Meeting Abstract C1 SW TEXAS STATE UNIV,DEPT CHEM,POLYMER RES GRP,SAN MARCOS,TX 78666. NASA,LANGLEY RES CTR,HAMPTON,VA 23665. 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 MAR 24 PY 1996 VL 211 BP 14 EP POLY PN 2 PG 1 WC Chemistry, Multidisciplinary SC Chemistry GA UA485 UT WOS:A1996UA48501241 ER PT J AU Kranbuehl, D Hood, D Kriss, A Barksdale, R Loos, AC MacRae, JD Hasko, G AF Kranbuehl, D Hood, D Kriss, A Barksdale, R Loos, AC MacRae, JD Hasko, G TI Insitu FDEMS sensing and modeling of epoxy infiltration, viscosity and degree of cure during resin transfer molding of a textile preform SO ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY LA English DT Meeting Abstract C1 VIRGINIA POLYTECH INST & STATE UNIV,BLACKSBURG,VA 24061. COLL WILLIAM & MARY,WILLIAMSBURG,VA 23185. NASA,LANGLEY RES CTR,LOCKHEED ENGN & SCI CO,HAMPTON,VA 23665. NR 0 TC 1 Z9 1 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 MAR 24 PY 1996 VL 211 BP 17 EP PMSE PN 2 PG 1 WC Chemistry, Multidisciplinary SC Chemistry GA UA485 UT WOS:A1996UA48501672 ER PT J AU Oqlesby, DM AF Oqlesby, DM TI Optimization of oxygen partial pressure measurements by luminescent quenching SO ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY LA English DT Meeting Abstract C1 OLD DOMINION UNIV,DEPT CHEM & BIOCHEM,NORFOLK,VA 23529. NASA,LANGLEY RES CTR,EXPT TESTING TECHNOL DIV,HAMPTON,VA 23681. VIGYAN INC,HAMPTON,VA. 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 MAR 24 PY 1996 VL 211 BP 39 EP ANYL PN 1 PG 1 WC Chemistry, Multidisciplinary SC Chemistry GA UA482 UT WOS:A1996UA48200306 ER PT J AU Oqlesby, DM AF Oqlesby, DM TI An oxygen sensing coating with an internal temperature sensing luminophore SO ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY LA English DT Meeting Abstract C1 OLD DOMINION UNIV,DEPT CHEM & BIOCHEM,NORFOLK,VA 23529. NORFOLK STATE UNIV,DEPT CHEM,NORFOLK,VA 23540. NASA,LANGLEY RES CTR,EXPT TESTING TECHNOL DIV,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 MAR 24 PY 1996 VL 211 BP 40 EP ANYL PN 1 PG 1 WC Chemistry, Multidisciplinary SC Chemistry GA UA482 UT WOS:A1996UA48200307 ER PT J AU Eftekhari, A Pater, RH Singh, JJ AF Eftekhari, A Pater, RH Singh, JJ TI An investigation of microstructural characteristics of semi-interpenetrating polymer networks. 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 MAR 24 PY 1996 VL 211 BP 51 EP NUCL PN 2 PG 1 WC Chemistry, Multidisciplinary SC Chemistry GA UA485 UT WOS:A1996UA48500304 ER PT J AU Stoakley, DM StClair, AK AF Stoakley, DM StClair, AK TI Synthesis and characterization of self-metallizing palladium-doped polyimide films. 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 MAR 24 PY 1996 VL 211 BP 71 EP POLY PN 2 PG 1 WC Chemistry, Multidisciplinary SC Chemistry GA UA485 UT WOS:A1996UA48501298 ER PT J AU Kojiro, DR Carle, GC Valentin, JR Shen, RC AF Kojiro, DR Carle, GC Valentin, JR Shen, RC TI Analytical concepts 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. 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 MAR 24 PY 1996 VL 211 BP 75 EP ANYL PN 1 PG 1 WC Chemistry, Multidisciplinary SC Chemistry GA UA482 UT WOS:A1996UA48200342 ER PT J AU Pusey, ML AF Pusey, ML TI Anion effects on lysozyme crystallization SO ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY LA English DT Meeting Abstract C1 NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,HUNTSVILLE,AL 35812. 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 MAR 24 PY 1996 VL 211 BP 118 EP BIOT PN 1 PG 1 WC Chemistry, Multidisciplinary SC Chemistry GA UA482 UT WOS:A1996UA48200573 ER PT J AU Tabazadeh, A Toon, B AF Tabazadeh, A Toon, B TI Lidar obseravtions of polar stratospheric clouds (PSCS): Implications for the formation of type IA PSCS 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 MAR 24 PY 1996 VL 211 BP 139 EP ANYL PN 1 PG 2 WC Chemistry, Multidisciplinary SC Chemistry GA UA482 UT WOS:A1996UA48200406 ER PT J AU Wolfe, D Paley, MS Frazier, DO AF Wolfe, D Paley, MS Frazier, DO TI Novel nonlinear optical polydiacetylenes possessing liquid crystalline properties for ordered thin film preparation SO ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY LA English DT Meeting Abstract C1 RICE UNIV,DEPT CHEM,HOUSTON,TX 77005. NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,SPACE SCI LAB,CHEM & POLYMER MAT GRP,HUNTSVILLE,AL 35812. 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 MAR 24 PY 1996 VL 211 BP 141 EP POLY PN 2 PG 2 WC Chemistry, Multidisciplinary SC Chemistry GA UA485 UT WOS:A1996UA48501368 ER PT J AU Evans, BR Lane, LM Woodward, J Margalit, R Hathaway, GM AF Evans, BR Lane, LM Woodward, J Margalit, R Hathaway, GM TI Modification of a xylanase from Bacillus pumilus with pentaammineruthenium(III) SO ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY LA English DT Meeting Abstract C1 OAK RIDGE NATL LAB,OAK RIDGE,TN 37831. CALTECH,JET PROP LAB,PASADENA,CA 91109. CALTECH,BECKMAN INST,PASADENA,CA 91125. 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 MAR 24 PY 1996 VL 211 BP 142 EP CELL PN 1 PG 2 WC Chemistry, Multidisciplinary SC Chemistry GA UA482 UT WOS:A1996UA48200920 ER PT J AU Simpson, JO Clair, AKS AF Simpson, JO Clair, AKS TI Effect of fluorine and polarization phenomena on dielectric properties in aromatic polyimides 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 MAR 24 PY 1996 VL 211 BP 159 EP POLY PN 2 PG 1 WC Chemistry, Multidisciplinary SC Chemistry GA UA485 UT WOS:A1996UA48501386 ER PT J AU Brown, KG Burns, KS AF Brown, KG Burns, KS TI The determination of gas permeability of polymeric materials using mass spectrometry SO ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY LA English DT Meeting Abstract C1 OLD DOMINION UNIV,NORFOLK,VA 23529. 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 MAR 24 PY 1996 VL 211 BP 177 EP PMSE PN 2 PG 1 WC Chemistry, Multidisciplinary SC Chemistry GA UA485 UT WOS:A1996UA48501832 ER PT J AU Brown, KG Burns, KS AF Brown, KG Burns, KS TI Polymerization at near zero gravity in the space shuttle: Experimental results SO ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY LA English DT Meeting Abstract C1 OLD DOMINION UNIV,NORFOLK,VA 23529. NASA,LANGLEY RES CTR,HAMPTON,VA 23665. 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 MAR 24 PY 1996 VL 211 BP 178 EP PMSE PN 2 PG 1 WC Chemistry, Multidisciplinary SC Chemistry GA UA485 UT WOS:A1996UA48501833 ER PT J AU Brown, KG Burns, KS AF Brown, KG Burns, KS TI Polymerization at near zero gravity in the space shuttle: Experimental design SO ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY LA English DT Meeting Abstract C1 OLD DOMINION UNIV,NORFOLK,VA 23529. 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 MAR 24 PY 1996 VL 211 BP 179 EP PMSE PN 2 PG 1 WC Chemistry, Multidisciplinary SC Chemistry GA UA485 UT WOS:A1996UA48501834 ER PT J AU Southward, RE Thompson, DW StClair, AK AF Southward, RE Thompson, DW StClair, AK TI Control of surface reflectivity conductivity in silvered polyimide films via in situ thermal reduction of silver(I) SO ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY LA English DT Meeting Abstract C1 COLL WILLIAM & MARY,DEPT CHEM,WILLIAMSBURG,VA 23187. COLL WILLIAM & MARY,DEPT APPL SCI,WILLIAMSBURG,VA 23187. NASA,LANGLEY RES CTR,HAMPTON,VA 23665. 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 MAR 24 PY 1996 VL 211 BP 245 EP PMSE PN 2 PG 1 WC Chemistry, Multidisciplinary SC Chemistry GA UA485 UT WOS:A1996UA48501900 ER PT J AU Southward, RE Thompson, DS Thornton, TA Thompson, DW StClair, AK AF Southward, RE Thompson, DS Thornton, TA Thompson, DW StClair, AK TI Lanthanide(III)-polyimide nanocomposites: Enhancement of dimensional stability. SO ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY LA English DT Meeting Abstract C1 DEPT CHEM & APPL SCI,WILLIAMSBURG,VA 23187. NASA,LANGLEY RES CTR,HAMPTON,VA 23665. 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 MAR 24 PY 1996 VL 211 BP 309 EP POLY PN 2 PG 1 WC Chemistry, Multidisciplinary SC Chemistry GA UA485 UT WOS:A1996UA48501536 ER PT J AU Fay, CC StClair, AK AF Fay, CC StClair, AK TI Dimensionally stable polyimide copolymers for microelectronics applications. 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 MAR 24 PY 1996 VL 211 BP 311 EP POLY PN 2 PG 1 WC Chemistry, Multidisciplinary SC Chemistry GA UA485 UT WOS:A1996UA48501538 ER PT J AU Eashoo, M Buckley, LJ AF Eashoo, M Buckley, LJ TI Low dielectric constant fibers from a fluorinated polyimide for electronic packaging. SO ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY LA English DT Meeting Abstract C1 USN,RES LAB,DIV CHEM,WASHINGTON,DC 20375. 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 MAR 24 PY 1996 VL 211 BP 313 EP POLY PN 2 PG 1 WC Chemistry, Multidisciplinary SC Chemistry GA UA485 UT WOS:A1996UA48501540 ER PT J AU Sunkara, HB Weissman, JM Penn, BG Frazier, DO Asher, SA AF Sunkara, HB Weissman, JM Penn, BG Frazier, DO Asher, SA TI Design of intelligent mesoscale periodic array structures utilizing smart hydrogel SO ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY LA English DT Meeting Abstract C1 NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,HUNTSVILLE,AL 35812. NATL RES COUNCIL,WASHINGTON,DC 20418. UNIV PITTSBURGH,DEPT CHEM,PITTSBURGH,PA 15260. 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 MAR 24 PY 1996 VL 211 BP 393 EP POLY PN 2 PG 1 WC Chemistry, Multidisciplinary SC Chemistry GA UA485 UT WOS:A1996UA48501620 ER PT J AU Wright, CA McGill, J Gong, JK AF Wright, CA McGill, J Gong, JK TI A first example of ''Wittig Reaction'' on a coordinated CO2 complex SO ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY LA English DT Meeting Abstract C1 SE MISSOURI STATE UNIV,DEPT CHEM,CAPE GIRARDEAU,MO 63701. NASA,LEWIS RES CTR,CLEVELAND,OH 44135. 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 MAR 24 PY 1996 VL 211 BP 488 EP CHED PN 1 PG 1 WC Chemistry, Multidisciplinary SC Chemistry GA UA482 UT WOS:A1996UA48201502 ER PT J AU Coutta, R Crouse, DJ Meador, MA AF Coutta, R Crouse, DJ Meador, MA TI Preparation and photocyclization of a 1,4-bis-(benzyloxyaroyl)benzene. SO ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY LA English DT Meeting Abstract C1 TENNESSEE TECHNOL UNIV,DEPT CHEM,COOKEVILLE,TN 38505. NASA,LEWIS RES CTR,CLEVELAND,OH 44135. 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 MAR 24 PY 1996 VL 211 BP 546 EP CHED PN 1 PG 1 WC Chemistry, Multidisciplinary SC Chemistry GA UA482 UT WOS:A1996UA48201560 ER PT J AU Heinemann, C Schwarz, H Koch, W Dyall, KG AF Heinemann, C Schwarz, H Koch, W Dyall, KG TI Relativistic effects in the cationic platinum carbene PtCH2+ SO JOURNAL OF CHEMICAL PHYSICS LA English DT Article ID TRANSITION-METAL IONS; GAS-PHASE; METHANE ACTIVATION; SMALL MOLECULES; METHYLENE; ABINITIO; HYDROCARBONS; CHEMISTRY; ENERGIES; TRIPLET AB Fully relativistic four-component Dirac-Fock Coulomb calculations in conjunction with a second-order perturbational estimate for the correlation energy have been performed in benchmark calculations on geometric and electronic structures as well as the binding energy of the cationic platinum carbene complex PtCH2+. The relativistic stabilization of this species amounts to as much as 50 kcal/mol and the combination of relativistic and correlation effects shorten the Pt-C bond length by nearly 1 bohr, changing the bond order from one to two. The relative importance of spin-free and spin-dependent relativistic effects on the geometry, the electronic structure, and the binding energy is evaluated by comparison to the Douglas-Kroll method. Relativistic effective core potentials are shown to describe the spin-free effects reliably. The best theoretical estimate for the bond dissociation energy underestimates the experimental value by 13% due to truncation errors in the one- and n-particle space treatments. The mixed Hartree-Fock/density-functional method Becke3-Lee-Yang-Parr performs surprisingly well with respect to the structure and binding energy of the target molecule. (C) 1996 American Institute of Physics. C1 NASA,AMES RES CTR,THERMOSCI INST,MOFFETT FIELD,CA 94035. RP Heinemann, C (reprint author), TECH UNIV BERLIN,INST ORGAN CHEM,STR 17 JUNI 135,D-10623 BERLIN,GERMANY. OI Koch, Wolfram/0000-0002-2399-8358 NR 97 TC 45 Z9 45 U1 0 U2 8 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 MAR 22 PY 1996 VL 104 IS 12 BP 4642 EP 4651 DI 10.1063/1.471210 PG 10 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA UA381 UT WOS:A1996UA38100030 ER PT J AU Martin, JML Schwenke, DW Lee, TJ Taylor, PR AF Martin, JML Schwenke, DW Lee, TJ Taylor, PR TI Is there evidence for detection of cyclic C-4 in IR spectra? An accurate ab initio computed quartic force field SO JOURNAL OF CHEMICAL PHYSICS LA English DT Article ID CARBON CLUSTERS; BASIS-SETS; INFRARED-SPECTRA; WAVE-FUNCTIONS; SPECTROSCOPY; EXCITATION; CONSTANTS; ABINITIO; ISOMERS; MODEL AB The quartic force field of cyclic C-4 has been computed using basis sets of spdf quality and augmented coupled cluster methods. The effect of core correlation and further basis set extension has been investigated. Vibrational energy levels have been obtained using perturbation theory and two different variational approaches. A severe Fermi resonance exists between the most intense vibration, nu(6), and nu(3) + nu(5) through an exceptionally large k(356) = -258.2 cm(-1); a large k(1356) = -54.8 cm(-1) causes significant higher-order anharmonicity, including a shift in nu(6) of +9 cm(-1). C-4 appears to be an excellent test case for methods for solving the vibrational Schrodinger equation, since perturbation theory breaks down even when the above resonances are accounted for. Our best estimate for nu(6), 1320 +/- 10 cm(-1), may suggest its assignment to a feature detected at 1284 cm(-1) in argon and 1302 cm(-1) in krypton matrix, but this would imply an unusually large matrix red shift in argon. (C) 1996 American Institute of Physics. C1 UNIV INSTELLING ANTWERP, DEPT CHEM, INST MAT SCI, B-2610 WILRIJK, BELGIUM. NASA, AMES RES CTR, MOFFETT FIELD, CA 94035 USA. SAN DIEGO SUPERCOMP CTR, SAN DIEGO, CA 92186 USA. RP Martin, JML (reprint author), LIMBURGS UNIV CENTRUM, DEPT SBM, NIVERSITAIRE CAMPUS, B-3590 DIEPENBEEK, BELGIUM. RI Lee, Timothy/K-2838-2012; schwenke, david/I-3564-2013; Martin, Jan/A-7457-2008 OI Martin, Jan/0000-0002-0005-5074 NR 50 TC 25 Z9 25 U1 1 U2 3 PU AMER INST PHYSICS PI MELVILLE PA CIRCULATION & FULFILLMENT DIV, 2 HUNTINGTON QUADRANGLE, STE 1 N O 1, MELVILLE, NY 11747-4501 USA SN 0021-9606 J9 J CHEM PHYS JI J. Chem. Phys. PD MAR 22 PY 1996 VL 104 IS 12 BP 4657 EP 4663 DI 10.1063/1.471212 PG 7 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA UA381 UT WOS:A1996UA38100032 ER PT J AU Bedworth, PV Cai, YM Jen, A Marder, SR AF Bedworth, PV Cai, YM Jen, A Marder, SR TI Synthesis and relative thermal stabilities of diphenylamino- vs piperidinyl-substituted bithiophene chromophores for nonlinear optical materials SO JOURNAL OF ORGANIC CHEMISTRY LA English DT Article C1 CALTECH,BECKMAN INST,PASADENA,CA 91125. CALTECH,JET PROP LAB,PASADENA,CA 91109. ROI TECHNOL,MONMOUTH JCT,NJ 08852. NR 15 TC 95 Z9 95 U1 1 U2 4 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 SN 0022-3263 J9 J ORG CHEM JI J. Org. Chem. PD MAR 22 PY 1996 VL 61 IS 6 BP 2242 EP 2246 DI 10.1021/jo9517555 PG 5 WC Chemistry, Organic SC Chemistry GA UB205 UT WOS:A1996UB20500064 ER PT J AU Moore, CE Cardelino, BH Wang, XQ AF Moore, CE Cardelino, BH Wang, XQ TI Static third-order polarizability calculations for C-60, C-70, and C-84 SO JOURNAL OF PHYSICAL CHEMISTRY LA English DT Letter ID NONLINEAR OPTICAL-PROPERTIES; C60; FULLERENES; CARBON AB Valence electron contributions to the static molecular third-order polarizabilities (gamma) are calculated for C-60, C-70, and two stable structures of C-84 (D-2 and D-2d). The method utilized is based on the finite-field approach coupled with semiempirical polarization calculations on all-valence electrons. An increase in the third-order polarizability contributions is observed for molecular structures with a reduction in group symmetry, in agreement with recent experimental observations for these fullerenes. This increase is attributed mainly to the appearance of aromatic structures within the molecules as well as to the increase in molecular volume. C1 SPELMAN COLL,DEPT CHEM,ATLANTA,GA 30314. NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,SPACE SCI LAB,HUNTSVILLE,AL 35812. CLARK ATLANTA UNIV,DEPT PHYS,ATLANTA,GA 30314. CLARK ATLANTA UNIV,CTR THEORET STUDIES PHYS SYST,ATLANTA,GA 30314. NR 26 TC 30 Z9 30 U1 0 U2 1 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 SN 0022-3654 J9 J PHYS CHEM-US JI J. Phys. Chem. PD MAR 21 PY 1996 VL 100 IS 12 BP 4685 EP 4688 DI 10.1021/jp9530257 PG 4 WC Chemistry, Physical SC Chemistry GA UB162 UT WOS:A1996UB16200001 ER PT J AU Ganapol, BD AF Ganapol, BD TI Solution to the linear BGK equation via the principles of invariance SO JOURNAL OF PHYSICS A-MATHEMATICAL AND GENERAL LA English DT Article ID KINETIC BOUNDARY-LAYER AB The solution to the linearized BGK equation of kinetic theory is obtained via the principles of invariance as formulated by Chandrasekhar. The solution represents an alternative to the singular eigenfunction method featuring regular integral equations which are more easily evaluated. Laplace transforms are obtained for the net flow velocity and velocity distribution for both the albedo and Milne problems with wall reflection. The transforms are then numerically inverted to a high degree of accuracy. Results are compared to those of Kainz and Titulaer. RP Ganapol, BD (reprint author), NASA,AMES RES CTR,ECOSYST SCI & TECHNOL BRANCH,MS 242-4,MOFFETT FIELD,CA 94035, USA. NR 9 TC 1 Z9 1 U1 0 U2 0 PU IOP PUBLISHING LTD PI BRISTOL PA TECHNO HOUSE, REDCLIFFE WAY, BRISTOL, ENGLAND BS1 6NX SN 0305-4470 J9 J PHYS A-MATH GEN JI J. Phys. A-Math. Gen. PD MAR 21 PY 1996 VL 29 IS 6 BP 1227 EP 1244 DI 10.1088/0305-4470/29/6/010 PG 18 WC Physics, Multidisciplinary; Physics, Mathematical SC Physics GA UC758 UT WOS:A1996UC75800010 ER PT J AU Dallas, JL Afzal, RS Stephen, MA AF Dallas, JL Afzal, RS Stephen, MA TI Demonstration and characterization of a multibillion-shot, 2.5-mJ, 4-ns, Q-switched Nd:YAG laser SO APPLIED OPTICS LA English DT Article DE accumulative exposure; optical damage; laser diode lifetime AB We have demonstrated and characterized a Q-switched Nd:YAG laser under continuous operation for over 7 billion shots. Through periodic monitoring of the laser's vital signs, the system dynamics were The initial and the final pump-laser diode No evidence of an accumulative effect leading decoupled wavelengths to optical damage at a fluence lower than the single-shot threshold was observed. RP Dallas, JL (reprint author), NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771, USA. NR 8 TC 12 Z9 13 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 MAR 20 PY 1996 VL 35 IS 9 BP 1427 EP 1429 DI 10.1364/AO.35.001427 PG 3 WC Optics SC Optics GA UA966 UT WOS:A1996UA96600006 PM 21085254 ER PT J AU Kogut, A Banday, AJ Bennett, CL Gorski, KM Hinshaw, G Reach, WT AF Kogut, A Banday, AJ Bennett, CL Gorski, KM Hinshaw, G Reach, WT TI High-latitude galactic emission in the COBE differential microwave radiometer 2 year sky maps SO ASTROPHYSICAL JOURNAL LA English DT Article DE cosmic microwave background; dust, extinction; radio continuum, ISM ID COSMIC BACKGROUND-RADIATION; INTERSTELLAR-MEDIUM; 408 MHZ; FLUCTUATIONS; GHZ; ANISOTROPY AB We cross-correlate the COBE(6) DMR 2 year sky maps with spatial templates from long-wavelength radio surveys and the far-infrared COBE DIRBE maps. We place an upper limit on the spectral index of synchrotron radiation beta(synch) < -2.9 between 408 MHz and 31.5 GHz. We obtain a statistically significant cross-correlation with the DIRBE maps, whose dependence on the DMR frequencies indicates a superposition of dust and free-free emission. The high-latitude dust emission (\b\ > 30 degrees) is well fitted by a single dust component with temperature T = 18(-7)(+3) K and emissivity epsilon proportional to (nu/nu(0))(beta) with beta = 1.9(-0.5)(+3.0). The free-free emission is spatially correlated with the dust on angular scales,larger than the 7 degrees DMR beam, with rms variations 5.3 +/- 1.8 mu K at 53 GHz and angular power spectrum P proportional to l(-3). If this correlation persists to smaller angular scales, free-free emission should not be a significant contaminant to measurements of the cosmic microwave anisotropy at degree angular scales for frequencies above 20 GHz. C1 NASA,GODDARD SPACE FLIGHT CTR,ASTRON & SOLAR PHYS LAB,UNIV SPACE RES ASSOC,GREENBELT,MD 20771. RP Kogut, A (reprint author), NASA,GODDARD SPACE FLIGHT CTR,ASTRON & SOLAR PHYS LAB,HUGHES STX CORP,CODE 685,GREENBELT,MD 20771, USA. RI Reach, William/C-4710-2008; Kogut, Alan/D-6293-2012; OI Reach, William/0000-0001-8362-4094 NR 33 TC 156 Z9 156 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 MAR 20 PY 1996 VL 460 IS 1 BP 1 EP 9 DI 10.1086/176947 PN 1 PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA TZ366 UT WOS:A1996TZ36600001 ER PT J AU Contopoulos, J AF Contopoulos, J TI General axisymmetric magnetohydrodynamic flows: Theory and solutions SO ASTROPHYSICAL JOURNAL LA English DT Article DE accretion, accretion disks; galaxies, jets; MHD ID LOCAL SHEAR INSTABILITY; WEAKLY MAGNETIZED DISKS; ACCRETION DISKS; JETS AB We formulate the theory of general axisymmetric, steady state, nonrelativistic, ideal magnetohydrodynamic (MHD) flows in the presence of pressure and gravity. Magnetic flux is continuously advected by the flow and accumulates in a region around the axis of symmetry. This situation might have direct astrophysical applications in accretion outflow scenarios around compact objects in stellar systems and active galactic nuclei. The present work is fundamentally different from ail previous steady state analyses which have assumed that the poloidal flow velocity v(p) is parallel to the poloidal magnetic field B-p. We obtain the condition which determines the critical points of the flow. We also obtain self-consistent self-similar solutions which describe an accretion/outflow process around a compact object, under conditions allowing for magnetic flux advection. C1 NASA,GODDARD SPACE FLIGHT CTR,HIGH ENERGY ASTROPHYS LAB,GREENBELT,MD 20771. NR 26 TC 15 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 MAR 20 PY 1996 VL 460 IS 1 BP 185 EP 198 DI 10.1086/176960 PN 1 PG 14 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA TZ366 UT WOS:A1996TZ36600014 ER PT J AU Paglione, TAD Marscher, AP Jackson, JM Bertsch, DL AF Paglione, TAD Marscher, AP Jackson, JM Bertsch, DL TI Diffuse gamma-ray emission from the starburst galaxy NGC 253 SO ASTROPHYSICAL JOURNAL LA English DT Article DE cosmic rays; galaxies, individual (NGC 253); galaxies, starburst; gamma rays, observations; gamma rays, theory; stars, statistics ID RADIO-CONTINUUM OBSERVATIONS; DENSE MOLECULAR GAS; NEARBY GALAXIES; COSMIC-RAYS; PARTICLE-ACCELERATION; SHOCK ACCELERATION; SUPERNOVA-REMNANTS; NGC-253; M82; TELESCOPE AB The starburst galaxy NGC 253 was observed with the Energetic Gamma Ray Experiment Telescope (EGRET) aboard the Compton Gamma Ray Observatory (CGRO) satellite. We obtain a 2 sigma upper limit to the gamma-ray emission above 100 MeV of 8 x 10(-8) photons cm(-2) s(-1). Because of their large gas column densities and supernova rates, nearby starburst galaxies were predicted to have gamma-ray fluxes detectable by EGRET. Our nondetection of gamma-rays from NGC 253 motivates us to reexamine in detail the premise of supernova acceleration of cosmic rays and the effect of enhanced cloud densities, photon densities, and magnetic fields on the high-energy spectra of galaxies. By modeling the expected gamma-ray and synchrotron spectra from NGC 253, we find that up to 20% of the energy from supernovae is transferred to cosmic rays in the starburst, which is consistent with supernova acceleration models. Our calculations match the EGRET and radio data well with a supernova rate of 0.08 yr(-1), a magnetic field B greater than or similar to 5.5 x 10(-5) G, a density n similar to 300 cm(-3), a photon density U-ph similar to 200 eV cm(-3), and an escape timescale tau(0) less than or similar to 10 Myr. C1 NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. RP Paglione, TAD (reprint author), BOSTON UNIV,DEPT ASTRON,725 COMMONWEALTH AVE,BOSTON,MA 02215, USA. OI Paglione, Tim/0000-0001-9139-0945 NR 66 TC 56 Z9 56 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 MAR 20 PY 1996 VL 460 IS 1 BP 295 EP 302 DI 10.1086/176969 PN 1 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA TZ366 UT WOS:A1996TZ36600023 ER PT J AU Dopita, MA Vassiliadis, E Meatheringham, SJ Bohlin, RC Ford, HC Harrington, JP Wood, PR Stecher, TP Maran, SP AF Dopita, MA Vassiliadis, E Meatheringham, SJ Bohlin, RC Ford, HC Harrington, JP Wood, PR Stecher, TP Maran, SP TI Hubble Space Telescope observations of planetary nebulae in the Magellanic Clouds .4. [O III] images and evolutionary ages SO ASTROPHYSICAL JOURNAL LA English DT Article DE ISM, structure; Magellanic Clouds; planetary nebulae, general; stars, evolution ID ASYMPTOTIC GIANT BRANCH; CCD SURFACE PHOTOMETRY; ANGULAR DIAMETERS; MASS-LOSS; GALAXIES; STARS; KINEMATICS; REDUCTION; CAMERA; FLUXES AB The Planetary Camera of the Hubble Space Telescope has been used to obtain images in the CO mi lambda 5007 line for a sample of 15 planetary nebulae in the Magellanic Clouds chosen to eliminate any selection bias in either excitation class or in flux [for log F(H beta) > -13.7 ergs cm(-2) s(-1)]. These images are used to derive the physical dimensions, the spatial structure, and the kinematic ages of the nebulae. The raw images were deconvolved using the Richardson-Lucy image restoration algorithm, and based on extensive tests of model images, a limit of 100 iterations of the algorithm was adopted. The restored images show clear evidence for size evolution across the H-R diagram. The younger, low-excitation, compact planetary nebulae tend to be systematically smaller than photoionization models based on ground-based data would predict, suggesting that these planetary nebulae have a central reservoir of dense atomic and molecular gas. This gas lies close to the central star and is undergoing ionization and being accelerated into outflow. Planetary nebulae previously classified as nitrogen-rich objects with massive central stars (Peimbert type I) show the bipolar ''butterfly'' symmetry that is also a characteristic of their Galactic counterparts. The derived kinematic ages range from less than 1000 yr up to almost 5000 yr but show little sign of systematic increase along the evolutionary tracks. The true ages of the larger objects are systematically underestimated because of acceleration of the nebular shell during its lifetime. Using both the empirical fit that we had previously derived for the expansion velocity as a function of the position on the H-R diagram, and the theoretical evolutionary tracks of the central star, we have derived two semiempirical estimates for the evolutionary timescales based upon the nebular size and the measured dynamical age. If these evolutionary timescales are to be consistent with the evolutionary age derived from theory, then He burners outnumber H burners in the approximate ratio 2:1. C1 SPACE TELESCOPE SCI INST,BALTIMORE,MD 21218. UNIV MARYLAND,DEPT ASTRON,COLLEGE PK,MD 20742. NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. RP Dopita, MA (reprint author), AUSTRALIAN NATL UNIV,INST ADV STUDIES,MT STROMLO & SIDING SPRING OBSERV,WESTON,ACT 2611,AUSTRALIA. RI Dopita, Michael/P-5413-2014 OI Dopita, Michael/0000-0003-0922-4986 NR 46 TC 39 Z9 39 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637 SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD MAR 20 PY 1996 VL 460 IS 1 BP 320 EP & DI 10.1086/176972 PN 1 PG 22 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA TZ366 UT WOS:A1996TZ36600026 ER PT J AU Baykal, A Swank, J AF Baykal, A Swank, J TI Pulse frequency changes of 1E 2259+586 and the binary interpretation SO ASTROPHYSICAL JOURNAL LA English DT Article DE binaries, close; pulsars, individual (1E 2259+586); X-rays, stars ID X-RAY PULSAR; SUPERNOVA REMNANT G109.1-1.0; NEUTRON-STARS; TIMING OBSERVATIONS; ACCRETION DISK; NOISE; 1E2259+586; EVOLUTION; MODEL; EXTRAORDINARY AB Pulse frequencies from the archival ROSAT observations of 1E 2259+586 are presented. A short-term spin-up episode superposed on the secular spin-down trend is observed. Combining the previously published pulse frequencies, we estimate the variance of the angular velocity over a 15 yr span of observations. The level of fluctuations in angular velocity is similar to that of established accreting binary neutron stars. These results favor accretion by a neutron star from a very low mass companion as the source of the X-ray luminosity, although accretion by a solitary neutron star from a residual disk might be possible. C1 MIDDLE EAST TECH UNIV, DEPT PHYS, ANKARA 06531, TURKEY. RP Baykal, A (reprint author), NASA, GODDARD SPACE FLIGHT CTR, HIGH ENERGY ASTROPHYS LAB, GREENBELT, MD 20771 USA. RI Swank, Jean/F-2693-2012 NR 62 TC 57 Z9 58 U1 0 U2 1 PU IOP PUBLISHING LTD PI BRISTOL PA DIRAC HOUSE, TEMPLE BACK, BRISTOL BS1 6BE, ENGLAND SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD MAR 20 PY 1996 VL 460 IS 1 BP 470 EP 477 DI 10.1086/176985 PN 1 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA TZ366 UT WOS:A1996TZ36600039 ER PT J AU Kolb, EW Tkachev, II AF Kolb, EW Tkachev, II TI Femtolensing and picolensing by axion miniclusters SO ASTROPHYSICAL JOURNAL LA English DT Article DE dark matter; elementary particles; gravitational lensing ID INVISIBLE AXION; PARTICLE; INSTANTONS; STRINGS; OBJECTS; DENSITY; SN1987A; BOUNDS; STARS; MASS AB Nonlinear effects in the evolution of the axion field in the early universe may lead to the formation of gravitationally bound clumps of axions, known as ''miniclusters.'' Minicluster masses and radii should be in the range M(mc) similar to 10(-12) M. and R(mc) similar to 10(10) cm, and in plausible early-universe scenarios a significant fraction of the mass density of the universe may be in the form of axion miniclusters. If such axion miniclusters exist, they would have the physical properties required to be detected by ''femtolensing.'' C1 UNIV CHICAGO,ENRICO FERMI INST,DEPT ASTRON & ASTROPHYS,CHICAGO,IL 60637. OHIO STATE UNIV,DEPT PHYS,COLUMBUS,OH 43210. RUSSIAN ACAD SCI,INST NUCL RES,MOSCOW 117901,RUSSIA. RP Kolb, EW (reprint author), NASA,FERMILAB ASTROPHYS CTR,FERMI NATL ACCELERATOR LAB,BATAVIA,IL 60510, USA. NR 35 TC 45 Z9 45 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 MAR 20 PY 1996 VL 460 IS 1 BP L25 EP & PN 2 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA TZ367 UT WOS:A1996TZ36700006 ER PT J AU Schatten, KH AF Schatten, KH TI An atmospheric radiative-convective model: Solar forgings SO ASTROPHYSICAL JOURNAL LA English DT Article DE Sun, general ID CLIMATE AB In this Letter, we provide a brief description of a new one-dimensional planetary atmospheric radiative-convective (PARC) model and its responses to solar forcings. To undertake this calculation, we ignore changing lower atmospheric effects and consider only variations in solar energy inputs. The model incorporates the following energies/transport processes: solar visible, IR, and UV radiations; and energy transports by conduction, eddy viscosity, and convection. We note the following changes over previous one-dimensional atmospheric models. (1) Rather than only a global energy balance, a detailed (local) energy balance is employed; thus, radiative and convective energy transports are both calculated explicitly, the latter with mixing-length theory (MLT). (2) The IR opacity of the atmospheric gases is calculated in a self-consistent fashion with the other energy inputs. The model was run with large solar variations sufficient to examine clearly possible solar forcing: variations of 10% in the ''solar constant'' and 9% in the solar UV. The model exhibits a 6.4 K and a 3 K increase in the lower atmospheric temperatures, respectively, to these forcings. The solar constant influence is similar to other climate models. The model responds significantly, however, to solar UV variations in a new and interesting fashion deserving of further study. The effect may be understood as a result of an elevation of the tau similar to 1 level in the atmosphere associated with the deposition of the UV energy. We suggest some observational tests: as solar activity increases, one would expect (1) the total optical depth of the model atmosphere in the IR to increase and (2) the altitude of the IR radiating region to increase. The model has numerous simplifications that warrant caution, if one were to assume blindly the results applied directly to the real Earth. C1 NASA,GSFC,TERR PHYS LAB,GREENBELT,MD 20771. NR 9 TC 1 Z9 1 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 MAR 20 PY 1996 VL 460 IS 1 BP L69 EP L72 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA TZ367 UT WOS:A1996TZ36700017 ER PT J AU Sembach, KR Danks, AC Lambert, DL AF Sembach, KR Danks, AC Lambert, DL TI High-resolution observations of interstellar C-2 toward zeta Ophiuchi SO ASTROPHYSICAL JOURNAL LA English DT Article DE ISM, molecules; line, profiles; stars, individual (zeta Ophiuchi) ID CLOUDS; STARS; GAS; EMISSION; DENSITY; CH AB We present high-resolution (lambda/Delta lambda approximate to 540,000) absorption-line observations of two weak C-2 lines in the 2-0 band of the Phillips system in the direction of zeta Ophiuchi. These high signal-to-noise ratio (S/N approximate to 230-380) data were obtained at the McDonald Observatory 2.7 m telescope using the coude echelle spectrograph in double-pass mode. The C-2 line profiles are resolved into two components, having a spacing of approximate to 1.14 km s(-1), as has been seen for other molecular species such as CN, CO, and CH. Unlike these molecules, however, the strengths of the two narrow C-2 components are very similar. We briefly discuss the implications these results have for understanding the chemical behavior of diatomic molecules in diffuse interstellar clouds. C1 MIT,SPACE RES CTR,CAMBRIDGE,MA 02139. GODDARD SPACE FLIGHT CTR,STX SYST,GREENBELT,MD 20771. UNIV TEXAS,DEPT ASTRON,AUSTIN,TX 78712. RP Sembach, KR (reprint author), MCDONALD OBSERV,AUSTIN,TX 78712, USA. NR 28 TC 6 Z9 6 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 MAR 20 PY 1996 VL 460 IS 1 BP L61 EP L64 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA TZ367 UT WOS:A1996TZ36700015 ER PT J AU Solomon, S Portmann, RW Garcia, RR Thomason, LW Poole, LR McCormick, MP AF Solomon, S Portmann, RW Garcia, RR Thomason, LW Poole, LR McCormick, MP TI The role of aerosol variations in anthropogenic ozone depletion at northern midlatitudes SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID AIRCRAFT SULFUR EMISSIONS; HETEROGENEOUS CHEMISTRY; STRATOSPHERIC OZONE; ANTARCTIC VORTEX; SULFATE AEROSOLS; GLOBAL OZONE; MT-PINATUBO; TRENDS; ERUPTION; WINTER AB Aerosol surface area distributions inferred from satelliteborne 1-mu m extinction measurements are used as input to a two-dimensional model to study the effects of heterogeneous chemistry upon anthropogenic ozone depletion at northern midlatitudes, It is shown that short-term (interannual) and longer-term (decadal) changes in aerosols very likely played a substantial role along with trends in anthropogenic chlorine and bromine in both triggering the ozone losses observed at northern midlatitudes in the early 1980s and increasing the averaged long-term ozone depletions of the past decade or so. The use of observed aerosol distributions enhances the calculated ozone depletion due to halogen chemistry below about 25 km over much of the past decade, including many periods not generally thought to be affected by volcanic activity. Direct observations (especially the relationships of NOX/NOY and ClO/Cl-Y ratios to aerosol content) confirm the key aspects of the model chemistry that is responsible for this behavior and demonstrate chat aerosol changes alone are not a mechanism for ozone losses ill the absence of anthropogenic halogen inputs to the stratosphere. It is also suggested that aerosol-induced ozone changes could be confused with Ii-year solar cycle effects in some statistical analyses, resulting in an overestimate of the trends ascribed to solar activity. While the timing of the observed ozone changes over about the past 15 years is in remarkable agreement with the model predictions that explicitly include observed aerosol changes, their magnitude is about 50% larger than calculated. Possible chemical and dynamical causes of this discrepancy are explored. On the basis of this work, it is shown that the timing and magnitude of future ozone losses at midlatitudes in the northern hemisphere are likely to be strongly dependent upon volcanic aerosol variations as well as on future chlorine and bromine loading. C1 NATL CTR ATMOSPHER RES, BOULDER, CO 80307 USA. NASA, LANGLEY RES CTR, AEROSOL RES BRANCH, HAMPTON, VA 23665 USA. RP Solomon, S (reprint author), NOAA, AERON LAB, R-E-AL8, 325 BROADWAY, BOULDER, CO 80303 USA. RI Portmann, Robert/C-4903-2009 OI Portmann, Robert/0000-0002-0279-6087 NR 72 TC 260 Z9 265 U1 1 U2 18 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD MAR 20 PY 1996 VL 101 IS D3 BP 6713 EP 6727 DI 10.1029/95JD03353 PG 15 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA UB986 UT WOS:A1996UB98600002 ER PT J AU Vitt, FM Jackman, CH AF Vitt, FM Jackman, CH TI A comparison of sources of odd nitrogen production from 1974 through 1993 in the Earth's middle atmosphere as calculated using a two-dimensional model SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID SOLAR PROTON EVENTS; NITRIC-OXIDE; STRATOSPHERIC OZONE; POLAR STRATOSPHERES; PARTICLE EVENTS; OCTOBER 1989; COSMIC-RAYS; MESOSPHERE; DENITRIFICATION; CYCLE-21 AB The odd nitrogen source strengths associated with solar proton events (SPEs), galactic cosmic rays (GCRs), and the oxidation of nitrous oxide in the Earth's middle atmosphere from 1974 through 1993 have been compared globally, at middle and lower latitudes (< 50 degrees), and at polar regions (> 50 degrees) with a two-dimensional photochemical transport model. As discovered previously, the oxidation of nitrous oxide dominates the global odd nitrogen source, while GCRs and SPEs are significant at polar latitudes. The horizontal transport of odd nitrogen, produced by the oxidation of nitrous oxide at latitudes < 50 degrees, was found to be the dominant source of odd nitrogen in the polar regions, with GCRs contributing substantially during the entire solar cycle. The source of odd nitrogen from SPEs was more sporadic; however, contributions during several years (mostly near solar maximum) were significant in the polar middle atmosphere. C1 NASA, GODDARD SPACE FLIGHT CTR, ATMOSPHERES LAB, GREENBELT, MD 20771 USA. RP Vitt, FM (reprint author), UNIV KANSAS, DEPT PHYS & ASTRON, LAWRENCE, KS 66045 USA. RI Jackman, Charles/D-4699-2012 NR 46 TC 72 Z9 72 U1 0 U2 2 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD MAR 20 PY 1996 VL 101 IS D3 BP 6729 EP 6739 DI 10.1029/95JD03386 PG 11 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA UB986 UT WOS:A1996UB98600003 ER PT J AU Nevison, CD Solomon, S Russell, JM AF Nevison, CD Solomon, S Russell, JM TI Nighttime formation of N2O5 inferred from the halogen occulatation experiment sunset/sunrise NOx ratios SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID HIGH-LATITUDE STRATOSPHERE; NITROGEN; SUNRISE; MIDDLE; MODEL AB The sunset/sunrise NOX ratios measured in 1994 by the Halogen Occultation Experiment (HALOE) onboard the Upper Atmosphere Research Satellite (UARS) peak at up to 2.8 in the tropics around 30 km and decrease to 1 at the stratopause. These ratios are interpreted by using a fully diurnal one-dimensional model, which considers gas phase reactive nitrogen chemistry, and a two-dimensional model, which includes a more complete set of chemical reactions. The diurnal cycle of nighttime N2O5 formation followed by daytime photolysis entirely accounts for the observed ratios above about 35 km. In the lower to middle stratosphere, additional reactions involving ClONO2 and HNO3 also appear to contribute to the observed diurnal variations in NOX. The limitations of a simple function of ozone, temperature, and length of night, which estimates diurnal variations in NOX based on gas phase reactive nitrogen chemistry, are tested through comparison to one-dimensional model results. The function approximates the one-dimensional model sunset/sunrise NOX ratios well in the lower stratosphere but overestimates them by up to 10% in the upper stratosphere above about 35 km, corresponding to a large overestimate of N2O5 formation. The function is extended to estimate sunrise N2O5 in the middle stratosphere. C1 NASA, LANGLEY RES CTR, DIV ATMOSPHER SCI, HAMPTON, VA 23670 USA. RP Nevison, CD (reprint author), NOAA, ENVIRONM RES LAB, R-E-AL8, 325 BROADWAY, BOULDER, CO 80303 USA. NR 22 TC 10 Z9 10 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD MAR 20 PY 1996 VL 101 IS D3 BP 6741 EP 6748 DI 10.1029/96JD00058 PG 8 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA UB986 UT WOS:A1996UB98600004 ER PT J AU Remsberg, EE Bhatt, PP Russell, JM AF Remsberg, EE Bhatt, PP Russell, JM TI Estimates of the water vapor budget of the stratosphere from UARS HALOE data SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID MIDDLE ATMOSPHERE; NUMERICAL-MODEL AB The water vapor budget of the stratosphere is diagnosed from correlation studies of the UARS Halogen Occultation Experiment sunset measurements of CH4 and H2O in the middle and upper stratosphere, where the correlations are most significant and highly negative. Analyses were conducted for the years 1992-1994 using the methods of (1) linear regression and (2) deterministic differences (or variances of the data). It is assumed that there is conservation of total hydrogen according to a methane oxidation chemical mechanism. Results consist of the zonal mean seasonal distributions of the chemical yield of H2O molecules from each molecule of CH4 (or the beta profile) and an estimate of the annual average value of H2O that enters the stratosphere from below (or [H2O](e)), presumably at the tropical tropopause. Average seasonal beta values range from 1.6 to 2.4, and their zonal mean patterns are in good agreement with the theoretical model distribution of LeTexier et al., especially for the upper stratosphere. The range for annual average [H2O](e) is 2.9 to 3.4 parts per million by volume (ppmv). When adjusted upward by 10% due to known negative biases of about 5% in both the midstratospheric CH4 and the H2O data, [H2O](e) becomes 3.2 to 3.7 ppmv and is more consistent with averages of in situ measurements of water vapor at low latitudes of the lower stratosphere. We also find coherent patterns in the seasonal estimates of zonal average water vapor yield that are related to (1) the downward descent of air at winter polar latitudes, (2) the presence of dehydrated air at high latitudes of the southern hemisphere lower stratosphere, and (3) the ascent and relative isolation of the annual (January) minimum in tropical water vapor. C1 SCI APPLICAT INT CORP, HAMPTON, VA 23666 USA. RP Remsberg, EE (reprint author), NASA, LANGLEY RES CTR, DIV ATMOSPHER SCI, MS 401B, HAMPTON, VA 23681 USA. 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 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD MAR 20 PY 1996 VL 101 IS D3 BP 6749 EP 6766 DI 10.1029/95JD03858 PG 18 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA UB986 UT WOS:A1996UB98600005 ER PT J AU Li, ZJ Friedl, RR Moore, SB Sander, SP AF Li, ZJ Friedl, RR Moore, SB Sander, SP TI Interaction of peroxynitric acid with solid H2O ice SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID PERNITRIC ACID; STRATOSPHERIC AEROSOLS; NO2; DECOMPOSITION; REACTORS; KINETICS; HOONO2; CLOUDS; HO2NO2; VAPOR AB The uptake of peroxynitric acid (PNA), HO2NO2 or HNO4, on solid H2O ice at 193 K (-80 degrees C) was studied using a fast Row-mass spectrometric technique. An uptake coefficient of 0.15 +/- 0.10 was measured, where the quoted uncertainty denotes 2 standard deviations. The uptake process did not result in the production of gas phase products. The composition of the condensed phase was investigated using programmed heating (3 K min(-1)) of the substrate coupled with mass spectrometric detection of desorbed species. Significant quantities of HNO4 and HNO3 desorbed from the substrates at temperatures above 225 K and 246 K, respectively. The desorbed HNO3, which was less than 9% of the desorbed HNO4 and remained unchanged upon incubation of the substrate, was likely due to impurities in the HNO4 samples rather than reaction of HNO4 on the substrate. The onset temperatures for HNO4 desorption increased with increasing H2O to HNO4 ratios, indicating that HNO4, like HNO3, tends to be hydrated in the presence of water. These observations suggest possible mechanisms for removal of HNO4 or repartitioning of total odd nitrogen species in the Earth's upper troposphere and stratosphere. C1 CALTECH, JET PROP LAB, PASADENA, CA 91109 USA. NR 31 TC 16 Z9 16 U1 0 U2 5 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD MAR 20 PY 1996 VL 101 IS D3 BP 6795 EP 6802 DI 10.1029/96JD00065 PG 8 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA UB986 UT WOS:A1996UB98600008 ER PT J AU Stenchikov, G Dickerson, R Pickering, K Ellis, W Doddridge, B Kondragunta, S Poulida, O Scala, J Tao, WK AF Stenchikov, G Dickerson, R Pickering, K Ellis, W Doddridge, B Kondragunta, S Poulida, O Scala, J Tao, WK TI Stratosphere-troposphere exchange in a midlatitude mesoscale convective complex .2. Numerical simulations SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID OZONE PRODUCTION; THUNDERSTORMS; MECHANISM; TRANSPORT; MODEL; MASS AB Mixing across the tropopause due to intense convective events may significantly influence the atmospheric chemical balance. Stratosphere-troposphere exchange acts as an important natural source of O-3 in the troposphere, and a source of H2O, HCs, CFCs, HCFCs, and reactive nitrogen in the stratosphere. The redistribution of atmospheric trace gases produces secondary radiative, dynamical and climate effects, influencing lower stratospheric temperatures and the tropopause height. During the 1989 North Dakota Thunderstorm Project, a severe storm which evolved into a mesoscale convective complex (MCC) on June 28-29 showed the unusual feature of an anvil formed well within the stratosphere and produced strong vertical mixing of atmospheric trace gases including H2O, CO O-3, and NOy as discussed by Poulida et al. [this issue] in Part 1 of this paper. In this paper the two-dimensional NASA Goddard Cumulus Ensemble (GCE) model was employed to simulate this convective storm using observed initial and boundary conditions. The sensitivity to the domain size, initial and boundary conditions, stability, and time resolution are evaluated. Synoptic-scale moisture convergence, simulated by moist boundary inflow, influences significantly the storm intensity, spatial structure, and trace gas transport, and produces a storm that reintensifies after the initial decay, mimicking the observed behavior of the MCC. The deformation of the tropopause documented with aircraft observations was qualitatively reproduced along with transport of stratospheric ozone downward into the troposphere, and the transport of trace species from the boundary layer upward into the stratosphere. If the chemistry and dynamics of this storm are typical of the roughly 100 MCCs occurring annually over midlatitudes, then this mechanism plays an important role in CO, NOy, and O-3 budgets and could be the dominant source of H2O in the lower stratosphere and upper troposphere over midlatitudes. C1 NASA, GODDARD SPACE FLIGHT CTR, GREENBELT, MD 20771 USA. SCI SYST & APPLICAT INC, LANHAM, MD USA. RP Stenchikov, G (reprint author), UNIV MARYLAND, DEPT METEOROL, COLLEGE PK, MD 20742 USA. RI Dickerson, Russell/F-2857-2010; Pickering, Kenneth/E-6274-2012; Georgiy, Stenchikov/J-8569-2013; Kondragunta, Shobha/F-5601-2010 OI Dickerson, Russell/0000-0003-0206-3083; Kondragunta, Shobha/0000-0001-8593-8046 NR 36 TC 39 Z9 42 U1 1 U2 5 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD MAR 20 PY 1996 VL 101 IS D3 BP 6837 EP 6851 DI 10.1029/95JD02468 PG 15 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA UB986 UT WOS:A1996UB98600012 ER PT J AU Allen, DJ Rood, RB Thompson, AM Hudson, RD AF Allen, DJ Rood, RB Thompson, AM Hudson, RD TI Three-dimensional radon 222 calculations using assimilated meteorological data and a convective mixing algorithm SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID OZONE PRODUCTION; VERTICAL TRANSPORT; AIR; STRATOSPHERE; TROPOSPHERE; RN-222; MODELS AB The distribution of Rn-222 is simulated using a three-dimensional chemistry and transport model driven by assimilated data. The multiyear calculation is the first to use meteorological data from the Goddard Earth Observing System data assimilation system (GEOS-1 DAS). In addition, this calculation is the first to use moist convection and boundary layer parameters directly from a DAS to calculate mixing via moist convection and turbulence. Previously, these quantities have been derived after the assimilation procedure. Model output and data are compared at sites selected to evaluate model performance in a range of dynamic environments. Simulated afternoon boundary layer concentrations are within 30% of observed concentrations. Simulated nighttime concentrations are approximate to 50% of measured values although the bias is greatly reduced (and even disappears at Socorro, New Mexico) when nocturnal sub-grid-scale turbulent mixing is suppressed. Continental profiles are ''C-like''; a result that is consistent with the moist convective algorithm's tendency to move material from the planetary boundary layer (PBL) to the upper troposphere directly. CTM-calculated Rn-222 at Bermuda closely matches observations even during periods of frontal passage showing that the atmospheric circulation is accurate and that ventilation of the continental PBL is realistic. Model-calculated Rn-222 concentrations in the marine upper troposphere are consistent with observations in the eastern Pacific and near Darvin. C1 NASA, GODDARD SPACE FLIGHT CTR, ATMOSPHERES LAB, GREENBELT, MD 20771 USA. RP Allen, DJ (reprint author), UNIV MARYLAND, DEPT METEOROL, COLLEGE PK, MD 20742 USA. RI Allen, Dale/F-7168-2010; Rood, Richard/C-5611-2008; Thompson, Anne /C-3649-2014 OI Allen, Dale/0000-0003-3305-9669; Rood, Richard/0000-0002-2310-4262; Thompson, Anne /0000-0002-7829-0920 NR 45 TC 78 Z9 78 U1 0 U2 3 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD MAR 20 PY 1996 VL 101 IS D3 BP 6871 EP 6881 DI 10.1029/95JD03408 PG 11 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA UB986 UT WOS:A1996UB98600014 ER PT J AU Yvon, SA Saltzman, ES Cooper, DJ Bates, TS Thompson, AM AF Yvon, SA Saltzman, ES Cooper, DJ Bates, TS Thompson, AM TI Atmospheric sulfur cycling in the tropical Pacific marine boundary layer (12 degrees S,135 degrees W): A comparison of field data and model results .1. Dimethylsulfide SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID ABSORPTION CROSS-SECTIONS; GAS-EXCHANGE; AIRBORNE MEASUREMENTS; PHOTOCHEMICAL MODEL; AEROSOL IONS; OCEAN; SULFIDE; AIR; OZONE; WATER AB Shipboard measurements of atmospheric and seawater DMS were made at 12 degrees S, 135 degrees W for 6 days during March 1992. The mean seawater DMS concentration during this period was 4.1 +/- 0.45 nM (1 sigma, n = 260) and the mean atmospheric DMS mole fraction was 453 +/- 93 pmol mol(-1) (1 sigma, n = 843). Consistent atmospheric diel cycles were observed, with a nighttime maximum and daytime minimum and an amplitude of approximately 85 pmol mol(-1). Photochemical box model calculations were made to test the sensitivity of atmospheric DMS concentrations to the following parameters: 1) sea-to-air flux, 2) boundary layer height, 3) oxidation rate, and 4) vertical entrainment velocities. The observed relationship between the mean oceanic and atmospheric DMS levels require the use of an air-sea exchange coefficient which is at the upper limit end of the range of commonly used parameterizations. The amplitude of the diel cycle in atmospheric DMS is significantly larger than that predicted by a photochemical model. This suggests that the sea-to-air DMS flux is higher than was previously thought, and the rate of daytime oxidation of DMS is substantially underestimated by current photochemical models of DMS oxidation. C1 NOAA, PACIFIC MARINE ENVIRONM LAB, SEATTLE, WA 98115 USA. UNIV MIAMI, ROSENSTIEL SCH MARINE & ATMOSPHER SCI, MIAMI, FL 33149 USA. NASA, GODDARD SPACE FLIGHT CTR, GREENBELT, MD 20771 USA. RI Yvon-Lewis, Shari/E-4108-2012; Bates, Timothy/L-6080-2016; Thompson, Anne /C-3649-2014 OI Yvon-Lewis, Shari/0000-0003-1378-8434; Thompson, Anne /0000-0002-7829-0920 NR 70 TC 57 Z9 57 U1 0 U2 5 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD MAR 20 PY 1996 VL 101 IS D3 BP 6899 EP 6909 DI 10.1029/95JD03356 PG 11 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA UB986 UT WOS:A1996UB98600016 ER PT J AU Sud, YC Yang, R Walker, GK AF Sud, YC Yang, R Walker, GK TI Impact of in situ deforestation in Amazonia on the regional climate: General circulation model simulation study SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID TROPICAL DEFORESTATION; BIOSPHERE MODEL; SCALE; GCM; PARAMETERIZATION; DROUGHT; ALBEDO; BIOTA; SIB AB Two sets of 5-year long integrations were performed with the GLA GCM with a simple biosphere model (SiB) to delineate the influence of Amazonian deforestation on the local as well as basinwide circulation and rainfall. The control case invoked a normally forested Amazonia, while the deforestation case distinguished the partially deforested Amazonia (until the year 1988) as savanna. Except for this one difference, all other initial and the prescribed boundary conditions were identical in both integrations. A differential analysis of these two simulations revealed the following. (1) There was a large decrease in evapotranspiration (1.15 mm d(-1), roughly 33%) in the deforested region, while the basinwide decrease was only 0.24 mm d(-1) (roughly 8%). (2) The associated decrease of precipitation in the deforested (basinwide) regions was about 0.30 (0.168) mm d(-1). A precipitation decrease that is smaller than evapotranspiration decrease reflects a mitigating influence of increased moisture convergence, particularly within the boundary layer that gets warmed by the increased surface fluxes of sensible heat and longwave radiation. This implies that precipitation decrease in response to the 1988-level of Amazonian deforestation could be reversed, i.e., reforestation is likely to emerge if the anthropogenic pressures were eliminated and deforestation were forestalled. (3) The changes in the surface wind and rainfall patterns together with increased runoff and surface temperature indicate potential hydrological as well as ecological consequences of deforestation. In our simulations, only small regions of the Amazon basin produced precipitation and circulation changes at 90% or better statistical significance level. This is a consequence of a more realistic deforestation in Amazonia as compared to the total deforestation scenario used in previous studies. C1 GEN SCI CORP, LAUREL, MD 20707 USA. UNIV SPACE RES ASSOC, SEABROOK, MD 20706 USA. RP Sud, YC (reprint author), NASA, GODDARD SPACE FLIGHT CTR, ATMOSPHERES LAB, GREENBELT, MD 20771 USA. NR 35 TC 24 Z9 28 U1 0 U2 5 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD MAR 20 PY 1996 VL 101 IS D3 BP 7095 EP 7109 DI 10.1029/95JD02754 PG 15 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA UB986 UT WOS:A1996UB98600032 ER PT J AU Wetzel, PJ Argentini, S Boone, A AF Wetzel, PJ Argentini, S Boone, A TI Role of land surface in controlling daytime cloud amount: Two case studies in the GCIP-SW area SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID MESOSCALE CIRCULATIONS; CANOPY REFLECTANCE; SOIL-MOISTURE; PHOTOSYNTHESIS; TRANSPIRATION; VEGETATION; GENERATION; PREDICTION AB Two summertime cases are studied, in which fields of low cumulus clouds develop out of an initially clear sky under quiescent synoptic scale conditions, Both sites fall within the southwest study area of the GEWEX (Global Energy and Water cycle Experiment) Continental-Scale International Project (GCIP). The cases are modeled using a one-dimensional soil-vegetation-boundary layer model known as the parameterization for land-atmosphere-cloud exchange (PLACE), PLACE accurately predicts cloud onset and amount in both cases, one from the First International Satellite Land Surface Climatology Project (ISLSCP) Field Experiment (FIFE) in Kansas and one from Oklahoma. Sensitivity tests with PLACE show further that in the Oklahoma case, morning cloud amount is highly sensitive to land surface characteristics, whereas in the FIFE case, much less sensitivity is found, primarily due to differences in the predawn atmospheric thermodynamic structure through which the boundary layer must grow, Analysis of observational data, including cloud amount inferred from GOES visible data and vegetation index from the advanced very high resolution radiometer (AVHRR) data confirm that the PLACE model predictions of sensitivities and of the sensitivity differences between cases are correct. In the Oklahoma case, atmospheric conditions and soil moisture are relatively uniform across the study area, but a significant gradient of satellite-derived vegetation index is observed. Clouds form quickly due to a very shallow nocturnal inversion, with strong lapse conditions above. They form first over the hotter, more sparsely vegetated areas. Over areas covered with deciduous forest, clouds were observed to form 1 to 2 hours later due to the suppression of vertical mixing caused by increased latent heat release. In the FIFE case, because of a deep preexisting stable layer in the atmosphere the primary cause of spatial variations in morning cloud amount appears to be the amount of moisture in low levels of the atmosphere. In the afternoon, once the stable layer has been eroded, the FIFE study area begins to demonstrate more sensitivity of cloud amount to surface characteristics. C1 CNR, IST FIS ATMOSFERA, I-00044 FRASCATI, ITALY. SCI SYST & APPLICAT INC, LANHAM, MD 20771 USA. RP Wetzel, PJ (reprint author), NASA, GODDARD SPACE FLIGHT CTR, MESOSCALE ATMOSPHER PROC BRANCH, CODE 912, GREENBELT, MD 20771 USA. OI ARGENTINI, STEFANIA/0000-0002-7939-0309 NR 9 TC 32 Z9 34 U1 0 U2 2 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD MAR 20 PY 1996 VL 101 IS D3 BP 7359 EP 7370 DI 10.1029/95JD02134 PG 12 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA UB986 UT WOS:A1996UB98600053 ER PT J AU Xue, YK Fennessy, MJ Sellers, PJ AF Xue, YK Fennessy, MJ Sellers, PJ TI Impact of vegetation properties on US summer weather prediction SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID SIMPLE BIOSPHERE MODEL; GENERAL-CIRCULATION MODELS; SIB; ROUGHNESS; CLIMATE; LENGTH AB Systematic biases in U.S. summer integrations with the Center for Ocean-Land-Atmosphere Studies (COLA) atmospheric general circulation model (GCM) have been identified and analyzed. Positive surface air temperature biases of 2 degrees-4 degrees K occurred over the central United States. The temperature biases were coincident with the agricultural region of the central United States, where negative precipitation biases also occurred. The biases developed in June and became very significant during July and August. The impact of the crop area vegetation and soil properties on the biases was investigated in a series of numerical experiments. The biases were largely caused by the erroneous prescription of crop vegetation phenology in the surface model of the GCM. The prescribed crop soil properties also contributed to the biases. On the basis of these results the crop model has been improved and the systematic errors in the U.S. summer simulations have been reduced. The numerical experiments also revealed that land surface effects on the atmospheric variables at and near the surface during the North American summer are very pronounced and persistent but are largely limited to the area of the anomalous land surface forcing. In this regard, the midlatitude land surface effects described here are similar to those previously found for tropical regions. C1 NASA, GODDARD SPACE FLIGHT CTR, GREENBELT, MD 20771 USA. RP Xue, YK (reprint author), CTR OCEAN LAND ATMOSPHERE STUDIES, CALVERTON, MD 20705 USA. NR 42 TC 102 Z9 106 U1 1 U2 7 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD MAR 20 PY 1996 VL 101 IS D3 BP 7419 EP 7430 DI 10.1029/95JD02169 PG 12 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA UB986 UT WOS:A1996UB98600057 ER PT J AU Bin, M Gaidis, MC Zmuidzinas, J Phillips, TG LeDuc, HG AF Bin, M Gaidis, MC Zmuidzinas, J Phillips, TG LeDuc, HG TI Low-noise 1 THz niobium superconducting tunnel junction mixer with a normal metal tuning circuit SO APPLIED PHYSICS LETTERS LA English DT Article ID WAVELENGTHS AB We describe a 1 THz quasioptical SIS mixer which uses a twin-slot antenna, an antireflection-coated silicon hyperhemispherical lens, Nb/Al-oxide/Nb tunnel junctions, and an aluminum normal-metal tuning circuit in a two-junction configuration. Since the mixer operates substantially above the gap frequency of niobium (v>2 Delta/h similar to 700 GHz), a normal metal is used in the tuning circuit in place of niobium to reduce the Ohmic loss. The frequency response of the device was measured using a Fourier transform spectrometer and agrees reasonably well with the theoretical prediction. At 1042 GHz, the uncorrected double-sideband receiver noise temperature is 840 K when the physical temperature of the mixer is 2.5 K. This is the first SIS mixer which outperforms GaAs Schottky diode mixers by a large margin at 1 THz. (C) 1996 American Institute of Physics. C1 JET PROP LAB,CTR SPACE MICROELECTR TECHNOL,PASADENA,CA 91101. RP Bin, M (reprint author), CALTECH,GEORGE W DOWNS LAB PHYS,PASADENA,CA 91125, USA. RI Gaidis, Michael/D-3327-2013 NR 21 TC 59 Z9 59 U1 0 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 MAR 18 PY 1996 VL 68 IS 12 BP 1714 EP 1716 DI 10.1063/1.115915 PG 3 WC Physics, Applied SC Physics GA UA597 UT WOS:A1996UA59700041 ER PT J AU Schatten, K Myers, DJ Sofia, S AF Schatten, K Myers, DJ Sofia, S TI Solar activity forecast for solar cycle 23 SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article AB In this paper, we predict the next cycle's activity and improve the timing of solar cycle predictions. Dynamo-based solar activity prediction techniques rely upon two properties inherent in the solar cycle: that solar magnetism oscillates between poloidal and toroidal components; and that there is a degree of ''magnetic persistence'' in dynamos, which in the cask of the Sun, results in the dependence of many magnetic related quantities (activity related quantities) upon the amount of magnetism embedded below the Sun's surface. Using the SODA (SOlar Dynamo Amplitude) index as a measure of magnetic persistence, we predict that solar cydle # 23 will reach a mean smoothed F10.7 peak of 182 +/- 30 solar flux units (sfu) and a mean sunspot number Rz of 138 +/- 30. This is particularly intriguing because the ''folklore'' is that odd cycles are larger than the preceding even cycle. Additionally, by tracking the equatorward march of solar activity, the timing of the cycle can be better estimated. From this, we estimate that the next solar maximum will occur near May, 2000 +/- 9 months. C1 YALE UNIV,DEPT ASTRON,NEW HAVEN,CT 06511. RP Schatten, K (reprint author), NASA,GODDARD SPACE FLIGHT CTR,TERR PHYS LAB,GREENBELT,MD 20771, USA. NR 15 TC 57 Z9 57 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 MAR 15 PY 1996 VL 23 IS 6 BP 605 EP 608 DI 10.1029/96GL00451 PG 4 WC Geosciences, Multidisciplinary SC Geology GA UD379 UT WOS:A1996UD37900001 ER PT J AU Mewaldt, RA Cummings, JR Leske, RA Selesnick, RS Stone, EC vonRosenvinge, TT AF Mewaldt, RA Cummings, JR Leske, RA Selesnick, RS Stone, EC vonRosenvinge, TT TI A study of the composition and energy spectra of anomalous cosmic rays using the geomagnetic field SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID ACCELERATION; COMPONENT; SOLAR; IONS AB We use instrumentation on SAMPEX and the Earth's field as a magnetic rigidity filter in a ''double spectrometer'' approach to measure the composition and energy spectra of anomalous cosmic rays (ACRs) with Z greater than or equal to 6. A ''pure'' sample of anomalous cosmic ray C, N, O, and Ne is obtained, with no significant evidence for other species. The bulk of ACRs are now known to be singly-charged, and the geomagnetic filter allows their energy spectra to be measured to higher energies than before. The anomalous oxygen spectrum is found to extend to at least similar to 100 MeV/nuc, which has implications for models of the acceleration of these ions. C1 NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. RP Mewaldt, RA (reprint author), CALTECH,PASADENA,CA 91125, USA. NR 27 TC 14 Z9 14 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 MAR 15 PY 1996 VL 23 IS 6 BP 617 EP 620 DI 10.1029/96GL00423 PG 4 WC Geosciences, Multidisciplinary SC Geology GA UD379 UT WOS:A1996UD37900004 ER PT J AU Taguchi, S Hoffman, RA AF Taguchi, S Hoffman, RA TI Control parameters for polar ionospheric convection patterns during northward interplanetary magnetic field SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID RECONNECTION; MAGNETOPAUSE; PERIODS; REGION; MODEL; ARCS; DE-2; CAP AB Using the DE 2 electric field data from 191 dawn-dusk passes, we have sought parameters that distinguish between the various polar ionospheric convection patterns for northward IMF. The passes were divided into the daytime and nighttime sectors, and categorized the convection into three convection patterns for each sector by focusing on flow having a horizontal scale of > 150 km. The three daytime sector patterns are convection of reverse polarity, i.e., sunward at the highest latitudes and antisunward on both sides of the sunward flow region, irregular convection having multiple sunward and antisunward flow regions, and convection having a single antisunward flow region at the highest latitude, which is similar to the pattern for southward IMF. The IMF clock (B-Y/B-Z) angle, the Earth's dipole tilt angle, and the IMF B-X/B-Z angle measured from the dipole axis are the parameters that cause the difference in the three convection patterns. In the nighttime sector three similar convection patterns are identified. The occurrence of these patterns is controlled by the IMF dock angle. Thus, the convection pattern for northward IMF is very sensitive to the direction of the IMF. The magnetospheric sources for the convection patterns are discussed. C1 UNIV ELECTROCOMMUN,DEPT ELECTR ENGN,TOKYO,JAPAN. RP Taguchi, S (reprint author), NASA,GODDARD SPACE FLIGHT CTR,EXTRATERR PHYS LAB,CODE 696,GREENBELT,MD 20771, USA. NR 18 TC 8 Z9 8 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 MAR 15 PY 1996 VL 23 IS 6 BP 637 EP 640 DI 10.1029/96GL00452 PG 4 WC Geosciences, Multidisciplinary SC Geology GA UD379 UT WOS:A1996UD37900009 ER PT J AU Mlynczak, MG Marshall, BT AF Mlynczak, MG Marshall, BT TI A reexamination of the role of solar heating in the O-2 atmospheric and infrared atmospheric bands SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID ABSORPTION; MODEL AB The role of heating due to absorption of solar radiation by molecular oxygen (O-2) in the A, B, and gamma atmospheric bands and in the infrared atmospheric band is reviewed. Prior studies have demonstrated the importance of heating by these O-2 bands in the vicinity of the tropopause. In the middle mesosphere, the heating associated with O-2 atmospheric bands is shown to rival that of the numerous individual solar and chemical heat sources. We show that heating in the O-2 atmospheric bands increases the total diabatic (i.e., solar plus exothermic chemical reaction) heating by 5 to 15 percent between 60 and 80 km. C1 G&A TECH SOFTWARE,HAMPTON,VA 23666. RP Mlynczak, MG (reprint author), NASA,LANGLEY RES CTR,MAIL STOP 401B,HAMPTON,VA 23681, USA. RI Mlynczak, Martin/K-3396-2012 NR 9 TC 25 Z9 25 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 MAR 15 PY 1996 VL 23 IS 6 BP 657 EP 660 DI 10.1029/96GL00145 PG 4 WC Geosciences, Multidisciplinary SC Geology GA UD379 UT WOS:A1996UD37900014 ER PT J AU Jensen, HJA Dyall, KG Saue, T Faegri, K AF Jensen, HJA Dyall, KG Saue, T Faegri, K TI Relativistic four-component multiconfigurational self-consistent-field theory for molecules: Formalism SO JOURNAL OF CHEMICAL PHYSICS LA English DT Article ID OPTIMIZATION; STATE AB A formalism for relativistic four-component multiconfigurational self-consistent-held calculations on molecules is presented. The formalism parallels a direct second-order restricted-step algorithm developed for nonrelativistic molecular calculations. The presentation here focuses on the differences required by the use of the Dirac Hamiltonian with the incorporation of time-reversal symmetry and point group symmetry for D-2h and subgroups, providing the expressions in this framework which correspond to the nonrelativistic expressions. It is found that an efficient algorithm requires only twice the memory used by the largest nonrelativistic calculation in the equivalent basis, due to the complex arithmetic. The feasibility of the calculations is then determined more by the disk space for storage of integrals and N-particle expansion vectors. (C) 1996 American Institute of Physics. C1 NASA, AMES RES CTR, THERMOSCI INST, MOFFETT FIELD, CA 94035 USA. UNIV OSLO, DEPT CHEM, N-0315 OSLO 3, NORWAY. RP Jensen, HJA (reprint author), ODENSE UNIV, DEPT CHEM, DK-5230 ODENSE M, DENMARK. RI Jensen, Hans Jorgen Aagaard/C-6523-2009 OI Jensen, Hans Jorgen Aagaard/0000-0002-8743-7381 NR 45 TC 57 Z9 57 U1 1 U2 6 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 MAR 15 PY 1996 VL 104 IS 11 BP 4083 EP 4097 PG 15 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA TY728 UT WOS:A1996TY72800025 ER PT J AU Liu, Y AF Liu, Y TI Fourier analysis of numerical algorithms for the Maxwell equations SO JOURNAL OF COMPUTATIONAL PHYSICS LA English DT Article ID FINITE-DIFFERENCE SCHEMES; TIME-DOMAIN; FDTD ALGORITHM; SCATTERING AB The Fourier method is used to analyze the dispersive, dissipative, and isotropy errors of various spatial and time discretizations applied to the Maxwell equations on multi-dimensional grids. Both Cartesian grids and non-Cartesian grids based on hexagons and tetradecahedra are studied and compared. The numerical errors are quantitatively determined in terms of phase speed, wavenumber, propagation direction, gridspacings, and CFL number. The study shows that centered schemes are more efficient and accurate than upwind schemes and the non-Cartesian grids yield superior isotropy than the Cartesian ones. For the centered schemes, the staggered grids produce less errors than the unstaggered ones. A new unstaggered algorithm which has all the best properties is introduced. Using an optimization technique to determine the nodal weights, the new algorithm provides the highest accuracy among all the schemes discussed. The study also demonstrates that a proper choice of time discretization can reduce the overall numerical errors due to the spatial discretization. (C) 1996 Academic Press, Inc. RP Liu, Y (reprint author), NASA,AMES RES CTR,MOFFETT FIELD,CA 94035, USA. NR 31 TC 67 Z9 69 U1 0 U2 5 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 MAR 15 PY 1996 VL 124 IS 2 BP 396 EP 416 DI 10.1006/jcph.1996.0068 PG 21 WC Computer Science, Interdisciplinary Applications; Physics, Mathematical SC Computer Science; Physics GA UC248 UT WOS:A1996UC24800012 ER PT J AU Gloersen, P Yu, J MolloChristensen, E AF Gloersen, P Yu, J MolloChristensen, E TI Oscillatory behavior in Arctic sea ice concentrations SO JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS LA English DT Article ID TERRESTRIAL FREE OSCILLATIONS; TAPER SPECTRAL-ANALYSIS; NIMBUS-7 SMMR AB We have done a frequency analysis of the 9-year record of sea ice concentrations obtained with the NASA Nimbus 7 scanning multichannel microwave radiometer (SMMR). Because of the periodic revisit time of the SMMR, we are able to examine recurrence of shorter-period oscillations, as aliased by the revisit frequency, and longer-period oscillations per se. A number of findings result from a sequence of two analysis schemes, as follows. We have first determined, then removed, the mean, linear trend, and seasonal cycle (the latter composed of five harmonics of the annual cycle) from the time series for each pixel of gridded SMMR ice concentration data in the Arctic, using multiple linear regression. We find that the 9-year trends are most positive in the Beaufort and East Greenland Seas, whereas the most negative areas are in the Barents Sea and the sea ice surrounding Svalbard; this is similar to trend patterns in the lengths of the sea ice season reported earlier by Parkinson [1992]. In the residual data the standard deviation ranges from 12% to 16% in the central Arctic basin, considerably above the estimated wintertime ice concentration accuracies of 5% in that region; this is in part due to fluctuations in the ice concentration rather than noise. Secondly, we have used Fourier analysis and multiple-taper filtering techniques to identify tentatively some of these fluctuations as tidal components or multiyear components similar to those found in the El Nino-Southern Oscillation Index, and we show their spatial distribution. However, there are some high-amplitude, periodic components that we have not yet been able to identify, we show the spatial distribution of one of these components. C1 HARVARD UNIV,MIT,DEPT EARTH ATMOSPHER & PLANETARY SCI,CAMBRIDGE,MA 02138. UNIV VERMONT,DEPT MATH & STAT,BURLINGTON,VT 05405. RP Gloersen, P (reprint author), NASA,GODDARD SPACE FLIGHT CTR,LAB HYDROSPHER PROC,OCEANS & ICE BRANCH,CODE 971,GREENBELT,MD 20771, USA. NR 27 TC 14 Z9 14 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-OCEANS JI J. Geophys. Res.-Oceans PD MAR 15 PY 1996 VL 101 IS C3 BP 6641 EP 6650 DI 10.1029/95JC02958 PG 10 WC Oceanography SC Oceanography GA UA574 UT WOS:A1996UA57400024 ER PT J AU Josberger, EG Gloersen, P Chang, A Rango, A AF Josberger, EG Gloersen, P Chang, A Rango, A TI The effects of snowpack grain size on satellite passive microwave observations from the Upper Colorado River Basin SO JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS LA English DT Article ID WATER EQUIVALENT; NIMBUS-7 SMMR; PARAMETERS; RADIOMETRY; COVER AB Understanding the passive microwave emissions of a snowpack, as observed by satellite sensors, requires knowledge of the snowpack properties: water equivalent, grain size, density, and stratigraphy. For the snowpack in the Upper Colorado River Basin, measurements of snow depth and water equivalent are routinely available from the U.S. Department of Agriculture, but extremely limited information is available for the other properties. To provide this information, a field program from 1984 to 1995 obtained profiles of snowpack grain size, density, and temperature near the time of maximum snow accumulation, at sites distributed across the basin. A synoptic basin-wide sampling program in 1985 showed that the snowpack exhibits consistent properties across large regions. Typically, the snowpack in the Wyoming region contains large amounts of depth hear, with grain sizes up to 5 lmm, while the snowpack in Colorado and Utah is dominated by rounded snow grains less than 2 mm in diameter. In the Wyoming region, large depth hear crystals in shallow snowpacks yield the lowest emissivities or coldest brightness temperatures observed across the entire basin. Yearly differences in the average grain sizes result primarily from variations in the relative amount of depth hear within the snowpack. The average grain size for the Colorado and Utah regions shows much less variation than do the grain sizes from the Wyoming region. Furthermore, the greatest amounts of depth hear occur in the Wyoming region during 1987 and 1992, years with strong El Nino Southern Oscillation, but the Colorado and Utah regions do not show this behavior. C1 NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. USDA ARS,HYDROL LAB,BELTSVILLE,MD 20705. RP Josberger, EG (reprint author), UNIV PUGET SOUND,US GEOL SURVEY,TACOMA,WA 98416, USA. NR 24 TC 16 Z9 17 U1 0 U2 2 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 SN 0148-0227 J9 J GEOPHYS RES-OCEANS JI J. Geophys. Res.-Oceans PD MAR 15 PY 1996 VL 101 IS C3 BP 6679 EP 6688 DI 10.1029/95JC02959 PG 10 WC Oceanography SC Oceanography GA UA574 UT WOS:A1996UA57400027 ER PT J AU Wolfenden, A Hall, KD Lerch, BA AF Wolfenden, A Hall, KD Lerch, BA TI The effect of heat treatment on Young's modulus, damping, and microhardness of SiC/Ti-15-3 SO JOURNAL OF MATERIALS SCIENCE LA English DT Article ID COMPOSITE AB Mechanical and physical properties of a laminated, continuous SiC-fibre-reinforced Ti-15V-3Cr-3Al-3Sn (Ti-15-3) composite were analysed. The dynamic elastic modulus and damping of specimens with both unidirectional and cross-ply laminates were measured with the PUCOT (piezoelectric ultrasonic composite oscillator technique). The values of density, elastic modulus, and damping were evaluated with respect to heat treatment of the specimens. Metallographic examination was also done on the specimens to assess any changes in the microstructure in terms of changes in the mechanical or physical properties. C1 NASA,LEWIS RES CTR,CLEVELAND,OH 44135. RP Wolfenden, A (reprint author), TEXAS A&M UNIV,DEPT MECH ENGN,COLLEGE STN,TX 77843, USA. NR 11 TC 6 Z9 6 U1 1 U2 2 PU CHAPMAN HALL LTD PI LONDON PA 2-6 BOUNDARY ROW, LONDON, ENGLAND SE1 8HN SN 0022-2461 J9 J MATER SCI JI J. Mater. Sci. PD MAR 15 PY 1996 VL 31 IS 6 BP 1489 EP 1493 DI 10.1007/BF00357857 PG 5 WC Materials Science, Multidisciplinary SC Materials Science GA UB534 UT WOS:A1996UB53400014 ER PT J AU Srinivasan, J Smith, GL AF Srinivasan, J Smith, GL TI Modification of n=O equatorial waves due to interaction between convection and dynamics - Comment SO JOURNAL OF THE ATMOSPHERIC SCIENCES LA English DT Article C1 NASA,LANGLEY RES CTR,RADIAT SCI BRANCH,HAMPTON,VA 23681. NR 4 TC 1 Z9 1 U1 0 U2 0 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 SN 0022-4928 J9 J ATMOS SCI JI J. Atmos. Sci. PD MAR 15 PY 1996 VL 53 IS 6 BP 917 EP 918 DI 10.1175/1520-0469(1996)053<0917:COOEWD>2.0.CO;2 PG 2 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA UB134 UT WOS:A1996UB13400008 ER PT J AU Krainsky, IL Asnin, VM Mearini, GT Dayton, JA AF Krainsky, IL Asnin, VM Mearini, GT Dayton, JA TI Negative-electron-affinity effect on the surface of chemical-vapor-deposited diamond polycrystalline films SO PHYSICAL REVIEW B LA English DT Article AB Strong negative-electron-affinity effects have been observed on the surface of as-grown chemical-vapor-deposited diamond using secondary-electron emission. The samples were randomly oriented polycrystalline diamond films terminated with hydrogen. The effect appears as an intensive peak in the low-energy part of the spectrum of the electron energy distribution and may be described in the model of effective negative electron affinity. RP Krainsky, IL (reprint author), NASA,LEWIS RES CTR,CLEVELAND,OH 44135, USA. NR 18 TC 55 Z9 55 U1 0 U2 2 PU AMERICAN PHYSICAL SOC PI COLLEGE PK PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA SN 0163-1829 J9 PHYS REV B JI Phys. Rev. B PD MAR 15 PY 1996 VL 53 IS 12 BP R7650 EP R7653 PG 4 WC Physics, Condensed Matter SC Physics GA UC947 UT WOS:A1996UC94700020 ER PT J AU Chakrabarti, SK AF Chakrabarti, SK TI Gravitational wave emission from a binary black hole system in the presence of an accretion disk SO PHYSICAL REVIEW D LA English DT Article ID SHOCKS; WINDS; MODEL AB We study the time evolution and gravitational wave emission properties of a black hole orbiting inside an accretion disk surrounding a massive black hole. We simultaneously solve the structure equations of the accretion disk in the presence of heating, cooling, and viscosity as well as the equations governing the companion orbit. The deviation from the Keplerian distribution of the angular momentum of the disk due to pressure and advection effects causes a significant exchange of angular momentum between the disk and the companion. This significantly affects the gravitational wave emission properties from the binary system. We show that when the companion is light, the effect is extremely important and must be taken into account while interpreting gravitational wave signals from such systems. RP NASA, GODDARD SPACE FLIGHT CTR, CODE 665, GREENBELT, MD 20771 USA. NR 34 TC 19 Z9 19 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 MAR 15 PY 1996 VL 53 IS 6 BP 2901 EP 2907 DI 10.1103/PhysRevD.53.2901 PG 7 WC Astronomy & Astrophysics; Physics, Particles & Fields SC Astronomy & Astrophysics; Physics GA UC220 UT WOS:A1996UC22000006 ER PT J AU Farrar, GR Kolb, EW AF Farrar, GR Kolb, EW TI Light photinos as dark matter SO PHYSICAL REVIEW D LA English DT Article ID NEUTRAL FERMIONS; CROSS-SECTIONS; CONSTRAINTS; CANDIDATES; MODELS; ABUNDANCES; COSMOLOGY; PARTICLES; NEUTRINOS; MASSES AB There are good reasons to consider models of low-energy supersymmetry with very light photinos and gluinos. In most of these models the lightest R-odd, color-singlet state containing a gluino, the R(0), has a mass in the 1-2 GeV range and the slightly lighter photino <(gamma)over tilde> would survive as the relic R-odd species. For the light photino masses considered here, previous calculations resulted in an unacceptable photino relic abundance. But we point out that processes other than photino self-annihilation determine the relic abundance when the photino and RO are close in mass. Including R(0) <-> <(gamma)over tilde> processes, we find that the photino relic abundance is most sensitive to the R(0)-to-<(gamma)over tilde> mass ratio, and within model uncertainties, a critical density in photinos may be obtained for an R(0)-to-<(gamma)over tilde> mass ratio in the range 1.2 to 2.2. We propose photinos in the mass range of 500 MeV to 1.6 GeV as a dark matter candidate, and discuss a strategy to test the hypothesis. C1 FERMILAB NATL ACCELERATOR LAB,NASA,FERMILAB ASTROPHYS CTR,BATAVIA,IL 60510. UNIV CHICAGO,ENRICO FERMI INST,DEPT ASTRON & ASTROPHYS,CHICAGO,IL 60637. RP Farrar, GR (reprint author), RUTGERS STATE UNIV,DEPT PHYS & ASTRON,POB 849,PISCATAWAY,NJ 08855, USA. NR 32 TC 24 Z9 24 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 MAR 15 PY 1996 VL 53 IS 6 BP 2990 EP 3001 DI 10.1103/PhysRevD.53.2990 PG 12 WC Astronomy & Astrophysics; Physics, Particles & Fields SC Astronomy & Astrophysics; Physics GA UC220 UT WOS:A1996UC22000012 ER PT J AU Schuraytz, BC Lindstrom, DJ Marin, LE Martinez, RR Mittlefehldt, DW Sharpton, VL Wentworth, SJ AF Schuraytz, BC Lindstrom, DJ Marin, LE Martinez, RR Mittlefehldt, DW Sharpton, VL Wentworth, SJ TI Iridium metal in Chicxulub impact melt: Forensic chemistry on the K-T smoking gun SO SCIENCE LA English DT Article ID CRETACEOUS-TERTIARY BOUNDARY; REFRACTORY INCLUSIONS; CA,AL-RICH INCLUSION; CRATER; METEORITE; IDENTIFICATION; PROJECTILE; SEDIMENTS; ELEMENTS; ASSEMBLAGES AB Iridium concentrations in successively smaller subsplits of melt rock and melt breccia from the Chicxulub impact basin were tracked to isolate and identify iridium carrier phases. Iridium-rich particles were isolated from two samples, and a micrometer-scale, silicate-enclosed aggregate of subhedral iridium metal grains was identified in one, confirming earlier reports of iridium at ground zero of the impact at the Cretaceous-Tertiary (K-T) boundary. The aggregate may be either a phase formed after the collision or a relict of the Chicxulub basin-forming meteorite. In either case, its presence indicates that even among the largest impact structures on Earth, meteoritic components may be preserved within the crater. C1 LUNAR & PLANETARY INST,HOUSTON,TX 77058. NATL AUTONOMOUS UNIV MEXICO,INST GEOFIS,COYOACAN 04510,DF,MEXICO. LOCKHEED MARTIN,ENGN & SCI,HOUSTON,TX 77058. NASA,LYNDON B JOHNSON SPACE CTR,PLANETARY SCI BRANCH,HOUSTON,TX 77058. NR 49 TC 24 Z9 24 U1 0 U2 2 PU AMER ASSOC ADVANCEMENT SCIENCE PI WASHINGTON PA 1200 NEW YORK AVE, NW, WASHINGTON, DC 20005 SN 0036-8075 J9 SCIENCE JI Science PD MAR 15 PY 1996 VL 271 IS 5255 BP 1573 EP 1576 DI 10.1126/science.271.5255.1573 PG 4 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA TZ983 UT WOS:A1996TZ98300038 ER PT J AU Weaver, ML Noebe, RD Kaufman, MJ AF Weaver, ML Noebe, RD Kaufman, MJ TI The influence of C and Si on the flow behavior of NiAl single crystals SO SCRIPTA MATERIALIA LA English DT Article ID DUCTILITY; ALLOYS C1 FLORIDA A&M UNIV,FLORIDA STATE UNIV,COLL ENGN,DEPT MECH ENGN,TALLAHASSEE,FL 32316. NASA,LEWIS RES CTR,CLEVELAND,OH 44135. UNIV FLORIDA,DEPT MAT SCI & ENGN,GAINESVILLE,FL 32611. RP Weaver, ML (reprint author), FLORIDA A&M UNIV,CTR NONLINEAR & NONEQUILIBRIUM AEROSCI,TALLAHASSEE,FL 32310, USA. RI Kaufman, Michael/A-7737-2012 NR 27 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 1359-6462 J9 SCRIPTA MATER JI Scr. Mater. PD MAR 15 PY 1996 VL 34 IS 6 BP 941 EP 948 DI 10.1016/1359-6462(95)00590-0 PG 8 WC Nanoscience & Nanotechnology; Materials Science, Multidisciplinary; Metallurgy & Metallurgical Engineering SC Science & Technology - Other Topics; Materials Science; Metallurgy & Metallurgical Engineering GA TW216 UT WOS:A1996TW21600017 ER PT J AU Kemp, P AF Kemp, P TI Phase shifter yields slope-polarity detection SO EDN LA English DT Article RP Kemp, P (reprint author), NASA,HOUSTON,TX 77058, USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU CAHNERS-DENVER PUBLISHING CO PI HIGHLANDS RANCH PA 8773 S RIDGELINE BLVD, HIGHLANDS RANCH, CO 80126-2329 SN 0012-7515 J9 EDN JI EDN PD MAR 14 PY 1996 VL 41 IS 6 BP 92 EP & PG 3 WC Engineering, Electrical & Electronic SC Engineering GA TZ938 UT WOS:A1996TZ93800021 ER PT J AU Lord, SM Switzer, GW Krainak, MA AF Lord, SM Switzer, GW Krainak, MA TI Using fibre gratings to stabilise laser diode wavelength under modulation for atmospheric lidar transmitters SO ELECTRONICS LETTERS LA English DT Article DE gratings in fibres; semiconductor junction lasers AB The authors report on the optical spectrum of a high power (150mW) laser diode under large signal intensity modulation with feedback from an external cavity fibre grating. Single longitudinal facet mode operation was maintained for 6kHz 1% and 3% duty cycle pulsed and 1Mbit/s psuedonoise code modulation with extinction ratios as small as 0.01. C1 MONTANA STATE UNIV,DEPT PHYS,BOZEMAN,MT 59717. NASA,GODDARD SPACE FLIGHT CTR,OPT BRANCH,GREENBELT,MD 20771. RP Lord, SM (reprint author), BUCKNELL UNIV,DEPT ELECT ENGN,LEWISBURG,PA 17837, USA. NR 5 TC 4 Z9 4 U1 0 U2 0 PU IEE-INST ELEC ENG PI HERTFORD PA MICHAEL FARADAY HOUSE SIX HILLS WAY STEVENAGE, HERTFORD, ENGLAND SG1 2AY SN 0013-5194 J9 ELECTRON LETT JI Electron. Lett. PD MAR 14 PY 1996 VL 32 IS 6 BP 561 EP 563 DI 10.1049/el:19960353 PG 3 WC Engineering, Electrical & Electronic SC Engineering GA UL772 UT WOS:A1996UL77200041 ER PT J AU Skalare, A McGrath, WR Bumble, B LeDuc, HG Burke, PJ Verheijen, AA Schoelkopf, RJ Prober, DE AF Skalare, A McGrath, WR Bumble, B LeDuc, HG Burke, PJ Verheijen, AA Schoelkopf, RJ Prober, DE TI Large bandwidth and low noise in a diffusion-cooled hot-electron bolometer mixer SO APPLIED PHYSICS LETTERS LA English DT Article AB Heterodyne measurements have been made at 533 GHz using a novel superconducting hot-electron bolometer in a waveguide mixer. The bolometer is a 0.3 mu m long niobium microbridge with a superconducting transition temperature of 5 K. The short length ensures that electron diffusion dominates over electron-phonon interactions as the electron cooling mechanism, which should allow heterodyne detection with intermediate frequencies (if) of several GHz. A Y-factor response of 1.15 dB has been obtained at an if of 1.4 GHz with 77 and 295 K loads, indicating a receiver noise temperature of 650 K DSB. The -3 dB rolloff in the if response occurs at 1.7 GHz. (C) 1996 American Institute of Physics. C1 YALE UNIV,DEPT APPL PHYS,NEW HAVEN,CT 06520. RP Skalare, A (reprint author), CALTECH,JET PROP LAB,CTR SPACE MICROELECTR TECHNOL,PASADENA,CA 91109, USA. RI Schoelkopf, Robert/J-8178-2012; Burke, Peter/F-3308-2010 NR 14 TC 54 Z9 55 U1 0 U2 3 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 MAR 11 PY 1996 VL 68 IS 11 BP 1558 EP 1560 DI 10.1063/1.115698 PG 3 WC Physics, Applied SC Physics GA TZ291 UT WOS:A1996TZ29100040 ER PT J AU Ptak, A Yaqoob, T Serlemitsos, PJ Kunieda, H Terashima, Y AF Ptak, A Yaqoob, T Serlemitsos, PJ Kunieda, H Terashima, Y TI The nature of the low-luminosity active galactic nuclei in NGC 3147 SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies, active; galaxies, individual (NGC 3147); X-rays, galaxies ID X-RAY BINARIES; SEYFERT-GALAXIES; VARIABILITY; REFLECTION; MATTER; LINES AB A recent optical study has identified an active nucleus (AGN) in the spiral galaxy NGC 3147 based on the discovery of broad (FWHM similar to 400 km s(-1)) [N II] line emission. This object was previously misclassified as a normal galaxy. Here we present the first X-ray spectrum obtained by ASCA in the 0.4-10 keV bandpass of this source. The X-ray spectrum is typical of Seyfert 1 galaxies, namely, it has little intrinsic absorption, a power-law continuum with a photon index of 1.80 +/- 0.09, and Fe K alpha emission at around 6.4 keV (rest frame) with an equivalent width greater than 130 eV. However, if it really is a Seyfert 1 galaxy, at a 2-10 keV luminosity of similar to 5 x 10(41) ergs s(-1), it should be highly variable, in keeping with the established trend that the lowest luminosity AGNs exhibit the greatest variability. However, no variability is observed within the 50 ks ASCA observation or between the ASCA observation and a ROSAT observation 2 weeks later. Alternatively, NGC 3147 may harbor an obscured AGN in which the observed X-ray spectrum is seen only in scattered light and the intrinsic X-ray luminosity may be an order of magnitude or two higher than observed. This interpretation would be consistent with a Seyfert 2 galaxy in the unified Seyfert model. We discuss the physical and geometrical constraints on the obscuring matter and the scattering zone in such a scenario. We point out the contrast with the X-ray spectrum of other Seyfert 2 galaxies which contain a soft, possibly thermal, component not present in NGC 3147. C1 NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. NAGOYA UNIV,DEPT ASTROPHYS,CHIKUSA KU,NAGOYA,AICHI 46401,JAPAN. RI Ptak, Andrew/D-3574-2012 NR 28 TC 41 Z9 42 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 MAR 10 PY 1996 VL 459 IS 2 BP 542 EP 546 DI 10.1086/176918 PN 1 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA TX195 UT WOS:A1996TX19500015 ER PT J AU Mitrofanov, IG Chernenko, AM Pozanenko, AS Briggs, MS Paciesas, WS Fishman, GJ Meegan, CA Sagdeev, RZ AF Mitrofanov, IG Chernenko, AM Pozanenko, AS Briggs, MS Paciesas, WS Fishman, GJ Meegan, CA Sagdeev, RZ TI The average intensity and spectral evolution of BATSE cosmic gamma-ray bursts SO ASTROPHYSICAL JOURNAL LA English DT Article DE gamma rays, bursts AB Statistical studies of BATSE gamma-ray bursts are presented: we average the time profiles, aligning the events at their highest peaks. Using the time histories in different energy channels, we summarize the general features of the average intensity and spectral evolution of gamma-ray bursts (GRBs) and compare the average evolution of bright and dim events. While no differences are found between the average intensity histories, the average hardness ratio histories demonstrate a hardness/brightness correlation. The observed lack of differences between the intensity histories of bright and dim bursts is incompatible with cosmological time dilation effects predicted by simple cosmological models. The combined results of no intensity history difference but a hardness history difference between bright and dim bursts places constraints on galactic models for the origin of GRBs. C1 UNIV ALABAMA,DEPT PHYS,HUNTSVILLE,AL 35899. NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,HUNTSVILLE,AL 35812. UNIV MARYLAND,COLLEGE PK,MD 20742. RP Mitrofanov, IG (reprint author), MOSCOW SPACE RES INST,PROFSOJUZNAYA ST 84-32,MOSCOW 117810,RUSSIA. NR 31 TC 51 Z9 53 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 MAR 10 PY 1996 VL 459 IS 2 BP 570 EP 578 DI 10.1086/176922 PN 1 PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA TX195 UT WOS:A1996TX19500019 ER PT J AU Dwek, E Smith, RK AF Dwek, E Smith, RK TI Energy deposition and photoelectric emission from the interaction of 10 eV to 1 MeV photons with interstellar dust particles SO ASTROPHYSICAL JOURNAL LA English DT Article DE dust, extinction; radiation mechanisms, nonthermal; ultraviolet, ISM ID X-RAY-IRRADIATION; MULTIPLE IONIZATION; SUPERNOVA-REMNANTS; INFRARED-EMISSION; ELECTRONS; CLOUDS; NOVA AB This paper presents detailed calculations of the energy deposited by energetic photons in spherical, uncharged, interstellar dust particles. The interaction of the photons in the solid creates fast electrons from photoionizations, Auger transitions, or Compton scattering, which deposit a fraction of their energy in the dust. Fluorescent transitions following a K-shell photoionization in iron also contribute to the heating. The efficiency of the dust heating depends on the initial photon energy and on the grain size and composition. Calculations are performed for carbon and silicate particles of radius 50 Angstrom to 1 mu m, irradiated by photons with energies between 10 eV, which is about equal to the threshold for the ejection of photoelectrons, and 1 MeV, beyond which pair production dominates the photon interaction in the solid. Our studies present a consistent treatment of the partitioning of the energy of photons that interact in the dust into an absorbed fraction and a fraction that is carried away by ejected electrons. The results are presented in tables listing the energy deposited in a dust particle, E(dep), as a function of incident photon energy, E(gamma), and plots depicting the energy carried away by the ejected electrons as a function of E(gamma). The results of this work are useful for calculating dust temperature fluctuations and equilibrium dust temperatures in astrophysical environments in which the dust is exposed to hard ultraviolet and X-ray emission and for calculating the photoelectric heating of clouds exposed to similarly hard radiation fields. C1 UNIV WISCONSIN,DEPT PHYS,MADISON,WI 53706. RP Dwek, E (reprint author), NASA,GODDARD SPACE FLIGHT CTR,ASTRON & SOLAR PHYS LAB,CODE 685,GREENBELT,MD 20771, USA. NR 26 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 MAR 10 PY 1996 VL 459 IS 2 BP 686 EP 700 DI 10.1086/176933 PN 1 PG 15 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA TX195 UT WOS:A1996TX19500030 ER PT J AU Kaspi, VM Tauris, TM Manchester, RN AF Kaspi, VM Tauris, TM Manchester, RN TI On the wind from the small magellanic cloud B1 V companion to PSR J0045-7319 SO ASTROPHYSICAL JOURNAL LA English DT Article DE binaries, general; Magellanic Clouds; pulsars, individual (PSR J0045-7319); stars, atmospheres; stars, early-type; stars, mass loss ID RADIATION-DRIVEN WINDS; HOT LUMINOUS STARS; MASS-LOSS RATES; STELLAR WINDS; O-STARS; SPECTROSCOPY AB We report on multifrequency radio timing observations of the unique binary pulsar PSR J0045 - 7319, the only known radio pulsar in the Small Magellanic Cloud. Observations made at epochs near periastron and apastron, when the pulsar was at distances of similar to 4 and similar to 34 stellar radii from its B1 V star companion, respectively, reveal no significant frequency dependence of the observed pulse-arrival times, implying a 3 sigma upper limit to variations of the integrated electron density along the line of sight of Delta DM < 0.9 pc cm(-3). Using simple geometric arguments we infer a 3 sigma upper limit to the ionized component of the B-star mass outflow of M < 3.4 x 10(-11)(upsilon(infinity)/upsilon(esc)) M(circle dot) yr(-1). This is the first constraint on a main-sequence B-star wind in the SMC and provides evidence in favor of the predicted metallicity dependence of models of radiation-driven winds in luminous stars. C1 AARHUS UNIV,INST PHYS & ASTRON,DK-8000 AARHUS C,DENMARK. CSIRO,AUSTRALIA TELESCOPE NATL FACIL,EPPING,NSW 2121,AUSTRALIA. RP Kaspi, VM (reprint author), CALTECH,JET PROP LAB,IPAC,4800 OAK GROVE DR,PASADENA,CA 91125, USA. NR 32 TC 14 Z9 14 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 MAR 10 PY 1996 VL 459 IS 2 BP 717 EP 720 DI 10.1086/176936 PN 1 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA TX195 UT WOS:A1996TX19500033 ER PT J AU Linnell, AP Hubeny, I Lacy, CHS AF Linnell, AP Hubeny, I Lacy, CHS TI EE Pegasi revisited: A spectrum synthesis and new light synthesis study SO ASTROPHYSICAL JOURNAL LA English DT Article DE binaries, eclipsing; stars, evolution; stars, individual (EE Pegasi) ID MODEL STELLAR ATMOSPHERES; ECLIPSING BINARIES; SYNTHESIS PROGRAM; MAIN-SEQUENCE; STARS; MASSES; SCALE; GRIDS AB A self-consistent physical model, described in an earlier paper by Linnell & Hubeny, has permitted fits of synthetic spectra to observed spectra of EE Pegasi. The synthetic spectra determine abundances for iron, calcium, and silicon. The same model has been the basis of an optimized light synthesis solution of an accurate light curve by Ebbighausen. The solution, requiring use of a model atmospheres option to represent the component star radiative properties, agrees with the standard solution by Lacy & Popper. The derived component parameters place them on an isochrone, determine a compositional Z, and are in accordance with evolution tracks by Schaller et al. The model is not restricted to systems with small distortion. C1 NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. UNIV ARKANSAS,DEPT PHYS,FAYETTEVILLE,AR 72701. RP Linnell, AP (reprint author), MICHIGAN STATE UNIV,DEPT PHYS & ASTRON,E LANSING,MI 48824, USA. NR 35 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 MAR 10 PY 1996 VL 459 IS 2 BP 721 EP 728 DI 10.1086/176937 PN 1 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA TX195 UT WOS:A1996TX19500034 ER PT J AU Wolff, CL AF Wolff, CL TI Convection: Periodic due to r-modes SO ASTROPHYSICAL JOURNAL LA English DT Article DE convection; hydrodynamics; stars, oscillations; Sun, oscillations ID ROTATING STAR; SOLAR AB Convection in a rotating fluid can acquire a periodic component where the convective timescale becomes comparable to or longer than the rotation period. Then, each local convective event becomes a source of Rossby-like oscillations. They carry off information that, in a spherical shell, can sum much later to stimulate an echo of the initial convective event. The two series of echos most likely to be detectable occur at intervals of six and 30 rotation periods and apply To events of large horizontal size. The waves can also impose other periodicities on the convection, and about a dozen in the range 75-800 days are clearly identified by comparing known regularities in solar activity with theoretical beat frequencies of global oscillations (r-modes). RP Wolff, CL (reprint author), NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771, USA. NR 21 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 MAR 10 PY 1996 VL 459 IS 2 BP L103 EP L106 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA TX196 UT WOS:A1996TX19600015 ER PT J AU Mattikalli, NM Devereux, BJ Richards, KS AF Mattikalli, NM Devereux, BJ Richards, KS TI Prediction of river discharge and surface water quality using an integrated geographical information system approach SO INTERNATIONAL JOURNAL OF REMOTE SENSING LA English DT Article AB A methodology is developed for the prediction of river discharge and surface water quality (indexed by nitrogen loading) of a predominantly rural catchment using simple models in an integrated Geographical Information System (GIS). River discharge is predicted using the Soil Conservation Service (SCS) runoff Curve Number model, and surface water quality by the export coefficient model. Main input variable to these models is information on land-use along with ancillary information such as soils. Land-use is an important parameter that affects both discharge and water quality, and it can be derived from classification of remotely sensed images. Unlike conventional models, the models employed here do not require large amounts of data on several hydro-meteorological variables. The models are applied to a rural catchment in eastern England where major land-use changes have occurred in the recent past. Historical land-use data are derived from a variety of sources including maps, aerial photographs and remotely sensed satellite images for various dates ranging from 1931 to 1989. A GIS is a valuable means to enable large amounts of spatial data to be integrated, and to facilitate data manipulation for the specific application of the models. Results are validated using observed runoff and water quality records, and it is shown that the model predictions are of acceptable accuracy. This study demonstrated an application of a GIS to employ simple models to predict river discharge and water quality. C1 UNIV CAMBRIDGE,DEPT GEOG,CAMBRIDGE CB2 3EN,ENGLAND. RP Mattikalli, NM (reprint author), NASA,GODDARD SPACE FLIGHT CTR,LAB HYDROSPHER PROC,HYDROL SCI BRANCH,CODE 974,GREENBELT,MD 20771, USA. NR 39 TC 16 Z9 16 U1 1 U2 4 PU TAYLOR & FRANCIS LTD PI LONDON PA ONE GUNDPOWDER SQUARE, LONDON, ENGLAND EC4A 3DE SN 0143-1161 J9 INT J REMOTE SENS JI Int. J. Remote Sens. PD MAR 10 PY 1996 VL 17 IS 4 BP 683 EP 701 PG 19 WC Remote Sensing; Imaging Science & Photographic Technology SC Remote Sensing; Imaging Science & Photographic Technology GA UC012 UT WOS:A1996UC01200004 ER PT J AU Leonard, CL McClain, CR AF Leonard, CL McClain, CR TI Assessment of interannual variation (1979-1986) in pigment concentrations in the tropical Pacific using the CZCS SO INTERNATIONAL JOURNAL OF REMOTE SENSING LA English DT Article ID 1982-83 EL-NINO; OCEAN; ATLANTIC AB Coastal Zone Color Scanner (CZCS) pigment concentrations, sea surface temperature, and sea level from 1979 through to mid-1986 in the tropical Pacific are examined. The relationships among surface pigment concentration, sea surface temperature and sea level during the Fl Nino/Southern Oscillation event of 1982-83 exhibit marked zonal variations. Sea level in the western and central Pacific decreased dramatically during the autumn of 1982 with both north-to-south and west-to-east time lags and corresponding increases in pigment concentrations. There was no apparent relationship between sea surface temperature and pigment in the Warm Pool. In contrast, sea surface temperature increases in the eastern Pacific along the Peruvian coast and the Galapagos Islands coincided with pronounced increases in sea level and decreases in surface pigment concentrations. Across the entire basin, pigment variability was linked to sea level height, and, presumably, thermocline depth with an inverse relationship between sea level and pigment occurring on both sides of the Pacific. C1 NASA, GODDARD SPACE FLIGHT CTR, LAB HYDROSPHER PROC, GREENBELT, MD 20771 USA. RP Leonard, CL (reprint author), UNIV MARYLAND, MARINE ESTUARINE ENVIRONM SCI GRAD PROGRAM, COLLEGE PK, MD 20742 USA. NR 35 TC 22 Z9 22 U1 0 U2 2 PU TAYLOR & FRANCIS LTD PI ABINGDON PA 4 PARK SQUARE, MILTON PARK, ABINGDON OX14 4RN, OXON, ENGLAND SN 0143-1161 J9 INT J REMOTE SENS JI Int. J. Remote Sens. PD MAR 10 PY 1996 VL 17 IS 4 BP 721 EP 732 PG 12 WC Remote Sensing; Imaging Science & Photographic Technology SC Remote Sensing; Imaging Science & Photographic Technology GA UC012 UT WOS:A1996UC01200006 ER PT J AU Blackburn, HM Mansour, NN Cantwell, BJ AF Blackburn, HM Mansour, NN Cantwell, BJ TI Topology of fine-scale motions in turbulent channel flow SO JOURNAL OF FLUID MECHANICS LA English DT Article ID LOW-REYNOLDS-NUMBER; HOMOGENEOUS ISOTROPIC TURBULENCE; VELOCITY-GRADIENT TENSOR; WALL TURBULENCE; BOUNDARY-LAYERS; FLOW; VORTICITY; FIELDS; SIMULATION; ALIGNMENT AB An investigation of topological features of the velocity gradient field of turbulent channel flow has been carried out using results from a direct numerical simulation for which the Reynolds number based on the channel half-width and the centreline velocity was 7860. Plots of the joint probability density functions of the invariants of the rate of strain and velocity gradient tensors indicated that away from the wall region, the fine-scale motions in the flow have many characteristics in common with a variety of other turbulent and transitional flows: the intermediate principal strain rate tended to be positive at sites of high viscous dissipation of kinetic energy, while the invariants of the velocity gradient tensor showed that a preference existed for stable focus/stretching and unstable node/saddle/saddle topologies. Visualization of regions in the flow with stable focus/stretching topologies revealed arrays of discrete downstream-leaning flow structures which originated near the wall and penetrated into the outer region of the flow. In all regions of the flow, there was a strong preference for the vorticity to be aligned with the intermediate principal strain rate direction, with the effect increasing near the walls in response to boundary conditions. C1 MONASH UNIV, DEPT MECH ENGN, CLAYTON, VIC 3168, AUSTRALIA. NASA, AMES RES CTR, MOFFETT FIELD, CA 94035 USA. STANFORD UNIV, DEPT AERONAUT & ASTRONAUT, STANFORD, CA 94305 USA. RI Blackburn, Hugh/C-5898-2008 OI Blackburn, Hugh/0000-0003-3469-5237 NR 35 TC 127 Z9 127 U1 0 U2 11 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 MAR 10 PY 1996 VL 310 BP 269 EP 292 DI 10.1017/S0022112096001802 PG 24 WC Mechanics; Physics, Fluids & Plasmas SC Mechanics; Physics GA UB754 UT WOS:A1996UB75400010 ER PT J AU Smrekar, SE Parmentier, EM AF Smrekar, SE Parmentier, EM TI The interaction of mantle plumes with surface thermal and chemical boundary layers: Applications to hotspots on Venus SO JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH LA English DT Article ID LOW-VISCOSITY ZONE; LITHOSPHERIC FLEXURE; HAWAIIAN VOLCANISM; APHRODITE TERRA; GEOID ANOMALIES; FLOOD BASALTS; EISTLA REGIO; HOT-SPOT; TECTONICS; SWELLS AB Large volcanic swells on Venus are believed to be a manifestation of mantle upwelling, or hotspots. The study of these regions provides important information on the interior of the planet. Numerical experiments are carried out to examine the interaction of mantle plumes with the thermal lithosphere and a layer of depleted mantle, a product of pressure-release melting, using an axisymmetric finite element and finite difference code that incorporates temperature-dependent viscosity and pressure-release melting. The lithosphere is defined as a high-viscosity lid; plumes are initiated and maintained by a prescribed temperature at the base of the computational domain The topographic uplift, the geoid-to-topography ratio, and the volume of pressure-release melt are compared to estimated values for possible hotspots on Venus to constrain the properties of plumes and the lithosphere. The effects of lithospheric thickness, depleted layer viscosity and thickness, mantle temperature, and plume temperature and duration on the surface observables are predicted. Models with a thermal lithospheric thickness of approximately 100-150 km are consistent with observations, assuming a mantle temperature of 1300 degrees C, a maximum plume temperature of approximately 1500 degrees C, and mantle plume durations of 150-250 m.y. To be consistent with estimated volumes of volcanics at Venusian hotspots, a significantly thinner thermal lithosphere requires a much cooler mantle; a thicker lithosphere requires a hotter mantle. Models with a depleted layer thickness of 100-250 km, in addition to a 100-km thick thermal lithosphere, predict the range of parameters found on Venus. Interpretation of large volcanic swells on Venus based on the evolutionary sequence predicted here implies that Beta, Atla, Western Eistla, and Imdr Regiones overlie either active or recently active mantle plumes. The geoid-to-topography ratio at Beta Regio is much larger than values found at other hotspots and may indicate that it is in an early stage of evolution or that the chemical or thermal boundary layers are significantly thicker. Bell, Dione, and Themis Regiones appear to represent very late stage, possibly now extinct, hotspots. An estimate of the total plume buoyancy flux for Venus is much lower than the value obtained for Earth. The small areal distribution of volcanism is consistent with a low level of ongoing resurfacing at a few active hotspots. C1 BROWN UNIV, DEPT GEOL SCI, PROVIDENCE, RI 02912 USA. RP Smrekar, SE (reprint author), CALTECH, JET PROP LAB, 4800 OAK GROVE DR, MS 183-501, PASADENA, CA 91109 USA. NR 67 TC 48 Z9 50 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 MAR 10 PY 1996 VL 101 IS B3 BP 5397 EP 5410 DI 10.1029/95JB02877 PG 14 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA UA372 UT WOS:A1996UA37200001 ER PT J AU Zuber, MT Parmentier, EM AF Zuber, MT Parmentier, EM TI Finite amplitude folding of a continuously viscosity-stratified lithosphere SO JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH LA English DT Article ID CENTRAL INDIAN-OCEAN; INTRAPLATE DEFORMATION; SPREADING RATE; PLATE; TECTONICS; RHEOLOGY; LAYER; INSTABILITIES; COMPRESSION; DEPENDENCE AB We study the development of finite amplitude folding of the lithosphere through the application of finite element models characterized by both discontinuous (layer over half-space) and continuous (strength envelope) viscosity distributions. Both models include strongly strain rate-dependent rheologies that approximate slip on pervasive faults. Folding with layers of uniform, contrasting viscosities is driven solely by the magnitudes of discontinuities in viscosity at layer interfaces; however, folds may also develop in a medium with a continuously varying viscosity distribution. The net driving force for folding in a region of continuous viscosity variation is the same as the driving force across a discontinuity with the same net viscosity contrast. Continuous and discontinuous viscosity variations give essentially identical fold growth rates if the depth over which the viscosity varies is small compared to the wavelength of folding or the depth of the viscosity variation. In the uniform viscosity layer model, flexural bending of the layer results in a state of extension on topographic highs and compression in topographic lows. In contrast, the strength envelope model is characterized by significant penetrative shortening near the surface that results in a state of compression everywhere along the fold. This model predicts layer thickening beneath fold troughs, as observed in the intraplate deformation zone in the central Indian Ocean. Buoyancy forces retard the rate of fold amplification but are inadequate to prevent folding for a range of realistic lithospheric rheological structures. C1 JOHNS HOPKINS UNIV, DEPT EARTH & PLANETARY SCI, BALTIMORE, MD 21218 USA. BROWN UNIV, DEPT GEOL SCI, PROVIDENCE, RI 02912 USA. NASA, GODDARD SPACE FLIGHT CTR, TERR PHYS LAB, GREENBELT, MD 20771 USA. NR 52 TC 27 Z9 27 U1 2 U2 4 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-9313 EI 2169-9356 J9 J GEOPHYS RES-SOL EA JI J. Geophys. Res.-Solid Earth PD MAR 10 PY 1996 VL 101 IS B3 BP 5489 EP 5498 DI 10.1029/95JB02514 PG 10 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA UA372 UT WOS:A1996UA37200008 ER PT J AU Wade, CE Vernikos, J Ertl, AC AF Wade, CE Vernikos, J Ertl, AC TI Diurnal and gender differences in hormonal responses to passive standing. SO FASEB JOURNAL 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 FEDERATION AMER SOC EXP BIOL PI BETHESDA PA 9650 ROCKVILLE PIKE, BETHESDA, MD 20814-3998 SN 0892-6638 J9 FASEB J JI Faseb J. PD MAR 8 PY 1996 VL 10 IS 3 BP 109 EP 109 PG 1 WC Biochemistry & Molecular Biology; Biology; Cell Biology SC Biochemistry & Molecular Biology; Life Sciences & Biomedicine - Other Topics; Cell Biology GA TZ284 UT WOS:A1996TZ28400108 ER PT J AU Gretebeck, RJ Schoeller, DA DavisStreet, JE Socki, RA Gibson, EK Lane, HW AF Gretebeck, RJ Schoeller, DA DavisStreet, JE Socki, RA Gibson, EK Lane, HW TI Use of the deuterium oxide method for measuring water intake during space flight. SO FASEB JOURNAL LA English DT Meeting Abstract C1 PURDUE UNIV,W LAFAYETTE,IN 47907. NASA,LYNDON B JOHNSON SPACE CTR,LOCKHEED MARTIN,KRUG LIFE SCI,HOUSTON,TX 77058. UNIV CHICAGO,CHICAGO,IL 60637. NR 0 TC 0 Z9 0 U1 0 U2 0 PU FEDERATION AMER SOC EXP BIOL PI BETHESDA PA 9650 ROCKVILLE PIKE, BETHESDA, MD 20814-3998 SN 0892-6638 J9 FASEB J JI Faseb J. PD MAR 8 PY 1996 VL 10 IS 3 BP 1147 EP 1147 PG 1 WC Biochemistry & Molecular Biology; Biology; Cell Biology SC Biochemistry & Molecular Biology; Life Sciences & Biomedicine - Other Topics; Cell Biology GA TZ284 UT WOS:A1996TZ28401147 ER PT J AU Lane, HW Alfrey, CP Morukov, BV Larina, IM Driscoll, TB Smith, SM AF Lane, HW Alfrey, CP Morukov, BV Larina, IM Driscoll, TB Smith, SM TI Red blood cell mass decreases during extended duration space flight SO FASEB JOURNAL LA English DT Meeting Abstract C1 NASA,LYNDON B JOHNSON SPACE CTR,BAYLOR COLL MED,HOUSTON,TX 77058. INST BIOMED PROBLEMS,MOSCOW,RUSSIA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU FEDERATION AMER SOC EXP BIOL PI BETHESDA PA 9650 ROCKVILLE PIKE, BETHESDA, MD 20814-3998 SN 0892-6638 J9 FASEB J JI Faseb J. PD MAR 8 PY 1996 VL 10 IS 3 BP 1683 EP 1683 PG 1 WC Biochemistry & Molecular Biology; Biology; Cell Biology SC Biochemistry & Molecular Biology; Life Sciences & Biomedicine - Other Topics; Cell Biology GA TZ284 UT WOS:A1996TZ28401684 ER PT J AU Hanson, CW Marshall, C Medsker, C Frasch, F Ehrhart, L Marshall, BE AF Hanson, CW Marshall, C Medsker, C Frasch, F Ehrhart, L Marshall, BE TI A graphical display of clinical cardiopulmonary data SO FASEB JOURNAL LA English DT Meeting Abstract C1 UNIV PENN,AMES RES CTR,DEPT ANESTHESIA,PHILADELPHIA,PA. DREXEL UNIV,PHILADELPHIA,PA 19104. NR 0 TC 1 Z9 1 U1 0 U2 0 PU FEDERATION AMER SOC EXP BIOL PI BETHESDA PA 9650 ROCKVILLE PIKE, BETHESDA, MD 20814-3998 SN 0892-6638 J9 FASEB J JI Faseb J. PD MAR 8 PY 1996 VL 10 IS 3 BP 1698 EP 1698 PG 1 WC Biochemistry & Molecular Biology; Biology; Cell Biology SC Biochemistry & Molecular Biology; Life Sciences & Biomedicine - Other Topics; Cell Biology GA TZ284 UT WOS:A1996TZ28401697 ER PT J AU Graves, AR Yelle, JM Smith, ML AF Graves, AR Yelle, JM Smith, ML TI Effect of brief preconditioning on carotid baroreflex control or R-R interval. SO FASEB JOURNAL LA English DT Meeting Abstract C1 NASA,LYNDON B JOHNSON SPACE CTR,HOUSTON,TX 77058. CASE WESTERN RESERVE UNIV,CLEVELAND,OH 44106. NR 0 TC 0 Z9 0 U1 0 U2 0 PU FEDERATION AMER SOC EXP BIOL PI BETHESDA PA 9650 ROCKVILLE PIKE, BETHESDA, MD 20814-3998 SN 0892-6638 J9 FASEB J JI Faseb J. PD MAR 8 PY 1996 VL 10 IS 3 BP 1955 EP 1955 PG 1 WC Biochemistry & Molecular Biology; Biology; Cell Biology SC Biochemistry & Molecular Biology; Life Sciences & Biomedicine - Other Topics; Cell Biology GA TZ284 UT WOS:A1996TZ28401957 ER PT J AU Gosselink, KL Grindeland, RE Roy, RR Zhong, VH Bigbee, AJ Edgerton, VR AF Gosselink, KL Grindeland, RE Roy, RR Zhong, VH Bigbee, AJ Edgerton, VR TI Growth hormone-like factor (GHLF) release from rat pituitary following activation of Ia afferents from fast hindlimb muscles. SO FASEB JOURNAL LA English DT Meeting Abstract C1 UNIV CALIF LOS ANGELES,DEPT PHYSIOL SCI,LOS ANGELES,CA 90095. UNIV CALIF LOS ANGELES,BRAIN RES INST,LOS ANGELES,CA 90095. NASA,AMES RES CTR,MOFFETT FIELD,CA 94035. NR 0 TC 3 Z9 3 U1 0 U2 0 PU FEDERATION AMER SOC EXP BIOL PI BETHESDA PA 9650 ROCKVILLE PIKE, BETHESDA, MD 20814-3998 SN 0892-6638 J9 FASEB J JI Faseb J. PD MAR 8 PY 1996 VL 10 IS 3 BP 2217 EP 2217 PG 1 WC Biochemistry & Molecular Biology; Biology; Cell Biology SC Biochemistry & Molecular Biology; Life Sciences & Biomedicine - Other Topics; Cell Biology GA TZ284 UT WOS:A1996TZ28402216 ER PT J AU Smith, SM Oranov, VS Morukov, BV Larina, IM Nillen, JL Lane, HW AF Smith, SM Oranov, VS Morukov, BV Larina, IM Nillen, JL Lane, HW TI Calcium homeostasis during extended-duration space flight. SO FASEB JOURNAL LA English DT Meeting Abstract C1 MOSCOW BIOMED PROBLEMS INST,MOSCOW,RUSSIA. KRUG LIFE SCI,HOUSTON,TX. NASA,LYNDON B JOHNSON SPACE CTR,HOUSTON,TX 77058. NR 0 TC 2 Z9 2 U1 0 U2 0 PU FEDERATION AMER SOC EXP BIOL PI BETHESDA PA 9650 ROCKVILLE PIKE, BETHESDA, MD 20814-3998 SN 0892-6638 J9 FASEB J JI Faseb J. PD MAR 8 PY 1996 VL 10 IS 3 BP 2702 EP 2702 PG 1 WC Biochemistry & Molecular Biology; Biology; Cell Biology SC Biochemistry & Molecular Biology; Life Sciences & Biomedicine - Other Topics; Cell Biology GA TZ284 UT WOS:A1996TZ28402703 ER PT J AU Baer, L Corbin, B Vasques, M Grindeland, RE AF Baer, L Corbin, B Vasques, M Grindeland, RE TI Effects of elevated humidity and temperature on growth of mice due to the use of microisolator tops SO FASEB JOURNAL LA English DT Meeting Abstract C1 NASA,AMES RES CTR,MOFFETT FIELD,CA 94035. GB TECH,HOUSTON,TX 77058. NR 0 TC 0 Z9 0 U1 0 U2 0 PU FEDERATION AMER SOC EXP BIOL PI BETHESDA PA 9650 ROCKVILLE PIKE, BETHESDA, MD 20814-3998 SN 0892-6638 J9 FASEB J JI Faseb J. PD MAR 8 PY 1996 VL 10 IS 3 BP 2959 EP 2959 PG 1 WC Biochemistry & Molecular Biology; Biology; Cell Biology SC Biochemistry & Molecular Biology; Life Sciences & Biomedicine - Other Topics; Cell Biology GA TZ284 UT WOS:A1996TZ28402957 ER PT J AU Ballard, RE Watenpaugh, DE Breit, GA Murthy, BG Hargens, AR AF Ballard, RE Watenpaugh, DE Breit, GA Murthy, BG Hargens, AR TI Intramuscular pressures in the human soleus during walking and running. SO FASEB JOURNAL LA English DT Meeting Abstract C1 NASA,AMES RES CTR,GRAVITAT RES BRANCH,MOFFETT FIELD,CA 94035. NR 0 TC 0 Z9 0 U1 0 U2 0 PU FEDERATION AMER SOC EXP BIOL PI BETHESDA PA 9650 ROCKVILLE PIKE, BETHESDA, MD 20814-3998 SN 0892-6638 J9 FASEB J JI Faseb J. PD MAR 8 PY 1996 VL 10 IS 3 BP 3157 EP 3157 PG 1 WC Biochemistry & Molecular Biology; Biology; Cell Biology SC Biochemistry & Molecular Biology; Life Sciences & Biomedicine - Other Topics; Cell Biology GA TZ284 UT WOS:A1996TZ28403156 ER PT J AU Williams, WJ Lee, SMC Fortney, SM Stuart, CA Whitson, PA AF Williams, WJ Lee, SMC Fortney, SM Stuart, CA Whitson, PA TI Cardiovascular responses to LBNP following bed rest: The effects of dietary sodium SO FASEB JOURNAL LA English DT Meeting Abstract C1 NASA,LYNDON B JOHNSON SPACE CTR,KRUG LIFE SCI,HOUSTON,TX 77058. UNIV TEXAS,MED BRANCH,GALVESTON,TX 77555. NR 0 TC 0 Z9 0 U1 0 U2 0 PU FEDERATION AMER SOC EXP BIOL PI BETHESDA PA 9650 ROCKVILLE PIKE, BETHESDA, MD 20814-3998 SN 0892-6638 J9 FASEB J JI Faseb J. PD MAR 8 PY 1996 VL 10 IS 3 BP 3298 EP 3298 PG 1 WC Biochemistry & Molecular Biology; Biology; Cell Biology SC Biochemistry & Molecular Biology; Life Sciences & Biomedicine - Other Topics; Cell Biology GA TZ284 UT WOS:A1996TZ28403296 ER PT J AU Watenpaugh, DE Ballard, RE Boda, WL Chang, DS LooftWilson, R Hargens, AR AF Watenpaugh, DE Ballard, RE Boda, WL Chang, DS LooftWilson, R Hargens, AR TI Does supine LBNP treadmill exercise simulate upright treadmill exercise? SO FASEB JOURNAL LA English DT Meeting Abstract C1 NASA,AMES RES CTR,GRAVITAT RES BRANCH,MOFFETT FIELD,CA 94035. NR 0 TC 0 Z9 0 U1 0 U2 0 PU FEDERATION AMER SOC EXP BIOL PI BETHESDA PA 9650 ROCKVILLE PIKE, BETHESDA, MD 20814-3998 SN 0892-6638 J9 FASEB J JI Faseb J. PD MAR 8 PY 1996 VL 10 IS 3 BP 3299 EP 3299 PG 1 WC Biochemistry & Molecular Biology; Biology; Cell Biology SC Biochemistry & Molecular Biology; Life Sciences & Biomedicine - Other Topics; Cell Biology GA TZ284 UT WOS:A1996TZ28403299 ER PT J AU Moore, AD Lee, SMC Charles, JB Fortney, SM Greenisen, MC AF Moore, AD Lee, SMC Charles, JB Fortney, SM Greenisen, MC TI Maximal exercise 24-48 hours prior to landing does not affect stand test results following space flight SO FASEB JOURNAL LA English DT Meeting Abstract C1 NASA,LYNDON B JOHNSON SPACE CTR,KRUG LIFE SCI,HOUSTON,TX 77058. NR 0 TC 0 Z9 0 U1 0 U2 1 PU FEDERATION AMER SOC EXP BIOL PI BETHESDA PA 9650 ROCKVILLE PIKE, BETHESDA, MD 20814-3998 SN 0892-6638 J9 FASEB J JI Faseb J. PD MAR 8 PY 1996 VL 10 IS 3 BP 3300 EP 3300 PG 1 WC Biochemistry & Molecular Biology; Biology; Cell Biology SC Biochemistry & Molecular Biology; Life Sciences & Biomedicine - Other Topics; Cell Biology GA TZ284 UT WOS:A1996TZ28403300 ER PT J AU Siconolfi, SF Koslovskaya, IB Layne, C Koriak, Y Gilbert, JH AF Siconolfi, SF Koslovskaya, IB Layne, C Koriak, Y Gilbert, JH TI Neuromuscular performance in crewmembers after a 115-day space flight SO FASEB JOURNAL LA English DT Meeting Abstract C1 NASA,MOTOR PERFORMANCE LAB,HOUSTON,TX 77058. KRUG LIFE SCI,HOUSTON,TX. INST BIOMED PROBLEMS,MOSCOW,RUSSIA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU FEDERATION AMER SOC EXP BIOL PI BETHESDA PA 9650 ROCKVILLE PIKE, BETHESDA, MD 20814-3998 SN 0892-6638 J9 FASEB J JI Faseb J. PD MAR 8 PY 1996 VL 10 IS 3 BP 3301 EP 3301 PG 1 WC Biochemistry & Molecular Biology; Biology; Cell Biology SC Biochemistry & Molecular Biology; Life Sciences & Biomedicine - Other Topics; Cell Biology GA TZ284 UT WOS:A1996TZ28403303 ER PT J AU Lee, SMC Williams, WJ Siconolfi, SF Gonzalez, R Greenleaf, JE Mikhaylov, V Kobzev, Y Fortney, SM AF Lee, SMC Williams, WJ Siconolfi, SF Gonzalez, R Greenleaf, JE Mikhaylov, V Kobzev, Y Fortney, SM TI Temperature regulation in crewmembers after a 115-day space flight SO FASEB JOURNAL LA English DT Meeting Abstract C1 NASA,LYNDON B JOHNSON SPACE CTR,HOUSTON,TX 77058. KRUG LIFE SCI INC,HOUSTON,TX. NASA,AMES RES CTR,MOFFETT FIELD,CA 94035. USARIEM,NATICK,MA. INST BIOMED PROBLEMS,MOSCOW,RUSSIA. GAGARIN COSMONAUT TRAINING CTR,STAR CITY,RUSSIA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU FEDERATION AMER SOC EXP BIOL PI BETHESDA PA 9650 ROCKVILLE PIKE, BETHESDA, MD 20814-3998 SN 0892-6638 J9 FASEB J JI Faseb J. PD MAR 8 PY 1996 VL 10 IS 3 BP 3302 EP 3302 PG 1 WC Biochemistry & Molecular Biology; Biology; Cell Biology SC Biochemistry & Molecular Biology; Life Sciences & Biomedicine - Other Topics; Cell Biology GA TZ284 UT WOS:A1996TZ28403301 ER PT J AU Clarke, MSF Feeback, DL AF Clarke, MSF Feeback, DL TI Mechanically-induced membrane wounding during parabolic flight SO FASEB JOURNAL LA English DT Meeting Abstract C1 NASA,LYNDON B JOHNSON SPACE CTR,BIOMED OPERAT & RES BRANCH,HOUSTON,TX 77058. NR 0 TC 0 Z9 0 U1 0 U2 0 PU FEDERATION AMER SOC EXP BIOL PI BETHESDA PA 9650 ROCKVILLE PIKE, BETHESDA, MD 20814-3998 SN 0892-6638 J9 FASEB J JI Faseb J. PD MAR 8 PY 1996 VL 10 IS 3 BP 3304 EP 3304 PG 1 WC Biochemistry & Molecular Biology; Biology; Cell Biology SC Biochemistry & Molecular Biology; Life Sciences & Biomedicine - Other Topics; Cell Biology GA TZ284 UT WOS:A1996TZ28403302 ER PT J AU Navidi, M Evans, J LooftWilson, R Wolinsky, I Arnaud, SB AF Navidi, M Evans, J LooftWilson, R Wolinsky, I Arnaud, SB TI Effect of dietary calcium on salt-induced calciuria in mature rats exposed to a space flight model. SO FASEB JOURNAL LA English DT Meeting Abstract C1 NASA,AMES RES CTR,MOFFETT FIELD,CA 94035. UNIV HOUSTON,HOUSTON,TX 77204. NR 0 TC 0 Z9 0 U1 0 U2 0 PU FEDERATION AMER SOC EXP BIOL PI BETHESDA PA 9650 ROCKVILLE PIKE, BETHESDA, MD 20814-3998 SN 0892-6638 J9 FASEB J JI Faseb J. PD MAR 8 PY 1996 VL 10 IS 3 BP 3307 EP 3307 PG 1 WC Biochemistry & Molecular Biology; Biology; Cell Biology SC Biochemistry & Molecular Biology; Life Sciences & Biomedicine - Other Topics; Cell Biology GA TZ284 UT WOS:A1996TZ28403309 ER PT J AU Wang, TJ Lang, CK Corbin, BJ Wade, CE AF Wang, TJ Lang, CK Corbin, BJ Wade, CE TI Effects of elevated ambient CO2 on well-being, growth and renal function of hindlimb suspended rats SO FASEB JOURNAL LA English DT Meeting Abstract C1 GB TECH INC,HOUSTON,TX 77058. NASA,AMES RES CTR,MOFFETT FIELD,CA 94035. NR 0 TC 0 Z9 0 U1 0 U2 0 PU FEDERATION AMER SOC EXP BIOL PI BETHESDA PA 9650 ROCKVILLE PIKE, BETHESDA, MD 20814-3998 SN 0892-6638 J9 FASEB J JI Faseb J. PD MAR 8 PY 1996 VL 10 IS 3 BP 3308 EP 3308 PG 1 WC Biochemistry & Molecular Biology; Biology; Cell Biology SC Biochemistry & Molecular Biology; Life Sciences & Biomedicine - Other Topics; Cell Biology GA TZ284 UT WOS:A1996TZ28403307 ER PT J AU Ortiz, RM Wade, CE AF Ortiz, RM Wade, CE TI Effects of habituated restraint en primates on urinary cortisol. SO FASEB JOURNAL LA English DT Meeting Abstract C1 NASA,AMES RES CTR,MOFFETT FIELD,CA 94035. LOCKHEED MARTIN,MOFFETT FIELD,CA 94035. NR 0 TC 0 Z9 0 U1 0 U2 0 PU FEDERATION AMER SOC EXP BIOL PI BETHESDA PA 9650 ROCKVILLE PIKE, BETHESDA, MD 20814-3998 SN 0892-6638 J9 FASEB J JI Faseb J. PD MAR 8 PY 1996 VL 10 IS 3 BP 3773 EP 3773 PG 1 WC Biochemistry & Molecular Biology; Biology; Cell Biology SC Biochemistry & Molecular Biology; Life Sciences & Biomedicine - Other Topics; Cell Biology GA TZ284 UT WOS:A1996TZ28403773 ER PT J AU Lang, KC Wang, TJ Alexander, RA Corbin, BJ Vasques, MF Steele, MK Wade, CE AF Lang, KC Wang, TJ Alexander, RA Corbin, BJ Vasques, MF Steele, MK Wade, CE TI Effects of 30-days of elevated ambient CO2 on acid-base homeostasis and renal handling of calcium in male rats. SO FASEB JOURNAL LA English DT Meeting Abstract C1 LOCKHEED MARTIN,GB TECH,MOFFETT FIELD,CA 94035. NASA,AMES RES CTR,MOFFETT FIELD,CA 94035. NR 0 TC 0 Z9 0 U1 0 U2 0 PU FEDERATION AMER SOC EXP BIOL PI BETHESDA PA 9650 ROCKVILLE PIKE, BETHESDA, MD 20814-3998 SN 0892-6638 J9 FASEB J JI Faseb J. PD MAR 8 PY 1996 VL 10 IS 3 BP 3795 EP 3795 PG 1 WC Biochemistry & Molecular Biology; Biology; Cell Biology SC Biochemistry & Molecular Biology; Life Sciences & Biomedicine - Other Topics; Cell Biology GA TZ284 UT WOS:A1996TZ28403794 ER PT J AU Moran, MM Alexander, RA Corbin, BJ Grindeland, RE AF Moran, MM Alexander, RA Corbin, BJ Grindeland, RE TI Influence of biotelemeter size on the physiology and behavioral patterns of rats. SO FASEB JOURNAL LA English DT Meeting Abstract C1 GB TECH,HOUSTON,TX 77058. NASA,AMES RES CTR,MOFFETT FIELD,CA 94035. NR 0 TC 0 Z9 0 U1 0 U2 0 PU FEDERATION AMER SOC EXP BIOL PI BETHESDA PA 9650 ROCKVILLE PIKE, BETHESDA, MD 20814-3998 SN 0892-6638 J9 FASEB J JI Faseb J. PD MAR 8 PY 1996 VL 10 IS 3 BP 3798 EP 3798 PG 1 WC Biochemistry & Molecular Biology; Biology; Cell Biology SC Biochemistry & Molecular Biology; Life Sciences & Biomedicine - Other Topics; Cell Biology GA TZ284 UT WOS:A1996TZ28403800 ER PT J AU Wastney, ME Smith, SM Nyquist, LE Lane, HW AF Wastney, ME Smith, SM Nyquist, LE Lane, HW TI Calcium kinetics based on stable isotope enrichment of saliva vs serum for use in space flight. SO FASEB JOURNAL LA English DT Meeting Abstract C1 GEORGETOWN UNIV,MED CTR,WASHINGTON,DC 20007. NASA,LYNDON B JOHNSON SPACE CTR,HOUSTON,TX 77058. NR 0 TC 0 Z9 0 U1 0 U2 0 PU FEDERATION AMER SOC EXP BIOL PI BETHESDA PA 9650 ROCKVILLE PIKE, BETHESDA, MD 20814-3998 SN 0892-6638 J9 FASEB J JI Faseb J. PD MAR 8 PY 1996 VL 10 IS 3 BP 4501 EP 4501 PG 1 WC Biochemistry & Molecular Biology; Biology; Cell Biology SC Biochemistry & Molecular Biology; Life Sciences & Biomedicine - Other Topics; Cell Biology GA TZ284 UT WOS:A1996TZ28404502 ER PT J AU Pohorille, A Wilson, MA AF Pohorille, A Wilson, MA TI Excess chemical potential of small solutes across water-membrane and water-hexane interfaces SO JOURNAL OF CHEMICAL PHYSICS LA English DT Article ID LIQUID WATER; MOLECULAR-DYNAMICS; BILAYER-MEMBRANES; LIPID BILAYER; GASES AB The excess chemical potentials of five small, structurally related solutes, CH4, CH3F, CH2F2, CHF3, and CF4, across the water-glycerol 1-monooleate bilayer and water-hexane interfaces were calculated at 300, 310, and 340 K using the particle insertion method. The excess chemical potentials of nonpolar molecules (CH4 and CF4) decrease monotonically or nearly monotonically from water to a nonpolar phase. In contrast, for molecules that possess permanent dipole moments (CH3F, CH2F, and CHF3), the excess chemical potentials exhibit an interfacial minimum that arises from superposition of two monotonically and oppositely changing contributions: electrostatic and nonelectrostatic. The nonelectrostatic term, dominated by the reversible work of creating a cavity that accommodates the solute, decreases, whereas the electrostatic term increases across the interface from water to the membrane interior. In water, the dependence of this term on the dipole moment is accurately described by second order perturbation theory. To achieve the same accuracy at the interface, third order terms must also be included. In the interfacial region, the molecular structure of the solvent influences both the excess chemical potential and solute orientations. The excess chemical potential across the interface increases with temperature, but this effect is rather small. Our analysis indicates that a broad range of small, moderately polar molecules should be surface active at the water-membrane and water-oil interfaces. The biological and medical significance of this result, especially in relation to the mechanism of anesthetic action, is discussed. (C) 1996 American Institute of Physics. C1 NASA,AMES RES CTR,PLANETARY BIOL BRANCH,MOFFETT FIELD,CA 94035. RP Pohorille, A (reprint author), UNIV CALIF SAN FRANCISCO,DEPT PHARMACEUT CHEM,SAN FRANCISCO,CA 94143, USA. FU NIGMS NIH HHS [GM47818-01] NR 47 TC 99 Z9 99 U1 1 U2 7 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 MAR 8 PY 1996 VL 104 IS 10 BP 3760 EP 3773 DI 10.1063/1.471030 PG 14 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA TX780 UT WOS:A1996TX78000039 PM 11539401 ER PT J AU Sellers, PJ Bounoua, L Collatz, GJ Randall, DA Dazlich, DA Los, SO Berry, JA Fung, I Tucker, CJ Field, CB Jensen, TG AF Sellers, PJ Bounoua, L Collatz, GJ Randall, DA Dazlich, DA Los, SO Berry, JA Fung, I Tucker, CJ Field, CB Jensen, TG TI Comparison of radiative and physiological effects of doubled atmospheric CO2 on climate SO SCIENCE LA English DT Article ID STOMATAL CONDUCTANCE; PHOTOSYNTHESIS; MODEL; TRANSPIRATION; LENGTH AB The physiological response of terrestrial vegetation when directly exposed to an increase in atmospheric carbon dioxide (CO2) concentration could result in warming over the continents in addition to that due to the conventional CO2 ''greenhouse effect.'' Results from a coupled biosphere-atmosphere model (SiB2-GCM) indicate that, for doubled CO2 conditions, evapotranspiration will drop and air temperature will increase over the tropical continents, amplifying the changes resulting from atmospheric radiative effects. The range of responses in surface air temperature and terrestrial carbon uptake due to increased CO2 are projected to be inversely related in the tropics year-round and inversely related during the growing season elsewhere. C1 COLORADO STATE UNIV,DEPT ATMOSPHER SCI,FT COLLINS,CO 80523. CARNEGIE INST WASHINGTON,DEPT PLANT BIOL,STANFORD,CA 94305. UNIV VICTORIA,DEPT EARTH & OCEAN SCI,VICTORIA,BC V8N 3X3,CANADA. RP Sellers, PJ (reprint author), NASA,GODDARD SPACE FLIGHT CTR,UNIV SPACE RES ASSOC,CODE 923,GREENBELT,MD 20771, USA. RI Berry, Joseph/B-8211-2009; collatz, george/D-5381-2012; Los, Sietse/G-8985-2012; Randall, David/E-6113-2011; OI Berry, Joseph/0000-0002-5849-6438; Randall, David/0000-0001-6935-4112; Los, Sietse/0000-0002-1325-3555 NR 27 TC 337 Z9 365 U1 5 U2 49 PU AMER ASSOC ADVANCEMENT SCIENCE PI WASHINGTON PA 1200 NEW YORK AVE, NW, WASHINGTON, DC 20005 SN 0036-8075 J9 SCIENCE JI Science PD MAR 8 PY 1996 VL 271 IS 5254 BP 1402 EP 1406 DI 10.1126/science.271.5254.1402 PG 5 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA TY961 UT WOS:A1996TY96100042 ER PT J AU McEwan, MJ Fairley, DA Scott, GBI Anicich, VG AF McEwan, MJ Fairley, DA Scott, GBI Anicich, VG TI Reactions of CH3+ with C2N2, CH2CHCN, and HC3N: A low-pressure high-pressure study SO JOURNAL OF PHYSICAL CHEMISTRY LA English DT Article ID RADIATIVE ASSOCIATION; INTERSTELLAR CLOUDS; CH3+/CH3CN SYSTEM; ION; CHEMISTRY AB The association of CH3+ with the three molecules C2N2, CH2CHCN, and HCCCN has been examined using ion cyclotron resonance (ICR) and selected ion flow tube (SIFT) techniques at room temperature. In each reaction, the mean lifetime of the complex (CH3 . N=C-R(+))* formed in the association has a major influence on the outcome of the reaction and the product channels that are observed using ICR and SIFT. Termolecular rate coefficients are reported for the association of CH3+ + C2N2 for the bath gases M = He, Ar, N-2, and C2N2. k(3) = 8.2 x 10(-24) cm(6) s(-1) (M = C2N2). In each system the association product channel occurs in competition with exothermic bimolecular channels. The complex lifetimes in all three systems are in the range 30-70 mu s. Very rapid ion-molecule association reactions have been observed in several systems of hydrocarbons and nitriles, and the implications for Titan ion chemistry are discussed briefly. C1 CALTECH,JET PROP LAB,PASADENA,CA 91109. NR 26 TC 8 Z9 8 U1 0 U2 1 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 SN 0022-3654 J9 J PHYS CHEM-US JI J. Phys. Chem. PD MAR 7 PY 1996 VL 100 IS 10 BP 4032 EP 4037 DI 10.1021/jp9525954 PG 6 WC Chemistry, Physical SC Chemistry GA TY919 UT WOS:A1996TY91900023 ER PT J AU Good, BS Banerjea, A AF Good, BS Banerjea, A TI Simulation of tip-sample interaction in the atomic force microscope SO JOURNAL OF PHYSICS-CONDENSED MATTER LA English DT Article ID EQUIVALENT-CRYSTAL THEORY; DEFECTS AB Recent simulations of the interaction between planar surfaces and model atomic force microscope (AFM) tips have suggested that there are conditions under which the tip may become unstable and 'avalanche' toward the sample surface. Here we investigate via computer simulation the stability of a variety of model AFM tip configurations with respect to the avalanche transition for a number of fee metals. We perform Monte Carlo simulations at room temperature using the equivalent-crystal theory (ECT) of Smith and Banerjea. Results are compared with recent experimental results as well as with our earlier work on the avalanche of parallel planar surfaces. Our results on a model single-atom tip are in excellent agreement with recent experiments on tunnelling through mechanically controlled break junctions. C1 SN BOSE NATL CTR BASIC SCI,CALCUTTA 700064,W BENGAL,INDIA. RP Good, BS (reprint author), NASA,LEWIS RES CTR,CLEVELAND,OH 44135, USA. NR 20 TC 14 Z9 14 U1 1 U2 2 PU IOP PUBLISHING LTD PI BRISTOL PA TECHNO HOUSE, REDCLIFFE WAY, BRISTOL, ENGLAND BS1 6NX SN 0953-8984 J9 J PHYS-CONDENS MAT JI J. Phys.-Condes. Matter PD MAR 4 PY 1996 VL 8 IS 10 BP 1325 EP 1333 DI 10.1088/0953-8984/8/10/005 PG 9 WC Physics, Condensed Matter SC Physics GA TZ274 UT WOS:A1996TZ27400005 ER PT J AU Kaljevic, I Patnaik, SN Hopkins, DA AF Kaljevic, I Patnaik, SN Hopkins, DA TI Three-dimensional structural analysis by the integrated force method SO COMPUTERS & STRUCTURES LA English DT Article ID FINITE-ELEMENT ANALYSIS; HYBRID-STRESS ELEMENTS; FORMULATION; BEHAVIOR AB The ''integrated force method'', which has been recently developed for analyzing structures, is extended in this paper for three-dimensional structural analysis. A general formulation to generate the stress interpolation matrix in terms of complete polynomials of the required order is developed first. The formulation is based on the definitions of stress tensor components in terms of stress functions. The stress functions are written as complete polynomials and substituted into expressions for stress components. After eliminating dependent coefficients, the expressions for stress components are obtained as complete polynomials, where coefficients are defined as generalized independent forces. Such derived components of the stress tensor identically satisfy Navier's equations of equilibrium. The resulting element matrices are invariant with respect to coordinate transformation and are free of spurious zero energy modes. The formulation provides a rational way to calculate the exact number of independent forces for the required order of approximation with complete polynomials. The reduction in the number of independent forces and its influence on the accuracy of the response are also analyzed. The stress fields derived here are next used to develop a comprehensive finite element library for the three-dimensional structural analysis using the ''integrated force method''. Elements of both tetrahedral and hexahedral shapes, capable of modeling arbitrary geometric configurations, are developed. A number of example problems with available analytical solutions are solved using the present developments and a good agreement of results with the analytical solutions is observed. The responses obtained using the ''integrated force method'' are also compared with those generated with the standard displacement method. A better overall performance of the ''integrated force method'' is observed. C1 NASA,LEWIS RES CTR,CLEVELAND,OH 44135. RP Kaljevic, I (reprint author), OHIO AEROSP INST,22800 CEDAR POINT RD,CLEVELAND,OH 44142, USA. NR 31 TC 11 Z9 11 U1 0 U2 2 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, ENGLAND OX5 1GB SN 0045-7949 J9 COMPUT STRUCT JI Comput. Struct. PD MAR 3 PY 1996 VL 58 IS 5 BP 869 EP 886 DI 10.1016/0045-7949(95)00171-C PG 18 WC Computer Science, Interdisciplinary Applications; Engineering, Civil SC Computer Science; Engineering GA TK176 UT WOS:A1996TK17600002 ER PT J AU Min, JB Tworzydlo, WW Xiques, KE AF Min, JB Tworzydlo, WW Xiques, KE TI Adaptive finite element methods for continuum damage modeling SO COMPUTERS & STRUCTURES LA English DT Article ID CONSTITUTIVE-EQUATIONS; STRATEGY AB The paper presents an application of adaptive finite element methods to the modeling of low-cycle continuum damage and life prediction of high-temperature components. The major objective is to provide automated and accurate modeling of damaged zones through adaptive mesh refinement acid adaptive time-stepping methods. The damage modeling methodology is implemented in a usual way by embedding damage evolution in the transient nonlinear solution of elasto-viscoplastic deformation problems. This nonlinear boundary-value problem is discretized by adaptive finite element methods. The automated h-adaptive mesh refinements are driven by error indicators, based on selected principal variables in the problem (stresses, nonelastic strains, damage, etc.). In the time domain, adaptive time-stepping is used, combined with a predictor-corrector time marching algorithm. The time step selection is controlled by required time accuracy. In order to take into account strong temperature dependency of material parameters, the nonlinear structural solution is coupled with thermal analyses (one-way coupling). Several test examples illustrate the importance and benefits of adaptive mesh refinements in accurate prediction of damage levels and failure time. C1 COMPUTAT MECH CO,AUSTIN,TX 78752. ADAPT RES CORP,HUNTSVILLE,AL 35805. RP Min, JB (reprint author), NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,HUNTSVILLE,AL 35812, USA. NR 24 TC 0 Z9 0 U1 0 U2 0 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, ENGLAND OX5 1GB SN 0045-7949 J9 COMPUT STRUCT JI Comput. Struct. PD MAR 3 PY 1996 VL 58 IS 5 BP 887 EP 900 DI 10.1016/0045-7949(95)00210-8 PG 14 WC Computer Science, Interdisciplinary Applications; Engineering, Civil SC Computer Science; Engineering GA TK176 UT WOS:A1996TK17600003 ER PT J AU Freeman, A Evans, DL vanZyl, JJ AF Freeman, A Evans, DL vanZyl, JJ TI SAR applications in the 21st century SO AEU-ARCHIV FUR ELEKTRONIK UND UBERTRAGUNGSTECHNIK-INTERNATIONAL JOURNAL OF ELECTRONICS AND COMMUNICATIONS LA English DT Article; Proceedings Paper CT New European Conference on Synthetic Aperture Radar (EUSAR 96) CY MAR 26-28, 1996 CL KONIGSWINTER, GERMANY SP German Def Res Lab, German Aerosp Res Estab, German Inst Elect Engineers, EUREL, URSI, IEEE, DGON DE synthetic aperture radar; radar interferometry; polarimetry; future applications AB SAR image data from a variety of spaceborne and airborne sensors will be much more commonplace in the early 21st century. Why will SAR data be used in some applications and what will it be used for? Part of the answer lies in SAR's ability to provide high-resolution imagery, independent of cloud cover or sun illumination, and in the sensitivity of radar measurements to certain physical characteristics of the area being imaged, such as surface roughness, structure, dielectric constant and, to some extent, motion. Another part of the answer is provided by the high-resolution topography and topographic change maps which can be generated using the technique of SAR interferometry. RP Freeman, A (reprint author), CALTECH,JET PROP LAB,4800 OAK GROVE DR,PASADENA,CA 91109, USA. NR 3 TC 2 Z9 2 U1 0 U2 0 PU S HIRZEL VERLAG PI STUTTGART PA POSTFACH 10 10 61, D-70 009 STUTTGART, GERMANY SN 0001-1096 J9 AEU-ARCH ELEKTRON UB JI AEU- Arch. Elektron. Ubertrag.tech.-Int. J. Electron. Commun. PD MAR PY 1996 VL 50 IS 2 BP 79 EP 84 PG 6 WC Engineering, Electrical & Electronic; Telecommunications SC Engineering; Telecommunications GA UG868 UT WOS:A1996UG86800003 ER PT J AU Smith, MW Northam, GB Drummond, JP AF Smith, MW Northam, GB Drummond, JP TI Application of absorption filter planar Doppler velocimetry to sonic and supersonic jets SO AIAA JOURNAL LA English DT Article; Proceedings Paper CT AIAA 33rd Aerospace Sciences Meeting CY JAN 09-12, 1995 CL RENO, NV SP AIAA AB An absorption filter planar Doppler velocimeter has been constructed and tested on a pressure-matched sonic jet and an overexpanded supersonic jet (M(design) = 1.9). The current system can acquire single-velocity-component single-shot planar images (15-ns exposures) at 30 Hz. A unique aspect of the system is the use of a single camera and lens, made possible by the application of an image splitter system. This development reduces the expense and experimental complexity of the technique. The most extensive of the three data sets taken comprises 1100 centerline planes of instantaneous velocity acquired in the overexpanded supersonic jet. Mean and rms velocity fields are presented for this data set; a mean centerline and a mean transverse profile are extracted and compared with profiles from a computational fluid dynamics solution generated using the LARCK computer code employing a k-epsilon turbulence model. RP Smith, MW (reprint author), NASA,LANGLEY RES CTR,HAPB GDD,MS 197,HAMPTON,VA 23681, USA. NR 14 TC 33 Z9 34 U1 0 U2 2 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 SN 0001-1452 J9 AIAA J JI AIAA J. PD MAR PY 1996 VL 34 IS 3 BP 434 EP 441 DI 10.2514/3.13086 PG 8 WC Engineering, Aerospace SC Engineering GA TZ293 UT WOS:A1996TZ29300002 ER PT J AU Baer, DS Nagali, V Furlong, ER Hanson, RK Newfield, ME AF Baer, DS Nagali, V Furlong, ER Hanson, RK Newfield, ME TI Scanned- and fixed-wavelength absorption diagnostics for combustion measurements using multiplexed diode lasers SO AIAA JOURNAL LA English DT Article; Proceedings Paper CT AIAA 33rd Aerospace Sciences Meeting CY JAN 09-12, 1995 CL RENO, NV SP AIAA ID PARAMETERS AB A multiplexed diode-laser sensor system comprising two diode lasers and fiber-optic components has been developed to nonintrusively monitor temperature and species mole fraction over a single path using both scanned- and fixed-wavelength laser absorption spectroscopy techniques. In the scanned-wavelength method, two InGaAsP lasers were current tuned at a 2-kHz rate across H2O transitions near 1343 mn and 1392 mn in the 2 nu(1) and nu(1) + nu(3) bands. Gas temperature was determined from the ratio of single-sweep integrated line intensities. Species mole fraction was determined from the measured line intensity and the calculated line strength at the measured temperature. In the fixed-wavelength method, the wavelength of each laser was fixed near the peak of each absorption feature using a computer-controlled laser Line-locking scheme. Rapid measurements of gas temperature were obtained from the determination of peak line-intensity ratios. The system was applied to measure temperature and species concentration in the postflame gases of an H-2-O-2 flame. The good agreement between the laser-based measurements obtained using scanned- and fixed-wavelength methods with those recorded with thermocouples demonstrates the flexibility and utility of the multiplexed diode-laser sensor system and the potential for rapid, continuous measurements of gasdynamic parameters in high-speed or transient flows with difficult optical access. C1 NASA,AMES RES CTR,MOFFETT FIELD,CA 94035. RP Baer, DS (reprint author), STANFORD UNIV,DEPT MECH ENGN,HIGH TEMP GASDYNAM LAB,STANFORD,CA 94305, USA. NR 8 TC 62 Z9 69 U1 2 U2 8 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 MAR PY 1996 VL 34 IS 3 BP 489 EP 493 DI 10.2514/3.13094 PG 5 WC Engineering, Aerospace SC Engineering GA TZ293 UT WOS:A1996TZ29300010 ER PT J AU Meyer, SA Sharma, SP Bershader, D Whiting, EE Exberger, RJ Gilmore, JO AF Meyer, SA Sharma, SP Bershader, D Whiting, EE Exberger, RJ Gilmore, JO TI Atomic oxygen line shape measurement at 130 nm with Raman-shifted laser SO AIAA JOURNAL LA English DT Article; Proceedings Paper CT AIAA 33rd Aerospace Sciences Meeting CY JAN 09-12, 1995 CL RENO, NV SP AIAA AB The absorption of vacuum ultraviolet light by atomic oxygen has been measured in the electric are-driven shock tube facility at NASA Ames Research Center. A probe beam is generated with a Raman shifted ArF excimer laser. By suitable tuning of the laser, absorption is measured over a range of wavelengths in the region of the P-3(1)-S-3(0) line at 130.49 nm. The Lorentzian full width at half-height due to collision broadening by atomic oxygen is measured at various wavelengths up to 1200 linewidths away from the line center. The measured linewidth is three times larger than that calculated with an established radiation code, and a possible explanation for the difference is discussed. This experiment demonstrates the viability of high order Raman shifters as light sources in impulse facilities where singnal averaging is not possible. C1 NASA,AMES RES CTR,MOFFETT FIELD,CA 94035. INST THERMOPHYS,MOFFETT FIELD,CA 94035. STANFORD UNIV,DEPT MECH ENGN,STANFORD,CA 94305. RP Meyer, SA (reprint author), STANFORD UNIV,DEPT AERONAUT & ASTRONAUT,STANFORD,CA 94305, USA. NR 23 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 MAR PY 1996 VL 34 IS 3 BP 508 EP 514 DI 10.2514/3.13097 PG 7 WC Engineering, Aerospace SC Engineering GA TZ293 UT WOS:A1996TZ29300013 ER PT J AU Dunagan, SE AF Dunagan, SE TI Long-range Schmidt-Cassegrain laser velocimeter for large wind-tunnel applications SO AIAA JOURNAL LA English DT Article; Proceedings Paper CT AIAA 33rd Aerospace Sciences Meeting CY JAN 09-12, 1995 CL RENO, NV SP AIAA AB A two-component dual-beam laser velocimeter was designed and fabricated for use in the NASA Ames 40 x 80 ft wind tunnel. The instrument design was predicated on the use of inexpensive, high-quality, Large-aperture Schmidt-Cassegrain telescope optics to perform both the Laser beam focusing and scattered Light collection functions. The instrument was configured to measure the streamwise and cross-stream components of velocity and enclosed in a streamlined optical assembly mounted on a two-dimensional traverse on the floor of the test section. The laser velocimeter probe volume was translated in the vertical direction by means of zoom optics. Coaxial backscattered light was collected through the same optical system and analyzed for Doppler shift. Single-mode polarization-maintaining fiber optics transmitted light from the remotely located laser into the optical assembly. A multimode fiber conveyed the scattered light to remotely located photodetectors. Standard frequency domain processing permitted analysis of Doppler signals with very poor signal-to-noise ratio. The system was evaluated in an optics laboratory in preparation for wind-tunnel test program applications. Sample data from this evaluation were presented as representative of the capability of the instrument. RP Dunagan, SE (reprint author), NASA,AMES RES CTR,ROTORCRAFT AEROMECH BRANCH,MOFFETT FIELD,CA 94035, USA. NR 11 TC 0 Z9 0 U1 0 U2 1 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 SN 0001-1452 J9 AIAA J JI AIAA J. PD MAR PY 1996 VL 34 IS 3 BP 515 EP 520 DI 10.2514/3.13098 PG 6 WC Engineering, Aerospace SC Engineering GA TZ293 UT WOS:A1996TZ29300014 ER PT J AU Venkatakrishnan, V AF Venkatakrishnan, V TI Perspective on unstructured grid flow solvers SO AIAA JOURNAL LA English DT Article; Proceedings Paper CT AIAA 33rd Aerospace Sciences Meeting CY JAN 09-12, 1995 CL RENO, NV SP Amer Inst Aeronaut & Astronaut ID NAVIER-STOKES EQUATIONS; COMPUTATIONAL FLUID-DYNAMICS; HYPERBOLIC CONSERVATION-LAWS; FINITE-ELEMENT FORMULATION; EULER EQUATIONS; CORRECTED TRANSPORT; CONNECTION MACHINE; DIFFERENCE-SCHEMES; ADAPTIVE MESHES; RIEMANN SOLVERS RP NASA, LANGLEY RES CTR, INST COMP APPLICAT SCI & ENGN, HAMPTON, VA 23681 USA. NR 190 TC 48 Z9 53 U1 0 U2 1 PU AMER INST AERONAUTICS ASTRONAUTICS PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091-4344 USA SN 0001-1452 EI 1533-385X J9 AIAA J JI AIAA J. PD MAR PY 1996 VL 34 IS 3 BP 533 EP 547 DI 10.2514/3.13101 PG 15 WC Engineering, Aerospace SC Engineering GA TZ293 UT WOS:A1996TZ29300017 ER PT J AU Watson, WR Jones, MG Tanner, SE Parrott, TL AF Watson, WR Jones, MG Tanner, SE Parrott, TL TI Validation of a numerical method for extracting liner impedance SO AIAA JOURNAL LA English DT Article AB We report the initial results of a test series to evaluate a method for extracting the normal incidence impedance of a locally reacting, acoustically absorbing liner located on the lower wall of a duct in a grazing incidence, multimodal, nonprogressive acoustic wave environment without flow. This initial evaluation tests the method's ability to converge to the known normal-incidence impedance of a solid steel plate, and to the normal-incidence impedance of an absorbing test specimen whose impedance has been measured In a conventional normal-incidence tube. The method converges to the normal-incident impedance values and thus is an adequate tool for extracting the impedance of specimens in a grazing-incidence, multimodal, nonprogressive acoustic wave environment for a broad range of source frequencies. C1 LOCKHEED ENGN & SCI CO,DIV RES,HAMPTON,VA 23666. RP Watson, WR (reprint author), NASA,LANGLEY RES CTR,DIV FLUID MECH & ACOUST,AERODYNAM & ACOUST METHOD BRANCH,HAMPTON,VA 23681, USA. NR 9 TC 11 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 MAR PY 1996 VL 34 IS 3 BP 548 EP 554 DI 10.2514/3.13102 PG 7 WC Engineering, Aerospace SC Engineering GA TZ293 UT WOS:A1996TZ29300018 ER PT J AU Locke, RJ Ockunzzi, KA AF Locke, RJ Ockunzzi, KA TI OH imaging in a lean burning high-pressure combustor SO AIAA JOURNAL LA English DT Article; Proceedings Paper CT AIAA 33rd Aerospace Sciences Meeting CY JAN 09-12, 1995 CL RENO, NV SP AIAA C1 NASA,LEWIS RES CTR,COMBUST TECHNOL BRANCH,CLEVELAND,OH 44135. NASA,LEWIS RES CTR,OPT MEASUREMENT SYST BRANCH,CLEVELAND,OH 44135. CASE WESTERN RESERVE UNIV,DEPT COMP ENGN,CLEVELAND,OH 44106. RP Locke, RJ (reprint author), NYMA INC,AEROPROP SYST DEPT,2001 AEROSP PKWY,BROOKPARK,OH 44142, USA. NR 6 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 0001-1452 J9 AIAA J JI AIAA J. PD MAR PY 1996 VL 34 IS 3 BP 622 EP 624 DI 10.2514/3.13113 PG 3 WC Engineering, Aerospace SC Engineering GA TZ293 UT WOS:A1996TZ29300029 ER PT J AU Murphy, TW Armus, L Matthews, K Soifer, BT Mazzarella, JM Shupe, DL Strauss, MA Neugebauer, G AF Murphy, TW Armus, L Matthews, K Soifer, BT Mazzarella, JM Shupe, DL Strauss, MA Neugebauer, G TI Visual and near-infrared imaging of ultraluminous infrared galaxies: The IRAS 2 Jy sample SO ASTRONOMICAL JOURNAL LA English DT Article ID LUMINOSITY FUNCTION; MOLECULAR-HYDROGEN; MERGING GALAXIES; FIELD GALAXIES; DISTRIBUTIONS; STARBURSTS; PHOTOMETRY; EMISSION; QUASARS; SYSTEM AB New near-infrared and visual images at 2.2 mu m and 6550 Angstrom are presented for 46 galaxies having infrared luminosities of L(IR)>8.5x10(11) L(.), 60 mu m flux densities greater than 1.94 Jy, and declinations greater than -35 degrees. These galaxies make up a significant fraction of a complete, northern hemisphere sample of ultraluminous infrared galaxies. Visual and/or near-infrared imaging data now exist for 56 ultraluminous infrared galaxies out to nearly 50 000 km s(-1). Of these 56 galaxies, 53 (95%) show evidence for current or past interactions. Among these systems, there are a large variety of visual morphologies, including strongly interacting pairs with apparent tidal tails, as well as single, distorted galaxies with close double nuclei. There are three galaxies which, to the limits of the imaging data, do not appear to have suffered a recent interaction or merger. Approximately 47% (25/53) of the interacting systems have double nuclei, with projected nuclear separations ranging from 0.3 to 48 kpc. Seven systems have nuclear separations larger than 10 kpc. If the 53 interacting galaxies are viewed as stages in the evolution of pairs of interacting spiral galaxies to a single, luminous AGN or starburst, the present imaging data can be used to estimate the lifetime of the bright infrared phase. Including only those sample galaxies with morphological evidence for interactions, we calculate a lower and an upper limit to the lifetime of the ultraluminous infrared phase of the sample as a whole to be 2x10(8) and 2x10(9) yr, respectively. Comparison of these dynamical estimates to models of the mergers of gas-rich galaxies and the rates at which fuel is exhausted by starbursts or AGN suggests the lifetime of the ultraluminous phase lies much closer to the smaller of these two values. Selecting galaxies based upon luminous infrared activity clearly biases the sample towards merging galaxies with small physical separations. However, the existence of pairs with large separations indicates that the ultraluminous phase may in some cases start early during the merger process. Alternatively, these systems may contain unresolved third nuclei responsible for triggering the ultraluminous activity. We briefly compare our results to recent models of merging spiral galaxies. (C) 1996 American Astronomical Society. C1 CALTECH, CTR INFRARED PROC & ANAL, JET PROP LAB, PASADENA, CA 91125 USA. INST ADV STUDY, SCH NAT SCI, PRINCETON, NJ 08540 USA. RP Murphy, TW (reprint author), CALTECH, PALOMAR OBSERV, 320-47, PASADENA, CA 91125 USA. NR 41 TC 163 Z9 163 U1 1 U2 1 PU IOP PUBLISHING LTD PI BRISTOL PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND SN 0004-6256 J9 ASTRON J JI Astron. J. PD MAR PY 1996 VL 111 IS 3 BP 1025 EP 1052 DI 10.1086/117849 PG 28 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA TX879 UT WOS:A1996TX87900004 ER PT J AU Malumuth, EM Waller, WH Parker, JW AF Malumuth, EM Waller, WH Parker, JW TI The stellar initial mass function in the giant H II region NGC 595 SO ASTRONOMICAL JOURNAL LA English DT Article ID WOLF-RAYET STARS; LARGE MAGELLANIC CLOUD; GALACTIC DISTRIBUTION; INTERSTELLAR-MEDIUM; OB ASSOCIATIONS; HII-REGIONS; M33; GALAXIES; ULTRAVIOLET; POPULATION AB As part of a larger effort to study the resolved and composite properties of the giant H II regions in Messier 33, we have analyzed multiband HST/WFPC-2 images of NGC 595 in terms of the ionizing cluster's resolved stellar population. Photometric reductions of the PC images yield 100 stars on the UV image, 272 stars on the U image, 345 stars on the B image, and 561 stars on the V image. A total of 267 stars are common to the U, B, and V images while 86 stars are detected on all 4 images. Although some clustering is evident, the degree of central concentration is less than that seen in 30 Doradus. The resulting U-B vs B-V diagram of the resolved stars is used to determine the reddening of each star. The average reddening derived from this diagram is E(B-V)=0.36+/-0.28 mag. The dereddened color-M(V) diagram is best fit by a model cluster having an age of 4.5+/-1.0 Myr, and hence initial masses no greater than 51 M(.). A total of 13 supergiant stars and 10 candidate WR stars [Drissen et al. (AJ, 105, 1400, 1993), and references therein] are identified with M(V)=-5 to -8 mag. The remainder are main-sequence O-type (98) and early B-type (>145) stars with M(V)=-1 to -6 mag, The ratio of WR to O stars is WR/O=0.11+/-0.01, roughly the same as found in the core of 30 Doradus. The resulting luminosity function has a slope of alpha=-0.71. The derived IMF has a slope of Gamma=-1.32+/-0.02 before subtracting a background component, and Gamma=-1.00+/-0.05 after subtracting a background based on photometry of the surrounding WF images. Integration of the derived IMF down to a lower mass limit of 4 M(.) yields a total mass of 7350 M(.), while integration down to 0.1 M(.) yields a total mass of 18 000 M(.). The total estimated ionizing luminosity is 5.0x10(50) photons s(-1), roughly half that which is inferred from the Her luminosity in this region. This shortfall of ionizing photons can be reconciled by allowing for a spread in the stellar ages, and/or by increasing the modeled EUV luminosity of the stars at the inferred cluster age. (C) 1996 American Astronomical Society. C1 NASA,GODDARD SPACE FLIGHT CTR,ASTRON & SOLAR PHYS LAB,HUGHES STX,GREENBELT,MD 20771. RP Malumuth, EM (reprint author), NASA,GODDARD SPACE FLIGHT CTR,ASTRON & SOLAR PHYS LAB,COMP SCI CORP,ASTRON PROGRAM,CODE 681,GREENBELT,MD 20771, USA. NR 57 TC 21 Z9 21 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 MAR PY 1996 VL 111 IS 3 BP 1128 EP & DI 10.1086/117858 PG 19 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA TX879 UT WOS:A1996TX87900013 ER PT J AU Clocchiatti, A Benetti, S Wheeler, JC Wren, W Boisseau, J Cappellaro, E Turatto, M Patat, F Swartz, DA Harkness, RP Brotherton, MS Wills, B Hemenway, P Cornell, M Frueh, M Kaiser, MB AF Clocchiatti, A Benetti, S Wheeler, JC Wren, W Boisseau, J Cappellaro, E Turatto, M Patat, F Swartz, DA Harkness, RP Brotherton, MS Wills, B Hemenway, P Cornell, M Frueh, M Kaiser, MB TI A study of SN 1992H in NGC 5377 SO ASTRONOMICAL JOURNAL LA English DT Article ID SPECTRAL ENERGY-DISTRIBUTIONS; EXTRAGALACTIC DISTANCE SCALE; PHOTOMETRIC STANDARD STARS; II SUPERNOVAE; UBVRI PHOTOMETRY; LIGHT CURVES; SPECTROPHOTOMETRIC STANDARDS; CELESTIAL EQUATOR; EXTINCTION; SN-1987A AB A photometric and spectroscopic analysis is presented of SN 1992H in NGC 5377 which was discovered by W. Wren at McDonald Observatory on UT 1992 February 11.5. SN 1992B displayed a distinct but truncated plateau suggesting that it was in some sense intermediate between a type II-linear and a fully developed type II-plateau event. Explosion is estimated to have occurred about 3 days before discovery. BV(RI)c light curves plus bolometric corrections based on the behavior of SN 1987A are used to compute a UVOIR bolometric light curve. This light curve shows a broad decline from early epochs that merges smoothly into the ''plateau'' at about 50 days after explosion. About 85 days after the explosion the light curve begins a precipitate decline of about 2 mag in 45 days. At that point, 130 days after the explosion, the light curve begins a linear decline with the timescale appropriate to that of Co-56 that lasts to the end of the observation at about 450 days. The early spectra show a continuum with H alpha in emission and H beta and He I lambda 5876 with broad P Cygni profiles. Velocities at this phase are in excess of 10 000 km s(-1). By 50 days after the explosion, H alpha shows a well-developed P Cygni profile. Lines of Ca H&K, Fe II, Sc II lambda 5526 and 5658, Na D, [Ca II] lambda lambda 7291, 7324, and the Ca II IR triplet are also observed on the plateau. On the tail, lines of [O I] lambda 5577 and [O I] lambda lambda 6300, 6364, and blends of [Fe II] are also observed. The latest spectra at about 450 days show a blue continuum. The B-V color evolution, the equivalent width of interstellar Na D, and the epoch of disappearance of He I lambda 5876 are used to estimate a color excess of E(B-V)=0.09+/-0.06. For this extinction, the expanding photosphere method is used to estimate a distance of 20.2+/-3.0 Mpc (mu=31.53+/-0.74). Models of the light curve show that the total mass ejected is about 11 M. with 0.075 M. of Ni-56. The latter is necessary to match both the distance-dependent amplitude of the exponential decline, but also the contrast between the plateau and the tail, which is independent of distance. The envelope of the progenitor must have extended to about 1000 R. with a density profile that dropped more slowly than exponential in order to match the relatively slow decline from the initial peak to the plateau. The decline from the plateau to the exponential tail was too precipitate in models with a distinct core-envelope discontinuity. It is unclear whether the smoother density contrast required is a constraint on the progenitor structure or may be induced by mixing in the explosion. Synthetic spectra in the late photospheric phase (50 and 119 days) are used to identify lines and estimate abundances. The results are consistent with solar abundances in the outer envelope. The evolution of the Ha line strength is consistent with an ejecta mass of 10-14 M., as derived from the light curve calculation. This is somewhat less that the lower limit to the ejecta mass derived by the constraint that sufficient gamma ray opacity be required to maintain the light curve near the Co-56 decay line for 450 days, which is greater than or similar to 15 M.. The evolution of the [Ca II] doublet and Ca II IR triplet were used to estimate the electron temperature and density and the mass of calcium. The electron temperature of the matter within 2500 km s(-1) is found to be similar to 5500 K, the electron density to be 2.5x10(9) cm(-3). The mass of Ca is estimated to be 3.5x10(-4) M.. If this matter has solar abundances, the total mass of hydrogen containing this Ca would be 4.4 M.. (C) 1996 American Astronomical Society. C1 UNIV TEXAS, MCDONALD OBSERV, AUSTIN, TX 78712 USA. UNIV TEXAS, DEPT ASTRON, AUSTIN, TX 78712 USA. NASA, GEORGE C MARSHALL SPACE FLIGHT CTR, SPACE SCI LAB, HUNTSVILLE, AL 35812 USA. UNIV PADUA, DIPARTIMENTO ASTRON, I-35122 PADUA, ITALY. OSSERV ASTRON PADOVA, I-35122 PADUA, ITALY. OI Cappellaro, Enrico/0000-0001-5008-8619; Benetti, Stefano/0000-0002-3256-0016; Turatto, Massimo/0000-0002-9719-3157 NR 69 TC 39 Z9 39 U1 0 U2 0 PU IOP PUBLISHING LTD PI BRISTOL PA DIRAC HOUSE, TEMPLE BACK, BRISTOL BS1 6BE, ENGLAND SN 0004-6256 J9 ASTRON J JI Astron. J. PD MAR PY 1996 VL 111 IS 3 BP 1286 EP 1303 DI 10.1086/117874 PG 18 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA TX879 UT WOS:A1996TX87900029 ER PT J AU Null, GW Owen, WM AF Null, GW Owen, WM TI Charon Pluto mass ratio obtained with HST CCD observations in 1991 and 1993 SO ASTRONOMICAL JOURNAL LA English DT Article ID STELLAR OCCULTATION AB We have analyzed Hubble Space Telescope Wide Field Camera observations of Pluto, Charon, and a reference star, acquired in 1991 and 1993, to observe Pluto's barycentric motion and determine the Charon/Pluto mass ratio, 0.124+/-0.008. Solution values for Charon orbital elements include the semimajor axis, 19662+/-81 km; inclination, 96.57+/-0.24 deg; eccentricity, 0.0072+/-0.0067; longitude of periapsis, 2+/-35 deg; and mean longitude, 123.58+/-0.43 deg. These elements are referred to the J2000 Earth equator and equinox at epoch JED 2446600.5. (C) 1996 American Astronomical Society. RP Null, GW (reprint author), CALTECH,JET PROP LAB,4800 OAK GROVE DR,PASADENA,CA 91109, USA. NR 20 TC 19 Z9 19 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 MAR PY 1996 VL 111 IS 3 BP 1368 EP 1381 DI 10.1086/117883 PG 14 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA TX879 UT WOS:A1996TX87900038 ER PT J AU Hartmann, T Williams, JG Soffel, M AF Hartmann, T Williams, JG Soffel, M TI Errors in the J(3) part of nutation series SO ASTRONOMICAL JOURNAL LA English DT Article ID INNER CORE DYNAMICS; RIGID-EARTH; FORCED NUTATIONS AB This paper points out that the nutation terms of Zhu & Groten [AJ, 98, 1104 (1989)] due to the tidal potential of degree 3 are erroneous. Correct values are deduced here and they coincide very well with those given in Kinoshita & Souchay [Celest. Mech., 48, 187 (1990)]. These errors explain the discrepancies between the evaluation of the theories of Zhu & Groten (1989) and Kinoshita & Souchay (1990), which can reach values up to 165 mu as. Also the two leading nutation terms due to the tidal potential of degree 4 are given. Finally, some of the computer programs (NUTC.F KSV_1994.F) for evaluating the J(3) nutation terms are also erroneous. (C) 1996 American Astronomical Society. C1 CALTECH, JET PROP LAB, PASADENA, CA 91109 USA. LOHRMANN OBSERV, INST PLANETARE GEODASIE, D-01062 DRESDEN, GERMANY. RP Hartmann, T (reprint author), UNIV TUBINGEN, MORGENSTELLE 10, D-72076 TUBINGEN, GERMANY. NR 16 TC 5 Z9 5 U1 0 U2 0 PU IOP PUBLISHING LTD PI BRISTOL PA DIRAC HOUSE, TEMPLE BACK, BRISTOL BS1 6BE, ENGLAND SN 0004-6256 J9 ASTRON J JI Astron. J. PD MAR PY 1996 VL 111 IS 3 BP 1400 EP 1404 DI 10.1086/117886 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA TX879 UT WOS:A1996TX87900041 ER PT J AU Briggs, MS Paciesas, WS Pendleton, GN Meegan, CA Fishman, GJ Horack, JM Brock, MN Kouveliotou, C Hartmann, DH Hakkila, J AF Briggs, MS Paciesas, WS Pendleton, GN Meegan, CA Fishman, GJ Horack, JM Brock, MN Kouveliotou, C Hartmann, DH Hakkila, J TI BATSE observations of the large-scale isotropy of gamma-ray bursts SO ASTROPHYSICAL JOURNAL LA English DT Review DE cosmology, observations; gamma rays, bursts; methods, statistical ID COSMOLOGICAL ORIGIN; GALACTIC DISK; HALO MODELS; OORT CLOUD; GALAXY; STATISTICS; LUMINOSITY; REPEATER; TESTS; MASS AB We use dipole and quadrupole statistics to test the large-scale isotropy of the first 1005 gamma-ray bursts observed by the Burst and Transient Source Experiment (BATSE). In addition to the entire sample of 1005 gamma-ray bursts, many subsets are examined. We use a variety of dipole and quadrupole statistics to search for Galactic and other predicted anisotropies and for anisotropies in a coordinate-system independent manner. We find the gamma-ray burst locations to be consistent with isotropy, e.g., for the total sample the observed Galactic dipole moment [cos theta] differs from the value predicted for isotropy by 0.9 sigma and the observed Galactic quadrupole moment [sin(2) b - 1/3] by 0.3 sigma. We estimate for various models the anisotropies that could have been detected. If one-half of the locations were within 86 degrees of the Galactic center, or within 28 degrees of the Galactic plane, the ensuing dipole or quadrupole moment would have typically been detected at the 99% confidence level. We compare the observations with the dipole and quadrupole moments of various Galactic models. Several Galactic gamma-ray bursts models have moments within 2 sigma of the observations; most of the Galactic models proposed to date are no longer in acceptable agreement with the data. Although a spherical dark matter halo distribution could be consistent with the data, the required core radius is larger than the core radius of the dark matter halo used to explain the Galaxy's rotation curve. Gamma-ray bursts are much more isotropic than any observed Galactic population, strongly favoring but not requiring an origin at cosmological distances. C1 NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,UNIV SPACE RES ASSOC,HUNTSVILLE,AL 35812. CLEMSON UNIV,DEPT PHYS & ASTRON,CLEMSON,SC 29634. MANKATO STATE UNIV,DEPT PHYS & ASTRON,MANKATO,MN 56002. RP Briggs, MS (reprint author), UNIV ALABAMA,DEPT PHYS,HUNTSVILLE,AL 35899, USA. RI Horack, John/J-6670-2016 NR 116 TC 99 Z9 99 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 MAR 1 PY 1996 VL 459 IS 1 BP 40 EP 63 DI 10.1086/176867 PN 1 PG 24 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA TV791 UT WOS:A1996TV79100004 ER PT J AU Hough, DH Vermeulen, RC Wood, DA Standifird, JD Cross, LL AF Hough, DH Vermeulen, RC Wood, DA Standifird, JD Cross, LL TI Multiple-epoch monitoring of the lobe-dominated superluminal quasar 3C 245 SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies, jets; quasars, individual (3C 245); radio continuum, galaxies ID COMPACT RADIO-SOURCES; COMPLETE SAMPLE; MOTION; STATISTICS; OBJECTS; 3C-245 AB We report confirmation of superluminal motion in the nucleus of the lobe-dominated quasar 3C 245, based on three new 10.7 GHz epochs and a consistent reanalysis of older 10.7 GHz data; the total time spanned is a decade. In the inner 2 mas, we have tracked two components that have consistent motions in a position angle of 290 degrees-300 degrees, well fitted with constant apparent transverse velocities of beta(app) = (2.4 +/- 0.1) h(-1) and beta(app) = (3.1 +/- 1.7) h(-1) (H-0 = 100 h km s(-1) Mpc(-1), q(0) = 0.5). We also present a new 8.4 GHz VLBI observation with superior short-baseline (u, v)-coverage that has yielded the best high-resolution image to date of a faint, steep-spectrum extension of the one-sided jet, reaching out to greater than or equal to 40 mas from the VLBI core and having a brightness peak at similar to 25 mas. We relate our findings to other properties of 3C 245 and interpret them in the context of relativistic beaming models and unification scenarios. We conclude that 3C 245 is in many ways a prototypical transition object between core- and lobe-dominated quasars. C1 CALTECH,JET PROP LAB,PASADENA,CA 91109. CALTECH,PASADENA,CA 91125. RP Hough, DH (reprint author), TRINITY UNIV,DEPT PHYS,SAN ANTONIO,TX 78212, USA. NR 36 TC 6 Z9 6 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 MAR 1 PY 1996 VL 459 IS 1 BP 64 EP 72 DI 10.1086/176868 PN 1 PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA TV791 UT WOS:A1996TV79100005 ER PT J AU Grandi, P Urry, CM Maraschi, L Wehrle, AE Madejski, GM Aller, MF Aller, HD Bailyn, CD Balonek, TJ Bock, TH Glass, IS Litchfield, SJ McHardy, IM Mulchaey, JS Reuter, HP Robson, EI Sadun, AC Sherry, W Steppe, H Stevens, JA Terasranta, H Tornikoski, M Wagner, SJ AF Grandi, P Urry, CM Maraschi, L Wehrle, AE Madejski, GM Aller, MF Aller, HD Bailyn, CD Balonek, TJ Bock, TH Glass, IS Litchfield, SJ McHardy, IM Mulchaey, JS Reuter, HP Robson, EI Sadun, AC Sherry, W Steppe, H Stevens, JA Terasranta, H Tornikoski, M Wagner, SJ TI 3C 279 multiwavelength monitoring .2. The ground-based campaign SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies, photometry; gamma rays, observations; quasars, individual (3C 279); radiation mechanisms, nonthermal; X-rays, galaxies ID EXTRAGALACTIC RADIO-SOURCES; MILLIMETER CONTINUUM MEASUREMENTS; SHOCKED RELATIVISTIC JETS; ENERGY GAMMA-RADIATION; BL LAC OBJECTS; QUASAR 3C-279; X-RAY; SYNCHROTRON EMISSION; SUPERLUMINAL MOTION; VARIABILITY AB The optically violently variable quasar 3C 279 was monitored simultaneously from radio to gamma-ray frequencies in 1992 December-1993 January. We report a detailed study of the ground-based results from radio to optical wavelengths. These data show that 3C 279 has a typical blazar spectrum, slightly rising at radio frequency and then progressively steeper above a first turnover frequency between 37 and 90 GHz. In the millimeter wavelength region, a simple power law is not an adequate description of the spectrum. We suggest that the millimeter ''shoulder'' corresponds to an additional emission component, self-absorbed between 150 and 375 GHz, possibly associated with the detachment of a new VLBI knot and with the start of radio flare. A flux increase of 20% over 20 days was observed at 37 and 90 GHz, while contemporaneously the R-band flux doubled in about two weeks. The lack of strong variability in contemporaneous X-ray light curves (possible X-ray variations are less than 30%) implies no direct (i.e., zero lag) correlation between the optical and X-ray fluxes. If X-rays are produced by inverse-Compton scattering of relativistic electrons on some seed photons, the above results exclude that the observed optical photons are the seeds and/or that the relativistic electrons radiating via synchrotron in the optical band are responsible for the scattering to X-ray energies. We suggest that the X-rays are instead produced through the inverse-Compton process by electrons of lower energy, which radiate via synchrotron in the radio to millimeter wave bands and which scatter either on the synchrotron photons themselves or on external photons. C1 SPACE TELESCOPE SCI INST,BALTIMORE,MD 21218. UNIV MILAN,DEPT PHYS,I-20133 MILAN,ITALY. CALTECH,INFRARED PROC ANAL CTR 1022,PASADENA,CA 91125. NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. UNIV MICHIGAN,ANN ARBOR,MI 48109. YALE UNIV,DEPT ASTRON,NEW HAVEN,CT 06520. COLGATE UNIV,DEPT ASTRON,HAMILTON,NY 13346. S AFRICAN ASTRON OBSERV,CAPE TOWN 7935,SOUTH AFRICA. UNIV CENT LANCASHIRE,CTR ASTROPHYS,PRESTON PR1 2HE,LANCS,ENGLAND. UNIV SOUTHAMPTON,DEPT PHYS,SOUTHAMPTON SO9 5NH,HANTS,ENGLAND. IRAM,E-18012 GRANADA,SPAIN. JOINT ASTRON CTR,HILO,HI 96720. AGNES SCOTT COLL,BRADLEY OBSERV,DECATUR,GA 30030. METSAHOVI RADIO RES STN,SF-02540 KYLMALA,FINLAND. LANDESSTERNWARTE KONIGSTUHL,W-6900 HEIDELBERG,GERMANY. RI Urry, Claudia/G-7381-2011 OI Urry, Claudia/0000-0002-0745-9792 NR 58 TC 17 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 MAR 1 PY 1996 VL 459 IS 1 BP 73 EP 81 DI 10.1086/176869 PN 1 PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA TV791 UT WOS:A1996TV79100006 ER PT J AU Nolan, PL Bertsch, DL Chiang, J Dingus, BL Esposito, JA Fichtel, CE Fierro, JM Hartman, RC Hunter, SD Kanbach, G Kniffen, DA Lin, YC Mattox, JR MayerHasselwander, HA Michelson, PF vonMontigny, C Mukherjee, R Schneid, E Sreekumar, P Thompson, DJ Willis, TD AF Nolan, PL Bertsch, DL Chiang, J Dingus, BL Esposito, JA Fichtel, CE Fierro, JM Hartman, RC Hunter, SD Kanbach, G Kniffen, DA Lin, YC Mattox, JR MayerHasselwander, HA Michelson, PF vonMontigny, C Mukherjee, R Schneid, E Sreekumar, P Thompson, DJ Willis, TD TI EGRET observations of gamma rays from point sources with galactic latitude +10 degrees1 MeV. We use a pulse model with separate rise and decay time constants and a peakedness parameter. Several trends in pulse shape as a function of energy and time of occurrence are apparent: Pulse width distributions are energy dependent, the mode shifting from similar to 600 ms at low energy to similar to 200 at high energy. The distribution of intervals between pulses exhibits a broad maximum near 1 s, presumably a characteristic emission timescale in long bursts. The most frequently occurring pulse shape is intermediate between exponential and Gaussian. Pulses show a tendency to self-similarity across energy bands. We find that average raw pulse shape dependence on energy is approximately power law, with an index of similar to-0.40, consistent with the autocorrelation analysis of Fenimore et al. Burst asymmetry on short time scales results from the tendency for most (similar to 90%) pulses to rise more quickly than they decay, the majority having rise-to-decay ratios of similar to 0.3-0.5, independent of energy. The dominant trend of spectral softening seen in most pulses arises partially from faster onsets at higher energy and longer decays at lower energies, although in addition, pulses sometimes peak earlier in the higher energy bands. We make an important connection between pulse asymmetry, width, and spectral softening: Among pulses for which shape is relatively well determined, the rise-to-decay ratio is unity or less; as this ratio decreases, pulses tend to be wider, the pulse centroid is more shifted to later times at lower energies, and pulses tend to be spectrally softer. C1 GEORGE MASON UNIV,FAIRFAX,VA 22030. UNIV SPACE RES ASSOC,WASHINGTON,DC. NASA,AMES RES CTR,MOFFETT FIELD,CA 94035. NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,HUNTSVILLE,AL 35812. UNIV ALABAMA,HUNTSVILLE,AL 35899. RP Norris, JP (reprint author), NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771, USA. NR 26 TC 311 Z9 321 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 MAR 1 PY 1996 VL 459 IS 1 BP 393 EP 412 DI 10.1086/176902 PN 1 PG 20 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA TV791 UT WOS:A1996TV79100039 ER PT J AU Ofman, L Davila, JM Shimizu, T AF Ofman, L Davila, JM Shimizu, T TI Signatures of global mode Alfven resonance heating in coronal loops SO ASTROPHYSICAL JOURNAL LA English DT Article DE MHD; Sun, corona; Sun, magnetic fields; waves ID X-RAY TELESCOPE; SOLAR CORONA; ABSORPTION; EFFICIENCY; FIELDS; WAVES AB The Yohkoh Soft X-Ray Telescope (SXT) observations of active region coronal loops transient brightening is analyzed, and the scaling of the thermal energy release with loop lengths is found to be E(th) similar to L(1.60+/-0.09). The numerically determined scaling of the global mode heating rate for the resonant absorption of Alfven waves, H similar to L, is found to agree with the heating rate deduced from the observed thermal energy scaling, provided that the magnetic field scales as B similar to L(-0.70+/-0.05) and the waves are driven with a omega(-1) spectrum. Previous analytical and numerical studies have shown that the heating due to resonant absorption of Alfven waves is most efficient at the global mode frequency. In agreement with these studies, we suggest that coronal loop transient X-ray brightenings occur when a given length coronal loop is perturbed at its global mode frequency by random footpoint motions, which results in more efficient heating of the loop. C1 NATL CTR ATMOSPHER RES, HIGH ALTITUDE OBSERV, BOULDER, CO 80307 USA. NASA, GODDARD SPACE FLIGHT CTR, ASTRON & SOLAR PHYS LAB, GREENBELT, MD 20771 USA. UNIV TOKYO, INST ASTRON, MITAKA, TOKYO 181, JAPAN. NR 23 TC 14 Z9 14 U1 0 U2 0 PU IOP PUBLISHING LTD PI BRISTOL PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND SN 0004-637X EI 1538-4357 J9 ASTROPHYS J JI Astrophys. J. PD MAR 1 PY 1996 VL 459 IS 1 BP L39 EP L42 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA TV794 UT WOS:A1996TV79400010 ER PT J AU McNamara, BJ Harrison, TE Ryan, J Kippen, RM McConnell, M Macri, J Kouveliotou, C Fishman, GJ Meegan, CA Green, DA Koranyi, DM Warner, PJ Waldram, EM Hanlon, L Bennett, K Spoelstra, TAT Metlov, VG Metlova, NV Feigelson, E Beasley, AJ Palmer, DM Barthelmy, SD Gary, DE Olsen, ET Levin, S Wannier, PG Janssen, MA Borovicka, J Pravec, P Hudec, R Coe, MJ AF McNamara, BJ Harrison, TE Ryan, J Kippen, RM McConnell, M Macri, J Kouveliotou, C Fishman, GJ Meegan, CA Green, DA Koranyi, DM Warner, PJ Waldram, EM Hanlon, L Bennett, K Spoelstra, TAT Metlov, VG Metlova, NV Feigelson, E Beasley, AJ Palmer, DM Barthelmy, SD Gary, DE Olsen, ET Levin, S Wannier, PG Janssen, MA Borovicka, J Pravec, P Hudec, R Coe, MJ TI Ground-based gamma-ray burst follow-up efforts: Results of the first two years of the BATSE COMPTEL NMSU rapid response network SO ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES LA English DT Article DE gamma rays, bursts ID RADIO; COUNTERPARTS AB In this paper we describe the capabilities of the BATSE/COMPTEL/NMSU Rapid Response Network and report on results obtained during its first 2 years of operation. This network is a worldwide association of 22 radio and optical observatories that perform follow-up searches of newly discovered gamma-ray burst error boxes by the Compton Gamma Ray Observatory. During the last 2 years, it has deeply imaged 10 gamma-ray error boxes over time frames from a few hours to a month after burst detection, and it finds no sources that can be associated unambiguously with a gamma-ray burst. We suggest that significant optical or radio emission is not produced by gamma-ray bursts more than a day after the burst. This result is consistent with recent theoretical models by Katz, Meszaros, Rees, & Papathanassiou, and Paczynski & Rhoads; however, our hours to days optical response time and radio sensitivity limits allow only a weak constraint to be placed on these models. Based upon this study and other published works, we suggest that future work should concentrate on acquiring deep optical images (m greater than or equal to 12) of small gamma-ray error boxes well within a day of the burst. Ideally, radio observations should begin as soon after the burst as possible, reach a sensitivity of less than or equal to 1 mJy, and be continued with occasional images being acquired for at least a month following burst detection. C1 UNIV NEW HAMPSHIRE, CTR SPACE SCI, DURHAM, NH 03824 USA. NASA, GEORGE C MARSHALL SPACE FLIGHT CTR, SPACE SCI LAB, HUNTSVILLE, AL 35899 USA. CAVENDISH LAB, MULLARD RADIO ASTRON OBSERV, CAMBRIDGE CB3 0HE, ENGLAND. ESTEC, DIV ASTROPHYS, 2200 AG NOORDWIJK, NETHERLANDS. WESTERBORK RADIO OBSERV, 9433 TA ZWIGGELTE, NETHERLANDS. MOSCOW MV LOMONOSOV STATE UNIV, STERNBERG ASTRON INST, CRIMEAN LAB, NAUCHNYI 334413, UKRAINE. PENN STATE UNIV, DEPT ASTRON & ASTROPHYS, DAVEY LAB 525, UNIVERSITY PK, PA 16802 USA. AUSTRALIA TELESCOPE NATL FACIL, EPPING, NSW 2121, AUSTRALIA. NATL RADIO ASTRON OBSERV, SOCORRO, NM 87801 USA. NASA, GODDARD SPACE FLIGHT CTR, USRA, GREENBELT, MD 20771 USA. CALTECH, PASADENA, CA 91125 USA. CALTECH, JET PROP LAB, PASADENA, CA 91109 USA. LAWRENCE LIVERMORE NATL LAB, LIVERMORE, CA 94550 USA. AUSTRALIAN NATL UNIV, MT STROMLO & SIDING SPRING OBSERV, WESTON, ACT 2611, AUSTRALIA. ASTRON INST, CR-25165 ONDREJOV, CZECH REPUBLIC. UNIV SOUTHAMPTON, DEPT PHYS, SOUTHAMPTON SO9 5NH, HANTS, ENGLAND. RP NEW MEXICO STATE UNIV, BOX 30001, DEPT 4500, LAS CRUCES, NM 88003 USA. RI Green, David/E-9609-2010; Barthelmy, Scott/D-2943-2012; Borovicka, Jiri/F-4257-2014; Pravec, Petr/G-9037-2014; Hudec, Rene/G-9018-2014; OI Green, David/0000-0003-3189-9998; Gary, Dale/0000-0003-2520-8396 NR 37 TC 8 Z9 8 U1 1 U2 2 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 MAR PY 1996 VL 103 IS 1 BP 173 EP 181 DI 10.1086/192273 PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA TV290 UT WOS:A1996TV29000007 ER PT J AU BEARMAN, G SPIRO, SI AF BEARMAN, G SPIRO, SI TI ARCHAEOLOGICAL APPLICATIONS OF ADVANCED IMAGING TECHNIQUES SO BIBLICAL ARCHAEOLOGIST LA English DT Article RP BEARMAN, G (reprint author), JET PROP LAB,IMAGING & SPECTROMMETRY TECHNOL SECT,PASADENA,CA 91109, USA. NR 13 TC 18 Z9 18 U1 0 U2 1 PU SCHOLARS PRESS PI ATLANTA PA PO BOX 15399, ATLANTA, GA 30333-0399 SN 0006-0895 J9 BIBLIC ARCHAEOL JI Biblic. Archeol. PD MAR PY 1996 VL 59 IS 1 BP 56 EP 66 DI 10.2307/3210537 PG 11 WC Archaeology SC Archaeology GA UE682 UT WOS:A1996UE68200008 ER PT J AU Goodpaster, AJ Berman, H Blechman, BM Burns, WF Horner, CA Jeffords, JM Krepon, M McNamara, RS Marshall, W Nitze, PH Nolan, JE Odeen, PA Ridgway, RL Sagan, SD Smith, WY Steinbruner, J Utgoff, V AF Goodpaster, AJ Berman, H Blechman, BM Burns, WF Horner, CA Jeffords, JM Krepon, M McNamara, RS Marshall, W Nitze, PH Nolan, JE Odeen, PA Ridgway, RL Sagan, SD Smith, WY Steinbruner, J Utgoff, V TI A four-step program to nuclear disarmament SO BULLETIN OF THE ATOMIC SCIENTISTS LA English DT Article C1 USA,WAR COLL,WASHINGTON,DC 20310. US SPACE COMMAND,COLORADO SPRINGS,CO. USAF,SPACE COMMAND,WASHINGTON,DC 20330. BROOKINGS INST,FOREIGN POLICY STUDIES PROGRAM,WASHINGTON,DC 20036. INST DEF ANAL,STRATEGY FORCES RESOURCE DIV,PRINCETON,NJ. NR 0 TC 0 Z9 0 U1 0 U2 0 PU EDUC FOUNDATION NUCLEAR SCI PI CHICAGO PA 6042 SOUTH KIMBARK, CHICAGO, IL 60637 SN 0096-3402 J9 B ATOM SCI JI Bull. Atom. Scient. PD MAR-APR PY 1996 VL 52 IS 2 BP 52 EP 55 PG 4 WC International Relations; Social Issues SC International Relations; Social Issues GA TZ909 UT WOS:A1996TZ90900021 ER PT J AU Carter, GA Dell, TR Cibula, WG AF Carter, GA Dell, TR Cibula, WG TI Spectral reflectance characteristics and digital imagery of a pine needle blight in the southeastern United States SO CANADIAN JOURNAL OF FOREST RESEARCH-REVUE CANADIENNE DE RECHERCHE FORESTIERE LA English DT Article ID RED EDGE; SLASH PINE; BLUE-SHIFT; LEAVES; DAMAGE AB A field study determined an optimal approach for the remote sensing of a pine needle blight of unknown cause that occurs frequently in the southeastern United States. Needle spectral reflectance was measured in five pairs of slash pines (Pinus elliottii Engelm. var. elliottii), each comprising a blighted and a nonblighted tree. Reflectance of blighted needles generally was greater within the 400-700 nm wavelength range and less in the 720-850 nm range compared with nonblighted needles (p less than or equal to 0.050). The relative change in reflectance, or reflectance sensitivity to the blight, was greatest near 680 nm. As predicted by the reflectance sensitivity, a black and white digital image at 680 +/- 5 nm revealed strong contrast of a blighted compared with a nonblighted tree; the blighted canopy was nearly white in the image, while the nonblighted canopy was dark grey. Contrasts were much less at 560 +/- 5, 694 +/- 3, and 700 +/- 5 nm, in the panchromatic visible spectrum (410-740 nm), and at 760 +/- 5 nm. Remote sensing of southeastern pine forests at 680 +/- 5 nm ultimately could provide regional estimates of blight occurrence and distribution, and thus contribute to determining its cause. C1 MISSISSIPPI STATE UNIV,BAY ST LOUIS,MS 39529. RP Carter, GA (reprint author), NASA,EARTH OBSERV RES OFF,BAY ST LOUIS,MS 39529, USA. NR 20 TC 28 Z9 35 U1 0 U2 4 PU NATL RESEARCH COUNCIL CANADA PI OTTAWA PA RESEARCH JOURNALS, MONTREAL RD, OTTAWA ON K1A 0R6, CANADA SN 0045-5067 J9 CAN J FOREST RES JI Can. J. For. Res.-Rev. Can. Rech. For. PD MAR PY 1996 VL 26 IS 3 BP 402 EP 407 DI 10.1139/x26-045 PG 6 WC Forestry SC Forestry GA UB978 UT WOS:A1996UB97800008 ER PT J AU Mearns, LO Rosenzweig, C Goldberg, R AF Mearns, LO Rosenzweig, C Goldberg, R TI The effect of changes in daily and interannual climatic variability on ceres-wheat: A sensitivity study SO CLIMATIC CHANGE LA English DT Article ID DAILY PRECIPITATION; SOLAR-RADIATION; TEMPERATURE; SIMULATION; EVENTS; MODELS AB We investigate the effect of changes in daily and interannual variability of temperature and precipitation on yields simulated by the CERES-Wheat model at two locations in the central Great Plains. Changes in variability were effected by adjusting parameters of the Richardson daily weather generator. Two types of changes in precipitation were created: one with both intensity and frequency changed; and another with change only in persistence. In both types mean total monthly precipitation is held constant. Changes in daily (and interannual) variability of temperature result in substantial changes in the mean and variability of simulated wheat yields, With a doubling of temperature variability, large reductions in mean yield and increases in variability of yield result primarily from crop failures due to winter kill at both locations. Reduced temperature variability has little effect. Changes in daily precipitation variability also resulted in substantial changes in mean and variability of yield. Interesting interactions of the precipitation variability changes with the contrasting base climates are found at the two locations. At one site where soil moisture is not limiting, mean yield decreased and variability of yield increased with increasing precipitation variability, whereas mean yields increased at the other location, where soil moisture is limiting. Yield changes were similar for the two different types of precipitation variability change investigated. Compared to an earlier study for the same locations wherein variability changes were effected by altering observed time series, and the focus was on interannual variability, the present results for yield changes are much more substantial. This study demonstrates the importance of taking into account change in daily (and interannual) variability of climate when analyzing the effect of climate change on crop yields. C1 NASA,GODDARD INST SPACE STUDIES,NEW YORK,NY 10025. COLUMBIA UNIV,NEW YORK,NY. RP Mearns, LO (reprint author), NATL CTR ATMOSPHER RES,POB 3000,BOULDER,CO 80307, USA. NR 33 TC 147 Z9 152 U1 1 U2 25 PU KLUWER ACADEMIC PUBL PI DORDRECHT PA SPUIBOULEVARD 50, PO BOX 17, 3300 AA DORDRECHT, NETHERLANDS SN 0165-0009 J9 CLIMATIC CHANGE JI Clim. Change PD MAR PY 1996 VL 32 IS 3 BP 257 EP 292 DI 10.1007/BF00142465 PG 36 WC Environmental Sciences; Meteorology & Atmospheric Sciences SC Environmental Sciences & Ecology; Meteorology & Atmospheric Sciences GA UA849 UT WOS:A1996UA84900003 ER PT J AU Kurtz, J Vulcan, T Steinberg, TA AF Kurtz, J Vulcan, T Steinberg, TA TI Emission spectra of burning iron in high-pressure oxygen SO COMBUSTION AND FLAME LA English DT Article ID COMBUSTION; METALS AB Emission spectra of burning vertical iron rods in high-pressure oxygen were taken and correlated with the different stages of the burn evolution. By applying the least squares method to the spectral curves, the corresponding equivalent blackbody temperatures were computed. Based on the assumption of a wavelength-independent emissivity between 495 and 780 nm, it was found that the surface-averaged temperatures of the molten iron/iron oxide droplets ranged from a minimal value of similar to 2500 K to a maximum value of similar to 3900 K (in 1630 kPa O-2) and the temperatures increased with the size (and age) of the droplets. C1 UNIV QUEENSLAND,DEPT MECH ENGN,BRISBANE,QLD 4072,AUSTRALIA. RP Kurtz, J (reprint author), NASA,WHITE SANDS TEST FACIL,PO DRAWER MM,LAS CRUCES,NM 88004, USA. OI Steinberg, Theodore/0000-0002-9270-4130 NR 24 TC 9 Z9 9 U1 0 U2 0 PU ELSEVIER SCIENCE INC PI NEW YORK PA 655 AVENUE OF THE AMERICAS, NEW YORK, NY 10010 SN 0010-2180 J9 COMBUST FLAME JI Combust. Flame PD MAR PY 1996 VL 104 IS 4 BP 391 EP 400 DI 10.1016/0010-2180(95)00156-5 PG 10 WC Thermodynamics; Energy & Fuels; Engineering, Multidisciplinary; Engineering, Chemical; Engineering, Mechanical SC Thermodynamics; Energy & Fuels; Engineering GA UB545 UT WOS:A1996UB54500002 ER PT J AU Miller, CD AF Miller, CD TI NASA uses ATM to link classrooms of the future SO COMMUNICATIONS NEWS LA English DT Article RP Miller, CD (reprint author), NASA CLASSROOM FUTURE,WASHINGTON,DC 20546, 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 0010-3632 J9 COMMUN NEWS JI Commun. News PD MAR PY 1996 VL 33 IS 3 BP 14 EP 15 PG 2 WC Telecommunications SC Telecommunications GA UB474 UT WOS:A1996UB47400012 ER PT J AU Clarke, MSF Feeback, DL AF Clarke, MSF Feeback, DL TI Mechanical load induces sarcoplasmic wounding and FGF release in differentiated human skeletal muscle cultures SO FASEB JOURNAL LA English DT Article DE skeletal muscle hypertrophy; differentiation ID FIBROBLAST GROWTH-FACTOR; MDX MOUSE MUSCLE; CARDIAC MYOCYTES; GENE-EXPRESSION; TISSUE-CULTURE; CELLS; HYPERTROPHY; LOCALIZATION; ACTIVATION; MYOFIBERS AB The transduction mechanism (or mechanisms) responsible for converting a mechanical load into a skeletal muscle growth response are unclear, In this study we have used a mechanically active tissue culture model of differentiated human skeletal muscle cells to investigate the relationship between mechanical load, sarcolemma wounding, fibroblast growth factor release, and skeletal muscle cell growth, Using the Flexcell Strain Unit we demonstrate that as mechanical load increases, so too does the amount of sarcolemma wounding. A similar relationship was also observed between the level of mechanical load inflicted on the cells and the amount of bFGF (FGF2) released into the surrounding medium. In addition, we demonstrate that the muscle cell growth response induced by chronic mechanical loading in culture can be inhibited by the presence of an antibody capable of neutralizing the biological activity of FGF. This study provides direct evidence that mechanically induced, sarcolemma wound-mediated FGF release is an important autocrine mechanism for transducing the stimulus of mechanical load into a skeletal muscle growth response. RP Clarke, MSF (reprint author), NASA,LYNDON B JOHNSON SPACE CTR,BIOMED OPERAT & RES BRANCH SD4,MUSCLE RES LAB,BLDG 37,HOUSTON,TX 77058, USA. NR 34 TC 81 Z9 81 U1 0 U2 0 PU FEDERATION AMER SOC EXP BIOL PI BETHESDA PA 9650 ROCKVILLE PIKE, BETHESDA, MD 20814-3998 SN 0892-6638 J9 FASEB J JI Faseb J. PD MAR PY 1996 VL 10 IS 4 BP 502 EP 509 PG 8 WC Biochemistry & Molecular Biology; Biology; Cell Biology SC Biochemistry & Molecular Biology; Life Sciences & Biomedicine - Other Topics; Cell Biology GA UE557 UT WOS:A1996UE55700014 PM 8647349 ER PT J AU Mittlefehldt, DW Lindstrom, MM Bogard, DD Garrison, DH Field, SW AF Mittlefehldt, DW Lindstrom, MM Bogard, DD Garrison, DH Field, SW TI Acapulco- and Lodran-like achondrites: Petrology, geochemistry, chronology, and origin SO GEOCHIMICA ET COSMOCHIMICA ACTA LA English DT Article ID H-CHONDRITE; CLASSIFICATION; METEORITES; METAL AB We have performed petrologic and geochemical studies of five primitive achondrites: ALHA81187 and ALHA81261 (Acapulco-like),EET 84302 (transitional, but Acapulco-like), and LEW 88280 and MAC 88177 (Lodran-like). We have also performed Ar-39-Ar-40 chronology on ALHA81187, ALHA81261, and EET 84302. LEW 88280 and MAC 88177 contain more ferroan olivines, orthopyroxenes, clinopyroxenes, and chromites than do the Acapulco-like achondrites. Plagioclase is present in only ALHA81187, ALHA81261, and EET 84302. Its composition does not track that of the mafic silicates; EET 84302, with the most calcic plagioclase, contains olivine and pyroxene with an mg# intermediate between ALHA81187 and ALHA81261. Similarly, spinels in EET 84302 have the same mg# as those in ALHA81187, while pyroxenes in the former are more ferroan than in the latter. Acapulco-like achondrites have Sm/Sc ratios between 0.8-1.5 times H chondrites, and Na/Sc ratios are between similar to 0.8-1.0 times H chondrites, indicating that silicate partial melts have not been lost from these rocks. Siderophile and chalcophile elements are fractionated and show a trend of increasing Ir/Ni ratios with decreasing Se/Co ratios. This variation is consistent with fractionation by partial melting in the Fe-Ni-S system. EET 84302 is very depleted in Se and troilite is a accessory phase, indicating essentially total loss of the low temperature Fe-Ni-S melt. In contrast, the Lodran-like achondrites are depleted in the highly incompatible lithophile elements relative to more compatible elements: Sm/Sc ratios are similar to 0.2-0.7 times and Na/Sc ratios are 0.04-0.18 times H chondrites. These data are consistent with a model for formation of the Lodran-like achondrites as partial melting residues. However, the low Ir/Ni and high Se/Co ratios in two Lodran-like achondrites suggest the metal + troilite in these rocks is dominated by the low melting fraction in the Fe-Ni-S system. This metal + troilite was added to the silicates after partial melting depleted them in a basaltic fraction. The Ar-Ar release spectra yield good plateau ages of 4.507 +/- 0.024 Ga (ALHA81187), 4.511 +/- 0.007 Ga (ALHA81261), and 4.519 +/- 0.017 Ga (EET 84302), in good agreement with previously determined Ar-Ar ages for other Acapulco-like achondrites. Together, the Ar-Ar ages demonstrate that metamorphism on the Acapulco-Lodran parent body occurred 4.51 +/- 0.02 Ga ago, roughly 50 Ma after its formation. The geochemical and petrologic evidence on the Acapulco- and Lodran-like achondrites suggest that heating on the parent body was localized and heterogeneous in space and time. The parent body was probably not subjected to parent body-wide magmatism, in contrast to the case for 4 Vesta and the HED meteorites. C1 NASA,LYNDON B JOHNSON SPACE CTR,PLANETARY MISS & MAT BRANCH SN2,HOUSTON,TX 77058. NASA,LYNDON B JOHNSON SPACE CTR,PLANETARY SCI BRANCH SN4,HOUSTON,TX 77058. TARLETON STATE UNIV,DEPT PHYS SCI,STEPHENVILLE,TX 76402. RP Mittlefehldt, DW (reprint author), LOCKHEED MARTIN ESS,C23,2400 NASA RD 1,HOUSTON,TX 77058, USA. NR 62 TC 71 Z9 71 U1 1 U2 5 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, ENGLAND OX5 1GB SN 0016-7037 J9 GEOCHIM COSMOCHIM AC JI Geochim. Cosmochim. Acta PD MAR PY 1996 VL 60 IS 5 BP 867 EP 882 DI 10.1016/0016-7037(95)00423-8 PG 16 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA TY433 UT WOS:A1996TY43300009 ER PT J AU Nettleton, WD Chadwick, OA AF Nettleton, WD Chadwick, OA TI Late quaternary, redeposited loess-soil developmental sequences, south Yemen SO GEODERMA LA English DT Article ID HOLOCENE; DESERT; SEDIMENT; RAINFALL; PERIOD; SEA AB Episodic desert loess and paleosol sequences in South Yemen provide a late Pleistocene to Holocene record of climatic change and soil development. At Sana, one paleosol based on its thickness and development formed during mid or early Holocene time in approximately four thousand years. The 2Akb horizon sample of this paleosol has a C-14 age of 7750 +/- 300 years. At Ibb the 2ABtb horizon of another paleosol has a C-14 age of > 33,100 years. Deposition (silt + very fine sand + clay) for the Sana site calculates to average 110 g m(-2) yr(-1) and includes 3.3 g or less of CaCO3 m(-2) yr(-1). This rate of desert loess and carbonate deposition is probably 2 to 5 times greater than that in the Lahontan Basin of the United States during the last 13 kyr, and about 2 to 5 times higher than that in the southwestern United States today. It is about the same as the 12 cm kyr(-1) (170 g m(-2) yr(-1)) estimated for central North Iran and the 10 cm kyr(-1) (0.1 mm yr(-1)) estimated for the Netivot section of the Negev of Israel but some 7 to 9 times less than the rate estimated for Wisconsinan loess in Iowa. Thickness of desert loess examined and the calculated rate of deposition indicate that the crater has been receiving desert loess for at least 15 kyr, and that the crater is pre Holocene. Pedogenic development of the Camborthids and Haplargids in the ground soils and that of the argillic horizons in the Sana paleosols suggest that these soils formed in a somewhat more humid phase than the present warm-tropical, semi-arid environment. The occurrence of mollic epipedons in the Sana paleosols, but not in the ground soils is evidence of a more humid past climate (mid or early Holocene). The Ibb paleosol, which formed at least partly during a more humid part of the late Pleistocene, is even more strongly developed than the mid or early Holocene Sana paleosols. C1 CALTECH,JET PROP LAB,PASADENA,CA 91109. RP Nettleton, WD (reprint author), USDA,NRCS NSSC,NATL SOIL SURVEY LAB,FED BLDG,ROOM 152,100 CENTENNIAL MALL N,LINCOLN,NE 68508, USA. NR 44 TC 18 Z9 18 U1 0 U2 0 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0016-7061 J9 GEODERMA JI Geoderma PD MAR PY 1996 VL 70 IS 1 BP 21 EP 36 DI 10.1016/0016-7061(95)00063-1 PG 16 WC Soil Science SC Agriculture GA UK485 UT WOS:A1996UK48500002 ER PT J AU Litaor, MI Mancinelli, R Halfpenny, JC AF Litaor, MI Mancinelli, R Halfpenny, JC TI The influence of pocket gophers on the status of nutrients in Alpine soils SO GEODERMA LA English DT Article ID COLORADO FRONT RANGE; VEGETATION; SAMPLERS; USA AB Soil and soil solutions from the Martinelli Slope Experiment on Niwot Ridge, Front Range, Colorado (40 degrees 3'N,105 degrees 36'W) were studied to evaluate the influence of pocket gophers (Thomomys talpoides) on nutrient cycling in the alpine soil environment. Concentrations of total C, N, exchangeable Ca and K were significantly lower in gopher mound soils (P < 0.05), whereas available NO3- and nitrogen fluxes were significantly higher in these soils (P < 0.001). Silt and clay contents were significantly higher (P < 0.01) in the surface horizons compared with the subsurface horizons of the intermounds, whereas particle size distributions exhibited more homogenous profile in the mounds. This pattern was explained by the mixing activity of the pocket gophers. The biological homogenization strongly influenced particle size distribution, bulk density, the availability of nutrients, and especially modified the N cycle within the alpine soil environment. C1 UNIV COLORADO,INST ARCTIC & ALPINE RES,BOULDER,CO 80309. NASA,AMES RES CTR,MOFFETT FIELD,CA 94035. NR 33 TC 30 Z9 32 U1 0 U2 9 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0016-7061 J9 GEODERMA JI Geoderma PD MAR PY 1996 VL 70 IS 1 BP 37 EP 48 PG 12 WC Soil Science SC Agriculture GA UK485 UT WOS:A1996UK48500003 ER PT J AU OConnell, S Chandler, MA Ruedy, R AF OConnell, S Chandler, MA Ruedy, R TI Implications for the creation of warm saline deep water: Late Paleocene reconstructions and global climate model simulations SO GEOLOGICAL SOCIETY OF AMERICA BULLETIN LA English DT Article ID EARLY EOCENE; OCEAN CIRCULATION; ELLESMERE ISLAND; CARBON-DIOXIDE; SOUTHERN-OCEAN; INDIAN-OCEAN; HISTORY; RECORD; EVENTS AB A global warming trend began during the late Paleocene that culminated in the early Eocene with the highest global temperatures of the Cenozoic, We have reconstructed late Paleocene surficial boundary conditions and modeled atmospheric conditions using the Goddard Institute for Spate Studies general circulation model version II (GISS GCM II). These experiments were conducted to test the hypothesis that warm saline deep water formed during the late Paleocene and to understand atmospheric circulation near the beginning of a period of global warming. The warming is attributed primarily to increased sea surface temperatures at high latitudes. The sensitivity of the climate to ocean temperature was tested using two sea surface temperature distributions, each delimited latitudinally by oxygen isotope values, but with different east-west gradients. The simulations discussed here contain several features unique among warm climate experiments. The first experiment (P-1) used latitudinally constant (zonal) sea surface temperatures, The zonally distributed sea surface temperatures strengthen the general circulation of the atmosphere. In particular, Hadley Cell circulation is intensified, leading to extremes of precipitation in the equatorial region and extreme evaporation across subtropical oceans, The unusual results prompted a second experiment with modern east-west sea surface temperature gradients superimposed and referred to as P-Gradient (P-Grad). The east-west gradients in the sea surface temperature field exert a strong influence on the general atmospheric circulation, but the extreme zonality prevails, Under extreme zonal conditions it is possible to create a model where evaporation is in excess of precipitation by as much as 3 mm/day. If this occurred in restricted areas in a generally warmer ocean, such as the late Paleocene eastern Tethys Ocean and parts of the South Atlantic Ocean, it should be possible to create very saline water, which could become a component in warm saline deep water formation. C1 COLUMBIA UNIV,CTR CLIMATE SYST RES,NEW YORK,NY 10025. COLUMBIA UNIV,GODDARD INST SPACE STUDIES,NEW YORK,NY 10025. NASA,GODDARD INST SPACE STUDIES,SSAI,NEW YORK,NY 10025. RP OConnell, S (reprint author), WESLEYAN UNIV,DEPT EARTH & ENVIRONM SCI,265 CHURCH ST,MIDDLETOWN,CT 06459, USA. NR 84 TC 30 Z9 30 U1 0 U2 1 PU GEOLOGICAL SOC AMERICA PI BOULDER PA PO BOX 9140 3300 PENROSE PLACE, BOULDER, CO 80301 SN 0016-7606 J9 GEOL SOC AM BULL JI Geol. Soc. Am. Bull. PD MAR PY 1996 VL 108 IS 3 BP 270 EP 284 PG 15 WC Geosciences, Multidisciplinary SC Geology GA TY592 UT WOS:A1996TY59200002 ER PT J AU Purucker, ME Sabaka, TJ Langel, RA AF Purucker, ME Sabaka, TJ Langel, RA TI Conjugate gradient analysis: A new tool for studying satellite magnetic data sets SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID SOURCE INVERSION; ANOMALY DATA AB Conjugate gradient and sparse matrix techniques are utilized in the solution of a geomagnetic inverse problem. Global crustal data, sets collected from low-earth orbit are quickly inverted (using a design matrix approach) or continued to a common altitude (using a normal matrix approach) even when using parameterizations of 10000 or more dipoles. The sparsity results from the rapid decay of the magnetic field with distance from the dipole. Iterative techniques such as the conjugate gradient save computer time and space when compared to more direct approaches using the Householder transformation, thus allowing problems that were intractable to all but the largest supercomputers to be performed on workstations of only moderate power. C1 NASA,GODDARD SPACE FLIGHT CTR,GEODYNAM BRANCH,GREENBELT,MD 20771. RP Purucker, ME (reprint author), GODDARD SPACE FLIGHT CTR,HUGHES STX,GEODYNAM BRANCH,CODE 921,GREENBELT,MD 20771, USA. RI Sabaka, Terence/D-5618-2012 NR 12 TC 28 Z9 29 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 MAR 1 PY 1996 VL 23 IS 5 BP 507 EP 510 DI 10.1029/96GL00388 PG 4 WC Geosciences, Multidisciplinary SC Geology GA TZ786 UT WOS:A1996TZ78600024 ER PT J AU Chandra, S Varotsos, C Flynn, LE AF Chandra, S Varotsos, C Flynn, LE TI The mid-latitude total ozone trends in the northern hemisphere SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID STRATOSPHERIC OZONE; TOMS DATA; TEMPERATURE AB The total column ozone trends derived from satellite measurements at northern mid-latitudes during winter and spring seasons appear to be significantly larger than predicted by recent 2-D photochemical models. Analyses of 13 to 14 years of the Nimbus-7 TOMS total ozone measurements suggest that satellite-derived trends during winter and spring months are influenced by interannual variability associated with dynamical perturbations in the atmosphere. Such perturbations cause large longitudinal spread in total ozone trends at mid-latitudes. For example, the decadal trends in column ozone during February over the 10 degrees latitude band centered at 40 degrees N vary from about -9% to about -4% with error bars of 4 to 6% at the 2 sigma level. During the same month the zonally averaged trend is about -6 +/- 3%. The trends in certain geographical regions or locations, such as the Mediterranean region (35 degrees to 45 degrees N, 0 degrees to 30 degrees E) and Athens, Greece (38 degrees N, 24 degrees E), track the seasonal trends derived from the zonally-averaged data. Given the large uncertainties of the regional and local trends, such similarities may be fortuitous. By using the lower stratospheric and tropospheric temperatures as indices of dynamical variability in the ozone trend analysis, the total ozone trends are reduced by 1 to 3% per decade. For the winter months (December, January and February), the midlatitude trends (zonally averaged) are respectively -3.7 +/- 2.5 and -5.1 +/- 2.8% per decade with and without using the lower stratospheric temperature as an index of dynamical variability. C1 UNIV ATHENS,DEPT APPL PHYS,GR-10680 ATHENS,GREECE. SOFTWARE CORP AMER,LANHAM,MD 20706. RP Chandra, S (reprint author), NASA,GODDARD SPACE FLIGHT CTR,CODE 916,GREENBELT,MD 20771, USA. RI Flynn, Lawrence/B-6321-2009; Varotsos, Costas/H-6257-2013 OI Flynn, Lawrence/0000-0001-6856-2614; Varotsos, Costas/0000-0001-7215-3610 NR 16 TC 72 Z9 74 U1 0 U2 5 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD MAR 1 PY 1996 VL 23 IS 5 BP 555 EP 558 DI 10.1029/96GL00305 PG 4 WC Geosciences, Multidisciplinary SC Geology GA TZ786 UT WOS:A1996TZ78600036 ER PT J AU Kessel, RL Chen, SH Green, JL Fung, SF Boardsen, SA Tan, LC Eastman, TE Craven, JD Frank, LA AF Kessel, RL Chen, SH Green, JL Fung, SF Boardsen, SA Tan, LC Eastman, TE Craven, JD Frank, LA TI Evidence of high-latitude reconnecting during northward IMF: Hawkeye observations SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID MAGNETIC-FIELD; DAYSIDE MAGNETOPAUSE; POLAR; INTERPLANETARY; MAGNETOSPHERE; CUSP AB Reconnection is accepted as an important process for driving the solar wind/magnetospheric interaction although it is not fully understood. In particular, reconnection for northward interplanetary magnetic field (IMF) at high-latitudes tailward of the cusp, has received little attention in comparison with equatorial reconnection for southward IMF. Using Hawkeye data we present the first direct observations of reconnection at the high-latitude magnetopause (75 degrees) during northward IMF in the form of sunward flowing protons. This flow is nearly field aligned, approximately Alfvenic, and roughly obeys tangential momentum balance. The magnetic field shear is large at the magnetopause and there is a non-zero B-N component suggesting the existence of a rotational discontinuity and reconnection. The Hawkeye observations support several recent simulations at least qualitatively in terms of flow directions expected for high-latitude reconnection during northward IMF. C1 UNIV MARYLAND,COLLEGE PK,MD 20742. UNIV ALASKA,FAIRBANKS,AK 99701. UNIV IOWA,IOWA CITY,IA. RP Kessel, RL (reprint author), NASA,GODDARD SPACE FLIGHT CTR,HUGHES STX,GREENBELT,MD 20771, USA. RI Fung, Shing/F-5647-2012 NR 16 TC 136 Z9 138 U1 1 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 MAR 1 PY 1996 VL 23 IS 5 BP 583 EP 586 DI 10.1029/95GL03083 PG 4 WC Geosciences, Multidisciplinary SC Geology GA TZ786 UT WOS:A1996TZ78600043 ER PT J AU Farrell, WM AF Farrell, WM TI Are Neptune's highly dispersed whistlers really Z-mode radiation? SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID MAGNETOSPHERE; DENSITIES; EMISSION; FIELD AB Evidence is presented that the unusual lightning-generated whistler signals detected very near Neptune are possibly impulsive emissions propagating in the z-mode. Unlike terrestrial whistlers in the plasmasphere, the Neptunian emissions might be propagating in a region where the plasma-to-cyclotron frequency ratio is much less than one. If the nightside plasma density is indeed low, the z-mode will extend down to unusually low frequencies. The observed events may then be interpreted as z-mode instead of the whistler mode. Propagation in the z-mode may explain many of the unusual emission features, including the low frequency limit of 6 kHz and the very large dispersions. Given an atmospheric emission source, this result suggests that Neptune's ionospheric electron density is relatively low. In order for the dispersive events to be observed at Voyager in the z-mode, some locations in the nightside ionosphere are required to have densities as low as about 100 cm(-3). A possible magnetospheric source for the emission is also discussed. RP Farrell, WM (reprint author), NASA,GODDARD SPACE FLIGHT CTR,EXTRATERR PHYS LAB,CODE 695,GREENBELT,MD 20771, USA. RI Farrell, William/I-4865-2013 NR 13 TC 1 Z9 1 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 MAR 1 PY 1996 VL 23 IS 5 BP 587 EP 590 DI 10.1029/95GL03090 PG 4 WC Geosciences, Multidisciplinary SC Geology GA TZ786 UT WOS:A1996TZ78600044 ER PT J AU Roberts, DA Ghosh, S Goldstein, M AF Roberts, DA Ghosh, S Goldstein, M TI Nonlinear evolution of interplanetary Alfvenic fluctuations with convected structures SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID SOLAR-WIND TURBULENCE; MAGNETOHYDRODYNAMIC FLUCTUATIONS; INNER HELIOSPHERE; ORIGIN AB At least at solar minimum, many regions in slow solar wind near the heliospheric current sheet have very low Alfvenicity. Motivated by recent suggestions that the interaction of the waves with the observed striated density, temperature, and magnetic field structures in the low Alfvenicity regions causes the decay of outward dominance, we have used two- and three-dimensional MHD codes to simulate such situations to determine the evolution. We find that outward propagating waves in the presence of structures become only slightly less Alfvenic (unlike observations), and that what were initially parallel propagating waves fairly rapidly become nearly isotropic with a self-similar spectrum typical of turbulence (similar to observations). These simulations suggest that the low Aflvenicty regions must arise from some other cause, such as ''microstreams'' that are eradicated as they decrease the Alfvenic correlations. RP Roberts, DA (reprint author), NASA,GODDARD SPACE FLIGHT CTR,EXTRATERR PHYS LAB,GREENBELT,MD 20771, USA. RI Roberts, Dana/D-4625-2012 NR 16 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 MAR 1 PY 1996 VL 23 IS 5 BP 591 EP 594 DI 10.1029/96GL00382 PG 4 WC Geosciences, Multidisciplinary SC Geology GA TZ786 UT WOS:A1996TZ78600045 ER PT J AU Forsyth, RJ Horbury, TS Balogh, A Smith, EJ AF Forsyth, RJ Horbury, TS Balogh, A Smith, EJ TI Hourly variances of fluctuations in the heliospheric magnetic field out of the ecliptic plane SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID INTERPLANETARY ALFVENIC FLUCTUATIONS; SOLAR-WIND; AU; TURBULENCE; EVOLUTION; ULYSSES AB Magnetic field fluctuations at high heliographic latitudes are discussed in terms of the latitude and radial dependence of their variances, as observed by the Ulysses spacecraft. The increased level of transverse fluctuations in fast solar wind flows from the polar coronal holes is similar to that found in high speed streams near the ecliptic. However, continuous observations in the fast solar wind both southward and northward of the solar equatorial plane has allowed the determination of the radial dependence of fluctuations on hourly and shorter timescales, free from additional energy input from stream-stream interactions or from coronal mass ejections and in the presence of a slowly evolving, low frequency Alfvenic population. The conclusion is that fluctuations in the inertial range in the homogeneous polar coronal flows decay faster than predicted by the WKB approximation. However, even minor compression effects can increase the energy in these fluctuations. C1 CALTECH, JET PROP LAB, PASADENA, CA 91109 USA. RP Forsyth, RJ (reprint author), UNIV LONDON IMPERIAL COLL SCI TECHNOL & MED, BLACKETT LAB, PRINCE CONSORT RD, LONDON SW7 2BZ, ENGLAND. NR 24 TC 38 Z9 38 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD MAR 1 PY 1996 VL 23 IS 5 BP 595 EP 598 DI 10.1029/96GL00416 PG 4 WC Geosciences, Multidisciplinary SC Geology GA TZ786 UT WOS:A1996TZ78600046 ER PT J AU Knudsen, RL Jensen, BJ AF Knudsen, RL Jensen, BJ TI Blends of reactive diluents with phenylethynyl-terminated arylene ether oligomers SO HIGH PERFORMANCE POLYMERS LA English DT Article ID END-CAPPING AGENTS; POLYETHERS AB A series of blends containing phenylethynyl-terminated arylene ether (PETAE) oligomers and phenylethynyl-containing reactive diluents were prepared and characterized. Most of the blends prepared met the objective of this work which was to further modify the PETAE oligomers in order to improve solvent resistance, increase modulus and adhesive strength, and reduce melt viscosity. The cured blends generally have higher glass transition temperatures and improved mechanical properties compared with the analogous thermoplastic polymers. C1 COLL WILLIAM & MARY,DEPT APPL SCI,WILLIAMSBURG,VA 23187. NASA,LANGLEY RES CTR,HAMPTON,VA 23681. NR 10 TC 17 Z9 17 U1 2 U2 5 PU IOP PUBLISHING LTD PI BRISTOL PA TECHNO HOUSE, REDCLIFFE WAY, BRISTOL, ENGLAND BS1 6NX SN 0954-0083 J9 HIGH PERFORM POLYM JI High Perform. Polym. PD MAR PY 1996 VL 8 IS 1 BP 57 EP 66 DI 10.1088/0954-0083/8/1/004 PG 10 WC Polymer Science SC Polymer Science GA UT392 UT WOS:A1996UT39200004 ER PT J AU Belton, MJS Chapman, CR Klaasen, KP Harch, AP Thomas, PC Veverka, J McEwen, AS Pappalardo, RT AF Belton, MJS Chapman, CR Klaasen, KP Harch, AP Thomas, PC Veverka, J McEwen, AS Pappalardo, RT TI Galileo's encounter with 243 Ida: An overview of the imaging experiment SO ICARUS LA English DT Article AB We provide an overview of the execution, data, and results of the solid state imaging (SSI) experiment at the encounter of the Galileo spacecraft with the asteroid 243 Ida. Ninety-six images of the asteroid, representing 18 time samples during a rotation period (4.633 h), were transmitted to Earth as a result of the UT 1993 August 28.70284 encounter. This provided coverage of similar to 95% of the surface and achieved ground resolutions as high as 25 m/pixel. Coverage of most of Ida's surface is available in four colors, with limited regions in five colors, at resolutions up to 105 m/pixel. A natural satellite of Ida, called Dactyl, was discovered in a prograde (with respect to Ida's spin), near-equatorial, orbit moving slowly (similar to 6 m/sec) with a separation of 85 km from Ida. Ida's shape is highly irregular; by comparison, Dactyl's global topography is quite smooth. The best fit ellipsoid to Ida's shape has principal dimensions 59.8 x 25.4 x 18.6 km, mean radius 15.7 km, and volume 16,100 +/- 1900 km(3). Dactyl's mean radius is only 0.7 km. Ida's spin axis (right ascension: 348.76 degrees +/- 7.5 degrees; declination: 87.10 degrees +/- 0.4 degrees; J2000) was found to align with the principal axis of inertia to within the error of measurement. This is consistent with a homogeneous density distribution. Dactyl's rotation rate is unknown, but its long axis was pointed in the direction of Ida at the time of observation, suggesting synchronism of its orbital motion and spin. Constraints on Dactyl's orbit yield 4.2 +/- 0.6 x 10(19) g for Ida's mass and 2.6 +/- 0.5 g/cm(3) for its bulk density. Unless Ida's bulk porosity is exceptionally high, Ida has moderate to low NiFe content. Subtle color variations across the surface of Ida are associated with fresh craters, but, unlike the case for Asteroid 951 Gaspra, are not correlated with topographic features such as ridges. This difference may be a reflection of a deeper and/or more mobile regolith on Ida. Dactyl's spectral reflectance is similar to, but quantitatively distinct from the surface of Ida itself. This difference may reflect compositional differences between Dactyl and Ida, which in turn may have originated in an only partially differentiated Koronis parent body. Results on the origin, collisional history, and geology of Ida and Dactyl are the subject of many of the papers in this special issue. There is general agreement that these asteroids originated in the catastrophic breakup of the Koronis parent body and that the formation of asteroid-satellite systems may be relatively common in such events. The age and collisional history of the pair present a dilemma: using standard interpretations of the cratering record on Ida's surface, an age > 1 byr. is indicated. However, the lifetime of Dactyl against collisional disruption is many times less than this. Novel ideas are presented concerning the collisional history of these two small objects that may resolve this dilemma. These ideas result from analysis of the geological record on the surface of Ida, Dactyl, and, by comparison, Gaspra-all of which are examined in this special issue. The execution of the Galileo flybys of Gaspra, Ida, and Dactyl provide important lessons for future flybys of small bodies. We present our views on the limitations faced by the Galileo imaging experimenters and indicate how future missions can be made more quantitative and productive through the application of innovative electronic control systems and detector technology. (C) 1996 Academic Press, Inc. C1 PLANETARY SCI INST,TUCSON,AZ 85705. CALTECH,JET PROP LAB,PASADENA,CA 91109. CORNELL UNIV,CTR RADIOPHYS & SPACE RES,ITHACA,NY 14853. US GEOL SURVEY,FLAGSTAFF,AZ 86001. ARIZONA STATE UNIV,DEPT GEOL,TEMPE,AZ 85287. RP Belton, MJS (reprint author), NATL OPT ASTRON OBSERV,TUCSON,AZ 85719, USA. NR 33 TC 42 Z9 43 U1 0 U2 4 PU ACADEMIC PRESS INC JNL-COMP SUBSCRIPTIONS PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 SN 0019-1035 J9 ICARUS JI Icarus PD MAR PY 1996 VL 120 IS 1 BP 1 EP 19 DI 10.1006/icar.1996.0032 PG 19 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA UF009 UT WOS:A1996UF00900001 ER PT J AU Helfenstein, P Veverka, J Thomas, PC Simonelli, DP Klaasen, K Johnson, TV Fanale, F Granahan, J McEwen, AS Belton, M Chapman, C AF Helfenstein, P Veverka, J Thomas, PC Simonelli, DP Klaasen, K Johnson, TV Fanale, F Granahan, J McEwen, AS Belton, M Chapman, C TI Galileo photometry of asteroid 243 Ida SO ICARUS LA English DT Article ID BIDIRECTIONAL REFLECTANCE SPECTROSCOPY AB Galileo imaging observations over phase angles 19.5 degrees to 109.8 degrees are combined with near-opposition Earth-based data to derive the photometric properties of Ida. To first order these properties are uniform over the surface and well modeled at lambda = 0.55 mu m by Hapke parameters <(omega)over tilde>, = 0.22, h = 0.020, B-0 = 1.5, g = -0.33, and theta = 18 degrees with corresponding geometric albedo p = 0.21+/-(0.03)(0.01): and Bond albedo A(B) = 0.081+/-(0.017)(0.008). Ida's photometric properties are more similar to those of ''average S-asteroids'' (P. Helfenstein and J. Veverka 1989, Asteroids II, Univ. of Arizona Press, Tucson) than are those of 951 Gaspra. Two primary color units are identified on Ida: Terrain A exhibits a spectrum with relatively shallower 1-mu m absorption and a relatively steeper red spectral slope than average Ida, while Terrain B has a deeper 1-mu m absorption and a less steep red slope. The average photometric properties of Ida and Terrain A are similar while those of Terrain B differ mostly in having a slightly higher value of <(omega)over tilde>(0) (0.22 versus 0.21), suggesting that Terrain B consists of slightly brighter, more transparent regolith particles. Galileo observations of Ida's satellite Dactyl over phase angles 19.5 degrees to 47.6 degrees suggest photometric characteristics similar to those of Ida, the major difference being Dactyl's slightly lower albedo (0.20 compared to 0.21). (C) 1996 Academic Press, Inc. C1 CALTECH,JET PROP LAB,PASADENA,CA 91109. UNIV HAWAII,INST GEOPHYS,HONOLULU,HI 96822. US GEOL SURVEY,FLAGSTAFF,AZ 86001. KITT PEAK NATL OBSERV,NATL OPT ASTRON OBSERV,TUCSON,AZ 85726. PLANETARY SCI INST,TUCSON,AZ 85705. RP Helfenstein, P (reprint author), CORNELL UNIV,CTR RADIOPHYS & SPACE RES,ITHACA,NY 14853, USA. NR 19 TC 84 Z9 85 U1 0 U2 0 PU ACADEMIC PRESS INC JNL-COMP SUBSCRIPTIONS PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 SN 0019-1035 J9 ICARUS JI Icarus PD MAR PY 1996 VL 120 IS 1 BP 48 EP 65 DI 10.1006/icar.1996.0036 PG 18 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA UF009 UT WOS:A1996UF00900005 ER PT J AU Veverka, J Helfenstein, P Lee, P Thomas, P McEwen, A Belton, M Klaasen, K Johnson, TV Granahan, J Fanale, F Geissler, P Head, JW AF Veverka, J Helfenstein, P Lee, P Thomas, P McEwen, A Belton, M Klaasen, K Johnson, TV Granahan, J Fanale, F Geissler, P Head, JW TI Ida and Dactyl: Spectral reflectance and color variations SO ICARUS LA English DT Article ID METAL AB Galileo SSI color data between 0.4 and 1.0 mu m demonstrate that both Ida and Dactyl are S-type asteroids with similar, but distinct spectra, Small but definite color variations are also observed on Ida itself and involve both the blue part of the spectrum and the depth of the 1-mu m pyroxene-olivine band. Ida's surface can be classified into two color terrains: Terrain A has a shadower 1-mu m absorption and a steeper visible red slope than does Terrain B. Qualitatively, the color-albedo systematics of these two terrains follow those noted for color units on Gaspra and the variations in 1-mu m band depth with weathering described by Gaffey et al. (Gaffey, M. J., J. F. Bell, R. H. Brown, T, H. Burbine, J. Piatek, K. L. Reed, and D. A. Chaky 1993. Icarus 106, 573-602). Terrain A, with its slightly lower albedo, its shallower 1-mu m band, and its slightly steeper visible red slope relative to Terrain B could be interpreted as the ''more processed,'' ''more mature,'' or the ''more weathered'' of the two terrains. Consistent with this interpretation is that Terrain A appears to be the ubiquitous background on most of Ida, while Terrain B is correlated with some small craters as well as with possible ejecta from the 10-km Azzurra impact structure. Because of these trends, it is less likely that differences between Terrains A and B are caused by an original compositional inhomogeneity within the body of Ida, although they do fail within the range known to occur within the Koronis family. The spectrum of Dactyl is similar to, but definitely different from, that of Terrain B on Ida. It does not conform to the pattern that obtains between the colors and albedos of Terrains A and B: the satellite's 1-mu m band is deeper than that of Terrain B, but its albedo is lower, rather than higher, By itself, the deeper band depth could be interpreted, following Gaffey et at, to mean that Dactyl is a less weathered version of Terrain B on Ida, but such an interpretation is at odds with Dactyl's redder spectral slope. Thus, the explanation for the color difference between Dactyl and Ida is likely to be different from that which accounts for the differences between the two terrains on Ida. Given that Dactyl and Ida have very similar photometric properties (Helfenstein, P., J. Veverka, P. C. Thomas, D. P. Simonelli, K. Klassen, T. V. Johnson, F. Fanale, J. Granahan, A. S. McEwen, M. J. S. Belton, and C. R. Chapman 1996 Icarus 120, 48-65), thus ruling out any dramatic texture differences between the two surfaces, the most likely explanation is that the satellite has a slightly different composition (more pyroxene?) than Ida. The spectral difference is within the range reported by Binzel et al. (Binzel, R. P., S. Xu, and S. J. Bus 1993. Icarus 106, 608-611.) for members of the Koronis family, and could be caused by compositional inhomogeneities of the Koronis parent body rather than by post-breakup regolith processes. (C) 1996 Academic Press, Inc. C1 US GEOL SURVEY,FLAGSTAFF,AZ 86001. NATL OPT ASTRON OBSERV,TUCSON,AZ 85726. CALTECH,JET PROP LAB,PASADENA,CA 91109. UNIV HAWAII,INST GEOPHYS,HONOLULU,HI 96822. UNIV ARIZONA,LUNAR & PLANETARY LAB,TUCSON,AZ 85721. BROWN UNIV,DEPT GEOL SCI,PROVIDENCE,RI 02912. RP Veverka, J (reprint author), CORNELL UNIV,SPACE SCI BLDG,ITHACA,NY 14853, USA. NR 32 TC 33 Z9 33 U1 0 U2 0 PU ACADEMIC PRESS INC JNL-COMP SUBSCRIPTIONS PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 SN 0019-1035 J9 ICARUS JI Icarus PD MAR PY 1996 VL 120 IS 1 BP 66 EP 76 DI 10.1006/icar.1996.0037 PG 11 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA UF009 UT WOS:A1996UF00900006 ER PT J AU Greenberg, R Bottke, WF Nolan, M Geissler, P Petit, JM Durda, DD Asphaug, E Head, J AF Greenberg, R Bottke, WF Nolan, M Geissler, P Petit, JM Durda, DD Asphaug, E Head, J TI Collisional and dynamical history of Ida SO ICARUS LA English DT Article ID ASTEROID FAMILIES; FRAGMENTATION AB The history of Ida is constrained by its membership in the Koronis family, its satellite Dactyl, the record of impacts left on its surface, and other dynamical,morphological, and spectral properties. Models of crater production and comparably effective erasure processes, combined with the current size-frequency distribution of craters, suggest that the age of the surface is either about 50 myr or >1 byr. The younger age may be inconsistent with the degraded appearance of many craters, while the older age conflicts with the collisional life expectancy of Dactyl. Consideration of Dactyl's evolution may resolve this issue as well as shed light on the formation of Dactyl, the density of Ida, and possible source regions for Ida and Dactyl within the Koronis parent body. (C) 1996 Academic Press, Inc. C1 NASA,AMES RES CTR,MOFFETT FIELD,CA 94035. BROWN UNIV,PROVIDENCE,RI 02912. OBSERV NICE,F-06003 NICE,FRANCE. RP Greenberg, R (reprint author), UNIV ARIZONA,LUNAR & PLANETARY LAB,TUCSON,AZ 85721, USA. RI Nolan, Michael/H-4980-2012 OI Nolan, Michael/0000-0001-8316-0680 NR 35 TC 64 Z9 64 U1 0 U2 0 PU ACADEMIC PRESS INC JNL-COMP SUBSCRIPTIONS PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 SN 0019-1035 J9 ICARUS JI Icarus PD MAR PY 1996 VL 120 IS 1 BP 106 EP 118 DI 10.1006/icar.1996.0040 PG 13 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA UF009 UT WOS:A1996UF00900009 ER PT J AU Sullivan, R Greeley, R Pappalardo, R Asphaug, E Moore, JM Morrison, D Belton, MJS Carr, M Chapman, CR Geissler, P Greenberg, R Granahan, J Head, JW Kirk, R McEwen, A Lee, P Thomas, PC Veverka, J AF Sullivan, R Greeley, R Pappalardo, R Asphaug, E Moore, JM Morrison, D Belton, MJS Carr, M Chapman, CR Geissler, P Greenberg, R Granahan, J Head, JW Kirk, R McEwen, A Lee, P Thomas, PC Veverka, J TI Geology of 243 Ida SO ICARUS LA English DT Article ID IMPACT CRATERS; SOLAR-SYSTEM; PHOBOS; EJECTA; DEIMOS; SPECTROSCOPY; REGOLITHS; ORIGIN; MODEL; MOON AB The surface of 243 Ida is dominated by the effects of impacts. No complex crater morphologies are observed. A complete range of crater degradation states is present, which also reveals optical maturation of the surface (darkening and reddening of materials with increasing exposure age), Regions of bright material associated with the freshest craters might be ballistically emplaced deposits or the result of seismic disturbance of loosely-bound surface materials. Diameter/depth ratios for fresh craters on Ida are similar to 1:6.5, similar to Gaspra results, but greater than the 1:5 ratios common on other rocky bodies. Contributing causes include rim degradation by whole-body ''ringing,'' relatively thin ejecta blankets around crater rims, or an extended strength gradient in near-surface materials due to low gravitational self-packing, Grooves probably represent expressions in surface debris of reactivated fractures in the deeper interior, Isolated positive relief features as large as 150 m are probably ejecta blocks related to large impacts. Evidence for the presence of debris on the surface includes resolved ejecta blocks, mass-wasting scars, contrasts in color and albedo of fresh crater materials, and albedo streaks oriented down local slopes. Color data indicate relatively uniform calcium abundance in pyroxenes and constant pyroxene/olivine ratio. A large, relatively blue unit across the northern polar area is probably related to regolith processes involving ejecta from Azzurra rather than representing internal compositional heterogeneity. A small number of bluer, brighter craters are randomly distributed across the surface, unlike on Gaspra where these features are concentrated along ridges. This implies that debris on Ida is less mobile and/or consistently thicker than on Gaspra. Estimates of the average depth of mobile materials derived from chute depths (20-60 m), grooves (greater than or equal to 30 m), and shallowing of the largest degraded craters (20-50 m minimum, similar to 100 m maximum) suggest a thickness of potentially mobile materials of similar to 50 m, and a typical thickness for the debris layer of 50-100 m. (C) 1996 Academic Press, Inc. C1 NASA,AMES RES CTR,DIV SPACE SCI,MOFFETT FIELD,CA 94035. NATL OPT ASTRON OBSERV,TUCSON,AZ 85719. US GEOL SURVEY,BRANCH ASTROGEOL STUDIES,MENLO PK,CA 94025. PLANETARY SCI INST,TUCSON,AZ 85705. UNIV ARIZONA,LUNAR & PLANETARY LAB,TUCSON,AZ 85721. UNIV HAWAII MANOA,HAWAII INST GEOPHYS,HONOLULU,HI 96822. BROWN UNIV,DEPT GEOL SCI,PROVIDENCE,RI 02912. US GEOL SURVEY,FLAGSTAFF,AZ 86001. CORNELL UNIV,CTR RADIOPHYS & SPACE RES,ITHACA,NY 14853. RP Sullivan, R (reprint author), ARIZONA STATE UNIV,DEPT GEOL,BOX 871404,TEMPE,AZ 85287, USA. NR 99 TC 86 Z9 86 U1 1 U2 2 PU ACADEMIC PRESS INC JNL-COMP SUBSCRIPTIONS PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 SN 0019-1035 J9 ICARUS JI Icarus PD MAR PY 1996 VL 120 IS 1 BP 119 EP 139 DI 10.1006/icar.1996.0041 PG 21 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA UF009 UT WOS:A1996UF00900010 ER PT J AU Geissler, P Petit, JM Durda, DD Greenberg, R Bottke, W Nolan, M AF Geissler, P Petit, JM Durda, DD Greenberg, R Bottke, W Nolan, M TI Erosion and ejecta reaccretion on 243 Ida and its moon SO ICARUS LA English DT Article ID IMPACT PROCESSES; PHOBOS; DEIMOS; MODEL AB Galileo images of Asteroid 243 Ida and its satellite Dactyl show surfaces which are dominantly shaped by impact cratering. A number of observations suggest that ejecta from hypervelocity impacts on Ida can be distributed far and wide across the Ida system, following trajectories substantially affected by the low gravity, nonspherical. shape, and rapid rotation of the asteroid. We explore the processes of reaccretion and escape of ejecta on Ida and Dactyl using three-dimensional numerical simulations which allow us to compare the theoretical effects of orbital dynamics with observations of surface morphology. The effects of rotation, launch location, and initial launch speed are first examined for the case of an ideal triaxial ellipsoid with Ida's approximate shape and density. Ejecta launched at low speeds (V much less than V-esc) reimpact near the source craters, forming well-defined ejecta blankets which are asymmetric in morphology between leading and trailing rotational surfaces. The net effect of cratering at low ejecta launch velocities is to produce a thick regolith which is evenly distributed across the surface of the asteroid. In contrast, no clearly defined ejecta blankets are formed when ejecta is launched at higher initial velocities (V similar to V-esc). Most of the ejecta escapes, while that which is retained is preferentially derived from the rotational trailing surfaces. These particles spend a significant time in temporary orbit around the asteroid, in comparison to the asteroid's rotation period, and tend to be swept up onto rotational leading surfaces upon reimpact. The net effect of impact cratering with high ejecta launch velocities is to produce a thinner and less uniform soil cover, with concentrations on the asteroids' rotational leading surfaces. Using a realistic model for the shape of Ida (P. Thomas, J. Veverka, B. Carcich, M. J. S. Belton, R. Sullivan, and M. Davies 1996, Icarus 120, 000-000), we find that an extensive color/albedo unit which dominates the northern and western hemispheres of the asteroid can be explained as the result of reaccretion of impact ejecta from the large and evidently recent crater ''Azzurra.'' Initial ejection speeds required to match the color observations are on the order of a few meters per second, consistent with models (e.g., M. C. Nolan, E. Asphaug, H. J. Melosh, and R. Greenberg 1996, Icarus, submitted; E. Asphaug, J. Moore, D. Morrison, W. Bent, and R. Sullivan 1996, Icarus 120, 158-184) that multikilometer craters on Ida form in the gravity-dominated regime and are net producers of locally retained regolith. Azzurra ejecta launched in the direction of rotation at speeds near 10 m/ sec are lofted over the asteroid and swept up onto the rotational leading surface on the opposite side. The landing locations of these particles closely match the distribution of large ejecta blocks observed in high resolution images of Ida (P. Lee, J. Veverka, P. Thomas, P. Helfstein, M. J. S. Belton, C. Chapman, R. Greeley, R. Pappalardo, R. Sullivan, and J. W. Head 1996, Icarus 120, 87-105). Ida's shape and rotation allow escape of ejecta launched at speeds far below the escape velocity of a nonrotating sphere of Ida's volume and presumed density. While little ejecta from Ida is captured by Dactyl, about half of the mass ejected from Dactyl at speeds of up to 20 m/sec eventually falls on Ida. Particles launched at speeds just barely exceeding Dactyl's escape velocity can enter relatively long-term orbit around Ida, but few are ultimately reaccreted by the satellite. Because of its low gravity, erosion of Dactyl would take place on exceedingly short time scales if unconsolidated materials compose the satellite and crater formation is in the gravity regime. If Dactyl is a solid rock, then ifs shape has evolved from a presumably irregular initial fragment to its present remarkably rounded figure by collision with a population of impactors too small to be detected by counting visible craters. As the smallest solar system object yet imaged by a spacecraft, the morphology of Dactyl is an important clue to the asteroid population at the smallest sizes. (C) 1996 Academic Press, Inc. C1 OBSERV NICE,F-06304 NICE,FRANCE. NATL ASTRON & IONOSPHERE CTR,ARECIBO OBSERV,ARECIBO,PR 00613. NASA,AMES RES CTR,MOFFETT FIELD,CA 94035. RP Geissler, P (reprint author), UNIV ARIZONA,LUNAR & PLANETARY LAB,TUCSON,AZ 85721, USA. RI Nolan, Michael/H-4980-2012 OI Nolan, Michael/0000-0001-8316-0680 NR 44 TC 79 Z9 80 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 MAR PY 1996 VL 120 IS 1 BP 140 EP 157 DI 10.1006/icar.1996.0042 PG 18 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA UF009 UT WOS:A1996UF00900011 ER PT J AU Asphaug, E Moore, JM Morrison, D Benz, W Nolan, MC Sullivan, RJ AF Asphaug, E Moore, JM Morrison, D Benz, W Nolan, MC Sullivan, RJ TI Mechanical and geological effects of impact cratering on Ida SO ICARUS LA English DT Article ID PHOBOS; FRAGMENTATION AB Asteroids respond to impact stresses differently from either laboratory specimens or large planets. Gravity is typically so small that seismic disturbances of a few cm s(-1) can devastate unconsolidated topography. Yet the presence of regolith and the likelihood that many asteroids are gravitational assemblages tell us that gravity cannot generally be ignored. We use numerical models for impact fracture in solids to examine the initial stage of crater formation on asteroid 243 Ida, up to the cessation of fracture and the establishment of the cratering flow; at this stage we can infer final crater diameters but not profiles. We find that a modified strength scaling applies for craters up to a few 100 m in diameter forming in rock subject to Ida's gravity, and that gravity controls all craters larger than similar to 1 km. ''Bright annuli'' around a number of intermediate craters may be the result of low-velocity surface disturbances, rather than bright proximal ejecta deposits. We also consider large impactors, to which Ida presents a curved, finite target surface with irregular gravity. These can excavate asymmetrical concavities. Stresses from large events can refocus and cause fracture far from the crater; using the shape of Ida as a basis for 3D hydrocode simulations, we show that impact genesis of the Vienna Regio concavity can cause fracture in Pola Regio, where grooves are observed in spacecraft images. Other simulations indicate that the formation of the similar to 10 km crater Azzurra might have reopened these fractures, which may account for their fresh appearance. This mechanism of groove formation requires an interior which coherently transmits elastic stress. While this precludes a classic ''rubble pile'' asteroid, it does allow well-joined fault planes, and welded blocks or pores smaller than the stress pulse. (C) 1996 Academic Press, Inc. C1 UNIV ARIZONA,STEWARD OBSERV,TUCSON,AZ 85721. UNIV ARIZONA,LUNAR & PLANETARY LAB,TUCSON,AZ 85721. ARIZONA STATE UNIV,DEPT GEOL,TEMPE,AZ 85287. RP Asphaug, E (reprint author), NASA,AMES RES CTR,MS 245-3,MOFFETT FIELD,CA 94035, USA. RI Nolan, Michael/H-4980-2012 OI Nolan, Michael/0000-0001-8316-0680 NR 67 TC 88 Z9 88 U1 1 U2 5 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 MAR PY 1996 VL 120 IS 1 BP 158 EP 184 DI 10.1006/icar.1996.0043 PG 27 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA UF009 UT WOS:A1996UF00900012 ER PT J AU Belton, MJS Mueller, BEA DAmario, LA Byrnes, DV Klaasen, KP Synnott, S Breneman, H Johnson, TV Thomas, PC Veverka, J Harch, AP Davies, ME Merline, WJ Chapman, CR Davis, D Denk, T Neukum, G Petit, JM Greenberg, R Storrs, A Zellner, B AF Belton, MJS Mueller, BEA DAmario, LA Byrnes, DV Klaasen, KP Synnott, S Breneman, H Johnson, TV Thomas, PC Veverka, J Harch, AP Davies, ME Merline, WJ Chapman, CR Davis, D Denk, T Neukum, G Petit, JM Greenberg, R Storrs, A Zellner, B TI The discovery and orbit of 1993 (243)1 Dactyl SO ICARUS LA English DT Article ID ASTEROIDS AB Dactyl was discovered in solid state imaging (SSI) data on February 17, 1994, during the long playback of approach images from the Galileo spacecraft's encounter with the asteroid 243 Ida. Forty-seven images of the Ida-Dactyl pair were obtained, A detailed search for other satellites was made, No confirmed detections were made, all other candidate features being consistent with radiation hits. We deduce a manifold of osculating two-body orbits that approximate Dactyl's motion over the observed orbital are depending on the assumed mass of Ida. At the time of Galileo's encounter, Dactyl was found to be 85 km from the center of Ida, moving at similar to 6 m . sec(-1) in the same direction as Ida's retrograde spin, The inclination of its orbit is similar to 172 degrees in Ida's equatorial system (IAU definition), It was not possible to obtain a definitive orbit or measure of Ida's mass from the observed motion even though supplemental techniques (search for Dactyl's shadow on Ida, changes in angular diameter and brightness, and attempts to determine the spin of Dactyl) were explored. The influence of Ida's irregular gravitational field and solar perturbations on two-body motion are evaluated and found to be undetectable in the observed orbital are. These effects may, however, strongly influence the motion over orbital time scales. Limits to the value of Ida's gravitation parameter, GM,are derived. A robust lower limit, GM > 0.0023 km(3) . sec(-2), is obtained by requiring Dactyl's orbit to be bound. Hubble Space Telescope observations, which show no evidence of Dactyl on a hyperbolic orbit, excludes values of GM in the range 0.00216 < GM < 0.0023 km(3) . sec(-2). An upper limit, GM < 0.0031 km(3) . sec(-2), deduced by requiring that the orbital motion has a long lifetime in a realistic approximation to Ida's gravitational field, is illustrated with numerical calculations. Ida's mass is therefore constrained to the range 4.2 +/- 0.6 x 10(19) g, which, together with a volume of 16,100 +/- 1900 km(3) (Thomas P.C., M.J.S.Belton, B. Carcich, C. R. Chapman, M. E. Davies, R. Sullivan, and J. Veverka 1996. Icarus 120, 20-32.) yields a bulk density of 2.6 +/- 0.5 g . cm(-3) (Belton, M. J. S., C. R. Chapman, P. C. Thomas, M. E. Davies, R. Greenberg, K. Klaasen, D. Byrnes, L. D'Amario, S. Synnott, T. V. Johnson, A. McEwen, W. Merline, D. R. Davis, J-M. Petit, A. Storrs, J. Veverka, and B. Zellner 1995. Nature 374, 785-788.). (C) 1996 Academic Press, Inc. C1 CALTECH,JET PROP LAB,PASADENA,CA 91109. CORNELL UNIV,CTR RADIOPHYS & SPACE RES,ITHACA,NY 14853. RAND CORP,SANTA MONICA,CA 90406. PLANETARY SCI INST,TUCSON,AZ 85705. DLR,INST PLANETENERKUNDUNG,BERLIN,GERMANY. OBSERV NICE,NICE,FRANCE. UNIV ARIZONA,LUNAR & PLANETARY LAB,TUCSON,AZ 85721. SPACE TELESCOPE SCI INST,BALTIMORE,MD 21218. GEORGIA SO UNIV,DEPT PHYS,STATESBORO,GA 30460. RP Belton, MJS (reprint author), NATL OPT ASTRON OBSERV,TUCSON,AZ 85719, USA. NR 24 TC 36 Z9 36 U1 0 U2 0 PU ACADEMIC PRESS INC JNL-COMP SUBSCRIPTIONS PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 SN 0019-1035 J9 ICARUS JI Icarus PD MAR PY 1996 VL 120 IS 1 BP 185 EP 199 DI 10.1006/icar.1996.0044 PG 15 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA UF009 UT WOS:A1996UF00900013 ER PT J AU Veverka, J Thomas, PC Helfenstein, P Lee, P Harch, A Calvo, S Chapman, C Belton, MJS Klaasen, K Johnson, TV Davies, M AF Veverka, J Thomas, PC Helfenstein, P Lee, P Harch, A Calvo, S Chapman, C Belton, MJS Klaasen, K Johnson, TV Davies, M TI Dactyl: Galileo observations of Ida's satellite SO ICARUS LA English DT Article AB Galileo's flyby of 243 Ida in August 1993 led to the discovery of a small satellite, Dactyl, some 85 km from the asteroid's center. From Earth at mean opposition, the satellite is a V = +20.3 mag object (some 6.7 magnitudes fainter than Ida). Forty-seven images of the satellite at 18 different observing times were played back, including one multicolor sequence in which the satellite is resolved adequately to distinguish surface markings (similar to 105 m/pxl) and three higher resolution single-color views (89, 39, and 24 m/pxl). The satellite, mean radius = 0.7 km, is an elongated, but not angular body with principal diameters of 1.6 x 1.4 x 1.2 km. In the highest resolution view, the longest axis points approximately in the direction of Ida, and its shortest axis is perpendicular to the orbital plane. The spin period is slow (> 8 hr?) and may be synchronous. The satellite shows no conspicuous sharp edges and is much less irregular in shape than Ida. Limb profiles are remarkably smooth over distances of 200-300 m. The geometric albedos of the two objects are similar (0.20 vs 0.21), as are the 0.4-1.0-mu m colors. Like Ida, Dactyl is an S-asteroid, but has a slightly deeper 1-mu m band than Ida (by 5-8%). While no identical regions (in color) are seen on Ida, the color difference is consistent with color variations reported within the Koronis family and may be due to a slightly higher pyroxene/olivine ratio on the satellite. More than a dozen craters ranging from less than or similar to 90 to 280 m diameter are visible in the best image (39 m/pxl at 470 phase). The largest contains an off-centered, positive relief feature some 75 m across. The image includes an intriguing crater chain, but no grooves, ridges, or sharp edges are evident. In terms of limb roughness, Dactyl is much smoother than Ida, but comparable to the two satellites of Mars, Phobos and Deimos. While the satellite's origin is uncertain, a likely scenario would have the satellite date from the breakup of the Koronis family. It is interesting that crater densities on the satellite are similar to those on Ida itself. (C) 1996 Academic Press, Inc. C1 PLANETARY SCI INST,TUCSON,AZ 85705. NATL OPT ASTRON OBSERV,TUCSON,AZ 85719. CALTECH,JET PROP LAB,PASADENA,CA 91109. RAND CORP,SANTA MONICA,CA 90407. RP Veverka, J (reprint author), CORNELL UNIV,CTR RADIOPHYS & SPACE RES,ITHACA,NY 14853, USA. NR 18 TC 17 Z9 17 U1 0 U2 0 PU ACADEMIC PRESS INC JNL-COMP SUBSCRIPTIONS PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 SN 0019-1035 J9 ICARUS JI Icarus PD MAR PY 1996 VL 120 IS 1 BP 200 EP 211 DI 10.1006/icar.1996.0045 PG 12 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA UF009 UT WOS:A1996UF00900014 ER PT J AU Chapman, CR Veverka, J Belton, MJS Neukum, G Morrison, D AF Chapman, CR Veverka, J Belton, MJS Neukum, G Morrison, D TI Cratering on Gaspra SO ICARUS LA English DT Article ID 951 GASPRA; ASTEROIDS; FRAGMENTATION; SATELLITES; FAMILIES; EARTH AB Galileo flyby images of 951 Gaspra show a crater population dominated by fresh craters several hundred meters in diameter and smaller. They must represent a production population because their spatial density is low (few overlaps) and because degraded craters are underabundant; equilibrium may be attained at diameters near to or below the resolution limit of the best image, We have counted, measured, and classified craters from the highest resolution, ''high phase'' image, which shows >600 craters in 90 km(2). The differential population index (0.2-0.6 km) for the fresh, obvious craters is very ''steep'' (-4.3 +/- 0.3). It probably reflects the index of asteroidal projectiles; it is much steeper than the theoretical value of -3.5 for collisional equilibrium, Gaspra's crater population differs from that observed on Phobos but resembles those observed on the Moon and Mars at these sizes (consistent also with the near-Earth asteroid population), Gaspra's fresh craters are superposed on a landscape that appears ''smoothed'' at a vertical scale of hundreds of meters. Some ''soft,'' subdued crater-like features, commonly similar to>500 m across, are visible, Some of these are associated with the linear grooves on Gaspra and may be endogenic features. Many others are probably pre-existing impact craters deeply blanketed or otherwise much degraded. Gaspra's largest-scale shape is highly irregular, perhaps faceted, The biggest facet exceeds the largest crater (relative to body radius) ever observed on a satellite or expected from collisional fragmentation models. Facets cannot be successive crater-forming impacts; later scars would have destroyed earlier ones, Far-encounter images show a more lumpy than faceted visage of Gaspra; two craters are similar to 3 km in diameter, but not even half the radius of Gaspra, We expect that Gaspra was created by collisional fragmentation of a larger parent body. Its gross configuration may reflect collisional spallation of the parent, Certainly, megaregolithic processes of reaccumulation and blanketing and/or shaking are evident, due to subsequent sub-catastrophic collisions, Gaspra's subdued craters peek through the effects of the last such collision. That smoothed surface has been cratered ever since by the steep production function, which, however must become shallower again below 10 m, Since the overall density of fresh craters is low, Gaspra must be relatively youthful, Scaled to a calculated 0.5 Gyr age for bodies of its size, based on asteroid collision models and assuming that Gaspra does not have metallic strength, its cratering lifetime is similar to 0.2 Gyr, with large modeling uncertainties. The cumulative volume of all visible craters could create a regolith only <10 m deep, even if all ejecta were retained by Gaspra's weak gravity. Gaspra's modern soil-like regolith, produced by the steep production function, is probably very thin, Indeed, Gaspra's surface must be under net erosion and provides an inadequate environment for any mature weathering and reworking of its surface layer during the past 0.2 Gyr, (C) 1996 Academic Press, Inc. C1 PLANETARY SCI INST,TUCSON,AZ 85705. CORNELL UNIV,ITHACA,NY 14850. NATL OPT ASTRON OBSERV,TUCSON,AZ 85721. DLR,BERLIN,GERMANY. NASA,AMES RES CTR,MOFFETT FIELD,CA 94035. NR 56 TC 59 Z9 59 U1 0 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 MAR PY 1996 VL 120 IS 1 BP 231 EP 245 DI 10.1006/icar.1996.0048 PG 15 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA UF009 UT WOS:A1996UF00900017 ER PT J AU Tausworthe, RC Lyu, MR AF Tausworthe, RC Lyu, MR TI A generalized technique for stimulating software reliability SO IEEE SOFTWARE LA English DT Article C1 AT&T BELL LABS,RES,MURRAY HILL,NJ 07974. RP Tausworthe, RC (reprint author), NASA,JET PROP LAB,INFORMAT SYST DEV & OPERAT DIV,4800 OAK GROVE DR,PASADENA,CA 91109, USA. NR 15 TC 10 Z9 13 U1 0 U2 0 PU IEEE COMPUTER SOC PI LOS ALAMITOS PA 10662 LOS VAQUEROS CIRCLE, PO BOX 3014, LOS ALAMITOS, CA 90720-1264 SN 0740-7459 J9 IEEE SOFTWARE JI IEEE Softw. PD MAR PY 1996 VL 13 IS 2 BP 77 EP 88 DI 10.1109/52.506464 PG 12 WC Computer Science, Software Engineering SC Computer Science GA TX798 UT WOS:A1996TX79800011 ER PT J AU Chinn, GC Epp, LW Hoppe, DJ AF Chinn, GC Epp, LW Hoppe, DJ TI A hybrid finite-element method for axisymmetric waveguide-fed horns SO IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION LA English DT Article AB A new method for finding radiation patterns and the reflection coefficients associated with an axisymmetric waveguide fed horn is presented, The approach is based on a hybrid finite element method (FEM) wherein the electromagnetic fields in the FEM region are coupled to the fields outside by two surface integral equations. Because of the local nature of the FEM, this formalism allows for the presence of inhomogeneities to be included in the problem domain, The matrix equation which results from the application of this method is shown to be complex-symmetric. Comparisons of calculated and measured data for two different horns show good agreement. RP Chinn, GC (reprint author), CALTECH,JET PROP LAB,PASADENA,CA 91109, USA. NR 12 TC 15 Z9 15 U1 0 U2 0 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 SN 0018-926X J9 IEEE T ANTENN PROPAG JI IEEE Trans. Antennas Propag. PD MAR PY 1996 VL 44 IS 3 BP 280 EP 285 DI 10.1109/8.486294 PG 6 WC Engineering, Electrical & Electronic; Telecommunications SC Engineering; Telecommunications GA TZ871 UT WOS:A1996TZ87100002 ER PT J AU Gaidis, MC Friedrich, S Segall, K Prober, DE Szymkowiak, AE Moseley, SH AF Gaidis, MC Friedrich, S Segall, K Prober, DE Szymkowiak, AE Moseley, SH TI A superconducting X-ray spectrometer with a tantalum absorber and lateral trapping SO IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY LA English DT Article ID TUNNEL-JUNCTIONS; QUASIPARTICLE; RESOLUTION; DETECTORS; ENERGY AB We report the development of Nb-Ta-Al-Al2O3-Al superconducting tunnel junction structures for high energy resolution and high efficiency X-ray detection, These devices utilize a Ta X-ray absorber with superconductor ''bandgap engineered'' quasiparticle trapping to improve charge collection, Experimental results at 0.3 K are presented, showing energy resolution of 102 eV full-width-half-maximum for 6 keV X-rays, Collected charge is in excess of 5 x 10(6) electrons. The absorption efficiency is better than 35%; Devices thermally cycle with no change in characteristics. C1 NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. RP Gaidis, MC (reprint author), YALE UNIV,DEPT APPL PHYS,NEW HAVEN,CT 06520, USA. RI Gaidis, Michael/D-3327-2013 NR 19 TC 7 Z9 7 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 1051-8223 J9 IEEE T APPL SUPERCON JI IEEE Trans. Appl. Supercond. PD MAR PY 1996 VL 6 IS 1 BP 1 EP 4 DI 10.1109/77.488272 PG 4 WC Engineering, Electrical & Electronic; Physics, Applied SC Engineering; Physics GA UJ419 UT WOS:A1996UJ41900001 ER PT J AU Parnas, BR AF Parnas, BR TI Noise and neuronal populations conspire to encode simple waveforms reliably SO IEEE TRANSACTIONS ON BIOMEDICAL ENGINEERING LA English DT Article ID STOCHASTIC RESONANCE AB Sensory systems rely on populations of neurons to encode information transduced at the periphery into meaningful patterns of neuronal population activity. This transduction occurs in the presence of intrinsic neuronal noise. This is fortunate. The presence of noise allows more reliable encoding of the temporal structure present in the stimulus than would be possible in a noise-free environment. Simulations with a parallel model of signal processing at the auditory periphery have been used to explore the effects of noise and a neuronal population on the encoding of signal information. The results show that, for a given set of neuronal modeling parameters and stimulus amplitude, there is an optimal amount of noise for stimulus encoding with maximum fidelity. C1 UNIV CALIF BERKELEY,DEPT ELECT ENGN & COMP SCI,BERKELEY,CA 94720. RP Parnas, BR (reprint author), NASA,AMES RES CTR,BIOCOMPUTAT CTR,MS 239-11,MOFFETT FIELD,CA 94035, USA. NR 21 TC 16 Z9 16 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 0018-9294 J9 IEEE T BIO-MED ENG JI IEEE Trans. Biomed. Eng. PD MAR PY 1996 VL 43 IS 3 BP 313 EP 318 DI 10.1109/10.486289 PG 6 WC Engineering, Biomedical SC Engineering GA TX675 UT WOS:A1996TX67500010 PM 8682544 ER PT J AU Jin, MY AF Jin, MY TI Optimal range and Doppler centroid estimation for a ScanSAR system SO IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING LA English DT Article ID SYNTHETIC APERTURE RADAR; SAR DATA AB This paper presents a new range and Doppler centroid estimation algorithm for a ScanSAR system, This algorithm is based on processing the image data in the overlapped region of two bursts of the same beam or adjacent beams, It leads to highly accurate radar pointing angles that are paramount to achieving good radiometric performance in ScanSAR imagery. The achievable accuracy is derived theoretically and verified by tests performed using SIR-C ScanSAR data and ERS data, This algorithm is computationally efficient and easy to implement, The proposed Doppler centroid estimation algorithm is also an excellent candidate for a strip mode SAR system. RP Jin, MY (reprint author), CALTECH, JET PROP LAB, 4800 OAK GROVE DR, PASADENA, CA 91109 USA. NR 20 TC 28 Z9 31 U1 3 U2 4 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI PISCATAWAY PA 445 HOES LANE, PISCATAWAY, NJ 08855-4141 USA SN 0196-2892 J9 IEEE T GEOSCI REMOTE JI IEEE Trans. Geosci. Remote Sensing PD MAR PY 1996 VL 34 IS 2 BP 479 EP 488 DI 10.1109/36.485125 PG 10 WC Geochemistry & Geophysics; Engineering, Electrical & Electronic; Remote Sensing; Imaging Science & Photographic Technology SC Geochemistry & Geophysics; Engineering; Remote Sensing; Imaging Science & Photographic Technology GA UC326 UT WOS:A1996UC32600018 ER PT J AU Velusamy, K Garg, VK AF Velusamy, K Garg, VK TI Laminar mixed convection in vertical elliptic ducts SO INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER LA English DT Article ID HEAT-TRANSFER; NUMERICAL-ANALYSIS; DEVELOPING FLOW; ANNULUS; FINS AB A control volume based numerical solution is described for the fully developed mixed convection in vertical ducts of elliptic cross-section; The duct wail is supplied with a uniform axial heat rate while the thickness and thermal conductivity of the duct wall are such that the wall temperature is circumferentially uniform. Results for velocity and temperature distributions, friction factor, Nusselt number and critical Rayleigh number are presented for a wide range of duct aspect ratios and Rayleigh numbers. It is found that during mixed convection, fluid with a higher axial velocity exists around the foci of the elliptical cross-section, leading to substantial heat transfer enhancement in this region of the duct. The ratio of friction factor during muted convection to that during forced convection is low in elliptical ducts compared to that in a circular duct. Also, the ratio of Nusselt number to friction factor is higher for elliptic ducts compared to that for a circular duct, irrespective of the value of the Rayleigh number. The critical Rayleigh number, at which how reversal is initiated in the core region, is higher for elliptic ducts compared to that for a circular duct. C1 NASA,LEWIS RES CTR,AYT CORP,CLEVELAND,OH 44135. INDIRA GANDHI CTR ATOM RES,THERMAL HYDRAUL SECT,KALPAKKAM 603102,TAMIL NADU,INDIA. NR 29 TC 10 Z9 10 U1 0 U2 1 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, ENGLAND OX5 1GB SN 0017-9310 J9 INT J HEAT MASS TRAN JI Int. J. Heat Mass Transf. PD MAR PY 1996 VL 39 IS 4 BP 745 EP 752 DI 10.1016/0017-9310(95)00163-8 PG 8 WC Thermodynamics; Engineering, Mechanical; Mechanics SC Thermodynamics; Engineering; Mechanics GA TL662 UT WOS:A1996TL66200008 ER PT J AU Siegel, R AF Siegel, R TI Two-flux method for transient radiative transfer in a semitransparent layer SO INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER LA English DT Article RP Siegel, R (reprint author), NASA,LEWIS RES CTR,CLEVELAND,OH 44135, USA. NR 7 TC 15 Z9 16 U1 0 U2 3 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, ENGLAND OX5 1GB SN 0017-9310 J9 INT J HEAT MASS TRAN JI Int. J. Heat Mass Transf. PD MAR PY 1996 VL 39 IS 5 BP 1111 EP 1115 DI 10.1016/0017-9310(95)00178-6 PG 5 WC Thermodynamics; Engineering, Mechanical; Mechanics SC Thermodynamics; Engineering; Mechanics GA TQ137 UT WOS:A1996TQ13700013 ER PT J AU Elishakoff, I Marcus, S Starnes, JH AF Elishakoff, I Marcus, S Starnes, JH TI On vibrational imperfection sensitivity of Augusti's model structure in the vicinity of a non-linear static state SO INTERNATIONAL JOURNAL OF NON-LINEAR MECHANICS LA English DT Article DE dynamics of rigid links; influence of imperfections on link vibrations; rigid body dynamics ID SHELLS AB In this paper we present a closed-form solution for vibrational imperfection sensitivity-the effect of small imperfections on the vibrational frequencies of perturbed motion around the static equilibrium slate of Augusti's model structure (a rigid link, pinned at one end to a rigid foundation and supported at the other by a linear extensional spring that retains its horizontality as the system deflects). We also treat a modified version of that model with attendant slightly different dynamics. It is demonstrated that the vibrational frequency decreases as the initial imperfections increase. C1 TECHNION ISRAEL INST TECHNOL,DEPT MATH,IL-32000 HAIFA,ISRAEL. NASA,LANGLEY RES CTR,HAMPTON,VA 23664. RP Elishakoff, I (reprint author), FLORIDA ATLANTIC UNIV,DEPT MECH ENGN,BOCA RATON,FL 33431, USA. NR 20 TC 4 Z9 4 U1 0 U2 0 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, ENGLAND OX5 1GB SN 0020-7462 J9 INT J NONLINEAR MECH JI Int. J. Non-Linear Mech. PD MAR PY 1996 VL 31 IS 2 BP 229 EP 236 DI 10.1016/0020-7462(95)00054-2 PG 8 WC Mechanics SC Mechanics GA UH295 UT WOS:A1996UH29500011 ER PT J AU Aboudi, J Pindera, MJ Arnold, SM AF Aboudi, J Pindera, MJ Arnold, SM TI Thermoelastic theory for the response of materials functionally graded in two directions SO INTERNATIONAL JOURNAL OF SOLIDS AND STRUCTURES LA English DT Article ID THERMAL RESIDUAL-STRESSES; CERAMIC-METAL INTERFACES; FINITE-ELEMENT ANALYSIS AB A recently developed micromechanical theory for the thermoelastic response of functionally graded composites with nonuniform fiber spacing in the through-thickness direction is further extended to enable analysis of material architectures characterized by arbitrarily nonuniform fiber spacing in two directions. In contrast to currently employed micromechanical approaches applied to functionally graded materials, which decouple the local and global effects by assuming the existence of a representative volume element al every point within the composite, the new theory explicitly couples the local and global effects. The analytical development is based on volumetric averaging of the various field quantities, together with imposition of boundary and interfacial conditions in an average sense. Results are presented that illustrate the capability of the derived theory to capture local stress gradients at the free edge of a laminated composite plate due to the application of a uniform temperature change. It is further shown that it is possible to reduce the magnitude of these stress concentrations by a proper management of the microstructure of the composite plies near the free edge. Thus by an appropriate tailoring of the microstructure it is possible to reduce or prevent the likelihood of delamination at free edges of standard composite laminates. C1 NASA, LEWIS RES CTR, STRUCT FATIGUE BRANCH, CLEVELAND, OH 44135 USA. RP Aboudi, J (reprint author), UNIV VIRGINIA, DEPT CIVIL ENGN & APPL MECH, CHARLOTTESVILLE, VA 22903 USA. NR 19 TC 72 Z9 73 U1 2 U2 9 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0020-7683 J9 INT J SOLIDS STRUCT JI Int. J. Solids Struct. PD MAR PY 1996 VL 33 IS 7 BP 931 EP 966 DI 10.1016/0020-7683(95)00084-4 PG 36 WC Mechanics SC Mechanics GA TN354 UT WOS:A1996TN35400002 ER PT J AU Shin, JW AF Shin, JW TI Characteristics of surface roughness associated with leading-edge ice accretion SO JOURNAL OF AIRCRAFT LA English DT Article AB Detailed measurements of surface roughness dimensions associated with leading-edge ice accretions are presented to provide information on characteristics of roughness and trends of roughness development with various icing parameters. Data were obtained from icing tests conducted in the Icing Research Tunnel at NASA Lewis Research Center using a NACA 0012 airfoil. Dimensions measured include diameters, heights, and spacing of roughness elements along with chordwise icing limits. Results confirm the existence of smooth and rough ice zones and that the boundary between the two zones (surface roughness transition region) moves upstream towards stagnation region with time. The heights of roughness elements increase as the total temperature and the liquid water content increase; however, the airspeed has little effect on the roughness height. Results also show that the roughness in the surface roughness transition region grows during a very early stage of accretion, but reaches a critical height and then remains fairly constant. Results also indicate that a uniformly distributed roughness model is only valid at a very early stage of the ice accretion process. RP Shin, JW (reprint author), NASA,LEWIS RES CTR,HIGH SPEED RES PROPULS PROJECT OFF,CLEVELAND,OH 44135, USA. NR 12 TC 11 Z9 11 U1 1 U2 6 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 MAR-APR PY 1996 VL 33 IS 2 BP 316 EP 321 DI 10.2514/3.46940 PG 6 WC Engineering, Aerospace SC Engineering GA UD291 UT WOS:A1996UD29100011 ER PT J AU Mehta, UB AF Mehta, UB TI Strategy for developing air-breathing aerospace planes SO JOURNAL OF AIRCRAFT LA English DT Article AB Hypersonic air-breathing propulsion, utilizing scramjets, can fundamentally change transatmospheric accelerators for transportation to and from low Earth orbits. The value and limitations of ground tests, flight tests, and computations are presented, and scramjet development requirements are discussed. Near-full-scale hypersonic propulsion flight tests are essential for developing a prototype hypersonic propulsion system, To determine how this development should be carried out, some technical and programmatic lessons learned from past programs are presented. A conceptual two-stage-to-orbit prototgpe/experimental aerospace plane is recommended as a means of providing access-to space and for developing hypersonic air-breathing propulsion. RP Mehta, UB (reprint author), NASA,AMES RES CTR,MOFFETT FIELD,CA 94035, USA. NR 31 TC 6 Z9 7 U1 0 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 MAR-APR PY 1996 VL 33 IS 2 BP 377 EP 385 DI 10.2514/3.46948 PG 9 WC Engineering, Aerospace SC Engineering GA UD291 UT WOS:A1996UD29100019 ER PT J AU Rossow, VJ Fong, RK Wright, MS Bisbee, LS AF Rossow, VJ Fong, RK Wright, MS Bisbee, LS TI Vortex wakes of two transports measured in 80 by 120 foot Wind Tunnel SO JOURNAL OF AIRCRAFT LA English DT Article AB Measurements are reported on the characteristics of the vortex wakes that trail from 0.03-scale models of a B-747 and a DC-10. Included are the downwash distributions obtained with a hot-film anemometer probe for the standard landing configurations, and the rolling moments induced on various following wings by the vortex wakes of several configurations of both wake-generating models. Both sets of data are presented for downstream distances of 81 and 162 ft, i.e., scale distances of 0.5 and 1.0 mile. RP Rossow, VJ (reprint author), NASA,AMES RES CTR,LOW SPEED AERODYNAM BRANCH,M-S N247-2,MOFFETT FIELD,CA 94035, USA. NR 20 TC 7 Z9 7 U1 0 U2 0 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 SN 0021-8669 J9 J AIRCRAFT JI J. Aircr. PD MAR-APR PY 1996 VL 33 IS 2 BP 399 EP 406 DI 10.2514/3.46951 PG 8 WC Engineering, Aerospace SC Engineering GA UD291 UT WOS:A1996UD29100022 ER PT J AU Byun, C Guruswamy, GP AF Byun, C Guruswamy, GP TI Wing-body aeroelasticity on parallel computers SO JOURNAL OF AIRCRAFT LA English DT Article ID ALGORITHM; FORM AB This article presents a procedure for computing the aeroelasticity of wing-body configurations on multiple-instruction, multiple-data parallel computers. In this procedure, fluids are modeled using Euler equations discretized by a finite difference method, and structures are modeled using finite element equations. The procedure is designed in such a way that each discipline can be developed and maintained independently by using a domain decomposition approach. A parallel integration scheme is used to compute aeroelastic responses by solving the coupled fluid and structural equations concurrently while keeping modularity of each discipline. The present procedure is validated by computing the aeroelastic response of a wing and comparing with experiment. Aeroelastic computations are illustrated for a high speed civil transport type wing-body configuration. RP Byun, C (reprint author), NASA,AMES RES CTR,MCAT INST,MOFFETT FIELD,CA 94035, USA. NR 30 TC 6 Z9 6 U1 0 U2 0 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 SN 0021-8669 J9 J AIRCRAFT JI J. Aircr. PD MAR-APR PY 1996 VL 33 IS 2 BP 421 EP 428 DI 10.2514/3.46954 PG 8 WC Engineering, Aerospace SC Engineering GA UD291 UT WOS:A1996UD29100025 ER PT J AU Abid, R Speziale, CG AF Abid, R Speziale, CG TI The freestream matching condition for stagnation point turbulent flows: An alternative formulation SO JOURNAL OF APPLIED MECHANICS-TRANSACTIONS OF THE ASME LA English DT Article ID BOUNDED ENERGY-STATES; SHEAR-FLOW AB The problem of plane stagnation point flow with freestream turbulence is examined from a basic theoretical standpoint. It is argued that the singularity which arises in the standard K-epsilon model results from the use of an inconsistent freestream boundary condition. The inconsistency lies in the implementation of a production-equals-dissipation equilibrium hypothesis in conjunction with a freestream mean velocity field that corresponds to homogeneous plane strain-a turbulent flow for which the standard K-epsilon model does not predict such a simple equilibrium. The ad hoc adjustment that has been made in the constants of the epsilon-transport equation to eliminate this singularity is shown to be inconsistent for homogeneous plane-strain turbulence as well as other benchmark turbulent flows. An alternative means to eliminate this singularity-without compromising model predictions in more basic turbulent flows-is proposed based on the incorporation of nonequilibrium vortex stretching effects in the turbulent dissipation rate equation. C1 BOSTON UNIV,DEPT AEROSP & MECH ENGN,BOSTON,MA 02215. RP Abid, R (reprint author), NASA,LANGLEY RES CTR,HIGH TECHNOL CORP,HAMPTON,VA 23681, USA. NR 17 TC 5 Z9 5 U1 0 U2 0 PU ASME-AMER SOC MECHANICAL ENG PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017 SN 0021-8936 J9 J APPL MECH-T ASME JI J. Appl. Mech.-Trans. ASME PD MAR PY 1996 VL 63 IS 1 BP 95 EP 100 DI 10.1115/1.2787215 PG 6 WC Mechanics SC Mechanics GA UC815 UT WOS:A1996UC81500013 ER PT J AU Sullivan, RM AF Sullivan, RM TI The effect of water on thermal stresses in polymer composites SO JOURNAL OF APPLIED MECHANICS-TRANSACTIONS OF THE ASME LA English DT Article AB The fundamentals of the thermodynamic theory of mixtures and continuum thermochemistry are reviewed for a mixture of water and polymer. A specific mixture which is mechanically elastic, where the strain states remain infinitesimal and where water concentration gradients are possible is considered. An expression for the partial pressure of water in the mixture is obtained from Gibbs relation based on certain assumptions regarding the thermodynamic state of the water in the mixture. Along with a simple diffusion equation, this partial pressure expression may be used to simulate the thermostructural behavior of polymer composite materials due to water in the free volumes of the polymer. These equations are applied to a specific polymer composite material during isothermal heating conditions. The thermal stresses obtained by the application of the theory are compared to measured results to verify the accuracy of the approach. RP Sullivan, RM (reprint author), GEORGE C MARSHALL SPACE FLIGHT CTR,STRUCT & DYNAM LAB,MARSHALL SPACE FLIGHT CTR,AL 35812, USA. NR 16 TC 1 Z9 1 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 MAR PY 1996 VL 63 IS 1 BP 173 EP 179 DI 10.1115/1.2787195 PG 7 WC Mechanics SC Mechanics GA UC815 UT WOS:A1996UC81500026 ER PT J AU Tokay, A Short, DA AF Tokay, A Short, DA TI Evidence from tropical raindrop spectra of the origin of rain from stratiform versus convective clouds SO JOURNAL OF APPLIED METEOROLOGY LA English DT Article ID DROP-SIZE DISTRIBUTIONS; SQUALL-LINE; PRECIPITATION STRUCTURE; VERTICAL MOTIONS; AIR MOTIONS; REFLECTIVITY; CLUSTERS; DISDROMETER; SATELLITE; PROFILES AB An analysis of temporal variations in gamma parameters of raindrop spectra is presented utilizing surface-based observations from the Tropical Ocean Global Atmosphere Couple Ocean-Atmosphere Experiment. An observed dramatic change in the N-o parameter, found to occur during rainfall events with little change in rainfall rate, is suggestive of a transition from rain of convective origin to rain originating from the stratiform portion of tropical systems. An empirical stratiform-convective classification method based on No and R (rainfall rate) is presented. Properties of the drop size spectra from the stratiform classification are consistent with microphysical processes occurring within an aggregation/melting layer aloft, which produces more large raindrops and fewer small to medium size raindrops than rain from the convective classification, at the same rainfall rate. The occurrence of precipitation was found to be 74% (stratiform) and 26%.(convective), but total rainfall, on the other hand, was 32% and 68%, respectively. Case studies of the tropical systems studied here indicate that heavy convective showers are generally followed by longer intervals of lighter rain from the stratiform portion of the cloud systems. Differences in the shapes of the frequency distributions of the integral rainfall parameters (i.e., liquid water content, rainfall rate, and radar reflectivity) suggest that the lognormal distribution applies to some, but not all cases. The analysis shows that almost all the precipitation with a radar reflectivity above 40 dBZ falls within the convective classification. Regarding radar reflectivity versus rainfall rate relationships, the exponent is lower and the intercept is higher in the tropical stratiform classification than in the tropical convective classification. Collision and evaporation rates, which are important for cloud-modeling studies, indicate substantial variation at different rainfall rates and between the two types. RP Tokay, A (reprint author), NASA,GODDARD SPACE FLIGHT CTR,TRMM OFF,GREENBELT,MD 20771, USA. NR 52 TC 323 Z9 343 U1 3 U2 21 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 MAR PY 1996 VL 35 IS 3 BP 355 EP 371 DI 10.1175/1520-0450(1996)035<0355:EFTRSO>2.0.CO;2 PG 17 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA UB905 UT WOS:A1996UB90500005 ER PT J AU Xue, YK Bastable, HG Dirmeyer, PA Sellers, PJ AF Xue, YK Bastable, HG Dirmeyer, PA Sellers, PJ TI Sensitivity of simulated surface fluxes to changes in land surface parameterizations - A study using ABRACOS data SO JOURNAL OF APPLIED METEOROLOGY LA English DT Article ID SIMPLE BIOSPHERE MODEL; TROPICAL DEFORESTATION; CLIMATE CHANGE; AMAZON DEFORESTATION; FOREST; CONDUCTANCE; FIELD; GCM AB The simplified Simple Biosphere model(SSiB) has been validated using observed meteorological, turbulent flux, and vegetation property data from the Anglo-Brazilian Amazonian Climate Observation Study (ABRA-COS) over a forest clearing site. The results show that SSiB is able to simulate the observed fluxes realistically. The differences between the simulated and observed latent and sensible heat fluxes are less than 10 W m(-2). Compared to previous deforestation experiments, the new vegetation dataset produces significantly different latent heat fluxes and surface temperatures in off-line and general circulation model (GCM) simulations. Using the new dataset, the GCM simulated surface temperature is about 2 K higher, and the simulated latent heat flux is about 25 W m(-2) lower than that generated using a previous dataset. These differences can be expected to result in substantially different responses in rainfall and atmosphere circulation. The parameters that are most significant in producing such large differences are leaf area index and soil properties. This study again demonstrates that to realistically assess the climatic impact of land surface degradation a realistic specification of the land surface conditions within GCMs is crucial. C1 INST HYDROL, WALLINGFORD OX10 8BB, OXON, ENGLAND. NASA, GODDARD SPACE FLIGHT CTR, GREENBELT, MD 20771 USA. RP Xue, YK (reprint author), CTR OCEAN LAND ATMOSPHERE STUDIES, 4041 POWDER MILL RD, SUITE 302, CALVERTON, MD 20705 USA. RI Dirmeyer, Paul/B-6553-2016 OI Dirmeyer, Paul/0000-0003-3158-1752 NR 48 TC 38 Z9 41 U1 4 U2 7 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 USA SN 0894-8763 J9 J APPL METEOROL JI J. Appl. Meteorol. PD MAR PY 1996 VL 35 IS 3 BP 386 EP 400 DI 10.1175/1520-0450(1996)035<0386:SOSSFT>2.0.CO;2 PG 15 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA UB905 UT WOS:A1996UB90500007 ER PT J AU Nolas, GS Slack, GA Caillat, T Meisner, GP AF Nolas, GS Slack, GA Caillat, T Meisner, GP TI Raman scattering study of antimony-based skutterudites SO JOURNAL OF APPLIED PHYSICS LA English DT Article ID LAFE4P12 STRUCTURE; SPECTRA; COAS3; COSB3; COP3 AB Raman spectra of single-crystal CoSb3 and RhSb3 and of polycrystalline IrSb3 have been studied. We have also studied four different polycrystalline-filled skutterudite samples, Ir4LaGe3Sb9, Ir4NdGe3Sb9, Ir4SmGe3Sb9, and Fe4CeSb12, where rare-earth ions occupy the voids in the skutterudite structure. These void-filling ions interact with some of the lattice vibrations in this structure and produce a shift and broadening of the observed lines. The most prominent lines in all of the samples are the Sb-4 ring-breathing modes. (C) 1996 American Institute of Physics. C1 CALTECH,JET PROP LAB,PASADENA,CA 91109. GM CORP,CTR RES & DEV,PHYS & PHYS CHEM DEPT,WARREN,MI 48090. RP Nolas, GS (reprint author), RENSSELAER POLYTECH INST,DEPT PHYS,TROY,NY 12180, USA. NR 33 TC 55 Z9 57 U1 0 U2 11 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 MAR 1 PY 1996 VL 79 IS 5 BP 2622 EP 2626 DI 10.1063/1.361132 PG 5 WC Physics, Applied SC Physics GA TY119 UT WOS:A1996TY11900068 ER PT J AU FritschYelle, JM Charles, JB Jones, MM Wood, ML AF FritschYelle, JM Charles, JB Jones, MM Wood, ML TI Microgravity decreases heart rate and arterial pressure in humans SO JOURNAL OF APPLIED PHYSIOLOGY LA English DT Article DE autonomic; sympathetic; blood pressure; systolic; diastolic ID SYMPATHETIC ACTIVITY; BLOOD-PRESSURE; FLIGHT; MUSCLE AB Spaceflight causes adaptive changes in cardiovascular physiology, such as postflight orthostatic intolerance, that can have deleterious effects on astronauts. in-flight cardiovascular data are difficult to obtain, and results have been inconsistent. To determine normative in-flight changes in Shuttle astronauts, we measured heart rate, arterial pressure, and cardiac rhythm disturbances for 24-h periods before, during, and after spaceflight on Shuttle astronauts performing their normal routines. We found that heart rate, diastolic pressure, variability of heart rate and diastolic pressure, and premature ventricular contractions all were significantly reduced in flight. Systolic pressure and premature atrial contractions also tended to be reduced in flight. These data constitute the first systematic evaluation of in-flight changes in basic cardiovascular variables in Shuttle astronauts and suggest that a microgravity environment itself does not present a chronic stress to the cardiovascular system. C1 KRUG LIFE SCI,HOUSTON,TX 77058. RP FritschYelle, JM (reprint author), NASA,LYNDON B JOHNSON SPACE CTR,SPACE BIOMED RES INST,FRITSCH YELLE SD5,HOUSTON,TX 77058, USA. NR 24 TC 90 Z9 96 U1 3 U2 7 PU AMER PHYSIOLOGICAL SOC PI BETHESDA PA 9650 ROCKVILLE PIKE, BETHESDA, MD 20814 SN 8750-7587 J9 J APPL PHYSIOL JI J. Appl. Physiol. PD MAR PY 1996 VL 80 IS 3 BP 910 EP 914 PG 5 WC Physiology; Sport Sciences SC Physiology; Sport Sciences GA UE825 UT WOS:A1996UE82500030 PM 8964756 ER PT J AU Hymer, WC Grindeland, RE Salada, T Nye, P Grossman, EJ Lane, PK AF Hymer, WC Grindeland, RE Salada, T Nye, P Grossman, EJ Lane, PK TI Experimental modification of rat pituitary growth hormone cell function during and after spaceflight SO JOURNAL OF APPLIED PHYSIOLOGY LA English DT Article DE microgravity; cell culture; cell gravisensing; growth hormone assays ID ANTERIOR-PITUITARY; C-FOS; HETEROGENEITY; MICROGRAVITY; PROLACTIN; VARIANTS; PROTEINS; INVITRO; SERUM AB Space-flown rats show a number of flight-induced changes in the structure and function of pituitary growth hormone (GH) cells after in vitro postflight testing (W. C. Hymer, R. E. Grindeland, I. Krasnov, I. Victorov, K. Motter, P. Mukherjee, K. Shellenberger, and M. Vasques. J. Appl. Physiol. 73, Suppl.: 151S-157S, 1992). To evaluate the possible effects of microgravity on growth hormone (GH) cells themselves, freshly dispersed rat anterior pituitary gland cells were seeded into vials containing serum +/- 1 mu M hydrocortisone (HC) before flight. Five different cell preparations were used: the entire mixed-cell population of various hormone-producing cell types, cells of density < 1.071 g/cm(3) (band 1), cells of density > 1.071 g/cm(3) (band 2), and cells prepared from either the dorsal or ventral part of the gland. Relative to ground control samples, bioactive GH released from dense cells during flight was reduced in HC-free medium but tvas increased in HC-containing medium. Band 1 and mixed cells usually showed opposite HC-dependent responses. Release of bioactive GH from ventral flight cells was lower; postflight responses to GH-releasing hormone challenge were reduced, and the cytoplasmic area occupied by GH in the dense cells was greater. Collectively, the data show that the chemistry and cellular makeup of the culture system modifies the response of GH cells to microgravity. As such, these cells offer a system to identify gravisensing mechanisms in secretory cells in future microgravity research. C1 NASA,AMES RES CTR,MOFFETT FIELD,CA 94035. NASA,LOCKHEED ENGN & SCI CO,MOFFETT FIELD,CA 94035. RP Hymer, WC (reprint author), PENN STATE UNIV,ALTHOUSE LAB 006,DEPT BIOCHEM & MOLEC BIOL,UNIVERSITY PK,PA 16802, USA. NR 33 TC 21 Z9 22 U1 1 U2 1 PU AMER PHYSIOLOGICAL SOC PI BETHESDA PA 9650 ROCKVILLE PIKE, BETHESDA, MD 20814 SN 8750-7587 J9 J APPL PHYSIOL JI J. Appl. Physiol. PD MAR PY 1996 VL 80 IS 3 BP 955 EP 970 PG 16 WC Physiology; Sport Sciences SC Physiology; Sport Sciences GA UE825 UT WOS:A1996UE82500036 PM 8964762 ER PT J AU Hymer, WC Salada, T Avery, L Grindeland, RE AF Hymer, WC Salada, T Avery, L Grindeland, RE TI Experimental modification of rat pituitary prolactin cell function during and after spaceflight SO JOURNAL OF APPLIED PHYSIOLOGY LA English DT Article DE microgravity; cell culture ID ESTROUS-CYCLE; ASSAY; LYMPHOCYTES; ANTAGONISM; SECRETION; RECEPTORS; LOCATION; HORMONE; SPACE; GLAND AB This study was done to evaluate the effects of microgravity on prolactin (PRL) cells of the male rat pituitary gland. We used the identical passive closed-vial cell culture system that was described for the culture of growth hormone cells (W C. Hymer, R. E. Grindeland, T. Salada, P. Nye, E. Grossman, and P. Lane. J. Appl. Physiol. 80: 955-970, 1996). After an 8-day spaceflight, all flight media (containing released PRL), as well as extracts (containing intracellular PRL), contained significantly lower amounts of immunoreactive PRL than their corresponding ground control samples. On the other hand, these same samples, when assessed for their biological activities by two different in vitro lymphocyte assays, yielded disparate results that may reflect posttranslational modifications to the hormone molecule. Other data showed that 1) the apparent molecular weights of released PRL molecules were not altered by microgravity, but 2) the region from which the PRL cells came (dorsal or ventral) made a significant difference in the amount and activity of PRL released from the flight cells. Because there is much current interest in the role that PRL may play in the regulation of the immune system and because changes in both cellular and humoral immunity accompany spaceflight, this study could help define future microgravity research in this area. C1 NASA,AMES RES CTR,MOFFETT FIELD,CA 94035. RP Hymer, WC (reprint author), PENN STATE UNIV,ALTHOUSE LAB 006,DEPT BIOCHEM & MOLEC BIOL,UNIVERSITY PARK,PA 16802, USA. FU NCI NIH HHS [CA-23248] NR 26 TC 3 Z9 3 U1 0 U2 0 PU AMER PHYSIOLOGICAL SOC PI BETHESDA PA 9650 ROCKVILLE PIKE, BETHESDA, MD 20814 SN 8750-7587 J9 J APPL PHYSIOL JI J. Appl. Physiol. PD MAR PY 1996 VL 80 IS 3 BP 971 EP 980 PG 10 WC Physiology; Sport Sciences SC Physiology; Sport Sciences GA UE825 UT WOS:A1996UE82500037 PM 8964763 ER PT J AU Ferguson, FT Nuth, JA Lilleleht, LU AF Ferguson, FT Nuth, JA Lilleleht, LU TI Experimental studies of the vapor phase nucleation of refractory compounds .4. The condensation of magnesium SO JOURNAL OF CHEMICAL PHYSICS LA English DT Article ID HOMOGENEOUS NUCLEATION; SILVER; SIO AB Magnesium nucleation was studied over the range of approximately 700 to 950 K in a gas evaporation apparatus. Measured supersaturation ratios ranged from approximately 37 to 4.2 over this temperature range, respectively. A comparison of these data and Classical Nucleation Theory shows that the two are not consistent. Although there is a good correlation between the supersaturation and the temperature data when plotted in accordance with Scaled Nucleation Theory, some of the derived parameters are slightly below the limits predicted by the theory. (C) 1996 American Institute of Physics. C1 UNIV VIRGINIA,DEPT CHEM ENGN,CHARLOTTESVILLE,VA 22903. RP Ferguson, FT (reprint author), NASA,GODDARD SPACE FLIGHT CTR,CODE 691,GREENBELT,MD 20771, USA. RI Ferguson, Frank/C-9493-2012; Nuth, Joseph/E-7085-2012 NR 14 TC 20 Z9 20 U1 0 U2 3 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 MAR 1 PY 1996 VL 104 IS 9 BP 3205 EP 3210 DI 10.1063/1.471085 PG 6 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA TW809 UT WOS:A1996TW80900006 ER PT J AU Akapo, SO AF Akapo, SO TI Separation of light hydrocarbons on micropacked bidentate alkylsilane silica columns by gas chromatography SO JOURNAL OF CHROMATOGRAPHIC SCIENCE LA English DT Article ID MOLECULAR-WEIGHT HYDROCARBONS; PLOT CAPILLARY COLUMN; TITANS ATMOSPHERE; NITRILES; PHASES RP Akapo, SO (reprint author), NASA,AMES RES CTR,MOFFETT FIELD,CA 94035, USA. NR 32 TC 7 Z9 7 U1 0 U2 0 PU PRESTON PUBLICATIONS INC PI NILES PA 7800 MERRIMAC AVE PO BOX 48312, NILES, IL 60648 SN 0021-9665 J9 J CHROMATOGR SCI JI J. Chromatogr. Sci. PD MAR PY 1996 VL 34 IS 3 BP 130 EP 138 PG 9 WC Biochemical Research Methods; Chemistry, Analytical SC Biochemistry & Molecular Biology; Chemistry GA TY111 UT WOS:A1996TY11100005 ER PT J AU Fu, R Liu, WT Dickinson, RE AF Fu, R Liu, WT Dickinson, RE TI Response of tropical clouds to the interannual variation of sea surface temperature SO JOURNAL OF CLIMATE LA English DT Article ID TOP ENTRAINMENT INSTABILITY; NINO SOUTHERN OSCILLATION; CONVECTIVE BOUNDARY-LAYER; EL-NINO; EQUATORIAL PACIFIC; WALKER CIRCULATION; SATELLITE DATA; OCEAN; CLIMATE; PARAMETERIZATION AB Connections between the large-scale interannual variations of clouds, deep convection, atmospheric winds, vertical thermodynamic structure, and SSTs over global tropical oceans are examined over the period July 1983-December 1990. The SST warming associated with El Nino had a significant impact on the global tropical cloud field, although the warming itself was confined to the equatorial central and eastern Pacific. Extensive variations of the total cloud field occurred in the northeastern Indian, western and central Pacific, and western Atlantic Oceans. The changes of high and middle clouds dominated the total cloud variation in these regions. Total cloud variation was relatively weak in the eastern Pacific and the Atlantic because of the cancellation between the changes of high and low clouds. The variation of low clouds dominated the total cloud change in those areas. The destabilization of the lapse rate between 900 and 750 mb was more important for enhancing convective instability than was the change of local SSTs in the equatorial central Pacific during the 1987 El Nino. This destabilization is associated with anomalous rising motion in that region. As a result, convection and high and middle clouds increased in the equatorial central Pacific. In the subtropical Pacific, both the change of lapse rate between 900 and 750 mb associated with anomalous subsidence and the decrease of boundary-layer buoyancy due to a decrease of temperature and moisture played an important role in enhancing convective stability. Consequently, convection, as well as high and middle clouds, decreased in these areas. The change of low clouds in the equatoral and southeastern Atlantic was correlated to both local SSTs and the SST changes in the equatorial eastern Pacific. In this area, the increase of low clouds was consistent with the sharper inversion during the 1987 El Nino. The strengthening of the inversion was not caused by a local SST change, although the local SST change appeared to be correlated to the change of low clouds. The coherence between clouds and SST tendency shows that SST tendency leads cloud variation in the equatorial Pacific. Thus, the change of clouds does nor dominate the sign of SST tendency even though the cloud change was maximum during the 1987 El Nino. In some areas of the Indian, subtropical Pacific, and North Atlantic Oceans, cloud change leads SST tendency. Cloud change might affect SST tendency in these regions. C1 CALTECH,JET PROP LAB,PASADENA,CA. RP Fu, R (reprint author), UNIV ARIZONA,INST ATMOSPHER PHYS,PAS BLDG 81,TUCSON,AZ 85721, USA. RI Fu, Rong/B-4922-2011 NR 60 TC 17 Z9 17 U1 0 U2 3 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 SN 0894-8755 J9 J CLIMATE JI J. Clim. PD MAR PY 1996 VL 9 IS 3 BP 616 EP 634 DI 10.1175/1520-0442(1996)009<0616:ROTCTT>2.0.CO;2 PG 19 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA UJ642 UT WOS:A1996UJ64200006 ER PT J AU Hu, FQ Hussaini, MY Manthey, JL AF Hu, FQ Hussaini, MY Manthey, JL TI Low-dissipation and low-dispersion Runge-Kutta schemes for computational acoustics SO JOURNAL OF COMPUTATIONAL PHYSICS LA English DT Article ID FINITE-DIFFERENCE SCHEMES AB In this paper, we investigate accurate and efficient time advancing methods for computational acoustics, where nondissipative and nondispersive properties are of critical importance. Our analysis pertains to the application of Runge-Kutta methods to high-order finite difference discretization. In many CFD applications, multistage Runge-Kutta schemes have often been favored for their low storage requirements and relatively large stability limits. For computing acoustic waves, however, the stability consideration alone is not sufficient, since the Runge-Kutta schemes entail both dissipation and dispersion errors. The time step is now limited by the tolerable dissipation and dispersion errors in the computation. In the present paper, it is shown that if the traditional Runge-Kutta schemes are used for time advancing in acoustic problems, time steps greatly smaller than those allowed by the stability limit are necessary. Low-dissipation and low-dispersion Runge-Kutta (LDDRK) schemes are proposed, based on an optimization that minimizes the dissipation and dispersion errors for wave propagation. Optimizations of both single-step and two-step alternating schemes are considered. The proposed LDDRK schemes are remarkably more efficient than the classical Runge-Kutta schemes for acoustic computations. Moreover, low storage implementations of the optimized schemes are discussed. Special issues of implementing numerical boundary conditions in the LDDRK schemes are also addressed. (C) 1996 Academic Press, Inc. C1 NASA,LANGLEY RES CTR,INST COMP APPL SCI & ENGN,HAMPTON,VA 23681. RP Hu, FQ (reprint author), OLD DOMINION UNIV,DEPT MATH & STAT,NORFOLK,VA 23529, USA. RI Hu, Fang/A-8206-2009 NR 16 TC 313 Z9 347 U1 2 U2 16 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 MAR 1 PY 1996 VL 124 IS 1 BP 177 EP 191 DI 10.1006/jcph.1996.0052 PG 15 WC Computer Science, Interdisciplinary Applications; Physics, Mathematical SC Computer Science; Physics GA UA066 UT WOS:A1996UA06600012 ER PT J AU Barber, PG Fripp, AL Debnam, WJ Woodell, G Berry, RF Simchick, RT AF Barber, PG Fripp, AL Debnam, WJ Woodell, G Berry, RF Simchick, RT TI Experimental verification of agreement between thermal and real time visual melt-solid interface positions in vertical Bridgman grown germanium SO JOURNAL OF CRYSTAL GROWTH LA English DT Article ID FURNACE AB Measurements of the liquid-solid interface position during crystal growth were made by observing the discontinuity of the temperature gradient with movable thermocouples in a centerline, quartz capillary placed inside a sealed quartz ampoule of germanium in a vertical Bridgman furnace. Simultaneously, in situ, real time visual observations, using X-ray imaging technology, determined the position of the melt-solid interface. The radiographically detected interface position was several millimeters from the thermal interface position and the direction of displacement depended upon the direction of thermocouple insertion. Minimization of this spurious heat flow was achieved by using an unclad thermocouple that had each of its two wire leads entering the capillary from different ends of the furnace. Using this configuration the visual interface coincided with the thermal interface. Such observations show the utility of using in situ, real time visualization to record the melt-solid interface shape and position during crystal growth; and they suggest improvements in furnace and ampoule designs for use in high thermal gradients. C1 NASA,LANGLEY RES CTR,HAMPTON,VA 23681. LOCKHEED ENGN & SCI CO,HAMPTON,VA 23666. RP Barber, PG (reprint author), LONGWOOD COLL,DEPT NAT SCI,FARMVILLE,VA 23909, USA. NR 11 TC 1 Z9 1 U1 0 U2 0 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0022-0248 J9 J CRYST GROWTH JI J. Cryst. Growth PD MAR PY 1996 VL 160 IS 1-2 BP 55 EP 58 DI 10.1016/0022-0248(95)00896-9 PG 4 WC Crystallography; Materials Science, Multidisciplinary; Physics, Applied SC Crystallography; Materials Science; Physics GA UC077 UT WOS:A1996UC07700009 ER PT J AU Ewing, FL Forsythe, EL vanderWoerd, M Pusey, ML AF Ewing, FL Forsythe, EL vanderWoerd, M Pusey, ML TI Effects of purification on the crystallization of lysozyme SO JOURNAL OF CRYSTAL GROWTH LA English DT Article ID EGG-WHITE LYSOZYME; PROTEIN CRYSTAL; PHASE-TRANSITION; GROWTH; IMPURITIES; EXAMPLE AB We have additionally purified a commercial lysozyme preparation by cation exchange chromatography, followed by recrystallization. This material is 99.96% pure with respect to macromolecular impurities. At basic pH, the purified lysozyme gave only tetragonal crystals at 20 degrees C. Protein used directly from the bottle, prepared by dialysis against distilled water, or which did not bind to the cation exchange column had considerably altered crystallization behavior. Lysozyme which did not bind to the cation exchange column was subsequently purified by size exclusion chromatography. This material gave predominately bundles of rod-shaped crystals with some small tetragonal crystals at lower pHs. The origin of the bundled rod habit was postulated to be a thermally dependent tetragonal <----> orthorhombic change in the protein structure. This was subsequently ruled out on the basis of crystallization behavior and growth rate experiments. This suggests that heterogeneous forms of lysozyme may be responsible. These results demonstrate three classes of impurities: (1) small molecules, which may be removed by dialysis; (2) macromolecules, which are removable by chromatographic techniques; and (3) heterogeneous forms of the protein, which can be removed in this case by cation exchange chromatography. Of these, heterogeneous forms of the lysozyme apparently have the greatest affect on its crystallization behavior. C1 NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,HUNTSVILLE,AL 35812. UNIV SPACE RES ASSOC,HUNTSVILLE,AL 35812. UNIV ALABAMA,BIRMINGHAM,AL 35294. NR 34 TC 37 Z9 38 U1 3 U2 9 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0022-0248 J9 J CRYST GROWTH JI J. Cryst. Growth PD MAR PY 1996 VL 160 IS 3-4 BP 389 EP 397 DI 10.1016/0022-0248(95)00933-7 PG 9 WC Crystallography; Materials Science, Multidisciplinary; Physics, Applied SC Crystallography; Materials Science; Physics GA UE763 UT WOS:A1996UE76300028 ER PT J AU Synnestvedt, RG AF Synnestvedt, RG TI An effective method for modelling stiction in multibody dynamic systems SO JOURNAL OF DYNAMIC SYSTEMS MEASUREMENT AND CONTROL-TRANSACTIONS OF THE ASME LA English DT Article ID FRICTION AB This paper presents an effective method for developing dynamic equations which realistically model dynamics of multibody mechanical systems with stiction, or stick-slip friction. This method is used in three examples-a mass-spring system, a top, and a robot linkage-to illustrate the facility with which the method is implemented. The method dynamically partitions sets of dynamic equations to model a system through discontinuities, changes in degrees of freedom and changes in states. Comparisons of this method with others is presented for simple and complex systems. RP Synnestvedt, RG (reprint author), NASA,AMES RES CTR,CTAS AUTOMAT LAB,MOFFETT FIELD,CA 94035, USA. NR 17 TC 4 Z9 4 U1 0 U2 1 PU ASME-AMER SOC MECHANICAL ENG PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017 SN 0022-0434 J9 J DYN SYST-T ASME JI J. Dyn. Syst. Meas. Control-Trans. ASME PD MAR PY 1996 VL 118 IS 1 BP 172 EP 176 DI 10.1115/1.2801141 PG 5 WC Automation & Control Systems; Instruments & Instrumentation SC Automation & Control Systems; Instruments & Instrumentation GA UC803 UT WOS:A1996UC80300026 ER PT J AU Bakes, CM Goldberg, FN AF Bakes, CM Goldberg, FN TI ATM networks and their applications at the NASA Lewis Research Center - A case study SO JOURNAL OF ENGINEERING AND TECHNOLOGY MANAGEMENT LA English DT Article DE ATM; broadband ISDN; SONET; congestion control; cluster computing; cooperative computing ID TRAFFIC MANAGEMENT; CONGESTION CONTROL; LAYER OAM; B-ISDN; ISSUES; IMPLEMENTATION; SCHEMES AB This paper provides an overview of ATM networks and a discussion of their role in supporting high-level technological research at the NASA Lewis Research Center in the U.S, NASA Lewis operates a variety of local and wide area networks and is introducing ATM to meet specialized requirements for transporting multimedia traffic, including text, voice, video, real time visualization data, and data collected from scientific experiments, ATM employs fast packet switching and statistical multiplexing to allow many sources to flexibly share network bandwidth and it provides an integrated transport, multiplexing, and switching technology for BISDN. SONET/SDH may be used as a physical layer protocol for optical transmission of ATM cells. ATM, together with SONET, provides standardized high-speed transmission for a wide variety of traffic types and performance requirements. NASA Lewis researchers are experimenting with cluster computing for solving large problems and are testing ATM for use as the transport fabric to support this activity. Video experiments have been conducted over a private ATM network which has links to the Ames and Langley Research Centers. NASA Lewis is exploring the use of ATM to facilitate collaboration between experimental and analytical researchers at geographically dispersed locations and to provide personnel at remote sites with access to NASA Lewis facilities. ATM service classes, the BISDN protocol reference model, and congestion control issues are also addressed in this paper. C1 NASA,LEWIS RES CTR,TELECOMMUN & NETWORKING BRANCH,CLEVELAND,OH 44135. RP Bakes, CM (reprint author), KENT STATE UNIV,GRAD SCH MANAGEMENT,DEPT ADM SCI,KENT,OH 44242, USA. NR 34 TC 4 Z9 4 U1 0 U2 3 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0923-4748 J9 J ENG TECHNOL MANAGE JI J. Eng. Technol. Manage. PD MAR PY 1996 VL 13 IS 1 BP 1 EP 28 DI 10.1016/0923-4748(96)00003-3 PG 28 WC Business; Engineering, Industrial; Management SC Business & Economics; Engineering GA VF605 UT WOS:A1996VF60500001 ER PT J AU Hamdan, K Sung, LY AF Hamdan, K Sung, LY TI Stochastic modeling of length of day and universal time SO JOURNAL OF GEODESY LA English DT Article ID ROTATION AB We propose a general stochastic model for the UT1/LOD system and derive the corresponding Kalman filter model. This stochastic model consists of an arbitrary sum of continous time autoregressive moving average (ARMA) processes, each chosen to characterize a different frequency band. The transition matrix which corresponds to the overall system and the time-dependent process noise covariance matrix are derived. Based on the general formulation, several models for UT1 were derived from spectral analysis of the Space 92 UT1 series (Gross,1993). Using Space 92 as the reference series, the candidate models were compared based on their ability to predict UT1 and LOD up to 30 days in the absence of data. These candidate models were compared with the JPL operational Kalman Earth Orientation Filter (KEOF) which assumes a random walk model for LOD (Morabito et al.,1987). The results of the comparison revealed that autoregressive modeling the 40-50 day oscillation in the LOD reduces the LOD prediction error by 10prediction. RP Hamdan, K (reprint author), CALTECH,JET PROP LAB,SPACE GEODET SCI & APPLICAT GRP,4800 OAK GROVE DR,PASADENA,CA 91109, USA. NR 17 TC 5 Z9 5 U1 1 U2 1 PU SPRINGER VERLAG PI NEW YORK PA 175 FIFTH AVE, NEW YORK, NY 10010 SN 0949-7714 J9 J GEODESY JI J. Geodesy PD MAR PY 1996 VL 70 IS 6 BP 307 EP 320 DI 10.1007/s001900050021 PG 14 WC Geochemistry & Geophysics; Remote Sensing SC Geochemistry & Geophysics; Remote Sensing GA UC368 UT WOS:A1996UC36800001 ER PT J AU Ogilvie, KW Coplan, MA Yellin, KA AF Ogilvie, KW Coplan, MA Yellin, KA TI Coronal holes near the equatorial plane and the solar wind abundance of iron SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID EARTHS MAGNETOSHEATH; OXYGEN ABUNDANCES; CARBON AB Composition analysis of the solar wind from two equatorial coronal holes has been carried out with the Ion Composition Instrument on the ISEE-3 spacecraft. The abundances of oxygen, neon and iron were determined as coronal hole-related material flowed past the spacecraft. The results show that the edges of the hole-related flow are sharply defined with abundances closer to the abundances in the photosphere than in the slower solar wind. These results are similar to those found in flows from the southern polar coronal hole and suggest an underlying unity between the polar and equatorial regions of the sun. C1 UNIV MARYLAND, INST PHYS SCI & TECHNOL, COLLEGE PK, MD 20742 USA. RP Ogilvie, KW (reprint author), GODDARD SPACE FLIGHT CTR, EXTRATERR PHYS BRANCH, GREENBELT, MD 20771 USA. NR 17 TC 0 Z9 0 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0148-0227 J9 J GEOPHYS RES-SPACE JI J. Geophys. Res-Space Phys. PD MAR 1 PY 1996 VL 101 IS A3 BP 4805 EP 4811 DI 10.1029/95JA03150 PG 7 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA TY349 UT WOS:A1996TY34900003 ER PT J AU Cargill, PJ Chen, J Spicer, DS Zalesak, ST AF Cargill, PJ Chen, J Spicer, DS Zalesak, ST TI Magnetohydrodynamic simulations of the motion of magnetic flux tubes through a magnetized plasma SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID EARTHS MAGNETOSPHERE; CONVECTION ZONE; CLOUDS; RECONNECTION; FIELDS; TOPOLOGY; SHOCK AB Magnetohydrodynamic simulations of the evolution of a flux tube accelerated through a stationary magnetized plasma are presented. As the flux tube. moves through the external plasma, its shape becomes distorted and reconnection can take place between the flux tube and external fields. The coupling between the moving flux tube and the external plasma is generally efficient, with simulated flux tube velocities many times smaller than those expected from frictionless motion. The reconnection between the flux tube and external field takes place when there is a unidirectional external field component in the direction of flux tube propagation. The reconnection is intrinsically nonsymmetric around the flux tube boundary. The principal reconnection site is at the rear of the flux tube, where strong vortices convect the external field toward the flux tube. Drag coefficients (C-D) that parameterize this interaction have been determined. When the flux tube is continually accelerated, C-D > 1 is appropriate, consistent with previously used ad hoc values. Examples of when the flux tube is accelerated for a short time but allowed to continue interacting with the external plasma are presented. It is shown that in the absence of reconnection, the coupling time is several Alfven wave transit times across the flux tube. However, when reconnection takes place, this coupling can cease to occur, and the flux tube may move frictionlessly (C-D approximate to 0). The results are discussed in terms of interplanetary magnetic clouds, and it is suggested that the observations of comoving coronal mass ejection and solar wind plasma can be accounted for by drag between the two. C1 NASA, GODDARD SPACE FLIGHT CTR, CTR COMPUTAT SCI, GREENBELT, MD 20771 USA. RP Cargill, PJ (reprint author), USN, RES LAB, DIV PLASMA PHYS, BEAM PHYS BRANCH, CODE 6790, WASHINGTON, DC 20375 USA. NR 35 TC 111 Z9 112 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 MAR 1 PY 1996 VL 101 IS A3 BP 4855 EP 4870 DI 10.1029/95JA03769 PG 16 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA TY349 UT WOS:A1996TY34900008 ER PT J AU Moses, JJ Slavin, JA Heelis, RA AF Moses, JJ Slavin, JA Heelis, RA TI Ionospheric signature of the tail neutral line during the growth phase of a substorm SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID MAGNETOSPHERIC SUBSTORMS; GEOMAGNETIC STORM; CURRENTS; MODEL; CONVECTION; DEFLATION; FLYWHEEL; FLUX; WIND AB An isolated substorm occurred on October 21, 1981 at the end of a large geomagnetic storm. Observations of particles and fields were made during the presumed growth phase of this substorm by the DE 2 satellite. The ionospheric convection at the time indicates a pattern commonly observed during the maximum of substorms with convection velocities averaging similar to 500 m/s in an eastward channel of flow in the premidnight sector. Despite the convection signature, geomagnetic conditions were quiet with the AL index >-50 nT and very weak field-aligned current. We will present an in-depth study of the nightside gap region within the channel of eastward flow. We will discuss the possible effects of a neutral wind flywheel on the convection. Also, we will present a detailed analysis of the electrodynamic structures within the nightside gap which indicates a magnetospheric source. Possible ionospheric signatures of the tail neutral line are discussed. C1 UNIV TEXAS,PHYS PROGRAM,WB HANSON CTR SPACE SCI,RICHARDSON,TX 75083. NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. RP Moses, JJ (reprint author), UNIV LONDON,UNIV LONDON QUEEN MARY & WESTFIELD COLL,ASTRON UNIT,MILE END RD,LONDON,ENGLAND. RI Slavin, James/H-3170-2012 OI Slavin, James/0000-0002-9206-724X NR 19 TC 0 Z9 0 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 SN 0148-0227 J9 J GEOPHYS RES JI J. Geophys. Res-Space Phys. PD MAR 1 PY 1996 VL 101 IS A3 BP 5067 EP 5073 DI 10.1029/95JA03380 PG 7 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA TY349 UT WOS:A1996TY34900025 ER PT J AU Aggson, TL Laakso, H Maynard, NC Pfaff, RF AF Aggson, TL Laakso, H Maynard, NC Pfaff, RF TI In situ observations of bifurcation of equatorial ionospheric plasma depletions SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID ELECTRIC-FIELD OBSERVATIONS; SPREAD-F; BUBBLES AB Vector electric field measurements from the San Marco D satellite are utilized to investigate the bifurcation of ionospheric plasma depletions (sometimes called ''bubbles'') associated with nightside equatorial spread F. These depletions are identified by enhanced upward ExB convection in depleted plasma density channels in the nighttime equatorial ionosphere. The in situ determination of the bifurcation process is based on de electric field measurements of the bipolar variation in the zonal flow, westward and eastward, as the eastbound satellite crosses isolated signatures of updrafting plasma depletion regions. We also present data in which more complicated regions of zonal velocity variations appear as the possible result of multiple bifurcations of updrafting equatorial plasma bubbles. C1 NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. FINNISH METEOROL INST,DEPT GEOPHYS,SF-00101 HELSINKI,FINLAND. MISSION RES CORP,NASHUA,NH 03062. RI Pfaff, Robert/F-5703-2012 OI Pfaff, Robert/0000-0002-4881-9715 NR 12 TC 27 Z9 27 U1 1 U2 2 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 SN 0148-0227 J9 J GEOPHYS RES JI J. Geophys. Res-Space Phys. PD MAR 1 PY 1996 VL 101 IS A3 BP 5125 EP 5132 DI 10.1029/95JA03837 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA TY349 UT WOS:A1996TY34900030 ER PT J AU Joiner, J Aikin, AC AF Joiner, J Aikin, AC TI Temporal and spatial variations in upper atmospheric Mg+ SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID METALLIC-IONS; F-REGION; GEOMAGNETIC-ACTIVITY; MAGNETIC STORM; SPORADIC-E; THERMOSPHERE; ULTRAVIOLET; CIRCULATION; LAYER AB Long-term behavior of magnesium ions in the upper atmosphere has been observed at wavelengths near 2800 Angstrom using the Nimbus 7 solar backscattered ultraviolet (SBUV) instrument. Observations were made in the continuous spectral scan mode that operated approximately once a month from 1979 to 1986. Total column abundance of Mg+ near local noon is the quantity derived from the nadir-viewing SBUV observations, Mg+ total column abundances vary as a function of magnetic activity, solar sunspot activity, season, dip latitude, and longitude, as the result of changes in chemistry and ion transport. Increased Mg+ column abundances are observed during periods of high magnetic activity at all latitudes. Total Mg+ column abundances are observed to increase with solar sunspot activity at low and middle latitudes. Seasonal variation in the midlatitude Mg+ column abundance is observed with a maximum near summer solstice. The total column abundances derived here are complementary to previous metallic ion studies in the upper E and F regions. C1 HUGHES STX CORP,GREENBELT,MD. RP Joiner, J (reprint author), NASA,GODDARD SPACE FLIGHT CTR,ATMOSPHERES LAB,CODE 9103,GREENBELT,MD 20771, USA. RI Joiner, Joanna/D-6264-2012 NR 36 TC 18 Z9 18 U1 0 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 SN 0148-0227 J9 J GEOPHYS RES JI J. Geophys. Res-Space Phys. PD MAR 1 PY 1996 VL 101 IS A3 BP 5239 EP 5249 DI 10.1029/95JA03517 PG 11 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA TY349 UT WOS:A1996TY34900040 ER PT J AU Moore, TE Chandler, MO Pollock, CJ Reasoner, DL Arnoldy, RL Austin, B Kintner, PM Bonnell, J AF Moore, TE Chandler, MO Pollock, CJ Reasoner, DL Arnoldy, RL Austin, B Kintner, PM Bonnell, J TI Plasma heating and flow in an auroral arc SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID TRANSVERSE ION-ACCELERATION; LOWER HYBRID ACCELERATION; MONTE-CARLO CALCULATIONS; F-REGION; VELOCITY DISTRIBUTION; IONOSPHERIC PLASMA; CYCLOTRON RESONANCE; ELECTROSTATIC-WAVES; ALTITUDE; MAGNETOSPHERE AB We report direct observations of the three-dimensional velocity distribution of selected topside ionospheric ion species in an auroral context between 500 and 550 km altitude. We find heating transverse to the local magnetic field in the core plasma, with significant heating of O+, He+ and H+, as well as tail heating events that occur independently of the core heating. The O+ velocity distribution departs from bi-Maxwellian, at one point exhibiting an apparent ring-like shape. However, these observations are shown to be aliased within the amoral are by temporal variations that are not well-resolved by the core plasma instrument. The de electric field measurements reveal superthermal plasma drifts that are consistent with passage of the payload through a series of vortex structures or a larger scale circularly polarized hydromagnetic wave structure within the auroral are. The de electric field also shows that impulsive solitary structures, with a frequency spectrum in the ion cyclotron frequency range, occur in close correlation with the tail heating events. The drift and core heating observations lend support to the idea that core ion heating is driven at low altitudes by rapid convective motions imposed by the magnetosphere. Plasma wave emissions at ion frequencies and parallel heating of the low-energy electron plasma are observed in conjunction with this amoral form; however, the conditions are much more complex than those typically invoked in previous theoretical treatments of superthermal frictional heating. The observed ion heating within the are clearly exceeds that expected from frictional heating for the light ion species H+ and He+, and the core distributions also contain hot transverse tails, indicating an anomalous transverse heat source. C1 UNIV NEW HAMPSHIRE,DEPT PHYS,DURHAM,NH 03824. CORNELL UNIV,SCH ELECT ENGN,ITHACA,NY 14853. RP Moore, TE (reprint author), NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,SPACE SCI LAB,HUNTSVILLE,AL 35812, USA. RI Moore, Thomas/D-4675-2012 OI Moore, Thomas/0000-0002-3150-1137 NR 55 TC 41 Z9 41 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 SN 0148-0227 J9 J GEOPHYS RES JI J. Geophys. Res-Space Phys. PD MAR 1 PY 1996 VL 101 IS A3 BP 5279 EP 5297 DI 10.1029/95JA03154 PG 19 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA TY349 UT WOS:A1996TY34900043 ER PT J AU Wu, Q Kilelen, TL Deng, W Burns, AG Winningham, JD Spencer, NW Heelis, RA Hanson, WB AF Wu, Q Kilelen, TL Deng, W Burns, AG Winningham, JD Spencer, NW Heelis, RA Hanson, WB TI Dynamics Explorer 2 satellite observations and satellite track model calculations in the cusp cleft region SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID INTERPLANETARY MAGNETIC-FIELD; POLAR CUSP; ALIGNED CURRENTS; AURORAL EVENT; LOW-ALTITUDE; LARGE-SCALE; THERMOSPHERE; BOUNDARY; VIKING; CAP AB We present two detailed case studies of the ionospheric and thermospheric response to soft particle precipitation in the cusp/cleft region using multi-instrument observations from the Dynamics Explorer 2 (DE 2) satellite during orbits 688 and 748, together with supporting model calculations. The experimental data set is among the most comprehensive reported to date and includes a specification of both the soft particle input to the atmosphere and the detailed local atmospheric response to these inputs. Specifically, observations are presented of precipitating ion and electron fluxes, ion and neutral horizontal and vertical wind speeds, neutral temperatures and densities, and volume emission rates for the OI 630.0-nm red line, which is often used as a thermospheric signature of soft electron precipitation. The two orbits were chosen to provide representative cases for active (orbit 688; Kp=5; interplanetary magnetic field (IMF) B-Z=-O.5 nT) and quiet (orbit 748; Kp=1; IMF B-Z=+7.8 nT) geomagnetic conditions. Some of the data were used to provide boundary conditions and inputs to a satellite track code that was used to calculate the ionospheric structure below and along the orbital track. The satellite track code enables us to calculate the Joule- and particle-heating altitude profiles and the ionization rate altitude profile. During each of the two orbits the region of soft electron precipitation associated with the cusp/cleft region was clearly identifiable. The principal findings of this study are as follows: (1) The maxima in the cusp/cleft soft electron (<100 eV) precipitating flux were similar to 3x10(-3) and similar to 5x10(-4) ergs/(cm(2) s sr eV) for orbits 688 and 748, respectively, and these fluxes produced oxygen red-line volume emission rate maxima of 580 ph/(cm(3) s) for the active orbit (688) and similar to 80-90 ph/(cm(3) s) for the quiet orbit (748). For both orbital passes the red line enhancements were evident above the background dayglow, peaking at altitudes near 325 km. (2) The calculated ionization rate peaked at an altitude near 265 km, or 60 lan lower than the altitude of the enhancement in the 630.0-nm volume emission rate; the difference is ascribed to low-altitude quenching of the emission. (3) Large changes in magnitude and direction for both the observed cusp/cleft neutral winds and ion drifts were observed, particularly to the poleward side of the region, with the ion drifts exhibiting more shearlike reversals and the neutral winds undergoing more rotationallike reversals. (4); Despite the negative IMF B-Z (-0.5 nT) during orbit 688, the convection characteristic of the ion drifts was consistent with a northward IMF for both orbits. (5) The satellite track code results showed maxima in particle and Joule heating rates at similar to 260 and 120 km altitude, respectively. The Joule heating rate was greater than the particle heating rate at all altitudes below the satellite, and the Joule heating peaked on the poleward side of the cusp/cleft precipitation region. (6) Both ion and relative neutral vertical velocities exhibited perturbations in the upward sense on the poleward side of the cusp/cleft, consistent with intense local heating and upwelling. C1 SW RES INST,SAN ANTONIO,TX. UNIV MARYLAND,RES FDN,NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD. UNIV TEXAS,CTR SPACE SCI,RICHARDSON,TX 75083. RP Wu, Q (reprint author), UNIV MICHIGAN,DEPT ATMOSPHER OCEAN & SPACE SCI,SPACE PHYS RES LAB,2455 HAYWARD ST,ANN ARBOR,MI 48109, USA. RI Burns, Alan/L-1547-2013 NR 41 TC 7 Z9 7 U1 0 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 SN 0148-0227 J9 J GEOPHYS RES JI J. Geophys. Res-Space Phys. PD MAR 1 PY 1996 VL 101 IS A3 BP 5329 EP 5342 DI 10.1029/95JA01819 PG 14 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA TY349 UT WOS:A1996TY34900046 ER PT J AU Maghami, PG Gupta, S Elliott, KB Joshi, SM AF Maghami, PG Gupta, S Elliott, KB Joshi, SM TI Integrated controls-structures design methodology: Redesign of an evolutionary test structure SO JOURNAL OF GUIDANCE CONTROL AND DYNAMICS LA English DT Article ID OPTIMIZATION AB An optimization-based integrated controls-structures design methodology for a class of flexible space structures is described, and the phase-0 controls-structures-integration evolutionary model, a laboratory testbed at NASA Langley, is redesigned using this integrated design methodology. The integrated controls-structures design is posed as a nonlinear programming problem to minimize the control effort required to maintain a specified line-of-sight pointing performance, under persistent white noise disturbance. Static and dynamic dissipative control strategies are employed for feedback control, and parameters of these controllers are considered as the control design variables. Sizes of strut elements in various sections of the controls-structures-integration evolutionary model are used as the structural design variables. Design guides for the struts are developed and employed in the integrated design process to ensure that the redesigned structure can be effectively fabricated. The superiority of the integrated design methodology over the conventional design approach is demonstrated analytically by observing a significant reduction in the average control power needed to maintain specified pointing performance with the integrated design approach. C1 VIGYAN INC,HAMPTON,VA 23666. NASA,LANGLEY RES CTR,STRUCT DYNAM BRANCH,HAMPTON,VA 23681. NASA,LANGLEY RES CTR,DYNAM & CONTROL BRANCH,HAMPTON,VA 23681. RP Maghami, PG (reprint author), NASA,LANGLEY RES CTR,GUIDANCE & CONTROL BRANCH,HAMPTON,VA 23681, USA. NR 28 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 0731-5090 J9 J GUID CONTROL DYNAM JI J. Guid. Control Dyn. PD MAR-APR PY 1996 VL 19 IS 2 BP 316 EP 323 DI 10.2514/3.21621 PG 8 WC Engineering, Aerospace; Instruments & Instrumentation SC Engineering; Instruments & Instrumentation GA UA391 UT WOS:A1996UA39100009 ER PT J AU Maghami, PG Gupta, S Elliott, KB Walz, JE AF Maghami, PG Gupta, S Elliott, KB Walz, JE TI Experimental validation of an integrated controls-structures design methodology SO JOURNAL OF GUIDANCE CONTROL AND DYNAMICS LA English DT Article AB The first experimental validation of an integrated controls-structures design methodology for a class of large-order, flexible space structures is described. Integrated redesign of the controls-structures-interaction evolutionary model, a laboratory testbed at NASA Langley, was described earlier. The redesigned structure was fabricated, assembled in the laboratory, and experimentally tested against the original structure. Experimental results indicate that the structure redesigned using the integrated design methodology requires significantly less average control power than the nominal structure with control-optimized designs, while maintaining the required line-of-sight pointing performance, Thus, the superiority of the integrated design methodology over the conventional design approach is experimentally demonstrated. Furthermore, amenability of the integrated design structure to other control strategies is evaluated, both analytically and experimentally, Using linear-quadratic-Gaussian optimal dissipative controllers, it is observed that the redesigned structure leads to significantly improved performance with alternate controllers as well. C1 VIGYAN INC,HAMPTON,VA 23666. NASA,LANGLEY RES CTR,STRUCT DYNAM BRANCH,HAMPTON,VA 23681. NASA,LANGLEY RES CTR,COMPUTAT STRUCT BRANCH,HAMPTON,VA 23681. RP Maghami, PG (reprint author), NASA,LANGLEY RES CTR,GUIDANCE & CONTROL BRANCH,HAMPTON,VA 23681, USA. NR 11 TC 1 Z9 1 U1 0 U2 0 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 SN 0731-5090 J9 J GUID CONTROL DYNAM JI J. Guid. Control Dyn. PD MAR-APR PY 1996 VL 19 IS 2 BP 324 EP 333 DI 10.2514/3.21622 PG 10 WC Engineering, Aerospace; Instruments & Instrumentation SC Engineering; Instruments & Instrumentation GA UA391 UT WOS:A1996UA39100010 ER PT J AU Phan, MQ Juang, JN AF Phan, MQ Juang, JN TI Designs of learning controllers based on autoregressive representation of a linear system SO JOURNAL OF GUIDANCE CONTROL AND DYNAMICS LA English DT Article ID DYNAMIC CONTROL AB Learning controllers that improve tracking performance through repeated trials are derived. The design is based on an autoregressive representation of a linear system. This input-output model can be interpreted in terms of an observer in state-space form. The control input is modified at every repetition as the system learns to produce a desired response, even in the presence of unknown repetitive disturbances. The coefficients of a nominal autoregressive model are first identified from input-output data. Using the identified coefficients, simple linear feedback learning controllers are designed that can correct for the errors that remain. An optimal learning gain matrix is also derived given the identified model. Numerical examples are provided to illustrate the proposed learning approach. C1 NASA, LANGLEY RES CTR, STRUCT DYNAM BRANCH, HAMPTON, VA 23681 USA. RP PRINCETON UNIV, DEPT MECH & AEROSP ENGN, PRINCETON, NJ 08544 USA. NR 16 TC 29 Z9 31 U1 0 U2 0 PU AMER INST AERONAUTICS ASTRONAUTICS PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091-4344 USA SN 0731-5090 EI 1533-3884 J9 J GUID CONTROL DYNAM JI J. Guid. Control Dyn. PD MAR-APR PY 1996 VL 19 IS 2 BP 355 EP 362 DI 10.2514/3.21626 PG 8 WC Engineering, Aerospace; Instruments & Instrumentation SC Engineering; Instruments & Instrumentation GA UA391 UT WOS:A1996UA39100014 ER PT J AU Zhao, YY Slattery, RA AF Zhao, YY Slattery, RA TI Capture conditions for merging trajectory segments to model realistic aircraft descents SO JOURNAL OF GUIDANCE CONTROL AND DYNAMICS LA English DT Article AB A typical commercial aircraft trajectory consists of a series of Eight segments, An aircraft switches from one segment to another when certain specified variables reach their desired values, Trajectory synthesis for air traffic control automation must be consistent with practical pilot procedures, We examine capture conditions for merging trajectory segments to model commercial aircraft descent ill trajectory synthesis, These conditions translate into bounds on measurements of atmospheric wind, pressure, and temperature, They also define ranges of thrust and drag feasible for a descent trajectory, Capture conditions are derived for the Center-TRACON Automation System developed at NASA Ames Research Center for automated air traffic control, Various uses of capture conditions are discussed, A Boeing 727-200 aircraft is used to provide numerical examples of capture conditions. C1 NASA,AMES RES CTR,AIR TRAFF MANAGEMENT BRANCH,MOFFETT FIELD,CA 94035. RP Zhao, YY (reprint author), UNIV MINNESOTA,DEPT AEROSP ENGN & MECH,MINNEAPOLIS,MN 55455, USA. NR 9 TC 3 Z9 3 U1 0 U2 0 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 SN 0731-5090 J9 J GUID CONTROL DYNAM JI J. Guid. Control Dyn. PD MAR-APR PY 1996 VL 19 IS 2 BP 453 EP 460 DI 10.2514/3.21639 PG 8 WC Engineering, Aerospace; Instruments & Instrumentation SC Engineering; Instruments & Instrumentation GA UA391 UT WOS:A1996UA39100027 ER PT J AU Wada, BK Rahman, Z Kedikian, R Kuo, CP AF Wada, BK Rahman, Z Kedikian, R Kuo, CP TI Vibration isolation, suppression and steering (VISS) SO JOURNAL OF INTELLIGENT MATERIAL SYSTEMS AND STRUCTURES LA English DT Article; Proceedings Paper CT ICAST 95 CY NOV 13-15, 1995 CL KEY WEST, FL AB The opportunities for precision space instruments will increase if they can be accommodated on a non-precise spacecraft or platform. In order to meet the precision requirements of various space instruments, the objective was to develop a six degree of freedom Vibration Isolation, Suppression and Steering (VISS) subsystem that interfaces the instrument to the spacecraft or platform. This paper results from a study to design a flight experiment to validate the VISS subsystem for a Mid-Wave Infra Red (MWIR) Camera on top of a small spacecraft. One of the major challenges is to develop a long stroke PZT actuator that is redundant and compact, with low stiffness and power efficiency. The test performance of the actuator design and the predicted VISS performance of the design is included. RP Wada, BK (reprint author), CALTECH,JET PROP LAB,4800 OAK GROVE DR,PASADENA,CA 91109, USA. NR 4 TC 0 Z9 0 U1 0 U2 3 PU TECHNOMIC PUBL CO INC PI LANCASTER PA 851 NEW HOLLAND AVE, BOX 3535, LANCASTER, PA 17604 SN 1045-389X J9 J INTEL MAT SYST STR JI J. Intell. Mater. Syst. Struct. PD MAR PY 1996 VL 7 IS 2 BP 241 EP 245 PG 5 WC Materials Science, Multidisciplinary SC Materials Science GA UX562 UT WOS:A1996UX56200017 ER PT J AU Blue, CA Blue, RA Lin, RY Lei, JF Williams, WD AF Blue, CA Blue, RA Lin, RY Lei, JF Williams, WD TI Joining of Hastelloy X to Inconel 718 using an infrared process SO JOURNAL OF MATERIALS PROCESSING TECHNOLOGY LA English DT Article DE infrared joining; Hastelloy X; Inconel 718; joint microstructure; joint shear strength; braze-affected zone AB Joining of Hastelloy X to Inconel 718 by a rapid infrared processing technique has been investigated al 1150 degrees C using a nickel-based brazing alloy AMS 4777, Ni-7Cr-3Fe-3.2B-4.5Si-0.06C in wt.%. With-this infrared technique, joining typically was completed in seconds in ambient argon. The effects of the infrared joining time on the joint and base material microstructures, elemental distribution within the microstructures and the resulting joint shear strength were investigated. Results show that excellent joint shear strengths of as high as 503 MPa were obtained when processed at approximately 1150 degrees C for 120 s, Micro-structural examinations of the joint with an optical microscope and a scanning electron microscope indicate that good wetting existed between the brazing alloy and both Hastelloy X and Inconel 718. The braze-affected zone width increased with increasing joining time but did not show a direct correlation with the joint strength. Hastelloy X and Inconel 718 exhibited no noticeable change in microstructures due to the rapid heating cycle of infrared processing. C1 NASA,LEWIS RES CTR,CLEVELAND,OH 44135. RP Blue, CA (reprint author), UNIV CINCINNATI,DEPT MAT SCI & ENGN,ML 12,CINCINNATI,OH 45221, USA. NR 13 TC 4 Z9 4 U1 2 U2 4 PU ELSEVIER SCIENCE SA LAUSANNE PI LAUSANNE 1 PA PO BOX 564, 1001 LAUSANNE 1, SWITZERLAND SN 0924-0136 J9 J MATER PROCESS TECH JI J. Mater. Process. Technol. PD MAR 1 PY 1996 VL 58 IS 1 BP 32 EP 38 DI 10.1016/0924-0136(95)02104-3 PG 7 WC Engineering, Industrial; Engineering, Manufacturing; Materials Science, Multidisciplinary SC Engineering; Materials Science GA UX581 UT WOS:A1996UX58100005 ER PT J AU Dubey, RR Khandelwal, GS Cucinotta, FA Wilson, JW AF Dubey, RR Khandelwal, GS Cucinotta, FA Wilson, JW TI Microscopic optical model calculations of He-4, C-12-nucleus absorption cross sections SO JOURNAL OF PHYSICS G-NUCLEAR AND PARTICLE PHYSICS LA English DT Article ID NUCLEUS ELASTIC-SCATTERING; FULL-FOLDING-MODEL; INTERMEDIATE ENERGIES; IMPULSE APPROXIMATION; MATTER AB Calculations of absorption cross sections using a microscopic first-order optical potential for heavy-ion scattering are compared with experiments. In-medium nucleon-nucleon (NN) cross sections were used to calculate the two-body scattering amplitude. A medium-modified first-order optical potential was obtained for heavy-ion scattering using the in-medium two-body scattering amplitude. A partial wave expansion of the Lippmann-Schwinger equation in momentum space was used to calculate the absorption cross sections for various systems. The results are presented for the absorption cross sections for He-4-nucleus and C-12-nucleus scattering systems and are compared with the experimental values in the energy range 18-83A MeV. The use of the in-medium NN cross sections is found to result in significant reduction of the free space absorption cross sections in agreement with experiment. C1 NASA,LANGLEY RES CTR,HAMPTON,VA 23681. RP Dubey, RR (reprint author), OLD DOMINION UNIV,NORFOLK,VA 23529, USA. FU NCPDCID CDC HHS [NCCI-42] NR 41 TC 3 Z9 3 U1 0 U2 0 PU IOP PUBLISHING LTD PI BRISTOL PA TECHNO HOUSE, REDCLIFFE WAY, BRISTOL, ENGLAND BS1 6NX SN 0954-3899 J9 J PHYS G NUCL PARTIC JI J. Phys. G-Nucl. Part. Phys. PD MAR PY 1996 VL 22 IS 3 BP 387 EP 396 DI 10.1088/0954-3899/22/3/012 PG 10 WC Physics, Nuclear; Physics, Particles & Fields SC Physics GA UA492 UT WOS:A1996UA49200012 PM 11542267 ER PT J AU Rimlinger, MJ Shih, TIP Chyu, WJ AF Rimlinger, MJ Shih, TIP Chyu, WJ TI Shock-wave boundary-layer interactions with bleed through rows of holes SO JOURNAL OF PROPULSION AND POWER LA English DT Article AB Computations were performed to investigate three-dimensional, shock-wave/boundary-layer interactions on a flat plate with bleed through four staggered rows of circular holes that discharge into the same plenum. The focus of the computations was to examine holy bleed through rows of holes affect bleed rate and the pressure and Mach number distributions. The effects of the following parameters on the flow were investigated: 1) with and without shock-wave impingement on the boundary layer and 2) spacings between bleed holes in the streamwise and spanwise directions. Results show that just two rows of bleed holes arranged in a staggered fashion placed upstream of the incident shock are adequate in blocking the shock-induced adverse pressure gradient from propagating further upstream. Results also show that the spacings between the centers of holes can exceed the hole diameter not just in the streamwise direction, but also in the spanwise direction, and still be able to control shock-induced flow separation. This study is based on the ensemble-averaged, ''full compressible'' Navier-Stokes (N-S) equations closed by the Baldwin-Lomax algebraic turbulence model. Solutions to the ensemble-averaged N-S equations were obtained by an implicit, partially split, two-factored algorithm with flux-vector splitting in the streamwise direction on a chimera overlapping grid. C1 NASA,AMES RES CTR,APPL AEODYNAM BRANCH,MOFFETT FIELD,CA 94035. RP Rimlinger, MJ (reprint author), CARNEGIE MELLON UNIV,DEPT MECH ENGN,PITTSBURGH,PA 15213, USA. NR 24 TC 8 Z9 8 U1 0 U2 0 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 SN 0748-4658 J9 J PROPUL POWER JI J. Propul. Power PD MAR-APR PY 1996 VL 12 IS 2 BP 217 EP 224 DI 10.2514/3.24016 PG 8 WC Engineering, Aerospace SC Engineering GA UB282 UT WOS:A1996UB28200001 ER PT J AU Liscinsky, DS True, B Holdeman, JD AF Liscinsky, DS True, B Holdeman, JD TI Crossflow mixing of noncircular jets SO JOURNAL OF PROPULSION AND POWER LA English DT Article; Proceedings Paper CT AIAA 33rd Aerospace Sciences Meeting CY JAN 09-12, 1995 CL RENO, NV SP AIAA ID ELLIPTIC JET; FLOW AB An experimental investigation has been conducted of the isothermal mixing of a turbulent jet injected perpendicular to a uniform crossflow through several different types of sharp-edged orifices. Jet penetration and mixing was studied using planar Mie scattering to measure time-averaged mixture fraction distributions of circular, square, elliptical, and rectangular orifices of equal geometric area injected into a constant velocity crossflow. Hot-wire anemometry was also used to measure streamwise turbulence intensity distributions at several downstream planes. Mixing effectiveness was determined using 1) a spatial unmixedness parameter based on the variance of the mean jet concentration distributions and 2) by direct comparison of the planar distributions of concentration and of turbulence intensity. No significant difference in mixing performance was observed for the six configurations based on comparison of the mean properties. C1 NASA,LEWIS RES CTR,CLEVELAND,OH 44135. RP Liscinsky, DS (reprint author), UNITED TECHNOL RES CTR,CHEM SCI,E HARTFORD,CT 06108, USA. NR 48 TC 21 Z9 21 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 MAR-APR PY 1996 VL 12 IS 2 BP 225 EP 230 DI 10.2514/3.24017 PG 6 WC Engineering, Aerospace SC Engineering GA UB282 UT WOS:A1996UB28200002 ER PT J AU Srivastava, R Reddy, TSR Mehmed, O AF Srivastava, R Reddy, TSR Mehmed, O TI Flutter analysis of propfans using a three-dimensional Euler solver SO JOURNAL OF PROPULSION AND POWER LA English DT Article ID CASCADES; SCHEME AB A three-dimensional aeroelastic solver is developed and applied to investigate the flutter of a propfan. The unsteady airloads are obtained by solving three-dimensional Euler equations. An implicit-explicit hybrid scheme is used to reduce computational time for the solution of Euler equations. A finite element model is used to obtain structural properties, and a deforming grid technique is used to simulate elastic deformations of the blade. The aeroelastic equations are formulated in normal mode form and are solved for flutter using both the time and frequency domain methods, The analysis is used to calculate the dynamic aeroelastic stability of a single rotation propfan model for which classical flutter was measured at subsonic relative flows. Comparisons with the experimental data and other calculated results are given. C1 UNIV TOLEDO,TOLEDO,OH 43606. RP Srivastava, R (reprint author), NASA,LEWIS RES CTR,CLEVELAND,OH 44135, USA. NR 19 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 0748-4658 J9 J PROPUL POWER JI J. Propul. Power PD MAR-APR PY 1996 VL 12 IS 2 BP 267 EP 273 DI 10.2514/3.24023 PG 7 WC Engineering, Aerospace SC Engineering GA UB282 UT WOS:A1996UB28200008 ER PT J AU Savage, M Rubadeux, KL Coe, HH Coy, JJ AF Savage, M Rubadeux, KL Coe, HH Coy, JJ TI Spur, helical, and spiral bevel transmission life modeling SO JOURNAL OF PROPULSION AND POWER LA English DT Article; Proceedings Paper CT AIAA/ASME/SAE/ASEE 30th Joint Propulsion Conference CY JUN 27-29, 1994 CL INDIANAPOLIS, IN SP AIAA, ASME, SAE, ASEE ID RELIABILITY AB Computer estimation of the life, dynamic capacity, and reliability of aircraft transmissions enables comparisons of transmission service life at the design stage for optimization. Through modular programming, a variety of transmissions may be analyzed with the same software, including spur, helical, and spiral bevel reductions as well as series combinations of these reductions. The basic spur and helical reductions include, single mesh, compound, and parallel path plus reverted star and planetary gear trains, The spiral bevel reductions include single and dual input drives with arbitrary shaft angles, The analysis may be performed in either the SI metric or the English inch system of units, The reliability and life analysis are based on the two parameter Weibull distribution lives of the component gears and bearings, A program output file describes the overall transmission and each constituent transmission, its components, and their locations, capacities, and loads, Primary output is the dynamic capacity and 90% reliability and mean lives of the unit transmissions and the overall system that can be used to estimate service overhaul frequency requirements. Two examples are presented to illustrate the information available for single element and series transmissions. C1 NASA,LEWIS RES CTR,CLEVELAND,OH 44135. RP Savage, M (reprint author), UNIV AKRON,DEPT MECH ENGN,AKRON,OH 44325, 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 0748-4658 J9 J PROPUL POWER JI J. Propul. Power PD MAR-APR PY 1996 VL 12 IS 2 BP 283 EP 288 DI 10.2514/3.24025 PG 6 WC Engineering, Aerospace SC Engineering GA UB282 UT WOS:A1996UB28200010 ER PT J AU Choy, FK Huang, S Zakrajsek, JJ Handschuh, RF Townsend, DP AF Choy, FK Huang, S Zakrajsek, JJ Handschuh, RF Townsend, DP TI Vibration signature analysis of a faulted gear transmission system SO JOURNAL OF PROPULSION AND POWER LA English DT Article; Proceedings Paper CT AIAA/ASME/SAE/ASEE 30th Joint Propulsion Conference CY JUN 27-29, 1994 CL INDIANAPOLIS, IN SP AIAA, ASME, SAE, ASEE ID TIME AB A comprehensive procedure in predicting faults in gear transmission systems under normal operating conditions is presented. Experimental data were obtained from a spiral bevel gear fatigue test rig at NASA Lewis Research Center. Time-synchronous-averaged vibration data were recorded throughout the test as the fault progressed from a small single pit to severe pitting over several teeth, and finally tooth fracture. A numerical procedure based on the Wigner-Ville distribution was used to examine the time-averaged vibration data. Results from the Wigner-Ville procedure are compared to results from a variety of signal analysis techniques that include time-domain analysis methods and frequency analysis methods. Using photographs of the gear tooth at various stages of damage, the limitations and accuracy of the various techniques are compared and discussed, Conclusions are drawn from the comparison of the different approaches as well as the applicability of the Wigner-Ville method in predicting gear faults. C1 NASA,LEWIS RES CTR,AEROSP DIRECTORATE,CLEVELAND,OH 44135. USA,AVIAT SYST COMMAND,AEROSP DIRECTORATE,CLEVELAND,OH 44135. RP Choy, FK (reprint author), UNIV AKRON,DEPT MECH ENGN,AKRON,OH 44325, USA. NR 13 TC 12 Z9 12 U1 0 U2 1 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 MAR-APR PY 1996 VL 12 IS 2 BP 289 EP 295 DI 10.2514/3.24026 PG 7 WC Engineering, Aerospace SC Engineering GA UB282 UT WOS:A1996UB28200011 ER PT J AU Appelbaum, J Flood, DJ Crutchik, M AF Appelbaum, J Flood, DJ Crutchik, M TI Solar radiation on Mars: Tracking photovoltaic array SO JOURNAL OF PROPULSION AND POWER LA English DT Article AB A photovoltaic power source for surface-based operation on Mars can offer many advantages. Detailed information on solar radiation characteristics on Mars and the insolation on various types of collector surfaces are necessary for effective design of future planned photovoltaic systems. In this article we present analytical expressions for solar radiation calculation and solar radiation data for single-axis (of various types) and two-axis tracking surfaces and compare the insolation to horizontal and inclined surfaces. For clear skies (low atmospheric dust load) tracking surfaces result in higher insolation than stationary surfaces, whereas for highly dusty atmospheres, the difference is small. The insolation on the different types of stationary and tracking surfaces depends on latitude, season, optical depth of the atmosphere, and the duration of system operation. These insolations have to be compared for each planned mission. C1 NASA,LEWIS RES CTR,PHOTOVOLTA BRANCH,CLEVELAND,OH 44135. TEL AVIV UNIV,FAC ENGN SYST,IL-69978 TEL AVIV,ISRAEL. NR 3 TC 3 Z9 3 U1 0 U2 1 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 SN 0748-4658 J9 J PROPUL POWER JI J. Propul. Power PD MAR-APR PY 1996 VL 12 IS 2 BP 410 EP 419 DI 10.2514/3.24044 PG 10 WC Engineering, Aerospace SC Engineering GA UB282 UT WOS:A1996UB28200029 ER PT J AU Park, K Zink, LR Evenson, KM Chance, KV Nolt, IG AF Park, K Zink, LR Evenson, KM Chance, KV Nolt, IG TI Pressure broadening of the 83.869 cm(-1) rotational lines of OH by N-2, O-2, H-2, and He SO JOURNAL OF QUANTITATIVE SPECTROSCOPY & RADIATIVE TRANSFER LA English DT Article ID RESONANCE; SPECTRUM AB We present pressure broadening coefficients of the 83.869 cm(-1) (2.514 THz) F-1, 5/2(-) <-- F-1, 3/2(+) rotational lines of OH by N-2, O-2, H-2, and He at 293 and 192 K. We also remeasured the position of the manifold of lines, with results that are in excellent agreement with a previous accurate determination. The frequency of the strongest component of the transition (F = 2 <-- 3) and its 2 sigma uncertainty is 2,514,316.37(3) MHz. C1 NATL INST STAND & TECHNOL,BOULDER,CO 80303. HARVARD SMITHSONIAN CTR ASTROPHYS,CAMBRIDGE,MA 02138. NASA,LANGLEY RES CTR,HAMPTON,VA 23681. RP Park, K (reprint author), UNIV OREGON,DEPT PHYS,EUGENE,OR 97403, USA. OI Chance, Kelly/0000-0002-7339-7577 NR 11 TC 16 Z9 16 U1 1 U2 3 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 MAR PY 1996 VL 55 IS 3 BP 285 EP 287 DI 10.1016/0022-4073(95)00172-7 PG 3 WC Optics; Spectroscopy SC Optics; Spectroscopy GA UA459 UT WOS:A1996UA45900002 ER PT J AU Gnoffo, PA Weilmuenster, KJ Braun, RD Cruz, CI AF Gnoffo, PA Weilmuenster, KJ Braun, RD Cruz, CI TI Influence of sonic-line location on Mars Pathfinder Probe aerothermodynamics SO JOURNAL OF SPACECRAFT AND ROCKETS LA English DT Article ID FLIGHT EXPERIMENT; SCHEMES; CODE AB Flowfield solutions over the Mars Pathfinder Probe spanning the trajectory through the Martian atmosphere at angles of attack from 9 to 11 deg are obtained. Aerodynamic coefficients derived from these solutions reveal two regions where the derivative of pitching moment with respect to angle of attack is positive at small angles of attack, The behavior is associated with the movement of the sonic line between the blunted nose and the windside shoulder of the 70-deg half-angle cone in a gas with a low effective ratio of specific heats, The translation first occurs as the shock layer gas chemistry evolves from highly nonequilibrium to near equilibrium, above approximately 6.5 km/s and 40-km altitude, causing the effective specific heat ratio to decrease. The translation next occurs in an equilibrium Row regime as velocities decrease through 3.5 km/s and the specific heat ratio increases again with decreasing enthalpy. Laminar, windside heating levels may decrease with increasing angle of attack resulting from an increase in the effective radius of curvature with sonic line movement from the hemispherical nose to the aft shoulder of the blunt cone. C1 NASA,LANGLEY RES CTR,VEHICLE ANAL BRANCH,HAMPTON,VA 23681. RP Gnoffo, PA (reprint author), NASA,LANGLEY RES CTR,GAS DYNAM DIV,AEROTHERMODYNAM BRANCH,HAMPTON,VA 23681, USA. NR 38 TC 24 Z9 30 U1 1 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 MAR-APR PY 1996 VL 33 IS 2 BP 169 EP 177 DI 10.2514/3.26737 PG 9 WC Engineering, Aerospace SC Engineering GA UE755 UT WOS:A1996UE75500001 ER PT J AU Swenson, GR Rairden, RL Jennings, DE Ahmadjian, M AF Swenson, GR Rairden, RL Jennings, DE Ahmadjian, M TI Vehicle glow measurements on space transportation system flight 62 SO JOURNAL OF SPACECRAFT AND ROCKETS LA English DT Article ID SHUTTLE GLOW; ENVIRONMENT; EMISSIONS AB Spacecraft glows are primarily a result of satellite surfaces (and their gas clouds) interacting with the rarefied atmosphere in low Earth orbit, Studies of glow were performed in March 1934 on Space Transportation System flight 62 as part of the Office of Astronautics and Space Technology payload objectives, Together the experimental investigation of spacecraft glow and the spacecraft kinetic infrared test instruments made observations encompassing the far-ultraviolet, ultraviolet, visible, and infrared spectral regions, The experiment included the release of N-2 that was expected to atom exchange with atmospheric O to form surface reactive constituents N and NO. Emission measurements indicate that ground state N-2 at orbital velocities does not atom exchange;Is previously believed, Another key finding was the lack of N-2 Lyman-Birge-Hopfield emissions in the far ultraviolet, Thruster activity, particularly in low elliptical orbit, is found to cause bright enhancements of OI 5577 and 6300 Angstrom emissions in the Shuttle environment. This investigation studied the effects of altitude, temperature, two paint materials (2306 black Chemglaze(R) and A276 white Chemglaze), ram-wake orientation, thruster gas clouds, and thruster effluent surface doping on the glow intensity and spectral character. C1 NASA,GODDARD SPACE FLIGHT CTR,ORG 6932,GREENBELT,MD 20771. USAF,PHILLIPS LAB,GEOPHYS DIRECTORATE,MC PL,XPG,BEDFORD,MA 01731. RP Swenson, GR (reprint author), LOCKHEED MISSILES & SPACE CO INC,PALO ALTO RES LAB,DEPT 9120,BLDG 252,3251 HANOVER ST,PALO ALTO,CA 94304, USA. RI Jennings, Donald/D-7978-2012 NR 27 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 MAR-APR PY 1996 VL 33 IS 2 BP 240 EP 249 DI 10.2514/3.26747 PG 10 WC Engineering, Aerospace SC Engineering GA UE755 UT WOS:A1996UE75500011 ER PT J AU Lauriente, M Vampola, AL Inamti, P Bilitza, D AF Lauriente, M Vampola, AL Inamti, P Bilitza, D TI Experimental validation of particle model drift theories SO JOURNAL OF SPACECRAFT AND ROCKETS LA English DT Article AB Using a two-dimensional longitude-latitude cross-correlation technique, a database consisting of single event effects, which were produced in the TOPEX satellite by energetic protons, is correlated with the location of the South Atlantic anomaly as predicted by the AP8MAX model. The results show that a current-epoch magnetic field model used with the API particle model accurately predicts the location of the proton South Atlantic anomaly. Furthermore, the cross-correlation technique provides a means of determining the energy threshold needed to produce the single-event effects. The cross-correlation study indicates that the TOPEX single-event effects are produced by protons with a minimum proton energy of 80-90 MeV. C1 UNIV RES FDN,GREENBELT,MD 20770. HUGHES STX,TECH STAFF,GREENBELT,MD 20771. RP Lauriente, M (reprint author), NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771, USA. NR 9 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 MAR-APR PY 1996 VL 33 IS 2 BP 250 EP 254 DI 10.2514/3.26748 PG 5 WC Engineering, Aerospace SC Engineering GA UE755 UT WOS:A1996UE75500012 ER PT J AU Vayner, BV Ferguson, DC AF Vayner, BV Ferguson, DC TI Low-frequency waves in the plasma environment around the shuttle SO JOURNAL OF SPACECRAFT AND ROCKETS LA English DT Article ID SPACE-SHUTTLE AB As a part of the Solar Array Module Plasma Interaction Experiment program, the Langmuir probe was employed to measure plasma characteristics during the flight of STS-62, The entire data set could be divided into two parts: i) low-frequency sweeps to determine voltage-current characteristics and to find the electron temperature and number density and ii) high-frequency turbulence data caused by electrostatic noise around the Shuttle. Broadband noise was observed at 250-20,000-Hz frequencies, Measurements were performed in RAM conditions; thus it seems reasonable to believe that the influence of spacecraft operations on plasma parameters was minimized, It is shown that ion acoustic waves were observed, and two kinds of instabilities are suggested to explain the origin of these waves. According to the purposes of the experiment, samples of solar cells were placed in the cargo bay of the Shuttle, and high negative bias voltages were applied to them to initiate arcing between these cells and the surrounding plasma. The arcing onset was registered by special counters, and data were obtained that included the amplitudes of current, duration of each are, and the number of arts per one experiment, The data were analyzed for two different situations: with arcing and without arcing. Electrostatic noise spectra for both situations were obtained, and strong correlations between the number of arcs and the intensity of noise were established. RP Vayner, BV (reprint author), NASA,LEWIS RES CTR,SPACE ENVIRONM EFFECTS BRANCH,CLEVELAND,OH 44135, 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 MAR-APR PY 1996 VL 33 IS 2 BP 255 EP 261 DI 10.2514/3.26749 PG 7 WC Engineering, Aerospace SC Engineering GA UE755 UT WOS:A1996UE75500013 ER PT J AU Noever, DA Cronise, RJ Wessling, FC McMannus, SP Mathews, J Patel, D AF Noever, DA Cronise, RJ Wessling, FC McMannus, SP Mathews, J Patel, D TI Gravitational effects on closed-cellular-foam microstructure SO JOURNAL OF SPACECRAFT AND ROCKETS LA English DT Article AB Polyurethane foam has been produced in low gravity for the first time. The cause and distribution of different void or pore sizes are elucidated from direct comparison of unit-gravity and low gravity samples. Low gravity is found to increase the pore roundness by 17% and reduce the void size by 50%, The standard deviation for pores becomes narrower (a more homogeneous foam is produced) in low gravity. Both a Gaussian and a Weibull model fail to describe the statistical distribution of void areas, and hence the governing dynamics do not combine small voids in either a uniform or a dependent fashion to make larger voids. Instead, the void areas follow an exponential law, which effectively randomizes the production of void sizes in a nondependent fashion consistent more with single nucleation than with multiple or combining events. C1 UNIV ALABAMA,DEPT CHEM,HUNTSVILLE,AL 35899. RP Noever, DA (reprint author), NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,BIOPHYS BRANCH,ES76,HUNTSVILLE,AL 35812, 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 MAR-APR PY 1996 VL 33 IS 2 BP 267 EP 271 DI 10.2514/3.26751 PG 5 WC Engineering, Aerospace SC Engineering GA UE755 UT WOS:A1996UE75500015 ER PT J AU Librescu, L Lin, W Nemeth, MP Starnes, JH AF Librescu, L Lin, W Nemeth, MP Starnes, JH TI Vibration of geometrically imperfect panels subjected to thermal and mechanical loads SO JOURNAL OF SPACECRAFT AND ROCKETS LA English DT Article ID FLUTTER AB The results of a study of the vibration response of transversely isotropic flat and curved panels subjected to temperature fields and to mechanical loads into the postbuckling load range are presented, The results were obtained using a higher-order transverse-shear-deformation theory of shallow shells that includes the effects of geometric nonlinearities and initial geometric imperfections, The results focus on the interaction between the temperature field, the applied mechanical load, and the fundamental frequency associated with small vibrations about the prebuckling and postbuckling equilibrium states. Results are presented for a wide range of temperatures and mechanical load magnitudes and of geometric parameters. The results show that transverse-shear flexibility has a significant effect on the analytical prediction of panel response and that the fundamental frequency of a panel may be substantially overestimated in the prebuckling load range and underestimated in the postbuckling load range, Results are also presented that indicate that the fundamental frequency of flat panels generally increases as the initial geometric imperfection amplitude increases for both the prebuckling and postbuckling load ranges, The results, however, also indicate that the fundamental frequency of curved panels generally decreases in the prebuckling load range and increases in the postbuckling load ranges. C1 NASA,LANGLEY RES CTR,STRUCT MECH BRANCH,HAMPTON,VA 23681. RP Librescu, L (reprint author), VIRGINIA POLYTECH INST & STATE UNIV,DEPT ENGN SCI & MECH,BLACKSBURG,VA 24061, USA. NR 16 TC 41 Z9 41 U1 0 U2 4 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 MAR-APR PY 1996 VL 33 IS 2 BP 285 EP 291 DI 10.2514/3.26754 PG 7 WC Engineering, Aerospace SC Engineering GA UE755 UT WOS:A1996UE75500018 ER PT J AU Rokey, MJ Wall, SD AF Rokey, MJ Wall, SD TI Effects on operations of highly adaptive missions SO JOURNAL OF SPACECRAFT AND ROCKETS LA English DT Article ID MAGELLAN; VENUS AB A nonadaptive operations strategy was used by the Magellan mission to Venus, whereas an adaptive strategy was used for the Spaceborne Imaging Radar-C mission to Earth. The operational strategies employed by these missions are described, along with overviews of both missions and a summary of their systems and capabilities. The effects of adaptivity on the operations systems are discussed, and a summary of advantages of each strategy is given. RP Rokey, MJ (reprint author), CALTECH,JET PROP LAB,4800 OAK GROVE DR,MAIL STOP 301-250D,PASADENA,CA 91109, USA. NR 10 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 MAR-APR PY 1996 VL 33 IS 2 BP 298 EP 304 DI 10.2514/3.26756 PG 7 WC Engineering, Aerospace SC Engineering GA UE755 UT WOS:A1996UE75500020 ER PT J AU Bauer, F Maestrello, L Ting, L AF Bauer, F Maestrello, L Ting, L TI Acoustic field in unsteady moving media SO JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA LA English DT Article AB In the interaction of an acoustic field with a moving airframe, a canonical initial value problem for an acoustic field induced by an unsteady source distribution q(t,x) with q=0 for t less than or equal to 0, in a medium moving with a uniform unsteady velocity U(t)<(iota)over cap> in the coordinate system x fixed on the airframe, is encountered. Signals issued from a source point S in the domain of dependence D of an observation point P at time t will arrive at point P more than once corresponding to different retarded times tau in the interval [0,t]. The number of arrivals is called the multiplicity of the point S. The multiplicity equals one if the velocity U remains subsonic and can be greater when U becomes supersonic. For an unsteady uniform flow U(t)<(iota)over cap>, rules are formulated for defining the smallest number of I subdomains V-i of D with the union of V-i equal to D. Each subdomain has multiplicity 1 and a formula for the corresponding retarded time. The number of subdomains V-i with nonempty intersection is the multiplicity m of the intersection. The multiplicity is at most I. Examples demonstrating these rules are presented for media at accelerating and/or decelerating supersonic speed. C1 NASA,LANGLEY RES CTR,HAMPTON,VA 23681. RP Bauer, F (reprint author), NYU,COURANT INST MATH SCI,251 MERCER ST,NEW YORK,NY 10012, USA. NR 6 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 0001-4966 J9 J ACOUST SOC AM JI J. Acoust. Soc. Am. PD MAR PY 1996 VL 99 IS 3 BP 1291 EP 1305 DI 10.1121/1.414707 PG 15 WC Acoustics; Audiology & Speech-Language Pathology SC Acoustics; Audiology & Speech-Language Pathology GA UA036 UT WOS:A1996UA03600002 ER PT J AU Lee, KN Miller, RA AF Lee, KN Miller, RA TI Oxidation behavior of mullite-coated SiC and SiC/SiC composites under thermal cycling between room temperature and 1200 degrees-1400 degrees C SO JOURNAL OF THE AMERICAN CERAMIC SOCIETY LA English DT Article ID SILICON-CARBIDE; COATINGS; CERAMICS AB Refractory oxide barrier coatings are a promising approach for improving the environmental durability of silicon-based ceramics in severe environments, The oxidation durability of a newly developed fully crystalline mullite coating on SIC and SiC/SiC composites was investigated under thermal cycling between room temperature and 1200 degrees-1400 degrees C with a higher frequency (1- or 2-h) and a lower frequency (20-h) cycling for times up to 1200 h, The new mullite coating exhibited significantly improved adherence and resistance to cracking when compared to conventional mullite coatings, Current issues include oxidation of SiC-based substrates, void formation at the coating/substrate interface, and cracking in the coating through the thickness. C1 NASA,LEWIS RES CTR,CLEVELAND,OH 44135. NR 19 TC 53 Z9 55 U1 2 U2 16 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 MAR PY 1996 VL 79 IS 3 BP 620 EP 626 PG 7 WC Materials Science, Ceramics SC Materials Science GA UB624 UT WOS:A1996UB62400008 ER PT J AU Stutte, GW Yorio, NC Wheeler, RM AF Stutte, GW Yorio, NC Wheeler, RM TI Interacting effects of photoperiod and photosynthetic photon flux on net carbon assimilation and starch accumulation in potato leaves SO JOURNAL OF THE AMERICAN SOCIETY FOR HORTICULTURAL SCIENCE LA English DT Article ID SOLANUM-TUBEROSUM-L; LIFE SUPPORT SYSTEMS; GROWTH; PLANTS; LIGHT; SPACE AB The effect of photoperiod (PP) on net carbon assimilation rate (A(net)) and starch accumulation in newly mature canopy leaves of 'Norland) potato (Solanum tuberosum L.) was determined under high (412 proportional to mol .(m-)2 . s(-1)) and low (263 proportional to mol . m(-2). s(-1)) photosynthetic photon flux (PPF) conditions. The A(net) decreased from 13.9 to 11.6 and 9.3 mu mol . m(-2). s(-1), and leaf starch increased from 70 to 129 and 118 mg . g(-1) drymass (DM) as photoperiod (PP) was increased from 12/12 to 18/6, and 24/0, respectively. Longer PP had a greater effect with high PPF conditions than with low PPF treatments, with high PPF showing greater decline in A(net). Photoperiod did not affect either the CO2 compensation point (50 mu mol . mol(-1)) or CO2 saturation point (1100-1200 mu mol . mol(-1)) for A(net). These results show an apparent limit to the amount of starch that can be stored (approximate to 15% DM) in potato leaves. An apparent feedback mechanism exists for regulating A(net) under high PPF, high CO2 and long PP, but there was no correlation between A(net) and starch concentration in individual leaves. This suggests that maximum A(net) cannot be sustained with elevated CO2 conditions under long PP (greater than or equal to 12 hours) and high PPF conditions. If a physiological limit exists for the fixation and transport of carbon, then increasing photoperiod and light intensity under high CO2 conditions Is not the most appropriate means to maximize the yield of potatoes. C1 NASA,OFF BIOMED OPERAT,KENNEDY SPACE CTR,FL 32899. RP Stutte, GW (reprint author), DYNAMAC CORP,MAIL CODE DYN 3,KENNEDY SPACE CTR,FL 32899, USA. NR 25 TC 20 Z9 21 U1 0 U2 4 PU AMER SOC HORTICULTURAL SCIENCE PI ALEXANDRIA PA 701 NORTH SAINT ASAPH STREET, ALEXANDRIA, VA 22314-1998 SN 0003-1062 J9 J AM SOC HORTIC SCI JI J. Am. Soc. Hortic. Sci. PD MAR PY 1996 VL 121 IS 2 BP 264 EP 268 PG 5 WC Horticulture SC Agriculture GA TX782 UT WOS:A1996TX78200017 PM 11539332 ER PT J AU Moon, PF Stabenau, EK AF Moon, PF Stabenau, EK TI Anesthetic and postanesthetic management of sea turtles SO JOURNAL OF THE AMERICAN VETERINARY MEDICAL ASSOCIATION LA English DT Article DE sea turtles; anesthesia, general; isoflurane ID CENTRAL CHEMICAL CONTROL; ACID-BASE; BLOOD; VENTILATION AB Objective-To examine the physiologic effects of inhalation anesthesia in aquatic turtles to improve anesthetic techniques and postanesthetic monitoring. Design-Retrospective case series. Animals-9 Kemp's ridley sea turtles. Procedure-Isoflurane was used as the general anesthetic during 14 minor surgical procedures. Turtles were orotracheally intubated, and a surgical plane of anesthesia was maintained with 2.7 +/- 0.4% (mean +/- SE) isoflurane. The duration of anesthesia was 131 +/- 12 minutes. Pulse rate, blood pressure, blood gases (Pa-O2 and Pa-CO2) and pH, blood lactic acid concentration, and capnography were used to evaluate the physiologic responses of sea turtles to isoflurane. Results-An isoflurane concentration of 3.4 +/- 0.3% provided anesthetic induction in 7 +/- 1 minutes. The mean duration of the recovery phase was 241 +/- 31 minutes. The duration of the recovery phase was not affected by the duration of anesthesia, type of carrier gas, method of ventilatory weaning, or use of selected pharmacologic agents. The recovery phase was characterized by hypoxemia, progressive acidemia, hypercapnia, and lactic acidosis. Awakening in the turtles was preceded by a characteristic tachycardia and tachypnea. All sea turtles recovered from isoflurane anesthesia without apparent adverse effects within 24 hours. Clinical Implications-Isoflurane appears to be safe and effective in providing surgical anesthesia in turtles that require a timely return to an aquatic environment. This study should assist veterinarians in predicting the physiologic responses of aquatic turtles to inhalation agents. C1 UNIV TEXAS,MED BRANCH,DEPT ANESTHESIOL,GALVESTON,TX 77550. UNIV TEXAS,MED BRANCH,DEPT PHYSIOL & BIOPHYS,GALVESTON,TX 77550. NATL MARINE FISHERIES SERV,GALVESTON LAB,GALVESTON,TX 77551. NR 25 TC 10 Z9 10 U1 0 U2 5 PU AMER VETERINARY MEDICAL ASSOC PI SCHAUMBURG PA 1931 N MEACHAM RD SUITE 100, SCHAUMBURG, IL 60173-4360 SN 0003-1488 J9 J AM VET MED ASSOC JI J. Am. Vet. Med. Assoc. PD MAR 1 PY 1996 VL 208 IS 5 BP 720 EP & PG 9 WC Veterinary Sciences SC Veterinary Sciences GA TX075 UT WOS:A1996TX07500018 PM 8617631 ER PT J AU Wu, DL Fishbein, EF Read, WG Waters, JW AF Wu, DL Fishbein, EF Read, WG Waters, JW TI Excitation and evolution of the quasi-2-day wave observed in UARS/MLS temperature measurements SO JOURNAL OF THE ATMOSPHERIC SCIENCES LA English DT Article ID QUASI 2-DAY WAVE; BAROCLINIC INSTABILITY; MIDDLE ATMOSPHERE; SUMMER MESOSPHERE AB The quasi-2-day wave is known as a strong and transient perturbation in the middle and upper atmosphere that often occurs shortly after solstice. The excitation mechanisms of this transient wave have been discussed for years, but no clear answer has yet been attained. In this paper, propagating characteristics of the a-day wave are studied based on g-mon temperature measurements from the Microwave Limb Sounder onboard the Upper Atmosphere Research Satellite. The studies are focused on the wave events that happened in January 1993 and in July-August 1993. The observations suggest that winter planetary waves could be responsible far triggering the summer 2-day wave through long penetration into the summer stratosphere. A connection is evident in the evolution of the wave amplitude between the summer 2-day wave generation and winter wave penetration, The data also suggest that the enhancement of the wave amplitude is a manifestation of both a local unstable wave and a global normal-mode Rossby wave. RP Wu, DL (reprint author), CALTECH,JET PROP LAB,4800 OAK GROVE DR,PASADENA,CA 91109, USA. RI Wu, Dong/D-5375-2012 NR 18 TC 74 Z9 74 U1 0 U2 0 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 SN 0022-4928 J9 J ATMOS SCI JI J. Atmos. Sci. PD MAR 1 PY 1996 VL 53 IS 5 BP 728 EP 738 DI 10.1175/1520-0469(1996)053<0728:EAEOTQ>2.0.CO;2 PG 11 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA TZ888 UT WOS:A1996TZ88800005 ER PT J AU Ratnakumar, BV Timmerman, P Sanchez, C DiStefano, S Halpert, G AF Ratnakumar, BV Timmerman, P Sanchez, C DiStefano, S Halpert, G TI Predictions from the macrohomogeneous model of an aerospace Ni-Cd battery SO JOURNAL OF THE ELECTROCHEMICAL SOCIETY LA English DT Article ID NICKEL-HYDROXIDE ELECTRODE; MATHEMATICAL-MODEL; POROUS-ELECTRODES; CELL; DISCHARGE AB The mathematical porous-electrode model developed at Texas A&M University has been combined with a planar model for the surface active layer to formulate a pseudo two-dimensional model for a sealed nickel-cadmium cell. The porous electrode model is based on a macrohomogeneous description of the electrodes and takes into account various processes such as mass transport in the liquid phase and porosity and conductivity changes in the solid phase. The planar electrode model describes the processes occurring across the surface layer of active material, i.e., solid-state diffusion of protons and conductivity changes in the nickel oxide, and the charge-transfer across the film-electrolyte interface. Also, various routines have been added to the pseudo two-dimensional model thus integrated, to allow predictions for any nickel-cadmium battery under any desired charge-discharge schedule. From a comparison with the experimental data of an aerospace cell, the model parameters describing charge-discharge behavior of a Ni-Cd cell have been optimized to obtain a closer prediction with the experimental data. Upon optimizing the model parameters, the performance of the aerospace nickel-cadmium cell has been simulated under various experimental conditions, i.e., at different rates and temperatures. Also, generic Ragone plots for the cell and typical Tafel plots for cadmium and nickel electrodes at different states of charge have been constructed from the simulations. Finally, this model has been made available for any interested user through COSMIC NASA's Computer Management and Information Center, along with documentation in six volumes describing the code, principles, and operating instructions. RP Ratnakumar, BV (reprint author), CALTECH,JET PROP LAB,4800 OAK GROVE DR,PASADENA,CA 91109, USA. NR 35 TC 13 Z9 14 U1 1 U2 1 PU ELECTROCHEMICAL SOC INC PI PENNINGTON PA 10 SOUTH MAIN STREET, PENNINGTON, NJ 08534 SN 0013-4651 J9 J ELECTROCHEM SOC JI J. Electrochem. Soc. PD MAR PY 1996 VL 143 IS 3 BP 803 EP 812 DI 10.1149/1.1836541 PG 10 WC Electrochemistry; Materials Science, Coatings & Films SC Electrochemistry; Materials Science GA UC203 UT WOS:A1996UC20300014 ER PT J AU Krasich, M AF Krasich, M TI Expanding our technical excellence SO JOURNAL OF THE INSTITUTE OF ENVIRONMENTAL SCIENCES LA English DT Editorial Material RP Krasich, M (reprint author), CALTECH,JET PROP LAB,4800 OAK GROVE DR,M-S 301-466,PASADENA,CA 91109, USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU INST ENVIRONMENTAL SCI PI MT PROSPECT PA 940 E NORTHWEST HIGHWAY, MT PROSPECT, IL 60056 SN 1052-2883 J9 J INST ENVIRON SCI JI J. Inst. Environ. Sci. PD MAR-APR PY 1996 VL 39 IS 2 BP 22 EP 22 PG 1 WC Engineering, Environmental; Environmental Sciences; Instruments & Instrumentation SC Engineering; Environmental Sciences & Ecology; Instruments & Instrumentation GA UH325 UT WOS:A1996UH32500002 ER PT J AU Wu, D Outlaw, RA Ash, RL AF Wu, D Outlaw, RA Ash, RL TI Extraction of oxygen from CO2 using glow-discharge and permeation techniques SO JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A-VACUUM SURFACES AND FILMS LA English DT Article ID ADSORPTION; AG(111); SILVER AB A promising method to extract oxygen from CO2, which constitutes more than 95% of the Mars atmosphere, is by using glow-discharge dissociation of CO2 combined with the permeation of the generated oxygen through a Ag membrane. Quadrupole mass spectrometry was utilized to measure the oxygen flux through a 0.35-mm-thick, 2.01 cm(2) area membrane separating a two-chamber system. On the upstream side of the membrane, a de glow discharge was established with 350 V and 5 mA current. It was found that as much as 75% of the CO2 was dissociated to form CO and O (part of which recombined to form O-2) The atomic and molecular oxygen generated were adsorbed on the membrane surface, subsequently dissolved into the Ag, and diffused through the membrane thickness to the downstream surface where it desorbed as molecular oxygen. The resulting oxygen flux was studied as a function of upstream CO2 pressure, discharge current, discharge probe to membrane distance, and membrane temperature. It was found that the atomic oxygen generated a much higher concentration gradient across the membrane than did the molecular oxygen which resulted in a correspondingly higher oxygen flux through the membrane. The total oxygen flux through the membrane with a CO2 glow-discharge pressure of 5 Torr and a membrane temperature of 450 degrees C was found to be greater than 10(14) cm(-2) s(-1). This method can be used to continuously and efficiently supply oxygen for astronauts in a future manned mission to Mars. (C) 1996 American Vacuum Society. C1 NASA,LANGLEY RES CTR,HAMPTON,VA 23681. RP Wu, D (reprint author), OLD DOMINION UNIV,NORFOLK,VA 23508, USA. NR 15 TC 8 Z9 8 U1 0 U2 7 PU AMER INST PHYSICS PI WOODBURY PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 SN 0734-2101 J9 J VAC SCI TECHNOL A JI J. Vac. Sci. Technol. A-Vac. Surf. Films PD MAR-APR PY 1996 VL 14 IS 2 BP 408 EP 414 DI 10.1116/1.580098 PG 7 WC Materials Science, Coatings & Films; Physics, Applied SC Materials Science; Physics GA UA575 UT WOS:A1996UA57500024 ER PT J AU Henderson, DO Tung, YS Mu, R Ueda, A Collins, WE Burger, A Chen, KT Frazier, DO AF Henderson, DO Tung, YS Mu, R Ueda, A Collins, WE Burger, A Chen, KT Frazier, DO TI Atomic force microscopy of mercury iodide crystal growth from porous media at room temperature SO JOURNAL OF VACUUM SCIENCE & TECHNOLOGY B LA English DT Article; Proceedings Paper CT 8th International Conference on Scanning Tunneling Microscopy and Related Methods (STM 95) CY JUL 25-29, 1995 CL SNOWMASS, CO SP Amer Vacuum Soc, AVS Nanometerscale Sci & Technol Div, Naval Res Lab, USN, Off Naval Res, USA Res Off, Natl Sci Fdn ID MICROSTRUCTURE; GLASS; HGI2 AB A real time observation of the growth of, agglomerates of pyramidal crystallites of mercuric iodide on a porous glass surface using tapping mode atomic force microscopy is reported. Crystallites are observed to grow from the pores (5.0 nm diameter) onto the surface of the porous glass impregnated with mercuric iodide. immediately after fracturing the impregnated porous glasses, topographical images reveal a surface with a root mean square roughness of 75-130 nm over a 5 mu m x 5 mu m area, which is typical for surfaces of fractured porous glass. After 3 h, 60-90 nm pyramidal structures with a high aspect ratio (pyramid base to height) begin to appear on the surface. Some of the pyramidal structures agglometrate and form structures much larger and higher than the surrounding ones. The bottom of some of these agglomerated pyramids form equilateral triangles with dimensions of 300-500 nm, exhibiting a preferred orientation on the surface. 6 h after fracturing, micrometer-size crystallites are observed. Most of the pyramidal structures are no longer observed and mostly needlelike features are covering the surface. Step heights consistent with multiples of the c axis of alpha-mercuric ioide are observed on the micrometer-sized crystallites. Some pyramidal structures are observed between the large crystallites, with sizes comparable to the early stage pyramidal structures. Raman and electronic spectra are also reported for mercuric iodide confined in porous glasses. The Raman spectra have peaks located at 39 and 141 cm(-1), indicating that the confined mercuric iodide is stabilized in the yellow, orthorhombic (beta phase) at room temperature. Confinement of mercuric iodide in pores with radii smaller than 3.75 nm results in the appearance of a new band at 145 cm(-1) in the Raman spectra, suggesting tine presence of a new or modified beta phase of mercuric iodide. Further evidence supporting the presence of a new phase of mercuric iodide is found in the electronic spectra where an energy gap of 2.7 eV is observed, and lies between the energy gaps of the red, tetragonal, alpha phase (2.2 eV) and the: yellow, orthorhombic beta phase (3.1 eV) of mercuric iodide. The atomic force microscopy measurements provide a unique method for real time monitoring of the crystal growth and morphology changes of nanocrystalline mercuric iodide, while the spectroscopy provides insight to the phonon structure and energy gaps of the confined material. (C) 1996 American Vacuum Society. C1 NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,SPACE SCI LAB,CHEM & POLYMER MAT BRANCH,HUNTSVILLE,AL 35812. RP Henderson, DO (reprint author), FISK UNIV,DEPT PHYS,CHEM PHYS LAB,NASHVILLE,TN 37208, USA. NR 17 TC 1 Z9 1 U1 0 U2 0 PU AMER INST PHYSICS PI WOODBURY PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 SN 1071-1023 J9 J VAC SCI TECHNOL B JI J. Vac. Sci. Technol. B PD MAR-APR PY 1996 VL 14 IS 2 BP 1083 EP 1089 DI 10.1116/1.588405 PG 7 WC Engineering, Electrical & Electronic; Nanoscience & Nanotechnology; Physics, Applied SC Engineering; Science & Technology - Other Topics; Physics GA UH890 UT WOS:A1996UH89000101 ER PT J AU Sogard, SM Olla, BL AF Sogard, SM Olla, BL TI Food deprivation affects vertical distribution and activity of a marine fish in a thermal gradient: Potential energy-conserving mechanisms SO MARINE ECOLOGY PROGRESS SERIES LA English DT Article DE behavior; temperature; starvation; bioenergetics; Walleye pollock ID POLLOCK THERAGRA-CHALCOGRAMMA; JUVENILE WALLEYE POLLOCK; EASTERN BERING SEA; DICENTRARCHUS-LABRAX; ONCORHYNCHUS-NERKA; TEMPERATURE-CHANGE; PREDATOR PRESENCE; SALMO-GAIRDNERI; SOCKEYE-SALMON; RAINBOW-TROUT AB The effects of reduced food availability on the behavior of juvenile walleye pollock Theragra chalcogramma were examined in laboratory experiments designed to test for potential energy-conserving responses. Groups of juvenile fish were held on 1 of 6 ration treatments ranging from ad libitum to near starvation, and then vertical distribution and activity levels were quantified in a 2.5 m deep water column under isothermal and thermally stratified conditions. Stratification resulted in a general shift to the upper, warmer layer in the 2 experiments employing a sharp thermocline at mid-depth, but the occurrence of fish in the colder bottom layer varied with different ration treatments. Movement into cold water increased in intermediate ration groups compared to high ration groups. Since reduced temperatures should reduce metabolic costs, this behavior is consistent with our hypothesis that food deprivation should invoke energy-saving behaviors. However, activity levels increased for fish held on intermediate rations, suggesting that the greater movement into cold water was a corollary result of increased searching for food. Fish in the lowest ration treatments had decreased activity levels, but also decreased their movement into cold water when a sharp thermocline was present, negating potential bioenergetic benefits. In the third experiment, there was a gradual thermal gradient from surface to bottom rather than a sharp thermocline. Temperatures associated with vertical positions of the fish were determined. In this experiment, clear energy-conserving responses to temperature were displayed by food-deprived fish; the average temperatures occupied by fish on starvation rations were 3 to 4 degrees C colder than those of the higher ration groups. Based on the high Q(10) for metabolic rates of juvenile pollock, these reduced temperatures potentially conferred energy savings of up to 34%, relative to the metabolic expenditures of fish on high rations. The contrast in behavior for the lowest ration groups between sharply stratified and gradually stratified conditions suggested that the severity of the temperature gradient influenced the fishes' ability to take advantage of cold water as an energetic refuge. The behavior of fish in the laboratory was consistent with prior observations in the Bering Sea, where juvenile walleye pollock remained in surface waters if food availability was high, but initiated vertical migration into deeper, colder water with reduced prey densities. Results of this study demonstrated a broad flexibility in the behavioral mechanisms used by walleye pollock to deal with declining food levels. The initial response to food limitation was increased activity, indicative of greater searching behavior. With extended food deprivation, a switch to energy-conserving behavior was evident. The temperature responses of fish experiencing severe food limitation provided support for a bioenergetic hypothesis of diel vertical migration. RP Sogard, SM (reprint author), OREGON STATE UNIV, HATFIELD MARINE SCI CTR, NATL MARINE FISHERIES SERV, ALASKA FISHERIES SCI CTR, NEWPORT, OR 97365 USA. NR 64 TC 71 Z9 71 U1 1 U2 18 PU INTER-RESEARCH PI OLDENDORF LUHE PA NORDBUNTE 23, D-21385 OLDENDORF LUHE, GERMANY SN 0171-8630 J9 MAR ECOL PROG SER JI Mar. Ecol.-Prog. Ser. PD MAR PY 1996 VL 133 IS 1-3 BP 43 EP 55 DI 10.3354/meps133043 PG 13 WC Ecology; Marine & Freshwater Biology; Oceanography SC Environmental Sciences & Ecology; Marine & Freshwater Biology; Oceanography GA UG429 UT WOS:A1996UG42900004 ER PT J AU Curreri, PA Kaukler, WF AF Curreri, PA Kaukler, WF TI Real-time X-ray transmission microscopy of solidifying Al-In alloys SO METALLURGICAL AND MATERIALS TRANSACTIONS A-PHYSICAL METALLURGY AND MATERIALS SCIENCE LA English DT Article ID SOLIDIFICATION MICROSTRUCTURES; TOPOGRAPHY; CRYSTALS; GROWTH; MELT AB Real-time observations of transparent analog materials have provided insight, yet the results of these observations are not necessarily representative of opaque metallic systems. In order to study the detailed dynamics of the solidification process, we develop the technologies needed for real-time X-ray microscopy of solidifying metallic systems, which has not previously been feasible with the necessary resolution, speed, and contrast. In initial studies of Al-In monotectic alloys unidirectionally solidified in an X-ray transparent furnace, in situ records of the evolution of interface morphologies, interfacial solute accumulation, and formation of the monotectic droplets were obtained for the first time: A radiomicrograph of Al-30In grown during aircraft parabolic maneuvers is presented, showing the volumetric phase distribution in this specimen. The benefits of using X-ray microscopy for postsolidification metallography include ease of specimen preparation, increased sensitivity, and three-dimensional analysis of phase distribution. Imaging of the solute boundary layer revealed that the isoconcentration lines are not parallel (as is often assumed) to the growth interface. Striations in the solidified crystal did not accurately decorate the interface position and shape. The monotectic composition alloy under some conditions grew in an uncoupled manner. C1 UNIV ALABAMA,CTR MICROGRAV & MAT RES,HUNTSVILLE,AL 35899. RP Curreri, PA (reprint author), NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,SPACE SCI LAB,HUNTSVILLE,AL 35812, USA. OI Kaukler, William/0000-0002-7758-269X NR 32 TC 26 Z9 27 U1 0 U2 9 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 MAR PY 1996 VL 27 IS 3 BP 801 EP 808 DI 10.1007/BF02648968 PG 8 WC Materials Science, Multidisciplinary; Metallurgy & Metallurgical Engineering SC Materials Science; Metallurgy & Metallurgical Engineering GA UC668 UT WOS:A1996UC66800027 ER PT J AU Jenniskens, P AF Jenniskens, P TI Meteor stream activity .3. Measurement of the first in a new series of Leonid outburst SO METEORITICS & PLANETARY SCIENCE LA English DT Article AB In 1994 November, a shower of bright Leonid meteors signaled what is likely the first meteor outburst of Leonids associated with the upcoming return of comet P/Tempel-Tuttle to perihelion. Measurements of meteor activity and the meteor brightness distribution are presented. By comparing the present observation with those of past Leonid returns, a forecast is made of the time, the duration, the intensity, and the mean meteor brightness of Leonid outbursts that may occur if previously observed patterns are repeated in the forthcoming years. C1 DUTCH METEOR SOC,2318 NB LEIDEN,NETHERLANDS. RP Jenniskens, P (reprint author), NASA,AMES RES CTR,MAIL STOP 239-4,MOFFETT FIELD,CA 94035, USA. NR 33 TC 41 Z9 41 U1 0 U2 0 PU METEORITICAL SOC PI FAYETTEVILLE PA DEPT CHEMISTRY/BIOCHEMISTRY, UNIV ARKANSAS, FAYETTEVILLE, AR 72701 SN 0026-1114 J9 METORIT PLANET SCI JI Meteorit. Planet. Sci. PD MAR PY 1996 VL 31 IS 2 BP 177 EP 184 PG 8 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA UA636 UT WOS:A1996UA63600007 ER PT J AU Saizar, P Pachoulakis, I Shore, SN Starrfield, S Williams, RE Rothschild, E Sonneborn, G AF Saizar, P Pachoulakis, I Shore, SN Starrfield, S Williams, RE Rothschild, E Sonneborn, G TI Nova V351 Puppis 1991: A multiwavelength study of the nebular phase SO MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY LA English DT Article DE stars, individual, Nova Puppis 1991; novae, cataclysmic variables; ultraviolet, stars ID INFRARED CORONAL LINES; HYDRODYNAMIC MODELS; ABUNDANCES; OXYGEN; VULPECULAE; EVOLUTION; MAGNESIUM; NEON AB We combine ground-based optical and IUE spectrophotometry to study the physical conditions in the shell of Nova V351 Puppis 1991. The structure and the evolution of the shell during the early nebular (i.e. optically thin) phase are discussed in this paper. The reddening, derived from recombination lines, is E(B - V) = 0.72 +/- 0.10. The optical/UV light curves imply a distance of 3.0 +/- 0.5 kpc. These values are found to be consistent with a study of the reddening in the stellar field near the nova. Abundances from the emission-line spectra yield enhancements within the predictions of thermonuclear runaway models for classical novae, Relative to solar by number, they are: He/H = 1.7, C/H = 3.5, N/H = 130, O/H = 38, Ne/H = 120, Al/Si = 28. The shell shows a low ejected mass (M(ej) similar to 10(-7) M(.)), implying a high-mass white dwarf. The optical spectra reveal a strong red excess, which we tentatively attribute to the red companion. The strength of this continuum suggests that the companion is either a giant or an irradiated main-sequence star. C1 INDIANA UNIV,DEPT PHYS & ASTRON,S BEND,IN 46634. ARIZONA STATE UNIV,DEPT PHYS & ASTRON,TEMPE,AZ 85287. SPACE TELESCOPE SCI INST,BALTIMORE,MD 21218. GODDARD SPACE FLIGHT CTR,LAB ASTRON & SPACE SCI,GREENBELT,MD 20771. RP Saizar, P (reprint author), UNIV PENN,DEPT PHYS & ASTRON,PHILADELPHIA,PA 19104, USA. RI Sonneborn, George/D-5255-2012; OI Pachoulakis, Ioannis/0000-0001-5202-9698 NR 43 TC 21 Z9 21 U1 0 U2 0 PU BLACKWELL SCIENCE LTD PI OXFORD PA OSNEY MEAD, OXFORD, OXON, ENGLAND OX2 0EL SN 0035-8711 J9 MON NOT R ASTRON SOC JI Mon. Not. Roy. Astron. Soc. PD MAR 1 PY 1996 VL 279 IS 1 BP 280 EP 292 PG 13 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA TZ231 UT WOS:A1996TZ23100029 ER PT J AU Feibelman, TP Bennett, JW Cibula, WG AF Feibelman, TP Bennett, JW Cibula, WG TI Cantharellus tabernensis: A new species from the southeastern United States SO MYCOLOGIA LA English DT Article DE Aphyllophorales; chanterelles; internal transcribed spacer; ITS; ribosomal DNA AB A new species, Cantharellus tabernensis, is described from mixed pine and hardwood forests of southern Mississippi. A yellowish brown pileus with a dark brown disk and a bright orange hymenophore and stipe morphologically separate this chanterelle from other species. The new species is shown to have a long internal transcribed spacer (ITS) region of the nuclear ribosomal DNA, consistent with other Cantharellus species. Restriction fragment length polymorphism analysis of the 5' end of the nuclear large ribosomal subunit gene supports the status of C. tabernensis as a distinct species. C1 TULANE UNIV,DEPT CELL & MOLEC BIOL,NEW ORLEANS,LA 70118. NASA,JOHN C STENNIS SPACE CTR,BAY ST LOUIS,MS 39529. RP Feibelman, TP (reprint author), TULANE UNIV,DEPT ECOL EVOLUT & ORGANISMAL BIOL,NEW ORLEANS,LA 70118, USA. NR 19 TC 11 Z9 12 U1 1 U2 3 PU NEW YORK BOTANICAL GARDEN PI BRONX PA PUBLICATIONS DEPT, BRONX, NY 10458 SN 0027-5514 J9 MYCOLOGIA JI Mycologia PD MAR-APR PY 1996 VL 88 IS 2 BP 295 EP 301 DI 10.2307/3760934 PG 7 WC Mycology SC Mycology GA UG305 UT WOS:A1996UG30500017 ER PT J AU Barbiellini, G Basini, G Bellotti, R Bocciolini, M Boezio, M Brancaccio, FM Bravar, U Cafagna, F Candusso, M Carlson, P Casolino, M Castellano, M DeCataldo, G Circella, M Codino, A Finetti, N Francke, T Giglietto, N Golden, RL Grimani, C Hof, M Marangelli, B DeMarzo, CN Mitchell, JW Morselli, A DePascale, MP Papini, P Perego, A Piccardi, S Picozza, P Ricci, M Schiavon, P Simon, M Sparvoli, R Spillantini, P Spinelli, P Stephens, SA Stochaj, SJ Streitmatter, RE Suffert, M Vacchi, A Weber, N Zampa, N AF Barbiellini, G Basini, G Bellotti, R Bocciolini, M Boezio, M Brancaccio, FM Bravar, U Cafagna, F Candusso, M Carlson, P Casolino, M Castellano, M DeCataldo, G Circella, M Codino, A Finetti, N Francke, T Giglietto, N Golden, RL Grimani, C Hof, M Marangelli, B DeMarzo, CN Mitchell, JW Morselli, A DePascale, MP Papini, P Perego, A Piccardi, S Picozza, P Ricci, M Schiavon, P Simon, M Sparvoli, R Spillantini, P Spinelli, P Stephens, SA Stochaj, SJ Streitmatter, RE Suffert, M Vacchi, A Weber, N Zampa, N TI Performance of the CAPRICE RICH detector during the 1994 balloon flight SO NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT LA English DT Article; Proceedings Paper CT 2nd International Workshop on Ring Imaging Cherenkov Detectors (RICH95) CY JUN 12-16, 1995 CL UPPSALA, SWEDEN SP Royal Swedish Acad Sci, Nobel Inst Phys, Swedish Nat Sci Res Council AB A RICH detector capable of detecting unit charged particles, e.g. antiprotons and positrons, has been used successfully for the first time in a balloon-borne magnet spectrometer. The thin and compact CAPRICE RICH detector uses a NaF solid radiator, TMAE vapour as photo converter and cathode pad readout in the photosensitive MWPC operated at low gain. 15 photoelectrons are detected per ring for beta = 1, perpendicular incidence particles giving a resolution on the Cherenkov angle of 8 mrad, increasing to 14 mrad at 20 degrees C incidence angle. Besides particle identification on an event-by-event basis it efficiently rejects multiparticle events and albedo particles. C1 ROYAL INST TECHNOL,S-10044 STOCKHOLM,SWEDEN. NEW MEXICO STATE UNIV,PARTICLE ASTROPHYS LAB,LAS CRUCES,NM 88003. NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. CTR RECH NUCL,STRASBOURG,FRANCE. UNIV PERUGIA,DIPARTIMENTO FIS,I-06100 PERUGIA,ITALY. IST NAZL FIS NUCL,I-06100 PERUGIA,ITALY. IST NAZL FIS NUCL,LAB NAZL FRASCATI,I-00044 FRASCATI,ITALY. UNIV FLORENCE,DIPARTIMENTO PHYS,I-50144 FLORENCE,ITALY. IST NAZL FIS NUCL,I-50125 FLORENCE,ITALY. UNIV ROMA TOR VERGATA,DIPARTIMENTO FIS,I-00173 ROME,ITALY. IST NAZL FIS NUCL,ROME,ITALY. UNIV TRIESTE,DIPARTMENTO FIS,I-34127 TRIESTE,ITALY. UNIV BARI,DIPARTIMENTO FIS,TRIESTE,ITALY. UNIV SIEGEN,W-5900 SIEGEN,GERMANY. IST NAZL FIS NUCL,SEZ BARI,TRIESTE,ITALY. 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 Papini, Paolo/0000-0003-4718-2895; Boezio, Mirko/0000-0002-8015-2981; Morselli, Aldo/0000-0002-7704-9553; Picozza, Piergiorgio/0000-0002-7986-3321; giglietto, nicola/0000-0002-9021-2888; Castellano, Marcello/0000-0002-4211-2903; Cafagna, Francesco/0000-0002-7450-4784; Vacchi, Andrea/0000-0003-3855-5856; SPINELLI, Paolo/0000-0001-6688-8864; Bellotti, Roberto/0000-0003-3198-2708; casolino, marco/0000-0001-6067-5104; Sparvoli, Roberta/0000-0002-6314-6117 NR 8 TC 19 Z9 19 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 MAR 1 PY 1996 VL 371 IS 1-2 BP 169 EP 173 DI 10.1016/0168-9002(95)01152-8 PG 5 WC Instruments & Instrumentation; Nuclear Science & Technology; Physics, Nuclear; Physics, Particles & Fields SC Instruments & Instrumentation; Nuclear Science & Technology; Physics GA UG163 UT WOS:A1996UG16300024 ER PT J AU Perthame, B Shu, CW AF Perthame, B Shu, CW TI On positivity preserving finite volume schemes for Euler equations SO NUMERISCHE MATHEMATIK LA English DT Article ID CONSERVATION-LAWS; ELEMENT METHOD; SPACE DIMENSIONS; CONVERGENCE AB We consider the positivity preserving property of first and higher order finite volume schemes for one and two dimensional Euler equations of gas dynamics. A general framework is established which shows the positivity of density and pressure whenever the underlying one dimensional first order building block based on an exact or approximate Riemann solver and the reconstruction are both positivity preserving. Appropriate Limitation to achieve a high order positivity preserving reconstruction is described. C1 BROWN UNIV,DIV APPL MATH,PROVIDENCE,RI 02912. NASA,LANGLEY RES CTR,ICASE,HAMPTON,VA 23681. RP Perthame, B (reprint author), UNIV PARIS 06,ANAL NUMER LAB,TOUR 55-65,5EME ETAGE,4 PL JUSSIEU,F-75252 PARIS 05,FRANCE. RI Shu, Chi-Wang/A-3216-2013 OI Shu, Chi-Wang/0000-0001-7720-9564 NR 13 TC 77 Z9 80 U1 0 U2 3 PU SPRINGER VERLAG PI NEW YORK PA 175 FIFTH AVE, NEW YORK, NY 10010 SN 0029-599X J9 NUMER MATH JI Numer. Math. PD MAR PY 1996 VL 73 IS 1 BP 119 EP 130 DI 10.1007/s002110050187 PG 12 WC Mathematics, Applied SC Mathematics GA UD629 UT WOS:A1996UD62900007 ER PT J AU Sharma, RC Kramsch, DM Lee, PL Colletti, P Jiao, Q AF Sharma, RC Kramsch, DM Lee, PL Colletti, P Jiao, Q TI Quantitation and localization of regional body fat distribution - A comparison between magnetic resonance imaging and somatometry SO OBESITY RESEARCH LA English DT Article DE MRI; intra-abdominal fat; subcutaneous abdominal fat; anthropometry; cynomolgus monkeys ID ADIPOSE-TISSUE DISTRIBUTION; COMPUTED-TOMOGRAPHY; CARDIOVASCULAR-DISEASE; OBESITY; MEN; WOMEN; RISK; MONKEYS; PARTICIPANTS; FOLLOW AB The emerging concept that various fat compartments are metabolically active and play separate and decisive roles in the pathogenesis of coronary atherosclerosis, hypertension, insulin resistance, diabetes and stroke, has given obesity research a new direction, Of particular interest is the relative amount of intra-abdominal fat thought to be responsible for the metabolic complications, We studied the precise fat distribution and its correlations with the metabolic parameters in 44 non-human primates (Macaca fascicularis), Intra-abdominal, subcutaneous, and total abdominal fat (IAF, SAF, TAF) were assessed by magnetic resonance imaging (MRI) and somatometry, Quantitative computer analyses of abdominal MRI scans revealed predominant IAF distribution, Box plot analysis of IAF and SAF revealed wide diversity in the amounts of fat, especially in monkeys with body mass index (BMI) <30 kg/m(2). Primates with similar BMI in each quartile revealed an extensive heterogeneity in IAF as well as SAF, Numerous significant correlations within site-specific somatometric measurements as well as within the MRI determinants of abdominal fat were seen, However, only body weight correlated with IAF and skinfolds could predict SAF, After adjusting for body weight, partial correlation analysis showed a significant correlation (P<0.05) between total cholesterol and IAF, Conclusion: MRI revealed considerable heterogeneity of IAF, SAF and TAF in a cohort of primates believed to be homogeneous by somatometric definition, Male cynomolgus monkeys appear to be a valuable model for a systematic evaluation of fat, Individuals with identical body weight and height may show a diverse pattern of fat distribution. C1 UNIV SO CALIF,LOS ANGELES CTY MED CTR,DEPT RADIOL,IMAGING CTR,LOS ANGELES,CA 90033. JET PROP LAB,PASADENA,CA. RP Sharma, RC (reprint author), UNIV SO CALIF,DIV CARDIOL,DEPT MED,2250 ALCAZAR ST,CSC 132,LOS ANGELES,CA 90033, USA. FU NHLBI NIH HHS [HL41074] NR 35 TC 5 Z9 5 U1 0 U2 0 PU NORTH AMER ASSOC STUDY OBESITY PI BATON ROUGE PA 6400 PERKINS RD, BATON ROUGE, LA 70808 SN 1071-7323 J9 OBES RES JI Obes. Res. PD MAR PY 1996 VL 4 IS 2 BP 167 EP 178 PG 12 WC Endocrinology & Metabolism; Nutrition & Dietetics SC Endocrinology & Metabolism; Nutrition & Dietetics GA TZ378 UT WOS:A1996TZ37800008 PM 8681050 ER PT J AU Hellings, R Giampieri, G Maleki, L Tinto, M Danzmann, K Hough, J Robertson, D AF Hellings, R Giampieri, G Maleki, L Tinto, M Danzmann, K Hough, J Robertson, D TI Heterodyne laser tracking at high Doppler rates SO OPTICS COMMUNICATIONS LA English DT Article AB A design is described for a transmitter/receiver system that may be used in a spaceborne laser heterodyne tracking system to produce a high-precision interferometer. We present a two-color laser scheme that enables accurate phase measurement even in the presence of a large Doppler offset between the incoming and outgoing signals. The beat note between the two lasers provides a built-in frequency reference, while the delay line produced by the travel time of the tracking signal provides a stable self-comparison that measures drift in the frequency reference so that it may be corrected for. The resulting noise in the link is only the residual laser phase jitter and the shot noise in the phase measurement. C1 UNIV HANNOVER,INST ATOM & MOL PHYS,SPEKT ABT,W-3000 HANNOVER,GERMANY. UNIV GLASGOW,DEPT PHYS,GLASGOW G61 1BD,LANARK,SCOTLAND. RP Hellings, R (reprint author), CALTECH,JET PROP LAB,4800 OAK GROVE DR,PASADENA,CA 91109, USA. NR 1 TC 15 Z9 15 U1 0 U2 0 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0030-4018 J9 OPT COMMUN JI Opt. Commun. PD MAR 1 PY 1996 VL 124 IS 3-4 BP 313 EP 320 DI 10.1016/0030-4018(95)00684-2 PG 8 WC Optics SC Optics GA UE671 UT WOS:A1996UE67100022 ER PT J AU Mu, R Xue, Y Henderson, DO Frazier, DO AF Mu, R Xue, Y Henderson, DO Frazier, DO TI Thermal and vibrational investigation of crystal nucleation and growth from a physically confined and supercooled liquid SO PHYSICAL REVIEW B LA English DT Article ID MOLECULAR-DYNAMICS; PHASE-TRANSITION; POROUS SILICA; 2,4,6-TRINITROTOLUENE; CYCLOHEXANE; SOLIDS; GLASS AB Differential scanning calorimetry and temperature-dependent Raman-scattering investigation of 2,4,6 trinitrotoluene (TNT) confined in four different pore-sized silica hosts have been conducted. The results suggested that (i) nucleation occurs at the pore center rather than at the pore walls; (ii) although the freezing transition of the bulk has a volume reduction of about 10%, the freezing transition of the confined phase maintains its interconnectivity; (iii) that TNT confined in 10-nm pores without bulk on the outer surface shows no freezing transition upon cooling and shows recrystallization and melting transitions upon heating suggests that the characteristic curves of nucleation and growth are modified resulting from the surface and physical confinement effects. In addition, our Raman study suggests that (i) the freezable confined TNT retains the similar solid structure to its bulk; (ii) the TNT physically confined in d(p) less than or equal to 5-nm pores may exist in a cluster form. C1 NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,SPACE SCI LAB,HUNTSVILLE,AL 35812. RP Mu, R (reprint author), FISK UNIV,DEPT PHYS,PHYS CHEM LAB,NASHVILLE,TN 37208, USA. NR 18 TC 23 Z9 24 U1 0 U2 9 PU AMERICAN PHYSICAL SOC PI COLLEGE PK PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA SN 0163-1829 J9 PHYS REV B JI Phys. Rev. B PD MAR 1 PY 1996 VL 53 IS 10 BP 6041 EP 6047 DI 10.1103/PhysRevB.53.6041 PG 7 WC Physics, Condensed Matter SC Physics GA TZ773 UT WOS:A1996TZ77300018 ER PT J AU Zhou, Y Rubinstein, R AF Zhou, Y Rubinstein, R TI Sweeping and straining effects in sound generation by high Reynolds number isotropic turbulence SO PHYSICS OF FLUIDS LA English DT Letter ID DECORRELATION AB The sound radiated by isotropic turbulence is computed using inertial range scaling expressions for the relevant two-time and two-point correlations. The result depends on whether the decay of Eulerian time correlations is dominated by large scale sweeping or by local straining: the straining hypothesis leads to an expression for total acoustic power given originally by Proudman, whereas the sweeping hypothesis leads to a more recent result due to Lilley. (C) 1996 American Institute of Physics. RP Zhou, Y (reprint author), NASA,LANGLEY RES CTR,INST COMP APPLICAT SCI & ENGN,HAMPTON,VA 23681, USA. NR 18 TC 13 Z9 14 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 MAR PY 1996 VL 8 IS 3 BP 647 EP 649 DI 10.1063/1.868849 PG 3 WC Mechanics; Physics, Fluids & Plasmas SC Mechanics; Physics GA TY091 UT WOS:A1996TY09100001 ER PT J AU Speziale, CG Abid, R Blaisdell, GA AF Speziale, CG Abid, R Blaisdell, GA TI On the consistency of Reynolds stress turbulence closures with hydrodynamic stability theory SO PHYSICS OF FLUIDS LA English DT Article ID 3-DIMENSIONAL INSTABILITY; HOMOGENEOUS TURBULENCE; STRAINED VORTICES; ROTATING FRAME; SHEAR FLOWS; FLUID AB The consistency of second-order closure models with results from hydrodynamic stability theory is analyzed for the simplified case of homogeneous turbulence. In a recent study, Speziale, Gatski, and Mac Giolla Mhuiris [Phys. Fluids A 2, 1678 (1990)] showed that second-order closures are capable of yielding results that are consistent with linear stability theory for the case of homogeneous shear flow in a rotating frame. It is demonstrated in this paper that this success is due to the fact that the stability boundaries for rotating homogeneous shear flow are not dependent on the details of the spatial structure of the disturbances. For those instances where they are-such as in the case of elliptical flows where the instability mechanism is more subtle-the results are not so favorable. The origins and extent of this modeling problem are examined in detail along with a possible resolution based on Rapid Distortion Theory (RDT) and its implications for turbulence modeling. (C) 1996 American Institute of Physics. C1 NASA,LANGLEY RES CTR,HIGH TECHNOL CORP,HAMPTON,VA 23681. PURDUE UNIV,SCH AERONAUT & ASTRONAUT,W LAFAYETTE,IN 47907. RP Speziale, CG (reprint author), BOSTON UNIV,DEPT AEROSP & MECH ENGN,725 COMMONWEALTH AVE,BOSTON,MA 02215, USA. NR 32 TC 17 Z9 17 U1 0 U2 2 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 MAR PY 1996 VL 8 IS 3 BP 781 EP 788 DI 10.1063/1.868861 PG 8 WC Mechanics; Physics, Fluids & Plasmas SC Mechanics; Physics GA TY091 UT WOS:A1996TY09100013 ER PT J AU Lillywhite, HB Ballard, RE Hargens, AR AF Lillywhite, HB Ballard, RE Hargens, AR TI Tolerance of snakes to hypergravity SO PHYSIOLOGICAL ZOOLOGY LA English DT Article ID GRAVITY AB Sensitivity of carotid blood flow to increased gravitational force acting in the head-to-tail direction (+G(z)) was studied in diverse species of snakes hypothesized to show adaptive variation of response. Tolerance to increased gravity was measured as the maximum graded acceleration force at which carotid bloodflow ceased and was shown to vary according to gravitational adaptation of species defined by their ecology and behavior. Multiple regression analysis showed that gravitational habitat, but not body length, had a significant effect on G(z) tolerance. At the extremes, carotid blood flow decreased in response to increasing G force and approached zero near +1G(z) in aquatic and ground-dwelling species, whereas in climbing species carotid flow was maintained at forces in excess of +2G(z). Tolerant (arboreal) species were able to withstand hypergravic forces of +2 to +3G(z) for periods up to 1h without cessation of carotid blood flow or loss of body movement and tongue picking. Data suggest that the relatively right skin characteristic of tolerant species provides a natural antigravity suit and is of prime importance in counteracting G(z) stress on blood circulation. C1 NASA,AMES RES CTR,DIV LIFE SCI,MOFFETT FIELD,CA 94035. NR 24 TC 7 Z9 7 U1 0 U2 1 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637 SN 0031-935X J9 PHYSIOL ZOOL JI Physiol. Zool. PD MAR-APR PY 1996 VL 69 IS 2 BP 293 EP 303 PG 11 WC Physiology; Zoology SC Physiology; Zoology GA TW418 UT WOS:A1996TW41800005 PM 11540105 ER PT J AU Collier, MR Lepping, RP AF Collier, MR Lepping, RP TI Jovian magnetopause breathing SO PLANETARY AND SPACE SCIENCE LA English DT Article ID JUPITER; VOYAGER; SATURN AB Five closely spaced magnetic field directional discontinuities observed by Voyager 1 late on 2 March 1979 are analyzed using a variance technique. These discontinuities showed magnetic field signatures characteristic of magnetopause crossings occurring periodically at approximate to 36 min intervals but without dramatic changes in the low energy (<6 keV) plasma density. The locally obtained variance estimates of the discontinuity normal directions show no systematic variation consistent with magnetopause surface waves, are always within 19 degrees of the average normal direction, and their average gives excellent agreement, to within 2 degrees, with a well-known large-scale model of Jupiter's magnetopause. In addition, energetic ions (>5 MeV) of magnetospheric origin were present at elevated levels relative to typical magnetosheath rates throughout all crossings. These results suggest the discontinuities are magnetopause crossings resulting from a possible semiglobal breathing mode of the magnetopause boundary with a period of 66 min, and amplitude of 1.2 R(J), and a mean position of 49.9 R(J). The maximum boundary speed is 140 km s(-1) with a magnetopause thickness of 21 +/- 11 x 10(3) km. C1 NASA,GODDARD SPACE FLIGHT CTR,EXTRATERR PHYS LAB,GREENBELT,MD 20771. RP Collier, MR (reprint author), UNIV MARYLAND,DEPT PHYS,COLLEGE PK,MD 20742, USA. RI Collier, Michael/I-4864-2013 OI Collier, Michael/0000-0001-9658-6605 NR 27 TC 3 Z9 3 U1 0 U2 0 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, ENGLAND OX5 1GB SN 0032-0633 J9 PLANET SPACE SCI JI Planet Space Sci. PD MAR PY 1996 VL 44 IS 3 BP 187 EP 197 DI 10.1016/0032-0633(95)00117-4 PG 11 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA UB420 UT WOS:A1996UB42000002 ER PT J AU Tripathy, BC Brown, CS Levine, HG Krikorian, AD AF Tripathy, BC Brown, CS Levine, HG Krikorian, AD TI Growth and photosynthetic responses of wheat plants crown in space SO PLANT PHYSIOLOGY LA English DT Article ID INDUCED PHOTODYNAMIC DAMAGE; ELECTRON-TRANSPORT ACTIVITY; O-2 EVOLUTION; CHLOROPLASTS AB Growth and photosynthesis of wheat (Triticum aestivum L. cv Super Dwarf) plants grown onboard the space shuttle Discovery for 10 d were examined. Compared to ground control plants, the shoot fresh weight of space-grown seedlings decreased by 25%. Postflight measurements of the O-2 evolution/photosynthetic photon flux density response curves of leaf samples revealed that the CO2-saturated photosynthetic rate at saturating light intensities in space-grown plants declined 25% relative to the rate in ground control plants. The relative quantum yield of CO2-saturated photosynthetic O-2 evolution measured at limiting light intensities was not significantly affected. In space-grown plants, the light compensation point of the leaves increased by 33%, which likely was due to an increase (27%) in leaf dark-respiration rates. Related experiments with thylakoids isolated from space-grown plants showed that the light-saturated photosynthetic electron transport rate from H2O through photosystems II and I was reduced by 28%. These results demonstrate that photosynthetic functions are affected by the microgravity environment. C1 NASA,KENNEDY SPACE CTR,FL 32899. DYNAMAC CORP,KENNEDY SPACE CTR,FL 32899. SUNY STONY BROOK,DEPT BIOCHEM & CELL BIOL,STONY BROOK,NY 11794. NR 35 TC 54 Z9 60 U1 0 U2 11 PU AMER SOC PLANT PHYSIOLOGISTS PI ROCKVILLE PA 15501 MONONA DRIVE, ROCKVILLE, MD 20855 SN 0032-0889 J9 PLANT PHYSIOL JI Plant Physiol. PD MAR PY 1996 VL 110 IS 3 BP 801 EP 806 DI 10.1104/pp.110.3.801 PG 6 WC Plant Sciences SC Plant Sciences GA UA599 UT WOS:A1996UA59900011 PM 8819868 ER PT J AU Kim, WS AF Kim, WS TI Virtual reality calibration and preview/predictive displays for telerobotics SO PRESENCE-TELEOPERATORS AND VIRTUAL ENVIRONMENTS LA English DT Article; Proceedings Paper CT 1st International Conference on Vision and Movement in Man and Machines, in Honor of Professor Lawrence Stark (Starkfest 94) CY JUN 24-26, 1994 CL UNIV CALIF BERKELEY, DEPT PHYSIOL OPT, BERKELEY, CA HO UNIV CALIF BERKELEY, DEPT PHYSIOL OPT ID TELEOPERATION AB A virtual reality (V/R) calibration technique of matching a virtual environment of simulated three-dimensional (3-D) graphic models with actual camera views of the remote site task environment has been developed. This VR calibration enables high-fidelity pre view/predictive displays with calibrated graphics overlay on live video. Reliable and accurate calibration is achieved by operator-interactive camera calibration and object localization procedures based on new linear/nonlinear least-squares algorithms that can handle multiple-camera views. Since the object pose becomes known through the VR calibration, the operator can now effectively use the semiautomatic computer-generated trajectory mode in addition to the manual teleoperation mode. The developed VR calibration technique and the resultant high fidelity preview/predictive displays were successfully utilized in a recent JPL/NASA-GSFC (Jet Propulsion Laboratory/Goddard Space Flight Center) telerobotic servicing demonstration. Preview/predictive displays were very useful for both noncontact and contact tasks, providing an effective VR interface with immediate visual prediction/verification to the operator. The positioning alignment accuracy achieved using four-camera views in inserting a tool into the ORU hole was 0.5 l cm on the average with a 1.07 cm maximum error at 95% confidence level. Results also indicate that the object localization with two well-chosen, e.g., near orthogonal camera views, could be nearly as accurate as that with four-camera views. RP CALTECH, JET PROP LAB, 4800 OAK GROVE DR, PASADENA, CA 91109 USA. NR 42 TC 23 Z9 24 U1 0 U2 0 PU MIT PRESS PI CAMBRIDGE PA ONE ROGERS ST, CAMBRIDGE, MA 02142-1209 USA SN 1054-7460 EI 1531-3263 J9 PRESENCE-TELEOP VIRT JI Presence-Teleoper. Virtual Env. PD SPR PY 1996 VL 5 IS 2 BP 173 EP 190 PG 18 WC Computer Science, Cybernetics; Computer Science, Software Engineering SC Computer Science GA UV204 UT WOS:A1996UV20400003 ER PT J AU Ellis, SR AF Ellis, SR TI Presence of mind: A reaction to Thomas Sheridan's ''further musings on the psychophysics of presence'' SO PRESENCE-TELEOPERATORS AND VIRTUAL ENVIRONMENTS LA English DT Article ID VISUAL-DISPLAY AID; SPATIAL INFORMATION; PERSPECTIVE AB An operators' sense of remote presence during teleoperation or use of virtual environment interfaces is analyzed as to what characteristics it should have to qualify it as an explanatory scientific construct. But the implicit goal of designing virtual environment interfaces to maximize presence is itself questioned in a second section in which examples of human-machine interfaces beneficially designed to avoid a strong sense of egocentric presence are cited. In conclusion, it is argued that the design of a teleoperation or virtual environment system should generally focus on the efficient communication of causal interaction. In this view the sense of presence, that is of actually being at the simulated or remote workplace, is an epiphenomena of secondary importance for design. RP Ellis, SR (reprint author), NASA, AMES RES CTR, DEPT LIFE SCI, MOFFETT FIELD, CA 94035 USA. NR 33 TC 51 Z9 51 U1 0 U2 1 PU MIT PRESS PI CAMBRIDGE PA 55 HAYWARD STREET, CAMBRIDGE, MA 02142 USA SN 1054-7460 J9 PRESENCE-TELEOP VIRT JI Presence-Teleoper. Virtual Env. PD SPR PY 1996 VL 5 IS 2 BP 247 EP 259 PG 13 WC Computer Science, Cybernetics; Computer Science, Software Engineering SC Computer Science GA UV204 UT WOS:A1996UV20400008 PM 11539412 ER PT J AU Rybicki, G Weinberg, I Scheiman, D VargasAburto, C Uribe, R AF Rybicki, G Weinberg, I Scheiman, D VargasAburto, C Uribe, R TI High and low-energy proton radiation damage in p/n InP MOCVD solar cells SO PROGRESS IN PHOTOVOLTAICS LA English DT Article; Proceedings Paper CT 14th Space Photovoltaic Research and Technology Conference (SPRAT XIV) CY OCT 22-26, 1995 CL LEWIS RES CTR, CLEVELAND, OH HO LEWIS RES CTR ID P-INP; ELECTRON AB Indium phosphide p(+)/n/n(+) solar cells, fabricated by metal organic chemical vapor deposition, were irradiated with 0.2-MeV and 10-MeV protons to a fluence of 10(13) cm(-2). The power output degradation, I-V behavior, carrier concentration and defect concentration were observed at intermediate points throughout the irradiations. The 0.2-MeV proton-irradiated solar cells suffered much greater and more rapid degradation in power output than those irradiated with 10 MeV protons. The efficiency losses were accompanied by larger increases in the recombination currents in the 0.2-MeV proton-irradiated solar cells. The low-energy proton irradiations also had a larger impact on the series resistance of the solar cells. Despite the radiation-induced damage, the carrier concentration in the base of the solar cells showed no reduction after 10-MeV or 0.2-MeV proton irradiations and even increased during irradiation with 0.2-MeV protons. In a deep-level transient spectroscopy study of the irradiated samples, the minority carrier defects H4 and H5 at E(v) + 0.33 and E(v) + 0.52 eV and the majority carrier defects E7 and E10 at E(c) - 0.39 and E(c) - 0.74 eV were observed. The defect introduction rates for the 0.2-MeV proton irradiations were about 20 times higher than for the 10-MeV proton irradiations. The defect E10, observed here after irradiation, has been shown to act as a donor in irradiated n-type InP and may be responsible for obscuring carrier removal. The results of this study ave consistent with the much greater damage produced by low-energy protons whose limited range causes them to stop in the active region of the solar cell. C1 KENT STATE UNIV,KENT,OH 44242. NYMA INC,BROOKPARK,OH. RP Rybicki, G (reprint author), NASA,LEWIS RES CTR,PHOTOVOLTA BRANCH,MS 302-1,21000 BROOKPK RD,CLEVELAND,OH 44135, USA. NR 18 TC 1 Z9 1 U1 2 U2 4 PU JOHN WILEY & SONS LTD PI W SUSSEX PA BAFFINS LANE CHICHESTER, W SUSSEX, ENGLAND PO19 1UD SN 1062-7995 J9 PROG PHOTOVOLTAICS JI Prog. Photovoltaics PD MAR-APR PY 1996 VL 4 IS 2 BP 101 EP 110 DI 10.1002/(SICI)1099-159X(199603/04)4:2<101::AID-PIP126>3.0.CO;2-M PG 10 WC Energy & Fuels; Materials Science, Multidisciplinary; Physics, Applied SC Energy & Fuels; Materials Science; Physics GA UL529 UT WOS:A1996UL52900003 ER PT J AU Scheiman, DA Jenkins, PP Brinker, DJ Appelbaum, J AF Scheiman, DA Jenkins, PP Brinker, DJ Appelbaum, J TI Low-intensity low temperature (LILT) measurements and coefficients on new photovoltaic structures SO PROGRESS IN PHOTOVOLTAICS LA English DT Article; Proceedings Paper CT 14th Space Photovoltaic Research and Technology Conference (SPRAT XIV) CY OCT 22-26, 1995 CL LEWIS RES CTR, CLEVELAND, OH HO LEWIS RES CTR AB Past NASA missions to Mars, Jupiter and the outer planets were powered by radioisotope thermal generators. Although these devices proved to be reliable, their high cost and highly toxic radioactive heat source has mad them far less desirable for future planetary missions. This has resulted in a renewed search for alternate energy sources, some of them being photovoltaics (PV) and thermophotovoltaics. Both of these alternate energy sources convert light/thermal energy directly into electricity. In order to create a viable PV database for planetary mission planners and cell designers, we have compiled low-intensity low-temperature (LILT) I-V data on single-junction and multi-junction high-efficiency, solar cells. The cells tested here represent the latest PV technology. Using these LILT data to calculate short-circuit current, open-circuit voltage and fill factor as a function of temperature and intensity, an accurate prediction of cell performance under the AMO spectrum can be determined When combined with quantum efficiency at low temperature data, one can further enhance the data by adding spectral variations to the measurements. This paper presents an overview of LILT measurements and is only intended to be used as a guideline for material selection and performance predictions. As single-junction and multi-junction cell technologies emerge, new test data must be collected Cell materials included ave Si, GaAs/Ge, GaInP/GaAs/GaAs, InP, InGaAs/InP, InP/InGaAs/InP and GaInP. Temperatures range down to as low as -180 degrees C and intensities range from I sun down to 0.02 sun. The coefficients presented in this paper represent experimental results and are intended to provide the user with approximate numbers. C1 NASA, LEWIS RES CTR, CLEVELAND, OH 44135 USA. TEL AVIV UNIV, IL-69978 TEL AVIV, ISRAEL. RP Scheiman, DA (reprint author), NYMA INC, BROOKPARK, OH 44142 USA. NR 8 TC 6 Z9 7 U1 0 U2 3 PU WILEY-BLACKWELL PI MALDEN PA COMMERCE PLACE, 350 MAIN ST, MALDEN 02148, MA USA SN 1062-7995 J9 PROG PHOTOVOLTAICS JI Prog. Photovoltaics PD MAR-APR PY 1996 VL 4 IS 2 BP 117 EP 127 DI 10.1002/(SICI)1099-159X(199603/04)4:2<117::AID-PIP123>3.0.CO;2-C PG 11 WC Energy & Fuels; Materials Science, Multidisciplinary; Physics, Applied SC Energy & Fuels; Materials Science; Physics GA UL529 UT WOS:A1996UL52900005 ER PT J AU Curtis, H Marvin, D AF Curtis, H Marvin, D TI One year of flight data from the PASP plus experiment SO PROGRESS IN PHOTOVOLTAICS LA English DT Article; Proceedings Paper CT 14th Space Photovoltaic Research and Technology Conference (SPRAT XIV) CY OCT 22-26, 1995 CL LEWIS RES CTR, CLEVELAND, OH HO LEWIS RES CTR AB Results from the first year of operation of the PASP Plus flight experiment are given. The experiment consists of sixteen individual solar cell modules on twelve different panels. Both planar and concentrator technologies are represented as well as several different cell types. The orbit is 363 x 2552 km at an inclination of 70 degrees. There are two main purposes of PASP Plus: to determine the interactions between the space plasma and solar arrays biased to +/-500 V and to determine the long-term radiation performance of a wide variety of solar cell types. C1 AEROSP CORP, ALBUQUERQUE, NM USA. RP Curtis, H (reprint author), NASA, LEWIS RES CTR, CLEVELAND, OH 44135 USA. NR 1 TC 0 Z9 0 U1 0 U2 1 PU WILEY-BLACKWELL PI MALDEN PA COMMERCE PLACE, 350 MAIN ST, MALDEN 02148, MA USA SN 1062-7995 J9 PROG PHOTOVOLTAICS JI Prog. Photovoltaics PD MAR-APR PY 1996 VL 4 IS 2 BP 139 EP 146 DI 10.1002/(SICI)1099-159X(199603/04)4:2<139::AID-PIP129>3.0.CO;2-N PG 8 WC Energy & Fuels; Materials Science, Multidisciplinary; Physics, Applied SC Energy & Fuels; Materials Science; Physics GA UL529 UT WOS:A1996UL52900007 ER PT J AU Gaddy, EM AF Gaddy, EM TI Cost trade between multijunction, gallium arsenide and silicon solar cells SO PROGRESS IN PHOTOVOLTAICS LA English DT Article; Proceedings Paper CT 14th Space Photovoltaic Research and Technology Conference (SPRAT XIV) CY OCT 22-26, 1995 CL LEWIS RES CTR, CLEVELAND, OH HO LEWIS RES CTR AB Multijunction (MJ),(1) gallium arsenide (GaAs) and silicon (Si) solar cells have respective test efficiencies of approximately 24%, 18.5% and 14.8%. Multijunction and gallium arsenide solar cells weigh more than silicon solar cells and cost approximately five times as much per unit power at the cell level.(2) A trade is performed for the Tropical Rainfall Measuring Mission (TRMM)spacecraft to determine which of these cell types would have offered an overall performance and price advantage to the spacecraft. A trade is also performed for the multijunction cells under the assumption that they will cost over ten times that of silicon cells at the cell level. The trade shows that the TRMM project, less the cost of the instrument, ground systems and mission operations, would spend approximately $552 000 per kilogram to launch and support dagger science in the case of the spacecraft equipped with silicon solar cells. If these cells are exchanged for gallium arsenide solar cells, an additional 31 kg of science can be launched and serviced at a price of approximately $90 000 per kilogram. The 31 kg array weight reduction is shown to derive from the smaller area of the array and hence reductions in the weight of the array substrate and supporting structure. If the silicon solar cells are changed out for multijunction solar cells, an additional 45 kg of science above the silicon baseline can be launched and supported at a price of approximately $58 000 per kilogram. The trade shows that even if the multijunction cells are priced over ten times that of silicon cells, a price that is much higher than projected the additional 45 kg of science ave launched and serviced at $180 000 per kilogram. This is still much less than the original $552 000 per kilogram to launch and service the science. Data and qualitative factors are presented to show that these figures are subject to a great deal of uncertainty. Nonetheless, the benefit of the higher efficiency solar cells for TRMM is far greater than the uncertainties in the analysis. RP Gaddy, EM (reprint author), NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771, USA. NR 6 TC 1 Z9 1 U1 1 U2 2 PU JOHN WILEY & SONS LTD PI W SUSSEX PA BAFFINS LANE CHICHESTER, W SUSSEX, ENGLAND PO19 1UD SN 1062-7995 J9 PROG PHOTOVOLTAICS JI Prog. Photovoltaics PD MAR-APR PY 1996 VL 4 IS 2 BP 155 EP 161 PG 7 WC Energy & Fuels; Materials Science, Multidisciplinary; Physics, Applied SC Energy & Fuels; Materials Science; Physics GA UL529 UT WOS:A1996UL52900009 ER PT J AU Landsman, W Simon, T Bergeron, P AF Landsman, W Simon, T Bergeron, P TI The white-dwarf companions of 56 Persei and HR 3643 SO PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF THE PACIFIC LA English DT Article ID UVBY-BETA PHOTOMETRY; ABSOLUTE MAGNITUDES; G-SUPERGIANTS; F-TYPE; STARS; ULTRAVIOLET; CALIBRATION; POPULATION; FREQUENCY; EVOLUTION AB We have obtained low-dispersion IUE spectra of the stars 56 Persei (F4 V) and HR 3643 (F7 II), as part of a survey of late-type stars with a 1565 Angstrom flux excess in the TD-I ultraviolet sky survey. The IUE spectrum of each star reveals the presence of a hot white-dwarf companion. We fit the Ly alpha profile and ultraviolet continuum using pure hydrogen models, but the distance of the primary star is also needed to uniquely constrain the white-dwarf parameters. We derive T-eff=16,420+/-420 K, log g=8.46+/-0.2 for the white dwarf companion to 56 Per, using the photometric distance of 30.1+/-2.8 pc. The implied white-dwarf mass is 0.90+/-0.12 M., considerably above the median mass (similar to 0.6 M.) of single white dwarfs. The parameters of the white dwarf in HR 3643 are not well constrained, mainly due to a large uncertainty in the distance. By assuming a reasonable range of gravity for the white dwarf (7.320 keV) bursts fall into two distinct types: the non-repeating gamma-ray bursters(1), several thousand of which have been detected but whose origin remains unknown, and the soft gamma-ray repeaters (SGRs), of which there are only three(2). The SGRs are known to be associated with supernova remnants, suggesting that the burst events most probably originate from young neutron stars(3). Here we report the detection of a third type of transient high-energy source. On 2 December 1995, we observed the onset of a sequence of hard X-ray bursts from a direction close to that of the Galactic Centre(4). The interval between bursts was initially several minutes, but after two days, the burst rate had dropped to about one per hour and has been largely unchanged since then. More than 1,000 bursts have now been detected, with remarkably similar light curves and intensities; this behaviour is unprecendented among transient X-ray and gamma-ray sources. We suggest that the origin of these bursts might be related to the spasmodic accretion of material onto a neutron star. C1 NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,HUNTSVILLE,AL 35812. ASTRON INST ANTON PANNEKOEK,1098 SJ AMSTERDAM,NETHERLANDS. CTR HIGH ENERGY ASTROPHYS,1098 SJ AMSTERDAM,NETHERLANDS. UNIV ALABAMA,DEPT PHYS,HUNTSVILLE,AL 35899. CTR SPACE RES,DEPT PHYS,CAMBRIDGE,MA 02139. RP Kouveliotou, C (reprint author), UNIV SPACE RES ASSOC,4950 CORP DR,SUITE 100,HUNTSVILLE,AL 35806, USA. NR 25 TC 100 Z9 100 U1 0 U2 1 PU MACMILLAN MAGAZINES LTD PI LONDON PA 4 LITTLE ESSEX STREET, LONDON, ENGLAND WC2R 3LF SN 0028-0836 J9 NATURE JI Nature PD FEB 29 PY 1996 VL 379 IS 6568 BP 799 EP 801 DI 10.1038/379799a0 PG 3 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA TX501 UT WOS:A1996TX50100049 ER PT J AU Martin, BG Lee, HP Jones, EW AF Martin, BG Lee, HP Jones, EW TI GaAs/AlAs/Si heterostructures for blocking dark current injection in impurity-band-conduction photodetectors SO APPLIED PHYSICS LETTERS LA English DT Article AB An experimental investigation was made of GaAs and GaAs/AlAs barriers on Si for blocking injected dark current in impurity-band-conduction (TBC) infrared photodetectors. Reducing dark current would improve detector performance. Experimental results indicate that barrier heights of the order of 0.29 eV were obtained. Current versus bias behavior at temperatures less than or equal to 20 K showed successful blocking of injected electron dark current for negative applied biases in the operating range for IBC detectors. (C) 1996 American Institute of Physics. C1 UNIV CALIF IRVINE,DEPT ELECT ENGN & COMP SCI,IRVINE,CA 92717. CALTECH,JET PROP LAB,PASADENA,CA 91109. RP Martin, BG (reprint author), ANAL CONSULTANTS,LAKE FOREST,CA 92630, USA. NR 12 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 0003-6951 J9 APPL PHYS LETT JI Appl. Phys. Lett. PD FEB 26 PY 1996 VL 68 IS 9 BP 1250 EP 1252 DI 10.1063/1.115942 PG 3 WC Physics, Applied SC Physics GA TW766 UT WOS:A1996TW76600026 ER PT J AU Kosowsky, A AF Kosowsky, A TI Cosmic microwave background polarization SO ANNALS OF PHYSICS LA English DT Article ID COLD DARK MATTER; GRAVITATIONAL-WAVES; RADIATION; ANISOTROPY; FLUCTUATIONS; PERTURBATIONS; UNIVERSES; NEUTRINOS AB Polarization of the cosmic microwave background, though not yet detected, provides a source of information about cosmological parameters complementary to temperature fluctuations. This paper provides a complete theoretical treatment of polarization fluctuations. After a discussion of the physics of polarization, the Boltzmann equation governing the evolution of the photon density matrix is derived from quantum theory and applied to microwave background fluctuations, resulting in a complete set of transport equations for the Stokes parameters from both scalar and tensor metric perturbations. This approach is equivalent at lowest order in scattering kinematics to classical radiative transfer, and provides a general framework for treating the cosmological evolution of density matrices. The metric perturbations are treated in the physically appealing longitudinal gauge. Expressions for various temperature and polarization correlation functions are derived. Detection prospects and theoretical utility of microwave background polarization are briefly discussed. (C) 1996 Academic Press, Inc. C1 UNIV CHICAGO,ENRICO FERMI INST,DEPT PHYS,CHICAGO,IL 60637. NASA,FERMI NATL ACCELERATOR LAB,FERMILAB ASTROPHYS CTR,BATAVIA,IL 60510. NR 82 TC 109 Z9 109 U1 0 U2 1 PU ACADEMIC PRESS INC JNL-COMP SUBSCRIPTIONS PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 SN 0003-4916 J9 ANN PHYS-NEW YORK JI Ann. Phys. PD FEB 25 PY 1996 VL 246 IS 1 BP 49 EP 85 DI 10.1006/aphy.1996.0020 PG 37 WC Physics, Multidisciplinary SC Physics GA TV305 UT WOS:A1996TV30500002 ER PT J AU Raman, G Taghavi, R AF Raman, G Taghavi, R TI Resonant interaction of a linear array of supersonic rectangular jets: An experimental study SO JOURNAL OF FLUID MECHANICS LA English DT Article ID INSTABILITY WAVES; SCREECH TONES; NOISE AB This paper examines a supersonic multi-jet interaction problem that we believe is likely to be important for mixing enhancement and noise reduction in supersonic mixer-ejector nozzles. We demonstrate that it is possible to synchronize the screech instability of four rectangular jets by precisely adjusting the inter-jet spacing. Our experimental data agree with a theory that assumes that the phase-locking of adjacent jets occurs through a coupling at the jet lip. Although synchronization does not change the frequency of the screech tone, its amplitude is augmented. The synchronized multi-jets exhibit higher spreading than the unsynchronized jets, with the single jet spreading the least. We compare the near-field noise of the four jets with synchronized screech to the noise of the sum of four jets operated individually. Our noise measurements reveal that the more rapid mixing of the synchronized multi-jets causes the peak jet noise source to move upstream and to radiate noise at larger angles to the flow direction. Based on our results, we have grounds to believe that screech synchronization is advantageous for noise reduction internal to a mixer-ejector nozzle, since the noise can now be suppressed by a shorter acoustically lined ejector. C1 UNIV KANSAS,DEPT AEROSP ENGN,LAWRENCE,KS 66045. RP Raman, G (reprint author), NASA,EXPTL FLUID DYNAM SECT,NYMA INC,LEWIS RES CTR GRP,BROOKPARK,OH 44142, USA. NR 49 TC 17 Z9 17 U1 2 U2 2 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 FEB 25 PY 1996 VL 309 BP 93 EP 111 DI 10.1017/S0022112096001577 PG 19 WC Mechanics; Physics, Fluids & Plasmas SC Mechanics; Physics GA UA816 UT WOS:A1996UA81600004 ER PT J AU Hartle, RE Donahue, TM Grebowsky, JM Mayr, HG AF Hartle, RE Donahue, TM Grebowsky, JM Mayr, HG TI Hydrogen and deuterium in the thermosphere of Venus: Solar cycle variations and escape SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS LA English DT Article ID PLANETARY-ATMOSPHERES; IONOSPHERE; FRACTIONATION; TEMPERATURE; WATER; MODEL; WINDS; IONS AB A strong solar cycle variation in hydrogen and deuterium densities is observed in the nightside thermosphere of Venus when Pioneer Venus Orbiter (PVO) measurements made during the first three Venus years of the mission are compared with those made during the preentry phase of the mission. Solar maximum conditions prevailed during the former period, while near solar minimum conditions occurred during the latter. Pronounced density enhancements in H of 6.5 times and D of 4 times are observed in the nightside bulge region as solar activity decreased from maximum to near-minimum values. We attribute the buildup of H and D to a reduction in the escape fluxes as solar activity decreased, a behavior that is consistent with the known properties of the dominant escape processes due to the charge separation electric field (E) and charge exchange (CE). Application of this simple concept leads to expressions for the H and D escape fluxes which relate solar cycle variations of the respective bulge densities and escape fluxes to the dayside source fluxes. Planet averaged escape fluxes in the ranges 1.23 x 10(7) cm(-2) s(-1) < <(Phi)>(e) (H) less than or equal to 1.45 x 10(7) cm(-2) s(-1) and 1.61 x 10(5) cm(-2) s(-1) less than or equal to <(Phi)>(e) (D) less than or equal to 2.15 x 10(5) cm(-2) s(-1) are obtained by this method without specifying any particular escape mechanism. Considering the uncertainties in the measured parameters, these flux ranges are in reasonable agreement with the escape fluxes derived from the specific processes, E and CE. When fractionation without or with an external source of water (e,g., comets) is applied to the range of possible escape fluxes, a fractionation factor f = 0.44 is obtained and an ancient reservoir of water equivalent to the range 125 m to 570 m of liquid uniformly distributed on the surface or 3.7% to 17% of a full terrestrial ocean is derived. When the specific escape processes E and E + CE are considered, the f values are 0.15 and 0.1 and the magnitudes of the reservoirs are lower, having a range of equivalent depths of 4.1 m to 36.8 m, respectively. C1 UNIV MICHIGAN,DEPT ATMOSPHER OCEAN & SPACE SCI,SPACE PHYS RES LAB,ANN ARBOR,MI 48104. RP Hartle, RE (reprint author), NASA,GODDARD SPACE FLIGHT CTR,ATMOSPHERES LAB,GREENBELT,MD 20771, USA. RI Grebowsky, Joseph/I-7185-2013 NR 38 TC 22 Z9 22 U1 1 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 FEB 25 PY 1996 VL 101 IS E2 BP 4525 EP 4538 DI 10.1029/95JE02978 PG 14 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA TX641 UT WOS:A1996TX64100002 ER PT J AU Crisp, D Meadows, VS Bezard, B deBergh, C Maillard, JP Mills, FP AF Crisp, D Meadows, VS Bezard, B deBergh, C Maillard, JP Mills, FP TI Ground-based near-infrared observations of the Venus nightside: 1.27-mu m O-2(a(1)Delta(g)) airglow from the upper atmosphere SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS LA English DT Article ID COLLISION-INDUCED EMISSION; MOLECULAR-OXYGEN; LASER EXCITATION; GAS-PHASE; THERMOSPHERE; MESOSPHERE; DYNAMICS; RATES; PHOTOCHEMISTRY; SPECTROSCOPY AB Near-infrared spectroscopic observations of Venus taken in 1975 revealed O-2(a(1) Delta(g)> airglow from both the dayside and nightside of the planet with emission rates 10(12) photons cm(-2) s(-1) into 4 pi sr). These large emiss sion rates indicated that most of the atomic oxygen produced through the photolysis of CO2 on the dayside of Venus eventually recombined to produce O-2 in the excited (a(1) Delta(g)) state. This result was initially surprising because available laboratory measurements indicated O-2(a(1) Delta(g)) yields from atomic oxygen recombination reactions that were no larger than a few percent, More recent observations reveal even larger O-2(a(1) Delta(g)) airglow intensities as well as dramatic spatial and temporal variations in this airglow, High-resolution (0.3 cm(-1)) spectra of the Venus nightside taken with the Canada France Hawaii Telescope/Fourier transform spectrometer in 1991 show spectrally integrated O-2(a(1) Delta(g)) intensities as large as 1.1 mW m(-2) sr(-1). Once these values are corrected for viewing angle and reflection from the underlying clouds, they indicate emission rates near 3 MR. These spectra also yield rotational temperatures of 186 +/- 6 K in the emitting layer (90 to 115 km), Spectral image cubes taken with the Angle-Australian Telescope/infrared imaging spectrometer and the Canada France Hawaii Telescope/imaging Fourier transform spectrometer during 1991, 1993, and 1994 provide a more complete description of the spatial and temporal variability in this emission, Images extracted at wavelengths within the O-2(a(1) Delta(g)) Q-branch (1.269 mu m) often show contrasts larger than 10 to 1 across the nightside. Even though the disk-averaged intensities are comparable to those seen in 1975, some localized regions have airglow emission rates larger than 5 MR. The brightest emission is often confined to 1000- to 2000-km- diameter regions, These bright regions have been detected over a broad range of latitudes and local times, but they are most often seen at low latitudes and at local times between midnight and 0300 on Venus, The intensity of the brightest spots can change by 20% in less than 1 hour, and they can vanish entirely in less than 1 day, These new observations are providing improved constraints on atmospheric chemical and dynamical models of the upper mesosphere and lower thermosphere of Venus. C1 OBSERV PARIS,MEUDON SECT,F-92195 MEUDON,FRANCE. INST ASTROPHYS,F-95014 PARIS,FRANCE. CALTECH,DIV GEOL & PLANETARY SCI,PASADENA,CA 91125. UNIV SYDNEY,SYDNEY,NSW 2006,AUSTRALIA. ANGLO AUSTRALIAN OBSERV,SYDNEY,NSW 2006,AUSTRALIA. RP Crisp, D (reprint author), CALTECH,JET PROP LAB,4800 OAK GROVE DR,MS169-237,PASADENA,CA 91109, USA. NR 54 TC 81 Z9 81 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 FEB 25 PY 1996 VL 101 IS E2 BP 4577 EP 4593 DI 10.1029/95JE03136 PG 17 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA TX641 UT WOS:A1996TX64100007 ER PT J AU Ebisawa, K Titarchuk, L Chakrabarti, SK AF Ebisawa, K Titarchuk, L Chakrabarti, SK TI On the spectral slopes of hard X-ray emission from black hole candidates SO PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN LA English DT Article DE accretion; black hole physics; radiation mechanisms, compton and inverse compton; radiative transfer; stars, neutron; X-rays, general ID ACCRETION DISKS; LMC X-3; COMPTONIZATION; DISCOVERY; RADIATION; FLOW; ULTRAVIOLET; LMC-X-3 AB In the high state of black hole candidates, in which 2-10 keV luminosity is relatively high, the energy index of the power-law like hard X-ray emission above similar to 10 keV is typically similar to 1.5. On the other hand, in the low state, the hard X-ray energy index is 0.3-0.9. In this paper, we suggest that this difference of the hard X-ray spectral slopes may be due to two different Comptonization mechanisms. We propose that, in the high state, the hard component is governed by the Comptonization due to the built motion of the almost freely falling (convergent accretion) flow close to the black hole, rather than thermal Comptonization. The spectral slope of the hard component is insensitive to the disk accretion rate governing the soft component, hence is nearly invariant in spite of the soft component variations. The power-law component due to the bulk motion Comptonization has a sharp cut-off at around the electron rest mass energy, which is consistent with high energy observations of the high state. In the low state, the spectrum is formed due to thermal Comptonization of the low-frequency disk radiation by a sub-Keplerian component (possibly undergoing a centrifugally-supported shock) which is originated from the Keplerian disk. In the limit of low disk accretion rate, the power law index is uniquely determined by the mass accretion rate of the sub-Keplerian component. C1 TATA INST FUNDAMENTAL RES, BOMBAY 400005, MAHARASHTRA, INDIA. GEORGE MASON UNIV, CSI, FAIRFAX, VA USA. RP NASA, GODDARD SPACE FLIGHT CTR, CODE 6602, GREENBELT, MD 20771 USA. NR 49 TC 63 Z9 63 U1 1 U2 1 PU OXFORD UNIV PRESS PI OXFORD PA GREAT CLARENDON ST, OXFORD OX2 6DP, ENGLAND SN 0004-6264 EI 2053-051X J9 PUBL ASTRON SOC JPN JI Publ. Astron. Soc. Jpn. PD FEB 25 PY 1996 VL 48 IS 1 BP 59 EP 65 DI 10.1093/pasj/48.1.59 PG 7 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA TX404 UT WOS:A1996TX40400010 ER PT J AU Kursinski, ER Hajj, GA Bertiger, WI Leroy, SS Meehan, TK Romans, LJ Schofield, JT McCleese, DJ Melbourne, WG Thornton, CL Yunck, TP Eyre, JR Nagatani, RN AF Kursinski, ER Hajj, GA Bertiger, WI Leroy, SS Meehan, TK Romans, LJ Schofield, JT McCleese, DJ Melbourne, WG Thornton, CL Yunck, TP Eyre, JR Nagatani, RN TI Initial results of radio occultation observations of Earth's atmosphere using the global positioning system SO SCIENCE LA English DT Article ID GRAVITY-WAVES; ASSIMILATION; NEPTUNE AB Recent radio occultation measurements using Global Positioning System satellite transmitters and an orbiting receiver have provided a globally distributed set of high-resolution atmospheric profiles, suggesting that the technique may make a significant contribution to global change and weather prediction programs. Biases in occultation temperatures relative to radiosonde and model data are about 1 kelvin or less in the tropics and are generally less than 0.5 kelvin at higher latitudes. Data quality is sufficient to quantify significant model errors in remote regions. Temperature profiles also reveal either an equatorial Rossby-gravity or an inertio-gravity wave. Such waves provide a fundamental source of momentum for the stratospheric circulation. C1 CALTECH,JET PROP LAB,PASADENA,CA 91125. UNITED KINGDOM METEOROL OFF,BRACKNELL RG12 2SZ,BERKS,ENGLAND. COB,CLIMATE PREDICT CTR,WASHINGTON,DC 20233. RP Kursinski, ER (reprint author), CALTECH,DIV GEOL & PLANETARY SCI,PASADENA,CA 91125, USA. NR 29 TC 177 Z9 197 U1 0 U2 11 PU AMER ASSOC ADVANCEMENT SCIENCE PI WASHINGTON PA 1200 NEW YORK AVE, NW, WASHINGTON, DC 20005 SN 0036-8075 J9 SCIENCE JI Science PD FEB 23 PY 1996 VL 271 IS 5252 BP 1107 EP 1110 DI 10.1126/science.271.5252.1107 PG 4 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA TW701 UT WOS:A1996TW70100035 ER PT J AU Pilewskie, P Valero, FPJ AF Pilewskie, P Valero, FPJ TI How much solar radiation do clouds absorb? Response SO SCIENCE LA English DT Article ID ABSORPTION; HAZE C1 UNIV CALIF SAN DIEGO,SCRIPPS INST OCEANOG,LA JOLLA,CA 92093. RP Pilewskie, P (reprint author), NASA,AMES RES CTR,MAIL STOP 245-4,MOFFETT FIELD,CA 94035, USA. NR 10 TC 13 Z9 13 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 FEB 23 PY 1996 VL 271 IS 5252 BP 1134 EP 1136 DI 10.1126/science.271.5252.1134 PG 3 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA TW701 UT WOS:A1996TW70100045 PM 17792301 ER PT J AU Bryant, RG Jensen, BJ Hergenrother, PM AF Bryant, RG Jensen, BJ Hergenrother, PM TI Chemistry and properties of a phenylethynyl-terminated polyimide SO JOURNAL OF APPLIED POLYMER SCIENCE LA English DT Article ID END-CAPPING AGENTS; POLYETHERS AB As part of an ongoing effort to develop processable, high-performance resins for aerospace applications, a phenylethynyl-terminated imide (PETI) oligomer designated LaRC(TM) PETI-1 was developed. This reactive oligomer has a number-average molecular weight of 6300 g/mol and a T-g of 218 degrees C. Upon curing the reactive oligomer at 350 degrees C for 1 h, a tough material with a T-g of 249 degrees C was obtained. The properties of cured PETI-1 in the form of composites, adhesive specimens, thin films, and neat resin moldings are excellent. The synthesis, characterization, and mechanical properties of this polyimide are discussed. (C) 1996 John Wiley & Sons, Inc. C1 NASA,LANGLEY RES CTR,HAMPTON,VA 23681. NR 25 TC 25 Z9 30 U1 0 U2 7 PU JOHN WILEY & SONS INC PI NEW YORK PA 605 THIRD AVE, NEW YORK, NY 10158-0012 SN 0021-8995 J9 J APPL POLYM SCI JI J. Appl. Polym. Sci. PD FEB 22 PY 1996 VL 59 IS 8 BP 1249 EP 1254 DI 10.1002/(SICI)1097-4628(19960222)59:8<1249::AID-APP7>3.3.CO;2-I PG 6 WC Polymer Science SC Polymer Science GA TR924 UT WOS:A1996TR92400007 ER PT J AU Nickolaisen, SL Miller, CE Sander, SP Hand, MR Williams, IH Francisco, JS AF Nickolaisen, SL Miller, CE Sander, SP Hand, MR Williams, IH Francisco, JS TI Pressure dependence and metastable state formation in the photolysis of dichlorine monoxide (Cl2O) SO JOURNAL OF CHEMICAL PHYSICS LA English DT Article ID CORRELATED MOLECULAR CALCULATIONS; GAUSSIAN-BASIS SETS; ULTRAVIOLET-SPECTRUM; HOCL AB The photodissociation of dichlorine monoxide (Cl2O) was studied using broadband flash photolysis to investigate the influence of variations in the photolysis wavelength domain, bath gas pressure and bath gas identity on the yield and temporal dependence of the ClO product. ClO yields were independent of bath gas pressure when the photolysis spectral band extended to 200 nm (quartz cutoff) but for photolysis restricted to wavelengths longer than about 250 nm, ClO yields decreased with increasing bath gas pressure and there was a pressure-dependent delay in the formation of ClO. Under these conditions, a weak, highly structured absorption spectrum was observed in the range 16 600-26 000 cm(-1) with a lifetime on the order of 500 ms. A portion of the spectrum could be analyzed (22 000-26 000 cm(-1)) which showed progressions having differences of 283, 443, and 505 cm(-1). Ab initio calculations were performed to evaluate vertical excitation energies and oscillator strengths from the lowest-energy singlet (X(1)A(1)) or triplet (1(3)B(1)) states to various excited states. The calculations indicated that the 2(3)A(2)<--1(3)B(1) transition has an unusually large oscillator strength. The transition energy, 3.05 eV, is consistent with the observed metastable spectrum. The observed pressure dependence of ClO formation could be modeled using a mechanism which assumed that Cl2O excitation at wavelengths longer than about 300 nm leads to rapid intersystem crossing to two metastable states in the triplet manifold. These states undergo competitive dissociation to ClO+Cl and collisional relaxation to the ground state; The dynamics of Cl2O may serve as a model for other molecules of importance in the earth's lower stratosphere such as CIONO2 where filtering of the solar spectrum by ozone restricts photolysis to the weak tail of the absorption continuum. (C) 1996 American Institute of Physics. C1 CALTECH,JET PROP LAB,PASADENA,CA 91109. UNIV BATH,SCH CHEM,BATH BA2 7AY,AVON,ENGLAND. PURDUE UNIV,DEPT CHEM,W LAFAYETTE,IN 47907. CALIF STATE UNIV LOS ANGELES,DEPT CHEM & BIOCHEM,LOS ANGELES,CA 90032. RI Williams, Ian/A-7598-2012 NR 25 TC 41 Z9 41 U1 1 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 FEB 22 PY 1996 VL 104 IS 8 BP 2857 EP 2868 DI 10.1063/1.471109 PG 12 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA TV787 UT WOS:A1996TV78700014 ER PT J AU Langhoff, SR AF Langhoff, SR TI Theoretical infrared spectra for polycyclic aromatic hydrocarbon neutrals, cations, and anions SO JOURNAL OF PHYSICAL CHEMISTRY LA English DT Article ID DIFFUSE INTERSTELLAR BANDS; EMISSION FEATURES; IRAS SOURCES; MICRON EMISSION; ULTRAVIOLET; CARBON; DUST; NAPHTHALENE; EVOLUTION; MOLECULES AB Calculations are carried out using density functional theory (DFT) to determine the harmonic frequencies and intensities of the neutrals and cations of 13 polycyclic aromatic hydrocarbons (PAHs) up to the size of ovalene. Calculations are also carried out for a few PAH anions. The DFT harmonic frequencies, when uniformly scaled to account primarily for anharmonicity, agree with the matrix isolation fundamentals to within an average error of about 10 cm(-1). Electron correlation is found to significantly reduce the intensities of many of the cation harmonics, bringing them into much better agreement with the available experimental data. While the theoretical infrared spectra agree well with the experimental data for all of the neutral systems and for many of the cations, there still remain discrepancies with the experimental matrix isolation data for some species that are difficult to rationalize entirely in terms of limitations in the calculations. In agreement with previous theoretical work, the present calculations show that the relative intensities for the astronomical unidentified infrared (UIR) bands agree reasonably well with those for a distribution of polycyclic aromatic hydrocarbon (PAH) cations but not with a distribution of PAH neutrals. We also observe that the infrared spectra of highly symmetrical cations such as coronene agree much better with astronomical observations than do those of, for example, the polyacenes such as tetracene and pentacene. The total integrated intensities for the neutral species are found to increase linearly with size, while the total integrated intensities are much larger for the cations and scale more nearly quadratically with size. We conclude that emission from moderate-sized highly symmetric PAH cations such as coronene and larger could account for the UIR bands. RP Langhoff, SR (reprint author), NASA,AMES RES CTR,MOFFETT FIELD,CA 94035, USA. NR 60 TC 390 Z9 392 U1 6 U2 61 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 SN 0022-3654 J9 J PHYS CHEM-US JI J. Phys. Chem. PD FEB 22 PY 1996 VL 100 IS 8 BP 2819 EP 2841 DI 10.1021/jp952074g PG 23 WC Chemistry, Physical SC Chemistry GA TX257 UT WOS:A1996TX25700010 ER PT J AU Schwenke, DW AF Schwenke, DW TI Variational calculations of rovibrational energy levels and transition intensities for tetratomic molecules SO JOURNAL OF PHYSICAL CHEMISTRY LA English DT Article ID VIBRATIONAL LINE STRENGTHS; TRIATOMIC-MOLECULES; 4-ATOM MOLECULES; ACETYLENE; COLLISIONS; DYNAMICS; SYSTEMS; STATES; H2D+ AB A description is given of an algorithm for computing rovibrational energy levels for tetratomic molecules. The expressions required for evaluating transition intensities are also given. The variational principle is used to determine the energy levels, and the kinetic energy operator is simple and evaluated exactly. The computational procedure is split up into the determination of one-dimensional radial basis functions, the computation of a contracted rotational-bending basis, followed by a final variational step coupling all degrees of freedom. An angular basis is proposed whereby the rotational-bending contraction takes place in three steps. Angular matrix elements of the potential are evaluated by expansion in terms of a suitable basis, and the angular integrals are given in a factorized form which simplifies their evaluation. The basis functions in the final variational step have the full permutation symmetries of the identical particles. Sample results are given for HCCH and BH3. RP Schwenke, DW (reprint author), NASA,AMES RES CTR,MAIL STOP 230-3,MOFFETT FIELD,CA 94035, USA. RI schwenke, david/I-3564-2013 NR 32 TC 78 Z9 81 U1 0 U2 8 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 SN 0022-3654 J9 J PHYS CHEM-US JI J. Phys. Chem. PD FEB 22 PY 1996 VL 100 IS 8 BP 2867 EP 2884 DI 10.1021/jp9525447 PG 18 WC Chemistry, Physical SC Chemistry GA TX257 UT WOS:A1996TX25700015 ER PT J AU McKenzie, RL AF McKenzie, RL TI Measurement capabilities of planar Doppler velocimetry using pulsed lasers SO APPLIED OPTICS LA English DT Article DE aerodynamic measurements; laser Doppler velocimetry; planar velocimetry; velocity fields; wind tunneling; three-dimensional flow measurements ID HYPERFINE-STRUCTURE; IODINE MOLECULE; SPECTROSCOPY; NM AB Analytical models of a spectral filter that contains iodine vapor and of the noise sources associated with charge-coupled-device (CCD) detector technology are combined with a planar Doppler velocimetry (PDV) signal analysis to evaluate the measurement capabilities of PDV for quantitative aerodynamic research and production wind-tunnel testing applications. The criteria for optimizing the filter cell and calibrating the frequency scale of its transmission function are described. The measurement uncertainty limits owing to scientific-grade CCD detector performance are then evaluated, and an analysis is developed of the scattering properties of aerosols suitable for aerodynamic flow seeding. The combined results predict that single-pulse PDV measurements with velocity measurement uncertainties as small as 2 m/s should be possible in aerodynamic test facilities for measurement distances of tens of meters. (C) 1996 Optical Society of America RP McKenzie, RL (reprint author), NASA,AMES RES CTR,MS 260-1,MOFFETT FIELD,CA 94035, USA. NR 28 TC 41 Z9 43 U1 0 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 FEB 20 PY 1996 VL 35 IS 6 BP 948 EP 964 DI 10.1364/AO.35.000948 PG 17 WC Optics SC Optics GA TY059 UT WOS:A1996TY05900011 PM 21069093 ER PT J AU Blake, TA Chackerian, C Podolske, JR AF Blake, TA Chackerian, C Podolske, JR TI Prognosis for a mid-infrared magnetic rotation spectrometer for the in situ detection of atmospheric free radicals SO APPLIED OPTICS LA English DT Article DE atmospheric sensing; Faraday effect; infrared spectroscopy; magnetic rotation spectroscopy; nitric oxide; nitrogen dioxide ID COLOR CENTER LASER; SPECTROSCOPY; FARADAY; VOIGT AB Mid-infrared magnetic rotation spectroscopy (NIRS) experiments on nitric oxide (NO) are quantitatively modeled by theoretical calculations. The verified theory is used to specify an instrument that can make in situ measurements on NO and NO2 in the Earth's atmosphere at a sensitivity level of a few parts in 10(12) by volume per second. The prototype instrument used in the experiments has an extrapolated detection limit for NO of 30 parts in 10(9) for a 1-s integration time over a 12-cm path length. The detection limit is an extrapolation of experimental results to a signal-to-noise ratio of one, where the noise is considered to be one-half the peak-to-peak baseline noise. Also discussed are the various factors that can limit the sensitivity of a MRS spectrometer that uses liquid-nitrogen-cooled lead-salt diode lasers and photovoltaic detectors. (C) 1996 Optical Society of America C1 NASA,AMES RES CTR,MOFFETT FIELD,CA 94035. NR 42 TC 26 Z9 26 U1 0 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 FEB 20 PY 1996 VL 35 IS 6 BP 973 EP 985 DI 10.1364/AO.35.000973 PG 13 WC Optics SC Optics GA TY059 UT WOS:A1996TY05900013 PM 21069095 ER PT J AU Digel, SW Lyder, DA Philbrick, AJ Puche, D Thaddeus, P AF Digel, SW Lyder, DA Philbrick, AJ Puche, D Thaddeus, P TI A large-scale CO survey toward W3, W4, and W5 SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxy, structure; ISM, clouds; ISM, individual (W3, W4, W5); ISM, molecules; radio lines, ISM ID MOLECULAR CLOUD COMPLEXES; 1ST GALACTIC QUADRANT; H-II REGIONS; SOLAR CIRCLE; SPIRAL STRUCTURE; OUTER GALAXY; MILKY-WAY; RADIAL-DISTRIBUTION; IRAS SOURCES; ARM AB A CO J = 1-0 survey of the outer Galaxy toward W3, W4, and W5 is described. The bright molecular emission in the W3 region in the Perseus arm is prominent, and little emission is seen at greater Galactocentric distances. The extensive local emission in the survey contains the large molecular cloud complex associated with Cam OB1. Between the local and Perseus arm emission, a nearly empty gap in velocity is seen across the entire longitude range. On the assumptions that the kinematically derived width of the gap is the true width and that the X ratio is constant, the arm-interarm contrast of CO is greater than or equal to 25:1 in surface density. A few clouds are detected beyond the Perseus arm, and only one cloud, already known, is detected at extreme Galactocentric distances, beyond the Perseus and outer arms. The cumulative mass distribution of the clouds in the Perseus arm has power-law index 0.65 +/- 0.15, and the clouds there are systematically less luminous in CO by a factor 3.5 +/- 2 than clouds near the solar circle. The distribution of molecular gas with Galactocentric distance in the outer Galaxy is compared with that of luminous Infrared Astronomy Satellite point sources that trace massive star-forming regions. The agreement is generally good, with evidence for enhanced star formation relative to the surface density of molecular gas in the W3 region and perhaps also in the outer arm. C1 NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. NATL RES COUNCIL CANADA,HERZBERG INST ASTROPHYS,DOMINION RADIO ASTROPHYS OBSERV,PENTICTON,BC V2A 6K3,CANADA. RP Digel, SW (reprint author), HARVARD SMITHSONIAN CTR ASTROPHYS,60 GARDEN ST,MS 72,CAMBRIDGE,MA 02138, USA. NR 52 TC 60 Z9 60 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 FEB 20 PY 1996 VL 458 IS 2 BP 561 EP 575 DI 10.1086/176839 PN 1 PG 15 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA TU810 UT WOS:A1996TU81000017 ER PT J AU Smith, DM Leventhal, M Cavallo, R Gehrels, N Tueller, J Fishman, G AF Smith, DM Leventhal, M Cavallo, R Gehrels, N Tueller, J Fishman, G TI Limits on reported transient emission events near 0.5 MeV from the crab and 1E 1740.7-2942 SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxy, center; gamma rays, observations; ISM, individual (Crab Nebula); stars, individual (Nova Muscae 1991, 1E 1740.7-2942); X-rays, bursts ID X-RAY NOVA; LINE; MUSCA; JET AB The SIGMA coded-mask telescope aboard the Granat observatory has reported transient emission near 0.5 MeV lasting for about 1 day from three Galactic objects: the Crab, black hole candidate Nova Muscae 1991, and, on two occasions, black hole candidate 1E 1740.7-2942 (1E) near the Galactic center. Two of these events (the Crab and one from 1E) have occurred since the launch of the Compton Gamma Ray Observatory (CGRO). Jung et al. searched for the 1E transient of 1992 using the Oriented Scintillation Spectrometer Experiment on CGRO but did not confirm the result. We use the Burst and Transient Source Experiment (BATSE) on CGRO to search for both this event and the Crab transient. We find a 3 sigma upper limit of 1.7 x 10(-3) photons s(-1) cm(-2) compared to the reported flux of (5.1 +/- 1.7) x 10(-3) photons s(-1) cm Crab transient, and sigma 3 sigma upper limit of 1.8 x 10(-3) photons s(-1) cm(-2) versus (4.28(-1.5)(+2.7)) x 10(-3) photons s(-1) cm(-2) reported for the 1E event. Therefore, we do not confirm the two 1 day SIGMA transients for which BATSE data are available. C1 NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,HUNTSVILLE,AL 35812. RP Smith, DM (reprint author), UNIV MARYLAND,DEPT ASTRON,COLLEGE PK,MD 20742, USA. RI Gehrels, Neil/D-2971-2012; Tueller, Jack/D-5334-2012 NR 22 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 FEB 20 PY 1996 VL 458 IS 2 BP 576 EP 579 DI 10.1086/176840 PN 1 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA TU810 UT WOS:A1996TU81000018 ER PT J AU Joblin, C Tielens, AGGM Allamandola, LJ Geballe, TR AF Joblin, C Tielens, AGGM Allamandola, LJ Geballe, TR TI Spatial variation of the 3.29 and 3.40 micron emission bands within reflection nebulae and the photochemical evolution of methylated polycyclic aromatic hydrocarbons SO ASTROPHYSICAL JOURNAL LA English DT Article DE dust, extinction; infrared, ISM, lines and bands; molecular processes; reflection nebulae ID CARBONACEOUS COMPOSITE QCC; MU-M EMISSION; INFRARED-EMISSION; IRAS SOURCES; PHOTODISSOCIATION REGIONS; MOLECULAR CLOUDS; INTERSTELLAR; FEATURES; SPECTRUM; NGC-2023 AB Spectra of 3 mu m emission features have been obtained at several positions within the reflection nebulae NGC 1333 SVS3 and NGC 2023. Strong variations of the relative intensities of the 3.29 mu m feature and its most prominent satellite band at 3.40 mu m are found. It is shown that (i) the 3.40 mu m band is too intense with respect to the 3.29 mu m band at certain positions to arise from hot band emission alone, (ii) the 3.40 Irm band can be reasonably well matched by new laboratory spectra of gas-phase polycyclic aromatic hydrocarbons (PAHs) with alkyl (-CH3) side groups, and (iii) the variations in the 3.40 mu m to 3.29 mu m band intensity ratios are consistent with the photochemical erosion of alkylated PAHs. We conclude that the 3.40 mu m emission feature is attributable to -CH3 side groups on PAH molecules. We predict a value of 0.5 for the peak intensity ratio of the 3.40 and 3.29 mu m emission bands from free PAHs in the diffuse interstellar medium, which would correspond to a proportion of one methyl group for four peripheral hydrogens. We also compare the 3 mu m spectrum of the proto-planetary nebula IRAS 05341+0852 with the spectrum of the planetary nebula IRAS 21282+5050. We suggest that a photochemical evolution of the initial aliphatic and aromatic hydrocarbon mixture formed in the outflow is responsible for the changes observed in the 3 mu m emission spectra of these objects. C1 JOINT ASTRON CTR,HILO,HI 96720. RP Joblin, C (reprint author), NASA,AMES RES CTR,MS 245-6,MOFFETT FIELD,CA 94035, USA. NR 59 TC 101 Z9 102 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 FEB 20 PY 1996 VL 458 IS 2 BP 610 EP 620 DI 10.1086/176843 PN 1 PG 11 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA TU810 UT WOS:A1996TU81000021 PM 11538557 ER PT J AU Salama, F Bakes, ELO Allamandola, LJ Tielens, AGGM AF Salama, F Bakes, ELO Allamandola, LJ Tielens, AGGM TI Assessment of the polycyclic aromatic hydrocarbon-diffuse interstellar band proposal SO ASTROPHYSICAL JOURNAL LA English DT Review DE dust, extinction; ISM, molecules; line, identification; molecular processes ID VIBRONIC ABSORPTION-SPECTRA; MATRIX-ISOLATED NAPHTHALENE; OPTICAL-EMISSION BANDS; PHOTOELECTRON-SPECTRA; ELECTRONIC-SPECTRA; RADICAL CATIONS; SOLID ARGON; POLYNUCLEAR AROMATICS; EXTINCTION CURVE; RED RECTANGLE AB The potential link between neutral and/or ionized polycyclic aromatic hydrocarbons (PAHs) and the diffuse interstellar band (DIB) carriers is examined. Based on the study of the general physical and chemical properties of PAHs, an assessment is made of their possible contribution to the DIB carriers. It is found that, under the conditions reigning in the diffuse interstellar medium, PAHs can be present in the form of neutral molecules as well as positive and/or negative ions. The charge distribution of small PAHs is dominated, however, by two charge states at one time with compact PAHs present only in the neutral and cationic forms. Each PAH has a distinct spectral signature depending on its charge state. Moreover, the spectra of ionized PAHs are always clearly dominated by a single band in the DIB spectral range. In the case of compact PAH ions, the strongest absorption band is of type A (i.e., the band is broad, falls in the high-energy range of the spectrum, and possesses a large oscillator strength), and seems to correlate with strong and broad DIBs. For noncompact PAH ions, the strongest absorption band is of type I (i.e., the band is narrow, falls in the low-energy range of the spectrum, and possesses a small oscillator strength), and seems to correlate with weak and narrow DIBs. Potential molecular size and structure constraints for interstellar PAHs are derived by comparing known DIB characteristics to the spectroscopic properties of PAHs. It is found that (i) only neutral PAHs larger than about 30 carbon atoms could, if present, contribute to the DIBs. (ii) For compact PAHs, only ions with less than about 250 carbon atoms could, if present, contribute to the DIBs. (iii) The observed distribution of the DIBs between strong/moderate and broad bands on the one hand and weak and narrow bands on the other can easily be interpreted in the context of the PAH proposal by a distribution of compact and noncompact PAH ions, respectively. A plausible correlation between PAH charge states and DIB ''families'' is thus provided by the PAH-DIB proposal. Following this proposal, DIB families would reflect conditions within a cloud which locally determine the relative importance of cations, anions, and neutral species, rather than tracers of a specific species. Observational predictions are given to establish the viability of the PAH hypothesis. It is concluded that small PAH ions are very promising candidates as DIB carriers provided their population is dominated by a finite number (100-200) of species. A key test for the PAH proposal, consisting of laboratory and astronomical investigations in the ultraviolet range, is called for. C1 PRINCETON UNIV OBSERV, PRINCETON, NJ 08544 USA. RP NASA, AMES RES CTR, DIV SPACE SCI, MOFFETT FIELD, CA 94035 USA. RI Salama, Farid/A-8787-2009 OI Salama, Farid/0000-0002-6064-4401 NR 113 TC 184 Z9 184 U1 0 U2 19 PU IOP PUBLISHING LTD PI BRISTOL PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND SN 0004-637X EI 1538-4357 J9 ASTROPHYS J JI Astrophys. J. PD FEB 20 PY 1996 VL 458 IS 2 BP 621 EP 636 DI 10.1086/176844 PN 1 PG 16 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA TU810 UT WOS:A1996TU81000022 PM 11538558 ER PT J AU Rudolph, AL Brand, J deGeus, EJ Wouterloot, JGA AF Rudolph, AL Brand, J deGeus, EJ Wouterloot, JGA TI Far outer galaxy H II regions SO ASTROPHYSICAL JOURNAL LA English DT Article DE H II regions; ISM, individual (S127); radio continuum, ISM; surveys stars, formation ID INITIAL MASS FUNCTION; IRAS SOURCES; MOLECULAR CLOUDS; STAR FORMATION; SOLAR CIRCLE; VELOCITY-FIELD; VLA SURVEY; CO; NEIGHBORHOOD; ABUNDANCES AB We have made a multiwavelength (6, 3.6, and 2 cm), high-resolution (3 ''-6 '') radio continuum survey of IRAS-selected sources to search for and study H II regions in the far-outer Galaxy. We identified 31 sources with R greater than or similar to 15 kpc and L(FIR) greater than or similar to 10(4) L., indicating the presence of high-mass star formation. We have observed 11 of these sources with the Very Large Array (VLA). The 6 and 2 cm observations were made using ''scaled arrays,'' making possible a direct and reliable determination of spectral indices. Of the 39 sources we detected at 6 cm, 10 have spectral indices consistent with optically thin free-free emission from H II regions and are within 45 '' of the associated IRAS source. Combining our data with previous VLA observations by other investigators we analyzed a sample of 15 of the most remote H II regions found in our Galaxy, located at R = 15-18.2 kpc. The sizes of the H II regions range from less than or similar to 0.10 to 2.3 pc. Using the measured flux densities and sizes, we determined their electron densities, emission measures, and excitation parameters, as well as their Lyman continuum fluxes needed to keep the nebulae ionized. The sizes and electron densities indicate that most of the sources are (ultra)compact H II regions. Seven of the 15 H II regions have sizes less than or similar to 0.20 pc. The large number of compact H II regions suggests that the time these regions spend in a compact phase must be much longer than their dynamical expansion times. Five of the 15 H II regions have cometary shapes; the remainder are spherical or unresolved. Comparison of our data with molecular line maps suggests that the cometary shape of the two H II regions in S127 may be due to pressure confinement of the expanding ionized gas, as in the ''blister'' or ''champagne flow'' models of H II regions. Comparison of our data with the IRAS data indicates that the five most luminous H II regions are consistent with a single zero-age main sequence O or B star exciting a dust-free H II region. C1 HARVEY MUDD COLL, DEPT PHYS, CLAREMONT, CA 91711 USA. CNR, IST RADIOASTRON, I-40129 BOLOGNA, ITALY. UNIV MARYLAND, DEPT ASTRON, COLLEGE PK, MD 20742 USA. UNIV COLOGNE, INST PHYS 1, D-50937 COLOGNE, GERMANY. RP NASA, AMES RES CTR, MAIL STOP 245-6, MOFFETT FIELD, CA 94035 USA. NR 52 TC 35 Z9 35 U1 0 U2 0 PU IOP PUBLISHING LTD PI BRISTOL PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND SN 0004-637X EI 1538-4357 J9 ASTROPHYS J JI Astrophys. J. PD FEB 20 PY 1996 VL 458 IS 2 BP 653 EP 669 DI 10.1086/176847 PN 1 PG 17 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA TU810 UT WOS:A1996TU81000025 ER PT J AU Band, DL Ryder, S Ford, LA Matteson, JL Palmer, DM Teegarden, BJ Briggs, MS Paciesas, WS Pendleton, GN Preece, RD AF Band, DL Ryder, S Ford, LA Matteson, JL Palmer, DM Teegarden, BJ Briggs, MS Paciesas, WS Pendleton, GN Preece, RD TI Batse gamma-ray burst line search .4. Line candidates from the visual search SO ASTROPHYSICAL JOURNAL LA English DT Article DE gamma rays, bursts; line, identification; methods, statistical ID CYCLOTRON; SPECTRA AB We evaluate the significance of the line candidates identified by a visual search of burst spectra from BATSE's Spectroscopy Detectors. None of the candidates satisfy our detection criteria: an F-test probability less than 10(-4) for a feature in one detector and consistency among the detectors that viewed the burst. Most of the candidates are not very significant and are likely to be fluctuations. Because of the expectation of finding absorption lines, the search was biased toward absorption features. We do not have a quantitative measure of the completeness of the search, which would enable a comparison with previous missions. Therefore, a more objective computerized search has begun. C1 NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20770. UNIV ALABAMA,HUNTSVILLE,AL 35899. RP Band, DL (reprint author), UNIV CALIF SAN DIEGO,CASS 0111,LA JOLLA,CA 92093, USA. OI Preece, Robert/0000-0003-1626-7335 NR 20 TC 18 Z9 18 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 FEB 20 PY 1996 VL 458 IS 2 BP 746 EP 754 DI 10.1086/176855 PN 1 PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA TU810 UT WOS:A1996TU81000033 ER PT J AU Ramanamurthy, PV Fichtel, CE Kniffen, DA Sreekumar, P Thompson, DJ AF Ramanamurthy, PV Fichtel, CE Kniffen, DA Sreekumar, P Thompson, DJ TI Possible evidence for pulsed emission of high-energy gamma-rays by PSR B0656+14 SO ASTROPHYSICAL JOURNAL LA English DT Article DE gamma rays, observations; pulsars, individual, (PSR B0656+14) ID RAPIDLY SPINNING PULSARS; RADIATION; DISCOVERY; CRAB AB We present here possible evidence for a seventh high-energy gamma-ray pulsar, PSR B0656 + 14, pulsating in gamma rays at E greater than or equal to 50 MeV with the same 384.9 ms periodicity as in radio, using the data obtained during 1991 April to 1993 December by the Energetic Gamma-Ray Experiment Telescope (EGRET) aboard the Compton Gamma Ray Observatory. Since the pulsed flux is very low, we adapted a weighting method in our analysis of the data to detect the pulsar. With this technique, we found that the null hypothesis (viz., that it is not a pulsar) is probable only at a level of less than or equal to 2.6 x 10(-7) The phase-selected data corresponding to the peak seen in the events light curve reveals the existence of a high-energy gamma-ray source positionally consistent with the pulsar. We found that the phase-averaged high-energy gamma-ray pulsed flux from PSR B0656 + 14 is (4.1 +/- 1.4) x 10(-8) photons cm(-2) s(-1) at E greater than or equal to 100 MeV, and the exponent of the differential photon number spectrum, -2.8 +/- 0.3. The pulsar appears to have an efficiency of approximately 0.001 in converting its spin-down energy-loss rate into high-energy gamma-rays at E greater than or equal to 100 MeV. C1 HAMPDEN SYDNEY COLL,DEPT PHYS,HAMPDEN SYDNEY,VA 23943. RP Ramanamurthy, PV (reprint author), NASA,GODDARD SPACE FLIGHT CTR,CODE 661,GREENBELT,MD 20771, USA. RI Thompson, David/D-2939-2012 OI Thompson, David/0000-0001-5217-9135 NR 31 TC 68 Z9 68 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 FEB 20 PY 1996 VL 458 IS 2 BP 755 EP 760 DI 10.1086/176856 PN 1 PG 6 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA TU810 UT WOS:A1996TU81000034 ER PT J AU Guhathakurta, M Holzer, TE MacQueen, RM AF Guhathakurta, M Holzer, TE MacQueen, RM TI The large-scale density structure of the solar corona and the heliospheric current sheet SO ASTROPHYSICAL JOURNAL LA English DT Article DE Sun, corona; Sun, magnetic fields ID MAGNETIC-FIELD; WIND AB We have investigated the three-dimensional distribution of the polarization-brightness product (pB) and then quantitatively determined the electron density distribution relative to the inferred heliographic current sheet during the declining phase of solar cycle 20 (1973-1976). The current sheet is taken as the center of the bright, dense structures from combined synoptic pB data from ground-based K-coronameter and the white-light coronagraph aboard Skylab. Analyses of pB scans as a function of minimum distance from the current sheet (theta(min)) over the radial distance range 1.13 to 5.0 R. (from Sun center) led to the following new results: (1) a quantitative description of pB obtained around the inferred neutral line is given by the following equation: pB(rho, theta(min)) = pB(p)(rho) + [pB(cs)(rho) - pB(p)(rho)]e(-theta min2/w2(r)), where rho is the shortest distance to the line of sight from the Sun center, pB(cs)(rho) and pB(p)(rho) are the observed polarized brightness at the current sheet and the poles, respectively, and w(r) is the half-width of the distribution; (2) the electron density obtained by inverting the pB data is given by N(r, theta(mg)) = N-p(r) + [N-cs(r) - N-p(r)]e(-theta mg2/w2(r)), where N(r, theta(mg)) is the number of free electrons per cm(3), N-cs(r) and N-p(r) are the electron densities at the current sheet and the poles, respectively, and theta(mg) is the magnetic latitude. Here theta(mg) is given by theta mg = sin(-1) [-cos theta sin alpha sin (phi -phi(o)) + sin theta cis alpha], where theta and phi are heliographic latitude and longitude, alpha is the tilt angle of the dipole axis with the rotation axis, and phi(o) is the intersecion of the heliomagnetic and heliographic equators; (3) during the period studied (the last third of the solar cycle), the mean pB at the current sheet and above the polar holes is approximately independent of the phase of the solar cycle; and (4) the organization of pB data about the neutral line allows inference of the boundary of the polar coronal holes. The usefulness of one-dimensional white-light density constraint in solar wind modeling has already been demonstrated by Habbal et al. The present three-dimensional model should prove very useful in better understanding of the global hydromagnetic structure of the corona and the solar wind, relating as it does to the magnetic structure of the corona, as opposed to heliocentric coordinates. For example, the density model could provide constraints on coronal temperature, flow velocity, and magnetic structure subject to a suitable analysis of geometric effects, which in turn would provide constraints on energy balance in the coronal expansion. C1 NATL CTR ATMOSPHER RES,HIGH ALTITUDE OBSERV,BOULDER,CO 80307. RHODES COLL,DEPT PHYS,MEMPHIS,TN 38112. CATHOLIC UNIV AMER,DEPT PHYS,WASHINGTON,DC 20064. RP Guhathakurta, M (reprint author), NASA,GODDARD SPACE FLIGHT CTR,CODE 682,GREENBELT,MD 20771, USA. NR 43 TC 69 Z9 69 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 FEB 20 PY 1996 VL 458 IS 2 BP 817 EP 831 DI 10.1086/176860 PN 1 PG 15 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA TU810 UT WOS:A1996TU81000038 ER PT J AU vanderHooft, F Kouveliotou, C vanParadijs, J Rubin, BC Crary, DJ Finger, MH Harmon, BA vanderKlis, M Lewin, WHG Norris, JP Fishman, GJ AF vanderHooft, F Kouveliotou, C vanParadijs, J Rubin, BC Crary, DJ Finger, MH Harmon, BA vanderKlis, M Lewin, WHG Norris, JP Fishman, GJ TI Timescale invariance of rapid X-ray variability of the black hole candidate GRO J1719-24 SO ASTROPHYSICAL JOURNAL LA English DT Article DE accretion, accretion disks; binaries, close; stars, individual (GRO J1719-24); X-rays, stars AB We present the results of an analysis of the time variability of the soft X-ray transient GRO J1719-24 (Nova Oph 1993), as observed with BATSE. Our analysis covers the entire similar to 80 day outburst, beginning with the first detection of this black hole candidate on 1993 September 25. We obtained power density spectra (PDSs) of the data in the 20-100 keV energy band, covering the frequency interval 0.002-0.488 Hz. The PDSs show a significant quasi-periodic oscillation peak, the centroid frequency of which increased from similar to 0.04 Hz at the onset of the outburst to similar to 0.3 Hz at the end. Additional noise is present in the PDSs, which we describe in terms of two components. We find that the evolution of the PDSs can be described as a gradual stretching by a factor of similar to 7.5 in frequency of the power spectrum, accompanied by a decrease of the power level by the same factor, such that the integrated power in a scaled frequency interval remains constant. C1 CTR HIGH ENERGY ASTROPHYS,1098 SJ AMSTERDAM,NETHERLANDS. UNIV SPACE RES ASSOC,HUNTSVILLE,AL 35806. NASA,GEORGE C MARSHALL SPACE FLIGHT CTR,HUNTSVILLE,AL 35812. UNIV ALABAMA,DEPT PHYS,HUNTSVILLE,AL 35899. MIT,CAMBRIDGE,MA 02139. NASA,GODDARD SPACE FLIGHT CTR,GREENBELT,MD 20771. RP vanderHooft, F (reprint author), UNIV AMSTERDAM,ASTRON INST ANTON PANNEKOEK,KRUISLAAN 403,1098 SJ AMSTERDAM,NETHERLANDS. NR 19 TC 19 Z9 19 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 FEB 20 PY 1996 VL 458 IS 2 BP L75 EP & PN 2 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA TU811 UT WOS:A1996TU81100006 ER PT J AU Woo, R AF Woo, R TI 1985 Voyager 2 radio ranging measurements of coronal density: Asymmetry in the radial profiles explained SO ASTROPHYSICAL JOURNAL LA English DT Article DE interplanetary medium; solar wind; sun, corona ID ELECTRON-DENSITIES; SOLAR CORONA; WAVELENGTHS; CONJUNCTION AB An asymmetry in the radial variation of electron density above the east and west limbs of the Sun was inferred from centimeter wavelength ranging measurements conducted by Voyager 2 during its 1985 solar conjunction. The Voyager 2 ranging measurements, which took place in the heliocentric distance range of 7-40 R(.), have been compared with the white-light coronagraph measurements of the underlying corona collected by the Mark III K-coronameter located at the Mauna Loa Solar Observatory. It is shown that the disparity in radial profiles is not real but is instead caused by longitudinal variations stemming from the probing of significantly different source regions as revealed in the white-light measurements. These results improve our understanding of the probing abilities of ranging measurements and their relationship to white-light measurements. They reinforce the notion that the high-precision and high-sensitivity features of ranging measurements are more fully exploited in the investigation of density variations across the ubiquitous low-contrast raylike structures that permeate the corona, rather than in determining radial density profiles. RP Woo, R (reprint author), CALTECH,JET PROP LAB,4800 OAK GROVE DR,MS 238-725,PASADENA,CA 91109, USA. NR 22 TC 1 Z9 1 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637 SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD FEB 20 PY 1996 VL 458 IS 2 BP L87 EP L90 DI 10.1086/309922 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA TU811 UT WOS:A1996TU81100009 ER PT J AU Wright, EL Hinshaw, G Bennett, CL AF Wright, EL Hinshaw, G Bennett, CL TI Producing megapixel cosmic microwave background maps from differential radiometer data SO ASTROPHYSICAL JOURNAL LA English DT Article DE cosmic microwave background; methods, data analysis AB A major goal of cosmology is to obtain sensitive, high-resolution maps of the cosmic microwave background anisotropy. Such maps, as would be produced by the recently proposed Microwave Anisotropy Probe (MAP), will contain a wealth of primary information about conditions in the early universe. To mitigate Systematic effects when observing the microwave background, it is desirable for the raw data to be collected in differential form: as a set of temperature differences between points in the sky. However, the production of large (megapixel) maps from a set of temperature differences is a potentially severe computational challenge. We present a new technique for producing maps from differential radiometer data that has a computational cost that grows in the slowest possible way with increasing angular resolution and number of map pixels. The required CPU time is proportional to the number of differential data points, and the required random-access memory is proportional to the number of map pixels. We test our technique, and demonstrate its feasibility, by simulating 1 yr of a spaceborne anisotropy mission. C1 NASA,GODDARD SPACE FLIGHT CTR,ASTRON & SOLAR PHYS LAB,HUGHES STX CORP,GREENBELT,MD 20771. RP Wright, EL (reprint author), UNIV CALIF LOS ANGELES,DEPT PHYS & ASTRON,LOS ANGELES,CA 90095, USA. NR 4 TC 47 Z9 47 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 S WOODLAWN AVE, CHICAGO, IL 60637 SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD FEB 20 PY 1996 VL 458 IS 2 BP L53 EP & PN 2 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA TU811 UT WOS:A1996TU81100001 ER PT J AU Rinsland, CP Zander, R Demoulin, P Mahieu, E AF Rinsland, CP Zander, R Demoulin, P Mahieu, E TI ClONO2 total vertical column abundances above the Jungfraujoch Station, 1986-1994: Long-term trend and winter-spring enhancements SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID INFRARED SPECTROSCOPIC MEASUREMENTS; CHLORINE NITRATE CLONO2; BALLOON-BORNE; SOLAR SPECTRA; Q-BRANCH; OZONE; STRATOSPHERE; ATMOSPHERE; HNO3; SPACELAB-3 AB Total vertical column abundances of chlorine nitrate (ClONO2) have been retrieved from 0.006 cm(-1) resolution solar absorption spectra recorded at the International Scientific Station of the Jungfraujoch (ISSJ) in the Swiss Alps (altitude 3.58 km, latitude 46.5 degrees N, longitude 8.0 degrees E) on 105 days between June 1986 and November 1994. The analysis is based on spectral fittings of the ClONO2 nu(4) band Q branch at 780.21 cm(-1) and the interferences occurring in the same spectral region. The ISSJ measurements show a regular long-term increase in the ClONO2 column with an occasional factor of 2 to 3 enhancements during the midwinter to early spring. Excluding data from this time of the year, the ISSJ database reflects a linear rate of increase and la uncertainty equal to (4.0 +/- 0.7)% yr(-1) referenced to 1990.0. The corresponding ClONO2 total vertical columns for mid-1986 and mid-1994 are equal to 0.92 and 1.26 x 10(15) molecules cm(-2), respectively. The high ClONO2 columns and high HF/HCl column ratios sometimes measured during winter indicate the occasional presence of chemically processed air above the station. This is corroborated by trajectories calculated for the stratospheric air masses sounded on these occasions. C1 NASA, LANGLEY RES CTR, DIV ATMOSPHER SCI, HAMPTON, VA 23681 USA. RP Rinsland, CP (reprint author), UNIV LIEGE, INST ASTROPHYS, B-4000 LIEGE, BELGIUM. NR 53 TC 13 Z9 13 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD FEB 20 PY 1996 VL 101 IS D2 BP 3891 EP 3899 DI 10.1029/95JD03349 PG 9 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA TW970 UT WOS:A1996TW97000005 ER PT J AU Stothers, RB AF Stothers, RB TI Major optical depth perturbations to the stratosphere from volcanic eruptions: Pyrheliometric period, 1881-1960 SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Review ID EL-CHICHON; ICE-SHEET; ATMOSPHERIC TRANSMISSION; EXPLOSIVE VOLCANISM; AEROSOLS; DUST; SULFUR; CLOUD AB A detailed chronology of major stratospheric dust veils from 1881 to 1960 has been constructed by searching the primary literature for relevant observational data of various kinds, especially pyrheliometry. Data from 23 observing sites in both hemispheres have been reduced in a rigorous fashion to yield a table of pyrheliometric optical depth perturbations as a function of year, month, and latitude band. To convert to visual reference wavelengths, the tabular entries should be multiplied by a time-dependent factor that is somewhat greater than unity. Ten measurable volcanic dust veils have been established in this manner and have been analyzed as to their generation, transport, decay, and total mass. These clouds arose from eruptions of Krakatau (1883), an unidentified volcano (1890), Soufriere and Pelee (1902), Santa Maria (1902), Ksudach (1907), Katmai (1912), Puyehue (1921), Paluweh (1928), Komagatake (1929), and Quizapu (1932). Other turbidity indicators have also been used in the analysis, including starlight extinction, purple twilight glows, color of Sun and Moon, polarization of blue sky light, Bishop's ring around the Sun, and dark lunar eclipses. Global stratospheric aerosol loadings have been computed from the peak turbidities. Agreement with the aerosol masses derived from polar ice cores is good in the important cases of Krakatau, Santa Maria, and (after a major correction of the ice core value) Katmai. During the long period 1881-1992, about 80% of all stratospheric aerosols generated by the largest sulfur-producing eruptions were emplaced during the two short time intervals 1883-1902 and 1982-1991. The long-term (1881-1992) average annual production rate of stratospheric SO2 from the largest eruptions was 0.8 Tg yr(-1), about half the average rate since 1981. Implications of the principal results are discussed. RP NASA, GODDARD INST SPACE STUDIES, 2880 BROADWAY, NEW YORK, NY 10025 USA. NR 233 TC 67 Z9 72 U1 4 U2 14 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 FEB 20 PY 1996 VL 101 IS D2 BP 3901 EP 3920 DI 10.1029/95JD03237 PG 20 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA TW970 UT WOS:A1996TW97000006 ER PT J AU Herber, A Thomason, LW Dethloff, K Viterbo, P Radionov, VF Leiterer, U AF Herber, A Thomason, LW Dethloff, K Viterbo, P Radionov, VF Leiterer, U TI Volcanic perturbation of the atmosphere in both polar regions: 1991-1994 SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID PINATUBO AEROSOLS; MOUNT-PINATUBO; MT-PINATUBO; STRATOSPHERIC AEROSOL; CERRO HUDSON; ARCTIC HAZE; ERUPTIONS; OZONE; POLLUTION; SATELLITE AB Long-term measurements by sunphotometers of the spectral dependence of aerosol optical depth are reported for several sites in the Arctic and Antarctic for the period January 1991 through December 1994. In the Antarctic a pronounced increase of atmospheric turbidity was observed at the end of September 1991. The observed wavelength dependence in aerosol optical depth indicated that the increase was due to the presence of fresh and therefore small stratospheric aerosol particles associated with the eruption of Cerro Hudson in August 1991. After the breakdown of the polar vortex in mid-November 1991 we measured a second significant increase of the aerosol optical depth. At this time the 1.0-mu m aerosol optical depth was approximately 0.12 or about 10 times background levels. This second increase is shown to be the result of the influx of Mount Pinatubo aerosols. A similar perturbation of the aerosol optical depth was observed in the Arctic with the return of sunlight in March 1992. However, the increased loading of the Arctic stratosphere by the Pinatubo aerosols was already evident al high northern latitudes in satellite measurements at the end of 1991. Stratospheric Aerosol and Gas Experiment II stratospheric 1.0-mu m optical depth measurements show that meridional transport of Pinatubo aerosol from equatorial to middle and higher latitudes is greatest in the winter/spring hemisphere. This observation explains the observed seasonal trend of aerosol optical depth during the posteruption. A significant decrease of the perturbation by Mount Pinatubo aerosol was observed in both polar regions by the end of 1994. The measured 1.0-mu m aerosol optical depths at this time were only approximate to 0.04; these values exceed the background level by about 0.01-0.02. Therefore the aerosol optical depth values are still slightly higher than during undisturbed conditions. In addition, we show that the occurrence of volcanic aerosols caused changes in the spectral dependence of the aerosol optical depth in the Arctic and the Antarctic. These variations, including the changes in the aerosol size distribution, derived from the aerosol optical depth, are discussed in comparison to undisturbed conditions. C1 METEOROL OBSERV LINDENBERG DEUTSCH WETTERDIENST, D-15864 LINDENBERG, GERMANY. ARCTIC & ANTARCTIC RES INST, ST PETERSBURG 199226, RUSSIA. NASA, LANGLEY RES CTR, DIV ATMOSPHER SCI, HAMPTON, VA 23681 USA. EUROPEAN CTR MEDIUM RANGE WEATHER FORECASTS, READING RG2 9AX, BERKS, ENGLAND. RP Herber, A (reprint author), ALFRED WEGENER INST, RES UNIT POTSDAM, RES DEPT, TELEGRAFENBERG A43, D-14473 POTSDAM, GERMANY. RI Viterbo, Pedro/B-7184-2008; Dethloff, Klaus/B-4879-2014; OI Viterbo, Pedro/0000-0001-6587-3062; Thomason, Larry/0000-0002-1902-0840 NR 52 TC 35 Z9 42 U1 0 U2 4 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD FEB 20 PY 1996 VL 101 IS D2 BP 3921 EP 3928 DI 10.1029/95JD02462 PG 8 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA TW970 UT WOS:A1996TW97000007 ER PT J AU Grant, WB Browell, EV Long, CS Stowe, LL Grainger, RG Lambert, A AF Grant, WB Browell, EV Long, CS Stowe, LL Grainger, RG Lambert, A TI Use of volcanic aerosols to study the tropical stratospheric reservoir SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID MT-PINATUBO; MOUNT-PINATUBO; POTENTIAL VORTICITY; MIDDLE LATITUDES; POLAR VORTEX; EL-CHICHON; OZONE; ERUPTIONS; CLOUD; SO2 AB Aerosol data obtained by the advanced very high resolution radiometer on NOAA 11, the improved stratospheric and mesospheric sounder on the upper atmospheric research satellite, one airborne lidar system, and several ground-based lidar systems up to 2-1/2 years after the eruption of Mount Pinatubo are used to study stratospheric dynamics. In particular, this study focuses on the tropical stratospheric reservoir and transport from it to northern midlatitudes following the eruption of Mount Pinatubo. This includes: The build-up and removal rates for sulfate aerosol, the position and motion of the center of the reservoir, and the position and width of its boundaries at altitudes of the volcanic aerosols. Ozone data from the total ozone mapping spectrometer were also used to study the position and width of the reservoir boundaries. In addition, ground-based lidar stratospheric aerosol data are used to study aerosol transport from the reservoir to the northern hemisphere as it relates to winds in the tropical stratosphere. Finally, historical in situ and satellite data were used to examine how the time and location of volcanic injections into the stratosphere affect the aerosol decay rates and seasonal variations of aerosol optical depth in the midlatitude stratosphere. C1 UNIV OXFORD, OXFORD OX1 3PU, ENGLAND. NOAA, NWS, NMC, CLIMATE ANAL CTR, CAMP SPRINGS, MD 20746 USA. NOAA, NATL ENVIRONM SATELLITE DATA & INFORMAT SERV, ORA, SATELLITE RES LAB, WASHINGTON, DC 20233 USA. NASA, LANGLEY RES CTR, DIV ATMOSPHER SCI, HAMPTON, VA 23681 USA. RI Grainger, Roy/E-8823-2011; Grant, William/B-8311-2009 OI Grainger, Roy/0000-0003-0709-1315; Grant, William/0000-0002-1439-3285 NR 84 TC 84 Z9 84 U1 0 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD FEB 20 PY 1996 VL 101 IS D2 BP 3973 EP 3988 DI 10.1029/95JD03164 PG 16 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA TW970 UT WOS:A1996TW97000011 ER PT J AU Mote, PW Rosenlof, KH McIntyre, ME Carr, ES Gille, JC Holton, JR Kinnersley, JS Pumphrey, HC Russell, JM Waters, JW AF Mote, PW Rosenlof, KH McIntyre, ME Carr, ES Gille, JC Holton, JR Kinnersley, JS Pumphrey, HC Russell, JM Waters, JW TI An atmospheric tape recorder: The imprint of tropical tropopause temperatures on stratospheric water vapor SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID MIDDLE ATMOSPHERE; DEHYDRATION; CIRCULATION; PARAMETERIZATION; PERFORMANCE; TRANSPORT; BREAKING; MODEL AB We describe observations of tropical stratospheric water vapor q that show clear evidence of large-scale upward advection of the signal from annual fluctuations in the effective ''entry mixing ratio'' q(E) of air entering the tropical stratosphere, In other words, air is ''marked,'' on emergence above the highest cloud tops, like a signal recorded on an upward moving magnetic tape, We define q(E) as the mean water vapor mixing ratio, at the tropical tropopause, of air that will subsequently rise and enter the stratospheric ''overworld'' at about 400 K. The observations show a systematic phase lag, increasing with altitude, between the annual cycle in q(E) and the annual cycle in q at higher altitudes, The observed phase lag agrees with the phase lag calculated assuming advection by the transformed Eulerian-mean vertical velocity of a q(E) crudely estimated from 100-hPa temperatures, which we use as a convenient proxy for tropopause temperatures, The phase agreement confirms the overall robustness of the calculation and strongly supports the tape recorder hypothesis, Establishing a quantitative link between q(E) and observed tropopause temperatures, however, proves difficult because the process of marking the tape depends subtly on both small- and large-scale processes, The tape speed, or large-scale upward advection speed, has a substantial annual variation and a smaller variation due to the quasi-biennial oscillation, which delays or accelerates the arrival of the signal by a month or two in the middle stratosphere. As the tape moves upward, the signal is attenuated with an e-folding time of about 7 to 9 months between 100 and 50 hPa and about 15 to 18 months between 50 and 20 hPa, constraining possible orders of magnitude both of vertical diffusion K-z and of rates of mixing in from the extratropics. For instance, if there were no mixing in, then K-z would be in the range 0.03-0.09 m(2) s(-1); this is an upper bound on K-z. C1 UNIV COLORADO, NOAA, COOPERAT INST RES ENVIRONM SCI, BOULDER, CO 80309 USA. UK UNIV GLOBAL ATMOSPHER MODELLING PROGRAMME, READING, BERKS, ENGLAND. NOAA, ENVIRONM RES LABS, AERON LAB, BOULDER, CO USA. NATL CTR ATMOSPHER RES, DIV ATMOSPHER CHEM, BOULDER, CO 80307 USA. UNIV WASHINGTON, DEPT ATMOSPHER SCI, SEATTLE, WA 98195 USA. CALTECH, JET PROP LAB, PASADENA, CA 91109 USA. NASA, LANGLEY RES CTR, HAMPTON, VA 23665 USA. UNIV CAMBRIDGE, DEPT APPL MATH & THEORET PHYS, CAMBRIDGE CB3 9EW, ENGLAND. RP Mote, PW (reprint author), UNIV EDINBURGH, DEPT METEOROL, KINGS BLDG, EDINBURGH EH9 3JZ, MIDLOTHIAN, SCOTLAND. RI Rosenlof, Karen/B-5652-2008 OI Rosenlof, Karen/0000-0002-0903-8270 NR 62 TC 441 Z9 444 U1 2 U2 24 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD FEB 20 PY 1996 VL 101 IS D2 BP 3989 EP 4006 DI 10.1029/95JD03422 PG 18 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA TW970 UT WOS:A1996TW97000012 ER PT J AU Mauzerall, DL Jacob, DJ Fan, SM Bradshaw, JD Gregory, GL Sachse, GW Blake, DR AF Mauzerall, DL Jacob, DJ Fan, SM Bradshaw, JD Gregory, GL Sachse, GW Blake, DR TI Origin of tropospheric ozone at remote high northern latitudes in summer SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID GAS-PHASE REACTION; OH; CHEMISTRY; PRODUCT; AIR; NOX; PHOTOCHEMISTRY; STRATOSPHERE; TRANSPORT; EXCHANGE AB We quantify the tropospheric ozone budget over remote high northern latitudes in summer using chemical and meteorological measurements between 0 and 6-km made during the summer of 1990 Arctic Boundary Layer Expedition (ABLE 3B). We include all components of the ozone budget, both sinks (in situ photochemical loss and deposition); and sources (in situ photochemical production, advection of pollution ozone into the legion, production in biomass wildfire plumes, and downwards transport from the upper troposphere/stratosphere). In situ production and loss of ozone are calculated with a photochemical model. The net influx of pollution ozone from North America and Eurasia is estimated from the average enhancement ratio of Delta O-3/Delta C2Cl4 observed in pollution plumes and scaled by the net influx of C2Cl4. The contribution of ozone produced in biomass wildfire plumes is estimated from the average enhancement ratio of Delta O3/Delta CO in aged fire plumes. Regional photochemical production and loss in the 0-6 km column are found to be approximately equal; hence, net photochemical production is near zero. However, when ozone production and loss terms are separated, we find that dispel sed in situ photochemical production driven by background NO levels (5-10 pptv) is the largest source term in the ozone budget (62%). Influx of stratospheric ozone is of secondary importance (27%). long-range transport of pollution ozone makes a small contribution (9%), and photochemical production of ozone within biomass wildfire plumes is a relatively negligible term (2%) in the budget. Biomass fires and transport of anthropogenic pollution into the region may however have a major effect on the ozone budget through enhancement of background NOx mixing ratios which increase dispersed photochemical production. Using a 1-D time-dependent photochemical model between 0 and 6 km, we obtain good agreement between the observed and model-generated vertical ozone profiles. We find that in situ photochemistry within the 0-6 km column accounts for nearly 90% of the ozone mixing ratio within the boundary layer, while above 5 km it accounts for only about 40%. Although photochemical production of ozone within the 0-6 km column is larger than the other source terms combined, the 1-D model results indicate that influx from above is necessary to account for the observed increase in ozone mixing ratios with altitude. C1 UNIV CALIF IRVINE, DEPT CHEM, IRVINE, CA 92717 USA. HARVARD UNIV, DIV APPL SCI, CAMBRIDGE, MA 02138 USA. NASA, LANGLEY RES CTR, HAMPTON, VA 22331 USA. GEORGIA INST TECHNOL, SCH EARTH & ATMOSPHER SCI, ATLANTA, GA 30332 USA. RP Mauzerall, DL (reprint author), HARVARD UNIV, DEPT EARTH & PLANETARY SCI, 20 OXFORD ST, CAMBRIDGE, MA 02138 USA. RI Mauzerall, Denise/I-5977-2013 OI Mauzerall, Denise/0000-0003-3479-1798 NR 59 TC 68 Z9 70 U1 1 U2 11 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD FEB 20 PY 1996 VL 101 IS D2 BP 4175 EP 4188 DI 10.1029/95JD03224 PG 14 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA TW970 UT WOS:A1996TW97000025 ER PT J AU Clarke, AD Porter, JN Valero, FPJ Pilewskie, P AF Clarke, AD Porter, JN Valero, FPJ Pilewskie, P TI Vertical profiles, aerosol microphysics, and optical closure during the Atlantic Stratocumulus Transition Experiment: Measured and modeled column optical properties SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID RADIATIVE CHARACTERISTICS; ATMOSPHERIC SULFUR; LIGHT-ABSORPTION; SAHARAN DUST; PARTICLES; CLIMATE; SULFATE; ACID AB During the Atlantic Stratocumulus Transition Experiment (ASTEX) in June 1992, two descents in cloud-free regions allowed comparison of the change in aerosol optical depth as determined by an onboard total-direct-diffuse radiometer (TDDR) to the change calculated from measured size-resolved aerosol microphysics and chemistry. Both profiles included a pollution haze layer from Europe, but the second also included the effect of a Saharan dust layer above the haze. The separate contributions of supermicrometer (coarse) and submicrometer (fine) aerosol were determined, and thermal analysis of the pollution haze indicated that the fine aerosol was composed primarily of a sulfate/water mixture with a refractory sootlike core. The soot core increased the calculated extinction by about 10% in the most polluted drier layer relative to a pure sulfate aerosol but had significantly less effect at higher humidities. A 3-km descent through a boundary layer air mass dominated by pollutant aerosol with relative humidities (RH) 10-77% yielded a close agreement between the measured and calculated aerosol optical depths (550 nm) of 0.160 (+/-0.07) and 0.157 (+/-0.034), respectively. During descent the aerosol mass scattering coefficient per unit sulfate mass (inferred) varied from about 5 to 16 m(2) g(-1) and was primarily dependent upon ambient RH. However, the total scattering coefficient per total fine mass was far less variable at about 4 +/-0.7 m(2) g(-1). A subsequent descent through a Saharan dust layer located above the pollution aerosol layer revealed that both layers contributed similarly to aerosol optical depth. The scattering per unit mass of the coarse aged dust was estimated at 1.1 +/- 0.2 m(2) g(-1). The large difference (50%) in measured and calculated optical depth for the dust layer exceeded estimated measurement uncertainty (12%). This is attributed to inadequate data on the spatial variability of the aerosol field within the descent region, a critical factor in any validation of this type. Both cases demonstrate that surface measurements may be a poor indicator of the characteristics and concentration of the aerosol column. C1 UNIV CALIF SAN DIEGO, CALIF SPACE INST, LA JOLLA, CA 92093 USA. NASA, AMES RES CTR, MOFFETT FIELD, CA 94035 USA. RP Clarke, AD (reprint author), UNIV HAWAII, SCH OCEAN & EARTH SCI & TECHNOL, HONOLULU, HI 96822 USA. NR 29 TC 46 Z9 47 U1 0 U2 4 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD FEB 20 PY 1996 VL 101 IS D2 BP 4443 EP 4453 DI 10.1029/95JD03140 PG 11 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA TW970 UT WOS:A1996TW97000047 ER EF